阅读说明：本技术 钛复合材料以及热加工用钛材 (Titanium composite material and titanium material for hot working ) 是由 北浦知之 白井善久 藤井秀树 于 2016-07-29 设计创作，主要内容包括：一种钛复合材料,其为具备第一表层部2,内层部4和第二表层部3的钛复合材料1,第一表层部2以及第二表层部3由钛合金形成,内层部4由具有空隙的工业用纯钛形成,第一表层部2以及第二表层部3的至少一者的厚度为2μm以上,并且,钛复合材1占总厚度的比例为40％以下,与空隙的板厚方向垂直的截面中的体积率为超过0％且30％以下。(A titanium composite material (1) comprising a first surface layer part (2), an inner layer part (4), and a second surface layer part (3), wherein the first surface layer part (2) and the second surface layer part (3) are formed of a titanium alloy, the inner layer part (4) is formed of an industrially pure titanium having voids, the thickness of at least one of the first surface layer part (2) and the second surface layer part (3) is2 [ mu ] m or more, the proportion of the titanium composite material (1) to the total thickness is 40% or less, and the volume fraction in a cross section perpendicular to the direction of the thickness of the voids is more than 0% and 30% or less.)

1. A titanium material for hot working, comprising a housing and 1 or more kinds selected from the group consisting of titanium sponge, briquettes obtained by compressing titanium sponge and industrial pure titanium scrap, which are filled in the housing,

a portion constituting a surface layer after hot working as a part of the case is formed of a titanium alloy,

the degree of vacuum inside the vacuum chamber is 10Pa or less.

2. The titanium material for hot working according to claim 1, wherein a chemical composition of the titanium alloy is in mass%

Platinum group elements: 0.01 to 0.25 percent,

Rare earth elements: 0 to 0.2 percent of,

Co：0～0.8％、

Ni：0～0.6％、

And the balance: ti and impurities.

3. The titanium material for hot working according to claim 2, wherein the platinum group element is Pd and/or Ru.

4. The titanium material for hot working according to any one of claims 1 to 3, wherein 1 or more chemical compositions selected from the group consisting of the titanium sponge, the compact obtained by compressing the titanium sponge, and the industrial pure titanium scrap, which are filled in the housing, are contained in mass%

C: less than 0.1 percent of,

H: less than 0.015%,

O: less than 0.4 percent of,

N: less than 0.07 percent of,

Fe: less than 0.5 percent,

And the balance: ti and impurities.

5. A method for producing a titanium composite material by hot rolling the titanium material for hot working according to any one of claims 1 to 4,

the titanium composite material comprises a first surface layer part, an inner layer part and a second surface layer part,

the first surface layer portion and the second surface layer portion are formed of the titanium alloy,

the inner layer portion is formed of commercially pure titanium having voids,

at least one of the first surface layer portion and the second surface layer portion has a thickness of 2 μm or more and accounts for 40% or less of the total thickness of the titanium composite material,

the volume fraction of the voids in a cross section perpendicular to the plate thickness direction exceeds 0% and is 30% or less,

the volume fraction of the voids in a cross section perpendicular to the sheet thickness direction is calculated as follows: after embedding the titanium composite material in a resin so that the cross section of the titanium composite material can be observed, the observation surface was polished and mirror-finished using a diamond or alumina polishing solution, an optical micrograph of the center portion of the plate thickness was taken at a magnification of 500 times using an observation sample subjected to the mirror-finishing, the area ratio of the voids observed in the optical micrograph taken was measured, and the measurement results of 20 sheets were averaged to calculate the porosity.

Technical Field

The present invention relates to a titanium composite material and a titanium material for hot working.

Background

Titanium materials are excellent in properties such as corrosion resistance, oxidation resistance, fatigue resistance, hydrogen embrittlement resistance, and neutron blocking property. These characteristics can be achieved by adding various alloying elements to titanium.

Titanium materials are lightweight and excellent in corrosion resistance, and therefore are used in, for example, a seawater cooling condenser in a power plant, a heat exchanger for seawater desalination machinery, a reactor for chemical machinery, a cooler, and the like.

Industrial pure titanium exhibits excellent corrosion resistance particularly in an environment containing nitric acid, chromic acid, or the like, seawater, an environment containing chloride ions, or the like. However, high corrosion resistance cannot be expected in an environment containing hydrochloric acid, sulfuric acid, or the like, and in addition, interstitial corrosion may occur in an environment containing chlorine ions or the like.

Therefore, various alloys have been developed in which a small amount of platinum group elements (such as Ru, Rh, Pd, Os, Ir, and Pt) is added to titanium, such as Ti-0.2Pd (ASTMGrade7 and ASTMGrade 11). Further, a corrosion-resistant titanium alloy such as Ti-0.5Ni-0.05Ru in which Ni and Ru are used in place of Pd is developed, which is inexpensive and has excellent corrosion resistance.

Titanium materials have been used in the field of aircrafts due to their excellent specific strength and corrosion resistance, and are also used in a large number of exhaust devices for automobiles and motorcycles. In particular, in place of conventional stainless steel materials, industrial pure titanium materials of JIS2 grade have been used mainly for two-wheeled vehicles from the viewpoint of weight reduction of vehicles. In recent years, heat-resistant titanium alloys having higher heat resistance have been used in place of JIS2 grade industrial pure titanium materials. Further, the present invention is also used for a muffler having a catalyst used at a high temperature for removing harmful components in exhaust gas.

The temperature of the exhaust gas exceeds 700 c and sometimes temporarily reaches 800 c. Therefore, the materials used in the exhaust device are required to have strength, oxidation resistance, and the like at temperatures around 800 ℃, and further, the high-temperature heat resistance index of the creep speed at 600 to 700 ℃ is regarded as important.

On the other hand, in order to improve the high-temperature strength, such a heat-resistant titanium alloy requires addition of elements for improving the high-temperature strength and the oxidation resistance, such as Al, Cu, and Nb, which is expensive compared to industrial pure titanium.

Jp 2001-234266 a (patent document 1) discloses a composition containing Al: 0.5 to 2.3% (in the present specification, "%" relating to chemical components means "% by mass" unless otherwise specified) of a titanium alloy having excellent cold workability and high-temperature strength.

Japanese patent laid-open No. 2001-89821 (patent document 2) discloses a Fe: 1% over 5% O (oxygen): 0.05 to 0.75%, further comprising Si: 0.01. e^0.5[Fe]～5·e^-0.5[Fe]Titanium alloy ([ Fe ] having excellent oxidation resistance and corrosion resistance]And (c) represents the content (% by mass) in the alloy, and e represents a constant of a natural logarithm).

Jp 2005-290548 a (patent document 3) discloses a method for producing a titanium alloy containing Al: 0.30 to 1.50%, Si: 0.10 to 1.0% of a heat-resistant titanium alloy sheet having excellent cold workability and a method for producing the same.

Jp 2009-: 0.5 to 1.8%, Si: 0.1-0.6%, O: 0.1% or less, and Nb as necessary: 0.1 to 1.0% and the balance Ti and inevitable impurities, and a surface-protective film.

Further, japanese patent application laid-open No. 2013-142183 (patent document 5) discloses a composition containing Si: 0.1-0.6%, Fe: 0.04-0.2%, O: 0.02 to 0.15%, 0.1 to 0.3% of total content of Fe and O, and the balance of Ti and unavoidable impurity elements, and has high-temperature strength at 700 ℃ and oxidation resistance at 800 ℃.

Industrial titanium cold-rolled sheets (for example, industrial pure titanium cold-rolled sheets) are used in a wide range of applications, except for the use of sheets formed into a predetermined shape, such as plate heat exchangers and FC separators. Therefore, in addition to formability, industrial titanium cold-rolled sheets are required to be light and thin and have a high added environment (under high load) due to an improvement in fatigue strength.

On the other hand, even pure titanium, like other metal materials, has an inverse relationship between ductility and strength (fatigue strength) which dominate formability.

Jp 2008-195994 a (patent document 6) discloses a method of modifying the surface of a titanium product and improving the fatigue strength of the titanium product by performing plasma nitriding of a titanium product made of pure titanium, an α -type titanium alloy, a β -type titanium alloy, or an α + β -type titanium alloy as a treatment target to form a hardened layer on the surface of the treatment target, and performing particle collision treatment in which 1 or 2 or more kinds of particles are collided with the treatment target after the plasma nitriding treatment to remove a compound layer existing on the surface of the hardened layer.

Jp 2013-76110 a (patent document 7) discloses a technique of sequentially providing: a method for surface treatment of a substrate comprising a titanium alloy and titanium, the substrate comprising a step A of subjecting the surface of the substrate to particle blasting, a step B of subjecting the surface of the substrate to a first heat treatment in a temperature zone T1, a step C of subjecting the surface of the substrate to a second heat treatment in a temperature zone T2, and a step D of subjecting the surface of the substrate to a third heat treatment in a temperature zone T3, wherein the method satisfies the relationship of T1 > T2 > T3 and wherein T1 is 900 to 1000 ℃. That is, according to this surface treatment method, an amorphous layer, a fine particle layer (α phase, particle diameter: about 300nm), and a submicron layer (α phase, particle diameter: about 500nm nanoparticle layer (β phase, particle diameter: about 3000nm) are formed in this order from the front surface side in the vicinity of the surface of the titanium material, thereby improving the fatigue strength.

It is known that commercially pure titanium is mainly composed of an α phase having an hcp (dense hexagonal lattice) structure, and is embrittled by formation of hydride when the α phase absorbs hydrogen in a large amount. Therefore, depending on the use environment, hydrogen may be absorbed to cause embrittlement, which may cause a fracture accident. In "titanium processing technology" (non-patent document 1), for example, accidents caused by hydrogen absorption in a mechanical facility for handling a non-oxidizing acid or in a urea-ammonia environment or a hydrogen environment have been reported. Therefore, a titanium alloy material having excellent hydrogen embrittlement resistance has been proposed.

Jp 2013-163840 a (patent document 8) discloses a titanium alloy containing 50 vol% or more of a β phase and 500 to 6000ppm of hydrogen and having a large elongation at break, and shows an example in which embrittlement does not occur even if a large amount of hydrogen is contained.

In facilities for treating radioactive waste such as nuclear power-related facilities, neutron beam shielding plates capable of shielding thermal neutrons are used. 19.9% of boron 10 (B) present in nature¹⁰B) The neutron shielding effect is highest. Stainless steel containing B or the like is generally used as a raw material of the neutron beam shielding plate.

Japanese patent publication Sho-58-6704 (patent document 9) discloses a method of preparing Kunakopaito (クーナコパイト) (2 MgO.3B)₂O₂·13H₂O)、Meya Hotsu ferrite(メーヤホツフェライト)(3CaO·3B₂O₂·7H₂O)、colemanite(コレマナイト)(2CaO·3B₂O₂·5H₂O) or the like, and a cured product obtained by kneading an inorganic binder such as hemihydrate gypsum or calcium aluminate cement with water, and contains 5 mass% or more of a neutron beam blocking material B. However, the neutron beam shielding material disclosed in patent document 9 is made of cement, and therefore has a problem in corrosion resistance, manufacturability, and workability.

The use of a titanium alloy containing B, which has superior corrosion resistance compared to stainless steel, as a neutron beam blocking material has also been studied. For example, japanese patent application laid-open No. 1-168833 (patent document 10) discloses a hot-rolled sheet using a boron-containing titanium alloy containing 0.1 to 10 mass% of B, and the balance being titanium and inevitable impurities.

Further, Japanese patent laid-open No. 5-142392 (patent publication)Document 11) discloses filling a hollow metal tank with a boron-containing material (NaB)₄O₇、B₂O₃、PbO、Fe₂O₃Etc.) and the metal oxide mixed therein to form a cured radiation shielding material. According to patent document 11, a neutron beam is mainly blocked by boron and hydrogen, and gamma rays are blocked by a box and a metal therein or the like.

The titanium material is generally produced by the following method. First, titanium oxide as a raw material is chlorinated by a Kroll method to produce titanium tetrachloride, and then reduced with magnesium or sodium to produce sponge-like metallic titanium (titanium sponge) in a lump form. The titanium sponge was press-formed into a titanium consumable electrode, and a titanium ingot was produced by performing vacuum arc melting using the titanium consumable electrode as an electrode. At this time, alloy elements are added as necessary to produce a titanium alloy ingot. Thereafter, the titanium alloy ingot is cogging, forged, and rolled to produce a titanium slab, and the titanium slab is further subjected to hot rolling, annealing, acid pickling, cold rolling, and vacuum heat treatment to produce a titanium sheet.

Further, as a method for producing a titanium thin plate, a method for producing a titanium powder by cogging, hydrogenation pulverization, dehydrogenation, powder crushing, and classification of a titanium ingot, and a method for producing a titanium powder by powder rolling, sintering, and cold rolling of a titanium powder are known.

Jp 2011-42828 a (patent document 12) discloses a method for producing a titanium sheet from titanium powder obtained by directly producing titanium powder from titanium sponge without using a titanium ingot, wherein a sintered sheet is produced by sintering a pre-sintering compact formed by molding a viscous composition containing titanium metal powder, a binder, a plasticizer, and a solvent into a sheet shape, the sintered sheet is pressed to produce a sintered pressed sheet, and the sintered pressed sheet is re-sintered, wherein the fracture elongation of the sintered sheet is 0.4% or more, the density ratio is 80% or more, and the density ratio of the sintered pressed sheet is 90% or more.

Jp 2014-19945 a (patent document 13) discloses a method for producing a titanium alloy having excellent quality by a powder method, in which an appropriate amount of iron powder, chromium powder or copper powder is added to a titanium alloy powder prepared from a titanium alloy scrap or a titanium alloy ingot as a raw material to prepare a composite powder, the composite powder is subjected to carbon steel capsule extrusion, a capsule on the surface of the obtained round bar is melted and removed, and then a solution treatment or a solution treatment and an aging treatment are further performed.

Jp 2001-131609 a (patent document 14) discloses a method for producing a titanium compact in which metal contact occurs in 20% or more of the total length of grain boundaries of the compact by filling a copper capsule with a titanium sponge powder, then performing a warm extrusion process at an extrusion ratio of 1.5 or more and an extrusion temperature of 700 ℃ or less, forming, removing copper on the outer side, and performing an outer peripheral process.

As a technique for rolling a hot rolled material into a thin plate when the hot rolled material is a so-called difficult-to-work material such as pure titanium or a titanium alloy which has insufficient ductility under hot conditions and a high thermal deformation resistance value, a stack rolling method is known. The lap-rolling method is a method of hot rolling a core material such as a titanium alloy having poor workability covered with a protective material such as inexpensive carbon steel having good workability.

Specifically, for example, a release agent is applied to the surface of the core material, and at least the upper and lower 2 surfaces thereof are covered with a protective material, or the four peripheral surfaces are covered with a gasket material in addition to the upper and lower surfaces, and the periphery is welded, assembled, and hot-rolled. In the laminated plate rolling, a core material as a material to be rolled is covered with a protective material and hot rolled. Therefore, since the surface of the core material does not directly contact a cold medium (air or a roll), and the temperature of the core material can be suppressed from decreasing, even if the core material has poor workability, the sheet can be manufactured.

Japanese patent application laid-open No. 63-207401 (patent document 15) discloses a method of assembling a sealed covering box, and Japanese patent application laid-open No. 09-136102 (patent document 16) discloses a method of forming a seal 10^-3A method for manufacturing a sealed covered box by sealing a protective material at a vacuum degree of torr or higher, and further, japanese patent laid-open publication No. 11-057810 (patent document 17) discloses covering 10 with a carbon steel (protective material)^-2A method for manufacturing a sealed covering box by sealing by high energy density welding under vacuum below torr level.

On the other hand, as a method of producing a material having high corrosion resistance at low cost, a method of bonding a titanium material to a surface of a material as a base material is known.

Jp 08-141754 a (patent document 18) discloses a method for producing a titanium clad steel sheet in which a steel material is used as a base material and titanium or a titanium alloy is used as a binder, and a joint surface between the base material and the binder is vacuum-evacuated and then welded and assembled to form an assembled slab for rolling, and the assembled slab is joined by hot rolling.

Jp 11-170076 a (patent document 19) discloses a method for producing a titanium-coated steel material by laminating titanium foils on the surface of a base steel material containing 0.03 mass% or more of carbon via an insert material having a thickness of 20 μm or more, the insert material being formed of any one of pure nickel, pure iron, and low-carbon steel having a carbon content of 0.01 mass% or less, and then irradiating the titanium foils with a laser beam from either side in the laminating direction to melt-bond at least the vicinity of the edge portion of the titanium foils to the base steel material over the entire circumference.

Further, jp 2015-045040 a (patent document 20) illustrates a method of melting the surface of a porous titanium raw material (titanium sponge) formed into an ingot shape by an electron beam under vacuum to produce a titanium ingot having a dense titanium surface layer, and hot-rolling and cold-rolling the titanium ingot to produce a dense titanium blank (titanium ingot) having a porous portion formed into an ingot shape from the porous titanium raw material and a dense covering portion made of dense titanium and covering the entire surface of the porous portion, with very little energy.

Documents of the prior art

Patent document

Patent document 1, Japanese patent laid-open No. 2001-234266

Patent document 2 Japanese patent laid-open No. 2001-89821

Patent document 3, Japanese patent laid-open No. 2005-290548

Patent document 4 Japanese patent laid-open publication No. 2009-68026

Patent document 5 Japanese patent laid-open publication No. 2013-142183

Patent document 6 Japanese laid-open patent publication No. 2008-195994

Patent document 7 Japanese patent laid-open publication No. 2013-76110

Patent document 8 Japanese patent laid-open publication No. 2013-163840

Patent document 9 Japanese patent publication No. 58-6704

Patent document 10 Japanese examined patent publication No. Hei 1-168833

Patent document 11, Japanese patent laid-open No. 5-142392

Patent document 12 Japanese patent laid-open publication No. 2011-

Patent document 13 Japanese patent laid-open No. 2014-19945

Patent document 14 Japanese laid-open patent publication No. 2001-131609

Patent document 15 Japanese patent laid-open No. 63-207401

Patent document 16 Japanese laid-open patent publication No. H09-136102

Patent document 17, Japanese patent laid-open publication No. 11-057810

Patent document 18, Japanese patent laid-open publication No. H08-141754

Patent document 19 Japanese patent application laid-open No. 11-170076

Patent document 20, Japanese patent laid-open publication No. 2015-

Non-patent document

Non-patent document 1 processing technology of titanium, edited by Nippon titanium Association of Kabushiki Kaisha, News of Japan Industrial Co., p.214 to 230, published in 1992 in 11 months

Disclosure of Invention

Problems to be solved by the invention

As described above, since the titanium alloy having improved corrosion resistance contains rare and expensive platinum group elements, the production cost thereof is greatly increased.

Since Al is added to the titanium alloy disclosed in patent document 1, formability, particularly bulging formability due to working in the direction of decreasing thickness, is adversely affected.

The titanium alloy disclosed in patent document 2 has a high total content of Fe and O, and therefore has a strength exceeding 800N/mm at room temperature²Too strong and elongation of20% or less, and the moldability is poor.

In the titanium alloy disclosed in patent document 3, Al is added in the same manner as described above, and therefore, there is a possibility that cold workability, particularly bulging formability due to working in the direction of decreasing the thickness, is adversely affected.

The titanium alloy disclosed in patent document 4 has sufficient workability and oxidation resistance, but contains a large amount of expensive Nb, and therefore the alloy cost increases.

Further, the titanium alloy disclosed in patent document 5 has sufficient high-temperature oxidation characteristics, but the entire surface of the plate is alloyed, so that the alloy cost increases.

According to the method disclosed in patent document 6, since C and N having high solid solution strengthening ability are used for forming the hardened layer, they can be hardened and improved in fatigue strength by solid solution, but rapid reduction in ductility is caused, and formability is poor.

Further, according to the results of the studies by the present inventors, it is not easy to improve the formability in the surface treatment method disclosed in patent document 7.

Further, in the inventions disclosed in patent documents 6 and 7, a special surface treatment is required for the titanium material, and an increase in the production cost cannot be avoided.

As a measure against embrittlement by hydrogen, it is common to perform surface treatment having hydrogen absorption resistance after processing a product, or perform electric corrosion prevention. However, the number of steps for product processing and construction is increased, and thus it is inevitable to increase the cost, and a titanium material having excellent hydrogen embrittlement resistance cannot be provided at low cost.

Further, as in the method disclosed in patent document 8, in order to make 50% by volume or more of the entire raw material a β phase, it is necessary to contain a large amount of expensive additive elements, and therefore the cost increases.

The hot-rolled sheet disclosed in patent document 10 has a high B content, and therefore, the cost is undeniably increased, and the workability is also poor, and it is practically difficult to use the sheet as a neutron beam shielding plate.

Further, in the radiation shielding material disclosed in patent document 12, a box material made of metal is filled with a boron-containing substance, and the processing after the filling of the boron-containing substance is difficult.

Conventionally, when a titanium material is produced by hot working, titanium sponge is press-formed to produce a titanium consumable electrode, a titanium ingot is produced by vacuum arc melting using the titanium consumable electrode as an electrode, the titanium ingot is further cogging, forging, and rolling to produce a titanium slab, and the titanium slab is hot-rolled, annealed, pickled, and cold-rolled to produce the titanium material.

In this case, a process for producing a titanium ingot by melting titanium must be added. Methods for producing titanium powder by performing powder rolling, sintering, and cold rolling are known, and in the method for producing titanium powder from a titanium ingot, a step of melting titanium is naturally added.

In the method of producing a titanium material from a titanium powder, for example, an expensive titanium powder is used as a raw material without a melting step, and thus the obtained titanium material is very expensive. The same applies to the methods disclosed in patent documents 15 and 16.

In the lamination rolling, the core material covered with the protective material is completely a slab or an ingot, and the manufacturing cost cannot be reduced by a melting process or by using expensive titanium powder as a raw material.

Further, in patent document 20, although dense titanium material can be produced with very little energy, the surface of the sponge titanium formed into a cast mass is melted, and the dense titanium surface layer portion and the internal components are specified to be pure titanium or a titanium alloy of the same kind, and it is not possible to form a titanium alloy layer uniformly and over a wide range only in the surface layer portion, for example, and to reduce the production cost.

On the other hand, steel is often selected as the base material among materials capable of producing inexpensive corrosion-resistant materials and bonding titanium or a titanium alloy to the surface of the base material. Therefore, when the titanium layer on the surface is lost, the corrosion resistance is impaired. Even if a titanium material is used as the base material, a complete cost improvement cannot be expected if a titanium material produced through a normal production process is used.

The present invention aims to obtain a titanium material having desired characteristics at low cost by reducing the content of alloying elements (the amount of specific alloying elements that exhibit target characteristics) added to improve various characteristics required for the titanium material, such as corrosion resistance, oxidation resistance, fatigue resistance, hydrogen embrittlement resistance, neutron blocking property, and the like, and by suppressing the production cost of the titanium material.

Means for solving the problems

The present invention is made to solve the above problems, and is mainly directed to the following titanium composite material and titanium material for hot working.

(1) A titanium composite material comprising a first surface layer part, an inner layer part and,

the titanium composite material of the second skin portion,

the first surface layer portion and the second surface layer portion are formed of a titanium alloy,

the inner layer portion is formed of commercially pure titanium having voids,

at least one of the first surface layer portion and the second surface layer portion has a thickness of 2 μm or more and accounts for 40% or less of the total thickness of the titanium composite material,

the volume fraction of the voids in a cross section perpendicular to the plate thickness direction is more than 0% and 30% or less.

(2) The titanium composite material according to the item (1), wherein at least one of the first surface layer portion and the second surface layer portion has a chemical composition in mass%

Platinum group elements: 0.01 to 0.25 percent,

Rare earth elements: 0 to 0.2 percent of,

Co：0～0.8％、

Ni：0～0.6％、

And the balance: ti and impurities.

(3) The titanium composite material according to the above (2), wherein the platinum group element is Pd and/or Ru.

(4) The titanium composite material according to the above (2) or (3), wherein the chemical composition contains, in mass%, a rare earth element: 0.001 to 0.2%.

(5) The titanium composite material according to any one of the above (2) to (4), wherein the chemical composition contains, in mass%)

Selected from the group consisting of Co: 0.05 to 0.8%, and,

Ni: 0.05-0.6% of more than 1 species.

(6) The titanium composite material according to any one of the above (1) to (5), wherein the chemical composition of the industrially pure titanium is calculated as mass%

C: less than 0.1 percent of,

H: less than 0.015%,

O: less than 0.4 percent of,

N: less than 0.07 percent of,

Fe: less than 0.5 percent,

And the balance: ti and impurities.

(7) A titanium material for hot working, comprising a housing and 1 or more kinds selected from the group consisting of titanium sponge, briquettes obtained by compressing titanium sponge and industrial pure titanium scrap, which are filled in the housing,

the portion constituting the surface layer after hot working, which is a part of the case, is composed of a titanium alloy.

(8) The titanium material for hot working as set forth in the above (7), wherein the chemical composition of the titanium alloy is in mass%

Platinum group elements: 0.01 to 0.25 percent,

Rare earth elements: 0 to 0.2 percent of,

Co：0～0.8％、

Ni：0～0.6％、

And the balance: ti and impurities.

ADVANTAGEOUS EFFECTS OF INVENTION

The titanium composite material according to the present invention has a surface layer portion made of a titanium alloy and an inner layer portion made of industrially pure titanium, and therefore has the same characteristics as a titanium material made of the same titanium alloy as a whole, but can be produced at low cost.

Drawings

Fig. 1 is an explanatory view showing an example of the structure of the titanium composite material described in the present invention.

Fig. 2 is an explanatory view showing the structure of a titanium material as a hot working material of the titanium composite material according to the present invention.

Fig. 3 is an explanatory view showing a plane bending fatigue test material.

Fig. 4 is an example of a structure photograph showing a case of being produced by the method described in the present specification.

Fig. 5 is a schematic view of a titanium material in which titanium sponge and scrap are filled in a slab-like case formed by assembling Ti — B alloy plates.

Detailed Description

The present inventors have made extensive studies to solve the above-mentioned problems, and as a result, have found a method of reducing the amount of a specific alloy element exhibiting desired properties by alloying only the surface layer portion of a titanium plate as a final product and suppressing the production cost of a titanium material, and as a result, filling and sealing a relatively inexpensive material such as titanium sponge under reduced pressure in a casing made of a titanium alloy material, and hot-working the titanium material to obtain a titanium composite material.

The present invention is based on the above findings. The titanium composite material and the titanium material for hot working according to the present invention will be described below with reference to the drawings. In the following description, "percent" of each element content means "% by mass" unless otherwise specified.

1. Titanium composite material

1-1. integral structure

As shown in fig. 1, a titanium composite material 1 according to the present invention is a titanium composite material 1 including a first surface layer portion 2, an inner layer portion 4, and a second surface layer portion 3, the first surface layer portion 2 and the second surface layer portion 3 are formed of a titanium alloy, and the inner layer portion 4 is formed of industrially pure titanium having a void. In this way, the corrosion resistance and other characteristics of the titanium composite material are ensured by the surface layer portions (the first surface layer portion 2 and the second surface layer portion 3) which come into contact with the external environment. The first surface layer 2 and the second surface layer 3 are made of a titanium alloy having various excellent properties as compared with commercially pure titanium.

The titanium composite material 1 as a whole has the same characteristics as a titanium material made of the same titanium alloy, but can be produced at low cost.

1-2. a first surface layer part and a second surface layer part

The first surface layer 2 and the second surface layer 3 are made of a titanium alloy as described above. There is no particular limitation on the chemical composition of the titanium alloy. Titanium alloys are generally known as α type, α + β type, and β type. Further, it is known that α stabilizing elements include Al, O, and N, β stabilizing elements include V, Mo, Cr, Fe, Nb, and Ta, and neutral elements that do not belong to any of the above groups include Zr, Sn, and Hf.

Table 1 shows elements that are known to contribute to improvement in characteristics of a titanium alloy by being contained therein. For the titanium alloy according to the present invention, for example, more than 0% by mass of a titanium alloy selected from the group consisting of O: 0-0.5%, N: 0-0.2%, C: 0-2.0%, Al: 0-8.0%, Sn: 0-10.0%, Zr: 0-20.0%, Mo: 0 to 25.0%, Ta: 0-5.0%, V: 0 to 30.0%, Nb: 0-40.0%, Si: 0-2.0%, Fe: 0-5.0%, Cr: 0-10.0%, Cu: 0-3.0%, Co: 0-3.0%, Ni: 0 to 2.0%, platinum group element: 0-0.5%, rare earth elements: 0-0.5%, B: 0 to 5.0%, and Mn: 0 to 10.0% of 1 or more species, thereby imparting a desired function to the surface of the titanium material.

Elements other than those described above that can be contained in titanium are generally known as metal materials, and strength is improved by solid solution strengthening and precipitation strengthening (when there is no solid solution or when precipitates are formed), and creep characteristics can be improved by the contained elements. These elements are exemplified by the elements ranging from hydrogen (1) to astatine (85) in atomic number (except for the inert gas element which is a group 18 element), and are allowed to reach a total of about 5%.

The balance other than the above is Ti and impurities. The impurities may be contained in a range not impairing the target properties, and the other impurities are mainly impurity elements mixed from raw materials and scraps and elements mixed in production, and examples thereof include elements represented by C, N, O, Fe, H, and the like, and elements mixed from raw materials such as Mg, Cl, and the like; si, Al, S, and the like mixed in the production. If these elements are about 2% or less, the range in which the target characteristics of the present application are not impaired is considered.

Further, as shown in table 1, the titanium alloy according to the present invention preferably contains, in mass%, a metal selected from the group consisting of O: 0.01-0.5%, N: 0.01-0.2%, C: 0.01 to 2.0%, Al: 0.1 to 8.0%, Sn: 0.1 to 10.0%, Zr: 0.5 to 20.0%, Mo: 0.1 to 25.0%, Ta: 0.1-5.0%, V: 1.0 to 30.0%, Nb: 0.1 to 40.0%, Si: 0.1-2.0%, Fe: 0.01-5.0%, Cr: 0.1 to 10.0%, Cu: 0.3-3.0%, Co: 0.05 to 3.0%, Ni: 0.05 to 2.0%, platinum group element: 0.01-0.5%, rare earth elements: 0.001-0.5%, B: 0.01 to 5.0%, and Mn: 0.1-10.0% of more than 1 species.

The titanium alloy of the present invention more preferably contains a metal selected from the group consisting of O: 0.02-0.4%, N: 0.01-0.15%, C: 0.01 to 1.0%, Al: 0.2 to 6.0%, Sn: 0.15 to 5.0%, Zr: 0.5 to 10.0%, Mo: 0.2 to 20.0%, Ta: 0.1-3.0%, V: 2.0 to 25.0%, Nb: 0.15 to 5.0%, Si: 0.1 to 1.0%, Fe: 0.05-2.0%, Cr: 0.2 to 5.0%, Cu: 0.3-2.0%, Co: 0.05 to 2.0%, Ni: 0.1 to 1.0%, platinum group element: 0.02-0.4%, rare earth elements: 0.001-0.3%, B: 0.1 to 5.0%, and Mn: 0.2 to 8.0% of 1 or more, and further preferably contains an oxygen atom selected from the group consisting of: 0.03-0.3%, N: 0.01-0.1%, C: 0.01-0.5%, Al: 0.4 to 5.0%, Sn: 0.2 to 3.0%, Zr: 0.5 to 5.0%, Mo: 0.5 to 15.0%, Ta: 0.2-2.0%, V: 5.0 to 20.0%, Nb: 0.2 to 2.0%, Si: 0.15-0.8%, Fe: 0.1-1.0%, Cr: 0.2 to 3.0%, Cu: 0.3-1.5%, Co: 0.1 to 1.0%, Ni: 0.1 to 0.8%, platinum group element: 0.03-0.2%, rare earth elements: 0.001-0.1%, B: 0.2 to 3.0%, and Mn: 0.2-5.0% of more than 1 species.

[ Table 1]

TABLE 1

Further, for example, a titanium alloy determined by JIS specifications shown below can be used.

JIS 11-JIS 23 grades (JIS4600 (2012) titanium and titanium alloy-plates and strips): contains Pd, Ru, Ni, Co, etc., and is excellent in corrosion resistance and crevice corrosion resistance.

JIS50 grade (JIS4600 (2012) titanium and titanium alloys — plates and strips): ti-1.5Al is excellent in corrosion resistance, hydrogen absorption resistance and heat resistance.

JIS60 grade (JIS4600 (2012) titanium and titanium alloys — plates and strips): is Ti-6Al-4V, high strength and high universality.

JIS61 grade (JIS4600 (2012) titanium and titanium alloys — plates and strips): ti-3Al-2.5V, good weldability, formability and machinability.

JIS80 grade (JIS4600 (2012) titanium and titanium alloys — plates and strips): ti-4Al-22V, high strength and excellent cold workability.

Further, other titanium alloys having chemical components not specified in JIS may be used. For example, as follows.

Titanium alloy having heat resistance: ti-6Al-2Sn-4Zr-2Mo-0.08Si, Ti-6Al-5Zr-0.5Mo-0.2Si, Ti-8Al-1Mo-1V and the like.

Low alloy and high strength titanium alloy: ti-1 to 1.5Fe-0.3 to 0.5O-0.01 to 0.04N, etc.

Low alloy and heat resistant titanium alloy: ti-1Cu, Ti-1Cu-0.5Nb, Ti-1Cu-1Sn-0.35Si-0.5Nb, etc.

Titanium alloy excellent in creep resistance: ti-6Al-2Sn-4Zr-6Mo, etc.

Titanium alloy having high strength and good cold workability: Ti-15V-3Cr-3Sn-3Al, Ti-20V-4Al-1Sn, and the like.

Titanium alloy with high strength and high toughness: Ti-10V-2Fe-3Al, and the like.

Titanium alloy excellent in wear resistance: ti-6Al-4V-10Cr-1.3C, etc.

At least one of the first surface portion 2 and the second surface portion 3 (at least the surface portion that is in contact with the external environment) preferably contains an alloy element that exhibits the target characteristics, with the balance being Ti and impurities. The following elements are exemplified as alloy elements exhibiting the target characteristics, but are not limited thereto.

(a) Alloying elements exhibiting corrosion resistance: 0.01 to 0.25% by mass of a platinum group element (Pd and/or Ru), and optionally, 0.2% or less of a rare earth element, and Co: 0.8% or less, Ni: 0.6% or less, 1 or more.

(b) Alloying elements exhibiting oxidation resistance: more than 1 selected from 0.10-0.60% of Si, 0.1-2.0% of Nb, 0.3-1.0% of Ta and 0.3-1.5% of Al, and more than 1 selected from 1.5% or less of Sn, 1.5% or less of Cu and 0.5% or less of Fe (wherein, the total is 2.5% or less) according to requirements.

(c) Alloying elements exhibiting fatigue resistance: at least 1 selected from 0.08-1.0% of Fe, Cr, Ni, Al and Zr in total.

(d) Alloying elements exhibiting hydrogen embrittlement resistance: 1 or more species selected from the group consisting of Mo, V and Nb in the range of 8.0 < Mo equivalent < 20.0 (wherein Mo equivalent is Mo content (mass%) + V content (mass%)/1.5 + Nb content (mass%)/3.6.).

(e) Alloy elements exhibiting neutron blocking property: 0.1 to 3.0% of B.

The respective cases (a) to (e) are described below.

(a) Including alloying elements exhibiting corrosion resistance

(thickness)

When the thickness of the surface layer portion, which is in contact with the external environment, of the first surface layer portion 2 and the second surface layer portion 3 is too small, corrosion resistance is not sufficiently obtained. The thicknesses of the first surface portion 2 and the second surface portion 3 vary depending on the thickness of the material used for production and the subsequent processing rate, but a sufficient effect is exhibited if the thickness is2 μm or more. Therefore, the thickness of at least one of the first surface portion 2 and the second surface portion 3 (at least the surface portion that contacts the external environment) is preferably 2 μm or more, and more preferably 5 μm or more.

On the other hand, when the first surface layer 2 and the second surface layer 3 are thick, there is no problem in corrosion resistance, but the cost advantage is small because the proportion of the titanium alloy in the entire titanium composite material increases. Therefore, the thickness of each of the first surface layer 2 and the second surface layer 3 is preferably 40% or less, and more preferably 30% or less, with respect to the total thickness of the titanium composite material 1.

The thicknesses of the first surface layer portion 2 and the second surface layer portion 3 of the titanium composite material 1 depend on the thickness of a titanium alloy material constituting the later-described casing 6 and the working ratio at the time of hot working performed later. For example, when a titanium composite material 1 having a thickness of 5mm is produced by hot working a hot working titanium material 5 (hereinafter, simply referred to as "titanium material 5") having a thickness of 75mm using a casing 6 made of a titanium material having a thickness of 10mm, the first surface layer portion 2 and the second surface layer portion 3 in the titanium composite material 1 each have a thickness of about 667 μm and account for about 13% of the total thickness of the titanium composite material 1.

(chemical composition)

In the titanium composite material 1 according to the present invention, in order to improve the corrosion resistance of at least one of the first surface layer portion 2 and the second surface layer portion 3 (at least the surface layer portion that comes into contact with the external environment), various alloying elements shown below may be contained.

Platinum group elements: 0.01 to 0.25 percent

The platinum group element has an effect of reducing the hydrogenation voltage of the titanium alloy and maintaining the natural potential in the inactive region, and can be contained as an alloy element exhibiting corrosion resistance. If the content of the platinum group element (the total content when a plurality of platinum group elements are contained) is less than 0.01%, the corrosion resistance is insufficient, and if it exceeds 0.25%, not only improvement of the corrosion resistance is not expected so much, but also the cost of the raw material increases. When the platinum group element is contained, the content is 0.01 to 0.25%. The content of the platinum group element is preferably 0.03% or more, more preferably 0.05% or more, preferably 0.20% or less, more preferably 0.15% or less.

Any element of the platinum group elements used in the present invention is useful for improving the corrosion resistance of the titanium alloy, and particularly, it is desirable to contain Pd having a high corrosion resistance improving effect per unit content. In addition, relatively inexpensive Ru can be used instead of Pd.

When a rare earth element is added to a titanium alloy containing a platinum group element, Ti and the platinum group element are rapidly eluted when exposed to a corrosive environment, and the concentration of the platinum group element in a solution in the vicinity of the titanium alloy increases. As a result, precipitation of platinum group elements in the titanium alloy is promoted, and even if the amount of melting of the titanium alloy is small, platinum group elements can be efficiently precipitated, leading to improvement in corrosion resistance.

Rare earth elements: 0 to 0.2 percent

Sc, Y, light rare earth elements (La to Eu) and heavy rare earth elements (Gd to Lu) exist in the rare earth elements, and the above effects can be expected when any rare earth element is added. The same effects can also be expected when a mixture or compound of rare earths such as misch metal (misch metal, Mm) or didymium mixed metal (Nd — Pr alloy) before separation and purification is used.

In consideration of the above, it is considered that the rare earth element to be added does not need to be 1 kind, and a plurality of kinds of elements may be contained at the same time, and the corrosion resistance is improved by the above-described effects. At this time, the total content of the rare earth elements means the total content of the above elements.

When the content of the rare earth element is excessive, the above effect is saturated, and therefore, not only a higher corrosion resistance improving effect cannot be obtained but also the economical efficiency is deteriorated. Therefore, the content of the rare earth element is preferably 0.2% or less, more preferably 0.02% or less. On the other hand, in order to sufficiently obtain the effect of dissolving Ti and platinum group elements in the active state region of the titanium alloy and promoting the precipitation of the platinum group elements on the alloy surface, it is preferable to contain 0.001% or more of a rare earth element.

Co：0～0.8％

Ni：0～0.6％

Co and Ni are elements that improve the corrosion resistance of the titanium alloy by changing the hydrogenation voltage, and are added in combination with platinum group elements and/or rare earth elements, thereby achieving extremely high corrosion resistance. However, even if Co is contained in an amount of more than 0.8% and Ni is contained in an amount of more than 0.6%, the effects are saturated, and this is not preferable from the viewpoint of economic efficiency. Therefore, when these elements are contained, the Co content is 0.8% or less, and the Ni content is 0.6% or less. The Co content is preferably 0.7% or less, and the Ni content is preferably 0.5% or less. In order to obtain the above effects reliably, Co and Ni are preferably contained in an amount of 0.05% or more, and more preferably 0.2% or more.

The balance other than the above is Ti and impurities. The impurities may be contained in a range not impairing the target characteristics, and other impurities may be contained as impurity elements mainly mixed from the scrap, such as Cr, Ta, Al, V, Cr, Nb, Si, Sn, Mn, Mo, and Cu, and it is permissible that the impurities are 0.5% or less in total, together with C, N, Fe, O, and H, which are common impurity elements.

(b) Including alloying elements exhibiting oxidation resistance

(thickness)

When the thickness of the surface layer portion of the first surface layer portion 2 and the second surface layer portion 3 which is in contact with the external environment is too thin, oxidation resistance cannot be sufficiently obtained. The thicknesses of the first surface portion 2 and the second surface portion 3 vary depending on the thickness of the raw material used for production or the subsequent processing rate, but a sufficient effect is exhibited if the thickness is5 μm or more. Therefore, the thickness of at least one of the first surface portion 2 and the second surface portion 3 (at least the surface portion that contacts the external environment) is preferably 5 μm or more, and more preferably 10 μm or more.

On the other hand, when the first surface layer 2 and the second surface layer 3 are thick, there is no problem in oxidation resistance, but the cost advantage is small because the proportion of the titanium alloy in the entire titanium composite material increases. Therefore, the thickness of each of the first surface layer 2 and the second surface layer 3 is preferably 40% or less, and more preferably 30% or less, with respect to the total thickness of the titanium composite material 1.

The thicknesses of the first surface layer portion 2 and the second surface layer portion 3 of the titanium composite material 1 depend on the thickness of a titanium alloy material constituting the later-described casing 6 and the working ratio at the time of hot working performed later. For example, when a titanium composite material 1 having a thickness of 5mm is produced by hot working a titanium material 5 for hot working having a thickness of 250mm, the shell 6 being made of a 1mm thick titanium material, the titanium composite material 1 has a titanium alloy layer thickness of the first surface layer portion 2 and the second surface layer portion 3 of about 20 μm and occupies about 0.4% of the total thickness of the titanium composite material 1.

(chemical composition)

The oxidation of titanium takes an oxidation form called internal diffusion, which is caused by oxygen diffusing in the oxide film and bonding with titanium on the surface. Therefore, if the diffusion of oxygen is suppressed, oxidation is suppressed. In the titanium alloy, Si and Nb are added to improve the oxidation resistance at 600 to 800 ℃ at high temperatures.

When Si is added, silicon oxide is formed on the surface layer and acts as a barrier when exposed to a high-temperature atmosphere, thereby suppressing diffusion of oxygen into the titanium and improving oxidation resistance. In addition, Ti has a valence of 4, while Nb has a valence of 5. Therefore, Nb is dissolved in the titanium oxide film, and the pore concentration of oxygen in the oxide film decreases, thereby suppressing oxygen diffusion in the oxide film.

In the titanium composite material 1 according to the present invention, in order to improve the oxidation resistance of at least one of the first surface layer portion 2 and the second surface layer portion 3 (at least the surface layer portion that is in contact with the external environment), various alloying elements shown below may be contained.

Si：0.10～0.60％

Si has an effect of improving oxidation resistance at a high temperature of 600 to 800 ℃. When the Si content is less than 0.10%, the improvement amount of the oxidation resistance is small. On the other hand, if the Si content exceeds 0.60%, the influence on the oxidation resistance is saturated, and the workability at room temperature and high temperature is remarkably reduced. Therefore, when Si is contained, the content is set to 0.10 to 0.60%. The Si content is preferably 0.15% or more, more preferably 0.20% or more, preferably 0.50% or less, more preferably 0.40% or less.

Nb：0.1～2.0％

Nb has an effect of improving oxidation resistance at high temperatures. The content of Nb is 0.1% or more for improving oxidation resistance. On the other hand, even if the Nb content exceeds 2.0%, the effect is saturated, and Nb is an expensive additive element, which increases the alloy cost. Therefore, when Nb is contained, the content is set to 0.1 to 2.0%. The Nb content is preferably 0.3% or more, more preferably 0.5% or more, preferably 1.5% or less, more preferably 1.2% or less.

Ta：0.3～1.0％

Ta also has the effect of improving oxidation resistance at high temperatures. The content of Ta is 0.3% or more for the purpose of improving oxidation resistance. On the other hand, even if the content of Ta exceeds 1.0%, Ta is an expensive additive element, and therefore, not only does the alloy cost increase, but also β phase may be generated due to the heat treatment temperature. Therefore, when Ta is contained, the content thereof is set to 0.3 to 1.0%. The Ta content is preferably 0.4% or more, more preferably 0.5% or more, preferably 0.9% or less, more preferably 0.8% or less.

Al：0.3～1.5％

Al is an element that improves oxidation resistance at high temperatures. On the other hand, Al is contained in a large amount, and the ductility at room temperature is remarkably reduced. When the Al content is 0.3% or more, the oxidation resistance is sufficiently exhibited. When the Al content is 1.5% or less, the processing under the cold-holding condition can be sufficiently performed. Therefore, when Al is contained, the content is set to 0.3 to 1.5%. The Al content is preferably 0.4% or more, more preferably 0.5% or more, and preferably 1.2% or less.

Although Si, Nb, Ta, and Al can improve oxidation resistance even when they are contained alone, they can further improve high-temperature oxidation resistance by being contained in combination.

The element may contain 1 or more selected from Sn, Cu, and Fe.

Sn：0～1.5％

Sn is an α -phase stabilizing element and, like Cu, is an element that improves high-temperature strength. However, if the Sn content exceeds 1.5%, twinning deformation is suppressed, and the processability at room temperature is lowered. Therefore, when Sn is contained, the content thereof is 1.5% or less. The Sn content is preferably 1.2% or less. When the above effects are desired, the Sn content is preferably 0.2% or more, more preferably 0.4% or more.

Cu：0～1.5％

Cu is an element for improving high-temperature strength. Further, since a solid solution is formed to some extent in the α phase, the β phase is not formed even when used at high temperature. However, when the Cu content exceeds 1.5%, a β phase may be generated depending on the temperature. Therefore, when Cu is contained, the content thereof is 1.5% or less. The Cu content is preferably 1.4% or less, more preferably 1.2% or less. When the above-described effects are desired, the Cu content is preferably 0.2% or more, and more preferably 0.4% or more.

Fe：0～0.5％

Fe is a β -phase stabilizing element, but if it is small, the formation of β -phase is small, and the oxidation resistance cannot be greatly affected. However, if the Fe content exceeds 0.5%, the amount of β -phase produced increases, and the oxidation resistance deteriorates. Therefore, when Fe is contained, the content thereof is set to 0.5% or less. The Fe content is preferably 0.4% or less, more preferably 0.3% or less.

When the total content of Sn, Cu, and Fe exceeds 2.5%, workability at room temperature is lowered, and a β phase may be generated depending on the temperature. Therefore, when 1 or more selected from Sn, Cu, and Fe is contained, the total content is preferably 2.5% or less.

The balance other than the above is Ti and impurities. The impurities may be contained in a range not impairing the target characteristics, and other impurities, such as Cr, V, Cr, Mn, and Mo, may be contained as impurity elements mainly mixed from scrap, and it is permissible that the total content of these impurity elements is 5% or less, together with C, N, O and H which are common impurity elements.

(c) Case of containing alloy element exhibiting fatigue resistance

(thickness)

When the thickness of the surface layer portion contacting the external environment is too small, the fatigue resistance of the first surface layer portion 2 and the second surface layer portion 3 cannot be sufficiently obtained. The thicknesses of the first surface portion 2 and the second surface portion 3 vary depending on the thickness of the raw material used for production or the subsequent processing rate, but a sufficient effect is exhibited if the thickness is5 μm or more. Therefore, the thickness of at least one of the first surface portion 2 and the second surface portion 3 (at least the surface portion that contacts the external environment) is preferably 5 μm or more, and more preferably 10 μm or more. The thicknesses of the first surface layer 2 and the second surface layer 3 are each preferably 1% or more of the total thickness of the titanium composite material 1.

On the other hand, when the first surface portion 2 and the second surface portion 3 are thick, there is no problem in fatigue resistance, but formability is reduced. In addition, the proportion of the titanium alloy in the entire titanium composite material is increased, and therefore the cost advantage becomes small. Therefore, the thicknesses of the first surface portion 2 and the second surface portion 3 are preferably 100 μm or less, and more preferably 50 μm or less, respectively. The thicknesses of the first surface layer 2 and the second surface layer 3 are preferably 20% or less, and more preferably 10% or less, respectively, with respect to the total thickness of the titanium composite material 1.

(chemical composition)

In the titanium composite material 1 of the present invention, in order to improve fatigue resistance of at least one of the first surface layer portion 2 and the second surface layer portion 3 (at least the surface layer portion which is in contact with the external environment), various alloying elements shown below may be contained.

1 or more selected from Fe, Cr, Ni, Al, and Zr: 0.08 to 1.0 percent

Since the starting point of fatigue fracture is the surface of the plate material, the crystal grain size of the α phase is preferably 15 μm or less in order to obtain high fatigue resistance while maintaining formability. The crystal grain size of the α phase is preferably 10 μm or less, and more preferably 5 μm or less.

The crystal grain size of the alpha phase is set to 15 μm or less, and the total content of Fe, Cr, Ni, Al and Zr is set to 0.08% or more in order to obtain high fatigue resistance. On the other hand, if the total content of these elements exceeds 1.0%, ductility such as elongation and formability may be greatly reduced. Therefore, the total content of 1 or more selected from Fe, Cr, Ni, Al and Zr is set to 0.08-1.0%.

The balance other than the above is Ti and impurities. The impurities may be contained in a range not impairing the target characteristics, and as the impurity elements mainly mixed from the scrap, other impurities include Sn, Mo, V, Mn, Nb, Si, Cu, Co, Pd, Ru, Ta, Y, La, Ce, and the like, and it is permissible that the total amount of these impurities is 5% or less, together with C, N, O and H which are common impurity elements.

(mechanical characteristics)

The titanium composite material 1 has high fatigue strength and a fatigue strength ratio (10) while maintaining excellent formability⁷Secondary fatigue strength/tensile strength) of 0.65 or more. The higher the fatigue strength ratio, the more excellent the fatigue characteristics, and the titanium material is usually 0.5 to 0.6, so that the higher the fatigue strength ratio, the higher the fatigue characteristicsWhen the amount is 0.65 or more, the fatigue characteristics are excellent as compared with those of a general titanium material, and when the amount is 0.70 or more, the fatigue characteristics are further excellent.

Further, the elongation at break in the direction perpendicular to the rolling direction of the titanium composite material 1 was 25% or more. In the forming process, the elongation largely affects, and the larger the elongation is, the more excellent the formability is.

(d) Containing alloying elements exhibiting resistance to hydrogen embrittlement

(thickness)

If the thickness of the surface layer portion of the first surface layer portion 2 and the second surface layer portion 3 which is in contact with the external environment is too small, the hydrogen absorption resistance is not sufficiently obtained. On the other hand, when the titanium alloy of the first surface part 2 and the second surface part 3 is thick, there is no problem in the hydrogen absorption resistance, but the ratio of the titanium alloy of the first surface part 2 and the second surface part 3 to the entire raw material increases, and thus the manufacturing cost increases. Therefore, the thickness of at least one of the first surface layer 2 and the second surface layer 3 (at least the surface layer that contacts the external environment) is set to 2 to 20% with respect to the total thickness of the titanium composite material 1.

The thicknesses of the first surface layer portion 2 and the second surface layer portion 3 of the titanium composite material 1 depend on the thickness of a titanium alloy material constituting the later-described casing 6 and the working ratio at the time of hot working performed later. For example, when a titanium composite material 1 having a thickness of 5mm is produced by hot working a hot working titanium material 5 having a thickness of 60mm using a casing 6 made of a titanium material having a thickness of 5mm, the titanium alloy layers of the first surface layer portion 2 and the second surface layer portion 3 in the titanium composite material 1 each have a thickness of about 0.4 μm and account for about 8% of the total thickness of the titanium composite material 1.

(chemical composition)

In the titanium composite material 1 according to the present invention, in order to improve the hydrogen absorption resistance of at least one of the first surface layer portion 2 and the second surface layer portion 3 (at least the surface layer portion that is in contact with the external environment), various alloying elements shown below may be contained.

Mo equivalent of more than 8.0 and less than 20.0

Wherein, Mo equivalent ═ Mo content (mass%) + V content (mass%)/1.5 + Nb content (mass%)/3.6.

The hydrogen absorption resistant layer obtained is a titanium alloy layer containing a β stabilizing element in a certain range. The reason why the β phase is defined is that although the α phase of titanium forms hydride even at a hydrogen concentration of only a few 10ppm, the β phase of titanium alloy has a characteristic that embrittlement due to hydrogen is not easily generated because hydrogen can be dissolved in a solid solution of approximately 1000ppm or more.

When a eutectoid β stabilizing element such as Fe or Cr is included, titanium forms a compound with the element, and there is a concern that embrittlement may occur. However, when Mo, V and Nb are contained in a range satisfying "8.0 < Mo equivalent < 20.0" among the β stabilizing elements, the β phase is stable even if Fe and Cr are present at the same time, and does not form a compound phase, so embrittlement does not occur.

Here, the lower limit of the Mo equivalent is an amount of alloy necessary to obtain a sufficient amount of the β phase. The upper limit is determined according to the following: titanium alloys containing a large amount of alloy addition are expensive, and therefore are not suitable for use in terms of cost. The titanium alloy material used for the case 6 does not necessarily need to be completely in the β phase, and even if the α phase is precipitated in the β phase, the β phase may cover the periphery of the α phase.

For forming the alloy layer of the first surface layer portion 2 and the second surface layer portion 3, a β -type titanium alloy existing in the case 6 described below can be used. For example, Ti-15V-3Cr-3Al-3Sn, Ti-8V-3Al-6Cr-4Mo-4Zr (BetaC), Ti-11.5Mo-6Zr-4.5Sn (BetaIII). When such a conventional β -type titanium alloy is used for the case 6, the total content of additional elements other than the above elements, such as Cr, Sn, Al, and Zr, is allowable to be 15% or less. This is because these elements are contained in the conventional β -type titanium alloy for the purpose of adjusting the heat treatability, strength and cold workability, and do not cause a decrease in the Mo equivalent defined in the present invention. Further, for example, Si, Fe, or the like may be contained.

The balance other than the above is Ti and impurities. The impurities may be contained in a range not impairing the target characteristics, and other impurities, such as Ta, Si, Mn, and Cu, may be present as impurity elements mainly mixed from the scrap, and 5% or less in total of C, N, Fe, O, and H, which are common impurity elements, is allowable.

(e) Including an alloy element exhibiting neutron blocking property

(thickness)

When the thickness of the surface layer portion in contact with the external environment is too small, the first surface layer portion 2 and the second surface layer portion 3 cannot sufficiently obtain the neutron beam shielding effect. On the other hand, when the first surface layer 2 and the second surface layer 3 are thick, although the neutron beam shielding effect is improved, the manufacturing cost increases because the titanium alloy accounts for a larger proportion of the entire raw material. Therefore, the thickness of at least one of the first surface layer 2 and the second surface layer 3 (at least the surface layer that contacts the external environment) is set to 5 to 40% with respect to the total thickness of the titanium composite material 1.

The neutron beam shielding effect is related to the thickness and the processing rate of the first surface layer 2 and the second surface layer 3 with respect to the total thickness of the titanium composite material 1. For example, when a titanium composite material 1 having a thickness of 10mm is produced by hot working a titanium material 5 for hot working having a thickness of 100mm using a 20mm shell 6, the titanium alloy layers of the first surface layer part 2 and the second surface layer part 3 in the titanium composite material 1 have a thickness of 2mm and a thickness of 20% of the total thickness of the titanium composite material 1 (the sum of both surfaces is 40%).

In order to increase the thickness of the first surface portion 2 and the second surface portion 3, the thickness of the alloy plates to be bonded at the time of manufacturing the case 6 may be increased. However, if the thickness of the alloy plate is too large, it is difficult to weld the alloy plate to form the case 6. Therefore, by reducing the thickness of the titanium material 5 for hot working as it is, the ratio of the total thickness of the alloy plate to the titanium material 5 can be relatively increased.

(chemical composition)

In the titanium composite material 1 according to the present invention, the alloy element is contained to provide the neutron beam shielding effect in the first surface layer portion 2 and the second surface layer portion 3. The reason for selecting the additive elements and the reason for limiting the addition amount range thereof will be described in detail below.

B：0.1～3.0％

Among the components B, the components B are,¹⁰b is present in 19.9%, the¹⁰B has large absorption cross section area of thermal neutronsThe beam shielding effect is large. If the B content is less than 0.1%, the neutron beam shielding effect cannot be sufficiently obtained, and if the B content exceeds 3.0%, cracks and deterioration in workability may occur during hot rolling.

In the titanium alloy containing B, B or TiB may be added to titanium₂Can be made of boride. Furthermore, use of H₃ ¹⁰BO₃、¹⁰B₂O¹⁰B₄C and the like contain¹⁰B raw material for boron concentration (¹⁰B content is substantially 90% or more), the neutron beam shielding effect is large even if the B content is small, and therefore, the method is extremely effective.

Using H₃ ¹⁰BO₃、¹⁰B₂O、¹⁰B₄In the case of C, H and O are thickened in the alloy layer, and H is removed from the raw material during heat treatment such as vacuum annealing, and therefore, this is not a problem, and O and C can be produced without any problem if they are 0.4 mass% O or less and 0.1 mass% C or less, respectively, which are the upper limits contained in the industrial pure titanium.

The balance other than the above is Ti and impurities. The impurities may be contained in a range not impairing the target characteristics, and other impurities may be contained as impurity elements mainly mixed from the scrap, such as Cr, Ta, Al, V, Cr, Nb, Si, Sn, Mn, Mo, and Cu, and it is permissible that the impurities are contained in an amount of 5% or less in total, together with C, N, Fe, O, and H, which are common impurity elements.

(use)

A polyethylene material having a B content of 3.0 to 4.0 mass% and a sheet thickness of 10 to 100mm is used in a device for radiation therapy such as particle beam therapy and BNCT (boron neutron capture therapy). In addition, in the nuclear energy-related facility, a stainless steel plate having a B content of 0.5 to 1.5 mass% and a plate thickness of 4.0 to 6.0mm is used for the nuclear fuel storage rack. By using the titanium composite material 1 in which the B content and the thickness (B-thickened layer thickness) of the first surface layer 2 and the second surface layer 3 are adjusted, the same or more characteristics as those of the above-described material can be exhibited.

1-3. inner layer part

(chemical composition)

The pure titanium component of the inner layer 4 of the titanium composite material 1 depends on the component of the titanium sponge used in the production as described later. The titanium composite material 1 of the present invention may be industrial pure titanium of JIS1 grade, JIS2 grade, JIS3 grade or JIS4 grade among pure titanium prescribed in JIS. Namely, industrial pure titanium containing 0.1% or less of C, 0.015% or less of H, 0.4% or less of O, 0.07% or less of N, 0.5% or less of Fe, and the balance Ti.

By using the industrial pure titanium of JIS 1-4 grade, a titanium material having sufficient workability and no cracks and integrated with the titanium alloy on the surface after hot working was obtained. Among them, titanium is an active metal, and therefore, when titanium sponge is a fine powder having an average particle diameter of 0.1mm or less, the surface area per unit mass becomes large, and it is inevitable to take care of trapping (thickening) of O in actual operation.

The O content in the inner layer portion of the titanium composite material can be adjusted according to desired mechanical properties, and when high strength is required, the O content can be up to 0.4% at maximum. If the O content exceeds 0.4%, cracks may occur, and a titanium material integrated with the titanium alloy on the surface after hot working cannot be obtained. On the other hand, when ductility is required as compared with strength, the O content is preferably made lower, preferably 0.1% or less, more preferably 0.05% or less.

(void fraction)

The titanium composite material 1 of the present invention is produced by hot working and cold working using a titanium material 5 described later as a raw material. At this time, voids formed in the pure titanium portion of the titanium material 5 are pressed together with hot working and cold working, but are not completely removed, and a portion remains in the inner layer portion 4. If the number of voids in the inner layer portion 4 is too large, the mechanical properties (strength and ductility) of the metal as a main body are deteriorated, and therefore, it is desirable that the number of voids is as small as possible.

However, a large reduction in pressure is required to completely crimp the voids, and the shape (thickness) of the produced titanium composite material 1 is limited, which further increases the production cost. On the other hand, if the titanium composite material 1 is configured to contain voids to the extent that the voids have sufficient mechanical properties (strength, ductility, etc.), the density of the titanium inside becomes low, and therefore, the titanium composite material 1 to be produced can be expected to be lightweight.

In this case, if the void ratio in the inner layer portion 4 is 30% or less, the titanium composite material 1 is manufactured so that the inner layer portion 4 is integrated with the first surface layer portion 2 and the second surface layer portion 3. In order to efficiently produce the titanium composite material 1, it is desirable that the porosity at that time is 10% or less by performing hot and cold working in excess of a certain amount.

As described above, the porosity is reduced when the mechanical properties of the bulk metal are important, and the porosity is increased when the weight of the material is reduced, and the porosity can be selected according to the application. The porosity in the inner layer 4 at this time is preferably more than 0% and 30% or less, more preferably more than 0% and 10% or less.

(method of calculating void fraction)

The proportion of voids remaining in the inner layer portion 4 of the titanium composite material 1 (void ratio) is calculated as follows. After the titanium material was embedded in a resin so that the cross section of the titanium material could be observed, the observed surface was polished and mirror-finished using a diamond or alumina polishing liquid. An optical micrograph of the thick center portion of the plate was taken at a magnification of 500 times using the observation sample subjected to the mirror-surface refining. The area ratio of voids observed in the optical microscope photograph taken was measured, and the average of the measurement results of 20 pieces was calculated as the void ratio. The microscope used for observation is preferably a normal optical microscope because it is possible to clearly observe the specimen by using a differential interference microscope capable of polarized light observation.

2. Material for hot working of titanium composite material

Fig. 2 is an explanatory diagram showing the structure of a titanium material 5 for hot working as a material for hot working of the titanium composite material 1. The titanium composite material 1 in which the first surface layer portion 2 and the second surface layer portion 3 are formed of a titanium alloy and the inner layer portion 4 is formed of pure titanium is manufactured by, for example, sealing the entire circumference with a titanium alloy material having various properties as shown in fig. 2 to produce a case 6, filling the inside of the case 6 with a titanium block 7, decompressing the inside of the case 6 to produce a titanium material 5, and hot-working the titanium material 5 as a hot-working material. The respective structures of the raw materials are described in detail below.

2-1. titanium block

(chemical composition)

The titanium nuggets 7 filled in the titanium material 5 for hot working according to the present invention are ordinary titanium nuggets produced by a conventional smelting process such as Kroll process, and commercially pure titanium equivalent to JIS1 grade, JIS2 grade, JIS3 grade, or JIS4 grade can be used as the component thereof.

(shape)

The titanium block 7 includes 1 or more kinds of titanium blocks selected from titanium sponge, compact blocks obtained by compressing titanium sponge, and industrial pure titanium scrap. The size of the titanium block 7 is preferably 30mm or less in average particle diameter. If the average particle size is larger than 30mm, handling during transportation becomes difficult, and there is a problem that the titanium material or the like is difficult to enter during processing, and as a result, the work efficiency is deteriorated. Further, the filling ratio when filling the case 6 may be low, and the density of the titanium composite material 1 produced by hot working may be low, which may cause a reduction in properties such as ductility.

On the other hand, if the size of the titanium block 7 is too small, dust becomes a problem when filling the housing 6, and there is a fear that not only is there a trouble in handling, but also the surface area per unit mass becomes large, and thickening of O occurs during handling. Therefore, the average particle diameter of the titanium block 7 is preferably 0.1mm or more, more preferably 1mm or more.

It is considered to use pure titanium powder subjected to mm (mechanical milling) treatment as a very fine powder having an average particle diameter of 0.1mm or less. The MM treatment is a treatment of charging the powder and hard balls into a can, sealing the can, and vibrating a can mill to pulverize the powder. Since the surface of the MM-treated fine powder is in an active state, it is necessary to treat the fine powder with an inert gas so that the fine powder does not absorb O and N in the atmosphere when the pure titanium powder is recovered from the tank.

Further, when MM treatment is performed on pure titanium having low concentrations of O and N, the powders are pressed against each other or the pure titanium is pressed against the surface of the hard ball or can because of high ductility. Therefore, the yield of the pure titanium powder obtained by MM treatment is poor. For this reason, the production of pure titanium powder by MM treatment requires a large amount of labor and cost, and is not suitable for mass production.

There is also a method of producing titanium fine powder from titanium sponge by a hydrogenation dehydrogenation method. However, the surface area per unit mass increases, and the O concentration is easily increased by surface oxidation, so that it is difficult to control the material quality. Therefore, the present invention using titanium sponge as it is excellent in quality and cost.

When titanium sponge is press-formed into a compact for use, a part or all of the titanium sponge may be replaced with scrap (pure titanium scrap) or titanium powder.

2-2. shell

(chemical composition)

The titanium alloy of the above alloy composition is used as the titanium alloy of the first surface layer part 2 and the second surface layer part 3 of the titanium composite material 1 as the final product.

(shape)

Since the shape of the titanium alloy material used as the housing 6 depends on the shape of the titanium material 5 used as the material for hot working, a plate material, a pipe material, or the like can be used without being particularly shaped. Among them, the thickness of the titanium alloy material used for the case 6 is important for the titanium composite material 1 manufactured through the manufacturing steps such as hot working, cold working, and annealing in order to have high functionality and excellent surface properties by alloying of the surface layer.

If the thickness is less than 1mm, the case 6 is broken and broken in vacuum during hot working accompanied by plastic deformation, and the titanium block 7 inside is oxidized. In addition, the undulations of the titanium block 7 filled in the titanium material 5 are transferred to the surface of the titanium material 5, and large surface undulations are generated on the surface of the titanium material 5 during the hot working. As a result, the surface properties, mechanical properties such as ductility, and the like, and further desired properties of the produced titanium composite material 1 are adversely affected.

Even if surface defects are not generated during hot working or cold working, the thickness of the titanium alloy portion in the produced titanium composite material 1 may be locally reduced, and sufficient characteristics may not be exhibited. Further, when the case 6 is too thin, the weight of the titanium block 7 filled therein cannot be supported, and therefore the titanium material 5 is deformed due to insufficient rigidity during holding or processing at room temperature or under hot conditions.

When the thickness of the titanium alloy material used for the case 6 is 1mm or more, hot working can be performed without these problems, and the titanium composite material 1 having excellent surface properties and desired characteristics can be produced. The thickness of the titanium alloy material is more preferably 2mm or more.

On the other hand, if the thickness of the titanium alloy material becomes too large, the proportion of the case 6 in the produced titanium material 5 for hot working increases, and the proportion of the titanium nuggets 7 in the titanium material 5 relatively decreases, so that the yield decreases and the cost increases.

2-3. titanium material for hot working

Next, a titanium material 5 manufactured using the titanium block 7 and the case 6 will be described.

(shape)

The shape of the titanium material 5 is not limited to a specific shape, and is determined by the shape of the titanium composite material 1 to be produced. When the plate material is to be produced, the titanium material 5 is produced in a rectangular parallelepiped shape, and when the rod, wire or extrusion material is to be produced, the titanium material 5 is produced in a polygonal prism shape such as a cylindrical shape or an octagonal prism shape. The size of the titanium material 5 is determined by the size (thickness, width, length) of the product and the amount of production (weight).

(interior)

The titanium material 5 is sealed with the case 6 over the entire circumference and filled with the titanium block 7. The titanium block 7 is a block-shaped grain, and therefore, a space (gap) exists between grains. In order to improve the handling properties of the titanium block 7 and to reduce these gaps, the titanium block 7 may be compression molded in advance and then incorporated into the titanium material 5. If air remains in the gap in the titanium material 5, the titanium block 7 is oxidized and nitrided during heating before hot working, and the ductility of the produced titanium composite material 1 is reduced. Therefore, the inside of the titanium material 5 is decompressed to a high degree of vacuum.

(degree of vacuum)

In order to prevent oxidation and nitridation of the titanium block 7 during hot working, the degree of vacuum in the titanium material 5 is set to 10Pa or less, preferably 1Pa or less. When the internal pressure (absolute pressure) of the titanium material 5 is greater than 10Pa, the titanium block 7 is oxidized or nitrided by the remaining air. The lower limit is not particularly limited, but in order to extremely reduce the degree of vacuum and to increase the manufacturing cost such as the improvement of the airtightness of the apparatus and the reinforcement of the vacuum evacuation apparatus, it is necessary to make the degree of vacuum less than 1 × 10^-3Pa。

(welding)

The method for welding the case 6 may be arc welding such as TIG welding or MIG welding, electron beam welding, laser welding, or the like, and is not particularly limited. The welding atmosphere is a vacuum atmosphere or an inert gas atmosphere so that the surfaces of the titanium block 7 and the case 6 are not oxidized or nitrided. Finally, when the seam of the case 6 is welded, the titanium material 5 is placed in a container (chamber) in a vacuum atmosphere and welded, and preferably, the inside of the titanium material 5 is kept in a vacuum.

3. Method for producing titanium composite material

Next, a method for producing the titanium composite material 1 by hot working the titanium material 5 of the present invention as a material for hot working will be described.

The titanium composite material (product) 1 is formed by hot working a titanium material 5 as a material for hot working. The method of thermal processing may be selected according to the shape of the article.

In the production of a plate, a titanium material 5 in a rectangular parallelepiped shape (slab) is heated to produce a hot-rolled titanium plate. If necessary, the steel sheet may be processed to be thin after removing an oxide layer on the surface by pickling or the like after hot rolling, and then cold rolling.

When a round bar or a wire rod is manufactured, a titanium material 5 having a cylindrical or polygonal shape (billet) is heated, hot-rolled or hot-extruded to manufacture a round bar or a wire rod of titanium. Further, after the oxide layer is removed by pickling or the like after hot working, cold rolling may be performed as necessary, and further the work may be made thinner.

Further, in the production of the extruded material, the titanium material 5 having a cylindrical or polygonal shape (billet) is heated and hot-extruded to produce titanium materials having various cross-sectional shapes.

The heating temperature before hot working may be the same as that in the case of hot working a general titanium slab or billet. The temperature is preferably 600 ℃ or higher and 1200 ℃ or lower depending on the size of the titanium material 5 and the degree of hot working (the working ratio). When the heating temperature is too low, the high-temperature strength of the titanium material 5 becomes too high, which causes cracks in hot working, and the joining of the titanium block 7 and the case (titanium alloy portion) 6 becomes insufficient. On the other hand, when the heating temperature is too high, the structure of the obtained titanium composite material 1 becomes coarse, and therefore sufficient material characteristics cannot be obtained, and the shell (titanium alloy portion) 6 on the surface becomes thin due to oxidation. When the heating temperature is set to 600 to 1200 ℃, hot working can be performed without such a problem.

The degree of working at the time of hot working, that is, the working ratio, can be selected to control the porosity of the interior of the titanium composite material 1. The working ratio is a ratio (percentage) obtained by dividing the difference between the cross-sectional area of the titanium material 5 and the cross-sectional area of the titanium composite material 1 after hot working by the cross-sectional area of the titanium material 5.

When the reduction ratio is low, the gaps between the titanium blocks 7 in the titanium material 5 are not sufficiently pressed, and therefore remain as voids after the hot working. The titanium composite material 1 containing a large number of such voids has only a portion containing voids which is lightweight. However, since many voids are present inside, mechanical properties are not sufficiently exhibited. On the other hand, the working ratio increases, the porosity decreases, and the mechanical properties improve. Therefore, when the mechanical properties of the produced titanium composite material 1 are regarded as important, the higher the reduction ratio, the more preferable.

Specifically, the reduction ratio is 90% or more, and the grain boundary gaps of the titanium nuggets 7 in the titanium material 5 can be sufficiently pressed and the voids in the titanium composite material 1 can be reduced. Although it is preferable that the higher the reduction ratio, the more reliably the voids in the titanium composite material 1 are eliminated, the cross-sectional area of the titanium material 5 must be increased, and the hot working must be repeated several times. As a result, a long manufacturing time is required, and the working ratio is preferably 99.9% or less.

The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1

(example 1-1)

Titanium sponge (JIS1 grade, 2 grade, 3 grade, particle size 0.25 to 19mm) and pure titanium scrap (JIS1 grade, 2 grade, 3 grade) produced by Kroll method were used as titanium nuggets to be filled in a titanium material. Furthermore, a Ti-0.06Pd alloy plate (thickness 0.5-20 mm) was used as a housing, and a rectangular parallelepiped having a thickness of 50-100 mm, a width of 100mm and a length of 120mm was produced.

In the production of the titanium material, first, 5 titanium plates were put in a trial manner to form a box shape, and then titanium sponge was filled therein to cover the opening of the trial case with the titanium plate. In some titanium materials, titanium sponge formed into a billet shape (sponge billet) or a material prepared by mixing titanium sponge with pure titanium scrap to prepare a billet is used in place of titanium sponge. The titanium material to be tested was depressurized (vacuumed) to a predetermined pressure in a vacuum chamber, and then the seam of the case was welded by electron beam welding over the entire circumference to seal the case. The degree of vacuum in the chamber at this time was set to 8.7X 10 as shown in Table 2^-3～7.6×10^-2Pa。

In some of the titanium materials (test nos. 16 and 17 in table 2), 1 sheet of a shell having a hole in the center of the plate and a titanium pipe having an inner diameter of 6mm was TIG welded thereto was prepared, and the titanium material was trial-installed so that the shell became a rear end surface at the time of rolling.

Thereafter, the titanium material thus fabricated was welded by electron beams over the entire circumference, and the inside of the titanium material was reduced in pressure to a predetermined degree of vacuum (6.9 × 10) through a titanium tube^-1About 1.2Pa), and after the pressure reduction, the titanium tube was pressure-bonded to maintain the degree of vacuum in the titanium material.

Through the above steps, a case sealed with a titanium alloy plate over the entire circumference was formed, the inside of the case was filled with a titanium block, and the inside of the case was depressurized to a predetermined degree of vacuum.

The titanium material thus produced was heated to 850 ℃ in an atmospheric atmosphere, and then hot rolled to obtain a hot rolled sheet having a thickness of 5 mm. Then, both the inner surface and the outer surface were subjected to descaling treatment using shot blasting and hydrofluoric/nitric acid. Further, the sample material of the present invention is produced by cold rolling to obtain a titanium plate having a thickness of 1mm, and annealing by heating to 600 to 750 ℃ in a vacuum or an inert gas atmosphere for 240 minutes.

A test piece having a thickness of 1mm, a width of 30mm and a length of 40mm was cut out from the hot-rolled sheet, the cut surface and the surface to which the corrosion-resistant titanium alloy sheet was not attached were covered with an anticorrosive tape so as not to be exposed to a corrosive environment, and then immersed in 3% boiling hydrochloric acid (pH 0 at room temperature) for 96 hours, and then the corrosion rate was calculated from the weight change before and after the corrosion test.

The produced titanium composite material was embedded in a resin so as to enable cross-sectional observation, polished and etched, and then observed with an optical microscope to measure the thickness of the titanium alloy layer at the surface layer portion. The thickness of the titanium alloy layer at the surface layer portion measured was divided by the total thickness of the titanium composite material, and calculated as the ratio of the surface layer portion.

In order to calculate the proportion of voids remaining in the pure titanium portion of the titanium composite material (hereinafter, void ratio), the resin was embedded so as to allow observation of the cross section of the sample, and then the sample was polished and mirror-finished, and then an optical micrograph was taken at a magnification of 500. The area ratio of voids was calculated from the photographed optical microscope photograph, and the measurement results of 5 sheets were averaged to calculate the void ratio. The surface properties of the produced titanium composite material were evaluated by visual observation for the presence or absence of flaws.

For comparison with the titanium composite material of the present invention, the corrosion test was performed using commercially available 1mm plates of pure titanium (JIS 1-3 grade) and corrosion-resistant titanium alloy (Ti-0.06% Pd, ASTM Gr 17).

The results are summarized in table 2.

[ Table 2]

The test nos. 1 to 4 as comparative examples are commercially available pure titanium materials (JIS1 to 3 grades) and corrosion resistant titanium materials (Ti-0.06Pd, astm gr.17) produced through melting, decomposition and forging steps, respectively, and the results thereof are indexes for evaluating the performance of the titanium composite material of the present invention described later.

Each of test Nos. 5 to 14 and 16 to 19 as examples of the present invention showed more excellent corrosion resistance than the commercially available pure titanium material produced through the melting, decomposition and forging steps shown in test Nos. 1 to 3 in Table 2, and had corrosion resistance equivalent to the commercially available corrosion-resistant titanium material produced through the melting, decomposition and forging steps shown in test No. 4.

Among these, in test No.5, there was no problem in corrosion rate, but the content of the surface layer portion was large, and the proportion of the titanium alloy portion was relatively large, and therefore the raw material cost was high.

Test No.15 has a result that the corrosion resistance is better than that of pure titanium because the surface layer portion is thin, but is inferior to that of the corrosion-resistant titanium alloy.

In tests 18 and 19, as pure titanium in the titanium material, a titanium composite material was produced by using a sponge compact containing pure titanium scrap, which is a pure titanium scrap, in a sponge compact or a part of the titanium sponge. These materials have excellent corrosion resistance equivalent to that of a corrosion-resistant titanium alloy, as in the case of using titanium sponge inside.

(examples 1 to 2)

Titanium sponge (JIS1 grade, particle size 0.25mm to 19mm) produced by Kroll method was used as the titanium block to be filled in the titanium material. Further, as the case, a rectangular parallelepiped was produced with a thickness of 75mm, a width of 100mm, and a length of 120mm using a titanium alloy (thickness 10mm) containing a predetermined composition.

In the production of the titanium material, first, 5 titanium plates were put in a trial manner to form a box shape, and then titanium sponge was filled therein to cover the opening of the trial case with the titanium plate. The titanium material thus obtained was subjected to vacuum reduction to 8.7X 10 in a vacuum chamber^-3Pa, then sealing the seam of the housing by electron beam welding over the entire circumference.

Through the above steps, a case sealed over the entire circumference with a plate material made of a titanium alloy was formed, the interior of the case was filled with titanium sponge, and the interior of the case was depressurized to a predetermined degree of vacuum.

The titanium material thus produced was heated to 850 ℃ in an atmospheric atmosphere, and then hot rolled to obtain a hot rolled sheet having a thickness of 5 mm. A test piece having a thickness of 5mm, a width of 30mm and a length of 40mm was cut out from the test piece, and then the same evaluation as in example 1-1 was performed.

In order to compare with the titanium composite material of the present invention, the corrosion test described above was carried out using commercially available 5mm plates of pure titanium (JIS1 grade) and corrosion-resistant titanium alloy (Ti-0.06% Pd, ASTM Gr 17).

These results are summarized in table 3.

[ Table 3]

Commercially available pure titanium material (JIS1 grade) produced through the melting, decomposition and forging step and commercially available corrosion-resistant titanium material produced through the melting, decomposition and forging step as test nos. 20 to 23 of comparative examples were used as indexes for evaluating the performance of the titanium composite material described in the present invention described later.

All of test nos. 24 to 48 as examples of the present invention had corrosion resistance equivalent to that of commercially available corrosion-resistant titanium materials produced through the melting, decomposition and forging steps shown in test nos. 21 to 23, and also exhibited corrosion resistance superior to that of commercially available pure titanium materials produced through the melting, decomposition and forging steps shown in test No. 20.

In test nos. 24 to 27, the titanium alloy at the surface layer portion contained Pd as a platinum group element, and excellent corrosion resistance was imparted thereto.

In test No.28, the titanium alloy contained Pd and Ru as platinum group elements in the surface layer portion, and thus was provided with excellent corrosion resistance.

In test nos. 29 and 30, the titanium alloy contained Pd as a platinum group element and Co in the surface layer portion, and thus was provided with excellent corrosion resistance.

In test nos. 31 to 41, the titanium alloy contained Pd or Ru as a platinum group element and Y, Dy, La, didymium, Pr, Ce, and Mm as a rare earth element in the surface layer portion, thereby providing excellent corrosion resistance.

In test nos. 42 and 43, the titanium alloy contained Pd as a platinum group element, Nd and Sm as rare earth elements, and further contained Co in the surface layer portion, thereby providing excellent corrosion resistance.

In test nos. 44 and 45, the titanium alloy contained Ru and Ni as platinum group elements in the surface layer portion, and excellent corrosion resistance was imparted thereto.

In test No.46, the titanium alloy contained Pd as a platinum group element, Y as a rare earth element, and further Ni in the surface layer portion, thereby providing excellent corrosion resistance.

In test No.47, Pd, Co, and Ni as platinum group elements were added to the titanium alloy at the surface layer portion, thereby providing excellent corrosion resistance.

Further, in test No.48, Pd as a platinum group element, Y as a rare earth element, and further Co and Ni were added to the titanium alloy at the surface layer portion, thereby providing excellent corrosion resistance.

(examples 1 to 3)

Titanium sponge (JIS1 grade, particle size 0.25mm to 19mm) produced by Kroll method was used as the titanium block to be filled in the titanium material. In addition, as the shell, a Ti-0.06Pd alloy plate is used for manufacturing a cuboid with the thickness of 25-75 mm, the width of 100mm and the length of 120 mm.

In the production of the titanium material, first, 5 titanium plates were put in a trial manner to form a box shape, and then titanium sponge was filled therein to cover the opening of the trial case with the titanium plate. The titanium material thus obtained was subjected to vacuum reduction to 8.7X 10 in a vacuum chamber^-3Pa, then sealing the seam of the housing by electron beam welding over the entire circumference.

Through the above steps, a case sealed with a titanium alloy plate over the entire circumference was formed, the interior of the case was filled with titanium sponge, and the interior of the case was depressurized to a predetermined degree of vacuum.

The titanium material thus produced was heated to 850 ℃ in an atmospheric atmosphere, and then hot-rolled to obtain a hot-rolled sheet having a thickness of 20 mm. The obtained hot-rolled pickled plate was subjected to vacuum annealing at 725 ℃, and then to shot peening and pickling refining with hydrofluoric/nitric acid, thereby obtaining a titanium composite material. A test piece 20mm in thickness, 50mm in width and 50mm in length was cut out from the test piece, and the same evaluation as in examples 1-1 and 1-2 was performed.

These results are summarized in table 4.

[ Table 4]

All of test nos. 51 to 55 as examples of the present invention showed more excellent corrosion resistance than the commercially available pure titanium material produced through the melting, decomposition and forging steps shown in test No.49, and had corrosion resistance equivalent to the commercially available corrosion-resistant titanium material produced through the melting, decomposition and forging steps shown in test No. 50.

Example 2

(example 2-1)

In test nos. 1 to 18 shown in table 5, after a rectangular case 6 having a thickness of 250mm × a width of 1000mm × a length of 4500mm, which is formed of a titanium alloy plate containing at least 1 or more of Si, Nb, Ta, and Al, was produced, titanium blocks 7 (1 or more selected from briquettes, scrap, and titanium sponge) made of industrial pure titanium were filled therein at a rate of about 8 × 10^-2The resultant was sealed in a vacuum atmosphere of Pa to prepare a titanium material 5 as a hot rolling material.

Thereafter, the titanium material 5 was heated to 820 ℃ and hot-rolled to a thickness of 5mm, and then both the inner surface and the outer surface were subjected to descaling treatment using shot blasting and hydrofluoric/nitric acid.

Further, the titanium composite material 1 is cold-rolled to a thickness of 1mm, and as an annealing treatment, a heat treatment is performed by heating to 600 to 750 ℃ in a vacuum or an inert gas atmosphere and holding the temperature for 240 minutes.

A20 mm. times.20 mm test piece from these test pieces was subjected to surface and edge grinding with #400 sandpaper, exposed to air at 700 ℃ and 750 ℃ for 200 hours, and the change in weight before and after the test was measured to determine the amount of oxidation increase per unit cross-sectional area.

[ Table 5]

In test No.1 as a comparative example, the inner layer 4 was JIS2 grade pure titanium for industrial use, and did not have the first surface layer 2 and the second surface layer 3. Therefore, the oxidation increase in heating at 700 ℃ for 200 hours was 40g/m²The amount of oxidation increase in heating at 750 ℃ for 200 hours was 100g/m²Above, it is very high.

In test No.2, the inner layer 4 was formed of industrial pure titanium JIS1 grade, and the first surface layer 2 and the second surface layer 3 contained Si and had a sufficient thickness when the thickness was 5 μm or more. Therefore, the oxidation increase in heating at 700 ℃ for 200 hours was 25g/m²The amount of oxidation increase in heating at 750 ℃ for 200 hours was 70g/m²Hereinafter, excellent oxidation resistance was exhibited. In addition, the porosity is less than 1%, and the mechanical properties are good.

In test No.3, the inner layer 4 was formed of industrial pure titanium JIS2 grade, and the first surface layer 2 and the second surface layer 3 contained Si and had a sufficient thickness when the thickness was 5 μm or more. Therefore, the oxidation increase in heating at 700 ℃ for 200 hours was 25g/m²The amount of oxidation increase in heating at 750 ℃ for 200 hours was 70g/m²Hereinafter, excellent oxidation resistance was exhibited. In addition, the porosity is less than 1%, and the mechanical properties are good.

In test No.4, the inner layer 4 was formed of industrial pure titanium JIS3 grade, and the first surface layer 2 and the second surface layer 3 contained Si and had a sufficient thickness of 5 μm or more. Therefore, the oxidation increase in heating at 700 ℃ for 200 hours was 25g/m²The amount of oxidation increase in heating at 750 ℃ for 200 hours was 70g/m²Hereinafter, excellent oxidation resistance was exhibited. In addition, emptyThe porosity is less than 1%, and the mechanical property is good.

In test nos. 5 to 18, the inner layer 4 was JIS2 grade pure titanium for industrial use, and the first surface layer 2 and the second surface layer 3 contained 1 or more species selected from Si, Nb, Ta, and Al, and had a sufficient thickness when the thickness was 5 μm or more. Therefore, the oxidation increase in heating at 700 ℃ for 200 hours was 25g/m²The amount of oxidation increase in heating at 750 ℃ for 200 hours was 70g/m²Hereinafter, excellent oxidation resistance was exhibited. In addition, the porosity is less than 1%, and the mechanical properties are good.

(example 2-2)

In test nos. 19 and 20 of table 6, after a case 6 having a thickness of 50mm × a width of 1000mm × a length of 4000mm was produced from a Nb-containing titanium alloy plate, a titanium block 7 (a billet and titanium sponge) made of industrial pure titanium was filled therein at about 8 × 10^-2The resultant was sealed in a vacuum atmosphere of Pa to prepare a titanium material 5 as a hot rolling material.

The titanium material 5 was heated to 820 ℃ and hot-rolled to a thickness of 20mm, and then both the surface and the inner surface were subjected to descaling treatment using shot blasting and hydrofluoric/nitric acid. Further, as the annealing treatment, a heat treatment is performed by heating to 600 to 700 ℃ in a vacuum or an inert gas atmosphere and holding for 240 minutes.

[ Table 6]

In test nos. 19 and 20, the inner layer 4 was a JIS2 grade of industrial pure titanium, and the first surface layer 2 and the second surface layer 3 were formed of a titanium alloy containing Nb. The void ratio of the inner layer 4 is also not less than 30%. The first surface portion 2 and the second surface portion 3 have a thickness of 5 μm or more and a sufficient thickness. Therefore, the oxidation increase in heating at 700 ℃ for 200 hours was 25g/m²The amount of oxidation increase in heating at 750 ℃ for 200 hours was 70g/m²Hereinafter, excellent oxidation resistance was exhibited.

(examples 2 to 3)

As shown in Table 7, in test No.21, a titanium alloy plate made of Ti-1.0Cu-1.0Sn-0.35Si-0.25Nb, in test No.22, a titanium alloy plate made of Ti-1.0Cu-0.5Nb, and in test No.23, a housing 6 having a thickness of 250mm, a width of 1000mm, a length of 4500mm, was fabricated using a titanium alloy plate made of Ti-0.25Fe-0.45Si, and then, a titanium block 7 (a billet and titanium sponge) made of industrial pure titanium was filled therein to a thickness of about 8X 10^-2The titanium material 5 was produced by sealing in a vacuum atmosphere of Pa, and used as a material for hot rolling.

Thereafter, the steel sheet was heated to 820 ℃ and hot-rolled to a thickness of 5mm, and then the inner surface was subjected to descaling treatment of removing about 40 μm on each surface (80 μm on both surfaces) by shot blasting and hydrofluoric/nitric acid.

Further, the titanium composite material 1 is cold-rolled to a thickness of 1mm, and heat treatment is performed as annealing treatment by heating to 600 to 700 ℃ in a vacuum or inert gas atmosphere and holding for 240 minutes.

[ Table 7]

In any of test nos. 21 to 23, the first surface layer portion 2 and the second surface layer portion 3 contained 1 or more of Si and Nb. The void ratio of the inner layer 4 is also as low as less than 0.1%. Further, the first surface portion 2 and the second surface portion 3 have a sufficient thickness even when the thickness is5 μm or more. Therefore, the oxidation increase in heating at 700 ℃ for 200 hours was 25g/m²The amount of oxidation increase in heating at 750 ℃ for 200 hours was 70g/m²Hereinafter, excellent oxidation resistance was exhibited.

Example 3

(example 3-1)

As shown in fig. 1 and 2, a titanium block 7 was filled in a case 6 of a titanium alloy plate to prepare a titanium material 5, and the titanium material 5 was rolled to prepare a test piece.

The titanium material 5 has an overall thickness of 125mm, the total content of Fe, Cr, Ni, Al, and Zr in the case 6 is 0.03 to 1.1%, and the chemical composition of the titanium block 7 inside is in the range of O: 0.030 to 0.33%, Fe: the range of 0.028-0.086% is C: 0.01% or less, H: 0.003 or less, N: 0.006% or less. In order to compare the influence of the hot rolling rate, a titanium material 5 having a thickness of 25mm and 50mm as a whole was partially formed.

Specifically, a case 6 is produced by using a titanium alloy plate having adjusted concentrations and thicknesses of Fe, Cr, Ni, Al, and Zr on the outer periphery, a compressed body (billet) obtained by compression molding titanium sponge is filled in the case 6, and then a lid of a titanium material 5 is welded.

A titanium material 5 in which a part of titanium sponge having an unformed shape was filled as it was prepared, and a titanium material 5 in which a part of titanium sponge and 10% or 30% of scrap material having the same composition as that of titanium sponge was cut into pieces of about 25mm square and filled was prepared.

In the welding method, electron beam welding is performed in a vacuum atmosphere in which the degree of vacuum in the interior of the titanium material 5 is 10Pa or less in order to prevent oxidation and nitridation of the titanium block 7 during hot working.

Thereafter, the steel sheet was hot-rolled to a thickness of 5mm, and then, descaling (shot blasting and acid pickling), cold rolling, and annealing were performed to obtain a titanium composite material 1. The thicknesses of the first surface layer 2 and the second surface layer 3 which are the element-thickened regions (titanium alloy) are adjusted by the thickness of the outer titanium alloy sheet 6 and the surface removal amount at the time of descaling.

Each test material as the titanium composite material 1 was evaluated for the α -phase crystal grain size, tensile strength, elongation, fatigue strength, and formability at each position under the conditions shown below.

(alpha phase Crystal particle diameter)

The thicknesses of the first surface portion 2 and the second surface portion 3 were measured by EPMA. In a microstructure photograph taken by an optical microscope, the average crystal grain size of the α phase at a position of 1 to 10% of the sheet thickness is calculated at the inner layer portion and the surface layer portion by the cutting method according to jis g0551 (2005).

(tensile Strength, elongation)

A tensile test specimen (half size of the tensile test specimen JIS 13-B) having a parallel portion of 6.25X 32mm, a width of 25mm between gauge points, a chuck portion of 10mm and a total length of 80mm was prepared, and a tensile test was conducted at a tensile rate of 0.5%/minute between gauge points and at a tensile rate of 30%/minute or less at 0.2% proof stress until the 0.2% proof stress was measured. Here, the tensile strength and the total elongation in the direction perpendicular to the rolling direction were evaluated.

(fatigue Strength)

Using the plane bending fatigue test material shown in fig. 3 and a tokyo balance plane bending tester, a fatigue test was performed under the conditions of a stress ratio R of-1 and a frequency of 25 Hz. Here, the number of repetitions until fracture at each stress amplitude was obtained, a stress fatigue curve was prepared, and the evaluation was performed even if 10⁷Fatigue limit (fatigue strength) at which the secondary repeated bending does not break.

(moldability)

The Beijing test mechanism of Chinese imperial cent earthen stone is used in model SAS-350D deep drawing test machineThe ball nose punch of (1) was used to perform a ball nose bulging test on a titanium plate processed into a shape of 90mm × 90m × 0.5 mm. The bulge test was conducted by applying a high-viscosity oil (#660) manufactured by japan oil corporation, placing a plastic sheet thereon, and comparing the bulge height at the time of fracture of the test material so that the punch does not directly contact the titanium plate.

Since the bulge height in the ball nose bulge test is strongly affected by the oxygen concentration, 21.0mm or more in JIS1, 19.0mm or more in JIS2, and 13.0mm or more in JIS3 were judged as good formability (o mark in the table). The case where the above is not satisfied is determined to be defective (x mark in the table).

(metallographic structure)

Fig. 4 shows an example of a tissue photograph produced by the above-described method. Fig. 4 (a) is a photograph of the structure of test No.1 (comparative example, general titanium material), fig. 4 (b) is a photograph of the structure of test No.5 (inventive example), fig. 4 (c) is a photograph of the structure of test No.12 (inventive example), and fig. 4 (d) is a photograph of the structure of test No.17 (inventive example).

Fig. 4 (b) to 4 (d) are examples of the present invention, and the first surface layer 2 and the second surface layer 3 have different thicknesses.

The test results are summarized in tables 8 and 9. Table 8 shows the case where commercially pure titanium corresponding to JIS1 grade was used for titanium block 7, and table 9 shows the case where commercially pure titanium corresponding to JIS2 and 3 grade was used for titanium block 7. Note that the symbols N1 to N4 in the column of "level of form of raw material used inside the case" in tables 8 and 9 indicate the following types and ratios.

N1: briquettes using 100% titanium sponge

N2: keeping the original shape of the titanium sponge to be 100 percent

N3: mixed titanium sponge 90% and scrap 10% briquettes of the same composition

N4: briquettes of 70% titanium sponge mixed with 30% waste of the same composition

[ Table 8]

Test nos. 4 to 33 in table 8 are inventive examples that completely satisfy the conditions specified in the present invention, and test nos. 1 to 3 are comparative examples that do not satisfy the conditions specified in the present invention.

Test nos. 1 to 3 are titanium alloy sheets corresponding to JIS1, and have formability and fatigue strength as the criteria for evaluating formability and fatigue strength of the inventive examples. The fatigue strength ratios of test Nos. 1 to 3 were 0.63, and 0.55, respectively, and were normal values.

The elongation obtained in tests No.4 to 33: 30-46%, tensile strength: 295-341 MPa, fatigue strength: 197-251 MPa, fatigue strength ratio: 0.67 to 0.78, bulge height: 21.0 to 21.7mm, excellent in both moldability and fatigue strength.

[ Table 9]

Test nos. 36 to 43 and 46 to 53 in table 9 are inventive examples that completely satisfy the conditions specified in the present invention, and test nos. 34, 35, 44 and 45 are comparative examples that do not satisfy the conditions specified in the present invention.

Test Nos. 34 and 35 are titanium alloy sheets corresponding to JIS2 grade, and test Nos. 44 and 45 are titanium alloy sheets corresponding to JIS3 grade. Each of test nos. 34, 35, 44 and 45 had formability and fatigue strength as criteria for evaluating formability and fatigue strength of the inventive examples. The fatigue strength ratios of test nos. 34 and 35 were 0.58 and 0.59, respectively, and the fatigue strength ratios of test nos. 44 and 45 were 0.59 and 0.58, respectively. Are all normal values.

The elongation rates of the tests Nos. 36 to 43 and 46 to 53 were as follows: 25-33%, tensile strength: 341-614 MPa, fatigue strength: 255-421 MPa, fatigue strength ratio: 0.65 to 0.77, bulge height: mechanical properties of 10.0 to 20.6mm, and excellent formability and fatigue strength.

Example 4

(example 4-1)

Titanium sponge (JIS2 grade, particle size 0.25 to 19mm) produced by Kroll process was used as the titanium block filled in the casing. In addition, a beta-type titanium alloy Ti-15V-3Cr-3Sn-3Al plate (thickness is 1-15 mm) is used as a shell, and a cuboid with the thickness of 45-80 mm, the width of 100mm and the length of 120mm is manufactured.

In the case of manufacturing the case, first, 5 titanium plates were put in a trial manner to form a box shape, and then titanium sponge was filled therein to cover the opening of the trial case with the titanium plate. The titanium material to be subjected to the test loading is placed in a vacuum chamber, and the pressure is reduced (vacuum) to a predetermined pressure, and thereafter, the entire periphery of the titanium material is sealed by electron beam welding. The degree of vacuum in the chamber at this time was 8.7X 10 as shown in Table 10^-3～2.2×10^-2Pa。

Through the above steps, a case sealed with a β -type titanium alloy over the entire circumference was formed, the interior of the case was filled with titanium sponge, and the interior of the titanium material was depressurized to a predetermined degree of vacuum.

The produced shell was heated to 850 ℃ in the air atmosphere, and then hot rolled at a reduction ratio of 92 to 97% as shown in table 10, to obtain a hot rolled sheet having a thickness of 4.8 to 5.0 mm. Then, annealing is performed at 600 to 650 ℃ for 4 to 10 hours in a vacuum atmosphere. Further, shot blasting and acid pickling were performed to remove the oxide layer.

The produced titanium composite material was embedded in a resin so as to enable observation of the cross section, polished and etched, and then observed with an optical microscope to measure the thickness of the surface layer portion. The measured thickness of the surface layer portion was divided by the total thickness of the titanium composite material, and calculated as a ratio of the surface layer portion.

In order to calculate the proportion of voids remaining in the pure titanium portion of the titanium composite material (hereinafter, void ratio), the resin was embedded so as to allow observation of the cross section of the sample, and then the sample was polished and mirror-finished, and then an optical micrograph was taken at a magnification of 500. The area ratio of voids was calculated from the photographed optical microscope photograph, and the measurement results of 5 sheets were averaged to calculate the void ratio.

For comparison with the titanium composite material of the present invention, a commercially available 5mm plate of pure titanium (JIS2 grade) was used.

The titanium composite material of the present invention and each of the titanium plates of the comparative examples were each exposed to 1 vol% of H in a hydrogen-absorbing atmosphere₂+99 vol% Ar atmosphere at 500 ℃ for 5 hours.

After exposure, an impact test piece with a 4.8 to 5mm × 10mm × 55mm and 2mmV notch was prepared with the test piece length direction as the rolling direction and the notch direction as the plate thickness penetration direction. Next, hydrogen embrittlement was evaluated by an impact value obtained by dividing the impact absorption energy of the charpy impact test by the cross-sectional area of the test piece. Here, the impact value of the pure titanium 2 grade material before exposure to the hydrogen-absorbing environment was 2.5X 10²J/cm²Therefore, less than 2.0J/cm which is reduced by 20% or more²The case of (2) causes hydrogen embrittlement.

The results are summarized in table 10.

[ Table 10]

Watch 10

Means outside the definition of the invention.

Test No.1 is an example of an industrial pure titanium 2-grade material produced without using a housing. The impact value is as low as less than 2.0X 10 due to the influence of exposure to hydrogen environment²J/cm²。

On the other hand, test Nos. 2 to 6 satisfying the specification of the present invention have impact values as high as 2.0X 10²J/cm²The above results.

(example 4-2)

An example of changing the alloy species of the case of embodiment 4-1 is shown. The thickness of the titanium plate used for the housing was 3mm, the total thickness of the titanium material was 60mm, and the thickness after hot rolling was 4.8 to 5.0mm, and other sample preparations were carried out in the same manner as in example 4-1. This example is shown in table 11.

[ Table 11]

TABLE 11

Test Nos. 7 to 9 satisfy the requirements of the present invention, and the impact values were as high as 2.0X 10²J/cm²The above results.

(examples 4 to 3)

An example in which the type of titanium sponge filled in example 4-1 was changed to JIS3 grade was shown. The thickness of the titanium plate used for the housing was 3mm, the total thickness of the titanium material was 60mm, and the thickness after hot rolling was 4.8 to 5.0mm, and other sample preparations were carried out in the same manner as in example 4-1.

Here, the impact value of JIS3 grade used was 0.5X 10²J/cm²Will thus be reduced by more than 20% by 0.4X 10²J/cm²The following is judged as embrittlement by hydrogen. This example is shown in table 12.

[ Table 12]

TABLE 12

Means outside the definition of the invention.

No.10 is an example of an industrial pure titanium grade 3 material produced without using a case. The impact value is as low as less than 0.5X 10 due to the influence of exposure to hydrogen environment²J/cm²。

No.11 satisfies the requirements of the present invention, and the impact value is as high as 0.5X 10²J/cm²The result of (1).

Example 5

(example 5-1)

The neutron beam shielding plates of test nos. 1 to 24 shown in table 13 were manufactured by the following method.

[ Table 13]

First, the Ti-B alloy sheet of the case 6 is prepared by using TiB in advance₂Or¹⁰B concentration of boron (H)₃ ¹⁰BO₃，₁₀B₂O¹⁰B₄C) B was added to the ingot and melted, and the ingot was hot rolled. After hot rolling, the plate is passed through a continuous pickling line containing hydrofluoric/nitric acid to remove oxidized scale on the surface of the hot rolled plate.

The Ti-B alloy sheet was rolled at about 8X 10^-3The alloy plate was welded to a position corresponding to 5 surfaces of the slab by electron beam welding in a vacuum atmosphere of Pa, thereby producing a hollow case 6.

More than 1 kind selected from titanium sponge, a compact obtained by compressing titanium sponge and titanium scrap finely cut to 30mm × 30mm × 30mm or less are put into the housing 6, and the remaining 1 surface is similarly subjected to electron beam welding to produce a titanium material 5 having a thickness of 100mm and a vacuum inside.

By changing the thickness of the alloy sheet, the ratio of the surface layer portion to the total thickness of the hot-rolled sheet can be adjusted.

Fig. 5 is a schematic view of the titanium material 5 in which the Ti — B alloy plate is assembled into the slab-like case 6 and the titanium block 7 is filled therein.

The titanium material 5 was heated at 800 ℃ for 240 minutes using a steel mill, and then hot rolled to produce a strip coil having a thickness of about 4 to 20 mm.

The hot-rolled strip coil was passed through a continuous pickling line containing hydrofluoric/nitric acid, and was cut to about 50 μm per one side, and then the occurrence of cracks was visually observed. The depth of the surface layer portion (B-densified layer) was measured by cutting out a part of the hot-rolled sheet after pickling (3 positions of the front end, the center, and the rear end in the longitudinal direction from the center in the width direction), grinding the cut part, and performing SEM/EDS analysis to determine the ratio of the surface layer portion to the sheet thickness and the B content of the surface layer portion (the average value among the observed positions).

Further, 20L-direction bending test pieces were collected from the widthwise central portion at 3 positions of the front end, the center, and the rear end in the longitudinal direction, and subjected to bending tests based on JISZ2248 (metal material bending test method). The test temperature was set at room temperature, and a 3-point bending test was performed to a bending angle of 120 degrees to evaluate the presence or absence of crack generation, and the crack generation rate was determined.

In addition, for the evaluation of the neutron beam shielding effect, Am-Be (4.5MeV) was used as a radiation source, and a test piece having a thickness of 500mm × 500mm × 4-20 mm was fixed at a position 200mm from the radiation source. The detector was set at a position 300mm from the radiation source, and the radiation equivalent of the peak of the target energy was measured using the industrial pure titanium JIS1 grade (4mm thick) and test pieces (4 to 20mm thick) of the control test piece, and the neutron beam shielding effect was evaluated based on the ratio of the values (the value of each test piece is described with the term "1" representing the neutron beam shielding effect of the industrial pure titanium JIS1 grade).

The results are summarized in Table 13.

The comparative examples and the invention examples of test Nos. 1 to 10 were based on the base material variety of pure titanium JIS1 grade.

In test No.1 as a comparative example, the case 6 was made of commercially pure titanium containing no B instead of the Ti — B alloy plate. The hot rolled sheet did not crack even in the bending test.

Test No.2 as an example of the present invention was a case where a titanium material 5 having a thickness of 100mm was hot-rolled to a thickness of 20 mm. Since the ratio of the first surface layer 2 to the second surface layer 3 was 5% and the B content of the first surface layer 2 and the second surface layer 3 was 0.5%, no crack was generated in the hot-rolled sheet, and no crack was generated even when the bending test was performed.

In the tests Nos. 3 to 7, the titanium material 5 having a thickness of 100mm was hot-rolled to a thickness of 10mm, and the ratio, B content and porosity of the first surface layer part 2 and the second surface layer part 3 were changed. Since the ratio of the first surface layer 2 to the second surface layer 3 is in the range of 5 to 40% and the B content of the first surface layer 2 and the second surface layer 3 is in the range of 0.1 to 3.0%, no crack is generated in the hot-rolled sheet, and no crack is generated even in the bending test.

In the test Nos. 8 to 10, the titanium material 5 having a thickness of 100mm was hot-rolled to a thickness of 4mm, and the ratio and the B content of the first surface layer part 2 and the second surface layer part 3 were changed. Since the ratio of the first surface layer 2 to the second surface layer 3 is in the range of 5 to 40% and the B content of the first surface layer 2 and the second surface layer 3 is in the range of 0.1 to 3.0%, no crack is generated in the hot-rolled sheet, and no crack is generated even in the bending test.

The examples of the present invention shown in tests 11 to 17 were conducted in the case where the base material type was pure titanium JIS2 grade.

Test No.11 was a case where a titanium material 5 having a thickness of 100mm was hot-rolled to a thickness of 20 mm. Since the ratio of the first surface layer 2 to the second surface layer 3 is in the range of 5 to 40% and the B content of the first surface layer 2 and the second surface layer 3 is in the range of 0.1 to 3.0%, no crack is generated in the hot-rolled sheet, and no crack is generated even in the bending test.

In the test Nos. 12 to 14, the titanium material 5 having a thickness of 100mm was hot-rolled to a thickness of 10mm, and the ratio or the B content of the first surface layer part 2 and the second surface layer part 3 was changed. Since the ratio of the first surface layer 2 to the second surface layer 3 is in the range of 5 to 40% and the B content of the first surface layer 2 and the second surface layer 3 is in the range of 0.1 to 3.0%, no crack is generated in the hot-rolled sheet, and no crack is generated even in the bending test.

In the tests Nos. 15 to 17, the titanium material 5 having a thickness of 100mm was hot-rolled to a thickness of 4mm, and the ratio or the B content of the first surface layer part 2 and the second surface layer part 3 was changed. Since the ratio of the first surface layer 2 to the second surface layer 3 is in the range of 5 to 40% and the B content of the first surface layer 2 and the second surface layer 3 is in the range of 0.1 to 3.0%, no crack is generated in the hot-rolled sheet, and no crack is generated even in the bending test.

The invention examples of tests 18 to 24 were conducted with the base material variety being pure titanium JIS3 grade.

Test No.18 was a case where the titanium material 5 having a thickness of 100mm was hot-rolled to a thickness of 20 mm. Since the ratio of the first surface layer 2 to the second surface layer 3 is in the range of 5 to 40% and the B content of the first surface layer 2 and the second surface layer 3 is in the range of 0.1 to 3.0%, no crack is generated in the hot-rolled sheet, and no crack is generated even in the bending test.

In the test Nos. 19 to 21, the titanium material 5 having a thickness of 100mm was hot-rolled to a thickness of 10mm, and the ratio or the B content of the first surface layer part 2 and the second surface layer part 3 was changed. Since the ratio of the first surface layer 2 to the second surface layer 3 is in the range of 5 to 40% and the B content of the first surface layer 2 and the second surface layer 3 is in the range of 0.1 to 3.0%, no crack is generated in the hot-rolled sheet, and no crack is generated even in the bending test.

In the test Nos. 22 to 24, the titanium material 5 having a thickness of 100mm was hot-rolled to a thickness of 4mm, and the ratio or the B content of the first surface layer part 2 and the second surface layer part 3 was changed. Since the ratio of the first surface layer 2 to the second surface layer 3 is in the range of 5 to 40% and the B content of the first surface layer 2 and the second surface layer 3 is in the range of 0.1 to 3.0%, no crack is generated in the hot-rolled sheet, and no crack is generated even in the bending test.

Furthermore, based on the results of the evaluation by the above-described technique, although the neutron beam shielding effect was not confirmed in test No.1 as a comparative example, the neutron beam shielding effect was confirmed in nos. 2 to 24 as inventive examples, which are all 1 or more in any case.

In the stainless steel plate (4mm thick) having a B content of 0.5% used for the nuclear fuel storage rack, the neutron shielding effect was 23.7. The test nos. 4 to 7, 10, 13, 14, 17, 20 and 21 obtained higher neutron beam shielding effects than the stainless steel sheets.

(example 5-2)

The neutron beam shielding plates of test nos. 25 to 34 shown in table 14 were manufactured by the following method.

[ Table 14]

A Ti-B case 6 having a different plate thickness and chemical composition was combined in the same procedure as in example 5-1 to prepare a titanium material 5 having a thickness of 100mm and filled with titanium sponge and cut scraps.

The titanium material 5 was heated at 800 ℃ for 240 minutes using a steel mill and then hot rolled to produce a strip coil having a thickness of about 5 mm.

The hot-rolled strip coil was passed through a continuous pickling line containing hydrofluoric/nitric acid, and then cold-rolled to obtain a titanium plate having a thickness of 1mm, and as an annealing treatment, the titanium plate was heated to 600 to 750 ℃ in a vacuum or inert gas atmosphere and then subjected to a heat treatment for 240 minutes to obtain a titanium composite material 1.

In the titanium composite material 1 as a cold-rolled sheet, the occurrence of cracks was visually observed in the surface inspection step after annealing. The depth of the first surface layer portion 2 and the second surface layer portion 3 (B-densified layer) was measured by cutting and polishing a part of the titanium composite material 1 (taken from the widthwise central portion at each of 3 positions of the front end, the center, and the rear end in the longitudinal direction), and performing SEM/EDS analysis on the part to obtain the ratio of the thickness of the first surface layer portion 2 and the second surface layer portion 3 to the titanium composite material 1 and the B content of the first surface layer portion 2 and the second surface layer portion 3 (the average value among the observed positions).

Further, 20L-direction bending test pieces were collected from the widthwise central portion at 3 positions of the front end, the center, and the rear end in the longitudinal direction, and subjected to bending tests based on JISZ2248 (metal material bending test method). The test temperature was set to room temperature, and a 3-point bending test was performed until the bending angle reached 120 degrees, to evaluate the presence or absence of crack generation, and the crack generation rate was determined.

In addition, for evaluation of neutron beam shielding effect, Am-Be (4.5MeV) was used as a radiation source, and a 500mm × 500mm × 1mm thick test piece was fixed at a position 200mm from the radiation source. The detector was set at a position 300mm from the radiation source, and the radiation equivalent of the peak of the target energy was measured using a test piece (1mm thick) and a test piece (1mm thick) of a test piece of pure titanium for industrial use JIS1, respectively, and the neutron beam shielding effect was evaluated based on the ratio of the values (the value of each test piece is described assuming that the neutron beam shielding effect of pure titanium for industrial use JIS1 is 1).

The results are summarized in Table 14.

The comparative examples and the invention examples of test Nos. 25 to 28 were based on the base material variety of pure titanium JIS1 grade.

In test No.25 as a comparative example, the case 6 was made of commercially pure titanium containing no B instead of the Ti — B alloy plate. The cold-rolled sheet does not have cracks or the like, and cracks do not occur even in a bending test.

The test nos. 26 to 28 of the present invention examples were conducted while changing the ratio, B content, and porosity of the first surface portion 2 and the second surface portion 3. Since the ratio of the first surface part 2 to the second surface part 3 is in the range of 5 to 40% and the B content of the first surface part 2 and the second surface part 3 is in the range of 0.1 to 3.0%, no crack is generated in the cold-rolled sheet and no crack is generated even in the bending test.

In the present invention examples of test nos. 29 to 31, the base material was classified as pure titanium JIS2, and the ratio, B content, and porosity of the first surface portion 2 and the second surface portion 3 were changed. Since the ratio of the first surface part 2 to the second surface part 3 is in the range of 5 to 40% and the B content of the first surface part 2 and the second surface part 3 is in the range of 0.1 to 3.0%, no crack is generated in the cold-rolled sheet and no crack is generated even in the bending test.

In the invention examples of Nos. 32 to 34, the base material was classified as pure titanium JIS3 grade, and the ratio, B content and porosity of the first surface portion 2 and the second surface portion 3 were changed. Since the ratio of the first surface part 2 to the second surface part 3 is in the range of 5 to 40% and the B content of the first surface part 2 and the second surface part 3 is in the range of 0.1 to 3.0%, no crack is generated in the cold-rolled sheet and no crack is generated even in the bending test.

Furthermore, based on the results of the evaluation by the above-described technique, although the neutron beam shielding effect was not confirmed in test No.25 as a comparative example, the neutron beam shielding effect was confirmed in any of nos. 26 to 34 as inventive examples, which were 1 or more.

Description of the reference numerals

1. Titanium composite material

2. A first surface layer part

3. Second surface layer part

4. Inner layer part

5. Titanium material for hot working

6. Shell body

7. Titanium block