Method for producing titanium material for hot rolling and method for producing hot rolled material
阅读说明：本技术 热轧用钛材的制造方法以及热轧材的制造方法 (Method for producing titanium material for hot rolling and method for producing hot rolled material ) 是由 井上洋介 三户武士 高桥一浩 国枝知徳 森健一 宮崎义正 于 2019-05-14 设计创作，主要内容包括：本发明提供一种在热轧钛材中表面缺陷少的、特别是由对钛坯料的塑性应变赋予处理引起的表面缺陷少的热轧用钛材的制造方法。一种热轧用钛材的制造方法,其包括：表面缺陷去除工序,其包括通过选自由切削、磨削以及研磨构成的组中的至少一种以上对钛坯料的表面进行处理,由此沿着长尺寸方向设置在长尺寸方向正交面(10)的高低差(H)超过0.1mm、倾斜角(θ)为45°以下的多个倾斜面(20)的步骤；以及塑性应变赋予工序,在表面缺陷去除工序之后,对表面赋予塑性应变。(The invention provides a method for producing a titanium material for hot rolling, which has few surface defects in the hot-rolled titanium material, particularly few surface defects caused by plastic strain imparting treatment to a titanium billet. A method for producing a titanium material for hot rolling, comprising: a surface defect removal step of processing the surface of the titanium material by at least one selected from the group consisting of cutting, grinding, and polishing, thereby providing a plurality of inclined surfaces (20) having a height difference (H) of a plane (10) orthogonal to the longitudinal direction of more than 0.1mm and an inclination angle (theta) of 45 DEG or less along the longitudinal direction; and a plastic strain imparting step of imparting plastic strain to the surface after the surface defect removing step.)
1. A method for producing a titanium material for hot rolling, comprising:
a surface defect removal step of processing the surface of the titanium material by at least one selected from the group consisting of cutting, grinding, and polishing, thereby providing a plurality of inclined surfaces having a height difference of more than 0.1mm and an inclination angle of 45 ° or less on a plane orthogonal to the longitudinal direction along the longitudinal direction; and
and a plastic strain imparting step of imparting plastic strain to the surface after the surface defect removing step.
2. The method of manufacturing a titanium material for hot rolling according to claim 1,
the inclination angle is 10-30 degrees.
3. The method of producing a titanium material for hot rolling according to claim 1 or 2,
the height difference is less than 8 mm.
4. The method for producing a titanium material for hot rolling according to any one of claims 1 to 3,
in the surface defect removal step, the surface is treated by at least cutting, and a circular cutting tool having a curvature radius of 2mm or more and 50mm or less is used as the cutting.
5. The method of producing a titanium material for hot rolling according to any one of claims 1 to 4,
the surface defect removing step is performed so that the length of the contour line of the orthogonal surface in the longitudinal direction and the number of the inclined surfaces are 4 to 40 per 3000 mm.
6. The method for producing a titanium material for hot rolling according to any one of claims 1 to 5, wherein,
further comprising: and a step of casting a titanium ingot or a titanium plate blank to obtain the titanium blank before the surface defect removing step.
7. The method of manufacturing a titanium material for hot rolling according to claim 6, wherein,
further comprising: and a step of obtaining the titanium material by casting the titanium ingot and then performing a cogging process before the surface defect removal step.
8. The method for producing a titanium material for hot rolling according to any one of claims 1 to 7, wherein,
in the plastic strain applying step, the surface of the titanium material is hit with at least one of a steel ball having a radius of 3 to 30mm and a steel tool having a tip shape with a radius of curvature of 3 to 30mm, thereby forming a plurality of dimples on the surface.
9. A method of manufacturing a hot rolled material, comprising:
a step of obtaining a titanium material for hot rolling by performing the method for producing a titanium material for hot rolling according to any one of claims 1 to 8; and
and a step of hot rolling the titanium material for hot rolling.
Technical Field
The present invention relates to a method for producing a titanium material for hot rolling and a method for producing a hot rolled material.
Background
A titanium ingot produced using a mold is used as a titanium ingot, and the titanium ingot is subjected to cogging (breaking down) processing by cogging (forging) or the like to produce a titanium material for hot rolling such as a slab (slab) or billet (billet). Further, the titanium material for hot rolling can be directly cast into a shape corresponding to the shape of the slab or billet after the cogging treatment by the electron beam melting method or the plasma arc melting method, which has a high degree of freedom in the shape of the mold.
The titanium material for hot rolling is subjected to hot rolling after removing the oxynitride film and surface defects present on the surface, and the slab is processed into a plate (thick plate, thin plate) or a strip, and the billet is processed into a rod or a wire.
A large titanium ingot industrially used as a titanium ingot contains coarse crystal grains having a solidification structure of several tens mm. When such a titanium ingot is hot-rolled without cogging, the coarse crystal grains may be deformed unevenly, and large surface defects may be generated. When a sheet or strip is produced by hot rolling, large wrinkles are generated in the side surfaces and corner portions due to the coarse solidification structure in addition to the rolled surface, and the wrinkles extend to the rolled surface side, thereby causing surface defects called seam defects (seamindefects) or edge cracks. When a bar or a wire rod is produced by hot rolling, wrinkles occur in a free surface portion or a bite portion which does not contact with a rolling roll, as in the case of producing a plate or a strip, and become surface defects.
In order to suppress the above-described problems, when a large titanium ingot is used, an cogging treatment is generally performed. However, in the cogging process, a so-called dead metal (dead metal) portion may be generated. That is, in the cogging treatment, the contact portion between the titanium ingot and the machining tool is restrained by the frictional resistance, the deformation amount becomes small, and the dead zone metal portion may be generated. When a titanium material for hot rolling having a dead zone metal portion with an insufficient amount of deformation is hot rolled, the above-described surface defects may occur.
Disclosure of Invention
Problems to be solved by the invention
According to one embodiment, there is provided a method for producing a titanium material for hot rolling having few surface defects in a hot rolled material, particularly few surface defects caused by plastic strain imparting treatment to a titanium billet. Further, according to another embodiment, there is provided a method of manufacturing a hot-rolled material using the titanium material for hot rolling manufactured by the above-described manufacturing method.
Means for solving the problems
The present inventors have made extensive studies and found that the occurrence of surface defects due to plastic strain imparting treatment can be suppressed by providing a plurality of inclined surfaces having a height difference of more than 0.1mm in the longitudinal direction of the surface of a titanium material and an inclination angle of 45 ° or less on the surface of the titanium material. The present inventors have further made extensive studies and completed the invention including the embodiments described below.
That is, the present invention provides a method for producing a titanium material for hot rolling, including: a surface defect removal step of processing the surface of the titanium material by at least one selected from the group consisting of cutting, grinding, and polishing, thereby providing a plurality of inclined surfaces having a height difference of more than 0.1mm and an inclination angle of 45 ° or less on a plane orthogonal to the longitudinal direction along the longitudinal direction; and a plastic strain imparting step of imparting plastic strain to the surface after the surface defect removing step.
In one embodiment of the method for producing a titanium material for hot rolling of the present invention, the inclination angle is 10 ° to 30 °.
In one embodiment of the method for producing a titanium material for hot rolling of the present invention, the height difference is 8mm or less.
In one embodiment of the method for producing a titanium material for hot rolling according to the present invention, in the surface defect removal step, at least the surface is treated by cutting, and as the cutting, a circular cutting tool having a curvature radius of 2mm or more and 50mm or less is used.
In one embodiment of the method for producing a titanium material for hot rolling according to the present invention, the surface defect removing step is performed so that the number of the inclined surfaces is 4 to 40 per 3000mm of the length of the contour line of the long-dimension-direction orthogonal surface.
In one embodiment of the method for producing a titanium material for hot rolling according to the present invention, the method further includes: and a step of casting a titanium ingot or a titanium plate blank to obtain the titanium blank before the surface defect removing step.
In one embodiment of the method for producing a titanium material for hot rolling according to the present invention, the method further includes: and a step of obtaining the titanium material by casting the titanium ingot and then performing a cogging process before the surface defect removal step.
In one embodiment of the method for producing a titanium material for hot rolling according to the present invention, in the plastic strain applying step, the surface of the titanium material is hit with at least one of a steel ball having a radius of 3 to 30mm and a steel tool having a tip shape with a radius of curvature of 3 to 30mm, thereby forming a plurality of dimples (dimples) on the surface.
In another aspect, the present invention is a method of manufacturing a hot rolled material, including: obtaining a titanium material for hot rolling by performing the above-described method for producing a titanium material for hot rolling; and a step of hot rolling the titanium material for hot rolling.
Effects of the invention
According to one embodiment, there is provided a method for producing a titanium material for hot rolling having few surface defects in a hot rolled material, particularly few surface defects caused by plastic strain imparting treatment to a titanium billet. Further, according to another embodiment, there is provided a method of manufacturing a hot-rolled material with few surface defects.
Drawings
Fig. 1 is a schematic explanatory view of a plane orthogonal to the longitudinal direction for explaining the level difference of the inclined surface of the titanium material surface and the inclination angle.
Fig. 2A is a schematic explanatory view showing a long-dimension-direction orthogonal surface of an example of an inclined surface of a titanium plate blank from which surface defects have been removed by a square cutting tool.
Fig. 2B is a schematic explanatory view showing a long-dimension-direction orthogonal surface of an example of the inclined surface of the titanium plate blank from which the surface defect has been removed by the circular cutting tool.
Fig. 2C is a schematic explanatory view showing a longitudinal direction orthogonal surface of an example of the inclined surface of the titanium plate blank from which the surface defect has been removed by grinding or polishing.
Fig. 3 is a schematic perspective view showing an example of the overall shape of the titanium plate blank from which the surface defects have been removed.
Fig. 4 is an example of a schematic explanatory view showing before and after plastic strain is applied.
Fig. 5A is an example of a schematic cross-sectional view of a plane orthogonal to the longitudinal direction of a titanium slab from which surface defects have been removed.
Fig. 5B is another example of a schematic cross-sectional view of a plane orthogonal to the longitudinal direction of the titanium slab from which the surface defects have been removed.
Fig. 5C is another example of a schematic cross-sectional view of a plane orthogonal to the longitudinal direction of the titanium slab from which the surface defects are removed.
Fig. 5D is an example of a schematic cross-sectional view of a long-dimension-direction orthogonal plane of the titanium billet from which the surface defects are removed.
FIG. 6 is a flowchart for explaining the method of producing the hot rolled material in examples 1 to 6 and comparative examples 1 to 3.
Fig. 7 is a schematic perspective view showing the entire surface of the titanium plate blank from which the surface defects were removed in examples 5 and 6 and comparative example 3.
Detailed Description
Hereinafter, embodiments of the present invention will be described. However, the present invention can be carried out in various ways without departing from the scope of the invention, and should not be construed as being limited to the description of the embodiments exemplified below.
To explain the outline of the process, a titanium ingot or a titanium plate blank is cast to obtain a titanium blank, the titanium blank is subjected to a plastic strain imparting treatment to be a hot-rolled titanium material, and the hot-rolled titanium material is hot-rolled to be a hot-rolled material. The surface subjected to the plastic strain imparting treatment is generally a hot rolled surface.
The composition of the titanium material is not particularly limited, and a pure titanium material or a titanium alloy material can be used. The titanium alloy material is an alloy material of titanium and a metal such as Fe, Sn, Cr, Al, V, Mn, Zr, Mo, and specific examples thereof include: ti-6-4 (Ti-6 Al-4V), Ti-5 Al-2.5 Sn, Ti-8-1-1 (Ti-8 Al-1 Mo-1V), Ti-6-2-4-2 (Ti-6 Al-2 Sn-4 Zr-2 Mo-0.1 Si), Ti-6-6-2 (Ti-6 Al-6V-2 Sn-0.7 Fe-0.7 Cu), Ti-6-2-4-6 (Ti-6 Al-2 Sn-4 Zr-6 Mo), SP700 (Ti-4.5 Al-3V-2 Fe-2 Mo), Ti-17 (Ti-5 Al-2 Sn-2 Zr-4 Mo-4 Cr), beta-CEZ (Ti-5 Al-2 Sn-4 Zr-4 Mo-2 Cr-1 Fe), TIMETAL555, Ti-5553 (Ti-5 Al-5 Mo-5V-3 Cr-0.5 Fe), Ti-5 Al-2 Sn-4 Zr-4 Mo-1 Fe, Ti-5 Al-3 Mo-3 Cr-0.5 Fe, Ti-5 Al-3 Mo-3-0.5 Mo-10, Ti-5-2-5-3-5 Mo, Ti-5-2-5-3-, Beta C (Ti-3 Al-8V-6 Cr-4 Mo-4 Cr), Ti-8823 (Ti-8 Mo-8V-2 Fe-3 Al), 15-3 (Ti-15V-3 Cr-3 Al-3 Sn), BetaIII (Ti-11.5 Mo-6 Zr-4.5 Sn), Ti-13V-11 Cr-3 Al and the like. In these specific examples, the numerals attached to the element symbols indicate the contents (mass%) of the respective alloying elements.
Both a cast material (so-called direct cast material) having a shape equivalent to a slab or billet and a material subjected to a cogging treatment are included in the titanium ingot. The shape of the titanium billet is not particularly limited, and may be, for example, a slab (slab), a bloom (bloom), a billet (billet), or the like.
In the cast state and the cogging state, when the orthogonal surface (sometimes referred to as an orthogonal cross section) is observed along the longitudinal direction, the cross sectional shape is unstable, and it is advantageous to machine the surface of the titanium material. Further, surface defects such as cracks (defects) exist on the surface. Therefore, it is preferable that the surface layer portion is removed/formed and trimmed (shaped) by subjecting the surface of the titanium material to at least one treatment selected from the group consisting of cutting, grinding, and polishing, prior to the plastic strain applying treatment described later.
As a specific example of the removal processing, there are illustrated: machining by a planer type milling machine, cutting typified by machining by a planer type planer, grinding typified by machining by a grindstone, and polishing typified by polishing. The inclination angle of the inclined surface described later can be reduced by appropriately setting conditions for performing the treatment by at least one or more selected from the group consisting of cutting, grinding, and polishing.
For example, by using a square cutting tool having a cutting angle of 45 ° or less or using a circular cutting tool having a curvature radius of 2mm (2R) or more, a preferable inclined surface can be efficiently formed. A circular cutting tool is more preferable than a square cutting tool because the inclination angle of the inclined surface can be reduced by increasing the radius of curvature. In particular, the radius of curvature of the circular cutting tool is preferably 2mm or more and 50mm or less. In this range, the cutting machine can be downsized, and a preferable inclined surface can be efficiently formed.
The operation of making the inclination angle of the inclined surface to be described later to 45 ° or less may be performed by grinding processing using a hand grinder (hand grinder) or the like. Grinding by a hand grinder may be easily performed when the number of inclined surfaces to be ground is small, when the height of the inclined surfaces is small, or the like.
When the titanium ingot is a slab, the longitudinal direction of the slab is usually the rolling direction. In the present invention, a cross section perpendicular to the rolling direction of the slab and parallel to the thickness direction is generally referred to as a long-dimension-direction perpendicular plane. When the slab rolling surface is square, the direction along any one side of the square may be the longitudinal direction.
On the other hand, in the case where the titanium billet is a billet, the long dimension direction of the billet is usually the rolling direction. In the present invention, a cross section which is perpendicular to the rolling direction of the billet and is a circular surface or a substantially circular surface is generally referred to as a long dimension direction perpendicular surface.
In one embodiment, before the plastic strain imparting treatment, a surface of the titanium material is provided with an inclined surface having a height difference of more than 0.1mm in a longitudinal direction of a plane orthogonal to the longitudinal direction. The step may be provided by cutting or the like described later, or may be formed during casting. In general, the cross-sectional shape of an ingot (ingot) after casting is unstable, and the surface thereof needs to be treated, and pretreatment is required before hot rolling. If the shape of the inclined surface is adjusted to a precise rectangular/circular shape so that the height difference is 0.1mm or less, not only the yield is reduced, but also a work load is generated. Therefore, it is important to define the shape of the inclined surface having a height difference exceeding 0.1mm in the longitudinal direction of the titanium material to suppress surface defects caused by the plastic strain applying treatment. The upper limit value side of the difference in level of the inclined surface may be appropriately selected in consideration of the plastic strain applying treatment, and the upper limit value of the difference in level of one inclined surface is preferably set to 8mm or less, more preferably 4mm or less. As shown in fig. 1, the height difference H is a distance between parallel lines PL1 and PL2 that are longest in a distance between two parallel lines PL1 and PL2 that are tangent to the contour line CL of the titanium billet surface and one
In the present invention, the height difference means an average value of the height differences of the inclined surfaces.
The inclination angle of the inclined surface is determined by the following method. That is, as shown in fig. 1, when the titanium material is observed on the
In the present invention, the inclination angle means an average value of inclination angles on a plurality of inclined surfaces.
The tilt angle will be described with reference to fig. 2A to 2C, taking a titanium blank as a slab as an example. In the titanium material shown in this example, the inclined surface is provided along the longitudinal direction on the above-mentioned longitudinal direction orthogonal surface. For example, as shown in fig. 2A, when the surface of a titanium material is cut by a square cutting tool, the
In the case where a particularly deep surface defect exists on the surface of the cast titanium material, the local inclined surface 25 (fig. 3) is also generated when at least one of the cutting and the grinding is partially performed on the periphery thereof in order to remove the surface defect. In this case, the inclination angle θ of the
The inclination angle of the inclined surface provided on the titanium blank is set to 45 DEG or less. If the inclination angle exceeds 45 °, surface defects are likely to occur in hot rolling after the plastic strain application treatment. In some cases, surface defects may be found in the titanium material for hot rolling after the plastic strain application treatment. This is because the stepped portion accompanied by the level difference existing on the surface of the titanium material is involved in the titanium material by plastic working, which causes surface defects. Specifically, when plastic strain is applied to the surface of the titanium material by hammering with a machining tool or the like on the
Since the surface defects in the titanium material for hot rolling caused by the rolling into the titanium billet can be detected by the penetrant testing, the surface defects can be removed again by grinding or the like after the plastic strain is applied. However, when the surface defect is removed by grinding or the like after the plastic strain is applied, the plastic strain applying layer at that portion is also removed at the same time. Therefore, the effect of plastic strain is impaired in this portion, and surface defects due to solidification structures are likely to occur on the surface of the hot-rolled material after hot rolling, resulting in an increase in cost due to an increase in the number of steps. In order to avoid such a problem, it is desirable that the shape of the inclined surface of the titanium material surface is adjusted in advance before the plastic strain applying treatment without causing surface defects in the plastic strain applying treatment.
Preferably, the surface of the titanium material is treated so that the number of the inclined surfaces is 4 to 40 per the length of the contour line of the perpendicular surface in the longitudinal direction of the 3000mm titanium material. From the viewpoint of bringing the shape after cutting or the like close to the shape before cutting or the like as much as possible and reducing the yield loss, the number of the inclined surfaces is preferably 4 or more, more preferably 8 or more, further preferably 12 or more, and further more preferably 16 or more as a lower limit. From the viewpoint of controlling the time required for cutting or the like within an industrially allowable time, the upper limit of the number of the inclined surfaces is preferably 40 or less, more preferably 30 or less, further preferably 24 or less, and further more preferably 20 or less. The contour lines of the long-dimension-direction orthogonal surfaces are captured as lines, and the lengths thereof are obtained.
Fig. 5A to 5C illustrate an example of the
Fig. 5D illustrates an example of the
The method of imparting plastic strain to the surface of the titanium billet may be appropriately selected. For example, the method described in International publication No. 2010/090352 can be used. There is a method of forming a plurality of dimples of a predetermined size by cold striking the surface of a titanium material with at least one of a steel tool having a tip shape with a radius of curvature of 3 to 30mm (3 to 30R) and a steel ball having a radius of curvature of 3 to 30mm (3 to 30R) to plastically deform the surface by a predetermined amount. The dimple of a predetermined size is formed on the surface of a dimple formed by cold plastic deformation, when the depth (height) of the dimples and the distance between the dimples are expressed by the average height (Wc) of the profile curve elements of waviness, the depth of the dimple, and the average length (WSm) of the profile curve elements of waviness in the surface property parameters described in JIS B0601(2001), it is preferable that Wc is in the range of 0.2 to 1.5mm, and WSm is in the range of 3 to 15 mm. More preferably, Wc is in the range of 0.3 to 1.0mm, and WSm is in the range of 4 to 10 mm.
The surface of the titanium material is subjected to plastic strain application treatment to obtain a titanium material for hot rolling. The hot-rolled titanium material is hot-rolled to obtain a hot-rolled material. The conditions and facilities of the hot rolling may be appropriately selected in consideration of the hot rolled material to be produced.
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