阅读说明：本技术 一种高强高韧铁镍铬基耐热合金及其制备方法 (High-strength high-toughness iron-nickel-chromium-based heat-resistant alloy and preparation method thereof ) 是由 秦学智 吴云胜 郭永安 王常帅 侯介山 周兰章 于 2020-07-14 设计创作，主要内容包括：一种高强高韧铁镍铬基耐热合金及其制备方法,成分按重量百分比含C 0.03～0.1％,Cr 14～17％,Mo 3～4％,Mn 1～2％,W 0～0.5％,Nb 0～1％,N 0～0.03％,B 0～0.002％,Zr 0～0.05％,Ni 35～38％,Y 0～0.05％,余量为Fe；方法为：(1)采用热解石墨、金属铁、金属铬、金属镍、金属钼、金属锰、金属钨、金属铌、金属锆、镍硼合金、铝钇合金、氮化铬作为原料；(2)将原料真空冶炼,浇铸制成铸锭；(3)在1000～1180℃进行锻造制成棒材,锻造比8～9；(4)锻造棒材在1000～1180℃进行压延轧制；(5)压延棒材在1040～1100℃进行热处理。本发明的产品具有较高的强度、优异的塑性和冲击性能,可以在不高于750℃的条件下长期使用。(The high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy comprises, by weight, 0.03-0.1% of C, 14-17% of Cr, 3-4% of Mo, 1-2% of Mn, 0-0.5% of W, 0-1% of Nb, 0-0.03% of N, 0-0.002% of B, 0-0.05% of Zr, 35-38% of Ni, 0-0.05% of Y and the balance of Fe; the method comprises the following steps: (1) pyrolytic graphite, metallic iron, metallic chromium, metallic nickel, metallic molybdenum, metallic manganese, metallic tungsten, metallic niobium, metallic zirconium, nickel-boron alloy, aluminum-yttrium alloy and chromium nitride are used as raw materials; (2) vacuum smelting the raw materials, and casting to prepare a cast ingot; (3) forging the mixture at 1000-1180 ℃ to prepare a bar material, wherein the forging ratio is 8-9; (4) rolling and rolling the forged bar at 1000-1180 ℃; (5) and carrying out heat treatment on the rolled bar at 1040-1100 ℃. The product of the invention has higher strength, excellent plasticity and impact property, and can be used for a long time under the condition of not higher than 750 ℃.)

1. The high-strength high-toughness iron-nickel-chromium-based heat-resistant alloy is characterized by comprising, by weight, 0.03-0.1% of C, 14-17% of Cr, 3-4% of Mo, 1-2% of Mn, 0-0.5% of W, 0-1% of Nb, 0-0.03% of N, 0-0.002% of B, 0-0.05% of Zr, 35-38% of Ni, 0-0.05% of Y and the balance of Fe and unavoidable impurities; the tensile strength of the material at 750 ℃ is more than or equal to 265MPa, the yield strength is more than or equal to 137MPa, the elongation is more than or equal to 40 percent, and the reduction of area is more than or equal to 60 percent.

2. The Fe-Ni-Cr-based heat-resistant alloy according to claim 1, wherein the composition comprises, by weight, 0.04 to 0.09% of C, 14 to 17% of Cr, 3 to 3.5% of Mo, 1.2 to 1.8% of Mn, 0 to 0.2% of W, 0.1 to 0.5% of Nb, 0 to 0.02% of N, 0.001 to 0.002% of B, 0 to 0.02% of Zr, 35 to 37% of Ni, 0 to 0.02% of Y, and the balance of Fe and unavoidable impurities; the tensile strength of the material at 750 ℃ is more than or equal to 275MPa, the yield strength is more than or equal to 137MPa, the elongation is more than or equal to 45 percent, and the reduction of area is more than or equal to 65 percent.

3. The preparation method of the high-strength high-toughness iron-nickel-chromium-based heat-resistant alloy according to claim 1 is characterized by comprising the following steps of:

(1) pyrolytic graphite, metallic iron, metallic chromium, metallic nickel, metallic molybdenum and metallic manganese are used as raw materials; when the high-strength and high-toughness iron-nickel-chromium-based heat-resistant alloy contains tungsten, niobium, zirconium, boron, yttrium or nitrogen, metal tungsten, metal niobium, metal zirconium, nickel-boron alloy, aluminum-yttrium alloy or chromium nitride are respectively adopted as the addition raw materials, and the addition raw materials and pyrolytic graphite, metal iron, metal chromium, metal nickel, metal molybdenum and metal manganese are jointly adopted as the raw materials;

(2) carrying out vacuum smelting on the raw materials according to the components, and then casting to prepare an ingot; when the raw materials contain the aluminum yttrium alloy, the Al forms inevitable impurities in the smelting process;

(3) forging the cast ingot at 1000-1180 ℃ to prepare a bar material, wherein the forging ratio is 8-9;

(4) rolling and rolling the forged bar at 1000-1180 ℃ to prepare a rolled bar;

(5) and (3) carrying out heat treatment on the rolled bar at 1040-1100 ℃ for 30-120 min, and carrying out air cooling or water cooling to normal temperature to prepare the high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy.

4. The method for preparing the high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy according to claim 3, wherein in the step (2), the vacuum smelting condition is that the vacuum degree is less than or equal to 1 Pa.

5. The method for preparing the high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy according to claim 3, wherein in the step (3), the average grain size of the forged bar is 4-8 grades.

6. The method for preparing the high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy according to claim 3, wherein in the step (4), the rolling is performed for 5-9 times, and the ratio of the diameter of the rolled bar to the diameter of the heat-treated bar is 1 (4-5).

7. The method for preparing the high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy according to claim 3, wherein in the step (4), the average grain size of the rolled bar is 10-14 grades.

8. The preparation method of the high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy according to claim 3, wherein in the step (5), the average grain size of the high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy is 4-6 grades.

9. The application of the high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy disclosed by claim 1 to manufacturing of thin-wall pipes for nuclear power plants with the working temperature of 350-750 ℃.

Technical Field

The invention belongs to the technical field of heat-resistant alloy materials, and particularly relates to a high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy and a preparation method thereof.

Background

The development of the nuclear power in the world can be divided into four generations, namely a prototype reactor power station, a large commercial nuclear power station, an advanced light water reactor nuclear power station (such as AP1000, EPR and the like) and 6 reactor type nuclear power stations to be developed (such as a molten salt reactor, a gas-cooled fast reactor, a sodium-cooled fast reactor and the like); the sodium-cooled fast reactor is the first choice of a fourth-generation advanced nuclear energy system, has extremely high safety, and can remarkably improve the utilization rate of uranium and greatly reduce nuclear waste.

Safety is the lifeline of nuclear power; the safety of the nuclear power station is not only a problem in the operation stage, but also exists in the design and construction stage of the nuclear power station; as a large and precise complete system, the safe operation of the nuclear power station needs the mutual matching of all key parts and the long-term normal operation, which puts strict requirements on the safety and reliability of nuclear power key equipment and materials. The components in the reactor are various in types, complex in structure and high in precision requirement, and are required to bear tests such as high temperature, neutron radiation, coolant corrosion and the like; thus, the general principle of selecting materials for the components in the stack is generally: the strength is properly high, the plasticity and toughness are good, and the shock resistance and fatigue resistance can be realized; the neutron absorption interface, the neutron capture cross section and the induced radioactivity are small; the coating is resistant to irradiation, corrosion and good in compatibility with a coolant; large thermal conductivity and small thermal expansion coefficient; good welding and machining process performance.

For example, a certain new nuclear power plant pipe requires a parent material with high strength and excellent plasticity, namely tensile strength and yield strength at 750 ℃ are respectively higher than 265MPa and 137MPa, elongation is higher than 35%, and reduction of area is more than 60%. Generally, the materials satisfying the harsh condition can only be solid solution strengthening type deformation heat-resistant alloys, and only 22 of the more than 160 heat-resistant alloys recorded in the Chinese high-temperature alloy handbook are solid solution strengthening type deformation alloys; among the 18 alloys, the alloy takes Ni or Co as a matrix, contains high Cr + W + Mo elements (more than or equal to 25 wt.%), has poor economy and is not beneficial to commercialization of future fast reactor; moreover, the alloys have high hardness and difficult deformation, are easy to precipitate harmful TCP phases such as sigma, mu or Laves and the like, seriously damage the structural or performance stability of the alloys in a long service period, and further threaten the reliability and safety of the whole nuclear power system; the other 4 alloys take iron, nickel and chromium as matrixes, but cannot be used for manufacturing certain novel nuclear power station pipe fittings due to insufficient strength and plasticity or unstable structure and performance; therefore, the development of new alloys is of great significance.

Disclosure of Invention

The invention aims to provide a high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy and a preparation method thereof, wherein Fe, Ni and Cr are used as matrix elements, and the proportion of C, N, Nb, Mn and other elements is controlled and adjusted to prepare a thin-wall pipe fitting with excellent strength and toughness and working temperature below 750 ℃.

The high-strength high-toughness iron-nickel-chromium-based heat-resistant alloy comprises, by weight, 0.03-0.1% of C, 0-17% of Cr14, 3-4% of Mo, 1-2% of Mn, 0-0.5% of W, 0-1% of Nb, 0-0.03% of N, 0-0.002% of B, 0-0.05% of Zr, 35-38% of Ni, 0-0.05% of Y, and the balance of Fe and unavoidable impurities; the tensile strength of the material at 750 ℃ is more than or equal to 265MPa, the yield strength is more than or equal to 137MPa, the elongation is more than or equal to 40 percent, and the reduction of area is more than or equal to 60 percent.

The high-strength high-toughness iron-nickel-chromium-based heat-resistant alloy comprises, by weight, 0.04-0.09% of C, 0-17% of Cr14, 3-3.5% of Mo, 1.2-1.8% of Mn, 0-0.2% of W, 0.1-0.5% of Nb, 0-0.02% of N, 0.001-0.002% of B, 0-0.02% of Zr, 35-37% of Ni, 0-0.02% of Y, and the balance of Fe and unavoidable impurities; the tensile strength of the material at 750 ℃ is more than or equal to 275MPa, the yield strength is more than or equal to 137MPa, the elongation is more than or equal to 45 percent, and the reduction of area is more than or equal to 65 percent.

The inevitable impurities of the high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy comprise, by weight, not more than 0.01% of O, not more than 0.001% of Pb, not more than 0.0001% of Bi, not more than 0.005% of As, not more than 0.01% of Sb, not more than 0.005% of Sn, not more than 0.1% of Al, not more than 0.1% of Co, not more than 0.2% of Si, not more than 0.1% of Cu, not more than 0.015% of P and not more than.

The preparation method of the high-strength high-toughness iron-nickel-chromium-based heat-resistant alloy comprises the following steps of:

1. pyrolytic graphite, metallic iron, metallic chromium, metallic nickel, metallic molybdenum and metallic manganese are used as raw materials; when the high-strength and high-toughness iron-nickel-chromium-based heat-resistant alloy contains tungsten, niobium, zirconium, boron, yttrium or nitrogen, metal tungsten, metal niobium, metal zirconium, nickel-boron alloy, aluminum-yttrium alloy or chromium nitride are respectively adopted as the addition raw materials, and the addition raw materials, pyrolytic graphite, metal iron, metal chromium, metal nickel, metal molybdenum and metal manganese are jointly used as the raw materials;

2. carrying out vacuum smelting on the raw materials according to the components, and then casting to prepare an ingot; when the raw materials contain the aluminum yttrium alloy, the Al forms inevitable impurities in the smelting process;

3. forging the cast ingot at 1000-1180 ℃ to prepare a bar material, wherein the forging ratio is 8-9;

4. rolling and rolling the heat-treated bar at 1000-1180 ℃ to prepare a rolled bar;

5. and (3) carrying out heat treatment on the rolled bar at 1040-1100 ℃ for 30-120 min, and carrying out air cooling or water cooling to normal temperature to prepare the high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy.

In the step 2, the vacuum smelting condition is that the vacuum degree is less than or equal to 1 Pa.

In the step 3, the average grain size of the forged bar is 4-8 grades.

In the step 4, the rolling is carried out for 5 to 9 passes, and the ratio of the diameter of the prepared rolled bar to the diameter of the heat-treated bar is 1 (4-5).

In the step 4, the average grain size of the rolled bar is 10-14 grades.

In the step 5, the average grain size of the high-strength and high-toughness iron-nickel-chromium-based heat-resistant alloy is 4-6 grades.

The high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy is used for manufacturing thin-wall pipes for nuclear power stations with the working temperature of 350-750 ℃.

The thin-wall pipe fitting of a certain nuclear power station is subjected to the effects of high temperature, multiple stress (dead weight, molten metal scouring, impact load, earthquake), corrosion, irradiation and the like in a service environment, and the comprehensive performance (such as tensile performance, impact performance and the like) can be continuously degraded along with the time; particularly, under the irradiation action, a large number of point defects and He atoms are generated in the pipe fitting alloy; he atom has small radius, is difficult to dissolve in a matrix, is not combined with other atoms, and is easy to migrate in the alloy under the action of stress; it gathers to the interface such as dislocation, phase boundary or grain boundary, etc. together with point defect, form He bubble, equivalent to hole or crackle; under the drive of free energy and internal stress of a system, He bubbles absorb surrounding point defects and He atoms grow and tend to be connected with each other, namely crack propagation, so that the pipe fitting alloy is subjected to swelling deformation or embrittlement; in this case, the self-weight, sodium liquid scouring, impact load or earthquake can be the cause, so that the crack continues to spread and finally the alloy is broken; in addition, under the action of stress, point defects are gathered along a favorable direction, so that dislocation directional climbing can be caused to generate creep deformation or creep deformation acceleration, and serious damage can be caused to the alloy; it can be seen that the pipe alloy needs to have as high a strength as possible, since the higher the strength, the greater the resistance to He bubble or crack formation, or if formed, the difficulty to grow and the smaller the size; the pipe alloy also needs to have as good plasticity as possible, since the higher the plasticity, the greater the resistance to crack propagation and the less likely it will propagate.

The pipe alloy has high strength and plasticity of a starting point, and has important significance for resisting various forms of tissue and performance degradation during service; through the optimization research of chemical components, a thermal deformation process, a heat treatment process and the like, the pipe alloy has the optimal comprehensive performance, so that the residual strength and plasticity of the alloy can still ensure the safety of the pipe (the design service life is 40 years) and the whole nuclear facility even if the alloy undergoes service degradation.

The principle of the invention is as follows:

c: proper amount of C improves the casting performance of the alloy, forms carbide with Cr, Mo, Nb and the like, improves the high-temperature strength of the alloy, and prevents grain boundary coarsening. When the C content exceeds 0.1%, the hot workability of the alloy is impaired;

cr: dissolved in austenite, and improves the high-temperature oxidation resistance and corrosion resistance of the alloy. In order to maintain sufficient high temperature oxidation resistance and corrosion resistance, a large Cr content is required; cr increases the thermal expansion coefficient and the instability of the structure of the alloy, so the content is not suitable to be too high;

mn: mn has the function of removing O. Mn improves the solid solubility of N, thereby being beneficial to a nitriding process; when the alloy reacts with N to form MnN, the alloy hardness is improved; mn also has the function of stabilizing austenite; excess Mn tends to form deleterious Laves phases;

mo: the atomic radius is large, and the alloy matrix has obvious solid solution strengthening effect;

w: in many superalloys, W, Mo appears simultaneously as a strengthening element; the atomic radii of the two are similar, but the weight of Mo atoms is only half of that of W atoms, so the strengthening efficiency of Mo is much higher than that of W; w is the most easily formed M₆C carbide, and Mo is the element most apt to form a mu phase; w, Mo proper matching can avoid M₆Excessive precipitation of C or mu phase can also make the strengthening efficiency of the C or mu phase be best exerted;

nb: the alloy has strong solid solution strengthening effect, is combined with C, N to form NbC and NbN, can pin grain boundaries, plays a role in stabilizing alloy structure, reduces the growth rate of crystal grains at high temperature, and prevents the properties of the alloy such as impact and the like from being damaged or slightly damaged. Nb can also improve the radiation swelling resistance of the alloy and improve the compatibility of the alloy and a coolant. However, too high Nb easily causes element segregation and easily forms Laves or phases, which damages alloy properties;

n: in most superalloys (especially cast superalloys), N is considered a detrimental element, the lower the control the better. Some wrought superalloys, however, contain trace amounts of N, since N not only stabilizes M₂₃C₆Carbide delays coarsening, and can also stabilize the alloy gamma matrix and expand the stable existing temperature range of the matrix; moreover, N, Cr, Mn and Nb can be chemically synthesized into CrN, MnN and NbN, so that the hardness and strength of the alloy are improved; for example, the Fe-Ni-Cr-based solid solution strengthening deformation high-temperature alloys such as GH1016, GH1040, GH1131 and GH1139 contain N with the content of 0.1-0.45%; the content of N in the alloy is not suitable to be too high so as to ensure that the alloy has excellent plasticity;

b: strengthening grain boundary and delaying M₂₃C₆Coarsening carbide;too high a content will lower the melting point of the alloy;

zr: strengthening the crystal boundary, promoting the formation of MC carbide and having the function of pinning the crystal boundary; the content is too high to reduce the melting point of the alloy;

y: trace amount of Y can obviously improve the oxidation resistance and the corrosion resistance of the alloy, but is easy to form inclusions to pollute the alloy;

ni: the expanded austenite region of the matrix, which is the main element for forming and stabilizing austenite; ni reduces the diffusion rate of each element in the alloy and improves the hardenability; proper Ni can enable the alloy to have better heat resistance and corrosion resistance, higher strength and fatigue performance; ni is scarce and is an important strategic material, so that the Ni is used as little as possible or not used under the condition that the performance meets the requirement;

fe: the alloy has lower cost and good hot workability.

According to the invention, by optimizing the content of each alloy element, adverse effects are inhibited as much as possible, beneficial effects are exerted to the greatest extent, a desired alloy is obtained, and the alloy performance is obviously improved; the product of the invention has higher strength, excellent plasticity and impact property, and can be used for a long time under the condition of not higher than 750 ℃.

Drawings

FIG. 1 is a metallographic structure of a forged bar material in example 1 of the present invention;

FIG. 2 is a metallographic structure chart of a rolled bar in example 1 of the present invention;

FIG. 3 is a metallographic structure diagram of a high-strength high-toughness Fe-Ni-Cr-based heat-resistant alloy in example 1 of the present invention.

Detailed description of the preferred embodiments

The equipment adopted for observing the metallographic structure in the embodiment of the invention is an inverted universal material microscope made by ZEISS Axiovert 200MAT of Germany.

The diameter of the high-strength and high-toughness Fe-Ni-Cr-based heat-resistant alloy in the embodiment of the invention is 12-18 mm.

The metal nickel adopted in the embodiment of the invention is electrolytic nickel with the trade mark Ni9990, the metal chromium with the trade mark JGr99-A, the metal molybdenum with the trade mark Mo-1/Mo-2(GB/T3462-82), the metal tungsten with the trade mark W-1(GB/T3459-82), the metal niobium with the trade mark Nb-1(GB/T6896-86), and the pyrolytic graphite is an SDP graphite electrode (GB/T1426-1978).

The impurity weight content of the metal zirconium, the nickel boron alloy, the chromium nitride and the aluminum yttrium alloy adopted in the embodiment of the invention is less than 1%.

The nickel-boron alloy adopted in the embodiment of the invention contains B15.634% by weight.

The chromium nitride alloy adopted in the embodiment of the invention contains N5 percent by weight.

The aluminum yttrium alloy adopted in the embodiment of the invention contains Y84% by weight.

SISC-IAS image analysis software is adopted for measuring the average grain size in the embodiment of the invention, and the standard is GB/T6394 metal average grain size determination method.

The standard for measuring tensile strength, yield strength, elongation and reduction of area in the examples of the present invention was GB/T228.2-2015.

The inevitable impurities in the embodiment of the invention are less than or equal to 0.01 percent of O, less than or equal to 0.001 percent of Pb, less than or equal to 0.0001 percent of Bi, less than or equal to 0.005 percent of As, less than or equal to 0.01 percent of Sb, less than or equal to 0.005 percent of Sn, less than or equal to 0.1 percent of Al, less than or equal to 0.1 percent of Co, less than or equal to 0.2 percent of Si, less than or equal to 0.1 percent of Cu, less than or equal.

The vacuum smelting steps in the embodiment of the invention are as follows:

1. putting pyrolytic graphite, metallic iron, metallic chromium, metallic nickel, metallic molybdenum and metallic manganese into a vacuum induction furnace, and heating the pyrolytic graphite, the metallic iron, the metallic chromium, the metallic nickel, the metallic molybdenum and the metallic manganese under a vacuum condition until the pyrolytic graphite, the metallic iron, the metallic chromium, the metallic nickel, the metallic molybdenum and the metallic manganese are completely molten;

2. stirring and refining for 5-20 min to finish vacuum smelting;

3. when the high-strength high-toughness iron-nickel-chromium-based heat-resistant alloy contains tungsten or niobium, respectively adopting metal tungsten or metal niobium as an additive raw material, and putting the metal tungsten or metal niobium together with pyrolytic graphite, metal iron, metal chromium, metal nickel, metal molybdenum and metal manganese into a vacuum induction furnace;

4. when the high-strength and high-toughness iron-nickel-chromium-based heat-resistant alloy contains zirconium, boron, yttrium or nitrogen, respectively adopting metal zirconium, nickel-boron alloy, aluminum-yttrium alloy or chromium nitride as the addition raw materials, after the stirring and refining in the step 2 are finished, adding the metal zirconium, nickel-boron alloy, aluminum-yttrium alloy or chromium nitride into the melt which is finished with the refining, and continuously stirring for 1-5 min to finish the vacuum smelting;

5. when the high-strength high-toughness iron-nickel-chromium-based heat-resistant alloy contains boron and more than one element of zirconium, yttrium and nitrogen, taking a nickel-boron alloy as a first addition raw material, respectively taking metal zirconium, an aluminum-yttrium alloy and/or chromium nitride as a second addition raw material, after the stirring and refining in the step 2 are finished, adding the nickel-boron alloy into the melt which is finished with the refining, continuously stirring for 1-5 min, and then adding the second addition raw material; when the second addition raw material is an alloy, adding the second addition raw material, and stirring for 1-5 min to finish vacuum smelting; when the second addition raw material is more than two alloys, adding one alloy and stirring for 1-5 min to finish vacuum smelting.

In the embodiment of the invention, a muffle furnace is adopted for heat treatment.

In the embodiment of the invention, an air hammer is used for forging.

In the embodiment of the invention, a transverse rolling mill is used for rolling.

The following are preferred embodiments of the present invention.

The room temperature impact energy (V-notch) of the high-strength and high-toughness iron-nickel-chromium-based heat-resistant alloy of embodiments 1 to 12 of the present invention is: 364J, 358J, 332J, 356J, 380J, 378J, 345J, 294J, 390J, 275J, 360J, and 351J.