High-nitrogen austenitic stainless steel and preparation method thereof

Abstract

The invention discloses high-nitrogen austenitic stainless steel and a preparation method thereof, and the preparation method comprises the following steps: (1) smelting and die casting raw materials to obtain a stainless steel cast ingot; (2) performing heat treatment on the stainless steel cast ingot, wherein the heat treatment is performed according to a preset temperature curve; (3) pre-deforming the stainless steel cast ingot subjected to heat treatment to obtain a pre-deformed blank; (4) carrying out hot working on the pre-deformed blank to obtain a stainless steel plate; and (5) the stainless steel plate is subjected to aftertreatment, and the high-nitrogen austenitic stainless steel is obtained. By implementing the method, hot working cracks can be avoided, and the prepared high-nitrogen austenitic stainless steel has good size uniformity and mechanical property.

Description

Technical Field

[0001] The invention relates to the technical field, and in particular to a high-nitrogen austenitic stainless steel and a preparation method thereof. Background Art

[0002] High nitrogen austenitic stainless steel uses sufficient nitrogen to replace expensive nickel, which can not only form a stable austenite phase area, but also greatly expand the range of austenite. At the same time, it uses the solid solution strengthening effect of nitrogen to further improve its comprehensive mechanical properties. At present, high nitrogen austenitic stainless steel has been widely used in chemical, petroleum and nuclear industries due to its excellent corrosion resistance, wear resistance and low-temperature mechanical properties. The nitrogen content of high nitrogen austenitic stainless steel is above 0.4%. With the improvement of smelting technology, the nitrogen content of industrially produced high nitrogen austenitic stainless steel can reach 0.8% to 1.0%. However, the addition of nitrogen will reduce the high-temperature thermoplasticity of austenitic stainless steel. With the increase of nitrogen content, the work hardening of austenitic stainless steel is aggravated, and the deformation resistance during hot working is increased, which damages its hot forming ability and causes cracking of the blank during hot working, seriously affecting its application. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing high nitrogen austenitic stainless steel, which can avoid the generation of hot working cracks and ensure a stable hot working process of the high nitrogen austenitic stainless steel.

[0004] The technical problem that the present invention also solves is to provide a high nitrogen austenitic stainless steel with good hot working performance, and the obtained high nitrogen austenitic stainless steel has good dimensional uniformity and mechanical properties.

[0005] In order to solve the above problems, the present invention discloses a method for preparing high nitrogen austenitic stainless steel, comprising the following steps:

[0006] (1) smelting and die casting the raw materials to obtain stainless steel ingots;

[0007] (2) heat treating the stainless steel ingot, wherein the heat treatment is performed according to a preset temperature curve;

[0008] (3) pre-deforming the stainless steel ingot after heat treatment to obtain a pre-deformed body;

[0009] (4) hot working the pre-deformed body to obtain a stainless steel plate;

[0010] (5) Post-processing the stainless steel sheet to obtain the high nitrogen austenitic stainless steel.

[0011] As an improvement of the above technical solution, the preset temperature curve in step (2) includes:

[0012] The temperature is raised from room temperature to 500°C to 600°C at a rate of 300°C / h to 350°C / h;

[0013] The temperature is increased from 500℃~600℃ to 800℃~980℃, and the heating rate is 400℃ / h~450℃ / h;

[0014] The temperature is raised from 800℃~980℃ to 1210℃~1250℃, and the heating rate is 150℃ / h~250℃ / h;

[0015] Keep warm at 1210℃~1250℃ for 1h~5h.

[0016] As an improvement of the above technical solution, the pre-deformation in step (3) is low-temperature rolling, and the processing temperature range of the pre-deformation is 50°C to 400°C;

[0017] After the pre-deformation, the deformation amount of the pre-deformed blank is 10% to 30%.

[0018] As an improvement of the above technical solution, the hot working in step (4) is hot rolling, and the processing temperature range of the hot working is 1000° C. to 1200° C.;

[0019] After the hot working, the deformation amount of the high nitrogen austenitic stainless steel plate is 30% to 70%.

[0020] As an improvement of the above technical solution, the hot working is multi-stage and multi-pass hot rolling, the starting rolling temperature of the hot working is 1100°C to 1200°C, and the final rolling temperature is 1000°C to 1060°C.

[0021] As an improvement of the above technical solution, in the multi-stage and multi-pass hot rolling process, the deformation amount in the latter stage is greater than the deformation amount in the previous stage.

[0022] As an improvement of the above technical solution, the hot rolling includes four stages, each stage includes 2 to 5 passes, the deformation amount in the first stage is 11.8% to 12.5%, the deformation amount in the second stage is 13.5% to 14.4%, the deformation amount in the third stage is 14.2% to 15.3%, and the deformation amount in the fourth stage is 18.2% to 19.1%.

[0023] As an improvement of the above technical solution, the components of the high nitrogen austenitic stainless steel raw material include, by mass percentage: C≤0.04%, Si≤0.3%, Mn 15%~20%, Ni≤2%, Cr 22%~24%, N0.5%~0.8%, Mo≤3%, and the remainder is Fe and unavoidable impurities.

[0024] As an improvement of the above technical solution, the components of the high nitrogen austenitic stainless steel raw material include, by mass percentage, C 0.015% to 0.023%, Si 0.2% to 0.25%, Mn 18.5% to 19.5%, Ni1.53% to 1.57%, Cr 22.79% to 23.53%, N 0.6% to 0.7%, Mo 2.60% to 2.71%, the remainder being Fe and unavoidable impurities, and Cr / N=33 to 38.

[0025] Correspondingly, the present invention also discloses a high-nitrogen austenitic stainless steel, which is prepared by the above-mentioned preparation method.

[0026] The implementation of the present invention has the following beneficial effects:

[0027] 1. The preparation method of high nitrogen austenitic stainless steel provided by the present invention first performs heat treatment with a preset temperature curve before the hot working process to reduce element segregation and precipitation of metal intermediate phases, then introduces appropriate defects through pre-deformation to regulate the precipitation behavior of Cr2N in the high nitrogen austenitic stainless steel, and finally eliminates deformation defects through hot working. The deformation resistance during the hot working process is small, and the surface cracks or edge cracks generated are significantly reduced.

[0028] 2. The present invention optimizes the alloy composition of high nitrogen austenitic stainless steel, reduces element segregation and precipitation of metal intermediate phases, and improves the hot working performance of high nitrogen austenitic stainless steel by combining heat treatment and pre-deformation processes.

[0029] 3. The hot processing of the present invention adopts multi-stage and multi-pass hot rolling. By controlling the total deformation and the deformation in each stage, the thickness accuracy of the stainless steel plate is effectively controlled, and finally high-nitrogen austenitic stainless steel with high precision and high surface quality is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a process flow chart of the preparation of high nitrogen austenitic stainless steel of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0032] See also Figure 1 The present invention provides a method for preparing high nitrogen austenitic stainless steel, comprising the following steps:

[0033] S100, smelting and die casting the raw materials to obtain a stainless steel ingot;

[0034] The components of the high nitrogen austenitic stainless steel raw material include, by mass percentage: C≤0.04%, Si≤0.3%, Mn 15%-20%, Ni≤2%, Cr 22%-24%, N 0.5%-0.8%, Mo≤3%, and the balance is Fe and unavoidable impurities.

[0035] N can not only form a stable austenite phase, but also expand the range of austenite. The addition of N can effectively improve the toughness, fatigue performance and wear resistance of high nitrogen austenitic stainless steel, but excessive N will cause the high nitrogen austenitic stainless steel to precipitate harmful nitrides, which is not conducive to the improvement of mechanical properties and corrosion resistance. Therefore, N is controlled to be 0.5% to 0.8%, preferably, N is 0.6% to 0.7%.

[0036] Cr will form ferrite while hindering the expansion of austenite phase, and is usually combined with elements such as Ni, Mn, N, and C to obtain a single austenite structure under high Cr conditions. Moreover, Cr and N are easy to combine to form compounds such as CrN and Cr2N, which destroy the toughness and plasticity of the material. Therefore, Cr is controlled to be 22% to 24%, preferably, Cr is 22.79% to 23.53%, and Cr / N is controlled to be 33 to 38. If Cr / N is less than 33, the precipitation strengthening effect is not obvious; if Cr / N is greater than 38, the corrosion resistance of high nitrogen austenitic stainless steel deteriorates.

[0037] In high nitrogen austenitic stainless steel, sufficient Ni can completely eliminate the residual ferrite in the material and significantly reduce the tendency of ferrite to form, thereby obtaining a single austenitic structure. However, the price of Ni is relatively high. In addition, Ni will accelerate the precipitation of nitrides, affecting the performance of stainless steel. Therefore, the Ni content is controlled to be no more than 2%, preferably, Ni is 1.53% to 1.57%.

[0038] Mn can stabilize the austenite structure and can work together with Cr to increase the solubility of N in steel. The Mn content is controlled to be 15% to 20%, preferably, the Mn content is 18.5% to 19.5%.

[0039] Too high a C content will result in precipitation of intergranular carbides, which will affect the performance. Therefore, the C content is controlled not to exceed 0.04%, and preferably, the C content is 0.015% to 0.023%.

[0040] The addition of Si can improve the acid resistance of steel, but too high Si content will lead to the increase of ferrite phase. Therefore, Si is controlled to be ≤ 0.3%, preferably, Si is 0.2% to 0.25%.

[0041] The addition of Mo can improve the pitting corrosion resistance and crevice corrosion resistance of stainless steel. Mo is controlled to be ≤ 3%, preferably, Mo is 2.60% to 2.71%.

[0042] The present invention controls the content of Cr, Mn, Mo and other elements by adjusting the alloy elements, promotes the dissolution and interaction of N, and forms a single austenite structure, especially controls the ratio of Cr to N, and ensures that the high nitrogen austenitic stainless steel has good hot working performance. In addition, to achieve the above technical effects, it is also necessary to cooperate with the subsequent processing of the present invention:

[0043] S200, heat treating the stainless steel ingot, wherein the heat treatment is performed according to a preset temperature curve;

[0044] The preset temperature curve includes:

[0045] The temperature is raised from room temperature to 500°C to 600°C at a rate of 300°C / h to 350°C / h;

[0046] The temperature is increased from 500℃~600℃ to 800℃~980℃, and the heating rate is 400℃ / h~450℃ / h;

[0047] The temperature is raised from 800℃~980℃ to 1210℃~1250℃, and the heating rate is 150℃ / h~250℃ / h;

[0048] Keep warm at 1210℃~1250℃ for 1h~5h.

[0049] The present invention performs heat treatment by presetting a temperature curve. Compared with directly heat treating the stainless steel ingot in the range of 1210℃~1250℃, the heat treatment method of the present invention can avoid excessive grain growth and excessive oxidation of the ingot under the premise of ensuring that the element segregation is fully reduced and the dendrite structure is fully ablated, thereby achieving the purpose of fully homogenizing the composition and organization and improving the subsequent hot working performance. In the range of room temperature to 500℃~600℃, the heating rate is strictly controlled to avoid temperature differences caused by too fast heating speed and to avoid the generation of cracks; in the process of heating from 500℃~600℃ to 800℃~980℃, the heating rate can be appropriately increased to improve production efficiency; in the process of heating from 800℃~980℃ to 1210℃~1250℃, the uniformity of the austenite structure can be improved and the heating rate can be appropriately reduced.

[0050] S300, pre-deforming the stainless steel ingot after heat treatment to obtain a pre-deformed body;

[0051] The pre-deformation is low temperature rolling, and the processing temperature range of the pre-deformation is 50°C to 400°C;

[0052] After the pre-deformation, the deformation amount of the pre-deformed blank is 10% to 30%.

[0053] Appropriate defects are introduced through pre-deformation to promote the recrystallization recovery of high nitrogen austenitic stainless steel during hot working.

[0054] S400, hot processing the pre-deformed body to obtain a stainless steel plate;

[0055] The hot working is hot rolling, and the working temperature range of the hot working is 1000° C. to 1200° C.;

[0056] After the hot working, the deformation amount of the high nitrogen austenitic stainless steel plate is 30% to 70%.

[0057] During the hot rolling process, the coarse grains are broken under the action of pressure, the casting defects inside the alloy disappear, the cast alloy structure is transformed into a deformed structure, and the processing performance of the alloy is greatly improved.

[0058] In a preferred embodiment, the hot working is multi-stage multi-pass hot rolling, the starting rolling temperature of the hot working is 1100°C to 1200°C, and the final rolling temperature is 1000°C to 1060°C. Preferably, the starting rolling temperature of the hot working is 1120°C to 1180°C, and the final rolling temperature is 1020°C to 1050°C. It should be noted that limiting the final rolling temperature to the above range can avoid edge cracks during the hot rolling process.

[0059] More preferably, the deformation amount in the latter stage of the hot rolling is greater than the deformation amount in the former stage.

[0060] Specifically, the hot rolling includes four stages, each stage includes 2 to 5 passes, the deformation amount in the first stage is 11.8% to 12.5%, the deformation amount in the second stage is 13.5% to 14.4%, the deformation amount in the third stage is 14.2% to 15.3%, and the deformation amount in the fourth stage is 18.2% to 19.1%.

[0061] By controlling the deformation amount at different stages of hot rolling, we can ensure that the grains are fully broken and the coordinated deformation of the crystals is achieved, while avoiding the obstruction of dislocation movement at the grain boundaries. Combined with the composition, heat treatment and pre-deformation process of the high-nitrogen austenitic stainless steel raw materials, the thickness of the stainless steel sheet can be more accurately controlled. The resulting stainless steel sheet has good thickness uniformity and a dense organizational structure.

[0062] S500, post-processing the stainless steel plate to obtain the high nitrogen austenitic stainless steel.

[0063] In one embodiment, the post-treatment includes keeping the stainless steel sheet at 960°C to 990°C for 40min to 90min, and cooling it after it is taken out of the furnace. The cooling method can be air cooling, wind cooling or water cooling. In one embodiment, the stainless steel sheet is water-cooled to room temperature, and the average cooling rate is ≥100°C / s. In addition, according to different product performance requirements, cold rolling, pickling and other treatments can also be performed to finally obtain a finished product.

[0064] The present invention also provides a high nitrogen austenitic stainless steel, which is hot-processed by the above-mentioned hot processing method. The high nitrogen austenitic stainless steel has good hot processing performance, and the obtained high nitrogen austenitic stainless steel has good corrosion resistance and mechanical properties.

[0065] The present invention will be further described below with specific embodiments:

[0066] Example 1

[0067] This embodiment provides a method for preparing high nitrogen austenitic stainless steel, comprising the following steps:

[0068] S100, smelting and die casting the raw materials to obtain a stainless steel ingot;

[0069] The components of the high nitrogen austenitic stainless steel raw material include, by mass percentage, 0.03% C, 0.28% Si, 16.5% Mn, 1.8% Ni, 23.7% Cr, 0.75% N, 2.8% Mo, and the balance is Fe and inevitable impurities.

[0070] S200, heat treating the stainless steel ingot, wherein the heat treatment is performed according to a preset temperature curve;

[0071] The preset temperature curve includes:

[0072] Heating from room temperature to 1230°C at a rate of 400°C / h;

[0073] Keep warm at 1230℃ for 3h.

[0074] S300, pre-deforming the stainless steel ingot after heat treatment to obtain a pre-deformed body;

[0075] The pre-deformation is low temperature rolling, and the deformation amount of the stainless steel ingot is controlled to be 20% at 200°C.

[0076] S400, hot processing the pre-deformed body to obtain a stainless steel plate;

[0077] The hot working is multi-stage and multi-pass hot rolling, with the starting rolling temperature being 1150° C. and the final rolling temperature being 1020° C. The hot rolling includes four stages, each stage includes 2 passes, and the deformation amount in each stage is 13.5%.

[0078] S500, water-cooling the stainless steel plate to room temperature to obtain the high nitrogen austenitic stainless steel.

[0079] Example 2

[0080] This embodiment provides a method for preparing high nitrogen austenitic stainless steel, comprising the following steps:

[0081] S100, smelting and die casting the raw materials to obtain a stainless steel ingot;

[0082] The components of the high nitrogen austenitic stainless steel raw material include, by mass percentage, 0.02% C, 0.23% Si, 19% Mn, 1.55% Ni, 23.14% Cr, 0.65% N, 2.68% Mo, and the remainder is Fe and unavoidable impurities.

[0083] S200, heat treating the stainless steel ingot, wherein the heat treatment is performed according to a preset temperature curve;

[0084] The preset temperature curve includes:

[0085] The temperature was raised from room temperature to 900°C at a rate of 400°C / h;

[0086] 900℃ to 1230℃, heating rate is 360℃ / h;

[0087] Keep warm at 1230℃ for 3h.

[0088] S300, pre-deforming the stainless steel ingot after heat treatment to obtain a pre-deformed body;

[0089] The pre-deformation is low temperature rolling, and the deformation amount of the stainless steel ingot is controlled to be 20% at 200°C.

[0090] S400, hot processing the pre-deformed body to obtain a stainless steel plate;

[0091] The hot working is multi-stage and multi-pass hot rolling, with the starting rolling temperature being 1150° C. and the final rolling temperature being 1020° C. The hot rolling includes four stages, each stage includes 2 passes, and the deformation amount in each stage is 13.5%.

[0092] S500, water-cooling the stainless steel plate to room temperature to obtain the high nitrogen austenitic stainless steel.

[0093] Example 3

[0094] This embodiment provides a method for preparing high nitrogen austenitic stainless steel, comprising the following steps:

[0095] S100, smelting and die casting the raw materials to obtain a stainless steel ingot;

[0096] The components of the high nitrogen austenitic stainless steel raw material include, by mass percentage, 0.02% C, 0.23% Si, 19% Mn, 1.55% Ni, 23.14% Cr, 0.65% N, 2.68% Mo, and the remainder is Fe and unavoidable impurities.

[0097] S200, heat treating the stainless steel ingot, wherein the heat treatment is performed according to a preset temperature curve;

[0098] The preset temperature curve includes:

[0099] Heating from room temperature to 580°C at a rate of 330°C / h;

[0100] The temperature was raised from 580°C to 900°C at a rate of 400°C / h;

[0101] The temperature was raised from 900°C to 1210°C at a rate of 180°C / h;

[0102] Keep warm at 1210℃ for 2.5h.

[0103] S300, pre-deforming the stainless steel ingot after heat treatment to obtain a pre-deformed body;

[0104] The pre-deformation is low temperature rolling, and the deformation amount of the stainless steel ingot is controlled to be 20% at 200°C.

[0105] S400, hot processing the pre-deformed body to obtain a stainless steel plate;

[0106] The hot working is multi-stage and multi-pass hot rolling, with the starting rolling temperature being 1150° C. and the final rolling temperature being 1020° C. The hot rolling includes four stages, each stage includes 2 passes, and the deformation amount in each stage is 13.5%.

[0107] S500, water-cooling the stainless steel plate to room temperature to obtain the high nitrogen austenitic stainless steel.

[0108] Example 4

[0109] This embodiment provides a method for preparing high nitrogen austenitic stainless steel, comprising the following steps:

[0110] S100, smelting and die casting the raw materials to obtain a stainless steel ingot;

[0111] The components of the high nitrogen austenitic stainless steel raw material include, by mass percentage, 0.018% C, 0.22% Si, 19.1% Mn, 1.54% Ni, 22.92% Cr, 0.68% N, 2.65% Mo, and the remainder is Fe and unavoidable impurities.

[0112] S200, heat treating the stainless steel ingot, wherein the heat treatment is performed according to a preset temperature curve;

[0113] The preset temperature curve includes:

[0114] Heating from room temperature to 550°C at a rate of 320°C / h;

[0115] The temperature was raised from 550°C to 950°C at a rate of 420°C / h;

[0116] Heating from 950°C to 1230°C at a rate of 160°C / h;

[0117] Keep warm at 1230℃ for 3h.

[0118] S300, pre-deforming the stainless steel ingot after heat treatment to obtain a pre-deformed body;

[0119] The pre-deformation is low temperature rolling, and the deformation amount of the stainless steel ingot is controlled to be 20% at 200°C.

[0120] S400, hot processing the pre-deformed body to obtain a stainless steel plate;

[0121] The hot working is multi-stage and multi-pass hot rolling, with the starting rolling temperature being 1150° C. and the final rolling temperature being 1020° C. The hot rolling includes four stages, each of which includes two passes, with the deformation amount of the first stage being 12.1%, the deformation amount of the second stage being 13.8%, the deformation amount of the third stage being 14.9%, and the deformation amount of the fourth stage being 18.7%.

[0122] S500, water-cooling the stainless steel plate to room temperature to obtain the high nitrogen austenitic stainless steel.

[0123] Comparative Example 1

[0124] This comparative example provides a method for preparing high nitrogen austenitic stainless steel, comprising the following steps:

[0125] S100, smelting and die casting the raw materials to obtain a stainless steel ingot;

[0126] The high nitrogen austenitic stainless steel raw material comprises the following components by mass percentage: C 0.05%, Si 0.3%, Mn 17.8%, Ni 2.4%, Cr 24%, N 0.58%, Mo 3%, and the balance is Fe and unavoidable impurities.

[0127] S200, heat treating the stainless steel ingot, wherein the heat treatment is performed according to a preset temperature curve;

[0128] The preset temperature curve includes:

[0129] Heating from room temperature to 1230°C at a rate of 400°C / h;

[0130] Keep warm at 1230℃ for 3h.

[0131] S300, performing heat treatment on the heat-treated stainless steel ingot to obtain a stainless steel plate;

[0132] The hot working is multi-stage and multi-pass hot rolling, with the starting rolling temperature being 1150° C. and the final rolling temperature being 980° C. The hot rolling includes four stages, each stage including 2 passes, and the deformation amount of each stage is 13.5%.

[0133] S400, water-cooling the stainless steel plate to room temperature to obtain the high nitrogen austenitic stainless steel.

[0134] The high nitrogen austenitic stainless steel obtained in Examples 1 to 4 and Comparative Example 1 was tested for performance, and the specific results are as follows:

[0135]

[0136] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A method for preparing high nitrogen austenitic stainless steel, characterized in that: The following steps are involved: (1) smelting and die casting the raw materials to obtain stainless steel ingots; (2) heat treating the stainless steel ingot, wherein the heat treatment is performed according to a preset temperature curve; (3) pre-deforming the stainless steel ingot after heat treatment to obtain a pre-deformed body; (4) hot working the pre-deformed body to obtain a stainless steel plate; (5) Post-processing the stainless steel sheet to obtain the high nitrogen austenitic stainless steel.

2. The method for preparing high nitrogen austenitic stainless steel according to claim 1, characterized in that: The preset temperature curve in step (2) includes: The temperature is raised from room temperature to 500°C to 600°C at a rate of 300°C / h to 350°C / h; The temperature is increased from 500℃~600℃ to 800℃~980℃, and the heating rate is 400℃ / h~450℃ / h; The temperature is raised from 800℃~980℃ to 1210℃~1250℃, and the heating rate is 150℃ / h~250℃ / h; Keep warm at 1210℃~1250℃ for 1h~5h.

3. The method for preparing high nitrogen austenitic stainless steel according to claim 1, characterized in that: The pre-deformation in step (3) is low temperature rolling, and the processing temperature range of the pre-deformation is 50°C to 400°C; After the pre-deformation, the deformation amount of the pre-deformed blank is 10% to 30%.

4. The method for preparing high nitrogen austenitic stainless steel according to claim 1, characterized in that: The hot working in step (4) is hot rolling, and the processing temperature range of the hot working is 1000° C. to 1200° C.; After the hot working, the deformation amount of the high nitrogen austenitic stainless steel plate is 30% to 70%.

5. The method for preparing high nitrogen austenitic stainless steel according to claim 4, characterized in that: The hot working is multi-stage and multi-pass hot rolling, the starting rolling temperature of the hot working is 1100°C to 1200°C, and the final rolling temperature is 1000°C to 1060°C.

6. The method for preparing high nitrogen austenitic stainless steel according to claim 5, characterized in that: In the multi-stage and multi-pass hot rolling process, the deformation amount in the latter stage is greater than the deformation amount in the former stage.

7. The method for preparing high nitrogen austenitic stainless steel according to claim 6, characterized in that: The hot rolling includes four stages, each stage includes 2 to 5 passes, the deformation amount in the first stage is 11.8% to 12.5%, the deformation amount in the second stage is 13.5% to 14.4%, the deformation amount in the third stage is 14.2% to 15.3%, and the deformation amount in the fourth stage is 18.2% to 19.1%.

8. The method for preparing high nitrogen austenitic stainless steel according to claim 1, characterized in that: The components of the high nitrogen austenitic stainless steel raw material include, by mass percentage: C≤0.04%, Si≤0.3%, Mn15%-20%, Ni≤2%, Cr 22%-24%, N 0.5%-0.8%, Mo≤3%, and the balance is Fe and unavoidable impurities.

9. The method for preparing high nitrogen austenitic stainless steel according to claim 8, characterized in that: The components of the high nitrogen austenitic stainless steel raw material include, by mass percentage, C 0.015%-0.023%, Si 0.2%-0.25%, Mn 18.5%-19.5%, Ni 1.53%-1.57%, Cr 22.79%-23.53%, N 0.6%-0.7%, Mo 2.60%-2.71%, the remainder being Fe and unavoidable impurities, and Cr / N=33-38.

10. A high nitrogen austenitic stainless steel, characterized in that: The preparation is obtained by the preparation method according to any one of claims 1 to 9.

Images