High-strength medium-nitrogen austenitic stainless steel plate and method of manufacturing

Abstract

The application provides a high-strength medium-nitrogen austenitic stainless steel plate and a preparation method, and relates to the technical field of high-strength and high-toughness stainless steel.The chemical components of the high-strength austenitic stainless steel plate are as follows in percentage by mass: C 0.065-0.075%, Si 0.35-0.50%, Mn 5.60-6.50%, P≤0.047%, S≤0.002%, Cr 18.40-18.90%, Ni 2.95-3.50%, Mo 0.025-0.090%, Cu 1.05-1.70%, N 0.20-0.25%, and the balance of Fe and inevitable impurities.The cost of the medium-nitrogen austenitic stainless steel ingot obtained by the application is lower than that of a high-nitrogen austenitic stainless steel ingot, the maximum tensile strength can reach 1167MPa, the yield strength is 1021MPa, the elongation after fracture is 41.2%, the product of strength and plasticity is 48.1GPa·%, and the minimum average grain size can reach 0.89μm, thus overcoming the dilemma between strength and plasticity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-toughness stainless steel, and particularly relates to a high-strength medium-nitrogen austenitic stainless steel plate and a preparation method thereof. BACKGROUND

[0002] Austenitic stainless steel is widely used in the fields of aerospace, petrochemical industry, transportation, catering and kitchen utensils, etc. due to its excellent corrosion resistance, high toughness and plasticity, and non-magneticity. Nickel is the main alloying element in austenitic stainless steel, which mainly functions to form and stabilize austenitic structure.

[0003] Medium-nitrogen austenitic stainless steel is a new type of steel developed by using manganese and nitrogen elements to replace the precious and scarce nickel element. Both manganese and nitrogen are strong austenite-forming elements. Manganese plays a role in stabilizing austenite and increasing the solid solubility of nitrogen in steel. The addition of nitrogen can significantly improve the strength of the steel without affecting the plasticity, toughness and non-magneticity of the steel. Therefore, medium-nitrogen austenitic stainless steel is suitable for equipment and parts that bear heavy loads and have high requirements for corrosion resistance, such as the retainer ring of a generator rotor, the non-magnetic sleeve ring of a drilling rod for oil drilling, and the exhaust valve of an automobile engine.

[0004] High-nitrogen austenitic stainless steel has a nitrogen content of more than 0.4-0.6%, which exceeds the solubility of nitrogen in the molten liquid at normal pressure, and therefore needs to be smelted and poured under pressure. Due to the high nitrogen content in high-nitrogen austenitic stainless steel, a large amount of chromium nitride phase is easily precipitated after welding, affecting the corrosion resistance, and pores are easily generated in the weld. Therefore, high-nitrogen austenitic stainless steel is mainly used in the solid solution state. If the cold deformation is too high, the plasticity and toughness will decrease, and therefore the high-nitrogen austenitic stainless steel should be mainly used in a state with a low cold deformation. The smelting and pouring under pressure and the limitation of the application state make the high-nitrogen austenitic stainless steel not widely used at present.

[0005] Therefore, medium-nitrogen austenitic stainless steel is the type that can best exert the advantages of nitrogen-containing austenitic stainless steel. Super austenitic stainless steel is basically medium-nitrogen steel, mainly because it has excellent corrosion resistance and high strength.

[0006] For example, Chinese patent CN112831722A discloses an extremely thin gauge super high strength austenitic stainless steel and a production method. The steel is prepared by continuous casting, heating the thin slab, high-pressure water descaling, rolling, laminar cooling, coiling, cold rolling, high-temperature annealing, and cooling to room temperature. The content of nickel and molybdenum in the composition is relatively high, and large reduction rolling is adopted for both hot rolling and cold rolling, which increases the production cost and reduces the elongation.

[0007] Chinese patent CN113755753A discloses a kind of based on heterostructure multi-type reinforced austenitic stainless steel and manufacturing method, it is prepared by hot rolling or forging, solid solution treatment, cold rolling treatment and tempering, the content of nickel and molybdenum in its composition is higher, cold rolling takes large reduction rolling, increase production cost, tensile strength and elongation are lower.

[0008] Chinese patent CN114934240A discloses a kind of preparation method of super-high-strength high-corrosion-resistance high-nitrogen austenitic stainless steel, it is by introducing suitable defects by cold deformation, the precipitation behavior of Cr2N in high-nitrogen austenitic stainless steel is regulated, while eliminating the decrease of stainless steel corrosion resistance caused by cold deformation defects and second phase precipitation, the mechanical strength is greatly improved by defect and second phase composite strengthening;Obviously, too high cold deformation leads to low plasticity.

[0009] Chinese patent CN109837470A discloses a kind of high-strength nitrogen-containing economic austenitic stainless steel and its manufacturing method, the content of manganese and molybdenum in its composition is higher, it needs to be cold-rolled twice and flexible annealing twice, there is no precipitate in metallographic structure, and yield strength is not more than 810MPa.

[0010] Chinese patent CN112143973A discloses a kind of high-strength high-corrosion-resistance super-austenitic stainless steel and its preparation method, alloy element selection is more, alloy element content is higher, cost is high, the tensile strength and yield strength of obtained austenitic stainless steel are lower.

[0011] Therefore, it is necessary to study a kind of high-strength medium-nitrogen austenitic stainless steel plate and its preparation method to overcome the shortcomings of prior art, to solve or alleviate one or more of the above problems. SUMMARY

[0012] The technical problem to be solved by the present application is that the current high-strength nitrogen-containing austenitic stainless steel plate has the technical defects of high content of high-cost alloy elements in its composition, large reduction rolling in hot rolling and cold rolling, which increases production cost, low elongation and / or yield strength, low strength-plasticity product, limited application range, and is not conducive to large-scale industrial production and promotion.

[0013] To solve the above technical problems, the technical solutions provided by the present application are as follows:

[0014] The application discloses a high-strength medium-nitrogen austenitic stainless steel plate, and chemical components of the high-strength austenitic stainless steel plate are as follows in percentage by mass: C 0.065-0.075%, Si 0.35-0.50%, Mn 5.60-6.50%, P ≤0.047%, S ≤0.002%, Cr 18.40-18.90%, Ni 2.95-3.50%, Mo 0.025-0.090%, Cu 1.05-1.70%, N 0.20-0.25%, and the balance of Fe and inevitable impurities.

[0015] Preferably, the high-strength austenitic stainless steel plate has a thickness of 0.6-0.7 mm, a microstructure of a mixed structure of fine-grained residual austenite + ultra-fine-grained reversed austenite, a nanometer precipitated phase with a size of 20-70 nm dispersedly distributed, an austenite volume fraction of more than 96%, and an average grain size reaching a sub-micron level.

[0016] Preferably, the high-strength austenitic stainless steel plate has a temperature M d30 at which a deformation of 30% generates 50% martensite, a starting temperature M s of austenite to martensite transformation, and a nickel equivalent Ni eq , and the calculation methods are as follows:

[0017] M d30 (℃) = 551-462 (%C + %N) -9.2 (%Si) -8.1 (%Mn) -13.7 (%Cr) -29 (%Ni + Cu)

[0018] -18.5 (%Mo) -1.42 (GS-8)

[0019] Ms (℃) = 545-330 (%C) -14 (%Cr) -13 (%Cu) -23 (%Mn) -5 (%Mo) -13 (%Ni) -7 (%Si)

[0020] Ni eq = %Ni + 0.65 (%Cr) + 0.98 (%Mo) + 1.05 (%Mn) + 0.35 (%Si) + 12.6 (%C).

[0021] Preferably, the high-strength austenitic stainless steel plate has a martensite transformation temperature range of 34 ℃ ≤ M s ≤ 83 ℃, -60 ℃ ≤ M d30 ≤ 25 ℃, and a nickel equivalent of 21.7 ≤ Ni eq ≤ 23.9.

[0022] Preferably, the high-strength austenitic stainless steel plate has a tensile strength of 1020-1170 MPa, a yield strength of 810-1030 MPa, an elongation of 40-50%, and a product of strength and elongation of 40-50 GPa·%.

[0023] A method for preparing a high-strength medium-nitrogen austenitic stainless steel plate as described above, the method comprising the following steps:

[0024] S1, weighing raw materials according to the chemical composition of the high-strength austenitic stainless steel plate, and smelting and casting to obtain a continuous casting billet of high-strength austenitic stainless steel;

[0025] S2, hot rolling the continuous casting billet of S1 to obtain a hot-rolled plate;

[0026] S3, solid solution treatment of the hot-rolled plate of S2 to obtain a solid solution plate;

[0027] S4, multi-pass small reduction warm rolling of the solid solution plate of S3 to obtain a warm-rolled plate;

[0028] S5, multi-pass small reduction cold rolling of the warm-rolled plate of S4 to obtain a cold-rolled plate;

[0029] S6, rapid annealing treatment of the cold-rolled plate of S5 to obtain a high-strength austenitic stainless steel plate product.

[0030] Preferably, the warm-rolled plate of S4 has a thickness of 3-4 mm, the warm rolling is performed at a temperature of 270-550℃, and the number of passes is 18-24 with a single-pass deformation of 3-6%.

[0031] Preferably, the cold-rolled plate of S5 has a thickness of 0.6-0.7 mm, the cold rolling is performed for 15-20 passes with a single-pass deformation of 3-5%.

[0032] Preferably, the rapid annealing treatment of S6 is performed at a temperature of 750-850℃ for 10-60 s, and then water-cooled to room temperature.

[0033] Preferably, in the preparation method, the multi-pass small reduction warm rolling introduces a large number of dislocations in the austenitic structure, and simultaneously induces dynamic recrystallization to refine the grain size. The multi-pass small reduction cold rolling induces martensitic transformation, and in the subsequent rapid annealing process, the reversed austenite nucleates at the martensite lath boundaries and lath bundle boundaries, and the grains are further refined.

[0034] The above technical solution has at least the following beneficial effects compared with the prior art:

[0035] The scheme has the advantages that the high-strength medium-nitrogen austenitic stainless steel plate is of the Cr-Mn-N austenitic stainless steel, the selection of high-cost alloy elements and the content thereof are obviously reduced compared with the existing Cr-Ni austenitic stainless steel, the production cost of the material can be effectively reduced, the high-strength medium-nitrogen austenitic stainless steel plate has higher cost performance, a wider application range and stronger market competitiveness than the Cr-Ni austenitic stainless steel.

[0036] The process steps of the high-strength medium-nitrogen austenitic stainless steel plate are simple and easy to operate, the high-strength medium-nitrogen austenitic stainless steel plate with the required performance is obtained through hot rolling, solid solution, multi-pass small reduction warm rolling, multi-pass small reduction cold rolling and rapid annealing, the size of the dispersed nanometer precipitates is not more than 70nm, the precipitates are Cr7C3 and Cr 23 C6, the growth of reversed austenitic grains can be inhibited, and the dislocation expansion can be hindered.

[0037] The austenitic volume fraction of the high-strength austenitic stainless steel prepared by the preparation method reaches more than 96%, which is almost full austenitic structure, the tensile strength is 1020-1170MPa, the yield strength is 810-1030MPa, the elongation after fracture is 40-50%, and the product of strength and plasticity is 40-50GPa·%, so that the high-strength austenitic stainless steel has high strength and toughness.

[0038] The cost of the medium-nitrogen austenitic stainless steel ingot obtained by smelting and casting is lower than that of the high-nitrogen austenitic stainless steel ingot, the tensile strength can reach 1167MPa at most, the yield strength is 1021MPa, the elongation after fracture is 41.2%, the product of strength and plasticity is 48.1GPa·%, and the average grain size can reach 0.89μm at least (since the grain size of the sample matrix structure has a large span, the average grain size is the area weighted average value), so that the dilemma of balancing strength and plasticity is overcome.

[0039] In summary, compared with other traditional methods, the method needs less high-cost alloy elements and has less content, the process is simple, the preparation process is short, the cost is low, the efficiency is high, the prepared material has high strength and toughness, the application range of the prepared material is wide, and the method is beneficial to industrial large-scale production and promotion. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0041] Figure 1 The engineering stress-strain curve diagrams of the high-strength medium-nitrogen austenitic stainless steel plate of embodiments 1, 2, 3 and 4 of the present application;

[0042] Figure 2 EBSD band contrast map of Example 1, 2, 3, 4 of the high-strength medium-nitrogen austenitic stainless steel plate according to the present application;

[0043] Figure 3 XRD map of Example 1, 2, 3, 4 of the high-strength medium-nitrogen austenitic stainless steel plate according to the present application;

[0044] Figure 4 TEM map of the nanometer precipitates of Example 1 of the high-strength medium-nitrogen austenitic stainless steel plate according to the present application. DETAILED DESCRIPTION

[0045] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the described embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without any inventive effort fall within the scope of protection of the present application.

[0046] Example 1

[0047] A high-strength medium-nitrogen austenitic stainless steel plate, the chemical composition of the high-strength austenitic stainless steel plate is as follows in terms of mass percentage: C 0.071%, Si 0.47%, Mn 6.02%, P 0.036%, S 0.0006%, Cr 18.43%, Ni 2.98%, Mo 0.031%, Cu 1.70%, N 0.22%, and the balance being Fe and inevitable impurities.

[0048] The martensite transformation temperature of the high-strength austenitic stainless steel plate is: M s = 69℃, M d30 = -15℃, and the nickel equivalent is: Ni eq = 22.4.

[0049] The preparation method of the high-strength medium-nitrogen austenitic stainless steel plate comprises the following steps:

[0050] S1, weighing raw materials according to the chemical composition ratio of the high-strength austenitic stainless steel plate, and smelting and casting to obtain a continuous casting billet of high-strength austenitic stainless steel;

[0051] S2, hot rolling the continuous casting billet of S1 to obtain a hot-rolled plate;

[0052] S3, solid solution treatment of the hot-rolled plate of S2 to obtain a solid solution plate;

[0053] S4, the solid solution plate of S3 is warm-rolled on a laboratory Φ310mm two-high single-stand reversible rolling mill (model: YZ-310-2-60), the warm-rolled plate thickness is 3mm, the warm-rolling temperature is 480℃, the warm-rolling pass number is 21, the single pass deformation is 3-6%, to obtain the warm-rolled plate; every 3 passes, the steel plate is kept at 480℃ for 5min, and air-cooled to room temperature after rolling;

[0054] S5, the warm-rolled plate of S4 is cold-rolled on a laboratory Φ130mm four-high single-stand reversible rolling mill (model: YZ-130-4-90-350), the cold-rolled plate thickness is 0.6mm, the cold-rolling pass number is 16, the single pass deformation is 3-5%, to obtain the cold-rolled plate;

[0055] S6, the cold-rolled plate of S5 is subjected to rapid annealing treatment, the rapid annealing treatment temperature is 770℃, the holding time is 30s, and water-cooled to room temperature, to obtain the high-strength austenitic stainless steel plate finished product.

[0056] The high-strength medium-nitrogen austenitic stainless steel prepared in this embodiment is subjected to relevant performance tests, the steel plate after heat treatment is processed into a standard tensile specimen according to GB / T228.1-2010 “Metallic materials-tensile testing-Part 1:Method of test at room temperature”, the room temperature tensile strain rate is 1.0×10 -3 s -1 The engineering stress-strain curve is shown in Figure 1 , the microstructure morphology is shown in Figure 2 , the XRD characterization result is shown in Figure 3 , and the nano precipitates are shown in Figure 4 .

[0057] The high-strength austenitic stainless steel plate has a thickness of 0.6mm, a microstructure of 30% fine-grained residual austenite + 70% ultra-fine-grained reversed austenite mixed structure, a dispersedly distributed nano precipitate with a size of 20-70nm, an average grain size of 0.89μm, an austenite volume fraction of more than 96%, and an average grain size reaching a sub-micron level.

[0058] The high-strength austenitic stainless steel plate has a tensile strength of 1167MPa, a yield strength of 1021MPa, an elongation after fracture of 41.2%, and a product of strength and plasticity of 48.1GPa·%, far exceeding the strength and toughness level of existing austenitic stainless steel.

[0059] Example 2

[0060] A high-strength medium-nitrogen austenitic stainless steel plate, a chemical composition of the high-strength austenitic stainless steel plate is respectively: C 0.071%, Si 0.47%, Mn 6.02%, P 0.036%, S 0.0006%, Cr 18.43%, Ni 2.98%, Mo 0.031%, Cu 1.70%, N 0.22%, and the balance is Fe and inevitable impurities.

[0061] Martensite transformation temperature of the high-strength austenitic stainless steel plate: M s = 69℃, M d30 = -15℃, nickel equivalent: Ni eq = 22.4.

[0062] The preparation method of the high-strength medium-nitrogen austenitic stainless steel plate, the preparation method comprises the following steps:

[0063] S1, the raw materials are weighed according to the chemical composition of the high-strength austenitic stainless steel plate, and a high-strength austenitic stainless steel continuous casting billet is obtained by smelting and casting;

[0064] S2, the continuous casting billet of S1 is hot-rolled to obtain a hot-rolled plate;

[0065] S3, the hot-rolled plate of S2 is subjected to solid solution treatment to obtain a solid solution plate;

[0066] S4, the solid solution plate of S3 is subjected to warm rolling on a laboratory Φ310mm two-high single-stand reversible rolling mill (model: YZ-310-2-60), the thickness of the warm-rolled plate is 3mm, the warm-rolling temperature is 480℃, the warm-rolling pass number is 21, the time is 5min, the single-pass deformation amount is 3-6%, and the warm-rolled plate is obtained; every 3 passes, the steel plate is kept at 480℃ for 5min, and then air-cooled to room temperature after rolling;

[0067] S5, the warm-rolled plate of S4 is subjected to cold rolling on a laboratory Φ130mm four-high single-stand reversible rolling mill (model YZ-130-4-90-350), the thickness of the cold-rolled plate is 0.6mm, the cold-rolling pass number is 16, and the single-pass deformation amount is 3-5%, and the cold-rolled plate is obtained;

[0068] S6, the cold-rolled plate of S5 is subjected to rapid annealing treatment, the rapid annealing treatment temperature is 820℃, the holding time is 10s, and the cold-rolled plate is water-cooled to room temperature, and the high-strength austenitic stainless steel plate finished product is obtained.

[0069] The high-strength medium-nitrogen austenitic stainless steel prepared in the embodiment is subjected to relevant performance tests, the steel plate after heat treatment is processed into a standard tensile specimen according to GB / T228.1-2010 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method", and the room temperature tensile strain rate is 1.0×10 -3s -1 The engineering stress-strain curve is shown in Figure 1 The microstructure is shown in Figure 2 The XRD characterization result is shown in Figure 3

[0070] The high-strength austenitic stainless steel plate has a thickness of 0.6 mm, a microstructure of a mixed structure of 40% fine-grained residual austenite + 60% ultra-fine-grained reversed austenite, a dispersed distribution of nano-precipitates with a size of 20-70 nm, an average grain size of 1.15 μm, and an austenite volume fraction of more than 96%.

[0071] The high-strength austenitic stainless steel plate has a tensile strength of 1096 MPa, a yield strength of 915 MPa, an elongation after fracture of 43.7%, and a product of strength and plasticity of 47.9 GPa·%, which is far superior to the strength and toughness level of existing austenitic stainless steels.

[0072] Embodiment 3

[0073] A high-strength medium-nitrogen austenitic stainless steel plate, the high-strength austenitic stainless steel plate having chemical components in mass percentages of C 0.069%, Si 0.36%, Mn 5.61%, P 0.046%, S 0.0020%, Cr 18.52%, Ni 3.26%, Mo 0.089%, Cu 1.06%, N 0.21%, and the balance being Fe and inevitable impurities.

[0074] The high-strength austenitic stainless steel plate has a martensite transformation temperature of M s = 75℃, M d30 = 2℃, and a nickel equivalent of Ni eq = 22.3.

[0075] The preparation method of the high-strength medium-nitrogen austenitic stainless steel plate comprises the following steps:

[0076] S1. Measuring raw materials according to the chemical component proportions of the high-strength austenitic stainless steel plate, and smelting and casting to obtain a continuous casting billet of high-strength austenitic stainless steel;

[0077] S2. Hot-rolling the continuous casting billet of S1 to obtain a hot-rolled plate;

[0078] S3. Solid solution treating the hot-rolled plate of S2 to obtain a solid solution plate;

[0079] ​S4, the solid solution plate of S3 is warm-rolled on a laboratory Φ310mm two-high single-stand reversible rolling mill (model: YZ-310-2-60), the warm-rolled plate thickness is 3mm, the warm-rolling temperature is 380℃, the warm-rolling pass number is 23, the time is 5min, the single pass deformation is 3-6%, to obtain the warm-rolled plate; every 3 passes, the steel plate is kept at 380℃ for 5min, and air-cooled to room temperature after rolling;

[0080] S5, the warm-rolled plate of S4 is cold-rolled on a laboratory Φ130mm four-high single-stand reversible rolling mill (model YZ-130-4-90-350), the cold-rolled plate thickness is 0.6mm, the cold-rolling pass number is 19, the single pass deformation is 3-5%, to obtain the cold-rolled plate;

[0081] S6, the cold-rolled plate of S5 is subjected to rapid annealing treatment, the rapid annealing treatment temperature is 820℃, the holding time is 10s, and water-cooled to room temperature, to obtain the high-strength austenitic stainless steel plate finished product.

[0082] The high-strength medium-nitrogen austenitic stainless steel prepared in this embodiment is subjected to relevant performance tests, the steel plate after heat treatment is processed into a standard tensile specimen according to GB / T228.1-2010 “Metallic materials-tensile testing-Part 1:Method of test at room temperature”, the room temperature tensile strain rate is 1.0×10 -3 s -1 The engineering stress-strain curve is shown in Figure 1 , the microstructure morphology is shown in Figure 2 , and the XRD characterization result is shown in Figure 3 .

[0083] The thickness of the high-strength austenitic stainless steel plate is 0.6mm, the microstructure is a mixed structure of 42% fine-grained residual austenite + 58% ultra-fine-grained reversed austenite, dispersedly distributed with nanometer precipitated phases with a size of 20-70nm, the average grain size is 1.16μm, and the austenite volume fraction reaches more than 96%.

[0084] The tensile strength of the high-strength austenitic stainless steel plate is 1082MPa, the yield strength is 925MPa, the elongation after fracture is 41.8%, and the strength-plasticity product is 45.2GPa·%, which is far superior to the strength and toughness level of existing austenitic stainless steel.

[0085] Example 4

[0086] A high-strength medium-nitrogen austenitic stainless steel plate, a chemical composition of the high-strength austenitic stainless steel plate is respectively: C 0.065%, Si 0.50%, Mn 6.40%, P 0.043%, S 0.0008%, Cr 18.67%, Ni 3.03%, Mo 0.029%, Cu 1.65%, N 0.24%, and the balance is Fe and inevitable impurities.

[0087] Martensite transformation temperature of the high-strength austenitic stainless steel plate: M s = 50 DEG C, M d30 = -29 DEG C, nickel equivalent: Ni eq = 22.9.

[0088] The preparation method of the high-strength medium-nitrogen austenitic stainless steel plate comprises the following steps:

[0089] S1, raw materials are weighed according to the chemical composition of the high-strength austenitic stainless steel plate, and a continuous casting billet of the high-strength austenitic stainless steel is obtained by smelting and casting;

[0090] S2, the continuous casting billet of S1 is hot-rolled to obtain a hot-rolled plate;

[0091] S3, the hot-rolled plate of S2 is subjected to solid solution treatment to obtain a solid solution plate;

[0092] S4, the solid solution plate of S3 is subjected to warm rolling on a laboratory Φ310mm two-high single-stand reversible rolling mill (model: YZ-310-2-60), the thickness of the warm-rolled plate is 3mm, the warm rolling temperature is 280 DEG C, the number of passes of warm rolling is 24, the time is 5min, the single-pass deformation amount is 3-6%, and the warm-rolled plate is obtained; every 3 passes, the steel plate is kept at 280 DEG C for 6min, and air-cooled to room temperature after rolling;

[0093] S5, the warm-rolled plate of S4 is subjected to cold rolling on a laboratory Φ130mm four-high single-stand reversible rolling mill (model YZ-130-4-90-350), the thickness of the cold-rolled plate is 0.6mm, the number of passes of cold rolling is 22, and the single-pass deformation amount is 3-5%, and the cold-rolled plate is obtained;

[0094] S6, the cold-rolled plate of S5 is subjected to rapid annealing treatment, the rapid annealing treatment temperature is 870 DEG C, the holding time is 8s, and the water cooling is to room temperature, and the high-strength austenitic stainless steel plate finished product is obtained.

[0095] The high-strength medium-nitrogen austenitic stainless steel prepared in the embodiment is subjected to relevant performance tests, the steel plate after heat treatment is processed into a standard tensile specimen according to GB / T228.1-2010 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method", the room temperature tensile strain rate is 1.0x10 -3s -1 The engineering stress-strain curve is shown in Figure 1 The microstructure is shown in Figure 2 The XRD characterization result is shown in Figure 3

[0096] The thickness of the high-strength austenitic stainless steel plate is 0.6mm, the microstructure is a mixed structure of 58% fine-grained residual austenite + 42% ultra-fine-grained reversed austenite, and the size of the dispersed nanometer precipitates is 20-70nm, the average grain size is 1.38um, and the austenite volume fraction reaches more than 96%.

[0097] The tensile strength of the high-strength austenitic stainless steel plate is 1026MPa, the yield strength is 819MPa, the elongation after fracture is 44.9%, and the product of strength and plasticity is 46.1GPa%, which is far higher than the strength and toughness level of existing austenitic stainless steel.

[0098] The above scheme, the present application proposes a kind of high-strength medium-nitrogen austenitic stainless steel plate, belongs to Cr-Mn-N austenitic stainless steel, compared with existing Cr-Ni austenitic stainless steel, its high-cost alloy element selection and content significantly reduce, can effectively reduce the production cost of material, make it have higher performance price ratio than Cr-Ni austenitic stainless steel, wider application range and stronger market competitiveness.

[0099] The process steps of the present application are simple and easy to operate, and the high-strength medium-nitrogen austenitic stainless steel plate with the required performance is obtained by hot rolling, solid solution, multi-pass small reduction warm rolling, multi-pass small reduction cold rolling and rapid annealing, the size of the dispersed nanometer precipitates is not more than 70nm, and the precipitates are Cr7C3 and Cr 23 C6, which can inhibit the growth of reversed austenite grains and hinder dislocation expansion.

[0100] The austenite volume fraction of the high-strength austenitic stainless steel prepared by the preparation method of the present application can reach more than 96%, which is almost full austenite structure, the tensile strength is 1020-1170MPa, the yield strength is 810-1030MPa, the elongation after fracture is 40-50%, and the product of strength and plasticity is 40-50GPa%, which has both strength and toughness.

[0101] The cost of the medium-nitrogen austenitic stainless steel ingot obtained by smelting and casting is lower than that of high-nitrogen austenitic stainless steel ingot, the tensile strength can reach 1167MPa at most, the yield strength is 1021MPa, the elongation after fracture is 41.2%, the product of strength and plasticity is 48.1GPa%, and the average grain size can reach 0.89um at least (since the grain size of the sample matrix structure has a large span, the average grain size is the area weighted average value), overcoming the dilemma of balancing strength and plasticity. ​

[0102] In summary, the method of the present application requires less high-cost alloying elements and less content, the process is simple, the preparation process is short, the cost is low, the efficiency is high, the material prepared has high strength and toughness, the application range of the material prepared is wide, and the material is suitable for large-scale industrial production and popularization.

[0103] The above is the preferred embodiment of the present application. It should be pointed out that for ordinary skilled persons in the technical field, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A high-strength medium-nitrogen austenitic stainless steel sheet, characterized by, The high-strength medium-nitrogen austenitic stainless steel plate has the following chemical components in percentage by mass: C 0.065-0.075%, Si 0.35-0.50%, Mn 5.60-6.50%, P≤0.047%, S≤0.002%, Cr 18.40-18.90%, Ni 2.95-3.50%, Mo 0.025-0.090%, Cu 1.05-1.70%, N 0.20-0.25%, and the balance of Fe and inevitable impurities. The high-strength medium-nitrogen austenitic stainless steel plate has a thickness of 0.6-0.7 mm, a microstructure of a mixed structure of fine-grained residual austenite + ultra-fine-grained reversed austenite, dispersedly distributed nanometer precipitated phases with a size of 20-70 nm, an austenite volume fraction of more than 96%, and an average grain size of a sub-micron level. The high-strength medium-nitrogen austenitic stainless steel plate has a tensile strength of 1020-1170 MPa, a yield strength of 810-1030 MPa, an elongation after fracture of 40-50%, and a product of strength and plasticity of 40-50 GPa·%.

2. The high-strength medium-nitrogen austenitic stainless steel sheet according to claim 1, characterized by, M: temperature at which 30% deformation generates 50% martensite d30 M: temperature at which austenite starts to transform into martensite s Ni: nickel equivalent eq The calculation method is as follows: ； ； 。 3. The high-strength medium-nitrogen austenitic stainless steel sheet according to claim 2, characterized by The high-strength medium-nitrogen austenitic stainless steel plate has a martensite transformation temperature range: 34℃ ≤ M s ≤ 83℃, -60℃ ≤ M d30 ≤ 25℃, and a nickel equivalent: 21.7 ≤ Ni eq ≤ 23.

9.

4. A method of producing the high-strength medium-nitrogen austenitic stainless steel sheet according to any one of claims 1 to 3, characterized by, The preparation method comprises the following steps: S1, weighing raw materials according to the chemical component proportions of the high-strength medium-nitrogen austenitic stainless steel plate, smelting and casting to obtain a continuous casting billet of the high-strength medium-nitrogen austenitic stainless steel; S2, hot-rolling the continuous casting billet of S1 to obtain a hot-rolled plate; S3, solid-solution treating the hot-rolled plate of S2 to obtain a solid-solution plate; S4, multi-pass warm-rolling the solid-solution plate of S3 with a small reduction to obtain a warm-rolled plate; S5, multi-pass cold-rolling the warm-rolled plate of S4 with a small reduction to obtain a cold-rolled plate; S6, rapid annealing the cold-rolled plate of S5 to obtain a high-strength medium-nitrogen austenitic stainless steel plate product.

5. The method of producing a high-strength medium-nitrogen austenitic stainless steel sheet according to claim 4, characterized by, The warm-rolled plate of S4 has a thickness of 3-4 mm, a warm-rolling temperature of 270-500℃, a number of warm-rolling passes of 18-23, and a single-pass deformation of 3-6%.

6. The method of producing a high-strength medium-nitrogen austenitic stainless steel sheet according to claim 4, characterized by, The cold-rolled plate of S5 has a thickness of 0.6-0.7 mm, a number of cold-rolling passes of 15-20, and a single-pass deformation of 3-5%.

7. The method of producing a high-strength medium-nitrogen austenitic stainless steel sheet according to claim 4, characterized by, The rapid annealing of S6 is performed at a temperature of 750-850℃, a holding time of 10-60 s, and water cooling to room temperature.

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