High-toughness non-magnetic stainless steel plate suitable for ultralow temperature of-269 DEG C and manufacturing method of high-toughness non-magnetic stainless steel plate

Abstract

The invention relates to a high-toughness non-magnetic stainless steel plate suitable for ultralow temperature of-269 DEG C and a manufacturing method of the high-toughness non-magnetic stainless steel plate, and belongs to the technical field of high-strength stainless steel. The high-toughness non-magnetic stainless steel plate comprises the following chemical components: less than or equal to 0.006% of C, 0.35-0.45% of N, less than or equal to 0.0020% of O, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 21.0-22.0% of Cr, 15.0-16.5% of Ni, 2.3-2.6% of Mo, 6.2-10.0% of Mn, less than or equal to 0.20% of Si, less than 0.04% of Nb, 0.15-0.25% of V, 0.10-0.15% of Cu, less than or equal to 0.02% of Al, less than or equal to 0.02% of Ti and less than or equal to 0.05% of Co. The novel stainless steel has ultrahigh strength, high toughness, complete austenite stability and low magnetic conductivity at the temperature of-269 DEG C.

Description

Technical Field

[0001] The present invention relates to the technical field of high-strength stainless steel, and in particular to a high-strength and tough non-magnetic stainless steel plate suitable for ultra-low temperature of -269°C and a manufacturing method thereof. Background Art

[0002] Ultra-low temperature engineering is crucial to economic development and scientific and technological innovation. Among them, "large-scale nuclear fusion devices" are the most exemplary ultra-low temperature engineering, which are major scientific devices related to energy security. Breakthroughs in ultra-low temperature technology have an irreplaceable supporting role in energy revolution (such as controlled nuclear fusion), cutting-edge scientific devices (such as superconducting accelerators), and deep space exploration (such as spacecraft cryogenic propulsion systems and high-energy particle cooling systems).

[0003] With the development of ultra-low temperature technology, traditional austenitic stainless steel (such as grade 316LN stainless steel) is mainly used to prepare engineering equipment. It has good low-temperature stability, but its -269℃ yield strength (~1000 MPa) and anti-sensitization ability can no longer meet the requirements of engineering equipment (such as new generation fusion devices) for material extreme performance, resulting in a sharp drop in the reliability of the material under deep low temperature and strong magnetic field environment. With the development of technology, the invention patent with publication number CN117286426A discloses a high-strength non-magnetic austenitic stainless steel, which has good non-magnetic properties, and its -269℃ yield strength is 1250~1420MPa, and its tensile strength is 1700~1831MPa.

[0004] With the surge in complexity and performance requirements of engineering equipment in extreme low temperature environments (-269°C), almost stringent requirements are placed on structural materials. Existing materials or stainless steel cannot meet the requirements of ultra-high strength (yield strength ≥1500MPa at -269°C, tensile strength ≥1900MPa), high toughness and non-magnetic properties. Therefore, a new type of stainless steel with ultra-high strength, high toughness, complete austenite stability and low magnetic permeability at -269°C is urgently needed. Summary of the invention

[0005] In view of the above analysis, the present invention aims to provide a high-strength and high-toughness non-magnetic stainless steel plate suitable for ultra-low temperature of -269°C and a manufacturing method thereof, which has high strength and toughness at -269°C and low relative magnetic permeability.

[0006] On the one hand, the present invention provides a high-strength and toughness non-magnetic stainless steel plate, whose chemical composition, measured by weight percentage, is: C≤0.006%, N: 0.35~0.45%, O≤0.0020%, P≤0.010%, S≤0.005%, Cr: 21.0~22.0%, Ni: 15.0~16.5%, Mo: 2.3~2.6%, Mn: 6.2~10.0%, Si≤0.20%, Nb<0.04%, V: 0.15~0.25%, Cu: 0.10~0.15%, Al≤0.02%, Ti≤0.02%, Co≤0.05%, and the balance is Fe and unavoidable impurities.

[0007] Furthermore, the chemical composition of the high-strength and toughness non-magnetic stainless steel plate is: C≤0.006%, N: 0.37~0.45%, O≤0.0020%, P≤0.010%, S≤0.005%, Cr: 21.0~21.5%, Ni: 15.0~15.4%, Mo: 2.3~2.5%, Mn: 7.0~10.0%, Si≤0.20%, Nb<0.04%, V: 0.15~0.19%, Cu: 0.10~0.15%, Al≤0.02%, Ti: 0.012~0.02%, Co: ≤0.04%, and the balance is Fe and unavoidable impurities.

[0008] Furthermore, at the ultra-low temperature of -269°C liquid helium, the yield strength of the stainless steel plate is above 1500MPa, the tensile strength is above 1900MPa, the elongation after fracture is above 30%, the V-type impact energy is 150~170J, and the fracture toughness is 160~200MPa·m 1 / 2 , and the relative magnetic permeability is less than 1.01.

[0009] Furthermore, the grain size grade of the stainless steel plate is 4-7.

[0010] On the other hand, the present invention provides a method for manufacturing the high-strength and toughness non-magnetic stainless steel sheet, comprising the following steps: S1: The ingredients are prepared according to the alloy composition, and the electroslag ingot is obtained after electric furnace smelting and electroslag remelting; S2: subjecting the electroslag ingot to high temperature diffusion and then forging to obtain a forging blank; S3: rolling the obtained forging billet to obtain a rolled plate; S4: Finally, the obtained rolled plate is subjected to a solid solution treatment to obtain a high-strength and tough non-magnetic stainless steel plate.

[0011] Furthermore, AOD and LF smelting are carried out after the electric furnace smelting; the steel pouring temperature is 1480-1520°C.

[0012] Furthermore, during electroslag remelting, the slag system is a ternary slag system of CaF2-Al2O3-CaO, and remelting is performed under an argon protective atmosphere. After the remelting is completed, the ingot is removed for more than 1 hour.

[0013] Furthermore, the temperature of the high-temperature diffusion is 1190-1210°C, and during the forging process, the start forging temperature is ≥1050°C, and the final forging temperature is ≥900°C.

[0014] Furthermore, during the rolling process, the holding temperature before rolling is 1160-1180°C, the start rolling temperature is ≥1050°C, and the final rolling temperature is ≥900°C.

[0015] Furthermore, the holding temperature of the solution treatment is 1000-1100° C., the holding time is 30-150 min, and after the solution treatment, the steel is rapidly cooled to room temperature by water quenching.

[0016] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1. The present invention controls the C content to be less than 0.006% and the oxygen content to be less than 0.002% through the design of alloy components; accurately controls the N content to be between 0.35% and 0.45%; at the same time, it is necessary to strictly control the Mn content to be between 6.2% and 10.0%, the Nb content to be less than 0.04%, and the Mo content to be between 2.3% and 2.6%; limits the Ti and Al element contents, and through the interaction between the elements, plays a role in solid solution strengthening and grain refinement, and at the same time significantly reduces the content of high-temperature niobium nitride, titanium nitride, and aluminum nitride in stainless steel, thereby ensuring the strength and toughness of the stainless steel sheet; at an ultra-low temperature of -269°C liquid helium, the yield strength of the stainless steel sheet is above 1500MPa, the tensile strength is above 1900MPa, the elongation after fracture is above 30%, the V-type impact energy is 150-170J, and the fracture toughness is 160-200MPa·m 1 / 2 , and the relative magnetic permeability is less than 1.01; 2. The present invention provides a method for preparing stainless steel plates based on the compounding of alloy components, mainly through the processes of smelting, forging, rolling and heat treatment in electric furnaces and electroslag remelting. On the one hand, it can reduce production costs, use electric furnaces instead of medium-frequency induction furnaces, and does not affect the performance of the final stainless steel plates; on the other hand, based on the coordinated regulation of composition-method-organization, through technical means such as high nitrogen interstitial solid solution strengthening, fine grain strengthening and carbon / nitride precipitation strengthening, the yield strength of the steel of the present invention at -269°C is higher than 1500MPa, and at the same time, the grain structure is uniform and the grains are refined, which can reach level 4-7; 3. The stainless steel plate produced by the present invention has high strength and toughness, is non-magnetic, and can fully withstand the use of liquid helium at a temperature of -296°C. Therefore, it can be used in strong magnetic field superconducting magnets, deep space exploration and structural parts of ultra-low temperature devices at a temperature of -296°C liquid helium.

[0017] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components; Figure 1 is the microstructure diagram of Example 1; Figure 2 is the microstructure diagram of Example 2; Figure 3 is the microstructure diagram of Example 4; Figure 4 is a grain size diagram of Example 5; Figure 5 This is a microscopic characterization diagram of the fracture surface after the tensile test at -269°C of Example 2; Figure 6 for Figure 5 A magnified image of area A; Figure 7 This is a microscopic characterization diagram of the fracture surface after the tensile test at -269°C of Example 3; Figure 8 for Figure 7 A magnified image of area A; Fig. 9 This is a physical picture of the plate material of Example 2. DETAILED DESCRIPTION

[0019] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0020] Ultra-low temperature engineering is crucial to economic development and scientific and technological innovation. With the development of ultra-low temperature technology, traditional austenitic stainless steel (such as grade 316LN stainless steel) is mainly used to prepare engineering equipment or structural parts for ultra-low temperature use. 316LN stainless steel has good low-temperature stability, but its yield strength at -269℃ is around 1000MPa. With the surge in complexity and performance requirements of engineering equipment in extreme low temperature environments (-269℃), almost harsh requirements are placed on structural materials. Existing materials or stainless steel cannot meet the requirements of ultra-high strength (yield strength ≥1500 MPa, tensile strength ≥1900MPa), high toughness and non-magneticity.

[0021] Therefore, the present invention provides a high-strength and tough non-magnetic stainless steel plate, whose chemical composition, by weight percentage, is: C≤0.006%, N: 0.35~0.45%, O≤0.0020%, P≤0.010%, S≤0.005%, Cr: 21.0~22.0%, Ni: 15.0~16.5%, Mo: 2.3~2.6%, Mn: 6.2~10.0%, Si≤0.20%, Nb<0.04%, V: 0.15~0.25%, Cu: 0.10~0.15%, Al≤0.02%, Ti≤0.02%, Co≤0.05%, and the balance is Fe and unavoidable impurities.

[0022] Compared with the prior art, the present invention controls the C content to be less than 0.006% and the oxygen content to be less than 0.002% through the design of alloy components; accurately controls the N content to be between 0.35% and 0.45%; at the same time, it is necessary to strictly control the Mn content to be between 6.2% and 10.0%, the Nb content to be less than 0.04%, and the Mo content to be between 2.3% and 2.6%; limits the Ti and Al element contents, and through the interaction between the elements, plays a role in solid solution strengthening and grain refinement, and at the same time significantly reduces the content of high-temperature niobium nitride, titanium nitride, and aluminum nitride in stainless steel, thereby ensuring the strength and toughness of the stainless steel plate; at an ultra-low temperature of -269°C liquid helium, the yield strength of the stainless steel plate is above 1500MPa, the tensile strength is above 1900MPa, the elongation after fracture is above 30%, the V-type impact energy is 150-170J, and the fracture toughness is 160-200 MPa·m 1 / 2 , and the relative magnetic permeability is less than 1.01.

[0023] The role of each element in the present invention is as follows: Carbon: C is an austenite stabilizing element. eq Formula, it is more effective than Ni in stabilizing austenite. However, the presence of C element makes it easy to precipitate carbides Cr at the grain boundaries. 23 C6, resulting in Cr-poor matrix near the austenite grain boundary, which greatly reduces its intergranular corrosion resistance.23 C6 carbide precipitates and maintains the C content in the steel, and a combination of C and N can be used. Therefore, the carbon content in the steel of the present invention needs to be controlled to be ultra-low. Taking all factors into consideration, the carbon content of the steel of the present invention is controlled within 0.006%.

[0024] Nitrogen: Nitrogen is an interstitial alloying element dissolved in the austenite lattice and can play a role in solid solution strengthening. eq Formula, N is a stronger austenite forming element and austenite stabilizer than Ni. In Cr-Ni steel, N reduces the content of delta-ferrite. Therefore, in the present invention, the nitrogen content is precisely controlled in the range of 0.35-0.45%.

[0025] Chromium: Chromium is a ferrite stabilizing element. Increasing the chromium content will promote high temperature Cr2N and medium temperature M 23 The formation of C6 will seriously deteriorate the high temperature forgeability and low temperature toughness of the steel. In addition, chromium passivates the steel, so the increase in chromium content improves the corrosion resistance of the steel. The addition of Cr improves the oxidation resistance of the alloy at higher temperatures, and compared with interstitial alloying elements, Cr also has a moderate solid solution strengthening effect. The addition of Cr can increase the yield strength and tensile strength of the steel. Therefore, the chromium content of the steel of the present invention ranges from 21.0 to 22.0%.

[0026] Nickel: Nickel is an alloying element that stabilizes austenite. It can also inhibit the formation of high temperature delta ferrite. As more and more nickel is added to 18%Cr ferritic stainless steel, the structure gradually transforms into austenite. There is a certain relationship between the Ni and Cr content required to maintain the austenitic structure. At the 18%Cr level, if the %Ni is about 8%, the austenitic structure persists at room temperature. When the Cr content is higher or lower, the Ni content must be adjusted to maintain a complete austenitic structure, and vice versa. In addition, nickel can improve the low temperature properties of nickel-chromium based austenitic stainless steel. Taking all factors into consideration, the nickel content of the steel of the present invention ranges from 15.0 to 16.5%.

[0027] Molybdenum: Molybdenum is an alloying element that forms ferrite. After adding Mo, the hardness of the alloy is improved, but the effect of Mo is smaller than that of C and N. Mo introduces lattice strain, which increases the tensile strength and yield strength of the alloy. The addition of Mo can also improve the hot strength of the alloy and reduce the hot plasticity of the alloy. Mo also promotes the formation of intermetallic phases, especially the sigma phase that causes room temperature embrittlement. In order to minimize the ferrite content in the cast (austenite) product at room temperature, the composition balance must be carefully controlled during the steelmaking process. Taking all factors into consideration, the molybdenum content of the steel of the present invention is 2.3-2.6%.

[0028] Manganese: As the core alloying element of high-nitrogen austenitic stainless steel, manganese achieves efficient solid solution and structural stability of nitrogen through a dual mechanism: first, its unique electronic layer structure can form a strong binding force with nitrogen atoms, significantly improving the solubility of nitrogen in the austenite matrix during high-temperature smelting, becoming a key carrier in the design of high-nitrogen steel; at the same time, as a strong austenite-forming element, it expands the γ phase region, allowing the high-nitrogen austenite structure to remain metastable at room temperature, effectively inhibiting high-temperature δ ferrite, thereby reducing the magnetic permeability.

[0029] In terms of process, the addition of manganese reduces the critical cooling rate to the range that can be operated by conventional quenching, ensuring that thick-section components obtain a fully austenitic structure, and its substitution effect on nickel significantly reduces material costs while maintaining phase stability. Based on the above synergistic effect, in order to ensure the best balance between high nitrogen solid solution strengthening effect and processing performance, the manganese content of the steel of the present invention is 6.2-10.0%.

[0030] Silicon: Si is a ferrite-forming element and can improve the corrosion resistance of steel. It also plays a deoxidizing role in the alloy smelting process. The Si element generally reduces the mechanical properties of the alloy and increases the tendency of welding hot cracking. Excessive addition of Si elements will increase the probability of ferrite precipitation in the alloy, and induce the precipitation of chromium carbide at the grain boundaries, which will deplete the Cr element at the grain boundaries and deteriorate the mechanical and corrosion resistance of the alloy. Therefore, strict control is required. Considering the above, the silicon content in the steel of the present invention is controlled within 0.2%.

[0031] Phosphorus and sulfur: P and S are impurity elements in steel. P can significantly reduce the corrosion resistance of chromium-nickel stainless steel to various concentrations of nitric acid in the solid solution state and sensitized state. S can reduce the thermoplasticity of stainless steel, affect the hot workability of steel, and also reduce the corrosion resistance of stainless steel. Since the steel of the present invention adopts the low-cost electric furnace + electroslag remelting double ultra-pure smelting process and uses pure metal materials for smelting, the phosphorus and sulfur contents are controlled within 0.010% and 0.005% respectively.

[0032] Oxygen: O is a harmful element in steel. O element mainly exists in the form of various inclusions, which seriously reduces the processing performance, plasticity and fatigue performance of steel. In summary, the oxygen content in the steel of the present invention is controlled within 0.0020% (20ppm).

[0033] Vanadium: A small amount of V can refine the grains and improve the strength and toughness of the steel. However, excessive V will form V(C,N) with C and N, reducing the low-temperature toughness of the steel. In summary, the vanadium content in the steel of the present invention is 0.15-0.25%.

[0034] Niobium: Adding Nb to stainless steel can prevent intergranular corrosion. Nb can refine grains and reduce the overheat sensitivity and temper brittleness of steel, improve strength, but reduce plasticity and toughness. Taking all factors into consideration, the niobium content in the steel of the present invention is controlled to be less than 0.04%.

[0035] Copper: Copper is a common stainless steel alloy element with a wide range of uses. In austenitic stainless steel, the addition of copper can improve its strength and corrosion resistance, but it also reduces its oxidation resistance. Therefore, the copper content in the steel of the present invention is 0.10-0.15%.

[0036] Aluminum: Al is a commonly used deoxidizer in steel. Adding a small amount of Al to steel can refine the grains and improve impact toughness. Aluminum also has antioxidant and corrosion resistance. Al combined with Cr and Si can significantly improve the high-temperature non-scaling performance and high-temperature corrosion resistance of steel. However, Al will form high-temperature AlN, which will damage the plastic toughness and hot working properties of steel. Therefore, the aluminum content in the steel of the present invention must be strictly controlled within 0.02%.

[0037] Titanium: The addition of Ti can refine austenite grains and indirectly improve the strength and toughness of the material. However, excessive Ti will combine with N or C in the steel to form hard and brittle TiN or TiC inclusions. Therefore, the titanium content in the steel of the present invention must be strictly controlled within 0.02%.

[0038] Cobalt: Co is an austenite stabilizing element. It can improve the high temperature strength and creep resistance of the material when dissolved in the matrix. In the nuclear industry, Co may be used to regulate the irradiation performance of the material, but attention should be paid to its activation problem. Excessive Co may interfere with the stability of austenite, promote the precipitation of brittle intermetallic phases (such as σ phase), and cause the material to become brittle at high temperatures. Therefore, the cobalt content in the steel of the present invention must be strictly controlled within 0.05%.

[0039] Specifically, its chemical composition, by weight percentage, is: C≤0.006%, N: 0.37~0.45%, O≤0.0020%, P≤0.010%, S≤0.005%, Cr: 21.0~21.5%, Ni: 15.0~15.4%, Mo: 2.3~2.5%, Mn: 7.0~10.0%, Si≤0.20%, Nb<0.04%, V: 0.15~0.19%, Cu: 0.10~0.15%, Al≤0.02%, Ti: 0.012~0.02%, Co≤0.04%, and the balance is Fe and unavoidable impurities.

[0040] The present invention provides a method for manufacturing a high-strength and tough non-magnetic stainless steel plate, comprising the following steps: S1: The ingredients are prepared according to the alloy composition, and the electroslag ingot is obtained after electric furnace smelting and electroslag remelting; S2: subjecting the electroslag ingot to high temperature diffusion and then forging to obtain a forging blank; S3: rolling the obtained forging billet to obtain a rolled plate; S4: Finally, the obtained rolled plate is subjected to a solid solution treatment to obtain a high-strength and tough non-magnetic stainless steel plate.

[0041] Compared with the prior art, the present invention provides a method for preparing stainless steel plates based on the compounding of alloy components, mainly through the processes of smelting, forging, rolling and heat treatment in electric furnaces and electroslag remelting. On the one hand, it can reduce production costs, use electric furnaces instead of medium-frequency induction furnaces, and does not affect the performance of the final stainless steel plates; on the other hand, based on the coordinated regulation of composition-method-organization, through high nitrogen interstitial solid solution strengthening, fine grain strengthening and carbon / nitride precipitation strengthening and other technical means, the yield strength of the steel of the present invention at -269°C is higher than 1500MPa, and at the same time, the grain structure is uniform and the grains are refined, which can reach level 4-7.

[0042] Specifically, in step S1, AOD and LF smelting are performed after electric furnace smelting; the steel pouring temperature is 1480-1520°C.

[0043] Specifically, in step S1, during electroslag remelting, the slag system is a ternary slag system of CaF2-Al2O3-CaO, and remelting is performed under an argon protective atmosphere. After the remelting is completed, the ingot is removed for more than 1 hour.

[0044] It should be noted that the present invention adopts 40t electric furnace + AOD + LF smelting, oxygen blowing, argon decarburization, and nitrogen blowing to increase nitrogen in the AOD refining process. Al deoxidation is used in the LF refining stage to fine-tune the alloy and ensure that each element reaches the target composition.

[0045] The preferred process for electroslag remelting includes: using a die-cast electrode rod (i.e., a steel ingot obtained after smelting in an electric furnace + AOD + LF) as a consumable electrode for electroslag remelting, the slag system is a CaF2-Al2O3-CaO ternary slag system, remelting under an argon protective atmosphere, and removing the ingot >1h after the end of remelting.

[0046] In the present invention, the weight ratio of CaF2, Al2O3 and CaO in the CaF2-Al2O3-CaO ternary slag system is 70:15:15.

[0047] Specifically, the temperature of the high-temperature diffusion is 1190-1210°C. During the forging process, the start forging temperature is ≥1050°C and the final forging temperature is ≥900°C.

[0048] Specifically, the forging ratio is greater than 6.

[0049] It should be noted that in the present invention, Cr and N elements form a Cr2N brittle phase, and high-temperature diffusion is performed at 1190-1210°C before forging to completely dissolve the Cr2N brittle phase. High-temperature diffusion within this temperature range also makes the Nb element diffuse more evenly, thereby ensuring the strength and toughness of the final stainless steel plate.

[0050] In the present invention, the temperature of the high temperature diffusion may be 1190°C, 1195°C, 1200°C, 1205°C or 1210°C.

[0051] In the present invention, a forging method of one upsetting and one drawing is adopted in the forging process, and the forging ratio is controlled to be greater than 6, and the electroslag ingot with a specification of φ770 is deformed into a forging blank with a thickness of δ100-180mm.

[0052] Specifically, during the rolling process, the holding temperature before rolling is 1160-1180°C, the start rolling temperature is ≥1050°C, and the final rolling temperature is ≥900°C.

[0053] Specifically, the rolling ratio is not less than 2.

[0054] It should be noted that, in the present invention, the holding temperature before rolling is controlled at 1160-1180°C, and the rolling ratio is controlled to be not less than 2, and the grain size can be controlled to avoid excessive coarse grains by deforming the forging blank with a thickness of δ100-180mm to the plate with a thickness of δ4-90mm. Appropriate rolling temperature is conducive to the diffusion of alloy elements, thereby obtaining a more uniform structure. The holding temperature before rolling of the present invention can be 1160°C, 1167°C, 1170°C, 1175°C or 1180°C.

[0055] Specifically, the holding temperature of the solution treatment is 1000-1100° C., the holding time is 30-150 min, and after the solution treatment, the steel is rapidly cooled to room temperature by water quenching.

[0056] It should be noted that in the present invention, solution treatment is required after rolling, and the solution temperature is controlled to be 1000-1100°C, which can be 1000°C, 1010°C, 1020°C, 1030°C, 1030°C, 1050°C, 1060°C, 1070°C, 1080°C, 1090°C or 1100°C, preferably 1050-1070°C.

[0057] In the present invention, when the solution temperature exceeds 1100°C, the grains grow abnormally and become coarser, reducing the strength and toughness of the stainless steel plate; when the solution temperature is lower than 1000°C, the precipitated phase cannot be dissolved back, which will also affect the performance of the stainless steel plate.

[0058] Specifically, the stainless steel plate provided by the present invention is used in the structural parts of high-magnetic field superconducting magnets, deep space exploration and ultra-low temperature devices at a liquid helium temperature of -296°C.

[0059] It should be noted that the stainless steel sheet produced by the present invention has high strength and toughness. At the ultra-low temperature of -269°C liquid helium, the yield strength of the stainless steel sheet is above 1500MPa, the tensile strength is above 1900MPa, the elongation after fracture is above 30%, the V-type impact energy is 150~170J, and the fracture toughness is 160~200MPa·m 1 / 2 , and the relative magnetic permeability is less than 1.01, which can fully withstand the use of liquid helium temperature of -296℃. Therefore, it can be used in strong magnetic field superconducting magnets, deep space exploration and ultra-low temperature device structures at -296℃ liquid helium temperature.

[0060] In order to more clearly describe the present invention, it is further illustrated by the following examples and comparative examples.

[0061] Example 1 The method for manufacturing the stainless steel sheet comprises the following steps: S1: The ingredients are prepared according to the alloy composition, and the electroslag ingot is obtained after remelting in an electric furnace and electroslag; The smelting process uses 40t electric furnace, AOD and LF. The slag system in electroslag remelting is CaF2-Al2O3-CaO=70%:15%:15%; S2: The φ770mm electroslag ingot is diffused at high temperature and then forged to obtain a forging billet of 150mm×630mm×L with a forging ratio of 8; The temperature of the high temperature diffusion is 1210°C. During the forging process, the start forging temperature is 1110°C and the final forging temperature is 940°C. S3: rolling the obtained forging billet to obtain a rolled plate of δ75 mm thick × 630 mm wide × L, with a rolling ratio of 2; During the rolling process, the holding temperature of the forging billet before rolling is 1170°C, the starting rolling temperature is 1060°C, and the final rolling temperature is 900°C; S4: finally, the obtained rolled billet is subjected to a solution treatment, wherein the holding temperature of the solution treatment is 1050° C., the holding time is 120 min, and after the solution treatment, the billet is rapidly cooled to room temperature by water quenching to obtain a high-strength and tough non-magnetic stainless steel sheet.

[0062] The chemical composition of the plate in this embodiment is shown in Table 1.

[0063] Embodiment 2-5 The ingredients and preparation process of Examples 2-5 are substantially the same as those of Example 1, and the differences are shown in Tables 1 and 2.

[0064]

[0065]

[0066] Comparative Example 1 Comparative Example 1 adopts the preparation method and component ratio of Example 1 in the invention patent with publication number CN117286426A. The details are as follows: Chemical composition: C: 0.0058%, N: 0.27%, O: 0.0013%, P: 0.0046%, S: 0.00:36%, Cr: 21.67%, Ni: 14.47%, Mo: 1.92%, Mn: 6.0%, Si: 0.13%, Nb: 0.07%, V: 0.13%, Cu: 0.15%, Al: 0.008%, H: 0.00057%; Preparation method: Smelting: medium frequency induction furnace and electroslag remelting, where the slag system of electroslag remelting is CaF2-Al2O3-CaO-MgO quaternary slag system; Forging: High temperature diffusion is carried out before forging, and the temperature is 1210℃; the billet forging temperature is 1070℃; the final forging temperature is 890℃; Heat treatment process: solution temperature is 1120℃, keep warm for 2h.

[0067] Comparative Example 2 The preparation process of Comparative Example 2 is substantially the same as that of Example 1, except that the material used in Comparative Example 2 is 316LN.

[0068] Comparative Example 3 The preparation process of Comparative Example 3 is substantially the same as that of Example 1, except that the N content in Comparative Example 3 is 0.27% and the Mn content is 5.5%.

[0069] Comparative Example 4 The preparation process of Comparative Example 4 is substantially the same as that of Example 1, except that the Ti content in Comparative Example 4 is 0.05% and the Co content is 0.08%.

[0070] Comparative Example 5 The preparation process of Comparative Example 5 is substantially the same as that of Example 1, except that the solution temperature in Comparative Example 5 is 1170°C.

[0071] Performance Testing The above-mentioned Examples 1-5 and Comparative Examples 1-5 were subjected to performance tests, mainly including yield strength, tensile strength, impact toughness, elongation after fracture, and fracture toughness. The test temperature was -269°C, and the test results are shown in Table 3.

[0072]

[0073] Combined with Examples 1-5 and Comparative Examples 1-5 and referring to Figures 1 to 9It can be seen that by using the composition ratio and manufacturing method of Examples 1-5 of the present invention, the yield strength of the obtained stainless steel plate is 1514-1693MPa, the tensile strength is 1920-1983MPa, the elongation after fracture is 33-40%, the V-type impact energy is 153~169J, and the fracture toughness K IC 162-193MPa·m 1 / 2 , and the relative magnetic permeability is less than 1.01.

[0074] In addition, by observing the microstructure diagram and the fracture microscopic characterization diagram, it can be seen that the grain size of the steel plate of the present invention is uniform, the size distribution is uniform, and the grain size can reach 4-7 levels. The microstructure is an austenite matrix without M 23 C6 carbide and δ-ferrite. A large number of dimples are found in the cross-section after the -269℃ tensile test, indicating that the invented steels all have ductile fracture.

[0075] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A high-strength and tough non-magnetic stainless steel sheet, characterized in that: Calculated by weight percentage, its chemical composition is: C≤0.006%, N: 0.35~0.45%, O≤0.0020%, P≤0.010%, S≤0.005%, Cr: 21.0~22.0%, Ni: 15.0~16.5%, Mo: 2.3~2.6%, Mn: 6.2~10.0%, Si≤0.20%, Nb<0.04%, V: 0.15~0.25%, Cu: 0.10~0.15%, Al≤0.02%, Ti≤0.02%, Co≤0.05%, and the balance is Fe and unavoidable impurities.

2. The high-strength and tough non-magnetic stainless steel sheet according to claim 1, characterized in that: Calculated by weight percentage, its chemical composition is: C≤0.006%, N: 0.37~0.45%, O≤0.0020%, P≤0.010%, S≤0.005%, Cr: 21.0~21.5%, Ni: 15.0~15.4%, Mo: 2.3~2.5%, Mn: 7.0~10.0%, Si≤0.20%, Nb<0.04%, V: 0.15~0.19%, Cu: 0.10~0.15%, Al≤0.02%, Ti: 0.012~0.02%, Co≤0.04%, and the balance is Fe and unavoidable impurities.

3. The high-strength and tough non-magnetic stainless steel sheet according to claim 1, characterized in that: At the ultra-low temperature of -269℃ liquid helium, the yield strength of the stainless steel plate is above 1500MPa, the tensile strength is above 1900MPa, the elongation after fracture is above 30%, the V-type impact energy is 150~170J, and the fracture toughness is 160~200MPa·m 1 / 2 , and the relative magnetic permeability is less than 1.

01.

4. The high-strength and tough non-magnetic stainless steel sheet according to claim 1, characterized in that: The grain size grade of the stainless steel plate is 4-7.

5. A method for manufacturing a high-strength and tough non-magnetic stainless steel sheet according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: The ingredients are prepared according to the alloy composition, and the electroslag ingot is obtained after electric furnace smelting and electroslag remelting; S2: subjecting the electroslag ingot to high temperature diffusion and then forging to obtain a forging blank; S3: rolling the obtained forging billet to obtain a rolled plate; S4: Finally, the obtained rolled plate is subjected to a solid solution treatment to obtain a high-strength and tough non-magnetic stainless steel plate.

6. The method for manufacturing a high-strength and tough non-magnetic stainless steel sheet according to claim 5, characterized in that: AOD and LF smelting are carried out after electric furnace smelting; the pouring temperature of steel is 1480-1520℃.

7. The method for manufacturing a high-strength and tough non-magnetic stainless steel sheet according to claim 5, characterized in that: During electroslag remelting, the slag system is a ternary slag system of CaF2-Al2O3-CaO, and remelting is carried out under an argon protective atmosphere. The ingot is removed >1h after the remelting is completed.

8. The method for manufacturing a high-strength and tough non-magnetic stainless steel sheet according to claim 5, characterized in that: The temperature of the high temperature diffusion is 1190-1210°C. During the forging process, the start forging temperature is ≥1050°C and the final forging temperature is ≥900°C.

9. The method for manufacturing a high-strength and tough non-magnetic stainless steel sheet according to claim 5, characterized in that: During the rolling process, the holding temperature before rolling is 1160~1180℃, the starting rolling temperature is ≥1050℃, and the final rolling temperature is ≥900℃.

10. The method for manufacturing a high-strength and tough non-magnetic stainless steel sheet according to claim 5, characterized in that: The holding temperature of the solution treatment is 1000-1100° C., the holding time is 30-150 min, and after the solution treatment, the steel is rapidly cooled to room temperature by water quenching.

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