High-strength austenoferritic stainless steel and process for its production

Abstract

The application discloses a kind of high-strength austenitic-ferritic type stainless steel and its preparation process, including the following mass percentage components: C≤0.03%, Si 0.38-0.80%, Mn≤1.00%, P≤0.03%, S≤0.015%, Cr 24.0-26.0%, Ni 6.5-8.5%, Mo 3.0-4.0%, W 0.50-3.50%, N 0.24-0.32%, the rest is Fe and inevitable impurities.The application controls the Si content in steel at about 0.54% to improve the yield strength of steel;2.5% of ferrite forming and modifying element tungsten W is added to control and balance the phase ratio in steel and improve the strength.Using the "induction vacuum degassing furnace smelting + atmosphere protection electroslag furnace remelting" process, the ingot quality is improved, laying the foundation for improving the strength of steel.

Description

Technical Field

[0001] This invention relates to the field of austenitic-ferritic stainless steel technology, specifically to a high-strength austenitic-ferritic stainless steel and its preparation process. Background Technology

[0002] Duplex stainless steel refers to stainless steel where ferrite and austenite each comprise approximately 50%. This type of steel combines the characteristics of both austenitic and ferritic stainless steels. Compared to ferritic stainless steel, it has higher plasticity and toughness, no room temperature brittleness, and significantly improved resistance to intergranular corrosion and weldability. It also retains the 475℃ brittleness and high thermal conductivity of ferritic stainless steel, and exhibits superplasticity. Compared to austenitic stainless steel, it has higher strength and significantly improved resistance to intergranular corrosion and chloride stress corrosion. Duplex stainless steel also has excellent pitting corrosion resistance and is a nickel-saving stainless steel.

[0003] O22Cr25Ni7Mo4N is an austenitic-ferritic super duplex stainless steel. It is the best steel in terms of resistance to localized corrosion, especially pitting corrosion. It also has the characteristics of high strength, resistance to chloride stress corrosion, and weldability. It is suitable for harsh corrosive environments such as marine, petrochemical, oil refining, vacuum salt production, and flue gas desulfurization.

[0004] However, the main disadvantage of O22Cr25Ni7Mo4N stainless steel is its low strength. After solution treatment, its yield strength is about 550MPa and its tensile strength is about 800MPa, which is difficult to meet the increasing demand for stainless steel strength. In addition, (1) the yield of Si element in the smelting process is not very stable, and it is difficult to accurately control the Si content in the steel to about 0.54%; (2) the yield of W element in the smelting process fluctuates relatively much, and W element has a high melting point and high specific gravity, making it difficult to melt quickly and distribute evenly in the molten steel. It is quite difficult to accurately and evenly control the W content in the steel to about 2.5%; (3) the main difficulty of the low temperature aging process is to stabilize and accurately control the ratio of austenite and ferrite duplex structure in the shaft forging to about 50%. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength austenitic-ferritic stainless steel and its preparation process, so as to solve the technical problem of low strength of O22Cr25Ni7Mo4N in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The present invention provides a high-strength austenitic-ferritic stainless steel comprising the following components by mass percentage: C≤0.03%, Si 0.38-0.80%, Mn≤1.00%, P≤0.03%, S≤0.015%, Cr 24.0-26.0%, Ni 6.5-8.5%, Mo 3.0-4.0%, W 0.50-3.50%, N 0.24-0.32%, with the remainder being Fe and unavoidable impurities.

[0008] Furthermore, it includes the following components by mass percentage: C ≤ 0.025%, Si 0.55%, Mn 0.50%, P ≤ 0.03%, S ≤ 0.003%, Cr 24.5%, Ni 7%, Mo 3.2%, W 2.00%, N 0.28%, with the remainder being Fe and unavoidable impurities.

[0009] Furthermore, the high-strength austenitic-ferritic stainless steel has a tensile strength ≥839MPa, a yield strength ≥632MPa, an elongation after fracture ≥30%, and a hardness ≤295HB.

[0010] A process for preparing a high-strength austenitic-ferritic stainless steel includes the following steps:

[0011] S1. Prepare raw materials according to the composition of austenitic-ferritic stainless steel.

[0012] S2. Induction vacuum degassing furnace smelting: melting, pre-deoxidation, vacuum treatment, final deoxidation, casting and tapping;

[0013] S3. Protective atmosphere electroslag furnace remelting: Prepare slag material, remelt, slowly cool and demold to obtain electroslag remelted ingot;

[0014] S4. Perform upsetting, drawing, and rounding forging;

[0015] S6. Perform heat treatment: solution treatment and aging treatment;

[0016] S7. Stainless steel finished products are obtained through machining.

[0017] Furthermore, the induction vacuum degassing furnace smelting specifically involves:

[0018] (1) Except for chromium nitride, the furnace charge is loaded in one go;

[0019] (2) Melt and slag simultaneously to prevent the molten steel from being exposed;

[0020] (3) The diffusion deoxidizer is Al-CaO agent, which is added while melting, with a total amount of about 40 kg per furnace;

[0021] (4) Full melting, temperature 1610℃, feed aluminum wire 5m / t, take samples for full analysis;

[0022] (5) After sampling, remove the residue and feed J-Ca wire at a rate of 3 m / t;

[0023] (6) Evacuate the vacuum, with a vacuum degree ≤100Pa, and maintain for ≥15 minutes;

[0024] (7) After breaking the void, take a full sample for analysis, add 1 kg / t of J-Ce, feed 3 m / t of J-Ca wire, add chromium nitride, and fill with N2;

[0025] (8) The tapping temperature is 1600℃±10℃, and 1kg / t of Ni-Mg is added with the tapping steel;

[0026] (9) Calming time ≥ 5 min; Argon gas is filled into the mold before casting.

[0027] Furthermore, the protective atmosphere electroslag furnace remelting specifically refers to:

[0028] (1) After the electrode is cut, clean the surface with a grinding wheel to remove the glass water and oxide layer, and then weld the dummy electrode.

[0029] (2) Stainless steel shavings are used as arc igniters. They must be baked at ≥500℃ for 2 hours with a base of stainless steel.

[0030] (3) Slag: 115kg of binary pre-melted slag, 5kg of MgO; baked at ≥700℃ for 6h, with 20g / t of aluminum powder added to the slag, and no deoxidizer added during the smelting process;

[0031] (4) Before arc initiation, purge with nitrogen at 30% flow rate for 5 minutes;

[0032] (5) Slag removal shall be carried out according to the basic slag removal process;

[0033] (6) The smelting current shall be based on the corresponding crystallizer process;

[0034] (7) Filling time ≥ 60 minutes, with residual tailings ≥ 80 kg;

[0035] (8) Cool for 150 minutes, cover cooling for ≥24 hours, air cooling.

[0036] Furthermore, the forging process specifically includes:

[0037] (1) The electroslag ingot is heated to 850℃ and the temperature is uniformized for more than 1.5 hours;

[0038] (2) The electroslag ingot is upset, and the upset ratio is ≥2.5;

[0039] (3) Heating process: heating temperature 1160℃, forging start temperature ≥1050℃, forging stop temperature ≥900℃;

[0040] (4) The hammer heating temperature is 1150℃;

[0041] (5) After forging, air cool and rough turn.

[0042] Furthermore, the solution treatment involves heating to 600°C at a heating rate of 80°C / h and holding at this temperature for 120 min; heating to 1050°C at a heating rate of 100°C / h and holding at this temperature for 600 min; then water cooling to below 400°C; and then air cooling to room temperature.

[0043] Furthermore, the aging treatment involves heating to 580±10℃ at a heating rate of 75-85℃ / h and holding at this temperature for 900 minutes; then air cooling to room temperature.

[0044] Based on the above technical solution, the embodiments of the present invention can produce at least the following technical effects:

[0045] (1) The austenitic-ferritic stainless steel provided by the present invention adopts the process of "induction vacuum degassing furnace smelting + atmosphere-protected electroslag furnace remelting" to improve the quality of steel ingots and lay the foundation for improving the strength of steel. By using nitrogen to increase nitrogen in the induction vacuum degassing furnace, the stability of austenite is improved, the phase ratio in duplex stainless steel is balanced, and the strength is improved.

[0046] (2) The austenitic-ferritic stainless steel provided by the present invention controls the Si content in the steel to about 0.54% to improve the yield strength of the steel; 2.5% of ferrite forming and modifying element tungsten W is added to control and balance the phase ratio in the steel and improve the strength.

[0047] (3) The austenitic-ferritic stainless steel provided by the present invention adopts "high temperature solution process + low temperature aging" heat treatment. The strength of the steel is further improved through solution strengthening and aging strengthening. The transfer time during the heat treatment process is shortened to less than 10 seconds. At the same time, it is immersed in water at an angle or horizontally to ensure good solution effect.

[0048] (4) The austenitic-ferritic stainless steel provided by the present invention effectively improves the strength of steel, has high mechanical strength and good ductility at atmospheric temperature and sub-zero temperature, good resistance to abrasion, corrosion and cavitation in marine environment, and can also be used in acidic working environment. Detailed Implementation

[0049] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0051] Raw material description:

[0052] Pure iron: The pure iron used is produced by Changxiang Special Steel Manufacturing Co., Ltd. of Jiangyou City;

[0053] FeCr: The FeCr55C25 produced by Guanghan Lituo Metallurgical Furnace Materials Co., Ltd. is used, containing 56% Cr;

[0054] Ni plate: The Ni plate used is manufactured by Jinchuan Group Co., Ltd., No. 2 Ni;

[0055] J-Mo: Molybdenum metal produced by Jinchuan Group Co., Ltd.

[0056] J-NCr: Chromium nitride produced by China Special Alloy Co., Ltd.

[0057] JW: Uses metallic tungsten produced by Xiamen Tungsten Industry;

[0058] Fe-Si: Ferrosilicon produced by Guanghan Xingkaiyue Company.

[0059] High-strength austenitic-ferritic stainless steels were prepared in Examples 1 and 2, and their chemical composition (by mass percentage) is shown in Table 1, while their raw material proportions (by weight) are shown in Table 2.

[0060] Table 1

[0061]

[0062]

[0063] Table 2

[0064] Example 1 Example 2 Pure iron (kg) 520 530 0Cr13Ni8Mo2Al scrap steel (kg) 860 850 0Cr17 scrap steel (kg) 1500 1500 0Cr17Ni12Mo2 scrap steel (kg) 1450 1430 FeCr55CO3 (kg) 1842 1851 J-Mo(kg) 188 187 Ni plate (kg) 269 271 NCr (kg) 242 240 JW(kg) 160 158 Fe-Si(kg) 11 11 Mg-Ni (kg) 6 6

[0065] Example 1

[0066] ① Prepare the raw materials by mixing the ingredients according to the mass percentage of their chemical components;

[0067] ② Induction vacuum degassing furnace smelting

[0068] B1. Add the raw materials prepared in step ① to the induction vacuum degassing furnace for melting. The melting rate of the induction vacuum degassing furnace is 40 kg / min. At the same time, lime and fluorite powder are added to form slag to prevent the molten steel from being exposed.

[0069] B2. Add diffusion deoxidizer while the raw materials are melting; add the diffusion deoxidizer after the molten pool is visible, adding 5 kg every 30 minutes;

[0070] The diffusion deoxidizer is an Al-CaO agent; wherein the weight ratio of CaO to Al is 80:20; the diffusion deoxidizer is added to the molten steel at a rate of 6.6 kg / t.

[0071] B3. When the temperature inside the smelting furnace rises to 1606℃ and the raw materials are completely melted into molten steel, samples are taken for full analysis, and the chemical composition of the molten steel is adjusted according to the chemical composition of the high-strength austenitic-ferritic stainless steel in Example 1.

[0072] B4. After the results of the full analysis of the sample reach the chemical composition of the high-strength austenitic-ferritic stainless steel in Example 1 of Table 1, slag removal is performed.

[0073] B5. After slag removal is completed, feed aluminum wire and J-Ca wire for pre-deoxidation;

[0074] The mass ratio of the fed aluminum wire to the molten steel is 0.9:1000; the mass ratio of the fed J-Ca wire to the molten steel is 0.1-0.115:1000.

[0075] B6. After the aluminum wire and J-Ca wire are fed, the smelting furnace is closed and a vacuum is drawn to allow the molten steel to be vacuum treated for 20 minutes at a vacuum degree ≤100Pa and a temperature of 1611℃.

[0076] B7. After the vacuum treatment of the molten steel is completed, a vacuum breaking treatment is carried out. After the vacuum breaking treatment, a sample is taken for full analysis to verify the accuracy of the chemical composition adjustment in B3. If the chemical composition in the molten steel does not match the chemical composition in the high-strength austenitic-ferritic stainless steel of Example 1, it is adjusted again to match the chemical composition in the high-strength austenitic-ferritic stainless steel of Example 1.

[0077] B8. Final deoxidation: Heat the molten steel to 1611℃, then add cerium to the molten steel, feed J-Ca wire at the same time, and add nickel-magnesium alloy before tapping the steel. Final deoxidation ensures that the oxygen content is ≤30ppm.

[0078] The cerium is added to the molten steel at a rate of 1 kg / t; the J-Ca wire is added to the molten steel at a rate of 0.105 kg / t; the nickel-magnesium alloy is added to the molten steel at a rate of 1 kg / t.

[0079] B9. After final deoxidation, the steel is tapped at a temperature of 1610℃. After tapping, the steel is cast into an electrode rod by the ingot casting method to obtain a remelted electrode rod for electroslag remelting.

[0080] Before casting, the molten steel is first calmed for ≥5 minutes; and before pouring, argon gas is first introduced into the steel ingot mold at a pressure of 0.2 MPa for 2 minutes.

[0081] ③ Electroslag remelting to obtain steel ingots;

[0082] C1. Slag Material Preparation: The slag material consists of the following components by weight: 115 parts of binary premelted slag; 5 parts of magnesium oxide; and 0.3 parts of aluminum powder.

[0083] C2. After heating the slag to a molten state, pour it into the crystallizer. Slowly insert the remelted electrode rod obtained in step ② into the molten slag. Before arc ignition, fill with argon gas. During arc ignition, control the current at 9000A, the voltage at 41V, and the time at 60min. Then, energize the arc for remelting. During remelting, control the current at 10200A, the voltage at 39V, and the time at 150min. After remelting, fill the slag. During filling, control the current at 9000A, the voltage at 36V, and the time at 30min.

[0084] Before inserting the remelting electrode rod into the molten slag, the remelting electrode is cut with a cap (the cap is a concentrated shrinkage area set to prevent shrinkage and voids during the cooling process of the molten steel), and then the remelting electrode rod is baked at a temperature greater than 500℃ for 2 hours. Argon gas is introduced before arc ignition by introducing argon gas into the crystallizer for 5 minutes with the proportional valve opening at 30%. When obtaining the steel ingot through electroslag remelting, the arc is ignited using stainless steel shavings, and a bottom pad (a 20-40mm piece is cut on the electrode after the cap is cut) is sawn from this steel grade and baked at ≥500℃ for 2 hours.

[0085] C3. After electroslag remelting and filling, the steel ingot is slowly cooled and then demolded to obtain an electroslag remelted ingot;

[0086] The slow cooling of the steel ingot is as follows: first, natural cooling for 150 minutes, then hood cooling for ≥24 hours, and finally air cooling to ≤50℃;

[0087] ④ Forged round steel

[0088] D1. Flatten both ends of the electroslag remelted ingot obtained in step ③, and cut off the bottom pad and shrinkage cavity; heat to 850℃ for a homogenization time of more than 1.5 hours, and heat to 1160℃; perform upsetting, drawing, and rounding forging on the electroslag remelted ingot, and air cool it after forging to obtain round steel.

[0089] ⑤Rough turning of round steel bars

[0090] After air cooling in step 4, the ends of the round steel are flattened, rough machined, and inspected for defects before being sent for heat treatment.

[0091] ⑥ Heat treatment

[0092] F1, Solution treatment

[0093] The temperature is increased to 600℃ at a rate of 80℃ / h and held at this temperature for 120 min; the temperature is increased to 1050℃ at a rate of 100℃ / h and held at this temperature for 600 min; then the temperature is cooled to below 400℃ by water; and then cooled to room temperature by air.

[0094] F2, Timeliness Processing

[0095] Heat to 580±10℃ at a heating rate of 75-85℃ / h and hold at this temperature for 900 min; then air cool to room temperature.

[0096] ⑦ Machining

[0097] Stainless steel finished products are obtained by precision machining on a horizontal lathe.

[0098] Example 2

[0099] ① Prepare the raw materials by mixing the ingredients according to the mass percentage of their chemical components;

[0100] ② Induction vacuum degassing furnace smelting

[0101] B1. Add the raw materials prepared in step ① to the induction vacuum degassing furnace for melting. The melting rate of the induction vacuum degassing furnace is 40 kg / min. At the same time, lime and fluorite powder are added to form slag to prevent the molten steel from being exposed.

[0102] B2. Add diffusion deoxidizer while the raw material is melting; add the diffusion deoxidizer after the molten pool is visible, adding 4 kg every 25 minutes;

[0103] The diffusion deoxidizer is an Al-CaO agent; wherein the weight ratio of CaO to Al is 80:20; the diffusion deoxidizer is added to the molten steel at a rate of 6.4 kg / t.

[0104] B3. When the temperature inside the smelting furnace rises to 1580℃ and the raw materials are completely melted into molten steel, samples are taken for full analysis, and the chemical composition of the molten steel is adjusted according to the chemical composition of the high-strength austenitic-ferritic stainless steel in Example 2.

[0105] B4. After the results of the full analysis of the sample reach the chemical composition of the high-strength austenitic-ferritic stainless steel in Example 2, slag removal is performed.

[0106] B5. After slag removal is completed, feed aluminum wire and J-Ca wire for pre-deoxidation;

[0107] The mass ratio of the fed aluminum wire to the molten steel is 1:1000; the mass ratio of the fed J-Ca wire to the molten steel is 0.1:1000.

[0108] B6. After the aluminum wire and J-Ca wire are fed, the smelting furnace is closed and a vacuum is drawn to allow the molten steel to be vacuum treated for 20 minutes at a vacuum degree ≤100Pa and a temperature of 1580℃.

[0109] B7. After the vacuum treatment of the molten steel is completed, a vacuum breaking treatment is performed. After the vacuum breaking treatment, a sample is taken for full analysis to verify the accuracy of the chemical composition adjustment in B3. If the chemical composition in the molten steel does not match the chemical composition in the high-strength austenitic-ferritic stainless steel of Example 2, it is adjusted again to match the chemical composition in the high-strength austenitic-ferritic stainless steel of Example 2.

[0110] B8. Final deoxidation: Heat the molten steel to 1600℃, then add cerium to the molten steel, feed J-Ca wire at the same time, and add nickel-magnesium alloy before tapping the steel. Final deoxidation ensures that the oxygen content is ≤30ppm.

[0111] The cerium is added to the molten steel at a rate of 0.8 kg / t; the J-Ca wire is added to the molten steel at a rate of 0.1 kg / t; and the nickel-magnesium alloy is added to the molten steel at a rate of 1.2 kg / t.

[0112] B9. After final deoxidation, the steel is tapped at a temperature of 1600℃. After tapping, the steel is cast into electrode rods by ingot casting method to obtain remelted electrode rods for electroslag remelting.

[0113] Before casting, the molten steel is first calmed for ≥5 minutes; and before pouring, argon gas is first introduced into the steel ingot mold at a pressure of 0.2 MPa for 2 minutes.

[0114] ③ Electroslag remelting to obtain steel ingots;

[0115] C1. Slag Material Preparation: The slag material consists of the following components by weight: 110 parts of binary premelted slag; 6 parts of magnesium oxide; and 0.4 parts of aluminum powder.

[0116] C2. After heating the slag to a molten state, pour it into the crystallizer. Slowly insert the remelted electrode rod obtained in step ② into the molten slag. Before arc ignition, fill with argon gas. During arc ignition, control the current at 10000A, the voltage at 40V, and the time at 50min. Then, ignite the arc to remelt. During remelting, control the current at 10500A, the voltage at 41V, and the time at 150min. After remelting, fill the slag. During filling, control the current at 10000A, the voltage at 37V, and the time at 20min.

[0117] Before inserting the remelting electrode rod into the molten slag, the remelting electrode is cut with a cap (the cap is a concentrated shrinkage area set to prevent shrinkage and voids during the cooling process of the molten steel), and then the remelting electrode rod is baked at a temperature greater than 500°C for 2 hours. Argon gas is introduced before arc ignition by introducing argon gas into the crystallizer for 5 minutes with the proportional valve opening at 30%. When obtaining the steel ingot through electroslag remelting, the arc is ignited using stainless steel cutting chips, and the bottom pad is sawn from this steel grade and baked at ≥500°C for 2 hours.

[0118] C3. After electroslag remelting and filling, the steel ingot is slowly cooled and then demolded to obtain an electroslag remelted ingot;

[0119] The slow cooling of the steel ingot is as follows: first, natural cooling for 150 minutes, then hood cooling for ≥24 hours, and finally air cooling to ≤50℃;

[0120] ④ Forged round steel

[0121] D1. Flatten both ends of the electroslag remelted ingot obtained in step ③, and cut off the bottom pad and shrinkage cavity; heat to 850℃ for a homogenization time of more than 1.5 hours, and heat to 1160℃; perform upsetting, drawing, and rounding forging on the electroslag remelted ingot, and air cool it after forging to obtain round steel.

[0122] ⑤Rough turning of round steel bars

[0123] After air cooling in step 4, the ends of the round steel are flattened, rough machined, and inspected for defects before being sent for heat treatment.

[0124] ⑥ Heat treatment

[0125] F1, Solution treatment

[0126] The temperature was increased to 580℃ at a rate of 75℃ / h and held at this temperature for 130 min; the temperature was increased to 1040℃ at a rate of 95℃ / h and held at this temperature for 620 min; then the temperature was cooled to below 400℃ by water; and then cooled to room temperature by air.

[0127] F2, Timeliness Processing

[0128] Heat to 580±10℃ at a heating rate of 75-85℃ / h and hold at this temperature for 900 min; then air cool to room temperature.

[0129] ⑦ Machining

[0130] Stainless steel finished products are obtained by precision machining on a horizontal lathe.

[0131] Performance testing:

[0132] (1) The stainless steel materials prepared in Examples 1-2 were subjected to performance testing. The test results are shown in Table 3:

[0133] Table 3

[0134] Tensile strength (MPa) Yield strength MPa Elongation after fracture % Hardness HB Example 1 854 642 33.0 289 Example 2 839 632 35.5 285 Performance requirements ≥800 ≥550 ≥25 ≤310

[0135] (2) Following the formulation and preparation method of Example 1, the high-strength austenitic-ferritic stainless steel was prepared by melting at different times and in different vacuum melting furnaces. The performance parameters of the prepared stainless steel are shown in Table 4.

[0136] Table 4

[0137]

[0138]

[0139] Finally, it should be noted that:

[0140] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation process for high-strength austenitic-ferritic stainless steel, characterized in that, The austenitic-ferritic stainless steel comprises the following components by mass percentage: C≤0.03%, Si 0.38-0.80%, Mn≤1.00%, P≤0.03%, S≤0.015%, Cr 24.0-26.0%, Ni 6.5-8.5%, Mo 3.0-4.0%, W 1.98-2.05%, N 0.24-0.32%, with the remainder being Fe and unavoidable impurities; the high-strength austenitic-ferritic stainless steel has a tensile strength ≥839 MPa, a yield strength ≥632 MPa, an elongation after fracture ≥30%, and a hardness ≤295HB; the preparation process includes the following steps: S1. Prepare raw materials according to the composition of austenitic-ferritic stainless steel. S2, Induction Vacuum Degassing Furnace Smelting: Melting, Pre-deoxidation, Vacuum Treatment, Final Deoxidation, Casting and Steel Tapping; In S2, during melting, the raw material is heated to 1600-1650℃ and completely melted into molten steel. During vacuuming, the molten steel is vacuum treated at a vacuum degree ≤100Pa and a temperature of 1611℃ for 20 minutes. Before casting, protective gas is applied and the steel is calmed. S3, Protective Atmosphere Electroslag Remelting: Prepare slag material, remelt, slowly cool and demold to obtain electroslag remelted ingot; the slag material in S3 includes, by weight, 115 parts of binary premelted slag; 5 parts of magnesium oxide; 0.3 parts of aluminum powder; the slow cooling is: first, natural cooling for 150 min, then hood cooling for ≥24 h, and finally air cooling to ≤50℃; S4. Perform upsetting, drawing, and rounding forging; S5. Perform heat treatment: solution treatment and aging treatment; the solution treatment in S5 is to heat to 600℃ at a heating rate of 80℃ / h and hold at this temperature for 120min; then heat to 1050℃ at a heating rate of 100℃ / h and hold at this temperature for 600min; then water cool to below 400℃; then air cool to room temperature; the aging treatment in S5 is to heat to 580±10℃ at a heating rate of 75-85℃ / h and hold at this temperature for 900min; then air cool to room temperature. S6. Stainless steel finished products are obtained through machining.

2. The preparation process of high-strength austenitic-ferritic stainless steel according to claim 1, characterized in that, Before forging, the material is heated to 850℃ and the temperature is uniformized for more than 1.5 hours.

3. The preparation process of high-strength austenitic-ferritic stainless steel according to claim 1, characterized in that, The austenitic-ferritic stainless steel comprises the following components by mass percentage: C≤0.025%, Si 0.55%, Mn 0.50%, P≤0.03%, S≤0.003%, Cr 24.5%, Ni 7%, Mo 3.2%, W 2.00%, N 0.28%, with the remainder being Fe and unavoidable impurities.

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