Austenite hydrogen-resistant stainless steel and preparation method thereof

Abstract

The invention discloses austenite hydrogen-resistant stainless steel and a preparation method thereof, and belongs to the field of metal materials. The austenitic hydrogen-resistant stainless steel comprises the following chemical components in percentage by mass: less than or equal to 0.06% of C, less than or equal to 1.00% of Si, 3.00-5.00% of Mn, 19.50-22.00% of Cr, 11.00-13.00% of Ni, 1.50-2.00% of Mo, 1.50-3.50% of Cu, 0.20-0.30% of V, 0.10-0.23% of Nb, 0.30-0.40% of [N], less than or equal to 0.01% of P, less than or equal to 0.004% of S, less than or equal to 0.003% of [O] and the balance of Fe. The preparation method comprises the steps of vacuum induction melting, high-temperature homogenization, forging, hot rolling and heat treatment. The method solves the problems that traditional austenitic stainless steel is poor in hydrogen embrittlement resistance and an existing process is difficult to consider precise regulation and control of high purity, low impurities and hydrogen trap elements at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of metal materials, relates to a method for improving the hydrogen embrittlement resistance of austenitic stainless steel, and specifically relates to an austenitic hydrogen-resistant stainless steel and a preparation method thereof. Background Art

[0002] With the continuous growth of global energy demand and the increasing attention to environmental protection, hydrogen energy, as a clean, efficient and renewable energy, has received widespread attention. The combustion product of hydrogen energy is only water, and it does not produce greenhouse gases such as carbon dioxide. It is considered to be one of the potential solutions to the depletion of traditional fossil fuels and the greenhouse effect caused by large-scale carbon dioxide emissions. However, the storage and transportation of hydrogen has always been one of the key difficulties in the application of hydrogen energy. In a long-term hydrogen-rich environment, hydrogen molecules or hydrogen ions will gradually be reduced to hydrogen atoms. Hydrogen atoms can easily penetrate into the interior of the storage and transportation materials and interact with material defects (such as dislocations, grain boundaries, twins, inclusions, etc.), resulting in a sharp degradation of the mechanical properties of the material and even brittle fracture (hydrogen embrittlement), which seriously restricts the large-scale application of hydrogen energy technology.

[0003] Among many metal materials, austenitic stainless steel (such as 316L) exhibits better hydrogen embrittlement resistance than ferrite and martensitic stainless steel due to its lower hydrogen diffusion coefficient and higher hydrogen solubility. At present, the mainstream production processes of hydrogen-resistant austenitic stainless steel are concentrated on electric furnace smelting, continuous casting, forging / rolling and heat treatment processes. However, electric furnace smelting has problems such as low alloy purity, high inclusion content, and difficulty in effectively volatilizing the five harmful elements (Pb, Sb, Bi, Sn, As), which increases the risk of grain boundary segregation of the material and increases the sensitivity to hydrogen embrittlement. In contrast, vacuum induction melting technology can promote the volatilization of harmful elements through a high vacuum environment, accurately control the ratio of active elements (such as hydrogen trap-forming elements such as V and Nb), and recover precious metal raw materials, thereby significantly improving the purity, toughness and corrosion resistance of the material.

[0004] Although vacuum induction melting has obvious advantages in improving the performance of stainless steel, there are still few domestic patents on the vacuum induction preparation process of austenitic hydrogen-resistant stainless steel. For example, although the Chinese patent with application publication number CN116590595A discloses a production process for improving the hydrogen embrittlement resistance of stainless steel hydrogen storage equipment, including double vacuum smelting, forging, heat treatment and welding forming, it does not optimize and study the specific process of vacuum induction melting. Similarly, although the Chinese patent with application publication number CN116590630A involves a low-cost austenitic stainless steel for high-pressure hydrogen storage and its preparation method, including purification smelting, homogenization, forging, heat treatment and other steps, it only uses a vacuum smelting process to prepare ingots, lacking in-depth research and optimization of the vacuum induction melting process.

[0005] Therefore, it is particularly necessary to develop a vacuum induction preparation process for austenitic hydrogen-resistant stainless steel. By optimizing the specific process parameters of vacuum induction melting, the hydrogen embrittlement resistance of austenitic stainless steel can be further improved to meet the application requirements of hydrogen energy storage and transportation equipment under extreme conditions such as high pressure and high temperature. This will not only help promote the development of hydrogen energy technology, but also provide safer and more reliable material selection for engineering applications in related fields. Summary of the invention

[0006] The technical problem to be solved by the present invention is that traditional austenitic stainless steel is prone to brittle fracture due to the interaction between hydrogen atom diffusion and defects in a hydrogen environment, and the existing process is difficult to achieve high purity, low impurities and precise control of hydrogen trap elements.

[0007] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0008] In a first aspect, the present invention provides a method for preparing austenitic hydrogen-resistant stainless steel, wherein an ingot is obtained by vacuum induction melting, and then the ingot is subjected to high-temperature homogenization, forging, hot rolling and heat treatment to obtain the austenitic hydrogen-resistant stainless steel.

[0009] In the above preparation method, the vacuum induction melting specifically comprises the following steps:

[0010] a. Loading: Load metal chromium, molybdenum bars, niobium bars, pure iron bars, electrolytic copper, nickel plates and return materials into the crucible of the vacuum induction furnace, and load FeV80, high-purity silicon, CrN alloy and Ni-Mg alloy into the charging bin;

[0011] b. Melting: After the molten pool is formed, stop vacuuming and fill with nitrogen. Add FeV80 and high-purity silicon in sequence before the molten pool is completely melted;

[0012] c. Refining: After refining, cool down and add CrN alloy. After complete melting, shut down the power and cool down and add Ni-Mg alloy.

[0013] d. Pouring: The ingot is obtained by tapping and pouring, and its chemical composition, by mass percentage, includes C≤0.06%, Si≤1.00%, 3.00≤Mn≤5.00%, 19.50%≤Cr≤22.00%, 11.00%≤Ni≤13.00%, 1.50%≤Mo≤2.00%, 1.50%≤Cu≤3.50%, 0.20%≤V≤0.30%, 0.10%≤Nb≤0.23%, 0.30%≤[N]≤0.40%, P≤0.01%, S≤0.004%, [O]≤0.003%, and the balance is Fe.

[0014] Furthermore, in the above step a, the return material is a return material of high manganese and high nitrogen stainless steel, and its chemical composition is: C0.095%, Si 0.32%, Mn 18.36%, Cr 19.43%, Ni 0.12%, [N] 0.48%, and the balance is Fe.

[0015] Furthermore, in the above step a, the purity of the high-purity silicon is ≥99%.

[0016] Furthermore, in the above step a, when charging the furnace, the return material, metallic chromium and electrolytic copper are first loaded into the bottom of the crucible, and then the molybdenum bars, niobium bars and pure iron rods are loaded, and the nickel plate is placed on the top layer.

[0017] Furthermore, in the above step a, the charging bin is loaded with FeV80, high purity silicon, CrN alloy and Ni-Mg alloy in layers and intervals in sequence.

[0018] Furthermore, in the above step a, the return material, pure iron rod, nickel plate and molybdenum bar need to be subjected to surface shot blasting treatment to remove oil and dirt before loading into the furnace.

[0019] Furthermore, in the above step a, the Ni-Mg alloy needs to be descaled before being loaded into the warehouse.

[0020] Furthermore, in the above step b, vacuuming is started after the loading is completed, and when the vacuum degree in the furnace is less than 6Pa, power is supplied to preheat and raise the temperature.

[0021] Furthermore, in the above step b, when nitrogen is charged, the nitrogen pressure in the furnace is controlled to be ≥50000Pa.

[0022] Furthermore, in the above step c, the refining temperature is 1550±15°C, and the refining time is 15 to 25 minutes.

[0023] Furthermore, in the above step c, when melting the Ni-Mg alloy, the molten pool temperature is controlled to be no higher than 1500°C.

[0024] Furthermore, in the above step d, the tapping temperature is 1450-1475° C., and pouring is performed under a nitrogen protective atmosphere, and vacuuming is not allowed before the molten steel is completely solidified.

[0025] In the above preparation method, the high temperature homogenization is specifically: the ingot is subjected to high temperature homogenization treatment, the temperature of the high temperature homogenization is 1190±10°C, and the insulation time is 20h.

[0026] In the above preparation method, the forging process is specifically as follows: the ingot after high temperature homogenization is forged into a square material of 150 mm×150 mm, the initial forging temperature of the forging process is ≥1080°C, and the final forging temperature is ≥950°C.

[0027] In the above preparation method, the hot-rolled product is specifically: the square material is heated to 1160±10℃ and kept warm for 3h before hot rolling. The starting rolling temperature of the hot-rolled product is ≥1050℃, the final rolling temperature is ≥880℃, and a hot-rolled plate with a thickness of 30mm is obtained after 8 rolling passes, which is then air-cooled to room temperature to obtain a plate.

[0028] In the above preparation method, the heat treatment is specifically: heat treating the plate, solution treating at 1050±10°C for 30 minutes, and water cooling to room temperature to obtain austenitic hydrogen-resistant stainless steel.

[0029] In a second aspect, the present invention provides austenitic hydrogen-resistant stainless steel produced by the above production method.

[0030] The tensile strength of the above-mentioned austenitic hydrogen-resistant stainless steel is ≥758MPa, the elongation is ≥40.2%, the cross-sectional shrinkage is ≥68%, and the impact toughness is ≥77.3J.

[0031] The beneficial effects of the present invention are as follows: the present invention aims at the advantages of preparing metal materials by vacuum induction melting, and develops a process for preparing austenitic hydrogen-resistant stainless steel by vacuum induction melting. Through the combined optimization of charging sequence, vacuum-nitrogen alternating control, phased addition of hydrogen trap elements and utilization of return materials in the vacuum induction melting process, a semi-coherent nanoscale precipitation phase (V / Nb-C / N) is formed, which significantly reduces the hydrogen diffusion rate and inhibits hydrogen embrittlement. The smelting process designed by the present invention recycles precious metal materials, reduces the content of the five harmful elements of lead, antimony, bismuth, tin and arsenic (the five harmful elements are easily segregated at the grain boundaries, and interact with hydrogen to deteriorate the mechanical properties of the material), and at the same time, the composition control of hydrogen trap-forming elements (vanadium, niobium) is more precise, and the resulting material exhibits excellent hydrogen embrittlement resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a scanning transmission electron microscope high-angle annular dark field imaging of the austenitic hydrogen-resistant stainless steel obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clear, the present application is further described in detail below in combination with the implementation methods. Unless otherwise defined, all scientific and technological terms used herein have the same meanings as understood by ordinary technicians in the field.

[0034] The invention provides an austenitic hydrogen-resistant stainless steel, the chemical composition of which is calculated by mass percentage: C≤0.06%, Si≤1.00%, 3.00≤Mn≤5.00%, 19.50%≤Cr≤22.00%, 11.00%≤Ni≤13.00%, 1.50%≤Mo≤2.00%, 1.50%≤Cu≤3.50%, 0.20%≤V≤0.30%, 0.10%≤Nb≤0.23%, 0.30%≤[N]≤0.40%, P≤0.01%, S≤0.004%, [O]≤0.003%, and the balance is Fe.

[0035] In some embodiments of the present invention, the raw materials for preparing austenitic hydrogen-resistant stainless steel include return materials, metallic chromium, electrolytic copper, molybdenum bars, niobium bars, pure iron rods, nickel plates, FeV80, high-purity silicon, CrN alloys and Ni-Mg alloys.

[0036] In some embodiments of the present invention, the return material is a return material of high manganese and high nitrogen stainless steel, and its chemical composition is: C 0.095%, Si 0.32%, Mn 18.36%, Cr 19.43%, Ni 0.12%, [N] 0.48%, and the remainder is Fe; the purity of the high-purity silicon is ≥99%.

[0037] In some embodiments of the present invention, raw materials are carefully prepared according to the chemical composition of austenitic hydrogen-resistant stainless steel. For example, return materials, pure iron rods, nickel plates and molybdenum bars need to be surface shot blasted to remove oil and dirt; Ni-Mg alloys need to remove oxide scales; all raw materials are stored in a dry space for standby use to prevent the raw materials from absorbing moisture and oxidation again.

[0038] The present invention also provides a method for preparing the above-mentioned austenitic hydrogen-resistant stainless steel, which specifically includes vacuum induction melting, high-temperature homogenization, forging, hot rolling and heat treatment steps.

[0039] In the above preparation method, the vacuum induction melting specifically comprises the following steps.

[0040] Step 1, charging: According to the material composition control requirements, prepare the raw materials of each element. When charging the furnace, first load the return material, metallic chromium and electrolytic copper into the bottom of the crucible of the vacuum induction furnace, and then load the molybdenum bar, niobium bar and pure iron rod, and put the nickel plate on the top layer; FeV80, high-purity silicon, CrN alloy and Ni-Mg alloy are loaded into the charging bin in layered intervals.

[0041] In some embodiments of the present invention, if all the nickel plates cannot be added at one time when the nickel plates are used for capping, the excess nickel plates can be cut into small pieces and added to the molten pool simultaneously during the subsequent Ni-Mg alloy addition stage.

[0042] The charging sequence of the present invention has the effect of reducing the mixing of impurities, which is specifically embodied as follows:

[0043] (1) Placing the return material, metallic chromium and electrolytic copper at the bottom of the crucible can preferentially remove the residual trace harmful elements (such as Pb, Sb, Bi, etc.) through high-temperature volatilization, effectively preventing impurities from mixing into the molten steel during the melting process;

[0044] (2) Metal chromium and electrolytic copper are loaded into the bottom in advance, which can form a stable molten pool in the early stage of smelting, provide a uniform heat field for subsequent material melting, and reduce the mixing of impurities caused by local temperature fluctuations;

[0045] (3) The bottom material (return material, metal chromium, electrolytic copper) is melted first to form a basic melt, and then the middle and upper materials (molybdenum, niobium, pure iron) are gradually melted to avoid crucible erosion caused by local overheating of high melting point metals and reduce impurities in refractory materials (such as SiO 2 、Al 2 O 3 ) dissolution;

[0046] (4) The addition of electrolytic copper can adjust the melt fluidity. It is easy to combine with sulfur to form Cu at high temperature. 2 After melting, S preferentially floats to the surface of the melt and is adsorbed by the slag phase, further reducing the residual impurities.

[0047] Step 2, melting: start to evacuate after loading is completed, start to supply power and preheat when the vacuum degree in the furnace is less than 6Pa; stop evacuating when the charge forms a molten pool by naked eye, fill with high-purity nitrogen (99.99%), and control the nitrogen pressure in the furnace to be ≥50000Pa (the higher the nitrogen pressure, the better, while ensuring no leakage); then continue to increase the power linearly, and add FeV80 and high-purity silicon in sequence before the charge is almost melted.

[0048] The invention uses high vacuum smelting to volatilize harmful elements such as lead, antimony, bismuth, tin and arsenic as much as possible during the melting of raw materials, thereby reducing the enrichment of harmful elements at grain boundaries.

[0049] Step 3, refining: after the charge is completely melted, enter the refining phase, control the refining temperature to 1550±15℃, and the refining time to 15-25min; after the refining is completed, cool down and add CrN alloy, then quickly heat up and melt at high power; after the CrN alloy is melted, immediately turn off the power to cool down, add Ni-Mg alloy for deep deoxidation, turn on the power and increase the power to melt the alloy, ensuring that the molten pool temperature is not higher than 1500℃.

[0050] Since nitrogen protection needs to be filled before the vacuum induction refining period, it is impossible to maintain refining under the vacuum bar. Therefore, the present invention selects the return material of high manganese and high nitrogen stainless steel in the batching stage. Its role is to reduce the impurity content brought into the raw material and recover the precious metal raw material, and secondly, to ensure that sufficient N enters the final material matrix. The nitrogen element in the return material works together with the CrN alloy to form a nitrogen protection atmosphere, inhibit the oxidation reaction, reduce the oxygen content, and thus reduce the risk of oxide inclusions. At the same time, the present invention improves the raw material utilization rate through layered charging, ensures the accurate ratio of precious metals (such as Mo, Nb) and active elements (such as V, Si), reduces oxidation losses, and improves the uniformity of alloy components.

[0051] Step 4, pouring: Thermocouple temperature measurement, the steel tapping temperature is 1450 ~ 1475 ℃, poured into 200mm × 200mm ingots, before the molten steel is completely solidified, no vacuum is allowed. After the surface of the ingot is cleaned, the composition of the ingot produced by the process is detected, and the chemical composition, by mass percentage, includes C≤0.06%, Si≤1.00%, 3.00≤Mn≤5.00%, 19.50%≤Cr≤22.00%, 11.00%≤Ni≤13.00%, 1.50%≤Mo≤2.00%, 1.50%≤Cu≤3.50%, 0.20%≤V≤0.30%, 0.10%≤Nb≤0.23%, 0.30%≤[N]≤0.40%, P≤0.01%, S≤0.004%, [O]≤0.003%, and the balance is Fe.

[0052] In the above preparation method, the high temperature homogenization is specifically as follows: the ingot is subjected to high temperature homogenization treatment, the temperature of the high temperature homogenization is 1190±10℃, and the holding time is 20h. The forging blanking is specifically as follows: the ingot after high temperature homogenization is forged into a square material of 150mm×150mm, the initial forging temperature of the forging blanking is ≥1080℃, and the final forging temperature is ≥950℃. The hot rolling product is specifically as follows: the square material is heated to 1160±10℃ and kept for 3h before hot rolling, the starting rolling temperature of the hot rolling product is ≥1050℃, the final rolling temperature is ≥880℃, and after 8 passes of rolling, a hot-rolled plate with a thickness of 30mm is obtained, and the plate is obtained by air cooling. The heat treatment is specifically as follows: the plate is heat treated, solution treated at 1050±10℃ for 30min, and water cooled to room temperature to obtain austenitic hydrogen-resistant stainless steel.

[0053] Specific examples will be listed below to explain the scheme of the present invention. It will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the examples, the techniques or conditions described in the literature in this area or the product instructions are used. Reagents or instruments used that do not indicate manufacturers are all conventional products that can be obtained commercially.

[0054] Example 1 Preparation of austenitic hydrogen-resistant stainless steel, the detailed steps are as follows:

[0055] (1) Selected raw materials: Selected metal chromium, molybdenum bars, niobium bars, pure iron bars, high-purity silicon (99%), electrolytic copper, nickel plates, FeV80, Ni-Mg alloy, CrN alloy and high manganese and high nitrogen stainless steel return materials (chemical composition is C 0.095%, Si 0.32%, Mn 18.36%, Cr 19.43%, Ni 0.12%, [N] 0.48%, the balance is Fe); the return materials, pure iron bars, nickel plates and molybdenum bars need to be shot blasted on the surface to remove oil and dirt, and the Ni-Mg alloy must be sprayed to remove the oxide scale. All raw materials are stored in a dry space for use to prevent the raw materials from absorbing moisture and oxidation again.

[0056] (2) Loading: According to the material composition control requirements, the raw materials of each element are prepared, and the P content of the raw materials is 60ppm and the S content is 25ppm. First, the return material, metallic chromium and electrolytic copper are loaded into the bottom of the crucible, and then molybdenum bars, niobium bars and pure iron rods are loaded, and the nickel plate is placed on the top layer; FeV80, high-purity silicon, CrN alloy and Ni-Mg alloy are loaded in the charging bin in turn at intervals.

[0057] (3) Melting: After loading, vacuuming begins. When the vacuum degree is less than 6 Pa, power is supplied to preheat the furnace. When a molten pool is formed by the charge, vacuuming is stopped and high-purity nitrogen (99.99%) is filled until the nitrogen pressure in the furnace reaches 54,000 Pa. The power is then increased linearly. FeV80 and high-purity silicon are added before the charge is almost completely melted.

[0058] (4) Refining: After the charge is completely melted, the refining phase begins. The refining temperature is 1535°C and the refining time is 25 min. After the refining is completed, the temperature is lowered and CrN alloy is added. Then, the temperature is rapidly increased at high power to melt the alloy. After the CrN alloy is melted, the power is immediately turned off to cool the alloy. Ni-Mg alloy is added for deep deoxidation. The power is then turned on and the power is increased to melt the alloy. The final temperature of the molten pool is determined to be 1470°C.

[0059] (5) Steel pouring: The temperature was measured by thermocouple and the steel tapping temperature was 1450°C. The steel was poured into a 200 mm × 200 mm square ingot under nitrogen protective atmosphere. Vacuuming was not allowed before the molten steel was completely solidified.

[0060] (6) Composition and performance testing: After taking out the ingot, cut off the head and tail, clean the surface, and the chemical composition of the ingot is shown in Table 1 (the balance is Fe and unavoidable impurities).

[0061] (7) High temperature homogenization: The ingot is subjected to high temperature homogenization treatment at a temperature of 1190±10°C and a holding time of 20h.

[0062] (8) Forging: The ingot after high temperature homogenization is forged into a square material of 150 mm × 150 mm. The initial forging temperature of the forging is 1088 °C and the final forging temperature is 961 °C.

[0063] (9) Hot-rolled product: The square material is heated to 1160±10°C and kept at this temperature for 3 hours before hot-rolling. The starting rolling temperature of the hot-rolled product is 1060°C, and the final rolling temperature is 908°C. After 8 passes (the reduction in each pass is: 25.0%, 24.0%, 20.0%, 18.1%, 17.9%, 15.2%, 12.8%, 11.8%), a hot-rolled plate with a thickness of 30 mm is obtained, and the plate is air-cooled to room temperature to obtain a plate.

[0064] (10) Heat treatment: The plate is heat treated by solution treatment at 1050±10°C for 30 min and then water cooled to room temperature to obtain austenitic hydrogen-resistant stainless steel.

[0065] Example 2 Preparation of austenitic hydrogen-resistant stainless steel, the detailed steps are as follows:

[0066] (1) Selected raw materials: Selected metal chromium, molybdenum bars, niobium bars, pure iron bars, high-purity silicon (99%), electrolytic copper, nickel plates, FeV80, Ni-Mg alloy, CrN alloy and high manganese and high nitrogen stainless steel return materials (chemical composition is C 0.095%, Si 0.32%, Mn 18.36%, Cr 19.43%, Ni 0.12%, [N] 0.48%, the balance is Fe); the return materials, pure iron bars, nickel plates and molybdenum bars need to be shot blasted on the surface to remove oil and dirt, and the Ni-Mg alloy must be sprayed to remove the oxide scale. All raw materials are stored in a dry space for use to prevent the raw materials from absorbing moisture and oxidation again.

[0067] (2) Loading: According to the material composition control requirements, the raw materials of each element are prepared, and the P content and S content of the raw materials are 52ppm and 18ppm, respectively. First, the return material, metal chromium and electrolytic copper are loaded into the bottom of the crucible, and then molybdenum bars, niobium bars and pure iron rods are loaded, and finally, half of the total weight of the nickel plate is placed on the top layer; FeV80, high-purity silicon, CrN alloy and Ni-Mg alloy are loaded into the charging bin in turn at intervals.

[0068] (3) Melting: After loading, vacuuming begins. When the vacuum degree is less than 6 Pa, power is supplied to preheat the furnace. When a molten pool is formed by the charge, vacuuming is stopped and high-purity nitrogen (99.99%) is filled until the nitrogen pressure in the furnace reaches 56,000 Pa. The power is then increased linearly. FeV80 and high-purity silicon are added before the charge is almost completely melted.

[0069] (4) Refining: After the charge is completely melted, the refining phase begins. The refining temperature is 1565°C and the refining time is 15 min. After the refining is completed, the temperature is lowered and the CrN alloy is added. Then, the temperature is rapidly increased at high power to melt the alloy. After the CrN alloy is melted, the power is immediately turned off to cool the alloy. The remaining half of the nickel plate (cut into small pieces) and the Ni-Mg alloy are added for deep deoxidation. The power is then turned on and the power is increased to melt the alloy. The final temperature of the molten pool is determined to be 1490°C.

[0070] (5) Steel pouring: The temperature was measured by thermocouple and the steel tapping temperature was 1475°C. The steel was poured into a 200 mm × 200 mm square ingot under nitrogen protective atmosphere. Vacuuming was not allowed before the molten steel was completely solidified.

[0071] (6) Composition and performance testing: After taking out the ingot, cut off the head and tail, clean the surface, and the chemical composition of the ingot is shown in Table 1 (the balance is Fe and unavoidable impurities).

[0072] (7) High temperature homogenization: The ingot is subjected to high temperature homogenization treatment at a temperature of 1190±10°C and a holding time of 20h.

[0073] (8) Forging: The ingot after high temperature homogenization is forged into a square material of 150 mm × 150 mm. The initial forging temperature of the forging is 1093 °C and the final forging temperature is 969 °C.

[0074] (9) Hot-rolled products: The square materials are heated to 1160±10°C and kept at this temperature for 3h before being hot-rolled. The starting rolling temperature of the hot-rolled products is 1062°C, and the final rolling temperature is 900°C. After 8 passes (the reduction in each pass is 25.0%, 24.0%, 20.0%, 18.1%, 17.9%, 15.2%, 12.8%, and 11.8%, respectively), a hot-rolled plate with a thickness of 30 mm is obtained, which is then air-cooled to room temperature to obtain a plate.

[0075] (10) Heat treatment: The plate is heat treated by solution treatment at 1050±10°C for 30 min and then water cooled to room temperature to obtain austenitic hydrogen-resistant stainless steel.

[0076] Comparative Example 1 Preparation of austenitic hydrogen-resistant stainless steel, the main difference between its preparation method and that of Example 1 is:

[0077] In step (1), an equal amount of electrolytic manganese is used to replace the return material of high manganese and high nitrogen stainless steel;

[0078] In step (2), electrolytic manganese, metallic chromium and electrolytic copper are placed at the bottom of the crucible;

[0079] The remaining steps are the same as those in Example 1. The chemical composition of the ingot is shown in Table 1 (the balance is Fe and unavoidable impurities), and the mechanical properties of the material are shown in Table 2.

[0080] Comparative Example 2 Preparation of conventional 316L austenitic stainless steel, the main difference between its preparation method and that of Example 1 is:

[0081] In step (1), the selected raw materials do not include niobium bars, electrolytic copper, nickel plates, FeV80 and CrN alloy, and an equal amount of electrolytic manganese is used to replace the return material of high manganese and high nitrogen stainless steel;

[0082] In step (2), electrolytic manganese and metallic chromium are placed at the bottom of the crucible, and then molybdenum bars, pure iron and nickel plates are placed in sequence; high-purity silicon and Ni-Mg alloy are loaded into the feeding bin in layers and intervals in sequence;

[0083] In step (3): the vacuum state is maintained during the melting period without nitrogen filling;

[0084] In step (4): the vacuum state is maintained in the early stage of the refining period, and argon gas protection is filled before the deoxidizer (high purity silicon and Ni-Mg alloy) is added;

[0085] The remaining steps are the same as those in Example 1. The chemical composition of the ingot is shown in Table 1 (the balance is Fe and unavoidable impurities), and the mechanical properties of the material are shown in Table 2.

[0086] Table 1 Chemical composition of ingot (in mass percentage, %)

[0087] C Si Mn Cr Ni Mo Cu V Nb N O Example 1 0.043 0.16 3.14 19.89 12.54 1.59 1.87 0.22 0.18 0.39 0.0022 Example 2 0.039 0.20 4.83 21.68 11.96 1.88 3.04 0.25 0.14 0.38 0.0025 Comparative Example 1 0.031 0.20 3.79 20.85 12.32 1.62 2.43 0.23 0.16 0.29 0.0056 Comparative Example 2 0.025 0.45 1.56 17.3 13.57 2.45 - - - 0.0025 0.0020

[0088] The austenitic hydrogen-resistant stainless steel obtained in Example 1 was analyzed by scanning transmission electron microscopy. Figure 1 As shown. Figure 1 It can be seen that in the austenitic hydrogen-resistant stainless steel prepared by the present invention, microalloying elements such as vanadium and niobium form semi-coherent nanoscale precipitation phases with carbon and nitrogen. These precipitation phases can provide a strong hydrogen trap for diffusing hydrogen (hydrogen atoms are pinned in the trap) while refining the grains and improving the strength and toughness of the material, further reducing the diffusion rate of hydrogen in austenite, greatly reducing the interaction between hydrogen and material defects such as dislocations and twins, and further improving the hydrogen resistance of the material.

[0089] The mechanical properties of the austenitic stainless steel obtained in the above examples and comparative examples were tested, and then the materials were electrochemically charged with hydrogen under the conditions of 3% NaCl + 0.3% NH 4 SCN solution, current density 50A / m 2 , hydrogen charging time 72h, temperature 50℃, and finally the obtained material was subjected to slow strain rate tensile test at room temperature. The results are shown in Table 2.

[0090] Table 2 Hydrogen embrittlement resistance

[0091]

[0092] As shown in Table 2, the hydrogen embrittlement resistance of the austenitic hydrogen-resistant stainless steel prepared by the method of the present invention is significantly improved compared with the traditional 316L austenitic stainless steel. By comparing Example 1 with Comparative Example 1, it can be seen that the hydrogen embrittlement resistance of Comparative Example 1 is significantly reduced. The reason is that the return material is not used in the preparation of Comparative Example 1, resulting in a low N content in the final material, low material strength, and a decrease in the density of the semi-coherent nanoscale precipitation phase; since high vacuum cannot be maintained for degassing during the melting and refining period, the O content in the material is significantly increased, and the inclusion density is increased, thereby damaging the toughness and plasticity of the material.

[0093] The present invention solves the problem that traditional austenitic stainless steel is prone to brittle fracture due to the interaction of hydrogen atom diffusion and defects in a hydrogen environment, and that the existing process is difficult to balance high purity, low impurities and precise control of hydrogen trap elements. The prepared austenitic hydrogen-resistant stainless steel has good hydrogen embrittlement resistance, a simple preparation process, and broad application prospects.

Claims

1. A method for preparing austenitic hydrogen-resistant stainless steel, characterized in that: The ingot is obtained by vacuum induction melting, and then the ingot is subjected to high temperature homogenization, forging, hot rolling and heat treatment to obtain austenitic hydrogen-resistant stainless steel. Wherein, the vacuum induction melting comprises the following steps: a. Loading: Load metal chromium, molybdenum bars, niobium bars, pure iron bars, electrolytic copper, nickel plates and return materials into the crucible of the vacuum induction furnace, and load FeV80, high-purity silicon, CrN alloy and Ni-Mg alloy into the charging bin; b. Melting: After the molten pool is formed, stop vacuuming and fill with nitrogen. Add FeV80 and high-purity silicon in sequence before the molten pool is completely melted; c. Refining: After refining, cool down and add CrN alloy. After complete melting, shut down the power and cool down and add Ni-Mg alloy. d. Pouring: The ingot is obtained by tapping and pouring, and its chemical composition, by mass percentage, includes C≤0.06%, Si≤1.00%, 3.00≤Mn≤5.00%, 19.50%≤Cr≤22.00%, 11.00%≤Ni≤13.00%, 1.50%≤Mo≤2.00%, 1.50%≤Cu≤3.50%, 0.20%≤V≤0.30%, 0.10%≤Nb≤0.23%, 0.30%≤[N]≤0.40%, P≤0.01%, S≤0.004%, [O]≤0.003%, and the balance is Fe.

2. The method for preparing austenitic hydrogen-resistant stainless steel according to claim 1, characterized in that: In step a, the return material is a return material of high manganese and high nitrogen stainless steel, and its chemical composition is: C 0.095%, Si 0.32%, Mn 18.36%, Cr19.43%, Ni 0.12%, [N] 0.48%, and the balance is Fe; The purity of the high-purity silicon is ≥99%.

3. The method for preparing austenitic hydrogen-resistant stainless steel according to claim 1, characterized in that: In step a, when charging the furnace, the return material, metallic chromium and electrolytic copper are first loaded into the bottom of the crucible, and then molybdenum bars, niobium bars and pure iron bars are loaded, and the nickel plate is placed on the top layer; The charging bin is loaded with FeV80, high purity silicon, CrN alloy and Ni-Mg alloy in turn at intervals in layers.

4. The method for preparing austenitic hydrogen-resistant stainless steel according to claim 1, characterized in that: In step a, the return material, pure iron rod, nickel plate and molybdenum bar need to be subjected to surface shot blasting treatment to remove oil and dirt before loading into the furnace; Ni-Mg alloy needs to be descaled before loading.

5. The method for preparing austenitic hydrogen-resistant stainless steel according to claim 1, characterized in that: In step b, after the loading is completed, vacuuming is started, and when the vacuum degree in the furnace is less than 6Pa, power is supplied to preheat the temperature; When filling with nitrogen, control the nitrogen pressure in the furnace to ≥50000Pa.

6. The method for preparing austenitic hydrogen-resistant stainless steel according to claim 1, characterized in that: In step c, the refining temperature is 1550±15°C and the refining time is 15 to 25 minutes; When melting Ni-Mg alloy, the molten pool temperature is controlled not to be higher than 1500°C.

7. The method for preparing austenitic hydrogen-resistant stainless steel according to claim 1, characterized in that: In step d, the tapping temperature is 1450-1475° C., and pouring is performed under a nitrogen protective atmosphere. Vacuuming is not allowed before the molten steel is completely solidified.

8. The method for preparing austenitic hydrogen-resistant stainless steel according to claim 1, characterized in that: The ingot is subjected to high temperature homogenization treatment, wherein the high temperature homogenization temperature is 1190±10°C and the holding time is 20h; Forging the high-temperature homogenized ingot into a square material of 150 mm×150 mm, wherein the initial forging temperature of the forging is ≥1080°C and the final forging temperature is ≥950°C; The square material is heated to 1160±10°C and kept at this temperature for 3 hours before hot rolling. The starting rolling temperature of the hot rolled material is ≥1050°C and the final rolling temperature is ≥880°C. After 8 passes of rolling, a hot rolled plate with a thickness of 30 mm is obtained, and the plate is air-cooled to room temperature to obtain a plate; The plate is heat treated, solution treated at 1050±10°C for 30 min, and water cooled to room temperature to obtain austenitic hydrogen-resistant stainless steel.

9. An austenitic hydrogen-resistant stainless steel, characterized in that: The method is prepared according to any one of claims 1 to 8.

10. The austenitic hydrogen-resistant stainless steel according to claim 9, characterized in that: Its tensile strength is ≥758MPa, elongation is ≥40.2%, section shrinkage is ≥68%, and impact toughness is ≥77.3J.

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