High-manganese austenitic cryogenic steel plate for liquid hydrogen storage tank and preparation method thereof

Abstract

A high-manganese austenitic cryogenic steel plate for a liquid hydrogen storage tank includes following chemical compositions in percentage by mass: carbon (C): 0.36-0.45%, silicon (Si): 0.20-0.35%, manganese (Mn): 28-34.5%, phosphorus (P)≤0.010%, sulfur(S)≤0.005%, aluminum total (Alt): 0.02%-0.04%, niobium (Nb): 0.010%-0.10%, vanadium (V): 0.010%-0.015%, chromium (Cr): 3.50%-6.50%, nickel (Ni): 0%-1.50%, copper (Cu): 0.30%-0.50%, and a balance being iron (Fe) and inevitable impurities. A preparation method includes following steps: weighing and mixing raw materials according to the mass percentages for all chemical compositions except Mn, Nb, and V to obtain a mixture, then sequentially performing smelting continuous casting, annealing, heating control, and rolling to obtain the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank; and adding Mn, Nb, and V according to the mass percentages during a ladle furnace (LF) refining process.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Chinese Patent Application No. 202510240795.1, filed on Mar. 3, 2025, the contents of which are hereby incorporated by reference.TECHNICAL FIELD

[0002] The present disclosure belongs to the technical field of wide and heavy steel plate production, and particularly relates to a high-manganese austenitic cryogenic steel plate for a liquid hydrogen storage tank and a preparation method thereof.BACKGROUND

[0003] Under the new situation of accelerating the green and low-carbon transformation of energy, hydrogen energy is regarded as the energy with the greatest development potential in the 21st century, featuring high calorific value, zero carbon emissions, and renewability. Cryogenic liquid hydrogen storage offers characteristics such as high density, high refueling efficiency, and good safety, showing enormous development potential. Among these, cryogenic liquid hydrogen storage involves compressing hydrogen, cooling it below-253 degrees Celsius, liquefying it, and storing it in insulated vacuum containers, which imposes stringent requirements on the performance of cryogenic energy storage tanks. The conventional material for liquid hydrogen storage tanks is generally stainless steel. With the expansion of hydrogen energy usage, the high cost of manufacturing liquid hydrogen storage tanks using stainless steel has made the development of low-cost liquid hydrogen storage tank steel highly significant.

[0004] The patent CN113957353A discloses a high-manganese type high-toughness steel suitable at 4.2 Kelvin. By adding a certain content of aluminum (Al) or chromium (Cr), copper (Cu) elements, and combining controlled cooling with controlled rolling processes and subsequent heat treatment processes, the high-manganese type high-toughness steel obtains an evenly organized equiaxed single-phase austenitic microstructure, meeting the requirement for high toughness in structural materials under extremely low-temperature environments and reducing production costs. However, the martensite temperature (Ms) of this composition is higher than the liquid hydrogen storage temperature (−254 degrees Celsius), indicating that the austenitic microstructure possesses a certain driving force for phase transformation at liquid hydrogen temperatures, posing a risk of martensitic transformation under ultra-low temperature conditions. Meanwhile, this composition system requires the addition of a large amount of Al element. Because the Al element is prone to oxidation, the control during the smelting process is difficult, and issues such as nozzle clogging are prone to occur during the casting process.

[0005] Therefore, there is an urgent need to provide a high-manganese austenitic cryogenic steel plate for liquid hydrogen storage tanks and a preparation method thereof, which may not only meet the ultra-low temperature impact requirements at −254 degrees Celsius but also possess high stability.SUMMARY

[0006] Aiming at the above technical problem, the present disclosure proposes a high-manganese austenitic cryogenic steel plate for a liquid hydrogen storage tank and a preparation method thereof.

[0007] To achieve the above purpose, the present disclosure provides the following technical schemes.

[0008] One of the technical schemes of the disclosure is as follows.

[0009] A high-manganese austenitic cryogenic steel plate for a liquid hydrogen storage tank includes following chemical compositions in percentage by mass:

[0010] carbon (C): 0.36-0.45%, silicon (Si): 0.20-0.35%, manganese (Mn): 28-35%, phosphorus (P)≤0.010%, sulfur(S)≤0.005%, aluminum total (Alt): 0.02%-0.04%, niobium (Nb): 0.010%-0.10%, vanadium (V): 0.010%-0.015%, chromium (Cr): 3.50%-6.50%, nickel (Ni): 0%-1.50%, copper (Cu): 0.30%-0.50%, and a balance being iron (Fe) and inevitable impurities.

[0011] The beneficial effects are as follows. To ensure the requirements of high strength, relatively high low-temperature impact toughness, and weather resistance for the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank, the present disclosure adopts microalloying with multiple elements including Nb, V, Cr, Ni, and Cu. Adding Cr and Ni elements may increase the stacking fault energy of high-manganese steel, inhibit strain-induced phase transformation and twinning, reduce work hardening capability, and thereby improve low-temperature impact toughness. A small amount of Cu element provides a certain strengthening effect and may also enhance the weather resistance of the cryogenic steel plate. The microalloying elements Nb and V mainly refine the grain size of the steel plate by inhibiting recrystallization, thereby increasing strength and toughness.

[0012] Optionally, the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank includes the following chemical compositions in percentage by mass:

[0013] C: 0.44%, Si: 0.33%, Mn: 29%, P<0.010%, S≤0.005%, Alt: 0.03%, Nb: 0.050%, V: 0.015%, Cr: 5.00%, Ni: 1.00%, Cu: 0.30%, and the balance being Fe and inevitable impurities.

[0014] In another optional scheme, the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank includes the following chemical compositions in percentage by mass:

[0015] C: 0.37%, Si: 0.35%, Mn: 34.5%, P≤0.010%, S≤0.005%, Alt: 0.02%, Nb: 0.060%, V: 0.013%, Cr: 4.80%, Ni: 1.30%, Cu: 0.30%, and the balance being Fe and inevitable impurities.

[0016] In another optional scheme, the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank includes the following chemical compositions in percentage by mass:

[0017] C: 0.39%, Si: 0.32%, Mn: 32%, P<0.010%, S≤0.005%, Alt: 0.03%, Nb: 0.070%, V: 0.01%, Cr: 5.50%, Ni: 0.00%, Cu: 0.40%, and the balance being Fe and inevitable impurities.

[0018] Optionally, the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank has a thickness of 6-60 millimeters.

[0019] The second technical scheme of the disclosure is as follows.

[0020] A preparation method for a high-manganese austenitic cryogenic steel plate for a liquid hydrogen storage tank includes the following steps:

[0021] weighing and mixing raw materials according to above mass percentages for all chemical compositions except the Mn, the Nb, and the V to obtain a mixture, then sequentially performing smelting continuous casting, annealing, heating control, and rolling to obtain the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank;

[0022] where a smelting continuous casting process includes: converter / electric furnace roughing, ladle furnace (LF) refining, and vacuum degassing (VD) / ruhrstahl-heraeus (RH) vacuum treatment. The Mn, Nb, and V are added according to the mass percentages during the LF refining process. In this process, the molten steel composition is detected and analyzed. Based on the analysis results, the mass percentage content of chemical compositions in the molten steel is adjusted promptly and precisely controlled to ensure the molten steel composition meets the requirements.

[0023] The converter / electric furnace roughing means that during the roughing process, a converter or electric furnace is used for roughing to produce molten steel (liquid steel) from hot metal.

[0024] VD / RH vacuum treatment: VD and RH are two secondary refining processes, mainly used to remove gases (such as hydrogen, nitrogen) and non-metallic inclusions from the liquid steel to improve the quality of the steel.

[0025] Optionally, during the converter / electric furnace roughing process, when the P content in the molten steel reaches P≤0.006%, dephosphorization is stopped, and the steel is tapped and transferred to LF refining.

[0026] Optionally, during the LF refining process, Mn, Nb, and V are added when the temperature is raised to 1600-1620 degrees Celsius. The selected raw materials for addition are manganese alloy, niobium alloy, and vanadium alloy. The manganese alloy includes electrolytic manganese and ferromanganese. The niobium alloy and vanadium alloy are mainly in the form of lump alloys, namely ferroniobium and ferrovanadium. The composition is ensured to meet the requirements.

[0027] Optionally, the conditions during the VD / RH vacuum treatment process are:

[0028] a vacuum degree of ≤66.7 megapascals, maintained for more than 15 minutes; and after breaking vacuum (the process of returning to atmospheric pressure after the vacuum treatment stage), soft blowing for 7 minutes.

[0029] Optionally, the casting is mold casting or continuous casting.

[0030] In an embodiment, when the casting is mold casting, the mold casting pouring temperature is controlled at liquidus (the maximum temperature limit at which the material is completely in liquid state)+45 degrees Celsius; and

[0031] when the casting is continuous casting, the continuous casting pouring temperature is controlled at liquidus+30 degrees Celsius.

[0032] Optionally, the conditions during the annealing process are:

[0033] a charging temperature of ≥100 degrees Celsius, an annealing temperature of 870-890 degrees Celsius, an annealing holding duration of 24 hours, and heating and cooling rates before and after the annealing both being≤80 degrees Celsius per hour.

[0034] Optionally, the conditions during the heating control process are:

[0035] a charging temperature of ≥100 degrees Celsius, a heating rate after charging of ≤100 degrees Celsius per hour, holding for 3 hours when heating to 500 degrees Celsius, holding for 2 hours when heating to 800 degrees Celsius, holding for 2 hours when heating to 1100 degrees Celsius, holding for 5-8 hours when heating to 1200 degrees Celsius, and then discharging for the rolling.

[0036] Optionally, the rolling process adopts a two-stage rolling+direct quenching (DQ) process;

[0037] where the temperature for the first stage of rolling is 1000-1080 degrees Celsius;

[0038] the temperature for the second stage of rolling is 880-930 degrees Celsius; and

[0039] after rolling, DQ cooling is performed, with a cooling rate of 15 degrees Celsius per second≤a quenching cooling rate<22 degrees Celsius per second.

[0040] Compared with the existing technology, the present disclosure has the following advantages and technical effects.

[0041] The high-manganese austenitic cryogenic steel prepared by the present disclosure has a thickness of 6-60 millimeters, a room-temperature yield strength of ≥436 megapascals, a tensile strength of 824-867 megapascals, an elongation of ≥60%, and an impact value at −254 degrees Celsius of ≥124 joules.

[0042] The high-manganese austenitic cryogenic steel prepared by the present disclosure exhibits good low-temperature toughness. While meeting the ultra-low temperature impact requirement at −254 degrees Celsius, its microstructure also possesses high stability. The martensite temperature (Ms) of the steel plate remains below −254 degrees Celsius, and the austenite stability coefficient is greater than zero, proving that the high-manganese austenitic cryogenic steel prepared by the present disclosure has no driving force for phase transformation at liquid hydrogen temperatures, thereby avoiding the risk of martensitic transformation under low-temperature conditions. This enables it to replace austenitic stainless steel materials and facilitates widespread application in ultra-low temperature containers such as liquid hydrogen storage tanks.BRIEF DESCRIPTION OF THE DRAWING

[0043] The drawing, which constitutes a part of this disclosure, is used to provide a further understanding of this disclosure. The illustrative embodiments and descriptions of this disclosure are used to explain this disclosure, and do not constitute an improper limitation of this disclosure. In the drawing:

[0044] The FIGURE is a flow chart of a preparation method for a high-manganese austenitic cryogenic steel plate for a liquid hydrogen storage tank according to an embodiment of the present disclosure.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] Various exemplary embodiments of the present disclosure are now described in detail. This detailed description should not be considered as limiting the present disclosure but should be understood as a more detailed description of certain aspects, characteristics, and embodiments of the present disclosure.

[0046] It should be understood that the terms used in the present disclosure are only for describing particular embodiments and are not intended to limit the present disclosure. In addition, for the numerical ranges in the present disclosure, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range and any other stated value or intermediate value within the stated range is also included in the present disclosure. The upper limit and lower limit of these smaller ranges may be independently included or excluded from the range.

[0047] Unless otherwise stated, all technical and scientific terms used herein have the same meanings as commonly understood by a person of ordinary skill in the technical field of the present disclosure. Although only optional methods and materials are described in the present disclosure, any methods and materials that are similar or equivalent to those described herein may also be used in the implementation or testing of the present disclosure. All documents mentioned in this specification are incorporated by reference to disclose and describe methods and / or materials related to the documents. In case of any conflict with any incorporated document, the content of this specification shall prevail.

[0048] Various modifications and variations may be made to the specific embodiments described in the specification of the present disclosure without departing from the scope or spirit of the present disclosure, which will be apparent to those skilled in the art. Other embodiments derived from the specification of the present disclosure will be apparent to those skilled in the art. The specification and embodiments of the present disclosure are exemplary only.

[0049] Regarding the terms used herein such as “comprise”, “include”, “have”, “contain”, etc., they are all open-ended terms, meaning inclusion but not limited to.

[0050] Embodiments of the present disclosure disclose a high-manganese austenitic cryogenic steel plate for a liquid hydrogen storage tank, including the following elements in percentage by mass: carbon (C): 0.36-0.45%, silicon (Si): 0.20-0.35%, manganese (Mn): 28-35%, phosphorus (P)≤0.010%, sulfur(S)≤0.005%, aluminum total (Alt): 0.02%-0.04%, niobium (Nb): 0.010%-0.10%, vanadium (V): 0.010%-0.015%, chromium (Cr): 3.50%-6.50%, nickel (Ni): 0%-1.50%, copper (Cu): 0.30%-0.50%, and a balance being iron (Fe) and inevitable impurities.

[0051] In some optional embodiments, the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank has a thickness of 6-60 millimeters.

[0052] In some optional embodiments, the austenite stability coefficient (Δ) of the high-manganese austenitic cryogenic steel plate satisfies Δ≥0, and the martensite temperature (Ms) is <−254 degrees Celsius.

[0053] As shown in the FIGURE, embodiments of the present disclosure further disclose a preparation method for a high-manganese austenitic cryogenic steel plate for a liquid hydrogen storage tank, including the following steps:

[0054] weighing and mixing raw materials according to above mass percentages for all chemical compositions except the Mn, the Nb, and the V to obtain a mixture, and subjecting the mixture to smelting, casting, and annealing to obtain a steel billet; where the smelting includes: converter / electric furnace roughing, ladle furnace (LF) refining, and vacuum degassing (VD) / ruhrstahl-heraeus (RH) vacuum treatment; and adding the Mn, the Nb, and the V according to the mass percentages during an LF refining process; and

[0055] then, sequentially subjecting the steel billet to heating, rolling, and direct quenching (DQ) treatment to obtain the high-manganese austenitic cryogenic steel plate.

[0056] In some optional embodiments, during the converter / electric furnace roughing process, dephosphorization is stopped when the P content in the molten steel reaches P≤0.006%, and the steel is tapped and transferred to LF refining.

[0057] During the LF refining process, Mn, Nb, and V are added when the LF refining temperature is raised to 1600-1620 degrees Celsius. The selected raw materials for addition are manganese alloy, niobium alloy, and vanadium alloy. The manganese alloy includes electrolytic manganese and ferromanganese, ensuring the composition meets the requirements.

[0058] In some optional embodiments, before VD / RH vacuum treatment, the Mn content is controlled according to the internal upper limit (that is, the amount of Mn added is controlled according to the Mn content required for the prepared steel plate), the vacuum degree is ≤66.7 megapascals, and this condition is maintained for more than 15 minutes.

[0059] In some optional embodiments, after vacuum treatment, mold casting and continuous casting may be used as two casting methods. Among them, the mold casting pouring temperature is controlled at liquidus+45 degrees Celsius; and the continuous casting pouring temperature is controlled at liquidus+30 degrees Celsius.

[0060] In some optional embodiments, the billet after casting is promptly subjected to warm-temperature annealing, with a charging temperature of ≥100 degrees Celsius, an annealing temperature of 870-890 degrees Celsius, an annealing holding duration of 24 hours, and heating and cooling rates before and after annealing of ≤80 degrees Celsius per hour.

[0061] In some optional embodiments, a stepwise heating method is adopted for the pre-rolling heating process: first, a charging temperature of ≥100 degrees Celsius is ensured, a heating rate after charging of ≤100 degrees Celsius per hour is maintained, holding for 3 hours when heating to 500 degrees Celsius, holding for 2 hours when heating to 800 degrees Celsius, holding for 2 hours when heating to 1100 degrees Celsius, holding for 5 to 8 hours when heating to 1200 degrees Celsius, and then discharging for rolling.

[0062] In some optional embodiments, the rolling process adopts a two-stage rolling+DQ process. The temperature for the first stage of rolling is 1000-1080 degrees Celsius. The temperature for the second stage of rolling is 880-930 degrees Celsius. DQ cooling is performed after rolling, with a cooling rate of 15 degrees Celsius per second≤a quenching cooling rate<22 degrees Celsius per second.

[0063] In addition, the present disclosure also discloses an application of the high-manganese austenitic cryogenic steel for liquid hydrogen storage tanks in liquid hydrogen storage tanks.

[0064] In the present disclosure, the term “room temperature” refers to 20-30 degrees Celsius unless otherwise specified. The calculation formula for the austenite stability of the high-manganese austenitic cryogenic steel plate in the following embodiments is:

[0065] Δ=Ni+0.5Mn+35C-0.0833 (Cr+1.5Mo−20)2−12. In the formula, the elements represent their mass percentage in the final prepared steel plate, and any element not present is taken as 0. The same applies to the following formula.

[0066] The calculation formula for the martensitic transformation temperature of the high-manganese austenitic cryogenic steel plate is:Ms(° F.)=75(14.6−Cr)+110(8.9−Ni)+60(1.33−Mn)+50(0.47−Si)+3000(0.068−C—N),Ms=(Ms(° F.)−32)=1.8.In the formula, F represents Fahrenheit temperature, and Ms (° F.) indicates that the calculation result is in the Fahrenheit temperature scale; and Ms without (° F.) is in the Celsius temperature scale.

[0068] The technical scheme of the present disclosure is further illustrated below through embodiments.Embodiment 1

[0069] A high-manganese austenitic cryogenic steel plate with a thickness of 10 millimeters includes the following chemical compositions in percentage by mass:

[0070] C: 0.44%, Si: 0.33%, Mn: 29%, P<0.010%, S≤0.005%, Alt: 0.03%, Nb: 0.050%, V: 0.015%, Cr: 5.00%, Ni: 1.00%, Cu: 0.30%, and the balance being Fe and inevitable impurities.

[0071] In this embodiment, the austenite stability coefficient of the high-manganese austenitic cryogenic steel plate is 0.16, which satisfies Δ≥0; and the martensitic transformation temperature is −645 degrees Celsius, and Ms<−254 degrees Celsius.

[0072] A preparation method for a high-manganese austenitic cryogenic steel plate specifically includes the following steps.

[0073] (1) Smelting continuous casting process: raw materials for all chemical compositions except Mn, Nb, and V are weighed and mixed according to the above mass percentages to obtain a mixture, and the mixture is sequentially subjected to converter / electric furnace roughing, LF refining, and VD / RH vacuum treatment, followed by casting to obtain a steel billet.

[0074] Among them, the converter / electric furnace roughing process is as follows. Dephosphorization is stopped when the P content in the molten steel reaches 0.006%, and the steel is tapped and transferred to LF refining.

[0075] The LF refining process is as follows. Mn, Nb, and V are added according to the mass percentages during the LF refining process, that is, manganese alloy, niobium alloy, and vanadium alloy are added when the LF refining temperature is raised to 1600 degrees Celsius. The manganese alloy used during the refining process mainly includes electrolytic manganese and ferromanganese, ensuring that the composition meets the requirements.

[0076] The VD / RH vacuum treatment process is as follows. A vacuum degree of ≤66.7 megapascals is maintained for 15 minutes; and after breaking vacuum, the soft blowing time is controlled at 7 minutes.

[0077] The casting is continuous casting: the casting temperature is controlled at 1368 degrees Celsius, and the continuous casting billet thickness specification is 200 millimeters.

[0078] (2) Annealing process: the billet after casting is promptly subjected to warm-temperature annealing, with a charging temperature of 110 degrees Celsius, an annealing temperature of 870 degrees Celsius, an annealing holding duration of 24 hours, and heating and cooling rates before and after annealing of 80 degrees Celsius per hour.

[0079] (3) Heating process: a charging temperature of 100 degrees Celsius is used, a heating rate after charging of 100 degrees Celsius per hour is maintained, holding for 3 hours when heating to 500 degrees Celsius, holding for 3 hours when heating to 800 degrees Celsius, holding for 3 hours when heating to 1100 degrees Celsius, holding for 6 hours when heating to 1200 degrees Celsius, and then discharging for rolling.

[0080] (4) Rolling process: the starting rolling temperature for the first stage of rolling is 1077 degrees Celsius, the finishing rolling temperature is 1020 degrees Celsius, and the air-cooled thickness is 50 millimeters; the starting rolling temperature for the second stage of rolling is 930 degrees Celsius, and the finishing rolling temperature is 850 degrees Celsius; and after rolling, a DQ process is performed, with a cooling rate of 22 degrees Celsius per second, to obtain a sample with a thickness of 10 millimeters.Embodiment 2

[0081] A high-manganese austenitic cryogenic steel plate with a thickness of 60 millimeters includes the following chemical compositions in percentage by mass:

[0082] C: 0.37%, Si: 0.35%, Mn: 34.5%, P<0.010%, S≤0.005%, Alt: 0.02%, Nb: 0.060%, V: 0.013%, Cr: 4.80%, Ni: 1.30%, Cu: 0.30%, and the balance being Fe and inevitable impurities.

[0083] In this embodiment, the austenite stability coefficient of the high-manganese austenitic cryogenic steel plate is 0.25, which satisfies Δ≥0; and the martensitic transformation temperature is −723 degrees Celsius, and Ms<−254 degrees Celsius.

[0084] A preparation method for a high-manganese austenitic cryogenic steel plate specifically includes the following steps.

[0085] (1) Smelting continuous casting process: raw materials for all chemical compositions except Mn, Nb, and V are weighed and mixed according to the above mass percentages to obtain a mixture, and the mixture is sequentially subjected to converter / electric furnace roughing, LF refining, and VD / RH vacuum treatment, followed by casting to obtain a steel billet.

[0086] Among them, the converter / electric furnace roughing process is as follows. Dephosphorization is stopped when the P content in the molten steel reaches 0.006%, and the steel is tapped and transferred to LF refining.

[0087] The LF refining process is as follows. Mn, Nb, and V are added according to the mass percentages during the LF refining process, that is, manganese alloy, niobium alloy, and vanadium alloy are added when the LF refining temperature is raised to 1608 degrees Celsius. The manganese alloy used during the refining process mainly includes electrolytic manganese and ferromanganese, ensuring that the composition meets the requirements.

[0088] The VD / RH vacuum treatment process is as follows. A vacuum degree of ≤66.7 megapascals is maintained for 15 minutes; and after breaking vacuum, the soft blowing time is controlled at 10 minutes.

[0089] The casting is mold casting: the casting temperature is controlled at 1367 degrees Celsius, and the mold casting billet thickness specification is 500 millimeters.

[0090] (2) Annealing process: the billet after casting is promptly subjected to warm-temperature annealing, with a charging temperature of 110 degrees Celsius, an annealing temperature of 870 degrees Celsius, an annealing holding duration of 24 hours, and heating and cooling rates before and after annealing of 100 degrees Celsius per hour.

[0091] (3) Heating process: a charging temperature of 115 degrees Celsius is used, a heating rate after charging of 90 degrees Celsius per hour is maintained, holding for 3 hours when heating to 500 degrees Celsius, holding for 2 hours when heating to 800 degrees Celsius, holding for 2 hours when heating to 1100 degrees Celsius, holding for 5 hours when heating to 1200 degrees Celsius, and then discharging for rolling.

[0092] (4) Rolling process: the starting rolling temperature for the first stage of rolling is 1066 degrees Celsius, the finishing rolling temperature is 1000 degrees Celsius, and the air-cooled thickness is 120 millimeters; the starting rolling temperature for the second stage of rolling is 900 degrees Celsius, and the finishing rolling temperature is 870 degrees Celsius; and after rolling, a DQ process is performed, with a cooling rate of 15 degrees Celsius per second, to obtain a sample with a thickness of 60 millimeters.Embodiment 3

[0093] A high-manganese austenitic cryogenic steel plate with a thickness of 30 millimeters includes the following chemical compositions in percentage by mass:

[0094] C: 0.39%, Si: 0.32%, Mn: 32%, P<0.010%, S≤0.005%, Alt: 0.03%, Nb: 0.070%, V: 0.01%, Cr: 5.50%, Ni: 0.00%, Cu: 0.40%, and the balance being Fe and inevitable impurities.

[0095] In this embodiment, the austenite stability coefficient of the high-manganese austenitic cryogenic steel plate is 0.14, which satisfies Δ≥0; and the martensitic transformation temperature is −622 degrees Celsius, and Ms<−254 degrees Celsius.

[0096] A preparation method for a high-manganese austenitic cryogenic steel plate specifically includes the following steps.

[0097] (1) Smelting continuous casting process: raw materials for all chemical compositions except Mn, Nb, and V are weighed and mixed according to the above mass percentages to obtain a mixture, and the mixture is sequentially subjected to converter / electric furnace roughing, LF refining, and VD / RH vacuum treatment, followed by casting to obtain a steel billet.

[0098] The converter / electric furnace roughing process is as follows. Dephosphorization is stopped when the P content in the molten steel reaches 0.006%, and the steel is tapped and transferred to LF refining.

[0099] The LF refining process is as follows. Mn, Nb, and V are added according to the mass percentages during the LF refining process, that is, manganese alloy, niobium alloy, and vanadium alloy are added when the LF refining temperature is raised to 1620 degrees Celsius. The manganese alloy used during the refining process mainly includes electrolytic manganese and ferromanganese, ensuring that the composition meets the requirements.

[0100] The VD / RH vacuum treatment process is as follows. a vacuum degree of ≤66.7 megapascals is maintained for 15 minutes; and after breaking vacuum, the soft blowing time is controlled at 5 minutes.

[0101] The casting is continuous casting: the casting temperature is controlled at 1363 degrees Celsius, and the continuous casting billet thickness specification is 200 millimeters.

[0102] (2) Annealing process: the billet after casting is promptly subjected to warm-temperature annealing, with a charging temperature of 110 degrees Celsius, an annealing temperature of 870 degrees Celsius, an annealing holding duration of 24 hours, and heating and cooling rates before and after annealing of 80 degrees Celsius per hour.

[0103] (3) Heating process: a charging temperature of 100 degrees Celsius is used, a heating rate after charging of 100 degrees Celsius per hour is maintained, holding for 3 hours when heating to 500 degrees Celsius, holding for 3 hours when heating to 800 degrees Celsius, holding for 3 hours when heating to 1100 degrees Celsius, holding for 6 hours when heating to 1200 degrees Celsius, and then discharging for rolling.

[0104] (4) Rolling process: the starting rolling temperature for the first stage of rolling is 1080 degrees Celsius, the finishing rolling temperature is 1025 degrees Celsius, and the air-cooled thickness is 70 millimeters; the starting rolling temperature for the second stage of rolling is 920 degrees Celsius, and the finishing rolling temperature is 860 degrees Celsius; and after rolling, a DQ process is performed, with a cooling rate of 19 degrees Celsius per second, to obtain a sample with a thickness of 30 millimeters.Comparative Example 1

[0105] The difference from Embodiment 3 lies in the chemical compositions in the steel plate, specifically:

[0106] A steel plate with a thickness of 30 millimeters includes the following chemical compositions in percentage by mass:

[0107] C: 0.39%, Si: 0.32%, P≤0.010%, S≤0.005%, Alt: 0.03%, Nb: 0.070%, V: 0.01%, Cr: 5.50%, Ni: 0.00%, Cu: 0.40%, and particularly, its manganese content is Mn: 23%, with the balance being Fe and inevitable impurities.

[0108] The preparation process and condition parameters are the same as those in Embodiment 3.

[0109] In this comparative example, the austenite stability coefficient of the high-manganese austenitic cryogenic steel plate is −4.36, which does not satisfy Δ≥0.

[0110] Effect Verification is as follows.

[0111] Tensile and impact performance tests are conducted on the high-manganese austenitic cryogenic steel plates prepared in Embodiments 1-3.

[0112] The tensile test is performed according to the GB / T 228.1-2021 standard, with a tensile rate of 1 millimeter per minute and the test direction being transverse.

[0113] The −254 degrees Celsius low-temperature impact test is conducted according to GB / T 229-2020, with the test direction being transverse. Three samples are taken from each embodiment for the low-temperature impact test.

[0114] The test results are shown in Table 1.TABLE 1Tensile and impact performance results of thesteel plates prepared in Embodiments 1-3Rp0.2 / Rm / Mega-Mega-−254 degrees Celsius (° C.)pascalpascalCharpy V-notch impact(MPa)(MPa)A50 / %energy (Akv) / Joules (J)Embodiment 152286762135124158Embodiment 243682468183167149Embodiment 351884565178204187Comparative53889639788226Example 1Note:Rp0.2 represents room-temperature yield strength; Rm represents tensile strength; A50 represents elongation; and −254° C. Akv represents the impact value at −254° C.

[0115] As may be seen from Table 1, the performance of the steel plates prepared using Embodiments 1-3 of the present disclosure meets the following indicators: room-temperature yield strength of 436-522 megapascals, tensile strength of 824-867 megapascals, elongation of ≥60%, and impact value at −254 degrees Celsius of ≥124 Joules.

[0116] The above descriptions are only optional specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art may easily think of changes or substitutions within the technical scope disclosed by the present disclosure, and all such changes or substitutions should fall within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A high-manganese austenitic cryogenic steel plate for a liquid hydrogen storage tank, comprising following chemical compositions in mass percentages:carbon (C): 0.36-0.45%, silicon (Si): 0.20-0.35%, manganese (Mn): 28-34.5%, phosphorus (P)≤0.010%, sulfur(S)≤0.005%, aluminum total (Alt): 0.02%-0.04%, niobium (Nb): 0.010%-0.10%, vanadium (V): 0.010%-0.015%, chromium (Cr): 3.50%-6.50%, nickel (Ni): 0%-1.50%, copper (Cu): 0.30%-0.50%, and a balance being iron (Fe) and inevitable impurities;wherein a preparation method for the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank comprises following steps:weighing and mixing raw materials according to above mass percentages for all the chemical compositions except the Mn, the Nb, and the V to obtain a mixture, then sequentially performing smelting continuous casting, casting, annealing, heating control, and rolling to obtain the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank;wherein a process of the smelting continuous casting comprises: converter / electric furnace roughing, ladle furnace (LF) refining, and vacuum degassing (VD) / ruhrstahl-heraeus (RH) vacuum treatment;adding the Mn, the Nb, and the V according to the mass percentages during a process of the LF refining; andwherein the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank has a yield strength of 436-522 megapascals at room temperature, a tensile strength of 824-867 megapascals, an elongation of ≥60%, and an impact value at −254 degrees Celsius of ≥124 joules.

2. The high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank according to claim 1, wherein the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank has a thickness of 6-60 millimeters.

3. A preparation method for a high-manganese austenitic cryogenic steel plate for a liquid hydrogen storage tank, comprising following steps:weighing and mixing raw materials according to the mass percentages in claim 1 for all chemical compositions except the Mn, the Nb, and the V to obtain the mixture, then sequentially performing the smelting continuous casting, the casting, the annealing, the heating control, and the rolling to obtain the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank;wherein the process of the smelting continuous casting comprises: the converter / electric furnace roughing, the LF refining, and the VD / RH vacuum treatment; andadding the Mn, the Nb, and the V according to the mass percentages during the process of the LF refining.

4. The preparation method for the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank according to claim 3, wherein during a process of the converter / electric furnace roughing, dephosphorization is stopped when a P content in molten steel reaches P≤0.006%, and the molten steel is tapped into the LF refining.

5. The preparation method for the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank according to claim 3, wherein during the process of the LF refining, the Mn, the Nb, and the V are added when a temperature is raised to 1600-1620 degrees Celsius.

6. The preparation method for the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank according to claim 3, wherein conditions during a process of the VD / RH vacuum treatment are:a vacuum degree of ≤66.7 megapascals, maintained for more than 15 minutes; and after breaking vacuum, soft blowing for 7 minutes.

7. The preparation method for the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank according to claim 3, wherein the casting is mold casting or continuous casting.

8. The preparation method for the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank according to claim 3, wherein conditions during a process of the annealing are:a charging temperature of ≥100 degrees Celsius, an annealing temperature of 870-890 degrees Celsius, an annealing holding duration of 24 hours, and heating and cooling rates before and after the annealing both of ≤80 degrees Celsius per hour.

9. The preparation method for the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank according to claim 3, wherein conditions during a process of the heating control are:a charging temperature of ≥100 degrees Celsius, a heating rate after charging of ≤100 degrees Celsius per hour, holding for 3 hours when heating to 500 degrees Celsius, holding for 2 hours when heating to 800 degrees Celsius, holding for 2 hours when heating to 1100 degrees Celsius, holding for 5-8 hours when heating to 1200 degrees Celsius, and then discharging for the rolling.

10. The preparation method for the high-manganese austenitic cryogenic steel plate for the liquid hydrogen storage tank according to claim 3, wherein a process of the rolling comprises two-stage rolling and direct quenching (DQ);wherein a temperature for a first stage of the rolling is 1000-1080 degrees Celsius;a temperature for a second stage of the rolling is 880-930 degrees Celsius; anda cooling rate during the DQ is 15 degrees Celsius per second≤a quenching cooling rate<22 degrees Celsius per second.

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