Low-cost cryogenic high-toughness high-manganese steel for liquid hydrogen storage tanks and method of manufacture

Abstract

This invention provides a low-cost, ultra-low temperature, high-toughness high-manganese steel for liquid hydrogen storage tanks and its preparation method, relating to the technical field of low-temperature steelmaking. The chemical composition of the high-manganese steel, by mass percentage, is: C 0.37-0.47%, Mn 26-30%, Al 2.7-3.3%, P≤0.01%, S≤0.001%, with the remainder being Fe and unavoidable impurities; wherein the microstructure consists of a single-phase austenite structure, with an average austenite grain size of 14-18 μm. This invention regulates stacking fault energy by designing the alloy composition, and simultaneously ensures a single, uniform austenitic structure through high-temperature homogenization, hot rolling, and solution treatment. These two processes synergistically enhance the material's strength, plasticity, and impact toughness at extremely low temperatures of -269℃. At -196℃, the steel exhibits a tensile strength ≥1171 MPa, elongation after fracture ≥93.1%, strength-ductility product ≥109 GPa%, and Charpy impact toughness ≥239 J. At -269℃, the steel exhibits a tensile strength ≥1410 MPa, elongation after fracture ≥64.5%, strength-ductility product ≥91 GPa%, and Charpy impact toughness ≥233 J.

Description

Technical Field

[0001] This invention relates to the field of low-temperature steelmaking technology, specifically to a low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks and its preparation method. Background Technology

[0002] Hydrogen, as a fuel, is non-toxic, harmless, has good combustion performance, and emits no carbon, making it a key area for development in the clean energy industry both domestically and internationally. Hydrogen storage technology, serving as a bridge between hydrogen production and application, is a crucial link in the entire hydrogen energy industry chain. Cryogenic liquid hydrogen storage, among current mainstream storage and transportation solutions, offers advantages such as high hydrogen storage density, high refueling efficiency, and good safety, and thus has the greatest development potential.

[0003] Liquid hydrogen has a temperature of -253℃ (20K). To ensure the safety of liquid hydrogen storage and transportation, liquid hydrogen storage and transportation containers need to maintain good strength and toughness at this temperature, which places higher demands on the ultra-low temperature performance of metal materials.

[0004] Currently, 9Ni steel is the preferred alloy material for cryogenic applications. However, Ni resources are scarce in my country, and the cost of Ni is high, necessitating a low-cost cryogenic steel to replace 9Ni steel. Manganese (Mn) exhibits similar physicochemical properties to Ni during alloying. By developing a high-manganese steel for cryogenic applications using Mn as a substitute for Ni, a low-cost, ultra-low temperature, high-toughness high-manganese steel for liquid hydrogen storage tanks can be prepared. This steel possesses good low-temperature toughness while significantly reducing material costs compared to 9Ni steel. While numerous patents exist for high-manganese steel, they all suffer from various technical shortcomings, failing to achieve comprehensive performance, particularly high plasticity and high impact toughness at low temperatures, in a cost-effective and efficient manner.

[0005] For example, Chinese patent CN119351865A discloses a high-manganese steel for ultra-low temperatures and its manufacturing method. In terms of composition, the content of impurities such as P, S, N, O, and H is strictly controlled, and alloying with Cr, Cu, and Ni reduces the Ni content while ensuring ultra-low temperature toughness at -196℃ and a transverse impact energy of ≥120J at -196℃. In terms of manufacturing methods, innovative processes such as smelting, continuous casting, and solution treatment are used to finally obtain high-manganese steel plates for ultra-low temperatures. However, the addition of multiple alloying composite components such as Cr, Cu, and Ni to high-manganese steel makes the smelting process relatively complex and the cost still relatively high, ultimately resulting in generally lower low-temperature impact toughness.

[0006] Chinese patent CN118756060B discloses a high-strength, high-toughness high-manganese steel for cryogenic applications and its preparation method. Through compositional design, the stacking fault energy at -196℃ is controlled at 40-45 mJ / m². 2The process involves the TWIP effect, with the addition of Ti and W composite reinforcement. A three-stage controlled cooling process is employed in its preparation. Surface gradient nanostructure reinforcement is achieved through heavy impact with a metal impact pin, ultimately yielding a high-strength, high-toughness high-manganese steel for cryogenic applications, exhibiting an impact toughness ≥200J at -196℃. However, the addition of Ti and W composite reinforcement complicates the smelting process and increases costs. Furthermore, the high stacking fault energy design hinders the large-scale formation of deformation twins, preventing the high-manganese steel from reaching its optimal low-temperature toughness.

[0007] Chinese patent CN116855848A discloses a high-manganese steel plate for cryogenic storage tanks with stable anisotropic properties and its production method. Based on Fe, Mn, and C elements, Cr and Mo are added for alloying. An innovative rolling process is employed, introducing transverse rolling and optimizing the post-rolling cooling process, resulting in a high-manganese steel plate with uniform internal and external microstructure and good anisotropic toughness at low temperatures. At -196℃, the transverse and longitudinal impact energy of the hot-rolled steel plate are both ≥100J. However, the addition of Cr and Mo alloying increases production costs and complicates the smelting process; while the high-manganese steel exhibits good anisotropic toughness, its low-temperature impact toughness is relatively low.

[0008] Chinese patent CN115074615B discloses an environmentally friendly ultra-low temperature high-manganese steel and its manufacturing method. By precisely controlling the Mn content to 13-17%, it significantly reduces smelting dust pollution and the risk of manganese poisoning compared to traditional high-manganese steel (>24%). Simultaneously, Ni, Cu, V, N, and Nb are added for alloying. A combined process of "TMCP + DQ controlled rolling and cooling + solution treatment" is employed to obtain an environmentally friendly ultra-low temperature high-manganese steel with a balanced strength and toughness, exhibiting an impact toughness ≥100J at -196℃. This invention reduces the Mn content but adds multiple alloying elements, increasing production costs and complicating the smelting process; furthermore, the high-manganese steel has relatively low low-temperature toughness.

[0009] Chinese patent CN121161150A discloses a high-manganese steel that balances ultra-low temperature mechanical properties and surface quality, and its preparation method. By adding 0.43% C, 24.0% Mn, and 3.6% Cr, a highly stable austenitic structure is obtained. The composite addition of V and Ti forms multi-scale carbonitride dispersed precipitates. Segregation is controlled throughout the preparation process, employing a stepped heating process and online solution treatment technology to obtain a high-manganese steel that balances high strength, high toughness, and high surface quality. The impact toughness at -196℃ is ≥130J, and at -269℃ it is ≥80J. However, the composite addition of V and Ti increases the alloy production cost and the difficulty of the smelting process, and the low-temperature impact toughness of this high-manganese steel is relatively low.

[0010] Currently, most inventions of high-manganese steel for low-temperature applications involve the addition of multiple alloying composite components, which increases production costs and is detrimental to the smelting process. Low-temperature research is mostly focused on -196℃, with fewer inventions at -269℃. Furthermore, most inventions have low low-temperature impact toughness and have not achieved high impact toughness values.

[0011] Therefore, the present invention aims to obtain a high-manganese steel with simplified alloy composition, low cost, and synergistic improvement in plasticity and impact toughness, and the high-manganese steel has high impact toughness at both -196℃ and -269℃. Summary of the Invention

[0012] The technical problem this invention aims to solve is that existing high-manganese steels for cryogenic applications suffer from high alloy complexity in composition design, leading to high costs and low efficiency. Furthermore, cryogenic research primarily focuses on -196℃, failing to reach -269℃, resulting in a lack of synergistic improvement in strength, ductility, and impact toughness. The manufacturing processes are also complex, difficult to operate, and unsuitable for large-scale industrial production. To address these issues, this invention proposes a low-cost, -269℃ ultra-low temperature, high-toughness high-manganese steel for liquid hydrogen storage tanks and its preparation method.

[0013] The main objective of this invention is to provide a low-cost, low-temperature high-manganese steel for liquid hydrogen storage tanks that exhibits both high plasticity and high impact toughness at extremely low temperatures. This invention also provides a method for manufacturing the aforementioned low-cost, low-temperature high-manganese steel for liquid hydrogen storage tanks.

[0014] To address the high cost of 9Ni steel for cryogenic applications, this invention designs a low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks by substituting Mn for Ni. This meets the requirements of cryogenic liquid hydrogen containers while simplifying the alloy composition and reducing the cost of alloy materials. Furthermore, the preparation method of the high-manganese steel material has been improved. Through the combined effect of these two methods, a high-manganese steel material for liquid hydrogen containers with stable microstructure and properties, excellent plasticity and toughness at cryogenic temperatures, and low cost is finally obtained.

[0015] A low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks is disclosed. The chemical composition of this steel, by mass percentage, is: C 0.37-0.47%, Mn 26-30%, Al 2.7-3.3%, P≤0.01%, S≤0.001%. The mass percentages of Mn and Al satisfy the relationship: 1.5×Mn + 4×Al between 54-55%, with the remainder being Fe and unavoidable impurities. The microstructure of this steel consists of a single-phase austenitic structure with an average austenitic grain size of 14-18 μm. The stacking fault energy of this steel at -269℃ is controlled at 18-25 mJ / m.2 .

[0016] In order to ensure that the high manganese steel of the present invention undergoes twinning-induced plasticity during deformation at extremely low temperatures, the elemental composition of the high manganese steel of the present invention should be within the given range to ensure that the alloy stacking fault energy is within an appropriate range.

[0017] This invention selects to control the stacking fault energy by optimizing the ratio of Mn, Al, and C elements, so that it is 18-25 mJ / m at -269℃. 2 This, in turn, affects the low-temperature deformation mechanism of high-manganese steel, causing twinning-induced plastic deformation to dominate and synergistically improving the alloy's strength, plasticity, and toughness. Specifically:

[0018] Carbon (C) is a core element affecting the properties of steel materials, playing a crucial role in the performance of high-manganese steel. In high-manganese steel, C exists as interstitial solid solution atoms, pinning dislocations and thus increasing strength but reducing plasticity. Low C content hinders the formation of a single austenite phase in high-manganese steel, while excessive C leads to the formation of cementite grain boundary networks or the precipitation of large carbides, making high-manganese steel prone to brittle fracture.

[0019] Manganese (Mn) is a key component of high-manganese steel. It can broaden the austenite phase region, lower the martensite initiation temperature, and improve the stability of the austenite phase. When the Mn content is 16–33 wt.%, each 1 wt.% increase in Mn can increase the stacking fault energy by 18 mJ / m. 2 However, when the Mn content exceeds 30 wt.%, a brittle β-Mn phase may be generated, which leads to a significant reduction in the ductility of high-manganese steel and increases the possibility of brittle fracture.

[0020] Al can act as an exogenous nucleating agent, refining grains and improving material strength. Adding Al to austenitic steel can increase its yield strength and elongation, but it reduces its work hardening capacity. In high-manganese steel, adding Al can increase stacking fault energy, inhibit the formation of ε-martensite, and promote the stability of single-phase austenite. However, excessive Al may combine with nitrogen to form aluminum nitride (AlN), which precipitates and accumulates mainly along grain boundaries, causing grain boundary embrittlement and thus reducing the material's toughness. Furthermore, excessively high Al content can easily lead to the formation of oxide residues, affecting material properties.

[0021] Potential functions for each element were constructed using molecular dynamics, and corresponding FCC alloy models were built to calculate stacking fault energy. Considering the influence of each element content on stacking fault energy and other alloy properties, the following values ​​were ultimately selected: C content between 0.37% and 0.47%, Mn content between 26% and 30%, Al content between 2.7% and 3.3%, with the remainder being Fe and unavoidable impurities.

[0022] Optionally, the low-cost liquid hydrogen storage tank uses ultra-low temperature high-toughness high-manganese steel with a yield strength ≥653MPa, tensile strength ≥1171MPa, elongation after fracture ≥93.1%, and strength-ductility product ≥109GPa at -196℃; and Charpy impact toughness ≥239J at -196℃ based on a thickness of 10mm.

[0023] Optionally, the low-cost liquid hydrogen storage tank uses ultra-low temperature high-toughness high-manganese steel with a yield strength ≥967MPa, tensile strength ≥1410MPa, elongation after fracture ≥64.5%, and strength-ductility product ≥91GPa at -269℃; and Charpy impact toughness ≥233J at -269℃ based on a thickness of 10mm.

[0024] A method for preparing low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks, comprising the following preparation steps:

[0025] S1. Smelting: The elemental composition and mass percentage of each alloying element of the ultra-low temperature high-toughness high-manganese steel used in low-cost liquid hydrogen storage tanks are configured and weighed. After smelting, the high-manganese steel billet is cast.

[0026] S2, High-temperature homogenization + hot forging: The high-manganese steel billet of S1 is heated to undergo high-temperature homogenization treatment, and then hot forging is performed to obtain low-cost liquid hydrogen storage tank ultra-low temperature high-toughness high-manganese steel forging.

[0027] S3, High-temperature solution treatment + multi-pass rough rolling: The low-cost liquid hydrogen storage tank forging of S2 is first subjected to high-temperature solution treatment, and after removing the iron oxide scale, it is subjected to multi-pass rough rolling to obtain the rough hot-rolled plate.

[0028] S4, Finish rolling + water quenching: The rough hot-rolled plate of S3 is subjected to two passes of finish rolling, followed by water quenching to room temperature to obtain the final hot-rolled plate;

[0029] S5. Short-time solution treatment: The final hot-rolled plate of S4 is subjected to short-time solution treatment to obtain low-cost, low-temperature, high-toughness, high-manganese steel plate for liquid hydrogen storage tanks.

[0030] Optionally, the smelting temperature in S1 is 1600-1650℃, the casting temperature is 1550-1600℃, and the high manganese steel billet is bullet-shaped with dimensions of 110×110×130mm-120×110×130mm, including the riser length in the length direction.

[0031] Optionally, the heating rate of the high-temperature homogenization treatment in S2 is 10-20℃ / min, the temperature is 1150-1250℃, the holding time is 10-15h, and the sample is placed in the heating furnace when it reaches the desired temperature.

[0032] Optionally, before hot forging in S2, the riser of the high manganese steel billet needs to be removed, the forging temperature is 950-1100℃, the forging ratio is 1.1:1-1.2:1, and the high manganese steel forging material with a size of 100×100×120mm-110×100×120mm is forged.

[0033] Optionally, the high-temperature solution treatment temperature in S3 is 1050-1150℃, the holding time is 2-4h, and the sample is laid out when the heating furnace reaches the desired temperature; the iron oxide scale is removed before rough rolling, the initial rolling temperature is 1000-1050℃, a total of 5 rolling passes are performed, the deformation amount of each pass is 25-30%, the final rolling temperature is 930-950℃, and the thickness of the rough hot-rolled plate is 25-27mm.

[0034] Optionally, in S4, the iron oxide scale is removed before finishing rolling. The initial rolling temperature is 900-920℃, and two rolling passes are performed. The deformation amount in each pass is 20-25%. The final rolling temperature is 850-870℃, and the thickness of the hot-rolled plate is 11-13mm. After hot rolling, the plate is quenched in water at 25-30℃ to room temperature, and the cooling rate is controlled at 7-10℃ / min.

[0035] Optionally, the temperature for short-term solution treatment in S5 is 880-920℃, and the solution treatment time is 20-30min; the thickness of the ultra-low temperature high-toughness high-manganese steel plate for low-cost liquid hydrogen storage tank is 10-15mm, and the microstructure is composed of austenitic single-phase structure with an average austenitic grain size of 14-18μm.

[0036] Technical principle of the invention:

[0037] The deformation mechanism of high-manganese steel is generally controlled by stacking fault energy. The stacking fault energy of high-manganese steel is less than 18 mJ / m. 2 During deformation, a martensitic phase transformation occurs, including close-packed hexagonal martensite and body-centered cubic martensite; that is, the deformation process exhibits a transformation-induced plasticity (TRIP) effect. Stacking fault energy is 18-40 mJ / m. 2 During deformation, full dislocations decompose into partial dislocations, and the movement of these partial dislocations forms deformation twins, i.e., twin-induced plasticity (TWIP) effect; stacking fault energy is greater than 40 mJ / m 2 At this stage, full dislocations are difficult to decompose, and deformation of high-manganese steel is dominated by dislocation cross-slip or plane slip. If the stacking fault energy is too low, martensitic phase transformation will occur during deformation, which is detrimental to low-temperature toughness; if the stacking fault energy is too high, the TWIP effect will be weakened, and deformation twins will decrease during deformation, which is also detrimental to low-temperature toughness.

[0038] This invention calculates stacking fault energy using molecular dynamics simulations and designs the stacking fault energy range by compositional design, causing the TWIP effect during deformation to improve the ultra-low temperature ductility and toughness of high-manganese steel. The calculated stacking fault energy results for the Fe-Mn-Al-C system high-manganese steel described in this invention are as follows: Figure 1As shown. Unlike the common approach of improving performance by adding alloying elements such as Cr, Mo, Nb, and Ti, this design adopts a simplified alloy composition, using only four elements: Fe, Mn, Al, and C. The focus is on controlling the composition content to improve performance. Finally, through stacking fault energy calculations, the composition range of high-manganese steel was obtained, in mass percentage: C 0.37-0.47%, Mn 26-30%, Al 2.7-3.3%, P≤0.01%, S≤0.001%, with the remainder being Fe and unavoidable impurities. Within this composition range, the stacking fault energy of high-manganese steel at -269℃ is 18-25 mJ / m. 2 During the deformation process, the TWIP effect is dominant, achieving a synergistic improvement in the strength, plasticity, and toughness of high-manganese steel at extremely low temperatures.

[0039] In terms of preparation methods, high-temperature homogenization and solid solution homogenization processes are used to ensure a single and uniform austenitic structure with an average size of 14-18 μm, and sufficient re-dissolution of precipitated phases, thereby ensuring the material's ultra-low temperature performance.

[0040] The above technical solution has at least the following advantages compared with the existing technology:

[0041] The above-mentioned solution proposes a low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks and its preparation method. It can solve the problems of high alloy complexity in the composition design of existing high-manganese steel for low temperature applications, which leads to high cost and low efficiency; as well as the fact that low temperature research is mostly focused on -196℃ and has not reached -269℃, the strength, plasticity and impact toughness obtained cannot be improved synergistically, and the preparation process is complex, difficult to operate, and unsuitable for large-scale industrial production.

[0042] This invention calculates the stacking fault energy of high-manganese steel with different compositions using molecular dynamics simulations, and utilizes composition design to control the stacking fault energy of high-manganese steel at -269℃ to 18-25 mJ / m 2 This, in turn, affects the deformation mechanism of high manganese steel, making it dominated by a strong TWIP effect during deformation, thereby achieving a synergistic improvement in the strength, plasticity, and toughness of high manganese steel at extremely low temperatures.

[0043] This invention does not add common high-manganese steel alloying composites such as Ni, Cr, Mo, Nb, and Ti. Instead, it uses only four elements—Fe, Mn, Al, and C—and employs stacking fault energy simulation calculations to rationally design the component ratios. By utilizing the TWIP effect of austenitic alloy deformation, it obtains high-manganese steel with excellent ductility and toughness at extremely low temperatures. The simplified high-manganese steel alloy composition reduces the smelting cost and simplifies the process. Furthermore, given the current practice of mostly adding alloying elements to improve performance, this invention offers a new approach to improving the performance of high-manganese steel.

[0044] The low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks described in this invention has the following properties: at -196℃, yield strength ≥ 653 MPa, tensile strength ≥ 1171 MPa, elongation after fracture ≥ 93.1%, and strength-ductility product ≥ 109 GPa; based on a 10 mm thickness, Charpy impact toughness ≥ 239 J at -196℃; at -269℃, yield strength ≥ 967 MPa, tensile strength ≥ 1410 MPa, elongation after fracture ≥ 64.5%, and strength-ductility product ≥ 91 GPa; based on a 10 mm thickness, Charpy impact toughness ≥ 233 J at -269℃. This meets the material requirements for liquid hydrogen containers.

[0045] In summary, compared with traditional low-temperature steel preparation methods, the method of this invention controls the stacking fault energy by designing the alloy composition content, and ensures a single, uniform austenitic structure through processes such as high-temperature homogenization, hot rolling, and solution treatment. The two work together to ensure a synergistic improvement in the material's strength, plasticity, and impact toughness at an extremely low temperature of -269℃. This method is simple to operate, environmentally friendly, low in cost, and highly efficient, making it suitable for large-scale industrial production and application. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] The BC image in the attached diagram below, short for Bands Contrast, also often referred to as Pattern Quality, is a grayscale image generated simultaneously by the EBSD system when acquiring Kikuchi diffraction patterns. It reflects the clarity of the Kikuchi diffraction pattern. It is essentially an electronic image showcasing the "perfection" of the sample surface; the brightness of each pixel represents only the diffraction pattern quality at that point and is independent of the specific orientation of the grains.

[0048] The GB map in the attached figure below stands for Grain Boundary map, which is a specialized map used in EBSD analysis to display and distinguish the boundary characteristics between different grains within a material.

[0049] Figure 1 This is a graph showing the calculated stacking fault energy of Fe-Mn-Al-C high-manganese steel according to the present invention.

[0050] Figure 2 This is the BC+GB diagram of the microstructure of the low-cost liquid hydrogen storage tank using ultra-low temperature high-toughness high-manganese steel described in Embodiment 1 of the present invention;

[0051] Figure 3 This is the BC+GB diagram of the microstructure of the low-cost liquid hydrogen storage tank using ultra-low temperature high-toughness high-manganese steel described in Embodiment 2 of the present invention;

[0052] Figure 4 This is the BC+GB diagram of the microstructure of the low-cost liquid hydrogen storage tank using ultra-low temperature high-toughness high-manganese steel described in Embodiment 3 of the present invention;

[0053] Figure 5 This is the BC+GB diagram of the microstructure of the low-cost liquid hydrogen storage tank using ultra-low temperature high-toughness high-manganese steel described in Embodiment 4 of the present invention;

[0054] Figure 6 This is the BC+GB diagram of the microstructure of the low-cost liquid hydrogen storage tank using ultra-low temperature high-toughness high-manganese steel described in Embodiment 5 of the present invention;

[0055] Figure 7 This is the BC+GB diagram of the microstructure of the low-cost liquid hydrogen storage tank using ultra-low temperature high-toughness high-manganese steel described in Embodiment 6 of the present invention. Detailed Implementation

[0056] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0057] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0058] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction is not emphasized, their intended meanings are consistent.

[0059] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0060] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0061] A low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks is disclosed. The chemical composition of this steel, by mass percentage, is: C 0.37-0.47%, Mn 26-30%, Al 2.7-3.3%, P≤0.01%, S≤0.001%. The mass percentages of Mn and Al satisfy the relationship: 1.5×Mn + 4×Al between 54-55%, with the remainder being Fe and unavoidable impurities. The microstructure of this steel consists of a single-phase austenitic structure with an average austenitic grain size of 14-18 μm. The stacking fault energy of this steel at -269℃ is controlled at 18-25 mJ / m. 2 .

[0062] In order to ensure that the high manganese steel of the present invention undergoes twinning-induced plasticity during deformation at extremely low temperatures, the elemental composition of the high manganese steel of the present invention should be within the given range to ensure that the alloy stacking fault energy is within an appropriate range.

[0063] This invention selects to control the stacking fault energy by optimizing the ratio of Mn, Al, and C elements, so that it is 18-25 mJ / m at -269℃. 2 This, in turn, affects the low-temperature deformation mechanism of high-manganese steel, causing twinning-induced plastic deformation to dominate and synergistically improving the alloy's strength, plasticity, and toughness. Specifically:

[0064] Carbon (C) is a core element affecting the properties of steel materials, playing a crucial role in the performance of high-manganese steel. In high-manganese steel, C exists as interstitial solid solution atoms, pinning dislocations and thus increasing strength but reducing plasticity. Low C content hinders the formation of a single austenite phase in high-manganese steel, while excessive C leads to the formation of cementite grain boundary networks or the precipitation of large carbides, making high-manganese steel prone to brittle fracture.

[0065] Manganese (Mn) is a key component of high-manganese steel. It can broaden the austenite phase region, lower the martensite initiation temperature, and improve the stability of the austenite phase. When the Mn content is 16–33 wt.%, each 1 wt.% increase in Mn can increase the stacking fault energy by 18 mJ / m. 2 However, when the Mn content exceeds 30 wt.%, a brittle β-Mn phase may be generated, which leads to a significant reduction in the ductility of high-manganese steel and increases the possibility of brittle fracture.

[0066] Al can act as an exogenous nucleating agent, refining grains and improving material strength. Adding Al to austenitic steel can increase its yield strength and elongation, but it reduces its work hardening capacity. In high-manganese steel, adding Al can increase stacking fault energy, inhibit the formation of ε-martensite, and promote the stability of single-phase austenite. However, excessive Al may combine with nitrogen to form aluminum nitride (AlN), which precipitates and accumulates mainly along grain boundaries, causing grain boundary embrittlement and thus reducing the material's toughness. Furthermore, excessively high Al content can easily lead to the formation of oxide residues, affecting material properties.

[0067] Potential functions for each element were constructed using molecular dynamics, and corresponding FCC alloy models were built to calculate stacking fault energy. Considering the influence of each element content on stacking fault energy and other alloy properties, the following values ​​were ultimately selected: C content between 0.37% and 0.47%, Mn content between 26% and 30%, Al content between 2.7% and 3.3%, with the remainder being Fe and unavoidable impurities.

[0068] Specifically, the low-cost liquid hydrogen storage tank uses ultra-low temperature high-toughness high-manganese steel with a yield strength ≥653MPa, tensile strength ≥1171MPa, elongation after fracture ≥93.1%, and strength-ductility product ≥109GPa at -196℃; and Charpy impact toughness ≥239J at -196℃ based on a thickness of 10mm.

[0069] Specifically, the low-cost liquid hydrogen storage tank uses ultra-low temperature high-toughness high-manganese steel with a yield strength ≥967MPa, tensile strength ≥1410MPa, elongation after fracture ≥64.5%, and strength-ductility product ≥91GPa at -269℃; based on a thickness of 10mm, the Charpy impact toughness at -269℃ is ≥233J.

[0070] A method for preparing low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks, comprising the following preparation steps:

[0071] S1. Smelting: The elemental composition and mass percentage of each alloying element of the ultra-low temperature high-toughness high-manganese steel used in low-cost liquid hydrogen storage tanks are configured and weighed. After smelting, the high-manganese steel billet is cast.

[0072] S2, High-temperature homogenization + hot forging: The high-manganese steel billet of S1 is heated to undergo high-temperature homogenization treatment, and then hot forging is performed to obtain low-cost liquid hydrogen storage tank ultra-low temperature high-toughness high-manganese steel forging.

[0073] S3, High-temperature solution treatment + multi-pass rough rolling: The low-cost liquid hydrogen storage tank forging of S2 is first subjected to high-temperature solution treatment, and after removing the iron oxide scale, it is subjected to multi-pass rough rolling to obtain the rough hot-rolled plate.

[0074] S4, Finish rolling + water quenching: The rough hot-rolled plate of S3 is subjected to two passes of finish rolling, followed by water quenching to room temperature to obtain the final hot-rolled plate;

[0075] S5. Short-time solution treatment: The final hot-rolled plate of S4 is subjected to short-time solution treatment to obtain low-cost, low-temperature, high-toughness, high-manganese steel plate for liquid hydrogen storage tanks.

[0076] Specifically, the smelting temperature of S1 is 1600-1650℃, the casting temperature is 1550-1600℃, and the high manganese steel billet is bullet-shaped with dimensions of 110×110×130mm-120×110×130mm, including the riser length in the length direction.

[0077] Specifically, the heating rate of the high-temperature homogenization treatment in S2 is 10-20℃ / min, the temperature is 1150-1250℃, the holding time is 10-15h, and the sample is released when the heating furnace reaches the desired temperature.

[0078] Specifically, before hot forging in S2, the riser of the high manganese steel billet needs to be removed. The forging temperature is 950-1100℃, the forging ratio is 1.1:1-1.2:1, and high manganese steel forgings of 100×100×120mm-110×100×120mm are forged.

[0079] Specifically, the high-temperature solution treatment temperature in S3 is 1050-1150℃, the holding time is 2-4h, and the sample is laid out when the heating furnace reaches the desired temperature; the iron oxide scale is removed before rough rolling, the initial rolling temperature is 1000-1050℃, a total of 5 rolling passes are performed, the deformation amount of each rolling pass is 25-30%, the final rolling temperature is 930-950℃, and the thickness of the rough hot-rolled plate is 25-27mm.

[0080] Specifically, in S4, the iron oxide scale is removed before finishing rolling. The initial rolling temperature is 900-920℃, and two rolling passes are performed. The deformation amount in each pass is 20-25%. The final rolling temperature is 850-870℃, and the thickness of the hot-rolled plate is 11-13mm. After hot rolling, it is quenched in water at 25-30℃ to room temperature, and the cooling rate is controlled at 7-10℃ / min.

[0081] Specifically, the temperature for short-time solution treatment in S5 is 880-920℃, and the solution treatment time is 20-30min; the thickness of the ultra-low temperature high-toughness high-manganese steel plate for low-cost liquid hydrogen storage tanks is 10-15mm, and the microstructure consists of austenitic single-phase structure with an average austenitic grain size of 14-18μm.

[0082] Example 1

[0083] This embodiment discloses a low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks. The chemical composition of the low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks, by mass percentage, is: C 0.43%, Mn 28.86%, Al 2.77%, P≤0.01%, S≤0.001%, 1.5×Mn+4×Al 54.37%, with the remainder being Fe and unavoidable impurities.

[0084] A method for preparing low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks, comprising the following preparation steps:

[0085] S1. Smelting: The elemental composition and mass percentage of each alloying element of the ultra-low temperature high-toughness high-manganese steel used for low-cost liquid hydrogen storage tanks are configured and weighed. The smelting temperature is 1650℃ and the casting temperature is 1600℃. The high-manganese steel billet is bullet-shaped with dimensions of 110×110×130mm, including the riser length in the length direction.

[0086] S2, High-Temperature Homogenization + Hot Forging: The high-manganese steel billet of S1 is heated to undergo high-temperature homogenization treatment. The heating rate is 20℃ / min, the temperature is 1200℃, and the holding time is 12h. The billet is then laid out after the heating furnace reaches the desired temperature. After that, it is hot forged. Before hot forging, the riser of the high-manganese steel billet needs to be removed. The forging temperature is 950-1000℃, and the forging ratio is 1.1:1, to obtain a low-cost, low-temperature, high-toughness high-manganese steel forging for liquid hydrogen storage tanks with dimensions of 110×100×120mm.

[0087] S3, High-temperature solution treatment + multi-pass rough rolling: The low-cost liquid hydrogen storage tank forgings of S2 are first subjected to high-temperature solution treatment at 1100℃ for 2 hours, and then laid out in the heating furnace. After removing the iron oxide scale from the furnace, multi-pass rough rolling is performed. Before rough rolling, the iron oxide scale is removed. The initial rolling temperature is 1050℃, and a total of 5 rolling passes are performed. The deformation amount of each pass is 25-27%, and the final rolling temperature is 930-940℃ to obtain a rough hot-rolled plate with a thickness of 25mm.

[0088] S4, Finish Rolling + Water Quenching: The rough hot-rolled plate of S3 is subjected to two-pass finish rolling. Before finish rolling, the iron oxide scale is removed. The initial rolling temperature is 910℃, and a total of 2 passes are performed. The deformation amount of each pass is 20-25%. The final rolling temperature is 850-860℃, and the thickness of the hot-rolled plate is 11mm. After hot rolling, it is quenched in water at 30℃ to room temperature. The cooling rate is controlled at 10℃ / min to obtain the final hot-rolled plate.

[0089] S5. Short-time solution treatment: The final hot-rolled plate of S4 is subjected to short-time solution treatment at a temperature of 900℃ for 25 minutes to obtain a low-cost, low-temperature, high-toughness, high-manganese steel plate for liquid hydrogen storage tanks with a thickness of 11mm.

[0090] The results show that: Figure 2 The microstructure of high-manganese steel after solution treatment is shown in the figure. Statistical observation reveals that the microstructure of the steel after solution treatment consists of a single-phase austenitic structure with an average austenitic grain size of 16.5 μm. The optimal properties achievable are: a yield strength of 653 MPa, a tensile strength of 1171 MPa, an elongation after fracture of 93.1%, and a strength-ductility product of 109 GPa at -196℃; and a Charpy impact toughness of 239 J at -196℃ (based on a 10 mm thickness). At -269℃, the yield strength is 967 MPa, the tensile strength is 1410 MPa, the elongation after fracture is 64.5%, and the strength-ductility product is 91 GPa; and a Charpy impact toughness of 235 J at -269℃ (based on a 10 mm thickness).

[0091] Example 2

[0092] This embodiment discloses a low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks. The chemical composition of the low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks, by mass percentage, is: C 0.42%, Mn 28.92%, Al 2.81%, P≤0.01%, S≤0.001%, 1.5×Mn+4×Al 54.62%, with the remainder being Fe and unavoidable impurities.

[0093] A method for preparing low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks, comprising the following preparation steps:

[0094] S1. Smelting: The elemental composition and mass percentage of each alloying element of the ultra-low temperature high-toughness high-manganese steel used for low-cost liquid hydrogen storage tanks are configured and weighed. The smelting temperature is 1630℃ and the casting temperature is 1580℃. The high-manganese steel billet is bullet-shaped with dimensions of 115×110×130mm, including the riser length in the length direction.

[0095] S2, High-Temperature Homogenization + Hot Forging: The high-manganese steel billet of S1 is heated to undergo high-temperature homogenization treatment. The heating rate is 18℃ / min, the temperature is 1250℃, and the holding time is 11h. The billet is then laid out after the heating furnace reaches the desired temperature. After that, it is hot forged. Before hot forging, the riser of the high-manganese steel billet needs to be removed. The forging temperature is 1000-1100℃, and the forging ratio is 1.1:1, to obtain a low-cost, low-temperature, high-toughness high-manganese steel forging for liquid hydrogen storage tanks with dimensions of 110×100×120mm.

[0096] S3, High-temperature solution treatment + multi-pass rough rolling: The low-cost liquid hydrogen storage tank forgings of S2 are first subjected to high-temperature solution treatment at 1050℃ for 3 hours, and then laid out after the furnace reaches the desired temperature. After removing the iron oxide scale from the furnace, multi-pass rough rolling is performed. Before rough rolling, the iron oxide scale is removed. The initial rolling temperature is 1030℃, and a total of 5 rolling passes are performed. The deformation amount of each pass is 25-27%, and the final rolling temperature is 940-950℃ to obtain a rough hot-rolled plate with a thickness of 27mm.

[0097] S4, Finish Rolling + Water Quenching: The rough hot-rolled plate of S3 is subjected to two-pass finish rolling. Before finish rolling, the iron oxide scale is removed. The initial rolling temperature is 920℃, and a total of 2 passes are performed. The deformation of each pass is 21-23%. The final rolling temperature is 860-870℃, and the thickness of the hot-rolled plate is 12.4mm. After hot rolling, it is quenched in water at 27℃ to room temperature. The cooling rate is controlled at 8℃ / min to obtain the final hot-rolled plate.

[0098] S5. Short-time solution treatment: The final hot-rolled plate of S4 is subjected to short-time solution treatment at a temperature of 880℃ for 20 minutes to obtain a low-cost, low-temperature, high-toughness, high-manganese steel plate for liquid hydrogen storage tanks with a thickness of 12.4mm.

[0099] The results show that: Figure 3 The microstructure of high-manganese steel after solution treatment is shown in the figure. Statistical observation reveals that the microstructure of the steel after solution treatment consists of a single-phase austenitic structure with an average austenitic grain size of 14.7 μm. The optimal properties achievable are: at -196℃, the steel has a yield strength of 662 MPa, a tensile strength of 1185 MPa, an elongation after fracture of 93.3%, and a strength-ductility product of 111 GPa; based on a 10 mm thickness, the Charpy impact toughness at -196℃ is 241 J; at -269℃, the steel has a yield strength of 968 MPa, a tensile strength of 1421 MPa, an elongation after fracture of 65.1%, and a strength-ductility product of 93 GPa; based on a 10 mm thickness, the Charpy impact toughness at -269℃ is 233 J.

[0100] Example 3

[0101] This embodiment discloses a low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks. The chemical composition of the low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks, by mass percentage, is: C 0.45%, Mn 29.17%, Al 2.76%, P≤0.01%, S≤0.001%, 1.5×Mn+4×Al 54.795%, with the remainder being Fe and unavoidable impurities.

[0102] A method for preparing low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks, comprising the following preparation steps:

[0103] S1. Smelting: The elemental composition and mass percentage of each alloy element of the ultra-low temperature high-toughness high-manganese steel used for low-cost liquid hydrogen storage tanks are configured and weighed. The smelting temperature is 1620℃ and the casting temperature is 1550℃. The high-manganese steel billet is bullet-shaped with dimensions of 120×110×130mm, including the riser length in the length direction.

[0104] S2, High-temperature homogenization + hot forging: The high-manganese steel billet of S1 is heated to undergo high-temperature homogenization treatment. The heating rate is 15℃ / min, the temperature is 1150℃, and the holding time is 14h. The billet is then laid out after the heating furnace reaches the desired temperature. After that, it is hot forged. Before hot forging, the riser of the high-manganese steel billet needs to be removed. The forging temperature is 1000-1050℃, and the forging ratio is 1.1:1, to obtain a low-cost, low-temperature, high-toughness high-manganese steel forging for liquid hydrogen storage tanks with dimensions of 107×100×120mm.

[0105] S3, High-Temperature Solution Treatment + Multi-Pass Rough Rolling: The low-cost liquid hydrogen storage tank forgings of S2 are first subjected to high-temperature solution treatment at 1150℃ for 4 hours, and then laid out in the heating furnace. After removing the iron oxide scale from the furnace, multi-pass rough rolling is performed. Before rough rolling, the iron oxide scale is removed. The initial rolling temperature is 1025℃, and a total of 5 rolling passes are performed. The deformation amount of each pass is 25-29%, and the final rolling temperature is 930-935℃, resulting in a rough hot-rolled plate with a thickness of 26.5mm.

[0106] S4, Finish Rolling + Water Quenching: The rough hot-rolled plate of S3 is subjected to two-pass finish rolling. Before finish rolling, the iron oxide scale is removed. The initial rolling temperature is 915℃, and a total of 2 passes are performed. The deformation of each pass is 23-25%. The final rolling temperature is 860-865℃, and the thickness of the hot-rolled plate is 12.8mm. After hot rolling, it is quenched in water at 25℃ to room temperature. The cooling rate is controlled at 7℃ / min to obtain the final hot-rolled plate.

[0107] S5. Short-time solution treatment: The final hot-rolled plate of S4 is subjected to short-time solution treatment at a temperature of 890℃ for 30 minutes to obtain a low-cost, low-temperature, high-toughness, high-manganese steel plate for liquid hydrogen storage tanks with a thickness of 12.8mm.

[0108] The results show that: Figure 4The microstructure of high-manganese steel after solution treatment is shown in the figure. Statistical observation reveals that the microstructure of the steel after solution treatment consists of a single-phase austenitic structure with an average austenitic grain size of 16.0 μm. The optimal properties achievable are as follows: at -196℃, the steel has a yield strength of 661 MPa, a tensile strength of 1180 MPa, an elongation after fracture of 93.2%, and a strength-ductility product of 110 GPa; based on a 10 mm thickness, the Charpy impact toughness at -196℃ is 243 J; at -269℃, the steel has a yield strength of 971 MPa, a tensile strength of 1411 MPa, an elongation after fracture of 65.0%, and a strength-ductility product of 92 GPa; based on a 10 mm thickness, the Charpy impact toughness at -269℃ is 237 J.

[0109] Example 4

[0110] This embodiment discloses a low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks. The chemical composition of the low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks, by mass percentage, is: C 0.41%, Mn 28.85%, Al 2.75%, P≤0.01%, S≤0.001%, 1.5×Mn+4×Al 54.275%, with the remainder being Fe and unavoidable impurities.

[0111] A method for preparing low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks, comprising the following preparation steps:

[0112] S1. Smelting: The elemental composition and mass percentage of each alloying element of the ultra-low temperature high-toughness high-manganese steel used for low-cost liquid hydrogen storage tanks are configured and weighed. The smelting temperature is 1640℃ and the casting temperature is 1590℃. The high-manganese steel billet is bullet-shaped with dimensions of 114×110×130mm, including the riser length in the length direction.

[0113] S2, High-Temperature Homogenization + Hot Forging: The high-manganese steel billet of S1 is heated to undergo high-temperature homogenization treatment. The heating rate is 19℃ / min, the temperature is 1190℃, and the holding time is 15h. The billet is then laid out after the heating furnace reaches the desired temperature. After that, it is hot forged. Before hot forging, the riser of the high-manganese steel billet needs to be removed. The forging temperature is 1030-1100℃, and the forging ratio is 1.1:1, to obtain a low-cost, low-temperature, high-toughness high-manganese steel forging for liquid hydrogen storage tanks with dimensions of 105×100×120mm.

[0114] S3, High-Temperature Solution Treatment + Multi-Pass Rough Rolling: The low-cost liquid hydrogen storage tank forgings of S2 are first subjected to high-temperature solution treatment at 1080℃ for 3 hours, and then laid out in the heating furnace. After removing the iron oxide scale from the furnace, multi-pass rough rolling is performed. Before rough rolling, the iron oxide scale is removed. The initial rolling temperature is 1040℃, and a total of 5 rolling passes are performed. The deformation amount of each pass is 26-28%, and the final rolling temperature is 930-945℃, resulting in a rough hot-rolled plate with a thickness of 26.3mm.

[0115] S4, Finish Rolling + Water Quenching: The rough hot-rolled plate of S3 is subjected to two-pass finish rolling. Before finish rolling, the iron oxide scale is removed. The initial rolling temperature is 905℃, and a total of 2 passes are performed. The deformation of each pass is 20-22%. The final rolling temperature is 850-855℃, and the thickness of the hot-rolled plate is 12.5mm. After hot rolling, it is quenched in water at 26℃ to room temperature. The cooling rate is controlled at 8℃ / min to obtain the final hot-rolled plate.

[0116] S5. Short-time solution treatment: The final hot-rolled plate of S4 is subjected to short-time solution treatment at a temperature of 920℃ for 29 minutes; a low-cost, low-temperature, high-toughness, high-manganese steel plate for liquid hydrogen storage tanks with a thickness of 12.5mm is obtained.

[0117] The results show that: Figure 5 The microstructure of high-manganese steel after solution treatment is shown in the figure. Statistical observation reveals that the microstructure of the steel after solution treatment consists of a single-phase austenitic structure with an average austenitic grain size of 18.0 μm. The optimal properties achievable are: at -196℃, the steel has a yield strength of 660 MPa, a tensile strength of 1172 MPa, an elongation after fracture of 93.1%, and a strength-ductility product of 109 GPa; based on a 10 mm thickness, the Charpy impact toughness at -196℃ is 240 J; at -269℃, the steel has a yield strength of 969 MPa, a tensile strength of 1413 MPa, an elongation after fracture of 64.7%, and a strength-ductility product of 91 GPa; based on a 10 mm thickness, the Charpy impact toughness at -269℃ is 235 J.

[0118] Example 5

[0119] This embodiment discloses a low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks. The chemical composition of the low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks, by mass percentage, is: C 0.44%, Mn 28.83%, Al 2.82%, P≤0.01%, S≤0.001%, 1.5×Mn+4×Al 54.525%, with the remainder being Fe and unavoidable impurities.

[0120] A method for preparing low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks, comprising the following preparation steps:

[0121] S1. Smelting: The elemental composition and mass percentage of each alloying element of the ultra-low temperature high-toughness high-manganese steel used for low-cost liquid hydrogen storage tanks are configured and weighed. The smelting temperature is 1620℃ and the casting temperature is 1580℃. The high-manganese steel billet is bullet-shaped with dimensions of 110×110×130mm, including the riser length in the length direction.

[0122] S2, High-Temperature Homogenization + Hot Forging: The high-manganese steel billet of S1 is heated to undergo high-temperature homogenization treatment. The heating rate is 13℃ / min, the temperature is 1175℃, and the holding time is 14h. The billet is then laid out after the heating furnace reaches the desired temperature. After that, it is hot forged. Before hot forging, the riser of the high-manganese steel billet needs to be removed. The forging temperature is 950-990℃ and the forging ratio is 1.1:1, resulting in a low-cost, low-temperature, high-toughness high-manganese steel forging for liquid hydrogen storage tanks with dimensions of 103×100×120mm.

[0123] S3, High-temperature solution treatment + multi-pass rough rolling: The low-cost liquid hydrogen storage tank forgings of S2 are first subjected to high-temperature solution treatment at 1130℃ for 3 hours, and then laid out in the heating furnace. After removing the iron oxide scale from the furnace, multi-pass rough rolling is performed. Before rough rolling, the iron oxide scale is removed. The initial rolling temperature is 1010℃, and a total of 5 rolling passes are performed. The deformation amount of each pass is 27-28%, and the final rolling temperature is 930-935℃, resulting in a rough hot-rolled plate with a thickness of 25.9mm.

[0124] S4, Finish Rolling + Water Quenching: The rough hot-rolled plate of S3 is subjected to two-pass finish rolling. Before finish rolling, the iron oxide scale is removed. The initial rolling temperature is 915℃, and a total of 2 passes are performed. The deformation of each pass is 20-24%. The final rolling temperature is 850-855℃, and the thickness of the hot-rolled plate is 12.7mm. After hot rolling, it is quenched in water at 27℃ to room temperature. The cooling rate is controlled at 8℃ / min to obtain the final hot-rolled plate.

[0125] S5. Short-time solution treatment: The final hot-rolled plate of S4 is subjected to short-time solution treatment at a temperature of 915℃ for a treatment time of 29min; a low-cost, low-temperature, high-toughness, high-manganese steel plate for liquid hydrogen storage tanks with a thickness of 12.7mm is obtained.

[0126] The results show that: Figure 6The microstructure of high-manganese steel after solution treatment is shown in the figure. Statistical observation reveals that the microstructure of the steel after solution treatment consists of a single-phase austenitic structure with an average austenitic grain size of 16.2 μm. The optimal properties achievable are: a yield strength of 659 MPa, a tensile strength of 1177 MPa, an elongation after fracture of 93.5%, and a strength-ductility product of 110 GPa at -196℃; and a Charpy impact toughness of 241 J at -196℃ (based on a 10 mm thickness). At -269℃, the yield strength is 969 MPa, the tensile strength is 1423 MPa, the elongation after fracture is 65.2%, and the strength-ductility product is 93 GPa; and a Charpy impact toughness of 233 J at -269℃ (based on a 10 mm thickness).

[0127] Example 6

[0128] This embodiment discloses a low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks. The chemical composition of the low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks, by mass percentage, is: C 0.40%, Mn 28.91%, Al 2.73%, P≤0.01%, S≤0.001%, 1.5×Mn+4×Al 54.285%, with the remainder being Fe and unavoidable impurities.

[0129] A method for preparing low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks, comprising the following preparation steps:

[0130] S1. Smelting: The elemental composition and mass percentage of each alloy element of the ultra-low temperature high-toughness high-manganese steel used for low-cost liquid hydrogen storage tanks are configured and weighed. The smelting temperature is 1635℃ and the casting temperature is 1580℃. The high-manganese steel billet is bullet-shaped with dimensions of 117×110×130mm, including the riser length in the length direction.

[0131] S2, High-Temperature Homogenization + Hot Forging: The high-manganese steel billet of S1 is heated to undergo high-temperature homogenization treatment. The heating rate is 12℃ / min, the temperature is 1195℃, and the holding time is 12h. The billet is then laid out after the heating furnace reaches the desired temperature. After that, it is hot forged. Before hot forging, the riser of the high-manganese steel billet needs to be removed. The forging temperature is 970-1030℃, and the forging ratio is 1.1:1, to obtain a low-cost, low-temperature, high-toughness high-manganese steel forging for liquid hydrogen storage tanks with dimensions of 110×100×120mm.

[0132] S3, High-temperature solution treatment + multi-pass rough rolling: The low-cost liquid hydrogen storage tank forgings of S2 are first subjected to high-temperature solution treatment at 1055℃ for 2.5 hours. The sample is then laid out after the furnace reaches the set temperature. After removing the iron oxide scale from the furnace, multi-pass rough rolling is performed. The iron oxide scale is removed before rough rolling. The initial rolling temperature is 1045℃, and a total of 5 rolling passes are performed. The deformation amount of each pass is 26-29%, and the final rolling temperature is 930-935℃, resulting in a rough hot-rolled plate with a thickness of 26.3mm.

[0133] S4, Finish Rolling + Water Quenching: The rough hot-rolled plate of S3 is subjected to two-pass finish rolling. Before finish rolling, the iron oxide scale is removed. The initial rolling temperature is 915℃, and a total of 2 passes are performed. The deformation of each pass is 20-21%. The final rolling temperature is 865-8670℃, and the thickness of the hot-rolled plate is 11.8mm. After hot rolling, it is quenched in water at 24℃ to room temperature. The cooling rate is controlled at 9℃ / min to obtain the final hot-rolled plate.

[0134] S5. Short-time solution treatment: The final hot-rolled plate of S4 is subjected to short-time solution treatment at a temperature of 905℃ for 23 minutes to obtain a low-cost, low-temperature, high-toughness, high-manganese steel plate for liquid hydrogen storage tanks with a thickness of 11.8mm.

[0135] The results show that: Figure 7 The microstructure of high-manganese steel after solution treatment is shown in the figure. Statistical observation reveals that the microstructure of the steel after solution treatment consists of a single-phase austenitic structure with an average austenitic grain size of 16.4 μm. The optimal properties achievable are: a yield strength of 658 MPa, a tensile strength of 1187 MPa, an elongation after fracture of 93.3%, and a strength-ductility product of 111 GPa at -196℃; and a Charpy impact toughness of 239 J at -196℃ (based on a 10 mm thickness). At -269℃, the yield strength is 973 MPa, the tensile strength is 1415 MPa, the elongation after fracture is 64.6%, and the strength-ductility product is 91 GPa; and a Charpy impact toughness of 237 J at -269℃ (based on a 10 mm thickness).

[0136] Comparative Example 1

[0137] A high-manganese steel that balances ultra-low temperature mechanical properties and surface quality is characterized by the following chemical composition and mass percentage: C 0.35-0.55%, Si 0.11-0.22%, Mn 22.5-25.5%, P≤0.020%, S≤0.005%, Cr 3.0-4.0%, V 0.03-0.10%, Ti 0.03-0.10%, Al 0.01-0.10%, Ca 0.0003-0.0050%, with the balance being Fe and other unavoidable impurities.

[0138] The preparation method includes the following steps in sequence: smelting, continuous casting, annealing and grinding, heating, hot rolling and online solution treatment.

[0139] In the examples, the optimal low-temperature impact energy of a 10mm thick sample is 149J at -196℃ and 89J at -269℃.

[0140] The above-mentioned solution proposes a low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks and its preparation method. It can solve the problems of high alloy complexity in the composition design of existing high-manganese steel for low temperature applications, which leads to high cost and low efficiency; as well as the fact that low temperature research is mostly focused on -196℃ and has not reached -269℃, the strength, plasticity and impact toughness obtained cannot be improved synergistically, and the preparation process is complex, difficult to operate, and unsuitable for large-scale industrial production.

[0141] This invention calculates the stacking fault energy of high-manganese steel with different compositions using molecular dynamics simulations, and utilizes composition design to control the stacking fault energy of high-manganese steel at -269℃ to 18-25 mJ / m 2 This, in turn, affects the deformation mechanism of high manganese steel, making it dominated by a strong TWIP effect during deformation, thereby achieving a synergistic improvement in the strength, plasticity, and toughness of high manganese steel at extremely low temperatures.

[0142] This invention does not add common high-manganese steel alloying composites such as Ni, Cr, Mo, Nb, and Ti. Instead, it uses only four elements—Fe, Mn, Al, and C—and employs stacking fault energy simulation calculations to rationally design the component ratios. By utilizing the TWIP effect of austenitic alloy deformation, it obtains high-manganese steel with excellent ductility and toughness at extremely low temperatures. The simplified high-manganese steel alloy composition reduces the smelting cost and simplifies the process. Furthermore, given the current practice of mostly adding alloying elements to improve performance, this invention offers a new approach to improving the performance of high-manganese steel.

[0143] The low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks described in this invention has the following properties: at -196℃, yield strength ≥ 653 MPa, tensile strength ≥ 1171 MPa, elongation after fracture ≥ 93.1%, and strength-ductility product ≥ 109 GPa; based on a 10 mm thickness, Charpy impact toughness ≥ 239 J at -196℃; at -269℃, yield strength ≥ 967 MPa, tensile strength ≥ 1410 MPa, elongation after fracture ≥ 64.5%, and strength-ductility product ≥ 91 GPa; based on a 10 mm thickness, Charpy impact toughness ≥ 233 J at -269℃. This meets the material requirements for liquid hydrogen containers.

[0144] In summary, compared with traditional low-temperature steel preparation methods, the method of this invention controls the stacking fault energy by designing the alloy composition content, and ensures a single, uniform austenitic structure through processes such as high-temperature homogenization, hot rolling, and solution treatment. The two work together to ensure a synergistic improvement in the material's strength, plasticity, and impact toughness at an extremely low temperature of -269℃. This method is simple to operate, environmentally friendly, low in cost, and highly efficient, making it suitable for large-scale industrial production and application.

[0145] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0146] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0147] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0148] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A low-cost, ultra-low temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks, characterized in that... The chemical composition of the ultra-low temperature high-toughness high-manganese steel used in the low-cost liquid hydrogen storage tank, by mass percentage, is: C 0.37-0.47%, Mn 26-30%, Al 2.7-3.3%, P≤0.01%, S≤0.001%. The mass percentage of Mn and Al satisfies the relationship: 1.5×Mn+4×Al is between 54-55%, with the remainder being Fe and unavoidable impurities. The microstructure of the ultra-low temperature high-toughness high-manganese steel used in the low-cost liquid hydrogen storage tank consists of a single-phase austenitic structure with an average austenitic grain size of 14-18 μm. The stacking fault energy of the ultra-low temperature high-toughness high-manganese steel used in the low-cost liquid hydrogen storage tank is controlled at 18-25 mJ / m at -269℃. 2 .

2. The low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks according to claim 1, characterized in that, The low-cost liquid hydrogen storage tank uses ultra-low temperature high-toughness high-manganese steel with a yield strength ≥653MPa, tensile strength ≥1171MPa, elongation after fracture ≥93.1%, and strength-ductility product ≥109GPa at -196℃; based on a thickness of 10mm, the Charpy impact toughness at -196℃ is ≥239J.

3. The low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks according to claim 1, characterized in that, The low-cost liquid hydrogen storage tank uses ultra-low temperature high-toughness high-manganese steel with a yield strength ≥967MPa, tensile strength ≥1410MPa, elongation after fracture ≥64.5%, and strength-ductility product ≥91GPa at -269℃; based on a thickness of 10mm, the Charpy impact toughness at -269℃ is ≥233J.

4. A method for preparing low-cost, high-toughness, high-manganese steel for liquid hydrogen storage tanks according to claim 1, characterized in that, The preparation method of the low-cost liquid hydrogen storage tank using ultra-low temperature high-toughness high-manganese steel includes the following preparation steps: S1. Smelting: The elemental composition and mass percentage of each alloying element of the ultra-low temperature high-toughness high-manganese steel used in low-cost liquid hydrogen storage tanks are configured and weighed. After smelting, the high-manganese steel billet is cast. S2, High-temperature homogenization + hot forging: The high-manganese steel billet of S1 is heated to undergo high-temperature homogenization treatment, and then hot forging is performed to obtain low-cost liquid hydrogen storage tank ultra-low temperature high-toughness high-manganese steel forging. S3, High-temperature solution treatment + multi-pass rough rolling: The low-cost liquid hydrogen storage tank forging of S2 is first subjected to high-temperature solution treatment, and after removing the iron oxide scale, it is subjected to multi-pass rough rolling to obtain the rough hot-rolled plate. S4, Finish rolling + water quenching: The rough hot-rolled plate of S3 is subjected to two passes of finish rolling, followed by water quenching to room temperature to obtain the final hot-rolled plate; S5. Short-time solution treatment: The final hot-rolled plate of S4 is subjected to short-time solution treatment to obtain low-cost, low-temperature, high-toughness, high-manganese steel plate for liquid hydrogen storage tanks.

5. The method for preparing low-cost, low-temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks according to claim 4, characterized in that, The smelting temperature of S1 is 1600-1650℃, the casting temperature is 1550-1600℃, and the high manganese steel billet is bullet-shaped with dimensions of 110×110×130mm-120×110×130mm, including the riser length in the length direction.

6. The method for preparing low-cost, low-temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks according to claim 4, characterized in that, The heating rate for high-temperature homogenization treatment in S2 is 10-20℃ / min, the temperature is 1150-1250℃, the holding time is 10-15h, and the sample is placed after the heating furnace reaches the desired temperature.

7. The method for preparing low-cost, low-temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks according to claim 4, characterized in that, Before hot forging in S2, the riser of the high manganese steel billet needs to be removed. The forging temperature is 950-1100℃, the forging ratio is 1.1:1-1.2:1, and the high manganese steel forging material with a size of 100×100×120mm-110×100×120mm is forged.

8. The method for preparing low-cost, low-temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks according to claim 4, characterized in that, The S3 medium-high temperature solution treatment temperature is 1050-1150℃, the holding time is 2-4h, and the sample is laid out when the heating furnace reaches the temperature; the iron oxide scale is removed before rough rolling, the initial rolling temperature is 1000-1050℃, a total of 5 rolling passes are carried out, the deformation amount of each rolling pass is 25-30%, the final rolling temperature is 930-950℃, and the thickness of the rough hot-rolled plate is 25-27mm.

9. The method for preparing low-cost, low-temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks according to claim 4, characterized in that, Before finishing rolling in S4, the iron oxide scale is removed. The initial rolling temperature is 900-920℃, and the rolling is carried out in two passes. The deformation amount of each pass is 20-25%. The final rolling temperature is 850-870℃, and the thickness of the hot-rolled plate is 11-13mm. After hot rolling, the plate is quenched in water at 25-30℃ to room temperature, and the cooling rate is controlled at 7-10℃ / min.

10. The method for preparing low-cost, low-temperature, high-toughness, high-manganese steel for liquid hydrogen storage tanks according to claim 4, characterized in that, The temperature for short-term solution treatment in S5 is 880-920℃, and the solution treatment time is 20-30min; the thickness of the ultra-low temperature high-toughness high-manganese steel plate for low-cost liquid hydrogen storage tanks is 10-15mm, and the microstructure is composed of austenitic single-phase structure with an average austenitic grain size of 14-18μm.

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