A hydrogen storage pressure vessel steel plate treated with ti-ca and a method of manufacturing the same

Abstract

The application provides a Ti-Ca treated hydrogen storage pressure vessel steel plate and a manufacturing method thereof. The steel plate comprises the following components in percentage by weight: C: 0.09% to 0.12%, Si: 0.25% to 0.40%, Mn: 1.10% to 1.30%, P: ≤0.015%, S: ≤0.005%, Cr: 0.30% to 0.40%, Ni: 0.20% to 0.30%, Mo: 0.15% to 0.25%, V: 0.09% to 0.15%, Nb: 0.01% to 0.02%, Ti: 0.01% to 0.02%, Al: 0.003% to 0.005%, Ca: 0.006% to 0.008%, V / C≥1, Ti / Ca: 1 to 3, and the balance of Fe and inevitable impurities. The production method of the steel plate comprises smelting, continuous casting, heating, rolling, cooling and heat treatment. The microstructure of the steel plate is tempered sorbite + acicular ferrite, and the volume percentage of the tempered sorbite structure is 92% to 96%. The yield strength ReL of the steel plate is greater than or equal to 650 MPa, the tensile strength Rm is 800 to 920 MPa, the elongation A is greater than or equal to 21%, the low-temperature impact toughness KV2 at-50 DEG C is greater than or equal to 100 J, the tensile yield strength ReL at-50 DEG C is greater than or equal to 660 MPa, the tensile strength Rm is 820 to 930 MPa, and the elongation is greater than or equal to 21%. The steel plate is welded by using large linear energy of 100 to 140 kJ / cm, the yield strength R eL of the heat-affected zone (HAZ) is greater than or equal to 690 MPa, the tensile strength R m is 830 to 950 MPa, the elongation is greater than or equal to 17%, and the impact toughness KV2 of the heat-affected zone (HAZ) at-50 DEG C is greater than or equal to 70 J.

Description

Technical Field

[0001] This invention relates to the field of pressure vessel steel plate preparation for hydrogen storage, specifically to a pressure vessel steel plate for hydrogen storage treated with Ti-Ca and its manufacturing method, which is particularly suitable for gaseous hydrogen storage tanks. Background Technology

[0002] Oxide metallurgy refers to the process where certain types and sizes of non-metallic inclusions in steel promote the nucleation and induced nucleation of intragranular ferrite in the coarse-grained zone of the heat-affected zone during welding. Ferrite nucleates and grows on the non-metallic inclusions within the overheated austenite grains, forming radially shaped intragranular acicular ferrite laths that divide the austenite grains into multiple smaller segments. These acicular ferrite laths are interlocked, and the laths are mostly located at large-angle grain boundaries. This requires more energy to propagate cracks, effectively improving the toughness of the steel. Steel plates are typically manufactured using high-efficiency, high-heat-input welding methods, with welding heat inputs exceeding 100 kJ / cm, enabling one-pass welding of hydrogen storage pressure vessel steel plates. This significantly reduces manufacturing costs and improves production efficiency. Therefore, researching hydrogen storage pressure vessel steel plates with excellent weldability and resistance to hydrogen-induced cracking has become an urgent task for the steel industry.

[0003] Hydrogen energy boasts advantages such as wide availability, convenient storage and transportation, high utilization efficiency, and clean and environmentally friendly characteristics, making it a crucial means to support the clean transformation of fossil fuels and the large-scale development of renewable energy. However, the compatibility of steel plates with high-pressure hydrogen is a key consideration for pressure vessel steel plates used in hydrogen storage. At room temperature or low temperatures, hydrogen is generally considered to be stored in commonly used carbon steel without the risk of bubbling or cracking. However, the diffusion of hydrogen within metals under high pressure can still lead to a reduction in the mechanical properties of steel, particularly its plasticity and toughness. Therefore, there is an urgent need to develop a high-performance pressure vessel steel plate for hydrogen storage to meet the needs of the steel industry. For example, in CN115896616A, "An Easily Weldable Normalized Pressure Vessel Steel Plate and Its Manufacturing Method", the chemical composition is: C: 0.16-0.19%, Si: 0.15-0.40%, Mn: 1.45-1.65%, P: ≤0.010%, S: 0.003-0.010%, Ni: 0.40-0.80%, and other elements. The design of the pressure vessel steel plate has a relatively complex composition and a high carbon equivalent setting range, making the steel plate prone to welding hot cracks, which affects the processing and manufacturing of the steel plate. In CN112813353A, "An Ultra-High Temperature SPWHT High Toughness Normalized Steel for Vessels and Its Manufacturing Method", the normalizing process and simulated post-weld heat treatment process are optimized by adopting a reasonable proportion and rolling process, but the low temperature impact toughness cannot be guaranteed, and the strength of the steel plate is low after normalizing heat treatment and simulated post-weld heat treatment. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to provide a Ti-Ca treated steel plate for hydrogen storage containers and its manufacturing method. This involves a combination of compositional design, a two-stage controlled rolling process, and a tempering heat treatment. The mechanical properties of the steel plate from this invention, as well as the mechanical properties obtained after simulated post-weld heat treatment, meet the following requirements: yield strength ReL ≥ 650 MPa, tensile strength Rm: 800~920 MPa, elongation A ≥ 21%, -50℃ low-temperature impact toughness KV2 ≥ 100 J, and -50℃ low-temperature tensile yield strength R... eL ≥660MPa, tensile strength R m 820~930MPa, elongation ≥21%; welded to steel plates using a high heat input of 100~140kJ / cm, yield strength R of the weld heat-affected zone (HAZ) eL ≥690MPa, tensile strength R m 830~950MPa, elongation ≥17%, impact toughness KV2≥70J in the heat-affected zone (HAZ) at -50℃. The (20-50)mm thick steel plate has excellent strength, low-temperature impact toughness, and uniform and fine microstructure, which can meet the manufacturing and application requirements of steel plates for pressure vessels.

[0005] The objective of this invention is achieved as follows:

[0006] A pressure vessel steel plate for hydrogen storage, treated with Ti-Ca, comprises the following components by weight percentage: C: 0.09%–0.12%, Si: 0.25%–0.40%, Mn: 1.10%–1.30%, P: ≤0.015%, S: ≤0.005%, Cr: 0.30%–0.40%, Ni: 0.20%–0.30%, Mo: 0.09%–0.18%, V: 0.09%–0.15%, Nb: 0.01%–0.02%, Ti: 0.01%–0.02%, Al: 0.003%–0.005%, Ca: 0.006%–0.008%, V / C ≥ 1, Ti / Ca: 1–3. The balance is Fe and unavoidable impurities.

[0007] Furthermore, V / C ≥ 1.

[0008] Furthermore, Ti / Ca: 1~3.

[0009] Furthermore, the steel plate has a yield strength ≥650MPa, tensile strength 800~950MPa, A ≥21%, and low-temperature impact toughness ≥100J at -50℃.

[0010] Furthermore, the microstructure of the steel microplate is tempered sorbite + acicular ferrite, with the tempered sorbite microstructure having a volume percentage of 92-96%; the microstructure has a grain size of 8-10, and the average size of the composite inclusions is 2-4 μm.

[0011] Furthermore, the thickness of the steel plate is 20–50 mm.

[0012] To achieve the above objectives, this invention designs a hydrogen storage container steel plate treated with Ti-Ca, and the chemical composition (by mass%) of the steel used is as follows:

[0013] C: 0.09%–0.12%, Si: 0.25%–0.40%, Mn: 1.10%–1.30%, P: ≤0.015%, S: ≤0.005%, Cr: 0.30%–0.40%, Ni: 0.20%–0.30%, Mo: 0.09%–0.18%, V: 0.10%–0.30%, Nb: 0.01%–0.02%, Ti: 0.01%–0.02%, Al: 0.003%–0.005%, Ca: 0.006%–0.008%, V / C ≥ 1, Ti / Ca: 1–3, balance Fe and unavoidable impurities.

[0014] The rationale for the design of the components in this invention is as follows:

[0015] This invention, based on the strengthening elements C, Si, and Mn, reduces the Mn content in steel to ensure sufficient strength while lowering costs. To maintain high strength, the addition of V enhances the grain size, increasing the number of large-angle grain boundaries and inhibiting crack propagation, thus reducing weld crack sensitivity. Adjusting the V / C ratio increases carbide formation, improving hydrogen storage capacity and resistance to hydrogen corrosion under low-temperature, high-pressure conditions. Increasing Cr content reduces carbide dissolution rates, improving toughness and hardenability, and also reduces localized decarburization caused by H atom penetration and diffusion in the metal lattice. The Cr-containing carbides generated after heat treatment dissolve in the matrix and refine grains, improving hydrogen resistance. Adding Ti, followed by Ti-Ca treatment, increases the number of composite inclusions, refines austenite grains, and promotes acicular ferrite formation, enhancing strength and toughness. Furthermore, Ti-Ca treatment improves the mechanical properties of the weld heat-affected zone (HAZ).

[0016] C: 0.09%~0.12%

[0017] In steel, carbon (C) forms various carbides with alloying elements, which strengthen the steel and directly improve its strength. However, excessively high C content can lead to poor toughness, plasticity, and weldability. To ensure that the steel plate has a good balance of low-temperature impact toughness, strength, and weldability during use, the C content is limited to 0.09% to 0.12%.

[0018] Si: 0.25%~0.40%

[0019] Si is an element that increases the activity of carbon in steel. In the high concentration region of silicon, it can reduce the diffusion flux of carbon to carbides, inhibit the coarsening of carbides, and a certain amount of Si can improve the strength of steel plates, improve the hardenability of steel, and reduce the ductile-brittle transition temperature and improve the plasticity of steel within a certain range. Therefore, the Si content is limited to 0.25% to 0.40%.

[0020] Mn: 1.10%~1.30%

[0021] Mn plays a role in solid solution strengthening in steel. It can dissolve in large quantities in the Fe matrix, increasing the strength and hardness of the steel plate, improving hot working properties, preventing hot cracking, and improving the distribution morphology of sulfides. Furthermore, a content in the range of 0.6%–1.6% can improve the toughness of weld metal and the solubility of Nb and V in steel. However, excessively high Mn content can easily lead to segregation in the steel plate, which is detrimental to plasticity and toughness. Therefore, Mn content is limited to 1.10%–1.30%.

[0022] P: ≤0.015%

[0023] Phosphorus (P) is a harmful element in steel, significantly impacting low-temperature impact toughness and being highly prone to segregation. Therefore, its content should be kept low during steelmaking. This invention controls P within a range that does not affect performance; thus, the P content is controlled below 0.015%.

[0024] S: ≤0.005%

[0025] S is also a harmful element in steel. It easily forms MnS in steel, generating defects and becoming the source of cracks in subsequent processing. It also has a great impact on the toughness of steel. However, considering the operability and cost of steelmaking, S is controlled below 0.005%.

[0026] Cr: 0.30%~0.40%

[0027] Cr, as the main element in this patent, is an element that stabilizes carbides. Adding chromium reduces the dissolution rate of carbides, improves the toughness and hardenability of steel, and reduces local decarburization caused by the penetration and diffusion of H atoms in the metal lattice. During the quenching and tempering process, the generated Cr23C6 type carbide dissolves in the matrix and plays a role in refining the grains. Therefore, the Cr content is controlled between 0.30% and 0.40%.

[0028] Ni: 0.20%~0.30%

[0029] Ni is a major element for stabilizing austenite in steel. Ni can exist in austenite and ferrite in a solid solution with Fe, thus improving the strength of steel, refining the grain size, and improving the low-temperature impact toughness of steel. However, due to the high cost of nickel and the difficulty in removing iron oxide scale from steel plates, which increases costs, the Ni content is limited to between 0.20% and 0.30%.

[0030] Mo: 0.09%~0.18%

[0031] Mo in steel can shrink the austenite transformation zone, promote ferrite transformation, and dissolve in ferrite, austenite, and carbides, thereby increasing the strength of the steel plate. After quenching and tempering, it can improve the steel plate's resistance to temper brittleness, reduce internal residual stress, and improve the steel plate's plasticity. Therefore, the Mo content is controlled between 0.09% and 0.18%.

[0032] V: 0.09%~0.15%

[0033] At high temperatures, vanadium (V) can dissolve into austenite, increasing the hardenability of steel. Microalloying promotes the formation of more VC, VN, and V(C,N) complexes in steel. These carbides stabilize and pin at grain boundaries, inhibiting grain boundary movement and grain growth. Through precipitation strengthening, sedimentation strengthening, and grain refinement, the hardness of the steel plate is ensured, while its strength and plasticity are improved, as well as its toughness and tempering stability. Adjusting the V to C ratio increases the formation of vanadium and carbon carbides in the steel, enhancing its hydrogen storage capacity and resistance to hydrogen corrosion under low-temperature, high-pressure service environments. Therefore, V is limited to 0.10%–0.30%.

[0034] Nb: 0.01%~0.02%

[0035] In steel, Nb can inhibit austenite recrystallization during rolling, promote grain refinement, improve strength and toughness, reduce overheating sensitivity and temper brittleness, improve weldability, and also produce solid solution strengthening. Nb(C,N) precipitates in large quantities at grain boundaries and dislocations. Therefore, Nb is limited to 0.01% to 0.02%.

[0036] Ti: 0.01%~0.02%

[0037] Ti, as the main element in this patent, can form a large number of dispersed fine TiN or TiO particles. After Ti treatment during steelmaking, fine inclusion particles TiO can be obtained, which can promote the formation of acicular ferrite within the grains during solidification, thereby refining the grains. Ti (C, N) that precipitates first at high temperatures can promote the precipitation of Nb and V. However, when w(Ti) ≥ 0.09%, it will reduce the content of acicular ferrite and deteriorate the low-temperature toughness of the steel plate. Therefore, the Ti content is limited to 0.01% to 0.02%.

[0038] Al: 0.003%~0.005%

[0039] Al acts as a primary deoxidizer in steel, fixing nitrogen, refining grains, and improving steel toughness. Adding Al before Ca treatment ensures adequate Ca yield in the steel. Therefore, the Al content is limited to 0.003%–0.005%.

[0040] Ca: 0.006%~0.008%

[0041] In steel, calcium (Ca) acts as a deoxidizer and desulfurizer, and can alter the morphology and distribution of non-metallic inclusions. Increasing the number of inclusions can refine the austenite grain size; after heat treatment, the inclusions become spheroidized and smaller, providing nucleation sites for acicular ferrite. It can also effectively refine and control the microstructure of the weld heat-affected zone (HAZ) to improve its toughness. Therefore, the Ca content is limited to 0.006%–0.008%. Appropriate amounts of Ca combined with trace amounts of Ti can increase the number of inclusions to refine the austenite grains; therefore, the Ti / Ca ratio is limited to 1–3.

[0042] The second technical solution of the present invention is to provide a method for manufacturing a pressure vessel steel plate for hydrogen storage using Ti-Ca treatment, including smelting, continuous casting, heating, rolling, cooling, and heat treatment;

[0043] This invention provides a method for preparing pressure vessel steel plates for hydrogen storage using Ti-Ca treatment. The method involves batching materials according to the chemical composition range designed according to this invention, employing Ti-Ca elemental treatment during oxygen converter smelting to fully utilize the effects of oxide metallurgy, followed by vacuum treatment, and then continuous casting with full-process protective pouring. During solidification, fine composite inclusions are generated, refining the grain size of the cast billet. The finished steel plate has a thickness of 20–50 mm. The rolling process employs two-stage controlled rolling and cooling to refine the microstructure and control the size and distribution of inclusions. These inclusions can inhibit the growth of austenite grains in the weld heat-affected zone (HAZ) during subsequent welding, improving the low-temperature toughness of the HAZ. After tempering heat treatment, the inclusions become spheroidized, providing nucleation sites for acicular ferrite, further homogenizing the microstructure and giving the steel plate low weld crack sensitivity. Finally, the mechanical properties and hydrogen resistance of the steel plate are tested to obtain the pressure vessel steel plate for hydrogen storage.

[0044] The specific production process steps are as follows:

[0045] smelting

[0046] Molten steel is first pretreated in an argon station. After pretreatment, it undergoes Ti deoxidation, followed by deep dephosphorization and desulfurization to reduce the P content to below 0.015% and the S content to below 0.005%. Al addition is then strictly controlled, and after Al deoxidation, Ca treatment is performed 10-20 minutes later to deform non-metallic inclusions. An LF furnace is used for refining and composition adjustment, ensuring an argon soft blowing time of ≥12 minutes and a refining time of 30-60 minutes. RH vacuum treatment is then employed for further refining and composition adjustment, maintaining the steel temperature at 1600-1630℃ and a vacuum treatment time of 40-80 minutes. This allows harmful inclusions in the molten steel to fully float to the surface, ensuring the purity of the steel and sufficient time for microalloying. By deforming non-metallic inclusions in the molten steel, the role of oxide metallurgy is utilized to improve the quality of the continuously cast billet, obtaining beneficial composite inclusion particles that provide heterogeneous nucleation sites for subsequent microstructure formation.

[0047] casting

[0048] The billet is poured under argon protection throughout the casting process, employing a light reduction technique with a reduction of 2-5 mm. The casting speed is controlled at 1.0-1.4 m / min to eliminate internal defects, improve surface quality, and allow beneficial composite inclusions to provide nucleation sites for grain refinement. Secondary cooling water is maintained at 5000-6000 L / min, and the casting superheat is 15-30℃ to reduce center segregation and porosity, improving internal quality. The billet straightening temperature is controlled at 950±30℃ to ensure quality and reduce crack formation, resulting in continuously cast billets with a thickness of 250-360 mm. Finally, slab cleaning, slow cooling, and continuous casting billet quality inspection are performed.

[0049] heating

[0050] The heating of continuously cast billets is divided into a preheating section, a heating section, and a soaking section: the preheating section is controlled at 780±30℃, the heating section is controlled at 1250~1280℃, and the soaking section is controlled at 1200-1240℃, with a total furnace time of 210-240min. By heating the billet in three stages, the core temperature of the billet reaches 1180~1220℃, ensuring that the billet microstructure is fully austenitic. However, when the heating temperature is higher than 1280℃, it is easy to cause excessive grain growth inside the billet, which affects the distribution of beneficial inclusions inside the microstructure.

[0051] Rolling

[0052] After the billet exits the furnace, a two-stage controlled rolling and cooling technology is employed. First, rough rolling is performed, with the initial rolling temperature controlled at 1130–1180℃ and the rolling speed controlled at 1.3–1.8 m / s. The single-pass reduction rate in rough rolling is controlled at 12%–18%, ensuring a total reduction rate of ≥60% to fully refine the austenite grains. For finish rolling, the initial rolling temperature is 900±50℃, the rolling speed is controlled at 2.0–2.5 m / s, and the final pass rolling temperature is controlled at 820–840℃. The single-pass reduction rate in finish rolling is ≥10%, ensuring a total reduction rate of ≥55%. This further flattens and elongates the grains, and the increased grain boundary area provides more nucleation sites for subsequent phase transformation. By controlling the total reduction rate of roughing and finishing rolling, sufficient grain refinement of the steel plate is ensured, eliminating internal defects. After rolling, controlled cooling is performed, with an initial cooling temperature of 740-800℃, a reddening temperature of 560-630℃, and a cooling rate of 10-21℃ / s. This ensures fine grains, promotes the formation of fine precipitates, and improves the mechanical properties of the steel plate. The steel plates are then stacked for slow cooling at 450-550℃, with 11-15 sheets stacked for 16-24 hours to allow sufficient time for the removal of H and O from the steel. The resulting steel plate has a thickness of 20-50mm.

[0053] Heat treatment

[0054] The steel plates are stacked and slowly cooled before undergoing quenching and tempering heat treatment. To ensure the performance indicators of the steel plates, a quenching and tempering heat treatment process is performed. The quenching temperature is 930±10℃, the quenching heating rate is 1.5±0.3min / mm, the tempering temperature is 610±10℃, and the tempering heating rate is 1.2±0.2min / mm. After heat treatment, air cooling is performed. Through quenching and tempering heat treatment, beneficial composite inclusion particles are spheroidized and made fine, and the distribution of fine precipitates in the microstructure is uniform. This ensures that the steel plate has high strength, good low-temperature performance, and a uniform microstructure, consisting of tempered sorbite + acicular ferrite, with tempered sorbite (92-96% by volume) + acicular ferrite (4-8% by volume), a grain size of 8-10, and an average composite inclusion size of 2-4μm.

[0055] The beneficial effects of this invention are as follows:

[0056] This invention aims to develop high-performance pressure vessel steel plates for hydrogen storage. It designs an efficient and economical alloy composition process that balances cost and performance. During smelting, Ti-Ca treatment is employed using oxide metallurgy to obtain fine composite inclusions, refining the grain size of the cast billet and improving the quality of the continuously cast billet. A two-stage controlled rolling and cooling process is used to refine the microstructure and control the size and distribution of inclusions. These inclusions inhibit the growth of austenite grains in the weld heat-affected zone (HAZ) during subsequent welding, improving the mechanical properties of the HAZ. After tempering heat treatment, the inclusions become spheroidized, providing nucleation sites for acicular ferrite, further homogenizing the microstructure and giving the steel plate low weld crack sensitivity. Finally, the mechanical properties and hydrogen resistance of the steel plate are tested, resulting in a pressure vessel steel plate suitable for hydrogen storage.

[0057] 1. The steel plate of the present invention has a uniform and fine microstructure. The final microstructure is tempered sorbite + acicular ferrite, with tempered sorbite (92-96% by volume) + acicular ferrite (4-8% by volume). The grain size is 8-10, and the average size of the composite inclusions is 2-4μm, which makes the steel plate have excellent comprehensive mechanical properties.

[0058] 2. The steel plate of this invention has a thickness of 20-50mm. After tempering heat treatment, the steel plate for containers exhibits high strength, good low-temperature performance, and good resistance to hydrogen-induced cracking. Its mechanical properties are: yield strength ReL≥650MPa, tensile strength Rm:800-920MPa, elongation A≥21%, -50℃ low-temperature impact toughness KV2≥100J, and -50℃ low-temperature tensile yield strength R... eL ≥660MPa, tensile strength R m 820~930MPa, elongation ≥21%.

[0059] 3. This invention uses a high heat input of 100-140 kJ / cm to weld steel plates, and the yield strength R of the weld heat-affected zone (HAZ) is [not specified]. eL ≥690MPa, tensile strength R m 830~950MPa, elongation ≥17%, impact toughness KV2 ≥70J in the heat-affected zone (HAZ) of welding at -50℃.

[0060] 4. The hydrogen-induced cracking (HIC) resistance of the steel plates was determined according to GB / T 8650-2015 "Evaluation Method for Resistance to Hydrogen-Induced Cracking of Pipeline Steel and Pressure Vessel Steel". The results show that the designed steel grade has good HIC resistance. Hydrogen-induced cracking resistance: Crack length percentage (CLR) ≤ 5%, Crack thickness percentage (CTR) ≤ 5%, Crack sensitivity percentage (CSR) ≤ 3%.

[0061] 5. This invention uses a simulated post-weld heat treatment process to test the mechanical properties of steel plates. The simulated post-weld heat treatment temperature is 600-640℃, and the holding time is 120-360 min. The mechanical properties are: yield strength ReL≥650MPa, tensile strength Rm: 800~920MPa, elongation A≥21%, and low-temperature impact toughness KV2≥100J at -50℃. Detailed Implementation

[0062] The present invention will be further illustrated below through examples.

[0063] According to the component ratio of the technical solution, the embodiments of the present invention perform smelting, continuous casting, heating, rolling, cooling, and heat treatment, characterized in that:

[0064] smelting

[0065] First, Ti treatment is performed for deoxidation, followed by Ca treatment to deform non-metallic inclusions in the molten steel. The composition is then adjusted using an LF furnace for dephosphorization and desulfurization, ensuring an argon soft blowing time of ≥12 min and a refining time of 30–60 min. Finally, RH vacuum treatment is used for refining and adjusting the composition, ensuring the molten steel temperature is between 1600 and 1630℃ and the vacuum treatment time is between 40 and 80 min.

[0066] heating

[0067] The preheating section is controlled at 780±30℃, the heating section is controlled at 1250~1280℃, the soaking section is controlled at 1200-1240℃, and the total time the slab is in the furnace is 210-240min.

[0068] Rolling

[0069] The initial rolling temperature is controlled at 1130–1180℃, the rolling speed at 1.3–1.8 m / s, and the single-pass reduction rate in roughing is controlled at 12%–18%, ensuring a total roughing reduction rate ≥60% to fully refine the austenite grains. The initial rolling temperature in finishing is 900±50℃, the rolling speed at 2.0–2.5 m / s, the final rolling pass temperature is controlled at 820–840℃, the roll speed at 0.5–0.7 m / s, and the single-pass reduction rate in finishing is ≥10%, ensuring a total finishing reduction rate ≥55%.

[0070] cool down

[0071] After rolling, the steel plates are cooled in a controlled manner. The initial cooling temperature is 740-800℃, the reddening temperature is 560-630℃, and the cooling rate is 10-21℃ / s. Then, the steel plates are stacked and cooled slowly at a temperature of 450-550℃. The number of stacked plates is 11-15, and the stacking time is guaranteed to be 16-24 hours.

[0072] Heat treatment

[0073] The steel plate is first subjected to a quenching and tempering heat treatment process. The quenching temperature is 930±10℃ and the quenching heating rate is 1.5±0.3min / mm. The tempering temperature is 610±10℃ and the tempering heating rate is 1.2±0.2min / mm. After the quenching and tempering heat treatment is completed, it is air-cooled.

[0074] Furthermore, in the continuous casting process, the billet is cast under argon protection throughout the pouring process, and a light reduction technique is used to cast the billet, with the reduction amount controlled at 2-5mm, the billet pulling speed controlled at 1.0-1.4m / min, the casting superheat at 15-30℃, and the billet straightening temperature controlled at 950±30℃.

[0075] The embodiments are detailed in the embodiments of the present invention. These embodiments are only general descriptions of the present invention and do not limit the scope of the present invention. Table 1 shows the chemical composition of the embodiments, Table 2 shows the smelting and casting methods of the embodiments, Table 3 shows the rolling process parameters of the embodiments, Table 4 shows the cooling and heat treatment process parameters of the embodiments, Table 5 shows the mechanical properties of the embodiments, Table 6 shows the mechanical properties of the weld heat-affected zone of the embodiments, Table 7 shows the mechanical properties of the steel after post-weld heat treatment of the embodiments, and Table 8 shows the microstructure, grain size and hydrogen-induced cracking resistance test results of the embodiments.

[0076] Table 1 Chemical composition (wt%) of the examples

[0077]

[0078] Table 2. Smelting and Casting Methods in Examples

[0079]

[0080] Table 3 Rolling process parameters of the embodiment

[0081]

[0082] Table 4 Cooling and heat treatment process parameters for the embodiments

[0083]

[0084] Table 5 Mechanical properties of the embodiments

[0085]

[0086] Table 6 Mechanical properties of the weld heat-affected zone in the examples

[0087]

[0088] Table 7 Mechanical properties of steel after post-weld heat treatment in the examples.

[0089]

[0090] Table 8. Microstructure, grain size, and hydrogen-induced cracking resistance test results of the examples.

[0091]

[0092] Samples were taken from heat-treated steel plates for performance testing. Tests were conducted according to GB / T 228.3-2019 "Metallic materials - Tensile testing - Part 1: Low-temperature testing" and GB / T 229-2020 "Metallic materials - Charpy impact test," demonstrating that the steel plate possesses high strength and toughness, good low-temperature performance, and is suitable for low-temperature service environments for hydrogen storage. Grain size was determined according to GB / T6394-2017 "Method for determination of average grain size of metals," and the grain size of the steel plate was all above grade 8.5, indicating low crack susceptibility. The HIC resistance of the steel plate was determined according to GB / T 8650-2015 "Evaluation method for resistance to hydrogen-induced cracking of pipeline steel and pressure vessel steel," and the results showed that the designed steel grade has good HIC resistance.

[0093] As can be seen from the above, the container steel plate of the present invention, with a thickness of 20-50mm, after tempering heat treatment, exhibits high strength, good low-temperature impact toughness at -50℃, and good resistance to hydrogen-induced cracking. Its mechanical properties are: yield strength ReL≥650MPa, tensile strength Rm:800-920MPa, elongation A≥21%, low-temperature impact toughness KV2≥100J at -50℃, and low-temperature tensile yield strength R... eL ≥660MPa, tensile strength R m820~930MPa, elongation ≥21%; welded to steel plates using a high heat input of 100~140kJ / cm, yield strength R of the weld heat-affected zone (HAZ) eL ≥690MPa, tensile strength R m 830~950MPa, elongation ≥17%, impact toughness KV2 ≥70J in the heat-affected zone (HAZ) of welding at -50℃.

[0094] To illustrate the present invention, the present invention has been appropriately and sufficiently described above through embodiments. The above embodiments are only for illustrating the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent substitutions, improvements, etc., should be included within the protection scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. A hydrogen storage pressure vessel steel sheet treated with Ti-Ca, characterized by, By weight percentage, the following components are included: C: 0.09%~0.12%, Si: 0.25%~0.40%, Mn: 1.10%~1.30%, P: ≤0.015%, S: ≤0.005%, Cr: 0.30%~0.40%, Ni: 0.20%~0.30%, Mo: 0.09%~0.18%, V: 0.1%~0.3%, Nb: 0.01%~0.02%, Ti: 0.01%~0.02%, Al: 0.003%~0.005%, Ca: 0.006%~0.008%, V / C≥1, Ti / Ca: 1.4~3, the balance being Fe and unavoidable impurities; yield strength ReL≥ 650 MPa, tensile strength Rm: 800~920 MPa, elongation A≥21%, low temperature impact toughness KV2≥100 J at -50℃, low temperature tensile yield strength R eL ≥ 660 MPa, tensile strength R m : 820~930 MPa, elongation≥21%.

2. The hydrogen storage pressure vessel steel plate treated with Ti-Ca according to claim 1, characterized by, The steel plate is welded by using large heat input of 100-140 kJ / cm, and the yield strength R eL ≥690 MPa, the tensile strength R m : 830-950 MPa, the elongation ≥17%, and the impact toughness KV2 of the welded heat affected zone at -50 ℃ is ≥70 J.

3. The hydrogen storage pressure vessel steel plate treated with Ti-Ca according to claim 1, characterized in that, The steel microstructure is tempered sorbite + acicular ferrite, the volume percentage of the tempered sorbite structure is 92-96%, the microstructure grain size is 8-10, and the average size of the composite inclusions is 2-4 microns.

4. The hydrogen storage pressure vessel steel plate treated with Ti-Ca according to claim 1, characterized by, The steel plate thickness is 20-50 mm.

5. A manufacturing method of a pressure vessel steel plate for hydrogen storage treated with Ti-Ca according to any one of claims 1-4, comprising smelting, continuous casting, heating, rolling, cooling, heat treatment, characterized in that, smelting The molten steel is first pretreated by an argon station, after the treatment, Ti treatment deoxidation is first performed, then deep dephosphorization and desulfurization treatment is performed to reduce the P content in the molten iron to below 0.015% and the S content to below 0.005%, then the addition of Al is strictly controlled, Ca treatment is performed 10-20 minutes after Al deoxidation to deform the non-metallic inclusions; LF furnace refining is adopted to adjust the composition, the argon soft blowing time is ensured to be greater than or equal to 12 minutes, and the refining time is 30-60 minutes; RH vacuum treatment is adopted to further refine and adjust the composition, and the molten steel temperature is ensured to be 1600-1630 DEG C, and the vacuum treatment time is 40-80 minutes; heating The preheating section is controlled at 780±30 DEG C, the heating section is controlled at 1250-1280 DEG C, the soaking section is controlled at 1200-1240 DEG C, and the total slab in-furnace time is 210-240 minutes; rolling The rough rolling temperature is controlled at 1130-1180 DEG C, the rolling speed is controlled at 1.3-1.8 m / s, the rough rolling single pass reduction rate is controlled at 12%-18%, the total rough rolling reduction rate is ensured to be greater than or equal to 60% to sufficiently refine the austenite grains; the finish rolling rough rolling temperature is 900±50 DEG C, the rolling speed is controlled at 2.0-2.5 m / s, the finish rolling single pass reduction rate is greater than or equal to 10%, and the total finish rolling pass reduction rate is ensured to be greater than or equal to 55%; cooling After rolling, the steel plate is controlled to cool, the open cooling temperature is 740-800 DEG C, the red temperature is 560-630 DEG C, the cooling speed is 10-21 DEG C / s, then the steel plate is stacked and slowly cooled, the slow cooling temperature is 450-550 DEG C, the stacking number is 11-15, and the stacking time is ensured to be 16-24 hours; heat treatment The steel plate is first treated by a quenching and tempering heat treatment process, the quenching temperature is 930±10 DEG C, the quenching heating rate is 1.5±0.3 min / mm, the tempering temperature is 610±10 DEG C, the tempering heating rate is 1.2±0.2 min / mm, and the quenching and tempering heat treatment is performed after air cooling.

6. The method of manufacturing a hydrogen storage pressure vessel steel sheet treated with Ti-Ca according to claim 5, characterized by, In the continuous casting process, the casting blank is cast under argon protection in the whole casting process, the casting blank is cast by light pressing down technology, the pressing down amount is controlled at 2-5 mm, the casting blank speed is controlled at 1.0-1.4 m / min, the casting superheat is 15-30 DEG C, and the blank straightening temperature is controlled at 950±30 DEG C.

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