70MPa-grade low-temperature container steel plate for hydrogen energy storage and transportation and manufacturing method thereof

Abstract

The invention belongs to the field of metal materials, and provides a 70MPa-grade low-temperature container steel plate for hydrogen energy storage and transportation and a manufacturing method of the 70MPa-grade low-temperature container steel plate, and the steel plate comprises the following components in percentage by weight: 0.15%-0.18% of C, 0.12%-0.16% of Si, 0.74%-0.98% of Mn, less than or equal to 0.01% of P, less than or equal to 0.01% of S, 1.12%-1.44% of Ni, 0.47%-0.75% of Cr, 0.01%-0.02% of V, 0.11%-0.19% of Mo, 0.022%-0.034% of N, 0.002%-0.0028% of La and the balance of Fe and inevitable impurities. The manufacturing method comprises the steps of smelting, continuous casting, four-stage efficient slab heating, two-stage rolling, two-stage cooling and heat treatment. The steel plate produced by the method has good obdurability matching and high and low temperature service performance, and the steel plate has excellent hydrogen-induced crack resistance, sulfide stress cracking resistance and stress corrosion resistance; and the steel plate has good wear resistance, and meets the manufacturing and application requirements of the high-performance steel plate for hydrogen energy storage and transportation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal materials, and particularly relates to a 70MPa-grade low-temperature container steel plate for hydrogen energy storage and transportation and a manufacturing method thereof. BACKGROUND

[0002] In view of the deficiencies of traditional low-temperature container steel plates in the field of hydrogen energy storage and transportation, the development of the present 70MPa-grade special steel plate is urgently necessary. Previous studies have shown that although austenitic stainless steel has excellent low-temperature toughness, its high cost limits its large-scale application; and although traditional low-temperature nickel-based steel has outstanding comprehensive performance, its economic stability is unstable due to the fluctuation of nickel price, and its welding process is complex. In addition, hydrogen energy storage and transportation mainly faces the problems of upper limit of pressure of high-pressure gaseous hydrogen storage and hydrogen embrittlement, and high energy consumption and adiabatic requirement of low-temperature liquid hydrogen storage. The development of the 70MPa-grade low-temperature container steel plate aims to promote the breakthrough of hydrogen energy storage and transportation technology by improving the hydrogen storage density and solving the contradiction between material performance. The material needs to meet the balance between strength under high pressure and low-temperature toughness, and has the properties of hydrogen embrittlement resistance and corrosion resistance. With the rapid development of hydrogen energy industry, there is an increasing demand for efficient and safe hydrogen storage containers in the fields of transportation, industry and energy. The limitations of traditional materials in low-temperature and high-pressure environments promote the localization replacement to become an important direction.

[0003] The steel plate disclosed in the published patent application "130mm~150mm thickness ultra-low-temperature steel plate and production method thereof" (CN104561772A) is composed of the following components by weight percentage: C: 0.06~0.09%, Si: 0.25~0.40%, Mn: 1.60~1.70%, P:<0.010%, S:<0.003%, Nb: 0.02~<0.03%, Ni: 0.60~0.70%, Als: 0.20~0.40%, and the rest is Fe and residual elements. The tensile strength / yield strength level is relatively low, which is difficult to meet the use requirements of higher strength grade hydrogen storage steel plate; the low-temperature performance of the steel plate at a temperature below-80℃ is not studied, and the thickness specification is only for large-thickness steel plate with a thickness of 150mm or more, and the thin-gauge steel plate applicable to hydrogen energy storage and transportation is not specifically analyzed. Therefore, it is not suitable for the production of high-density hydrogen storage steel. SUMMARY

[0004] The present application aims to overcome the above problems and deficiencies and provide a 70MPa-grade low-temperature container steel plate for hydrogen energy storage and transportation and a manufacturing method thereof, which has good strength and toughness matching, high and low temperature service performance, excellent hydrogen-induced cracking resistance, sulfide stress cracking and stress corrosion (SSC) performance, and good wear resistance, and meets the manufacturing and application requirements of high-performance hydrogen energy storage and transportation steel plate.

[0005] The purpose of the present application is achieved as follows:

[0006] A 70MPa-grade hydrogen energy storage and transportation cryogenic container steel plate, the composition of the steel plate is as follows in terms of percentage by weight: C: 0.15%-0.18%, Si: 0.12%-0.16%, Mn: 0.74%-0.98%, P: ≤0.01%, S: ≤0.01%, Ni: 1.12%-1.44%, Cr: 0.47%-0.75%, V: 0.01%-0.02%, Mo: 0.11%-0.19%, N: 0.022%-0.034%, La: 0.002%-0.0028%, and the balance being Fe and unavoidable impurities.

[0007] Further, C / La≥62 in the steel plate.

[0008] Further, Ni / N≥35 in the steel plate.

[0009] Further, Mn / C=4-6.5 in the steel plate.

[0010] Further, Cr / 50V≤1 in the steel plate.

[0011] Further, 0.25≤Pcm=C+Si / 30+(Mn+Cr) / 20+Ni / 60≤0.30 in the steel plate.

[0012] Further, the microstructure of the steel plate is refined sorbite+ferrite+nanoscale spherical bainite, and the refined sorbite:ferrite:nanoscale spherical bainite is (5-7):(3-5):(2-4) in terms of percentage by volume, the grain size is 8-9 levels, and the distance between the lamellar structures of the sorbite is not greater than 88nm, and the diameter size of the spherical bainite is 21-42nm; the second phase particles are uniformly dispersed in the steel plate, wherein the size of the second phase particles Cr(C and / or N) and V(C and / or N) is ≤45nm, and the size of the spherical second phase particles La(O and / or S and / or N) that is not greater than 12nm is ≤25nm.

[0013] Further, the thickness of the steel plate is 42-95 mm; at room temperature, at the 1 / 2 position of the steel plate: the tensile strength is 870-894 MPa, the yield strength is 804-824 MPa, the elongation after fracture A is greater than or equal to 35%, at the 1 / 4 position of the steel plate: the tensile strength is 870-898 MPa, the yield strength is 812-830 MPa, the elongation after fracture A is greater than or equal to 29%; under the condition of-60 DEG C, the average transverse impact energy KV2 is greater than or equal to 290 J, at the 1 / 4 position of the steel plate, the tensile strength is 880-912 MPa, the yield strength is 812-834 MPa, the elongation after fracture A is greater than or equal to 27%; under the condition of-80 DEG C, the average transverse impact energy KV2 is greater than or equal to 285 J, at the 1 / 4 position of the steel plate: the tensile strength is 906-919 MPa, the yield strength is 821-862 MPa, the elongation after fracture A is greater than or equal to 26.5%; the NDDT of the steel plate is less than or equal to-100 DEG C; under the condition of a temperature of 450-550 DEG C and a preset stress of 260-400 MPa, the steel plate has a creep rupture time of not less than 6800 h.

[0014] Further, according to the hydrogen-induced cracking (HIC) test in GB / T8650-2006 and NACE TM0284 'Pipeline and Pressure Containert Steel Evaluation Test Methods for Resistance to HIC', after the steel plate is subjected to a 96 h test in solution A and solution B, the crack sensitivity CSR (%), the crack length rate CLR (%) and the crack width rate CTR (%) are all 0, and the steel plate has excellent hydrogen-induced cracking resistance; according to the test in GB / T4157-2006 and NACE TM0177-201 'Resistance of Metals to Sulfide Stress Cracking and Stress Corrosion in H2S Environments', the steel plate is subjected to a tensile stress test in an acidic aqueous solution containing hydrogen sulfide, and the result shows that no cracks occur in the sample, and the steel plate has excellent sulfide stress cracking and stress corrosion (SSC) resistance; according to the test in GB / T17897-2016 'Corrosion of Stainless Steels - Ferric Sulfate Double-Jug Test Method', the corrosion rate of the steel plate in solution A and solution B is not greater than 0.0027 g / m 2 h; according to the test in GB / T3960-2016 'Plastics - Determination of the Sliding Friction and Wear Characteristics of Plastic Materials - Part 1: General Test Method', the result shows that the volume wear of the steel plate is not greater than 0.00073 cm 3 , and the steel plate has good wear resistance.

[0015] The component design reasons of the application are as follows:

[0016] C is the main element to ensure the strength of the steel plate, and also determines the toughness of the steel plate. In order to ensure the strength of the steel plate and meet the strength requirement of the 70MPa grade low temperature steel plate for hydrogen energy storage and transportation, the C content in the steel plate should be optimized and controlled. On the other hand, the hardenability of the steel plate has an impact on the uniformity of the microstructure and performance of the full thickness of the thick gauge steel plate. When the C content in the steel plate is within a certain range, the steel plate has good wear resistance and excellent service performance. However, too high C content will affect the machining performance of the steel. In order to ensure the good low temperature toughness of the steel plate, the C content range is set to 0.15%~0.18%.

[0017] Si is commonly used as a reducing agent and oxidizing agent in steel. In the present application, part of Si comes from the Si element in the spheroidizing agent, reducing the introduction of other impurities. On the other hand, adding appropriate amount of Si in the steel makes the steel have better wear resistance and elastic limit, yield strength and yield ratio. Because the steel plate is mainly used for the manufacture of hydrogen energy storage and transportation low temperature steel plate, there are certain requirements for the internal high purity and strict control of the size and quantity of inclusions for hydrogen resistance performance. However, when the Si content in the steel plate is too high, it is easy to cause the large size inclusions of the steel plate to exceed the standard, which is not conducive to the low temperature service performance of the steel plate. Therefore, the Si content range is set to 0.12%~0.16%.

[0018] Mn is a basic element in steel. Mn can significantly expand the austenite region in steel, ensure the critical temperature range, improve the uniformity of the steel structure, refine the structure, and play a solid solution strengthening role, which can increase the strength and hardness of the steel while ensuring the hardenability. In addition, the price is relatively low. However, in order to reduce the impact of MnS inclusions in the steel on the hydrogen-induced cracking resistance of the steel plate, the Mn content range is set to 0.74%~0.98%. C and Mn work together to significantly improve the strength, toughness, wear resistance and processing performance of the steel plate through solid solution strengthening, phase transformation control, mechanical property complementation and process optimization. Therefore, the Mn / C is controlled within the range of 4~6.5.

[0019] S and P are harmful elements in steel. In order to ensure the purity of the steel, reduce the large size inclusions in the steel plate and ensure the good plastic toughness, it must be strictly controlled. Therefore, the present application limits P≤0.01%, S≤0.01%.

[0020] Ni and N elements: in terms of affecting the composition of the organization, both are austenite stabilizing elements, Ni can expand the gamma phase zone and form an infinite solid solution, significantly improve the strength, plasticity and low temperature toughness of the steel. In the present application, the synergistic effect of Ni and N is used to achieve positive results. The addition of N can further strengthen this effect, and the partial substitution of N makes the austenite more stable, prevents martensitic transformation during cold working, and reduces the amount of Ni. In terms of the influence on mechanical properties, N significantly improves the strength of the steel through solid solution strengthening, grain refinement and precipitation hardening (such as V-N nitride in the present application), and does not sacrifice plasticity. The solid solution strengthening effect of Ni is superimposed, so that the steel still has good low temperature toughness while maintaining high strength. In terms of creep and fatigue resistance: N improves the high temperature stress rupture strength of the steel, and Ni improves the high temperature oxidation resistance, and the two synergistically improve the service performance of the steel in high temperature environment. In terms of improving unique performance, N is enriched at the passivation film / metal interface to inhibit the autocatalytic process of pitting corrosion, and cooperates with Cr, Mo and other elements to form a corrosion-resistant surface layer. Ni then stabilizes the austenite structure, reduces the precipitation of harmful phases, and further improves the corrosion resistance of the steel plate. N refines the grains and reduces the softening of the heat affected zone, and Ni reduces the weld crack sensitivity, and the synergistic effect of the two ensures the welding performance. At the same time, because Ni is a scarce resource, N is abundant and low in cost. By partially replacing N, the alloy cost can be significantly reduced while upgrading the performance. Therefore, the Ni content is controlled at 1.12-1.44%, the N element is controlled at N:0.022-0.034%, and the Ni / N is preferably ≥35.

[0021] Cr is a strong carbide forming element, Cr in steel is easy to combine with C / N, form fine chromium carbide particles, still exist in high temperature zone, inhibit pearlite cementite spheroidizing and graphitization at high temperature, avoid the strength decrease caused by organization degradation, at the same time also ensure the high temperature stress rupture performance of the steel plate; Cr expands the incubation period of the supercooled austenite isothermal transformation curve, improves the hardenability, ensures the uniform hardening of the large thickness container steel plate. On the other hand, Cr forms a dense Cr2O3 passivation film on the surface of the steel, fixes the free state O in the steel plate, and effectively blocks the erosion of oxidizing media (such as H2S, Cl⁻). Especially in low temperature (-60℃ below) high pressure hydrogen environment, it can reduce the hydrogen permeation rate, ensure the corrosion resistance, oxidation resistance and hydrogen resistance of the steel plate. In order to ensure the good toughness, plasticity, processing performance and service performance of the steel plate, the content of Cr in the present application is set to Cr:0.47%-0.75%.

[0022] V in the steel combines with C, N to form nanoscale VN / VC precipitates, which pin the grain boundaries during hot working, inhibit austenite grain growth, refine ferrite / pearlite structure, and improve low temperature impact toughness. V carbides act as hydrogen traps, capturing diffusible hydrogen atoms, reducing hydrogen segregation concentration at grain boundaries, and increasing hydrogen-induced cracking (HIC) initiation stress threshold, ensuring good hydrogen-induced cracking resistance and service performance in hydrogen environment. Dispersively distributed VN particles ensure the yield strength of the steel plate through the Orowan strengthening mechanism, while maintaining the elongation at a relatively ideal level, i.e. ensuring good strength and toughness matching. The V content range in the present application is set to 0.01~0.02%.

[0023] Cr-V synergistic effect, composite reinforcement and microstructure optimization: The solid solution strengthening of Cr and the precipitation strengthening of V are superimposed, which makes the steel plate have good tensile strength and improved low temperature impact performance. Cr inhibits the coarsening of V(C,N) at high temperature, while V(C,N) promotes the uniform distribution of Cr carbides at grain boundaries, forming a "double-phase strengthening network" and delaying the strength decline caused by long-term aging at high temperature. In terms of synergistic improvement of service performance, the passivation film of Cr and the hydrogen trapping effect of V form a double protection, making the steel plate have good H corrosion resistance, meeting the strict safety requirements of hydrogen energy storage and transportation; Cr increases the recrystallization temperature, and V reduces the overheating sensitivity, making the steel plate realize precise control of deformation strengthening and phase change during hot working, improving production efficiency while ensuring excellent performance of the steel plate. Therefore, preferably, in the present application, Cr / 50V≤1, and the size of the second phase Cr / V carbon / nitride particles is ≤48nm.

[0024] La purifies the molten steel, modifies the inclusion morphology, refines the grain, and improves the low-temperature toughness and corrosion resistance, significantly improving the comprehensive performance of the steel plate. Specifically, La combines with impurities such as oxygen and sulfur to form high-melting-point compounds, effectively purifying the molten steel and reducing stress concentration; nanoscale spherical Ce(O / S / N) particles simultaneously inhibit grain growth, refine the grain structure, and improve the uniformity of the structure, laying the foundation for improving low-temperature toughness. In addition, La also enhances the corrosion resistance of the steel plate by forming a dense corrosion product layer, and may reduce the diffusion and aggregation of hydrogen in the steel, reducing the risk of hydrogen embrittlement. These effects collectively improve the safety and reliability of the steel plate in extreme environments, providing an important guarantee for hydrogen energy storage and transportation equipment. In addition, considering the comprehensive production cost, the La content is set to 0.002~0.0028%. La refines the carbide to nanoscale and improves the distribution, and the solid solution strengthening of C together improves the strength of the steel plate while ensuring the super toughness of the low-temperature impact energy. La-modified inclusions reduce hydrogen segregation, and La-C compounds act as hydrogen traps to reduce the risk of hydrogen embrittlement. In addition, the synergy of La and C also optimizes the welding performance. La and C achieve a synergistic improvement in strength, toughness, and hydrogen embrittlement resistance in 70MPa grade low-temperature container steel plates through mechanisms such as carbide regulation, inclusion modification, hydrogen embrittlement inhibition, and welding performance optimization, providing a high-performance, low-cost solution for hydrogen energy storage and transportation equipment. Therefore, it is preferred to control C / La≥62.

[0025] The second technical solution of the present application is to provide a 70MPa grade low-temperature container steel plate manufacturing method for hydrogen energy storage and transportation, including smelting, continuous casting, four-stage efficient slab heating, two-stage rolling, two-stage cooling, and heat treatment.

[0026] (1) Smelting: including electric furnace smelting, LF refining, and RH refining.

[0027] The electric furnace smelting uses high-quality scrap steel and molten iron as raw materials, controls the size of the charging material to be between 72~81mm, and the mass percentage of molten iron is more than 76%; during smelting, magnesium-silicon spheroidizing agent is added, with a dosage of 3.4%~4.5% per ton of steel; the oxygen blowing time for decarburization is 261~343s; the oxygen blowing time for dephosphorization is 252~329s, and the phosphorus mass fraction in the molten steel is controlled to be within 0.01%;

[0028] The LF refining dephosphorization oxygen blowing time is 344~398s, and the sulfur content is controlled to be below 0.01%;

[0029] The RH refining starting temperature is 1662~1670℃, the oxygen blowing amount is 26~29m 3 , the net circulation time is 591~652s, and the static time before pouring is 266~321s.

[0030] In the process of electric furnace smelting, high-quality scrap steel and molten iron are used as raw materials, the size of the charging material is controlled between 72-81 mm, the molten iron content is controlled above 76%, the steel purity is ensured, the process time is shortened, and the difficulty of subsequent process is reduced. In the smelting process, the magnesium-silicon spheroidizing agent is added at a rate of 3.4%-4.5% per ton of steel to ensure the uniformity of the original structure, refine the as-cast grain, and shorten the smelting time. The dephosphorization and decarburization smelting parameters are strictly controlled, the oxygen blowing control is 261-343 s; in order to effectively reduce the content of harmful element P, the dephosphorization oxygen blowing control is 252-329 s, the mass fraction of phosphorus in the molten steel is controlled to be less than 0.01%; further deep desulfurization treatment is carried out in the LF refining furnace, the desulfurization oxygen blowing control is 344-398 s, and the sulfur content is controlled to be less than 0.01%; the degassing is completed in the RH furnace, the initial temperature control is 1662-1670℃, the oxygen blowing amount control is 26-29 m 3 , the net circulation time is 591-652 s, and the static time before pouring is 266-321 s. Through the optimization of the smelting process parameters, the oxidation of molten steel is reduced, the content of inclusions in steel is controlled, the internal defects are reduced, and the purpose of purifying the purity of steel is achieved.

[0031] (2) Continuous casting:

[0032] After breaking the vacuum, slab continuous casting machine is used for casting, the casting temperature is 1580-1591℃, the superheat is 13-15℃, and the casting speed is 2.0-2.3 mm / s; during the continuous casting process, the continuous casting billet light pressing process and / or electromagnetic stirring process are used to reduce the central segregation degree of the casting billet and improve the quality of the casting billet, wherein the light pressing rate is controlled at 1%-3%, the current is 396-419 A, and the frequency is 4-8 Hz; the casting billet is put into the stacking and slow cooling after being offline, the cooling speed is 11-15℃ / h, and the stacking and slow cooling time is 36-48 h.

[0033] After breaking the vacuum, slab continuous casting machine is used for casting, high-temperature casting is used to make impurities float to the surface, thereby ensuring the internal quality of the original casting billet, and the casting temperature is controlled at 1580-1591℃, the superheat is set to 13-15℃, and the casting speed is 2.0-2.3 mm / s. By controlling the casting temperature, the original as-cast structure is refined. In order to optimize the internal quality of the continuous casting billet, reduce segregation, cavities and other defects, the continuous casting billet light pressing process and / or electromagnetic stirring process are used to reduce the central segregation degree of the casting billet and improve the quality of the casting billet, wherein the light pressing rate is controlled at 1-3%, the current is 396-419 A, and the frequency is 4-8 Hz; the casting billet is put into the stacking and slow cooling after being offline, the cooling speed is 11-15℃ / h, and the stacking and slow cooling time is 36-48 h.

[0034] (3) Four-stage efficient slab heating:

[0035] The continuous casting slab is sent to the heating furnace for heating, and the slab is heated out of the furnace after four-stage heating.

[0036] The temperature interval of the preheating section is 782-833℃, the temperature interval of the low-temperature soaking section is 987-1010℃, the temperature interval of the high-temperature short-time soaking section is 1151-1192℃, the soaking time is 42-54min, and the temperature interval of the high-temperature efficient homogenizing section is 1222-1256℃;

[0037] The slab heating rate is controlled at 12-19℃ / min, the total furnace time is controlled at 3.9-5.4h, and the cooling rate is controlled at 33-42℃ / min.

[0038] The continuous casting slab is sent to the heating furnace for heating, and the slab heating undergoes four-stage heating and then is discharged. The temperature interval of the preheating section is 782-833℃, the temperature interval of the low-temperature soaking section is 987-1010℃, the temperature interval of the high-temperature short-time soaking section is 1151-1192℃, the soaking time is 42-54min, and the temperature interval of the high-temperature efficient homogenizing section is 1222-1256℃. The slab heating rate is controlled at 12-19℃ / min, the total furnace time is controlled at 3.9-5.4h, and the cooling rate is controlled at 33-42℃ / min. Through the four-stage heating mode, the uniformity of the internal organization of the slab is further improved, the original size of the precipitated phase particles is controlled, the internal stress of the steel plate is fully released, and meanwhile, the uniformity of the internal and external temperatures of the slab is ensured, which is beneficial to the reprocessing.

[0039] (4) Two-stage rolling:

[0040] The rolling adopts a two-stage controlled rolling method;

[0041] The first stage is original austenite organization refining rolling, the starting rolling temperature is 1058-1096℃, the end rolling temperature is 961-998℃, the "large-small-... large reduction rate" rolling control process is adopted, and the large reduction rate range is controlled at 7%-10% and the small reduction rate range is controlled at 2%-4%;

[0042] The second stage is dual-phase zone rolling, the starting rolling temperature is 946-974℃, the final rolling temperature is 847-880℃, the "reduction rate decreasing" rolling control process is adopted, and the second stage dual-phase zone rolling reduction rate is 6%-10%.

[0043] The rolling is carried out by two-stage controlled rolling method, the first stage is original austenite structure refining rolling, the starting rolling temperature is 1058-1096℃, the end rolling temperature is 961-998℃, a "large-small-... large reduction rate" rolling control process is adopted, and the large reduction rate range is controlled to be 7%-10%, the small reduction rate range is controlled to be 2%-4%, high-temperature austenite zone rolling is adopted, the steel plate deformation resistance is reduced, the original austenite structure is fully refined, the grain is fully recrystallized, the internal structure of the steel plate is refined, and the uniformity of the structure is improved. The second stage is dual-phase zone rolling, the starting rolling temperature is 946-974℃, the end rolling temperature is 847-880℃, a "reduction rate decreasing" rolling control process is adopted, and the dual-phase zone rolling reduction rate range of the second stage is controlled to be 6%-10%, with the increase of the grain boundary area, the ferrite nucleation rate is increased in the subsequent phase change process, the internal structure of the steel plate is fully refined, and the austenite grains are further flattened and elongated.

[0044] (5) Two-stage cooling:

[0045] The first stage is a structure homogenization controlled cooling stage, the controlled cooling starting temperature is 835-876℃, and the cooling speed is 26-34℃ / s; the second stage is a precipitation strengthening controlled cooling stage, the cooling starting temperature is 512-539℃, and the cooling speed is 86-104℃ / s.

[0046] The first stage is a structure homogenization controlled cooling stage, the controlled cooling starting temperature is 835-876℃, and the cooling speed is controlled to be 26-34℃ / s, the cooling speed and temperature in the rolling process are controlled, the abnormal growth of the steel plate grains is reduced, the primary network carbide is prevented from being precipitated, the dislocation movement caused by deformation is reduced, and the internal structure of the steel plate is optimized. The second stage is a precipitation strengthening controlled cooling stage, the controlled starting temperature is 512-539℃, and the cooling speed is 86-104℃ / s, the high-speed cooling is adopted, the austenite is kept in a hardened state, the nucleation is promoted, the structure is refined, the strain-induced precipitation is inhibited, more micro-alloying elements are reserved, the precipitation strengthening effect is improved, and the mechanical properties of the steel plate are improved.

[0047] (6) Heat treatment:

[0048] The heat treatment of the steel plate is a low-temperature die welding heat treatment stage, the temperature is controlled to be 555-592℃, the heating rate is 0.6-0.9min / mm, the holding time is 165-200min; the high-temperature die welding heat treatment stage controls the temperature to be 605-642℃, the heating rate is 0.8-1.1min / mm, the holding time is 45-60min, and the cooling rate is controlled to be 36-49℃ / min.

[0049] Due to the addition of C, Si, Mn, Ni, Cr, Mo, V, La, N and other elements in the steel, the steel plate can obtain excellent ferrite + sorbite + spheroidal bainite structure after rolling. However, the grain size distribution of the steel plate is uneven, and there is a stress and thermal stress concentration, and a delay crack is prone to occur during flame cutting. Therefore, heat treatment should be used in time to soften and eliminate stress. In order to further control the internal structure of the steel plate and ensure the production efficiency, the two-stage welding heat treatment is adopted to ensure that the strength of the steel plate is not lost, and at the same time, the steel plate has appropriate plasticity, toughness and low temperature impact toughness, corrosion resistance and good processing performance. Therefore, the low temperature welding heat treatment stage of the steel plate is controlled at 555~592℃, the heating rate is controlled at 0.6~0.9min / mm, and the holding time is in the range of 165~200min; the high temperature welding heat treatment stage is controlled at 605~642℃, the heating rate is controlled at 0.8~1.1min / mm, and the holding time is in the range of 45~60min, and the cooling rate is controlled at 36~49℃ / min.

[0050] The beneficial effects of the present application are:

[0051] (1) On the basis of C, Si and Mn strengthening elements, by adding appropriate amount of Ni, Cr, V and La alloy elements, optimizing the control of N element, and strictly controlling the content of harmful elements P and S, combined with the optimization of production process, uniform and refined sorbite + ferrite + nanoscale spheroidal bainite is obtained, the proportion of the three is in the range of (5~7:): (3~5): (2~4) according to volume percentage, the grain size is in the range of 8~9, and the distance between the lamellar structures of sorbite is not more than 88nm, and the spheroidal bainite is in the range of 21~42nm. The second phase particles are uniformly dispersed in the steel plate, wherein the size of the second phase particles Cr (C and / or N) and V (C and / or N) is ≤45nm, and the size of the spheroidal second phase particles La (O and / or S and / or N) not more than 12nm is ≤25nm, which ensures the strength, plasticity and low temperature toughness of the steel plate, and ensures that the steel plate has good corrosion resistance and wear resistance.

[0052] (2) The mechanical properties of the steel plate for storage tanks obtained by the specific production process are as follows: at room temperature, the steel plate 1 / 2: the tensile strength range is 870-894 MPa, the yield strength range is 804-824 MPa, A% ≥ 35, the steel plate 1 / 4: the tensile strength range is 870-898 MPa, the yield strength range is 812-830 MPa, A% ≥ 29; under the condition of-60 ℃, the average transverse impact energy KV2 is ≥ 290 J, the steel plate 1 / 4: the tensile strength range is 880-912 MPa, the yield strength range is 812-834 MPa, A% ≥ 27; under the condition of-80 ℃, the average transverse impact energy KV2 is ≥ 285 J, the steel plate 1 / 4: the tensile strength range is 906-919 MPa, the yield strength range is 821-862 MPa, A% ≥ 26.5; the NDDT of the steel plate is ≤-100 ℃; under the condition of a temperature of 450-550 ℃ and a preset stress of 260-400 MPa, the steel plate has a creep rupture time of not less than 6800 h, that is, good strength and toughness matching and high and low temperature service performance.

[0053] (3) According to the hydrogen induced cracking (HIC) experiment in GB / T8650-2006 and NACE TM0284 "Evaluation Methods for Resistance of Pipeline and Pressure Vessel Steels to Hydrogen Induced Cracking", after the steel plate is subjected to a 96 h experiment in solution A and solution B, the crack sensitivity CSR (%), the crack length rate CLR (%) and the crack width rate CTR (%) are all 0, and the steel plate has excellent hydrogen induced cracking resistance; according to GB / T4157-2006 and NACE TM0177-201 "Resistance of Metals to Sulfide Stress Cracking and Stress Corrosion in H2S Environments", the steel plate is subjected to a tensile stress experiment in an acidic aqueous solution containing hydrogen sulfide, and the result shows that no cracks occur in the sample, and the steel plate has excellent sulfide stress cracking and stress corrosion (SSC) resistance; according to GB / T17897-2016 "Method for Corrosion Test of Stainless Steel by Ferric Chloride Point Etching", the steel plate shows a corrosion rate of not more than 0.0027 g / m 2 h in solution A and solution B; according to GB / T3960-2016 "Plastic Sliding Friction and Wear Test Method", the result shows that the volume wear of the steel plate is not more than 0.00073 cm 3 , and the steel plate has good wear resistance. That is, the steel plate has excellent strength, low temperature toughness, service performance and plate shape in the (42-95) mm thickness specification, and meets the manufacturing and application requirements of high performance hydrogen energy storage and transportation steel plate. DETAILED DESCRIPTION

[0054] The application is further described below by examples.

[0055] The embodiment of the present application smelts, continuously casts, four-stage high-efficiency slab heating, two-stage design rolling, two-stage cooling and two-stage welding heat treatment according to the component ratio of the technical scheme.

[0056] (1) Continuous casting:

[0057] After vacuum breaking, the slab is cast by a slab continuous casting machine, the casting temperature is 1580-1591℃, the superheat is 13-15℃, and the casting speed is 2.0-2.3mm / s; the continuous casting slab is subjected to light pressing down process and / or electromagnetic stirring process, and the casting slab is cooled by stacking and slow cooling, the cooling speed is 11-15℃ / h, and the stacking and slow cooling time is 36-48h;

[0058] (2) Four-stage high-efficiency slab heating:

[0059] The continuous casting slab is sent to a heating furnace for heating, and the slab is discharged after four-stage heating; the slab heating rate is 12-19℃ / min, the total furnace time is 3.9-5.4h, and the cooling rate is 33-42℃ / min;

[0060] The temperature range of the preheating section is 782-833℃, the temperature range of the low-temperature soaking section is 987-1010℃, the temperature range of the high-temperature short-time soaking section is 1151-1192℃, and the holding time is 42-54min; the temperature range of the high-temperature efficient homogenization section is 1222-1256℃;

[0061] (3) Two-stage rolling:

[0062] The rolling is controlled by two-stage rolling method;

[0063] The first stage is original austenite organization refining rolling, the starting rolling temperature is 1058-1096℃, the rolling end temperature is 961-998℃, the rolling control process is adopted, and the large reduction rate range is controlled to be 7%-10% and the small reduction rate range is controlled to be 2%-4%;

[0064] The second stage is dual-phase zone rolling, the starting rolling temperature is 946-974℃, the final rolling temperature is 847-880℃, the rolling control process is adopted, and the second stage dual-phase zone rolling reduction rate is 6%-10%;

[0065] (4) Two-stage cooling:

[0066] The first stage is organization homogenization controlled cooling stage, the controlled cooling starting temperature is 835-876℃, and the cooling speed is 26-34℃ / s; the second stage is precipitation strengthening controlled cooling stage, the cooling starting temperature is 512-539℃, and the cooling speed is 86-104℃ / s;

[0067] (5) Heat treatment:

[0068] The temperature of the steel plate low-temperature die welding heat treatment stage is controlled at 565-582 DEG C, the heating rate is 0.6-0.9 min / mm, and the holding time is 165-200 min; the temperature of the high-temperature die welding heat treatment stage is controlled at 605-612 DEG C, the heating rate is 0.8-1.1 min / mm, the holding time is 45-60 min, and the cooling rate is controlled at 36-49 DEG C / min.

[0069] Further, smelting includes electric furnace smelting, LF refining, RH refining,

[0070] In the electric furnace smelting process, high-quality scrap steel and molten iron are used as raw materials, the furnace charging size is 72-81 mm, and the mass percentage of molten iron is more than 76%; magnesium-silicon spheroidizing agent is added during smelting, the ton steel addition amount is 3.4%-4.5%; the oxygen blowing time for decarburization is 261-343 s; the oxygen blowing time for dephosphorization is 252-329 s, and the mass fraction of phosphorus in the molten steel is controlled to be less than 0.01%;

[0071] The oxygen blowing time for desulfurization in the LF refining is 344-398 s, and the sulfur content is controlled to be less than 0.01%;

[0072] The RH refining starting temperature is 1662-1670 DEG C, the oxygen blowing amount is 26-29 m 3 , the net circulation time is 591-652 s, and the static time before pouring is 266-321 s.

[0073] Further, in the continuous casting process, the reduction rate of the continuous casting billet under light pressing is 1%-3%; in the electromagnetic stirring process, the current is 396-419 A, and the frequency is 4-8 Hz.

[0074] The components of the example steel and the comparative steel of the present application are shown in Table 1. The main process parameters of the example steel and the comparative steel of the present application in smelting are shown in Table 2. The main process parameters of the example steel and the comparative steel of the present application in continuous casting are shown in Table 3. The main process parameters of the example steel and the comparative steel of the present application in heating are shown in Table 4. The main process parameters of the example steel and the comparative steel of the present application in rolling are shown in Table 5. The main process parameters of the example steel and the comparative steel of the present application in cooling and heat treatment are shown in Table 6. The mechanical properties of the example steel and the comparative steel of the present application are shown in Table 7. The evaluation results of the microstructure, grain size and second phase particles of the example steel and the comparative steel of the present application are shown in Table 8. The evaluation results of the microstructure and inclusions of the example steel and the comparative steel of the present application are shown in Table 9. The experimental results of the service performance of the example steel and the comparative steel of the present application are shown in Table 10.

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085] According to the above results, it can be concluded that the present application provides a production (42~95) mm thickness specification steel plate, obtaining the steel plate 1 / 2: the tensile strength range is 870~894MPa, the yield strength range is 804~824MPa, the elongation after fracture A≥35%, the steel plate 1 / 4: the tensile strength range is 870~898MPa, the yield strength range is 812~830MPa, the elongation after fracture A≥29%; under the condition of-60℃, the average transverse impact energy KV2 is≥290J, the steel plate 1 / 4, the tensile strength range is 880~912MPa, the yield strength range is 812~834MPa, the elongation after fracture A≥27%; under the condition of-80℃, the average transverse impact energy KV2 is≥285J, the steel plate 1 / 4: the tensile strength range is 906~919MPa, the yield strength range is 821~862MPa, the elongation after fracture A≥26.5%; the NDDT of the steel plate is≤-100℃; the total sum of the inclusion grade of the steel plate is≤1.0, the grain size is 8~9 levels; the microstructure is composed of sorbite + ferrite + nanoscale spherical bainite, the proportion of the three is (5~7:): (3~5):(2~4) according to the volume percentage, and the distance between the lamellar structure of sorbite is not more than 88nm, and the spherical bainite is between 21~42nm; the second phase particles in the steel plate are uniformly dispersed, wherein the size of the second phase particles Cr (C and / or N), V (C and / or N) is≤45nm, and the size of the spherical second phase particles La (O and / or S and / or N) not more than 12nm is≤25nm. Under the condition of temperature 450~550℃, preset stress 260~400MPa, the steel plate has a fracture time of not less than 6800h in the stress rupture test; has good corrosion resistance (hydrogen induced cracking resistance, H2S corrosion resistance, pitting corrosion resistance) and wear resistance, that is, according to the hydrogen induced cracking (HIC) test in GB / T8650-2006 and NACE TM0284 "Pipeline steel and pressure vessel steel hydrogen induced cracking resistance evaluation method", the crack sensitivity CSR (%), crack length rate CLR (%) and crack width rate CTR (%) of the steel plate are all 0 after 96h test in solution A and solution B, and the steel plate has excellent hydrogen induced cracking resistance; according to GB / T4157-2006 and NACE TM0177-201 "Metal in H2S environment Sulfide stress cracking and stress corrosion" test, the steel plate is subjected to tensile stress test in acidic aqueous solution containing hydrogen sulfide, and the result shows that no crack occurs in the sample, and the steel plate has excellent sulfide stress cracking and stress corrosion (SSC) performance; according to GB / T17897-2016 "Metal and alloy corrosion stainless steel ferric chloride pitting corrosion test method", the steel plate shows that the corrosion rate in solution A and solution B is not more than 0.0027g / m 2 ·h; according to GB / T3960-2016 "Plastic sliding friction wear test method", the result shows that the volume wear amount of the steel plate is not more than 0.00073cm3 The steel plate has good wear resistance. That is, the steel plate with a thickness of (42-95) mm, which is excellent in strength, low-temperature toughness, service performance and plate shape, meets the manufacturing and application requirements of high-performance hydrogen energy storage and transportation steel plates.

[0086] In order to describe the present application, the above-mentioned embodiments are appropriately and sufficiently described by examples, the above embodiments are only used to illustrate the present application, and are not limited to the present application. Any modification, equivalent replacement, improvement and the like made by those skilled in the art without departing from the spirit and scope of the present application shall be included in the protection scope of the present application, and the patent protection scope of the present application shall be defined by the claims.

Claims

1. A 70MPa grade low temperature container steel plate for hydrogen energy storage and utilization, characterized in that: The composition of the steel plate is as follows by weight percentage: C: 0.15%~0.18%, Si: 0.12%~0.16%, Mn: 0.74%~0.98%, P: ≤0.01%, S: ≤0.01%, Ni: 1.12%~1.44%, Cr: 0.47%~0.75%, V: 0.01%~0.02%, Mo: 0.11%~0.19%, N: 0.022%~0.034%, La: 0.002%~0.0028%, and the balance is Fe and unavoidable impurities.

2. The 70MPa grade low-temperature container steel plate for hydrogen energy storage and use according to claim 1, characterized in that: C / La in steel plate ≥62.

3. The 70MPa grade low-temperature container steel plate for hydrogen energy storage and use according to claim 1, characterized in that: Ni / N in steel plate ≥35.

4. The 70MPa grade low-temperature container steel plate for hydrogen energy storage and use according to claim 1, characterized in that: Mn / C in steel plates is 4~6.

5.

5. The 70MPa grade low-temperature container steel plate for hydrogen energy storage and use according to claim 1, characterized in that: Cr / 50V in steel plate ≤ 1.

6. The 70MPa grade low-temperature container steel plate for hydrogen energy storage and use according to claim 1, characterized in that: The microstructure of the steel plate is refined troostite + ferrite + nano-scale spherical bainite, and the volume percentage is as follows: refined troostite: ferrite: nano-scale spherical bainite = (5~7): (3~5): (2~4), the grain size is 8~9, and the distance between the lamellar structures of troostite is no more than 88nm, and the diameter of the spherical bainite is 21~42nm; the second phase particles in the steel plate are uniformly dispersed, among which the size of the second phase particles Cr (C and / or N) and V (C and / or N) is ≤45nm, and the spherical second phase particles La (O and / or S and / or N) with a size no more than 12nm are ≤25nm.

7. The 70MPa grade low-temperature container steel plate for hydrogen energy storage and use according to claim 1, characterized in that: The thickness of the steel plate is 42~95mm; at room temperature, the tensile strength at 1 / 2 of the steel plate is 870~894MPa, the yield strength is 804~824MPa, and the elongation after fracture is A ≥35%, 1 / 4 of the steel plate: tensile strength 870~898MPa, yield strength 812~830MPa, elongation after fracture A ≥29%; under -60℃ condition, transverse impact energy KV 2 Average value ≥ 290J, at 1 / 4 of the steel plate, tensile strength 880~912MPa, yield strength 812~834MPa, elongation after fracture A ≥27%; under -80℃ condition, transverse impact energy KV 2 Average value ≥ 285J, 1 / 4 of the steel plate: tensile strength 906~919MPa, yield strength 821~862MPa, elongation after fracture A ≥26.5%; NDDT of steel plate ≤-100℃; when the temperature is in the range of 450~550℃ and the preset stress is 260~400MPa, the fracture time of the steel plate in the endurance test is not less than 6800h.

8. A method for manufacturing a 70 MPa grade low-temperature container steel plate for hydrogen energy storage and use according to any one of claims 1 to 7, characterized in that: Including smelting, continuous casting, four-stage high-efficiency slab heating, two-stage rolling, two-stage cooling, and heat treatment; (1) Continuous casting: After breaking the vacuum, the slab continuous casting machine is used for casting, with a casting temperature of 1580-1591°C, a superheat of 13-15°C, and a casting rate of 2.0-2.3 mm / s. The continuous casting slab is subjected to a soft reduction process and / or an electromagnetic stirring process. The slab is stacked and slowly cooled after it comes off the line. The cooling rate is 11-15°C / h, and the stacking slow cooling time is 36-48 hours. (2) Four-stage high-efficiency slab heating: The continuous casting slab is sent to the heating furnace for heating. The slab is heated through four stages before being taken out of the furnace. The slab heating rate is 12~19℃ / min, the total time in the furnace is 3.9~5.4h, and the cooling rate is 33~42℃ / min. The temperature range of the preheating section is 782~833℃, the temperature range of the low-temperature soaking section is 987~1010℃, the temperature range of the high-temperature short-time soaking section is 1151~1192℃, and the holding time is 42~54min; the temperature range of the high-temperature high-efficiency homogenization section is 1222~1256℃; (3) Two-stage rolling: The rolling adopts a two-stage controlled rolling method; In the first stage, the original austenite structure is refined by rolling, with the starting rolling temperature at 1058~1096℃ and the ending rolling temperature at 961~998℃. The "large-small-...large reduction rate" controlled rolling process is adopted, with the maximum reduction rate being 7%~10% and the minimum reduction rate being 2%~4%. In the second stage of dual-phase rolling, the starting rolling temperature is 946~974℃, the final rolling temperature is 847~880℃, and the "reduction rate decreasing" rolling control process is adopted. The reduction rate of the second stage dual-phase rolling is 6%~10%; (4) Two-stage cooling: The first stage is the microstructure homogenization controlled cooling stage, with a cooling start temperature of 835~876℃ and a cooling rate of 26~34℃ / s; the second stage is the precipitation strengthening controlled cooling stage, with a cooling start temperature of 512~539℃ and a cooling rate of 86~104℃ / s; (5) Heat treatment: The heat treatment of the steel plate is as follows: in the low-temperature mold welding heat treatment stage, the temperature is controlled at 555~592℃, the heating rate is 0.6~0.9min / mm, and the holding time is 165~200min; in the high-temperature mold welding heat treatment stage, the temperature is controlled at 605~642℃, the heating rate is 0.8~1.1min / mm, the holding time is 45~60min, and the cooling rate is controlled at 36~49℃ / min.

9. The method for manufacturing a 70MPa grade low-temperature container steel plate for hydrogen energy storage and use according to claim 8, characterized in that: Smelting includes electric furnace smelting, LF refining, and RH refining; During the electric furnace smelting process, high-quality scrap steel and molten iron are used as raw materials. The charge size is 72-81mm, and the molten iron mass percentage is above 76%. During the smelting process, the amount of magnesium-silicon nodulizer added per ton of steel is 3.4%-4.5%. The decarburization oxygen blowing time is 261-343 seconds; the dephosphorization oxygen blowing time is 252-329 seconds, and the phosphorus mass fraction in the molten steel is controlled to be within 0.01%. The oxygen blowing time for LF refining desulfurization is 344~398s, which controls the sulfur content below 0.01%; RH refining starting temperature is 1662~1670℃, oxygen blowing volume is 26~29m 3 , net circulation time is 591~652s, and calming time before pouring is 266~321s.

10. The method for manufacturing a 70MPa grade low-temperature container steel plate for hydrogen energy storage and use according to claim 8, characterized in that: During the continuous casting process, the reduction rate of the continuous casting billet under light pressure is 1%~3%; the current in the electromagnetic stirring process is 396~419A and the frequency is 4~8Hz.

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