Hydrogen-resistant and corrosion-resistant steel for geological hydrogen storage reservoir casing and preparation method thereof

Abstract

This invention relates to the field of steel technology, and particularly to a hydrogen-resistant and corrosion-resistant steel for geological hydrogen storage tank casing and its preparation method. The steel comprises C, Si, Mn, Cr, Ni, Mo, Ta, V, Nb, Mg, Ti, Ca, P, S, Fe, and unavoidable impurities. The mass percentages of Ta, Nb, and V conform to 0.03% ≤ Ta + Nb + V ≤ 0.10% and 0.5 ≤ (Ta + Nb) / V ≤ 2, respectively. The mass percentages of Mg and Ti conform to a Mg / Ti ratio of 1:3~5. This invention enables the formation of a high-density, dispersed composite (Nb, Ta, V, Ti)C precipitate in the steel, providing higher density deep hydrogen trapping sites to capture diffusible hydrogen and inhibit hydrogen embrittlement. The inclusions are Mg-Ti-O@CaS composite inclusions with a core-shell structure, significantly increasing the proportion of core-shell inclusions and refining their size to near micrometers, thus reducing the probability of pitting corrosion.

Description

Technical Field

[0001] This invention relates to the field of steel technology, and in particular to a hydrogen-resistant and corrosion-resistant steel for casing of a geological hydrogen storage tank and its preparation method. Background Technology

[0002] Salt cavern gas storage facilities built using underground salt rock layers are internationally recognized as ideal sites for large-scale hydrogen storage due to their advantages such as high porosity, low permeability, and low operating costs. In the wellbore structure of salt cavern hydrogen storage facilities, the casing is the first barrier to isolate high-pressure hydrogen from the geological environment and ensure the integrity of the wellbore. Its service environment is extremely harsh, involving long-term exposure to high-pressure hydrogen and exposure to Cl... - SO4 2- Corrosive media such as hydrogen embrittlement and CO2 can cause damage. Under high-pressure hydrogen gas (typically 3-20 MPa), hydrogen molecules penetrate into the steel, decompose into hydrogen atoms, and accumulate at grain boundaries, inclusions, and other defects, leading to hydrogen embrittlement. In corrosive media such as brine and CO2, the casing also faces the risk of pitting corrosion and other corrosion failures. Furthermore, the casing must withstand the enormous geostress of the overlying rock strata, the compressive stress generated by salt rock creep, and the alternating loads caused by internal pressure fluctuations, placing higher demands on the material's strength and toughness. Therefore, salt cavern hydrogen storage tank casings face multiple risks, including hydrogen embrittlement, corrosion, and mechanical failure.

[0003] However, although there has been some research on hydrogen pipeline steel in the existing technology (such as X52 / X65 steel), there is still a lack of patent applications for special casing steel for deep salt cavern hydrogen storage under conditions of high hydrogen pressure, complex stress, and coexistence of corrosion.

[0004] Therefore, there is an urgent need to provide a special casing steel for deep salt cavern hydrogen storage facilities that combines high strength, low hydrogen embrittlement sensitivity, and excellent corrosion resistance, as well as its preparation method. Summary of the Invention

[0005] One objective of this invention is to provide a hydrogen-resistant and corrosion-resistant steel for casing of geological hydrogen storage facilities. This steel forms a large number of nanoscale (Nb, Ta, V, Ti)C composite precipitates and near-micron-sized Mg-Ti-O@CaS composite inclusions with a core-shell structure. These inclusions can form numerous micro- and nano-scale second phases within the steel, acting as deep hydrogen traps within the grains to suppress hydrogen embrittlement, and also serving as strengthening units to improve strength through precipitation strengthening and grain refinement. Simultaneously, the refinement and core-shell formation of the inclusions also reduce the probability of pitting corrosion, thereby achieving a synergistic improvement in hydrogen embrittlement resistance, corrosion resistance, and high strength, meeting the requirements of deep-earth salt cavern hydrogen storage facilities.

[0006] The second objective of this invention is to provide a method for preparing hydrogen-resistant and corrosion-resistant steel for casing of geological hydrogen storage facilities. The preparation method is simple and easy to control. To achieve the above objectives, one of the technical solutions adopted by the present invention is as follows: a hydrogen-resistant and corrosion-resistant steel for casing of a geological hydrogen storage facility, comprising, by mass percentage of chemical composition, C: 0.28%–0.33%, Si: 0.02%–0.07%, Mn: 0.40%–0.70%, Cr: 0.80%–1.10%, Ni: 0.15%–0.25%, Mo: 0.40%–0.55%, Ta: 0.01%–0.03%, V: 0.01%–0.04%, Nb: 0.01%–0.05%, Mg: 0.006%–0.016%, Ti: 0.018%–0.080%, Ca: 0.001%–0.005%, P ≤0.020%, S ≤0.01%, with the remainder being Fe and unavoidable impurities; Furthermore, the mass percentages of the chemical composition of Ta, Nb, and V conform to 0.03%≤Ta+Nb+V≤0.10% and 0.5≤(Ta+Nb) / V≤2, and the mass percentages of the chemical composition of Mg and Ti conform to Mg / Ti of 1:3~5; The microstructure of the steel matrix is ​​tempered sorbite, with dispersed (Nb, Ta, V, Ti)C composite precipitates of 2-50 nm in size and Mg-Ti-O@CaS composite inclusions of 0.5-2 μm in size.

[0007] The basic functions of the main elements and processes in this invention are as follows: C: Carbon (C) improves the hardenability of steel and forms reinforcing phases such as carbides, thereby increasing strength and hardness. Low carbon content may result in insufficient strength; while excessively high carbon content can lead to difficulties in sleeve forming and processing, and consume chromium, reducing corrosion resistance. Therefore, to achieve a balance between strength and corrosion resistance, a C content of 0.28%–0.33% is selected.

[0008] Si: Si is one of the deoxidizing elements. When the Si content is below 0.10%, the deoxidation effect is poor, and a large number of non-metallic inclusions are easily left, reducing the resistance to hydrogen embrittlement; while when the Si content is above 0.40%, it increases the tendency for cold embrittlement. Therefore, the Si content is selected to be 0.02% to 0.07%.

[0009] Mn: Mn mainly functions as a deoxidizer and solid solution strengthener, and can also appropriately improve hardenability. However, excessively high Mn content may lead to segregation bands, which is detrimental to mechanical properties. Therefore, considering all performance requirements, the Mn content is selected as 0.40%–0.70%.

[0010] Cr: Cr can form a dense oxide film on the surface of steel, improving corrosion resistance and effectively enhancing hardenability. However, excessive Cr content can lead to the formation of coarse, Cr-rich carbides at grain boundaries, reducing resistance to hydrogen embrittlement. Therefore, the Cr content is selected to be 0.80%–1.10%.

[0011] Ni: Ni can improve the hardenability and toughness of steel without significantly increasing the carbon equivalent, and enhance resistance to pitting corrosion, thereby inhibiting the initiation of surface corrosion cracks. Low Ni content cannot guarantee hardenability and toughness, but excessive Ni content can alter carbide morphology and promote hydrogen-induced crack propagation, thus having a detrimental effect. Therefore, the Ni content is selected as 0.15%–0.25%.

[0012] Mo: Mo mainly improves strength by precipitating M2C-type carbides and acts as a hydrogen trap to prevent hydrogen embrittlement. When the Mo content is low, a sufficient number of M2C-type carbides that are beneficial to resisting hydrogen embrittlement cannot be formed. However, when the Mo content is too high, it will promote the formation of coarse carbides, which will become new crack sources, and the resistance to hydrogen embrittlement will decrease instead of increase. Therefore, the Mo content is selected as 0.40% to 0.55%.

[0013] Ta (Ta) is a strong carbide-forming element, primarily combining with C, V, Nb, and Ti to precipitate a composite (Nb, Ta, V, Ti)C phase. This precipitate not only enhances strength through precipitation strengthening but also synergistically improves toughness through grain refinement. Compared to other precipitates, this phase, being rich in Ta, is less prone to coarsening, effectively avoiding the harmful effects of coarsening. Furthermore, the high Ta content in steel also acts as a strong hydrogen trap, reducing the content of diffusible hydrogen and improving resistance to hydrogen embrittlement. However, excessively high Ta content increases costs and its performance-enhancing effect tends to saturate. Therefore, the Ta content is selected to be 0.01%–0.03%.

[0014] V: V is another strong carbide-forming element that can combine with Ta, Nb, Ti, and C to precipitate a high-density composite (Nb, Ta, V, Ti)C phase, thereby simultaneously improving strength and resistance to hydrogen embrittlement. However, excessively high V content can lead to coarsening and growth of the precipitated phase, causing temper brittleness and reducing the material's resistance to hydrogen embrittlement and toughness. Therefore, V is selected to be 0.01%–0.04%.

[0015] Nb is also a strong carbide-forming element, capable of combining with Ta, V, Ti, and C in steel to form a large number of (Nb,Ta, V, Ti)C complex carbides. However, excessively high Nb content leads to excessively high costs, and its beneficial effect on resisting hydrogen embrittlement tends to saturate. Therefore, Nb is selected at 0.01%–0.05%.

[0016] The inventors discovered through extensive preliminary research that the mass percentages of the chemical composition of Ta, Nb, and V meet the requirements of 0.03%≤Ta+Nb+V≤0.10% and 0.2≤(Ta+Nb) / V≤0.5, resulting in better size and quantity of precipitated phases.

[0017] Ti: Titanium is a strong deoxidizer, preferentially reacting with oxygen in molten steel to form fine, dispersed titanium oxides (such as Ti₂O₃ and TiO₂). These fine particles are suspended in the molten steel and subsequently promote grain refinement during solidification. Furthermore, trace amounts of Ti remaining in the molten steel during smelting enhance the Ta-Nb-V composite microalloying effect during subsequent heat treatment, increasing the number density of (Nb, Ta, V, Ti)₂C precipitates. However, excessively low Ti content results in poor deoxidation. Conversely, excessively high Ti content can easily cause oxide agglomeration, having a detrimental effect. Therefore, a Ti content of 0.018%–0.080% is selected.

[0018] Mg: Mg is a strong deoxidizer that reacts with existing inclusions in molten steel, refining their size and thus reducing the harmful effects of large inclusions. When the Mg content is too low, its effect is not significant. When the Mg content is too high, it can easily cause the molten steel to boil, posing a risk. Therefore, a Mg content of 0.006%–0.016% is selected.

[0019] Ca: Ca has a certain deoxidizing effect and can modify inclusions in steel, causing them to spheroidize. Simultaneously, the fed calcium, while modifying oxides, reacts with sulfur in the molten steel to form a CaS shell around the existing oxide core. If the Ca content is too low, the inclusion modification effect is not significant; if the Ca content is too high, it will lead to larger and harmful inclusions. Therefore, a Ca content of 0.006%–0.016% is selected.

[0020] Preferably, the mass percentages of the chemical composition of Ta, Nb, and V conform to the following: 0.04% ≤ Ta + Nb + V ≤ 0.06%.

[0021] In this invention, by controlling the mass percentage of the chemical composition of Ta, Nb, and V to meet the requirements of 0.04%≤Ta+Nb+V≤0.06%, the performance requirements can be met while reducing production costs.

[0022] Preferably, the mass percentages of the chemical composition of Ta, Nb, and V conform to the following: 0.06% ≤ Ta + Nb + V ≤ 0.10%.

[0023] This invention significantly improves performance by controlling the mass percentages of the chemical components of Ta, Nb, and V to be 0.06% ≤ Ta + Nb + V ≤ 0.10%.

[0024] Preferably, the mass percentage of the chemical composition of Mg and Ti conforms to a Mg / Ti ratio of 1:4.

[0025] This invention significantly improves performance by further controlling the mass percentage of Mg and Ti chemical components to match a Mg / Ti ratio of 1:4.

[0026] Preferably, the yield strength of the hydrogen-resistant and corrosion-resistant steel used for the geological hydrogen storage tank casing is ≥ 758 MPa, the hydrogen embrittlement sensitivity is ≤ 15% under a high-pressure hydrogen environment of 15 MPa, and the corrosion resistance meets the requirement of ≤ 0.024 mm / a.

[0027] The second technical solution adopted by the present invention to achieve the objective is as follows: a method for preparing the hydrogen-resistant and corrosion-resistant steel for the casing of a geological hydrogen storage tank, wherein raw materials are selected according to the preset chemical composition weight percentage, and then the raw materials are sequentially processed through steelmaking, continuous casting, heating, rolling and tempering processes to obtain the hydrogen-resistant and corrosion-resistant steel for the casing of a geological hydrogen storage tank; The steelmaking process includes converter smelting, LF refining, and VD vacuum treatment, with deep desulfurization carried out in the LF refining stage.

[0028] In LF refining, LF is short for Ladle Furnace.

[0029] Vacuum degassing (VD) is an out-of-furnace refining method that involves placing a ladle in a vacuum chamber, evacuating the ladle, and combining this with argon blowing and stirring at the bottom of the ladle to reduce the gas content in the molten steel, fine-tune its composition, and improve its cleanliness.

[0030] Preferably, during the LF refining stage, when the mass percentage of S in the molten steel drops to ≤ 0.005% and the oxygen level is between 20 and 100 ppm, an appropriate amount of ferrotitanium is added to make the mass percentage of Ti between 0.018% and 0.080%.

[0031] After deep desulfurization at the LF refining station, when the sulfur content of the molten steel drops to ≤ 0.005% and the oxygen level is between 20 and 100 ppm, an appropriate amount of ferrotitanium is added. This is because most of the oxygen in the molten steel has been removed at this stage, which can minimize the reaction time of titanium with oxygen and nitrogen in the air at high temperature, and prevent the formation of large-sized or agglomerated oxides.

[0032] Preferably, before the VD vacuum treatment, an inert gas is blown in and Ca-Mg wire is fed in, so that the mass percentage of Ca is controlled at 0.001% to 0.005%, the mass percentage of Mg is controlled at 0.006% to 0.016%, and the flow rate of the inert gas is ≤ 30L / min.

[0033] Preferably, the inert gas is argon.

[0034] Before VD vacuum treatment, inert gas is continuously blown into the bottom, and Ca-Mg wire is fed in according to a predetermined amount. This is because the oxygen content in the molten steel is at an extremely low level at this stage. The addition of Mg can further deoxidize the steel and combine with the existing Ti-rich oxides (from the previous deoxidation) in the molten steel to modify them into Mg-Ti-O ternary oxides. Ca can react with S and form a CaS shell around the existing oxide core, ultimately forming a Mg-Ti-O@CaS composite inclusion.

[0035] This invention employs Mg-Ti-Ca oxide metallurgical technology to modify inclusions. The sequential addition of Ti and Mg under a suitable oxygen atmosphere synergistically promotes oxide nucleation with Ti and refines oxide size with Mg, forming a high-density, fine Mg-Ti-O oxide "core." Simultaneously, the addition of Ca combines with S in the molten steel to form a CaS "shell" attached to the oxide nucleation site. This is the first successful modification of inclusions into a core-shell-like Mg-Ti-O@CaS composite inclusion, significantly increasing the proportion of core-shell inclusions in the steel and refining their size to near-micron dimensions. This significantly reduces the promoting effect of large inclusions on pitting corrosion and significantly improves corrosion resistance. Moreover, unlike the harmful effects of traditional inclusions, this inclusion, refined to the micron scale, no longer leads to hydrogen-induced crack initiation. Instead, it acts as a deep hydrogen trap to inhibit hydrogen embrittlement, simultaneously improving resistance to hydrogen embrittlement.

[0036] Preferably, the quenching and tempering process includes quenching and tempering treatment, with the quenching temperature being 890-940℃ and the holding time being 2-5 min; and the tempering temperature being 600-640℃ and the tempering time being 15-45 min.

[0037] The quenching temperature is 890-940℃ because composite (Nb, Ta, V)C carbides are most easily formed and have a higher precipitation density in this temperature range. This can simultaneously improve strength and resistance to hydrogen embrittlement through significant precipitation strengthening, grain refinement, and hydrogen trapping.

[0038] The present invention has the following beneficial effects: This invention employs a unique Ta-Nb-V composite microalloying composition to obtain high-density, dispersed composite (Nb, Ta, V, Ti)C precipitates in steel, which are smaller in size and more resistant to coarsening and growth. Therefore, it can achieve a significant precipitation strengthening effect and high strength. In addition, this type of composite carbide can provide a higher density of deep hydrogen trapping sites, thereby more significantly capturing diffusible hydrogen and inhibiting hydrogen embrittlement fracture.

[0039] In this invention, by controlling the ratio of Ta-Nb-V elements to satisfy 0.03%≤Ta+Nb+V≤0.10% and 0.5≤(Ta+Nb) / V≤2, the advantages of V element being relatively inexpensive and effectively promoting the formation of precipitated phases can be effectively utilized, while avoiding the problem of excessively high costs caused by excessively high Ta+Nb content.

[0040] The unique formulation and preparation method of this invention, combined with the sequential coupling of Mg-Ti-Ca composite treatment technology and Ta-Nb-V composite microalloying, fully leverages the promoting effect of residual Ti elements in the molten steel during the metallurgical process on the subsequent nucleation of microalloyed carbides, thereby achieving a performance improvement effect of 1+1>2. The developed geological hydrogen storage tank casing has a strength level of 110 KSI (there are currently no dedicated hydrogen storage casings of this strength level in China) and exhibits excellent resistance to hydrogen embrittlement: hydrogen embrittlement sensitivity ≤ 15% under 15 MPa high-pressure hydrogen environment. Attached Figure Description

[0041] Figure 1 The scanning electron microscope morphology of the microstructure of the steel matrix prepared in Example 1 of this invention; Figure 2 Scanning electron microscopy morphology and energy dispersive spectroscopy (EDS) analysis of the core-shell-like Mg-Ti-O@CaS inclusions in the steel matrix prepared in Example 1 of this invention; Figure 3 Transmission electron microscopy (TEM) morphology and elemental distribution EDS image of the (Nb, Ta, V, Ti)C precipitates in the steel matrix prepared in Example 1 of this invention. Figure 4 The quantitative statistical results are for the (Nb, Ta, V, Ti)C precipitates in the steel matrices prepared in Examples 1-4 and Comparative Examples 1-10. Figure 5 The quantitative statistical results are for inclusions in the steel matrices prepared in Examples 1-4 and Comparative Examples 1-10. Detailed Implementation

[0042] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0043] The preparation method of the hydrogen-resistant and corrosion-resistant steel for the casing of the geological hydrogen storage tank of the present invention includes the following steps: (1) Select raw materials according to the preset chemical composition weight percentage to make steel molten steel; (2) The molten steel is continuously cast to obtain a continuously cast billet; (3) The continuous casting billet is heated to 1230-1260℃ to obtain a heated continuous casting billet; (4) The heated continuous casting billet is rolled at a final rolling temperature of 870-900℃ and a rolling reduction of 30-40% to obtain rolled steel. (5) The rolled steel is subjected to quenching and high-temperature tempering to obtain the hydrogen-resistant and corrosion-resistant steel for the casing of the geological hydrogen storage tank.

[0044] In step (1), the chemical composition by mass percentage includes C: 0.28%–0.33%, Si: 0.02%–0.07%, Mn: 0.40%–0.70%, Cr: 0.80%–1.10%, Ni: 0.15%–0.25%, Mo: 0.40%–0.55%, Ta: 0.01%–0.03%, V: 0.01%–0.04%, Nb: 0.01%–0.05%, Mg: 0.006%–0.016%, Ti: 0.018%–0.080%, Ca: 0.001%–0.005%, P ≤0.020%, S ≤0.01%, with the remainder being Fe and unavoidable impurities; Furthermore, the mass percentages of the chemical composition of Ta, Nb, and V conform to 0.03%≤Ta+Nb+V≤0.10% and 0.5≤(Ta+Nb) / V≤2, while the mass percentages of the chemical composition of Mg and Ti conform to Mg / Ti of 1:3~5.

[0045] Steelmaking includes converter smelting, LF refining, and VD vacuum treatment.

[0046] After deep desulfurization at the LF refining station, when the S content of the molten steel drops to ≤ 0.01% and the oxygen level is 20-100 ppm, an appropriate amount of ferrotitanium is added to make the Ti content 0.018-0.080%.

[0047] Before VD vacuum treatment, keep the bottom purging with argon and feed Ca-Mg wire according to the predetermined amount, with Ca controlled at 0.001-0.005% and Mg content controlled at 0.006-0.016%, and argon flow rate ≤ 30 L / min.

[0048] In step (5), the quenching temperature is 890-940℃ and the holding time is 2-5 min; the tempering temperature is 600-640℃ and the tempering time is 15-45 min.

[0049] The hydrogen-resistant and corrosion-resistant steels for geological hydrogen storage tank casings in Examples 1-4 and Comparative Examples 1-10 were prepared according to the mass percentages in Table 1, and then processed using the following steps: steelmaking, continuous casting, heating, rolling, and quenching and tempering were performed sequentially to obtain the hydrogen-resistant and corrosion-resistant steels for geological hydrogen storage tank casings. The smelting process included converter smelting, LF refining, and VD vacuum treatment; specific quenching and tempering process parameters are shown in Table 2.

[0050] Table 1 lists the mass percentage of each element in the hydrogen-resistant and corrosion-resistant steel used for geological hydrogen storage tank casings in Examples 1-4 and Comparative Examples 1-10. Comparative Examples 1-6 have different compositions but the same manufacturing process as Example 1, while Comparative Examples 7-10 have the same compositions but different manufacturing processes than Example 3.

[0051] Table 1 shows the chemical composition (mass fraction %) of the embodiments and comparative examples of the present invention.

[0052] Table 2 shows the heat treatment process parameters for the embodiments and comparative examples of the present invention.

[0053] The performance of hydrogen-resistant and corrosion-resistant steel used for the casing of geological hydrogen storage tanks in Examples 1-4 and Comparative Examples 1-10 was tested. Tensile tests were conducted according to GB / T 228.1-2000, and hydrogen embrittlement sensitivity tests were conducted according to GB / T 34542.2-2018. Smooth, round rod-shaped samples were used in a 15 MPa high-pressure hydrogen environment with a strain rate of 10... -5 s -1 The test results are listed in Table 3. Corrosion resistance was demonstrated in a simulated brine solution containing trace amounts of oxygen (3 mg / L) (15 wt.% NaCl + 450-550 mg / L Ca). 2+ +30-35 mg / L Mg 2+ In the process, the corrosion cycle was 7 days, and the obtained corrosion rates are shown in Table 3.

[0054] Table 3 shows the mechanical, hydrogen embrittlement, and corrosion properties of the embodiments and comparative examples of the present invention.

[0055] As can be seen from Table 3, the yield strength of the hydrogen-resistant and corrosion-resistant steel used for the casing of the geological hydrogen storage tank in Examples 1-4 is above 758 MPa (110 KSI grade). It not only has excellent resistance to hydrogen embrittlement (i.e., hydrogen embrittlement sensitivity is as low as 15%), but also excellent corrosion resistance (i.e., corrosion rate is less than 0.025 mm / a), which meets the standard requirements. Figure 1 The image shows the scanning electron microscope (SEM) morphology of the steel matrix prepared in Example 1 of this invention; the microstructure characterization in the image shows that the steel microstructure is tempered sorbite. SEM images of Examples 2-4 are also shown. Figure 1 similar.

[0056] Figure 2 Scanning electron microscopy (SEM) morphology and energy dispersive spectroscopy (EDS) analysis of inclusions in the steel matrix prepared in Example 1 of this invention show that the inclusions are Mg-Ti-O@CaS composite inclusions with a core-shell structure and near-micron scale. The SEM morphology and EDS analysis of Examples 2-4 are also presented. Figure 2 similar.

[0057] Figure 3 The images show the transmission electron microscopy (TEM) morphology and elemental distribution (EDS) of the precipitated phase in the steel matrix prepared in Example 1 of this invention. The images show that the precipitated phase is a high-density, diffusely distributed nano-precipitated phase, specifically a (Nb, Ta, V, Ti)C composite precipitated phase. The TEM morphology and elemental distribution (EDS) images of Examples 2-4 are also shown. Figure 3 similar.

[0058] The hydrogen-resistant and corrosion-resistant steel used for the casing of the geological hydrogen storage tank in Comparative Example 1 did not contain Ta and Nb, and therefore did not meet the requirements of 0.03%≤Ta+Nb+V≤0.10% and 0.5≤(Ta+Nb) / V≤2, resulting in insufficient yield strength and resistance to hydrogen embrittlement.

[0059] The Ta content in the hydrogen-resistant steel used for the casing of the geological hydrogen storage tank in Comparative Example 2 is too high, failing to meet the requirements of 0.03%≤Ta+Nb+V≤0.10% and 0.5≤(Ta+Nb) / V≤2, resulting in insufficient resistance to hydrogen embrittlement.

[0060] The hydrogen-resistant and corrosion-resistant steel used for the casing of the geological hydrogen storage tank in Comparative Example 3 did not contain V, and did not meet the requirements of 0.03%≤Ta+Nb+V≤0.10% and 0.5≤(Ta+Nb) / V≤2, resulting in insufficient yield strength and resistance to hydrogen embrittlement.

[0061] The hydrogen-resistant steel used for the casing of the geological hydrogen storage facility in Comparative Example 4 has a high V content and does not meet the requirements of 0.03%≤Ta+Nb+V≤0.10% and 0.5≤(Ta+Nb) / V≤2, resulting in insufficient resistance to hydrogen embrittlement.

[0062] In Comparative Example 5, the hydrogen-resistant and corrosion-resistant steel used for the casing of the geological hydrogen storage facility did not contain Ca-Mg alloy wire, and the Ca and Mg contents were 0. As a result, the resistance to hydrogen embrittlement was insufficient, and the corrosion resistance was significantly insufficient.

[0063] In Comparative Example 6, Ca-Mg wire was fed into the hydrogen-resistant and corrosion-resistant steel used for the casing of the geological hydrogen storage facility. The Mg content was controlled at 0.006%, but the Ti addition was 0.010, and the Mg / Ti ratio did not meet the requirement of 1:3~1:5. As a result, the resistance to hydrogen embrittlement and the corrosion resistance were insufficient.

[0064] The quenching temperature of the hydrogen-resistant and corrosion-resistant steel used in the geological hydrogen storage casing of Comparative Example 7 was too high, resulting in insufficient resistance to hydrogen embrittlement.

[0065] The quenching temperature of the hydrogen-resistant and corrosion-resistant steel used for the casing of the geological hydrogen storage tank in Comparative Example 8 was too low, resulting in insufficient yield strength and resistance to hydrogen embrittlement.

[0066] The tempering temperature and time of the quenching and tempering treatment of the hydrogen-resistant and corrosion-resistant steel used in the casing of the geological hydrogen storage facility in Comparative Example 9 were too high and too long, resulting in insufficient yield strength.

[0067] The tempering temperature and time of the quenching and tempering treatment of the hydrogen-resistant and corrosion-resistant steel used in the geological hydrogen storage tank casing of Comparative Example 10 were too low and too short, resulting in insufficient resistance to hydrogen embrittlement.

[0068] Figure 4 The figures show the quantitative statistical results of (Nb, Ta, V, Ti)C precipitates in the steel matrices prepared in Examples 1-4 and Comparative Examples 1-10. As can be seen from the figures, compared to Examples 1-4, the microalloying element content is lower in the other comparative examples (except for Comparative Examples 2 and 4), resulting in lower precipitate density, which will adversely affect hydrogen embrittlement. In Comparative Examples 2 and 4, the precipitate density is also higher due to the excessively high content of microalloying elements Ta or V.

[0069] Figure 5 The figures show the quantitative statistical results of inclusions in the steel matrices prepared in Examples 1-4 and Comparative Examples 1-10. As can be seen from the figures, compared with the examples, there is less Mg-Ca in Comparative Example 5 and less Ti in Comparative Example 6, resulting in a smaller proportion of "core-shell" structures in the inclusions and larger sizes, which will have an adverse effect on hydrogen embrittlement and corrosion resistance.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydrogen-resistant and corrosion-resistant steel for casing of a geological hydrogen storage tank, characterized in that: Based on the mass percentage of chemical composition, it includes C: 0.28%–0.33%, Si: 0.02%–0.07%, Mn: 0.40%–0.70%, Cr: 0.80%–1.10%, Ni: 0.15%–0.25%, Mo: 0.40%–0.55%, Ta: 0.01%–0.03%, V: 0.01%–0.04%, Nb: 0.01%–0.05%, Mg: 0.006%–0.016%, Ti: 0.018%–0.080%, Ca: 0.001%–0.005%, P ≤0.020%, S ≤0.01%, with the remainder being Fe and unavoidable impurities; Furthermore, the mass percentages of the chemical composition of Ta, Nb, and V conform to 0.03%≤Ta+Nb+V≤0.10% and 0.5≤(Ta+Nb) / V≤2, and the mass percentages of the chemical composition of Mg and Ti conform to Mg / Ti of 1:3~5; The microstructure of the steel matrix is ​​tempered sorbite, with dispersed (Nb, Ta, V, Ti)C composite precipitates of 2-50 nm in size and Mg-Ti-O@CaS composite inclusions of 0.5-2 μm in size.

2. The hydrogen-resistant and corrosion-resistant steel for geological hydrogen storage tank casing according to claim 1, characterized in that: The mass percentages of the chemical composition of Ta, Nb, and V meet the requirement of 0.04% ≤ Ta + Nb + V ≤ 0.06%.

3. The hydrogen-resistant and corrosion-resistant steel for geological hydrogen storage tank casing according to claim 1, characterized in that: The mass percentages of the chemical composition of Ta, Nb, and V meet the requirement of 0.06% ≤ Ta + Nb + V ≤ 0.10%.

4. The hydrogen-resistant and corrosion-resistant steel for geological hydrogen storage tank casing according to claim 1, characterized in that: The chemical composition mass percentages of Mg and Ti conform to a Mg / Ti ratio of 1:

4.

5. The hydrogen-resistant and corrosion-resistant steel for geological hydrogen storage tank casing according to claim 1, characterized in that, The hydrogen-resistant and corrosion-resistant steel used for the casing of the geological hydrogen storage tank has a yield strength ≥ 758 MPa, a hydrogen embrittlement sensitivity ≤ 15% under a high-pressure hydrogen environment of 15 MPa, and a corrosion resistance of ≤ 0.024 mm / a.

6. A method for preparing hydrogen-resistant and corrosion-resistant steel for casing of a geological hydrogen storage tank as described in any one of claims 1-5, characterized in that: Raw materials are selected according to the preset chemical composition weight percentage, and then the steelmaking process, continuous casting process, heating process, rolling process, and tempering process are carried out in sequence to obtain the hydrogen-resistant and corrosion-resistant steel for the casing of the geological hydrogen storage tank. The steelmaking process includes converter smelting, LF refining, and VD vacuum treatment, with deep desulfurization carried out in the LF refining stage.

7. The preparation method according to claim 6, characterized in that, During the LF refining stage, when the S mass percentage in the molten steel drops to ≤ 0.005% and the oxygen level is between 20 and 100 ppm, an appropriate amount of ferrotitanium is added to make the Ti mass percentage between 0.018% and 0.080%.

8. The preparation method according to claim 6, characterized in that, Before VD vacuum treatment, inert gas is blown in and Ca-Mg wire is fed in, so that the mass percentage of Ca is controlled at 0.001% to 0.005%, the mass percentage of Mg is controlled at 0.006% to 0.016%, and the flow rate of inert gas is ≤ 30 L / min.

9. The preparation method according to claim 6, characterized in that, The tempering process includes quenching and tempering treatments. The quenching temperature is 890-940℃ and the holding time is 2-5 min. The tempering temperature is 600-640℃ and the tempering time is 15-45 min.

Images