High-strength hydrogen-resistant steel and preparation method thereof

Abstract

The invention provides high-strength hydrogen-resistant steel and a preparation method thereof.The preparation method of the high-strength hydrogen-resistant steel comprises the following steps that S1, a blank is obtained through smelting; s2, the blank is subjected to continuous casting or die casting, and a casting blank is obtained; s3, the casting blank is heated and rolled, and steel is obtained; and S4, the steel is quenched and cooled to the room temperature or below, then tempering treatment is conducted, and the high-strength hydrogen-resistant steel is obtained. Wherein the heat preservation temperature before quenching ranges from 800 DEG C to 820 DEG C, the temperature of the tempering treatment ranges from 600 DEG C to 630 DEG C, and the heat preservation time of the tempering treatment ranges from 50 min to 70 min. The high-strength hydrogen-resistant steel provided by the invention has both high strength and high hydrogen embrittlement resistance.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen-resistant steel technology, specifically relating to a high-strength hydrogen-resistant steel and its preparation method. Background Technology

[0002] Modern industry demands increasingly higher material properties, especially in the automotive, aerospace, and energy sectors, requiring materials that combine high strength with good ductility. However, traditional high-strength steels are prone to hydrogen-induced cracking in hydrogen environments, limiting their applications. Therefore, developing high-strength steels with excellent hydrogen resistance has become a research hotspot.

[0003] While austenitic steels possess excellent hydrogen resistance in existing technologies, their low yield strength makes them insufficient to meet the demands of modern industry for lightweight and high strength. Introducing martensite as a reinforcing phase is a primary method for improving the mechanical properties of steel materials; however, hydrogen atoms preferentially accumulate in the martensitic phase and its interaction regions with heterogeneous interfaces, accelerating crack propagation and potentially leading to a significant decrease in mechanical properties even in low-hydrogen-content environments. Therefore, developing steels with both high strength and high resistance to hydrogen embrittlement is of significant engineering importance for improving the safety of hydrogen storage and transportation. Summary of the Invention

[0004] In view of this, the present invention provides a high-strength hydrogen-resistant steel and its preparation method, which can combine high strength and high resistance to hydrogen embrittlement.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing high-strength hydrogen-resistant steel, comprising the following steps: S1. Obtain the billet through smelting; S2. The billet is continuously cast or die-cast to obtain a cast billet; S3. The cast billet is heated and rolled to obtain steel. S4. Quench the steel, cool it to below room temperature, and then temper it to obtain high-strength hydrogen-resistant steel; wherein the holding temperature before quenching is 800~820 ℃, the temperature of the tempering treatment is 600~630 ℃, and the holding time of the tempering treatment is 50~70 min.

[0006] Preferably, in step S1, the smelting includes sequentially performing primary smelting in an electric arc furnace or converter, ladle refining, and vacuum degassing.

[0007] Preferably, the billet comprises, by mass fraction: C: 0.02~0.05%, Si: 0.18~0.28%, Mn: 0.55~0.75%, P≤0.005%, S≤0.003%, O≤0.003%, Ni: 8.5~9.5%, Mo: 0.003~0.006%, with the balance being Fe and unavoidable impurities.

[0008] Preferably, in step S2, the continuous casting is carried out under protective casting conditions, using low superheat casting and dynamic light pressure control.

[0009] Preferably, the superheat of the low superheat casting is 5~25 °C; and / or, The solid content in the dynamically lightly compressed section of the billet is 0.6~0.9; and / or, The protective casting process includes argon-protected casting throughout.

[0010] Preferably, in the continuous casting, a protective slag is used, wherein the basicity of the protective slag is greater than 1.2, and the mass fraction of Al2O3 is less than 5%; and / or, Electromagnetic stirring is used in the continuous casting process.

[0011] Preferably, in step S3, the billet is heated to 1150~1200 ℃.

[0012] Preferably, in step S3, the rolling process includes sequential roughing and finishing rolling, wherein: The initial rolling temperature of the roughing mill is 1080~1150 ℃; and / or, The single-pass reduction rate of the last three roughing passes is greater than or equal to 15%; and / or, The thickness to be heated is greater than or equal to 1.8H, where H is the finished thickness; and / or, The initial rolling temperature of the finishing mill is 950~980 ℃.

[0013] Secondly, the present invention also provides a high-strength hydrogen-resistant steel, which is prepared according to the method for preparing high-strength hydrogen-resistant steel.

[0014] Preferably, the microstructure of the high-strength hydrogen-resistant steel includes a new phase martensite with a short rod-like shape and quenched martensite, wherein the volume fraction of the new phase martensite is 35-45%, and the new phase martensite contains reverse-transformed austenite, which is nanoscale and porous.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The method for preparing high-strength hydrogen-resistant steel provided by the present invention limits the holding temperature before quenching and the temperature and time of tempering treatment, which enables the high-strength hydrogen-resistant steel to have both high strength and high resistance to hydrogen embrittlement. Attached Figure Description

[0016] Figure 1 Metallographic image of the high-strength hydrogen-resistant steel obtained in Example 2 of this invention; Figure 2 Metallographic image of the high-strength hydrogen-resistant steel prepared in Comparative Example 1 of this invention; Figure 3 This is a metallographic image of the high-strength hydrogen-resistant steel prepared in Comparative Example 2 of the present invention. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0018] In a first aspect, the present invention provides a method for preparing high-strength hydrogen-resistant steel, comprising the following steps: S1. Obtain the billet through smelting; S2. The billet is continuously cast or die-cast to obtain a cast billet; S3. The cast billet is heated and rolled to obtain steel. S4. Quench the steel, cool it to below room temperature, and then temper it to obtain high-strength hydrogen-resistant steel; wherein the holding temperature before quenching is 800~820 ℃, the temperature of the tempering treatment is 600~630 ℃, and the holding time of the tempering treatment is 50~70 min.

[0019] In this invention, the pre-quenching holding temperature is 800~820 ℃, which effectively avoids significant growth of the original austenite grains, eliminates the adverse effects of coarse grains on mechanical properties, and helps ensure that the material has good comprehensive mechanical properties. At the same time, it can promote the solid solution of alloying elements, reduce the tendency of element segregation, and make the material composition more uniform, which is conducive to improving the stability and consistency of the overall performance of the material. The tempering temperature is 600~630 ℃, and the tempering holding time is 50~70 min, which is conducive to the formation of a new phase of martensite. The new phase of martensite has high strength, which can ensure the overall macroscopic performance of the material. The reverse austenite distributed inside the new phase of martensite can act as a hydrogen trap network, which has the functions of hydrogen capture and hydrogen inhibition, and can improve the plasticity and toughness of the material, enhancing the performance and reliability of the material in hydrogen-containing environments. Thus, the high-strength hydrogen-resistant steel produced can have both high strength and high resistance to hydrogen embrittlement. In addition, the tempering temperature is relatively low, which is conducive to energy conservation, emission reduction and production cost reduction.

[0020] It should be noted that after the billet is heated, it can be kept at a constant temperature to reduce surface oxidation. During the heating process, an atmosphere protection can be used to reduce surface oxidation. The protective gas can be nitrogen or argon. After the billet is heated and taken out of the furnace, it can be descaled by high-pressure water and then rolled. The rolling can be atmosphere protection rolling or coating protection rolling. The coating material can be high-temperature resistant glass-based protective coating or ceramic-based protective coating. The coating thickness can be 0.5~2 mm. After quenching, it can be rapidly cooled to below room temperature. The quenching medium can be water, polymer aqueous solution or salt bath.

[0021] In some embodiments, in step S1, the smelting includes sequentially performing primary smelting in an electric arc furnace or converter, ladle refining, and vacuum degassing.

[0022] In some embodiments, the billet comprises, by mass fraction: C: 0.02~0.05%, Si: 0.18~0.28%, Mn: 0.55~0.75%, P≤0.005%, S≤0.003%, O≤0.003%, Ni: 8.5~9.5%, Mo: 0.003~0.006%, with the balance being Fe and unavoidable impurities.

[0023] It should be noted that a carbon (C) content of 0.02~0.05 wt% imparts good toughness and weldability to the material. Low carbon content reduces carbide formation, which, while decreasing hardness and strength, improves plasticity and toughness. It also reduces hardening and cracking tendency in the heat-affected zone during welding, making it suitable for applications requiring high weld quality. Phosphorus (P) increases cold brittleness, while sulfur (S) causes hot brittleness. A phosphorus content of ≤0.005 wt% and a sulfur content of ≤0.003 wt% improve steel purity, toughness, fatigue resistance, and corrosion resistance. An oxygen (O) content of ≤0.003 wt% helps reduce oxide inclusions, improving steel quality and properties, such as fatigue performance and toughness. A nickel (Ni) content of 8.5~9.5% is also important. The silicon (Si) content is 0.18~0.28 wt%, and the manganese (Mn) content is 0.55~0.75 wt%. Within a reasonable range, silicon can improve the strength and hardness of steel and also has a certain deoxidizing effect. Manganese can improve the strength, toughness and hardenability of steel and can also form MnS with sulfur, thus reducing the harmful effects of sulfur.

[0024] In some embodiments, in step S2, the continuous casting is carried out under protective casting conditions, employing low superheat casting and dynamic light reduction control.

[0025] In some embodiments, the superheat of the low superheat casting is 5~25 °C.

[0026] In some embodiments, the solid fraction (fs) in the dynamically lightly compressed interval slab is 0.6 to 0.9.

[0027] In some embodiments, the protective casting includes argon-protected casting throughout the process.

[0028] In some embodiments, a protective slag is used in the continuous casting process, wherein the basicity of the protective slag is greater than 1.2 and the mass fraction of Al2O3 is less than 5%.

[0029] In some embodiments, electromagnetic stirring is employed in the continuous casting process.

[0030] In some embodiments, in step S3, the billet is heated to 1150~1200 °C.

[0031] In some embodiments, in step S3, the rolling process includes sequential roughing and finishing rolling, wherein the initial rolling temperature of the roughing rolling is 1080~1150 ℃.

[0032] In some embodiments, the single-pass reduction rate of the last three passes of the roughing mill is greater than or equal to 15%.

[0033] In some embodiments, the thickness to be heated is greater than or equal to 1.8H, where H is the finished product thickness.

[0034] In some embodiments, the initial rolling temperature of the finishing mill is 950~980 ℃.

[0035] Secondly, the present invention also provides a high-strength hydrogen-resistant steel, which is prepared according to the method for preparing high-strength hydrogen-resistant steel.

[0036] In some embodiments, the microstructure of the high-strength hydrogen-resistant steel includes a new phase martensite with a short rod morphology and a fan-shaped distribution, and quenched martensite, wherein the volume fraction of the new phase martensite is 35-45%, and the new phase martensite contains reverse-transformed austenite, which is nanoscale and porous.

[0037] Example 1 A method for preparing high-strength hydrogen-resistant steel includes the following steps: (1) Smelting: A converter is used for smelting. High-quality low-phosphorus and low-sulfur scrap steel, pig iron and nickel-based materials are added into the furnace in proportion. After oxygen blowing decarburization, ladle refining (LF) and vacuum degassing (VD) treatment, billet is obtained. The composition of billet is: C: 0.02 wt%, Si: 0.18 wt%, Mn: 0.75 wt%, P≤0.005 wt%, S≤0.003 wt%, O≤0.003 wt%, Ni: 8.5 wt%, Mo: 0.003 wt%, with the balance being Fe and unavoidable impurity elements; (2) Continuous casting: The billet is continuously cast under protective casting conditions, with low superheat casting and dynamic light reduction control, and argon protection casting throughout the process; the casting superheat is controlled at 15℃; the light reduction range is controlled at fs=0.80, where fs is the solid phase content in the billet; low Al2O3 and high basicity protective slag are used, and electromagnetic stirring is applied to reduce center segregation; (3) Heating: The billet is heated to 1150℃ and kept at that temperature until it is homogeneous. An atmosphere is used to protect the surface during the heating process to reduce surface oxidation. (4) Rolling: After the billet is taken out of the furnace, it is descaled by high pressure water and then subjected to two-stage controlled rolling of rough rolling and finish rolling. The initial rolling temperature of rough rolling is 1080℃, and the single-pass reduction rate of the three passes after rough rolling is 20%. The thickness to be heated is 1.8H, where H is the finished thickness. The finish rolling adopts high-temperature rolling, and the initial rolling temperature is 950℃.

[0038] (5) Heat treatment: The rolled steel is quenched at a holding temperature of 800℃ before quenching, and then rapidly cooled to below room temperature. It is then tempered at a tempering temperature of 600℃ for 50 min to obtain high-strength hydrogen-resistant steel.

[0039] Example 2 A method for preparing high-strength hydrogen-resistant steel is the same as that in Example 1, except that in step (5), the pre-quenching holding temperature is 810℃, the tempering temperature is 620℃, and the holding time is 60 min.

[0040] Example 3 A method for preparing high-strength hydrogen-resistant steel is the same as that in Example 1, except that in step (5), the pre-quenching holding temperature is 820 ℃, the tempering temperature is 630 ℃, and the holding time is 70 min.

[0041] Comparative Example 1 A method for preparing high-strength hydrogen-resistant steel is the same as that in Example 2, except that the tempering temperature in step (5) is 540°C.

[0042] Comparative Example 2 A method for preparing high-strength hydrogen-resistant steel is the same as that in Example 2, except that the tempering temperature in step (5) is 580°C.

[0043] Comparative Example 3 A method for preparing high-strength hydrogen-resistant steel is the same as that in Example 2, except that the tempering temperature in step (5) is 640°C.

[0044] Comparative Example 4 A method for preparing high-strength hydrogen-resistant steel is the same as that in Example 2, except that in step (5), the tempering holding time is 40 min.

[0045] Comparative Example 5 A method for preparing high-strength hydrogen-resistant steel is the same as that in Example 2, except that in step (5), the tempering holding time is 80 min.

[0046] Performance Tests and Results The high-strength hydrogen-resistant steels prepared in Example 2, Comparative Example 1, and Comparative Example 2 were subjected to metallographic analysis according to the national standard GB / T 15749-2008. The results are shown in the figure. Figures 1-3 .

[0047] The high-strength hydrogen-resistant steels prepared in Examples 1-3 and Comparative Examples 1-7 were subjected to tests for mechanical properties and hydrogen embrittlement properties. The mechanical properties (yield strength and tensile strength) were tested according to GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature", and the hydrogen embrittlement properties (hydrogen-induced plasticity loss rate) were tested according to the constant strain rate hydrogen embrittlement sensitivity method described in GBT15970.1-2018 "Corrosion of metals and alloys - Stress corrosion testing". The results are shown in Table 1.

[0048] Table 1. Mechanical properties and hydrogen embrittlement resistance of high-strength hydrogen-resistant steels prepared in each embodiment and comparative example.

[0049] Depend on Figures 1-3 It can be seen that the microstructure in Example 2 contains a large number of finely interwoven, grayish-bright microstructures (short rod-shaped, fan-shaped distribution), while the microstructures in Comparative Examples 1 and 2 are smaller in number and more elongated in size. The finely interwoven, grayish-bright microstructures, as a new phase of martensite, have a favorable distribution that can strengthen the microstructure and improve its uniformity.

[0050] As shown in Table 1, regarding strength properties, the tensile strength and yield strength of the high-strength hydrogen-resistant steels prepared in Examples 1-3 are significantly higher than those in Comparative Examples 1-3, both in the uncharged and hydrogen-charged states. Regarding resistance to hydrogen embrittlement, the hydrogen-charged plasticity loss rate of the high-strength hydrogen-resistant steels prepared in Examples 1-3 is significantly lower than that in Comparative Examples 1-3. Regarding plasticity, the elongation of the high-strength hydrogen-resistant steels prepared in Examples 1-3 decreases less from the uncharged to the hydrogen-charged state, and is significantly lower than that in Comparative Examples 2-5. This indicates that the high-strength hydrogen-resistant steel provided by this invention possesses high strength and high resistance to hydrogen embrittlement, and exhibits minimal plasticity loss after hydrogen charring.

[0051] Unless otherwise specified, all raw materials used in this invention are existing substances that can be purchased directly from the market.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. 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 method for producing a high-strength hydrogen-resistant steel, characterized by, The method comprises the following steps: S1, obtaining a billet by smelting; S2, continuously casting or die casting the billet to obtain a casting billet; S3, heating the casting billet and rolling to obtain a steel material; S4, quenching the steel material, cooling to below room temperature, and then tempering to obtain a high-strength hydrogen-resistant steel; wherein the holding temperature before quenching is 800-820 ℃, the tempering temperature is 600-630 ℃, and the holding time of the tempering is 50-70 min.

2. The method of producing a high-strength hydrogen-resistant steel according to claim 1, characterized by, In step S1, the smelting comprises sequentially performing arc furnace or converter preliminary smelting, secondary refining outside the furnace, and vacuum degassing.

3. The method of producing a high-strength hydrogen-resistant steel according to claim 1, characterized by, The billet comprises, by mass fraction: C: 0.02-0.05 %, Si: 0.18-0.28 %, Mn: 0.55-0.75 %, P≤0.005 %, S≤0.003 %, O≤0.003 %, Ni: 8.5-9.5 %, Mo: 0.003-0.006 %, and the balance of Fe and inevitable impurities.

4. The method of claim 1, wherein the high-strength, hydrogen-resistant steel is prepared by the steps of: In step S2, the continuous casting is performed under protective pouring conditions, and low superheat pouring and dynamic soft reduction control are adopted. ​ 5. The method of producing a high-strength hydrogen-resistant steel according to claim 4, characterized in that, The superheat of the low superheat pouring is 5-25 ℃; and / or, The solid phase fraction in the casting billet in the dynamic soft reduction interval is 0.6-0.9; and / or, The protective pouring comprises full-range argon protective pouring.

6. The method of producing a high-strength hydrogen-resistant steel according to claim 4, characterized by, In the continuous casting, a protective slag is used, wherein the basicity of the protective slag is greater than 1.2, and the mass fraction of Al2O3 is less than 5 %; and / or, In the continuous casting, electromagnetic stirring is adopted.

7. The method of claim 1, wherein the high-strength, hydrogen-resistant steel is prepared by the steps of: In step S3, the casting billet is heated to 1150-1200 ℃. ​ 8. The method of claim 1, wherein the high-strength, hydrogen- resistant steel is prepared by the steps of: In step S3, the rolling comprises sequentially performing rough rolling and finish rolling, wherein: ​ The rough rolling temperature is 1080-1150 ℃; and / or, The single-pass reduction rate of the last three passes of the rough rolling is greater than or equal to 15 %; and / or, The thickness after waiting for a certain time is greater than or equal to 1.8H, wherein H is the finished product thickness; and / or, The finish rolling temperature is 950-980 ℃.

9. A high-strength hydrogen-resistant steel, characterized in that, The high-strength hydrogen-resistant steel is prepared by the method according to any one of claims 1-8.

10. The high strength hydrogen resistant steel according to claim 9, characterized in that, The microstructure of the high-strength hydrogen-resistant steel comprises new-phase martensite in a feather-like distribution in short rod form and quenched martensite, wherein the volume fraction of the new-phase martensite is 35-45 %, and the new-phase martensite is distributed with reverted austenite, which is in nanometer size and in a porous form.

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