Vanadium-containing high manganese steel, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a vanadium-containing high manganese steel, and a preparation method therefor and the use thereof. By combining chemical components with a controlled rolling process, the steel exhibits an excellent ultra‑low‑temperature resistance and a strong resistance to hydrogen damage, while avoiding the addition of multiple precious metal elements and simplifying the process. The present application has wide application prospects and is more suitable for manufacturing storage and transport containers for ultra-low temperature media in complex environments.

Description

A vanadium-containing high-manganese steel, its preparation method and application Technical Field

[0001] This invention relates to a vanadium-containing high-manganese steel, its preparation method, and its applications, and more particularly to a vanadium-containing high-manganese steel with excellent low-temperature performance, its preparation method, and its applications. Background Technology

[0002] Containers for storing and transporting cryogenic media are usually made of nickel steel and austenitic stainless steel. Due to the limited reserves of Ni ore, nickel steels such as Invar steel (36% Ni), 316 stainless steel (12% Ni), and 9% Ni steel are less economical. Austenitic stainless steel has low strength and a large coefficient of expansion, which cannot meet the requirements for use in extreme low-temperature environments of -269℃.

[0003] CN104894471 discloses a high-manganese, high-alumina vanadium-containing non-magnetic steel plate with the following chemical composition: C: 0.14%–0.20%, Mn: 21.50%–25.00%, Al: 1.50%–2.50%, V: 0.04%–0.10%, N < 0.05%, with the balance being Fe and unavoidable impurities. Its yield strength is only 280–300 MPa, and its tensile strength is 550–700 MPa, which is insufficient to meet the high-strength requirements of steel plates.

[0004] CN102409227 discloses a hot-rolled strip steel with low relative magnetic permeability. Its chemical composition is: C: 0.25%–0.35%, Si: 0.5%–0.6%, Mn: 25%–26%, Al: 3.8%–4.2%, V: 0.06%–0.10%, P: 0.02%–0.03%, S: 0.02%–0.03%, with the remainder being Fe and unavoidable impurities. The excessively high Al content easily leads to hot-rolling cracks, reducing the yield.

[0005] CN108929993 discloses a microalloyed, high-strength, high-ductility, non-magnetic steel plate with the following chemical composition: C: 0.10%–0.20%, 0 < Si ≤ 0.4%, Mn: 20%–26%, Al: 2.0%–3.0%, Ti: 0.01%–0.02%, Nb: 0.04%–0.09%, with the balance being Fe and other unavoidable impurities. However, its impact energy at -196℃ is only ≥110J, which is insufficient to meet the storage and transportation requirements of cryogenic media such as liquid hydrogen and liquid helium. Summary of the Invention

[0006] Objectives of this invention: The first objective is to provide a vanadium-containing high-manganese steel with high strength and excellent low-temperature performance. The second objective is to provide a method for preparing the aforementioned high-manganese steel. The third objective is to provide an application of the aforementioned high-manganese steel in ultra-low temperature environments.

[0007] Technical solution: The vanadium-containing high-manganese steel of the present invention, by weight percentage, comprises C: 0.35%–0.55%, Si: 0.11%–0.22%, Mn: 22.5%–25.5%, P≤0.020%, S≤0.005%, Cr: 3.0%–4.0%, V: 0.03%–0.10%, Alt: 0.01%–0.10%, Ca: 0.0003%–0.0050%, with the balance being Fe and other unavoidable impurities.

[0008] Preferably, the vanadium-containing high-manganese steel composition, by weight percentage, comprises C: 0.43%, Si: 0.17%, Mn: 24.0%, Cr: 3.6%, V: 0.08%, Alt: 0.06%, Ca: 0.002%, with the balance being Fe and unavoidable impurity elements.

[0009] Preferably, the vanadium-containing high-manganese steel composition, by weight percentage, comprises C: 0.35%, Si: 0.11%, Mn: 22.5%, Cr: 3.0%, V: 0.03%, Alt: 0.01%, Ca: 0.0003%, with the balance being Fe and unavoidable impurity elements.

[0010] Preferably, the vanadium-containing high-manganese steel composition, by weight percentage, comprises C: 0.55%, Si: 0.22%, Mn: 25.5%, Cr: 4.0%, V: 0.10%, Alt: 0.10%, Ca: 0.005%, with the balance being Fe and unavoidable impurity elements.

[0011] When used as a structural material in an ultra-low temperature environment of -269℃, the material's mechanical properties are subject to high requirements. Therefore, as an ultra-low temperature structural material, it is necessary to redesign the alloy composition to improve mechanical properties while reducing material costs, thus making it more suitable for practical applications.

[0012] The composition design principle of the vanadium-containing high-manganese steel described in this invention is as follows:

[0013] Austenitic microstructures possess excellent strength, plasticity, and toughness characteristics, along with lower service temperatures. While adding high Ni content can achieve an austenitic microstructure, such as 316 austenitic stainless steel with 12% Ni content, the alloy cost is high. Mn can inhibit the transformation of austenite to martensite and can therefore be used as a substitute for Ni to obtain an austenitic microstructure. Since the effect of Mn on austenite stability is approximately half that of Ni, the Mn content in the ultra-low temperature steel of this invention is preferably 22.5% to 25.5%, more preferably 24.0%.

[0014] Specifically, this invention, while obtaining an austenitic matrix structure, preferably adds a certain amount of V, and in conjunction with a corresponding rolling process, forms a dispersed V carbonitride precipitate phase. V can effectively refine the grains and improve the strength and toughness of high-manganese steel. Simultaneously, the refined grains and dispersed carbonitride distribution can reduce the initiation and propagation of fatigue cracks in high-manganese steel under alternating stress, thereby improving its fatigue resistance and enhancing its reliability under dynamic load conditions. To enable the cryogenic steel of this invention to have higher resistance to hydrogen damage when used in the construction of liquid hydrogen storage tanks, the dispersed V carbonitride precipitate phase also acts as a hydrogen trap to hinder hydrogen atom diffusion. Through 10 -6 Quantitative characterization was performed using strain rate tensile tests, and the sensitivity of the ultra-low temperature steel of the present invention to a hydrogen environment was ≤0.15. The V content in the ultra-low temperature steel of the present invention is preferably 0.03% to 0.10%, more preferably 0.08%.

[0015] C has a strong austenite stabilizing effect and is an effective element for improving austenite stability. Furthermore, C can hinder dislocation movement and increase strength. From the perspective of austenite stabilization, the addition of C can increase the stacking fault energy of austenite, causing austenite to twinnize under strain instead of undergoing a martensitic phase transformation. The strain-induced twinning mechanism of austenite can significantly improve plasticity. The C content in the ultra-low temperature steel of this invention is preferably 0.35% to 0.55%, more preferably 0.43%.

[0016] Although Cr is a ferrite-forming element, it can lower the martensite transformation temperature, thereby improving the stability of austenite. Excessive Cr content leads to intensified carbide precipitation and reduced toughness. Therefore, the Cr content in the ultra-low temperature steel of this invention is preferably 3.0% to 4.0%, more preferably 3.6%.

[0017] This invention achieves a highly stable austenitic microstructure by adding 0.43% C, 24.0% Mn, and 3.6% Cr. Even after pre-exposing the microstructure to a true strain of 0.35 and then subjecting it to cryogenic treatment at -269℃, martensite remains absent. Simultaneously, the stacking fault energy of the austenite at -269℃ is controlled to be between 18 and 21 mJ·m. -2 The combination of dislocation and twinning achieves a balance between strength and toughness, resulting in the ultra-low temperature steel of this invention having a Charpy impact absorption energy ≥60J at -269℃.

[0018] In addition to the aforementioned chemical components, this invention has optimized the types and contents of other added elements. Si can provide a certain degree of solid solution strengthening, but Si segregation at grain boundaries weakens grain boundaries and increases intergranular brittleness. Furthermore, Si reduces plasticity. Therefore, this invention preferably controls the Si content to 0.11%–0.22%, more preferably 0.17%. Al, as a deoxidizing element in the manufacturing process, can also improve the performance of welded joints, but excessive addition easily forms coarse precipitates and impairs toughness. Therefore, this invention preferably controls the Al content to 0.01%–0.10%, more preferably 0.006%. Ca can react with oxygen and sulfur in steel to form stable compounds such as CaO and CaS. These compounds can float to the surface of the molten steel and be removed, thereby reducing the oxygen and sulfur content in the steel and improving the purity of the steel. At the same time, a small amount of Ca can change the morphology and distribution of inclusions in the steel, reduce the adverse effects of inclusions on the steel properties, and improve the toughness and plasticity of the steel. Therefore, the present invention preferably controls the Ca content at 0.0003% to 0.0050%, more preferably 0.002%.

[0019] It should be noted that the actual content of alloying elements during material manufacturing fluctuates within a small range near the design range, which is an unavoidable fluctuation in normal industrial production. Although this invention clearly specifies the content range of each element, within a reasonable deviation range, it will not significantly affect the effectiveness of this invention.

[0020] Preferably, the microstructure of the vanadium-containing high-manganese steel is a fully austenitic structure.

[0021] Further preferably, in the microstructure of the vanadium-containing high-manganese steel, more than 95% of the volume is austenitic.

[0022] Preferably, the thickness of the vanadium-containing high-manganese steel is 15-50 mm.

[0023] Preferably, the vanadium-containing high-manganese steel has a room temperature yield strength Rp0.2 ≥ 450 MPa, a room temperature tensile strength Rm ≥ 800 MPa, and a room temperature elongation after fracture ≥ 50%.

[0024] Preferably, the vanadium-containing high-manganese steel has a yield strength Rp0.2 at -269℃ ≥ 1000MPa, a tensile strength Rm at -269℃ ≥ 1400MPa, and an elongation at -269℃ ≥ 46%.

[0025] Preferably, the vanadium-containing high-manganese steel has an impact energy Akv ≥ 150 J at -196℃ and an impact energy Akv ≥ 60 J at -269℃.

[0026] The method for preparing vanadium-containing high-manganese steel according to the present invention includes the following steps:

[0027] (1) Heating: Heating temperature 1160~1210℃, total furnace time 1.5~1.7min / mm×bill thickness;

[0028] (2) Descaling: Remove the iron oxide scale from the heated billet. The high-pressure water pressure is 22-24 MPa.

[0029] (3) Rolling: The initial rolling temperature is 1060~1100℃, and the final rolling temperature is 900~930℃;

[0030] (4) Cooling: The inlet water temperature is 880~910℃, the outlet water temperature is 130~240℃, and the cooling rate is 27~48℃ / s.

[0031] The heating process uses a walking beam furnace, and the rolled steel plate is cooled by ACC cooling. The thickness of the rolled steel plate is 15-50mm.

[0032] The preparation principle of the vanadium-containing high-manganese steel of the present invention is as follows:

[0033] To achieve sufficient grain refinement and strain accumulation through thermomechanical rolling, and thus sufficient strength in the finished steel plate, a sufficient compression ratio is required in the selection of slab thickness, i.e., the ratio of slab thickness (H) to finished steel plate thickness (h) (H / h). This invention controls the compression ratio between 6 and 12.

[0034] Because the thermal conductivity of the ultra-low temperature steel of this invention is only about one-third that of ordinary low-alloy steel, it is necessary to ensure that slabs of different thicknesses have sufficient furnace heating time to ensure complete austenitization. This invention controls the furnace time at (1.5–1.7 min / mm) × H, where H is the slab thickness. For example, when the slab thickness is 220 mm, the furnace time is 330–374 min.

[0035] After being heated in a walking beam furnace, the slabs are removed from the furnace and then pass through a descaling box to remove iron oxide scale. High-pressure water at a pressure of 22-24 MPa is used to ensure the descaling effect.

[0036] The slab is descaled in a descaling box before rolling. The initial rolling temperature is 1060–1100℃, and the final rolling temperature is controlled at a relatively low level, i.e., 900–930℃. Thermomechanical rolling refines the austenite grains, accumulates sufficient strain, and improves the strength of the finished steel plate. Sufficient slab thickness is beneficial for improving the thermomechanical rolling effect.

[0037] After rolling, the steel plate enters an ultra-fast cooling system for high-pressure water cooling. The inlet water temperature is 880–910℃, and the cooling rate is 17–48℃ / s to the outlet water temperature of 130–240℃. The accelerated cooling serves two purposes: firstly, it preserves the accumulated thermomechanical rolling strain and improves the strength of the steel plate; secondly, it inhibits carbide precipitation and improves the plasticity of the steel plate.

[0038] The vanadium high-manganese steel described in this invention is used in the manufacture of storage and transportation containers or pipelines for liquefied ethylene, liquefied natural gas, liquid hydrogen or liquid helium, specifically in terrestrial, marine or aerospace environments.

[0039] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0040] This invention, through a combination of chemical composition and rolling process, produces a high-manganese steel with excellent resistance to ultra-low temperatures and hydrogen damage. It exhibits a Charpy impact energy ≥60J at -269℃, while also being free of precious metals such as Ni / Mo / Cu, containing fewer alloying elements, and eliminating post-processing steps, resulting in significant economic advantages. Its applications are broad, encompassing the storage and transportation of various cryogenic media such as liquefied ethylene, liquefied natural gas, liquid hydrogen, and liquid helium, and it is suitable for diverse and complex environments including land, sea, and air. Attached Figure Description

[0041] Figure 1 is a microstructure diagram of the steel plate prepared in Example 1. Detailed Implementation

[0042] The technical solution of the present invention will be further described below with reference to the embodiments.

[0043] The testing of yield strength, tensile strength, elongation after fracture, and impact energy shall be conducted in accordance with GB / T 228.1-2021 Metallic materials, tensile testing - Part 1: Test method at room temperature, GB / T 228.3-2019 Metallic materials, tensile testing - Part 3: Test method at low temperature, GB / T 228.4-2019 Metallic materials, tensile testing - Part 4: Test method in liquid helium, and GB / T 229-2020 Metallic materials, Charpy pendulum impact test method.

[0044] Example 1

[0045] An economical vanadium-containing high-manganese ultra-low temperature steel and its preparation method are disclosed. The chemical composition (mass percentage) is: C: 0.43%, Si: 0.17%, Mn: 24.0%, Cr: 3.6%, V: 0.08%, Alt: 0.06%, Ca: 0.002%, with the balance being Fe and unavoidable impurities. The slab thickness is 220 mm, and the rolled steel plate thickness is 25 mm. The slab is heated in a walking beam furnace to a target temperature of 1180℃ for a total furnace time of 1.6 hours. A descaling box is used to remove the iron oxide scale from the heated slab after exiting the furnace, with a high-pressure water pressure of 23 MPa. The initial rolling temperature is 1080℃, and the final rolling temperature is 920℃. The rolled steel plate is accelerated cooled using an ultra-fast cooling system, with an inlet water temperature of 903℃, an outlet water temperature of 186℃, and a cooling rate of 32℃ / s. The steel plate has an austenitic microstructure. Its room temperature yield strength is 483 MPa, room temperature tensile strength is 862 MPa, room temperature elongation after fracture is 53%, -269℃ yield strength is 1072 MPa, -269℃ tensile strength is 1483 MPa, -269℃ elongation after fracture is 47.5%, -196℃ impact energy is 158 J, and -269℃ impact energy is 67 J.

[0046] Example 2

[0047] An economical vanadium-containing high-manganese ultra-low temperature steel with a tensile strength of 800 MPa and its preparation method are disclosed. The chemical composition (mass percentage) is: C: 0.35%, Si: 0.11%, Mn: 22.5%, Cr: 3.0%, V: 0.03%, Alt: 0.01%, Ca: 0.0003%, with the balance being Fe and unavoidable impurities. The slab thickness is 180 mm, and the rolled steel plate thickness is 15 mm. The slab is heated in a walking beam furnace to a target temperature of 1160 °C for a total furnace time of 1.7 hours. A descaling box is used to remove the iron oxide scale from the heated slab after exiting the furnace, with a high-pressure water pressure of 24 MPa. The initial rolling temperature is 1106 °C, and the final rolling temperature is 905 °C. The rolled steel plate is accelerated cooled using an ultra-fast cooling system, with an inlet water temperature of 881 °C, an outlet water temperature of 137 °C, and a cooling rate of 48 °C / s. The steel plate has an austenitic microstructure. The room temperature yield strength is 489 MPa, the room temperature tensile strength is 871 MPa, and the room temperature elongation after fracture is 52%. The -269℃ yield strength is 1086 MPa, the -269℃ tensile strength is 1491 MPa, the -269℃ elongation after fracture is 46.5%, the -196℃ impact energy is 153 J, and the -269℃ impact energy is 62 J.

[0048] Example 3

[0049] An economical vanadium-containing high-manganese ultra-low temperature steel with a tensile strength of 800 MPa and its preparation method are disclosed. The chemical composition (mass percentage) is: C: 0.55%, Si: 0.22%, Mn: 25.5%, Cr: 4.0%, V: 0.10%, Alt: 0.10%, Ca: 0.005%, with the balance being Fe and unavoidable impurities. The slab thickness is 320 mm, and the rolled steel plate thickness is 50 mm. The slab is heated in a walking beam furnace to a target temperature of 1210℃ for a total furnace time of 1.5 hours. A descaling box is used to remove the iron oxide scale from the heated slab after exiting the furnace, with a high-pressure water pressure of 22 MPa. The initial rolling temperature is 1063℃, and the final rolling temperature is 934℃. The rolled steel plate is accelerated cooled using an ultra-fast cooling system, with an inlet water temperature of 912℃, an outlet water temperature of 238℃, and a cooling rate of 17℃ / s. The steel plate has an austenitic microstructure. Its room temperature yield strength is 476 MPa, room temperature tensile strength is 861 MPa, and room temperature elongation after fracture is 53.5%. Its -269℃ yield strength is 1066 MPa, -269℃ tensile strength is 1461 MPa, -269℃ elongation after fracture is 46.5%, -196℃ impact energy is 159 J, and -269℃ impact energy is 68 J.

Claims

1. A vanadium-containing high manganese steel, characterized in that, By weight percentage, its composition includes C: 0.35%–0.55%, Si: 0.11%–0.22%, Mn: 22.5%–25.5%, P≤0.020%, S≤0.005%, Cr: 3.0%–4.0%, V: 0.03%–0.10%, Alt: 0.01%–0.10%, Ca: 0.0003%–0.0050%, with the balance being Fe and other unavoidable impurities.

2. Vanadium-containing high manganese steel according to claim 1, characterized in that, By weight percentage, its composition includes C: 0.43%, Si: 0.17%, Mn: 24.0%, Cr: 3.6%, V: 0.08%, Alt: 0.06%, Ca: 0.002%, with the balance being Fe and unavoidable impurity elements.

3. The vanadium-containing high manganese steel of claim 1, wherein, By weight percentage, its composition includes C: 0.35%, Si: 0.11%, Mn: 22.5%, Cr: 3.0%, V: 0.03%, Alt: 0.01%, Ca: 0.0003%, with the balance being Fe and unavoidable impurity elements.

4. The vanadium-containing high manganese steel of claim 1, wherein, By weight percentage, its composition includes C: 0.55%, Si: 0.22%, Mn: 25.5%, Cr: 4.0%, V: 0.10%, Alt: 0.10%, Ca: 0.005%, with the balance being Fe and unavoidable impurity elements.

5. The vanadium-containing high manganese steel of claim 1, wherein, Its thickness is 15-50mm.

6. The vanadium-containing high manganese steel of claim 1, wherein, Its room temperature yield strength Rp0.2≥450MPa, room temperature tensile strength Rm≥800MPa, and room temperature elongation after fracture≥50%.

7. The vanadium-containing high manganese steel of claim 1, wherein, Its yield strength at -269℃ Rp0.2≥1000MPa, tensile strength at -269℃ Rm≥1400MPa, and elongation after fracture at -269℃≥46%.

8. The vanadium-containing high manganese steel of claim 1, wherein, Its impact energy at -196℃ is Akv≥150J, and its impact energy at -269℃ is Akv≥60J.

9. A method of producing the vanadium-containing high manganese steel according to claim 1, characterized by, Includes the following steps: (1) Heating: Heating temperature 1160~1210℃, total furnace time 1.5~1.7min / mm×bill thickness; (2) Remove scales; (3) Rolling: The initial rolling temperature is 1060~1100℃, and the final rolling temperature is 900~930℃; (4) Cooling: The inlet water temperature is 880~910℃, the outlet water temperature is 130~240℃, and the cooling rate is 27~48℃ / s.

10. The use of the vanadium-rich high-manganese steel of claim 1 in the manufacture of storage and transportation containers or pipelines for liquefied ethylene, liquefied natural gas, liquid hydrogen or liquid helium.

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