Vanadium-containing high manganese steel and preparation method and application thereof

Abstract

The invention discloses vanadium-containing high manganese steel and a preparation method and application thereof. According to the high-manganese steel, chemical components are matched with a rolling process, so that the ultralow temperature resistance and the hydrogen damage resistance of the high-manganese steel are excellent, meanwhile, various precious metal elements are not added, and the process is simplified. The method is wide in application prospect and is more suitable for manufacturing ultralow-temperature medium storage and transportation containers in complex environments.

Description

Technical Field

[0001] The invention relates to a vanadium-containing high manganese steel and a preparation method and application thereof, and in particular to a vanadium-containing high manganese steel with excellent low-temperature performance and a preparation method and application thereof. Background Art

[0002] Storage and transportation containers for ultra-low temperature media are usually made of nickel steel and austenitic stainless steel. Due to the small reserves of Ni ore, nickel steels such as Invar steel (36% Ni), 316 stainless steel (12% Ni), and 9% Ni steel are less economical, while austenitic stainless steel has low strength and a large expansion coefficient and cannot meet the use requirements of the extreme low temperature environment of -269℃.

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

[0004] CN102409227 discloses a hot-rolled steel strip with low relative magnetic permeability, the chemical composition of which is C: 0.25% to 0.35%, Si: 0.5% to 0.6%, Mn: 25% to 26%, Al: 3.8% to 4.2%, V: 0.06% to 0.10%, P: 0.02% to 0.03%, S: 0.02% to 0.03%, and the rest is Fe and unavoidable impurities. The Al content is too high, which is very easy to form hot rolling cracks and reduce the yield rate.

[0005] CN108929993 discloses a microalloyed high-strength and high-plastic non-magnetic steel plate, whose chemical composition is C: 0.10%-0.20%, 0<Si≤0.4%, Mn: 20%-26%, A1: 2.0%-3.0%, Ti: 0.01%-0.02%, Nb: 0.04%-0.09%, and the remainder is Fe and other unavoidable impurities. The impact energy at -196℃ is only ≥110J, which is difficult to meet the storage and transportation requirements of ultra-low temperature media such as liquid hydrogen and liquid helium. Summary of the invention

[0006] Purpose of the invention: The first purpose of the present invention is to provide a vanadium-containing high manganese steel with high strength and excellent low temperature performance. The second purpose is to provide a preparation method of the high manganese steel, and the third purpose is to provide an application of the high manganese steel in an ultra-low temperature environment.

[0007] Technical solution: The vanadium-containing high manganese steel of the present invention comprises, by weight percentage, 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%, and the balance is Fe and other inevitable impurities.

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

[0009] Preferably, in terms of weight percentage, the composition of the vanadium-containing high manganese steel includes C: 0.35%, Si: 0.11%, Mn: 22.5%, Cr: 3.0%, V: 0.03%, Alt: 0.01%, Ca: 0.0003%, and the remainder is Fe and unavoidable impurity elements.

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

[0011] When used as a structural material in an ultra-low temperature environment of -269℃, the mechanical properties of the material are highly required. Therefore, as an ultra-low temperature structural material, it is necessary to redesign the alloy composition to improve the mechanical properties while reducing the material cost, so as to be more conducive to practical application.

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

[0013] Austenite structure has excellent strength, plasticity, toughness matching and lower operating temperature. Although adding high content of Ni can obtain austenite structure, such as 316 austenite stainless steel with 12% Ni content, the alloy cost is high. Mn can inhibit the transformation of austenite to martensite, so it can be used as a substitute element for Ni to obtain austenite structure. Since the effect of Mn on the stability of austenite is about half that of Ni, the content of Mn in the ultra-low temperature steel of the present invention is preferably 22.5% to 25.5%, more preferably 24.0%.

[0014] In particular, while obtaining the austenite matrix structure, the present invention preferably adds a certain amount of V, cooperates with the corresponding rolling process, and forms a V carbonitride dispersion phase. V can effectively refine the grains and improve the toughness of high manganese steel. At the same time, the refined grains and dispersed carbonitrides can reduce the initiation and expansion of fatigue cracks in high manganese steel under alternating stress, thereby improving its fatigue resistance and enhancing its reliability under dynamic load conditions. In order to make the ultra-low temperature steel of the present invention have higher resistance to hydrogen damage when used to build liquid hydrogen storage tanks, the V carbonitride dispersion phase also acts as a hydrogen trap to hinder the diffusion of hydrogen atoms. By 10 -6 The strain rate tensile test is used for quantitative characterization, and the sensitivity of the ultra-low temperature steel of the present invention to the hydrogen environment is ≤0.15. The V content in the ultra-low temperature steel of the present invention is preferably 0.03% to 0.10%, and more preferably 0.08%.

[0015] C has a strong austenite stabilizing effect and is also an effective element for improving austenite stability. Moreover, C can hinder dislocation movement and improve strength. From the perspective of austenite stabilization, the addition of C can increase the stacking fault energy of austenite, so that austenite produces twins instead of martensitic transformation when strained. The strain-induced twinning mechanism of austenite can significantly improve plasticity. The C content in the ultra-low temperature steel of the present invention is preferably 0.35% to 0.55%, more preferably 0.43%.

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

[0017] The present invention obtains a highly stable austenite structure by adding 0.43% C, 24.0% Mn and 3.6% Cr. After pre-straining 0.35 true strain and then performing -269°C deep cryogenic treatment, martensite structure still does not appear. At the same time, the stacking fault energy of austenite at -269°C is controlled to 18-21mJ·m -2 The matching of strength and toughness is achieved by the composite mechanism of dislocation + twinning, so that the Charpy impact absorption energy of the ultra-low temperature steel of the present invention at -269°C is ≥60J.

[0018] In addition to the above chemical composition, the present invention optimizes the types and contents of other added elements. Among them, Si can produce a certain degree of solid solution strengthening, but Si segregation at the grain boundary will weaken the grain boundary and increase the intergranular brittleness. In addition, Si will also reduce plasticity. Therefore, the present invention preferably controls the content of Si to 0.11% to 0.22%, and more preferably 0.17%. Al, as a deoxidizing element in the manufacturing process, can also improve the performance of the welded joint, but excessive addition is easy to form a coarse precipitate phase and damage toughness. Therefore, the present invention preferably controls the content of Al to 0.01% to 0.10%, and more preferably 0.006%. Ca can react with oxygen and sulfur in steel to form stable compounds, such as CaO, CaS, etc. 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 shape and distribution of inclusions in the steel, reduce the adverse effects of inclusions on steel properties, and improve the toughness and plasticity of the steel. Therefore, the present invention preferably controls the Ca content to 0.0003% to 0.0050%, more preferably 0.002%.

[0019] It should be noted that the actual content of alloying elements in the material manufacturing process fluctuates within a certain small range near the design range, which is an inevitable fluctuation in normal industrial production. Although the present invention clearly stipulates the content range of each element, it will not have a significant impact on the effect of the present invention within a reasonable deviation range.

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

[0021] More preferably, in the microstructure of the vanadium-containing high manganese steel, more than 95% by volume is austenite structure.

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

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

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

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

[0026] The method for preparing vanadium-containing high manganese steel of the present invention comprises the following steps:

[0027] (1) Heating: Heating temperature 1160-1210°C, total furnace time 1.5-1.7 min / mm × billet thickness;

[0028] (2) Descaling: Remove the iron oxide scale of the heated blank, with a high-pressure water pressure of 22-24 MPa;

[0029] (3) Rolling: the starting rolling temperature is 1060-1100°C, and the final rolling temperature is 900-930°C;

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

[0031] Among them, the heating adopts a walking beam heating furnace, and the ACC cooling method is used to accelerate the cooling of the rolled steel plate. The thickness specification of the rolled steel plate is 15 to 50 mm.

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

[0033] In order to obtain sufficient grain refinement and strain accumulation through thermomechanical rolling and obtain sufficient finished steel plate strength, a sufficient compression ratio is required in the selection of slab thickness, that is, the ratio (H / h) of slab thickness (H) to finished steel plate thickness (h). The present invention controls the compression ratio to 6 to 12.

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

[0035] The slab is heated in a walking beam heating furnace and then taken out of the furnace. It passes through a descaling box to remove the oxidized iron scale. The high-pressure water pressure is 22 to 24 MPa to ensure the descaling effect.

[0036] The slab is rolled after being descaled by the descaling box. The starting rolling temperature is 1060-1100℃, and the final rolling temperature is controlled to be relatively low, i.e. 900-930℃. Thermomechanical rolling refines the austenite grains, accumulates sufficient strain, and improves the strength of the finished steel plate. The slab has sufficient thickness, which is conducive to improving the thermomechanical rolling effect.

[0037] After rolling, the steel plate enters the ultra-fast cooling equipment for high-pressure water cooling, with the water inlet temperature of 880-910°C and the cooling rate of 17-48°C / s to the water outlet temperature of 130-240°C. The role of accelerated cooling is, on the one hand, to retain the accumulation of thermomechanical rolling strain and improve the strength of the steel plate, and on the other hand, to inhibit the precipitation of carbides and improve the plasticity of the steel plate.

[0038] The vanadium high manganese steel of the present invention is used in the manufacture of storage and transportation containers or transmission pipelines for liquefied ethylene, liquefied natural gas, liquid hydrogen or liquid helium, and is specifically used in land, marine or aviation environments.

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

[0040] The invention combines chemical composition with rolling process to make the designed high manganese steel have excellent ultra-low temperature resistance and hydrogen damage resistance, and the Charpy impact absorption energy at -269°C is ≥60J. At the same time, no precious metal elements such as Ni / Mo / Cu are added, the alloy elements are relatively small, and the post-processing process is eliminated in the process, which has significant economic advantages. It has a wide range of application prospects and can be applied to the storage and transportation of various ultra-low temperature media such as liquefied ethylene, liquefied natural gas, liquid hydrogen, liquid helium, etc., and is suitable for various complex environments such as land, sea, and aviation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the microstructure diagram of the steel plate prepared in Example 1. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described below in conjunction with embodiments.

[0043] The tests of yield strength, tensile strength, elongation after fracture and impact energy shall refer to "GB / T 228.1-2021 Tensile test of metal materials Part 1: Room temperature test method", "GB / T 228.3-2019 Tensile test of metal materials Part 3: Low temperature test method", "GB / T 228.4-2019 Tensile test of metal materials Part 4: Liquid helium test method" and "GB / T 229-2020 Charpy pendulum impact test method for metal materials".

[0044] Example 1

[0045] An economical vanadium-containing high-manganese ultra-low temperature steel and a preparation method thereof, wherein 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%, and the remainder is Fe and unavoidable impurity elements. The slab thickness is 220 mm, and the rolled steel plate thickness is 25 mm. The billet is heated using a walking beam heating furnace, with a target temperature of 1180°C and a total furnace time of 1.6 hours. A descaling box is used to remove the iron oxide scale of the billet after heating and furnace discharge, and the high-pressure water pressure is 23 MPa. The starting rolling temperature is 1080°C, and the final rolling temperature is 920°C. Ultra-fast cooling equipment is used to accelerate the cooling of the rolled steel plate, with a water inlet temperature of 903°C, a water outlet temperature of 186°C, and a cooling rate of 32°C / s. The steel plate structure is austenite, with a room temperature yield strength of 483MPa, a room temperature tensile strength of 862MPa, a room temperature elongation of 53%, a -269℃ yield strength of 1072MPa, a -269℃ tensile strength of 1483MPa, a -269℃ elongation of 47.5%, a -196℃ impact energy of 158J, and a -269℃ impact energy of 67J.

[0046] Example 2

[0047] An economical ultra-low temperature steel containing high manganese containing vanadium with a tensile strength of 800 MPa and a preparation method thereof, wherein 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%, and the remainder is Fe and unavoidable impurity elements. The thickness of the slab is 180 mm, and the thickness of the rolled steel plate is 15 mm. The billet is heated using a walking beam heating furnace, with a target temperature of 1160°C and a total furnace time of 1.7 hours. A descaling box is used to remove the iron oxide scale of the billet after heating and taking it out of the furnace, and the high-pressure water pressure is 24 MPa. The starting rolling temperature is 1106°C, and the final rolling temperature is 905°C. The rolled steel plate is accelerated to cool using ultra-fast cooling equipment, with a water inlet temperature of 881°C, a water outlet temperature of 137°C, and a cooling rate of 48°C / s. The steel plate structure is austenite, with a room temperature yield strength of 489MPa, a room temperature tensile strength of 871MPa, a room temperature elongation of 52%, a -269℃ yield strength of 1086MPa, a -269℃ tensile strength of 1491MPa, a -269℃ elongation of 46.5%, an -196℃ impact energy of 153J, and a -269℃ impact energy of 62J.

[0048] Example 3

[0049] An economical vanadium-containing high-manganese ultra-low temperature steel with a tensile strength of 800MPa and a preparation method thereof, wherein 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%, and the remainder is Fe and unavoidable impurity elements. The slab thickness is 320mm, and the rolled steel plate thickness is 50mm. The billet is heated using a walking beam heating furnace, with a target temperature of 1210°C and a total furnace time of 1.5H. A descaling box is used to remove the iron oxide scale of the billet after heating and furnace discharge, and the high-pressure water pressure is 22MPa. The starting rolling temperature is 1063°C, and the final rolling temperature is 934°C. Ultra-fast cooling equipment is used to accelerate the cooling of the rolled steel plate, with a water inlet temperature of 912°C, a water outlet temperature of 238°C, and a cooling rate of 17°C / s. The steel plate structure is austenite, with a room temperature yield strength of 476MPa, a room temperature tensile strength of 861MPa, a room temperature elongation of 53.5%, a -269℃ yield strength of 1066MPa, a -269℃ tensile strength of 1461MPa, a -269℃ elongation of 46.5%, an -196℃ impact energy of 159J, and a -269℃ impact energy of 68J.

Claims

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

2. The vanadium-containing high manganese steel according to claim 1, characterized in that: In terms of 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%, and the balance is Fe and inevitable impurity elements.

3. The vanadium-containing high manganese steel according to claim 1, characterized in that: In terms of 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%, and the balance is Fe and inevitable impurity elements.

4. The vanadium-containing high manganese steel according to claim 1, characterized in that: In terms of 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%, and the balance is Fe and inevitable impurity elements.

5. The vanadium-containing high manganese steel according to claim 1, characterized in that: Its thickness is 15 to 50 mm.

6. The vanadium-containing high manganese steel according to claim 1, characterized in that: Its room temperature yield strength Rp0.2≥450MPa, room temperature tensile strength Rm≥800MPa, room temperature elongation after break ≥50%.

7. The vanadium-containing high manganese steel according to claim 1, characterized in that: Its yield strength Rp0.2 at -269°C is ≥1000MPa, its tensile strength Rm at -269°C is ≥1400MPa, and its elongation after break at -269°C is ≥46%.

8. The vanadium-containing high manganese steel according to claim 1, characterized in that: Its impact energy at -196℃ Akv≥150J, and its impact energy at -269℃ Akv≥60J.

9. A method for preparing vanadium-containing high manganese steel according to claim 1, characterized in that: The following steps are involved: (1) Heating: Heating temperature 1160-1210°C, total furnace time 1.5-1.7 min / mm × billet thickness; (2) Descaling; (3) Rolling: the starting rolling temperature is 1060-1100°C, and the final rolling temperature is 900-930°C; (4) Cooling: The water inlet temperature is 880-910°C, the water outlet temperature is 130-240°C, and the cooling rate is 27-48°C / s.

10. Use of the vanadium high manganese steel according to claim 1 in manufacturing storage and transportation containers or transmission pipelines for liquefied ethylene, liquefied natural gas, liquid hydrogen or liquid helium.

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