High-strength case steel and method for producing same, drive axle housing
By controlling the microalloying composition of high-strength shell steel and using controlled rolling and cooling technology, the problem of reduced strength after hot stamping of the drive axle shell was solved, achieving the high strength and low cost effect of cold stamping process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUNAN VALIN LIANYUAN IRON & STEEL CO LTD
- Filing Date
- 2024-11-28
- Publication Date
- 2026-05-19
AI Technical Summary
In existing technologies, the strength of the drive axle housing is significantly reduced after hot stamping, which cannot achieve the effect of lightweighting and is also costly.
By controlling the microalloying composition of high-strength shell steel and using controlled rolling and cooling technologies, the requirements of cold stamping processes can be met, including specific component ratios and rolling processes such as multi-pass rolling and laminar flow cooling, thereby refining the grains and improving the strength and plasticity of the material.
The cold stamping process for the drive axle housing was achieved, reducing costs. Furthermore, the cold stamping process resulted in no cracking and low internal stress, meeting the requirements for high strength and toughness.
Smart Images
Figure CN119530659B_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of high-strength steel technology, and particularly relates to a high-strength shell steel and its preparation method, and a drive axle shell. Background Technology
[0002] Green and low-carbon development has become an important direction for the development of the automotive industry. The current development trend of commercial vehicles is to reduce emissions and energy consumption. Currently, drive axle housings with a thickness of ≥10mm all require hot stamping. The strength of steel after hot stamping is greatly reduced, and the lightweight effect cannot be achieved. Summary of the Invention
[0003] This application provides a high-strength shell steel and its preparation method, as well as a drive axle shell. Compared with existing thick-gauge hot-stamping steel, the high-strength shell steel of this application can meet the cold-stamping process requirements of the drive axle and reduce costs.
[0004] In a first aspect, a high-strength shell steel, comprising, by weight percentage: C: 0.06wt% to 0.18wt%; Mn: 1.00wt% to 1.60wt%; Si: 0.05wt% to 0.35wt%; Nb: 0.01wt% to 0.06wt%; V: 0.02wt% to 0.06wt%; Ti: 0.01wt% to 0.02wt%; S ≤ 0.008wt%; P: ≤ 0.02wt%; N: ≤ 0.006wt%; and the balance being Fe and unavoidable trace elements.
[0005] Compared with existing thick-gauge hot-stamped steel, the high-strength shell steel of this application can meet the cold-stamping process requirements of the drive axle, reduce costs, and the high-strength shell steel of this application does not crack and has low internal stress after cold stamping.
[0006] In a first possible implementation, the microstructure of the high-strength shell steel comprises 0–20% pearlite, 0–5% bainite, and the balance ferrite; and / or, the average grain size of the high-strength shell steel is ≤4 μm.
[0007] In combination with the above possible implementation methods, the high-strength shell steel meets one or more of the following conditions (1) to (4): (1) the yield strength of the high-strength shell steel is ≥490MPa; (2) the tensile strength of the high-strength shell steel is ≥580MPa; (3) the elongation after fracture of the high-strength shell steel is ≥20%; (4) the low-temperature impact toughness of the high-strength shell steel at -20℃ is ≥34J.
[0008] In a second aspect, a method for preparing high-strength shell steel includes: providing a continuously cast slab, the continuously cast slab containing the components of the first aspect; heating the continuously cast slab to obtain a heated slab; and rolling the heated slab to obtain a rolled steel plate.
[0009] In the first possible implementation, in the step of heating the continuously cast slab to obtain the heated slab, the cumulative time of the continuously cast slab in the furnace is >150 min, and the time in the soaking zone is ≥30 min. The heating temperature of the continuously cast slab is 1180℃~1230℃ to control the size of the original austenite grains.
[0010] In the above implementation, under this heating condition, the microalloying elements in the continuously cast slab are completely dissolved and form carbonitrides, which further hinder the growth of the original austenite grains and refine the grains.
[0011] Combining the above possible implementation methods, the steps of rolling the heated slab to obtain rolled steel plate include rough rolling and finish rolling. Preferably, the rough rolling adopts multi-pass rolling, the exit thickness of the rough rolled steel plate is ≤56mm, the heated slab is subjected to rough descaling treatment before rough rolling, and the slab after rough rolling is subjected to finish descaling treatment.
[0012] Based on the above possible implementation methods, the inlet temperature of the finishing mill is 950℃~1100℃, and the outlet temperature of the finishing mill is 820℃~880℃; and / or, in the finishing mill step, the cumulative reduction rate of the ferrite region is ≥20%.
[0013] In the above implementation, when the inlet temperature of the finishing mill is 950℃~1100℃, the rolling temperature range can be controlled, and the thickness of the surface iron oxide scale can be controlled during low-temperature fast rolling of thick-gauge products. The outlet temperature of the finishing mill is 820℃~880℃. During rolling in the ferrite region, with the increase in large reduction, the grain boundaries or deformation zones of the deformed austenite act as nucleation sites for ferrite, thereby refining the grains. Furthermore, the gradual precipitation of microalloying elements can also improve strength, promote grain refinement, and enhance the material's plasticity and toughness.
[0014] Combining the above possible implementation methods, the rolled steel plate is subjected to laminar flow cooling treatment to obtain the cooled steel plate. The laminar flow cooling treatment is front-end centralized cooling and does not use ultra-fast cooling.
[0015] Combining the above possible implementation methods, the cooled steel plate is coiled to obtain a steel coil, which is then naturally cooled to room temperature. The coiling temperature is 555℃~620℃ to allow the microalloying elements to be fully released during cooling, ensuring the strength and plasticity of the product.
[0016] Thirdly, a drive axle housing is prepared by using high-strength housing steel prepared by the method of the first aspect and / or by using high-strength housing steel prepared by the method of the second aspect. Attached Figure Description
[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is a microstructure diagram of the high-strength shell steel in Example 1.
[0019] Figure 2 This is a microstructure diagram of the high-strength shell steel in Example 2.
[0020] Figure 3 This is a microstructure diagram of the high-strength shell steel in Example 3.
[0021] Figure 4 This is a microstructure diagram of the high-strength shell steel in Comparative Example 1. Detailed Implementation
[0022] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.
[0023] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.
[0024] The foregoing description of this application is not intended to describe every disclosed embodiment or implementation. The following description illustrates exemplary embodiments in more detail. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. In each example, the enumeration is merely representative and should not be construed as exhaustive. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0025] Currently, green and low-carbon development has become an important direction for the automotive industry. Commercial vehicles, as the main body of road transportation, account for over 50% of fuel consumption and 56% of carbon emissions in the automotive industry. Therefore, the current development direction for commercial vehicles is lightweighting. However, currently, drive axle housings with a thickness of ≥10mm all require hot stamping, which significantly reduces strength and fails to achieve the desired lightweighting effect.
[0026] In view of the above problems, this application provides a high-strength shell steel and its preparation method, as well as a drive axle shell. Compared with existing thick-gauge hot-stamping steel, the high-strength shell steel of this application can meet the cold stamping process requirements of the drive axle and reduce costs.
[0027] In a first aspect, a high-strength shell steel, comprising, by weight percentage: C: 0.06wt% to 0.18wt%; Mn: 1.00wt% to 1.60wt%; Si: 0.05wt% to 0.35wt%; Nb: 0.01wt% to 0.06wt%; V: 0.02wt% to 0.06wt%; Ti: 0.01wt% to 0.02wt%; S ≤ 0.008wt%; P: ≤ 0.02wt%; N: ≤ 0.006wt%; and the balance being Fe and unavoidable trace elements.
[0028] The inventors discovered that by controlling the microalloying composition of steel and using controlled rolling and cooling technology, the high-strength shell steel of this application can meet the cold stamping process requirements of drive axles compared to existing thick-gauge hot stamping steel, thereby reducing costs. Furthermore, the high-strength shell steel of this application exhibits no cracking and low internal stress after cold stamping.
[0029] In some specific embodiments, the microstructure of the high-strength shell steel comprises about 0 to 20% pearlite, 0 to 5% bainite, and the balance ferrite; and / or, the average grain size of the high-strength shell steel is ≤4 μm, for example, it can be any combination of 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, or higher.
[0030] In some specific embodiments, the high-strength shell steel satisfies one or more of the following conditions (1) to (4): (1) The yield strength of the high-strength shell steel is ≥490 MPa, for example, it can be 490 MPa, 500 MPa, 510 MPa, 520 MPa, 530 MPa, 540 MPa, 550 MPa, or any combination of the above values; (2) The tensile strength of the high-strength shell steel is ≥580 MPa, for example, it can be 580 MPa, 590 MPa, 600 MPa, 610 MPa. (2) 620MPa, 630MPa, 640MPa, 650MPa, or any combination of the above values; (3) The elongation after fracture of the high-strength shell steel is ≥20%, for example, it can be any combination of 20%, 22%, 24%, 26%, 28%, 30%, or the above values; (4) The low-temperature impact toughness of the high-strength shell steel at -20℃ is ≥34J, for example, it can be any combination of 34J, 50J, 80J, 100J, 120J, 150J, 200J, or the above values.
[0031] In some specific embodiments, the thickness of the high-strength shell steel is 6mm to 16mm, for example, it can be any combination of 6mm, 8mm, 10mm, 12mm, 14mm, 16mm or more.
[0032] In a second aspect, a method for preparing high-strength shell steel includes: providing a continuously cast slab, the continuously cast slab containing the components of the first aspect; heating the continuously cast slab to obtain a heated slab; and rolling the heated slab to obtain a rolled steel plate.
[0033] In some specific embodiments, in the step of heating the continuously cast slab to obtain the heated slab, the cumulative furnace time of the continuously cast slab is >150 min, for example, it can be any combination of 151 min, 170 min, 210 min, 230 min, 250 min, or above, and the time in the soaking zone is ≥30 min, for example, it can be any combination of 30 min, 32 min, 35 min, 38 min, 40 min, 45 min, or above, and the heating temperature of the continuously cast slab is 1180℃~1230℃, for example, it can be any combination of 1180℃, 1190℃, 1200℃, 1210℃, 1220℃, 1230℃, or above, in order to control the size of the original austenite grains.
[0034] In the above specific embodiment, under this heating condition, the microalloying elements in the continuously cast slab are completely dissolved and form carbonitrides, which further hinder the growth of the original austenite grains and refine the grains.
[0035] In some specific embodiments, the step of rolling the heated slab to obtain a rolled steel plate includes rough rolling and finish rolling. Preferably, the rough rolling adopts multi-pass rolling, such as 4-pass rolling, 5-pass rolling, 6-pass rolling, 7-pass rolling, etc. The exit thickness of the rough rolled steel plate is ≤56mm, such as 35mm, 40mm, 42mm, 45mm, 48mm, 50mm, 52mm, 54mm, 56mm, or any combination of the above values. The heated slab is subjected to rough descaling treatment before rough rolling, and the slab after rough rolling is subjected to finish descaling treatment.
[0036] In some specific embodiments, the inlet temperature of the finishing mill is 950℃~1100℃, for example, it can be any combination of 950℃, 980℃, 1000℃, 1020℃, 1050℃, 1080℃, 1100℃, or above; the outlet temperature of the finishing mill is 820℃~880℃, for example, it can be any combination of 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, or above; and / or, in the finishing mill step, the cumulative reduction rate of the ferrite region is ≥20%, for example, it can be any combination of 20%, 22%, 25%, 28%, 30%, 35%, 40%, or above.
[0037] In some specific embodiments, when the inlet temperature of the finishing mill is 950℃~1100℃, the rolling temperature range can be controlled, and the thickness of the surface iron oxide scale can be controlled during low-temperature fast rolling of thick-gauge products. The outlet temperature of the finishing mill is 820℃~880℃. During rolling in the ferrite region, with the increase in large reduction, the grain boundaries or deformation zones of the deformed austenite act as nucleation sites for ferrite, thereby refining the grains. Furthermore, the gradual precipitation of microalloying elements can also improve strength, promote grain refinement, and enhance the material's plasticity and toughness.
[0038] In some specific implementations, the rolled steel sheet is subjected to laminar flow cooling to obtain a cooled steel sheet. The laminar flow cooling process is a front-end centralized cooling process that does not use ultra-fast cooling.
[0039] In some specific embodiments, the cooled steel sheet is coiled to obtain a steel coil, which is then naturally cooled to room temperature. The coiling temperature is 555℃ to 620℃, for example, it can be any combination of 555℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, or higher, so that the microalloying elements are fully released during cooling, ensuring the strength and plasticity of the product.
[0040] Thirdly, a drive axle housing is prepared by using high-strength housing steel prepared by the method of the first aspect and / or by using high-strength housing steel prepared by the method of the second aspect.
[0041] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.
[0042] It should be understood that in the embodiments of this application, "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean that B is determined solely based on A; B can also be determined based on A and / or other information.
[0043] The following embodiments describe the contents disclosed in this application in more detail. These embodiments are for illustrative purposes only.
[0044] Because various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all raw materials used in the examples are commercially available or prepared by conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.
[0045] The steel performance testing experiments in this application were conducted according to the methods in GB / T 228.1-2021 and GB / T 229-2020.
[0046] Example 1
[0047] A high-strength shell steel is prepared by the following method:
[0048] The continuously cast slab provided contains, by weight percentage, C: 0.0759wt%, Mn: 1.0827wt%, Si: 0.1711wt%, Nb: 0.0195wt%, V: 0.0356wt%, Ti: 0.0142wt%, S: 0.0031wt%, P: 0.0158wt%, with the remainder being Fe and unavoidable trace elements.
[0049] The continuously cast slab is heated to 1205℃ in a heating furnace, with a soaking time of 32 minutes and a total furnace time of 182 minutes. This allows the microalloying elements to be completely dissolved and form carbonitrides, which hinder the growth of the original austenite grains, refine the grains, and obtain the heated continuously cast slab.
[0050] After the heated continuous casting slab exits the furnace, it undergoes high-pressure water rough descaling, followed by five round-trip rolling in a rough rolling mill with an exit diameter of 54mm. Finally, it undergoes fine descaling to obtain a finely descaled rough-rolled slab.
[0051] After fine descaling, the rough-rolled slab enters a 7-stand finishing mill to produce a rolled steel plate with a thickness of 12.0 mm. The rolled steel plate undergoes laminar flow cooling to obtain a cooled steel plate. The laminar flow cooling process involves centralized front-end cooling without the use of ultra-rapid cooling. The starting rolling temperature of the finishing mill is 987℃, the cumulative reduction rate in the ferrite rolling zone is 22%, and the exit temperature of the finishing mill is 846℃.
[0052] The cooled steel plate is coiled at 595℃ to obtain a steel coil. The steel coil is air-cooled on the transport chain and then stored in a warehouse for low-temperature stacking cooling to obtain high-strength shell steel.
[0053] The high-strength shell steel in this embodiment, after undergoing transverse mechanical property testing, has a yield strength of 538 MPa, a tensile strength of 617 MPa, an elongation after fracture of 24%, and a low-temperature impact energy of 171 J at -20℃.
[0054] like Figure 1 As shown, the microstructure of the high-strength shell steel in this embodiment contains a small amount of bainite (2% to 3%) and the remainder of ferrite, with an average grain size of 3.2 μm.
[0055] Example 2
[0056] A high-strength shell steel is prepared by the following method:
[0057] The continuously cast slab provided contains, by weight percentage, C: 0.0661wt%, Mn: 1.3394wt%, Si: 0.2055wt%, Nb: 0.0393wt%, V: 0.0245wt%, Ti: 0.0187wt%, S: 0.0025wt%, P: 0.0153wt%, with the remainder being Fe and unavoidable trace elements.
[0058] The continuously cast slab is heated to 1198℃ in a heating furnace, with a soaking time of 34 minutes and a total furnace time of 204 minutes. This allows the microalloying elements to be completely dissolved and form carbonitrides, which hinder the growth of the original austenite grains, refine the grains, and obtain the heated continuously cast slab.
[0059] After the heated continuous casting slab exits the furnace, it undergoes high-pressure water rough descaling and then passes through a rough rolling mill for five round trips. The rough rolling mill exits at 55mm. Finally, it undergoes fine descaling to obtain a finely descaled rough-rolled slab.
[0060] After fine descaling, the rough-rolled slab enters a 7-stand finishing mill to produce a rolled steel plate with a thickness of 16.0 mm. The rolled steel plate undergoes laminar flow cooling to obtain a cooled steel plate. The laminar flow cooling process involves centralized front-end cooling without the use of ultra-rapid cooling. The starting rolling temperature of the finishing mill is 970℃, the cumulative reduction rate in the ferrite rolling zone is 21%, and the exit temperature of the finishing mill is 842℃.
[0061] The cooled steel plate is coiled at 555℃ to obtain a steel coil. The steel coil is air-cooled on the transport chain and then stored in a warehouse for low-temperature stacking cooling to obtain high-strength shell steel.
[0062] The high-strength shell steel in this embodiment, after undergoing transverse mechanical property testing, has a yield strength of 542 MPa, a tensile strength of 635 MPa, an elongation after fracture of 22.5%, and a low-temperature impact energy of 127 J at -20℃.
[0063] like Figure 2 As shown, the microstructure of the high-strength shell steel in this embodiment contains a small amount of pearlite (15%–16%) and bainite (1%–5%), with the remainder being ferrite, and the average grain size is 3.8 μm.
[0064] Example 3
[0065] A high-strength shell steel is prepared by the following method:
[0066] The continuously cast slab provided contains, by weight percentage, C: 0.0825wt%, Mn: 1.4052wt%, Si: 0.1954wt%, Nb: 0.0289wt%, V: 0.0287wt%, Ti: 0.0195wt%, S: 0.0024wt%, P: 0.0168wt%, with the remainder being Fe and unavoidable trace elements.
[0067] The continuously cast slab is heated to 1208℃ in a heating furnace, with a soaking time of 33 minutes and a total furnace time of 224 minutes. This allows the microalloying elements to be completely dissolved and form carbonitrides, which hinders the growth of the original austenite grains, refines the grains, and yields the heated continuously cast slab.
[0068] After the heated continuous casting slab exits the furnace, it undergoes high-pressure water rough descaling and then passes through a rough rolling mill for five round trips. The rough rolling mill exits at 54mm. Finally, it undergoes fine descaling to obtain a finely descaled rough-rolled slab.
[0069] After fine descaling, the rough-rolled slab enters a 7-stand finishing mill to produce a rolled steel plate with a thickness of 16.0 mm. The rolled steel plate undergoes laminar flow cooling to obtain a cooled steel plate. The laminar flow cooling process involves centralized front-end cooling without the use of ultra-rapid cooling. The starting rolling temperature of the finishing mill is 987℃, the cumulative reduction rate in the ferrite rolling zone is 21.5%, and the exit temperature of the finishing mill is 845℃.
[0070] The cooled steel plate is coiled at 558℃ to obtain a steel coil. The steel coil is air-cooled on the transport chain and then stored in a warehouse for low-temperature stacking cooling to obtain high-strength shell steel.
[0071] The high-strength shell steel in this embodiment, after undergoing transverse mechanical property testing, has a yield strength of 547 MPa, a tensile strength of 648 MPa, an elongation after fracture of 23.0%, and a low-temperature impact energy of 148 J at -20℃.
[0072] like Figure 3 As shown, the microstructure of the high-strength shell steel in this embodiment is mainly ferrite, with a small amount of pearlite (15% to 17%) and bainite (1% to 5%) and the balance of ferrite, and an average grain size of 3.6 μm.
[0073] Comparative Example 1
[0074] A type of shell steel is prepared by the following method:
[0075] The continuously cast slab is provided, which, by mass percentage, contains C: 0.1051 wt%, Mn: 1.4871 wt%, Si: 0.104 wt%, Nb: 0.0247 wt%, V: 0.0345 wt%, S: 0.0045 wt%, P: 0.0187 wt%, with the remainder being Fe and unavoidable trace elements.
[0076] After fine descaling, the rough-rolled slab enters a 7-stand finishing mill to produce a rolled steel plate with a thickness of 11.0 mm. The rolled steel plate undergoes laminar flow cooling to obtain a cooled steel plate. The laminar flow cooling process involves centralized front-end cooling without the use of ultra-rapid cooling. The starting rolling temperature of the finishing mill is 1007℃, and the exit temperature of the finishing mill is 864℃.
[0077] The cooled steel plate is coiled at 585℃ to obtain a steel coil. The steel coil is air-cooled on the conveyor chain and then stored in a warehouse for low-temperature stacking cooling to obtain the shell steel.
[0078] The shell steel in this comparative example, after transverse mechanical property testing, has a yield strength of 480 MPa, a tensile strength of 595 MPa, an elongation after fracture of 18.5%, and a low-temperature impact energy of 56 J at -20℃.
[0079] like Figure 4 As shown, the microstructure of the high-strength shell steel in this embodiment is mainly ferrite (75% to 85%), with a small amount of pearlite (15% to 25%) and an average grain size of 8.2 μm.
[0080] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A method for preparing high-strength shell steel, characterized in that, include: A continuously cast slab is provided, comprising, by weight percentage, the following components: C: 0.06wt%~0.18wt%, Mn: 1.00wt%~1.60wt%, Si: 0.05wt%~0.35wt%, Nb: 0.01wt%~0.0289wt%, V: 0.02wt%~0.0356wt%, Ti: 0.01wt%~0.02wt%, S≤0.008wt%, P:≤0.02wt%, N:≤0.006wt%; and the balance being Fe and unavoidable trace elements; The continuously cast slab is heated to obtain a heated slab. The cumulative time of the continuously cast slab in the furnace is >150 min, and the time in the soaking zone is ≥30 min. The heating temperature of the continuously cast slab is 1180℃~1230℃. The heated slab is subjected to rough rolling and finish rolling to obtain rolled steel plate; wherein, the rough rolling adopts multi-pass rolling, the exit thickness of the rough rolled steel plate is ≤56mm, the heated slab is subjected to rough descaling treatment before rough rolling, and the slab after rough rolling is subjected to finish descaling treatment; the inlet temperature of the finish rolling is 950℃~1100℃, and the outlet temperature of the finish rolling is 820℃~880℃; in the finish rolling step, the cumulative reduction rate of the ferrite region is ≥20%; The rolled steel plate is subjected to laminar flow cooling treatment to obtain a cooled steel plate. The laminar flow cooling treatment is front-end centralized cooling and does not use ultra-fast cooling. The high-strength shell steel is composed of the following components by weight percentage: C: 0.06wt%~0.18wt%, Mn: 1.00wt%~1.60wt%, Si: 0.05wt%~0.35wt%, Nb: 0.01wt%~0.0289wt%, V: 0.02wt%~0.0356wt%, Ti: 0.01wt%~0.02wt%, S≤0.008wt%, P:≤0.02wt%, N:≤0.006wt%; and the balance Fe and unavoidable trace elements; The microstructure of the high-strength shell steel includes 0-20% pearlite, 1-5% bainite, and the balance ferrite. The average grain size of the high-strength shell steel is ≤4μm.
2. The preparation method according to claim 1, characterized in that, The high-strength shell steel satisfies one or more of the following conditions (1) to (4): (1) The yield strength of the high-strength shell steel is ≥490MPa; (2) The tensile strength of the high-strength shell steel is ≥580MPa; (3) The elongation after fracture of the high-strength shell steel is ≥20%; (4) The low-temperature impact toughness of the high-strength shell steel at -20℃ is ≥34J.
3. The preparation method according to claim 1, characterized in that, The cooled steel plate is coiled to obtain a steel coil, which is then naturally cooled to room temperature. The coiling temperature is 555℃~620℃.
4. A drive axle housing, characterized in that, High-strength shell steel prepared by the preparation method according to any one of claims 1-3.