Method for producing Fe-Mn-Al-C series light steel by dynamic misalignment asynchronous rolling

Abstract

The application develops a method for producing Fe-Mn-Al-C series light steel by dynamic staggered asynchronous rolling, realizes the gradient distribution of mechanical properties of light steel differential thick plate, carries out preliminary heat treatment process on different areas of the light steel differential thick plate, including plate strip induction heating to austenite recrystallization zone, austenite non-recrystallization zone and keeping room temperature state, uses dynamic staggered asynchronous rolling process in the traditional variable thickness rolling process, sets constant stagger angle and controls plate strip deformation by different speed of upper and lower rolling rollers, carries out quenching, tempering and annealing process after rolling to control the structure and performance of the differential thick plate. The application can realize limited reduction to improve the deformation penetration of the plate strip core and the overall deformation uniformity, and solves the problem of insufficient and uneven deformation of the core of high-strength, high-toughness and difficult-to-deform Fe-Mn-Al-C series light steel during rolling.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy, and in particular to a method for producing Fe-Mn-Al-C lightweight steel by dynamic staggered asynchronous rolling. Background Technology

[0002] Under the dual-carbon strategy, actively promoting the concept of green manufacturing, the application of advanced manufacturing technologies and advanced steel materials in the fields of transportation, hoisting machinery, and other engineering equipment manufacturing is one of the direct ways to achieve green manufacturing. In recent years, the combination of Fe-Mn-Al-C lightweight steel and variable thickness rolling technology has attracted widespread attention due to its excellent weight reduction potential. Variable thickness rolling technology is an important way to achieve lightweighting of engineering equipment, but it cannot combine strips with different microstructures and properties, limiting the comprehensive mechanical properties of differential thickness plates and failing to meet the different performance requirements of strips in different regions of engineering equipment. Fe-Mn-Al-C lightweight steel has received increasing attention due to its excellent mechanical properties such as high strength and high toughness. For Fe-Mn-Al-C lightweight steel that is difficult to deform, high strength, and high toughness, when rolling using traditional rolling methods, the deformation in the core of the strip in the traditional variable thickness rolling process is small. The resulting thickness-oriented microstructure and property inhomogeneity reduces the service performance of the strip. Uneven deformation of the rolled piece can cause the strip to bend, affecting the shape accuracy.

[0003] Based on the above considerations, dynamic misaligned asynchronous rolling technology is used in the variable thickness rolling of Fe-Mn-Al-C lightweight steel. Dynamic misaligned asynchronous rolling is a newly developed asymmetric rolling method for metal sheets where the upper and lower rolls simultaneously have misalignment and different speed ratios. It allows for shear deformation, enabling the sheet to penetrate deeper into the core compared to conventional rolling. Simultaneously, the misalignment between the rolls can control the sheet bending caused by the different speeds of the rolls. This approach can solve the rolling problems of difficult-to-deform metal materials, producing differential thickness plates with different thickness combinations, low density, and high strength, suitable for the requirements of engineering machinery steel. Furthermore, it enables the control of the microstructure and properties of differential thickness plates and strips. Specifically, a pre-heat treatment process is added before the variable thickness rolling process, induction heating different areas of the strip to different temperatures. In the final heat treatment process, different quenching temperatures, cooling rates, and heat treatment processes are selected to achieve different properties in different areas of the strip. This meets the requirements of practical engineering applications without sacrificing structural strength and practical application needs, achieving multi-functional steel and differentiated properties within the same material. Therefore, this invention proposes a method for producing Fe-Mn-Al-C lightweight steel by dynamic staggered asynchronous rolling. This invention is of great significance in achieving green manufacturing, energy conservation and emission reduction, and industrial upgrading. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for producing Fe-Mn-Al-C lightweight steel using dynamic misaligned asynchronous rolling. By employing dynamic misaligned asynchronous rolling technology in the conventional variable thickness rolling process, the misalignment of the upper and lower rolls forms a rubbing zone. The shear force in the rubbing zone causes the strip deformation to penetrate more deeply into the core than conventional rolling. Simultaneously, it can control strip bending caused by different speeds. Furthermore, a preparatory heat treatment process is added before and after the variable thickness dynamic misaligned asynchronous rolling to regulate the microstructure and properties. This method can solve the rolling problem of difficult-to-deform metal materials and improve the comprehensive mechanical properties and shape control of Fe-Mn-Al-C lightweight steel strips.

[0005] The technical solution of the present invention is as follows: Specifically, this invention provides a method for producing Fe-Mn-Al-C lightweight steel using dynamic staggered asynchronous rolling. The Fe-Mn-Al-C lightweight steel has an austenitic + ferrite dual-phase microstructure, with the following chemical composition: 0.60%-1.00% C, 10.0%-25.0% Mn, 5.0%-12.0% Al, P < 0.003%, S < 0.002%, 0.40%-0.60% Si, 0.033%-0.053% Nb, with the balance being Fe and impurities. The density of the Fe-Mn-Al-C lightweight steel is 6.65-7.05 g / cm³. 3 The horizontal speed of the rolling mill is set to a fixed value. Variable thickness dynamic misalignment asynchronous rolling is achieved by continuously and dynamically adjusting the roll gap up and down. This includes the following steps: S1, continuous casting; S2, Preparatory heat treatment; S3, Single-pass variable thickness dynamic misaligned asynchronous rolling; S4. Final heat treatment; S5, Straightening, Shearing; S6, winding; The Fe-Mn-Al-C lightweight steel strip obtained by continuous casting is subjected to preheating treatment; the strip zone I is heated to 1100℃-1200℃ in a medium-frequency induction heating furnace, where the normalizing temperature is reached at 727℃-950℃ and the strip zone I reaches the austenitic recrystallized state; the strip zone II is induction heated to reach the austenitic non-recrystallized state, with the temperature of the strip zone II being 750℃-900℃; the strip zone III is not heated; the Fe-Mn-Al-C lightweight steel strip is then subjected to variable thickness dynamic staggered asynchronous rolling. In single-pass variable thickness dynamic misaligned asynchronous rolling, the horizontal speed of the mill is set to a fixed value, the friction coefficient is set to 0.7, the roll speed ratio is set to 1.2, the misalignment is set to 2mm, the upper and lower work roll diameters are R, the upper work roll speed is v1, and the lower work roll speed is v2. Under mill load, a powerful hydraulic cylinder roll gap control system continuously changes the roll gap size, and the single-pass reduction is controlled between 0-6mm, so that the 15mm equal thickness slab achieves the set thickness variation after rolling, that is, the thickness of the thick zone is 12mm and the length of the thick zone is 85mm; the thickness of the thin zone is 9mm and the length of the thin zone is 100mm; the slope of the thickness continuous transition zone is 1:100 and the length is 90mm; then the final heat treatment process is carried out. After rolling, the strip is induction heated to maintain the temperature of zones I and II at 950℃ and 750℃ respectively. Zones I and II are then subjected to laminar flow cooling to complete the high-temperature quenching and sub-temperature quenching processes. Zones I and II are then induction heated to 200℃-300℃ and 500℃-600℃ respectively for tempering. Zone III is heated to 950℃-1000℃ for annealing, with an annealing time of 30min-120min.

[0006] Furthermore, in the variable thickness dynamic misaligned asynchronous rolling parameters, the misalignment angle is constant, the upper and lower roll speeds are different, and the deformation region is divided into three zones: I, II, and III. A rolling force and rolling torque model is calculated, which differs from existing variable diameter and variable speed dynamic misaligned asynchronous rolling models. and These are the neutral points of the contact arcs of the upper and lower rolls, respectively. This refers to the misalignment between the upper and lower rolls. The length of the rolling deformation zone, with the neutral point as the reference point. exist( , ), exist( , Within the range of ), the rolling deformation zone is divided into the back slip zone, the rolling roll zone, and the front slip zone; the rolling force and rolling torque model is as follows:

[0007]

[0008]

[0009]

[0010]

[0011]

[0012]

[0013]

[0014]

[0015] In the formula: For the rolling force of the upper roll, For the rolling force of the lower roll, For the rolling torque of the upper roll, The rolling torque of the lower roll, For the width of the rolled piece, For a constant offset angle, For misalignment quantity, The length of the deformation zone. , These are the contact arcs within the deformation zone, The variable angle of the axis, , These represent the unit pressure exerted on the upper and lower surfaces within the deformation zone, respectively. , These represent the shear stresses on the upper and lower surfaces within the deformation zone, respectively. Zones I, II, and III are the back-slip zone, rolling zone, and front-slip zone, respectively.

[0016] Furthermore, the laminar cooling rate of strip I is greater than the critical quenching cooling rate of Fe-Mn-Al-C lightweight steel. The tempering temperature of strip I is maintained at 200℃-300℃ and air-cooled to room temperature. The resulting microstructure of strip I is tempered martensite and uniform fine granular carbide.

[0017] Furthermore, the tempering temperature in zone II of the strip is maintained at 500℃-600℃, and zone II of the strip is air-cooled to room temperature to obtain tempered sorbite structure.

[0018] Furthermore, the laminar flow cooling device consists of an upper water spray mechanism and a lower water spray mechanism. It cools the high-temperature strip I and II regions by spraying cooling water. The laminar flow cooling treatment adjusts the arrangement of the cooling water spray mechanism and the cooling water flow rate according to the I and II regions of the Fe-Mn-Al-C system lightweight steel strip, improving the accuracy and stability of flow rate zone control. After high-temperature and sub-temperature quenching of the Fe-Mn-Al-C system lightweight steel strip I and II regions, the cooling rate is precisely controlled to obtain the microstructure transformation products martensite and ferrite respectively.

[0019] Furthermore, the plate and strip are annealed in Zone III at 950℃-1000℃ for a time of less than 120 minutes. This reduces the high-temperature ferrite content by at least 52%, and the austenite grains coarsen and the carbides are completely dissolved in the austenite matrix.

[0020] Furthermore, the heating method of the medium-frequency induction heating furnace is an induction heating device that combines transverse and longitudinal magnetic fields. The longitudinal magnetic field provides uniform temperature in the width direction, while the transverse magnetic field provides uniform temperature in the thickness direction. The arrangement of the magnetic conductors inside the induction heating furnace is changed, and the arrangement can be either sheet-like or ring-like, to obtain a customized temperature field. A nozzle cooling device is added to the medium-frequency induction heating furnace, and the nozzle cooling device is arranged in the plate and strip area where heating is not required and heat conduction is avoided, so as to prevent the local induction heating process of the plate and strip from affecting the temperature control of the designated area.

[0021] Compared with the prior art, the present invention has the following advantages: (1) The present invention provides a method for producing Fe-Mn-Al-C lightweight steel by dynamic misaligned asynchronous rolling. In the traditional variable thickness rolling process, the rolls are misaligned and the upper and lower rolls have different speeds. The misaligned layout will generate a rolling zone and shear force, which can make the plate penetrate to the core more than conventional rolling through shear deformation. At the same time, the amount of misalignment between the rolls can control the bending of the plate caused by the different speeds of the rolls, and improve the core deformation penetration and overall deformation uniformity of the strip. The present invention solves the problems of insufficient and uneven central deformation and strip deformation when rolling Fe-Mn-Al-C lightweight steel, a high-strength, high-toughness, and difficult-to-deform metal material.

[0022] (2) This invention provides a method for producing Fe-Mn-Al-C lightweight steel using dynamic staggered asynchronous rolling, which can differentiate the microstructure and properties of plates with varying thicknesses. By performing various pre-heat treatment processes and final heat treatment processes on different regions of the strip, including induction heating to different temperature ranges and variable thickness rolling at room temperature, followed by high-temperature quenching-low-temperature tempering, sub-temperature quenching-high-temperature tempering, and annealing processes, high strength, hardness, wear resistance, plasticity, toughness, and corrosion resistance can be obtained. This invention can replace traditional laser welding technology to obtain strips with multiple properties, resulting in Fe-Mn-Al-C lightweight steel strips with both low density and good performance distribution, ensuring that lightweighting and multi-functional steel are achieved as much as possible without sacrificing the strength of equipment structural components. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the dynamic misalignment asynchronous rolling deformation zone of Fe-Mn-Al-C system lightweight steel with varying thickness; Figure 2 This is a schematic diagram of the production process of Fe-Mn-Al-C series lightweight steel variable thickness plate; Figure 3 This is a schematic diagram showing the division of microstructure and property control regions in Fe-Mn-Al-C series lightweight steel plates with varying thickness differences. Detailed Implementation

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0025] A schematic diagram of the rolling deformation zone is shown below. Figure 1 As shown in the diagram, the production process flow chart is as follows: Figure 2 As shown in the diagram, the tissue performance regulation region is divided as follows: Figure 3 As shown.

[0026] This invention provides a method for producing Fe-Mn-Al-C lightweight steel using dynamic staggered asynchronous rolling. The Fe-Mn-Al-C lightweight steel has an austenitic + ferrite dual-phase microstructure and a chemical composition of: 0.60%-1.00% C, 10.0%-25.0% Mn, 5.0%-12.0% Al, P < 0.003%, S < 0.002%, 0.40%-0.60% Si, 0.033%-0.053% Nb, with the balance being Fe and impurities. The density of the Fe-Mn-Al-C lightweight steel is 6.65-7.05 g / cm³. 3 The horizontal speed of the rolling mill is set to a fixed value. Variable thickness dynamic misalignment asynchronous rolling is achieved by continuously and dynamically adjusting the roll gap up and down. This includes the following steps: S1, continuous casting; S2, Preparatory heat treatment; S3, Single-pass variable thickness dynamic misaligned asynchronous rolling; S4. Final heat treatment; S5, Straightening, Shearing; S6, winding; The Fe-Mn-Al-C lightweight steel strip obtained by continuous casting is subjected to preheating treatment; the strip zone I is heated to 1100℃-1200℃ in a medium-frequency induction heating furnace, where the normalizing temperature is reached at 727℃-950℃ and the strip zone I reaches the austenitic recrystallized state; the strip zone II is induction heated to reach the austenitic non-recrystallized state, with the temperature of the strip zone II being 750℃-900℃; the strip zone III is not heated; the Fe-Mn-Al-C lightweight steel strip is then subjected to variable thickness dynamic staggered asynchronous rolling. In single-pass variable thickness dynamic misaligned asynchronous rolling, the horizontal speed of the mill is set to a fixed value, the friction coefficient is set to 0.7, the roll speed ratio is set to 1.2, the misalignment is set to 2mm, the upper and lower work roll diameters are R, the upper work roll speed is v1, and the lower work roll speed is v2. Under mill load, a powerful hydraulic cylinder roll gap control system continuously changes the roll gap size, and the single-pass reduction is controlled between 0-6mm, so that the 15mm equal thickness slab achieves the set thickness variation after rolling, that is, the thickness of the thick zone is 12mm and the length of the thick zone is 85mm; the thickness of the thin zone is 9mm and the length of the thin zone is 100mm; the slope of the thickness continuous transition zone is 1:100 and the length is 90mm; then the final heat treatment process is carried out. After rolling, the strip is induction heated to maintain the temperature of zones I and II at 950℃ and 750℃ respectively. Zones I and II are then subjected to laminar flow cooling to complete the high-temperature quenching and sub-temperature quenching processes. Zones I and II are then induction heated to 200℃-300℃ and 500℃-600℃ respectively for tempering. Zone III is heated to 950℃-1000℃ for annealing, with an annealing time of 30min-120min.

[0027] In the variable thickness dynamic misaligned asynchronous rolling parameters, the misalignment angle is constant, the upper and lower roll speeds are different, and the deformation region is divided into three zones: I, II, and III. A rolling force and rolling torque model is calculated, which differs from existing dynamic misaligned asynchronous rolling models with different diameters and speeds. and These are the neutral points of the contact arcs of the upper and lower rolls, respectively. This refers to the misalignment between the upper and lower rolls. The length of the rolling deformation zone, with the neutral point as the reference point. exist( , ), exist( , Within the range of ), the rolling deformation zone is divided into the back slip zone, the rolling roll zone, and the front slip zone; the rolling force and rolling torque model is as follows:

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036] In the formula: For the rolling force of the upper roll, For the rolling force of the lower roll, For the rolling torque of the upper roll, The rolling torque of the lower roll, For the width of the rolled piece, For a constant offset angle, For misalignment quantity, The length of the deformation zone. , These are the contact arcs within the deformation zone, The variable angle of the axis, , These represent the unit pressure exerted on the upper and lower surfaces within the deformation zone, respectively. , These represent the shear stresses on the upper and lower surfaces within the deformation zone, respectively. Zones I, II, and III are the back-slip zone, rolling zone, and front-slip zone, respectively.

[0037] The laminar cooling rate of strip I is greater than the critical quenching cooling rate of Fe-Mn-Al-C lightweight steel. The tempering temperature of strip I is maintained at 200℃-300℃ and air-cooled to room temperature. The resulting microstructure of strip I is tempered martensite and uniform fine granular carbide.

[0038] The tempering temperature in zone II of the strip is maintained at 500℃-600℃, and the strip II is air-cooled to room temperature to obtain tempered sorbite structure.

[0039] The laminar flow cooling device consists of an upper water spray mechanism and a lower water spray mechanism. It cools the high-temperature strip I and II zones by spraying cooling water. The laminar flow cooling treatment adjusts the arrangement of the cooling water spray mechanism and the cooling water flow rate according to the I and II zones of the Fe-Mn-Al-C lightweight steel strip, improving the accuracy and stability of flow rate zone control. After high-temperature and sub-temperature quenching of the Fe-Mn-Al-C lightweight steel strip I and II zones, the cooling rate is precisely controlled to obtain the microstructure transformation products martensite and ferrite respectively.

[0040] The strip is annealed in Zone III at 950℃-1000℃ for a time of less than 120 minutes. The high-temperature ferrite content is reduced by at least 52%, and the austenite grains are coarsened and the carbides are completely dissolved in the austenite matrix.

[0041] The heating method of the medium-frequency induction heating furnace is an induction heating device that combines transverse and longitudinal magnetic fields. The longitudinal magnetic field provides uniform temperature in the width direction, while the transverse magnetic field provides uniform temperature in the thickness direction. Furthermore, the arrangement of the magnetic conductors inside the induction heating furnace is changed, using either sheet or ring arrangement to obtain a customized temperature field. A nozzle cooling device is added to the medium-frequency induction heating furnace, and the nozzle cooling device is arranged in the plate and strip area where heating is not required and heat conduction is avoided, so as to prevent the local induction heating process of the plate and strip from affecting the temperature control of the designated area.

[0042] Example 1 This embodiment: The Fe-Mn-Al-C lightweight steel of the present invention has an austenitic + ferrite dual-phase structure, with the following chemical composition: 0.60%-1.00% C, 10.0%-25.0% Mn, 5.0%-12.0% Al, P<0.003%, S<0.002%, 0.40%-0.60% Si, 0.033%-0.053% Nb, with the balance being Fe and unavoidable impurities. The density of the Fe-Mn-Al-C lightweight dual-phase steel is 6.65~7.05 g / cm³. 3 Ignoring the variation in workpiece width before rolling, a 15mm uniform thickness plate (I zone) of Fe-Mn-Al-C lightweight steel obtained by continuous casting is pre-heat treated and then subjected to variable thickness rolling to obtain a set thickness variation: the thickness of the thick zone is 12mm and the length of the thick zone is 85mm; the thickness of the thin zone is 9mm and the length of the thin zone is 100mm; the slope of the continuous thickness transition zone is 1:100 and the length is 90mm; then, a final heat treatment is performed, including the following steps: In the production process of this embodiment, the Fe-Mn-Al-C series lightweight steel plates of equal thickness obtained by continuous casting are subjected to preheating treatment; the temperature of the strip I region is induction heated to 1100℃-1200℃ to eliminate Widmanstätten and banded structures, and the strip I region reaches the austenite recrystallization state, and then a variable thickness dynamic misaligned asynchronous rolling process is carried out.

[0043] In single-pass variable thickness dynamic misaligned asynchronous rolling, the initial rolling temperature of strip zone I is 1100℃-1200℃, and the final rolling temperature is 950℃-1050℃. The horizontal speed of the mill is set to a fixed value, the friction coefficient of variable thickness dynamic misaligned asynchronous rolling is set to 0.7, the roll speed ratio is set to 1.2, and the misalignment amount is set to 2mm. The upper and lower rolls have the same diameter but different roll speeds. Under the condition of mill load, the roll gap control system of powerful hydraulic cylinder is used to continuously change the roll gap size, with a reduction of 6mm, so that the 15mm equal thickness slab achieves the set longitudinal thickness change after rolling; then the final heat treatment process is carried out.

[0044] The austenite-refined austenite grains in strip region I were obtained by induction heating and held at 950℃. Strip region I underwent high-temperature quenching via laminar flow cooling, with the cooling rate exceeding the critical quenching rate. It was then subjected to low-temperature tempering, maintaining the temperature of strip region I between 200℃ and 300℃, followed by air cooling to room temperature. Strip regions II and III were annealed at 950℃-1000℃ for 30 minutes, followed by air cooling to room temperature. Strip region I yielded tempered martensite and uniformly fine granular carbide microstructure. The high-temperature ferrite content in strip regions II and III was reduced by at least 52%, and the austenite grains were coarsened, with the carbides completely dissolved in the austenite matrix.

[0045] Through the above-mentioned process, the Fe-Mn-Al-C series lightweight steel strip can solve the problem of strip bending by variable thickness dynamic staggered asynchronous rolling process. Moreover, the core deformation is more uniform under limited reduction. The differential thickness plate I region can obtain excellent hardness and wear resistance, while the strip II and III regions have excellent plasticity and toughness. This method significantly improves the strip's post-rolling deformation, microstructure uniformity and mechanical properties, and can widely improve the rolling and microstructure property control of Fe-Mn-Al-C series lightweight steel high-strength and high-toughness materials.

[0046] Example 2 This embodiment: The Fe-Mn-Al-C lightweight steel of the present invention has an austenitic + ferrite dual-phase structure, with the following chemical composition: 0.60%-1.00% C, 10.0%-25.0% Mn, 5.0%-12.0% Al, P<0.003%, S<0.002%, 0.40%-0.60% Si, 0.033%-0.053% Nb, with the balance being Fe and unavoidable impurities. The density of the Fe-Mn-Al-C lightweight dual-phase steel is 6.65~7.05 g / cm³. 3 Ignoring the variation in workpiece width before rolling, a 15mm uniform thickness plate of Fe-Mn-Al-C lightweight steel obtained by continuous casting is subjected to pre-heat treatment in Zone II, followed by variable thickness rolling to obtain a set thickness variation: the thickness of the thick zone is 12mm, and the length of the thick zone is 85mm; the thickness of the thin zone is 9mm, and the length of the thin zone is 100mm; the slope of the continuous thickness transition zone is 1:100, and the length is 90mm; then, a final heat treatment process is performed, including the following steps: In this embodiment, the Fe-Mn-Al-C series lightweight steel plates of equal thickness obtained by continuous casting are subjected to preheating treatment; the temperature of the strip II region is controlled at 750℃-900℃ by induction heating to the range of austenitization temperature to the non-recrystallization temperature of austenite, and the strip II region is in the state of non-recrystallization of austenite; then variable thickness dynamic misalignment asynchronous rolling is performed.

[0047] In single-pass variable thickness dynamic misaligned asynchronous rolling, the initial rolling temperature of strip zone II is 750℃-900℃, and the final rolling temperature is 650℃-750℃. The horizontal speed of the mill is set to a fixed value, the friction coefficient of variable thickness dynamic misaligned asynchronous rolling is set to 0.7, the roll speed ratio is set to 1.2, and the misalignment amount is set to 2mm. The upper and lower rolls have the same diameter but different roll speeds. Under the condition of mill load, the roll gap control system of powerful hydraulic cylinder is used to continuously change the roll gap size. The slope of the thickness continuous transition zone is 1:100, so that the 15mm equal thickness slab achieves the set longitudinal thickness change after rolling. Then, the final heat treatment process is carried out.

[0048] After induction heating of region II of the Fe-Mn-Al-C lightweight steel strip to 650℃, region II underwent sub-critical quenching via laminar flow cooling, resulting in a uniformly distributed fine ferrite microstructure containing a small amount of martensite. Region II was then subjected to high-temperature tempering at 500℃-600℃, followed by air cooling to room temperature, yielding tempered sorbite. Regions I and III of the strip were annealed at 950℃-1000℃ for 30 minutes, followed by air cooling to room temperature. The high-temperature ferrite content in regions I and III decreased, and the austenite grains coarsened while the carbides were completely dissolved in the austenite matrix.

[0049] Through the above-mentioned process, the Fe-Mn-Al-C series lightweight steel strip can solve the problem of strip bending by variable thickness dynamic staggered asynchronous rolling process. Moreover, the core deformation is more uniform under limited reduction. The differential thickness plate II region can obtain excellent plasticity and toughness, while the strip I and III regions have good strength, toughness and corrosion resistance. This method significantly improves the strip's post-rolling deformation, microstructure uniformity and mechanical properties, and can widely improve the rolling and microstructure property control problems of Fe-Mn-Al-C series high-strength and high-toughness materials.

[0050] Example 3 This embodiment: The Fe-Mn-Al-C lightweight steel of the present invention has an austenitic + ferrite dual-phase structure, with the following chemical composition: 0.60%-1.00% C, 10.0%-25.0% Mn, 5.0%-12.0% Al, P<0.003%, S<0.002%, 0.40%-0.60% Si, 0.033%-0.053% Nb, with the balance being Fe and unavoidable impurities. The density of the Fe-Mn-Al-C lightweight dual-phase steel is 6.65~7.05 g / cm³. 3Ignoring the variation in workpiece width before rolling, a 15mm uniform thickness plate of Fe-Mn-Al-C lightweight steel obtained by continuous casting is subjected to pre-heat treatment in Zone III, followed by variable thickness rolling to obtain a set thickness variation: the thickness of the thick zone is 12mm, and the length of the thick zone is 85mm; the thickness of the thin zone is 9mm, and the length of the thin zone is 100mm; the slope of the continuous thickness transition zone is 1:100, and the length is 90mm; then, a final heat treatment process is performed, including the following steps: In this embodiment, the Fe-Mn-Al-C series lightweight steel plates of equal thickness obtained by continuous casting are subjected to preheating treatment. The temperature of the strip in zones I and II is induction heated to 1100℃-1200℃ in a medium-frequency induction heating furnace, while zone III is not heated. A nozzle cooling device is added to the medium-frequency induction heating furnace, and the nozzle cooling device is arranged in the strip area where heating is not required and heat conduction is avoided, so as to prevent the local induction heating process of the strip from affecting the temperature control of the designated area. Then, variable thickness dynamic staggered asynchronous rolling is performed.

[0051] In single-pass variable thickness dynamic misaligned asynchronous rolling, the horizontal speed of the mill is set to a fixed value, the friction coefficient of variable thickness dynamic misaligned asynchronous rolling is set to 0.7, the roll speed ratio is set to 1.2, the misalignment amount is set to 2mm, the upper and lower rolls have the same diameter but different roll speeds, and the roll gap size is continuously changed by a powerful hydraulic cylinder roll gap control system under the condition of mill load, with the reduction amount set to 3mm, so that the 15mm equal thickness slab billet achieves the set longitudinal thickness change after rolling; then the final heat treatment process is carried out.

[0052] The Fe-Mn-Al-C lightweight steel strip was subjected to high-temperature quenching and low-temperature tempering in zones I and II. The temperatures in zones I and II were controlled at 950℃-1050℃ and 200℃-300℃, respectively. The tempered microstructure consisted of tempered martensite and uniform, fine-grained carbides. In a medium-frequency induction furnace, zone III of the strip was heated to 950℃-1000℃ for annealing for 30-120 minutes. This process reduced the ferrite content at high temperatures, coarsened the austenite grains, and ensured complete dissolution of carbides within the austenite matrix. The extended annealing time increased the content of the B2 phase precipitated within the austenite. The B2 phase, with an ordered body-centered cubic structure and an ideal chemical formula of FeAl, improved the corrosion resistance of the Fe-Mn-Al-C lightweight steel strip.

[0053] Through the above-mentioned process, the variable thickness dynamic staggered asynchronous rolling process can solve the problem of plate bending in Fe-Mn-Al-C lightweight steel strips. Moreover, the core deformation is more uniform under limited reduction. The differential thickness plate can obtain excellent hardness and wear resistance in regions I and II, while region III has good toughness and corrosion resistance. This method significantly improves the deformation, microstructure uniformity and mechanical properties of the strip after rolling, and can widely improve the rolling and microstructure control of high-strength and high-toughness Fe-Mn-Al-C lightweight steel materials.

[0054] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for producing Fe-Mn-Al-C series lightweight steel by dynamic staggered asynchronous rolling, characterized in that, Fe-Mn-Al-C lightweight steel has an austenitic + ferrite dual-phase microstructure. Its chemical composition is: 0.60%-1.00% C, 10.0%-25.0% Mn, 5.0%-12.0% Al, P<0.003%, S<0.002%, 0.40%-0.60% Si, 0.033%-0.053% Nb, with the balance being Fe and impurities. The density of Fe-Mn-Al-C lightweight steel is 6.65-7.05 g / cm³. 3 The horizontal speed of the rolling mill is set to a fixed value. Variable thickness dynamic misalignment asynchronous rolling is achieved by continuously and dynamically adjusting the roll gap up and down. This includes the following steps: S1, continuous casting; S2, Preparatory heat treatment; S3, Single-pass variable thickness dynamic misaligned asynchronous rolling; S4. Final heat treatment; S5, Straightening, Shearing; S6, winding; The Fe-Mn-Al-C lightweight steel strip obtained by continuous casting is subjected to preheating treatment; the strip zone I is heated to 1100℃-1200℃ in a medium-frequency induction heating furnace, where the normalizing temperature is reached at 727℃-950℃ and the strip zone I reaches the austenitic recrystallized state; the strip zone II is induction heated to reach the austenitic non-recrystallized state, with the temperature of the strip zone II being 750℃-900℃; the strip zone III is not heated; the Fe-Mn-Al-C lightweight steel strip is then subjected to variable thickness dynamic staggered asynchronous rolling. In single-pass variable thickness dynamic misaligned asynchronous rolling, the horizontal speed of the mill is set to a fixed value, the friction coefficient is set to 0.7, the roll speed ratio is set to 1.2, the misalignment is set to 2mm, the upper and lower work roll diameters are R, the upper work roll speed is v1, and the lower work roll speed is v2. Under mill load, a powerful hydraulic cylinder roll gap control system continuously changes the roll gap size, and the single-pass reduction is controlled between 0-6mm, so that the 15mm equal thickness slab achieves the set thickness variation after rolling, that is, the thickness of the thick zone is 12mm and the length of the thick zone is 85mm; the thickness of the thin zone is 9mm and the length of the thin zone is 100mm; the slope of the thickness continuous transition zone is 1:100 and the length is 90mm; then the final heat treatment process is carried out. After rolling, the strip is induction heated to maintain the temperature of zones I and II at 950℃ and 750℃ respectively. Zones I and II are then subjected to laminar flow cooling to complete the high-temperature quenching and sub-temperature quenching processes. Zones I and II are then induction heated to 200℃-300℃ and 500℃-600℃ respectively for tempering. Zone III is heated to 950℃-1000℃ for annealing, with an annealing time of 30min-120min.

2. The method for producing Fe-Mn-Al-C series lightweight steel by dynamic staggered asynchronous rolling according to claim 1, characterized in that: In the variable thickness dynamic misaligned asynchronous rolling parameters, the misalignment angle is constant, the upper and lower roll speeds are different, and the deformation region is divided into three zones: I, II, and III. A rolling force and rolling torque model is calculated, which differs from existing dynamic misaligned asynchronous rolling models with different diameters and speeds. and These are the neutral points of the contact arcs of the upper and lower rolls, respectively. This refers to the misalignment between the upper and lower rolls. The length of the rolling deformation zone, with the neutral point as the reference point. exist( , ), exist( , Within the range of ), the rolling deformation zone is divided into Zone I, Zone II, and Zone III; the rolling force and rolling torque model is as follows: ； ； ； ； ； ； ； ； In the formula: For the rolling force of the upper roll, For the rolling force of the lower roll, For the rolling torque of the upper roll, The rolling torque of the lower roll, For the width of the rolled piece, For a constant offset angle, For misalignment quantity, The length of the deformation zone. , These are the contact arcs within the deformation zone, The variable angle of the axis, , These represent the unit pressure exerted on the upper and lower surfaces within the deformation zone, respectively. , These represent the shear stresses on the upper and lower surfaces within the deformation zone, respectively. Rolling deformation zones I, II, and III are the back slip zone, rolling zone, and front slip zone, respectively.

3. The method for producing Fe-Mn-Al-C series lightweight steel by dynamic staggered asynchronous rolling according to claim 1, characterized in that: The laminar cooling rate of strip I is greater than the critical quenching cooling rate of Fe-Mn-Al-C lightweight steel. The tempering temperature of strip I is maintained at 200℃-300℃ and air-cooled to room temperature. The resulting microstructure of strip I is tempered martensite and uniform fine granular carbide.

4. The method for producing Fe-Mn-Al-C series lightweight steel by dynamic staggered asynchronous rolling according to claim 1, characterized in that: The tempering temperature in zone II of the strip is maintained at 500℃-600℃, and the strip II is air-cooled to room temperature to obtain tempered sorbite structure.

5. The method for producing Fe-Mn-Al-C series lightweight steel by dynamic staggered asynchronous rolling according to claim 1, characterized in that: The laminar flow cooling device consists of an upper water spray mechanism and a lower water spray mechanism. It cools the high-temperature strip I and II zones by spraying cooling water. The laminar flow cooling treatment adjusts the arrangement of the cooling water spray mechanism and the cooling water flow rate according to the I and II zones of the Fe-Mn-Al-C lightweight steel strip, improving the accuracy and stability of flow rate zone control. After high-temperature and sub-temperature quenching of the Fe-Mn-Al-C lightweight steel strip I and II zones, the cooling rate is precisely controlled to obtain the microstructure transformation products martensite and ferrite respectively.

6. The method for producing Fe-Mn-Al-C series lightweight steel by dynamic staggered asynchronous rolling according to claim 1, characterized in that: The strip is annealed in Zone III at 950℃-1000℃ for a time of less than 120 minutes. The high-temperature ferrite content is reduced by at least 52%, and the austenite grains are coarsened and the carbides are completely dissolved in the austenite matrix.

7. The method for producing Fe-Mn-Al-C series lightweight steel by dynamic staggered asynchronous rolling according to claim 1, characterized in that: The heating method of the medium-frequency induction heating furnace is an induction heating device that combines transverse and longitudinal magnetic fields. The longitudinal magnetic field provides uniform temperature in the width direction, while the transverse magnetic field provides uniform temperature in the thickness direction. Furthermore, the arrangement of the magnetic conductors inside the induction heating furnace is changed, using either sheet or ring arrangement to obtain a customized temperature field. A nozzle cooling device is added to the medium-frequency induction heating furnace, and the nozzle cooling device is arranged in the plate and strip area where heating is not required and heat conduction is avoided, to prevent the local induction heating process of the plate and strip from affecting the temperature control of the designated area.

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