A method for preparing a 65Mn steel plate

Abstract

The application relates to the technical field of metallurgy and rolling, and particularly relates to a preparation method of a 65Mn steel plate. The method comprises the following steps: first heating a casting blank with a set chemical composition; wherein the casting blank has an initial temperature; first descaling the casting blank after the first heating, and then rough rolling to obtain an intermediate blank; second heating the intermediate blank, and controlling the heating rate of the second heating; second descaling the intermediate blank after the second heating, and then finish rolling to obtain a hot-rolled strip; and laminar cooling the hot-rolled strip, and then coiling to obtain the 65Mn steel plate; wherein the laminar cooling comprises: heat preservation treatment. The application solves the technical problem that a black ash defect is prone to occurring on the surface of an existing 65Mn steel plate.

Description

Technical Field

[0001] This application relates to the fields of metallurgy and steel rolling technology, and in particular to a method for preparing 65Mn steel plate. Background Technology

[0002] The MCCR casting and rolling line, the world's first multi-mode fully continuous casting and rolling production line, employs pioneering technologies such as electromagnetic induction heaters, tunnel-type soaking furnaces, and high-speed thin slab continuous casting machines. It takes only 25 minutes from molten steel to coil, offering numerous advantages including a short process, low investment, low energy consumption, multiple modes, and high efficiency. It can achieve various rolling modes such as headless and single-slab rolling, and can produce a wide range of steel grades, from ordinary cold-formed steel to high-strength steel. It also has significant advantages in the production of medium and high carbon steel; the short process shortens the high-temperature oxidation time, resulting in less surface oxide scale and decarburization in medium and high carbon steel.

[0003] However, when producing 65Mn medium-high carbon steel plates on the MCCR short-process production line, surface black and gray defects are prone to occur, affecting surface quality. Summary of the Invention

[0004] This application provides a method for preparing 65Mn steel plate to solve the technical problem that black and gray defects easily appear on the surface of existing 65Mn steel plates.

[0005] In a first aspect, this application provides a method for preparing 65Mn steel plate, the method comprising:

[0006] A first heating is performed on a billet having a set chemical composition; wherein the billet has an initial temperature;

[0007] The first heating billet is subjected to a first descaling process, followed by rough rolling to obtain an intermediate billet;

[0008] The intermediate billet is subjected to a second heating, and the heating rate of the second heating is controlled.

[0009] The intermediate billet after the second heating is subjected to a second descaling, followed by finish rolling to obtain hot-rolled strip steel;

[0010] The hot-rolled strip is subjected to laminar flow cooling and then coiled to obtain 65Mn steel plate; wherein, the laminar flow cooling includes: heat preservation treatment.

[0011] Optionally, the initial temperature is 930-1050℃.

[0012] Optionally, the temperature of the first heating is 1180-1210℃, and / or the heating time is 15-20 min.

[0013] Optionally, the heating rate of the second heating is 10-20℃ / s.

[0014] Optionally, the outlet temperature of the insulation treatment is 680-700℃.

[0015] Optionally, the winding temperature is 600-630℃.

[0016] Optionally, the second descaling of the intermediate billet after the second heating, followed by finish rolling to obtain hot-rolled strip steel, includes:

[0017] The intermediate billet after the second heating is subjected to a second descaling, and the pressure of the second descaling is controlled, followed by finishing rolling to obtain hot-rolled strip steel; wherein the descaling pressure of the first stand and the descaling pressure of the second stand are controlled.

[0018] Optionally, the descaling pressure of the first frame is 5-10 MPa, and / or the descaling pressure of the second frame is 30-38 MPa.

[0019] Optionally, the set components include:

[0020] C, Mn, Si, Alt, P, and Fe; among which,

[0021] The C content is 0.61-0.67 wt%, the Mn content is 0.8-2 wt%, the Si content is 0.15-0.3 wt%, the Alt content is 0.01-0.05 wt%, and the P content is 0.002-0.012 wt%.

[0022] Optionally, the first heating of the cast billet having a set chemical composition is performed; wherein the cast billet has an initial temperature, and the process further includes:

[0023] Molten steel is continuously cast, and the casting speed is controlled to obtain a cast billet; wherein the casting speed is 4.0-5.5 m / min.

[0024] The technical solutions provided in this application have the following advantages compared with the prior art:

[0025] The preparation method of the 65Mn steel plate provided in this application embodiment, under the existing MCCR short process, achieves semi-fine control of the C and P element content. At the same time, it reduces the oxidation time in the billet heating and controls the heating rate of the second heating to improve the density of the iron oxide scale. The heat preservation treatment during cooling can reduce the internal stress of the iron oxide scale and also reduce the porosity of the final iron scale, thereby avoiding the black and gray defects on the surface of 65Mn steel. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic flowchart illustrating a method for preparing a 65Mn steel plate provided in this application embodiment;

[0029] Figure 2 This is a surface oxide scale morphology diagram of a 65Mn steel plate provided in Embodiment 1 of this application;

[0030] Figure 3 This is a surface oxide scale morphology diagram of a 65Mn steel plate provided in Embodiment 2 of this application;

[0031] Figure 4 This is a surface oxide scale morphology diagram of a 65Mn steel plate provided in Embodiment 3 of this application;

[0032] Figure 5 A surface oxide scale morphology image of a 65Mn steel plate provided in Comparative Example 1 of this application;

[0033] Figure 6 This is a morphology diagram of the surface iron oxide scale of a 65Mn steel plate provided as Comparative Example 2 of this application. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0036] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0037] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0038] Firstly, this application provides a method for preparing 65Mn steel plate; please refer to [link to relevant documentation]. Figure 1 The method includes:

[0039] In this embodiment, the overall process route is: steel smelting - continuous casting - roller tunnel furnace - high-pressure descaling (HSB) - rough rolling - induction heating - high-pressure descaling (FSB) - finish rolling - laminar flow cooling - coiler. An MCCR continuous casting and rolling production line is used.

[0040] S1. A first heating is performed on a billet having a set chemical composition; wherein the billet has an initial temperature;

[0041] In some embodiments, the specified components include: C, Mn, Si, Alt, P, and Fe; wherein,

[0042] The C content is 0.61-0.67 wt%, the Mn content is 0.8-2 wt%, the Si content is 0.15-0.3 wt%, the Alt content is 0.01-0.05 wt%, and the P content is 0.002-0.012 wt%.

[0043] In the embodiments of this application, the positive effects of controlling the C content to 0.61-0.67% by weight are: it can ensure the final strength, wear resistance, hardness and hardenability of the product, while ensuring that the strip steel surface does not have defects such as decarburization and intergranular oxidation, and ensuring that the tool steel product meets the user's needs; if the C content exceeds this range, it may affect the strength performance, wear resistance and surface quality of the final product to a certain extent, and is prone to decarburization, segregation or insufficient wear resistance, which will affect the surface quality and microstructure of the product to a certain extent.

[0044] The positive effects of controlling the Mn content to 0.8-2% by weight include: ensuring the tensile strength and hardenability of the product, while improving the oxidation resistance of the strip surface and reducing the risks of decarburization and iron oxide scale shedding. If the Mn content exceeds this range, it may affect the surface quality and performance of the final product to some extent, easily leading to microstructure segregation, insufficient hardenability, or excessively high tensile strength and hardness, rendering the product unusable.

[0045] The positive effects of controlling the Si content to 0.15-0.3% by weight include: ensuring the tensile strength and hardenability of the product, while improving the oxidation resistance of the strip surface and reducing the risk of iron oxide scale peeling. If the Si content exceeds this range, it may affect the surface quality and performance of the final product to some extent, easily leading to red rust, insufficient hardenability, or intergranular oxidation, which will affect the surface quality and microstructure of the product to a certain extent.

[0046] The positive effects of controlling the Alt content to 0.01–0.05% by weight are: fixing the N element in the steel and preventing the formation of excessive TiN. Exceeding this range may affect the purity and fluidity of the molten steel and the quality of the slab, and form surface inclusions.

[0047] The positive effects of controlling the P content to 0.002-0.012% by weight are: to a certain extent, the strength, hardness and corrosion resistance of the product are guaranteed, especially when high carbon steel undergoes ferrite transformation, it can play a strengthening role. Exceeding this range may cause a decrease in plasticity, impact toughness and corrosion resistance, especially at low temperatures, it is easy to form cold brittleness.

[0048] In some embodiments, the initial temperature is 930-1050°C.

[0049] In this embodiment, "initial temperature" refers to the initial temperature of the billet during the first heating process. Controlling this initial temperature to 930-1050℃ has the following positive effects: reducing the thickness of the iron oxide scale formation, ensuring the surface quality of the strip, while simultaneously reducing furnace energy consumption and lowering costs. If the temperature is too high, it can cause decarburization and over-oxidation to some extent, resulting in defects such as iron oxide ash and black ash on the strip surface, affecting user performance. If the temperature is too low, it can affect the rolling stability of the rolling mill to some extent. This steel grade has a high carbon content and alloy content, resulting in a large rolling mill load, necessitating consideration of the rolling temperature. Specifically, the initial temperature can be 930℃, 950℃, 1000℃, 1050℃, etc.

[0050] In some embodiments, the temperature of the first heating is 1180-1210°C, and / or the heating time is 15-20 min.

[0051] In this embodiment, the "first heating" is carried out in a tunnel furnace with a furnace pressure of 10-15 Pa. Control

[0052] The positive effects of a first heating temperature of 1180-1210℃ and a first heating time of 15-20 minutes are: ensuring the temperature uniformity of the slab within the tunnel furnace. If the heating temperature is too high or the heating time is too long, it can cause decarburization and over-oxidation to some extent, resulting in defects such as iron oxide scale and black ash on the strip surface, affecting user performance. If the heating temperature is too low or the heating time is too short, it can affect the rolling stability of the rolling mill to some extent, easily causing mill deviation. Specifically, the first heating temperature can be 1180℃, 1190℃, 1200℃, 1210℃, etc., preferably 1190-1200℃, and the first heating time can be 15 minutes, 17 minutes, 20 minutes, etc. The temperature of the slab after the first heating is 1180-1210℃.

[0053] In some embodiments, the first heating of the billet having a predetermined chemical composition is performed; wherein the billet has an initial temperature, and the process further includes:

[0054] Molten steel is continuously cast, and the casting speed is controlled to obtain a cast billet; wherein the casting speed is 4.0-5.5 m / min.

[0055] In this embodiment, the positive effects of controlling the continuous casting speed to 4.0-5.5 m / min include: reducing the oxidation time of the slab, decreasing the thickness of the iron oxide scale, and simultaneously controlling the mill inlet temperature to ensure rolling stability. Specifically, the continuous casting speed can be 4.0 m / min, 4.3 m / min, 4.5 m / min, etc. Preferably, the continuous casting speed is 4.5-5.5 m / min. The thickness of the cast slab is 110-115 mm.

[0056] S2. The first heating billet is descaled and then rough rolled to obtain an intermediate billet;

[0057] S3. Perform a second heating on the intermediate billet and control the heating rate of the second heating;

[0058] In some embodiments, the heating rate of the second heating is 10-20°C / s.

[0059] In this embodiment, the "second heating" is induction heating. Controlling the heating rate of this induction heating to 10-20℃ / s has the following positive effects: it ensures the slab quickly reaches a reasonable mill inlet temperature under a certain steel feeding speed, thus guaranteeing rolling stability. If the heating rate is too high, it can cause severe oxidation on the surface of the intermediate slab, easily leading to the indentation of iron oxide scale after entering the mill. If the heating rate is too low, it may fail to meet the mill's rolling temperature requirements, causing excessive mill load, leading to accidents such as deviation and affecting the uniformity of the strip structure. Specifically, the heating rate can be 10℃ / s, 15℃ / s, 20℃ / s, etc. After high-pressure descaling (HSB), the billet enters three large reduction mills for continuous roughing and rolling to obtain intermediate billets. The intermediate billets then enter induction heating. When producing 65Mn, the induction heating device is in series with 9 groups. When producing 65Mn, groups 1-4 and 7-9 are turned on, while groups 5 and 6 are turned off to reduce the growth stress of iron oxide scale and prevent secondary oxidation of iron oxide scale during induction heating.

[0060] S4. The intermediate billet after the second heating is subjected to a second descaling, followed by finish rolling to obtain hot-rolled strip steel;

[0061] In some embodiments, the second descaling of the intermediate billet after the second heating, followed by finish rolling to obtain hot-rolled strip steel, includes:

[0062] The intermediate billet after the second heating is subjected to a second descaling, and the pressure of the second descaling is controlled, followed by finishing rolling to obtain hot-rolled strip steel; wherein the descaling pressure of the first stand and the descaling pressure of the second stand are controlled.

[0063] In some embodiments, the descaling pressure of the first frame is 5-10 MPa, and / or the descaling pressure of the second frame is 30-38 MPa.

[0064] In this embodiment, after induction heating, the intermediate billet undergoes fine descaling. To more effectively remove surface iron oxide scale, a dual descaling mode is adopted: low-pressure descaling on the first stand + high-pressure descaling on the second stand. This has the positive effect of ensuring thorough removal of iron oxide scale from the slab surface while minimizing process temperature drop. Side water spraying is used between intermediate stands F3-F4 in the finishing rolling zone to prevent oxidation of the strip exposed to air between stands. Controlling the descaling pressure of the first stand to 5-10 MPa and the descaling pressure of the second stand to 30-38 MPa has the positive effect of ensuring thorough removal of iron oxide scale from the slab surface while minimizing process temperature drop. Specifically, the descaling pressure of the first stand can be 5 MPa, 7 MPa, 9 MPa, 10 MPa, etc., and the descaling pressure of the second stand can be 30 MPa, 33 MPa, 36 MPa, 38 MPa, etc.

[0065] S5. The hot-rolled strip is subjected to laminar flow cooling and then coiled to obtain 65Mn steel plate; wherein, the laminar flow cooling includes: heat preservation treatment.

[0066] In this embodiment, a laminar flow cooling process is adopted. The laminar flow cooling process is extremely important for controlling the density of the iron oxide scale on the surface of the strip. The iron oxide scale on the surface of the strip after rolling has processing stress. If the strip is cooled immediately in the laminar flow cooling stage, it will lead to poor strip shape and deformation of the strip, which will aggravate the internal stress of the iron oxide scale on the surface. Therefore, cooling cannot be started immediately in the initial stage of laminar flow cooling. In order to better prevent poor strip shape caused by excessively rapid cooling of the strip, heat preservation treatment is adopted in the middle section of laminar flow cooling to ensure good strip shape, improve the uniformity of surface temperature of the strip width, and release the stress of the iron oxide scale.

[0067] In some embodiments, the outlet temperature of the insulation treatment is 680-700°C.

[0068] In this embodiment, "thermal insulation treatment" refers to the positive effects of using a thermal insulation cover and slow cooling mode to control the outlet temperature of the thermal insulation treatment at 680-700℃: ensuring normal phase transformation structure after delamination, and ensuring normal tensile strength and elongation after delamination. If the outlet temperature of the thermal insulation treatment is too high, it will affect the winding temperature to a certain extent, resulting in insufficient tensile strength, uneven structure, and substandard final product performance. If the outlet temperature of the thermal insulation treatment is too low, it will cause the winding temperature to be too low, resulting in excessive tensile strength, and may also lead to excessive cooling and poor sheet shape. Specifically, the outlet temperature of the thermal insulation treatment can be 680℃, 690℃, 700℃, etc.

[0069] In some embodiments, the winding temperature is 600-630°C.

[0070] In this embodiment, the positive effects of controlling the coiling temperature to 600-630℃ are: ensuring the strip steel structure is normal, meeting the requirements for tensile strength and elongation, and reducing the amount of tertiary iron oxide scale formation. Specifically, the coiling temperature can be 600℃, 610℃, 620℃, 630℃, etc.

[0071] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0072] Specific implementation steps:

[0073] S1. A first heating is performed on a billet having a set chemical composition; wherein the billet has an initial temperature;

[0074] S2. The heated billet is first descaled, and then rough rolled to obtain an intermediate billet;

[0075] S3. Perform a second heating on the intermediate billet and control the heating rate of the second heating;

[0076] S4. The intermediate billet after the second heating is subjected to a second descaling, followed by finish rolling to obtain hot-rolled strip steel;

[0077] S5. The hot-rolled strip is subjected to laminar flow cooling and then coiled to obtain 65Mn steel plate; wherein, the laminar flow cooling includes heat preservation treatment. For specific process steps, please refer to Table 1 and Table 2.

[0078] Table 1. Chemical composition (wt%) of 65Mn steel plate, the remainder being Fe and unavoidable impurities.

[0079] Serial Number C Mn Si Alt P Example 1 0.62 1.6 0.23 0.03 0.008 Example 2 0.64 1.3 0.17 0.05 0.007 Example 3 0.63 1.4 0.22 0.03 0.002 Comparative Example 1 0.68 1.2 0.28 0.05 0.015 Comparative Example 2 0.64 1.3 0.17 0.05 0.07

[0080] Table 2. Manufacturing process parameters for 65Mn steel plates

[0081]

[0082]

[0083] For Example 1: During the first heating, the tunnel furnace pressure was 10 Pa. When producing 65Mn, induction heating devices 1-4 groups and 7-9 groups were turned on, while groups 5 and 6 were turned off. The surface quality of the strip steel was photographed after uncoiling. The control of C, P, etc. in the composition, the initial temperature of the billet during the first heating, the descaling mode, and the slow cooling mode with the layer cooling insulation hood all met the requirements of the embodiments of this application. The heating rate in induction heating was slightly higher, and the black and gray defects on the surface of the steel plate were reduced but still existed. The control effect was only partially successful. Please refer to [link / reference]. Figure 2 .

[0084] For Example 2: In the first heating stage, the tunnel furnace pressure was 10 Pa, and the induction heating device was in a 9-group series configuration. When producing 65Mn, groups 1-4 and 7-9 were activated, while groups 5 and 6 were deactivated. The strip surface quality was photographed after uncoiling. The control of C and P in the composition and the slow cooling mode with the layered cooling insulation hood met the requirements of this application's embodiment. However, the initial temperature of the billet during the first heating was close to the upper limit required by this application's embodiment, and the descaling pressure of the first stand in the finishing mill was slightly lower than the lower limit required by this application's embodiment. A small amount of black and gray defects remained on the final steel plate surface. The control effect was basically successful. Please refer to [link / reference]. Figure 3 .

[0085] For Example 3: In the first heating stage, the tunnel furnace pressure was 14 Pa, and the induction heating device was in a 9-group series configuration. When producing 65Mn, groups 1-4 and 7-9 were activated, while groups 5 and 6 were deactivated. The strip surface quality was assessed by photographing the strip after uncoiling. Key control points, such as the C and P content in the composition, were monitored. The first heating temperature and time, the induction heating rate, and the slow cooling mode of the layered cooling insulation hood met the requirements of this application's embodiments. The descaling mode and coiling temperature also met the requirements of this application's embodiments. Ultimately, the black and gray defects on the steel plate surface were largely eliminated, indicating successful control. Please refer to [link to relevant documentation]. Figure 4 .

[0086] For Comparative Example 1: In the first heating stage, the tunnel furnace pressure was 12 Pa, and the induction heating device was in a 9-group series configuration. Groups 1-9 were activated during the production of 65Mn. The surface quality of the strip was photographed after uncoiling. Key control points, such as the C and P content, exceeded the upper limits required by the embodiments of this application. The induction heating rate was too high, and the slow cooling mode with an insulation cover was not used in the intermediate cooling stage. Furthermore, the first heating time slightly exceeded the upper limit required by the embodiments of this application. Ultimately, a large number of black and gray defects were present on the steel plate surface, indicating a failure in control effectiveness. Please refer to [link / reference needed]. Figure 5 .

[0087] For Comparative Example 2: During the first heating, the tunnel furnace pressure was 8 Pa, and the induction heating device was in a 9-group series configuration. When producing 65Mn, groups 1-4 and 7-9 were activated, while groups 5 and 6 were deactivated. The strip surface quality was photographed after uncoiling. Key control points, such as the control of C and P in the composition, and the slow cooling mode of the layered cooling insulation hood, met the requirements of the embodiments of this application. However, the initial temperature of the billet during the first heating significantly exceeded the upper limit required by the embodiments of this application, and the single-row scaling mode at the finishing mill entrance did not meet the requirements of the embodiments of this application. Ultimately, a small amount of black and gray defects existed on the surface of the steel plate, indicating a failure in control effectiveness. Please refer to [link / reference needed]. Figure 6 .

[0088] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing 65Mn steel plate, characterized in that, The method includes: A first heating is performed on a billet having a set chemical composition; wherein the billet has an initial temperature; The first heating billet is subjected to a first descaling process, followed by rough rolling to obtain an intermediate billet; The intermediate billet is subjected to a second heating, and the heating rate of the second heating is controlled. The intermediate billet after the second heating is subjected to a second descaling, followed by finish rolling to obtain hot-rolled strip steel; The hot-rolled strip is subjected to laminar flow cooling and then coiled to obtain 65Mn steel plate; wherein, the laminar flow cooling includes: heat preservation treatment; The heating rate of the second heating is 10-20℃ / s, and the outlet temperature of the heat preservation treatment is 680-700℃; The specified chemical composition includes: C content of 0.61-0.67% by weight and P content of 0.002-0.012% by weight.

2. The method according to claim 1, characterized in that, The initial temperature is 930-1050℃.

3. The method according to claim 1, characterized in that, The temperature of the first heating is 1180-1210℃, and / or the heating time is 15-20 min.

4. The method according to claim 1, characterized in that, The winding temperature is 600-630℃.

5. The method according to claim 1, characterized in that, The process of performing a second descaling on the intermediate billet after the second heating, followed by finish rolling to obtain hot-rolled strip steel, includes: The intermediate billet after the second heating is subjected to a second descaling, and the pressure of the second descaling is controlled, followed by finishing rolling to obtain hot-rolled strip steel; wherein the descaling pressure of the first stand and the descaling pressure of the second stand are controlled.

6. The method according to claim 5, characterized in that, The descaling pressure of the first frame is 5-10 MPa, and / or the descaling pressure of the second frame is 30-38 MPa.

7. The method according to claim 1, characterized in that, The specified chemical components also include: Mn, Si, Alt, and Fe; among them, The content of Mn is 0.8-2 wt%, the content of Si is 0.15-0.3 wt%, and the content of Alt is 0.01-0.05 wt%.

8. The method according to claim 1, characterized in that, A first heating is performed on a billet having a predetermined chemical composition; wherein the billet has an initial temperature, and the process includes: Molten steel is continuously cast, and the casting speed is controlled to obtain a cast billet; wherein the casting speed is 4.0-5.5 m / min.

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