CN117019869A - Preparation method of 65Mn steel plate - Google Patents

Abstract

The application relates to the technical field of metallurgy and steel rolling, in particular 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 cast strand has an initial temperature; performing first descaling on the first heated casting blank, and performing rough rolling to obtain an intermediate blank; performing second heating on the intermediate blank, and controlling the heating rate of the second heating; performing second descaling on the intermediate billet after second heating, and performing finish rolling to obtain hot rolled strip steel; performing laminar cooling on the hot rolled strip steel, and then coiling to obtain a 65Mn steel plate; wherein the laminar cooling comprises: and (5) heat preservation treatment. The application solves the technical problem that the surface of the existing 65Mn steel plate is easy to generate black ash defects.

Description

Preparation method of 65Mn steel plate

Technical Field

The application relates to the technical field of metallurgy and steel rolling, in particular to a preparation method of a 65Mn steel plate.

Background

The MCCR casting and rolling production line is used as the first multi-mode full-continuous casting and rolling production line in the world, adopts the innovative technologies of an electromagnetic induction heater, a tunnel soaking furnace, a high-pulling-speed sheet billet continuous casting machine and the like, only takes 25 minutes from molten steel to steel coil, has the advantages of short flow, low investment, low energy consumption, multi-mode, high efficiency and the like, can realize multi-mode rolling without heads, single billets and the like, has wider production steel grade range, and can realize common cold forming to high-strength steel. The production of the medium-high carbon steel also has obvious advantages, the high-temperature oxidation time is shortened in a short process, and the surface scale and decarburization of the medium-high carbon steel are slight.

However, when producing 65Mn medium-high carbon steel plates in an MCCR short-flow production line, surface black ash defects easily occur, and the surface quality is affected

Disclosure of Invention

The application provides a preparation method of a 65Mn steel plate, which aims to solve the technical problem that the surface of the existing 65Mn steel plate is easy to generate black ash defects.

In a first aspect, the present application provides a method for preparing a 65Mn steel sheet, the method comprising:

first heating a casting blank with a set chemical composition; wherein the cast strand has an initial temperature;

performing first descaling on the first heated casting blank, and performing rough rolling to obtain an intermediate blank;

performing second heating on the intermediate blank, and controlling the heating rate of the second heating;

performing second descaling on the intermediate billet after second heating, and performing finish rolling to obtain hot rolled strip steel;

performing laminar cooling on the hot rolled strip steel, and then coiling to obtain a 65Mn steel plate; wherein the laminar cooling comprises: and (5) heat preservation treatment.

Optionally, the initial temperature is 930-1050 ℃.

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

Optionally, the temperature rising rate of the second heating is 10-20 ℃/s.

Optionally, the outlet temperature of the heat preservation treatment is 680-700 ℃.

Optionally, the coiling temperature is 600-630 ℃.

Optionally, the second descaling is performed on the intermediate billet after the second heating, and then finish rolling is performed to obtain hot rolled strip steel, including:

performing second descaling on the intermediate billet after second heating, controlling the pressure of the second descaling, and performing finish rolling to obtain hot rolled strip steel; wherein the descaling pressure of the first rack and the descaling pressure of the second rack are controlled.

Optionally, the descaling pressure of the first stand is 5-10MPa, and or the descaling pressure of the second stand is 30-38MPa.

Optionally, the setting component includes:

C. mn, si, alt, P and Fe; wherein,

the content of C is 0.61-0.67 wt%, mn is 0.8-2 wt%, si is 0.15-0.3 wt%, alt is 0.01-0.05 wt%, and P is 0.002-0.012 wt%.

Optionally, the casting blank with the set chemical composition is subjected to first heating; wherein, the casting blank has initial temperature, before still includes:

continuously casting the molten steel, and controlling the drawing speed of continuous casting to obtain a casting blank; wherein the continuous casting has a pulling rate of 4.0-5.5m/min.

Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:

according to the preparation method of the 65Mn steel plate, under the existing MCCR short-flow process, the semi-fine control of the content of C and P elements is performed, meanwhile, the oxidation time in heating of a casting blank is reduced, the heating rate of second heating is controlled to improve the density of iron scales, the internal stress of the iron scales can be reduced through heat preservation treatment in cooling, the porosity degree of the final iron scales is also reduced, and therefore the black gray defect of the surface iron scales of 65Mn is avoided.

Drawings

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

In order to more clearly illustrate the embodiments of the application or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, and it will be obvious to a person skilled in the art that other drawings can be obtained from these drawings without inventive effort.

FIG. 1 is a schematic flow chart of a method for preparing a 65Mn steel plate according to an embodiment of the present application;

FIG. 2 is a surface scale morphology chart of a 65Mn steel plate provided in example 1 of the present application;

FIG. 3 is a surface scale morphology chart of a 65Mn steel plate provided in example 2 of the present application;

fig. 4 is a surface scale morphology chart of a 65Mn steel plate provided in embodiment 3 of the present application;

FIG. 5 is a surface scale morphology chart of a 65Mn steel plate provided in comparative example 1 of the present application;

fig. 6 is a surface scale morphology chart of a 65Mn steel plate provided in comparative example 2 of the present application.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Various embodiments of the application may exist in a range of forms; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the application; it is therefore to be understood that the range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that a description of a range 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, wherever applicable. In addition, whenever a numerical range is referred to herein, it is meant to include any reference number (fractional or integer) within the indicated range.

In the present application, unless otherwise specified, terms such as "upper" and "lower" are used specifically to refer to the orientation of the drawing in the figures. In addition, in the description of the present specification, the terms "include", "comprising" and the like mean "including but not limited to". Relational terms such as "first" and "second", and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Herein, "and/or" describing an association relationship of an association object means that there may be three relationships, for example, a and/or B, may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural. Herein, "at least one" means one or more, and "a plurality" means two or more. "at least one", "at least one" or the like refer to any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple, respectively.

Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present application are commercially available or may be prepared by existing methods.

In a first aspect, the present application provides a method for preparing a 65Mn steel sheet, referring to fig. 1, the method comprising:

in the embodiment of the application, the total process route is as follows: molten steel smelting-continuous casting-roller tunnel furnace-high pressure descaling HSB-rough rolling-induction heating-high pressure descaling FSB-finish rolling-laminar cooling-coiling machine. An MCCR continuous casting and rolling line is used.

S1, performing first heating on a casting blank with a set chemical composition; wherein the cast strand has an initial temperature;

in some embodiments, the setting component comprises: C. mn, si, alt, P and Fe; wherein,

the content of C is 0.61-0.67 wt%, mn is 0.8-2 wt%, si is 0.15-0.3 wt%, alt is 0.01-0.05 wt%, and P is 0.002-0.012 wt%.

In the embodiment of the application, the positive effect of controlling the content of C to be 0.61-0.67 wt%: the final strength, wear resistance, hardness and hardenability of the product can be ensured, and meanwhile, the defects of decarburization, inter-crystal oxidation and the like on the surface of the strip steel are avoided, so that the tool steel product can meet the requirements of users; if the content of C exceeds this range, the strength property and the wear resistance and the surface quality of the final product may be affected to some extent, decarburization, segregation or insufficient wear resistance may be easily formed, and the surface quality and the texture property of the product may be affected to some extent.

The positive effect of controlling the Mn content to be 0.8-2 wt%: the tensile strength and hardenability of the product can be ensured, the oxidation resistance of the surface layer of the strip steel can be improved, and the risks of decarburization, iron scale falling and the like are reduced. If the Mn content exceeds this range, it may affect the surface quality and properties of the final product to some extent, and it is easy to form tissue segregation, insufficient hardenability, or excessively high tensile strength, excessively hard hardness, and unusable, and to some extent, it may affect the surface quality and texture properties of the product.

The positive effect of controlling the Si content to be 0.15-0.3 wt%: the tensile strength and hardenability of the product can be ensured, meanwhile, the oxidation resistance of the surface layer of the strip steel can be improved, and the risks of iron scale falling off and the like are reduced. If the Si content exceeds this range, it may affect the surface quality and properties of the final product to some extent, red rust may be easily formed, hardenability may be insufficient, or intergranular oxidation may be affected to some extent.

The positive effect of controlling the content of Alt to be 0.01-0.05 wt%: the N element in the steel is fixed, excessive TiN is prevented from being formed, and exceeding the range can influence the purity and the fluidity of molten steel and the quality of a plate blank, so that surface inclusions are formed.

The positive effect of controlling the content of P to be 0.002-0.012 wt%: the strength, hardness and corrosion resistance of the product are ensured to a certain extent, particularly, the product can play a role in strengthening when high-carbon steel has ferrite transformation, and when the product is out of the range, the plasticity, the impact toughness and the corrosion resistance can be reduced, and particularly, cold brittleness is easy to form at low temperature.

In some embodiments, the initial temperature is 930-1050 ℃.

In the embodiment of the application, the "initial temperature" represents the initial temperature of the casting blank in the first heating, and the positive effect of controlling the initial temperature to be 930-1050 ℃ is that: the oxide scale generation thickness is reduced, the surface quality of strip steel is ensured, and the energy consumption and the cost of a heating furnace are reduced. If the temperature is too high, decarburization and peroxidation can be caused to a certain extent, so that the defects of iron sheet ash, black ash and the like appear on the surface of the strip steel, and the use of a user is influenced; if the temperature is too low, the rolling stability of the rolling mill is affected to a certain extent, the carbon content and alloy of the steel grade are high, the load of the rolling mill is high, and the rolling temperature needs to be considered. Specifically, the initial temperature may be 930 ℃, 950 ℃, 1000 ℃, 1050 ℃, etc.

In some embodiments, the first heating is at a temperature of 1180-1210 ℃, and/or the first heating is for a time of 15-20 minutes.

In the embodiment of the application, the first heating is performed in a tunnel furnace, and the furnace pressure of the tunnel furnace is 10-15Pa. Control of

The first heating temperature is 1180-1210 ℃, and the first heating time is 15-20min, which has the positive effects that: and the temperature uniformity of the slab in the tunnel furnace is ensured. If the heating temperature is too high or the heating time is too long, decarburization and peroxidation can be caused to a certain extent, so that the defects of iron sheet ash, black ash and the like appear on the surface of the strip steel, and the use of a user is influenced; if the heating temperature is too low or the heating time is too short, the rolling stability of the rolling mill is affected to a certain extent, and the rolling mill is easy to deviate. Specifically, the temperature of the first heating may be 1180 ℃, 1190 ℃, 1200 ℃, 1210 ℃, etc., preferably the temperature of the first heating is 1190-1200 ℃, and the time of the first heating may be 15min, 17min, 20min, etc. The temperature of the casting blank after the first heating is 1180-1210 ℃.

In some embodiments, the first heating is performed on the casting billet having the set chemical composition; wherein, the casting blank has initial temperature, before still includes:

continuously casting the molten steel, and controlling the drawing speed of continuous casting to obtain a casting blank; wherein the continuous casting has a pulling rate of 4.0-5.5m/min.

In the embodiment of the application, the positive effect of controlling the continuous casting pulling speed to be 4.0-5.5m/min is that: the oxidation time of the slab process is reduced, the oxide scale generation thickness is reduced, the inlet temperature of the rolling mill is controlled, and the rolling stability is ensured. Specifically, the drawing speed of the continuous casting may be 4.0m/min, 4.3m/min, 4.5m/min, or the like. Preferably, the continuous casting has a drawing speed of 4.5-5.5m/min. The thickness of the casting blank is 110-115mm.

S2, performing first descaling on the casting blank subjected to first heating, and performing rough rolling to obtain an intermediate blank;

s3, performing second heating on the intermediate blank, and controlling the heating rate of the second heating;

in some embodiments, the second heating has a ramp rate of 10-20 ℃/s.

In the embodiment of the application, the heating mode of the second heating is induction heating, and the heating rate of the induction heating is controlled to be 10-20 ℃/s, which has the positive effects that: on the premise of a certain steel feeding speed, the plate blank is ensured to quickly reach reasonable inlet temperature of the rolling mill, and rolling stability is ensured. If the temperature rising rate is too high, the surface of the intermediate billet is seriously oxidized to a certain extent, and oxidized iron sheets are easily pressed in after entering a rolling mill; if the temperature rising rate is too small, the rolling temperature requirement of the rolling mill can not be met to a certain extent, and the rolling mill is too high in load, so that accidents such as deflection and the like are caused, and the uniformity of the strip steel structure is affected. Specifically, the temperature rise rate may be 10 ℃/s, 15 ℃/s, 20 ℃/s, or the like. After high-pressure descaling HSB, the intermediate blank is obtained by entering three large-reduction rolling mills for rough rolling and continuous reduction, the intermediate blank is subjected to induction heating, when 65Mn is produced, the induction heating device is in a 9-group serial mode, when 65Mn is produced, the induction heating device is started to start 1-4 groups of numbers, and 7-9 groups of numbers, and 5-6 groups of numbers are closed, so that the growth stress of iron scales is reduced, and the secondary oxidation of the iron scales is prevented during induction heating.

S4, performing second descaling on the intermediate billet after the second heating, and performing finish rolling to obtain hot rolled strip steel;

in some embodiments, the second descaling the intermediate billet after the second heating, and then finish rolling to obtain a hot rolled strip comprises:

performing second descaling on the intermediate billet after second heating, controlling the pressure of the second descaling, and performing finish rolling to obtain hot rolled strip steel; wherein the descaling pressure of the first rack and the descaling pressure of the second rack are controlled.

In some embodiments, the first rack has a descaling pressure of 5-10MPa and or the second rack has a descaling pressure of 30-38MPa.

In the embodiment of the application, the intermediate billet is subjected to fine descaling after induction heating, and in order to remove the surface iron scales more effectively, a first frame small-pressure descaling mode and a second frame large-pressure double-row descaling mode are adopted, and the method has the positive effects that: ensures that the oxidized iron sheet on the surface of the plate blank is removed and simultaneously reduces the temperature drop of the process as much as possible. And side water spraying is used between the middle racks F3-F4 of the finish rolling area, so that strip steel among the racks is prevented from being oxidized when being exposed to air. The scale removal pressure of the first frame is controlled to be 5-10MPa, and the scale removal pressure of the second frame is controlled to be 30-38 MPa: ensures that the oxidized iron sheet on the surface of the plate blank is removed and simultaneously reduces the temperature drop of the process as much as possible. Specifically, the descaling pressure of the first stand may be 5MPa, 7MPa, 9MPa, 10MPa, etc., and the descaling pressure of the second stand may be 30MPa, 33MPa, 36MPa, 38MPa, etc.

S5, carrying out laminar cooling on the hot rolled strip steel, and then coiling to obtain a 65Mn steel plate; wherein the laminar cooling comprises: and (5) heat preservation treatment.

In the embodiment of the application, a laminar cooling process is adopted, the laminar cooling process is extremely important for controlling the compactness of the iron sheet on the surface of the strip steel, the rolled strip steel surface is provided with processing stress, if the strip steel is immediately cooled in a laminar cooling stage, poor plate shape can be caused, the strip steel is deformed to aggravate the internal stress of the surface iron sheet, therefore, the strip steel cannot be immediately put into cooling in the initial stage of laminar cooling, and in order to better prevent the poor plate shape caused by the excessively fast cooling of the strip steel, the middle stage of laminar cooling adopts heat preservation treatment, the good plate shape is ensured, the uniformity of the surface temperature of the plate width is improved, and the stress of the iron sheet is also released.

In some embodiments, the outlet temperature of the soak treatment is 680-700 ℃.

In the embodiment of the application, the heat preservation treatment is adopted in a heat preservation cover slow cooling mode, and the positive effect of controlling the outlet temperature of the heat preservation treatment to be 680-700 ℃ is that: the normal phase change structure after layer cooling is ensured, and the normal tensile strength and elongation after layer cooling is ensured. If the outlet temperature of the heat preservation treatment is too high, the coiling temperature can be influenced to a certain extent, the tensile strength is insufficient, and the tissue uniformity and the final product performance are not up to standard; if the outlet temperature of the heat preservation treatment is too low, the coiling temperature is low to a certain extent, the tensile strength is high, and meanwhile, the cooling is possibly caused to be too large, so that the shape of the plate is poor. Specifically, the outlet temperature of the incubation treatment may be 680 ℃, 690 ℃, 700 ℃, or the like.

In some embodiments, the temperature of the coiling is 600-630 ℃.

In the embodiment of the application, the positive effect of controlling the coiling temperature to be 600-630 ℃ is that: the normal structure of the strip steel is ensured, the requirements of tensile strength and elongation are met, and the generation amount of the three-time oxide scale is reduced. Specifically, the temperature of the winding may be 600 ℃, 610 ℃, 620 ℃, 630 ℃, or the like.

The application will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application. The experimental procedures, which are not specified in the following examples, are generally determined according to national standards. If the corresponding national standard does not exist, the method is carried out according to the general international standard, the conventional condition or the condition recommended by the manufacturer.

The specific implementation steps are as follows:

s1, performing first heating on a casting blank with a set chemical composition; wherein the cast strand has an initial temperature;

s2, performing first descaling on the heated casting blank, and performing rough rolling to obtain an intermediate blank;

s3, performing second heating on the intermediate blank, and controlling the heating rate of the second heating;

s4, performing second descaling on the intermediate billet after the second heating, and performing finish rolling to obtain hot rolled strip steel;

s5, carrying out laminar cooling on the hot rolled strip steel, and then coiling to obtain a 65Mn steel plate; wherein the laminar cooling comprises: and (5) heat preservation treatment. See tables 1 and 2 for specific process steps.

TABLE 1 chemical composition (wt%) of 65Mn Steel sheet, balance Fe and unavoidable impurities

Sequence 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

Table 2 preparation process parameters of 65mn steel sheet

For example 1: the furnace pressure of the tunnel furnace in the first heating is 10Pa, and the induction heating device is started for 1-4 groups of numbers and 7-9 groups of 5 and 6 groups of numbers are closed when 65Mn is produced. The surface quality of the strip steel is photographed by uncoiling after coiling and offline, the initial temperature of the first heating of the casting blank is controlled by C, P in components, the descaling mode and the slow cooling mode of the layer cooling heat preservation cover meet the requirements of the embodiment of the application, the heating rate in the induction heating is slightly high, finally, the black ash defect on the surface of the steel plate is reduced but still exists, and the control effect is semi-successful, and the method is shown in fig. 2.

For example 2: the furnace pressure of the tunnel furnace in the first heating is 10Pa, the induction heating device is in a 9-group series mode, and the induction heating device is started for 1-4 groups of numbers and 7-9 groups of numbers and 5 and 6 groups of numbers are closed when 65Mn is produced. The surface quality of the strip steel is shot by uncoiling after coiling and offline, the control of C, P and the like in components and the slow cooling mode of the layered cooling heat preservation cover accord with the requirements of the embodiment of the application, but the initial temperature of the casting blank for first heating is close to the upper limit of the embodiment of the application, the descaling pressure of the finish rolling first frame is slightly lower than the lower limit of the embodiment of the application, and finally, the black ash defects on the surface of the steel plate exist in a small amount, and the control effect is basically successful, and the method is shown in fig. 3.

For example 3: the furnace pressure of the tunnel furnace in the first heating is 14Pa, the induction heating device is in a 9-group series mode, and the induction heating device is started for 1-4 groups of numbers and 7-9 groups of numbers and 5 and 6 groups of numbers are closed when 65Mn is produced. The surface quality of the strip steel is shot by uncoiling after coiling and offline, key control points are controlled by C, P in components, the first heating temperature and time, the heating rate of induction heating and the slow cooling mode of a layer cooling heat preservation cover meet the requirements of the embodiment of the application, the descaling mode and the coiling temperature also meet the requirements of the embodiment of the application, and finally the black ash defect on the surface of the steel plate is basically eliminated, and the control effect is successful, and the figure 4 is shown.

For comparative example 1: the furnace pressure of the tunnel furnace in the first heating is 12Pa, the induction heating device is in a 9-group series mode, and the number of groups is 1-9 when 65Mn is produced. The surface quality of the strip steel is shot by uncoiling after coiling and offline, key control points such as C, P in components are controlled to exceed the upper limit required by the embodiment of the application, the induction heating temperature rising rate is high, the middle section of layer cooling does not adopt a heat preservation cover slow cooling mode, meanwhile, the first heating time is slightly beyond the upper limit required by the embodiment of the application, and finally, black ash defects on the surface of the steel plate exist in a large quantity, the control effect is failed, and the method is shown in fig. 5.

For comparative example 2: the furnace pressure of the tunnel furnace in the first heating is 8Pa, the induction heating device is in a 9-group series mode, and the induction heating device is started for 1-4 groups of numbers and 7-9 groups of numbers and 5 and 6 groups of numbers are closed when 65Mn is produced. The surface quality of the strip steel is shot by uncoiling after coiling and offline, key control points such as C, P in components and the like are controlled, a slow cooling mode of a layer cooling heat preservation cover meets the requirements of the embodiment of the application, but the initial temperature of the casting blank for first heating greatly exceeds the upper limit of the requirements of the embodiment of the application, a single-row descaling mode of a finish rolling inlet does not meet the requirements of the embodiment of the application, black ash defects on the surface of a final steel plate exist in a small amount, and the control effect fails, and is shown in fig. 6.

The foregoing is only a specific embodiment of the application to enable those skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A method for producing a 65Mn steel sheet, comprising:

first heating a casting blank with a set chemical composition; wherein the cast strand has an initial temperature;

performing first descaling on the first heated casting blank, and performing rough rolling to obtain an intermediate blank;

performing second heating on the intermediate blank, and controlling the heating rate of the second heating;

performing second descaling on the intermediate billet after second heating, and performing finish rolling to obtain hot rolled strip steel;

performing laminar cooling on the hot rolled strip steel, and then coiling to obtain a 65Mn steel plate; wherein the laminar cooling comprises: and (5) heat preservation treatment.

2. The method of claim 1, wherein the initial temperature is 930-1050 ℃.

3. The method of claim 1, wherein the first heating is at a temperature of 1180-1210 ℃, and/or the first heating is for a time of 15-20min.

4. The method of claim 1, wherein the second heating is at a ramp rate of 10-20 ℃/s.

5. The method of claim 1, wherein the soak treatment has an outlet temperature of 680-700 ℃.

6. The method according to claim 1, characterized in that the temperature of the reeling is 600-630 ℃.

7. The method of claim 1, wherein said second descaling said second heated intermediate billet and then finish rolling said intermediate billet to provide a hot rolled strip comprising:

performing second descaling on the intermediate billet after second heating, controlling the pressure of the second descaling, and performing finish rolling to obtain hot rolled strip steel; wherein the descaling pressure of the first rack and the descaling pressure of the second rack are controlled.

8. The method of claim 7, wherein the first rack has a descaling pressure of 5-10MPa and or the second rack has a descaling pressure of 30-38MPa.

9. The method of claim 1, wherein the setting component comprises:

C. mn, si, alt, P and Fe; wherein,

the content of C is 0.61-0.67 wt%, mn is 0.8-2 wt%, si is 0.15-0.3 wt%, alt is 0.01-0.05 wt%, and P is 0.002-0.012 wt%.

10. The method of claim 1, wherein the first heating is performed on a cast strand having a set chemical composition; wherein, the casting blank has initial temperature, before still includes:

continuously casting the molten steel, and controlling the drawing speed of continuous casting to obtain a casting blank; wherein the continuous casting has a pulling rate of 4.0-5.5m/min.