CN116426839A

CN116426839A - Enamelled steel sheet and preparation method thereof

Info

Publication number: CN116426839A
Application number: CN202310127776.9A
Authority: CN
Inventors: 刘再旺; 曹荣华; 王全礼; 杨利斌; 梁立川; 刘顺明; 韩赟; 滕华湘; 刘李斌; 熊爱明; 梁轩; 张志敏; 乔建军; 缪成亮; 郭敏
Original assignee: Shougang Group Co Ltd; Beijing Shougang Co Ltd; Shougang Jingtang United Iron and Steel Co Ltd
Current assignee: Shougang Group Co Ltd; Beijing Shougang Co Ltd; Shougang Jingtang United Iron and Steel Co Ltd
Priority date: 2023-02-17
Filing date: 2023-02-17
Publication date: 2023-07-14

Abstract

The invention provides an enameled pressed steel and a preparation method thereof, which belong to the technical field of enameled pressed steel production, wherein the enameled pressed steel comprises the following chemical components in percentage by mass: alt:0.03 to 0.15 percent, B: 0.004-0.015%, N:0.01 to 0.03 percent; the BN particles formed by the combination of N and B have good stability, are not easy to dissolve at high temperature, and have the function of stably improving the anti-scaling performance; alt reacts with the rest N to generate AlN, which can play roles in refining grains and preventing the grains from growing during enameling, and can ensure that the strength of the steel plate is not reduced and reversely increased at high temperature under the cooperation of specific process control conditions. Therefore, the enameled pressed steel has good anti-scaling performance, and the problem that the strength of the existing enameled pressed steel is reduced in high Wen Tang fever can be solved.

Description

Enamelled steel sheet and preparation method thereof

Technical Field

The application relates to the technical field of enamelled steel sheet production, in particular to an enamelled steel sheet and a preparation method thereof.

Background

The enamelled steel sheet is a composite material integrating the dual properties of the steel sheet and the enamel, has the dual advantages of the strength of the steel sheet, the wear resistance, the high temperature resistance, the corrosion resistance, the color vividness and the like of the enamel, and is widely applied to the industries of light industry, household appliances, chemical industry, buildings and the like. The biggest problem in enamel steel production is that the phenomenon of "scaling" is easy to occur-the flaking phenomenon similar to fish scales. In addition to the scaling, another important problem faced by enamelled steel is that the strength of the steel sheet is significantly reduced during high Wen Tang firing.

At present, most of manufacturing methods of cold-rolled enamel steel plates are to add Cu, nb, ti and other alloy elements into low-carbon steel to improve the anti-scaling performance of the steel, but the anti-scaling performance of the steel can only solve the scaling problem of enamel products, but the problem of strength reduction of the steel plates in the enamel process is not solved.

Disclosure of Invention

The embodiment of the application provides an enameled pressed steel and a preparation method thereof, which are used for solving the problem that the strength of the existing enameled pressed steel is reduced in high Wen Tang burning.

In a first aspect, embodiments of the present application provide an enameled pressed steel, the chemical composition of which includes, in mass fractions: the enamelled steel sheet comprises the following chemical components in percentage by mass: alt:0.03 to 0.15 percent, B: 0.004-0.015%, N:0.01 to 0.03 percent.

Further, the mass fractions of N and B of the enameled pressed steel satisfy the relation one:

[N]-1.4×[B]≥0，

where [ N ] represents the mass fraction of N and [ B ] represents the mass fraction of B.

Further, the mass fraction of N, B and Al of the enameled pressed steel satisfies the relation two:

[ Al ] -1.93 x ([ N ] -1.4 x [ B ]) ≡0.02%, or

[ Al ] -1.93 x ([ N ] -1.4 x [ B ]) is not less than 0.02% and [ N ] -1.4 x [ B ] is not less than 0,

wherein [ Al ] represents the mass fraction of Al, [ N ] represents the mass fraction of N, and [ B ] represents the mass fraction of B.

Further, the chemical components of the enameled pressed steel include, in mass fraction: c is less than or equal to 0.07 percent, si is less than or equal to 0.03 percent, mn:0.2 to 0.6 percent.

In a second aspect, embodiments of the present application provide a method for manufacturing an enameled pressed steel according to the first aspect, the method comprising:

heating and rolling the plate blank of the enamelled steel plate to obtain a hot rolled plate;

performing laminar cooling and coiling on the hot rolled plate to obtain a hot rolled coil;

pickling and cold rolling the hot rolled coil to obtain a chilled coil;

and annealing and flattening the chilled coil to obtain the enameled pressed steel.

Further, the heated process parameters include: the temperature is 1280-1380 ℃, and the furnace time is 200-300 min.

Further, the rolling process parameters include: the initial rolling temperature is 1080-1180 ℃, and the final rolling temperature is 880-970 ℃.

Further, the technological parameters of the laminar cooling include: the cooling speed is more than 15 ℃/s; and/or

The technological parameters of coiling comprise: the temperature is 350-600 ℃.

Further, the technological parameters of the cold rolling include: the total rolling reduction is 50-85%; and/or

The annealing adopts a continuous annealing process, and the process parameters of the continuous annealing comprise: the annealing soaking temperature is 780-850 ℃, the slow cooling temperature is 530-650 ℃, the quick cooling temperature is 400-420 ℃, and the overaging temperature is 350-380 ℃.

Further, the roller surface of the leveling roller is a roller surface subjected to roughening treatment, the roller surface roughness is more than or equal to 4.0 mu m, and the leveling process parameters are as follows: the flattening elongation is 0.3-1.3%.

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

the embodiment of the application provides an enameled pressed steel, which comprises the following chemical components in percentage by mass: alt:0.03 to 0.15 percent, B: 0.004-0.015%, N:0.01 to 0.03 percent; the balance of iron and unavoidable impurities; the BN particles formed by the combination of N and B have good stability, are not easy to dissolve at high temperature, and have the function of stably improving the anti-scaling performance; alt reacts with the rest N to generate AlN, which can play roles in refining grains and preventing the grains from growing during enameling, and can ensure that the strength of the steel plate is not reduced and reversely increased at high temperature under the cooperation of specific process control conditions. Therefore, the enameled pressed steel has good anti-scaling performance, and the problem that the strength of the existing enameled pressed steel is reduced in high Wen Tang fever can be solved.

Drawings

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

In order to more clearly illustrate the embodiments of the invention 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 photograph of second phase precipitation particles of example 1 of the present invention;

FIG. 2 is a photograph showing the result of electrostatic enameling according to example 1 of the present invention.

Detailed Description

The advantages and various effects of the present invention will be more clearly apparent from the following detailed description and examples. It will be understood by those skilled in the art that these specific embodiments and examples are intended to illustrate the invention, not to limit the invention.

Throughout the specification, unless specifically indicated otherwise, the terms used herein should be understood as meaning as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification will control.

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

The enamelled steel sheet is a composite material integrating the dual properties of the steel sheet and the enamel, has the dual advantages of the strength of the steel sheet, the wear resistance, the high temperature resistance, the corrosion resistance, the color vividness and the like of the enamel, and is widely applied to the industries of light industry, household appliances, chemical industry, buildings and the like. The biggest problem in enamel steel production is that the phenomenon of "scaling" is easy to occur-the flaking phenomenon similar to fish scales. In addition to scale explosion, another important problem faced by enamelled steel is that the strength of the steel sheet is significantly reduced during the enameling process.

The technical scheme provided by the embodiment of the invention aims to solve the technical problems, and the overall thought is as follows:

in a first aspect, embodiments of the present application provide an enameled pressed steel, the chemical composition of which includes, in mass fractions: c: less than or equal to 0.07 percent, alt:0.03 to 0.15 percent, B: 0.004-0.015%, N:0.01 to 0.03 percent; the balance being iron and unavoidable impurities.

In the present application, the chemical components of the enamelled steel sheet are iron and unavoidable impurities in addition to the above elements. Wherein Alt generally refers to the total aluminum content, including acid soluble aluminum (Als) and aluminum oxide (Alo).

The embodiment of the application provides an enameled pressed steel, which comprises the following chemical components in percentage by mass: alt:0.03 to 0.15 percent, B: 0.004-0.015%, N:0.01 to 0.03 percent; the balance of iron and unavoidable impurities; the BN particles formed by the combination of N and B have good stability, are not easy to dissolve at high temperature, and have the function of stably improving the anti-scaling performance; alt reacts with the rest N to generate AlN, which can play roles in refining grains and preventing the grains from growing during enameling, and can ensure that the strength of the steel plate is not reduced and reversely increased at high temperature under the cooperation of specific process control conditions. Therefore, the steel plate provided by the embodiment of the application can solve the problem that the strength of the existing enamelled steel plate is reduced in high Wen Tang burning.

As an implementation manner of the embodiment of the present invention, the mass fraction of N and B of the enameled pressed steel satisfies a relation of one:

[N]-1.4×[B]≥0，

In the application, N is mainly combined with B to form BN particles, the effect of anti-scaling performance can be achieved, the mass fraction of N and B is controlled to be N-1.4XB not less than 0, and the element B can be completely fixed by N, so that the casting blank is prevented from generating crack defects.

As an implementation mode of the embodiment of the present invention, the mass fraction of N, B and Al of the enameled pressed steel satisfies the relation two:

[ Al ] -1.93 x ([ N ] -1.4 x [ B ]) ≡0.02%, or

In the method, alt reacts with the rest N to generate AlN, and the defects of aging, embrittlement and the like are caused by solid solution N in the steel, so that the Alt and B, N meet the quantitative relation of Al-1.93 x (N-1.4 xB) not less than 0.02%, and the sufficient quantity of Al can be ensured.

As an implementation mode of the embodiment of the invention, the chemical components of the enamelled steel sheet further include, in mass fraction: c is less than or equal to 0.07 percent, si is less than or equal to 0.03 percent, mn:0.2 to 0.6 percent.

In the application, the element C is oxidized to generate CO and CO in the enameling process ₂ When the gas is equal and the carbon content is too high, bubble defects are easy to generate, and the quality of the enamel surface is damaged. On the other hand, carbon is a base for improving strength, and the matrix can be directly reinforced by solid solution strengthening. Si as deoxidizerIn removing oxygen in molten steel, si is a harmful element in enamel steel, and the increase of Si content can obviously reduce the adhesiveness of enamel and damage the surface quality, so that the Si content is controlled below 0.03%. Manganese reacts with sulfur to generate manganese sulfide, so that S brittleness is eliminated, and meanwhile, mn can improve the strength of steel, but the Mn content is too high, so that a banded structure is easy to cause, and enamel performance is not facilitated. In general, sulfur is an impurity element in steel, and is liable to form brittle substances, and in the present invention, S: less than or equal to 0.012%; phosphorus is an impurity element, tends to gather in grain boundaries, increases brittleness of a steel sheet, deteriorates formability of the steel sheet, and is likely to generate bubbles and black spots during enameling, affecting surface quality, and in this application, phosphorus can be controlled to 0.02% or less.

pickling and cold rolling the hot rolled coil to obtain a chilled coil;

In the application, by inhibiting the AlN from precipitating in the hot rolling and annealing processes and precipitating in a large amount in the enameling process, on one hand, the grain growth in the enameling process can be inhibited to cause softening, and on the other hand, the effect of precipitation strengthening can be achieved, so that the strength of the steel plate after enameling is not only reduced but also increased.

As an implementation of the embodiment of the present invention, the heating process parameters include: the temperature is 1280-1380 ℃, and the furnace time is 200-300 min.

In the method, the heating temperature and the heating time are controlled, so that the steel billet can be fully austenitized, BN and AlN formed in the steel billet are fully dissolved, and controllable precipitation is carried out in the subsequent working procedure, so that the expected effect is achieved.

As an implementation of the embodiment of the present invention, the rolling process parameters include: the initial rolling temperature is 1080-1180 ℃, and the final rolling temperature is 880-970 ℃.

In the application, the whole rolling interval keeps a higher temperature, because the total solid solution temperature of BN is higher than that of AlN, BN particles are fully precipitated in the temperature interval, the anti-scaling performance of subsequent steel is guaranteed, and the precipitation amount of AlN particles is limited so as to be precipitated in the subsequent enameling process.

As an implementation manner of the embodiment of the present invention, the process parameters of the laminar cooling include: the cooling speed is more than 15 ℃/s; and/or the process parameters of the reeling include: the temperature is 350-600 ℃.

In the present application, rapid cooling and low-temperature coiling can suppress precipitation of AlN.

As an implementation mode of the embodiment of the invention, the process parameters of the cold rolling include: the total rolling reduction is 50-85%; and/or the annealing adopts a continuous annealing process, and the process parameters of the continuous annealing comprise: the annealing soaking temperature is 780-850 ℃, the slow cooling temperature is 530-650 ℃, the quick cooling temperature is 400-420 ℃, and the overaging temperature is 350-380 ℃.

In the application, the high cold rolling reduction rate can store enough distortion energy in the steel, is favorable for texture development, improves the forming performance of the steel plate, reduces the recrystallization temperature and is favorable for recrystallization after annealing. The high-temperature annealing process is adopted, the temperature is close to the range of the enameling temperature, the strength decline trend after enameling is reduced, the lower slow cooling temperature and the quick cooling temperature provide larger driving force for carbide precipitation in steel, and the overaging temperature is controlled to be beneficial to the precipitation of tertiary cementite, so that the anti-scaling performance is further improved.

As an implementation mode of the embodiment of the invention, the roller surface of the flat roller is a roller surface subjected to roughening treatment, the roughness of the roller surface is more than or equal to 4.0 mu m, and the technological parameters of the flattening are as follows: the flattening elongation is 0.3-1.3%.

In the application, off-line or on-line leveling is adopted for leveling, and the principle of the leveling process in the invention is that the surface of the plate obtains larger roughness under the condition of adopting smaller leveling elongation, and a rough surface structure is beneficial to improving enamel adhesiveness. Leveling work hardening provides a driving force for post-honing strength reduction, which should be minimized. The surface roughness Ra of the chilled rolls in the application is more than or equal to 1.3 mu m.

The invention will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention. 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.

Example 1:

an enamelled steel sheet and a method for producing the same, characterized by comprising the steps of:

(1) And (3) slab preparation: after molten iron is pretreated, a plate blank is obtained through converter smelting, RH/LF/CAS refining and continuous casting; wherein, the chemical compositions of the slab are shown in a table 1 in mass fraction;

(2) Heating the slab at 1280 ℃ for 280min, starting rolling at 1080 ℃, and controlling the final rolling temperature to 880 ℃ to obtain a hot rolled plate;

(3) Laminar cooling is carried out on the hot rolled plate at a cooling speed of 16 ℃/s, and then coiling is carried out at 450 ℃ to obtain a hot rolled coil;

(4) Pickling and cold rolling the hot rolled coil to obtain a chilled coil; wherein the total reduction of the cold rolling is 65%;

(5) Carrying out continuous annealing process and leveling on the chilled rolls to obtain enamel steel plates; wherein the annealing soaking temperature is 820 ℃, the slow cooling temperature is 620 ℃, the quick cooling temperature is 420 ℃, and the overaging temperature is 360 ℃; the roller surface of the leveling roller is roughened, the roller surface roughness is 4.0 mu m, the leveling elongation is 0.6%, and the leveling result is that the surface roughness Ra of the finished steel coil is more than or equal to 1.3 mu m.

Example 2:

(2) Heating the slab at 1300 ℃ for 200min, then starting rolling at 1170 ℃, and controlling the final rolling temperature to 960 ℃ to obtain a hot rolled plate;

(3) Laminar cooling is carried out on the hot rolled plate at a cooling speed of 18 ℃/s, and then coiling is carried out at 350 ℃ to obtain a hot rolled coil;

(4) Pickling and cold rolling the hot rolled coil to obtain a chilled coil; wherein the total reduction of the cold rolling is 75%;

(5) Carrying out continuous annealing process and leveling on the chilled rolls to obtain enamel steel plates; wherein the annealing soaking temperature is 780 ℃, the slow cooling temperature is 560 ℃, the quick cooling temperature is 410 ℃, and the overaging temperature is 380 ℃; the roller surface of the leveling roller is roughened, the roller surface roughness is 4.5 mu m, the leveling elongation is 1.2%, and the leveling result is that the surface roughness Ra of the finished steel coil is more than or equal to 1.3 mu m.

Example 3:

(2) Heating the slab at 1370 ℃ for 300min, starting rolling at 1100 ℃, and controlling the final rolling temperature to be 920 ℃ to obtain a hot rolled plate;

(3) Laminar cooling is carried out on the hot rolled plate at a cooling speed of 16 ℃/s, and then coiling is carried out at 540 ℃ to obtain a hot rolled coil;

(4) Pickling and cold rolling the hot rolled coil to obtain a chilled coil; wherein the total reduction of the cold rolling is 83%;

(5) Carrying out continuous annealing process and leveling on the chilled rolls to obtain enamel steel plates; wherein the annealing soaking temperature is 820 ℃, the slow cooling temperature is 620 ℃, the quick cooling temperature is 420 ℃, and the overaging temperature is 350 ℃; the roller surface of the leveling roller is roughened, the roller surface roughness is 4.5 mu m, the leveling elongation is 0.8%, and the leveling result is that the surface roughness Ra of the finished steel coil is more than or equal to 1.3 mu m.

Example 4:

(2) Heating the slab at 1290 ℃ for 210min, then starting rolling at 1130 ℃, and controlling the final rolling temperature to 900 ℃ to obtain a hot rolled plate;

(3) Laminar cooling is carried out on the hot rolled plate at a cooling speed of 20 ℃/s, and then coiling is carried out at 430 ℃ to obtain a hot rolled coil;

(4) Pickling and cold rolling the hot rolled coil to obtain a chilled coil; wherein the total reduction of the cold rolling is 60%;

(5) Carrying out continuous annealing process and leveling on the chilled rolls to obtain enamel steel plates; wherein the annealing soaking temperature is 840 ℃, the slow cooling temperature is 630 ℃, the quick cooling temperature is 400 ℃, and the overaging temperature is 375 ℃; the roller surface of the leveling roller is roughened, the roller surface roughness is 5.0 mu m, the leveling elongation is 0.3%, and the leveling result is that the surface roughness Ra of the finished steel coil is more than or equal to 1.3 mu m.

Comparative example 1:

the chemical components of the slab are shown in table 1 in mass fraction, the heating temperature in the embodiment 1 is changed to 1180 ℃, the heating time is changed to 190min, the starting rolling temperature is changed to 1060 ℃, the coiling temperature is changed to 550 ℃, the total rolling reduction rate of cold rolling is changed to 65%, the annealing soaking temperature is changed to 730 ℃, the slow cooling temperature is changed to 660 ℃, the quick cooling temperature is changed to 440 ℃, and the overaging temperature is changed to 400 ℃; the roll surface roughness was changed to 3.0 μm, the leveling elongation was changed to 0.8%, and the rest was the same as in example 1.

Comparative example 2:

the chemical components of the slab are shown in table 1 in mass fraction, the heating temperature in the embodiment 1 is changed to 1140 ℃, the heating time is changed to 200min, the initial rolling temperature is changed to 1070 ℃, the coiling temperature is changed to 730 ℃, the total rolling reduction rate of cold rolling is changed to 77%, the annealing soaking temperature is changed to 760 ℃, the slow cooling temperature is changed to 680 ℃, the quick cooling temperature is changed to 420 ℃, and the overaging temperature is changed to 383 ℃; the roll surface roughness was changed to 2.4 μm, the leveling elongation was changed to 0.7%, and the rest was the same as in example 1.

Table 1 chemical composition (wt.%) of slabs of examples and comparative examples

	C	Si	Mn	S	P	Alt	B	N
									Example 1	0.035	0.02	0.20	0.006	0.012	0.039	0.006	0.011
Example 2	0.063	0.01	0.14	0.012	0.017	0.144	0.014	0.027
									Example 3	0.015	0.03	0.55	0.005	0.015	0.087	0.012	0.018
Example 4	0.003	0.01	0.13	0.009	0.009	0.072	0.015	0.028
									Comparative example 1	0.052	0.01	0.3	0.010	0.0013	0.037	0.002	0.003
Comparative example 2	0.003	0.01	0.14	0.012	0.0010	0.037	-	0.014

Performance tests were performed on the steel sheets of examples and comparative examples: samples were cut at 1/4 of the width of the sheet for a conventional tensile test while hydrogen permeation samples were sampled and measured to calculate TH values of the steel sheet. (TH value measurement, measurement and calculation according to national Standard GB/T29515-2013 hydrogen permeation method for cold rolled Steel sheet Scale explosion sensitivity test for enamel)

The steel plates of each example and comparative example were subjected to small-sample enameling in a laboratory by taking 5 templates at different positions, the enameling method was electrostatic dry powder enameling, the scaling phenomenon was observed, and the enamel-removed samples were subjected to a tensile test after removing the porcelain layer to observe the change in strength. The test results are shown in Table 4.

Table 4 TH values and mechanical properties of the steel sheets of examples and comparative examples

In summary, the embodiment of the application provides an enamel steel plate, which adopts BN and AlN precipitated particles which are manufactured in a large amount in steel as hydrogen traps, and compared with other enamel steel adopting TiC and Fe3C as hydrogen traps, the enamel steel plate has good stability, is not easy to dissolve during enamel firing, and can not cause the reduction of the anti-scaling performance after enamel firing; the AlN is prevented from precipitation in the hot rolling and annealing processes through process control, so that the AlN is precipitated in the enamel firing process, on one hand, the AlN prevents crystal grains from growing during enamel firing, and on the other hand, the AlN has a precipitation strengthening effect; the annealing process adopts high-temperature annealing and small-leveling elongation process, reduces the grain growth driving force in the enameling process, and increases the strength of the enamelled steel sheet after enameling under multiple actions.

It should be understood that the endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and that the range or value is to be understood as encompassing values close to the range or value. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

It should be noted that in this document, relational terms such as "first" and "second" and the like are 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. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. In addition, the term "and/or" appearing herein is merely an association relationship describing the associated object, and means that three relationships may exist, for example, a and/or B may mean: a exists alone, A and B exist together, and B exists alone.

The foregoing is only a specific embodiment of the invention to enable those skilled in the art to understand or practice the invention. 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 invention. Thus, the present invention 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

1. An enameled steel sheet characterized by comprising the following chemical components in mass percent: alt:0.03 to 0.15 percent, B: 0.004-0.015%, N:0.01 to 0.03 percent.

2. The enameled steel sheet according to claim 1, wherein the mass fractions of N and B of the enameled steel sheet satisfy a relation of:

[N]-1.4×[B]≥0，

3. The enameled steel sheet according to claim 1, wherein the mass fraction of N, B and Al of the enameled steel sheet satisfies the relation two:

[ Al ] -1.93 x ([ N ] -1.4 x [ B ]) ≡0.02%, or

4. A sheet according to any one of claims 1 to 3, wherein the chemical components of the sheet further comprise, in mass fraction: c is less than or equal to 0.07 percent, si is less than or equal to 0.03 percent, mn:0.2 to 0.6 percent.

5. A method for producing an enamelled steel sheet according to any one of claims 1 to 4, comprising:

pickling and cold rolling the hot rolled coil to obtain a chilled coil;

6. The method of claim 5, wherein the heated process parameters include: the temperature is 1280-1380 ℃, and the furnace time is 200-300 min.

7. The method according to claim 5, wherein the rolling process parameters include: the initial rolling temperature is 1080-1180 ℃, and the final rolling temperature is 880-970 ℃.

8. The method of claim 5, wherein the process parameters of the laminar cooling include: the cooling speed is more than 15 ℃/s; and/or

9. The method according to claim 5, wherein the process parameters of the cold rolling include: the total rolling reduction is 50-85%; and/or

10. The method according to claim 5, wherein the flattened roller surface is a roughened roller surface, the roughness of the roller surface is not less than 4.0 μm, and the flattening process parameters are as follows: the flattening elongation is 0.3-1.3%.