CN112264469A

CN112264469A - Method for reducing filiform spot defect on surface of electro-galvanized plate

Info

Publication number: CN112264469A
Application number: CN202010919627.2A
Authority: CN
Inventors: 熊飞; 高云; 刘念; 王靓; 张鹏武; 黄东
Original assignee: Wuhan Iron and Steel Co Ltd
Current assignee: Wuhan Iron and Steel Co Ltd
Priority date: 2020-09-04
Filing date: 2020-09-04
Publication date: 2021-01-26

Abstract

The invention discloses a method for reducing filiform scar defects on the surface of an electro-galvanized plate, which comprises the following steps: smelting the molten steel of the electro-galvanized plate to obtain a continuous casting billet; heating the continuous casting billet before rolling, rough rolling, finish rolling, cooling after rolling and coiling to obtain a hot rolled plate; pickling the hot rolled plate to obtain an electrogalvanizing substrate with good surface quality; in the heating before rolling, the discharging temperature of the plate blank is 1180-1220 ℃; the hot rolling comprises rough rolling and finish rolling, wherein in the rough rolling, 1+5 passes are adopted for rolling, the outlet temperature of the rough rolling is controlled to be 1020-1050 ℃, the final rolling temperature is controlled to be 910-930 ℃, the descaling water at the inlet of the rough rolling is fully opened, and the descaling water at the outlet of the rough rolling is increased; the pickling speed is 140-160 m/min. The method has the advantages of stable process control, strong operability, obvious improvement on the spot defect, and stable incidence of the spot defect on the surface of the electrogalvanized plate below 2%.

Description

Method for reducing filiform spot defect on surface of electro-galvanized plate

Technical Field

The invention relates to the technical field of ferrous metallurgy, in particular to a method for reducing filiform spot defects on the surface of an electro-galvanized plate.

Background

The electro-galvanized sheet has good corrosion resistance, processability, weldability and paintability, and is widely applied to industries of automobiles, household appliances and the like. In the actual production, the occurrence of filiform spot defect on the surface of the electro-galvanized plate greatly influences the comprehensive benefit of the product.

Among the filiform scar defects on the surface of the galvanized plate, the filiform scar is a typical representative, and the filiform scar is frequently generated on the surface of the galvanized plate, and the occurrence rate fluctuation is large and can reach 35 percent at most. At present, a method for reducing the defects is to add a flash nickel plating process before galvanization, but the flash nickel plating technology can generate scrapped bath solution and rinsing wastewater containing nickel ions, and the nickel ions are heavy metal ions, so that the toxicity is high, and the environmental pollution is high. With the stricter and stricter requirements on the pollutant emission in China, the application of the flash nickel plating is more and more limited. In addition, researchers have proposed a process for flash plating iron before galvanization, which is currently not clear in effect, and requires modification of production equipment, requiring additional capital investment.

Therefore, how to develop a method for reducing the filiform scar defect on the surface of the electro-galvanized plate becomes a technical problem to be solved urgently.

Disclosure of Invention

The invention aims to provide a method for reducing filiform stain defects on the surface of an electrogalvanized plate, which has the advantages of stable process control, strong operability, obvious improvement on the filiform stain defects and stable incidence rate of the filiform stain defects on the surface of the electrogalvanized plate of less than 2 percent.

In order to achieve the above object, the present invention provides a method for reducing filiform scar defects on the surface of an electrogalvanized sheet, comprising:

smelting the molten steel of the electro-galvanized plate to obtain a continuous casting billet;

heating the continuous casting billet before rolling, rough rolling, finish rolling, cooling after rolling and coiling to obtain a hot rolled plate;

pickling the hot rolled plate to obtain an electro-galvanized plate with good surface quality;

in the heating before rolling, the discharging temperature of the plate blank is 1180-1220 ℃;

the hot rolling comprises rough rolling and finish rolling, wherein in the rough rolling, 1+5 passes are adopted for rolling, the outlet temperature of the rough rolling is controlled to be 1020-1050 ℃, the final rolling temperature is controlled to be 910-930 ℃, the descaling water at the inlet of the rough rolling is fully opened, and the descaling water at the outlet of the rough rolling is increased;

the pickling speed is 140-160 m/min.

Further, the chemical components of the electro-galvanized plate are as follows by mass fraction: c is less than or equal to 0.10 percent; mn: 0.12 to 0.50 percent; p is less than or equal to 0.035%; s is less than or equal to 0.025 percent, and Al is more than or equal to 0.015 percent; ti: 0.045% -0.075%; the balance of Fe and inevitable impurities;

further, the increasing of the descaling water at the rough rolling outlet comprises the following steps: descaling water is added at the outlet of the roughing mill R21 and R24.

Further, two-pass descaling is adopted during descaling.

Furthermore, in the rough rolling, the rolling speed is controlled to be 1-2.8 m/s, the total deformation of the rough rolling is controlled to be 80-83%, and the inlet temperature of the rough rolling is controlled to be 1060-1090 ℃. The arrangement is favorable for controlling the precision of the blank shape and the rolling stability;

furthermore, in the finish rolling, 7-pass rolling is adopted, the passing speed of F7 is controlled to be 10.5-11.5 m/s, the scale is removed after F1 is increased, and the outlet temperature of the finish rolling is 910-930 ℃. This arrangement is advantageous for further enhancing the descaling effect while ensuring that the finish rolling is carried out in the austenitic region.

Further, in the finish rolling, a new high-speed steel roll is used for rolling. This arrangement can contribute to an improvement in the board surface quality.

Further, in the heating before rolling, the time of a casting blank in a high-temperature period is controlled to be 95-110 min, and the furnace time of the casting blank is controlled to be 220-260 min. The arrangement is favorable for controlling the oxidation layer of the steel billet within a proper range;

further, the pickling adopts a shallow slot turbulent pickling mode, which specifically comprises the following steps: and (3) crushing the iron sheet by an S roller after uncoiling, and then pickling the strip steel in a pickling tank at the pickling temperature of 75-85 ℃.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

the method for reducing the filiform spot defect on the surface of the electro-galvanized plate, provided by the invention, does not need equipment transformation, and controls a rolling process and an acid pickling process, wherein in the heating before rolling, the tapping temperature of the plate blank is 1180-1220 ℃; the hot rolling comprises rough rolling and finish rolling, wherein in the rough rolling, 1+5 passes are adopted for rolling, the outlet temperature of the rough rolling is controlled to be 1020-1050 ℃, the final rolling temperature is controlled to be 910-930 ℃, the descaling water at the inlet of the rough rolling is fully opened, and the descaling water at the outlet of the rough rolling is increased; the pickling speed is 140-160 m/min. The parameters are simultaneously met, so that the filiform stain defect on the surface of the electro-galvanized plate can be reduced, and compared with the existing production process, the process control is stable, the operability is strong, the filiform stain defect is obviously improved, and the occurrence rate of the filiform stain defect on the surface of the electro-galvanized plate is stable and is below 2%.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 is a flow chart of a method for reducing filiform scar defects on the surface of an electro-galvanized sheet according to an embodiment of the present invention;

FIG. 2 is a metallographic structure morphology of a surface portion of a hot-rolled plate sample of comparative example 5;

FIG. 3 is a metallographic structure morphology diagram of a surface portion of a hot-rolled plate sample in example 1;

FIG. 4 is a surface topography of a sample of comparative example 7;

FIG. 5 is a surface topography map of the sample of comparative example 6.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings 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. If there is a conflict, the present specification will control.

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

In order to solve the technical problems, the embodiment of the invention provides the following general ideas:

according to an exemplary embodiment of the present invention, there is provided a method for reducing filiform mark defects on a surface of an electrogalvanized sheet, as shown in fig. 1, comprising:

s1, smelting the molten steel of the electro-galvanized plate to obtain a continuous casting billet;

s2, heating the continuous casting billet before rolling, rough rolling, finish rolling, cooling after rolling and coiling to obtain a hot rolled plate;

s3, carrying out acid washing on the hot rolled plate to obtain an electro-galvanized plate with good surface quality;

the pickling speed is 140-160 m/min.

The principle of the process control of the invention is as follows:

the reason why the discharging temperature of the plate blank is controlled to be 1180-1220 ℃ is as follows: the austenitizing of the core of the plate blank can be incomplete due to too low temperature, and the surface iron scale can be excessive due to too high temperature, so that the cleaning difficulty is increased.

Rolling is carried out by adopting 1+5 passes, the descaling water at the rough rolling inlet is fully opened, and the reason for increasing the descaling water at the rough rolling outlet is as follows:

in the prior art, 3+3 passes of rolling are usually adopted in the rough rolling stage, the rough rolling inlet opening descaling water is changed into 1+5 passes of rolling, the inlet opening descaling water is opened, and the outlet descaling water is increased.

The reason for controlling the rough rolling outlet temperature to be 1020-1050 ℃ is as follows: after the new rough rolling descaling process is adopted, the temperature of the plate blank is greatly reduced due to the reduction of the descaling speed, and the outlet temperature of the rough rolling is controlled within the range in order to ensure the finish rolling and finishing temperature.

The reason for controlling the finishing temperature to be 910-930 ℃ is as follows: the purpose of the process control setting is to roll in the temperature range without causing the steel grade to fall into a two-phase region for rolling, thereby avoiding the generation of surface filiform scar defects caused by mixed crystal. The austenite ferrite transformation temperature of the steel is analyzed and researched, when the temperature is 900 ℃ or below, austenite is transformed to ferrite, when the rolling temperature falls into the temperature range, the phenomenon that proeutectoid ferrite and austenite coexist simultaneously can be caused, and the proeutectoid ferrite is precipitated firstly in the subsequent cooling process, so that the crystal grains are coarser than ferrite crystal grains generated in the austenite transformation process, and the mixed crystal phenomenon can be caused. The surface mixed crystal texture can be inherited in the cold rolling process, so that the plate surface of a cold-rolled plate has a mixed crystal phenomenon, zinc particles on the surface of the electroplating process have the characteristic of oriented growth, and finally, the growth directions of the zinc particles at the coarse part of the crystal particles and the fine part of other crystal particles show obvious difference and are macroscopically represented as filiform spot mark defects. By observing the structure of the steel plate in the original rolling process (the finish rolling temperature is 890 ℃), the structure in the depth range of 0.1mm of the surface layer of the steel plate is thicker than the internal structure, and the grain size is different by 3 grades; and when the steel plate is rolled at the finishing temperature of 910-930 ℃, no mixed crystal characteristic is observed on the surface layer of the steel plate.

The pickling speed is controlled to be 140-160 m/min for the following reasons: the process setting is to select the optimal pickling speed of the steel based on a laboratory pickling test and on-line tracking adjustment, the influence of the pickling speed on the surface of a hot rolled plate is researched by performing tests of different pickling speeds on the hot rolled plate in a laboratory simulation field corrosion environment, and meanwhile, the surface of a sample after pickling is observed by adopting an SEM (scanning electron microscope) so as to determine the optimal pickling scheme and perform on-line pickling tracking. Through the combination of the test and the field process, the optimal pickling speed is provided, and when the speed is 140-160 m/min, the pickling surface condition is good. The short pickling time can cause iron oxide residues on the surface, the long pickling time can cause uneven surface pickling, coarse ferrite grains exist in a partial area, and the mixed grains can occur at the part after cold rolling, so that the filiform spot defect occurs in the electroplating process.

As a preferred embodiment, the chemical components of the electro-galvanized plate are as follows in mass fraction: c is less than or equal to 0.10 percent; mn: 0.12 to 0.50 percent; p is less than or equal to 0.035%; s is less than or equal to 0.025 percent, and Al is more than or equal to 0.015 percent; ti: 0.045% -0.075%; the balance of Fe and inevitable impurities;

the control principle in the chemical composition design of the invention is as follows:

c is less than or equal to 0.10 percent, is the most effective element for improving the strength of the steel, can cause the generation of grain boundary carbide due to the over high carbon content, seriously influences the plasticity of the material, and comprehensively considers that the carbon content is controlled within 0.10 percent.

Mn: 0.12 to 0.50 percent of manganese, can improve the strength by dissolving in ferrite and austenite, can cause the reduction of elongation and segregation by overhigh content, and comprehensively considers that the manganese content is controlled to be 0.12 to 0.50 percent.

Ti: 0.045-0.075 percent of the total content of the Ti, the N in the steel can be fixed, and Ti precipitates can play the roles of grain refinement and precipitation strengthening, but the plasticity is reduced due to the excessively high content of the Ti, and the percentage content is controlled to be 0.045-0.075 percent in comprehensive consideration.

More than or equal to 0.015 percent of Al, a deoxidizer in steel, and simultaneously, crystal grains can be refined, the impact toughness is improved, and the comprehensive consideration of the percentage content is controlled to be more than or equal to 0.015 percent.

P, S is a harmful impurity element in steel, P in steel is easy to form segregation in steel, reduces the toughness of steel, S is easy to form sulfide inclusion, and deteriorates the performance of steel plate, P content is less than or equal to 0.035%, S content is less than or equal to 0.025%.

As a preferred embodiment, the increasing of the descaling water at the rough rolling outlet comprises: descaling water is added at the outlet of the roughing mill R21 and R24.

In a preferred embodiment, two-pass descaling is adopted during descaling, and the descaling speed is 1-1.5 m/s. The descaling speed in the range is beneficial to descaling and more effectively removing surface iron oxide; too low affects the rolling rhythm, and too high descaling is not thorough, so that the incidence of filiform scar defects can be increased.

In a preferred embodiment, in the rough rolling, the rolling speed is controlled to be 1-2.8 mm/s, the total deformation of the rough rolling is controlled to be 80-83%, and the inlet temperature of the rough rolling is controlled to be 1060-1090 ℃. At the temperature, uniform and fine austenite structures can be obtained by controlling the rolling speed and the reduction of each pass, and surface iron scale can be effectively removed by matching with the descaling speed as a preferred embodiment, in the finish rolling, 7 passes are adopted for rolling, the plate passing speed of F7 is controlled to be 10.5-11.5 m/s, the descaling is carried out after the F1 is increased, the total deformation of the finish rolling is controlled to be 90-93%, and the outlet temperature of the finish rolling is 910-930 ℃. The finish rolling process can be ensured to be carried out in an austenite region through the control of the rolling speed and the reduction, a uniform ferrite structure can be obtained by adopting the rolling process, the phenomenon of mixed crystals is avoided, the descaling capability can be further improved by descaling after F1 is increased, and the defect of filiform scars caused by incomplete removal of ferric oxide is avoided.

In a preferable embodiment, in the heating before rolling, the time of the high-temperature section of the casting blank is controlled to be 95-110 min, and the furnace time of the casting blank is controlled to be 220-260 min. The heating time of the heating process is controlled to avoid the generation of uneven structure and over-thick ferric oxide on the surface caused by the heating time.

In a preferred embodiment, the coiling temperature is 600 to 650 ℃. Coiling at this temperature can reduce the load on the coiler and also avoid the occurrence of internal oxidation.

In a preferred embodiment, the pickling is performed by shallow slot turbulent pickling, specifically: after uncoiling, crushing and stripping the surface iron oxide scale by using an s roller, and then pickling in three pickling tanks.

In a preferred embodiment, the pickling temperature is 75 to 85 ℃. The pickling temperature can enable iron oxide to react rapidly in the pickling tank, and when the temperature is too high, the acid in the acid liquor volatilizes too fast, so that the frequency of replacing the pickling solution in the acid tank is increased, and meanwhile, the pickling tank has certain harm to the environment; too low a temperature may result in insufficient pickling at a set rate.

The following will explain in detail a method for reducing filiform scar defect on the surface of electro-galvanized sheet according to the present application with reference to examples, comparative examples and experimental data.

S1, smelting the molten steel of the electro-galvanized plate to obtain a continuous casting billet; the chemical components of the electro-galvanized plate are shown in Table 1;

TABLE 1 Mass fractions of chemical Components of examples and comparative examples

Group of	C％	Si％	Mn％	Al％	Ti％	P％	S％
								Example 1	0.002	0.03	0.25	0.5	0.07	0.01	0.01
Example 2	0.002	0.02	0.15	0.5	0.045	0.03	0.02
								Example 3	0.005	0.01	0.12	0.5	0.075	0.035	0.025
Example 4	0.002	0.03	0.25	0.5	0.07	0.01	0.01
								Example 5	0.002	0.03	0.25	0.5	0.07	0.01	0.01
Comparative example 1	0.002	0.03	0.25	0.5	0.07	0.01	0.01
								Comparative example 2	0.002	0.03	0.25	0.5	0.07	0.01	0.01
Comparative example 3	0.002	0.03	0.25	0.5	0.07	0.01	0.01
								Comparative example 4	0.002	0.03	0.25	0.5	0.07	0.01	0.01
Comparative example 5	0.002	0.03	0.25	0.5	0.07	0.01	0.01
								Comparative example 6	0.002	0.03	0.25	0.5	0.07	0.01	0.01
Comparative example 7	0.002	0.03	0.25	0.5	0.07	0.01	0.01
								Comparative example 8	0.002	0.03	0.25	0.5	0.07	0.01	0.01

S3, heating the continuous casting billet before rolling, rough rolling, finish rolling, cooling after rolling and coiling to obtain a hot rolled plate; the descaling water at the rough rolling inlet is fully opened, and the descaling water is added at the outlets of rough rolling R21 and R24; the process parameters of heating temperature, rough rolling, finish rolling, cooling after rolling and coiling are shown in table 2;

s4, carrying out acid cleaning on the hot rolled plate to obtain the electro-galvanized plate without filiform spot mark defects on the surface.

TABLE 2

Observing and evaluating the acid cleaning quality of the acid cleaned electro-galvanized plates of each example and each comparative example, carrying out 100 times for each group, and counting the incidence rate of filiform scar defects; the results are shown in Table 3.

TABLE 3

Group of	Whether or not the filiform scar defect is generated	Incidence of filiform scar defects
			Example 1	Whether or not	1％
Example 2	Whether or not	1％
			Example 3	Whether or not	2％
Example 4	Whether or not	1％
			Example 5	Whether or not	2％
Comparative example 1	Is that	20％
			Comparative example 2	Is that	35％
Comparative example 3	Is that	25％
			Comparative example 4	Is that	20％
Comparative example 5	Is that	15％
			Comparative example 6	Is that	30％
Comparative example 7	Is that	35％
			Comparative example 8	Is that	12％

From the data in table 3, it can be seen that:

in the comparative example 1, 3+3 passes are adopted in the initial rolling pass, the content of other components and process parameters are basically the same as those of the example 1, filiform scar defects exist, and the incidence rate of the filiform scar defects on the surface of the galvanized plate is up to 20%.

The temperature of the plate blank in the comparative example 2 is 1150 ℃, which is less than 1180-1220 ℃ of the invention, the contents of other components and process parameters are substantially the same as those in the example 1, the filiform scar defect exists, and the incidence rate of the filiform scar defect on the surface of the galvanized plate is up to 35%.

In the comparative example 3, the furnace outlet temperature of the plate blank is 1280 ℃, which is higher than the range of 1180-1220 ℃ of the invention, the contents of other components and process parameters are substantially the same as those in the example 1, the filiform scar defect exists, and the incidence rate of the filiform scar defect on the surface of the galvanized plate reaches 25%.

In the comparative example 4, the temperature of the RT2 at the rough rolling outlet is 1100 ℃ which is higher than the temperature of the invention within the range of 1020-1050 ℃, the content of other components and the process parameters are basically the same as those of the example 1, the filiform scar defect exists, and the incidence rate of the filiform scar defect on the surface of the galvanized plate reaches 20%.

In the comparative example 5, the finishing temperature is 890 ℃ which is less than the temperature of 910-930 ℃ of the invention, the contents of other components and process parameters are substantially the same as those of the example 1, the filiform scar defect exists, and the incidence rate of the filiform scar defect on the surface of the galvanized plate is up to 15%.

In the comparative example 6, the pickling speed is 130m/min which is less than the range of 140-160 m/min of the invention, the contents of other components and process parameters are substantially the same as those of the example 1, the filiform scar defect exists, and the incidence rate of the filiform scar defect on the surface of the galvanized plate is up to 30%.

In the comparative example 7, the pickling speed is 170m/min, which is larger than the range of 140-160 m/min of the invention, the contents of other components and process parameters are substantially the same as those of the example 1, the filiform scar defect exists, and the incidence rate of the filiform scar defect on the surface of the galvanized plate is up to 35%.

In the comparative example 8, the descaling speed is 1.8m/s, which is more than 1-1.5 m/s of the invention, the content of other components and the process parameters are substantially the same as those in the example 1, the filiform scar defect exists, and the incidence rate of the filiform scar defect on the surface of the galvanized sheet is up to 12%.

In the embodiments 1-5 of the invention, the spot defect is obviously improved, and the incidence rate of the spot defect on the surface of the electrogalvanized plate is less than or equal to 2 percent.

The data show that the plate blank discharging temperature is 1180-1220 ℃ in the heating before rolling; the hot rolling comprises rough rolling and finish rolling, wherein in the rough rolling, 1+5 passes are adopted for rolling, the outlet temperature of the rough rolling is controlled to be 1020-1050 ℃, the final rolling temperature is controlled to be 910-930 ℃, the descaling water at the inlet of the rough rolling is fully opened, and the descaling water at the outlet of the rough rolling is increased; the pickling speed is 140-160 m/min. The parameters are satisfied simultaneously, so that the filiform spot defect on the surface of the electro-galvanized plate can be reduced.

And descaling at a rate higher than 1.5m/s also increases the incidence of filiform scar defects.

Description of the accompanying drawings 2-4

FIG. 2 is a metallographic structure morphology of a surface portion of a hot-rolled plate sample of comparative example 5 (final rolling temperature 890 ℃); the existence of surface filiform scar defects;

FIG. 3 is the metallographic structure of the surface portion of the hot rolled plate sample of example 1 (finish rolling temperature 910 deg.C); the surface filiform scar defect does not exist;

the above fig. 2 and fig. 3 show that the final rolling temperature is not within the range of 910-930 ℃ of the invention, and the filiform scar defect exists in the metallographic structure morphology of the surface part of the hot rolled plate sample.

FIG. 4 shows the surface morphology of the sample of comparative example 7, the pickling speed is 170m/min, which is larger than the range of 140-160 m/min of the present invention, resulting in too short pickling time and surface iron oxide residue.

FIG. 5 shows the surface morphology of the sample of comparative example 6, the pickling speed is 130m/min, which is less than 140-160 m/min of the present invention, and the pickling time is too long, so that the surface pickling is not uniform, coarse ferrite grains exist in a part of the area, and the mixed grain phenomenon occurs in the part after cold rolling, so that the filiform scar defect occurs in the electroplating process.

Finally, it should also be noted that 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.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A method for reducing filiform scar defects on the surface of an electrogalvanized plate, which is characterized by comprising the following steps:

pickling the hot rolled plate to obtain an electrogalvanizing substrate with good surface quality;

the pickling speed is 140-160 m/min.

2. The method for reducing filiform scar defects on the surface of an electro-galvanized plate according to claim 1, wherein the electro-galvanized plate comprises the following chemical components in percentage by mass: c is less than or equal to 0.10 percent; mn: 0.12 to 0.50 percent; p is less than or equal to 0.035%; s is less than or equal to 0.025 percent, and Al is more than or equal to 0.015 percent; ti: 0.045% -0.075%; the balance of Fe and inevitable impurities.

3. The method for reducing filiform mark defects on the surface of an electrogalvanized sheet according to claim 1, wherein the increase of rough rolling outlet descaling water comprises the following steps: descaling water is added at the outlet of the roughing mill R21 and R24.

4. The method for reducing filiform mark defects on the surface of an electro-galvanized plate according to claim 1, characterized in that the descaling is performed by two-pass descaling.

5. The method for reducing filiform scar defects on the surface of an electrogalvanized plate according to claim 1, characterized in that the rough rolling is performed at a rolling speed of 1-2.8 m/s, a total deformation of the rough rolling is controlled to be 80-83%, and a rough rolling inlet temperature is controlled to be 1060-1090 ℃.

6. The method for reducing filiform scar defects on the surface of an electrogalvanized plate according to claim 1, characterized in that in the finish rolling, 7-pass rolling is adopted, the speed of F7 passing through the plate is controlled to be 10.5-11.5 m/s, the plate is descaled after F1 is increased, and the outlet temperature of the finish rolling is 910-930 ℃.

7. The method for reducing filiform mark defects on the surface of an electro-galvanized plate according to claim 1, wherein the high-temperature period of the casting blank is controlled for 95-110 min during the heating before rolling, and the furnace time of the casting blank is controlled for 220-260 min.

8. The method for reducing filiform scar defects on the surface of an electro-galvanized plate according to claim 1, wherein the cooling after rolling is carried out at a speed of 25-35 ℃/s to 600-650 ℃.

9. The method for reducing filiform scar defects on the surface of an electro-galvanized plate according to claim 1, characterized in that the coiling temperature is 600-650 ℃.

10. The method for reducing the filiform scar defects on the surface of the electro-galvanized plate as claimed in claim 1, wherein the pickling adopts a shallow slot turbulent pickling mode, and specifically comprises the following steps: and (3) crushing the iron sheet by an S roller after uncoiling, and then pickling the strip steel in a pickling tank at the pickling temperature of 75-85 ℃.