CN114214540B

CN114214540B - Galvanized steel sheet and coating and preparation method thereof

Info

Publication number: CN114214540B
Application number: CN202111422824.4A
Authority: CN
Inventors: 蒋光锐; 朱国森; 周建; 张亮; 商婷; 滕华湘; 周欢; 李研; 周纪名; 刘全利; 徐呈亮; 秦汉成; 刘广会
Original assignee: Shougang Group Co Ltd
Current assignee: Shougang Group Co Ltd
Priority date: 2021-11-26
Filing date: 2021-11-26
Publication date: 2022-10-21
Anticipated expiration: 2041-11-26
Also published as: CN114214540A

Abstract

The invention particularly relates to a galvanized steel sheet and a coating and a preparation method thereof, belonging to the technical field of steel preparation, wherein the chemical components of the coating comprise the following components in percentage by mass: 0.8 to 1.8 percent of aluminum element, 0.8 to 1.5 percent of magnesium element, 0.05 to 0.5 percent of alloy element and the balance of zinc element and inevitable impurity elements; the alloy elements comprise Cu and/or Ag; under the conditions of the components of the plating solution, a zinc-rich phase is precipitated when the plating layer is solidified, and then an eutectic structure is precipitated. The zinc-rich phase contains less Al and Mg in mass fraction, so that a dense oxide film is not easily formed on the surface, and the phosphating coating process is facilitated.

Description

Galvanized steel sheet and coating and preparation method thereof

Technical Field

The invention belongs to the technical field of steel preparation, and particularly relates to a galvanized steel sheet, a coating of the galvanized steel sheet and a preparation method of the galvanized steel sheet.

Background

The zinc-aluminum-magnesium coating is a novel coating material with excellent corrosion resistance, contains aluminum element and magnesium element, and is applied to the manufacture of parts of automobiles and household appliances. In the manufacturing process of automobile and household electrical appliance parts, the surface is often required to be coated, and a layer of electrophoretic paint film is obtained on the surface. Before the electrophoretic paint film is coated, in order to improve the bonding force between the electrophoretic paint film and the surface of the steel part, a phosphating treatment technology is often adopted to obtain a layer of phosphating film, mainly phosphate crystal grains, on the surface of the steel part. The zinc-aluminum-magnesium plating layer has certain problems in coating treatment, which is shown in that the crystal grains of the phosphating film are larger, the local phosphating film is incompletely covered, this results in poor adhesion of the electrophoretic film and also makes the electrophoretic paint film easily peel off after electrophoresis in an atmospheric corrosive environment.

Disclosure of Invention

The application aims to provide a galvanized steel sheet, a coating of the galvanized steel sheet and a preparation method of the galvanized steel sheet, and aims to solve the problem that an electrophoretic paint film of a part subjected to electrophoresis is easy to peel off in an atmospheric corrosion environment at present.

The embodiment of the invention provides a coating of a galvanized steel sheet, which comprises the following chemical components in percentage by mass: 0.8 to 1.8 percent of aluminum element, 0.8 to 1.5 percent of magnesium element, 0.05 to 0.5 percent of alloy element and the balance of zinc element and inevitable impurity elements; the alloying elements include Cu and/or Ag.

Optionally, the coating includes a zinc-rich phase and an eutectic structure, the volume fraction of the zinc-rich phase is 85% -95%, the mass percentages of aluminum and magnesium in the zinc-rich phase are not more than 0.5%, and the size of the zinc-rich phase is 200 μm-500 μm.

Based on the same inventive concept, the embodiment of the invention also provides a galvanized steel sheet, which comprises a steel substrate, a coating covered on the surface of the steel substrate and an oxide layer covered on the surface of the coating, wherein the chemical components of the coating comprise the following components in percentage by mass: 0.8 to 1.8 percent of aluminum element, 0.8 to 1.5 percent of magnesium element, 0.05 to 0.5 percent of alloy element and the balance of zinc element and inevitable impurity elements; the alloying elements include Cu and/or Ag.

Optionally, the thickness of the oxide layer is not more than 50nm, and the oxide of the oxide layer is an oxygen vacancy type MO _n-x Said oxygen deficient type MO _n-x The ratio of oxygen vacancies (n-x)/n is not more than 80%.

Based on the same inventive concept, the embodiment of the invention also provides a preparation method of the galvanized steel sheet, which comprises the following steps:

preheating the plating solution to obtain a preheated plating solution;

preheating a steel substrate to obtain a preheated steel substrate;

immersing the preheated steel substrate into the preheated plating solution, and then cooling to obtain a steel plate with a plating layer;

soaking the steel plate with the coating in an acid solution, and then rinsing and drying to obtain a galvanized steel plate;

wherein the chemical components of the coating comprise the following components in percentage by mass: 0.8 to 1.8 percent of aluminum element, 0.8 to 1.5 percent of magnesium element, 0.05 to 0.5 percent of alloy element and the balance of zinc element and inevitable impurity elements; the alloying elements include Cu and/or Ag.

Optionally, the acid solution is a non-oxidizing acid solution, and the pH of the acid solution is 3 to 5.

Optionally, the non-oxidizing acid solution comprises one of sulfuric acid, oxalic acid, phosphoric acid, or hydrochloric acid.

Optionally, the soaking time is 1s-10s.

Optionally, the oxygen partial pressure ratio in the cooled atmosphere is not more than 5%, and the cooling speed is 1K/s-10K/s.

Optionally, the temperature for preheating the steel substrate is 400 ℃ to 450 ℃.

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

the coating of the galvanized steel sheet provided by the embodiment of the invention comprises the following chemical components in percentage by mass: 0.8 to 1.8 percent of aluminum element, 0.8 to 1.5 percent of magnesium element, 0.05 to 0.5 percent of alloy element and the balance of zinc element and inevitable impurity elements; the alloy elements comprise Cu and/or Ag; under the conditions of the components of the plating solution, a zinc-rich phase is precipitated firstly when the plating layer is solidified, and then an eutectic structure is precipitated. The zinc-rich phase contains less Al and Mg in mass fraction, so that a dense oxide film is not easily formed on the surface, and the phosphating coating process is facilitated.

The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below 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 provided by an embodiment of the invention.

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 illustrative of 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 general idea of the embodiment of the application is as follows:

according to an exemplary embodiment of the present invention, there is provided a plating layer of a galvanized steel sheet, the plating layer having a chemical composition including, in mass fraction: 0.8 to 1.8 percent of aluminum element, 0.8 to 1.5 percent of magnesium element, 0.05 to 0.5 percent of alloy element and the balance of zinc element and inevitable impurity elements; the alloying elements include Cu and/or Ag.

The corrosion resistance of the coating can be obviously improved by adding a proper amount of Al and Mg into the coating of the galvanized steel sheet, and the mechanism is that the Al and Mg in the coating can be preferentially dissolved into a water film on the surface of the coating in the atmospheric environment, the water film reacts with carbon dioxide in the air, and a compact protective film is precipitated, can stably exist in neutral and alkalescent environments, and can promote an electrolyte solution on the surface of the coating to be changed into an alkalescent solution, so that the corrosion resistance of the coating is improved.

Meanwhile, al in the hot dip plating solution can perform aluminothermic reaction with oxides and iron scales remained on the surface of the high-strength steel during hot dip plating, so that the oxides on the surface of the high-strength steel are reduced, the cleanness of the surface of the strip steel is improved, the wettability of the plating solution on the surface of the high-strength steel is improved, and the plating leakage defect is prevented.

Therefore, not less than 0.8% of Mg and not less than 0.8% of Al are added to the plating layer. However, if the content of Mg is too high, large Mg-Zn phases are easy to form, which causes the brittleness of the coating, and the coating is easy to oxidize and volatilize at high temperature, which forms coating holes and causes the serious reduction of the coating quality. The too high Al content can cause the size of an aluminum-rich phase precipitated in the coating to be too large, and a large-range aluminum-poor area is formed near the aluminum-rich phase when the coating is solidified, so that the fluidity of the plating solution near the aluminum-rich phase is weakened, the physical properties of the plating solution are fluctuated severely, and the thickness difference of the coating at different positions is large. Meanwhile, mg and Al in the coating easily react with contact oxygen on the surface of the coating to form a compact oxide film. The oxide film can delay the speed of the phosphating reaction in the subsequent coating process, so that the phosphating reaction can not be fully carried out, and metal ions required in the growth of the phosphating film are difficult to release quickly, thereby causing the crystal grain size of the phosphating film to be larger and the growth of a local phosphating film to be incomplete. Due to the problem of the phosphating film, the bonding force of the electrophoretic film is reduced, and the corrosion resistance of the electrophoretic film in the air is reduced. Therefore, the Mg content in the plating layer is not more than 1.5 percent, and the Al content is not more than 1.8 percent. Meanwhile, if the contents of Al and Mg elements are too large, the zinc-rich ratio in the coating layer is caused to be less than 85%, which impairs the phosphating ability of the galvanized steel sheet.

A small amount of alloy elements Ag or/and Cu are added into the coating. A small amount of Ag and Cu and zinc in the coating can form solid solution, and the solid solubility of Al and Mg in zinc is reduced to be below 0.5%, so that the zinc crystal grains hardly contain Al and Mg, an obvious compact oxide film cannot be formed when the zinc crystal grains are in contact with oxygen, and the quality of a phosphating film on the surface of the zinc crystal grains is improved. The invention requires that the content of the added Ag and/or Cu is not less than 0.05 percent, so that the solid solubility of Al and Mg in zinc can be obviously reduced. However, if the amount of Ag and/or Cu added is too large, the corrosion potential of Zn increases, and Cu-Zn and Ag-Zn compounds may precipitate, impairing the sacrificial anode protection effect of the galvanized layer on the steel and lowering the corrosion resistance of the galvanized steel sheet. Therefore, the addition amount is not more than 0.5%.

At the same time, the addition of Cu and/or Ag also contributes to the reduction of the zinc rich grain size.

As an optional embodiment, the coating comprises a zinc-rich phase and a eutectic structure, wherein the volume fraction of the zinc-rich phase is in a range of 85-95%, the mass percentages of Al and Mg elements in the zinc-rich phase are not more than 0.5%, and the size range of the zinc-rich structure is 200-500 microns.

Under the conditions of the components of the plating solution, a zinc-rich phase is precipitated firstly when the plating layer is solidified, and then an eutectic structure is precipitated. The zinc-rich phase contains less Al and Mg in mass fraction, so that a dense oxide film is not easily formed on the surface, and the phosphating coating process is facilitated. Therefore, the volume fraction of the zinc-rich phase is controlled to be more than 85 percent in the invention. However, if the volume fraction of the zinc-rich phase is too high, the eutectic structure in the coating layer is enriched with Al and Mg to a large extent, which makes it easy to form a thick and dense oxide film on the surface of the eutectic structure. And eutectic structures are intensively distributed at the positions of zinc-rich phase grain boundaries, so that the local phosphating performance of a zinc coating is extremely deteriorated, and a stable phosphating film is not easy to form. Thus, the invention requires that the volume fraction of the zinc-rich phase does not exceed 95%. In order to improve the phosphating performance of the zinc-rich phase, the invention requires that the mass percentages of Al and Mg elements in the zinc-rich phase are not more than 0.5 percent, and the size range of a zinc-rich structure is 200-500 micrometers. The mass percentage of Al and Mg elements in the zinc-rich phase is too high, so that an obviously compact oxide film is formed on the surface of the zinc-rich phase, and the phosphating coating capability is weakened. The zinc-rich phase has too large size, and under the condition that the volume fraction of the zinc-rich phase is not changed, the grain boundary is coarse, and the positions are eutectic structures containing more Al and Mg elements, so that the phosphating performance of the grain boundary position is obviously reduced. Leading to extreme deterioration of local phosphating performance of the zinc coating and being not beneficial to forming a stable phosphating film. However, if the size of the zinc-rich phase is too small, the distance between the eutectic structures is small, and even if a dense oxide film is not easily formed on the surface of the zinc-rich phase, the oxide film on the surface of the eutectic structures, which is thick, affects the growth of the oxide film on the surface of the zinc-rich phase. The size of the zinc-rich phase cannot be less than 200 microns.

According to another exemplary embodiment of the present invention, there is provided a galvanized steel sheet including a steel substrate, a plating layer covering a surface of the steel substrate, and an oxide layer covering a surface of the plating layer, wherein a chemical composition of the plating layer includes, in mass fraction: 0.8 to 1.8 percent of aluminum element, 0.8 to 1.5 percent of magnesium element, 0.05 to 0.5 percent of alloy element and the balance of zinc element and inevitable impurity elements; the alloying elements include Cu and/or Ag.

As an alternative embodiment, the thickness of the oxide layer is not more than 50nm, and the oxide of the oxide layer is MO of the oxygen vacancy type _n-x Said oxygen deficient type MO _n-x The ratio of oxygen vacancies (n-x)/n is not more than 80%.

The oxide film on the surface of the galvanized steel sheet is an important factor for determining the quality of the coating. The oxide film can react with the phosphating solution firstly in the phosphating processThe hydrogen ions in the phosphating solution will react with the oxide to form metal cations and water. If this reaction speed is too slow, it results in insufficient concentration of metal cations in the phosphating solution, resulting in slow crystallization of the phosphating, making the phosphating grains too large and, at the same time, locally difficult to crystallize to be covered by the phosphating film. Therefore, the thickness and kind of the oxide film have a significant influence. The smaller the thickness of the oxide film, the more favorable the reaction of the phosphating solution. Therefore, it is required not to exceed 50nm. The morphology of the oxide film includes both normal oxide and deficient oxide, wherein deficient oxide means that the oxygen atoms in the oxide are deficient. The stability of the oxide in the acidic phosphating solution is poor, on one hand, the chemical potential energy of the oxide is high and unstable due to oxygen deficiency, and on the other hand, the oxide is loose and porous due to the oxygen deficiency. Thereby being beneficial to accelerating the oxide reaction speed. In the invention, the oxide is required to be MO of oxygen vacancy type _n-x The ratio of oxygen deficiency (n-x)/n is not more than 80%. Where n refers to the number of oxygen atoms in the normal oxide formed by 1 metal cation M, such as 1.5 for aluminum oxide, 1 for magnesium oxide, 1 for zinc oxide, etc. If the vacancy proportion is too large, the stability of the oxide is stronger and the reaction speed is slower.

According to another exemplary embodiment of the present invention, there is provided a method of manufacturing a galvanized steel sheet, the method including:

s1, preheating a plating solution to obtain a preheated plating solution;

s2, preheating a steel substrate to obtain a preheated steel substrate;

as an alternative embodiment, the temperature of the preheated steel substrate is in the range of 400 ℃ to 450 ℃.

The preheating of the steel sheet is carried out in order to obtain a dense coating and to obtain the necessary corrosion resistance, and therefore the temperature cannot be lower than 400 ℃ nor higher than 450 ℃. Too high temperature of the steel plate can cause excessive shrinkage when the plating layer is solidified, and local thickness unevenness occurs, thereby causing local corrosion resistance to be reduced. If the temperature of the steel sheet is too low, the plating layer may be incomplete.

S3, immersing the preheated steel substrate into the preheated plating solution, and then cooling to obtain a steel plate with a plating layer; wherein the chemical components of the coating comprise the following components in percentage by mass: 0.8 to 1.8 percent of aluminum element, 0.8 to 1.5 percent of magnesium element, 0.05 to 0.5 percent of alloy element and the balance of zinc element and inevitable impurity elements; the alloying elements include Cu and/or Ag.

As an alternative embodiment, the partial pressure ratio of oxygen in the cooled atmosphere does not exceed 5%, and the cooling speed is 1K/s to 10K/s.

Cooling of the steel sheet is a necessary step to obtain a smooth and well adherent coating. During cooling, the coating on the surface of the steel sheet may come into contact with surrounding media, such as air, such as nitrogen, such as water vapor, etc. These media all have the common feature of having a certain oxygen content. The oxygen content does not mean the content of oxygen molecules. For example, in steam or carbon dioxide, oxygen is not present, but since steam and carbon dioxide themselves contain oxygen atoms, these compounds can decompose at high temperatures to decompose oxygen atoms. It is therefore appropriate to evaluate the oxygen content by the partial pressure of oxygen in the atmosphere. If the atmospheric pressure is 100%, the oxygen partial pressure ratio can be obtained by measuring the oxygen partial pressure in the atmosphere. The oxygen content is too high, the surface of the plating layer can be quickly oxidized, and a normal oxide with high thickness and high density is formed. Therefore, the oxygen content cannot be too high, and it is suitable that it does not exceed 5%.

It is clear that the cooling process significantly affects the grain size of the coating. Generally, the cooling speed is high, the crystal grains are finer, but at the same time, the alloy components dissolved and mixed in the liquid are not easy to separate. Therefore, the cooling speed is increased, so that the zinc crystal grains can be finer on one hand, but Al and Mg in zinc cannot be discharged smoothly on the other hand, and more Al and Mg are contained in the zinc crystal grains in the coating. Conversely, the cooling rate is too slow, on the one hand allowing sufficient time for Al and Mg to be expelled from the zinc particles, but again resulting in coarse grains. Therefore, the cooling rate is required to be in the range of 1 to 10K/s.

S4, soaking the steel plate with the coating in an acid solution, and then rinsing and drying to obtain a galvanized steel plate;

as an alternative embodiment, the acid solution is a non-oxidizing acid solution, said acid solution having a pH of 3 to 5.

Specifically, the non-oxidizing acid solution includes one of sulfuric acid, oxalic acid, phosphoric acid, or hydrochloric acid.

As an alternative embodiment, the soaking time is 1s-10s.

After cooling, the coated steel sheet is immersed in an acid solution in order to loosen the oxide film on the surface, i.e. to remove the oxygen atoms of the oxide and to obtain more oxygen vacancy type MO _n-x An oxide. The acid solution used for soaking is non-oxidizing acid, otherwise, a compact oxide film is formed on the surface. Too low a pH of the acid liquor may corrode the coating, resulting in reduced corrosion resistance, and may also result in hydrogen infiltration into the steel, presenting a risk of hydrogen embrittlement. If the pH is too high, the effect on the oxide film is not significant, particularly on the oxide film of Al. The pH range is thus 3-5. The soaking time is too long, so that the plating layer is corroded by acid liquor, and the corrosion resistance is reduced. If the soaking time is too short, the effect is not obvious. So the soaking time is 1-10 seconds.

The galvanized steel sheet of the present application, and the plated layer and the production method thereof will be described in detail below with reference to examples, comparative examples, and experimental data.

Examples and comparative examples

A galvanized steel sheet, the galvanized steel sheet comprises a steel substrate, a coating covering the surface of the steel substrate and an oxide layer covering the surface of the coating, and the characteristics of the coating are shown in the following table:

the oxide layer was characterized as shown in the following table:

the preparation method of the galvanized steel sheet comprises the following steps:

s1, preheating a plating solution to obtain a preheated plating solution;

s2, preheating a steel substrate to obtain a preheated steel substrate;

s3, immersing the preheated steel substrate into the preheated plating solution, and then cooling to obtain a steel plate with a plating layer;

the specific process parameter values in the method are shown in the following table:

examples of the experiments

The galvanized steel sheets obtained in examples 1 to 7 and comparative examples 1 to 5 were subjected to corrosion evaluation. The corrosion evaluation method comprises the steps of putting the galvanized steel sheet into a circulating corrosion test box, carrying out 20 circulating corrosion tests, measuring the mass loss of the plating before and after the tests, and evaluating the corrosion resistance of the plating by using the mass loss amount on a unit area, wherein the less the mass loss is, the better the corrosion resistance is; then, carrying out phosphating treatment on the galvanized steel plate, and evaluating the crystal size and the phosphating film coverage rate of a phosphating film by using an electron microscope; then carrying out electrophoresis treatment on the phosphated galvanized steel sheet; evaluating the adhesive force of the electrophoretic film by adopting a cupping test method, and evaluating the height of cupping when the electrophoretic film is broken, wherein the higher the height is, the better the adhesive force performance of the electrophoretic film is; and evaluating the corrosion resistance of the electrophoretic film by using a circulating corrosion test method, and engraving two mutually crossed marks on the surface of the electrophoretic film, wherein the crossed included angle is 60 degrees, the width of each mark is 1mm, and the depth of each mark reaches the surface of the coating. Then putting the galvanized steel plate with the nicks into a cyclic corrosion test box, carrying out 20 cyclic corrosion tests, measuring the average width of the nicks again, and evaluating the variation of the average nick width of the nicks before and after corrosion, wherein the larger the variation is, the worse the corrosion resistance is; the results are shown in the following table:

from the above table, it can be seen that the galvanized steel sheet prepared by the method provided in the present application has excellent corrosion resistance, and at the same time, can be applied to the "phosphating-electrophoresis" coating treatment process in the manufacture of automobile and household electrical appliance parts.

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

the galvanized steel sheet provided by the embodiment of the invention has excellent corrosion resistance, and can be suitable for a phosphating-electrophoresis coating treatment process in the manufacturing of automobile household appliance parts.

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. The coating of the galvanized steel sheet is characterized by comprising the following chemical components in percentage by mass: 0.8 to 1.8 percent of aluminum element, 0.8 to 1.5 percent of magnesium element, 0.05 to 0.5 percent of alloy element and the balance of zinc element and inevitable impurity elements; the alloy element is Cu and/or Ag;

the coating comprises a zinc-rich phase and a eutectic structure, the volume fraction of the zinc-rich phase is 85% -95%, the mass percentages of aluminum and magnesium in the zinc-rich phase are not more than 0.5%, and the size of the zinc-rich phase is 200-500 μm.

2. A galvanized steel sheet is characterized by comprising a steel substrate, a coating covering the surface of the steel substrate and an oxide layer covering the surface of the coating, wherein the chemical composition of the coating comprises the following components in percentage by mass: 0.8 to 1.8 percent of aluminum element, 0.8 to 1.5 percent of magnesium element, 0.05 to 0.5 percent of alloy element and the balance of zinc element and inevitable impurity elements; the alloy element is Cu and/or Ag;

the thickness of the oxide layer is not more than 50nm, and the oxide of the oxide layer is MO of oxygen vacancy type _n-x Said oxygen deficient type MO _n-x The ratio of oxygen vacancies (n-x)/n is not more than 80%.

3. A method of producing a galvanized steel sheet, characterized by comprising:

preheating the plating solution to obtain a preheated plating solution;

preheating a steel substrate to obtain a preheated steel substrate;

wherein the chemical components of the coating comprise the following components in percentage by mass: 0.8 to 1.8 percent of aluminum element, 0.8 to 1.5 percent of magnesium element, 0.05 to 0.5 percent of alloy element and the balance of zinc element and inevitable impurity elements; the alloy element is Cu and/or Ag;

the oxygen partial pressure proportion in the cooled atmosphere is not more than 5%, and the cooling speed is 1-10K/s.

4. The method for producing a galvanized steel sheet according to claim 3, characterized in that the acid solution is a non-oxidizing acid solution, and the pH of the acid solution is 3 to 5.

5. The method of manufacturing a galvanized steel sheet according to claim 4, characterized in that the non-oxidizing acid solution includes one of sulfuric acid, oxalic acid, phosphoric acid, or hydrochloric acid.

6. The method for producing a galvanized steel sheet according to claim 3, characterized in that the time for immersion is 1s to 10s.

7. The method of producing a galvanized steel sheet according to claim 3, characterized in that the temperature of the preheated steel substrate is 400 ℃ to 450 ℃.