KR20110073573A - Galvanized steel sheet and method for manufacturing the same - Google Patents

Abstract

In the method for producing a galvanized steel sheet, the galvanizing is applied to the steel sheet, the surface contains zinc ions in the range of 5 to 100 g / l as the zinc ion concentration, the pH is 4 to 6, and the liquid temperature (liquid). The aqueous solution having a temperature of 20 to 70 ° C is brought into contact with each other and then held for 1 to 60 seconds, followed by washing with water and drying. As a solution containing zinc, it is preferable to contain the sulfate of zinc, for example. By the above method, the oxide layer which has an average thickness of 10 nm or more and consists mainly of zinc on the steel plate surface is formed, and can produce a galvanized steel sheet which has the outstanding press formability in a short time and stably.

Description

Galvanized steel sheet and its manufacturing method {GALVANIZED STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stably producing a zinc-based plated steel sheet having a small sliding resistance at the time of press molding and having excellent press formability, and a zinc-based plated steel sheet having excellent press formability.

Zinc-based galvanized steel sheet is widely used in a wide range of fields, mainly for automotive body applications. The zinc-based galvanized steel sheet for such a use is press-formed and provided for use. However, the zinc-based galvanized steel sheet has a disadvantage in that press formability is inferior to that of a cold rolled steel sheet. This is because the sliding resistance of the galvanized steel sheet in the press die is larger than that of the cold rolled steel sheet. That is, the zinc-based galvanized steel sheet is less likely to flow into the press mold at a portion where the sliding resistance between the mold and the bead is large, and fracture of the steel sheet is likely to occur.

Here, among galvanized steel sheets, an alloyed hot dip galvanized steel sheet which is subjected to an alloying treatment after hot dip galvanizing is particularly excellent in weldability and paintability in comparison with a hot dip galvanized steel sheet not subjected to alloying treatment. As a vehicle body use, it is used more suitably.

An alloyed hot-dip galvanized steel sheet forms a Fe-Zn alloy phase by galvanizing a steel plate, heat-processing, and spreading Fe in a steel plate and Zn in a plating layer, and generating an alloying reaction. This Fe-Zn alloy phase is usually a coating film composed of a Γ phase, a δ ₁ phase, and a ζ phase, and as the Fe concentration decreases, that is, in the order of the Γ phase → δ ₁ phase → ζ phase, hardness and Melting point tends to be lowered. For this reason, an alloyed hot-dip galvanized steel sheet which has a high hardness, a high Fe coating film having high melting point and hardly adhersion, is effective in view of slipability, and which emphasizes press formability, The average Fe concentration in a film is manufactured a little high.

However, in the coating of high Fe concentration, a hard and soft Γ phase is easily formed at the plating-steel plate interface, which causes a phenomenon of peeling from the interface during processing, so-called powdering.

As a method for solving the above problems, Patent Document 1 and Patent Document 2 form an oxide film mainly composed of ZnO by subjecting the surface of the zinc-based plated steel sheet to an electrolytic treatment, an immersion treatment, a coating oxidation treatment, or a heat treatment. The technique which improves weldability and workability is disclosed.

However, when the technique of patent documents 1 and 2 is applied to an alloyed hot-dip galvanized steel sheet, an alloy oxide hot-dip steel sheet is inferior in surface reactivity because an Al oxide exists. And since the surface unevenness is large, the improvement effect of press formability cannot be obtained stably. That is, since surface reactivity is low, even if it carries out electrolytic treatment, immersion treatment, application | coating oxidation process, heat processing, etc., it is difficult to form a predetermined | prescribed film on the surface, and it is a part with low reactivity, ie, a part with many amounts of Al oxides. The film thickness becomes thinner. In addition, since the unevenness of the surface is large, the direct contact with the press die at the time of press molding becomes the convex portion of the surface, but the sliding resistance at the contact portion between the thin film thickness of the convex portion and the mold is increased, thereby improving press formability. The effect is not sufficiently obtained.

Then, in patent document 3, after hot-dip galvanizing, the steel plate is alloyed by heat processing, and temper rolling is further performed, and it contacts with the acidic solution which has a pH buffer effect, and hold | maintains for 1 to 30 second. The technique which forms an oxide layer in a plating surface layer by holding and washing with water is disclosed.

Similarly, in the method of forming an oxide layer uniformly on the surface flat part of the hot-dip galvanized steel plate which does not perform alloying process, in patent document 4, the hot-dip galvanized steel plate after temper rolling is contacted with the acidic solution which has a pH buffering effect, Thereafter, a method of washing with water and drying after holding for a predetermined time in a state where a liquid film of an acidic solution is formed on a steel sheet surface is disclosed.

Japanese Laid-Open Patent Publication No. 53-60332 Japanese Patent Application Laid-Open No. 2-190483 Japanese Laid-Open Patent Publication No. 2003-306781 Japanese Laid-Open Patent Publication No. 2004-3004

When the technique disclosed by the said patent documents 3 and 4 is applied, favorable press formability can be obtained in conventional manufacturing conditions. However, in recent years, development of the manufacturing method which produces | generates a thicker oxide film in a shorter time for the improvement of productivity is desired, and when it is performed on such conditions, the technique disclosed by patent documents 3, 4 does not form sufficient oxide film. And good press formability may not be obtained.

In view of such circumstances, an object of the present invention is to provide a production method capable of stably producing a zinc-based galvanized steel sheet having excellent press formability and a zinc-based galvanized steel sheet having excellent press formability.

MEANS TO SOLVE THE PROBLEM The present inventors earnestly researched in order to solve the said subject. As a result, the following recognition was obtained.

The acidic solution used for the technique of patent documents 3 and 4 has a pH buffering effect in order to accelerate dissolution of zinc. Therefore, it can be considered that the rise of pH is delayed and the formation of the oxide layer is delayed. And in order to supplement zinc which forms an oxide layer with the zinc eluted from the plating film, the elution time of zinc is included in the formation time of an oxide film. As a result, it can be considered that it is difficult to produce a thick oxide film in a short time.

Thus, the present inventors devised a technique of generating an oxide film in a shorter time by eliminating zinc elution time by containing zinc ions in advance in an aqueous solution for producing an oxide film. However, the formation of the oxide film was not promoted simply by containing zinc ions in advance in the aqueous solution. In particular, at pH 2 shown in the Example of patent documents 3 and 4, even if it contained zinc in a process liquid, formation of the oxide film was not accelerated.

The reason for this is that in the technique of Patent Documents 3 and 4, since the pH near the surface rises due to the reduction of hydrogen ions simultaneously occurring when the zinc is eluted, the zinc oxide is easily generated. It is considered that the addition of only does not increase the pH in the vicinity of the surface and does not form an environment in which zinc oxide is easily formed.

Therefore, the present inventors devised a technique in which the pH of the aqueous solution is set to pH 4 to 6 in which zinc oxide is easily produced. Then, by setting the pH of the treatment liquid to 4 to 6, it was found that zinc is produced as a hydroxide due to a slight increase in the surface pH caused by the slight elution of zinc in the plated coating film.

This invention is made | formed based on the above recognition, The summary is as follows.

[1] After applying zinc-based plating to the steel sheet, the steel sheet is subjected to contact treatment with an aqueous solution, held for 1 to 60 seconds after the completion of the contact treatment, followed by washing with water and drying to form an oxide layer on the surface of the steel sheet. In the manufacturing method of a plated steel plate, the said aqueous solution which carries out contact treatment of a steel plate contains zinc ion in the range of 5-100 g / l as zinc ion concentration, pH is 4-6, liquid temperature is 20- It is 70 degreeC, The manufacturing method of the galvanized steel plate.

[2] The method for producing a galvanized steel sheet according to the above [1], wherein the aqueous solution contains a sulfate of zinc.

[3] The method for producing a galvanized steel sheet according to the above [1] or [2], wherein a liquid film formed on the surface of the steel sheet after contact with the aqueous solution is 5 to 30 g / m 2.

[4] An oxide layer containing zinc mainly as a metal component is produced by the method for producing a galvanized steel sheet according to any one of the above [1] to [3], and an average thickness of 10 nm or more is formed on the surface of the steel sheet. Galvanized steel sheet, characterized in that.

In addition, in this invention, a zinc-based galvanized steel plate is a plated steel plate in which the film containing zinc as a main component was formed in the surface, and it is a hot-dip galvanized steel plate (abbreviately called GI steel plate), an alloyed hot dip galvanized steel plate (it is simply called GA steel plate) ), An electrogalvanized steel sheet (abbreviatedly referred to as EG steel sheet), an evaporated galvanized steel sheet, or an alloy galvanized steel sheet containing alloy elements such as Fe, Al, Ni, and MgCo.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the principal part of the oxide layer forming treatment equipment used in the Example.
2 is a schematic front view showing a friction coefficient measuring device.
It is a schematic perspective view which shows the bead shape and dimension in FIG.
It is a schematic perspective view which shows the bead shape and dimension in FIG.
5 is a diagram showing the effect of zinc ion concentration on the oxide film thickness.

Best Mode for Carrying Out the Invention [

According to the present invention, after the zinc-based plating is applied to the steel sheet, the steel sheet is subjected to contact treatment with an aqueous solution, held for 1 to 60 seconds after the completion of the contact treatment, and then washed with water and dried to form an oxide layer on the surface of the galvanized steel sheet. In forming, as said aqueous solution, zinc ion is contained in the range of 5-100 g / l as zinc ion concentration, pH is 4-6 and liquid temperature is 20-70 degreeC. Thus, it is an important requirement and characteristic in this invention to make the aqueous solution which contact-processes a steel plate containing zinc ion of predetermined density | concentration, and prescribed | regulated pH and liquid temperature. Thereby, sufficient oxide layer can be formed in a short time in order to ensure favorable press formability.

After the end of the contact treatment, in the case of the immersion treatment, after the immersion process is finished, in the case of the spray treatment, the spray process is finished, and in the case of roll coating, it indicates after the coating process is finished. will be.

By using the aqueous solution containing zinc ion as an aqueous solution which carries out contact treatment of a steel plate, it becomes possible to omit the elution time of zinc. At this time, zinc ion is zinc ion concentration and it is set as the range of 5-100 g / l. If the zinc ion concentration is less than 5 g / l, sufficient zinc is not supplied and the formation of the oxide layer does not occur. On the other hand, when it exceeds 100 g / l, the sulfuric acid concentration contained in the oxide layer formed becomes high, and when an oxide dissolves in the chemical conversion treatment process performed after that, it is feared to contaminate a process liquid.

In order to form a stable zinc compound as an oxide layer, it is preferable to add zinc ions as a sulfate. When it adds as a sulfate, it is thought that sulfate ion is blown into the oxide layer formed and it has an effect which stabilizes an oxide layer.

As described above, the formation of the oxide film is not promoted by simply containing zinc ions in the treatment liquid in advance. Therefore, in this invention, it is necessary to make pH into pH 4-6 which zinc oxide is easy to produce | generate. When the pH of the treatment liquid is set to 4 to 6, zinc is generated as a hydroxide due to the slight increase in the surface pH caused by the slight elution of zinc in the plated film. As a result of these, zinc elution time is omitted, and zinc oxide can be produced. When the pH exceeds 6, zinc ions are precipitated (formation of hydroxides) in the aqueous solution and are not formed as oxides on the surface of the steel sheet. In addition, when pH is less than 4, as mentioned above, it inhibits formation of the oxide layer by delay of pH rise.

About the temperature of aqueous solution, you may be 20-70 degreeC. Since the formation reaction of an oxide layer occurs when it maintains for a predetermined time after contact with aqueous solution, it is effective to control the sheet temperature at the time of holding | maintenance to the range of 20-70 degreeC. If it is less than 20 degreeC, it will take a long time for the formation reaction of an oxide layer, and a fall of productivity will be caused. On the other hand, when it exceeds 70 degreeC, although reaction advances comparatively fast, on the contrary, it becomes easy to produce a processing nonuniformity on the steel plate surface.

The aqueous solutions used in Patent Documents 3 and 4 are acidic and have a pH buffering action. However, in the present invention, since an aqueous solution containing zinc ions is used, a sufficient oxide layer can be formed without raising the pH of the aqueous solution sufficiently to cause dissolution of zinc. In addition, it is considered that it is advantageous for the formation of an oxide that a rise in pH occurs quickly. Therefore, pH buffering is not necessarily necessary.

In the present invention, since the oxide layer excellent in slipperiness can be stably formed when the aqueous solution in contact with the surface of the steel sheet contains zinc, other metal ions, inorganic compounds and the like are contained in the aqueous solution as impurities or intentionally. Even if it does not impair the effect of this invention. And even if N, P, B, Cl, Na, Mn, Ca, Mg, Ba, Sr, Si or the like is blown into the oxide layer, it is applicable as long as the effects of the present invention are not impaired.

After contacting a zinc-based galvanized steel sheet with the aqueous solution which consists of more than one, it is preferable that this aqueous solution exists in the shape of a thin liquid film on the steel plate surface. This is because if the amount of the aqueous solution present on the surface of the steel sheet is large, the pH of the aqueous solution hardly rises even when dissolution of zinc occurs, and it takes a long time to form an oxide layer. From this viewpoint, it is preferable and effective to adjust the quantity of the aqueous solution film formed on the steel plate surface to 30 g / m <2> or less. Moreover, the liquid film amount of 5 g / m <2> or more is suitable for the purpose of preventing drying of a liquid film. As mentioned above, Preferably, the liquid film formed on the steel plate surface after contact with the said aqueous solution shall be 5-30 g / m <2>. In addition, the amount of the aqueous solution film can be adjusted by squeeze roll, air wiping, or the like.

In addition, after immersion in aqueous solution, time to water washing (holding time until water washing) shall be 1 to 60 second. If the time until washing with water is less than 1 second, since the aqueous solution is washed away before a sufficient oxide layer is formed, a slippery improvement effect cannot be obtained. On the other hand, productivity will fall in the holding time when it exceeds 60 second. Since it is an object of the present invention to manufacture stably even in a short time, the holding time is 60 seconds or less in view of sufficiently exhibiting the effects of the present invention.

As mentioned above, the surface of the coated steel plate of this invention mainly contains zinc as a metal component, and the oxide layer of 10 nm or more of average thickness is obtained.

In addition, the main component of zinc is 50 mass% or more of zinc as a metal component.

In addition, the oxide layer in this invention means the layer which consists of an oxide, a hydroxide, etc. which mainly contained zinc as a metal component. It is necessary that the average thickness of this oxide layer is 10 nm or more. When the average thickness of the oxide layer becomes thinner than 10 nm, the effect of lowering the sliding resistance is insufficient. On the other hand, when the average thickness of the oxide layer containing zinc as an essential component exceeds 100 nm, it is unpreferable because a film breaks during press work and a skid resistance rises and weldability tends to fall.

In addition, there is no restriction | limiting in particular in the method of contact-processing a zinc-based galvanized steel plate in the aqueous solution containing zinc, The method of immersing a galvanized steel plate in aqueous solution, the method of spraying an aqueous solution in a plated steel plate, and plating an aqueous solution through an application | coating roll. The method of apply | coating to a steel plate etc., It is preferable to exist in the surface of a steel plate finally in the shape of a thin liquid film.

In addition, about manufacturing the alloyed hot-dip galvanized steel sheet which concerns on this invention, although Al needs to be added in the plating bath, additional element components other than Al are not specifically limited. That is, even if Al contains or adds Pb, Sb, Si, Sn, Mg, Mn, Ni, Ti, Li, Cu, etc., it is applicable as long as the effect of this invention is not impaired.

Example

Next, an Example demonstrates this invention further in detail.

After the hot-dip galvanizing of 45 g / m <2> and Al concentration of 0.20 mass% on the cold-rolled steel plate of 0.8 mm of plate | board thickness, GI steel plate which carried out temper rolling was produced. Further, on a cold rolled steel sheet with a plate thickness of 0.8 mm, a plating coating amount of 45 g / m 2, single-sided Fe concentration of 10 mass%, and Al-concentration of 0.20 mass% by single-alloyed hot-dip galvanizing method. To form a GA steel sheet further subjected to temper rolling. Moreover, on the cold-rolled steel plate of 0.8 mm of plate | board thickness, the EG steel plate which has a plating film of 30 g / m <2> of plating adhesion amounts per single side was produced by the said galvanizing method of the conventional method.

Next, the oxide layer was formed using the processing apparatus of the structure shown in FIG. First, an aqueous solution in which steel sheets S such as GI steel sheet, GA steel sheet and EG steel sheet obtained by the above are treated in the solution tank 2 as shown in Tables 1-1 and 1-2, Immerse in Next, the liquid film amount of the steel plate surface was adjusted with the squeeze roll 3. The liquid film amount was adjusted by changing the pressure of the squeeze roll. Subsequently, the washing tank 5 and the washing tank 6 are simply passed through, the washing tank 7 is sprayed and washed with hot water at 50 ° C. on a steel sheet, dried with a dryer 8, and an oxide layer is applied to the plating surface. Formed. Moreover, the washing tank 1 can be provided before the solution tank 2.

The aqueous solution which immersed in the solution tank 2 used the aqueous solution which added the predetermined amount of zinc sulfate heptahydrate for the purpose of adding zinc ion. In addition, the solution which adjusted the pH with sulfuric acid for the solution containing 20 g / l sodium acetate for some comparison was also used.

The holding time until the washing with water is the time until the liquid film amount is adjusted with the squeeze roll 3 and the washing starts in the washing tank 7, and by adjusting the line speed, the squeeze roll 3 is partially adjusted. ) The steel plate was wash | cleaned immediately after a squeeze using the shower washing | cleaning apparatus 4 of the exit side.

Next, with respect to the steel sheet produced as described above, it is judged whether it has a sufficient external appearance as a vehicle exterior plate, and the measurement of a friction coefficient and the actual formability are explained in more detail as a method of easily evaluating press formability. A spherical head bulging test was conducted for the purpose of simulating. In addition, the measuring method is as follows.

(1) Press formability evaluation test (friction coefficient measurement test)

In order to evaluate press formability, the friction coefficient of each test material was measured as follows.

2 is a schematic front view showing a friction coefficient measuring device. As shown in the same figure, the friction coefficient measurement sample 11 taken from the specimen is fixed to the sample stage 12, and the sample stage 12 is the upper surface of the slide table 13 which is horizontally movable. It is fixed at. On the lower surface of the slide table 13, an up-and-down movable slide table support 15 having a roller 14 in contact with the slide table 13 is provided, which is pushed up to the sample 11 for friction coefficient measurement by the bead 16 by pushing it up. The first load cell 17 for measuring the sticking load N is attached to the slide table support 15. In order to measure the sliding resistance F for horizontally moving the slide table 13 along the rail 19 in the state where the pushing force is applied, the second load cell 18 has one side of the slide table 13. It is attached to the end of the. In addition, Sugimura Kagaku Co., Ltd. washing oil preton R352L manufactured by Sugimura Chemical Co., Ltd. was applied to the surface of the friction coefficient measurement sample 11 and tested.

3 and 4 are schematic perspective views showing the shape and dimensions of the used beads. The lower surface of the bead 16 slides while being pushed against the surface of the sample 11. The shape of the bead 16 shown in FIG. 3 is 10 mm in width, 12 mm in the sliding direction length of a sample, and the lower part of both ends of a sliding direction consists of a curved surface of curvature 4.5 mmR, and the lower surface of the bead to which a sample is pushed is 10 mm in width, and a sliding direction length Have a plane of 3 mm. The shape of the bead 16 shown in FIG. 4 is 10 mm in width, 69 mm in the sliding direction length of a sample, and the lower part of both ends of a sliding direction consists of a curved surface of curvature 4.5 mmR, and the lower surface of the bead to which a sample is pushed is 10 mm in width, and a sliding direction length It has a plane of 60 mm.

The friction coefficient measurement test was performed under the two conditions shown below.

[Condition 1]

Using the bead shown in FIG. 3, the pushing load N was 400 kgf and the drawing speed (horizontal movement speed of the slide table 13) of a sample was 100 cm / min.

[Condition 2]

Using the bead shown in FIG. 4, the pushing load N was 400 kgf, and the drawing speed (horizontal movement speed of the slide table 13) of a sample was 20 cm / min.

The friction coefficient (μ) between the specimen and the beads was calculated by the formula: μ = F / N.

(2) oral ejaculation test

The test piece of 200x200 mm size was elongated by the hydraulic bulge tester using the punch of 150 mm (phi), and the maximum shaping | molding height at the time of breakage was measured. At this time, a wrinkle pressing force of 100 Ton was applied for the purpose of preventing the inflow of the material, and lubricating oil was applied only to the surface where the punch contacted. The used lubricant is the same as the friction coefficient measurement test mentioned above.

(3) Measurement of thickness (oxide film thickness) of oxide layer

The film thickness using a Si wafer thermal oxidation SiO ₂ film is formed of 96nm as a reference material, and by measuring the O · Kα X-rays of the fluorescent X-ray analyzer, was determined in terms of the average thickness of the SiO ₂ layer. The analysis area is 30 mmφ.

The test results obtained from the above are shown in Table 1-1 and Table 1-2.

Table 1-1

Table 1-2

The following matters became clear from the test results shown in Table 1-1 and Table 1-2.

(1) Since Nos. 1, 47, and 60 are not treated with a solution, an oxide film sufficient to improve the sliding property is not formed in the flat portion, and the friction coefficient is high.

(2) Nos. 2 to 4, Nos. 48 to 50, and Nos. 61 to 63 are comparative examples using an acidic solution having a pH buffering action. Although the coefficient of friction is low and the maximum formation height is high at 30 seconds or more, the treatment of 10 seconds does not satisfy the reduction of the sufficient friction coefficient and the improvement of the maximum molding height.

(3) Nos. 5 to 7 are comparative examples using an acidic solution having a pH buffering action. High friction coefficient is shown.

(4) Nos. 8 to 10, Nos. 51 to 53, and Nos. 64 to 66 contain zinc ions, but the amounts thereof are comparative examples having a smaller amount than the scope of the present invention. Although the coefficient of friction is low and the maximum formation height is high at 30 seconds or more, the treatment of 10 seconds does not satisfy the reduction of the sufficient friction coefficient and the improvement of the maximum molding height.

(5) Nos. 11 to 13, Nos. 54 to 56, and Nos. 67 to 69 are examples of the present invention which have been treated in a solution containing zinc ions, and the friction coefficient is lowered and the maximum molding height is also increased. have. Nos. 14 to 16 and Nos. 44 to 46 are examples of the present invention in which the zinc ion concentration in the liquid is increased under the same treatment conditions as in Nos. 11 to 13. The friction coefficient is low stabilized, and the maximum molding height is further increased. Similarly, Nos. 57 to 59 and Nos. 70 to 72 are examples of the present invention in which the zinc ion concentration in the liquid is increased under the same treatment conditions as those of Nos. 54 to 56. The friction coefficient is low stabilized, and the maximum molding height is further increased.

(6) No. 17-22 are the examples which changed the time until the solution film was formed in the steel plate surface and water washing was performed. In No. 17 which washed with water without holding, the friction coefficient only slightly decreased, whereas in Nos. 18 to 22, which had a holding time of 1 second or more, the friction coefficient was lowered, and the elongation property was also stably improved.

(7) Nos. 23 to 40 are examples in which the treatment liquid temperature was changed, but Nos. 23 to 25 having a low treatment liquid temperature had sufficient effects of improving the friction coefficient and the maximum molding height in comparison with the other examples. Not. On the other hand, Nos. 32 to 34 are examples where the treatment liquid temperature is high, and the effect of improving the coefficient of friction and the maximum molding height is sufficient, but there are many treatment unevennesses, and they do not exhibit a good appearance as an automotive exterior plate.

(8) No. 35-40 is the example of this invention which changed the liquid film formation quantity with respect to No.20-22. Compared with the same retention time until water washing, when the amount of the liquid film is large, a sufficient reduction in the friction coefficient and an improvement in the maximum molding height are obtained. However, the friction coefficient is slightly higher than the case where the liquid film amount is small. Lowered.

(9) Although Nos. 41 to 43 are comparative examples using a treatment liquid having a pH lower than the range of the present invention, the effect of lowering the friction coefficient is not recognized as compared with Nos. 20 to 22, and the degree of improvement in the maximum molding height is also observed. Can't see

FIG. 5 is a diagram showing the effect of zinc ion concentration on the oxide film thickness using Nos. 8 to 22 and Nos. 44 to 46 of Tables 1-1 and 1-2. According to Fig. 5, when the concentration of zinc is 5 g / l or more, the oxide film thickness is sufficiently thick even if the holding time is short (for example, 10 seconds), and the oxide film thickness becomes thin when the holding time is short. It can be seen that the problem is solved.

According to the present invention, a zinc-based galvanized steel sheet can be stably manufactured even in a short time production condition, which is space-saving, has low sliding resistance during press molding, and has excellent press formability. And, for example, even when producing a high strength galvanized steel sheet which has a high molding load and is easy to generate die galling, the slip resistance at the time of press molding is small, and excellent press formability can be obtained. In view of excellent press formability, the present invention can be applied to a wide range of fields mainly on automobile body applications.

Claims (4)

The zinc-based galvanized steel sheet which forms an oxide layer on the surface of a steel plate by performing zinc-plating on a steel plate, carrying out a contact treatment with aqueous solution, holding for 1 to 60 seconds after completion | finish of a contact process, and performing water washing and drying. In the production method of the above, the aqueous solution for contact-treating the galvanized steel sheet contains zinc ions in the range of 5 to 100 g / l as zinc ion concentration, has a pH of 4 to 6, and a liquid temperature of 20 It is -70 degreeC, The manufacturing method of the galvanized steel plate characterized by the above-mentioned. The method of claim 1,
In the said aqueous solution, the sulfate of zinc is contained, The manufacturing method of the zinc-based galvanized steel plate. The method according to claim 1 or 2,
A liquid film formed on the surface of a steel sheet after contact with the aqueous solution is 5 to 30 g / m 2. It is manufactured by the manufacturing method of the zinc-based galvanized steel plate in any one of Claims 1-3, The oxide layer which consists mainly of zinc as a metal component was formed in the steel plate surface on the average thickness 10 nm or more, It is characterized by the above-mentioned. Galvanized steel sheet.

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