JP3303768B2 - Manufacturing method of galvanized steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a press formability,
The present invention relates to a method for producing a galvanized steel sheet having excellent spot weldability and adhesiveness.

[0002]

2. Description of the Related Art Galvanized steel sheets are widely used as various kinds of rust-proof steel sheets because they have various excellent characteristics. In order to use this galvanized steel sheet as an anti-corrosion steel sheet for automobiles, in addition to corrosion resistance, paint compatibility, etc., it is required to have excellent press formability, spot weldability and adhesion as the performance required in the body manufacturing process. It is important that

[0003] However, galvanized steel sheets generally have a disadvantage that press formability is inferior to cold-rolled steel sheets.
This is because the sliding resistance between the galvanized steel sheet and the press mold,
This is because it is larger than that of the cold rolled steel sheet. That is, since the sliding resistance is large, the zinc-plated steel sheet hardly flows into the press die in a portion where the sliding resistance between the bead and the galvanized steel sheet is extremely large, and the steel sheet is easily broken.

[0004] As a method for improving the press formability of a galvanized steel sheet, a method of applying a high-viscosity lubricating oil has been widely used. However, in this method, there are problems such as the occurrence of coating defects due to poor degreasing in the coating process due to the high viscosity of the lubricating oil, and the unstable press performance due to running out of oil during pressing. Therefore, there is a strong demand for improving the press formability of a zinc-based plated steel sheet.

[0005] In a zinc-based plated steel sheet, copper as an electrode reacts with molten zinc at the time of spot welding to easily form a brittle alloy layer. Therefore, the copper electrode is severely worn, its life is short, and the cold rolled steel sheet is used. There is a problem that the continuous hitting property is inferior.

Further, in the manufacturing process of an automobile body,
Various types of adhesives are used for the purpose of preventing rust and damping the body, but in recent years it has become clear that the adhesion of galvanized steel sheets is inferior to that of cold-rolled steel sheets. Have been.

As a method for solving the above-mentioned problems, Japanese Patent Application Laid-Open Nos. 53-60332 and 2-190483 disclose electrolytic treatment, immersion treatment, coating oxidation treatment, or heat treatment on the surface of a zinc-based plated steel sheet. (Hereinafter referred to as "prior art 1") by forming an oxide film mainly composed of ZnO to improve weldability or workability.

[0008] Japanese Patent Application Laid-Open No. 4-88196 discloses that a zinc-based plated steel sheet contains 5 to 60 g / l of sodium phosphate and has a pH of 2
Dipping the plated steel sheet in the aqueous solution of ~
In addition, a technique for forming an oxide film mainly composed of P oxide by spraying the aqueous solution to improve press formability and chemical conversion treatment (hereinafter, referred to as “prior art 2”) is disclosed.

Japanese Patent Application Laid-Open No. Hei 3-91093 discloses a press-forming property and a chemical conversion treatment by forming Ni oxide on the surface of a galvanized steel sheet by electrolytic treatment, dipping treatment, coating treatment, coating oxidation treatment or heat treatment. (Hereinafter referred to as “prior art 3”).

Japanese Patent Application Laid-Open No. 58-67885 discloses a technique for improving the corrosion resistance by generating metals such as Ni and Fe on the surface of a galvanized steel sheet (hereinafter referred to as "prior art 4"). I have.

[0011]

However, the above-mentioned prior art has the following problems. Prior art 1 is a method of generating an oxide mainly composed of ZnO on the surface of a plating layer by the above-described various treatments. Therefore, the effect of reducing the sliding resistance between the press die and the plated steel sheet is small, and the press formability is low. Has little effect of improving the adhesiveness, and has no effect of improving the adhesiveness.

Prior Art 2 is a method of forming an oxide film mainly composed of P oxide on the surface of a zinc-based plated steel sheet, and thus has a problem that spot weldability and adhesion are deteriorated.

Prior Art 3 is a method of forming a single-phase Ni oxide film on the surface of a galvanized steel sheet, and thus has no effect of improving the adhesiveness and spot weldability. Prior art 4 is a method of forming a metal film such as Ni and Fe on the surface of a galvanized steel sheet, and thus the effect of improving press formability is not sufficient.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a method for producing a zinc-based plated steel sheet having excellent press formability, spot weldability and adhesiveness.

[0015]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that an appropriate Fe-Ni-Zn-based coating It has been found that press formability, spot weldability and adhesiveness can be significantly improved by forming.

Here, the proper Fe-Ni-Zn-based coating means the following (1) to (5): (1) The lower part of the coating is a metal layer made of Fe, Ni and Zn, and the surface part of the coating. Is a layer composed of oxides and hydroxides of Fe, Ni and Zn (hereinafter referred to as “oxide-based layer”)
(2) the total of the Fe content and the Ni content in the coating is in the range of 10 to 1500 mg / m ² ,
(3) The sum of the Fe content and the Ni content (mg / mg
Fe content relative to m ²⁾ Ratio of (mg / m ^2): Fe
/ (Fe + Ni) is in the range of 0.1 to 0.8,
(4) The sum of the Fe content and the Ni content in the coating (mg /
Zn content relative to m ²⁾ Ratio of (mg / m ^2): Zn
/ (Fe + Ni) is 1.6 or less (however, Z
n / (Fe + Ni) = 0 is not included because n is included), and (5) that the thickness of the oxide-based layer in the surface layer portion of the film is in the range of 4 to 50 nm. I got the knowledge that there is.

The reason why the press formability of a zinc-based plated steel sheet is inferior to that of a cold-rolled steel sheet is that zinc having a low melting point and a mold cause an adhesion phenomenon under a high surface pressure, thereby increasing the sliding resistance. Is the cause. In order to prevent adhesion between zinc and a mold, the present inventors form a harder and higher-melting coating than a zinc or zinc alloy plating layer on the surface of a plating layer on the surface of a zinc-based plated steel sheet. Was considered effective. Based on this consideration, as a result of studying, by forming an appropriate Fe-Ni-Zn-based coating on the surface of a zinc-based plated steel sheet, the sliding resistance between the plating layer surface and the press mold during press forming is reduced. And found that the press formability was improved. This is considered to be because the Fe—Ni—Zn-based coating is hard and the oxide-based layer present in the surface layer portion of the coating has a high melting point, so that adhesion to a mold during press molding does not easily occur.

The reason why the continuous spotting property in spot welding of a galvanized steel sheet is inferior to that of a cold-rolled steel sheet is that the molten zinc contacts the copper of the electrode at the time of welding to form a brittle alloy layer. This is because the deterioration of the film becomes severe. The present inventors have studied various coatings to improve spot weldability, and have found that a metal coating made of Fe, Ni, and Zn is particularly effective. Although the reason is not clear, it is considered that the metal film made of Fe, Ni and Zn has a high melting point and high electric conductivity. In the Fe—Ni—Zn-based coating according to the present invention, since the lower layer of the coating is a metal layer made of Fe, Ni and Zn, excellent continuous spotting properties can be obtained. Fe in the present invention
Although the -Ni-Zn-based coating has an oxide-based layer with low electric conductivity on the surface layer, by controlling the thickness, adverse effects on the continuous hitting property can be avoided.

It has been known that the adhesion of a galvanized steel sheet is inferior to that of a cold-rolled steel sheet, but the cause has not been clarified. However, the Fe-Ni-Z with the Fe content properly controlled on the surface of the galvanized steel sheet.
It has been found that by forming an n-based film, excellent adhesiveness can be obtained.

The present invention has been made on the basis of the above-described findings.
This is a method for producing a zinc-plated steel sheet having excellent press formability, spot weldability and adhesiveness by forming a Ni-Zn-based film, and the gist thereof is as follows.

Fe²⁺Ion, Ni²⁺Ions and Zn²⁺I
Containing Fe²⁺Ion and Ni ²⁺Total concentration with ions
The degree is 0.3 to 2.0 mol / l, Fe²⁺Ion concentration
0.02 to 1.0 mol / l, Zn²⁺Ion concentration exceeds 0
0.5 mol / l, and the pH is in the range of 1-3.
Acid sulfate solution having a temperature in the range of 30 to 70 ° C.
Steel pre-zinc-plated in a liquid electrolyte
The plate is used as a cathode and the current density is 10 to 150 A / dm^TwoRange of
The electrolytic treatment is performed in the enclosure, and then the electrolytic treatment is performed.
In addition to the above-mentioned zinc-coated steel sheet, the pH is further set to 3 to 5.5.
With the post-treatment liquid within the range, the processing time t (sec) is
Formula: 50 / T ≦ t ≦ 10, where T: temperature of the post-treatment liquid
(° C), characterized by performing post-processing
It is.

[0022]

Next, the reasons for limiting the numerical values of the manufacturing conditions of the present invention will be described. Fe ²⁺ ion and Ni ^{2+ in} electrolyte
If the total concentration with ions is less than 0.3 mol / l, burning of the plating occurs and the adhesion of the Fe-Ni-Zn-based coating is reduced, and the effect of improving press formability, spot weldability and adhesion is obtained. Absent. On the other hand, the total concentration is 2.0 mo
If it exceeds 1 / l, the solubility limit is reached, and when the temperature is low, precipitation of nickel sulfate and ferrous sulfate occurs. Therefore, the total concentration of Fe ²⁺ ions and Ni ²⁺ ions in the electrolyte should be in the range of 0.3 to 2.0 mol / l.

By forming an Fe—Ni—Zn-based coating having an appropriately controlled Fe content on the surface of a zinc-based plated steel sheet, excellent adhesiveness can be obtained. When the concentration of Fe ²⁺ ions in the electrolytic solution is 0.02 mol / l or less, Fe—Ni
The sum of the Fe content and the Ni content in the Zn-based coating (mg
/ M ² ) to the Fe content (mg / m ² )
/ (Fe + Ni) cannot be set to 0.1 or more, and the effect of improving the adhesiveness becomes insufficient. In addition, Fe in the electrolytic solution
^When the concentration of ²⁺ ions exceeds 1.0 mol / l, Fe-
Fe content to the sum (mg / m ²⁾ between the Fe content and the Ni content of the Ni-Zn-based coating in (mg / m ²⁾ ratio Fe / (Fe + Ni) can be 0.8 or less And the effect of improving spot weldability is insufficient. Therefore, the concentration of Fe ²⁺ ions in the electrolyte is 0.02 to 1.0.
It should be in the mol / l range.

When the concentration of Fe ²⁺ ions in the electrolytic solution increases, the generation rate of Fe ⁺³ ions by air oxidation or anodic oxidation increases. Since this Fe ^{+ 3} ion is easily changed to iron hydroxide sludge, a large amount of sludge is generated in a bath having a high Fe2 ⁺ ion concentration, and this sludge adheres to the surface of the galvanized steel sheet and causes a pressing flaw. Surface defects are likely to occur. In this sense, the Fe ²⁺ ion concentration is 0.6 mol /
It is desirably set to 1 or less.

The Zn ²⁺ ion concentration in the electrolyte is as follows:
In order to form an Fe—Ni—Zn-based coating, it is necessary that at least a Zn ²⁺ ion concentration exists. On the other hand, when the Zn ²⁺ ion concentration exceeds 0.5 mol / l,
The effect of improving press formability and spot weldability is insufficient. Therefore, the Zn ²⁺ ion concentration in the electrolytic solution is more than 0 to
It should be in the range of 0.5 mol / l.

The electrolytic solution contains boric acid, citric acid, acetic acid, oxalic acid, malonic acid, tartaric acid, salts thereof, or ammonium sulfate for the purpose of improving the adhesion of the Fe—Ni—Zn-based film. PH buffering agent such as

The electrolyte contains Co, which is contained in the plating layer of the zinc-based plated steel sheet used in the present invention.
Mn, Mo, Al, Ti, Sn, W, Si, Pb, Nb
And cations such as Ta and hydroxides and oxides;
Anions other than sulfate ions may be inevitably contained.

When the pH of the electrolytic solution is less than 1, the generation of hydrogen becomes the main component of the cathode reaction, and the current efficiency is greatly reduced. On the other hand, when the pH exceeds 3, a hydroxide of ferric iron is precipitated. Therefore, the pH of the electrolyte should be controlled within the range of 1-3.

If the temperature of the electrolytic solution is lower than 30 ° C., plating burning will occur and the adhesion of the Fe—Ni—Zn-based film will be reduced, and the effect of improving press formability, spot weldability and adhesiveness cannot be obtained. On the other hand, if the temperature exceeds 70 ° C,
As the amount of evaporation of the electrolyte increases, it becomes difficult to control the concentration of Fe ²⁺ ions, Ni ²⁺ ions, and Zn ²⁺ ions. Therefore, the temperature of the electrolyte should be in the range of 30-70 ° C.

If the current density of the electrolysis is less than 10 A / dm ² , the generation of hydrogen becomes the main component of the cathodic reaction, and the current efficiency is greatly reduced. On the other hand, if the current density exceeds 150 A / dm ² , burning of the plating occurs, and the adhesion of the Fe—Ni—Zn-based coating is reduced, and the effect of improving press formability, spot weldability, and adhesion cannot be obtained. Therefore, the current density of the electrolysis should be in the range of 10 to 150 A / dm ² .

Next, the reasons for limiting the numerical values in the post-processing will be described. When the thickness of the oxide-based layer on the surface layer of the Fe-Ni-Zn-based coating is 4 nm or more, the effect of improving the formability is greatly increased. On the other hand, since the oxide-based layer has a large electric resistance, when its thickness exceeds 50 nm, the spot weldability decreases. Therefore, the thickness of the oxide-based layer in the surface layer of the Fe-Ni-Zn-based film should be within the range of 4 to 50 nm, but the surface layer of the Fe-Ni-Zn-based film obtained by the above-described electrolytic treatment. The thickness of the oxide-based layer of
It is less than 4 nm.

The present inventors have repeatedly studied to develop a post-processing technique for increasing the thickness of the oxide-based layer in the surface layer of the Fe—Ni—Zn-based coating to 4 nm or more.
The thickness of the oxide-based layer on the surface layer of the Fe-Ni-Zn-based film is increased to 4 nm or more by performing immersion treatment or spray treatment with a post-treatment solution having a pH in the range of 3 to 5.5. I found that I can do it.

The mechanism by which the thickness of the oxide-based layer on the surface layer of the Fe-Ni-Zn-based coating is increased by this post-treatment is considered as follows. When immersion treatment or spray treatment is performed with a post-treatment liquid having a pH of 3 to 5.5, Fe-Ni
Dissolution reactions (2) and (3) of Zn and Fe in the Zn-based coating and in the plating layer, and a hydrogen generation reaction (4) occur.

[0034] ^{Zn → Zn 2+ + 2e - ----------------} (2) Fe → Fe 2+ + 2e - -------------- ^{- (3) H + + e} - → (1/2) by _{H 2 ------------ (4) (4} ) reaction formula, for H ⁺ ions are consumed,
In the vicinity of the surface of the Fe-Ni-Zn coating, the pH of the post-treatment liquid
Rises. Therefore, once dissolved Zn ²⁺ and Fe ²⁺
Is taken into the Fe—Ni—Zn-based coating as a hydroxide, and as a result, the thickness of the oxide-based layer increases.

When the pH of the post-treatment liquid is less than 3, the thickness of the oxide-based layer does not increase by the post-treatment. This is thought to be because the reactions of the formulas (2) and (3) occur, but the pH of the post-treatment solution does not rise near the surface of the Fe—Ni—Zn-based coating to a level at which hydroxides of Zn and Fe are formed. Can be on the other hand,
When the pH of the post-treatment liquid exceeds 5.5, the effect of increasing the thickness of the oxide-based layer is small. It is considered that this is because the reaction rates of the equations (2) and (3) become extremely slow. Therefore, the pH of the post-treatment solution should be adjusted within the range of 3-5.5.

Further, the post-processing required time t (sec) for forming the oxide-based layer on the surface layer of the Fe-Ni-Zn-based coating to have a thickness of 4 nm or more was examined. as a result,
It has been found that the required time t strongly depends on the temperature T (° C.) of the post-treatment liquid, and that the required time t is greatly reduced as the temperature T increases. The post-processing required time t (sec) for setting the thickness of the oxide-based layer on the surface layer of the Fe-Ni-Zn-based coating to 4 nm or more can be represented by t ≧ 50 / T. If t is less than 50 / T, the thickness of the oxide-based layer will be less than 4 nm, and the effect of improving press formability will be insufficient. However, the upper limit of the post-processing time should be 10 sec or less from the viewpoint of productivity. Therefore, the post-processing required time t (sec) should be within the range of 50 / T to 10 sec.

The temperature of the post-treatment liquid is not particularly limited, but a higher temperature is advantageous from the viewpoint that the processing time can be shortened. As a method of the post-treatment, a spray treatment, a dipping treatment, or the like can be employed. In the immersion treatment, a fluid may be given to the post-treatment liquid.

The component composition of the post-treatment liquid is not particularly limited, and an aqueous solution of various acids, an aqueous solution obtained by diluting an electrolytic solution with water, or the like can be used. In the present invention, the zinc-based plated steel sheet used for forming the Fe—Ni—Zn-based coating on the surface includes a zinc-based plated layer formed on the surface of the steel sheet by a hot-dip plating method, an electroplating method, a vapor-phase plating method, or the like. Any steel plate may be used as long as it is formed. The components of this zinc-based plating layer include pure Zn, Fe, Ni, Co, Mn, C
r, Al, Mo, Ti, Si, W, Sn, Pb, Nb, Ta and other metals (however, Si is also treated as a metal) or oxides, or a single phase containing one or more organic substances Or it consists of multiple plating layers. Further, the plating layer may contain fine particles such as SiO ₂ and Al ₂ O ₃ . Further, as the zinc-based plated steel sheet, a multi-layer plated steel sheet and a functionally graded plated steel sheet in which the composition of the plating layer is changed can be used.

[0039]

Next, the present invention will be described in more detail with reference to examples. As the zinc-coated steel sheet before forming a film by electrolytic treatment according to the method of the present invention and the comparative method, the following GA,
One of the GI and EG formed with any plating type was used.

GA: alloyed hot-dip galvanized steel sheet (10 wt.%
Fe, balance Zn), and the amount of adhesion is 60 g / m ² on both sides. GI: Hot-dip galvanized steel sheet, adhesion amount is 90 on both sides
g / m ² .

EG: Electrogalvanized steel sheet with an adhesion amount of 40 g / m ² on both sides. Fe ²⁺ ion,
Cathodic electrolytic treatment was performed in an electrolytic solution consisting of an acidic sulfate aqueous solution containing Ni ²⁺ ions and Zn ²⁺ ions. In addition, boric acid was added to the electrolytic solution as a pH buffer. As the electrolytic treatment conditions, the (Fe ²⁺ + Ni ²⁺ ) concentration in the electrolytic solution, the Fe ²⁺
The concentration, Zn ²⁺ concentration, pH and temperature, current density and other conditions were appropriately changed. Then, post-processing was performed.
As the post-treatment conditions, the post-treatment solution was prepared by appropriately diluting the above-mentioned electrolyte solution with water, an aqueous solution of sulfuric acid or an aqueous solution of hydrochloric acid, and the pH and the like were appropriately changed, and the post-treatment time and other conditions were appropriately changed. Thus, an Fe—Ni—Zn-based coating was formed on the surface of the zinc-based plated steel sheet.

Tables 1 to 5 show Fe-Ni for Examples 1 to 25, which are methods within the scope of the present invention, and Comparative Examples 1 to 28, which are methods that deviate at least one condition within the scope of the present invention.
-Details of the conditions for forming the Zn-based film will be described.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

[0047]

[Table 5]

According to the above various manufacturing conditions, Fe-Ni
-Specimens were collected from each of the zinc-based plated steel sheets on which the Zn-based coating was formed. Specimens were also collected from those that were not subjected to the electrolytic treatment and post-treatment, or those that were not subjected to only post-treatment. Next, for the collected specimens, an analysis test on the Fe-Ni-Zn-based film, and press-forming properties, spot weldability, and adhesion of the zinc-based plated steel sheet having the Fe-Ni-Zn-based film formed thereon A characteristic evaluation test was performed. The analytical test method and the characteristic evaluation test method are as follows.

(1) Analysis test “The total value of the Fe content and the Ni content in the film (mg /
m ² ), Fe / (Fe + Ni) ratio (content (mg / m ² ) ratio) in the film, and Zn / (Fe +
Ni) ratio (content (mg / m ² ) ratio) ”Since the lower plating layer contains Fe and Zn among the component elements of the Fe—Ni—Zn-based coating, the upper Fe— It is difficult to completely separate the component elements in the Ni—Zn-based coating from the component elements in the lower plating layer. Therefore, only the element Ni not included in the lower plating layer was quantitatively analyzed by the ICP method. Further, after the Ar ion sputtering, the measurement of each component element in the Fe—Ni—Zn-based film by the XPS method is repeated from the surface, so that F
The composition distribution of each component element in the depth direction was measured perpendicular to the surface of the e-Ni-Zn-based coating. In this measurement method, Fe-Ni not contained in the lower plating layer is used.
-The average depth of the depth at which the element Ni of the Zn-based coating is at the maximum concentration and the depth at which the element is no longer detected is Fe-
The thickness of the Ni—Zn-based film was set. Then, based on the results of the ICP method and the XPS method, the amount and composition of the Fe—Ni—Zn-based coating were calculated. Next, the total value of the Fe content (mg / m ² ) and the Ni content (mg / m ² ) in the coating, and the content of Fe / (Fe + Ni) in the coating (mg / m ² )
² ) The ratio and the Zn / (Fe + Ni) content (mg / m ² ) ratio in the coating were calculated.

"Thickness of oxide-based layer on surface layer of film" By combining Ar ion sputtering and X-ray photoelectron spectroscopy (XPS) or Auger electron spectroscopy (AES), Fe
-The thickness of the oxide-based layer on the surface layer of the Ni-Zn-based coating was measured. After Ar ion sputtering to a predetermined depth on the surface of the specimen, each element in the coating was measured by XPS or AES, and this was repeated. In this measurement method,
At a certain depth, the amount of oxygen due to oxide or hydroxide reaches a maximum concentration and then decreases and becomes constant. The depth at which the oxygen concentration was よ り of the sum of the maximum concentration and the constant concentration at a position deeper than the maximum concentration was defined as the thickness of the oxide-based layer. Note that SiO ₂ was used as a standard sample for the sputtering rate. The sputter rate was 4.5 nm / min.

(2) Property evaluation test "Friction coefficient measurement test" In order to evaluate press formability,
The friction coefficient of each specimen was measured by the following device as follows.

FIG. 1 is a schematic front view showing a friction coefficient measuring device. As shown in the figure, a sample 1 for measuring a coefficient of friction collected from a specimen is fixed to a sample table 2, and the sample table 2 is
It is fixed to the upper surface of the horizontally movable slide table 3. On the lower surface of the slide table 3, a vertically movable slide table support 5 having rollers 4 in contact therewith
The first load cell 7 for measuring the pressing load N of the bead 6 against the friction coefficient measurement sample 1 by being pushed up is attached to the slide table support 5. With the pressing force applied, a second load cell 8 for measuring a sliding resistance force F for moving the slide table 3 in the horizontal direction is provided at one end of the slide table 3 in the horizontal movement direction. Is attached to one end of the slide table 3. As a lubricating oil, Noxlast 5 manufactured by Nippon Parkerizing Co., Ltd. was used.
The test was performed by applying 50HN to the surface of the sample 1.

The friction coefficient μ between the specimen and the bead is
Formula: Calculated by μ = F / N. However, pressing load N: 400
kgf, sample withdrawal speed (horizontal movement speed of slide table 3): 100 cm / min.

FIG. 2 is a schematic perspective view showing the shapes and dimensions of the beads used. The bead 6 slides while being pressed against the surface of the sample 1. The underside shape is width 1
It has a flat surface of 0 mm and a length of 3 mm in the sliding direction, and each line having a width of 10 mm on its front and rear surfaces is in contact with a quarter of the cylindrical surface having 4.5 mmR as shown in FIG.

[Continuous spotting test] In order to evaluate the spot weldability, a continuous spotting test was performed for each specimen. Two identical specimens were stacked, sandwiched between a pair of electrode tips from both sides, and resistance welding (spot welding) in which current was concentrated by applying pressure was performed continuously under the following conditions.

Electrode tip: Dome type with a tip diameter of 6 mm. Pressure: 250 kgf. Welding time: 0.2 sec. Welding current: 11.0 kA. Welding speed: 1 point / sec. During welding, the diameter of the melt-solidified metal part (nugget) generated at the joint of two superposed welding base materials (specimens) is less than 4 × t ^1/2 (t: one sheet thickness, mm) The number of hit points that were hit continuously until the value was reached was used. The number of hit points is hereinafter referred to as electrode life.

[Adhesion Test] The following test specimens for adhesion test were prepared from the respective test specimens. FIG. 3 is a schematic perspective view illustrating the assembling process. As shown in FIG.
m, two test pieces 10 having a length of 200 mm are overlapped and bonded via a 0.15 mm spacer 11 so that the thickness of the adhesive 12 becomes 0.15 mm,
An adhesive test specimen 13 was prepared, and 150 ° C. × 10 min. Baking. The test specimen thus prepared was bent into a T-shape as shown in FIG. 4 and subjected to 200 mm / min. , And the average peel strength (n = 3 times) when the test piece was peeled was measured. The peel strength was determined by calculating an average load from a load chart of a tensile load curve at the time of peeling, and expressed in units of kgf / 25 mm. In FIG. 4, P indicates a tensile load. The adhesive used was a PVC-based hemming adhesive.

The results of the above analysis test and characteristic evaluation test were
The results are shown in Tables 6 to 10.

[0059]

[Table 6]

[0060]

[Table 7]

[0061]

[Table 8]

[0062]

[Table 9]

[0063]

[Table 10]

From the conditions for forming the Fe—Ni—Zn-based coatings in Tables 1 to 5 and the test results in Tables 6 to 10, the following matters are clear. (1) When the Fe—Ni—Zn-based coating was not formed (Comparative Examples 1, 25, and 27), the scope of the present invention was irrespective of the plating type of the galvanized steel sheet, GA, GI, and EG. As compared with the case where the Fe—Ni—Zn-based film in the above was formed, the press formability, spot weldability and adhesiveness were all inferior.

(2) When the Fe ²⁺ ion concentration in the electrolytic solution is lower than the range of the present invention (Comparative Examples 2 and 3),
The content ratio of Fe / (Fe + Ni) in the Ni—Zn-based coating is small, and the adhesion is inferior to the case where the ion concentration is in the range of the present invention.

(3) When the Fe ²⁺ ion concentration in the electrolytic solution is higher than the range of the present invention (Comparative Example 11),
The content ratio of Fe / (Fe + Ni) in the Ni—Zn-based coating is too large, and the effect of improving spot weldability is insufficient.

(4) When the Zn ²⁺ ion concentration in the electrolytic solution is higher than the range of the present invention (Comparative Example 12),
The content ratio of Zn / (Fe + Ni) in the Ni—Zn-based coating is too large, and the effect of improving press formability and spot weldability is insufficient.

(5) When the Fe—Ni—Zn-based film was formed by the electrolytic treatment, but the post-treatment was not performed (Comparative Examples 4 to 8, 26 and 28), the Fe—Ni—Zn-based film was formed. The thickness of the oxide-based layer in the surface layer portion of the film is as thin as 1.0 nm or less, and the press formability is slightly inferior to the case where both the electrolytic treatment and the post-treatment within the scope of the present invention are performed.

(6) When the current density of electrolysis is smaller than the range of the present invention (Comparative Example 9), the content of Fe + Ni in the Fe—Ni—Zn-based coating is small, and the current density is within the range of the present invention. The press formability, the spot weldability and the adhesiveness were inferior to those in the above. On the other hand, when the current density of electrolysis is higher than the range of the present invention (Comparative Example 10)
Is caused by plating burn, the adhesion of the Fe-Ni-Zn-based coating is reduced, and the press-forming property, the spot welding property and the adhesion are inferior to those in the case where the current density is within the range of the present invention. I have.

(7) When the concentration of Fe ²⁺ ion + Ni ²⁺ ion in the electrolytic solution is lower than the range of the present invention (Comparative Example 1)
In the case of 3), plating burning occurs, the adhesion of the Fe-Ni-Zn-based coating is reduced, and the press formability, spot weldability, and adhesion are inferior to the case where the ion concentration is within the range of the present invention. ing.

(8) When the pH of the electrolytic solution is lower than the range of the present invention (Comparative Example 15), the content of Fe + Ni in the Fe—Ni—Zn-based coating is small, and the pH is within the range of the present invention. The press formability, the spot weldability and the adhesiveness were inferior to the case of the above.

(9) When the temperature of the electrolytic solution is lower than the range of the present invention (Comparative Example 15), burning of the plating occurs and F
The adhesiveness of the e-Ni-Zn-based coating is reduced, and the press formability, spot weldability, and adhesiveness are inferior to the case where the temperature is within the range of the present invention.

(10) When the pH of the post-treatment liquid is lower than the range of the present invention (Comparative Examples 16 and 17), Fe-
The thickness of the oxide-based layer on the surface layer of the Ni-Zn-based coating is small, and the press formability is slightly inferior to the case where the pH is within the range of the present invention. On the other hand, the pH of the post-treatment solution is
Cases larger than the range of the present invention (Comparative Examples 21 and 2)
2) also in the case where the thickness of the oxide-based layer on the surface layer of the Fe-Ni-Zn-based coating is small and the pH is within the range of the present invention (Example 1).
5 and 16), the press formability is slightly inferior.

(11) When the post-processing time is shorter than the range of the present invention (Comparative Examples 18, 19, 20, 22, 23)
Indicates that the thickness of the oxide-based layer on the surface layer of the Fe-Ni-Zn-based coating is small, and the time is within the range of the present invention.
Slightly inferior in press formability.

(12) In all of Examples 1 to 25 which were treated under the electrolytic treatment conditions and the post-treatment conditions within the scope of the present invention, the Fe + Ni content in the formed Fe—Ni—Zn-based film, Fe / ( Fe + Ni) content ratio, Zn / (Fe
+ Ni) content ratio, and the thickness of the oxide-based layer in the surface layer portion are within an appropriate range for improving the press formability, spot weldability, and adhesion, and there is no plating burn.
Efficient production was possible. And, the Fe-Ni
All of the zinc-based plated steel sheets having a Zn-based film formed on the surface have remarkably improved press formability and excellent spot weldability and adhesiveness.

[0076]

As described above, according to the present invention, the Fe-Ni-Zn coating formed on the surface of the galvanized steel sheet is harder than the zinc plating layer, and the surface layer of the coating. Since the oxide-based layer present at a high temperature has a high melting point, the sliding resistance between the plating layer surface and the press mold during press molding is reduced. In addition, since the Fe—Ni—Zn-based coating has a high melting point and a high electric conductivity, it has an effect of improving continuous hitting property in spot weldability. Furthermore, Fe-
The presence of Fe in the Ni—Zn-based coating has the effect of improving the adhesiveness. As described above, according to the present invention, it is possible to provide a method for producing a zinc-based plated steel sheet having excellent press formability, spot weldability, and adhesiveness, and an industrially useful effect is provided.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing a friction coefficient measuring device.

FIG. 2 is a schematic perspective view showing the shape and dimensions of a bead in FIG.

FIG. 3 is a schematic perspective view illustrating an assembling process of an adhesive test specimen.

FIG. 4 is a schematic perspective view illustrating a load of a tensile load when a peel strength is measured in an adhesion test.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Sample for friction coefficient measurement 2 Sample table 3 Slide table 4 Roller 5 Slide table support 6 Bead 7 First load cell 8 Second load cell 9 Rail 10 Specimen 11 Spacer 12 Adhesive 13 Specimen for adhesion test N Pressing load F Sliding Dynamic resistance P Tensile load

Continued on the front page (72) Inventor Shuji Nomura 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Yoshitaka Sakurai 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Junichi Inagaki 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Masaru Sagiyama 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-9-263970 (JP, A) JP-A-9-143792 (JP, A) JP-A-9-143661 (JP, A) JP-A-9-143660 (JP, A) JP-A-10 −317187 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 2/00-2/40 C25D 5/26

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein the Fe ²⁺ ion, the Ni ²⁺ ion and the Zn ²⁺
Containing ions, the total concentration of Fe ²⁺ ions and Ni ²⁺ ions is 0.3 to 2.0 mol / l, the concentration of Fe ²⁺ ions is 0.02 to 1.0 mol / l, and the concentration of Zn ²⁺ ions Is more than 0 to 0.5 mol / l, the pH is in the range of 1 to 3, and the temperature is in the range of 30 to 70 ° C. The treated steel sheet was used as a cathode, an electrolytic treatment was performed at a current density of 10 to 150 A / dm ² , and a pH of 3 to 5.5 was obtained in the next step.
With the post-treatment liquid within the range, the processing time t (sec) is
The following formula (1): 50 / T ≦ t ≦ 10 (1) where T: Satisfies the temperature (° C.) of the post-treatment liquid And a method of manufacturing a galvanized steel sheet, which comprises performing a post-treatment.