JP3191646B2 - Manufacturing method of galvanized steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a galvanized steel sheet, and more particularly to a method for producing a galvanized steel sheet having excellent press formability, 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 drawback that press formability is inferior to cold-rolled steel sheets. This is because the sliding resistance between the galvanized steel sheet and the press die is greater than that of the cold-rolled steel sheet. The galvanized steel sheet hardly flows into the press die, and the steel sheet is easily broken.

[0004] As a method for improving the press formability of a zinc-based plated steel sheet, a method of applying a high-viscosity lubricating oil is generally widely used. However, in this method, since the lubricating oil has a high viscosity, there is a problem that a coating defect occurs due to poor degreasing in the next coating process, and there is a problem that press performance becomes unstable due to lack of oil, etc. There is a high demand for improved press formability of galvanized steel sheets.

On the other hand, in a zinc-based plated steel sheet, copper, which is an electrode, and molten zinc easily react during spot welding to form a brittle alloy layer. Therefore, the copper electrode is severely worn and its life is short. There is a problem that continuous hitting properties are inferior to cold-rolled steel sheets.

Further, in the manufacturing process of an automobile body,
Various adhesives are used for the purpose of rust prevention and vibration damping, etc., but it has recently become clear that galvanized steel sheets are inferior in adhesiveness to cold rolled steel sheets.

As a method for solving the above problem, Japanese Patent Laid-Open No.
JP-A-3-60332 and JP-A-2-190483 disclose electrolytic treatment, immersion treatment, coating oxidation treatment, or heat treatment on the surface of a galvanized steel sheet.
A technique for generating an oxide film mainly composed of ZnO to improve weldability or workability (hereinafter, referred to as “prior art 1”) is disclosed.

JP-A-4-88196 discloses that a galvanized steel sheet is immersed in an aqueous solution containing 5 to 60 g / l of sodium phosphate and having a pH of 2 to 6 on the surface of the galvanized steel sheet.
Electrolytic treatment and spraying of the above aqueous solution provide P
A technique for forming an oxide film mainly composed of an oxide to improve press formability and chemical conversion treatment (hereinafter referred to as “prior art 2”) is disclosed.

Japanese Patent Application Laid-Open No. Hei 3-190933 discloses a technique (hereinafter referred to as "prior art 3") for producing a Ni oxide to improve press formability and chemical conversion treatment (hereinafter referred to as "prior art 3"). Japanese Patent No. 67885 discloses a technique of improving the corrosion resistance by generating metals such as Ni and Fe by, for example, but not limited to, electroplating or chemical plating on the surface of a zinc-based plated steel sheet (hereinafter referred to as “prior art 4”). ).

[0010]

The prior art 1 described above has the following problems. That is, prior art 1
In this method, an oxide mainly composed of ZnO is generated on the surface of the plating layer by various treatments. Therefore, the effect of reducing the sliding resistance between the press die and the plated steel sheet is small, and the effect of improving the press formability is reduced. Is small. Further, an oxide mainly composed of ZnO deteriorates 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 therefore has a large effect of improving press formability and chemical conversion treatment. There is a problem that the adhesiveness is deteriorated. Here, the spot weldability refers to the continuous spotting property in spot welding of a thin steel sheet, and generally, the continuous spotting property is the number of times that spot welding can be performed continuously without care or replacement of the electrode tip for welding. And consistent with the electrode life that can be used continuously (the same in this application).

Prior Art 3 is a single-phase Ni oxide film, so that press formability is improved, but there is a problem that adhesiveness is deteriorated.

Prior Art 4 is a method of producing only a metal such as Ni, so that the corrosion resistance is improved. However, since the metallic properties of the film are strong, the effects of improving press formability and spot weldability are not sufficient. Furthermore, there is a problem that sufficient adhesion cannot be obtained because the wettability of the metal to the adhesive is small.

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 inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that an appropriate Fe-Ni-O-based film is formed on the surface of the plating layer of a zinc-based plated steel sheet. It has been found that press forming, spot weldability, and adhesion can be significantly improved by forming.

Here, an appropriate Fe—Ni—O-based coating is as follows: The amount of the coating is 10% in terms of the total amount of metal in the coating.
１1500 mg / m ² , and the sum of the Fe content and the Ni content (wt.
%) To the ratio of the Fe content (wt.%)
Also called "Fe ratio in film", "Fe / (Fe + N
i) ") is in the range of 0.05 to 0.9, preferably in the range of 0.1 to 0.5, and the oxygen content of this coating is 0.5 to 10 wt. % Was found to be satisfied.

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, under high surface pressure, the low melting point zinc and the mold cause an adhesion phenomenon, so that the sliding resistance is low. It is because it increases. In order to prevent this, it is effective to form a harder and higher melting point coating than the zinc or zinc alloy plating layer on the surface of the plating layer of the zinc-based plated steel sheet. The sliding resistance between the mold and the mold is reduced, and the zinc-plated steel sheet easily slides into the press mold, and the press formability is improved.

The reason why the continuous spotting property in spot welding of a zinc-based plated steel sheet is inferior to that of a cold-rolled steel sheet is that the molten zinc at the time of welding comes into contact with the copper of the electrode to form a brittle alloy layer. In addition, the deterioration of the electrodes becomes severe. Therefore, as a method of improving the continuous hitting property of a zinc-based plated steel sheet, it is effective to form a high-melting film on the plating surface. The present inventors have studied various coatings in order to improve the spot weldability of galvanized steel sheets, and have found that Ni metal is particularly effective. Although the details of this reason are not clear, it is considered that the reason is that Ni metal has a high melting point and high electric conductivity.

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. The present inventors have investigated the cause and found that the adhesiveness is controlled by the composition of the oxide film on the surface of the steel sheet. That is, in the case of a cold-rolled steel sheet, the oxide film on the surface of the steel sheet is mainly composed of Fe oxide, whereas in the case of a zinc-based plated steel sheet, the oxide film is mainly composed of Zn oxide. The adhesiveness differs depending on the composition of the oxide film.
Adhesion was inferior to oxide. Therefore, by forming a film containing Fe oxide on the surface of a galvanized steel sheet as in the present invention, it has become possible to improve the adhesiveness.

As described above, the oxygen content of the Fe—Ni—O-based coating is 0.5 to 10 wt. % Is essential. The following knowledge for realizing this condition was also obtained. It is considered that the main component of oxygen in the Fe—Ni—O-based coating is oxygen of the eutectoid iron oxide. By increasing the deposition rate of the film, it is necessary to create a state in which diffusion of metal ions cannot be made in time, that is, a so-called plating burn state. That is, it is essential to perform electrolysis at a current density exceeding a limit current determined by the composition of the electrolytic plating bath and the electrolysis conditions.

The present invention has been made on the basis of the above-described findings, and by appropriately forming an Fe—Ni—O-based coating on the surface of a plating layer of a zinc-based plated steel sheet, the press formability, This is a method for producing a galvanized steel sheet having excellent spot weldability and adhesiveness, as described below. Here, the microstructure and morphology of the Fe—Ni—O-based coating are at least metals of Ni and Fe,
Also, any film may be used as long as it is a film made of a mixture containing oxides of Ni and Fe, and the bonding state of the elements constituting the film is not limited.

The method for producing a zinc-based plated steel sheet according to the first aspect of the present invention is characterized in that a zinc-based plated steel sheet is used as a cathode in a plating solution composed of an aqueous solution containing nickel sulfate and ferrous sulfate to perform electrolysis. When forming a film on the surface of the plating layer of the plated steel sheet, the total concentration of nickel sulfate and ferrous sulfate in the plating solution is 0.1 to 2.0 mol / mol.
l, desirably in the range of 0.1-0.5 mol / l, pH in the range of 1.0-3.0,
Moreover, the sum of the nickel ion concentration and the ferrous ion concentration in the plating solution: M (mol / l), the average plating solution flow rate of the plating solution: U (m / s), and the current density in electrolysis:
Between I _K (A / dm ² ) and the following equation (1): I _K / (U ^1/2 M) = 50-150 ----- By performing electrolysis under the conditions that satisfy the relationship (1), F
It is characterized by forming an e-Ni-O-based film.

The method for producing a galvanized steel sheet according to the second aspect of the present invention is the method for producing a galvanized steel sheet according to the first aspect,
The plating layer on the surface of galvanized steel sheet is 7-15 wt.%
Characterized in that it is an alloyed hot-dip galvanized layer containing iron in the range of

According to a third aspect of the present invention, there is provided a method for manufacturing a galvanized steel sheet, comprising the steps of:
It is characterized in that the plating layer on the surface of the galvanized steel sheet is an electrogalvanized layer or a hot-dip galvanized layer.

In this application, in the present invention and in connection therewith, the term “coating” is used to refer to an Fe—Ni—O-based coating as an upper layer formed on the surface of a plating layer of a zinc-based plated steel sheet. On the other hand, when referring to zinc or a zinc-based plating layer as a lower layer, it is referred to as “plating layer”, and the two are distinguished.

[0026]

Next, the reason for limiting the manufacturing conditions of the present invention as described above will be described. In the present invention, Fe-Ni-
Nickel sulfate and ferrous sulfate are used as components of a plating solution used to form an O-based film because of the use of Fe
-By electrolyzing a zinc-based plated steel sheet on which a Ni-O-based film is to be formed as a cathode, Fe, N
This is because it is suitable for containing i and O to form a film.

The total concentration of nickel sulfate and ferrous sulfate is set to 0.1 to 2.0 mol / l, preferably 0.1 to 2.0 mol / l.
The reason for setting the concentration to 1 to 0.5 mol / l is as follows. If the total concentration is less than 0.1 mol / l, the conductivity of the plating bath is low, so that the electrolysis voltage becomes high, and a rectifier of higher voltage is required, which is not suitable. On the other hand, when the total concentration exceeds 2.0 mol / l, when the temperature is low, the solubility limit of nickel sulfate and / or ferrous sulfate is reached, and the concentration of nickel sulfate and / or ferrous sulfate is reduced. This produces a precipitate. Further, since the limit current density becomes large, plating burning cannot occur unless electrolysis is performed at an extremely high current density. In such a case, the electrolysis time for obtaining the optimal amount of the Fe—Ni—O-based film deposited is extremely short, less than 1 second, and it is difficult to control this. From this viewpoint, the total concentration is set to 2.0 mo
1 / l or less, preferably 0.5 mol
/ L or less.

The electrolytic solution contains Z contained in the plating layer of the zinc-based plated steel sheet used in the present invention.
n, Co, Mn, Mo, Al, Ti, Sn, W, Si,
It may contain cations such as Pb, Nb and Ta, hydroxides and oxides, and anions other than chlorine, fluorine, bromine and iodine ions which do not affect the electrolytic reaction.

Next, the reason why the electrolytic solution having a pH of the plating solution in the range of 1.0 to 3.0 is used is as follows.
If the pH of the electrolytic solution is less than 1.0, the generation of hydrogen during electrolysis is the main component of the cathode reaction, and the current efficiency is greatly reduced.
On the other hand, when the pH of the electrolytic solution exceeds 3, a hydroxide of ferric iron precipitates.

Although the temperature of the plating bath is not particularly limited, if the temperature is less than 30 ° C., the conductivity of the plating bath becomes low, so that the electrolysis voltage becomes high and the Fe—Ni—O—
The oxygen content of the system coating tends to increase. On the other hand, if this temperature exceeds 70 ° C., the amount of evaporation of the electrolytic solution increases, making it difficult to control the nickel and iron ion concentrations. Therefore, the temperature of the plating bath is desirably in the range of 30 to 70 ° C.

Next, in general, the limit current density I _Kd for the component metal, which is the limit at which plating burn does not occur, is expressed by the following equation (2), and the diffusion coefficient D of the deposited metal ion in the bath, and It is proportional to the precipitated metal ion concentration M and inversely proportional to the thickness δ of the diffusion layer formed on the steel sheet surface. I _Kd = nFD (M / δ) ------------------------- (2) where n is the charge number of the metal ion and F is Faraday constant,
D: diffusion coefficient of metal ions, M: concentration of precipitated metal ions in the bath. In contrast, the present inventor has critical current and density I _Kd, deposited metal ion concentration M, the relationship between the average plating solution flow velocity U and the bath temperature result of extensive investigations, the limiting current density I _Kd
Has been found to be proportional to the square root of the deposited metal ion concentration M and the average plating solution flow rate U. That is, the following (3)
Formula: I _Kd = k (U ^1/2 M) --------------------------------- (3) I _Kd : Limit current density (A / dm ² ) U: average plating solution flow rate (m / s) M: total concentration of all metal ions in the plating solution (mol /
l) k: It was found that there was a relationship of: By transforming the equation (3), the following equation (4) is obtained: I _Kd / (U ^1/2 M) = k ---------------------- ( 4) is obtained.

The inventor of the present application has further studied and found that Fe
-The oxygen content of the Ni-O-based film is 0.5 wt. %, The value of the constant k needs to be 50 or more, and the oxygen content is 10 wt. It has been found that it is necessary to make the value of the constant k 150 or less in order to make it equal to or less than%. Therefore, the oxygen content of the Fe—Ni—O-based coating is set to 0.5 to 10 wt. %, The total concentration of all metal ions in the plating solution: M
(Mol / l), average plating solution flow rate: U (m / s), and current density during electrolytic plating: I _K (A / dm ² )
However, the following equation (1) should be satisfied: I _K / (U ^1/2 M) = 50 to 150 (1) Here, the average plating solution flow rate refers to an average value of the plating solution flow rate at an intermediate point between the anode and the cathode. In the present invention, most of the deposited metal ions in the plating bath are nickel ions and ferrous ions, and other metal ions except for the ferric ions are Fe-Ni-O-based coatings. Has little effect on precipitation. Since the ferric ion lowers the deposition efficiency of the Fe—Ni—O-based coating and deteriorates the galvanized steel sheet, it is preferable that the ferric ion be 0.09 mol / l or less.

In the present invention, the surface is made of Fe--Ni--O
The galvanized steel sheet used for forming the system coating includes a galvanized layer having an iron content of 7 to 15 wt.%, An electrogalvanized layer, And a hot-dip galvanized layer. The reason is that galvanized steel sheets having these plating layers are more workable than press-rolled steel sheets and zinc-nickel alloy-plated steel sheets, in particular press formability, and
This is because forming the Fe—Ni—O-based coating according to the present invention on the surface of the plating layer greatly improves the press formability and spot weldability, since the weldability is poor.

It should be noted that the Fe-
The zinc-plated steel sheet before the Ni—O-based film is formed is a steel sheet having a zinc-based plating 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. The composition of the zinc-based plating layer is pure zinc, Fe, N
i, Co, Mn, Cr, Al, Mo, Ti, Si, W,
It is made of a metal (such as Sn, Pb, Nb and Ta) (however, Si is also treated as a metal) or an oxide, or a single or multiple plating layer containing one or more organic substances. Further, SiO ₂ and Al ₂ O are formed on the plating layer.
Fine particles such as ₃ may be contained. Further, as the zinc-based plated steel sheet, a multi-layer plated steel sheet having a different composition of a plating layer and a functionally graded plated steel sheet can be used.

The Fe—Ni—O coating formed on the surface of the plating layer of the zinc-coated steel sheet under the above-described conditions eliminates the adhesion phenomenon between the steel sheet and the mold during press forming, and reduces the sliding resistance. It becomes smaller, the sliding into the mold becomes better, the formation of a brittle alloy layer between the electrode copper and the electrode during spot welding is suppressed, and the continuous hitting property is improved.
The effect of improving the adhesiveness by the action of the film containing e-oxide is exhibited.

The Fe—Ni—O-based film formed on the surface of the plating layer of the zinc-based plated steel sheet under the above-described limited conditions eliminates the adhesion phenomenon between the steel sheet and the mold during press forming, and reduces the sliding resistance. It becomes smaller, the sliding into the mold becomes better, the formation of a brittle alloy layer between the electrode copper and the electrode during spot welding is suppressed, and the continuous hitting property is improved.
The effect of improving the adhesiveness by the action of the film containing e-oxide is exhibited. However, Fe-N
If the attached amount of the i-O-based film is less than 10 mg / m ² , the effect of improving press formability cannot be obtained, while 1500 mg / m ^2.
If it exceeds m ² , the effect of improving press formability is saturated.
Therefore, the adhesion amount of the Fe—Ni—O-based coating is 10 to 15
It is desirable to be within the range of 00 mg / m ² .

Fe content in Fe—Ni—O-based coating and N
i content (w.%) and the Fe content (w
t. %) (Fe / (Fe + Ni) in the film)
If it is less than 0.05, the effect of improving the adhesiveness is not exhibited.
On the other hand, if Fe / (Fe + Ni) in the coating exceeds 0.9, the Ni content in the coating decreases, so that
The ratio of the high melting point Zn—Ni alloy formed during welding is reduced, and as a result, the electrode is greatly deteriorated, and the effect of improving spot weldability is not exhibited. Therefore, it is desirable that Fe / (Fe + Ni) in the coating be in the range of 0.05 to 0.9, particularly in the range of 0.1 to 0.5.

The oxygen content in the Fe—Ni—O-based coating is
It is desirable to be within the range of 0.5 to 10 wt.%. When the oxygen content is less than 0.5 wt.%, The metallic properties of the film become strong, and the effect of improving press formability is reduced. On the other hand, when the oxygen content exceeds 10 wt.%, The amount of oxide is large. As a result, the electrical resistance of the surface is increased, the weldability is reduced, and the generation of phosphate crystals is suppressed, so that the chemical conversion property is deteriorated.

[0039]

Next, the present invention will be further described with reference to examples. As the galvanized steel sheet before the electrolytic treatment according to the method of the present invention and the comparative method, a galvanized steel sheet formed with any one of the following GA, GI and EG was used. GA: 10 wt. %, And the balance was Zn alloyed hot-dip galvanized layer, and the adhesion amount was 60 g / m ² on both sides. GI: A hot-dip galvanized layer was formed, and the adhesion amount was 90 g / m ² on both sides. EG: An electrogalvanized layer was formed, and the adhesion amount was 40 g / m ² on both sides.

Using the above-mentioned galvanized steel sheet as a cathode, an electrolytic treatment is carried out in a mixed solution of nickel sulfate and ferrous sulfate at a predetermined concentration, and the surface of the galvanized steel sheet is Fe-Ni
An -O-based film was formed. However, some were only immersed in the electrolytic solution and were not subjected to electrolytic treatment. Tables 1 and 2
In Examples 1 to 1 subjected to electrolytic treatment under the conditions within the scope of the present invention
30 and the electrolysis conditions of Comparative Examples 2 to 12, 14, 15, 17 and 18 in which at least one condition was out of the scope of the present invention, and Comparative Examples 1 and 13 in which electrolysis was not performed And 16 immersion conditions are also shown. The table shows the plating type of the steel sheet before electrolytic treatment, the component composition of the electrolytic solution, pH, temperature, and plating conditions. As can be seen from Tables 1 and 2, both Examples and Comparative Examples
The component composition and the pH value of the electrolytic solution are within the range of the present invention, but all of the comparative examples are conditions of the present invention (1).
Formula: I _K / (U ^1/2 M) = 50-150 is not satisfied.

[0041]

[Table 1]

[0042]

[Table 2]

With respect to each specimen obtained in the above Examples and Comparative Examples, the amount of Fe—Ni—O based coating (in terms of the total amount of metal in the coating), the Fe content (wt. Fe content (wt.%) With respect to the sum of the content (wt.%)
%) And the oxygen content (wt.%) Were measured as follows.

[Adhesion amount of film and Fe / F in film
Measurement of e + Ni] For the specimens of GI and EG plating types, the Fe—Ni—O-based film was dissolved and peeled with dilute hydrochloric acid together with the surface layer of the underlying plating layer (Zn-based plating layer, the same applies hereinafter), and the ICP The amount and composition of the Fe—Ni—O-based coating were measured by quantitative analysis of Fe and Ni according to the method. Then, Fe / F in the film
e + Ni was calculated. In the case of the GA specimen, since the lower plating layer contains the component element in the Fe—Ni—O-based film in the specimen of GA, the upper Fe—Ni—O—
It is difficult to completely separate the component elements in the system coating and the component elements in the lower plating layer. Therefore, only the component elements of the Fe—Ni—O-based film not contained in the lower plating layer were quantitatively analyzed by the ICP method. Further, after Ar ion sputtering, the composition distribution of each component element with respect to the depth of the plating layer was measured by repeating the measurement of each component element in the Fe-Ni-O-based coating from the coating surface by the XPS method. In this measurement method, the distance between the depth at which the component element of the Fe—Ni—O-based film not contained in the lower plating layer is the maximum concentration and the position at half the depth at which the element is no longer detected. Was the thickness of the Fe—Ni—O-based coating. Then, based on the results of the ICP method and the XPS method, the amount and composition of the Fe—Ni—O-based coating were calculated. Next, Fe / Fe + Ni in the film was calculated.

[Measurement of the Oxygen Content of the Film] The oxygen content of the film was determined from the results of the Auger electron spectroscopy (AES) analysis in the depth direction.

Tables 3 and 4 show the results of the above measurements for the test specimens of Examples 1 to 30 and Comparative Examples 1 to 18.

[0047]

[Table 3]

[0048]

[Table 4]

Next, in order to evaluate the press formability, spot weldability and adhesiveness of each of the above specimens, a friction coefficient measurement, a continuous spotting test in spot welding and an adhesiveness test were carried out by the following methods. The results are shown in Tables 3 and 4.

[Measurement of Coefficient of Friction] FIG. 1 is a schematic front view showing a friction coefficient measuring device. As shown in FIG. 1, 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 has a horizontally movable slide table 3.
It is fixed to the upper surface of. On the lower surface of the slide table 3, there is provided a vertically movable slide table support 5 having a roller 4 in contact with the slide table 3. By pushing up this, a sample for measuring a friction coefficient by a bead 6 is provided. A first load cell 7 for measuring a pressing load N on the first table 1 is mounted on the slide table support 5. With the pressing force applied, a second end for measuring the sliding resistance 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. A load cell 8 is attached to one end of the slide table 3.

The coefficient of friction 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. In addition, the following two types of beads were used for the size and shape, and press formability was evaluated under two conditions.

FIG. 2 is a schematic perspective view showing the shape and dimensions of a first type bead (hereinafter referred to as "bead type A") used. The lower surface of the bead 6 slides while being pressed against the surface of the sample 1. The underside shape is 10m wide
m, a flat surface having a length of 3 mm in the sliding direction, and each line having a width of 10 mm on the front and rear surfaces thereof has a length of 4.5 mmR and is 1/4 of a cylindrical surface.
The cylindrical surfaces are in contact as shown in FIG.

FIG. 3 is a schematic perspective view showing the shape and dimensions of a second type bead (hereinafter referred to as "bead type B") used. In the bead type B, the length of the sliding surface of the bead type A in the sliding direction is increased from 3 mm to 60 mm, and the other parts are the same as the bead type A.
In both cases of the bead type A and the bead type B, Knoxlast 550HN manufactured by Nippon Parkalidging Co., Ltd. was provided on the upper surface of the friction coefficient measurement sample 1 as a lubricating oil.
Was tested.

[Continuous Dotting Test] Two specimens having the same NO.
Resistance welding (spot welding) in which the sheets were stacked, sandwiched between a pair of electrode tips of a spot welding machine from both sides, and energized under pressure to concentrate the current was continuously performed under the following welding conditions. -Electrode tip: dome type with a tip diameter of 6 mm-Pressure: 250 kgf-Welding time: 12 cycles (60 Hz)-Welding current: 11.0 KA-Welding speed: 1 point / sec. As the evaluation of the continuous hitting property, the diameter of the molten and solidified metal part (shape: goishi, hereinafter referred to as a nugget) generated at the joint of two superposed welding base materials (specimens) during spot welding was 4 points. The number of continuous dots welded until the thickness became less than × t ^1/2 (t: sheet thickness of one sheet) 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. 4 is a schematic perspective view illustrating the assembling process. As shown in FIG.
A test specimen 13 in which two test specimens 10 having a length of 200 mm and a length of 200 mm were overlapped and bonded via a spacer 11 having a diameter of 0.15 mm so that the thickness of the adhesive 12 became 0.15 mm.
And baking at 150 ° C. × 10 min. The test specimen thus prepared was bent into a T-shape as shown in FIG.
A tensile test was performed at a speed of m / min, and an average peel strength (n = 3 times) when the test piece was peeled was measured. The peel strength is
The average load was determined from the load chart of the tensile load curve at the time of peeling, and was expressed in the unit: kgf / 25 mm. In FIG.
Indicates a tensile load. The adhesive used was a PVC-based hemming adhesive.

The following items are clear from the test results shown in Tables 3 and 4. Now, equation (1): I _K / (U ^1/2 M)
Let X be the left side of = 50-150. X = I _K / (U ^1/2 M) -------------------------------- (5) As described above In Comparative Examples, only the value of X is out of the range of the present invention, and Comparative Examples 2, 4, 6, 8, 10 to 1 in which the value of X is less than 50
In Examples 2, 14, and 17, the oxygen content in the Fe-Ni-O-based coating was less than 0.5 wt.%, But in Examples, the oxygen content was 0.5 to 10 wt.%. In range. These comparative examples are inferior in adhesiveness irrespective of the type of plating as compared to the examples, and inferior in press formability as compared with examples of the same plating type. In Comparative Examples 3, 5, 7, 9, 15, and 18 in which the value of X exceeded 150, the oxygen content in the Fe—Ni—O-based coating exceeded 10 wt.%. And these comparative examples are inferior to Examples of the same plating type in spot weldability. In Comparative Examples 1, 13 and 16 in which the Fe—Ni—O-based film was not formed only by immersion in the electrolytic solution, all of the press formability, spot weldability and adhesiveness were compared with those of the examples. Inferior regardless of plating type.

As can be seen from Tables 3 and 4, the press formability, spot weldability and adhesiveness of the galvanized steel sheet differed in the level of their characteristic values when the electrolytic treatment was not performed by the method of the present invention. There is. Therefore, the characteristic values of Comparative Examples 1, 13 and 16 not subjected to the electrolytic treatment according to the method of the present invention were changed to the plating types GA and
The reference values of the characteristic values in the case of EG and GI were used, and the ratios of the characteristic values in Examples and other comparative examples to the reference values were calculated and defined as improvement indexes of the respective characteristic values. Tables 5 and 6
Next, the index of improvement in press formability, spot weldability and adhesiveness in each of Examples and Comparative Examples is shown by plating type.

[0058]

[Table 5]

[0059]

[Table 6]

As can be seen from the results of Tables 5 and 6, when the press formability, spot weldability and adhesiveness were evaluated for each plating type, each characteristic value was improved in the examples as compared with the comparative example. .

[0061]

The present invention has been configured as described above.
Fe- formed on the surface of the plating layer of zinc-based plated steel sheet
Since the Ni—O-based film is harder and has a higher melting point than the zinc or alloyed galvanized layer, the proper amount of the Ni—O-based film slides between the plated layer surface and the press die during press molding. The dynamic resistance decreases, and the zinc-based plated steel sheet easily slides into the press die. In addition, the presence of the Fe—Ni—O-based high-melting film improves continuous spotting properties in spot welding. Further, Fe in the Fe—Ni—O-based coating
The presence of the oxide improves the peel strength of the adhesive plate. Therefore, according to the present invention, it is possible to provide a galvanized steel sheet having excellent press formability, spot weldability, and adhesiveness, which brings about an industrially useful effect.

[Brief description of the drawings]

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

FIG. 2 shows a first type of bead in FIG. 1 (bead type A).
It is a schematic perspective view which shows the shape and dimension of.

FIG. 3 shows a bead of the second type in FIG. 1 (bead type B).
It is a schematic perspective view which shows the shape and dimension of.

FIG. 4 is a schematic perspective view illustrating a process of assembling a test piece for an adhesion test.

FIG. 5 is a schematic perspective view illustrating a load of a tensile load at the time of measuring a peel strength in an adhesion test.

[Explanation of symbols]

 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 Ray 10 specimens, 11 spacers, 12 adhesives, 13 specimens for adhesion test, P tensile load, F sliding resistance, N pressing load.

Continued on the front page (72) Inventor Junichi Inagaki 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Masaaki Yamashita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-8-189577 (JP, A) JP-A-62-33795 (JP, A) JP-A-60-169587 (JP, A) JP-A-5-39588 (JP, A) JP-A-1-149990 (JP, A) JP-A-7-258886 (JP, A) JP-A-4-176878 (JP, A) JP-A-3-191093 (JP, A) (58) Int.Cl. ⁷ , DB name) C25D 3/56 C25D 5/26

Claims (3)

(57) [Claims] 1. A film is formed on a surface of a plating layer of a zinc-based plated steel sheet by performing electrolysis using a zinc-based plated steel sheet as a cathode in a plating solution comprising an aqueous solution containing nickel sulfate and ferrous sulfate. Wherein the total concentration of the nickel sulfate and the ferrous sulfate in the plating solution is 0.1 to 2.0.
mol / l, the pH is in the range of 1.0 to 3.0, and the sum of the nickel ion concentration and the ferrous ion concentration in the plating solution: M (mol / l) When,
Between the average plating solution flow rate of the plating solution: U (m / s) and the current density in the electrolysis: I _K (A / dm ² ), the following equation (1): I _K / (U ^{1 /} by performing the electrolysis in ² M) = ^50~150 --------------------- conditions relationship is satisfied in (1), Fe-Ni- O A method for producing a zinc-based plated steel sheet, comprising forming a zinc-based coating. 2. The method for producing a galvanized steel sheet according to claim 1, wherein the plating layer of the galvanized steel sheet is an alloyed hot-dip galvanized layer having an iron content of 7 to 15 wt.%. 3. The method according to claim 1, wherein the plating layer of the galvanized steel sheet is an electrogalvanized layer or a hot-dip galvanized layer.