JPH1025597A - Production of galvanized steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form electrolyzed coating small in sliding resistance to a press die, high in the m.p. and showing good adhesive properties and chemical convertibility on the surface of a galvanized steel sheet. SOLUTION: In the method of forming coating on the surface of a plating layer of a galvanized steel sheet by executing electrolysis with the galvanized steel sheet as the cathode in an aq. soln. contg. nitrogen sulfate, ferrous sulfate and zinc sulfate, the following conditions are satisfied: the electrolysis is executed under the conditions in which the total concn. of Ni<2+> , Fe<2+> and Zn<2+> ions is regulated to 0.1 to 2.0mol/l, the pH is regulated to 1.0 to 3.0, the relations among the total of the concns. of the Ni<2+> , Fe<2+> and Zn<2+> ions in the plating soln.: M(mol/l), the average flow rate of the plating soln.: U(m/s) and the current density: Ik (A/dm<2> ) satisfy Ik /(U<1/2> M)=50 to 150. Thus, Fe-Ni-Zn-O base coating is formed. Preferably, the plating layer of the galvanized steel sheet is composed of any of a galvannealing layer contg. 7 to 15wt.% Fe, an electrogalvanizing layer and a galvanizing layer.

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, adhesiveness, and chemical conversion treatment properties.

[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 a rust-proof steel sheet for automobiles, in addition to corrosion resistance and paint compatibility, the performance required in the vehicle body manufacturing process includes press formability, spot weldability, adhesiveness and chemical conversion. It is important that the processability is excellent.

[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. Accordingly, there is a strong demand for improving the press formability of a zinc-based plated steel sheet.

On the other hand, 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, so that the copper electrode is severely worn, its life is short, and cold-rolled. There is a problem that continuous hitting properties are inferior to steel sheets.

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

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.

Japanese Patent Application Laid-Open No. 3-249182 discloses that a surface of a zinc-based plated steel sheet is made of Mn oxide, phosphoric acid and other oxides.
A technique (hereinafter, referred to as "prior art 2") for improving press formability and chemical conversion property coated with a Mn-based oxide film 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”).

[0010] Japanese Patent Application Laid-Open No. Hei 3-72882 discloses a method in which one or more metals selected from the group consisting of Fe, Ni and Co are substituted and precipitated on the surface of a galvanized steel sheet.
Japanese Patent Application Laid-Open Publication No. H11-163,086 discloses a technique for improving the corrosion resistance by generating a metal such as Ni and Fe on the surface of a zinc-based plated steel sheet by, for example, electroplating or chemical plating (hereinafter referred to as “prior art 4”). I have.

Japanese Patent Publication No. 58-15554 discloses that a cationic electrodeposition coatability is improved by providing a continuous coating surface layer of Fe-Zn based on Zn 40 wt.% Or less or a surface layer containing a small amount of Ni or the like in this system. A technique to be improved (hereinafter, referred to as “prior art 5”) is disclosed.

Japanese Patent Application Laid-Open No. 61-207597 discloses a technique for improving workability by forming an electric Zn--Ni alloy plating layer containing Ni: 30 wt.% Or less as an upper layer of an alloyed galvanized steel sheet. Hereinafter, “Prior Art 6” is disclosed.

[0013]

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. There is a problem that the effect of the improvement is small, and that if the oxide mainly composed of ZnO is present on the plating surface, the adhesion is deteriorated.

Prior art 2 is a method of forming a Mn oxide and a P oxide on the surface of a galvanized steel sheet, so that the effect of improving the press formability and the chemical conversion treatment is great, but the spot weldability and the adhesiveness are improved. Has a problem that it deteriorates.

Prior Art 3 is a method of forming a single-phase Ni oxide film, so that the corrosion resistance is improved.
There is a problem that the adhesiveness is reduced. Prior art 4 uses N
Although this method involves forming only a metal such as i, the corrosion resistance is improved, but the effect of improving the press formability is not sufficient due to the strong metallic properties of the film. Furthermore, there is a problem that the wettability of the metal to the adhesive is low and sufficient adhesiveness cannot be obtained.

Prior art 5 or prior art 6 includes Fe,
Since it is a method of forming only metals such as Zn and Ni,
Due to the strong metallic properties of the film, the effect of improving press formability is not sufficient. Furthermore, there is a problem that the wettability of the metal to the adhesive is low and sufficient adhesiveness cannot be obtained.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a galvanized steel sheet excellent in press formability, spot weldability, adhesiveness and chemical conversion treatment.

[0018]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned problems, and as a result, it has been found that an appropriate Fe-Ni-O-based alloy It has been found that press formability, spot weldability, adhesiveness, and chemical conversion treatment properties can be improved by forming a film. According to Japanese Patent Application No. 6-257499, it is assumed that press formability is excellent, and Appropriately applied for a patent for a zinc-based plated steel sheet having excellent spot weldability, adhesion and chemical conversion treatment properties.

The inventors of the present invention have found that the zinc-coated steel sheet described above has a problem that the adhesion of the chemical conversion coating film is slightly inferior when the Fe—Ni—O coating film adhesion amount is large, and the chemical conversion treatment property is further improved. As a result of intensive studies to improve the quality of the steel, the appropriate Fe-Ni
-Press formability by forming a Zn-O-based film,
It has been found that spot weldability, adhesiveness and chemical conversion treatment can be improved.

Here, the proper Fe—Ni—Zn—O-based coating means the following (1) to (4): (1) Ni content is in the range of 10 to 1500 mg / m ² ,
(2) Zn content is in the range of 5 to 1500 mg / m ² ,
(3) Fe / (Fe + Ni) (weight ratio) in the coating is 0.05
(4) The oxygen content is in the range of 0.5 to 10
It was found that it was within the range of wt.%.

Conventional galvanized steel sheets are inferior in press formability to cold rolled steel sheets. This is because the sliding resistance between the zinc-plated steel sheet and the press die is large. The reason for this is that, under high surface pressure, the low melting point zinc and the mold cause an adhesion phenomenon. In order to prevent this, it is effective to form a film having a higher melting point than the zinc or zinc alloy plating layer on the surface of the plating layer of the zinc-based plated steel sheet. Fe-Ni- in the present invention
Since the Zn-O-based coating is hard and has a high melting point, by forming an Fe-Ni-Zn-O-based coating on the surface of a zinc-based plated steel sheet, the surface of the plating layer and the press die during press molding are formed. The sliding resistance is reduced, and the zinc-plated steel sheet easily slides into the press mold, and the press formability is improved. Further, Ni of the Fe-Ni-Zn-O-based coating in the present invention has a property of easily adsorbing components of the press oil when a new surface is exposed during sliding under a high surface pressure. It has the effect of preventing the phenomenon.

The conventional galvanized steel sheet is inferior to the cold-rolled steel sheet in continuous hitting property in spot welding. The reason for this is that the molten zinc at the time of welding diffuses into the copper of the electrode to form a fragile alloy layer, which causes an increase in the electrode tip diameter due to peeling of the alloy layer. Therefore, as a method for improving the continuous hitting property of zinc-based plated steel sheet,
It is effective to form a high melting point film on the plating surface to suppress the reaction between the plating metal and the copper electrode. The present inventors have studied various types of coatings to improve the spot weldability of galvanized steel sheets.
It has been found that the i-oxide film is particularly effective. The reason for this is not clear, but Ni reacts with Zn
-By forming a Ni alloy and suppressing the reaction between zinc and the copper electrode, or by suppressing the diffusion of zinc into the copper electrode by a very high melting point Ni oxide, thereby reducing the wear of the copper electrode. It is estimated to be.

It has been known that the adhesiveness of a conventional galvanized steel sheet is inferior to that of a cold-rolled steel sheet, but the cause has not been clarified. Then, the present inventors investigated the cause and found that the adhesiveness is governed 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 steel sheet surface is F
In contrast to e-oxides, zinc-based plated steel sheets mainly include Zn oxides. The adhesiveness differs depending on the composition of the oxide film, and the Zn oxide was inferior in adhesiveness to the Fe oxide. Therefore, by forming a film coated with an oxide film containing Fe oxide on the surface of a galvanized steel sheet as in the present invention, it is possible to improve the adhesiveness.

The conversion treatment property of the conventional galvanized steel sheet is as follows:
Inferior to cold-rolled steel sheet due to high Zn concentration on the steel sheet surface, resulting in coarse and uneven phosphate crystals formed and different quality of phosphate crystals I do. When the Zn concentration on the surface of the steel sheet is high, the phosphate crystals are mainly composed of whipite, and the secondary adhesion of hot water after coating is poor. This is because the Fe concentration in the phosphate film is low, so that when exposed to a moist environment after painting, the chemical conversion film condenses,
This is due to the loss of adhesion to the steel sheet.

In order to suppress the condensed water of the chemical conversion coating,
It is effective to include metals such as Fe and Ni in the phosphate crystals. The present inventors have found that a chemical conversion treatment property can be improved by forming an appropriate Fe-Ni-O-based film on the surface of a plating layer of a zinc-based plated steel sheet, and according to Japanese Patent Application No. 6-257499, Based on the premise that press formability is excellent, a patent application was filed for a zinc-based plated steel sheet having excellent spot weldability, adhesiveness, and chemical conversion treatment properties as appropriate depending on the application. In the galvanized steel sheet, Ni and Fe in the Fe-Ni-O-based film are incorporated into the phosphate crystals during the chemical conversion treatment, and the chemical conversion treatment film having good adhesion is obtained. It was found that crystals of phosphate were formed and not only the secondary adhesion of hot water but also the corrosion resistance were improved.

However, as a result of further studies by the present inventors, it was found that Ni originally had poor reactivity with the chemical conversion treatment solution, and that zinc phosphate crystals were unlikely to be formed on a pure Ni metal plate. . That is, formation of phosphate crystals in the chemical conversion treatment requires that Zn elutes into the chemical conversion treatment solution and hydrogen is generated in the solution. However, when Ni completely covers the steel sheet surface, elution of the metal into the chemical conversion treatment liquid is suppressed, resulting in poor reactivity. In the zinc-based plated steel sheet, when the Fe-Ni-O-based film adhesion amount increases,
This is the reason why the adhesion has deteriorated. On the other hand, Fe-
The reason why excellent performance was exhibited when the Ni-O-based coating amount was low is that the Fe-Ni-O-based coating was partially dissolved during the chemical conversion treatment, and a portion where the Zn of the original plate was exposed was formed. It was presumed that the reactivity of the treatment was improved.

Therefore, as a result of further study by the present inventors, it has been found that Fe-Ni
-By forming an appropriate Zn-O-based coating, the chemical conversion property does not deteriorate even when the coating amount is large, and if dense and uniform phosphate crystals are formed and only hot water secondary adhesion is used, It was also found that the corrosion resistance was improved.

As described above, at least the metals of Ni, Fe and Zn and N
A coating containing an oxide of i, Fe, and Zn and having a surface layer of an oxide (hereinafter, referred to as an “Fe—Ni—Zn—O-based coating”) is appropriately formed, so that the zinc-based plated steel sheet has: It has been found that excellent press formability, spot weldability, adhesiveness, and chemical conversion properties can be obtained. That is, it is an essential condition of the present invention that the Fe—Ni—Zn—O-based coating is formed on the surface of the plating layer.

As described above, it is essential that the oxygen content of the Fe—Ni—Zn—O-based coating be in the range of 0.5 to 10% by weight. The following knowledge for realizing this oxygen content was also obtained.

In order to co-deposit a metal oxide in a film by cathodic electrolysis, a state where diffusion of metal ions cannot be made in time is created by increasing a deposition rate of the film.
It is essential to make what is called a burnt plating state. The present inventors have intensively studied a technique for controlling the amount of eutectoid of an oxide on an Fe—Ni—Zn—O-based film, and have controlled Fe—Ni—Z
A technology was developed to control the oxygen content of the n-O-based coating within an appropriate range.

The present invention has been made on the basis of the above-mentioned findings, and it has been proposed that the surface of a zinc-based plated steel sheet
This is a method of producing a zinc-based plated steel sheet having excellent press formability, spot weldability, adhesiveness, and chemical conversion treatment properties by forming a Ni-Zn-O-based film. The gist of the method is as follows. The method for producing a zinc-based plated steel sheet according to claim 1, wherein the zinc-based plated steel sheet is used as a cathode in a plating solution containing nickel sulfate, ferrous sulfate and zinc sulfate, and electrolysis is performed on the surface of the plated layer. Forming a zinc-based plated steel sheet,
When the total concentration of Ni ²⁺ , Fe ²⁺ and Zn ²⁺ ions is 0.1
~ 2.0 mol / l and the pH is 1.0
-3.0, and the sum of the Ni ion concentration, the first Fe ion concentration and the Zn ion concentration in the plating solution: M (mol / l), and the average plating solution flow rate: U (m / s). ) When,
The relationship between the current density in electrolysis: I _K (A / dm ² ) is expressed by the following equation (1): I _K / (U ^1/2 M) = 50-150 ----------- ----------- (1) By performing electrolysis under the condition that satisfies (1), Fe-Ni-Z
It is characterized by forming an n-O-based film.

According to a second aspect of the present invention, there is provided the method for producing a zinc-based plated steel sheet according to the first aspect of the invention, wherein the plating layer of the zinc-based plated steel sheet contains Fe in the range of 7 to 15 wt. It is characterized by being a hot-dip galvanized layer.

[0033] The method of manufacturing a zinc-based plated steel sheet according to the third aspect is characterized in that, in the method of the first aspect, the plating layer of the zinc-based plated steel sheet is an electrogalvanized layer or a hot-dip galvanized layer. It has.

[0034]

Next, the reasons for limiting the manufacturing conditions of the present invention will be described. The reason why an acidic sulfate aqueous solution containing nickel sulfate, ferrous sulfate and zinc sulfate is used as the electrolytic solution is that it is suitable for efficiently containing Fe, Ni, Zn and O to form a film. .

If the total concentration of Fe ²⁺ , Ni ²⁺ and Zn ^{2+ in} the electrolyte is less than 0.1 mol / l, the conductivity of the bath is low and the electrolysis voltage is high, so that a higher voltage rectifier is required. Not suitable. On the other hand, when the total concentration exceeds 2.0 mol / l, the solubility limit is reached, and when the temperature is low, precipitation of nickel sulfate, ferrous sulfate and zinc sulfate occurs. Also,
Since the critical current density is increased, plating burning cannot occur unless electrolysis is performed at an extremely high current density. Therefore, the total concentration of Fe ²⁺ , Ni ²⁺ and Zn ^{2+ in} the electrolyte should be limited to the range of 0.1 to 2.0 mol / l.

When the pH of the bath is less than 1.0, hydrogen generation becomes the main component of the cathodic reaction and the current efficiency is greatly reduced.
If H exceeds 3.0, a hydroxide of the second Fe precipitates out. The present inventor has determined that the limiting current density I _Kd (A / dm ² ), the concentration of deposited metal ions M (mol / l), and the average plating solution flow rate: U (m /
As a result of repeated studies on the relationship between s) and the bath temperature (° C.), it was found that the critical current density I _Kd was proportional to the metal ion concentration M and the square root of the average plating solution flow velocity U. That is, I _Kd = k (U ^1/2 M) where k is a constant. By modifying this, I _Kd / (U ^1/2 M) = k is obtained.

As a result of further studies, the present inventors have found that Fe
-In order to make the oxygen content of the Ni-Zn-O-based film 0.5 wt.% Or more, it is necessary to make the value of k 50 or more, and the oxygen content is 10 wt.% Or less. It has been found that it is necessary to make the value of the constant k 150 or less in order to obtain Therefore, in order to keep the oxygen content of the Fe—Ni—Zn—O-based coating in the range of 0.5 to 10 wt.%, The current density I _K at the time of electrolytic plating is I _K / (U ^{1 / 2} M) = 50 to 150 should meet the relationship. Here, the plating solution average flow rate refers to an average value of the plating solution flow rate at an intermediate point between the anode and the cathode.

Although there is no particular limitation on the temperature of the electrolytic solution, if the temperature is lower than 30 ° C., the conductivity of the bath is low, and the electrolytic voltage is high. It becomes difficult to control the nickel ion and iron ion concentrations. Therefore, the temperature of the electrolyte is 30 to 7
It is desirable to be within the range of 0 ° C.

In the present invention, most of the deposited metal ions in the plating bath are Fe ²⁺ , Ni ²⁺ and Zn ²⁺ , and other metal ions are Fe ²⁺ except for Fe ³⁺ ions. -Has little effect on the deposition of the Ni-Zn-O-based coating. Therefore, Co, Mn, Mo, Al, T
It may contain cations such as i, Sn, W, Si, Pb, Nb and Ta. However, Fe ³⁺ ion is Fe−
Since it lowers the deposition efficiency of the Ni-Zn-O-based coating,
It is desirable that the content be 0.09 mol / l or less.

Furthermore, the electrolyte may contain hydroxides and oxides, and further anions other than sulfate ions. The zinc-plated steel sheet used in the present invention is a steel sheet in which a plating layer is formed on the surface of a base steel sheet by one or more methods such as hot-dip plating, electroplating and vapor phase plating. is there.

The chemical composition of the zinc-based plating layer is, in addition to pure zinc, Fe, Ni, Co, Mn, Cr, Al, Mo, T
a single or multiple plating layer containing a predetermined amount of one or more of metals, oxides, hydroxides, or organic substances such as i, Si, W, Sn, Pb, Nb and Ta; What is necessary is just to consist of. Further, the plating layer may contain fine particles such as SiO ₂ and Al ₂ O ₃ . In addition, as a zinc-based plated steel sheet, a multi-layer plated steel sheet composed of a plurality of layers having the same component elements and different compositions from each other in a plating layer, or a composition element in the thickness direction of the plating layer in which the constituent elements of the plating layer are the same It is also possible to use a functionally graded plated steel sheet in which is continuously changed.

The zinc-plated steel sheet used in the present invention has a Fe content of 7 to 15 wt.%.
Alloyed hot-dip galvanized steel sheet, and electro-galvanized steel sheet and hot-dip galvanized steel sheet are most suitable. These galvanized steel sheets are inferior in workability and weldability as compared with cold-rolled steel sheets and zinc-nickel alloy-plated steel sheets, so that the effect obtained when the present invention is applied is large.

The Fe—Ni—Zn formed on the surface of the plating layer of the galvanized steel sheet manufactured under the above-described limited conditions.
Press-formability, spot weldability, adhesiveness, and chemical conversion treatment are improved by the —O-based coating. However, Fe
-Ni-Zn-O-based Ni content in the film can not be obtained the effect of improving the press formability is less than 10 mg / m ^2. On the other hand, when the content exceeds 1500 mg / m ² , the above-mentioned effect is saturated.
Therefore, the Ni content in the Fe—Ni—Zn—O-based coating is
Desirably, it is in the range of 10 to 1500 mg / m ² .

If the Zn content in the Fe—Ni—Zn—O-based coating is less than 5 mg / m ² , the effect of improving the chemical conversion property cannot be obtained. On the other hand, when the content exceeds 1500 mg / m ² , the effect of improving the chemical conversion property is saturated, and furthermore, the spot weldability and the adhesiveness are deteriorated, and the press formability is undesirably deteriorated. Therefore, it is desirable that the Zn content of the Fe—Ni—Zn—O-based coating be in the range of 5 to 1500 mg / m ² .

When the oxygen content in the Fe—Ni—Zn—O-based coating is less than 0.5 wt.%, The metallic properties of the coating become so strong that the effect of improving press formability and adhesiveness is not exhibited. On the other hand, if the oxygen content exceeds 10 wt.%, The amount of the oxide becomes too large, so that the formation of phosphate crystals is suppressed, and the chemical conversion property deteriorates. In addition, the electric resistance of the surface increases, and the weldability decreases. Therefore, Fe-Ni-Zn-
The oxygen content of the O-based coating is desirably in the range of 0.5 to 10 wt.%.

[0046] Fe-Ni-Zn-O-based ratio of Fe content in the coating (mg / m ²⁾ and Ni content Fe content to the sum of ^{(mg / m 2) (mg} / m 2) Fe / If (Fe + Ni) is less than 0.05, the effect of improving the adhesiveness is not exhibited. On the other hand, Fe /
If (Fe + Ni) exceeds 0.9, the content of Ni present in the coating decreases, and the proportion of the high melting point Zn—Ni alloy formed during welding decreases. The effect of improving weldability is not exhibited. Therefore, Fe / (Fe + Ni) in the coating is 0.05
It is desirable to be within the range of 0.9.

[0047]

Next, the present invention will be described in more detail with reference to examples. A zinc-plated steel sheet (hereinafter, referred to as an “original sheet”) before forming an Fe—Ni—Zn—O-based coating used in this example.
) Are the following three types (symbols GA, GI and EG).

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. The zinc-based plated steel sheet is used as a cathode, and a predetermined concentration of Fe ²⁺ ,
The electrolytic treatment was performed in an acidic sulfate bath containing Ni ²⁺ and Zn ²⁺ to apply Fe-Ni-
A specimen on which a Zn-O-based film was formed was prepared (however,
Some are not processed).

The concentrations of Fe ²⁺ , Ni ²⁺ and Zn ^{2+ in} the electrolyte were controlled by adjusting the amounts of ferrous sulfate, nickel sulfate and zinc sulfate to be added. Tables 1, 2 and 3
In Examples 1 to 1 subjected to electrolytic treatment under the conditions within the scope of the present invention
32, and electrolysis conditions of Comparative Examples 2 to 18, 20 to 24, and 26 to 30 in which electrolysis was performed under conditions at least one of which is out of the range of the present invention. Comparative Examples 1 and 1
Nos. 9 and 25 were not subjected to any electrolytic treatment.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

[Table 3]

Regarding the Fe—Ni—Zn—O-based film of each specimen, the contents of Ni and Zn in the film,
/ Fe + Ni and the oxygen content of the film were measured as follows. "Contents of Ni and Zn in the film and F in the film
e / Fe + Ni "in the lower plating layer is Fe-Ni-Z
Since it contains the component elements in the n-O-based film, the ICP method
It is difficult to completely separate the components in the upper Fe—Ni—Zn—O-based coating from the components in the lower plating layer. Therefore, of the elements in the Fe—Ni—Zn—O-based coating, only the elements not contained in the lower plating layer were quantitatively analyzed by the ICP method. Furthermore, after Ar ion sputtering, the composition distribution of each component element in the depth direction of the plating layer was measured by repeating the measurement of each component element in the Fe—Ni—Zn—O-based coating from the surface by the XPS method. In this measurement method, the element of the Fe—Ni—Zn—O-based film not contained in the lower plating layer is not detected at a depth (x) from the surface at which the element has the maximum concentration. The difference (y-x) between the depth (y) from the surface and the depth (x) from the surface showing the maximum concentration is 1
/ 2 plus depth from surface (x + (y−x) / 2),
That is, the average depth ((x + y) / 2) from the surface between the depth (x) from the surface showing the maximum concentration and the depth (y) from the surface where the element is no longer detected is Fe-Ni. -Zn
-Defined as the thickness of the O-based film. The amount and composition of the Fe—Ni—Zn—O-based coating were calculated from the results of the ICP method and the XPS method. Next, Fe /
(Fe + Ni) was calculated. "Oxygen Content of Film" The oxygen content was determined from the results of Auger electron spectroscopy (AES) analysis in the depth direction.

Tables 4 to 6 show the Ni content, the Zn content, the Fe / Fe + Ni content, and the oxygen content of the Fe—Ni—Zn—O-based coating film for the test samples of the examples and comparative examples. 2 shows the measurement results.

[0056]

[Table 4]

[0057]

[Table 5]

[0058]

[Table 6]

Next, in order to evaluate the press formability, spot weldability, adhesiveness and chemical conversion treatment of the test specimens of the examples and comparative examples, measurement of friction coefficient, continuous spot test in spot welding, adhesion A test and a test for investigating the state of formation and adhesion of phosphate crystals were conducted. Each evaluation test method is as follows. "Friction coefficient measurement test" To evaluate press formability,
The coefficient of friction of each specimen was measured by the following device.

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 60 mm in the sliding direction, and each line having a width of 10 mm on the front and rear surfaces is in contact with a quarter of the cylindrical surface having 4.5 mmR as shown in FIG. "Continuous spot test" To evaluate spot weldability,
A continuous hitting test was performed on each specimen.

[0063] Two identical specimens were stacked, and the same
Resistance welding (spot welding) in which current was concentrated by sandwiching between a pair of electrode tips and energizing under pressure was continuously performed 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. As the evaluation of the continuous hitting property, the diameter of the molten and solidified metal portion (nugget) generated at the joint portion of the two welded base materials (specimens) during spot welding was 4xt1 / 2 (t: 1 piece). (Thickness) 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 each test specimen.

FIG. 3 is a schematic perspective view for explaining the assembling process. As shown in the figure, width 25 mm, length 2
Two test pieces 10 of 00 mm are placed between them by 0.15 mm
The thickness of the adhesive 12 is 0.1
5 mm to form an adhesive test specimen 13 at 150 ° C. × 10 min. Baking. The specimen thus prepared was bent into a T-shape as shown in FIG.
/ 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.
P indicates a tensile load. The adhesive used was a PVC-based hemming adhesive. "Chemical conversion treatment test" In order to evaluate the chemical conversion treatment, the following test was performed.

Each test piece was treated with an immersion type zinc phosphate treatment solution (PBL30 manufactured by Nippon Parkerizing Co., Ltd.)
80), a treatment was carried out under ordinary conditions to form a zinc phosphate film on the surface. The crystal state of the zinc phosphate film thus formed was observed with a scanning electron microscope (SEM). It was divided into three stages according to its crystal state. The signs of the evaluation categories and their contents are as follows. ：: The crystals of the zinc phosphate film are dense and small. Δ: The crystals of the zinc phosphate film are slightly coarse and large. ×: The crystals of the zinc phosphate film are coarse or not formed. The specimen for "adhesion test of chemical conversion coating" was treated with the above-mentioned immersion type zinc phosphate treating agent for the undercoat of an automobile coating, and further treated for 20 minutes.
After performing ED coating at a coating pressure of μm, a chemical conversion coating adhesion test was performed. FIG. 5 schematically shows a method for evaluating the adhesion between the chemical conversion coating and the zinc-based plating layer itself. 100x
The thickness of the adhesive 16 is 0.15 mm through a spacer 15 of 0.15 mm between the specimens 14 having a size of 25 mm,
A test body was prepared so that the adhesion area was 25 × 10 mm, and baked at 170 ° C. for 30 minutes. The adhesive used was an epoxy structural adhesive. The specimen 14 is a variety of steel sheets having a thickness of 0.8 mm. However, depending on the material, the strength of the specimen is small and the base material may be broken during a tensile test. Steel plate reinforcing plate 1
The sample was designated as 7 and used as an adhesion test specimen 18 of the chemical conversion coating. The test piece was pulled at a speed of 200 mm / min using a tensile tester, the average peel strength at the time of peeling was measured, and the peeled surface was observed with a scanning electron microscope (SEM).

The peeling occurs at the weakest point.
When GA (alloyed hot-dip galvanized steel sheet) is used,
Peeling occurs at the interface between the GA film and the steel sheet, and the peel strength is GA
The interface adhesion strength between the coating and the steel sheet. When GI (hot-dip galvanized steel sheet) and EG (electro-galvanized steel sheet) are used, cohesive failure occurs inside the adhesive, and the peel strength is the strength of the adhesive itself.

The evaluation of the adhesion between the chemical conversion coating and the zinc-based plating layer itself was evaluated as follows.
When the peel strength was lower than that of the untreated material, it was evaluated as x.
Tables 7 to 9 also show the evaluation test results of the press formability, spot weldability, adhesiveness and chemical conversion treatment described above.

[0068]

[Table 7]

[0069]

[Table 8]

[0070]

[Table 9]

The following items are clear from Tables 7 to 9.
First, the results of the comparative examples will be described. (1) In the comparative examples 1, 19, and 25, no Fe—Ni—Zn—O-based coating was formed because no electrolytic treatment was performed. Therefore, irrespective of the type of plating of the original plate, all of them are inferior in the crystal state of the film in the press formability, spot weldability, adhesiveness and chemical conversion processability, except for the adhesion of the chemical conversion film in chemical conversion processability.

(2) Comparative Examples 5, 7, 12, 14, 23 and 29 are cases where the value of I _K / (U ^1/2 M) is less than 50 outside the range of the present invention. Therefore, even if the other electrolysis conditions are within the range of the present invention, the oxygen content in the electrolytically treated film is lower than the appropriate value range (0.5 to 10 wt.%), And therefore, regardless of the plating type of the original plate. Poor press formability and adhesion.

(3) Comparative Examples 2 to 4, 9 to 11, and 20 to 2
Nos. 2 and 26 to 28 are cases where the electrolytic bath does not contain Zn ²⁺ ions. Therefore, even if the other electrolysis conditions are within the range of the present invention, Zn is not contained in the electrolyzed film, and therefore, regardless of the plating type of the original plate, the adhesion of the chemical conversion film is inferior.

(4) Comparative Examples 6, 8, 13, 15, 24 and 30 are cases where the value of I _K / (U ^1/2 M) exceeds 150 which is outside the range of the present invention. Therefore, even if other electrolysis conditions are within the range of the present invention, the oxygen content in the electrolyzed film is higher than the appropriate value range (0.5 to 10 wt.%),
Regardless of the plating type of the original sheet, the spot weldability and the adhesion of the chemical conversion film are poor.

(5) Comparative Examples 16 to 18 show that F in the electrolytic bath
This is the case when the total concentration of e ²⁺ , Ni ²⁺ and Zn ²⁺ ions is higher than the scope of the present invention. In this case, even if the current density is increased, it is difficult to make I _K / (U ^1/2 M) equal to or more than 50, and the oxygen content in the Fe—Ni—O-based coating falls within the appropriate value range (0.5 ~ 10wt.%) And F in the film
e / (Fe + Ni) (weight ratio) is in an appropriate value range (0.05 to 0.9).
Greater than). Therefore, press formability and adhesiveness are poor.

On the other hand, (6) Examples 1-32 are all excellent in press formability, spot weldability, adhesiveness and chemical conversion treatment.

[0077]

According to the present invention having the above-described structure, the Fe--N film formed on the surface of the plating layer of the zinc-based plated steel sheet can be used.
Since the i-Zn-O-based coating is harder and has a higher melting point than the zinc or zinc alloy plating layer, the sliding resistance between the plating layer surface and the press die during press forming of the zinc-based plated steel sheet. And the galvanized steel sheet slides easily into the press die. Further, in order to ensure the formation of a high melting point Zn-Ni alloy during welding due to the presence of the Fe-Ni-Zn-O-based coating, particularly, since a predetermined amount of Ni is contained,
The wear of the electrode is suppressed, and as a result, the continuous hitting property in spot welding is improved. Furthermore, the presence of the Fe oxide contained in the oxide film on the surface layer of the Fe—Ni—Zn—O-based coating improves the peel strength of the adhesive plate. Further, the chemical conversion coating film has excellent adhesion since Ni and Fe in the Fe—Ni—Zn—O-based coating film are incorporated into the phosphate crystals, and has a hot water due to the formation of dense and uniform phosphate crystals. It also has excellent secondary adhesion. In the case of chemical conversion treatment, F
Since Zn in the e-Ni-Zn-O-based film is eluted, the reaction is not suppressed, so that Fe-Ni-Zn-O
Even if the coating amount of the system coating increases, the adhesion does not deteriorate.

Therefore, according to the present invention, press formability,
A method for producing a zinc-based plated steel sheet having excellent spot weldability, adhesiveness, and chemical conversion treatment properties can be provided, and industrially extremely useful effects can be obtained.

[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.

FIG. 5 is a schematic perspective view illustrating a method for evaluating the adhesion between the chemical conversion coating and the zinc-based plating layer itself.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sample for friction coefficient measurement 2 Sample stand 3 Slide table 4 Roller 5 Slide table support 6 Bead 7 1st load cell 8 2nd load cell 9 Rail 10 Specimen 11 Spacer 12 Adhesive 13 Adhesive specimen 14 Specimen 15 Spacer 16 Adhesive agent 17 Reinforcement plate 18 Adhesion test piece N Pressing load F Sliding resistance P Tensile load

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Ritaka Sakurai 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor: Junichi Inagaki 1-1-2, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Inventor Masaaki Yamashita 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd.

Claims (3)

[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 containing nickel sulfate, ferrous sulfate and zinc sulfate. The total concentration of Ni ²⁺ , Fe ²⁺ and Zn ²⁺ ions is in the range of 0.1 mol / l or more and 2.0 mol / l or less, and the pH is It is in the range of 1.0 or more and 3.0 or less, and the Ni ²⁺ , F
The sum of the e ²⁺ and Zn ²⁺ ion concentrations: M (mol / l), the average flow rate of the plating solution: U (m / s), and the current density in the electrolysis: I _K (A / dm ² ). Is the following equation (1): I _K / (U ^1/2 M) = 50-150 (1) By performing the electrolysis under the condition of satisfying
-A method for producing a galvanized steel sheet, comprising forming a Zn-O-based film. 2. The method according to claim 1, wherein the plating layer of the galvanized steel sheet is an alloyed hot-dip galvanized layer containing an iron content in a range 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.