JP3191688B2 - 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. 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.

[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”).

[0010]

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.

The 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, so that the effect of improving press formability and chemical conversion treatment is great, but the spot weldability and There is a problem that the adhesiveness is deteriorated.

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. 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 and adhesiveness.

[0013]

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, have found that an appropriate Fe-Ni-Zn-based metal It has been found that by forming a film, press formability, spot weldability and adhesion can be significantly improved.

Here, an appropriate Fe—Ni—Zn-based metal film is defined as (1) to (3): (1) The total of the Fe content and the Ni content of the film is 10 to
(2) Fe content (mg / m ² )
m ²⁾ and Ni content (the ratio Fe / (Fe + Ni Fe content to the sum of ^{mg / m 2) (mg /} m 2)) is from 0.05 to 0.
9, preferably in the range of 0.1 to 0.5;
The content (mg / m ²⁾ and Ni content (mg / m ²⁾ and the Zn content to the sum of (mg / m ²⁾ ratio Zn / (Fe + Ni)
Was found to satisfy the condition of 0.01 to 1.6, preferably 0.01 to 0.7.

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 the zinc and the mold having a low melting point under high surface pressure cause a cohesion phenomenon, so that the sliding resistance increases. Is the cause. 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 on the surface of the zinc-based plated steel sheet. The Fe-Ni-Zn-based metal film of the present invention comprises:
Since it is hard and has a high melting point, by forming an Fe-Ni-Zn-based metal film 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 the zinc-based plated steel sheet easily slips into the press mold, and press formability is improved.

The reason why the spotting property of the continuous welding in the spot welding of the zinc-based plated steel sheet is inferior to that of the 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. Therefore, as a method for improving the continuous hitting property of a zinc-based plated steel sheet, it is considered effective to form a high melting point film on the plated surface. The present inventors have studied various types of coatings in order to improve the spot weldability of galvanized steel sheets, and have found that Ni metal is particularly effective. Although the reason for this is not clear, it is considered that Ni metal has a high melting point and high electric conductivity.

It has been known that the galvanized steel sheet has inferior adhesiveness to the cold-rolled steel sheet, but the cause is not clear. Then, the present inventors investigated the cause and found that F in the Fe—Ni—Zn-based metal film was
e was found to be effective in improving the adhesion. However, the mechanism by which the adhesion is improved by the presence of Fe is not clear.

The present invention has been made on the basis of the above-mentioned findings, and has a press formability and a spot by forming a Fe—Ni—Zn-based metal film on the surface of a plating layer of a zinc-based plated steel sheet. This is a method for producing a galvanized steel sheet having excellent weldability and adhesiveness, the gist of which is as follows.

[0019]

[0020] The present invention provides a method for producing 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 acidic sulfate aqueous solution containing Fe ²⁺ ions, Ni ²⁺ ions, and Zn ²⁺ ions. F on the surface of the plating layer of the steel sheet
In the method for producing a zinc-based plated steel sheet comprising forming an e-Ni-Zn-based metal film, the total concentration of the Fe ²⁺ ions, the Ni ²⁺ ions, and the Zn ²⁺ ions in the plating solution is 0. 0.3 to 2.0 mol / l, the pH of the plating solution is in the range of 1 to 3, the temperature of the plating solution is in the range of 30 to 70 ° C., and the current density is in the range of 30 to 70 ° C. The electrolysis is performed under conditions within the range of 1 to 150 A / dm ² , and further, Fe ²⁺
Ion concentration (mol / l) and Ni ²⁺ ion concentration (mo
l / l) and the Zn ²⁺ ion concentration (mol /
1) the ratio is in the range of more than 0 to 0.5; and
And a Zn ²⁺ ion concentration X (mol /
l), the average plating solution flow velocity U (m / s), and the current density
It is characterized in that the electrolysis is performed under the condition that the relationship between the degree I _K (A / dm ² ) and the following equation (1) satisfies the following equation (1): I _K / (U ^1/2 X) ≧ 100 (1) Have

[0021]

Next, the reasons for limiting the manufacturing conditions of the present invention will be described. Fe ²⁺ , Ni ²⁺ and Zn as electrolytes
^{The reason} for using an aqueous solution of acidic sulfate containing ^{2+ is} that it is suitable for efficiently containing Fe, Ni and Zn to form a film.

If the total concentration of Fe ²⁺ , Ni ²⁺ and Zn ^{2+ in} the electrolyte is less than 0.3 mol / l, the conductivity of the bath is low and the electrolysis voltage is high, and if the current density is high, the plating is Burning occurs and nickel or iron hydroxide is involved and weldability is reduced. 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. Therefore, the total concentration of Fe ²⁺ , Ni ²⁺ and Zn ^{2+ in} the electrolyte should be limited to the range of 0.3 to 2.0 mol / l.

The plating solution contains C contained in the plating layer of the zinc-based plated steel sheet used in the present invention.
o, Mn, Mo, Al, Ti, Sn, W, Si, Pb,
Cations such as Nb and Ta, hydroxides and oxides, as well as anions other than sulfate ions may be inevitably contained.

If the pH of the electrolytic solution is less than 1, hydrogen generation becomes the main component of the cathodic reaction, and the current efficiency is greatly reduced.
When H exceeds 3, a hydroxide of the second Fe precipitates out.
Therefore, the pH of the electrolyte should be limited to the range of 1-3.

When the temperature of the electrolytic solution is lower than 30 ° C., the conductivity of the bath is low, the electrolytic voltage is high, and when the current density is high, burning of the plating occurs and the nickel and iron hydroxides are involved and the weldability is reduced. I do. On the other hand, when the temperature exceeds 70 ° C., the amount of evaporation of the electrolytic solution increases, and it becomes difficult to control the nickel ion and iron ion concentrations. Therefore, the temperature of the electrolyte should be limited to the range of 30 to 70 ° C.

When the current density is less than 1 A / dm ² , the generation of hydrogen becomes the main component of the cathode 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 hydroxides of Fe, Ni and Zn are involved and the weldability is reduced. Therefore, the current density should be limited to the range of 1 to 150 A / dm ² .

Zn in the Fe—Ni—Zn-based metal film is
Has the effect of improving the press formability, the ratio of Fe content of this effect in the coating (mg / m ²⁾ and Ni content Zn content to the sum of ^{(mg / m 2) (mg} / m 2) Zn / (Fe +
Ni) is from 0.01 to 1.6, more preferably 0.01.
The effect is further enhanced by limiting the range to 0.7 to 0.7.

The present inventor has found that Zn / (Fe + N
In order to make i) 0.7 or less, Fe ²⁺
The ratio of Zn ²⁺ ion concentration to the sum of the ion concentration and the Ni ²⁺ ion concentration of 0.5 or less, and Z of the plating solution
n ²⁺ ion concentration X (mol / l) and plating solution average flow rate U (m
/ s) and the current density I _K (A / dm ² ), the following (1)
Expression: I _K / (U ^1/2 X) ≧ 100 The relationship of (1) is satisfied. It has been found that it is necessary to perform electrolysis under conditions. Therefore, more preferably, the ratio of the Zn ²⁺ ion concentration to the sum of the Fe ²⁺ ion concentration and the Ni ²⁺ ion concentration in the plating solution is set to 0.5 or less, and the Zn ²⁺ ion concentration X in the plating solution is further reduced. (Mol / l), the average flow rate U (m / s) of the plating solution, and the current density I _K (A / dm ² ) are electrolyzed under the conditions satisfying the relationship of the above equation (1). Should.

The Fe-Ni- used in the present invention
As the galvanized steel sheet for forming the Zn-based metal film, an alloyed hot-dip galvanized steel sheet having an Fe content of 7 to 15 wt.%, And an electrogalvanized steel sheet and a 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.

[0030]

Next, the present invention will be described in more detail with reference to examples. The following three plating types (reference GA, GI and E
The Fe-Ni-Zn-based metal film was formed on the surface of the zinc-based plated steel sheet G) by subjecting it to a cathodic electrolysis treatment in a mixed solution of nickel sulfate, ferrous sulfate and zinc sulfate. However, this includes a part treated in a solution containing no zinc sulfate and a part not treated.

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. Tables 1 to 4 show Examples 1 to 24 in which the electrolytic treatment was performed under the conditions within the scope of the present invention, and at least one of the electrolytic treatment conditions.
Electrolytic treatment conditions are shown for Comparative Examples 1 to 16 in which one was outside the scope of the present invention or where no electrolytic treatment was performed.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4]

[0037] Fe-N of each specimen in Examples and Comparative Examples
For the i-Zn-based metal film, the following was measured by the following method. Total value of Fe content and Ni content: Fe + Ni (mg
/ m ^2), the ratio of Fe content (mg / m ²⁾ and Ni content (Fe content to the sum of ^{mg / m 2) (mg /} m 2): Fe / (Fe +
Ni), and the ratio of Fe content (mg / m ²⁾ and Ni content (mg / m ²⁾ and the Zn content to the sum of ^{(mg / m 2): Zn} / (Fe +
Ni) [Measurement method] Since the lower plating layer contains the component elements in the Fe-Ni-Zn-based metal film, the ICP method uses the components in the upper Fe-Ni-Zn-based metal film and the lower layer plating. It is difficult to completely separate the component elements in the layer.
Therefore, of the elements in the Fe—Ni—Zn-based metal film, 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-based metal film from the surface by the XPS method. In this measurement method, the surface where the element is not detected at a depth (x) from the surface where the element of the Fe—Ni—Zn-based metal film not contained in the lower plating layer shows the maximum concentration is defined. Of the difference (y-x) between the depth from the surface (shown as y) and the depth from the surface showing the maximum concentration (x) 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
It was defined as the thickness of the system metal film. Then, based on the results of the ICP method and the XPS method, the amount and composition of the Fe—Ni—Zn-based metal film were calculated. Next, the total value of the Fe content and the Ni content in the film, Fe / (Fe +
Ni) (content ratio), and Zn / (Fe + Ni)
(Content ratio) was calculated.

Tables 5 and 6 show the results of the measurements for the Fe—Ni—Zn-based metal films formed on the surfaces of the zinc-based plated steel sheets of Examples and Comparative Examples.

[0039]

[Table 5]

[0040]

[Table 6]

Next, in order to evaluate the press formability, spot weldability and adhesiveness of the specimens of Examples and Comparative Examples, a friction coefficient measurement, a continuous spot test in spot welding and an adhesiveness test were performed. . Each evaluation test method is as follows.

[Friction Coefficient Measurement Test] In order to evaluate press formability, the friction coefficient of each specimen was measured by the following apparatus.

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 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.

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 spot test] In order to evaluate the spot weldability, a continuous spot test was performed for each specimen.

[0052] Two identical specimens are 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 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.

Tables 5 and 6 also show the results of the above-described evaluation tests for the test specimens of the examples and comparative examples. Table 1
4 and Tables 5 and 6, the following is clear. (1) In the case where the Fe—Ni—Zn-based metal film was not formed (Comparative Examples 1, 13 and 15), the Fe—Ni—Zn-based metal film was within the scope of the present invention regardless of the plating type of the zinc-based plated steel sheet.
As compared with the case where the Ni—Zn-based metal film is formed, the press formability, spot weldability and adhesiveness are all inferior.

(2) When the film was formed in an electrolytic bath containing no Zn ²⁺ ions (Comparative Examples 2 to 5, 14 and 16), the Zn / (Fe + Ni) ratio in the film was 0 Is a Fe-Ni-based metal, and Fe-N within the scope of the present invention regardless of the plating type of the zinc-based plated steel sheet.
The press formability is inferior to the case where an i-Zn-based metal film is formed.

(3) When the film was formed in an electrolytic bath having a pH outside the range of the present invention (Comparative Examples 8 to 10), the current efficiency was lowered and the Fe—Ni—Zn-based metal film Since the amount of adhesion was small, the press formability, spot weldability and adhesiveness were all inferior.

(4) When film formation treatment is performed in an electrolytic bath having a low total concentration of Fe ²⁺ ions, Ni ²⁺ ions and Zn ²⁺ ions outside the range of the present invention (Comparative Examples 11 and 12) Has low conductivity in the bath and high electrolysis voltage
In addition, the effect of improving the weldability is small due to the inclusion of hydroxides of Fe and Fe.

(5) When the film was formed at a low current density outside the range of the present invention (Comparative Example 6), Fe--Ni
-Since the amount of the Zn-based metal film attached is small, the press formability, spot weldability and adhesiveness are all poor. On the other hand, when the film formation treatment was performed at a large current density outside the range of the present invention (Comparative Example 7), plating burning occurred and the hydroxides of Fe, Ni and Zn were involved, so that the effect of improving spot weldability was improved. Is small.

(6) In contrast, Examples 1 to 24, which are within the scope of the present invention, are all excellent in press formability, spot weldability and adhesiveness. Then, when it is within the scope of the present invention and falls under the invention described in claim 2 (Examples 2 to 4, 7 to 13, 15, 16)
And 19 to 24) are more excellent in press formability.

[0055]

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-based metal film 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 molding is reduced. In addition, the presence of the high-melting Fe—Ni—Zn-based metal film has the effect of improving continuous spotting properties in spot weldability. Further, the presence of Fe in the Fe—Ni—Zn-based metal film has an effect of improving the adhesiveness. Therefore, according to the present invention, it is possible to provide a method for producing a galvanized steel sheet having excellent press formability, spot weldability, and adhesiveness, and an industrially extremely useful effect is 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.

[Description of Signs] 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 Adhesive test specimen 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 Nippon Kokan Co., Ltd. (72) Inventor: Junichi Inagaki 1-1-2, Marunouchi, Chiyoda-ku, Tokyo Japan Inside of Kokan Co., Ltd. (72) Inventor Masaaki Yamashita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Kokan Co., Ltd. (56) References JP-A-7-3417 (JP, A) JP-A-7-145469 ( JP, A) JP-A-57-47890 (JP, A) JP-A-59-173289 (JP, A) JP-A-10-30191 (JP, A) JP-A-9-143788 (JP, A) 62-5239 (JP, B2) JP 7-103474 (JP, B2) JP 63-20316 (JP, B2) JP 7-103475 (JP, B2) (58) Fields surveyed (Int .Cl. ⁷ , DB name) C25D 5/26 C25D 3/56

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein the Fe ²⁺ ion, the Ni ²⁺ ion and the Zn
^In a plating solution composed of an aqueous solution of an acidic sulfate containing ²⁺ ions, electrolysis is performed using a zinc-based plated steel sheet as a cathode, so that Fe-Ni-
In the method for producing a zinc-based plated steel sheet comprising forming a Zn-based metal film, the total concentration of the Fe ²⁺ ions, the Ni ²⁺ ions, and the Zn ²⁺ ions in the plating solution is 0.3 to 2 0.0 mol / l, the pH of the plating solution is in the range of 1-3, the temperature of the plating solution is in the range of 30-70 ° C, and the current density is 1-150 A / dm ^2, the electrolysis is performed under the conditions within the range of dm ² , and further, the concentration of Fe ²⁺ ions in the plating solution
(Mol / l), and Ni ²⁺ ion concentration (mol / l)
Of Zn ²⁺ ion concentration (mol / l) to the sum of
Is within the range of more than 0 to 0.5, and
The concentration of Zn ²⁺ ion X (mol / l)
The average liquid flow velocity U (m / s) and the current density I _K (A /
dm ² ) , wherein the electrolysis is carried out under conditions satisfying the following equation (1): I _K / (U ^1/2 X) ≧ 100 (1) Production method.