JP3191687B2 - 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 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,
The reason for this is that when the sliding resistance is large, the galvanized steel sheet flows into the press mold at the part where the sliding resistance between the bead and the galvanized steel sheet is large. And the steel sheet is likely to break.

[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. 4-88196 discloses a method of forming an oxide film mainly composed of P oxide on the surface of a galvanized steel sheet (hereinafter referred to as “prior art 2”). Japanese Patent Application Laid-Open No. Hei 3-91093 discloses that a nickel-based oxide is formed on a surface of a galvanized steel sheet by electrolytic treatment, immersion treatment, coating treatment, coating oxidation treatment or heat treatment to improve press formability and chemical conversion treatment properties. (Hereinafter referred to as “prior art 3”).

[0009]

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 P oxide on the surface of a galvanized steel sheet, so that the effect of improving press formability and chemical conversion treatment is great, but spot welding,
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 press formability is improved.
On the other hand, 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.

[0012]

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 press-formability, spot weldability and adhesiveness can be significantly improved by forming a film.

The zinc-plated steel sheet of the present invention has a Fe—Ni—Zn-based metal film formed on at least one surface of a plated layer. The total amount with the Ni content is 10 to 15
In the range of 00mg / m ^2, preferably in the range of 10~800mg / m ^2, further, Fe content of the Fe-Ni-Zn-based metal coating in (mg / m ²⁾ and Ni content (mg / m ²⁾ Fe content to the sum of (mg / m ²⁾ ratio of 0.05
0.9, desirably in the range of 0.1 to 0.5, and Fe in the Fe-Ni-Zn-based metal film.
The ratio of the content (mg / m ²⁾ and Ni content Zn content to the sum of ^{(mg / m 2) (mg} / m 2) is in the range of 0.01 to 1.6, preferably 0. It is characterized by being within the range of 01 to 0.7. In addition, Fe-Ni-Zn
The base metal film may contain an impurity element that is inevitably mixed.

The press formability of a conventional galvanized steel sheet is inferior to that of a cold rolled steel sheet. This is because, under a high surface pressure between the zinc-based plated steel sheet and the press die, the low-melting point zinc and the die cause an adhesion phenomenon, so that the sliding resistance increases. 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. Since the Fe—Ni—Zn-based metal film in the present invention is hard and has a high melting point, forming the Fe—Ni—Zn-based metal film on the surface of a zinc-based plated steel sheet allows the surface of the plating layer to be pressed during press forming. The sliding resistance with the mold decreases, and the zinc-based plated steel sheet slides easily into the press mold, and the press formability improves.

[0015] Continuous spotting properties in spot welding of conventional galvanized steel sheets are inferior to those of cold-rolled steel sheets. The cause is that, as described above, the molten zinc at the time of welding comes into contact with the copper of the electrode to form a fragile alloy layer, so that the electrode is greatly deteriorated, and the diameter of the electrode tip is enlarged due to peeling of the alloy layer. is there. Therefore, as a method for improving the continuous hitting property of a zinc-based plated steel sheet, it is effective to form a high melting point film on the plating surface and suppress the reaction between the plated metal and the copper electrode. 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. The reason for this is not clear, but it is presumed that Ni metal has a high melting point and high electrical conductivity.

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

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS By forming an appropriate Fe-Ni-Zn-based metal film on the surface of a galvanized steel sheet, press formability, spot weldability and adhesion are improved.
Therefore, the reason for limiting the chemical composition in the Fe—Ni—Zn-based metal film will be described.

[Sum of Fe content and Ni content of film]
When the sum of the Fe content (mg / m ² ) and the Ni content (mg / m ² ) of the Fe—Ni—Zn-based metal film is less than 10 mg / m ² , the press formability, spot weldability, and adhesion are improved. When the effect is not obtained, on the other hand, when it exceeds 800 mg / m ² , the above effect is saturated, leading to an increase in manufacturing cost, and further, 1500 mg / m ^2.
If it exceeds 300, the generation of phosphate crystals is suppressed, and the chemical conversion property deteriorates. Therefore, F of the Fe—Ni—Zn-based metal film
The sum of the e content and the Ni content should be limited to the range of 10 to 1500 mg / m ² , preferably 10 to 800 mg / m ^2.
It should be limited to a range of / m ^2.

[Fe (mg / m ² ) / (Fe (mg / m ² )
m ² ) + Ni (mg / m ² ))] Fe—content (mg / m ² ) based on the sum of the Fe content (mg / m ² ) and the Ni content (mg / m ² ) of the Fe—Ni—Zn-based metal film m ² ) (hereinafter Fe /
If (Fe + Ni)) is less than 0.05, the effect of improving the adhesion is insufficient, while if it exceeds 0.9, the effect of improving the spot weldability is reduced. Therefore, Fe / (Fe + Ni) of the Fe—Ni—Zn-based metal film should be limited to the range of 0.05 to 0.9. Desirably, it is better if it is limited to the range of 0.1 to 0.5.

[Coating Zn (mg / m ² ) / (Fe (mg / m ²
m ² ) + Ni (mg / m ² )] The Zn content (mg / m ² ) based on the sum of the Fe content (mg / m ² ) and the Ni content (mg / m ² ) of the Fe—Ni—Zn-based metal film. ² ) (hereinafter Zn /
By appropriately controlling ((Fe + Ni)), press formability is dramatically improved. This improvement effect is due to the Z
n / (Fe + Ni) is obtained in the range of 0.01 to 1.6, and particularly remarkable in the range of 0.01 to 0.7.

Zinc plating used in the present invention
A steel sheet is a hot-dip plating method, an electric
The plating layer is formed by methods such as
Steel sheet, and the chemical composition of the zinc-based plating layer is pure
In addition to zinc, Fe, Ni, Co, Mn, Cr and Al
Single or multiple layers containing one or more
What is necessary is just to consist of a stick layer. Also, the above plating layer
SiO_Two, Al_TwoO _ThreeAnd the like.
In addition, as a zinc-based plated steel sheet, component elements of the plating layer
Is composed of multiple layers with the same composition but different composition.
The components of the steel plate and the plating layer are the same and the plating layer
Functionally graded plating with continuously changing composition in the thickness direction
It is also possible to use steel plates.

Further, in the present invention, F
The method for forming the e-Ni-Zn-based metal film is not particularly limited, but the method of electrolytic deposition from an electrolyte containing Fe, Ni and Zn ions is the simplest and the processing cost is low. However, the coating can also be formed by a dry process such as CVD and PVD.

[0023]

Next, the present invention will be described in more detail with reference to examples. In this example, the following was used as the zinc-based plated steel sheet before forming the Fe-Ni-Zn-based metal film.

GA: alloyed hot-dip galvanized steel sheet (10 w
% Fe, balance Zn), and the amount of adhesion was 60 g /
a m ^2. GI: Hot-dip galvanized steel sheet, adhesion amount is 9 on both sides
It is 0 g / m ² .

EG: Electrogalvanized steel sheet with an adhesion amount of 40 g / m ² on both sides. Zn-Fe: Electric Zn-Fe alloy plated steel sheet (15 wt.% F
e), and the adhesion amount is 40 g / m ² on both sides.

Zn-Ni: Electric Zn-Ni alloy plated steel sheet (12 wt.% Ni), the amount of adhesion is 30 g / m ² on both sides. Zn-Cr: Electric Zn-Cr alloy plated steel plate (4 wt.% Cr)
And the adhesion amount is 20 g / m ² on both sides.

Zn-Al: A hot-dip Zn-Al alloy-plated steel sheet (5 wt.% Al), and the adhesion amount is 60 g / m ² on both sides. An Fe—Ni—Zn-based metal film was formed on the surface of the plated layer of the zinc-plated steel sheet of the seven plating types. The film was formed by performing cathodic electrolysis in a mixed solution of nickel sulfate, ferrous sulfate and zinc sulfate.

Table 1 shows the composition of the electrolytic bath components and the electrolytic conditions when forming the Fe—Ni—Zn-based metal film. Within the range of each condition shown in the table, Fe-N within the range of the present invention was used.
Example A galvanized steel sheet having an i-Zn-based metal film and a comparative example having or not having an Fe-Ni-Zn-based metal film outside the scope of the present invention were prepared.

[0029]

[Table 1]

Tables 2 to 6 show the component compositions of the Fe—Ni—Zn-based metal films of Examples 1 to 57 and Comparative Examples 1 to 23.

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

[0035]

[Table 6]

The method for measuring the component composition of the Fe—Ni—Zn-based metal film is as follows. [Fe + Ni (mg / mg / Fe / Ni-Zn based metal film)
m ² ), Fe / (Fe + Ni) (content ratio), and Zn / (Fe + Ni) (content ratio)] Since the lower plating layer contains the component elements of the Fe—Ni—Zn-based metal film, the ICP In the method, the upper layer Fe-Ni-
It is difficult to completely separate the components in the Zn-based metal film and the component elements in the lower plating layer. Therefore, ICP
By the method, among the elements in the Fe—Ni—Zn-based metal film,
Only elements not contained in the lower plating layer were quantitatively analyzed. 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, Fe—N not contained in the lower plating layer is used.
The depth from the surface at which the element of the i-Zn-based metal film shows the maximum concentration (x) and the depth from the surface at which the element is no longer detected (say y) and the depth from the surface at the maximum concentration Depth (x + (y−x) / 2) from the surface obtained by adding の of the difference (y−x) from the depth (x), that is, depth (x) from the surface showing the maximum concentration The average depth ((x + y) / 2) from the surface to the depth (y) from the surface where the element is no longer detected was defined as the thickness of the Fe—Ni—Zn-based metal film. Then, the amount and composition of the Fe—Ni—Zn-based metal film were calculated from the results of the ICP method and the results of the XPS method. Then, the sum of the Fe content and the Ni content in the coating, Fe / (Fe + Ni) in the coating, and Z
n / (Fe + Ni) was calculated.

[Characteristic Evaluation Test] Next, with respect to the test pieces of Examples and Comparative Examples, in order to evaluate press formability, spot weldability and adhesiveness, measurement of friction coefficient, continuous spot test in spot welding, and An adhesion test was performed.

Tables 2 to 6 also show the above test results. 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 method.

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
A cylindrical surface having 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 and having a width of 4.5 mmR.
The / 4 cylindrical surface is in contact as shown in FIG.

Continuous Dotting Test In order to evaluate the spot weldability, a continuous dotting test was performed for each specimen.

The same two test pieces were stacked,
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 an evaluation of the continuous hitting property, the diameter of the molten and solidified metal part (nugget) generated at the joint of the two welded base materials (specimens) during spot welding was 4 × t1 / 2 (t: 1). (The sheet thickness of the 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 test specimens. FIG.
FIG. 3 is a schematic perspective view illustrating the assembling process. As shown in the figure, two specimens 25 each having a width of 25 mm and a length of 200 mm are placed between a 0.15 mm spacer 11 and a spacer 11.
Are bonded together so that the thickness of the adhesive 12 becomes 0.15 mm, and an adhesive test body 13 is prepared.
50 ° 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 the average load from the load chart of the tensile load curve at the time of peeling, and the unit: k
gf / 25 mm. In FIG. 4, P indicates a tensile load. The adhesive used was a PVC-based hemming adhesive.

Tables 2 to 6 also show the results of the above test for evaluation of press formability, spot weldability and adhesion. Table 2
6, the following matters are clear. (1) In the case where the plating type of the zinc-based plated steel sheet is the same, the one in which the Fe—Ni—Zn-based metal film is not formed (Comparative Examples 1, 12, 14, 16, 18, 20, and 2)
When comparing 2) with an example in which an Fe-Ni-Zn-based metal film within the scope of the present invention is formed, the press formability, spot weldability and adhesiveness are all inferior. This result is the same regardless of the plating type.

(2) Even if a Fe—Ni—Zn-based metal film is formed, when the total amount of the Fe content and the Ni content in the film is out of the range of the present invention (Comparative Example 2) The press formability, spot weldability and adhesiveness were all inferior to those of the examples. When the total amount of the Fe content and the Ni content is out of the range of the present invention (Comparative Example 3), the press formability, the spot weldability, and the adhesiveness are comparable to those of the examples. However, the chemical conversion property deteriorated.

(3) Even if a Fe—Ni—Zn-based metal film is formed, the ratio of Zn / Fe + Ni in the film is out of the range of the present invention (Comparative Example 10), or Fe— When a Ni-based metal film is formed (Comparative Examples 9, 13, 15, 17, 19, 21, and 23)
Are inferior in press formability. On the other hand, Zn /
When the ratio of Fe + Ni is large outside the range of the present invention (Comparative Example 11), the press formability is poor.

(4) Even if a Fe—Ni—Zn-based metal film is formed, the ratio of Fe / Fe + Ni in the film is small outside the range of the present invention (Comparative Examples 5 and 6), or
In the case where a Zn-Ni-based metal film containing no is formed (Comparative Example 4), the adhesiveness is poor. On the other hand, when the ratio of Fe / Fe + Ni in the coating is out of the range of the present invention (Comparative Examples 7 and 8), the spot weldability is poor.

On the other hand, (5) All of those within the scope of the present invention (Examples 1 to 57) are excellent in all of press formability, spot weldability and adhesiveness.

[0050]

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.
The i-Zn-based metal film is harder than the zinc or zinc alloy plating layer and has a high melting point, so that the sliding resistance between the plating layer surface and the press mold during press molding is reduced, This has the effect of improving the continuous spotting property in spot welding. 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 galvanized steel sheet excellent in press formability, spot weldability, and adhesion, and an industrially extremely useful effect is provided.

[Brief description of the drawings]

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

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

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

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

[Explanation of symbols]

 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 N Pressing load F Sliding Resistance P Tensile load

Continuing on the front page (72) Inventor Ritsutaka Sakurai 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (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-7-3417 (JP, A) JP-A-7-145469 (JP, A JP-A-57-47890 (JP, A) JP-A-59-173289 (JP, A) JP-A-10-30199 (JP, A) JP-B-62-5239 (JP, B2) JP-B-7-1 103474 (JP, B2) JP-B-63-20316 (JP, B2) JP-B-7-103475 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) C25D 3/00-7 / 12 C23C 2/00-2/40 C23C 28/00-30/00

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein at least one surface of the plating layer has F
A galvanized steel sheet having an e-Ni-Zn-based metal film formed thereon, wherein the total of the Fe content and the Ni content in the Fe-Ni-Zn-based metal film is 10 mg / m ² or more and 1500 or more.
mg / m ² or less, and the Fe-Ni-Z
Fe content (mg / m ² ) and Ni content (m
g / m ² ), the ratio of the Fe content (mg / m ² ) to the sum of the Fe content (mg / m ² ) is in the range of 0.05 to 0.9, and Content (mg /
m ²⁾ and Ni content (the ratio of mg / m ²⁾ and the Zn content to the sum of (mg / m ²⁾ is zinc, characterized in that in the range of 0.01 to 1.6 Plated steel sheet.