JP2794351B2 - Method of forming automobile body using pre-coated metal plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a lightweight automobile body made of a steel plate and an aluminum metal plate, which does not cause corrosion by dissimilar metals.

[0002]

2. Description of the Related Art In recent years, in the automobile industry, the thickness of automobiles has been reduced in order to reduce the weight of automobile bodies and to reduce fuel consumption from the viewpoint of energy saving. Furthermore, in order to ensure resistance to external loads, the steel sheet for automobiles needs to have a moderate increase in strength as the thickness is reduced. However, there is a limit in reducing the weight of the vehicle body, and there is also a limit in the strength associated therewith. Therefore, in order to further reduce the weight, it is conceivable to use an aluminum metal plate which is a metal other than the steel plate. However, it is not enough just to reduce the weight, and moderate strength and press workability are required,
The vehicle body cannot be composed entirely of aluminum metal plates, and both steel plates and aluminum metal plates can be used together. In this case, when a steel sheet and an aluminum metal sheet are mixed and used, there is a problem that there is a difference in the chemical conversion properties of the two metals, especially in the phosphating properties, and that contact corrosion occurs due to dissimilar metals. there were.

Along with this, it is necessary to establish a joining technique for dissimilar metals. For this joining technique, for example, as disclosed in Japanese Patent Application Laid-Open No. 58-163584, a light metal portion and a heavy metal portion, for example, an aluminum member are used. In an integral connection with the steel sheet, between the light metal parts, both components of the composite member consisting of a base layer and at least one different metal overlay, metallurgically bonded to the base layer by extrusion. There is a corresponding material diffusion welded technology. This method is intended to enable a steel floor to be joined to a curved aluminum side plate of an automobile body, for example.

[0004]

As described above, there is a trend to use aluminum metal plates to reduce the weight of automobiles.
However, in the case of mixed use with a steel sheet, since the same chemical conversion treatment cannot be performed on the steel sheet and the aluminum metal plate, there is a problem that after the press forming, a chemical conversion treatment is performed on another line, and then welding and painting must be performed. In addition, since the chemical conversion property is different between the steel plate and the aluminum metal plate, problems occur in paint adhesion and corrosion resistance. Further, when the steel plate and the aluminum metal plate come into contact with each other, there is a problem that at that portion, dissimilar metals come into contact and corrosion occurs. Further, in Japanese Patent Application Laid-Open No. 58-163584, it is true that a welded connection is made between one light metal portion and the other heavy metal portion, thereby forming a metal plate having different thicknesses. Butt contact is possible, but the problem of corrosion reactions due to dissimilar metal contact between light and heavy metal parts has not been solved.

[0005]

Means for Solving the Problems The inventors have conducted various studies to solve such a problem, and as a result,
It is an object of the present invention to provide a method of manufacturing an automobile body using a pre-coated metal plate which does not cause corrosion between different kinds of metals. The gist of the invention is that in a method of forming an automobile body using a steel plate and an aluminum plate, a pre-coated steel plate and a pre-coated aluminum plate are each press-formed into a body part and then joined to form a white body. A method for forming an automobile body using a pre-coated metal plate.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows a process of forming an automobile body using a pre-coated steel plate and a pre-coated aluminum plate. Here, as the steel sheet, a hot-rolled steel sheet, a cold-rolled steel sheet, and a surface-treated steel sheet by Zn or Zn alloy plating or Al or Al alloy plating can be used. In addition, the chemical conversion treatment step
As a pre-treatment, a steel sheet subjected to a degreasing treatment is subjected to a chemical conversion treatment to secure the adhesion of the coating film. The spray method, dip method, roll coating method,
There are a reaction cell method and an air-knife drawing method. These chemical conversion treatments are usually carried out continuously on the same line as the pre-coat coating in the next step, but can also be carried out in the steel sheet production line in the previous step. The pre-coating is performed by a usual coil coating line. That is, after performing the above-mentioned chemical conversion treatment, the roll coater and the curtain floor
Paint the paint with a coater etc., hot air oven, high frequency heating furnace,
Cured by infrared furnace or irradiation of radiation. Coating of primers such as epoxy, polyester, polyurethane, etc.-Topcoat of 2-30 μm and polyurethane, polyester, acrylic, vinyl chloride, etc.
It is common to apply a coating of 2 to 200 μm, but if primer coating is omitted, or a resin-based overcoat similar to the topcoat is further applied on topcoat. There is also.

On the other hand, as an aluminum plate, JIS standard 5
000 series, 6000 series and the like can be applied. As a chemical conversion treatment of an aluminum plate, a chromate treatment is most suitable from the viewpoint of compatibility with an aluminum plate and paintability. For this purpose, electrolytic chromate treatment, coating type chromate treatment, or resin chromate treatment containing hexavalent chromium ion and trivalent chromium ion, and an acrylic polymer emulsion or a water-dispersible polyester system, phosphorus After any of the acid chromate treatments, a precoat coating is performed in the same manner as the steel plate. Of course, a phosphate treatment is also applicable. Next, press-forming is performed on the vehicle body, and the above-described press-formed vehicle body component formed of a pre-coated steel plate and the vehicle-mounted press molded component formed of an aluminum plate are joined and bonded. In this case, bonding and bonding are mainly performed by using an adhesive, but the invention is not particularly limited to only the adhesive, and mechanical bonding or a combination of these bonding methods may be used. When an adhesive is used here, the adhesive may be a one-part epoxy type, a two-part type epoxy type, a one-part type urethane type, a two-part type urethane type, an acrylic type, a polyamide type, or an acrylic type combined with a primer. And a thermosetting polyester film adhesive, but are not limited thereto.

FIG. 2 is a sectional view showing an example of a bonded state between a precoated steel sheet and a precoated aluminum sheet according to the present invention.
A precoated steel sheet in which a chemical conversion coating 3 is formed on a steel sheet 1 and then an undercoat coating 4 and a topcoat coating 5 are formed, and a primer coating 4 and a topcoat in which a chemical conversion coating 7 is formed on an aluminum plate 2. -Preco with the coating film 5 formed-
This is to join the aluminum plate.

[0009]

As described above, when a steel plate and an aluminum plate are used as a pre-coated metal plate, they can be subjected to chemical conversion treatment on separate lines.
It is not necessary to make the both chemical conversion treatments the same, and treatments of a type suitable for each of the steel sheet and the aluminum sheet, such as phosphate treatment, chromate treatment, composite oxide film treatment, heavy metal replacement treatment, etc., are performed under optimal conditions. Becomes possible. Further, since the coating film on the surface of the pre-coated steel plate and the pre-coated aluminum plate has an insulating property, there is no direct contact between the steel and the aluminum, so that corrosion of different metals can be avoided.

[0010]

EXAMPLE A continuous coil coating line with a sheet thickness of 1.0
After degreasing the steel sheet having a thickness of 2 mm, a spray treatment was performed for 10 seconds using a zinc phosphate treatment liquid. An epoxy-based primer is roll-coated on a steel sheet having the zinc phosphate-treated coating with a roll coater.
Was coated with 5 μm, and baked with hot air for 30 seconds so that the reached plate temperature was 210 ° C. After cooling, a urethane-modified polyester-based top coat was applied again with a roll coater to a thickness of 20 μm, baked for 60 seconds so that the ultimate sheet temperature reached 230 ° C., and cooled to obtain a pre-coated steel sheet. This was pressed into body parts. On the other hand, an aluminum plate having a thickness of 0.8 mm is immersed in a chromate treatment bath in a coil coating line in the same manner as a steel plate, washed with water and dried to form a conversion coating composed of chromium oxide on the surface. Under the same conditions, an epoxy-based primer and a urethane-modified polyester-based topcoat were formed to obtain a precoated aluminum plate. This was pressed into body parts. Pleco pressed into body parts
The steel plate and the pre-coated aluminum plate were joined by using an epoxy thermosetting adhesive at a temperature of 200 ° C. for 10 minutes. As a result, the T-pill strength was 25 kg / 2.
Both were able to be bonded with an extremely high bonding strength of 5 mm. Subsequently, an alkyd resin-based paint was applied as a middle coat and baked to a thickness of 35 μm, and an alkyd resin-based top coat was further formed to a thickness of 40 μm to manufacture an automobile body made of a steel plate and an aluminum plate. It was confirmed that this vehicle body did not undergo any kind of metal-to-metal corrosion.

[0011]

As described above, by implementing the present invention, there is no dissimilar metal contact between the steel plate and the aluminum plate,
Therefore, a lightweight automobile body or parts having excellent corrosion resistance and no corrosion can be obtained, and the production of a lightweight automobile body by joining dissimilar metals, which is extremely industrially advantageous, has become possible at low cost.

[Brief description of the drawings]

FIG. 1 is a view showing a manufacturing process of a light-weight automobile bonding metal sheet according to the present invention;

FIG. 2 is a cross-sectional view showing a bonded state between a steel plate and an aluminum plate according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel plate 2 Aluminum plate 3 Chemical conversion treatment layer 4 Primer coating 5 Top coat coating 6 Adhesive 7 Chemical conversion coating.

Claims (1)

(57) [Claims] 1. A method for forming an automobile body using a steel plate and an aluminum plate, wherein a white body is formed by press-forming a pre-coated steel plate and a pre-coated aluminum plate to body parts, respectively, and then joining them. A method for forming an automobile body using a precoated metal plate.