JPH10258370A - Pre-coated metal plate having excellent formability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the pre-coated metal plate(PCM) capable of executing beautiful forming without generating the breakage of material and peeling of a coat at the time of forming. SOLUTION: In this PCM, two same PCMs of 30 mm in width superposed so that surfaces become the outside are held with a flat plate of die and the projecting die for draw beads having the half circular column type projecting part of 8 mm dia. and pressed with the load of 900 kg. When these two PCMs are simultaneously drawn from the dies, the drawing load is >=80 kg to <250 kg in average, and moreover peeling of the coat is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precoated metal sheet having excellent formability when used for home electric appliances and building materials.

[0002]

2. Description of the Related Art In the fields of building materials, home appliances, sundries, automobiles, etc., a pre-painted metal plate (pre-coated metal plate: PCM) is used instead of the conventional post-coating method of forming and assembling and painting a metal plate. ) Is preformed and formed into a product by joining. When molding a PCM, the material and clearance of the mold are properly selected, and even if the mold and the coating film are rubbed, damage to the coating film, peeling of the coating film, breakage of the material, etc. may occur. Need not be. Also,
If the coating film itself is not selected to have good slipperiness, the mold and the coating film will squeeze during the molding process, and especially the drawing ratio will be 1.5.
In the case of forming work including the above severe drawing, the material frequently breaks. On the other hand, if the sliding property of the coating film is too good, the pressing of the flange portion at the time of molding becomes difficult, and the molded portion may be wrinkled or even molded.

[0003]

However, there has been little knowledge about how much the slip property of a coating film can be controlled to perform an appropriate molding process. It can be said that material breakage does not occur in the case of PCM having a low coefficient of friction of the coating film to some extent, but there is no guarantee that the coating film will not peel during molding. An object of the present invention is to provide a PCM that can surely perform beautiful molding.

[0004]

In order to achieve the above object, the physical properties of the coating film are defined by a method capable of simultaneously evaluating the slipperiness of the coating film and the adhesion of the coating film. It was thought that the physical properties of the PCM coating film should be controlled. Therefore, PCM coated with various paints was subjected to an actual press with a drawing ratio of 2.1, and the presence or absence of peeling of the coating film or material breakage was examined.
The present invention has been completed by comparing these results with a drawing load when the precoated metal sheet is pulled out between a flat mold and a convex mold for draw beads and the form of the coating film after the drawing. Was.

According to the present invention, two identical precoated metal plates each having a width of 30 mm are superimposed on each other so that the front surface thereof is on the outside, and a flat die and a semi-cylindrical convex portion of 8 mmφ are provided. When the two precoated metal plates are simultaneously pulled out from the mold with a load of 900 kg, the average of the pulling load is 80 kg or more and less than 250 kg, and the peeling of the coating film is not caused. It is a precoated metal sheet excellent in molding workability, characterized in that it does not occur.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an evaluation method for defining physical properties of a coated film of a precoated metal sheet of the present invention will be described.
As described above, the same PCM is evaluated by being overlapped so that the front surface is outside. This is so that the same pulling load and the same peeling form are exhibited regardless of the back surface of the PCM. By observing the painted surface after pulling out the sample and rubbing against the convex mold, the galling property can be evaluated, and the obtained pulling load is nothing but the slipperiness of the surface to be measured. Therefore, this evaluation method can be said to be a method capable of simultaneously evaluating the slipperiness and the adhesion of the coating film.

[0007] PCM which does not fall within the range specified by this evaluation method cannot perform good molding. If the average of the pulling load is less than 80 kg, the PCM itself slips between the punch and the die and cannot be formed even if the pressing pressure during molding is increased. Alternatively, beautiful molding cannot be performed due to wrinkles on the side surface of the molded body. If the average of the pulling load is 250 kg or more, the mold and the PCM coating film are squeezed, and material breakage occurs during molding. In addition, no matter what the pulling load is, if the coating film after peeling is peeled off, the coating film peels off even in actual processing.

In order to make the physical properties of the coating film fall within the specified range, it is useful to improve the adhesion between the original plate and the paint constituting the PCM and the cohesive force of each layer. Further, in order to improve the slipperiness of the coating film, it is useful to add wax to the paint to such an extent that the adhesion of each layer does not decrease.

The metal sheet as the base material of the present invention includes cold-rolled steel sheets, hot-rolled steel sheets, various types of plated steel sheets (for example, zinc-plated, zinc-alloy-plated, tin-plated, lead-plated, aluminum-plated, chromium-plated steel sheets), stainless steel A plate, a titanium plate, an aluminum plate or the like can be used, and these may be used as they are or after being subjected to a normal chemical conversion treatment. Further, in order to improve the adhesion between the metal plate and the coating film, as an undercoat paint of the metal plate, for example, nylon, polyacrylic, polyethylene, polypropylene, polyester, polyurethane, epoxy, polyamide, phenol, polyolefin and the like were applied. A thing may be used.

[0010] As a resin of a coating film formed on a metal plate,
Epoxy resins, high-molecular polyester resins, epoxy-modified polyester resins, acrylic resins, urethane resins, and the like can be used.

The method for producing the PCM of the present invention includes:
In a line for manufacturing ordinary PCM, it can be manufactured by the same method as usual. For example, as a method for forming the resin coating on the surface of the metal plate, a dipping method, a curtain flow method, a roll coating method, a bar coating method, an electrostatic method, a brush coating method, a T-die method, a laminating method, and the like are used. Examples of the baking method include hot air, room temperature, near infrared rays, far infrared rays, and induction heating. The baking temperature (attained plate temperature) is generally about 150 ° C. to 260 ° C., and the attainment time is about 15 to 120 seconds. The film thickness is usually 1 to 50 μm
Is preferred.

[0012]

The present invention will be described below with reference to examples and comparative examples. All the precoated metal sheets evaluated were 0.6 mm thick hot-dip galvanized steel sheets (YP: 1
9 kg / mm ² , TS: 34 kg / mm ² , EL: 45
%)It was used. As a pretreatment, a coating type chromate treatment was performed. The coating composition on the front side consists of a polyester-based paint as a primer, a dry film thickness of 5 μm, applied by a bar coat and baked, and then a polyester-based paint as a top coat on the dry film thickness. 20 μm was applied by a bar coat and baked. At this time, those were prepared by variously changing the presence / absence of the pretreatment, the type of the primer and the resin of the top coating and the baking temperature, and the amounts of various waxes added to the top coating. As a result, Examples and Comparative Examples of the present invention in which the adhesion between the original plate and the primer, the adhesion between the primer and the top, the cohesive force of the top coating film, and the slipperiness of the coating film surface were variously produced. All back surfaces were used without being painted.

Two samples of the example and the comparative example were overlapped so that the back surfaces thereof were in contact with each other, and were sandwiched between two molds.
As the mold, a bead mold having a flat plate on one side and a semi-cylindrical convex part of 8 mmφ on the other side was used. The pressing load is 900
kg. After that, the two-layered sample was
The wire was pulled out at a speed of m / min, and the pulling load (average value) at that time was measured. Further, the state of peeling of the coating film at the portion rubbed with the convex mold was observed.

[0014] These examples and comparative examples are compared with a drawing ratio of 2.
Table 1 shows the results obtained by subjecting the press to equivalent to 1. From this result, it can be determined that the comparative example has a material breakage or a peeling off of the coating film in the actual press, but the example has a beautiful forming process.

[0015]

[Table 1A]

[0016]

[Table 1B]

[0017]

As described above, the precoated metal sheet of the present invention does not cause material breakage and peeling of the coating film.
A beautiful molding process can be performed.

Claims (1)

[Claims] 1. An identical precoated metal plate 2 having a width of 30 mm.
The sheets are stacked so that the front side is on the outside, sandwiched between a flat mold and a convex mold for a draw bead with a semi-cylindrical convex part of 8 mmφ, and pressed with a load of 900 kg. When two of these precoated metal plates were simultaneously pulled out from the meantime, the average of the pulling load was 80%.
A precoated metal sheet having an excellent moldability, which is not less than 250 kg and less than 250 kg, and does not cause peeling of a coating film.