JP2593254B2 - Painted stainless steel sheet with excellent design and scratch resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated stainless steel plate, and more particularly to a coated stainless steel plate which is coated with a transparent coating and has excellent design and excellent scratch resistance.

[0002]

2. Description of the Related Art Stainless steel sheets are excellent in corrosion resistance, but recently, from the viewpoints of design and contamination resistance, products in which various paints are coated on the surface of stainless steel sheets, that is, various painted stainless steel sheets are often used. It is being manufactured. In the case of painting on stainless steel plates, there are a method of painting stainless steel plates into various molded products and then painting (post-coat type), and a method of painting in a plate-like state and processing them into various molded products (pre-coat type). .

[0003] In the latter case, the coating film undergoes considerable deformation during processing into a molded product, for example, bending or pressing, and the flexibility and adhesion of the coating film are required to be stronger than that of post coating. You. For this reason, when pre-coating a stainless steel plate, in addition to performing a washing process to remove stains on the surface of the stainless steel plate, a pre-treatment is performed on the surface of the stainless steel plate to improve the adhesion of the coating film. Is generally performed.

[0004] Pretreatment includes mechanical treatment and chemical treatment. The mechanical pretreatment is a method of giving an appropriate roughness to the surface of the stainless steel sheet by rolling with a dull roll, shot blasting, polishing using a polishing belt, or the like. Chemical pretreatment includes chemical treatment such as phosphate treatment and chromate treatment, treatment with an organic acid such as tannic acid, and treatment with an inorganic acid such as nitric hydrofluoric acid.

[0005] The pretreatment performed before painting a stainless steel plate is usually performed by combining mechanical treatment and chemical treatment. For example, JP-A-52-22517 discloses excessive pickling and reduction by a dull roll, and JP-A-57-16174 discloses a treatment with an organic acid and surface roughness adjustment by dul skin pass, shot blasting, and buff polishing. Japanese Patent Application Laid-Open No. 56-119779 proposes adjustment of surface roughness by a dull skin pass and phosphate treatment. Further, a method of performing a heat treatment in a specific gas atmosphere without performing a chemical treatment is also disclosed in JP-A-2-35967.
No. 1993.

The conventional surface roughness and the surface roughness disclosed in the above-mentioned publication include an appropriate roughness. If the surface is too rough, it is described in Japanese Patent Application Laid-Open No. 57-16174. Thus, it was recognized that the finished surface of the coating film became rough and the appearance was impaired in design. In addition, the flexibility of the coating film is adjusted by controlling the amount of the curing agent in the coating material and the baking temperature at the time of coating, but increasing the flexibility of the coating film depends on the hardness of the coating film, that is, the resistance of the coating film. On the contrary, it deteriorates from the point of the scratching property. In the case of pre-coat type coating, peeling or cracking of the coating due to processing loses the meaning of the coating, so the flexibility of the coating rather than the hardness and scratch resistance of the coating , Adhesion is more important.

[0007]

In order to paint a stainless steel plate, an opaque colored paint is generally used as shown in "Nisshin Steel Technical Report No. 49," Colored Painted Stainless Steel Plate ", pp. 107-114. In recent years, however, painting with transparent paint has been increasingly used to make use of the base of stainless steel plates.

[0008] The present invention relates to a method for coating with a transparent paint,
It is an object of the present invention to provide a coated stainless steel sheet that has the above-mentioned precoat type coating conditions and is excellent in design.

[0009]

The present invention is characterized by having a transparent coating film on a dull finish surface having a surface average roughness Ra of not less than 2.5 μm and having excellent design and scratch resistance of the coating film. Painted stainless steel plate.

[0010]

The present inventors have conducted intensive studies on the relationship between the surface roughness of a stainless steel sheet and the characteristics of a coating film when the coating is performed with a transparent paint, and have obtained the following findings. In other words, in the adjustment of the surface roughness of a stainless steel plate that has been carried out as a pre-treatment of the conventional coating, if the surface is much rougher than the conventional one, the finished surface of the opaque coating certainly has a roughened surface and the appearance is poor in design. However, in the case of the transparent coating, the reflection on the surface of the coating film and the reflection on the surface of the stainless steel plate through the transparent coating were combined, and it was found that the coating had a unique design in appearance.

[0011] In addition, they have found a new fact that the scratch resistance of the coating film is remarkably improved. By making the surface roughness of the stainless steel sheet much higher than the level conventionally used under the same paint and the same coating conditions, the scratch resistance is remarkably improved, and the adhesion of the coating film is not deteriorated. The present invention has been completed based on the above findings.

That is, according to the present invention, the surface average roughness Ra
A coated stainless steel sheet having a transparent coating film on a dull finish surface of 2.5 μm or more and having excellent design and excellent scratch resistance of the coating film. In the present invention, the reason why the surface roughness of the stainless steel plate is 2.5 μm or more in terms of average roughness Ra is that when it is less than 2.5 μm, there is almost no effect of improving the scratch resistance of the coating film.

Further, in the present invention, the type of surface finish of the stainless steel plate is limited to dull finish. This is because the surface roughness needs to be non-directional. Belt polishing is unsuitable because the surface roughness shows completely different anisotropy in the polishing direction and in the direction perpendicular thereto. In order to improve the scratch resistance of the coating film, it is necessary to increase the surface roughness in any direction. The method of making the surface of the stainless steel plate a dull finish is not particularly limited in the present invention. Rolling by dull roll, sit blasting by steel shot, glass bead, or the like is applied.

The coating of the present invention is limited to a transparent coating.
This is because, in the case of the opaque coating film, in the case of the rough surface of the present invention, the coating film surface becomes rough and the appearance is significantly poor in design.
Only in the case of a transparent coating film, the unique design of the present invention can be exhibited. The transparent coating film includes, besides colorless and transparent, a colored transparent coating film to which a small amount of a coloring pigment is added. The point is that it is only necessary that the surface of the underlying stainless steel plate can be visually recognized through the coating film.

The type of paint for forming the coating film is not particularly limited. Any material may be used as long as it forms a transparent coating film. Typical examples thereof include a fluorine resin-based paint, an acrylic resin-based paint, and a silicone polyester resin-based paint.

[0016]

Embodiments of the present invention will be described below. Example 1 A SUS 304 stainless steel plate having a thickness of 1.5 mm and adjusted to various surface roughnesses was baked with a fluororesin-based transparent paint, and the working adhesion and scratch resistance of the paint film were investigated. Table 1 shows the results. The thickness of the coating film was set to be constant at about 20 μm.

According to JIS G 3312, a 180 ° bending test was conducted with the inside bending radius of 1.5 mm and the painted surface bent outward. The coating was evaluated by observing the state of peeling of the coating film. In accordance with JIS K 5400, the scratch resistance was evaluated by performing a pencil hardness test with the damage of the coating film as a criterion.

Nos. 1, 2 and 3 of the present invention are those in which the surface roughness of the stainless steel sheet is 2.5 μm or more which is the condition of the present invention in terms of the average roughness Ra. .
Under the same paint and baking conditions as in Nos. 7 and 8, the adhesiveness of the bent portion was not reduced, and the scratch resistance of the coating film was improved by 3 or 4 ranks. Comparative Example No. 4 is an example in which the same paint as the conventional example was used, but the baking temperature was increased to 230 ° C. Baking at a higher temperature improved the scratch resistance of the coating by three ranks, but reduced the adhesion of the bent portion.

Comparative Example No. 5 is an example in which a paint having a higher proportion of a curing agent than usual was used. Coating was performed with the same baking temperature as in the conventional example. Although the scratch resistance of the coating film was improved by 4 ranks, the adhesion at the bent portion was reduced. Comparative Example N
o.6 is an example in which the roughness is higher than the level of the surface roughness conventionally used, but is smaller than the roughness condition of the present invention. In this case, no improvement in the scratch resistance of the coating film was observed.

Example 2 An acrylic resin-based transparent paint was baked at a baking temperature of 200 ° C. on a SUS 304 stainless steel plate having a thickness of 1.5 mm and adjusted to various surface roughnesses. The coating thickness after baking was kept constant at about 15 μm. Table 2 shows the results. Compared to the conventional example No. 11, the surface roughness is expressed by the average roughness Ra, which is 2.5 μm which is the condition of the present invention.
In Examples 9 and 10 of the present invention described above, the scratch resistance of the coating film was improved by two or three ranks without deteriorating the adhesion at the bent portion.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

As described above, in the prior art, it was not possible to improve the scratch resistance of the coating film without deteriorating the adhesion of the processed portion. The combination of the large dull finish surface and the transparent paint makes it possible to economically provide a coated stainless steel sheet having excellent coating resistance to scratches and high design. Further, the development of a new paint and the development of a more complicated and expensive manufacturing process are not necessary for achieving the object of the present invention, which is industrially extremely advantageous.

Claims (1)

(57) [Claims] 1. A coated stainless steel sheet having excellent design properties and scratch resistance of a coating film, characterized by having a transparent coating film on a dull finish surface having a surface average roughness Ra of 2.5 μm or more.