JPS6214239B2 - - Google Patents

Description

[Detailed Description of the Invention] 1. Field of Industrial Application The present invention relates to a method for producing a single-sided colored stainless steel plate in which only one side of the stainless steel plate is colored and the other side is left uncolored, that is, the stainless steel plate is left uncolored. be.

2. Prior Art Various methods have been studied for coloring stainless steel sheets, but the Birmingham Research Institute of International Nickel (abbreviated as Inco) in the UK has developed a coloring control method for coloring with good reproducibility. The method described in JP-A-48-11243 is the method described in JP-A-48-11243, and the method for curing the colored film is described in JP-A-46-
Since the invention of the method described in Publication No. 7308 (electrolysis using a stainless steel plate as a cathode in an electrolytic solution that can precipitate Cr, such as a mixed aqueous solution of chromic acid and sulfuric acid), production has started on an industrial scale. As a colored stainless steel sheet, it has come to be widely used for kitchen appliances such as bathtubs and sinks, entrance doors of apartment buildings, roofs of buildings, and exterior walls of buildings.

The manufacturing method of colored stainless steel sheets by the method invented by Inco, the so-called Inco method, involves degreasing,
Manufactured through coloring and curing processes. The main manufacturing method is batch coloring using cutting plates, and in some cases continuous coloring is performed in which the stainless steel strip is continuously immersed in a coloring bath and a hardening bath.

The surface finishes of stainless steel sheets subjected to batch coloring or continuous coloring include bright annealing finish, hairline finish, No. 4 finish, pearl bright finish, shot finish, etc., and the uses and purposes for which they are used as colored stainless steel sheets. A suitable surface finish is selected according to the following.
Among these surface finishes, except for the bright annealing finish, it is common that only one side (finished side) of the stainless steel plate is applied, and only a light polishing treatment is applied to the other side (back side). be. In addition, even with bright annealing finishing, the side with good gloss and no unevenness or flaws will be the finished side, and some poor gloss, unevenness, or flaws will be allowed on the back side.

Such stainless steel sheets are first immersed in a coloring bath and colored using a batch or continuous method.
Since the colored film is extremely soft, it is easily scratched or peeled off by friction. Furthermore, when colored stainless steel sheets are piled up or colored stainless steel strips are rolled up, there are disadvantages such as color change in areas where contact pressure is high, and the colored stainless steel strip cannot be put to practical use as it is. For this purpose, a subsequent batch or continuous curing process is performed. That is, after coloring,
For example, the colored film is made hard and durable by cathodic electrolytic treatment in a curing bath such as a mixed acid bath of chromic acid and phosphoric acid. Such a hardening treatment eliminates the above-mentioned drawbacks. However, since the coloring is done by a simple dipping process, both sides of stainless steel plates are colored, whereas the hardening process is done by an electrolytic process in which electrodes are placed facing the product side in a hardening bath. Generally, the back side is not hardened at all, or is only slightly hardened due to the current passing through, and the colored film is not sufficiently durable for practical use.

Colored stainless steel sheets manufactured through hardening treatment are processed into the desired product by bending, drawing, spot welding, seam welding, bonding with adhesives, etc. Since the surface is also colored and the back surface has not been sufficiently hardened, problems often occur during the above-mentioned processing. For example, double-sided colored stainless steel plates require higher current for spot welding or seam welding than double-sided uncolored stainless steel plates and single-sided colored stainless steel plates (the back side has the colored film removed by polishing). There are problems such as the narrow range of welding conditions, the accumulation of dust on the electrodes, which impairs workability, the adhesion after welding is poor, and the corrosion resistance of the welded part depending on the steel type.

For this reason, after processing an uncolored stainless steel plate into a product, it may be subjected to coloring and hardening treatment. However, when coloring a product after processing, it is difficult to color the entire product in the same color if the product has a complex shape. In addition, due to the heat effect during welding, the heat affected zone of welded products has a different color from the part that is not affected by heat, and there is a problem that the entire product is not colored uniformly. It will reduce the value. Furthermore, a colored film that has not been hardened has a problem in that its corrosion resistance is inferior to that of an uncolored stainless steel sheet and a colored stainless steel sheet that has been hardened.

3. Object of the Invention The object of the present invention is to provide a method for manufacturing a stainless steel plate colored on one side, which solves the drawbacks and problems of a stainless steel plate colored on both sides.

4 Structure and operation of the invention The present invention involves coloring a stainless steel plate by immersing it in a coloring bath made of a mixed aqueous solution of sulfuric acid, chromic acid, or chromate, and then hardening it with a mixed aqueous solution of sulfuric acid, phosphoric acid, and chromic acid. A method of curing a colored film by cathodic electrolysis treatment in a bath, which is characterized by mechanically removing the colored film on the back surface of a colored stainless steel sheet taken out from the coloring bath, and then immersing it in a hardening bath for hardening treatment. .

In addition, in the present invention, the coloring treatment and hardening treatment of the stainless steel plate are performed using a means conventionally known as the Inco method, as described above.
The coloring treatment is performed by immersing the stainless steel plate in a coloring bath to give it a desired color, and the hardening treatment is performed by electrolyzing the colored stainless steel plate in the hardening bath using the steel plate as a cathode. This is done by cathodic electrolysis).

As a means for removing the colored film in the present invention, it is preferable to use a method in which a roll whose surface is made of an elastic material is rotated while being in contact with the surface of the steel plate. It is also possible to use a method of polishing with an endless belt sander or the like, or a method of polishing by projecting abrasive grains such as shot or grit.

A roll whose surface is made of an elastic material may be a three-dimensional structure made by bonding nylon or polyester synthetic fibers with an adhesive, or a roll with alumina or silicon carbide abrasive grains attached to the fiber surface. Particularly preferred are rolls whose surfaces have a three-dimensional structure.

When polishing with sandpaper, buffing, etc. with alumina or silicon carbide abrasive grains attached to the surface of paper or cloth, it is difficult to polish while applying a constant load to the surface to be polished because the abrasive material has no elasticity. This may cause wear. In addition, it is not very desirable because it tends to clog, which changes the polished surface and shortens the life of the abrasive.
On the other hand, when a roll with an elastic surface is rotated while in contact with the steel plate surface, when the roll is pressed against the steel plate surface, the spring effect applies a load uniformly to the entire steel plate surface, causing uneven wear. Hateful. In addition, if the roll surface is made of fibers with a three-dimensional structure as described above, even if the surface abrasive grains of the abrasive material wear out, new abrasive grains will come out one after another, so it will be stable without clogging. Abrasive power and a polished surface can be obtained. In addition, when polishing a colored film, it is possible to polish it with one kind of abrasive material of roughness, but it is also possible to prepare several kinds of abrasive materials with different roughness and polish them in order from coarse abrasive material to fine abrasive material. It is more efficient, the surface finish is better, and the abrasive can be used for a long time. In addition, as the roll whose surface is made of an elastic material, a brush roll in which steel wire or synthetic fibers such as nylon are applied in the form of a brush can also be used.

The colored film on the back side of the colored stainless steel plate is removed before hardening. This is because, as mentioned above, the colored film before hardening is very soft and has the property of being easily peeled off by friction, thereby increasing the efficiency of the polishing operation. If the process of removing the colored film is after the curing process,
Depending on the cathode electrolytic conditions during the hardening process, the current flows to the back surface as well, resulting in the hardening process. Therefore,
Polishing workability decreases.

5 Examples Examples of the present invention will be described below.

Example 1 A mixed acid of 250 g of chromic acid and 500 g of sulfuric acid
A SUS304 bright annealed stainless steel strip with a plate thickness of 0.3 mm and a plate width of 8 mm was placed in a coloring tank kept at 100°C with a dipping roll interval of 1.5 m at a line speed of 1.1.
Dipping was carried out continuously at a rate of m/min to obtain a blue colored stainless steel strip. Next, this colored stainless steel strip is led to a water washing tank, and at the same time as washing is performed, nylon and polyester synthetic fibers provided in the washing tank are adhered with an adhesive to form Scotchibrite, which is one of the elastic bodies. (Trademark of Sumitomo 3M Company)
(Standard: 5A-VF, GP
A wheel) was brought into contact with the back surface of the colored stainless steel strip under pressure, and at the same time it was rotated at 2,000 revolutions per minute in the opposite direction to the direction of movement of the steel strip to polish and remove the colored film. Next, in a hardening treatment tank with an immersion roll interval of 1 m, cathodic electrolysis was performed at a current density of 2 A/dm ² to perform a hardening treatment, and then,
The product was washed with water, dried, and wound up to obtain a single-sided colored stainless steel strip as a treated material of the present invention. At the same time, as a comparative material, a colored stainless steel strip was obtained in which the colored film on the back surface was not removed, only the front surface was hardened, and the back surface was not hardened. The treated materials of the present invention and the comparative materials were stacked so that the back surfaces were inside, and direct spot welding was performed (welding conditions: electrode tip diameter 2.8 mm, welding current 2600 amperes, pressure 120 kg, welding time 3).
Spot welding was performed continuously in seconds). When the peel strength of the welded part of this welded material was examined by a tensile test, it was found that the comparative material peeled from the welded part at the 470th welding point, whereas the material treated in the present invention did not peeled off from the welded part even at the 500th welded point. Fractured from the base metal around the weld.

Example 2 A bright annealed SUS304 steel plate with a length of 1000 mm, a width of 800 mm, and a thickness of 0.6 mm was placed in a batch coloring tank containing a coloring solution with the same composition as in Example 1 at 80°C.
A gold-colored stainless steel plate was obtained by dipping for 10 minutes and 20 seconds. Next, it was washed with water and dried. Next, place and fix the colored stainless steel with the back side facing up on a table with 20 mm thick felt glued to a 0.3 mm thick mild steel plate. ) endless belt (standard:
5A-VF) and push up the table using hydraulic pressure, while applying a load between the colored stainless steel plate and the endless belt, move the table at a speed of 25 m/min with the endless belt stationary to remove the colored film. was polished and removed. Then in a hardening treatment tank
After performing a hardening treatment at 0.5 A/dm ² for 10 minutes, washing with water and drying were performed to obtain a single-sided colored stainless steel plate as a treated material of the present invention. At the same time, a colored stainless steel plate was obtained as a comparative material, in which the front side was hardened without undergoing a polishing process after coloring, but the back side was not hardened. The treated material of the present invention and the comparative material were stacked so that the back side was inside, and direct spot welding was performed (welding conditions: electrode tip diameter 4.0 mm, welding current 4700 amperes, pressure 230 kg,
When continuous welding was performed (welding time: 5 seconds) and the tensile strength of the weld was examined, the comparison material peeled from the weld at the 457th weld point, whereas the material treated with the present invention
Even at the 500th point, the base metal broke and there was no separation from the weld.

Example 3 The corrosion resistance of the front surface of the treated materials of the present invention obtained in Examples 1 and 2 and the back surface of the comparative materials was evaluated using a CASS test (JIS
D0201-1971) i.e. 0.26 in 1 part of 5% saline solution
A solution prepared by dissolving 1 g of cuprous chloride and adding acetic acid to a pH of 3.0 was sprayed at a pressure of 1 kg/cm ² for 520 hours in a tank kept at 50°C, and the area where rust occurred was investigated. was as follows.

Treated material of the present invention Comparative material Material of Example 1 Less than 5% 60% Material of Example 2 Less than 5% 30% 6 Effects of the invention According to the present invention, the colored film on the unhardened surface of a colored stainless steel plate is removed. By doing so, weldability and corrosion resistance can be significantly improved compared to those with a colored film that has not been hardened.

Claims (1)

[Claims] 1. A stainless steel plate is immersed in a coloring bath consisting of a mixed aqueous solution of sulfuric acid and chromic acid or chromic hydrochloric acid,
A method of cathodic electrolytic treatment in a hardening bath consisting of sulfuric acid or a mixed aqueous solution of phosphoric acid and chromic acid, characterized in that the colored film on the back side of the stainless steel sheet that has come out of the coloring bath is removed and then hardened. A method for manufacturing colored stainless steel sheets. 2. The method for manufacturing a single-sided colored stainless steel sheet according to claim 1, wherein the means for removing the colored film is to rotate a roll whose surface is made of an elastic material on the surface of the steel sheet.