JPS6070199A - Production of stainless steel sheet colored on one side - Google Patents

Abstract

PURPOSE:To produce easily a stainless steel sheet colored on one side by dipping a stainless steel sheet in a coloring bath to color both surfaces thereof then removing the coloring layer from one side and subjecting the surface to a surface hardening treatment. CONSTITUTION:The surface of a stainless steel is degreased and cleaned and thereafter the steel sheet is dipped into a coloring bath consisting of an aq. mixed soln. composed of sulfuric acid, chromic acid or chromate to form a coloring film on both surfaces. A roll which consists of nylon or polyester synthetic fibers, has the surface consisting of an elastic material and is stuck with abrasive grains of alumina or silicon carbide on the surface is rotated to contact with the coloring layer on one side of the colored stainless steel plate thereby removing the soft coloring layer and exposing the base metal of the stainless steel. The stainless steel sheet is then subjected to a cathodic electrolytic treatment in a hardening bath which is mixed acid bath composed of chromic acid and phosphoric acid. The soft coloring layer on one side is thus hardened.

Description

[Detailed Description of the Invention] 3. Industrial Field of Application The present invention relates to a method for manufacturing a stainless steel plate in which only one side of the stainless steel plate is colored and the other side is not colored, that is, the stainless steel plate is left as a stainless steel base. It is.

3.2 Prior Art Various methods have been studied for coloring stainless steel sheets, but the Birmingham laboratory of International Nickel Co., Ltd. (abbreviated as Inco Ltd.) in the United Kingdom has developed a coloring control method for coloring stainless steel sheets with good reproducibility. As a method, JP-A-1973-
Since the method described in Japanese Patent Application Laid-open No. 11243 was invented as a hardening treatment method for colored coatings, it has been produced on an industrial scale, and colored stainless steel sheets have been used for bathtubs and sinks. It has come to be widely used for kitchen appliances such as kitchen appliances, entrance doors of apartments, roofs of buildings, and exterior walls of buildings.

In the method invented by Inco, the so-called Inco method, colored stainless steel sheets are manufactured through the steps of degreasing, coloring, and hardening. The main manufacturing method is batch coloring using cutting cloth, 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, A4 finish, halbrite finish, shot finish, etc., and the surface finish is suitable depending on the use and purpose for which the colored stainless steel sheet is used. A material with a suitable surface finish is selected.

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 plyte annealing finishing, the side with good gloss and no unevenness or flaws is the finished product side, and some poor gloss, unevenness, or flaws are allowed on the back side.

Such stainless steel sheets are first immersed in a coloring bath and colored using a batch or continuous method, but the colored film is extremely soft and easily scratches or peels off due to friction. Furthermore, when colored stainless steel sheets are stacked or colored stainless steel strips are rolled up, there are drawbacks 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, cathodic decomposition treatment is performed in a hardening bath such as a mixed acid bath of chromic acid and phosphoric acid to make the colored film hard and durable. Such a hardening treatment eliminates the aforementioned drawbacks. However, since coloring is done by simple dipping treatment, both sides of stainless steel plates are colored, whereas hardening treatment is done by electrolytic treatment in which electrodes face the product side in a hardening bath, so the back side is hardened. Generally, no treatment is performed at all, or only a slight hardening treatment is performed due to the current passing through, and the colored film is not sufficiently durable for practical use.

Colored stainless steel sheets produced through hardening treatment are then subjected to mechanical processing such as bending, drawing, spot welding, seam welding, or bonding with adhesives to form the desired product. However, since the back 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 in spot welding or seam welding than double-sided uncolored stainless steel plates and single-sided colored stainless steel plates (the colored film on the back side has been removed by polishing). There are problems such as: - The range of appropriate welding conditions is narrow; - Dust accumulates on the electrode, impairing workability; - Poor adhesion after welding; and - Depending on the steel type, the corrosion resistance of the welded part decreases.

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, welded products suffer from the effects of heat during welding, and the heat-affected zone becomes a different color from the area that is not affected by heat, resulting in the 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.

3.3 Purpose of the Invention The object of the present invention is to provide a method for manufacturing a stainless steel plate (5) colored on one side, which solves the drawbacks and problems of a stainless steel plate colored on both sides.

3.4 Structure and operation of the invention The present invention involves coloring a stainless steel plate by immersing it in a coloring bath consisting of a mixed aqueous solution of sulfuric acid and chromic acid or chromate.
The method of curing the colored film by immersing the sheet in a hardening bath is characterized in that the colored film on the back surface of the colored stainless steel sheet taken out from the coloring bath is mechanically removed, and then the sheet is immersed in a hardening bath for hardening treatment. shall be.

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. Further, 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 grid can also be used.

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 is a roll having a three-dimensional structure (6) on its surface.

When polishing with sandpaper, puff, 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.

Further, since it is easy to clog, the polished surface changes, and the life of the abrasive is shortened, which is not preferable.

On the other hand, when a roll whose surface is made of an elastic material is rotated while in contact with the steel plate surface, when the roll is pressed against the steel plate surface, the load is uniformly applied to the entire steel plate surface due to the spring effect. Less likely to wear out. 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 come out one after another, resulting in stable polishing power and a polished surface without clogging. 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 material 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 N-colored stainless steel plate is said to be mechanized. 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 step of removing the colored film is performed after the curing process, depending on the cathode electrolytic conditions during the curing process, current may also be applied to the back surface, resulting in the curing process. As a result, polishing workability deteriorates.

3.5 Example Examples of the present invention will be described below.

Example 1 A mixed acid of 250 g/l of chromic acid and 500 g/l of sulfuric acid was kept at 100°C and a 5US304 bright coated with a board thickness of 0.3 mm and a board width of 80 cm was placed in a coloring tank with a dipping roll interval of 1.5 m. Annealed stainless steel strip line speed 1.1m
The immersion was continued at a rate of 1/min to obtain a blue colored stainless steel strip. Next, this colored stainless steel strip is led to a washing tank, and at the same time as it is washed with water, Scotch prite (as one of the elastic bodies formed by adhering nylon and polyester synthetic fibers provided in the washing tank with an adhesive) is introduced. sumitomo 3
A roll (standard: 5A-V) formed using
F, GP wheel) is pressed against the back surface of the colored stainless steel strip, and at the same time, the colored film is polished and removed by applying 2000 rotations/rotation so that the rotation is in the opposite direction to the advancing direction of the steel strip. did. Next, in a hardening tank with a 1 m spacing between the immersed rolls, the steel strip was hardened by cathodic electrolysis at a current density of 2 A/dm, then washed with water, dried, and rolled up to produce a single-sided colored stainless steel strip. At the same time, as a comparison material, a colored stainless steel strip was obtained in which only the front side was hardened without removing the colored film on the back side, but the back side was not hardened. This invention (9) The brightly treated material and the comparison material were stacked one on top of the other so that the back side was inside, and were directly spot welded (welding conditions: two-electrode tip diameter 2.8 mm, welding current 2600 amperes, pressure (120 kg, welding time: 3 seconds), spot welding was performed continuously.

When this welding material was examined for peel strength at the weld by a tensile test, it was found that the comparative material peeled from the 470th weld point, while the inventive treated material did not peel from the 500th weld point. , fractured from the base metal around the weld.

Example 2 A SUS 304 ply annealed steel plate with a length of 1000 mm, a width of 800 wn, and a thickness of 0.6 mm was immersed in a batch coloring tank containing a coloring solution having the same composition as in Example 1 at 80°C for 10 minutes and 20 seconds. As a result, a gold-colored stainless steel plate was obtained. Next, it was washed with water and dried. Next, the colored stainless steel was placed and fixed with the back side facing up on a table with 20 m thick felt glued to a 0.3 s+ mild steel plate, and Scotchprite (trademark of Sumitomo 3M Company) )
The endless belt (10) (standard: 5 A-VF) was brought into contact with the platform, and the platform was pushed up using hydraulic pressure, and while a load was applied between the colored stainless steel plate and the endless belt, the platform was moved up to 25 m with the endless belt stationary. The colored film was polished and removed by moving at a speed of 1 minute. Then in a hardening treatment tank 0.5 A/
After performing a hardening treatment for am2.10 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 comparison material were stacked one on top of the other with the back side facing inside, and were directly spot welded (m contact conditions: electrode tip tip diameter 4.
．． 0, welding current 4700 amperes, pressure 230 K
When the tensile strength of the welded part was examined by continuous welding (welding time: 5 seconds), the comparison material peeled from the welded part at the 457th welding point, whereas the inventive treated material peeled from the base metal even at the 500th welding point. was broken, and there was no peeling 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 by CAS S test (JISD020
1-1971), that is, 0.26 g in 5-ti saline solution 11
A solution prepared by dissolving cuprous chloride of The following notice was given.

Treated material of the present invention Comparative material Material of Example 1 Less than 5% 60% Material of Example 2 Less than 596 30 3.6 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 in which a 7n color film that has not been hardened is present.

Patent applicant Nippon Steel Corporation Procedural amendment (voluntary) January 9, 1980 Director of the Patent Office Mr. Kazuo Wakasugi■, Indication of case 1982 Patent Application No. 178203 2, Title of invention Colored on one side Stainless steel sheet manufacturing method 3, relationship with the case of the person making the amendment Patent applicant Takeshi, representative of Nippon Steel Corporation, 2-6-3 Otemachi, Chiyoda-ku, Tokyo (665) 1) Yutaka 6, subject of amendment Column for detailed explanation of the invention in the specification (1) (Jr%) 7. Contents of amendment (1) Page 2 of the specification, lines 6 to 7 “JP-A-49-21339
"No." is corrected to "Unexamined Japanese Patent Publication No. 46-7308."

(2)

Claims (2)

[Claims] (1) A single-sided colored stainless steel plate, which is a method of coloring a stainless steel plate by sequentially immersing it in a coloring bath and a hardening bath, in which a colored film on the back side of the stainless steel plate that has come out of the coloring bath is removed, and then hardening treatment is performed. manufacturing method. (2) The means to remove the colored film is to rotate a roll whose surface is made of an elastic material on the surface of the steel plate! A method for manufacturing a single-sided colored stainless steel sheet according to claim 1.