JPH0210104B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to enameled stainless steel products such as building materials, kitchen utensils, bathtubs, and pipes for chemical plants, etc., and does not require any special pretreatment and can be applied to stainless steel surfaces. This invention relates to a method for producing an enamel glaze that has excellent adhesion. (Prior art and its problems) Stainless steel is rust resistant, highly corrosion resistant, and retains its shine for a long time, so it is used for architectural interior and exterior walls, kitchen products,
It is used in many areas such as bathtubs, wash basins, and vehicles. However, while stainless steel has its advantages, it is also susceptible to scratch rust, crevice corrosion caused by contact between dissimilar metals, dirt, and dirt.
It has disadvantages such as being easily attacked by Cl ^- ions and not being able to be colored freely. Therefore, various methods of enameling stainless steel have been studied in the past as a way to further enhance the properties of stainless steel and at the same time eliminate these drawbacks, but the current situation is that nothing that is fully satisfactory has yet been achieved. . In other words, in order for the enamel glaze to have sufficient adhesion to the base metal, the base metal must be sufficiently oxidized at the firing temperature of the glaze, but stainless steel is considerably oxidized at the firing temperature of normal iron enamel glazes. It was thought that good adhesion could not be achieved because the glaze was stable and did not oxidize sufficiently for the glaze to react with the base material. Therefore, in order to obtain good adhesion between stainless steel and glaze, the surface of stainless steel must be roughened mechanically or chemically. Studies have been conducted on methods of introducing special metal oxides that promote or attack the oxidation of stainless steel into the frit that makes up the glaze. As a method, for example, by mechanically or chemically providing an uneven pattern with a concave depth of 80 to 400 μm and a roughness of the concave surface of 2 to 30 μm, the stainless steel and the glaze are brought into close contact. However, it is extremely difficult to industrially form a concave roughness of 2 to 30 μm and to confirm it. Also, stainless steel is heated in advance in an oxidizing atmosphere to form an oxide film on the surface, and then immersed in an aqueous solution containing divalent nickel ions to evenly adhere the nickel ions to the oxide film. A method for strengthening the adhesion of stainless steel and glaze has been disclosed (Japanese Patent Publication No. 55-30588), but this method has a problem in that it requires two steps to pre-treat the stainless steel. (It goes without saying that sufficient adhesion cannot be obtained by mere surface roughening methods such as sandblasting, shotblasting, and chemical etching methods commonly used in the enamel industry.) There is a method of introducing 1 to 3 wt% MoO ₃ into the frit component that can be fired at a relatively low temperature (Japanese Patent Publication No. 14819/1983), but this method involves baking a transparent glaze directly onto the stainless steel once. The result is a craft-like enamel product that shows the metallic luster pattern unique to stainless steel, and its frit composition is also very specific. Furthermore, an enamel frit with good adhesion to stainless steel has been disclosed, in which 5 to 30 wt% Fe ₂ O ₃ is introduced into a glass mainly composed of borosilicate, which does not contain a fluorine component. 52-810), this method introduces a large amount of Fe ₂ O ₃ during the production of the frit, which causes significant contamination of the glass melting furnace and kiln, making it extremely uneconomical for the production of the frit. Due to the large amount of Fe ₂ O ₃ component, Fe ₂ O ₃ is precipitated in the glass matrix by repeated firing two to three times, and the glaze tends to devitrify, resulting in unstable adhesion. As mentioned above, stainless steel enamel is not yet a completed technology, and is a technical field in which further improvement is desired. (Object of the Invention) The present invention aims to improve the problems of the conventional methods as described above, and provides an enamel glaze that has extremely good adhesion to stainless steel by a relatively simple means. (Structure of the Invention) The present invention provides an enamel glaze for stainless steel characterized in that 5 to 50 parts by weight of iron oxide is added to 100 parts by weight of the frit in addition to the usual mill additives when the frit is milled. It is in the manufacturing method. (Embodiment and operation) In the present invention, in addition to the usual mill additives such as clay, silica, borax, magnesium carbonate, magnesium oxide, potassium carbonate, sodium nitrite, and water, especially Iron oxide is added as a mill additive in a proportion of 5 to 50 parts by weight per 100 parts by weight of frit. As the frit, a normal stainless steel frit can be freely used and is not particularly limited. Any amount of conventional mill additives may also be used as desired. The glaze obtained by milling is applied to a degreased stainless steel surface, and when dried and fired at 700 to 900°C, it forms an enamel layer that has excellent adhesion to the stainless steel. Since the glaze of the present invention has very good adhesion, it is sufficient to simply degrease the stainless steel surface as a pre-treatment for glazing, and it is not necessary to use conventional mechanical or chemical means. There is no need to roughen the surface. It is not clear why the addition of iron oxide as a mill additive results in an enamel glaze that has good adhesion to the stainless steel surface, but no decrease in adhesion was observed even after repeated firing. Since the glaze of the present invention contains a large amount of Fe ₂ O ₃ , it takes on a brownish color after firing. Therefore, the final product usually has a two-layer structure by further applying an upper layer of glaze. The reason why the amount of iron oxide added in the present invention is limited to 5 to 50 parts by weight is that if it is less than 5 parts by weight, the adhesion between the stainless steel and the glaze is insufficient, and if it exceeds 50 parts by weight, the fire resistance of the glaze increases and is normal. This is because firing is impossible under these firing conditions, and the adhesion between the stainless steel and the glaze is significantly reduced. Next, the present invention will be explained in more detail with reference to Examples. (Example) In carrying out the invention, the Enamel Technology Guidebook (August 20, 1980, published by the Japan Enamel Industry Association)
7 A, B, C frits (Table 1) shown in page 55, 5-10 Frit composition for steel sheet underglazing,
Same book, page 56, table 5-11, titanium frit No. 1,
No. 4 (Table 2), and also No. 1 (Table 3) of the same book, page 57, 5-14 table stand Gusuri frit were prepared.

【table】

【table】

【table】

[Table] Example 1 Frits 7-A, 7-B, and 7-C were milled according to the mill formulation shown in Table 4 to obtain glazes A and B. All mill formulations are parts by weight.

[Table] After degreasing SUS-304 stainless steel with a thickness of 0.4 mm and a size of 10 cm x 10 cm, spray glaze A evenly on one side to a coating of 4 g/10 cm x 10 cm. After drying, heat at 740℃. Baked for 4 minutes. The degree of adhesion of the obtained test piece was measured using a P, E, I adhesion tester and was found to be 98%, which was very good. Example 2 Glazes C and D were obtained by milling titanium frits No. 1 and No. 4 according to the milling proportions shown in Table 5.

[Table] Glaze B obtained in Example 1 was sprayed on only one side of SUS-430 stainless steel with a thickness of 1.0 mm and a size of 10 cm x 15 cm to give a thickness of 6 g/10 cm x 15 cm, followed by glaze C. was applied uniformly at a rate of 2g/10cm x 15cm, dried and then baked at 870°C for 3 minutes.
When observing the cross section of the obtained test piece, we found that
It had essentially a two-layer structure: a glaze layer in contact with the stainless steel and a thin opalescent layer covering it. The degree of adhesion of this test piece was measured using a P, E, I adhesion tester and was found to be 100%. Add 6g/10cm of Glaze D on top of this two-layered test piece.
The mixture was applied uniformly to a ratio of 15cm x 15cm and baked at 820°C for 3 minutes. The degree of adhesion of this test piece was measured using a P, E, I adhesion tester and was 85%, which was very good. Example 3 Glaze E was obtained by milling frit No. 1 for machine glazing according to the milling composition shown in Table 6.

[Front] Add Glaze E to a plate with a thickness of 0.6 mm and a size of 30 cm x 30 cm.
After degreasing SUS-340 stainless steel, 36g/30
It was sprayed on to a size of cm x 30 cm, dried and then baked at 820°C for 4 minutes. The degree of adhesion of the obtained test piece was measured with a P, E, I adhesion tester and was found to be 90%. On top of this test piece, 40g/30cm x 30g of glaze D obtained in Example 2 was added.
Spray to a ratio of cm and heat at 800℃ for 4 hours.
Bake for a minute. The adhesion P, E, I of the obtained test piece was measured with an adhesion tester, and it was 85%.
The surface was very smooth and beautiful. (Effects of the Invention) The present invention does not introduce Fe ₂ O ₃ into the frit, but simply uses it as a mill additive.
The manufacturing process is also easy and economical. According to the glaze obtained in the present invention, there is no need to perform any special pretreatment on stainless steel, and enameled stainless steel products with good adhesion can be obtained.

Claims (1)

[Claims] 1 When milling the frit, in addition to the usual mill additives, 5 parts by weight of iron oxide are added to 100 parts by weight of the frit.
A method for producing enamel glaze for stainless steel, characterized by adding ~50 parts by weight.