JPS63153286A - Insulating surface-treated steel sheet having excellent heat resistance and its production - Google Patents

Abstract

PURPOSE:To obtain the title insulating steel sheet having excellent heat resistance by forming the films of the oxides of Zr and Ti on the surface of an aluminized steel sheet, etc., and then coating a soln. of the alkoxides of Al and Si thereon. CONSTITUTION:An alcoholic soln. contg. >=0.005wt% >=1 kind among the alkoxide of Zr or Ti or the metal acetylacetonate is coated on the surface of a steel sheet plated with Al or an Al-Zn alloy. The plated sheet is heated at 200-600 deg.C, and the material is dehydrated and condensed to form the film of a metal oxide. An alcoholic soln. contg. >=0.01% >=1 kind among the alkoxide of Al or Si and a metal acetylacetonate is coated on the above-mentioned film to form a film. By this method, a surface-treated steel sheet having excellent heat resistance and insulating property and good appearance is obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention forms a metal oxide film on the surface of a heat-resistant plated steel plate, such as an aluminum plated steel plate or an aluminum-zinc alloy plated steel plate, thereby improving heat resistance and electrical insulation properties. The present invention relates to a surface-treated steel sheet provided with and a method for manufacturing the same.

(Prior Art) Aluminum-based or aluminum-zinc alloy-based plated steel sheets have excellent heat resistance, and have thus far been used for various heat-resistant applications. However, in recent years, their uses have expanded beyond mere heat-resistant uses to include electrical uses where they are heated or generate heat, and heat-resistant and insulating properties have come to be required.

Conventionally, the methods of imparting heat-resistant insulation to these plated steel sheets include applying silicone polymer, silicone face, fluororesin paint, or polyimide resin paint, and forming an enamel film, which have been used in some cases. .

However, in either method, if the film thickness is set within a range that allows good workability, pinholes will occur and the insulation will be insufficient.On the other hand, if the film is thickened to eliminate pinholes, the adhesion will decrease and the steel plate There was a problem in that the cosmetic properties and heat reflection properties of the surface were impaired.

For this reason, a method of imparting heat resistance and insulation by forming an inorganic oxide film on the surface of the steel sheet has been studied. A so-called sol-del process involves adding a catalyst to cause hydrolysis and dehydration condensation to form a sol, and applying the sol to a steel plate and firing it to form a film of alumina or silica with a high specific resistance value. A method using the law is being considered.

(Problem to be solved by the invention) However, this method requires the addition of an acid catalyst such as Kumaiso acid such as hydrochloric acid or nitric acid or an organic acid to the solution in order to cause the hydrolysis and dehydration condensation reaction of the alkoxide. Therefore, if the plating layer is sensitive to acid, such as aluminum plating or aluminum-zinc alloy plating, hydrogen will be generated when applied, causing pinholes in the film. For this reason, it has been difficult to improve the insulation properties even with this method.

Furthermore, when the plating layer is corroded by acid, the appearance is impaired, and there is also the problem that the heat reflection and cosmetic properties due to gloss are reduced.

(Means for Solving the Problems) In order to solve the problem of pinholes and deterioration of appearance, the present invention applies a Zr or Ti oxide film to the steel sheet surface before applying an alkoxide solution of ^1 or Si. Form it ^l
+ The acid catalyst of the Si alkoxide solution was prevented from reacting with the Metsusa layer.

That is, the present invention forms an oxide film of Zr or Ti or both on the surface of an aluminum-based or aluminum-zinc alloy plated steel sheet, and further coats ^I, Si, or both oxides on this oxide film. 0.005% by weight or more of one or more Zr or Ti alkoxides or acetylacetonate metal salts to form a film to reduce pinholes and appearance deterioration, and to prevent the formation of Zr or Ti oxide films. By applying the alcohol solution containing the alcohol and heating it at 200 to 600°C, the formation of an oxide film of ^1 and Si can be prevented.
alkoxide or 1 of 7cetyl 7cetonate metal salt
This was carried out by applying an alcohol solution containing 0.01% by weight or more of the species or two or more species.

The reason why an oxide film of Zr, stone, or both is formed as the lower layer in the present invention is that these oxide films are resistant to acids and have excellent heat resistance and insulation properties. This oxide film has a film thickness of 0.01μ or more, preferably 0.
．． 01 to 0.1μ, generally about 0.05μ.If it is less than 0.01μ, pinholes will occur. If the coating can be formed uniformly, it may be made thicker than 0.1 .mu.m, but if the coating is made this thick, the coating will be less flexible and will be prone to cracking and peeling.

The thickness of the upper Al or Si oxide film or both is 0.
．． 0.05 μm or more, preferably 0.05 to 0.5 μm, generally about 0.1 μm. 0.05μ-
If it is less than 0, the effect on heat resistance and insulation will be reduced.
．． If the thickness is made thicker than the 5μ theory, problems like those in the lower layer will occur.

The lower oxide film is formed by applying an alcoholic solution of Zr or Ti alkoxide or acetyl 7cetonate metal salt to the steel plate and subjecting it to heating and dehydration condensation.

These compounds undergo hydrolysis and dehydration condensation reactions very quickly compared to other metal alkoxides or acetyl 7cetonate metal salts, so they usually do not require an acid catalyst, and when the alcohol solution is applied to a steel plate, it will be released in the air. The moisture easily causes hydrolysis and dehydration condensation reactions, forming a film.

Therefore, even when applied to a steel plate, it does not corrode the plating layer, cause pinholes in the coating, or change the appearance.

The alcohol solution concentration is set to a dilute concentration of 0.005% by weight or more in order to reduce the film thickness as described above.

Thermal dehydration condensation is carried out at 200 to 600°C. If the temperature is lower than 200°C, the dehydration condensation will not proceed completely and a complete oxide film will not be formed. If the temperature exceeds 600°C, the alcohol in the solvent will rapidly evaporate, causing pinpoint damage. A hole occurs.

Preferred Zr and Ti alkoxides to be applied to the lower layer include norconium isopropoxide, zirconium methoxide, zorconium isobutoxide, zirconium octylate, titanium ethoxide, titanium propoxide, and titanium butoxide. Examples of acetyl 7cetonate metal salts include zirconium acetylacetonate and titanium acetylacetonate.

Coating of these compounds is carried out by dissolving one or more of the above compounds in alcohol at o, oos weight percent or more, but the alcohol used is not particularly limited as long as it can uniformly disperse the above compounds. For example, methanol, ethanol, isopropyl alcohol, butyl alcohol, etc. are sufficient. In addition to alcohol, a low boiling point solvent such as toluene or xylene can also be used.

The solution may be applied to the steel plate by a method capable of uniformly applying the solution, such as a dipping method, a spray method, or a spin method.

The formation of the upper layer oxide film can be carried out using the conventional Sol-Del method even when forming the lower layer.As the alkoxide, aluminum ethoxide, aluminum isopropoxide, aluminum isobutoxide, aluminum 9ee-
Butoxide, methyl silicate, ethyl silicate, etc. may be used.

In order to form a film of 0.05 to 0.5 μ-, the alkoxide concentration of 81 or Si or both in the furfur solution should be 0.01% by weight or more.
In order to cause a dehydration condensation reaction, water and an acid catalyst are usually added, and the amount added is 0.01% by weight or more in the case of water and 0.001% by weight or more in the case of acid. As the acid, an inorganic acid such as hydrochloric acid or phosphoric acid or an organic acid such as acetic acid may be used.

Note that this upper layer can also be formed using an alcohol solution of an acetylacetonate metal salt of ^I or Si. When forming a film with the above thickness using this metal salt, the salt concentration, water and acid catalyst concentration, and type of acid may be the same as those for alkoxides. After the condensation reaction is sufficiently carried out, the coating can be applied in the same manner as the lower layer. In the case of alkoxides, the heating after coating on the steel plate is usually 200 to 600°C as described above.
The same procedure may be applied to this acetyl 7cetonate salt.

According to the present invention, an aluminum-based plated steel sheet such as a hot-dip or vapor-deposited aluminized steel sheet (4 to 55%)
Heat-resistant insulation can be imparted to aluminum-zinc alloy plated steel sheets such as ^1-71.

(Example) Example 1 A hot-dip aluminized steel plate with a thickness of 0.4 mm was immersed in a 0.2 sol/g isopropyl alcohol solution of zirconium acetyl 7cetonate for 15 minutes in a 1 liter Ni sonic bath in a 77-ton tank, and was immersed in a 0.2 sol/g isopropyl alcohol solution of 5 mva/g. It was pulled up at a constant speed of seconds to uniformly apply the solution. This was placed in an electric furnace at 400°C for 10 minutes, and the lower Norconi 7 film (thickness: 0.05
μ So) was formed.

On the other hand, a separately prepared IR plate was immersed in a 0.1 mol/e ethanol solution of titanium 7-cetyl 7-cetonate, pulled up at a constant speed of 1 working/second, and coated uniformly. This is 40
It was heated in an electric furnace at 0° C. for 5 minutes to form a lower titania film (film thickness: 0.04 μm).

The steel plate on which the lower layer of the Norconi 7 coating or titania coating was formed as described above and the steel plate without the coating were immersed in an ethyl silicate solution or an aluminum isopropoxide solution prepared as below, and pulled up at a constant speed. The solution was applied evenly.

(1) Ethyl silicate solution Ethyl silicate 509, ethanol 1909, water 45
9 and salt fi0.99 were mixed, and the ethyl silicate was sufficiently hydrolyzed and condensed by stirring to form a sol.

(2) Aluminum isopropoxide solution A 10091 aqueous solution of aluminum isopropoxide was heated to 80°C and stirred for 30 minutes or more to cause sufficient hydrolysis and condensation reaction to form a sol.

After coating, the film is placed in an electric furnace at 500°C for 5 minutes to form an upper layer of alumina film or silica film (It! thickness approx. 0.1 μm).
formed a ring).

The insulation properties, number of pinholes, and heat resistance of these surface-treated steel sheets were as shown in Table 1. The heat resistance was evaluated by measuring the oxidation weight gain after performing 10 cycles of heating and cooling at 600°C (the same evaluation was performed in Example 2.3 below).

Further, when the appearance was observed, the steel plate of the present invention retained its luster and had a silvery white appearance before treatment.

Table 1 Example 2 A vapor-deposited aluminum-plated steel plate with a thickness of 0.3 m + ring was degreased for 20 minutes in the same manner as in Example 1, and then immersed in a 0.1 theory of/g n-butanol solution of zirconium isopropoxide. The coating was then pulled up at a constant speed of 1 stroke/second to uniformly coat the coating. This was placed in an electric furnace at 350° C. for 10 minutes to form a lower layer of Norconi 7 skin II (film thickness: 0°04 μm).

Next, the Norfuni 7 film-formed steel sheet and the non-film-formed steel sheet were treated with methyl silicate 259 and aluminum cetyl acetonate 259. □ was immersed in a solution consisting of 2009% n-butanol, 509% water, and 1.29% nitric acid, which was subjected to hydrolysis and dehydration condensation, and was pulled up at a constant speed to uniformly apply the solution. Place in the furnace for 7 minutes to form a mixed oxide film of silica and alumina (thickness 0.1 to 0.5
A layer was formed and used as the upper layer.

The insulation properties and heat resistance of these surface-treated steel sheets were as shown in Table 2. Further, the appearance of the surface-treated steel sheet of the present invention was as good as in Example 1.

Table 2 Example 3 A ^1-Zn alloy plated steel plate with a thickness of 0.4 mm was prepared in Example 1.
After degreasing for 25 minutes in the same manner as above, immersed in a 0.1 mof/g n-butanol solution of titanium impropoxide,
The solution was uniformly applied by pulling up at a constant speed of 2 am and 1 second. This was placed in an electric furnace at 450° C. for 3 minutes to form a lower titania skin M (film thickness O, O 6 μm higher).

Next, this steel plate and the lower layer unformed steel plate were bonded to aluminum n-
Butoxide was dispersed in water with 1009/e, heated to 85°C and stirred for IIcf, then 1.49 concentrated nitric acid was added and stirred for 3 hours. An alumina film (0.2μ thick) was formed.

The insulation properties and heat resistance of these surface-treated steel sheets were as shown in Table 3. Moreover, the appearance of the surface-treated steel sheet of the present invention was the state before treatment.

Table 3 (Effects) As mentioned above (the surface-treated steel sheet of the present invention has a heat-resistant alumina and/or titania film with few pinholes formed on the lower layer, so it has excellent heat-resistant insulation properties. Since it is acid resistant, the plating layer will not be corroded even if a solution containing an acid catalyst is applied during manufacturing, and the appearance of the plating will be maintained.

Claims (2)

[Claims] (1) Forming an oxide film of Zr or Ti or both on the surface of an aluminum-based or aluminum-zinc alloy plated steel sheet, and further forming an oxide film of Al or Si or both on this oxide film. An insulating surface-treated steel sheet with excellent heat resistance. (2) Applying an alcohol solution containing 0.005% by weight or more of one or more Zr or Ti alkoxides or acetylacetonate metal salts to the surface of an aluminum-based or aluminum-zinc alloy-based plated steel sheet, After forming an oxide film of the metal by heating at 200 to 600°C, Al or S is applied on the film.
A method for producing an insulating surface-treated steel sheet with excellent heat resistance, comprising applying an alcohol solution containing 0.01% by weight or more of one or more of the alkoxides or acetylacetonate metal salts of (i).