JPH05171402A - Roll with corrosion resistance to molten metal - Google Patents

Abstract

PURPOSE:To fill even micropores and microcracks in a roll with a pore sealing agent by subjecting the roll to pore sealing treatment with a product obtd. by hydrolyzing and condensing tetraalkoxysilane and trialkoxysilane. CONSTITUTION:Pores and cracks in a thermally sprayed ceramic layer are sealed with a product obtd. by cohydrolyzing and condensing Si(OR<1>)4 and R<2> Si(OR<3>)3 under selected synthesis conditions of the amt. of water added, temp., a catalyst, etc. Corrosion resistance to a molten metal can be imparted to a roll thermally sprayed with ceramics by subjecting the roll to pore sealing treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roll having corrosion resistance to molten metal, and more particularly to a roll having a sealed ceramic sprayed coating showing excellent durability and corrosion resistance when immersed in a molten metal such as molten zinc. Regarding rolls.

[0002]

2. Description of the Related Art In a continuous hot-dip galvanizing line for steel sheets, a roll sprayed with a metal having corrosion resistance to hot-dip zinc is used, but the intermetallic compound of iron-zinc present in the zinc bath adheres to the roll. However, there is a drawback in that the steel plate is flawed.

On the other hand, when the ceramic is sprayed on the roll, the intermetallic compound does not adhere to the ceramic, so that the above-mentioned steel plate flaw is prevented. However, since the ceramic sprayed coating has through-pores or cracks that reach the substrate, when the ceramic spray-roll is immersed in a zinc bath, molten zinc reaches the roll substrate through the through-pores and cracks, reacts with the base metal and There is a problem that a compound is generated to push up the thermal spray coating, and finally the thermal spray coating is peeled off.

In order to make up for this drawback, many methods for sealing the thermal sprayed ceramic layer have been proposed. That is, Al,
A method of impregnating an alkoxy metal such as Zr, Ti or Si and then cracking it to form an oxide (Japanese Patent Laid-Open No. 52-77).
116, JP-A-52-82913), a method of impregnating a metal alkyl compound, an alkoxy compound and the like, cracking, heating to a high temperature to diffuse and seal the pores (Japanese Patent Publication No. 59-1274).
7), a method of performing a pore-sealing treatment using a colloidal solution of silicic acid anhydride (Japanese Patent Laid-Open No. 63-100169), a ceramic membrane having pores is impregnated with a metal alkoxide, and then immersed in a water / alcohol solution for hydrolysis and heat drying. To seal the pores (JP-A-2-271512), a method of sealing the sprayed layer with a silicone resin (JP-A-54-46145), ethyl silicate or silica obtained by hydrolyzing ethyl silicate. A method in which fine alumina is added to a suspension to form a slurry and the slurry is impregnated to seal the pores (Japanese Patent Application Laid-Open No. 57-57287).
-70275) and the like are disclosed.

[0005]

However, when the alkoxysilane monomer is dissolved alone or in the form of a mixture in a suitable solvent to impregnate the pores and cracks of the sprayed coating,
These alkoxysilanes vary depending on the compound,
For example, in the case of methyltriethoxysilane, 143
C., tetraethoxysilane has a boiling point of 165.5.degree. C., and methyltributoxysilane has a boiling point of 134.degree. C. at 20 mmHg. 59-12747 and JP-A-5
The method of impregnating a monomer as in 7-70275 has a problem that the impregnated monomer is evaporated during the heat treatment and a sufficient effect cannot be obtained. On the other hand, as in JP-A-57-70275, when finely powdered alumina is mixed with ethyl silicate that has been hydrolyzed under the condition that precipitation of silica occurs and it is used as a slurry, the fine pores of the sprayed coating are sufficiently There is a problem that it is difficult to seal the holes.

An object of the present invention is alumina, zirconia,
The present invention provides a roll having excellent corrosion resistance to molten metal by sealing pores and cracks existing in a ceramic sprayed coating such as titania.

[0007]

According to the present invention, a ceramic-sprayed roll is impregnated with a cohydrolysis condensate of a tetraalkoxysilane represented by Chemical formula 1 and a trialkoxysilane represented by Chemical formula 2, and thereafter. A roll having corrosion resistance to molten metal, which is characterized in that pores and cracks in a ceramic sprayed layer are sealed by being heat-cured.

[0008]

Embedded image Si (OR ¹ ) _{4 wherein} R ¹ represents an alkyl group having 1 to 4 carbon atoms.

[0009]

Embedded image R ² Si (OR ³ ) _{3 wherein} R ² is a hydrocarbon group having 1 to 6 carbon atoms, and R ³ is 1 to 1 carbon atoms.
4 represents an alkyl group.

According to the present invention, a ceramic-sprayed roll is impregnated with a mixture of a tetraalkoxysilane hydrolyzed condensate represented by Chemical formula 1 and a trialkoxysilane hydrolyzed condensate represented by Chemical formula 2. A roll having corrosion resistance to molten metal, which is characterized in that pores and cracks in the ceramic sprayed layer are sealed by heat curing thereafter.

[0011]

Embedded image Si (OR ¹ ) _{4 wherein} R ¹ represents an alkyl group having 1 to 4 carbon atoms.

[0012]

Embedded image R ² Si (OR ³ ) _{3 wherein} R ² is a hydrocarbon group having 1 to 6 carbon atoms, and R ³ is 1 to 1 carbon atoms.
4 represents an alkyl group.

[0013]

The inventor of the present invention has made extensive studies to solve the above-mentioned problems, and as a result, using a hydrolyzed condensate of tetraalkoxysilane and trialkoxysilane, a ceramic-sprayed roll is subjected to sealing treatment to obtain a molten metal. Therefore, a roll having corrosion resistance has been obtained.

According to the invention, what is used as the sealing agent is a solution of the following:

(1) Hydrolyzed condensate of tetraalkoxysilane represented by Chemical formula 1

[0016]

Embedded image Si (OR ¹ ) _{4 wherein} R ¹ is methyl group, ethyl group, isopropyl group, n-
Propyl group and various butyl groups (2) Hydrolyzed condensate of trialkoxysilane represented by Chemical formula 2

[0017]

Embedded image R ² Si (OR ³ ) _{3 wherein} R ² is a hydrocarbon group having 1 to 6 carbon atoms, such as an alkyl group such as a methyl group or an ethyl group and a phenyl group, R ³
The same alkyl group as R ¹ in Chemical formula 1 In the above hydrolysis condensation, water is added to an alkoxysilane such as tetraalkoxysilane or trialkoxysilane alone or mixed, and the mixture is stirred in the presence of a catalyst such as hydrochloric acid or acetic acid. While heating, the temperature is increased. The alcohol produced at this time is refluxed. Further, the hydrolysis condensation is controlled to the extent that silica is not deposited by controlling the degree of condensation. Each of the various alkoxysilanes may be hydrolyzed and condensed alone, or may be mixed and then cohydrolyzed and condensed.

The hydrolysis and condensation of the alkoxysilanes such as tetraalkoxysilane and trialkoxysilane to be used occur through a complicated process. When an alkyltrialkoxysilane is shown as an example,

[0019]

Embedded image RSi (OR ′) ₃ + H ₂ O → RSi (OR ′) ₂ (OH) + R′OH RSi (OR ′) ₂ (OH) + H ₂ O → RSi (OR ′) (OH) ₂ + R ′ OH RSi (OR ′) (OH) ₂ + H ₂ O → RSi (OH) ₃ + R′OH 2RSi (OH) ₃ → RSi (OH) ₂ 0 (OH) ₂ SiR + H ₂ O (RSi (OH) ₂ ) ₂ O + RSi (OH) ₃ → RSi (OH) ₂ O (OH) ₂ SiO (OH) ₂ SiR →→→ (RSiO ₃ ≡) _n (where R and R'represent an organic group such as an alkyl group). To form a siloxane network and gelate.

As is well known, this reaction can be controlled by the synthesis conditions such as the amount of water added, temperature, catalyst, etc. By selecting appropriate conditions, it is easy to impregnate the pores and cracks of the sprayed layer and suitable for sealing. A condensate can be provided.

For impregnation of pores and cracks of the sprayed layer, alcohol such as ethyl alcohol, i-propyl alcohol and n-butyl alcohol is added as a solvent to the hydrolyzed condensate to form a uniform solution, and the viscosity and surface tension are increased. It can also be done more effectively by controlling.

The reason why tetraalkoxysilane and trialkoxysilane are particularly selected as the alkoxysilane is not so clear, and dialkoxysilane can be used. However, when dialkoxysilane is used, the alkyl group in the siloxane network is used. A large amount of organic groups such as groups will remain, and when immersed in a high temperature molten metal, it decomposes to generate more gas, leaving pores and peeling of the sprayed layer, which is not preferable.

Although it is possible to carry out the sealing by using a part of the alkoxysilane instead of acetoxysilane, acetic acid produced in the hydrolysis condensation of acetoxysilane is
It may react with the metal that is the roll base material to generate rust, which is not preferable.

Impregnation of the hydrolyzed condensate of alkoxysilane into the sprayed layer can be carried out by usual brush coating, spray coating, dipping or the like. The impregnation can be performed more effectively by degassing the roll under vacuum and then immersing the roll in the hydrolyzed condensate solution of the alkoxysilane for impregnation.

The roll impregnated with the hydrolyzed condensate of alkoxysilane is preferably heated relatively slowly to evaporate and remove the solvent, water, and alcohol produced by hydrolysis, and finally at 100 to 300 ° C. Holding for a few minutes to a few hours gives good results.

In some cases, it is also effective to repeat the steps of impregnation to drying and heating twice or more in order to achieve more complete sealing. As a matter of course, in the course of this heating and drying, the hydrolysis and condensation of the alkoxysilane further proceed to form a gel, and an extremely strong dense sealing treatment of the polysiloxane is performed.

[0027]

EXAMPLES The present invention will be described more specifically with reference to examples, but the examples do not limit the scope of the present invention.

Zirconia was sprayed to a thickness of 100 μm on an iron round bar having a diameter of 40 mm and a length of 500 mm to obtain a test roll. This was subjected to a sealing treatment as described below.

100 parts by weight of methyltriethoxysilane,
Add 50 parts by weight of tetraethoxysilane to 50 parts by weight of hydrochloric acid.
40 parts by weight of water in which 0 ppm was dissolved was added dropwise at room temperature with stirring, the temperature was raised to 80 ° C., co-hydrolysis condensation was carried out under reflux for 2 hours, and then cooled to room temperature, and 1-n-butanol was added.
A uniform impregnating liquid was prepared by adding 100 parts by weight. The test roll was immersed in this impregnating solution for 10 minutes and left for 30 minutes to impregnate the pores with the solution. Thereafter, the temperature was gradually raised in the air over 30 minutes and the temperature was raised to 150 ° C. for 30 minutes. Further, the steps of dipping to heat treatment were repeated three times to obtain a test roll in which pores and cracks were sufficiently sealed.

When the cross section of the sprayed layer of this roll was observed by EPMA, it was observed that silicon penetrated into the fine pores inside. This roll was immersed in a continuous hot-dip galvanizing line, and after 30 days, the morphological change of the surface was observed. Table 1 shows the morphology of the sprayed surface after immersion in a zinc bath.
In the case of the sealing treatment, the film was not peeled off and the adhesion of the iron-zinc intermetallic compound was not observed. On the other hand, in the case where the sealing treatment was not carried out, the film was partly peeled off, and the intermetallic compound was further adhered thereto.

Using a test plate subjected to the same type of thermal spraying as described above, the reliability of the sealing treatment was evaluated by the ferroxyl test method among the porosity test methods of the ceramic thermal spray test method (JIS H8666). The ferroxyl test results are shown in Table 2.
Shown in. 0.5 pieces / cm ² without sealing treatment
While the spots of No. 1 were observed, none of them had been subjected to the sealing treatment, indicating that the sealing was certainly performed.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

As described above, according to the present invention, pores are sealed by performing a pore-sealing treatment on a ceramic-sprayed roll using a hydrolyzed condensate of tetraalkoxysilane and trialkoxysilane. There is an effect that you can. This is because by using the hydrolyzed condensate of tetraalkoxysilane or trialkoxysilane, the evaporation loss of these alkoxysilanes is virtually zero during the heat treatment after impregnation, and the fine pores and cracks in the ceramic sprayed layer are eliminated. This is because it is possible to sufficiently impregnate the pore-sealing agent.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michio Kosai 4-1-2-4 Kaginonishi, Joto-ku, Osaka City Asahi Chemical Industry Co., Ltd.

Claims (2)

[Claims] 1. A roll which has been subjected to ceramic spraying,
Is impregnated with a co-hydrolysis condensate of a tetraalkoxysilane represented by and a trialkoxysilane represented by Chemical formula 2,
A roll having corrosion resistance to molten metal, which is characterized in that pores and cracks in the ceramic sprayed layer are sealed by heat curing thereafter. Embedded image Si (OR ¹ ) _{4 wherein} R ¹ represents an alkyl group having 1 to 4 carbon atoms. Embedded image R ² Si (OR ³ ) _{3 wherein} R ² represents a hydrocarbon group having 1 to 6 carbon atoms, and R ³ represents an alkyl group having 1 to 4 carbon atoms. 2. A ceramic-sprayed roll having the chemical formula 1
By impregnating a mixture of the hydrolyzed condensate of tetraalkoxysilane represented by the formula 2 and the hydrolyzed condensate of the trialkoxysilane represented by Formula 2, and then curing by heating, the pores and cracks in the ceramic sprayed layer are sealed. A roll having corrosion resistance to molten metal, characterized by being subjected to hole treatment. Embedded image Si (OR ¹ ) _{4 wherein} R ¹ represents an alkyl group having 1 to 4 carbon atoms. Embedded image R ² Si (OR ³ ) _{3 wherein} R ² represents a hydrocarbon group having 1 to 6 carbon atoms, and R ³ represents an alkyl group having 1 to 4 carbon atoms.