JPS6048550B2 - Corrosion-resistant paint for high-temperature molten metals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating material for forming a corrosion-resistant film at high temperatures to protect surfaces that come into contact with molten metal.

It is well known that metals exhibit significant corrosive behavior in their molten state.

Therefore, in metal smelting, melting, or casting operations, equipment surfaces that come into contact with molten metal must be made of corrosion-resistant materials. Conventionally, stainless steel materials or ceramic refractories have been used as corrosion-resistant materials for molten metal, but steel materials inevitably undergo deterioration phenomena such as annealing, oxidation, and electrolytic corrosion, and refractories suffer from corrosion during their composition. Erosion occurs when metal oxides dissociate oxygen under low oxygen pressure, diffuse into the molten metal, form molten slag, and react with the refractory.

In addition, refractory materials - L - J - π - 4 - - LL day Λ d door: Yo, L 4 - 7Li - 11n, the construction method is not only difficult, but also used for equipment with complex shapes. I can't. In view of the above circumstances, the present invention has been developed to form an inorganic sintered film that exhibits particularly good corrosion resistance against molten metal, withstands high temperatures, firmly adheres to the underlying object, and does not deteriorate over a long period of time. The aim is to provide paint. The composition of the corrosion-resistant paint of the present invention is, firstly, a substance that has excellent corrosion resistance against molten metal, that is, an inorganic compound that is substantially inert to molten metal, and has an adhesion work of 65 to molten metal.
■Blending an inorganic compound with a grade of RGLC A or higher in an amount of approximately 30 to 75% by weight in the solid content of the paint (hereinafter referred to as a specific inorganic compound), and secondly, using a powder of this substance as a coating film. A silicone resin is blended as a heat-resistant binder for stable fixation, and thirdly, the applied coating film is sintered to form a strong, dense inorganic sintered film on the underlying surface when heated. A fourth method is to incorporate a sintering accelerator and a mineralizing agent that promotes and strengthens the formation of an inorganic sintered film together with the sintering accelerator at high temperatures.

The coating material of the present invention will be explained in detail below. The selection of the specific inorganic compound used in the coating material of the present invention was made based on knowledge obtained from many experiments.
The first requirement in the composition of the corrosion-resistant paint of the present invention is that the specific inorganic compound has (1) low wettability to the molten metal, and (2) low metal leaching to the molten metal. Item (3) It is necessary that reaction products with molten metal are unlikely to be generated.

The wettability mentioned in (1) above is related to the action (work amount) of separating two phases: solid (inorganic etc. according to the first requirement above) and liquid (molten metal). is 65■Rgld, such as M
gO,. 2CaO,. SiO.

, ZrO. , TiO2, ZrO2, SjO2, SiCN
Si3N4, BN) AIN is preferable. The reason for choosing (2) with less metal leached into the molten metal is that metal oxides that form ceramics are said to have little oxygen dissociation, but they tend to self-dissociate under low oxygen pressure. Ingredients (MexOy)
02 is further dissociated. For example, Al and Mg melts have very strong reducing power, and are usually SiO2, N. O. −
SiO. of SiO. However, MgO is difficult to be reduced by molten A1, and N
. O. On the contrary, it is reduced by molten MgO. In this respect, nitrides (Sl3N,,BN)AIN) and carbides (SIC), which have no dissociated oxygen, are effective for N and Mg melts, and among metal oxides, MgON2CaO, which has less 02 dissociation. =SiO2, ZrO2TiO2
Good. (3) Those that do not generate reaction products with molten metal are listed as MgT=! P(7) reacts with MgO to form a reaction product MgO. Al2O3 (spinel), reacts with Al2O3 in Al to form Al. O3-SIO. This is to prevent the generation of MgO)2Ca0-SiO from metal oxides, as in the case of (2) above. , ZrO. , T
iO. But metal carbonization! SIC than nitride and Sl than nitride. N,,BN,. AIN is selected. Therefore, from the above, particularly desirable materials in the present invention are MgO)2Ca0-SiO2, ZrO2, TjO2,
SiC,. Si3N4, BN) AIN can be mentioned. The second requirement of the paint of the present invention, which is the use of a silicone resin as a heat-resistant binder, is due to the fact that it is used in the same way as paints using general organic polymer vehicles, such as brush painting, roller coating, etc. It is possible to use methods such as spraying and dipping, and it is possible to firmly and stably fix the paint on the substrate.Related to the third requirement mentioned below, the paint film can be heated to have a good inorganic sintering property. This is because the siloxane component of silicone resin plays an important role when transferring to the conjunctival membrane.

As the silicone resin, for example, solutions, emulsions, suspensions, etc. of methyl silicone resin, straight silicone resin mainly consisting of alkyl silicone, and modified silicone resin such as silicone polyester resin are used. The third requirement for the paint of the present invention is that a sintering accelerator be added to the paint in order to form a good inorganic sintered film. Even if the above-mentioned specific inorganic compound exhibits good corrosion resistance to molten metal, it must firmly adhere to the base and settle to form a good pore-free inorganic film, and the film must be resistant to molten metal. It is important to have corrosion resistance, and sintering/sintering accelerators play an important role in this.

As ceramic particles, SiO2 substances tend to be reduced by molten metal or to form reaction products.

However, SiO. When it becomes vitrified and becomes dense and non-porous, it becomes SiO. Even though it is a reducing component, corrosion is extremely low. For example, when in contact with an Al melt (950°C) for 3 hours, chamorous (Al2O.-SiO) is formed.
The thickness of the eroded layer is 0.18 cm in the case of porosity of 22%), whereas it is less than 0.01 crrL in case of silica glass alone. In the present invention, the silicone resin is converted into siloxane (SiO,) by heating, and this acts with the sintering accelerator to efficiently vitrify and form a sintered film. The inorganic sintered film thus formed exhibits good corrosion resistance against molten metal. The sintering accelerator is an accelerator for converting the paint film into an inorganic sintered film. That is, it acts with the siloxane (amorphous silica) produced when the silicone resin is decomposed by heating, and promotes the formation of the paint film into an inorganic sintered film. This sintering accelerator is incorporated into the paint either alone or in combination as a mineralizer. Sintering accelerator is 300
It softens around ℃ and reacts with siloxane, which is a decomposition product of silicone resin by heating, to produce a glassy melt.
The glassy melt fuses the specific inorganic substance to form an inorganic sintered film on the base.

As the sintering accelerator, feldspars, low melting point frits, water glass, etc. are used.

The mineralizing agent used as a sintering accelerator is heated to 300°C.
Substances around the area, especially SiO.

S
jO. The melting point of the substance is lowered to promote and strengthen the formation of an inorganic sintered film together with the sintering accelerator. As the mineralizing agent, hanitrides such as CaF2, Na2SiF6, NH, Cl, etc. are used.

In addition to the above-mentioned composition, flake minerals and fibrous substances such as potassium titanate, mullite, alumina, zircon, mica, etc. are preferably used as physical condition improvers to improve areas subject to thermal shock or deformation stress.

In addition, coating agents include dispersants, leveling agents, antifoaming agents,
There are thixotropic agents, emulsifiers, etc., and these are appropriately selected and used.

The solvent used in the present invention is silicone-based. Any material that dissolves the resin can be used without particular limitation, such as hydrocarbons, esters, ketones, halogenated carbons, and alcohols.

Also, when silicone resin is used in the form of an emulsion or suspension without being dissolved. water is the solvent.
The amount of the specific inorganic substance or its compound used in the paint of the present invention is preferably in the range of approximately 30 to 75% by weight (the same applies hereinafter), and optimally 35 to 60%, based on the solid content of the paint.

By adding at least 30%, wetting resistance to high-temperature molten metals, that is, corrosion resistance, is significantly improved. can be improved by 75%
If it exceeds 100%, a stable and good coating film cannot be easily obtained. If it is less than 25%, the corrosion resistance is significantly inferior to that of high-temperature melting metals, and it is completely unsuitable as a paint for high-temperature melting metals. When the sintering accelerator is used alone, the amount added is 5 to 30% in the paint composition excluding the solvent, and when a mineralizing agent is added, the sintering accelerator is in the range of 5 to 30%. A part of it is used by replacing it with a sintering accelerator. The amount of solvent used in the paint composition is determined as appropriate, taking painting workability into consideration. The method for preparing the corrosion-resistant coating for molten metal of the present invention is not particularly limited, and may be carried out using any ordinary coating machine, such as a ball mill, sand mill, or roll mill.

The corrosion-resistant paint thus obtained is coated on the surface of a base material such as metal or refractory material by a conventional method, and then cured with silicone resin at 150°C to 300°C for 30 to 12 minutes, resulting in a coating of 500 to 800°C. A corrosion-resistant inorganic film is formed by raising the temperature to a high temperature of °C.

The inorganic coating obtained by the present invention exhibits excellent corrosion resistance against a wide range of chemically active substances at high temperatures.

Next, specific examples of manufacturing the coating material of the present invention and examples of its use will be shown.

Production Example 1 50% straight silicone varnish KR275 (manufactured by Shin-Etsu Chemical Co., Ltd.) 30% (same below based on weight), fused magnesia particle size 3.5-4.0μ (manufactured by Kyoritsu Ceramics Co., Ltd.) 35%, phosphoric acid frit # 4021 softening point 380°C (Japanese enamel (made by +Wa) 12% was added, and to this, 1.5% of a dispersant (BYK-PlO4S manufactured by Marine Krodt) and 4.5% of a leveling agent (Biketol Special) were added. After addition, xylene 6% and ethyl cellosolve acetate 11 were added as solvents.
% and dispersed for 30 minutes using a sheaker with built-in glass beads to obtain a paint having a solid content concentration of 63% and a viscosity of 1100 cps (centiboads) (200C).

Production example 2 50% straight silicone varnish KR-282 and the same K
R-220 (25% mixture of Shin-Etsu Chemical (manufactured by Kiki) at a ratio of 8:2, Titanium Blitz 760, sonic point 56)
5°C (manufactured by Nippon Enamel Co., Ltd.) 6.7%, magnesium fluoride (MgF2) 2.8%, potassium titanate whisker (manufactured by Otsuka Chemical Co., Ltd.) 4.5%, phosphoric acid frit #42
01 at 3%, β-SlC3.5-2.5μ92% or more (
Adding 38% of Ibigawa Electric Industry Co., Ltd., 3.8% of the same leveling agent as in Example 1, 1.2% of the dispersing agent of Example 1, 9% of the solvent ethyl cellosolve acetate and 6% of xylene, Gala J
Solid content concentration 63 by dispersing 3 gin with the built-in subbead sheaker
%, and a viscosity of 105 Ps (25°C) was obtained.

Production Example 3 Straight silicone varnish of Example 2 34% Muscovite 7.8%, α-Si.

N, (Toshiba Ceramic (made by Kiki) 30% titanium frit #7605 (softening point 565°C) made by Nippon Enamel Co., Ltd.) 5%, Power Pon Milled Fiber (made by Toho Rayon Co., Ltd.) 0.6 %, Simgon (fine powder talc) 3.8%,
Dispersant BYKPlO4Sl. 3%, the leveling agent Piketol S 2.5%, and xylene 15% were added and dispersed with a shaker with built-in glass beads for 3 minutes to obtain a solid content concentration of 61.
% and a viscosity of 110 Ps (temperature 20°C) was obtained.
Production Example 4 Same straight silicone varnish as Example 1 KR-2755
0%, BN (manufactured by Shin-Etsu Chemical Co., Ltd.) 13.5%, talc MS 5%, titania (TlO2) 13.5%, borosilicate frit #4101 (softening point 580°C, manufactured by Nippon Enamel Co., Ltd.) 5.5%, dispersant BYKP-104S1.
5%, leveling agent Piketol S2.5%, xylene 8
．． 5% was added and dispersed in three powders using a sheaker equipped with glass beads to obtain a paint having a solid content of 62.5% and a viscosity of 112 Ps (20°C).

Production example 5 Silicone varnish 1505 (43%) manufactured by Lone Poulenc
30%, tetrasilicon mica 5%, Dical (2Ca0-SI
O.

) 29.8%, 10% phosphate frit 4021, 7% fine talc microace, BY as pigment dispersant
K-PlO4Sl. 5%, leveling agent Piketol S2
%, defoaming! IBYK-0 to 0.7%, 1 as solvent
- 5% of 2-dichloroethane and 9% of toluene were added and dispersed in a ball mill for 24 hours to obtain a uniformly dispersed paint with a concentration of 63.9% (viscosity 1650 cpS). Application Example 1 The coatings obtained in Production Examples 1, 2, and 3 were used for lining an aluminum low-frequency melting furnace.

The base material was a mullite brick stacked wall (wall thickness: 12 cm), and after painting, air drying (5 hours) was repeated twice to obtain a coating film with an average thickness of 180 μm. Next, electricity is applied according to a conventional method, and an inorganic sintered skin is formed due to the heat transfer of aluminum melting. A film was formed. Traditionally, mullite bricks (porosity 2) were used.

1%) was used, but when aluminum was melted (850°C), corrosion of 2 to 2.2% occurred in 4 hours.

However, the paint obtained in Production Example 1 of the present invention under the same conditions had a
3μ, and those of Production Examples 2 and 3 were hardly eroded. Usage Example 2 A coating film having an average thickness of 120μ was formed by dip coating the entire surface of a stainless steel plate (SUS3O4) 100 x 20 x 2- with the paint composition of Production Examples 3 and 4, and air-dried for 2 hours.
Next, it was cured at 180°C for 1 hour, and further heated from room temperature to 300°C for 1 hour, from 300 to 500°C for 1 hour, and at 500°C for 2 hours to form an inorganic sintered film.

This coating sample piece was immersed in molten zinc at 700°C for 5 hours, and this was repeated 10 times, but almost no corrosion was observed in any of the sample pieces. Usage Example 3 The paint obtained in Production Example 5 was spray coated on the surface of a shamrock brick, left to stand for 2 hours, cured by heating at 200°C for 1 hour, and further heated to 80°C.
After raising the temperature to 0°C, it was kept for 1 hour and then returned to room temperature.

During this process, the coating film was uniform and no foaming or cracking occurred.
Next, when this coated surface was immersed in molten aluminum melted at approximately 750°C for 5 hours, the uncoated back surface was approximately 1T.
Although the coated surface was brittle and eroded at the depth of the run, there was no change at all and no surface coating was observed.

Claims (1)

[Claims] 1. A corrosion-resistant paint for high-temperature molten metal that is made by blending an inorganic compound that is substantially inert to molten metal, a silicone resin, a sintering accelerator, and a solvent, and that has a work of adhesion to molten iron of 650 erg/cm^2 or more. A corrosion-resistant paint for high-temperature melting metals, characterized in that the inorganic compound contained in the solid content of the paint is approximately 30 to 75% by weight.