JPS62107079A - Method for coating inside surface of exhaust apparatus - Google Patents

Abstract

PURPOSE:To form an inside surface coating having excellent heat insulating and fire resisting characteristics by attaching a swiveling feed pipe to the aperture at one end of an exhaust apparatus for an exhaust gas, blowing an inorg. binder, with fire resisting heat insulating material, fire resisting material, etc. therethrough to form a fire resisting heat insulating layer and fire resisting layers then heating these layers to a high temp. CONSTITUTION:The swiveling feed pipe is connected to the aperture at one end of the exhaust manifold of an internal combustion engine and an aq. soln. of 20-60wt% inorg. binder such as sodium silicate is blown in the formed of a mist to the inside surface of the manifold to form the layer of the aq. binder soln. by centrifugal force. Powder of the refractory heat insulating material such as pearlite is blown immediately thereafter and is stuck to the binder layer. The stuck powder is then dried and solidified by heating to about 300 deg.C. The aq. soln. of the above-mentioned sodium silicate is again swiveled and blown and immediately thereafter, refractory powder of zirconia, etc. is blown and stuck thereto and is solidified by drying at about 300 deg.C. The solidified powder is then heated to 800-1,000 deg.C, by which the inside surface coating layer having the excellent heat insulating and refractory characteristics is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for coating the inner surface of exhaust system equipment with excellent heat insulation and fire resistance.

[Conventional technology]

The internal combustion engine exhaust system equipment, especially the manifold, has the disadvantage that its inner surface is in contact with the high-temperature, high-pressure combustion gas discharged from the cylinder, so it is strongly affected by it and cannot be used for a long time, and it also has poor insulation properties. was there.

JP-A-58-991'80 discloses a method for applying a fire-resistant and heat-insulating coating to the inner surface of exhaust gas system equipment for an internal combustion engine, such as an exhaust manifold. In this method, a heat-resistant coating layer is formed by attaching a slurry made of a mixture of refractory raw material particles, an inorganic binder, and a frit to the inner surface of a metal device body that is in contact with high-temperature exhaust gas, and then the heat-resistant coating layer is formed. While the layer is in a wet state, refractory insulation material particles are attached to the surface thereof to form a refractory insulation layer, and then the heat resistant coating layer is solidified, and refractory raw material particles and inorganic materials are applied to the surface of the refractory insulation layer. A heat-resistant coating layer is formed by adhering a slurry made of a mixture of a binder and a frit, and if necessary, a fire-resistant heat-insulating layer made of the same material as the fire-resistant heat-insulating layer is applied to the surface of the outer heat-resistant coating layer. Heat-resistant coating layers made of the same material as the heat-resistant coating layer are sequentially repeated to form required layers. By this method, a coating is formed in which the three layers of the heat-resistant coating layer, the fire-resistant heat insulating layer, and the heat-resistant coating layer are integrated and laminated.

[Problem that the invention seeks to solve]

However, in the above method, since the coating material is coated in the form of a slurry, the amount of water in the coating layer must be relatively large, causing cracks during drying and large shrinkage during heat treatment.

Peeling and breakage are likely to occur. Also, does it generate heat when it is rapidly heated by high-temperature exhaust gas? There is a high possibility that cracks will occur due to the impact.

[Means for solving problems]

The Ministry of Invention and others has conducted various studies to address these shortcomings, and as a result, they have developed a fireproof and heat-resistant layer that does not crack or peel by forming a fireproof heat insulating layer and a fireproof layer on the inner surface of exhaust system equipment and performing heat treatment.
They discovered that it is possible to form a heat insulating coating, leading to the completion of the present invention.

That is, the method for coating the inside surface of exhaust system equipment of the present invention is a method for coating the inside surface of exhaust system equipment that forms a fireproof heat insulating layer and a fireproof layer on the inside surface of the exhaust system equipment, and is a method for coating the inside surface of exhaust system equipment by forming a fireproof heat insulating layer and a fireproof layer on the inside surface of the exhaust system equipment. Connect a swirling feed pipe that feeds the material in the form of a swirl or mist, feed the inorganic binder from the swirl feed pipe, and immediately feed the fireproof heat insulating material to form a fireproof heat insulating layer. , After drying and solidifying by heat treatment, feed an inorganic binder, immediately feed a refractory material to form a fireproof layer, dry and harden by heat treatment, and if necessary, apply the above fireproof insulation layer and fireproof layer. A desired layer is formed.

Inorganic binders used to impart adhesive properties in the coating method of the present invention include silicate binders such as sodium silicate, potassium silicate, lithium silicate, monobasic aluminum phosphate, monobasic calcium phosphate, monobasic phosphoric acid, etc. Phosphate binders such as magnesium, condensed phosphates, phosphoric acid,
Sol binders such as colloidal silica, colloidal alumina, and colloidal zirconia, ethyl silicate, and the like are suitable.

The binder is used in the form of an aqueous solution, and its concentration is between 20 and 6
0 wt% is preferred. If it is lower than 20%, the adhesive strength is low and it is easy to peel off. Moreover, if it is higher than 60%, the coating operation becomes difficult. More preferably, it is 25 to 55 wt%.

Appropriate amounts of curing agents can also be added to the binder solution. Although the curing agent differs depending on the type of binder, any known curing agent can be used. Examples of silicate binders include sodium silicate, calcined aluminum phosphate, dicalcium silicate, and carbon dioxide. For primary aluminum phosphate, there are basic oxides such as magnesia and lime, calcium aluminate, ammonium fluoride, and the like.

The fireproof heat insulating material used to provide heat insulation properties is an inorganic heat insulating material such as glass balloon, foamed silica, and perlite. The particle size of the powder is generally in the range of 10 to 500 μm. If it is smaller than 10 μm, cracks and cracks due to shrinkage may occur.
Peeling occurs, and if it is larger than 500 μm, it is difficult to form a smooth film layer. A more preferable particle size range is 20 to 20
It is 0 μm. As the refractory material, commonly used materials such as Pyrex glass, fused silica, cordierite, chamotte, mullite, alumina, zircon, and zirconia may be used, but zirconia is particularly preferred because of its low thermal conductivity. The particle size of the refractory powder is generally in the range of 10 to 500 μm. If it is smaller than 10 μm, agglomeration between particles tends to occur, making it difficult to form a smooth film layer, and easily shrinking under the influence of high heat. Moreover, if it is larger than 500 μm, it is difficult to form a smooth film. A more preferable particle size range is 20 to 200 μm.

The coating method of the present invention includes a step of forming a fireproof heat insulating layer and a step of forming a resistant layer.

When forming a fireproof heat insulating layer, first, an inorganic binder solution is swirled and applied to the inner surface of the exhaust system equipment.

As a result, the inner surface of the exhaust system equipment is uniformly wetted with the binder solution. When the refractory heat insulating material powder is fed in a swirling manner, it firmly adheres to the inorganic binder solution due to centrifugal force, and powder that is insufficiently adhered is blown away by the swirling airflow, forming a uniform fireproof heat insulating layer. The thickness of this layer varies depending on the concentration and thickness of the binder solution, but is generally between 0.1 and 1.5 mm.

The binder solution-impregnated refractory insulation powder layer formed by the above method has a significantly lower moisture content than a layer applied in the form of a slurry. This is a significant feature of the invention. Due to these characteristics, the heat insulating layer will not crack or the layer will peel off during the subsequent drying and solidification process by heat treatment.

The heat treatment of the layer is carried out by gradually heating it to about 300°C. Rapid heating should be avoided as this may cause cracking and delamination of the layers. Preferably, the layer is allowed to air dry at room temperature, with subsequent increases in temperature. For example, after air drying, hold at 50℃ for 1 hour, then 100℃
Hold for 1 hour. To further improve stability, 30
It is desirable to heat to 0°C.

Next, if necessary, a binder solution is further applied on the above-described refractory heat insulating material layer by the same method, and the refractory heat insulating material powder is adhered thereto, followed by drying and solidification by heat treatment. This cycle is repeated several times to obtain a relatively thick refractory insulation layer. In order to ensure sufficient heat insulation properties, the fireproof heat insulation layer needs to be 1.5 mm or more.

It is necessary to form a refractory layer on the refractory heat insulating layer thus formed. The refractory layer is formed by a method including the steps of first feeding an inorganic binder solution through a rotating feed pipe to deposit it, immediately feeding refractory material powder through a rotating feed pipe, and drying and solidifying it by heat treatment.

The specific conditions are substantially the same as the conditions for forming the fireproof heat insulating layer except for using the fireproof material powder.

The refractory layer can be formed only by a cycle consisting of the above steps, but the steps may be repeated several times if necessary. By this method, a refractory layer of 0.5 mm or more is formed.

The exhaust system equipment on which the coating layer consisting of the refractory heat insulating layer and the refractory layer has been formed is heated to 800 to 1,000°C in a furnace.
The coating process is completed by heat treatment for 5 to 120 minutes.

In this case, if the temperature is lower than 800°C, the water glass will not vitrify and a complete coating layer will not be formed, and if the temperature exceeds 1°000°C, no effect can be expected and it is disadvantageous in terms of thermal energy. The most preferred temperature is 850-970°C.

This heat treatment may be performed by heating in a furnace or by passing hot air through exhaust system equipment.

〔Example〕

The present invention will be explained in detail by the following examples.

Example 1 The inner surface of a cast iron manifold having an oxide film that had been previously degreased with an alkaline solution of PHIO to 11 was baked as a hardening agent in a sodium silicate aqueous solution with a silica ratio of 2.9 and a concentration of 45 wt% as a first step. 5 to which 10 wt% of aluminum phosphate (H, B hardener manufactured by Hoechst) was added.
It was delivered in the form of a spray along with 1 kg/cm" of air through a rotating feed pipe.

Immediately used as a heat insulating material with a bulk specific gravity of 0.2 and a particle size of 44 to 150μ
After the 6-m whitebait balloons were fed from the rotating feed pipe and the whitebait balloons were sufficiently attached, the temperature was raised to 50°C and held for 1 hour, and then the temperature was raised to 50°C and held for 1 hour.
The temperature was raised to 300°C and held for 1 hour, and finally to 300°C and held for 1 hour. This heat treatment completely solidified the fireproof heat insulating layer. Repeat this process two more times until thickness 3
A fireproof heat insulating layer of mm was formed.

In the second step, the same inorganic binder as above is applied on top of the fireproof heat insulating layer, and the particle size is 44 to 150 μm.
After scattering the stabilized zirconia particles, the same heat treatment as above was performed to form a fireproof layer with a thickness of 0.5 mm.

The manifold on which the refractory heat insulating layer and the refractory layer were formed was heat treated in a furnace at 950° C. for 1.5 hours to complete the coating operation.

No cracks were observed in the coating layer of the obtained manifold, and even though the manifold was heated with combustion gas at 1,000°C and cooled with air 100 times, no cracks or peeling of the coating layer were observed. There wasn't.

Example 2 As a first step, a silica ratio of 3.0. A sodium silicate aqueous solution having a degree of 40 wt % and 8 wt % of calcined aluminum phosphate (H, B hardener manufactured by Hoechst Co., Ltd.) added as a hardening agent was fed through a rotating feed pipe. Immediately, pearlite having a bulk specific gravity of 0, 22 and a particle size of 44 to 150 μm was fed as a heat insulating material through a rotating feed pipe. Heat treatment was performed in the same manner as in Example 1 to completely solidify the fireproof heat insulating layer. This process was repeated two more times to form a fireproof heat insulating layer with a thickness of 3 mm.

As a second step, the same inorganic binder as above is fed from the swirling feed pipe onto the fireproof heat insulating layer, and the particle size is 44 to 1.
After scattering stabilized zirconia grains of 50 .mu.m, the same heat treatment as above was carried out to form a refractory layer with a thickness of 0.5 mm.

The manifold on which the fireproof heat insulating layer and the fireproof layer were formed was heat treated in the same manner as in Example 1 to complete the coating operation.

No cracks were observed in the coating layer of the obtained manifold, and even though the manifold was heated with combustion gas at 1,000°C and cooled with air 100 times, no cracks or peeling of the coating layer were observed. There wasn't.

Although this embodiment has been described with respect to a manifold, the present invention is not limited thereto, and can be applied to forming a coating layer on exhaust system equipment such as boat liners and turbine housings.

〔Effect of the invention〕

The method of the present invention involves feeding a refractory insulation powder or a refractory material powder to a binder solution with a swirling air flow to make it adhere to the binder solution.
Since it forms a fireproof heat insulating layer and a refractory layer, it does not crack or peel even after drying and solidifying, and it does not crack or peel even after repeated cycles of heating and cooling with high-temperature gas.

In addition, since the binder solution, fireproof insulation material, and refractory material are fed by swirling airflow through the swirling feed pipe, it is possible to obtain an even and uniform coating layer, and by repeating coating several times, the desired thickness can be achieved. A coating layer can be obtained.

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Claims (1)

[Claims] In the internal coating method for exhaust system equipment that forms a fireproof heat insulating layer and a refractory layer on the inside surface of the exhaust system equipment, swirling feeding is used to swirl and feed a powder or mist material to an opening at one end of the exhaust system equipment. Connect the pipes, feed the inorganic binder from the above-mentioned swirl feed pipe, immediately feed the fireproof heat insulating material to form a fireproof heat insulating layer, dry and solidify by heat treatment, and then feed the inorganic binder. A method for coating the inner surface of exhaust system equipment, characterized by immediately feeding a refractory material to form a refractory layer, drying and solidifying it by heat treatment, and optionally forming the above-mentioned refractory heat insulating layer and refractory layer as desired. .