JPS62107084A - Method for coating inside surface of exhaust apparatus - Google Patents

Abstract

PURPOSE:To form an inside surface coating layer having excellent heat insulating, refractory and water resistant characteristics by connecting a swiveling feed pipe and suction pipe for raw materials to the apertures at both ends of an exhaust apparatus for an exhaust gas and formed a refractory heat insulating layer consisting of an inorg. binder, refractory heat insulating material, and refractory material, refractory layer and protective layer consisting of a slurry of an inorg. binder and protective material. CONSTITUTION:The swiveling feed pipe and suction pipe are connected to the apertures at both ends of the exhaust manifold of an internal combustion engine and an aq. soln. of 20-60wt% concn. of sodium silicate is swiveled and sucked in the form of a mist to the inside surface of the manifold. 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 solidified by heating. The refractory layer consisting of the inorg. binder and refractory material such as zirconia is similarly formed thereon and thereafter the slurry consisting of the refractory material powder contg. the above- mentioned inorg. binder is stuck thereon and is solidified by heating to form the protective layer. The layer is heated for 5-120min at 800-1,000 deg.C, by which the inside surface coating layer is formed.

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, fire resistance, and water 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 No. 58-99180 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 wave rII layer is solidified, and refractory raw material particles are applied to the surface of the refractory insulation layer. No 4!
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 of the same type as the fire-resistant heat-insulating layer is applied to the surface of the outer heat-resistant coating layer. A heat-resistant coating layer made of the same material as the heat-resistant coating layer is sequentially repeated to form a required layer. 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, cracks occur during drying, and shrinkage during heat treatment is large, resulting in peeling and breakage. tends to occur. Also, does it generate heat when it is rapidly heated by high-temperature exhaust gas? There is a great possibility that cracks will occur due to ifl'.

[Means for solving problems]

In view of these shortcomings, the inventors of the present invention have repeatedly conducted various studies and found that by forming a fireproof heat insulating layer, a fireproof layer, and a protective layer on the inner surface of exhaust system equipment, and performing heat treatment, a fireproof and heat insulating layer without cracking or peeling can be achieved.・We discovered that it is possible to form a water-resistant coating and completed the present invention.

That is, the method for coating the inner surface of exhaust system equipment of the present invention is a method for coating the inner surface of exhaust system equipment, which forms a fireproof heat insulating layer, a fireproof layer, and a protective layer on the inner surface of the exhaust system equipment,
Connect a swirling feed pipe that swirls and feeds powder or mist material to the opening at one end of the exhaust system equipment, connect a suction pipe to the opening at the other end, and connect the swirling feed pipe to the opening at the other end. The inorganic binder is fed, and the refractory insulation material is immediately fed to form a fireproof insulation layer, and after drying and solidification by heat treatment, the inorganic binder is fed, and the refractory material is immediately fed to form the fireproof layer. is formed, dried and solidified by heat treatment, the above-mentioned fireproof insulation layer and fireproof layer are formed as desired, and then a protective layer is formed by adhering a slurry of a protective material containing an inorganic binder. ,000
Heat treatment is performed at ℃ for 5 to 120 minutes.

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,
These are colloidal silica, colloidal alumina, and colloidal zirconia.

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. For example, silicate binders include sodium silicate, calcined aluminum phosphate, dicalcium silicate, carbon dioxide, and the like. For 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 refractory material powder is generally 10 to E100 μm.
A range of is appropriate. If it is smaller than 10 μm, the distance between particles is
M collection tends to occur, making it difficult to form a smooth film layer,
Easily shrinks 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.

As the protective material, one or more of the above-mentioned refractory materials are used, and the particle size is suitably 20 μm or less.

To further enhance water resistance, a small amount of frit may be added.

The coating method of the present invention includes a step of forming a fireproof heat insulating layer, a step of forming a fireproof layer, and a step of forming a protective 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 this refractory insulation powder is fed in a swirling manner, it firmly adheres to the inorganic binder solution due to centrifugal force.

The insufficiently adhered powder is blown away by the swirling airflow, and a uniform fireproof insulation layer is formed. The thickness of this layer varies depending on the concentration and thickness of the binder solution, but is generally between 0.1 and 1
．． It is 5mm.

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-mentioned refractory heat insulating material layer by the same method, and the refractory heat insulating material powder is adhered thereto, followed by #J 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.

A protective layer, which is the final layer, is formed on top of this fireproof layer, and the protective layer is formed by attaching a slurry of protective material powder containing an inorganic binder solution, and drying and solidifying it by heat treatment to form the protective layer. .

The exhaust system equipment on which the coating layer consisting of the refractory insulation layer, the refractory layer, and the protective layer was formed was heated in the furnace at
The coating process is completed by heat treatment at 000°C for 5 to 120 minutes.

If the fi is lower than 800°C, the water glass will not vitrify and a complete protective layer will not be formed, and if it 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.

Also, if the inside surface of the exhaust system equipment is narrow and short, coating can be done using either the swirling feed pipe or the suction pipe, but if the inside surface of the exhaust system equipment is wide and long, the swirling feed pipe and the suction pipe can be used for coating. A uniform coating surface can be obtained using both tubes.

〔Example〕

The present invention will be explained in further 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 air at a concentration of kg/cm2 from 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 1'50.
A μm shirasu balloon was delivered through a rotating feed tube.

After the Shirasu balloon was sufficiently attached, it was kept at room temperature for 1 hour, then raised to 50℃ and kept for 1 hour, and then heated to 50℃ 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.

As a third step, a sodium silicate aqueous solution (silicate ratio: 2.8°, concentration: 42 wt.
%) in a weight ratio of 1:1 was poured to form a 0.2 mm protective layer. In this way, a manifold that forms a fireproof insulation layer, a fireproof layer, and a protective layer is made in a furnace at 950°C.
The coating process was completed by heat treatment at ℃ for 16.5 hours.

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 concentration of 40 wt % and 8 wt % of calcined aluminum phosphate (H, B hardener manufactured by Hoechst Co., Ltd.) added thereto as a hardening agent was fed through a rotating feed pipe. Bulk specific gravity 0 immediately as insulation material
．． 22. Pearlite with a particle size of 44 to 150 μm was fed from 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.

As a third step, a sodium silicate aqueous solution (silicate ratio 2.8, concentration 42W) is applied to alumina with a particle size of 2 to 6 μm on the fireproof layer.
A protective layer with a thickness of 0.2 mm was formed by pouring a slurry containing 1:1 weight ratio of 1:1 wt%).

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

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 describes 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 fireproof layer, no cracking or peeling occurs even after drying and solidification, and no cracking or peeling occurs even after repeated cycles of heating and cooling with high-temperature gas.

The protective layer, which is the final layer, has a fine particle size of 20 μm or less, so it is dense and prevents moisture generated by decomposition when the fuel gasoline is combusted from condensing in cold regions and penetrating into the fireproof layer and heat insulation layer. In addition, it is a layer provided to smooth the inner surface of the manifold and reduce airflow resistance, and is applied thinly using slurry.

In addition, the binder solution, fireproof insulation material, and fireproofing material are fed and sucked in by the swirling airflow through the swirling feed pipe and suction pipe, so it is possible to obtain a uniform coating layer without any unevenness, and coating can be repeated several times. Accordingly, a coating layer of desired thickness can be obtained.

Claims (1)

[Claims] In an internal coating method for exhaust system equipment that forms a fireproof heat insulating layer, a fireproof layer, and a protective layer on the inside surface of exhaust system equipment, a powder or mist material is fed into an opening at one end of the exhaust system equipment while swirling it. Connect the swirl feed pipe, connect the suction pipe to the opening at the other end, feed the inorganic binder from the swirl feed pipe, and immediately feed the fireproof insulation material to form a fireproof heat insulation 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, and then a protective slurry containing an inorganic binder is applied to form a protective layer, and heated at 800 to 1,000°C.
A method for coating the inner surface of exhaust system equipment, characterized by heat treatment for 5 to 120 minutes.