JPS61163282A - Production of heat insulating metallic member - Google Patents

Abstract

PURPOSE:To form a refractory heat insulating coating having no crack and peeling by coating an inorganic binder on the inside surface of a metallic member, sticking a refractory heat insulating material thereon, heat-treating it and thereafter coating the inorganic binder again to stick the powder of the refractory material thereon. CONSTITUTION:After subjecting the inside surface of a metallic member to the degreasing treatment, a soln. of an inorganic binder such as sodium silicate is coated thereon and immediately the powder of a refractory heat insulating material such as 'SHIRASU' (volcanic glass) balloon is stuck and thereafter heat-treated to dry and solidify it. The refractory adiabatic layer is formed by performing this process in one and more times. A soln. of the inorganic binder is coated on the surface of this heat insulating layer and immediately the powder of the refractory this heat insulating layer and immediately the powder of the refractory material such as zirconia is stuck and heat-treated to dry and solidify it. The refractory layer is formed by performing this process of the second in one and more times. By this method, the refractory heat insulating coating having a required thickness can be formed in the excellent operation efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a heat insulating metal member having excellent heat insulating properties and durability.

[Conventional technology]

Exhaust system equipment of internal combustion engines, especially the inner surface of the manifold, is in contact with the high temperature and high pressure combustion gas discharged from the cylinder, so it is strongly affected by it, making it difficult to use for a long time, and also has the disadvantage of poor insulation properties. There is.

Japanese Patent Application Laid-Open 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 temperature controlled state, refractory insulation material particles are attached to the surface of the layer to form a refractory insulation layer, and then the heat resistant coating layer is solidified and refractory raw material particles 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 an inorganic 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. A heat-resistant coating layer made of the same material as the heat-resistant coating layer is sequentially repeated to form a required layer. With this method,
A coating is formed by integrating and laminating three layers: the heat-resistant covering MN, the fire-resistant heat insulating layer, and the heat-resistant coating layer.

[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. Furthermore, there is a high possibility that cracks will occur due to thermal shock when the material is rapidly heated by high-temperature exhaust gas.

[Means for solving problems]

In view of these drawbacks, the inventor has conducted various studies and found that after applying a bonding agent to the inner surface of the metal part 4, the powder of the coating material is applied, and heat treatment is performed to prevent cracking and peeling. The inventors discovered that it is possible to form a fire-resistant and heat-insulating coating, leading to the completion of the present invention.

That is, the method for manufacturing the heat insulating metal part) A of the present invention includes (a
l Apply an inorganic binder solution to the inner surface of the metal member, (b)
Immediately, a fireproof insulation material powder is attached to the solution layer, and (c+
A fireproof insulation layer is formed by performing the first step including drying and solidification by heat treatment at least once, and then an inorganic binder solution is applied to the surface of the +di fireproof insulation layer,
te + Immediately add refractory powder to the layer of inorganic binder solution (=
A fire-resistant layer is formed by carrying out the second step, which includes the step of drying and solidifying by the ((l i) treatment, at least once).

Inorganic binders used to impart adhesive properties in the method of the present invention include silicate binders such as sodium silicate, potassium silicate, lithium silicate, monobasic aluminum phosphate,
Colloidal silica, ethyl silicate, etc. are suitable.

The binder is used in the form of an aqueous solution, and its concentration is between 20 and 6
Qwt% is preferred. If it is lower than 2Qwt%, the adhesive strength is small and peeling is likely to occur. Moreover, if it is higher than 6Qwt%, coating work 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, calcium 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 shirasu balloon, foamed silica, and perlite. The average particle size of the powder generally ranges from 10 to 500 μm. When it is smaller than 10 μm, cracking and peeling occur due to shrinkage, and when it is larger than 500 μm, it is difficult to form a smooth coating layer.

The preferred particle size range is 20-200 μm.

As the refractory material, commonly used materials such as chamotte, alumina, zircon, and zirconia may be used, but zirconia is particularly preferred because of its low thermal conductivity. The average particle size of the refractory powder generally ranges from 10 to 500 μm. 10μ
If it is smaller than m, agglomeration between particles tends to occur, making it difficult to form a smooth coating 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. The preferred particle size range is 20-200 μm.

The method of the present invention includes the steps of forming a refractory insulation layer and forming a refractory layer.

When forming a fireproof heat insulating layer, an inorganic binder solution is first applied to the inner surface of a metal member. As a result, the inner surface of the metal part is evenly wetted with the binder solution. A fireproof insulation material powder is attached to this. As a method of attachment, there are methods such as scattering the powder on the surface of the binder solution, or filling the metal member with the powder and leaving it for a certain period of time. The latter method is preferable from an efficiency standpoint. In the case of the latter method, the interior of the metal member is filled with refractory insulation powder and, when left for a certain period of time, the binder solution penetrates between the powder particles and a sufficient amount of the powder is wetted. Some pressure may be applied throughout the powder to facilitate this process. Next, the powder is taken out from inside the metal member, and the powder that is insufficiently adhered is blown away by air flow.
Remove. In this way, a layer of refractory insulation powder fully impregnated with binder solution is formed. The thickness of this layer varies depending on the concentration and thickness of the binder solution, but is generally 100
~1500 μm.

The binder solution-impregnated refractory insulation powder layer formed by the above method has significantly less moisture than a layer applied in the form of a slurry. This is a significant feature of the invention. Due to this feature, the layer does not crack or peel 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 it may cause cracking and peeling of the layers.

Preferably, the layer is allowed to air dry at room temperature, with subsequent increases in temperature. For example, after air drying, it is held at 50°C for 1 hour, and then held at 100°C for 1 hour.

In order to further improve stability, it is desirable to heat up to 300°C.

Next, if necessary, a binder solution is further applied in the same manner on the fireproof heat insulating material layer described in section 2 above, and the fire proof 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. To ensure sufficient heat insulation, the fireproof insulation layer must be at least 1.5 mm thick.

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 applying an inorganic binder solution, adhering a refractory material powder, and drying and solidifying by heat treatment. The specific conditions are:
The conditions for forming the refractory heat insulating layer are substantially the same except that refractory material powder is used. 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 or more thickness is formed.

〔Example〕

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

Example 1 As a first step, a sodium silicate aqueous solution with a silica ratio of 2.9 and a concentration of 4.5 wt% was added as a hardening agent to the inner surface of a cast iron manifold that had been previously degreased with an alkaline solution with a pH of 10 to 11. Calcined aluminum phosphate (Hoechst H,
B hardener) was added in an amount of 1 Q w t%. Immediately use Kaza1JJi0.2, particle size 4 as a heat insulating material.
Shirasu balloons of 4 to 150 μm were sprayed.

After the Shirasu balloon was sufficiently attached, it was held at room temperature for 1 hour, then raised to 50°C and held for 1 hour, and then heated to 50°C.
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. This process was repeated two more times to form a refractory insulation layer with a thickness of 311 mm.

As a second step, the same inorganic binder as above is applied on top of the above fireproof heat insulating layer, and stabilized zirconia particles with a particle size of 44 to 150 μm are further sprinkled, and then the same heat treatment as above is performed to reduce the thickness to 0. A refractory layer of .51 was formed.

(No cracks were observed in the M-treated fireproof and heat-insulating coating, and even though the heat-insulating manifold was repeatedly heated with combustion gas at 1000°C and allowed to cool, no cracks or peeling of the coating were observed.

On the other hand, a fire-resistant and heat-insulating coating made by applying the same material in the form of a slurry had many cracks during drying and solidification, and the cracks widened further when heated and cooled under the same conditions.

Example 2 As a first step, calcined aluminum phosphate (Hoechst) was added to a sodium silicate aqueous solution with a silica ratio of 3.0 concentration and 40 wt% on the inner surface of a cast iron manifold that had been previously degreased with an alkaline solution with a pH of 10 to 11. A coating containing 13 wt % of MH, B hardener) was applied. Immediately used as a heat insulator with a bulk specific gravity of 0.22 and a particle size of 44-150μ
Spread m perlite. 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 3 mm thick fireproof heat insulating layer.

As a second step, the same inorganic binder as described in Section 2 is applied on top of the above fireproof heat insulating layer, and the particle size is 44 to 150 μm.
After scattering the stabilized zirconia grains, the same heat treatment as above was performed to form a fireproof layer with a thickness of 500 μm.

No cracks or peeling were observed in the resulting fireproof and heat-insulating coating, and even though the heat-insulating manifold was repeatedly heated with combustion gas at 1000°C and allowed to cool, no cracks were observed in the coating layer. .

On the other hand, a fireproof and heat-insulating coating made by applying the same material in the form of a slurry showed many cracks during drying and solidification, and the cracks expanded further when heated and cooled under the same conditions.

Although this embodiment describes a heat insulating manifold, the present invention is not limited thereto, but can be applied to the formation of a fire-resistant heat insulating coating on metal members such as chemical equipment or heating equipment that handle high-temperature gas.

〔Effect of the invention〕

The method of the present invention forms a fireproof heat insulating layer or fireproof layer by attaching fireproof heat insulating material powder or refractory material powder to a binder solution, so that cracks or peeling do not occur even after drying and solidification, and heating with high temperature gas No cracking or peeling occurs even after repeated cooling cycles. Further, since the concentration of the binder in the binder solution can be increased, work efficiency is improved. By repeating the application of the binder solution and the powder deposition, the desired thickness of the refractory insulation coating can be obtained.

Non-False (Patent Attorney Takaishi Tachibana)

Claims (1)

[Claims] A method for manufacturing a heat insulating metal member, comprising: (a) applying an inorganic binder solution to the inner surface of the metal member;
b) Immediately depositing a refractory insulation powder on the layer of inorganic binder solution; (c) forming a refractory insulation layer by performing at least one first step comprising drying and solidifying by heat treatment; (d) applying an inorganic binder solution to the surface of the refractory heat insulating layer; (e) immediately adhering a refractory material powder to the layer of the inorganic binder solution; and (f) drying and solidifying by heat treatment. A method characterized in that the refractory layer is formed by carrying out at least one of two steps.