JPS61244817A - Manufacture of heat insulating manifold - Google Patents

Abstract

PURPOSE:To obtain fire-resistant and heat insulating coating prevented from generating a crack and exfoliation, by applying a binding agent to the internal surface of a manifold thereafter feeding a heat insulating material, consisting of inorganic fiber, and fire-resistant material dust respectively with gas adhering to the internal surface of the manifold. CONSTITUTION:When a manifold is manufactured, the method, first applying an inorganic binding agent solution to an internal surface of the cast iron made manifold and immediately feeding a fire-resistant heat insulating material, consisting of inorganic fiber, with gas adhering to a layer of said solution, dries said layer to be solidified by heat treatment. And a fire-resistant heat insulating layer is formed by performing at least one time the first step including a process as described in the above. Next the method, applying the inorganic binding agent solution to a surface of said heat insulating layer and immediately feeding a fire-resistant material dust with gas adhering to said solution layer, dries the layer to be solidified by heat treatment. And a fire-resistant layer is formed by performing at least one time the second step including a process as said in the above.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a heat insulating manifold 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 Laid-Open No. 58-99180 discloses a method of 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. The 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 and the above-mentioned Heat-resistant coating layers and heat-resistant coating layers made of the same material 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 water content 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. There is also a high risk of cracking due to thermal shock when rapidly heated by high-temperature exhaust gas.Furthermore, since the coating material is slurry-like, it is extremely difficult to apply it to the inner surface of the manifold with a uniform thickness. be.

[Means for solving problems]

In view of these shortcomings, the inventors of the present invention have conducted various studies, and after applying a binder to the inner surface of the manifold, a heat insulating material made of inorganic fibers and a refractory material powder are delivered together with gas to adhere them evenly. The inventors discovered that by forming a heat insulating layer and a fire resistant layer with a certain thickness and performing heat treatment, it is possible to form a fire resistant and heat insulating coating that does not crack or peel, leading to the completion of the present invention.

That is, the method for manufacturing a heat insulating manifold of the present invention includes (a)
Apply an inorganic binder solution to the inner surface of the cast iron manifold,
(b) Immediately supply a fireproof insulation material made of inorganic fiber with gas to the solution layer to adhere it, and (c) perform at least one first step including drying and solidification by heat treatment to form a fireproof insulation layer. , then (d
) Apply an inorganic binder solution to the surface of the fireproof insulation layer,
) A refractory layer is formed by immediately applying a refractory material powder together with a gas to adhere to the layer of an inorganic binder solution, and (f) performing at least one second step including a step of drying and solidifying by heat treatment. It is.

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
0 wt% is preferred. If it is lower than 20 wt%, the adhesive force is small and peeling is likely to occur. Moreover, if it is higher than 60 wt%, 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 fluoride, calcined phosphate binders include basic oxides such as magnesia and lime, calcium aluminate, ammonium fluoride, and the like.

The fireproof heat insulating material used to provide heat insulation is inorganic fiber such as ceramic fiber, glass fiber, or carbon fiber.

The diameter of the fiber used in the present invention is generally 1 to 8 μm.
, the length ranges from 0.5 to 10 mm.

If the diameter is smaller than 1 μm or the length is shorter than 0.5 mm, cracking or peeling will occur due to shrinkage, and if the diameter is larger than 8 μm, the length is longer than 10 mm, it will be difficult to uniformly supply the gas. be. The preferred fiber diameter is 2-4 μm
, the length is 1-6 mm.

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.

If it is larger than 500 μm, it will be 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 refractory insulation layer, an inorganic binder solution is first applied to the inner surface of the manifold. This evenly wets the inner surface of the manifold with the binder solution.

A fireproof insulation material made of inorganic fiber is attached to this. Examples of attachment methods include scattering inorganic fibers on the surface of the binder solution, and feeding inorganic fibers together with gas into a manifold to cause attachment.

The latter method is preferable from an efficiency standpoint.

In the case of the latter method, when the inorganic fiber refractory insulation material is fed into the manifold together with gas, it adheres uniformly to the inner surface of the manifold, and the binder solution penetrates between the inorganic fibers to wet a sufficient amount of the fibers. become.

To facilitate this process, the gas outlet side may be sealed and some pressure may be applied. Next, the supply of inorganic fibers is stopped, and only gas is supplied to blow off and remove insufficiently adhered fibers with the gas flow. In this way,
A layer of refractory insulation is formed which is fully impregnated with the binder solution. The thickness of this layer depends on the concentration and thickness of the binder solution, but is generally between 100 and 1500 μm.

The binder solution-impregnated refractory insulation layer formed by the above method was compared with the layer applied in the form of a slurry.

Very little moisture. This is a significant feature of the invention.

Due to this feature, cracks do not occur in the layer or the layer peels off during the drying/solidification process by the primary 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 delamination of the layers.

Preferably, the layer is allowed to air dry at room temperature, and then the temperature is gradually increased. For example, after air drying, it is held at 50''C for 1 hour and then 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 on the above-mentioned fireproof insulation layer by the same method.

A fireproof insulation material is attached, and it is dried and assimilated by heat treatment. This cycle is repeated several times to obtain a relatively thick refractory insulation layer. In order to ensure sufficient heat insulation, the fireproof 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 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 mm or more is formed.

〔Example〕

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

Example 1 The inner surface of a spheroidal graphite cast iron manifold that had been previously degreased with an alkaline solution of PHIO to 11 was coated with calcined phosphoric acid as a hardening agent in a sodium silicate aqueous solution with a silicate ratio of 2.9 and a concentration of 45 wt% as a first step. Aluminum (Hoechst H,
A coating containing 10 wt % of B hardener) was applied.

Fiber diameter 2-4μm length 2-4mm immediately as insulation material
of ceramic fibers were delivered together with air.

After the ceramic fibers were sufficiently attached, the temperature was kept at room temperature for 1 hour, then the temperature was raised to 50°C and held for 1 hour, the temperature was further raised to 100°C and held for 1 hour, and finally the temperature was raised to 300°C. It was kept warm for 1 hour. This heat treatment completely solidified the fireproof heat insulating layer.

This process was repeated two more times to form a 3 mm thick fireproof insulation layer.

As a second step, the same inorganic binder as above is applied on the fireproof heat insulating layer, and the particle size is 44 ~
A fireproof layer of mm was formed.

No cracks were observed in the obtained fire-resistant heat-insulating coating, and although the heat-insulating manifold was repeatedly heated with combustion gas at 100°C and allowed to cool, the fire-resistant heat-insulating coating showed many cracks during drying and solidification. was observed, and the cracks further expanded under the same heating and cooling conditions.

Example 2 As a first step, calcined aluminum phosphate was added as a hardening agent to a sodium silicate aqueous solution with a silicate ratio of 3.0 and a concentration of 40 wt% on the inner surface of a spheroidal graphite cast iron manifold that had been previously degreased with an alkaline solution of PHIO to 11. (Hoechst H, B
A coating containing 8 wt % of hardener) was applied. Immediately, glass fibers having a fiber diameter of t~4 μm and a length of 1 to 5 mm were fed together with air as a heat insulating material. Heat treatment was performed in the same manner as in Example 1 to completely solidify the fireproof heat insulating layer. This process was repeated twice to form a fireproof heat insulating layer with a thickness of 3 mm.

As a second step, the same inorganic binder as above is applied on the fireproof insulation layer, stabilized zirconia particles with a particle size of 44 to 150 μm are fed together with air, and then the same heat treatment as above is performed. A fireproof layer with a thickness of 500 μm was formed.

No cracks or peeling were observed in the resulting fire-resistant and heat-insulating coating, and although 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, indicating that it was fire-resistant. Many cracks were observed in the heat-insulating coating during drying and assimilation, and these cracks were further enlarged by heating and cooling under the same conditions.

Although this embodiment describes a heat insulating manifold made of spheroidal graphite cast iron, the present invention is not limited thereto, and the same objective can be achieved with a manifold made of vermicular cast iron or ordinary cast iron.

It can also be applied to the formation of fire-resistant and heat-insulating coatings for metal members such as chemical equipment and heating equipment that handle high-temperature gases.

〔Effect of the invention〕

The method of the present invention forms a refractory insulation layer or a refractory layer by feeding a refractory insulation material made of inorganic fiber or refractory material powder together with a gas to adhere to a binder solution.
No cracking or peeling occurs even after drying and solidification.

Furthermore, the inorganic fiber heat insulating layer has an excellent buffering effect against the expansion and contraction of the refractory layer due to heating and cooling, so it does not crack or peel even after repeated heating and cooling cycles using high-temperature gas.

Furthermore, 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 deposition of gas-delivered insulation fibers or refractory powder, a uniform, desired thickness of the refractory insulation coating can be obtained.

Claims (1)

[Claims] (a) An inorganic binder solution is applied to the inner surface of a cast iron manifold, and (b) a fireproof insulating material made of inorganic fiber is immediately delivered to the layer of the inorganic binder solution together with a gas to adhere. (c) forming a fireproof heat insulating layer by performing the first step including drying and solidifying by heat treatment at least once; and (d) applying an inorganic binder solution on the surface of the fireproof heat insulating layer. (e) Immediately deposit the refractory material powder on the layer of the inorganic binder solution by feeding it with a gas, and (f) perform the second step at least once including the step of drying and solidifying by heat treatment. A method for manufacturing a heat insulating manifold characterized by forming layers.