JPH0538565A - Ceramic calcined body for internal chill - Google Patents

Abstract

PURPOSE:To prevent the cracking and crazing to be generated on the inside surface of the hollow ceramic calcined body. CONSTITUTION:Pulverized quartz glass is pressurized and stuck to the inside surface of a molding 1 consisting of hollow aluminum titanate and is calcined in an electric furnace 3 kept at 1550 deg.C, by which the ceramic calcined body 4 formed with the quartz glass layer 2 on the inside surface is produced. Consequently, the generation of peeling between the ceramic calcined body and the quartz glass is obviated and the cracking and crazing generated in the ceramics are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic fired body mainly used as a heat insulating member in a cylinder liner of an internal combustion engine, an exhaust port, an exhaust manifold, etc. It relates to a ceramic fired body.

[0002]

2. Description of the Related Art In recent years, research into ceramics for automobile parts has been conducted from the viewpoint of improving performance. In particular, due to the excellent heat resistance of ceramics, application research on engine parts is being actively conducted. For example, when it is applied to an exhaust port or an exhaust manifold, it is necessary to form a hollow body, but ceramics are easily damaged by thermal shock during heating or cooling, or shock during handling. It is considered that the method of casting with metal is an effective means, and in Japanese Patent Laid-Open No. 1-317677, ceramics having aluminum titanate as a main crystal is used as an inner layer and metal for casting is used as an outer layer. Disclosed is a ceramic composite that is in close contact. Since such ceramics containing aluminum titanate as the main crystal have low thermal conductivity, the structure in which the ceramics are cast is excellent in heat insulating property. Also, since it is a low strength material and has a small Young's modulus, When cast metal is cast, shrinkage of the cast metal can be easily absorbed. Therefore, the shrinkage of the cast metal can be followed in the cooling process, so that the ceramic is not broken and the ceramic is not dropped from the cast metal.

[0003]

However, when it is used for an exhaust port for a cylinder head of an internal combustion engine, an exhaust manifold, etc. for the purpose of improving output by heat insulation, etc., incomplete combustion components in fuel and metal oxide particles Flies and collides with the inside. In such a case, the low-strength material is a negative factor, and when the particles collide, a part of the inner wall of the molded body is scraped off or cracks occur.
Therefore, the cast-firing ceramic fired body of the present invention is produced in the ceramic fired body by protecting the portion where exhaust gas flowing inside the hollow ceramic fired body comes into contact with the ceramic with a material having higher hardness and higher strength than the ceramic. The purpose is to prevent cracks and cracks.

[0004]

The ceramic sinter for cast bodies according to the present invention has a linear expansion coefficient of -0.5 × 10 ^-6 / K.
A feature is that a quartz glass layer is provided on the inner surface of a hollow ceramic fired body made of a material of 0.5 × 10 ⁻⁶ / K. As the ceramic material having a linear expansion coefficient within the above range, aluminum titanate, potassium dizinc phosphate, lithium aluminosilicate, or the like can be used. As a method of forming a quartz glass layer on the inner surface of the ceramic fired body, pressure is applied to the crushed quartz glass to directly adhere to the inner surface of the formed body, followed by firing to melt the quartz glass to form an organic medium or A method of attaching with an adhesive or the like, for example, crushed quartz glass is added to a polyester-based adhesive, a curing agent is added after mixing, and the mixture is applied to the inner surface of the ceramic molded body, cured, and then baked to form an adhesive. A method of disappearing it can be considered.

[0005]

[Function] Since the hardness and strength of quartz glass are superior to the hardness and strength of cast ceramics, by providing a layer of quartz glass in a portion where exhaust gas flows, incomplete combustion components in the fuel and metal Even if small particles of oxide fly and collide, the ceramics can be protected with a layer of quartz glass having excellent resistance to particle collision. Also, with quartz glass,
Since there is almost no difference in the linear expansion coefficient among the above-mentioned aluminum titanate, potassium dizinc phosphate, lithium aluminosilicate, etc., the interface between the quartz glass and the ceramic fired body can be used at various temperatures from low to high. Thermal stress hardly occurs, and even if it does occur, its value is very small. Therefore, the inner surface of the ceramic fired body can be protected without peeling at the interface between the ceramic fired body and the quartz glass.

[0006]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. First, a slip for forming the ceramic liner produced in this example is produced. 6% by weight of ferric oxide and 2% by weight of silicon oxide as sintering aids
80% of the powder concentration is obtained by using ammonium polycarboxylate as a deflocculant in aluminum titanate powder containing
Distilled water was added so as to be mixed and mixed with a ball mill to prepare a slip. Table 1 shows the hardness, strength, melting point and linear expansion coefficient of aluminum titanate and quartz glass.

[0007]

[Table 1]

The finished slip was poured into a predetermined gypsum mold, and after being inlaid, the excess slip was drained to form a cylindrical shape having an outer diameter of 40 mm, an inner diameter of 32 mm and a thickness of 4 mm. Next, this molded body 1 is taken out of the gypsum mold after drying, and quartz glass crushed to an average particle size of 0.05 mm is pressed against the inner surface of the molded body 1 at a pressure of about 1 kgf / cm ^{2 to} a thickness of 0.2 mm. To be attached. As shown in FIG. 2, the molded body 1 obtained by the above process was held in the electric furnace 3 at a temperature of 1550 ° C. for 4 hours for firing. Since the melting point of the quartz glass is about 1600 ° C., the quartz glass reaches a temperature near or exceeding the melting point at this point, and the quartz glass melts to form the quartz glass layer 2 on the inner surface of the molded body 1. A cross section of the finished fired body 4 is shown in FIG. Next, the fired body obtained in the above step was placed in a mold, and a molten aluminum alloy was poured to cast it. FIG. 3 shows a cross section of the obtained cast body. In this way, the outer peripheral surface of the fired body 4 is made of an aluminum alloy and has a thickness of 6 mm.
The metal layer 5 is formed. (Comparative Example 1) After forming history by the same method as in the above-mentioned example, the ceramic liner in which the quartz glass layer is not formed on the inner surface was produced by firing in that state, and casted with aluminum alloy. (Comparative Example 2) A ceramic liner having an alumina layer formed on the inner surface was formed after molding by the same method as in the above-mentioned example, and casted with aluminum alloy. Table 2 shows the hardness, strength, melting point and linear expansion coefficient of alumina.

[0009]

[Table 2]

(Evaluation) A high-temperature durability test was conducted on the cast doll body thus obtained. That is, when a high temperature gas of 1000 ° C. was continuously flowed into the fired body 4 at a flow rate of 50 m / s for 100 hours, cracks occurred in the fired body in which the quartz glass layer was not formed on the inner surface. The fired body 4 formed in the example did not have defects such as cracks.
Particles obtained by pulverizing the alumina calcined body into about 1 mm square were introduced into the above-mentioned high temperature gas and a particle collision test was conducted. Similarly, no problems such as chipping occurred on the inner surface of the calcined body 4 of the example. It was In Comparative Example 2, peeling occurred between the fired body and quartz glass, whereas no peeling was observed in the fired body of the example. This is shown in Table 1 for the linear expansion coefficient of aluminum titanate and quartz glass.
Since there is almost no difference as shown in Fig. 5, it is difficult for thermal stress to occur at the interface between the fired body 5 and the quartz glass layer 2 from the low temperature to the high temperature of the operating environment. Thought to be a thing. Further, since aluminum titanate has a large number of fine pores, the quartz glass permeates into the pores in the fired body 4 during firing, and the bond between the two is further strengthened. Furthermore, the melting point of quartz glass is 160
Since the temperature is about 0 ° C. near the firing temperature of aluminum titanate, the formation of the quartz glass layer and the firing of the ceramic can be performed at the same time, and after the quartz glass is once melted,
Since the inner surface of the ceramic part is layered, the surface roughness is improved,
The exhaust resistance of exhaust gas flowing inside can be reduced. Further, when the metal layer 5 made of an aluminum alloy is cooled and solidified during casting, compressive stress is applied to the fired body 4 from the outer periphery. However, since aluminum titanate is a low-strength material, the stress can be absorbed by the deformation of the outer surface side of the fired body 4, and the fired body 4 can be prevented from cracking.

[0011]

EFFECTS OF THE INVENTION According to the ceramic fired body for cast iron of the present invention, by providing a layer of quartz glass having almost no difference in linear expansion coefficient on the inner surface of the ceramic fired body, peeling occurs between the two. Moreover, it is possible to prevent cracks or cracks generated when particles such as exhaust gas flowing inside the hollow ceramic fired body collide with the ceramics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a fired body of this example.

FIG. 2 is an explanatory diagram of a firing apparatus of this example.

FIG. 3 is a cross-sectional view of a cast-in toy body according to the present embodiment.

[Explanation of symbols]

 1 ... Molded body 2 ... Quartz glass layer 3 ... Electric furnace 4 ... Firing body 5 ... Metal layer

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Claims (1)

[Claims] 1. A linear expansion coefficient of −0.5 × 10 ⁻⁶ / K to
1. A ceramic fired body for cast bodies, characterized in that a quartz glass layer is provided on the inner surface of a hollow ceramic fired body for cast bodies made of a material of 0.5 × 10 ⁻⁶ / K.