JPS6021173A - Production of ceramic-inserted casting - Google Patents

Abstract

PURPOSE:To obviate cracking in ceramics owing to insert casting by coating a compsn. consisting of refractory powder, binder, solvent and thermoplastic resin insoluble in the solvent on the surface of the ceramics/and evaporating the resin by heating to form a porous cushion material layer. CONSTITUTION:A compsn. consisting of refractory powder, binder, solvent and thermoplastic resin insoluble in the solvent is coated on the surface of a ceramics in contact with a molten metal and is heated to the temp. higher than the thermal decomposition temp. of the resin to evaporated the resin, thereby forming a porous cushion material layer which is then inserted by the molten metal. Water glass, colloidal silica, etc. are used for the binder and a solvent suitable for the binder used is used for the solvent. The binder and the solvent are used at about 10-15wt% in total. >=1 Kind among PP, PE, etc. are used at about 5- 40wt% for the thermopolastic resin/and the grain size thereof is made to about <=200mu. The thickness of the porous cusion material layer is made to about <=1/15 the wall thickness of the metal for insert casting.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing ceramic castings, in which a cushioning material is added to the ceramics for casting in order to prevent cracks in the ceramics due to thermal shock during casting or shrinkage after casting. The present invention relates to a method of forming and manufacturing ceramic castings.

Products made of ceramic molded bodies cast in molten metal are used in high-temperature areas such as the combustion chamber and exhaust system of internal combustion engines in order to improve heat insulation properties and thermal efficiency. Such molded bodies for castings are required to have the following properties during casting or use.

b) Must have a certain degree of flexibility, withstand thermal shock during molten metal casting, and do not cause cracks in castings or ceramics.

(Example) During use, it should be able to withstand shocks such as vibrations and cooling/heating cycles, and should have good durability.

In order to meet these demands, flexible ceramic molded bodies with high strength and a small Young's modulus are promising.
In Japanese Patent Application No. 58-3571, the applicant et al. added at least one of silicate sorter, silicozirconate sorter, and Hyal Enfill sorter to the refractory powder, and at least one of blast furnace slag, calcilis slag, and magnetic slag. We propose flexible ceramics characterized by forming a composition formed by blending a seed into a desired shape and then heating and firing it,
We are getting good results.

However, this method is effective for castings and ceramics with relatively large wall thicknesses, but it is not suitable for castings or ceramics with small wall thicknesses because it is not sufficient to prevent unexpected thermal shocks and vibrations during operation. I am reminded that I cannot buffer it.

The present invention was made to solve the above concerns, and by providing a buffer layer on the surface of the ceramic that comes into contact with the molten metal, it is possible to buffer thermal shock during casting and vibration during operation. The present invention provides a method for producing a ceramic casting.

That is, the present invention provides a method for manufacturing ceramic castings in which ceramics placed at a predetermined position in a mold are cast with molten metal, in which refractory powder, a binder, a solvent, and polypropylene, polyethylene, polystyrene, which is insoluble in the solvent,
After applying a composition containing one or more granular thermoplastic resins such as polymethacrylate and polyethylene terephthalate to a desired thickness, heating to a temperature higher than the thermal decomposition temperature of the resin,
The present invention relates to a method for manufacturing a ceramic cast material, characterized in that the entire porous buffer material layer is formed by volatilizing the resin.

The method of the present invention can be applied to surface-treated materials such as ceramics for castings and other ceramics that require flexibility.

FIG. 2 is an enlarged view of section A in FIG. 1, which is a cross-sectional view of a pipe in which ceramics for castings according to the method of the present invention is cast.

In FIGS. 1 and 2, 1 is ceramic, 2 is a buffer material layer formed by the method of the present invention, and 3 is a cast metal.

The buffer material)@2 is applied as a coating material to the surface of the ceramic 1 that comes into contact with the molten metal, and then heated to make it porous.

The coating material is Zr, 5i04. ZrO2,A
120B.

The main component is refractory powder such as MgO. The refractory powder used is preferably of the same quality as the ceramic 1 to be used. This is because if the materials are of the same quality, the coating layer is less likely to peel off due to differences in expansion coefficient during heating.

The binder used is preferably a binder with high temperature properties such as water glass, colloidal silica, or ethyl silicate. The buffer material layer 2 using these binders will not peel off even if it comes into contact with molten metal during υj wrapping. Furthermore, excellent durability can be obtained when used as a ceramic cast product.

Add water if water glass or colloidal silica is used as the binder, or add a solvent such as ethanol or isopropyl alcohol if ethyl silicate is used as the binder, and form a slurry with the above refractory powder. do.

To this slurry, one or more granular thermoplastic resins such as polypropylene, polyethylene, polystyrene, polymethacrylate, polyethylene terephthalate, etc., which are insoluble in the solvent, are blended. These thermoplastic resins have the property of being easily depolymerized by heating, and the cushioning material layer 2 obtained by applying these thermoplastic resins to the surface of the coating material all-ceramic 1 and then heating the resin il 1 min. It becomes hollow and porous. Since the thermoplastic resin is easily depolymerized, it is difficult to leave residues, and it is difficult to leave residues. ) are less likely to occur.

The particle size of the thermoplastic resin is not particularly limited, but may be 200 mm,
m or less is desirable. The particle size of the resin determines the size of the nitrogen cavity obtained after heating, so the finer the particle size, the easier it is to adjust the coating thickness of the coating layer.
The complexities of the obtained buffer material layer 2 also tend to be constant. These granular thermoplastic resins are preferably intermediate products before being pelletized, and the particle size of the intermediate products is 20011 mm.
The following fine particles.

The amount of the thermoplastic resin added is preferably 5 to 40% by weight. If the amount is less than 5M, the number of pores in the cushioning material obtained after heating is small, so that it is not possible to alleviate thermal shock during casting and shrinkage after casting, which is the objective of the present invention. Also, 40
If it exceeds % by weight, independent nitridation cannot be obtained and peeling is likely to occur.

The total amount of the casing, binder and solvent added is preferably 15 to 50% by weight. If it is less than 15% by weight, it cannot be coated because it does not become a slurry, and if it is more than 50% by weight, the fluidity is too low and the refractory and resin separate, resulting in a buffer material layer with uniform pores. I can't do it. Of these, the amount of binder added is
It is desirable that the amount is 5% by weight or more of the total formulation. At 5% by weight or less,
The adhesion of the coating layer after heating is insufficient and it is easy to peel off. The upper limit of the amount of binder added is preferably 50% by weight for the above-mentioned reasons.

The refractory is added as the remaining amount of the above formulation,
It is added in a range of 10 to 80% by weight.

A coating agent having the above-mentioned composition is applied to the surface of the ceramic 1 to a desired thickness. The thicker the coating layer, the more effective it is against thermal shock and shrinkage during casting, but if the thickness is at least about 1715 mm thick, which is the thickness of the casting metal, it will prevent cracks from occurring in the casting or ceramics during casting. can. In addition, the cushioning material layer tends to be weak in strength because it has many pores. Therefore, in products that are used under severe conditions, such as engine exhaust pipes that are subjected to severe vibrations, the cushioning material layer tends to break down over long periods of operation. Therefore, for products that are used under severe conditions, it is desirable that the thickness of the buffer material layer be approximately 115 times the thickness of the cast metal or less. However, this does not apply if the strength conditions are not severe.

Note that the thermoplastic resin in the coating agent is depolymerized by maintaining the temperature at 400°C or higher.

Moreover, the reason why the buffer material layer 2 is made porous in the present invention is as follows.

Although ceramics have excellent heat resistance and heat insulation properties, they have almost no flexibility. Therefore, when casting with metal, thermal shock during pouring and subsequent contraction of the metal may cause the casting or
Ceramics have the disadvantage of being prone to cracking. Of these,
Thermal shock during pouring can be partially solved by using ceramics, etc. (see Japanese Patent Application No. 58-3571), but it is difficult to completely prevent cracks during shrinkage.

The prevention of cracks during shrinkage is solved by providing a porous buffer layer on the ceramic surface. The pores in the buffer material layer are formed by decomposition of the resin, and are fine spherical independent pores. Since the buffer material layer is more porous than ceramics, it will break under a low load. In addition, since the pores are independent, the pores break down in order from the surface on which the load is applied, making it difficult for the load to be transmitted to the inside.

Due to this action, the cushioning material layer is destroyed from the surface as the cast metal shrinks after pouring, and the cushioning material layer and the internal ceramics, which are not subject to shrinkage, are less likely to be destroyed.

Next, examples of the present invention will be given.

Embodiment FIG. 6 is a partial sectional view showing a ceramic cast exhaust pipe of a single-head engine. Ceramic 11 has an inner diameter of φ
The cast metal 15 has a diameter of φ75 and a length of 200 mm.

The composition of ceramics 11 is as follows.

Zircon powder 8 wt% Calcilis slag bwt% Water glass 12wt Yu The above mixture was filled into a mold to obtain a desired shape.

In addition, ceramics 11 with this composition has a 900 to 1,20
It is desirable to perform the firing in a temperature range of 0°C. If the temperature is below 900℃, the soda content in the water glass will remain, resulting in poor water absorption and lack of durability as an exhaust pipe.If fired at temperatures above 1.200℃, a high-strength product can be obtained, but the Dimensional changes are large and it is not possible to form the desired shape. 900
Ceramics fired in the temperature range of ~1.200°C 11
The properties are that the dimensional change before and after firing is 0.5% or less, the compressive strength is 5.5 to 4 Yu/tomo2, and the strain is around 1.7 threads.

The composition of the coating material used to form the buffer material layer 12 is as follows.

Zircon powder 56.5 wt% Calcilis slag 5.5 wt Ice water glass 9.5 wt% Water 1 6.5 wt% Polypropylene powder 14 wt% The zircon powder, calcilis slag, and water glass in this coating material are the same as the ceramics 11 mentioned above. This is the same as above, with the addition of water as a solvent and polypropylene powder.

The coating material was applied to the outer periphery of the unfired ceramic 11 to a thickness of about 0.7 mm. The ceramic coated with the coating material was fired at 1000° C. for about 5 hours. After firing, the thickness of the buffer material layer 12 obtained by volatilizing the resin and water in the coating material was about 0.4 days.

A ceramic 11 with a buffer material layer 12 and a ceramic 11 without a buffer material layer 12 for comparison were placed at predetermined positions in the mold, and the casting material was 5.5%.
Cast iron with a composition of C, 3% S1, 0.6% Mn, 1.2
The hot water was poured at a temperature of 80 to 1.300°C.

As a result, most of the ceramics 11 without the buffer material layer 12 had cracks and peeling due to shrinkage of the casting after pouring, whereas the ceramics 11 with the buffer material layer 12 had cracks and peeling. A sound exhaust pipe made of Ceramic 11 without any cracks was obtained. Also, during operation, the ceramics 11 without the buffer material 7112 cracked and fell off due to engine vibration, whereas the buffer material N11
Those treated with this showed good durability.

As described above, according to the method of the present invention, it is possible to cast ceramics 11 without causing cracks, and it is effective in alleviating vibrations even during operation. can play.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of a ceramic cast VJ product according to the method of the present invention, Fig. 2 is an enlarged view of A in Fig. 1, and Fig. 6 is a diagram showing an example of a single-head engine manufactured by the method of the present invention. It is a diagram showing an exhaust pipe f made of ceramics. Sub-agent 1) Meifuku agent Ryo Hagiwara -

Claims (1)

[Claims] In a method for manufacturing ceramic castings in which the entire molten ceramic metal is cast in a predetermined position in a mold, the surface of the ceramic that comes into contact with the molten metal is coated with refractory powder, a binder, a solvent, and a material insoluble in the solvent. A composition containing one or more granular thermoplastic resins is applied to a desired thickness, and then heated to a temperature higher than the thermal decomposition temperature of the resin to volatilize the resin, thereby forming a porous buffer. A method for manufacturing a ceramic cast material, characterized by interposing a material layer.