JPS61209954A - Manufacture of silicon carbide base refractory material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a silicon carbide refractory material.

Silicon carbide has traditionally been used as a refractory material with excellent heat resistance and thermal shock resistance. The manufacturing method is pressure sintering or pressureless sintering, but while pressure sintering can produce dense and high-strength products, it can only produce products with simple shapes and requires complicated equipment. It's expensive.

Pressureless sintering has also been carried out, but since it involves the addition of boron and carbon and is a solid phase reaction, the properties are affected by the state of dispersion of the additives, and its reliability has not always been satisfactory.

This invention is a method of manufacturing a highly reliable, high-density, high-strength sintered body by sintering at normal pressure by taking advantage of the heat resistance and thermal shock resistance inherent to silicon carbide.

In the conventional pressureless sintering method, ultrafine powder is used and sintering is performed using a solid phase reaction, resulting in a volumetric shrinkage of about 20%. For this reason, strain tends to remain in the sintered body.

The present inventors investigated the cause of this strain and found that it is greatly influenced by the surface oxidation state of the main raw material, SiC.

The surface of silicon carbide particles is oxidized by air even at room temperature, and this is more noticeable in the case of ultrafine particles of 1 μm or less. That is, it is clear that the amount of oxidation is proportional to surface area as well as time and temperature.

This oxygen on the surface of silicon carbide affects the reaction with boric acid and other sintering aids, but especially in AJ! This is noticeable when N is used. IN is S; In the C-IN-C system, the reaction proceeds in the liquid phase at 2000 to 2200°C, so it is clearly a more preferable sintering aid than 1Fjl acid in terms of homogeneity, but as mentioned above, It is susceptible to interference by oxygen on the SiC surface.

Although it is possible to suppress this interference by incorporating C into the reaction system, this alone is not sufficient.

In the conventional pressureless sintering method, A, l! It is known that N is used as a sintering aid, but in this case, WC, BC,
B, A, l! It is used together with other sintering aids such as 203, etc., and it has not been possible to obtain a sufficiently dense product (90% or more of the theoretical density) using AI N-C alone as in the present invention. This is because no consideration was given to the influence of moisture in the molded article.

Therefore, in the present invention, dried blended powder is used,
In addition, a binder with moisture content suppressed to 1% or less is used. This is because AfIN in particular easily reacts with moisture and decomposes, so iN mixed with moisture
This is because it has become clear that the substance changes in quality and becomes ineffective as a sintering aid. Therefore, in order to prevent moisture from entering the molded product, consideration must be given not only to the moisture content in the raw material powder but also in the binder used.

Since silicon carbide, aluminum nitride, and carbon are granular, it is relatively easy to dry them. That is, when firing a molded body, it can be volatilized from the particle surface at a low temperature in the initial stage of heating.

However, even though ordinary binders are hydrophobic, they often contain water, and even during firing, they do not volatilize as easily as the water attached to the particle surface. Even if silicon powder with low surface oxidation is used, it is easily oxidized by the moisture in the binder, and this causes sr C-A, l! This will have an adverse effect on the NC reaction system.

The binder can be used as it is or diluted with a solvent, etc., but the water content that does not affect the above reaction or can be ignored is 1% or less, preferably substantially no water content. shall not be included.

This invention will be explained below with reference to Examples.

Example 90 parts of Shi-S+C powder with an average particle size of 0.5 μ 5 parts of AIN powder with an average particle size of 4.0 μ in dry state (
10 parts of phenol resin (water content: 0.3%) and ioo parts of acetone (water content: 0.2%>) were added to a mixed powder with a water content of 0.1%, and the mixture was granulated.

This compact was sintered under normal pressure at 2100°C in an atmosphere of A.The density of this product was 3.15 (corresponding to 98% of the theoretical density), the bending strength at room temperature was 550 MPa, and the bending strength at 1200°C was 650 MPa. Ta.

As a comparative example, commonly used phenol resin (water content 1.1%) and acetone (water content 1.3%) were used, and sintered bodies were obtained in the same manner as in the examples.

This material had a density of 2.75 and a room temperature strength of 250 MPa. AI! The addition ratios of N and C are both SiC
It is preferably within the range of 1 to 10% by weight,
If it deviates from this range, high density and high strength cannot be obtained. Similarly, if the firing temperature is outside the range of 2000 to 2200°C, preferred density and strength cannot be obtained.

Note that the present invention is not limited to only the St C-AIN-C ternary system, but is based on the BC9A, l! Conventional sintering aids such as 203 can also be used.

Inventor Yukifumi Sakai Inventor: Hiroshi Deshiro Inventor: Teruyasu Aquaregia

Claims (2)

[Claims] (1) 1 to 10% by weight of SiC powder in dry state
1. A method for producing a silicon carbide material, which comprises mixing C, blending a binder with a moisture content of 1% or less, molding, and firing at 2000 to 2200°C in a non-oxidizing atmosphere. (2) The method for producing a silicon carbide refractory material according to claim 1, wherein the binder contains substantially no water.