JPS63108B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a ceramic pulverizing medium, particularly a medium for a pulverizer and mixer used in the process of pulverizing ceramic raw powder to submicron size. Silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), zirconium oxide (ZrO ₂ ), etc. have recently attracted attention as fine ceramics.
It is also well known that these sintered bodies exhibit high strength at high temperatures.
However, since these fine ceramic materials must first be pulverized to submicron size and then sintered, there is a major problem in pulverization. In other words, this ceramic material is usually crushed using a ball mill, Boulton mill, or vibrating mill, but in this case, even if a rubber-lined crusher is used to prevent wear, the ceramic materials are fed into the crusher. Since the medium is carbon steel, tungsten carbide, alumina, etc., it is impossible to avoid wear of the medium during grinding. For example, if SiC is ground to about 0.8 to 1 μm using carbon steel balls, the fine powder contains about 5% iron, and if Si ₃ N ₄ is ground to 0.8 to 1 μm with a tungsten carbide ball,
There was a disadvantage that the Si ₃ N ₄ powder contained approximately 1% tungsten, which resulted in a disadvantage that the high temperature strength of the ceramic sintered body made from it was reduced. For this reason, methods are being considered for pulverizing this fine ceramic material using SiC, which has a high hardness compared to diamond, as the medium, but SiC sintered bodies made by hot pressing are very expensive and expensive. However, products made by normal pressure or gas pressure sintering have low strength, so they have not yet been put to practical use. The present invention relates to a ceramic grinding medium which solves these disadvantages, and which has a specific gravity of
It is characterized by being composed of a silicon carbide-silicon (SiC-Si) sintered body with a molecular weight of 2.8 or more. To explain this, the present inventors have conducted various studies on the media for ceramics grinding, and found that if a SiC-Si sintered body is used, it will have high hardness and will not wear out in a normal mill. Therefore, there is little risk of contamination as impurities in the ceramics to be crushed;
In addition, this SiC-Si sintered body is made by mixing SiC and carbon powder, molding it, and then infiltrating it with molten silicon, so it is inexpensive.
The present invention was completed by confirming that this method enables ceramics to be crushed more advantageously than conventional methods. The SiC-Si sintered body used in the method of the present invention is itself known as a fine ceramic material, and the grinding medium based on this material is a combination of SiC powder and a carbon source material such as carbon, as described above. After mixing the powder and a hydrocarbon compound such as phenolic resin and molding it into the desired shape and size at normal pressure,
It can be made by immersing it in a bath of molten silicon. The shape and size of this molded product can be determined depending on the shape and size of the ceramics to be crushed, but for example, the diameter is 25 mm.
It may be formed into a ball shape or a column shape of 12.5 mmφ x 12.5 mm. When this molded product is immersed in a molten Si bath, most of the Si becomes SiC due to the reaction between the carbon source material and Si, but some of it remains in the molded product as Si, resulting in SiC-Si sintering. Becomes a body. but,
If the amount of Si contained in this SiC-Si sintered body is too small, there is a disadvantage that the material strength will not be achieved.
If the amount is too large, the strength will decrease, and in this case, the wear resistance will also deteriorate, so in order to achieve the purpose of the present invention, it is necessary to
It is preferably in the range of 40%, preferably in the range of 7 to 20%. In addition, this SiC-Si sintered body should be free of other substances as much as possible, but depending on the purpose, it may contain titanium carbide, boron carbide, tungsten carbide, boron nitride, aluminum nitride, silicon nitride, or oxide. It may be a mixture containing 1% by weight or less of one or more compounds selected from silicon, and with this, the material strength and wear of the sintered body are almost the same as in the case of SiC-Si. , an additional effect is that sintering progresses more easily. Note that this SiC-Si sintered body has a size of, for example, 4 mm x 3 mm.
40-65Kg/3-point bending strength using a 10mm test piece
mm ² , but from the standpoint of maintaining its strength, its specific gravity is 2.8 (Si content in SiC-Si is approximately 40
%) or more, and this should preferably be in the range of 3.0 to 3.2 with a Si content of around 10%. Next, examples of the method of the present invention will be given. Example 1 Silicon carbide particles (SiC) with an average particle size of 44 μm were
The surface of the product was placed in a rubber-lined vibration mill, Boulton mill, or ball mill, and SiC-Si media (Si content 10
%, specific gravity 3.10), carbon steel media (specific gravity 7.90), and alumina media (specific gravity 3.63), and wet milling under the conditions shown in Table 1. The time and amount of impurities mixed in were as shown in Table 2, and it was confirmed that the SiC-Si medium was the most excellent.

【table】

[Table] Cannot be used as a medium.
In addition, we made 20 test pieces of 4 mm x 3 mm x 10 mm by cutting the SiC-Si medium used here, and measured the three-point bending strength of these.
However, for comparison, the three-point bending strength of a medium made from a SiC sintered body made by normal pressure sintering and gas pressure sintering was 25 to 35 Kg/ ^{mm2 .} , which broke within a few hours in the ball mill mentioned above. Example 2 Silicon nitride (Si ₃ N ₄ ) particles with an average particle size of 44 μm were placed in a rubber-lined vibration mill or ball mill, and the SiC-Si medium used in Example 1 and the tungsten carbide (WC) medium [specific gravity 6.70〕
When wet pulverization was performed under the same conditions as in Table 1 in Example 1, the results shown in Table 3 were obtained, confirming that the SiC-Si medium was excellent in this case as well. It was done.

【table】

Claims (1)

[Scope of Claims] 1. A ceramic pulverizing medium comprising a silicon carbide-silicon sintered body having a specific gravity of 2.8 or more. 2. The ceramic grinding medium according to claim 1, wherein the silicon carbide-silicon sintered body contains 3 to 40% silicon. 3 The silicon carbide-silicon sintered body contains 1% by weight or less of one or more compounds selected from titanium carbide, boron carbide, tungsten carbide, boron nitride, aluminum nitride, silicon nitride, and silicon oxide. A ceramic grinding medium according to claim 1 or 2.