The manufacturing of tungsten carbide die and repairing of old mold are inseparable from mechanical grinding. Relatively speaking, the grinding process is more complicated, which including rough grinding, fine grinding, fine grinding and polishing. Under normal production conditions, the die wear is not very serious. So, the grinding usually includes fine grinding, fine grinding and polishing.

 

 

1, Grinding Additives

Common abrasives used for mechanical attrition are diamond powder, boron carbide, silicon carbide and alumina. In addition to hardness, abrasives need to have edges and corners. The abrasive itself is also worn when grinding, and the grinding performance decreases when the corners become round. Boron carbide is the most commonly used abrasive for carbide grinding at present.

 

Boron carbide (B4C) is a gray black rhombohedral crystal with a metallic luster on the surface and decomposition and volatilization at temperatures above 2600 degrees. Boron carbide is chemically stable, insoluble in water, and does not react with acids and bases. It has good corrosion resistance. The hardness of boron carbide is second only to diamond, and has the characteristics of wear resistance and pressure resistance. The grinding rate is 60% ~ 70% of the diamond, and it is more than 5 times of the high quality green silicon carbide. 

 

Carborundum (SiC) includes black silicon carbide, green silicon carbide and cubic silicon carbide (green). The hardness and brittleness of green silicon carbide are higher than that of black silicon carbide, which is similar to boron carbide. However, its price is much cheaper than that of boron carbide. Cubic silicon carbide particles have good integrity and high toughness, which can be used for polishing.

 

The crystal of alumina is columnar or conical. Because of its different inclusions and different colors, it is called white jade with a colorless and transparent color. It is called "Ruby" with chrome red and transparent, and cobalt blue and transparent is called sapphire. Alumina for abrasives include white corundum, light yellow single crystal corundum, brown alumina, pink fused alumina (red or purplish red) and fused alumina zirconia (brown gray). Corundum hardness is slightly higher than that of tungsten carbide, white or light yellow corundum grinding performance is better, chrome corundum and zirconia corundum are good toughness, more for grinding and polishing.

 

2, Particle Size of Abrasive

Abrasive is crushed into different granularity according to the roughness of grinding. Powdery abrasive can not be used directly, it needs to be added into liquid in a certain proportion to make abrasive. The liquid is usually water, mineral oil and vegetable oil. They can make the abrasive evenly distributed and adsorbed in the mold hole to reduce the spatter of the abrasive.