The abrasives used to make resinoid grinding wheels do not require high magnetic material content, but they have strict requirements on the surface quality of abrasive particles. Because graphite and dust are attached to the surface of the abrasives, the bonding force between the resin and the abrasive particles can be reduced and weakened, resulting in a reduction in the hardness and strength of the resinoid grinding wheels. In order to improve the bonding ability between the abrasives and the binder, and to improve the strength, toughness, and wear resistance of the abrasives, the abrasives should be subjected to necessary additional treatment. The treatment methods for abrasives include calcination, particle shaping, surface coating, and surface corrosion.
1. Calcination treatment of abrasive grains
The microhardness, toughness and hydrophilicity of abrasive grains can be significantly improved by calcining corundum abrasive at 800~1300℃ for 2~4h. When the temperature exceeds 1300℃, the performance of abrasive grains decreases. Calcination treatment has a significant effect on corundum abrasives, but not on SiC abrasives.
2. Use special processes to manufacture abrasive grains
The corundum abrasive is produced by the frit method. The frit method has the characteristics of large crystal particles, which increases the strength and hardness of abrasive grains. The rolling method is used in the abrasive grain processing method. It can increase the flake and sword-shaped particles while ensuring the roughness of the abrasive surface. After rolling and screening, the content of the basic abrasive particles and the uniformity of the strength can be improved, and debris, dust and coarse particles can be cleaned.
3. Abrasive surface coating treatment
It is to apply a thin layer of material on the surface of the abrasive, and then heat treat and loosen the screening. Its function is to improve the hydrophilicity of the abrasive surface and increase the surface roughness. The coating treatment methods include metal salt treatment, resin treatment, ceramic liquid-silane treatment and alkaline corrosion treatment. Different coating treatment methods are used to treat corundum abrasives according to different requirements for resinoid grinding wheels.
4. Plating treatment of superhard surface
The surface of superhard abrasive is coated with a coating layer of different materials, which becomes a new type of abrasive with different properties. The purpose of plating is to give superhard abrasive particles and special physical and chemical properties, thereby improving the performance and use effect of the abrasive and improving the durability of the resinoid grinding wheels.
The coating materials used in production include copper, nickel, molybdenum, copper alloy, copper-tin-titanium alloy, non-metallic materials such as ceramics, titanium carbide, titanium nitride and other refractory hard materials.
At present, copper-plated and nickel-plated diamond and CBN abrasives are commonly used to manufacture resinoid grinding wheels, and about 90% of resin-bonded diamond abrasives use diamond abrasives coated with metal films. Using plated CBN abrasives can reduce the number of abrasive grains from 60% to 30%. Copper-plated abrasives are used for dry grinding, and tin-plated abrasives are used for wet grinding.
