The selection of grinding wheel mainly considers abrasive, particle size, hardness, binder, etc.
The selection of grinding wheel abrasive is mainly related to the material, heat treatment method and hardness of the workpiece to be ground. The grinding wheel shall have high hardness, wear resistance, heat resistance and certain toughness. At the same time, it shall also have sharp corners to facilitate metal cutting. At present, abrasives are mainly divided into the following three categories according to different components:
(1) Carbide: mainly black silicon carbide, green silicon carbide, boron carbide, cubic silicon carbide, etc. it is suitable for grinding stainless steel, cast iron, brass and non-metallic materials.
(2) Oxide system: mainly brown corundum, white corundum, zirconium corundum, single crystal corundum, microcrystalline corundum, etc. it is suitable for grinding carbon steel, high-speed steel, bearing steel, tool steel, etc.
(3) Superhard abrasive: it mainly includes natural diamond, artificial diamond, cubic boron nitride, etc. it generally grinds materials with high hardness and brittleness. At the same time, diamond-like Abrasives can also be used as grinding wheel dressing tools.
Corundum and ceramic abrasives are recommended for gear tooth surface grinding of carburizing and quenching.
- Particle size
Particle size refers to the size of the grinding wheel particle size. The smaller the grinding wheel particle size, the smaller the particle size brand; On the contrary, the larger the particle size grade is. The choice of grinding wheel grain size is directly related to the machining time and tooth surface roughness during gear grinding.
2.1 applicable conditions of coarse grain grinding wheel
Select a coarse-grained grinding wheel for grinding under the following conditions:
(1) Parts with high toughness and low hardness.
(2) Materials with poor thermal conductivity and easy to burn.
(3) When the feed rate is large.
(4) When the requirements of tooth surface roughness are not high, that is, on the premise of meeting the requirements of roughness, the grinding wheel with coarser particle size shall be selected as far as possible.
(5) When the contact area between the tooth surface and grinding is large, the grinding wheel with larger particle size shall be selected to prevent grinding burns caused by excessive heat during grinding.
2.2 applicable conditions of fine grain grinding wheel
Select fine-grained grinding wheel for grinding under the following conditions:
(1) During tooth surface grinding, the retention of formed grinding wheel is improved to ensure high grinding tooth accuracy.
(2) When the tooth surface roughness is required to be high.
(3) Grinding parts with small tooth surface modulus.
The grinding wheel with particle size of 46 ~ 80 should be selected during the grinding of carburized and quenched gears, which can increase the contact area between the grinding wheel and the tooth surface and reduce the roughness of the tooth surface. At the same time, the grinding wheel shall have a certain chip holding space to ensure chip removal and heat dissipation performance.
The hardness of grinding wheel refers to the difficulty of grinding particles on the surface of grinding wheel breaking or falling off from the bond under the action of axial force and radial force of machine tool when the grinding wheel rotates at high speed during gear grinding. The general principles for selecting grinding wheel with soft hardness are as follows:
(1) In order to increase the grinding contact area of gears with low material hardness, grinding wheels with soft hardness can be used.
(2) For grinding tooth surfaces with low thermal conductivity and sensitive material to thermal temperature, soft grinding wheel shall be selected.
(3) When the linear speed of the grinding wheel is high, the grinding wheel with soft hardness shall be used.
(4) In order to improve grinding efficiency, soft grinding wheel can be selected. The general principles for selecting hard grinding wheel are as follows:
(1) When the tooth surface to be ground is intermittent, the grinding wheel with hard hardness shall be selected.
(2) In order to maintain good grinding accuracy, the grinding wheel with hard hardness is selected. When grinding the carburized and quenched gear, the grinding wheel with medium hardness and relatively hard hardness shall be selected for grinding.
Bond is the abrasive material that binds the abrasives together. The strength, impact resistance and heat resistance of the grinding wheel mainly depend on the type and nature of the bond of the grinding wheel. For the gear grinding of carburizing and quenching, the grinding wheel with ceramic bond should be selected for grinding.