Stainless steel is widely used in our life, whether in processing equipment manufacturing, chemical industry, food industry, or daily life. Now let's introduce the grinding process of stainless steel in machining.
Grinding characteristics
1. High plasticity and severe work hardening. The elongation of stainless steel is 1.5 times that of 45 steel, and the extrusion deformation during grinding is large, causing serious cold and hard phenomenon on the grinding surface.
2. High grinding temperature. Stainless steel has poor thermal conductivity, and the thermal conductivity is only 1/3 of 45 steel, so the temperature in the grinding area is high. The linear expansion coefficient of stainless steel is large, so it is easy to lead to errors in dimensional measurement, especially when grinding long shafts and thin-walled parts, it is easy to produce warpage and uneven thickness.
3. Chip adhesion. The abrasive grains of the grinding wheel are easy to be adhered by chips, and the grinding wheel is blocked. The friction intensifies the increase of grinding force and grinding heat. Therefore, the machined surface is burned, and the machined surface roughness of the workpiece becomes worse. According to different types of stainless steel, the situation of grinding wheel blockage is also different.
Selection of grinding wheel
1. Abrasive: white corundum is generally selected, because white corundum abrasive has good cutting performance and self sharpening. When grinding stainless steel inner holes, the abrasive particles are easy to passivate and the grinding wheel is easy to block. It is better to use microcrystalline corundum or single crystal corundum. Using zirconium corundum grinding wheel, the effect is also very good, not only the grinding efficiency is high, but also the workpiece is not easy to burn.
2. Grain size: when grinding stainless steel excircles, medium grain size grinding wheels are generally used. Among them, f36 and F46 particle sizes are selected for rough grinding, F60 particle sizes are selected for fine grinding, and sometimes F46 or F60 particle sizes are often selected for both rough and fine grinding. Inner circle and end face
For grinding, because the contact arc between the grinding wheel and the workpiece is large, the coarse-grained grinding wheel should be selected.
3. Bond: generally, ceramic bond grinding wheel is selected. Because ceramic bond has high heat resistance and corrosion resistance, it has the advantages of porous, not afraid of moisture and not affected by alkaline coolant.
4. Hardness: the hardness of stainless steel grinding wheel should be slightly softer than that of ordinary carbon steel, so that the grinding wheel has better self sharpening. The hardness of the grinding wheel is too high, the blunt abrasive particles are not easy to fall off, and the grinding wheel is seriously blocked, resulting in the increase of grinding force and grinding heat, and serious burns. The hardness of the grinding wheel is too soft, and the abrasive particles fall off too fast, so that the grinding wheel cannot maintain the correct geometry, and the grinding wheel needs to be trimmed frequently.
Selection of process parameters
1. Wheel speed: when using ceramic bonded wheel to grind stainless steel, the wheel speed is in the range of 30-35m/s, while when using resin bonded wheel, it is 30-50m / s.
2. Workpiece speed: workpiece speed has a great influence on grinding burn. For materials with poor thermal conductivity and easy to burn, properly increasing the speed of the workpiece can reduce the surface burn of the workpiece.
3. Axial feed rate of worktable: the axial feed rate of worktable mainly affects the surface roughness of grinding workpiece.
4. Radial feed rate of workbench: when grinding stainless steel, because the material is tough and soft, the radial feed rate is smaller than when grinding ordinary carbon steel.