Technological measures for preventing carbide inserts from grinding crack defects
Carbide inserts has high hardness,high brittleness, poor thermal conductivity, heat shrinkage rate, usually should be grinding with diamond grinding wheel with diamond grinding wheel. But the price is expensive, not easy to wear after repair, so many factories still use the ordinary grinding wheel for grinding.In the grinding process, the higher in hardness. Ordinary wheel, abrasive easily passivated, sharp blade surface friction to produce local high temperature, the formation of additional thermal stress caused by thermal deformation and cracks, directly affect the service life of the cutter and machining quality.Therefore,we should take the necessary measures to prevent grinding cracks. Through processing practice, summed up the technological measures the following can effectively prevent or reduce the grinding crack.
1.negative edge grinding method
Negative grinding method refers to a sharpening tool, first in the rake face or flank grinding out a negative edge. The hard alloy belongs to brittle materials, the grinding wheel vibration due to the cutting tool by impact load, prone to crack; at the same time, the instant heating and cooling the grinding zone the thermal stress may exceed the strength limit of cemented carbide and hot cracks. The negative edge grinding method can improve the strength of carbide inserts, blade to enhance anti vibration and impact load bearing capacity, and increase the heating area, to prevent the grinding heat large guide blade, so as to reduce or prevent cracks.
2.wheel with molybdenum infiltration
At room temperature, the powder and ethanol mixed solution made of molybdenum disulfide, then in a sealed container (to prevent evaporation of ethanol) will be the new ordinary wheel soaked in the mixed solution, removed after 14 hours, natural dry for 18 to 20 hours, the grinding wheel grinding wheel dry completely.By the treatment with internal voids of molybdenum disulfide the abrasive grains can lubricates the grinding wheel chip is good, is not easy to be blocked. The test proved that the grinding hard alloy blade with molybdenum wetted, sharp grinding, abrasive easily passivated, the deformation of the workpiece is small,smooth chip, chip shape with a band, take away most of the grinding heat. In order to improve the grinding effect, improve the blade yield.
3.reasonable selection of grinding parameters
If the excessive friction in the process of grinding, the grinding temperature can lead to a sharp rise, hard alloy blade is prone to burst, so the reasonable selection of grinding parameters is very important. The reasonable grinding parameters commonly used for circumferential speed of v=10 ~ 15m/min, =0.5 ~ 1.0m/min longitudinal feed f f =0.01 ~ 0.02mm/,horizontal stroke. Manual grinding. The longitudinal and transverse feed are not too large.
4.other technical measures
The knife rod rigidity tool holding spindle instability,beating can cause grinding cracks, therefore, by machine,grinding,machining system of fixture and tooling composition should have sufficient rigidity, and should control the grinding wheel axial and radial runout.
There are many factors caused by carbide inserts produce grinding crack,only choose the appropriate grinding wheel,the grinding process is reasonable,which can effectively avoid cracks, improve the grinding quality.