(1) Effect of room temperature hardness of workpiece material.
Under normal circumstances, similar materials has high hardness, will has low machinability. When the material hardness is high, the contact length between the chip and the rake surface decreases, so the normal stress on the rake surface increases, and the friction heat concentrates on the smaller contact surface of the chip, which makes the cutting temperature rise and wear more severe. When the material hardness is too high, it even causes the burn and break of the tool point.
(2) The influence of high temperature hardness of workpiece material on machinability.
The higher the hardness of the workpiece is, the lower the machinability is. The hardness of tool material decreases with the cutting temperature. When the material's high temperature hardness is high, the ratio of the hardness of the tool material to the material hardness of the workpiece decreases, and the wear of the tool is greatly affected. This is an important reason for the low machinability of superalloys and heat-resistant steels.
(3) The effect of hard point on machinability of workpiece material.
The more sharp the shape of the hard material in the workpiece, the wider the distribution, and the lower the machinability of the workpiece. Hard point abrasion the tool has two: one is the hard point the hardness is very high, with a knife scrape; the second is the workpiece material at the grain boundary micro hard points can improve the strength and hardness of material, and the increase of cutting resistance of shear deformation, the machinability of materials decreased.
(4) The influence of the work hardening property on machinability.
The higher the work hardening property of the workpiece, the lower the machinability. The surface hardness of some high manganese steel and austenitic stainless steel is 1.4 - 2.2 times higher than that of the original matrix. The material has a high degree of hardening, first of all, to increase the cutting force and increase the cutting temperature; Second, the tool is scratched by hardened chipping, and the secondary flank produces boundary wear; Third, when the tool cutting hardened surface, the wear will intensifies.