关键词: 硬切削, 锯齿形切屑, 绝热剪切, 剪应力

Abstract:

Chips in hard cutting of hardened steel SKD11 were collected and observed by metallographic microscope and SEM; chip metallurgical textures and configuration under different cutting speeds were investigated. Dynamic shearing stress and temperature in adiabatic shear zones were discussed. Results show that in hard cutting of SKD11, saw-tooth chips are formed under both of low and high cutting speeds. Degree of segmentation increases with the increase of cutting speed. The saw-tooth chip formation could be due to fracture and adiabatic shearing; and with the increase of cutting speed, the chip formation mechanism changes from fracture to adiabatic shearing. During adiabatic shearing process, shearing stress develops as a quadratic curve, and cutting temperature shows distinct influence on the dynamic shearing stress. By increasing cutting speed, cutting temperature can be increased, which will weaken the hardening effect and reduce the maximum shear stress, cause occurrence of shearing instability and then reduce cutting force.

Key words: hard cutting, saw-tooth chip formation, adiabatic shearing, shearing stress