关键词: 低温液氮冷却, 高速切削, 淬硬钢, 切屑, 刀具磨损

Abstract: In view of the lack of relevant research on chip formation and tool wear mechanism in high-speed cutting of hardened steel under cryogenic liquid nitrogen cooling, a high-speed cutting of hardened steels under liquid nitrogen cooling was studied and compared with dry cutting. The cutting force, cutting temperature, characteristics of chip and tool wear were analyzed, and the mechanism of cooling and lubrication, chip formation and tool wear were discussed. The results show that compared with dry cutting, the cutting temperature of cryogenic liquid nitrogen cooling cutting is reduced by 6.9%-9.9%, and the cutting force is increased by 10.1%-12.8% due to material hardening. Compared with dry cutting, chip serration increases obviously under cryogenic liquid nitrogen cooling, which is related to the larger stress and strain in the first deformation zone and the transition from thermoplastic shear instability to periodic brittle fracture in chip formation. Cryogenic liquid nitrogen reduces cutting heat generation in cutting interfaces, the strong jet of liquid nitrogen blows away the chips, and the strong heat transfer capacity quickly take away the heat in the cut areas. Compared with the dry cutting, cryogenic liquid nitrogen may significantly reduce the adhesive wear, alleviate the tool micro-spalling by cooling and strengthen the tool, and improve the tool life by 28.6%-47.1%. Under cryogenic liquid nitrogen cooling conditions, adhesion is no longer one of the main wear mechanism, abrasive wear and impact wear are the main wear mechanism, and flank flaking and micro collapse blade are the main tool damage forms.

Key words: cryogenic liquid nitrogen cooling, high-speed cutting, hardened steel, chip, tool wear