Abstract:  Aiming at the problems of dry cutting aluminum alloys that were prone to scale thorns and poor surface integrity under low and medium cutting speeds, the orthogonal cutting experiments of aluminum alloy 7075 were carried out at different machining parameters using liquid nitrogen. The surface topography of workpieces and distribution of scale thorns were analyzed through scanning electron microscope, and the dimensions of scale thorns were measured by 3D surface profiler accurately. The effects of cutting speeds, feed rates, rake angles and cooling strategies (dry cutting, liquid nitrogen cooling, cutting fluid) on the distributions and sizes of scale thorns were analyzed. Based on the formation theory of scale thorns, the effects of machining parameters and liquid nitrogen cooling on the formation processes of scale thorns were discussed. Accumulated metals were a necessary and sufficient condition of the formation of scale thorns, and might be inhibited by improving tribological properties between chip and rake face. The results show that high cutting speed, low feed rate and large tool rake angle may reduce the thickness of accumulated metals, and inhibit the formation of scale thorns. Under cryogenic cutting conditions, the distribution density and size of the scale thorns are less than that of dry cutting, and a finishing surface topography of workpieces may be obtained.

Key words: cryogenic cutting, scale thorn, aluminum alloy 7075, surface quality

摘要： 针对干切削铝合金工件表面易产生鳞刺、表面完整性较差的问题，采用液氮冷却方式在不同切削参数下对7075铝合金进行了正交切削试验，使用扫描电子显微镜和3D光学轮廓仪分别表征了已加工表面形貌、鳞刺分布和鳞刺尺寸，分析了切削速度、进给量、刀具前角和冷却方式（干切削、液氮冷却、切削液）对已加工表面鳞刺分布和尺寸的影响，并基于鳞刺形成理论讨论了切削参数和液氮冷却对鳞刺形成过程的影响。金属层积是鳞刺形成的充分必要条件，通过改善刀屑接触摩擦特性能够抑制鳞刺的形成。试验结果表明，较高切削速度、小进给量和大刀具前角能减小金属层积厚度，抑制鳞刺的形成。低温切削下已加工表面鳞刺分布密度和尺寸均小于常温切削，可得到较为光整的已加工表面。

关键词: 低温切削, 鳞刺, 7075铝合金, 表面质量