PCBN刀具主偏角对铝合金材料表面的影响

Effects of the main angle of PCBN tool on aluminum alloy material surface

用PCBN(polycrystalline cubic boron nitride)刀具以90°刀尖角车削7050-T7451铝合金圆棒,探讨了刀具主偏角对铝合金材料表面完整性、表层微观晶粒组织和残余应力的影响.实验结果表明:以60°主偏角加工时,铝合金材料表面的微观形貌最好,硬度值最大,且表面晶粒组织致密,颗粒大小均匀;当主偏角过大时,铝合金材料表面的塑性变形大,易出现大面积的撕裂现象,而主偏角过小,则易引起刀具振动,使积屑瘤脱落,铝合金材料表面易形成"鳞刺";主偏角为75°,85°时,后刀面与已加工试件表面间的摩擦加剧,表面散热条件变差,有轻微退火软化现象,导致铝合金材料表面硬度略有减小;随主偏角增大,已加工铝合金材料表面压应力减小,且减小趋势增大.

PCBN （polycrystalline cubic boron nitride） cutting tool is used to lathe 7050-T7451 aluminum alloy with tool nose angle of 90 degree, and the influences on the integrity, surface mi- crostructure, residual stress of surface of aluminum alloy material from tool cutting edge angle of PCBN cutting tools are also researched. The experimental results prove that when processed with 60° tool cutting edge angle, micro morphology of alloy aluminum material surface is best, the hard- ness value is the biggest, and the surface grain structure is compact with uniform particle size. When the tool cutting edge angle becomes over-sized, plastic deformation on alloy aluminum materi- al surface is large, large area of tearing will appear easily. While the tool cutting edge angle is too small, it is easy to cause vibration of the tool, so that the Built-up edge can fall off, the surface of alloy aluminum material is easy to form the ＂scale＂. When the tool cutting edge angle becomes 75°, 85°, the friction between tool flank and the surface of the processed specimen is increased, the heat dissipation condition of the surface becomes worse, and the slight annealing softening phenomenon will consequently occur, which leads to a slight decrease of hardness of alloy aluminum material. With the increase of cutting edge angle tool, the residual compressive stress on the surface of alloy aluminum material is reduced, and the decrease trend increases.