To investigate the differences in machinability of bismuth,lead and sulfur free-cutting steels,and to understand the effect of bismuth on machinability of free-cutting steels and its mechanism,a comparative cutting test was carried out on three types of wire rods of sulfur free-cutting steel 1215MS,bismuth free-cutting steel 1215Bi,and lead free-cutting steel 12L14 by using Kistler force sensors,surface roughness measurement instruments,and other tools.The results show that under cutting conditions of a rotational speed of w=1 200 r/min,a cutting depth of ap=0.4 mm,a feed rate of f=0.2 mm/r,and the same cutting tools and cutting angles,the cutting forces of the three free-cutting steel wire rods 1215MS,1215Bi,12L14 are 130 N,123 N,116 N,respectively.The surface roughness values Ra are 5.3 μm,4.9 μm,4.6 μm,and the proportion of C-type chips are 28％,37％,42％,respectively.The machinability of free-cutting steel 1215Bi is comparable to that of free-cutting steel 12L14,and was significantly better than that of free-cutting steel 1215MS.For bismuth-added free-cutting steel,Bi exists in the form of Bi particles or is attached to the surface of MnS,forming Bi-MnS composite inclusions.The cutting heat generated during cutting causes Bi particles to melt,playing a role in lubrication,improving chip breaking and the machinability.
维普
万方数据
