锰硫比对1215MS易切削钢力学和切削性能的影响

Effect of Mass Ratio of Manganese to Sulfur on Mechanical Properties and Cutability of 1215MS Free- Cutting Steel

通过理论计算、扫描电子显微镜、三维腐刻技术、拉伸试验和切削试验等方法,探究了锰硫比对1215MS易切削钢中硫化物析出特性,及其对钢的力学性能和切削性能的影响。结果表明:钢中硫化物的吉布斯自由能随着锰硫比的减小而降低,其形核率和尺寸则增大;相比锰硫比较高的试样,锰硫比较低的试样中MnS夹杂物数量更多、尺寸更大,尤其是细系MnS;长条状MnS夹杂物会导致钢材力学性能的各向异性,锰硫比较低的试样中MnS的长宽比较大,导致其强度低于锰硫比较高的试样;低锰硫比和高锰硫比试样的断裂方式分别为准解理断裂和韧性断裂;低锰硫比试样相比高锰硫比试样具有更好的表面光洁度和切削性能。

Effect of mass ratio of manganese to sulfur on precipitation characteristics of sulfide in 1215MS free-cutting steel and its influence on mechanical properties and cutability of the steel were investigated through theoretical calculation, scanning electron microscope, three-dimensional etching technology, tensile test and cutting test. The results showed that the Gibbs free energy of sulfide in steels decreased with the increase in mass ratio of manganese to sulfur(Mn/S ratio), while the nucleation rate and size of sulfide increased. Compared with the samples with high Mn/S ratio, the samples with low Mn/S ratio had more and larger MnS inclusions, especially the fine series MnS. The long strip MnS inclusions would lead to the anisotropic mechanical properties of the steel. The length to width ratio of MnS in the samples with low Mn/S ratio was larger, resulting in its strength lower than that of the samples with high Mn/S ratio. The fracture modes of the samples with low or high Mn/S ratio were quasi-cleavage fracture and ductile fracture, respectively. The sample with low Mn/S ratio had better surface finish and cutability than did the sample with high Mn/S ratio.