硫系、碲系、铅系易切削钢组织及硫化物对比分析

易切削钢中的夹杂物和组织是影响其切削性能的重要因素,为开发环保型无铅易切削钢,并探究其与含铅易切削钢中组织及硫化物的差异,采用光学显微镜和电子显微镜对1215MS(硫系)、1215Te(碲系)及12L14(铅系)易切削钢中基体组织和硫化物夹杂进行了对比观察与统计分析,结合非水溶液电解法分析了Pb、Te两种元素对钢中夹杂物形貌的影响。结果表明:3种易切削钢基体中组织均为铁素体、珠光体;碲能降低MnS夹杂物长宽比,其长宽比在1~3之间的比例为57%,高于硫系易切削钢1215MS的40%以及铅系易切削钢12L14的33%;碲在易切削钢中生成MnTe,使轧制后的MnS的形貌趋于球状、椭球状、纺锤状,改质作用显著,而铅在易切削钢中以铅单质存在,对硫化物的改质效果有限。

Structure and sulfide comparative analysis of sulfur,tellurium and lead free-cutting steels

The inclusion and structure in free-cutting steel are two important factors influencing the machinability. In order to develop environmental friendly lead-free free-cutting steels, and to explore the difference of structure and sulfide compared to the lead-bearing free-cutting steels, the matrix structure and sulfide inclusions in 1215MS (sulfur), 1215Te (tellurium) and 12L14 (lead) free-cutting steels were observed and statistically analyzed by optical microscope and electron microscope. The influence of Pb and Te on the inclusion morphology in steel was analyzed by non-aqueous solution electrolysis method. The results showed that the structures of three kinds of free-cutting steels were all composed of ferrite and pearlite. Tellurium could reduce the length-width ratio of MnS inclusions, and the proportion with length-width ratio in range of 1-3 was 57%, which was higher than the 40% of 1215MS and the 33% of 12L14 steel. Tellurium could form MnTe in free-cutting steel, and the morphology of MnS trended to spherical, ellipsoid and spindles after rolling, which had remarkable effect of modification. Lead existed as Pb simple substance in free-cutting steel, which had limited effect on the modification of sulfide.