Comparison of morphology of sulfides in free cutting non-quenched and tempered steel
(0) Free cutting non-quenched and tempered steel is mainly used to manufacture parts of automobile,which decreases the cost of production because of avoiding quenched and tempered process.And this kind of steel can improve steel cutting property through enhancing sulphur content to form a large amount of sulfides.Therefore,free cutting non-quenched and tempered steel is popular with automobile manufacturers and steel companies since it has been developed in 1970s.But it is not easy to produce high quality free cutting non- quenched and tempered steel because it needs seriously control the morphology of sulfides.Elongated sulfides will result in steel anisotropy,and globular or spindle will not lead to this problem,so we should control the sulfides to be globular and spindle.In this paper,three free cutting non-quenched and tempered steel specimens were analyzed by metallographic microscope and electron scanning microscope( ESM) with energy disperse spectroscopy ( EDS).The sulfides of different specimens were classified into 1,1 - 3,3 - 6,6 - 9,> 9,according to length-width ratio and we consider sulfides with length-width ratio of 1 as globular,1 - 6 as spindle,6 - 9 as short elongated,more than 9 as elongated.At the same time the sulfides in steel were grated according to their morphologies and distribution.The difference of sulfides including composition,size,type and morphology was showed and reasons of the difference were discussed which is meaningful to research how to control the sulfides of this kind of steel in the future.The result shows that pure MnS can be the elongated with length-width ratio of more than 9 and the spindle with length-width ratio of less than 6.The compound sulfides with core are almost all spindle and globular,and above 90% of them are with length-width ratio of 3 or less which illustrates cores of sulfides can prevent them from being elongated.Pure MnS accounts for above 95% in elongated sulfides,and compound sulfides with cores account for 25% in spindle sulfides.which shows that main sulfides are pure MnS and compound sulfides account for a small percentage.There are three types of compound sulfides including MnS with the core of Al2O3,MnS with the core of TiN and MnS with TiN.Compared with specimen B and C,specimen A has higher content of O so that there can form more compound sulfides with the core of Al2O3 and the percentage of spindle or globular sulfide is higher than that of specimen B and C.
free cutting non-quenched and tempered steel sulfides length-width ratio core
YOU Dali YUE Feng WU Huajie CUI Heng TIAN Enhua WANG Zhenwei
Engineering Research Institute,University of Science and Technology Beijing,Beijing 100083,China
国内会议
上海
英文
1-6
2013-06-01（万方平台首次上网日期，不代表论文的发表时间）