Thermodynamic Calculation and Experimental Study of MnS in Sulfur Containing Free-cutting Steel
Author of the article:WANG Yinghu
Author's Workplace：Pangang Group Research Institute Co.,Ltd.,Panzhihua 617000,China;State Key Laboratory of Marine Equipment Made of Metal Material and Application,Anshan 114009,China
Key Words：thermodynamic calculation sulfur containing free-cutting steel Thermo-Calc software manganese sulfide
Abstract：
Thermo-Calc thermodynamic calculation and metallographic microscope,scanning electron microscope(SEM),energy spectrometer(EDS),X-ray diffractometer(XRD)and other experimental studies were used to study the effect of the main alloy elements in sulfur-containing free-cutting steel on the precipitation temperature of MnS,the phase transition process of sulfur-containing free-cutting steel and the morphology,composition and distribution characteristics of MnS.The results show that the precipitation temperature of MnS increases with the increase of manganese and sulfur content.When the content of manganese and sulfur is too high,MnS will nucleate and precipitate in molten steel.The content of carbon and chromium has little effect on the precipitation temperature of MnS.The equilibrium phase transitions of sulfur-containing free-cutting steel during the heating process are successively as follows:ferritic transformation to austenite,M23C6 dissolution,austenite transformation to high temperature ferrite,ferrite transformation to liquid phase,manganese sulfide dissolution,liquid phase;MnS color is light gray,mostly distributed along grain boundaries,only a small part precipitated in grain,its morphology is mainly spindle shape,elongated and spherical.
