Abstract
The effects of alloying elements on eutectic temperature was investigated. Most alloying elements have a linear relationship with content and eutectic temperature. But S, Mn and Rare Earth Metal (RE), both of which are sulfide forming elements, have transition points. In this research, the interaction between S and sulfide forming elements was investigated from the viewpoint of eutectic temperature, using a thermal analysis system consisting of three cups.
The theoretical relation between Mn and S contents at the transition point can be expressed as Mn % = 1.71 S % + 0.4, where the difference between the graphite and cementite eutectic temperatures is maximum. The soluble S amount and soluble Mn amount at the transition points are always 0.023 % and 0.44 %, respectively. When S, RE, Ca and Ba coexist, the eutectic temperature is determined by the soluble S amount. The sulfide itself does not affect the eutectic temperature. The Ca and Ba contained in the inoculant increase the eutectic temperature difference, in addition to causing nucleation. Highly concentrated soluble S retards the growth of eutectic cells and curves the graphite.
