Non-Metallic Inclusions in Carbon Steel Containing Rare Earth Metals

Abstract

The effect of rare earth metals (RE) on composition of carbon steel and the quantity, size and morphologies of inclusions were experimentaly determined. Optical scann-ing electron microscopy and X-ray diffraction analysis as well as empirical calculations resulted that the RE affected the chemical composition of carbon steel and inclusions. The sulphur content did not vary. The inclu-sion quantity was increased. The RE modified inclusions, especially sulphides into small-smooth size under 4um. The steels containing from 0.01% to 0.02%RE have develo- ped globular oxysulphide inclusions of lb type, where as steels containing from 0.04% to 0.043% RE contain angular sulphide inclusions of Illb type. When the RE content in steel was over 0.062%RE harmful cluster sulphide inclu-sions of IV type was formed.Thus it was concluded that the RE beneficial affected the formation and modification of non-metallic inclusions in carbon steel.