Abstract: w(Ca)/w(Al) is an essential parameter in assessment of calcium treatment and the amount of calcium fed into molten steel. FactSage software was employed to systematically study the factors including temperature, oxygen content and sulfur content which affect the process of calcium treatment, and the relevant effects were obtained. With different w(Ca)/w(Al) the precipitations of inclusions were analyzed in 20Mn2 steel, and it was shown that when the w(Ca)/w(Al) reached 0.10, liquefaction extent of inclusions was highest and temperature interval of liquid phase arrived at maximum value. In the case of w(Ca)/w(Al)=0.10, steel specimen was sampled and analyzed. It was indicated that inner compositions of inclusions were correlated with nucleation temperature and peripheries of inclusions were comprised of CaS formed during the cooling process. Meanwhile, number of inclusions declined and mean diameters of inclusions increased after calcium treatment.

Key words: calcium treatment, low-carbon and aluminum-containing steel, w(Ca)/w(Al), inclusions