Preparation of test specimens
The charge calculation was carried out for the target chemical composition. Raw materials such as mild steel, pig iron, ferro-alloys and pure metals were used as charge materials. The test specimens were produced using a 30kg capacity high frequency induction furnace with alumina lining. Charge materials were melted and superheated to 1853K. After holding at the temperature of 1853K, the melt was poured from 1793 to 1773K into preheated CO2 molds with cavity size of 25mm in diameter and 65mm in length as shown in Fig. 1. The surface of the top riser was immediately covered with preheated dry exothermic powder to prevent rapid cooling of the riser. The size of test piece is in diskshape with 7mm in thickness.