Cementite-surface-free cast iron prodn. - by adding modifying mixt. comprising silico-calcium, silico-mischmetal, silumin and cupola coke

摘要

A cast iron modifier contg. (by wt.) 30-40% Si, 2-8% rare earth elements, 10-20% Ca, 15-30% Al, 10-30% C, 0.1-0.3% S, balance Fe is added to molten cast iron in the form of a mixt. of 30-55 wt.% silicocalcium, 15-30 wt.% silumin, 5-25 wt.% silicomischmetal, and 10-30 wt.% cupola coke. The amt. added is 0.4-0.8% by wt. The modifier enables high quality castings or 5-10 mm. wall thickness to be mfd. in metal moulds without formation of cementite on the surface of the castings, thus eliminating the need for costly high-temp. annealing.