Mechanism of “black line” formation in chilled cast iron camshafts

The mechanism of “black line” (B-line for short) defect formation in a chilled cast iron camshaft is analysed using computer simulation combined with the results of the manufacturing operation. The results show that the B-line is formed due to an unstable condition when liquid metal flows in a mould: the positioning of chills in the mould is a key factor in the generation of this defect. To eliminate B-lines, chills must be situated in the lower part of the mould, with relation to the pouring position, and mould filling has to be as stable as possible.