engleski

Effect of inoculation on formation of chunky graphite in ductile iron castings

Chunky graphite is one of the most deleterious graphite degeneration in thick-walled ductile iron castings. This defect normally appears in the thermal center of the casting and dramatically decreases the mechanical properties. Chunky graphite formation is primarily caused by the reduction of cooling rate and melt composition. Addition of subversive elements (Bi, Sb, Pb, Sn, ...) associated with a small amount of Ce are known to be beneficial to avoid chunky graphite. In this study the effect of Bi and Ce addition at different cooling rates on the graphite morphology and mechanical properties of ductile cast iron EN-GJS-400-18-LT was investigated. Y- blocks with wall thicknesses of 25 mm and 75 mm and cylindrical blocks with diameter 200 mm and height 300 mm were cast. The presence of chunky graphite in the thermal center of the cylindrical blocks and the decrease of mechanical properties were revealed, regardless of the presence of Bi.

chunky graphite ; cooling rate ; graphite morphology ; thick-walled ductile iron castings

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