Abstract
A purpose of this study is to clarify the generation behavior of the separation on the Charpy impact test and influence of MnS morphorogy on impact properties of warm-worked middle carbon ferrite-pearlite steel. In the warm-worked steels, the separation occurs on the fractured surfaces of the test pieces. Therefore brittle fracture is suppressed in the room temperature and completely changes to ductile fracture. High temperature working is advantageous to improve impact properties by preventing the outbreak of the separation. MnS elongated in the rolling direction has the same effect as the separation. Therefore it is effective for impact properties improvement to reduce elongated MnS by reduction of S content. Furthermore, it is effective for impact properties improvement to make MnS granular by Ca addition.
