EFFECT OF RARE-EARTH TREATMENT ON THE BANDED MICROSTRUCTURE AND FRACTURE PROPERTIES OF A 16 MN STEEL

The two treatments, namely rare-earth (RE) additions to the mould and Ca Si injection into the ladle, were used to control the MnS inclusion shape in a 1 6 Mn steel. The critical crack opening displacement, delta(c), method and tensile testing were used to determine the fracture properties of the steel sheets. Scanning electron microscope (SEM) fractography of the fracture surface of tensile specimens tested at room temperature clearly showed the banded structure of the steel sheets in all, even modified, steels. The RE treatment improved the fracture properties both by sulphide inclusion shape control and by reducing microstructural heterogeneity.