Inclusions and fracture characteristics of HSLA steel forgings

A study has been made of the inclusions present in two low-alloy CrMoNiV steel forgings. Electron microscopy and X-ray diffraction were used to study the microstructures, identify the different types of inclusion and examine the fracture surfaces of Charpy specimens. The microstructural characteristics have been related to the variations in mechanical properties observed in the steels, which arise from small differences in composition and heat treatment. It was found that the upper shelf energy (USE) and ductility are directly linked to the amount and size distribution of MnS inclusions.