LAUSR

Non-metallic inclusions in steels are generally harmful to their material performance, so extensive researches have been conducted to reduce their presence in steels.1–4) However, the utilization of inclusions for control of microstructures and enhancement of mechanical properties is becoming of considerable interest.5–8) Manganese sulfide inclusions are typical inclusions detected in non-quenched and tempered (NQT) steels. Medium content of sulfur is usually added into steels for their beneficial effects on improving machinability,9,10) retarding grain growth11,12) and inducing intragranular ferrite.11,13,14) However, the large-sized elongated MnS inclusions, which exist in longitudinal section after deformation, are severely detrimental to the transverse mechanical properties of steels.15,16) Therefore, numerous studies focusing on the control of the morphology, size and distribution of MnS inclusions have been conducted over the years.17–20) MnS inclusions have been classified into three types according to their morphologies in ingots, i.e., (1) randomly dispersed globular sulfides (type I), (2) rod-like or dendritic Distribution and Morphology of MnS Inclusions in Resulfurized Non-Quenched and Tempered Steel with Zr Addition