Effect of early stages of thermomechanical processing on inclusions in high carbon steel

The effect of heat treatment and thermomechanical processing on size, size distribution, distribution and chemistry of non-metallic inclusions in a continuously cast high carbon steel was investigated using a Gleeble hot compression simulator at temperatures of 1050 and 1150°C and strains of 0·3 and 0·7 at strain rate 1 s−1. The results showed that the total number of inclusions classified into three main types, namely, sulphide, oxide and duplex, was reduced after the deformation at high temperature. Inclusions of different size and chemistry were found being present in different locations of the bloom, which was related with microsegregation in the as cast bloom. This suggested that inclusions were influenced by solidification conditions and subsolidus homogenisation. Furthermore, the observed changes of chemistry of inclusions during heat treatment and thermomechanical processing at high temperature (∼1100°C) are discussed. These changes were substantiated by evidence of devitrification of oxide inclusions including different manganese silicates.