On pinning effect of austenite grain growth in Mg-containing low-carbon steel

The pinning effect of adding the microalloying element Mg on the growth of austenite grain for low-carbon steel was investigated in this study. The grain growth pinning behaviour of austenite was observed in situ at high temperature using a high-temperature confocal scanning laser microscope at 1573 K for 300 s. The average austenite grain size was calculated using optical micrograph Leica software. In situ observation showed that the finely dispersed Mg inclusions can inhibit the boundary migration of austenite grains. MgO–MnS is the most effective inclusions for pinning of austenite grain boundaries in Mg-containing SS400, and the ratios of inclusion on austenite grain boundaries to the total inclusion are 43%. In addition, the increase in Mg addition reduces the grain mobility.