Composition change in oxide inclusions of stainless steel by heat treatment

Abstract

It is known that the oxide composition in stainless steel changes during heat treatment; however, the precise conditions to cause change are not clear. Therefore, the conditions necessary to change the oxide composition by heat treatment have been investigated using steels with different concentrations of Si, Mn, Ni and Cr. The MnO–SiO2 type inclusions changed into MnO–Cr2O3 type inclusions in steel containing 18%Cr and 8%Ni after heat treatment with a low silicon concentration. At high silicon content, the MnO–SiO2 type inclusion was stable after heat treatment. The change in the composition of oxide inclusions owing to heat treatment depended on the concentrations of Cr in steel. The critical Si content, below which the oxide composition change was observed after the heat treatment, decreased with the decrease in Cr content. In steel containing 1%Cr, the oxide composition change was not observed.