Insight into internal oxidation mechanism of hot rolled Si–Mn added high strength steel: Pure iron layer formation

In order to reveal special morphology formation mechanism of surface continuous Fe layer, through the vacuum sealing heat treatment experiment, the scale transformation process and the mechanism of oxygen pressure reduction in the coiling process of hot rolled steel are obtained. After discussion, it is considered that the surface pure Fe produced by heat treatment under the condition of vacuum sealing of C–Mn–Si steel sheet is due to the internal oxidation of Mn and Si in the substrate and decarburization reaction, and finally lead to the decomposition of oxide scale, resulting in the special structure of surface pure Fe, intermediate oxide scale and internal oxidation.