Effect of si- cr- mo on oxidation behavior of duplex steel and strip surface quality

The interactive effects of Si- Cr-Mo alloy elements on oxidation behavior at scale/metal interface in dual-phase steel are studied in present paper, through thermal simulation, scanning electron microscopy ( SEM) and electron probe analysis. The influence of alloy elements on hot coil surface quality under industrial production conditions are also discussed. Results show that the oxidation resistance of Si-Cr steel is stronger than that of Si-Cr-Mo steel, because of Cr- rich protective oxide film at scale/metal interface under elevated temperature. Comparing with steel alloyed by Si, the primary scale of the Si-Cr and Si-Cr-Mo steel are easier to be removed, owing to the reduction of anchor structure at scale/metal interface. However, Si and Cr element will form dense oxide film under 1,100 degrees C and above, which increases the difficulty of finishing descaling. Owing to the accumulation of Mo on the scale surface, the diffusion channel of Si and Cr elements is blocked, resulating in the increase of oxidation resistance and the decrease of SiCr oxide film at scale/metal interface. Therefore the surface quality of Si- Cr-Mo steel is significantly improved under industrial production. Suggestions conclued from present study can provide useful guidance for production of cold rolled dual-phase steel.