Comparative Study on the Cleanliness of Ultra-low Carbon Al-Killed Steel by Different Refining Processes

摘要

Cleanliness of aluminum-killed ultra-low carbon steel produced through BOF-RH-CC and BOF-LF-RH-CC was comparatively investigated by nitrogen-oxygen analysis, SEM analysis and thermodynamic calculation to seek for an optimum refining process. The results show that the non-metallic inclusions with area above 8 mu m(2) could be removed obviously in both the refining processes. Compared with BOF-RH-CC process, in RH refining stage, the size of inclusion and total oxygen control were better than the original process. Furthermore, BOF-LF-RH-CC process reduced the inclusion area ratio, the proportion of single inclusion area of < 8 mu m(2) increased from 85 to 95%, the proportion of Al2O3 inclusion less than 5 mu m(2) increased from 50 to 70%. Meanwhile, the desulfurization effect became pronounced and the temperature control of the double refining process was more stable than that of the original process.