EVOLUTION OF INCLUSIONS IN TI-BEARING ULTRA-LOW CARBON STEELS DURING RH REFINING PROCESS

摘要

Ultra-low carbon steel, in which titanium is used to fix the interstitial atoms such as C and N, is well used for automobile. During the RH refining process, the evolution of oxide inclusions was analyzed using ASPEX and acid extraction. It was found that after Ti addition a large amount of Al-Ti-O inclusions generated, and the Ti content in the oxides decreased as the refining time increased. It was estimated that most of the oxides could be removed before the time of 10 min after Ti addition. The average size of alumina increased while that of Al-Ti-O inclusions decreased during the refining process. After Ti addition, the Al_2O_3 clusters transformed to coral shape and there existed three types of Al-Ti-O inclusions. Accordingly, a formation mechanism of Al-Ti-O inclusion was proposed.