Difference Analysis in Steel Cleanness between Two RH Treatment Modes for SPHC Grade

Abstract

This paper studied the steel cleanness’ difference of grade SPHC by comparing two RH modes. Experiments were carried out at 210 ton BOF, RH and 60 ton tundish by sampling systematically. Under mode I, free oxygen was killed during BOF tapping; and inclusions had sufficient removal during RH vacuum treatment; under mode II, RH vacuum carbon de-oxidation was adopted firstly; and then residual oxygen was killed by grain aluminum. Results showed that, (1) total generation amount of inclusions in mode II was 1/2 of that in mode I due to low residual oxygen after vacuum carbon de-oxidation, but steel cleanness in mode I was better in tundish due to long inclusions removal time; (2) under mode I, total oxygen in tundish could be controlled below 20 ppm; and cast-ability in continuous casting process reached 15 heats; (3) under mode II, nitrogen could be controlled below <15 ppm, which was 1/2 of that in mode I; (4) by adopting mode II to reduce total generation amount of inclusions and nitrogen picking up, also to prolong 20 to 30 minutes calming time before casting to guarantee inclusions’ removal, low nitrogen, low total oxygen and good cast-ability could realize.