Study on the Source of Slag Inclusions in Steel by Zircon Tracer

Abstract

In order to investigate the source of slag inclusions, zircon sand (ZrO₂·SiO2) was added in the reducing slag of 10 t electric furnace and calcium zirconate (CaO·ZrO₂) was produced.
The behavior of slag inclusions studied by determining ZrO2 content in oxide inclusions extracted from steel specimens.
The results are as follows.
1) Slag inclusions were mainly originated from the tapping slag in electric furnace process, and a small part of them was originated from the altered layers of ladle bricks.
2) On the basis of some experiments, it was considered that fine slag grains mixed into molten steel as calcium zirconate reacted with α-Al₂O₃ that was producd by Al deoxidation in the ladle, and ZrO₂was dissociated from the calcium zirconate. Consequently, baddeleyite (ZrO₂) was found in slag inclusions.
3) Some considerations on zircon tracer method for investigating the source of slag inclusions were discussed comparatively with RI tracer method.