On the Behavior of Oxide Inclusions during the Steelmaking Process of Top-Teeming High Carbon Chromium Steel

Abstract

In order to investigate the source of oxide inclusions, variation in the composition and the microscopic structure of oxide inclusions in steelmaking process of top-teeming high carbon chromium steel were investigated.
In addition, oxide inclusions in ferrosilicon and effect of the use of low aluminium ferrosilicon on oxide inclusions in steel were also investigated.
The results were summarized as follows.
(1) It was found that spinel (MgO·Al₂O₃), a main constituent mineral of oxide inclusions, was produced by mutual reaction of deoxidation product formed by Al or aluminate inclusions in ferrosilicon with slag particles containing MgO₃, when ferrosilicon was added and mixed at the end of refining period.
(2) Increasing rate of Al203 content in molten steel was lowered by the use of low aluminium ferrosilicon, as compared with the use of commercial grade ferrosilicon. It resulted in decrease of Al₂O₃ content in the molten steel before tapping and in the ingot bottom. However, microscopic structure and mineral composition of oxide inclusions in steel were same as in the case of the use of commercial grade ferrosilicon.
(3) It was noted that macroscopic inclusions were greatly affected by Al content in ferrosilicon.