The influence of slag chemistry on the formation of sliver defects

ABSTRACT

The reoxidation of molten steel by oxidising slag directly affects the molten steel cleanliness. There is a good relationship between molten steel cleanliness and the defect sources of cold rolled sheets. The results show that there is a direct relationship of the slag composition to steel cleanliness and the rate of surface defects on the final products. The thermodynamic calculations show that the activity of iron oxide decreases with the increase of w(CaO)/w(Al₂O₃) specifically when the content of T.Fe in slag remains at lower levels. In order to enhance the absorption ability of the slag to Al₂O₃ inclusions, w(CaO)/w(Al₂O₃) should be controlled in the range of 1.0–1.4 in the liquid region of slag when T.Fe content in RH final slag is less than 6 mass%. By reasonable control of T.Fe content and w(CaO)/w(Al₂O₃) in the slag, the defect content of sheets significantly declines.

KEYWORDS:

• Inclusions
• cleanliness
• surface defect
• reoxidation
• oxidability of ladle slag

Disclosure Statement

No potential conflict of interest was reported by the author(s).