ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Regular Article
Transient Evolution of Inclusions during Calcium Modification in Linepipe Steels
Ying RenLifeng ZhangShusen Li
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2014 Volume 54 Issue 12 Pages 2772-2779

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Abstract

The laboratory experiments of Al2O3 inclusions modified by calcium treatment in linepipe steels with the S content of 30 ppm and 310 ppm were performed at 1873 K. Particularly, samples were taken before calcium treatment ( 1 minute before the calcium addition) and at various times (typically 1 minute, 10 minutes and 30 minutes) after calcium treatment to study the transient inclusions evolution during calcium modification. Traditional modification mechanism of Al2O3 inclusions is that Al2O3 inclusion is directly modified by dissolved calcium or indirectly modified via CaO formed from calcium and oxygen. In the current study, after Ca–Si alloy power addition, CaS outer layer were promptly formed on the angular Al2O3 inclusion. With the reaction of the CaS outer layer and the Al2O3 core or [O], the Al2O3 inclusion was modified to a spherical liquid calcium aluminate. Moreover, the equilibrium curve of Ca–O and Ca–S, the stability diagram of inclusions and equilibrium precipitation of inclusions during solidification in linepipe steels were calculated to study the formation of inclusions.

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© 2014 by The Iron and Steel Institute of Japan
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