Transformation of inclusions in Al-killed steels with different calcium contents during the heat treatment

ABSTRACT

The transformation of inclusions in solid Al-killed steels with different total calcium (T.Ca) contents during the heat treatment process at 1473 K was investigated through laboratory experiments. Calcium aluminate inclusions transformed to Al₂O₃-CaS during the heat treatment due to reactions between dissolved aluminum and sulfur in the steel matrix and CaO in inclusions. With the T.Ca content in steel reached to 0.003 wt-%, CaO inclusions can hardly transform to CaS inclusions completely due to the insufficient sulfur content. After the heat treatment, the content of CaO in inclusions in steel with 0.0002 wt-% T.Ca was less than 5 wt-%, while it was roughly 30 wt-% with 0.003 wt-% T.Ca in molten steel. The effect of T.Ca content on the transformation of inclusions was calculated using FactSage. Moreover, a kinetic model was developed to predict the transformation of inclusions with different T.Ca contents at heat treatment temperature.

KEYWORDS:

• Inclusions transformation
• heat treatment
• calcium treatment

Disclosure statement

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

Additional information

Funding

The authors are grateful for the support from S&T Program of Hebei [grant number 20311004D], the High Steel Center (HSC) at Yanshan University, Hebei Innovation Center of the Development and Application of High Quality Steel Materials, Hebei International Research Center of Advanced and Intelligent Manufacturing of High Quality Steel Materials.