Original Article

Effect of calcium treatment on non-metallic inclusions in an Al-killed Ti-bearing ferrite stainless steel

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, PR China
² School of Mechanical Engineering, Yanshan University, Qinhuangdao, Hebei 066004, PR China
³ Stainless Steel R&D Center, Central R and D Institute, Baoshan Iron and Steel Co., Ltd., Shanghai 201900, PR China
⁴ School of Mechanical and Materials Engineering, North China University of Technology, Beijing 100144, PR China

^* e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
^** e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 26 November 2024
Accepted: 15 July 2025

Abstract

The modification of inclusions with different calcium content in Al-killed Ti-bearing steels has been studied by laboratory experiments. The initial inclusion was MgO-Al₂O₃-TiO_x with a MgO · Al₂O₃ spinel core. For the steel with a low calcium content, only the MgO-Al₂O₃-TiO_x out layer was modified to a CaO-Al₂O₃-TiO_x out layer. The spinel core was gradually modified to a CaO-Al₂O₃-MgO or CaO-Al₂O₃ with the more calcium addition. The population density function (PDF) of inclusions showed a lognormal type after the calcium addition, and then shifted to a power-law type with time. It was indicated that the higher calcium content, the faster modification of inclusions reaching the equilibrium. Thermodynamic calculations showed that the composition inclusions were significantly related to the Al, Ti, and Ca contents. In this study, the calcium content in steel at 30 ppm was more conducive to the formation of liquid inclusions.