ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Formation of Non-Metallic Inclusion and Acicular Ferrite in Ti–Zr Deoxidized Steel
Yongkun YangDongping ZhanHong LeiGuoxing QiuZhouhua JiangHuishu Zhang
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JOURNALS OPEN ACCESS Advance online publication

Article ID: ISIJINT-2019-008

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Abstract

The formation of non-metallic inclusion and acicular ferrite (AF) during solidification is investigated by high temperature experiment, thermodynamic calculation and metallurgical analysis. The size distribution and composition of inclusions are carried out by optical microscope (OM), scanning electron microscope (SEM) equipped with energy-dispersive spectrometer (EDS) and image process software. The results indicate that adding Ti–Zr can modify the inclusions from Mn–Si–O–MnS to Ti–Zr–O–MnS, and the average size of inclusions can be refined obviously from 2.38 µm to 1.56 µm. The critical size of inclusion inducing AF is 0.21–0.37 µm, and the optimized size for AF nucleation induced by Ti–Zr–O–MnS inclusion is in range of 1.0–3.0 µm in this study. Moreover, for inducing AF nucleation, the inclusion larger than critical size is only necessary condition but not sufficient condition. A Mn-depletion zone resulted by MnS precipitating on Ti–Zr–O inclusion is observed adjacent to the Ti–Zr–O inclusion, which is believed to be one of the possible mechanisms to promote the nucleation of AF.

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© 2019 by The Iron and Steel Institute of Japan
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