The Effect of Alloying Elements on Formation and Evolution Mechanism of Manganese‐Containing Inclusions in Medium/High‐Manganese Steels

Abstract

The present work assesses the effect of alloying element of Mn, Al, C, and Si on formation and evolution behaviour of manganese‐containing inclusions in medium/high‐manganese steel. The results indicate that the manganese‐containing inclusions after Al addition were gradually transformed from MnO‐MnS into MnS, MnS‐Al2O3 and MnS‐Al2O3‐AlN‐TiN with large size of about 10 μm. Besides, as the Mn content increases, the main manganese‐containing inclusions are polyhedral MnS‐Al2O3 and MnS‐AlN with sharp edge, and the proportion of AlN and TiN in complex inclusions increases. Additionally, the increase of Mn content significantly reduces liquid phase temperature and extension of the solid‐liquid two phase zone, promoting the divorced eutectic transformation of type II to type III of MnS, lead to the polyhedral MnS preferentially precipitation at early stage of solidification process. Furthermore, it also observed that the main manganese‐containing inclusions were irregular MnS and MnS‐AlN with edge and larger sizes of 10–50μm in the case of manganese steel grades with high C or Si content, which is attributed to divorced eutectic transformation and increase of activity of S and Mn. Moreover, the C element possesses most obvious promoting effect on the precipitation of MnS, followed by Si and Mn elements.