Abstract
To verify the formation behaviors and mechanisms of intra-granular acicular ferrite (IAF) grains nucleated by Mg-Al-O in low carbon steel, the steels containing different Mg contents were refined in a vacuum induction furnace. The effect of Mg addition on the formation of IAF structure in Al-killed low carbon steel was investigated by optical microscope (OM) and scanning electron microscope with energy dispersive X-ray spectroscope (SEM-EDX). It reveals that the IAFs are only detected in Mg-added steels, and the volume fraction of IAF increases with the Mg concentration from 8×10−6 to 26×10−6. It shows that not only the MgO-Al2O3-MnS and MgO-Al2O3-P2O5 particles are the effective nucleation sites for IAF, but also the pure MgO • Al2O3 phase can promote the ferrite nucleation. A Mn-depletion zone (MDZ) is characterized adjacent to the MgO-Al2O3-MnS, which is believed to be one of the possible mechanisms to explain the IAF nucleation. The MDZ around the MgO-Al2O3-MnS inclusion would be induced by the MnS precipitation on the inclusion. It seems that the ability of Mg-containing inclusions to induce the nucleation of ferrite might be attributed to a new mechanism, i.e., the P-rich zone formed on a few Mg-Al-O inclusions might be another factor for promoting the IAF formation.
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Foundation Item: Item Sponsored by National Natural Science Foundation of China (51374059, 51374060); Scientific Research Fund of Liaoning Provincial Education Department of China (2012221013)
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Li, Xb., Min, Y., Yu, Z. et al. Effect of Mg addition on nucleation of intra-granular acicular ferrite in Al-killed low carbon steel. J. Iron Steel Res. Int. 23, 415–421 (2016). https://doi.org/10.1016/S1006-706X(16)30066-8
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DOI: https://doi.org/10.1016/S1006-706X(16)30066-8