Formation and evolution behavior of inclusions in Al-killed resulfurized free-cutting steel with magnesium treatment
Qing‑song Zhang1,2 , Yi Min1,2 , Jiu‑jian Xu1,2 , Cheng‑jun Liu1,2
Abstract ：To reveal the formation and evolution behavior of inclusions during magnesium treatment and resulfurization in Al-killed free-cutting steel, both laboratory experiments and thermodynamic calculations were carried out. The extracted samples were polished and analyzed by scanning electron microscopy and energy-dispersive spectroscopy. The results indicated that MgO formed immediately and then transferred to MgO·Al2 O3 with the homogenization of [Mg] in steel in the case of low magnesium addition (w [Mg] < 0.0020%). However, MgO would keep stable in the case of high magnesium addition (w [Mg] ≥ 0.0020%). In the process of resulfurization, the addition of sulfur forced the transformation of MgO to MgO·Al2 O3 accompanied with the formation of MgS if the mass fraction of [S] in steel was in the range 0.15%–0.70%. MgS precipitated as a solid solution containing a quantity of MnS, and the composition of the sulfide solution was calculated to be (Mg0.85 Mn0.15 )S when the mass fraction of [Mn] was 1.2%. The formation mechanisms of inclusions after magnesium and sulfur additions were discussed comprehensively, and proper models for the evolution of inclusions were set up.
Key words ：
Magnesium treatment
Resulfurization
Inclusion
Thermodynamics
Free-cutting steel
收稿日期: 2019-04-09
出版日期: 2020-06-25
引用本文:
Qing‑song Zhang,Yi Min,Jiu‑jian Xu, et al. null[J]. Journal of Iron and Steel Research International, 2020, 27(6): 631-642.
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