Metallurgical and Materials Transactions B

, Volume 48, Issue 1, pp 406–419 | Cite as

Optimization of Melt Treatment for Austenitic Steel Grain Refinement

  • Simon N. Lekakh
  • Jun Ge
  • Von Richards
  • Ron O’Malley
  • Jessica R. TerBush
Article

Abstract

Refinement of the as-cast grain structure of austenitic steels requires the presence of active solid nuclei during solidification. These nuclei can be formed in situ in the liquid alloy by promoting reactions between transition metals (Ti, Zr, Nb, and Hf) and metalloid elements (C, S, O, and N) dissolved in the melt. Using thermodynamic simulations, experiments were designed to evaluate the effectiveness of a predicted sequence of reactions targeted to form precipitates that could act as active nuclei for grain refinement in austenitic steel castings. Melt additions performed to promote the sequential precipitation of titanium nitride (TiN) onto previously formed spinel (Al2MgO4) inclusions in the melt resulted in a significant refinement of the as-cast grain structure in heavy section Cr-Ni-Mo stainless steel castings. A refined as-cast structure consisting of an inner fine-equiaxed grain structure and outer columnar dendrite zone structure of limited length was achieved in experimental castings. The sequential of precipitation of TiN onto Al2MgO4 was confirmed using automated SEM/EDX and TEM analyses.

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Copyright information

© The Minerals, Metals & Materials Society and ASM International 2016

Authors and Affiliations

  • Simon N. Lekakh
    • 1
  • Jun Ge
    • 2
  • Von Richards
    • 1
  • Ron O’Malley
    • 1
  • Jessica R. TerBush
    • 1
  1. 1.Missouri University of Science and TechnologyRollaUSA
  2. 2.University of Alabama at BirminghamBirminghamUSA

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