Article

Metallurgical and Materials Transactions A

, Volume 44, Issue 2, pp 717-728

Austenite Grain Structures in Ti- and Nb-Containing High-Strength Low-Alloy Steel During Slab Reheating

  • S. RoyAffiliated withDepartment of Metallurgical and Materials Engineering, Indian Institute of Technology (I.I.T.)
  • , D. ChakrabartiAffiliated withDepartment of Metallurgical and Materials Engineering, Indian Institute of Technology (I.I.T.) Email author 
  • , G. K. DeyAffiliated withMaterials Science Division, Bhabha Atomic Research Centre (BARC)

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Abstract

Austenite-grain growth was investigated in a couple of microalloyed steels, one containing Ti and the other containing Nb, Ti, and V, using different reheating temperatures between 1273 K and 1523 K (1000 °C and 1250 °C). Nature and distribution of microalloy precipitates were quantitatively analyzed before and after reheating. Interdendritic segregation (or microsegregation) during casting can result in an inhomogeneous distribution of microalloy precipitates in the as-cast slabs, which can create austenite grain size variation (even grain size bimodality) after reheating. Ti addition reduced the grain size variation; however, it could not eliminate the grain size bimodality in Nb-containing steel, due to the differential pinning effect of Nb precipitates. A model was proposed for the prediction of austenite grain size variation in reheated steel by combining different models on microsegregation during solidification, thermodynamic stability, and dissolution of microalloy precipitates and austenite grain growth during reheating.