Dissolution behaviour of NbC during slab reheating

Hong Yeob Lee, Kyong-Su Park, Jung Hyeung Lee, Yoon-uk Heo, Dong Woo Suh and H. K. D. H. Bhadeshia

Abstract

It is common practice to reheat continuously cast slabs prior to hot-rolling. Here we examine the dissolution of niobium carbide precipitates present in the cast slabs, as a function of the temperature during heating at a typical rate. It is found that because of the spread in the size of NbC particles present in the starting material, the amount of carbide that enters solution in austenite is significantly less that expected from equilibrium. Kinetic simulations and interrupted quenching experiments indicate that the precipitates persist well beyond the equilibrium dissolution temperature. The coarsening of the precipitates during heating, as opposed to a general lowering in the mean size due to dissolution, occurs only at heating rates some two orders of magnitude slower than typical.

ISIJ International 54 (2014) 1677-1681.

Download paper

Related papers

• "Role of Niobium in Influencing Transformation of
  Microalloyed Austenite"
  Metallurgical and Materials Transactions A, Vol. 26A, 1995, pp. 21-30.
  C. Fossaert, G. Rees, T. Maurickx and H. K. D. H. Bhadeshia
• "The Effect of Niobium in Solid Solution on the Transformation Kinetics of Bainite"
  Materials Science and Engineering A, Vol. A194, 1995, pp. 179-186.
  G. Rees, J. Perdrix, T. Maurickx and H. K. D. H. Bhadeshia
• "Competitive Effects of Niobium and Niobium Carbides
  on the Kinetics of the Bainite Reaction"
  Proceedings of Solid-Solid Phase Transformations '94, 1994
  T. Maurickx, G. Rees and H. K. D. H. Bhadeshia
• "Modelling Precipitation of Niobium Carbide in Austenite: Multicomponent Diffusion, Capillarity and Coarsening"
  Materials Science and Technology, Vol. 17, 2001, 403-408.
  N. Fujita and H. K. D. H. Bhadeshia
• "Modelling M₆C Precipitation in Niobium-Alloyed Ferritic Stainless Steel"
  Metallurgical and Materials Transactions A, Vol. 33A, 2002, 3339-3347.
  N. Fujita, H. K. D. H. Bhadeshia and M. Kikuchi