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


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.

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niobium carbides

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