Dissolution Behaviour of NbC during Slab Reheating

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. The initial condition of precipitates in slab is quantified with transmission electron microscopy. 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.