Influence of rare earth elements on solidification behavior of a high speed steel for roll using differential scanning calorimetry

The influence of rare earths (RE) on solidification behavior of a high speed steel for roll was investigated by using differential scanning calorimetry (DSC) in combination of microstructure analysis. It was found that the sequence of solidification was L→γ, L→γ+MC, L→γ+M2C, L→γ+M6C, respectively. The start temperature and the latent heat liberated by unit mass of L→γ and L→γ+MC increased with increase of RE addition, indicating that RE could trigger the crystallization of the primary γ and the MC carbide more effectively. The promoting effect of RE on the heterogeneous nucleation was believed to be an important cause of this effect. Grain refinement, discontinuous network of eutectic carbides and disperse and finer MC were observed in the samples with RE addition, moreover, RES could act as the heterogeneous nucleus of the MC. RE addition was favorable for stable M6C at the expense of the metastable M2C.