Effect of rare earth addition on continuous heating transformation of a high speed steel for rolls

The effect of rare earth (RE) on continuous heating transformation of a high speed steel for rolls was investigated by using differential scanning calorimetry (DSC) with combination of microstructure analysis. Determination of the Ac1 and Ac3, the starting temperature of carbide dissolution and melting upon heating, the enthalpy change for the α→γ transformation and overall carbide dissolution were also established. It was found that RE could reduce the volume fraction of large eutectic carbides and the chrysanthemum-like eutectic colonies but could not change the phase composition. RE made a little change to Ac1, but the variation in Ac3 and enthalpy for the α→γ followed an increasing pattern as the RE addition increased. The start temperatures of carbides dissolution increased with increase of RE addition, which may be associated with the influences of RE on the morphology of carbides, but the overall enthalpy change of carbides dissolution decreases as the RE addition increased. Moreover, the start temperature of melting also increased with increasing RE addition.