Carbide Precipitation Behavior During Normalizing Heat Treatment in Low-alloyed Cr-Mo-V-Ti Steel

Heat treatment condition for dissolution of the M23C6 carbides in 2.25Cr-1Mo-V-Ti material for thermal power plant tube was investigated using a dilatometer method. 2.25Cr-1Mo-V-Ti material was heat-treated at <TEX>900~1,100∘C</TEX> for 0, 10, 30 min to find the proper dissolution condition of M23C6 carbides. The phase identification and volume fraction of the carbide were measured by using OM, SEM, EBSD and TEM analysis. Optimal heat treatment condition of M23C6 carbide dissolution was selected by predicting dissolution temperature of carbide using Bs points appeared at dilatometer curve. Experimental results showed that the conditions of carbide dissolution was 900, 1,000, <TEX>1,100∘C</TEX> for 30 min. Eventually, the optimal heat treatment condition for dissolution was 30 min at <TEX>1,000∘C</TEX> considering the minimum coarsening of Austenite grain size.