The Cr–Mo–V steel, AISI H13, is belonged to hypereutectoid steel with about 8 wt.% alloying elements and 0.4 wt.% carbon. It is widely used throughout the world at present as hot-working dies, which is applied in traditional thermal deformation process of metallic material. Its operating temperature is up to 600°C, which is quite closed to the subsequent tempering temperature.1,2) Excellent high temperature strength, impact toughness, hot cracking resistance and thermal fatigue of H13 are required.3) Researches4,5) have shown that, to a great extent, there has the relation between the resistance to heat checking and impact toughness. Moreover, excellent impact toughness in transversal direction is a significant feature for H13 in NADCA criterion.1) However, due to solute redistribution of the alloying elements during solidification process, whose partition coefficient is less than 1, the initial solidified region promotes dendrites arms, containing low concentration of alloying elements and carbon. As the solidification proceeds, alloying elements and carbon continuously segregate out from the dendritic crystal, as a result, the chromium, molybdenum, vanadium and other alloying elements enrich in Dendrite Segregation Changes in High Temperature Homogenization Process of As-cast H13 Steel