LAUSR

AISI H13 hot die steel is widely used in hot rolling, hot extrusion, and hot forging because of remarkable fatigue resistance performance, notable hot strength and impact toughness.1) In addition, H13 steel contains approximately 8 wt.% carbide forming elements, such as V, Mo, Cr and/or Ti, Nb. Therefore, it is easy to find the primary carbide in H13 steel.2–5) Enrichment of the carbide forming elements at the last-to-solidify region during the solidification leads to the formation of the primary carbide.6) It is well known that the large primary carbides will act as the crack sources to reduce the service life of H13 steel.7,8) Lots of work has been done to reduce the detriment of the primary carbide in H13 steel. The number density, size, amount and mean area of primary carbides decrease significantly with the increased cooling rate, but the shape of the primary carbide is insensitive to cooling rate.9) The addition of elemental Mg in H13 steel can effectively modify Al2O3 into small dispersed MgAl2O4 or MgO, and then the dispersed oxides will act as the nucleation cores of the primary carbides to reduce their size.10–12) Furthermore, the oxide nucleation core in H13 steel can be modified into Ce–O or Ce–O–S after the addition of elemental Ce. The Ce–O and Ce–O–S cannot act as the nucleation core of the primary Distribution Characteristics and Thermal Stability of Primary Carbide in Cast Ce-H13 Steel