| abstract |
An object of the present invention is to improve the heat fatigue resistance and the erosion resistance of a casting mold, and to impart lubricity to the casting mold. The nitrogen diffusion layer is formed by diffusing a nitrogen element source such as ammonia gas into a cavity surface of a preform made of SKD61 material. Next, a hydrogen gas, an oxygen gas, and a hydrogen sulfide gas are supplied, and a mixture layer 34 containing only iron oxide and iron sulfide is formed on the nitrogen diffusion layer to obtain the fixed mold 12. [Selection diagram] FIG. |