Abstract: A method of the surface treatment of a mold for casting, which comprises subjecting a cavity surface of a fixed mold made by the use of a SCM420 material to first shot peening, a sulfurizing-nitriding treatment and second shot peening. The resulting cavity surface of the fixed mold exhibits a high hardness of 700 or higher in terms of Vickers hardness due to the presence of a sulfurized and nitrided layer, and further has a compression residual stress of more than 1200 Mpa and a largest height, which is a surface roughness value defined by JIS standard, of 8 ?m or less.

Abstract: A mold for casting primarily of SMC420, wherein a cavity forming portion comprising maraging steel, which has the toughness and the resistance to heat shock superior to those of SMC420, is provided in a vertical wall heading for a cavity surface from a molten metal inlet and a portion nearest to the molten metal inlet in the cavity surface, which are portions suffering relatively large heat shock in the contact with a molten metal. Also provided is a method for providing the cavity forming portion, which comprises filling a concave portion of the mold with a molten metal prepared by melting a welding rod by arc welding, in other words, carrying out an overlaying welding, and then cooling and solidifying the molten metal.

Abstract: A method of the surface treatment of a mold for casting, which comprises subjecting a cavity surface of a fixed mold made by the use of a SCM420 material to first shot peening, a sulfurizing-nitriding treatment and second shot peening. The resulting cavity surface of the fixed mold exhibits a high hardness of 700 or higher in terms of Vickers hardness due to the presence of a sulfurized and nitrided layer, and further has a compression residual stress of more than 1200 Mpa and a largest height, which is a surface roughness value defined by JIS standard, of 8 ?m or less.

Abstract: A mold for casting primarily of SMC420, wherein a cavity forming portion comprising maraging steel, which has the toughness and the resistance to heat shock superior to those of SMC420, is provided in a vertical wall heading for a cavity surface from a molten metal inlet and a portion nearest to the molten metal inlet in the cavity surface, which are portions suffering relatively large heat shock in the contact with a molten metal. Also provided is a method for providing the cavity forming portion, which comprises filling a concave portion of the mold with a molten metal prepared by melting a welding rod by arc welding, in other words, carrying our an overlaying welding, and then cooling and solidifying the molten metal.