Patent ID: 7398754

Claim:
A piston for internal combustion engine obtained by die-casting a hypereutectic Al—Si alloy comprising 11 to 18 wt % of Si, the piston comprising: a piston crown whose top face is a combustion chamber surface; a piston skirt portion; a pin holing of a piston pin; a pin boss which the pin holing of a piston pin pierces; and a top ring groove formed on an outer peripheral surface, wherein at least one of the combustion chamber surface, a pin boss rib which connects the pin boss and the crown, an outer peripheral surface of a lower portion of the pin boss, and a skirt rib which connects the pin boss and the piston skirt portion is a casting surface, a surface layer including the casting surface is composed of a first eutectic structure in which the primary crystal Si does not crystallize, at least one of the top ring groove and the pin holing of a piston pin is a finished surface which is obtained by eliminating the surface layer, and a layer including the finished surface is composed of a second eutectic structure in which the primary crystal Si crystallizes.