| 摘要 |
Provided is a piston for internal combustion engines which suffers no decrease in strength even in high-temperature environments. In a space in which oxygen is present, an aluminum-silicon alloy piston for internal combustion engines is subjected to a first jetting treatment in which iron-based alloy shots having a particle diameter of 20-200 µm, a thermal conductivity at 25°C of 30 W/m·k or less, and a specific gravity of 7.5 g/cm 3 or higher are jetted against the surface of the piston under the conditions of an arc height value of 0.07-0.13 mm(N) and successively to a second jetting treatment in which the shots are jetted against the piston surface under the conditions of an arc height value of 0.13-0.22 mm(N). Thereafter, a heat treatment is given to the piston surface at 170-190°C for 1.5 hours or longer in the presence of oxygen to form a surface modification layer in the range from the outermost surface to a depth of about 30 µm, the layer having a structure that includes an intergranular oxide constituted of an oxide of an aluminum-iron alloy at the boundaries of crystal grains of aluminum and/or an aluminum-based alloy. |
