1. Cause analysis
This type of cylinder head has special structure, high integration and complex production process. The number of sand cores is up to 27, and the inner cavity sand cores are made of hot core box coated sand. When molten iron is poured, a large amount of gas is generated by heating, which can not be completely discharged into the cavity, and air hole defects are formed in the cavity (see Figure)
(1) After the sand core of injector hole is soaked and dried, it shall be baked at low temperature. The baking temperature is set at 180 ℃ and the baking time is 4H to reduce the gas generation of sand core.
(2) Before lowering the core of each coated sand core, drill a vent hole at the core head and lead the vent hole out of the mold.