The tensile strength of gray cast iron cylinder head body is required to reach 300 MPa, and the tensile strength of bolt hole body is required to reach more than 270 MPa; The internal and external surfaces are smooth and clean, and the particle size of residual impurities is not greater than 500 μ m. There are no casting defects such as fins, sand inclusions, residues, pores, shrinkage porosity, shrinkage cavities, cracks, etc.
The requirements for air tightness test are as follows:
(1) The pressure medium is gas. The detection pressure of the water jacket pressure is 3 bar, the pressurization time is 18 s, the pressure stabilization time is 15 s, the inspection time is 4 S, and the leakage pressure difference is below 41 PA.
(2) The pressure medium is gas, the detection pressure of the inlet pressure is 3 bar, the pressurization time is 15 s, the pressure stabilization time is 12 s, the inspection time is 12 s, and the leakage pressure difference is below 99 PA; The test pressure of the exhaust duct is 3 bar, the pressurization time is 12s, the stabilization time is 12s, the inspection time is 4 S, and the leakage pressure difference is below 150 PA.