Finite differential method was used to simulate the formation of power steering pump shell.Based on the simulated results

origination of the defects

such as entrapment-gas

shrinkage and so on

was analyzed

and countermeasures were presented to reduce mould-trial and mould-repair in practical production and to decrease the reject rate.The simulated results show that there exist serious entrapment-gas

shrinkage porosity（hole） in the castings

which is attributed to the complex structure of the castings with un-even wall-thickness.So the design of gating system

exhaustion of the mould and sequential solidification of the castings in process of casting should be paid attention to.