This article introduces the test of producing the cast iron with low stress and high strength by adopting such techniques as high Si/C proportion

Mo and Cu low alloy treatment and enforcing treatment process. In the meantime

the elasticity modulus and stress failure property of ordinary cast iron are tested against those of the cast iron with high stress on the motionless flexure and opening loop equipment. The results show that high strength cast iron with high Si/C proportion

Mo and Cu low alloy treatment can meet the requirements to the hight rigidity and high stability of the thin-wall basic casting of a large fine instrument.