Fe-C-Si-based method of casting alloy casting

摘要

PROBLEM TO BE SOLVED: To control the amount of graphite after carbide fine spheroidizing heat treatment and to obtain mechanical properties not lower than those of spheroidal graphite cast iron and equal to those of carbon steel for machine structural use, particularly high Young's modulus, by setting the area ratio of graphite existing in the metallic structure, after casting, of an Fe-C-Si alloy casting at a value lower than a specific value. ;SOLUTION: A casting material, composed of an Fe-C-Si alloy which consists of, by weight, 1.45-3.03% C, 0.7-3% Si, and the balance Fe with inevitable impurities and in which the amount of eutectic crystals Ec is regulated to 50%, is used. A mold is filled with the casting material in a liquid-phase state or in a solid-liquid coexisting state, which is solidified at ≥500°C/min average solidification rate V₁. The resultant casting is cooled down to a temp. in the eutectoid transformation finishing temp. range at ≥900°C/min average cooling rate V₂. By this procedure, an Fe-C-Si alloy casting, in which the area ratio A₁ of graphite existing in a metallic structure is regulated to 5%, is obtained. This casting is then subjected to carbide fine spheroidizing heat treatment. By this method, the alloy casting, having about 8% area ratio A₂ of graphite, increased in Young's modulus E, and excellent in tensile strength, hardness HB, etc., can be obtained.;COPYRIGHT: (C)1998,JPO