HIGH-NICKEL AUSTENITIC VERMICULAR GRAPHITE CAST IRON WITH LOW THERMAL EXPANSION

摘要

PURPOSE:To enable the manufacture of machine parts having a low coefficient of thermal expansion and excelling in thermal conductivity, vibration absorptivity, and tensile strength, by composing the parts of precision machine tools and the like out of high-Ni austenitic vermicular graphite cast iron having a specific composition. CONSTITUTION:As the material for the sections requiring a low coefficient of thermal expansion, such as the parts of precision machine tools, accurate measuring instruments and the like, the high-Ni austenitic cast iron containing 1.5-2.4% C, 1.0-2.7% Si, 27.0-37.0% Ni, 3.0% Cr, 15% Co, 0.015-0.035% Mg, and 0.3% Ti is used. The form of graphite in the cast iron is mainly composed of vermicular graphite which is intermediate between flake graphite and spheroidal graphite, so the material having low thermal expansion as well as superior mechanical strength which is the merit of spheroidal graphite cast iron can be obtained without deteriorating thermal conductivity, vibration absorptivity, and free-cutting which are the advantage of flake graphite cast iron.