HEAT TREATMENT OF TOUGH AND STRONG SPHEROIDAL GRAPHITE CAST IRON

摘要

PURPOSE:To eliminate the need for strict control of a heat treatment temp. and to obtain tough and strong spheroidal graphite cast iron by subjecting the spheroidal graphite cast iron incorporated therein with prescribed ratios of C, Si, Mn, P, Cu, Ni, etc. to heat treatment. CONSTITUTION:Cast iron consiting of 3-4% C, 2.2-3.7% Si, =1% Mn, =0.1% P,=0.02% S, =0.07% a graphite spheroidizing element, 0.4-2% Cu, 0.7-3% Ni, and the balance Fe is melted. Such spheroidal graphite cast iron is heated to 10 deg.C/min average heating rate (temp. region of =600 deg.C) and is maintained at the temp. within an eutectoid transformation temp. section. The texture wherein ferrite, austenite and graphite coexists is formed. Such cast iron is cooled to form the texture wherein spheroidal graphite is crystallized in the base mixed with martensite grains or bainite grains and ferrite grains. The strong and tough cast iron is thus obtd. without the strict control of the heat treatment temp.