JPS6428342A - Cast iron for cylinder block - Google Patents

Abstract

PURPOSE:To improve strength and wear resistance, by specifying the pearlite area ratio in an iron matrix in which respective contents of C, Si, Mn, Cr, Mo, Nb, P, and S are specified. CONSTITUTION:This cast iron has a composition consisting of, by weight, 2.6-3.4% C, 1.8-2.4% Si, 0.2-1.0% Mn, 0.2-0.5% Cr, 0.2-0.5% Mo, 0.2-0.6% Nb, <=0.1% P, <=0.15% S, and the balance Fe and also has a structure in which the pearlite area ratio in a matrix is regulated to >=80%. This cast iron has high strength (40kgf/mm<2> class tensile strength) and superior wear resistance. In the above composition, casting is hindered when C and Si contents are below the lower limits, respectively, and, when they exceed the upper limits, strength characteristics are lost. When Mn content is below the lower limit, the harmfulness of S cannot be removed and, when it exceeds the upper limit, machinability is deteriorated. The contents of P and S are limited from the viewpoints of deterioration in machinability and high-temp. cracking, respectively, and, when Cr and Mo contents are blow the lower limits, a strength-improving effect is reduced and, when they exceed the upper limits, machinability is deteriorated. When Nb content is below the lower limit, a wear resistance-improving effect is reduced and, when it exceeds the upper limit, machinability is deteriorated. Further, strength- and wear resistance-improving effects are reduced when the area ratio of pearlite is below 80%.