Effect of Sn on Microstructure and Thermal Fatigue Resistance of Vermicular Graphite Iron

The effect of Sn content on the quantity, morphology, matrix structure and thermal fatigue resistance of compacted graphite cast iron for automobile brake drums was studied. The results show that Sn can obviously change the pearlite content in the vermicular iron, but has no obvious effect on the creep rate, and can change the thermal fatigue properties of the vermicular iron. When the Sn content is 0.06% (mass fraction, the same below), the pearlite content is up to 95%, and the interlayer spacing is 0.07 μm. When the Sn content increases, the graphite axis ratio gradually increases, and the graphite becomes slender and bifurcations increase. Under the cyclic conditions of 20~600℃, the thermal fatigue crack length of vermicular iron with 0.06% Sn is the shortest and the thermal fatigue resistance is the best