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Morteza Kalantar,Hamidreza Najafi,M. Reza Afshar 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.1
In this study, a comparison between V- and Nb-containing low-carbon microalloyed cast steels has been made in terms ofstrength and impact energy after intercritical heat treatment (IHT). After austenitizing at 950 °C and quenching in water,the alloys were intercritically heated at 760, 800 or 840 °C followed by quenching and tempering at 620 °C. In comparisonwith conventional heat treatment, IHT increased the impact energies at the expense of some reduction in the strength dueto the dual ferritic/martensitic microstructure. However, the impact energy of the alloy containing only V, especially afterintercritical heating at 760 and 800 °C, was higher than that of the Nb-containing samples. The improvement in the impactenergy required an optimum amount of coarse carbonitride precipitates. While, the impact fracture surface of the alloy V wascomposed of dimples indicating ductile fracture, cleavage facets in the fracture surface of Nb-containing samples indicatedbrittle fracture.