The High-Temperature Ductility of Some Low-Alloy Ferritic Steels

Abstract

Tensile tests have been carried out on four low-alloy ferritic steels at temperatures up to 700°C (973 K). The elongations of three high-purity steels increased rapidly at temperatures above 500°C (773 K), whereas the reductions in area decreased sharply in the same temperature range. This was dependent on the change of fracture mode from transgranular to intergranular. Comparative tests on a commercial material showed large elongations, large reductions in area, and transgranular fractures over the whole temperature range. These property differences have been related to the various carbides present in the structures. Metallographic evidence confirmed that large elongation values imply good crack-nucleation-resistance and that low values of reduction in area imply poor crack-propagation-resistance.