Hot ductility behavior of 800MPa Ultra High Strength Niobium Containing Steels

摘要

The hot ductility behavior of 800MPa ultra high strength niobium containing steels has been investigated with Gleeble 3500 hot simulator. Tensile test was carried out at 650°C–1300°C at a constant true strain rate of 0.001 s~(-1). Experimental results showed that steel A has quite well ductility, and the brittle zone is narrow. Due to pro-eutectoid ferrite film formation along the prior austenite grain boundary at 650°C-750°C, samples showed a loss of hot ductility, and the fracture morphology of the specimens was brittle intercrystalline fracture, indicating the third brittle zone of the steel. However, the third brittle zone can be avoided during continuous casting, if the temperature of straightening could be kept over 800°C.