No abstract

Hot cracking formation and its mechanism in invar alloys (Fe-36mass%Ni) during continuous casting was investigated. The invar alloy is very sensitive to hot cracking due to its low transition temperature of brittle to ductile fracture even though its solidification interval is narrow. At the cooling rate of 10°C/min the transition temperature of brittle to ductile fracture is about 113°C below the solidus temperature. An increased cooling rate in invar alloy increases transition temperature of brittle to ductile fracture. It is increased to about 43°C below the solidus temperature when the cooling rate is increased to 100°C/min. A mechanism of hot cracking formation in invar alloys has been proposed. Hot cracks in invar alloys with a fast cooling rate are formed between the primary dendrites due to the equiaxed solidification structure. However, at slow cooling rate, hot cracks are formed between the grain boundaries due to the columnar structure.