Precipitation of complex carbonitrides in a Nb–Ti microalloyed plate steel
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Complex carbonitrides precipitated in base metal and heat-affected zone (HAZ) in Nb–Ti hot-rolled microalloyed steel plates have been identified to be Ti-rich (Nb, Ti)(C, N). As the reheating temperature is decreased from 1,200 to 1,150 °C, the average particle size in base metal is decreased from 40 to 20 nm. The morphology of complex carbonitrides in the HAZ, however, is transformed from cuboidal to rectangle shape with length of over 500 nm. Reheating at low temperature 1,150 °C may improve the toughness of HAZ by reducing the austenite size at large heat input welding.
KeywordsAustenite Base Metal Impact Toughness Prior Austenite Particle Volume Fraction
The authors would like to express their gratitude to Dr. Jiaqiang Gao at the Testing Centre of Baosteel Research Institute for his help in TEM operations and valuable discussions. The authors are also indebted to Engineer Guobin Song for performing the weld simulations in a Gleeble 3800 system.