Effects of Minor Addition of Niobium on the Tempering Process of Undeformed and Deformed Lath Martensite

抄録

Effects of minor addition of niobium (0.039 mass%) on the tempering process of 0.15 mass% carbon steel were examined by a hardness test and optical- and electron-microscopy. All the specimens were solution-treated at 1523 K and then quenched to form martensite. Some of them were deformed 50% by cold rolling prior to the tempering at 923 K.
Experimental results obtained are summarized as follows: The recovery process of the lath martensite was markedly suppressed by the presence of niobium. In the case of the as-quenched lath martensite recrystallization was not observed, while in the case of the deformed lath martensite recrystallization occurred rapidly during the tempering. The recrystallization, however, was considerably retarded by niobium addition. Such effects of niobium on the recovery and the recrystallization behavior may be related to the precipitation of niobium carbide during the tempering.