Papers by Keyword: Finishing Rolling Temperature

Abstract: With the development of auto industry, the F/B dual phase steels were widely used in wheel and underpan due to their lower cost and higher hole expansion property. In the present investigation, the effects of the finishing rolling temperature and initial cooling temperature of ultra fast cooling (UFC) on microstructure and hole expansion property of a low carbon C-Mn steel were investigated using optical microscope (OM) and scanning electron microscope (SEM). It has been found that lowering the finishing rolling temperature can refine the microstructure and the volume fraction of ferrite is increased as the initial cooling temperature of UFC is lowered. Furthermore, both lowering the finishing rolling temperature and the initial cooling temperature of UFC can improve hole expansion property.

Abstract: The demand to replace Fe-V steel with Fe-Nb steel is evolving because of high costs of raw vanadium material. For the mass production of Fe-Nb steel, the most critical barrier is a poor impact toughness comparing with that of Fe-V steel. This study covers a microstructural investigation for ferrite grain size to explain the strength and toughness results as a function of V and Nb contents. The steel samples were made of three different compositions, i.e., Fe-V steel (Fe-0.05V-0.001Nb), Fe-V-Nb steel (Fe-0.014V-0.03Nb), and Fe-Nb steel (Fe-0.003V-0.033Nb). Rolling temperature to initiate was 1150°C for the all experiments. However, rolling temperature to finish was set differently for two conditions; 950°C and 860°C. The rolling to 860°C decreased the grain size for the ferrite phase and increased the impact toughness rather than the case of 950°C. The Fe-V-Nb steel exhibited similar value of the impact toughness with that for the Fe-V steel because of the low rolling temperature to finish, i.e., 860°C. The whole replace of V with Nb decreased the impact toughness significantly, however some extent of V content remained with Nb content showed the comparable toughness to the Fe-V steel by optimizing the controlled rolling process.