Technical Paper

The synergistic effect of niobium-molybdenum additions on the microstructure of low-carbon bainitic steel

Symposium on Fundamentals and Applications of Mo and Nb Alloying in High Performance Steels

The main purpose of this work was to elucidate the effect of Mo additions on the development of microstructure in hot rolled low-C Nb-containing bainitic steels. Three experimental steels have been investigated; they had the same base composition of 0.05%C-1.7%Mn-0.08%Nb (wt.%); one had no Mo addition and the other two contained 0.1 wt.% and 0.3 wt.%Mo, respectively. The steel strips were manufactured by a combined process of controlled rolling and accelerated cooling. After finish rolling at 900 °C, the steels were treated by accelerated cooling to 650 °C, 550 °C and 450 °C respectively, and immediately held at that temperature for 10 minutes so that the effects on coiling at the different temperatures could be simulated. Tempering treatments at 600 °C for different times ranging from 0.5 to 8 hours were performed to investigate the tempered structures and related properties. Through a series of Optical Microscopy (OM), SEM and TEM examinations and mechanical testing, the results indicated that the steel with the addition of 0.3 wt.%Mo had the advantage of producing a high volume fraction of granular bainite, which gained significant benefits from precipitation hardening whilst achieving increased elongation after the tempering treatment. (AU) © 2015 Companhia Brasileira de Metalurgia e Mineração (CBMM)
Technical Paper (PDF 4.23 MB)