Per: Andre Itman Filho (ifes), julia Chagas Lessa da Silva (ifes), Pedro Gabriel Bonella de Oliveira (eesc-usp), Raphael Mariano de Souza (ifes), Andre Itman Filho (ifes)
Abstract:
Microalloyed steels containing small amounts of carbide-forming elements such as molybdenum, niobium, vanadium, and titanium. The effectiveness of carbides depends on the size and precipitated volumetric fraction and is responsible for improving the mechanical strength by grain refining and precipitation hardening. To determine the quantity and different carbides, software such as FactSage is often used, which is integrated to the thermodynamic information of liquid and solid metallic solutions, oxides, nitrides and carbides. The FactSage allows to evaluate the quantity of precipitated carbides on cooling or heating during the wrought process. In this context, it is important to emphasize the importance of molybdenum in the phase transformation and carbides precipitation at different temperatures. Then, the objective of this research was to simulate the effect of molybdenum considering the contents of 0.09; 0.12, and 0.15% of this element in a microalloyed steel, with defined chemical composition. The simulation, was performed with the FactSage and varying the temperature from 300 to 1400 ºC. The results show that M23C6 carbides are more stable than MoC and M7C3, in addition, they are the main responsible for secondary hardening. However, after coalescence, the predominant phase is cementite, which remains stable until the start of austenitization.