Abstract:
In micro-alloyed steels with niobium, titanium, vanadium, molybdenum, and chromium it is important to evaluate the stoichiometries and the number of carbides formed with these elements. The effectiveness of carbides depends on the size and precipitated volumetric fraction and is responsible for improving mechanical strength, through grain refining and secondary hardening, a mechanism that replaces Fe3C cementite iron. However, it is very difficult to know the stoichiometry and the quantity of these carbides, through optical and scanning electron microscopy. In this case, a possible identification is with the FactSage software, which is a fully integrated computer system with access to the thermodynamic information of liquid and solid metallic solutions, oxides, nitrides, carbides, and others. The FactSage software allows researchers to evaluate the quantity and temperature of the solubilization of the precipitated carbides during cooling or heating, in the steel manufacturing stages. In this work, four fusions of microalloyed steels were elaborated and the determination of the types of carbides, considering the thermodynamic balance, was carried out with the FactSage software, version 8.0 from the FSteel database and varying the temperature between 100 to 1400 ºC. The result indicates the presence of carbides M3C2, M7C3, and M23C6, responsible for the increase in mechanical resistance and wear. The literature shows that carbides of type M7C3 and M23C6 are mainly of chromium and molybdenum and have complex stoichiometry, forming relatively coarse dispersions and related to secondary hardening and subsequent coalescence.