Ref.: MmeMcc08-004
Apresentador: Sergio Souto Maior Tavares
Autores (Instituição): Tavares, S.S.(Universidade Federal Fluminense); Pimenta, A.R.(Instituto Federal do Rio de Janeiro); Breves, I.M.(Universidade Federal Fluminense); Perez, G.(Universidade Federal Fluminense); Loureiro, R.P.(Universidade Federal do Ceará);
Resumo:
The interest for thermal and thermomechanical treatments to produce microstructural changes, in order to obtain a broad range of properties in a single grade of steel, has increased in the last years. Ferritic-martensitic structures can be produced in low carbon steels through inter-critical treatment with fast cooling. These steels are commonly referred to as dual phase steels (DP). Martensite derives from the austenite phase present in the inter-critical annealing temperature, which can be predicted by computational thermodynamics. The soft ferrite alongside the hard martensite provides higher mechanical resistance than the normalized steel. In this work, specimens from a low carbon steel (0.158 %C) were submitted to inter-critical heat treatments in three temperatures (760, 745 and 730 ºC) followed by rapid cooling. In agreement, the martensite volume fraction increased with the increase of the inter-critical annealing temperature. Tempering heat treatments at 300 ºC and 600 ºC were performed to improve toughness. Fine carbides were observed by high resolution scanning electron microscopy (SEM) in the ferrite and martensite phases. Tensile properties, toughness, hardness and microhardness were determined for all heat treatment conditions, including normalized samples, for comparison. Tensile properties and flow stress curves of selected conditions were determined. The results were correlated to the microstructural features. A wide range of mechanical properties were obtained with the same steel composition, and each of them can be selected as function of the service conditions.