Avaliação da influência das temperaturas de recozimento e superenvelhecimento nas propriedades mecânicas no aço Complex Phase da classe de 1000 MPa

Abstract

Complex Phase steels (CP steels) have been systematically studied since the end of the 1990s. However, the experimental conditions used are not always directly applicable in industrial production lines, leaving many gaps between the knowledge produced in academia and its application on an industrial scale. One of these gaps concerns the impact of the cooling rate on the mechanical properties of a high-strength Complex Phase steel. Therefore, the main objective of the present study is to evaluate the cooling rate effect on the mechanical properties of CP1000 MPa steel, currently processed. To this end, a dilatometric analysis, simulations of annealing cycles and cooling rates, microstructural characterization of the samples, analysis of mechanical properties, comparison of results and a final comparison evaluation were carried out. The mechanical properties of the steel studied are directly related to its microstructural characteristic: type, amount, morphology, and distribution of the constituents, which, in turn, among other aspects, depend on the chemical composition and processing parameters applied, particularly in continuous annealing. The effect of soaking temperature in the range of 780°C to 820°C and overaging temperature in the range of 260°C to 350°C on the microstructure and mechanical properties was investigated. Complex Phase steels are also characterized by high energy absorption and good hole expansion capability. The results revealed a significant influence of soaking and overaging temperatures on the microstructure, which dictates the tensile mechanical properties of the material. The holes expansion test results, in turn, increased slightly with overaging temperature but did not show a systematic influence of soaking temperature. The findings of this study indicate the need for strict process control, aiming to maintain the soaking temperature at 800°C along the entire coil, with the highest possible stability, and the overaging temperature between 280°C and 300°C.