Avaliação do processamento de aço trip-twip em escala piloto

Abstract

Currently, the structure of automobiles is composed of different types of steels, according to the specific function of each component. Parts that require high mechanical strength are produced with conventional high-strength steels (HSLA, CMn, IF-HSS etc.) or with the first generation of advanced high strength steels (AHSS - dual phase, TRIP, Complex Phase etc.). The second generation of steels, which includes the TWIP steel, is characterized by a combination of high strength with excellent formability. The TWIP steel (Twinning Induced Plasticity) is characterized by high manganese content (15-30%), which determines its fully austenitic microstructure at room temperature. The intense formation of twinned grains is the mechanism responsible for the excellent formability of this type of steel. This study aimed to evaluate the processing conditions of the TRIP-TWIP steel in pilot scale and provide subsidies for the industrial development of this type of steel at Usiminas. In the hot deformation step, the steel studied showed softening large capacity, especially at higher temperatures. The rolling load during cold rolling pilot reached peaks of around 200 t, values higher than those achieved during pilot process of the steels TRIP780 and DP1000. A homogeneous austenitic microstructure and mechanical properties values were consistent with those reported in the literature, obtained to the annealing temperature at 750°C. The increase in the amount of plastic deformation after annealing resulted in a significant enhance in the percentage of martensite ' instead of austenite, indicating that the main mechanism to increase plasticity of steel is assessed with TRIP effect, although they were also identified in twinned strain (TWIP effect) within the remaining austenite grain.