Avaliação microestrutural em ponta e cauda de bobinas de aços Dual Phase 780 e TRIP 780 laminadas a frio

Abstract

The automobile companies, one of the main areas of steel application, have as target to search for new steel in order to improve their products in comply with the regulations for gas emissions. Then, they look for steels with a good relationship between strength, weight and toughness in order to increase fuel economy and reduction of emissions. One of the materials with such requirements are the AHSS, these are characterized by having an exclusive multiphase microstructure that attributes this combination of properties to them. In addition, the manufacturing process also influences the microstructure and consequently the final properties, the process that generally applies to AHSS coils are hot/cold rolling and annealing via galvanizing process, in which, due to the application of strain on the material and temperature variation, microstructural changes can occur during processing. Therefore it is necessary to perform microstructural analysis of the product in various areas and the characterization techniques are increasingly indispensable in the study and development of modern steels. In this context, electron microscopy and diffraction methods are essential tools, in this work the backscattered electron diffraction technique (EBSD) was used. The results indicated a higher content of austenite retained in the tail position and a greater microstructural recrystallization in the head position. Comparing the TRIP samples, the TRIP 780 CQ had a lower content of austenite retained than the TRIP 780 in both regions. And finally, in the head position showed a higher average of grain size than tail position.