Caracterização mecânica e microestrutural do aço DP1200 soldado pelo processo GMAW

Abstract

The dual-phase steels belong to a category of steels named AHSS (Advanced High Strength Steels), which have been developed and are very promising for automotive applications. However, there are still questions regarding the study of the properties of these materials after processing (plastic forming, welding, machining). The welding process, by the way, is critical for these metals, as it can cause severe changes in the properties of the product, especially in the heat affected zone (HAZ). The GMAW (GasMetal Arc Welding) is an alternative widely used for AHSS joints, especially in cases for which a high level of reliability is desired and the other processes are not viable.This research aims to identify and characterize a DP1200 steel submitted to the GMAW process. During the research, the steel was analyzed by optical microscopy, tensile and Vickers microhardness tests. In addition, analytical methods were used to evaluate the thermal cycle of the material during welding. As a result, it was possible to characterize the steel mechanically and microstructurally, checking that the HAZ has 1.8m mm extension and was noticed predominance of the martensitic phase with coarse granulation; the UTS was reduced from 1236 to 804 MPa and the specific linear deformation decreased from 26.3% to 9.5%. It was also verified that the thermal models can be applied for this steel and are remarkably close to the experimental data.