Soldabilidade de aço multifásico da classe de resistência 1200 MPa pelo processo resistance mash seam welding

Abstract

Driven by increasing of automotive industry demands for higher performance and safety aligned with better fuel consumption, the development of Advanced High-Strength Steels (AHSS) aim higher-strength steels with good formability. Therefore, the production process needs to adapt to guarantee the productivity and safety of production lines. The influence of process parameters in Resistance Mesh Seam Welding process (RMSW) was evaluated for a 1200 MPa Dual Phase steel, adopting an integrated approach that considers the simultaneous effects of metallurgical characteristics, joint geometry, and key process parameters: welding current, linear electrode advancement speed, and contact force. The findings highlight the significant influence of welding current on heat input, which directly affects the fusion zone (FZ) area and the mechanical strength of the joint. Electrode force plays a critical role in promoting coalescence and ensuring process stability, while welding speed governs the extent of the heat-affected zone (HAZ). Additionally, weld geometry and the occurrence of intergranular cracking were identified as key factors impacting joint integrity. Dilatometric tests conducted under controlled cooling rates enabled the correlation of thermal cycles with the microstructural evolution in the welded regions, particularly the FZ and HAZ. These results were validated through simulation of the Continuous Cooling Transformation (CCT) curve, confirming the formation of martensitic microstructures under rapid cooling conditions. This study aims to provide a better metallurgy phenomena understanding of RMSW welded joints using, and the effect of variables in the welding process to microstructural and mechanical assessments, contributing to technological advancement for this steel joining process and to develop improvements in weld joints application performance.