Weldability Investigation on Lightweight Steels

A novel class of AHSS (Advanced High Strength Sheet) for the automotive sector is under development. Such steels are featured by high Mn and Al content, low density (16% lower than conventional stainless steel), and high mechanical properties (up to 800MPa of yield strength and up to 55% of elongation at break). Due to the sector of application also other properties must be controlled e.g., weldability. Due to the high content of alloying elements and their nature, it is possible to forecast criticalities in such a process, like abnormal grain growth, and κ-carbides excessive precipitation. Such carbides are exploited for their strengthening effect in the case of coherent carbide intragranular precipitation, but they have a detrimental effect in the case of intergranular precipitation. An austenitic lightweight steel alloy (X100MnAl30-9) has been tested with a standard welding technique and different material starting conditions. The microstructure and mechanical properties of the joints have been investigated. Sturdy joints have been obtained with microstructure and mechanical properties coherent with expected ones and no detrimental effect of the welding has been observed in HAZ.