Title : Similar and dissimilar welding of advanced high strength steels (AHSS) by rotary friction welding process
Abstract:
In this work, advanced high strength steels (AHSS) were welded by the solid-state rotary friction welding (RFW) process with the aim of obtaining similar and dissimilar joints. Containing a specific microstructure, rods of first complex phase (CP) (i.e., as-cast + quench + temper), second high-Mn TWIP (TW) (as-cast + homogenization + hot rolling + cold rolling + secondary annealing + stress relieve) and third quenched and partitioning (Q&P) (as-cast + homogenization + hot rolling + cold rolling + interrupted quench + two steps partition) advanced steels generations were machined. Welds were carried out employing a homemade adapted machine under fixed parameters (i.e., chuck velocity and forging force). Thus, similar CP/CP and Q&P/Q&P and dissimilar CP/TW and Q&P/TW steel welds were obtained. Microstructural characterization of the metallic joint and the different welding regions was done by optical and scanning electron microscopy. In addition, microhardness measurements were done to estimate the mechanical resistance of the similar and dissimilar welds. Also, electrochemical tests were carried out for characterizing the corrosion response of the similar and dissimilar welds. In general, microstructural results have indicated that in the intermixing zone there is a redistribution of solute elements, behavior very marked in the dissimilar welds. Furthermore, the viscoplastic performance of thermo-mechanical processing of the different advanced steels have generated several interlayers in the welding zone, which are accompanied by various oxidation compounds, as well as some typical welding defects. Respect to the mechanical resistance, the dissimilar welds have shown the most noticeable differences in hardness in comparison with the similar ones, mostly attributed to the differences in chemistry and mechanical properties of each joined steel. So, the compositional and the microstructural condition of each advanced steel mostly affect the corrosion trend, being serious in the welding region due to the nature of intermixing process in both similar and dissimilar welds. Finally, it is emphasized that the RFW of various advanced steels may allow their use in very different scenarios than their current use (i.e., basic vehicle structure).
Audience Take Away Notes:
- The present research shows the metallic joining of experimental advanced high-strength steels (AHSS) in the solid-state by the rotary friction welding (RFW) process
- The RFW process is very efficient in terms of productivity, allowing a high number of joints to be obtained in a short time. It is also important to point out that this process makes it possible to weld even those alloys considered difficult to weld using the more conventional melting processes
- The RFW process can be one of the reasons to multiply the applications of the AHSS in the manufacture of other types of automotive components such as camshafts, connecting rods, gears and homokinetic shafts, ball joints, etc
