Spot Weldability of High Carbon and Aluminum Bearing TRIP-Assisted Steels

Spot weldability of high carbon and aluminum bearing TRIP-assisted steels

G. S. Jung, D. W. Suh and H. K. D. H. Bhadeshia

Resistance spot welding is widely used bonding method in automotive industry. But most of the advanced high strength steels (AHSS) suffer from the spot weldability since they are inherently rich in alloying elements, particularly, in TRIP-assisted steels which require a certain level of C contents and cementite inhibitors such as Si to maintain austenite stability. We examine here the spot welding characteristics of TRIP-assisted steels which contain δ-ferrite as a consequence of their aluminium concentrations, and which are also rich in carbon when compared with conventional automotive steels. The resistance spot welds are tested both in shear and cross tensile tests in order to determine the so-called ductility ratio which is a parameter associated with the fitness of such welds for automotive applications. It seems that the presence of stable δ-ferrite is helpful in reducing hardness variations across the weld and heat-affected zone, and in achieving a significant ductility ratio.