Resistance Spot Welding of Uncoated and Zinc Coated Advanced High-Strength Steels (AHSS) — Weldability and Process Reliability-Influence of Welding Parameters

Abstract

In lightweight body shell mass production of automobiles, the resistance welding process for joining high-strength multi-phase steels, also called advanced high-strength steels (AHSS), is the most important joining procedure. For uncoated and hot dip zinc coated high-strenght TRIP steels and complex phase steels, statements, about process reliability in resistance spot welding based on three-dimensional weldability lobes will be given. A comparison of special two-dimensional weldability lobes of uncoated and hot dip zinc coated AHSS sheets will be given, too. The weldability lobes are realised with different electrode forces for short-, medium- and long-time welds. Especially the influence of the electrode force and of the welding time has been studied in three-dimensional weldability lobes. A procedure for welding parameter optimisation in regard to maximal process reliability for AHSS is applied. Based on the electrode wear and the process reliability, statements relating to the weldability of AHSS are formulated. Furthermore, results concerning the influence of the welding parameters on the hardness and the fatigue behaviour of the spot welded joints will be given.