Weldability comparison of different zinc coated high strength steel sheets in laser lap joining configuration without gap

Abstract

A significant breakthrough was recently achieved at DaimlerChrysler for laser lap joining of zinc coated steel sheets without a gap at the sheet interface [1]. Using this new process, two types of high strength steels and one low strength steel were welded and evaluated. The evaluation showed that all three steels were successfully welded with the new method. With the same thickness stack-up (1.2 mm /1.2 mm), it was found that the hot dipped galvanized (HDGI) dual phase “ DUAL-TEN™ 800” steel exhibited better weldability based on the size of the processing window when compared to hot dipped galvannealed (HDGA) dual phase “ DUAL-TEN™ 600” and HDGA interstitial free (IF) steels. Laser beam to steel interaction was studied for the three steels, with and without coating, by irradiating the laser beam on each sheet surface at different traveling speeds. Laser keyhole profiles were predicted for different welding conditions using an internally developed finite element modeling method. The preliminary results suggest that the major factor contributing to the difference in weldability is the coating type (HDGI vs. HDGA), with the HDGA coating leading to a narrower processing window than the one for the HDGI.A significant breakthrough was recently achieved at DaimlerChrysler for laser lap joining of zinc coated steel sheets without a gap at the sheet interface [1]. Using this new process, two types of high strength steels and one low strength steel were welded and evaluated. The evaluation showed that all three steels were successfully welded with the new method. With the same thickness stack-up (1.2 mm /1.2 mm), it was found that the hot dipped galvanized (HDGI) dual phase “ DUAL-TEN™ 800” steel exhibited better weldability based on the size of the processing window when compared to hot dipped galvannealed (HDGA) dual phase “ DUAL-TEN™ 600” and HDGA interstitial free (IF) steels. Laser beam to steel interaction was studied for the three steels, with and without coating, by irradiating the laser beam on each sheet surface at different traveling speeds. Laser keyhole profiles were predicted for different welding conditions using an internally developed finite element modeling method. The preliminary results su...