Gas Metal Arc Welding (GMAW) Process Optimization of 1.0 mm Usibor® 1500 P Steel to 1.5 mm Uncoated Dual Phase 780 (DP780) Steel Joint for Automotive Body Structural Applications 2010-01-0446

With the increasing demand for safety, energy saving and emission reduction, Advanced High Strength Steels (AHSS) have become very attractive steels for automobile makers. The usage of AHSS steels is projected to grow significantly in the next 5-10 years with new safety and fuel economy regulations. These new steels have significant manufacturing challenges, particularly for welding and stamping. Welding of AHSS remains one of the technical challenges in the successful application of AHSS in automobile structures due to heat-affected zones (HAZ) at the weld joint. In this study Gas Metal Arc Welding (GMAW) of a lap joint configuration consisting of 1.0 mm Usibor® 1500 steel to uncoated Dual Phase 780 (DP780) steel was investigated. The objective of the study was to understand the wire feed rate (WFR) and torch (or robot) travel speed (TTS) influence on lap joint tensile strength. Design of Experiments (DOE) methodology was used to understand the process parameter influence on the joint strength. Based on the statistical analysis, wire feed rate and torch travel speed were significant factors on static tensile strength. Also, two-way interaction effect between wire feed rate and torch travel speed was observed. Metallurgical properties of the lap joints were evaluated using optical microscopy. Significant drops in hardness at the HAZ were observed on both Usibor® 1500 P and DP780 steels.