Adrian Nicholas Alexander Elliott

Resistance Spot Welding (RSW) Evaluation of 1.0 mm Usibor® 1500 P to 2.0 mm Usibor® 1500 P Steel for Automotive Body Structure Applications

There has been a substantial increase in the use of advanced high strength steel (AHSS) in automotive structures in the last few years. The usage of these materials is projected to grow significantly in the next 5–10 years with the introduction of new safety and fuel economy regulations. AHSS are gaining popularity due to their superior mechanical properties and use in parts for weight savings potential, as compared to mild steels. These new materials pose significant manufacturing challenges, particularly for welding and stamping. Proper understanding of the weldability of these materials is critical for successful application on future vehicle programs. Due to the high strength nature of AHSS materials, higher weld forces and longer weld times are often needed to weld these advanced strength steels. In this paper, the weld current lobes, mechanical properties (shear tension and cross tension), metallographic cross-section and microhardness profile of 1.0 mm Usibor® 1500 P and 2.0 mm Usibor® 1500 P joint in a two-metal stackup are discussed. Weld lobes were developed with Medium Frequency Direct Current (MFDC) equipment, ISO-type B16 tips, weld force of 3.42 kN and hold time of 5 cycles. The weld times were varied at 12, 15 and 18 cycles, with each producing current ranges at or below 3.0 kA. Tensile shear and cross tension samples were made at weld time of 15 cycles, with samples showing average loads of 15.73 kN and 4.41 kN, respectively. Also, microhardness assessment using metallographic cross-sections were analyzed at three different weld cycles (12, 15, and 18 cycles). Voids were observed at 12 and 15 weld cycles, however there was no void at 18 cycles. Similar heat affected zones (HAZ) and weld zones were observed for three different weld cycles.© 2010 ASME

Gas Metal Arc Welding (GMAW) Process Optimization of 2.0 mm Uncoated Boron Steel to 1.0 mm Usibor® 1500 P Steel Joint for Automotive Body Structural Applications

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 2.0 mm uncoated boron steel and 1.0 mm Usibor® 1500 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. The interaction effect between wire feed rate and torch travel speed was not significant. 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 boron steels.Copyright

Resistance Spot Welding Evaluation of 1.4 mm Electro Galvanized (EG) Dual Phase 780 (DP780) and 1.6 mm Electro Galvanized Transformation Induced Plasticity 780 (TRIP780) Steel for Automotive Body Structural Applications

The usage of advanced high strength steel (AHSS) in automotive body structures is projected to grow significantly in the next 5–10 years with the introduction of new safety and fuel economy regulations. This is due to their superior mechanical properties and weight savings potential. These new materials pose significant manufacturing challenges, particularly for welding and stamping. Due to the high strength nature of AHSS materials, higher weld forces and longer weld times are often needed to weld these advanced steels. In this paper, the weldability of 1.4 mm electro galvanized (EG) Dual Phase 780 (DP780) welded to a 1.6 mm Electro Galvanized (EG) Transformation Induced Plasticity 780 (TRIP780) is discussed. Also, weld current lobes, mechanical properties (shear and cross tension), metallographic cross-section and micro-hardness profile in a two-metal stack-up are discussed. Weld Lobes and a full factorial Design of Experiment (DOE) was conducted. Weld current and hold time are the chosen factors for the DOE. Based on the DOE data analysis, weld current was the significant factor for tensile load and hold time was the significant factor for the cross tension load. There were no interaction effects observed between weld current and hold time o for tensile and cross tensions loads.Copyright