Resistance Spot Welding (RSW) of Advanced High Strength Steels (AHSS) for Automotive Body Construction

Abstract

There has been a substantial increase in the use of advanced high strength steel 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 new safety and fuel economy regulations. Advanced High Strength Steels (AHSS) are getting popular with superior mechanical properties and weight advantages compared to mild steel materials. These new materials have significant manufacturing challenges, particularly for welding and stamping. Proper understanding of the weldability of these materials is critical for successful application in future vehicle programs. Due to high strength nature of AHSS materials, higher weld forces and longer weld times are needed to weld AHSS materials. In this paper, weld lobe development for DP600, and DP780 steels are discussed. DP600 steels were joined with two different weld equipments and three different electrodes and their influence on mechanical properties are discussed. Development work on the effect of weld tips on button size, and shrinkage voids due to different welding variables is discussed. DP780 EG steel (1.0 mm) is also joined to itself. The weld lobes, mechanical properties (tensile shear and cross tension), cross-section examination, and microhardness of 1.0 mm DP780 EG to 1.0 mm DP780 EG weld joint results are discussed.

Critical review of automotive steels spot welding: process, structure and properties

“…As mentioned above, one of the major problems regarding RSW of AHSSs is their high probability to fail in interfacial mode. 35,55,[131][132][133][134][135] Failure mode of the spot welds affects their mechanical performance. Some authors 33,136,137 concluded that the load bearing capacity of spot welds is not significantly affected by the failure mode.…”

Regional Pre-Heat Treatment System Development and Applications for HAZ in RSW Joining of High-Strength Steels

“…AHSS steels have higher yield, tensile, and elastic modulus compared to other steel groups. While the tensile strength of high-strength (HSS) steels ranges from 270-700 MPa, the tensile strength of the newly developed high-strength AHSS steel groups exceeds 1000 MPa [16][17][18].…”