Microstructural characterization and mechanical properties of spot welded dissimilar advanced high strength steels

Muhammad Sohaib Khan, Ryerson University

Date of Award

2009

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Mechanical Engineering

First Advisor

Sanjeev Bhole

Second Advisor

Daolun Chen

Abstract

Increased use of advanced high strength steels (AHSS) in resistance spot welding is necessary for manufacturing safe and affordable vehicles. A significant body of work has been completed to document the resistance spot weldability of AHSS. However, in automotive applications, the dissimilar material combinations are very common in automotive construction. There is no literature regarding the resistance spot welding of dissimilar materials DP600 and HSLA 350 steels. The objective of this study was to investigate the weldability and mechanical properties of resistance spot weld performance was different than the similar material spot welds in each of the HSLA 350 ad DP600 steels and exhibited different heat affected zone hardness. The DP600 weld properties played a dominating role on the microstructure and mechanical properties of the dissimilar material spot welds. However, the fatigue performance of the dissimilar welds was similar to that of the HSLA welds. Fatigue tests on the dissimilar materials spot welds showed that at a given stress amplitude the 5.5. mm diameter nugget exhibited higher fatigue strength than the 7.5 mm diameter nugget.