Evaluation of joining performance of different coated steel sheets used in automotive applications

To meet corrosion target of automotive vehicles, different coated steel sheets are used in various parts of body in white, chassis and powertrain. Hot dip galvanized (GI) and hot hip galvannealed(GA) are the two most commonly used steel sheets across world. Other coatings such as Zn-Ni, Al-Si , Zn plating and electro galvanized zing coating are application specific coating, which are used suitably to meet different performance requirement. To meet robust corrosion and performance requirement, there is trend of increase in coated steel sheet use in automotive vehicle. While different coated steels are having different corrosion performance, they also exhibit different joining and paint adhesion performance. Spot welding is the most common technique used for joining automotive parts. Joint strength majorly depends on steel base material grade, chemistry and properties. However, coating on base material also influence joining performance. Major challenge is faced when different coated steel is used in same joint. Joint strength ultimately contributes to vehicle's durability and crash performance, hence play a very important role. It is very important to know the characteristic and joint performance of different coated steel under different joint combinations. This paper discusses joining of different coated steel with different combination (including bare steel), identification of suitable joining parameters & process, study of joint and mechanical & microstructural characterization of joint.