Dissimilar spot welding of aluminium alloy and galvannealed steel by metal flow-application of friction anchor welding to aluminium alloy and Zn-coated steel

ABSTRACT

Lap joints of an upper Al alloy (1.0-mm-thick A5052) and lower hot dip galvanized steel (1.2-mm-thick GI steel) were welded by a novel spot welding process for dissimilar metal lap joints using a new tool with the tip made of spherical ceramics, i.e. ‘Friction Anchor Welding.’ As a result, the rotating tool was plunged only to 1.3–1.4 mm from the Al alloy surface, and accordingly, a steel projection was not formed in the Al alloy sheet. Further, the Al alloy near the rotating tool was removed. However, near this removed area, the Zn layer on the GI steel melted and was removed by friction heat, and consequently, the GI steel and the Al alloy were welded. Thus, the tensile shear strength reached about 2.6 kN/point.

KEYWORDS:

• Dissimilar metals
• friction stirring
• projection
• Zn-coated steel
• aluminium alloy

Acknowledgments

This study received support from the Industry-University Joint Basic Research ‘Construction of new guidance principles based on heterostructural control, towards the creation of revolutionary structural metals’ of the Japan Science and Technology Agency (JST) for which we should like to express our gratitude. We are also profoundly grateful to Koji Murakami of the Okayama Prefectural Engineering Technology Center, for his assistance with X-ray microdiffraction during this study.