Interfacial Temperature Profiles in Simulated Resistance Spot Welding of Bare and Zinc-Coated Steel

TitleInterfacial Temperature Profiles in Simulated Resistance Spot Welding of Bare and Zinc-Coated Steel
Publication TypeJournal Article
Year of Publication2015
AuthorsKim, E, Eagar, TW
JournalWelding Journal
Volume94
Issue2
Pagination35S - 43S
Date Published2015/02//
Abstract

For better understanding of basic phenomena of resistance spot welding, temperature profiles were measured by monitoring the infrared emissions at 5 kHz from one dimensionally simulated welding of sheet metal disks between the electrodes of a resistance spot welding machine. The weld variables included the zinc coating thickness, coating morphology, workpiece thickness, and electrode force. For a given tap and heat control setting in the welding machine, as the coating thickness increased, the induced welding current increased due to a lower contact resistance created by the molten zinc layer. However, the temperatures experienced by the workpiece and electrode decreased. This was due to a decreased power absorption of the materials with lower electrical resistance of thicker coatings and the electrical characteristics of the spot welding machine. The temperature differences in welding of materials with different coating morphologies and specimen thicknesses are most pronounced at the faying interface. As the electrode force increased, the temperature differences between the materials decreased due to the decreased effect of the contact characteristics. The thicker material of bare steel became less sensitive to the contact characteristics as the electrode force increased. This was due to the decreased ratio of contact resistance to the total resistance. Thinner materials experience faster temperature rise and lose more heat to the electrodes.