Zinc Coating Influence on Spot-Weldability of Hot-Dip Galvanized Steel Sheets

HOT-DIP galvanized steel sheets have been increasingly used in the automotive industry. However, two major problems occur during spot-welding because of the presence of zinc:

1. 1/
   Welding parameters differ from those used for bare sheets
2. 2/
   Electrodes life span often decreases.

Two products have been thoroughly tested:

1. 1/
   Usinor MONOGAL^® sheet
2. 2/
   Two-sides hot-dip galvanized sheet with various zinc-coating thicknesses.

Welding parameters have been optimized by the determination of weldability lobes. Both products present a wide range of intensities, provided that weld current and electrode force are increased. The effect of an enventual variation of zinc-coating thickness is negligible.

Electrodes life satisfies the FORD 2000 spot welds acceptance test. At last, temperature measurements inside the electrodes have shown the interest in increasing the electrodes tip diameter.