Spot welding of different metals-Low carbon steel
Normally, mild steel can be spot welded from the thinnest gauges to a maximum of two pieces of 12 mm thickness. The restriction on the upper side is derived from the fact that with heavier material it is very difficult to concentrate the heat and the pressure at the point of the weld. If rust or scale is present, the time of welding may have to be considerably increased and in some cases, the mechanical pressure and the electrical power may also have to be increased by 25 % or even 50 %