I have two copper wires. Both are same material (ETP - Electrolyte Tough Pitch Copper). Both are same diameter (2.5mm). Both wire are cleaned well and ensured no oxidation at welding point. One wire welded with base plate (base plate material is Copper sheet with TIN plated, 2mm thickness). There is no issues. Welding quality is good, apperance is good and pull strength comes satisfactory level. Other wire experiment have problem. Other wire, we used to do small work hardening at welding point before weld. Due to this the weld point not round profile and it becomes little flatten profile. When we weld this with base plate, we are getting pull strength is lower than first wire experiment.

Our machine is Spot welding machine, 20KVa capacity with Miyachi Controller, 50Hz machine.

My question is that, why there is variation in pull strength (between two)? pl reply