Abstract
Variation in welding process which would cause instability of weld quality have been examined for flash welding of sheet material using about 3 mm thick steel sheets. Welding current, voltage and displacement of platen travel were recorded and photographs of arc between specimen ends were taken by streak photograph technique for the period from final flash-stage through initial upset-stage.
When observed at any fixed point, maximal time interval between flashing was determined to be over 100 ms. Such long interval was analyzed to cause oxidation and decreased temperature at the point and to result in deteriorated interface quality. Quick platen movement in initial upset-stage, so called "Initial upset displacement", was proved to be under the influence both of flashing during final flash-stage and voltage phase of power source at the moment of upset starting.
