Theoretical analysis of current distribution in electric resistance welding.

In order to manufacture a fairly heavy walled pipe, the distribution of the electric current in the strip edge of Vee apex zone was analyzed by comparing the measured and calculated electric circuit constants in Vee apex zone.From the result of the analysis it can be concluded that the current in strip edges has a tendency to flow uniformly as the strip thickness increases and, also, that the overheat at the corner of strip edges can be reduced to an allowable level by employing a small apex angle and mild welding condition.In addition, it is found that the large amount of upset is needed to obtain a sound quality of welding. So, the proper welding conditions of heavy wall are selected to be as follows, mild welding condition, i.e., slow welding speed, small apex angle and large amount of upset. A fairly heavy walled ERW pipe with large outside diameter of 24inchφ×19.05t are manufactured by applying the proper conditions. The toughness of the weld part is proved to have excellent toughness.