Investigation of Arc Starting Characteristics of D-C Welders With Reference to Electrode Freezing

A method for investigating the starting characteristics of an arc in d-c arc welding was developed and equipment was designed and built to simulate the behavior of an operator in starting such an arc. This testing equipment was used to compare the arc striking ability and the arc freezing tendency of an electrode when used with various types of welding generators. It was found that the determining factor is the electrode contact duration, that is, the time during which the operator leaves electrode and work in contact when he attempts to start an arc. Generators, to be satisfactory, should permit at least 40 milliseconds contact duration. Where the permissible contact duration between work and electrode is less than 40 milliseconds, only experienced welders are able to start an arc. Less trained men freeze the electrode to the work piece in a large percentage of their attempts. Five generators of different design were tested with the apparatus. Oscillograms of the current surge during the contact period were taken and the freezing point marked on the curves. It was found that the location of the freezing point depends on the shape of the current surge. Characteristics of a welding generator as developed in these tests which yield good striking and nonfreezing results are not contradictory to good general welding characteristics.