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Drawn arc welding

Joining process that welds two workpieces by the generation of an electric arc. It’s imperative that the detail has a defined protrusion.

Illustration of Drawn arc welding

The process

A: The top workpiece [1] is placed in the welding tool [2] and these are connected together with the bottom workpiece, and a power source. The welding tool is then moved down to the workpiece. Note that one workpiece has been prepared with a protrusion with a clear change in dimension.

B: An arc occurs and the material of the contact point is melted. Once this occurs the tool is again moved upwards.

C: The tool is then brought back down to the lower workpiece and the protrusion will be surrounded by melt.

D: After the melt has cooled, the desired weld joint is formed around the two workpieces.

The method is divided into two categories, "Standard Drawn Arc" and "Short Cycle Drawn Arc", which primarily differ with respect to the protrusion diameter and thickness of the workpiece. The protrusion may have a diameter of up to about 32mm and the thickness of the workpiece should be at least 1mm. "Standard Drawn Arc" is used when the protrusion has a diameter of 6mm and when the workpiece thickness is at least a third of this. "Short Cycle Drawn Arc" is used instead when the protrusion has a maximum diameter of 10mm and when the workpiece thickness is about one fifth of the diameter.

The difference between the two methods is that the "Standard Drawn Arc" requires that the protrusion is located in a flux and that a ceramic container is used. This is to encapsulate the large amount of melt created. "Short Cycle Drawn Arc" typically uses a larger current, which results in a shorter processing time and a container is therefore not necessary. Also the protrusion need not be coated with flux but instead a protective gas is applied. The gas should, in this case, be added before the melt occurs.