Transformer for flash butt welding

The transformer required for flash butt welding is similar to that needed for other resistance welding processes. Here, the transformer is to be of totally enclosed type to prevent flash or dirt. Usually flash butt welding machines have very sophisticated control making the equipment automatic. All the steps are to be precisely synchronised and therefore,
an automatic sequential controller will be provided.

Usually a motor driven variable speed flashing can with pneumatic or hydraulic upsetting mechanism is adopted. Heat control is accomplished using ignitrons or magnetic contactors. The electronic contacts have the following advantages over their magnetic counter parts:

1. Elimination of periodic maintenance such as contact dressing.
2. Control of upset current independent of flashing current.
3. Application of post heat current at a value different from that of either flash or upset current.
4. Use of dual flashing voltage in which flashing action can be started at one voltage and switched to another without interruption of the flash.

Flash butt welding machines capable of welding an area of 20,000 sq. mm. are available (10000 kVA).