To start a TIG welding process, the arc must be ignited to create an electrically conductive path between the tungsten electrode and the workpiece. The high temperature generated when the arc is ignited ensures that the shielding gas becomes electrically conductive. The ignition process in TIG welding is an important process that determines the further course of the weld and its quality.
Most frequently used today: contactless ignition
Modern welding systems or power sources have a high-frequency ignition. In older systems without this ignition aid, the arc must be started by means of contact ignition. Contact ignition is created by briefly brushing the tungsten electrode against the workpiece, which creates a short circuit and an arc between the welding electrode and the workpiece. The disadvantage of contact ignition is that a little material of the tungsten electrode remains in the molten pool with every ignition of this type. The reason for this is the higher melting temperature of the tungsten. As a result, the service life of the tungsten electrode is reduced on the one hand, and impurities get into the weld pool on the other.
With contactless high-frequency ignition, the starting arc bridges the non-conductive ambient air and provides contact between the electrode and the workpiece. The distance between the tungsten electrode tip and the workpiece should be between 1 and 3 mm in order to keep the distance to be bridged as small as possible. To ionise the gas between the tungsten electrode and the workpiece, a high-frequency pulse generator is used to produce the required high voltage. When igniting a TIG welding process, voltages of up to 15,000 volts are generated in this way – a very high voltage for the torch components.
Measure the voltage curve of the ignition process
From the power source to the welding torch and its components, the entire system must be designed for such a high voltage. In the case of a manual welding torch, for example, the switch modules must not be damaged by this high-voltage pulse. In order to be on the safe side as a developer of arc welding torches, we measure the voltage curve with very high temporal resolution in our ABICOR BINZEL welding and test laboratory ARClab. This provides information on whether the ignition process has run well and guarantees reliable, safe TIG welding.
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