Electrode Geometry Before Tungsten Electrodes

The choice of geometry will always affect electrode life, arc starting, weld penetration, and arc shape. Regardless of the geometry selected, the electrode configuration must be tested during welding procedure development. The geometry should be noted as a critical process variable for the weld procedure and held to close tolerances for all subsequent welds.

Electrode Diameter. The best place to start when choosing the electrode diameter is to consult the welding equipment manufacturer's recommendations. While small diameters are easier to arc-start, large diameters accommodate higher amperages and last longer than smaller diameters. However, ifcurrent levels are higher than recommended, the tungsten will deteriorate too rapidly, fall into the weld pool, and contaminate the weld. Conversely, if the current is too low for the electrode diameter, the arc will become unstable.

Electrode Included Angle (Taper). Electrodes for DC welding should be ground longitudinally and concentrically with diamond wheels to an included angle in conjunction with the tip/flat preparation.

A blunt taper with a large included angle results in longer electrode life, better weld penetration, narrower arc shape, and the ability to handle more amperage without eroding. A sharp taper with a small included angle offers less arc wander and a wider, more consistent arc.

Tip (Flat). The shape of the tungsten electrode tip is an important process variable in precision arc welding, because as the flat size increases, so does the chance of arc wander and starting difficulty. However, increasing the flat also improves weld penetration and increases electrode life.

An incorrect, inconsistent flat can cause pointed electrode tips to drop into the weld pool. It also can result in arc instability, reduced electrode life, and changes in arc voltage from one electrode to another.
 

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