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Tungsten and molybdenum electrodes for resistance welding

In the resistance welding process, the parts to be joined are pressed together and heated by an electric current until pools of molten material form at individual points between them. This operation requires high currents and large pressing forces.
During the welding of thick sheets, the forces between the electrode and the workpiece may reach as much as 450 MPa. This represents a considerable challenge for the welding electrodes that have to withstand these loads.
Welding electrodes made from Plansee refractory metals and their alloys have a relatively high level of electrical conductivity while also exhibiting outstanding stability at high temperatures. They therefore have a considerably longer service life than conventional materials such as copper and copper alloys.
Plansee welding electrodes made of tungsten, molybdenum and their alloys are particularly suitable for welding highly conductive materials such as copper. They are used in the following processes: spot welding, roller welding, projection welding and upset welding.

Soldering versus back casting

The better the joint between the tungsten electrode and the copper electrode is, the better and more reproducible your welding results will be. This is because defective joins reduce thermal conductivity and cause the electrical resistance of the electrode to fluctuate.
The advantages of back-cast electrodes at a glance:

  • Reliable join between the electrode and the shaft material
  • Constant level of resistance
  • Unvarying thermal conductivity
  • Reproducible electrode quality
  • Process stability in practical application

These leads to the benefits of a longer service life and uniform welding parameters. Plansee produces rods made of molybdenum, tungsten and alloys in different dimensions.
Spot welding joins two electrically conductive metal parts using the heat generated as a result of electrical resistance when an electrical current is passed through. Two electrodes press the metal sheets together and convert the welding current to heat at the contact surfaces. A large current is forced through the welding point. The metal melts at this point, thus producing the welded joint. The advantage of spot welding is that a large amount of energy can be concentrated on the spot in a very short time. The rest of the sheet is not subjected to excessive heating. Normally, sheet thicknesses will be between 0.5 and 3 mm.


Image provided by the courtesy of Plansee.