Comparing Cast and Soldered Electrodes
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Electrodes made from tungsten-lanthanum or TZM with a copper shaft are suitable for withstanding the high stresses involved in resistance spot welding. But cavities in the solder between the electrode and the shaft have a negative impact on the quality of the weld. Tests show that anyone wishing to avoid cavities should use cast electrodes rather than soldered electrodes.
Tungsten-lanthanum and the molybdenum alloy TZM have a high melting point and are stable at high temperatures. Copper electrode holders dissipate heat quickly. But with resistance welding, it is not only the material that matters; the manufacturing processes are also important.
Many manufacturers join tungsten-lanthanum or TZM and copper using a soldering process. The solder is not distributed evenly at the join between the electrode material and the electrode holder. This results in cavities that have an impact on the electrical resistance and thermal conductivity during welding. The problem is that the quality of the weld can fluctuate when electrodes are replaced.
Plansee does not employ any soldering processes when manufacturing its resistance welding electrodes, and instead casts its tungsten-lanthanum and TZM electrodes with copper in a vacuum. Molten copper completely encloses the electrode, creating a seamless join between the two materials. The welding parameters remain constant whenever an electrode is replaced. And the service life of the electrodes is also longer.
The Plansee team will be at the Schweißen und Schneiden trade show in Essen from the 16th to 21st of September to provide information on the material properties of their cast welding electrodes for resistance spot welding.