How to determine a standard weld strength?

The appropriate welding data which delivers the required standard weld strengths can thus be determined (Figure 4500.02.03). 0 3 4 Analogous to the parameter settings, geometrical values like weld spot and nugget diameter as well as distance from edge depend on the material.

How to avoid a metal pick-up tendency in a spot welding?

An intensive cooling of the electrodes is of paramount importance to avoid any electrode metal pick-up tendency. Due to the low resistance of the material aluminium, the spot welding must be carried out with high welding currents within short welding times using a special electrode force programme (Figure 4500.01.03).

How much energy is needed for welding aluminium?

For this reason, it is essential that the welding energy for aluminium be delivered within as short a time as possible. Thus, the current required for welding aluminium is about twice that for welding steel sheets of the same thickness, and this although the aluminium alloys have a much lower melting point.

Why do I need a larger weld spot diameter?

Larger weld spot diameters are necessary to attain the required shear strength with softer materials. The mechanical pretreatment can be carried out with simple equipment and does not require any special rooms. The softer alloys (pure aluminium, AlMn) tend to "smear" easily so that proper care must be taken while working with them.

Why is aluminium suitable for spot welding?

The high affinity of aluminium for oxygen, which causes metallic blank aluminium to be covered at once with a thin, dense and tightly adhering oxide film, has a major effect on the suitability of aluminium for spot welding. The oxide film has a high thermal stability and a melting temperature of over 2,000°C and is a non-conductor of electricity.

Can a weld be heat treated?

Heat-treatable alloys which have been age hardened, lose this hardening effect in the heat affected zone of the weld. A heat treatment of such components is, in principle, possible but its practical use is strongly limited by the part size and possible distortion expected.