Energy storage spot welding copper and aluminum

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.

How do weld spots work?

The amount of overlap and the distance between the weld spots depend on the electrical conductivity of the work material, i.e., the distance chosen between the weld spots increases with increasing electrical conductivity. The diameters of weld spot and weld nugget depend on the electrode geometry and on the number of weld spots.

Can aluminium be spot welded?

The state of a metal, whether hard or soft, depends on its metallurgical condition. Cold worked aluminium can generally be better spot-welded than aluminium in a soft condition (Figure 4500.01.01). The physical properties of the parts to be welded have a very strong effect on the quality of the joint.

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).

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.

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.