Can Aluminium Be Welded To Steel?

Aluminium can be welded to most other metals relatively easily with the use of adhesive bonding or mechanical fastening. However, in order to successfully weld aluminium to steel, certain special techniques are required.

When some metals such as copper, steel, titanium or magnesium are directly arc welded to aluminium, very brittle inter-metallic compounds start to form. In order to avoid this, metal other than the aluminium must be isolated from the molten aluminium during the arc welding process. Below we have listed two of the most common methods for doing this successfully.

Use of bimetallic transition inserts.

A popular method used when welding aluminium to steel is creating a bimetallic transition insert. Bimetallic transition inserts are also often used for producing welded connections of excellent quality within structural applications.

The inserts can be best described as sections of material comprised of two equal parts of both aluminium and steel or stainless steel already bonded together. The methods used to bond these materials and form the bimetallic transition are usually rolling, arc welding, friction welding and flash or hot pressure welding. Arc welding these steel aluminium transition inserts can be achieved with standard methods such as GMAW or GTAW. Although its rather self explanatory, one side of the insert would be welded steel to steel and the other would be welded aluminium to aluminium.

Best practice to consider when welding the inserts would be to perform the aluminium weld first in order to avoid overheating of the inserts. This method would also provide a larger “heat sink” when the steel weld is performed.

The bimetallic transition insert method is commonly used in:

• The joining of aluminium deck-houses and steel decks on boats and ships.
• The welding of aluminium tubing with steel or stainless steel tubes or sheets on heat exchangers.
• The production of arc-welded joints between aluminium and steel pipelines

Coat the steel prior to welding.

Another method commonly used to successfully weld aluminium to steel is ‘dip coating’, also commonly referred to as hot dip aluminising. This simply means that prior to welding the steel and aluminium together, the steel is first coated in aluminium.

Once coated, the steel member can be arc welded to the aluminium member, if care is taken to prevent the arc from impinging on the steel. A specific technique must be used during welding to direct the arc onto the aluminium member and to allow the molten aluminum from the weld pool to flow onto the aluminium coated steel.

Another coating method for welding aluminium to steel, called brazing, involves coating the steel surface with silver solder and then welding them together using an aluminium filler alloy.

It is important to note that neither of these coating-type joining methods are depended on for full mechanical strength and are usually used for sealing purposes only.

If you want to know more about welding aluminium to steel, or if you have questions that weren’t answered here, feel free to contact us.