How to Weld Aluminum to Steel: Specialized Techniques Are the Answer

Aluminum is a relatively easy metal to weld into others, but it gets tricky to learn how to weld aluminum to steel. There are several reasons for it, and specialized techniques answer how to weld these two different metals.

Why Weld Aluminum to Steel?

Many environmental and trade reasons may require welding aluminum to steel in an ever-changing world. This is primarily because of aluminum’s benefits and advantages over steel in terms of weight.

Sample the statistics around it that showcase that aluminum is three times lighter than steel. Aluminum (and its alloys) have a density of around 2.70 g/cm3 compared to a range of 7.75 to 8.05 g/cm3 for steels.

One of the reasons companies or firms consider welding aluminum to steel is escaping the weight penalty as several government mandates prohibit shipping heavy items to reduce greenhouse emissions.

A heavier vehicle will be more suited to meeting net carbon emissions, which is why steel stands at a marked disadvantage. It is an industrial liability now to replace steel with aluminum alloys.

However, keeping durability and robustness in mind, several companies go for welding steel with aluminum rather than replacing entire steel structures.

It is possible to weld steel and aluminum together using brazing and adhesive bonding techniques, but it doesn’t lead to a robust joint. This is why people turn to weld, which is stronger but more complex.

Why Is It Difficult to Weld Aluminum with Steel?

Several reasons make welding aluminum and steel difficult. However, it is still possible to do so with several caveats and specialized techniques.

The difficulties include the following:

• Different metallurgy and physical properties make welding these two elements difficult.
• Steel and aluminum are insoluble in each other and can lead to brittleness.
• The final product may be replete with several issues, such as brittle nature, which doesn’t create an ideal finished product.
• Aluminum has high thermal conductivity and a low melting point, making it a difficult metal to weld.
• Aluminum is devoid of visual indications, leading to several welding challenges during the welding process.

It would help if you remembered that aluminum is a highly sensitive metal that attracts impurities in its molten form. When you weld it to another substance, especially something as different as steel, the result can be a weak weld.

How to Weld Aluminum to Steel?

The main question is, can you weld aluminum to steel? Well, where there is a will, there is a way. You may consider bimetallic transition inserts, dip coating, or brazing methods to weld aluminum to steel.

However, do not expect perfect results for the reasons described above. You can, however, get a functional product.

Bimetallic Transition Inserts

This is a technique used by professional welders to weld aluminum to steel. It results in an excellent final product with inconsistencies usually reported while joining steel and aluminum.

This method primarily uses inserts composed of equal parts of steel or stainless steel (bonded to aluminum beforehand) along with aluminum. The techniques commonly deployed for this bimetallic transition include friction, explosion, arc, and flash welding.

As a general precautionary practice, it is advisable for the welder to bond aluminum to the aluminum side first and then does the same with steel to the steel side.

This bimetallic insertion method is a popular choice in certain industries and professions. These include:

Ships that require steel decks and for welding their aluminum deckhouses.

Welded aluminum and steel for heat exchangers.

To produce superior-quality arc-welded joints between steel and aluminum pipelines.

Dip Coating

The second method to weld aluminum and steel is using a laser. The laser generates high-intensity heat to create a stable brazing environment for the weld. This is followed by coating steel in aluminum to create the desired weld.

The arc welding method is used after this to weld aluminum to steel. There is specialized knowledge, technique, and expertise required to weld the direct arc onto aluminum and allow optimum time for the molten aluminum to flow unabated to the aluminum-coated steel.

Brazing

Brazing of aluminum to steel can be carried out using NOCOLOK® Flux + Al-Si filler alloy or with NOCOLOK® Sil Flux. While using these components, it is to be kept in mind that it is a complicated procedure and requires patience and skill.

Once you allow the flux to melt, the oxides ought to be removed to allow for a chemical reaction between Al and Fe. this leads to the formation of a thin layer of FeAl3.

It is this layer that forms the bond between aluminum and steel. However, you can’t be sure of the brittleness, which is largely present. Therefore, you will need to minimize the thickness of this layer to avoid any cracks and fractures.

This method is predominantly used in manufacturing kitchen utensils, such as pots and pans. Sometimes, it is also used to create aluminum-coated steel tubes.

A Word of Caution

Though we have discussed, at length, the various techniques used to commercially weld aluminum to steel, there are certain things you must take care of.

You cannot be 100% sure about the mechanical strength of the final component because of the deeply different nature of aluminum and steel. This is precisely why the welded material is used for sealing purposes.

Video: Welding Stainless Steel To Aluminum

Conclusion

Welding steel to aluminum can be done but requires special techniques. You cannot weld the two materials using standard methods because of several complications.

You must also not attempt to carry the welding yourself because of the risks involved. It is also prudent to be mindful of the talent and expertise required in the process. Always consult a professional who has experience welding aluminum to steel for safety and superior results.