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Welding Aluminum To Steel

05 March, 20 9:25 am · Leave a comment · Tom Masters
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How To Weld Aluminum To Steel: Is It Possible? What Are My Options?

welding a steel frame
If you’re new to welding, you may be wondering if it’s possible for you to weld aluminum to steel. Welding “like-to-like” metals like steel-to-steel and aluminum-to-aluminum is usually very straightforward. However, when you try to weld together two very different metals like aluminum and steel – such as two components manufactured by tube laser cutting – things can get a little bit more complicated. So, is it possible to weld aluminum to steel? What are your options for doing so? Let’s discuss everything you need to know.

Is It Possible To Weld Aluminum To Steel?

The answer is yes, and no. It’s not a good idea to directly arc weld disparate metals directly to aluminum. Welding a metal such as magnesium, titanium, copper or steel directly to aluminum is very difficult to do. This is because, when aluminum is melted by the high heat of arc welding, brittle “intermetallic” compounds will form. These crystallized structures are extremely brittle, and are prone to breakage. This makes them very fragile – so any steel component that’s welded directly to aluminum will be very weak at the weld bead. So, how can you avoid this? It’s simple – during the welding process, you must isolate the other metal from the aluminum. When aluminum melts into aluminum, these intermetallic compounds don’t form – which ensures that the welded metals can bond properly. There are two common methods for doing this successfully, and we’ll go over them below.

“Using a bimetallic transition insert is definitely the best way to weld steel to aluminum for structural applications”

Welding Aluminum To Steel With Bimetallic Transition Inserts

Using a bimetallic transition insert is definitely the best way to weld steel to aluminum for structural applications. It creates a weld that’s of excellent quality, and is just as strong as an aluminum-to-aluminum or steel-to-steel bond would be. A bimetallic transition insert is exactly what it sounds like. The size and shape will vary, but this insert is a section of material that’s made from one part aluminum, with an equal part of stainless steel that has been bonded directly to the aluminum.A wide variety of processes can be used to bond the steel and aluminum together to create the bimetallic insert. Rolling is a popular method, as is friction welding, explosion welding and hot pressure welding.

Once the insert has been built, it can be placed between the steel and the aluminum material that is being welded. Then, traditional GMAW or GTAW welding can be used to complete the weld. The steel section will be welded directly to the steel component – and the aluminum section will be welded directly to the aluminum component.Typically, the aluminum-to-aluminum weld is completed first to avoid overheating the inserts during the welding process. Once the initial weld is done, the aluminum components will help absorb heat and prevent the insert from overheating while the steel-to-steel weld is done. This method of welding is often used to join tubing on heat exchangers, create joints between steel and aluminum pipelines, and in shipbuilding to attach aluminum deck houses with steel decks.


Welding Aluminum To Steel With Dip Coating (Hot Dip Aluminizing)

In many cases, creating a bimetallic insert to weld aluminum to steel is not practical for smaller businesses or individual welders – since it requires a complicated industrial process and a custom-built insert. The other option you have for welding aluminum to steel is dip coating, which is also sometimes called “hot dip aluminizing.” In this process, the steel component is dipped into aluminum to coat it completely in the metal. This prevents the formation of intermetallic compounds during the welding process.

The molten aluminum from welding will contact the aluminum-coated steel part – and since it won’t contact the steel directly, the joint will be relatively strong. However, the process of doing this can be quite difficult for welders who are not experienced in the process. Arc welding is usually used. But the arc must not directly contact the steel. You must use a specialized technique to weld. The welding arc must be directed only on the aluminum component. Then, the aluminum that has melted into the weld pool must be directed onto the aluminum-coated steel. The arc must not contact the steel part directly.

“It’s important to note that this method of welding aluminum to steel should not be depended on for full mechanical strength”

If you are not careful when welding and the arc directly touches the aluminum-coated steel, it can quickly burn through the aluminum coating – which will result in steel melting and forming brittle intermetallic compounds with the aluminum. It’s important to note that this method of welding aluminum to steel should not be depended on for full mechanical strength. Aluminum and steel bonded with this coating-type joint method will not be nearly as strong as an aluminum-to-aluminum or steel-to-steel bond – or a bond created with bimetallic transition inserts. Instead, this method of welding is usually used only for seam sealing, and not for structural purposes. That means it’s quite a bit more limited, compared to bimetallic transition inserts.


Bolting Steel To Aluminum Is Usually A Better Option Than Welding

Even if you have the resources to create bimetallic inserts for your components when welding steel and aluminum, the cost of doing so can be prohibitive – and dip coated parts shouldn’t be used for structural applications. So, what should you do if you need to weld aluminum to steel for a structural application? In most cases, it’s faster, easier and much less expensive to simply bolt the components together. As long as you are not creating a bond that must be completely seamless – such as a pipe joint – bolting or riveting the components together is a much better option. However, there are some considerations you should keep in mind when bolting steel and aluminum together.
tig welding on pipe
First, you must make sure that you take steps to avoid corrosion. When steel and aluminum are connected and a conductor like salt water is present, voltage is produced. In turn, the aluminum will be preferentially corroded. To avoid corrosion at an aluminum/steel joint, you must insulate the steel and aluminum from each other. First, the components should both be painted to isolate them electrically. You should also use a plastic washer along with a nut and bolt when assembling the joint. Plastic is nonconducting, and will prevent galvanic corrosion between steel and aluminum parts.

Know How To Weld Aluminum And Steel – And Whether Or Not It’s A Good Idea!

We hope this information has been helpful, and educated you about some of the challenges of welding disparate metals like aluminum and steel. Welding aluminum to steel with bimetallic transition inserts is a great way to ensure a seamless, strong bond – and it’s useful for structural applications, but can be very expensive. In contrast, dip coating is cheaper and easier to do, but can’t be used for structural applications. So keep these factors in mind when you need to join steel and aluminum – and if neither type of welding seems appropriate, remember that good old nuts and bolts can do the job just as well, in most cases!



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