The Question, can you weld aluminum to steel?
I bet this is a question you have come across more than once. You have the same question yourself. The short answer, yes. However, it is not as straightforward as welding any other metal to steel.
Aluminum is a non-ferrous metal meaning it is very different from steel. The two metals have different melting points. For example, carbon steel melts at a temperature of 2500 degrees Fahrenheit while aluminum melts at a temperature of 1218 degrees Fahrenheit.
What this means is that the aluminum metal will melt before the steel metal starts to melt. This results in a weak fusion and the formation of brittle particles that further weaken the weld.
These particles cause the joint to be weak and increase the chances of bond failure. So how to weld aluminum to steel?
Methods of welding aluminum to steel
There are several techniques you can use to accomplish this kind of welding project. Well, there are several welding processes that are used to do these. The most common form of welding used for this is called solid-state welding.
There are several types of solid-state welding used to join aluminum to steel.
Diffusion welding entails the joining of two dissimilar metals by applying high pressure and temperatures. The metals are pressed together at elevated temperatures, usually 50-70% of the melting point. At this point, diffusion occurs, and the metals are fused.
Explosion welding is another form of welding used to join two dissimilar metals. And in most cases, the metals joined using this method are steel and aluminum. This method entails the use of controlled detonations to fuse one metal onto the surface of another.
This method can join a wide variety of non-compatible metals. It is preferred for joining aluminum and steel.
Weld aluminum to steel Using arc welding processes
The above-discussed welding processes are complex and impossible to do with conventional arc welders. This brings us to the question of whether it is possible to arc weld aluminum to steel. It is possible to weld aluminum to steel using arc welding processes. However, you will need to use special techniques to accomplish such a weld.
There are two main techniques used when welding aluminum to steel. In this article, I will be taking a closer at the two. And also give my personal opinions on each.
Bimetallic transition inserts
What are bimetallic transition inserts? These are inserts used for welding steel to aluminum. These inserts are made up of one part aluminum and equal part steel. However, the inserts can also be comprised of aluminum and another metal.
Thus they can be one part aluminum and an equal part copper. Metals such as copper, magnesium and stainless steel are easier to weld steel to. The process of welding two dissimilar metals to form bimetallic inserts is usually a lengthy one.
It involves processes such as friction welding, explosion welding, rolling, flash welding. These inserts can be purchased from most metal and electrodes.
How to weld steel to aluminum using bimetallic transition inserts
The process of welding steel to aluminum using these inserts is rather straightforward. Welding these inserts to the two aluminum and steel parts is possible. The steel part is fused to the steel base metal and the aluminum to the aluminum metal.
This removes the problem of the two dissimilar metals coming into contact. Instead, they are welded to the part of the insert made of the same metal. This method of welding aluminum and steel is commonly used in shipbuilding.
Also in the making of heat exchanges. The method is used to weld aluminum tubes and steel or stainless steel tubes together. Thus it is possible to weld stainless steel to aluminum using this method.
The method is also used in the welding together of steel and aluminum pipes. For hobbyists and professionals, you can use this method for auto body repair works.
Coating the steel in aluminum
Another method used to weld steel to aluminum is dip coating. It is also referred to as hot-dip aluminizing. The general idea here is to coat the steel metal with aluminum coating before welding the two.
The aluminum-coated steel base metal can then be arc welded onto the steel part. Alternatively, you can opt for blazing aluminum to steel. Blazing is a method of creating aluminum alloys that can then be welded onto the aluminum part.
Blazing is a process where you coat the surface of the steep metal with a silver solder. Then welding it together using an aluminum filler alloy. Generally speaking, brazing rods are similar to welding rods.
However, welding rods have a higher melting point than blazing rods.
How to weld steel to aluminum with a coating
The idea is to create an aluminum alloy using the steel base metal. The resultant metal is then welded onto the aluminum part.
Which is the better of the two?
Coating steel aluminum is not ideal for full mechanical works. The weld produced is usually not as strong. This method is used mainly for sealing purposes only.
The preferred method is using bimetallic inserts. The weld created is usually of high quality and very strong.
Therefore general purpose welding where you need a strong weld, using bimetallic inserts is recommended. The bimetallic inserts are created through explosion welding. And thus create a strong weld that is ideal for many different applications.
Aluminum is a special kind of metal and does not have the same properties as other popular metals. All the same, it is a popular metal due to its toughness and lightweight. Welding other metals such as copper, magnesium and titanium onto aluminum is therefore not straightforward.
However, with the help of bimetallic metal inserts, the process is made possible. These inserts are made of aluminum and any other metal. With these you can use any of the popular arc welding processes to weld the two metals together.
Metal Inert Gas and Tungsten Inert Gas are the two most common processes used when welding steel to aluminum using bimetallic inserts.