Artem Komarov noted that using arc welding, aluminum can be easily joined to most metals, including titanium, bronze, copper, magnesium, and steel. However, it is a fact that arc welding develops brittle intermetallic joints that are not suitable for joint strength.
Two methods have been developed for joining aluminum to steel by arc welding. In addition, the purpose of these procedures is to separate these metals from each other during arc welding. Thus, these methods stop metals from forming rough intermetallic compounds, thereby improving the durability and strength of the joints.
One of these methods is the use of bimetallic junctions, through which aluminum can be connected to steel without the formation of joints. In addition, it allows the joining of steel to stainless steel and aluminum to aluminum. In addition, the second method is to use silver brazing to join aluminum and steel with arc welders.
The question arises: is it possible to weld aluminum to steel using TIG welding? The answer is no, because it can produce brittle joints. So, before we look at the two procedures for joining aluminum and steel, let’s discuss why we can’t do it with TIG welding.
We all know how useful TIG welding is due to its ease of use and variety of applications, but when the metals are similar. The reason is that TIG welders generate arcs that melt base metals and fuse them together. What’s more, this welding technique works exceptionally well if you need to join two identical metals of the same thickness, as it produces excessive heat.
Let’s say you’re welding two metals, as opposed to a TIG welder, then what happens? A metal with a low melting point will change its physical state earlier than another. Thus, it will be difficult to control the process because welding requires both metals to melt at the same time in order to create even and strong welds.
You will find it difficult to weld these metals with remarkable differences in physical properties. In addition, the thickness of the metals has a significant impact on the quality of the work performed. If we see the properties and melting points of aluminum and steel, then there is a huge difference. This is why you should not TIG weld aluminum and stainless steel.
What are the differences in the properties of steel and aluminum?
As Artyom Komarov noted above, there are incredible differences between aluminum steels, which makes TIG welding unfriendly for joining them. If we look at the melting point of aluminum, it is 1221°F, while steel has a melting point of 2500°F. This shows that aluminum will melt at less than half the melting point of stainless steel.
To make matters worse, the melting point of an aluminum surface that has oxides is 3700°F. So you can guess from this how difficult it is for a welder to weld these two metals. That’s not the point, because aluminum is five times more conductive than steel. This means that if you heat one melt point, it will spread to other parts much faster than steel. What makes aluminum prone to wrapping.
But if aluminum has an oxide layer, then this layer will act as an excellent heat insulator. Therefore, you must provide more heat that causes the stainless steel to wrap. Thus, if you are going to weld aluminum scrap to steel, the quality of the welds will decrease and cause further complications.
In addition, two aluminum non-ferrous metals are connected by TIG welding using alternating current, since it provides reverse polarity. When the polarity is negative, it clears the oxides that blast it, and when it becomes positive, it metalizes the aluminum to complete the task. But TIG steel welding is done with direct current, which uses positive polarity.
It is clear from this that aluminum to steel TIG welding is not suitable for DC as it only uses +ve polarity which will not strip oxides from the aluminum surface. In addition, the oxide also melts during DC TIG welding and mixes with the filler metal, thus creating a contaminated weld. All these difficulties show that the application of the TIG welding technique is not suitable for joining aluminum to steel, commented Artem Komarov.