Last Updated on February 2021
Why Should You Join Aluminum to Steel?
Steels are much more robust than Aluminum and its alloys, having a density of approximately 7.75 to 8.05 g/cm3 compared to 2.7 g/cm3 for Aluminum. In other words, a similar quantity of Aluminum is about three times less compared to that of steel.
Most industries use steel for a wide range of structural projects. Therefore, based on steel’s thickness, there is an excellent weight consequence related to its usability. The current environmental guidelines are pushing companies to keep an eye on strict limits on the emission from greenhouse gases.
One significant way to reduce emissions is by lowering the mass of the vehicular structure. Using Aluminum alloys in various forms is currently of much industrial significance. On most occasions, it’s not easy to replace the whole steel structure using aluminum alloys. Therefore, you must fix the two metals.
Steels can be joined to Aluminum alloys relatively only using metal brazing or mechanical fasteners like a stud welder and adhesive bonding. Still, when the more considerable structural integrity is needed, welding is the best option. But welding steel to aluminum alloys is a stressor.
Why Is It Hard to Join Steel and Aluminum?
Steel and Aluminum alloys are different in terms of physical and metallurgy properties like melting temperature and thermal conductivity. Steel’s melting point is about 1370 degrees Celsius, two times that of Aluminum, which melts at about 660 degrees Celsius. Besides their extensively distinguishing melting points, both metals are nearly impossible to dissolve to the other. When the two metals react in the molten state, they form brittle intermetallic phases. Therefore, it’s evident that the issues above can cause challenges in fusion welding arc welding of Aluminum and steel.
The results of the welded joints lead to unsatisfactory characteristics, and based on their fragile state, usually are undesirable for most industrial usage.
How to Connect Steel and Aluminum?
Fusion welding processes application used in joining Aluminum and steel is widely-known to be hard. This is due to their differences in expansion coefficients, thermal conductivities, metal melting points, plus the ability to develop fragile intermetallic compounds.
Using lasers to develop a joint between Aluminum and steel is a reasonable step since heat’s top-most concentration in a small place produced with a laser signifies a situation under which a steady brazing environment might be created closely and moved fast to generate a link with few diffusion time to push the highly intermetallic compound formation.
Additionally, bimetallic transition inserts are also a different way to lower intermetallic formation while performing fusion welding. The attachments have single part steel and the remaining part aluminum, connected with friction welding, explosion, flash welding, hot pressure welding, and rollers.
Next, the bimetallic transition connection is then welded to the bulk steel and Aluminum individually. The largest size aluminum is fixed on the aluminum part of the transition attachment first since this activity leads to maximum heat drop once a large amount of steel is arc welded to the steel part of the transition attachment.
The main objective while welding the two metals is to maintain the temperature of welding low while minimizing the weld’s exposure time to high temperatures. That’s why procedures like friction welding are essential in developing bimetallic attachments between steel bulk and aluminum alloy elements.
On the other side, Rotary-friction welding refers to a joining process in a solid form that works through spinning a single work piece to the other using compressive axial force. Heat is then produced from the contact experienced on the surfaces that makes the bordering objects to plasticize.
After that, the compressive strength relocates the plasticized objects from the boundary, which facilitates metallurgical fixing methods. If you don’t enter the liquid form, friction weld will remain quite cold while processing. Furthermore, friction welding is quick to lower the exposure durations to the weld to extreme conditions. Similarly, friction welding is commercially essential when it comes to fixing a variety of different metals since intermetallic compound formation is lowered greatly.
Regardless of importance when carrying out friction welding for lowering the intermetallic occurrence between steel and aluminum alloys, precaution should take place using parameter selection. Regularly, while joining an aluminum alloy with stainless steel, an interlayer of clean Aluminum is used, which lowers the intermetallic formation drastically. All the intermetallic compounds formed as a result of friction between the aluminum alloys and welded steels are iron-aluminum based. So, there are expectations that the fragile components would be developed between pure Aluminum and steel, however, that’s not an issue.
Mostly, natural Aluminum is a bit stronger compared to aluminum alloy. In other words, the temperature needed to arrive at softer and pure Aluminum to move and create a weld is quite reduced compared to aluminum alloy. These minimal temperatures are essential as they lower the formation of brittle compounds.
Based on the complexity in developing strong welds between these metals, most commercial activities for connecting steel and aluminum alloys involve mechanical fasteners. While utilizing commercial clasps, and based on the activity, proper precaution should be carried out to get rid of galvanic corrosion like rust that happens on the aluminum alloy. Getting rid of this is easy. Just use aluminum alloy insulation from steel that takes place through using metal paint or insulating coating.