Welding aluminium to steel can be a bit of a challenge, even for the most skilled welders out there. While it is definitely achievable, there are some things to note before you can try to weld the two materials together. The type of techniques and processes used when welding aluminium are different to the techniques and processes used when welding steel. It is crucial to know the different techniques that are used when welding in order to weld successfully on different projects.
WHY IS WELDING ALUMINIUM TO STEEL DIFFICULT?
Aluminium and steel alloys are very different to each other with respect to their physical properties and their metallurgy, such as thermal conductivity and melting point. Steel’s melting point is nearly double that of aluminium. In addition to this, neither metal is soluble in the other. When molten, they form brittle intermetallic phases.
These issues can present challenges in fusion welding, such as arc welding of steel and aluminium. The resulting welds would have poor properties that would not be suitable for industrial applications. This would be due to how brittle the joint welds would be. When welding aluminium to steel, there are some things that you need to do in order to ensure that you do it properly and safely.
WHY SPECIAL TECHNIQUES ARE NEEDED TO WELD ALUMINIUM TO STEEL?
THE MATERIALS HAVE DIFFERENT MELTING POINTS
Welding is the process of melting two materials and bonding them together. With most materials, adhesive bonding and mechanical fastening are used to bond two materials together, but with steel and aluminium having different melting points, the process of bonding them together is infinitely more difficult.
With the usage of various alternate techniques that have been developed, welding aluminium to steel can be achieved successfully through a simplified process. Through adhesive bonding or mechanical fastening, aluminium can be welded onto most metals with relative ease.
THE MATERIALS HAVE DIFFERENT BONDING PROPERTIES
Aluminium has a melting point of 660°C while steel has a melting point 1497°C. This is an approximate 800°C difference in melting point. This difference in melting points creates a difficult barrier when it comes to bonding these two materials together.
Additionally, aluminium and steel have different properties that make it really difficult to bond them together. If they are not bonded correctly, then their fusion will not hold.
BRITTLE INTERMETALLIC COMPOUNDS
This lack of cohesive fusion will result in the creation of brittle intermetallic compounds. These intermetallic compounds that are weak will lead to the creation of breakage and weak points.
WHAT IS NEEDED FOR WELDING ALUMINIUM TO STEEL?
The following methods can be used to weld aluminium to steel:
- Bimetallic Transition Inserts
- Coating the materials (Dip Coating)
BIMETALLIC TRANSITION INSERTS
Bimetallic transition inserts are materials that are used when bonding together two different materials such as aluminium and steel. They are used to create welding connections that are of a great standard within structural applications.
These inserts are one part aluminium, and equal part steel or stainless steel already bonded to the aluminium. Rolling, explosion welding, friction welding, flash welding (also called hot pressure welding), and arc welding are some of the different techniques used to create these bimetallic transition inserts.
Arc welding aluminium transition inserts are done by welding one side of the insert steel to steel, while the other side is welded aluminium to aluminium.
It is best to perform aluminium-to-aluminium welding first, as this allows you to avoid overheating while also providing a larger heat sink when the steel-to-steel weld is being done.
The bimetallic transition insert method is used to:
- Join aluminium deckhouses and steel decks on ships
- Weld aluminium tubing with steel or stainless steel tube sheets on heat exchangers
- Produce arc-welded joints between aluminium and steel pipelines
COATING THE STEEL PRIOR TO WELDING (DIP COATING)
Dip coating (a method many use for successful results), also known as hot dip aluminizing, is another method that is used when welding aluminium to steel. In other words, before one begins welding steel to aluminium, the steel is coated in aluminium. One of the downsides to this is that it can be a bit costly, but it does result in a greater bonding between the materials. Another downside to this method is that it is more advanced and requires a professional welder.
After it has been coated, the steel can be arc welded to the aluminium, so long as one makes sure that the arc does not negatively affect the steel. Through the use of a special technique, the arc is welded onto the aluminium, and the molten aluminium is then taken and applied directly onto the aluminium-coated steel.
Brazing, which is another coating method used to bond aluminium to steel, is coating the steel surface with silver solder, and then bonding them together using aluminium filler alloy.
It should be noted that these methods are specifically used for sealing purposes and are not used for mechanical strength.
ALUMINIUM WELDING NEAR ME?
Notefull KZN, as a black female owned company with ISO: 3834, SAIW accreditation and BBBEE certification level 1, offers Aluminium Welding services for various industries and applications not only in Richards Bay but KwaZulu-Natal, and all of South Africa’s provinces. We pride ourselves on welding services of the highest quality standards. Our specialized welding service is renowned for its workmanship, and our facilities have a large range of procedures built up over many years. This enables us to undertake many critical tasks to suit almost every type of welding job.
We weld Aluminium, Steel & More, our welding team specialises in the welding of aluminium, stainless steel and of course mild steel (carbon steel). If you require welding or fabrication services on other specialised metals not mentioned here please don’t hesitate to contact us. Looking for aluminium welders near you? Our welding services are available for both businesses and individuals; no job is too big or too small! Start the journey of seeing affordable quality results today by getting the right service you need.