Aluminium alloys can be joined to steels relatively easily using techniques such as adhesive bonding, mechanical fasteners or brazing, but when superior structural integrity is required, welding is preferred. However, welding of aluminium alloys to steel is difficult.
Through the process of arc welding, aluminum would be in a liquefied state by the time the steel begins to melt. Arc welding the two metals together would also create a brittle compound and would not create a strong fusion.
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.
Steel cannot be welded to aluminum by using conventional welding techniques, like SMAW (arc welding), GMAW (MIG) or GTAW (TIG). However, there are some workarounds and alternatives that might provide acceptable results.
TIG welding is most commonly used to join thin sections of alloy steel, stainless steel and nonferrous metals such as aluminum, magnesium and copper alloys. The process grants the operator greater control over the arc, allowing for strong, high-quality welds.
Material thickness: Most reputable MIG machines can be used to weld aluminium down to 3mm thickness. To successfully weld materials thinner than 3mm, it may be neccessary to use specialist MIG or TIG welders with pulse capability. (Note: to TIG weld aluminium, you will need an "AC/DC" machine such as the 202T).
So why is aluminum so difficult to weld? This material is soft, highly sensitive and is insulated by a tough oxidized layer. While in its molten state, aluminum is susceptible to impurities, which can lead to porous, weak welds. Aluminum and its alloys have a great affinity for oxygen.
The truth is that MIG welding aluminum is possible; it's tricky and requires proper settings and technique, but it's easier than the rumors make it out to be. However, since there are so many ways that aluminum welding projects can go wrong, it also requires practice and training to get them right consistently.
Applying coatings to both materials. The coating on the cathode is the most important and must be in good condition, otherwise the galvanic corrosion could be worsened. Separating the two materials by inserting a suitably sized spacer. Installing a sacrificial anode that is anodic to both metals.
When MIG welding aluminum, the desired mode is spray transfer. This process is a very smooth transfer of molten metal droplets from the end of the electrode to the molten pool. The droplets crossing the arc are smaller in diameter than the electrode.
Another option for gluing metal is Loctite Epoxy Weld Bonding Compound. A convenient alternative to welding, it's the strongest solution for bonding most metals, including iron, steel, aluminum, brass, copper, and pewter.
A good way to reduce corrosion is to use an isolating coating or paint on the aluminum and the steel to isolate them electrically. Insulating washers are also effective in isolating the two dissimilar materials and creating a relatively safe surface area.
Some examples of material combinations that cannot be fusion welded successfully are aluminum and steel (carbon or stainless steel), aluminum and copper, and titanium and steel. Nothing can be done to alter their metallurgical properties. That leaves changing your process.
Health Risks of Aluminum Welding Fume Exposure
Exposure to fumed aluminum and aluminum oxides can cause both acute and chronic conditions ranging from lung disease to nervous system damage. Acute symptoms of aluminum weld fume exposure include: Irritation of the eyes, nose, throat, and lungs.
Welding aluminum without a welder is possible if you know which methods will yield the best results for your project requirements. Soldering and brazing are great options if strength isn't critical, while cold weld adhesives offer more versatility when dealing with complex shapes or irregularly sized parts.
The right Welder is essential if you're going to work with aluminum. For aluminum, a TIG – tungsten inert gas – welding machine is a better choice than a MIG machine. While MIG machines can be used, TIG machines are preferred by most professionals taking on complex aluminum welding tasks.
While many people worry that stainless steel fasteners, such as screws, bolts, nuts, or host of other options, won't work with aluminum due to the risk of galvanic corrosion between the two very different metals, the truth is that stainless steel is the metal of choice for fasteners to secure your aluminum materials.
Stainless with stainless, aluminum with aluminum, brass with brass. Mixing metals can affect the strength of the application, the lifespan of the fasteners, the corrosion of the materials, etc.
Having said that, it is safest to avoid a metal that is very reactive, such as brass, and opt rather for one of the least reactive metals, such as stainless steel. That will give you peace of mind in case the coating peels away or disintegrates.
The first step is to make sure you have the right equipment for gasless MIG welding aluminum. You will need a special type of wire designed specifically for aluminum, as well as an appropriate spool gun or torch. You may also need special shielding gases such as pure argon or carbon dioxide (CO2).
Most welders believe that aluminum is a difficult type of metal to weld compared to steel. That is the reason why most of them prefer to start out by learning to weld steel before moving on to aluminum. Unlike what other people know, welding aluminum is difficult because it simply uses a different method.
MIG welding aluminum is typically considered to be difficult, and is a very different process from MIG welding mild steel. While MIG welding mild steel relies heavily on carbon dioxide (CO2), MIG welding aluminum uses the industrial gases of argon or helium.
Aluminum. The first impression of aluminum is that since it is pliable and easily manipulated, it should be easy to weld. In reality, it is considered to be the most difficult metal to weld since it is an alloy and therefore mixed with other metals. Some have even called welding with aluminum a “nightmare.”
High strength alloys (e.g. 7010 and 7050) and most of the 2xxx series are not recommended for fusion welding because they are prone to liquation and solidification cracking. The technique of Friction Stir Welding is particularly suited to aluminium alloys.
Stress cracking can occur when an aluminum weld cools and excessive shrinkage stresses are present during solidification. This could be due to a concave bead profile, too slow of a travel speed, a highly restrained joint, or depression in the end of the weld (crater crack).