Welding aluminum and its alloys is much more challenging in comparison of steel alloys. In comparison to steel, aluminum has higher conductivity and lower melting point. These properties can lead burning of aluminum during welding specially in case of thinner aluminum sheets. Feeder wire made up of aluminum can be very much softer in comparison to the steel ones, which may result in tangling of feeder. These factors make selection of aluminum wire for welding specifically application dependent and the welder skill is also the important thing that has to be taken on note as aluminum welding is delicate process.
Other important factors that make aluminum welding more challenging in comparison of steel, is that as aluminum is coated with oxide layer which has melting temperature of 3700 degree Celsius which is almost 3 times of aluminum melting point of 1200 degree Celsius. This factor makes it difficult, as if you don not remove of this oxide layer before welding then the aluminum below this layer will melt and will mix with oxide layer forming very weak welds.
As we mentioned that aluminum has very good conductivity to heat as of steel alloy, so it requires higher ampere of current and faster electrode movement and along with this distinguish factors there is requirement of welding skill for making adjustments and have perfect welds.
1. MIG Welding Aluminum
The process of welding aluminum with MIG welder is very messy procedure, the most important thing you need to attach spool gun first before welding. For attaining best welded joint with lessening the messiness we will suggest you to preheat the metal before starting the weld.
What is a Spool Gun?
The spool gun has spool of wire accompanied in it to shorten the travel distance of the wire before entering it inside of the weld pool. The spool gun is much needed equipment as aluminum metal wire as very much softer than steel ones which make them harder to travel through the machine effectively. Just go through the settings manual of your machine about instructions for switching to spool gun. Then just simply first unplug your MIG gun and replace it with spool gun. Most commonly there will be a switch, which enables the machine to know about this alteration of Guns
Which MIG Wire for Aluminum?
For welding aluminum metals sheets, you will require aluminum wire. The most prominent used aluminum wires are 4043, 5356 and 5554. You have to select the grade of wire as per you application or the grade of aluminum you are using and always be acknowledged about your alloy properties. Talking about different wires, 5356 has very high tensile strength can be used for strong welds and 4043 is predominately used for welding silicon alloys which offers better control over weld pools and has better compatibility with base range of alloys. The 5554 wire is used for welding other grade sheets like 5454, 5154.
Clean the Metal
In MIG welding procedure, dirt is very important factor that effects your weld joint, in case of steel welding though you can tolerate little bit of dirt but in aluminum welding we really have to clean the metal before starting the welding. We have to remove all kind of contaminations, oil stains from the metal surface and the thin layer of aluminum oxide over the metal surface, can be removed by rubbing the metal piece with a wire brush made up of stainless steel.
Speed
As, we all know that aluminum is very conductive metal specially in comparison of steel, so there is requirement of high voltage for effective welding. Higher voltage will generate adequate amount of heat, you simply just need to move your spool gun quickly as this heat can burn through the metal piece especially thin aluminum sheets. You can apply push technique instead of pulling the bead.
Shielding Gas
In MIG welding of aluminum, we will use pure argon or an argon/helium mix. Helium gas is very cost and very less effective for the use as shielding gas, but sometimes it is required in case you are thicker metal pieces as there is a need of more heat. Co2 gas is not applicable in this case as Co2 or argon/ Co2 mix will oxidize the aluminum, which is not required.
2. TIG welding Aluminum
The TIG welding of aluminum is very commonly used TIG welding method. TIG welding is one of the hardest to learn in welding and the hardest thing about it controlling arc. If you are naïve in the welding field then you must first learn the TIG welding of the steel before going on to the Aluminum one, and don’t be afraid and disappointed with the failures.
AC Current
The most important factor while having TIG welding of aluminum is that you have to use alternating current. Alternating current is require to break through the oxide layer of aluminum oxide present over metal sheet. Direct current cannot break through this and will ruin your weld. DC welding is possible but main problem is that its penetration problem with oxide layer.
Some TIG welders uses the square wave functions which is used for cleaning the metal while welding, but it is advisable to clean metal manually. It is very important factor while welding to remove the oxide layer and making it ruin your weld. You can use stainless steel wired brush to remove the layer and there are some solvents available in the market for removing any kind of grease and oil dirt before starting TIG welding.
Which Tungsten Electrode?
The selection of electrodes is totally depends upon the personal preference as well the kind of machine you have. As such in case of TIG inverter machine, then 100 % pure tungsten electrodes won’t give the efficient results on high amperage. So instead of going with 100 % pure one you can try 2 % thoriated tungsten electrode or 2 % lanthanated electrodes, which are very efficient and have high amperage tolerance.
You have to prepare your electrode by balling its end. You have two options either to form the end into point of ball or have the ball on the end. It’s totally on your personal preference, I personally recommend to have the ball on the end. For balling the electrode simply you have to connect and fire up the machine until the end turns in to ball. One factor to consider is that ball should not more than 1.5 times of dia of the electrode.
Filler Rod
The selection of rod is another important aspect of TIG welding, but before selecting it you must have knowledge about the grade of aluminum you are using. 4043 rods are most commonly used rods.
Preheating
In TIG welding, preheating the aluminum metal before you further proceed to main process is advisable as it will make penetration better and you will find very easy to control and manage the arc.
3. Stick Welding Aluminum
The stick welding of aluminum is messier and very untidy method in comparison to all methods mentioned above. In this method like others preheating and the cleaning of the surface dirt and oxide layer with stainless steel brush are most important factors that you should do before starting the welding. For welding, you have to set up welder to DCEP reverse polarity. In comparison to other process there is a requirement of bit more patience in starting the arc while stick welding aluminum. So hang to it and you will get used to it.
Electrode Rods
In this method, we have to use that the electrodes which are specifically designed for Stick welding of aluminum like as 4043 is the most commonly used electrode for stick welding. There are also other rode are used for other purposes. As this is a most untidy process, so make sure that the workspace is fully ventilated, as there is lots of smoke produced during this process. There is a large amount of slag produced during this process and electrodes burns out very quickly so there is requirement of quick motion across the joints. After completion of the welding, you have to chip off the slag and clean the weld.
Conclusion
These the three methods of welding the aluminum metal. You can use any one of them according to you preference and your application properties. In case you have any problem and ambiguity regarding the procedure feel free to write to us, we will love to help you out.