im wondering what happens if you MIG weld aluminum with the correct wire but without using a shielding gas? Would it just be extremely messy or does there HAVE to be an inert gas flowing for it to bond?thanks
Mig Welding Aluminum Without Gas
In the presence or air, the aluminum oxidizes so fast that making a bond becomes extremely difficult. The shielding gas prevents oxidation by excluding oxygen. The gas doesn't enter into the process, it just inhibits oxidation.
What is your machine that you will be using? Can you weld AC on it? Do you have a High Freq. Box? Will you GTAW it or use GMAW? What Alloy of Aluminum is it? Need much more info than you have provided. If GMAW best to have a pull or a push / pull wire feed system such as in a spool gun. Aluminum is too soft to just push from a wire feeder unit.
Aluminum is much more reactive than steel, and you will instantly get porosity and cold lap if you don't use a shielding gas. If your using mig/tig you should always have a shielding gas, self-shielding wires are garbage. And you might beable to put small weak tack without using a shielding gas, but if there is any stress at all it will break off and you are going to have to grind it out if you want to put good weld on top of it anyway because there will be so much oxidation in that area. Basically welding aluminum without a shielding gas = a bad idea. Same goes for aluminum alloys and magnesium, except they are even worse.
welding reaches high enough heats that the oxygen and hydrogen, and nitrogen that naturally occure in our atmosphere will combine and or otherwise interfere with the re-solidification of the molten metal. This will completely destroy the new molecular structure and there will be no strength in the new metal. All welding uses some form of preventing the atmospheres oxygen,nitrogen, and hydrogen from effecting the alloy structure. Other elements can also be combined in the chemical reaction if your environment or your project are not clean. All metals oxidize on their surface. That means combine with oxygen. It is the process we call rust when refering to iron which in the case of iron never stops rusting until it rusts away. for the most part all other metals oxidize on their surface and stop. this is what gives their great protection and helps in deciding their use,as with aluminum. You can create environments that will cause thsese other metals to continue to oxidize as with electrolosis, but that is getting more complex. SOO with aluminum it is a good idea to brush the oxidation layer off the surfaces to be welded so this oxidised aluminun does not become a source of contamination in the new weld metal. It is recomended to use a clean stainless steel bristle brush as an iron brush can contaminate. Brushing can generally last for many hours even days but you can see the dull color re appear as it oxidizes over time. Another comon source of oxygen and hydrogen is water. That is what the purpose of low hydrogen electrodes is, though these are not used in aluminum. The military builds the aluminum hulls for the bradley and other vehicles in San Jose partly because the relative humidity is best for mig welding aluminum there. so you can see the concepts can become conflicting. Always use argon with aluminum. Argon can be mixed with small percentages of helium too.
