Welding aluminum

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Our resident wisecat
May 15, 2007
On the alley fence meowing, somewhere in TN.
I'm really surprised to find that alot of welders are not aware of the fact that you need to preheat aluminum before welding it.
The main reason for this is because of the moisture content of the aluminum.
The material is like a sponge. When you preheat the material the moisture is pulled out and it will accept the weld better. Of course the amount of heat needed is going to depend on the thickness of the material.
I'm just touching on this for now. Some of the other members can add info. to this subject if they like.:)

How do u do that?


If I'm welding alum. sheet... .030 to .125 thou.
I use a simple hand held bottle torch. I heat it a little past the point of seeing the moisture go away.
If I'm welding plate, I'll use a rosebud on the torches and heat way upwards of that point. The welding shops have heat sticks you can rub on metal to check for proper heat range. They melt at a given temp.
You will be surprised how much better your aluminum welding will be after preheating.


What’s your take on this alumaloy stuff you use with a propane torch?

I’ve not heard very positive things from people that have seen similar products at trade shows, but some of the stuff they do on their infomercial is pretty slick.
I’m not referring to a structural weld, just trim pieces, interior stuff, and small brackets.

It may be worth a try. I've never used it.
A couple of things I would be concerned about would be if there is enough heat to properly sink into the parent material. Also, would the product "match" to the trim pieces, color wise would you be able to see a ring around the new material after polishing.
It may be ok but I would do some research before trying to repair anything rare.

I built t-tops for lurhs, all we used was anodized aluminum, we never preheated any of it, welds just fine, i could see that being helpful on thick plate, but thin stuff , do not see the need, heat travels through aluminum real quick anyways, as soon as you get your bead started, the heat has traveled way past the area your working on, not saying your wrong in any way, i just really dont see the need.
One of the reasons I preheat, is because when TIG welding there is nothing worse than having the moisture pull out of the alum. when you first strike the
torch. If your not experienced in this, it can explode out onto your tungsten and your stopping to clean.
You also need to preheat when TIG welding on the thick stuff. I have found that the material excepts the weld better.
MIG welding is more forgiving, but any "pro" I've every spoke with, still does this.

Try this experiment, place a piece of 1" thick alum. in the fridge over night.
Pull out the piece and go straight to TIG welding.
After you get over the popcorn effect, heat up the alum. and try again.
While this example is to the extreme, it will show the benefits of preheating.

Try this only if the wife doesn't mind seeing T-6 sitting beside the leftovers.:D
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