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Welding aluminum

J

JRSutton

Well-known Member
I'm good enough with a stick welder or mig welder to make my own general repairs, but far from an "expert".

Have a friend with an aluminum trailer that has some stress cracks in a non-critical area. He was asking if I could weld them.

I said no since it's aluminum - but it did get me thinking.

Aside from tig (I'm couldn't possibly justify new equipment) - just how hard IS it to weld aluminum?

I've never done it, never seen it done, don't know anybody who does it.

Just never had the need. So I've never even looked into it.

CAN you even do it with a mig welder?

Must be very easy to blow through the material, no?
 
Hello JRSutton,
Aluminum can be welded with a MIG. If you have run a MIG with steel it may not be hard to learn for you. Cost of equipment is the issue.
If it is not a critical area, can you plated instead? Drill a hole at the end of the cracks first. It will prevent further cracking.
Guido.
 
In most cases you can get by with the average Mig welder. You'll need U-groove drive rolls for the size aluminum wire you want to run. And a nylon liner in your Mig gun. Shorter the gun the better. And if you can do it, place the feeder above the work. Let gravity help you. If by chance your Mig welder will accept a spool gun that would be the way to go, or a push pull gun. You will need 100% argon gas.
To help things out, preheat the first couple inches of the weld zone. See how these two welds are cold for the first couple inches? (Right side).



 
Few months ago I played around with some aluminum SMAW. Haven't done this since the early 1980s. Now I remember why I didn't like it. :lol:


 
Now i am by no means and expert on this welding Alu. thing as i was forced into it out of need from owning a dump trailer . What i have learned is (1) you need more heat (amp) it must be clean and when you think it is clean clean some more .(2) you push the weld not pull. Next if the Alu. is stress cracking then the metal is done for.
 
If you have MIG it isn't that much to go TIG. As for welding Aluminum it is a lot easier than we believe as far as skills go BUT you need knowledge to know what the heck you're doing. I am not a welder and all my aluminum welding experience was during work shops at the EAA convention, If you know what you're doing as far a set up I find it easier than steel. As far a thinness at EAA we saw guys welding pop cans together. After a 1/2 hour instruction they had my 14 y.o. daughter pushing a 3/8" wide bead across two 1/8" thick aluminum plates she was welding together with an Oxy-acetylene torch. The instructor said the last time he saw a bead like that was on a 1930's coach built aluminum Rolls Royce body.
 
My son tig welds it and he does it for a living. I know nothing about it. His welding has to pass a ridgid inspection. Thats all I know.
 
MIG and TIG are entirely different and require different machines. How can "stress cracks" not be critical? In a classroom with a qualified instructor and the proper machine set up, it's a lot easier than doing it on your own with marginal equipment. Aluminum is tricky to learn. It does not turn red hot. It gets shiny and next you know, you have a big hole. It might save you a lot of grief to have someone experienced with aluminum weld it for you.
 
I've welded aluminum for 40 years. Trailers are built out of 5000 series aluminum so you have to use 5000 series wire in your MIG, like 5356. If you don't the welds will crack. Found out the hard way, had to do a whole job over.
 
Today's mig welder on aluminum works better when you preheat the area to be welded. What I have done is make an acetylene only flame and blacken the area with soot, then open the oxygen and make a neutral flame. Heat the blackened area till the soot is gone, then weld it. The above method works good for tig also.

For tig you need to preheat the area with a torch or else use your tig torch to preheat some. Watch the weld area as it turns fluid and add some filler rod and weld as if you were gas welding. There is a little in technique involved that was not mentioned. I had a female apprentice that was tig welding after I gave her a couple of demos. I have never seen aluminum get hot and make a big hole right away. The weldor would have had to have done something way wrong.

I had the chance to learn oxygen/acetylene welding aluminum many years ago but we had a Tig machine so I passed it up, big mistake.
 
I never said aluminum would make a big hole right away. I said it doesn't get red hot and you can end up with a hole if you don't know what to look for. If you have the right machine for the thickness you're doing, you shouldn't need to preheat unless it's a thick section. Most TIG welders use a foot pedal so they can up the amps at the start and then adjust down and up where necessary.
 
Where do you live? If you are near enough I would do it for you. You can run al. wire through a reg mig gun but it sucks. You need 100% argon gas to do it and it works better with harder wire like 5356. As said either a push/pull gun or spool gun works best because the wire is so soft it is hard to get it to feed. You can use stick too, but again it's tuff, especially on thin stuff. You are better off to find someone who has the right equipment and get it done right. The proper equipment is faily expensive partially because it takes more power for aluminum because the heat spreads and disapates so fast. On my miller with the spoolgun I almost never use high range for steel but almost never use low range for aluminum.
 
I must have misunderstood this statement "Aluminum is tricky to learn. It does not turn red hot. It gets shiny and next you know, you have a big hole." You might want to look into a Tig class.

I always preheat the aluminum I weld, if it is thin I will preheat it with the Tig torch before I try to make a fluid spot to start welding. I once did a coffee pot strainer. The center was broken out where the stem goes down to the bottom of the pot. I used a 350 amp syncrowave Miller, turned down to 15 amps if I remember correctly. For filler rod I used a piece of .035 aluminum wire. That aluminum was a lot less than 1/16 and I preheated it.
 
Would you like to offer any pointers. I have had a few classes over the years. Every instructor I have ever had preheated their work area with the Tig torch before starting a weld and after the weld was completed waited un-till the post flow ended before leaving the weld area. I have done a fair amount of aluminum over the years, the thinnest being the coffee pot strained and the thickest was some 3/4 inch aluminum for a robot fixture, and a lot of things in between. If you have some tips or pointers you should share them with the people on this forum.
 
I know some really good TIG welders and have taken TIG at school and during my apprenticeship from some very qualified instructors. One of the welders I know does critical aircraft welding and used to be the head welder for Canadian Airlines. He got the job because his dad owned a specialty welding shop and had done some local work for Canadian Airlines. Their welder was retiring because it was too hard to TIG weld with arthritis. They flew him from Alberta to Toronto to do a weld test which he passed with flying colors, no pun intended. Even when he did the TIG test during his apprenticeship, he did one weld. It was significantly better than the instructors so they asked him to help the other students. He was a little ticked because the highest mark they would give was 75% and his weld should have easily been 100%. Yes, he was that good of a TIG welder and having your dad own the shop, he had a lot of practice.

On thicker aluminum, preheat for sure but I have never been advised, read or ever seen anyone preheat aluminum 1/4" and under. The only time I can ever see preheating thinner aluminum is if the machine you're using doesn't have enough amps for the thickness. Perhaps JonMN could comment since he's done a lot of aluminum. I would think he'd hate building aluminum trailers if he had to preheat before every weld. Aluminum heats up really fast anyways. It is common knowledge to leave the shielding gas on for a few seconds after finishing any TIG weld. That's why the better TIG machines have pre flow and post flow timers on them. Actually that was one of the questions on the journeyman welder test. Post flow keeps contaminates out of the puddle until the weld cools enough and also keeps the tungsten from getting contaminated until it cools.
 
Some aluminum wire machines will work better if the base metal is preheated. There are better machines that don't need the base metal preheated. Many years aboard ship we had a Westinghouse power unit that powered a spool gun. The super structure was all aluminum. We could take that spool gun and weld 1/4 inch material to the bulkhead without preheating anything, the welds washed in nice. The bulkheads could have been 3/8" aluminum not sure. Some of the machines I have seen today don't work like that old Westinghouse. Most of our work was Tig. On occasion we would take a Trail blazer miller with a push/pull wire attachment out in the building to weld a piece that was too big or took too much time to take down and bring into the shop. That was welded without preheating.

What I have found when Tig butt welding aluminum, even 1/8" if the aluminum is not hot enough and you are not adding filler rod a crack will start behind the weld. On fillet welds that was not a problem, you add filler rod as you go, or I do.

I have never seen anyone start an arc with a tig machine on aluminum and immediately start applying filler rod, it is always preheated some. It welds better when the aluminum is hot.
 
You always establish a puddle before adding filler metal. A lot of times on aluminum you have to weld cracks a specific way to avoid more cracks. Sometimes drilling a hole at the end of crack is required, the same as cast iron. Preheating from establishing the puddle isn't the same as preheating with a torch.
 
I've never preheated anything other than the amount of time it takes to get a puddle started with the tig. I do have to say that both my spoolgun and tig machines have more than enough power to burn right through 1/2" and thicker aluminum tho. I suppose that if you had a small machine it might work to preheat it to make up for a lack of amps and duty cycle. The thickest piece I ever worked on was an aluminum jig from a factory that was 5" thick and 5' square. I just used the spool gun to burn it in then smoothed it with the tig. Took all day to do it and was still to hot to touch the next morning when I came in to work.
 
When I start a Tig weld I do not just leave the torch in one place and establish a puddle. I take the torch and move it two to three inches up and down the weld area for a few minuted to pre-heat the base metal then I will go to the spot I want the weld to start and make a puddle, and start the weld.

This crack I mentioned was on a butt weld joint, not a crack that was in the aluminum before I received it. I still feel aluminum welds better if it is hot.
A good example is the pictures that puddles posted.
 
I highly doubt Puddles preheated any of the welds he showed. Heat travels through aluminum so fast just striking an arc preheats it. That's why they have foot pedals to control amperage. Turn it up to establish the puddle and turn it down to fill the crater. Aluminum takes a lot more amps to weld the same thickness as steel because it draws the heat away. Some aluminum is crack sensitive and you have to use a different technique to prevent cracks. It could be welding the ends first to add reinforcement, back step welding, etc.
 
It's been quite some time since I've had to pre heat any aluminum that I want to Tig weld. My Miller Dynasty 300 doesn't even start to struggle until about 3/8-inch thick material. But I really need to get into the habit of pre heating when using my spool gun! My Lincoln Invertec V350-Pro does not have run in amps. Like some of the dedicated aluminum Mig machines, say like Miller's 350P.

http://www.millerwelds.com/products/mig/product.php?model=M00151
 
I did not say puddles preheated anything. What puddles did show is the quality of a weld as the aluminum got hotter when welded with a stick electrode. Aluminum does not get magically hot all over as you start to weld.
 
"This crack I mentioned was on a b utt weld joint, not a crack that was in the aluminum before I received it. I still feel aluminum welds better if it is hot.
A good example is the pictures that puddles posted."

When you talk about preheating and the next sentence is about about Puddles example, just about everyone will think that means Puddles preheated his pieces before welding. Puddles showed an example of an excellent TIG weld and why stick welding isn't used much for aluminum. He did say for some MIG machines, aluminum would benefit from preheating so you don't have a cold start. The original topic was regarding preheating thin aluminum for TIG welding.

Actually aluminum does get hot all over when you start welding. It's not magic though, it's the properties of aluminum and why aluminum wires aren't used in houses anymore and make poor welding cables. They heat up too quickly and won't carry as much current. That's why you need more amps to weld aluminum than the same thickness of steel. Take a torch and heat one end of a piece of aluminum and do the same thing on a similar piece of steel. The aluminum will get hot a lot further away from the heat source than the steel and it won't take long. You need to do more reading and less typing before you go into long debates trying to convince yourself you understand what's going on. It's no different when you couldn't understand why thieves would sell stolen welding cable to scrap yards instead of to welders.
 
I have Tig welded a lot of aluminum in the last 30 years so I do understand how to weld it. You need more Tig time welding various setups thicknesses and aluminum is general. My first 15 years was mostly stick electrode, and steel mig, the last 30 had a lot of aluminum tig and a little aluminum mig also.

As for your welding cables topic in one sentence you said used welding cables sell for a little less than new cables, in your next sentence you said thieves sell their stolen cables for scrap price instead of getting the higher almost new price. Some of the things you say doesn't make sense. Maybe things are done differently in Canada.

In another topic on this forum you said I was almost right in what I posted, You posted the exact same thing I said only worded differently which you said was the correct procedure. Your phrase came right out of the text book. but it said the exact same thing I said. You need a little help in understanding things. Maybe that's why you are in a welding supply store instead of in the field.
Have a great day stick, You will always be right.
 
How things are worded can make a big difference. I don't make sense? As far as the welding cables thread, you couldn't seem to comprehend that thieves are looking for quick, easy money with no questions asked. Copper brings good easy money. I'm not the only one that tried to explain that to you. Running the TIG torch over thin aluminum to preheat it before welding makes no sense.

Maybe I work in welding supplies because the company wanted someone with a welding background to help the customers? I don't have any textbooks with me. I do have several welding tickets and years of experience though. If you've been welding for 45 years, what tickets have you acquired?
 
Certified on vertical up and overhead stick electrode within the last 4 months or so 3/8" plate. Certified vertical up Tig stainless steel 3/8" plate within last 4 months. Have certified before but those are the current ones.
 
TIG stainless on 3/8" plate seems like an awfully big weld for TIG? TIG is usually tested on pipe up here. Do you have to renew tickets every 2 years to keep your certification? Up here your Journeyman/Red seal ticket is good forever but pressure tickets and structural tickets need to be renewed every 2 years. A lot of the re-certifying and testing is just s cash cow. It cost's about a $100 per position for each process. Sometimes you can do one test that covers all positions for your retest. For the pressure ticket retest, most welders do a 2" double extra heavy in the 6G position because it qualifies 3 different tickets. Small bore, heavy wall and all position.
 

From what I've read over the years on all these welding forums, it sure seems to me Alberta has some of the most stringent weld testing in the world!
The one tank shop I worked in, we had to retest every three months. But that was a NRC rule, because we built nuclear waste tanks that were to carry contaminated clothing and tools from the Hanford Nuclear Reservation in Eastern Washington to a burial site in South Carolina.
 
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