Any experienced gas welders know if all types of aluminum can be gas welded? Have some 16 gauge scrap I've been trying to practice on but cant get the metal to flow, not even to tack the corners, can see the pieces come to temp but then surface just goes a dull grey and becomes mushy, kind of looks like slag on the top of a smelter when melting aluminum. Using a oxy/acet, cobra torch, tip size 00, have cobalt lenses, have tried neutral flame, oxidizing and carbonizing, all with same results. Have cleaned with stainless brush, 240 sand paper and acetone, looks just the same as uncleaned. No flux, cant even get to the point of using filler rod. Only thought I have left is that some there are types of alloy that cant be gas welded?
Aluminum is a fairly reactive metal, and can't be welded unless you use some sort of flux or an inert gas envelope i.e. mig or tig welding.
Ah well, here I go....(I did actually weld for a living onct upon a time) It's not for the faint of heart or easily frustrated person. Proper flux & rod, slightly non-carburizing tip(reducing), preheat (lots of preheat on big tin), steady hand, and sorcerer eyes and its a dream. Aluminum is so porous - dirty old aluminum is nigh on impossible because the contaminants get so deep in the metal. Are you against watching a video?
We were taught to gas welded aluminium sheet years ago with filler rod when I was at college learning my trade. Using a carburising flame a layer of soot was generated over where we were welding and when the soot burnt off, the aluminium was ready to gas weld. You had to be quick and careful in case you panel collapsed right before your eyes. We fabricated a door frame and then wheeled up an alloy skin that was folded over the frame and filed up. The instructor then cut the skin with a chisel and we had to weld it back together and file and planish the repair. Don't ask me to do it now as I can't remember that far back or the technique other than that!
I just went through t his ordeal. Like C. John said, the right flux, proper cleaning, slightly carburizing flame. And no, not all alloys are weld-able. Some are weld-able, but you can't hammer and dolly afterwards.
90 or 100 years ago aluminium was O/A welded by stirring the puddle with a metal rod, mixing the metal from the pieces being welded and the filler metal - the oxide "skin" on aluminium prevents them to flow together on their own. Ofcourse the oxides are still there, mixed into the weld causing weak spots. Since then fluxes that dissolve the very tough aluminium oxides has been invented, and if you want to have any kind of weld quality, you HAVE to use them.
I have seen a jewelers torch used with flux and rod on thin sheet aluminum to join body panels, took a lot of practice but looked pretty good .
I don't think 2024 can be welded. If you ever get a chance to see a stock P-51 wing tip that hasn't been all filled over to make it look pretty , take a look at the weld bead joining the top and bottom halves together. Amazing work they did during WW2
On the P51 work: I remember reading that a lot of the people who did that sort of work went blind. You need very specific eyewear to filter out the harmful rays that – I think – are actually a product of the flux. (?)
as a general rule, gas welded joints can be hammered and dollied, this is the chief reason to use gas over tig. 3003-h14 and 6061-t6 would be a yes, 6061 T4 you may have trouble with it cracking.
As has been written already flux is a must. I gas welded aluminum in high school, originally to pass a welding course then later on irrigation equipment in the field. We used a flux coated rod that was originally meant for stick welding but it worked really well with a torch. Clean is an absolute must, I used to keep a stainless steel brush that the Ag teacher gave me that never got used on anything but aluminum and some acid flux for soldering copper (a liquid)that I would wipe it with if it was really dirty. That worked for me. @falcongeorge I was not aware of the cobalt lenses I used to use those tigging. But we are talking nearly 50 years ago now and perhaps we didn't know any better. Well that and I never did it day in and day out it was just something else to help me support my self when I was in high school.
Thanks for the replies, I think g-son hit on the problem. I've gas welded thicker aluminum before with no problems, was trying my luck on thinner stuff. I've watched a ton of videos and it's about half and half of those who Flux only the filler rod and those who Flux the pieces being welded and the filler rod. So I got new stainless brushes and getting some thinner filler rod and will give it a go fluxing the filler and the pieces being welded
Something else I will mention here, I posted in @Pat's album about the race car nose he built, he mentioned that he used tig with an 1100 rod and it planished nicely, but I havent tried this myself. Benno mentioned cleanliness, this is critical. The guy that taught me also told me that when you are making something from scratch, rather than using rod, cut a thin strip of the parent material and use that.
OP, do yourself a favour, instead of practicing on mystery material, pony up and get your hands on some 3003, its the right alloy for this sort of deal, and depending on what you have there, will probably make your life easier. You really need to start off with all the odds stacked in your favour if you want to learn this skill, its not real easy. Also, line pressure should be a bit lower than for the same thickness of steel, and the flame should be neutral or slightly cooler. A slight oxidizing flame is real bad news on aluminum, it will cause poor fusion, and the weld is junk. Gas welding aluminum is persnickity stuff. Really good, two stage regs that are stable at low pressures are a really big help, but thats pretty much the case on thin sheet steel as well.
I just noticed you are trying to do this without the proper flux. I dont like to use the word "impossible", but...
It's much more like mixing mashed potatoes than moving a puddle and sweating the metals together. It can be a very beautiful weld
I was in a corn field with an old guy when I was in high school, we were patching up a Wade rain maker that had been mildly abused. I was welding up the cracked water line and he was reattaching the cast end to the tube. He walked over when I was done and looked and said, "I think you're getting the hang of it kid." Then I walked over and looked at his stack of dimes and knew that the hang of it only meant that I managed to make a repair. Welding is 10% knowledge and 90% practice.
When I worked at Bellflower Auto Center I watched Eddie Potter gas weld the bellypan for one of Ray's new chassis (might have been Butters & Gerard) - he cut a thin strip of the material off and used that as filler - don't know what alloy the material was but I'd guess 3003 or 5052. I've tried it, and even with the Tinman lens and flux, and really clean material it's not too easy. I was using a small aircraft torch, and remember that the angle I held it relative to the surface made a lot of difference as to the outcome.
Using the same base material to get filler strips from lets you get the weld finished and polished with no ghosts of alloy discrepancy in the weld. Kinda funny but that is either not important at all or it is the most important thing.
If the welded area it to get paint down the road cleaning every bit of flux off it is a must. Flux bleed isn't something you want to ever see on a painted car. Bob
None of the advice in this thread so far is worth the time it takes to read it all. This piece of advice is especially bad as it has been proven that the use of cobalt blue welding lenses contributes to getting cataracts later in life.
I helped a fabricator from Shelby-American when he did the aluminum panels and grille insert in the Henry-J we raced in the '60's. He used 3003-H14 .050 and always had me get thin strips sheared from the 3003 to use for rod and always used flux on the rod. Incredibly beautiful welds.
The Jalopy Journal
