Alu welding? (Sort of OT, sorry)

[Axle]

I went out throwing today and broke another ( ) one of my javelins, but I really liked this one. This particular jav (like most every one I've seen) is alu, maybe an 1.25 inches round, hollow, with a wall thickness of 2-4mm or so. It's a pretty clean break, right above this tip, and I was wondering if anyone thinks it's possible to fix by welding/soldering/anything else you WB-stick-together-masters can think of? Can you even weld alu?

It's got to be pretty sturdy, though, I toss this thing 150-165ft (I know I suck) so it gets a beating. Also, how much does weld weight? It's pretty percision balanced (4lbs), so it can't go weighing an extra .5lb up front, I'll end up dead

Thoughts, anyone?

Thanks & sorry for OT, but y'all are the most knowledgeable metal working people I know

[Joe]

I would recomend taking it to a machine shop near by. Also check hobby shops to see if they know of anyone who does custom Aluminum TIG work. (TIG welding is how you weld Aluminum.. the machines are highly expensive, and to weld TIG is more an Art than a science.)

I have seen many people do TIG work for hobby R/C stuff that is just perfect.

[LiquidRulez]

I agree with Joe.

It takes alot of practice to master Tig welding ALum.
welding AL is an art form IMO.......Not for the novice...

And the weld is usually stronger than the original bond anyway.

LR

[bigben2k]

Dido.

You need a certain amount of experience to weld aluminium: it's easy to weld it poorly, but it's hard to weld it right.

[8-Ball]

Is there any way you could find out the composition of the alloy. If not, the series would suffice.

Certain series can't be easily welded and would become brittle.

Get any information you can and I'll get back to you on it.

I should know now actually, but I haven't revised my "advanced engineering alloys" option yet.

That said, a competent TIG welder with experience should also know this information.

8-ball

[Axly]

i agree with previous speakers.. you would be very disappointed when a large piece of your alu-pieces suddenly go "plop" and melt to a puddle.

[bigben2k]

What you're looking for is a relatively easy stubweld: check out bike shops, if there are any in your area. In fact, look up welding in your yellows.

[8-Ball]

Again, you need to be careful. Aluminium alloys used in bikes are chosen largely because they are weldable. Many Al alloys aren't.

A large number of Aluminium alloys gain there strength from precipitation hardening. These alloys are aged to give optimum precipitation size and distribution. Heating can lead to coarsening of the microstructure, where a small number of precipitates will grow at the expense of others leading to a fewer number of large precipitates. These ppts are characterised by incoherent interfaces with the matrix so now, rather than strengthening and toughening the alloy by there interaction with dislocations, the precipitates will embrittle the material, with the high energy incoherent interfaces acting as favourable crack nucleation and propagation sites.

It is this low ceiling to the operating temperature of these common alloys which lead to the development, at great expense, of 7000 series alloys for the aviation industry.

It just so happened that these and other similar alloys were ideal for bikes. However, for the majority of applications, it is not necessary to use an alloy which can be welded, if it doesn't need to be welded.

It is for this reason that I asked if axle happened to know which specific alloy the javelin was made from, so I could check it in my notes.

This is what I have been studying as my degree for the last three years.

8-ball

[crane]

I have a jar of aluminum brazing flux made by American Chemical and Flux Products. Says here it is for brazing and welding all aluminum alloys. You mix the powder flux with h2o to make a paste, apply to the weld joint . The liquid stage acts as a temperature indicator at which stage the brazing alloy should be added.

Does it work? well..... I've had limited succsess with smaller parts brazing together ok. Larger parts need alot of heat and that is out of my capabilities at home here. What is neat about the stuff is you can use it to solder Aluminum and copper together... its pretty neat watching a piece of AL tin up and solder just like copper.
I have more than I can ever use if you or anyone want a sample to play with.

[8-Ball]

After looking through some of my notes, it turns out that it is some of the 2000 and 7000 series alloys which can suffer from welding.

If this is the alloy used, then I would consider not welding as it would be significantly weaker at the joint.

Most other alloys should be ok.

I hope this helps.

8-ball

[chewyboy]

welding al isn't exactly the easiest thing to do in the world but if you get someone that is good at it, the final result should look like the edge of a roll of coins. good luck with it.

[Axle]

Helps very much indeed, thank you all!!

I don't know, though, this TIG stuff sounds pretty expensive. I'll ask the few places I know weld around here and see what they can do... I know some people over at the career institue which happens to teach welding, so I'll check that out too. The jav itself is from the 70s, and I got it for free, so I don't know how much it'd be worth to fix. I mean I don't like it $50 much , but I'm going to ask around on tuesday (Happy Easter tomorrow, ey )

I don't happen to know what it's made out of, sorry, all the lables wore off quite a long time ago, but I can tell you it doesn't rub off on my hands (like my 6061 Easton stick), if that helps?. As for doing it myself... eeee.... I don't know; I'm pretty stupid when it comes to all things "art".

Thanks again, though, everyone I didn't think it could be fixed, but now I'm defiently going to check it out

[bigben2k]

Do let us know how it turns out!

[mrmoustache]

aluminum can also be mig welded.

[myv65]

Originally posted by bigben2k
What you're looking for is a relatively easy stubweld

Spoken as only one that's never attempted to weld something this thin before could do. Most welds in stuff this thin, including bike frames, use socket welds. That's a whole lot different than trying to butt weld something 2-4mm thick.

Your chances of getting back the "original feel" are virtually nil. When welding stuff this thin, it's darn near impossible to achieve the original strength. It's just too easy to burn through, and without proper penetration, the strength will suffer. Generally speaking, a backing ring is used for welding thin pipe sections. While the weight would be minor, it would also be at about the farthest point it could be from the center of gravity. Minor, but enough to change the natural trajectory. Sure, you could weight the opposite end with a couple of ounces to compensate, but then you're upping the overall weight even more.

As 8-ball has also indicated, material properties are dictated by both composition and rate of cooling. Even if you could get a decent weld, ambient air cooling may or may not be what you want.

You've nothing to lose by trying (unless it costs you $$$), but I would not get my hopes up too high.

[bigben2k]

True. We use stubwelds in our oil drilling equipment, and it seems to work well, but it may simply be an operational requirement, as the diameter must remain the same.

The hardest part, I suspect, is lining up the two pieces perfectly, and would have to include cutting an angle into the edges to be joined, for the welding to take place.

I don't believe that it would be impossible on Alu 2 to 4 mm thick, but I've never done it, nor seen it done. I can however imagine that the process would be exactly the same, but would require a much smaller feed wire.

I don't believe that a socket weld would be desirable here.:shrug:

[Joe]

Originally posted by mrmoustache
aluminum can also be mig welded.

Yeh thats theory more than practice... no professional shop does MIG aluminum welding. Robots will use MIG welding for automotive aluminum etc... but no one who wants it done right by hand will use MIG.

TIG is the only weld that is able to be trusted and clean ( not alot of excess metal) for Aluminum.

[Arcturius]

As was mentioned above, brazing may be the best way to approach this, if the thickness of the wall is near the 2mm figure (or less), and depending on the price quotes you get for TIG welding.

If the 4mm figure is more accurate, and the alloy is correct, then TIG welding should be a quite reasonable proposition--for someone experienced.
I have done TIG welding before, and while I would not call it an art form, it is certainly more difficult than welding any other material you are likely to work with. It was difficult for me to tell when the Al was getting hot, as it really doesn't change color the way steel does, and would just 'puddle up' all of a sudden, like solder.

I never got to MIG weld Al, since the wirefeed welder at (high) school was setup for welding steel, and I've never really had the incentive to hunt down another one to play with.

Brazing on the other hand, is pretty darned easy, is possible on basically any metal (as far as I know), moderately strong, and will add little weight to your javelin. Plus, you can do it with a few dollars worth of materials, and a cheap torch.

[jaydee]

I been a certified welder for 8 years and was taught in the field by people who used to weld Subs. We mainly use mig and stick but have the equipment to do tig. I would say don't bother. Something made to precision like that will never come out the same. The heat will warp it, it would have to be precision ground inside and out. It would never be the same and would probably just re-break around the welds after a few throws.

Cut your losses and find a new one.

[hydrogen18]

im no expert on alu welding other than the row of coins thing, but brazing is darn near impossible. I've spent a good amount of time with my mapp torch and alu brazing rod and have only ever achieved one good solid joint. I've been working with thin material most of the time(mainly alu angle from the hardware store) and what usually happens is that i dont get it hot enough and it doesnt bond, or it get waay too hot and begans to melt which means the end joint is annealed and very weak, or sometimes it will just fall to the floor and form a ball of alu. Brazing steel with bronze rod is very easy and very strong i must say though.

[mrmoustache]

Originally posted by Joe
TIG is the only weld that is able to be trusted and clean ( not alot of excess metal) for Aluminum.

seemed to me like he was gonna need to grind a bunch of excess off anyway.

[Axle]

I talked to the welding guy today... he took a look at it and said what JayDee did- even if he were to do it perfectly it would soon break again. Oh well, nothing (more) lost

Thanks to everyone for the advice- even if it didn't work out at least I'm a little more schooled now

[JFettig]

has anyone here tried to weld aluminum? I have mig welded aluminum, Its kinda weird stuff. I was doing really good on one kind of wire and we ran out, stuck a diff kind on and it sucked.... I was making some nice beads. Its really hard and something that needs to be mastered if you really wanna do that....
the reason its soo hard,(most of you should know) is because the heat spreads out so fast. itll melt a large portion of the metal if your not careful.

[Joe]

Also an issue is that you cant tell how hot the metal is. Aluminum doesnt change color when its at melting temp... so you could be welding all happy. the ploop... its a puddle.

Also it sucks if you go to grab a peice and accidentally grab one you were just welding on ( did that a few times in classes I took for TIG welding hehehe), yeh 1000 Deg aluminum plate sucks to grab

[ChrioN]

http://www.technoweld.co.uk

works lika sharm