Welding aluminum tubing

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Hello list members,I have a general question about welding aluminum tubing.  I am going tomorrow to fit and weld 4 air conditioning tubes that are installed on a high end car.  I have never seen anything like this one.  The tubes run from the trunk of the car to the engine compartment.  They were damaged as they run under the car as well and apparently the driver ran over something that squished the lines so they have to be replaced.The factory replacements are divided into two sections which are welded in the middle roughly.  The body shop will install the tubes and I will cut, fit and weld them.  They are about  1/2"  and 3/8" tubes, a pair of each.  They are about a 14 gauge wall thickness.Question:  can I just butt the ends together or do I need to allow some shrinkage room, say a 1/16" gap or more?   Any thoughts on this?As a rule of thumb I have always butted tubing together and on pipe, beveled them.  Thanks for your thought,Tony
Reply:I don't think you will have that much shrinkage. I think I would just butt it maybe with a small bevel on the tube, and use 5356 for the filler for strength of the weld. A couple of passes I think would be plenty. If you gap it and penetrate too much weld into the diameter of the tube, you might cut off the flow.Is the mechanic going to pressure test with nitrogen to check for leaks?Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Hi Shovelon,thanks for your feedback.  I proposed to the mechanic that we plug one end and just pressurize  the tubes one at a time with compressed air and a tapered rubber nozzle air gun using soapy water on the welded joints.  That's what I have always used as a general leak test tool.What is the procedure using nitrogen and is it more effective?Thanks,TonyLast edited by therrera; 09-25-2011 at 02:11 PM.Reason: to add more info
Reply:Originally Posted by therreraHi Shovelon,thanks for your feedback.  I proposed to the mechanic that we plug one end and just pressurize  the tubes one at a time with compressed air and a tapered rubber nozzle air gun using soapy water on the welded joints.  That's what I have always used as a general leak test tool.What is the procedure using nitrogen and is it more effective?Thanks,Tony
Reply:Hi Dave,that was some good info to work into the job.  I like the sleeve approach a thousand times better than a welded but joint and will see if I can find some tubing laying around their shop that will do the trick.  I have done about a dozen or so AC line repairs, so far so good.I have found that there is a high demand for aluminum welding here in my neck of the woods but I suspect that is a universal situation.  So I have found myself getting more and more into it to the point where most of my work is aluminum based.Avoiding the crater will be tricky as my field welder does not have a variable control.  It is only a torch mounted on-off switch.  What I do when I end my bead is to quickly move to the side of the puddle and back away from where I finished the bead and quickly remove my torch while going in a circular motion, then cutting the arc.  This reduces the crater effect.I and to upgrade my welder to a multi-function job so I can stick-tig and mig with the same machine, including a variable torch switch.Thanks,Tony
Reply:I know this is a welding forum.... and you want to practice your welding, etc..but as a Mechanic I  would never consider just butt connecting something like that subject to vibration and heating /cooling cycles...  I would be looking for a sleeve to fit over it for several inches on both sides of the joint and either solder, braze or epoxy it together..whichever was the best for the materials being used.... Particularly since you do not have the fancy controls some of these guys do on their tigs....Even if you wanted to tig it for the practice... you could sleeve and epoxy that joint afterwards to make sure it never leaked...Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:Hello BGM,Actually, this is not practice.  This is the real deal.  However, not having had to deal with this situation before I make it a habit to consult with my peers on projects where I have little or no experience.I had not considered sleeving these joints.  After hearing that suggestion from Dave the first time, there is no question that is the way to go.  Hearing that you also propose that is the correct way to do it, that just adds icing to the cake.As a practicing welder there are few jobs that I will walk away from (even if I've never done them before) because I have a lot of self confidence in my skill and I through this forum I have access to experience beyond mine.  The ones I walk away from are those that are evident should not be welded or because I am not equipped technically to do them (need a crane, large oven, etc.).Finally, I have butt welded heater tubing for cars and trucks many times without issues.  Granted those are steel but a well made joint and weld should be as solid as the tube itself.  They too are subject to vibration and heating and cooling cycles.  Having said that, I acknowledge that a sleeve is a better design and easier to weld to boot.Thanks for your advice and I'll report and take pictures tomorrow.TonyLast edited by therrera; 09-25-2011 at 06:59 PM.Reason: to add more ingo
Reply:Tony,    I skimmed the rest of the post and missed Dave mentioning the sleeve..but I am not questioning your welding.... I think we have established that welding heat almost always changes the original  nature of the material at the weld... and we seldom have any way to reintroduce either the hardening or tempering to restore it to original... thus I always consider it compromised and adding a sleeve or other support or doubling up on the sealing , where available,  just seems prudent in terms of reputation or the work needed to take something back apart... and in AC work NO leaks are acceptable...except the one built into auto air conditioner compressors to keep the front seal lubed...  By ' practice' I was referring to the fact that welders like to weld... not that it was not a serious project...Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:Originally Posted by therreraHi Shovelon,thanks for your feedback.  I proposed to the mechanic that we plug one end and just pressurize  the tubes one at a time with compressed air and a tapered rubber nozzle air gun using soapy water on the welded joints.  That's what I have always used as a general leak test tool.What is the procedure using nitrogen and is it more effective?Thanks,Tony
Reply:Originally Posted by shovelon..... And bendable refrigerant tube is 6063, so temper is not in question.......
Reply:Originally Posted by GBMThese types of declarations always catch my eye...is this 1. By Law ?2. Apply to ANY age car ?3. Apply to a car of any country of origin ? He only said ' hi end car'..4. Your example started out ' commercial and residential ' techs... does this mean that all automotive AND all home and commercial bendable tube is 6063 ?5.How would one Test to see if that were the case for the AC one was working on ?  In case some mechanic over the years did not know that was the ' required' tubing ?What would be the risk of failure if one was wrong on the type of tubing  vs. the cost of a sleeve or backup procedure ?
Reply:Okay people,here is my report with some pictures.  I ran into the exact problem that I was cautioned about when breaking the arc, pinhole (dimple).  I  had to weld four tubes and only got to two before I had to bow out of the job and am going to try and locate a local welder who is equipped to field weld aluminum tubing.My beads came out reasonably well formed, good penetration, etc.  Because I lacked a variable remote to lower the amperage as I broke the arc, I left dimples at each arc break.  This was Okay while I was bringing my bead around the tubing because i simply blended the dimple into the bead as I added more metal, filling the joint, but at the final pass when I had to meet my starting point that dimple proved persistent.With a lot of finagling I was able to break my arc and not leave a pinhole but it was hit and miss.  We pressure tested one tube  after I touched it up when a leak was detected, but the second one,  I found myself chasing a leak around the tube.  That's when I proposed I stop.  I was somewhat embarrassed in all honesty.I have welded such tubing before, but always on my bench and my home shop welder has a foot pedal so it posed no problem.  My field machine is another issue and I think I just ran into it's limitation, finally.  I also found out a few weeks ago that my gas drive does not have the amperage needed to weld on an aluminum car hauler built with 1/4" plate (even preheating it with a torch).  It barely was able to produce a puddle.  I had to have the customer come to my shop so I could put my 300 amp machine on it.  My gas drive is a 200 amp Miller AEAD200LE.  Pre Bobcat technology.I used 1/16" tungsten  on the AC tubing and the welding itself went very smooth.So after I post this I am going to make some calls to welders in my are to see if anyone is equipped to handle a delicate job like this.  I think welding thin wall tubes (especially aluminum) is probably the most difficult type of welding I have encountered.   I don't think there are many welders out there who would want to take on this job, but I'll find out soon enough.I am thinking of teaching myself to gas weld aluminum and wonder it that approach would eliminate this problem?I made an alignment jig from a little angle iron I cut form a corner of some 2" square tubing and used it with some vice grips to align the tubing while I tacked a started the bead.  Once I had half of it welded I removed it and started on the opposite half.Thanks for your advice and help.  I am bracing myself for the flames.TonyPS: I was not able to locate some tubing to sleeve it with as I had hoped.  The client wanted to "just get it welded" so I proceeded just butting them together.  Before actually welding it I tried calling the factory to see what the recommended procedure was but they wouldn't give me the time of day because I was not a dealer's service center.  The car is a 2011 GM Arcadia.  Maybe this type of job is a sleeve and epoxy situation.  What do you think? Attached ImagesLast edited by therrera; 09-26-2011 at 10:08 PM.Reason: To add more info
Reply:LOL, Welcome to my world.  Mechanicing...Every project I get into has most of these elements.... Like so many people have described refusing to work on some trailers where the owner was trying to dictate an unsafe method.... letting the owner determine how you fix it places your reputation in jeopardy..... if it leaks in months or even years he will complain about your work and never tell anyone that he dictated the incorrect procedure...  When doing a sleeve and epoxy you do not have to have the same material for the sleeve as the tube... anything strong to keep the epoxy in place and spread the incredible strength of the epoxy across several square inches....   Starting out trying to do one of the hardest welding feats .... without all the bells and whistles one might need..... don't feel bad that it went south quickly.....Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:GM Acadia highend? I was thinking this was a custom built rod or something. Is this GM heavily modded or something? Kudos to you for both trying and stopping when your equipment met its match.
Reply:Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:Originally Posted by therreraI have found that there is a high demand for aluminum welding here in my neck of the woods but I suspect that is a universal situation.  So I have found myself getting more and more into it to the point where most of my work is aluminum based.
Reply:I will have to dmit that I did not read the whole text of all of the solutions given, just want to chime in on a little of what i know On high presure units such as transport refigeration like thermo king, we use to silver soder those lines, but you do have to be good at it.  And because I went in to management I have not done alot in many years, but in the last shop I was running just a short time ago, we had a frtliner with an aluminum line like what you are talking about.  Due to use not being able to get the line from frtliner and the truck needing to roll, I took the complete line to a shop, like a hoseman.  Not sure if you have one down there in Yuma, but it could be called hoseman or something else.  When I took it in they silver sodered it up and away I went.  Now if that wont work and as I said I did not read the entire post but, a section of ruber a/c hose can be crimped in to the area that needs the work done unless the owner does not want it that way.  Dont if I have helped but tig is not the only way to go with this, you just need to find some one that is good with a torch to braze them together. Ron
Reply:Originally Posted by GBM.... either solder, braze or epoxy it together..whichever was the best for the materials being used....
Reply:I wasnt sure I made any sense after I got done, but at least 1 person knew what I was getting at thanks.Ron
Reply:If this site were called ' WeldingSolderingBrazingRivetingEpoxing.com'  it would be easier to suggest some of these other solutions... but Welding comes to mind first and knowing some of these people can do a particular type of repair on something encourages people to try it themselves...which is great at a certain level... but if reputation or safety are on the line not so much..... not taking some metals to their melting point.... and particularly not in a straight line connection...often has a lot of advantages...Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:I know this a a welding site but there is a kit available from doorman the makes compression fitting for a/c line repairs.  We use ours all the time. When you pressurize the lines make sure you get at lease 200 psi in the system. Because of the properties of refrigerant the static pressures can go from a vacume to 300+ lbs.  Dependent on temperature.Miller Thunderbolt AC/DCMillermatic 211 and spoolmatePower Plasma 50Syncrowave 180 SDMike
Reply:Thanks Mike...can you point us to the  one you are referring to ?   Does it require any special tools to install ?   Like an internal bead roller ?Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:Also could have flared the ends and installed a threaded coupler joint.Chopnhack: when I read high end I also was not thinking a chevy.
Reply:Hi all,well thanks for all the suggestions and alternate approaches to this situation.  Using hind sight, if I was faced with this repair again, I would not choose to weld it even if I had a welder capable of delicate work.The design of the parts almost screamed using a sleeve and approach other than welding.  From a production standpoint, welding these are very time consuming whereas the other options from epoxying them to using compression fittings would take a fraction of the time therefore more cost effective for both the repair shop and the client.  I even went as far as to purchase a pound of 5356 1/16" tig rod for this job.  Well..I needed to have some on hand anyway.I think that my mind gets stuck in "welding" only approach to things when a bolt or rivet might suffice.The idea of renting a machine is a good one.  I will keep that one in mind for the reasons stated if faced with this type of situation again.  I will plan on how to upgrade my equipment so that jobs don't slip through my fingers for lack of the right hardware.My old gas drive Miller is well suited for general purpose welding and with the high frequency box of doing aluminum of a more coarse nature.  I routinely repair rims, engine blocks,  parts and tranny cases with it and it does just fine.I definitely want to learn how to weld aluminum with a torch and have recently been called on to weld aluminum body panels by a local body shop.  The old miller set to it's lowest setting and on idle can tackle those like a champ.  I was surprised when I first attempted it.I read that aluminum body panes are best done with a torch and not a TIG, so I would like to give it a try and see for myself.  It has to do with the fact that the torch will anneal the metal whereas the TIG will leave it hard, brittle.I think you are right that I have stumbled onto a niche market with the aluminum and want to explore all aspects of working with it.  I suggest that others explore this niche if you have aluminum (especially mobile) capability as it may prove a source of income that is not being tapped.  I have had people come to me as far as an hour and a half away to bring me their aluminum repairs.  The focus is on repair not the fabrication end of it where I think the more traditional shops are better setup for that.  The body shop that calls me in for their aluminum work told me that they will be calling me more as aluminum is being used more widely in the auto industry.Those of you who are hurting for work due to the downturn in things should really consider marketing themselves in this area.  Put a few craiglist ads out there saying that you can weld aluminum and you might be surprised at the results.  While I am still struggling as our economy here in Arizona has been totally hosed (housing and construction was a mainstay of our economy here), aluminum has rescued me from total oblivion.  I can at least pay our bills and feed us even if barely.Thanks again and you're right,  I got a kick out of  the "A man has to know his limitations" video.  That was good!!Finally, on the "high end" thing.....When I went to see the job last Saturday I only glanced at the car as it was already in the air and I thought it had a Mercedes logo on it.  So I labeled it "high end" in my mind and reported it as such.  I didn't notice what it was until I wanted to call the factory to find out the recommended repair procedure and had to get the model and year.  Oh well.....my bad.TonyLast edited by therrera; 09-27-2011 at 09:38 PM.Reason: To add some more info, clarity
Reply:Well Tony, I am not going to worry about you.  People who are able and willing to look at other suggestions and evaluate them on the merits...as compared to seeing them as an assault on their ideas... are not going to have the kinds of problems most people have... I know you are going to do well at whatever you attempt. GregWeldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.Tony, GM doesn't have a replacement pipe for this with some kind of compression fittings or connectors as was mentioned before? Just seems odd they would be welded from the factory as a hard line with no other points of removal. Torch welding is something I've also looked at getting into...but people still think it is wizardry and as such the places I've found that sell the flux and rods to do it with charge an arm and a leg.
Reply:I wonder if you could have swedged the joint, the welded it?
Reply:Hello people,Swedged the joint and then welded it?  If I understand it, do you mean opening up one of the tubes so that the other fits into it?  If so, I think that would have worked as well, kind of like a compromise between a sleeve and a straight butt joint.  However it still wouldn't solve the issue I faced of not having total control over my heat so I could gracefully break the arc and avoid a pinhole.I also asked the question to the repair shop guy whether they provided any instructions for the joining of the tubes?  He said no and that even the parts guys who ordered the damn thing didn't know how it was supposed to go together.  The repair guy said that it was sold to him with a "good luck" attitude.Maybe GM and the dealerships have a "don't tell" policy.  My gut feeling is that this part does have an accompanying kit of fittings and probably an instruction manual somewhere in their repair books.  Logic tells me that it is highly unlikely that they expect their dealerships to have highly skilled welders on their staff to weld these tubes together.  It is more probable that the parts guy just sold the repair shop the parts but conveniently failed to mention that there was an "installation kit" for the part.When I talked to the repair guy yesterday at the end of the day he said that they might end up taking it to the dealer themselves and take the hit with the cost as they couldn't find anyone else that would or could finish the welding.  Fancy that?  I told him I thought he should just cut out my weld and sleeve the tubes together using epoxy but I think he was desperate and just wanted to "get it over with" so I don't think he took me seriously.After hearing the suggestions on this thread it becomes more obvious to me that these parts were NOT designed to be welded together.   Furthermore, I will have a more open approach to a repair from now on.  I thought I was pretty open and have at times advised clients against welding something, but I see that I still hang on to welding as the only solution thinking.  This one as a case in point.It was a good experience though and although I lost several hours on site with no pay, it was a good lesson both technically and in terms of keeping an open mind.Thanks all,TonyPS: the original lines were one piece with no breaks front the rear.  It's the replacement that was split into front and back sections that had to be joined in the middle.Last edited by therrera; 09-28-2011 at 01:21 AM.Reason: too add information
Reply:Tony, I would think that opening one end and shoving the other end would not be good as it would disrupt the smooth inner bore. A compression type coupler fitting over the outside allows the smooth inner bore to be retained.When I used to work in the semiconductor industry, i would see the union plumbers use an orbital welder on small diameter stainless tubing. I don't know why that same approach wouldn't work in this scenario, except the cost of the machine. And yes, the orbital head was on a tether to the main power supply and controls so it could be used in a mobile situation like you had there. The one thy used was made by Arc Machines. It stored programs for many different weld procedures depending on tubing diameter and wall thickness.Company video brochure here.. Just thinking out loud...PapaLast edited by papaharley03; 09-28-2011 at 01:39 AM.Lincoln Idealarc 250 (circa 1962)Lincoln Weldpak 155 w/Mig KitLincoln Squarewave TIG 175
Reply:Those are very cool but not so much cheap. I'd love to have one!
Reply:I've seen those orbital welders in photos and now on video.    I don't know if they can do aluminum or not and I suppose if so, they could be employed in this type of scenario.  However the fact still remains that these joints can be joined for one thousandth the expense by just getting some compression fittings and joining the tubes the old fashioned way, mechanically.Nice video though.Tony
Reply:Tony,Just a couple comments/suggestions.If you plan to do pipe/tubing you need to make yourself up a better jig.  I used a piece of 1" angle and tack welded it to a length of 1/4"x 1 1/2" barstock.  I then took the porta-band and cut out a 3/4" notch in the angle.  That way I can clamp the fixture to the tubing and weld all the way around with only moving the fixture once.  The notch in the angle keeps the bead from interfering with the fixture.I don't think you "explored all options" before you undertook this job or walked away from it.  Any decent machine shop could easily make the sleeves you needed from aluminum round bar stock.  Drill the center to the tubing OD.  Turn the exterior down to desired thickness.  Sleeve.  Silver solder in place.  Easy.  I wouldn't trust a butt joint in this application.You mention aluminum repairs.  I agree.  It's a lot of what I do, especially in the marine field.  However, trying to do "proper" aluminum repairs with inferior equipment will hurt your reputation in the long run, no matter how "skilled" you think you are.I've got some pretty decent equipment for "mobile tig repairs" and I've worked with aluminum for quite awhile but I would have never tried to simply butt weld that tubing.Going to GM for a solution probably wasn't the best bet.  However, I'm betting that (and several posters have made reference recommendations) there are compression fittings designed specifically for this purpose.  GM (as with all manufacturers) designs their vehicles for ease of assembly not ease of repair.  When I had to replace the transmission on my GMC Envoy, I had to cut out a section of the exhaust pipe to drop the transmission.  Dealer would have probably just sleeved it and clamped it and called it good.  I sleeved it and then welded it.  No room for a mig gun, but it's amazing sometimes the places you can get with a 20 series torch and a button backcap (and a mirror).Solutions to problems are not always to get a bigger hammer.  Sometimes it just means you need a "different" hammer.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:sweging would have worked it is like sweating copper which is or was used for high pressure refer units but again it takes familiarity with the process, just a different hammer as mentioned.
Reply:Originally Posted by Ron Padillasweging would have worked it is like sweating copper which is or was used for high pressure refer units but again it takes familiarity with the process, just a different hammer as mentioned.