Some welding questions

Discussion in 'Workshop Tips and Secrets / Tools' started by Deadly Precision, Aug 22, 2012.

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  1. Aug 26, 2012 #21

    PTAirco

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    I have yet to manage a weld in aluminium, but it's on my list of stuff to learn. I went to a forum at Oshkosh and watched a guy gas weld the stuff, but he recommended using hydrogen.

    The Henrob guy is an artist. For most welding, I doubt if the torch is that much superieo but I had mine for over 20 years and I am so used to it, I don't want to change. It is damned heavy though but after constant use you just adapt.
     
  2. Aug 29, 2012 #22

    jmt1991

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    Steveair,
    I have had a Henrob torch for about 14 years now and really like it. I do need to get the lightweight hoses that Tinman sells, because the regular hoses are heavy and tend to tug on the torch while you're welding. I've only used it to weld steel, but I'm sure you won't be disappointed with it. Another plus is that it uses very little acetylene and oxygen.
    Marty
     
  3. Aug 29, 2012 #23

    revkev6

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    we had a guy here at work go down and do some training with the guy in your link. amazing stuff! I own one of the everlast tigs that he reviews in some of his other videos.
     
  4. Aug 30, 2012 #24

    Deadly Precision

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    He's handy, for sure! It'd be great to learn from him. Seems he enjoys teaching a great deal. I've got the 200DX. There are a few things I don't like, the huge torch and heavy cables, for example. Overall, I'm pleased with the machine. I've owned it about eight months. A friend (very skilled welder) has had one for a few years and suggested it. I'm planning to get a small CK flex head.

    Oh hey, where ya at in Mass? I lived in Athol for several years.
     
  5. Oct 1, 2012 #25

    Alan Waters

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    It appears that while welding small diameter tubing cross drilling a hole is not necessary. It is however, necessary in larger diameter tubing where the volume of air to be heated and expelled is greater. Racing cars use lots of 1.500 and 1.625 diameter tubing and they will literally spit molten metal into the TIG torch in the tube has not been cross drilled.
     
  6. Oct 1, 2012 #26

    Head in the clouds

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    Are you sure Al? I've never experienced that, not to say it couldn't happen but I wonder why it would. By the time you're completing and sealing the weld any O2 is burnt up and nitrogen must be fully expanded? So where could the pressure come from?

    I've built a dozen or more spaceframes for Formula, GT and Stock racing and never seen a drilled member... except to inject fish oil which I think was pointless if the weld was sealed, and in which case they drilled it after heat treating/stress relieving, rather than before welding the clusters.
     
  7. Dec 2, 2012 #27

    Alan Waters

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    Oh yes. I'm sure. I don't know why it has never happened to you. It has happened to me many times. When you sew up that last .100 or so the expanding air inside the tube is rushing out the only exit left. Maybe it has to do with the speed of the welding. Are you using TIG or ox/fuel? I assume if the travel speed is slow enough the internal gasses would/ could have expanded to max. and no longer be under pressure.
     
  8. Dec 3, 2012 #28

    Workshoprat

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    Guys I hate to tell you this but if you have never had this happen then you just dont have an air tight weld. I have had this happen more than once and has been a real problem. Good thing is if it does happen you know you did something right. sorry I know thats gona ruffle some feathers but thats just the way it is.
     
  9. Dec 10, 2012 #29

    Brian Clayton

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    I TIG weld a good bit at work, and I am self taught. The best advice I can give you is:
    The material should be clean (clean enough you would put it in your mouth), consider even knocking off the mill scale too. And no rust at all.
    Fit the gaps watertite on thin CM tubing. 100 penetration is not a problem on this thin stuff and large filled up gaps have no strength. I use files the same diameter as my tubing for final fitting, really easy to get a perfect fit that way.

    Practice making a tight joint then "fusing" it together with just the torch and no filler. Best way to practice before adding rod. If you can fuse a joint together, you will be well on your way.

    DO NOT OVERHEAT the joint. Use absolutly no more heat than you need. Dull welds are usually weak welds. Should have the purple rainbow look when you are done.

    TIG is slow. Very Slow. If you are in a hurry, go do something else. People get in a hurry and turn the heat up so the welding will go faster. Dont.

    Good way to find the heat range is to start a puddle on a scrap piece. Puddle size will be about 1/4 inch or smaller. If you are too cold, puddle will be tiny, too hot will burn thru the tubing. Just right and you should be able to hold a puddle in one place all day long (Material heat sinks before overheat)

    My 2 cents anyway.....
     
  10. Dec 17, 2012 #30

    Lowrider

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    I'm not an expert but I did see the solution to the "blow out" problem on an EAA welding video where the last 1/8" or so of the closing weld will blow the edge of the puddle out unless you let it cool to a point of no color then form a puddle and close the weld without rod. Apparently, and I've done this, the rod will poke a hole in the puddle and leave a blow out there from the expanding air inside the tube. I think this can only happen if the tube is short and sealed because if you have a 5' piece of tube for the air to expand inside I don't think you will have the problem.

    JUst reporting what I saw.
     
  11. Dec 17, 2012 #31

    Brian Clayton

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    About blowout.... I can say thats is never been a problem for me. The cars I do use anywhere from 1 3/4 tube to 1/4 tube, varying in length from 1" to 12' in length. Never had to drill a relief hole. The only time I have ever had a issue with blowout, was trying to weld a tank (something with a large volume of air...and short enought so the heat would affect a large volume of air at the same time). I think that most tubing is long enough and the heat so localized that you dont heat the air enough to cause a signifigant pressure rise. I dont drill relief holes in any tube structures. Never seen any rust problems inside tubing either. Even on race car restorations from the 60's. Pitted bad from the outside from getting ignored outdoors from 30 years or more and still looked new on the inside.
     
  12. Jan 2, 2014 #32

    Jeffro311960

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    Re: Some welding questions ,what ever tig torch you get a gas lens is recommended. A

    Also make sure there is no draft, or the wind is not blowing so the argon gas will do its job, or you will get porosity. (full of little wholes) if this happens, you will have to grind it all out back to the clean metal. Tou need to practice on some scrap tubing. Also, when your flame is comming out of the weld drag the torch out of the weld slowly and angel the torch out of your puddle ahead of the weld, slowly. If you just come out too quick you will leave a whole in the weld.
     
  13. Jan 2, 2014 #33

    Pops

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    In building a tube fuselage, I drill a 1/16" dia hole in a high spot and after welding, and after ALL the welding is finished I put in the correct amount of Polyfiber's Tube seal oil,( by dia and length) and very quickly weld the 1/16" hole up. Using Tig. Trying to weld without a relief hole, pressure will build inside the tube and blow a hole in your weld puddle.
    Dan
     
  14. Jan 5, 2014 #34

    Alan Waters

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    I recently did extensive modification work on a Preceptor Pup fuselage. Using TIG, WeldTec #6 3/8 nozzle with gas lens, .040 tungsten, 8-10 CFH argon. Tubing was .500, .375 and .250 diameter .035 4130 CM. Filler rod is .030 ER70S-2. Bead width runs approx. .060 to .125. The difficulty of welding thin wall tubing is DIRECTLY relative to the fit. This can not be stressed enough. Get a really tight fit with no gaps and you will be able to sew up that joint in record time. If you have gaps, any gaps, you have problems. Number one being the ease of melting away the leading edge of the tube where it intersects another tube. If you want to be a good welder, learn to be an excellent fitter. How tight is a good fit? If you can insert a .030 filler rod between the tube joint it is too wide. [.035 tubing]

    About drilling holes. You have read all the above post as have I. I drill holes. 1/16 stub drill. If you take the time to think about the process you understand the air inside the tube has to expand. It has to go somewhere. The only reason I can think of where a welder would not have an occasional blow back is where gas welding is being used and the air inside the tube has expanded to its maximum. To me this says a lot more heat than needed has been put into the part.
     
    Last edited: Jan 5, 2014
  15. Jan 6, 2014 #35

    PTAirco

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    Hm. All I can say is that having welded hundreds of clusters (gas welded) I have never once had this problem. I used to be certified to weld on aircraft structures in the UK and had my welds analyzed and tested regularly, so I can at least claim some expertise.

    I just don't understand the mechanics of the perceived problem: Until the very last fraction of a second any air inside the tube is free to escape. The joint is now at its hottest and the air inside ought to have reached its maximum temperature and pressure, if any. As you close the weld and remove the torch the temperature goes down and so does the pressure. I just don't get where this sudden increase in pressure is supposed to come from to blow out the weld as it's finished.

    But that's just my experience. YMMV as they say.

    Oh - and I never drill holes in tubing if I can avoid it.
     
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  16. Jan 6, 2014 #36

    Alan Waters

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    Good point PT. It's not a sudden thing. It has to be the travel speed at which the weld is applied. As you said the air inside the tube expands to a certain point and is maxed out. If the weld is applied faster, and is closed before the air inside has expanded to maximum, that last .100 or so of the molten metal cannot hold back the expanding gases and becomes a miniature volcano for a fraction of a second. Just long enough to blow molten metal out and into the TIG cup. It boils down to the difference between gas welding and Tig welding.
     
    Last edited: Jan 6, 2014
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  17. Jan 6, 2014 #37

    Pops

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    The smaller the volume of the tube the easier to get a blow-out. In welding a small short tube, I'll drill a 1/16" dia hole and connect the inside volume of air to the other tube I'll welding so there is more volume for the air expansion. Easy to get a blow-out welding a short small dia tube with tig.
     
  18. Jan 7, 2014 #38

    BBerson

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    So are you saying this is a TIG welding problem, but not a problem with gas welding?
     
  19. Jan 7, 2014 #39

    Rosco

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    Gday Chaps ,Jody from Weldingtipsandtricks.com has a good video on welding 4130.Check it out He goes through all the problems and a lot of fixes for problems. Cheers Ross
     
  20. Jan 8, 2014 #40

    Alan Waters

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    Don't know about gas. I've never done it.
     

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