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Thread: how to weld 4130

  1. #16
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    Re: how to weld 4130

    Like I have said before.
    It is amazing to me with all the bad looking welds I have seen over the years (some on certified planes) that extremely few accidents can be blamed for it.

    This is a true testiment to how most steel tube aircraft designs are very forgiving as well as the welding process. Especially O/A torch.

    In another post I described some testing I did many years ago as to how bad a tube joint could be welded and still have amazing strength compared to the required load of the average application for that tube size and wall thickness.

    This is not an excuse to weld badly. Just an observation that tends to support the satistics.

    Welding with a torch seems to be the most forgiving.

    Welding with O/A and torch is like learing to milk a cow. You can take lessons from the farmer and learn on 10 cows or learn on your own on 50 cows.
    Pracrice, Practice, Practice, do some simple testing to build your confidence then practice some more.

  2. #17
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    Re: how to weld 4130

    How can the self-taught welder 'test' the quality of his work, WT? And judge it to be adequate for aviation purposes?

    As some have said, most designs are massively over-engineered and designed to spread loads and prevent one bad spot from bringing the aircraft down. Most would require multiple failures to cause a problem...

  3. #18
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    Re: how to weld 4130

    I don't have any experience with 4130 in aircraft but I have used it in racecar fabrication. it is extremely hard to get a joint as strong the tube. every car frame you will find today is tig'd. I have had many welds break on my purchased chassis in the past.

    I would suggest a couple things to anyone looking to weld an airplane.

    find a local community college that teaches welding. TAKE A COURSE. you will save time and money. gas and consumables to learn are not cheap.

    join a forum like "weldersweb". lots of the good welders on there can look at a picture of your weld and tell you exactly how to improve them. they will also tell you how to test your welds. (there is a cut, sand, polish, dye method that really shows your weld penetration well)


    I think O-A welding adds a couple more variables to the "art" of welding. OA and tig are both very hard to learn to do well. I just started to tig last winter and am mostly self taught. it's not easy to get those pretty stack of dimes looking welds.

    if it were me, I would think about either making a jig and fitting all my pieces or tack welding them together then have a professional welder weld everything up.

  4. #19
    Registered User FineFab's Avatar
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    Re: how to weld 4130

    Quote Originally Posted by Hawkeye View Post
    whats the better way to join 4130, via tig or gas? (Im welding .035 wall material)
    I learned gas welding specifically for aircraft. I then learned to TIG weld. Never have I looked back at gas welding. TIG give you much more control in all respects and in my opinion, is the superior method.

    Interesting, I believe learning gas welding first gave me a better understanding of heat control, puddle manipulation, and hand/eye coordination that gave me a jump at the TIG skills.

    Learn both, use TIG-

  5. #20
    Registered User Lasklus's Avatar
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    Re: how to weld 4130

    Sorry to break in on old topic but it brought me here, in my opinion, tig welding indeed is the best way!
    Nice and controlled welding is recommended and tig welding is the way to do just that.
    Regards Patrick Wouterse

    For (airplane) welding jobs all over the world!
    www.lasklus.nl

  6. #21
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    Re: how to weld 4130

    I was taught to weld with oxy/acetylene in Airframe school so my training (for aircraft welding) was probably better than even what is offered in the community colleges. With the torch we were instructed to bring the joint up to temperature, complete the weld and then slowly bringing the temperature down on the weld, which causes the least shock to the welded area and releases tensions that are built up during the weld process. TIG is a great way to perform welds in 4130 structures, but you still need to bring the welded area up to a cherry red heat range with a torch to relieve the tensions in the welded area as a result of using the TIG process. So really you need a TIG and an oxy/actylene setup to perform an acceptable aircraft quality weld.

    PS- Just because a weld "looks pretty" doesn't mean that it's a good weld. Your welding skill should be tested on sample pieces that are put in a vise and radically deformed with a hammer or vise-grips until you are sure that the welded area never fails first.

  7. #22
    Registered User Head in the clouds's Avatar
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    Re: how to weld 4130

    Quote Originally Posted by Elmog View Post
    I was taught to weld with oxy/acetylene in Airframe school so my training (for aircraft welding) was probably better than even what is offered in the community colleges. With the torch we were instructed to bring the joint up to temperature, complete the weld and then slowly bringing the temperature down on the weld, which causes the least shock to the welded area and releases tensions that are built up during the weld process. TIG is a great way to perform welds in 4130 structures, but you still need to bring the welded area up to a cherry red heat range with a torch to relieve the tensions in the welded area as a result of using the TIG process. So really you need a TIG and an oxy/actylene setup to perform an acceptable aircraft quality weld.

    PS- Just because a weld "looks pretty" doesn't mean that it's a good weld. Your welding skill should be tested on sample pieces that are put in a vise and radically deformed with a hammer or vise-grips until you are sure that the welded area never fails first.
    Stress relieving of welded 4130 doesn't need to be that hot (cherry red), between straw and dull red and slow cooling does the job.

  8. #23
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    Re: how to weld 4130

    Indeed, but stress relieving isnt always necessary after Tig, yes, always after oxy/actylene because you maken it so hot!
    The HAZ (heat affected zone) after oxy/actylene is very large and the chance of breaking even larger.
    We do not use the oxy/actylene fot stress relieving but a induction furnace and sometimes a stress hammer.

    We have different crushing tests and x-ray tests done on 4130 with Tig welded and no stress relieving after that, and when you use the right settings it almost always looks perfect and is stronger than the mother material.

    About youre ps, indeed, a pretty looking weld doesn't mean that it's a good weld, but a good weld mostly is pretty looking!
    Regards Patrick Wouterse

    For (airplane) welding jobs all over the world!
    www.lasklus.nl

  9. #24
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    Re: how to weld 4130

    I'm getting conflicting opinions on this so I'll ask it here. I have a Lincoln 230 amp AC/DC stick welder and I'm told you can buy a TIG torch and use argon ( I have it to weld AL) as a shield gas and do very credible welding without spending a ton of money on a TIG welder. Others say it will work but is not very practical on welding light materals such as 4130 on a Cub frame. I can do a fair job on O/A torch and rod but realize the welds must be normalized. TIG seems to be the prefered method.

    Also, why can't a MIG be used on aircraft? I have used a Century and a Lincoln for years on a variety of things and it works just fine when I start out with clean surfaces to weld. I know the TIG has more control of heat and makes a better weld but is it THAT much better?

    What do you welders think and what TIG would you recommend?

  10. #25
    Registered User Head in the clouds's Avatar
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    Re: how to weld 4130

    Quote Originally Posted by Lowrider View Post
    I'm getting conflicting opinions on this so I'll ask it here. I have a Lincoln 230 amp AC/DC stick welder and I'm told you can buy a TIG torch and use argon ( I have it to weld AL) as a shield gas and do very credible welding without spending a ton of money on a TIG welder. Others say it will work but is not very practical on welding light materals such as 4130 on a Cub frame. I can do a fair job on O/A torch and rod but realize the welds must be normalized. TIG seems to be the prefered method.

    Also, why can't a MIG be used on aircraft? I have used a Century and a Lincoln for years on a variety of things and it works just fine when I start out with clean surfaces to weld. I know the TIG has more control of heat and makes a better weld but is it THAT much better?

    What do you welders think and what TIG would you recommend?
    MIG was proposed over here for the production jig-welding of one popular CRMO framed 2 seater. The Authorities initially rejected the proposal out of hand but the would-be factory persisted and provided various test pieces with cluster joints made using OA flame welding, TIG and MIG.

    The TIG was neatest, flame was second and MIG didn't look that great at all.

    Without stress relief, which wasn't planned for these fuselages, the flame welded was weakest under shock loading, breaking at the heat affected zone (HAZ), TIG was second and MIG was strongest, surprisingly.

    The factory received approval to manufacture using MIG.

    Most of the airframes seem to be fine but the type gained a feared reputation because a few of them had weld fractures develop at the strut attach points and I believe there was at least one catastrophic airborne failure.

    From what I saw the strut attachments could have been designed much better so that the weld was not solely responsible for holding the struts attached. I think that a retro-fix was approved by adding a strap from side to side.

    If I was you I would experiment with the MIG as it is very much quicker than any other means and one of the reasons that factory wanted to use it was to allow much poorer fit-ups at the joints and just pour in more wire to fill the gaps. It seemed to work fine and had superior strength although the welds weren't all that elegant. Very thin wire and low current settings are the order of the day.

    The reason for the superior strength seemed to be two-fold. The MIG and poor fit-ups resulted in much larger fillets which in turn provided added support to the members, albeit with a little added weight. And, mindful of the damage that excess heat causes in the HAZ, the welders were told to keep the power low and make welds that were technically 'cold' and had limited penetration. That lack of penetration is what some blamed for the weld failures I mentioned earlier.

  11. #26
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    Re: how to weld 4130

    I use MIG for almost everything.
    Just use .023" wire. Pulse the trigger every second or so as needed to avoid burn through ( let it cool some between pulses) This helps slow the process. You can set the heat a bit hotter than normal when pulsing. This avoids cold starts while giving a similar average heat.

    And a loose fit is good for MIG. Need some room to shoot the wire into the gap and avoid large buildup.
    Head in the clouds likes this.

  12. #27
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    Re: how to weld 4130

    Thanks gents!

    You confirmed my long held belief that it's the quality of the weld that counts not the method of doing it. Pretty welds are nice but then, I'm going to prime and paint and cover the majority of them anyway....think I'll be a MIGger on this cub.

  13. #28
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    Re: how to weld 4130

    Quote Originally Posted by Lowrider View Post
    I'm getting conflicting opinions on this so I'll ask it here. I have a Lincoln 230 amp AC/DC stick welder and I'm told you can buy a TIG torch and use argon ( I have it to weld AL) as a shield gas and do very credible welding without spending a ton of money on a TIG welder. Others say it will work but is not very practical on welding light materals such as 4130 on a Cub frame. I can do a fair job on O/A torch and rod but realize the welds must be normalized. TIG seems to be the prefered method.
    This is possible, but you have to scratch for starting te arc, and thats not ideal, but its possible for sure...

    Quote Originally Posted by BBerson View Post
    I use MIG for almost everything.
    Just use .023" wire. Pulse the trigger every second or so as needed to avoid burn through ( let it cool some between pulses) This helps slow the process. You can set the heat a bit hotter than normal when pulsing. This avoids cold starts while giving a similar average heat.

    And a loose fit is good for MIG. Need some room to shoot the wire into the gap and avoid large buildup.
    Manually pulse is very difficult and takes practice, too long cooling interval gives a break in the penetration of the weld and make it very weak! So be careful wit this "every second or so" advise!
    Regards Patrick Wouterse

    For (airplane) welding jobs all over the world!
    www.lasklus.nl

  14. #29
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    Re: how to weld 4130

    Manually "pulsing" the weld is very much like a series of spot welds. Each "spot" blends to the one before it and the weld is very strong. It is used in metalwork of all kinds from racing cars to general automotive repair and sculptures - the kind where strength is as important as good looks. The small gap between the two pieces provide for 100% penetration (usually more than that when I do it) but the excess adds to the strength of the weld in the same way that a good filet does on any weld. The process keeps haz to a minimum and gives a very strong connection.
    Head in the clouds likes this.

  15. #30
    Registered User Head in the clouds's Avatar
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    Re: how to weld 4130

    Quote Originally Posted by Lasklus View Post
    Manually pulse is very difficult and takes practice, too long cooling interval gives a break in the penetration of the weld and make it very weak! So be careful wit this "every second or so" advise!
    Quote Originally Posted by PaulS View Post
    Manually "pulsing" the weld is very much like a series of spot welds. Each "spot" blends to the one before it and the weld is very strong. It is used in metalwork of all kinds from racing cars to general automotive repair and sculptures - the kind where strength is as important as good looks. The small gap between the two pieces provide for 100% penetration (usually more than that when I do it) but the excess adds to the strength of the weld in the same way that a good filet does on any weld. The process keeps haz to a minimum and gives a very strong connection.
    I agree Paul, manual pulsing is very effective and I use it a lot, even in TIG with an auto pulse function. But I can also see where Lasklus is coming from, especially where thicker material and a good fit-up might be concerned. Just a little too long between the pulses could cut the penetration to almost zero although it might look OK on the outside.

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