How to TIG Weld 4130 Chromoly Tubing

How to TIG Weld 4130 Chromoly Tubing

Hi, I’m Todd Bevis and I’m the engineer
and fabricator here at Cagnazzi Racing where we build the NHRA pro stock cars that
travel in excess of 210 mile an hour. The tubing you see behind me is all
4130 chromoly. It’s the mandated material used for NHRA Pro Stock drag race car. The tubing size used here is anything from an inch 5/8 .083 wall to as
small as quarter inch and as thin as 35 wall so the fit and the finish and the
attention to detail on this is paramount in all that we do. The fit on thin
wall small diameter tubing is so important in that it determines how much
heat is going to be put into the weld. If I have a fit that’s not very good and
I’m having to use a lot of filler rod and a lot of heat to get it to bridge
the gap, then I’m risking the possibility of embrittlement around the weld area
because of the heat concentration. So we try to make the heat the fit as tight as
we can without creating any gaps so we can use a little less filler rod and
accomplish the same goal. Filler rod typically goes with the size of the weld
that we’re doing. If I’m welding on something that’s 35 wall, I’m going to
use a 30,000 rod or a 40,000 rod. If I’m welding something that’s in an 83
wall or a 65 wall, moly tubing I’m going to use typically most of the time a 63
or a 1/16 welding rod. Sometimes a 3/32, depending on the
thickness of the two. The heats controlled by a foot pedal.
There’s a general rule of one amp for thousands of material thickness. So let’s
say I’m welding 65 wall tubing, I’m typically going to be on about 65 amps
on my welder, but it’s also controlled with a foot pedal that’s a rheostat so I
can, like a gas pedal in a car, I can give it more power or less power and which in
welding terms would be more heat or less heat. But that’s also affected by how
fast I weld or how slow I weld. The slower weld at a same amperage setting
is going to be a hotter weld because the heat is dissipating into the material
weld. Arc length is the distance from the tungsten to the piece that we’re
welding and with chromoly in TIG welding we want to keep that arc length as
small as possible without contaminating with the welding rod or touching of the
puddle that we’re trying to weld. As the arc length gets further away it requires
more power from the welder to push that arc off of the tungsten onto the weld. So
therefore you get a bigger spark and it’s spread out wider in there again
it’s going to spread the heat in welding chromoly we want to concentrate the heat
in a small area. When you’re welding, I try to tell people I’ve taught how to
weld that it’s like a signature. Whatever happens in the hand that you’re holding
the torch with is going to come out on your on your work or the weld that
you’re producing. So I use, there’s two different methods I try to teach you guys. You can
either use what I call a sewing machine method, where you kind of put a dob of
weld and you move, you put a dob and you move. And the movements may be like a
sixteenth of an inch or so or an eighth inch, depending on what you want to weld
to look like, because it’s going to reproduce what your hands do. You can
also take and do very small weld real smooth and feed the rod real smoothly
and it’ll leave a more smoother machine looking weld as opposed to weld stacked
on top of each other. So that is going to become a signature whatever. It’s like
writing in first grade. They give you a big pencil when you first start out it’s
a little squiggly and sloppy, but as you practice and you get better, the welding
will get better and then your weld become your signature and what you weld style is.

98 thoughts on “How to TIG Weld 4130 Chromoly Tubing

  1. Oh gosh! My dreamjob! I always wanted to TIG weld something for automotive branch and what's really important and what would require responsibilty from me.

  2. I know its really tough to just get to all those spots on that that car frame. The vid shows an easy spot where the camera can see the guy welding. There is all kinds of out of position spots there where I'm sure the welder has to stand on his head and cuss (and still produce decent work). Imagine crawling in and out of that frame to go grind your tungsten every time you dip it. Your skills and advice are good. Todd, Thanks for sharing. What was that number of tig rod you're running?

  3. Dear Peoplewhothinkthisguysucksatwelding…

    just because his welds dont look all pretty and stuff dont mean its a weak weld. its pretty much like judging a book by its cover, justcause its not full of colors, it dont mean its bland and boring.

  4. that one guy said try doing that out of position that guys not out of position that is gravy im a nuke welder in the shipyard i weld in submarines welding that cage up is not out of position try welding upside down with two mirrors and getting 100% on x ray or ut wish all i had to weld was a roll cage like that

  5. @martinmartiini its fucking youtube.. millions of dollars/euros or any other currency used each year on some internet leisure toy…

    Want another example? I'm pretty sure I can do this for nearly anything manufactured now.

  6. @martinmartiini Welded benches, welded seats, desks, tables and many other things are quite a waste of welding then.
    You can make all of them out of wood and save the welding for something important.

    There is enough filler material and electrodes to go around. They aren't a depleting resource like Oil. In welding schools they have to throw away thousands of dollars of welded material every week but it gets recycled into new steel and fillers.

  7. @martinmartiini If they didn't weld this thing together good it would crack and break, causing a danger to both the driver and anyone near him. the exact same reason they make sure cars are up to specification.

  8. Not the best welding, but not terrible either. Could tighten up the filler addition, pretty spaced out and some contamination showing at the end of the weld. His information is spot on though and the fit up and fabrication are great.

  9. Producing good welds inside a cage frame like that is very difficult. It's much easier doing it on the bench, but then how many flat chassis have you seen?
    I like the bit about how a weld is like your signature……my welds tend to say "whoa, boy. what happened here? Why all the squiggle and what's that lumpy bit you tried to grind off….?"

  10. his welds have plenty of color, chromoly turns crusty grey when its too hot. If this had anymore purple too it, it would be cold. i dont see why anyone bitches. We go for wider beads on our chassis, but hey we dont clean the tube much either 🙂

  11. Anyone that has never TIG welded in a jungle gym like this has zero room to talk. Working the pedal with your knee or heal while upside down is a whole other animal.

  12. there are different weld pedals or heat control devices, you can use a hand control that you and control to heat with just move your thumb up or down on it

  13. tell em bro. they obviously haven't left school or the bench yet LOL try doing that crap with a handful of mirrors and a manhole cut in a bulkhead the size of a basketball and you are the only welder with a long enough reach 😀 do work

  14. Most of these car are ass. with a mild steel rod, I agree that it should be with a 4130 rod but remember if you use a moly rod instead of mild you need to anneal your welds, I switched from the moly rod to a cronatron 333T rod and have had good success………..

  15. Hey mister weld inspector…show me where it's contaminated…?? I don't see porosity or any residue from said contamination. I see nice clean welds.

  16. 4130 is a terrible choice for welding chassis. The tubing has been drawn back allready and is not at its full hardness, So why put hard filler into it?Also, The melting temp of mildsteel vs er-80 vs 4130 is a big difference in how much heat you have to put into the joint. There is a reason NHRA requires er-70 filler and also a reason that NOBODY who knows what they are doing uses 4130 filler anymore. 4130filler wire is pefect when making small parts that get heat treated after fabrication.

  17. dam it bevis hahah haahaa ha.. seriously tho those welds don't look that great and I do work with a pedal upside down 6g need to hire me shiii….

  18. no you have to use er80s b2 for welding 4130 and 4140 im taking a 6g test tomorrow..on a 14 inch pipe..god help me

  19. Very informative video! I'm used to tig welding stainless and carbon steel and was asked to weld a chrome moly frame. This made me a little less nervous lol

  20. Thanks Tood…I remember when you had your own business…..I guess Cag is keeping you busy….I used to run some comp cars and I always wished I could tig….now I am going to learn because I have the time.,,any tips as to how to learn without ending up in some welding class…..all I want to do is weld some CM and some mild steel

  21. I really hate to be critical of someone else's work, however, If that frame was being fabricated for me; visual inspection of (some of) the welds would cause me to reject it for lack of Q.C.. By trade, I am a journeyman electrician, who frequently welds on power plant's in the construction and up grade phases. ( I purchased a Miller 330abp tig welder in 1979, and use it to this day in the shop- I use a miller Trailblazer 302 in the field with either a h.f. arc starter, or a Spoolmatic 3 spool gun for aluminum bus bar and aluminum cable tray fab / repair… 

  22. I see a lot of "internet experts" criticizing the beads, and I will say they look a bit squiggly…but how many of you can do that good with your knee, elbow, or other appendage on the pedal? There's a big difference between cage and chassis welding, and sitting in a comfy chair with all your parts on the table and your foot on the pedal.

  23. I know there is much debate on this but knowing what you guys build id like to ask what fill rod you use for chromoly? Thanks

  24. Ill take another look at the video but was inquiring about the filler of choice for chromoly and yes roll cages, as well as suspension components (a arms,etc.) Ive heard many say ER70S-2 is fine and some say Er80 is the best. I figure these guys being top-notch builders was curious what they use for the cages. Im getting ready to do mine and was wanting that input, thank you for your reply.

  25. Thanks for the video @Miller Welders, I am a fan of your equipement, specifically the Miller Dynasty 200DX.
    Now, my question is, how can I achieve a fit up that great? It seems like whenever I try to shape the welding end of tubing one side is uneven, so I grind it, now the other side is uneven, and after I go back and fourth with that I end up shortening the tube by 1/4"! surely there's a more effective way of achieving a good fit up.

  26. Thanks for the informative video. I am starting up my own shop and was asked about chrome-moly tube welding. Having never done this I have been on a search for all the info I can absorb. Seems there is differing opinions on filler metals so it becomes a bit diluted to me which is best. Thanks for the tip in responses about different fillers for cage and frame ( if I read it correctly)

  27. so basically you are not skilled enough to use a hand control I see….. lmao …. I weld for living and do at least two roll cages a month. and all the professionals I know do not use foot control . just shows sometimes its who you know in the industry to get these high paying jobs .. smh so sad

  28. My 17 yr old son has a 69 VW Bug He want to rebuild. He love his Mechanical class in HS. He would be so Stoked to have this welder to start His own Garage. Please Miller, Start my Son on the right Track. Oh I'm a single Mom with a love for Mechanical stuff too.

  29. All this money in parts and what hes building and guys gonna use a foot pedal and a knee rather than a hand controlled tig torch ?…

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