Welding questions December 29, 2011 10:32AM
My questions are based on moving to the SF class. When builders make frame rails for ag rear ends are they all TIG welded or is MIG welding ok? How about roll cages? If you buy a cage kit can you MIG weld it? Is that SFI will it pass inspection? I have a mig welder, but not a tig welding and only have done tig at school.
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Re: Welding questions December 29, 2011 11:16AM
You can MIG weld and it will pass inspection. I use .o30 wire and stargon gas.
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Re: Welding questions December 29, 2011 12:09PM
If the cage is Chromoly and mig welded will it still pass tech? In know in NHRA rules mild steel can be mig welded and chromoly must be tigged
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Re: Welding questions December 29, 2011 12:29PM
The trick to welding a roll cage or a frame, and having it pass inspection, is to always and I mean always weld without a helmet. Without the helmet in your way, you can see the welds really good. You also want to make sure you get good penetration, so turn the welder up to it's highest possible setting, wether you are using mig, tig, or stick, always weld at the highest possible setting. If you are using a MIG, make sure to point a fan directly at the arc while you are welding and have it on a very high setting, to make sure and blow all that pesky sheilding gas away. And the best welds will look like a a bird flew over and crapped all over it, and no matter what anyone tells you, those are the strongest welds too.
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Re: Welding questions December 29, 2011 01:36PM
weld without a helmet. what did i miss.
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Re: Welding questions December 29, 2011 02:35PM
A smart ass every minute here.

When they inspect your cage, they check the thickness with a sonic tester, measure the physical dimensions, make sure the tubes are present and in the correct locations, and otherwise check it visually for problems. Not sure if they can visually tell with certainty whether it's been MIG or TIG welded.

However, I believe the TIG-only-for-chrome-moly rule is right in the SFI spec for roll cages, and since the NTPA rule says the cage must meet the SFI spec, you probably should abide by it. I believe the advantage of chrome moly is the strength to weight ratio, but in the SF you should have plenty of weight to play with, I'd use mild steel and MIG it.
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Re: Welding questions December 30, 2011 01:45AM
YES, CMS needs TIG welded.
If you weld so bad with TIG that it looks like MIG, I would guess the cage isn't going to pass.
As for the "mild steel" suggestion, make sure it is DOM T U B I N G !! Not pipe. (Ask Harry Bledsoe)
The DOM can in fact be MIG welded.
To puller 321, that is some funny stuff there !!!! Too bad most on here take things so serious!
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Re: Welding questions December 30, 2011 02:10AM
x2 on the mig vs tig comparision. Each process produces a very distinctive weld bead. Very easy to tell the difference between the two, even when done badly. As stated above, if you're going to use mild steel, be sure to get DOM tubing, not HREW. DOM is seamless, HREW is not.
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Re: Welding questions December 30, 2011 02:26AM
I have to disagree with you about DOM tubing being seamless. DOM has a welded seam but it is drawn over a mandrel (DOM) after welding so you can't really see the seam but it is there. I make the grips that grip onto the tubing to pull it over the mandrel.
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Re: Welding questions December 30, 2011 02:52AM
I ve used both processes on moly. No problems at all. Google the process you want to use. Follow it and you will have no trouble. Make sure you do pre heat and post heat and insulate the joints for cooling. Use WE80S-B2 filler rod or wire. Argon gas for tig. And I don t remember the gas for wire. Just tell your supplier what you are wanting to weld and they should get the right gas to do it right. Remember anything will weld moly but its a matter of doing it right and only once.
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Re: Welding questions December 30, 2011 03:09AM
So Brian, have u welded a cm cage with a mig?
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Re: Welding questions December 30, 2011 05:06AM
Got to agree with Brian and the gas for mig on both moly and mild steel is 75/25 or stargon . We also did some bending tests to some weld samples of moly tube and found the mig welds to be slightly better as the samples would bend farther before cracking. It is hard to make the mig welds look as good as the tig welds but I know some fabricators who make mig welds that are hard to tell how they were done(lots of practice). The only way to make the tig welds on moly better in bending tests seems to be reheating the weld area to 1100F (using a temp stick) and cooling very slowly kind of annealing the welds. Another thing we do in critical weld area on moly frames in high stress areas which avoids the need for reheating is to tig weld the moly normally with 80000 rod and then after the whole frame is done to go back and reweld the critical areas(like where the rear axle is mounted or any tubes that brace the rear end housing or the hitch) with 309stainless steel filler rod and making a cover pass over the original weld. This makes the welds capable of bending a lot farther before cracking. This was originally done in roll cage and driver compartment areas on sprint cars for driver protection.
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Re: Welding questions December 30, 2011 12:35PM
Quote
J&R Machine
I have to disagree with you about DOM tubing being seamless. DOM has a welded seam but it is drawn over a mandrel (DOM) after welding so you can't really see the seam but it is there. I make the grips that grip onto the tubing to pull it over the mandrel.

If it has a welded seam, then it is HREW (hot rolled electric welded). HREW is formed by rolling a flat strip into a tube, then welding the seam, hence the name. It is then drawn to assure uniform circularity and size, as well as relieving stress caused by forming/welding. Tubing formed in this manner is unsuitable/undesireable for a roll cage because the seam is a weak point and can split under a load, causing it to fail. It is not uncommon for this seam to split when the tubing is bent, depending upon bend radius, etc. True DOM tubing is formed by heating a solid round rod until malleable, then forcing/drawing it over a pointed mandrel. The malleable material assumes the size and shape of the mandrel when it cools, resulting in a length of tubing of uniform wall thickness, size, shape, and surface tension with no seam. It is the forming process that differentiates the two.
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Re: Welding questions December 30, 2011 03:04PM
Here is a link to information about dom tubing.
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Attachments:
open | download - Speedy Metals Information for DOM Steel Tube.mht (61.4 KB)

Re: Welding questions January 03, 2012 01:40AM
Brian why have u not answered my question yet, its a simple yes or no answer.
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