Do you think it's easier to mig weld or tig weld tubing? And why or why not? a) When welding chromoly tubing? b) When welding mild steel tubing? If you feel it's easier to mig, then why does NHRA insist on tig when it comes to chromoly? Thanks again for considering yet another of my many neurotic posts.
Chrome Molly is a different alloy. As far as easier,if the joints are really nice tig would be easier. A little trick when doing this is to fill the tubes with the Welding gas. That helps get a better weld.
It has nothing to do with being easier, its about the materials. Mig is always easier as you just point and pull the trigger. Providing you have everything set up right. Certain materials respond differently to each type of weld. Other factors also apply, your skills, machine and set up, mat. thickness? I prefer to TIG, it look way better!
It's all about control, too. As mentioned, when you pull the trigger on a MIG, you've got what you've got; no more, no less heat or wire feed. Chrome-moly does NOT like a lot of heat in the welding process. The stuff welds like butter, MUCH easier than mild steel; but excess heat will destroy the material properties. A TIG with adjustable amperage control (usually a foot pedal) allows instant and infinite control of the heat going into the weld puddle. An experienced welder will be changing the amperage constantly as the bead progresses to use just enough heat for adequate weld penetration and no more. This is impossible with a typical MIG machine.
Yo, 31Vicki, that is a very intriguing tip. If you were TIG'ing, would you tap off of the Argon to pump into the tubes as you do the welding?
Sure its easier to GMAW tubing, thats why the NHRA requires GTAW. Seems like a no-brainer. Also most GMAW welds are not 100% penetration and you cant control the heat.
There is a thread about welding on here with some lengthy discutions. I'll try to find it? http://www.jalopyjournal.com/forum/showthread.php?t=299587&highlight=pretty+weldstread Found it! Start reading there is good info at points.
Sorry to hijack, but yes, filling the tubes with argon will prevent the back side of the weld from granulation, especially with stainless. (Also called sugaring, it looks like piles of gray sugar. Can also be prevented with experience, lol.) Its caused by overheating the area and oxygen entering the back side of the weld where there is no shielding gas. Side note, when i repair aluminum diesel fuel tanks at work I "purge" the tanks with Argon set at 5-7 cfm. It eliminates the oxygen. No oxygen, no boom.
Use a separate bottle and regulator, its just easier. I use the regulator from my mig when I do that. Works great for headers too. Couple rags in the end and couple around the hose let it purge. Night and day difference
If you are welding it up solid (closed like A-arm tubes would be) you don't want excessive gas trapped in when you button it up. It will blow out on you every time.
On pieces between 6-18" in length (roughly), it's necessary to drill a vent hole to allow the built up pressure to escape. This is best done into an adjoining tube (under the area where the notched tube is welded on).
Whoever says mig isn't 100% penetration is an idiot. No matter what process your supposed to know what the hell your doing and get 100% penetration if possible, your weld should be at least as strong as your base metal. Tig requires more skill as pipe has a changing work angle constantly Tig needs a very tight fit up, where mig is more forgiving. The question is which one are you better with? I would rather tig chromoly myself
Me personally would never fusion weld a header pipe. Maybe if it was stainless, shits strong as hell.
I think that's what it is basically boiling down to. i guess i should have asked which process is more straightfoward/ expedient or simplier; Mig is a little cheaper and faster. Of course if you are only doing one chassis and don't have a production line, then the question of faster is really moot.
C/Molly tubing is very different than M/S, (more like S/S) it requires more heat control, starts/stops can be a problem if the weld heats up or cools to quickly, this could cause cracks in the joint. That is why TIG would be the better option for C/M. M/S is very forgiving compared to most other metals, so IF you know how weld,it's really your discretion as to what process you use, given that you have equipment that can handle the thickness.
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