Mig welding chromoly

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Just wondering on the basics of mig welding chromoly can it be done?Thanks
Reply:Yes it can.  Of course the preferred method is TIG'ing.http://weldingweb.com/vbb/showthread.php?t=22818search, search, search.
Reply:If you are talking 4130, then yes!It can be welded with:O/ATigMigStickAtomic HydrogenCarbon ArcBrazedSilver solderedAll can be used provided the correct welding PROCESS is used from start to finish. And by process I mean cleaning, filler selection, pre heat, weld technique, post heat, inspection, process validation. There is no universal "preferred" method. Certain applications led themsemves better to one process or another from a economical perspective.
Reply:What is your application for the moly?  If it is for a drag race car, then no you cannot mig it because all of the sanctioning bodies specifically require moly to be tig welded.
Reply:CC, Actually you can get around the Tig foolishness with SFI. I have gotten exemptions for using OA welding based on engineering and test information that was provided to them. That silly Tig rule was set up in an effort to give more business to the large chassis shops and keep shade tree mechanics from killing themselves back when only the shops could afford the equipment. Now that anyone can buy a Tig, the rule makes no sense other than to give people the idea that there is some engineering basis for it. Sigh......
Reply:Thanks guys much appreciated no real plans for a cro-mo prOject yet but ya never knowMight try to tackle a tube frame for my mountain sled at some point once a few other projects are finished upJeff
Reply:Originally Posted by makoman1860CC, Actually you can get around the Tig foolishness with SFI. I have gotten exemptions for using OA welding based on engineering and test information that was provided to them. That silly Tig rule was set up in an effort to give more business to the large chassis shops and keep shade tree mechanics from killing themselves back when only the shops could afford the equipment. Now that anyone can buy a Tig, the rule makes no sense other than to give people the idea that there is some engineering basis for it. Sigh......
Reply:Originally Posted by Comp ChassisDont get me started with the sanctioning bodies and some of thier stupid rules, many of which they dont enforce, or even know how to enforce in some cases.  My biggest gripe is the whole chrome moly rule in the first place.  Yes it is stronger than mild steel, but then they allow reduced wall thickness of the tubing, so did they really make the car any stronger, or just reduce the weight of the chassis by 30%?
Reply:Originally Posted by Mario428Think about that a bit, they are looking to make it strong enough. If .120 wall mild steel is strong enough to pass SFI then the thinner CM is strong enough too. In their opinion the cage is strong enough using either, using CM just makes it lighter.
Reply:Matter-a-fact, I'm fix'n me up to "weld" me a race car ride now! Attached ImagesLincoln Power Mig 216Lincoln AC/DC-225/125Miller  625 X-Treme PlasmaMiller 211 Forney 95FI-A 301HF 91110Victor Journeyman O/PMilwaukee DaytonMakita  Baileigh NRA Life Member
Reply:I agree with comp chassis, IMO...The political game played in the major drag racing series is a whos who type deal..The thinner cm.pipe is used to reduce weight.!! Then the sanctioning body will change the rules to either add pipe or take away HP...because of a issue with safety I never want to see anyone hurt!! WHY make the pipe thinner when all along they have been taking power away to make the cars safer?? Who is the SFI?? That says alot..Miller 250DX HTP 221 DV AC/DCHenrob O-A Miller 180 MigMiller 150 Inverter   Hobart 10,000 Welder-Generator   Have a good day!!!
Reply:What I find to be frustrating, is the rules were made with absolutely no engineering information to support them. When I wanted to use a process besides Tig for chassis work, I asked them what infomation they had used to base their decision on. Answer....none....or more specificly they based the rules on what the prominent shops told them was "the best". No wonder there have been issues with weld failures in the drag world.....seriously 4130 has been in use for almost 90 years in welded tubular structures used in high performance applications, shouldnt be rocket science here.
Reply:Originally Posted by Comp ChassisI fully understand that, but, they have also ruled that mild steel chassis can go no faster than 7.5 seconds.  Anything faster must be built out of chrome moly.  So, yes moly is stronger same for same, but they allow it to be thinner which in reality makes it about the same as the mild steel, then require it to be mandatory in the fastest cars.  If they really want the cars to be stronger why the reduction in required wall thickness?
Reply:Way back when we welded our cars with 3/32 Lincoln LH-70 4130 had no problems and some sprint builders used it too. Did get a Tig and Nascar is all miged today I believe there is a 4130 filler metals made. Mig, tig and stick.
Reply:Originally Posted by PavinsteelmanWay back when we welded our cars with 3/32 Lincoln LH-70 4130 had no problems and some sprint builders used it too. Did get a Tig and Nascar is all miged today I believe there is a 4130 filler metals made. Mig, tig and stick.
Reply:The TIG thing with chromoly... Aircraft frames from 4130 were welded with O/A, and who knows what kind of methods some of the early Bernstein dragster chassis's used...To be honest, I do think about the chassis and its fabrication during use, however I put a lot weight on what happens during the/a crash. An improperly welded chromoly chassis won't deform and absorb impacts, it will just snap welds. NOT GOOD. I would actually prefer a weld that anneals and softens the material around the weld joints to allow them to deform during impact, rather than be brittle and break free... Even with these conditions, the chassis can be made to be very rigid.
Reply:I have always found it interesting that NASCAR which runs 3500 lb cars and  routinely crash at speeds approaching 200 mph specifies mild steel for their chassis.  Yet NHRA mandates chrome moly for their fastest cars.I had some dealing with SFI several years back regarding flex plate shields.  This was probably 15 years ago and at that time no one was making shields for 904 torqueflights.  The shield is essentially a 2" X 1/8" strip of strap metal formed around the bellhousing with mounting tabs.  In order to get the rights to put thier SFI sticker on these, I had to build 3 units, supply SFI with the 3 prototypes, 3 transmission cases and 3 flex plates.  My recollection was the testing phase where they would spin up and explode the flex plates to test the shields would cost me $20,000.00.  If my design passed the test (remember, the shield is nothing but a 2" strip of 1/8" strap iron) I could then pay them the sum of $25,000.00 per year for the rights to put their SFI stickers on my shields.