[jpence38]

I make repairs at a track on car frames and roll cages between heats and the repairs have to be fast, sound, and proper. TIG welding is too time consuming for making such repairs in this situation. I have never MIG welded 4130 before, only TIG. Can anybody tell me what the do's and don'ts are of MIG welding 4130???
I would like to make the repairs without preheat (as this takes time) and will be using an AWS Class ER80S-D2 filler with either a CO2 or an Ar/CO2 shielding gas on 1 1/2 in. diameter .095 wall thickness 4130 chromoly tube. Thanks

[anthonyfawley]

Mig may be a little difficult if its windy on the track and tends to cool kinda of quick. Under your circumstances I might try oxy-acetylene. You really dont need to pre heat under about an 1/8th inch wall but with oxy-acetylene you kind of are anyway, never hurts i guess. I think if you go that route you will want to use the 4130 filler though. If you still choose to mig it go with the stick with the ER80-D2, with 75/25 mix and probably wouldnt hurt to ping it like with cast iron. Good luck.

Anthony

[Rbeckett]

I make repairs at a track on car frames and roll cages between heats and the repairs have to be fast, sound, and proper. TIG welding is too time consuming for making such repairs in this situation. I have never MIG welded 4130 before, only TIG. Can anybody tell me what the do's and don'ts are of MIG welding 4130???
I would like to make the repairs without preheat (as this takes time) and will be using an AWS Class ER80S-D2 filler with either a CO2 or an Ar/CO2 shielding gas on 1 1/2 in. diameter .095 wall thickness 4130 chromoly tube. Thanks

Jim, be very carefull since most sanctioning bodies who run events like the NHRA, ARCA, SCCA and others might require TIG on 4130, Otherwise keep in mind that a MIG joint will yeild less than the TIG and probably be the weak link on a chassis that is repaired that way. I dont know what sanctioning body you would fall under, but make sure you consult the rule book just in case. It would really suck to do a repair and end up disqualifying a chassis because of using the wrong process and not conforming to their rules. Just my .02 though.

[Steve from Ohio]

4130 was originally designed to weld via Oxy/AC. Now that Oxy/AC is now considered old fashioned, Tig is now the defacto standard. Most racing authorities now require only Tig but gas welding is at least for me, the way I would go for 4130 if I did not care about what the "authorities" think. There are a whole lot of aircraft that were made from 4130 tubing and welded via gas that are still flying after many many years.