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hi everyone i'm new here and have found this site to have a good knowledge base so i'm wondering if i can shoot a couple of questions at you guy'sfirst off let me give a quick note on my experiencei have been welding for many years hobby kind of stuff cars, atv's,and just general welding around the shop with mig,  stick, and gas and have lately been wanting to get more into it, i plan on getting a tig in the near future here's my questionsfirst can you mig chromoly and if so a quick rundown of the processand second how does mig welding cast aluminum differ from other aluminums thanks   Ed...
Reply:Welcome to the site!!,  It can be mig welded. But don't use 4130 filler unless you plan to heat treat afterwards. Otherwise you'll have a brittle joint. 4130 is considered a heat treatable low alloy steel with relatively high carbon content. Rapid cooling, as with mig, produces a tendancy to form martensite with carbide precipitates in the weld zone, which promotes hot cracking. Using 4130 filler would just add even more carbon and make the problem worse. To reduce the cracking tendancy, you could use a mild steel filler and some preheat and postheat, around 200- 400 deg F. For this reason O/A is probably better than mig for 4130 since it heats and cools slower. That's for the chromoly steel.  I don't work with much aluminum but someone that does can chime inStangnetShop Full Of Stuff. Joey
Reply:i cannot stress enough that c.m. shouldnt be welded!  tig or o/a only.........cast alumunum is a beecth anyway you slice it !b-
Reply:Bonez, i believe most competitive auto racing groups require that 4130 be used with Tig onlyStangnetShop Full Of Stuff. Joey
Reply:I am new to this forum.I do know for a fact NHRA (National Hot Rod Association) and IHRA (International Hot Rod Association) both require 4130 be TIG welded only.  ( I worked as a tech inspector at a local drag strip a few years ago).  I would presume other sanctioning bodies (NASCAR, DIRT, WoO, etc.) have the same requirement.Hope this helps!
Reply:Originally posted by xtrmdrm I am new to this forum.I do know for a fact NHRA (National Hot Rod Association) and IHRA (International Hot Rod Association) both require 4130 be TIG welded only.  ( I worked as a tech inspector at a local drag strip a few years ago).  I would presume other sanctioning bodies (NASCAR, DIRT, WoO, etc.) have the same requirement.Hope this helps!
Reply:while that might be true the e.a.a. is mostly o/a welded and if its good enough for airplanes i think that it would be okay for a roll cage on a street car b-
Reply:Originally posted by bonez while that might be true the e.a.a. is mostly o/a welded and if its good enough for airplanes i think that it would be okay for a roll cage on a street car b-
Reply:CM can be welded with mild steel, its done all the time with MIG.www.urkafarms.com
Reply:The NHRA 2005 rule book states in Section 16 (General Regulations), Sub-section 4:11 (Roll Cage), second sentence, and I quote: "All 4130 chromoly tube welding must be done by approved TIG heliarc process; mild steel tube welding must be approved MIG wire feed or TIG heliarc process".  The IHRA wording is almost the same.Why, you ask, when other processes are sufficient?  I have no idea.  But rules are rules and the chassis certification teams DO inspect the welds for grinding, slag and porosity.  Maybe the powers that be at NHRA in Glendora, CA or IHRA in Norwalk, OH can clarify.I hope this helps...