welding 4130

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Hi, haven't posted in a while.I just got a possible job to weld 4130 hot rod stuff. The guy wants to weld with the 4130 with 312 SS filler.  In all of my time we have always used 70-S2 80-S2 or sometime s6 filler.  I'm pretty sure the 312 is not an acceptabe weld per NHRA new standards.So why would you use 312 SS.?? I asked the guys at work and they won't accept it either.  What's the deal???bentwings
Reply:Check or have the guy check the applicable rules for what is 'allowed' or not.312 -is- a possible filler for welding on 4130, but it is more expensive than the 'plain' steel fillers.http://www.lincolnelectric.com/knowl...hrome-moly.asp  The best laid schemes ... Gang oft agley ...
Reply:The FAA doesnt accept it, so why would you use it on a hot rod part? Sounds like this fellow has been reading too many car comics.
Reply:weld it with 4130 or 9018 B3 ( 2 1/4 CR - 1 MO).  This has worked for me for the past 30 years.  John GaultSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:Welding with 4130 or 9018 B3 in the as-welded condition on thin walled 4130 tubes is just begging for cracks..
Reply:4130 filler on 4130 parent material is a good match if you will or need to heat-treat after welding.  But to use it, you have to fuss more with pre and post heat and cooling and so forth.And heat-treated hardened 4130 tube would typically not be used for a tube frame on a car/bike/plane/roll-cage/etc, so 4130 filler would not gain any real benefit and just more complications in those applications.312 is a possible filler, but the more common would typically be 80S-D2 for a close match to the parent material properties of the 4130 or 70S-2/6 for a slight undermatch compared to the parent material (which could be compensated for in the joint design/construction so that the net joint strength closely matches the parent tube strength anyway).Check the applicable 'sanctioning' body (NHRA, FAA, whatever) for their rules on filler for welding 4130 tube.  The best laid schemes ... Gang oft agley ...
Reply:I recently visited a race shop that had just finished a cromolly cage in a sportscar, and I couldn't help but ask what filler they'd used and whether they did any special pre/post HT.  They used 312 on it, and said something about all the sanctioning bodies approve it on cromolly cages.  I don't remember ever coming across this in any rules I've read; instead most rules simply say to weld per AWS D1.1 and call it quits at that.  I am curious on this one....
Reply:Probably the best infomation i've come across (outside of dry, heavy going, metallurgy textbooks) on the subject of welding 4130...http://www.netwelding.com/Welding%204130.htm
Reply:that does seem odd but that added ductility would be nice i guess. all of the 4130 i have done has been for light aircraft and our specs called for the 70s-2. i am now dabbling in building bicycles and a common wire for those cro-moly alloys is the weld mold 880t it is a general purpose wire but has proved to be rather good for the dynamic loads that bicycle frames carry.
Reply:Originally Posted by bentwingsHi, haven't posted in a while.I just got a possible job to weld 4130 hot rod stuff. The guy wants to weld with the 4130 with 312 SS filler.  In all of my time we have always used 70-S2 80-S2 or sometime s6 filler.  I'm pretty sure the 312 is not an acceptabe weld per NHRA new standards.So why would you use 312 SS.?? I asked the guys at work and they won't accept it either.  What's the deal???bentwings