Tig welding 4130 chromoly

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I've got a buddy with a race car who wants me to touch up his roll cage. It appears the person who welded it before, left a bunch of "chicken poop" instead of weld. I used to weld 4130 quite frequently at my previous job, but that was all heavy wall stuff, this cage is about .125" wall. I'm wondering if I need to do the preheat and postheat as I used to do? Also my buddy assumes it is 4130, is there any way to get a good idea of the correct material? Any suggestions are welcomed.thanks, ModyCalgary, AB
Reply:Originally Posted by fastpokeI've got a buddy with a race car who wants me to touch up his roll cage. It appears the person who welded it before, left a bunch of "chicken poop" instead of weld. I used to weld 4130 quite frequently at my previous job, but that was all heavy wall stuff, this cage is about .125" wall. I'm wondering if I need to do the preheat and postheat as I used to do? Also my buddy assumes it is 4130, is there any way to get a good idea of the correct material? Any suggestions are welcomed.thanks, ModyCalgary, AB
Reply:Pretty sure I've read threads here that say it is common to TIG weld thin 4130 such as this with E70S-2 filler and no preheat/postheat.Did you try a search of threads here?Here you go, from Old Dad in a past thread:http://www.lincolnelectric.com/knowl...hrome-moly.aspLast edited by pulser; 02-26-2008 at 01:02 PM.
Reply:NHRA requires wall thickness to be 0.120" minimum if mild steel is used, and 0.083" minimum (IIRC) if 4130 steel is used.  Assuming you're talking about a drag race car, and your buddy's tubing wall thickness is 0.120-0.125", it is most likely mild steel.  4130 steel is preferred if a racer can afford it, since the thinner wall tubing results in a weight savings of 30%.  And, from what I've read about welding 4130 steel for race car and aircraft frames, pre and post weld heat treatments are not common.  If you weld a cage into a car, how would you accurately heat treat it at 1100-1250?  Put the whole car in a furnace?
Reply:Originally Posted by turboimpalaNHRA requires wall thickness to be 0.120" minimum if mild steel is used, and 0.083" minimum (IIRC) if 4130 steel is used.  Assuming you're talking about a drag race car, and your buddy's tubing wall thickness is 0.120-0.125", it is most likely mild steel.  4130 steel is preferred if a racer can afford it, since the thinner wall tubing results in a weight savings of 30%.  And, from what I've read about welding 4130 steel for race car and aircraft frames, pre and post weld heat treatments are not common.  If you weld a cage into a car, how would you accurately heat treat it at 1100-1250?  Put the whole car in a furnace?
Reply:You don't need pre or post heat..Grind down the crap welds as best you can and then do your thing and call it a day.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by fastpokeI've got a buddy with a race car who wants me to touch up his roll cage. It appears the person who welded it before, left a bunch of "chicken poop" instead of weld. I used to weld 4130 quite frequently at my previous job, but that was all heavy wall stuff, this cage is about .125" wall. I'm wondering if I need to do the preheat and postheat as I used to do? Also my buddy assumes it is 4130, is there any way to get a good idea of the correct material? Any suggestions are welcomed.thanks, ModyCalgary, AB
Reply:If you're dealing with a drag racing chassis then the link that pulser gave you is all you need...that is basically the industry standard. Also, you stated .125 wall, that would be mild steel as someone already stated. If you need more info to be comfortable with the answers given by Lincoln Electric and also the NHRA/IHRA rulebooks with references to SFI specs then you probably shouldn't be doing the job.Anything worth doing is worth doing RIGHT
Reply:Originally Posted by olddadIf you're dealing with a drag racing chassis then the link that pulser gave you is all you need...that is basically the industry standard. Also, you stated .125 wall, that would be mild steel as someone already stated. If you need more info to be comfortable with the answers given by Lincoln Electric and also the NHRA/IHRA rulebooks with references to SFI specs then you probably shouldn't be doing the job.
Reply:Originally Posted by pulserPretty sure I've read threads here that say it is common to TIG weld thin 4130 such as this with E70S-2 filler and no preheat/postheat.Did you try a search of threads here?Here you go, from Old Dad in a past thread:http://www.lincolnelectric.com/knowl...hrome-moly.asp
Reply:Originally Posted by Donald BranscomYes you weld 4130 with ER70-S2 filler wire. The ER just means cut length tig filler wire. The 70 is 70.000 psi. tensile strength.It is good to just pass a torch over the weld joint prior to welding. It may look dry but as soon as you pass the torch over the joint you will see moisture gather and then disappear.About RE WELDING.... Not good in critical applications.You would need to grind out the previous weld or part of it, check the fit up too if possible. Welding inspection cannot be done AFTER the fact.When the metal is welded a second time the HAZ (heat Affected zone) will suffer further degredation of the base metal. I would carefully think about that and what this weldment will be used for. Remember if it fails and costs someone their life will the relatives want to sue you ??? Just be carefull and make sure you have clear agreements and maybe somthing in writing to let the owner know you cannot be held responsible.You do not need to heat treat. just let it cool down on its own.There are hand held analyzers that can tell what metal you have, but they cost $3000.00Sometimes there is printed information on the tubing.If you can see inside the tubing there should be no seam sticking up.If you measure the outside of the TUBE it should be an even number like 1 inch or 1.5 or 2 inch then you know it is a tube and not PIPE. Make sure the weldment has no oil on it before welding.
Reply:just a thought--the brief showing of moisture is not moisture in the steel. water is the combustion by-product and the steel is initially cool enough for the moisture to condense on.then the steel rapidly warms to a point where the water cannot condense.
Reply:Originally Posted by makoman1860I aggree on re-welding it being vital to remove ALL of the old weld material. In the case of it being 4130 , reheating by welding again shouldnt bother the base material much, the weld temperature is bringing the weld area up to the austenizing temperature so no harm there. the HAZ grain size shouldnt grow enough to cause an issue.
Reply:Originally Posted by olddadBy reheating a finished weld after it has cooled you are in effect causing further embrittlement. The original weld will have already taken the moly to the accepted state, by further heating (or in this case reheating) the joint you are taking it into another state. Your statement would only be true if you were laying the initial weld...not subsequent welds after cooling.