If you tig weld chromemolly it needs to be heat normalized after. The process isnt that hard but you should know what your doing. Chromemolly is diffrent than mild steel.Tig welding mild steel doesent need anything but a good weld. Theres nothing wrong with mig welding but you dont weld chromemolly with a mig welder. I know its nice having a mild steel chassis over chromemolly at the circle track for repairs. Nothing like sprint cars.

 

Jdustu, you should reread some of the BS you’ve posted here and then you’re response to me. You either contradict yourself or state something just wrong in every case…

What, don’t you already know so you can educate the rest of us?

Not that it matters and I don’t know why I’m wasting my time, but you need a lot of heat but not particularly localized and you need to prevent oxidation. Mapp will work for aluminum braze but not weld, and no matter what you’ll need flux to gas weld aluminum otherwise you’ll get oxidation and you’ll never melt through the surface.

You _should_, you don’t have to. It makes no sense to use 4130 and not to heat treat it but it will work.

What the hell does “Tigging is better because its a 100% weld” mean? Penetration? You can get 100% penetration with MIG. I’m not sure what else 100% could mean.

“it brings the heat on slow and cools down slower for normalization.” Um, do you know what it takes to normalize 4130? Look it up, the rates that ANY welding process heat and cool are orders of magnitude off of what you need to normalize 4130. As a matter of fact, the only kind of heat treat that you’ll get with any welding process is just a very localized hardening

Oh man… it’s like you guys can’t focus on anything to even have a proper argument; most of this “discussion” is about one of you saying something, and then the other not paying attention to what that something is and latching onto a part of it, adding some incorrect details and then telling them that the details are wrong.

TIG welded chassis? NO, you can TIG weld a cassis out of carbon steel which will not heat treat at all.

Heat treat a 4130 chassis that was TIG welded… well if there was a good reason (besides some arbitrary rule) to build it out of 4130 then it would only make sense if you heat treated it, but of course, no one heat treats a whole chassis.

Since you all have such a hang up on TIG and 4130… explain to me why anyone (and this is quite common out there now) that 4130 air frames are MIG welded from the factory now.

 

You do NOT heat treat a welded Fuel Dragster, Fuel Funny Car or Pro-Mod chassis. They can not be Certified by NHRA unless the material is 100% 4130 because it is stronger. I have built many for 2 well known Chassis Builders & I declare that you are officially FULL of ****. Silverback,lets you & I put each other on our "ignore list" Your going on mine now so wave your MIG gun.

 

Wow , i didnt think this was going this far. Heat treating is just a way to normalize an area after welding. Chromemolly needs to be treated at the welded joints ,thats it. Ive seen alum. welded with no heat treat and by design it can fail. You heat treat heads after you weld. Now ive seen other people weld chassis with no heat treat and thats their deal. If its going to be x rayed or suspension it should be done, its not a big secret. I dont build airplanes so if sombody welds chrome. with mig thats their deal. Ive seen a offroad chassis migged in chrome and it had problems. Usally chassis are designed so well it wont flex and be a issue. As far as tig being 100% penatration and mig not, well look into it. Im not arguing just sharing with other people.

 

100% true

That’s a misconception, if you built a chassis/cage as per NHRA rules, the chromemolly chassis that is legal for faster speeds is not as strong and nowhere near as rigid as the same setup built out of mild steel which is not legal to the same speed (for example at the 8.50 in the 1/4mile point).

It’s a stupid rule, or at least one that doesn’t make sense the way it is written and enforced, which is the same reason why cup cars (nascar…) don’t allow 4130 cassis/cages.

 

In non-pro classes like xtreme-street 2 x3 inch rect. tubing with a 0.125 wall is equal to 1.625 O.D. round tubing with a .083 C.M. or .118 M.S. Many sportsman racers use M.S. because it is cheaper & can be MIG welded . C.M. must be TIG welded & is more difficult to work with.If you are going to "back-half" a door car M.S. is cheaper & often found on budget cars. C.M. can become brittle as (some say) it "work hardens or becomes brittle" with long term use.

 

You know, you just have a hold of some incomplete/confused information and are using incorrect terms to describe what you’re talking about.

“Heat Treating” is to use heat to change the granular/crystalline structure of the metal. In the case of chrome molly this involves temperatures above 1200* F and different cooling rates depending on what you're shooting for. For normalizing and allealing (to normalize you anneal, make it as soft as it will go, and then you heat treat it to slightly harden it back to normalized condition where it’s about the same strength as mild steel and workable) you have to spend _days_ at this kind of controlled temperature. Another thing that have to remember is that 4130 does not like to be heat treated to any state beyond a very thin section, somewhere in the range of .1” is about has far as you can go

What you appear to be describing is “stress relieving” where you heat your chrome molly structure with a torch, usually around the welds and let it cool slowly (usually tented in still air or buried in sand). If you get it right, don't exposed the heated area to any breezes... you don't significantly change the heat treat of the material, you just don't get it hot enough or keep it there long enough to make significant changes. For this to be at all effective you need to really have to preheat the 4130 before welding also.

WRT to stress relieving welded 4130 structures there is a bit of a valid debate what the correct way to do it is or if it’s necessary at all, the reason being that when properly tacked up and then welded with a TIG, or even more so with a MIG (faster welds that put less total heat into the structure), you don’t put that much stress into the welded structure to start with, like if you welded a 4 sided box out of tube and cut straight through one side the 2 sides of the cut would still stay pretty close to lined up, where a more traditional 4130 aircraft weld (done with a torch and ER70 mild steel rod) would put more heat into the structure and be less likely to still line up if you made such a cut, and in that case there is a better argument for post heating/stress relieving.

And yes, it is fairly common in the 4x4 world to see MIGed 4130 cages, and same deal with newer home built or partially factory built airplane chassis, and they do see problems, but they’re the same problems as you see with all welded, non heat treated (not stress relieved, heat treated…) CM structures. It’s not uncommon to see one of these airplanes after they experience an uncommonly hard landing where a whole mess of the joints are cracked right next to the welds. Basically the sudden stress and the hardened (and brittle) areas next to the welds combine to result in parts of the structure that are prone to cracking.

Plain and simple:
1- there is no limitation due to the process (MIG vs TIG) that will cause one or the other to not be able to make a weld with 100% penetration. Both if done correctly by a reasonably decent welder will do it. If you’re not able to get 100% penetration with a MIG it’s not the fault of the weld process but the fault of the welder’s ability, joint prep…
2- you don’t want 100% penetration in all welded joints, there are joints specifically designed with less then 100% penetration. Using correct filler with a proper fillet/bead, a 100% penetration weld in steel will be stronger then the base metal because the weld fillet + penetration will have a greater cross section then the base metal. In applications where that fillet is not giving you extra rigidity in that plane you’re just wasting money by running a 100% penetration weld (of course this consideration is much more an issue in heavy, industrial applications then in motorsports)

I honestly don’t see what you’re so worked up about in your last post, for the most part we agree.

My only point WRT to that comment right there is that, yes, everything you wrote is true (although I don’t think that any of us got into the work hardening aspect yet), but since C.M is not more rigid then MS at all and no matter who’s strength numbers you use it’s not 45% stronger then 1020 (based on comparing .120 to .083, I know the MS spec is .118, but real world you end up using stuff that ends up in the .120-.125” wall because that’s what’s available. I’ve heard of NASCAR and similar guys taking the heavier wall stuff and cutting it on a lathe to have a wall thickness EXACTLY to spec it’s whole length), that you end up with an inherently weaker chassis/cage if you follow the rules to the book and use the lightest CM that you’re allowed vs the lightest mild steel.

For example, totally leaving out the welding, assuming that you don’t hit any other limitations, you can build a mild steel chassis using mostly .118 wall MS that is legal to only 8.50, but as soon as you go 8.49 you’re required to build the same chassis out of CM, but now you can use .083” wall tubing in the same OD. Since in the same cross section normalized CM has the same rigidity and close to the same strength, that thinner wall CM cage that we have now is legal to go faster, but is both significantly (like as in around 40-45%) less rigid and strong.

 

what the heck are you talking about?

maybe instead of a sweeping(and wrong) statement like that you could post some evidence? oh wait, the last time you did that i showed that you were the one who was wrong....nevermind

yeah, and thanks for the aluminum gas welding advice.....aluminum oxidizes fast? you need to use flux? no way

 

Silverback. you know what im saying. Yes im misswording a little,typing isnt my thing. You self admitted that mig chrome. has problems, hence the tig welding. Yes i ment stress relieving and was hoping if people interested would look into it. Ive always tig chrome. and stress releive the joints and preheat, post heat. Read what i said before about no cold welds. I wasnt trying to give a play by play on chassis 101 and welding. Sombody wanted welder advice and yes the htp is a good welder. Get water cooled. Ive used about every tig made and its about the best bang for buck. Theirs a place for mig and a place for tig and when you have welded long enogh you will see that. Still look at tig as a 100% weld. Go look it up ,maybe i forgot in all this time. As far as using chrome. over mild, Its the rules ,its cost ,its what you want out of car, just a few things that factor a race chassis. Note i said few. I see you get what im saying, why split hairs.

 

motormonkey, not really splitting hairs, just putting down correct terms and differences so someone isn’t confused/mislead later on. Pointed out that that is probably what you meant, gave correct info, moved on.

For example, jdustu is an idiot. Not splitting hairs, stating fact, I’m done.

As far as welders, HTP is one of the better, underrated names out there, I’d put them with the thermal arc inverters as far as TIG welders, although both prices are climbing and making some of the big name welders look more appealing. As far as what I use… I use what is available in the shop I’m at which lately means a lot of Lincoln and Snap On (I’m sure someone else makes them for them, I suspect century or htp) welders as well as a BIG, OLD miller dialanarc the size of a fridge. What do I use in my own shop, Tan and Blue (I know, pretty much the same company). I’ve got a Hobart MIG and a Miller Synchrowave (the synchrowave is relatively new, before that I was using a TIG that I built myself which is now sitting in the dining room while I debate if it’s going to get used for parts or I’m going to keep it together as a portable unit, it’s much smaller then my sychrowave but can’t do aluminum), oh and an htp plasma cutter.

I use what is appropriate to the application. For example, this weekend I used the TIG to weld a fill and drain bung onto a 9” rear, and then the MIG for some custom brackets on that same rear (no point in running the TIG for something that involves a lot of filler and the most visible parts will have the welds ground flat to clear some fasteners anyway). Later I plan on using the TIG to fix and then add some fittings to some old school M/T valve covers, because it’s the most appropriate tool for the job. OTOH, sometimes I choose one or the other, or modify procedures just to give things the appearance people expect

 

You are right!! I thought the talk was about heat treating the whole thing!! I do believe some terms have been misused( at least by me) in the thread. I don't weld for a full time living like some of you. My welding was a by-product of growing up on a farm. We did not go to town to fix anything we could do at home. Got to be pretty fair with oxy & coat hangers..In high school we had old Lincoln Cracker Boxes!! Talked the family into one. Later in life the heli-arc came along,had to have one (I thought) for race car stuff......and on & on. Now I use a Miller Dynasty which I bought because my "fridge sized Lincoln" was not square wave & I wanted lift arc,an old Syncrowave 250 that I mostly use with a spool gun for alum.,ESAB Plasma Cutter,Victor oxy/ac outfit. Anyhow sorry, didn't really mean to DIS anyone. BTW Silverback.... I totally agree with your chassis/NHRA comments. That .118 used to be .125 & even they saw how foolish the CM/MS ratio was. Scott

 

poor ol stick welding is left out in this thread...

 

I agree i was in hurry so terms were off but my point was if your doing chrome reaserch it first. . I also agree htp is a understated machine as far as tig goes. I didnt care to much for their mig welder though. The best mig so far that i have used is miller. Its funny when you mentioned " refrigerator" welders. I used to use a linde tig. Heck my freind had a linde in his garage and needed a forklift to move it around. Ive had trouble with early lincoln electronic tigs with the boards burning up. I think its fixed now. The snap on stuff is italion. The esab, htp, and i think lincoln now is european. Whatever welder someone buys ,the inverter tech. is pretty nice for the money and the older trans. style welders have a nice steady arc.

 

i love it when someone resorts to name calling.....but i guess when you don't have leg to stand on that's what you have to do? i responded to your first post and pointed out the errors and assumptions you made.....you chose to ignore that, instead saying that i'm full of b.s. and calling me an idiot

maybe point out exactly where i'm wrong, and then i could learn form my many mistakes?

 

jdustu, Just to clear this up, I didnt call you a idiot. Not sure how that cut paste works but my name is tagged to a line i didnt write. Not sure if you think so.

 

yeah, i know whose doing the name calling

thanks though

 

Jdustu, I’ve already pointed out exactly where you were wrong and you chose to ignore the facts that I specifically cited WRT to why you were wrong. There is no debate here, unless you live in a world governed by different physical rules then the rest of us that is the case.

You should learn to tell the difference between someone who resorts to name calling “because they don’t have a leg to stand on” and one that makes a statement because they feel political correctness is nothing but a refuge for the meek and refuses to waste any more real time on someone who will not listen to anyone but themselves. I can keep repeating things till I’m blue in the face but it won’t do you any good till you decide that you’re going to listen.

For that matter, if you want to call me names go for it, I don’t really care, the only reason I said something in the first place is to state correct facts WRT to the discussion at hand. I don’t really care if you think I’m a flaming ******* as long as you add facts or interesting/useful opinions or experiences to the thread.

 

Wow, I was really expecting the board to sensor some of that

As far as stick welding…. The fact is that someone really talented with a stick welder could in theory install a mild steel cage that would be impossible to distinguish from one installed with a mig (especially a mig loaded with flux core), OTOH, to do that would take someone VERY talented… I know that I’ve installed subframe connectors in a pinch with a stick welder and was successful, but just for appearance sake I wouldn’t do it to anyone else’s car unless they understood that “this won’t look as nice as if I just had a mig setup.”

OTOH, no reason why you can’t grab a 2 lead TIG torch with a gas valve (I've bought real weldcraft 17 series torches for $20-40 on ebay, new), hook it up to the arc welder and do some scratch start tig welding with it, then you could do MS or CM totally legally...

 

yeah, and you were full of crap

this has nothing to freaking do with political correctness, and everything to do with you not grasping the concept of discussion.....usually when someone resorts to name calling, it's because they can't defend what they were saying in the first place......

you made a post decrying my "assertion" that a weld inspector would never ok a weld without testing it as "bullshit"....what i had actually said was that the inspectors i talked to had never seen a tig weld FAIL after it had PASSED a visual......so you started off by putting words in my mouth and i set you straight

then you added to that statement by saying that "the (tig)process lends itself to making pretty beads no matter what the conditions underneath are." which is completely untrue....the tig process, more than mig or stick, recquires good fit and a clean surface to make a bead that would pass visual inspection


you talk about me ignoring facts, and yet it looks to me to be the other way around......but if you want to ignore me as well then i won't be heartbroken, just refrain from calling me an idiot when you have no basis for that comment whatsoever

hmmmmm....sound familiar???

 

Ive got a question on a side note...


I jus picked up 160 ft of 1.625 .083 Chromoly from my friends at RIT in rochester ny for a absolutely smoking price. My car is hopefully heading to the chassis shop at Alfred States automotive college here in western ny this weekend for backhalf and roll cage fab and install. Both the shop intsrutctor at RIT (who is also head fabricator of the baja team and mini F1 team they run) and the chassis instructor at alfred explicitly told me that i would be fine having my cage and rear kit mig welded instead of tigged and because of that i do not have to have it heat treated. also mild can be welded to chromoly and vice versa with no problem. The reason its getn migged is becuase my car is sitting in as my buddies chassis project for class ( whom of which i do trust to do the job right) and they dont have the time to become experts with the TIG. Plus i just supply the materials and its free labor. fair enough, that being said should i stay with the Chromoly or try to sell it off to my local chassis shop in trade for mild steel.

Alot of what reading is starting to make me alittle nervous about having the moly in the car, Originally i thought the only reason that the moly had to be tigd was because NHRA required it to be. I already have the moly sitting on my shop floor and dont really go through the hassle of getting mild instead. So i guess im looking for a straight up answer can my chromoly cage be mig welded and still be safe? alot of the failures you guys discussed were in airplanes where im assuming the stresses are much higher than most drag cars.

oh, and i got the 160ft of moly for 65 bucks per 21ft stick, real cheap.

sorry for the long post but i need to get this clarified before im at the point of no return

-john