welding axle tubes....preventing damage

[g356gear]

hey guys,
I am installing a 4 link in my 69 camaro and I need to weld 4 3" tabs to the axle tubes. What is the best way to minimize heat damage to the differential? Diff is currently complete and still in the car since the tabs have to welded in with suspension at ride height.

[parsonsj]

The best way would be to grind the paint and prep the axle tubes for welding. Tack the brackets in place with the housing in the car. Remove the rear end from the vehicle, remove the axles from the housing, then finish welding. Check the axle tubes for warpage (make sure the housing ends are parallel). Straighten as necessary.

Re-install.

That's the "right" way. You can take all kinds of shortcuts to that. Many folks report simply welding the brackets onto the housing while in the car, never checking for warpage, and having no problems.

Let us know what you do, and how it works.

jp

[g356gear]

what is the clearance between the axle and the tube wall?

[parsonsj]

3" axle tube, 1" axle. Somewhere around 3/4" or so.

jp

[g356gear]

I was thinking of welding 1/2" at a time on each side and cooling as I went with a wet rag.

[Ranaexcavating]

Don't use a stick......... Mig requires much less heat. That is what I used when I welded the tubes on my 12 bolt.

[BRIAN]

It can be done but honestly you are taking a risk without a jig of some sort. How much of a risk??? If you tack on to where you want and take to a race fab shop they can set up in a fixture and weld it properly. The last few cars I have done were all done this way. It costs approx $200-250 which a lot better than hunting down bearing issues on a car that is assembled.

If not try building a simple fixture out of a simple 2x3 with some uprights that you can tack onto the outward and inward most parts of the tubes. It will at least prevent some distortion.


Good luck!!

[parsonsj]

I was thinking of welding 1/2" at a time on each side and cooling as I went with a wet rag.Can't recommend that. Getting a proper weld is way more important than distortion issues. We're not talking about some cosmetic bodywork issue: we're talking about serious problems if that weld fails.

jp

[JRouche]

Ok, there is the best way to do it and the worst, and something in between.. I chose the in between.

Im assuming you arent welding on the cast center, just the mild steel tubes...

As said, prep the metal, remove all the paint, bare metal. Make sure you arent supporting the car by the rear end. And support the axle tubes on each side of the weld so there isnt any strain at the weld area.

I tacked the bracket in at four places, top and bottom, left and right side. Cooled the tacks. And make the tacks HOT, solid tacks.. Then I welded a bead, MIG welded, about 1.5 inches and cooled with a damp, just short of dripping, rag. Move the rag around to get a new cool part of the rag, watch out for steam burns to your hands.

When the steam stopped and it was warm to the touch I welded another bead opposite to the last bead, other side of the bracket and low if I was high on the last one. Continued that way, making sure to get a solid (HOT) lead in from the last bead.

There isnt an issue with starting a new bead off of a cooled one for strength. As long as you dont have any contaminates there, MIG or TIG will keep the bead ends clean.

The tube never got beyond warm to the touch about two inches from the weld. I was welding on a ford 9" rear end so the tubes really are thick enough to not bend with a couple short cooled beads..

The best method?? Well no. Does it work, yes... A welding jig makes it possible to lay down one solid bead (which isnt any stronger, not for this purpose), its timely, a fab shop doesnt have time to cool a bunch of beads, I do. I dont have the time to rip down my rear end and haul it off to a shop or make my own jig.

Just my take on it.. Here is a photo set showing some of it. JR

https://www.pro-touring.com/forum/showthread.php?t=55420

[g356gear]

thanks for the input j. That was my plan, but my access to a mig is limited. I will see if I can find a guy that has a portable mig instead of a stick.

[Matt@RFR]

You've been given some bad info.

First of all, nobody has mentioned that GEAR LUBE IS FLAMABLE. It is hard to catch on fire, but it'll do it. Trust me on that one.

Next, quenching a weld with a wet rag will INCREASE warpage, because the faster the weld cools, the more it shrinks. It also builds more internal stress into the axle tube that is likely to relieve itself with use, so checking the rear end for square after welding but before driving it doesn't necessarily mean anything. Also, quenching will make the welds and surrounding area harder and possibly slightly brittle. Do NOT quench your welds.

There is one, and only one correct way of doing this: Clean the area until you're comfortable eating off of it. Tack your brackets on and remove from the car. Dissasemble the rear end and clean as much gear lube out of it as you can. Cut the housing ends off. Weld brackets. Re-install housing ends using a commercially available locating fixture and assemble car.

Metal is funny. There is no way to forecast how much it will warp due to heat input. I've seen several rear ends done up in the car, and a few of them had zero problems, but the rest of them ate axle bearings on one side only. My best guess is that the weldors position was totally different when welding the driver versus passenger side brackets, resulting in different warpage. If you want to take the chance, by all means, cut corners.

Also, just use your stick welder if you're comfortable with it. 7018 preferably. On the other hand, this is one of those questions that seems, if you have to ask, you shouldn't be doing it. Remember, if any of those brackets break, the possibility of causing serious injury or death to yourself and/or bystanders is very real.

[LowBuckX]

Why remove housing ends?

[JRouche]

You've been given some bad info.

Hahah, whatever dude. You sound a lil boated on yerself.



First of all, nobody has mentioned that GEAR LUBE IS FLAMABLE. It is hard to catch on fire, but it'll do it. Trust me on that one.

Ok, more useful info. Yeah, pretty obvious a petroleum product is flammable. Umm, only if its in contact with replenishing air supply. Did you have a sitch where you popped through the tube and had the oil spill out on yer weld. Bummer. But the oil in the tube is not gonna combust. Sorry but there isnt enough oxygen in the tube for that to happen. If yer lazy and dont cool the tube between beads then the oil may get burnt (doubtful), some degradation of the additives maybe (doubtful again) but cumbust into flames. LOL



Next, quenching a weld with a wet rag will INCREASE warpage, because the faster the weld cools, the more it shrinks. It also builds more internal stress into the axle tube that is likely to relieve itself with use,

What!!! Where did you hear that?? What books have you been reading??? My suggestion is to stop reading and start doing. Ok, so maybe you are, an accomplished welder and machinist.

Sorry but the book that you read that said the faster you quench the weld the more its gonna shrink is BS.. Molten metal, will come to its resting size (cooled) a specific size, all the same. You dont loose or gain the size of the bead by how fast its cooled. Many folks have the wrong idea that the joint pulled more cause it was cooled at a different rate. NO.. If it was cooled by a rapid method or cooled very slowly, say in and oven, its still gonna move the same amount.. Thats why we do have jigs, to force the joint to keep its as welded shape even during a slow cool.

And stresses???? What, its mild steel tubing, gimme a break.. And I have welded all types of metal. Low carbon steel, and high carbon (cast iron) and everything between. The low carbon steel (axle tubes) doesnt have any stresses in it to think about. Its about as normalized as it gets. And very low carbon content. What kind of stresses are involved. Heck, you have more of an issue with cold rolled mild steel plate than you will with this axle tube. Stresses??? From what. You talk like he is welding on some high carbon tube. 4140? Cast iron??? Sorry, I dont know where you are coming from.. I guess I just took offence to your remark that I gave bad info. If need be Ill discusse this off this forum, but I still stand by my advice... JR

[jerome]

When you quench carbon steel with water, you do not allow the carbon to diffuse evenly in the crystal structure, creating martensite, a brittle form of carbon steel. This is not a good crystal structure for suspension tabs.

JRouche, to answer your question about stress:
The localized hot area will try to expand, but the cold metal tube surrounding it will resist, causing stresses. The spot will not be able to expand within the curved "plane" of the tube. The heated spot must then expand perpendicular to that plane. Once it is hot, the metal is more malleable and the stresses will largely be gone. However, when it cools, there will be tension pulling the tube surrounding the spot, into the spot.

For example, heating and cooling a localized area on the top of the axle tube will create negative camber. This negative camber is due to the internal, residual stresses within the tube caused by the cooling and shrinkage of the local spot. Cut this local shrunk spot out, and your tube returns to zero camber. Matt is saying with fatigue and external stresses applied to the whole tube, the internal stress will diffuse and relieve itself, changing what you thought was perfect camber and housing end alignment to an incorrect setting.

I am not sure whether quenching causes more or less shrinkage and thus more distortion. There are definitely differences in density between different crystal structures, but it very much depends on exactly how it was cooled, and what the mechanical shape of the part cooled is. HOWEVER, water quenching does make the metal very hard and very brittle. This is not desirable, and there is no reason to quench the weld.

[JRouche]

When you quench carbon steel with water, you do not allow the carbon to diffuse evenly in the crystal structure, creating martensite, a brittle form of carbon steel. This is not a good crystal structure for suspension tabs.

JRouche, to answer your question about stress:
The localized hot area will try to expand, but the cold metal tube surrounding it will resist, causing stresses. The spot will not be able to expand within the curved "plane" of the tube. The heated spot must then expand perpendicular to that plane. Once it is hot, the metal is more malleable and the stresses will largely be gone. However, when it cools, there will be tension pulling the tube surrounding the spot, into the spot.

For example, heating and cooling a localized area on the top of the axle tube will create negative camber. This negative camber is due to the internal, residual stresses within the tube caused by the cooling and shrinkage of the local spot. Cut this local shrunk spot out, and your tube returns to zero camber. Matt is saying with fatigue and external stresses applied to the whole tube, the internal stress will diffuse and relieve itself, changing what you thought was perfect camber and housing end alignment to an incorrect setting.

I am not sure whether quenching causes more or less shrinkage and thus more distortion. There are definitely differences in density between different crystal structures, but it very much depends on exactly how it was cooled, and what the mechanical shape of the part cooled is. HOWEVER, water quenching does make the metal very hard and very brittle. This is not desirable, and there is no reason to quench the weld.

Hi.. Thanks for the info. From everything I have been taught mild steel, like 1018 does not have enough carbon to reach a martensitic state... All great info for a .2% or higher carbon steel.
Thanks, JR

[Matt@RFR]

The 'books' I reference are AWS D17.1 and AWS D1.1, D1.2, D1.3 and D1.6. There are many other specs that could be of more help concerning quenching low carbon steels, but I don't own them unfortunately. And if you doubt the use of such specs, please note that most DoD, DoT and current MilSpec welding specs refer to the AWS literature in a lot of areas.

Although I found nothing specific on quenching a hot weld, I can tell you that I've had many AWS CWI's, as well as Boeing inspectors and DoT inspectors watch me weld, and I can garuntee you that if I threw a wet rag on ANY hot weldment, red flags would be going up everywhere.

In D17.1 (Specification for fusion welding for aerospace applications), a Class A weld is defined as,
Critical applications. Welds that are fracture or fatigue critical or welds the single failure of which would cause loss of system, loss of major component, loss of control, unintentional release of critical stores or inability to release armament stores, or endangering personnel. and require 100% X-ray testing AND 100% mag particle or die penetrant testing. I fully realise that we are not working on military aircraft here, but given the above quote and the obvious importance placed on weld quality, why would you even take a chance? Read the above quote again, but this time keep in mind those brackets on the rear end. Fits, doesn't it?

Also, how do we know that the brackets that the original poster used were mild steel? There's lots of 4-Link brackets you can buy that are made out of 4130, but nobody asked that.

And as far as catching gear lube on fire; Again, why take the chance? No, it probably wouldn't burn the car down, but there is plenty of air in the rear end to support combustion...and besides, all rear ends are vented. I've never seen one combust and never will, because myself and all of my friends take the time to do things correctly.

The problem with a lot of this stuff is that there is very little documentation for some things. Take, for example, PWHT for 4130N weldments. There are a few documents that outline a tested process (Lincoln has a good one, which I think most are based off of), but there are still a LOT of guys who disagree. Do a search on the subject and you'll find some pretty epic battles over the subject, with no declared winner.

The example for this topic is quenching and its effect on warpage. No, there is no documentation on the subject and never will be because it's one of those areas of metal fabrication that falls under the 'art' category. All I can tell you is that, in my experience, if I ever wanted something to pull or shrink further than normal, I'd quench it as long as there was some form of PWHT to be performed. Example:

I used to build big tanks in excess of 30,000 gallons. Most were mild steel, and we ordered big ass plate to build them out of. Something like 1/4" x 10' x 20'. The edges of those plates were nowhere straight, and prior to rolling, two plates needed to be welded together to make up one section of a tank. The process was to fit both plates in a butt weld configuration on the floor as close as possible, and tack together. Starting from one end, weld as far as the fitup allowed, then alittle further. Immediately after welding, the last part of the weld was quenched to force the two plates together. Repeat until one side was welded. Flip, and weld other side with 7018 getting atleast 75% of T penetration, which would effectivly PWHT the quenching process done on the other side. As this was commonly done on DoT controlled vessels, this was all documented and and tested via X-ray and chemical analysis.

The difference between you and I, JRouche, is that I always choose the safest way to go. Yes, it takes a lot longer and it's a pain in the ass at times, but when I send a customer out of my shop, he or she can rest assured that the welds on their parts are comparable to critical welds on aircraft, if so needed, and I can provide plenty of documentation to prove it.


Hahah, whatever dude. You sound a lil boated on yerself. I never claimed to be anything else. All I can tell you is that I've been a welder for 16 years now, and have had the opportunity to build some incredibly complex and rigorously government and military regulated stuff, and I've had some great, in depth conversations with metallurgists and welding inspectors that have forgotten more than I'll ever know about this stuff. I've also been involved in a lot of not-so-critical work like rock crushers down to fixing an old lady's mobile home door. I know when to treat things like an aircraft and when not to, and 4-Link brackets on a rear end clearly (to me, anyway) fit in to the former category nicely, and I think my customers and employers appreciate that.

[parsonsj]

PWHTThat's Post-Weld Heat Treat(ment) for those watching at home. I think. Matt will let us know if I'm wrong.

jp

[JRouche]

The 'books' I reference are AWS D17.1 and AWS D1.1, D1.2, D1.3 and D1.6. There are many other specs that could be of more help concerning quenching low carbon steels, but I don't own them unfortunately.

Oh no, AWS is the standard for welding, the bible... Thats what I was looking for. Ok, you cite a few sections. Any specific references in the pubs (page number would help) that specifically talks about either gas or arc welding MILD steel and brittleness? If I see it in the AWS pubs then Im sold. I have the full set here, havent seen it while searching and searching, but Im not great in that area. Page number and Ill go read. I do agree with you. AWS is the reference to use. I use it all the time and can not dispute it.



Although I found nothing specific on quenching a hot weld, I can tell you that I've had many AWS CWI's, as well as Boeing inspectors and DoT inspectors watch me weld, and I can garuntee you that if I threw a wet rag on ANY hot weldment, red flags would be going up everywhere.

Im not saying you are not a great welder, that wasnt the issue at all. My instructor was an aerospace welder for years before going to education. And he would have never said to quench a critical weld with alloy. And my bro in law was a welder at san onofre nuky station for years and if I suggested quenching an alloy weld he would have just chuckled and changed the conversation.

I have full heat treating capabilities here. Including a couple of nice rockwell testers. Im just a hobbyist but hold pretty close tolerances when it comes to heat treatment of alloy steels. I understand ALL the processes with heat treating and various quenching methods.

But when you were welding on aircraft, were you using 1018 steel????






Also, how do we know that the brackets that the original poster used were mild steel? There's lots of 4-Link brackets you can buy that are made out of 4130, but nobody asked that.


They weren't.. If they were he wouldnt have been asking. But.... If by chance they were then YES!!! You are correct in all you said. And really, even if they werent, you are still correct. The proper way to weld the brackets up is what you said. But thats not the ONLY way. Thats ALL I am saying.



And as far as catching gear lube on fire; Again, why take the chance? No, it probably wouldn't burn the car down, but there is plenty of air in the rear end to support combustion...and besides, all rear ends are vented. I've never seen one combust and never will, because myself and all of my friends take the time to do things correctly.

Im sure you and all your friends do EVERYTHING correctly. Prolly why theres no room for anything else. Im not even trying to change the way you and your friends do things. You have it all and do it all just right, correctly. But there are a large group of folks, farmers, bikers, car guys and just average guys doing what ever they can to get things rolling. And Im part of that group. Me and my friends dont always have the means to do everything in life "correctly"..




The problem with a lot of this stuff is that there is very little documentation for some things. Take, for example, PWHT for 4130N weldments. There are a few documents that outline a tested process (Lincoln has a good one, which I think most are based off of), but there are still a LOT of guys who disagree. Do a search on the subject and you'll find some pretty epic battles over the subject, with no declared winner.


And right again. Im a member over at Lincoln. There is a large amount of information there. And like you said, some righteous battles.. I honestly didnt want a battle, Im not prepared, I only fight the fights I can win and Im by no means an expert on welding...




I never claimed to be anything else. All I can tell you is that I've been a welder for 16


Ok, I will or I do apologize for my rude comments. I was just heated. I saw you as taking a direct poke at me for my simple advice. I dont come here to get into a pissing contest. I come to learn mostly. Pick up tid bits of useful info. And there is alot of info, some good, some not so good. So I weed out what I want on my own.

And I see you are trying to keep a guy from snapping off his rear end. I still hold my point that its not gonna happen if its mild steel and all the methods I gave are followed.

Im not a fab shop with all the great tools and knowledge like you. I am building one car, mine. So if what I do causes me to loose my car or life then thats within my insurance policy. You are building products for others to use, you have to make sure to go that extra step to ensure there isnt any breakage.. I get that...

Anyway.. So... Solly for taking it personal, my bust. Ok, Im off to work on the car. Where the heck is that screw driver. Oh yeah, there it is, its acting like a control arm shaft, hope it holds up LOL JR

[g356gear]

Well....thanks for all the valuable info. I got a guy in with a MIG to do the welding and it worked out perfectly. We did 1/2-3/4" welds on each bracket, moved to the other side, repeated, and let cool for 10 min after each weld. I double checked with Frank at Prodigy on this method and that was what he recommended. He has had no issues after several installs. I asked the welder about the wet rag, and he said that tended to make the weld brittle. Better to let it cool slowly. It took about 2 hours but it worked out really well. We tacked them in and then dropped the assembly down to floor level so he could work on the axle.

[JRouche]

Well....thanks for all the valuable info. I got a guy in with a MIG to do the welding and it worked out perfectly. We did 1/2-3/4" welds on each bracket, moved to the other side, repeated, and let cool for 10 min after each weld. I double checked with Frank at Prodigy on this method and that was what he recommended. He has had no issues after several installs. I asked the welder about the wet rag, and he said that tended to make the weld brittle. Better to let it cool slowly. It took about 2 hours but it worked out really well. We tacked them in and then dropped the assembly down to floor level so he could work on the axle.

Outstanding.. I gotta stop giving advice and go back to doing what I do best. Swiping all your guys great ideas here. Glad you got it welded up. Cant wait to see the finished product pics, not nearly as much as you though huh.. Solly for turning your thread into a rats nest... Good job, JR