Another welding thread, Cast iron

Ok, I've had a lot better welders than me argue with this and I expect it will also happen here but this method has worked 100% of the time for me.
Subject, Welding cast iron manifolds.
The method I have found works best for me is actually pretty simple, no pre-heating is needed. Clean up the area and Vee out the crack at least 2/3 the thickness of the parent metal. Vee past the ends of the crack. I use the cheapest cast iron rod, not the Ni-rod or high nickel stuff. Run it in as hot as you can without burning through.
I've even done this with cheapo AC welders. Run a short bead, about 1/2 to 3/4", then with the pointed end of a chipping hammer, peen the weld until it cools almost to the touch. Your chipping hammer should be leaving little divots, this is relieving the surface tension of the welds as it cools and shrinks. If the manifold is in 2 pieces, tack in several places using the same technique. Also I jump around and don't weld all in the same area each time, a little here and a little there. Repeat until finished. When you think you are done, grind the area lightly. If you see any undercut it has to be filled. When you are done, finish with a flap wheel or less aggressive sanding disc like 80 grit. You'll want to see a pretty smooth surface. Also, sometimes you might need to bolt the manifold to an old head or clamp it to a welding bench to keep the pieces in place and straight.
On a side note, some manifolds are not repairable. A good success rate is also knowing which ones to pass on.
FWIW, my off topic daily driver has been running one of my welded manifolds for over 5 years, no problem.

 

I've repaired quite a few exhaust manifolds with my Henrob gas welder, and old piston rings. No peening necessary, and it even does an acceptable job on parts with crappy cast iron. Just have to put a blanket on it to cool slowly.

 

I've assisted in willow's way decades ago, and within the last few years had great success with low amp tig. There's a 9N tractor still goin with an axle housing ear I tigged with silicon bronze rod about 9yrs ago. The back blade's never been off since. 2yrs ago I tigged an old cast iron bistro chair leg with a unique alloy that I'd got a hold of for bumper repair. It's been dropped and banged around for 2 summers at the salon with no ill effects. I'll have to look up that stuff and tell ya's what it is, ut the repair was basic welding, slow cool, job done, no pre-heat. We're all guilty of over thinking sometimes. Blocks, manifolds, other heat-cycle stuff, I agree that cast iron rod is best. Logically, similar metals. I like the ring idea...

 

Using the methods described to this point, what works in one case may or may not work on the next. If the repair works then good. If not, don't be surprised.

 

I like the cast iron ring idea too. Do you have to make sure it's all cast iron or does it hurt if there's Moly in it?
An amusing part of this story is all of the old guys (when I was young) thought you could only weld cast iron if you preheat the whole piece. I'm sure it is necessary sometimes but I seldom do. But it isn't like I do this every day either.

CutawatAl, I WOULD actually be surprised if it didn't work.I've welded maybe a dozen manifolds this way in the last 30 years or so. Even a couple on circle track cars, and to my knowledge never had one come back apart.

 

Most piston rings have some moly in them, I can't see it making a difference. But I can see it as a great source of filler material.

If you do choose to preheat something, it really should be a uniform heating of the whole item or not at all. A localized heating with a torch will probably do more harm than good.

There are more ways to skin a cat, but most will make you puke. Your results may vary.

Bob

 

I have had excellent luck by knocking the flux off of a Ni rod and using it as a filler rod with TIG. As always, it depends on the condition/quality of the cast iron.

 

You can have custom arc welding rods made, to your alloy specifications.
I know a guy who took a sample from an engine block, sent it off to the company and they matched the sample, then made arc rods for him using the same alloy.

He strips the flux off, and then uses the rod as TIG filler. He V-s the crack as described above, welds for an inch and then peens the weld with the chipping hammer as it cools. Once it's cool to the touch, he moves on to the next inch.

Not only does that stress-relieve the crack, but it textures it so it has the same appearance as the surrounding cast metal.

He has repaired a LOT of rare engine blocks with this method, and it works every time.

-Brad

 

Brad, that sounds like the same basic technique. I'm not saying I invented the process but it was self taught over years of experimentation, including wasting a lot of brazing rod trying to duplicate some welds I had seen old timers do. I also taught myself to weld spring steel because the old timers told me it couldn't be done (successfully) but that's another whole subject.

 

Saw this done decades ago but instead of a chipping hammer he used a ball peen. Same thing, you are pushing the weld metal down into the weld area while it is first cooling which is when it shrinks the most.

 

Similar metal would be best. You can test the metal with a grinder and observe the sparks as a kind of backwoods way of telling. Cast iron shoots kind of yellow stars in a short spread out pattern and steel are smaller stars, and longer, less yellow and more focused spray pattern.

 

As HAMB Metallurgist, let me give some metallurgy behind why welding cast iron is difficult. I have posted this before, but it is good to repeat it.

Cast iron has very high carbon content, like 3-4% range, compared to steel with typically less than 0.4%. Most mild steel is less then 0.2%. All that excess carbon is what creates the difficulty for welding. What happens is the carbon wants to form iron carbides at the fusion line. Carbides are very brittle and not ductile. When a weld cools from liquid to solid especially and even from just solidified to room temp, it shrinks. This shrinking is what pulls on the carbides and you get cracking along the fusion line. If you look at cast iron repairs, that is usually where the weld fails, along the fusion line. It is not weld bead cracking.

The techniques of peening are good, they do help lower the tensile stress pulling against the fusion line region. Do it soon as you pull off the weld for max benefit. The cooling rate is not so critical once you get below red hot range, except for the overall thermal expansion differences. Pre-heating helps in that it minimizes the temp differential when the weld shrinks, so it has less potential for the tensile stresses. Nickel or other ductile filler metals are used to let the weld have more give than the surrounding base metal.

If you can weld it and have no cracks initially, chances are it will hold fine for many years. LIke any weld it is not as good as the orig solid base metal, but you can make a successful repair that will salvage the part.

 

I have seen and heard a lot of different methods of welding cast iron, some of them work and some of them don't.

Do what works best for you.

 

The only weld on iron that is as strong as the material itself is when the part is heated glowing yellow, welded at that temp, reheated , then cooled under controlled conditions. Anything else is weaker and will have stresses that encourages the part to break adjacent to the weld. Depending on how the part is made, in some cases the entire part doesn't need to be heated all the way above the critical temp, but if there is any doubt, all over heating is safest. And, depending on the iron and the design of the part, welding may or may not be successful. I have welded manifolds and welded and brazed quite a bit of iron myself, and I know professionals that have welded more iron than me. I have welded exhaust manifolds that didn't fail even though I expected them to. At the other extreme I have tried to weld manifolds that were so full of gas pockets and inclusions that they could not be welded at all. Based on my experience, and what I have observed, I am saying that field welding exhaust manifolds, and iron in general, is hit or miss.

 

when these guys say peening the weld that means your gonna end up with one arm looking like POPEYE'S! back inthe 80's in welding class i was attempting to fix a head off a austin healy that has a 5" crack in it and found out just how much work it is, thought i had done a pretty good job of welding it and had a fellow peening it and even after 4 minutes he stopped to hit the head and i was sanding their and heard a loud POP and holy shit their was a hairline crack the entire length of the weld. had to start all over and it sucked! guys that can properly weld cast earn their money!

 

Yeah, it is pretty much the same thing.

I was directing it more at the guy who said "it won't last" or "it'll work about 50 percent of the time" or whatever.

It's not rocket science... it's just amazingly slow and tedious, and has to be done in a very specific way.

In fact, the show I saw this method used at has also told me that the "right" way of bringing the whole thing up to temp and then controlling the cooling actually ruins the engine blocks. They described the metal and getting "powdery" or weaker, with the result being that it'll rip out head bolt threads in the deck with little effort.
Not exactly what they're looking for with building race engines! Again, we're talking 40 years' experience building race engines and high-end restorations.


-Brad

 

preheating to 800 degrees is what they do at "ALL CAST" in Tacoma Wa. and Larry is the guy!

 

If you think 100% of exuast manifolds are weldable you have not tryed to weld 100% of exuast manifolds.

 

I have always stick welded with good luck. Cast iron has a high CARBON. I also preheat. I use Ni/ cad rods or cold weld rod almost pure nickel, and it is expensive, or try MG 289 STICK ROD. Also, the problem is how strong the weld will be.That's the tricky thing. It's been a long time since I've done it, I'm sure there are many new methods. I used to call this junk welding, but it does take skill.


" Real hot rods don't have fenders. "

 

I guess you didn't bother to read the whole thing. I said I had 100% success but also said not all were repairable, it's knowing enough to stay away from ones that aren't going to hold.

 

I have been sucessful welding CI with MIG also. Intakes and exhausts.

I am always impressed by old CI machinery that has been brazed back together.

Last weekend, the train station in town brought out an electric train from the sheds that was built in the 1930's, I think. Maybe a GG1? anyway, a famous large Pennsylvania RR engine. They have two of them here. On both engines (Motors?) the side frames for the driving wheels have been reparied. Here's some pictures of nicely welded castings. All the breaks on all the frames were in the same areas, so the design was faulty. But the repairs look like they held up well.

 

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I've done brass. HELL, one of the first things I learned. The problem, you have to get everything hot, cherry red without blowing a hole through things and trying to keep the temperature even. You see no one using it anymore.

" Real hot rods don't have fenders "

 

This method has worked well for me for many years, with the only variation being, that I drill a 1/8 inch hole at the end of the crack to help stop it from traveling. Have welded cracked blocks, heads, manifolds, etc.

 

I say do what works for you but you need to remember that how (time and temperature) the block is heated and cooled gives different results as does the iron mix used in the casting. Many engine builders heat cycle brand new blocks to off set shift and surface harden them before machining just as a "seasoned" block is a preferred starting point. In no way is a properly heated block ruined but as he said the temper can be removed if it is done wrong and the casting will be soft. So cold mig peening a 348 truck block might pan out but I highly recommend dragging something like a Packard twelve to a furnace shop with some experience in the matter.

 

482-inch 409s, 425-horse numbers-matching 409s... etc. etc. for engines.
I've also seen him recreate an entire corner on a very early '55 Chevy bellhousing that had the right numbers and date codes, but was missing a mounting hole.

one of his repaired blocks was one of the high finishers in the NMCA Nostalgia Super Stock class last year (or the year before... I forget which). The season points winner, not simply a single lucky race.

I don't hang around guys who think they know what they're doing.
I hang around guys who have the history and the record that shows they know exactly what they're doing, and don't care whether others tell them it can be done or not. Like the sign in his shop says: "Those who say it can't be done need to get out of the way of those doing it."

I know another guy who has welded axle tubes to cast center sections for 30 years, and they don't crack. He uses a Mig and a special wire he's found.
Another case of "You can't do that," and yet he has, in everything from Nostalgia Funny Car to hard-core rock crawlers to weekend bracket cars to the Dana 44 with 51,000 miles under my '61 Suburban. "But you can't weld mild steel to cast steel! The weld will crack and it'll warp the tubes!"
Whatever.

From what I've seen with my own eyes, it can be done, if you know what you're doing.

-Brad
and by the way, I said he TIG welds with special rods of the same alloy and peens it, I didn't say Mig welding.

 

I've always used a needle scaler to peen welded repairs in cast iron with good results. Has to be about a million times faster than a chipping hammer...

 

Brad-


Yes you specifically said tig, others said mig but I quoted you because you are directly knocking the proper way to repair cast iron due somone else's success with a field method. I'm not saying it won't work but there are times not to chance it such as when patching a hole or welding a freeze or stress crack in the middle of a rare block. Building up a tab or welding on an ear like with the bellhousing is easy because it pulls in one direction as it cools so anyone can do it.

Harmonics alone will kill most of these repairs on an iron race block over time, my hat's off to his success but I highly recommend furnance welding over his method. If you can afford a real 425hp 409 today what's the hold up on a few bucks to be sure it's a sound repair away?

As for welding the Dana do you think the tubes bolt into the center from the factory ? Ever narrow a 10 or 12 bolt Chevy?

I have some interesting friends too but what one man can do is not instantly your area of expertise for hanging out with him and taking notes nor does that mean he is as good as it gets. I know a guy is not the same as I do it for a living and high end has many different levels beyond 74 degree powered Chevys.

For anyone else practise, weld some Ford inline 6 manifolds, the junk SBC in your plow truck you forgot to put antifreeze in, the chinese axle on your neighbors lawn tractor, then if you feel lucky try something more important. Just remember every day more and more of this stuff is ruined by people that jump in head first and it's twice as hard to repair it correctly after you've failed. For me it's really sad seeing rare stuff destroyed that needed a simple repair by the right pair of hands.

 

All this is very interesting. I had to reclock the collectors on some cast iron manifolds but they were for an Ls motor. I mig welded the manifolds and they came out great and after 2 years have yet to crack. Could this be due to the fact that the material has improved over the years? I noticed when cutting it the band saw went right through it as we'll. it almost seemed soft...


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Linclon [eutectic 22] welding rod can be used in two ways [TIG] as described by Lincoln: 1) Do normal weld prep; pre heat to 800° and maintain temp while welding short beads; peening weld..2) Do normal weld prep; Start welding at room temp [no pre heat] welding short beads and stopping as necessary to keep temp below 150°; peening weld..I have used methode #2 several times with good results..

 

For the record, in the case of BOTH of those axle brands, the tubes are NOT welded to the center section, per se.

They are a heavy press-fit into the center section. There are holes in the center section over where the tube presses in. Weld beads are run there, to make it impossible for the tubes to turn or pull out. The purpose is NOT to weld the steel to the Iron. They could just as easily be bolts, through those same holes, into threaded holes in the tubes. That is, in-face, how many aftermarket aluminum center sections work, in the 4x4 world work.

I have been building competition rock crawlers and desert race trucks for over 20-years. I have seen every failure know to man. Including some that have an effective momentary delivered torque of 88,000+ft.-lb. to the rear axle, or 44,000+ per tube with one blip of the throttle. The press-in and plug weld method can handle that, just fine. Something else will break first (and badly).