Welding cast iron?

[Terry]

Can you weld on cast iron? Like on a exhaust manifold, or does it require a special rod?

[squirrel]

I've never had much luck welding cast iron, but I've heard of some secrets, such as heating the parts to glowing with a torch first, then it will all cool at the same rate and not crack at the weld.

I suggest you play around with some scrap late model manifolds first to get your technique sorted out.

[Petejoe]

Yes, there are specialty electrodes for welding cast iron.
You could also braze it with a torch. I have had more luck this way.
Cut a V-groove in the split or seam and make sure you pre-heat it before welding.

[CharlieLed]

I am not a welding expert but even at my level I can say that I have done this. Grind out the crack until you have a nice "V" to hold the weld and to assure good penetration. Heat the kitchen oven up to the max temp (more about this later). Take a torch to heat the manifold around the area to be welded, the line of the weld should be glowing red. Using nickel rod and an arc welder weld the crack just as you would any other steel welding. It is important to keep the manifold hot with the torch while you are welding the joint. Once the welding has been completed immediately put the mainifold into the HOT oven, this will keep the temperature in the manifold even. Over the next few hours slowly reduce the temperature of the oven allowing the manifold to slowly come back to room temperature. This procedure is referred to as normalizing. Cast iron is very porous and does not like rapid changes in temperature, keep the piece evenly hot while working on it and then slowly reduce the temp after the welding is completed and you will happy with the results. Good luck...

[Rand Man]

An expert can weld a cracked cast iron engine block well enough to hold your radiator water pressure. An exhaust manifold is a lot harder job. One big factor in any weld is a clean surface. The manifold has probably been cracked for a while and soot finds its way all trough the crack. Rust can also build up inside. It's a challenge to get the proper penetration. The heat-cool cycles also tend to reform cracks.

[alchemy]

I have heard a trick for do-it-yourselfers. Heat the manifold on a gas barbeque grill to "well done". Then weld or braze with the appropriate rod (even heard MIGing works good). Then put back on the grill and cool the temp down slowly. Don't take out of the grill until cool to the touch.

Of course this is all after proper cleaning of rust and soot, and Veeing the crack.

Could drilling a small hole at the beginning and end of the crack also act as stops for the continuation of the crack?


- alchemy

[manyolcars]

[ QUOTE ]
Can you weld on cast iron? Like on a exhaust manifold, or does it require a special rod?

[/ QUOTE ]

It is WRONG to put brass on cast iron! Anyone can weld cast with a Henrob torch. Its easy and works well. This is one of those questions that comes up about once a week.

[Petejoe]

[ QUOTE ]
WRONG to put brass on cast iron!

[/ QUOTE ]
News to me. I have done it and have been taught it in classes years ago. Naturally the strength may not be the same as an electrode made for the application such as NI-ROD but it sure works and does have strength.

[telecaster_6]

Being a welding engineering student......i guess i should help out with this one..
It'v definitely possible to weld cast iron...but you need to take some precautions. Its very suseptable to cracking during the welding process... NEVER under any circumstances should you quench it... the slower you let it cool the better..cover it with kitty litter or leather if you can. Pre heat is very important too....Really you should find some literature on welding cast iron to find out the proper pre-heat temp. As for actually welding it....forget about mig welding it...brazing works well if your good at it...there are special SMAW (stick) electrodes that work very very well and are fairly easy to run...and there are special tig fillers that work well too....ALl of these fillers are of high nickel content to give the weld as close to the same mix as the base metal.

Hope this helped...hope i didnt confuse ya too much either..

[drgnwgn289]

as another welder and engineering student I would say that, unless you are an above average welder and have access to a henrob or a TIG machine you're best be at repairing a crack in cast iron is brazing. However, I have had luck with a MIG. As previously stated, a clean surface is the key. Sandblasting is always a good idea, just be sure no sand is left in the crack. If you weld it, you MUST preheat the part. Heating it in an oven or furnace is much better than heating with a torch, but the average dude doesn't have access to an oven that will get hot enough to do much good. When you heat with a torch, be sure to heat the entire part evenly, and not too rapidly.
If you use a MIG, use flux-core wire WITH gas also. After you weld it, find a way to cool it as slow as possible. I've had a lot of luck putting the part in an icechest filled with kitty litter. Put down enough in the bottom of the cooler so the part won't melt through it, then completely cover the part and close the lid. Let it cool for as long as it takes to reach ambient temperature (this will take a day easily). The whole point of this is to insulate the part, limiting heat transfer and cooling the part as slow as possible.
If you weld it, try not to lay down a really fat bead. When the weld cools, it contracts and creates residual stresses. If the weld is really wide, the contraction is lager and it will be more likely to break again. In the past, I've tried to pean the weld to relax the metal and reduce the residual stresses, but this is hard to do without breaking the part again.
Another good trick is to drill a small hole (1/16-1/8") at the tip of the crack. This distributes the stress at the tip of the crack over a larger surface area, in turn reducing the pressure (unit force per unit area) that caused the crack.
I've repaired several exhaust manifolds for Cat and AC deisels this way with very good results.
If you braze the part, preheating is negligable. Some say it works, some say it doesn't. During brazing, unlike welding, the two metals are not mixed in a liquid state and the composition of the metal at the joint is unchanged.
hope that does you a little good
Jake

[spark]

I welded a water pump housing with M.I.G (gas) heated the area with Oxy, welded it and placed in a box half filled with dry beach sand and covered the part with more dry sand.

The part was surrounded with about 6 inches of sand in all directions. I left it alone until the next day, it was still warm so left it siting on top of the sand for rest of the day. It worked well.

Also had a shop weld a broken door of a cast-iron stove they ground the enamel off and welded it with a Ark welder with a rod made for welding cast.

[50dodge4x4]

By far the best method to weld cast is by preheating, welding and cooling slowly, but it's not the only way. You can also weld cast by keeping it from getting too hot.

I have had some luck welding cast with a stick welder and nickle rod. I don't preheat. After the area is cleaned up, I weld with short weld beads (about 1/4" to 1/2" max), chip off the slag (pean the weld), wire brush, and weld with another short bead at the opisite end of the crack, pean with the chipping hammer, wire brush and move back to the first area. The idea is to keep the area as cool as possible (still touch with a gloved hand is about right), and pean the weld. This process takes some time, but it works.

If you are welding anything cast iron that bolts to something else, you need to have it surface ground. Unlike steel, cast iron will not "conform" to another surface, it will break. If the mating surfaces are not flat. I can gurantee the cast will break. Manifionds are a bitch to weld. Gene

[38Chevy454]

As many have said, it can be done, but it is not easy. Best results are obtained by the lots of pre-heat, hi nickel or all nickel rod (more ductile), and slow cooling method.

The problem with wleding cast iron os the real high carbon content. CI is like 3% carbon, whereas mild steel is about 0.2% carbon. The high carbon is what causes all the problems. You get fusion line cracking.

While some have had luck with other methods, it is probably more luck and the cracks that are present are small enough they don't create a problem. I am sure that some cracks are there.

Pre-heat (like 1200 F even) and post-heat and slow cool is the key.

[drgnwgn289]

Hey Terry!
I was just about to post about the whole carbon content thing...
A lot of times, when people think they have succesfuly welded cast iron, they have really just welded cast steel, and thats not hard. But that could be the cause of the varying rates of success of welding "cast iron"

[38Chevy454]

Good point drgnwgn289, many could be cast steel. Easy way to check if steel or cast iron is to do a quick spark test. Hold up to grinder and look for "carbon bursts" in the stream of sparks. It does work, especially if you have known materials to compare between. That is your old school technology lesson for today http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[50dodge4x4]

Guess I've been pretty lucky, http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif I've welded many exhaust manifolds over the years without the preheating. Gene

[BELLM]

Welded up a broken exhaust manifold on a 76 Olds used correct rod, preheated in oven, wrapped in an old hood insulation blanket. 24 hrs later went to take it out burned the hell out of my hand. Left it another 24 hrs, Was a total I built (about 78) sold to a friend manifold never cracked. Butit was completely broke into 2 pieces.

[ray]

a factor is why the manifold or whatever cracked in the first place. if the stress that caused the crack is still there, it WILL crack again. if it was something damaged, say from a overtightened bolt, or impact, it might last because the stress is gone once repaired. if the crack was from warping, resurface the mounting surface and you should be golden.

i'm in the middle of splitting a ford six manifold, there was a support bracket to the engine block, i will retain that, and brace the two halves of the split manifold together so the weight of the exhaust doesn't break off the new, dissimilar metal outlet i will be welding on.

[drgnwgn289]

with regards to what you are doing ray, it is much easier to weld steel to cast iron than it is to weld cast iron to cast iron.

[Brickster]

It is WRONG to put brass on cast iron! Anyone can weld cast with a Henrob torch. Its easy and works well. This is one of those questions that comes up about once a week.

[/ QUOTE ]

I welded a manifold with a Henrob for my shoebox so it would miss the steering box. Cast iron fill rod and the right flux. I preheated with a rose bud and just let it air cool. For more info try getting a hold of Jim Spradly at cuts-like-plasma.com he sells everything needed to do it.