Welding Cast Iron

I have read a lot of positive talk regarding the Palco 808 rods. Palco states no preheat required with these rods.

http://www.palcoweldingsupply.com/808.html

I've welded cast a few times, but never preheated. Instead I tried the slow method, welding small sections at a time, with lots of cooling time between welds. The stuff I welded wasn't under any stress.

i like to weld cast with 7018AC. for an exhaust manifold you will need to use a nickel
rod for cast iron. used exhaust manifolds are difficult to weld, 7018 will not apply. the
only rod i have gotten to work is a cast nickel. luckly you are not in need of strenght.
heat to around 400/500 degrees and weld. weld an inch or so and take your chipping
hammer and peck the area you welded and the rest of the manifold for 30 seconds or
so. weld again and peck, weld again and peck. this works really well to relieve the
stresses that occur in the welding process. as the piece is cooling after you are done
welding continue to peck at the manifold untill it cools to a level you can lay your hand
on. let it cool naturally while pecking on occasion. if you do not peck, you may hear a
loud pop, that being a new crack. do not forget to grind or clean the area to be welded.

The best electrode I've found for old cast iron is one made by Castolin Eutectic, Eutectrode 2-44 . Let's just say it's expensive!!! The second best is Ni Rod 99, but it isn't cheap either. The procedure I use when not preheating is to weld as cold as possible, no more than an inch at a time and then peen 'til cool enough to lay a hand on the weld. Another inch, peen and let cool, etc.

Ni Rod 66 is also available, a little cheaper than the 99 but it's not machinable, the 99 is. While a mild steel electrode like 7018 can be used on cast iron, it takes a lot of preheat, peening and slooow cooling to make it work.

all these answers are good but if you just need to build it up a little for better sealing just float a little braze on it then mill/ grind it back to where you need it less worries about cracking or melting your thin lip or if it is super thin i have even used silver solder to fill small gaps and cracks where strength is not important --- just my 2 cents --- scott

i would almost say to try something like JB weld or lab metal, for what you are dealing with i feel like either one of those would work fine

I have welded up exhaust manifolds and heat boxes before using my mig welder with mild steel wire. The same precautions apply. Clean the metal well first. When welding cold, don't let the manifold get any hotter than you can comfortably hold your hand on. Another problem about welding cast iron with mild steel wire is that the weld is not machineable after welding. The combination of cast iron and mild steel makes a weld as hard as cobalt steel. You can grind it down, but don't try putting machine tooling to it. Another thing is that mild steel oxidizes in the heat faster than the cast iron does. For a weld job that will last for years and years, mild steal will not take the heat of an exhaust manifold very well. It will rust out before the cast iron will.

On something like manifold I use railroad rod{ is cast iron in stick form] [may be hard to find these days] requires a good flux for welding problem cast-use torch same as brazing- but cast is easier to flow/ build/ shape while melted/ preheat & slow cool down.will machine & look like original iron..

I dont think I would risk welding it and cracking it. If the pits are only 30 or 40 thou deep then either filling it with soft braze and machining back or just machining it would be safer. The last manifold I had in this state I machined back with a planer. Easier to clamp the thing in a straight line and gently plane the thing back to square. Not only did I get the pits out but I got each branch back in line. The planer is a much more gentle and slower action on the work than a milling machine, and the thrust on the workpiece is all in one direction. Therefore clamping an awkward shaped workpiece like a manifold is much more straightforward.

Nick

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Thats old school technology! (I like it!) 👍 I would have suggested brazing and filing flat or flat board sanding. If I had access to a machine shop still, I would have surface ground it as there aren't many planer machines used anymore.
Nice Idea!
Jeff