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Welding Cast Iron

Hi all, A lot has been said on this site about welding cast iron. I'll admit right off that I have no experience doing this. However, last week in the shop where I work, a cast iron part broke in an automatic cut off machine. Needing to keep it going and avoiding down time, I took the part, 'V' grooved the two broken sections, and MIG welded them together. Ground and filed off the excess, and got the machine running again. A week later, it's still holding up! Mind you, I wasn't a bit fussy about doing all this because time was of the essence. I just had mild steel wire in the MIG welder, using 75%-25% argon - CO2 gas. So, for what it's worth, it worked for me. -- Al

I have had several cast iron parts break a second time at the point that I had brazed the repair correctly. Out of need, I welded them with .023 diameter mild steel wire and 100% Co2 gas. Under the same conditions, the parts have not broken again and I am quite pleased with even the looks of the mig weld on the cast iron. So with that I have no doubt that your mig weld repairs are holding up fine. – Marty

How would mig welding a flywheel hub work? – Dave

Myself, I would do it based on the experiences I have had welding cast iron with my mig. -- Marty

I am a welder by trade and the best thing that I know of to weld cast iron is a stick rod called Certanium. It is a very good rod and you don’t have to be a pro to use it. Try it you will like it and good luck. – Rod

Rod, is that the #889. If so, I too have had very good results using it. – John

Hi, its me again. I went out to the shop and got a stick of that Certanium rod and here is what it said: 889sp p/n12003 AC/DC all position rod, 1/8, 90 to125 amps for cast iron. It has a phone number but I can’t make it out very clear. Canada 1- 800-663-2800 PS: I agree with the person that said he doesn’t weld up flywheels. Cast iron with a lot of r.p.m. g-force is very scary! – Rod

While digging through reference books about iron for a mag charger, I learned that the recipe for cast iron is as varied as a Sunday dinner. This helped me understand why some of my welds have been good and some have failed. -- Ralph

Ralph, I was so glad to read your post. Maybe it has been said before, but I don't recall reading it. There have been so many threads concerning the methods of welding cast iron for a very simple reason. Your very wise statement of, "the recipe for cast iron is as varied as Sunday dinner" and oh how true. It's the same thing as so many threads concerning the removal of a stuck piston. For every stuck piston there is, there is a "best" method of "un-sticking" THAT PARTICULAR piston. For nearly every situation, there is a different set of circumstances so generally a different method of a "fix" applies. This Site is excellent since we all get to post our OPINIONS and experiences.

I think the reason is because we call what is in essence an entire group or family of metals "cast iron". Like the generic term "steel", the name simply doesn't convey much useful information beyond an average carbon content. Metallurgy has advanced enough that we can manipulate "cast iron" to have all sorts of properties, some that even defy what the average fellow thinks he KNOWS about the material. On the other hand, there are STILL quite a few places that simply make a mulligan stew type cast iron by throwing just about anything into the pot. They don't control their cooling rates either, so the physical and structural properties end up differing from batch to batch. -- Allen

I have been on a soap box for years telling about welding cast iron with a MIG welder. I found out by welding exhaust manifolds on automobiles. It is not a very strong weld and I don't know how much I would trust it on a flywheel, but as far as welding up a crack in the water hopper or welding a bracket back on, It seems to work just fine. Also, It is a very HARD weld. You can't machine it because It will break your tools! All you can do is grind it back to size or shape with a disc grinder. – David

The reason Mig (GMAW) works fairly well, some of the time, is because you have a lower heat input, therefore there is less thermal shock in the heat affected zone than with conventional arc welding. Running a cooler weld (essentially a localized re-casting) means less penetration, and a weaker joint. If you tried to run it hot - into transition, or metal spray, you'd find that the end result would be subject to the same problems as a conventionally welded repair. -- Allen

I weld a lot of cast iron. I use Ni-cad rods or cold weld rods made of almost pure nickel. These are not cheap, but really do the job. I have welded flywheels, but I would never do it for someone else. I want to keep my farm... – Kevin

The "smooth" rod I use on cast iron works really well. I think most of the old cast iron before WW-II is a much better cast iron than some of the 40's, 50's and 60's. The guy that sells me the rods won't tell me the company name or the numbers for the rod. There isn't any thing printed on the flux and I only buy them about a pound at a time, so there isn't a box with writing on it. I guess he wants me to just buy them from him. I think I pay about $1.50 each for them and they are well worth it. The smooth rod welds this old cast iron like mild steel. I don't know what it's made out of but they are a "whole bunch" better than any nickel rods I have ever used. I have bought the most expensive nickel rods I could find as well as the cheaper ones and they don't hold a candle to the smooth rod. The weld is soft enough to file as well. -- Don

I agree with Don on ni-rod, which is too hard, can't be machined and doesn't blend with the cast iron appearance wise. I use Palco 808 & 827 cast iron alloy machinable. It’s made in Ohio. There is a phone number on the rod but I'm not sure I should post it so if any SmokStakr's want it just email me. – Brian


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