Don't be Affraid to Weld Cast Iron

[Tom Wesenberg]

When I was 12 I worked for a farmer a few miles away. One day a cast iron part broke on his vacuum pump for his milking machines, so he threw it away. Back then many people seemed to think you couldn't weld cast iron. By the time I was 15 I learned cast iron could be welded or brazed to repair a break. About 30 years ago I hit a tree stump and broke the mounting ear on the quill on my Cub Cadet mower deck. My friend welded it with his Miller wire feed welder. The other day I saw this park bench with a broken leg setting in the weeds behind my friend's garage, so he gave it to me. I beveled the edge of the break and used my Lincoln SP-125 to repair it. The cast iron is fairly thin, so I didn't attempt to make it perfectly smooth, but left the weld a bit thick for added strength.

In the first picture you can see a couple of voids, so I had to weld them in after the picture was taken. I painted the bare boards and touched up some of the rust on the cast iron parts. After painting the weld, it really doesn't show unless you look for it
So, if you have a broken cast iron part, don't be afraid to weld it or braze it. I've also repaired broken cast iron by using nickel rod and my arc welder, as well as using my oxy/acc torch and cast iron filler rod and blue flux.

[BILL WILLIAMSON]

I too have welded it with cast iron rod & flux. You can run a beautiful, smooth bead, with a little practice. Flows much like using Stoodite, when hard facing plow shares. I've also done it with Nickel Arc, weld a little, then pein it with the pointy end of your chipping hammer.
Bill Dauber

[Guest]

Tom,
I have welded cast grey iron with both gas and stick successfully, but not MIG.
What wire are you using, and what shield gas?

Was the bench grey iron, or cast steel?
Grey iron is tough to weld.

[Tom Wesenberg]

Tom,
I have welded cast grey iron with both gas and stick successfully, but not MIG.
What wire are you using, and what shield gas?

Was the bench grey iron, or cast steel?
Grey iron is tough to weld.

The gas is Argon 75% and Carbon Dioxide 25%. The wire is ER 70S-6 and .023".

After I took the first picture I found another crack radiating out about an inch from the break, so I had to weld that also.
The third picture shows the rear leg that was broken. It's nice to have a good bench to sit on while working on some Model A parts.

[Brian in Wheeling]

Use a nickel based rod in an arc welder. Pre- heat to high heat, weld then cool Very slowly...even blurring in sand, if need be. Very slow cooling and pre-heat is key. There are different cast irons, grey and white, ductile, etc. Some are more successful than others...the hard cast is best, but all can be welded.
Brian

[Patrick]

As Brian says, heating and then slow cooling is important. I've always enjoyed sticking pieces of metal together.

[Greynomad]

I was told years ago that behind the Iron Curtain, replacement parts were few and repair facilities just as difficult to find. People had to repair what they had the best way they could. Cast Iron repairs were done using an arc welder with a copper wire wrapped around the electrode. I don't pretend to be a welder so I'll leave it to other to comment on that!

[bgarrett]

I have been welding cast iron with a Henrob torch for about 16 years. Excellent results, never had a problem

[tbirdtbird]

Henrob torch

Not familiar with that. My luck welding cast has been less than stellar, although I did MIG up an oil leak in a Toyota pickup block where the oil was pissing out a sand hole. Did it while it was running. For some reason it worked.

I am not sure I would have anyone weld a block. There are shops that know how to stitch them with pins, I bet George Miller can stitch.

Had a friend here with a 2-port Riley (a back-in-the-day overhead head for a Model A) that had a crack, took it to the best known welder around, and the guy welded it. As soon as it heated up it cracked worse than it was before. It shoulda been stitched

Can you expand on what that torch is about? Do you weld blocks and heads? A part that gets thermo-cycled to me would be the biggest challenge

[jordanka16]

When I was in high school my friend and I welded a lot of cast iron. We used electrodes made of nickel, and lots of preheat with a torch, and then gentle cooling by using a torch to gradually reduce the temperature. It works pretty well but it is by no means as good as welding on steel.

[Tony Hillyard]

Tom, I have the same bench that broke in the same place. I bought it new as a flat pack (I know it was Chinese as the box said so) kit from the local Lidl supermarket here in France. This was just to look good under one of our rose displays. Anyway, it broke when it was being moved. Like you I used my mig and now you can even sit on it!!!!

[Terry, NJ]

Tony, Tom, and every one! Yes you stuck two pieces of cast iron together. Now be careful that it doesn't break at the HAZ. That is the Heat Affected Zone, next to the weld. And I'm not sure of what to do about it. Maybe, Just maybe, because the heat from the MIG is so concentrated at the tip of the wire, you don't develop or weaken , or embrittle the HAZ. I don't know. Heads and manifolds are so permeated with carbon that they are very difficult to weld. I have described the process as trying to weld a an icicle to a hot frying pan. Little balls of welding material boil off and jump around. Nothing sticks. I ran a bunch of stringers on the outside to give me some metal to weld to. A friend once told me that to repair a Caterpillar dozer head, he put it in a furnace at 1200 degrees (F) for a few hours and then welded it with 6010 . 6010 is a rod that has a very violent arc. It's used for "Cleaning" welds and joints in pressure vessels and pipe line joints. It worked! Between the 6010 and the baking in the furnace, he got enough carbon out of the crack that the weld took. So welding Cast iron is a new and exciting world of frustration and occasional success and when you get good at it everyone beats a path to your door.
Terry

[Terry, NJ]

Not familiar with that. My luck welding cast has been less than stellar, although I did MIG up an oil leak in a Toyota pickup block where the oil was pissing out a sand hole. Did it while it was running. For some reason it worked.

I am not sure I would have anyone weld a block. There are shops that know how to stitch them with pins, I bet George Miller can stitch.

Had a friend here with a 2-port Riley (a back-in-the-day overhead head for a Model A) that had a crack, took it to the best known welder around, and the guy welded it. As soon as it heated up it cracked worse than it was before. It shoulda been stitched

I agree! Welding heads and manifolds is an invitation to a lot of problems. It should have been repaired some other way, either by brazing or stitching. Ni-rod is not that great!
Terry

[Patrick]

'And I'm not sure of what to do about it.'

I think thats were both pre-heat and slow proper cooling comes in. I've welded and brazed quite a bit of cast with good luck over the decades. I've not used MIG but think it would be interesting to try and see no reason why it wouldn't work fine.

[bgarrett]

Brass should not be applied to cast. Filler should be the same as the work. I'm sure you can look up Henrob. There was a guy demonstrating the Henrob at Pate and I was so impressed that I bought one. It will weld stainless too, also cuts. My first repair was the bolt hole on a small block chevy exhaust, The triangle shaped piece had broken off. I built it up with cast iron rod, grinded it to shape, then drilled and tapped the hole. Still good 16 years later. People who have never heard of the Henrob dont believe it, but there is no preheat needed.

[Patrick]

I've brazed quite a few manifolds over the years. One ended up being more braze than metal, that manifold was not available anywhere at the time.
One fella brought a car to me about 10 years ago and mentioned the manifold telling me I had brazed it 30-40 yrs previous which I had forgotten about. It was still a nice old 30 DeSoto, he has taken good care of it. I think I fixed the starter on that visit.

[George Miller]

When I was 15, I got a 1941 chev in pieces. As I was putting it together I wanted dual exhaust. I did not know you could not weld cast iron. So I used my Dads torch and fence wire to weld a extra out let to the exhaust manifold. I had learned from shop class about pre heat and slow cooling. So I welded it and then wrapped it in asbestos. It worked never had a problem with it.

[George Miller]

Not familiar with that. My luck welding cast has been less than stellar, although I did MIG up an oil leak in a Toyota pickup block where the oil was pissing out a sand hole. Did it while it was running. For some reason it worked.

I am not sure I would have anyone weld a block. There are shops that know how to stitch them with pins, I bet George Miller can stitch.

Had a friend here with a 2-port Riley (a back-in-the-day overhead head for a Model A) that had a crack, took it to the best known welder around, and the guy welded it. As soon as it heated up it cracked worse than it was before. It shoulda been stitched

Can you expand on what that torch is about? Do you weld blocks and heads? A part that gets thermo-cycled to me would be the biggest challenge

No do not try welding a block that is cracked in the seat area , stitch it with over lapping tapper threaded cast plugs. Then put a valve seat in the right way. They need to be a press fit and then roll in some metal around the insert. I always put a champer around the top of the insert to roll the metal on. If done this way they will stay. We use to do a lot of flat head Ford V8s in My Dads garage many years ago.

[Patrick]

'I did not know you could not weld cast iron.'

LOL ! Ignorance is bless at times isn't it. As long as you don't tell the piece of cast it works out.

[tbirdtbird]

OK, so I googled Henrob, got the lowdown and watched some vids
It is an O/A setup.
Not sure I see a difference between it and my regular O/A setup, for which I have several tips and can dial in my pressures any way I want. Neutral flame, oxidizing, carburizing, whatever process is needed

The trick to brazing/welding any metal no matter whether MIG, TIG, or gas is to have the correct rod, I am not sure the type of torch matters

I have watched cast O/A brazed by pros but they were pieces not subjected to thermal stress

Those of you above welding exhaust successfully, more power to you!
I knew a guy who had a cracked exhaust manifold welded by a pro 3 times and it re-cracked each time.
BTW it prolly cracked in the first place because he had the clamping bolts too tight.

There are also many different cast alloys, and I suspect this makes a difference in your success.

Now, malleable iron is a different bird, I would weld/braze that any day of the week, and have. It looks like cast but the alloy is quite different, not as brittle