Welding cast iron

[Carld]

Well, this didn't get any traction in the welding forum so I will try it here.

Has anyone tried this method of welding cast iron and did it work?

http://gasengine.farmcollector.com/I...m_medium=email

[TGTool]

Haven't tried it but it wouldn't cover all situations. If it needs any structural strength I wouldn't trust the solder, but I suppose it it works it's a useful trick for some things like the leak they referenced (other than exhaust manifold leaks).

[Black Forest]

I have never tried soldering cast iron. I have welded quite a bit of cast iron though.

[lazlo]

That's basically a ghetto version of brazing. Why use pure copper instead of bronze brazing rod, which will be a whole lot stronger?

[dian]

was it soft solder? might have worked in a water jacket.

[lazlo]

was it soft solder? might have worked in a water jacket.

He touched a copper pipe to cast iron heated to cherry red.

[dian]

"Next he took some solder and used just enough heat along the crack to melt the solder"

cherry red? i followed the link. sorry, where do you see that?

[Carld]

The job was to weld a crack in a Model T block. I can see where you could limit the heat by just getting it hot enough to tin the cast iron with the copper so as to not enlarge the crack. I think the crack would have to be V'ed and cleaned or fluxed well for the copper to bond. The integrity of the weld would lay in how well the copper bonded to the cast iron.

According to the text it wouldn't work in a stress area and best used to repair a water jacket crack.

I have not heard about this method and was wondering if anyone else has used it and what success they had.

[lazlo]

cherry red? i followed the link. sorry, where do you see that?

He's heating the iron and rubbing copper tubing on it until it melts. So the cast iron is well above the melting point of copper: 1981°F (1083°C)

"Using an acetylene torch, with a small tip, he played the heat on the crack while at the same time he would rub the crack with a piece of small copper tubing."

[Fasttrack]

He's heating the iron and rubbing copper tubing on it until it melts. So the cast iron is well above the melting point of copper: 1981°F (1083°C)

"Using an acetylene torch, with a small tip, he played the heat on the crack while at the same time he would rub the crack with a piece of small copper tubing."

I don't think so. I need to do some more research but I have a vague memory of this. The copper tubing is rubbed on the cast iron to burnish it and leave a sort of haze of copper behind. The casting doesn't have to be super hot to adsorb a layer of copper. I wish I could remember more about this ... I'm positive I ran across somewhere before...


EDIT: From my previous endeavors in repairing cast iron, I know a big issue to overcome is carbon and other contaminants. The abrasive bits from a grinding wheel or a skin of carbon dust from the cast iron itself will make the casting almost impossible to wet. That's why I always go through so much care using carbide burs, stainless steel brushes and acid etches. But I've just learned that copper is an alloy used in some cast iron to stabilize pearlite formation and as a graphitizer. Maybe there is some connection? The presence of adsorbed copper atoms improves wetability by controlling the formation of graphite or ... ?

[J. R. Williams]

Cast Iron

Cast iron welding is easy. Clean and grind a suitable groove for the weld, plenty of heat with the correct flux and cast iron rod. Finish the weld and allow to cool very slow. Cast iron flows very well.

[GKman]

The problem with welding or brazing cast iron is that the material has very little strength in tension. Heat the middle of a big piece (side of a block) it expands, the part hot enough to soften compresses permanently, weld the crack with something, let it cool. The cold area stays the same size, the area that was heated wants to get smaller so it pulls the part in two. Slow cooling evidently reduces the tension some, but nothing to depend on. Weld a broken ear back on a piece, it has room to shrink and can be mended successfully.

If the solder can be made to stick, the heat required is much lower, therefore the tension is reduced plus the solder would be soft and malleable enough to stretch as the iron cools. Looks like a sealing repair not a structural repair so whatever seals the leak is apt to be OK.

[dian]

lazlo, i really dont want to argue about it, it just wonder, how did you come up with "cherry read"?

[lazlo]

lazlo, i really dont want to argue about it, it just wonder, how did you come up with "cherry read"?

He's heating the iron and rubbing copper tubing on it until it melts. So the cast iron is well above the melting point of copper: 1981°F (1083°C)

1981°F (hot enough to melt copper) is bright yellow. Figure a couple of hundred degrees for the difference in thermal mass and contact point, and it's actually probably a lot hotter than cherry red (which is 1400°F ).

Overall, I stand by my first comment -- it's ghetto brazing, using copper tubing instead of brazing rod.

[Carld]

The actual statement was:

"Using an acetylene torch, with a small tip, he played the heat on the crack while at the same time he would rub the crack with a piece of small copper tubing. You could see the crack was getting a copper color to it. Very little heat was used, just enough so a copper tone was showing in the 'V'd sides of the crack."

Apparently he was only heating the cast iron enough to get the copper to rub onto the cast iron. There was no claim to getting it to red heat and in fact he said NOT to get the block to hot. You may be able to get the copper to rub onto the surface while cold but it may work better with some heat. If I find a cracked block I think I will try this method out.