welding cast iron

[52 Ford]

Preheat has four purposes in ferrous welding.

One is to reduce thermal stresses both during and after the weld caused by variation of temperature in the workpiece.

Two is to increase ductility so that some of the stress can relieve itself...in-process thermal stress-relief

Three is to cook off contaminants

Four is to slow the cooling of the weld and HAZ. Flame-hardening works by heating the surface rapidly so the undelying metal is still cool. When the heating is removed the hot surface is quenched and hardened by the heat being rapidly conducted away to the underlying cold metal. Just what you do not want, usually, in a weld

Fifth is to roast the weldor by radiant heat, so you are not shy to charge a lot of money for the job.

LOL at #5

When you're wrapped up head to toe in heavy leather surrounded by weld curtains on a humid, 100 degree day, you don't feel bad about what you charge.

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[JoeE.]

I have no problems trying to pre heat the C.I. item to be welded. I don't mind that at all.

What lessens my enthusiasm is trying to dream up a way to insulate it to keep it from rapidly cooling down.

That's ALWAYS the point at where I say "piss on it".

I don't actually do much, if any, CI repair. But, if I do, I never have any sort of a game plan on what to do to enable it to gradually cool down. I bet that's what a lot of guys have trouble with. Keeping a torch on it to keep it hot's easy...

Last CI thing I fixed was a Chevy 6 cylinder intake/exhaust manifold... from 1961. I just used 7018 Low hydrogen rod. It had a few cracks, and the face where the gasket seats on the exhaust had been corroded and eaten away. That's the surface I welded on, then ground off with an angle grinder. It worked. Ugly as hell, but all it needed was a surface that a gasket could seal.

 

[52 Ford]

I have no problems trying to pre heat the C.I. item to be welded. I don't mind that at all.

What lessens my enthusiasm is trying to dream up a way to insulate it to keep it from rapidly cooling down.

That's ALWAYS the point at where I say "piss on it".

I don't actually do much, if any, CI repair. But, if I do, I never have any sort of a game plan on what to do to enable it to gradually cool down. I bet that's what a lot of guys have trouble with. Keeping a torch on it to keep it hot's easy...

Last CI thing I fixed was a Chevy 6 cylinder intake/exhaust manifold... from 1961. I just used 7018 Low hydrogen rod. It had a few cracks, and the face where the gasket seats on the exhaust had been corroded and eaten away. That's the surface I welded on, then ground off with an angle grinder. It worked. Ugly as hell, but all it needed was a surface that a gasket could seal.

You FIXED a Chevy 6 banger? Gross.

 

[Ben]

I've been following this thread ,and I know most of the discussion has been arc welding CI which I have never had any luck with. I have always used a torch and brass rod. I noticed that tig and silicon bronze used. Would silicon bronze be a better choice with a Ac-Ox torch? I have both and a job repairing a large gray CI casting. I have my preheat rosebud planned for the job and a regular torch for the brazing. I have used the silicon bronze on galv sheet metal dust pipe with a carbon arc rod, works great there.
Thanks,
Ben

 

[magneticanomaly]

Silicon bronze should wrk fine, 'though I have mostly used "low-fuming bronze"

Be careful with rosebud preheat. you want the temp all over the casting to be as uniform as possible. Local intense heat not so good. Multiple propane burners, charcoal... wood-fire is what I most often use

 

[john.k]

if you havent had any experience (good or bad) with cast iron,I suggest a bronze filler weld first .....a good preheat can be had from a gas barbecue of good size.......street cleanup day is a good time to score a big 'un............any kind of braze,you must observe the rule of NOT smearing the graphite in the iron.....Ive found nickle bronze filler to be high strength,but often requires and initial flux with a scaling powder,then when the iron is wet ,use a pink borax flux......too much scaling powder will fill the braze with bubbles.

 

[john.k]

One thing Ive noted for a long time,is that if you use oxy/LP gas,then there is something comes thru the flame (wax maybe,or odourant?)and stops the filler fusing to the iron .....if you shield the iron from direct flame ,then the filler will flash allover instantly.....once the iron is wet,then no more problems with direct flame.........incidentally,there is also a technical reason for using an oxidising flame ,the zinc oxide formed facilitates the wetting.

 

[Ben]

I only heat the area around the joint, this is a heavy casting, I don't try to heat the entire casting. I use oxy-act. my setup is not for LP. I have done many, many braze jobs, I haven't used silicon bronze rod before always plain brass on many machines, dozer, tractors, etc. I'll try the silicon bronze on this repair. One thing the rosebud does is burn all the oil and grease off the cast iron, so it will be clean. the rosebud will also make it easier the preheat while the part is in the jig to hold it in position. I use a brazing flux Marquette No 1 flux which I have used with great success for 50 years.
Thanks for the pointers.
Ben

 

[52 Ford]

if you havent had any experience (good or bad) with cast iron,I suggest a bronze filler weld first .....a good preheat can be had from a gas barbecue of good size.......street cleanup day is a good time to score a big 'un............any kind of braze,you must observe the rule of NOT smearing the graphite in the iron.....Ive found nickle bronze filler to be high strength,but often requires and initial flux with a scaling powder,then when the iron is wet ,use a pink borax flux......too much scaling powder will fill the braze with bubbles.

I generally use flux coated low fuming bronze rods. I clean the parts the best I can with a wire brush, sandpaper, acetone, the usually.

Right now, the rods I have are Lincoln. I think I'm going to try Radnor (AirGas), next.

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[Rob F.]

I only heat the area around the joint, this is a heavy casting, I don't try to heat the entire casting. I use oxy-act. my setup is not for LP. I have done many, many braze jobs, I haven't used silicon bronze rod before always plain brass on many machines, dozer, tractors, etc. I'll try the silicon bronze on this repair. One thing the rosebud does is burn all the oil and grease off the cast iron, so it will be clean. the rosebud will also make it easier the preheat while the part is in the jig to hold it in position. I use a brazing flux Marquette No 1 flux which I have used with great success for 50 years.
Thanks for the pointers.
Ben

If you want to use oxy-propane to heat with all you do is take the regulator out of the acetylene bottle and put in in your BBQ bottle. Yes, it threads right in. Heating metal with oxy-propane is really nice, it is a little slower to heat so the surface is much less likely to burn as with acetylene. To do cutting you will need propane tips but welding tips and rosebud are just fine to use.

 

[52 Ford]

If you want to use oxy-propane to heat with all you do is take the regulator out of the acetylene bottle and put in in your BBQ bottle. Yes, it threads right in. Heating metal with oxy-propane is really nice, it is a little slower to heat so the surface is much less likely to burn as with acetylene. To do cutting you will need propane tips but welding tips and rosebud are just fine to use.

Oxy propane is a lot more economical than using acetylene.

If I was doing a lot of torch work, I'd use oxy-hydrogen.

I know that big glass blowing studios have on site oxygen generators to supply their torches. I imagine they do the same for hydrogen.

I think my next unnecessary purchase for my shop is going to be one of those small import "HHO" generators. I bet it'd be awesome with a small torch for brazing small parts and sheetmetal. Takes water and electricity and runs your torch.

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[dian]

dian

No visible flames when the carbon was coming off so I reckon it was more like evaporation than burning. You'd expect Carbon Dioxide and Carbon Monoxide if it were burning. Both transparent gases so a proper fire wouldn't smoke so much. Don't forget I was putting as little heat as possible with a minimum weld lay due to the amount of metal collapsing out of position when the carbon went. Pretty much no burn through or blobs of iron on the bench. The iron was just pulling back when the carbon went.

Re-defined my concept of bitch job from hell! Mousetrapped into a freebie too by social connections.

I have had flames when oil contamination was boiled out of somewhat porous cast iron. Very distinct and easily seen behind the arc. Burning continued after welding stopped. That time I did just enough weld to get the flames going, waited them out and did the lay over the burnt area.

Clive

i understand, graphite would not butn with self sustaining flame. but obviously you say it oxidises/disappears. that was the original question, if the carbon content gets reduced in the weld area.

 

[john.k]

You can use an oxidising,neutral or reducing flame for welding iron....but for brazing a reducing flame is best ....The preheat can be neutral though............neatest iron welding Ive seen was on classic motorbike iron heads.....the guy puts the head into a furnace (glassblowers furnace actually) and heats to dull red heat,then removes to an insulating bench and welds the missing iron with ordinary mig ...just mild steel wire......back to the furnace ,and when cool the weld is no different to the iron to be drilled and tapped where bosses are broken out,or stripped......same with broken fins.

 

[eKretz]

You can use an oxidising,neutral or reducing flame for welding iron....but for brazing a reducing flame is best ....The preheat can be neutral though............neatest iron welding Ive seen was on classic motorbike iron heads.....the guy puts the head into a furnace (glassblowers furnace actually) and heats to dull red heat,then removes to an insulating bench and welds the missing iron with ordinary mig ...just mild steel wire......back to the furnace ,and when cool the weld is no different to the iron to be drilled and tapped where bosses are broken out,or stripped......same with broken fins.

That will work just fine as long as it's slow cooled... As we've already hashed and rehashed. The carbon from the iron will migrate/diffuse into the weld, but as long as it's slowly cooled it won't hurt anything.

 

[Big B]

I have no problems trying to pre heat the C.I. item to be welded. I don't mind that at all.

What lessens my enthusiasm is trying to dream up a way to insulate it to keep it from rapidly cooling down.

That's ALWAYS the point at where I say "piss on it".

I don't actually do much, if any, CI repair. But, if I do, I never have any sort of a game plan on what to do to enable it to gradually cool down. I bet that's what a lot of guys have trouble with. Keeping a torch on it to keep it hot's easy...

Last CI thing I fixed was a Chevy 6 cylinder intake/exhaust manifold... from 1961. I just used 7018 Low hydrogen rod. It had a few cracks, and the face where the gasket seats on the exhaust had been corroded and eaten away. That's the surface I welded on, then ground off with an angle grinder. It worked. Ugly as hell, but all it needed was a surface that a gasket could seal.

My uncle told me that he used ashes to put the part in to cool down overnight. Just ashes like from a burnt out bonfire. And he told me that a large part would still be warm the next day. It seems like wrapping a part in fiberglass insulation would be another option.

 

[Big B]

My first experience welding cast iron was a bell housing for an old Toyota Land Cruiser if memory serves me correctly 40 some years later. A guy that I worked with told me that it was cracked and knew that I had a welder and asked me it I'd weld it for him.

I talked to one of our welders and he told me what rod I needed, I think it was Cetranium cast iron rod which was gray in color. I cleaned it off with it still on the vehicle and just did a short stich weld at a time and let it cool some in between welds. He told me many years later that it was still holding.

Another CI weld job was very memorable. It was a pair of exhaust manifolds for my speed boat. Small block Chevy powered boat that I had just bought that summer and I asked another coworker that was into boats what I needed to do to winterize it and he told me to drain the block. But he forgot to tell me about draining the manifolds and the next spring when I got it out and started it the leads were massive. There were two cracks almost the length of the manifolds so probably about 15 inches long.

I took an air grinder and ground a V in the cracks the full length and drilled small holes in what I thought were the ends of the cracks. Put them in our gas grill for an hour or so on high. (my wife was not amused but when I told her that it was something like $400/each for new ones she got over it). Pulled them out one at a time and used a rosebud tip to heat the area red hot and then switched over to a large welding tip and got to brazing. The bronze filler rod flowed and stuck to the CI just like if I was brazing steel. It was really easy with the parent metal being so hot. I put them back in the grill to cool but with that long of a braze I don't think it would have mattered much.

Unfortunately the cracks extended beyond where I drilled the holes and in the end I found aftermarket manifolds for about half price of the Mercruiser manifolds and replaced them.

I've seen a large bench vise that was brazed and still holding many years later. It appears to me that a good bronze weld job in CI is about as strong as if it had never been broken.

 

[Servicar rider]

Yesterday a customer (another shop) called in sort of a panic. He had dropped an antique Harley cylinder and broke a cooling fin off and needed it repaired immediately so he could finish the job before his customer came. About a 4" weld. He dropped it off and went out for lunch, and I had it done before he came back. No, it didn't go "TINK" and I dusted the bead with a flap wheel, and it blended in nice, customer was happy, and I made some quick cash.
I would like to share how I did it, but last week eKretz told everybody here that I had no idea what I was talking about and basically don't know shit, so I guess I'll keep my technique a secret? Too bad because maybe someone else could benefit?

 

[52 Ford]

last week eKretz told everybody here that I had no idea what I was talking about and basically don't know shit

Who cares?

Share. Or don't.

If you share, there's a chance you could help someone, though.

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[Servicar rider]

Sorry No, the one thing i'm sure about on internet forums is once somebody calls you out and you respond the thread turns into a pissing contest and things go downhill from there. I have no interest in doing that again.

 

[eKretz]

Yesterday a customer (another shop) called in sort of a panic. He had dropped an antique Harley cylinder and broke a cooling fin off and needed it repaired immediately so he could finish the job before his customer came. About a 4" weld. He dropped it off and went out for lunch, and I had it done before he came back. No, it didn't go "TINK" and I dusted the bead with a flap wheel, and it blended in nice, customer was happy, and I made some quick cash.
I would like to share how I did it, but last week eKretz told everybody here that I had no idea what I was talking about and basically don't know shit, so I guess I'll keep my technique a secret? Too bad because maybe someone else could benefit?

Thin skinned a little? I only called you out on the big diatribe about how preheating and slow cooling was totally unnecessary. And how nickel rod is useless for cast iron welding. You know, that part where you basically said everyone who does that has no idea what they're talking about and only does it because old timers used to? About that, you apparently don't have any idea what you're talking about. That's all I was referring to. Other than that I don't know you from Adam; nor whether you're FOS on other subjects. I can tell you I've done literally what must be close to a hundred repairs on cast iron structural items like connecting rods, rams and similar parts in punch presses and even a few "unobtainium" cast iron dump truck wheel hubs over the last thirty years, which are about the most severe environment there is for a weld repaired cast iron part, and I have had ZERO failures using nickel rods, good preheat and slow cooling. With readily machinable weld afterward.

Anyway, there's no secret to welding iron. There are a few methods to do it that will work, and they have mostly already been discussed here. Welding in short bursts to keep the part cooler and prevent a lot of expansion and contraction is no secret. I sure wouldn't use it in a critical structural repair though. Welding a cooling fin back on is not in that category. It didn't go TINK, and likely won't - unless someone bumps it with a little bit more than it can take. if it wasn't slow cooled it will have basically zero ductility in the area of the repair.

Gotta love these guys that claim to know all this secret crap, can't stand that shit. But I digress.