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method for welding cast iron?

Posted by hunter_tx (My Page) on
Fri, Sep 24, 04 at 22:30

Can cast iron be welded in any method that will produce a strong weld? I have an old cast iron bathtub that one of the leg brackets is broken on. It's a clean break, but I don't have any knowledge of welding methods other than how to weld general run-of-the-mill steel. We have a common stick welder and a small wire welder.
THanks, Mrs H


Follow-Up Postings:

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RE: method for welding cast iron?

Yes, it can be, but someone with more knowledge on that subject than I will have to tell you how. I broke a cast iron part on a mower, took it to a welder just east of Cedar Creek Lake who had a show place out in the country with a shop that I could not believe. He had taught welding for a number of years at UTA. He ground a bevel on the two parts then used a certain type heavy rod with an arc welder, ground that weld a little then went over it again. Strange thing to me was, that part had been broken and welded before but broke in a new place a couple of inches from where it had previously been welded. I would have to assume that the first weld was as strong as the rest of the part, at least. I would think that a leg could be welded back on a bath tub.
Bill P.


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RE: method for welding cast iron?

Hi Mrs. Hunter. Since no one is stepping up to answer your question more thoroughly than I have attempted to do, I will paste below a couple of links to welding sites that have message boards there, Perhaps you can get the kind of expert advice that you need there. Most of them have some type of forum or message board, you just have to look for them.
Hey, nice "Barn house" shapin up there. Y'all gonna live in that ? Looks like it will be nice enough to. Put you a safe room in the center of it for when them Texas tornados come along.
Bill P.

http://www.brainfarth.com/bone.html

http://www.hobartwelders.com/weldit/filler/stick.html

http://www.machinebuilders.net/


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RE: method for welding cast iron?

I've done this once and had no problem, but there are welding experts that have done it many times. I'm no expert but this seemed to work for me.

pre-heat the weld slowly.
Use a nickel rod and weld
Cover with something to make sure the weld cools slowly.

The trouble is that the welds crack when not done this way.
Thats probably why the first weld ended up breaking.

I stuck my weld in some sand to slow the cooling.

Good luck,

Kurt


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RE: method for welding cast iron?

Thanks to both of you for the replies.
Gonefishin, yes, we are going to live in the barn. We are empty nesters and needed a new project (grin). That's what it turned out to be. It's been fun learning a new medium. The barn will have 1152 sq ft of "house" for us to live in, 288 sq ft of guest and utility room, and a 144 sq foot workshop area all under the same roof. It's been a real learning experience and I have found out that I'm too old to be building a house. We are going to build a safe room in it. There's a pantry that is centrally located in the house portion that will be great for that purpose.
Are the fish biting where you are? It's been pretty unpredictable in the local lakes with the unusually cool and wet summer we had.
Mrs H


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RE: method for welding cast iron?

I was told by a good welder that the weld can crack afterwelding about 1/2" away in the heat effective zone if the welded material was not cooled slowley. I have welded cast iron with mixed results. You can buy a cast iron rod check with your welding supplier.


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RE: method for welding cast iron?

That sounds like a fun project if you are up to it and it helps to keep you going, to keep doing things as long as you don't over do it. I am still trying to learn to stay within my limitations too, but if you are doing things that you enjoy it is easy to keep going longer than you should. But that is also when accidents happen sometimes.
I have been too busy to do any fishing, and yes, it has been a weird year weather wise, but the fish are already wet and I can imagine some big ones out there swimming around or laying in wait for me! ":^) That is at least half the fun, but I like to go whether or not I catch anything! I like Lake Fork, one of the nations premier bass lakes. If you are familliar with it, you know that they do have some alligators there, along with the Florida strain of the big largemouth bass.
My friend John and I were fishing there early one morning between dawn and sun up. A big owl was making calls that probably could be heard for a couple of miles, the surface of the lake was like a mirror and we noticed a squirrel on the bank intent upon getting to a hickory nut laying on a stump about 10 yards out in the water. He kept fidgiting around starting to jump then changing his mind, finally got a running start, made a great leap, and barely made it to the stump, where he sat and ate the hickory nut. Then decided to go ashore and began circling the stump but there was not enough room to get a running start. He finally jumped as far as he could and started swimming ashore. A big alligator rose up out of the water and intercepted him and gave one chomp and swallowed him. John and I had been silently watching with interest. We sat there in the boat in shocked supprise for several seconds before John Exclaimed, "Dang Bill, did you see that ?" About the time I said "Yeah" the alligator's arm slowly raised up out of the water and laid another hickory nut on the stump. (TIC)(Joke)
Hope that you find a way to weld that cast iron leg back on, If you don't get a better answer, try Kurt's suggestion, and since you probably can't bury the welded on leg in sand to let it cool slowly, you might try low heat from a torch intermittently, increasing the intervals between caressing it lightly with the flame including the adjacent areas, gradually letting it get cooler that way. Just a thought. If you have used one to preheat the cast iron some, that might work. If it holds a lot of value to you, you probably need to check for someone in your area that has expertiese in welding cast iron.
Bill P.


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RE: method for welding cast iron?

Hehe, you got me on the one about the alligators. Really had me going there for a couple of minutes.
I suppose that to cover the weld and slow down the cooling, we could put a big sandbag over the welded area. Actually, the repair is not critical because it is on the side that will be against the wall, so we could, in reality, prop the tub on that corner to keep is stable and no one would ever be the wiser. I would just like to fix it or have a good welder fix it for me.
The barn is basically our primary experience with welding besides small projects, wo it would be better left to a pro. Thank you all for your suggestions. I will heed your advice and get someone with experience to do it. Our little local college offers welding classes. Maybe I should speak with the instructor and see if he has any suggestions.
Mrs H


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RE: method for welding cast iron?

The basic trick is to use 99% nickel rod in an AC arc welder. Deeply bevel the edges. Build it up bead by bead. As soon as you lay a short bead, peen the glowing bead with a hammer and keep peening for a little bit. That'll help even out the stresses. Then clean carefully and repeat. I've done this with great results (even with a cheap 110V welder) on very thin parts. No cracks so far.

Preheating makes it safer, but it's not required if you're careful. It's more of an issue with torch welding.

Or you could brass braze it, although it's not as strong or pretty.


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RE: method for welding cast iron?

I weld cast all the time... If you new at this then I suggest this way for you... Buy a nickle rod called cold weld... Clean up you parts and weld a 1/4 -3/8 long bead...
Walk away and come back later after it cools and do this again until its done... If you don't get it hot you will not have a problem...


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RE: method for welding cast iron?

See I told you there were pros around :) All I had to do do was give my crude instructions and the we get the correct replies and answers:). My process worked fine for me, but I had heard rumors/legends of this cold rod, but have never seen it. There was a story I heard about an old guy who welded cast all the time, but never let anyone watch to see his methods. Something about a cold rod. I think the mystery is solved....

Kurt


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RE: method for welding cast iron?

I use around 250 lbs of cold rod every year... Its not cheap... Buying small amounts can cost you $3.00 per 1/8 rod ... Sometimes I use my mig if I'm welding engine manifolds ... I used brazing and don't like it on cast... I also use a square weld rod just for cast. It gets melted on with a torch like in the old days... It wont work if the cast has been around oil... Oil always causes welding problems when welding cast... Pre-heating the broken part helps burn out the oil... Oil will turn into gas and make you weld pores ...


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RE: method for welding cast iron?

I do it like John in Ma stated, except for peening I use a standard welder's chipping hammer. I use the pointed end, not the flat end, to make little peck marks while it starts to cool (for the first minute or so). This displaces the metal to prevent stress build-up. Preheating is very important.


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RE: method for welding cast iron?

Peening can be done real easy with an air powered Needle descaler...


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RE: method for welding cast iron?

Mmmm, needle scalers. Good thing to have, Kev's right. Import catalogs have attatchments for air hammers at around $15.


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RE: method for welding cast iron?

One thing I do welding cast iron is after all the preheating, welding(Continuous bead), peening, etc., I place the welded part in an oven preheated to 300 deg. F. I then start turning the oven down 75 deg. every 15 min. so it will cool slowly. Once the oven is turned off I leave the part in until cool enough to pick up.


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RE: method for welding cast iron?

Hunter,

If you tub is a real old tub, it was probably a sand casting, and old sand castings are very dificult to weld.

We do restoration work, and we had an old six piece metal fireplace harth, and the horizontal top (the mantel) was cracked, and a small 1 1/2" x 6" piece was broken off. None of the local shops around hear would touch the project.

I ended up at our local CC talking to the dir. of the weling program, who turned the repair into a live project for one of the welding classes. We had three welds, 2 aprox 4-6" and the other Aprox 2". The metal mantel was aprox 9" D x 60" W. We were concerned that the heat from the welding would crack the top, so they chose to use TIG, and placed the mantel on a LARGE steel bench. The 1st weld went great, then as it was cooling, we started to get additional cracks in the top due to the cooling. We then placed lots of sand over the mantel, and had several students using Oxy Acc. keep the sand warm, along with the exposed portion of the mantel. The rest of the repair went extreamly well, and it took about 20-30 minutes to slowly cool down the repair work. One of the kids had one of those digital point thermoters, so we used that to monitor the cool down process.

Since then, we've done some of our own repairs, using about the same process and have had good results.

I hope this helps


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RE: method for welding cast iron?

Won't welding ruin the porcelain enamel on the water side of the bathtub?

Anyway, interested in this "cold rod". I have an old slant six block with a long crack in the cooling area. I have drilled, tapped, and used Iron-Tite plugs, down the entire length, but they tend to seep a bit.

I have thought about welding but the motor is in very good shape (burns no oil, good crank, great compression etc) that I'd rather not tear it apart for that.

Would I be able to use the cold rod on this external crack without pulling the motor?

The other possibility is forming a thick plate to go over the crack, then drilling/tapping new holes to hold it in place over a rubber gasket. All it needs to to is to contain the seeping.


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RE: method for welding cast iron?

If you could get to it to weld it, you could probably get to it to clean it with a pressure washer, let it dry good, then try some JB Weld on it. This is assuming that it is just cracked on the outside of the water jacket of course, which it seems to be, that it is not getting into the oil, and that it would not have to hold the full pressure of the cooling system, which don't seem like it would have to do. I have heard of people repairing motor blocks with it and it holding. And there are some radiator and block sealer products available at auto parts stores that you put into the cooling system that are sometimes sucessful (at least for awhile) on small leaks.
The newer J.B. Quick is like an epoxy stuff where you mix the contents, or some of them, of two tubes together then apply. In restoration of an old garden tractor, I repaired the bottom of the gas tank with it while looking for a replacement and it has held gas thus far. It seems a bit flexable when it is finished or cured.
Might be worth considering, and would be a lot easier than the other alternatives mentioned, if it works. Just my thoughts.
Bill P.


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RE: method for welding cast iron?

Well, there must be some pressure of the cooling system involved because it's part of the cooling system. However the most it does is seep. The seepage seems to go away when the block heats up, probably because the metal expands and seals tight. Then when it cools, there can be a little puddle - maybe a tablespoon - of coolant collecting on the flange below the area. This is a slant six so there's plenty of room to get to the area.

I have though of JB weld, but I would expect that it being brittle would eventually crack from the movement of the metal beneath it. I am thinking a cold weld would be stronger and less likely to crack. It's also why I thought grinding down the area flat (there is raised lettering, etc) and covering with a gasketed plate, might solve the seepage while still allowing for metal movement.

I suspect this crack came from freezing/expansion but it may also be a weak area in these types of blocks. And yes, it's only on the outside, the motor burns no oil, doesn't get oil in the water nor does it get water/coolant in the oil.


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RE: method for welding cast iron?

Rich, I am not trying to sell J.B. products, only post again because as I mentioned above the J.B. Quick is a little flexiable, and might be somewhat like the gasket you mentioned without the plate. It might not be what you want at all, and if it can be reached to be ground properly and cold welded that would probably be the best way to go. Depending on how much trouble and / or expense you want to go to. It would not take much to try a little of it on a couple of pieces of metal to see if you think it is worth a try.
I broke a cast iron piece on a mower, took it to a guy who had taught welding at UTA for some time and he ground it and welded it, very sucessfully.
Good luck with the repairs.
Bill P.


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RE: method for welding cast iron?

I found that Lock-tite works wonders for crack leaks...
Its the best for fixing leaks in steam pipes...


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RE: method for welding cast iron?

Hi Guys:
You may want to try "Devcon" ,you can get a Plastic Steel Putty that I think would work for filling the crack.I have used this material to form an ear on a drill press table that was broken off and lost. I have used it to fill small voids in cast iron castings. I would take a grinder and enlarge the crack even if you try to weld it.

Devcon may have a web site. You can get Devcon at any Grainger store. Granger web site is www.granger.com

Good Luck bill


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RE: method for welding cast iron?

One more question: I have a cracked grand piano 'harp' or main frame. The crack is in appx 5/16' thick cast iron sitting right on top of the wooden 'Pin Block.'
Can a MIG or other 'cool' process be used without totally burning the wood? I will try to put in a URL to show the crack.

Here is a link that might be useful: www.gbs.bz/crack.jpg


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