Brazing or welding cast iron

I need to repair a safety shield from a large "bench" grinder. The shield is cast iron and has a crack. I want to know what is the
easiest way to repair this, with the choices being: silicon bronze, fluxed silver brazing sticks, or TIG with 99% nickel.
i
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All are pretty simple, including cast iron welding rod -- more expensive than normal rod, but used similarly. Ordinary brazing should also work.
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Ignoramus13927 wrote:

I successfully repaired a friend's cast iron power steering pulley with blue flux coated brazing rod and oxy/ace. Your mileage may vary. Clean well and clamp precisely.
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I've used SMAW (stick) with Ni99 rod, because it was the process I had available, and it was pretty easy. Ground as big a "v" as I could and still align the pieces, repaired part is still in service. Granted, I re-enforced it at the same time, so it's now under a lot less stress...
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On Jul 14, 10:10 pm, Ignoramus13927 <ignoramus13...@NOSPAM. 13927.invalid> wrote:

Nickel, is the usual recommendation. I've always been told the whole castiron part has to be heated to prevent cracking, so it'd take a small bed of charcoal in addition to the TIG welder.
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Based on all I have heard so far:
1) I need to clean the cracks, regardless of joining method. This is a crack on a grinder's shield, so I think that I will try to wedge the crack a little wider and sandblast.
2) Brazing - Preheat in barbeque - Heat to read hot in forge - Apply silver braze
OR
2) Welding - Preheat in barbeque - Weld with TIG and 99 nickel rod
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I'm only a amateur / farm welder so this may be irrelevant - I bought rods specially for cast iron (no idea of their content) Heated parts with big blowtorch Stick welded the parts *Left the blowtorch on - only reduced it very, very slowly* (someone told me this was important) It worked
Joskin
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Don't forget slow cool down.
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The business about heating in a pile of charcoal and slow cooldown is not always necessary. Cracking occurs as a result of thermal stresses, which happen if the shape has a loop (or loops) such that the hot part and cool part are pulling in different directions. The simplest example would be a cast iron ring. After the repair, the heated part cools and shrinks. The rest of the ring is fighting the shrinkage, generally resultig in a crack near the repair. On the other hand, a simple butt-weld can shrink without developing stress, and all the fancy precautions are unnecessary.
If the grinder safety shield does not form any kind of loop around the cracked area, chances are you can just fix it and let it cool.
One thing that has not been mentioned is peening. If you weld in small increments, and peen the repair as it cools, you will relieve much of the stress and reduce the likelihood of cracking.
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I ended up stick welding it with Nickel 55 cast iron rod. I preheated it in a barbeque set to HIGH, then welded with 1/8" Ni 55 rod at 105 amps, then put back into the barbeque to cool down. I had to leave afterwards.
I will be home in 2 hours and then could clean up the weld and will see how well it worked. It did not outright crack during welding, and I have not yet looked at it after putting it in the grill to cool.
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Had a look at the Nickel 55 weld on this cast iron guard. The good news is that for the most part, there was good fusion, except for the last 1 inch where the bead appears a little cold. After slow cooling inside a hot grill, no cracks appeared. I think that this guard now is as good as new, for its intended purposes of guarding the wheel. This was, fortunately, a cheap repair.
i
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I have welded successfully many cast iron machine parts with OA and brazing rod with a ground out V. Many years ago I saw a book produced by one of the large welding supply companies (Linde) in which the author claimed that using a conventional grinding wheel to V a broken casting would produce an unsatisfactory job because the grinding process would smear the surface to be brazed with graphite from the cast iron. He advocated heating the metal to melting temperature and blowing the metal away by turning up the oxygen. He also described a process that he called "Lindewelding" which he claimed was a fast way to weld mild steel with OA. It involved using a carburizing flame which he claimed sped up the process by converting mild steel to high carbon steel which he said has a lower melting point. Have any of you heard of these seemingly crazy ideas?
Engineman
On Jul 15, 7:13�pm, Ignoramus32217 <ignoramus32...@NOSPAM. 32217.invalid> wrote:

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I cannot really evaluate what is crazy or not. I ended up heating this in a BBQ grill and welding with Nickel 55 stick welding rod. It ended up with a satisfactory weld over most of the cracks, though unfortunately about one inch of the weld was poor due to my poor welding (or possibly due to the part cooling, as the weld looked cold over that one inch).
i

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I have heard that grinding smears the surface with graphite. The remedy that I heard was to use a cutting torch to go over the area with an oxidizing flame after grinding. Getting the surface hot but not near melting temperature.
Dan
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Naturally hitting the carbon with an oxidizing flame produces CO2. A gas that takes the carbon off the iron and allows a proper weld.
I have used Nickel rods and heated the iron first. I found a caution - I was doing iron pipe flanges. Welding them to steel. (Lady wanted it) and the ones she brought were crappy flanges. They melted into a puddle. It was like the flange was full of air.
The US ones - I went out and bought - stick welded nicely. They held form.
I keep a few expensive hasmat black rods for just an occasion.
My cast iron engine produced a lot of carbon on the lathe. It seemed to be more carbon than iron. But it works like graphite as well.
Martin
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I have welded successfully many cast iron machine parts with OA and brazing rod with a ground out V. Many years ago I saw a book produced by one of the large welding supply companies (Linde) in which the author claimed that using a conventional grinding wheel to V a broken casting would produce an unsatisfactory job because the grinding process would smear the surface to be brazed with graphite from the cast iron. He advocated heating the metal to melting temperature and blowing the metal away by turning up the oxygen. He also described a process that he called "Lindewelding" which he claimed was a fast way to weld mild steel with OA. It involved using a carburizing flame which he claimed sped up the process by converting mild steel to high carbon steel which he said has a lower melting point. Have any of you heard of these seemingly crazy ideas?
Engineman
==============================================I've heard of the first one, but I've never tried to weld cast iron, so I have no idea how good it is. As for the second one, he's correct that high carbon steel has a slightly lower melting point than mild steel. But it does sound crazy, because welding high-carbon steel invites cracks. Again, though, it's not something I've tried.
-- Ed Huntress
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I have just brazed cast iron up in the past and some are still holding up in shop use 30 years later. Most of the things that I have brazed to together I have lost track of. I have brazed up a steady rest for a Summit lathe. Never did know how they broke it. Another time was the 1/2" thick gear box cover for a 24" American lathe. I have also done a few machine handles the same way. Never had a problem.
Richard W.
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I have brazed castings that were so large that it took three torches.. Two torches to keep the casting hot and one to lay the bronze... It works really well if done correctly. . Always just ground out the area of the crack with a side grinder usually a single "V" bevel almost all the way through the casting.. I have successfully welded good cast iron and cast steel with nickel arc 99 electrodes.. I welded some new teeth in a bevel gear on a drill press with nickel arc and later shaped the teeth in a lathe and with a file as I didnot at the time have any way to cut the new teeth other than with a file.. The gear is still working ok years later.. Mike

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"MEG" wrote: (clip) I welded some new teeth in a bevel gear on a drill press with

^^^^^^^^^^^^^^^^^^ When I was servicing Multilith offset presses, a customer stripped a few teeth out of a spur gear. A new gear could not be had for a few days, and to get the machine running again "temporarily," I built up some new teeth with brazing rod, using an oxy-acetylene torch. Like you, I used a file to shape the teeth. I did this by rolling the gear against a good gear, and removing metal until the gears meshed without feeling "lumpy." When the new gear came in, the "temporary" was still working fine, so we did not bother to change it out. Several years later, as far as I know, the printer still has the new gear on the shelf as a spare. In fairness, I have to admit that this was not transmitting much power.
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