Cast iron welding questions

Stainless will stick and be a much better color match that bronze.

One potential problem is that while you intend this to be a cosmetic only repair, you don't know that others in the future will do. Someone else might try to 'restore' and run the compressor years from now. An obviously incomplete repair (V grove with big strong tacks) might be safest over all.

Just some idle thoughts...

Yes, you are right. Someone may decide to run the compressor in the future. This will not be a problem though because a proper job, and I intend to do a proper job, will be plenty strong. Stainless steel will stick well but is not a good enough color match. I'm hoping for some rod that will blend in better, maybe even rust a little like the cast iron will because the pulley is exposed to the weather. Eric

The easiest way to fix it is to use a little preheat and Nickel-99 stick welding rods. Easy as pie.

My favourite cast repair rod is simple steel stick electrodes marketed as Feroweld or FE or similar. The deposit is VERY hard and non machinable or drillable, but can be easily ground to shape using common grinding disks. I have had good results by preheating and slow cooling and using short passes to limit heat build-up. I use an air powered needle scaler to peen the welds between passes and on the top pass while still hot to limit contraction forces. The finished weld is a good color match with common cast iron and the weld will rust.

I do not like any of the nickel rods sold for cast iron repair and only use them if the repair needs to be machined or drilled. FE rods are a LOT cheaper than nickel.

Good Luck, YMMV

A second thought, are you sure this pulley is actually cast iron and not cast steel? The grain of the fracture is a good indicator, but I would also use a cutting torch in the area you will be removing to form the weld vee and test if the iron will actually cut or just melts and blows away. Cast steel is a lot easier to weld than cast iron

Good Luck, YMMV

As somebody else notes you can tig it using stainless rod. However, the stainless bead will be very hard as the filler metal will absorb carbon from the cast iron. Of course, if you are going to only grind the weld bead down to look smooth there is no problems.

The only filler I know of that will have a perfect color match to cast iron is....cast iron.

The problem is to use cast iron filler rod you have to gas weld the cast iron. It does work and will match the base metal better than any other rod. I have a selection of cast iron rods. They are narrow cast square rods.

For cosmetics I would just use the bronze rod. Stainless steel or nickel rods require more heat and that may cause more problems than you already have. Enough good enamel spray paint and the bronze will never show.