cast iron repair

[cal-k]

is it possible to repain cast iron that hasn't cracked too much. it is an old Record vice (M4) that has cracked at the back end of the sliding bar (holds the moving jaw and crank). it is only hairline, and hasn't opened up much since it cracked, but it would be nice to fix. the iron is only 1/4 inch thickness max and the crack is maybe 2 inches long.
suggestions? tack weld? heat and clamp?

[racer3j]

When it comes to "welding" CI, one must be brave. You would have to open the crack into a "V." Then with high-temp flux( I use Peterson), true CI rod and a torch( I like my Dillon best but, truly, a traditional will do), patient pre-heat. It comes out better than a braze though a good braze will work too, with same prep. It shows more but I'm suspicious - traditional braze is likely as strong as a weld. Cast iron welds are a bit in the middle of a weld and a braze. That is the best I can do. With as much flux as CI takes to grab, I like to use my cobalt lenses- all of this is so similar to welding aluminum. On AL, I actually did the soda can trick- I am successful about 1 for 20. That is why I refer to it as a trick.mike-$$$ by the way, true CI rod is $10 and up per PIECE!! A fine person here threw in a rod with a blower that did NOT even have a crack. Sure are some great folks here!!

[Dave M]

I have to agree that repairing cast iron is hit or miss. No matter how you do it, a good soaking pre heat is a must. Just as important is a controlled cool down, it has to cool down as slow an consistent as possible. I cover the cast I have repaired with a mixture of heated sand and wood ash. good luck

[Thomas Dean]

I would much rather braze CI than use Ni rods. By the time you have this particular job hot enough to braze the heat will have the whole part hot. You will need to let cool SLOWLY tho. Grind bevels, and mak sure you grind a little to the edges of the bevels. Get to shiny metal, this will remove the mill scale, brass soen't take to this very good, if at all. The part you have discribed should not be a problem and brazing, for me, would be the way to go.

[Trollhammer]

Rockmount makes a cast iron welding rod that works, but it still is very limited. I'm not that great of a welder, but testing it out when my dad brought it home, I was able to run a bead with no problem. I showed him later on, and he said, "that's great, but don't ever take any business fixing cast iron based on that weld." he claims that its hit or miss and it may work for that weld, but the very next weld on the same piece will pop and crack like crazy. I believe Rockmount sells it as "Jupiter" and that its insanely expensive.

Mickey

[JAllcorn]

One thing that may determine how successful welding/brazing cast iron is the amount of grease or oil that has penetrated into the iron over the years. And, I have always been taught to drill a hole at the end of the crack (a little past it) to provide a "termination point" for the crack prior to beveling and welding. I still have some ox/ac cast rod, I think 1/4" dia. but haven't used them in 20 years.

Hi-Alloy and Castolin Eutectic carry cast iron specific rods and electrodes as follows for cast Iron: Hi-Alloy 23FC, Hi-Alloy 64, Hi-Alloy 400, Hi-Alloy 460, Hi-Alloy 460MC and Hi-Alloy Cast Iron Plus. Read the data sheet on each at Hi-Alloy - Products.

Castolin products include EutecTrode 2-44, EutecTrode Xuper 2240, EutecTrode XHD-2230, EnDOtec DO*23, EnDOtec DO*26. Castolin Eutectic Group

Some state they are for contaminated, greasy, etc. Each is somewhat different in procedure. Yes they are expensive but so is gasoline! :-(

Any of these may be hard to find locally. None of my welding suppliers carries these because there is not much call for them.

I have been successful taking a Ni55 electrode, chipping the flux OFF and TIG welding cast and/or cast to mild steel. I don't think that is recommended anywhere but I was trying to find a better solution where I could not get the product I wanted. Your mileage may vary!

[coben]

If you drill a small hole at the end of the crack before you start to weld it will help in stopping the crack from running.