Brazing Cast Iron-Your process?

What is the proper way to braze cast iron? I have a chipped step pulley I would like to build up and then machine the profile back into.
I have had mixed results in the past with brazing.
Would like to hear any tips and tricks from you guys. Essentially how you would proceed to do the braze.
Seems as either I don't seem to get it hot enough or get it too hot where it won't flow or stick to the base metal.
Do you prefer fluxed braze rods or the bare rods with the canned flux? Any particular brand or type?
Thanks in advance.
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wrote:

Why not weld? Use cast iron rod and an oxyacetylene torch. I'm no expert, but I've watched someone who was fix an exhaust manifold that way.
-- Mike ---------------------------------------------------------------- To reply via e-mail, remove the 'foolie.' from the address. I'm getting sick of all the SPAM... ----------------------------------------------------------------
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Agreed. Controlling a brazing job like that leads to madness. Regards. Ken.
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If you do a search for "maintenance welding alloys", you will come up with a flux coated rod suitable for welding dirty cast iron. Magna Alloys sells one in Australia called Magna 77 which is really good and matches your requirements.
There is one link you could investigate http://www.advantage-drillbits.com/brz3G.html
Prepare the surface with a file, NOT a grinder and preheat the part.
If you decide to try a stick welder, use a rod very high in nickel content I've found that to work well.
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Seems like an interesting process. How much? How does it work? How fast will it build up?
Marty

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I've repaired cast iron parts using ordinary coated brazing rods available from my local welding supplier. Clean, preheat, braze and then let cool slowly in a can of ashes.
I was looking at an article in Machinist's Workshop the other day where the author suggested Manganese/Bronze rod when repairing cast iron gears as a higher strength alternative.
Heat control is important. I've had reasonable luck building a temporary forge to allow preheating to 5-600 degrees, then using a torch to bring the repair area up to brazing temp. You can use a much smaller flame that way and have better control of the brazing zone.
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