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I have a cast iron muffler on a diesel lawn tractor with a crack. I don't handle cast at work and have never dealt with it in the past. Rather than shell out $400 for a new one, I'd like to try to repair this one first. I know cast is pretty sensitive to heat change. I'm looking for some advice on repairing this thing. It's not in a high stress area. I have a cheap little HF stick/tig here, but I have a lincoln square wave tig that will also do stick. Everything I do is mig, tig, or sub arc, so stick is bit of a gray area for me. I also read that brazing is a possibility? Any info is greatly appreciated. Thank you!
I welded some cast iron a while back by taking a nickel stick rod and cleaning off the black flux coating by hammering on it and then using a scotch brite pad and then tig- brazing.
It actually worked pretty good.
You have to clean the crack real good with a wire wheel.
Might give it a try.
You can stick weld it. Ni-99 rod will do just fine unless you plan on machining the weld afterwards. You either weld cast iron hot or cold no in betweens. To weld it hot, you preheat the entire piece to a certain temp, weld and leave in post heat, then only drop the temp a certain amount per hour until at ambient. Most people don't have the facilities for this. To weld it cold run short beads , 1" or so, letting the welds cool to room temp between welds. Cast iron wants to crack when the temp is changed drastically in one area of the casting. I've had good luck with the cold stitch welding technique, just don't apply too much heat for too long.
I've done as both fendermender and Wolfgar have suggested with great success. I welded some cast arms on our bandsaw 6 years ago and still going strong using nickel rod and TIG welding and have repaired numerous cast iron pieces by drilling holes at each end of the crack.
I've welded some cast iron stove pieces to put in the garden.
You _definitely_ need the right filler. I used some Forney
NI rods from the local hardware store -- they seem adequate
for my needs (and I didn't have to buy a huge amount)
For sh..s and grins I first tried doing it with my normal MIG
wire -- chewing gum would have been better at holding it
As to heat -- I've tried the "little bit at a time" approach
and had only a little luck. I still got the tinkling/cracking
sounds and have a few nice cracks to show for my efforts
and a weld or two failed
Next time I do it I'll try some pre/post heat -- even if it's
just a bernzomatic to raise it a couple hundred degrees.
I figure it's can't hurt.
Truth-in-advertising: I'm not very experienced at this
so it could have been my lack of experience more than