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Terry Coombs[_2_]

wrote:
On Sun, 13 Dec 2015 20:03:38 -0600, "Terry Coombs"
wrote:

The day I picked up the stove grates I also picked up a small "fire
pot" that was cracked/broken . The break is across a 2" horizontal
then about 1" vertical - kind of like an angle iron but not at 90° .
I attempted a repair on it yesterday , beginning with a tack at the
corner and one at the horizontal edge . That part went well ... but
when I tried to fill in between the two tacks it keeps cracking . I
have a hammer handy and begin peening before my helmet clears ... I
have not preheated this piece because of the size and awkwardness,
and I think that's what's killing me . The TIG heat is so localized
that the nearby mass of iron is acting as a chill and sucking the
heat out so fast I can't peen fast enough to stop the cracking . I
can't heat the whole part , but I can heat the repair area . The
part is like an oval sleeve , with nothing to restrict expansion in
any direction so I think I can safely heat just that area . The
question is how hot and will this help keep it from cracking ? I
tried some CI strips first , then the Invar 42 , same results with
both fillers ./
Are you anywhere near a pottery supply company? If so, get some
ceramic wool and wrap the piece after heating. As to how hot in my
experience if I heat cast iron to about 700 degrees it won't crack. I
have had the best luck heating to a dull red heat when observed in low
light, wrapping in ceramic wool, and welding. It's a pain because
everything is so hot but on the other hand no peening is required and
no cracking is happening. I have used this method with brazing rod,
aluminum bronze rod, stainless steel rod, and nickel alloy rods.
Eric

I don't have a pottery supply near , but I do have a large pile of
fiberglass batts . You think they'll work at the temps you use ? The grates
aren't so awkward in shape , I plan to build an enclosure with firebricks
and preheat with my foundry burner . Heat 'em both up and let one soak while
I weld on the other , swap as they cool .

--
Snag