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Terry Coombs[_2_]

wrote:
On Mon, 14 Dec 2015 18:43:35 -0600, "Terry Coombs"
wrote:

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 .
I don't know about the fiberglass batts because I think they use some
sort of glue to hold the fibers together. Tear a small chunk off and
point a torch at it to see if it burns. Not too close because the tiny
glass fibers may burn while in the torch flame. Your enclosure idea
is a good one. Lay the grate on some more fire brick while welding so
that it doesn't lose heat through conduction. You know, I bet the
fiberglass would be fine if it was just used to cover the part while
it was being welded. Try it. It just occurred to me that a fireplace
shop may also have ceramic woll.
Eric

Heh , we don't have one of those too . This is a very small (5,000) very
isolated town - the nearest freeway is a hundred miles away more or less .
Those 'glass batts were salvaged fom a tearout , cost me the labor to load
'em up .
Today I'm working on toy boxes for my 2 youngest grand daughters .
Tomorrow I'll be setting up for the CI job , get it outta the way so I can
go back to laying cement block yecchhh for our new cellar .
--
Snag