Kiln/furnace advice sought

I want to build a furnace to cast Inconel, which melts at ~ 1350 C.
I'm planning on using 1450 C as a target kiln maximum temperature, and 1550
C rated castable insulating refractory. Is this sensible?
I also need to be able to evacuate the furnace to a fairly high vacuum. I'm looking for a cylinder with a full-diameter removable, sealable lid, between 8 1/2 and 14 inches in diameter, and 11 and 16 inches high, which will take a vacuum at perhaps 100 C - the insulation is on the inside, it doesn't get very hot. Any suggestions? Something cheap.
I thought of using a small milk churn, but they are aluminium and not entirely cylindrical, and the lid is smaller than the body.
A gas bottle could be used, but it would need a lot of work to make a removable, resealable lid (and I'm a bit unhappy about cutting one open anyway).
Any other suggestions? I have this image in my head of a (stainless?) steel container of about the right size, with a lid that clips on, a small drum perhaps, but I can't identify it.
--
Peter Fairbrother


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and 1550

vacuum. I'm

between
will take

doesn't get

not
a
open
(stainless?) steel

drum
Peter,
100 deg C difference between your max temp and your melting point looks a bit close to me. The heat transfered from the kiln / furnace to the metal is proportional to the difference in temperature so as the metal gets close to melting it will take an age to heat up the last few degrees. What is your casting temperature - obviously more than 1350 C - but what temperature do you need for fluidity ?
What are you using as a heat source?
AWEM
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Andrew Mawson wrote:

Hi Andrew,
I don't know the casting temperature needed for inconels - in fact I know very little about casting inconel at all.
I have done some casting with lower-tmperature metals, where the hot molten metal is poured into a cooler mould and hardens quickly.
What I had in mind here was to heat both the mould and the metal to the same high temperature, allow the metal to flow slowly into the mould, then cool.
This may be a silly idea - I am a newbie, and am having a hard time finding references/books etc on the subject.
I don't mind going higher if needed, the figures given were just my first thoughts, which seem to have been a bit naive.
Any further advice would be welcome.
Electric heat, resistance, but what I have only goes to 1600 C element temperature. Thinking about using microwave/RF, but I thought to start off easy.
--
Peter Fairbrother


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C.
temperature,
lid,
make
one
small
furnace
as
more
know
molten
the same

then cool.

finding
first
element
start off

I'd be interested in the heating element that takes that temperature. Kanthal is the most common of the 'exotics' and that runs out of steam at 1350 C, and even then the atmosphere has to be controlled so that the film of aluminium oxide doesn't get stripped.
AWEM
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Try Kanthal Super http://www.pshcanada.com/kfels4.htm and http://tinyurl.com/gyj3j
Charles
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temperature.
steam
that
...mmm... that's an interesting development. Must be some complex metallurgy to it.
AWEM
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It's been around for more than 20 years - I remember designing some kit using it in the early 80's when Duncan Munro and I worked in the resistance heat treatment business.
Charles
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Andrew Mawson wrote:

It's just an idea, but I was thinking of using light bulbs - the "halogen" ones with quartz sheaths and tungsten elements. Is this silly?
I got some 9" extra-long ones, so the ends could be outside the furnace proper and cool-ish in use, as they have metal bits on to carry the current etc.. I won't be running them at full power.
The middle part is just fused quartz and tungsten (and halogen and argon) - quartz softens at 1,650 C iirc, and the tungsten goes to 3,000 C plus in ordinary use..
I may try Super Kanthal HT (thanks Charles!) tho' if they don't work.
--
Peter Fairbrother


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