On 11/02/2021 16:09, John wrote:
> On 02/11/21 16:04, John wrote:
>> On 02/10/21 16:14, Peter Fairbrother wrote:
>>> A belated Happy Christmas and a better 2021.
>>> Anybody got any ideas for high temperature seals? I want to build a
>>> small vacuum annealing furnace, up to about 1150C.
>>> The inside will be 4x4 steel box section with one welded end. My problem
>>> is the other end, which has to open but be sealable to vacuum.
>>> I don't want to use an outer cool sealable box (outside the insulation).
>>> Any ideas?
>>> Peter Fairbrother
>> Grind open end and cover absolutely flat, then use annealed copper
>> gasket between the two ?. Aka, cylinder head gasket material.
Not a bad idea.
>> Depends on how much vacuum leakage and absolute pressure is needed.
>> You may be able to tolerate a small leakage if the right vac pump is
Would prefer not to have to use continuous pumping.
> Of course, rethink this and use an inert gas rather then a vacuum ?...
A disposable  argon cylinder is about £15, a regulator to fit can be
had for about £10 (and I have >1 of both in my box of stuff).
Still needs some sort of seal, as the regulator gives a few psi, but
BTW if you are wondering why I don't want to use an over-insulation
gas/vacuum containment, it's because a) it's expensive - a pressure
cooker is the best solution I have found, and large tall pressure
cookers are rare and expensive - and b) I want to use Kanthal A1 for the
heating element, which needs an air/oxygen environment to maintain the
Kanthal wire would be wrapped over an electrically insulating thermally
conducing layer over the steel cross-section. Maybe glass tissue /
ciment fondu or ceramic paper / filled 1700C HT cement for the
Type N thermocouple (like type K but better long-term stability) with
PID controller - hmm, anyone got any ideas for a cheap programmable
 they say DO NOT REFILL in big letters 0 but they have a handy