Used heat treating mufle furnace

Want to buy;

For heating accurately to high critical temperature and holding for a short time. 230V single phase best, and chamber size at least 9 X 4 X 4
Thanks,
parts

partsproduction said:

For heating accurately to high critical temperature and holding for a short time. 230V single phase best, and chamber size at least 9 X 4 X 4
Thanks,
parts

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WTB I presume? I was about to ask what you wanted for it.

yea, I opened it hoping to buy a furnace :-)

Steve

I decided to buy new furnace.
Thanks, and I'm sorry I forgot "WTB" in the title.
parts

Somebody please correct me if my understanding is wrong. I was taught that a muffle was what was placed in a heat treatment furnace to protect the parts being treated against oxidation, not the furnace itself. Right or wrong?

In kilns the muffle is to protect the contents from direct contact with combustion components such as ash in a wood fired kiln. I seem to recall that it showed up as low walls inside the combustion ports to prevent the flame from impinging directly on wares inside.

There may be other usages of the term.

I've been hitting my head against my ignorance of the subject, I just want to stop eyeball heat treating, especially with some of the more exotic materials.
I assume the heat inside a muffle would normally be more uniform than what a part would get laying on the floor of the furnace.

I have a fisher furnace that I need to get rid of. Not quite sure right off the bat how big the inside is but it is bigger than your dimensions. Overall the whole thing is about a 24" cube on the outside. Trouble is that it probably is not real practical to ship. Would have to go freight strapped to a pallet.

Trouble is that it probably is not real practical to ship

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I'm afraid that's true. But thank you.

partsproduction said:

I've been hitting my head against my ignorance of the subject, I just want to stop eyeball heat treating, especially with some of the more exotic materials.
I assume the heat inside a muffle would normally be more uniform than what a part would get laying on the floor of the furnace.

Click to expand...

Heat uniformity can be a problem but the muffle won't necessarily fix that. Uniformity would be established by the design of the heat entry and exit. And a part lying on the floor will probably get to a uniform temperature - at least whatever temp that part of the kiln or furnace gets to. The time-at-heat is intended to make sure that the center of a blocky part gets to the same temperature as the surface and would through harden, at least to the extent that the quench also drops the temperature fast enough to ensure the change.

The atmosphere inside could be either oxidizing, reducing, or neutral and that could be important to know. If it's oxidizing, you don't want the carbon in your part (primarily on the surface) combining with oxygen and compromising the hardening process. If fuel fired, oil or natural gas, you can control that to some extent. Providing slightly more fuel than air required for compete combustion will ensure there's free carbon so it isn't drawn out of the part. An oxidizing atmosphere is slightly harder to manage. The loss of carbon problem is why some parts are wrapped in stainless foil during heat treat to shield it from the atmosphere in the furnace. The furnace atmosphere might also contribute to how fast the interior material degrades.

Not usually the most important factor to know in heat treat but good to have in the back of your head to avoid or solve problems occasionally.