Carbon Steel

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JohnCuthbert
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Re: Carbon Steel

Post by JohnCuthbert »

Am I missing something here? The data presented here
http://www.ee.ualberta.ca/~schmaus/vacf/outgas.html
kindly cited earlier give outgassing rates for mild steel of the order of 4E-7 to 1E-11
For stainless they give 4E-7 to 1E-13
Unless you are in a position to bake the whole system, under vacuum to 400C for ages there's not much difference between mild steel and stainless.
I have seen UHV systems with exposed copper and aluminium parts and they should outgas about as much as the mild steel, yet they work just fine.
We are not (as has been pointed out) trying to get UHV here.
Might it be better to concentrate the effort elsewhere?
(And, BTW, I suspect the only way to get an electroplated copper surface to stop outgassing like a baked bean fanatic the day after a real ale festival is to melt it.)
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Doug Coulter
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Re: Carbon Steel

Post by Doug Coulter »

They probably specified "clean" iron, which isn't that bad -- and their numbers show it not being that bad. Other sources spec slightly rusted carbon steel perhaps 400 times worse. But -- hit it with some shop air, it's not clean anymore -- you got water and rust more or less within 10 seconds if my electroplating experience is anything to go by; you have to go fast from pickle through rinse to the plating tank or it just doesn't work, it's already contaminated again. That's usually the issue. Those numbers you are quoting are pretty extreme spreads, which is actually realistic. Metal history has a lot to do with it.

You could be right about the copper, I wouldn't trust it after reading Kohl's chapter on it -- gotta get it with zero phosphorous, no oxygen etc even when using it as a bulk in a vacuum tube.
Having said that, I use it a lot here (OFHC) and no special troubles, but my base pressure is limited by other stuff (some viton). I can definately tell right off when I put any not-special-treated substance in the tank, though, and am careful about that.

I agree, this isn't going to be anyone's main problem unless you let the steel get rusty, once it's been nicely baked once. Or magnetized, but small fields don't seem to hurt fusor much, or mine wouldn't work.

I think the sputter or evap idea would be fun, if it turned out to be needed, though.
Why guess when you can know? Measure!
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Chris Bradley
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Re: Carbon Steel

Post by Chris Bradley »

For a fusor application, I think the concern might principally be that mild steel tends to suck up hydrogen (deuterium) less so than stainless. Actual outgassing of atmospheric content looks like it is much the same at non-UHV, otherwise. I say this from what I've read, not from what I know to be true.
Quantum
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Re: Carbon Steel

Post by Quantum »

As I've previously stated, We use aluminium chambers at work.

We also use viton seals.

Vapour deposition runs at similar pressures to fusors.

Our chambers are basically just multi-layered sandwiches of ally and viton.

If you want to avoid welding, and have access to aluminium machining facilities, it's worth a thought.
Dan Tibbets
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Re: Carbon Steel

Post by Dan Tibbets »

Link for a site with a number of vacuum topics

viewtopic.php?f=10&t=3344&hilit=http%3A ... htm#p21870

Dan Tibbets
Quantum
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Re: Carbon Steel

Post by Quantum »

I think the ideal solution to overcome the drawbacks of carbon/alloy steel would be goldplating. (We use gold plated springs and other components in our chambers at work.)

This would also make an impressive looking chamber.
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