Welding a vaccum chamber

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Can anyone point me to some info on welding an aluminum chamber for high vacuum applications? Thanks,The Apprentice
Reply:Aluminum chamber for high vacuum applications?So you will pull a high vacuum on this aluminum chamber?Does it need to be aluminum, could it be stainless steel?Vacuum chambers I work with for EB welding and helium leak testing are generally made of stainless steel.  The chamber is fabricated with very smooth internal welds and is a polished surface to minimize air molecules being stuck in crevices or rough surfaces.  O-ring seals and vacuum grease.I wonder if the surface of aluminum, aluminum oxide, is too porous (trapping air molecules), for very high vacuum applications.Last edited by pulser; 09-24-2007 at 11:03 AM.
Reply:Originally Posted by pulserAluminum chamber for high vacuum applications?So you will pull a high vacuum on this aluminum chamber?Does it need to be aluminum, could it be stainless steel?Vacuum chambers I work with for EB welding and helium leak testing are generally made of stainless steel.  The chamber is fabricated with very smooth internal welds and is a polished surface to minimize air molecules being stuck in crevices or rough surfaces.  O-ring seals and vacuum grease.I wonder if the surface of aluminum, aluminum oxide, is too porous (trapping air molecules), for very high vacuum applications.
Reply:Aluminum would probably work fine.  Just look at any engine application.  A sound engine can draw what some would describe as a perfect vacuum of 21-23 in.Hg. Intake manifolds and plenum chambers handle vaccum just fine.  It is also a light material.  It is easy to work with , polish and blend out welds and has the ability to maintain high flow rates if properly designed and finished.  Of cousre, you can always take things further, depending on how high tech it "needs" to be.  I wouldn't think some production like device like you described requires that you take the design to quantum physics level.With that said, stainless is good too.Hobart 140 Handler w/ gasHyperTherm Powermax 380 Plasmaoxy/acetylene
Reply:You want to either weld it on the inside, or do a full penetration weld....typically.  If it's HIGH vacuum, that is.
Reply:I talked to my buddy who designed the vacuum chamber and he's looking at aluminum and stainless steel as well. We are currently trying to land our first customer. I'm sure the customer will want some input on the final design. I'm not a welding expert by any means but I like to learn new things. I took a welding class last year and have been reading some welding books. I also got a copy of the Welding Design handbook from AWS. I'm going to do all the mechanical design and CAD work on the vacuum chamber. We will most likely contract the welding to a weld shop. I know several good ones in the area. But I want to understand the welding principles so we design and build a quality vacuum chambers.
Reply:We use both stainless and Alum. .  The Stainless is used to make a pressure vessel and the Alum then covers it with a vacuum chamber.  The whole setup has to be able to withstand 4k temps in the center and 300k on the outside.  The temp conversion  I do not know.  But it is real cold.......LOL.  From my understanding the 4k is somewhere around -400 degrees, but I have no clue.As for the welding with Alum.  we just weld away and use helium to do our leak checks with.  They have smaller particles the air or water and make it easy to find even the smallest of holes.  Hope that helps, it late here and I am tired.P.S.  Just make sure the Alum.  is thick enough to with stand the pressure.  We use I think 13mil for our Alum..
Reply:partagas C = K-273 so 4K is -269C 4C away from absolute zero.