Tungsten glow

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Warning - Newbie Question Coming Up:I just got a CK pyrex cup and gas lens kit for my tig torch (#19).  I practiced with a 1/16" zirconiated tungsten on 1/16" aluminum, 40-50 amps max.  The tungsten sticks out about 1/4" out of the pyrex cup, per instructions.  It glows orange about 1/2" up the tungsten from the (balled) tip.  Q: Is this normal?  It doesn't seem to happen when welding steel.Other notes: Gas is set at 12 cfm, and the gas flow feels about the same as with a regular alumina cup.
Reply:Yep, it gets real hot when doing ac welding.  thus the ball and extra heat.Various GrindersVictor Journeyman torch200cf Acet. 250cf oxygenLincoln 175 plus/alpha2 gunLincoln v205t tigLincoln 350mpEsab 650 plasmaWhen you can get up in the morning, Its a good day.Live each day like its your last.
Reply:Originally Posted by unisk8rWarning - Newbie Question Coming Up:I just got a CK pyrex cup and gas lens kit for my tig torch (#19).  I practiced with a 1/16" zirconiated tungsten on 1/16" aluminum, 40-50 amps max.  The tungsten sticks out about 1/4" out of the pyrex cup, per instructions.  It glows orange about 1/2" up the tungsten from the (balled) tip.  Q: Is this normal?  It doesn't seem to happen when welding steel.Other notes: Gas is set at 12 cfm, and the gas flow feels about the same as with a regular alumina cup.
Reply:I would not recommend using the pyrex cup for welding Al.  I say this because I was using my CK pyrex cup while welding Al, contaminated the electrode and some of the molten Al blew back and embedded itself in the pyrex itself, leaving small black inclusions in the cup.  These inclusions kind of defeat the purpose of having a clear cup, I have only had this happen with Al and not with Ti, SST or CS.
Reply:Tungston works best when hot.  something about Ions.  Yes its normal.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Thanks all!  Yup, this was on AC alum.  Not as much an issue with steel (electrode negative of course.)Pete
Reply:Originally Posted by David RTungston works best when hot.  something about Ions.
Reply:If electrons in metal need energy to leave it, then how would you explain electron tunneling? Or resonant tunneling with unity transmission?  Just busting.
Reply:Man, I've got to get all my books and notes back out.  Hold, I'll get a new note book too, and my old Ti-89.
Reply:Originally Posted by phila.renewalIf electrons in metal need energy to leave it, then how would you explain electron tunneling? Or resonant tunneling with unity transmission?  Just busting.
Reply:The fact that energy is needed for electrons to leave the tungsten surface caused cooling of the tunsten in that region, so if a tungsten is pushed over limit with current, it will fail (melt off) up the rod some distance from the "cooler" tip area.
Reply:Originally Posted by enlpckSame reason for the heater in a vacuum tube (am I the only on here htat remembers these?)