copper or aluminum for TIG backer?

admin

All,I've got to do a bunch of 20 gauge sheet metal patching on my car.  I only have a TIG welder, so I'll have to make due.  I like doing things the hard way.In the past I've always use copper as a backer on sheet metal welds.  I read somewhere that when Tig welding steel, it's always better to use an aluminum backer.  I'm curious if there is any difference.Those magnetic backers available these days are pretty nifty..  I've considered drilling holes in my copper and putting in some high temperature magnets.  I seem to recall magnets and TIG welding not mixing, but forget why.  Does anyone know?
Reply:A magnetic field from a magnet can misdirect the arc.Copper backers are nice, but alum backers will work.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:I thought so on the magnets...Are you saying that copper is better than aluminum for TIG?
Reply:I would think copper would work better since it has a higher thermal conductivity, although aluminum would still work pretty well.  They're both dissimilar metals, so the steel isn't going to weld itself to either.  Silver would be the ideal metal of choice, but it's way too expensive to justify using it as a welding heat sink.
Reply:Copper is second only to silver in thermal conductivity.
Reply:Originally Posted by heychrisI thought so on the magnets...Are you saying that copper is better than aluminum for TIG?