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RE: aluminum welding

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According to some information I read in the AWS Welding Handbook, fusion welding is out because of different melting temperatures for the metal, and the fact that neither metal is soluble in the other. If you attempt it, the result will be very brittle and subject to the usual problems associated with matching dissimilar metals--thermal expansion incompatibility, corrosion, etc.
 
The Welding Handbook says you can join them if the steel is first coated with a metal that is compatible with a suitable filler metal, but it doesn't sound like anything you can do very easily in the field.
 
My inclination would be to redesign the connection so you can bolt the pole on to the bell tower. You can isolate dissimilar metals with gaskets, washers, and bolt sleeves.
-----Original Message-----
From: SEAINT List [mailto:bwslist(--nospam--at)bwsmithse.com]
Sent: Monday, March 04, 2002 2:28 PM
To: seaint(--nospam--at)seaint.org
Subject: aluminum welding

Dear Collegues,
 
A roofer discovered badly "eaten" base of 3" diameter aluminum pole of a church cross on top of a bell tower.  The base of the pole was fixed by encasing it in concrete grout which was contained in open pan made with steel plates.  When I saw it, I was surprised to see the pole lasted as long as it did (built in 1958) as I know aluminum reacts with concrete.
 
My recommended remedial fix was to weld stainless steel fins on four sides of the cross pole and the mild steel pan.  The steel pan is secured to the tower roof framing.
 
The contractor has contacted seveal welders who all told him that it is not possible to weld stainless steel to aluminum.  Is this true?  I would appreciate any comments or resouce I could read.  My AWS D1.1 does not cover welding of disparate base materials.
 
Thank you,
 
Brad Smith, SE