Welding Tips and Tricks

We usually weld aluminum on a fairly routine basis using wire. I am confronted with a problem that I need help with. I am trying to weld a piece of 6061 tube 26" OD x 21-1/2 ID with wire. The tube has a 2.25" wall thickness. A 1-34 thick by 75" flange is to be welded on both ends of the tube. The problem is that we are not able to determine just what the proper heat should be on the tube before welding. A 1/2" weld is required by the drawing both inside and out. Our weld is failing on the tube side. Is there some type of literature avaiable to help me figure this problem out?

Scott

While a little preheat is good, too much preheat can degrade the mechanical properties of the aluminum. The last heat treatment for heat treatable alloys is 400° F so if you preheat the aluminum to 350° F and hold the temperature in that range while welding, the aluminum's mechanical properties are changed. If you are using too much preheat, then that could be your problem (stress corrosion cracking). In most cases, some preheat is acceptable to dry the moisture away from the piece, but preheat should be limited. What type and size of filler metal are you using ? What type of gas?

Pre- heat to 200, do not allow material to heat over 350, let cool to 200 before making another weld,if material and weld reaches 400 you just change the chemistry of the material and set youself out of procedure