aluminum and heat treating

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Ok, on another non welding forum a biking one actually theres a huge debate on whether you need to re-heat treat 6061 aluminum. One guy who is a welding student is saying that under a certain thickness (1/4- 3/8") you do not need to heat treat it to regain its strength. Being a amature welder, i have always been told 6061 and 7000 series alminum need to be re-heat treated after welding or they are only aprox 20% of there original strength. Any help from the Welder web gurus....
Reply:This is from "Metals And How To Weld Them" by T. B. Jefferson and Gorham Woods. Mr. Woods is a metallurgist. The book is available from Lincoln Electric. "Most of the heat treatable alloys ( 2000, 4000, 6000, and 7000 series) show considerable increase in properties as a result of heat treating and therefore are most susceptible to loss of strength and other damage from welding. The 6000 group have good weldability. Alloys that can be solution heat treated ( such as 6053 and 6061) permit partial or full restoration of their strength by heat treatment after welding, depending upon the application".I had some water tanks fabbed out of 6061 one time. I didn't have time to do it and had a shop that did a lot of aluminum work build them. They were not heat treated after welding. Every one of them failed in a weld from the stress of being bounced around on oil field roads.
Reply:Weld it and forget it..Unless its holding up a Battleship....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:For an aluminum bicycle frame, I'd recommend re-heat treating.  I believe the stresses can be very high in that application, and you'll need all the strength the aluminum alloy can provide.  Even if the annealed 6061 aluminum possessed sufficient strength for the loads encountered, the annealed material will have a much shorter fatigue life.  The lower strength material will crack through fatigue, and fail much sooner than the 6061 that has received the proper heat treatment.
Reply:I have re-welded broken aluminum welds on bikes for my buddy Lou..He owns Crossing Cycles in Franklin,Ma..www.crossingcycle.netSo far so good with the repairs with no post treatment.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterWeld it and forget it..Unless its holding up a Battleship....zap!
Reply:Originally Posted by Go1lumWhat is the point of designing and engineering a frame to be a certain strength if the welds become weaker after welding if not reheat treated?According to some info i have here for a 6061-T6 before welding has an average  tensile strength of 45,000 psi, average yield strength is 40,000 psi, and elongation of 12%. After welding it has an average tensile of 30,000 psi, average yield of 19,000 psi and elongation of 11%. Filler alloy is 5356
Reply:Originally Posted by Atomik777Ok, on another non welding forum a biking one actually theres a huge debate on whether you need to re-heat treat 6061 aluminum. One guy who is a welding student is saying that under a certain thickness (1/4- 3/8") you do not need to heat treat it to regain its strength. Being a amature welder, i have always been told 6061 and 7000 series alminum need to be re-heat treated after welding or they are only aprox 20% of there original strength. Any help from the Welder web gurus....
Reply:Originally Posted by Go1lumWhat is the point of designing and engineering a frame to be a certain strength if the welds become weaker after welding if not reheat treated?According to some info i have here for a 6061-T6 before welding has an average  tensile strength of 45,000 psi, average yield strength is 40,000 psi, and elongation of 12%. After welding it has an average tensile of 30,000 psi, average yield of 19,000 psi and elongation of 11%. Filler alloy is 5356
Reply:You guys want a laugh... Heres the thread.http://www.ecmtb.com/forum/showthrea...1&page=1&pp=20
Reply:Originally Posted by Atomik777You guys want a laugh... Heres the thread.http://www.ecmtb.com/forum/showthrea...1&page=1&pp=20
Reply:Lol.... Its just every time someone talks about getting a frame welded... that guy starts. But i believe the info i got from here might of finally shut him up.
Reply:Originally Posted by Atomik777You guys want a laugh... Heres the thread.http://www.ecmtb.com/forum/showthrea...1&page=1&pp=20