Originally Posted by 531phile
about 853 reynolds. Since they get stronger when they are heated, why not just heat them till no tommorrow to make the world's strongest bike frame or am I mising something?
It's the old strengh vs. ductility dichotomy.
As strength goes up, ductility goes down.
Stength is what allow the walls of the tubes to be thinner and weigh less while still supporting the rider.
Ductility is what keeps the tube from ripping apart when it gets bumped.
Super light tubes are made from alloys that allow their strength to go way up during heat treating. But those tubes are expensive, delicate, and have to be handled properly. If you impart too much heat into a joint when you're welding it, the strength will go down and you're left with thin tubes that are not strong enough to support a load.
The first popular HT tube set was Reynold 753. Most builders back then had so little experience with thin-wall, HT tubes that Reynold required them to braze a joint and send it back to the factory so that it could be tested to see if you were cooking the tubes or not.
These days TIG welding is so commom that companies like Reynolds make alloys like 853 that are specifically designed for it.