Originally Posted by
cubewheels
In the better quality production, they would anneal the whole frame for a period of time after welding. This helps toughen and reduce brittleness in the welded joints. It's possible they forgot to aneal that particular frame
Only with aluminium frames. Nobody anneals steel frames because you would lose the benefit of the cold-working. The welds are not brittle on a steel frame because they are done with a mild steel filler.