[redmodelt]

I read something on the annealing process when spinning brass which may apply. The brass is annealed before starting the spinning process. As work progress it may need to be re-annealed several times as it work hardens. The steel tube may be the same thing. While it starts out bendable as it goes through the bending process it self work hardens. My observations has been that while bending a steel tube, bends easy at first, but not so much to un-bend. Could have something to do with stretching the molecules, so no longer elastic.