Originally Posted by bulgie

Heating it to roughly the silver-brazing temperature range and holding it there a while would temper it more, trading a loss of strength for more ductility. Heating it to red hot, roughly brass brazing temperature, then letting it cool naturally in room temperature still air, would result in "normalized" steel, which contrary to popular belief is actually a pretty decent combo of strength and ductility in these low-alloy steels. It is essentially turning 753 into 531 "as-delivered", though maybe with a bit less strength than 531 due to 531 having cold-work done to it after normalizing. Also there would be a relatively soft tempered zone around the fringes of the part you got red-hot. Counter-intuitive, but the part that only got to silver temperature. That over-tempered area will be the weakest part of the tube, more like the strength of 531 after brazing, which is weaker than as-delivered.