That's right, MinnFlyer. Get the joint perfectly ready BEFORE applying any heat. Heat the joint until the solder JUST flows, then remove the heat. The silver solder we use melts below 500 degrees F, below the annealing temperature of most hardened steels. Use enough heat to get the job done quickly. A torch, iron, or gun that's too small will hold the metal just below the solder's melting point for a while, possibly altering the temper. Heat it quickly, do the job, and remove the heat. Molecular change will not occur in that short of a time.

Dr.1