My hobby is Knifemaking. In the knifemaking world there is so much mis-information and out right alchemy regarding heat treating and tempering blades that actual fact often becomes lost. Many bladesmiths subscribe to the 3 theory. That is anneal, normalize, quench and temper 3times each. I know that triple quenching can shrink the grain size in the steel, but others believe that annealing and normalizing can also get the same results. My understanding is that annealing softens the metal and makes it workable and normalizing relaxes the stress from forging. All the information I can find on normalizing indicate a soak time at temperature and slow cooling in air but nothing I can find indicate there is any benefit to repeating the process. The same goes with tempering. My understanding is that it is a function of time at the tempering temperature not the cycling of the metal to tempering heat repeatedly that allows the transformation from Martensite to Austenite.