When I see all the different recipes for HT and temper I wonder how many of us are really getting max performance out of the steels we choose. Then when I think of all the designer steels I wonder how necessary they all are. I think the sharpest blade I ever used was 440-c and that is almost old school these days. I read reviews of steels by end users and the results vary wildly. I can only think the HT did also.
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on recipes for heat treat and temper, i always refer back to the maker's recommendation and use that as a starting point. O1 for instance, all makers say heat to 1450-1500, soak for 10 to 30 minutes, quench in warm oil, temper for two hours. so my recipe of 1475(800C), soak for 8 to 12 minutes after part is heated thru, quench in 125F oil, temper at 300F for one hour. water quench, scrub, temper at 325 to 400 for one hour. it is following the mfg recommendations.
where i have an issue would be something like heat to 1600F, hold for one minute, quench in room temp ATF . heat to 1550F, hold for two minutes, quench, temper at 475 for Rc 58 and blade that will bend 90 degrees. that is not even close to industry standards and ATF is not a safe quenchant.
440C has been around a long time and is a proven performer. It is a fairly simple alloy, carbon, chrome, a dash of moly, a dash of silicon, and some manganese. it will polish nicely. but it is old, it is not cool, it has fairly simple straight forward heat treat.
