There are two basic methods of preparing the steel usually found on the internet:
Triple normalizing - heat and cool in air several times, usually at 1650F,1450F,1250F - accomplishes the stress removal very well, but does nothing to refine the grain. This is a common practice, and does no harm to any steel. On stock removal blades, it is enough to prepare the steel for final hardening. In a forged blade, there may be more severe grain and internal condition issues that are better dealt with by Thermal Cycling.
Triple austenitization accomplishes grain refinement to various degrees, depending on the temps and hold times. It does nothing to reduce stress, and may even add some. There are those who use this method, largely based on one makers procedures, but I can find no metallurgical reason for it making the blade harder or superiorly finer grained.
Those who want to use this method should refer to other people for advice on temperatures and procedures, as I don't do it or recommend it.
Here is more detail on my opinion:
I call the process that can gain the finest grain and hardest blade - Thermal Cycling.
It starts with grain refinement, proceeds with normalization and stress relief, and ends with hardening and tempering.
Start with a high end austenitization at around 1650F, a soak ( if needed and your equipment allows), and air cooling to black from 1650F (in some cases, a quench is used instead of air cooling, but is normally not needed)
Next, a cycle at low end austenitization, about 1450F, to re-refine the grain as small as possible...followed by a quench. Cool in the quenchant to room temp.
Then, a sub-critical soak at 1250-1350F and air cooling to below 900F to remove all stress and prepare the blade for the final hardening quench. You can water cool once the steel cools to black.
The final step is the actual austenitization and quench to harden the blade...followed by a double temper.
My normal procedure is:
1) Heat to well above non-magnetic (1550-1650F) and let cool to room temp (I water quench to speed the cooling once the steel is black/900F, or you can let it air cool )
2) Heat to just slightly ABOVE non-magnetic (1425-1450F) and quench. Cool to room temperature in the quenchant.
3) Heat to just BELOW non-magnetic (1250-1350F), hold here for a few minutes, and cool to room temp. (the blade may be water cooled after it turns black, or allowed to air cool)
4) Heat to the target temperature ( normally between 1450F and 1525F) and hold for sufficient time to allow the alloying to go into solution ( varies by steel type), then quench in the proper quenchant for the steel type. Allow to cool in the quenchant, or air cool after 5-10 seconds of quench. This step is the actual hardening step.
5) Temper twice for 1 hour each, with a water cooling between tempers. ( 400-425F is my normal temper)
looking forward to the progression to completion. Keep the pictures rolling.
