how to normalize and thermal cycle.

[bronyblacksmith]

I am going to be heat treating some knives (5160) "soon" and want to reduce grain size as much as possible.
I was thinking of heating to 1550 to black then 1400 to black and 1200 to black then 900 to room temp.
any advice is welcome thanks.

 

[jawilder]

Start at a higher temp - 1600. This is from Kevin Cashen's website on 5160:

Recommended Working Sequence For 5160 Forging: Heat to 2200 °F (1205 °C) maximum, and do not forge after forging stock has dropped below approximately 1600 °F (870 °C)
Normalizing: Heat to 1600 °F (870 °C) and cool in still air.
Annealing: For a predominately pearlitic structure, heat to 1525 °F (830 °C), then cool rapidly to 1300 °F (705 °C), then cool to 1200 °F (650 °C) at a rate not exceeding 20 °F (11 °C) per hour; or heat to 1525 °F (830 °C), cool rapidly to 1250 °F (675 °C), and hold for 6 hr. For a predominately spheroidized structure, heat to 1380 °F (750 °C), cool rapidly to 1300 °F (705 °C), then cool to 1200 °F (650 °C) at a rate not exceeding 10 °F (6 °C) per hour; or heat to 1380 °F (750 °C), cool rapidly to 1250 °F (675 °C), and hold for 10 hr.
Grinding or Machining
Hardening: Austenitize at 1525 °F (830 °C) and quench in oil.
Tempering: As-quenched hardness as high as 63 HRC.

 

[chad2]

thermal cycling on a stock removal blade can be done 3 times bring to 1350 degrees and let air cool to below 900 degrees or past no red the key is to let i t get below 900. and then right back in to 1350 = one cycle

 

[Stacy E. Apelt - Bladesmith]

Thermal cycling reduces the grain size and prepares the steel for austenitization and final hardening. The way I do it is:
Heat to 1650F, hold for a few minutes ..... quench in the quenchant for that steel.
Heat to 1350F, hold for a few minutes, and cool in air to black ( 900F).... quench.
Heat to 1250, cool to black.....quench. The steel should be a fine grain pearlitic structure and ready to harden.