5160/SUP9 are spring steels with close to identical compositions and chemistry. They are deep hardening steels and are quenched in oil. When heat treated correctly They are perfect for big knives and swords, where performance and toughness really matter.
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. After quenching, reheat to the temperature required to provide the desired hardness.