AMS 6523 is a sub-specification of Steel HP 9-4-20, which is low-alloy high-strength steel with a high concentration of cobalt and nickel. Available as plate, sheet or strip, AMS 6523 can be used for structural components in aircrafts such as rocket motor casings, armor plate, pressure vessels, and it can also be used for gears.
AMS 6523 is known to have excellent weldability and hardenability. This specification can’t be forged below temperatures of 1700° F (925° C). After the forging is finished, the parts can be annealed.
The heat treatment is the following:
Annealing – 4 hours at a temperature 1300° F (705° C), followed by air cooling to room temperature. Then, reheat to 1150° F (620° C) for 4-8 hours and air cool again to room temperature. For sub-critical anneal, the second step can be prolonged to 12-24 hours, followed by air cooling.
Normalizing – this process should always be carried out before hardening and tempering. Heat the part to 1650-1750° F (900-955° C) for one hour and then air cool to room temperature.
Hardening – heat the part to 1600° F (845-870° C) for one hour and use the oil quenching method for cooling.
Refrigeration – if austenite is present after hardening, cool to -100° F (-73° C) for 2 hours and then air-warm it to achieve room temperature.