Austenitic precipitation hardening steels retain their austenitic structure after annealing and hardening by ageing. At the annealing temperature of 1095 to 1120°C the precipitation hardening phase is soluble. It remains in solution during rapid cooling. When reheated to 650 to 760°C, precipitation occurs. This increases the hardness and strength of the material. Hardness remains lower than that for martensitic or semi-austenitic precipitation hardening steels. Austenitic alloys remain nonmagnetic.

Grade

Nb+Ta

630

min.

max

0.07

0.04

0.030

17.5

0.15

0.45

Also known as Alloy 630, type 17-4PH is the most widely used of all precipitation-hardening steels. Compared to other PH alloys, it requires a simple heat treatment to produce a wide range of properties, including its high strength. It has a slightly higher ferrite content than other PH grades, making it a bit more magnetic. To improve formability, heat treatments may be used before cold working.

stainless steel plate sheet04