PRECIPITATION HARDENING STEEL WITH IMPROVED TOUGHNESS AND METHOD
In some aspects, a heat treatment process is described for precipitation hardening steel. The heat treatment process can include a solution treatment for a precipitation hardening steel part. The solution treatment includes heating the precipitation hardening steel part to an austenitizing temperature. The heat treatment process can also include a quenching or cooling treatment, in which the precipitation hardening steel part is cooled to a martensitizing temperature. The heat treatment process can also include an aging treatment, in which the precipitation hardening steel part is heated to a temperature of 1000° F. and held at that temperature for five or more hours until a fracture toughness of the precipitation hardening steel part is greater than 120 ksi√in.
1 . A heat treatment process for precipitation hardening steel comprising:
a solution treatment for a precipitation hardening steel part, wherein the precipitation hardening steel part is heated in a furnace to an austenitizing temperature;
a cooling treatment for a precipitation hardening steel part, wherein the precipitation hardening steel part is cooled to a martensitizing temperature of at least −100° F.; and
an aging treatment for a precipitation hardening steel part, including heating the precipitation hardening steel part in a furnace at a temperature of at least 950° F. for at least 6 hours until a fracture toughness of the precipitation hardening steel part is greater than 120 ksi√in and until a yield strength is greater than 175 ksi.
2 . The heat treatment process of claim 1 , wherein the quenching treatment includes cooling the stainless steel part in a protective atmosphere.
3 . The heat treatment process of claim 1 , wherein the austenitizing temperature is a temperature of 1700° F.
4 . (canceled)
5 . The heat treatment process of claim 1 , wherein the temperature for the aging treatment is 1000° F. or greater.
6 . (canceled)
7 . The heat treatment process of claim 1 , wherein the aging treatment is for at least 7 hours.
8 . The heat treatment process of claim 1 , wherein the aging treatment is for at least 8 hours.
9 . The heat treatment process of claim 1 , wherein the precipitation hardening steel part is composed of precipitation-hardened 13Cr-8Ni stainless steel (PH 13-8, UNS S13800, XM-13).
10 - 19 . (canceled)