ASTM A240 UNS S31266 Stainless Steel Plate Austenitic Stainless High Alloy from BAOSTEEL

Super-austenitic stainless steels cover grades with high chromium (20 to 27 %), high nickel (18 to 31 %) and high molybdenum (4 to 6 %) contents. Within this family, the 6%Mo high nitrogen grade S31266 was developed to combine the beneficial influence of chromium, tungsten, molybdenum and nitrogen on its mechanical and corrosion properties. Due to 22 % nickel, 24 % chromium and 0.4 % nitrogen additions, this alloy exhibits a very stable microstructure, being less prone to intermetallic phase precipitation than the other highly alloyed super-austenitic stainless steels.

This paper deals with the corrosion resistance of S31266 in artificial geothermal water with moderate salinity and low pH. Long-term static exposures and electrochemical tests were conducted at various temperatures to evaluate the pitting, crevice and stress corrosion cracking resistance of this material.

The results show that S31266 is resistant up to 220 °C. As a consequence, it can be a good candidate material for geothermal applications involving a highly corrosive environment, especially salinity and low pH.

Chemical Composition of UNS S31266 Stainless Steel

Mechianical Properties of UNS S31266 Stainless Steel

Principal Design Features

One of the most widely used precipitation hardening grades in the business. While soft and ductile in the solution annealed condition, it is capable of high properties with a single precipitation or aging treatment. Characterized by good corrosion resistance, high harness, toughness and strength.

Machinability

Long, gummy chips characterize this alloys machinability. It can be machined in the annealed condition, however condition H1150M will yield best results. Post machining solution treatment of parts will be required prior to final hardening if machining in this condition.

Heat Treatment

CONDITION A--Soak at 1900 F (1038 C) for 30 minutes and cool below 60 F (16 C) for complete martensite transformation. CONDITION H 950- Treat Condition A material at 900 F(482 C) for 1 hour, air cool.. CONDITION H925, H1025, H1075, H1100, H1150- Soak solution treated material for 4 hours at specified temperature, air cool, CONDITION H1150M- Soak solution treated material at 1400 F (760 C) for 2 hours, air cool, then re-heat to 1150 F (620 C) for 4 hours and air cool.

Welding

Successfully welded by common fusion and resistance methods, this alloy should not be joined by oxyacetylene welding. AWS E/ER630 filler metal is recommended if required.

Forging

Soak for 1 hour at 2150 F (1177 C) prior to forging. Do not work below 1850 F (1010 C). Post-work solution treatment is required prior to final hardening.