Grade 310S (UNS S31008) is used when the application environment involves moist corrodents in a temperature range lower than that which is normally considered “high temperature” service. The lower carbon content of 310S does reduce its high temperature strength compared to 310.
Like other austenitic grades these have excellent toughness, even down to cryogenic temperatures, although other grades are normally used in this environment.
Grade 310L (and proprietary versions of this grade), is a 0.03% maximum carbon version of 310, sometimes used for very specific corrosive environments, such as urea production.
These properties are specified for flat rolled product (plate, sheet and coil) in ASTM A240/A240M. Similar but not necessarily identical properties are specified for other products such as pipe and bar in their respective specifications.
The high chromium content – intended to increase high temperature properties – also gives these grades good aqueous corrosion resistance. The PRE is approximately 25, and seawater resistance about 22°C, similar to that of Grade 316. Excellent resistance at normal temperatures, and when in high temperature service exhibits good resistance to oxidising and carburising atmospheres. Resists fuming nitric acid at room temperature and fused nitrates up to 425°C.
Subject to stress corrosion cracking but more resistant than Grades 304 or 316.
Good resistance to oxidation in intermittent service in air at temperatures up to 1040°C and 1150°C in continuous service. Good resistance to thermal fatigue and cyclic heating. Widely used where sulphur dioxide gas is encountered at elevated temperatures. Continuous use in 425-860°C range not recommended due to carbide precipitation, if subsequent aqueous corrosion resistance is needed, but often performs well in temperatures fluctuating above and below this range.
Grade 310 is generally used at temperatures starting from about 800 or 900°C – above the temperatures at which 304H and 321 are effective.
Solution Treatment (Annealing) – heat to 1040-1150°C and cool rapidly for maximum corrosion resistance. This treatment is also recommended to restore ductility after each 1000 hours of service above 650°C, due to long term precipitation of brittle sigma phase.
These grades cannot be hardened by thermal treatment.