310 Stainless Steel for Power Generation: Properties, Applications and Selection Guide

310 Stainless Steel in Power Generation: An Overview

Type 310 (UNS S31000) and its low-carbon variant 310S (UNS S31008) are high-alloy austenitic stainless steels containing 24.0-26.0 % chromium and 19.0-22.0 % nickel. This composition produces a stable austenitic microstructure that resists oxidation, scaling and thermal fatigue at temperatures where conventional 18-8 grades such as 304 and 316 lose strength quickly. In power generation equipment, 310 is therefore a standard choice for components exposed to sustained heat, combustion gases and repeated start-stop cycling.

The grade is covered by ASTM A240 for plate, sheet and strip, ASTM A312 for seamless and welded pipe, and ASTM A213 for boiler and superheater tubes. Because nickel content is roughly double that of 304, material cost is higher; the economic case rests on longer service life, lower scaling loss and reduced downtime in boiler, gas-turbine auxiliary and heat-exchanger applications.

Chemical Composition per ASTM A240

ASTM A240 specifies the following limits for plate, sheet and strip. Single values are maximums unless shown as a range.

Element	310 (UNS S31000)	310S (UNS S31008)
Carbon	0.25 max	0.08 max
Manganese	2.00 max	2.00 max
Silicon	1.50 max	1.50 max
Phosphorus	0.045 max	0.045 max
Sulfur	0.030 max	0.030 max
Chromium	24.0-26.0	24.0-26.0
Nickel	19.0-22.0	19.0-22.0

The only deliberate difference between 310 and 310S is the carbon limit. Lower carbon in 310S reduces the risk of chromium-carbide precipitation at grain boundaries during service, so 310S is preferred wherever welding is followed by long exposure in the sensitisation range.

Room-Temperature Mechanical Properties

Per ASTM A240, annealed plate, sheet and strip of 310 and 310S must meet the following minimums.

Property	310 / 310S (minimum)
Tensile strength	515 MPa (75 ksi)
Yield strength (0.2 % offset)	205 MPa (30 ksi)
Elongation in 50 mm	40 %

Above roughly 600 °C, load-bearing capacity falls steadily and design must be based on creep-rupture data rather than room-temperature yield strength. This is why 310 is usually selected for furnace linings, burner components, superheater tube supports and similar parts where stress levels are modest but temperature is extreme.

High-Temperature Behaviour and Typical Applications

In continuous service in air, 310 resists scaling up to about 1000 °C; in intermittent service the practical limit is about 1050 °C. The austenitic structure also gives good low-temperature toughness and resistance to thermal fatigue, which is critical for components that cycle between ambient and operating temperature. Performance degrades in sulphur-bearing or strongly carburising atmospheres, so the actual combustion environment must be checked before specifying 310.

Typical power generation applications include superheater and reheater tube supports, furnace wall components, burner nozzles, combustion-air preheater parts, soot-blower elements, expansion bellows and heat-exchanger baffles. Where aqueous chloride corrosion is the dominant risk, duplex or 6 % molybdenum super-austenitic grades are more appropriate than 310.

Welding and Heat Treatment

310 is welded with matching austenitic filler, for example AWS ER310 for gas tungsten arc welding. Preheat is not required, and interpass temperature should be kept low to limit thermal stress and sigma-phase risk. Post-weld solution annealing is not generally required; where maximum corrosion resistance is needed, the component may be annealed at about 1040-1120 °C followed by rapid cooling. Avoid long-term exposure in the 650-900 °C range, where sigma phase can form and reduce ductility and impact toughness.

FAQ

Q1. What is the difference between 310 and 310S? Only the carbon limit differs: 310 allows up to 0.25 % carbon, while 310S is limited to 0.08 %. 310S is preferred for welded construction and long-term high-temperature service.

Q2. What is the maximum service temperature of 310? Continuous oxidation resistance in air is about 1000 °C, with intermittent exposure possible to about 1050 °C. Mechanical load capacity above 600 °C must be checked against creep-rupture data.

Q3. Is 310 stainless steel magnetic? In the annealed condition 310 is essentially non-magnetic because of its fully austenitic structure, although welding or cold work can induce slight local magnetism.

Q4. Does 310 require post-weld heat treatment? Generally no. PWHT is usually unnecessary and can be harmful if it holds the material in the sigma-phase formation range for too long.

Q5. Can 310 replace 316 in seawater or chloride service? No. 310 is not a chloride-resistance grade. For marine and chloride-rich environments, use molybdenum-bearing grades such as 316 or, for severe duty, duplex or super-austenitic grades.