Stainless Steel 310
Stainless Steel 310 (UNS S31000) is a high-alloy austenitic grade with 24-26% chromium and 19-22% nickel. This composition gives it strong resistance to oxidation and thermal cycling, with continuous service ratings up to 1100°C (2012°F) in air.
1. Chemical Composition
The table below lists the elemental composition ranges for Stainless Steel 310. The high chromium and nickel concentrations give it its heat-resistant and corrosion-resistant properties.
| Grade | C | Mn | P | S | Si | Cr | Ni | Mo | N | Other |
| 310 | = 0.25 | = 2.00 | = 0.045 | = 0.030 | = 1.50 | 24.00–26.00 | 19.00–22.00 | — | — | — |
2. Mechanical Properties
The following table lists minimum mechanical properties for Stainless Steel 310 in the annealed condition. The high alloy content helps maintain strength at elevated operating temperatures.
| Grade | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Hardness (HB) |
| 310 | = 515 | = 205 | = 40 | = 217 |
3. Equivalent Grade
This table lists international standard equivalents for Stainless Steel 310, including ASTM, European, Japanese, Chinese, and Russian designation systems.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| 310 | S31000 | S31020 | 20Cr25Ni20 | SUS310 | X15CrNi25-21 | 1.4841 | 20X25H20C2 |
4. Key Technical Advantages
- Highest Oxidation Resistance in the Austenitic Series: With 24-26% Cr and 19-22% Ni, Grade 310 forms a dense, adherent chromium oxide scale that resists spalling through repeated thermal cycling. It outperforms 309 and 304 in this area.
- Stability in Carburising and Nitriding Atmospheres: The elevated nickel content reduces carbon activity and nitrogen absorption at the alloy surface, making 310 suitable for case-hardening furnace components and ammonia-cracker internals.
- Thermal Cycling Capability: Unlike many ferritic heat-resistant grades, the fully austenitic structure of 310 does not embrittle during repeated heating and cooling cycles between ambient and operating temperature.
- Sigma Phase Awareness: Prolonged exposure in the 600-900°C range can cause sigma phase precipitation, which lowers toughness at room temperature. Thermal processing schedules should account for this.
5. Common Manufacturing Standards
Stainless Steel 310 is manufactured and inspected under the following standards:
ASTM A312: Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes — TP310 designation.
ASTM A213: Standard Specification for Seamless Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes — T310 designation.
ASTM A511: Standard Specification for Seamless Stainless Steel Mechanical Tubing.
DIN EN 10095: Heat-resisting steels and nickel alloys (1.4845).
JIS G4311: Hot-rolled stainless steel bars for heat-resisting applications (SUS310).
JIS G3463: Stainless Steel Boiler and Heat Exchanger Tubes (SUS310).
GB/T 13296: Seamless stainless steel tubes for boiler and heat exchanger (06Cr25Ni20).
GOST 5632: High-alloy steels and alloys (20Ch25N20S2).
Standards Comparison Table:
| Standard | ASTM | EN/DIN | JIS | GB/T | GOST |
| Seamless Pipe | A312 (TP310S) | EN 10095 (1.4845) | G3459 (SUS310S) | 13296 | 5632 |
| Welded Pipe | A312 (TP310S) | EN 10217-7 (1.4845) | G3459 | - | - |
| Heat Exchanger Tube | A213 (T310S) / A249 | EN 10216-5 | G3463 (SUS310S) | 13296 | - |
6. Primary Applications
- Heat Treatment Furnaces: Radiant tubes, muffles, and retort liners in continuous annealing, carburising, and sintering furnaces at temperatures above 900°C.
- Ethylene Cracker Furnaces: Convection and radiation section tubing in steam cracking furnaces, where high skin temperatures and carburising gases are both present.
- Cryogenic and High-Temperature Dual-Service: Vessels and piping circuits that must operate from cryogenic conditions during startup through to elevated temperatures during normal operation.
- Cement and Lime Kilns: Heat-resistant components, inlet housing liners, and nose rings in oxidising kiln atmospheres at high temperature.
- Power Generation: Boiler components, superheater shields, and tube hangers in coal and biomass-fired boilers where ash deposits create corrosive, high-temperature conditions.