AISI 310 Stainless Steel
1. Introduction
310 (UNS S31000) is a high-chromium, high-nickel austenitic stainless steel designed for service in severe high-temperature environments where excellent oxidation resistance, structural stability, and creep performance are required. With chromium levels between 24–26% and nickel levels between 19–22%, the alloy provides significantly enhanced resistance to oxidation and thermal degradation compared with standard 18-8 stainless steels. Its higher carbon range, relative to 310S, supports increased high-temperature strength and creep resistance, making the grade suitable for demanding applications requiring long-term mechanical stability at elevated temperatures.
310 is widely used in industrial furnace equipment, thermal-processing systems, and components exposed to combustion gases or rapid thermal cycling. It offers reliable scale resistance up to very high temperatures and maintains good mechanical properties across a broad service range, supporting its use in load-bearing structures within heating and heat-treatment systems. Typical uses include furnace parts, retorts, radiant tubes, burner components, tube hangers, and trays designed for repeated thermal cycling in oxidising atmospheres.
310 and 310S: When to Choose
310 and 310S share an identical chromium and nickel range and are often considered interchangeable. The critical distinction lies in carbon content: 310 permits up to 0.25 wt% carbon, while 310S is restricted to 0.08 wt% maximum. This higher carbon level gives 310 superior creep strength and elevated-temperature load-bearing capacity, making it the preferred choice for structural components under sustained high-temperature stress. However, it also increases susceptibility to chromium carbide precipitation in the sensitisation range (427–899°C), making 310S the more appropriate selection for welded assemblies or applications where post-service corrosion resistance must be maintained. Where weldability and post-weld integrity are not primary concerns, 310 offers a mechanical performance advantage at the upper end of the service temperature range.
2. Chemical Composition
The chemical composition of 310 is defined by ASTM specifications for high‑temperature austenitic stainless steels. Its elevated chromium and nickel content is essential for providing oxidation resistance and structural stability during long‑term exposure to extreme temperatures.
Table 1 — Chemical Composition of 310 (UNS S31000)
| Element | Typical Limits (wt%) |
|---|---|
| Carbon (C) | up to 0.25 |
| Manganese (Mn) | up to 2.00 |
| Phosphorus (P) | up to 0.045 |
| Sulfur (S) | up to 0.030 |
| Silicon (Si) | up to 1.50 |
| Chromium (Cr) | 24.00–26.00 |
| Nickel (Ni) | 19.00–22.00 |
| Iron (Fe) | Balance |
This composition profile distinguishes 310 from 309 and 310S, particularly through its higher allowable carbon content, which improves high temperature strength and creep resistance but requires appropriate consideration during welding and thermal exposure.
3. Mechanical and Physical Properties
310 is formulated to retain strength, toughness, and dimensional stability during long‑term exposure to extremely high temperatures. The alloy’s higher carbon allowance compared with 310S provides improved high‑temperature strength and creep resistance, while its elevated chromium–nickel matrix ensures predictable mechanical behaviour across a wide service range.
3.1 Tensile Properties at Temperature
The tensile properties of 310 reflect its suitability for structural and load‑bearing applications in severe high‑temperature environments. Strength levels decrease gradually with rising temperature, while ductility increases, supporting the alloy’s resistance to thermal shock and cyclic heating.
Table 2 — Tensile Properties of 310 at Elevated Temperatures
| Temperature | Yield Strength | Tensile Strength | Elongation |
|---|---|---|---|
| 25 °C (77 °F) | 42.4 ksi / 292 MPa | 89.5 ksi / 617 MPa | 45% |
| 204 °C (400 °F) | 31.5 ksi / 217 MPa | 76.6 ksi / 528 MPa | 37.5% |
| 427 °C (800 °F) | 27.2 ksi / 188 MPa | 74.8 ksi / 516 MPa | 37% |
| 538 °C (1000 °F) | 24.2 ksi / 167 MPa | 70.1 ksi / 483 MPa | 36% |
| 649 °C (1200 °F) | 22.6 ksi / 156 MPa | 57.2 ksi / 394 MPa | 41.5% |
| 816 °C (1500 °F) | 19.7 ksi / 136 MPa | 30.3 ksi / 209 MPa | 66% |
| 871 °C (1600 °F) | — | 11.0 ksi / 76 MPa | 65% |
| 982 °C (1800 °F) | — | 7.0 ksi / 48 MPa | 77% |
| 1093 °C (2000 °F) | — | — | 121% |
3.2 Physical Properties
310 exhibits physical characteristics typical of high‑chromium, high‑nickel austenitic stainless steels, including low thermal conductivity, predictable thermal expansion, and a near‑non‑magnetic response in the annealed condition.
Density
0.29 lb/in³ (8.03 g/cm³)
Coefficient of Thermal Expansion
| Temperature Range | µin/in·°F | µm/m·K |
|---|---|---|
| 20–100 °C | 8.8 | 15.9 |
| 20–500 °C | 9.5 | 17.1 |
| 20–1000 °C | 10.5 | 18.9 |
4. Applications
310 is selected for service in extremely high‑temperature environments where components must withstand continuous or cyclic thermal exposure, oxidising conditions, and structural load at elevated temperatures. Its high chromium and nickel content enables reliable performance in industrial heating systems, thermal‑processing equipment, and chemical‑processing environments requiring superior oxidation and creep resistance.
4.1 Industrial Heat‑Processing Equipment
310 is widely used in high‑temperature furnace equipment where stability, scale resistance, and mechanical strength must be retained at temperatures approaching the upper limits of stainless‑steel capability.
Typical furnace and heating‑system applications include:
- Furnace conveyor belts and rollers
- Radiant tubes and retorts
- Burner components and refractory supports
- Oven linings and internal partitions
- Baskets and trays designed for repeated thermal cycling
- Tube hangers and structural components exposed to direct heat
4.2 Chemical Processing Environments
310 is suitable for high‑temperature service in chemical‑processing installations where resistance to hot corrosive gases is essential. Its chromium–nickel balance provides stability in environments containing:
- Hot concentrated acids
- Ammonia‑bearing atmospheres
- Sulphur dioxide and sulphur‑containing combustion gases
4.3 Food‑Processing and Organic‑Acid Systems
310 can be used in high‑temperature food‑processing operations involving contact with hot organic acids such as acetic and citric acid. Its resistance to general corrosion and scaling supports hygienic performance under thermal load.
4.4 Oxidation‑Resistant High‑Temperature Applications
Due to its elevated chromium content, 310 delivers excellent oxidation resistance in both continuous and cyclic high‑temperature service. Components maintain scale integrity in oxidising atmospheres, supporting long‑term performance at temperatures significantly above the capability of standard austenitic stainless steels.
4.5 Summary of Key Advantages
310 is typically chosen for:
- High‑temperature structural components
- Oxidising furnace environments
- Heating and thermal‑processing systems
- Applications requiring resistance to carburisation, sulphidation, and thermal cycling
5. Welding
310 is readily weldable using standard fusion welding techniques and behaves consistently with other fully austenitic high‑temperature stainless steels. The alloy can be joined using GTAW/TIG, GMAW/MIG, SMAW, and SAW processes. Its high chromium and nickel content provide stability during welding but require consideration of ferrite control and weld‑pool behaviour.
5.1 Carbon Control
Although 310 has a higher allowable carbon content than 310S, low‑carbon filler options such as ER309L may be selected when lower carbon in the weld metal is required for specific thermal exposure conditions.
5.2 Post‑Weld Cleaning
To restore full corrosion and oxidation resistance, weld scale and heat tint should be removed using:
- Stainless‑only wire brushing
- Grinding
- Pickling solutions containing nitric + hydrofluoric acids, followed by thorough water rinsing
6. Heat Treatment / Annealing
310 cannot be hardened by heat treatment. Heat treatment is instead used to restore a clean austenitic structure, remove carbide precipitation, and prepare components for high‑temperature service.
6.1 Solution Annealing
Temperature: 2050–2150 °F (1120–1175 °C)
Hold time: ~30 minutes per inch of thickness
Cooling: Rapid cooling (air or water quench)
6.2 Scale Formation and Removal
Annealing in air forms an adherent chromium‑rich oxide scale. Before further processing or service, this scale should be removed using mechanical or chemical methods.
7. Fabrication Characteristics
310 offers good overall fabricability for an austenitic stainless‑steel grade, though its high strength and rapid work‑hardening rate require appropriate process control.
8. Creep and Stress‑Rupture Behaviour
310 is formulated for long‑term service under sustained high‑temperature loading. Its higher carbon allowance relative to 310S contributes to improved creep strength and greater resistance to deformation in elevated‑temperature structural applications.
9. Conclusion
310 (UNS S31000) is a high‑temperature austenitic stainless steel offering excellent oxidation resistance, strong creep performance, and reliable structural stability during continuous or cyclic exposure to extreme heat. Its elevated chromium and nickel levels support the formation of a durable oxide scale, while its higher carbon content, relative to 310S, enhances high‑temperature strength and load‑bearing capability. These characteristics make 310 a dependable choice for furnace internals, radiant tubes, heat‑treatment fixtures, burner components, and chemical‑processing equipment.
The alloy also provides good fabrication and welding characteristics, enabling the manufacture of complex high‑temperature assemblies. Its combination of mechanical reliability, scale resistance, and metallurgical stability ensures long service life in demanding thermal environments.
