Description
The creep resistance becomes specifically important for the alloy to be used at elevated temperatures. In 1000 hours of use at 600°C, the creep rupture is about 200 MPa. The grade can be suitably used even at cryogenic temperatures.
The 310S type of the grade consists lower carbon content (about 0.08% max), while other composition remains the same. It is mainly used in high-ductility than high temperature strength applications. It is also used under wet corrosive environments at comparatively lower temperatures. The creep resistance enables the alloy to be used under thermal cyclic applications, also the alloy can be used in moderately carburizing, nitriding and sulphuric environments. Hence, it is widely used in chemical processing industries.
Continuous use at elevated temperature might result in carbide precipitation in the grain structure, which will require the material to be annealed before further use. With continuous service, the alloy will resist oxidation up to 1150°C, and with intermittent service, it can be used up to 1050°C. The tensile strength at 650°C will be around 450MPa, and will go down to around 300MPa at 750°C. The grain structure does not allow the grade to be hardened by heat treatment. The cold working will result in an increase in hardness as well as strength. The alloy has a high work hardening rate, and needs to be annealed properly after the process to remove internal stresses and make it ready for use.
Chemical Properties
| Grade | Ni | C | Cr | Mn | Si | P | S | N | |
| 310 | Min | 19.0 | – | 24.0 | – | – | – | – | – |
| Max | 22.0 | 0.25 | 26.0 | 2.0 | 1.50 | 0.045 | 0.030 | 0.10 | |
| 310S | Min | 19.0 | – | 24.0 | – | – | – | – | – |
| Max | 22.0 | 0.25 | 26.0 | 2.0 | 1.50 | 0.045 | 0.030 | – |
Physical Properties
| Density | 0.285 Ibs/in3/7.89 g/cm3 |
| Melting Point | 2470 – 2555°F/1354– 1402°C |
| Specific Heat @ 70°F | 0.12 BTU/lb-°F (32 – 212°F) 502 J/kg-°K (0 – 100°C) |
| Thermal Conductivity @ 70°F | 8.0 BTU/hr/ft2/ft/°F 10.8 W/m-°K |
| Elastic Modulus @ 70ºF (tension) | 28.5 x 106 psi 196 GPa |
| Electrical Resistivity @ 70°F | 30.7 Microhm-in at 68°F 78.0 Microhm-cm at 20°C |
| Annealing | 1742 – 2192°F (950 – 1200°C). |
General Data
| Standard | 310 | 310S |
| UNS | S31000 | S31008 |
| WERKSTOFF NR. | 1.4840 | 1.4845 |
| EN | X15CrNi25-20 | X8CrNi25-21 |
| BS | 310S24 | 310S16 |
| GOST | ||
| JIS | SUH 310 | SUH 310S |
| AFNOR |
Standards Specifications
PIPES & TUBES
| Summary | Standards |
| Standard Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes | ASTM A213 |
| Standard Specification for Welded Austenitic Steel Boiler, Superheater, Heat-Exchanger, and Condenser Tubes | ASTM A249 |
| Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes | ASTM A312 |
| Standard Specification for Electric-Fusion-Welded Austenitic Chromium-Nickel Stainless Steel Pipe for High-Temperature Service and General Applications | ASTM A358 |
| Standard Specification for Welded Large Diameter Austenitic Steel Pipe for Corrosive or High-Temperature Service | ASTM A409 |
| Standard Specification For Seamless Stainless Steel Mechanical Tubing | ASTM A511 |
FITTINGS & FLANGES
| Summary | Standards |
| Standard Specification for Wrought Austenitic Stainless Steel Piping Fittings | ASTM A403 |
| Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service | ASTM A182 |
Forms of Supply
Pipes and fittings, fittings and flanges, washers.
Corrosion Resistance
The grade is specifically used for its hot corrosion resistance. Although the grade is less prone to intergranular corrosion the chromium content keeps the corrosion resistance manageable even after long exposure to elevated temperatures. Also, the silicon content in the grade plays a driving factor in resisting corrosion.
The creep resistance lets the alloy perform under cyclic thermal applications and cyclic oxidation conditions. The grade also outperforms most of the grades in nitriding and carburizing several conditions. It can suitably resist fused nitrates up to 420°C and with appropriate service, the grade performs exceptionally well at high temperatures.
Heat Treatment
The grade resists hardening by heat treatment. It can be suitably annealed as required by heating it at about 1000 – 1150°C, then rapidly cooling by air or water for maximum corrosion resistance. The treatment is done for the precipitated carbide in the grain structure, after the use at elevated temperature for long time.
Weldability
The grade has good weldability and can be welded by standard techniques like fusion, TIG, MIG, SMAW, SAW, PLASMA and electric resistance welding. They can be suitably welded by matching grade electrodes or appropriate filler metals. Post weld annealing is normally not required, except for wet corrosion service. Surface oxides need to be removed to ensure full corrosion resistance after welding. It can be done by pickling on the surface.
Machining
The grade has a high work hardening rate. This can be a problem while machining the grade, the work hardened layers are thereby removed by sharp cutting tools, with appropriate speeds, and adequate lubrication. The chips of the metal work harden rapidly, and a chip breaker is required. Powerful machines might be required, with rigid tooling.
Applications
Boiler baffles, fluidises bed combustors, kilns, oven linings, thermowells, high temperature containers, refractory anchor bolts, cryogenic structures, food processing equipment, burners and combustor chambers, annealing covers, oil burner parts, carburising boxes, heat exchangers, welding filler wire and electrodes, muffles, retorts, coal gasifier components, radiant tubes, lead pots, fire box sheets.
Possible Grade and Alternatives
GRADE 304H
| Grade | Ni | C | Cr | Mn | Si | P | S | Fe | |
| 304H | Min | 19.0 | 0.04 | 24.0 | – | – | – | – | – |
| Max | 21.0 | 0.10 | 26.0 | 2.0 | 1.00 | 0.045 | 0.030 | 53.885 |
GRADE 321
| Grade | Ni | C | Cr | Mn | Si | P | Ti | S | N | Fe | |
| 321 | Min | 9.0 | – | 17.0 | – | – | – | – | – | – | 65.045 |
| Max | 12.0 | 0.08 | 19.0 | 2.0 | 1.00 | 0.045 | 5(C+N) -0.70 | 0.030 | 0.10 | – |
