Austenitic SS 310

Austenitic SS 310

ALLOY 310S / ALLOY 310H | 1.4845 | X8CRNI25-21 | S31008 / S31009

With a chromium content of about 25% and nickel content of 20%, Austenitic SS 310 is a multipurpose alloy generally used in high temperature applications. The grade has exceptional corrosion and oxidation resistance.

The high chromium and nickel content, which are meant for elevated temperature applications, also provide the required resistance to corrosion and better toughness than fellow austenitic grades even at room temperature. The chemical composition of the grade provides a balance in many properties. Its 0.25% carbon content (higher than any other grade in the series), enhances the creep properties of the alloy.

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
  • Physical properties
  • General data
  • Standards Specifications
  • Forms of Supply
  • Corrosion Resistance
  • Heat Treatment
  • Weldability
  • Machining
  • Applications
  • Possible grade alternatives
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 -
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).
Standard 310 310S
UNS S31000 S31008
WERKSTOFF NR. 1.4840 1.4845
EN X15CrNi25-20     X8CrNi25-21
BS 310S24 310S16
JIS SUH 310 SUH 310S
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

Pipes and fittings, fittings and flanges, washers.

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.

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.

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.

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.

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.

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 -

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