Sandvik 254 SMO

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Description

Sandvik 254 SMO is a high-alloy austenitic stainless steel developed for use in seawater and other aggressive chloride-bearing media. The steel is characterized by the following properties:


  • Excellent resistance to pitting and crevice corrosion, PRE = ≥42.5 (The PRE is defined as, in weight-%, PRE = %Cr + 3.3 x %Mo + 16 x %N)
  • High resistance to general corrosion
  • High resistance to stress corrosion cracking
  • Higher strength than conventional austenitic stainless steels
  • Good weldability

  • More technical information and charts that are relevant to the materials corrosion, mechanical and physical performance are displayed in the figures on the right side of the material page.


    Datasheet URL:

    Sandvik 254 SMO


    Datasheet updated 2019-11-06 09:12 (supersedes all previous editions)

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    Properties

    General

    Density

    ρ

    8 g/cm³ at 23 °C

    Mechanical

    Charpy impact energy

    aK,charpy

    60 J at -196 °C

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    EN 13445-2 (UFPV-2) and EN 10216-5

    Elastic modulus

    E

    195 GPa at 20 °C

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    Elongation

    A

    35 % at 23 °C

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    Elongation A2

    A2

    35 % at 23 °C

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    Hardness, Rockwell B

    HRB

    96 [-] at 23 °C

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    max.

    Tensile strength

    Rm

    675 - 850 MPa at 23 °C

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    Yield strength Rp0.1

    340 MPa at 20 °C

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    Yield strength Rp0.2

    Rp0.2

    310 MPa at 20 °C

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    min.

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    Thermal

    Coefficient of thermal expansion

    α

    1.6E-5 1/K at 100 °C

    for 30°C to the mentioned temperature

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    Specific heat capacity

    cp

    485 J/(kg·K) at 20 °C

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    Thermal conductivity

    λ

    10 W/(m·K) at 20 °C

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    Chemical properties

    Element

    Weight %

    Comment

    Fe

    -

    Balance

    Cr

    20 %

    Ni

    18 %

    Mo

    6.1 %

    Mn

    1 %

    max.

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    Technological properties

    Application areas

    Sandvik 254 SMO is used in the following applications:

  • Equipment for handling of seawater, such as, seawater cooling, cooling water pipes, ballast water systems, firefighting systems etc.
  • Hydraulic and instrumention tubing
  • Equipment in pulp bleaching plants
  • Components in gas cleaning systems
  • Tanks and pipelines for chemicals with high halide contents
  • Trademark information: 254 SMO is a trademark owned by Outokumpu OY.

    Cold Forming

    The excellent formability of Sandvik 254 SMO permits cold bending to very tight bending radii. Annealing is not normally necessary after cold bending.

    Compliance

    Approvals:

  • UNS S31254 (Sandvik 254 SMO) in the form of seamless pipe has been approved by the American Society of Mechanical Engineers (ASME) for use according to ASME Boiler and Pressure Vessel Code section VIII, div. 1. However, there is no approval for UNS S31254 in the form of seamless tube, but according to the ASME paragraph UG-15 it is allowed to use the design values for seamless pipe according to ASME section VIII, div. 1 also for seamless tube.
  • NACE MR 0175 (sulphide stress cracking resistant material for oil field equipment).

  • At high temperatures: Intermetallic phases are precipitated within the temperature range of 600–1000°C (1110–1830°F). Therefore, the steel should not be exposed to these temperatures for prolonged periods.

    Corrosion properties

    In solutions containing halides such as chloride and bromide ions, conventional stainless steels can be readily attacked by local corrosion in the form of pitting corrosion, crevice corrosion or stress corrosion cracking (SCC). In acid environments, the presence of halides also accelerates general corrosion.

    General corrosion: In pure sulphuric acid, Sandvik 254 SMO is much more resistant than ASTM TP316, and in naturally aerated sulphuric acid containing chloride ions Sandvik 254 SMO exhibits higher resistance than '904L', see Figure 2.


    Intergranular corrosion: Sandvik 254 SMO has a very low carbon content. This means that there is very little risk of carbide precipitation during heating, for example when welding. The steel passes the Strauss test (ASTM A262, practice E) even after sensitizing for one hour at 600–1000°C (1110–1830°F). However, due to the high alloying content of the steel, inter-metallic phases can precipitate at the grain boundaries in the temperature range 600–1000°C (1110–1830°F). These precipitations do not involve any risk of intergranular corrosion in the environments in which the steel is intended to be used. Thus, welding can be carried out without any risk of intergranular corrosion.


    Pitting and crevice corrosion: The pitting and crevice corrosion resistance of stainless steel is primarily determined by the content of chromium, molybdenum and nitrogen. Manufacture and fabrication, e.g. welding, are also of vital importance for the actual performance in service. A parameter for comparing the resistance to pitting in chloride environments is the PRE number (Pitting Resistance Equivalent). The PRE is defined as, in weight-%, PRE = %Cr + 3.3 x %Mo + 16 x %N.

    PRE-value for Sandvik 254 SMO = ≥42,5.

    The results of laboratory determination of the critical pitting temperature (CPT) in 3 % NaCl are shown in Figure 3, where it can be seen that Sandvik 254 SMO possesses very good resistance in water containing chlorides. Sandvik 254 SMO is, therefore, a suitable material for use in seawater.


    Stress corrosion cracking (SCC): Ordinary austenitic steels of the ASTM TP304 and TP316 type are prone to stress corrosion cracking (SCC) in chloride-containing solutions at temperatures exceeding about 60°C (140°F). For the austenitic steels, resistance to SCC increases with higher nickel and molybdenum contents. The tables below show the results of two accelerated tests, clearly demonstrating that Sandvik 254 SMO has a very good resistance to SCC.


    Stress corrosion cracking tests in boiling 25% NaCl solution, pH=1.5. U-bend specimens.

    GradeTime to failureRemark
    ASTM TP316<150 hPitting
    '904L'No failure (1000 h)Crevice corrosion
    Sandvik 254 SMONo failure (1000 h)No attack


    Stress corrosion cracking tests. Drop evaporation method* Stress: 0.9xRp0.2

    GradeTime to failure hours
    ASTM TP316105
    '904L'225
    Sandvik 254 SMO425
    * A 0.1 M NaCl solution is allowed to drop slowly onto an electrically heated tensile test specimen at 300ᵒC (570ᵒF).


    Crevice corrosion: The weak point of conventional stainless steels is their limited resistance to crevice corrosion. In seawater, for example, there is a considerably greater risk of crevice corrosion under gaskets, deposits or fouling. Tests in natural seawater at 60°C (140°F) have shown that Sandvik 254 SMO can be exposed for prolonged periods without suffering crevice corrosion. Figure 4 shows the results of accelerated crevice corrosion tests.

    Heat Treatment

    The tubes are delivered in heat treated condition. If additional heat treatment is needed due to further processing the following is recommended.

    Solution annealing: 1150–1200°C (2100–2190°F), quenching in water. Thin-walled tubes min. 1130°C (2060°F), quenching in air/water.

    Machining

    Sandvik 254 SMO is a high alloyed austenitic stainless steel and thus tougher inserts in metal cutting are needed than is the case for lower alloyed austenitic grades. When machining Sandvik 254 SMO considerably lower cutting speeds are recommended compared to the grades Sanmac 304/304L and Sanmac 316/316L, which have improved machinability.


    Avoid abrasion against copper/copper alloys or other similar metals which, if present in metallic form, can cause cracks during subsequent welding, hot processing or heat treatment.

    Other

    Forms of supply:

    Seamless tube and pipe are supplied in dimensions up to 230 mm (9.06 in.) outside diameter. The delivery condition is either solution annealed and white pickled, or solution annealed in a bright annealing process.


    Other forms of supply:

  • Welded tube and pipe
  • Fittings and flanges
  • Bar steel
  • Forged products
  • Cast products
  • Welding

    The weldability of Sandvik 254 SMO is good. Suitable methods of fusion welding are manual metal-arc welding (MMA/SMAW) and gas-shielded arc welding, with the TIG/GTAW method as first choice.


    In common with all fully austenitic stainless steels, Sandvik 254 SMO has low thermal conductivity and high thermal expansion. Welding plans should therefore be carefully selected in advance, so that distortions of the welded joint are minimized. If residual stresses are a concern, solution annealing can be performed after welding.


    For Sandvik 254 SMO, heat-input of <1.5 kJ/mm and interpass temperature of <100°C (210°F) are recommended. A string bead welding technique should be used.

    Nickel alloys with high molybdenum and chromium must be used as filler metals to have good corrosion resistance in the as-welded condition.


    Recommended filler metals:

    • TIG/GTAW or MIG/GMAW welding
      • ISO 18274 S Ni 6625/AWS A5.14 ERNiCrMo-3 (e.g. Exaton Ni60)
      • ISO 18274 S Ni 6059/AWS A5.14 ERNiCrMo-13 (e.g. Exaton Ni59)
    • MMA/SMAW welding
      • ISO 14172 E Ni 6625/AWS A5.11 ENiCrMo-3 (e.g. Exaton Ni60)
      • ISO 14172 E Ni 6059/AWS A5.11 ENiCrMo-13 (e.g. Exaton Ni59)

    This material data has been provided by Sandvik Materials Technology.

    All metrics apply to room temperature unless otherwise stated. SI units used unless otherwise stated.
    Equivalent standards are similar to one or more standards provided by the supplier. Some equivalent standards may be stricter whereas others may be outside the bounds of the original standard.