Sanicro® 35

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Description

Sanicro® 35 (UNS N08935) is an alloy combining the best features of a super austenitic stainless steel and a nickel alloy. The grade has excellent corrosion resistance, for service in sea-water applications and other highly corrosive environments. Sanicro® 35 is characterized by:


  • Excellent resistance to pitting and crevice corrosion
  • Excellent resistance to stress corrosion cracking (SCC)
  • High resistance to general corrosion in acid and caustic environments
  • High resistance to erosion-corrosion
  • Very high mechanical strength
  • Good weldability using nickel alloy consumables

  • 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.

    Related Standards

    Equivalent Materials

    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.

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    Properties

    General

    PropertyValueTemperature

    Density

    8.1 g/cm³

    Show Supplier Material materials with Density of 8.1 g/cm³ at 23.0 °C

    23.0 °C

    Mechanical

    PropertyValueTemperatureComment

    Elastic modulus

    190 GPa

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    20.0 °C

    185 GPa

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    100.0 °C

    180 GPa

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    200.0 °C

    175 GPa

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    300.0 °C

    170 GPa

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    400.0 °C

    Elongation A2

    35 %

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    23.0 °C

    min.

    Tensile strength

    750 MPa

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    20.0 °C

    min.

    680 MPa

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    100.0 °C

    min.

    620 MPa

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    200.0 °C

    min.

    600 MPa

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    300.0 °C

    min.

    580 MPa

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    400.0 °C

    min.

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    Yield strength Rp0.2

    425 MPa

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    20.0 °C

    min.

    350 MPa

    Show Supplier Material materials with Yield strength Rp0.2 of 350 MPa at 100.0 °C

    100.0 °C

    min.

    300 MPa

    Show Supplier Material materials with Yield strength Rp0.2 of 300 MPa at 200.0 °C

    200.0 °C

    min.

    275 MPa

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    300.0 °C

    min.

    250 MPa

    Show Supplier Material materials with Yield strength Rp0.2 of 250 MPa at 400.0 °C

    400.0 °C

    min.

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    Thermal

    PropertyValueTemperatureComment

    Coefficient of thermal expansion

    1.4E-5 1/K

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    100.0 °C

    for 30°C to the mentioned temperature

    1.45E-5 1/K

    Show Supplier Material materials with Coefficient of thermal expansion of 1.45E-5 1/K at 200.0 °C

    200.0 °C

    for 30°C to the mentioned temperature

    1.5E-5 1/K

    Show Supplier Material materials with Coefficient of thermal expansion of 1.5E-5 1/K at 300.0 °C

    300.0 °C

    for 30°C to the mentioned temperature

    1.55E-5 1/K

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    400.0 °C

    for 30°C to the mentioned temperature

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    Specific heat capacity

    450 J/(kg·K)

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    20.0 °C

    470 J/(kg·K)

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    100.0 °C

    500 J/(kg·K)

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    200.0 °C

    510 J/(kg·K)

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    300.0 °C

    530 J/(kg·K)

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    400.0 °C

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    Thermal conductivity

    10 W/(m·K)

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    20.0 °C

    12 W/(m·K)

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    100.0 °C

    13.5 W/(m·K)

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    200.0 °C

    15.5 W/(m·K)

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    300.0 °C

    17 W/(m·K)

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    400.0 °C

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    Electrical

    PropertyValueTemperature

    Electrical resistivity

    1E-6 Ω·m

    Show Supplier Material materials with Electrical resistivity of 1E-6 Ω·m at 23.0 °C

    23.0 °C

    Chemical properties

    Property

    Carbon

    0.03 %

    max.

    Chromium

    27 %

    Copper

    0.2 %

    Iron

    Balance

    Manganese

    0.8 %

    Molybdenum

    6.5 %

    Nickel

    35 %

    Nitrogen

    0.3 %

    Phosphorus

    0.03 %

    max.

    Silicon

    0.5 %

    max.

    Sulfur

    0.02 %

    max.

    Technological properties

    Property
    Application areas

    Due to its extremely good pitting and crevice corrosion properties, Sanicro® 35 is particularly suitable for applications where seawater is used for cooling or heating. Sanicro® 35 also has a high resistance to general corrosion in acid environments, making it suitable for a variety of applications.

    Cold Forming

    The force needed for bending Sanicro® 35 is higher than that for standard austenitic stainless steels which is a natural consequence of the higher yield strength. The excellent formability of the grade permits cold bending to tight bending radii.

    Compliance

    Approvals:

  • ASME Code Case 2982. Boiler and Pressure Vessel Code, Section VIII, Division I and II.
  • Pre-approval for Particular Material Appraisal (PMA), TÜV file 1326W043219
  • Compliance with NACE MR0175/ISO 15156-3:2015, (Petroleum, Petrochemical, and Natural Gas Industries -Materials for Use in H₂S Containing Environments in Oil and Gas Production - Part 3: Cracking-Resistant CRAs (Corrosion-Resistant Alloys) and Other Alloys) for type 4a and type 4c materials.
  • Compliance with ANSI/NACE MR0103/ISO 17495-1:2016, (Petroleum, petrochemical and natural gas industries-Metallic materials resistant to sulfide stress cracking in corrosive petroleum refining environments) for highly alloyed austenitic stainless steels and nickel alloys.

  • Intermetallic phases are precipitated at temperatures above 600°C (1110°F). Therefore, the steel should not be exposed to these temperatures for prolonged periods.

    Corrosion properties

    General corrosion: Sanicro® 35 has good resistance to hydrochloric acid compared to stainless steels with a lower chromium and molybdenum content and can, therefore, be useful in environments where hydrochloric acid is present. See Figure 1.


    Sanicro® 35 has a high resistance to sulfuric acid and nitric acid. Isocorrosion diagrams can be seen in Figure 2 and Figure 3.


    Sanicro® 35 also performs well in mixtures of formic acid and acetic acid, see Table 1.


    Table 1. Corrosion rate of Sanicro® 35 in mixtures of acetic acid (CH COOH) and formic acid (HCOOH) at boiling conditions.

    Concentration CH3COOH, %50505050
    Concentration HCOOH, %10152025
    Corrosion rate, mm/year0.000.000.000.01


    Sanicro® 35 performs well also in alkaline conditions showing high corrosion resistance in caustic solutions, see Table 2.


    Table 2. Corrosion rate of Sanicro® 35 in sodium hydroxide (NaOH) at various concentrations and temperatures.

    Concentration NaOH %40506070
    Temperature (°C)120120120130
    Corrosion rate, mm/year0.060.050.030.01


    Pitting corrosion: One of the main advantages of Sanicro® 35 is that it has excellent resistance to pitting corrosion. The pitting resistance comes from the high contents of chromium, molybdenum, and nitrogen. The PREN-number can be used to compare and rank alloys with respect to the chemical composition and possibility to resist pitting.


    The PRE is defined as, in weight-%


    PRE = %Cr + 3.3 x %Mo + 16 x %N


    The nominal PREN value for Sanicro® 35 is ~52, comparable to the nickel alloy Sanicro 625 (Alloy 625). This is significantly higher than e.g. the PREN values for super duplex and 6 Mo austenitic grades which are commonly used in seawater applications. For reference, Sandvik SAF 2507 and Sandvik 254 SMO have a minimum PRENvalue of 42.5.


    The critical pitting temperature (CPT) has been determined in 6% FeCl according to ASTM G48 practice C. The CPT has also been determined in a potentiostatic test in a 3M MgCl solution. The test was performed in a modified ASTM G150 test where the solution was changed from 1M NaCl to allow the CPT-measurement of highly alloyed materials. The measured CPT-values can be seen in Table 3.


    Table 3. CPT-values for Sanicro® 35 compared to Sandvik 254 SMO. The CPT was measured on coupons with P120 surface for the ASTM G48 test and P600 surface for the G150 mod. test.

    AlloyCPT (°C)
    Mod. G150 in 3M MgCl₂ASTM G48 method C
    Sanicro 35110>85¹⁾²⁾
    Sandvik 254 SMO6765³⁾
    Alloy C276N/A>85¹⁾²⁾
    Alloy 625N/A>85¹⁾²⁾
    1)According to the standard ASTM G48, the method was developed to be used up to 85°C.
    2)Method C
    3)Method E


    Crevice corrosion resistance is equally as important as pitting resistance since crevices can rarely be totally avoided. Sanicro® 35 has excellent crevice corrosion resistance in chloride environments. The critical crevice temperature (CCT) has been determined by potentiostatic tests in 1M NaCl according to standard ASTM G150 and by immersion tests in 6% FeCl test solution acidified with HCl according to ASTM G48, see Table 4.


    Table 4. CCT-values for Sanicro® 35 compared to some alloys according to various test methods. The applied potential was 700 mV vs. SCE as per ASTM G150. Flat coupons were tested with surfaces wet ground with P600 grit paper for the ASTM G150 test and with P120 for the ASTM G48 tests.


    AlloyCCT (°C)
    ASTM G150¹⁾ASTM G48 method D²⁾ASTM G48 method F³⁾
    Sanicro 3510052.545
    Alloy C27652.542.5
    Alloy 6254525
    Sandvik 254 SMO7535
    1)crevice formers according to ISO 18070 with applied momentum of 3 Nm
    2)applied momentum of 0.28Nm
    3)applied momentum of 1.58Nm


    Testing in seawater: Accelerated laboratory tests are very good for ranking different alloys, however, real application environment tests are also valuable. Materials are often used in a seawater environment which is very corrosive for many alloys. Sanicro® 35 has been tested for 90 days in natural seawater at 30°C where a biofilm is active and also in 0.5 ppm chlorinated seawater at elevated temperatures.


    Table 5. Flat specimens with surfaces ground with P120 grit paper tested in real seawater.


    Test conditionPitting corrosionCrevice corrosion¹⁾
    30°C natural seawaterNoNo
    80°C chlorinated seawater (0.5 ppm residual Cl)NoN/A
    1)crevice formers according to ISO 18070 with applied crevice pressure of 3 N/mm²


    Stress corrosion cracking: Ordinary austenitic steels of the ASTM 316 type are susceptible to chloride-induced stress corrosion cracking (SCC) in chloride bearing solutions at temperatures above about 60°C (140°F). This susceptibility declines with increasing nickel content. Chromium contents above 20% can also be beneficial. Sanicro® 35 has excellent resistance to SCC. This is demonstrated in Table 6, which shows the results of SCC tests in a 40% calcium chloride solution. The grade showed no cracking or corrosion after 500 hours of constant load testing, corresponding to 90% of the actual ultimate tensile strength at 100°C. It should be noted that the high loading of 90% of UTS naturally causes plastic deformation of the specimens.


    Table 6. Result of stress corrosion cracking test of different alloys in aerated 40% CaCl , at 100°C (210°F), pH 6.5.


    Alloy% of UTSTime to failure (h)Remark
    Sanicro 3590>500No attack
    Sanicro 2890>500No attack
    ASTM TP 31690<70Pitting and cracking


    Sanicro® 35 does not suffer from SCC in a NACE MR 0175 / ISO 15156 Test Level VI environment. Slow strain rate testing (SSRT) was performed on cold worked Sanicro® 35 material (140 ksi and 180 ksi), according to NACE TM0198. The environment had partial pressures of 500 psia H S and 500 psi CO . 20 wt-% sodium chloride was used as test solution and the temperature was 175°C ± 3°C. For both the 140 ksi and 180 ksi materials, two specimens were tested in the corrosive environment and one in nitrogen. All tests were carried out at the same baseline temperature. Both materials show ductile fractures with ratios of ≥92% for time to failure, elongation to failure, plastic strain to failure and reduction in area compared to inert environment, which indicates no SCC.


    Hydrogen embrittlement: Sanicro® 35 shows as expected excellent resistant to hydrogen embrittlement since it has high austenitic phase stability. Sanicro® 35 is not a precipitation-hardened grade which the latter may experience hydrogen embrittlement.


    Sanicro® 35 solution annealed material experienced no cracking in constant load testing at 4°C in 3% NaCl at -1050 mV at two different loads present in Table 7. This indicates that the alloy is not prone to hydrogen embrittlement and is a viable option for subsea applications.


    Table 7. Sanicro® 35 results from constant load testing at 4°C in 3% NaCl at -1050 mV SCE


    Load/Yield strength,%Load, MPaTime to failure,hCracking, Yes/No
    100427>500No
    120509>500No

    Expanding

    Sanicro® 35 can be expanded into tube sheets in the same way as standard austenitic stainless steels.

    Heat Treatment

    Tubes are delivered in solution annealed condition. If additional heat treatment is needed after further processing, please contact Sandvik.

    Other

    Forms of supply:

    Sanicro® 35 can be supplied as seamless tube and pipe.

    Welding

    The weldability of Sanicro® 35 is good and a suitable method for fusion welding is TIG welding (GTAW).


    Welding should be undertaken with low heat input, maximum 1.2 kJ/mm, and interpass temperature 100°C maximum. A stringer welding technique should be used. Preheating and post-weld heat treatment are not necessary. To maintain full corrosion resistance of the welded joint, welding must be followed by thorough cleaning to ensure the removal of all oxides and heat tint. Ar+2 %N₂ is recommended as shielding gas and backing gas with TIG welding to achieve the best combination of mechanical properties and corrosion resistance of the welded joints.


    Welding of fully austenitic stainless steels and nickel-base alloys often involves the risk of hot cracking in the welded joints if the weldment is under constrain. Sanicro® 35, however, possesses very high purity, and is thereby less prone to hot cracking than most of the nickel-base alloys.


    Nickel alloy UNS N06059 (ERNiCrMo-13, NiCr23Mo16) wire or rod is recommended as filler material for gas shielded arc welding. Welding without filler material should be avoided in the as-welded condition.