Sanicro® 69 Tube and pipe, seamless

Datasheet updated

2022-05-10 07:46
(supersedes all previous editions)

Sanicro® 69 is an austenitic nickel-chromium-iron alloy used primarily for steam generators in nuclear power plants (PWR). For this application it is used in the 'thermally treated' condition. This treatment results in chromium carbide precipitation at the grain boundaries but no significant chromium depletion. The grade has good structure stability and good weldability.

For the steam generator application the material is characterized by:

  • Extremely high resistance against stress corrosion cracking in primary side PWR water conditions
  • Improved pitting corrosion resistance in chloride containing solutions compared with Alloy 600

Sanicro® 69 is also characterized by:

  • Good corrosion resistance in caustic environments
  • Excellent performance in nitric acid solutions

Standards

  • UNS: N06690
  • W.Nr.: 2.4642
  • AFNOR: NC 30FE (RCCM)

Products standards
Seamless condenser and heat exchanger tubes: ASTM B163
Seamless tube and pipe: ASTM B167

Approvals
ASME Boiler and Pressure Vessel Code Case N-20 and N-474.
AFCEN RCCM M4105

For steam generator applications Sanicro® 69 is delivered to the most stringent individual specifications in order to assure maximum reliable performance in nuclear power plants.

Chemical composition (nominal)

Chemical composition (nominal) %
C Si Mn P S Cr Ni Fe
0.02 ≤0.5 ≤0.5 ≤0.020 ≤0.015 30 60 10

Normally the Co-content is max 0.05%. Lower contents can be specified after agreement.

Chemical composition (nominal) %

CSiMnPSCrNiFeCu
0.02 ≤0.5 ≤0.5 ≤0.020 ≤0.015 30 60 10 ≤0.5

Normally the Co-content is max 0.05%. Lower contents can be specified after agreement.

Applications

  • Steam generators in nuclear power plants.
  • Units in contact with nitric acid at elevated temperatures.
  • Equipment requiring high resistance to oxidation, carburization and nitriding.
  • Units exposed to caustic solutions at high temperature.

Corrosion resistance

Stress corrosion cracking

The thermally treated condition of Sanicro® 69 is developed specifically to resist stress corrosion cracking in steam generator environment at nuclear power plants. This has been confirmed by laboratory stress corrosion cracking tests in pure water (less than 5 ppm oxygen, 4-5 ppm hydrogen added) at 365°C (690°F).

No stress corrosion cracking was developed in Sanicro® 69 during the entire test period of 33 000 hours. Alloy 600 started to crack after 200 hours.

Intergranular corrosion

Sanicro® 69 has good resistance to intergranular corrosion in both the thermally treated condition and the solution annealed condition. Typical corrosion rates in the Huey test (65% HNO3, 5 x 48h, ASTM A262 Practice C) are 0.06 mm/year (2.4 mpy).

The figure below shows a TTS diagram for a heat of Sanicro® 69 with 0.03% carbon tested in the Huey test. The initial material was annealed at 1040°C (1900°F), 20 min/WQ.

As can be seen there is a very narrow area where Sanicro® 69 shows some tendency for sensitization.

General corrosion

Sanicro® 69 and Alloy C-276 have been corrosion tested in 20% HNO3+ 4%HF at 65 °C (150 °F). Sanicro® 69 had a corrosion rate of 0.625 mm/year (24.6 mpy) while Alloy C-276 suffered a corrosion rate of 23.7 mm/year (933 mpy).

Fabrication

Bending

The excellent formability of Sanicro® 69 permits cold-bending to very small bending radii. Annealing is normally not necessary after cold-bending owing to the high stress corrosion cracking resistance for Sanicro® 69.

Expanding

Sanicro® 69 is expanded into tube sheets in the same way as standard austenitic stainless steels.

Forms of supply

Seamless tube and pipe are supplied in the size range from 1/4" O.D. (6.35 mm) to 4" O.D. (101.6 mm) in wall thickness from 0.030" (0.9 mm) to 1" (25.4 mm).

Tube and pipe are delivered in the solution annealed and pickled condition.

PWR steam generator tubes are delivered in the bright annealed and thermally treated condition. The thermal treatment involves a treatment in vacuum furnace at about 720°C (1330°F) for normally 10 hours.

Heat treatment

For steam generator application the tubes are delivered in the thermally treated conditions. This means exposure at about 720°C (1330°F) for normally 10 hours. Prior to the thermal treatment the tubes are solution annealed at approximately 1100 °C (2010°F) for some minutes.

For other applications the tubes are delivered in the solution annealed condition. If additional solution annealing is necessary after further processing the following procedure is recommended:

1050-1150°C (1920-2100°F), 1-10 minutes, rapid cooling in air or water.

Mechanical properties

The following two tables give general nominal values.
At 20°C (68°F)

Proof strength
Rp0.2a)
MPa
ksi Tensile strength
Rm
MPa
ksi Elongation
Ab)
%
Hardness
Vickers
approx.
≥240 ≥35 ≥585 ≥85 ≥30
160


1 MPa = 1N/mm2
a)Rp0.2 corresponds to 0.2% offset yield strength.
b) Based on L0 = 5.65 ÖS0 where L0 is the original gauge length and S0 the original cross-section area.
At high temperatures

Temperature Proof strength Tensile Strength
°C °F Rp0.2 Rm
MPa ksi MPa ksi
min. min. min. min.
100 210 220 31.9 550 79.8
200 390 190 27.5 510 74.0
300 570 187 27.1 495 71.8
400 750 184 26.7 490 71.1
500 930 180 26.1 480 69.6
600 1110 175 25.4 440 63.8
700 1290 150 21.8 340 49.3


For steam generator tubing in the thermally treated condition the following higher proof strength values can be guaranteed.

Temperature Proof strength
°C °F Rp0.2
MPa ksi
20 68 280 40.6
100 210 260 37.7
200 390 240 34.8
350 660 210 30.5


Impact strength
Since Sanicro® 69 is a fully austenitic alloy it possesses good toughness down to -196°C (-320°F)

Physical properties

Density: 8.12 g/cm3; 0.293 lb/in3

Thermally Treated condition

Specific heat capacity
Temperature, °C J/(kg °C) Temperature, °F Btu/(lb °F)
23 460 73 0.11
100 480 200 0.11
200 495 400 0.12
300 505 600 0.12
400 510 800 0.12
500 520 1000 0.13
600 580 1100 0.14
Thermal conductivity
Temperature, °C W/(m °C) Temperature, °F Btu/(ft h°F)
23 11 73 6.5
100 13 200 7.5
200 14 400 8.5
300 16 600 9.5
400 18 800 10.5
500 19 1000 11.5
600 23 1100 13
Resistivity
Temperature, °C
μΩm Temperature, °F μΩin.
20 1.11 68 43.7
100 1.14 200 44.9
200 1.18 400 46.5
300 1.22 600 48.0
400
1.24 800 48.8
Thermal expansion 1)
Temperature, °C Per °C Temperature, °F Per °F
30-100 13.5 86-200 7.5
30-200 14 86-400 8
30-300 14.5 86-600 8
30-400 15 86-800 8.5
30-500 15.5 86-1000 8.5
30-600 15.5 86-1200 9

1) Mean values (x10-6)

Modulus of elasticity 1)
Temperature, °C MPa Temperature, °F ksi
20 210 68 30.5
100 206 200 30.0
200 201 400 29.1
300 195 600 28.1
400 189 800 27.1
500 182 1000 26.0
600 174 1200 24.8

1) (x103)

Welding

The weldability of Sanicro® 69 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.

For Sanicro® 69, heat-input of <1.0 kJ/mm and interpass temperature of <100°C (210°F) are recommended. A string bead welding technique should be used.

Recommended filler metals

TIG/GTAW or MIG/GMAW welding

ISO 18274 S Ni 6052/AWS A5.14 ERNiCrFe-7 (e.g. Exaton Ni68HP)

MMA/SMAW welding

ISO 14172 E Ni 6152/AWS A5.11 ENiCrFe-7 (e.g. Exaton Ni69)

Overlay welding

ISO 18274 S Ni 6043/AWS A5.14 ERNiCrFe-14 (e.g. Exaton Ni69HPQ) strip electrode is recommended for overlay welding of tube sheets and high-pressure vessels in cases where corrosion resistance, equal to that of Sanicro® 69, is required.

Disclaimer: Recommendations are for guidance only, and the suitability of a material for a specific application can be confirmed only when we know the actual service conditions. Continuous development may necessitate changes in technical data without notice. This datasheet is only valid for Alleima materials.