Sanicro® 69 Tube and pipe, seamless

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

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)

1 MPa = 1N/mm²
a)R_p0.2 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

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

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

1) Mean values (x10^-6)

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.