Sanicro 30 Cold‑Worked Alloy for High‑Temperature Nuclear Applications

Approvals: Approved for use according to ASME Boiler and Pressure Vessel Code Section III, division 1 and Section VIII, division 1 and 2

Heat treatment after cold bending is not normally necessary, but this point must be decided with regard to the degree of bending and the operating conditions. Heat treatment, if any, should take the form of stress relieving or solution annealing.

General corrosion: Sanicro® 30 has approximately the same resistance to organic and inorganic acids as steel of the ASTM TP 304 type. Its resistance to sodium hydroxide is very good except at the very highest concentrations and temperatures.

Pitting: The material has somewhat better resistance to pitting than steel of the ASTM TP 304 type.

Intergranular corrosion and stress corrosion cracking: In comparison with the standard Alloy 800, Sanicro® 30 has improved resistance both to intergranular corrosion and to intergranular stress corrosion cracking. This is obtained by a high degree of stabilization and a production sequence giving a small grain size. The resistance to trans- granular stress corrosion cracking is very good as for all high-nickel alloys.

Gas corrosion: In general this grade is not used at temperatures high enough for gas corrosion to be a problem. For such cases the appropriate metal to choose is Sanicro® 31HT. However, compared with Sanicro® 31HT, Sanicro® 30 has about the same resistance to gas corrosion.

The tubes are delivered in heat treated condition. If another treatment is needed after further processing the following is recommended.

Stress relieving: 800-875°C (1470-1605°F), 10-15 minutes, cooling in air.

Solution annealing: 950-1050°C (1740-1920°F), 1-10 minutes, rapid cooling in water or air.

Hot bending is carried out at 1050-850°C (1920-1560°F) and should be followed by solution annealing.

Forms of supply:

Tube and pipe are supplied hot- or cold-worked, solution-annealed and white-pickled or bright-annealed. The principal size range can be seen from the figure on the right, but also certain sizes can be delivered on request.

The weldability of Sanicro® 30 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.

Since the material 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 Sanicro® 30, 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 6082/AWS A5.14 ERNiCr-3 (e.g. Exaton Ni72HP)
• MMA/SMAW welding
  • ISO 14172 E Ni 6182/AWS A5.11 ENiCrFe-3 (e.g. Exaton Ni71)