Sanicro® 25 Tube and pipe, seamless

Standards

• UNS: S31035
• EN Number: 1.4990
• EN Name: X7NiCrWCuCoNb25-23-3-3-2

Product standards
Seamless tube and pipe: ASTM A213, ASTM A312

Approvals

• European Particular Material Appraisal (PMA)
• VdTÜV material data sheet 555, 23.10.2018
• The American Society of Mechanical Engineers (ASME) Boiler and Pressure
• ASME Code Case 2753-1, Section I and 2752-1, Section VIII Division 1
• China Pressure Vessel Approval CSCBPV BV-ME-210

Chemical composition (nominal)

Chemical composition (nominal) %

C	Si	Mn	P	S	Cr	Ni	W	Co	Cu	Nb	N
≤0.1	0.2	0.5	≤0.025	≤0.015	22.5	25	3.6	1.5	3.0	0.5	0.23

Applications

The high creep strength of Sanicro^® 25 combined with its good corrosion resistance makes it an extremely suitable option for use in superheaters and reheaters in advanced coal fired power boilers. Use in high temperature applications in other types of steam boilers employing different fuel types is also possible. The material has been specifically developed for use at material temperatures up to around 700°C (1300^oF).

Corrosion resistance

Hot corrosion

Sanicro^® 25 has very good resistance to hot corrosion in a coal ash environment.

Oxidation tests in air, performed as both isothermal tests at 650°C (1202^oF) and 750°C (1382^oF) for 1000, 2000 and 3000 hours and discontinuous tests with cooling to room temperature after 24, 50, 100, 200, 500, 1000, 1500, 2000 and 3000 hours, show a very low mass rate change.

Oxidation tests in aqueous steam at 600°C (1112^oF) and 700°C (1292^oF) for 500 and 1000 hours respectively, showed that Sanicro^® 25 has very good oxidation resistance.

Bending

The material can be bent at high as well as at low temperatures.

Recommended temperature range for hot bending is 850-1250°C (1560-2280°F) . Following hot bending, solution annealing is needed, unless the bending has been performed at controlled temperatures between 1180°C and 1250°C (2155°F and 2280°F).

Cold-bending should be followed by solution annealing if the cold deformation is >20% or the R/D ratio is ≤2.5, if the service temperature is in the creep range. For best corrosion properties at high temperatures it is recommended that solution annealing should be performed, even at lower degrees of cold forming.

See also the Heat treatment section.

Forms of supply

Sanicro^® 25 is supplied as cold pilgered solution annealed and white-pickled seamless tubes, in common reheater and superheater boiler tube dimensions.

The VdTÜV-material datasheet 555, 23.10.2018, applies for outside diameter 25 mm to 114.3 mm and wall thickness 4.5 mm -12.5 mm.

Heat treatment

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

Solution annealing

1180-1250°C (2155-2280°F) and quenched.

Contact Alleima for advice regarding further heat treatment issues.

Mechanical properties

At 20^oC (68^oF), annealed condition

1 MPa = 1 N/mm²

a) R_p0.2 and R_p1.0 correspond to 0.2% offset and 1.0% offset yield strength, respectively.
b) Based on L₀ = 5.65 √S_0, where L₀ is the original gauge length and S₀ is the original cross-section area.

At high temperatures, annealed condition

Impact strength

Due to its austenitic microstructure, Sanicro^® 25 has very good impact strength, both at room temperature and at cryogenic temperatures.

Creep rupture strength according to VdTÜV Wb555, 09.2018

Max allowable stress values according to ASME Code Case 2753-1, Section I and 2752-1, Section VIII Division 1.

¹⁾ Due to the relatively low yield strength of these materials, in some cases slightly higher stress values in this column were established at temperatures where slightly greater deformation was acceptable. These stress values are not recommended in applications where small amounts of distortion can cause leakage or malfunction.

Stress values shown in italics are obtained from time-dependent data.
The maximum use temperature is 1382^oF (750^oC).

Physical properties

Density: 8.32 kg/dm³; 0.29 lb/in³

1) Mean values

1) Mean values in temperature ranges (x10^-6)

1) Mean values in intermediate temperature ranges (x10^-6)

Modulus of elasticity ¹⁾

1) (x10³)

Welding

The weldability of Sanicro^® 25 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, Sanicro^® 25 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^® 25, 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 6617/AWS A5.14 ERNiCrCoMo-1 (e.g. Exaton Ni53, Alloy 617 mod)

MMA/SMAW welding

ISO 14172 E Ni 6117/AWS A5.11 ENiCrCoMo-1