Sanicro® 625 is an austenitic nickel-chromium alloy characterized by:
- Extremely good corrosion resistance in widely varying acidic and chloride containing environments
- High strength
- Excellent fabrication properties.
Sanicro® 625 can be used in a wide range of temperatures from -196°C to 815°C (-321°F to 1500°F). Typical uses include hydraulic and instrumentation systems, heat-exchangers and high-temperature applications. However, it should be noted that prolonged exposure to temperatures above 600°C (1100°F) may lead to embrittlement.
Standards
-
UNS: N06625 -
ISO: NW6625
Product standards
ASTM B444, Grade 1 and Grade 2
ASME SB444, Grade 1 and Grade 2
ISO 6207
Chemical composition (nominal)
| C | Si | Mn | P | S | Cr | Ni | Mo | Fe | Nb |
|---|---|---|---|---|---|---|---|---|---|
| 0.025 | 0.2 | 0.15 | ≤0.015 | ≤0.015 | 21.5 | 61 | 8.7 | 4 | 3.5 |
Applications
Sanicro® 625 is an extremely versatile nickel alloy, suitable for use in both oxidizing and reducing acidic environments, such as:
- Hydrochloric acid
- Nitric acid
- Phosphoric acid
- Chloride containing environments
The grade can also be used for a wide range of temperatures from -196°C to 815°C (-321°F to 1500°F). Typical areas of use include hydraulic systems, heat-exchangers and high-temperature applications.
Some industrial examples are:
- High temperature aerospace
- Chemical process industry
- Power industry
Corrosion resistance
Wet corrosion
Sanicro® 625 shows very good resistance to pitting corrosion, intergranular corrosion and is virtually immune to stress corrosion cracking in chloride-containing environments. The grade is able to withstand general corrosion in both severe oxidizing and non-oxidizing acids.
Resistance in chloride environments is also extremely good owing to the high PRE number, ≥48.
Pitting Resistance Equivalent, PRE
PRE = %Cr + 3.3 x %Mo + 16 x %N
High temperature corrosion
In addition to its excellent wet corrosion resistance, Sanicro® 625 is also able to resist oxidation and scaling at high temperature.
Forms of supply
Sanicro® 625 seamless nickel alloy tubing is supplied bright annealed in the outside diameter range 6 - 42 mm (0.25" - 1.625") and wall-thickness 0.89 - 5.0 mm (0.035" - 0.197"). Some dimensions may be supplied annealed and white pickled.
Tubing is supplied as:
- Annealed (Grade 1)
- Solution annealed (Grade 2)
Tolerances
| Size OD, mm |
Tolerances OD, mm |
Wall thickness % |
|---|---|---|
| 6-30 | +/-0.08 | +/-10 |
| 32-40 | +/-0.15 | +/-10 |
| 42 | +/-0.20 | +/-10 |
Mechanical properties
At 20oC, metric units
| Condition | Proof strength | Tensile strength | Elongation |
|---|---|---|---|
| Rp0.21) | Rm | A2" | |
| MPa | MPa | % | |
| Grade 12) | ≥415 | ≥827 | ≥30 |
| Grade 23) | ≥276 | ≥690 | ≥30 |
At 68oF, imperial units
| Condition | Proof strength | Tensile strength | Elongation |
|---|---|---|---|
| Rp0.21) | Rm | A2" | |
| ksi | ksi | % | |
| Grade 12) | ≥60 | ≥120 | ≥30 |
| Grade 23) | ≥40 | ≥100 | ≥30 |
1) Corresponds to 0.2% offset yield strength
2) Annealed at 871ºC (1600ºF) minimum
3) Solution annealed at 1093ºC (2000ºF) minimum
Welding
The weldability of Sanicro® 625 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® 625, heat-input of <1.2 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 6625/AWS A5.14 ERNiCrMo-3 (e.g. Exaton Ni60)
MMA/SMAW welding
ISO 14172 E Ni 6625/AWS A5.11 ENiCrMo-3 (e.g. Exaton Ni60)