Comprehensive Introduction to Hastelloy C-276 Pipe
Hastelloy C-276 is a high-performance nickel-based alloy known for its remarkable resistance to corrosion, making it a preferred choice in demanding industrial environments. It is especially effective in resisting pitting, crevice corrosion, and stress corrosion cracking, particularly in chloride-rich conditions. This makes it ideal for use in chemical processing, oil and gas, and other harsh environments.
Key Characteristics
- Corrosion Resistance: Hastelloy C-276 demonstrates excellent performance against both reducing and oxidizing acids such as sulfuric, hydrochloric, and acetic acids. It also resists seawater, chlorides, wet chlorine gas, and hypochlorite solutions. Its high molybdenum and tungsten content enhances localized corrosion resistance, and it maintains good oxidation resistance up to 1038°C (1900°F). However, it is not recommended for highly oxidizing environments like concentrated hot nitric acid.
- High-Temperature Performance: The alloy retains structural integrity at elevated temperatures, withstanding oxidation up to 1900°F (1038°C).
- Mechanical Properties: In the annealed condition, it has a yield strength of 41 ksi (345 MPa) and exhibits excellent toughness even at cryogenic temperatures. Cold working can increase strength but may require intermediate annealing due to its high work-hardening rate.
Heat Treatment
Hastelloy C-276 cannot be strengthened through heat treatment. It is typically solution annealed at 1121°C (2050°F) and rapidly cooled to ensure optimal properties. It can also be supplied in cold-worked or annealed conditions depending on application needs.
Workability
The alloy is suitable for hot working between 870°C and 1230°C (1600°F–2250°F). While cold forming is possible, it requires careful handling due to its tendency to work-harden quickly. Intermediate annealing is often necessary during cold forming processes.
Applications
Hastelloy C-276 is widely used in the chemical and petrochemical industries for components exposed to corrosive media. It is commonly found in piping systems, tubing, and valves in sour service environments containing H2S, CO2, and chlorides. Additionally, it is used in pharmaceuticals, paper production, and cryogenic applications where materials must perform at extremely low temperatures, down to -271°C (-455°F).
Chemical Composition
| C | Cr | Ni | Fe | Mn | Si | Mo | Co | P | S | V | W |
| ≤ 0.02% | 14.5 – 16.5% | BAL | 4 – 7% | ≤ 1% | ≤ 0.08% | 15 – 17% | ≤ 2.5% | ≤ 0.03% | ≤ 0.03% | ≤ 0.35% | 3 – 4.5% |
(mass %)
Standards
ASTM B622, ASME SB622
Typical Mechanical Properties (Annealed Condition)
| Tensile Strength | Yield Strength | Elongation |
| ≥ 100 ksi | ≥ 41 ksi | ≥ 40% |
*Higher strength can be achieved through cold working.
Physical Properties
| Property | Unit | 70°F | 200°F | 400°F | 600°F | 800°F | 1000°F | 1200°F |
| Density | lbs/in³ | 0.321 | - | - | - | - | - | - |
| Thermal Expansion | X10â»â¶/°F | - | 6.2 | 6.7 | 7.1 | 7.3 | 7.4 | 9.6 |
| Elastic Modulus | 10³ ksi | 29.8 | 29.1 | 28.3 | 27.3 | 26.4 | 25.5 | 22.37 |
| Poisson Ratio | - | 0.33 | - | - | - | - | - | 0.377 |
| Thermal Conductivity | Btu-in/h·ft²·°F | - | 77 | 90 | 104 | 117 | 132 | 152 |
| Specific Heat | Btu/lb·°F | 0.102 | - | - | - | - | - | 0.14 |
| Yield Strength | ksi | 41 | 40 | 38 | 34 | 33 | 33 | 11 |
| Tensile Strength | ksi | 100 | 99 | 99 | 94 | 92 | 87 | 44 |
Manufacturing Process
| Process | Description |
| Steel Making | Electric Arc Furnace followed by VOD or AOD for precise composition control. |
| Pipe Making | Seamless cold-finished pipe and tube manufacturing methods are commonly used. |
| Heat Treatment | Cannot be hardened via heat treatment; available in annealed or cold-hardened forms. |
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