Table of Contents
Hastelloy C276 pipe is widely used in chemical processing industries due to its exceptional corrosion resistance, high mechanical strength, and excellent weldability. This article explores the chemical composition, mechanical properties, processing techniques, and common applications of C276 pipe in chemical environments.
Chemical Composition of C276 Pipe
The corrosion resistance of C276 pipe largely stems from its unique chemical composition. The alloy primarily consists of nickel, molybdenum, chromium, and iron, along with trace elements that enhance performance in aggressive media.
| Element | Percentage (%) |
|---|---|
| Nickel (Ni) | Balance |
| Molybdenum (Mo) | 15.0–17.0 |
| Chromium (Cr) | 14.5–16.5 |
| Iron (Fe) | 4.0–7.0 |
| Tungsten (W) | 3.0–4.5 |
| Cobalt (Co) | 2.5 max |
| Manganese (Mn) | 1.0 max |
| Carbon (C) | 0.01 max |
| Silicon (Si) | 0.08 max |
| Sulfur (S) | 0.03 max |
Physical and Mechanical Properties
Hastelloy C276 exhibits robust physical properties that allow it to perform well under high pressure and temperature conditions in chemical processing plants.
| Property | Value |
|---|---|
| Density | 8.89 g/cm³ |
| Melting Range | 1325–1370 °C |
| Tensile Strength | 690 MPa (min) |
| Yield Strength (0.2% offset) | 283 MPa (min) |
| Elongation | 40% (min) |
| Hardness (Rockwell B) | ≤ 90 HRB |
Corrosion Resistance in Chemical Environments
C276 pipe is known for its resistance to a wide range of chemicals, including strong oxidizers, reducing agents, and mixed acid environments. It is especially resistant to pitting, stress-corrosion cracking, and crevice corrosion.
| Chemical Environment | Performance of C276 |
|---|---|
| Hydrochloric Acid | Excellent resistance across all concentrations |
| Sulfuric Acid | Good resistance up to moderate concentrations |
| Acetic Acid | Highly resistant |
| Phosphoric Acid | Good resistance |
| Sodium Hypochlorite | Excellent resistance |
Processing Techniques for C276 Pipe
Processing of C276 pipe includes forming, welding, machining, and heat treatment. Each step must follow stringent guidelines to retain corrosion-resistant properties.
Welding: C276 can be welded using techniques such as GTAW (TIG), GMAW (MIG), and SMAW. Filler metal of matching composition should be used to avoid galvanic corrosion.
Forming: Cold working is possible but requires more force than standard stainless steels. Intermediate annealing may be needed during complex forming operations.
Heat Treatment: Solution heat treatment at 1121°C followed by rapid quenching is recommended to restore corrosion resistance after forming or welding.
Machining: Use of carbide tools with low cutting speeds and high feed rates improves tool life and workpiece quality.
Typical Applications in Chemical Processing
C276 pipe is used in various equipment and piping systems that handle aggressive chemicals, high temperatures, and pressure. Its durability makes it suitable for:
| Application | Description |
|---|---|
| Reactor vessels | Withstands corrosive acids and oxidizing agents in reactors |
| Heat exchangers | Performs under thermal cycling and corrosive fluids |
| Scrubbers and stacks | Resists corrosion from sulfur compounds and chlorine gases |
| Evaporators | Maintains performance with aggressive fluid concentrations |
| Process piping | Handles various acidic and oxidizing solutions safely |
Fabrication Standards and Specifications
C276 pipes are produced in accordance with international standards to ensure quality and consistency in chemical processing systems.
| Standard | Specification |
|---|---|
| ASTM B622 | Seamless Pipe and Tube |
| ASTM B619 | Welded Pipe |
| ASTM B626 | Welded Tube |
| ASME SB622 | Boiler and Pressure Vessel Code Equivalent |
Availability and Dimensions
C276 pipe is available in various dimensions, schedules, and finishes to meet the needs of different chemical processing systems.
| Outer Diameter (OD) | Wall Thickness | Length |
|---|---|---|
| 1/8" to 12" | Sch 5 to Sch XXS | Up to 6 meters or as specified |
Related Questions
What is the chemical composition of Hastelloy C276 pipe?
Hastelloy C276 pipe is primarily composed of nickel, molybdenum, and chromium, with additions of iron and tungsten, offering superior corrosion resistance in aggressive environments.
How does C276 perform in hydrochloric acid?
C276 offers excellent resistance to hydrochloric acid across all concentrations, making it highly suitable for handling this corrosive chemical in industrial settings.
What standards apply to C276 seamless and welded pipes?
The most common standards for C276 pipe include ASTM B622 for seamless pipe and ASTM B619 for welded pipe, ensuring consistent quality and performance.