Alloy C276 Round Rod ASTM EN GB Standard
Alloy C276 (UNS N10276, Werkstoff Nr. 2.4819) is a nickel-molybdenum-chromium-tungsten alloy renowned for its exceptional corrosion resistance in the harshest industrial environments, particularly against oxidizing and reducing media. Hot-rolled Alloy C276 round bars are widely used in critical applications where durability, chemical stability, and mechanical strength are non-negotiable. Below is a comprehensive overview of its parameters, properties, production process, standards, equivalent grades, and applications.
1. Chemical Composition (Key Parameters)
The superior performance of Alloy C276 stems from its precisely controlled chemical composition, which balances corrosion resistance and mechanical properties. The typical composition (per ASTM B574) is as follows:
| Element | Content Range (%) | Primary Function |
| Nickel (Ni) | ≥ 57 | Base metal; provides structural stability and resistance to chloride stress corrosion cracking (SCC) |
| Chromium (Cr) | 14.5 - 16.5 | Enhances resistance to oxidizing media (e.g., nitric acid, air, and seawater) |
| Molybdenum (Mo) | 15.0 - 17.0 | Improves resistance to reducing media (e.g., sulfuric acid, hydrochloric acid) |
| Tungsten (W) | 3.0 - 4.5 | Boosts resistance to pitting and crevice corrosion; strengthens the alloy |
| Iron (Fe) | ≤ 5.0 | Reduces alloy cost while maintaining ductility |
| Carbon (C) | ≤ 0.01 | Minimizes carbide precipitation (avoids intergranular corrosion in high-temperature service) |
| Silicon (Si) | ≤ 0.08 | Controls oxidation during melting; limits impurity-induced brittleness |
| Manganese (Mn) | ≤ 1.0 | Enhances hot workability during rolling |
| Phosphorus (P) | ≤ 0.04 | Reduces embrittlement risks |
| Sulfur (S) | ≤ 0.03 | Minimizes cracking during fabrication |
2. Mechanical & Physical Properties
Hot-rolled Alloy C276 round bars exhibit a unique combination of high strength, ductility, and thermal stability, making them suitable for both ambient and elevated-temperature applications.
2.1 Mechanical Properties (Hot-Rolled Condition, per ASTM B574)
| Property | Test Standard | Value (Typical) | Unit |
| Tensile Strength (UTS) | ASTM E8 | ≥ 795 | MPa |
| Yield Strength (0.2% Offset) | ASTM E8 | ≥ 310 | MPa |
| Elongation (in 50 mm) | ASTM E8 | ≥ 40 | % |
| Hardness (Brinell) | ASTM E10 | ≤ 210 | HB |
Note: Post-heat treatment (e.g., solution annealing at 1120–1150°C followed by rapid quenching) can further optimize toughness and corrosion resistance by eliminating residual stresses.
2.2 Physical Properties
| Property | Value | Unit |
| Density | 8.89 | g/cm³ |
| Melting Range | 1325–1370 | °C |
| Thermal Conductivity (25°C) | 10.8 | W/(m·K) |
| Coefficient of Thermal Expansion (20–100°C) | 12.4 × 10⁻⁶ | /°C |
| Electrical Resistivity (25°C) | 1.37 × 10⁻⁶ | Ω·m |
3. Production Process of Hot-Rolled Alloy C276 Round Bars
The manufacturing process of hot-rolled Alloy C276 round bars adheres to strict quality controls to ensure consistency and performance. Key steps include:
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Raw Material Melting & Casting
- High-purity nickel, molybdenum, chromium, and tungsten are melted in an electric arc furnace (EAF) or vacuum induction melting (VIM) furnace to avoid contamination.
- The molten alloy is cast into cylindrical ingots (billets) via continuous casting or static casting, with diameters ranging from 150 mm to 500 mm.
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Homogenization Annealing
- Billets are heated to 1050–1100°C and held for 8–12 hours to eliminate chemical segregation and improve workability.
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Hot Rolling
- Annealed billets are heated to 1000–1100°C (the alloy’s optimal hot-working temperature range) and passed through a series of rolling mills.
- The billets are gradually reduced in diameter to form round bars of the desired size (common diameters: 10 mm–300 mm). Hot rolling enhances grain structure and mechanical strength.
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Solution Annealing & Quenching
- After rolling, bars undergo solution annealing at 1120–1150°C for 30–60 minutes, then rapidly quenched in water or air. This step dissolves carbides and precipitates, restoring maximum corrosion resistance.
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Surface Treatment
- Bars are descaled (via pickling with nitric-hydrofluoric acid) to remove oxide layers formed during rolling.
- Optional finishing processes: grinding, polishing, or turning to achieve precise dimensional tolerance (e.g., h9/h10) and surface roughness (Ra ≤ 6.3 μm).
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Quality Inspection
- Non-destructive testing (NDT): Ultrasonic testing (UT) for internal defects, magnetic particle testing (MT) for surface cracks.
- Chemical composition analysis (via 光谱 analysis, OES), mechanical property testing (tensile, hardness), and dimensional verification.
4. International Standards
Alloy C276 round bars are manufactured and inspected in compliance with global standards to ensure interoperability across industries. The most widely recognized standards are:
| Standard System | Standard Number | Specification Scope |
| ASTM (USA) | ASTM B574 | Standard Specification for Nickel-Chromium-Molybdenum-Tungsten Alloy (UNS N10276) Bars and Rods |
| EN (Europe) | EN 10088-3 | Stainless Steels and Heat-Resisting Steels – Part 3: Wrought Products (Alloy 2.4819) |
| GB (China) | GB/T 2054 | Nickel and Nickel Alloy Bars and Rods (Equivalent grade: N06276) |
| ISO | ISO 6208 | Nickel and Nickel Alloy Rods and Bars (General requirements for Alloy C276) |
5. Equivalent Grades
Alloy C276 is standardized under different designations worldwide. These grades have nearly identical chemical composition and performance, ensuring compatibility in cross-border projects:
| Standard System | Grade Designation | Corresponding Alloy |
| UNS (USA) | UNS N10276 | Alloy C276 |
| DIN/EN (Europe) | Werkstoff 2.4819 | Alloy C276 |
| GB (China) | N06276 | Alloy C276 |
| JIS (Japan) | NW2276 | Alloy C276 |
| BS (UK) | NA 21 | Alloy C276 |
6. Applications
Alloy C276 round bars are favored in industries requiring superior corrosion resistance and mechanical reliability under extreme conditions. Typical applications include:
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Chemical Processing Industry
- Components for sulfuric acid production (reactors, heat exchangers), hydrochloric acid handling (pumps, valves), and pharmaceutical synthesis (reaction vessels).
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Oil & Gas Industry
- Downhole tools, wellhead components, and pipeline parts for offshore and sour gas environments (resists H₂S and chloride-induced SCC).
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Environmental Engineering
- Flue gas desulfurization (FGD) systems, wastewater treatment equipment, and incinerator parts (withstands acidic fumes and high temperatures).
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Aerospace & Defense
- Engine components, rocket nozzles, and military hardware (tolerates high-temperature oxidation and chemical exposure).
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Other High-Performance Sectors
- Nuclear power plant components (resists radiation-induced degradation), marine engineering (seawater-resistant fasteners), and semiconductor manufacturing equipment (high-purity requirements).
