1. Overview of the Alloy

HNi65-5 is a high-nickel brass alloy defined under China’s national standard GB/T 5231. It contains 5.0–6.5% nickel, 64.0–67.0% copper, with the remainder primarily zinc. The alloy forms a single-phase α solid solution structure, which delivers excellent seawater corrosion resistance and long-term structural stability—making it especially suitable for demanding and extended service environments.

2. Chemical Composition (by mass percentage)

• Copper (Cu)：64.0–67.0%

• Nickel (Ni)：5.0–6.5%

• Zinc (Zn)：Balance

• Iron (Fe)：≤ 0.15%

• Lead (Pb)：≤ 0.03%

• Total Impurities：≤ 0.3%

The combined copper and alloying elements make up approximately 99.7%, ensuring material stability and consistency in performance.

3. Mechanical Properties (Annealed Condition)

• Yield Strength (Rp0.2)：≥ 179 MPa

• Tensile Strength (Rm)：≥ 366 MPa

• Elongation (A)：≥ 12%

• Reduction of Area (Z)：≥ 11%

• Brinell Hardness (HBW)：≈ 223

HNi65-5 provides an excellent balance of strength and ductility, making it suitable for pressure-bearing structures and complex-formed components.

4. Key Material Characteristics

• Outstanding Corrosion Resistance: The addition of nickel significantly improves resistance to seawater, salt spray, and acid-alkaline media, ideal for moist and corrosive environments.

• Excellent Workability: Performs well under hot rolling, cold rolling, extrusion, and drawing processes.

• Stable Microstructure: The α-phase solid solution ensures dimensional stability and resistance to stress corrosion cracking during long service periods.

• Good Electrical and Thermal Conductivity: While not as conductive as pure copper, HNi65-5 offers adequate conductivity for most electrical applications.

5. Typical Applications

• Marine Engineering: Seawater condenser tubes, heat exchangers, marine cooling systems.

• Chemical Industry: Corrosion-resistant structural components such as pump casings, valves, and reactor vessels.

• Electrical Engineering: Ground terminals, high-strength electrodes, conductive fittings.

• Precision Manufacturing: Instrument parts, aerospace components, fasteners.

• Hydrogen Energy: Hydrogen pipelines and electrolyzer assemblies—thanks to excellent hydrogen embrittlement resistance.

6. Common Grades in GB/T 5231-2022 Standard

GB/T 5231-2022 is a cornerstone standard in China’s copper and copper alloy industry. It outlines chemical requirements for plates, strips, rods, tubes, and wires. Below is a categorized summary of widely used and application-relevant grades:

• Pure Copper (High Conductivity)：T1, T2, TU1, TU2

• Brass (Cu-Zn Alloys)：H59, H62, H65, H68/H70

• Free-Cutting Brass (Lead-Added)：HPb59-1, HPb63-3

• Tin Brass (Cu-Zn-Sn)：HSn62-1, HSn70-1

• Aluminum Brass (Cu-Zn-Al)：HAl77-2, HAl59-3-2

• Manganese Brass (Cu-Zn-Mn)：HMn58-2, HMn58-3-1

• Nickel Brass / High-Nickel Brass (Cu-Zn-Ni)：HNi65-5, HNi70-1

• Specialty Alloys (High-Performance, Low Volume)：QCr0.5, CuCrZr, CuFe2P

7. Conclusion

HNi65-5 high-nickel brass is a versatile and high-performance material that excels in challenging environments requiring corrosion resistance, mechanical strength, and excellent workability. Its broad range of applications, from marine engineering to hydrogen energy, demonstrates its importance in modern industries. With its optimal balance of properties, HNi65-5 is an ideal choice for professionals seeking durable and reliable solutions in demanding conditions. For projects requiring long-term performance and stability, HNi65-5 is a material that ensures success.

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