C7521 Copper

Grade Designation & Standards

Standard Grade: C7521 (Nickel Silver/Zinc White Copper)

International Equivalents:

China GB/T: BZn18-18

USA ASTM: C75200

Applicable Standards:

JIS: JIS H3110-2018 (Phosphor Bronze and Nickel Silver Sheets, Plates, and Strips)

Other References: GB/T 4423-1992, ASTM B122

Key Features

1. Corrosion Resistance: Excellent performance in seawater, salt spray, and humid environments (corrosion rate ≤0.01 mm/a), ideal for marine applications.

2. Mechanical Properties: Tensile strength up to 540–640 MPa (hard state), elongation ≥3%, balancing strength and ductility.

3. Conductivity: Electrical conductivity ~5% IACS, thermal conductivity 40 W/(m·K), suitable for electrical and thermal applications.

4. Workability: Supports cold/hot working, stamping, and welding with smooth surface finish.

5. Aesthetic Appeal: Silver-white metallic luster, widely used in decorative and precision components.

Common Product Forms & Specifications

Product Form	Size Range	Delivery Condition
Strip	Thickness: 0.1–5.0 mm; Width ≤600 mm	Annealed (O), Hard (H)
Plate	Thickness: 0.1–50 mm; Width ≤1200 mm	Annealed (O), Half-hard (1/2H)
Rod	Diameter: 5–150 mm; Length: 1–6 m	Cold-drawn, Hot-rolled
Wire	Diameter: 0.1–12 mm	Coiled or Straight
Tube	OD: 3–200 mm; Wall Thickness: 0.5–20 mm	Annealed, Half-hard
Note: Customizable per JIS H3110 standards.

Chemical Composition

Element	Cu	Ni	Zn	Fe	Mn	Total Impurities
Content	62.0–66.0%	16.5–19.5%	Balance	≤0.25%	≤0.50%	≤1.5%
Typical impurities: Pb≤0.03%, others (e.g., Sn, Al) ≤0.5%.

Physical Properties

Property	Value	Remarks
Density	8.73–8.9 g/cm³	High density for structural stability
Melting Point	1170–1350°C	Casting temperature reference714
Electrical Conductivity	~5% IACS	Suitable for low-current applications
Thermal Conductivity	40 W/(m·K)	Moderate heat dissipation
Thermal Expansion Coefficient	17.1×10⁻⁶/°C (20–200°C)	Excellent dimensional stability at high temperatures

Mechanical Properties

Property	Annealed (O)	Hard (H)
Tensile Strength (Rm)	≥375 MPa	540–640 MPa
Yield Strength (Rp0.2)	≥130 MPa	≥450 MPa
Elongation (A50)	≥20%	≥3%
Hardness (HV)	≤110	150–210
Note: Data per JIS H3110. Annealed state suits deep drawing; hard state for high-strength parts.

Core Advantages

1. Marine-Grade Durability: Superior corrosion resistance in seawater, outperforming stainless steel.

2. High Strength-Ductility Balance: Tensile strength ≥540 MPa (hard state) with retained plasticity.

3. Surface Treatment Adaptability: Supports plating, polishing, and passivation for functional and decorative needs.

Product Applications

• Electronics: Transformer strips, connectors, RF cables.

• Marine Engineering: Seawater pipelines, valves, ship components.

• Medical Devices: Surgical tools, vascular stents (requires passivation).

• Automotive: Radiators, engine parts.

Processing Guidelines

1. Welding: Use TIG welding with nickel-based filler (e.g., ERCuNi); avoid zinc vaporization.

2. Machining: Carbide tools with sulfur-based coolant; cutting speed ≤80 m/min.

3. Heat Treatment: Anneal at 700–750°C (stress relief), low-temperature annealing at 250°C (dimensional stability).

Key Application Scenarios

• High-Frequency Electronics: Crystal oscillator housings, connector terminals.

• Deep-Sea Valves: High-pressure, corrosion-resistant valve components (hard state recommended).

• Decorative Hardware: Tableware, musical instruments, architectural panels.

FAQs of Copper C7521

Q1: How does C7521 differ from C7541?

A1: C7541 has higher nickel content (18–22%) for better corrosion resistance but at a higher cost.

Q2: Is C7521 suitable for acidic environments?

A2: Yes, but avoid prolonged exposure to strong acids (e.g., concentrated sulfuric acid); surface coatings are recommended.

Q3: How to prevent edge cracking in cold-rolled strips?

A3: Limit rolling reduction to ≤20% per pass, anneal post-processing, and ensure smooth rollers.

Standard References

• Chemical & Mechanical Properties: JIS H3110-2018, GB/T 4423-1992.

• Processing: ASTM B543 (Cu-Ni Alloy Tubes).

• Testing: ISO 6892-1 (Tensile Testing).

Note: This specification integrates JIS standards and industry data. Actual parameters may vary slightly due to manufacturing processes. Refer to supplier certifications for precise details.