White Copper Grade Selection Guide: Applications and Properties Comparison of C7521 and C7701

White copper, also known as foreign white copper or zinc white copper, is available in China under the designations BZn18-18 and BZn12-23, while in Japan it is labeled C7521 and C7701. Both grades are copper alloys with nickel as the primary additive. Specifically, copper-nickel binary alloys are called ordinary white copper, while white copper alloys with added elements such as manganese, iron, zinc, and aluminum are called complex white copper.

White copper is a copper alloy with added nickel and other elements (such as manganese, iron, zinc, and aluminum). Specific grades are distinguished in China and Japan.

The primary difference between nickel silver C7521 and C7701 lies in their copper content: C7521's copper content ranges from 62% to 66%, while C7701's copper content ranges from 54% to 58%. This makes C7701 harder than C7521.

Because copper, nickel, and zinc all possess excellent weldability, nickel silver alloys based on these three elements also exhibit excellent weldability. A comparison of C7521 and C7701 reveals that their nickel content is comparable, but their copper and zinc contents differ slightly. From a technical perspective, copper is more weldable than zinc, so the differences in copper and zinc content between the two grades may also contribute to their weldability differences. Testing has shown that C7521 welds approximately 0.03 seconds faster than C7701.

In practical applications, C7701 is often used for shielding enclosures, while C7521 is more suitable for oscillator enclosures. Furthermore, C7701 is often used as a spring material due to its higher hardness, while C7521 is often used for deep drawing. Therefore, C7701 is suitable for shielding enclosures, while C7521 is more suitable for oscillator enclosures. Notably, C7701 is slightly less expensive than C7521.

A comparison of performance parameters reveals that, in the same state, C7701 exhibits superior tensile strength and elongation to C7521, demonstrating superior mechanical properties and formability. However, for products requiring extremely high drawing depths, such as crystal enclosures, the material hardness must be within HV100, a requirement that C7521 in its O state can meet.

Because nickel silver contains zinc and nickel, its sheet and strip exhibit a bright silvery-white color. Higher zinc and nickel content increases material stability, creates a whiter appearance, and offers superior high-temperature resistance. Through multiple comparative tests, we've found that C7701 performs superior in high-temperature resistance, lasting longer and withstanding higher temperatures. Specifically, C7701 maintains no discoloration for over three minutes at temperatures exceeding 280°C, while C7521 exhibits highly unstable heat resistance at temperatures exceeding 260°C.

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