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China Zinc Alloy CNC Machining: Reliable Suppliers & Factory for Precision Parts and Die-Cast Blanks
Zinc alloys typically refer to alloys with zinc as the base, primarily alloyed with elements such as aluminum, copper, and magnesium. Their most prominent feature is excellent castability, making them suitable for manufacturing parts with complex shapes.
Simultaneously, their superior machinability allows subsequent CNC precision machining to easily achieve high dimensional accuracy and excellent surface finish.
Furthermore, zinc alloys offer good wear resistance, damping capacity, and comprehensive electromagnetic shielding (EMI/RFI) capability, making them an engineering material that combines functionality with economy.
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Common Zinc Alloy Grades and Characteristics
Grade 1
Zamak 3 (Zinc Alloy No. 3)
Characteristics
The most versatile and commonly used die-casting zinc alloy. It possesses the best fluidity and dimensional stability, along with good mechanical properties and surface treatment performance. Its low copper content means its creep resistance and strength are slightly lower than Zamak 5, but it offers better ductility.
Typical Applications
Complex thin-walled parts without extremely high strength requirements, such as toy models, zipper pulls, small gears, decorative items, and numerous consumer electronics housings.
Zamak 3 Typical Properties (As Die-Cast)
| Property | Value | Notes |
| Tensile Strength (MPa) | 280 – 320 | Good overall strength |
| Yield Strength (MPa) | — | |
| Elongation at Break (%) | 10 – 20 | Exhibits good ductility |
| Hardness (Brinell) | ~ 82 | |
| Density (g/cm³) | 6.6 | Significantly higher than aluminum and plastics |
| Note: Values are typical ranges, specific to casting process and condition. | ||
Grade 2
Zamak 5 (Zinc Alloy No. 5)
Characteristics
Based on Zamak 3 with the addition of about 1% copper, thereby increasing tensile strength, hardness, and creep resistance, but slightly reducing impact toughness and ductility. It is the most widely used high-strength die-casting zinc alloy.
Typical Applications
Functional and structural parts requiring higher strength and wear resistance, such as automotive door locks, fuel system components, tool housings, premium hardware, and business machine parts.
Zamak 5 Typical Properties (As Die-Cast)
| Property | Value | Notes |
| Tensile Strength (MPa) | 330 – 380 | Strength higher than Zamak 3 |
| Yield Strength (MPa) | — | |
| Elongation at Break (%) | 7 – 15 | |
| Hardness (Brinell) | ~ 91 | Higher hardness, more wear-resistant |
| Density (g/cm³) | 6.7 | Similar to Zamak 3 |
| Note: Values are typical ranges, specific to casting process and condition. | ||
Grade 3
ZA-8 (Zinc-Aluminum Alloy No. 8)
Characteristics
A zinc-aluminum alloy containing about 8.4% aluminum, typically produced by gravity casting. It has the best castability among all ZA series alloys and offers excellent bearing properties and wear resistance. Compared to the Zamak series, it retains better strength and dimensional stability at elevated temperatures.
Typical Applications
Bearings, bushings, sliders, wear-resistant components, and engineering structural parts that need to operate in moderately elevated temperature environments.
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Key Advantage: ZA-8 retains superior strength and dimensional stability at elevated temperatures compared to the Zamak series, making it ideal for heat-exposed industrial components.
Grade 4
Kirksite (Mold Zinc Alloy)
Characteristics
A zinc-based alloy specifically designed for manufacturing prototype molds, low-melting-point injection molds, and fixtures. It has a low melting point, is easy to machine, and can quickly and cost-effectively replicate complex mold cavities for small-batch plastic part trial production or sheet metal forming.
Typical Applications
Prototype injection molds, blow molds, sheet metal stamping/form dies, checking fixtures, and jigs.
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Cost-Efficiency Note: Kirksite enables rapid, low-cost tooling for small-batch production and prototyping — significantly reducing lead time and tooling investment compared to steel molds.
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Frequently Asked Questions (FAQ)
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What is the difference between Zamak 3 and Zamak 5?
Zamak 3 and Zamak 5 are both popular die-casting zinc alloys. The primary difference is that Zamak 5 contains approximately 1% more copper, which increases its tensile strength (330–380 MPa vs. 280–320 MPa), hardness (~91 vs. ~82 Brinell), and creep resistance. However, this comes at a slight cost to ductility and impact toughness. Zamak 3 is preferred when high ductility or superior surface finish is critical, while Zamak 5 suits parts demanding higher structural performance.
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What are the main advantages of zinc alloys over aluminum alloys in die casting?
Zinc alloys offer superior castability, enabling thinner walls, finer features, and more complex geometries than aluminum. They also have a lower melting point, which reduces energy costs and extends die life. Additionally, zinc alloys provide better electromagnetic shielding (EMI/RFI), excellent surface finish for plating and coating, and higher dimensional accuracy — making them highly competitive for precision consumer and industrial parts.
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When should ZA-8 be chosen over Zamak grades?
ZA-8 should be selected when the application involves moderately elevated operating temperatures or requires superior bearing and wear resistance. Its higher aluminum content (~8.4%) provides better thermal stability and strength retention at elevated temperatures compared to Zamak 3 or Zamak 5. Typical use cases include bearings, bushings, and structural components in industrial machinery.
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Can zinc alloy parts be CNC machined after die casting?
Yes. Zinc alloys have excellent machinability, making post-casting CNC precision machining straightforward. This allows manufacturers to achieve tight dimensional tolerances, superior surface finishes, and complex features that may not be achievable through die casting alone. The combination of die casting and CNC machining is a common and cost-effective production strategy for high-precision zinc alloy components.
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What surface treatments are compatible with zinc alloy die castings?
Zinc alloys are highly compatible with a wide range of surface treatments, including electroplating (chrome, nickel, copper), powder coating, painting, anodizing (for ZA series), chromate conversion coating, and physical vapor deposition (PVD). Their excellent surface finish as-cast makes them especially well-suited for decorative plating applications found in consumer electronics, automotive trim, and hardware products.
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What is Kirksite and why is it used for prototype molds?
Kirksite is a zinc-based alloy specifically formulated for tooling applications such as prototype injection molds, blow molds, and sheet metal forming dies. Its low melting point makes it easy to cast and machine, enabling rapid replication of complex mold cavities at a fraction of the cost of steel tooling. It is widely used in short-run production trials, allowing designers and engineers to validate part designs before committing to expensive hardened steel molds.
Finishes and Post-Processing Options
The zinc alloy substrate is highly suitable for various surface treatments to enhance decoration, protection, or functionality:
Electroplating: Such as chrome, nickel, gold, or silver plating, providing a highly decorative appearance, excellent wear and corrosion resistance. This is the most common choice.
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Passivation or Chromate Conversion Coating:
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Powder Coating:
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Painting:
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Physical Vapor Deposition (PVD):
Design and Machining Considerations
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Process Selection:
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Design Considerations:
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Material Selection:
Zamak 3 and 5 are suitable for the vast majority of general-purpose parts requiring good appearance and strength; ZA-8 is better for wear and bearing applications; for making rapid tooling, choose specialized alloys like Kirksite.
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