Technical Characteristics and Engineering Applications of Brass Parts

1. Correlation Between Alloy Composition and Performance

 

• High-copper alloys (≥70%, e.g., red brass): With an elongation of ≥45% and hardness ≤80HB, they are suitable for precision thin-walled parts requiring cold stamping (e.g., electrical connectors).
• High-zinc alloys (≤35%, e.g., yellow brass): Featuring a tensile strength of ≥400MPa and hardness ≥110HB, they are adapted for structural parts bearing moderate loads (e.g., pipe supports).

 

 

• Lead (Pb, 0.8%-3.5%): Reduces cutting resistance, enabling parts to reach IT6 grade machining accuracy, suitable for complex structural parts processed by CNC milling.
• Tin (Sn, 0.5%-2%): Improves seawater corrosion resistance (salt spray test ≥500h), forming naval brass for marine pipeline parts.
• Arsenic (As, 0.02%-0.05%): Inhibits dezincification corrosion, extending the service life of hot water pipeline parts.

2. Core Processing Technologies and Technical Requirements

 

1. CNC Precision Machining: Using cemented carbide tools (e.g., WC-Co tools) at a spindle speed of 8,000-12,000r/min, achieving a hole diameter tolerance of ±0.01mm. It is suitable for high-precision parts such as sensor housings and valve cores.
2. Sand Casting: Applied to complex parts with a wall thickness of ≥5mm (e.g., valve bodies). The density of castings (porosity ≤2%) must be controlled to avoid pressure leakage.
3. Cold Extrusion Molding: Leveraging the high plasticity of brass (section shrinkage rate ≥60%) to achieve non-cutting processing, increasing part strength by 15%-20% compared to cast parts. It is commonly used for mass-produced bolts and nuts.

3. Typical Engineering Application Scenarios

1. Fluid Control Field: Brass parts must meet pressure resistance (≥1.6MPa) and sealing requirements. For example, pipe joints adopt a conical sealing structure with nitrile rubber O-rings, ensuring a leakage rate of ≤0.01mL/min.
2. Electrical Field: With an electrical conductivity of ≥28MS/m, brass parts require nickel plating (plating thickness 5-10μm) to reduce contact resistance (≤5mΩ), suitable for terminals and switch contacts.
3. Musical Instrument Field: Brass must have stable acoustic impedance (approximately 38×10^6 kg/(m²·s) at 20℃), and the surface roughness of parts should be Ra ≤0.8μm to avoid airflow disturbance affecting tone.

4. Quality Judgment and Selection Criteria

1. Quality Inspection Indicators:
   • Composition: Using a spectral analyzer to ensure the deviation of alloy elements is ≤±0.2%.
   • Dimensional Accuracy: Verifying key dimension tolerances against the GB/T 15746 standard (China National Standard) via a coordinate measuring machine.
   • Corrosion Resistance: After the Neutral Salt Spray (NSS) test, the corrosion area should be ≤5%.
2. Selection Principles:
   • Choose alloys based on working conditions: Lead brass for hot water environments, tin brass for marine environments.
   • Select processes based on precision: CNC grinding for IT5 grade precision parts, cold extrusion for mass-produced parts.
   • Opt for surface treatments based on the environment: Cadmium plating (superior corrosion resistance to nickel plating) for humid environments, natural oxidation for high-temperature environments.