Identifying Brass Alloys
There are many different brass alloys available, each with their own unique properties based on varying copper, zinc and sometimes additional alloying element percentages. Here are some of the most common brass alloys used for machined parts:
- C260 (60% Cu, 39.25% Zn) - The most widely used general purpose brass. Offers good cold workability and machining characteristics. Commonly called "cartridge brass".
- C352 (52% Cu, 36% Zn) - Has excellent hot workability. Often used for parts that require extensive hot forming or extrusion.
- C360 (60% Cu, 39.25% Zn, 0.75% Pb) - Known as "free machining brass" due to the lead content which improves machinability. Used for turned parts and precision components.
- C385 (85% Cu, 5% Sn, 5% Zn, 5% Pb) - An admiralty brass that contains tin and lead. Provides excellent corrosion resistance especially in marine environments.
- C46400 (64% Cu, 34% Zn, 1.5% Si, 0.03% P) - A brass with added silicon. Has superb dezincification corrosion resistance. Used for valve components and fittings.
- C93700 (97% Cu, 3% Si) - A silicon bronze alloy. It has very high strength and corrosion resistance. Used for springs and other highly stressed components.
When sourcing brass machined parts, make sure the supplier provides certification on the exact brass alloy composition. This will allow you to match the appropriate alloy to your functional requirements for machinability, strength, corrosion resistance, etc.
Inspecting Brass Parts Quality
Once you've sourced brass parts from a Chinese manufacturer, you'll want to thoroughly inspect the pieces upon receipt to ensure they meet specifications. Here are key quality checks to perform:
- Dimensional Accuracy - Verify that all specified dimensions, tolerances, surface finishes, and geometries have been achieved. This can be done with precision measuring tools like calipers, micrometers, and profilometers.
- Surface Defects - Look for any pits, porosity, scratches, die lines, or other flaws on the surface under bright light and magnification. Brass parts should have a uniform smooth surface free of defects.
- Deburring - Make sure all machined edges have been properly deburred and rounded. Sharp edges indicate poor workmanship.
- Leak Testing - If the parts are for fluid or gas systems, they should be leak tested to ensure proper sealing and fit.
- Metallurgical Testing - You can perform alloy verification with x-ray fluorescence testing and check material soundness with techniques like ultrasonic inspection.
- Functional Testing - Finally, test the components under actual working conditions. This gives full assurance the parts perform as required for the application.
Any defects found may require further investigation of the supplier's manufacturing processes and quality control procedures. High quality brass parts should conform fully to specifications without issue.
Tips for Sourcing Brass Parts from China
To consistently source high quality brass machined components from China, follow these tips:
- Find suppliers that specialize in brass manufacturing rather than generalized metal fabrication shops. They will have dedicated brass machining capabilities.
- Require ISO 9001 or other quality certifications to ensure rigorous quality control systems are in place.
- Clearly specify the brass alloy, dimensional tolerances, surface finish requirements, heat treatments, and all other critical parameters for the parts in detail.
- Request samples for inspection before full production orders.
- Perform site audits and inspection visits to witness manufacturing operations firsthand.
- Use inspection and quality clauses in your contracts to control product acceptance.
- Build relationships with suppliers and communicate closely throughout the project.
- Order early lead time samples to test and adjust manufacturing procedures before full ramp up.
With diligent sourcing practices and thorough inspection procedures, China can be an economical source for high quality machined brass components that fit your exact specifications. Taking efforts to verify alloy materials, dimensional precision, surface finishes, and performance characteristics will ensure you achieve parts compliance and satisfaction. Carefully qualifying and working closely with your Chinese brass machining partner will maximize results. CNC Milling