Brass is suitable for casting, and its casting properties surpass those of bronze and copper.
Currently, brass castings are widely used across various industries.
Casting Performance Advantages
Brass (Cu-Zn alloy) significantly improves fluidity due to the addition of zinc, resulting in moderate shrinkage and low segregation tendency, making it suitable for the manufacture of complex castings. Compared to bronze, brass maintains high strength while being more cost-effective. It is widely used in wear-resistant parts such as bearings, bushings, and gears, as well as corrosion-resistant components such as valves.
Applications
Brass castings are commonly found in machinery manufacturing, shipbuilding, aviation, and automotive industries, demonstrating excellent formability and wear resistance, particularly in the production of complex shapes.
How to Reduce the Shrinkage of Brass Castings?
Brass castings shrink during the casting process, caused by the volume change of the liquid metal as it cools and solidifies. Excessive shrinkage can lead to dimensional deviations, internal stress concentrations, and even cracks in the casting. The following is a systematic approach to reducing the shrinkage of brass castings:
1. Optimizing the Material Ratio
Zinc Content Control: The zinc content in brass directly affects shrinkage. Generally, shrinkage is relatively low when the zinc content is within the 20-40% range. H62 brass (62% copper, 38% zinc) has a shrinkage of approximately 1.5-1.8%, while H80 brass (80% copper, 20% zinc) has a shrinkage of approximately 1.2-1.5%.
Trace Element Additions:
Adding 0.5-1% aluminum can increase the melting point by 20-30°C while reducing shrinkage.
Adding 0.3-0.5% phosphorus copper alloy effectively deoxidizes and reduces oxide inclusions.
Adding 1-3% lead improves machinability with minimal impact on shrinkage.
Impurity Control: Iron impurities exceeding 0.15% can lower the melting point by 15-20% and increase shrinkage. Every 0.01% increase in oxygen content lowers the melting point by approximately 8°C.
2. Process Parameter Optimization
Smelting Process:
The melting temperature is controlled between 900-940°C (adjusted depending on the specific alloy grade) to prevent excessive zinc volatilization. Inert gas (nitrogen, argon) is used to blanket the melt to reduce oxidation and hydrogen absorption. Refining agents or rotary degassing equipment are used to remove H₂ and O₂ from the melt.
Pouring Process:
The pouring temperature is controlled between 950-1050°C. A multi-gating design is used to ensure uniform mold filling of the molten metal. Riser and chiller placement are optimized to compensate for volume loss caused by shrinkage.
Cooling Control:
The cooling water flow rate is adjusted to avoid excessive cooling that can lead to gas entrapment. Water-cooled molds or electromagnetic stirring are used to accelerate solidification and reduce porosity.
Through these comprehensive controls, the shrinkage of brass castings can be effectively controlled within the ideal range of 1.2-1.8%, resulting in dimensionally precise castings with excellent internal quality. In actual production, the most appropriate process combination should be selected based on the specific alloy grade and casting structure. If you have large-scale brass casting needs, you can choose to cooperate with Mulan Metal. Mulan Metal has 12 years of casting production experience and has helped customers in more than 30 countries complete their casting production business support and received unanimous recognition. We look forward to your cooperation consultation.
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