The quality control of brass casting is mainly guaranteed through two aspects, one is to strictly control the chemical composition of casting brass. Brass is a Cu Zn binary alloy with zinc as the main alloy element, which is generally called brass or ordinary brass. Ordinary brass has certain strength, hardness and good casting performance, but its wear resistance and corrosion resistance are poor, especially for flowing seawater, steam and inorganic acid.
In order to improve the mechanical, physical and chemical properties of copper castings, it is necessary to add a certain amount of alloy elements in the processing of sand casting, so as to form special brass suitable for different environments, such as navy brass, free cutting brass, high strength manganese brass and die casting brass. On the other hand, it is necessary to select suitable casting process. There are some differences in melting point, fluidity, solidification shrinkage, sensitivity of melt to gas, volatility and hot cracking tendency among cast brass alloys, so the suitable casting methods are also different.
At present, the casting methods of brass castings mainly include: die casting, sand casting, centrifugal casting, continuous casting and investment casting. Different alloys need to be selected according to different requirements. Zinc in cast brass is the main factor affecting the casting properties of cast brass. The vaporization point of zinc is about 907 ℃, and the melting point of cast brass is about 900 ℃. During melting and pouring, zinc has a great tendency of evaporation and oxidation.
The advantage of brass investment casting is that it has good fluidity. However, the shrinkage of manganese brass is large, and it is easy to have shrinkage cavity, cold crack and deformation. In view of this situation, appropriate technological measures should be taken in the casting process
- 1. In order to reduce the casting stress of brass casting, the sand core with good yielding property should be selected during casting, which is beneficial to prevent crack and deformation.
- 2. Set up riser to strengthen feeding.
- 3. In the process of casting, good structure design of gating system should be adopted to achieve good solidification effect and smooth filling of liquid flow. The layout of runner should make copper casting evenly cooled.