In the process of machining copper, the crystallization characteristics of copper alloys with different compositions are different, the casting performance is different, and the casting process characteristics are also different.

1. Tin bronze: The crystallization characteristic is that the crystallization temperature range is wide and the solidification area is wide. Poor fluidity in casting performance, easy to produce shrinkage, not easy to oxidize. The process is characterized by directional solidification (sequential solidification) of thick-walled parts, and simultaneous solidification of complex thin-walled parts and general thick-walled parts.

2. Aluminum bronze and aluminum brass: The crystallization characteristic is that the crystallization temperature range is small, which is the characteristic of layer-by-layer solidification. In terms of casting performance, it has good fluidity, easily forms concentrated shrinkage cavities, and is easily oxidized. The characteristic of the process is that the aluminum bronze casting system is a bottom injection type, and the aluminum brass casting system is an open type.

3. Silicon brass: The crystalline feature is between tin bronze and aluminum bronze. Casting performance is the best (in special brass). The characteristic of the process is the sequential solidification process, the middle injection type pouring system, and the size of the dark riser is small.

Brass is a copper alloy with zinc as the main added element. It has a beautiful yellow color and is collectively called brass. The copper-zinc binary alloy is called ordinary brass or simple brass. Brass with more than three yuan is called special brass or complex brass. Brass alloys containing less than 36% zinc are composed of solid solutions and have good cold workability. For example, brass containing 30% zinc is commonly used to make bullet casings, commonly known as bullet casing brass or seven-three brass. Brass alloys with a zinc content of 36 to 42% are composed of solid solutions, of which the most commonly used is zinc alloy with 40% zinc. In order to improve the performance of ordinary brass, other elements are often added, such as aluminum, nickel, manganese, tin, silicon, lead, etc. Aluminum can improve the strength, hardness and corrosion resistance of brass, but it reduces the plasticity. It is suitable for the condenser of sea wheel and other corrosion-resistant parts. Tin can improve the strength of brass and the corrosion resistance of seawater, so it is called navy brass, which is used as ship thermal engineering equipment and propeller. Lead can improve the cutting performance of brass; this free-cutting brass is often used as a watch part. Brass castings are commonly used to make valves and pipe fittings. Explosion-proof crescent wrenches commonly used in ships are made of brass and aluminum.