Copper alloys with different compositions have different crystallization characteristics, different casting properties and different casting process characteristics.
1, tin bronze: crystallization is characterized by a wide crystallization temperature range and a wide solidification region. The fluidity of casting performance is poor, shrinkage porosity is easy to occur and oxidation is not easy. 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 is characterized by a small crystallization temperature range, which shows layer-by-layer solidification. Casting performance is good, easy to form concentrated shrinkage cavity and easy to be oxidized. It is characterized in that the aluminum bronze pouring system is bottom pouring type, and the aluminum brass pouring system is open.
3. Silicon brass: The crystallization characteristics are between tin bronze and aluminum bronze. The casting performance is the best (among special brass). The process is characterized by sequential solidification process, intermediate gating system and small size concealed riser.
Brass is a kind of copper alloy with zinc as the main additive element, which has a beautiful yellow color and is collectively called brass. Copper-zinc binary alloy is called ordinary brass or simple brass. Brass containing more than three elements is called special brass or complex brass. Brass alloy with zinc content less than 36% is composed of solid solution and has good cold working performance. For example, brass containing 30% zinc is often used to make shell casings, commonly known as shell brass or 73 brass. Brass alloy containing 36 ~ 42% zinc is composed of solid solution, of which 64 brass containing 40% zinc is the most commonly used. In order to improve the properties of ordinary brass, other elements are often added, such as aluminum, nickel, manganese, tin, silicon, lead and so on. Aluminum can improve the strength, hardness and corrosion resistance of brass, but reduce the plasticity, which is suitable for corrosion-resistant parts such as condenser pipes of seagoing ships. Tin can improve the strength of brass and its corrosion resistance to seawater, so it is called navy brass and used as marine thermal equipment and propeller. Lead can improve the machinability of brass; This kind of free-cutting brass is often used as clock parts. Brass castings are usually used to make valves and pipe fittings. The explosion-proof crescent wrenches for fire hydrants commonly used on ships are made of brass and aluminum.