For group 3 alloys, the fusion must be done quickly and in a slightly oxidizing atmosphere. This is due the large solidification interval, rapid cooling or creating a high thermal gradient.
The process is more effective methods than using the single feeder at sprue so they are used in coupling working at a lower casting temperature capable to allow a filling of the homogeneous mold. In this case, before starting the casting, the scorching process is carried out by adding phosphorus flux (generally Cu 85% -P15% alloy). The metals are dosed carefully in order to remove the oxygen while leaving a minimum quantity necessary to increase the fluidity of the metal during the process.
To avoid internal porosity or, in the case of mechanical processing, surface dispersion phenomena, the residual phosphorus content in the final alloy must be between 0.01% and 0.02%. If a Metal Machining Company works with Cu-Zn alloys, when checking the temperature before casting, in addition to the copper-phosphorus alloy, it is also necessary to add pure zinc necessary to replace the one that evaporates during melting.
The same applies to the temperature maintenance (in a well-functioning foundry, each mold should provide controlled casting temperature control by immersion pyrometer). An additional parameter to keep in mind is the temperature of the mold in which to cast the alloy.
The ovens used by Metal Machining Company for the casting of copper alloys come in four variants. Electric arc furnace: in use since the beginning of the twentieth century, has had rapid development and spread; it is currently used to keep the melt at a temperature and as a container for molds. The energy required for fusion is provided by an electric arc that is established between graphite electrodes inside the oven itself.
Induction furnace: it is the most widespread type of oven in the world thanks to the easy control of the melting temperature and the fact that it is not very polluting. There are two basic types: the coreless (without core, suitable for casting) and the channel (channel, used for overheating and temperature maintenance).
Crucible furnace: it is used for the casting of very small objects that require scarce quantities of metal and for discontinuous casting processes. If a cylindrical furnace fed by fossil coal, the heat developed can be increased thanks to fuel gas flows. The metal is poured from above and during the descent melts, hit by the heat flow coming from below, then collects on the bottom of the cylinder. The use of this oven has now fallen into disuse, but it was the most used until the end of the nineteenth century.
