Brass die casting is a type of copper alloy die casting that has very good corrosion resistance and mechanical properties. However, owing to the need of high metal temperatures and short life of the die casting mold, this type of die casting is not widely used.
Of all the alloys used in brass die casting, the yellow brass die casting alloys are very commonly used by Mexican die casters. The main advantages of brass die casting when compared to the other types of die casting are good surface finish, increased production rates, and precise dimensional control.
Induction brass melting is the preferred method of brass die casting, as melt loss via dross formation is low in this type of casting and offers faster melting and better control of temperature and brass composition. In addition, this method also facilitates less absorption of gas by the metal.
In brass die casting, the speed with which the metal melt is also important to decrease the vaporization of the volatile elements, especially zinc. Fluxes are usually not necessary to die cast brass alloys, however, as dirt is an unavoidable element, Mexican die casters use a little amount of flux to ensure cleanliness of the metal. A typical flux used in brass die casting will consist of one pound of silica and three pounds of anhydrous borax per hundred pounds of brass.
Melting for the brass die casting can be done under reducing or oxidizing conditions (induction melting make use of oxidizing conditions) and irrespective of the conditions, it is important to keep gas absorption at minimum, as the absorbed gas needs to be removed before pouring the metal into the mold.
Usually, brass melting is done in a neutral atmosphere and a protective covering is provided to prevent the absorption of hydrogen and oxygen. Charcoal is commonly used to offer this protective covering and an inert gas like nitrogen is used to remove the already dissolved hydrogen from the molten metal.
Cold chamber die casting molds and machines that are used to die cast aluminum and other alloys are suitable to die cast brass alloys and the ram pressures can range from 1000 to 10,000 psi. The speed of the die cast plunger can vary from 2 to 250 psi and the regulations of pressure, speed, venting, gating, and temperatures are the same as other alloys.