MANGANESE BRONZE

In melting manganese bronze, it is essential to maintain careful control of the chemical composition, especially of the copper and zinc content. The practice of "flaring" or heating manganese bronze until the zinc dis­tills off, is of questionable "alue and may cause indeterminate zinc losses
which, in turn, will change mechanical properties of the alloy. Heat the metal only to the temperature
needed to pour sound castings.
Due to the dross-fanning tendencies of manganese bronze, gating should be such that there is a minimum of turbulence when the metal enters the mold. Top or bottom gating may be used, and strainer cores, choke gates and dross traps can be applied effectively to produce clean and sound castings. Gates and runners should be wide and thin so that the metal may skim itself before entering the mold cavity. The sprue should be filled quickly and kept full.
Manganese bronze has a high solidification shrinkage and large risers must be used so that all parts of the casting are adequately fed. Chills can be advantageously used to reduce the size and number of risers. Insulating sleeves and hot-topping compounds help in making risers feed more efficiently or in reducing riser size.