Much planning goes into a pour; what temperature should the metal be for each mold, how much to fill it, what order to pour, will the pour cup need to be to be kept hot … The molds represent a tremendous investment of time and effort. There is terrific hydraulic pressure as the molten metal rushes into the mold cavity. It has to hold or the casting could be lost.
Ceramic shell molds are poured hot, anywhere from 800 to 1500 degrees to insure that they fill and catch all the detail in the mold’s surface. Stainless steel wire,” S” hooks and steel “U” clips help them withstand the hydraulic pressure of the inrushing metal and resist runouts. Sand molds are usually rammed up in moist sand in a bottomless casting pit. If there is a runout, the hard-packed damp sand will usually stop it.
Metal temperature is closely monitored with immersion pyrometers to be sure it is right for thin section castings but not too hot for the thick pieces. Aluminum is poured anywhere from 1125 to 1300 degrees, silicon bronze 2100 to 2300 degrees, silicon brass 2000 to 2100, and iron 2400 to 2800 degrees.
Max-Cast mainly uses induction furnaces to melt iron and bronze. They are quieter, cooler and more efficient than our gas-air furnaces, but we still use the combustion furnaces occasionally for aluminum and for one shot bronze castings from 150 to 500 pounds.