Simple Solutions That Work! Issue 17

25 BACK TO BASICS Continued on next page A utomated hydraulic, electronic and electric operations of all phases of the casting process, including casting removal and ladling, have dramatically increased production. The process aluminum casting alloys are the most versatile of all common foundry alloys and generally have the highest castability ratings. Aluminum is adaptable to many of the commonly used casting methods and can be readily cast in metal molds mounted on CMH casting machines for high volume, cost- effective castings. In general, aluminum alloys have the following characteristics: • Good fluidity – important for filling thin sections • Low melting point – lower melting and casting temperatures relative to those required for many other materials • Lower density – the lighter weight of aluminum allows for easier handling in the foundry, compared to ferrous alloys • Fast heat exchange – heat transfer from the molten Tilt Pour Permanent Mold Casting Guide aluminum to the mold is relatively fast, providing faster castings cycles in metal molds • Good chemical reproduction – chemical stability is relatively good • Good as-cast surface finish – surfaces are lustrous and have few blemishes The tilt pour process using involves the production of castings by pouring liquid aluminum into permanent molds and tilting the mold, allowing a controlled flow of liquid aluminum to fill the mold cavity by gravity. The process involves the following steps: • A refractory mold wash is sprayed onto the surfaces of a preheated mold that will be in direct contact with the molten metal alloy. • Cores, if applicable, are inserted, and the mold is closed by the ram cylinder. • The alloy, heated above its melting temperature, is poured into a pouring cup. • The tilting device tilts down allowing the liquid alloy to fill the mold cavity at a controlled rate. • After the alloy has been allowed to solidify, metal cores and other loose mold members are withdrawn, the mold is opened, and the casting is ejected (usually with the casting machine in the tilted-up position). • Steps two and four are repeated until repair of the mold coating is required, at which time step one is repeated. • Usual foundry practices are followed for trimming gates and risers. When permanent mold casting is combined with nonmetallic cores, such as sand cores, the process is referred to as semi-permanent mold. Applications for Permanent Mold Castings Aluminum castings are widely used throughout industry. As the United States government mandates more fuel-efficient cars, the demand for permanent mold castings has steadily increased. Suspension links, intake manifolds, pistons, and other functional parts of internal-combustion engines are typical applications. Other applications include aviation engines, missiles, motor housings, portable tools, nozzles, fan cases, outdoor lighting standards, gear cases, lawn mower chassis, barbeque grills, and kitchen pots and pans. JOHN HALL President CMH Manufacturing Company ARTICLE TAKEAWAYS: • Tilt Pour Permanent Mold - advantages & disadvantages • Understanding aluminum characteristics • Typical casting applications