Aluminum casting is a process in which molten aluminum is poured into a mold and allowed to solidify. The primary advantage of casting aluminum over other methods such as cutting the part from solid material is that after the mold has been made, a part of any complexity may be made with equal ease.
Aluminum sand casting is a common method of casting in which a pattern stamps the template into a sand mold. It works well with metals such as aluminum that have low melting points.
Aluminum die casting is especially useful for making many parts with a large amount of detail, making die casting a popular method of metal manufacturing. The interior of a machined mold known as a die is lubricated and closed. The molten aluminum is forced into the die under high pressure and aluminum is allowed to solidify while the pressure is maintained. The die is then opened and the casting is ejected.
Three points you should contemplate when considering the use of aluminum die casting are:
- Identifying the correct alloy to use in your project;
- Whether or not to use pore-free die casting;
- If your timetable will allow for the use of cold-chamber machines.
Determine the specific diecast aluminum alloy that you needThe Aluminum Association has established the nomenclature for diecast aluminum alloys in the United States. Each alloy series consists of a three-digit number followed by a decimal point. The first digit provides the alloying metal, the second digit gives the percentage of aluminum and the third digit identifies the specific alloy. The number after the decimal point is 0 for casting and 1 for ingots.
Use the pore-free alloy die casting processThis method of die casting injects pure oxygen into the die before each shot of aluminum. These castings are stronger and can still be welded.
Use cold-chamber machines for aluminum alloy die casting.The primary disadvantage of this method is the requirement to transfer the molten aluminum to the cold-chamber machine results in a slower cycle time.
- The startup cost for aluminum die casting is high. The dies must be made from hardened tool steel because cast iron can't handle the pressures involved.
- The high temperature of the molten aluminum contributes significantly to the maintenance cost of die casting. The die itself is subject to wear and erosion and other sources of failure include thermal fatigue and heat checking.