Sand mold, metal mold and graphite mold can be used for low pressure die casting. The filling process is different from gravity casting such as metal mold casting and sand mold casting, and also different from pressure casting with high-pressure and high-speed filling. It has the following advantages:
1) Pure metal liquid filling improves the purity of castings. Because the slag generally floats on the surface of the liquid metal, and the mold filling is realized by the liquid metal at the lower part of the crucible through the riser in low-pressure casting, which completely avoids the possibility of the slag entering the mold cavity.
2) The metal liquid filling is stable, which reduces or avoids the tumbling, impact and splash of metal liquid during filling, so as to reduce the formation of oxidation slag.
3) The casting has good formability. The filling of liquid metal under pressure can improve the fluidity of liquid metal, which is conducive to the formation of castings with clear outline and smooth surface, and is more favorable for the forming of large thin-wall castings.
4) When the casting crystallizes and solidifies under pressure, it can get sufficient feeding and compact structure.
5) The recovery rate of liquid metal is improved. Generally, a riser is not required, and the non condensed metal in the riser can be refluxed to the crucible for reuse, which greatly improves the recovery rate of liquid metal, and the recovery rate can generally reach 90%
6) Convenient production and operation, good working conditions, high production efficiency, easy to realize mechanization and automation