When higher mechanical properties are required in the cast piece, such as higher elongation or strength, gravity die casting, and to a limited extent pressure die casting, are used. In gravity die casting, there is the possibility of using sand cores. Large differences in wall thicknesses can be favourably influenced with the help of risers. Cylinder heads for water-cooled engines represent a typical application.
In the low-pressure gravity die process with its upward and controllable cavity filling, the formation of air pockets is reduced to a minimum and, consequently, high casting quality can be achieved. In addition to uphill filling, the overpressure of approx. 0.5 bar has a positive effect on balancing out defects caused by shrinkage. The low-pressure die casting process is particularly advantageous in the casting of rotationally symmetrical parts, e.g. in the manufacture of passenger vehicle wheels.