5. Optimizing manufacturing costs

5.1 Casting spheroidal graphite cast irons

Spheroidal graphite cast iron is generally cast in a sand mold (except for pipe centrifuging, which uses a cylindrical metal mold). Casting in a sand mold enables complex shapes to be obtained, which in turn enables operating stresses to be distributed more evenly. These complex shapes enable several functions to be combined in a single part.

To obtain a sound part, there are only two constraints: the rigidity and surface hardness of the mold cavity during solidification of the cast iron. The eutectic of austenite and spheroidal graphite solidifies over a wide temperature range. The formation of graphite is accompanied by an increase in volume, which is not counteracted by the still-pasty solidifying layer. This layer...