45 - Graphite Shape Degradation at the Surface of Chemically Bonded Sand Molds and Cores

Abstract:

Standard specifications of ductile irons are all based on machined test bars either cast separately or from test bars attached to castings. Even when many customers are specifying properties in the castings, the properties are determined on machined test bars from sections cut from castings. Customers also routinely test the castings themselves (ES testing) to prove out the design. In these testing of full castings or part of castings, cast surfaces as well as machined surfaces are subjected to simulated stresses. Surface conditions are very important especially under fatigue loading conditions. When casting buyers change suppliers, it is not uncommon to encounter failures due to different surface conditions as a result of variations in shot blasting, matrix and or graphite morphology.