Avoiding Gas defects Through Mold and Core Package Design

摘要

Voids associated with gas from cores, molds. binders and additives can be difficult to detect and often are not found until the castings are cleaned, machined and inspected. Computer programs have been developed to minimize turbulence by predicting metal flow, but bubbles, folds, oxides and voids produced by mold and core gases during pouring can affect porosity as well. Metalcasters historically have used their experience to design mold and core packages in a "pour and pray" method because little data existed to help select a binder, coating or core vent geometry to predict or eliminate gas porosity. The central issues associated with mold/core gas evolution and defect formation are: 1. What is the volume of gas produced when molten metal hits a mold or core surface prepared with a particular binder?