Quality assesment of casting filling method

The reliability of cast components is dependent on the quality of the casting process. This can be characterised by the robustness (repeatability) and specific fluid flow characteristics within the running system. During this transient filling phase the prevention of free surface turbulence and thus oxide entrainment is critical to the mechanical integrity of the component [1,2,3]. Past research has highlighted that return waves are major causes of free surface entrainment [4]. To reduce the entrainment occurring during the transitional filling of the runner a steady quiescent flow must be developed.

Using FLOW-3D(1), the Froude number was extracted to allow the quantitative assessment of air entrainment for four different designs of sump at the end of the runner. The results show that, for the designs used, the addition of a correctly designed sump can be advantageous. However, an incorrect design may reduce the Froude number but can greatly increase the persistence of the return wave and entrainment and is therefore extremely detrimental to the cast component. Additionally, the in-gate design is of utmost importance in controlling the back pressure and thus the persistence of the back wave between the in-gate and the downsprue exit. This has a direct effect of the level of oxide entrainment.