固相移動がない場合のひけ巣発生の数値解析法

抄録

  A numerical technique is presented, which can simulate the formation of shrinkage cavity in castings of complicated shapes. In this technique, the mold cavity and mold are divided into small finite elements and the heat- and mass-conservation laws and the D' Arcy's law in each element are expressed in the form of finite difference equations by the inner nodal point method. The shrinkage flow is considered by solving alternately the heat- and flow fields. It is assumed that the shrinkage cavity forms in a free surface element, elements where the pressure is under a critical pressure and/or of which pressure head is minimum. The porosity is calculated by giving a boundary pressure to the elements where the shrinkage cavity forms. As numerical examples, riser- and end-effects and shrinkage cavity in risers in steel plate castings were analysed. The results were fairly well supported by experimental ones. The position, where the metal solidifies at last, varied with the shrinkage flow. Although the improvement of the analysis requires accurate permeability and other data and the development of a model considering the solid phase movement and heat transfer during pouring, the proposed technique may be useful for the prediction of the position and quantity of shrinkage cavities in castings.