NATURALLY PRESSURISED FILLING SYSTEM DESIGN

摘要

The conventional unpressurised and pressurised filling system designs employed to fill molds under gravity perform poorly, creating generous quantities of entrainment defects (bubbles, bifilms and sand inclusions), and thereby efficiently degrading castings and their properties. The new concept of the naturally pressurised system is described, and its successes and limitations are examined. It seems that contact pouring may be the only good solution at the present time to the gravity pouring of heavy steel castings using a bottom-teemed ladle. It is clear that ultimately, foundries should be designed to avoid the pouring of melts at any point during the melting or casting process. Thus new melt handling technology is required for the designs of foundries, and only counter-gravity filling of molds is seen to be capable of routinely producing substantially defect-free castings.