Analysis of Blow Holes in Castings

Nitin R Bhone

M-Tech Dissertation 2004

Abstract

It is very difficult to get defect free casting. Blowholes are one of the major casting defects caused due to evolution of gases during casting process. It is necessary to study and analyze the origin of the gases, how they are generated, the causes and how they can be minimized. This project aims to develop systematic approach based on available knowledge and experience of experts in this area. Also fluid mechanics techniques can be used for blowhole prediction. Therefore, this stage aims at studying blowholes, their principle of formation, causes and remedies, preparing a knowledge base and applying basic physical concepts for preparation of some mathematical model for mold filling and solidification phenomenon. The report covers blowhole formation due to gas generation during casting, origin of these gases and nature of blowhole due to these gases. It also throws some light on reducing amount of gas by venting and vacuum techniques and accordingly how to prevent blowhole formation. It shows different mathematical equations derived for mold filling phenomenon considering back pressure of gases and for solidification of metal affecting blowhole formation. Further it gives algorithm and flowchart for solving these equations using computer.