EFFECT OF PROCESS VARIABLES ON THE QUALITY OF LM6 ALLOY CASTINGS PRODUCED BY FULL MOULD PROCESS

Abstract

Full Mould Process is the latest sand moulding process. it utiliBes physical bonding only in dry and free flowing sand without any conventional binders. The sand mass in moulding box is first vibrated and then a pattern made of polystyrene or any other gasifiable material is placed on the sand after been attached by gates and sprues. Then the sand is poured around the pattern such that the top of the sprue just protrudes through the molding box. The sand is poured around the pattern and vibrated to attain compaction. The pattern may be coated by suitable pattern coating to obtain good surface finish. Vacuume may be applied to the moulding box. A porous plate is placed on top of the moulding box. A pouring cup should be placed on top of thus sprue and molten mete.1 poured into it. The objective of the present investigation was to study the effects of parameters on the. characteristics like bulk density, percent volume porosity, dimensional accuracy, surface finish, tensile strength, impact strength and Brinell hardness of casting. The alloy chosen for making casting was aluminium silicon (LM6). A statistical second order central composite orthogonal experimental design was used to plan out the experiment for all studies done in the present investigation. Various measurements were made on mould or casting for a specific characteristic of mould or casting. Based on these observations the regression models were formulated and tested for adequacy. The relationships of various parameters for a given characteristics were computed with the help of this model through which the behaviour of the Full Mould Process analyzed. The following studies were conducted: 1. A three-factors at five-levels experiment were conduce ed to study the behaviour of bulk density, percent mean deviation of casting from pattern dimension, tensile strength, impact strength and Brinell hardness of casting and percent volume porosity. Three parameters for this study were (1) Sand grain fineness, (2) Vibrating time, (3) Vacuum. 2. Microstructure analysis was done to study the constituents of alloy and their effect on characteristics. 3. X-Ray Radiography test was conducted for soundness of casting. rt C