INVESTIGATION OF PARAMETERS AFFECTING THE STRENGTH AND HARDNESS OF , CASTING PRODUCED BY CENTRIFUGAL CASTING PROCESS

Abstract

Investigations were carried out to study the effect of pouring rate, pouring temperature and mould revolution speed on the surface hardness and tensile strength of the centrifugally cast aluminium castings. For this purpose an old centrifugal casting machine was renovated and used. Commercially pure aluminium cylinders were cast by pouring molten metal into the dried and rotating mould with specific pre—selected process variables as stated above. The investigation was planned with 3 factorial experimental design with three levels for each factor. From castings, so produced test specimens for tQnsile strength and surface hardnesses were produced. For tensile strength, the Hounsefield Tensometer and for hardness, Brinell hardness tester were used. Models to predict the strength and hardness separately were made in the form of regression equations relating various parameters with the strength and hardness. It was established that surface hardness of the castings is totally independent of the pouring rate, pouring temperature and mould revolution speed and their interactions. The model predicting the tensile strength revealed that the parameters and their interactions do have a significant effect on the strength of the casting produced. It was also concluded that for manufacturing of cylinders of high strength the optimum mould revolutions should be kept within a range of 1060 rpm to 1250 rpm. The most suitable ranges for pouring rates and pouring temperatures were found to be within 200-250 gm/sec, and 750-975°C respectively.