DEVELOPMENT OF A SET UP FOR PRODUCING IN-SITU WELDED JOINT m ALUMINO-THERMIC WELDING PROCESS

Abstract

This dissertation work presents literature survey of past and current applications of "Thermit Welding Process" for making welded joints of different metals in different configurations. Earliest known use of this process is joining of rails. The study of literature on alumino-thermic process, survey of industrial resources and the futuristic technological requirements have led to the great potential of this process in making electrical connections for power transmission, distribution and its other applications such as, earthing circuits, lightning protection, cathodic protection etc. The main thrust of this work is to discuss existing methods and the experimental work of making electrical connections, using alumino- thermic welding process to obtain reliable, strong, sound and corrosion free quality joints. The experimental work encompassed preparation of semi-permanent graphite mould made from commercially available graphite blocks. These graphite blocks were designed and made as "Crucible-cum-Mould" cavity so that the crucible portion- containing -powdered metal_ mix when initiated for burning, allows the molten metal to flow in to the cavity through the tap hole to produce a welded joint having desired configuration, size and properties. The quality of various joints of cables and rods of similar metals, made in this investigation were subjected to tests for strength, electrical properties, microstructure etc, to ensure suitability and acceptance of this process for making electrical connections. The tests and analysis of welded joints revealed that the joints were sometimes sound and sometimes partially sound. The tensile strength of various joints was found to be slightly less than that of the parent metal conductors. The electrical resistance in the case of copper conductors was found to be increased at the joint where as in the aluminium conductors, it decreased. The unsoundness was due to the porosity and slag entrapment which consequently affected the strength as well as electrical resistance. The process of making cast weld has been established. However, the quality of joints has to be improved by further investigations.