Spot plunged arc welding using covered electrode

Abstract

The present paper reports on spot plunged arc welding with a covered electrode, for which it is possible to obtain a penetration depth of 25 mm (or greater) in a single spot. Covered electrodes are used in the process. The electrode coverings contain ‘active’ elements to increase the molten pool movement and the arc constriction. The two effects combine to give a penetration that is deeper than that obtained in the usual manual arc welding process with a covered electrode. The majority of the present paper is focused on a description of the spot plunged arc welding process with a covered electrode. A diagram shows movement of the cold and hot electrode ends during welding. The welding process is described in seven phases in terms of the covered electrode movement. A table gives an approximate chemical composition of the coating of the covered electrode. Several macrographs of spot welds in lap joints made on plates of different thicknesses are shown. Chemical compositions of the weld metal and the parent metal are given. As an indicator of the economy of spot plunged arc welding, a melting rate is indicated. Several figures show the shape and volume of the melted parent metal and filler material.