Heat generation patterns and temperature profiles in electroslag welding
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THE electroslag welding process is a potentially attractive operation for the welding of thick plates, needed in the construction of ships, storage tanks, pressure vessels, bridges, buildings and other structures. Most of the earlier work has been carried out in the U.S.S.R., which is well documented; Zin addition useful work has been done also by the British Welding Institute 2 and by the U.S. Steel Corporation) However, in all this previous work emphasis has been placed on the physical characterization of the weld, for a variety of operating conditions and rather less attention has been paid to the representation of the more fundamental aspects of the heat and fluid flow phenomena that are associated with electroslag welding. There appears to be agreement in the welding literature that the size of the heat affected zone, the sequence of solidification and the slag metal reactions play a key role in determining the weld properties. It is also appreciated that the size, shape and nature of the weld pool is a key factor in the production of sound welds. The work to be described in the present paper is part of a program of research which is addressed to the development of an improved fundamental, quantitative understanding of the physical factors that govern the electroslag welding process. From a physical standpoint the electroslag welding process involves heat transfer accompanying phase change, which is markedly influenced by the fluid flow phenomena in the weld pool, driven by both thermal
T. DEBROY, formerly with the Department of Materials Science and Engineering, Massachusetts Institute of Technology, is now Assistant Professor of Metallurgy, Penn. State University, University Park, PA 16802. T. W. EAGAR and J. SZEKELY are Associate Professor and Professor, respectively, Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139. Manuscript submitted October 15, 1979.
natural convetion and by an glectromagnetic force field in a system which is truly three dimensional. The development of a fully comprehensive representation of this system would be a very difficult task so that the approach adopted is to highlight certain key aspects of the problem. In a previous paper, we examined the role of the electromagnetic and the buoyancy fields in determining the velocity and the temperature profiles in the weld pools, for idealized, mathematically twodimensional (axisymmetrical or plate-like) systems? It was found that the buoyancy and the electromagnetic forces produce vigorous agitation in the molten weld pool and that the nature of this agitation is quite markedly affected by the geometry. When the current field is nonparallel, as is the case with wire electrodes, the electromagnetic force field plays a major role, while for parallel fields, as produced by flat plates, the flow field is driven essentially by buoyancy forces. While this previous work established the existence of vigorous agitation in the weld pool and indicated the important role played by the system
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