Heat Transfer in Welding - A Numerical Approach

The effectiveness and profitability of welding operation depends upon the efficiency of each individual phases of the process namely, joint configuration, welding parameters, quality of weldments and subsequent repair of defective welds. Out of the four phases, welding process parameters and quality control are the foremost areas where evaluation of data is carried out extensively. These data in turn are used for the selection of the most suitable process of welding along with its parameters, for a particular use. The thermal based problems, e.g. transient heat transfer in weld and base metal, transient thermal stress and strains, transient metal movement during distortion, residual stresses and distortion after welding, etc. may easily be solved by numerical techniques employing computer facilities. This paper first describes the different numerical techniques generally employed in solving these welding problems along with their suitability and applicability. Later, it elaborates a generalised approach of numerical technique for predicting temperature histories in a weld cross section and associated cooling rates. The validity of the model was ascertained through experiments carried out on indigeneously produced HSLA steel plates employing submerged arc and carbon-dioxide welding process. A comperative study with Rosenthal equation confirms a better match of the numerical technique with the experimental values. The cooling rate information thus obtained may then be used to assess the related microstructure and mechanical property changes for a particular steel.