Abstract
Hot dip galvanising is an effective method for protecting steel fabrications against corrosion. However, large temperature gradients generated in fabrications, coupled with the release of internal residual stresses, can cause severe distortion during galvanising. This paper describes an investigation into the nature of distortion in beams and procedures for minimising this distortion during hot dip galvanising. Mathematical models are developed to simulate the temperature changes during the dipping and cooling processes and to analyse the distortion resulting from the associated thermal stresses. Convective heat transfer coefficients for both dipping and quenching cycles are calculated from experimental data. A two-dimensional analysis of the heat flow through a beam cross-section is implemented using a finite difference model. The resulting temperature profiles determine the thermal stresses used in a beam deflection analysis which predicts elastic and plastic distortions of the beam. Predictions are compared with measured distortions.
MST/1641
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