Prediction and Prevention of Liquid Zinc Induced Cracking in Tubular Structures of 590 MPa Steel Based on Elastic-Plastic-Thermal Stress Analysis

摘要

This paper describes a prediction method for liquid zinc induced cracking at the toe of fillet weld between thin tube of 590MPa steel and thick ring-plate during hot-dip galvanizing. Design conditions to prevent cracking in such structures are also suggested. To investigate the cracking mechanism in the above structures, elastic-plastic -thermal stress analyses (FEM) were performed at three processes of galvanizing : dipping into molten zinc, air-cooling and water-cooling. The results are summarized as follows. ①The strain under tensile stressing is accumulated at the toe of fillet weld, by the deformation of the tube due to the temperature difference between the tube and ring-plate during galvanizing. ②The final accumulated strain (epsilon _(fa)) and the critical strain for crack initiation (epsilon (ca)) could be estimated by the three parameters of tubular structures : thickness ratio of the ring-plate to the steel tube (t_r/t_p), stress concentration factor of fillet weld (Kt) and carbon equivalent for zinc induced cracking (CEZ). ③