抄録
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. (1)The 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. (2)The final accumulated strain (εfa) and the critical strain for crack initiation (εca) could be estimated by the three parameters of tubular structures : thickness ratio of the ring-plate to the steel tube (tr⁄tp), stress concentration factor of fillet weld (kt) and carbon equivalent for zinc induced cracking (CEZ) . (3)The hypothesis that a crack might be initiated when εfa exceeds εca is validated by reviewing the results of the experiments conducted before under variuos conditions. (4)To prevent a crack initiation, tr⁄tp should be kept less than 2. 5 under the appropriate quality control of materials and welding procedures.
