Abstract: Experiments of uniaxial tension and ratcheting of material of coke tower 15CrMoR are carried out under 20 ℃, 200 ℃, 300 ℃, and 400 ℃. The ratcheting strain of the material is predicted by OW-II model, which could predict the stable ratcheting strain rate of the material well. The transient temperature field under oil-feeding and water quenching are numerically simulated with the help of dynamic coordinate system method, which yields the axial temperature difference and its characteristic value for the simplified characteristic temperature load to be used in the cyclic plastic analysis of coke drum. According to the cyclic plastic analysis of coke drum cycled between oil-feeding and water quenching, the bottom alignment of temperature difference ranges produces much ratchet strain rate. In addition, the co-existence of cyclic internal pressure would increase the ratcheting strain of the structure. By parametric study, the ratchet boundary is determined for the temperature gradient under oil-feeding and water quenching. It indicates that, when temperature difference range of water quenching is smaller, the ratchet boundaries would be influenced much more by the cyclic internal pressure.

Key words: coke drum, constitutive mode, moving axial temperature front, ratcheting