Numerical Simulation Of Welding Deposit Repairing Process For Steam Turbine Rotor

Welding deposit repairing technology is a process of cladding an alloy material with a certain performance on the surface of the parent material by using a high-temperature heat source.The process can give the parent material special performance or restore the original shape and size of the parent material.A steam turbine is a rotating power machine that converts the energy of steam(with certain temperature and pressure)into mechanical energy.The blade root groove of the rotor of an existing steam turbine was damaged during service,which will be repaired by welding deposit repairing technology.In order to predict,control and optimize welding residual deformation,this paper uses numerical simulation methods to analyze the thermal-stress coupling effect of the impeller body submerged arc welding(SAW)process.The main research contents and The innovative progress is as follows:(1)ANSYS software is used to carry out geometric and numerical modeling of turbine steel rotor impeller body to obtain the distribution of temperature in deposit repairing layers.According to the results of welding simulation,the characteristics of welding pool depth,heat affected zone range and interlayer heat treatment effect with the course of welding are analyzed.During the whole welding process,there is an obvious heat treatment effect between layers,that is,the front layer preheats the back layer,and the latter layer post-heat treatment the front layer.In addition,the short-time post-weld heat treatment can not quickly eliminate the temperature gradient in the rotor.(2)An elastic-plastic theoretical model of the surfacing process was established to analyze the distribution and change law of the stress field during the welding repair process.The results show that the stress distribution in the welding process is closely related to the welding path.Comparing the distribution of three-dimensional stress throughout the overlay welding process,it can be found that effective post-weld heat treatment can not only greatly reduce the peak welding stress accumulated during welding,but also make the distribution of residual stress in the final rotor uniform.For shaft parts,the axial welding stress is concentrated on the parts of the surfacing layer close to the twoend faces because the cooling rate at both end faces of the rotor is faster than the middle part.With the increase of the number of welding layers,based on the theory of "repainting" the dynamic stress between layers,the welding stress decreases gradually from the parent material to the surfacing layer surface.(3)By observing and comparing the axial and radial deformation of the impeller body during the welding process,it can be found that,as a whole,the axial direction of the impeller body shows an axial shrinkage deformation from the two sides to the middle.The radial compression deformation caused by non-uniform local heating and cooling during the welding process has little effect on the rotor.By comparing the axial deformation of the impeller body before and after the welding heat treatment,the post-heat treatment reduces the welding residual stress,but the cumulative effect of thermal deformation makes the welding deformation increase and eventually becomes uniform.By comparing the equivalent stress and residual deformation of the impeller body before and after welding heat treatment,it can be found that the heat treatment effect of 580 ℃ × 20 h is more ideal.