| On the basis of the national "Thirteen Five-Year Development Plan",which strongly advocates "construction industrialization and greening",steel skeleton is the "skeleton" of assembling monolithic building,and its quality is very important.Resistance butt welding is a high-efficiency,material-saving and convenient construction solid-state connection method.The characteristics of the welding heat-affected zone have an important influence on the performance of the welded joint,and the corresponding quality of the welded joint is higher.For the different principles of resistance butt welding and the existing equipment of stirrups,the welding method of isobaric DC resistance butt welding was selected.In this thesis,the finite element simulation was used to simulate the heat conduction of the temperature field of the resistance butt welded joint of the stirrup in the steel frame.By establishing the thermo-electrical finite element coupling model of the HRB400 stirrup resistance butt welding heat conduction process,the simulation process was calculated.In the middle,the influence of temperature on the physical property parameters of the material was fully considered,and the welding temperature field of the steel bar was analyzed.Compared with the experimental results,it was proved that the model is accurate to reflect the change process of the temperature field of resistance butt welding.The temperature field variation and its influencing factors under different parameters were studied by using the established thermo-electric coupling model.The temperature field curves of the temperature along the axial distance from the weld were analyzed during the resistance butt welding process and the distribution of changes in the temperature field.The curve analysis of the axial cross-section temperature variation with time under the same welding current was carried out,and the welding time of the resistance butt welding was very short.As the current increases,the heat increases continuously,and the convection and heat radiation heat loss was accompanied by the welding process.At this current,the axial section of the weldment exhibits a good temperature gradient distribution,and a suitable welding current was determined.Under the condition that the suitable welding current parameters are obtained based on the simulation,combined with the main process parameters of the pre-developed equipment of the hoop welding at the present stage,the tensile strength test of the hoop welding quality is carried out.It is determine that the welding current parameters obtained by the simulation analysis,the welding time parameters controlled by the welding controller,and the four main influencing factors of the upsetting pressure and the shaft center deviation parameters controlled by the mechanical structure as the welding process parameters test analysis of tensile strength.Using the SPSS software tool to establish the orthogonal table of the selected welding process parameters,and the effect index was determined based on the quality acceptance criteria of the steel welded joints.Then the effect curve and the range analysis method are used to determine the optimal parameter matching setting and the influence factors of the primary and secondary tensile strength of the welded closed stirrup.Finally,according to the verification of the selected process parameter values and the actual production comparison,it is proved that the selected welding process parameters improve the welding excellent rate by about 10%,which lays a foundation for the equipment development of the automatic welding machine closed stirrups. |
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