Numerical Simulation Of Flash Butt Welding For Thin-walled Capillary Ring Forming Process

Thin-walled stainless steel capillary ring is widely used in high temperature,high pressure,weak acid and alkali corrosive environment as sealing element.In the manufacture of such capillary ring,it is usually round in a circle from a straight tube,and then use welding method connected it's end face into a closed ring.So welding method and the performance of the joint of the capillary ring have become the key to sealing performance.The flash butt welding as its own characteristics and advantages is widely used in this type of tube fittings docking.Therefore,for the thin-walled stainless steel capillary ring,this paper used the finite element software ABAQUS to simulate the forming process of the flash butt welding,and analysed the influence of the process parameters on the joint forming.Based on the basic mechanical properties of thin-walled stainless steel capillary ring(1Cr18Ni9Ti),the constitutive model of the material(the Johnson-Cook model)was established.The key technical problems such as algorithm selection,geometric model establishment,element type selection and meshing,load and boundary conditions are solved in the process of model establishing of flash butt welding for thin-walled stainless steel capillary ring.Based on the ABAQUS/Explicit module,the three-dimensional elastoplastic finite element model of the thin-walled stainless steel capillary ring flash butt welding process with both simulation accuracy and computational efficiency was established.The reliability of the model was verified by experiments.Based on the finite element model of the thin-walled stainless steel capillary ring flash butt welding,the distribution and variation of the stress-strain on welding process and the mass distribution on the weldment are systematically studied.It is found that the equivalent stress and equivalent plastic strain on the weldment are increasing with the forming process,and the rest of the weld part is affected by the axial compressive stress in addition to the axial tensile stress in the 0.2mm far away from end face and its adjacent area The distribution of the equivalent plastic strain is similar to the mass distribution of the weldment,and the maximum value appears at the end face of the weldment,and the maximum value of the equivalent plastic strain is 1.102.Based on the three-dimensional finite element model which above mentioned,the effect of process parameters on the height and inclination of the burr in the joint forming process was studied,and the influence of the process parameters on the jointforming was discussed.It is found that the effect of upset speed to the joint forming is not outstanding.But the influence of the upset allowance on the joint forming is more obvious,and the larger the upset allowance is,the great the plastic deformation of the joint.When the upset allowance is less than 1.6mm,The degree of plastic deformation of the joint parts of the weldment is obviously insufficient,which is not conducive to the joint forming.The extension has an effect on both temperature field and joint forming.The smaller the extension is,the distribution of temperature field on the axial part of weldment narrower.And when extension is 2.3mm,the the plastic deformation of the welding joint is largest,the joint forming best.