| K-TIG welding technology,as an efficient welding technology,has developed rapidly in China in recent years.The K-TIG welding process can achieve single-sided welding and double-sided forming,with high welding efficiency and good welding seam forming quality.The Q345 R used as a pressure vessel generally has to be welded through multiple layers of multi-pass welding.Such a welding method has problems of low efficiency and high cost.As an efficient welding method,K-TIG welding has the advantages of single-sided welding and double-sided forming,which can make up for the shortcomings of high efficiency and low cost brought by the traditional welding method.This article combines K-TIG welding,an efficient welding technology,with a method of applying a controlled electromagnetic field to weld Q345 R.By changing the parameters of the electromagnetic field,we explore the effect of the magnetic field on the welding arc,weld formation,and welding pool stress.And the influence of the microstructure and mechanical properties of the welded joint.Based on the principle of three-phase AC asynchronous motor and the principle of magnetic field generated by energized solenoid,a magnetic field generating device was trial-produced in this paper.At the same time,the welding equipment was briefly introduced.In order to study the force and shape change of welding arc under different types of magnetic field.Firstly,the changes of the arc’s force and movement form are analyzed theoretically.Secondly,the arc form is collected by a high dynamic camera,and the change of the arc form is explained in conjunction with the theoretical analysis.The test results show that: when the rotating magnetic field acts,the difference of the welding arc’s rotating radius gradually increases with the increase of the rotating frequency;when the longitudinal magnetic field acts,when the excitation waveform is a half wave,the difference in arc radius change is larger,when When the excitation waveform is full wave or sine wave,the difference in arc radius change is not very large;when the composite magnetic field is applied,the arc is relatively stable,and the difference in rotation radius change is not very large.Theoretically analyze the welding seam forming and the welding pool stress under the action of magnetic field.The test results show that when the rotating magnetic field acts,theweld width will gradually increase with the increasing frequency of the rotating magnetic field,and the molten pool will be subjected to the upward or downward Lorentz force;when the longitudinal magnetic field acts,the welding The slit melt width is narrower when the excitation waveform is half-wave,and wider when the excitation waveform is full-wave or sine wave,and the Lorentz force received by the molten pool is clockwise or counterclockwise;when the composite magnetic field acts,The change of the weld fusion width in the frequency range decreases with the increase of the frequency of the rotating magnetic field in the composite magnetic field.The force received by the molten pool is the combined force when the above two magnetic fields act alone.Finally,in this paper,the microstructure and mechanical properties of the welded joint under the magnetic field are studied.The results show that: when the excitation frequency is30 Hz or 40 Hz in the rotating magnetic field,the ferrite content in the weld structure is more and the grain diameter is smaller.The distribution is also relatively uniform;in the longitudinal magnetic field,when the excitation waveform is a half wave,the weld structure and mechanical properties are better.In the compound magnetic field,when the excitation parameter is half wave +10 Hz,the welding effect obtained is good. |
