Study On Welding Technology And Signal Acquisition Of Medium And Large Diameter Hollow Studs

Aiming at the defects of pores and non-welding in the welding process of medium and large diameter Q235 hollow studs and 45 steel,a welding method using a stabilizing agent for hollow studs of medium diameter?16mm was proposed.For the large diameter?20mm hollow studs,the welding method of arc magnetic field and arc stabilizer is adopted.The above welding methods can effectively reduce the porosity in the weld,improve the mechanical properties and improve the microstructure.The ?16mm hollow stud process test using an arc stabilizer was performed.The optimal process parameters were:welding current 600A,welding time 1100ms,arc stabilizer addition amount 0.4g,joint shear strength 327MPa,impact toughness 28.72J cm^-2.The arc stabilizer can stabilize and expand the arc-induced cathode electron emission.The low-density oxide produced protects the molten pool,reduces porosity,reduces the upper bainite content in the weld,and forms a good welded joint.A ?20mm hollow stud process test using an arc rotating magnetic field and an arc stabilizer was performed.The optimal process parameters were:welding time 1450ms,welding current 800A,arc magnetic field current 0.43A,and arc stabilizer 0.55g.Shear resistance.The strength can reach 317MPa and the impact toughness is 31.88 J cm^-2.The rotating arc-stirred molten pool reduces solute enrichment and subcooling,and reduces coarse dendrites in the weld.The arc is constrained by the magnetic field and the solid phase transition time is increased,which reduces the width of the fusion zone.The width of the fusion zone on the base material side of the arc stabilizer stud welding is 886?m,and the width of the fusion zone of the arc-spinning field-arc stabilizer is reduced to 388?m.The results of the arc image processing show that the arc in the absence of a magnetic field is a thick beam and has no tendency to move.Under the longitudinal magnetic field,the arc moves in a bundle around the annular end surface of the hollow stud when the current rises,and when the current reaches a stable state,the shape changes to a bell-shaped shape with a narrow upper and lower width,and rotates back and forth along the annular end surface.The higher the applied magnetic field strength,the larger the rotation range.The arc 5ms movement range is less than a quarter of the end face when the arc current is 0.25A.When the arc current is 0.61A,the arc 5ms has moved a half of the ring end face.Wavelet analysis is performed on the collected electrical signals.There is a corresponding relationship between voltage and current.When the current appears in the valley(wave peak),the voltage must appear in the peak(wave valley),and the current in the stud welding stage has a steep peak voltage drop.Under the control of the magnetic field,the arc moves on the end face with uneven combustion,the arc moves to a position where the amount of combustion is small,the length of the arc column is compressed,and the voltage decreases.When the arc moves to a position with a large amount of combustion,the length of the arc column increases and the voltage rises.The arc column length changes make the voltage and current signals also fluctuate.