Research On Arc Sensor Characteristic Signal Of Hyperbaric Gmaw Seam Tracking

Hyperbaric welding,which is mainly used for underwater or underground structure maintenance,is carried out in high-pressure gas environment higher than atmospheric pressure.Hyperbaric arc welding is a high-quality maintenance method for submarine pipelines,and the application of GMAW in high-pressure environment has the advantages of high welding efficiency and strong adaptability.For pipeline maintenance,it is difficult to control groove machining accuracy and assembly precision of the replacement pipe and the original pipeline due to limitation of working environment on repair site,so the welding system is required to have excellent seam tracking function.But the current arc tracking technology is developed in atmospheric pressure environment,the research of GMAW arc tracking in high pressure environment has not been reported.In the range of 0.7MPa(gauge pressure)the research on arc sensor characteristic signal of hyperbaric GMAW seam tracking,which is based on the experiment of hyperbaric GMAW welding,is carried out in this paper.Welding experiment is carried out in a specially designed hyperbaric environment simulation system,which can provide the compressed air hyperbaric environment with the highest pressure of 2.0MPa,and experimental pressure range in this paper is 0.1NPa-0.7MPa.In this paper,a three-axis automatic welding experiment device controlled by PLC is developed having functions of traveling,adjusting arc axial height,transverse swinging,which is realized when the welding torch is moved to welding centre line.The mechanical body of the three axial automatic welding experiment device is placed in the vertical working chamber of the hyperbaric environment simulation system,the control cabinet and the hand control box are placed outside the chamber,and the movement of the welding torch is controlled by the hand control box.Besides,the signal acquisition system is built in this paper,and welding current signal is collected by the Lab VIEW program and then processed by filtering method.V-shaped groove welding experiment was carried out under 0.1MPa-0.7MPa,optimal parameters were obtained on results of weld forming,weld macroscopic metallography and weld tensile strength,in which welding current waveform will be used to extract characteristic signal of arc tracking.The characteristic signal equation in arc axial direction was derived,which shows that a linear equation can be built between welding torch height and average welding current,and equation coefficients are only related to wire feeding speed when the environmental conditions are fixed.Torch height welding experiment under 0.1MPa-0.7MPa is carried out at two different wire feeding speeds of 13m/min and 10m/min,welding current signals are collected,filtered and averaged in Lab VIEW,then fitted curves are obtained by Matlab,and lastly characteristic signal equation in arc axial direction corresponding to experimental condition is built.Influence of environmental pressure on characteristic signal equation in arc axial direction is analyzed using hyperbaric welding theory.Characteristic signal equations in transverse direction for v-shaped groove and trapezoidal groove are derived on the basis of characteristic signal equation in arc axial direction.Under 0.1 MPa-0.7MPa,root pass welding in v-shaped groove and filling pass welding in trapezoidal groove are carried out with wire feeding speed of 13m/min and lOm/min respectively,welding current signals corresponding to welding torch offset are collected,filtered and accumulated by integration method,and test result shows that actual offset is bigger than 80%of set offset and is satisfied in seam tracking.Tracking accuracy under hyperbaric environment is analyzed,and difference between v-shaped groove and trapezoidal groove is given.Theoretical basis and experimental data for arc sensor characteristic signal of hyperbaric GMAW seam tracking are provided in this paper,which can be expected to play an active role in automatic welding or robotic welding of underwater structure repair.