Research On The Welding Seam Tracking System Of Narrow Gap Full Position P-GMAW Arc Sensor

Medium thick plates with thickness between 10～20mm were usually used in laying with long distance pipelines.Welding wire filling quantity and production cost can be reduced by narrow gap welding,meanwhile the pipeline construction speed is improved.Narrow gap welding is an important way to improve the quality of pipeline welding because of small heat input,fine weld structure,good joint toughness and good comprehensive mechanical properties.However,the near-vertical sidewall will seriously affect the arc behavior in the welding process,and the serious magnetic bias blowing will cause the arc to deviate from the center of the weld and affect the welding quality.The tracking control of welding seam is the key factor to improve welding quality and production efficiency.Thus,it is necessary to research and analyze the characteristic parameters of all-position welding arc sensing.Then the accuracy of seam tracking is futher improved and the intelligent welding equipment with arc sensing seam tracking is developed on the basis of guaranteeing the welding seam forming quality of all-position pipeline welding.First of all,the conflict original experiment system between which can only gather welding current,welding voltage synchronously and the functional requirement for narrow gap P-GMAW all position welding seam tracking experiment is noticed after analyzing the research status of all-position welding forming and seam tracking.So improved system which can collect the welding current,welding voltage,welding torch location in slope mouth and arc image synchronously is developed based on Labview and TMS320F2812.The narrow gap side wall will produce spot pressure on the droplet and prevent the droplet from transitioning to the pool along the arc axis.In vertical welding and inverted welding positions,the molten pool will also produce spot pressure which is similar to the side wall to prevent the droplet transition,meanwhile,gravity has a negative effect on the forming of welding seam.So it is necessary to reduce the droplet transition distance and increase the electromagnetic force to ensure the smooth droplet transition.The relationship between arc force and welding parameter including arc length correction,wire feeding speed is analyzed based on the unitized setting mode of welding parameters of welding power and the adjusting effect of expert system.Contrast test is designed to optimum welding parameters.Forming of welding seam is improved,finally welding seam is well-formed.On the basis of the integral difference method,the regression equations of each arc sensing characteristic parameters in vertical welding and inverted welding positions were established through the deviation experiment.It is found that melting pool and short arc condition which are necessary for well-formed in the vertical welding and reverse welding have great influence on the regression equation of characteristic parameters.It is found that the decrease of arc length and thickening of weld layer resulted in the decrease of sensitivity of weld seam tracking by analyze the influence of arc length and thickness of welding layer on the tracking accuracy.In the process of vertical welding and overhead welding,the arc length correction and welding speed should be as large as possible,and the wire feeding speed should be as small as possible to improve the accuracy of weld tracking on the basis of ensuring well weld formation.Finally,a closed-loop tracking control system is designed according to the functional requirements of the tracking system.The software and hardware of the all-position arc sensing welding seam tracking system are designed based on CAN bus and TMS320F2812.Meanwhile the materialization of the equipment is realized.The welding seam tracking test of vertical welding and inverted welding was completed based on this tracking system.Futhermore,the correctness of the tracking law was verified.