Detection And Analysis Of Penetration Information In Pulsed Gas Metal Arc Welding

Weld penetration control is the core problem of welding quality control of intelligent manufacturing.The best result is to obtain uniform and stable weld penetration in the welding process.However,the effect of penetration control is usually unstable due to different welding conditions in different welding stages.The primary aim of this paper is to find characteristic variables which can reflect the weld penetration states of the beginning and stable stages of pulsed gas metal arc welding.This research has important theoretical meaning for enriching the weld pool sensing information and realizing precise control.The weld penetration state law of the beginning stage of GMAW-P,which is simulated by stationary welding,is studied by keeping the weld torch and workpiece still and lasting 2 seconds.Different weld penetration states are realized by changing the wire feed speed(WFS).The results indicate that the fluctuation value of peak voltage(?U)decreases first and then keep horizontal.The status weld penetration is achieved at the time when turning point appears.The weld penetration state law of the stable stage of GMAW-P is analyzed through multi-information sensing.The results indicate that ?U and the average value of peak voltage(Mean_U)both can identify whether the full penetration occurs or not.However,the electric signal delay exists and the predictive control needs to be adopted.The laser reflection stripes of different weld penetration in the peak period are analyzed.Two characteristic signals,respectively laser stripe curvature and pixel accumulation of the whole peak period,are proposed based on different welding process,including before droplet transfer and the whole peak period.The results show that each stripe cannot be distinguished from the laser reflection stripes of over penetration,which shows “Xiao yan” shape and the outline curvature of stripes is the largest.The laser reflection stripes can be distinguished clearly.The stripe curvature of partial penetration gradually decreases as the penetration increases and the stripe curvature of critical penetration is the smallest.The pixel accumulation can accurately reflect the weld penetration,which will decreases when full penetration occurs,but increases when partial penetration.