Method For Detecting Water Content Of Comb-shaped Capacitor Electrode Coating

Developing fast and non-destructive testing methods is critical for detection of moisture of welding electrode coatings.In this paper,a novel capacitance-based welding electrode coating moisture detection method was proposed,and the working mechanism of the method was analyzed and confirmed.Specifically,a welding electrode coating moisture detection method based on the planar comb capacitors was put forward,the structure of the moisture sensors was optimized and the structural parameters were identified.As per the standards specified in code “Covered Electrodes for Manual Metal Arc Welding of Non-Alloy and Fine Grain Steels”(GB/T 5117-2012),the weight-loss method was employed to calibrate the moisture of welding electrode coatings,and the J707 welding electrodes of two diameters were used as samples for experimental study.The experiments revealed that when the moisture of the coating was below 2.3%,the moisture of the coatings and the capacitance of the coatings measured by the planar comb capacitors presented a linear relationship.Based on the experiment result on the J707 electrodes,a welding electrode coating moisture detection system based on comb capacitors was designed,in which the detection accuracy of the sensors met the requirements for practical application.The major work in this research is as follows.(1)Existing welding electrode coating moisture detection methods were reviewed,and several moisture detectors available on the market were compared.The specifics of earlier generations of moisture detectors were analyzed,and a new detection method based on planar comb capacitors was proposed.(2)The working principles and categories of welding electrode coating moisture sensors were analyzed,and the design scheme for the comb capacitor-based electrode moisture sensors is proposed.The structural parameters of the sensors were optimized based on electrostatic field finite element analysis using the software ANSYS Maxwell to provide a basis for design of the comb capacitive sensors.(3)As per the standards specified in the code “Covered Electrodes for Manual Metal Arc Welding of Non-Alloy and Fine Grain Steels”(GB/T 5117-2012),calibration tests were performed to test the performance indicators of the comb capacitors,which confirmed that the capacitive sensors met the requirements for welding electrode moisture detection.In the calibration tests,such error analysis methods as the cubic polynomial regression equations,unary linear regression equations and the least square regression method were employed to determine the saturated water content of the coating.(4)A welding electrode coating moisture sensors system based on comb capacitors was designed.The hardware and the software of the system was described in detail,and high-precision testing of the capacitance of the sensors was performed.The digital filter module was introduced to the software of the system,which improved the accuracy and reduced errors of detection.