Research On Detection And Quality Evaluation Of Stainless Steel Resistance Spot Welding Process

Resistance spot welding is the main welding method in the manufacture of stainless steel products.The resistance spot welding formation process is the comprehensive action of multiple physical fields such as heat,electricity and force,and the forming process of the nugget is completely closed.It is difficult to evaluate the quality of resistance spot welding.In this disseration,the spot welding process of SUS304 stainless steel is taken as the research object,and the quality evaluation of stainless steel spot welding joints is deeply studied.In order to meet the demand of electrical signals in resistance spot welding,a hardware platform of process detection system which can collect,display and transmit welding current,interelectrode voltage,dynamic resistance and welding power in real time is built in this paper.The scheme of measuring the secondary output current of resistance spot welding is compared,and the current conditioning circuit with flexible rogowski coil as the current sensor is designed to realize the accurate detection of welding current.According to the functions of the experimental platform,the control software of the process detection system was designed.The main program,ADC acquisition program,RS485 serial communication program,timer program,over-limit monitoring program,etc.were designed to realize the digitization of the process detection system control.Completed the manmachine interface color touchscreen interface design,the main interface design content including interface during the welding process curve of the wave form,parameter setting,fault alarm prompt interface setting and monitoring interface,realize the real-time waveform display,input and output parameters of concise and visual display of process data.Based on the above work,the detection platform of SUS304 stainless steel spot welding process is built.The process parameters of resistance spot welding of SUS304 stainless steel sheet were optimized.Comparison and analysis on the electrode wear,small margin,pressure fluctuation between electrode and surface state change between the electrode under the influence factors such as voltage curve and the dynamic resistance curve,extracted the five characteristics: dynamic resistance is the maximum,minimum,dynamic resistance dynamic resistance value,maximum voltage between electrodes and electrode voltage RMS.A stainless steel spot welding quality evaluation model based on BP neural network was established.The model takes the above five characteristics as input and the tensile strength as the output.The results show that the neural network can better evaluate the quality of stainless steel resistance spot welding joints.