Research On Pulsed Eddy Current Testing Technology For Austenitic Stainless Steel Pressure Equipment

Austenitic stainless steel has been widely used in anti-corrosion petrochemical equipment.With the development of social economy,China’s demand for energy has also increased sharply.In order to ensure the safety of these austenitic stainless steel devices,there is an urgent need for a technology.It is quickly tested without downtime.Due to its wide spectral composition,pulsed eddy current testing technology can obtain multi-level defect information inside the pressure equipment in one test,which is suitable for non-stop detection of pressure equipment.But the market lacks pulse eddy current testing equipment suitable for austenitic stainless steel pressure equipment,so the main research contents of this paper include:(1)The finite element simulation model of austenitic sta inless steel pulse eddy current testing was established by ANSYS software.By looking at the eddy current distribution on the specimen at any time,it was found that the eddy current spreads faster in austenitic stainless steel than in ferromagnetic materials.At the same time,it can be seen that the detection area of the pulse eddy current detection becomes larger with time.Therefore,the peak value and peak time of the differential signal in the time domain feature quantity of the pulsed eddy current detection signal are used to characterize the results of the pulsed eddy current testing of the austenitic stainless steel.(2)It is proposed to reduce the pulse eddy current detection area by adding the can core.The simulation results show that the magnetic field can be limited to the primary magnetic field.The peak value of the differential signal at the thickness of 38 mm after the core is raised from 0.14 V to 0.25 V.The parametric analysis of the pulsed eddy current testing probe is carried out by using the simulation model.According to the conclusion that the coil width has the greatest influence on the detection sensitivity under the condition that the excitation coil density remains unchanged.The pulse eddy current testing probe was designed independently,and the experimental platform of pulsed eddy current testing of austenitic stainless steel was built.The pulse eddy current detection signal acquisition and analysis software was written by Matlab.Through subsequent experiments,it is verified that the experimental platform can realize the pulsed eddy current detection of 316 stainless steel stepped wall thickness plate with reference thickness of 20 mm under lifting distance less than 20 mm.(3)Firstly,the influence of excitation parameters and cladding parameters on the detection is simulated by using the peak and peak time feature of differential signals.Then the corresponding verification experiments,experiments and simulations are carried out on the constructed austenitic stainless steel pulse eddy current experimental platform.The conclusions reached are the same.The results show that the excitation pulse frequency has no effect on the peak and peak time when the excitation pulse frequency is below 10 Hz.The larger the excitation pulse d uty cycle,the larger the differential signal peak value and the smaller the peak time.The stainless steel protective layer has no influence on the peak value and peak time.The aluminum protective layer reduces the peak value of the differential signal and increases the peak time.The galvanized steel protective layer has the greatest influence on the peak value and peak time of the differential signal,and the peak value of the differential signal is significantly reduced.