Research On Ultrasonic Phased Array Detection Technology For Austenitic Stainless Steel Pipe Weld

Austenitic stainless steel is widely used in petrochemical,nuclear power and other industries for its excellent performance.Due to imperfect welding process and harsh working environment,austenitic stainless steel pipe welds are prone to cracks and other defects,and there are major safety hazards.Due to the coarse grain structure of the weld,there is an anisotropic and heterogeneous interface,which makes the defect detection a difficult problem.Ultrasonic phased array detection technology has been widely used in defect detection of such coarse crystal materials by virtue of its unique beam focusing and deflection capability.In this paper,combined with the relevant literature,for the ultrasonic phased array inspection of austenitic stainless steel pipe welds,a TRL(Transmitter/Receive Longitudinal Wave)phased array probe is selected.The TRL phased array probe combines the advantages of traditional TRL probe pseudo-focusing and phased array probe dynamic focusing,and has the advantages of flexible beam control and good focusing effect.In this paper,the simulation and experimental test methods are used to simulate and experimentally study the sound field of the TRL phased array probe.The defects are measured in the transverse hole defect test block and the austenitic stainless steel pipe test block.The main contents of the paper include :1)A two-dimensional phased array probe with a frequency of 2.25MHz(element number of 10×3,bore diameter of 19mm×12mm)and a TRL wedge of type SE53-N45L(TR/roof8°)(wedge angle of 45°,the roof angle of 8°,and the natural depth of focus of 10mm)are selected.As research objects,a research scheme of probe sound field characteristics is designed.2)Under the different experimental conditions of different deflection angles of the same focusing depth and different focusing depths of the same deflection angle,the simulation and experimental tests are carried out.Results show that there is a large error between the actual focused beam and the law.Only when the focusing depth of the sound beam is set near the natural depth of the wedge of 10 mm,and the sound beam is deflected to a nominal angle of 45°of the wedge,can deflection focusing effect be better,which is very important for the setting of the phased array law and the selection of the wedge.3)The effect of the focusing law of TRL phased array probe is evaluated by measuring the depth of the transverse hole defect of the test block.In the process of measuring,it is found that the measuring value and the real value of the defect depths are approximately quadratic function relationship,and the regression function is obtained.The measuring value of the defect depths within 10mm~30mm can be corrected to obtain more accurate values,which improves the detection reliability.4)Phased array inspection of several cracks heights are performed on the austenitic stainless steel pipe test block with natural defects,and the results of direct inspection and corrected inspection and the cracks' designed heights are compared.The results show that the error range of the corrected cracks heights changes from the previous-2.4~1.8mm to-2~-0.2mm and error root mean square changes from 1.61 mm to 0.98 mm,both of which are significantly reduced.This shows that the phased array probe and the TRL wedge can realize the full volume coverage of the sound wave to the pipeline under inspection,and the correction method improves the defect quantitative precision.