Study On The On-line Ultrasonic Testing Technology For The Ellipticity Of Steel Tube

Pipeline transportation has become an indispensable way to transport materials over long distances and a kind of transportation in practical application.If the ovality of two tube is significantly different from each other and is forced to welded lead to the stress distribution is uneven in the joints that result in the crack or even break,which bring the great risk of the safety and service life of the whole pipeline.In this paper,the ellipticity of pipeline is detected by ultrasonic testing method.Firstly,analyzing the pipe production process and applying Accident-causing Theory to analyze the factors of production of causing the ovality of steel pipe exceeds the standard to make the fishbone chart.And in combination with analysis of steel pipe transportation and storage environment to establish the Hierarchical analysis model,which has the evaluation basis is provided to ensure that the ellipticity is up to standard.The paper completed the design and processing of ultrasonic transducer and water immersion focusing probe according to the characteristics of the two kinds of probes designed coupling device.And Ensure the accuracy and precision of ultrasonic testing system’s test results by experiments.The emissive frequency of normal probe is 2.5MHz.The piezoelectric material is PZT-5X and the wafer diameter is 14mm.The material of damping block is epoxy resin and tungsten powder.The protective film is made of plexiglass.The protective film of normal probe is made curved surface,and the curvature is the same as the outer surface of the drill pipe.Then determine the matching inductance is 4.3?10^-15H after analyzing the matching circuit of probe.With the increase of the transmission frequency,the directivity of the sound beam becomes better,and the length of the near field region increases after analyzing different frequency（2MHz、2.5MHz、3MHz and 4MHz）simulation of circular transducer ultrasonic field.The internal flow field of the three coupling devices is simulated and analyzed with the fluent.After improving the coupling device,the air bubbles can be discharged in the coupling device and steadily in speed and pressure.Finally,by using a water immersion focusing probe to test the samples,which bipartition two part include ranging experiment and wall thickness detection.Analyzing the data,the error is around 0.5mm.The ultrasonic testing device in this paper can be used in the actual production process.