Ultrasonic flaw detection method for identifying hollow-bead defect of submerged arc welded pipe

Abstract

An ultrasonic flaw detection method for identifying a hollow-bead defect of a submerged arc welded pipe is disclosed. Through metallographic phase anatomy on hollow beads and gas pore defects in welding seams in an actual checkout procedure in a production site, morphologies and characteristics of the defects are acquired, the defects are initially confirmed according to a waveform and position ofrefection wave at a submerged arc welding toe, and relative positions of the probe and the defects on the basis of an ultrasonic flaw detection theory, and are finally confirmed by a high-precision longitudinal wave probe. Through the method, a determination error can be avoided to the greatest extent, thereby saving a part of the degradation and head-cut tubes, avoiding the risk of leakage of the hollow bead defect, and saving a large number of tubes which originally need to be degraded.

Description

technical field [0001] The invention relates to an ultrasonic flaw detection technology of a transverse wave water film method, more specifically an ultrasonic flaw detection method for identifying bead trapping defects of submerged arc welded pipes. Background technique [0002] Longitudinal welded pipe factory is a production department specially responsible for the production of large diameter longitudinal submerged arc welded pipes. At present, it has supplied large-scale energy engineering projects at home and abroad such as the Third West-East Gas Pipeline, QGC (Queensland, Australia), and TANAP (Turkey). The transmission medium is mainly natural gas, and the transmission pressure is high, so the product has the characteristics of high risk. The most common spherical volume defects in different specifications of UOE welded pipes are pores and beads. Among them, the inclusion of beads is due to the fact that pores and beads will be generated at the bottom of the molte...

AI Technical Summary

Problems solved by technology

Its shape is spherical and semicircular. Because it contains beads, it is easy to produce small cracks under the stress of diameter expansion and hydraulic pressure, while ordinary pore defects generally do not produce cracks and linear defects under stress. Therefore, the bead defect is not allowed to exist on the pipeline for transporting natural gas, and the air hole is evaluated according to the diameter and number of points to see if it can be released. Assessing what would otherwise be a bead defect as a porosity within the standard range would pose a serious quality risk

The limitation of the above method is that the beads in many weld beads are very small, and the display on the radiographic image is not obvious or even basically invisible, especially when the nominal thickness of the base metal is more than 22mm and the bead inside the bead is very small. If the bead is small, it is difficult to find it on the ray DR

At the same time, there are also two small air holes at the same position with different depths. When the ray is irradiated on the DR ray plate, the image presented is similar to the bead defect, so it is easy to mistake the weld air hole for the bead at this time, and the judgment standard of the two is Differently, bead defects are not allowed to exist on the pipeline for transporting natural gas, and the pores are evaluated according to the diameter and number of points whether they can be released. If the pores within the standard range are evaluated as bead, it will cause unnecessary waste, while porosity, which is originally a bead defect, is rated within the standard range and poses a serious quality risk

[0004] To sum up, the current radiographic flaw detection method cannot comprehensively and effectively characterize weld beads and weld pores, the detection efficiency is low, and it is easy to cause misjudgment of batches of qualified pipe materials, resulting in the quality of submerged arc welded pipe products. be effectively guaranteed

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