Method for nondestructive examination of oxide thickness distribution in stainless steel tubes

Abstract

The invention discloses a method for nondestructive examination of oxide thickness distribution in stainless steel tubes, vortex flow transducer is sticked on external wall of bend section in stainless steel tubes, motivated by a multi-frequency signal, vortex flow sensing signal is obtained by the vortex flow transducer, the signal is processed by a computer processing system into data in correspondence position corresponding to oxide thickness of bend section in stainless steel tubes after signal amplification, phase sensitive detection and frequency mixing of interference signals, whole perisporium of the stainless tube is detected by surrounding, a plurality of data in a plurality of positions correspondinig to oxide thickness of bend section in stainless steel tube to be tested is obtained, the computer processing system proceeds imaging treatment according to data of oxide thickness corresponding to stainless steel tubes, images corresponding to stainless steel tubes for mapping oxide vortex flow sensing signals are obtained; and then a pseudo-three-dimensional image corresponding to shape of stainless steel tube is obtained, and oxide distribution conditioin inside the stainless steel is displayed.

Description

technical field [0001] The invention relates to a non-destructive testing method, in particular to a method for non-destructive testing of the oxide skin thickness distribution in a stainless steel tube. Background technique [0002] Non-destructive testing NDT (nondestructive test) is a detection method that does not damage or affect its future performance or use on materials or workpieces. By using NDT, defects existing in the interior and surface of materials or workpieces can be found, and workpieces can be measured. It can determine the internal composition, structure, physical properties and state of materials or workpieces. Non-destructive testing technology has been widely used in various industrial fields, such as manufacturing, aerospace, petrochemical and other fields. [0003] Stainless steel pipes are commonly used as heat exchanger pipes in power stations. During long-term use, the inner walls of the pipes are prone to oxide scales. Oxide skin is a layer of s...

AI Technical Summary

Problems solved by technology

This method can be used to detect whether there are internal oxides in the austenitic stainless steel pipe, and, according to the proportional relationship between the stray magnetic field strength and the amount of magnetic substances in the pipe, it can also reflect the amount of internal oxides to a certain extent. However, There are two types of scale in the elbow section of the stainless steel pipe, one is the primary scale, which is closely attached to the inner wall of the stainless steel tube, and the other is the drop-type scale, which is formed from the primary scale In the parts accumulated after cracking and peeling, the contact between the dropped oxide scales is in a loose state, and there are gaps between them, that is, there is no corresponding relationship between the amount of oxide scales and the thickness. Due to the large gap between the oxide skins, the thickness may be thicker, and the blockage of the stainless steel pipe will be more serious. However, the existing detection method cannot detect the virtual thickness of the oxide skin. In addition, the current Some magnetic detection methods are not sensitive to the boundary and cannot effectively detect the boundary condition of the scale. Therefore, it is more important to detect the distribution of scale thickness in the stainless steel pipe, which is an important basis for judging whether the blockage in the elbow section of the stainless steel pipe will cause the pipe to burst

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