Grain characteristic-based improved split spectrum method in cast iron ultrasonic flaw detection

Abstract

The invention aims to provide a new method for ultrasonic flaw detection of a pressure-bearing cast iron device, namely a grain characteristic-based improved split spectrum method in ultrasonic flaw detection of the pressure-bearing cast iron device, wherein compared with a conventional cast iron flaw detection, the method enables a system to obtain higher signal-to-noise ratio, faster response time and higher flexibility. Because an internal organizational structure of cast iron is not uniform and the grain size is larger, when ultrasonic waves are used for flaw detection, attenuation of the ultrasonic waves is larger when in propagation, sporadic reflection is prone to generate, and forest-like or grass-like echoes are produced, resulting in poor flaw detection sensitivity. The method utilizes effects of an average grain size and an crystal orientation angle (an included angle of the acoustic wave incident direction and the grain axis) of the cast iron internal grain characteristics on ultrasonic scattering and attenuation, a noise time-frequency characteristic and a flaw echo frequency dispersion characteristic with obvious grain characteristics are caused, optimized split spectrum parameters are obtained through analysis of noise and echo signals, and thus with utilization of the split spectrum technology, the scattering noise can be well reduced and the ultrasonic echo signal sensitivity can be well improved.

Description

technical field [0001] The invention relates to an ultrasonic detection technology for pressure-bearing cast iron equipment, in particular to an improved method for the application of separation spectrum technology in the ultrasonic flaw detection of pressure-bearing cast iron equipment. Background technique [0002] At present, my country has tens of thousands of cast iron boilers and pressure vessels in service, and many buried gas pipelines are also made of cast iron. Once an accident occurs to these in-service pressure-bearing cast iron equipment, it will inevitably cause immeasurable damage to the national economy and the personal safety of on-site workers. Since cast iron materials have the characteristics of coarse grains, high carbon content, high hardness, and poor toughness, there is no mature method for non-destructive testing of cast iron pressure equipment at home and abroad. Therefore, it is committed to researching a more accurate and convenient method. , Mor...

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Problems solved by technology

[0004] Problem solving: In view of practical engineering problems, there are two main problems to be solved in the ultrasonic detection of defects in pressure-bearing cast iron equipment: First, how to effectively solve the problem of using separation spectrum technology for the detection of cast iron materials with coarse grains or large acoustic attenuation The reflection and scattering of acoustic energy at the crystal interface causes the problem of low signal-to-noise ratio of the echo signal, and how to effectively set the parameters required for the separation spectrum

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