电磁超声技术在焊缝检测中的应用

电磁超声技术利用洛伦兹力或磁致伸缩原理在金属或磁性材料中激发出超声波,它是一种超声无损检测新技术。相对于其他无损检测技术而言,电磁超声具有所有的超声检测的优势。声波的激发发生在材料的表面而不是在传感器内部。所以它与传统的基于压电换能器的超声检测相比,具有无需耦合剂、可非接触、可适用于超低温或超高温环境、有利于工业自动化以及可方便有效地实现横波检测及导波检测等优势。Innerspec Technologies公司致力于电磁超声技术的研发和应用,在近十几年中开发了150多台工业在线电磁超声检测系统,广泛应用于钢铁、汽车制造、石油天然气管道和压力容器等领域。作为一种超声波技术,电磁超声可以应用于各种厚度测量、缺陷检测以及材料表征。举例讨论了电磁超声在焊缝检测中的应用。第一个应用是利用导波对激光拼焊板的检测。第二个应用是电阻焊钢管的在线检测。利用沿着周向传播的超声导波对焊缝进行检测,克服了由于焊缝位置偏转对传统超声焊缝检测设备带来的困难。第三个应用是水平横波以及多通道电磁超声相控阵技术实现奥氏体不锈钢焊缝的检测。

EMAT and its Application in Weld Inspection

Electromagnetic acoustic transducer（EMAT） is a new technology for ultrasonic nondestructive testing based on the physical principles of Lorentz force and magnetostriction.As an ultrasonic testing（UT） method,it has all the benefits of UT compared with other methods.Instead of generating sound in the transducer,EMAT generates ultrasonic waves on the surface of a test part.Therefore,compared with conventional piezoelectric transducers,EMAT testing has the benefit of no couplant,non contact,feasible for extreme low or high temperature,and convenient for industrial automation.In addition,EMAT is very convenient to generate SH waves and all types of guided waves.Dedicated to the development and commercialization of EMAT technology,Innerspec technologies has developed more than 150 industrial EMAT inspection systems for steel,automobile,oil and gas transportation,pressure vessel,and power generation industries.As a UT technique EMAT is suitable for thickness measurement,flaw detection,and material characterization.In this paper,we will focus our discussion on a few applications of weld inspection.The first application is a laser weld inspection in tailor welded blanks,in which guided waves are used to inspect the thin plates.The second application is an inline inspection of electric resistance weld（ERW） tube using circumferential guided waves.The thickness of the tube varies between 1.5mm and 8mm.The third application for thick austenitic welds in power industry is using angle beam EMAT phased array and our 8 channel high power portable EMAT instrument.