电磁超声是超声波无损检测的一个分支。该技术利用电磁场的相互作用，在被测材料表面产生超声波。因此，电磁超声无损检测过程无需使用耦合剂，并且支持非接触检测。不停工情况下的在役管道以及其他压力容器的剩余壁厚测量是当今无损检测领域的一个研究热点。在常温管道测量方面，使用传统的压电超声可以比较精确地测量管道的剩余壁厚。但是，在高温管道测量方面，目前高温耦合剂还是存在易于挥发、效果不稳定的缺点，而且价格昂贵，不利于实际应用。文章介绍了电磁超声测厚的基本原理、电磁超声厚度测量的仪器设备、探头及其使用范围。结合高温管道测厚的实际应用案例，对电磁超声测厚应用进行了阐述、分析和总结。最后得出，电磁超声由于无需接触、不需要耦合剂等特点，对材料的高温测厚具有独特的优势。

Electromagnetic acoustic transducer technology (EMAT) is a branch of ultrasonic nondestructive testing. This technology utilizes interaction between electromagnetic fields to generate ultrasonic waves. The technique directly generates waves on the surface of the material. Therefore, no couplant is needed. In service thickness measurement of pressure piping at high temperature is a very hot topic in the field of NDT. Measure and monitor the corrosion of critical piping condition without stopping its usage provides enormous benefit to the safety of plants as wells cost savings. Conventional ultrasonic testing with high temperature probes and couplant is one option. However, the disadvantage is that the evaporation of the coupling puts very stringent requirements on the operator to get good measurement data. In addition, the high temperature couplant is also very costly to be used in a large amount. In this paper, the basic principle of EMAT technology, the equipment and sensors for thickness measurement, unique features of operation were all introdued. And also the laboratory and field test results and analysis were supplied. At last, we can get the condusion that EMAT technology fills in the need of high temperature thickness measurement because couplant is not needed for the inspection.