利用电磁超声横波检测二冷区尾端连铸坯壳厚度

使用电磁超声横波对二冷区尾端的连铸坯壳厚度进行检测，并建立了有限元仿真模型。选取Q235连铸小钢坯作为被测对象。为减小永磁铁的提离距离、在被测体内部生成更大的感应涡流，文章利用多物理场有限元仿真软件建立了一种不同于一般结构的电磁超声换能器仿真模型：圆柱形永磁体两侧并行排列螺旋线圈。分析了永磁铁尺寸对磁场涡流的影响以及电磁超声横波在被测钢坯内不同时间、不同位置的传播情况。计算了被测体中的磁通密度模和电流密度模，同时计算了产生的涡流大小及质点位移情况。研究结果表明：该结构的电磁超声换能器可以在连铸坯壳内成功激发并接收电磁超声横波，且横波穿透力强、效率高，能够成功探测连铸钢坯的回波信号并计算出坯壳的厚度。

Measurement of the continuous casting shell thickness at the end of secondary cooling zone by using electromagnetic ultrasonic shear wave

In this paper, the problem using electromagnetic ultrasonic shear wave to measure continuous casting shell thickness at the end of secondary cooling zone is studied, and the finite element simulation model is established. A Q235 continuous casting billet is selected as the tested object. In order to reduce the lift distance of the permanent magnet and generate larger induced eddy current in the measured body, a simulation model of the electromagnetic ultrasonic transducer (EMAT) different from the general structure is established by using the multi physical field finite element simulation software. In this structure, two spiral coils are arranged in parallel on both sides of a cylindrical permanent magnet. The influence of the size of the permanent magnet on the eddy current of the magnetic field and the propagation of the electromagnetic ultrasonic shear wave in the billet at different times and positions are analyzed. The magnetic flux density modulus and current density modulus in the measured body are calculated, and the eddy current size and particle displacement are also calculated. The results show that the electromagnetic ultrasonic transducer with this structure can successfully excite and receive the electromagnetic ultrasonic shear wave on the surface of the continuous casting shell; the shear wave has strong penetration and high efficiency, it can successfully detect the echo signal and calculate the shell thickness of continuous casting billet.