钢板硬斑的增量涡流扫查成像方法与仪器

硬斑测试是高端钢板产品质量评价的关键内容。本文基于增量涡流检测原理，研制了国产化的钢板硬斑磁检测仪器，并对仪器功能和性能进行了实验测试。首先，研制了增量涡流检测传感器，开发了基于交流电桥测试和相位旋转解调方法的增量涡流检测电路，集成了专用仪器；其次，利用仪器在Cr12MoV钢板和X70管线钢中开展了多组检测试验，结果表明：传感器的横向分辨率可达10 mm,增量涡流信号解调波形峰峰值U_p随表面硬度增加近似线性下降。在高出基准34.8%的硬斑区域内，U_p值下降约75%。利用U_p这一敏感参数对X70管线钢进行扫查成像，可准确识别出宽约10 mm的硬斑。上述研究结果为高端钢板硬斑的在线无损检测提供了方法和仪器支撑。

Incremental eddy current scanning method and instrument for hard spots imaging in steel plates

The hard spot detection is one of the key contents during quality evaluation of high-end steel plate products. In this study, a domestically developed instrument based on the principle of incremental eddy current method is presented for detecting hard spots in steel plates. The function and performance of the developed instrument are experimentally examined. First, a sensor of incremental eddy current and its detection circuit are developed by using AC-bridge, phase rotation and demodulation techniques. As a result, a specialized instrumentation of incremental eddy current is integrated. Secondly, several groups of experimental testing are performed on steel plate of Cr12MoV and pipeline steel of X70 with the developed instrument. The obtained results show that the spatial resolution of the sensor can reach around 10 mm. The peak-to-peak value (Up ) of the demodulated waveform of the incremental eddy current signal is used as feature parameter, which demonstrates approximately linear decreasing trend as the increase of the surface hardness. The value of Up is decreased by at least about 75% in the hard spot region in which the hardness is about 34. 8% higher than the baseline. Magnetic imaging of pipeline steel of X70 is realized by using the parameter of Up and the hard spots with a width around 10 mm is accurately identified from the imaging results. The above research results provide support in method and instrument for on-line, nondestructive testing of hard spots in high-end steel plates.