With the increased use of high-performance thin steels, detecting internal or external micro defects in a manufacturing process has become critical for the steel manufacturing process’s cost and quality management. For detecting defects, magnetic-based nondestructive testing (NDT) methods have been researched widely due to their simplicity, ease of use, and contactless nature. However, magnetic-based approaches suffer from low sensitivity, thus limiting their use. Here, we present a highly sensitive tunneling magnetoresistive (TMR) imaging system to detect sub-surface defects in thin steel samples. Artificially created holes in the steel plates were magnetically imaged by measuring magnetic flux leakage (MFL). The experimental results were compared against the simulated results to confirm the visibility of the holes. We also confirmed the successful visualization of the sub-surface defects in the steel plates formed during the real manufacturing processes. Thus, based on these results, we believe the TMR method holds great potential as an NDT technique for steel manufacture management.

中文翻译：

---

高灵敏度无损隧道磁阻成像：模拟和实验验证

随着高性能薄钢的使用越来越多，检测制造过程中的内部或外部微缺陷已成为钢铁制造过程成本和质量管理的关键。为了检测缺陷，基于磁性的无损检测 (NDT) 方法因其简单、易用和非接触性而得到广泛研究。然而，基于磁性的方法灵敏度低，因此限制了它们的使用。在这里，我们提出了一种高灵敏度隧道磁阻 (TMR) 成像系统来检测薄钢样品中的亚表面缺陷。通过测量漏磁通 (MFL) 对钢板上人工制造的孔进行磁性成像。将实验结果与模拟结果进行比较，以确认孔的可见性。我们还证实了在实际制造过程中形成的钢板中亚表面缺陷的成功可视化。因此，基于这些结果，我们相信 TMR 方法作为钢铁制造管理的无损检测技术具有巨大的潜力。