Abstract
Inclusions in steel are entrapped foreign materials, which may be metallic or non-metallic. The inclusions disrupt the structural homogeneity of the steel and affect its mechanical properties. Moreover, nonmetallic inclusions such as calcium and magnesium can be propagated as narrow cracks in steel strips after the rolling process. In this paper, we propose the use of magnetic flux leakage testing involving the fusion of images obtained by arrays of linearly integrated Hall sensors (LIHaS) and linearly integrated giant magnetoresistance sensors (LIGiS) for inspecting inclusions in steel strips. In the proposed method, the normal (Bz) and tangential (Bx) components of the magnetic leakage field around an inclusion are detected by means of LIHaS and LIGiS, respectively. The images of the magnetic leakage field were obtained at different scanning (magnetization) directions relative to the rolling direction. The Bz and Bx images of the inclusion are then combined by using image fusion technique to enhance the detection of the inclusion. The effectiveness of the proposed image fusion technique was experimentally verified by using LIHaS and LIGiS images of an inclusion in a cold-rolled steel strip.