Multi-channel non-destructive testing of steel strip stress based on magneto-elastic effect

Internal stress is an important factor that affects the quality of strip products. Most online detection methods for internal strip stress have been realised by contact sensors. However, contact sensors are expensive to manufacture and tend to scratch the strip surface. The purpose of this study was to develop a multi-channel non-contact stress detection system that can reflect the longitudinal stress inhomogeneity of the strip in the width direction. First, a finite element model of residual stress detection based on the magneto-elastic effect was established in COMSOL, and it was calculated that the detection sensitivity was optimal when the sensor was arranged at 45°. Magnetic shielding technology effectively reduces the minimum interference-free distance of the sensor. A prototype of the detection system was built, the accuracy of the simulation model and the feasibility of the online detection of common steel grades are proved by experiments. The simulation model can directly solve issues related to the sensor’s induced voltage and the minimum interference-free distance, thereby reducing the design cycle and trial production cost of the sensor and providing new ideas for the development of magnetic shielding technology. The experimental results demonstrated that the detection method was feasible, reliable, and displayed high detection precision.