This paper reports a novel use of magnetic technique to characterize the degradation in mild steel within the elastic range. Firstly, the mild steel specimens were stretched to several different kinds of stress within the elasticity. After the tensile test, a shift of hysteresis loop was observed in the tensile specimen, and the variations of magnetic parameters such as Coercivity (H_c), Remanence (B_r), maximum permeability (µ_m), and hysteresis loop area (S) were also evident. When the tensile stress increases to the elastic limit (310 MPa), the H_c increased 16.44% compared with the original specimen, which manifested the variation of the magnetic property in mild steel. The magnetic property variation in material are closely interrelated with its microstructure change. The existence of internal residual stress/strain as well as the dislocation structure change are the main factors affect the magnetic property. The experiment results revealed that the magnetic technique was sensitive to the microstructural change in the mild steel, which has the promising potential to characterize the material degradation at the early stage.

本文报道了一种新颖的磁技术应用来表征低碳钢在弹性范围内的降解。首先，将低碳钢试样在弹性范围内拉伸到几种不同的应力。拉伸试验后，在拉伸试样中观察到磁滞回线的位移，并且磁参数的变化，例如矫顽力（H _c），剩磁（B _r），最大磁导率（_μm）和磁滞回线面积（S）也很明显。当拉伸应力增加到弹性极限（310 MPa）时，H _c比原始试样增加了16.44％，这表明低碳钢的磁性能有所变化。材料的磁性能变化与其微观结构变化密切相关。内部残余应力/应变的存在以及位错结构的变化是影响磁性能的主要因素。实验结果表明，磁性技术对低碳钢的显微组织变化敏感，具有表征早期材料降解的潜力。