焊接长钢轨焊缝性能的磁弹测试

Testing of Hardness on Long Rail Welded Joint with Magneto-elasticity Noise Technique

实验发现，铁磁材料被交变磁场局部磁化以后，材料内部的磁畴发生不可逆运动和跳跃式位移，释放出的磁弹噪声，强烈地依赖于材料的弹性形变、表面热处理状态、组织结构等。采用该信号依赖于材料特征的这项技术检测了哈尔滨铁路局焊轨厂生产的60 kg/m U74无缝钢轨的表面硬度，并与布氏硬度法检测取得了一致结果。为该项磁法无损检测技术开拓了应用前景。

Magneto-elasticity noise is a physical effect which is caused by irreversible movement of magnetized domain vector and domain walls during the magnetization of part of the ferromagnetic material induced by the alternating magnetic field. It is found in the experiment that this signal is affected by the state of the elastic deformation, the heat treatment, and the microscopic of material, etc. This technique is used for testing surface hardness of 60kg/m U74 rail welded joint by Harbin Weld Rail Plant. Testing results by means of magnetic Barkhausen noises（MBN） method are as well as Brinell ball testing results. This nondestructive testing technique would have a strong life and an extensive market.