Residual Stress Caused Magnetic Field Abnormal Change upon Arc Welding Joint

Residual stress concentration of wielding joints is an essential factor to structure safety. It is found that the residual stress can generate a change of magnetic field in arc welding experiments. Things become simple by measuring the distribution of the surface fields and finding the connection between the fields and the stress. However, we believe that the magnetizing field caused by electrical current in arc welding plays an important role. Also, the geomagnetic field is sometimes considered as a critical point to the field's change. In this paper, experiments were carried out to study the role of arc current by comparing the methods of arc wielding and laser welding. The magnetic field was measured upon the welding sites with almost the same residual stress by controlling the input welding energy. The results of these two different welding methods varied. Magnetic fields of arc welding samples were changed more sharply than the laser ones. This means that the magnetic field caused by electrical arc current is important to the surface field. Therefore, by analyzing the status of arc current, electro-magnetic methods can be used as non-destructive testing tool of the arc wielding joints just by directly testing the surface magnetic field without magnetization.