Effects of an External Magnetic Field on the Microstructural and Mechanical Properties of the Fusion Zone in TIG Welding

Abstract

Welding is a widely used process that requires continuous developments to meet new application demands of mechanical projects under severe conditions. The homogeneity of metallurgical and mechanical properties in welded joints is the key factor for any welding process. The applications of external magnetic fields, mechanical vibration, and ultrasound are the fundamental steps to achieve success in improving these properties. The present work aimed at determining suitable processing conditions to achieve the desired balance between metallurgical and mechanical properties of 304L steel in TIG (Tungsten Inert Gas) welding under the application of an external magnetic field. The microstructural characteristics of the weld bead were analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). In order to evaluate the mechanical properties of the welded specimen, its Vickers microhardness map and Charpy impact energy at −20 °C were obtained. In addition, corrosion tests were carried out in the saline medium to compare the corrosion resistance of the joint with that of the base metal and that without the magnetic field. It was found that the external magnetic field decreased the percentage of delta ferrite, improved the filling of the weld pool with the weld metal, and decreased the primary and secondary dendritic spacings. The Vickers microhardness value under the magnetic field was found to be lower than that without the magnetic field, and the Charpy test showed no significant variation in energy absorption. Moreover, the welded joint produced under the external magnetic field manifested less resistance to corrosion.

How to avoid solidification cracking in arc welding of aluminum alloys: a review on weld metal grain refinement approaches

“…In the arc oscillation method, grain refinement is carried out by breaking the dendrites and increasing nucleation points [116][117][118]. In this technique shown schematically in figure 9, an alternative external magnetic field is used to deflect the welding arc in a controlled manner.…”

Effect of Magnetic Field Induce Arc in Autogenous TIG Welding of 304 Stainless Steel Butt Joint

“…According to studies, the use of external magnetic fields in conventional TIG welds may increase the depth of weld penetration and reduce the impact of welding defects. Metallurgical and mechanical properties of 304L steel in TIG welding under the application of a permanent external magnetic field for butt joint applications has also been studied recently [17]. However, there is no literature on using the EMF-TIG with dynamic activation method for butt joint application.…”