Influence of heat on the performance of stack welded thin sheets of CRNGO electrical steel

Abstract

An attempt is made to investigate mechanical-microstructural-magnetic properties on the welded Cold Rolled Non-Oriented Electrical steel (CRNGO) sheets. Single 0.5 mm thin sheets susceptible to Tungsten Inert gas (TIG) welding current are stacked and edge welded using a range of welding current from 30 A to 110 A. The influence of weld with varying current is analyzed through various testing for joint performance, micro-hardness, Residual stress, weld seam characterization, Grain size variation and Magnetic property evaluation of post-welded samples. The results showed the variations of micro-hardness varies by 33 HV and 42 HV at the Heat affected zone (HAZ) and Fusion zone (FZ), respectively. The relative residual stress ranged from 26.85 MPa to 127.6 MPa, weld strength ratio is about 42.9%, depth to width ratio varies from 0.446 to 0.527. The ferritic and largest fine grains size of 79.7 μm is transformed to coarse 282 μm in HAZ. The changes of magnetic properties showed a significant increase in core loss and magnetic field strength with decrease in the relative permeability. The study is useful for electric motor industries to generate varieties during stacked welding of transformer core as per the need of the application.