Investigations on Magnetic and Corrosive Characteristics of Thin Cold-Rolled Nonoriented Electrical Steel Sheets Post Gas Tungsten Arc and Laser Welding

Abstract

Thin sheets (0.5 × 10−3 m) of cold-rolled nonoriented (CRNO) electrical steel are widely used for rotating electrical machines. Gas tungsten arc (GTA) and, recently, laser welding are used for welding M-43 grade CRNO steel. The performance of CRNO is thus explored because of changes in low-carbon, high-silicon content and thin insulation coatings post welding. The welding current for GTA varied from 30 to 110 A, whereas a laser of 800 W was used to estimate the heat affected zone (HAZ), fusion zone (FZ), and weld characteristic ratio. Ferritic phases with polygonal grain size, percent silicon content, magnetic losses, and welded corrosive samples corrosion rate (in mils penetration per year) are compared with the base material (average grain size 55 ± 12 μm). Five different corrodent (NaCl, NaOH, HCl, H2O, H2CO3) environments were created for 2,000 h as per ASTM B895-16(2020)e1, Standard Test Methods for Evaluating the Corrosion Resistance of Stainless Steel Powder Metallurgy (PM) Parts/Specimens by Immersion in a Sodium Chloride Solution, and ASTM G31-72(1999), Standard Practice for Laboratory Immersion Corrosion Testing of Metals standards. The GTA weld samples revealed much-increased weld geometry with welding current, and a significant increase in grain sizes up to 189.2 ± 4 μm for GTA and 187 ± 3 μm for the laser sample near the weld zone is observed. Microhardness variation is found to be in the range of 55 HV for GTA and 51 HV for laser samples in the FZ region with reference to the base metal hardness of 227 HV. In addition, the increase in core loss of 58.72 % for GTA and 39.82 % for laser samples with reference to nonwelded samples is observed.