Hardness Characteristics of AISI 1020 Low Carbon Steel Weldment Produced by Tungsten Inert Gas Welding

Abstract

The present study investigates the post-weld characteristics of AISI 1020 low carbon steel weldment produced by Tungsten Inert Gas (TIG) welding  at distinct arc current steps. Scanning Electron Microscopy (SEM) was used for imaging the microstructure and morphology of the welds while  Energy Dispersive Spectroscopy (EDS) was employed in checking the mechanical properties and characterization of the weld. LECO micro-hardness  tester with a load of 150 kg was used in determining the Rockwell Hardness Number of each welded sample. Increased welding current led to  increase in the arc heat, causing the grains to recrystallize and increase in sizes, as such, reducing hardness of the weldment and the Heat Affected  Zone (HAZ). At welding current of 96.14, 120, 155, 190 and 213A, hardness values of 176.3, 164.2, 136.4, 112.5 and 93.6 were obtained from the  fusion zone of each welded specimen while hardness values of 192.2, 174.3, 144.6, 124.8 and 106.3 were obtained from the HAZ of each welded  specimen. However, the base metal was not affected as uniform hardness of 115.2 was observed for all the welded samples due to the absence of  arc heat disorienting the atoms in the metal lattice.