Effects of Electric Power Arc Inputs on the Microstructure and Mechanical Properties of 0.4%C Steel

Received 07 July 2020 Revised 25 July 2020 Accepted 18 August 2020 Available online 31 August 2020 The effect of electric power arc inputs on the microstructure and fracture surface of 0.4%C steel was analyzed. The power inputs were controlled by varied welding current, arc voltage of 40 volts, welding speed of 3.2mm/sec and electrode gauge of 3.2mm. The currents were varied at 100A for low heat input, 112.5A for medium heat input and 125A for high heat input. Microstructural and fracture analyses were carried out on the specimens to determine their microstructural configurations. The results showed that increasing the welding current from 100A-125A caused a corresponding increase in microstructure of the specimens. At 100A, the time for solidification was less and resulted in smaller fine grains. At 125A, the time required for solidification increases and yielded coarse grains. On the mechanical properties, the results showed that the selected welding parameters had significant influence on the mechanical properties, the results indicated that the joints made by using low heat input exhibited higher tensile strength (515.90 Mpa) and from scanning electron microscopy (SEM) of tensile test fractured surface exhibited ductile failure, higher hardness strength (179.5 HRC) and impact toughness value of (6.5 Joules) than those welded with medium and high heat inputs respectively which exhibited brittle failure as the heat inputs increases.