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

Abstract

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.