THE EFFECT OF WELDING ON THE ELECTRICAL CONDUCTIVITY OF ASTM A36 CARBON STEEL

Abstract

This research aims to evaluate the effect of shielded metal arc welding (SMAW) on the electrical conductivity of ASTM A36 structural carbon steel weldment as used in engineering construction such as electrified above ground structural applications and/or cathodic protected underground structures. The single “V” groove joint design was adopted and the welding was carried out using manual metal arc welding. The four probe DC testing method and Vickers microhardness were used for electrical characterization and microhardness determination of the different regions of the weldment respectively. Microstructural examination was achieved by the use of a metallurgical optical microscope. The heat affected zone (HAZ) had the poorest response to electron flow on account of the presence of second phase particles (rosette carbide precipitates) and the effect of weld spatter from the micrographs; more so, an asymmetric hardness profile was observed in the HAZ ranging from 108 to 165 HV0.5. The overall resistance of the couple (5.994 ± 0.43 x 10-4Ω) was found to be more than that of the parent metal (PM). Heretofore as observed from the research, the electrical property of A36 weldment is adversely affected by SMAW welding; and there is a correlation between its microhardness and microstructure