C. I. Nwoye, C. C. Nwogbu, A. O. Agbo, J. U. Odo, S. O. Nwakpa
Materials Science and Metallurgy Engineering. 2013, 1(2), 37-41DOI:
Abstract: This paper showcases the reliability level associating welding voltage dependence of heat affected zone (HAZ) hardness of aluminium, cast iron and mild steel weldments cooled in groundnut oil. These materials were welded using shielded metal arc technique and the HAZ hardness of the various groundnut oil cooled weldments determined. Three models were derived and used as tools for the empirical analysis of the influence of welding voltage on the HAZ hardness of the weldments. The results of the analysis show that the HAZ hardness of weldments is significantly and reliably affected by the operational welding voltage. Results evaluations largely show that on welding aluminium, cast iron and mild steel, and similarly cooling their respective weldments in groundnut oil, the model: ξ=[(ηv/(η+v))((βaβm+βaβc)/βcβm)0.2396], empirically predicts aluminium weldment HAZ hardness as equivalent of HAZ hardness interaction between cast iron and mild steel. Aluminium weldment HAZ hardness was evaluated as a product of a multiplication operation between the general voltage product rule (GVPR) ((βa βm + βa βc)/ βc βm)0.2396 and the ratio; HAZ hardness product of cast iron and mild steel/ HAZ hardness sum of cast iron and mild steel (ην /( η + ν )). Predicted values of the HAZ hardness of cast iron and mild steel were comparatively analyzed and also found very reliably dependent on the GVPR which is a collective function of their respective welding voltage. The validity of the model was rooted on the core model expression; (βa /βc + βa/βm ) = (ζ /ν + ζ / η)4.1737 where both sides of the expression were correspondingly equal. Computational analysis of generated results shows that aluminium, cast iron & mild steel weldment HAZ hardness per unit welding voltage as evaluated from experiment and derived model were 1.4714, 4.1818 & 2.3318 (VHN)V-1 and 1.4714, 4.1821 & 2.3319 (VHN)V-1 respectively. Deviational analysis indicates that the maximum deviation of model-predicted HAZ hardness from the experimental results is less than 0.006%. This translates into over 99.99% operational confidence and reliability level for the derived models and over 0.9999 reliability coefficient for the welding voltage dependence of HAZ hardness.