Factorial analysis of heat affected zone hardness of some metals was evaluated. Three models were derived and used as tools for evaluating the welding current influence on the predictability of HAZ hardness in aluminium, cast iron, and mild steel weldments similarly cooled in palm oil. It was discovered that on welding these materials, and similarly cooling their respective weldments in palm oil, the model predicts aluminium weldment HAZ hardness by multiplying the determined general current product rule (GCPR) with the ratio: HAZ hardness product of cast iron and mild steel/HAZ hardness sum of cast iron and mild steel . Computational analysis of experimental and model-predicted results indicates that aluminium, cast iron, and mild steel weldment HAZ hardness per unit welding current as evaluated from experiment and derived model are 3.3917, 4.8333, and 2.7944 and 3.3915, 4.8335, and 2.7946 (VHN) A−1, respectively. Deviational analysis shows that the maximum deviation of model-predicted HAZ hardness from the experimental results is less than 0.007%. This invariably implies over 99.99 % confidence level for the derived models.

Desulphurization of iron ore was carried out using an oxidant; powdered potassium chlorate (KClO3) of mass-input range (5-12g) and temperature range (500-800°C). The limit of desulphurization was evaluated considering the initial ore sulphur content and removed sulphur concentration. Investigation on the process analysis and mechanism of the desulphurization process revealed that oxygen gas from the decomposition of KClO3 interacted with sulphur through molecular combination within the Gas Evolution Temperature Range (GETR); 375-502°C. Sulphur transformation into vapour within this temperature range was observed to facilitate easy reaction with oxygen gas to form SO2, A limit of desulphurization; 92.22% was experimentally achieved following successful reduction of the initial ore sulphur content to 0.007 % using 12g of KClO3 at a treatment temperature of 800°C. A model was derived and used as a tool for empirical analysis of limit of desulphurization based on treatment temperature, mass-input of KClO3, sulphur loss-sulphur initial ratio. Deviational analysis indicates that the derived model gives best-fit process analysis with a deviation range of just 0.65-8.82%, from experimental results and invariably an operational confidence level range 91.18-99.35%. The deviation range corresponds to limit of desulphurization range: 31.4019-86.6128%, treatment temperature range: 600-800°C, KClO3 mass-input range: 7-12g and range of sulphur loss-sulphur initial ratio: 0.3444-0.5556. Hence, the derived model can exclusive, be significantly and viably operational within these process conditions.

The predictability of hardness of the heat affected zone (HAZ) in aluminum weldments cooled in palm oil, based on hardness of similarly cooled mild steel and cast iron weldments has been ascertained. The general model:indicates that HAZ hardness of aluminium weldment is dependant on the ratio of product to sum of HAZ hardness of mild steel and cast iron weldments cooled in palm oil under the same conditions. The maximum deviations of the model-predicted HAZ hardness values α, μ and β from the corresponding experimental values α exp, μ exp and β exp were less than 0.04% indicating the reliability and validity of the model.