Estimation of Welding Voltage from Welding Current and Arc Length in SMAW Process
The relationship between welding voltage, welding current and arc length was investigated in this study. Shielded metal arc welding (SMAW) process was used to weld API 5L X65 line pipes at welding current of 80 – 200A and arc length of 1.5 – 3.5mm. First and second order polynomial equation and Amson models were also used to study the welding voltage as a function of current and arc length. The results revealed that increase in current and arc length lead to corresponding increase in voltage. The welding voltage increased from 19.48 – 23.82V at constant arc length of 1.5mm and from 22.25 – 26.77V at 3.5mm arc length, as current increased from 80 – 200A. Voltage increase was more influenced by increase in arc length than increase in current. Welding currents between 140A and 180A and arc length between 2mm and 3mm are recommended for optimum quality welded joints. The analysis of the model performance showed that there was high correlation between the predicted and the measured welding voltage values (R2 up to 99%). However, the predictions from the second-order polynomial model slightly edged the Amson and the first-order polynomial models. Therefore, using either of these models could be helpful in deciding on the range of welding input parameters that can be used to optimise welding quality and productivity in the SMAW process.