Improvement of weld heat affected zone (HAZ) using Taguchi method

Heat Affected Zone (HAZ) is the area on a weldment mostly affected by the intensity of the applied heat without melting. This area mostly deteriorates faster due to microstructural changes that occur due to the intensity of the applied heat during welding operations. Weld structural failures can be catastrophic and unpredictable at times. When there is no loss of human life involved, damages as a result of weld failure usually takes more time and cost more to repair/replace. For these reasons, a weld with good quality integrity cannot be over-emphasized. The larger the HAZ, the wider the area with microstructural alteration, the lesser the quality integrity of the weldment. In this study, extensive research was conducted to reduce weld HAZ using the Taguchi method. This method makes use of signal to noise ratio of responses to achieve optimality. From applying this model, it was observed that the best input parameters, that improved the weld quality was achieved. These input parameters were current of 120A, voltage of 10V and gas flow rate of 144L/min. From the analysis of variance (ANOVA), it was found that current contributed about 9.58% to the weld quality, which was the most influential process parameters. The confirmation test done, shows that the weldment produced by using the optimum process parameters had an improvement of 1.37db and 0.88mm reduction in HAZ, over the weldment made by existing parameters.