Thammasat Int. J. Sc. Tech., Vol. 15, No. 3, July-September 2010 1 Process Parameter Optimization in ARC Welding of Dissimilar Metals Lenin N., Sivakumar M. and Vigneshkumar D. Department of Mechanical Engineering, National Engineering College, Kovilpatti, Tamilnadu, India. E-mail: n.lenin@gmail.com Abstract Welding is a basic manufacturing process for making components or assemblies. Recent welding economics research has focused on developing the reliable machinery database to ensure optimum production. In this paper, the optimization of welding input process parameters for obtaining greater weld strength in the manual metal arc (MMA) welding of dissimilar metals like stainless steel and carbon steel is presented. The Taguchi method is adopted to analyze the effect of each welding process parameter on the weld strength, and the optimal process parameters are obtained to achieve greater weld strength. Experimental results are provided to illustrate the proposed approach. Keywords: Dissimilar metals welding, MMA welding, Taguchi method, optimal parameters, Tensile strength of the weld 1. Introduction In high pressure boilers, alloy materials are used for making the super heater and economizer. The cost of alloy steel is very high and hence, in order to reduce the cost, the alloy steels may be combined with carbon steel. Hence, cost reduction is the main objective together with a better quality weld, so we use dissimilar metals welding. A better quality weld in dissimilar metal welding is obtained by optimizing the process parameters because they play a vital role in deciding the weld strength. Some important parameters are welding current, welding voltage, welding speed, arc length, etc. These parameters can be selected based on screening experiments. The actual number of experiments has been minimized by using an orthogonal array and experiments have to be conducted. Once these parameters are optimized, then a perfect weld, i.e. good weld strength, can be achieved. 2. Taguchi method for the optimiza- tion of process parameters Optimization of process parameters is the key step in the Taguchi method [1] for achieving high quality without increasing cost. This is because optimization of process parameters can improve quality characteristics and the optimal process parameters obtained from the Taguchi method are insensitive to the variation of environmental conditions and other noise factors. Basically, classical process para- meter design is complex and not easy to use. A large number of experiments have to be carried out when the number of process parameters increases. To solve this task, the Taguchi method uses a special design of orthogonal arrays to study the entire process parameter space with a small number of experiments only. A loss function is then