This paper presents a novel welding quality evaluation approach based on the analysis by the response surface methodology and controlling the process capability of the friction stir welding (FSW) process of pipes. This method has been implemented in an experimental work developed by alternating the FSW process main parameters: rotation speed, pipe wall thickness and travel speed. Different samples were friction stir welded using ranges of 485- 1800 rpm, 4-10 mm/min and 2-4 mm for the rotation speed, the travel speed and the pipe wall thickness respectively. DMAIC (Define, Measure, Analyze, Improve, Control) methodology was used as an approach for analyzing the attachment potency and technical commonplace demand of the FSW process. The analysis controlled the tensile strength of the Al 6061 friction stir welded joints. The study determined the optimum values from the corresponding range for the parameters to get the best tensile strength