Optimization for Friction Welding Input Factors to Maximize Tensile Strength and Minimize Axial Shortening in ASTM A516 Grade 70 steel Rods

Abstract

The Intention of this work is to state a design of process parameters in the continuous drive friction welding of ASTM A516 Grade 70 steel, 12 mm diameter and 100 mm length circular rods by using central composite design (CCD) in response surface methodology (RSM). The ASTM A516 Grade 70 steel finds its extensive usage in pump shafts and heat exchangers. In this work friction pressure/ time (MPa/s), upset pressure/ time (MPa/s) and rotational speed (rps) are fed into the central composite design as input parameters. The input and output relationship are modeled to estimate axial shortening, impact toughness and ultimate tensile strength of welded joints. The optimization was accomplished to maximize impact toughness (J) & ultimate tensile strength (MPa) and minimize axial shortening (mm). The confirmation test was also conducted by setting the optimized parameters. The microstructure of the weldment and heat affected zone (HAZ) of welded specimens has been examined and shown in this study. At optimized conditions the ultimate tensile strength, impact toughness and axial shortening obatained are 512.37MPa, 18.86J and 15.82 mm respectively. The error between optimum conditions and experimental run for the properties ultimate tensile strength, impact toughness and axial shortening predicted are 0.67%,3.37% and 9.06% respectively. This work narrates a method to get better welding conditions over a wide search in lesser number of trials.

Keywords

• response surface methodology
• central composite design
• ultimate tensile strength
• impact toughness
• axial shortening