Design of Optimal Parameter for Solid-State Welding of EN 10028-P355 GH Steel Using gray Incidence Reinforced Response Surface Methodology

EN 10028-P355 GH steel is normalized steel used in high-temperature applications including pipes carrying hot fluids. Fusion welding of such class of steels produces a larger heat affected zone, unwanted metallurgical changes and increased hardness in the weld area. The study explores the possibility of using a solid-state welding process (continuous drive friction welding) on EN 10028-P355 GH steel. The experimentation involves an L₂₇ orthogonal array with the welding parameters like frictional pressure, forging pressure, friction time, forging time and rotational speed varied in three levels. The quality characteristics observed include the yield strength, tensile strength, axial shortening and impact toughness. The merits of gray theory are combined the statistical analysing capabilities of response surface methodology in an integrated approach of gray incidence reinforced response surface methodology to select the optimal friction welding inputs (frictional pressure-93.94 MPa, friction time-5.22 s, upset pressure-138.14 MPa, forging time-3.58 s and rotational speed-1282.67 rpm). The optimal friction welding inputs were validated with proper experiments, and microscopic images concerned with optimal bond is also analyzed. The study will offer the guiding database to weld EN 10028-P355 GH steel in solid-state using continuous drive friction welding.