Damage mode determination of electric resistance spot welding of galvanized and chrominated micro alloyed steel sheets

DAMAGE MODE DETERMINATION OF ELECTRIC RESISTANCE SPOT WELDING OF GALVANIZED AND CHROMINATED MICRO ALLOYED STEEL SHEETS SUMMARY Keywords: Welding, Spot Welding, Micro Alloyed Steel Sheets, Automotive. The application of electric resistance spot welding in various industries widely increasing. Especially in automotive industry, the application of it has reached the highest level. Electric resistance spot welding is being applied for car bodies, reinforcing steel sheets and chassis fittings. The sheets used in these parts are galvanized micro alloyed chrome plated steel sheets with corrosion resistance and good welding properties. The investigation of effects of welding parameters of joints' and in connection with it the tensile-shear and tensile-peel strength is an important subject. In this study information has been given about the importance of the subject, in the first chapter the principles and fundamentals of electric resistance spot welding in the second chapter galvanizing chrome plating and metallurgical and physical properties of micro alloyed steel sheets in the third chapter. In the fourth chapter, information has been given for experimental studies performed. A timer controlled electric resistance spot welding machine of 120 kVA capacity and pneumatic application mechanism with single lever was used. Welding current periods of 5, 10, 12, 15 were selected and welding current kA was adjusted to 5 kA to 12 kA by increasing 1 kA at every step. Electrode pressure was fixed as 6 kN. Obtained welding joints were tested for tensile shear, tensile peel and hardness of Vickers. The joints' cores were examined and investigated for then effects of core sizes on tensile shear and tensile peel strength. As a conclusion, the proper parameters are proper for electric resistance spot welding of galvanized and chrome plated micro alloyed steel sheets. XII