Determination of Optimal Resistance Spot Welding Parameter on Low Carbon Steel Welding Quality Abstract—The welding quality in the form of nugget diameter and the tensile strength of resistance spot welding in low carbon steel was experimentally investigated. Two types of low carbon steel; the uncoated plate of SPC 270D and the coated plate of SCGA 270D with the same thickness of 0.7 mm were used and studied in this experiment. The process determination of optimal welding conditions was done based on welding current and welding time for the combination of each material and also their mixed. This work revealed that both of the weld current and weld time parameters have a great influence on the quality of the spot welded joints, in the form of nugget diameter formation and its corresponding tensile shear load. The latter is needed to be examined in order to understand the failure mode of joints. The results which plotted as graphs and the confirmation by figures are discussed. Keywords—Resistance spot welding, welding parameters, weld nugget diameter, tensile-shear load I. INTRODUCTION Resistance Spot Welding (RSW) has a great interest application in many fabrication industries. Upon of those industries, automotive industries may become the greatest applicant towards RSW due to the characteristic of inexpensive processes, effective way to join the metal sheets even in the different thickness and also the susceptibility processes to be automated [1]. Up to 4000 points spot of RSW, mostly in the form of lap joints can be implemented for creating a single monocoque body of vehicle. This will become the particular advantage of using RSW in automated production lines with high production quantities. It is become often for automobile maker to improve the vehicle body to meet the customer needs from the view of body safety enhancement, weight reduction eco-car, included providing anti-corrosion guarantees on the body of automobile. Regarding to the last matter, the use of coated material (galvanized one) becomes a choice to be implemented in production lines and the amounts have been increased significantly to prevent the manufacturer brand decreases in customer eyes. As the resistance spot welding is still the dominant welding process for auto body assembly, which involved both of coated and uncoated steel, therefore it is necessary to consider the optimal welding parameter to secure the reliability of structured vehicle white body both in productivity and quality. This experimental study deals with the determination of optimal resistance spot welding parameter both of the coated and uncoated low carbon steel without causing expulsion. It is generally known that the expulsion is responsible for the failure of achieving minimal nugget size and affected the weld strength value due to metal loss. The result of this study is intended to be used to control the amount of heat generated from weld current electrical energy to be transformed into the suitable size of weld nugget diameter and its strength of the weld joints considering to the energy saving and financial aspect. II. MATERIAL AND EXPERIMENT PROCEDURE 2.1 Material The low carbon steels of material that have been used in this experiment are the uncoated sheet of SPC 270D and the coated sheet of SCGA 270D, which are widely used for automobile bodies. The data of each chemical composition and mechanical properties of those materials reported by steel maker supplier (JFE Corp.) can be looked in the Table 1. Each of those materials in the same thickness of 0.7 mm was cut in to specimens with the dimension of 110 x 20 mm. The specimens were then overlapped for the purpose of tensile shear test with the arrangement like depicted in Fig. 1. This arrangement will be applied to investigate the optimal welding parameters for the combination of SPC-SPC, SPC-SCGA and SCGA-SCGA respectively. Tota Pirdo Kasih Department of Industrial Engineering, Bina Nusantara University, Jl. KH Syahdan No. 9, Palmerah, Jakarta Barat, Indonesia. Email: tkasih@binus.edu Iwan Tutuka Pambudi and Budi Santoso, Production Technical and Manufacturing Process, Astra Manufacturing Polytechnic, Jl. Gaya Motor Raya No.8, Jakarta, Indonesia. E-mail: itpambudi@yahoo.com and 14330.toso.tpm@gmail.com The authors wish to thank PT. Astra Daihatsu Motor for supporting the materials and providing facilities during the research experiments. 2014 2nd International Conference on Technology, Informatics, Management, Engineering & Environment Bandung, Indonesia, August 19-21, 2014 75 978-1-4799-4805-5/14/$31.00 ©2014 IEEE