The Similar and Dissimilar Spot Welding of 304 and 316L Austenitic Stainless Steels

Being one of the oldest electric welding processes, the resistance spot welding offers practical and time saving applications in the field of joining metals of several manufacturing industries such as automotive, white goods and machinery. Even light weight metals, i.e. aluminum and magnesium has lately been taking attention of researchers and producers, the steels, especially austenitic stainless steels are still being used in wide range of applications due to their combination of excellent corrosion resistance with comparably low price, good machinability, reasonable weldability and good mechanical properties. Spot welding process is controlled by three essential parameters; mechanical (pressure), electric (heat) and electronics (time). In this study, AISI 304 and 316L stainless steel sheets of 1 mm of thickness were used as welding metals. Thus, AISI 304 welding metal couples, AISI 316L welding metal couples and AISI 304 and 316L welding metal couples were selected to ensure a combination of similar and dissimilar metals. Welding procedures were carried out using a current and time controlled electric spot welding machine. To investigate the influence of the parameters (pressure, heat and time) on the welding of the different types of stainless steels and their combination, the parameters were set constant. The current was set to 10,000 A, the pressure was 4 kN and  the duration was 10 seconds for each. After spot welding applications, some of the specimens were cut and prepared for metallographic examination and hardness measurements. The rest of them was shaped for tensile strength measurement using Instron Universal Testing Machine. The hardness of the specimens were observed being altered in the range of 186-240 HV(average) and their tensile shear forces in the scale of 1486-1549 N (average).