Investigating feasibility of interlayers in Resistance Spot Welding of low-carbon steel sheets

In this study, experiments without interlayers and with interlayers of copper and stainless-steel sheets were performed. Design of Experiments based Full-Factorial Method was employed to generate experimental combinations. A total 81 samples were welded and tested in Universal Testing Machine to determine their Breaking Load. To investigate feasibility considering vehicle lightweightness, a novel LTW (Load-to-Weight) ratio has been proposed. Calculated LTW ratio for each experiment clearly showed that samples with stainless-steel interlayer outperformed over samples with copper interlayer and samples without interlayer. For feasibility in terms of machine durability, electrode corrosion has been found as the most auspicious parameter among all. Spot welding electrodes attain air oxidation above 700 °C. An FEA solver has been employed to determine time for electrodes to remain above air oxidation temperature during a single welding cycle through numerical simulation. A novel LTT (Load-to- Time) ratio has been proposed to find experimental combinations considering feasibility regarding electrode corrosion. LTT ratio, applied to experimental combinations with SS interlayer helped in selection of suitable process parameter combinations. Selected combinations through LTW and LTT ratio can be further proposed to industries. Study advocates method to calculate LTW ratio initially, following calculation of LTT ratio and eventually selecting process parameters contemplating feasibility in lightweightness and electrode corrosion.