Performance Evaluation of Resistance Spot Welded Interstitial Free Steel Under Cryogenic Conditions

Abstract

Shear tensile (strain rate 10(2)/s) performance of spot welded joints at cryogenic temperatures has been studied considering it as a simple method to indicate the crash resistance performance. The strength of different resistance spot welded joints of interstitial free steel under various heat input conditions has also been evaluated at room temperature for comparison. Micromechanism of fracture of the spot welded joints is investigated by scanning electron microscopy. Although an increase in shear tensile strength with decreasing test temperature is observed in all the spot welds, considerable variations in fracture mode exist in contrast to the room temperature test. The high heat input spot welds remain ductile at all test temperatures, however, low heat input welds become considerably brittle at cryogenic temperatures. Furthermore, medium heat input welds can maintain ductility until 0 degrees C and there is loss of ductility with further lowering of test temperature.