Flash Butt Weld Ability of Dual Phase Steel Sheet Studied by Microshear Test Method

Abstract

Flash butt welding of dual phase steel sheet (3.7 mm) has been carried out by using different final jaw distances (FJD) of 20,30 and 40 mm and their influence on weld thermal cycle has been studied. The influence of variation in FJD on the micro-structure, microhardness and microshear strength across the weld are investigated. The mechanical properties such as ultimate tensile strength and reduction in cross sectional area of different region of heat affected zone (HAZ) are estimated by using the corresponding microshear test results. The variation in FJD has been found to affect the weld thermal cycle significantly so the microstructure and mechanical peroperties of the weldment. The region of HAZ at a.distance of about 6.0 mm from the weld centre has been found to be the weakest region of HAZ where temperature during welding rises put to about 620 ± 20°C resulting into tempering of martensite in it. The use of microshear test method has been found very much effective to study the mechanical properties of various regions of HAZ at an interval of 0.7 mm. The studies infer that the use of a comparatively higher FJD of the order of 40 mm may be beneficial for improving the post weliformability of dual phasesteel due to reduction in variation of mechanical properties observed at different regions of HAZ.