Influence of Longitudinal Oscillation on Tensile Properties of Medium Carbon Steel Welds of Different Thickness

Abstract

The effects of specimen thickness on tensile properties of medium carbon steel welds prepared under longitudinal oscillation were investigated. Medium carbon steel workpieces were welded at different frequencies and amplitudes of longitudinal oscillation. Frequencies and amplitudes of oscillations were varied in the range of 0 to 400 Hz and 0 to 40μm, respectively. Specimens were made for tension tests and microstructure examinations from stationary and oscillatory welded workpieces. Test specimens 8mm, 10mm and 12mm thick were tested and yield strength, ultimate tensile strength, percentage of elongation, breaking strength, impact strength and hardness were determined. Metallographic examination of the test specimens was carried out. Yield strength, ultimate tensile strength, breaking strength, improves significantly but percentage of elongation (+5.5%) reduces in oscillatory (longitudinal) prepared welds in comparison to stationary welded test specimens. The maximum increase in tensile properties (yield strength-21%, U.T.S.-26% and breaking strcngth-39%) in oscillatory prepared welds is at 400Hz -5μm and the minimum increase is at 80Hz - 5μm condition. The oscillatory prepared weld grain size in the case of stationary prepared weld was 38 μm. With increase in specimen thickness from 8mn to 12mm there was some change in values of tensile properties for oscillatory prepared welds. The values are significantly more than the values obtained from stationary prepared welds. The increase in values of tensile properties under longitudinal oscillation is attributed to grain refinement, dendrite fragmentation and grain detachment mechanisms.