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1.
Influence of kinematic factors of friction stir welding on the characteristics of welded joints of forged plates made of EN AW 7049 A aluminium alloy
Milenko Perović, Sebastian Baloš, Dražan Kozak, Darko Bajić, Tomaž Vuherer, 2017, original scientific article

Abstract: In this paper, the influence of rotation speed and welding speed on the impact strength, microstructure and cross section micro hardness of FSW welded joints of Al-Zn-Mg-Cu high strength aluminium alloy is studied. Rotation speed was varied from 750 min−1 to 850 min−1 and welding speed from 60 mm/min to 80 mm/min. It was found that the energy of crack propagation is up to three times higher than the energy of crack initiation. This ratio was found by testing the Charpy notched specimens taken from left and right from the weld centre, 4 mm from the notch in a direction opposite to a direction of welding. Micro hardness distribution in the nugget does not show large dissipation of value regardless if the measuring point is in the upper or lower section of the nugget. Weld microstructure characteristics and zones are clearly defined at the basis of grain size and material flow.
Keywords: dynamic recrystallization, friction stir welding, impact strength, micro hardness distribution
Published: 12.07.2017; Views: 734; Downloads: 296
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2.
The influence of electric arc activation on the speed of heating and the structure of metal in welds
Oleksandr Savytsky, Mychailo Savytsky, Darko Bajić, Yuriy Shkrabalyuk, Tomaž Vuherer, 2016, original scientific article

Abstract: This paper presents the results of a research related to the impact of electric arc activation onto drive welding energy and metal weld heating speed. It is confirmed that ATIG and AMIG methods, depending on metal thickness, single pass weldability and chemical composition of activating flux, enable the reduction of welding energy by 2-6 times when compared to conventional welding methods. Additionally, these procedures create conditions to increase metal weld heating speed up to 1,500-5,500 °C/s-1. Steel which can be rapidly heated, allows for a hardened structure to form (with carbon content up to 0.4%), together with a released martensitic structure or a mixture of bainitic-martensitic structures. Results of the research of effectiveness of ATIG and AMIG welding showed that increase in the penetration capability of electric arc, which increases welding productivity, is the visible side of ATIG and AMIG welding capabilities.
Keywords: arc welding, active flux, penetration, heating speed, driving energy
Published: 07.07.2017; Views: 608; Downloads: 283
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