Effect of the structure and properties of welded zones made of Sv-AK5 welding wire at robotic surfacing

Abstract

The study covers the effect of welding arc current (47, 57, and 67 A) on the structure and properties of deposited samples obtained by robotic electric arc surfacing. Sv-AK5 (ER4043) welding wire of the Al-Si system was used as a filler material. Surfacing was carried out on a substrate in the form of a 6 mm thick plate made of AMg6 alloy (Al-Mg system). During surfacing, a typical two-phase structure of a hypoeutectic composition is formed in samples typical for Al–Si alloys with a silicon content of 5 %. Along the height of deposited layers, there is a tendency to structure enlargement in the direction from the substrate, which is associated with the accumulation of heat in layers deposited along the height. As welding arc current increases, α-Al-based dendrites and eutectic silicon crystals are refined with an increase in the density and a decrease in the microhardness of deposited samples. The increase in density is due to the reduced proportion and size of gas pores, as well as refined structural components. The decrease in microhardness is associated with the increased proportion of the soft phase (α-Al dendrites) and decreased quantity of hard eutectic silicon crystals. The average content of silicon in samples deposited in three modes is in the range of 5.46–5.91%, which corresponds to the chemical composition of Sv-AK5 (ER4043) welding wire. Higher welding arc current contributes to an increase in the tensile strength and a slight decrease in the offset yield strength and relative elongation. The features of changes in the mechanical properties of deposited samples are determined by of the specific cast structure of deposited layers formed under conditions of directional solidification in the direction from the substrate.