ВПЛИВ ШВИДКОСТІ ПЛАЗМОВО-ДУГОВОГО ЗВАРЮВАННЯ РІЗНОПОЛЯРНИМ АСИМЕТРИЧНИМ СТРУМОМ НА ФОРМУВАННЯ З’ЄДНАНЬ ВИСОКОМІЦНИХ АЛЮМІНІЄВИХ СПЛАВІВ.

The effect of change in the speed of movement of the heating source in plasma-arc welding of aluminium alloys of 2.0 mm thick of three Al–Mg–Mn (AMg5M, AMg6), Al–Cu–Mn (1201) and Al–Cu–Li (1460) alloying systems on the microstructure and hardness of the weld metal and near-weld zone, on the formation of inner pores and mechanical properties of welded joints was considered. Changes in the distribution of temperature fields and indices of the stress-strain state of welded specimens were analyzed. It was found that for each type of alloys there is a certain “peak” welding speed, with exceeding of which there is no significant reduction in residual deformations and stresses, as well as a decrease in the width of the base metal heating zone. Instead, mechanical properties of welded joints are deteriorated because of an increase in the number of pores in the weld metal and the formation of inadmissible undercuts in the upper part of the weld in the area of transition from the weld to the base metal. On the example of Al–Mg–Mn alloy it is shown that such regularities are also typical not only for the thickness of 2.0 mm, but also observed during welding of specimens with the range of thicknesses of 4–8 mm. This allows using these results to predict indices of strength of the welded joint and weld metal for these thicknesses when the speed of plasma-arc welding at a variable polarity asymmetrical current is increased higher than the “peak” value. [ABSTRACT FROM AUTHOR]