Peculiarities of welding pool degassing at surface deposition of aluminium alloys with powder wire

Abstract

The article contains the analysis of the conventional methods of surface deposition of aluminium alloys. It was shown that at surface deposition of aluminium alloys interstices, arising at hydrogen bubbles formation in the weld pool lat the moment of its crystallization are the most probable defects. An additional source of hydrogen supply into the weld pool springs up at surface deposition of aluminium alloys-this is the powder electrode charge. So, a model of formation of gas bubbles with due regard to this factor was developed. Presence of various surface defects, like cavities, shears, and micro-cracks is a factor, promoting formation of gaseous hydrogen phase inside a drop of electrode metal. Further development of gas bubbles, entrapped into the weld pool goes on by their consolidation and hydrogen diffusion from the molten metal into gaseous section. Intensification of bubble degassing, both at the stage of molten metal drop and at the welding pool stage is the most efficient way. The process of degassing depends on the amount of hydrogen, introduced into the weld pool. Proposed was an analytical dependence of evaluation of the original hydrogen concentration in the weld pool upon the coefficient of powder wire filling and dimensions of the charge particles. Experimental research of the influence of the parameters of powder wire upon the porosity of deposited metal made it possible to determine an optimal range of charge granulation and the coefficient of powder wire filling, ensuring intensive degassing during the period of its existence in liquid state and reaching deposited metal with sufficient density