Determination of parameters of mechanical pulse action on the weld pool for the metal structuring in automatic arc deposition welding

Abstract

The strength and other operational characteristics of the metal during arc deposition welding processes are determined by the presence of columnar crystals, the growth of which occurs as a result of metal overheating in the molten bath. To control the columnar crystals growth, a variety of methods are used, including pulse impacts on the weld pool or creating mechanical vibrations of the part during deposition welding. In the latter case, the periodic removal of the heat source from the point of the weld pool overheating prevents the growth of columnar crystallites and thus improves the weld metal structure. The developed engineering method for calculating the effective parameters of the mechanical vibrations of the weld pool during automatic deposition welding of cylindrical parts in CO2 is based on the theory of heat transfer at welding. It is shown that deposit welding on the mild steel St.3 with the Sv08G2C wire of the 1.2 mm diameter should be carried out with the 1...12 Hz vibration frequency at the amplitude equal to 1/2 of the deposition welding step. Experimental verification of various mode parameters showed that, compared to the welding performed without vibration of the weld pool, the weld bead width is increased by 16...23% in the deposited layer, there are no cracks, and its durability improved by 1.3...1.7 times. The improvement of mechanical properties of the deposited layer is due to grinding of metal grains exposed to the controlled vibrations of the part. At that, there are hardly any weld metal columnar structures, which are observed at conventional deposition welding.