ON THE EFFECT OF PREHEATING CURRENT ON STRENGTH OF JOINTS DURING RESISTANCE PROJECTION WELDING
The studies established patterns of the effect of preheating current on the magnitude of axial travel of a movable electrode used to determine the degree of projection preheating and the beginning moment of increase in power from preheating to welding. It is proposed to use the magnitude of electrode travel as a criterionfor the formation of a high-quality joint in the process of resistance projection welding with programmed powercontrol. The obtained time dependencies of the pull-off force during testing of welded joints showed that at an optimal preheating current equal to 45 %...55 % of the welding current, a welded joint is formed that has consistently high mechanical properties. Dependencies of the fusion line width showed that an increase in the preheating current contributes to a more rapid formation of the fusion line at the welding stage.