До розрахунку довжини вильоту електрода при механізованому зварюванні сталей у захисних газах

Abstract

Роботу присвячено визначенню довжини зон вильоту електрода, в яких нагрів електрода визначається власно нагрівом від струму та нагрівом від краплі. Це дозволяє з великою точністю визначати необхідне значення довжини вильоту електрода під час зварювального процесу для забезпечення його якості.

The work is devoted to determination of the zones of electrode extension, in which electrode heating is determined by heating from electric current and heating from the drop. Thermal processes in these sections of electrode extension are described by different equations. Point of “junction” of these solutions is located in some distance from the boundary of the electrode with the drop and is characterized by electrode preheating temperature and length of the part of electrode extension corresponding to this temperature. The presented calculation procedure is based on solution of the Fourier’s differential equation of heat conductivity with introduction of virtual limits and boundary conditions of the fourth kind. This is a problem with inner nonlinearity, as the thermophysical parameters depend on temperature. If the electrode preheating temperature is assigned in calculations, it will be exactly the mandatory additional condition that allows solving the problem of heat balance. Thus, after certain transformations, expressions were derived which allow calculation of temperature gradient in the first section of electrode extension and temperature gradient in a point with temperature that is equal to that of electrode preheating. Derived equations allow to determineon the length of electrode extension section that is adjacent to the drop, where an abrupt temperature rise begins, because of the heat coming from the drop. Given calculations allowed plotting a graph which make possible to determineon the portion of temperature gradient increment due to heat coming from the drop. A point with zero coordinate on abscissa axis corresponds to the boundary between the electrode and the drop. Having determined the length of electrode extension section adjacent to the drop, it is also possible to determine the full length of electrode extension. Thus, the described calculation procedure yields a precised value of length of the zone, in which electrode heating is determined by heating from passing current, and length of electrode zone, in which the main thermal processes are determined by heating from the drop. This enables studying the heat balance of the drop in a more detailed and accurate manner than before.