Abstract
A paper of Rosenthal published in 1941 shows that the heat conducted to the electrode from the molten tip is 0.20 of the total arc heat V1, and so the heat delivered to the base metal is 0.65, 0.15 being the loss due to the radiation and convection of arc column. According to Rosenthal the above calculated result coincides well with the experimental data reported in 1938.
It is evident from the paper that the heat part 0.20 is not radiated from the electrode surface, and that as the temperature rise does not exist in a remote part beyond about 1cm (1″/4) from the elec-trode tip, there is no heat flow and consequently no heat loss due to conduction can be observedni such a part. The heat conducted from the tip as far as 1cm is absorbed usefully to preheat the electrode metal before the metal reaches the arc surface. In other words, the heat energy conducted from the molten tip by the thermodynamic motions of metal molecules is transported back to the electrode tip as the metal part which absorbed the energy moves to the tip with the melting speed of the electrode. So the loss is only 0.15 instead of 0.35.
In the experiment of 1938, the input arc power is calculated as V1, V and 1 being the effective values of arc voltage and current of a. c. respectively. But the wave from of arc voltage being nearly rectangular, so the power is 0.90 V1 and therefore the experimental data 0.65 becomes 0.72. The figure may get somewhat greater if the reduction of true power due to the instantenuous short circuits caused by irregular motions of molten tip metal is tanken into consideration, or if the input power is measured by a wattmeter or a watthourmeter. It is also remarkable that the base metal energy might be more incresed owing to the convection from the arc column, if the breadth of the base metal were greaterr than 12 mm and the protecting plate (forthermocouples) were uncovered as may be the case of practical welding.
