Flux can be satisfactorily improved by including Mn and Si in it as deoxidizing agents. But the deoxidation effects differ according to the different compositions of the solvents used. On different kinds of flux, experiments have been conducted in this connection under the following conditions : 1) When the flux containing charcoal powder with C as its major component has been compared with one containing ilmenite and dextrin ; 2) When only the solvent of CaO and A12O3 is esed ; and 3) When SiO2 or MnO2 is-added to the above solvent. The following are the results ascertained by such experiments : When C on one hand and Mn and Si on the other co-exist. the amounts of C and Mn in the mild steel arc welds go up and an avderse effect takes place ; ilmenite and organic substanece (dextrine) give a favorable effect on deoxidation ; and Mn and Si are effective deoxidation ; and Mn and Si are effective deoxidizers even when the CaO-A12O3 slag is basic. It has also been confirmed that, when SiO2 and MnO2 are added to the solvent containing deoxidation agent, there is a deteriorating trend in the quality of mild steel arc welds as the amount of such addition increases above a certain limit.
The efficiency values of the wedding arc (the ratio of heat absorbed by the base metal to the electrically supplied arc energy) were measured using 'a certain electrode (B-17 of the Robe Seikosho, the diameter of the core wire is 4mm) under v-arious'conditions : different kinds of current (a. c. and d. c., straight and reverse polarity) different welding currents (100A, 120A and 160A), different arc voltages obtained by maintaining different arc lengths. The results (Fig. 8 and Table 1) which are quite reasonable from the theory of arc phenomena, show that the efficiency value decreases as the arc voltage increases, yet it is independent of the current employed. Among the electrodes coated with calcium carbonate, barium carbonate, alumina and boric acid respectively, those which give higher arc voltage show lower efficiency values and it gives also lower efficency value for given electrode when the polarity of higher arc Voltage is used, e. i. BaCO3 coated electrode under straight polarity and Al2O3 coated electrodes under reverse polarity (Fig. 9) show low efficiency value.