Among many factors which affect the apparent specific gravity of deposited metal, the chemical composition of electrode-coating is an important one. In the present work, the author has studied on the composition of coating consisting of flux only for the simplification.
Using different kinds of flux and rods of extremely low carbon steel, many kinds of coated electrode were prepared. The single V butt joint of soft steel plates was made by hand welding, and the apparent specific gravity of the deposited metal was measured. From the result the following relations between the apparent specific gravity of deposited metal and the composition of coated flux were found.
(1) Silica in the flux generally increases the combustion of carbon in molten steels and decreases the apparent specific gravity of deposited metal, owing to the formation of blow holes.
(2) Calcium oxide is an important constituent in the flux acting probably as the stabilizer of electric arc.
(3) Charcoal powder in the flux has a tendency to increase blow holes in the deposited metal.
(4) Coexistence of silica and calcium fluoride in the flux causes to increase blow holes in the deposited metal, owing probably to the formation of gaseous silicon fluoride, SiF₄.
(5) The presence of a large amount of oxide of high melting point, such as Cr₂O₃, reduces the apparent specific gravity of deposited metal, owing to the formation of blow holes by the oxi-dation of carbon and also to the inclusion of slag which is difficult of separation.
(6) In the case of carbonate exist in the flux, the apparent specific gravity of deposited metal is not always large.
(7) Sodium compounds, for examples Na₂SiO, Na₂CO₃ and NaHCO₃, in the flux generally increase the apparent specific gravity of deposited metal, while the addition of a large. quantity of borax gives the inverse result.
(8). Addition of potassium ferrocyanide in the flux decreases the apparent specific gravity of deposited metal, owing to the formation of cyanogen.

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In this experiment the mild steel mother plate goes forward with constant speed. A flux coated electrode was hold vertically to the mother plate and was contineously lowered down in order to maintain the constant arc length. As a coating material aluminium oxide, graphite, silicon dioxide, lithium carbonate, magnetic iron oxide, magnesium carbonate, manganese dioxide, calcium carbonate, titanium oxide, strontium carbonate and barium carbonate were independently used under constant welding current.
The wiath, height and depth of each deposited metal Were measured. With a few exceptions the coating material which indicated higher arc voltage was preferable to lower one with regard to penetration and fluidity of deposite. These facts, however, were reversed under constant electric power of welding i. e. when the experiment was carried out under constant heat energy the fluidity and penetration of deposite gained from the electrode was coated with a compound of alkali or alkali earth metal was preferable.

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