The effect of quantity of coating used only flux, on the terminal voltage, the apparent specific gravity of deposited metal, the nitrogen and the carbon contents in deposited metal was studied, and the following results were obtained. (1) As the quantity or thickness of coating increases, the terminal voltage which is necessary for the same welding current increases. (2) As the quantity of flux increases, the nitrogen content in deposited metal decreases. (3) The nitrogen content in deposited steel varies with composition of the coated flux. Using an electrode of low carbon steel rod coated with a large quantity of good flux, a deposited metal containing very low nitrogen content, 0.007-0.009%, was obtained. (4) As the quantity of flux increases, the carbon content in deposited steel increases at first and then tends to decrease, forming a maximum at a certain value. (5) In most cases of flux used, the apparent specific gravity of deposited steel increases with the increasing quantity of flux, the magnitude varying with the composition of flux.
The theoretical consideration on the results above described was given. The mechanism of the formation of blow holes in the deposited metal was discussed. The microstructures of deposited metals were throughly examined, and it was confirmed that the braunite or the eutectoid of iron and Fe
4N appears in iron containing more than about 0.1% N, and that the nitride needles in those more than about 0.02/ N.
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