The welding current equations of the stored energy type spot welder are obtained, in consideration of the exciting current of the welding transformer, from three differential equations. Then the measured constants of the practical circuit, and the assumed resistance values on the secondary side of the welding transformer which are approximate to the practical values, are applied in the equations. Thus several wave forms of the welding current are shown.
It is widely adopted in mechanical industries to heap up hard metals by arc welding when parts of machinery which are required to be errosion-resistible are produced or repaired ; but in case that these special electrodes can not be used because of economical considerations — especially to-day in Japan it is very difficult to obtain tbem, instead of them common mild steel electrodes may be used in these parts. For the purpose to study the properties of deposited mild steels to wear, the authors carried out the dry-slip-wear test in which 0.33%C steel was combined with deposited steels of (a) coated electrode (b) bare electrode (c) substitute high Mn electrode respectively. As the result of this test under various conditions, it was known that the wear-resistance of deposited mild steel differs from that of common C-steel containing the same contents of C as deposited mild steel, and that (a) is best and (c) (b) follow this. The wear of (a) is much than the same % C-steel under the conditions of Tearing Wear. Low resistance to wear of (b) and (c) is due to their brittle structure.
The weld metal cracks together with surface and inner blow-holes appeared as the result of quality changes in coatings and core rods. The viscosity increase of slag was supposed to be the cause of surface holes which vanished by decreasing acidic components (SiO2) in the coatings. This idea was also available to prevent the weld metal cracks, although the reason could not be illustrated. The blow-holes in weld metal were closely' associated to the fineness rather than the quality change of coatngs in this case, and severe inspection upon the grain size prevented their occurences. The core rods of poor quality could be detected dy crack tests about deposited metal using special testing specimens. Whole manufactory arrangements were improved to secure complete mixing of the flux, and the reli. abilities of electrodes were greatly advanced.