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OERL1KON ELECTRODES (GT. BRITAIN) LTD. Kelvin Way,
Page 77
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Crawley, Sussex. L'OR welding mild steel, inexpensive trans.': formers (giving a.c. arcs) of low opencircuit voltage are perfectly acceptable. But for the successful use of low-hydrogen electrodes and most stainless steel types, which have special coatings, direct-current generators or rectifiers provide a more stable arc and smoother metal transfer than when the open circuit of a.c. transformers is increased. Apart from the question of cost —it is not unusual for a d.c. welding plant to cost twice as much as an a.c. transformer of equal capacity—the use of a d.c. power source introduces magnetic are blow which can sometimes be troublesome.
The Ocrlikon EFS.250 a.c. welding unit overcomes these problems because it operates at a frequency of 425 cycles per second_ This rise in frequency promotes better arc ignition. improved stability and a reduction in weld spatter, and also makes positional welding more easy. Welding output is regulated by coarse and fine control switches providing 35 settings between 15 and 255 amp.; open-circuit voltage is 75. The machine is mounted on a pair of robust, rubber-tyred wheels.
A wide range of arc-welding electrodes is produced by Oerlikon, the latest to be introduced being Ferrocord, Superzirkon, Ferricito and Supercito. These are iron-powder electrodes suitable for various applications.