This system is used in repairing iron castings in a way which resembles soldering. A crack or cavity is filled up with drops of cast iron or cast steel which melt from a rod as shown in Fig. 262. This view shows the method of filling a blowhole cavity in the end of the cast-iron mill-roll R. The upper end of the roll (shown in cross section) is surrounded by a piece of pressed coke b enclosed in moulding sand c held in a sheet-iron casing d. Enclosing the whole upper end of the roll is a mass of coke k surrounded by a checker-work g of fire bricks. This body of coke smoulders, keeping the roll hot during welding. A rod of cast iron s is clamped to the positive lead p of a direct-current conductor, and is manipulated by the insulated handle h. The negative lead n of the circuit is attached to the roll at a convenient point.

Fig. 262. - Arrangement for Arc Welding.

The lower end of the rod s is melted away by the arc, and is de-posited in the cavity until the latter is filled.