ELECTRIC ARC WELDING

This method bears no relation to the one just considered, except that the
source of heat is the same in both cases. Arc welding makes use of the
flame produced by the voltaic arc in practically the same way that
oxy-acetylene welding uses the flame from the gases.

If the ends of two pieces of carbon through which a current of electricity
is flowing while they are in contact are separated from each other quite
slowly, a brilliant arc of flame is formed between them which consists
mainly of carbon vapor. The carbons are consumed by combination with the
oxygen in the air and through being turned to a gas under the intense heat.

The most intense action takes place at the center of the carbon which
carries the positive current and this is the point of greatest heat. The
temperature at this point in the arc is greater than can be produced by any
other means under human control.

An arc may be formed between pieces of metal, called electrodes, in the
same way as between carbon. The metallic arc is called a flaming arc and as
the metal of the electrode burns with the heat, it gives the flame a color
characteristic of the material being used. The metallic arc may be drawn
out to a much greater length than one formed between carbon electrodes.

Arc Welding is carried out by drawing a piece of carbon which is of
negative polarity away from the pieces of metal to be welded while the
metal is made positive in polarity. The negative wire is fastened to the
carbon electrode and the work is laid on a table made of cast or wrought
iron to which the positive wire is made fast. The direction of the flame is
then from the metal being welded to the carbon and the work is thus