Page 169 - Electromechanical Devices and Components Illustrated Sourcebook

Chapter 7 Heating 131

Arc Welding a separate rod. This process is very precise and is applicable
to almost any type of metal.
Probably the most common use for arc heating is electric
welding. This is a very common process that is used in all
types of manufactured products. There are many different Metal Inert Gas (MIG)
types of electric arc welding processes; however, there are
three that are the most common. Metal inert gas welding is similar to the TIG process, except
the tungsten electrode is replaced with a continuous feed wire,
as shown in Figure 7-14. The wire acts as both the electrode
Stick Rod and the filler material. Because the wire cannot carry particu-
larly high currents, MIG welding is generally relegated to
Figure 7-12 shows a stick rod welding operation. The elec-
general purpose applications that do not require critical weld
trode is connected to a power supply, either AC or DC,
strength.
depending on the type of electrode used. The electrode is a
steel wire with a hard flux cover. The arc produces extremely
high localized heating and melts both the electrode wire and
the base metal. The molten wire precipitates to the base metal
and solidifies. The hard flux cover is vaporized and forms a
cloud that protects the arc from inclusion of the atmosphere.
Core
Insulator
Copper Cup Shield Gas Orifice
Continuous Feed Wire Wire Tip
Welding Rod
Arc
Weld Material Shield Gas
Flux Cover
Wire Core
Shielding Cloud Base Metal
Slag Arc Figure 7-14 Metal Inert Gas Arc Welding (MIG)

Atomic-Hydrogen
Base Metal
One of the highest temperature arc heating processes is also
Figure 7-12 Stick Rod Welding
a welding application. The atomic-hydrogen cycle produces
base metal temperatures as high as 6000 F. An arc is formed
between two tungsten electrodes. Hydrogen is flowed
Tungsten Inert Gas (TIG) through the arc. As the hydrogen passes through the heat of
the arc, it disassociates itself into singular atoms and absorbs
Tungsten inert gas welding uses a tungsten electrode to a great deal of energy. When the hydrogen leaves the arc, it
precipitate the arc to the base metal, as shown in Figure 7-13. A recombines and releases the stored energy in the form of
flow of inert gas, usually argon, is flowed around the arc to heat. Figure 7-15 shows an atomic-hydrogen arc welding
prevent inclusion of the atmosphere. The filler is added from process.

Shielding Gas Orifice

Ceramic Cup Tungsten
Electrode Tungsten Electrodes
Filler Rod Arc Arc
Weld Material Inert Gas Weld Material Hydrogen
Shield

Base Metal Base Metal
Figure 7-13 Tungsten Inert Gas Arc Welding (TIG) Figure 7-15 Atomic-Hydrogen Arc Welding