©
COPYRIGHT 1998 THE ESAB GROUP, INC. LESSON
II 2) 1%
Thoriated Tungsten
(AWS EWTh-1)
Color Code: Yellow
Good current carrying capacity, easy
arc starting and provide a stable arc. Less susceptible
to contamination. Designed for DC applications of nonferrous materials.
3) 2%
Thoriated Tungsten
(AWS EWTh-2)
Color Code: Red
Longer life than 1% Thoriated electrodes.
Maintain the pointed end longer, used for light
gauge critical welds in aircraft work. Like 1%, designed for DC applications
for nonferrous
materials. 4) .5%
Thoriated Tungsten
(AWS EWTh-3)
Color Code: Blue Sometimes
called "striped" electrode because it has 1.0-2.0% Thoria inserted in a
wedge-shaped groove throughout its
length. Combines the good properties of pure and
thoriated electrodes. Can be used on either AC or DC applications.
5) Zirconia
Tungsten (AWS
EWZr) Color Code: Brown
Longer life than pure tungsten. Better
performance when welding with AC. Melts more easily
than thoriam-tungsten when forming rounded or tapered tungsten end. Ideal
for applications
where tungsten contamination must be minimized. 2.3.6
Summary
- Gas Tungsten Arc Welding is one of the major welding
processes today.
The quality of the welds produced and the ability to weld very thin metals
are the major features.
The weld metal quality is high since no flux is used, eliminating the problem
of slag inclusions
in the weld metal. It is used extensively in the aircraft and aerospace
industry, where high
quality welds are necessary and also for welding the more expensive metals where
the weld defects
become very costly. Metals as thin as .005" can be welded due to the ease
of controlling
the current. 2.3.6.1
The major disadvantages of the process
are that it is slower than welding with consumable
electrodes and is little used on thicknesses over 1/4" for this reason. Shielding
gas and tungsten electrode costs make
the process relatively expensive. 2.4
GAS METAL ARC WELDING
Gas Metal Arc Welding*
is an arc welding process that uses the heat of an electric
arc established
between a consumable metal electrode and the work to be welded. The electrode
is a bare metal wire that is transferred
across the arc and into the molten weld puddle. The
* Gas
Metal Arc Welding (GMAW) is the current technology approved by the American Welding
Society. Formerly
known as "MIG" (Metal Inert Gas) Welding.
