©
COPYRIGHT 1998 THE ESAB GROUP, INC. LESSON
II deposition
rates but minimum penetration. Alternating current is often used as a trailing
arc in tandem
arc applications. In this type of application, the leading DCEP arc provides
deep penetration,
and the closely trailing AC arc provides high deposition with a minimum of arc
blow. 2.6.5
Electrodes
- A variety of ferrous and nonferrous electrodes are
used in submerged arc
welding. They are usually solid electrodes refined with the appropriate
alloys at the steel mill,
and then shipped to electrode manufacturers where they are drawn down to a specific
diameter and packaged. There
is another type of sub arc electrode known as a composite
electrode, that is fabricated in the
same manner as a flux cored electrode. A chief advantage
of this type is that the alloying elements
can be added to the core of the electrode more cheaply
than a steel mill can produce those same alloys in a solid form. The electrodes
for SAW vary in
diameter from 1/16 inch to 1/4 inch with the larger diameters being the most
widely used. 2.6.6
Summary
- Submerged arc welding has some advantages over other
welding processes.
Since the radiance of the arc is blanketed by the loose flux, there is no
need for a protective
welding hood (although safety glasses are recommended), there is no spatter and
only a very minimal amount of fumes
escape from under the blanket. High welding currents,
quite commonly in the 300 to 1600 ampere
range, are used. These high currents, combined with
fast travel speeds, make SAW a high deposition process that is especially suitable
for applications
that require a series of repetitious welds. Some setups allow two or more
elec- trodes to
be fed simultaneously into the joint, further increasing the deposition rate and
speed. 2.6.6.1
Although SAW has these advantages,
it does have some limitations. The flux must be
deposited and collected for every welding pass. This requires additional
equipment and handling.
Also because of the loose flux, the process is limited to the flat and horizontal
positions. The equipment for
SAW is commonly quite bulky which limits its mobility, and
although the process works well on
thick materials, it usually is not satisfactory for thin gauge
material. The process requires
care in the operation. The amperages commonly used may
cause excessive heat buildup in the
base metal, that may result in distortion or brittleness.
