|
|
| Terms of Use - Contact Us - Make a Donation |
|
Arc Welding Positions The types of welds, joints,
and welding positions used in manual-shielded metal arc welding are very similar to those
used in oxygas welding. Naturally, the techniques are somewhat different because of the
equipment involved is different.
Flat-Position Welding Earlier reexplained that
welding can be done in any position, but it is much simpler when done in the flat
position. In this position, the work is less tiring, welding speed is faster, the molten
puddle is not as likely to run, and better penetration can be achieved. Whenever possible,
try to position the work so you can weld in the flat position. In the flat position, the
face of the weld is approximately horizontal. Joint Type Butt joints
are the primary type of joints used in the flat position of welding; however,
flat-position welding can be made on just about any type of joint providing you can rotate
the section you are welding on to the appropriate position. Techniques that are useful in
making butt joints in the flat position, with and without the use of backing strips, are
described below. BUTT JOINTS WITHOUT
BACKING STRIPS.— A butt joint is used to join two plates having surfaces in about
the same plane. Several forms of butt joints are shown in figure 7-17. Plates up to 1/8 inch thick
can be welded in one pass with no special edge preparation. Plates from 1/8 to 3/16 inch
in thickness also can be welded with no special edge preparation by welding on both sides
of the joint. Tack welds should be used to
keep the plates aligned for welding. The electrode motion is the same as that used in
making a bead weld. In welding 1/4-inch plate or
heavier, you should prepare the edges of the plates by beveling or by J-, U-, or
V-grooving, whichever is the most applicable. You should use single or double bevels or
grooves when the specifications and/or the plate thickness requires it. The first bead is
deposited to seal the space between the two plates and to weld the root of the joint. This
bead or layer of weld metal must be thoroughly cleaned to remove all slag and dirt before
the second layer of metal is depos-ited. In making multipass welds, as
shown in figure 7-18, the second, third, and fourth layers of weld metal are made with a
weaving motion of the electrode. Clean each layer of metal before laying additional beads.
You may use one of the weaving motions shown in figure 7-19, depending upon the type of
joint and size of electrode.
In the weaving motion,
oscillate or move the elec-trode uniformly from side to side, with a slight hesitation at
the end of each oscillation. Incline the electrode 5 to 15 degrees in the direction of
welding as in bead weld-ing. When the weaving motion is
not done properly, undercutting could occur at the joint, as shown in figure 7-20.
Excessive welding speed also can cause undercut-ting and poor fusion at the edges of the
weld bead. BUTT JOINTS WITH BACKING
STRIPS.— Welding 3/16-inch plate or thicker requires backing strips to ensure
complete fusion in the weld root pass and to provide better control of the arc and the
weld metal. Prepare the edges of the plates in the same manner as required for welding
without backing strips.
When specified, place a seal
bead along the root of the joint. Bear in mind that many times
it will not always be possible to use a backing strip; therefore, the welder must be able
to run the root pass and get good penetration without the formation of icicles.
|
| Published
by SweetHaven Publishing Services Based upon a text provided by the U.S. Navy |
Copyright © 2001-2006 SweetHaven Publishing Services |
