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VIII. Techniques for Basic
Weld Joints
Arc Length, Gas Cup Size, and
Electrode Extension
As a rule of thumb, the arc length is normally one electrode
diameter as seen in Figure 8.1. This would hold true when AC
welding with a balled end on the electrode. When welding
with direct current using a pointed electrode, the arc length
may be considerably less than the electrode diameter. Torches
held in a fixed position allow for holding a closer arc than for
manually held torches.
3
2
4
°
90
1
°
10-15
4
5
6
°
10-25
5
6
ELECTRODE
1/16 in
WO
R
K
3/16 in
Bottom View Of Gas Cup
Figure 8.1
Illustration shows the relationship between electrode diameter
and arc length.
Figure 8.2
Gas cup size and torch positions. 1-Workpiece, 2-Work Clamp,
3-Torch, 4-Filler Rod (If Applicable), 5-Gas Cup, 6-Tungsten Electrode.
The inside diameter of the gas cup should be at least three
times the tungsten diameter to provide adequate shielding
gas coverage. For example, if the tungsten is 1/16" in diameter,
the gas cup should be a minimum of 3/16" diameter.
Figure 8.2 is an example of gas cup size and torch position.
GAS CUP
Tungsten extension is the distance the tungsten extends out
beyond the gas cup of the torch. Electrode extension may
vary from flush with the gas cup to no more than the inside
diameter of the gas cup. The longer the extension the more
likely it will accidentally contact the weld pool, filler rod being
fed in by the welder, or touch the side of a tight joint. A general
rule would be to start with an extension of one electrode
diameter. Joints that make the root of the weld hard to reach
will require additional extension.
ELECTRODE
WORK
Figure 8.3
Resting the gas cup against the work in preparation for a high-
frequency start.
Manual Welding Techniques
Making the Stringer Bead
The torch movement used during manual welding is
illustrated in Figure 8.4. Once the arc is started, the electrode
is held in place until the desired weld pool is established. The
torch is then held at a 75˚ angle from the horizontal as shown
in the illustration and is progressively moved along the joint.
When filler metal is used, it is added to the leading edge of
the pool.
Torch Position for Arc Starting
with High Frequency
The torch position shown in Figure 8.3 illustrates the recom-
mended method of starting the arc with high frequency when
the torch is held manually. In this way the operator can posi-
tion the torch in the joint area and after lowering the welding
hood, close the contactor switch and initiate the arc. By resting
the gas cup on the base metal there is little danger of touching
the electrode to the work. After the arc is initiated, the torch
can be raised to the proper angle for welding.
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Tungsten Without Filler Rod
°
75
Welding direction
Form pool
Tilt torch
Move torch to front
of pool. Repeat process.
Tungsten With Filler Rod
°
75
°
15
Welding direction
Form pool
Tilt torch
Add filler metal
Remove rod
Move torch to front
of pool. Repeat process.
Figure 8.4
Torch movement during welding.
The torch and filler rod must be moved progressively and
smoothly so the weld pool, the hot filler rod end, and the
solidifying weld are not exposed to air that will contaminate
the weld metal area or heat affected zone. Generally a large
shielding gas envelope will prevent exposure to air.
The filler rod is usually held at about a 15˚ angle to the surface
of the work and slowly fed into the molten pool. Or it can be
dipped in and withdrawn from the weld pool in a repetitive
manner to control the amount of filler rod added. During
welding, the hot end of the filler rod must not be removed
from the protection of the inert gas shield. When the arc is
turned off, the postflow of shielding gas should not only
shield the solidifying weld pool but the electrode and the hot
end of the filler rod.
90˚
70˚
Butt Weld and Stringer Bead
Torch and Rod Position
When welding a butt joint, be sure to center the weld pool on
the adjoining edges. When finishing a butt weld, the torch
angle may be decreased to aid in filling the crater. Add
enough filler metal to avoid an unfilled crater.
20˚
Figure 8.5
Welding the butt weld and stringer bead.
Cracks often begin in a crater and continue through the bead.
A foot operated amperage control will aid in the finishing of a
bead as amperage can be lowered to decrease pool size as
filler metal is added.
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Lap Joint
Torch and Rod Position
Having established an arc, the pool is formed so that the edge
of the overlapping piece and the flat surface of the second
piece flow together. Since the edge will become molten
before the flat surface, the torch angle is important. The edge
will also tend to burn back or undercut. This can be controlled
by dipping the filler rod next to the edge as it tries to melt
away. Enough filler metal must be added to fill the joint as
shown in the lap joint illustration. Finish the end of the weld
the same as before by filling the crater.
20˚
70˚
10˚
T-Joint
Torch and Rod Position
A similar situation exists with the T-joint as with the lap joint.
An edge and a flat surface are to be joined together. The edge
again will heat up and melt sooner. The torch angle illustrated
will direct more heat onto the flat surface. The electrode may
need to be extended further beyond the cup than in the previous
butt and lap welds in order to hold a short arc. The filler rod
should be dipped so it is deposited where the edge is melting
away. Correct torch angle and placement of filler rod should
avoid undercutting. Again, the crater should be filled to avoid
excessive concavity.
20˚
Figure 8.6
Welding the lap joint.
40˚
Corner Joint
Torch and Rod Position
The correct torch and filler rod positions are illustrated for the
corner joint. Both edges of the adjoining pieces should be
melted and the pool kept on the joint centerline. When adding
filler metal, sufficient deposit is necessary to create a convex
bead. A flat bead or concave deposit will result in a throat
thickness less than the metal thickness. On thin materials,
this joint design lends itself to autogenous welding or fusions
welding without the addition of filler rod. Good fit-up is
required for autogenous welding.
70˚
20˚
30˚
Figure 8.7
Welding the T-joint.
90˚
70˚
20˚
Figure 8.8
Welding the corner joint.
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Techniques for Out-of-Position
Weld Joints
During the welding process, all action is centered in the weld
pool. The weld pool is the point at which fusion and penetration
occur. With practice controlling the pool becomes quite easy
while welding in the flat position. Eventually as additional
experience is acquired, welding out-of-position will be much
easier for the welder. Controlling the weld pool and penetration
is the prime concern for all positions of welding.
Vertical down welding makes use of both surface tension and
arc force to hold the molten weld pool in the joint. Mastery of
the vertical down technique is useful when welding on thin
material. Practicing the vertical up and down techniques on a
flat sheet or plate will greatly assist the welder who desires to
move on to pipe welding because nearly all pipe beads are
accomplished with the same techniques. However, vertical
down is rarely used when TIG welding thicker sections of
plate or pipe.
Welding in the Overhead Position
There are many variables to take into consideration in out-of-
position welding, such as amperage, travel speed, tungsten type
and torch position. Volumes could be devoted to this subject
alone. Therefore, we will try to provide a few tips and make a
few general statements regarding out-of-position weld joints.
Welding in the Vertical Position
Figure 8.10
Welding in the overhead position.
Welding in the overhead position is thought by most welders
to be the most difficult of all positions. The welder who can
consistently produce high quality overhead welds is much
sought after by industry.
As with vertical welding techniques, gravity is the enemy of
overhead welding. Unlike the vertical position, overhead
welding cannot rely on the building of shelves on which to
place consecutive beads. Instead, it relies on surface tension
of the pool, arc force, and a combination of lower amperage
and higher travel speeds.
Figure 8.9
Welding in the vertical position.
Gravity is the enemy of all out-of-position welding. In the vertical
position, both up and down, gravity will try to pull the molten
weld pool downward and out of the joint. A good welder
however, will learn to use gravity to his or her advantage.
One of the techniques used in vertical welds that can be utilized
in the overhead position is extending the tungsten electrode
and resting the gas cup against one or both sides of the joint
to be welded. This procedure is usually used only in groove
welds and some fillet welds. When the welder is putting in fill
passes he can extend a few fingers on either the torch hand
or the filler rod hand and actually rest them on the plate to be
welded. This will help steady the hand.
In vertical up welding, the weld is begun at the bottom of the
joint with the filler metal being added from above. Attempt to
establish a “shelf” with each dab of filler metal for the next
filler metal addition to rest on. If the joint is wide, work back
and forth across the joint to establish this shelf.
If the joint to be welded is a V-groove, the tungsten electrode
extension can be increased, and the gas cup can be rested
against the edges of the joint and maneuvered back and forth.
This will greatly assist in providing a steady hand, although
this technique makes it difficult to actually see the weld pool.
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Techniques for Pipe Welding
Pipe welding with the GTAW process requires a great deal
of skill, and should only be attempted when the welder has
mastered the principles of GTAW welding on plate.
GTAW produces the highest quality pipe weld of all the arc
processes and with a minimum of distortion.
As with our previous segments on out-of-position welding,
the different combinations of metals, positions, tungstens,
gases and so on make this a subject to which an entire book,
or even library, could be devoted. Therefore this segment will
be limited to a few helpful hints and tips.
Consumable inserts are items often used in pipe welding.
Consumable inserts are composed of the same type of material
that is being welded and are used to keep root passes uniform.
The consumable insert is melted into the root pass and
becomes an integral part of the weld bead.
Because most pipe joints require a gapped joint, protection of
the weld bead in the form of gas coverage inside the pipe is
necessary. This coverage can be accomplished by covering
the ends of the pipe with pipe caps made for that purpose, or
by simply covering the ends with paper and tape, and then
inserting a shielding gas hose.
GTAW pipe welding also requires a special treatment of the
tungsten electrode tip. A common electrode would be a 1.5%
lanthanated or 2% thoriated tungsten. Once the tip is ground
to a point, the very tip is flattened to a width of about .020.
This small flat spot helps to distribute the arc evenly at the
joint edges.
One of the most popular techniques for GTAW welding of pipe
joints is the walking-the-cup technique. This technique utilizes
a specific manner of manipulating the torch, along with a
series of increasingly larger gas cups to produce consistently
good welds with a minimum of fatigue.
Figures 8.11 and 8.12
Demonstrations of two common methods of
grasping the torch for pipe welding. There is no single “correct” method
of doing this and each welder is encouraged to experiment with several
different methods until one is found that is most comfortable, and results
in satisfactory welds.
Heat input to the overhead weld pool is extremely important.
Generally speaking, the heat input of an overhead joint would
be less than the amount used for a comparable weld in the
horizontal or flat position. This keeps the pool size small and
thereby prevents sagging or the weld pool from falling out of
the joint.
The possibility of falling molten metal makes the need of
proper protective clothing and equipment absolutely essential.
Never attempt to make this type of weld without all safety
gear in place.
No doubt the overhead position is difficult. It is extremely
fatiguing for the welder to accomplish, making it a slow
process and increasing the time needed to accomplish the
job. This is one of the major reasons industrial use of
overhead welding is kept to a minimum.
Figure 8.13
Demonstration of how the torch and filler rod are held to
accomplish the “walking-the-cup” method of pipe welding.
The two sections of pipe to be welded should be gapped
slightly less than the diameter of the filler rod to be used. The
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