Chapter 4
Chapter 4
Shielded Metal Arc
Welding of Plate
OBJECTIVES
After completing this chapter, the student should be able to
set the welding amperage correctly.
explain the effect of changing arc length on a weld.
control weld bead contour during welding by using the proper
weave pattern.
demonstrate an ability to control undercut, overlap, porosity, and
slag inclusions when welding.
explain the effect of electrode angle on a weld.
KEY TERMS
amperage range
arc length
cellulose-based fluxes
chill plate
electrode angle
lap joint
mineral-based fluxes
rutile-based fluxes
square butt joint
stringer bead
tee joint
weave pattern
INTRODUCTION
Shielded metal arc welding (SMAW), or stick welding, is the most often
used method of joining plate. This method provides a high temperature and
concentration of heat, which allow a small molten weld pool to be built up
quickly. The addition of filler metal from the electrode adds reinforcement
and increases the strength of the weld. SMAW can be performed on almost
any type of metal 1/8 in. (3 mm) thick or thicker. A minimum of equipment
is required, and it can be portable.
High-quality welds can be consistently produced on almost any type of
metal and in any position. The quality of the welds produced depends
largely upon the skill of the welder. Developing the necessary skill level
requires practice. However, practicing the welds repeatedly without
changing techniques will not aid in developing the required skills. Each
time a weld is completed it should be evaluated, and then a change
should be made in the technique to improve the next weld.
65
66
Section 2
Shielded Metal Arc Welding
1"
(25 mm)
3"
4
(19 mm)
Welding Principles and Applications
MATERIAL:
1/4" x 6" MILD STEEL PLATE
PROCESS:
SMAW ARC STRIKING
NUMBER:
EXPERIMENT 4–1
DRAWN BY:
JACK CHIPMAN
F IGURE 4-1 Striking an arc.
PRACTICE 4-1
Shielded Metal Arc Welding Safety
Using a welding work station, welding machine, welding electrodes, welding helmet, eye and ear protection,
welding gloves, proper work clothing, and any special protective clothing that may be required, demonstrate, to your
instructor and other students, the safe way to prepare yourself and the welding work station for welding. Include in
your demonstration appropriate references to burn protection, eye and ear protection, material specification data
sheets, ventilation, electrical safety, general work clothing,
special protective clothing, and area clean-up.
Complete a copy of the “Student Welding Report” listed
in Appendix I or provided by your instructor. ◆
EXPERIMENT 4-1
Striking the Arc
Using a properly set up and adjusted arc welding
machine, the proper safety protection, as demonstrated in
Practice 4-1, E6011 welding electrodes having a 1/8-in.
(3-mm) diameter, and one piece of mild steel plate, 1/4-in.
(6-mm) thick, you will practice striking an arc, Figure 4-1.
With the electrode held over the plate, lower your helmet. Scratch the electrode across the plate (like striking a
large match), Figure 4-2. As the arc is established, slightly
raise the electrode to the desired arc length. Hold the arc
in one place until the molten weld pool builds to the
F IGURE 4-2 Striking the arc. Photo courtesy of Larry Jeffus.
desired size. Slowly lower the electrode as it burns off and
move it forward to start the bead.
If the electrode sticks to the plate, quickly squeeze the
electrode holder lever to release the electrode. Break the
electrode free by bending it back and forth a few times. Do
Chapter 4
Shielded Metal Arc Welding of Plate
67
BROKEN FLUX
ELECTRODE
WORKPIECE
ARC FORCED TO
THE BACKSIDE
F IGURE 4-3 If the flux is broken off the end completely or
on one side, the arc can be erratic or forced to the side.
F IGURE 4-4 Striking the arc on a spot.
Courtesy of Larry Jeffus.
not touch the electrode without gloves, because it will still
be hot. If the flux breaks away from the end of the electrode, throw out the electrode because restarting the arc
will be very difficult, Figure 4-3.
Break the arc by rapidly raising the electrode after completing a 1-in. (25-mm) weld bead. Restart the arc as you
did before, and make another short weld. Repeat this
process until you can easily start the arc each time. Turn
off the welding machine and clean up your work area
when you are finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
VERY LITTLE SHIELDING
GAS COVERAGE
SMALL
WELD
POOL
WELD BEAD
HIGH WITH
LITTLE FUSION
F IGURE 4-5 Welding with the amperage set too low.
Courtesy of Larry Jeffus.
EXPERIMENT 4-2
Striking the Arc Accurately
Using the same materials and setup as described in
Experiment 4-1, you will start the arc at a specific spot in
order to prevent damage to the surrounding plate.
Hold the electrode over the desired starting point. After
lowering your helmet, swiftly bounce the electrode
against the plate, Figure 4-4. A lot of practice is required
to develop the speed and skill needed to prevent the electrode from sticking to the plate.
A more accurate method of starting the arc involves
holding the electrode steady by resting it on your free hand
like a pool cue. The electrode is rapidly pushed forward so
that it strikes the metal exactly where it should. This is an
excellent method of striking an arc. Striking an arc in an
incorrect spot may cause damage to the base metal.
Electrode
Practice starting the arc until you can start it within
1/4 in. (6 mm) of the desired location. Turn off the welding machine and clean up your work area when you are
finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
Effect of Too High or Too Low
Current Settings
Each welding electrode must be operated in a particular
current (amperage) range, Table 4-1. Welding with the current set too low results in poor fusion and poor arc stability,
Figure 4-5. The weld may have slag or gas inclusions
because the molten weld pool was not fluid long enough for
the flux to react. Little or no penetration of the weld into the
Classification
Size
E6010
E6011
E6012
E6013
E7016
E7018
3/32 in. (2.4 mm)
1/8 in. (3.2 mm)
5/32 in. (4 mm)
40–80
70–130
110–165
50–70
85–125
130–160
40–90
75–130
120–200
40–85
70–120
130–160
75–105
100–150
140–190
70–110
90–165
125–220
T ABLE 4-1 Welding amperage range.
68
Section 2
Shielded Metal Arc Welding
ELECTRODE BECOMES
DISCOLORED DUE TO
EXCESSIVE HEAT
SPATTER
EXCESSIVE GAS
(SMOKE)
LARGE MOLTEN WELD
POOL WITH LITTLE BUILD UP
F IGURE 4-6 Welding with too high an amperage.
F IGURE 4-7 Hard weld spatter fused to base metal.
Courtesy of Larry Jeffus.
Courtesy of Larry Jeffus.
base plate may also be evident. With the current set too low,
the arc length is very short. A very short arc length results in
frequent shortening and sticking of the electrode.
The core wire of the welding electrode is limited in the
amount of current it can carry. As the current is increased,
the wire heats up because of electrical resistance. This preheating of the wire causes some of the chemicals in the covering to be burned out too early, Figure 4-6. The loss of the
proper balance of elements causes poor arc stability. This
condition leads to spatter, porosity, and slag inclusions.
An increase in the amount of spatter is also caused by
a longer arc. The weld bead made at a high amperage setting is wide and flat with deep penetration. The spatter is
excessive and is mostly hard. The spatter is called hard
because it fuses to the base plate and is difficult to remove,
Figure 4-7. The electrode covering is discolored more
than 1/8 in. (3 mm) to 1/4 in. (6 mm) from the end of the
electrode. Extremely high settings may also cause the
electrode to discolor, crack, glow red, or burn.
(A) WELD BEFORE CLEANING
EXPERIMENT 4-3
Effects of Amperage Changes
on a Weld Bead
For this experiment, you will need an arc welding
machine, welding gloves, safety glasses, welding helmet,
appropriate clothing, E6011 welding electrodes having a
1/8-in. (3-mm) diameter, and one piece of mild steel plate,
1/4 in. (6 mm) to 1/2 in. (13 mm) thick. You will observe
what happens to the weld bead when the amperage settings are raised and lowered.
Starting with the machine set at approximately 90 A
AC or DCRP, strike an arc and make a weld 1 in. (25 mm)
long. Break the arc. Raise the current setting by 10 A,
strike an arc, and make another weld 1 in. (25 mm) long.
Repeat this procedure until the machine amperage is set
at the maximum value.
Replace the electrode and reset the machine to 90 A.
Make a weld 1 in. (25 mm) long. Stop and lower the current setting by 10 A. Repeat this procedure until the
machine amperage is set at a minimum value.
(B) WELD AFTER CLEANING
F IGURE 4-8 Weld before cleaning and after cleaning.
Courtesy of Larry Jeffus.
Cool and chip the plate, comparing the different
welds for width, buildup, molten weld pool size, spatter,
slag removal, and penetration, Figure 4-8 (A) and (B). In
addition, compare the electrode stubs. Turn off the
welding machine and clean up your work area when you
are finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
Chapter 4
/ / / C AU T I O N \ \ \
Do not change the current settings during welding. A change in the setting may cause arcing
inside the machine, resulting in damage to the
machine.
Electrode Size and Heat
The selection of the correct size of welding electrode
for a weld is determined by the skill of the welder, the
thickness of the metal to be welded, and the size of the
metal. Using small diameter electrodes requires less skill
than using large diameter electrodes. The deposition rate,
or the rate that weld metal is added to the weld, is slower
when small diameter electrodes are used. Small diameter
electrodes will make acceptable welds on thick plate, but
more time is required to make the weld.
Large diameter electrodes may overheat the metal if they
are used with thin or small pieces of metal. To determine if
a weld is too hot, watch the shape of the trailing edge of the
molten weld pool, Figure 4-9. Rounded ripples indicate the
weld is cooling uniformly and that the heat is not excessive.
If the ripples are pointed, the weld is cooling too slowly
because of excessive heat. Extreme overheating can cause a
burnthrough, which is hard to repair.
To correct an overheating problem, a welder can turn
down the amperage, use a shorter arc, travel at a faster
rate, use a chill plate (a large piece of metal used to absorb
excessive heat), or use a smaller electrode at a lower current setting.
EXPERIMENT 4-4
Excessive Heat
Using a properly set up and adjusted arc welding
machine, the proper safety protection, E6011 welding
electrodes having a 1/8-in. (3-mm) diameter, and three
pieces of mild steel plate, 1/8 in. (3 mm), 3/16 in. (4.8
mm), and 1/4 in. (6 mm) thick, you will observe the
effects of overheating on the weld. Make a stringer weld
AMOUNT OF HEAT
DIRECTED AT WELD
Shielded Metal Arc Welding of Plate
69
on each of the three plates using the same amperage setting, travel rate, and arc length for each weld. Cool and
chip the welds. Then compare the weld beads for width,
reinforcement, and appearance.
Using the same amperage settings, make additional
welds on the 1/8-in. (3-mm) and 3/16-in. (4.8-mm)
plates. Vary the arc lengths and travel speeds for these
welds. Cool and chip each weld and compare the beads for
width, reinforcement, and appearance. Make additional
welds on the 1/8-in. (3-mm) and 3/16-in. (4.8-mm)
plates, using the same arc length and travel speed as in the
earlier part of this experiment, but at a lower amperage
setting. Cool and chip the welds and compare the beads
for width, reinforcement, and appearance.
The plates should be cooled between each weld so that
the heat from the previous weld does not affect the test
results. Turn off the welding machine and clean up your
work area when you are finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
Arc Length
The arc length is the distance the arc must jump from
the end of the electrode to the plate or weld pool surface.
As the weld progresses, the electrode becomes shorter as
it is consumed. To maintain a constant arc length, the
electrode must be lowered continuously. Maintaining a
constant arc length is important, as too great a change in
the arc length will adversely affect the weld.
As the arc length is shortened, metal transferring
across the gap may short out the electrode, causing it to
stick to the plate. The weld that results is narrow and has
a high buildup, Figure 4-10.
Long arc lengths produce more spatter because the metal
being transferred may drop outside of the molten weld pool.
The weld is wider and has little buildup, Figure 4-11.
There is a narrow range for the arc length in which it is
stable, metal transfer is smooth, and the bead shape is controlled. Factors affecting the length are the type of electrode, joint design, metal thickness, and current setting.
WELD POOL
HIGH NARROW BEAD WITH
A HEAVY SLAG COVER
TOO LOW
CORRECT
TOO HOT
F IGURE 4-9 The effect on the shape of the molten weld
pool caused by the heat input.
F IGURE 4-10 Welding with too short an arc length.
Courtesy of Larry Jeffus.
70
Section 2
Shielded Metal Arc Welding
ELECTRODE
ARC
ROOT OPENING
F IGURE 4-11 Welding with too long an arc length.
Courtesy of Larry Jeffus.
F IGURE 4-13 The arc may jump to the closest metal,
reducing root penetration.
See SMAW video series.
EXPERIMENT 4-5
Effect of Changing the Arc Length
on a Weld
ELECTRODE FLUX
TOUCHES BASE METAL
F IGURE 4-12 Welding with a drag technique.
Courtesy of Larry Jeffus.
Some welding electrodes, such as E7024, have a thick
flux covering. The rate at which the covering melts is slow
enough to permit the electrode coating to be rested
against the plate. The arc burns back inside the covering
as the electrode is dragged along touching the joint,
Figure 4-12. For this type of welding electrode, the arc
length is maintained by the electrode covering.
An arc will jump to the closest metal conductor. On
joints that are deep or narrow, the arc is pulled to one side
and not to the root, Figure 4-13. As a result, the root
fusion is reduced or may be nonexistent, thus causing a
poor weld. If a very short arc is used, the arc is forced into
the root for better fusion.
Because shorter arcs produce less heat and penetration,
they are best suited for use on thin metal or thin-to-thick
metal joints. Using this technique, metal as thin as 16 gauge
can be arc welded easily. Higher amperage settings are
required to maintain a short arc that gives good fusion with
a minimum of slag inclusions. The higher settings, however,
must be within the amperage range for the specific electrode.
Finding the correct arc length often requires some trial
and adjustment. Most welding jobs require an arc length
of 1/8 in. (3 mm) to 3/8 in. (10 mm), but this distance
varies. It may be necessary to change the arc length when
welding to adjust for varying welding conditions.
Using an arc welding machine, welding gloves, safety
glasses, welding helmet, appropriate clothing, E6011
welding electrodes having a 1/8-in. (3-mm) diameter, and
one piece of mild steel plate, 1/4 in. (6 mm) to 1/2 in. (13
mm) thick, you will observe the effect of changing the arc
length on a weld.
Starting with the welding machine set at approximately
90 A AC or DCRP, strike an arc and make a weld 1 in.
(25 mm) long. Continue welding while slowly increasing
the arc length until the arc is broken. Restart the arc and
make another weld 1 in. (25 mm) long. Welding should
again be continued while slowly shortening the arc length
until the arc stops. Quickly break the electrode free from
the plate, or release the electrode by squeezing the lever on
the electrode holder.
Cool and chip both welds. Compare both welding
beads for width, reinforcement, uniformity, spatter, and
appearance. Turn off the welding machine and clean up
your work area when you are finished welding.
Complete a copy of the “Student Welding Report” listed
in Appendix I or provided by your instructor. ◆
Electrode Angle
The electrode angle is measured from the electrode
to the surface of the metal. The term used to identify the
electrode angle is affected by the direction of travel,
generally leading or trailing, Figure 4-14. The relative
angle is important because there is a jetting force blowing the metal and flux from the end of the electrode to
the plate.
Leading Angle A leading electrode angle pushes
molten metal and slag ahead of the weld, Figure 4-15.
When welding in the flat position, caution must be taken
to prevent cold lap and slag inclusions. The solid metal
ahead of the weld cools and solidifies the molten filler
metal and slag before they can melt the solid metal. This
rapid cooling prevents the metals from fusing together,
Chapter 4
Shielded Metal Arc Welding of Plate
71
DIRECTION OF TRAVEL
TRAILING
ANGLE
RIGHT
ANGLE
LEADING
ANGLE
F IGURE 4-14 Direction of travel and electrode angle.
DIRECTION OF TRAVEL
ELECTRODE
WELD
BEAD
AREA AHEAD
OF THE MOLTEN
WELD POOL
LIMITED DEPTH OF PENETRATION
MOLTEN WELD POOL
F IGURE 4-15 Leading, lag or pushing electrode angle.
FIGURE 4-17 Metal being melted ahead of the molten weld
pool helps to ensure good weld fusion. Courtesy of Larry Jeffus.
■
SLAG
■
Use a penetrating-type electrode that causes little
buildup.
Move the arc back and forth across the molten
weld pool to fuse both edges.
A leading angle can be used to minimize penetration
or to help hold molten metal in place for vertical welds,
Figure 4-18.
NO FUSION
SLAG TRAPPED
UNDER WELD
F IGURE 4-16 Some electrodes, such as E7018, may not
remove the deposits ahead of the molten weld pool, resulting in discontinuities within the weld.
Figure 4-16. As the weld passes over this area, heat from
the arc may not melt it. As a result, some cold lap and
slag inclusions are left.
The following are suggestions for preventing cold lap
and slag inclusions:
■ Use as little leading angle as possible.
■ Ensure that the arc melts the base metal completely,
Figure 4-17.
Trailing Angle A trailing electrode angle pushes the
molten metal away from the leading edge of the molten
weld pool toward the back where it solidifies, Figure 4-19.
As the molten metal is forced away from the bottom of the
weld, the arc melts more of the base metal, which results in
deeper penetration. The molten metal pushed to the back of
the weld solidifies and forms reinforcement for the weld,
Figure 4-20.
EXPERIMENT 4-6
Effect of Changing the Electrode
Angle on a Weld
Using a properly set up and adjusted arc welding
machine, the proper safety protection, E6011 welding
72
Section 2
Shielded Metal Arc Welding
A
B
C
A
B
C
SECTION A-A
(A)
SECTION B-B
(B)
SECTION C-C
(C)
F IGURE 4-18 Effect of a leading angle on weld bead buildup, width, and penetration. As the angle increases toward the vertical position (C), penetration increases.
WELDING DIRECTION
F IGURE 4-19 Trailing electrode angle.
A
B
C
A
B
C
SECTION A-A
(A)
SECTION B-B
(B)
SECTION C-C
(C)
F IGURE 4-20 Effect of a trailing angle on weld bead buildup, width, and penetration. Section A-A shows more weld buildup
due to a greater angle of the electrode.
Chapter 4
electrodes having a 1/8-in. (3-mm) diameter, and one
piece of mild steel plate, 1/4 in. (6 mm) to 1/2 in. (13 mm)
thick, you will observe the effect of changes in the electrode angle on a weld.
Start welding with a sharp trailing angle. Make a weld
about 1 in. (25 mm) long. Closely observe the molten weld
pool at the points shown in Figure 4-21. Slowly increase the
electrode angle and continue to observe the weld.
When you reach a 90° electrode angle, make a weld
about 1 in. (25 mm) long. Observe the parts of the weld
molten weld pool as shown in Figure 4-21.
Continue welding and change the electrode angle to a
sharp leading angle. Observe the weld molten weld pool
at the points shown in Figure 4-22.
During this experiment, you must maintain a constant
arc length, travel speed, and weave pattern if the observations and results are to be accurate.
Cool and chip the weld. Compare the weld bead for
uniformity in width, reinforcement, and appearance.
Turn off the welding machine and clean up your work
area when you are finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
WELDING DIRECTION
ARC FORCE
Shielded Metal Arc Welding of Plate
73
Electrode Manipulation
The movement or weaving of the welding electrode can
control the following characteristics of the weld bead:
penetration, buildup, width, porosity, undercut, overlap,
and slag inclusions. The exact weave pattern for each
weld is often the personal choice of the welder. However,
some patterns are especially helpful for specific welding
situations. The pattern selected for a flat (1G) butt joint is
not as critical as is the pattern selection for other joints
and other positions.
Many weave patterns are available for the welder to
use. Figure 4-23 shows ten different patterns that can be
used for most welding conditions.
The circular pattern is often used for flat position welds
on butt, tee, outside corner joints, and for buildup or surfacing applications. The circle can be made wider or longer
to change the bead width or penetration, Figure 4-24.
The “C” and square patterns are both good for most 1G
(flat) welds, but can also be used for vertical (3G) positions. These patterns can also be used if there is a large gap
to be filled when both pieces of metal are nearly the same
size and thickness.
The “J” pattern works well on flat (1F) lap joints, all
vertical (3G) joints, and horizontal (2G) butt and lap (2F)
welds. This pattern allows the heat to be concentrated on
the thicker plate, Figure 4-25. It also allows the reinforcement to be built up on the metal deposited during
the first part of the pattern. As a result, a uniform bead
contour is maintained during out-of-position welds.
WELD BEAD
MOLTEN WELD POOL
V
UPSIDE DOWN V
F IGURE 4-21 Welding with a trailing angle.
Courtesy of Larry Jeffus.
See SMAW video series.
CIRCULAR
C
SQUARE
J
WELDING DIRECTION
ARC FORCE
ZIGZAG
T
STRAIGHT STEPPED
FIGURE 8
MOLTEN WELD POOL
FIGURE 4-22 Welding with a leading angle.
Courtesy of Larry Jeffus.
F IGURE 4-23 Weave patterns.
74
Section 2
Shielded Metal Arc Welding
WEAVE PATTERN
THIS WEAVE PATTERN RESULTS
IN A NARROW BEAD WITH
DEEP PENETRATION.
THIS WEAVE PATTERN RESULTS
IN A WIDE BEAD WITH
SHALLOW PENETRATION.
F IGURE 4-24 Changing the weave pattern width to
change the weld bead characteristics.
VERTICAL FILLET WELD
F IGURE 4-26 “T” pattern.
SHELF SUPPORTS MOLTEN WELD POOL, MAKING
THE SHAPE OF THE WELD BEAD UNIFORM
STEPPING
ELECTRODE
BACK AND FORTH
MOLTEN WELD
POOL
LESS HEAT CAN CONDUCT
INTO THE EDGE THAN INTO
THE BASE PLATE
F IGURE 4-25 The “J” pattern allows the heat to be concentrated on the thicker plate.
The “T” pattern works well with fillet welds in the vertical (3F) and overhead (4F) positions, Figure 4-26. It
also can be used for deep groove welds for the hot pass.
The top of the “T” can be used to fill in the toe of the weld
to prevent undercutting.
The straight step pattern can be used for stringer beads,
root pass welds, and multiple pass welds in all positions.
For this pattern, the smallest quantity of metal is molten
at one time as compared to other patterns. Therefore, the
weld is more easily controlled. At the same time that the
electrode is stepped forward, the arc length is increased so
that no metal is deposited ahead of the molten weld pool,
Figure 4-27 and Figure 4-28. This action allows the
molten weld pool to cool to a controllable size. In addition, the arc burns off any paint, oil, or dirt from the metal
before it can contaminate the weld.
The figure 8 pattern and the zigzag pattern are used as
cover passes in the flat and vertical positions. Do not
weave more than 2 1/2 times the width of the electrode.
F IGURE 4-27 The electrode is moved slightly forward and
then returned to the weld pool. Courtesy of Larry Jeffus.
NO METAL
WAS DEPOSITED
F IGURE 4-28 The electrode does not deposit metal or melt
the base metal. Courtesy of Larry Jeffus.
These patterns deposit a large quantity of metal at one
time. A shelf can be used to support the molten weld pool
when making vertical welds using either of these patterns,
Figure 4-29.
Chapter 4
Shielded Metal Arc Welding of Plate
75
WELDING
TABLE
SURFACE
SHELVES
F IGURE 4-30 Change the plate angle to find the most
comfortable welding position.
F IGURE 4-29 Using the shelf to support the molten pool
for vertical welds. Courtesy of Larry Jeffus.
Positioning of the Welder
and the Plate
The welder should be in a relaxed, comfortable position before starting to weld. A good position is important
for both the comfort of the welder and the quality of the
welds. Welding in an awkward position can cause welder
fatigue, which leads to poor welder coordination and
poor-quality welds. Welders must have enough freedom
of movement so that they do not need to change position
during a weld. Body position changes should be made
only during electrode changes.
When the welding helmet is down, the welder is blind
to the surroundings. Due to the arc, the field of vision of
the welder is also very limited. These factors often cause
the welder to sway. To stop this swaying, the welder
should lean against or hold on to a stable object. When
welding, even if a welder is seated, touching a stable
object will make that welder more stable and will make
welding more relaxing.
Welding is easier if the welder can find the most comfortable angle. The welder should be in either a seated or a
standing position in front of the welding table. The welding
machine should be turned off. With an electrode in place in
the electrode holder, the welder can draw a straight line
along the plate to be welded. By turning the plate to several
different angles, the welder should be able to determine
which angle is most comfortable for welding, Figure 4-30.
Practice Welds
Practice welds are grouped according to the type of
joint and the type of welding electrode. The welder or
instructor should select the order in which the welds are
made. The stringer beads should be practiced first in each
position before the welder tries the different joints in each
position. Some time can be saved by starting with the
stringer beads. If this is done, it is not necessary to cut or
tack the plate together, and a number of beads can be
made on the same plate.
Students will find it easier to start with butt joints. The
lap, tee, and outside corner joints are all about the same
level of difficulty.
Starting with the flat position allows the welder to
build skills slowly, so that out-of-position welds become
easier to do. The horizontal tee and lap welds are almost
as easy to make as the flat welds. Overhead welds are as
simple to make as vertical welds, but they are harder to
position. Horizontal butt welds are more difficult to perform than most other welds.
Electrodes Arc welding electrodes used for practice
welds are grouped into three filler metal (F number) classes
according to their major welding characteristics. The groups
are E6010 and E6011, E6012 and E6013, and E7016 and
E7018.
F3 E6010 and E6011 Electrodes
Both of these electrodes have cellulose-based fluxes. As
a result, these electrodes have a forceful arc with little slag
left on the weld bead.
F2 E6012 and E6013 Electrodes
These electrodes have rutile-based fluxes, giving a
smooth, easy arc with a thick slag left on the weld bead.
F4 E7016 and E7018 Electrodes
Both of these electrodes have a mineral-based flux. The
resulting arc is smooth and easy, with a very heavy slag
left on the weld bead.
The cellulose- and rutile-based groups of electrodes have
characteristics that make them the best electrodes for starting specific welds. The electrodes with the cellulose-based
fluxes do not have heavy slags that may interfere with the
welder’s view of the weld. This feature is an advantage for flat
tee and lap joints. Electrodes with the rutile-based fluxes
(giving an easy arc with low spatter) are easier to control and
are used for flat stringer beads and butt joints.
Unless a specific electrode has been required by a
Welding Procedure Specification (WPS), welders can
select what they consider to be the best electrode for a
specific weld. Without a WPS a recommendation can
be made and should be tried, but often the welder has
the final choice. An accomplished welder can make
76
Section 2
Shielded Metal Arc Welding
STARTING TAB
POROSITY AREA
F IGURE 4-31 Porosity is found on the starting tab where it
will not affect the weld. Courtesy of Larry Jeffus.
F IGURE 4-33 New welders frequently see only the arc and
sparks from the electrode. Courtesy of Larry Jeffus.
WELD SPATTER
SOLID
SLAG
MOLTEN FLUX
ARC
MOLTEN WELD
POOL
F IGURE 4-32 Stringer bead. Courtesy of Larry Jeffus.
defect-free welds on all types of joints using all types of
electrodes in any weld position.
Electrodes with mineral-based fluxes should be the last
choice. Welds with a good appearance are more easily made
with these electrodes, but strong welds are hard to obtain.
Without special care being taken during the start of the
weld, porosity will be formed in the weld. Figure 4-31
shows a starting tab used to prevent this porosity from
becoming part of the finished weld. More information on
electrode selection can be found in Chapter 18.
Stringer Beads
A straight weld bead on the surface of a plate, with little
or no side-to-side electrode movement, is known as a
stringer bead. Stringer beads are used by students to practice
maintaining arc length, weave patterns, and electrode angle
so that their welds will be straight, uniform, and free from
defects. Stringer beads, Figure 4-32, are also used to set the
machine amperage and for buildup or surfacing applications.
The stringer bead should be straight. A beginning welder
needs time to develop the skill of viewing the entire welding
area. At first, the welder sees only the arc, Figure 4-33. With
practice, the welder begins to see parts of the molten weld
pool. After much practice, the welder will see the molten
weld pool (front, back, and both sides), slag, buildup, and
F IGURE 4-34 More experienced welders can see the
molten pool, metal being transferred across the arc, and
penetration into the base metal. Courtesy of Larry Jeffus.
the surrounding plate, Figure 4-34. Often, at this skill level,
the welder may not even notice the arc.
A straight weld is easily made once the welder develops
the ability to view the entire welding zone. The welder
will occasionally glance around to ensure that the weld is
straight. In addition, it can be noted if the weld is uniform
and free from defects. The ability of the welder to view the
entire weld area is demonstrated by making consistently
straight and uniform stringer beads.
After making practice stringer beads, a variety of
weave bead patterns should be practiced to gain the
ability to control the molten weld pool when welding
out-of-position.
PRACTICE 4-2
Straight Stringer Beads in the Flat
Position Using E6010 or E6011 Electrodes,
E6012 or E6013 Electrodes, and E7016 or
E7018 Electrodes
Using a properly set up and adjusted arc welding
machine, proper safety protection, as demonstrated in
Practice 4-1, arc welding electrodes with a 1/8-in. (3mm)
Chapter 4
diameter, and one piece of mild steel plate, 6 in. (152 mm)
long 1/4 in. (6 mm) thick, you will make straight
stringer beads.
■ Starting at one end of the plate, make a straight
weld the full length of the plate.
■ Watch the molten weld pool at this point, not the
end of the electrode. As you become more skillful,
it is easier to watch the molten weld pool.
■ Repeat the beads with all three (F) groups of electrodes until you have consistently good beads.
■ Cool, chip, and inspect the bead for defects after
completing it. Turn off the welding machine and
clean up your work area when you are finished
welding.
Shielded Metal Arc Welding of Plate
77
CORRECT
TRAVEL
SPEED
CORRECT
SHELF SIZE
TOO LARGE
SHELF SIZE
TRAVEL
TOO FAST
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
PRACTICE 4-3
Stringer Beads in the Vertical Up Position
Using E6010 or E6011 Electrodes, E6012
or E6013 Electrodes, and E7016 or E7018
Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-2, you will make vertical up stringer
beads. Start with the plate at a 45° angle.
This technique is the same as that used to make a vertical weld. However, a lower level of skill is required at
45°, and it is easier to develop your skill. After the welder
masters the 45° angle, the angle is increased successively
until a vertical position is reached, Figure 4-35.
Before the molten metal drips down the bead, the back
of the molten weld pool will start to bulge, Figure 4-36.
When this happens, increase the speed of travel and the
weave pattern.
F IGURE 4-36 E7018 vertical up weld. Courtesy of Larry Jeffus.
90°
45°
FIGURE 4-37 Change the plate angle as welding skill
improves.
Cool, chip, and inspect each completed weld for defects.
Repeat the beads as necessary with all three (F) groups of
electrodes until consistently good beads are obtained in this
position. Turn off the welding machine and clean up your
work area when you are finished welding.
Complete a copy of the “Student Welding Report” listed
in Appendix I or provided by your instructor. ◆
INCREASE THE PLATE
ANGLE FROM 45° TO 90°.
PRACTICE 4-4
45°
WELD
F IGURE 4-35 Once the 45° angle is mastered, the plate
angle is increased successively until a vertical position (90°)
is reached.
Horizontal Stringer Beads Using E6010
or E6011 Electrodes, E6012 or E6013
Electrodes, and E7016 or E7018
Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-2, you will make horizontal stringer
beads on a plate.
When the welder begins to practice the horizontal
stringer bead, the plate may be reclined slightly, Figure
4-37. This placement allows the welder to build the
78
Section 2
Shielded Metal Arc Welding
D
C
B
A
A
B
C
D
LIQUID
LIQUID
SOLID
SECTION A-A
SECTION B-B
SOLID
SECTION C-C
SECTION D-D
F IGURE 4-38 The progression of a horizontal bead.
F IGURE 4-39 The tack weld should be small and uniform
to minimize its effect on the final weld. Courtesy of Larry Jeffus.
required skill by practicing the correct techniques successfully. The “J” weave pattern is suggested for this practice. As the electrode is drawn along the straight back of
the “J,” metal is deposited. This metal supports the
molten weld pool, resulting in a bead with a uniform contour, Figure 4-38.
Angling the electrode up and back toward the weld
causes more metal to be deposited along the top edge of
the weld. Keeping the bead small allows the surface tension to hold the molten weld pool in place.
Gradually increase the angle of the plate until it is vertical and the stringer bead is horizontal. Repeat the beads
as needed with all three (F) groups of electrodes until
consistently good beads are obtained in this position.
Turn off the welding machine and clean up your work
area when you are finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
Square Butt Joint
The square butt joint is made by tack welding two
flat pieces of plate together, Figure 4-39. The space
between the plates is called the root opening or root
gap. Changes in the root opening will affect penetration. As the space increases, the weld penetration also
increases. The root opening for most butt welds will
vary from 0 in. (0 mm) to 1/8 in. (3 mm). Excessively
large openings can cause burn-through or a cold lap at
the weld root, Figure 4-40.
ROOT OPENING
LACK OF
FUSION
INCREASING ROOT OPENING
F IGURE 4-40 Effect of root opening on weld penetration.
Chapter 4
After a butt weld is completed, the plate can be cut apart
so it can be used for rewelding. The strips for butt welding
should be no smaller than 1 in. (25 mm) wide. If they are
too narrow, there will be a problem with heat buildup.
If the plate strips are no longer flat after the weld has
been cut out, they can be tack welded together and flattened with a hammer, Figure 4-41.
TACK
WELD
ANVIL
F IGURE 4-41 After the plates are tack welded together,
they can be forced into alignment by striking them with a
hammer.
Shielded Metal Arc Welding of Plate
79
PRACTICE 4-5
Welded Square Butt Joint in the Flat
Position (1G) Using E6010 or E6011
Electrodes, E6012 or E6013 Electrodes,
and E7016 or E7018 Electrodes
Using a properly set up and adjusted arc welding
machine, proper safety protection, arc welding electrodes
having a 1/8-in. (3-mm) diameter, and two or more pieces
of mild steel plate, 6 in. (152 mm) long 1/4 in. (6 mm)
thick, you will make a welded square butt joint in the flat
position, Figure 4-42.
Tack weld the plates together and place them flat on
the welding table. Starting at one end, establish a molten
weld pool on both plates. Hold the electrode in the molten
weld pool until it flows together, Figure 4-43. After the
gap is bridged by the molten weld pool, start weaving the
electrode slowly back and forth across the joint. Moving
the electrode too quickly from side to side may result in
slag being trapped in the joint, Figure 4-44.
Continue the weld along the 6-in. (152-mm) length
of the joint. Normally, deep penetration is not required
for this type of weld. If full plate penetration is required,
the edges of the butt joint should be beveled or a larger
than normal root gap should be used. Cool, chip, and
inspect the weld for uniformity and soundness. Repeat
6"
(152 mm)
1"
2
(38 mm)
1
1"
2
(38 mm)
1
Welding Principles and Applications
MATERIAL:
1/4" x 6" MILD STEEL PLATE
PROCESS:
SMAW BUTT JOINT 1G
NUMBER:
PRACTICE 4-4
F IGURE 4-42 Square butt joint in the flat position.
DRAWN BY:
CAROL JEFFUS
80
Section 2
Shielded Metal Arc Welding
TRAPPED SLAG
WELD BACK OVER
ARC STRIKE
MOLTON
WELD POOL
ARC STRIKE
(A)
F IGURE 4-44 Moving the electrode from side to side too
quickly can result in slag being trapped between the plates.
Courtesy of Larry Jeffus.
ARC STRIKE
BEING WELDED
OVER
(B)
F IGURE 4-43 (A) After the arc is established, hold it in one
area long enough to establish the size of molten weld pool
desired. (B) Weld back over the arc strike to melt it into
the weld. Courtesy of Larry Jeffus. See SMAW video series.
plates, Figure 4-45. Build the bead size slowly so that the
molten weld pool has a shelf for support. The “C,” “J,” or
square weave pattern works well for this joint.
As the electrode is moved up the weld, the arc is
lengthened slightly so that little or no metal is deposited
ahead of the molten weld pool. When the electrode is
brought back into the molten weld pool, it should be lowered to deposit metal, Figure 4-46.
As skill is developed, increase the plate angle until it is
vertical. Cool, chip, and inspect the weld for uniformity
and defects. Repeat the welds with all three (F) groups of
electrodes until you can consistently make welds free of
defects. Turn off the welding machine and clean up your
work area when you are finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
PRACTICE 4-7
the welds as needed to master all three (F) groups of
electrodes in this position. Turn off the welding machine and clean up your work area when you are finished
welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
PRACTICE 4-6
Vertical (3G) Up-Welded Square Butt
Weld Using E6010 or E6011 Electrodes,
E6012 or E6013 Electrodes, and E7016 or
E7018 Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-5, you will make vertical up-welded
square butt joints.
With the plates at a 45° angle, start at the bottom and
make the molten weld pool bridge the gap between the
Welded Horizontal (2G) Square Butt Weld
Using E6010 or E6011 Electrodes, E6012
or E6013 Electrodes, and E7016 or E7018
Electrodes
Using the same setup, materials, and electrodes as
described in Practice 4-5, you will make a welded horizontal square butt joint.
■ Start practicing these welds with the plate at a slight
angle.
■ Strike the arc on the bottom plate and build the
molten weld pool until it bridges the gap.
If the weld is started on the top plate, slag will be
trapped in the root at the beginning of the weld because
of poor initial penetration. The slag may cause the weld to
crack when it is placed in service.
The “J” weave pattern is recommended in order to
deposit metal on the lower plate so that it can support
Chapter 4
Shielded Metal Arc Welding of Plate
81
6"
(152 mm)
45° *
1"
2
(38 mm)
1
* THIS ANGLE SHOULD BE INCREASED
UNTIL THE PLATE IS VERTICAL.
1"
2
(38 mm)
1
Welding Principles and Applications
MATERIAL:
1/4" x 6" MILD STEEL PLATE
PROCESS:
SMAW BUTT JOINT INCLINED UP
NUMBER:
PRACTICE 4–5
DRAWN BY:
CAROL JEFFUS
F IGURE 4-45 Square butt joint in the vertical up position.
KEEP THIS MOVEMENT SHORT,
3"
1"
(3mm) TO
(10mm), TO KEEP
8
8
SHIELDING GAS PROTECTION
OVER THE MOLTEN WELD POOL
WELD
F IGURE 4-47 Edge joint.
MOLTEN WELD POOL
WELD BEAD
F IGURE 4-46 Electrode movement for vertical up welds.
the bead. By pushing the electrode inward as you cross
the gap between the plates, deeper penetration is
achieved.
As you acquire more skill, gradually increase the plate
angle until it is vertical and the weld is horizontal.
■
■
Cool, chip, and inspect the weld for uniformity and
defects.
Repeat the welds with all three (F) groups of electrodes until you can consistently make welds free of
defects. Turn off the welding machine and clean up
your work area when you are finished welding.
Complete a copy of the “Student Welding Report” listed
in Appendix I or provided by your instructor. ◆
Edge Weld
An edge weld joint is made by placing the edges of the
plate evenly, Figure 4-47. When assembling the edge joint
82
Section 2
Shielded Metal Arc Welding
■
■
TACK WELD
BOTH ENDS
■
■
■
F IGURE 4-48 Make tack welds at the ends of the joint.
■
Clamp the plates flat together and make a tack weld
along each end of the plates.
Starting at one end of the plate, make a straight
weld the full length of the plate. Make the weld
bead as wide as the width of the edge joint.
Watch the molten weld pool, not the end of the
electrode.
Cool, chip, and inspect the weld for uniformity and
defects.
Repeat the welds as needed with all three (F)
groups of electrodes until you can consistently
make welds free of defects.
Turn off the welding machine and clean up your
work area when you are finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
WELD SIZE
PLATE THICKNESS
F IGURE 4-49 Edge weld size.
the plates should be clamped tightly together; there should
not be any gap between the plates. Both edges of the plate
assembly can be welded. Make the tack welds to hold the
plates together along the ends of the joint, Figure 4-48.
The size of the weld should equal the thickness of the
plate being joined. A good indication the weld is being
made large enough is when the weld bead width is equal
to the width of the joint, Figure 4-49. The weld bead
should also have a slight buildup.
PRACTICE 4-8
Edge Weld in the Flat Position Using E6010
or E6011 Electrodes, E6012 or E6013
Electrodes, and E7016 or E7018 Electrodes
Using a properly set up and adjusted arc welding
machine, proper safety protection, as demonstrated in
Practice 4-1, arc welding electrodes with a 1/8-in. (3-mm)
diameter, and two pieces of mild steel plate, 6 in. (152
mm) long 1/4 in. (6 mm) thick, you will make a weld
on an edge joint, Figure 4-50.
PRACTICE 4-9
Edge Joint in the Vertical Down Position
Using E6010 or E6011 Electrodes, E6012
or E6013 Electrodes, and E7016 or E7018
Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-8, you will make a vertical down weld
on an edge joint. Start with the plates at a 45° angle.
This technique is the same as that used to make vertical down welds. However, a lower level of skill is required
at 45°, and it is easier to develop your skill. After you master the 45° angle, the angle is increased successively until
a vertical position is reached, Figure 4-51.
■ Make the weld bead as wide as the joint.
Controlling a weld bead this size is more difficult,
but you must develop the skill required to control
this larger molten weld pool.
■ Cool, chip, and inspect the weld for uniformity and
defects.
■ Repeat the welds as needed with all three (F)
groups of electrodes until you can consistently
make welds free of defects. Turn off the welding
machine and clean up your work area when you are
finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
PRACTICE 4-10
Edge Joint in the Vertical Up Position
Using E6010 or E6011 Electrodes, E6012
or E6013 Electrodes, and E7016 or E7018
Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-8, you will make a vertical up weld on
an edge joint. Start with the plates at a 45° angle.
Chapter 4
Shielded Metal Arc Welding of Plate
83
Welding Principles and Applications
MATERIAL:
1/4" x 6" Mild Steel Plate
PROSCESS:
SMAW Edge Joint
NUMBER:
PRACTICE 4-8
F IGURE 4-50 Practice 4-8 edge joint.
D
EL
W
90.0˚
45.0˚
F IGURE 4-51 Vertical down.
DRAWN BY:
Wally Heermans
84
Section 2
Shielded Metal Arc Welding
D
EL
W
90.0˚
45.0˚
F IGURE 4-52 Vertical up.
machine and clean up your work area when you are
finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
PRACTICE 4-11
CORRECT
TOO SLOW
F IGURE 4-53 Watch the trailing edge of the weld pool to
judge the correct travel speed.
This technique is the same as that used to make vertical up welds. However, a lower level of skill is required at
45°, and it is easier to develop your skill. After you master
the 45° angle, the angle is increased successively until a
vertical position is reached, Figure 4-52.
Before the molten metal drips down the bead, the back
of the molten weld pool will start to bulge, Figure 4-53.
When this happens, increase the speed of travel and the
weave pattern.
■
■
Cool, chip, and inspect the weld for uniformity and
defects.
Repeat the welds as needed with all three (F)
groups of electrodes until you can consistently
make welds free of defects. Turn off the welding
Edge Joint in the Horizontal Position
Using E6010 or E6011 Electrodes, E6012
or E6013 Electrodes, and E7016 or E7018
Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-8, you will make a horizontal weld on
an edge joint. When you begin to practice the horizontal
weld, the plate may be reclined slightly, Figure 4-54. This
placement allows the welder to build the required skill by
practicing the correct techniques successfully. The “J”
weave or stepped pattern is suggested for this practice. As
the electrode is drawn back to the back edge of the weld
pool, metal is deposited. Use the metal being deposited to
support the molten weld pool.
Angling the electrode up and back toward the weld
causes more metal to be deposited along the top edge of
the weld. Keeping the bead small allows the surface tension to hold the molten weld pool in place.
Gradually increase the angle of the plate until it and the
weld bead are horizontal.
■
Cool, chip, and inspect the weld for uniformity and
defects.
Chapter 4
Shielded Metal Arc Welding of Plate
85
STRIKE THE
ARC HERE
90.0˚
45.0˚
F IGURE 4-54 Incline angle.
■
Repeat the welds as needed with all three (F)
groups of electrodes until you can consistently
make welds free of defects. Turn off the welding
machine and clean up your work area when you are
finished welding.
F IGURE 4-55 Strike the arc in the joint.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
PRACTICE 4-12
Edge Joint in the Overhead Position Using
E6010 or E6011 Electrodes, E6012 or E6013
Electrodes, and E7016 or E7018 Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-8, you will make an overhead weld on
an edge joint.
■ With the electrode pointed in a slightly trailing
angle, Figure 4-55, strike the arc in the joint.
■ Keep a very short arc length.
■ Use the stepped pattern and move the electrode forward slightly when the molten weld pool grows to
the correct size, Figure 4-56.
STEP THE
ELECTRODE
F IGURE 4-56 Step the electrode. Courtesy of Larry Jeffus.
As the molten weld pool gets larger it has a tendency to
quickly become convex. If you keep the arc in the molten
weld pool once the joint is filled and the weld face is flat
it will quickly overfill and become convex. This can result
in the weld face forming drips of metal hanging from the
weld like icicles, Figure 4-57.
■ When the molten weld pool cools and begins to
shrink, move the arc back near the center of the weld.
■
■
■
Hold the arc in this new location until the molten
weld pool again grows to the correct size.
Step the electrode forward again and keep repeating
this pattern until the weld progresses along the
entire weld joint length.
Cool, chip, and inspect the weld for uniformity and
defects.
Icicles
F IGURE 4-57 Welding too slow or with too high of an
amperage setting will result in the weld metal dripping
down like icicles.
86
■
Section 2
Shielded Metal Arc Welding
Repeat the welds as needed with all three (F)
groups of electrodes until you can consistently
make welds free of defects. Turn off the welding
machine and clean up your work area when you are
finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
Outside Corner Joint
An outside corner joint is made by placing the plates at
a 90° angle to each other, with the edges forming a V
groove, Figure 4-58. There may or may not be a slight root
opening left between the plate edges. Small tack welds
should be made approximately 1/2 in. (13 mm) from both
ends of the joint.
The weld bead should completely fill the V groove
formed by the plates and may have a slightly convex sur-
F IGURE 4-58 V formed by an outside corner joint.
face buildup. The back side of an outside corner joint can
be used to practice fillet welds, or four plates can be made
into a box tube shape, Figure 4-59.
PRACTICE 4-13
Outside Corner Joint in the Flat Position
Using E6010 or E6011 Electrodes, E6012
or E6013 Electrodes, and E7016 or E7018
Electrodes
Using a properly set up and adjusted arc welding
machine, proper safety protection, as demonstrated in
Practice 4-1, arc welding electrodes with a 1/8-in. (3-mm)
diameter, and two pieces of mild steel plate 6 in. (152
mm) long 1/4 in. (6 mm) thick, you will make a weld
on an outside corner joint.
■ Starting at one end of the plate, make a straight
weld the full length of the plate.
■ Watch the molten weld pool at this point, not the
end of the electrode. As you become more skillful,
it is easier to watch the molten weld pool.
■ Cool, chip, and inspect the weld for uniformity and
defects.
■ Repeat the welds as needed with all three (F)
groups of electrodes until you can consistently
make welds free of defects. Turn off the welding
machine and clean up your work area when you are
finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
FOUR WELDS
F IGURE 4-59 Box tube made from four outside corner joint welds.
Shielded Metal Arc Welding of Plate
Chapter 4
PRACTICE 4-14
This technique is the same as that used to make vertical up welds. However, a lower level of skill is required
at 45°, and it is easier to develop your skill. After the
welder masters the 45° angle, the angle is increased successively until a vertical position is reached, Figure 4-61.
Before the molten metal drips down the bead, the back
of the molten weld pool will start to bulge, Figure 4-62.
When this happens, increase the speed of travel and the
weave pattern.
■ Cool, chip, and inspect the weld for uniformity and
defects.
■ Repeat the welds as needed with all three (F)
groups of electrodes until you can consistently
make welds free of defects. Turn off the welding
machine and clean up your work area when you are
finished welding.
Outside Corner Joint in the Vertical Down
Position Using E6010 or E6011 Electrodes,
E6012 or E6013 Electrodes, and E7016 or
E7018 Electrodes
Using the same setup, materials, and electrodes as listed
in Practice 4-13, you will make a vertical down weld on an
outside corner joint. Start with the plate at a 45° angle.
This technique is the same as that used to make vertical down welds. However, a lower level of skill is required
at 45°, and it is easier to develop your skill. After you master the 45° angle, the angle is increased successively until
a vertical position is reached, Figure 4-60.
■ Cool, chip, and inspect the weld for uniformity and
defects.
■ Repeat the welds as needed with all three (F)
groups of electrodes until you can consistently
make welds free of defects. Turn off the welding
machine and clean up your work area when you are
finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
PRACTICE 4-16
Outside Corner Joint in the Horizontal
Position Using E6010 or E6011 Electrodes,
E6012 or E6013 Electrodes, and E7016 or
E7018 Electrodes
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
PRACTICE 4-15
Using the same setup, materials, and electrodes as
listed in Practice 4-13, you will make a horizontal weld on
an outside corner joint. When the welder begins to practice the horizontal weld, the joint may be reclined slightly,
Figure 4-63. This placement allows the welder to build
the required skill by practicing the correct techniques successfully. The “J” weave or stepped pattern is suggested
for this practice. As the electrode is drawn back into the
weld pool, metal is deposited. This metal supports the
Outside Corner Joint in the Vertical Up
Position Using E6010 or E6011 Electrodes,
E6012 or E6013 Electrodes, and E7016 or
E7018 Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-13, you will make a vertical up weld on
an outside corner joint. Start with the plate at a 45° angle.
W
EL
D
90.0˚
45.0˚
F IGURE 4-60 Start with a 45° angle and increase it to 90°.
87
88
Section 2
Shielded Metal Arc Welding
W
EL
D
90.0˚
45.0˚
F IGURE 4-61 Vertical up.
J WEAVE
CORRECT
TOO SLOW
F IGURE 4-62 Watch the trailing edge of the weld pool to
judge the correct travel speed.
STEPPING
F IGURE 4-64 “J” weave or stepping.
molten weld pool, resulting in a bead with a uniform contour, Figure 4-64.
Angling the electrode up and back toward the weld
causes more metal to be deposited along the top edge of
the weld. Keeping the bead small allows the surface tension to hold the molten weld pool in place.
Gradually increase the angle of the plate until it is vertical and the weld bead is horizontal.
■
■
F IGURE 4-63 Incline angle.
Cool, chip, and inspect the weld for uniformity and
defects.
Repeat the welds as needed with all three (F)
groups of electrodes until you can consistently
make welds free of defects. Turn off the welding
machine and clean up your work area when you are
finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
Chapter 4
Shielded Metal Arc Welding of Plate
PRACTICE 4-17
Outside Corner Joint in the Overhead
Position Using E6010 or E6011 Electrodes,
E6012 or E6013 Electrodes, and E7016 or
E7018 Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-13, you will make an overhead welded
outside corner joint.
■ With the electrode pointed slightly into the joint,
Figure 4-65, strike the arc in the joint.
■ Keep a very short arc length.
■ Use the stepped pattern and move the electrode forward slightly when the molten weld pool grows to
the correct size, Figure 4-66.
89
As the molten weld pool gets larger it has a tendency to
quickly become convex. If you keep the arc in the molten
weld pool once the joint is filled and the weld face is flat
it will quickly overfill and become convex. This can result
in the weld face forming drips of metal hanging from the
weld like icicles, Figure 4-67.
■ When the molten weld pool cools and begins
to shrink, move the arc back near the center of
the weld.
■ Hold the arc in this new location until the molten
weld pool again grows to the correct size.
■ Step the electrode forward again and keep repeating
this pattern until the weld progresses along the
entire weld joint length.
■ Cool, chip, and inspect the weld for uniformity and
defects.
■ Repeat the welds as needed with all three (F)
groups of electrodes until you can consistently
make welds free of defects. Turn off the welding
machine and clean up your work area when you are
finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
Lap Joint
A lap joint is made by overlapping the edges of the two
plates, Figure 4-68. The joint can be welded on one side
or both sides with a fillet weld. In Practice 4-7, both sides
should be welded unless otherwise noted.
As the fillet weld is made on the lap joint, the buildup
should equal the thickness of the plate, Figure 4-69. A
good weld will have a smooth transition from the plate
surface to the weld. If this transition is abrupt, it can cause
stresses that will weaken the joint.
STRIKE THE
ARC HERE
F IGURE 4-65 Strike arc in the joint.
STEP THE
ELECTRODE
F IGURE 4-66 Stepping the electrode to control weld size.
90
Section 2
Shielded Metal Arc Welding
GOOD ROOT
FUSION
F IGURE 4-70 Watch the root of the weld bead to be sure
there is complete fusion. Courtesy of Larry Jeffus.
ICICLES
F IGURE 4-67 Welding too slowly or with too high of an
amperage setting will result in the weld metal dripping
down like icicles.
FILLET WELDS
AMOUNT OF OVERLAP
F IGURE 4-68 Lap joint.
F IGURE 4-71 Lap joint. Courtesy of Larry Jeffus.
fused together. The weave pattern will help prevent this
problem, Figure 4-71.
SMOOTH WELD
TRANSITION
PRACTICE 4-18
LEG
THICKNESS
LEG
SMOOTH WELD
TRANSITION
F IGURE 4-69 The legs of a fillet weld generally should be
equal to the thickness of the base metal.
Penetration for lap joints does not improve their
strength; complete fusion is required. The root of fillet
welds must be melted to ensure a completely fused joint.
If the molten weld pool shows a notch during the weld,
Figure 4-70, this is an indication that the root is not being
Welded Lap Joint in the Flat Position (1F)
Using E6010 or E6011 Electrodes, E6012
or E6013 Electrodes, and E7016 or E7018
Electrodes
Using a properly set up and adjusted arc welding
machine, proper safety protection, arc welding electrodes
having a 1/8-in. (3-mm) diameter, and two or more pieces
of mild steel plate, 6 in. (152 mm) long 1/4 in. (6 mm)
thick, you will make a welded lap joint in the flat position,
Figure 4-72.
Hold the plates together tightly with an overlap of no
more than 1/4 in. (6 mm). Tack weld the plates together.
A small tack weld may be added in the center to prevent
distortion during welding, Figure 4-73. Chip the tacks
before you start to weld.
The “J,” “C,” or zigzag weave pattern works well on
this joint. Strike the arc and establish a molten pool
directly in the joint. Move the electrode out on the bottom plate and then onto the weld to the top edge of the
Chapter 4
Shielded Metal Arc Welding of Plate
91
WELD BOTH SIDES.
45°
6"
(152 mm)
1"
2
(13 mm)
1"
(13 mm) IS THE MAXIMUM
2
TO CONSERVE METAL.
1"
2
(38 mm)
1
Welding Principles and Applications
MATERIAL:
1/4" x 6" MILD STEEL PLATE
PROCESS:
SMAW BUTT JOINT 1F
NUMBER:
PRACTICE 4-7
DRAWN BY:
PATTI BRADSHAW
F IGURE 4-72 Lap joint in the flat position.
SMALL
TACK WELDS
1"
(6 mm)
4
1"
(6 mm)
4
6" (152 mm)
OVERLAP
OF 1" (6 mm)
4
F IGURE 4-73 Tack welding the plates together.
top plate, Figure 4-74. Follow the surface of the plates
with the arc. Do not follow the trailing edge of the weld
bead. Following the molten weld pool will not allow for
good root fusion and will cause slag to collect in the
root. If slag does collect, a good weld is not possible.
Stop the weld and chip the slag to remove it before the
weld is completed. Cool, chip, and inspect the weld for
uniformity and defects. Repeat the welds with all three
(F) groups of electrodes until you can consistently
make welds free of defects. Turn off the welding
machine and clean up your work area when you are finished welding.
92
Section 2
Shielded Metal Arc Welding
root. The fillet must be equally divided between both
plates for good strength. After completing the weld, cool,
chip, and inspect the weld for uniformity and defects.
Repeat the welds using all three (F) groups of electrodes
until you can consistently make welds free of defects.
Turn off the welding machine and clean up your work
area when you are finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
TRAILING EDGE OF
WELD BEAD
SURFACE TO
BE WELDED
PRACTICE 4-20
SURFACE TO
BE WELDED
F IGURE 4-74 Follow the surface of the plate to ensure
good fusion.
Complete a copy of the “Student Welding Report” listed
in Appendix I or provided by your instructor. ◆
Lap Joint in the Vertical Position (3F)
Using E6010 or E6011 Electrodes, E6012
or E6013 Electrodes, and E7016 or E7018
Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-18, you will make a vertical up
welded lap joint.
■
■
PRACTICE 4-19
Welded Lap Joint in the Horizontal
Position (2F) Using E6010 or E6011
Electrodes, E6012 or E6013 Electrodes,
and E7016 or E7018 Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-18, you will make a welded horizontal
lap joint.
The horizontal lap joint and the flat lap joint require
nearly the same technique and skill to achieve a proper
weld, Figure 4-75. Use the “J,” “C,” or zigzag weave pattern to make the weld. Do not allow slag to collect in the
■
■
■
■
■
■
LEG
LEG
Start practicing this weld with the plate at a 45°
angle.
Gradually increase the angle of the plate to vertical
as skill is gained in welding this joint. The “J” or
“T” weave pattern works well on this joint.
Establish a molten weld pool in the root of the
joint.
Use the “T” pattern to step ahead of the molten
weld pool, allowing it to cool slightly. Do not
deposit metal ahead of the molten weld pool.
As the molten weld pool size starts to decrease,
move the electrode back down into the molten weld
pool.
Quickly move the electrode from side to side in the
molten weld pool, filling up the joint.
Cool, chip, and inspect the weld for uniformity and
defects.
Repeat the welds as necessary with all three (F)
groups of electrodes until you can consistently
make welds free of defects. Turn off the welding
machine and clean up your work area when you are
finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
PRACTICE 4-21
Lap Joint in the Overhead Position (4F)
Using E6010 or E6011 Electrodes, E6012
or E6013 Electrodes, and E7016 or E7018
Electrodes
F IGURE 4-75 The horizontal lap joint should have a fillet
weld that is equal on both plates.
Using the same setup, materials, and electrodes as
listed in Practice 4-18, you will make an overhead welded
lap joint.
Chapter 4
Shielded Metal Arc Welding of Plate
93
ICICLES
F IGURE 4-78 Overfilling the molten weld pool will result in
drips of metal called icicles.
F IGURE 4-76 Point the electrode slightly toward the root
of the joint.
LESS HEAT IS CONDUCTED
INTO THIS PLATE
THAN
INTO THIS PLATE.
OVER FILL
F IGURE 4-79 Tee joint.
CORRECT FILL
■
■
■
UNDER FILL
F IGURE 4-77 Correct fillet weld size for overhead welds.
With the electrode pointed slightly into the joint,
Figure 4-76, strike the arc in the inside corner of
the lap joint.
■ Keep a very short arc length.
■ Use the stepped pattern and move the electrode forward slightly when the molten weld pool grows to
the correct size, Figure 4-77.
As the molten weld pool gets larger it has a tendency to
quickly become convex. If you keep the arc in the molten
weld pool once the joint is filled and the weld face is flat
it will quickly overfill and become convex. This can result
in the weld face forming drips of metal hanging from the
weld like icicles, Figure 4-78.
■
■
■
When the molten weld pool cools and begins to
shrink, move the arc back near the center of the
weld.
Hold the arc in this new location until the molten
weld pool again grows to the correct size.
Step the electrode forward again and keep repeating
this pattern until the weld progresses along the
entire weld joint length.
Cool, chip, and inspect the weld for uniformity and
defects.
Repeat the welds as needed with all three (F)
groups of electrodes until you can consistently
make welds free of defects. Turn off the welding
machine and clean up your work area when you are
finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
Tee Joint
The tee joint is made by tack welding one piece of metal
on another piece of metal at a right angle, Figure 4-79. After
the joint is tack welded together, the slag is chipped from the
tack welds. If the slag is not removed, it will cause a slag
inclusion in the final weld.
The heat is not distributed uniformly between both
plates during a tee weld. Because the plate that forms the
stem of the tee can conduct heat away from the arc in only
one direction, it will heat up faster than the base plate.
Heat escapes into the base plate in two directions. When
using a weave pattern, most of the heat should be directed
to the base plate to keep the weld size more uniform and
to help prevent undercut
A welded tee joint can be strong if it is welded on both
sides, even without having deep penetration, Figure 4-80.
The weld will be as strong as the base plate if the size of
94
Section 2
Shielded Metal Arc Welding
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
PRACTICE 4-23
WELD
SIZE
WELD
SIZE
WELD
SIZE
F IGURE 4-80 If the total weld sizes are equal, then both
tee joints would have equal strength.
the two welds equals the total thickness of the base plate.
The weld bead should have a flat or slightly concave
appearance to ensure the greatest strength and efficiency,
Figure 4-81.
PRACTICE 4-22
Tee Joint in the Flat Position (1F) Using
E6010 or 6011 Electrodes, E6012 or E6013
Electrodes, and E7016 or E7018
Electrodes
Using a properly set up and adjusted arc welding
machine, proper safety protection, arc welding electrodes
having a 1/8-in. (3-mm) diameter, and two or more pieces
of mild steel plate, 6 in. (152 mm) long 1/4 in. (6 mm)
thick, you will make a welded tee joint in the flat position,
Figure 4-82.
After the plates are tack welded together, place them
on the welding table so the weld will be flat. Start at one
end and establish a molten weld pool on both plates.
Allow the molten weld pool to flow together before starting the bead. Any of the weave patterns will work well on
this joint. To prevent slag inclusions, use a slightly higher
than normal amperage setting.
When the 6-in. (152-mm) -long weld is completed,
cool, chip, and inspect it for uniformity and soundness.
Repeat the welds as needed for all these groups of electrodes until you can consistently make welds free of
defects. Turn off the welding machine and clean up your
work area when you are finished welding.
Tee Joint in the Horizontal Position (2F)
Using E6010 or E6011 Electrodes, E6012
or E6013 Electrodes, and E7016 or E7018
Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-22, you will make a welded tee joint in
the horizontal position.
Place the tack welded tee plates flat on the welding
table so that the weld is horizontal and the plates are flat
and vertical, Figure 4-83. Start the arc on the flat plate
and establish a molten weld pool in the root on both
plates. Using the “J” or “C” weave pattern, push the arc
into the root and slightly up the vertical plate. You must
keep the root of the joint fusing together with the weld
metal. If the metal does not fuse, a notch will appear on
the leading edge of the weld bead. Poor or incomplete
root fusion will cause the weld to be weak and easily
cracked under a load.
When the weld is completed, cool, chip, and inspect
it for uniformity and defects. Undercut on the vertical
plate is the most common defect. Repeat the welds with
all three (F) groups of electrodes until you can consistently make welds free of defects. Turn off the welding
machine and clean up your work area when you are finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
PRACTICE 4-24
Tee Joint in the Vertical Position (3F) Using
E6010 or E6011 Electrodes, E6012 or E6013
Electrodes, and E7016 or E7018 Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-22, you will make a welded tee joint in
the vertical position.
FORCE
FLAT TO
CONCAVE
CONTOUR
STRESS LINES
F IGURE 4-81 The stresses are distributed more uniformly through a flat or concave fillet weld.
FORCE
CONVEX
CONTOUR
Chapter 4
Shielded Metal Arc Welding of Plate
95
90° +
– 5°
3"
(76 mm)
1"
2
(38 mm)
1
6"
(152 mm)
Welding Principles and Applications
MATERIAL:
1/4" x 6" MILD STEEL PLATE
PROCESS:
SMAW TEE JOINT 1F
NUMBER:
DRAWN BY:
PRACTICE 4–10
CAROLYN ADAMS
F IGURE 4-82 Tee joint in the flat position.
PAUSE
F IGURE 4-83 Horizontal tee.
Practice this weld with the plate at a 45° angle. This
position will allow you to develop your skill for the vertical position. Start the arc and molten weld pool deep in
the root of the joint. Build a shelf large enough to support
the bead as it progresses up the joint. The square, “J,” or
“C” pattern can be used, but the “T” or stepped pattern
will allow deeper root penetration.
For this weld, undercut is a problem on both sides of
the weld. It can be controlled by holding the arc on the
side long enough for filler metal to flow down and fill it,
Figure 4-84. Cool, chip, and inspect the weld for uniformity and defects. Repeat the welds as necessary with all
three (F) groups of electrodes until you can consistently
F IGURE 4-84 Pausing just above the undercut will fill it.
This action also causes undercut, but that will be filled on
the next cycle.
make welds free of defects. Turn off the welding
machine and clean up your work area when you are finished welding.
Complete a copy of the “Student Welding Report” listed
in Appendix I or provided by your instructor. ◆
96
Section 2
Shielded Metal Arc Welding
PRACTICE 4-25
Tee Joint in the Overhead Position (4F)
Using E6010 or E6011 Electrodes, E6012
or E6013 Electrodes, and E7016 or E7018
Electrodes
Using the same setup, materials, and electrodes as
listed in Practice 4-12, you will make a welded tee joint in
the overhead position.
Start the arc and molten weld pool deep in the root of
the joint. Keep a very short arc length. The stepped pattern will allow deeper root penetration.
For this weld, undercut is a problem on both sides of
the weld with a high buildup in the center. It can be controlled by holding the arc on the side long enough for
filler metal to flow in and fill it. Cool, chip, and inspect the
weld for uniformity and defects. Repeat the welds as necessary with all three (F) groups of electrodes until you can
consistently make welds free of defects. Turn off the welding machine and clean up your work area when you are
finished welding.
Complete a copy of the “Student Welding Report”
listed in Appendix I or provided by your instructor. ◆
Summary
The shielded metal arc welding process is most often
referred to in welding shops as stick welding. Some people
say that it gets this name for one of two reasons. The first
is most obviously as a result of the stick shape of the electrode. The second reason is experienced by all new
welders; it is the tendency for the electrode to stick to the
workpiece. All new welders experience this, and your ability to control the sticking of the electrode can be improved
as you develop the proper arc-striking techniques.
For a new welder, it is often difficult to concentrate
on anything other than the bright sparks and glow at
the end of the electrode. But, with time, as you develop
your skills, your visual field will increase, allowing you
to see a much larger welding zone. This skill comes
with time and practice. Developing this skill is essential
for you to become a highly proficient welder. Nothing
enhances your welding skills more than time under the
hood, actually welding, cleaning off the weld, inspecting it, determining the necessary corrections to be
made, and immediately trying to produce the next weld
with a higher level of quality.
Keeping Shipshape through
Underwater Welding
A Miami-based diving contractor helps customers avoid
unscheduled drydocks by making top-quality underwater
welding repairs.
Just like a bus, train, or airplane, a ship follows a time
schedule. Any disruption to that schedule translates into
thousands of dollars or more in lost revenue because cargo
is not arriving on time or passengers cannot take their
cruises. When underwater welding repairs are needed to get
a vessel back on schedule, one of the companies ship owners turn to is Miami Diver, Inc.
Based in Miami, Florida, the company specializes in
underwater ship maintenance, including repairs, husbandry, and surveys. Six of their twelve Miami employees
are diver/welders.
Being able to work “within the ship’s schedule is actually
the primary reason we’re called in,” said Kevin Peters, president of Miami Diver. That means the company’s employees
travel all over the world to repair ships, and, at times, if a
ship can continue underway, stay aboard and work whenever it reaches a port of call.
Chapter 4
Shielded Metal Arc Welding of Plate
97
Miami Diver performs dry repairs using hyperbaric welding chambers and closed cofferdams, as well as wet welding
repairs. The welders must work not only to the requirements
of ANSI/AWS D3.6M:1999, Specification for Underwater
Welding, but also to those of the various ship classification
societies.
Achieving “Surface-Quality”
Wet Welds
While underwater wet welding offers advantages, such
as speed, versatility, and cost effectiveness, the ship classification societies consider wet welds temporary repairs, that
must be redone in drydock.
AWS D3.6 divides underwater wet welds into four classes—
A, B, C, and O—based on varying sets of required properties
defined by mechanical tests, surface appearance, and nondestructive examination requirements. The specification defines
the four classes as follows:
■
Class A welds “are intended to be suitable for applications and design stresses comparable to their conventional surface welding counterparts by virtue of specifying comparable properties and testing
requirements.”
■
Class B welds “are intended for less critical applications where lower ductility, moderate porosity, and
other limited discontinuities can be tolerated.”
■
Class C welds “need only satisfy lesser requirements
than class A, B, and O and are intended for applications where the load-bearing function is not a primary consideration.”
■
Class O underwater welds must also meet the
requirements of another code or specification.
Two years ago, in anticipation of possible changes in the
American Bureau of Shipbuilding’s regulations and believing the company could provide added value to its customers by qualifying its welders to the requirements of the
D3.6 standard, Peters began researching wet welding electrodes. While certain that he and the other welders could
meet the B and C class requirements, Peters was not as optimistic about meeting the requirements of the all-weldmetal tensile test for A-class welds. The specification
requires a minimum of 14% elongation. Less elongation can
result in a lack of weld ductility.
Peters purchased quantities of each brand of underwater
welding electrode. Welds were made in the training tank at
the company’s Miami office, then subjected to visual and
destructive testing. “In the end, we found one electrode we
had never used before called Hydro-Weld FS,” Peters
recalled. “We found that electrode exceeded any of our
expectations as far as elongation.”
A transition to the new electrode proved somewhat difficult, however. The electrode the company had been using
was equivalent to an E7014 shielded metal arc welding electrode, while the new electrode was an E6013 equivalent.
“Even topside, those have different arcs,” Peters said.
The pad eyes that will hold this cofferdam to the side of
the ship were welded using A-class wet welding procedures. As a result, the welds were classified as a permanent
repair, which will not have to be reworked when the vessel
goes into drydock. (Photo courtesy of Miami Diver, Inc.)
“When you’re accustomed to a certain rod for so long, to
get [the welders] to switch was somewhat of an obstacle.”
Intensive Training
As they practiced with the new electrode, the welders
found they were not getting enough penetration. Although
adjustments were made following a series of phone calls
between Miami and the United Kingdom, where HydroWeld is headquartered, the problem was not solved. Peters
decided to bring in experts from the electrode manufacturer
and conduct a training class.
Joining forces with Trident BV and Cores Diving, Peters
shipped over a pallet of electrodes for the class. The companies’ goal was not only to become proficient in using the
new electrode but also to become the first diving contractors in the underwater ship repair industry to offer “surfacequality, structural wet welds” that could be accepted as permanent wet welding repairs. HydroWeld wrote the wet
welding procedure specifications the welders would follow
and conducted the ten-day-long training program.
Involving the Classification
Societies
Miami Diver brought in representatives from the six
largest ship classification societies—American Bureau of
Shipping, Lloyds Register of Shipping, Det Norske Veritas,
Bureau Veritas, Rina, and Germanischer Lloyd—to witness
the qualification of the welding procedures and welder
qualifications. An independent laboratory was hired to perform tests on the weld coupons.
Three positions were used to produce the coupons: 2F
horizontal, 3F vertical, and 4F overhead. Groove weld specimens for the Charpy impact and all-weld-metal tensile tests
as well as a longitudinal fillet weld shear strength test specimen were produced.
In the end, the classification societies confirmed that the
specimens complied with, or exceeded, the requirements of
AWS D3.6M for class-A welds.
98
Section 2
Shielded Metal Arc Welding
The bolts are underwater wet welds that held the gagging
plates to the housing of the propulsion pod. (Photo courtesy of
A diver/welder welding the gagging plates to the Azipod.
(Photo courtesy of Miami Diver, Inc.)
Miami Diver, Inc.)
“When the whole thing was over, it was probably in the
neighborhood of $75,000, $80,000, to run that course
[because] you have to take that many men off hire and pay
the manufacturer,” Peters said. “The consumables alone
were in excess of $10,000. Then [you have to pay] the class
societies.”
As a result, some wet welds previously considered temporary are now deemed permanent. The customer can also
avoid unscheduled drydocks, even for repairs that continue
to be classified as temporary. “You can get a temporary
repair that will allow the vessel to trade on its normal charter until the next scheduled drydock,” Peters said.
Underwater Welding Jobs
The A-class weld procedures proved useful during a
recent repair job in the Indian Ocean. The vessel, a semisubmersible drill rig modified into a platform from which
rockets launch satellites, is paired with a command ship. The
platform’s drydock schedule is once every ten years. The
owner tries to avoid unscheduled drydocks because the vessel is so large the only available drydock is in Asia. Moving
the vessel there and back is extremely expensive.
A problem developed in the bow thrusters, an integral
part of the platform’s dynamic positioning system that limited its ability to pitch. The only way to fix the problem was
in a dry environment, so workers from Miami Diver West
(the California subsidiary of Miami Diver) welded 13-ft 13-ft cofferdams, which could be attached to the side of
the ship.
Jim Allen, president of Miami Diver West, explained they
built the cofferdam large enough so that, if necessary, the
entire bow thruster could be disassembled, removed, and
replaced with a new one. Using an enclosed cofferdam to
create a dry welding environment has been done many
times before, Allen said, but this one was different because
they built interchangeable feet, which would allow it to
meet the curvature of either the platform or the command
ship. “That way we can utilize the same box for different
repairs,” Allen said.
The A-class wet welding procedures were key to the
repair, Allen said, because Det Norske Veritas classified the
wet welds used to join the twelve pad eyes that would hold
the cofferdam to the hull as permanent. Classified as permanent, the welds did not need to be reworked in drydock.
Once the cofferdam was pumped dry, the pad eyes needed
to hold 50 tons to the hull in a watertight seal.
“Obviously, the welds have been proven now that
they’ve actually held the box under,” Peters said.
Securing a Propulsion System
The company also followed the A-class wet welding procedures when it performed temporary repairs on a cruise
ship stuck at the Port of Miami dock.
A leak had developed in the starboard Azipod, the part of
a pod propulsion system that eliminates the need for a rudder
or stern thrusters, which hangs below the vessel and can
rotate 360°. Because of the leak, the ship needed to go to
Newport News, Virginia, to be placed into drydock for repair.
While the ship could run on its own power using the port pod,
any movement of the propeller blades inside the leaking pod
could damage its armature and the ship’s electric motor. Time
was critical because the cruise line estimated each day the ship
remained off hire cost the company $1 million in lost revenue.
It was first suggested the propeller blades be removed,
but no one was sure how long that would take. Miami Diver
came up with what it thought was a better solution. “We
told them, ‘We have wet weld procedures with Lloyds,
under A class,’ ” Peters recalled. “ ‘We’ll make gagging
plates and wet weld them to the Azipod—to the outer housing of the pod—and we’ll prevent the prop from rotating,’ ”
The A-class wet welding procedures helped sell the concept,
Peters said, because the classification society had already
approved those procedures. The cruise line agreed to the
proposal, as did the pod manufacturer, provided the welds
could pass a 50-ton load test. The manufacturer was concerned because the pod was under warranty.
“We removed two of the main fastenings to the hub and
we fabricated new bolts that were studs,” Peters explained.
Chapter 4
“This enabled us to lay a 1 1/2-in. plate over the hub of the
propeller and bolt it to the propeller. Then the remaining
part of the plate, approximately 1 ft, crossed over the pod
housing, and it was welded with a full 1-in. by 2-ft-long fillet weld.”
The company brought in four welders from Los Angeles,
welders from Holland, and part of its Miami-based crew for
the project. They worked around the clock—four hours at a
time in the water—to complete the job. Much of that time
Shielded Metal Arc Welding of Plate
99
was spent in preparation, such as cutting plates, machining
the bolts, and removing an epoxy coating from the pods.
In all, they fit and welded four gagging plates onto the
housing of the Azipod. “The load test was not even an issue
with us,” Peters said. “We put four plates on, but we could
have held it with one plate.” Once the propeller blades
could no longer move, the cruise ship successfully made its
journey to Newport News.
Photos and article courtesy of the American Welding Society.
Review
1. Describe two methods of striking an arc with an
electrode.
12. Describe the difference between using a leading and
a training electrode angle.
2. Why is it important to strike the arc only in the
weld joint?
13. Can all electrodes be used with a leading angle?
Why or why not?
3. What problems may result by using an electrode at
too low a current setting?
14. What characteristics of the weld bead does the
weaving of the electrode have?
4. What problems may result by using an electrode at
too high a current setting?
15. What are some of the applications for the circular
pattern in the flat position?
5. According to Table 4-1, what would the amperage
range be for the following electrodes?
16. Using a pencil, draw two complete lines of the
weave patterns you are most comfortable making.
a. 1/8 in. (3.2 mm),
E6010
c. 3/32 in. (2.4 mm),
E7016
17. Why is it important to find a good welding
position?
b. 5/32 in. (4 mm),
E7018
d. 1/8 in. (3.2 mm),
E6011
18. Which electrodes would be grouped in the following F numbers: F3, F2, F4?
6. What makes some spatter “hard”?
7. Why should you never change the current setting
during a weld?
8. What factors should be considered when selecting
an electrode size?
9. What can a welder do to control overheating of the
metal pieces being welded?
10. What effect does changing the arc length have on
the weld?
11. What arc problems can occur in deep or narrow
weld joints?
19. Give one advantage of using electrodes with
cellulose-based fluxes.
20. What are stringer beads?
21. Describe an ideal tack weld.
22. What effect does the root opening or root cap have
on a butt joint?
23. What can happen if the fillet weld on a lap joint
does not have a smooth transition?
24. Which plate heats up faster on a tee joint? Why?
25. Can a tee weld be strong if the welds on both sides
do not have deep penetration? Why or why not?
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement