Welding and Metal Fabrication, 1st ed.

Welding and Metal Fabrication, 1st ed.
Chapter
9
Shielded Metal Arc
Welding Plate
OBJECTIVES
After completing this chapter, the student should be able to:
•
•
•
•
Demonstrate the safe way to set up a welding station.
Explain the differences among F2, F3, and F4 electrodes.
Demonstrate welding fabrication skills.
Demonstrate welding skills by making square butt, outside corner,
lap, and tee joints.
KEY TERMS
amperage range
arc length
cellulose-based fluxes
chill plate
electrode angle
electrode manipulation
lap joint
leading electrode angle
mineral-based fluxes
outside corner joint
rutile-based fluxes
spatter
square butt joint
striking the arc
stringer bead
tack welds
tee joint
trailing electrode
angle
weave pattern
INTRODUCTION
Shielded metal arc welding (SMAW) or stick welding is the most commonly
used welding process. Stick welding is popular for a number of reasons. It can
be used to make strong durable welds in a wide range of metal thicknesses and
types. Transformer-type welders can sit for years without being used and still
work when needed, and the welding rods have an almost unlimited storage life,
as long as they are kept dry. These factors mean that the equipment is there
when you need it to make a repair or build a project.
165
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166
CHAPTER 9
In addition to the standard rods that can be used
to make welds in steel 1/8 in. (3 mm) and thicker,
there are a wide variety of specialty electrodes. These
specialty rods allow you to use the same welding
machine to weld on cast iron, stainless steel, and aluminum. There are rods for cutting that will cut cast
iron and stainless steel; these are metals that cannot
be cut with oxygen and acetylene. Wear-resistant and
buildup rods can be used to repair scraper and frontend loader blades and buckets.
The basic stick-welding skills you will learn in
this chapter are used for almost every welding fabrication project. Welding is a skill that takes practice
to perfect. The repetition in the chapter practices and
projects is designed to give you the opportunity to
develop your skills. The more time you spend welding,
the better your welding skills will become.
ELECTRODES
Arc welding electrodes used for practice welds are
grouped into three filler metal classes (F number)
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. E6010 and E6011 are
the most utilitarian welding electrodes for welding
fabrication. They can be used on metal that has a little
rust, oil, or dirt without seriously affecting the weld’s
strength. The E6010 electrodes can weld only with
direct current (DC) welding machines. Because E6011
electrodes can be used with alternating current (AC),
smaller transformer-type welders that put out only AC
welding current can be used.
They do not have forceful arcs, so they can be used
on thinner metals such as some thicker sheet metal
gauges that are used as guards on equipment.
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. Of these two electrodes, E7018 is the one used most often to make
high-strength welds on equipment. Store these electrodes in a dry place. If they get wet, they will still
weld, but the welds will not be as strong.
The cellulose- and rutile-based groups F3 and
F2 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 fillet, stringer beads, and
butt joints.
Unless a specific electrode is required for a job,
welders can select what they consider to be the best
electrode for a specific weld. Welders often have
favorite electrodes to use on specific jobs.
Electrodes with mineral-based fluxes, group F4,
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 9-1 shows a general comparison of the
weld penetration and buildup each electrode will produce with approximately the same amperage. More
information on electrode selection can be found in
Chapter 26.
F2 E6012 and E6013 Electrodes
Effect of Too High or Too Low
Current Settings
These electrodes have rutile-based fluxes, giving a
smooth, easy arc with a thick slag left on the weld
bead. Both E6012 and E6013 are easy electrodes to use.
Each welding electrode must be operated in a particular current (amperage) range, Table 9-1. Welding with the current set too low results in poor fusion
E6010
FIGURE 9-1
E6011
E6012
E6013
E7016
E7018
Comparison of electrode type and weld bead shapes. © Cengage Learning 2012
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Shielded Metal Arc Welding Plate
ELECTRODE DIAMETER AND AMPERAGE RANGE
5"
3"
1"
AWS
CLASSIFICATION
32
32
8
40–80
70–130
110–165
E6010
50–70
85–125
130–160
E6011
40–90
75–130
120–200
E6012
40–85
70–120
130–160
E6013
75–105
100–150
140–190
E7016
70–110
90–165
125–220
E7018
167
ELECTRODE BECOMES
DISCOLORED DUE TO
EXCESSIVE HEAT
EXCESSIVE GAS
(SMOKE)
Table 9-1
Welding Amperage Range for Common
Electrode Types and Sizes
and poor arc stability, Figure 9-2. 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 baseplate 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 9-3. 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 baseplate
and is difficult to remove, Figure 9-4. The electrode
covering is discolored more than 1/8 in. (3 mm) to
LARGE MOLTEN WELD
POOL WITH LITTLE BUILDUP
FIGURE 9-3
Welding with too high an amperage.
Larry Jeffus
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.
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. The 1/8-in. (3-mm) electrode is the most
commonly used size for metal fabrication. It can be
used to make welds on thin metal up to thick plates.
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 a thick
plate, but more time is required to make the weld.
SPATTER
VERY LITTLE SHIELDING
GAS COVERAGE
WELD BEAD
SMALL
HIGH WITH
WELD LITTLE FUSION
POOL
FIGURE 9-2
Larry Jeffus
Welding with the amperage set too low.
FIGURE 9-4
Hard weld spatter is fused to base metal
and is difficult to remove. Larry Jeffus
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168
CHAPTER 9
AMOUNT OF HEAT
DIRECTED AT WELD
WELD POOL
HIGH NARROW BEAD WITH
A HEAVY SLAG COVER
TOO LOW
CORRECT
TOO HOT
FIGURE 9-5 The effect on the shape of the molten
weld pool caused by the heat input.
© Cengage Learning 2012
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 9-5.
Rounded ripples indicate that 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.
Arc Length
The arc length is the distance that 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 9-6.
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 9-7.
There is a narrow range for the arc length in
which it is stable, metal transfer is smooth, and the
FIGURE 9-6
Welding with too short an arc length.
Larry Jeffus
bead shape is controlled. Factors affecting the length
are the class of electrode, joint design, metal thickness, and current setting.
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 9-8. For this class of welding electrode, the arc length is maintained by the electrode covering. E7024 electrodes require very little
welding skill to use. Because of the size of the molten
weld pool, they are usually used only in the flat position on thick metal.
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 9-9. As a result,
the root fusion is reduced or may be nonexistent,
FIGURE 9-7
Welding with too long an arc length.
Larry Jeffus
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
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.
ELECTRODE FLUX
TOUCHES BASE METAL
FIGURE 9-8
169
Welding with a drag technique.
Larry Jeffus
ELECTRODE
ARC
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 9-10. 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 Electrode Angle
ROOT OPENING
FIGURE 9-9 The arc may jump to the closest metal,
reducing root penetration. © Cengage Learning 2012
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
A leading electrode angle pushes molten metal and
slag ahead of the weld, Figure 9-11. 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, Figure 9-12. 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.
DIRECTION OF TRAVEL
TRAILING
ANGLE
FIGURE 9-10
RIGHT
ANGLE
LEADING
ANGLE
Direction of travel and electrode angle. © Cengage Learning 2012
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170
CHAPTER 9
DIRECTION OF TRAVEL
ELECTRODE
WELD
BEAD
AREA AHEAD
OF THE MOLTEN
WELD POOL
LIMITED DEPTH OF PENETRATION
FIGURE 9-11
MOLTEN WELD POOL
Leading, lag, or pushing electrode angle.
© Cengage Learning 2012
FIGURE 9-13
Metal being melted ahead of the molten
weld pool helps to ensure good weld fusion. Larry Jeffus
The following are suggestions for preventing cold
lap and slag inclusions:
SLAG
• Use as little leading electrode angle as possible.
• Ensure that the arc melts the base metal completely,
NO FUSION
SLAG TRAPPED
UNDER WELD
FIGURE 9-12
Some electrodes, such as E7018, may
not remove the deposits ahead of the molten weld pool,
resulting in discontinuities within the weld. © Cengage
Learning 2012
Figure 9-13.
• Use a penetrating-class 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 9-14.
A
B
C
A
B
C
SECTION A-A
(A)
SECTION B-B
(B)
SECTION C-C
(C)
FIGURE 9-14
Effect of a leading angle on weld bead buildup, width, and penetration. As the angle
increases toward the vertical position (C), penetration increases. © Cengage Learning 2012
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
WELDING DIRECTION
FIGURE 9-15
Trailing electrode angle. © Cengage
Learning 2012
Trailing Electrode 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 9-15. 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 9-16.
Electrode Manipulation
The movement or weaving of the welding electrode,
called electrode manipulation, can control the
171
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 9-17 shows 10 different patterns that
can be used for most welding conditions.
The circular pattern is often used for flat position
welds on butt, tee, and 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 9-18.
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 9-19. 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.
A
B
C
A
B
C
SECTION A-A
(A)
SECTION B-B
(B)
SECTION C-C
(C)
FIGURE 9-16 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. © Cengage Learning 2012
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172
CHAPTER 9
SHELF SUPPORTS MOLTEN WELD POOL, MAKING
THE SHAPE OF THE WELD BEAD UNIFORM
V
UPSIDE DOWN V
CIRCULAR
C
SQUARE
J
LESS HEAT CAN CONDUCT
INTO THE EDGE THAN INTO
THE BASEPLATE
ZIGZAG
T
FIGURE 9-19
The “J” pattern allows the heat to be
concentrated on the thicker plate.
© Cengage Learning 2012
STRAIGHT STEPPED
FIGURE 9-17
FIGURE 8
Weave patterns.
© Cengage Learning 2012
The “T” pattern works well with fillet welds in the
vertical (3F) and overhead (4F) positions, Figure 9-20.
It can also 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 9-21
and Figure 9-22. 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.
WEAVE PATTERN
THIS WEAVE PATTERN RESULTS
IN A NARROW BEAD WITH
DEEP PENETRATION
THIS WEAVE PATTERN RESULTS
IN A WIDE BEAD WITH
SHALLOW PENETRATION
FIGURE 9-18
Changing the weave pattern width
to change the weld bead characteristics.
© Cengage Learning 2012
VERTICAL FILLET WELD
FIGURE 9-20
“T” pattern. © Cengage Learning 2012
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
STEPPING
ELECTRODE
BACK AND FORTH
173
SHELVES
MOLTEN WELD
POOL
FIGURE 9-21 The electrode is moved slightly forward
and then returned to the weld pool. Larry Jeffus
FIGURE 9-23
The figure 8 pattern and the zigzag pattern are
used as cover passes in the flat and vertical positions.
Do not weave more than two-and-a-half times the
width of the electrode. 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 9-23.
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 fillet 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.
Practice Welds
Practice welds are grouped according to the type of
joint and the class 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
NO METAL
WAS DEPOSITED
FIGURE 9-22
The electrode does not deposit metal or
melt the base metal. Larry Jeffus
Using the shelf to support the molten
pool for vertical welds. Larry Jeffus
Positioning of the Welder
and the Weld 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 onto a stable object. When welding, even if a welder is seated,
touching a stable object will make the welder more
stable and will make welding more relaxing.
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
174
CHAPTER 9
(B)
WELDING
TABLE
SURFACE
(C)
(A)
FIGURE 9-24
Not all field welding can be done in a comfortable position. Larry Jeffus
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 9-24A,
B, and C.
PRACTICE 9-1
Shielded Metal Arc Welding Safety
Skill to be learned: The safe setup of a welding
station and the use of proper personal protective
equipment (PPE).
Using a welding workstation, 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 workstation 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 cleanup.•
STRIKING AN ARC
All welds start with an arc strike. It is the process of
establishing a stable arc between the end of the electrode
and the work. At first, striking an arc can be difficult
because it may seem that the end of the electrode wants
to stick to the plate. With practice, you will be able to
strike an arc and establish a weld bead without much
thought. One important thing to remember is that on
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
175
most code welding jobs, an arc strike outside of the weld
zone may be considered a defect. Start now building a
habit of always striking the arc in the weld joint just
ahead of where you are going to be welding. That way
the arc strike will become part of the finished weld.
hot dish. This reduces the heat transfer from the dish
to the hot plate.
PROJECT 9-1
Materials
• 5 to 10 1/8-in. diameter E6011 electrodes
• 1 6-in. square piece of 1/4-in. thick mild steel plate
• 4 cork or felt pads
• Paint
• Clear finish
Striking the Arc to Build a Hot Plate
Skill to be learned: The ability to start and hold an
arc to produce a weld bead.
Project Description
Hot plates serve two main purposes—to protect the
surface of a kitchen countertop or table from damage
caused by a hot skillet or other cooking utensil and
to prevent a cold surface from cooling a dish before
the food can be served. The hot plate you are going to
fabricate serves both of these purposes. The cork or
felt pads placed on the four corners of the bottom of
the hot plate serve as insulators and surface protectors. They keep any heat picked up by the hot plate
from being transferred to the surface and keep the
metal hot plate from scratching the surface.
The short welds on the surface of the hot plate
limit the contact area between the hot plate and the
Project Materials and Tools
The following items are needed to fabricate the hot
plate.
Tools
• Arc welder
• PPE
• Angle grinder
• Wire brush
• Square
• Soapstone
Layout
Using a square, 12-in. rule and soapstone, lay out the
plate as shown in the project drawing, Figure 9-25.
6"
1"
116
7"
16
1"*
1"**
2
7"
1" 16
1 16
A
A
45o
1"**
2
6"
G
1" - 1 1"
2
TYP.
GRIND TOP
OF WELD FLAT
1"* 1"
2
SECTION A-A
HOT PLATE
FIGURE 9-25
Project 9-1. © Cengage Learning 2012
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176
CHAPTER 9
Welding
Using a properly set up and adjusted arc welding
machine and the proper safety protection as demonstrated in Practice 9-1, you will make a series of weld
beads on the hot plate surface following the soapstone
layout.
NOTE: Before starting on any project, test the setup of
the welder by making a few test welds on a piece of scrap
metal. That way you can make any adjustments in the
welding amperage settings before starting on the project.
With the electrode held over the plate, lower your
helmet. Scratch the electrode across the plate (like
striking a large match), Figure 9-26. 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 desired size. Slowly lower the
electrode as it burns off, and slowly move it forward
to start the weld bead.
NOTE: 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 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 9-27.
Break the arc by rapidly raising the electrode after
completing a 1-in. long weld bead. You will be making
BROKEN FLUX
ARC FORCED TO
THE BACK SIDE
FIGURE 9-27
If the flux is broken off the end completely
or on one side, the arc can be erratic or forced to the side.
Larry Jeffus
another weld on the next marked spot. Move the electrode end over the starting point for the next weld.
Restart the arc as you did before, and make another
short weld. Repeat this process until you have made
all of the welds.
A more accurate way of striking the arc is to
hold the electrode steady by resting it on your free
hand like a pool cue over the desired starting point.
After lowering your helmet, swiftly bounce the electrode against the plate, Figure 9-28. A lot of practice
is required to develop the speed and skill needed to
prevent the electrode from sticking to the plate. But
striking an arc in an incorrect spot may cause damage
to the base metal.
NOTE: Sometimes the welding fumes may partially
cover the marks next to the weld you just made. If that
happens, do not wipe the fumes off because you may
erase the lines. Instead, use the soapstone to retrace
ELECTRODE
WORKPIECE
FIGURE 9-26
Learning 2012
Scratch striking an arc. © Cengage
FIGURE 9-28
Bounce striking an arc to start it on a
spot. © Cengage Learning 2012
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
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Shielded Metal Arc Welding Plate
the line. You can usually do this by hand without the
need for a straightedge.
3"
16
3"
As you make more and more of the welds, you will
become more efficient at starting the arc. When you
have completed all of the welds, turn off the welding
machine and clean up your work area.
Finishing
Cool off the metal, chip the slag, and wire brush the
surface. Sometimes the metal may warp from the heat
and welds. If necessary, you can flatten your hot plate
enough for it to be used by using a hammer and anvil.
Paint the top and side surfaces with a latex paint.
Once the paint is dry, grind the tops off of the welds
as shown in the drawing. Do not grind too hard
because that could cause excessive heat, which could
damage the paint. Check the surface to see that it is
flat enough to prevent a pot or dish from rocking. Do
any additional grinding to make the tops of the welds
flat. Paint the hot plate with a coat of clear latex finish
to keep it from rusting.
Paperwork
Complete a copy of the time sheet in Appendix I, the
bill of materials in Appendix III, or use forms provided
by your instructor.•
TACK WELDS
Tack welds are a temporary method of holding parts
in place until they can be completely welded. Usually,
all of the parts of a weldment should be assembled
before any finishing welding is started. This will help
reduce distortion. Tack welds must be strong enough
to withstand any forces applied during assembly
and any force caused by weld distortion during final
welding. They must also be small enough to be incorporated into the final weld without causing a discontinuity in its size or shape, Figure 9-29.
PROJECT 9-2
Tack Welding Assembly of a Pencil Holder
Skill to be learned: The tack welding of parts in
place so they can be finished welded.
Project Description
The pencil holder will be assembled and tack welded
in preparation for welding. The same skills you learned
by making short welds as you fabricated the hot plate
177
4"
TACK
WELDS
FIGURE 9-29
Tack welding outside corner joint.
© Cengage Learning 2012
will be used to make the pencil holder. In this application short stringer welds will be used as tack welds to
hold the parts in place so they can be welded.
Project Materials and Tools
The following items are needed to fabricate the pencil
holder.
Materials
• 1 to 2 1/8-in. diameter E6012 or E6013 electrodes
• 4 ´ 4-in. rectangular pieces of 3/16-in. thick mild
steel plate
• 1 3-in. square piece of 3/16-in. thick mild steel plate
Tools
• Arc welder
• Plasma cutting torch, oxyfuel cutting torch, or
shear
• PPE
• Wire brush
• Chipping hammer
• Square
• C-clamp or magnetic clamp
• Soapstone
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178
CHAPTER 9
3"
3"
(A)
FIGURE 9-31
(B)
Magnetic clamps. Larry Jeffus
3"
8
4"
3"
8
3"
8 LOCATIONS
1"
4
FIGURE 9-30
3"
8
gloved hand and make a small tack weld. If you use
your square, keep it as far away as possible from the
tack weld so it will not be damaged.
Make the tack welds as shown in the project
drawing, Figure 9-30. Keep the tack welds small so
they will not affect the finished weld.
Paperwork
Complete a copy of the time sheet in Appendix I, the
bill of materials in Appendix III, or use forms provided by your instructor.•
Project 9-2. © Cengage Learning 2012
STRINGER BEADS
Layout
Using a square, 12-in. rule and soapstone, lay out the
plate as shown in the project drawing, Figure 9-30.
Cutting Out
If flat 3/16-in. bar stock is available, all you will have
to do is shear the metal to length. However, if you
are using sheet stock, you will have to thermally cut
the parts using either a flame or plasma torch. (See
Chapters 21 and 22 for details on flame and plasma
cutting.) If the parts are thermally cut, clean off any
slag before you assemble the parts.
Fabrication
The parts will need to be held square as they are tack
welded. A C-clamp or magnetic clamp can be used to
hold the parts in place for tack welding, Figure 9-31.
Sometimes you can hold the parts in place with your
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. They are also used by experienced welders to set the welding machine amperage.
An example of an application for stringer beads
is using them to build up a worn surface or apply a
chemical- or mechanical-resistant weld metal to the
surface. They may also be used to add an effect to the
surface of a piece of art.
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 9-32. 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
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
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Shielded Metal Arc Welding Plate
FIGURE 9-34
179
Another arc striking project. © Cengage
Learning 2012
FIGURE 9-32
New welders frequently see only the arc
and sparks from the electrode. Larry Jeffus
WELD SPATTER
SOLID
SLAG
MOLTEN FLUX
Project Description
The surface welds applied to the pencil holder are for
artistic decoration only. They add depth and individual interest to the finished project. Other projects
with a similar application of welds might include a
fish on which the welds appear to be scales or birds
on which they appear to be feathers, Figure 9-34.
Project Materials and Tools
The following items are needed to finish the pencil
holder.
ARC
MOLTEN WELD
POOL
Materials
• 5 to 10 1/8-in. diameter E6012 or E6013 electrodes
• 1 assembled pencil holder
• 4 cork or felt pads
• Paint or clear finish
FIGURE 9-33
More experienced welders can see the
molten pool, metal being transferred across the arc, and
penetration into the base metal. Larry Jeffus
the surrounding plate, Figure 9-33. 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.
PROJECT 9-3
Stringer Bead to Surface a Pencil Holder
Skill to be learned: The control of the welding
electrode to produce uniform weld beads in the flat
position.
Tools
• Arc welder
• PPE
• Square
• Steel rule
• Angle grinder
• Wire brush
• Soapstone
Welding
Using a properly set up and adjusted arc welding
machine and the proper safety protection as demonstrated in Practice 9-1, you will make a series of
stringer weld beads on the surface of the pencil holder
that was assembled in Project 9-2.
The first stringer weld bead will actually be a
square butt joint weld. It will be used to prevent the
plates from excessively distorting as the remainder of
the stringer welds are made. Start the weld at the edge
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180
CHAPTER 9
C OR R E C T
TOO HOT AND
TOO SLOW
Making the weld narrow with a higher
buildup by using a short arc length can add dimension to the
finished project’s surface appearance. Larry Jeffus
FIGURE 9-37 Comparison of the appearance of weld
beads with correct temperature and overheated base metal.
of the plate and weld all the way to the opposite end.
Try to keep the weld width and travel speed consistent
all the way down the plate, Figure 9-35. When the first
weld is completed, roll the pencil holder over so that
the next weld can be made to close the next butt joint.
Repeat this until all four corners are welded.
Cool the part and look at the welds. See how consistent you were in your travel speed and electrode
movement. You can tell when you were welding faster
because the weld will be thinner with less buildup,
Figure 9-36. The weld will be wider with more
buildup when you travel slower. The width of the
weld, spacing of the weld bead ripples, and smoothness of the sides of the weld are all indicators of how
constant you were in your side-to-side manipulation.
Alternate both the direction of the weld and the
side that you are welding on. The alternating of the
direction will make the finished welds look neater, and
by switching sides you will not be as likely to overheat
the metal. Watch the back side of the weld pool to see if
the weld is getting too hot, Figure 9-37. Chip and wire
brush the welds after each pass. Look at the weld bead
for uniformity in width, height, and spacing of ripples.
FIGURE 9-35
AMOUNT OF HEAT
DIRECTED AT WELD
WELD POOL
TOO LOW
© Cengage Learning 2012
NOTE: If the project is becoming overheated, you can
cool it by quenching it in water. Normally, welds are not
quenched in water because that might cause cracks and
it makes them brittle. But the weld’s strength is not a
factor in the usability of this artistic project.
When all of the sides are completely covered with
weld beads, cool the project. Next, you will make the
last series of welds, numbers 3 and 4, as shown in the
drawing, Figure 9-38.
Finishing
Cool off the metal, chip the slag, and wire brush the
surface. A power wire brush can be used to give the
welds a polished, shiny appearance. The project can
be painted with a clear coat or colored coat of latex
paint. Stick the felt or cork pads on the corners of the
bottom to protect the surface of the furniture.
CORRECT
Paperwork
Complete a copy of the time sheet in Appendix I, the
bill of materials in Appendix III, or use forms provided by your instructor.•
TOO HOT
Square Butt Joint
FIGURE 9-36
Comparison of weld beads and heat input.
© Cengage Learning 2012
The square butt joint is made by tack welding two
flat pieces of plate together, Figure 9-39. The space
between the plates is called the root opening or root
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
gap. Changes in the root opening affect penetration.
As the space increases, the weld penetration also
increases. The root opening for most butt welds varies
from 0 to 1/8 in. (3 mm). Excessively large openings
can cause burnthrough or a cold lap at the weld root,
Figure 9-40.
Square butt joints are used to join plate and
structural steel shapes up to 1/4-in. thick. The advantage of using the square butt joint is that often the
edges of the metal can be used just as they are without having to do additional edge beveling. Not having
to bevel the edge of the metal saves time and money
for the fabricator, Figure 9-41.
3"
3"
181
3
2
PROJECT 9-4
Butt Welds to Build a Smoke Box
1
4"
Skill to be learned: The control of the welding electrode to produce uniform butt weld joints in the flat
position.
4
PENCIL HOLDER
FIGURE 9-38
Project 9-3. © Cengage Learning 2012
FIGURE 9-39 The tack weld should be small and
uniform to minimize its effect on the final weld.
Project Description
A smoke box is a small flat box that wood chips are
placed in so that food cooked on a gas barbecue grill
will have a wood fire flavor. The smoke box is used by
placing several hickory, mesquite, or other aromatic
wood chips in the box and covering them with the
box lid. The lid prevents the wood from burning so it
only smokes.
With the box closed, place it as close to the grill
burners as possible. If your barbeque grill has lava
stones, move enough of them aside so you can place
the smoke box just above the burner flames. If your
barbeque grill uses ceramic plates, one can be moved
to make room for the smoke box, or just set it on top
of the ceramic plate. The only thing that is important
is that the box be placed so it will get hot enough for
the wood chips inside to smoke.
Larry Jeffus
ROOT OPENING
LACK OF
FUSION
INCREASING ROOT OPENING
FIGURE 9-40
Effect of root opening on weld penetration. © Cengage Learning 2012
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182
CHAPTER 9
• Tape measure
• C-clamp or magnetic clamp
• Soapstone
10'-0"
6'-6"
3'-3"
Layout
Using a square, 12-in. rule and soapstone, lay out the
bar stock as shown in the project drawing, Figure 9-42.
Cutting Out
The first step is to cut the mild steel bar stock to
length with a shear or thermally.
Fabrication
This project will be fabricated in steps.
6'-3"
1st Step—Assemble the top
■ Assemble and tack weld together six of the
5 1/2-in. long bars into a square flat plate with
no root space, Figure 9-42.
TYP.
2-6
TYP.
DETAIL
B-B
2' 5"
TYP.
DETAIL
C-C
DETAIL
TRAILER
FIGURE 9-41
Square butt joints on utility trailer.
© Cengage Learning 2012
Project Materials and Tools
The following items are needed to fabricate the
smoke box.
Materials
• 24 to 30 1/8-in. diameter F2 or F3 class electrodes
• 8 1 ´ 6-in. pieces of 3/16-in. to 1/4-in. thick mild
steel plate
• 7 1 ´ 5 1/2-in. pieces of 3/16-in. to 1/4-in. thick
mild steel plate
• 2 1 ´ 7-in. pieces of 3/16-in. to 1/4-in. thick mild
steel plate
Tools
• Arc welder
• Plasma cutting torch, oxyfuel cutting torch, or shear
• PPE
• Wire brush
• Angle grinder
• Chipping hammer
• Square
2nd Step—Assemble the smoke box
■ Assemble and tack weld together six of the
6-in. long bars into a square flat plate with a
1/8-in. root space, Figure 9-42.
■ Tack weld the two 1 ´ 7-in. and two of the
1 ´ 6-in. long bars on the sides of the first plate,
tack welded together to form a shallow box.
3rd Step—Forming the handle
■ The smoke box handle will be made from one of
the 5 1/2-in. long pieces of metal bar. Using an
oxyfuel torch, heat across one end of the bar 1/2 in.
from the end. Place the hot end in a vise, and
bend it at a right angle. Repeat this process on
the other end to make the long U-shaped handle.
Welding
Using a properly set up and adjusted arc welding
machine and the proper safety protection as demonstrated in Practice 9-1, you will make a series of welds
on the joints on the top of the smoke box.
These welds can be made using the skills that you
developed while doing the stringer beads on the pencil holder. The difference in making these welds and
the stringer beads is that these welds must join two
pieces of metal together. To do this you must watch
the weld bead to see that it is flowing together and
make the weld straight down the joint. The molten
weld metal formed on the two sides of the joint will not
just flow together forming a single weld bead joining
the plates. You must make sure you are traveling
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
1"
52
6"
1"
8
FIGURE 9-42
183
0"
Project 9-4. © Cengage Learning 2012
slowly enough so that the weld side is adequate to
allow the molten weld pools to flow together and not
just form on the two edges of the weld, Figure 9-43.
The welds must be straight so that the weld beads
are evenly spaced on both sides of the weld joints,
Figure 9-44. You must watch the leading edge of the
weld pool to make sure your weld bead is centered on
the weld joint. If the weld does not follow along the
center of the weld joint, the joint will not be as strong
as it should be. Weak weld joints can be serious.
Cool, chip, and inspect each weld joint after you
have finished the weld. Look at the weld to see if it
has uniform width and buildup and follows the weld
joint. A lack of uniform width might indicate you
were not using a consistent weave pattern. A lack in
uniformity in buildup might indicate that your rate of
travel down the joint was not steady.
Finish welding the top by making all the welds
along both sides of the weld joint on the top plate
WELD JOINT
WELD DOES NOT FOLLOW JOINT
WELD FOLLOWS JOINT
FIGURE 9-43 Moving the electrode from side to side
too quickly can result in slag being trapped between the
plates. Larry Jeffus
FIGURE 9-44
The weld bead must track down the
center of the joint so it is equally distributed on both
sides. © Cengage Learning 2012
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
184
CHAPTER 9
HANDLE
FIGURE 9-45
LID
Smoke box handle.
© Cengage Learning 2012
until you have completed all 12 welds. Remember
to cool and chip the welds between each one so you
can see what changes in technique you need to make.
This also ensures that the weldment does not become
overheated.
Measure the length of the box handle and center
it from both sides and the ends of the box top. Tack
weld both ends before welding it in place with short
welds across the outside of both ends of the handle,
Figure 9-45.
The root space on the box may make it easier to
follow the weld joint, but it makes it harder to get the
weld metal to flow together. Too fast a travel speed
along this joint will result in a lack of fusion between
the two plates. To ensure that this does not happen,
you must watch the back edge of the molten weld bead.
If it is smooth and rounded, the molten weld metal is
joining. Sometimes this can be difficult to see because
of the flux covering. The lighter flux produced by
F3 class electrodes does not cause this problem as much
as the class F2 and F4 electrodes do. One indicator
that the weld metal is not joining is a slight difference
in the shade of red at the trailing edge of the weld.
When there is a gap in the weld metal, the flux will
have a slightly lighter red color.
NOTE: There can be enough weld stresses produced to
break a tack weld. When tack welds break, they often
produce a sharp pinging sound. If you hear this sound
FIGURE 9-46
while you are welding, stop and locate the broken tack.
Use clamps, if necessary, to force the joint back into
position before tack welding it into place again.
Weld the joint on the outside of the box first. As
before, cool, chip, and inspect each of the welds after
they are completed. Make the butt welds around the
side of the plate so that the sides are secured to the bottom plate. Use the same techniques for these welds as
you did for the other butt joint welds.
The butt welds inside the box may have some
degree of arc blow. If arc blow occurs, refer back to
that section in this chapter to see how you might
solve the problem. Try changing from a DC to AC
welding current, and try changing the direction in
which you are welding in addition to the other suggested arc blow controls. Observe how each arc blow
control worked in this application. Under different
conditions the results you observed here, other than
changing the class of welding current, may differ.
Limited visibility may be another problem you
might have when making the inside welds. The welds
must be started all the way at the end, next to the side.
This will require a trailing electrode angle, but you cannot end the weld with the same angle. There are several
ways of solving this problem. One way is to gradually
change from a trailing angle at the beginning to a leading angle at the end of the weld, Figure 9-46. The second way to ensure that the weld is made all the way
across the joint is to stop the weld in the center of the
joint. Clean and chip the weld end crater and complete
the weld by starting on the opposite end and welding
back to the center, Figure 9-47. Try both methods to
see which works best for you.
Remember to cool, chip, and inspect the welds
after each pass to see what changes you might need to
make in your technique.
Finishing
Cool off the metal, chip the slag, and wire brush
the surface. Grind any welds that interfere with the
Rotating the electrode to improve visibility helps when welding in a confined space. © Cengage
Learning 2012
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
185
10'-0"
6'-6"
FIRST WELD
3'-3"
SECOND WELD
FIGURE 9-47
to the center.
Starting the weld at the edge and welding
6'-3"
© Cengage Learning 2012
top fitting into the box. No additional finishing is
required.
TYP.
2-6
TYP.
Paperwork
Complete a copy of the time sheet in Appendix I, the
bill of materials in Appendix III, or use forms provided by your instructor.•
DETAIL
An outside corner joint is made by placing the plates
at an angle to each other, with the edges forming a
V-groove, Figure 9-48. The angle between the plates
may range from a very slight 15° angle to almost flat
at a 165° angle. 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
each end of the joint. The weld bead should completely fill the V-groove formed by the plates and may
have a slightly convex surface buildup.
FIGURE 9-48
V formed by an outside corner joint.
© Cengage Learning 2012
TYP.
DETAIL
C-C
TRAILER
FIGURE 9-49
Outside Corner Joint
DETAIL
B-B
2' 5"
Outside corner joints on utility trailer.
© Cengage Learning 2012
Outside corner joints are used at the corners of
tanks, boxes, and ships. Four plates can be made into
a square tube; three can be made into a triangular
tube, Figure 9-49.
PROJECT 9-5
Outside Corner Welds to Build a Candlestick
Skill to be learned: The control of the welding electrode to produce uniform outside corner welds in
the flat position.
Project Description
Candles come in a variety of sizes and lengths. It is
common to display them on some type of stand. The
stand can serve to raise a short candle above other
decorations, or several different heights of candlesticks
may be used to display candles in an arrangement.
Most candles today are made from “drip-free” wax to
avoid wax damaging furniture or fabric such as tablecloths. Some people prefer the nostalgic appearance
of candle wax running down the side of a candle. You
can build your candlestick holder with a top plate large
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
186
CHAPTER 9
enough to catch this dripping wax or small enough to
allow the wax to run down the holder too.
2"
Project Materials and Tools
The following items are needed to fabricate the pair
of four-sided candlestick holders.
Materials
• 10 to 15 1/8-in. diameter F2 or F3 class electrodes
• 8 1 1/2 ´ 8-in. pieces of 3/16-in.- to 1/4-in. thick
mild steel plate
• 2 2-in. square pieces of 3/16-in. to 1/4-in. thick mild
TYP.
8"
A
A
steel plate
• 2 3-in. square pieces of 3/16-in. to 1/4-in. thick mild
steel plate
• 8 cork or felt pads
Tools
• Arc welder
• Plasma cutting torch, oxyfuel cutting torch, or
shear
•
•
•
•
•
•
•
•
SECTION A-A
PPE
3"
Wire brush
CANDLESTICK
Angle grinder
Chipping hammer
FIGURE 9-50
Project 9-5. © Cengage Learning 2012
Square
Steel rule
C-clamp or magnetic clamp
Soapstone
Layout
Using a square, 12-in. rule and soapstone, lay out
the bar stock as shown in the project drawing,
Figure 9-50.
Welding
Make sure to strike the arc in the V-groove of the outside corner joint. Although F3 class electrodes may
produce a lot of weld spatter that can stick to the sides
of the plates, it does not have the same effect that
THE PLATES OF AN OUTSIDE
CORNER JOINT FORM A “V”SHAPED GROOVE.
Cutting Out
The first step is to cut the mild steel bar stock to
length with a shear or thermally.
Fabrication
Tack weld the 1 1/2-in. metal bars together so they
make a square tube. The corners of the plates should
meet so they form a 90° V, Figure 9-51. Place the tack
welds about 1 in. from the ends of the joints so they
do not interfere with the starting or stopping of the
welds. The top and bottom plate will be assembled
following the welding of the outside corner joints.
FIGURE 9-51
Outside corner joint layout.
© Cengage Learning 2012
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Shielded Metal Arc Welding Plate
187
HARDNESS ZONE
SECTION A - A
A
STEEL RULE
A
FIGURE 9-52
bead.
Effect of arc strike outside of the weld
SQUARE
Larry Jeffus
striking the arc has on the plate surface, Figure 9-52.
The weld spatter can be cleaned off or left to add texture to the finished candlestick.
There may be some arc blow at the ends of the
weld. The appearance of these welds is part of the
finished part’s appearance. So, you cannot start
at the ends and weld to the center of the weld as
you may have done when welding out the smoke
box. Because the welds’ appearance is important,
if arc blow does occur, you cannot just stop. You
will need to control the arc and weld pool to keep
them uniform. Try holding a very short arc length
as a way of controlling the arc blow if it becomes
a problem.
Cool, chip, and inspect each weld joint after you
have finished the weld. Look at the weld to see if it
has uniform width and buildup and follows the weld
joint. A lack of uniform width might indicate you
were not using a consistent weave pattern. A lack in
uniformity in buildup might indicate that your rate
of travel down the joint was not steady.
When all of the welds are completed on both
candlesticks, lay out the center of the top and bottom plates. Center the square tube on the bottom
plate and square it to the baseplate before making
a single small tack weld on one corner. Stand the
candlestick up next to the square, Figure 9-53. Measure the distance from each of the sides of the top
of the tube to see that it is standing up vertically on
the base. If the tube is not vertical within 1/8 in.,
the tack weld can be bent slightly to make the tube
vertical. If the tack weld cannot bend enough, it can
be broken off and a new tack made.
NOTE: A magnetic level can be used to check if the
tube is vertical before tack welding, Figure 9-54.
FIGURE 9-53
Checking squareness with a square.
© Cengage Learning 2012
Once the tube is vertical on the baseplate, make two
or three more tack welds to hold it in place. Recheck
the tube to see that it is still vertical within tolerance.
The top plate must be centered on the tube and
square to the tube and to the baseplate. One way to
accomplish this is to stand the tube on the top plate
and use a square and measuring tape to align the plate
before tack welding it in place, Figure 9-55.
Make a fillet weld around the top and bottom plates
to hold the tube in place. Refer to the following tee joint
welding instruction, if necessary, to make these welds.
The height of the second candlestick must be
within ±1/8 in. of the first one. You may need to grind
the end of the tube or increase the joint spacing to
ensure that both candlesticks are the same height.
Finishing
Cool and chip the welds. There are a number of ways
to finish this project in addition to painting it a color
or a clear finish. Following are some possibilities:
• Leave the welds and spatter as they are.
• Grind all the welds and surfaces smooth.
• Write a greeting, holiday saying, your name, draw a
heart or other symbol with weld beads, or cut them
in with a torch.
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188
CHAPTER 9
FILLET WELDS
MAGNETIC LEVEL
AMOUNT OF OVERLAP
FIGURE 9-56
Lap joint. © Cengage Learning 2012
Paperwork
Complete a copy of the time sheet in Appendix I, the
bill of materials in Appendix III, or use forms provided by your instructor.•
Lap Joint
A lap joint is made by overlapping the edges of the
two plates, Figure 9-56. The joint can be welded on
one side or both sides with a fillet weld. In most cases,
both sides of the joint should be welded. When just
one side is welded, the joint is not as strong, and water
can cause rust to form in the joint space, Figure 9-57.
As the fillet weld is made on the lap joint, the buildup
should equal the thickness of the plate, Figure 9-58.
RUST FORMED
BETWEEN WELDS
FIGURE 9-54
Checking squareness with a level.
© Cengage Learning 2012
FIGURE 9-57
Crevice corrosion caused by water
trapped in the space between metal plates at a lap joint.
Larry Jeffus
SMOOTH WELD
TRANSITION
STEEL RULE
THICKNESS
SQUARE
SMOOTH WELD
TRANSITION
MEASURE ONE SIDE THEN THE OTHER
FIGURE 9-55
Centering the top plate.
© Cengage Learning 2012
FIGURE 9-58
Correct lap joint bead shape.
© Cengage Learning 2012
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
189
10'-0"
6'-6"
3'-3"
GOOD ROOT
FUSION
FIGURE 9-59
Correct crater fill at the end of a lap joint.
Larry Jeffus
6'-3"
TYP.
2-6
TYP.
DETAIL
B-B
2' 5"
TYP.
DETAIL
DETAIL
C-C
© Courtesy of Larry Jeffus
TRAILER
FIGURE 9-60
Lap joint weld. Larry Jeffus
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.
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, Figure 9-59. But if the molten weld pool
shows a notch during the weld, this is an indication
that the root is not being fused together. The weave
pattern will help prevent this problem, Figure 9-60.
Lap joints are often used when joining plates
or when plates are stiffened with an angle iron or
another structural shape. They are also used when
joining structural steel, Figure 9-61.
PROJECT 9-6
Fillet Welds in Lap Joints to Build a Birdhouse Roof
Skill to be learned: The control of the welding electrode to produce uniform fillet welds in lap joints
FIGURE 9-61
Lap joints on utility trailer.
© Cengage Learning 2012
in the flat position. In addition, the square butt and
outside corner welding skills learned in the previous
projects will be reinforced. Measuring, fitting, and
assembling fabrication skills and techniques will be
developed.
Project Description
The roof of a house is usually covered with shingles
that are lapped one on top of the other. The lap joints
on the roof of your birdhouse are designed to give it
the look of shingles.
This project will be fabricated in three parts.
Part 1—The roof of the birdhouse will be fabricated using lap joint welds.
Part 2—The walls and floor will be fabricated using
butt joint welds.
Part 3—The corners of the walls, floor, and roof
ridge will be joined using outside corner welds.
Part 1 Project Materials and Tools
The following items are needed to fabricate the birdhouse roof.
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
190
CHAPTER 9
Materials
• 24 to 30 1/8-in. diameter F2 or F3 class electrodes
• 12 1 1/2 ´ 8-in. pieces of 3/16-in. to 1/4-in. thick
mild steel plate
5 1/2 in. wide, and the overlaps of each joint must
be equal. To determine the amount of the overlap
required, you must find the total width of all five of the
1 1/2-in. wide bars.
Total width = number of bars ´ width of each bar
Total width = 5 ´ 1 1/2
Total width = 7 1/2 in.
Tools
• Arc welder
• Plasma cutting torch, oxyfuel cutting torch,
or shear
• PPE
• Wire brush
• Angle grinder
• Chipping hammer
• Square
• Steel rule
• C-clamp or magnetic clamp
• Soapstone
To find the overlap dimension for each of the four
overlaps, you must first find the total overlap. To get
this you must subtract the roof width of 5 1/2 in. from
the total bar width of 7 1/2 in.
Total overlap = total width - roof width
Total overlap = 7 1/2 - 5 1/2
Total overlap = 2 in.
The five bars make a total of four overlap joints. So
the dimension of each overlap will be 1/4 of the total
overlap.
Layout
Using a square, 12-in. rule and soapstone, lay out the
bar stock as shown in the project drawing, Figure 9-62.
Overlap = total overlap ¸ number of overlaps
Overlap = 2 ¸ 4
Overlap = 1/2 in.
Cutting Out
The first step is to cut the mild steel bar stock to
length with a shear or thermally.
Lay out the bars so that they overlap 1/2 in. and have
a total width of 5 1/2 in. Holding the bars in place,
make a small tack weld on the end of each overlap,
Figure 9-63. Placing the tack welds on the ends will
keep them out of the way of the lap welds.
Once both lap weld panels are tack welded
together, recheck to see that the overall panel width
Fabrication
The two roof panels will be constructed with five
1 1/2 ´ 8-in. pieces of bar stock. The roof must be
TYP.
90o
1 1"
2
1"
8
1 1"
2
2"
6"
TYP.
TYP.
5 1"
2
BIRDHOUSE
FIGURE 9-62
Project 9-6. © Cengage Learning 2012
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
TACK WELDS
FIGURE 9-63
Tack welding lap joints.
© Cengage Learning 2012
of 5 1/2 in. is accurate. If necessary, grind off a tack
weld and adjust the overlap so that the finished panel
width is correct within ±1/8 in.
Welding
The lap joint panel will need to be braced at an
approximate 45° angle so that the face of the weld
will be flat. Also, the welds will have to be alternated
from side to side to minimize the distortion of the
roof panel.
The welding heat is not evenly distributed
between the two plates of a lap joint. The edge of the
top plate is easily overheated as compared to the surface of the bottom plate, Figure 9-64. To keep the top
plate’s edge from melting back, direct most of the
arc’s heat on the surface of the bottom plate. Using
the “J” weave pattern with the long top of the J on
the bottom plate surface, and the short bottom of the
J just touching the top edge of the top plate should
keep the weld away from the top plate edge.
LESS HEAT CAN CONDUCT
INTO THE EDGE SO IT HEATS
UP FASTER
A “J” WEAVE MAKING THE SHAPE
OF THE WELD BEAD UNIFORM
MORE HEAT CAN CONDUCT
INTO THE THE BASEPLATE
SO IT HEATS UP SLOWER
FIGURE 9-64
Effect of different plate thicknesses on
joint heating. © Cengage Learning 2012
191
One problem that occurs with all fillet welds is
slag entrapment at the root of the weld. This occurs
as a result of not getting enough of the arc’s heat
down in the root of the joint. More heat can be
directed into the joint root by dipping the tip of the
electrode into the root as the J-weld pattern passes
over the weld root.
Cool, chip, and inspect each weld joint after you
have finished the weld. Look at the weld to see if it
has uniform width and buildup and follows the weld
joint. A lack of uniform width might indicate you
were not using a consistent weave pattern. A lack in
uniformity in buildup might indicate that your rate
of travel down the joint was not steady. Match your
welding speed so that each weld is made with only
one electrode.
Remember to alternate the welds from side to
side to reduce weld distortion. When the welding is
completed on the first panel, weld the second roof
panel lap joints.
Part 2 Project Materials and Tools
The following items are needed to fabricate the walls
and floor of the birdhouse.
Materials
• 24 to 30 1/8-in. diameter F2 or F3 class electrodes
• 8 1 1/2 ´ 6-in. pieces of 3/16-in. to 1/4-in. thick
mild steel plate
• 8 1 1/2-by 5 1/2-in. pieces of 3/16-in. to 1/4-in.
thick mild steel plate
• 1 3/8-in. diameter 2-in. long piece of round bar
stock or reinforcement rod
Tools
• Arc welder
• Plasma cutting torch, oxyfuel cutting torch, or shear
• PPE
• Wire brush
• Angle grinder
• Chipping hammer
• Square
• Steel rule
• C-clamp or magnetic clamp
• Soapstone
Layout
Using a square, 12-in. rule and soapstone, lay out the
bar stock as shown in the project drawing, Figure 9-62.
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
192
CHAPTER 9
6"
SIDES
BOTTOM
1"
52
CUT
METAL SAVED
5 1"
2
45o
3 1"
4
FIGURE 9-65
FRONT & BACK
Laying out the birdhouse.
© Cengage Learning 2012
6"
The front and back wall butt panels may be laid out in
one of two ways. They can be laid out as a square, or
they can be laid out and precut to shape, Figure 9-65.
The square layout is easiest, and the precut saves
metal. Both methods are acceptable.
Cutting Out
The first step is to cut the mild steel bar stock to length
with a shear or thermally.
Fabrication
This project will be fabricated in steps.
st
1 Step—Assemble the bottom
■ Assemble and tack weld together four of the
5 1/2-in. long bars into a square flat plate with
a 1/8-in. root space, Figure 9-66.
2nd Step—Assemble both sides
■ Assemble and tack weld together two panels
of the 5 1/2-in. long bars into rectangular flat
plates with a 1/8-in. root space.
FIGURE 9-66
Birdhouse panel layout.
© Cengage Learning 2012
the inside so they will not affect the welds. The
corners will form outside corner joints and can
be tack welded either on the inside or outside
of the birdhouse. The welding stresses may be
strong as the butt joints are welded, so make
several tack welds along the joints.
Welding
Using a properly set up and adjusted arc welding
machine and the proper safety protection as demonstrated in Practice 9-1, you will make a series of welds
on the joints on the top of the birdhouse.
The welds must be straight so that the weld beads
are evenly spaced on both sides of the weld joints,
Figure 9-44. Alternate the welds made from panel to
panel so you do not overheat the weldment and to
reduce weld stresses.
3rd Step—Assemble both the front and back
■ Assemble and tack weld together two panels of
the 6-in. long bars into square flat plates with a
1/8-in. root space.
■ If the end pieces are not cut to shape, you must
make the tack welds inside the area that will
remain after the ends are cut to shape. That way,
the parts will stay together after the ends are cut.
4th Step—Assemble the sides, bottom, front, and
back panels
■ Assemble both sides and both end panels on
the bottom, Figure 9-67. Put the tack welds to
FIGURE 9-67
Birdhouse panel assembly.
© Cengage Learning 2012
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
Cool, chip, and inspect each weld joint after you
have finished the weld. Look at the weld to see if it
has uniform width and buildup and follows the weld
joint. A lack of uniform width might indicate you
were not using a consistent weave pattern. A lack in
uniformity in buildup might indicate that your rate of
travel down the joint was not steady.
Finish all the butt joint welds before starting on
the outside corner welds. If necessary, grind off any
of the ends of the butt welds if they extend into the
outside corner joint groove. This will make it easier to
keep the outside corner welds even. Make the welds
that join the bottom to the sides and the bottom to the
front and back panels first so that the birdhouse corner
welds will be made last and will be on top of those welds.
This will give the birdhouse a more finished look.
Set the two roof panels on top of the assembled
birdhouse. You may have to shift them around to find
the best fit. The ridge of the panels should be as straight
and uniform as possible. Tack weld the panels together.
Make a small fast outside corner weld across the ridge
of the roof panels. Making the weld fast and small will
minimize the weld distortion. Do not weld the roof to
the base of the birdhouse. Leaving it loose will allow you
to clean out the house after each season.
The 3/8-in. diameter 2-in. long piece of round bar
stock or reinforcement rod is welded in place last.
Finishing
Lay out the 1 1/2-in. hole on the front side and thermally cut it out.
Cool and chip the welds and any slag left from
cutting the hole. A power wire brush can be used to
give the welds a polished, shiny appearance. Fit the
roof onto the base. It should fit solidly. If it has distorted from the weld, a hammer and anvil can be used
to reshape it as necessary.
The project can be painted with a clear coat or
colored coat of latex paint.
Paperwork
Complete a copy of the time sheet in Appendix I, the
bill of materials in Appendix III, or use forms 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 9-68.
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.
193
LESS HEAT IS CONDUCTED
INTO THIS PLATE
THAN
INTO THIS PLATE
FIGURE 9-68
Tee joint.
WELD
SIZE
FIGURE 9-69
© Cengage Learning 2012
WELD
SIZE
Tee joint welded on both sides.
© Cengage Learning 2012
The heat is not distributed uniformly between
both plates during a tee weld. The plate that forms
the stem of the tee can conduct heat away faster
than the baseplate. Heat escapes into the baseplate
in two directions. When using a weave pattern, most
of the heat should be directed to the baseplate to
keep the weld size more uniform and to help prevent
an undercut.
A welded tee joint can be strong if it is welded
on both sides, even without having deep penetration,
Figure 9-69. The weld will be as strong as the base
plate if the size of the two welds equals the total
thickness of the baseplate. The weld bead should
have a flat or slightly concave appearance to ensure
the greatest strength and efficiency, Figure 9-70.
Tee joints can be used to join two pieces of metal
at a right angle. The joining of a ship’s bulkhead to
the hull forms a tee joint. Joists in buildings form a
tee joint with the header, Figure 9-71.
PROJECT 9-7
Fillet Welds on Tee Joints to Make a C-Clamp
Skill to be learned: The control of the welding electrode to produce uniform fillet welds in tee joints in
the flat position. Additional welding skills learned
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
194
CHAPTER 9
in the previous projects will be reinforced. Detailed
fabrication skills and techniques required to align
and square parts will be developed.
THIS STRESS POINT CAN
CAUSE A CRACK
FORCE
Project Description
C-clamps are one of the most commonly used fabrication hand tools. They are used to both hold parts in
place until tack welds can be made and to force parts
together. Sometimes enough force can be applied
with one or more C-clamps to bend one part so it fits
properly to another part.
As the bolt is turned, forcing parts together, it is
important that the upper jaw turn on the bolt so that
no twisting force is applied to the parts. If the top jaw
twists, it can cause both the top and bottom C-clamp
jaws to slip. This C-clamp has an upper jaw assembly of a nut and three different washers that allow the
upper jaw to turn freely as the clamping pressure is
applied with the C-clamp. A little light oil can be used
so the jaw will turn easier.
CONVEX
CONTOUR
(A)
FORCE
FLAT TO
CONCAVE
CONTOUR
(B)
Project Materials and Tools
The following items are needed to fabricate the
C-clamp.
FIGURE 9-70
The stresses are distributed more
uniformly through a flat or concave fillet weld.
© Cengage Learning 2012
Materials
• 5 to 10 1/8-in. diameter F2 and/or F3 electrodes
• 2 1 ´ 12-in. pieces of 3/16-in. to 1/4-in. thick mild
steel plate to form the back beam
• 2 1 ´ 5-in. pieces of 3/16-in. to 1/4-in. thick mild
steel plate to form the bottom beam
• 2 1 ´ 6-in. pieces of 3/16-in. to 1/4-in. thick mild
steel plate to form the top beam
• 3/8-in. diameter 4-in. long rod handle
• 3/4-10NC 14-in. bolt
• 3/4-10NC connector
• 3/4-10NC nut upper jaw part
• 3/4-in. flat washer upper jaw part
• 1-in. flat washer upper jaw part
• 3/8-in. washer upper jaw part
• 1-in. diameter 3/16-in. to 1/4-in. thick lower jaw
10'-0"
6'-6"
3'-3"
6'-3"
TYP.
2-6
TYP.
DETAIL
B-B
2' 5"
TYP.
DETAIL
TRAILER
FIGURE 9-71
Tee joints on a utility trailer.
© Cengage Learning 2012
DETAIL
C-C
Tools
• Arc welder
• PPE
• Angle grinder
• Wire brush
• Square
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
• Soapstone
• Arc welder
• Plasma cutting torch, oxyfuel cutting torch, or
• Steel rule
• C-clamp or magnetic clamp
Layout
Using a square, 12-in. rule and soapstone, lay out the
plate as shown in the project drawing, Figure 9-72.
shear
•
•
•
•
195
PPE
Wire brush
Cutting Out
The first step is to cut the mild steel bar stock to length
with a shear or thermally.
Chipping hammer
Square
2
4 1"
2
3" 10NC NUT
4
3" FLAT WASHER
4
1
1" FLAT WASHER
3" FLAT WASHER
8
3" DIAMETER HANDLE
8
DETAIL A
G
3" 10NC 14" BOLT
4
A
5"
TOP BEAM
3" 10NC THREADED CONNECTOR
4
TYP.
BACK
BEAM
UPPER JAW
12"
DETAIL A
BOTTOM
BEAM
A
TYP.
LOWER JAW
SECTION A-A
6"
C-CLAMP
FIGURE 9-72
Project 9-7. © Cengage Learning 2012
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
196
CHAPTER 9
Fabrication
This project will be fabricated in steps.
TOP JAW
ASSEMBLY
1st Step—Assemble the top, back, and bottom tee
beams
■ Center one 1-in. bar in the center of the matching
length bar.
■ Make tack welds on opposite sides of the vertical
tee joint bar to keep it square.
■ The tack welds should be approximately 1/2 in.
long and about 1 in. from the ends of the joint.
■ Make an additional set of tack welds in the
center of the 12-in. long back beam.
2nd Step—Assembling C-clamp beams
■ Once the three tee beams are welded, they can
be assembled according to the layout shown in
Figure 9-72.
■ Use the square or the magnetic clamp to hold
the beams squarely together.
■ Make tack welds on the beam joints to hold
them in alignment for welding.
3rd Step—Assemble the bolt and top jaw assembly
■ Screw the 3/4-10NC 14-in. connector onto the
3/4-10NC 14-in. bolt
■ Place the 3/4-in. flat washer on top of and in the
center of the 1-in. flat washer and use the C-clamp
to hold them tightly together on the welding
table. Use the steel rule to check the center.
■ Make four small fi llet welds as shown on
the number 1 welding symbol in Detail A,
Figure 9-72. Cool and chip the welds.
■ Screw the 3/4-10NC nut just far enough onto
the bolt so that the assembled washers will fit
as shown in Detail A, Figure 9-72.
■ Place the 3/8-in. washer on the end of the bolt
and hold it in place with your gloved finger.
■ Rest the electrode on your gloved hand, lower
your helmet, and fill the hole in the 3/8-in.
washer by making a small plug weld.
■ Screw the nut down on the bolt far enough so
that the top of the plug weld can be ground flat.
■ Screw the nut back down to the end so that the
washer assembly is close but not tight to the
3/8-in. washer. The washer assembly needs to be
loose enough to turn but not so loose that the
3/8-in. washer will extend past the washer assembly as the C-clamp is tightened, Figure 9-73.
BOTTOM JAW
(A)
FIGURE 9-73
(B)
C-clamp screw assembly.
© Cengage Learning 2012
NOTE: If the center washer touches when the C-clamp
is tightened on a surface, it may not stay in place. If this
happens, you can add another 1-in. washer to the one
already on the top jaw assembly by tack welding the
edges of the washers together.
■
Protect the bolt threads from weld spatter, and
make four small fillet welds to hold the nut
in place as shown on the number 2 welding
symbol in Detail A, Figure 9-72. Cool and chip
the welds.
■
Center the 3/8-in. rod on top of the head of the
bolt.
■
Protect the bolt threads from weld spatter, and
weld the rod to the bolt head.
4th Step—Mounting the screw assembly to the
C-clamp beams
■
Run the connector up the threads of the bolt
so that the upper C-clamp jaw is touching the
bottom jaw and the connector is even with the
top beam.
■
Align a flat side of the connector so it is centered on the top beam. Grind off any excessive
weld bead material that might interfere with
these parts fitting tightly together.
■
Protect the bolt threads from weld spatter, and
tack weld the connector to the top beam.
■
Run the bolt in and out to be sure it is lined up
with the lower jaw and moves freely.
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
Welding
Using a properly set up and adjusted arc welding
machine and the proper safety protection as demonstrated in Practice 9-1, you will make a series of weld
beads on the C-clamp surface following the soapstone
layout.
Set the tee joint so that the weld surface will be
flat. Strike an arc directly in the bottom of the joint
about 1/2 in. away from the end. Keep a slightly longer-than-normal arc length as you bring the tip of the
electrode to the end of the tee joint. Lower the tip of
the electrode and establish the welding pool. Make
sure the welding pool extends across the joint so both
sides of the tee are being fused together.
NOTE: Allow these welds to cool slowly. Unlike the
other projects in this chapter, the strength of these
welds is very important. You want to pay special attention to the welds that join the top, back, and bottom
beams together.
Once all of the beams have been welded, they can
be assembled as outlined in the second step above.
It is important that the welds you make to hold the
beams together are strong. If you feel that any of
these welds is not as strong as it should be, you can
use the angle grinder to remove the weld. Grinding
out a weld to reweld a joint is common practice in
high-strength welding applications. When you are
grinding out the weld, try to avoid grinding away any
of the base metal.
Once the beams are welded, check to see that
weld distortion did not cause them to twist out of
197
shape by placing the C-clamp frame on a flat surface.
The frame should lie flat and not “rock.” If it is not
flat, you can use a vise and twist it back into shape
before attaching the screw.
Weld spatter can be a problem if it gets on the
screw threads. F3 electrodes produce a lot more hard
spatter than do F2 or F4 class electrodes. Hard spatter
is spatter that fuses to the metal surface and cannot just
be wiped off. For that reason you may want to use one
of these electrodes to assemble and attach the C-clamp
screw. But you will have to protect the screw threads
from spatter regardless of the class of electrode you use.
The screw threads can be protected by using one
of the commercially available anti-spatter products.
You can also wrap the threads with a damp shop
towel. Do not use a wet towel because it could quench
the welds, making them brittle and weak.
Finishing
Cool off the metal, chip the slag, and wire brush the
surface. As long as the C-clamp is kept dry, it will
not rust. If you are using it in a damp area, you may
want to spray it with a light oil to prevent rusting.
One advantage of building your own C-clamp
is that if the screw threads get damaged by weld
spatter, you can cut off the end and remove and
replace the bolt.
Paperwork
Complete a copy of the time sheet in Appendix I, the
bill of materials in Appendix III, or use forms provided by your instructor.•
SUMMARY
In this chapter you have learned enough layout, cutting, fabrication, and welding skills to build the utility trailer shown in Figure 9-74. As you have built
projects in this chapter, you have been learning the
welding skills needed to build this trailer. The welds
on the trailer are similar to the ones you have been
practicing. Examples of similar welds have been highlighted in figures in this chapter. This utility trailer is
small and designed to be lightweight and easily built
using the skills that you have already learned. The
small size of this utility trailer will allow it to be positioned so that all of the welds can be made in the flat
position. The axel, springs, trailer hitch, and lighting
required to make it fully functional and street legal
are available commercially or over the Internet.
SMAW is often the process of choice for building
one-of-a-kind or special projects like the utility trailer.
In a factory, this trailer might be made on a production line with the FCA or GMA welded processes, but
SMAW would probably be the best process if only
one or two units are needed.
At one time almost everything welded was welded
with the shielded metal arc welding process. But today,
more and more welds are being done with gas metal
arc welding and flux cored arc welding processes.
However, no one believes SMAW is a dying process.
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
198
CHAPTER 9
10'-0"
6'-6"
3'-3"
8"
5'-4"
DETAIL A
DETAIL C
6'-3"
DETAIL B
TYP.
2-6
TYP.
2' 4"
DETAIL B
TYP.
DETAIL C
DETAIL A
TRAILER
FIGURE 9-74
Utility trailer drawings. © Cengage Learning 2012
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Shielded Metal Arc Welding Plate
It will be a vital skill for many years to come, primarily because it is very flexible and versatile compared to
the other processes. Some of its flexibility comes from
the fact that it is much easier to change the class or size
of an SMAW electrode than to change the electrode
199
wire in a GMAW or FCAW welder. Some of its versatility comes from the fact that it can be used under
less-than-ideal conditions. SMAW can be used when
it is wet or windy or on rusty or dirty metal and still
make acceptable welds.
REVIEW QUESTIONS
1. What electrode types are found in the following
classes: F3, F2, and F4?
2. What class of electrodes is the most utilitarian for
welding fabrication?
3. What class of electrodes is best for welding on
thin metals?
4. What class of electrodes has a smooth easy arc
and produces welds with very heavy slag?
5. According to Figure 9-1, which electrode would
have the deepest penetration and least buildup?
6. According to Table 9-1, what would the amperage range be for a 1/8-in. E7018 electrode?
7. If an electrode’s core wire overheats, what effect
can this have on the weld?
8. How can you determine if a weld is too hot?
9. What can happen if the arc length is too short?
10. Which electrode angle may push metal and slag
ahead of the weld?
11. What welding electrode manipulation weave
pattern is good for flat lap joints?
12. What can cause welder fatigue that can lead to
poor welds?
13. List some of the PPE required to weld safely.
14. Why should you always practice striking the arc
in the weld groove?
15. What should you do before starting to weld on
any project?
16. What should you do if the electrode gets stuck to
the metal?
17. What is the purpose of a tack weld?
18. Why are tack welds kept small?
19. Why do welders not normally quench welds in
water?
20. What is the normal range for the root opening for
a square butt weld?
21. Up to what thickness of plate and structural steel
are square butt joints used?
22. What sound might you hear if weld stresses break
a tack weld?
23. What effect would changing from a DC to AC
welding current have on arc blow?
24. What can a magnetic level be used for?
25. Why is the J weave pattern used for lap joint welds?
26. Why is most of the heat directed to the baseplate
of a tee joint?
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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