Visual Inspection of Welds 280
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Class Outline
Class Outline
Objectives
Weld Quality
Visually Inspecting a Weld
Visual Inspection Procedure
Visual Inspection Equipment
Procedure Before Welding
Procedure During Welding
Procedure After Welding
Weld Discontinuities
Distortion: Internal Stress, Porosity, and Slag Inclusion
Distortion: Weld Spatter, Incomplete Fusion, and Melt-Through
Weld Size
Weld Profile
Cracking
Summary
Lesson: 1/15
Objectives
l Describe weld quality.
l Describe visually inspecting a weld.
l Describe the procedure used to visually inspect a weld.
l List the equipment used to visually inspect a weld.
l Describe operator procedure before welding.
l Describe operator procedure during welding.
l Describe operator procedure after welding.
l Describe weld discontinuities.
l Identify internal stress, porosity, and slag inclusion.
l Identify weld spatter, incomplete fusion, and melt-through.
l Identify weld size discontinuities.
l Identify weld profile discontinuities.
l Identify weld cracks.
Figure 1. Welding is essential to the
construction of many everyday objects like
appliances and automobiles.
Copyright © 2014 Tooling U, LLC. All Rights Reserved.
Lesson: 1/15
Objectives
l Describe weld quality.
l Describe visually inspecting a weld.
l Describe the procedure used to visually inspect a weld.
l List the equipment used to visually inspect a weld.
l Describe operator procedure before welding.
l Describe operator procedure during welding.
l Describe operator procedure after welding.
l Describe weld discontinuities.
l Identify internal stress, porosity, and slag inclusion.
l Identify weld spatter, incomplete fusion, and melt-through.
l Identify weld size discontinuities.
l Identify weld profile discontinuities.
l Identify weld cracks.
Figure 1. Welding is essential to the
construction of many everyday objects like
appliances and automobiles.
Figure 2. The quality and integrity of a
weldment is important because a defective
weld in the body of an aircraft could have
disastrous consequences.
Figure 3. A welding machine supplies electric
current to create the arc that melts the filler
metal into a weldment.
Copyright © 2014 Tooling U, LLC. All Rights Reserved.
Figure 3. A welding machine supplies electric
current to create the arc that melts the filler
metal into a weldment.
Lesson: 2/15
Weld Quality
Welding is essential to the construction and fabrication of many vital components, finished
products, and structures. The safety and satisfaction of consumers depends on the quality
assurance of welds. Figure 1 shows the weld on a ladder, and Figure 2 shows a weld repair to a
rototiller. Several methods of non-destructive examination are used to assure the quality of a
welded part. Visual inspection is the primary method for examining the quality of a weld made by
any welding process. Other methods include penetrant, magnetic, radiographic, ultrasonic,
electromagnetic, and leak inspection.
Quality indicates how well a part conforms to its specifications, or "specs." Specifications are the
design parameters that set the limits of acceptable deviation for a part's intended application.
Figure 3 shows a welder checking the specs on a part drawing. Each part and process has its own
specs for quality, typically listed in the part drawing as the part's tolerances.
Factors that can affect the quality of a welded part include the following:
l
l
l
l
l
l
l
The design of a weldment.
The selection of the proper welding process.
The proper preparation of the joint prior to welding.
The verification that procedure meets the demands of fabricating the part.
The pretest of the welding process.
The attention of personnel to the quality of the part.
The in-process monitoring of quality.
Figure 1. A weld connects the step of a ladder
with the ladder's vertical beams.
Persons responsible for fabricating welded products are responsible for the proper and thorough
inspection of their welds. This class will teach you about the visual inspection of welds, the
equipment used during a visual inspection, the proper inspection procedure, and the common
discontinuities in the surface of a weld.
Figure 2. Welding has a number of
applications, including uses around the home,
the farm, and for the car.
Copyright © 2014 Tooling U, LLC. All Rights Reserved.
Figure 3. By looking at a weld's part drawing,
Lesson: 2/15
Weld Quality
Welding is essential to the construction and fabrication of many vital components, finished
products, and structures. The safety and satisfaction of consumers depends on the quality
assurance of welds. Figure 1 shows the weld on a ladder, and Figure 2 shows a weld repair to a
rototiller. Several methods of non-destructive examination are used to assure the quality of a
welded part. Visual inspection is the primary method for examining the quality of a weld made by
any welding process. Other methods include penetrant, magnetic, radiographic, ultrasonic,
electromagnetic, and leak inspection.
Quality indicates how well a part conforms to its specifications, or "specs." Specifications are the
design parameters that set the limits of acceptable deviation for a part's intended application.
Figure 3 shows a welder checking the specs on a part drawing. Each part and process has its own
specs for quality, typically listed in the part drawing as the part's tolerances.
Factors that can affect the quality of a welded part include the following:
l
l
l
l
l
l
l
The design of a weldment.
The selection of the proper welding process.
The proper preparation of the joint prior to welding.
The verification that procedure meets the demands of fabricating the part.
The pretest of the welding process.
The attention of personnel to the quality of the part.
The in-process monitoring of quality.
Figure 1. A weld connects the step of a ladder
with the ladder's vertical beams.
Persons responsible for fabricating welded products are responsible for the proper and thorough
inspection of their welds. This class will teach you about the visual inspection of welds, the
equipment used during a visual inspection, the proper inspection procedure, and the common
discontinuities in the surface of a weld.
Figure 2. Welding has a number of
applications, including uses around the home,
the farm, and for the car.
Copyright © 2014 Tooling U, LLC. All Rights Reserved.
Figure 3. By looking at a weld's part drawing,
the operator can check a weld's specs.
the farm, and for the car.
Figure 3. By looking at a weld's part drawing,
the operator can check a weld's specs.
Lesson: 3/15
Visually Inspecting a Weld
The purpose of visual inspection is to find any weld surface discontinuity that is not permissible
under the tolerances and specs of the part. Visual inspection may reveal problems with the
fabrication process. A discontinuity in the weld surface may indicate a faulty process or technique.
Visual inspection reveals surface flaws in a weld, such as the weld spatter in Figure 1. All welds
should be visually inspected. The American Welding Society (AWS) offers certification in the
visual inspection of welds.
Visual inspection occurs before, during, and after the part has been welded. Figure 2 shows a weld
in the process of fabrication. Visual inspection can be conducted while work is in progress, which
allows a welder to correct faults during welding. Visually inspecting a weld during welding can also
reveal incorrect procedures, processes, and techniques.
Figure 1. Close visual weld inspection can
reveal spatter.
Visual inspection is the most economical and affordable type of non-destructive testing, but it must
be done consistently and constantly to be effective. While visual inspection has a low cost, it
requires a trained welder to inspect a weld for quality. Figure 3 shows trained welders visually
inspecting a weld. Even though it provides an affordable method for determining quality, visual
inspections can detect only surface discontinuities. Discontinuities under the surface of a weld
require further testing, such as X-ray testing.
Figure 2. A weld should be inspected during
welding.
Copyright © 2014 Tooling U, LLC. All Rights Reserved.
Lesson: 3/15
Visually Inspecting a Weld
The purpose of visual inspection is to find any weld surface discontinuity that is not permissible
under the tolerances and specs of the part. Visual inspection may reveal problems with the
fabrication process. A discontinuity in the weld surface may indicate a faulty process or technique.
Visual inspection reveals surface flaws in a weld, such as the weld spatter in Figure 1. All welds
should be visually inspected. The American Welding Society (AWS) offers certification in the
visual inspection of welds.
Visual inspection occurs before, during, and after the part has been welded. Figure 2 shows a weld
in the process of fabrication. Visual inspection can be conducted while work is in progress, which
allows a welder to correct faults during welding. Visually inspecting a weld during welding can also
reveal incorrect procedures, processes, and techniques.
Figure 1. Close visual weld inspection can
reveal spatter.
Visual inspection is the most economical and affordable type of non-destructive testing, but it must
be done consistently and constantly to be effective. While visual inspection has a low cost, it
requires a trained welder to inspect a weld for quality. Figure 3 shows trained welders visually
inspecting a weld. Even though it provides an affordable method for determining quality, visual
inspections can detect only surface discontinuities. Discontinuities under the surface of a weld
require further testing, such as X-ray testing.
Figure 2. A weld should be inspected during
welding.
Figure 3. Visual inspection is cost effective for
the manufacturing process.
Copyright © 2014 Tooling U, LLC. All Rights Reserved.
Lesson: 4/15
Visual Inspection Procedure
Inspection at all stages of production is vital. When producing a part, visual inspection begins
before welding, occurs during welding, and continues after welding is complete. Figure 1 shows an
operator inspecting a weld during welding. Inspecting a part's materials before welding limits bad
and damaged materials from continuing in production. Inspecting the base and filler metals before
welding helps prevent the production of a defective product.
The most productive time to visually inspect a weld is during welding. During welding,
discontinuities can be detected while the welder is still able to correct them. Inspecting a weld
during welding helps eliminate the need for reworking or scrapping a weld, which are costs to be
avoided. A skilled welder inspects welds during welding to ensure a quality part. Visual inspection
after welding is much less productive because the opportunity to correct a defect has passed.
However, a visual inspection after welding can indicate an acceptable or defective part, preventing a
bad part from continuing in production and reaching the consumer. Figure 2 shows a completed
weld. Regardless, a welder should visually inspect the part before, during, and after welding.
Figure 1. Visual inspection happens at every
stage in the fabrication of a weld, especially
during welding.
Figure 2. Inspecting welds for quality is
important because many welded parts can be
dangerous if they fail.
Lesson: 5/15
Visual Inspection Equipment
While visual inspection relies on the eyes of the welder, a few items make the inspection more
thorough. The visual inspection of a weld can involve several items, including:
l
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l
l
l
A part drawing for verifying the specs and tolerances.
Weld gages for measuring the dimensions of a weld bead.
A straight-edge ruler for measuring the dimensions of a weld.
A light source for illuminating a weld for inspection.
A magnifying glass (Figure 1) for close examination of welds.
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The fillet gage shown in Figure 2 measures both convex and concave fillet welds. To measure a
convex fillet weld, select the long, flat part of the gage that matches the specified weld size on
the part drawing. Place the lower edge of the long, flat part on one base metal plate at the weld, so
Lesson: 5/15
Visual Inspection Equipment
While visual inspection relies on the eyes of the welder, a few items make the inspection more
thorough. The visual inspection of a weld can involve several items, including:
l
l
l
l
l
A part drawing for verifying the specs and tolerances.
Weld gages for measuring the dimensions of a weld bead.
A straight-edge ruler for measuring the dimensions of a weld.
A light source for illuminating a weld for inspection.
A magnifying glass (Figure 1) for close examination of welds.
The fillet gage shown in Figure 2 measures both convex and concave fillet welds. To measure a
convex fillet weld, select the long, flat part of the gage that matches the specified weld size on
the part drawing. Place the lower edge of the long, flat part on one base metal plate at the weld, so
that the upper edge of the gage touches the other base metal plate. To measure a concave fillet
weld, select the long, flat part on the gage that matches the specified weld size on the part
Figure 1. Magnifying lenses can help an
inspector see surface discontinuities.
drawing. Place the lower edge of the long, flat part on one base metal plate, so that the curvature
on the gage touches the weld bead and the upper edge of the blade touches the other base metal
plate. Compare your measurements of the weld to the part drawing's specifications to verify that
the part has been welded properly.
Figure 2. Fillet gages measure a fillet weld's
dimensions.
Lesson: 6/15
Procedure Before Welding
Before striking an arc as in Figure 1, the welder should examine the base and filler metal materials
for quality, type, size, possible discontinuities, and cleanliness from grease, oil, and paint. The joint
preparation should be inspected for the proper alignment of parts and fixturing. The welder should
inspect the pieces to be joined for straightness and flatness. The pieces to be joined should meet
the dimensions specified in the part drawing. Figure 2 shows a properly aligned welded part. As the
final step before welding, the welder should verify that the correct processes, procedures, and
equipment are used to make the workpiece properly functioning in its final application.
Before striking an arc, you should:
l
l
l
l
l
l
Review the part drawing and specifications.
Verify that the correct welding process will be used to meet the performance demands of the
final product.
Establish hold points.
Examine the base materials.
Examine the alignment of joints.
Review the storage of consumables (Figure 3).
Copyright
2014 Tooling
U,materials,
LLC. All Rights
Reserved.
By
visually© inspecting
the
welding
equipment, and fabrication process prior to welding, a
welder can help prevent the manufacture of a defective weld.
Figure 1. Weld materials should be inspected
before the arc is struck.
Lesson: 6/15
Procedure Before Welding
Before striking an arc as in Figure 1, the welder should examine the base and filler metal materials
for quality, type, size, possible discontinuities, and cleanliness from grease, oil, and paint. The joint
preparation should be inspected for the proper alignment of parts and fixturing. The welder should
inspect the pieces to be joined for straightness and flatness. The pieces to be joined should meet
the dimensions specified in the part drawing. Figure 2 shows a properly aligned welded part. As the
final step before welding, the welder should verify that the correct processes, procedures, and
equipment are used to make the workpiece properly functioning in its final application.
Before striking an arc, you should:
l
l
l
l
l
l
Review the part drawing and specifications.
Verify that the correct welding process will be used to meet the performance demands of the
final product.
Establish hold points.
Examine the base materials.
Examine the alignment of joints.
Review the storage of consumables (Figure 3).
Figure 1. Weld materials should be inspected
before the arc is struck.
By visually inspecting the materials, welding equipment, and fabrication process prior to welding, a
welder can help prevent the manufacture of a defective weld.
Figure 2. Inspecting weld materials and joint
alignment before welding helps to prepare the
operator for a quality weld.
Figure 3. A welder should inspect electrodes,
fluxes, and shielding gases before welding to
verify that they are the correct consumables
and in proper condition.
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Lesson: 7/15
Lesson: 7/15
Procedure During Welding
Visually inspecting during welding is the most productive time to inspect a weld because flaws can
be fixed before they harden into discontinuities. Figure 1 shows a welder while welding. Once the
weld has cooled and solidified, reworking it becomes more difficult and more expensive. For multilayer welds, you should inspect and clean the weld after each pass. The root pass on a weld is the
most critical because it is susceptible to slag inclusion and cracking. Figure 2 illustrates a root pass.
A crack or discontinuity in the root pass of a weld can spread to the additional weld layers. Figure 3
illustrates a crack spreading from the root pass. During welding, an operator should look for signs
of problems that may cause crater cracks or weld bead defects. Visual inspection during welding
detects under-welding and over-welding.
Discontinuities detected during welding can be corrected, and visual inspection requires a welder
attentive to the procedure. When visually inspecting during welding, you should:
l
l
l
l
Verify the preheat temperature and interpass temperature (Figure 4).
Verify that equipment and materials conform to the specifications of the welding procedure.
Examine the weld root pass while welding and before adding another weld layer.
Examine each subsequent weld layer.
By examining a weld during fabrication and correcting discontinuities, a welder can help prevent
defective welds from continuing in the manufacturing process.
Figure 1. If a welder inspects his or her work
while welding, surface flaws and discontinuities
can be corrected.
Figure 2. A quality root pass is important
because the weld root is susceptible to
cracking.
Figure 3. A crack in a weld's root pass can
spread to additional weld layers.
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Figure 4. A welder can use a preheat and
interpass temperature calculator to verify the
welding temperatures.
spread to additional weld layers.
Figure 4. A welder can use a preheat and
interpass temperature calculator to verify the
welding temperatures.
Lesson: 8/15
Procedure After Welding
After a weld has cooled and solidified, the welder should inspect the part for discontinuities on the
surface. Once a weld has solidified, it becomes expensive and difficult to correct, if it is repairable at
all. The purpose of visually inspecting a weld after welding is to determine if a weld is acceptable
based on specifications defined in the part drawing.
All welded parts should be visually inspected after welding. You should:
l
l
l
Examine the weld surface quality for discontinuities (Figure 1).
Verify that the weld dimensions conform to the part drawing's specifications (Figure 2).
Review any subsequent requirements of the part drawing.
By identifying discontinuities and determining the acceptability of a weld, a welder and inspector can
help prevent a defective weld from continuing in the manufacturing process and reaching the
consumer. Figure 3 shows a range of discontinuities.
Figure 1. A welder examines the surface of a
weld for discontinuities.
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Figure 2. A welder should always measure a
completed weld to verify that it meets its
specs.
Lesson: 8/15
Procedure After Welding
After a weld has cooled and solidified, the welder should inspect the part for discontinuities on the
surface. Once a weld has solidified, it becomes expensive and difficult to correct, if it is repairable at
all. The purpose of visually inspecting a weld after welding is to determine if a weld is acceptable
based on specifications defined in the part drawing.
All welded parts should be visually inspected after welding. You should:
l
l
l
Examine the weld surface quality for discontinuities (Figure 1).
Verify that the weld dimensions conform to the part drawing's specifications (Figure 2).
Review any subsequent requirements of the part drawing.
By identifying discontinuities and determining the acceptability of a weld, a welder and inspector can
help prevent a defective weld from continuing in the manufacturing process and reaching the
consumer. Figure 3 shows a range of discontinuities.
Figure 1. A welder examines the surface of a
weld for discontinuities.
Figure 2. A welder should always measure a
completed weld to verify that it meets its
specs.
Figure 3. A number of variables can affect the
welding process, so welders should always
visually inspect a weld to find evidence of
improper technique.
Copyright © 2014 Tooling U, LLC. All Rights Reserved.
welding process, so welders should always
visually inspect a weld to find evidence of
improper technique.
Lesson: 9/15
Weld Discontinuities
Visual inspection identifies discontinuities in a weld surface. A discontinuity is an irregularity in the
specified and expected composition of a weld. Discontinuities in the surface of a weld can be within
or outside of tolerances according to the welded part's design. Figure 1 shows several
discontinuities. A discontinuity becomes a defect if and only if the discontinuity exceeds the
tolerances considered worthy of rejection by the weld's specifications. Discontinuities may or may
not be defects depending on the part's specifications and codes. Some discontinuities will make a
part defective, while some discontinuities in a weld will not result in a defective part.
There are five classes of discontinuities:
1. Distortion is a disfigurement that signals the joint was not prepared properly. Distortion is
minimized by carefully selecting the weld sequence and joint designs, as well as using rigid
fixtures.
2. An incorrect weld size is detected easily with the appropriate weld gage and the part drawing.
The incomplete penetration or excess penetration of a weld joint can create an incorrect
weld size.
Figure 1. Discontinuities are irregularities in
3. An incorrect weld profile can affect a weld's performance under stress.
the surface of a weld such as porosity, slag
4. Incorrect final dimensions of a weld can make a part unsuitable for its final application.
inclusion, distortion, and cracking.
5. A crack is the formation of narrow breaks and openings in the surface of a weld. Visual
inspection easily detects cracking (Figure 2).
By identifying a discontinuity, a welder and inspector can establish the cause of the discontinuity.
Figure 2. Cracking is a serious weld
discontinuity and can make a part defective.
Lesson: 10/15
Distortion: Internal Stress, Porosity, and Slag Inclusion
Distortion discontinuities are disfigurements in a weld's structure according to the part drawing's
specifications. Distortion discontinuities include internal stress, porosity, slag inclusion, weld
spatter, incomplete fusion, and melt-through. Thermal expansion and contraction create internal
stress in the weld material, and the stress remains in the weld. Figure 1 illustrates internal stress.
Trapped gases inside the weld material create porosity, which is the appearance of tiny bubbles on
a weld bead. Figure 2 shows porosity. Several factors can cause porosity in the surface of a weld,
including excessive welding speed, a rusty or dirty metal plate, a wet electrode, wet flux, insufficient
flux coverage, and arc blow. Excessive porosity can weaken a weld, but a small degree of porosity
is allowable.
Like gases, other particles can permeate a weld. Slag inclusion happens when a nonmetallic solid
material gets in the weld metal or between the weld metal and base metal. Slag inclusion results
from the mutual dissolution of flux and nonmetallic impurities in some welding processes. Figures 3
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© 2014
U, LLC.
Rights Reserved.
and
4 show
slag Tooling
inclusion.
SlagAll
inclusions
can affect the strength and integrity of a weld in its final
application. Inclusions of slag at the surface of a weld typically indicate one or more of the following:
Figure 1. Thermal contraction and expansion
create internal stress in a weld.
Lesson: 9/15
Weld Discontinuities
Visual inspection identifies discontinuities in a weld surface. A discontinuity is an irregularity in the
specified and expected composition of a weld. Discontinuities in the surface of a weld can be within
or outside of tolerances according to the welded part's design. Figure 1 shows several
discontinuities. A discontinuity becomes a defect if and only if the discontinuity exceeds the
tolerances considered worthy of rejection by the weld's specifications. Discontinuities may or may
not be defects depending on the part's specifications and codes. Some discontinuities will make a
part defective, while some discontinuities in a weld will not result in a defective part.
There are five classes of discontinuities:
1. Distortion is a disfigurement that signals the joint was not prepared properly. Distortion is
minimized by carefully selecting the weld sequence and joint designs, as well as using rigid
fixtures.
2. An incorrect weld size is detected easily with the appropriate weld gage and the part drawing.
The incomplete penetration or excess penetration of a weld joint can create an incorrect
weld size.
Figure 1. Discontinuities are irregularities in
3. An incorrect weld profile can affect a weld's performance under stress.
the surface of a weld such as porosity, slag
4. Incorrect final dimensions of a weld can make a part unsuitable for its final application.
inclusion, distortion, and cracking.
5. A crack is the formation of narrow breaks and openings in the surface of a weld. Visual
inspection easily detects cracking (Figure 2).
By identifying a discontinuity, a welder and inspector can establish the cause of the discontinuity.
Figure 2. Cracking is a serious weld
discontinuity and can make a part defective.
Lesson: 10/15
Distortion: Internal Stress, Porosity, and Slag Inclusion
Distortion discontinuities are disfigurements in a weld's structure according to the part drawing's
specifications. Distortion discontinuities include internal stress, porosity, slag inclusion, weld
spatter, incomplete fusion, and melt-through. Thermal expansion and contraction create internal
stress in the weld material, and the stress remains in the weld. Figure 1 illustrates internal stress.
Trapped gases inside the weld material create porosity, which is the appearance of tiny bubbles on
a weld bead. Figure 2 shows porosity. Several factors can cause porosity in the surface of a weld,
including excessive welding speed, a rusty or dirty metal plate, a wet electrode, wet flux, insufficient
flux coverage, and arc blow. Excessive porosity can weaken a weld, but a small degree of porosity
is allowable.
Like gases, other particles can permeate a weld. Slag inclusion happens when a nonmetallic solid
material gets in the weld metal or between the weld metal and base metal. Slag inclusion results
from the mutual dissolution of flux and nonmetallic impurities in some welding processes. Figures 3
and 4 show slag inclusion. Slag inclusions can affect the strength and integrity of a weld in its final
application. Inclusions of slag at the surface of a weld typically indicate one or more of the following:
Copyright © 2014 Tooling U, LLC. All Rights Reserved.
l Faulty technique by the welder
l Improper electrode manipulation
l Improper electrode size
Figure 1. Thermal contraction and expansion
create internal stress in a weld.
Lesson: 10/15
Distortion: Internal Stress, Porosity, and Slag Inclusion
Distortion discontinuities are disfigurements in a weld's structure according to the part drawing's
specifications. Distortion discontinuities include internal stress, porosity, slag inclusion, weld
spatter, incomplete fusion, and melt-through. Thermal expansion and contraction create internal
stress in the weld material, and the stress remains in the weld. Figure 1 illustrates internal stress.
Trapped gases inside the weld material create porosity, which is the appearance of tiny bubbles on
a weld bead. Figure 2 shows porosity. Several factors can cause porosity in the surface of a weld,
including excessive welding speed, a rusty or dirty metal plate, a wet electrode, wet flux, insufficient
flux coverage, and arc blow. Excessive porosity can weaken a weld, but a small degree of porosity
is allowable.
Like gases, other particles can permeate a weld. Slag inclusion happens when a nonmetallic solid
material gets in the weld metal or between the weld metal and base metal. Slag inclusion results
from the mutual dissolution of flux and nonmetallic impurities in some welding processes. Figures 3
and 4 show slag inclusion. Slag inclusions can affect the strength and integrity of a weld in its final
application. Inclusions of slag at the surface of a weld typically indicate one or more of the following:
l
l
l
l
l
l
l
l
l
Figure 1. Thermal contraction and expansion
create internal stress in a weld.
Faulty technique by the welder
Improper electrode manipulation
Improper electrode size
Lack of adequate access for welding the joint
Improper cleaning of the weld between passes
Excessive welding current
Incorrect polarity
Excessive arc length
Too steep of a travel angle during welding.
With so many variables to control, the welder should focus during welding to prevent slag inclusion.
Figure 2. Porosity can weaken a weld.
Figure 3. Slag inclusion can affect the
performance of a welded part in its final
application.
Copyright © 2014 Tooling U, LLC. All Rights Reserved.
application.
Figure 4. Slag inclusion can indicate a number
of welding problems, including excessive
current or excessive arc length.
Lesson: 11/15
Distortion: Weld Spatter, Incomplete Fusion, and Melt-Through
Weld spatter, shown in Figure 1, is not considered a serious discontinuity, unless its presence
interferes with an additional operation or the serviceability of the part. Small particles of nonmetallic
material are expelled during the fusion of the weld and base metals, creating weld spatter. Only the
weld spatter on the base metal should concern the visual inspector of a weld, because it could
create dimples in a workpiece's coat of paint, causing an aesthetically undesirable part.
Incomplete fusion, shown in Figure 2, is the lack of full integration between the weld metal and
adjoining weld beads. Incomplete fusion is caused by faulty technique, improper preparation of the
base metal, insufficient welding heat, lack of access to the adjoining beads, and improper weld joint
design.
Figure 1. Weld spatter can make a weld
defective.
Melt-through, illustrated in Figure 3, occurs when a joint is welded from only one side and the
welder visibly reinforces the weld root. Melt-through creates a defective part when it results in
excessive root reinforcement. Welded parts with distortion discontinuities should be evaluated for
acceptability.
Figure 2. Incomplete fusion happens when the
the weld metal and weld beads do not fully
bond.
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Lesson: 11/15
Distortion: Weld Spatter, Incomplete Fusion, and Melt-Through
Weld spatter, shown in Figure 1, is not considered a serious discontinuity, unless its presence
interferes with an additional operation or the serviceability of the part. Small particles of nonmetallic
material are expelled during the fusion of the weld and base metals, creating weld spatter. Only the
weld spatter on the base metal should concern the visual inspector of a weld, because it could
create dimples in a workpiece's coat of paint, causing an aesthetically undesirable part.
Incomplete fusion, shown in Figure 2, is the lack of full integration between the weld metal and
adjoining weld beads. Incomplete fusion is caused by faulty technique, improper preparation of the
base metal, insufficient welding heat, lack of access to the adjoining beads, and improper weld joint
design.
Figure 1. Weld spatter can make a weld
defective.
Melt-through, illustrated in Figure 3, occurs when a joint is welded from only one side and the
welder visibly reinforces the weld root. Melt-through creates a defective part when it results in
excessive root reinforcement. Welded parts with distortion discontinuities should be evaluated for
acceptability.
Figure 2. Incomplete fusion happens when the
the weld metal and weld beads do not fully
bond.
Figure 3. Melt-through can result in excessive
reinforcement.
Lesson: 12/15
Weld Size
A weld consists of several parts, as illustrated in Figure 1:
l The weld face is the exposed surface of a weld on the side from which the welding was
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performed.
l The weld root is the point at which the back of the weld intersects the base metal surfaces.
Lesson: 12/15
Weld Size
A weld consists of several parts, as illustrated in Figure 1:
l
l
l
l
The weld face is the exposed surface of a weld on the side from which the welding was
performed.
The weld root is the point at which the back of the weld intersects the base metal surfaces.
A root opening provides access to the root of the weld. The root opening is where fusion
should occur between the weld metal and adjoining weld beads.
The weld toe is the point at which the weld face and the base metal meet. The weld toe can
experience cracking and undercut.
Weld size discontinuities can arise from incompletely or excessively penetrating a weld joint. Too
much and too little penetration can make a weld that is outside of tolerance. The part drawing
provides the welder the necessary specifications of a weld's size and placement. The part specs
define the dimensions of a part, while the welder determines the quality of the weld.
Incomplete penetration of a weld joint occurs when weld metal does not extend through the
joint thickness, leaving an unpenetrated and unfused area in the joint. Figure 2 shows incomplete
penetration. Incomplete penetration can result from insufficient welding heat, improper joint design,
or improper lateral control of the welding arc. As illustrated in Figure 3, excess penetration results
in an excess of weld metal on the back side of a joint. Excessive heat, slow movement, and poor
joint alignment can cause excessive penetration. The excessive penetration of a joint happens
during the root pass, because the root pass is the first layer of weld metal in the joint. So, welders
should be careful during the root pass of a weld. Welded parts with weld size discontinuities should
be evaluated by the welder and inspector for acceptability.
Figure 1. A weld's size is specified on the part
drawing.
Figure 2. Incomplete penetration can leave the
root of a weld joint unfilled, weakening the
weld.
Figure 3. Several welding variables can affect
the penetration of a weld joint, making the
joint insufficiently or excessively penetrated.
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Lesson: 13/15
Weld Profile
Visually inspecting a weld's profile can identify potentially defective parts. Weld profile discontinuities
include the following:
l
l
l
l
l
l
Overlap (Figure 1) is the protrusion of unfused weld metal beyond the weld toe or weld root.
Overlap forms a mechanical notch and is almost always unacceptable in a welded part.
Insufficient travel speed and improper preparation of the base metal can result in overlap.
Undercut (Figure 2) is a groove melted into the base metal at the weld toe or weld root that
is left unfilled by weld metal. The groove concentrates stress on the part and the weld.
Improper welding techniques or excessive welding currents can result in undercut. Undercut
within the tolerances of the part's specifications is not considered a defect.
Underfill (Figure 3) occurs when the weld face or root surface of a groove weld extends
below the adjacent surface of the base metal. Underfill results from the failure of a welder to
completely fill the weld joint.
Excess convexity (Figure 4) is the distance from the weld face perpendicular to a line joining
the weld toes that arcs out and away from the weld joint. Excess convexity has a greater
potential for weld failure, causing premature weld failure, longitudinal cracking, and crater
cracking. Excessive current input and excessive travel speeds can cause excess convexity.
Excess concavity (Figure 4) is the distance from the weld face perpendicular to a line joining
the weld toes that arcs in and toward the weld joint. Excessive heat in the overhead welding
position and insufficient filler metal can cause excess concavity.
Excessive reinforcement occurs in groove welds when more weld metal is used than is
required to fill a joint. Excessive reinforcement creates high concentrations of stress at the
weld toes and usually results from over welding.
Figure 1. Overlap is the protrusion of unfused
weld metal beyond the weld toe.
Welded parts with weld profile discontinuities should be evaluated by the welder and inspector for
acceptability.
Figure 2. Undercut can result from the use of
improper welding techniques.
Figure 3. Underfill is a weld profile
discontinuity.
Figure 4. Excess concavity and convexity can
be defects depending on a part's specs.
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Lesson: 14/15
Cracking
A crack in a weld is a discontinuity that can indicate a defective part. A longitudinal crack, shown
in Figure 1, is parallel to the weld axis and may exist along the centerline of the weld or near the
weld toes. Sometimes a longitudinal crack is called a centerline crack. An improper width-to-depth
ratio, contaminants with low melting points, and a concave weld surface can result in a longitudinal
crack. Reducing the width-to-depth ratio to between 1:1 and 1.4:1, limiting excessive penetration,
and decreasing voltage and travel speed can prevent longitudinal cracks.
A transverse crack, shown in Figure 2, is perpendicular to the weld axis and may exist completely
within the weld metal or may extend from the weld metal into the base metal. Excess hydrogen, an
excessively strong weld metal, and high levels of residual stress result in transverse cracks.
Increasing the pre-heat temperature, using consumables of a lower strength, and increasing postheat can prevent transverse cracks.
A crater crack, shown in Figure 3, occurs at the crater of a weld when welding is improperly
terminated. Also, inadequately filling the crater can result in a crater crack. Sometimes crater cracks
are called star cracks, although they may appear in other shapes and can initiate a longitudinal
crack. Filling the crater to a slightly convex shape prior to terminating the arc, back stepping at the
end of the weld, and using the crater fill machine settings can prevent crater cracks.
A heat affected zone crack, shown in Figure 4, is a cold crack that forms in the heat-affected
zone of a base metal. Excess hydrogen, high contents of carbon in the base metal, and high levels
of residual stress can result in heat affected zone cracks. Sometimes heat affected zone cracks are
called underbead cracks. Using consumables with a low hydrogen content, controlling the hydrogen
content in the weld metal, increasing the pre-heat temperature, and increasing the post-heat
temperature can prevent heat affected zone cracks. Welded parts with cracks should be evaluated
by the welder and inspector for acceptability.
Figure 1. Longitudinal cracks are parallel to the
weld axis.
Figure 2. Transverse cracks are perpendicular
to the weld axis.
Figure 3. A crater or star crack occurs at the
center of a weld.
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center of a weld.
Figure 4. Heat affected zone cracks occur in
the base metal.
Lesson: 15/15
Summary
Visual inspection is the primary method for examining the quality of a weld made by any welding
process. Quality indicates how well a part conforms to its specs. Persons responsible for fabricating
welded products are responsible for the proper and thorough inspection of their welds.
The purpose of visual inspection is to find any weld surface discontinuity, which is not permissible
under the specs of the part. Visual inspection occurs before, during, and after welding. The most
productive time to visually inspect a weld is during welding, because the welder can still correct
discontinuities.
By identifying discontinuities and determining the proper acceptability of a weld, a welder and
inspector can help prevent a defective weld from continuing in the manufacturing process and
reaching the consumer. Weld discontinuities include distortion, incorrect weld size, incorrect weld
profile, incorrect final dimensions, and cracks. Identifying a discontinuity can help establish the
cause of the discontinuity. A discontinuity becomes a defect if and only if the discontinuity exceeds
the tolerances considered worthy or rejection by the weld’s specifications. Discontinuities may or
may not be defects.
Figure 1. Visually inspecting a weld helps to
verify that the welded part meets its specs.
Figure 2. The most productive time to visually
inspect a weld is during welding.
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Lesson: 15/15
Summary
Visual inspection is the primary method for examining the quality of a weld made by any welding
process. Quality indicates how well a part conforms to its specs. Persons responsible for fabricating
welded products are responsible for the proper and thorough inspection of their welds.
The purpose of visual inspection is to find any weld surface discontinuity, which is not permissible
under the specs of the part. Visual inspection occurs before, during, and after welding. The most
productive time to visually inspect a weld is during welding, because the welder can still correct
discontinuities.
By identifying discontinuities and determining the proper acceptability of a weld, a welder and
inspector can help prevent a defective weld from continuing in the manufacturing process and
reaching the consumer. Weld discontinuities include distortion, incorrect weld size, incorrect weld
profile, incorrect final dimensions, and cracks. Identifying a discontinuity can help establish the
cause of the discontinuity. A discontinuity becomes a defect if and only if the discontinuity exceeds
the tolerances considered worthy or rejection by the weld’s specifications. Discontinuities may or
may not be defects.
Figure 1. Visually inspecting a weld helps to
verify that the welded part meets its specs.
Figure 2. The most productive time to visually
inspect a weld is during welding.
Figure 3. Visually inspecting a weld is
important to the safety of those involved in the
welded part's application.
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Class Vocabulary
Class Vocabulary
Term
Definition
American Welding Society
Arc Blow
AWS
Centerline Crack
Concave
Consumable
Convex
Crack
Crater Crack
Defect
Discontinuity
Distortion
AWS. A professional organization that supports the welding industry and promotes welding and related
processes.
A condition resulting from the interaction of an electric current and the magnetic field the current induces.
Arc blow can cause excessive spatter, incomplete fusion, and porosity.
American Welding Society. A professional organization that supports the welding industry and promotes
welding and related processes.
A gap or break in the surface of a weld parallel to the weld axis that may be along the centerline of the
weld or near the weld toes. A centerline crack is also called a longitudinal crack.
Curving inward like the inside of a bowl.
An electrode that conducts electricity to the arc but also melts into the weld as a filler metal.
Curving outward like the exterior of a circle or sphere.
A discontinuity characterized by a break or gap in the surface of a weld. Cracks can be classified as
longitudinal, transverse, crater, and heat affected zone.
A gap or break in the surface of a weld that occurs at the crater of a weld because welding was improperly
terminated. Crater cracks are also called star cracks.
An irregularity in the specified and expected composition of a weld that exceeds the part design's
tolerances. A defect is a rejectable discontinuity.
An irregularity in the specified and expected composition of a weld. A discontinuity is not always a defect.
A disfigurement that signals that a weld joint was not prepared properly.
Excess Concavity
The distance from the weld face perpendicular to a line joining the weld toes that arcs in and toward the
weld joint.
Excess Convexity
The distance from the weld face perpendicular to a line joining the weld toes that arcs out and away from
the weld joint. Excess convexity has a greater potential for weld failure, causing longitudinal cracking and
crater cracking.
Excess Penetration
Excessive Reinforcement
A discontinuity characterized by an excess of weld metal on the back side of the joint. Excessive heat, slow
movement, and poor joint alignment can cause excessive penetration.
The use of more weld metal than is required to fill a groove weld joint. Excessive reinforcement creates
high concentrations of stress at the weld toes.
Fillet Gage
A device that determines whether or not a fillet weld is within specified tolerances. A fillet gage is a specific
kind of weld gage.
Fillet Weld
A type of weld that is triangular in shape and joins two surfaces at right angles to each other in a lap joint,
T-joint, or corner joint. Fillet welds are the most common types of welds.
Heat Affected Zone Crack
Hold Point
Incomplete Fusion
A cold gap or break in the surface of a weld that forms in the heat-affected zone of a base metal. Heat
affected zone cracks are also called underbead cracks.
A predetermined stopping point in the fabrication process at which the weld must be inspected. Hold
points are used between passes of multi-layer welds to assure a weld is properly cleaned between passes.
The lack of complete integration between the weld metal and adjoining weld beads. Incomplete fusion is
caused by faulty operator technique, improper preparation of the base metal, insufficient welding heat, lack
of access to the adjoining beads, and improper joint design.
Incomplete
Penetration
A discontinuity
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U, LLC. All Rights
Reserved. characterized by an unpenetrated and unfused area in a joint that occurs when weld metal
does not extend through the thickness of the joint. Incomplete penetration can result from insufficient
welding heat, improper joint design, and improper lateral control of the welding arc.
of access to the adjoining beads, and improper joint design.
Incomplete Penetration
A discontinuity characterized by an unpenetrated and unfused area in a joint that occurs when weld metal
does not extend through the thickness of the joint. Incomplete penetration can result from insufficient
welding heat, improper joint design, and improper lateral control of the welding arc.
Internal Stress
A force from within the material of an object that attempts to deform that object. In a weldment, internal
stress is caused by thermal expansion and contraction as the weld metal cools and solidifies.
Interpass Temperature
A specific temperature range of the base material. The interpass temperature should not fall below the
preheat temperature.
Longitudinal Crack
A gap or break in the surface of a weld parallel to the weld axis that may be along the centerline of the
weld or near the weld toes. A longitudinal crack is also called a centerline crack.
Melt-Through
Non-Destructive Examination
Overlap
Part Drawing
Porosity
Preheat Temperature
Root Opening
Root Pass
The visible reinforcement of a weld root that happens when a joint is welded from only one side.
The evaluation of a weld, or material to be welded, that does not affect the servicability of the weld or
material. Non-destructive examination costs less because the part is not destroyed.
The protrusion of unfused weld metal beyond the weld toe or weld root. Overlap is almost always
unacceptable in a welded part.
A document that includes the specifications for a part's production.
A discontinuity characterized by the appearance of tiny voids or bubbles on a weld bead, resulting from
trapped gases in a material. Excessive porosity can weaken a weld.
A specific temperature to which the base material is heated prior to welding.
The point at which fusion should occur between the weld metal and adjoining weld beads. The root
opening provides access to the root of a weld.
The first layer of a multi-layer weld. The root pass is the most critical layer of a weld because it is
susceptible to slag inclusion and cracking.
Slag Inclusion
A discontinuity resulting from the mutual dissolution of flux and nonmetallic impurities in some welding
processes. Slag inclusion can affect the strength and integrity of a weld in its final application.
Specifications
The design parameters that set the limits of acceptable deviation for a part's intended application.
Specifications are also called specs.
Specs
Star Cracks
The design parameters that set the limits of acceptable deviation for a part's intended application. Specs
are also called specifications.
A gap or break in the surface of a weld that occurs at the crater of a weld because welding was improperly
terminated. Star cracks are also called crater cracks.
Transverse Crack
A gap or break in the surface of a weld perpendicular to the weld axis that may be completely within the
weld metal or may extend from the weld metal into the base metal. Excess hydrogen, an excessively
strong weld metal, and high levels of residual stress result in transverse cracks.
Underbead Crack
A cold gap or break in the surface of a weld that forms in the heat-affected zone of a base metal.
Underbead cracks are also called heat affected zone cracks.
Undercut
Underfill
A groove melted into the base metal at the weld toe or weld root that is left unfilled by weld metal. The
groove concentrates stress on the weld and could be a defect if outside the part's tolerances.
The extension of a weld face or root surface of a groove weld below the adjacent surface of the base
metal. Underfill results from the failure of a welder to completely fill the weld joint.
Weld Face
The exposed surface of a weld on the side from which the welding was done.
Weld Gage
A device that determines whether or not a weld is within specified tolerances. Some weld gages are
designed for specific weld types like the fillet weld gage.
Weld Root
The point at which the back of a weld intersects the surfaces of the base metal.
Weld Spatter
Small particles of nonmetallic material that are expelled during the fusion of the weld and base metals.
Weld spatter is considered a serious discontinuity if it interferes with the servicability of the part or with an
additional operation, like painting.
Weld Toe
The point at which the weld face and the base metal meet. Weld toes can experience cracking and
undercut.
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Weldment
A welded joint.
Weld Toe
Weldment
The point at which the weld face and the base metal meet. Weld toes can experience cracking and
undercut.
A welded joint.
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