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Design of Weld Joints and Welding Errors
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DESIGN OF WELD JOINTS
&WELDING ERRORSWELDING ERRORS
ME 473 WELDING TECHNOLOGY
Instructor: Yrd.Doç.Dr. Oğuzhan Yılmaz
Department of Mechanical Engineering The University of Gaziantep
Design of Weld Joints and WeldsDesign of Weld Joints and Welds
� Five basic joints are used for bringing two members together
for welding:
� 1: Butt joint: a joint between two members aligned approximately in the
same plane.
� 2: Corner joint: a joint between two members located approximately at
right angles to each other in the form of an L.
� 3: T-joint: a joint between two members located approximately at right
WeldingWelding TechnologyTechnology
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� 3: T-joint: a joint between two members located approximately at right
angles to each other in the form of a T.
� 4: Lap joint: a joint between two overlapping members located in
parallel.
� 5: Edge joint: a joint between the edges of two or more parallel or
nearly parallel members.
� When more than two members are brought together, the joint is a
combination of one of the five basic joint. The most popular joint is cross
or cruciform.
Dr. Oğuzhan Yılmaz
Five basic joints typesFive basic joints types
WeldingWelding TechnologyTechnology
3Dr. Oğuzhan Yılmaz
Weld TypesWeld TypesThere are eight seperate and distinct welds:
�� FilletFillet weldweld::
� This is the most commonly used weld. The fillet weld is so named because of itscross-sectional shape. Simple and cheap to assemble & weld.
� The fillet is regarded as being on the joint and is defined as a weld of
approximately triangular cross section joining of two surfaces approximately at right angles to each other.
WeldingWelding TechnologyTechnology
4Root
Toe
Toe
Weld face
Dr. Oğuzhan Yılmaz
Weld TypesWeld Types�� Groove Groove weldweld::
� This is the second most popular weld.
� It is defined as a weld made in the groove between two members to be joined.
� The groove weld is regarded as being in the joint.
� There are 7 main basic groove weld designs, and they can be used as single or
double welds.
WeldingWelding TechnologyTechnology
5Dr. Oğuzhan Yılmaz
Weld TypesWeld Types�� Back or backing weld:Back or backing weld:
� This is a special weld made on the back side or root side of a previous weld.
� The root of the original weld is gouged, chipped, or ground to sound metal before backing weld is made. This will improve the quality of the weld joint by assuring complete penetration.
WeldingWelding TechnologyTechnology
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�� Plug or slot welds:Plug or slot welds:
� These are made using prepared holes. They are considered together since the welding symbol to specify them is the same.
� If the hole is round , it is plug weld; if it is elongated, it is a slot weld.
Dr. Oğuzhan Yılmaz
Weld typesWeld types�� Spot or Projection welds:Spot or Projection welds:
� These welds can be applied by different welding processes, which change the
actual weld; Resistance welding, electron beam welding, laser welding etc.
�� Seam welds:Seam welds:
� This weld in cross section looks similar to a spot weld.
� The weld geometry is influenced by the welding process employed.
� Electron beam welding, laser, arc welding etc.
Stud weld:Stud weld:
WeldingWelding TechnologyTechnology
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�� Stud weld:Stud weld:
� This is a special type of a weld produced by a stud welding process, used for
joining a metal stud or similar part to a wokpiece.
�� Surfacing weld:Surfacing weld:
� This weld is composed of one or more stringer or weave beads deposited on
base metal as an unbroken surface.
� It is not used to make a joint.
� It is used to build up surface dimensions, or provide protection of the base metal
from a hostile environment.
Dr. Oğuzhan Yılmaz
Weld types: Weld symbolsWeld types: Weld symbols
WeldingWelding TechnologyTechnology
8Dr. Oğuzhan Yılmaz
Weld types: Weld symbolsWeld types: Weld symbols
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• A field welded fillet weld is required
on both sides of the “T” joint.
• The solid triangle (or flag) indicates
the weld is to be made in the field.
Dr. Oğuzhan Yılmaz
Weld types: Weld terminologyWeld types: Weld terminology
WeldingWelding TechnologyTechnology
10Dr. Oğuzhan Yılmaz
Weld types: Welding symbolsWeld types: Welding symbols
WeldingWelding TechnologyTechnology
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COMBINED WELDING SYMBOLS
Dr. Oğuzhan Yılmaz
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WELDING ERRORS
�� Lack of FusionLack of Fusion
� Lack of fusion occurs when there is no fusion between the weld
metal and the surfaces of the base metal.
� Lack of fusion is caused by:
� Too low current
� Too high welding speed
� Incorrect torch/gun angle
Welding errors & failuresWelding errors & failures
WeldingWelding TechnologyTechnology
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� Incorrect torch/gun angle
� Incorrect angle preparation
� There is no efficient non-destructive method. Visual inspection can
be used during welding and with bend test.
� Also ultrasonic testing, liquid penetrant test or magnetic particle
testing methods can be applicable.
Dr. Oğuzhan Yılmaz
Welding errors and failures: Lack of FusionWelding errors and failures: Lack of Fusion
WeldingWelding TechnologyTechnology
14Dr. Oğuzhan Yılmaz
Welding errors and failures: Incomplete penetrationWelding errors and failures: Incomplete penetration
� This type of defect is found in any of three ways: � When the weld bead does not penetrate the
entire thickness of the base plate.
� When two opposing weld beads do not interpenetrate.
� When the weld bead does not penetrate the toe of a fillet weld but only bridges across it.
� Welding current has the greatest effect on penetration.
WeldingWelding TechnologyTechnology
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penetration.
� Incomplete penetration is usually caused by the use of too low a welding current and can be eliminated by simply increasing the amperage.
� Other causes can be the use of too slow a travel speed and an incorrect torch angle. Both will allow the molten weld metal to roll in front of the arc, acting as a cushion to prevent penetration. The arc must be kept on the leading edge of the weld puddle
This type of defect can be easily detected by visual inspection.
Dr. Oğuzhan Yılmaz
Welding errors and failures: UndercuttingWelding errors and failures: Undercutting
� Undercutting is a defect that appears as a groove
in the parent metal directly along the edges of the
weld.
� It is most common in lap fillet welds, but can also
be encountered in fillet and butt joints.
� This type of defect is most commonly caused by
� improper welding parameters; particularly the travel speed and arc voltage.
WeldingWelding TechnologyTechnology
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speed and arc voltage.
Dr. Oğuzhan Yılmaz
Welding errors and failures: PorosityWelding errors and failures: Porosity
� Porosity is the result of gas entrapment in the solidifying metal.
� Porosity can take many shapes on a
radiograph but often appears as dark round or irregular spots or specks appearing singularly, in clusters, or in
rows.
Sometimes, porosity is elongated and
WeldingWelding TechnologyTechnology
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� Sometimes, porosity is elongated and may appear to have a tail. This is the
result of gas attempting to escape while the metal is still in a liquid state and is
called wormhole porosity.
� All porosity is a void in the material and it will have a higher radiographic density
than the surrounding area.
wormhole porosityDr. Oğuzhan Yılmaz
Welding errors and failures: InclusionWelding errors and failures: Inclusion
� Solid inclusions are normally expected to be a subsurface type of defect and would include any foreign material entrapped in
the deposited weld metal.
� The most common type of solid inclusion is a slag inclusion defined as nonmetallic solid
material entrapped in weld metal or between weld metal and base metal.
WeldingWelding TechnologyTechnology
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weld metal and base metal.
Slag
inclusion
Dr. Oğuzhan Yılmaz
Welding errors and failures: Weld cracksWelding errors and failures: Weld cracks
� A crack is a fracture-type discontinuity characterized by a sharp tip and high ratio of length and width to opening displacement.
� Cracks are perhaps the most serious of the defects that occur in the welds or weld
joints in weldments.
� Cracks are considered dangerous because they create a serious reduction in strength.
� They can propagate and cause sudden failure. They are most serious when impact
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loading and cold-temperature service are involed.
� There are many types of cracks:
� Surface cracks
� Transverse cracks:
� Longitudinal carcks:
� Creater cracks:
� Toe cracks
� Underbead cracks
Dr. Oğuzhan Yılmaz
Welding errors and failures: Weld cracksWelding errors and failures: Weld cracks
WeldingWelding TechnologyTechnology
20Dr. Oğuzhan Yılmaz
Welding errors and failures: DistortionWelding errors and failures: Distortion
� Most of the welding processes involve heat. High temperature heat is largely
responsible for welding distortion, warpage, and stresses.
� When metal is heated it expands, and it expands in all directions.
� Welding-distortion or deformation or warping of weldments during welding is a
natural outcome of intrinsic non-uniform heating and cooling of the joint.
� Distortion is the result of the action of internal stresses which are produced while
welding, and remain in the part after heating is removed, as briefly explained in the
following.
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following.
Dr. Oğuzhan Yılmaz
Welding errors and failures: other errorsWelding errors and failures: other errors
OVERLAP
UNDERFILL
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OVERLAP
SPATTER
UNACCEPTABEL WELD PROFILES
Dr. Oğuzhan Yılmaz
End of the chapter….
&
End of the term…
23
End of the term…
Thank you
YOU ARE YOU ARE ALL NOW ALL NOW ‘WELDING ‘WELDING SPECIALISTsSPECIALISTs’, ’, AREN’T YOU?AREN’T YOU?ALL THE BEST…ALL THE BEST…