Design of Weld Joints and Welding Errors

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


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.


4Root

Toe

Toe

Weld face


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.



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.


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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.


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:


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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.


Weld types: Weld symbolsWeld types: Weld symbols



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.


Weld types: Weld terminologyWeld types: Weld terminology



Weld types: Welding symbolsWeld types: Welding symbols


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COMBINED WELDING SYMBOLS


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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


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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.


Welding errors and failures: Lack of FusionWelding errors and failures: Lack of Fusion



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.


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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.


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.


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speed and arc voltage.


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


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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.


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weld metal and base metal.

Slag

inclusion


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


Welding errors and failures: Weld cracksWelding errors and failures: Weld cracks



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.


Welding errors and failures: other errorsWelding errors and failures: other errors

OVERLAP

UNDERFILL


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OVERLAP

SPATTER

UNACCEPTABEL WELD PROFILES


End of the chapter….

&

End of the term…

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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…

Design of Weld Joints and Welding Errors

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