Terms & Definitions
A Weld:*
A union between materials caused by heat,
and or pressure
A Joint:*
A configuration of members
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Types of Welds
Butt welds:*
Fillet welds:*
Spot/Seam welds:*
Plug/Slot welds:*
Edge welds:*
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Types of Joints
Butt joints: *
T joints: *
Lap joints: *
Corner joints:*
Closed
corner
Open
corner*
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Weld Preparations
Remember, the purposes of a weld preparation is to allow access
for the welding process, penetration and fusion through the area
of the joint and its faces*
The basic rule is this:
The more you take out, then the more you must put back in*
This has major effects on economics and distortion control etc
The root face, root gap and angle of bevel values, the choice of
single, or double sided preparations, are dictated only by the type
of welding process, the position and accessibility of the joint*
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Weld Preparations
Angle of bevel*
Root face*
Included angle*
Root radius*
Root gap*
Root landing*
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Types of Single Butt Preparation
Single bevel
Single V
Single J
Single U*
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Types of Double Butt Preparation
Double bevel
Double V
Double J
Double U*
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Welded Joints
Butt Joints
A butt welded butt joint*
A fillet welded butt joint*
A compound welded butt joint*
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Welded Joints
T Joints
A fillet welded T joint*
A butt welded T joint*
A compound welded T joint*
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Welded Joints
Lap Joints
A fillet welded Lap joint*
A spot welded Lap joint*
A compound welded Lap joint*
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Welded Joints
Closed Corner Joints
A fillet welded Closed Corner joint*
A butt welded Closed Corner joint*
A compound welded Closed Corner joint*
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Welded Joints
Open Corner Joints
An inside fillet welded Open Corner joint*
An outside fillet welded Open Corner joint*
A double fillet welded Open Corner joint*
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A Butt Welded Butt Joint
Actual Throat Thickness*
1.2.3.4. Weld Toes*
Weld Face*
Weld Width*
Design Throat Thickness*
1
2
A
B
3
HAZ*
Weld Root*
4
Fusion Boundary*
Fusion Zone*
A + B = Excess Weld Metal**
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Sizing of Fillet Welds
Vertical Leg Length*
Weld face*
Horizontal Leg Length*
Excess weld metal **
Design throat*
Actual throat*
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Nominal & Effective Throat Thickness
“a” = Nominal throat thickness “s” = Effective throat thickness
a
s
Deep throat fillet welds from FCAW & SAW etc*
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Fillet Weld Profiles
Convex
Concave
Mitre
*
oncave is preferred for joints subject to fatigue loa
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Effect of a Poor Toe Blend Angle
6 mm
80°
Very Poor Weld Toe Blend Angle
3 mm*
20°
Improved Weld Toe Blend Angle
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Effect of a Poor Toe Blend Angle
It is also possible that the height of excess weld metal is within
the accepted limit of an applied standard, but the toe blend is
unacceptable, as shown below*
90°
3 mm
Extremely poor toe blend, but excess weld metal is within limits*
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Summary of Terms
Weld:
A Union of materials
Joint:
A Configuration of members
Weld Preparation:
Preparing a joint to allow access and fusion.
Types of Weld:
Butt. Fillet. Spot. Seam Plug. Slot. Edge.
Types of Joint:
Butt. T. Lap. Corner (Open & Closed)
Types of Preparation:
Preparation Terms:
Bevel’s. V’s. J’s. U’s. Single & Double Sided.
Bevel/included angle. Root face/gap. Land/Radius
Weldment Terms:
Weld face & root. Fusion zone & boundary. HAZ.
Weld toes.Weld width
Weld Sizing (Butts):
DTT. ATT. Excess weld metal.
Weld Sizing (Fillets):
DTT. ATT. Excess weld metal. Leg length *
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Duties of a Welding Inspector
It is the duty of all welding inspectors:
To ensure that welding operations are carried out in
accordance with written, or agreed practices or
specifications
Before
During
After
*
All Welding Operations
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Duties of a Welding Inspector
Discuss the following
Before Welding:
1) Safety:
Legislation and safe working practices
2) Documentation:
Spec. Drawings. Procedures. Welder approvals. Certificates. Mill sheets
3) Welding Process and ancillaries:
Cables. Regulators. Ovens. Quivers etc
Equipme
4) Incoming Consumables:
Materials/welding consumables (Size. Condition. Specification. Storage)
5) Marking out preparation & set up:
Method. Angles/Root face/gap values. Distortion control. Pre-heat prior to
tack welding if applicable*
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Duties of a Welding Inspector
During Welding:
1) Pre-Heating. (Method and control)
2) In process distortion control (Balance or sequence welding)
3) Consumable control. (Correct baking and storage prior to use)
4) Welding process (Related parameters i.e. volts/amps. gas flow rate)
5) Welding run sequence and inter-pass cleaning
6) Minimum/maximum Inter-pass temperatures
7) Full compliance with all elements given on the WPS*
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Duties of a Welding Inspector
After Welding:
1) Visual Inspection
2) Non Destructive testing
3) Repairs*
4) Repair procedures (NDT/Excavation/Welding/Welder approval)
5) PWHT
6) Hydro-static testing
7) Submission of all inspection reports to QC departments*
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Responsibilities of a Welding Inspector
To Observe
Activities &
Imperfections*
To Record
Activities &
Imperfections*
To Compare
Activities &
Imperfections*
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Attributes of an effective Welding Inspector
Some attributes/skills of an effective Welding Inspector:*
•Honest
•Literate
•Respected
•Dedicated
•Impartial
•Observant
•Decisive
•Analytical*
•Knowledgeable
•Experienced
•Record keeping skills
•Communication skills
•Safety conscious
•Inquisitive
•Responsible
•Diplomatic skil l*
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A Welding Inspectors Toolbox
A Welding Inspectors toolbox should contain*
A welding gauge (Cambridge style, or high low gauges etc)
A tape measure and scale
A wire brush
A magnifying glass
A torch and mirror
A specification, pen and report, or note paper
Any other aids to visual inspection*
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Specialised Aids for Inspection
Inspection may utilise the following specialised equipment:*
Boroscopes (For assessing root runs in small Ø pipes)
Flow-meter (For measuring gas flow rates in MIG/MAG/TIG)
Simple NDT equipment (Penetrants and MPI)
Complex NDT equipment (Radiography or Ultrasonics)
Note: Both simple and complex NDT methods requires the
specialised skills of qualified operators/technicians*
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Imperfections in Welded Joints
Welding imperfections can be categorized into groups:
1)
2)
3)
Cracks
Gas Pores & Porosity
Solid Inclusions
4)
Lack of fusion
5)
Profile & Lack of Filling
6)
7)
Mechanical or Surface damage
Misalignment*
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Cracks
A HAZ hydrogen crack, initiated at the weld toe
Most cracks are initiated from stress concentrations *
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Gas pores and Porosity
Surface breaking porosity
Shrinkage cavity*
Coarse cluster porosity
Fine cluster porosity
Hollow root bead
Blow hole > 1.6 mm Ø
An isolated internal porosity
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Solid Inclusions
Surface breaking solid inclusion
Internal solid inclusion causing
a lack of inter-run fusion*
Internal solid inclusion
Internal solid inclusion causing
a lack of sidewall fusion
Solid inclusions caused by
undercut in the previous weld run
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Lack of Fusion
Lack of sidewall fusion &
incompletely filled grove*
Overlap (Causing cold laps)
Lack of inter-run fusion
Lack of sidewall fusion
Lack of root fusion
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Profile Imperfections
Spatter
An Incompletely filled groove
A
Lack of root fusion
Bulbous, or irregular contour
Arc Strikes
Poor toe blend
B
Incomplete root penetration
*
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Profile Imperfections
Shrinkage grooves
Crater pipe
Root concavity
*
Excess penetration, and burn through
Root oxidation in Stainless Steel
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Undercut in Butt Welds
Root Run or “Hot pass” undercut
Parent metal, surface undercut
Weld metal, surface undercut*
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Undercut in Fillet Welds
Weld metal, surface undercut
Parent metal, “top toe” undercut*
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Mechanical and Surface Damage
Any surface damage caused by:
Grinding
Hammering/chisel marks
Slag chipping hammer marks
Torn cleats (Hammered off attachments)
Arc strikes
All of the above may cause serious weakness to the weld area*
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Misalignment
Linear
Excess weld metal height
Lowest plate to highest point
Linear misalignment measured in mm
3 mm
Angular
15
Angular misalignment measured in degrees*
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Mechanical Testing
Why ?*
To establish the level of mechanical properties*
Which properties ?*
1)
2)
3)
4)
Hardness*
Toughness*
Tensile strength*
Ductility*
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What are Mechanical Properties?
Mechanical:*
Describes the actions of “force & motion”
Properties:*
Something that makes one material useful for a
job. These include the properties of:
Hardness:*
The ability of a material to resist indentation
Toughness:*
The ability of a material to absorb impact energy
Tensile strength:*
The ability to resist the action of a pulling force
Ductility:*
The ability to deform plastically under tension*
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Introduction to Mechanical Testing
We test welds to establish minimum levels of mechanical
properties, and soundness of the welded joint*
We divide tests into Quantitative & Qualitative methods:*
1) Quantitative tests:
(Have units)*
2) Qualitative tests:
(Have no units)*
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Introduction to Mechanical Testing
Types of tests include:
1) Quantitative tests:
Hardness tests
Toughness tests
Tensile strength tests*
2) Qualitative tests:
Macro tests
Bend tests
Fracture tests*
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Testing the Weldment
The test weld is usually cut into sections as follows:
The location of specimens will depend upon the standard
Charpy V test
Tensile test
Start/ Stop
Bend test*
Macro/Hardness test
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Hardness Testing
The specimen below has been polished and is
ready to be hardness tested
= Hardness Survey
Thickness
Base metal
HAZ Fusion boundary Weld metal
Further hardness surveys may be taken as the thickness
of the specimen increases*
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Hardness Testing
Generally we use a diamond or steel ball to form an indentation
We measure the width of the indentation to gauge the hardness*
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Hardness Testing
1)
Vickers Diamond Pyramid: Always uses a diamond*
2)
Brinell hardness test:
Always uses a steel ball*
3)
Rockwell hardness test:
Uses a ball, or diamond
depending on the scale*
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Charpy V Testing
Machined notch
10 x 10 mm
The specimen may be tested from different areas of the weld.*
Graduated scale
of absorbed
energy in Joules*
Pendulum Hammer
Location of specimen
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Toughness Testing
1)
Charpy V test: 10 x 10 (Specimen horizontal) Joules*
2)
Izod test:
10 x 10 (Specimen vertical) Ft.lbs*
3)
CTOD test:
Specimen used is actual design size.
Detailed fracture report. mm*
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Charpy V Testing
Mn < 1.6 % increases
toughness in steels*
Joules absorbed
Transition
Zone
47 Joules
Ductile Fracture
Three specimens are normally
tested at each temperature.
28 Joules
Transition Temperature Range
Brittle Fracture
-40 -30 -20 -10 0 +10 +20 +30 + 40
Testing temperature
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Transverse Tensile Test
A Section of weld is cut, or machined out across the test piece
and tested in tension to failure. The units are usually in N/mm²
Transverse reduced test piece*
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Radius Reduced Transverse Tensile Test
Radius
(For radius reduced test specimens only)
Weld
Test gripping area
HAZ
Direction of test
Plate material
Reduced Section
Used to assess the tensile strength of the weld metal
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All Weld Metal Tensile Test
BS 709 / BS En 10002
All Weld Metal Tensile Testing
Direction of the test *
Tensile test piece cut
along weld specimen.
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Ductility Elongation %
Firstly, before the tensile test 2 marks are made 50mm apart
50 mm
During the test, Yield point & Tensile strength are measured
The specimen is put together and the marks are re-measured
75 mm
A new measurement of 75mm will indicate Elongation E50 %*
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Macro Inspection
1) Excess Weld Metal Height
8) Poor Toe Blend*
7) Laminations
6)Porosity
2) Lack of Sidewall Fusion
5) Root Penetration
3) Lack of Root Fusion
4) Slag inclusion & Lack of inter-run fusion
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Bend Tests
Bend tests are used to establish fusion in the area under test
Guide
A Guided root bend test*
Lack of root fusion shown here*
Former
Test Piece
Force
Further tests include face, side and longitudinal bend tests*
For material over 12 mm thickness, side bend test may be used*
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Bend Tests
Specimen prior to test*
Specimen after test*
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Fillet Weld Fracture Tests
1
Saw cut
Hammer blow
2
X
3
Line of fusion
3
1
Fracture line
Full fracture
X
3
2
1
2
Y
Inspect both surfaces
Any strait line indicates a
“Lack of root fusion”*
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Butt Nick Break Tests
Saw Cuts
A
B
Hammer blow
Fracture line
Inspect both surfaces
C
Lack of root penetration
or fusion
Inclusions on fracture line*
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Summary of Mechanical Testing
We test welds to establish minimum levels of mechanical
properties, and soundness of the welded joint
We divide tests into Qualitative & Quantitative methods:*
Quantitative: (Have units)
Qualitative: (Have no units)
Hardness (VPN & BHN)
Macro tests
Toughness (Joules & ft.lbs)
Bend tests
Strength (N/mm2 & PSI)
Fillet weld fracture tests
Ductility/Elongation (E%)
Butt Nick break tests*
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Macro Inspection
The main difference between Macro & Micro is that Micro is
the study of the micro-structure at much higher magnification
The limit of Macro inspection is magnification < X 10
The specimen is usually cut from a stop/start in the test piece
The cut specimen is polished to a fine finish (400 grit)
The specimen must be inspected, before etching*
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Macro Inspection
Remember! The process of inspection is to first:
Observe, then Report, then Compare!*
Use the TWI macro sheets provided to observe and then
make a report on a separate sheet of what you observe*
When you have finished reporting, turn the macro sheet
over and compare your observations with those given on
the back of the sheet* (1 hour)
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Welding Procedures
A definition of the term “Procedure”?*
A systematic method of producing an aim*
Therefore, a “Welding procedure” is?*
A systematic method of producing a sound weld*
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Welding Procedures
What do “you” think about the following statements?*
•
•
Do all welding procedures need to be written?*
•
Do all welding procedures need to be approved?*
•
Most procedures are approved, but not all?
An approved welding procedure is one that has been tested to
ensure that the procedure as carried out, produces a weld that
satisfies a minimum level of quality for the mechanical, physical
or chemical properties desired. If these are not required, then
“procedural approval is unnecessary”*
Most production welding procedure are formatted on written
documents or computer spreadsheets, but they need not be written
and may be a product of experience
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Welding Procedures
A Welding Procedure is a recipe of variable parameters, which
will produce the same results of certain quality & properties if
carried out in the same way each time*
To evaluate a Provisional Welding Procedure we need to
check if all the parameters set will work together to produce
the desired results*
.*
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Welding Procedures
Once the weld has been completed it is usually visually
inspected, then Radiography or Ultrasonic testing is usually
applied*
Finally, and most importantly, Mechanically tested to ensure
that the desired level of mechanical properties have been met*
If all the desired properties have been met, then a procedure
qualification record (WPQR or WPAR) is completed with all
the test results, and the procedure then becomes qualified*
From this data, a workable document for production welding is
prepared and called a Welding Procedure Specification. (WPS)*
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Welding Procedures
Examples of “Extents of Approval” include:*
a) Diameter of pipe, or thickness of plate
b) Welding position, amperage range, or number of runs
c) Process (On multi process procedures only)
d) Certain material groups
e) Change of consumable to one of the same classification
Only if the class is given in the original procedure
f) Heat input range (kJ/mm)*
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Welder Approval
Once the procedure has been approved it is then important to
test each welder, to ensure that he has the skill to reach the
minimum level of quality in the weld, as laid down in the
application standard*
There is no need to carry out the mechanical tests of the
procedure, although bend tests are often used to ensure good
side wall fusion
Normally; visual, x ray, bends, fractures and macro’s are used
in welder approval tests*
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Welder Approval
When supervising a welder test the welding inspector should:*
1) Check the welding process, condition of equipment and test area for suitability.
2) Check that extraction systems, goggles and all safety equipment are available.
3) Check grinders, chipping hammers, wire brush and all hand tools are available.
4) Check materials to be welded are correct and stamped correctly for the test.
5) Check welding consumables specification, diameter, and treatment with WPS.
6) Check the welder’s name and stamp details are correct.
7) Check that the joint has been correctly prepared and tacked, or jigged.
8) Check that the joint and seam is in the correct position for the test.
9) Explain the nature of the test and check that the welder understands the WPS.
10) Check that the welder carries out the root run, fill and cap as per the WPS.
11) Ensure welders identity and stop start location are clearly marked.
12) Supervise or carry out the required tests and submit results to Q/C department.*
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