Ndt Weld RepairCSWIP.pdf

The 4 of the common types of NDT used when
assessing weldments are:
Penetrant Testing.
We use Non Destructive Testing (NDT) when we wish to
assess the integrity of a structure without destroying it
Magnetic Particle Testing.
Ultrasonic Testing.
Radiographic Testing*
Non Destructive Testing

Two types of penetrants are:
Colour contrast Fluorescent Penetrant
Colour contrast Fluorescent Penetrant
1) Colour contrast 2) Fluorescent Penetrant*
Any penetrant that has been drawn into a crack by
capillary action will be drawn out into the
developer*
Once the contact time has elapsed, the penetrant
is removed and a developer is then applied*
First the work must be cleaned thoroughly, then a
penetrant is applied for a speciﬁed time*
Penetrant Testing
Penetrant Testing
Penetrant Testing
Penetrant Testing
Procedure

Apply Penetrant Clean then apply
Developer
Result*
Method
Colour Contrast Penetrant

Advantages Disadvantages
4) Simple equipment 4) No permanent
record*
3) Extremely messy
2) Surface ﬂaws only
1) Highly clean metal
3) Low cost method
2) All materials (Non Porous)
1) Low operator skill level
Advantages and Disadvantages

1) Wet ink 2) Dry powder 3) Fluorescent ink
The types of magnetic media used are:
1) Wet ink 2) Dry powder 3) Fluorescent ink*
The weld length must be crossed at 90° by the magnetic
field*
A magnetic ink is applied which will concentrate in
areas of flux leakage, as those caused by flaws*
First the work must be cleaned and a whitener applied
for contrast. A magnetic flux is then applied by
permanent magnet, electro magnet, or straight current*
Procedure
Magnetic Particle Testing

Contrast paint Magnet & Ink
Method
Result*

4) No permanent record*
4) Simple equipment
3) Can cause arc strikes
#
2) De-magnetize after
use
1) Fe Magnetic metal
only
3) Relatively cheap
2) Sub surface ﬂaws
1) Low operator skill level
# When using the straight current prod
technique

Procedure
Any imperfections will rebound the sound waves causing
a signal to occur on the cathode ray tube*
A probe is then applied with the correct angle for the
weld preparation and sound waves are transmitted*
First the work must be cleaned thoroughly, then a
couplant is applied to increase sound transmission*
Ultrasonic Testing
Ultrasonic Testing
Ultrasonic Testing
Ultrasonic Testing

Apply Couplant Sound wave
Signal rebounded
from Lack of
fusion
Signal rebounded
from Lack of
fusion
Signal rebounded
from Lack of
fusion
Signal rebounded
from Lack of
fusion
CRT display
Method
Result*
Ultrasonic Testing
Ultrasonic Testing
Ultrasonic Testing
Ultrasonic Testing

4) Portable/instant
results
4) No permanent record*
3) Requires calibration
2) Diﬃcult to interpret
1) High operator skill
3) No safety
requirements
2) Most materials
1) Can ﬁnd lack of fusion

The 2 types of radiation used in industrial radiography:
1) X rays (from Cathode Ray Tube)
2) Gamma rays (from a Radioactive Isotope)*
Any imperfections in line with the beam of radiation will
be shown on the film after exposure and development*
A film is placed inside a cassette between lead screens.
It is then placed to the rear of the object to be
radiographed A radiographic source, is exposed to the
work and film for a pre-calculated time*
Procedure
Radiographic Testing

Radioactive source
Method
Film
cassette
Load ﬁlm Exposure to
Radiation
Interpret Graph
IQI
Develope
d Graph
Latent image on the
ﬁlm

4) Gamma ray is portable 4) Safety requirements*
3) Lack of sidewall fusion
2) Diﬃcult interpretation
1) High operator skill
3) Assess root pen’ in pipe
2) Most materials
1) A permanent record ?

New TWI Video
“Non Destructive Testing”
30 Minutes

Coffee Break
Coffee Break
Coffee Break
Coffee Break

Weld Repairs
Weld Repairs
Weld Repairs
Weld Repairs
Weld Repairs:
Weld repairs can be divided into two speciﬁc areas:
1) Production repairs
2) In service repairs*
Production repairs are usually identiﬁed by the Welding
Inspector, or NDT operator during the process of
inspection, or evaluation of reports to the code, or
applied standard*

Weld Repairs
Weld Repairs
Weld Repairs
Weld Repairs
A typical defect is shown below: *
Prior to repair the defect may need to undergo the
following:
1) A defect analysis and report 2) An
assessment of defect extremity 3) An excavation
procedure 4) NDT procedures 5)
A welding repair procedure 6) Welder approval
to the approved repair procedure 7) Any subsequent
treatments procedures i.e. PWHT *

Plan View of defect with drilled
ends
Side View of defect excavation*
Completed repair*
Weld Repairs
Weld Repairs
Weld Repairs
Weld Repairs
*

NDT conﬁrmation of successful repair:
After the excavation has been ﬁlled the weldment
should then be undergo a complete retest using
NDT to ensure no further defects have been
introduced by the repair. NDT may also need to be
further applied after any additional post weld heat
treatment has been carried out*
Weld Repairs
Weld Repairs
Weld Repairs
Weld Repairs

Residual welding stresses are deﬁned as those stresses
that remain inside a material after welding has been
carried out
Stresses are caused by the heat of welding, which
produces local expansion and contraction to take
place
If a metal was heated & cooled uniformly no stresses
would remain, as expansion & contraction would be
uniform
Welding causes only local heating and cooling
conditions to exist, hence some residual stresses to
remain in the metal*
Residual Stress & Distortion

Residual stresses can have very complex
patterns in welded constructions.
In simple butt welded plates they may be
indicated as shown below:
Compressive

Tensile  Tensile 
Directions of Welding Related Stresses
*

Longitudinal
Transverse
Short
transverse
Plan View
of plate
End View
of plate
Weld
We can say that expansion/contraction has three
directions.
Directions of Expansion/Contraction

One effect of welding related stresses is distortion
Distortion is the movement of material in one area
caused by expansion and contraction, and local elastic/
plastic movement that misshapes the component*
The various types of distortion produced are caused by
the directions and amount of expansion and
contractional stresses involved, and the ability of the
material to resist the stress without the formation of
elastic/plastic strain, or deformation
It is this deformation that produces distortion in a
product*
Effects of Expansion/Contraction

Distortion*
Angular
Transverse
distortion
Longitudinal
distortion

The volume of weld metal in a joint will also effect
the amount of local expansion and contraction
Hence the more volume of weld metal then the
overall amount of distortion will be higher*
Effects of Weld Volume on Distortion

Many methods are used to control the effects of
distortion.
Perhaps the best of these is to to pre set the materials to
allow distortion to bring it to its ﬁnal shape. This method
is called offsetting, or pre-setting*
a) Practical
b) Practical
c) Impractical*
Control of Distortion

Other forms of distortion control stop the movement of
material from occurring by using such methods as
clamping, jigging, strong backs, and tacking etc*
Back-step & balance welding are sequences which
may also be used to control the effects of distortion*
These methods will reduce the distortion, but will also
amass the maximum amount of residual stresses to
exist*

1) Heating
2) Soaking
3) Cooling
Temp
Time
1
2
3
All heat treatments applied to metals are cycles of 3
elements.
Heat Treatments
Heat Treatments
Heat Treatments
Heat Treatments

Annealing: Used to make metals soft and
ductile
For steels, the component is heated above its UCT,
or upper critical temperature, soaked for 1
hour/25mm of thickness and left in the furnace to
cool Produces a coarse grain structure &
low toughness*
Normalising: Used to make steels
tough
As for annealing, but the steel is removed from the
furnace after soaking to cool in still air
Produces a ﬁne grain structure with good
toughness*
Heat Treatments
Heat Treatments
Heat Treatments
Heat Treatments

Hardening: Used to make some steels harder
Used to increase the hardness of some plain
carbon & alloy steels. Plain carbon > 0.3%
The cycle is the same as previously but the
cooling is rapid i.e. Quenched in water, oil, but
sometimes air*
Tempering: Used after hardening to balance the
properties of Toughness & Hardness
The temperature range is from 220 – 723 °C
The cooling part of the cycle should not be too
rapid, but over heating will over temper the
steel*
Heat Treatments
Heat Treatments
Heat Treatments
Heat Treatments

Used after welding to release residual
stresses, caused by welding operations*
By heating the steel, the yield point is suppressed/reduced
relieving residual stresses as plastic strain at a much lower
level of stress*
Force/Stress required to
induce plastic strain*
The effect of
heat on the
position of the
yield point*
Stres
s
Strain
PWHT:
Y
Heat Treatments
Heat Treatments
Heat Treatments
Heat Treatments

Pre-Heating: Used mainly on steels to retard the
cooling rate of a hardenable steel and
reduce the hardening effect (Martensite
formation)
Is also used to help diffusion of
Hydrogen from the HAZ of hardenable
steels to avoid hydrogen cracking.
Typically < 350 °C
Is also used to produce a more uniform
rate of cooling, and control distortion, or
effects of high contractional strains*
Heat Treatments
Heat Treatments
Heat Treatments
Heat Treatments

Gas Welding & Cutting
*

Neutral
Name Pictorial view Uses
Fusion welding most
metals. Flame temp >
3,200 °C*
Oxidising
Bronze Welding*
Carburising
Hard surfacing &
fusion & Brazing
Aluminium & alloys*

A jet of pure oxygen reacts with high temperature iron
(>1100  C) to produce Fe3 O4 by exothermic reaction.
This dross is then removed by the pressure of the
oxygen jet*
Oxy/Fuel Gas Cutting
Different types of fuel gases may be used for the pre-
heating ﬂame in oxy fuel gas cutting: i.e.
Acetylene. Hydrogen. Propane. Etc*
By adding Iron powder to the ﬂame we are able to cut
most metals “Iron Powder Injection”*
The high intensity of heat and rapid cooling will cause
hardening in low alloy, and medium, or high C steels
They are thus pre-heated to avoid the hardening effect*

Slightly rounded top edge
caused by too close a nozzle
gap
50m
m
The “Kerf”
Flutes

MMA electrodes are specially produced for cutting and
gouging. Oxy/Arc and Arc/Air are arc cutting process that
produce lots of fume and arc air produce a high noise level.
All these processes require good extraction, and ear
protection is vital for arc/air
Both oxy arc and arc air use special types of electrodes
and gas supplies, which will be described by the course
lecturer*
Arc Cutting Processes

Safety is the responsibility everyone.
As respected oﬃcers, it is the duty of all welding
inspectors to ensure that safe working practices are
strictly followed.
Safety in welding can be divided into several areas,
some of which are as follows:
(Areas to be expanded brieﬂy by the lecturer/
presenter)
1) Welding/cutting process safety.*
2) Electrical safety.*
3) Welding fumes & gases. Use & storage of gases.*
4) Safe use of lifting equipment.*
5) Safe use of hand tools and grinding machines.*
Safety in Welding Operations

1)
2)
3)
4)
5)
The hazards of infra red and/or ultra violet light
The hazards of heat, burns and ﬁre
The hazards of toxic and non toxic gases from
process, coatings, or purging, and gases stored at
high pressure
The hazards of working with high voltages & currents
The hazards of working in conﬁned spaces*
Careful consideration should be given to safety
hazards when using a particular welding process. This
may include:*
Welding Process Safety

1)
2)
3)
4)
5)
6)
Removing any combustible materials from the area
Checking all containers to be cut are fume free and
have a Permit to Work
Providing ventilation and extraction where required
Ensuring good gas safety is being practised
Keeping oil and grease away from oxygen
Using ear defenders when arc air cutting
Careful consideration should be given to safety
when using gas, or arc cutting systems by:*
Cutting Process Safety

Safe working with electrical power is mostly common
sense. Ensure that insulation is used where required
and that cables and connections are in good condition.
(Check the duty cycle)*
Gases should be stored separately, and cylinders should
be secured when used in the vertical position, especially
oxygen*
Exposure to dangerous welding fumes and gases from
electrodes, plating, i.e.ozone, nitrous oxide, phosgene,
cadmium, beryllium are to name just a few. Always use
extraction/breathing systems. If in any doubt, stop the
work*
General Safety
General Safety
General Safety
General Safety

From the points that have been covered in the
safety lecture, and/or the Video, complete
the safety check list exercise in your course
text*
General Welding Safety

“Weldability” is a term used in welding engineering to
describe the ease of which a material can be welded by
the common welding processes and still retain the
properties for which it was designed*
If we say that a material has limited weldability, it
means that we need to take special measures to
ensure that the properties as required are maintained*
Most materials are weldable with certain processes.
weldability
weldability
The weldability of steel is mainly dependant on carbon
content & alloying, though most steels have a degree of
weldability*
The Weldability of Steels

1) Hydrogen induced HAZ cracking in Low Alloy Steels
2) Hydrogen weld metal cracking in Micro Alloy Steels
3) Solidiﬁcation cracking in Ferritic steels
4) Lamellar tearing in Ferritic steels
4) Lamellar tearing in Ferritic steels
5) Inter-granular corrosion in Stainless Steels*
The Weldability of Steels for CSWIP 3.1

Plain carbon steels contain only iron & carbon as main
alloying elements, traces of Mn Si Al S & P may also be
present*
3) High Carbon Steel 0.6 – 1.4% Carbon*
2) Medium Carbon Steel 0.3 – 0.6%
Carbon*
1) Low Carbon Steel 0.01 – 0.3% Carbon*
Plain Carbon Steels:*
Steels are classiﬁed into groups as
follows:*
Classiﬁcation of Steels

An Alloy steel is one that contains more than Iron &
Carbon as a main alloying elements*
Alloy steels are divided into 2 groups:*
Low Alloy Steels< 7% extra alloying
elements
High Alloy Steels> 7% extra alloying
elements
*
*

Iron is an element that can exist in 2 types of cubic
structures, depending on the temperature. This is an
important feature*
A most important function in the metallurgy of steels, is
the ability of iron to dissolve carbon in solution*
The carbon atom is very much smaller than the iron
atom and does not replace it in the atomic structure,
but ﬁts between it*
Iron
atoms
Carbon
atoms*
Basic Atomic Structure of Steels
The following basic foundation information on
metallurgy will not form any part of your CSWIP
examination*

α Alpha iron
This structure occurs below 723 °C and
is body centred, or BCC in structure
It can only dissolve up to 0.02% Carbon
Also known as Ferrite or BCC iron*
At temperatures below Ac/r 1, (LCT) iron exists like this*
Compressed representation could appear like
this
*

γ Gamma iron
This structure occurs above the UCT in
Plain Carbon Steels and is FCC in
structure.
It can dissolve up 2.06% Carbon
Also called Austenite or FCC
iron*
At temperatures above the Ac/r 3, (UCT) iron exists like
this*
this
*

If steel is heated and then cooled slowly in equilibrium,
then exact reverse atomic changes take place*
If a steel that contains more than 0.3% Carbon is cooled
quickly, then the carbon does not have time to diffuse out
of solution, hence trapping the carbon in the BCC form of
iron. This now distorts the cube to an irregular
cube, or tetragon*
This supersaturated solution is called Martensite and
is the hardest structure that can be produced in steels*

Martensite can be deﬁned as:
A supersaturated solution of carbon in
BCT iron (Body Centred Tetragonal)
It is the hardest structure we can
produce in steels*
this
If some steels are cooled quickly their structure looks like
this*
*

Ferrite:  Low carbon solubility. Maximum 0.02%*
Austenite:  High carbon solubility. Maximum 2.06%*
Solubility of Carbon in BCC & FCC phases of steels*
Martensite: The hardest phase in steels, which is
produced by rapid cooling from the Austenite phase
It mainly occurs below 300 °C*
TheImportant Points of Steel Microstructures

The atomic structures of plain carbon steels have been
briefly identified and explained in this lecture*
To summarize the effect of increasing the hardness of
steels by thermal treatment, it can be said that the
formation of Martensite is caused by the entrapment of
carbon in solution, produced by rapid cooling from
temperatures above the Upper Critical*
In plain carbon steels there must be sufficient carbon to
trap. In low alloy steels however, the alloying
elements play a significant part in the thermal hardening
of steels*
Summary of Steel Microstructures

Crack type: H² HAZ & weld metal cracking
Location: a. HAZ (Longitudinal)
b. Weld metal (Transverse) Steel types: a.
All hardenable steels including:
b. HSLA steels
c. Quench & Tempered steels
Microstructure: Martensite*
Occurs when:
Hydrogen is above 15 ml/100 gm weld metal
Hardness is above 350 VPN
Stress is greater than 0.5 of the yield stress
Temperature is below 300 ºC*
Hydrogen Induced Cracking

Hydrogen absorbed
in a long, or unstable
arc
Hydrogen produced
from oil, or paint on
plate
Cellulosic electrodes
produce hydrogen as a
shielding gas
Hydrogen crack
Hydrogen crack
Martensite forms from γ
H2 diffuses to γ in
HAZ*
H2
H2

To ﬁnd a simple method we would need to look at the
effect of increasing carbon content on the properties of
iron*
It is however important to match the strength of the weld
to the strength of the plate, and so a simple way of
matching weld strength must be found and utilised*
Typically the level of alloying is in the region of 0.05% and
elements such as vanadium molybdenum and titanium.
are used. It would be impossible to match this micro
alloying in the electrode due to the effect of losses
across an electric arc*
HSLA or Micro-Alloyed Steels are high strength steels
that derive their high strength from ﬁnite alloying*
Hydrogen Induced Cracking in HSLA Steels

Ductility
Hardness
Tensile
Strength
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.2 1.4 1.6 % Carbon
0.83 % Carbon (Eutectoid)*
Increasing the carbon content will increase the strength,
but will also increase greatly the formation of martensite in
the weld. This may now produce H2 Cracks across
weld*
Effects of Carbon on the Properties of Iron

Transverse Weld
Cracks in HSLA Steels*
Longitudinal contractional strain
Low ductility weld metal
H2 HAZ Cracks
in Alloy steels*
Hydrogen Induced Cracking Steels

6) Avoid any restraint, and use high ductility weld
metal*
5) Carry out any speciﬁed PWHT as soon as possible*
4) Remove any paint, oil or moisture from the plate or
pipe*
“ ”
“ ”
3) If using a cellulosic E 6010 for the root run, insert
the “Hot pass” as soon as possible. (Before HAZ <
300 °C)*
2) Use Low Hydrogen processes with short arcs &
ensure consumables are correctly baked & stored as
required*
1) Maintain calculated preheats, and never allow the
inter-pass temperature to go below the pre-heat
value*
Prevention of Hydrogen Induced Cracking

Crack type: Solidification cracking Location:
Weld centre (longitudinal) Steel types:
High sulphur & phosphorus steels. Microstructure:
Columnar grains In direction of solidification*
Occurs when:
Liquid iron sulphides are formed around solidifying
grains. High contractional strains are present
High dilution processes are being used.
There is a high carbon content in the weld metal*
Solidification Cracking Fe Steels

1) The ﬁrst steps in eliminating this problem would be to
choose a low dilution process, and change the joint
design*
2) Grind and seal in any lamination and avoid further
dilution*
3) Add Manganese to the electrode to form spherical
Mn/S which form between the grain and maintain grain
cohesion*
4) As carbon increases the Mn/S ratio required increases
exponentially and is a major factor. Carbon content %
should be a minimised by careful control in electrode
and dilution*
5) Limit the heat input, hence low contraction, &
minimise restraint*
Control of Solidiﬁcation Cracking

Liquid Iron Sulphide
ﬁlms
Solidiﬁcation
crack
Contractional strain
*

Spherical Mn Sulphide balls
form between solidiﬁed
grains
Cohesion and strength
between grains
remains
Contractional strain
Prevention of Solidiﬁcation Cracking
*
Add Manganese to weld
metal

Crack type: Lamellar tearing Location:
Below weld HAZ Steel types: High sulphur &
phosphorous steels Microstructure: Lamination &
Segregation*
Occurs when:
High contractional strains are through the short
transverse direction. There is a high sulfur content in
the base metal.
There is low through thickness ductility in the base
metal.
There is high restraint on the work*
Lamellar Tearing
Lamellar Tearing
Lamellar Tearing
Lamellar Tearing

High contractional
strains
Lamellar tear
Restraint
Lamellar Tearing
Lamellar Tearing
Lamellar Tearing
Lamellar Tearing

Plate to be
tested* Full fusion compound
welded cruciform
joint*
Machined
test piece*
The test piece is machined from the cruciform joint
and placed under tension. If Lamellar tearing was
present it would fail at a low value*
Contractional
strain*
Testing for Lamellar Tearing
Through
thickness tensile
test*

•
•
•
•
•
Assessment of susceptibility to Lamellar
Tearing:
Carry out through thickness tensile test
Carry out cruciform welded tensile test
Carry out Ultra-sonic testing
Carry out penetrant testing of plate edges
Carry out full chemical analysis (S < 0.05%)*
CheckingforLamellarTearingSusceptability

Methods of avoiding Lamellar Tearing:*
Control of Lamellar Tearing
1) Avoid restraint*
2) Use controlled low sulfur plate *
3) Grind out surface and butter *
4) Change joint design *
5) Use a forged T piece (Critical Applications)*

Re-design
weld*
Grind and inﬁll with
ductile weld metal*
Control
restraint*
For critical work a
forged T piece may be
used*
Forged T
Piece

Crack type: Inter-granular corrosion
Location: Weld HAZ. (longitudinal)
Steel types: Stainless steels
Microstructure: Sensitised grain boundaries*
Occurs when:
An area in the HAZ has been sensitised by the formation
of chromium carbides. This area is in the form of a line
running parallel to and on both sides of the weld.
This depletion of chromium will leave the effected
grains low in chromium oxide which is what produces
the corrosion resisting effect of stainless steels.
If left untreated corrosion and failure will be rapid*
Intergranular Corrosion

During the welding of stainless steels, a small grain area
in the HAZ, parallel to the weld will form chromium
carbide at the grain boundaries. This depletes this grain of
the corrosion resisting chrome oxide
We say that the steel has become “Sensitised” or has
become sensitive to corrosion*

3) A sensitised Stainless Steel may be de-sensitised
by heating it to above 1100 °C where the Chrome
carbide will be dissolved. The steel is normally
quenched from this temperature to stop re-
association*
Control of Intergranular Corrosion
1) Use Stabilised Stainless Steels*
2) Use Low Carbon Stainless Steels ( Below .04%)*

Attempt the end of course Multi Choice question paper
answering 30 questions
Time allowed 30 minutes
Attempt the speciﬁc question paper answering 4 from 6
questions
Time allowed 1 hour
WIS 5 E Only
End of Course Examination

Practice observing & reporting using the pipes or
plates and forms provided
Use your nominated pipe code for all your visual
inspections.
Practice this up and till the end of the day, or as
directed by your course lecturer*
WIS 5 Only
Practical Inspection Practice

Ndt Weld RepairCSWIP.pdf

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