Ultrasonic Ultrason ic Testing
• Duration
:
9.5 Days (Mon – Fri)
• Start
:
8:30 am
• Coffee Break
:
10:00 – 10:30 am
• Lunch
:
12:30 – 1:30 pm
• Tea Break : • Day End
3:00 – 3:30 pm :
5:00 pm
Course se Obje Object ctiv ive: e: To trai train n and and prep prepar are e part partic icip ipan ants ts to obta obtain in • Cour required skill and knowledge in Ultrasonic Testing and to meet the examination schemes requirements.
Most common NDT methods: Penetrant Testing (PT) Magnetic Particle Testing (MT)
Mainly used for surface testing
Eddy Current Testing (ET) Radiographic Testing (RT) Ultrasonic Testing (UT)
Mainly used for Internal Testing
• Which method is the best ? Depends on many factors and conditions
• To understand and appreciate the capability and limitation of UT
Sound is transmitted in the material to be tested The sound reflected back to the probe is displayed on the Flaw Detector
The distance the sound traveled can be displayed on the Flaw Detector The screen can be calibrated to give accurate readings of the distance
Signal from the backwall
Bottom / Backwall
Basic Principles of Ultrasonic Testing The presence of a Defect in the material shows up on the screen of the flaw detector with a less distance than the bottom of the material The BWE signal
Defect signal
Defect
0
10 20
30
40
50 60
60 mm
The depth of the defect can be read with reference to the marker on the screen
Thickness / depth measurement The closer closer the the reflector to the surface, the signal will be more to the left of the screen
B
C
30
A
46
68
The thickness is read from the screen
C B A
The THINNER the material the less distance the sound travel
Principles of Sound
Sound • Wavelength : The distance required to complete a cycle • Measured in Meter or mm
• Frequency : The number of cycles per unit time Cycles per second (cps) • Measured in Hertz (Hz) or Cycles
• Velocity : How quick the sound travels Distance per unit time • Measured in meter / second (m / sec)
• Sound cannot travel in vacuum • Sound energy to be transmitted / transferred from one particle to another
SOLID
LIQUID
GAS
• The velocity of sound in a particular material is CONSTANT • It is the product of DENSITY and ELASTICITY of the material • It will NOT change if frequency changes • Only the wavelength changes • Examples: V Compression in steel
: 5960 m/s
V Compression in water
: 1470 m/s
V Compress Compression ion in air : 330 m/s 5 M Hz
STEEL
WATER
AIR
What is the velocity difference in steel compared with in water? 4 times If the frequency remain constant, in what material does sound has the highest velocity, steel, water, or air? Steel If the frequency remain constant, in what material does sound has the shortest wavelength, steel, water, or air? Air Remember the formula = v / f
ULTRASONIC UL TRASONIC TESTING Very High Frequency 5 M Hz
Glass High Frequency 5 K Hz DRUM BEAT Low Frequency Sound 40 Hz
• Sound : mechanical vibration
What is Ultrasonic? Very High Frequency sound – above 20 KHz 20,000 cps
Sonic / Audible Human
Ultrasonic > 20kHz = 20,000Hz
16Hz ‐ 20kHz
0
10
100
1K
10K 100K 1M 10M 100m Ultrasonic Testing 0.5MHz ‐ 50MHz
Ultrasonic : Sound with frequency above 20 KHz
Number of cycles per • Frequency : second
1 second 1 cycle per 1 second = 1 Hertz
1 second 3 cycle per 1 second = 3 Hertz
1 second 18 cycle per 1 second = 18 Hertz
THE HIGHER THE FREQUENCY THE SMALLER THE WAVELENGTH
• 1 Hz =
1 cycle per second
• 1 Kilohertz =
1 KHz =
• 1 Megahertz
=
1000Hz
1 MHz
= 1000 000Hz
20 KHz
=
20 000 Hz
5 M Hz
=
5 000 000 Hz
Wavelength Wavelength is the distance required to complete a cycle. Sound waves are the vibration of particles in solids, liquids or gases. Particles vibrate about a mean position. wavelength Displacement
wavelength
One cycle
The distance taken to complete one cycle
Wavelength
Velocity
V f Frequency
1 M Hz
5 M Hz
LONGEST
10 M Hz
= v / f
F
25 M Hz SMALLEST
F
Which probe has the smallest wavelength? Which probe has the longest wavelength?
Therefore:
V
or
f V
f
or
V f
5MHz compression wave probe in steel
5,900,000 5,000,000
1.18mm
• Which of the following compressional probe has the highest sensitivity? • 1 MHz • 2 MHz • 5 MHz • 10 MHz
10 MHz
Wavelength and frequency • The higher the frequency the smaller the wavelength • The smaller the wavelength the higher the sensitivity Sensitivity : The smallest detectable • Sen flaw by the system or technique
• In UT the smallest detectable flaw is ½
wavelength)
(half the
• Dead Zone • Near Zone or Fresnel Zone • Far Zone or Fraunhofer Zone
NZ
FZ
Main Beam
Intensity varies Exponential Decay
Distance
The side lobes has multi minute main beams Two identical defects may give different differe nt amplitudes of signals
Near Zone
Side Lobes
The main beam or the centre beam has the highest intensity of sound energy Main Lobe
Main Beam
Any reflector hit by the main beam will reflect the high amount of energy
Near Zone
Far Zone
• Thickness measurement
• Thickness measurement
• Detection of defects
• Defect detection
• Sizing of large defects only
• Sizing of all defects
Near zone length zone length as small small as as possible
Near Zone
D
2
4
V f 2
Near Zone
D f
4 V
• What is the near zone length of a 5MHz compression probe with a crystal diameter of 10mm in steel?
2
Near Zone
10
2
D f
4 V
5 , 000 , 000
4 5 , 920 , 000
21 . 1 mm
Near Zone
D
2
4
2
D f
4 V
• The bigger the diameter the bigger the near zone • The higher the frequency the bigger the near zone • The lower the velocity the bigger the near zone
Should large diameter crystal probes have a high or low frequency?
Which of the above probes has the longest Near Zone ?
1 M Hz 1 M Hz
5 M Hz
5 M Hz
Near Zone
D
2
4
2
D f
4 V
• The bigger the diameter the bigger the near zone • The higher the frequency the bigger the near zone • The lower the velocity the bigger the near zone
Should large diameter crystal probes have a high or low frequency?
• In the far zone sound pulses spread out as they move away from the crystal
/2
Sine
2
K D
or
KV Df
Sine
2
K D
or
KV Df
Edge,K=1.22 20dB,K=1.08 6dB,K=0.56 Beam axis or Main Beam
Sine
2
K D
or
KV Df
• The bigger the diameter the smaller the beam spread • The higher the frequency the smaller the beam spread
Which has the larger beam spread, a compression or a shear wave probe?
• What is the beam spread of a 10mm,5MHz compression wave probe in steel?
Sine
2
1 . 08
Df
5000
KV
0 . 1278
5920 10
7 . 35
o
Which of the above probes has the Largest Beam Spread ?
1 M Hz 1 M Hz
5 M Hz
5 M Hz
Beam Spread
Sine
2
K D
or
KV Df
• The bigger the diameter the smaller the beam spread • The higher the frequency the smaller the beam spread
Which has the larger beam spread, a compression or a shear wave probe?
Testing close to side walls
• Pulse Echo • Through Transmission • Transmission with Reflection
• Single probe sends and receives sound • Gives an indication of defect depth and dimensions • Not fail safe
B
B A
No indication from defect A (wrong orientation)
Transmitting and receiving probes on opposite sides of the specimen Presence of defect indicated by reduction in transmission signal
No indication of defect location Fail safe method
Tx
Rx
Advantages
Disadvantages
• Less attenuation
• Defect not located
• No probe ringing • No dead zone
• Defect can’t be identified
• Orientation does not matter
• Vertical defects don’t show • Must be automated • Need access to both surfaces
T
Also known as: Tandem Technique or Technique or Pitch and Catch Technique
R
• A short pulse of electricity is applied to a piezo‐ electric crystal • The crystal begins to vibration increases to maximum amplitude and then decays Maximum
10% of Maximum
Pulse length
• The longer the pulse, the more penetrating the sound • The shorter the pulse the better the sensitivity and resolution
Sho Short pulse, 1 or 2 cycles
Long pulse 12 cycle cles
5 cycles for weld testing
• Dead Zone • Near Zone or Fresnel Zone • Far Zone or Fraunhofer Zone
NZ
FZ
Main Beam
Intensity varies Exponential Decay
Distance
The side lobes has multi minute main beams Two identical defects may give different differe nt amplitudes of signals
Near Zone
Side Lobes
The main beam or the centre beam has the highest intensity of sound energy Main Lobe
Main Beam
Any reflector hit by the main beam will reflect the high amount of energy
Near Zone
Far Zone
• Thickness measurement
• Thickness measurement
• Detection of defects
• Defect detection
• Sizing of large defects only
• Sizing of all defects
Near zone length as small as possible
Near Zone
D
2
4
V f 2
Near Zone
D f
4 V
• What is the near zone length of a 5MHz compression probe with a crystal diameter of 10mm in steel?
2
Near Zone
10
2
D f
4 V
5 , 000 , 000
4 5 , 920 , 000
21 . 1 mm
Near Zone
D
2
4
2
D f
4 V
• The bigger the diameter the bigger the near zone • The higher the frequency the bigger the near zone • The lower the velocity the bigger the near zone
Should large diameter crystal probes have a high or low frequency?
Which of the above probes has the longest Near Zone ?
1 M Hz 1 M Hz
5 M Hz
5 M Hz
Near Zone
D
2
4
2
D f
4 V
• The bigger the diameter the bigger the near zone • The higher the frequency the bigger the near zone • The lower the velocity the bigger the near zone
Should large diameter crystal probes have a high or low frequency?
• In the far zone sound pulses spread out as they move away from the crystal
/2
Sine
2
K D
or
KV Df
Sine
2
K D
or
KV Df
Edge,K=1.22 20dB,K=1.08 6dB,K=0.56 Beam axis or Main Beam
Beam Spread
Sine
2
K D
or
KV Df
• The bigger the diameter the smaller the beam spread • The higher the frequency the smaller the beam spread
Which has the larger beam spread, a compression or a shear wave probe?
• What is the beam spread of a 10mm,5MHz compression wave probe in steel?
Sine
2
1 . 08
Df
5000
KV
0 . 1278
5920 10
7 . 35
o
Which of the above probes has the Largest Beam Spread ?
1 M Hz 1 M Hz
5 M Hz
5 M Hz
Sine
2
K D
or
KV Df
• The bigger the diameter the smaller the beam spread • The higher the frequency the smaller the beam spread
Which has the larger beam spread, a compression or a shear wave probe?
Testing close to side walls
• Sound will be either transmitted across or reflected back Reflected
Interface
Transmitted
How much is reflected and transmitted depends upon the relative acoustic impedance of the 2 materials
REFLECTION DIFFRACTION
• Angle of Incidence = Angle of Reflection
60o
60o
Incident
Transmitted The sound is refracted due to differences in sound velocity in the 2 DIFFERENT materials
• Only occurs when: The incident angle is other than 0° 30° Water
Steel
Water
Steel
Steel
Steel Refracted
• Only occurs when: The incident angle is other than 0° The Two Materials has different VELOCITIES
30°
30°
Steel
Water
Steel
Steel 65° 30°
No Refraction
Refracted
Normal
Incident
I
Material 2
Sine I Sine R
Material 1
R
Refracted
Vel in Material 1 Vel in Material 2
C
Sine I
20
Sine R Perspex
Vel in Material1 Vel in Material 2
Sine 20
Sine 48.3
Steel
0 . 4580
48.3 C
2730 5960
0 . 4580
C
Sine I
15
Vel in Material1
Vel in Material 2
Sine R
Sine 15
Perspex
Sine R
Steel
SinR
34.4 C
SinR R
2730 5960
Sin 15
5960 2730
0 .565
34 .4
C
20
Perspex Steel 48.3 C
24 S
C
C
When an incident beam of sound approaches an interface of two different materials: REFRACTION occurs
Perspex Steel
There may be more than one waveform transmitted into the second material, example: Compression and Shear
C SS
C
When a waveform changes into another waveform: MODE CHANGE
If the angle of Incident is increased the angle of refraction refraction also increases
C
Perspex Steel
90°
Up to a point where the Compression Wave is at 90° from the Normal
This happens at the
FIRST CRITICAL ANGLE
S
C
C 27.4
Compression wave refracted at 90 degrees
C
33 S
C
C
57
S (Surface Wave) 90
Shear wave refracted at 90 degrees Shear wave becomes a surface wave
1st Critical Angle Calculatio Calculation n C 27.2
Sine I
Sine 90 Perspex C Steel
S
5960
Sin 90 SinI
SinI
2730
1
2730 5960
0 .458
I 27 .26
2nd Critical Angle Calculation C
Sine I
C 57.4
Sine 90 Perspex
Steel
S
3240
Sin 90 SinI
SinI
2730
1
2730 3240
0 .8425
I 57 .4
Before the 1st. Critical Angle: There are both Compression and Shear wave in the second material
1st. C nd
2 .
At the FIRST CRITICAL ANGLE Compression wave refracted at 90°
Shear wave at 33 degrees in the material
90° Beyond the 2nd. Critical Angle: All waves are reflected out of the material. NO wave in the material.
S C
33°
Between the 1st. And 2nd. Critical Angle: Only SHEAR wave in the material. Compression is reflected out of the material.
At the 2nd. Critical Angle: Shear is refracted to 90° and become SURFACE wave
Summary • Stan Standar dard d angl angle e pro probe bes s betw betwee een n 1st 1st and and 2nd critical angles (45,60,70) • Stat Stated ed ang angle le is ref refra ract cted ed angle angle in stee steell • No ang angle le pro probe be und under er 35, 35, and and more more than 80: to avoid being 2 waves in the same material. One Defect Two Echoes C
C
S
S
• Calculate the 1st critical angle for a perspex/copper interface • V Comp perspex : 2730m/sec 4700m/sec sec • V Comp copper : 4700m/
SinI
2730 4700
0 . 5808
35 . 5
• Hammers (Wheel tapers) • Magnetostrictive • Lasers • Piezo‐electric
magnetostrictive
• When exposed to an alternating current a crystal expands and contracts • Conver Convertin ting g elec electri trical cal energy energy into into mechan mechanica icall
‐
+
+
‐
‐
+
Piezo‐Electric Materials QUARTZ
LITHIUM SULPHATE
• Resistant to wear
• Efficient receiver
• Insoluble in water
• Low electrical impedance
• Resists ageing
• Operates on low voltage
• Inefficient converter of energy
• Water soluble
• Needs a relatively high voltage
• Useable only up to 30ºC
Very rarely used nowadays
• Low mechanical strength Used mainly in medical
• Powders heated to high temperatures
Examples
• Pressed into shape
• Lead metaniobate (Pb Nb O6)
• Cooled in very strong electrical fields
• Barium titanate (Ba Ti O3)
• Lead zirconate titanate (Pb Ti O3 or Pb Zr O3)
Most of the probes for conventional usage use
PZT : Lead Zirconate Titanate
Z
• The most important part of the probe is the crystal • The crystal are cut to a particular way and thickness to give the intended properties
X
• Most of the conventional crystal are X – cut to produce Compression wave Y
X
X
• The frequency of the probe depends on the THICKNESS of the crystal • Formula for frequency:
Ff = V / 2t Where
Ff = the Fundamental Fundamental frequency V = the velocity in the crystal t = the thickness of the crystal
Fundamental Fundamental frequency is the the frequency of the material ( crystal ) where at that frequency the material will vibrate.
• The Thinner the crystal the Higher the frequency • Which of the followings has the Thinnest crystal ? 1 MHz Compression probe 5 MHz Compression probe 10 MHz Shear probe 25 MHz Shear probe
25 MHz Shear Probe
• Compression Probe • Normal probe • 0°
Electrical connectors
Housing Damping Transducer
• Shear Probe • Angle probe Backing medium
Damping Transducer Probe Shoe
Perspex wedge
Advantages
Twin Crystal Transm ansmit itte terr
Recei eceive verr
• Can be focused • Measure thin plate • Near surface resolution Disadvantages • Difficult to to use on curved surfaces • Sizing sm small de defects
Separator / Insulator
Focusing lens
• Signal amplitude / focal spot length
Comparing the intensity of 2 signals
I 0
I 1
P0 P1
Electrical power proportional to the square of the voltage produced 2
P0 (V 0)
2
P1 (V 1)
2
Hence
I 0 (V 0)
2
I 1 (V 1)
Sound Intensity 2 I 0 (V 0)
2
Will lead to large ratios
I 1 (V 1)
Therefore
I 0
(V 0)2
Log..10 Log..10 2 I 1 (V 1) Log..10 Log..10
I 0 I 1
I 0 I 1
2 Log..10
V 0 V 1
20 Log..10
BEL
V 0 V 1
dB
2 signals at 20% and 40% FSH. What is the difference between them in dB’s?
dB 20 Log..10
dB 20 Log..10
H 0 H 1
40 20
dB 20 0.3010
dB 6dB
20Log..102
2 signals at 10% and 100% FSH. What is the difference between them in dB’s?
dB 20 Log..10
dB 20 Log..10 dB
20 1
dB 20dB
H 0 H 1
100 10
20Log..1010
• 2:1=
6bB
• 4 : 1=
12dB
• 5 : 1=
14dB
• 10 : 1
=
20dB
• 100 : 1
=
40dB
Automated Inspections • Pulse Echo • Thro Throug ugh h Tr Transm ansmis issi sion on • Trans ransmi miss ssio ion n with with Refl Reflec ecti tion on • Conta ntact scann anning • Gap scanning • Immersion testi sting
• Probe held a fixed distance above the surface (1 or 2mm) • Couplant is fed into the gap
• Component is placed in a water filled tank • Item is scanned with a probe at a fixed distance above the surface
Water path distance
Front surface
Back surface Defect
Water path distance
• Sensitivity • Defect sizing • Scanning procedures
• The ability of an ultrasonic system to find the smallest specified defect at the maximum testing range
Depends upon • Prob Probe e and and flaw flaw det detec ector tor combi combinat natio ion n • Mate Materi rial al prop proper erti ties es • Probe frequency • Signa ignall to nois noise e rati ratio o
• Smallest defect at maximum test range • Back wall echo • Disc equivalent • Grass levels • Notches • Side Drilled Holes, DAC Curves
Example: The defect echo is set to FSH (Full Screen Height)
6 dB Drop • For sizing large planar reflectors only • Signal / echo reduced to half the height • Example: 100% to 50% 80% to 40% 70% to 35% 20% to 10% Centre of probe marked representing the edge of defect.
Defect
BWE
The back wall echo reduced as some part of the beam now striking the defect The echo of the defect has NOT yet maximise as the whole beam Not yet striking the defect Plan View
Defect
Now the whole beam is on the defect Back wall echo is now may be reduced or disappeared
Plan View
Defect
BWE
The probe is moved back until the echo is reduced by half of it’s original height At this point the probe centre beam is directly on the edge of the defect Plan View
The probe is then removed and the centre is marked, and repeat to size the whole defect
• Maximum Amplitude Technique For sizing multifaceted defect – eg. crack Not very accurate Small probe movement
Multifaceted defect : crack
The whole probe beam is on the on the defect At this point, multipoint of the defect reflect the sound to the probe The echo (signal) show as a few peaks
Multifaceted defect : crack The probe is moved out of the defect, the signal disappeared If the edge of the beam strike the edge of the defect, a very small echo appears
If the probe is moved into the defect, the signals height increase One of the peak maximised At this point the MAIN BEAM is directly at the edge of the defect
Remember: The peak which maximised does not have to be the tallest or the first one
Length
The probe is to be moved to the other end of the defect The signals will flactuate as the beam hits the different faces of the defects The probe is moved back into the defect and to observe a peak of the signal maximises
Mark the point under the centre of the probe which indicates the edge of the defect The length of the defect is measured
The equalization technique can ONLY be used if the defect is halfway the thickness Defect
BWE
At this point the whole beam is on the The BWE is at it maximum back wall At this point the whole beam is on the defect At the edge of the defect, half of the beam is on the defect, and another half is on the back wall
The Defect echo is at it maximum The defect echo is at equal height as the back wall The point is marked as the edge of defect
Defect
BWE
20 dB Beam profile 10%
When the main beam is on the defect the defect signal is at it maximum If the probe is moved and the signal is observed until it is reduced to 10% (20dB Drop), the edge of the beam is on the edge of the defect Repeat the above at the other side of the defect Using the pre‐constructed Beam profile and a plotting card, the defect maybe sized
Product Technology Welding
A Weld : Definitions • A union between pieces of metal at faces rendered plastic or liquid by heat,pressure or both. BS 499
• A continuous defect surrounded by parent material NASA
Welds • An ideal weld must give a strong bond between materials with the interfaces disappearing
To achieve this • Smooth,flat or matching surfaces • Surfaces shall be free from contaminants • Metals shall be free from impurities • Metals shall have identical crystalline structures
Welding • A unio union n betw betwee een n piec pieces es of of meta metall at face faces s rendered plastic or liquid by heat,pressure or both. BS 499 Possible energy sources • Ultrasonics • Electron be beam • Friction • Electric re resistan tance • Electric arc
Electric Arc Welding Electrode Power supply Work piece Clamp(Earth)
Electric Arc Welding • Electric discharge produced between cathode and anode by a potential difference (40 to 60 volts) • Discharge ionises air and produces ‐ve electrons and +ve ions • Electrons impact upon anode, ions upon cathode • Impact of particles converts kinetic energy to heat (7000o C) and light • Amperage controls number of ions and electrons, Voltage controls their velocity
Electric Arc Welding Arc Welding Processes
• Manual metal arc • Tungsten Inert Gas • Metal Inert Gas • Submerged Arc Differences between them • Meth Method ods s of of shi shiel eldi ding ng the the arc arc • Cons Consum umab able le or or NonNon-co cons nsum umab able le ele electr ctrod ode e • Degree of of au autom tomation
Zones in Fusion Welds • Fusion Zone
Zones in Fusion Welds • Fusion Zone • Heat Affected Zone
Zones in Fusion Welds • Fusion Zone • Heat Affected Zone • Parent Material or Base Metal
Joint Design Butt Weld
Corner Joint
Lap Joint
Edge Weld T Joint
Manual Metal Arc (MMA) Consumable electrode Flux coating Arc Evolved gas shield
Core wire
Slag Weld metal Parent metal
Manual Metal Arc Welding • Shielding provided by decomposition of flux covering • Electrode consumable • Manual process
Welder controls
• Arc length • Angle of electrode • Speed of travel • Amperage settings
Tungsten Inert Gas (TIG) Gas nozzle
Filler wire Non‐consumable tungsten electrode Gas shield Weld metal
Arc Parent metal
Metal Inert Gas (MIG) Reel feed
Gas nozzle
Consumable electrode(filler electrode(filler wire)
Gas shield Weld metal
Arc Parent metal
Submerged Arc Reel feed Flux retrieval
Consumable electrode Flux feed
Slag Weld metal Parent metal
Electroslag Filler wire Water cooled copper shoes
Molten flux
Weld metal
Welding Defects Cracks
4 Crack Types
• Solidification cracks • Hydrogen induced cracks • Lamellar tearing • Reheat cracks
Welding Defects Cracks Classified by Shape
Classified by Position
• Longitudinal
• HAZ
• Transverse • Branched • Chevron
• Centreline • Crater • Fusion zone • Parent metal
Welding Defects Cracks Solidification
• Occurs during weld solidification process • Steels with high sulphur content (low ductility at elevated temperature) • Requires high tensile stress • Occur longitudinally down centre of weld • eg Crater cracking
Welding Defects Cracks Hydrogen Induced
• Requires susceptible grain structure, stress and hydrogen • Hydrogen enters via welding arc • Hydrogen source ‐ atmosphere or contamination of preparation or electrode • Moisture diffuses out into parent metal on cooling • Most likely in HAZ
Welding Defects Cracks Lamellar Tearing
• Step like appearance • Occurs in parent material or HAZ • Only in rolled direction of the parent material • Associated with restrained joints subjected to through thickness stresses on corners, tees and fillets • Requires high sulphur or non‐metallic inclusions
Welding Defects Cracks Re‐Heat Cracking
• Occurs mainly in HAZ of low alloy steels during post weld heat treatment or service at elevated temperatures • Occurs in areas of high stress and existing defects • Prevented by toe grinding, elimination of poor profile material selection and controlled post weld heat treatment
Welding Defects • Incomplete root penetration
Causes
• Too large or small a root gap • Arc too long • Wrong polarity for joint preparation preparation • Electrode too large for
• Incorrect electrode angle • Too fast a speed of travel for current
Welding Defects • Root concavity
Causes • Root gap to too large • Insu Insufffici ficie ent arc ener nergy • Exce Excess ssiv ive e back back purg purge e (TIG (TIG))
Welding Defects • Lack of fusion
Causes • Cont Contam amin inat ated ed wel weld d prep prepar arat atio ion n • Amperage too low • Ampera Amperage ge too high high (wel (welder der increa increases ses speed speed of travel)
Welding Defects • Undercut
Causes • Exce Excess ssiv ive e weld weldin ing g curr curren entt • Weldi elding ng spe speed too too hig high • Inco Incorr rrec ectt elec electr trod ode e angl angle e • Excessive we weave • Electrode to too large
Welding Defects • Incompletely Filled Groove
Causes • Insu Insuff ffic icie ient nt weld weld meta metall depo deposi site ted d • Impr Improp oper er weld weldin ing g tec techn hniq ique ue
Welding Defects • Gas pores / Porosity
Causes • Exce Excess ssiv ive e mois moistu ture re in in flux flux or or prep prepar arat atio ion n • Cont Contam amin inat ated ed prep prepar arat atio ion n • Low we welding cu current • Arc length to too long • Dama Damage ged d el electr ectrod ode e flu flux x • Removal of of ga gas sh shield
Welding Defects • Inclusions ‐ Slag
Causes • Insu Insuff ffic icie ient nt clea cleani ning ng betw betwee een n pas passe ses s • Cont Contam amin inat ated ed wel weld d prep prepar arat atio ion n • Weldi elding ng over over irre irregu gula larr prof profilile e • Inco Incorr rre ect wel welding ding spe speed • Arc length to too long
Welding Defects • Inclusions ‐ Tungsten
Causes • Cont Contam amin inat atio ion n of wel weld d duri during ng TIG TIG wel weldi ding ng process
Welding Defects • Burn Through
Causes • Exce Excess ssiv ive e ampe ampera rage ge dur durin ing g weld weldin ing g of root root • Exce Excess ssiv ive e ro root gri grindin nding g • Impr Improp oper er weld weldin ing g tech techni niqu que e
Welding Defects • Arc Strikes
• Spatter
Causes
Causes
• Elect lectro rod de stra strayi ying ng onto onto • Excessive ar arc en energy parent metal • Excessive sive arc le length • Elect lectro rod de ho holder lder with with • Damp electrodes poor insulation • Arc blow • Poor oor con contact tact of ear earth clamp
• Inherent • Processing • In Service
• Heat treatment cracks • Grinding cracks • Friction induced cracks
Cyclic stress
• Fatigue cracks • Stress corrosion cracks
Fatique crack
• Hydrogen induced cracks
Hydrogen
Steel Production Casting
Wrought Production Extrusion Forging Rolling
Defects
Inherent Processing Service
Heat Treatment
Welding
