DIFFERENT TYPES OF WELDING TESTS
DIFFERNTS TYPES OF WELDING TESTS
There are many types of welding tests used to
check the quality, strength, and reliability of welded joints. These
tests are broadly classified into two categories:
Non-Destructive Tests (NDT)
👉
Tests that do not damage the welded part. Used for inspection during or after
welding.
- Visual
Inspection (VT) – Checking weld size, shape, cracks,
porosity, undercut, and surface defects with naked eye or magnifying
tools.
- Liquid
Penetrant Test (LPT / PT) – Uses dye solution
to detect surface cracks and porosity.
- Magnetic
Particle Test (MPT) – For ferromagnetic metals
(like steel); detects surface and slightly subsurface cracks.
- Ultrasonic
Testing (UT) – High-frequency sound waves detect
internal defects like voids, cracks, and inclusions.
- Radiographic
Testing (RT / X-ray or Gamma Ray Test) – Uses
radiation to produce images of internal weld defects.
- Eddy
Current Testing (ECT) – Uses electromagnetic
induction to detect cracks and thickness variations.
2. Destructive Tests (DT)
👉
The welded sample is broken or destroyed to check its mechanical properties.
- Tensile
Test – Measures the strength of the welded joint
under pulling force.
- Bend
Test – Welded specimen is bent to check ductility and
soundness of the weld.
- Impact
Test (Charpy/Izod) – Checks toughness of weld at
different temperatures.
- Hardness
Test – Determines hardness across weld metal, heat
affected zone (HAZ), and base metal.
- Nick
Break Test – Sample is fractured to examine
weld fusion, porosity, and inclusions.
- Fatigue
Test – Determines the ability of the weld to
withstand repeated cyclic loads.
- Creep
Test – Checks weld strength under constant load and
high temperature over time.
- Macro
& Micro Examination – The weld is
polished/etched and examined under microscope to study structure,
penetration, and grain flow.
✅ Summary:
- NDT
→ No damage, used for inspection (VT, PT, MPT, UT, RT, ECT).
- DT
→ Sample is destroyed, used for strength testing (Tensile, Bend, Impact,
Hardness, Fatigue, etc.).
Would you like me to make a simple table (NDT
vs DT with examples, purpose, and defects detected) so it’s easy to memorize?
Types of Welding Tests
1. Non-Destructive Tests (NDT)
👉
Used when we want to check welds without damaging the component. Mostly
done in industries like pipelines, boilers, aircraft, shipbuilding.
a) Visual Inspection Test (VT)
- First
and simplest test.
- Inspector
checks weld bead size, shape, alignment, surface cracks, porosity,
undercut, overlap.
- Tools:
weld gauges, magnifying glass, borescopes.
- Purpose:
Detects surface-level problems before deeper testing.
b) Liquid Penetrant Test (LPT / PT)
- A
colored or fluorescent liquid dye is applied on weld surface.
- The
dye enters surface cracks → developer is sprayed → cracks become visible.
- Works
on non-magnetic materials (stainless steel, aluminum, copper).
- Purpose:
Detects very fine cracks, pinholes, porosity.
c) Magnetic Particle Test (MPT)
- Magnetic
field applied on the weld → fine iron particles are spread → they gather
at cracks.
- Works
only on ferromagnetic metals (iron, steel, nickel, cobalt).
- Purpose:
Finds surface and slightly below-surface cracks.
d) Ultrasonic Testing (UT)
- High-frequency
sound waves are sent into the weld using a probe.
- If
sound reflects back (echo), it means there’s a crack or void.
- Portable
machine with screen shows defect location & size.
- Purpose:
Detects internal defects like lack of fusion, slag inclusion,
porosity.
e) Radiographic Testing (RT – X-ray /
Gamma Ray)
- Weld
is exposed to X-rays or gamma rays → a film (like an X-ray of a bone) is
developed.
- Defects
like porosity, cracks, slag, lack of penetration show as dark/light spots.
- Purpose:
Very accurate for detecting internal weld flaws.
f) Eddy Current Testing (ECT)
- Uses
electromagnetic induction.
- A
coil carrying AC current is placed on weld → change in magnetic field
shows cracks, thickness variation.
- Purpose:
Good for detecting surface cracks and corrosion, often used in aerospace.
2. Destructive Tests (DT)
👉
Done on a sample piece of weld (test coupon). The sample is destroyed to
check mechanical properties.
a) Tensile Test
- A
sample is pulled in a tensile testing machine until it breaks.
- Shows
ultimate tensile strength (UTS) of weld.
- Purpose:
To confirm the weld is as strong as base metal.
b) Bend Test
- Welded
specimen is bent to a certain angle (usually 180°).
- If
cracks appear → weld is weak.
- Purpose:
Checks ductility, soundness, and fusion.
c) Impact Test (Charpy / Izod)
- Weld
sample is hit with a hammer at high speed.
- Measures
energy absorbed before fracture.
- Purpose:
Determines toughness, especially at low temperature (important for
ships, pressure vessels).
d) Hardness Test
- Indenter
(ball, diamond, or pyramid) is pressed into weld.
- Hardness
across Weld Metal, Heat Affected Zone (HAZ), and Base Metal is
measured.
- Purpose:
Ensures weld is not too soft (weak) or too hard (brittle).
e) Nick Break Test
- A
notch is made in the weld sample → then fractured.
- Surface
of fracture is examined for porosity, slag, lack of fusion.
- Purpose:
Quick method to check weld quality inside.
f) Fatigue Test
- Sample
is loaded repeatedly with cyclic loads (like vibration).
- Purpose:
To check weld life under fluctuating stress (important for vehicles,
aircraft).
g) Creep Test
- Weld
is subjected to constant load at high temperature for a long time.
- Purpose:
Used in boilers, turbines, and power plants where metals operate under
heat for years.
h) Macro & Micro Examination
- Macro
test: Weld is polished, etched with acid → checked
with naked eye/magnifier for penetration, cracks, grain flow.
- Micro
test: Weld examined under microscope → checks
microstructure, grain size, inclusions.
- Purpose:
To study metallurgical properties of weld.
✅
Summary Table
|
Category |
Test |
Purpose |
Defects Detected |
|
NDT |
Visual (VT) |
Surface inspection |
Cracks, porosity, undercut |
|
Dye Penetrant (PT) |
Surface flaws |
Fine cracks, pinholes |
|
|
Magnetic Particle (MPT) |
Surface & near surface flaws |
Cracks in ferromagnetic metals |
|
|
Ultrasonic (UT) |
Internal flaws |
Voids, lack of fusion |
|
|
Radiographic (RT) |
Internal flaws |
Porosity, slag inclusion |
|
|
Eddy Current (ECT) |
Surface flaws |
Thin cracks, corrosion |
|
|
DT |
Tensile |
Strength |
Breaking strength |
|
Bend |
Ductility & fusion |
Cracks, poor fusion |
|
|
Impact |
Toughness |
Brittle fracture |
|
|
Hardness |
Hardness variation |
Brittle/soft spots |
|
|
Nick Break |
Internal inspection |
Slag, porosity |
|
|
Fatigue |
Life under cyclic load |
Fatigue |
DIFFERNTS
TYPES OF WELDING TESTS
There are many types of welding tests used to
check the quality, strength, and reliability of welded joints. These
tests are broadly classified into two categories:
Non-Destructive Tests (NDT)
👉
Tests that do not damage the welded part. Used for inspection during or after
welding.
- Visual
Inspection (VT) – Checking weld size, shape, cracks,
porosity, undercut, and surface defects with naked eye or magnifying
tools.
- Liquid
Penetrant Test (LPT / PT) – Uses dye solution
to detect surface cracks and porosity.
- Magnetic
Particle Test (MPT) – For ferromagnetic metals
(like steel); detects surface and slightly subsurface cracks.
- Ultrasonic
Testing (UT) – High-frequency sound waves detect
internal defects like voids, cracks, and inclusions.
- Radiographic
Testing (RT / X-ray or Gamma Ray Test) – Uses
radiation to produce images of internal weld defects.
- Eddy
Current Testing (ECT) – Uses electromagnetic
induction to detect cracks and thickness variations.
2. Destructive Tests (DT)
👉
The welded sample is broken or destroyed to check its mechanical properties.
- Tensile
Test – Measures the strength of the welded joint
under pulling force.
- Bend
Test – Welded specimen is bent to check ductility and
soundness of the weld.
- Impact
Test (Charpy/Izod) – Checks toughness of weld at
different temperatures.
- Hardness
Test – Determines hardness across weld metal, heat
affected zone (HAZ), and base metal.
- Nick
Break Test – Sample is fractured to examine
weld fusion, porosity, and inclusions.
- Fatigue
Test – Determines the ability of the weld to
withstand repeated cyclic loads.
- Creep
Test – Checks weld strength under constant load and
high temperature over time.
- Macro
& Micro Examination – The weld is
polished/etched and examined under microscope to study structure,
penetration, and grain flow.
✅ Summary:
- NDT
→ No damage, used for inspection (VT, PT, MPT, UT, RT, ECT).
- DT
→ Sample is destroyed, used for strength testing (Tensile, Bend, Impact,
Hardness, Fatigue, etc.).
Would you like me to make a simple table (NDT
vs DT with examples, purpose, and defects detected) so it’s easy to memorize?
Types of Welding Tests
1. Non-Destructive Tests (NDT)
👉
Used when we want to check welds without damaging the component. Mostly
done in industries like pipelines, boilers, aircraft, shipbuilding.
a) Visual Inspection Test (VT)
- First
and simplest test.
- Inspector
checks weld bead size, shape, alignment, surface cracks, porosity,
undercut, overlap.
- Tools:
weld gauges, magnifying glass, borescopes.
- Purpose:
Detects surface-level problems before deeper testing.
b) Liquid Penetrant Test (LPT / PT)
- A
colored or fluorescent liquid dye is applied on weld surface.
- The
dye enters surface cracks → developer is sprayed → cracks become visible.
- Works
on non-magnetic materials (stainless steel, aluminum, copper).
- Purpose:
Detects very fine cracks, pinholes, porosity.
c) Magnetic Particle Test (MPT)
- Magnetic
field applied on the weld → fine iron particles are spread → they gather
at cracks.
- Works
only on ferromagnetic metals (iron, steel, nickel, cobalt).
- Purpose:
Finds surface and slightly below-surface cracks.
d) Ultrasonic Testing (UT)
- High-frequency
sound waves are sent into the weld using a probe.
- If
sound reflects back (echo), it means there’s a crack or void.
- Portable
machine with screen shows defect location & size.
- Purpose:
Detects internal defects like lack of fusion, slag inclusion,
porosity.
e) Radiographic Testing (RT – X-ray /
Gamma Ray)
- Weld
is exposed to X-rays or gamma rays → a film (like an X-ray of a bone) is
developed.
- Defects
like porosity, cracks, slag, lack of penetration show as dark/light spots.
- Purpose:
Very accurate for detecting internal weld flaws.
f) Eddy Current Testing (ECT)
- Uses
electromagnetic induction.
- A
coil carrying AC current is placed on weld → change in magnetic field
shows cracks, thickness variation.
- Purpose:
Good for detecting surface cracks and corrosion, often used in aerospace.
2. Destructive Tests (DT)
👉
Done on a sample piece of weld (test coupon). The sample is destroyed to
check mechanical properties.
a) Tensile Test
- A
sample is pulled in a tensile testing machine until it breaks.
- Shows
ultimate tensile strength (UTS) of weld.
- Purpose:
To confirm the weld is as strong as base metal.
b) Bend Test
- Welded
specimen is bent to a certain angle (usually 180°).
- If
cracks appear → weld is weak.
- Purpose:
Checks ductility, soundness, and fusion.
c) Impact Test (Charpy / Izod)
- Weld
sample is hit with a hammer at high speed.
- Measures
energy absorbed before fracture.
- Purpose:
Determines toughness, especially at low temperature (important for
ships, pressure vessels).
d) Hardness Test
- Indenter
(ball, diamond, or pyramid) is pressed into weld.
- Hardness
across Weld Metal, Heat Affected Zone (HAZ), and Base Metal is
measured.
- Purpose:
Ensures weld is not too soft (weak) or too hard (brittle).
e) Nick Break Test
- A
notch is made in the weld sample → then fractured.
- Surface
of fracture is examined for porosity, slag, lack of fusion.
- Purpose:
Quick method to check weld quality inside.
f) Fatigue Test
- Sample
is loaded repeatedly with cyclic loads (like vibration).
- Purpose:
To check weld life under fluctuating stress (important for vehicles,
aircraft).
g) Creep Test
- Weld
is subjected to constant load at high temperature for a long time.
- Purpose:
Used in boilers, turbines, and power plants where metals operate under
heat for years.
h) Macro & Micro Examination
- Macro
test: Weld is polished, etched with acid → checked
with naked eye/magnifier for penetration, cracks, grain flow.
- Micro
test: Weld examined under microscope → checks
microstructure, grain size, inclusions.
- Purpose:
To study metallurgical properties of weld.
✅
Summary Table
|
Category |
Test |
Purpose |
Defects Detected |
|
NDT |
Visual (VT) |
Surface inspection |
Cracks, porosity, undercut |
|
Dye Penetrant (PT) |
Surface flaws |
Fine cracks, pinholes |
|
|
Magnetic Particle (MPT) |
Surface & near surface flaws |
Cracks in ferromagnetic metals |
|
|
Ultrasonic (UT) |
Internal flaws |
Voids, lack of fusion |
|
|
Radiographic (RT) |
Internal flaws |
Porosity, slag inclusion |
|
|
Eddy Current (ECT) |
Surface flaws |
Thin cracks, corrosion |
|
|
DT |
Tensile |
Strength |
Breaking strength |
|
Bend |
Ductility & fusion |
Cracks, poor fusion |
|
|
Impact |
Toughness |
Brittle fracture |
|
|
Hardness |
Hardness variation |
Brittle/soft spots |
|
|
Nick Break |
Internal inspection |
Slag, porosity |
|
|
Fatigue |
Life under cyclic load |
Fatigue |
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