This power-point presentation explains about the welding technique with proper diagram provided just beside it. further in this presentation one can find about the various types of defects both internal and external that are obtained on the welded region with clear and neat diagrams. continuing after this non-destructive tests are clearly written down stating about liquid-dye penetrant test, magnetic particle testing, eddy current inspection and visual inspection. brief introduction about non-destructive tests and their main purpose are written down. for clear explanation of the topics self made diagrams are also attached in the presentation. everyone can feel very comfortable understanding the presentation. clear and very easy language is being used in the whole presentation. moreover a presentation becomes more attractive when it has more of diagrams.. every single material written down in this presentation is being clearly depicted by using a good and understandable diagrams with vibrant colors which feel more appealing to the readers.

1. BIPIN TRIPATHI
KUMAON INSTITUTE
OF TECHNOLOGY
TITLE
INSPECTION OF WELDS
SUBMITTED BY
MANMOHAN GOYAL
MECHANICAL DEPARTMENT,
3RD YEAR

2. WHAT IS WELDING
Welding may be defined as the process of joining two sheets of
metals under the application of heat and pressure or both heat and
pressure.
A filler material or consumable material may be used which itself
participates in the welding operation and pours down in the cavity
present between the sheets via the capillary action when it is
moved over the workpiece where the weld is to be created.
This filler material acts as a combiner and increases the strength of
the material as a whole and combines the 2 pieces.
The filler material may be same as that of the workpiece material or
may be different. In case of same material the weld created is
homogenous in nature.

3. DEFECTS OBSERVED IN WELDS
A welding defect may be defined as the irregularities that are seen on the surface.
These are basically the imperfections which are observed in the welded areas which might cause a
decrease in the strength of the weld.
Welding defects basically refers to the flaws which have exceeded the tolerance limit.
Thus, welding defects may be defined as the normal variations from the original properties.
Welding defects occurs during the welding operation but they are visible to us once the welding
operation is complete.
Welding defects occurs when the welding operation has not been performed properly.
Welding defects may be seen either on the surface of the workpiece or in the core of the workpiece.
Internal welding defects include slag inclusion and incomplete fusion while external welding defects
include weld crack, spatter, porosity, overlap, crater etc.

4. EXTERNAL WELD DEFECTS
WELD CRACKS
This is the most common type of welding defects
observed on the workpiece.
Weld cracks can be observed on the surface of the
workpiece, or in the internal structure of the
workpiece, or at the heat affected zone (heat
affected zone is the zone which is in direct contact of
the heat which is generated due to the completion of
the circuit during welding operation).
The main reason for the formation of the cracks is
sudden heating and sudden cooling of the workpiece
because of which un-necessary tensions develop
inside the workpiece causing the cracks.

5. SPATTER
This is another kind of external defect.
This defect occurs when some metal material from
the electrode comes out from the electrode
and gets stuck on the surface of the workpiece and
remains at the position.
The main reason for this defect to occur is improper
use of inert gases. The inert gas are flushed at a very
high speed from the spaces provided in the weld
torch so that they can remove the unwanted material
from the region, where the operation needs to be
done. Moreover it also removes the unwanted gases
from the atmosphere from that region. When this
flushing is not done properly there are chances that
some impurities be it from the atmosphere or the
electrode itself falls in the weld pool and cause a
defect.

6. POROSITY
This is another kind of welding defect.
This type of defect is observed when the gas or air
bubble gets trapped on the surface of the
workpiece .
This type of defect mainly occurs whenever there is
rust present on the surface.
This defect can be decreases by proper flushing of
the unwanted material via the inert gas usage.
While another way of decreasing this defect is to
properly clean the surface and make sure that the
surface is free from any kind of impurity or rust, oil
etc.

7. Under cut
If the weld creates a cup like structure at the
edges of the heat affected zone than that defect is
known as under-cut defect.
It reduces the strength of the workpiece.
Overlap
When the weld exceeds the limits of the heat
affected zone and overlaps the workpiece to some
part it is known as overlap defect.

8. INTERNAL WELD DEFECTS
SLAG INCLUSION
When the weld pool solidifies and the welded part
contains extra impurities like parts of the electrode that
might have chipped off during welding operation is known
as slag inclusion.
The most common type of slag inclusion in Tungsten slag
inclusion observed in TIG popularly known as Tungsten
inert gas welding, where tungsten electrode material gets
chipped out and falls in the weld pool creating defects.

9. INCOMPLETE FUSION
Incomplete fusion defect occurs when the welded
material does not completely fills up the space or the
cavity and solidifies before filling up the entire cavity.
Since a space is left behind in the cavity, the strength of
the workpiece decreases.
It occurs when the welded material solidifies before it
has completely filled up the gap.
This defect though can be reduced by managing the
proper heating of the welded material so that it
completely penetrates into the cavity without leaving
much space behind and solidifies uniformly.

10. INCOMPLETE PENETRATION
When the melted material does not fills up the
deepest part of the cavity, that defect is called
incomplete penetration defect.
This defect occurs due to improper pouring technique
or less material poured in the cavity.

11. NON-DESTRUCTIVE INSPECTION
Non-destructive inspection may be defined as the inspection of the welds without causing any physical
harm or damage to the workpiece that has been taken under consideration.
In non-destructive tests various materials are used which helps the user identify the exact location of the
defect or flaw in the workpiece.
This defects might be visible to us in the form of colours combination or we can detect the location of the
defects by seeing the results on the digital screen.
These defects dentification helps the user to minimize or rectify it in the possible ways.
Thus, non-destructive inspection are the tests which are responsible for detecting any kind flaws or
irregularities in the welds created on the workpiece.
These defects are different from destructive inspection because in destructive testing the changed
behaviour of the workpiece under tensile loading is studied whereas in non-destructive testing the flaws
in the welds are detected and how they can be minimized is studied.

12. LIQUID DYE PENETRANT TEST
Liquid dye penetrant test is the most common type of non-destructive inspection which is used to detect
the flaws in the weld on the workpiece.
In liquid dye penetrant test, 3 liquids are taken under consideration. First is the cleaner which is used for
cleaning the workpiece in order to keep the surface free from any kind of contamination and dust or dirt.
Second is the penetrant that is evenly sprayed over the workpiece which is to be inspected. This
penetrant taken has vibrant colours like orange, red that leaves a print behind and helps in detecting the
location of the flaw. Third is the developer which is used to absorb the penetrant from the cavity. This
developer is white in colour so that when it is applied on the workpiece and it absorbs the penetrant from
the cavity it changes its colours and with the help of that the user can easily detect the exact location of
the flaw, since the penetrant has already left a print behind.
In this no damage is done to the surface of the workpiece or to the welded region.

13. PROCESS
First the workpiece that has been taken under consideration is perfectly cleaned with a clean cloth and
the cleaner. The main reason behind the cleaning is to keep the surface free from any kind of
contaminant particles.
Then after the cleaning is performed, the penetrant is uniformly sprayed over the surface of the
workpiece. The penetrant is given some time so that it completely fills up the cavity if present, via the
capillary action. This time is approximately 8-9 minutes.
Then the extra amount of liquid penetrant that remains on the surface is removed by a clean cloth.
Then a layer of developer is applied on the surface of the workpiece. The main purpose of the developer
is to absorb the penetrant that has been present in the cavity and is not removed during the cleaning
process.
Since the developer is white in colour and when it absorbs the penetrant gets the colour of penetrant.
The user can easily detect the flaw by seeing at the developer that where it is showing a change in its
colour and secondly by seeing at the print that the penetrant has left behind.
Then again the surface is cleaned with the help of a cleaner and suitable methods are taken to minimize
the defect.

14. ADVANTAGES DISADVANTAGES
Liquid dye penetrant test is easy to perform. Liquid dye penetrant test is only capable of
detecting small defects on the surface of the
workpiece.
Liquid dye penetrant test can be performed at low
costs.
Liquid dye penetrant test cannot be performed on
the surfaces which are already painted or wet. It
needs to be cleaned again and again.
Liquid dye penetrant test is portable. Only three
bottles are required that are cleaner, developer
and penetrant sprays.
The sprays which are used to detect the flaws can
be sometimes toxic.

16. MAGNETIC PARTICLE TESTING
Magnetic particle testing is another type of non-destructive testing which is used for detecting flaws or
imperfections in the weld.
In this the weld has been done on a conductive material. Since the material s conductive n nature
therefore it can be magnetised with the help of a horse-shoe or a permanent magnet.
When the conductive material is brought near permanent magnet the two ends of the material develops
opposite polarities.
One polarity is the north pole and other polarity is the south pole.
It is common that magnetic flux lines originate from north pole to south pole outside the material and from
south pole to north pole inside the material in straight lines.

17. PROCESS
We know that magnetic field lines originate from north to south pole outside the magnet and from south
pole to north pole inside the magnet.
If the workpiece is free from any kind of defects the magnetic field lines inside the workpiece goes
undeflected, while if there is some type of cavity present in the workpiece the magnetic flux lines gets
deflected by some angle due to the cavity present and a new magnetic field starts originating from that
cavity which causes magnetic flux leakage.
Now some coloured iron powder are sprinkled over the workpiece and these iron fillings are greatly
attracted by the strong magnetic field created due to the cavity present.
The user can easily detect the location of the crack since these fillings gets attracted in the cavity due to
new magnetic field created.
PRINCIPLE: If the cavity is not there the magnetic flux lines goes undeflected while if there is some kind
of cavity then the magnetic flux lines gets deflected from their original path and creates a new strong
magnetic field at the cavity causing magnetic flux leakage.

19. EDDY CURRENT INSPECTION
Eddy current inspection is another very good technology for detecting surface defects.
Eddy current is that type of current that flows through a conductive material until a wire coiled around the
material carries current. As soon as the current is switched off the conductive material that has
developed a polarity loose the polarity.
It means that the conductive material will develop north and south pole until the current passes through
the coil wounded around it.
This conductive material is connected to a power source which is used for providing a current supply to
the coil.
Another connection is provided to this conductive material that is attached with the digital screen, so that
the irregularities in the pattern obtained on the screen can be seen by the user and the defect location
can be detected.
If the workpiece is free from any kind of defects than a regular circular pattern is obtained on the screen
while if there is some kind of irregularities on the workpiece then the pattern on the digital screen will
vary accordingly.

20. PROCESS
In this the conductive material is taken under consideration and it is magnetised by winding a coil around
the material. When current was passed through the wire a polarity was getting developed on either sides
of the material. Due to this delocalized polarity development a delocalized magnetic field was obtained. It
was called delocalized magnetic field because it remains in the material until a regular current supply is
given to the material.
Once a magnetic field is there this material is brought close to the workpiece which is to be inspected.
Due to this motion the magnetic field lines also penetrates from the surface of the workpiece.
If the surface of the workpiece is free from any kind of defects than a circular regular pattern is obtained
on the digital screen whereas if some defect is there on the surface then an irregularity is seen in the
pattern of the digital screen.
The material is moved over the entire workpiece to check the welds.
The conductive material is connected to the digital screen via the cable which was transmitting the
signals and those signals are just the top view of the magnetic field lines that were penetrating through
the workpiece.
When the defect was observed the default direction of the magnetic flux lines changes because of which
the circular pattern that was obtained on the screen also varies, and the location of the defect can be
detected.

21. PRINCIPLE
The main principle of the working of eddy current inspection is that if the workpiece is free from any kind
of defect than a regular circular pattern is obtained on the digital screen that is connected to the
conductive material via cable, that has been locally magnetised with the help of a coil wounded around it,
while if the workpiece consists of any defect than the original pattern of the circle varies accordingly due
to the change in the direction of the magnetic flux lines.
The polarity gets developed on the conductive material according to the following law:

23. VISUAL INSPECTION
The visual inspection is the most common and easy type of weld inspection.
In this the welding area is clearly inspected by our naked eyes.
In this technique no physical harm is done to the workpiece.
This technique is very useful and efficient in detecting the cracks which are present on the surface
and the minor scratches which are easily seen on the surface of the workpiece.
The defects which are present in the core of the workpiece are not detected.
The main advantages of this technique is that it is inexpensive, almost no special apparatus is required,
it is easily portable.
The main disadvantages of this technique is that it is not able to detect the small flaws present on
the surface and in the interior of the workpiece, there are chances that while interpreting the flaws
the user can make errors (as it is a common tendency of humans to make mistakes).