Report : weld metal temperature measurement devices

1. i
Mahatma Gandhi Mission’s
College of Engineering and Technology
Noida, U.P., India
Seminar Report
On
“WELD METAL TEMPERATURE MESUREMENT”
As
Part of B.Tech curriculum
Submitted by:
DEVASHISH KUMAR
VIII
Semester
1409540017
Under the Guidance of:
Mr. Umesh Yadav
MGM COET, Noida
(Seminar Coordinator) Submitted to:
Mr.Ram Prakash HOD
Mechanical Engineering Department
MGMCOET,Noida,U.P.,INDIA

2. ii
Mahatma Gandhi Mission’s
College of Engineering and Technology
Noida, U.P., India
Department of Mechanical Engineering
CERTIFICATE
This is to certify that Mr. DEVASHISH KUMAR of B.Tech. Mechanical Engineering, Class
BT-ME. Roll No: 1409540017 has delivered to seminar on the topic “WELD METAL
TEMPRATURE MESUREMENT” His seminar presentation and report during the academic
year 2017-2018 as the part of B.Tech Mechanical Engineering Curriculum was good.
(Guide) (Seminar Coordinator) (Head of the Department)

3. iii
ACKNOWLEDGMENT
I would like to express my deep sense of gratitude to my supervisor Mr. Umesh Yadav sir,
Mechanical Engineering Department, MGM Collage of Engineering and Technology, Noida,
India, for his guidance, support and encouragement throughout this seminar work. Moreover, I
would like to acknowledge the Mechanical Engineering Department, MGM.COET, Noida for
providing me all possible help during this work moreover, I would like to sincerely thank
everyone who directly and indirectly helped me in complete this work
Signature:
Name: DEVASHISH KUMAR
Roll no: 1409540017
Date:

4. iv
ABSTRACT
Highly accurate temperature measuring equipment is now widely available at very reasonable
costs but, whilst this should be making the task of making temperature measurement easy, many
users make simple mistakes that benefits of using high specification sensors and measuring
equipment. When most people have a requirement to measure a temperature, their first reaction
is to purchase the highest specification, most expensive sensor and measuring instrument they
can afford. Manufacturer, this is a reaction as it welding metal by the help of equipment. It is
however the wrong way to set about accurate temperature measurements. Consider what you are
trying to measure the temperature of An example that seems simple at first is measuring arc
welding temperature to 250°C approx. The problem here is that weld metal temperature is not
measured without any instrument temperature measurement. Sensors at three different heights
record the temperatures in one of Pico Technology's store rooms. The sensor readings differ by
at least 1°C so clearly, no matter how accurate the individual sensors, we will never be able to
measure room temperature to 1°C accuracy. Standard tables show the voltage produced by
thermocouples at any given temperature. For example, a K type thermocouple (the most popular)
at 300 °C will produce 12.2 mV. This generation of a voltage, does mean thermocouples (unlike
RTDs and thermistors) are self-powered and require no excitation current. Unfortunately it is not
possible to simply connect a voltmeter to the thermocouple to measure this voltage as doing so
creates a second, undesired thermocouple junction.

5. v
TABLE OF CONTENTS
Certificate ii
Acknowledgement iii
Abstract iv
Table of content V
List of figure Vii
List of table Viii
CHAPTER-1 INTRODUCTION 1-3
1.1 Weld Metal 1
1.1.1 Difference Between Weld Metal And Filler Metal 2
1.2 Weld Metal Temperature Measurement 2
CHAPTER-2 TEMPERATURE MEASURING DEVICE 4-15
2.1 Widos Plastic Welding Accessories Thermometer 4
2.2 Infrared Thermometer 4
2.2.1 Why Infrared Is Used 6
2.3 Ferriteoscope 7
2.4 Tempil Sticks 9
2.5 Thermocouple 10
2.6 Skin Type Thermocouple 12
2.7 Estik Electronic Surface Thermometer 14
CHAPTER-3 WORKING OF DEVICES 16-22
3.1 Working and principle of thermocouples 16
3.1.1 Material for thermocouple 17
3.1.2 Cold junction compensation 17
3.1.3 Compensating wires 18
3.1.4 Selection of thermocouple 18

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3.2 Infrared thermometer 19
3.2.1 Measurement principles 19
3.2.2 Infrared monitoring 20
3.2.3 Experimental procedure 21
CHAPTER 4 POWER AND CHARGE DENSITY IN WELDING
PROCESS
23-26
4.1 Power density and temperature measurement 23
4.2 Effect of power density 24
4.3 Need of Power Density Of Welding Process 25
CONCLUSIONS 27
REFERENCES 28

7. vii
LIST OF FIGURE
Sr.no. Name of figure Page no.
1.1 Welding temperature measurement devices 3
2.1 Widos Plastic Welding Accessories Thermometer 4
2.2 Infrared thermometer 7
2.3 Ferriteoscope 9
2.4 Tempil sticks 10
2.5 Thermocouple 11
2.6 Skin type thermocouple 12
2.7 Weld pad 13
2.8 Washer pad 13
2.9 Estik electronic thermometer 14
3.1 Principle of measurement of temperature by a thermocouple and
Arrangement of thermocouple to form a thermopile
16
3.2 Zone box 16
3.3 Thermocouple Material Vs EMF 19
3.4 Equipment setup 20
3.5 Infrared Monitoring 21
4.1 Effect of energy density and time on energy input 24
4.2 Effect of power density of heat source on heat input required for
welding
25
4.3 Effect of welding process on angular distortion of weld joint as a
function of plate thickness
26
4.4 Schematic diagram showing effect of heat input on tensile strength
of aluminum alloy
26
4.5 Power density of different welding processes 26

8. viii
Table of content
Sr.no. Name of table Page no.
1.1.1 Difference between weld metal and filler metal 2
2.1 Specification of infrared thermometer 5
2.2 Technical data of feriteoscope 8
2.3 Technical data of thermocouple 11
2.4 Technical data of estick electronic thermometer 15
3.1 Available thermocouples 17
3.2 Compensating wires are color coded. 18
3.3 Welding parameters 21
4.1 Heat intensity and maximum temperature related with different
welding processes
23

9. 1
CHAPTER 1
INTRODUCTION
1.1 WELD METAL
Weld metal is the material that has melted and re-solidified as a result of the welding operation.
In cases where no filler material is added (Resistance, electron beam, laser and some
autogenously arc welding), the weld metal has the same composition as the parent material.
Where filler materials are added to the weld pool, the composition of the weld metal usually
differs from that of the parent material. For stainless steels, the differences between the parent
material and weld compositions, along with the effect of dilution from the parent materials into
the weld pool combined with the filler materials. Weld metal can be described as ' matching',
'under-matching' or 'overmatching' with respect to the parent material, which usually describes
the strength of the weld metal, but it may also describe the chemical composition. For example,
when welding a joint between 2.25Cr1Mo material and 9Cr1Mo material, filler which matches
the chemical composition of the lower alloyed material will be used, so 'under matching' the
higher alloyed 9Cr1Mo material with respect to the composition and strength. The selection of
the proper filler material is not based on matching the chemistry with the base steel. Rather, it is
based on matching the weld metal and base steel properties. Using a filler material with
chemistry identical to that of the base steel may not deliver the desired results, since the micro-
structures of the weld metal are entirely different from those of the base steel. For many C and
low alloy steels, the solidification and rapid cooling rate involved in fusion welding result in a
weld metal which has higher strength and lower toughness properties than the base steel when
they are of the same chemistry. Therefore, the filler material frequently contains a lower C level
than the base steel. The strength of the weld metal is not improved by increasing the C content,
but by adding the alloying elements which provide solid-solution or precipitation strengthening
and modification of the micro-structures.

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1.1.1 DIFFERENCE BETWEEN WELD METAL AND FILLER METAL
WELD METAL FILLER METAL
1 The molten area during welding is called
weld metal. it is a combination of molten
base material due to heat and deposited
molten filler material. It is also called as
weld nugget. After welding, the whole
weld metal will be solidified.
1
1
1
The external material which is used
for deposition (electrode) during
welding. It can be in the rod form or
wire form.
2
2
weld metal has the same composition as
the parent material and no filler material is
added.
2
2
Filler materials are added externally
to the weld pool during welding
1.2 WELD METAL TEMPERATURE MESUREMENT
The thermal history of weld metal gives a good indication of the behavior of the weld thereafter.
For example, the thermal behavior of the weld bead affects the properties of transformable steel.
To record the thermal history of a weld bead platinum metal thermocouples may be inserted
during the welding process but until recently many of them melted in use and the instruments
became open circuit. C. Pedder of the Welding Institute’s Metallurgical Department at Abington
Hall, Cambridge, has now described a simple technique in which platinum: 13 percent rhodium-
platinum harpoon thermocouples of 0.5 mm wire arc used. The wires are insulated in twin bore
ceramic insulators supported in a close-fitting steel tube so that they protrude 3 mm beyond the
insulator, which itself protrudes 5 mm beyond the steel tube end. They dip into the pool of weld
metal which completes the circuit by acting as the thermocouple hot junction. Tests showed
similar results to those using conventional thermocouples up to 1000oC. The e.m.f. differed by
less than 0.01 mV (10°C at 1000oC). Manual and semi-automatic methods have been used to

11. 3
plunge the thermocouple accurately into the weld metal pool. welder can also operate the
harpoon thermocouple, and when used with implant cracking test equipment the thermocouple
records the thermal cycle and also actuates the implant loading mechanism at the predetermined
temperature. Weld thermal cycles and cooling times have been measured by the harpoon
thermocouple for the MMA,MIG and submerged arc processes. It has also made possible the
thermal analysis of weld metal austenite transformation immediately after deposition, whereas
previous dilatometer studies gave transformation characteristics of reheated metal. The thermal
analysis process uses a differential amplifier to convert thermocouple output to a voltage
proportional to the cooling rate.
Fig 1.1 welding temperature measurement devices

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CHAPTER 2
TEMPERATURE MEASURING DEVICE
2.1 WIDOS PLASTIC WELDING ACCESSORIESTHERMOMETER
You are looking for a tool to check the exact temperature of the heating element when processing
plastics welding. Then the WIDOS temperature measuring device with surface probe is right for
you. The temperature measuring device with surface probe is a handy tool and allows exact
measurement accuracy. The electronic temperature measuring device with digital display is
suitable for the use on the construction site and in the workshop. Measurement range probe up to
400 °C, Measurement range tool up to 1150 °C.1 meter feed line.
Fig 2.1 Widos Plastic Welding Accessories Thermometer
2.2 INFRARED THERMOMETER
The IR thermometer works by focusing light that is coming from the object in the form of IR
rays and funneling that light into a detector. Which is also known as a thermopile? It is in the
thermopile that the IR radiation is turned into heat A. which is then turned A to A electricity,
which is then measured. It is ultimately the amount of electricity that is generated by the rays
being put out by the object in question that will provide a reading that is displayed on the
thermometer. The reading will be generated in a manner of second, meaning an infrared
thermometer is a quick way to gather a temperature reading in a number of different scenarios.

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Features
 Small in size easily fit in your pocket
 Laser targeting for fast, precise measurements
 Backlit display for easy reading in dark work areas
 8:1 distance to spot ratios measures a 10 cm spot from 10 meters to target.
 ± 2% basic accuracy gives you readings you can trust.
Table 2.1 Specification of infrared thermometer
Temperature range -18 °C to 275 °C (0 °F to 525 °F)
Accuracy:
Ambient operating
temperature between
21oC (69oF and 77oF)
100 °C to 275 °C
(212 °F to 525 °F)
2 % of reading
0 °C to 100 °C
(32 °F to 212 °F)
±2 °C (±3.5 °F)
low 0 °C (32 °F) ±3 °C (±5.5 °F)
Response time (95%) <500mSec
Spectral response 6.5 to 18 microns
Emissivity Preset to E=0.95
Optical resolution (D:S) 8:1 (calculated at 90 % energy)
Repeatability ±1 % of reading or ±1 °C (±2 °F) whichever is greater
Ambient operating range 0 °C to 50 °C (32 °F to 120 °F)
Relative humidity 10-90 % RH non-condensing, 30 °C (86 °F)
Storage temperature 20 °C to 65 °C without battery (-4 °F to 150 °F without battery)
Weight/dimensions (with
battery)
200 g 152 x 102 x 38 mm (6 x 4 x 1.5 in)
Power 9V battery
Battery life 4 Hours
Display resolution 0.2 °C (0.5 °F)
Display hold 7 Seconds

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2.2.1 WHY INFRARED IS USED
There are a number of reasons why you should consider choosing infrared technology for your
temperature reading needs. When shopping for a thermometer to add to your stable of
equipment, consider purchasing a quality infrared thermometer for some of the following
reasons.
1. ACCURACY
Obviously, you need to be confident that you are getting an accurate reading from your
thermometer when you put it to use, and infrared models have a great reputation for
accuracy. The technology used in these products is simple yet advanced, and you should
be able to rely on the information that you receive provided that the thermometer is used
in the right way.
2. SAFETY
One of the great things about being able to check on temperature remotely is that you
don’t actually need to touch the object in question. If you are trying to take the
temperature of the particularly hot item. You won’t need to place your hand, or even
another piece of equipment, onto the hot surface. Just by aiming your IR thermometer at
the object you wish to measure, you can get all of the information you need without
putting yourself at risk.
3. CONTAMINATION PREVENTION
Another benefit to the remote measuring system is avoidance of contamination. This is
particularly important within the food service world. But it applies A in Aother
application as well. Since you don’t need to touch the item that you are measure, you
won’t need to worry about contaminating that product with the probe of the thermometer.
Rather than having to make sure that all of your temperature measuring equipment is
properly sterilized prior to each use, you can simply point the IR gun at the item being
measured and forget any worries about contamination problems.
4. DURABILITY
you want an infrared thermometer that is tough enough to stand up to the demands of the
jobsite, workshop or just being bounced around in your toolbox.

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Fig 2.2 Infrared Thermometer
2.3 FERITEOSCOPE
It is easy to measure the ferrite content accurately when using the FERITSCOPE FMP30. Upon
probe placement on the surface of the specimen, the reading is displayed automatically and
stored in the instrument. The probe can also be placed onto hard to reach areas. For such
applications, the instrument features an “external start” function to trigger the measurements
with the push of a button. This is ideal for measurements in pipes, bore holes or grooves. Finding
weld seams in polished surfaces is made easy through the “continuous display” instrument
function. When scanning the surface with the probe with this function enabled, the continuous
readings are displayed only. A change in the ferrite content reading indicates that the weld seam
has been found. For easy ferrite content measurements along a weld seam, the instrument offers
the “continuous measurement capture” function. When scanning the weld seam with the probe
positioned, the continuous readings are captured and stored. This provides a ferrite content
profile along the weld seam. Measurement influencing factors do not significantly affect the
FERITSCOPE FMP30. Ferrite content measurements can be carried out regardless of the
substrate material properties starting at a plating thickness of 3 mm. Corrective calibrations with
customer-specific calibration standards or correction factors (included) can be used to take
influences of the specimen shape (strong curvature), plating and substrate thicknesses into

16. 8
account. The calibration is always stored measurement-application specific in the respective
application memory.
Table 2.2 Technical Data of Feriteoscope
Display Graphical backlit LCD display
Measurable coatings  Ferrite content measurements in weld seams and
claddings made of austenitic or duplex steel.
 Determination of the portion of deformation
martensite in austenitic materials.
Measuring modes Magnetic induction measurement method
Dimensions  Instrument: 170 mm x 90 mm x 35 mm (L x W x
H)
 LCD display: 44 mm x 57 mm (L x W)
Weight approx. 340 g (without probe, ready to operate).
Permissible ambient temperature
during operation
+10 °C ... +40 °C
Permissible storage temperature + 5 C°... + 60 °C
Permissible relative air humidity 30 ... 90% (non-condensing)
Power supply  4 x 1.5 V NiMH rechargeable batteries with about
45hour service life at 2100 mAh, (Size AA or
Mignon)
 AC adapter 9 V 150 mA, 100V - 230 V
Power consumption  0.3 W with the LCD display not illuminated
 0.5 W with the LCD display illuminated.
Connectors  Probe:10-pin round plug
 AC adapter:2-pin barrel connector
Minimum time between two
measurements
About 0.2 seconds in the free-running mode
Minimum lift-off distance between
two measurements
min. 25 mm

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Fig 2.3 Ferriteoscope
2.4 TEMPIL STICKS
Tempil sticks has been leading the development and introduction of innovative and precise
temperature indication technologies for a wide variety of markets, welders and industry etc. Our
cost effective visual solutions check critical temperatures in welding and manufacturing
processes, monitor environment in your supply chains, and ensure the performance of your
products or services in the field. Our temperature measurement product line includes temperature
indicating sticks, electronic surface thermometer, infrared thermometer, medical sterilization
inks, weld able primers, heat absorbing coating and compounds, and temperature indicating
labels, strips, inks, and liquids. Tempil will deliver the surface measurement solution you count
on, when you need them the most. The welder strokes a mark on the metal with a Tempilstik
crayon as the metal is heated. The temperature indicators are made of materials with calibrated
melting points. When the temperature rating of the selected indicator is reached, the dry opaque

18. 10
mark undergoes a phase change to a distinct melted appearance. Phase-change temperature
indicators are preferred because they are accurate, simple to use, inexpensive, and make good
thermal equilibrium contact with the surface of the material.
Fig 2.4 Tempil Sticks
2.5 THERMOCOUPLE
A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming
electrical junctions at differing temperatures. A thermocouple produces a temperature dependant
voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure
temperature. Thermocouples are a widely used type of temperature sensor. Commercial
thermocouples are inexpensive, interchangeable, are supplied with standard connectors, and can
measure a wide range of temperatures. In contrast to most other methods of temperature
measurement, thermocouples are self powered and require no external form of excitation. The
main limitation with thermocouples is accuracy; system errors of less than one
degree Celsius (°C) can be difficult to achieve. Thermocouples are widely used in science and
industry. Applications include temperature measurement for kilns, gas turbine exhaust, diesel

19. 11
engines, and other industrial processes. Thermocouples are also used in homes, offices and
businesses as the temperature sensors in thermostats, and also as flame sensors in safety devices.
Table 2.3 Technical Data of thermocouple
Calibration Temperature range Standard limits of
error
Special limits of error
J 0O to 750OC
(32O to 1382OF)
Greater of 2.2°C or
0.75%
Greater of 1.1°C or 0.4%
K -200° to 1250°C
(-328° to 2282°F)
Greater of 2.2°C or
0.75%
Greater of 2.2°C or 0.75%
E -200° to 900°C
(-328° to 1652°F)
Greater of 1.7°C or
0.5%
Greater of 1.0°C or 0.4%
T -250° to 350°C
(-328° to 662°F)
Greater of 1.0°C or
0.75%
Greater of 0.5°C or 0.4%
Fig 2.5 Thermocouple

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2.6 SKIN TYPE THERMOCOUPLE
Skin Type Thermocouple are designed to measure the temperature of the body. It is bonded to
the surface of the body to which temperature is to be measured through a insulating pad, so that
it collects temperature. This model of thermocouple is typically used with in high temperature
industry and corrosive environments where fast and accurate temperature measurement is
critical.
Fig 2.6 skin type thermocouple
INSTALLATION OF SKIN TYPE THERMOCOUPLE
Mostly Skin Type thermocouple are directly welded to the surface to which we have to measure
the temperature with thermally insulating pad so that only surface temperature is collected rather
than surrounding air temperature. For a thermocouple to work at its optimum range, the
thermocouple sheath must remain in close contact with the tube. The weld pad should be
positioned at the critical point and the remaining cable should be routed away from the direct
heat along the coolest side of the vessel. This installation technique is important as it allows the
thermocouple to utilize the process tube as a heat sink.
TYPES OF SKIN TYPR THERMOCOUPLE
1. WELD PAD
 Weld Pad is an inexpensive design.
 Designed for flat or curved surfaces.

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 The pad is notched to match the mi-cable diameter. This allows the thermocouple
junction to be in close proximity to the measuring surface.
 A shield option is available for greater accuracy.
 Compact design allows for ease of installation when there are space limitations.
 Pad can incorporate any mi-cable diameter.
 A continuous single-pass weld from the pad to the tube surface is sufficient for
attachment.
 Weld pads can be mounted longitudinal or right angled to the pipe surface.
Fig 2.7 weld pad
2. WASHER PAD
 Accuracy less than V-Pad, Shroud Sensor.
 Easy and hassle free installation.
 Interchangeable.
Fig 2.8 washer pad

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Application
 Chemical and petrochemical industries.
 Energy and power plant technology.
 Furnaces, kilns, ovens and boilers.
 Oil and gas industries.
2.7 ESTIK ELECTRONIC SURFACE THERMOMETER
Fig 2.9 Estik electronic thermometer
We are presenting our finely manufactured collection of Estik Electronic Surface
Thermometer which is supplied by us within the stipulated time frame. This is considered as the
revolutionary and technologically advanced device used to measure surface temperature. When
comes in contact, these thermometer provide fast and quick read out of the preferred surface
temperature. Offered range of Estik Electronic Surface Thermometer measure the temperature
from 0C to 537C and is easily available at market leading prices.
Features:
 Accuracy
 Quick in measurements
 Durable quality

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Table 2.4 Technical data of Estik electronic thermometer
Temperature range (+32 to 999oF) (0 to 537oF)
Accuracy +/-2% or +/- 2o whichever is greater
Dimensions (L*w*H) 7.02” x 1.62” x 1.65”
17.83cm x 4.12cm x 4.20cm
Weight 195.4 gram (6.9)
Display 3 x AAA
Battery type Within 15 seconds of last reading
Automatic shut off High temperature MPPO
Estik holder material Styrene block copolymer

24. 16
CHAPTER 3
WORKING OF DEVICES
3.1 Working and Principle of Thermocouples
When two dissimilar metals such a iron and copper are gained to form a closed circuit, current
flow when one junction is at higher temperature and the other one is at lower temperature as
shown in the figure 3.1. The emf driving the current is called a thermoelectric emf and the
phenomenon is known as thermoelectric effect or See back effect. Usually a thermoelectric emf
is very small. A pair of dissimilar metals welded together at their junction forms what is called a
thermocouple. When several thermocouples are arranged in series, the emf is added together to
give an appreciable output, this arrangement is called thermopile as shown in the figure.
Fig 3.1 Principle of measurement of temperature by a thermocouple and Arrangement of
thermocouple to form a thermopile

25. 17
Fig 3.2 Zone boxes
3.1.1 Materials for thermocouple:
 Melting point of thermocouple materials must be higher than the measuring temperature.
 The dissimilar materials on joining should be able to produce large emf for accuracy of
measurements.
 Temperature is determined indirectly i.e. through calibrations of emf with temperature.
As for as possible, the linear variation of emf with temperature is desired.
 Thermocouple materials should be resistant to atmospheres in furnaces.
Table 3.1 Available thermocouples
Type
Positive wire
(+)
Negative wire
(-)
Maximum
temp C
Suitable
under
T Cu Ni45Cu55 370 Oxidizing&
Reducing
K Ni90Cr10 Ni95Mn2At2Si 1260 Oxidizing&
Inert
J Fe Ni45Cu55 760 Oxidizing&
Reducing
E Pr70Rh30 Pt94Rh6 1750 Oxidizing,
Inert& Vacuum
3.1.2 Cold junction compensation
Application of see back effect to thermocouple requires that one end of the junction (cold) must
be at constant temperature. The standard calibration data for all thermocouples are based on O�
cold junction temperature. In practice it may not be possible to keep cold junction at zero degree
temperature. Hence standard data need to be corrected. One way is to add the environmental
temperature to the value of temperature determined by thermocouple measurement. In another

26. 18
method, thermistor may be put in the thermo‐couple circuit. The voltage drop across thermistor
depends on environmental temperature which then compensates for the error.
3.1.3 Compensating wires
Compensating wires are those wires which are connected from the thermocouple to the
temperature indicator. Compensating wires should have same emf as that of thermocouples.
Table 3.2 Compensating wires are color coded.
Positive wire Color Thermocouple
Fe White Fe‐constantan
Ni Cr Yellow Chromel ‐ alumel
Cu Blue Cu‐NI base
Ni Cr Purple Chromel constantan
Ni ‐ Cr ‐ Si Orange Nicrosil / Nisil
The negative wires in all thermocouples are red.
3.1.4 Selection of thermocouples
 Type of furnace; whether batch or continuous and the frequency of measurement.
 Furnace atmosphere: The furnace atmosphere may be oxidizing or reducing, inert or
vacuum. Accordingly thermocouples are selected. For example Pt, Pt‐Rh can be used
in oxidizing.


27. 19
Fig 3.3 Thermocouple Material Vs EMF
3.2 INFRARED THERMOMETER
An infrared thermometer measures temperature by detecting the infrared energy emitted by all
materials which are at temperatures above absolute zero, (0°Kelvin). The most basic design
consists of a lens to focus the infrared (IR) energy on to a detector, which converts the energy to
an electrical signal that can be displayed in units of temperature after being compensated for
ambient temperature variation. This configuration facilitates temperature measurement from a
distance without contact with the object to be measured. As such , the infrared thermometer is
useful for measuring temperature under circumstances where thermocouples or other probe type
sensors cannot be used or do not produce accurate data for a variety of reasons. Some typically
circumstances are where the object to be measured is moving; where the object is surrounded by
an EM field, as in induction heating; where the object is contained in a vacuum or other
controlled atmosphere; or in applications where a fast response is required.
3.2.1 MEASUREMENT PRINCIPLES
As previously stated IR energy is emitted by all materials above 0°K. Infrared radiation is part of
the Electromagnetic Spectrum and occupies frequencies between visible light and radio waves.
The IR part of the spectrum spans wavelengths from 0.7 micrometers to 1000 micrometers
(microns). Within this wave band, only frequencies of 0.7 microns to 20 microns are used for
practical, everyday temperature measurement. This is because the IR detectors currently
available to industry are not sensitive enough to detect the very small amounts of energy
available at wavelengths beyond 20 microns. Though IR radiation is not visible to the human
eye, it is helpful to imagine it as being visible when dealing with the principles of measurement
and when considering applications, because in many respects it behaves in the same way as
visible light. IR energy travels in straight lines from the source and can be reflected and absorbed
by material surfaces in its path. In the case of most solid objects which are opaque to the human
eye, part of the IR energy striking the object’s surface will be absorbed and part will be reflected.
Of the energy absorbed by the object, a proportion will be re-emitted and part will be reflected
internally. This will also apply to materials which are transparent to the eye, such as glass, gases
and thin, clear plastics, but in addition, some of the IR energy will also pass through the object.

28. 20
Fig 3.4 Equipment setup
3.2.2 Infrared Monitoring
The welding research in adaptive control has leading some researchers to identify infrared
monitoring as a valuable tool in detecting the variations occurred in welding condition. The
concept of penetration control by infrared base on monitoring the welded plate temperature
distribution The radiation and convection heat changing with the environment and the heat
transfer between welding pool metal liquid and solid part of base material determine the
temperature distribution profile in both, the internal region and the welding plate surface . When
infrared sensors are used in monitoring the surface temperature distribution, it is studied the
relations between temperature distributions characteristics and bead geometry with the objective
of developing an efficient control system. The superficial temperature distribution can be used as
indication of defects formations, distortions appearance and welding joint misalignment besides
disturbances identifications in welding penetration. The welding penetration variation control
can be possible once the welding pool radial convection pattern with are responsible by the
variation of the penetration in welding joints, can be identify through welding pool temperature
distribution. To produce a good quality welding, it should be obtained welding without variations
in the processes conditions, maintaining a regular and repeated pattern in distribution of
superficial temperature

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Fig 3.5 Infrared Monitoring
3.2.3 Experimental procedure
Welding beads were deposited in specimens (SAE 1020) within 4 different shapes (fig. 1). Fig. 2
shows a set of welding parameters data collection equipments. The experiments were carried out
in a robotic cell composed by: Megatronic TIG BDH 320 tipple welding machine, ABB IRB
2000 robot. Tab. 1 show the welding parameters used in all experiment.
Table 3.3 Welding Parameters
The welding pool monitoring system were composed by infrared thermometer, acquisition
system and analyses data composed by A/D converter with 16 channels and software. The
TIG Welding
Welding position Bead on plate
Gas Argon
Current(amp) 150
Voltage(volt) 12
Welding speed (mm/s) 2.5
Gas Flow (l/min) 10
Electrode Ewth-2 2%

30. 22
infrared thermometer and the TIG welding torch were fixed to robot clamp through an aluminum
device, which permits monitoring the welding pool during the welding. The infrared
thermometer generated one analogical signal of 1 m V cc/C collected by the acquisition system
in a rate of 350samples/sec. The tests were identified by the legend C Pxy, where x indicates the
type of test specimen and y the number of the test. All tests specimens were marked with two
points indicated beginning and the end of the welding bead (“O” and “F”). The test specimens
type 1 and 3 look for simulate one step signal through width and thickness respectively, and P1,
P2 and P3 the location of the alteration places. Test specimens 2 and 4 look for simulate ramp
signal through width and thickness respectively, being the point P1, the location point situated in
the beginning of the alteration place.

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CHAPTER 4
POWER AND CHARGE DENSITY IN WELDING PROCESS
4.1 Power Density, Temperature of Heat Source, Heat Input, Mechanical Properties:
Fusion welding processes can be looked into on the basis of range of energy density which they
can apply for melting the faying surfaces of base metal for joining. Heat required for fusion of
faying surfaces of components being welded comes from different sources in different fusion
welding processes (gas, arc and high energy beam). Each type of heat source has capability to
supply heat at different energy densities (kW/mm2). Even for a given arc power (arc current I X
1 arc voltage V), different welding processes provide heat at different energy densities due to the
fact that it is applied over different areas on the surface of base metal in case of different
processes. Energy density (kW/mm2) is directly governed by the area over which heat is applied
by a particular process besides welding parameters. Power density in ascending order from gas
welding to arc welding to energy beam based welding processes is shown in table 4.1. Typical
values of energy densities and approximate maximum temperature generated during welding by
different processes are shown in Table 4.1.
Table 4.1 Heat intensity and maximum temperature related with different welding
processes
Sr. No. Welding process Heat density (W/cm2 ) Temperature (0 C)
1 Gas welding 102 -103 2500-3500
2 Shielded meta arc welding 104 >6000
3 Gas metal arc welding 105 8000-10000
4 Plasma arc welding 106 15000-30000
5 Electron beam welding 107 -108 20,000-30000
6 Laser beam welding >108 >30,000

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4.2 EFFECT OF POWER DENSITY
Energy density associated with a particular welding process directly affects amount of heat
required to be supplied for fusion of the faying surfaces. An increase in power density decreases
the heat input required for melting and welding of work pieces because it decreases time over
which heat is to be applied during welding for melting. The decrease in heat application time in
turn lowers the amount of heat dissipated away from the faying surfaces to the base metal so the
most of the heat applied on the faying surfaces is used for their fusion only. However, it is
important to note that heat required for melting the unit quantity of a given metal is constant and
is a property of material. Heat for melting comprises sensible heat and latent heat. Latent heat for
steel is 2kJ/mm3. Fusion welding processes are based on localized melting using high-density
heat energy. To ensure melting of base metal in short time it is necessary that energy density of
welding process is high enough (Fig. 4.1). Time to melt the base metal is found inversely
proportional to the power density of heat source i.e. power of (arc or flame) / area of work piece
over which it is applied (W/cm2). Lower the energy density of heat source greater will be the
heat input needed for fusion of faying surface welding as a large amount of heat is dissipated to
colder base material of work piece away from the faying surface by thermal conduction (Fig.
4.1)
Fig. 4.1 Effect of energy density and time on energy input
Heat input to workpiece Power density of heat source Increasing damage to workpiece
Increasing penetration, welding speed, weld quality and equipment cost Gas welding Arc

33. 25
welding High energy beam welding Fig. 4.2 Effect of power density of heat source on heat input
required for welding.
Fig. 4.2 Effect of power density of heat source on heat input required for welding
4.3 NEED OF OPTIMUM POWER DENSITY OF WELDING PROCESS
As stated, low power density processes need higher heat input than high power density
processes. Neither too low nor too high heat input is considered good for developing a sound
weld joint. As low heat input can lead to lack of penetration and poor fusion of faying surfaces
during welding while excessive heat input may cause damage to the base metal in terms of
distortion, softening of HAZ and reduced mechanical properties (Fig. 4.3). High heat input has
been reported to lower the tensile strength of many aluminum alloys of commercial importance
due to thermal softening of HAZ and development of undesirable metallurgical properties of the
element (Fig. 4.4). Moreover, use of high power density offers many advantages such as deep
penetration, high welding speed and improved quality of welding joints. Welding process (where
melting is required) should have power density approximately 10(W/mm2). Vaporization of
metal takes place at about 10,000W/mm2 power-density. Processes (electron and laser beam)
with such high energy density are used in controlled removal of metal for shaping of difficult to
machine metals. Welding processes with power density in ascending order are shown in Fig. 4.5.

34. 26
Fig. 4.3 Effect of welding process on angular distortion of weld joint as a function of plate
thickness
Fig. 4.4 Schematic diagram showing effect of heat input on tensile strength of aluminium alloy
weld joints.
Fig. 4.5 Power densities of different welding processes

35. 27
CONCLUSION
We remember from our school science classes that the movement of molecules and atoms
produces heat (kinetic energy) and the greater the movement, the more heat that is
generated. Temperature Sensors measure the amount of heat energy or even coldness that is
generated by an object or system, allowing us to “sense” or detect any physical change to that
temperature producing either an analogue or digital output. There are many different types
of Temperature Sensor available and all have different characteristics depending upon their
actual application. A temperature sensor consists of two basic physical types:
 Contact Temperature Sensor Types
These types of temperature sensor are required to be in physical contact with the object
being sensed and use conduction to monitor changes in temperature. They can be used to
detect solids over a wide range of temperatures. The Thermocouple is by far the most
commonly used type of all the temperature sensor types. Thermocouples are popular due
to its simplicity, ease of use and their speed of response to changes in temperature, due
mainly to their small size. Thermocouples also have the widest temperature range of all the
temperature sensors from below -200oC to well over 2000oC.
 Non-contact Temperature Sensor Types
These types of temperature sensor use convection and radiation to monitor changes in
temperature. They can be used to detect liquids and gases that emit radiant energy as heat
rises and cold settles to the bottom in metal or detect the radiant energy being transmitted
from an object in the form of infrared radiation.

36. 28
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Catalysis, Palm Beach, 1972
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