Welding Technology

ME692

Dr. Virkeshwar Kumar

NL1-115R, Manufacturing Science Lab
Department of Mechanical Engineering
IIT Kanpur
Email: virkeshwar@iitk.ac.in
Phone: 0512-259-2334
Course details: L18
✓ Tuesday and Friday (2-3:15 PM): 3 hrs/ week
✓ Prerequisites for UG: TA 201 and TA202
✓ There are no prerequisites for PG students.

Evaluation/Grading
✓ Attendance (10%): less than 80%: 0 marks, ≥80%: 10 marks

✓ Quiz (20%): Two quizzes

✓ Mid-sem (28%)

✓ End-sem (42%)
 Grading Policy: Relative and
Granular Grading
Quiz Weightage % Date of Quizzes: L18, L19 and L20
Quiz 1 10 13th Feb evening (6:00 PM-7:30 PM)
Quiz 2 10 6th April evening (6:00 PM-7:30 PM)

Mid Sem 28%

End Sem 42%

First-class: 5th Jan, Last class: 19th Apr

Holiday: 26th Jan,8th Mar, 29th Mar

Mid-Sem Exam: Feb 19-24, 2024

Mid-Sem Recess: Mar 23-31, 2024
 Energy loss during fusion welding
TSurrounding
Electrode
(Conduction)

Radiation
Filler rod (light) Convection
(Conduction)
Arc
Metal vapours+ gases
Convection
Molten droplet Convection

Weld Conduction
Pool

Base materials
 Mode of Heat Transfer
Conduction mode of heat transfer
Conduction in solids: lattice vibrations of the molecules
and the movement of free electrons.
In gases and liquids: collisions and diffusion of the
molecules during their random motion.
Fourier’s law of heat conduction T

𝑹𝒂𝒕𝒆 𝒐𝒇 𝒉𝒆𝒂𝒕 𝒄𝒐𝒏𝒅𝒖𝒄𝒕𝒊𝒐𝒏:

𝒅𝑻
𝑸𝒄𝒐𝒏𝒅 = −𝒌𝑨
𝒅𝒙
Th
Heat is conducted from high to low
temperature.
Heat is conducted in the positive x- Tl
direction. 0
x
l
 Mode of Heat Transfer
Convection mode of heat transfer

✓ Convection - Transfer of thermal energy through a mass

movement. It involves the combined effects of conduction and
fluid motion.
✓ The faster the fluid motion, the greater the convection heat
transfer.
Newton’s law of cooling
𝑹𝒂𝒕𝒆 𝒐𝒇 𝒉𝒆𝒂𝒕 𝒄𝒐𝒏𝒗𝒆𝒄𝒕𝒊𝒐𝒏

𝑸𝒄𝒐𝒏𝒗𝒆𝒄𝒕𝒊𝒐𝒏 = 𝒉𝑨(Tw-TS)
Mode of Heat Transfer
Convection mode of heat transfer
 Mode of Heat Transfer
Radiation mode of heat transfer

✓ Radiation - Transfer of thermal energy by the emission and

absorption of electromagnetic radiation.
✓ Unlike conduction and convection, the transfer of energy by
radiation does not require the presence of an intervening
medium.
Stefan–Boltzmann law: 𝑹𝒂𝒕𝒆 𝒐𝒇 𝒉𝒆𝒂𝒕 𝒓𝒂𝒅𝒊𝒂𝒕𝒊𝒐𝒏
𝑸𝒆𝒎𝒊𝒕 = 𝜺𝝈𝑨𝑻𝟒𝑾
and the net rate of radiation heat transfer between these
two surfaces: 𝑸 = 𝜺𝝈𝑨(𝑻𝟒𝑾 − 𝑻𝟒𝑺 )
 Mode of Heat Transfer

https://vacaero.com/information-resources/vac-aero-training/202678-
vacuum-furnace-hot-zones-metal-and-carbon-configurations.html
 Energy loss during fusion welding
TSurrounding
Electrode
(Conduction)

Radiation
Filler rod (light) Convection
(Conduction)
Arc
Metal vapours+ gases
Convection
Molten droplet Convection

Weld Conduction
Pool

Base materials
 Transfer efficiency of processes
✓Transfer efficiency (η) varies between 0 to 1.
η = H net/H input= H net /(P/V)
η = H net /(IU/V)
Where H net is the actual power received by the weldment
(e.g., measured by calorimetry).

✓Any heat that is lost to the surrounding mass of workpieces

can and usually does result in adverse effects.
✓For example, Heat-affected zone.
✓Almost without exception, material properties in a HAZ are
degraded compared to the base material.
 Heat affected Zone (HAZ)
2600 1498 1100 796 662 500 25
°C

Bai et al. 2017, ISIJ International

Heat affected Zone (HAZ) in a welding process: the work

material experiences Microstructure changes without
melting.Heat-affected
 Transfer efficiency of processes

For submerged arc (SA) welding, the efficiency factor (η) has
been reported in the range of 90 to 98%, for SMA and GMA
welding from 65 to 85%, and for GTA welding from 22 to 75%,
depending on polarity and materials.
Transfer efficiency of processes

Flux
Wire electrode
Flux
Molten slag
Arc Solidified Slag

Molten metal
Weld Metal
Base metal Metal drop
 Melting efficiency
✓The primary function of a heat source for fusion welding is to
melt material.
✓The resulting liquid establish material continuity by filling the
gaps in the joint.
✓Melting efficiency is the fraction of the actual energy input, H net,
that is used for actually melting material.

Additional Area, Ar
✓The overall weld cross-
sectional area, AW = Am +Ar
✓If no filler is added: AW = Am
Weld pool Area, Am
 Melting efficiency
𝑄𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 = 𝜌𝑚 [𝐿 + 𝐶𝑚 𝑇𝑃 − 𝑇𝑓 + 𝐶𝑠 (𝑇𝑓 − 𝑇0 )] J/m3
Latent heat Sensible heat Sensible heat
in melt in solid

Melting efficiency: f=Q required×AW/H net

η = H net /(IU/V) f=Q required×AWV/ηIU

Additional Area, Ar

Weld pool Area, Am AW=fηH input/ Q required

 Fusion welding: Energy Density
Heat input to workpiece

Energy Density: Power input/Effective area

gas 10W/cm2
Welding
~3K°C
50W/cm2
arc
Welding
~6K°C

10kW/cm2
high energy
beam welding ~20-30K°C
Power density of heat source
Energy Density: Type of Penetration
 Numerical Problems
1. Determine the net heat input for a butt welding job
carried out at an arc voltage of 30V and a current of 200A
at a welding speed of 300mm/min. Assume the heat
transfer efficiency is 0.9.
 Numerical Problems
2. Determine the melting efficiency for a butt welding job
carried (area= 35 mm2) out at an arc voltage of 30V and a
current of 200A at a welding speed of 300mm/min.
Assume the heat transfer efficiency is 80%, and for
melting 10 J/mm3 is required.
 Numerical Problems
3. In a welding process under steady-state conditions, the
voltage and current are measured at 18 V and 160 A,
respectively. Heat loss during arc creation is 40% of heat
input. Heat loss through conduction, convection, and
radiation from the workpiece is 800W. The effective
power is used to melt the workpiece. Calculate the
melting efficiency.
 Numerical Problems
3. In a welding process under steady-state conditions, the
voltage and current are measured at 18 V and 160 A,
respectively. Heat loss during arc creation is 40% of heat
input. Heat loss through conduction, convection, and
radiation from the workpiece is 800W. The effective
power is used to melt the workpiece. Calculate the
melting efficiency.
Solid-State Welding Process
 Solid-State Welding Process
✓Solid-state welding processes: Bringing the materials’
atoms (or ions or molecules) to equilibrium spacing
principally through plastic deformation.
✓Application of pressure at temperatures below the melting
point of the base material
✓Without the addition of any filler.
https://www.youtube.com/watch?v=5zGVwfVPwns&ab_channel=TWILtd

1. Diffusion welding
2. Friction welding
3. Pressure welding
 Diffusion Welding
✓Diffusion welding (DFW) is a solid- state welding process
that produces a weld by the application of pressure at
elevated temperature (0.5-0.7Tm) with no macroscopic
deformation or relative motion of the workpieces.

Unique advantages:
✓Dissimilar materials and metals as well as ceramics can be
joined directly
✓Large areas can be bonded or welded
✓There will be no heat-affected zone as such
 Diffusion Welding

Placing two similar or With time grain diffuses at

dissimilar plates under interfacial boundary.
dynamic load and controlled
heated environment

Grain boundary migration Elimination of

and closes interfacial pores and creation
voids of solid bonded part
Diffusion Welding
 Ultrasonic friction welding
✓Source of motion in friction welding can be pure mechanical
vibration or ultrasonically induced vibration

✓The amplitude of relative motion is very small, but the frequency is

very high

✓Frequency greater than around 30 kHz.

✓Ultrasonic vibration scrubs materials together while under

pressure, generates heat, and produces a weld, usually without a
distinct forging step.

https://www.youtube.com/watch?v=H
aMkiKrE-tg&ab_channel=Abbeon
 Friction Welding
✓Friction welding: To convert mechanical energy into heat for
welding using the relative movement between pieces.
✓Coalescence of materials occurs under the compressive force:
Relative motion between two plates: rotation or by angular or
linear reciprocation.

https://www.youtube.com/watch?v=RTEP9QdTn5k&t=91s&ab_channel=SLSanda

Conventional friction welding:

✓Amplitude of vibration is relatively large (fractions of to several

millimetres)
✓Frequency is quite low (typically, 102-103 cycles per second).
 Friction Welding
https://www.youtube.com/watch?v=iG3t0Q7UuCU&ab_channel=TWILtd
 Friction Welding
Forge force

Rotational speed
Forge Upset
Distance
Upset

Upset
Force
Friction speed
Fiction welding force Upset
Distance

Time
Friction Upset
Completion of
Distance
welding

A: relative to motion under moderate pressure

B-C: Frictional heating occurs and softens the material

C-D: Forging pressure is applied to complete the weld.

D: Establishes metallurgical continuity and bonding.
 Friction Welding
The relative motion between workpieces can generate friction.
The three motions are (1) rotation, (2) angular reciprocation, and
(3) linear reciprocation.

Rotational angular Linear

friction reciprocating reciprocating
welding friction welding friction welding
 Friction Stir Welding

✓ TWI developed
friction stir welding
(FSW) in 1991.

✓Non-consumable tool
rotates and plunges
into the workpiece.

Forces
from
clamping
 Friction Stir Welding
https://www.youtube.com/watch?v=BQYLdw8W5wE&ab_channel=MSUGradstudent
 Friction Stir Welding
✓ Frictional heating is generated by a rapidly rotating tool placed
between the pieces under pressure. This variation is called
(friction) stir welding.

✓ Maximum temperature~80% of melting point.

t d d<t

Garg et al., 2019, The International Journal of

Advanced Manufacturing Technology
 Friction Stir Welding
✓ Advancing side: Rotating tool linear velocity vector and the
welding direction are one and in the same direction.

✓ Retreating Side: Rotating tool linear velocity vector of rotating

tool and the welding direction are opposite to each other
Probe
Friction Stir Welding

Garg et al., 2019, The International Journal of

Advanced Manufacturing Technology
Amount of heat generated during FSW
✓The welding tool performs dual movement: translation (tr)
and rotation (rot).
✓The total amount of generated heat is the sum of
translation Qttr and rotational-generated heat Qtrot

Qt=Qttr+Qtrot
✓ Amount of translation heat is significantly smaller than the
amount of rotational heat

Qt=Qttr+Qtrot
Amount of heat generated during FSW
Flat Surfaces

Shoulder RSh

Shoulder tip Probe side

h
RPr
Probe tip
Amount of heat generated during FSW

in Watt
Amount of heat generated during FSW
Amount of heat generated during FSW
Amount of heat generated during FSW
 Amount of heat generated during FSW
Flat Surfaces: Probe tip

dϴ
ϴ
r

RPr dr
 Amount of heat generated during FSW
Flat Surfaces: Probe side

h
 Amount of heat generated during FSW
Flat Surfaces: Probe side

h
 Amount of heat generated during FSW
Flat Surfaces: Shoulder tip

dϴ

ϴ
RPr r

dr

RSh
 Amount of heat generated during FSW
Flat Surfaces: Shoulder tip

dϴ

ϴ
RPr r

dr

RSh
 Amount of heat generated during FSW
Flat Surfaces:
 Amount of heat generated during FSW
Taper Surfaces

Rsh

Probe side
Rpr
Amount of heat generated during FSW
Taper Surfaces
 Amount of heat generated during FSW
Taper Surfaces
 Amount of heat generated during FSW
Taper Surfaces
Amount of heat generated during FSW
Amount of heat generated during FSW
Heat Generation ratio
Amount of heat generated during FSW
Heat Generation ratio
Amount of heat generated during FSW
 Numerical Question: FSW
1. FSW process is carried out by a normal force of 15kN with a
rotational speed of 650 RPM. The coefficient of friction is 0.2,
and the weld area is 55 mm2. Calculate the shear stress
developed in FSW and condition whether the sticking
friction or sliding friction holds good for Al alloys AA 2014.
AA 2014 alloy: σ0=414 MPa
 Numerical Question: FSW
1. FSW process is carried out by a normal force of 15kN with a
rotational speed of 650 RPM. The coefficient of friction is 0.2,
and the weld area is 55 mm2. Calculate the shear stress
developed in FSW and condition whether the sticking
friction or sliding friction holds good for Al alloys AA 2014.
AA 2014 alloy: σ0=414 MPa
 Numerical Question: FSW

Sticking friction: Deformation: When friction stress is greater

than the flow shear stress of the material.
 Numerical Question: FSW
2. For a friction stir welding process, the rotating tool has a
rectangular cross-section with a side of a and b. If the shear
contact stress between the workpiece and tool is 𝝈𝟎 , the
angular velocity of the tool is ω, and the coefficient of
friction between the tool and workpiece is μ. Drive an
expression using elemental analysis for the heat generated
during the process during N rotations of the tool.
 Numerical Question: FSW
2. For a friction stir welding process, the rotating tool has a
rectangular cross-section with a side of a and b. If the shear
contact stress between the workpiece and tool is 𝝈𝟎 , the
angular velocity of the tool is ω, and the coefficient of
friction between the tool and workpiece is μ. Drive an
expression using elemental analysis for the heat generated
during the process during N rotations of the tool.
Numerical Question: FSW
Numerical Question: FSW
Numerical Question: FSW
Numerical Question: FSW
Numerical Question: FSW
Numerical Question: FSW
Numerical Question: FSW
ARC Welding
 Electric ARC Welding

Electrode
Electric
_
Power
source Arc
Workpiece +

✓Electric welding arcs can be operated in three ways.

✓With a direct current (DC) flow under the emf from a source
with fixed polarity, DCEN or DCEP
✓With an alternating current (AC) flow periodically reverses or
alternates polarity.
 Basics in ARC Welding
✓ Ordinary matter is made up of atoms/molecules that have

positively charged nuclei and negatively charged electrons

surrounding them.

✓ Conductors are materials in which charges can move freely.

✓ Insulators are materials in which electric charge is not

easily transported.
 Discharge
Conductor Air Conductor

Power source

✓ Decrease in the gap between conductors: no current flow

✓ If we apply more energy between two conductors:
Thermionic emission
✓ Further decrease in the gap as well as apply high energy…
air ionized
✓Thermionic emission is the liberation of electrons from an
electrode by its temperature.
 Discharge
Conductor Air Conductor

Power source

✓ More electrons will interact with air, so gas atoms and

molecules will become ionized.
✓ Ionized: gas atoms or molecules lose electrons during the
process, so then they become positive ions. This process
creates more energy carriers (electrons, ions). It conducts
energy and charges.
✓ This process is known as discharge.