i have made a presentation on welding and welding transformer, here i included types of weldings and their advantages and types of welding transformer and their working, construction, application, advantages..

1. Prepared By;
Hanif Pathan
hpathan29@gmail.com

2.  Introduction
 Types of welding
 Classification of welding processes
 Construction
 Working
 Types of welding transformer
 Auxiliary equipment
 Advantages- Disadvantages
 Application

3.  Welding is a materials joining process which produces
coalescence of materials by heating them to suitable
temperatures with or without the application of pressure or
by the application of pressure alone, and with or
without the use of filler material.
 Welding is used for making permanent joints.
 It is used in the manufacture of automobile bodies, aircraft
frames, railway wagons, machine frames, structural
works, tanks, furniture, boilers, general repair work and
ship building.

4. 1. Pressure Welding
 The piece of metal to be joined are heated to a plastic state
and forced together by external pressure
 (Ex) Resistance welding.
2. Non-Pressure Welding
 The material at the joint is heated to a molten state and
allowed to solidify.
 (Ex) Gas welding, Arc welding.

5. 1. Arc welding
 Carbon arc
 Metal arc
 Metal inert gas
 Tungsten inert gas
 Plasma arc
 Submerged arc
 Electro-slag
2.Gas Welding
 Oxy-acetylene
 Air-acetylene
 Oxy-hydrogen
3.Resistance Welding
 Butt
 Spot
 Seam
 Projection
 Percussion

6. 4.Thermit Welding
5.Solid State Welding
 Friction
 Ultrasonic
 Diffusion
 Explosive
6.Newer Welding
 Electron-beam
 Laser
7.Related Process
 Oxy-acetylene cutting
 Arc cutting
 Hard facing
 Brazing
 Soldering

7. Alternating Current (from Transformer)
 More efficiency
 Power consumption less
 Cost of equipment is less
 Higher voltage – hence not safe
 Not suitable for welding non ferrous metals
 Not preferred for welding thin sections
 Any terminal can be connected to the work or electrode

8. Direct Current (from Generator)
 Less efficiency
 Power consumption more
 Cost of equipment is more
 Low voltage – safer operation
 suitable for both ferrous non ferrous metals
 preferred for welding thin sections
 Positive terminal connected to the work
 Negative terminal connected to the electrode

9.  Welding transformer consists of a step-down transformer
with a tapped secondary having an adjustable reactor in
series with it for obtaining drooping V/I characteristics.
 It has a magnetic core with primary winding which is thin
and has large number of turns on one arm.
 A secondary winding with less number of turns and high
cross-sectional area on the other arm.
 So we get less voltage and high current from the
secondary winding output.

10.  The secondary is tapped to give different voltage/current
settings.

11. • A dc welding transformer also has same type of winding
the only difference is that we connect a rectifier(which
converts ac to dc) at the secondary to get dc output.
• We also connect a inductor or filter to smooth the dc
current. This will be construction of dc welding
transformer. The diagrams are shown below.

12.  The welding transformer reduces the voltage from the source
voltage to a lower voltage that is suitable for welding.
 Usually between 15 and 45 volts. The secondary current is quit
high and it may be typically 200A to 600A, but it could be
much higher.
 The secondary may have several taps for adjusting the
secondary voltage to control the welding current. The taps are
typically connected to a several high-current plug receptacles
or to a high-current switch.
 One end of the secondary is connected to the welding
electrode, whereas the other end is connected to the pieces to
be welded .If any high current flows, heat is produced due to
the contact resistance between the electrode and the pieces to
be welded.

13.  When a high current flows a large amount of I2R heat is
produced due to contact resistance between welding
pieces and electrode.
 The generated heat melts a trip of the electrode and the
gap between the two pieces is filled.

14. The four basic types of welding transformers are
 The saturable high reactance type
 The external reactor type
 The integral reactor type
 The reactor type

15.  In the diagram these partial fluxes have been marked as ɸL1 and
ɸL2. In other words, they are responsible for the reactance of the
coils and the respective reactive voltage drops across them. As
the current increases, the leakage fluxes also increase and so
does the e.m.f. of self-induction. This is why an increase in the
primary or secondary current results in increase in the reactive
voltage drop across the respective windings.

16.  This type of welding transformer consists of a normal
reactance, single phase, step down transformer and a
separate reactor or choke.
 The inductive reactance’s and resistances of the windings
in such a welding transformer are low, so that its
secondary voltage varies but a little with the welding
current. The required drooping or negative volt-ampere
characteristic is ensured by the reactor placed in the
secondary of the welding circuit The reactor consists of a
steel core and a winding wound with a wire designed to
carry the maximum allowable current.

17.  the arc voltage decreases with increase in current, or with
increase in voltage drop across the reactor. This gives a
negative or drooping volt-ampere characteristic.

18.  The welding transformer of the integral reactor type, has a
primary winding I, a secondary winding II, and a reactor
winding III. Apart from the main limbs, the core has additional
limbs carrying the reactor winding. The current is adjusted by
means of moving core C placed between the additional limbs.

19.  In this welding transformer an isolated low voltage, low
amperage dc circuit is employed to change the effective
magnetic characteristics of the magnetic core.
 Thus, a large amount of ac is controlled by using a
relatively small amount of dc, hence making it possible to
adjust the output volt-ampere characteristic curve from
minimum to maximum. For example, when there is no dc
flowing in the reactor coil, it has its minimum impedance
and thus maximum output of the welding transformer.

20.  As the magnitude of dc is increased with the help of
rheostat in the dc circuit, there are more continuous
magnetic lines of force thus the impedance of the reactor
is increased and the output current of the welding
transformer is decreased. This method has the advantage
of removing movable parts and flexing conductors and is
often used for gas tungsten arc welding power supplies.
 To achieve the desired aim of low voltage and high current
the reactor coils are connected in opposition to the dc
control coil.

21.  as shown in figure, Placing an air-gap in the reactor core is
one method of reducing this distortion.
 Alternatively, a large choke can be inserted in the dc
control circuit. Either method, or a combination of the
two, will produce the desired result.

22.  A generator (D.C.) or Transformer (A.C.)
 Two cables- one for work and one for electrode
 Electrode holder
 Electrode
 Protective shield
 Gloves
 Wire brush
 Chipping hammer
 Goggles

24.  Low operation and maintenance cost
 Low wear
 No arc blow
 Less post welding cleaning
 Greater affidavit rates
 High welding speeds
 This setup can be move easily for different operation
places.
 Size is relatively less than other welding process’s
equipments.
 No chances of blasting during operation like gas welding.
 Controlling is easy during operation.

25.  Higher introductory setup cost.
 Higher upkeep cost due to requirement of additional
electronic parts.
 Highly skilled labour is required.
 Its polarity cannot be changed.
 Internal residual is set up in part which is welded due to
continue heating and cooling of that part during operation.
 It is not suitable for welding of cast iron and non-ferrous
metals.

26. there are various types in electric arc welding so they are
used for different types of application based on metal type
and operation.
 Gas metal arc welding (GMAW)
 Gas tungsten arc welding (GTAW)
 Shielded metal arc welding (SMAW)
 Flux cored arc welding (FCAW)
 Energy beam arc welding (EBW)
 Atomic hydrogen welding (AHW)
 Plasma arc welding

27.  Aerospace industry
 Aviation industry
 Welding of non ferrous metals
 Space vehicles
 Components made of magnesium and aluminum
 To weld thin joints
 Sealing of nuclear fuel canisters before burial.

28. This type of welding can be used for welding of following
metals
 Low alloy and high tensile steels
 Low carbon steels
 Stainless stell and high-resisting steels
 Cast iron

29.  Electronic welding
 Instrument panels welding
 Fuel tanks
This process is used in those application where rapid welding
is needed is necessary Eg. Stainless steels and special alloys
Atomic hydrogen welding (AHW)

30.  Marine and aerospace industries
 Electronic industry
 Used for repair tools, die and mold
 Used for welding of turbine blade.
 Welding of titanium parts

31. Thank You