The document discusses various joining and assembly processes. It begins by defining assembly as joining elements together to form a final product, which can be done by human workers or machines. It then discusses various fusion welding processes like oxyfuel welding, arc welding, plasma arc welding, and laser beam welding. It also discusses solid state welding processes like friction welding, ultrasonic welding, roll bonding, and diffusion welding. The key information is that the document provides an overview of various welding and assembly techniques.

1. Welding / Assembly
Joining Process

2. What is assembly?
 joining elements together, which shapes a
final product. Assembly process can be made
by human workers (uneducated but skilled)
or by specialized machines and robots.
 Example: Cars, computers, engines,
celphone etc.

3. Introduction
Aspect of manufacturing:
1.Impossible to manufacture as a single product
e.g chairs, computer, etc.
2.More economical to manufacture as individual
components, which are then assembled
e.g bicycle
3.For maintenance or replacement purposes
e.g. car accessories and engines.
4.Different materials due to different properties requirement
e.g. cooking pots and pans.
5.Ease and less costly of transportation
e.g. Bicycle

4. Joining Processes
 1. Welding
 2. Soldering and Brazing
 3. Mechanical Fastening
 4. Adhesive Bonding
But our presentation will focus on welding

5. Welding
Fusion
Solid State
Welding Welding

6. Fusion
Oxyfuel- Welding Pressure-
Gas Gas
Welding Welding
Electron-
Beam Arc Welding Laser-Beam
Welding Welding
Non
Consumable Consumable
electrode Electrode
- Shielded metal-arc welding
- Gas tungsten-arc welding -Submerged-arc welding
-Plasma-arc welding -Gas Metal-arc welding
-Atomic Hydrogen Welding -Flux cored-arc welding
-Electrogas welding
- Electroslag welding

7. Solid State
Roll Welding Cold
Bonding/ Welding
Welding
Ultrasonic Diffusion
Explosion
Welding Welding
Welding
Friction
Resistance Welding
Welding
-Resistance spot welding
- Resistance seam welding
-Inertia friction welding - High-frequency resistance
- Linear friction welding welding
- Friction stir welding - Resistance projection welding
- Flash welding
- Stud welding
- Percussion welding

8. Fusion Welding Process
1) OXYFUEL-GAS WELDING (OFW)
- OFW uses a fuel gas combined with oxygen to produce
flame
- Function of the flame - act as a source of the heat to melt
the metals at the joint.
- Common gas welding process uses acetylene (oxyacetylene
gas welding - OAW).
-Application: structural sheet metal fabrication, automotive
bodies, and various repair work.

9. Fusion Welding Process
- OAW process utilizes the heat generated by the
combustion of acetylene gas (C2H2)in a mixture
of oxygen.
- These primary combustion process, occurs in the
inner core of the flame, involves the reaction of:
C2H2+ O2---------->2CO + H2+ Heat (1/3 total
heat generated in the flame)
- The secondary combustion process involves
further burning of hydrogen and carbon
monoxide:
2CO + H2+1.5O2------------>2CO2+ H2O + Heat
(2/3 of the total heat)

10. Fusion Welding Process
a. General view of oxy
torch
b. Cross-section of a torch
used in oxyacetylene
welding. The acetelyne
valve is opened first; the
gas is lit with spark
lighter or a pilot light;
then the oxygen valve is
opened and the flame
adjusted.
c. Basic equipment used in
oxyfuel-gas welding. All
acetylene fittings are left
handed while oxygen are
right handed. Oxygen
regulators are usually
painted green, acetelyne
regulators red.

11. Flame types
1. Neutral - ratio 1:1 , no excess oxygen
2. Oxidizing - greater oxygen supply (excess oxygen),
harmful for steel due to oxidizes. Only suit for nonferrous
metal like copper & copper based alloys.
3. Carburizing - insuffientof oxygen (excess acetytelene),
low temperature, thus suitfor applications requiring low
heat like brazing, soldering, flame hardening.
Filler metals
1. To supply additional metal to the weld zone during
welding.
2. Filler rods or wire and may be coated by flux
3. The purpose of flux is to retard oxidation of the welded
surfaces.

12. Oxyacetelene Flames Use in
Welding

13. Fusion Welding Process
2) PRESSURE GAS WELDING
- Involved with two components starts by heating the
interface.
- Once when the interface begins to melt, the torch is
withdrawn.
- A force is applied to press both components together and
maintain until the interface solidifies.
- The joined end with the occurrence of a flash.

14. Pressure Gas Welding

15. Fusion Welding Process
3) ARC-WELDING PROCESSES
- In arc welding, the heat is obtained from electrical
energy – by using AC or a DC power supply.
- The process involved can be either consumable or non-
consumable electrode.
- An arc is produced between the tip of electrode and
the work piece which need to be welded.
- The arc produces temperatures approximately 30,000
degrees celsius.

16. Arc Welding Processes
a.) NON CONSUMABLE ELECTRODE
- The electrode is a tungsten electrode type.
- Need externally supplied shielding gas because of
the high temperature involved in order to prevent
oxidation of the weld zone.
- DC is used and the polarity is important.
- For straight polarity which is also known as direct-
current electrode negative (DCEN); the workpiece is
positve (anode) , while the electrode is negative
(cathode).

17. Arc Welding Processes
- It will produce welds that are narrow and deep.
- For reverse polarity which is also known as direct-current
electrode positive (DECP); the workpiece is negative and
electrode positive.
- In this process, weld penetration is less, and the weld zone
is shallower and wider.

18. Non Consumable Electrode
i) GAS TUNGSTEN-WELDING (GTAW)
- Also known as TIG welding
- Suitable for thin metals.
- This process is expensive because of the cost of inert gas
- Provides welds with very high quality and surface finish
- Filler metal is supplied from a filler wire
- The shielding gas is usually argon or helium

19. Non Consumable Electrode
- This filler metals are similar to the metal that need to be
welded, and flux is not used.
- In this operation, tungsten electrode is not consumed,
therefore a constant and stable arc gap is maintained at a
constant current level.
- Power supply either 200A DC or 500A AC; depending on
the metals to be welded.
- Generally, AC is suitable for aluminum and magnesium.
- Thorium or zirconium may be used in the tungsten
electrodes to improve the electron emission characteristics.

20. Non Consumable Electrode
- Contamination of the tungsten electrode by molten metal
ca cause discontinuities in the weld.
- Therefore, contact between the electrode with the molten
metal pool should be avoided.

21. Gas Tungsten-Arc Welding

22. Non Consumable Electrode
ii) PLASMA-ARC WELDING (PAW)
- In this welding operation, a concentrated plasma arc is
produced and directed towards the weld area.
- The arc is stable and the temperature can reaches up to
33,000 degrees celsius.
- PAW has less thermal distortion, and higher energy
concentration – permitting deeper and narrower welds.
- Plasma: it is an ionized hot gas composed of nearly equal
number of electrons and ions.

23. - This plasma initiated between the tungsten electrode and
the small orifice by a low current pilot arc.
- Operating current: usually below 100A.
- Filler metal is fed into the arc during welding process.
- There are two methods of plasma-arc welding:
a) Transferred-arc method
- Work piece being welded is part of the electrical
circuit. The arc transfers from the electrode to
the work piece.
b) Nontransferred method
- The arc occurs between the electrode and the
nozzle. The heat is carried to the workpiece by
the plasma gas.

24. - Welding speeds from 120 to 1000 mm/min.
- Can be welded with part thickness less than 6mm.
Plasma-arc Welding Process

25. Consumable Electrode
i) SHIELDING METAL-ARC WELDING
- Old method , simplest, held manually.
- Most of all industries and maintenance welding
currently performed with this process.
- The electric arc is generated by touching the tip of a
coated electrode against the workpiece.
- Need to have a sufficient distance and movement to
maintain the arc.

26. Consumable Electrode
- The heat generated, melts a portion of the electrode tip,
its coating, and the base metal in the intermmediate arc
area.
- The molten metal consists of a mixture of the base metal
(work piece), the electrode metal, and substance from the
coating on the electrode; thus this mixture forms the weld
when it solidifies.
- The electrode coating deoxidizes the weld area and
provides a shielding gas to protect it from oxygen in the
environment.

27. Consumable Electrode
- The equipment consists of a power supply, cables and
electrode holder.
- Power supply: can be either DCor AC, ranges between 50 to
300A.
- For sheet metal welding, DC is preferred because of the
steady arc produces.

28. Shielded Metal-Arc Welding

29. Consumable Electrode
ii) SUBMERGED-ARC WELDING (SAW)
- The weld arc is shielded by a granular flux consisting of
lime, silica, manganese oxide,calcium flouride.
- The flux is fed into the weld zone from a hopper by gravity
flow through a nozzle.
- The thick layer of flux completely cover s the molten metal
and it prevents from spatterand sparks.
- The flux also acts as a thermal insulator by promoting deep
penetration of heat into theworkpiece.

30. Consumable Electrode
- The consumable electrode is a coil of bare round wire 1.5 to
10 mm in diameter; andfed automatically through a tube
which is called welding gun.
- Electric current: range between 300 to 2000 A.
- Power supply: single or three phase power point; rating up
to 440V.
- Due to flux is a gravity fed type; therefore this welding
process is limited largely towelds into flat or horizontal
position.

31. Consumable Electrode
- Circular weld can be made on pipes or cylinders ²provided
that they are rotatedduring welding process.
-Suitable for carbon and alloy steel and stainless steel sheet
or plates.
- Welding speeds: as high as 5 m/min.

32. Submerged-Arc Welding

33. Consumable Electrode
iii) GAS METAL-ARC WELDING
- Also known as metal inert-gas (MIG).
- The weld area is shielded by an effectively inert atmosphere
of argon, helium, carbondioxide, or other various gas
mixtures.
- The temperatures generated are relatively low.
- Suitable only for thin sheets which is less than 6mm.

34. Consumable Electrode
-The consumable bare wire is fed automatically through a
nozzle into the weld arccontrolled by wire-feed drive motor.
-There are 3 types of GMAW process:
a)Spray transfer.
b)Globular transfer.
c)Short circuiting.

35. Gas Metal-Arc Welding

36. Types of Gas-Metal Arc Process
a) SPRAY TRANSFER
- Small size of molten metal droplets from the electrode
are transferred to the weld area at a rate of several
hundred droplets per second.
- The transfer is spatter free and very stable.
- Using high DC current and voltages with large diameter
of electrodes.
 - The electrodes are used with argon or an argon rich gas
mixture act as a shielding gas.

37. Types of Gas-Metal Arc Process
b) GLOBULAR TRANSFER
- Utilizes with carbon-dioxide-rich gases, and globules are
propelled by the forces of the electric-arc transfer of a
metal, resulting in considerable spatter.
- High welding current are used - greater weld penetration
and higher welding speed
c) SHORT CIRCUITING
- The metal is transferred in individual droplets, as the
electrode tip touches the molten weldmetal and short
circuits.
- Low currents and voltages are utilized.
- Electrodes are made from small-diameter wire.
- Power required: § 2 kW.

38. Consumable Electrode
iv) ELECTRON BEAM WELDING
- Can be welded almost any metal; butt or lap welded and
the thicknesses up to 150mm.
- The thickness of the workpiececan range from foil to plate.
- Generally, there is no involvement of shielding gas, flux, or
filler metal.
- Distortion and shrinkage in the weld area is minimal.
- Heat is generated by high velocity narrow-beam electrons.
- Capacity of electron guns range up to 100 kW.

39. Consumable Electrode
- The kinetic energy of the electrons is converted into heat
as they strike the workpiece.
- Required special equipment to focus the beam on
the workpiece, typically in vacuum.
- The higher the vacuum, the more the beam penetrates, and
the greater is the depth-to width ratio, range between 10
and 30.
- Sizes of the welds are much smaller compared to
conventional process.
- Parameters can be controlled accurately at welding speeds
as high as 12 m/min; thiscan be done by using automation
and servo motor.

40. Consumable Electrode
v) LASER-BEAM WELDING
- Utilizes a high power laser beam as the source of heat.
- The beam can focused onto a very small area, and due to
this it has high energy density and deep penetrating capability.
- This process is suitable for welding deep and narrow joints
with depth-to-width ratios ranging from 4 to 10.
- The laser beam may be pulsed for a application such as the
spot welding of thinmaterials with power level up to 100 kW.

41. Consumable Electrode
- Minimum shrinkage and distortion, good strength and
generally are ductile and free ofporosity.
- Can be automated to be used on a variety of materials
with thicknesses up to 25mm.
- Typical metals and alloys welded:
aluminum, titanium, ferrous metals, copper.
- Welding speeds: range from 2.5 m/min to as high as 80
m/min for thin metals.

42. Consumable Electrode
Advantages of LBW over EBW:
Laser beams can be shaped, manipulated, and focused
optically by using fiber optics, therefore the process can be
automated easily. The beams do not generate x-rays.
The quality of the weld is better than in EBW with less
tendency for incomplete fusion, spatter, porosity, and less
distortion.
Example of laser Welding: laser welding of razor blades

43. SOLID STATE WELDING PROCESSES
• Forge Welding
• Cold Welding
• Roll Welding
•Hot pressure Welding
•Diffusion Welding
•Explosion Welding
•Friction Welding
•Ultrasonic Welding

44. Forge Welding
- Welding process in
which components to be joined are heated to hot working tem
perature range and then forged together by hammering or si
milar means
- Historic significance in development of manufacturing
Technology
- Process dates from about 1000 B.C., When blacksmiths
learned to weld two pieces of metal
- Of minor commercial importance today except for its
variants

45. Roll Welding (ROW)
- SSW process in which pressure sufficient to cause coalescen
ce is applied by means of rolls, either with or without external
heat
- Variation of either forge welding or cold welding, depending
on whether heating of work parts is done prior to process
- If no external heat, called cold roll welding
- If heat is supplied, hot roll welding

46. Roll Welding

47. Roll Welding Application
- Cladding stainless steel to mild or low alloy steel for
corrosion resistance
-Bimetallic strips for measuring temperature
- “Sandwich" coins for U.S mint

48. Diffusion Welding (DFW)
- SSW process uses heat and pressure, usually in a controlled
atmosphere, with sufficient time for diffusion and coalescence
to occur
- Plastic deformation at surfaces is minimal
- Primary coalescence mechanism is solid state diffusion
- Limitation: time required for diffusion can range from seconds
to hours

49. DFW Applications
- Joining of high-strength and refractory metals in
aerospace and nuclear industries
- Can be used to join either similar and dissimilar metals
-For joining dissimilar metals, a filler layer of different
metal is often sandwiched between base metals to
promote diffusion

50. Explosion Welding (EXW)
- SSW process in which rapid coalescence of two metallic
surfaces is caused by the energy of a detonated explosive
-No filler metal used
-No external heat applied
- No diffusion occurs -time is too short
-Bonding is metallurgical, combined with mechanical
interlocking that results from a rippled or
wavy interface between the metals

51. Explosive Welding
-Commonly used to bond two dissimilar metals, in particular t
o clad one metal on top of abase metal over large areas

52. Friction Welding (FRW)
- SSW process in which coalescence is achieved by frictional
heat combined with pressure
- When properly carried out, no melting occurs at faying
surfaces
- No filler metal, flux, or shielding gases normally used
- Process yields a narrow HAZ
- Can be used to join dissimilar metals
- Widely used commercial process, amenable to automation
and mass production

53. Friction Welding

54. Application and Limitation of FRW
Applications:
- Shafts and tubular parts
- Industries: automotive, aircraft, farm equipment,
petroleum and natural gas
Limitations:
- At least one of the parts must be rotational
- Flash must usually be removed
Upsetting reduces the part lengths (which must be taken
into consideration in product design)

55. Ultrasonic Welding (USW)
-Two components are held together, oscillatory shear
stresses of ultrasonic frequency are applied to interface to
cause coalescence
- Oscillatory motion breaks down any surface films to allow
intimate contact and strong metallurgical bonding between
surfaces
- Although heating of surfaces occurs, temperatures are
well below Tm
-No filler metals, fluxes, or shielding gases
- Generally limited to lap joints on soft materials such as
aluminum and copper

56. Ultrasonic Welding

57. USW Applications
- Wire terminations and splicing in electrical and electronics
industry
- Eliminates need for soldering
- Assembly of aluminum sheet metal panels
- Welding of tubes to sheets in solar panels
Assembly of small parts in automotive industry

58. Weldability
- Capacity of a metal or combination of metals to be
welded into a suitably designed structure, and for the
resulting weld joint(s) to possess the required
metallurgical properties to perform satisfactorily in intended
service
Good weldability characterized by:
- Ease with which welding process is accomplished
-Absence of weld defects
Acceptable strength, ductility, and toughness in
welded joint