This document provides an overview of Welding Technology I course contents including: 1) An introduction to Shielded Metal Arc Welding (SMAW) and the classifications, symbols, equipment, and safety associated with welding. 2) Details on welding processes, how to read welding blueprints, and define welding symbols and their components such as size, length, contour, and other specifications. 3) A review of common welding equipment including welding machines, cables, electrode holders, and tools like chipping hammers and wire brushes. 4) A discussion of welding safety and the importance of developing safe habits through repetition of safety regulations and proper use of personal protective equipment.

1. Welding Technology I
MAT 113
Chapter one
Introduction to Welding

2. Course Contents
1. Introduction to Shielded Metal Arc Welding (SMAW)
1.1. Introduction to Welding
1.2. Classifications of Welding
1.3. Welding Symbols and Blue Print Reading
1.4. Welding Equipment & Tools
1.5. Welding Safety

3. 1.1. Introduction to Welding

4. Introduction
• Manufacturing technology primarily involves
sizing, shaping and imparting desired
combination of the properties to the material
so that the component or engineering system
being produced to perform indented function
for design life.
welding technology 4

5. Cont”
welding technology 5

6. Joining and Fastening Processes
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7. Cont”
Selection of suitable manufacturing process
– Complexity of geometry of the component,
– Number of units to be produced,
– Properties of the materials (physical, chemical,
mechanical and dimensional properties) to be
processed and
– economics.
welding technology 7

8. Welding
• Welding is a process of joining two similar or dissimilar
metals by fusion,
– with or with out the application of pressure,
– and with or with out use of filler metal.
• The fusion of metal take place by heat.
• Welding is used for making permanent joints
• The heat may be obtained from:
– Electric arc,
– Electric resistance,
– Chemical reaction,
– Friction or
– Radiant energy

9. Cont”
• It is used in the manufacture of automobile
bodies, aircraft frames, railway wagons,
machine frames,
 Many buildings and bridges are fabricated by
welding.
 Welding also used for the manufacture and
repair of mining and oil machinery,

10. 1.2. Classification of Welding Processes
 Depending upon the combination of
temperature and pressure from a high
temperature with no pressure to a high pressure
with low temperature, a wide range of welding
processes has been developed

11. Based on the pressure
1. Plastic Welding or Pressure Welding
• The piece of metal to be joined are heated to
a plastic state and forced together by external
pressure. Eg. Resistance welding
2. Fusion Welding or Non-Pressure Welding
• The piece of metal to be joined are heated to
a molten state and allowed to solidify. Eg.
Gas welding, Arc welding.
Cont”

12.  Based on the source of energy
I. Arc welding
a. Metal arc welding
b. Metal inert gas welding
c. Tungsten inert gas welding
d. Plasma arc welding
e. Submerged arc welding
II. Gas Welding
a. Oxy-acetylene welding
b. Oxy-hydrogen welding
c. Air-acetylene welding
Cont”

13. III. Resistance Welding
 Spot welding
 Seam welding
 Projection welding
IV. Solid State Welding
a. Friction welding
b. Ultrasonic welding
c. Diffusion welding
d. Explosive welding
V. Newer (Radiant Energy) Welding
a. Electron-beam welding
b. Laser welding
Cont”

14.  There are no hard and fast rules, which govern
the type of welding that is to be used for a
particular job.
 In general, the controlling factors are
- Kind of metals to be joined,
- Costs involved,
- Nature of products to be fabricated, and
- Production techniques.
Selection of the proper welding process

15. Cont”
Advantage of welding
 A good weld is as strong as the base metal
 A large number of metals/ alloys can be joined by welding
 Repair by welding is very easy
 Welding can be easily mechanized
 Portable welding equipment is available
 General welding equipment is not very costly
Disadvantage of welding
 Welding produces the harmful radiation, fumes and spatter
 A skilled welder is required
 Welding heat produces metallurgical changes
 Cost of equipment (initial cost) is high
 Edge preparation is required before welding
 More safety devices are required

16.  Drawings or sketches are used to convey the ideas of an
engineer to the skilled craftsman working in the shop.
 As a welder, you must be able to work from a drawing in
order to fabricate metal parts exactly as the engineer has
designed them.
 Many of the different types of lines & symbols that are
used in drawings help for blueprint reading in doing
welding.
1.3. Welding Symbols and Blue Print Reading

17.  In the AWS system a complete welding symbol consists
of the following elements:
a. Reference line (always shown horizontally)
b. Arrow
c. Basic weld symbol
d. Dimensions and other data
e. Supplemental symbols
f. Finish symbols
g. Tail
h. Specification process or other references.
Cont”

18. Cont”
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19.  The basic welding symbol consists of a reference line, a
leader line and arrow, and, (a tail).
 The tail is added for specific information or notes in regard
to welding specifications, processes or reference information.
Cont”

20.  Any welding symbol placed on the upper side of the
reference line indicates weld opposite side.
 Any welding symbol placed on the lower side of the
reference line indicates weld arrow side.
Figure 1.3. Placing of welding symbol
Cont”

21. Figures 1.5. Opposite side Figure 1.6. Arrow side
 Welding symbol placed above and below the reference line means
to weld both sides
Figure 1.7. Welding symbol placed above and below the reference line

22. Size of weld
 The weld must be fully dimensioned
 The size of a weld refers to the length of the leg or side of
the weld.
 The size is placed directly to the left of the welding
symbol,
 The two legs are assumed to be equal in size unless
otherwise dimensioned
Cont”

23.  If a double weld is needed, the size of each weld must be
included.
Figure 1.9. Size of double weld
Cont”

24.  If the legs or sides of the weld are to be different, the dimensions of
the sides must be indicated to the left of the welding symbol
 Because the symbol does not indicate which the 50 leg is and
which is the 25 Figure 1.10, the detail drawing must include the
dimensions.
Figure 1.10. Drawing must include the dimensions
Cont”

25. Length of weld
 If a weld must be made to a special length, it must be
indicated.
 This is done by a dimension directly to the right of the
weld symbol.
Figure 1.11. A dimension for length of weld
Cont”

26. Figure 1.12. Dimension to show length of weld
Cont”

27. Figure 1.13. All around weld
Cont”

28.  Abbreviations or letter designation are usually added to
the tail of the basic welding symbol.
Figure 1.14. Information in the tail of the welding symbol
Cont”

29. Contour symbol
 If a special finish must be made to a weld, a contour
symbol must be added to the welding symbol.
 There are three kinds of contour symbols used:
Figure 1.15. Kinds of contour symbols

30.  The contour symbol is added directly above or below the welding
symbol.
 If the welding symbol is above the reference line, the contour
symbol is placed above the welding symbol.
 If the welding symbol is placed below the reference line, the
contour symbol is placed below the welding symbol.
Figure 1.16. Flush contour symbol
Cont”

31.  Finish weld must be concave and ground to a 0.125 µm
(micrometers) surface finish.
Figure 1.17. Finish number designation
Cont”

32. Figure 1.18. Showing finished weld
Cont”

33.  Figure 1.19, represents that the finish weld must be
machined flat on the top surface to a surface finish of
0.125 µm.
 The weld must be convex on the bottom surface with a
hammered finish.
Figure 1.19. Showing machined & hammered finish weld

34.  The depth or actual size of the weld includes the
penetration of the complete weld.
Figure 1.20. Actual weld & groove size of the weld
Depth or actual size of weld

35.  The depth or actual size of the weld is deeper than the depth of
the chamfer.
 Occasionally, the depth or actual size of the weld is less than the
size of the chamfer.
Figure 1.21. Example for the depth or actual size of the weld
Cont”

36.  In order to show the depth or actual size of the weld and the size or
chamfer of groove, a dual dimension is used and both are added to
the left of the welding symbol.
 In order to differentiate between the two, the size or chamfer of
groove is added to the extreme left of the welding symbol.
 The size of the depth or actual size of the weld is added directly to
the left of the welding symbol, but in parentheses.
Figure 1.22. A dual dimension

37.  Usually the weld is larger than the groove.
Figure 1.23. Groove size as welded

38.  If the weld is less than the size of the chamfer, the
dimensions are added to the left of the welding symbol
in the exact same manner.
Figure 1.24. Weld less than the size of the chamfer

39. Root Opening
 The allowed space between parts is called root opening
Figure 1.25. Root opening
 The root opening is applied the welding symbol.
Figure 1.26. Welding symbol for different Root opening

40. Chamfer Angle
 In a groove weld, a V or bevel groove must be held to tight
tolerances, the angle must also be included with the size dimension
in order to obtain exact required geometric size and shape of all
manufactured parts.
 The angle is also added inside the welding symbol. Note that the
leader line and arrow point toward the part with the chamfer.
 Because the welding symbol is place above the reference line, the
chamfer and weld are on the side opposite from the arrow.
Figure 1.27. Chamfer angle included with the size dimension

41. Groove Radius
 If a J or U groove weld held to tight tolerances, the angle
and radius must be included with the size dimensions in
order to obtain the exact required geometric size and
shape of all manufactured parts.
 The angle is also added inside the welding symbol and
the required radius is called-off as a note.
 Note that the leader line and arrow point toward the part
with the groove.
 Because the welding symbol is placed below the
reference line, the groove and weld is on the side of the
arrow.

42. Figure 1.28. Welding symbol for angle and radius of groove
Cont”

43. Back & Melt through Weld
 A back weld is a weld applied to the opposite side of the
joint after the major weld has been applied.
 A backing weld is a weld applied first, followed by the
major weld.
 Both use the same welding symbol and both are to
strengthen a weld. The back weld is also used for
appearance.
 If a welding melt through is required, the same symbol
is used, except it is filled in solid.

44. Figure 1.29. Back & Melt through Weld
Surface Weld
 If a surface must have material added to it or built-up, a surface
weld is added.
 This welding symbol is not used to indicate the joining parts
together; therefore, the welding symbol is simply added below the
reference line.
Figure 1.30. Welding symbol for surface weld

45. Size of Surface Weld
 If the surface is to be built-up and a special height is not
required, the welding is drawn as illustrated in Figure
1.30.
 If the surface is to be built-up and a specific height is
required, the required height is added directly to the left
of the welding symbol.
Figure 1.31. Size of surface weld

46.  Arc welding equipments are the basic equipment used
for joining two or more work pieces together.
 This equipment are; -
 Welding machines
 Welding cables
 Electrode holders
 Ground clamps
1.4. Welding Equipment & Tools

47.  Arc welding machines are equipments that provide
current to produce an electric arc when the electrode is
struck on the work pieces.
 The three basic types of arc welding machines are;
1. The generator (engine driven) DC welding machines
2. The transformer (AC) welding machines
3. The rectifier welding machines
 Arc welding machines are classified as either AC or DC.
 DC welding machines may be motor driven generators, or
rectifier welders.
Cont”

48.  Arc welding cables: two cables of to carry the current from
the welder to the work and back to the welder.
 The ground cable is attached to the work pieces or table and
the other cable is attached to the electrode holder.
Figure 1.35. Arc welding cable
Cont”

49.  It is important to use the correct diameter cable specified
for the welding machine.
 If the cable is too small for the current, it overheats and
power is lost.
 A larger cable is necessary to carry a required voltage any
distance from the machine.
Cont”

50.  Proper ground connections can be made in several ways.
Figures 1.36. A proper ground connection.
Figures 1.37. A removable ground clamp
Cont”

51.  Electrode Holder:. is a handle-like tool attached to the cable
that holds the electrode during welding.
Figure 1.38. The electrode holder.
Cont”

52.  Chipping hammer: is used to remove the slag from the
weld. It has two striking ends, a pointed end and a flat
end that runs parallel to the handle.
Cleaning Tools:
Figure 1.39. Chipping hammers

53. 2. Wire brushes: are used to clean the work piece and for
further cleaning of the weld bead.
• This helps to expose any blowholes that might need to
be refilled.
Figure 1.40. Wire brush
Cont”

54. 3. Tongs: are used for holding and picking up hot metals
in welding.
Cont”
Figure 1.41. Close mouth tong

55. 1.5. Welding Safety
 Have you ever heard the saying "some people are
accident-prone"?
 The implication is that accidents just seem to follow some
individuals no matter what they do.
 They just seem plagued with bad luck. Actually, there is
no such thing as being accident-prone.
 People have accidents simply because they are careless,
or indifferent to safety regulations.
 In many ways, safety can be considered a habit, a kind of
behavior. A habit is acquired; you are not born with it.
 It is the result of repetition - doing something over and
over again until it becomes part of you.

56. Arc Welding PPE

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58. welding technology 58