Projection Welding

1
Projection Welding
2
Projection Welding

• Learning Activities
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• Do on-line workbook

• Lesson Objectives
• When you finish this lesson you will understand
• The advantages and limitation of projection
  welding
• Projection design for various thickness
  materials
• Typical Applications of the process

Keywords Projection Welding, Projection Design,
Thin Material Projections, Thick Material
Projections
3
Introduction to Projection Welding
(a) (b) (c) (d)
Reference Welding Handbook, Volume 2, p.566,
AWS
4
Examples of Various Projection Designs
(a)
(b)
(c) (d) (e)
Reference Welding Handbook, Volume 2, p.562,
AWS
5
Examples of Various Projection Designs (CONT.)
(f) (g) (h)
(i) (j)
Reference Welding Handbook, Volume 2, p.562,
AWS
6
Considerations for Various Materials

• Mild and HSLA Steels
• Both are considered readily projection weldable.
• Both can adequately retain projection welding
  shape until adequate heating has occurred and are
  weldable using either embossed or solid
  projections.
• The HSLA steels may, depending on the particular
  composition, suffer an array of metallurgical
  problems.
• Galvanized Steels
• Projection welding can offer some major
  advantages in resistance welding galvanized
  steel.
• The relatively low contact resistance is a major
  concern.
• The use of a projection can put contact
  resistance back into the welding circuit directly
  at the faying surface. This, in turn, results in
  lower welding currents and possibly better
  electrode-life characteristics as compared to
  resistance spot welding.

7
Considerations for Various Materials (CONT.)

• Aluminum and Aluminum Alloys
• They are considered not projection weldable.
• Most aluminum alloys are of too low a strength to
  allow the projection to survive under the
  necessary welding forces.
• The oxide formed appears to prevent the
  solid-state bond necessary to form the type of
  joint.
• High Alloy Steels
• Projection welding is also quite readily
  applicable to the higher alloy steels.
• The major concern here is material hardenability.
  Adequate precautions must be taken to prevent
  the development of brittle microstructures.

8
Considerations for Various Materials (CONT.)

• Copper Alloys
• Projection welding has definite implied
  advantages for resistance welding copper and its
  alloys. Just as for the galvanized steels, the
  weld circuit resistance can be localized at the
  faying surface.
• Effective projection welding is largely a
  function of the specific copper alloy used.
• With respect to embossed projection welding, the
  suitability for welding appears to vary with the
  material strength level.
• Higher-strength copper alloys are relatively
  projection weldable. However, lower-strength
  alloys appear to have difficulty retaining
  projection shape under the applied welding force.
• Most copper alloys appear to be weldable with one
  or more forms of solid projection welding

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Advantages of Projection Welding

• Ease of obtaining satisfactory heat balance for
  welding difficult combinations
• More uniform results in many applications
• Increased output per machine because several
  welds are being made simultaneously
• Longer electrode life

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Advantages of Projection Welding (CONT.)

• Welds may be placed more closely together
• Parts are more easily welded in an assembly
  fixture
• Finish, or surface appearance, is often improved
• Parts may be projection welded that could not be
  otherwise resistance welded

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Limitations of Projection Welding

• Requires an additional operation to form
  projections
• Requires accurate control of projection height
  and precise alignment of the welding dies with
  multiple welds
• Requires thickness limitation for sheet metals
• Requires higher capacity equipment than spot
  welding

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Requirements for A Projection in Sheet Material

• Rigid enough to support the initial weld force
  before current is applied.
• Sufficient mass to raise a spot or weld nugget in
  the plane surface to welding temperature. If it
  is too small it will collapse before the other
  surface is heated.
• Collapse without extruding between the parts.
• Surfaces should be in intimate contact after
  welding.
• Not be partially sheared. Such projections are
  weak, tear out easily and are of low shear
  strength.
• Easy to form, so that the punch and die require
  little maintenance.
• Cause minimal distortion of the part during
  forming.

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Basic Projection Design in Steel Sheet
Punch Die
Spherical Radius
A
D
45
T
H
15
Projection Wall Thickness Should Be at Least
70 of Sheet Thickness
B
D
Point Radius R
Projection Should Blend into Stock Surface
without Shouldering
Reference Welding Handbook, Volume 2, p.563,
AWS
14
Bubble - Button Type Projections
(a) (c) (b) (d)
ltT
Reference Resistance Welding Manual, p.3-3,
RWMA
15
Projections for 0.500-in 0.250-in Stock
120
60
90
0.52
45
0.15
0.45
0.094
0.50
0.25
When the thickness is greater than 0.125-in, the
projection will not be completely forged back
Reference Resistance Welding Manual, p.3-4,
RWMA
16
Embossed Annular Projection
Reference Resistance Welding Manual, p.3-5,
RWMA
17
Punch Die Dimensions for Spherical Dome
Projections
Reference Welding Handbook, Volume 2, p.563,
AWS
18
Projection Types for Sheet and Solid Applications
Spherical Projections
Elongated Projections
Reference Metals Handbook, Volume 6 (Welding,
Brazing and Soldering), p.503-524, ASM
19
Projection Types for Sheet and Solid Applications
(CONT.)
Annular Projection on Pin-and-Tenon Joint
Annular Projections
Cross-Wire Weld
Pyramidal Projections
Reference Metals Handbook, Volume 6 (Welding,
Brazing and Soldering), p.503-524, ASM
20
Projection Welded Front Axle and Radiator Support
for Tractors
Reference Resistance Welding Manual, p.3-4,
RWMA