Transcript No Slide Title

Physics of Projection Welding
Projection Physics
Lesson Objectives
When you finish this lesson you will
understand:
• The collapse of the projection during
welding
• Factors effecting the projection
collapse
Learning Activities
1. View Slides;
2. Read Notes,
3. Listen to lecture
4. Do on-line
workbook
Keywords
Current Concentration, Projection Collapse
Projection Welding of Low Carbon Steel (Two Equal Thicknesses)
[Reference: Resistance Welding Manual, p.3-13, RWMA]
Functions of Electrode Force

The electrode force must hold the projection firmly against the
mating part during the initial period of “weld time” where the current
density is high and the collapse rate is rapid.

The electrode force must cause complete collapse after welding, so
the resulting sheet separation is minimized.

The electrode force has a major influence on the degree of porosity
in the weld nugget. It must be low enough to give proper projection
collapse without metal expulsion and yet high enough to produce
comparatively sound welds.

The suitable dynamic force characteristic must prevail without
producing excessive initial impact force.
Tensile-Shear Strength
(lbs)
Effect of Weld Time
4500
Nugget Diameter
4000
3500
3000
2500
2000
1500
1000
500
Projection
Collapse
Weld Time (Cycles)
0
0
1
4
6
10
12
Weld Time (Cycles)
16
20
Factors Affecting Heat Balance
• Projection Design
• Part Thickness
• Die Material Backing up
the Weld
• Metal Conductivity
• Heating Speed
Projection Weld Formation
Stage 1
Stage 3
Stage 2
Stage 4
[Reference: Resistance Welding Manual, p.3-9, RWMA]
Projection Weld Formation
(CONT.)
Stage 5
Stage 7
Stage 6
Stage 8
[Reference: Resistance Welding Manual, p.3-9, RWMA]
Link to projection weld video
Recommended Projection
Designs
T
L
H
D
T:
D:
H:
L:
Thickness of thinnest outside piece
Diameter of projection
Height of projection
Minimum contacting overlap
T(in.)
D(in.)
H(in.)
L(in.)
0.010-0.014
0.016-0.020
0.025
0.031-0.034
0.044-0.050
0.062-0.070
0.078
0.094
0.109
0.125
0.140
0.156
0.171
0.187
0.203
0.250
0.055
0.067
0.081
0.094
0.119
0.156
0.187
0.218
0.250
0.281
0.312
0.343
0.375
0.406
0.437
0.531
0.015
0.017
0.020
0.022
0.028
0.035
0.041
0.048
0.054
0.060
0.066
0.072
0.078
0.085
0.091
0.110
1/8
5/32
3/16
7/32
9/32
3/8
7/16
1/2
5/8
11/16
3/4
13/16
7/8
15/16
1
1-1/4
[Reference: Recommended practice for resistance welding, AWS
Document C1.1-66, AWS, 1966]
Effect of Welding Time
Stage 1
Stage 5
Stage 2
Stage 6
Stage 3
Stage 7
Stage 4
Stage 8
[Reference: Resistance Welding Manual, p.3-9, RWMA]
Variation in Weld Head Position
during Projection Welding 0.062-inch
Thick
Steel
Initial Collapse
Final Collapse
Current
Electrode
Position
Nugget
Expansion
Weld
60 Cycle Timing Trace
[Reference: A study of projection welding, Welding Journal Research
Supplement, 27(12), p.712s-713s, Hess & Childs]
Cool
Variation in Weld Force during
Projection Welding 0.125-inch Thick
Steel
1000 lbs.
Weld
Time
[Reference: A study of projection welding, Welding Journal Research
Supplement, 27(12), p.712s-713s, Hess & Childs]
Cool
Effect of Welding Current
Welding Current, Amps
20,000
30 cycles
45 cycles
60 cycles
15,000
10,000
D = 0.40”
H = 0.027”
Electrode Force: 1500 lbs
Projection:
5,000
0
0.25 0.50
Diameter of Fused Zone, in.
[Reference: A study of
projection welding, Welding
Journal Research Supplement,
27(12), p.712s-713s, Hess &
Childs]
Relations between Weld Current, Weld
Time and Weld Strength on 0.040-inch
Thick Mild Steel
Weld Strength, lbs
1500
Shear
1000
Nominal Tension
500
Projection
10 cycles
15 cycles
20cycles
4000
5000
D = 0.10”
H = 0.025”
Electrode Force
400 lbs
6000
7000
Welding Current, Amps
[Reference: Further studies in
projection welding, Welding
Journal Research Supplement,
28(1), p.15s-23s, Hess & Childs]
Effect of Projection Shape
Weld Strength, lbs
1500
Shear
1000
Normal Tension
500
Projections
D
H
0.010” 0.025”
0.140” 0.025”
4000
5000
Electrode Force
lbs
400
450
6000
Welding Current, Amps
7000
[Reference: Further studies in
projection welding, Welding
Journal Research Supplement,
28(1), p.15s-23s, Hess & Childs]
Fused Zone Diameter, inches
Effect of Electrode Material
RWMA Classification
Group B, Class 12
0.20
RWMA
Classification
Group A, Class 3
RWMA Classification
Group A, Class 2
0.10
Weld Time: 15 cycles
0
4000
5000
6000
7000
Welding Current, Amps
[Reference: Further studies in projection welding, Welding
Journal Research Supplement, 28(1), p.15s-23s, Hess & Childs]
Effect of Weld Spacing on
Nugget Development
(a) 1-in. Spacing
(b) 3/4-in. Spacing
(c) 1/2-in. Spacing
[Reference: A study of projection welding, Welding Journal Research
Supplement, 27(12), p.712s-713s, Hess & Childs]
Additive Effect of Projection Weld
Strengths for Multiple Welded
Assemblies
Projection:
D = 0.10”
H = 0.025”
AISI 1010
AISI 1015
AISI 1020
Weld Strength, lbs
4000
3000
Shear
Weld Current:
No. of welds x 6340 Amps
Electrode Force:
No. of welds x 400 lbs
Weld Spacing: 0.75”
Weld Time: 15 cycles
2000
1000
Normal Tension
0
0
1
2
3
4
Number of Welds
[Reference: Further studies in
projection welding, Welding
Journal Research Supplement,
28(1), p.15s-23s, Hess & Childs]
Variations in Projection Weld
Hardness
400
Thickness: 0.125”
Weld Time: 45 cycles
Hardness, VPN
1020
300
1015
1010
200
Fused Zone
100
0
0.25
0.50
0.75
1.00
Distance across Weld, inches
[Reference: A study of projection welding, Welding Journal Research
Supplement, 27(12), p.712s-713s, Hess & Childs]
Effect of Material Hardenability
on Weld Strength
Weld Strength, lbs
1500
Shear
1000
Projection:
D = 0.10”
H = 0.025”
Electrode Force:
400 lbs
Normal Tension
500
0
4000
Weld Time:
15 cycles
5000
6000
AISI 1010
AISI 1015
AISI 1020
7000
Welding Current, Amps
[Reference: Further studies in
projection welding, Welding
Journal Research Supplement,
28(1), p.15s-23s, Hess & Childs]
Projection Height, inches
Cold Projection Collapse
Annular : 0.110” Diam.
Spherical: 0.075” Diam.
Spherical: 0.085 Diam.
Spherical: 0.065 Diam.
0.020
0.010
0
0
100
200
300
Electrode Force, lbs
[Reference: The projection welding of 0.010 and 0.020 inch steel sheet,
Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken]
Nugget Development Using Spherical
Projections for 0.020-in. Thick Steel
3760 Amps
4950 Amps
4260 Amps
5330 Amps
[Reference: The projection welding of 0.010 and 0.020 inch steel sheet,
Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken]
Nugget Development Using Annular Projections
for 0.020-in. Thick Steel
4740 Amps
5100 Amps
5520 Amps
5940 Amps
[Reference: The projection welding of 0.010 and 0.020 inch steel sheet,
Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken]
Plug Diameter, inches
Current Range Characteristics
0.20
0.020”-1010 Steel
Annular Projection
Height: 0.015”
Diameter: 0.110”
Weld Time: 6 cycles
Electrode Force: 225 lbs
0.10
0
2000
Spherical Projection
Height: 0.020”
Diameter: 0.075”
Weld Time: 6 cycles
Electrode Force: 150 lbs
3000
4000
5000
Weld Current, Amps
[Reference: The projection welding of 0.010 and 0.020 inch steel sheet,
Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken]
6000
Strength Characteristics
0.020”-1010 Steel
Load, lbs
200
Spherical Projection
Height: 0.020”
Diameter: 0.075”
Electrode Force: 75 lbs
Weld Time: 6 cycles Pickled in 50% HCl
Shear Strength
Normal Tension
100
0
1000
Annular Projection
Height: 0.016”
Diameter: 0.077”
Electrode Force: 110lbs
Shear Strength
Normal Tension
2000
3000
4000
Welding Current, Amps
[Reference: The projection welding of 0.010 and 0.020 inch steel sheet,
Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken]
Effect of Weld Force on Strength
Characteristics
Load, lbs
Annular Projection
Height: 0.015”
Diameter: 0.110”
Weld Time: 6 cycles
200 Electrode Force: 110 lbs
Electrode Force: 130 lbs
Shear
Normal Tension
100
0.020”-1010 Steel
0
2000
3000
4000
5000
6000
Welding Current, Amps
[Reference: The projection welding of 0.010 and 0.020 inch steel sheet,
Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken]
Projection Welding Schedule of
Light-Gauge Steels
[Reference: Resistance Welding Manual, p.3-13, RWMA]
Additive Effect of Multiple Projection
Welds
Load, lbs
Annular Projection
Height: 0.015”
Diameter: 0.110”
1000 Shear
Normal Tension
Theoretical
0.020”-1010 Steel
500
Weld Time: 6 cycles
Weld Current: 5200 Amps/weld
Weld Pressure: 225 lbs/weld
0
0
1
2
3
4
Number of Welds
[Reference: The projection welding of 0.010 and 0.020 inch steel sheet,
Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken]
Projection Design for LightGauge Steels
0.010”
0.020”
0.040”
30°
0.062”
30°
30°
Sheet Projection Projection Punch Top Punch
Thickness Diameter
Height
Diameter Height
in.
in.
in.
in.
in.
0.010
0.020
0.040
0.062
0.125
0.110
0.110
0.140
0.170
0.300
0.015
0.015
0.025
0.042
0.055
0.058
0.094
0.176
0.125”
[Reference: The projection welding of 0.010 and 0.020 inch steel sheet,
Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken]
0.035
0.045
0.058
Typical Embossed Projection Design for
Heavy-Gauge Steel Sheets
120°
60°
0.15”
0.52”
45°
0.094”
0.50”
90°
0.45”
0.25”
[Reference: Resistance Welding Manual, p.3-4, RWMA]
Recommended Projection Geometries and
Punch & Die Design for Heavy-Gauge
Steel Sheets
[Reference: Resistance Welding Manual, p.3-15, RWMA]
Projection Dimensions Vs. Sheet
Thickness
Projection Dimension, inches
0.60
0.50
0.40
Diameter
0.30
[Reference: Projection welding of steel
in heavy gauges and in dissimilar
thicknesses, Welding Journal Research
Supplement, 31(3), p.113s-125s,
Nippes & Gerken]
0.20
0.10
0
Height
0.10
0.20
Current
Force
Electrode Force and Current Sequence
for Heavy-Gauge Steel Sheets
Time
Current
Force
Electrode Force and Current Sequence for
Heavy-Gauge Steel Sheets (CONT.)
Time
Nugget Vs. Current for Different Weld
Times
Diameter, inches
0.8
0.6
Weld Time: 150 cycles
Weld Time: 200 cycles
Weld Time: 250 cycles
Weld Time: 300 cycles
0.4
20,000
22,000
24,000
26,000
28,000
30,000
Welding Current, Amps
[Reference: Projection welding of steel in heavy gauges and in dissimilar
thicknesses, Welding Journal Research Supplement, 31(3), p.113s-125s,
Nippes & Gerken]
Nugget Size Vs. Welding Current for
Different Electrode Forces
Diameter, inches
0.8
0.6
0.4
Electrode Force: 3000 lbs
Electrode Force: 4000 lbs
Electrode Force: 5000 lbs
20,000
22,000
24,000
26,000
28,000
30,000
Welding Current, Amps
[Reference: Projection welding of steel in heavy gauges and in dissimilar
thicknesses, Welding Journal Research Supplement, 31(3), p.113s-125s,
Nippes & Gerken]
Weld Strength Vs. Welding Current
Load, lbs x 102
28
Two step current start, total weld time
250 cycles 20 cycles for each step
225 cycles weld time, forge force applied
for first 25 cycles and end of weld
24
Shear Strength
20
16
Normal Strength
12
8
15,000
20,000
25,000
30,000
Welding Current, Amps
[Reference: Projection welding of steel in heavy gauges and in dissimilar
thicknesses, Welding Journal Research Supplement, 31(3), p.113s-125s,
Nippes & Gerken]