Physics of Projection Welding

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Physics of Projection Welding. Projection Physics. Learning Activities View Slides; Read Notes, Listen to lecture Do on-line workbook. Lesson Objectives When you finish this lesson you will understand: The collapse of the projection during welding

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Projection Physics

• Learning Activities
• View Slides;
• Listen to lecture
• Do on-line workbook
• Lesson Objectives
• When you finish this lesson you will understand:
• The collapse of the projection during welding
• Factors effecting the projection collapse

Keywords

Current Concentration, Projection Collapse

[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.
Effect of Weld Time

Tensile-Shear Strength

(lbs)

Nugget Diameter

Projection

Collapse

Weld Time (Cycles)

Weld Time (Cycles)

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]

Recommended Projection Designs

T(in.) D(in.) H(in.) L(in.)

0.010-0.014 0.055 0.015 1/8

0.016-0.020 0.067 0.017 5/32

0.025 0.081 0.020 3/16

0.031-0.034 0.094 0.022 7/32

0.044-0.050 0.119 0.028 9/32

0.062-0.070 0.156 0.035 3/8

0.078 0.187 0.041 7/16

0.094 0.218 0.048 1/2

0.109 0.250 0.054 5/8

0.125 0.281 0.060 11/16

0.140 0.312 0.066 3/4

0.156 0.343 0.072 13/16

0.171 0.375 0.078 7/8

0.187 0.406 0.085 15/16

0.203 0.437 0.091 1

0.250 0.531 0.110 1-1/4

T

L

H

D

T: Thickness of thinnest outside piece

D: Diameter of projection

H: Height of projection

L: Minimum contacting overlap

[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

Nugget

Expansion

Electrode

Position

Weld Cool

60 Cycle Timing Trace

[Reference: A study of projection welding, Welding Journal Research

Supplement, 27(12), p.712s-713s, Hess & Childs]

1000 lbs.

Weld Cool

Time

[Reference: A study of projection welding, Welding Journal Research

Supplement, 27(12), p.712s-713s, Hess & Childs]

Effect of Welding Current

20,000

30 cycles

45 cycles

60 cycles

15,000

Welding Current, Amps

10,000

[Reference: A study of

projection welding, Welding

Journal Research Supplement,

27(12), p.712s-713s, Hess &

Childs]

Projection: D = 0.40”

H = 0.027”

Electrode Force: 1500 lbs

5,000

0 0.25 0.50

Diameter of Fused Zone, in.

Relations between Weld Current, Weld Time and Weld Strength on 0.040-inch Thick Mild Steel

1500

Shear

Weld Strength, lbs

1000

Nominal Tension

[Reference: Further studies in

projection welding, Welding

Journal Research Supplement,

28(1), p.15s-23s, Hess & Childs]

500

Projection

D = 0.10”

H = 0.025”

Electrode Force

400 lbs

10 cycles

15 cycles

20cycles

4000 5000 6000 7000

Welding Current, Amps

Effect of Projection Shape

1500

Shear

1000

Weld Strength, lbs

Normal Tension

500

[Reference: Further studies in

projection welding, Welding

Journal Research Supplement,

28(1), p.15s-23s, Hess & Childs]

Projections Electrode Force

DHlbs

0.010” 0.025” 400

0.140” 0.025” 450

4000 5000 6000 7000

Welding Current, Amps

Effect of Electrode Material

RWMA Classification

Group B, Class 12

0.20

RWMA

Classification

Group A, Class 3

RWMA Classification

Group A, Class 2

Fused Zone Diameter, inches

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 Current:

No. of welds x 6340 Amps

Electrode Force:

No. of welds x 400 lbs

Weld Spacing: 0.75”

Weld Time: 15 cycles

4000

Shear

3000

Weld Strength, lbs

2000

[Reference: Further studies in

projection welding, Welding

Journal Research Supplement,

28(1), p.15s-23s, Hess & Childs]

1000

Normal Tension

0

0 1 2 3 4

Number of Welds

Variations in Projection Weld Hardness

Thickness: 0.125”

Weld Time: 45 cycles

400

1020

300

1015

Hardness, VPN

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

Projection:

D = 0.10”

H = 0.025”

Electrode Force:

400 lbs

1500

Shear

1000

Weld Strength, lbs

Normal Tension

500

[Reference: Further studies in

projection welding, Welding

Journal Research Supplement,

28(1), p.15s-23s, Hess & Childs]

AISI 1010

AISI 1015

AISI 1020

Weld Time:

15 cycles

0

4000 5000 6000 7000

Welding Current, Amps

Cold Projection Collapse

Annular : 0.110” Diam.

Spherical: 0.075” Diam.

Spherical: 0.085 Diam.

Spherical: 0.065 Diam.

0.020

Projection Height, inches

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]

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]

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]

Current Range Characteristics

0.020”-1010 Steel

Annular Projection

Height: 0.015”

Diameter: 0.110”

Weld Time: 6 cycles

Electrode Force: 225 lbs

0.20

Plug Diameter, inches

0.10

Spherical Projection

Height: 0.020”

Diameter: 0.075”

Weld Time: 6 cycles

Electrode Force: 150 lbs

0

2000 3000 4000 5000 6000

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]

Strength Characteristics

Spherical Projection

Height: 0.020” Diameter: 0.075”

Electrode Force: 75 lbs

Weld Time: 6 cycles Pickled in 50% HCl

Shear Strength

Normal Tension

0.020”-1010 Steel

200

100

Annular Projection

Height: 0.016”

Diameter: 0.077”

Electrode Force: 110lbs

Shear Strength

Normal Tension

0

1000 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

Annular Projection

Height: 0.015” Diameter: 0.110”

Weld Time: 6 cycles

Electrode Force: 110 lbs

Electrode Force: 130 lbs

Shear

200

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

Annular Projection

Height: 0.015”

Diameter: 0.110”

Shear

Normal Tension

Theoretical

1000

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 Light-Gauge Steels

0.010”

0.020”

0.040”

0.062”

0.125”

Projection

Diameter

in.

Sheet

Thickness

in.

Projection

Height

in.

Punch Top

Diameter

in.

Punch

Height

in.

30°

0.010 0.110 0.015

0.020 0.110 0.015

0.040 0.140 0.025 0.058 0.035

0.062 0.170 0.042 0.094 0.045

0.125 0.300 0.055 0.176 0.058

30°

30°

[Reference: The projection welding of 0.010 and 0.020 inch steel sheet,

Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken]

120°

60°

90°

0.52”

45°

0.15”

0.45”

0.094”

0.50”

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

0.60

0.50

Diameter

0.40

Projection Dimension, inches

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

Height

0.10

0 0.10 0.20

Current Force

Time

Current Force

Time

Nugget Vs. Current for Different Weld Times

0.8

0.6

Diameter, inches

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]

0.8

0.6

Diameter, inches

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

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

28

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]