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Seam Welding
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Seam Welding
Lesson Objectives
When you finish this lesson you will
understand:
The various forms of seam welding
Nugget formation mechanisms
Quality testing of Seam Welds
Learning Activities
1. View Slides;2. Read Notes,
3. Listen to lecture
4. Do on-line
workbook
5. Homework
Keywords
Roll Spot Weld, Overlapping Seam Weld, Continuous Seam Weld,Lap Seam Weld, Mash Seam Weld, Metal Finish Seam Weld, Butt
Seam Weld, Foil Butt Seam Weld, Projection Seam Weld, Weld
Current-Pulse Time, Welding Speed, Overlap Distance, Nugget
Formation, Seam Weldability, Pillow Test
http://we019.eng.ohio-state.edu/wenc/wenc.cfmhttp://www-iwse.eng.ohio-state.edu/we602A/workbook.htm8/13/2019 2c1 Seam Welding
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Introduction to Resistance Seam Welding
Upper Electrode Wheel
Workpiece
Lower Electrode Wheel
Throat
Knurl or Friction
Drive Wheel
Roll Spot Weld
Overlapping Seam
Weld
Continuous Seam
Weld
[Reference: Welding Handbook,Volume 2, p.553, AWS]
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Lap Seam Weld
Electrodes Overlapping
Weld
Nuggets
Travel
Front view Side View
[Reference: Welding Handbook, Volume 2, p.554, AWS]
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Effect of Weld Current and Pulse Timing
3 on, 2 off (60%) 4 on, 3 off (57%)
Resistance Welder Manufacturers Association Bulletin # 23
6 on, 5 off (54%)
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6 on, 5 off (54%)
75% 66% 60% 54% 50% 46% Heat
Effect of Cool Time (Heat %)
on Nugget Properties
Resistance Welder Manufacturers Association Bulletin # 23
@ 6 Cycle Heat
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Increased Electrode Force
increases nugget penetration
Increased Electrode Force causes
increase in nugget width whilereducing penetration, more
electrode cooling
Resistance Welder Manufacturers Association Bulletin # 23
Effect of Electrode Force
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Welding Speed
Resistance Welder Manufacturers Association Bulletin # 23
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Seam Welding Multiple Thickness Sheets
Resistance Welder Manufacturers Association Bulletin # 23
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Resistance Welder Manufacturers Association Bulletin # 23
Improper
selection of
Parameters
Leads to
Porosity in
Weld
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Mash Seam WeldSlightly Lapped
Sheets Wide, Flat
Electrodes
Weld Nuggets
Before welding After Welding
[Reference: Welding Handbook, Volume 2, p.554, AWS]
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Effect of Sheet Overlap on
Mash Lap Joint properties
Resistance Welder Manufacturers
Association Bulletin # 21
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Resistance Welder Manufacturers
Association Bulletin # 21
Effect of Electrode Force
on Mash Seam Weld
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Metal Finish Seam WeldChamfered
Electrode
Broad, Flat
Electrode
Flash
Finish
Side
Before Welding After Welding
[Reference: Welding Handbook, Volume 2, p.554, AWS]
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Effect of Weld Current
and Electrode Force on
Finish Seam Welds
Resistance Welder Manufacturers Association Bulletin # 24
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Effect of Current on Metal
Finish Seam Weld
Resistance Welder Manufacturers
Association Bulletin # 21
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Resistance Welder Manufacturers Association Bulletin # 24
Recommended
Sheet
Positioning
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Porter, Galvanizing and welding structural steel,
Metal Construction, Nov 1983
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ASM Handbook Vol6, 1993
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Nugget Formation in Continuous Seam Weld
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Waddell, Mechanism of weld formation,
Welding and Metal Fabrication, Aug 1995
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Waddell, Mechanism of weld formation,
Welding and Metal Fabrication, Aug 1995
12
3 4Stage 1 Takes 1 - 4
cycles, Increased
resistance due to
increased temp
outweighs reduction in
resistance due to better
surface contact throughasperity softening and
surface oxide
breakdown
Peak occurs earlierwith thinner
materials
Resistance Curve for Establishment
of Leading Edge of a Continuous Nugget
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Waddell, Mechanism of weld formation,
Welding and Metal Fabrication, Aug 1995
12
3 4Stage 2 Drop in
resistance because ofcurrent shunting into
the mushy and solid
state bonded region
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Waddell, Mechanism of weld formation,
Welding and Metal Fabrication, Aug 1995
12
3 4
Stage 3 Instability in
current path, nugget
approaching a steadystate growth mode
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Stage 1Stage 2 Stage 3
Nugget Initiates Nugget Moves
Toward ExitApproaching
Steady State
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Waddell, Mechanism of weld formation,
Welding and Metal Fabrication, Aug 1995
12
3 4Stage 4 Steady State
Growth of Nugget
until either expulsion
or current off time and
new nugget formation
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Actual Data(effect of Speed)
2 m/min
4 m/mim
Attorre, Heat Development in Resistance Seam Weld
Ironmaking and Steelmaking, 1996
Particular Interest in Steady State Region
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Waddell, Mechanism of weld formation,
Welding and Metal Fabrication, Aug 1995
Increased Current
Ahead of nugget
Less Heat Extractedthrough Electrode
Larger thru Sheet
Nugget Growth
At Higher Speed
At Lower Speeds
Through Sheet
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Waddell, Mechanism of weld formation,
Welding and Metal Fabrication, Aug 1995
2 m/min
6 m/min
16 m/min
Through Sheet
Nugget Growth
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S S
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Steady State Heat Flow Patterns(Examine HAZ in Front of Nugget Formation)
NuggetHAZ
Nugget
Nugget
HAZ
HAZ
Type A
Type B
Type C
EnterExit
Increased Speed
Length of Heat Zone
Unstable
Transition Pattern
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Welding Speed
HeatZo
neDistance 0.7 mm
1.2 mm
2.0 mm
Sheet Thickness
For Type A Pattern
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Waddell, Mechanism of weld formation,
Welding and Metal Fabrication, Aug 1995
2 m/min
10 m/min
At High Speeds,Current Flow and
Heat Generation
Extended to Sheet
Surface
Higher Speeds move from A to C
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LongitudinalTransverse
EnterEnd
Exit
End
Higher Speeds Result in Nugget Moving toward
Exit End and Expulsion on Exit
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Increased
Electrode
Force
Increased IndentationNugget Moves Back
Heat Zone Increases
Contact
Area
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Nugget Formation in Pulsed Welds
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ASM Handbook Vol6, 1993
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ASM Handbook Vol6, 1993
Schematic of seam weld.
Length of electrode footprint holds 3 welds
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ASM Handbook Vol6, 1993
RSW Certification Training Class, Boeing
Irregular nuggets
irregular pulses that does not give time for heat flow
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Time
Dynam
icResistance
Attorre, The influence of welding parameters on formation of solute bands,
Welding In the World, Vol37, 1996
Series of Overlapping Nuggets
Continuous
Seam Weld
Parameter (Lobe) Curves for Seam Weld
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Porter, Galvanizing and welding structural steel,
Metal Construction, Nov 1983
Pulsed Current Continuous CurrentNo Cooling BetweenPulses in Continuous
Therefore Lower Current
( )
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What About Coated Sheets?
R i t S W ld bilit f L C b
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Uncoated SteelHot-Dipped Galvanized
AWS Welding Handbook , Vol 4, 1998
Resistance Seam Weldability of Low-Carbon
Steel
Surface Eruption, Cu Contamination Cracking
Non-Continuous
Seam
Lower Speed
Higher Current
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Peterson, High Speed Seam Welding..AWS Sheet Metal Welding Conf. VI, 1994
Weld
Exit Entry
High Speed
Expulsion
Coating
Coating Melts andExtrudes Out
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Peterson, High Speed Seam Welding..AWS Sheet Metal Welding Conf. VI, 1994
Coated Steels have lower contact resistance
delaying heating until coating is removed thus
slower speeds are required to get coating out
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Factors Limiting Travel Speed
Bulk ResistivityThe higher the bulk resistivity of the material, the higher the heating (H=I2Rt) and thus
the higher the travel speed possible
Current DensityAs travel speed increases, more material is presented to the rolls per half cycle of current
thus reaching a limit to the current density in the part
Conductive Coating MaterialsWhen conductive coatings are present at the faying surface, they offer an increased shut
path for current and thus also reduce current density. Welding takes place when these
coatings are melted and extruded out of the weld zone.
ExpulsionWith increased travel speed, complete nugget formation is delayed until the weld forms
outside the pressure influence of the rolls (see next slide) and expulsion is easier.
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Projection Seam WeldsExperimental Procedure to Maximize Current Density
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Peterson, High Speed Seam Welding..AWS Sheet Metal Welding Conf. VI, 1994
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Peterson, High Speed Seam Welding..
AWS Sheet Metal Welding Conf. VI, 1994
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Tensile Tests
Pillow Tests
Seam Weld
Quality Tests
Resistance Welder Manufacturers
Association Bulletin # 21
Typical data from Pillow Testing
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6 x 6 inch Pillow
6 x 10 inch Pillow
Typical data from Pillow Testing
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Douglas Process Standard DPS 10.800,McDonnell Douglas Corp, 1996
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Seam Welding
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