Electric Resistance Welded Tubing
(Low Frequency Resistance Welding)
High Frequency Induction Welding
ERW & High Frequency Welding
Lesson Objectives
When you finish this lesson you will
understand:
• The difference between low
frequency Electric Resistance Welding
and High Frequency Welding
• Applications of each
Learning Activities
1. View Slides;
2. Read Notes,
3. Listen to lecture
4. Do on-line
workbook
5. Do Homework
Keywords
Electric Resistance Welding, High Frequency Welding, Tube
Welding, Proximity Conductor, Induction Coil, Induction
Current, Impeder, Seam Annealing
Resistance Tube Welding (ERW)
W. Stanley, Resistance Welding
McGraw-Hill, 1950
The Making Shaping & Treating of Steel,
USS Corp, 1964
The Making Shaping & Treating of Steel,
USS Corp, 1964
Current Flow in a conductor as a
function of Frequency
DC
60 HZ AC
KiloHertz AC
High Frequency
High Frequency
Induction Welding
Appreciating Hig-Frequency Welding
Welding Journal, July 1996
Metals Handbook, Vol 6
ASM International, 1983
Impeder Inside the
Core Promotes
Path ADC
Linnert, Welding Metallurgy
AWS, 1994
High Frequency Welding
Applications
HF
Induction Coil
HF
HF
Tube Butt SeamTube Butt Seam
Tube Mash Seam
[Reference: Welding Handbook, Volume 2, p.653, AWS]
High Frequency Welding
Applications (CONT.)
HF
HF
Strip Butt
T-Joint
HF
HF
Spiral Tube Fin
Spiral Tube
[Reference: Welding Handbook, Volume 2, p.653, AWS]
High Frequency Welding
Applications (CONT.)
HF
Induction
Coil
Projection Seam
HF
HF
Pipe Butt
Bar Butt
[Reference: Welding Handbook, Volume 2, p.653, AWS]
AWS Welding Handbook
Typical Tube Welding Conditions for Steels
30 m/min (100 ft/min)at:
600 kW power for
12 mm-wall (1/2 in);
diameter of 200 - 1200 mm (8 - 48 in)
60 -240 m/min (200-800 ft/min)
100-400kW power
0.6 - 1.6 mm walls (0.025 - 0.065 in)
diameter of 25 - 50 mm (1 - 2 in)
Note high speed
Frequency KHz
Current Penetration Depth, in
Metals Handbook, Vol 6
ASM International, 1983
Circuitry & Control
Control Devices
Input Voltage Regulation
• SCR’s control input voltage constant
• Filters used on rectifier output to reduce ripple
• Variations cause intermittent fusion “stitching”
Speed Control
• Feedback Control on weld power as a function of mill speed
• Reduces scrap on start and stop
Weld Temperature Control
• Optical Pyrometer aimed at “v” adjusts weld power
460 V
60 Hz
DC
Reduce
Ripple
50 - 65% Efficient
Solid State
Circuit Made of Three
Components
• Filter
• Tube or SS HF Converter
• Tank Circuit
AWS Welding Handbook
>80% Efficient
HF Resonance
Circuit
Ep
AC/DC Converter
Grid
Feedback
Circuit
Ip=Plate Current
Ig= Grid Current
Ep= Plate Voltage
Ip
Ig
Eff 
Ip (onload)  Ip (offload)
Ip (onload)
If Efficiency is Below 55% Modifications are needed
Nominal Target =75%
Ishizaka, HF Resistance Seam Welding,
The Fabricator, Nov 1993
Efficiency Improvements Can Come From Two Sources
• The Power Circuit
• The Workpiece Arrangement
HF Resonance
Circuit
Ep
AC/DC Converter
Grid
Feedback
Circuit
Ip
Ig
Proper Matching
Relationship between the plate voltage and plate current; and
the relationship between plate voltage and grid current are
nearly coincident with the rated impedance line.
Ishizaka, HF Resistance Seam Welding,
The Fabricator, Nov 1993
HF Resonance
Circuit
Ep
AC/DC Converter
Grid
Feedback
Circuit
Ip
Ig
Overload Matching
Occurs when load impedance is too small in comparison
with the rated impedance
• Increase the turns ratio
of current transformer
• Reduce tank
capacitance
Ishizaka, HF Resistance Seam Welding,
The Fabricator, Nov 1993
HF Resonance
Circuit
Ep
AC/DC Converter
Grid
Feedback
Circuit
Ip
Ig
Light Load Matching
• Reduce the turns ratio
of current transformer
• Increase tank
capacitance
Ishizaka, HF Resistance Seam Welding,
The Fabricator, Nov 1993
Current flows more to edge when
• Edges are closer
• “v” length is shorter
Caution: Can get Premature Arcs
• Insert Impeder
• Impeder Mass Closer to Tube
• Cool Impeder
Effect of Weld Speed on Power and Performance
Power = E*I
B = Fixed Power (losses etc)
A*Sp = Weld Power
U=The relative power B:A
B has less of an effect at
higher travel speeds
Induction Coils
• Cu Tubing or Bar
• Normally water cooled
• Surround = efficiency
• Mag. Strength reduces
with distance = 1/8 - 1
inch between coil and
work
AWS Welding Handbook
Contacts
• Cu or Hard Cermets
• 0.25 - 1 in2
• 500 - 5000 Amps
• Cooling required
• 5 - 50 lbs force
• Life = 1K - 300K feet
AWS Welding Handbook
Impeders
(Current Flow Around inside Surface of
Tubes can cause reduced efficiency. The
impeder increases the inductive
reactance around inside wall of tube.)
• Ferritic Material
• Cooled: keep below Curie Temp
• Extend from “v” to 1 1/2 tube
diameters upstream of “v”
Mandrels
• Used to treat inside weld bead shape or scarfing
• Nonmagnetic Material like Austenitic SS (Impeders also needed)
Seam
Annealing
Robotron Web Site
Advantages of High-Frequency
Welding
• Produce welds with very narrow heat-affected zones
• High welding speed and low-power consumption
• Able to weld very thin wall tubes
• Adaptable to many metals
• Minimize oxidation and discoloration as well as
distortion
• High efficiency
Limitations of High-Frequency
Welding
• Special care must be taken to avoid radiation
interference in the plant’s vicinity
• Uneconomical for products required in small
quantities
• Need the proper fit-up
• Hazards of high-frequency current
Some Products of High-Frequency
Welding
[Reference: Welding Handbook, Volume 2, p.665, AWS]
HF Welding