Electric Resistance Welded Tubing Low Frequency Resistance Welding
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 Mc. Graw-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 Kilo. Hertz AC High Frequency
High Frequency Induction Welding Appreciating Hig-Frequency 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 Seam Tube Mash Seam [Reference: Welding Handbook, Volume 2, p. 653, AWS]
High Frequency Welding Applications (CONT. ) HF HF Strip Butt HF T-Joint 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 k. W 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 -400 k. W 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 Meter 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
Ip=Plate Current Ig= Grid Current Ep= Plate Voltage 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
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
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
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 in 2 • 500 - 5000 Amps • Cooling required • 5 - 50 lbs force • Life = 1 K - 300 K 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
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