Electric Resistance Welded Tubing (Low Frequency Resistance Welding)

1. Electric Resistance Welded Tubing (Low Frequency Resistance Welding) High Frequency Induction Welding

2. ERW & High Frequency Welding • Learning Activities • View Slides; • Read Notes, • Listen to lecture • Do on-line workbook • Do Homework • 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 Keywords Electric Resistance Welding, High Frequency Welding, Tube Welding, Proximity Conductor, Induction Coil, Induction Current, Impeder, Seam Annealing

3. Resistance Tube Welding (ERW) W. Stanley, Resistance Welding McGraw-Hill, 1950

4. The Making Shaping & Treating of Steel, USS Corp, 1964

5. The Making Shaping & Treating of Steel, USS Corp, 1964

6. Current Flow in a conductor as a function of Frequency KiloHertz AC High Frequency DC 60 HZ AC

7. High Frequency Induction Welding Appreciating Hig-Frequency Welding Welding Journal, July 1996

8. Metals Handbook, Vol 6 ASM International, 1983

9. Impeder Inside the Core Promotes Path ADC Linnert, Welding Metallurgy AWS, 1994

10. High Frequency Welding Applications Induction Coil HF HF HF Tube Butt Seam Tube Butt Seam Tube Mash Seam [Reference: Welding Handbook, Volume 2, p.653, AWS]

11. 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]

12. High Frequency Welding Applications (CONT.) HF Induction Coil Projection Seam HF HF Bar Butt Pipe Butt [Reference: Welding Handbook, Volume 2, p.653, AWS]

13. AWS Welding Handbook

14. 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

15. Meter Current Penetration Depth, in Frequency KHz

16. Metals Handbook, Vol 6 ASM International, 1983

17. Circuitry & Control

18. 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

19. 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 >80% Efficient AWS Welding Handbook

20. 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

21. Efficiency Improvements Can Come From Two Sources • The Power Circuit • The Workpiece Arrangement

22. 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

23. 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

24. Light Load Matching • Reduce the turns ratio of current transformer • Increase tank capacitance Ishizaka, HF Resistance Seam Welding, The Fabricator, Nov 1993

25. Current flows more to edge when • Edges are closer • “v” length is shorter Caution: Can get Premature Arcs

26. Insert Impeder • Impeder Mass Closer to Tube • Cool Impeder

27. Effect of Weld Speed on Power and Performance U=The relative power B:A B has less of an effect at higher travel speeds Power = E*I B = Fixed Power (losses etc) A*Sp = Weld Power

28. 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

29. 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

30. 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)

31. Seam Annealing Robotron Web Site

32. 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

33. 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

34. Some Products of High-Frequency Welding [Reference: Welding Handbook, Volume 2, p.665, AWS]

35. Homework HF Welding