EFD Induction

1. EFD Induction Terac – straightening with induction Presentation by: Mark Wells Product & Application Manager (Europe) Presented by: Tom Brown Regional Sales Manager (USA)

2. Distortion through welding • Welding and other manufacturing processes where heat is introduced will leave stresses in the metal during subsequent cooling, causing distortion or warping • Distortion can be unsightly, prevent correct fit and even add weakness to the assembly

3. References • THE MANAGEMENT OF THIN PLATE DISTORTION N.A. McPHERSON BAE Systems – Surface Fleet Solutions (With reference to: Prediction and Prevention of Excessive Unfairness in Arleigh Burke (DDG-51) Class Deckhouse fabrication, Kirk, M., Conrardy, C., DeBiccari, A. and Michaleris, P) • INDUCTION HEAT STRAIGHTENING – A DISTORTION REWORK REDUCTION TOOL FOR THIN PLATE N.A.McPherson & A.Coyle BAE Systems, Surface Fleet Solutions M. A. Wells, EFD Induction a.s.

4. Overview – Ship Building • Despite improvements in manufacturing techniques the ship-building industry is hugely affected by distortion “Typically figures of 25,000-30,000 man-hours have been quoted for the heat straightening cost for frigates and offshore patrol vessels…”¹

5. Overview – Ship Building “..it has been estimated that the total could be up to ten times the heat straightening figures, once factors such as schedule interruptions, stripping down equipment, repainting etc are taken into consideration.”¹

6. Improvements in rework requirement

7. Thermal forming / straightening • Strategically heating metals with or without mechanical force is used to bend plates, beams, pipes etc • Straightening (by heat) is mainly done by shortening (shrinking) of the long areas / surfaces (Picture shows straightening by flame)

8. Thermal straightening – by flame • The traditional method of straightening plates in ship-building is to use a flame on the convex surfaces of distorted areas • The heated zone is quite shallow and on cooling, the heated side of the plate contracts more than the “cold” side • Shrinkage of the surface causes excess material to expand vertically • Typically used on >5mm plate

9. Thermal straightening – by flame By heating a number of areas the plate can be flattened

10. Thermal straightening – by flame Shrinking of surface to straighten the bulge • Adds stress to (and shrinks) the treated surface • Requires skilled operators • Risk of overheating of the surface • Hydrogen ingress • Noisy • Heating-up of the local environment • Toxic fumes Flame straightening can only be achieved when heating from the convex side

11. Alternative “traditional” method • Using a “straight edge”

12. Alternative “traditional” method • Mechanical force to pull the sheet against the straight edge

13. Alternative “traditional” method • 25 – 50mm stitch welds to keep the plate “straight”

14. Alternative “traditional” method • Apply heat (by flame) to keep the plate straight before removing the straight edge using grinders

15. Alternative “traditional” method 2 • Weld bolts to the affected area

16. Alternative “traditional” methods • Requires skilled operators • Very hard work • Time consuming • Sacrificial materials • Noisy • Unsightly results

17. There is a better way…. With straight edge With induction

18. Thermal straightening – by induction • The inductor generates an eddy current in the steel plate, which generates a rapid heat increase to a concentrated heating zone. • The Terac equipment is tuned not to exceed Curie temperature therefore magnetic steel cannot overheat Video – through heating

19. Thermal straightening – by induction Chart shows times to achieve Curie temperature (Approx. 740°C) at the surface and through the steel plate

20. Thermal straightening – by induction • The straightening effect occurs when the heated material expands and contracts • A rapid, through - heating, forces the heated area to expand vertically • Deformation is permanent • During cooling down, the material around the heated zone will shrink equally in all directions and due to this, the plate becomes shorter

21. Thermal straightening – by induction • Permanent vertical expansion evidence

22. Thermal straightening – by induction • Shrinking close to the welds is shrinking at the weld-affected points and is sufficient in most situations

23. Thermal straightening – by induction • Shrinking close to the welds from one side decreases the convex AND concave bulges

24. Thermal straightening – by induction

25. Typical heating pattern – first pass

26. Typical heating pattern – second pass

27. Typical heating pattern – third pass

28. Typical heating pattern – first pass

29. Operational Trial at BAE Systems – Surface Fleet “This section covers work carried out in a shipyard involved in the construction of naval vessels with a high proportion of thin plate in the structure.” ² “A number of areas were induction heat straightened following a laid down sequence. Deflections on areas were measured before, during and after the induction heat straightening process.” ²

30. Operational Trial at BAE Systems – Surface Fleet “The induction heating process was compared against a standard, but well controlled , flame heating procedure. This procedure followed the laid down sequence used for the induction heating.” ² “In this specific area of the ship the maximum allowable deflection was 6mm. The evaluation consisted of establishing the percentage of the structure brought within tolerance. It should be noted that the intention was not produce a perfectly flat structure, but one that was within the required tolerances.” ²

31. Operational Trial at BAE Systems – Surface Fleet “In this instance the induction heating system achieved between 93 and 95% within tolerance, and the flame heating achieved between 51 and 56%. This consisted of both low and high deflections.” ² “the time savings were estimated at about 75%. Other cost savings which could be incorporated into this were material costs (studs), strongbacks, and process costs such as grinding off the stud scars and rewelding and grinding any undercut.” ²

32. Metallurgical Results at BAE Systems – Surface Fleet “Plate material was treated in the same manner as the actual structure. Testing was carried out in these areas to determine material properties such as strength, toughness and hardness. In addition, an evaluation was made of the steel microstructure in the treated areas and in reference areas of the plates.” ² “For comparison purposes, a carefully controlled flame heating procedure was used on 5mm thick DH 36 plate, following a similar pattern to that used for the induction heating.” ²

33. Metallurgical Results BAE Systems – Surface Fleet “The comparison of strength and toughness revealed very little significant difference among the induction heated samples. There was a very slight drop in toughness in the heated areas, and a similar drop in yield strength (~ 7%). However in the flame heated areas there was a reduction in toughness of almost 45% and a 7% reduction in yield strength.” ²

34. Metallurgical Results at BAE Systems – Surface Fleet “The hardness of the material did show some differences, as the localised cooling and heating of the area was inevitably going to change the steel microstructure in the area.” ² “there is between 6% and 15% increase in hardness of the induction heated areas compared to the parent plate material. For the flame heated material the increase was 16%.” ²

35. Performance Results ²

36. With Terac….

37. Terac System Fits very well into the shipyard environment

38. Terac System Fits very well into the shipyard environment

39. Terac operation

40. Terac System The latest Terac is the result of almost 30 years experience gained working in the shipyard environment Turnkey systems – just add power

41. Terac System The latest Terac is the result of almost 30 years experience gained working in the shipyard environment Turnkey systems – just add power

42. Terac Inductor Unit • Heavy Duty/Lightweight Construction • Integrated HHT (Transformer) • Electro-Magnets to ensure fixed position during heating • Weight 10 kg • Cable Length 15m

43. Terac operation • Simple, robust operator controls

44. Terac – working range

45. Hand Held Unit II • “Beck Special” • New development in October 2009 • For use with balancer unit • 160mm coil length • Magnets help to keep the coil in place whilst heating • (Panel condition means that magnets cannot be guaranteed to take the whole weight of the unit)

47. Hand Held Unit II • 2 x Buttons • 2 x LED’s • 90° suspension points • Timer selection Switch

48. Heat Generator State-of-the-art induction equipment for today’s industry 3 x 400 V mains supply, 25/40 kW output power

49. Terac Capacitor Unit • Integrated cooling circuit and feed to inductor • Integrated Twin Timers for programming of the heating time • Lockable Cover • 30m cable length from Heat Generator

50. Terac Inductor Unit • Heavy Duty/Lightweight Construction • Integrated HHT (Transformer) • Electro-Magnets to ensure fixed position during heating • Weight 10 kg • Cable Length 15m