Electric arc method for treating the surface of lithoplate and other metals

• US 5,462,609 A
• Filed: 01/11/1993
• Issued: 10/31/1995
• Est. Priority Date: 03/18/1991
• Status: Expired due to Term

• Current Assignee: Alcoa Incorporated (Howmet Aerospace, Inc.)
• Original Assignee: Aluminum Company of America (Howmet Aerospace, Inc.)
• Inventors: Patrick, Edward P., Pajerski, A. Victor
• Primary Examiner(s): Simmons, David A.
• Assistant Examiner(s): Koehler, Robert R.
• Application Number:
  US08/003,094
• Time in Patent Office: 1,023 Days
• Field of Search: 148/241, 148/277, 148/285, 148/222, 148/224, 148/524, 148/526, 148/565, 148/566, 219/118, 219/68, 219/69.1, 219/69.11, 219/123, 219/125.12, 219/137 R, 430/278, 205/214
• US Class Current: 148/241
• CPC Class Codes: B21B 2001/383 Cladded or coated products
• CPC Class Codes: B22D 11/008 of clad ingots, i.e. the molten metal being cast against a continuous strip forming part of the cast product
• CPC Class Codes: B23K 35/0238 layered
• CPC Class Codes: B23K 35/286 Al as the principal constituent
• CPC Class Codes: B32B 15/016 all layers being formed of aluminium or aluminium alloys
• CPC Class Codes: B41N 1/083 made of aluminium or aluminium alloys or having such surface layers B41N1/086 takes precedence
• CPC Class Codes: B41N 3/032 Graining by laser, arc or plasma means
• CPC Class Codes: Y10T 428/12042 Porous component
• CPC Class Codes: Y10T 428/12451 Macroscopically anomalous interface between layers
• CPC Class Codes: Y10T 428/12611 Oxide-containing component

Abstract

An essentially flat "arc-grained" surface of a sheet of aluminum alloy is produced with a coarse and non-uniform microstructure which, after it is coated with a durable phosphate-free coating, provides excellent lithoplate. Though such arc-grained microstructure is much coarser than an electrochemically etched surface typically used on lithoplate, the very coarse surface is peculiarly well-adapted to provide durable lithoplate after it is coated with a phosphate-free protective surface. After the coated surface is coated with a photoresist the excellent resolution of prints is maintained over a large number of repeated uses in an off-set printing press. A method of producing lithoplate comprises, controlledly rastering an A-C, or D-C reverse polarity plasma-generating electric arc on an aluminum sheet less than 30 mils thick, kept distortion-free on a mounted surface such as on a cylindrical drum; then coating the arc-grained surface with a hard and durable, inert phosphate-free coating while maintaining a capillary microstructure in the surface adapted to provide a support for a photoresist for use in lithographic printing of adequate resolution.

Claims

1. A method of increasing the surface area of a metal surface, said method comprising;

conducting an electric arc between the leading edge of an electrode and said metal surface, said leading edge being the surface of said electrode adjacent said metal surface;

moving said arc around a substantially closed loop path generally defined by leading edge of said electrode; and

effecting relative movement between said arc and said metal surface in such a manner to contact an extensive area of said surface.

2. The method of claim 1 wherein said relative movement is effected by moving said arc in a plurality of adjacent pass lines around said closed loop path on said leading edge.

3. The method of claim 1 wherein said relative movement is effected by moving said arc around an elongated electrode and moving said electrode in relation to said metal so as to form a plurality of adjacent pass lines.

4. The method of claim 1 wherein said relative movement is effected by moving said arc back and forth around said closed loop path on said leading edge and across a substantial portion of the width of said surface and moving said metal transversely to the movement of said arc.

5. A method of treating a metal surface for use as lithographic sheet, said method comprising:

(a) moving a band of metal, having a width and length, in a first direction which is generally parallel to said length;

(b) conducting an electric arc between an electrode and a surface of said moving metal, said electrode having a closed loop leading surface for establishing a closed loop arc path; and

(c) continuously moving said arc along said closed loop leading surface of said leading surface and across a substantial portion of said width of said moving metal in such a manner as to contact an extensive area of said surface with said arc.

6. The method of claim 5 wherein said moving metal has a thickness,of 5-30 mils.

7. The method of claim 5 wherein said moving arc has a velocity of about 6-19 mm/sec.

8. The method of claim 5 wherein said moving metal has a width of from about 1 to about 5 feet.

9. The method of claim 5 wherein said moving metal is aluminum or an aluminum alloy having a velocity of from about 10 cm to about 2 meters per second.

10. The method of claim 5 in which recitation (b) includes:

conducting a continuous electric arc to a surface of said moving metal passing adjacent said electrode.

11. The method of claim 5 in which recitation (b) includes:

conducting an electric arc between at least one elongate electrode and a surface of said moving metal passing adjacent said electrode, said electrode being substantially parallel to said surface.

12. The method of claim 5 in which recitation (b) includes:

conducting an electric arc between at least one elongate electrode and a surface of said moving metal passing adjacent said electrode, said elongate electrode extending across a substantial portion of the width of said metal.

13. The method of claim 5 in which recitation (b) includes:

conducting an electric arc between at least one elongate oval or elliptical electrode traversing a substantial part of the width of said moving metal surface.

14. The method of claim 5 in which recitation (b) includes:

conducting an electric arc between two or more electrodes and a surface of said moving metal passing adjacent said electrode.

15. The method of claim 5 in which recitation (b) includes:

conducting an electric arc between two or more elongate electrodes and a surface of said moving metal passing adjacent said electrode.

16. The method of claim 5 in which recitation (c) includes:

magnetically moving said arc along said closed loop arc path of said leading surface.

17. The method of claim 5 in which recitation (c) includes:

using

using at least one permanent magnet to move said arc along said closed loop arc path generally defined by said leading surface.

18. The method of claim 5 in which recitation (c) includes:

using at least one electromagnet to move said arc along said closed loop arc path generally defined by said leading surface.

19. The method of claim 5 in which recitation (c) includes:

moving said electrode along said closed loop arc path generally defined by said leading surface back and forth across a substantial portion of said width of said metal so as to contact an extensive area of said surface with said arc.

20. The method of claim 5 in which recitation (c) includes:

directing said arc along an oval or elliptical path.

21. The method of claim 5 in which recitation (c) includes:

moving an electrode back and forth across a substantial portion of said width of said metal as the arc travels around an oval or elliptical path so as to contact an extensive area of said surface with said arc.

22. The method of claim 5 in which recitation (c) includes:

directing said arc in multiple passes across the same portion of the width of said moving metal surface.

23. The method of claim 5 which further comprises:

exposing a surface so treated to a media containing water to produce a surface containing boehmite.

24. The method of claim 5 which further comprises:

supplying a gas in the region of said arc to displace ambient atmosphere near the surface of said metal passing adjacent said electrode.

25. The method of claim 5 which further comprises:

supplying a gas in the region of said arc to displace ambient atmosphere near the surface of said metal passing adjacent said electrode, said gas comprising at least one gas from the group consisting of argon, helium and mixtures thereof.

26. The method of claim 5 which further comprises:

anodizing at least a portion of the surface so treated.

27. A method of increasing the surface area of the surface of aluminum metal using a substantially non-metal depositing electric arc, said method comprising:

(a) moving aluminum metal having a width and length in a first direction which is generally parallel to said length;

(b) conducting an electric arc between an elongate electrode and a surface of said metal passing adjacent said electrode, said elongate electrode having an elongate oval or elliptical shaped leading surface and said elongate oval or elliptical shaped leading surface extending across a substantial portion of the width of said metal; and

(c) magnetically moving said arc along said oval or elliptical shaped leading surface and back and forth across a substantial portion of said width of said moving metal so as to contact an extensive area of said surface with said arc, said arc following a path generally defined by said shaped leading surface of said electrode.

28. The method of claim 27 which further comprises:

exposing at least some of said increased surface to a media containing water to produce a surface containing boehmite.

29. The method of claim 27 which further comprises:

providing gas in the region of said arc.

30. The method of claim 27 which further comprises:

supplying a gas in the region of said arc, said gas comprising at least one gas from the group consisting of argon, helium and mixtures thereof.

31. A method of treating the surface of a metal, said method comprising:

(a) moving metal, having a width and length, in a first direction which is generally parallel to said length;

(b) conducting a non-metal depositing electric arc between an electrode having a closed loop leading surface and a surface of said moving metal passing adjacent said electrode, said closed loop surface generally having an oval shape; and

(c) continuously moving said arc in multiple occurrences along said closed loop leading surface so as to treat an extensive area of said surface with said arc.

32. The method of claim 31 wherein recitation (c) cleans an extensive area of said surface with said arc.

33. The method of claim 31 wherein recitation (c) increases the surface area of an extensive area of said surface.

34. The method of claim 31 which further comprises:

exposing at least some surface so treated to a media containing water to produce a surface containing boehmite.

35. The method of claim 31 which further comprises:

supplying a gas in the region of said arc.

38. The method of claim 31 in which recitation (a) includes:

providing a metal fabricated from aluminum or an aluminum alloy having a velocity of from about 10 cm to about 2 meters per second.

36. A method of roughening the surface of a metal, said method comprising:

(a) moving at least one electrode adjacent a surface of metal, having a width and length, in a first direction which is generally parallel to said length of said metal;

(b) conducting an electric arc between said electrode and said surface of said metal, said electrode having a closed loop leading surface adjacent said surface of metal; and

(c) magnetically moving said arc along said closed loop leading surface and across a substantial portion of said width of said metal so as to contact an extensive area of said surface with said arc.

37. The method of claim 36 wherein said metal has a thickness of 5-30 mils.

39. The method of claim 36 in which recitation (a) includes:

moving said electrode at a velocity from about 10 cm to about 2 meters per second.

40. The method of claim 36 in which recitation (a) includes:

moving said electrode at a velocity of about 6-19 mm/sec.

41. The method of claim 36 in which recitation (a) includes:

moving at least one elongate electrode adjacent said metal.

42. The method of claim 36 in which recitation (a) includes:

moving at least one elongate electrode adjacent said metal, said elongate electrode extending across a substantial portion of the width of said metal.

43. The method of claim 36 in which recitation (a) includes:

moving at least one elongate oval or elliptical electrode adjacent said metal, said elongate electrode extending across a substantial portion of the width of said metal.

44. The method of claim 36 in which recitation (a) includes:

moving two or more electrodes adjacent said metal.

45. The method of claim 36 in which recitation (a) includes:

moving two or more elongate electrodes in parallel pass lines across the width of said metal.

46. The method of claim 36 in which recitation (b) includes:

conducting a continuous electric arc between said moving electrode and a surface of said metal adjacent said electrode.

47. The method of claim 36 in which recitation (c) includes:

using at least one permanent magnet to move said arc along said closed loop leading surface and across a substantial portion of said width of said metal so as to contact an extensive area of said metal.

48. The method of claim 36 in which recitation (c) includes:

using at least one electromagnet to move said arc along said closed loop leading surface and across a substantial portion of said width of said metal so as to contact an extensive area of said metal.

49. The method of claim 36 in which recitation (c) includes:

moving said electrode back and forth along said closed loop leading surface.

50. The method of claim 36 in which recitation (d) includes:

moving said arc along an oval or elliptical path.

51. The method of claim 36 in which recitation (c) includes:

directing said arc in multiple passes across said moving metal.

52. The method of claim 36 which further comprises:

exposing said roughened surface to a media containing water to produce a surface containing boehmite.

53. The method of claim 36 which further comprises:

providing gas in the region of said arc.

54. The method of claim 36 which further comprises:

anodizing at least a portion of the surface of said roughened metal.

55. The method of claim 36 in which said metal is selected from the group consisting of sheet, plate and foil.

56. The method of claim 36 which further comprises:

supplying a gas in the region of said arc, said gas comprising at least one gas from the group consisting of argon, helium and mixtures thereof.

57. A method of roughening the surface of aluminum metal using an electric arc, said method comprising:

(a) moving at least one elongate electrode adjacent a surface of aluminum metal, said metal having a width and length in a first direction which is generally parallel to said length, said elongate electrode having a closed loop oval or elliptical shaped leading edge which extends across a substantial portion of the width of said metal;

(b) conducting an electric arc between said shaped leading edge of said electrode and said surface of said metal; and

(c) magnetically moving said arc along said shaped leading edge of said electrode and across a substantial portion of said width of said metal so as to contact an extensive area of said surface with said arc, said arc following a path generally defined by said shape of said shaped leading edge of said electrode.

58. The method of claim 57 which further comprises:

exposing said roughened surface to a media containing water to produce a surface containing boehmite.

59. The method of claim 57 which further comprises:

providing gas in the region of said arc.

60. The method of claim 57 which further comprises:

anodizing said roughened surface.

61. A method of producing a roughened metal comprising:

(a) moving a band of said metal having a width and a length; and

(b) continuously moving an electric arc along a closed loop leading edge of an electrode and across the width of said moving metal in adjacent arc pass lines so as to contact an extensive area of said metal.

62. A method of producing a roughened metal comprising:

(a) moving a band of said metal; and

(b) conducting an electric arc to said moving metal and repeatedly magnetically moving said arc along the leading surface of a closed loop path generally defined by an oval electrode and substantially across the width of said moving metal so as to contact an extensive area of said metal.

63. A method of producing a roughened metal comprising:

(a) moving a band of said metal; and

(b) conducting an electric arc between a closed loop elongate electrode and said metal and repeatedly traversing a substantial region of said metal by magnetically moving said arc along said electrode so as to cause said arc to roughen an extensive area of said metal.

64. A method of producing a roughened metal comprising:

(a) moving a band of said metal; and

(b) conducting an electric arc between a closed loop leading surface of an elongate electrode and said metal, said closed leading loop surface being the surface of said elongate electrode most adjacent said metal and repeatedly magnetically moving said arc along said electrode and around said closed loop leading surface and across a substantial width of said moving metal so as to cause said arc contact an extensive area of said metal.

65. A method of producing a roughened metal comprising:

(a) moving a band of said metal; and

(b) conducting an electric arc between an electrode having a closed loop leading surface adjacent said metal and traversing a substantial region of the width of said metal and repeatedly magnetically moving said arc along said closed loop leading surface and across the width of said metal so as to contact an extensive area of said metal.

66. A method of increasing the surface area of the surface of aluminum metal using a substantially non-metal depositing electric arc, said method comprising:

(a) moving aluminum metal having a width and length in a first direction which is generally parallel to said length;

(b) conducting an electric arc between at least one elongate electrode and a surface of said metal passing adjacent said electrode, said elongate electrode having an elongate oval or elliptical shape closed loop leading surface and extending across a substantial portion of the width of said metal; and

(c) moving said arc along said oval or elliptical shape and back and forth across a substantial portion of said width of said moving metal so as to contact an extensive area of said surface with said arc, said arc following a path generally defined by said oval or elliptical shape closed loop leading surface of said electrode.

67. The method of claim 66 in which recitation (c) includes:

magnetically moving said arc along said closed loop leading surface and across a substantial portion of said width of said metal so as to contact an extensive area of said metal.

68. The method of claim 66 which recitation (c) includes:

using at least one permanent magnet to move said arc along said closed loop leading surface and across a substantial portion of said width of said metal so as to contact an extensive area of said metal.

69. The method of claim 66 in which recitation (c) includes:

using at least one electromagnet to move said arc along said closed loop leading surface and across a substantial portion of said width of said metal so as to contact an extensive area of said metal.