Claims
- 1. A method of meniscus coating at least one surface of steel strip with metal, comprising:
- providing at least one horizontally disposed coating tray for coating only one surface of the strip with molten metal and having a departure lip, said departure lip having a width at least as wide as the strip and including an upwardly inclined upper surface elongated in the direction of the strip width, a lower surface, and a sharp terminal end defined by the intersection of said upper and lower surfaces positionable adjacent to and transversely with said one surface, said lower surface inclined downwardly and away from said strip for an entire length of said departure lip, providing said coating tray with molten metal, moving said strip transversely past said terminal end of said departure lip, wetting said one surface of said strip with said molten metal by meniscus contact so that said molten metal is pulled from said departure lip onto said one surface, and maintaining said molten metal in said coating tray at a level relative to the upper elevation of said terminal end of said departure lip so that a supply of said molten metal is available to be pulled from said coating tray as said strip moves past said terminal end.
- 2. The method of claim 1 wherein said level of said molten metal is maintained no more than 7 mm above and no more than 13 mm below said upper elevation of said departure lip.
- 3. The method of claim 1 wherein said departure lip is positioned 3-8 mm from said surface of said strip.
- 4. The method of claim 1 including the additional step of laterally displacing said coating tray relative to said strip.
- 5. The method of claim 1 including the additional step of stabilizing said strip relative to said departure lip.
- 6. The method of claim 5 wherein said strip is stabilized by passing said strip between a pair of rollers, said rollers being positioned below said departure lip on opposite sides of said strip and offset relative to one another.
- 7. The method of claim 1 including providing a plurality of coating trays.
- 8. The method of claim 7 wherein two of said coating trays are positioned on opposite sides of said strip whereby both surfaces of said strip are coated with said molten metal.
- 9. The method of claim 7 wherein one of said coating trays is positioned above another of said coating trays wherein said molten metal on said strip from said one coating tray is superimposed over said molten metal on said strip from said another coating tray.
- 10. The method of claim 7 wherein one of said coating trays is positioned above another of said coating trays, said one coating tray containing a different molten metal and including the additional step of cooling said strip after being coated with said molten metal from said another coating tray and prior to said strip being coated with said different molten metal from said one coating tray.
- 11. The method of claim 8 wherein said strip is passed substantially equidistant between the departure lips of said coating trays.
- 12. The method of claim 1 including the additional step of heating said strip to a temperature near the melting point of said molten metal prior to being moved past said departure lip.
- 13. The method of claim 1 including the additional step of cleaning said strip by heating in a reducing atmosphere to a temperature less than about 985.degree. C.
- 14. The method of claim 1 including the additional step of blowing pressurized non-oxidizing gas toward said coated surface to control the thickness of the coating layer.
- 15. The method of claim 1 wherein said coating tray is enclosed in a chamber containing a non-oxidizing atmosphere.
- 16. The method of claim 1 including the additional steps of replacing said coating tray with another coating tray containing a different molten metal and positioning the departure lip of said another coating tray to within 3-8 mm of said surface.
- 17. The method of claim 1 wherein said molten metal is a zinc alloy and including the additional step of replacing said molten zinc alloy with commercially pure zinc.
- 18. The method of claim 1 wherein said molten metal is zinc and including the additional steps of cleaning said strip by heating in a reducing atmosphere, cooling said strip to a temperature less than 500.degree. C., coating said heated strip with said molten zinc whereby a galvanize coating having no or minimal zinc iron alloy layer is formed.
- 19. The method of claim 1 wherein said level is maintained by adding make-up metal to said coating tray.
- 20. The method of claim 19 wherein said make-up metal is a liquid.
- 21. The method of claim 19 wherein said make-up metal is a solid.
- 22. The method of claim 19 wherein any excess make-up metal is recirculated.
- 23. The method of claim 1 including the additional step of heating said departure lip.
- 24. The method of claim 1 wherein said departure lip has a profiled terminal end.
- 25. The method of claim 24 wherein the longitudinal edges of said strip are not contacted by said molten metal coated onto said surface.
- 26. The method of claim 24 wherein said profiled departure lip is tapered.
- 27. The method of claim 24 wherein said profiled departure lip includes a slot for delivering a longitudinally extending stripe of said molten metal on said strip surface.
- 28. A method of meniscus coating at least one surface of steel strip with metal, comprising:
- providing at least one horizontally disposed coating tray for coating only one surface of the strip with molten metal and having a departure lip, said departure lip having a width at least as wide as the strip and including an upwardly inclined upper surface elongated in the direction of the strip width, a lower surface, and a sharp terminal end defined by the intersection of said upper and lower surfaces positionable adjacent to and transversely with said one surface, said lower surface inclined downwardly and away from said strip for an entire length of said departure lip, providing said coating tray with molten metal, moving said strip transversely past said terminal end of said departure lip, wetting said one surface of said strip with said molten metal by meniscus contact so that said molten metal is pulled from said departure lip onto said one surface, maintaining said molten metal in said coating tray at a level relative to the upper elevation of said terminal end of said departure lip so that a supply of said molten metal is available to be pulled from said coating tray as said strip moves past said terminal end, replacing said coating tray with another coating tray containing a different molten metal, and coating said different molten metal onto said one surface.
- 29. A method of meniscus coating at least one surface of steel strip with metal, comprising:
- providing at least one horizontally disposed coating tray for coating only one surface of the strip with molten metal and having a departure lip, said departure lip having a width at least as wide as the strip and including an upwardly inclined upper surface elongated in the direction of the strip width, a lower surface and a sharp terminal end defined by the intersection of said upper and lower surfaces, said terminal end positionable adjacent t and transversely with said one surface, said lower surface inclined downwardly and away from the vertical plane of said strip for an entire length of said departure lip, providing said coating tray with molten metal, cleaning said strip by heating to a temperature less than bout 985.degree. C. in a reducing atmosphere, moving said heated strip transversely past within 3-8 mm of said terminal end of said departure lip, wetting said one surface of said strip with said molten metal by meniscus contact so that said molten metal is pulled from said departure lip onto said one surface, maintaining said molten metal in said coating tray at a level relative to the upper elevation of said terminal end of said departure lip so that a supply of said molten metal is available to be pulled from said coating way as said snip moves past said terminal end, and blowing pressurized gas toward said coated surface to control the thickness of the molten coating.
- 30. A method of meniscus coating at least one surface of steel strip with metal, comprising:
- providing at least one horizontally disposed coating tray for coating only one surface of the snip with molten metal and having a departure lip, said departure lip having a width at least as wide as the snip and including an upwardly inclined upper surface elongate in the direction of the strip width, a lower surface and a sharp terminal end defined by the intersection of said upper and lower surfaces, said terminal end positionable adjacent to and transversely with said one surface, said lower surface inclined downwardly and away from the vertical plane of said strip for an entire length of said departure lip, providing said coating way with molten metal, cleaning said strip by heating m a temperature less than about 985.degree. C. in a reducing atmosphere, moving said strip transversely past said terminal end of said departure lip, wetting the entire width of said one surface of said strip with said molten metal by meniscus contact so that said molten metal is pulled from said departure lip onto said one surface, maintaining said molten metal in said coating tray at a level no more than 7 mm above and no more than 13 mm below the upper elevation of said terminal end of said departure lip so that a supply of said molten metal is available to be pulled from said coating tray as said strip moves past said terminal end, and blowing pressurized gas toward said coated surface to control the thickness of the molten coating.
- 31. A method of meniscus coating both surfaces of steel snip with metal, comprising:
- providing a spaced pair of horizontally disposed coating trays, each of said coating trays for coating one of the surfaces of the strip with molten metal and having a departure lip, each said departure lip having a width at least as wide as the strip and including an upwardly inclined upper surface elongated in the direction of the strip width, a lower surface, and a sharp terminal end defined by the intersection of said upper and lower surfaces positionable adjacent to and transversely with said one surface, said lower surface inclined downwardly and away from said strip for an entire length of said departure lip, providing each of said coating trays with a different molten metal, moving said strip transversely between said terminal ends of said departure lips, wetting the entire width of the surfaces of said strip with a molten metal by meniscus contact so that said molten metal is pulled from said departure lips onto said surfaces wherein each of said surfaces is coated with a different one of said molten metals, and maintaining said molten metal in said coating trays at a level relative to the upper elevation of said terminal ends of said departure lips so that a supply of said molten metal is available to be pulled from said coating trays as said strip moves between said terminal ends.
- 32. The method of claim 31 wherein one of said molten metals is tin and the other of said molten metals is zinc.
- 33. The method of claim 31 wherein one of said molten metals is zinc containing less than 0.15 wt. % aluminum and the other of said molten metals is a zinc alloy containing at least 0.15 wt. % aluminum.
- 34. A method of meniscus coating at least one surface of steel strip with metal, comprising:
- providing at least one horizontally disposed coating tray for coating only one surface of the snip with molten metal and having a departure lip, said departure lip having a width at least as wide as the strip and including an upwardly inclined upper surface elongated in the direction of the strip width, a lower surface and a sharp terminal end defined by the intersection of said upper and lower surfaces, said terminal cad positionable adjacent to and transversely with said one surface, said lower surface inclined downwardly and away from the vertical plane of said strip for an entire length of said departure lip, maintaining said coating tray in a non-oxidizing atmosphere, providing said coating tray with molten metal, cleaning said strip by heating to a temperature less than about 985.degree. C. in a reducing atmosphere, stabilizing said strip by moving between a pair of rollers with said one surface of said strip being moved transversely past said terminal end of said departure lip, said rollers being positioned below said departure lip on opposite sides of said strip, wetting the entire width of said one surface of said strip with said molten metal by meniscus contact so that said molten metal is pulled from said departure lip onto said one surface, maintaining said molten metal in said coating tray at a level no more than 7 mm above and no more than 13 mm below the upper elevation of said terminal end of said departure lip so that a supply of said molten metal is available to be pulled from said coating tray as said strip moves past said terminal end by adding make-up metal to said coating tray, and blowing pressurized non-oxidizing gas toward said coated surface to control the thickness of the molten coating.
- 35. A method of meniscus coating at least one surface of steel strip with metal, comprising:
- providing at least one horizontally disposed coating tray having a departure lip, providing said coating tray with molten zinc, cleaning the strip by heating in a reducing atmosphere, cooling said strip to a temperature less than 550.degree. C., moving said strip transversely past said departure lip, wetting a surface of said strip with said molten zinc by meniscus contact so that said molten zinc flows continuously from said departure lip onto said surface, interdiffusing iron from the substrate of said coated strip with the zinc coating, cooling said coated strip to substantially stop said diffusion whereby said zinc coating is completely alloyed with iron having no or minimal gamma phase zinc alloy using only the residual heat of said coated strip, and maintaining said molten zinc in said coating tray at a level relative to the upper elevation of said departure lip so that an uninterrupted flow of said molten zinc is delivered to said surface.
- 36. The method of claim 35 wherein said strip is cooled to no less than 515.degree. C. prior to said coating step, the time of said interdiffusion being less than 30 seconds whereby said zinc iron alloy has no more than 13 atomic % iron.
- 37. A method of meniscus coating at least one surface of steel strip with metal, comprising:
- providing at least one horizontally disposed coating tray for coating only one surface of the snip with molten metal and having a departure lip, said departure lip including an upwardly inclined upper surface elongated in the direction of the strip width and a sharp terminal end positionable adjacent to and transversely with said one surface, providing said coating tray with molten metal, rotating said coating way relative to said strip, moving said strip transversely past said terminal end of said departure lip, wetting said one surface of said strip with said molten metal by meniscus contact so that said molten metal is pulled from said departure lip onto said one surface, and maintaining said molten metal in said coating tray at a level relative to the upper elevation of said terminal end of said departure lip so that a supply of said molten metal is available to be pulled from said coating way as said strip moves past said terminal end.
- 38. A method of meniscus coating at least one surface of strip with metal, comprising:
- providing at least one horizontally disposed coating tray having a departure lip, said coating tray containing molten zinc, providing a steel strip, heating said strip in a reducing atmosphere to remove oil, dirt, iron oxide and the like so that said strip is readily wetted by said molten zinc, moving said heated strip at a temperature less than 550.degree. C. transversely past said departure lip, wetting a surface of said strip with said molten zinc by meniscus contact so that said molten zinc flows continuously from said departure lip onto said surface, maintaining said molten zinc in said coating tray at a level relative to the upper elevation of said departure lip so that an uninterrupted flow of said molten zinc is delivered to said surface, interdiffusing iron from said strip with the molten zinc coating on said surface and cooling said coated strip to substantially stop said interdiffusion whereby a galvannealed strip is formed using only the residual heat of said coated strip with the zinc coating being completely alloyed with iron and having no or minimal gamma phase zinc alloy.
- 39. The method of claim 38 including providing two coating trays, one of said coating trays being positioned on each side of said strip wherein both surfaces of said strip are coated with said molten zinc, said iron being completely interdiffused with said molten zinc coating of only one of said surfaces.
- 40. The method of claim 38 including providing two coating trays, one of said coating trays being positioned on each side of said strip wherein both surfaces of said strip are coated with said molten zinc, said iron being completely interdiffused with said molten zinc coating on both of said surfaces.
- 41. The method of claim 38 wherein said heated strip is cooled to no-less than 515.degree. C. prior to being coated with said molten zinc, the time of said interdiffusion being less than 30 seconds whereby said zinc iron alloy contains no more than 13 atomic % iron.
- 42. The method of claim 38 including providing two coating trays, one of said coating trays being positioned on each side of said strip, said molten zinc in one of said coating trays having at least 0.15 wt. % aluminum and said molten zinc in the other of said coating trays having less than 0.15 wt. % aluminum, wherein said molten zinc flowed from said one coating tray is substantially unalloyed with iron and said molten zinc flowed from said other coating tray is completely alloyed with iron.
- 43. The method of claim 42 wherein said temperature is at least 500.degree. C.
CROSS-REFERENCE TO RELATED APPLICATION
This is a continuation of U.S. application Ser. No. 07/803,278, filed on Dec. 4, 1991, now abandoned.
US Referenced Citations (10)
Foreign Referenced Citations (4)
Number |
Date |
Country |
61-12026 |
Apr 1986 |
JPX |
207556 |
Sep 1986 |
JPX |
235550 |
Oct 1986 |
JPX |
2085327 |
Apr 1982 |
GBX |
Continuations (1)
|
Number |
Date |
Country |
Parent |
803278 |
Dec 1991 |
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