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Continuous casting of aluminum

Imported: 24 Feb '17 | Published: 06 Jan '04

Ali Unal

USPTO - Utility Patents

Abstract

A method of continuous casting aluminum alloys between a pair of rolls. Molten aluminum alloy is delivered to a roll bite between the rolls and passes into the roll nip in a semi-molten state. A solid strip of cast aluminum alloy exits the nip at speeds of about 25 to about 400 feet per minute. Thin gauge (0.07-0.25 inch) strip may be produced at rates of up to 2000 pounds per hour per inch of cast strip width.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

A complete understanding of the invention will be obtained from the following description when taken in connection with the accompanying drawing figures wherein like reference characters identify like parts throughout.

The file of this patent contains at least one drawing executed in color. Copies of this patent with color drawing(s) will be provided by the Patent and Trademark Office upon request and payment of the necessary fee.

FIG. 1 is a schematic of a portion of a caster with a molten metal delivery tip and a pair of rolls;

FIG. 2 is an enlarged cross-sectional schematic of the molten metal delivery tip and rolls shown in FIG. 1 operated according to the prior art;

FIG. 3 is an enlarged cross-sectional schematic of the molten metal delivery tip and rolls shown in FIG. 1 operated according to the present invention;

FIG. 4 is a graph of force per unit width versus casting speed for the method of the present invention for an Si—Fe—Ni—Zn aluminum alloy;

FIG. 5 is a graph of force per unit width versus casting speed for the method of the present invention for a Mg—Mn—Cu—Fe—Si aluminum alloy,

FIG. 6 is a graph of the concentration of eutectic forming alloying elements versus strip depth in a strip of an Si—Fe—Ni—Zn aluminum alloy produced according to the present invention;

FIG. 7 is a graph of the concentration of peritectic forming alloying elements versus strip depth in the strip of an Si—Fe—Ni—Zn aluminum alloy produced according to the present invention;

FIG. 8

a is a photomicrograph at 25 times magnification of a transverse section of the strip of an Si—Fe—Ni—Zn aluminum alloy produced according to the present invention;

FIG. 8

b is a photomicrograph at 100 times magnification of the strip shown in FIG. 8

a;

FIG. 9

a is a photomicrograph at 25 times magnification of a transverse section of the strip of an Mg—Mn—Cu—Fe—Si aluminum alloy produced according to the present invention;

FIG. 9

b is a photomicrograph at 100 times magnification of the center portion of the strip shown in FIG. 9

a;

FIG. 10 is a graph of the concentration of eutectic forming alloying elements versus strip depth in a strip of an Mg—Mn—Cu—Fe—Si aluminum alloy produced according to the present invention;

FIG. 11 is a graph of the concentration of peritectic forming alloying elements versus strip depth in the strip of an Mg—Mn—Cu—Fe—Si aluminum alloy produced according to the present invention;

FIG. 12 is a photomicrograph at 50 times magnification of a transverse center section of the anodized strip of an Mg—Mn—Cu—Fe—Si aluminum alloy produced according to the present invention;

FIG. 13

a is a schematic of a caster made in accordance with the present invention with a strip support mechanism and optional cooling means; and

FIG. 13

b is a schematic of a caster made in accordance with the present invention with another strip support mechanism and optional cooling means.

Claims

1. A method of continuously casting aluminum alloy strip comprising the steps of:

2. The method of claim 1 wherein the semi-solid central layer includes a solid component and a molten component, the molten component being urged upstream from the nip.

3. The method of claim 1 wherein the concentration of the eutectic forming alloying elements in the central layer is less than the concentration of the eutectic forming alloying elements in each of the outer layers.

4. The method of claim 3 wherein the concentration of the eutectic forming alloying elements in the central layer is about 5 to about 20% less than the concentration of the eutectic forming alloying elements in each of the outer layers.

5. The method of claim 1 wherein the molten aluminum alloy has an initial concentration of peritectic forming alloying elements and the concentration of peritectic forming alloying elements in the central layer is greater than the initial concentration of the peritectic forming alloying elements.

6. The method of claim 5 wherein the concentration of the peritectic forming alloying elements in the central layer is greater than the concentration of the peritectic forming alloying elements in each of the outer layers.

7. The method of claim 6 wherein the concentration of the peritectic forming alloying elements in the central layer is about 5 to about 45% greater than the concentration of the peritectic forming alloying elements in each of the outer layers.

8. The method of claim 1 wherein the strip of metal exits the nip at a rate of over about 25 to about 400 feet per minute.

9. The method of claim 8 wherein the strip of metal exits the nip at a rate of over about 100 to about 300 feet per minute.

10. The method of claim 8 wherein the force applied by the rolls to the aluminium alloy passing through the nip is about 25 to about 300 pounds per inch of width of the strip.

11. The method of claim 1 wherein the force applied by the rolls to the aluminum alloy passing through the nip is about 25 to about 300 pounds per inch of width of the strip.

12. The method of claim 11 wherein a roll separating force applied by the rolls to the aluminum alloy passing through the nip is about 25 to about 200 pounds per inch of width of the strip.

13. The method of claim 12 wherein the force applied by the rolls to the aluminum alloy passing through the nip is about 100 pounds per inch of width of the strip.

14. The method of claim 1 wherein the solid strip has a thickness of about 0.07 to about 0.25 inch.

15. The method of claim 1 wherein a linear speed at which the solid strip is withdrawn from the nip is greater than the linear rate at which the molten aluminum alloy is delivered to the rolls.

16. The method of claim 15 wherein the linear speed at which the solid strip is withdrawn from the nip is about four times greater than the linear rate at which the molten aluminum alloy is delivered to the rolls.

17. The method of claim 1 wherein the strip exits the nip horizontally.

18. The method of claim 1 wherein the rolls each have a textured surface.

19. The method of claim 18 wherein the textured surface includes a plurality of surface irregularities having a height of about 5 to about 50 microns.

20. The method of claim 19 wherein the surface irregularities are spaced apart in a regular pattern of about 20 to about 120 irregularities per inch.

21. The method of claim 20 wherein the surface irregularities comprises grooves, dimples or knurls defined in the roll surface.

22. The method of claim 18 further comprising brushing the textured surfaces of the rolls.

23. The method of claim 1 wherein the rolls comprise a coating of a material to enhance separation of the strip from the rolls.

24. The method of claim 23 wherein the roll coating comprises chromium or nickel.

25. The method of claim 18 further comprising providing a fixed edge dam or an electromagnetic dam or both adjacent the molten metal.

26. The method of claim 1 wherein said step of delivering molten metal comprises positioning a delivery tip containing the molten metal a distance of about 0.02 inch from the rolls.

27. A strip of aluminum alloy comprising:

28. The strip of claim 27 wherein the concentration of said eutectic forming alloying elements in said central layer is about 5 to about 20% less than the concentration of said eutectic forming alloying elements in each said outer layer.

29. The strip of claim 27 wherein the concentration of said eutectic forming alloying elements in said central layer is less than the initial concentration of said eutectic forming alloying elements.

30. The strip of claim 27 wherein said eutectic forming alloying elements are selected from the group consisting of Si, Fe, Ni, Zn, Mg, Cu and Mn.

31. The strip of claim 27 wherein the molten aluminum alloy comprises peritectic forming alloying elements in an initial concentration and the concentration of said peritectic forming alloying elements in said central layer is greater than the concentration of said peritectic forming alloying elements in each said outer layer.

32. The strip of claim 31 wherein the concentration of said peritectic forming alloying elements in said central layer is about 5 to about 45% greater than the concentration of said eutectic forming alloying elements in each said outer layer.

33. The strip of claim 31 wherein the concentration of said peritectic forming alloying elements in said central layer is greater than the initial concentration of said peritectic forming alloying elements.

34. The strip of claim 27 wherein said peritectic forming alloying elements are selected from the group consisting of Ti, Cr, V and Zr.

35. The strip of claim 27 wherein the thickness of said strip is about 0.07 to about 0.25 inch.

36. The strip of claim 35 wherein the thickness of said central layer comprises about 20 to about 30% of the thickness of said strip.

37. The strip of claim 27 wherein said central layer comprises globular dendrites.

38. The strip of claim 37 wherein said globular dendrites are unworked.

39. A strip of aluminum alloy comprising:

40. The strip of claim 39 wherein the thickness of said strip is about 0.07 to about 0.25 inch.

41. The strip of claim 40 wherein the thickness of said central layer comprises about 20 to about 30% of the thickness of said strip.

42. The strip of claim 41 wherein said globular dendrites are unworked.

43. The strip of claim 39 wherein the concentration of peritectic forming alloying elements in said dendrites is greater than the concentration of peritectic forming alloying elements in said outer layers.