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1. (WO2005065856) PROCEDE ET APPAREIL D'EXTRUSION
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

CLAIMS:

1. A method of extrusion of a workpiece including:
providing an extrusion die assembly and a driving means for forcing the
workpiece through the extrusion die assembly;
causing a surface of the workpiece and a surface of driving means to contact to form an interface therebetween;
applying a force to the workpiece directed towards the interface to secure a frictional force at the interface;
forcing the workpiece through the die assembly using the frictional force;
plastically deforming the material of the workpiece during extrusion through the extrusion die assembly without changing the dimensions of the workpiece.

2. A method according to claim 1 including applying said force in a direction
substantially normal to the interface between the driving surface and said
surface of the workpiece thereby to secure said frictional force.

3. A method according to any preceding claim including pressing the driving
surface against the workpiece to secure said frictional force.

4. A method according to any preceding claim including pressing the workpiece against the driving surface to secure said frictional force.

5. A method according to claim 3 which includes providing a reactive pressure at the workpiece to balance the pressure applied thereto by the driving
surface.

6. A method according to claim 5 including providing a workpiece support
means such that the pressing of the driving surface against the workpiece results in the pressing of the workpiece against the workpiece support means thereby with the workpiece support means opposing the pressure from the driving surface.

7. A method according to claim 6 including providing the workpiece support with a support conveyor means, and conveying the workpiece over the workpiece support means using the support conveyor means as the workpiece moves in response to said frictional force.

8. A method according to claim 4 including providing a press means with press conveyor means for pressing the workpiece against the driving surface, and conveying the workpiece over the press means using the press conveyor means as the workpiece moves in response to said frictional force.

9. A method according to any of claims 7 and 8 wherein the conveyor means includes rollers and a belt supported by, and arranged to revolve around, the rollers.

10. A method according to any of claims 3 to 9 including providing a coefficient of friction between the drive surface and the workpiece which is greater than the coefficient of friction between the workpiece and the workpiece support means or between the workpiece and the press means.

11.A method according to claim 10 including determining the pressure with which the pressed contact is made according to the difference between the coefficient of friction between the drive surface and the workpiece and the coefficient of friction between the workpiece and the workpiece support means or between the workpiece and the press means.

12. A method according to any preceding claim including applying a variable reverse frictional force to a surface of the workpiece as it exits the extrusion die assembly thereby to generate a variable back pressure upon the workpiece thereby to apply a hydrostatic pressure to the workpiece within the extrusion die assembly.

13. A method according to any preceding claim including providing a first extrusion channel and a second extrusion channel contiguous with the first extrusion channel and inclined to the first channel at an extrusion angle, forcing the workpiece into the die assembly via the first extrusion channel to exit the die assembly via the second extrusion channel, wherein the first and second extrusion channels have the same dimension normal to the direction of travel of the workpiece through the respective extrusion channel in use corresponding to the thickness of the workpiece.

14. A method according to claim 13 including providing the first extrusion channel as a spacing between the driving surface and an opposed surface of the extrusion die assembly, and moving the driving surface relative to the opposed surface of the die assembly thereby to translate the workpiece through into the first extrusion channel and through the die assembly using said frictional force.

15. A method according to claim 14 including applying a controllable backpressure to the workpiece at the outlet of the second extrusion channel.

16. A method according to any preceding claim in which the driving surface is provided by a surface of a rotatable drive roll member, and the method includes rotating the drive roll member to drag the workpiece by friction therewith through the extrusion die assembly.

17. A method according to claim 16 in which the driving surface is provided by a substantially ungrooved surface of the drive roll member.

18. A method according to claim 16 or 17 in which the driving surface forms in part the first extrusion channel and drives the workpiece by friction developed therewith through the die assembly.

19. A method according to any previous claim in which the workpiece is in the form of a sheet including strip and plate, the ratio of the width to the thickness of the sheet workpiece is greater than 5, or greater than 10.

20. A method according to any of claims 16 to 19 in which the driving roll has an endless circumferential groove therein, a first die member of the die assembly comprises a shoe member which covers part of the length of the groove, forming the first extrusion channel therewith and a second die member of the die assembly comprises an abutment member which projects into the groove in the driving roll and forms with the first die member the second extrusion channel.

21. A method according to any previous claim comprising the step of heating the workpiece before and/or during the extrusion process.

22. A method according to any previous claim comprising the step of heat-treating the workpiece after extrusion through the extrusion die assembly.

23. A method according to claim 22 in which the step of heat-treating comprises continuous re-crystallisation annealing

24. A method according to any previous claim in which a plurality of continuous frictional angular extrusion processes through the die assembly is performed.

25. A method according to claim 24 in which a step of heat-treating comprising recovery annealing is performed in between any two said extrusion processes.

26. A method of refining the microstructure of the crystalline material to produce a fine grained or an ultra-fine grained microstructure using the method of extrusion according to any preceding claim.

27. An apparatus for extrusion of a workpiece including:
an extrusion die assembly and a driving means for forcing the workpiece through the extrusion die assembly, the driving means having a driving surface being arranged to contact a surface of the workpiece to form an interface therewith;
pressing means for applying a force to the workpiece directed towards the interface to secure a frictional force at the interface;
wherein the driving means is arranged to force the workpiece through the die assembly using the applied frictional force thereby to plastically deform the material of the workpiece during extrusion through the extrusion die
assembly, the die assembly being configured to enable said extrusion to occur without changing the dimensions of the workpiece.

28. An apparatus according to claim 27 in which the pressing means is arranged to apply said force in a direction substantially normal to the interface between the driving surface and said surface of the workpiece thereby to secure said frictional force.

29. An apparatus according to any of claims 27 to 28 in which the pressing means is arranged to press the driving surface against the to secure said frictional force.

30. An apparatus according to any of preceding claims 27 to 29 in which the pressing means is arranged to press the workpiece against the driving surface to secure said frictional force.

31. An apparatus according to claim 29 including balance means arranged to provide a reactive pressure at the workpiece to balance the pressure applied thereto by the driving surface.

32. An apparatus according to claim 31 in which the balance means includes a workpiece support means arranged such that the pressing of the driving surface against the workpiece results in the pressing of the workpiece against the workpiece support means such that the workpiece support means opposes the pressure from the driving surface.

33. An apparatus according to claim 32 in which the workpiece support has a support conveyor means arranged to convey the workpiece over the workpiece support means as the workpiece moves in response to said frictional force.

34. An apparatus method according to claim 30 in which the pressing means includes a press conveyor means for pressing the workpiece against the driving surface, and for conveying the workpiece over the press means as the workpiece moves in response to said frictional force.

35. An apparatus according to any of claims 33 and 34 wherein the conveyor means includes rollers and a belt supported by, and arranged to revolve around, the rollers.

36. An apparatus according to any of claims 32 to 35 in which the coefficient of friction between the drive surface and the workpiece is greater than the coefficient of friction between the workpiece and the workpiece support means or between the workpiece and the pressing means.

37. An apparatus according to claim 36 in which the pressure with which the pressed contact is made is determined according to the difference between the coefficient of friction between the drive surface and the workpiece and the coefficient of friction between the workpiece and the workpiece support means or between the workpiece and the pressing means.

38. An apparatus according to any of preceding claims 27 to 37 including backpressure means arranged to apply a variable reverse frictional force to a surface of the workpiece as it exits the extrusion die assembly thereby to generate a variable back pressure upon the workpiece to urge the workpiece back into the die assembly after it has been plastically deformed.

39. An apparatus according to any of preceding claims 27 to 38 including a first extrusion channel and a second extrusion channel contiguous with the first extrusion channel and inclined to the first channel at an extrusion angle, wherein the driving means is arranged to force the workpiece into the die assembly via the first extrusion channel to exit the die assembly via the second extrusion channel, wherein the first and second extrusion channels have the same dimension normal to the direction of travel of the workpiece through the respective extrusion channel in use corresponding to the thickness of the workpiece.

40. An apparatus according to claim 39 in which the first extrusion channel is defined by a spacing between the driving surface and an opposed surface of the extrusion die assembly, the driving means being arranged to move the driving surface relative to the opposed surface of the die assembly thereby to translate the workpiece through into the first extrusion channel and through the die assembly using said frictional force.

41. An apparatus according to claim 40 in which the backpressure means is arranged to apply a controllable backpressure to the workpiece at the outlet of the second extrusion channel.

42. Apparatus according to any of preceding claims 27 to 41 including a rotatable drive roll member, wherein the driving surface is a surface of a rotatable drive roll member arranged such that rotation of the drive roll member drags the workpiece by friction therewith through the extrusion die assembly.

43. Apparatus according to claim 42 in which the driving surface is a substantially ungrooved surface of the drive roll member.

44. Appararus according to claim 42 or 43 in which the driving surface is arranged to form, in part, the first extrusion channel and is arranged to drive the workpiece by friction developed therewith through the die assembly.

45. Apparatus according to any of claism 27 to 44 in which the workpiece is in the form of a sheet including strip and plate, the ratio of the width to the thickness of the sheet workpiece is greater than 5, or greater than 10.

46. Apparatus according to any of claims 42 to 45 in which the driving roll has an endless circumferential groove therein, and a first die member of the die assembly comprises a shoe member which covers part of the length of the groove thereby forming the first extrusion channel therewith and a second die member of the die assembly comprises an abutment member which projects into the groove in the driving roll and forms with the first die member the second extrusion channel.

47. An apparatus according to any of previous claims 27 to 46 including heating means for heating the workpiece before and/or during the extrusion process.

48. An apparatus according to any of previous claims 27 to 47 including heating means for heat-treating the workpiece after extrusion through the extrusion die assembly.

49. An apparatus according to claim 48 in which the heat treating means is arranged to apply continuous recrystallisation annealing to the workpiece.

50. An apparatus according to claim 48 or 49 in which the heat-treating means is arranged to apply recovery annealing in between any two said extrusions.

51. An apparatus for refining the microstructure of the crystalline material to produce a fine grained or an ultra-fine grained microstructure using the apparatus according to any preceding claim.