DEVICE AND METHOD FOR CONTINUOUSLY PRODUCING A METALLIC WORKPIECE IN STRIP FORM

Abstract

A method for continuously producing a strip-shaped metallic workpiece may involve introducing a molten mass into a casting region, solidifying the molten mass introduced into the casting region at least partially, and conveying the at least partially solidified molten mass out of the casting region. Hollow bodies may be added to the molten mass and encapsulated into the workpiece. Further, an apparatus for continuously producing a strip-shaped metallic workpiece may include a casting region into which a molten mass can be introduced and in which the molten mass introduced can solidify at least partially. The apparatus may also include a conveying device for conveying the molten mass out of the casting region, as well as a metering apparatus for adding hollow bodies to the molten mass.

Claims

1.-17. (canceled)

18. A method for continuously producing a strip-shaped metallic workpiece, the method comprising: introducing a molten mass into a casting region; adding hollow bodies to the molten mass; solidifying the molten mass at least partially; and conveying the molten mass out of the casting region.

19. The method of claim 18 wherein a material of the hollow bodies has a higher melting point than a material of the molten mass.

20. The method of claim 18 wherein the hollow bodies are hollow spheres.

21. The method of claim 18 wherein the hollow bodies comprise a metallic material, a ceramic material, or a combination thereof.

22. The method of claim 18 comprising preheating the hollow bodies prior to adding the hollow bodies to the molten mass.

23. The method of claim 18 wherein the hollow bodies are fixed in a carrier element, wherein the hollow bodies together with the carrier element are added to the molten mass.

24. The method of claim 23 comprising preheating the carrier element with the hollow bodies before the carrier element with the hollow bodies are added to the molten mass.

25. The method of claim 23 comprising melting the carrier element in the molten mass so as to release the hollow bodies that are fixed in the carrier element.

26. The method of claim 23 wherein the carrier element is a net or a film.

27. The method of claim 23 wherein the carrier element has a strip-like form and is added to the molten mass continuously.

28. The method of claim 18 comprising positioning an outlet of a metering apparatus beneath a surface of the molten mass and adding the hollow bodies to the molten mass by way of the outlet of the metering apparatus.

29. The method of claim 18 comprising positioning outlets of metering apparatuses beneath a surface of the molten mass and adding the hollow bodies to the molten mass by way of the outlets of the metering apparatuses.

30. The method of claim 18 comprising positioning the casting region between two oppositely rotating casting rollers that are cooled such that the molten mass solidifies and forms shells on roller surfaces of the two oppositely rotating casting rollers, wherein the shells are pressed together in a gap between the two oppositely rotating casting rollers.

31. The method of claim 30 comprising introducing the hollow bodies into a portion of the casting region that includes a geometric center between the two casting rollers.

32. The method of claim 18 comprising interrupting the addition of the hollow bodies to the molten mass to form regions in the strip-shaped metallic workpiece that are free from the hollow bodies.

33. An apparatus for continuously producing a strip-shaped metallic workpiece, the apparatus comprising: a casting region for receiving a molten mass, wherein the casting region is configured to solidify the molten mass at least partially; a conveying device for conveying the molten mass out of the casting region; and a metering apparatus for adding hollow bodies to the molten mass.

34. The apparatus of claim 33 wherein the conveying device comprises a casting roller or a belt.

35. A strip-shaped metallic workpiece produced by a method that comprises: introducing a molten mass into a casting region; adding hollow bodies to the molten mass; solidifying the molten mass at least partially; and conveying the molten mass out of the casting region.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0031] FIG. 1 shows a first exemplary embodiment of a production apparatus according to the invention in a schematic side view.

[0032] FIG. 2 shows a second exemplary embodiment of a production apparatus according to the invention in a schematic side view.

[0033] FIG. 3 shows a first exemplary embodiment of a workpiece produced by the method according to the invention in a perspective sectional illustration.

[0034] FIG. 4 shows a second exemplary embodiment of a workpiece produced by the method according to the invention in a schematic sectional illustration.

[0035] FIG. 5 shows a third exemplary embodiment of a workpiece produced by the method according to the invention in a schematic sectional illustration.

[0036] FIG. 6 shows a fourth exemplary embodiment of a workpiece produced by the method according to the invention in a schematic sectional illustration.

EMBODIMENTS OF THE INVENTION

[0037] In the various figures, the same parts are always provided with the same reference signs, and are therefore generally also named or mentioned only once in each case.

[0038] FIG. 1 shows a first exemplary embodiment of an apparatus 1 for continuously producing a strip-shaped metallic workpiece 15, which apparatus can be used to produce a workpiece 15 of reduced weight. The apparatus is embodied as a production apparatus in accordance with the vertical twin-roller method. It comprises a first casting roller 6 and a second casting roller 7, which are driven by a motor in opposite rotation. The directions of rotation of the two casting rollers 6, 7 are denoted by the arrows A, B. A gap 21 is provided between the casting rollers 6, 7, and preferably has a gap width in the range of 0.5 mm to 5 mm, particularly preferably of 3 mm.

[0039] A container 2 which is filled with liquid metallic molten mass 5 is arranged in a region above the casting rollers 6, 7. By way of example, the material of the molten mass 5 may contain steel, aluminum, titanium, zinc, copper, chromium, nickel, magnesium or a combination of said materials. The container 2 comprises a feed 3, which is arranged on the underside of the container and by way of which the liquid molten mass 5 is fed to a casting region 4 of the apparatus 1, which is also referred to as a melt pool. In this case, the feed 3 is immersed beneath the surface 20 of the liquid molten mass 5 introduced into the casting region 4.

[0040] The casting rollers 6, 7, in particular the roller surfaces of the casting rollers 6, 7 which come into contact with the molten mass 5 introduced into the casting region 4, are cooled by way of cooling assemblies which are not shown in the drawings. As a consequence of this cooling, the molten mass 5 solidifies at least partially on the roller surfaces, and therefore what are termed strip shells of partially solidified molten mass 11 form on the roller surfaces. The strip shells adhere to the casting rollers 6, 7, and are conveyed by the rotational movement of the casting rollers 6, 7 in the direction of the gap 21. The two strip shells which have formed on the first casting roller 6 and the second casting roller 7 are pressed together in the region before the gap 21, and fuse together. In this respect, the at least partially solidified molten mass 11 is conveyed out of the casting region 4. A strip-shaped workpiece 15 is formed and is discharged downward. The thickness of the workpiece 15 is dependent on the gap width of the gap 21, and lies in the range of 0.5 mm to 5 mm, and is preferably 3 mm. In subsequent process steps, the workpiece 15 can be rolled up and/or processed further.

[0041] In order to facilitate the start-up of the production apparatus 1, the production apparatus 1 comprises a starting belt 9, which is unwound from a coil 8.

[0042] According to the invention, in addition to the molten mass 5 which has already been introduced into the casting region 4, hollow bodies 12 are introduced in the case of the apparatus 1. The hollow bodies 12 are incorporated into the solidifying molten mass 5 and/or between the strip shells which have been formed from already partially solidified molten mass 11, and therefore said bodies are encapsulated into the workpiece 15 produced. The material of the hollow bodies 12, in particular the material of the outer skin of the hollow bodies 12, has a higher melting point than the material of the molten mass 5, and therefore melting of the hollow bodies 12 in the molten mass 5 does not have to be feared. The hollow bodies 12 form defined cavities within the workpiece 12, these cavities lowering the density of the workpiece 15 and therefore contributing to a reduction in weight. In this respect, a strip-shaped workpiece which is embodied in the manner of a syntactic foam is obtained. The hollow bodies 12 are preferably in the form of hollow spheres, the diameter of the hollow spheres lying in a range of less than 5 mm, preferably less than 3 mm, particularly preferably less than 2 mm. Use is preferably made of hollow bodies 12 made of a ceramic material, as a result of which the rigidity and/or the wear behavior of the workpiece 15 can be improved. By way of example, the hollow bodies 12 may comprise aluminum oxide (Al.sub.2O.sub.3), zirconium dioxide (ZrO.sub.2), silicon carbide (SiC), boron carbide (B.sub.4C), silicon nitride (Si.sub.3N.sub.4), titanium boride (TiB.sub.2), tungsten carbide (WC), titanium carbide (TiC) or silicon dioxide (SiO.sub.2). As an alternative or in addition, the hollow bodies 12 may comprise a metallic material, for example iron. The hollow bodies 12 preferably consist of an intermetallic compound. According to a further alternative, the hollow bodies 12 may consist of a combination of the aforementioned ceramic materials with one or more metals.

[0043] For the addition of the hollow bodies 12, the production apparatus 1 comprises a metering apparatus 22, which is arranged above the casting region 4. The metering apparatus comprises a carrier element 13. The hollow bodies 12 are fixed in the carrier element 13, such that they can be added, together with the carrier element 13, to the molten mass 5 introduced into the casting region 4, without there being a need to fear floating of the hollow bodies 12 in the molten mass 5. The carrier element 13 is in the form of a flexible, strip-like carrier element 13, for example a net, a tube or a film. The metering apparatus 22 further comprises a dispensing reel 14, on which the carrier element 14 equipped with hollow bodies 12 is present in rolled-up form. The material of the carrier element 14 has a melting point which lies at a lower temperature than the melting point of the hollow bodies and lies at a lower temperature than or the same temperature as the melting point of the material of the molten mass 5, such that the carrier element 14 is melted in the molten mass 5 and the hollow bodies 12 fixed in the carrier element 15 are released into the molten mass 5. Hollow bodies 12 are therefore fed continuously to the casting region 4 by way of the carrier element 15.

[0044] The production apparatus 1 further comprises a preheating device (not shown in the drawings), by way of which the carrier element 13 and the hollow bodies 12 are preheated, such that the risk of solidification of the molten mass 5 upon introduction of the carrier element 13 and hollow bodies 12 into the molten mass 5 is reduced. The preheating is effected to a temperature which is greater than 0.6 times the liquidus temperature of the molten mass 5, preferably greater than 0.7 times the liquidus temperature of the molten mass 5, particularly preferably greater than 0.9 times the liquidus temperature of the molten mass 5.

[0045] FIG. 2 shows a second exemplary embodiment of an apparatus 1 for continuously producing a strip-shaped metallic workpiece 15, said apparatus differing from the apparatus 1 according to the first exemplary embodiment only with regard to the addition of the hollow bodies 12 to the molten mass 5. The apparatus 1 according to the second exemplary embodiment comprises a metering apparatus 18 for adding the hollow bodies 12 which is embodied in the manner of a lance. An outlet 19 of the metering apparatus 18 is arranged beneath the surface 20 of the molten mass 5 received in the casting region 4. The hollow bodies 12 can be added loosely. To this end, the metering apparatus 18 is connected to a collecting container 25, in which the hollow bodies 12 are stored. The collecting container 25 may optionally be equipped with a heating apparatus for preheating the hollow bodies 12. It is preferable for the metering apparatus 18, in particular the outlet 19 of the metering apparatus 18, to be heated.

[0046] In a modification of the second exemplary embodiment, hollow bodies 12 which are fixed in a carrier element 15 are added to the molten mass 5 by way of the metering apparatus 18. To this end, by way of example, the carrier element 15 is unwound from a dispensing reel and introduced into the casting region 4 by the metering apparatus 18, in particular the outlet 19 thereof, beneath the surface 20 of the molten mass 5.

[0047] According to a further modification of the second exemplary embodiment, the production apparatus 1 comprises a plurality of metering apparatuses 18, in particular a plurality of lances. The outlets 19 of said metering apparatuses 18 can be oriented toward different portions of the casting region 4, such that hollow bodies are encapsulated into the workpiece 15 at different locations.

[0048] FIG. 3 shows a first exemplary embodiment of a strip-shaped metallic workpiece 15 which can be obtained using the apparatus 1 according to the invention or by the method according to the invention. The strip-shaped workpiece 15 has a substantially rectangular cross-sectional area. The surfaces 26 of the workpiece 15 have a smooth form. A lower concentration of hollow bodies 15 is present in the marginal region 16 which directly adjoins the outer contour of the workpiece than in the inner region 17 which lies in the interior of the workpiece 15. The marginal region 16 is preferably formed in a manner free from hollow bodies, whereas the inner region 17 has a dense packing of hollow bodies 12. In this respect, a workpiece 15 is formed in the manner of a metal sheet comprising a porous core and smooth surfaces 26. A workpiece 15 of this type combines the advantages of a reduction in weight owing to the porous core with good formability, good mechanical properties, such as high ductility, and/or joinability of the smooth surfaces which consist essentially of the material of the molten mass. The workpiece 15 may be supplied to subsequent processing steps as a near-net-shape semifinished product.

[0049] FIG. 4 shows a second exemplary embodiment of a strip-shaped metallic workpiece 15 in a schematic sectional illustration. To produce said workpiece 15, the addition of the hollow bodies 12 to the molten mass 5 was temporarily interrupted in order to alternately form portions 24 with a high hollow body concentration and portions 23 with a low concentration of hollow bodies, in particular free from hollow bodies, in the workpiece 15. In said portions 23 with a low concentration of hollow bodies, the workpiece 15 can be formed and/or joined in a subsequent processing step. The portions 24 with a high hollow body concentration and the portions 23 with a low concentration of hollow bodies extend in the workpiece 15 in the width direction and the thickness direction of the workpiece 15.

[0050] FIG. 5 shows a third exemplary embodiment of a strip-shaped metallic workpiece 15. During the production of said workpiece 15, the hollow bodies 12 were introduced simultaneously into a plurality of regions, such that a plurality of regions with an increased hollow body concentration were formed. The regions with an increased hollow body concentration are spaced apart from one another in the width direction and/or the thickness direction of the workpiece 15.

[0051] FIG. 6 shows a fourth exemplary embodiment of a strip-shaped metallic workpiece 15. During the production of said workpiece 15, the hollow bodies 12 were introduced simultaneously into a plurality of regions, such that a plurality of regions with an increased hollow body concentration were formed. The regions with an increased hollow body concentration are spaced apart from one another in the width direction and/or the thickness direction of the workpiece 15. In addition, the addition of the hollow bodies 12 to the molten mass 5 was temporarily interrupted in order to form alternating portions 24 with a high hollow body concentration and portions 23 with a low concentration of hollow bodies, in particular free from hollow bodies, in the workpiece 15.

[0052] The above-described apparatuses 1 implement a method for continuously producing a strip-shaped metallic workpiece 15, wherein a molten mass 5 is introduced into a casting region 4, the molten mass 5 introduced into the casting region 4 solidifies at least partially, and the at least partially solidified molten mass 11 is conveyed out of the casting region 4, wherein hollow bodies 12 are added to the molten mass 5 introduced into the casting region 4 and are encapsulated into the workpiece 15. It is thereby possible to achieve a reduction in the weight of the workpiece 15.

LIST OF REFERENCE SIGNS

[0053] 1 Production apparatus

[0054] 2 Container

[0055] 3 Feed

[0056] 4 Casting region

[0057] 5 Molten mass

[0058] 6 Casting roller

[0059] 7 Casting roller

[0060] 8 Coil

[0061] 9 Starting belt

[0062] 11 Solidified molten mass

[0063] 12 Hollow body

[0064] 13 Carrier element

[0065] 14 Dispensing reel

[0066] 15 Workpiece

[0067] 16 Marginal region

[0068] 17 Inner region

[0069] 18 Metering apparatus

[0070] 19 Outlet

[0071] 20 Surface of the molten mass

[0072] 21 Gap

[0073] 22 Metering apparatus

[0074] 23 Portion free from hollow bodies

[0075] 24 Portion with a high hollow body concentration

[0076] 25 Collecting container

[0077] 26 Surface

[0078] A Direction of rotation

[0079] B Direction of rotation