Method for producing an aluminum strip and casting-rolling system for producing an aluminum strip

Abstract

A method for producing an aluminum strip (2) in a coupled casting-rolling process, includes the following steps: a) melting an aluminum raw material comprising at least one aluminum alloy in at least one melting assembly (4); b) determining the alloy composition of the melt (3); c) casting the melt (3) to form a hot strip by means of at least one strip-casting machine (6); d) rolling the hot strip in a rolling system (14) comprising at least one rolling device for shaping the hot strip for thickness and/or width reduction; and e) regulating and/or controlling at least one shaping parameter of the rolling system (14) as a function of the alloy composition of the melt (3). The disclosure also relates to a casting-rolling system (1) for carrying out the method.

Claims

1.-24. (canceled)

25. A method for producing a cast aluminum strip in a coupled casting-rolling process, comprising: melting an aluminum raw material comprising an aluminum alloy in a melting assembly; determining an alloy composition of the melt; casting the melt to form a hot strip by a strip-casting machine; rolling the hot strip in a rolling system comprising a rolling device and thereby shaping the hot strip by reducing a thickness and/or a width thereof; and regulating and/or controlling a shaping parameter of the rolling system as a function of the alloy composition of the melt.

26. The method according to claim 25, wherein the coupled casting-rolling process is a continuous process.

27. The method according to claim 25, wherein the shaping parameter is selected from the group of parameters consisting of thickness reduction of the hot strip, width reduction of the hot strip, strip temperature of the hot strip, rolling speed, strip tension of the hot strip, rolling force, roll bending, axial adjustment of at least one roll, roll gap geometry, rolling torque, cooling of the rolls, and lubrication of the rolls.

28. The method according to claim 25, wherein the regulating and/or controlling comprises a pre-control of the rolling system for a given and/or selected strip length section of the cast aluminum strip as a function of the alloy composition.

29. The method according to claim 28, wherein the pre-control comprises specifying a target value for thickness and/or profile regulation of the rolling device.

30. The method according to claim 25, wherein the melt has a recyclate content in the form of aluminum scrap of at least 95 percent by weight.

31. The method according to claim 25, wherein the aluminum alloy is selected from the group consisting of aluminum alloys AA2XXX, AA5XXX, AA6XXX, and AA7XXX.

32. The method according to claim 25, wherein casting the melt produces the hot strip with a thickness of 10 mm to 30 mm.

33. The method according to claim 25, wherein casting the melt is effected at a casting speed of 4 m/min to 16 m/min.

34. The method according to claim 25, further comprising abrasive surface conditioning an upper side and/or a lower side of the cast aluminum strip.

35. The method according to claim 25, wherein the rolling is carried out at a temperature between 300 C. and 500 C. and with a thickness reduction of 20% to 75% per rolling mill stand in relation to an initial thickness of the hot strip.

36. The method according to claim 25, wherein the casting of the melt is carried out using at least one casting machine with a moving mold.

37. The method according to claim 25, further comprising operating a plurality of melting units with different alloy compositions in parallel.

38. The method according to claim 25, further comprising mixing melts with different alloy compositions.

39. The method according to claim 25, further comprising setting a temperature of the hot strip prior to rolling.

40. The method according to claim 25, further comprising quenching the cast aluminum strip downstream of the at least one rolling device.

41. An intermediate aluminum product obtained by the method in accordance with claim 25, comprising at least 95% by weight of recyclate.

42. A casting-rolling system for producing a cast aluminum strip, comprising: a melting assembly; a strip-casting machine; and a rolling device; means for determining an alloy composition of an aluminum melt; and a regulating and control device, configured for regulating and/or controlling a shaping parameter of the rolling device as a function of the alloy composition of the melt.

43. The casting-rolling system according to claim 42, wherein the strip-casting machine is a casting machine with a moving mold.

44. The casting-rolling system according to claim 42, wherein the melting assembly is a multi-chamber melting furnace.

45. The casting-rolling system according to claim 42, further comprising a plurality of rolling mill stands, each having two working rolls and at least two support rolls along with at least two hydraulic adjusting cylinders for setting a roll gap.

46. The casting-rolling system according to claim 42, further comprising means for abrasive surface conditioning of the cast aluminum strip, arranged upstream of the rolling device.

47. The casting-rolling system according to claim 42, further comprising a trimming shear, which is arranged downstream of a rolling device and upstream of a coiler.

48. The casting-rolling system according to claim 42, further comprising a scrap return system of process scrap into a storage level of the melting assembly.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0068] FIG. 1 shows a schematic representation of a casting-rolling process and

[0069] FIG. 2 shows a schematic representation of a control scheme of the method in accordance with the disclosure.

DETAILED DESCRIPTION

[0070] FIG. 1 shows a casting-rolling system 1 for producing an aluminum strip 2. The casting-rolling system 1 comprises a plurality of melting assemblies 4 for producing a melt 3 of aluminum. The melting assemblies 4, which are only shown schematically, can be designed as multi-chamber melting furnaces, for example. The melting assemblies 4 are fed with an aluminum raw material from a storage level 5, on which aluminum scrap is stored in various scrap stores A, B, C, D, among others. The aluminum scrap consists, for example, of can scrap obtained from a waste management company and partially of process scrap that is generated in the method described below.

[0071] The casting-rolling system 1 further comprises a strip-casting machine 6, which is designed, for example, as a so-called belt caster or block caster for producing cast strip 7, along with two rolling mill stands 15, which are connected downstream in the direction of transport and with which the aluminum strip 2 is reduced in thickness. The rolling mill stands 15 are arranged at a short distance of between 5 m and 20 m downstream of the strip-casting machine 6 in the direction of transport. Immediately connected downstream of the strip-casting machine 6 is a surface cleaning device 11 of the cast aluminum strip 2 and a capping shear 12 for cutting off the cast strip head and/or cast strip foot that is produced during the casting of the aluminum strip 2 and cannot be further processed. The pieces of cast strip 7 cut off by the capping shear 12 are collected in a scrap bunker 13A and fed to a system for process scrap 25, which returns unmixed process scrap to the storage level 5 and can thus be reintroduced into the production cycle. Optionally, a temperature influencing device 16, which is designed as a heating and/or cooling device, can be provided upstream of the rolling mill stands 15.

[0072] The rolling mill stands 15 each comprise two driven working rolls and two support rolls and a hydraulic adjustment system for the working rolls, via which the roll rise can be set. The rolling mill stands 15 also each comprise a working roll bending system and means for axial adjustment of the working rolls.

[0073] The aluminum melt 3 generated by the melting assemblies 4 is fed to the strip-casting machine 6 via a casting channel 8 with a regulated mass flow. To regulate the mass flow of the melt 3, a flow regulator 9 is provided in the casting channel 8, downstream of which a filter 10 is connected to filter impurities from the melt 3. Thus, the melt can be fed to the casting machine continuously, such that a quasi-continuous casting-melting-rolling process is possible. A strip cooling device 18 is arranged downstream of the two rolling mill stands 15 forming the rolling system 14 and is followed by a trimming shear 19. This is followed by a flying shear 21. Finally, two coilers 23 are provided for winding up the rolled aluminum strip. Further scrap bunkers 13B and 13C are arranged downstream of the trimming shear 19 and downstream of the flying shear 21 respectively, from which the process scrap can be fed via the system for process scrap 25. The material cuttings collected in the scrap bunkers 13A, 13B and 13C can be fed to the respective scrap stores A, B, C, D of the storage level 5 as unmixed scrap. Scrap logistics can be provided for the system for process scrap 25, which can be operated automatically, semi-automatically or manually.

[0074] The aluminum scrap pre-sorted in the scrap stores A, B, C, D is initially subjected to a two-stage melting process in the melting assemblies 4. The scrap is first heated until any paint and other organic compounds are evaporated. The steam can be reused as an energy source, for example. The aluminum is then melted down. By means of an analysis device 40, the chemical composition of the melt is analyzed, for example to determine the proportion of metal impurities in the form of iron, copper, silicon, chromium, magnesium, manganese, nickel, zinc and tin. As a function of the analysis, the alloy composition is recharged to achieve certain desired properties. For this purpose, corresponding proportions of process scrap and/or pure aluminum are fed from the storage level 5/from the scrap stores A, B, C, D. The temperature of the melt is also set by the proportion of scrap added.

[0075] The set melt is fed to the strip-casting machine 6 via the casting channel 8 with a regulated mass flow. The melt passes through the filter 10, which filters out any impurities in the melt. A casting nozzle, not more specifically designated, guides the melt into the solidification region. The mold of the strip-casting machine 6 is designed as a moving mold. The melt solidifies without relative movement to the mold. As a result, a highly intensive heat transfer arises and the melt can solidify relatively rapidly. The melt is molded with a thickness of 10 mm to 30 mm, particularly preferably with a thickness of 15 to 25 mm as a cast strip 7, wherein the casting speed is 4 m/min to 16 m/min. The rapid solidification of the melt prevents segregation and suppresses the precipitation of impurities in the form of iron, copper, silicon, chromium, nickel, zinc and tin, for example. The alloy components remain largely in solution. As a result, the casting process is more tolerant to impurities. The rigid, moving mold of the strip-casting machine 6 prevents the solidifying strand from detaching. The heat transfer remains uniformly high.

[0076] The solidified cast strip 7 is fed directly to the rolling system 14 and reduced in thickness to aluminum strip 2. Due to the fact that there is only a relatively small distance between the rolling system 14 and the strip-casting machine 6, as already explained above, separation processes in the rolled material are prevented.

[0077] The stitch reduction per rolling mill stand 15 is preferably between 25% and 70% per rolling mill stand. As a result, the cast structure of the cast strip 7 is transformed into a rolled structure of the aluminum strip 2 and a rolled texture in the material is generated. As also mentioned above, hydraulically acting actuators are arranged on each rolling mill stand 15, with which the roll rise and/or a roll bending system and/or an axial adjustment of the working rolls can be effected.

[0078] A regulation of the rolling system is provided as a function of the alloy composition of the melt 3, which is determined via the analysis device 40 and is fed to a regulating and/or control device designated by 50. This controls the actuators of the rolling mill stands 15 accordingly, wherein a pre-control of the rolling system 14 for a given or selected strip length section of the cast strip 7 is provided. The pre-control comprises the specification of at least one target value for thickness and/or profile regulation of at least one of the rolling mill stands 15. By means of the pre-control, the at least one thickness and/or profile regulation is corrected as soon as the molded cast strip 7 with a certain known alloy composition enters the rolling system 14.

[0079] The setting of the thickness, stitch reduction and width of the aluminum strip 2 result from various parameters that define the shaping resistance. Such parameters comprise the alloy composition, the strip temperature, the strip tension, the roll lubrication, the strip lubrication, the roll diameter, the roll geometry (bending, camber, crown), the rolling force and the rolling torque.

[0080] It is provided to regulate at least some of these parameters, wherein the calculation can be effected within the control device 50 and the control device uses a process model 55 or alternatively the calculation is effected within the process model 55 and the results of the calculation in the control device are converted into setting parameters of the casting-rolling system 1. In particular, it is provided that the results of the analysis device 40 for regulating and/or controlling act at least on the rolling system 14, preferably independently of the casting process and the strip-casting machine 6.

[0081] The control scheme is roughly schematically illustrated in FIG. 2. Method step a) designates the melting of the aluminum raw material, method step b) the analysis of the alloy composition of the melt, method step c) the casting of the melt by means of the strip-casting machine 6 and method step d) the rolling of the hot strip. In FIG. 2, identical parts of the casting-rolling system 1 are marked with the same reference signs.

[0082] The reference sign 60 designates a production planning and control module that is connected to the process model 55, in order to incorporate production specifications such as bandwidths, target thicknesses, target structures, etc. into the calculation. The production planning and control module 60 is used, for example, to influence the composition of the melt 3 via the target specification X, for example by feeding aluminum scrap from the various scrap stores A, B, C, D. The subsequent analysis device 40 determines the proportion of impurities in the melt 3, which is fed to the control device 50 as an input variable.

LIST OF REFERENCE SIGNS

[0083] 1 Casting-rolling system [0084] 2 Aluminum strip [0085] 3 Melt [0086] 4 Melting assemblies [0087] 5 Storage level [0088] 6 Strip-casting machine [0089] 7 Cast strip [0090] 8 Casting channel [0091] 9 Flow regulator [0092] 10 Filter [0093] 11 Surface cleaning device [0094] 12 Capping shear [0095] 13A, 13B, 13C Scrap bunker [0096] 14 Rolling system [0097] 15 Rolling mill stands [0098] 16 Temperature influencing device [0099] 17 Not assigned [0100] 18 Strip cooling devices [0101] 19 Trimming shear [0102] 20 Not assigned [0103] 21 Flying shear [0104] 23 Coiler [0105] 24 Collar bearing [0106] 25 Scrap return system [0107] 40 Analysis device [0108] 50 Control device [0109] 55 Process model [0110] 60 Production planning and control module [0111] A, B, C, D Scrap stores