Thermomechanical rolling of an aluminum plate

Abstract

In a rolling process for reverse thermomechanically rolling an aluminum plate involving a plurality of rolling passes, identifying data are determined for thermally guiding the rolling process. Then a value of a state variable, from which a temperature of the aluminum plate can be deduced, is continuously measured and a pass schedule is determined for the rolling process on the basis of the value of the measured state variable and of the identifying data. The pass schedule provides for a rolling pause between at least two successive rolling passes, during which rolling of the aluminum plate is interrupted for cooling purposes.

Claims

1. A method for reversing thermomechanical rolling of an aluminum plate in a rolling process including a plurality of rolling passes, comprising: specifying characteristic data, including a microstructure of the aluminum plate, a waiting thickness of the aluminum plate assigned to at least one rolling pass and at least one of rolling restart temperatures, a target temperature, a cooling temperature, and a cooling rate, for thermally controlling the rolling process; continuously determining values of at least one state variable including measured surface temperature profiles of the aluminum plate, from which a temperature of the aluminum plate can be derived; determining a pass schedule for the rolling process as a function of the characteristic data, including the waiting thickness of the aluminum plate assigned to at least one rolling pass and the at least one of rolling restart temperatures, the target temperature, the cooling temperature, and the cooling rate ,and the values of the at least one state variable obtained by said determining, including measured surface temperature profiles of the aluminum plate, the pass schedule making provision for a rolling pause between at least two successive rolling passes that starts as soon as a measured thickness of the aluminum plate is no longer above the waiting thickness assigned to a completed rolling pass, where during the rolling pause rolling of the aluminum plate is interrupted to allow the aluminum plate to cool down; and controlling the rolling process in accordance with the pass schedule, based on temperatures measured at different locations on the aluminum plate and the characteristic data, including the waiting thickness of the aluminum plate assigned to at least one rolling pass and the at least one of rolling restart temperatures, the target temperature, the cooling temperature, and the cooling rate.

2. The method as claimed in claim 1, wherein the characteristic data assigns a rolling restart temperature of the aluminum plate to at least one rolling pause, and wherein the pass schedule makes provision for the rolling pause to terminate as soon as the temperature of the aluminum plate reaches the rolling restart temperature.

3. The method as claimed claim 1, wherein the characteristic data includes a target temperature, and wherein the pass schedule determines a duration of at least one of the rolling pause and a rolling restart temperature of the aluminum plate after the rolling pause so that the temperature of the aluminum plate after a final rolling pass coincides with the target temperature.

4. The method as claimed claim 1, wherein the state variable is at least one of a temperature averaged over the measured thickness of the aluminum plate, a surface temperature, a residual hardening, phase fractions, grain sizes, and an enthalpy of the aluminum plate.

5. The method as claimed claim 1, wherein the characteristic data includes a cooling temperature, and further comprising, after a final rolling pass, supplying the aluminum plate to a cooling unit and cooling to the cooling temperature by the cooling unit.

6. The method as claimed in claim 5, wherein the characteristic data includes a cooling rate, and wherein in said cooling after the final rolling pass, the aluminum plate is cooled down to the cooling temperature at the cooling rate by the cooling unit.

7. The method as claimed claim 1, further comprising, performing at least one rolling pass of another aluminum plate during at least one rolling pause.

8. The method as claimed claim 1, further comprising predefining a rolling force threshold value as a function of at least one state variable of the aluminum plate, and wherein the pass schedule limits a rolling force during the rolling operation to a respective rolling force threshold value as a function of the values of the at least one state variable.

9. The method as claimed in claim 8, wherein the measured thickness of the aluminum plate is used as a state variable.

10. The method as claimed claim 1, further comprising predefining a thickness reduction threshold value as a function of at least one state variable of the aluminum plate, and wherein the pass schedule limits a reduction of the measured thickness of the aluminum plate during each rolling pass to a respective thickness reduction threshold value as a function of the values of the at least one state variable.

11. The method as claimed in claim 10, wherein the measured thickness of the aluminum plate is used as a state variable.

12. The method as claimed claim 1, further comprising cooling the aluminum plate by a cooling unit during at least one rolling pause.

13. The method as claimed claim 1, further comprising continuously acquiring measured values of at least one measurement variable associated with a temperature of the aluminum plate, and wherein the values of the at least one state variable are determined based on the measured values by a temperature model evaluating the measured values.

14. The method as claimed claim 1, further comprising constantly updating the pass schedule.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-described characteristics, features and advantages, as well as the manner in which these are achieved, will become clearer and more readily understandable in connection with the following description of exemplary embodiments which are explained in more detail with reference to a drawing.

(2) The FIGURE shows a flowchart of a method for reversing thermomechanical rolling of an aluminum plate into an aluminum sheet in a rolling process including a plurality of rolling passes, the method being performed by an automation system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(3) Reference will now be made in detail to the preferred embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

(4) The method entails the acquisition of measured values 1 of at least one measurement variable associated with a temperature of the aluminum plate. Measurement variables of the type are in particular temperatures at different locations on the aluminum plate and parameters that are characteristic of the aluminum plate, such as a microstructure.

(5) A current temperature of the aluminum plate is determined as state variable 3 of the aluminum plate on the basis of the acquired measured values 1 by a temperature model 2 of the aluminum plate evaluating the measured values 1, as is known from WO 2008/043684.

(6) Furthermore, characteristic data 4 for thermally controlling the rolling process is specified and stored in the automation system. The characteristic data comprises in particular waiting thicknesses, rolling restart temperatures, a target temperature, a cooling temperature, and a cooling rate.

(7) A pass schedule 5 for the rolling process is determined based on the determined current temperature of the aluminum plate and the characteristic data 4, which pass schedule 5 also comprises final control elements 6 required for achieving the characteristic data 4. Such final control elements 6 include a cooling-down time in the case of air cooling of the aluminum plate, a number of rolling passes, a throughput rate of the aluminum plate through a rolling mill stand, and/or water volumes of a cooling unit.

(8) On the basis of the pass schedule 5, the aluminum plate is rolled during each rolling pass until a waiting thickness assigned to the respective rolling pass is reached. The rolling of the aluminum plate is subsequently interrupted by a rolling pause until the plate has cooled down to a rolling restart temperature assigned to the rolling pause for initiation of the following rolling pass. In this case the aluminum plate can be cooled passively or actively by a cooling unit. The waiting thicknesses and rolling restart temperatures are dependent on the material and the target geometry of the aluminum plate. These variables can sometimes be derived from phase diagrams, in the case of aluminum plates made from aluminum-copper or aluminum-magnesium alloys, for example, but in general are determined empirically.

(9) The rolling restart temperature of the final rolling pass is determined with the aid of the temperature model 2 such that the temperature of the aluminum plate after the final rolling coincides with the target temperature. The target temperature can be characterized e.g. by a temperature averaged over the thickness of the aluminum plate, by a surface temperature or by an enthalpy.

(10) After the final rolling pass the aluminum plate is supplied to a cooling unit and cooled down to the cooling temperature at the cooling rate by the cooling unit.

(11) In one exemplary embodiment the pass schedule also takes into account further characteristic data, e.g. a maximum rolling force acting on the aluminum plate and/or a maximum thickness reduction of the aluminum plate during the individual rolling passes, in addition to the characteristic data 4 for thermally controlling the rolling process.

(12) In a further alternative or additional implementation of the exemplary embodiment the pass schedule is updated cyclically, e.g. after each pass of the aluminum plate through a cooling unit, on the basis of the determined current temperature, in particular the final control elements 6 for the further cooling phases also being updated in the process. In particular it is possible in this way in the event of a deviation of the actual data from the planning data to make repeated corrective interventions in order to achieve the target variables (in particular a target thickness and the target temperature of the aluminum plate).

(13) In another alternative or additional embodiment of the exemplary embodiment at least one further aluminum plate is rough-rolled during the cooling-down of the aluminum plate in a rolling pause. The method for staggered rolling of a plurality of aluminum plates known from EP 2 111 309 B1 is used for this purpose.

(14) Although the method has been illustrated and described in greater detail on the basis of a preferred exemplary embodiment, the method is not limited by the disclosed examples and other variations can be derived herefrom by the person skilled in the art without leaving the spirit and scope of protection of the claims which may include the phrase at least one of A, B and C as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 358 F3d 870, 69 USPQ2d 1865 (Fed. Cir. 2004).