Abstract
An aluminum hot strip rolling mill including a multi-stand tandem finishing rolling train (2), at least one winding reel (8) arranged downstream, in the rolling direction, of the multi-stand tandem finishing rolling train, a cooling section (4) provided in the outlet region of the aluminum hot strip rolling mill, and at least one trimmer (6) paired with the multi-stand tandem finishing rolling train and arranged downstream, in the rolling direction, in the rolling direction, of the multi-stand tandem rolling mill train.
Claims
1. A method of hot rolling an aluminum hot strip (7) of AlMg-alloy from AA5xxx-group in an aluminum hot strip rolling train, comprising the steps of: heating an aluminum alloy ingot of AlMg-alloy from AA5xxx-group in a temperature 450? C. to 570? C.; rough rolling the aluminum alloy ingot to an aluminum hot strip having a thickness from 20 mm to 50 mm in a roughing train of the aluminum hot strip rolling train in a temperature range above 400? C.; rolling the aluminum hot strip (7) in a multi-stand tandem finishing rolling train (2) of the aluminum hot strip rolling train with activated cooling devices (5) between the tandem stands (1) of the multi-stand tandem finishing rolling train (2) so that during rolling in last two tandem stand in a temperature range between 250? C. and 300? C., a deformation rate between 30% and 50% and a desired hot strip thickness between 2 mm and 8 mm is achieved; trimming of the hot strip; and winding of the aluminum hot strip, wherein the process of finish rolling of the strip element is carried out within a time period of less than 60 sec.
2. A method of hot rolling an aluminum hot strip (7) of AlMg-alloy from AA5xxx-group in an aluminum hot strip rolling train, comprising the steps of: heating an aluminum alloy ingot of AlMg-alloy from AA5xxx-group in a temperature 450? C. to 570? C.; rough rolling the aluminum alloy ingot to an aluminum hot strip having a thickness from 20 mm to 50 mm in a roughing train of the aluminum hot strip rolling train in a temperature range above 400? C.; rolling the aluminum hot strip (7) in a multi-stand tandem finishing rolling train (2) of the aluminum hot strip rolling train with activated cooling devices (5) between the tandem stands (1) of the multi-stand tandem finishing rolling train (2) so that during rolling in last two tandem stands in a temperature range between 250? C. and 300? C., a deformation rate between 30% and 50% and a desired hot strip thickness between 2 mm and 8 mm is achieved; trimming of the hot strip; and cooling of the aluminum hot strip in an outlet region of the aluminum hot strip rolling train with a cooling section (4) to a reeling temperature of below 250? C., and winding up the aluminum hot strip, wherein the process of finish rolling in the multi-stand tandem finishing rolling train (2) is carried out within a time period of less than 60 sec.
3. A method of hot rolling an aluminum hot strip (7) of AlMgSi-alloy from AA6xxx-group in an aluminum hot strip rolling train, comprising the steps of: heating an aluminum alloy ingot of AlMgSi-alloy from AA6xxx-group to a temperature from 490? C. to 570? C.; rough rolling the aluminum alloy ingot to an aluminum hot strip having a thickness from 20 mm to 50 mm in a roughing train of the aluminum hot strip rolling train in a temperature range above 400? C.; rolling the aluminum hot strip (7) in a multi-stand tandem finishing rolling train (2) of the aluminum hot strip rolling train with activated cooling devices (5) between tandem stands (1) of the multi-stand tandem finishing rolling train (2) so that during rolling in last two tandem stands in a temperature range between 300? C. and 370? C., a deformation rate between 30% and 50% and a desired hot strip thickness between 2 mm and 6 mm is achieved; trimming of the hot strip; and cooling of the aluminum hot strip in an outlet region of the multi-stand tandem finishing rolling train with a cooling section (4) to a reeling temperature of below 250? C., wherein the process of finish rolling in the multi-stand tandem finishing rolling train (2) is carried out within a time period of less than 60 sec.
4. A method of hot rolling aluminum hot strip (7) of AlMgSi-alloy from AA6xxx-group according to claim 3, wherein the cooling step comprises cooling of the aluminum hot strip to a reeling temperature from 150? C. to 230? C.
5. A method of hot rolling aluminum hot strip (7) of AlMgSi-alloy from AA5xxx-group according to claim 3, wherein the cooling step comprises cooling of the aluminum hot strip to a reeling temperature from 150? C. to 230? C.
Description
(1) The invention will be described in detail below with reference to the drawings.
(2) The drawings show:
(3) FIG. 1 a section of a finishing rolling train of an inventive aluminum hot strip rolling train;
(4) FIG. 2 a schematic view of particularities of strip drying means of the finishing rolling train according to FIG. 1;
(5) FIG. 3 a section of a finishing rolling train of an aluminum hot strip rolling train retrofitted according to the present invention;
(6) FIG. 4 a schematic view of a temperature-time diagram (cooling curve) obtained with the inventive aluminum hot strip rolling train in comparison with that of the state-of-the art;
(7) FIG. 5 a schematic view of a temperature-time diagram (cooling curve) obtained in a four-stand tandem finishing rolling train of the inventive aluminum hot strip rolling train, without an activated cooling section in the outlet region, in comparison with the state-of-the art; and
(8) FIG. 6 a schematic view of a process control.
(9) FIG. 1 shows a section of a tandem finishing rolling train of an aluminum hot strip rolling train according to the invention and including a multi-stand tandem rolling train 2 having four tandem stands 1, an upstream cooler 3 in the inlet region of the tandem finishing rolling train 2, and an associated cooling section 4 in the outlet region of the aluminum hot strip rolling train. Intermediate cooling means 5 is provided between separate tandem rolling stands 1. In the rolling direction, downstream of the tandem finishing rolling train 2 and in front of the cooling section 4, there is provided trimming shears 6, and in the rolling direction, downstream of the cooling section 4 and in front of the rolled aluminum hot strip-receiving winding reel 8, there is provided drying means 9. Between the tandem finishing rolling train 2 and the trimming shears 6, there are provided measuring apparatuses or measuring devices 10 with which strip temperature(s), strip speed(s), strip outer surface(s) and the like can be detected. These measuring apparatuses and devices 10 are operatively connected with shown in FIG. 6, control and regulating device 11 that can control and regulate, independently from each other, the tandem rolling stands 1, in particular the rolling speed, the cooling section 4, and the intermediate cooling means 5 and, if necessary or desired, the upstream strip cooler 3 and the drying means 9. The independent control and regulation of separate cooling devices consists, e.g., in that the activation and deactivation as well as the cooling medium mass flow rate applied to the aluminum hot strip 7 by the upstream strip cooler 3 but particularly by the intermediate cooling means 5 and the cooling section 4 can be carried out independent from one another and independent from the speed control. Therefore, it is possible, independently from each other, individually adapt and, independently from each other, adjust the rolling speed, intermediate cooling, end rolling temperature, and the reeling temperature for a respective to-be-rolled aluminum hot strip material of aluminum alloy. The strip drying means 9 which is arranged in front of the winding reel 8, makes it possible to remove the cooling medium which remains on the surface of the aluminum hot strip 7 after it passes the cooling section 4 and, thus, prevent surface defects. The cooling section 4 and the intermediate cooling means 5 are formed as laminar cooling means or spray cooling means. Advantageously, the cooling medium is (usually) water emulsion or demineralized water.
(10) FIG. 2 shows that the drying means 9 includes drying devices and cooling medium removing devices in form of catchers with counter-spraying means 12, counter-spraying means 13, so-called air knives 14, and suction means 15.
(11) FIG. 3 shows how the available aluminum strip rolling train can be readily retrofitted with cooling features according to the present invention. To this end, it is only necessary to extend the outlet region, if needed, and to move the available winding reel 8 to the position of the winding reel 8 to provide place for the cooling section 4 and the strip drying means 9, or to provide the winding reel 8 in addition to the winding reel 8. Between the tandem stands 1 of the tandem finishing rolling train 2, the intermediate cooling means 5 is retrofitted and, if desired, the upstream cooler 3 is provided on the inlet side.
(12) FIG. 4 shows cooling curves or temperature-time diagrams which provide for a noticeably more rapid cooling, and also for a temperature-dependent targeted cooling of the aluminum hot strip 7 according to the invention in the region of the multi-stand tandem finishing rolling train 2 of the inventive aluminum hot strip rolling train. While the cooling in tandem finishing rolling train 2 retrofitted according to the invention can be carried out within one minute or within 60 seconds and to noticeably lower temperatures, this cannot be achieved in installations according to the state-of-the art. FIG. 4 shows that the aluminum hot strip 7 after a rough rolling in a roughing rolling train of the aluminum hot strip rolling train, with the activated upstream cooler 3, the activated intermediate cooling means 5, and the cooling section 4, is rolled noticeably more rapidly to the end rolling temperature in the range between 300? C. and 360? C. and then is cooled to the winding temperature in the range from less than 200? C. to less than 250? C. before the aluminum hot strip 7 is wound on the winding reel 8, and is cooled further thereon.
(13) FIG. 5 shows the effect of the intermediate cooling means in the four-stand tandem finishing rolling train 2, wherein the activation and the operation of the cooling section 4 in the outlet region on the temperature-time diagram before winding of the aluminum hot strip 7 onto the winding reel 8 and the cooling of the coil is dispensed with. The course of the cooling curve or of the temperature time curve, without the intermediate cooling, is shown with a solid line, and the cooling curve or the temperature time curve, with the activated intermediate cooling means, is shown with a dash line. FIGS. 4 and 5 show how the cooling process of the rolling and rolled aluminum hot strip can be selectively controlled so that dependent on the desired results with regard to grain fineness and dependent on the alloy, separate cooling devices 3, 4 and 5 are used, upon being activated, or remain unused, without being activated.
(14) FIG. 6 shows schematically the control or regulating device 11 to which measured value detected by the measurement apparatuses or the measurement devices 10 and representing the results of rolling and the condition of the rolling process are fed back. These measured values are stored in a technological process model 16 incorporated in the control or regulating device 11. Those are so affected by the technological process model 16 which is incorporated and mapped in the control and/or regulating device 11, that the control and/or regulating processes change, taking into account changes of heat transfer coefficients during cooling of the aluminum hot strip 7. The technological process model 16 also takes into account the feedback of respective temperature levels of the aluminum hot strip 7 during separate passes in the tandem stands 1 of the tandem finishing rolling train 2 or the friction between the rolling emulsion or between separate rolls and a respective aluminum hot strip material when determining the control and/or regulating processes. As shown in FIG. 6, the technological process model 16 controls the setup of separate devices of the aluminum hot strip rolling train and, in particular, in the shown here, region of the tandem finishing rolling train 2 with the upstream cooler 3, intermediate cooling means 5, and the associated cooling section 4, and the drying means 9, generating regulating and/or control signals transmitted by the control and regulating device 11 to respective devices such as tandem stands 1, the upstream cooler 3, the cooling section 4, the intermediate cooling means 5, and the drying means 9. A component of the control and/or regulating device 11 is a computer, not shown in detail, in which the technological process model 16 is stored and which controls the course of the desired temperature-time diagram and the regulating device. The cooling devices 3, 4, and 5 can be so formed that they are controlled width-dependent with regard to the rolled aluminum hot strip.
(15) In particular, it is possible to set up, with the inventive aluminum hot strip rolling train, individual, specific and, if necessary, alloy-dependent time curves with regard to the temperature and/or deformation rates set up in the tandem stands, in order to obtain the desired results with regard to the structure of a respective aluminum alloy of a rolled aluminum hot strip and, thereby, certain material characteristics and/or strength. With the inventive aluminum hot strip rolling train, it is also possible to carry out, independently from each other, control of deformation, of the (cooling) time, and of the temperature without production losses. Rather, an increase of the production in comparison with the similar finishing rolling trains of the state-of-the art is possible. For each aluminum alloy, such conditions can be set up that the precipitates are finely distributed. Thereby, noticeably better uniform elongation values are achieved. Formation of large precipitates can be prevented by a rapid cooling, after the hot rolling of the aluminum hot strip, to a temperature in a range from more than 200? C. to less than 250? C. in which the diffusion processes are not slown down or are slown down to a lesser degree. The intermediate cooling means 5 is used with a particular advantage when the recrystallization is carried out only partially or not at all at relatively low temperatures, so that the remaining deformation energy can be used as activation energy for recrystalization in a coil wound on the winding reel 8.
