Method for producing a metal strip in a cast-rolling installation

Abstract

The invention relates to a method for producing a metal strip (1) in a cast-rolling installation (2), said cast-rolling installation (2) comprising the following: a casting machine (3), a first furnace (4), a first shear (S1), a roughing train (5), a second furnace (6), a second shear (S2), a finishing train (7), a cooling section (8), a reeling system (9), and a third shear (S3). In order to allow a flexible reaction to different operating conditions, at least one of the following operating modes is selected in order to produce the strip (1): a) a continuous rolling, in which the casting machine (3), the roughing train (5), and the finishing train (7) are operatively connected together; b) a continuous rolling in the roughing train (5) and a single-strip rolling in the finishing train (7); c) a single-strip rolling in the roughing train (5) and a single-strip rolling in the finishing train (7); and d) a semi-continuous rolling in the roughing train (5) and / or a semi-continuous rolling in the finishing train (7).

Description

[0001] The invention relates to a method for producing a metallic strip in a casting and rolling plant, the casting and rolling plant comprising: a casting machine for casting a slab, a first furnace following in the conveying direction of the metallic strip of the casting machine and / or a first roller table insulation section, a first shear arranged between the casting machine and the first furnace and / or the first roller table insulation section, a roughing train with a number of rolling stands, a second furnace following in the conveying direction of the metallic strip of the roughing train and / or a second roller table insulation section, a second shear arranged between the roughing train and the second furnace and / or the second roller table insulation section, a finishing train with a number of rolling stands, a cooling section, at least two coilers or one turning coiler and a third shear arranged between the cooling section and the coiling system.

[0002] The demands on the flexible operation of thin slab casting and rolling plants (CSP plants) are constantly increasing. The goal is to be able to adjust to various operating conditions. Adaptation to, for example, the rolled finished strip thickness or the casting speed is also desirable for quality and energy consumption reasons.

[0003] Thin slab casting and rolling mills for rolling individual strips or for continuous rolling have already been sufficiently mentioned in the prior art. For example, reference is made to DE 195 18 144 C2, DE 196 13 718 C1, EP 0 870 553 B1, WO 2007 / 073841 A1, WO 2009 / 012963 A1, and EP 2 569 104 B1. Further solutions, some of which also employ different operating modes, are known from US 2011 / 272116 A1 and WO 00 / 10741 A1. The preamble of claim 1 is based on US 2011 / 272116 A1.

[0004] However, the previously known solutions sometimes have disadvantages in terms of flexibility.

[0005] The invention is therefore based on Task The aim is to further develop a process of the type described above in such a way that a greater degree of flexibility is possible. In particular, this should allow for flexible response to different operating conditions. The proposed plant concept and operating mode should therefore be characterized by a high degree of flexibility.

[0006] This object is achieved by the method according to claim 1.

[0007] Preferably, at least one slab is placed in the first furnace and / or in the first roller table insulation section. Preferably, at least one slab or one transfer strip is also placed in the second furnace and / or in the second roller table insulation section.

[0008] The above-mentioned operating modes a), b), c), and / or d) can be selected depending on the final thickness of the strip. It is also possible for operating modes a), b), c), and / or d) to be selected depending on the start-up process of the casting-rolling mill. Furthermore, it is possible for operating modes a), b), c), and / or d) to be selected depending on an ongoing roll change in the roughing mill and / or the finishing mill.

[0009] First, one of the aforementioned operating modes is selected, and production is then carried out using this mode; accordingly, only one of the aforementioned options a), b), c), or d) is implemented at a given time. However, switching between the various aforementioned operating modes can also occur sequentially.

[0010] The average slab temperature at the outlet of the first furnace is preferably at least 1,000 °C, particularly preferably at least 1,100 °C.

[0011] The average pre-strip temperature at the outlet of the second furnace is preferably at least 1,100 °C, particularly preferably at least 1,150 °C.

[0012] A further development stipulates that the degree of deformation of the strip in the finishing train is: E = h V − h F / h V × 100 ≥ 96 % where h V is the pre-strip thickness and h F is the finished strip thickness. Specifically in this case, it is preferably provided that the average pre-strip temperature at the outlet of the second furnace is at least 1,150 °C, wherein the product of the strip thickness (h B ) and the strip speed (v B ) is at least 350 mm m / min, preferably at least 500 mm m / min.

[0013] It is preferably provided that inductive heating of the slab and / or the preliminary strip does not take place in the described procedure.

[0014] The temperature in the last active stand of the finishing train is preferably above the γ-α phase transformation, in particular above 820 °C.

[0015] The drawing illustrates an embodiment of the invention. The sole figure shows a schematic side view of a single-strand casting and rolling mill for the production of a strip.

[0016] The proposed thin slab casting and rolling plant concept consists of the following main components, which can be seen in the figure: The casting and rolling plant 2 for producing the strip 1 initially comprises a casting machine 3. A first furnace 4 is arranged downstream of the casting machine 3 in the conveying direction F of the material. The first furnace 4 is followed in the conveying direction F by a roughing train 5, which has a number of rolling stands R1 and R2. Downstream of the roughing train 5 is a second furnace 6, which in turn is followed by a finishing train 7 with several rolling stands F1, F2, F3, F4, F5, F6. Downstream of the finishing train 7 is a cooling section 8, followed by a coiler 9.

[0017] A first shear S1 is located between the casting machine 3 and the first furnace 4. A second shear S2 is located behind the roughing train 5 and in front of the second furnace 6. Finally, a third shear S3 is located just before the coiler 9.

[0018] At least one single slab can be accommodated in the first furnace 4 and / or in the first roller table insulation section; furthermore, at least one single slab can fit into the area between the first shear S1 and the first rolling stand R1 of the roughing mill 5. The roughing mill 5 preferably consists of one to four stands, with two stands being particularly preferred.

[0019] The second furnace 6 and / or the second roller table insulation section behind the roughing train 5 are designed such that at least one individual strip can be accommodated in its horizontal position or extension, or at least one individual strip can fit into the area between the second shear S2 and the first rolling stand F1 of the finishing train 7. The finishing train 7 usually consists of 1 to 7 stands, preferably 4 to 6 stands.

[0020] The first shear S1 is a slab shear for cutting the slabs leaving the casting machine 3. The second shear S2 is a pre-strip shear for cutting the pre-strips downstream of the roughing mill 5 and is preferably located upstream of the second furnace 6. Finally, the third shear S3 is a strip shear for cutting the strips upstream of the coiler 9.

[0021] Accordingly, the three scissors S1, S2 and S3 are provided in order to be able to realize the different operating modes mentioned above.

[0022] In the casting and rolling plant 1, no rapid heating (e.g. in the form of induction heating) is preferably provided, which is advantageous when using cheaper gas and from an energy point of view.

[0023] Instead of the first furnace 4 and / or the second furnace 6 (for example and preferably in the form of a roller hearth furnace), roller table insulation sections can alternatively be provided, which accommodate at least one individual slab or a single preliminary strip. In this case, an induction heater can also optionally be arranged downstream of said roller table insulation sections. An arrangement of furnace sections and roller table insulation sections in any order and combination upstream and / or downstream of the roughing train is also possible.

[0024] The length of the first furnace (4) or the first roller table insulation section or an arrangement of first furnace parts (4) and roller table insulation sections in any order and combination behind the first shear (S1) is shorter than the length of the second furnace (6) or the second roller table insulation section or an arrangement of second furnace parts (6) and roller table insulation sections in any order and combination behind the second shear (S2).

[0025] A single slab or a single pre-strip is long enough to be rolled or produced into a coil with a typical coil weight.

[0026] The casting-rolling plant (CSP plant) can be operated very flexibly through optimized operation of the aforementioned main components. Various operating modes are feasible in the roughing mill, the finishing mill, or the entire plant: According to the above-mentioned process mode a), continuous rolling is initially possible in the roughing mill 5 and continuous rolling in the finishing mill 7. In this case, the casting machine 3 and the roughing and finishing mills 5 and 7 are connected. Rolling occurs with the casting machine mass flow, and the strips are cut on the coiler 9 using the third shear S3.

[0027] According to the above-mentioned process mode b), continuous rolling in roughing train 5 with casting machine mass flow and individual strip rolling (batch operation) in finishing train 7 are still possible. Here, the individual pre-strips are separated at the second shear S2. The mass flow in finishing train 7 is higher during rolling than in roughing train 5 or the associated casting machine 3. This results in a combination of the advantages of continuous rolling in the relevant first stands with relatively high degrees of deformation and a better pre-strip geometry at the head and tail with the advantages of batch rolling in finishing train 7 and the resulting higher final rolling temperatures.

[0028] According to the above-mentioned process mode c), single-strip rolling (batch operation) is still possible in roughing mill 5 and single-strip rolling (batch operation) in finishing mill 7. In this case, the individual slabs are cut at the first shear S1. During the rolling process, roughing mill 5 and finishing mill 7 are both operated at a higher mass flow rate than casting machine 3. Temperature control can be influenced as desired by individually selecting the speed of the rolling mills.

[0029] According to the above-mentioned process mode d), further operation is finally possible: If the first furnace 4 and the second furnace 6, or the distances between the first shear S1 and the rolling stand R1 of the roughing train 5 and / or the second shear S2 and the rolling stand F1 of the finishing train 7, are sufficiently long to accommodate more than one slab (for example, two or three slabs), then semi-endless strip rolling from the first furnace 4 and / or the second furnace 6 or the corresponding plant sections is possible. The semi-endless slabs are then initially cut at the first shear S1 or the semi-endless pre-strips at the second shear S2, and the final division into individual strips takes place with the third shear S3 in front of the coiler 9.

[0030] Depending on the final thickness, during plant start-up (at the start of casting), before a roll change, or for temperature reasons, various operating modes can be selected and adjusted. Warming up the rolling mills, for example, can be carried out in batch mode on the roughing and finishing trains. Then, the roughing train can first be switched to endless mode. For thinner strips (preferably with thicknesses of less than or equal to 1.2 mm), endless strip rolling is recommended for the roughing and finishing trains. If a roll change is only planned in the finishing train, the finishing train is switched to batch mode.

[0031] To gain time for work roll changes in the finishing mill, it is advantageous to roll at an increased strip speed and / or with a temperature speed-up in the finishing mill and / or to reduce the casting speed and rolling speed in the roughing mill. To compensate for varying slab and / or roughing strip temperatures along the strip length during batch rolling and to generate as constant as possible finished strip temperatures downstream of the finishing mill, the roughing mill and / or finishing mill are operated with a temperature speed-up, or alternatively, the water flow in at least one interstand cooling system is adjusted accordingly.

[0032] An increase in flexibility is therefore possible with the proposed system.

[0033] The proposed casting-rolling plant (CSP plant) is characterized by several advantageous technical features and operating conditions: It features an optimal arrangement for slab cleaning (or descaling) at the exit of casting machine 3 (less than 2 m) behind the last strand roll. Alternatively, the slab is cleaned (descaled) between the last two strand roll pairs.

[0034] Roller conveyor insulation between the casting machine 3 or the slab cleaning station and the entrance to the first furnace 4 is advantageous. The insulation can be pivoted in the area of ​​the first shear S1. This minimizes energy and temperature losses in this transport area.

[0035] The use of compact, single-row descaling bars with a minimized specific descaling water quantity V spez is preferred, with the following condition: V spez in m 3< / h / m < 600 xv, preferably V spez in m 3< / h / m < 450 xv, with v being the transport speed of the rolled or cast product in the area of ​​the scale washer in m / s ("x" is the multiplication sign).

[0036] The active number of finishing stands n is preferably adapted to the finished strip thickness h F . The following approximate equation is used for this purpose: n ≥ 5 × h F − 0.6

[0037] This means that for thicker final strip thicknesses, 1, 2, or 3 stands are run up, starting with the last finishing stands, to achieve the correct final rolling temperature. To achieve good strip quality, strip cooling preferably begins within the finishing train, behind the last active stand. Pyrometers between the last finishing stands monitor the setting of the correct final rolling temperature and are used for control purposes.

[0038] The respective first furnace 4 and / or second furnace 6 or corresponding roller table areas with insulation can be divided into different sections (longitudinally) so that slabs or slab sections and / or transfer strips or transfer strip sections can be conveyed out. This can, for example, create buffer times, easily dispose of the cold strand, or simplify the rectification of malfunctions. Additionally, flame cutting machines can be provided upstream and / or downstream of the furnace sections.

[0039] The average slab temperature (definition: averaged over the thickness in the middle) at the outlet of the first furnace 4 is ≥ 1,000°C, preferably ≥ 1,100°C.

[0040] The average pre-strip temperature at the exit from the second furnace 6 is ≥ 1,100°C, preferably ≥ 1,150°C.

[0041] Through high forming (complete finishing line forming) E = h V − h F / h V × 100 ≥ 96 % (with h V = pre-strip thickness, h F = finished strip thickness) in the finishing train combined with a high pre-strip temperature of ≥ 1,150°C (at the exit from the second furnace 6) and a high mass flow in m / min mm of h B xv B ≥ 350 m / min mm (preferably h B xv B ≥ 500 m / min mm) or generally with the condition depending on the number of stands 2.316 × h B × v B × e − 0.167 × n ≥ 480 m / min mm (where n = number of stands, h B = slab thickness mm, v B = slab speed m / min), inductive post-heating within the finishing train can generally be dispensed with during endless rolling and the plant can be operated advantageously so that the forming takes place in the last active finishing stand above the γ-α phase transformation (e.g. 820°C). Optionally, inductive heating within the finishing train between the finishing stands is considered for the endless rolling or semi-endless rolling operating mode to set higher final rolling temperatures (e.g. ≥850°C) and / or to specifically influence the mechanical finished strip properties and / or at low casting speeds.

[0042] High forming in the finishing train (see definition above) with effective roll gap lubrication, preferably on all stands (optionally except the last active finishing stand), which achieves a rolling force reduction of >10% per stand due to lubrication, is also advantageous.

[0043] The transition from continuous rolling to batch rolling can be achieved by cutting at the first shear S1 without a transition wedge. The first shear S1 cuts, and the finish rolling of the continuous slab takes place without changing the setup in the rolling stands R1 / R2 of roughing mill 5. By either reducing the casting speed and / or accelerating the continuous slab rolling, a gap is created that allows the rolling stand R1 and / or the rolling stand R2 to start the subsequent slab with a new setup. List of reference symbols:

[0044] 1 Belt 2 Casting and rolling mill 3 Casting machine 4 First furnace 5 Roughing mill 6 Second furnace 7 Finishing mill 8 Cooling section 9 Coiler or coiler system S1first pair of scissors S2second pair of scissors S3third pair of scissors R1, R2Rolling stand of the roughing mill F1, F2Rolling stand of the finishing mill F3, F4Rolling stand of the finishing mill F5, F6Rolling stand of the finishing mill FConveying direction

Claims

1. Method of producing a metallic strip (1) in a casting and rolling plant (2), wherein the casting and rolling plant (2) comprises: - a casting machine (3) for casting a slab, - a first furnace (4) and / or a first roller path insulating section following the casting machine (3) in the conveying direction (F) of the metallic strip, - first shears (S1) arranged between the casting machine (3) and the first furnace (4) and / or the first roller path insulating section, - a roughing train (5) with a plurality of roll stands (R1, R2), - a second furnace (6) and / or a second roller path insulating section following the roughing train (5) in the conveying direction (F) of the metallic strip, - second shears (S2) arranged between the roughing train and the second furnace (6) and / or the second roller path insulating section, - a finishing train (7) with a plurality of roll stands (F1, F2, F3, F4, F5, F6), - a cooling path (8), - at least two coilers (9) or a reversing coiler and - third shears (S3) arranged between the cooling path (8) and the coiler installation (9), wherein one of the following operating modes is selected for production of the strip (1): a) endless rolling in which the casting machine (3), the roughing train (5) and the finishing train (7) are operatively connected with one another and rolling of the material is carried out with casting machine mass flow, wherein the finished strips are separated at the coiler installation (9) by means of the third shears (S3); b) endless rolling in the roughing train (5), in which the casting machine (3) and the roughing train (5) are operatively connected with one another and rolling of the material is carried out with casting machine mass flow, as well as individual strip rolling (batch operation) in the finishing train (7), wherein the pre-strips rolled in the roughing train (5) are separated by means of the second shears (S2) for individual strip rolling in the finishing train (7); c) individual strip rolling (batch operation) in the roughing train (5) and individual strip rolling (batch operation) in the finishing train (7), wherein the slabs produced in the casting machine (3) are separated by means of the first shears (S1) for individual strip rolling in the roughing train (5) and in the finishing train (7); d) semi-endless rolling in the roughing train (5) and / or semi-endless rolling in the finishing train (7), wherein the slabs produced in the casting machine (3) are separated by means of the first shears (S1) for semi-endless rolling in the roughing train (5) and / or wherein the pre-strips rolled in the roughing train (5) are separated by means of the second shears (S2) for semi-endless rolling in the finishing train (7), wherein the finished strips are separated at the coiler installation (9) by means of the third shears (S3), characterised in that rolling in the finishing train (7) is carried out with a plurality of roll stands, which takes place in accordance with the equation: 2.316 × h B × v B × e − 0.167 × n ≥ 480 m / min mm wherein n: number of stands in the finishing train (7) hB: thickness of the slab in mm vB: slab speed in m / min, and that the length of the first furnace (4) or the first roller path insulating section or an arrangement of first furnace parts (4) and roller path insulating sections in any sequence and combination behind the first shears (S1) is preferably shorter than the length of the second furnace (6) or the second roller path insulating section or an arrangement of second furnace parts (6) and roller path insulating sections in any sequence and combination behind the second shears (S2).

2. Method according to claim 1, characterised in that at least one slab is placed in the first furnace (4) or in the first roller path insulating section or an arrangement of first furnace parts (4) and roller path insulating sections in desired sequence and combination.

3. Method according to claim 1 or 2, characterised in that at least one slab or pre-strip is placed in the second furnace (6) or in the second roller path insulating section or an arrangement of second furnace parts (6) and roller path insulating sections in desired sequence and combination.

4. Method according to any one of claims 1 to 3, characterised in that the mean slab temperature at the outlet of the first furnace (4) is at least 1,000° C, preferably at least 1,100° C.

5. Method according to any one of claims 1 to 4, characterised in that the mean pre-strip temperature at the outlet of the second furnace (6) is at least 1,100° C, preferably at least 1,150° C.

6. Method according to any one of claims 1 to 5, characterised in that the degree of deformation of the strip (1) in the finishing train (7) is: E = h V − h F / h V × 100 ≥ 96 % with hV as the pre-strip thickness and hF as the finished strip thickness.

7. Method according to claim 6, characterised in that the mean pre-strip temperature at the outlet of the second furnace (6) is at least 1,150° C, wherein the product of the thickness of the strip (hB) and speed of the strip (vB) is at least 350 mm m / min, preferably at least 500 mm m / min.

8. Method according to any one of claims 1 to 7, characterised in that inductive heating of the slab and / or of the pre-strip is not undertaken.

9. Method according to any one of claims 1 to 8, characterised in that the temperature in the last active stand of the finishing train (7) lies above the γ-α phase conversion, in particular above 820° C.

10. Method according to any one of claims 1 to 7, characterised in that inductive heating is carried within the finishing train between the finishing stands for the operating mode of endless rolling or semi-endless rolling for the setting of higher final rolling temperatures ≥ 850° C and / or selective influencing of the mechanical finished strip properties and / or at low casting speeds.

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