EP3504013B2 - Method for producing a metal strip in a cast-rolling installation - Google Patents

Description

• eine Gießmaschine zum Gießen einer Bramme,
• einen in Förderrichtung des metallischen Bandes der Gießmaschine folgender erster Ofen oder/und eine erste Rollgangsdämmstrecke,
• eine erste Schere, die zwischen der Gießmaschine und dem ersten Ofen oder/und der ersten Rollgangsdämmstrecke angeordnet ist,
• eine Vorstraße mit einer Anzahl Walzgerüste,
• einen in Förderrichtung des metallischen Bandes der Vorstraße folgender zweiten Ofen oder/und eine zweite Rollgangsdämmstrecke,
• eine zweite Schere, die zwischen der Vorstraße und dem zweiten Ofen oder/und der zweiten Rollgangsdämmstrecke angeordnet ist,
• eine Fertigstraße mit einer Anzahl Walzgerüste,
• eine Kühlstrecke,
• mindestens zwei Haspel oder einen Wendehaspel und
• eine dritte Schere, die zwischen der Kühlstrecke und der Haspelanlage angeordnet ist.

The invention relates to a method for producing a metallic strip in a casting and rolling plant, wherein the casting and rolling plant comprises:

• 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 mill 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 line with a number of rolling stands,
• a cooling section,
• at least two reels or one reversing reel and
• a third shear, which is arranged between the cooling section and the coiling system.

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

Thin slab casting and rolling plants for rolling single strips or for continuous rolling are already mentioned in the state of the art. For example, reference is made to the DE 195 18 144 C2 , on the DE 196 13 718 C1 , on the EP 0 870 553 B1 , on the WO 2007/073841 A1 , on the WO 2009/012963 A1 and on the EP 2 569 104 B1 Other solutions, some of which also use different operating modes, are available from the US 2011/272116 A1 and from the WO 00/10741 A1 The preamble of claim 1 is based on the US 2011/272116 A1 .

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

The invention is therefore based on the object of further developing a method of the above-mentioned type in such a way that an increased degree of flexibility is possible; in particular, it should be possible to react flexibly to different operating conditions. The proposed system concept and the operating mode should therefore be characterized by a high degree of flexibility.

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

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 pre-strip is also placed in the second furnace and/or in the second roller table insulation section.

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 that the operating modes a), b), c) and/or d) are selected depending on the start-up process of the casting and rolling mill. It is also possible that the operating modes a), b), c) and/or d) are selected depending on a roll change taking place in the roughing mill and/or in the finishing mill.

First, one of the above-mentioned operating modes is selected and production is then carried out using this mode; accordingly, only one of the above-mentioned options (a), (b), (c) or (d) is implemented at a given time. However, switching between the various above-mentioned operating modes can also take place one after the other.

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.

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

mit h_V als der Vorbanddicke und h_F als der Fertigbanddicke. Speziell in diesem Falle ist bevorzugt vorgesehen, dass die mittlere Vorbandtemperatur am Auslauf des zweiten Ofens mindestens 1.150 °C beträgt, wobei das Produkt aus Dicke des Bandes (h_B) und Geschwindigkeit des Bandes (v_B) mindestens 350 mm m/min beträgt, vorzugsweise mindestens 500 mm m/min.A further development provides that the degree of deformation of the strip in the finishing line is: $$E=\left({\mathrm{h}}_{\mathrm{V}}-{\mathrm{h}}_{\mathrm{F}}\right)/{\mathrm{h}}_{\mathrm{V}}\times 100\ge 96\mathrm{\%}$$

with h _V as the pre-strip thickness and h _F as the finished strip thickness. In this case in particular, it is preferably provided that the average pre-strip temperature at the outlet of the second furnace is at least 1,150 °C, the product of the thickness of the strip (h _B ) and the speed of the strip (v _B ) being at least 350 mm m/min, preferably at least 500 mm m/min.

Preferably, in the described procedure, inductive heating of the slab and/or the preliminary strip does not take place.

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

An embodiment of the invention is shown in the drawing. The single figure shows a schematic side view of a single-strand casting and rolling plant for the production of a strip.

The proposed thin slab casting and rolling plant concept consists of the following main components, which are shown in the figure:
The casting and rolling plant 2 for producing the strip 1 initially has a casting machine 3. A first furnace 4 is arranged behind 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. Behind the roughing train 5 there 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. Behind the finishing train 7 there is a cooling section 8, which is followed by a coiler 9.

A first shear S1 is arranged 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.

At least one individual slab can be accommodated in the first furnace 4 and/or in the first roller table insulation section; it is also provided that at least one individual slab fits into the area between the first shear S1 and the first rolling stand R1 of the roughing train 5. The roughing train 5 preferably consists of 1 to 4 stands, with two stands being particularly preferred.

The second furnace 6 and/or the second roller table insulation section behind the roughing train 5 is designed in such a way that at least one individual preliminary strip can be accommodated in its horizontal position or extent or at least one individual preliminary strip fits 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 are provided.

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 behind the roughing train 5 and is preferably arranged in front of the second furnace 6. Finally, the third shear S3 is a strip shear for cutting the strips in front of the coiler 9.

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

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.

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 in which at least one individual slab or one individual preliminary strip can be accommodated; in this case, an induction heater can also optionally be arranged behind said roller table insulation sections. An arrangement of furnace parts and roller table insulation sections in any order and combination before and/or after the roughing train is also possible.

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).

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

The casting and rolling plant (CSP plant) can be operated very flexibly through optimized operation of the main components mentioned. Various operating modes can be implemented in the roughing mill, the finishing mill or in the entire plant:
According to the above-mentioned process mode a), firstly, continuous rolling is carried out in roughing train 5 and continuous rolling in the finishing train 7, ie in this case the casting machine 3 and the roughing and finishing trains 5, 7 are connected to each other. In this case, rolling takes place with the casting machine mass flow and the strips are separated on the reel 9 with the third shear S3.

According to the above-mentioned process mode b), continuous rolling in the roughing train 5 with casting machine mass flow and individual strip rolling (batch operation) in the finishing train 7 is also possible. In this case, the individual preliminary strips are separated at the second shear S2. The mass flow in the finishing train 7 is higher during rolling than in the roughing train 5 or the connected 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 preliminary strip geometry at the head and foot with the advantages of batch rolling in the finishing train 7 and the higher final rolling temperatures that can be achieved with it.

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

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 long enough to accommodate more than one slab (for example 2 or 3 slabs), then semi-continuous strip rolling is possible from the first furnace 4 and/or the second furnace 6 or the corresponding plant sections. The semi-continuous slabs are then first separated at the first shear S1 or the semi-continuous pre-strips at the second shear S2 and finally divided into individual strips with the third shear S3 in front of the coiler 9.

Depending on the final thickness or when starting up the system (when casting begins) or before a roll change or for temperature reasons, the different operating modes can be selected and set. The rolling mills can be warmed up in batch mode on the roughing and finishing train, for example. The roughing train can then 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 train. If a roll change is only planned in the finishing train, the batch mode is switched to for the finishing train.

In order to gain the changeover time for the work roll change in the finishing train, it is advantageous to roll with an increased strip speed and/or temperature speed-up in the finishing train and/or to reduce the casting speed and rolling speed in the roughing train. In order to compensate for different slab and/or roughing strip temperatures over the strip length during batch rolling and to generate as constant as possible finished strip temperatures behind the finishing train, the roughing train and/or the finishing train are operated with temperature speed-up or, alternatively, the water quantity in at least one interstand cooling system is changed accordingly.

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

The proposed casting and rolling plant (CSP plant) is characterized by various advantageous technical facilities and operating conditions:
The optimal arrangement for slab cleaning (or descaling) is at the outlet 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.

It is advantageous to have roller table insulation between the casting machine 3 or slab cleaning machine and the entrance to the first furnace 4. The insulation can be swiveled in the area of the first shear S1. This minimizes energy and temperature losses in this transport area.

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).

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: $$\mathrm{n}\ge 5\times {{\mathrm{h}}_{\mathrm{F}}}^{-0.6}$$

This means that for thicker final strip thicknesses, 1, 2 or 3 stands are opened, starting with the last finishing stands, in order to obtain a correct final rolling temperature for the finished strip. In order to produce 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.

The respective first furnace 4 and/or second furnace 6 or corresponding roller table areas with insulation can be divided into different areas (in the longitudinal direction) so that slabs or slab parts and/or pre-strips or pre-strip parts can be conveyed out. This can, for example, create buffer times, easily dispose of the cold strand or simplify the elimination of faults. In addition, flame cutting machines can be provided in front of and/or behind the furnace sections.

The mean 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.

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

(mit h_V = Vorbanddicke, h_F = Fertigbanddicke) in der Fertigstraße kombiniert mit einer hohen Vorbandtemperatur von ≥ 1.150°C (am Austritt aus dem zweiten Ofen 6) und einem hohen Massenfluss in m/min mm von h_B x v_B ≥ 350 m/min mm (vorzugsweise h_B x v_B ≥ 500 m/min mm) oder allgemein mit der Bedingung abhängig von der Gerüstanzahl $$2.316\times {\mathrm{h}}_{\mathrm{B}}\times {\mathrm{v}}_{\mathrm{B}}\times {\mathrm{e}}^{\left(-0.167\times \mathrm{n}\right)}\ge 480\mathrm{m}/\min \mathrm{mm}$$

(mit n = Gerüstanzahl, h_B = Brammendicke mm, v_B = Brammengeschwindigkeit m/min) kann auch in der Regel beim Endloswalzen auf eine induktive Nachheizung innerhalb der Fertigstraße verzichtet und die Anlage vorteilhaft betrieben werden, so dass die Umformung im letzten aktiven Fertiggerüst oberhalb der γ-α-Phasenumwandlung (z.B. 820°C) stattfindet. Optional ist eine induktive Erwärmung innerhalb der Fertigstraße zwischen den Fertiggerüsten für den Betriebsmode Endloswalzen oder Semi-Endloswalzen zur Einstellung höherer Endwalztemperaturen (z.B. ≥850°C) oder/und gezielter Beeinflussung der mechanischen Fertigbandeigenschaften oder/und bei niedrigen Gießgeschwindigkeiten angedacht.Through high forming (complete finishing line forming) $$E=\left({\mathrm{h}}_{\mathrm{V}}-{\mathrm{h}}_{\mathrm{F}}\right)/{\mathrm{h}}_{\mathrm{V}}\times 100\ge 96\mathrm{\%}$$

(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 $$2.316\times {\mathrm{h}}_{\mathrm{B}}\times {\mathrm{v}}_{\mathrm{B}}\times {\mathrm{e}}^{\left(-0.167\times \mathrm{n}\right)}\ge 480\mathrm{m}/\min \mathrm{mm}$$

(with 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 continuous 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). Optional inductive heating within the finishing train between the finishing stands is planned for the continuous rolling or semi-continuous 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.

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.

The transition from continuous rolling to batch rolling can be made 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 train 5. By either reducing the casting speed and/or accelerating the continuous slab rolling, a gap is created which allows the rolling stand R1 and/or the rolling stand R2 to start rolling the subsequent slab with a new setup.

List of reference symbols:

1

band

2

casting and rolling mill

3

casting machine

4

first oven

5

Vorstraße

6

second oven

7

finishing line

8

cooling section

9

reel or reel system

S1

first pair of scissors

S2

second pair of scissors

S3

third pair of scissors

R1, R2

rolling mill of the roughing mill

F1, F2

rolling mill of the finishing train

F3, F4

rolling mill of the finishing train

F5, F6

rolling mill of the finishing train

F

conveying direction

Claims (10)

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: $$2.316\times {\mathrm{h}}_{\mathrm{B}}\times {\mathrm{v}}_{\mathrm{B}}\times {\mathrm{e}}^{\left(-0.167\times \mathrm{n}\right)}\ge 480\mathrm{m}/\min \mathrm{mm}$$

   

   wherein

   n: number of stands in the finishing train (7)

   h_B: thickness of the slab in mm

   v_B: 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: $$E=\left({\mathrm{h}}_{\mathrm{V}}-{\mathrm{h}}_{\mathrm{F}}\right)/{\mathrm{h}}_{\mathrm{V}}\times 100\ge 96\mathrm{\%}$$

   

   with h_V as the pre-strip thickness and h_F 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 (h_B) and speed of the strip (v_B) 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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