EP3341142B1 - Method for operating an installation based on the csp concept - Google Patents

Description

1. Field of the Invention

The invention relates to a method for producing metal strips, preferably steel strips, with a thickness of 0.8 to 3.0 mm from previously cast thin slabs with a thickness of 40-140 mm, in batch or semi-endless operation. The invention further relates to a method for operating such a system.

To produce thin strips of the type mentioned at the outset with a thickness of 0.8 to 3.0 mm, preferably with a width of up to 2000 mm, preferably about 1880 mm (+/- 2%), so-called CSP- ® systems are used which, thanks to the compact system concept, enable particularly economical and environmentally friendly production of such thin strips with high productivity and excellent strip quality. The abbreviation CSP-® stands for "Compact Strip Production". In a CSP-® system, the liquid steel is cast into thin slabs, which are rolled out into thin strips in the tunnel mill without pre-rolling after temperature compensation in a tunnel kiln. Due to the direct connection of casting and rolling, a CSP-® system is characterized by a particularly low energy consumption - compared to conventional hot strip mills, up to 40% energy can be saved. Since the CSP-® system concept does not require a roughing stand to pre-roll the thin slab, the investment costs are also reduced. In addition, a hot strip produced on a CSP-® system is characterized by high quality, it has a uniform structure and homogeneous mechanical-physical properties over the entire strip length and width. The belt geometry is within the narrowest tolerances. In this field, the invention relates to a system which can be operated both in batch mode and in semi-endless mode, in particular can be switched between these modes.

The person skilled in the art describes what is known as batch operation as a mode of operation of the plant in which the thin slab emerging from the casting machine, depending on the thickness and even before entering the downstream tunnel kiln, is shortened to such a length that, after leaving the rolling device, a in the downstream coiler device Coil can be wound with a predetermined length and weight. In batch operation, exactly one coil is generated from each individual slab.

As so-called semi-endless operation, the person skilled in the art names a mode of operation of such a system, in which the thin slab is cut after leaving the casting machine in such a way that a so-called jumbo slab is produced, the length of which usually corresponds to an integral multiple of a slab from batch operation. From such a jumbo slab, which is also introduced into the tunnel furnace after it emerges from the casting machine, a thin strip is then rolled out in the subsequent rolling process, which is cut to the respective coil weights and lengths by means of flying shears after leaving the rolling device.

Systems of this type are used to produce thin strips of different thicknesses and different steel grades from low-carbon steel to advanced high-strength steel grades.

2. State of the art

Plants for the production of thin metallic strips from thin cast slabs have been known to the person skilled in the art for many years. The same applies to the CSP ® plant concept.

For example, the EP 2 195 124 B1 a compact and flexible CSP-® system for endless, semi-endless and batch operation. The system described here is designed in such a way that it can be operated in all three possible operating modes for such system types, two batching machines usually being provided in front of the rolling device for batch operation and a pair of scissors being arranged between the casting machine and the rolling device to be able to start rolling independently of the casting speed for the thin slab. For the semi-endless operation, a furnace length is again required that allows the generation of a jumbo slab, thus a furnace length that is longer than a single slab from the batch operation. Finally, the endless operation of such a system requires the arrangement of a heating device, in particular an inductive heating device, in the region of the roll direction, often between the individual roll stands or at least between groups of roll stands.

In addition, the WO 2011/141790 A2 a process and a plant for the production of flat rolled products, which also implements the CSP plant concept. Under certain conditions, this system also switches between all three operating modes mentioned above.

In the known systems and the known methods for operating such systems, there is the problem that the semi-endless operation can only be used when the rolling mill has been heated to a predetermined operating temperature, since otherwise especially in those rolling stands in which the roll gaps, if necessary provided with a prestress, are completely closed in order to, during the operational spring-back of the respective roll stands, under the influence of the rolling forces acting on the metal strip to be able to achieve the desired thin strip thicknesses at all, disturbances can occur. It is not uncommon for the initiation of semi-endless operation, particularly in the case of higher-strength grades, to cause malfunctions in the rolling operation, for example because the strip starts are not easily introduced into the roll gap.

3. Object of the invention

It was therefore an object of the invention to provide a method in which the above-described problems in the operation of the CSP-® system can be reliably avoided. This object is achieved in the sense of the invention with a method comprising the features of claim 1. Advantageous embodiments of the invention are disclosed in the description and in the dependent claims.

4. Summary of the invention

According to the invention, semi-endless operation can be used when the rolling device is warm from operation and a final thickness in the target area of the minimum final thickness has already been reached in batch operation. The first final thickness in semi-endless operation preferably corresponds to the last final thickness in batch operation, the minimum being subsequently achieved by means of a setting of at least the roll gap of a roll stand, preferably a plurality of roll nips of the roll stands of the rolling device, by means of so-called "flying-gauge change" Final thickness is set and reached in the thin strip.

The strip is preferably separated into coils with flying shears arranged behind the rolling device, which is arranged in front of the reel device, in particular the underfloor reels usually used here.

In a further preferred embodiment of the invention, the strip thickness changes during the rolling operation are carried out such that the strip head and the strip end are still within the thickness tolerances required by the market.

The invention thus provides a method with a correspondingly programmed control device which enables switching from batch mode to semi-endless mode, in which a part of a previously cast jumbo frame, preferably at least half of the jumbo frame, generates the minimum final thickness can be done without having to bring the hot strip to operating temperature under the influence of external energy; rather, the operating temperature of the installation according to the invention, in particular of its rolling stock, is set in batch operation or in semi-endless operation during the production of metal strips by selecting the correct rolling speed.

The method according to the invention thus allows the production of thin strips in the most energy-efficient operating mode using known system components and correspondingly controllable means with the lowest possible energy expenditure.

The method according to the invention is thus able to produce thin strips from a large number of steel grades both in batch operation and in semi-endless operation and in this case to produce particularly small thicknesses in an energy-efficient manner. Depending on the steel quality and the end product, the batch mode is principally used for larger final thicknesses and the semi-endless mode for thinner or thinner ones Final thicknesses selected, whereby the plant can achieve a total output of approx. 4 million tons per year in two-strand operation, thus using two casting machines arranged in parallel.

In a preferred embodiment of the invention, the rolling device has two groups of in each case a plurality of roll stands, in particular a first group with two roll stands and a second group with up to five roll stands arranged downstream of the first group. An induction heater can be arranged between these groups of roll stands, which is preferably provided such that it can be moved out of the rolling device and the entire rolling line. While induction heating in batch mode is not regularly used, the induction heating in semi-endless mode, in particular in the production of thin and thinnest final thicknesses of the metal strip by the rolling device, can be used to structure the hot strip throughout the entire rolling process to keep in the austenitic phase area.

In a further preferred embodiment of the invention, the switch from batch operation to semi-endless operation takes place during the rolling process, thus when the strip is in engagement with one or more rolling stands of the rolling device. The switching is preferably carried out after the rolling of a plurality, preferably more than two, particularly preferably between two to two and a half, of individual slabs. Thus, when the jumbo slabs cast for semi-endless operation and cut to length by the scissors arranged behind the casting machine become a standard size of z. B. has five single slab lengths, produces at least half of the coils generated from the jumbo slabs in the desired minimum final thickness in semi-endless operation.

For processing the rolled thin strips, it is preferred if a preferably flying shear is arranged behind the last roll stand and in front of the reel device, with which the thin strip produced can be cut to the desired length for the coil.

The length of the furnace between the casting machine and the rolling device is preferably dimensioned such that it corresponds at least to the length of a jumbo slab for carrying out the semi-endless operation. Usually the length of a jumbo slab will correspond to a multiple of the length of a single slab, the length of the furnace, preferably the tunnel kiln, being dimensioned such that a jumbo slab can hold five times the length of a long single slab (single slab with a maximum thickness of 40 mm) , The usual lengths of such tunnel ovens are approximately 250 m.

The method according to the invention is preferably carried out on a system as has already been discussed in detail above.

In the method according to the invention, thin slabs are preferably rolled into thin strips which leave the casting machine or the casting machines provided in parallel with a thickness of 40 to 140 mm. This provides a process that provides the largest possible product mix both in terms of the achievable final thicknesses and the steel grades to be processed.

It is preferred if the system produces steel strip of the "low carbon steel" quality, preferably steel strip with a thickness of 0.8 to 1.2 mm in semi-endless operation and steel strip with a thickness greater than 1.2 mm in batch operation ,

Likewise preferred is a method in which the system produces steel strips of the "medium-carbon steel" quality, preferably steel strips with a thickness of 1.4 to 1.8 mm in semi-endless operation and steel strips with thicknesses greater than 1.8 mm in batch mode.

Also preferred is a method in which the plant produces steel strips of the "high-carbon steel" quality, preferably steel strips with a thickness of 1.4 to 2.0 mm in semi-endless operation and steel strips with thicknesses greater than 2.0 mm in batch mode.

Likewise preferred is a method in which the plant produces steel strips of the "high-strength low-alloyed steel" quality, preferably steel strips with a thickness of 1.4 to 2.0 mm in semi-endless operation and with thicknesses greater than 2. 0 mm in batch mode.

Also preferred is a method in which the system produces steel strips of the "advanced high-strength steel" quality, preferably with a thickness of 1.4 mm to 2.5 mm in semi-endless operation and with thicknesses greater than 2.5 mm in batch mode.

5. Brief description of the figures

The invention is briefly explained below with reference to two figures, these figures representing preferred embodiments of preferred effects of the invention, without thereby limiting the scope of the invention, which is defined in the appended claims.

Figur 1

eine schematische Darstellung einer beim erfindungsgemäßen Verfahren eingesetzten CSP-®-Anlage, und

Figur 2

eine tabellarische Auflistung der erzeugbaren Banddicken und bearbeitbaren Stahlgüten, aufgeschlüsselt nach der jeweilige Betriebsart der Anlage.

The figures show:

Figure 1

a schematic representation of a CSP-® system used in the method according to the invention, and

Figure 2

a tabular list of the strip thicknesses and machinable steel grades that can be produced, broken down according to the operating mode of the system.

6. Detailed description of the figures

Figure 1 shows a schematic representation of a CSP-® system, which is capable of further processing the steel grades cast into thin slabs by means of the casting machine, both in batch operation and in semi-endless operation to thin strips with a desired final thickness. Behind the two casting machines 1 arranged in parallel, which feed the system at least in batch operation, scissors 2 are provided for dividing the thin slabs before the thin slabs enter the roller hearth furnace or furnaces 3. These roller hearth furnaces or tunnel furnaces 3 are used both for reheating and for comparing the thin slab temperature. At least the length of the upper tunnel kiln 3 is dimensioned such that at least one jumbo frame can be completely accommodated in the tunnel kiln 3 for carrying out semi-endless operation. The lower tunnel furnace 3 directly downstream of the parallel casting machine 1 can also have this length, but must be at least the length of a single slab for batch operation in order to be able to receive and heat this single slab when carrying out the batch operation. The second tunnel furnace 3 can also serve as a buffer for the upper casting machine tunnel furnace arrangement 1, 3 via a suitable switch device between the tunnel furnaces 3. Downstream of the upper tunnel furnace 3 and in front of the first roll stand group 5, a scale washer 4 is provided for removing surface scale, in order to thereby positively influence the rolling in the first group of roll stands 5, in particular to keep it free from surface damage caused by scale. Downstream of the first roll stand group 5 there is a pair of scissors 6 for cropping the strip heads and strip ends of the intermediate strip pre-rolled in the roll stand group 5, in order to thereby facilitate threading the strip into the second roll stand group 8. In addition, the separating shears 6 can be used to separate the rolling process within the first roll stand group 5 from the rolling process in the second roll stand group 8, in particular with regard to the speed of entry of the intermediate strip into the second roll stand group 8 after it has left the first roll stand group 5. Between the first Roll stand group 5 and the second roll stand group 8 is also one Induction heater 7 arranged, which can preferably be removed from the rolling line when the induction heater 7 is not required for performing the rolling process. This is regularly the case when the system according to the invention is operated in batch mode, or when strips with comparatively large thicknesses of 2 to 2.5 mm are to be produced in semi-endless mode. A laminar cooling section 9 for setting the desired coiling temperature for the thin strip is arranged downstream of the second roll stand group 8. This laminar cooling section 9 is preferably provided with means for controllably increasing cooling of the thin strip, usually liquid nozzles or nozzles, which are able to apply a mixture of air and a cooling liquid to the thin strip. A high-speed shear 10 is arranged between the laminar cooling section 9 and two separately controllable underfloor reels 11 for separating the rolled thin strip to the desired coil lengths.

Figure 2 shows, by way of example, a tabular list of the steel grades that can be processed on the plant in the process according to the invention and the strip thicknesses to be produced via the plant, which also indicates which steel grades and which strip thicknesses can be produced in the semi-endless rolling mode and the batch mode. In principle, "low-carbon steel" steel grades with final thicknesses greater than 1.4 mm can be produced in batch operation and in the thickness range 0.8 mm to 1.4 mm in semi-endless operation. The steel grade "advanced high-strength steel" is manufactured in the thickness range 1.4 to 2.5 mm in semi-endless operation.

LIST OF REFERENCE NUMBERS

1

casting machine

2

scissors

3

tunnel kiln

4

descaling

5

Rolling mill group

6

shears

7

induction heating

8th

Rolling mill group

9

Laminar cooling section

10

High speed shear

11

Underfloor reels

Claims (12)

1. Method of operating a plant for producing metal strips, preferably steel strips, of a thickness of 0.8 to 3.0 millimetres in batch operation or semi-endless operation and thicknesses greater than 2.5 millimetres in batch operation, comprising at least one casting machine (1) for casting thin slabs, rolling equipment (5, 8), which is arranged downstream of the at least one casting machine (1), with a plurality of roll stands for rolling the thin slabs to form metal strips of predetermined thickness, and at least one coiler (11) arranged downstream of the rolling equipment, wherein shears (2) and a furnace (3) are arranged between the at least one casting machine and the rolling equipment (5, 8),
   characterised in that
   the rolling gap of at least one roll stand is changed during the rolling process, and a control device so controls the plant that switching over from batch operation to semi-endless operation or back takes place in dependence on the metal quality, preferably steel quality, and the desired thickness of the metal strip to be produced, and that the switching over from batch operation to semi-endless operation is carried out in the course of the rolling process by the rolling equipment.
2. Plant according to claim 1, characterised in that switching-over from batch operation to semi-endless operation can be carried out in the course of the rolling process after the rolling of a plurality, preferably of more than two, particularly preferably between two and five, individual slabs.
3. Method according to claim 2, characterised in that the switching over from batch operation to semi-endless operation is carried out in the course of the rolling process when the rolling equipment (5, 8), particularly the work rolls of the respective roll stands, in batch operation have a predetermined operating temperature.
4. Method according to any one of claims 1 to 3, characterised in that the thin slabs have a thickness of 40 to 140 millimetres after leaving the at least one casting machine (1).
5. Method according to any one of claims 1 to 4, characterised in that the change of the at least one rolling gap during the rolling process is carried out in such a way that not only the strip end of the previously rolled metal strip, but also the strip head of the succeeding metal strip lie within the required thickness tolerances.
6. Method according to any one of claims 1 to 5, characterised in that the plant produces steel strip of the quality low-carbon steel, preferably steel strip with a thickness of 0.8 to 1.2 millimetres in semi-endless operation and with thicknesses greater than 1.4 millimetres in batch operation.
7. Method according to any one of claims 1 to 5, characterised in that the plant produces steel strip of the quality medium-carbon steel, preferably steel strip with a thickness of 1.4 to 1.8 millimetres in semi-endless operation and with thicknesses greater than 2.0 millimetres in batch operation.
8. Method according to any one of claims 1 to 5, characterised in that the plant produces steel strip of the quality high-carbon steel, preferably steel strip with a thickness of 1.4 to 2.0 millimetres in semi-endless operation and with thicknesses greater than 2.5 millimetres in batch operation.
9. Method according to any one of claims 1 to 5, characterised in that the plant produces steel strip of the quality high-strength low-alloyed steel, preferably steel strip with a thickness of 1.4 to 2.0 millimetres in semi-endless operation and with thicknesses greater than 2.5 millimetres in batch operation.
10. Method according to any one of claims 1 to 5, characterised in that the plant produces steel strip of the quality advanced-high-strength steel with a thickness of 1.4 to 2.5 millimetres, preferably in semi-endless operation.
11. Method according to any one of claims 1 to 10, characterised in that the production of metal strips in batch operation is carried without inductive heating of the strip and in semi-endless operation only in the production of high-strength qualities with small thicknesses, preferably high-strength low-alloyed steel with a thickness of 1.4 to 1.6 millimetres or advanced-high-strength steel with a thickness of 1.4 to 1.8 millimetres, with inductive heating.
12. Method according to any one of claims 1 to 11, characterised in that the rolling equipment in batch operation is supplied from two casting machines (1).

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