RU2750305C2 - Method for continuous manufacture of coiled hot-rolled strip in combined casting and rolling unit, method for activating combined casting and rolling unit and combined casting and rolling unit - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to the area of metallurgical manufacture and can be used in manufacturing a coiled hot-rolled steel strip in a combined casting and rolling unit. A continuously cast preform of a thin slab with a thickness of 45 to 70 mm and a width of 900 to 2300 mm is produced by continuous casting of steel melt in a through-feed crystalliser of a continuous casting machine. The thickness of the continuously cast preform is reduced to a value between 35 and 52 mm in the unit of movement thereof of the continuous casting machine. The continuously cast preform of a reduced thickness in the state of casting heating is rolled in no less than three passes producing a hot-rolled strip (15) with a thickness of 2.5 to 10 mm. The last rolling pass is performed in the austenitic range of the temperature of the steel. The hot-rolled strip is cooled in the cooling section of the combined unit followed by transverse cutting and coiling.

EFFECT: provided is possibility to produce a high-quality hot-rolled strip from various steels and to reduce startup time of the combined casting and rolling unit is ensured as a result.

23 cl, 7 dwg, 1 tbl

Description

Technology area

The present invention relates to the technical field of combined casting and rolling plants. These are installations in which a continuous casting machine for the continuous production of a continuous cast steel billet in a slab format, e.g. thin or medium slabs, is directly and in-line connected to a group of stands of a hot strip rolling mill. The hot-rolled strip after the mill stand group is cooled in a cooling section and then retracted, eg by coils. In the literature, these plants are also known, for example, as TSCR (Thin Slab Casting and Rolling) or Arvedi ESP (Endless Strip Production) plants.

In particular, the invention concerns working in endless mode combined plants for casting and rolling, in which the filling machine is designed as a machine for the continuous casting of thin slabs (Engl. TSER, T hin S lab E ndless R olling, endless rolling of thin slabs). In this case, an endless continuous-cast thin slab billet continuously produced in a thin slab continuous casting machine is fed directly in line and uncut to a group of rolling mill stands and rolled there to obtain an endless hot-rolled strip. This strip, after the group of rolling stands, is cooled again in the cooling section, then for the first time it is cut to a certain length or, respectively, a certain weight and coiled.

State of the art

Although Arvedi ESP is already significantly more compact than a CSP (Compact Strip Production) or QSP (Quality Strip Production) tunnel kiln, the operating costs and CO emissions have been greatly reduced. ₂ per tonne of hot strip, there is a need for even more compact combined casting and rolling plants to produce an annual hot strip production of 1 million tonnes or less.

Current solutions on the market, such as a continuous casting machine with a connected broadband mill, Arvedi ESP, Danieli QSP-DUE- or SMS CSP / CEM, are not compact enough for these small volumes and / or cannot be operated cost-effectively due to with significantly higher annual production volumes of approx. 2.5 million tonnes and high capital expenditure CAPEX (CAPital EXpenditure) with an annual production of approx. 1 million tons or less. Thus, in particular in small steel mills, there is a need for a compact combined casting and rolling plant that is economical to purchase and operate, but can nevertheless produce high quality hot strip of a wide variety of steel grades.

Also known from the prior art are twin-roll strip casting plants having a connected rolling mill. Although the twin-roll strip casting plant is very compact and produces strip directly, it has not yet been possible to implement this technology, since, in particular, reliable production of medium to high alloyed steels is not possible.

DE 10 2007 022 932 A1 discloses a combined casting and rolling plant for the production of steel strip, in which a milling machine 4 is arranged between a continuous casting machine and a hot rolling mill 4 for milling a continuous cast billet 3 of a thin slab. The mass flow of this continuous casting machine can be between 0.28 and 0.39 m² / min. Since the thin slab or, respectively, the pre-strip is subjected to (intermediate) heating before finishing rolling, hot rolling is not exclusively carried out from a casting heating state.

Also known from WO 2007/054237 A1 is a combined casting and rolling plant for the production of steel strip. The mass flow of this installation can be 0.441 m² / min. Since the pre-strip is subjected to intermediate heating before finishing rolling, hot rolling is not exclusively carried out from a casting heating state.

The concept of endless operation of a combined casting and rolling plant is known from WO 97/36699. At the same time, the temperature of the thin slab billet produced in the continuous casting machine is homogenized in a mixer furnace, after which the continuously cast thin slab billet is cleaned of scale, rolled in a seven-stand group of rolling mill stands, cooled and unwound. This publication indicates that starting from a specific productivity h ₀ * v _{C of} h ₀ * v _C > 0.487 m² / min., The hot-rolled strip can be finished rolling from the casting heating state of a continuously cast thin slab in the austenitic state. In particular, with relatively thin continuous billets of thin slabs, this concept, however, requires very high casting speeds, for example, with a slab thickness of 50 mm, a casting speed of approx. 10 m / min. In industrial practice, it turned out that the speed v _C > 6 m / min. casting are problematic as the reliability of the continuous casting machine is greatly reduced. When trying to achieve the specified specific productivity by using relatively thick slabs, for example with a slab thickness of 100 mm at a casting speed of approx. 5 m / min, although this leads to reliable conditions in the continuous casting machine, the mill stand group must have many stands (high CAPEX) in order to be able to produce hot strip having a thickness of <10 mm. In practical applications, it has also been found that the pre-rolled pre-strip has to be subjected to intermediate heating in a characteristic manner after 3 or 4 rolling passes. Thus, today's combined casting and rolling plants are usually operated at a casting speed of 5, 6 or 7 m / min, and the pre-strip is intermediate-heated in an induction furnace. However, due to the intermediate heating, the operating costs (OPEX) increase. Therefore, there is a need for an economical and simple combined casting and rolling plant (low CAPEX), which, on the one hand, can be operated reliably, and on the other hand, dispenses with intermediate heating (low OPEX), but can nevertheless carry out finishing rolling of high-quality hot-rolled strip having a thickness of 2.5 to 10 mm in the austenitic state.

How this problem can be solved is not clear from the prior art.

Summary of the invention

The object of the invention is to overcome the drawbacks of the prior art and to propose a method for the endless production of hot-rolled steel strip in a combined casting and rolling plant, as well as a compact, economical combined casting and rolling plant of the above-mentioned type, with which it can be produced at low costs. high-quality hot-rolled strip of various qualities of steel (low-, medium- and high-carbon, as well as HSLA (High-strength low-alloy steel, high-strength low-alloy steel), API, etc.). The method must be extremely reliable and provide extremely low operating costs. The combined casting and rolling plant according to the invention should be much more economical than comparable ESP / QSP / CSP plants. In addition, a simple way of starting up the combined casting and rolling plant should be proposed, so that the plant can be started up quickly and reliably.

This problem is solved by a method of endless production of coiled hot-rolled steel strip in a combined casting and rolling plant according to claim 1 of the claims. Preferred embodiments are the subject of the dependent claims.

Specifically, the solution to the problem of the invention is carried out by means of a method for the endless production of a coiled hot-rolled strip of steel in a combined casting and rolling installation, this combined casting and rolling installation including a continuous casting machine for the production of an endless continuous cast billet of a thin slab, a group of stands rolling mill, which has several rolling stands for hot rolling of a continuously cast billet of a thin slab to obtain a hot-rolled strip, a cooling section for cooling the hot-rolled strip, shears for cross-cutting the hot-rolled strip and a coiling device for coiling the hot-rolled strip having steps:

- continuous casting of steel melt in a continuous casting mold of a continuous casting machine to obtain a continuously cast thin slab billet, this continuous casting thin slab billet having a liquid core at the exit from the continuous casting mold, a thickness of 45 to 70 mm, preferably 55-65 mm , and a width of 900 to 2300 mm, preferably 1100-1900 mm;

- support, movement and reduction of the thickness of the continuous-cast billet of a thin slab in the unit for moving the continuous-cast billet of a continuous casting machine, while the continuously-cast billet of a thin slab reduced in thickness has a thickness h from 35 to 52 mm, preferably 40-50 mm , the _{casting speed v C} and the specific productivity D = h * v _c , which is 0.45 m ² / min. ≥D≥0.27m ² / min .;

- hot rolling of an endless thin slab continuously cast billet with reduced thickness in a group of rolling mill stands, wherein the continuously cast thin slab billet is rolled exclusively from its casting heating state in at least three, preferably three to five, especially preferably in four passes of rolling to obtain a hot-rolled strip having a thickness of 2.5 to 10 mm, and the last rolling pass is carried out in the austenitic temperature range of the steel;

- cooling of the hot-rolled strip in the cooling section;

- transverse cutting of the cooled hot-rolled strip; and

- unwinding of hot-rolled strip into coils in a reeling device.

The named continuous mold is made either straight or curved. However, a straight-through mold is preferred, since impurities in the steel melt can be taken up by the powdery flux, and therefore the internal quality of the thin slab continuously cast is improved.

A continuous-cast thin slab is formed in the continuous-flow mold, having a liquid core, which, when exiting the continuous-flow mold, has a thickness of 45 to 70 mm, preferably 55-65 mm, and a width of 900 to 2300 mm, preferably 1100-1900 mm. Continuously-cast thin slab billet in the unit for moving the continuous-cast billet following the continuous casting mold is supported, moved and reduced in thickness, so that the thinned continuous-cast billet of thin slab has a thickness h from 35 to 52 mm, preferably 40-50 mm and the specific productivity D = h * v _c , which is 0.45 m ² / min. ≥D≥0.27m ² / min. Thickness reduction can preferably be carried out with a liquid (so-called Liquid Core Reduction) or partially liquid core (so-called Soft Core Reduction) continuously cast thin slabs ... In the method according to the invention for the endless production of coiled hot-rolled strip, it is remarkable that not the highest possible productivity of a continuous casting machine, as in the prior art, is preferred, but an average specific productivity D of 0.27 to 0.45 m2 / min is preferred. Thereby, it is ensured that the continuous casting machine works reliably. An endless continuous cast billet of a thin slab after thickness reduction, without having been previously descaled or heated, i. E. solely from its foundry heating state, is rolled in a group of rolling mill stands in at least three, particularly preferably four rolling passes to obtain a hot-rolled strip having a thickness of 2.5 to 10 mm, the last rolling pass being carried out in the austenitic temperature range become. Thus, this hot rolled strip has an austenitic structure. Thereafter, the hot strip is cooled in a cooling section, cut to length with shears and coiled in a coiler.

In order to be able to fine-tune the energy content of the thin slab thinned in thickness, it is preferable when the control or regulating device of the continuous casting machine, using a mathematical model, continuously calculates the actual position of the lower end of the liquid core along the conveyance path of the continuously cast thin slab. slab in the unit for moving the continuously cast billet and the actual temperature profile along the path of transporting the continuously cast billet of a thin slab in the unit for moving the continuously cast billet and preferably in planes normal to it, and the continuously cast billet of the thin slab is continuously, in a controlled manner cooled in the unit moving the continuously cast billet taking into account the nominal position of the lower end of the liquid core, so that the actual position of the lower end of the liquid core corresponds as far as possible to the nominal position. In this case, it is preferable when the actual position of the lower end of the liquid core lies in the last third of the curved region of the unit for moving the continuous-cast billet or in the horizontal outlet region of the unit for moving the continuous-cast billet.

The temperature of the hot strip in the last rolling pass can be adjusted precisely when the actual temperature T _1actual. of the hot strip is measured after the last rolling pass in the group of rolling stands and before cooling in the cooling section, and the cooling of the continuously cast thin slab in the continuous casting unit and / or the _{casting speed v C is} adjusted in a controlled manner so that the actual temperature T _1fact. if possible corresponded to the nominal temperature T _1nom. ...

The coiling temperature of the hot strip can be adjusted precisely when the actual temperature T _2act. the endless hot strip is measured after cooling in the cooling section, and the cooling nozzles of the cooling section are activated in a controlled manner depending on the temperature, so that the actual temperature T _2fact. if possible corresponded to the nominal temperature T _2nom .

To reduce the thickness of the hot-rolled strip and improve the quality of its surface, it is convenient when the coil is then pickled and cold rolled in a cold rolling mill to a thickness of 0.3 to 7 mm in several rolling passes.

At the start-up of a combined casting and rolling plant, which includes a continuous casting machine for the production of an endless continuous cast billet of a thin slab, a group of rolling mill stands having several rolling stands for hot rolling a continuously cast billet of a thin slab to obtain a hot strip , a cooling section for cooling the hot strip, a shear for cross-cutting of the hot strip and a coiler for reeling the hot strip, the following steps are taken:

- starting the casting of the continuous casting machine, wherein the dummy, which hydraulically seals the continuous casting mold of the continuous casting machine in a hydraulically impermeable manner, is pulled out in the conveying direction from the continuous casting machine;

- support and movement of a thin slab following the dummy bar in the continuous casting unit of the continuous casting machine;

- passing the rolling stands of the group of rolling mill stands, while the seed passes the group of stands of the rolling mill not rolled;

- optional cooling of the unrolled continuous-cast billet of a thin slab in the cooling section;

- cutting off the seed with scissors;

- withdrawal of the dummy bar, whereby the dummy bar preferably passes the reeling device and in the direction of transport is folded behind the reeling device;

- transverse cutting of an unrolled continuous-cast billet of a thin slab with shears into the crushed material and the output of the crushed material;

- optionally increasing the casting speed and decreasing the thickness of the continuously cast billet of a thin slab in the unit for moving the continuously cast billet;

- attachment of rolling stands to a continuously cast thin slab billet and hot rolling of a continuously cast thin slab billet to obtain a hot-rolled strip;

- cooling of the hot-rolled strip in the cooling section;

- transverse cutting of the cooled hot-rolled strip; and

- unwinding of hot-rolled strip into coils in a reeling device.

First, the dummy bar is introduced into the continuous mold either in the direction of transport (top feeding), or against the direction of transport of the continuously cast thin slab (bottom feeding), so that it seals the mold hydraulically tightly. At the start of the casting of the continuous casting machine, a continuously cast thin slab is formed in the continuous casting mold, which is welded to the dummy head. After that, the dummy bar, including the subsequent continuous-cast billet of a thin slab, is pulled out of the mold and rests and moves in the unit for moving the continuous-cast billet. In order to prevent damage to the rolling stands by a dummy bar or, respectively, a relatively cold continuous-cast thin slab, the rolling stands are raised relative to the setting for rolling a hot-rolled strip having a thickness of 2.5 to 10 mm, so that the dummy bar can pass the unrolled group of mill stands. In another case, of course, it is also possible for the rolling stands to be raised already before starting up. Then the dummy bar is cut off by scissors from the subsequent continuously cast thin slab billet, and the dummy bar is removed from the roller table between the scissors and the reeling device or, respectively, reeling devices. This can be done particularly simply in such a way that the dummy bar is accelerated by the drive rollers of the roller table and, in the direction of transport, folds onto the roller table behind the reeling device. Subsequently, at least the unrolled continuous-cast thin slab is subjected to shear shredding into a shredded material, and the shredded material is discharged. The withdrawal can be carried out in such a way that the crushed material is introduced into the scrap basket under the roller table. Thereafter, it is preferable that the casting speed of the continuous casting machine is increased step by step, in particular up to the specific productivity D, where D = h * v _{c of} 0.45 m ² / min. ≥D≥0.27m ² / min., And the continuous-cast billet of a thin slab in the unit for moving the continuous-cast billet is subjected to a decrease in thickness using rollers of the conveying unit of the continuous-cast billet hydraulically attached to the continuously cast billet. Finally, rolling stands are attached to the continuously cast thin slab, so that the continuously cast thin slab is rolled into a hot strip, which hot strip is then cooled, cross cut and coiled.

One skilled in the art will appreciate that the conveying direction in the continuous casting machine changes from a vertical direction through a curved section to a horizontal direction and follows the material flow through the installation.

A simple, extremely compact and economical combined casting and rolling plant for the production of hot rolled steel strip has:

a continuous casting machine, which includes a continuous casting mold for the continuous production of a continuously cast billet of a thin slab, which, when exiting the continuous casting mold, has a liquid core, a thickness of 45 to 70 mm and a width of 900 to 2300 mm, and a continuous- a cast billet for supporting, moving and reducing the thickness of a continuously cast billet of a thin slab, having secondary cooling for cooling a continuously cast billet of a thin slab, while the continuously cast billet of a thin slab, after reducing the thickness, has a thickness of 35 to 52 mm, preferably 40- 50 mm, _{casting speed v C} and specific productivity of 0.45 m ² / min. ≥D≥0.27m ² / min., Includes:

- a group of rolling stands for hot rolling of a continuously cast thin slab of reduced thickness, this group of rolling stands located immediately after the continuous casting machine has at least three, preferably three to five, particularly preferably exactly four rolling stands, with this, by hot rolling the continuously cast thin slab billet exclusively from the state of its casting heating, a hot-rolled strip having a thickness of 2.5-10 mm is generated, and the last rolling pass is carried out in the austenitic temperature range of the steel;

- a cooling section for cooling the hot-rolled strip;

- shears for cross-cutting of cooled hot-rolled strip; and

- unwinding device for winding hot-rolled strip into coils.

Since the group of rolling stands is located immediately after the continuous casting machine, neither a heater nor a descaling device is located between the end of the continuous casting machine and the first rolling stand of the group of rolling stands. In this case, the continuously cast thin slab after the continuous casting machine is included in the group of rolling mill stands with a high surface and core temperature and is rolled there to obtain a hot-rolled strip exclusively from the state of its casting heating, while the last rolling pass is carried out in the austenitic region of steel temperature ...

For the compactness of the continuous casting machine, it is convenient when the curved section of the unit for moving the continuous cast billet has an arc radius of 4.5 to 6.5 m, preferably 5-6 m.

In order not to overcool the edge regions of the continuous-cast billet of a thin slab, it is convenient when the secondary cooling in several positions inside the unit for moving the continuous-cast billet has at least two spray nozzles moving in the direction of the width of the continuous-cast billet of a thin slab.

In order to take as much of the casting heat as possible from the continuous casting machine into the group of rolling stands, it is preferable when heat insulation panels (so-called heat shields Encopanel or, respectively, English heat covers), preferably a heat tunnel.

In addition, it has proven convenient when the horizontal distance between two rolling stands of a group of rolling mill stands is from 3 to 6 m, in particular from 4 to 5 m, and / or the length of the cooling section is from 10 to 60 m.

Finally, it is convenient to have a lifting device between the shears and the pair of pull rollers, whereby the hot strip is clamped by the pull rollers and the hot strip can be lifted by the lifting device, whereby the hot strip can be pulled away from the shears. With the so-called. Cobble In a combined casting and rolling plant, the hot strip is first cut with a shear, then the hot strip lying in the transport direction behind the shear is clamped by pulling rollers and lifted by a lifting device. As a result, the hot strip is pulled away from the shears, so that collision with the subsequent hot strip is avoided.

Brief Description of Drawings

Other advantages and features of the present invention follow from the description of non-limiting embodiments. The following, schematically depicted figures show:

Fig. 1 is a schematic view of a combined casting and rolling plant;

Fig. 2 is a view of the continuous casting machine of Fig. 1;

Fig. 3 shows different sections of a continuous casting unit for a continuous casting machine;

Fig. 4 is a view of a plurality of width-adjustable spray nozzles in a continuous casting unit of a continuous casting machine;

5: depiction of a temperature curve for the production of a thin, hot-rolled finished strip in a combined casting and rolling plant according to the invention;

Figures 6a and 6b show one front view of the lifting device in a non-raised and raised state;

Figures 7a-7b show the steps for starting up the combined casting and rolling plant according to the invention.

Description of embodiments

1 is a schematic illustration of a combined casting and rolling plant according to the invention for the production of hot-rolled hot-rolled steel strip. Vacuum-pretreated molten steel, having a carbon content of ≤ 1 ppm, is transported in ladles to a rotary ladle stand (figure 2 at the top left shows a ladle 8 suspended in a rotary ladle stand) of machine 1 for continuous casting and there with the help of a tundish 9 is poured into a pass-through mold 2 made in the form of a funnel-shaped crystallizer 2. In the pass-through mold 2, a continuously cast thin slab is formed, having a thin crust of a continuously cast billet, which has a thickness of 55 mm and a width of 1700 mm. The partially solidified continuous-cast billet 3 of a thin slab is continuously pulled out of the continuous-casting mold 2 and in the subsequent unit 4 for moving the continuous-cast billet is supported, moved and additionally cooled by means of spray nozzles (see Fig. 4, reference designation 19) of secondary cooling. Unit 4 for moving the continuous-cast billet has a vertical section 4a, a curved section 4b having several segments of the unit for moving the continuous-cast billet, and a horizontal section 4c (see Fig. 3). Figure 2 shows two segments 6 of the unit for moving a continuously cast billet. Each segment 6 of the unit for moving the continuously cast billet has several rollers of the unit for moving the continuous cast billet hydraulically attached to the continuously cast billet 3 of the thin slab, as a result of which the continuously cast billet 3 of the thin slab is reduced to a thickness of 45. Preferably, the continuously cast billet of the thin slab With a decrease in thickness, the slab has a liquid core 5 (the so-called Liquid Core Reduction, English rolling with a still liquid core) or a partially liquid core. In order to reduce as much as possible the mechanical work of deformation during subsequent rolling steps in the group of 14 stands of the rolling mill and to keep the heat of the casting heating in the continuous-cast billet 3 of a thin slab, secondary cooling in the unit 4 for moving the continuous-cast billet, as well as the _{casting speed v c, is} adjusted by the device 20 to control or regulate so that the continuous cast billet 3 of the thin slab solidifies through only in a predetermined position within the unit 4 for moving the continuous cast billet (see FIG. 3). The continuous casting machine 1 is operated at a casting speed v _{c of} 6 m / min. and specific productivity D = h * v _{c =} 0.27 m ² / min.

Controlled or regulated by the control or regulating device 20, the operation of the continuous casting machine 1 so that the lower end of the liquid core (i.e. the solidification point) of the continuous cast thin slab 3 is in a predetermined position within the continuous casting unit 4, known, for example, from WO 01/03867 A1. The corresponding disclosure is hereby incorporated by reference in this application.

Reduced in thickness, solidified through and through, not descaled and endless continuous-cast billet 3 of a thin slab immediately after continuous casting is rolled in four rolling stands F1 ... F4 of group 14 rolling mill stands to obtain a hot-rolled strip having a thickness of 3.2 mm (cm (See the following table for the individual thickness reductions and average temperatures).

up to F1 after F1 after F2 after F3 after F4 Thickness [mm] 45 nineteen nine 4.5 3.2 Ø Temperature [° C] 1090 1040 950 885 830

Tab. 1

Thereafter, the hot-rolled strip is cooled by the cooling section 16 to the coiling temperature, cut with scissors 17 and coiled by one of the coiling devices.

If a problem occurs in a group 14 of rolling stands or a cooling section 16, the hot-rolled strip is cut off by the shears 17, the section of the hot-rolled strip lying in the transport direction behind the shears 17 is clamped by pulling rollers (for example, a pair of pull rollers 18a of the coiling devices 18), and the lower part of the hot-rolled strip strip is pulled by the lifting device 10 from the shears 17. The hot-rolled strip coming from the group 14 of stands of the rolling mill is crushed by the shears 17 into short sections of the hot-rolled strip and removed, for example, by means of scrap baskets 11.

Figure 2 shows other parts of the continuous casting machine 1.

Fig. 3 shows in more detail the vertical portion 4a, the curved portion 4b and the horizontal portion 4c of the continuous casting unit 4 of the continuous casting machine 1. Due to the direct mold 2 and the vertical section 4a, inclusions are collected in the steel melt on the meniscus, they are taken up by the powdery flux and in the form of casting slag are used to lubricate the continuously cast billet. The radius R of the curved continuous casting unit 4b is shown in FIG. 3 and for the continuous casting machine according to the invention is approx. 5 m. The continuously cast thin slab 3 directly (ie without descaling) after the horizontal section 4c enters the first rolling stand F1 of the rolling mill stand group. Also shown in this figure is how a thin slab continuous-cast billet 3 having a liquid core 5 emerges from the through-mold 2 and decreases in thickness in the continuous-cast billet transfer unit 4. The continuously cast billet 3 of a thin slab, reduced in thickness, is pulled out of the continuous casting mold 2 by means of a pulling device 7 made in the form of a pair of drive rollers of the unit for moving the continuously cast billet. In order to hold the lower end of the liquid core of the continuously cast billet 3 of a thin slab in a certain position, the control and / or regulating device 20 controls the _{casting speed v c in a} controlled or controlled manner, optionally also reducing the thickness of the continuous cast billet 3 of a thin slab with using segments 6 of the unit for moving the continuously cast billet.

Figure 4 shows a width-adjustable secondary cooling in the unit 4 for moving the continuously cast billet. Both with narrow 3 and wide continuous-cast billets 3 'of a thin slab, overcooling of the edge regions of the continuous-cast billet 3 is prevented, while the outer two spray nozzles 19 are made with the possibility of displacement, both in the width direction and normal to the surface continuously - cast billet. The spray nozzles 19 are connected by spray nozzle holders 21, 21 'to a linear actuator 22, which displaces the spray nozzles 19 in the axial direction of the linear actuator 22. The middle spray nozzle 19 can be either fixed or, as shown, also movable.

Figure 5 shows the temperature curve in ° C for the production of a hot-rolled finished strip according to the invention in a combined casting and rolling plant; this figure corresponds to the above description and data in table 1. The core temperature is depicted, respectively, by the dotted line, the surface temperature by the dashed line, and the average temperature by the solid line. Steel melt of quality DD11 is subjected to vacuum treatment before continuous casting, as a result of which the carbon content in liquid steel is reduced to ≤1 ppm. In the continuous casting mold 2 of the continuous casting machine 1, a partially solidified continuous-cast thin slab 3 having a thickness of 55 mm and a width of 1700 mm is formed and reduced in thickness by Liquid Core Reduction to obtain a solidified continuous-cast thin slab 3 having thickness 45 mm. The solid-through continuous-cast thin slab 3 leaves the horizontal section 4c of the continuous casting machine 1 at a speed v _c = 6 m / min. casting and at the same time with a specific productivity D = h * v _{c =} 0.27m ² / min. The continuously cast thin slab 3, hardened through and through, without descaling, is brought to a group of 14 stands of a rolling mill and there, using four rolling stands F1-F4, it is crimped to a thickness of 3.2 mm. It should be noted that even with a very low specific productivity D = 0.27m ² / min. the last rolling pass in rolling stand F4 is carried out in the austenitic state of the steel. Thereafter, the hot strip is cooled in the cooling section 16, cut and coiled.

Fig. 6a shows the lifting device 10 of Fig. 1 in a not raised state, but in Fig. 6b in a raised state. When not raised, all lower rollers of the roller table incl. the two lifting rollers 13 to be lifted form a horizontal roller table 12. When, as described in the description of FIG. 1, a problem occurs during endless operation in or after the rolling mill 14, the endless hot strip is cut by the shears 17, clamped, and the two lifting rollers 13 move upward (see the raised state in Fig. 6b). Since the hot strip 15 is clamped in some position behind the shears 17, the bottom of the hot strip section is pulled away from the shears 17. This simply avoids collisions between the drawn strip section and the hot strip coming from the mill stand 14.

Figures 7a-7e show schematically the process steps for starting up the combined casting and rolling plant according to the invention.

Fig. 7a shows a combined casting and rolling plant prior to the start of casting of the continuous casting machine. The pass-through mold 2 is sealed hydraulically tightly by a dummy bar 30, which includes a dummy head 31 and a link chain 32. After the casting of the continuous casting machine 1 has started, the dummy bar 30 is pulled by pulling rollers 18a in the transport direction T from the cooled pass-through crystallizer 2. At the start of casting, the head 31 dummy bar is welded with the subsequent continuously cast billet 3 of a thin slab (see Fig. 7b), while the continuously cast billet 3 of a thin slab is supported by the unit 4 for moving the continuously cast billet (most often by the rollers of the unit for moving the continuously cast billet of segment 6 of the displacement unit continuously cast billet), is moved and additionally cooled by secondary cooling.

In Fig. 7b, the dummy bar has practically been pulled out of the continuous casting machine 1. Since the dummy bar 30 is significantly colder and harder than the subsequent continuous-cast thin slab 3, the rolling stands F1 ... F4 of the group 14 of the rolling mill stands are in a raised state, so that the dummy bar 30 can pass the group of 14 stands of the rolling mill not rolled. This prevents damage to the work rolls of the F1 ... F4 rolling stands.

In Fig. 7c, the dummy bar has already passed the mill stand group 14 and the cooling section 15 and has been cut off by shears 17 from the continuously cast thin slab 3. In the illustrated state, the dummy bar 30 has been separated from the shear 17 by the drive rollers 33 or, respectively, by the pull rollers.

In accordance with FIG. 7d, the dummy bar 30 was folded by the drive rollers 3 behind the pull rollers 18a of the coiler 18 onto the roller table 12. In addition, the _{casting speed v C of the} continuous casting machine 1 was increased and the continuous cast thin slab 3 was reduced in thickness with the help of the unit 4 for moving the continuously cast billet, as a result of which a wedge-shaped part 34 is formed. The unrolled continuous-cast billet 3 of a thin slab and the wedge-shaped part 34 are crushed by shears 17, and the crushed material is removed from the roller table 12 between the shears 17 and the reeling device 18, for example. , by sliding the crushed material horizontally across the conveying direction T. In addition, the rolling stands F1-F4 of the group 14 of rolling mill stands are now positioned step by step against the thinned continuous-cast slab 3, and the continuous-cast thin slab 3 is rolled to obtain a hot-rolled strip 15. This figure shows a point in time, when the first rolling stand F1 is adhered to the thinned thin slab 3, reduced in thickness. The passage through the F2-F4 stands still takes place without rolling.

In Fig. 7e, finally, all the rolling stands F1 ... F4 have been attached, so that the thinned continuously cast thin slab 3 is rolled to obtain a hot strip having a thickness of 2.5 to 10 mm. The hot-rolled strip 15 is cooled in the cooling section 16, after which it is cross-cut with shears 17 to the length or, respectively, the weight of the coil and is coiled into coils in the reeling device 18.

In contrast to the combined casting and rolling plants of the prior art, the installation according to the invention is much simpler, since, for example, it only needs a single shear 17 and does not require a descaling device at all. In addition, the start-up of this combined casting and rolling plant is much easier. However, the hot rolled strip 15 produced is excellent as a raw material for classical cold rolling.

Although the invention has been illustrated in more detail and described in detail with reference to the preferred embodiments, the invention is not limited to the disclosed examples, and other variations may be derived from therewith without departing from the scope of the invention.

LIST OF REFERENCE SYMBOLS

1 Continuous casting machine

2 Pass-through crystallizer

3, 3 'Continuously cast thin slab

4 Unit for moving a continuous cast billet

4a Vertical section of the unit for moving the continuous cast billet

4b Curved section of the unit for moving the continuous cast billet

4c Horizontal section of the unit for moving the continuous cast billet

5 Liquid core

6 Segment of the unit for moving a continuous cast billet

7 Pulling device

8 Bucket

9 Prom bucket

10 Lifting device

11 Scrap basket

12 Roller table

13 Lifting roller roller

14 Group of rolling mill stands

15 Hot rolled strip

16 Cooling section

17 Scissors

18 Rewinder

18a Pulling rollers

19 Spray nozzle

20 Control or regulation device

21, 21 'Spray nozzle holder

22 Linear drive

30 Seed

31 dummy head

32 Link chain

33 Drive roller

34 Wedge-shaped part

h Thickness of thin slab, reduced in thickness,

F1 ... F4 Rolling stand

D Specific productivity

R Radius

T Direction of transport

v _C Casting speed

Claims (57)

1. Method for the continuous production of coiled hot-rolled strip (15) from steel in a combined casting and rolling plant containing - a machine (1) for continuous casting for the production of an endless continuous-cast billet (3, 3 ') of a thin slab, having a continuous-flow mold (2) and a unit (4) for moving the endless continuous-cast billet; - a group (14) of rolling mill stands having rolling stands (F1 ... F4) for hot rolling of a continuously cast billet (3, 3 ') of a thin slab to obtain a hot-rolled strip (15); - section (16) cooling for cooling the hot-rolled strip (15); - scissors (17) for cross-cutting of hot-rolled strip (15); and - rewinding device (18) for reeling hot-rolled strip (15); including - continuous casting of steel melt in the continuous mold (2) of the machine (1) for continuous casting to obtain a continuously cast billet (3, 3 ') of a thin slab, which, when leaving the continuous mold (2), has a liquid core (5), thickness from 45 to 70 mm and width from 900 to 2300 mm; - providing support for a continuously cast billet (3, 3 ') of a thin slab, its movement and thickness reduction in the unit (4) for moving a continuously cast billet of a machine (1) for continuous casting, while a continuously cast billet ( 3, 3 ') of a thin slab has a thickness h from 35 to 52 mm, and the specific productivity D = h * v _c (m ² / min), where v _c is the casting speed, is 0.45≥D≥0.27; - hot rolling of an endless thin slab continuously reduced in thickness in a group (14) of rolling mill stands, while the continuously cast thin slab in its casting heating state is rolled in at least three rolling passes to obtain a hot-rolled strip (15) having a thickness of 2.5 to 10 mm, and the last rolling pass is carried out in the austenitic region of the temperature of the steel; - cooling the hot-rolled strip (15) in the cooling section (16); - transverse cutting of the cooled hot-rolled strip (15); and - unwinding the hot-rolled strip (15) into coils in a reeling device (18). 2. The method according to claim 1, characterized in that the continuously cast billet (3, 3 ') of a thin slab at the exit from the continuous mold (2) has a thickness of 55-65 mm and a width of 1100-1900 mm. 3. A method according to claim 1 or 2, characterized in that the thin slab (3, 3 ') reduced in thickness has a thickness of 40-50 mm. 4. A method according to any one of claims 1 to 3, characterized in that the continuously cast thin slab in the state of casting heating is rolled in four rolling passes. 5. A method according to any one of claims 1 to 3, characterized in that a continuous casting machine (1) is used with a control device (20), which, using a mathematical model, continuously calculates - the actual position of the lower end of the liquid core along the conveyance path of the continuously cast billet (3, 3 ') of the thin slab in the unit (4) for moving the continuously cast billet, and - the actual temperature profile along the path of transportation of a continuously cast billet (3, 3 ') of a thin slab in the unit (4) for moving a continuously cast billet and in planes normal to it, while continuous controlled cooling of the continuously cast billet is carried out (3, 3 ') a thin slab, taking into account the nominal position of the lower end of the liquid core in the unit (4) for moving the continuously cast billet, ensuring that the actual position of the lower end of the liquid core corresponds to the nominal position. 6. A method according to any one of claims 1 to 5, characterized in that after the last rolling pass in the group (14) of rolling mill stands and before cooling, the actual temperature T _{1fact is measured in the cooling section (16).} hot-rolled strip (15), and the cooling of the continuous-cast billet (3, 3 ') of the thin slab in the unit (4) for moving the continuous-cast billet and / or the _{casting speed v c is} adjusted in a controlled manner to ensure that the actual temperature T _1fact. nominal temperature T ₁ ... 7. A method according to any one of claims 1 to 6, characterized in that the thinning of the thin slab (3, 3 ') is carried out by soft reduction in the region still having a liquid core (5) or a partially liquid core. 8. A method according to any one of claims 1 to 7, characterized in that the actual temperature T _{2fact is measured.} endless hot-rolled strip (15) after cooling in the cooling section (16), which has cooling nozzles, which are activated in a controlled manner depending on the temperature, ensuring that the actual temperature T _2fact. nominal temperature T ₂ ... 9. A method according to any one of claims 1 to 8, characterized in that the hot-rolled strip (15) is then pickled and cold rolled in several passes in a cold rolling mill to a thickness of 0.3 to 7 mm. 10. Combined installation for casting and rolling for the production of coiled hot-rolled strip (15) of steel by the method according to any one of claims 1 to 9, containing a machine (1) for continuous casting, which includes a continuous casting mold (2) for the continuous production of a continuously cast billet (3, 3 ') of a thin slab, which, when leaving the continuous casting mold (2), has a liquid core (5), thickness from 45 up to 70 mm and width from 900 to 2300 mm; and unit (4) for moving the continuously cast billet to support, move and reduce the thickness of the continuously cast billet (3, 3 ') of a thin slab, having secondary cooling for cooling the continuously cast billet (3, 3') of a thin slab, while The continuously cast billet (3, 3 ') of a thin slab, after reducing the thickness, has a thickness of 35 to 52 mm, and the specific productivity D = h * v _s (m ² / min), where v _s is the casting speed, is 0.45 ≥D ≥ 0.27; - located immediately after the machine (1) for continuous casting, a group (14) of stands of a rolling mill for hot rolling of a thin slab (3, 3 ') reduced in thickness, which has at least three rolling stands (F1 ... F4) and is configured to obtain, by hot rolling, a continuously cast billet (3, 3 ') a thin slab in the state of its casting heating of a hot-rolled strip (15) having a thickness of 2.5 to 10 mm, and performing the last rolling pass in the austenitic temperature range become; - section (16) cooling for cooling the hot-rolled strip (15); - scissors (17) for cross-cutting of cooled hot-rolled strip (15); and - unwinding device (18) for winding hot-rolled strip (15) into coils. 11. Combined plant according to claim 10, characterized in that the continuously cast billet (3, 3 ') of a thin slab at the exit from the continuous mold (2) has a thickness of 55-65 mm and a width of 1100-1900 mm. 12. Combined plant according to claim 10 or 11, characterized in that the continuous-cast billet (3, 3 ') of a thin slab, after reducing the thickness, has a thickness of 40-50 mm. 13. Combined plant according to any one of claims 10-12, characterized in that the group (14) of the rolling mill stands has four rolling stands (F1 ... F4). 14. Combined plant according to any one of claims 10-13, characterized in that the machine (1) for continuous casting contains a control device (20) for continuous calculation using a mathematical model - the actual position of the lower end of the liquid core along the conveyance path of the continuously cast billet (3, 3 ') of the thin slab in the unit (4) for moving the continuously cast billet, and - the actual temperature profile along the path of transportation of a continuously cast billet (3, 3 ') of a thin slab in the unit (4) for moving a continuously cast billet and in planes normal to it, wherein the device (20) regulating adjustably configures the at least one quantity from the group consisting of cooling intensity in the secondary cooling and the speed v _with casting with the nominal position of the lower end of the liquid core node moving continuously cast billet with ensuring compliance actual position the lower end of the liquid core of a thin slab (3, 3 ') to the nominal position. 15. Combined installation according to any one of claims 10-14, characterized in that the curved section (4b) of the unit (4) for moving the continuously cast billet has a radius R of the arc from 4.5 to 6.5 m, preferably 5-6 m ... 16. Combined plant according to any one of claims 10-15, characterized in that in the area between the end of the horizontal section (4c) of the unit (4) for moving the continuously cast billet and the first stand (F1) of the group (14) of rolling mill stands, heat-insulating panels, preferably a heat tunnel. 17. Combined plant according to any one of claims 10-16, characterized in that the horizontal distance between two rolling stands (F1, F2, F3, F4) of the group (14) of rolling mill stands is from 3 to 6 m, in particular from 4 up to 5 m. 18. Combined plant according to any one of claims 10 to 17, characterized in that the length of the cooling section (16) is from 10 to 60 m. 19. Combined installation according to any one of claims 10-18, characterized in that between the shears (17) and a pair of pulling rollers (18a) there is a lifting device (10), while the pulling rollers (18a) are made with the possibility of clamping the hot-rolled strip ( 15), and the lifting device (10) is configured to lift the hot-rolled strip (15) to ensure it is pulled away from the shears (17). 20. A method for starting up a combined casting and rolling plant according to any one of claims 10-19, including - the start of casting of the continuous casting machine (1), whereby a dummy bar (30) is used to seal the continuous casting mold (2) of the continuous casting machine (1), which is pulled out in the transport direction (T) from the continuous casting mold (2); - providing support for the continuously cast billet (3, 3 ') of a thin slab following the dummy bar (30) and its movement in the unit (4) for moving the continuously cast billet of the continuous casting machine; - passing the rolling stands (F1 ... F4) of the group (14) of the rolling mill stands, while ensuring the passage of the seed (30) of the group (14) of the rolling mill stands without rolling; - cutting off the seed (30) with scissors (17); - withdrawal of the seed (30), - transverse cutting of an unrolled continuously cast billet (3, 3 ') of a thin slab with scissors (17) and removal of the crushed material; - reducing the thickness of the continuously cast billet (3, 3 ') of a thin slab in the unit (4) for moving the continuously cast billet; - installation of rolling stands (F1 ... F4) for a continuously cast billet (3, 3 ') of a thin slab and hot rolling of a continuously cast billet (3, 3') of a thin slab to obtain a hot-rolled strip (15); - cooling the hot-rolled strip (15) in the cooling section (16); - transverse cutting of the cooled hot-rolled strip (15); and - unwinding the hot-rolled strip (15) into coils in a reeling device (18). 21. A method according to claim 20, characterized in that when the dummy bar (30) is pulled out, it is ensured that it passes the reeling device (18) and folds behind it in the direction (T) of transportation. 22. The method according to claim 20 or 21, characterized in that after the withdrawal of the crushed material, the casting speed is increased. 23. A method according to any one of claims 20 to 22, characterized in that when the casting speed is increased, the specific productivity D = h * v _c (m ² / min) is set, which is 0.45>D> 0.27.

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