EP2697010B1 - Method and vertical continuous casting system for producing thick slabs from a metallic melt - Google Patents

Description

The invention relates to a method for producing thick slabs from a metallic melt on a vertical caster, wherein a steel strand with still liquid core poured in a vertical mold, continued in a subsequent, several strand guide segments with at least some driven and / or adjustable strand guide rollers having strand guide is divided and after the solidification of a separator in slab lengths, which are then discharged. The invention further relates to a vertical continuous casting plant for carrying out the method.

The long-demanded variety of formats with format thickness ranges from 50 to 450 mm and format width ranges from 900 to 3,200 mm is so far fulfilled in continuous casting in the execution as so-called sheet plant, vertical bending or vertical investment with turning of completely solidified strand (such as CSP vertical plant). Slab thicknesses greater than 300 mm are due to the metallurgical requirements for producing large sheet thicknesses with sufficiently high degree of deformation in the individual rolling phases, so that values of, for example, 85% ductile fracture fraction at -20 ° C can be reliably met even for thick sheets.

By publishing " Construction of a new vertical caster at the AG der Dillinger Hüttenwerke ", Stahl und Eisen 117 (1997), No. 11, pages 73 to 79 , a continuous casting plant of vertical design with turning of the steel strand after the solidification for the production of steel strands with casting widths of 1,400 to 2,200 mm and a steel strand thickness between 230 and 400 mm has become known. After that shown in picture 8 and in the publication described concept, the strand guide consists of four different support elements, namely the straight mold with vertically oriented Kokillenformhohlraum, a mechanically fixed in thickness first segment, two hydraulically salaried follower segments and five suitable for hydraulic soft-reduction segments. The hydraulically positionable strand guide segments allow variable strand guidance with dynamic sub-load adjustment and soft-reduction zone adjustment, so that the strand can be optimally reduced at any time and under all casting conditions and the segregation minimization requirements can be met.

From the DE 20 2010 015 499 U1 a vertical caster of the type mentioned is known. With such a system, it is possible to avoid problematic bending, especially in slabs or steel strands thicker than 300 mm. Such a vertical strand guide is suitable at casting speeds of about 0.3 to 0.4 m / min. to produce up to 400 mm thick slabs or steel strands until the final solidification crack-free.

The publication JP 2000015413 describes a continuous casting plant for the production of slabs with a thickness ≥ 250 mm and a width ≥ 1,500 mm.

The US 2008/0264598 A1 describes a continuous casting plant with sensors that monitor the casting process and with devices for correcting the casting process.

The invention has the object of providing a generic method and a vertical caster so educate that regardless of the resulting hot strip temperature profile in the individual sections of the strand guiding devices to the discharge of the separated slab a consistent and high quality, ie regarding slab geometry, slab surface and internal slab quality, in particular at 400 mm thickness exceeding slabs or steel strands reach, which can not be produced with a continuous casting process, but only via block casting with subsequent rolling process due to the crack sensitivity or brittleness. This in particular for the production of crack-sensitive steel grades, alloyed steels, such as drilling alloys, general and high-strength steels, acid gas-resistant tube and boiler plates and heavy plates.

This object is achieved by a method according to claim 1. Characteristic of the inventive method is that in a the strand guide subsequent plant section, which is arranged between a cast upstream in the casting direction roller unit and a downstream strand driver, without support and leadership of durcherstarrten steel strand detects its deviation from the vertical with a measuring means, and the steel strand is bent back into the vertical by increasing or reducing the contact forces and / or position change of the unsupported section of the plant upstream or downstream strand guide rollers before the steel strand has reached the separator.

The invention is based on the finding that the strand thickness required by the hydraulic system for the employment of the mold downstream strand guide segments, for example, up to nine segments, high pressures of about 25 MPa and exerted by the steel strand, opposing thermal forces required for such a large format thicknesses an emigration of the steel strand from the vertical in the direction of the broadsides can cause. This is certainly true even with format thicknesses above 300 to 400 mm. However, by the strand guide has been extended and subsequent to the last strand guide segment the unsupported plant section both upstream and downstream strand guide rollers, which may preferably also be stored in segments, can be with these strand guide rollers of the steel strand bent at discrepancies detected in the vertical, before he has subsequently reached the in its uppermost position positioned separating device, preferably a flame cutter. If no emigration or deviation is detected, these strand guide rollers hold the steel strand in the vertical. The determination of a deviation takes place here in the unsupported section of the system and is forwarded to the corresponding control of the strand guide rollers to a higher-level central computer.

Under unsupported system section is understood in this context that no strand guide rollers are provided over a certain length.

Preferred embodiments of the invention provide that the restoring forces or the forces holding the steel strand in the vertical are applied in a drive roller unit upstream of the unsupported installation section in the casting direction and / or by a strand driver downstream of the unsupported installation section.

It is within the scope of the invention that targeted only single strand guide rollers of the driver roller unit and / or the strand driver kraftbeaufschlagt employed against the steel strand and / or be positioned in a changed position to the steel strand. In the case of a driver roller unit consisting of three roller pairs, these are preferably the strand guide rollers of the two last roller pairs in the casting direction and / or the strand guide rollers of the roller driver advantageously having two roller pairs.

According to one embodiment of the invention, it is provided that a hard reduction can be carried out with the driver roller unit, so that in this case it is a drive reduction unit. In the case of hard reduction, the steel strand is compressed after its complete through solidification in order to compensate for density dips over the strand cross section caused by the solidification process.

It is provided according to the invention that during the passage of the unsupported installation section in the time window predetermined by the casting speed, a cold strand required for starting the vertical continuous casting installation is decoupled from the steel strand and discharged. The length of the unsupported plant section is designed so that at the variable casting speeds to be operated vertical caster even at the maximum casting speed, eg 0.6 to 1 m / min., The time available sufficient to decouple the cold strand of the warm steel strand and auszufördern.

A preferred embodiment of the invention provides that the decoupled cold strand taken up by the downstream strand driver is conveyed out with the strand driver and, at the same time, a second strand driver is moved from a rest position into the position leading the steel strand in an interplay. The strand drivers thus serve alternately once as a hot strand and once as a cold extruder driver, preferably designed as in the direction of the broad sides of the steel strand movable car.

The underlying object of the invention is achieved with a generic vertical caster, characterized in that in the casting direction of the strand guide plant section without the steel strand supporting strand guide rollers is formed and in this unsupported plant section deviations of the steel strand from the vertical direction detecting measuring means is arranged, which determines the actual values to a higher-level, central processing unit for correcting the deviation by increasing or reducing the Anstellkräfte or change in position at least some strand guide rollers that are upstream or downstream of the unsupported system section, forwards. There are therefore various, optionally complementary screws available to bend back out of the running direction steel strand back into the vertical.

According to a preferred proposal of the invention, the measuring means is designed as an acted upon by a position-controlled hydraulic cylinder multi-functional role. This is traced so that it always rests on the broad side of the steel strand, so that any deviation from the vertical direction can be determined immediately.

After starting the vertical caster, the multifunctional roll can also be used to decouple the cold strand from the cast steel strand by applying force. The trained with a suitably suitable head dummy strand can be retracted from above or preferably from below into the mold.

The concept of the vertical continuous casting plant according to the invention provides that the unsupported plant section in the casting direction is preceded by a driver roller unit consisting of driven, single-sided or double-sided driver roller pairs with position-controlled hydraulic cylinders acting on the driver rollers. Depending on the positioning of the driver roller unit or one of their strand guide or driver rollers or their employment on the steel strand of the steel strand is bent back in the vertical direction. In addition, the driver roll unit may also serve to perform a hard reduction.

According to a particular embodiment of the invention, the unsupported plant section for further supported and vertical steel strand guide in the casting direction downstream of at least two driven, one or two sides with associated position-controlled hydraulic cylinders to be acted upon and / or be acted upon by a bending force pairs of strand guide rollers strand driver, wherein the Strand driver is designed as a unit orthogonal to the casting direction, which is used in interaction with a second such orthogonal to the casting direction movable strand driver as a hot rod or cold extruder driver. While a strand driver used to start the vertical caster as a cold extruder driver and to feed out the decoupled cold strand, the second strand driver operates correspondingly in alternation works as a heat driver.

According to one embodiment of the invention, a flame cutter traveling along with the steel strand is provided as a separating device. The flame cutter thus shifts during the separating cut from an uppermost to a dependent on the respective slab length lowermost position.

According to a preferred embodiment of the invention, it is provided that a slab turner designed as a swiveling roller table takes over a severed slab length and pivots it for removal into the horizontal. The continuous material flow is guaranteed. For from the tilted in the horizontal swivel roller table, the slab length can be given immediately to a subsequent conveyor roller table, so that the swivel gear can be readily pivoted back to its upright position to take over a subsequent, slab length.

Further features and details of the invention will become apparent from the claims and the following description of a schematically illustrated in the single drawing figure concept of a vertical caster for producing steel strands with large thicknesses of particular 400 to 800 mm and format widths of 900 to 3200 mm.

In the drawing figure without casting platform with the local facilities a vertical caster 1 is shown schematically. The strand guide consists of a vertical mold 2, which in the casting direction according to arrow 3, a mechanically fixed in thickness first strand guide segment 4, several (for example, six to eight) hydraulically employed strand guide segments n1 _to , in these strand guide segments, the strand guide rollers 5 are arranged opposite to each other, a driver roller unit 6, an unsupported, no strand guide roles exhibiting system section 7, two strand drivers 8a and 8b, which can be retracted in the interplay - as indicated by the double arrows - in the strand guide, where they take over the function as a heat drive driver, as framed dashed lines indicated, a vertically moving, designed as a flame cutter 9 separating device 10 and ultimately connect to take over a separated from the produced steel strand 11 slab length 11a provided swivel gear 12. The slab length 11a spent by the pivoting process 12 in the horizontal is transported away by a conveyor 13 in the direction of arrow 14.

The unsupported plant section 7 (see page 10, line 13) upstream drive roller unit 6 comprises three pairs of rollers 6a, 6b, 6c, each with driven strand guide rollers 5a and these respectively associated, position-controlled hydraulic cylinders 15. In the following unsupported system section 11 is a measuring means 16, is formed arranged as a one of a position-controlled hydraulic cylinder 17 against the steel strand 11 acted upon measuring roller 18. The unpowered plant section 7 downstream strand driver 8a and 8b has according to the embodiment, two pairs of rollers with each driven strand guide rollers 5b, which - not shown - are also associated with position-controlled hydraulic cylinder or double cylinder.

Both the measuring means 16 or its hydraulic cylinder 15 and the two lower roller pairs 6b, 6c of the driver roller unit 6 and the strand drivers 8a, 8b or the hydraulic cylinders of the strand guide rollers 5b mounted therein are connected to a central processing unit 19, such as the dashed signal lines 20 indicated.

As soon as the measuring means 16 detects deviations of the steel strand 11 from the vertical via its measuring roller 18, the steel strand 11 is controlled by the central arithmetic unit 19 by either changing the position of the strand guide rollers 5a of the two lower roller pairs 6b and 6c of the driver roller unit 6 or by reducing or increasing the Anstellkräfte the strand guide rollers 5a of these pairs of rollers 6b, 6c bent back into the vertical.

Optionally, the bending back of the steel strand 11 into the vertical can be achieved by changing the position and / or reducing or increasing the setting forces of the strand guide rollers 5b of the strand driver 8a or 8b downstream of the unsupported plant section 7.

The hydraulic cylinder 17 with the measuring roller 18 of the measuring means 16 simultaneously serves to decouple the cold strand 21 from the subsequent warm steel strand or hot strand 11 after starting the vertical continuous casting plant 1. To feed out the decoupled cold strand 21, the cold strand 21 from the strand driver 8b is orthogonal to the casting direction, i. H. discharged from the broad side of the steel strand 11, as inclined in the drawing figure. At the same time as the discharge of the cold leg 21, the second strand driver 8a, which is likewise designed as a movable carriage, is moved from its rest position into the dashed framed strand guiding position, where it immediately takes over the guidance of the steel strand 11 as a hot strand driver following the unsupported system section 7. The distance of the strand guide rollers 5b of the strand driver 8a or 8b from each other can initially be sufficiently large, especially when the steel strand 11 is bent back by the strand driver 8a and 8b or its strand guide rollers 5b in the vertical. The controllability allows any positioning and / or role employment.

After pouring is according to the embodiment of the dashed framed strand driver 8a moved from its working position to its standby position shown by solid lines, while then the strand driver 8b is moved to retract the cold strand 21 from the head change position shown in solid lines in the dashed framed working position, to he is after the start of the vertical caster 1 and after the cold strand 21 has been decoupled from the cast steel strand 11 is moved in its play in the figure to the right next to the steel strand 11 moved head change position in the interplay with the strand driver 8a.

LIST OF REFERENCE NUMBERS

1

Vertikalstranggießanlage

2

Senkrechtkokille

3

Casting / Arrow

4

first strand guide segment

5

Strand guide roller

5a

Strand guide role (the driver role unit) / driver role

5b

Strand guide roller (the strand driver)

6

Driver roller unit

6a, b, c

roller pair

7

unsupported system section

8a, b

Strand driver (hot strand or cold strand driver)

9

oxygen torches

10

separator

11

Steel strand (hot strand)

11a

slab length

12

Swiveling roller table

13

Conveyor

14

Arrow transport

15

position-controlled hydraulic cylinder

16

measuring Equipment

17

position-controlled hydraulic cylinder

18

measuring roller

19

central processing unit

20

signal line

21

dummy bar

n1 _to

Strand guide segment

Claims (13)

1. Method of producing thick slabs in the form of steel strips (11) with a thickness exceeding 300 millimetres, in particular lying between 400 and 800 millimetres, and with format widths of 900 to 3,200 millimetres from a metallic melt on a vertical continuous casting plant (1), wherein a steel strip with still liquid core is cast in a vertical mould (2) and conducted onward to a following strip guide, which comprises a plurality of strip guide segments (n1_bis) with strip guide rollers (5; 5a; 5b) therein of which at least some are driven and/or adjustable, and after hardening through is subdivided by a separating device (10) into slab lengths (11a), which are thereafter conveyed out, characterised in that in a plant section (7), which follows the strip guide and which is arranged between a drive roller unit (6) upstream in casting direction (3) and a downstream strip driver (8a, 8b), deviation of the hardened-through steel strip (11), without support and guidance thereof, from the vertical is detected by measuring means (16) and the steel strip is bent back into the vertical by increasing or reducing the adjusting forces and/or positional change of strip guide rollers (5a, 5b), which are upstream or downstream of the unsupported plant section (7), before the steel strip (11) has reached the separating device (10).
2. Method according to claim 1, characterised in that the return bending forces or the forces keeping the steel strip (11) in the vertical are applied by a drive roller unit (6) upstream of the unsupported plant section (7) in casting direction (3).
3. Method according to claim 1 or 2, characterised in that the return bending forces or the forces keeping the steel strip (11) in the vertical direction are applied by a strip driver (8a; 8b) downstream of the unsupported plant section (7) in casting direction (3).
4. Method according to claim 2 or 3, characterised in that individual strip guide rollers (5a) of the drive roller unit (6) and/or the strip driver (8a; 8b) are, under the action of force, selectively adjusted towards the steel strip (11) and/or positioned in a position changed with respect to the steel strip (11).
5. Method according to any one of claims 2 to 4, characterised in that a hard reduction is carried out by the drive roller unit (6).
6. Method according to any one of claims 1 to 5, characterised in that during transit through the unsupported plant section (7) and in the time window predetermined by the casting speed a cold strip (21) required for starting up the vertical continuous casting plant (1) is decoupled from the steel strip (11) and conveyed out.
7. Method according to claim 8, characterised in that the cold strip (21) taken up by the downstream strip driver (8b) is conveyed out by the strip driver (8b) and in interaction therewith a second strip driver (8a) is at the same time moved out of a rest position into the position guiding the steel strip (11).
8. Vertical continuous casting plant (1) for producing thick slabs in the form of a steel strip (11) with a thickness exceeding 300 millimetres, in particular lying between 400 and 800 millimetres, and with format widths of 900 to 3,200 millimetres, from a metallic melt, comprising a vertical mould (2), a strip guide following thereon and comprising a plurality of strip guide segments (n1_bis), a following separating device (10) for subdividing the hardened-through steel strip (11) into slab lengths (11a) and equipment for transport away of the slab lengths (11a), for carrying out the method according to claim 1, wherein a plant section (7), which is downstream of the strip guide in casting direction (3) and which is arranged in casting direction (3) between an upstream drive roller unit (6) and a downstream strip driver (8a, 8b), is constructed without strip guide rollers supporting the steel strip (11), characterised in that a measuring means (16), which detects deviations of the steel strip (11) from the vertical running direction, in the form of a multi-functional roller (18) able to be acted on by a position-regulated hydraulic cylinder (17) is arranged in the unsupported plant section (7), wherein the measuring means (16) passes on the ascertained actual values to a superordinate central computer unit (19) for correction of the deviation by increasing or reducing the adjusting forces or positional change of at least some strip guide rollers (5a or 5b) upstream or downstream of the unsupported plant section (7).
9. Vertical continuous casting plant according to claim 8, characterised in that the multi-functional roller (18) decouples a cold strip (21) from the cast-on steel strip (11) by the action of force.
10. Vertical continuous casting plant according to one of claims 8 and 9, characterised in that a drive roller unit (6), which consists of driven drive roller pairs (6a, 6b, 6c), which are to be adjusted at one end or two ends, with position-regulated hydraulic cylinders (15) acting on the drive rollers (5a), is upstream of the unsupported plant section (7) in casting direction (3).
11. Vertical continuous casting plant according to any one of claims 8 to 10, characterised in that a strip driver (8a; 8b), which comprises at least two driven strip guide rollers (5b) to be adjusted at one side or both sides by associated position-regulated hydraulic cylinders (15) and/or to be acted on by a bending force, is mounted downstream of the unsupported plant section (7) for further supported and vertical strip guidance in casting direction (3), wherein the strip driver (8a; 8b) is constructed as a unit which is movable orthogonally to the casting direction (3) and which comes into use in interaction with a second such strip driver, which is movable orthogonally to the casting direction (3), as hot-strip or cold-strip driver.
12. Vertical continuous casting plant according to any one of claims 8 to 11, characterised by a torch cutter (9), which travels with the steel strip (11), as separating device (10).
13. Vertical continuous casting plant according to any one of claims 8 to 12, characterised in that a slab turner, which is constructed as a pivot roller path (12), takes over a separated slab length (11a) and pivots this into the horizontal for transport away.

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