WO2011038800A1

WO2011038800A1 - Device and method for the controlled secondary cooling of a strand casting system

Info

Publication number: WO2011038800A1
Application number: PCT/EP2010/004563
Authority: WO
Inventors: Markus Reifferscheid; Erich Hovestädt
Original assignee: Sms Siemag Aktiengesellschaft
Priority date: 2009-07-27
Filing date: 2010-07-26
Publication date: 2011-04-07
Also published as: EP2459335A1; DE102009034847A1; CN102470430A

Abstract

The invention relates to a device for controlled secondary cooling comprising a network of a strand casting system through which a cooling medium flows, which strand casting system can be adapted to the particular casting task, in particular in regard to the steel type and special tasks that result during the casting process, the device being characterized in that the network comprises at least one first pressure network, in which the pressure of the cooling medium is used as a task variable. The network comprises a plurality of branches for control groups, in particular for each segment (1) or each segment group (2, 3), in the distribution chamber (8) of the cooling medium, and apparatuses (23) for measuring pressure and/or for measuring flow rate are provided for each branch.

Description

Apparatus and method for controlled secondary cooling

a continuous casting plant

The invention relates to a device for controlled secondary cooling with a traversed by a cooling medium network of a continuous casting, which is adaptable to the respective casting task, in particular with regard to the steel grade and special tasks resulting during the casting process.

In the continuous casting of steel, the solidification is achieved by the primary cooling of the steel in the mold and the secondary cooling in the region of the strand guide. Within the strand guide water or a water-air mixture is injected under pressure in the area between the strand guide rollers remaining free areas directly on the strand shell; As a result, heat is removed from the strand.

Due to the large product range of new continuous casting plants, a large control range is needed in the secondary cooling, on the one hand to be able to cast LC steels quickly, with very large amounts of water are required, and on the other hand to direct the slab with peritectic steels and tubular steels in the directional range with sufficient temperature to be able to, with only very small amounts of water are set for cooling.

This task is solved by a dual-fluid cooling system with water-air spray nozzles, which have a large control range of about 1:14. By contrast, single-fluid nozzles working with water have a control range of only 1: 4 and are therefore only of limited suitability for many continuous casting plants because of the requirements described above.

CONFIRMATION COPY In addition, it is necessary to set a uniform over the width of the strand temperature so that, for. B. in the directional area, no cracks due to cold slab edges arise. This problem is solved by separately controlled spray zones, which cover different casting widths. In this case, a separate control loop is required for each width zone.

Currently, the secondary cooling is realized in continuous casting, that the actuators for the secondary cooling outside the segment are in the water distribution space. Through an electrically controlled valve, the amount of water can be set for a control loop. In this case, the current amount of water is determined for a control loop by means of a flow measurement within the controlled system. The amount of water set by the control loop is transferred to the segment by means of a water clamping plate of the segment and injected there via lines and nozzles onto the slab surface. Sealing elements on the clamping plate ensure that in the case of segment installation the coupling of the media is tight.

It should be noted that at least one transfer point in the water chuck plate is required per control loop. For large amounts of water u. U. also two transfer points are required. In a large number of control circuits, very complex water trays are sometimes required per segment.

An arrangement according to the prior art is shown in an example with reference to FIG. A strand guide in a system for casting a metal strand in a casting direction A has a plurality of segments 1 arranged one behind the other in the casting direction. Each segment 1 has two or more injection zones 2, 3, which are usually operated depending on the width of the strand to be cast. For example, for a narrow strand only nozzles 4 belonging to the spray zone 2 are used, while For a wide strand nozzles 5 of the spray zone 3 either alone or in conjunction with the nozzles 4 are used. The reference numeral 1a denotes the rollers of the strand guide segment. 1

For each zone 2, 3 there is a volumetric flow controller 11 or 12, by means of which, for each of the zones 2, 3, the volumetric flow is set in accordance with the desired cooling capacity. The volume flow controllers 11, 12 are each preceded by a pump 9, 10 for supplying the cooling medium, in particular the water, to the volume flow controllers and the zones. Although it is possible by means of a pressure gauge 3, 14 to determine the pressure in each of the control circuits 6, 7; However, this is not used for the control process. From the water distribution chamber 8 leading out lines of the control circuits 6, 7 are connected via a water clamping plate 15 with terminals 16, 17 to supply lines for the two zones 2, 3. The water tension plate 15 is the location of media transfer between the water distribution space 8 and the segment, d. H. per control loop leads a line from the water distribution chamber 8 to the water chuck 15. On the segment-side counterpart of the water chuck plate, the water is then fed to the spray nozzles. Sealing elements on the clamping plate 15 ensure that in segment installation, the coupling of the media is also tight.

This embodiment has segments that may be simple in terms of instrumentation and control devices, with only the nozzle bars and tubing being made on each segment, thereby minimizing the probability of failure. There is only a comparatively small number of actuators available, which in turn are easily accessible.

However, the disadvantages of this embodiment are that a plurality of pipelines with associated measuring and control organs is present in the water distribution space. Likewise, many pipelines are available for the different control circles on the segment required. The water and air transfer to the segment on the water plates is because of the large number of control loops consuming, since for each zone of a segment or a segment group a control loop in the water distribution space is required to adjust the total amount of water.

From EP 0 650 790 B1 a method for the thermal surface treatment of strands of fine-grained structural steel in a continuous casting machine is known, which is associated with a heating furnace for heating the strands of a hot batch to the elimination of compounds of aluminum, vanadium, niobium and and to eliminate or at least substantially reduce surface defects due to stress. The continuous casting machine used for this purpose has a mold, a secondary cooling chamber, an extraction and alignment unit and a cutting unit. The method used here comprises a first cooling step for strands within the secondary cooling chamber and a second cooling step for strands in front of the cutting unit. The method is characterized by surface quenching of the outer layer of the strands by means of a second cooling step achieved by intensive and concentrated cooling of the surface of the strands to control the surface temperature of the strands after the natural annealing caused by the hot core of the strands about 400 ° C and about 900 ° C, wherein this intensive and concentrated cooling is realized by spraying a water-based cooling fluid under pressure against the surface of the strands through a plurality of spray nozzles. The intensive and concentrated cooling depends on the dimensions of the strands and is applied immediately or immediately after the stripping and aligning step by the stripping and aligning unit.

From EP 1 550 523 A1 a method for the diversified regulation of the secondary cooling of a continuous casting plant is known, in which the secondary cooling tion to the current casting task with respect to the steel grade, the difficulties during the casting process, etc. is adjusted. In order to allow a flexible control that is more directly responsive to the cooling requirements of continuous casting, and to achieve a further improvement of the secondary cooling, the segments of the secondary cooling each have separate cooling circuits, which are controlled with an individual task-related setpoint specification.

It is the object of the invention to provide a flexibly usable device for secondary cooling.

According to the invention, this object is achieved in that the network comprises at least a first pressure network, in which the pressure of the cooling medium is used as a task size. The invention is based on the idea not to provide an amount of a cooling medium, but to provide a pressure, according to which then remove all consumers within the cooling system, the required amount of the cooling medium. Advantageously, devices for measuring the characteristic curves of nozzles assigned to the segments or segment groups can also be provided which, in the case of a fixed opening position of a valve, measure the flow through the control group assigned to the valve. It is possible to carry out wear measurements of the actuator groups and to update the characteristic curves according to the current wear. The same applies in the case of a clogging of the network.

Also proves to be advantageous, a device for cooling, provided in the per segment or segment group control over an associated controller or via a bus interface of a central control bus is. In the case of the controlled distribution per segment, it must be accepted that small errors can occur when adjusting the water quantities.

With a controlled distribution of the cooling medium per segment or per segment group, a constant pressure network is not necessary since the characteristic curves can be measured at any time. The prerequisite for this is that organs are provided for pressure measurement or flow measurement per segment or per segment group, ie per branch. The prerequisite here is that at full volume flow, there must be no large pressure drops in the pipeline to the valve.

In a constant pressure network, care must continue to be taken to ensure that valves equipped with a drive require only a small amount of space and are suitable for robust operation.

In an advantageous embodiment can be provided that a filled with the cooling medium buffer memory is provided as a volume memory, which is in pressure communication with the pressure network. As a result, the rigidity required for the constant pressure network can be achieved.

In addition, it is advantageous to use a second pressure network which serves as a network for generating a booster pressure in the cooling medium. As a result, a significantly higher pressure can be made available for special situations and a correspondingly higher cooling effect can be achieved.

It is also advantageous if several nozzles associated with a single valve can be individually calibrated as actuators. In order to be able to individually calibrate the "nozzle modules", ie a plurality of nozzles associated with a valve, as "actuators", it is proposed according to the invention to set up a measuring section via which, after their activation, the calibration of the characteristic curve of a Nozzle modules can be made. This can be done during maintenance or even in watering pauses. The advantage of this is that you can measure a nozzle module alone.

For example, it is provided that groups of nozzles, in particular nozzle rows, can be switched on and off by means of a valve assigned to them. Here, the valves set different, discrete amount of the cooling medium by switching. In one embodiment of the invention, it is sufficient to use valves which are only able to adjust various discrete quantities of the cooling medium by switching. The drive of the valves takes place for example via a stepper motor. Since one can set different values from segment to segment, overall good overall cooling can be achieved by setting various discrete values.

Preferably, the valves set different, discrete amounts of the cooling medium by switching, or the valves are controllable. Alternatively, the valves are designed as proportional valves, as stepped valves, as on / off valves or as volume flow control devices.

It is advantageously provided that the network comprises at least one volume flow regulator for adjusting the volume flow per control loop and that the coolant can be divided by means of setting members into a plurality of sub-circuits corresponding to pressure-volume flow characteristics.

Preferably, a pressure gauge measures the pressure, and the adjusting members, taking into account the pressure measured by the pressure gauge and the pressure-volume flow characteristic corresponding to the respective setting of the adjusting member, divide the coolant into the respective associated sub-circuit. Or the net includes pressure gauges for measuring the pressure Pressure gauges measured pressure values are then taken into account in the adjustment.

According to an advantageous embodiment of the invention, the network in the region of the distribution space on a single line, can be supplied via the pumped by a pump coolant to clamping plates of segments, wherein branches of the conduit in the region of the clamping plates and / or the segments are arranged.

The cooling system according to the invention can be realized both with one-component cooling (only water as coolant) and with two-component cooling (water and air as coolant).

In general terms, the invention relates to a device for controlled secondary cooling with a flowed through by a cooling medium network of a continuous casting plant, which is characterized in that a pump control loop or by a constant pressure network provides the necessary amount of the cooling medium and the quantitative distribution on the segments within the strand guide by valves with defined open positions (open, half open, etc.) or by proportional valves.

An inventive device for controlled secondary cooling is inventively advantageously characterized in that a pump control loop provides the necessary amount of the cooling medium is available and the quantitative distribution on the segments within the strand guide by valves with defined open positions (open, half open, etc.) or by proportional valves.

Preferably, in a device for controlled secondary cooling with a network through which a cooling medium flows, a continuous casting plant for distributing the cooling medium in the continuous casting plant and / or on a segment serving active actuators, in particular valves and / or regulators, on the segments.

The invention also relates to a method for regulated secondary cooling with a network of a continuous casting plant through which a cooling medium flows.

The method is inventively characterized in that the pressure of the cooling medium is regulated.

In a development of the method, it is provided that the pressure of the cooling medium is changed in a pulsating manner by switching the valves. In addition, valves can be used in various configurations. The valves are operated, for example, as on / off valves, as discrete or continuously switchable valves.

The pressure-volumetric flowcharts are calibrated at specific time intervals. However, the calibration preferably takes place outside of the casting operation in the continuous casting plant.

The invention will be explained in more detail in exemplary embodiments with reference to the figures. Show it:

FIG. 2 shows a schematic illustration of a segment of a strand guide in a continuous casting installation with devices for supplying a cooling liquid, wherein two adjustment elements are provided in the region of the segment, FIG.

3 pressure-volume flow characteristic curves for an open or only half-open setting member in a control group or measuring section within the strand guide of the casting plant, in particular within a spray zone of a segment, Fig. 4 shows an alternative embodiment for supplying a segment of the strand guide with cooling liquid, wherein within a segment three adjusting members are provided, and

Fig. 5 shows another embodiment for supplying a segment of

Strand guide with cooling liquid, wherein three volumetric flow controllers are arranged in the region of the segment and at the same time designed as setting members.

A first embodiment according to the invention (FIG. 2) provides that in a strand guide constructed as in the prior art in a system for casting a metal strand in a casting direction A, a plurality of segments 1 arranged one behind the other in the casting direction is provided , Each segment 1 has two or more spray zones 2, 3, which are operated depending on the width of the strand to be cast. As far as matches exist with the embodiments according to the prior art, the same reference numerals are used for this purpose as in Figure 1. Compared with the embodiment of the cooling device, the embodiment according to the invention differs according to FIG. 2 in that instead of two volumetric flow controllers 11, 12, only one volumetric flow regulator 19 is required in a coolant or water distribution chamber 8 and an upstream pump 18. Likewise, only a single connection 20 for supplying the coolant to the supply lines within the two zones 2, 3 within the segment 1 is also required in the area of the water clamping plate 8.

On the other hand, two adjusting members 21, 22 for distributing the coolant are arranged on the segment 1 of the two injection zones 2, 3 associated sub-circuits. The adjusting members 21, 22 are separately controllable or controllable or manually adjustable valves. For example, proportional valves, tap-change valves or valves which have only one open position and one closed position are suitable. In the case of the use of control valves, these receive their controlled variables from the control of the continuous casting plant. In any case, the pressure value of the coolant obtained in a pressure gauge 23 is taken into account.

Each of the two sub-circuits for the two zones 2, 3 has its own pressure-volume flow characteristic for the volume flow V, for example, measured in liters per minute, as a function of the refrigerant pressure p, for example, measured in bar, as shown in Fig. 3 , Wherein each opening state of the adjusting members 21, 22 has its own characteristic. This means that any change in the permeability of the coolant within the two SubKreisläufe is taken into account according to the invention. If this is reduced by gradual clogging of the conduits due to contaminants remaining in the tubes, or if the adjusters 21, 22 are no longer adjustable to the same extent as was the case with the new insert, then this circumstance flows into the mold the pressure-volume flow characteristic, which must be recalibrated at certain intervals.

If the pressure-volume flow characteristics for each of the segments 2, 3 are fixed after their calibration, using the volume flow controller 19 using the pressure obtained by the pressure gauge 23 can adjust a summed flow for both zones 2, 3, with the help of associated opening degree of the two adjusting members 21, 22 is decomposed into the required for the two zones 2, 3 partial flow rates or partial pressures.

Similar to the procedure explained with reference to FIGS. 2, 3, according to a further embodiment (FIG. 4), three setting members 24, 25 and 26 are provided on the segment, each one strand 27, 28, 29 within the conduit system for the supply of the two Zones 2, 3 are assigned. Incidentally, as shown in the embodiment shown in Fig. 2, the Volumetric flow for both zones 2, 3 determined in the volumetric flow controller 19 and divided into the required for the three strands 27, 28, 29 partial flow rates on the basis of the adjusting members 24, 25 and 26.

The alternatives illustrated in FIGS. 2 and 4 have in common that the volume flow per control loop is set, the pressure information in each case flowing into the coolant distribution. The coolant distribution is realized by the respective adjusting members, each subcircuit has its own characteristic, which depends on the position of the adjusting (open, half open, ... etc.). With known pressure or known characteristic ratio, the coolant distribution is fixed.

In the embodiment shown in Figure 5, the control elements are supplied on the segment of a constant current network, wherein the volume flow per control loop is set; in this case, the knowledge of the pressure information is irrelevant to the operation.

In the alternative (FIG. 5), instead of a single volumetric flow regulator 19 accommodated in the coolant distribution chamber 8, three individual volumetric flow regulators 36, 37, which are provided in the region of the segment 1 and serve directly as setting elements for regulating the coolant quantity in the strands 27, 28, 29 and 38 arranged one behind the other.

According to one embodiment of the invention, one control loop can be used per segment or per segment group in the water distribution space. In this case, it must be checked how many control loops are required in total. In a controlled distribution on a segment or a segment group, the total amount of water is adjusted via a control loop in the water distribution space. Subdivision on the segment or segments can be done that by means of actuators on the segment, the coolant, in particular the water is distributed to other control or regulating circuits. The quantities of water in the "water circuits" of the segment are no longer measured, but actuators, such as valves, are set to specific positions.

The actuators are set, for example, with stepper motors to predetermined positions. This will set a desired flow. Since all segments are independently adjustable, it is sufficient to provide few discrete setting options (for example four positions: off, low, medium, high). In extreme cases, such valves can be used as switching elements, which only have an open and a closed position.

LIST OF REFERENCE NUMBERS

segment

segmented rollers

splash zone

jet

Pump loop

Water distribution space

pump

Volume flow controller

pressure gauge

Water chipboard

connections

pump

Volume flow controller

connection

setting mechanism

pressure gauge

setting mechanism

strand 28 strand

29 strand

36 volumetric flow controller

37 volumetric flow controller

38 volumetric flow controller

42 line

43 line

44 line

A casting direction

Claims

claims

1. A device for controlled secondary cooling with a flowed through by a cooling medium network of a continuous casting, which is adaptable to the particular casting task, in particular with regard to the steel grade and special tasks resulting during the casting process, characterized in that

that the network comprises at least a first pressure network, in which the pressure of the cooling medium is used as a task size.

2. Apparatus according to claim 1,

characterized,

in that devices for pressure-volume-flow characteristic curves are provided for nozzles assigned to the segments (1) or segment groups (2, 3), which at a fixed opening position of a valve (21, 22; 24, 25, 26; 36, 37, 38 ), the flow through the valve associated with the control group (2, 3) measure.

3. Device according to one of claims 1 to 2,

characterized,

at least one central element is provided for measuring pressure and volumetric flow for determining characteristic curves.

4. Device according to one of claims 1 to 3,

characterized,

in that organs are provided for pressure and volume flow measurement per segment (1) or per segment group (2, 3).

5. Device according to one of claims 1 to 4,

characterized, that a filled with the cooling medium buffer memory is provided, which is in pressure communication with the pressure network.

Device according to one of claims 1 to 5,

characterized,

the network comprises a second pressure network serving as a network for generating a booster pressure in the cooling medium.

Device according to one of claims 1 to 6,

characterized,

that each spray group consisting of a single valve (21, 22; 24, 25, 26; 36, 37, 38) and the associated nozzles can be individually calibrated.

Device according to one of claims 1 to 7,

characterized,

in that groups of nozzles, in particular nozzle rows, can be switched on and off longitudinally or transversely to the casting direction by means of a valve (21, 22; 24, 25, 26; 36, 37, 38) assigned to them.

9. Apparatus according to claim 1-7,

characterized,

that groups of nozzles, in particular rows of nozzles, along or transversely to the casting direction by means of a valve (21, 22, 24, 25, 26, 36, 37, 38) assigned to them, set different, discrete quantities of the cooling medium by switching or the valves ( 21, 22, 24, 25, 26, 36, 37, 38) are controllable or controllable, in that the valves (21, 22, 24, 25, 26, 36, 37, 38) are proportional valves, step valves, uprights. / To valves or are designed as flow control devices.

Device according to claims 1-9, characterized,

in that at least one pressure gauge (23) measures the pressure and the setting members allocate the coolant to the respectively assigned sub-circuit in accordance with the pressure-volume flow characteristic.

11. The device according to claim 10,

characterized,

in that the network is designed as a constant pressure network and that the setting members allocate the coolant to the respectively assigned subcircuit, taking into account the pressure / volumetric flow characteristic corresponding to the respective setting of the adjusting member.

12. Device according to one of claims 1 to 11,

characterized,

the network in the region of the distribution space (8) has a single line, via which coolant conveyed by a pump (18) can be supplied to clamping plates (15) of segments (1) and branching of the line in the region of the clamping plates (15 ) and / or on the segments (1) are arranged.

13. Apparatus for controlled secondary cooling with a network of a continuous casting plant through which a cooling medium flows,

characterized,

that active actuators, in particular valves and / or regulators, are located on the segments for distributing the cooling medium in the continuous casting plant and / or on a segment.

14. A device for controlled secondary cooling with a traversed by a cooling medium network of a continuous casting plant, characterized according to claim 13, characterized

that a pump control loop or a constant pressure network the amount of Cooling medium, in particular the amount of water holds, and the quantitative distribution on the segments of the strand guide in or across the casting direction is made by volume flow regulator, which are located on the segments.

15. A device for regulated secondary cooling with a traversed by a cooling medium network of a continuous casting plant, characterized according to claim 13, characterized

that a pump control loop or a constant pressure network provides the required amount of the cooling medium regulated and the quantitative distribution on the segments of the strand guide by valves with defined open positions (open, half open, etc.) or by proportional valves.

Method using the devices 1-15 for controlled secondary cooling with a network of a continuous casting plant through which a cooling medium flows,

characterized,

that the pressure of the cooling medium is regulated.

Method according to claim 16,

characterized,

in that the pressure of the cooling medium is changed in a pulsating manner by switching the valves (21, 22, 24, 25, 26, 36, 37, 38).

Method according to claim 17,

characterized,

the valves (21, 22, 24, 25, 26, 36, 37, 38) are operated either as on / off valves, as discrete valves or as continuously switchable valves. 19. The method according to any one of claims 16 to 18, characterized,

in that the pressure-volume flow characteristics are calibrated at specific time intervals or when predetermined conditions occur, in particular outside the casting operation in the continuous casting plant.