WO2009115174A1 - Strand guiding device and method for the operation thereof - Google Patents

Abstract

The invention relates to a strand guiding device for guiding a strand after departing a die in a continuous casting system. The strand guiding device 100 comprises at least one strand guiding element 110, such as in the form of a segment roller, and at least one hydraulic cylinder 120 for contacting the strand guiding element. The invention further relates to a control device 130 connected upstream of a directional valve 140 for actuating the hydraulic cylinder 120. In order to be able to use such a strand guiding device 100 for a plurality of applications, according to the invention, the control device is designed for controlling the actual contact force of the hydraulic cylinder and the strand guiding element against the strand 200, wherein the actual contact force is regulated to a prescribed target contact force.

Description

 Strand guiding device and method for its operation

The present invention relates to a strand guiding device for guiding a strand in the form of thick slabs, slabs, thin slabs, blocks or Vorprofilen carbon steel, stainless steel or stainless steel from a mold in a continuous casting.

Strand guide devices of the type mentioned are basically known in the art, for. Example from the European patent EP 0 902 734 B1 or the German patent application DE 10 2005 051 051 A1. Both documents disclose a strand guiding device for guiding a steel strand after leaving a mold in a continuous casting plant. The strand guiding devices each comprise a strand guiding element, at least one hydraulic cylinder for adjusting the strand guiding element, a regulating device and a valve device for actuating the hydraulic cylinder in response to control signals of the regulating device. In both cases, the control device is used to carry out a position control of the hydraulic cylinder or the strand guiding element coupled thereto.

Based on this prior art, the invention has the object, a known strand guiding device and in particular a control device contained therein and a method for operating the strand guiding device to the effect that they are suitable for a plurality of alternative uses.

This object is solved in terms of apparatus by the subject matter of patent claim 1. Accordingly, the strand guiding device is characterized in that its regulating device is designed to control the Course of the actual Anstellkraft of the hydraulic cylinder and the strand guide element against the strand to a predetermined course of the desired Anstellkraft.

As already mentioned in the introduction, the term "strand" in the present description represents thick slabs, slabs, thin slabs, blocks, billets or pre-profiles, the latter in the form of Beam Blank BBL formats, these are, for example, precursors for double-T beams , or in the form of round profile formats The strand can be made of carbon steel, stainless steel or stainless steel.

The present invention is limited to the use of directional control valves as actuators between the control device and the hydraulic cylinder; Other types of valves are expressly not used in the present invention.

The claimed force control in conjunction with the directional control valve device allows a plurality of applications generally in the metallurgical industry, such. B. to promote the strand or the cold strand, to carry out a soft reduction or to detect the position of the sump tip within the cooling strand.

The claimed combination of force control and directional valves, especially when the latter are connected in the form of a bridge circuit, allows the control of a resultant piston force (double-sided cylinder chamber pressure control, all 4 individual valves are used here), or optionally the control of a single cylinder chamber force (or chamber pressure without Consideration of existing counteracting 2'ts cylinder chamber force).

This circuit variation thus allows a targeted hydraulic loading of the cylinder chambers (pressure or force) z. B. in case of failure, in case of security, or in case of failure of the required pressure sensors. A targeted / positive Cherte setting a cylinder chamber effect or a cylinder acting direction is thus made possible.

Directional control valves have the advantage that they are more robust than control valves; In particular, the quality of the oil or the purity of the oil may be worse than with control valves. Furthermore, directional valves allow the setting of a controlled and fixed control function, eg. As the setting of a locking position without electrical / mechanical tension or setting a defined pressure-force situation on the hydraulic cylinder when driving the individual directional control valves when they are connected in a bridge circuit. Furthermore, the directional valves are characterized by easy maintenance and servicing, in particular, no specially trained personnel is required. Finally, directional control valves are cheaper than control valves.

The claimed force control offers the advantage that - except for special applications, such. B. for detecting the position of the sump tip - basically no position sensor are required. When using the claimed force control to detect the position of the sump tip rollers and bearings are protected due to the respective predetermined force-target value from overloading. Nevertheless, contact between the rollers and the line is possible with regard to control (minimum force control). The minimum force control ensures that - always with a guaranteed cooling - always a rotating role is present, which has contact with the surface of the strand, so that a strand guide is continuous.

Definition: Softeruction means a compression of the strand by only a small thickness reduction, eg. For example, by 1 to 2 mm in order to improve the quality of his structure by z. B. segregations can be prevented. Softer reduction is preferably carried out in the region of residual solidification, that is to say in the range from 30% to 100% of the sump length. According to a preferred embodiment, the strand guide element is formed as an employee driven or non-driven single role. In the case of slab plants, the single roll is positioned within a segment by means of separately placed trusses, while the individual rolls are employed directly in block plants. In the latter case, the individual roles are individual drivers or straightening units. There are a number of possible applications for the individual rollers in the abovementioned systems, which are briefly outlined below without any claim to completeness:

The force-controlled single roles can z. B. are used for a cold strand transport at a defined setting of a preferably constant force setpoint. For a hot strand transport, the force setpoint is preferably specified variably as a function of the format width. In block plants, billet plants or pre-products, the claimed force control is suitable for performing soft-reduction and for setting the corrective force. In this case, the desired forces are also set variable, in these cases, however, process-dependent. To detect the position of the sump tip of the force-soli value is given in the form of a jump function as described in one of the independent method claims. Finally, the claimed force-controlled single roles are also suitable for the Ausfördem a strand; while a maximum force is set.

In addition to the individual roles just mentioned, the strand guiding elements may also be segmental upper or lower frames each having a plurality of rollers. When applying the claimed force control these segment frames are generally employed against spacers and adjusted in this way to a fixed position / mouth width (applies only to slab systems). The force control of the segment frame in slab plant advantageously allows the setting of various width-dependent hot strand set forces and the setting of Kaltstrangsollkräften. The force control according to the invention allows both the individual rollers described in the penultimate paragraph and the segment frame described in the last paragraph, an adjustment of the respective Anstellkräfte to the predetermined desired forces.

Advantageously, the strand guiding device comprises at least one pressure sensor for detecting the pressure in the chambers of the hydraulic cylinder. For this purpose, the pressure sensor can be arranged at any suitable location within the strand guide device; The pressure sensor is preferably arranged directly on the hydraulic cylinder, in the pressure lines between the directional control valve device and the hydraulic cylinder, or directly on the directional control valve device. In addition to the pressure sensor, the strand guiding device advantageously also comprises a conversion device for converting the detected pressure difference in the chambers of the hydraulic cylinder into an actual application force against the strand taking into account relevant effective surfaces for the pressure in the hydraulic cylinder.

The control device is advantageously designed in the form of a three-step controller, a higher-level controller or a controller with pulse width modulation.

Advantageously, the directional control valve device comprises at least four directional valves, which are connected in the form of a bridge circuit, wherein the bridge circuit is connected between a source and a sink for the hydraulic fluid for operating the hydraulic cylinder on its input side and the hydraulic raulikzylinder on its output side. For shading in the bridge circuit standard directional control valves can be used, so that the bridge circuit can be constructed in a modular manner. The bridge circuit advantageously allows one-sided pressurization of the piston in the hydraulic cylinder and thus a higher functionality. Finally, the bridge circuit allows the setting of a defined pressure / force situation on the hydraulic cylinder. Technically, the above object is achieved by the method claimed in claim 7. The advantages of this method according to the advantages mentioned above with reference to the strand guiding device.

According to a first application, the strand guiding device and the method for its operation for conveying the strand or the cold strand from the mold is used. It is advantageous if the predetermined course of the desired setting force with which the strand guide element is to press against the strand during a predetermined period of time, preferably during the entire period of strand guiding, is constant over time.

According to a second application, the claimed Strandführungs- device and the claimed method for their operation for the detection of the current position of the bottom tip of the strand can be used. For this purpose, the claimed strand guiding device is operated as follows:

a) Specifying a jump function for the course of the target contact force for a first strand guide element, preferably a driven roller or non-driven employee single role in slab plants, the desired force jumps from a first predetermined higher value to a subsequently reduced value;

b) observing an adjusting position of the hydraulic cylinder on the first strand guide element as a result of the reduced contact force; and

c) repeating steps a) and b) on at least one second strand guiding element along the strand guide; and d) locating the sump tip of the strand between the first and the second strand guide element, when set in the application of the two steps a) and b) in the two strand guide elements, the hydraulic cylinders at each same discontinued jump function to different positions.

The described method for detecting the position of the sump tip can be part of a force-controlled soft-reduction.

Finally, the above object is achieved by three use claims, each directed to one of the above uses, conveying the strand, performing a soft-reduction and deduction of the position of the sump tip.

The description is a total of two figures attached, wherein

FIG. 1 shows a strand guiding device according to the invention; and

2 shows an embodiment of a directional control valve device in the form of a bridge circuit

shows.

The strand guiding device according to the invention will be described in detail below with reference to the figures. In both figures, the same technical features are designated by the same reference numerals.

It can be seen in FIG. 1 that the strand guiding device 100 has a hydraulic cylinder 120 with a piston 122 adjustably mounted therein. The piston acts via a piston rod 124 and a strand guide The piston 122 divides the hydraulic cylinder 120 into a cylinder space 126 and an annular cylinder space 128. The pressure inside the cylinder space 126 is measured by means of a first pressure sensor 150-1, while the pressure in the annular cylinder space 128 by means of a second pressure sensor 150-2 is measured. The pressure values determined by the first and second pressure sensors are compared within a control device 130 and converted by means of a conversion device 132 into a value for the resulting force with which the strand guide element 110 presses on the strand 200. The conversion device 132 carries out this conversion, taking into account relevant effective areas for the pressure, in particular in the interior of the hydraulic cylinder.

The actual application force determined in this way by the conversion device 132 is subsequently compared with a predetermined desired application force in order to obtain a control deviation e for the adjustment force in this way. In accordance with the determined control deviation e, the control device 130 then calculates suitable control signals for a directional control valve device 140, in which FIG. 1 comprises only one directional control valve. The directional control valve can be switched into three different states: "0", "1" and "2" with the aid of the control device 130. The switching position "0" represents the so-called blocking position as shown in FIG. In the blocking position, the existing pressure lines 160-1, 160-2 to the hydraulic cylinder 120 and the pressure lines to the source Q and the sink S are each separated and locked. In contrast, the switching positions "1" and "2" each represent a passage position. More precisely, the switching position "1" causes a movement of the piston 122 and thus of the strand guide element 110 in Figure 1 to the left, that is away from the strand 200. The applied force on the strand is therefore in the switching position "1" less. In contrast, the switching position "2" causes a movement of the piston to the right, that is to say in the direction of the strand 200. The setting force is correspondingly increased. As an alternative to the one-way valve used in FIG. 1, FIG. 2 shows a bridge circuit of four-way valves 140'-1,... -4 as directional control valve device for controlling the hydraulic cylinder 120.

Finally, it should again be pointed out that the control device described above with reference to FIG. 1 regulates the actual measured contact force currently measured to the predefined setpoint application force. This force control in combination with the downstream directional control valve device 140 is particularly well suited for a plurality of different applications, especially for conveying a strand or cold strand from a mold, for performing soft-reduction or for detecting the position of the sump tip of a not completely solidified strand.

Claims

claims A strand guiding device (100) for guiding a strand (200), in particular a steel strand, after leaving a mold in a continuous casting plant, comprising: at least one strand guiding element (110); at least one hydraulic cylinder (120) for setting the strand guide element (110); a control device (130); and directional control valve means (140) for actuating the hydraulic cylinder (120) in response to signals from the control means; characterized in that the control device (130) is designed to control the course of the actual application force of the hydraulic cylinder (120) and the strand guide element (110) against the strand (200) to a predetermined course of the desired Anstellkraft. 2. strand guiding device (100) according to claim 1, characterized in that the strand guiding element (110) is formed as a driven Single roll, as a roll segment with a plurality of rolls or as a driven or non-driven single roll within a roll segment. 3. strand guide device (100) according to one of the preceding claims, characterized by at least one pressure sensor (150-1, 150-2) for detecting the pressure in the chambers of the hydraulic cylinder; and a conversion device (132) for converting this pressure or the pressure difference, taking into account relevant effective surfaces of the pressure in the actual application force. 4. strand guide device (100) according to claim 3, characterized in that the pressure sensor (150-1, 150-2) directly on the hydraulic cylinder, in the pressure lines (160-1, 160-2) between the directional control valve device (140) and the hydraulic cylinder (120) or is arranged directly on the directional control valve device. 5. strand guide device (100) according to one of the preceding claims, characterized in that the control device (130) in the form of a three-step controller, a higher-level controller or a controller with pulse width modulation is formed. 6. strand guide device (100) according to any one of the preceding claims, characterized in that the directional control valve device (140) has at least four-way valves, which in the form of a bridge circuit between a source (Q) and sink (S) for the hydraulic fluid and the hydraulic cylinder , (120) are interconnected. 7. A method for operating a strand guiding device (100) according to one of the preceding claims 1 to 6, characterized the course of the actual application force of the hydraulic cylinder (120) and of the associated strand guide element (110) against the strand (200) is regulated to a predetermined course of the desired application force. 8. The method according to claim 7, characterized in that the predetermined course of the target Anstellkraft for the strand guide element in the form of an employee driven or non-driven single role to promote a cold strand from the mold during a predetermined period of time is set constant, to promote a hot strand is variably set depending on the format width of the hot strand, for performing a soft- reduction or straightening force setting in block plants, billets and precursors process dependent variably specified to jump the detection of the position of the sump tip is set and to achieve a maximum Ausförderkraft to a maximum force becomes. 9. The method according to claim 7, characterized in that the predetermined course of the desired Anstellkraft for the strand guide element in the form of segment upper frame or segment subframe, if they are set in slabs over spacers to a fixed position or mouth width, a setting various width-dependent hot tensile forces or an adjustment of cold strand forces provides. 10. The method according to claim 7, characterized by comprising the following steps: a) predefinition of a step function for the profile of the desired setting force for a first strand guide element, wherein the setpoint force is transmitted from one next predetermined higher value to a subsequently reduced Value jumps; b) observing an adjusting position of the hydraulic cylinder (120) on the first strand guiding element due to the reduced stopping force; and c) repeating steps a) and b) on at least a second one Strand guide member (110) along the strand guide; and d) locating the sump tip of the strand (200) between the first and second strand guide elements (110) when, in the application of the two steps a) and b) in the two Strandführungsele- menten, the hydraulic cylinders in each case the same discontinued jump function to different Set positions. 11. Use of a strand guide device (100) according to any one of claims 1 to 6 for conveying the strand (200) in the form of a KaIt- strand or hot strand from the mold. 12. Use of a strand guide device (100) according to one of claims 1 to 6 for performing a soft reduction in the strand (200) or for straightening the strand. 13. Use of a strand guide device (100) according to one of claims 1 to 6 for detecting the position of the sump tip of the strand (200) within the strand guide.