Device for comparing the temperature profile of the strand of a continuous casting system

Abstract

The invention relates, on the one hand, to a strand guide unit for a continuous casting system for producing a strand, comprising strand guide rollers for guiding a strand on both sides and, on the other hand, to a continuous casting system. One object of the invention is to create a strand guide unit that produces a temperature distribution on the surface of the strand which is as uniform as possible during the continuous casting process. This influences the temperature distribution in the strand and improves the quality of the end product. The object is achieved in that the strand guide rollers of the strand guide unit each have at least three centre bearing points, wherein the at least two centre rolls each have the same length in the width direction. The two edge rolls of each strand guide roller have a difference in length to each other in the width direction that corresponds to half the length of a centre roll including half the width of a centre bearing point. Viewed in the casting direction, directly adjacent strand guide rollers are each mirrored around a plane that runs along half the total length of the strand guide rollers in the casting direction.

Description

[0001] Description

[0002] Title of the invention

[0003] Device for equalizing the temperature profile of the strand of a continuous casting plant

[0004] field of technology

[0005] The present invention is in the field of continuous casting technology and describes a strand guide unit for a continuous casting plant, or a continuous casting plant for casting steel to produce a strand in a continuous process.

[0006] On the one hand, the invention relates to a strand guide unit which has strand guide rollers which are arranged on both broad sides for guiding a strand on both sides, comprising roll bales arranged next to one another in the width direction, said roll bales being designed as edge bales or central bales.

[0007] For edge bales, a center bale is arranged on only one side. For center bales, additional roller bales are arranged on both sides.

[0008] At both ends of the roll bales, viewed in the width direction, there are bearing points which comprise edge bearing points and center bearing points, with the edge bearing points having an edge bale arranged on only one side and the center bearing points having roller bales arranged on both sides.

[0009] On the other hand, the invention relates to a continuous casting plant.

[0010] State of the art

[0011] In the continuous casting process of steel, the temperature profile of the strand downstream of the continuous casting machine plays a significant role in the quality of the end product. A locally uniform temperature profile of the strand is particularly important in ESP (Endless Strip Processing) plants. Here, endless steel strips are produced in a combined casting / rolling process. This means that the continuous casting machine is directly connected to the rolling mill. The temperature profile of the strand is therefore directly fed into the rolling process and has a significant influence on it. The requirement for strand temperature uniformity affects both the local profile of the strand's surface temperature in the width direction and the temperature distribution in the casting thickness direction.Due to the relatively rapid process from the liquid phase to the finished rolled product within a few minutes, the development of irregularities in the temperature profile of the cast product must be avoided as much as possible. Irregularities in the temperature profile of the cast product can only be inadequately corrected according to the current state of the art and thus lead to a deterioration in the quality of the rolled product.

[0012] After leaving the mold, heat is removed from the strand using several mechanisms. Spray cooling, also known as secondary cooling, removes heat from the strand using cooling water. The cooling water is applied to the strand through a large number of individual nozzles arranged in rows. The rows of nozzles are typically located between the strand guide rollers in the so-called roller gap. A row of nozzles consists of a certain number of individual nozzles that are arranged at equal distances from one another in the width direction. The cooling effect is based on convective heat transfer and is determined by many factors such as the spray distribution, the volume flow of the cooling water and the nozzle positions. According to the state of the art, spray nozzles are positioned offset from one row to the next by half a nozzle spacing in the width direction.However, this method cannot satisfactorily compensate for the non-uniformity of the local temperature distribution on the strand surface. Particularly at high casting speeds, where high cooling water flows are required, undesirable non-uniform strand temperature profiles occur. This is also referred to as streaking.

[0013] Another mechanism by which heat is removed from the strand is heat conduction from the strand to the strand guide. After leaving the mold, the strand is supported and guided by strand guide rollers. Due to the considerable support loads, these strand guide rollers are split and consist of several bales. These are supported in edge bearings and center bearings. Where center bearings are located, the contact between the strand and the strand guide roller is interrupted and thus also the heat conduction from the strand to the strand guide roller. However, cooling water can penetrate these areas (channeling) and thus affect the heat transfer. This is particularly true for high cooling water flows. Both of the effects described lead to uneven cooling of the strand.

[0014] Another mechanism that removes heat from the strand is thermal radiation from the strand to its surroundings. However, this heat transfer is not discussed in detail here. Summary of the Invention

[0015] One object of the invention is to create a strand guide unit for a continuous casting plant for producing a strand that creates the most uniform temperature distribution possible on the surface of the strand during the continuous casting process. This subsequently influences the temperature distribution within the strand and improves the quality of the final product.

[0016] According to one embodiment, the

[0017] Strand guide unit has strand guide rollers which are arranged on both broad sides for guiding a strand on both sides, comprising roll bales arranged next to one another in the width direction, wherein these roll bales are designed as edge bales or center bales.

[0018] For edge bales, a center bale is arranged on only one side. For center bales, additional roller bales are arranged on both sides.

[0019] At both ends of the roll bales, viewed in the width direction, there are bearing points which comprise edge bearing points and center bearing points, with the edge bearing points having an edge bale arranged on only one side and the center bearing points having roller bales arranged on both sides.

[0020] Each strand guide roller has at least three center bearing points, with at least two center rolls each having the same length in the width direction. The center bearing points each have the same width in the width direction. The center bearing point is the area located between individual roll rolls in the width direction. This is the area where the strand guide rollers are interrupted in the width direction and where, therefore, the cast strand is not supported.

[0021] The two edge rolls of each strand guide roller have a widthwise length difference corresponding to half the length of a center roll, including half the width of a center bearing point. Directly adjacent strand guide rollers, viewed in the casting direction, are each mirrored around a plane that runs along half the total length of the strand guide rollers in the casting direction.

[0022] The temperature distribution on the strand surface is significantly influenced by the cooling of the strand. This results from the heat transfer from the strand to its surroundings by convection, conduction, and radiation. Radiation is determined by temperature distributions, emission factors, and visibility factors. Heat transfer by convection occurs primarily through cooling water applied to the strand. Heat transfer by conduction from the strand to the strand guide rollers is determined by the bales and bearing points, which thus influence the temperature distribution of the strand. The described arrangement of the bearing points and bales leads to a recurring pattern and, viewed across the strand, contributes to the homogenization of heat transfer by conduction from the strand to the strand guide rollers. Furthermore, no more than three different bale lengths are required.

[0023] The problem is further solved by a strand guide unit in which all center rolls are of the same length and the center bearing points immediately following the center roll in the casting direction are each arranged centrally in relation to these center rolls in the width direction. The arrangement of the bearing points and rolls results in a recurring pattern and, viewed in the width direction, contributes to the homogenization of heat transfer via thermal conduction from the strand to the strand guide rollers. In this design, the number of center bearing points differs for successive strand guide rollers viewed in the casting direction. However, no more than three different roll lengths are required.

[0024] In an advantageous embodiment, each strand guide unit comprises roll bales with three different lengths and each strand guide roller comprises roll bales with two different lengths.

[0025] In a further advantageous embodiment, the invention comprises a nozzle arrangement comprising rows of nozzles, which in turn comprise individual nozzles. Heat transfer by convection occurs primarily through cooling water applied to the strand.

[0026] The nozzles are arranged at the same distance next to each other in the width direction, preferably in a gap between successive strand guide rollers seen in the casting direction. Rows of nozzles following one another in the casting direction and separated by strand guide rollers are laterally offset in the width direction with respect to the previous row of nozzles by between one seventh and one third of a nozzle spacing. If this lateral offset always occurs in the same direction, this would result in an increasingly greater displacement of nozzles towards one side of the strand in the width direction, thus leading to uneven cooling of the strand. This can be counteracted by the lateral offset returning to that of a previous row of nozzles after a certain number of rows of nozzles. Alternatively, the lateral offset can also occur in the opposite direction after a certain number of rows of nozzles.

[0027] This described arrangement of the nozzles leads to a blurring of the cooling water impact positions and, viewed across the strand, contributes to the homogenization of the convective heat transfer from the strand to the cooling water. The lateral offset of the rows of nozzles, viewed across the strand, leads to a continued shift in the impact point of the spray water on the strand, which moves in the casting direction through the strand guide unit. This results in a blurring of the local distribution of convective heat transfer at the strand surface and contributes to the homogenization of the strand's surface temperature.

[0028] In a further advantageous embodiment, the lateral positions of the individual nozzles in a nozzle row of a strand guide unit are repeated after every three to seven nozzle rows, viewed in the casting direction. This type of lateral nozzle offset (in the width direction) leads to a blurring of the local distribution of the convective heat transport on the strand surface. The smaller the lateral offset, viewed in the width direction, by a constant amount, of the successive nozzle rows in the casting direction, the more even the heat transport takes place and thus leads to a more uniform temperature distribution in the cast product or on its surface. Due to the repetition of the lateral positions of the individual nozzles in the nozzle rows, the number of different lateral positions is limited.

[0029] In a further advantageous embodiment, the edge bales and center bales of at least two, preferably of at least four strand guide rollers of the strand guide unit have grooves substantially in the circumferential direction in those lateral length sections where, viewed in the casting direction, the immediately adjacent strand guide rollers have no center bearing point.

[0030] Wherever there are central bearing points, the contact between the strand and the strand guide roller is interrupted and with it the heat conduction from the strand to the strand guide roller. To compensate for this effect, the edge balls and center balls have grooves in those lateral length sections (in the width direction) where, viewed in the casting direction, the immediately adjacent strand guide rollers do not have a central bearing point. Where there are no central bearing points, the heat transfer takes place due to the roller contact. The grooves in the edge balls and center balls reduce the contact area between the strand and the strand guide and thus reduce the heat transfer at this point. If the edge balls and center balls have grooves in the lateral sections where, viewed in or against the casting direction, there are no central bearing points on the immediately adjacent strand guide rollers, this can have a more or less negative impact.This partially offsets the reduction in heat transfer. This leads to a more uniform temperature distribution in the cast product or on its surface.

[0031] In a further advantageous embodiment, the grooves of the strand guide rollers of the strand guide unit are embodied in the circumferential direction. The grooves of any two strand guide rollers arranged one after the other in the casting direction are offset from one another in the width direction. At the points where grooves are present, there is no contact between the strand and the strand guide roller, and accordingly no direct heat conduction takes place. As a result, without the lateral offset described, what is known as stripe formation can occur. Stripes of different temperatures therefore form on the strand along the casting direction. The lateral offset (in the width direction) of the grooves of edge balls and center balls arranged one after the other, viewed in or against the casting direction, leads to a smearing of the local distribution of heat transfer on the strand surface. The lateral offset of the grooves of the edge balls and center balls arranged one after the other in the casting direction.The described striping is avoided or reduced in the middle bale.

[0032] In a further advantageous embodiment, the grooves of the strand guide rollers of the strand guide unit are designed in a spiral shape in the form of a helical line. At the points where grooves are present, there is no contact between the strand and the strand guide roller, and accordingly, no direct heat conduction occurs. The spiral design of the grooves results in a continuous lateral migration of the areas of the edge and center rolls with direct contact with the strand (in the width direction). This, in turn, can lead to so-called stripe formation. However, the stripes are not parallel to the casting direction, but rather inclined laterally (in the width direction) according to the pitch of the helical line of the grooves.Since every point on the strand surface repeatedly comes into contact with edge balls and center balls with spiral grooves as it passes through the strand guide, the local distribution of heat transfer at the strand surface is randomly smeared. Due to the significant number of consecutive edge balls and center balls with spiral grooves, the described streaking is avoided or reduced.

[0033] Short description of the drawings

[0034] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of an embodiment, which is explained in more detail in connection with the drawings.

[0035] Fig. 1 is a schematic representation of three strand guide rollers arranged one behind the other in the casting direction, consisting of edge rolls, center rolls, edge bearing points and center bearing points, as an exemplary embodiment of a part of a strand guide unit,

[0036] Fig. 2 is a schematic representation of three strand guide rollers arranged one behind the other in the casting direction, consisting of edge rolls, center rolls, edge bearing points and center bearing points, as an exemplary embodiment of a part of a strand guide unit, Fig. 3 is a schematic representation of three strand guide rollers and four nozzle rows arranged one behind the other in the casting direction, as an exemplary embodiment of a part of a strand guide unit,

[0037] Fig. 4 and Fig. 5 are schematic representations of three strand guide rollers arranged one behind the other in the casting direction, consisting of edge rolls, center rolls, edge bearing points and center bearing points, as exemplary embodiments of a part of a strand guide unit and

[0038] Fig. 6 is a side view of a strand guide unit for a continuous casting plant for producing a strand, comprising five strand guide rollers each, which are arranged on both broad sides for guiding a strand on both sides, and rows of nozzles, comprising individual nozzles, which are preferably arranged in a gap between adjacent strand guide rollers.

[0039] Description of the embodiments

[0040] Fig. 1 shows a representation of the basic arrangement of three strand guide rollers of a strand guide unit for guiding a strand. Each strand guide roller comprises several roll bales arranged side by side in the width direction 7, which are designed as edge bales 2 and center bales 3. Bearing points adjoin both ends of the roll bales, which comprise edge bearing points 1 and center bearing points 4. The strand guide rollers shown each have three center bearing points 4, with the center bales 3 each having the same length. The two edge bales 2 of each strand guide roller have a length difference x from each other, which corresponds to half the length of a center bale 3, including half the width of an adjacent bearing point 4. The following therefore applies:

[0041] 1 bx = - + -

[0042] 2 2

[0043] The bale arrangement of immediately adjacent strand guide rollers, seen in the casting direction 8, is mirrored around the symmetry plane 9 of the strand, which runs in the casting direction along half the total length of the strand guide rollers.

[0044] Fig. 2 shows a further illustration of the basic arrangement of three strand guide rollers of a strand guide unit for guiding a strand. Each strand guide roller comprises several roller bales arranged next to one another in the width direction 7, with these roller bales being designed as edge bales 2 or center bales 3. In the edge bales 2, a center bale is arranged on only one side, and in the at least one center bale 3, additional roller bales are arranged on both sides. Bearing points are located at both ends of the roller bales, which comprise edge bearing points 1 and center bearing points 4.

[0045] All center bales 3 have the same length and the center bearing points 4 immediately following the center bales in the casting direction 8 are each arranged centrally with respect to these center bales in the width direction 7.

[0046] Fig. 3 shows a representation of the basic arrangement of 3 strand guide rollers of a strand guide unit for guiding a strand as well as nozzle rows 6 comprising individual nozzles 5.

[0047] The individual nozzles 5 are arranged at equal spacings next to each other in the width direction 7. The nozzle rows 6 are preferably arranged in a gap between adjacent strand guide rollers.

[0048] The nozzle rows 6, which follow one another in the casting direction 8 and are separated by strand guide rollers, are laterally offset in the width direction 7 relative to the preceding nozzle row 6 by one-third of a nozzle spacing in the width direction 7. The last nozzle row, viewed in the casting direction, occupies the same position as the first nozzle row, viewed in the casting direction. This results in a recurring pattern that repeats after every three consecutive nozzle rows.

[0049] Fig. 4 and Fig. 5 show a representation of the basic arrangement of three strand guide rollers of a strand guide unit for guiding a strand, wherein the edge bales 2 and center bales 3 of at least two strand guide rollers have grooves 10 essentially in the circumferential direction in those areas, viewed in the width direction, where, viewed in the casting direction 8, the immediately adjacent strand guide rollers do not have a center bearing point 4. The areas of the grooves of the last strand guide roller shown in Fig. 4 and Fig. 5, viewed in the casting direction, can depend on a subsequent strand guide roller (not shown). However, it is not absolutely necessary for this strand guide roller to have grooves.

[0050] Fig. 6 shows a side view of a strand guide unit for a continuous casting plant for producing a strand 12, comprising five strand guide rollers 11 each, which are arranged on both broad sides 13a and 13b for guiding the strand on both sides. The nozzle rows, comprising individual nozzles 5, are preferably arranged in a gap between adjacent strand guide rollers 11.

[0051] Although the invention has been illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0052] List of reference symbols

[0053] 1 peripheral storage location

[0054] 2 edge balls

[0055] 3 middle balls

[0056] 4 center bearing point

[0057] 5 single nozzles

[0058] 6 nozzle rows

[0059] 7 Latitude direction

[0060] 8 Pouring direction

[0061] 9 plane of symmetry

[0062] 10 grooves

[0063] 11 Strand guide roller

[0064] 12 Strand 13a First broadside

[0065] 13b Second broad side x half the length of a middle bale + half the width of a storage area I Length of a middle bale b Width of a storage area

Claims

Claims 1. Strand guide unit for a continuous casting plant for producing a strand, comprising at least three, preferably at least five, strand guide rollers (11) each, which have a total length (L) in a width direction (7), which are arranged on both broad sides (13a, 13b) for bilateral guidance of a strand, comprising roll bales arranged next to one another in the width direction (7), these roll bales being designed as edge bales (2) or center bales (3), wherein a center bale is arranged on only one side of the edge bales (2), and further roll bales are arranged on both sides of the center bales (3), with bearing points adjoining both ends of the roll bales, which comprise edge bearing points (1) and center bearing points (4), wherein a roller bale is arranged on only one side of the edge bearing points (1), and roller bales are arranged on both sides of the center bearing points (4),characterized in that each strand guide roller has at least three central bearing points (4), wherein the at least two central bales (3) each have the same length in the width direction (7) and the central bearing points each have the same width in the width direction (7), and the two edge bales (2) of each strand guide roller have a length difference (x) with respect to one another in the width direction (7), which corresponds to half the length (l) of a central bale (3) including half the width (b) of a central bearing point, and directly adjacent strand guide rollers (11) viewed in the casting direction (8) are each mirrored about a plane (9) which runs along half the total length of the strand guide rollers in the casting direction.

2. Strand guide unit for a continuous casting plant for producing a strand, comprising at least three, preferably at least five strand guide rollers (11) each, which have a total length (L) in a width direction (7), which are arranged on both broad sides (13a, 13b) for guiding a strand on both sides, comprising roll barrels arranged next to one another in the width direction (7), wherein these roll bales are designed as edge bales (2) or center bales (3), wherein in the case of the edge bales (2) a center bale is arranged on only one side, and in the case of at least one center bale (3) further roll bales are arranged on both sides, with bearing points adjoining both ends of the roll bales, which comprise edge bearing points (1) and center bearing points (4), wherein in the case of the edge bearing points (1) a roll bale is arranged on only one side, and in the case of the center bearing points (4) roll bales are arranged on both sides, characterized in that all center bales (3) have the same length in the width direction (7) and the center bearing points (4) immediately following the center bales in the casting direction (8) are each arranged centrally in relation to these center bales in the width direction (7).

3. Strand guide unit according to claim 2, wherein each strand guide unit comprises roll bales of three different lengths and each strand guide roller comprises roll bales of two different lengths.

4. Strand guide unit according to one of claims 1 - 3, comprising a nozzle arrangement, wherein this nozzle arrangement comprises rows of nozzles (6), wherein each row of nozzles (6) comprises individual nozzles (5) which are arranged next to one another at the same distance in the width direction (7), wherein the rows of nozzles (6) are preferably arranged in a gap between successive strand guide rollers as seen in the casting direction (8), wherein, as seen in the casting direction (8), successive rows of nozzles (6) separated by strand guide rollers in the width direction (7) are each offset with respect to the preceding row of nozzles (6) between one seventh and one third of a nozzle spacing in the width direction (7) or occupy the same position as a preceding row of nozzles as seen in the casting direction.

5. Strand guide unit according to one of claims 1-3, comprising a nozzle arrangement, wherein this nozzle arrangement comprises rows of nozzles (6), wherein each row of nozzles (6) comprises individual nozzles (5), wherein the rows of nozzles (6) are preferably arranged in a gap between successive strand guide rollers seen in the casting direction (8), wherein the positions of the respective individual nozzles, seen in the width direction (7), of successive rows of nozzles (6) separated by strand guide rollers, seen in the casting direction (8), are always offset by the same amount in such a way that they are repeated after every three to seven rows of nozzles, seen in the casting direction (8).

6. Strand guide unit according to claims 1 to 5, wherein the edge bales (2) and center bales (3) of at least two, preferably of at least four strand guide rollers in those areas, seen in the width direction (7), have grooves (10) substantially in the circumferential direction, where, seen in the casting direction (8), the immediately adjacent strand guide rollers have no center bearing point (4).

7. Strand guide unit according to claim 6, wherein the grooves (10) of the strand guide rollers (11) are designed in the circumferential direction of the strand guide rollers, and the grooves (10) of strand guide rollers which are immediately consecutive in the casting direction (8) are offset from one another in the width direction (7).

8. Strand guide unit according to claim 6, wherein the grooves (10) are designed in the form of a helical line.

9. Continuous casting plant comprising at least one strand guide unit according to claims 1 to 8.

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