Method for producing a strand in a continuous casting plant, and continuous casting plant
The method automates descaling in continuous casting plants by controlling descaling intensity based on strand temperature and scale thickness, addressing inefficiencies in manual operation and reducing energy consumption and scale deposition.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SMS GROUP GMBH
- Filing Date
- 2026-01-13
- Publication Date
- 2026-07-23
AI Technical Summary
In conventional continuous casting plants, the thickness of scale on the strand is not always clearly visible, leading to inefficient descaling operations that either result in excessive scale deposition or unnecessary cooling, both of which affect the quality of the strand and increase energy consumption.
A method and system for automatically controlling the descaling process by determining the strand's temperature and scale thickness upstream of the descaler, using a plant control system to adjust the descaling intensity based on predetermined limits and hysteresis effects, and optimizing water application to ensure efficient scale removal without manual intervention.
The method ensures optimal descaling by minimizing manual operation, reducing energy consumption, and preventing scale deposition in downstream furnaces, thereby improving strand quality and operational efficiency.
Smart Images
Figure EP2026050683_23072026_PF_FP_ABST
Abstract
Description
[0001] Method for producing a strand in a continuous casting plant and continuous casting plant
[0002] The invention relates to a method for producing a strand in a continuous casting plant, in which the strand, after being deflected into a horizontal position, is freed from scale by means of a descaler, wherein the descaler is arranged in the conveying direction of the strand downstream of the supported strand guide (in particular downstream of an exit roller conveyor of the strand guide). The invention further relates to a continuous casting plant.
[0003] After the strand leaves the mold with a load-bearing shell during continuous casting, subsequent cooling and solidification take place in the secondary cooling zone. This is usually located in the strand guide area between the mold exit and the run-out roller conveyor.
[0004] In conventional continuous casting plants with a direct feed, a descaler is typically located in the shear area. In the descaler, high-pressure water is sprayed onto the strand to loosen the scale and flush it away along with any remaining casting powder. If scale remains on the strand's surface, it is detrimental that it deposits in the downstream furnace; this poses a risk of the scale chemically bonding with the furnace material.
[0005] However, continuous operation of the descaler is usually not necessary. Since applying water to the surface of the strand naturally also has a thermal effect, the aim is to activate the descaler only when required. This is managed by the operator of the continuous casting plant, who switches the descaler on and off as needed.
[0006] Page 1. The problem is that the existing scale thickness is not always clearly visible, so the operator of the continuous casting plant has to rely on experience when switching the descaler on and off. Alternatively, the operator can wait for a message from the downstream hot rolling mill indicating that the scale thickness is too great; in this case, the operator switches on the descaler.
[0007] Without sufficient descaling, excessive scale can reduce the quality of the strand and foul the furnace. However, with a very thin scale layer and the descaler running, the strand cools down unnecessarily, which has the disadvantage of requiring more energy for reheating in the subsequent furnace.
[0008] In light of the above facts, the invention is based on the objective of designing a generic method and computer program product, as well as a corresponding continuous casting plant, in such a way as to ensure optimal operation of the descaler. This should be achieved in particular automatically, i.e., without intervention by the operator of the continuous casting plant.
[0009] The solution to this problem by the invention is characterized by the method comprising the following steps:
[0010] a) Determination of the temperature of the strand in the conveying direction upstream of the descaler at a number of points along the conveying direction and across the strand thickness and / or strand width;
[0011] b) Determination of the thickness of the forming scale and / or individual scale phases on the strand surface above the conveying direction up to the descaler based on the determined temperature of the strand;
[0012] Page 2c) Influencing the intensity of the descaling process by means of a plant control system depending on the thickness of the scale formed and / or individual scale phases on the strand surface as determined at the location of the descaler.
[0013] The influence on the intensity of the descaling process according to step c) above can be an activation of the descaler as soon as the thickness of the formed scale and / or individual scale phases on the strand surface reaches or exceeds a predetermined first limit, and a deactivation of the descaler as soon as the thickness of the formed scale and / or individual scale phases on the strand surface reaches or falls below a predetermined second limit.
[0014] The first and second limit values can be the same. However, to create a hysteresis effect, a preferred embodiment of the invention provides that the first limit value is higher than the second; preferably, the first limit value is 5% higher than the second limit value. This avoids frequent switching on and off of the descaler.
[0015] The intensity of the descaling process according to step c) above can be influenced by changing the amount of water applied to the strand surface by the descaler. Alternatively or additionally, it is also possible that the intensity of the descaling process according to step c) above can be influenced by changing the pressure at which water is applied to the strand surface.
[0016] The intensity of the descaling process according to step c) above can be influenced depending on the total thickness of the scale that forms. Alternatively, it is also possible that the intensity of the descaling process according to step c) above can be influenced depending on
[0017] Page 3 of the thickness or the weight percentage of a single scale phase is determined. In the latter case, particular attention is paid to the scale phase being fayalite, as this scale phase is especially relevant.
[0018] The descaling of the strand can take place on the top of the strand and on the bottom of the strand, whereby the influence on the intensity of the descaling process according to step c) above is different on the top of the strand and on the bottom of the strand.
[0019] If the descaler is located on only one side of the strand (preferably only on the underside of the strand) or if it is only activated on one side, the strand cools down more on that side than on the side without descaling. To prevent uneven cooling of the strand and warping of the resulting slabs, a preferred embodiment of the invention incorporates the cooling effect of the descaler into the secondary cooling of the strand. For this purpose, for example, the amount of cooling water in the last cooling zone on the side with the activated descaler is reduced to such an extent that the surface temperatures of the top and bottom at the furnace inlet are as similar as possible, taking into account the current water volume and pressure of the descaler.
[0020] Thus, a corresponding further development of the invention provides that in the area of secondary cooling of the strand guide, the cooling of the side of the strand which is exposed to a higher intensity of the descaling process according to step c) above is reduced.
[0021] Since less cooling, as desired, results in higher temperatures, the scale thickness increases more on this side of the strand than on the other side. This leads to increased insulation and thus less heat radiation, causing the temperature to rise further. To calculate this recursively and thus reduce the cooling water...
[0022] To determine page 4, it may be provided that a separate fast calculation model (in addition to the always existing continuous casting model) is used, which performs a corresponding fast simulation calculation.
[0023] The determination of the temperature of the strand according to step a) above is preferably carried out computationally using an online model.
[0024] The determination of the thickness of the forming scale and / or individual scale phases according to step b) above is also preferably carried out computationally using an online model.
[0025] The determination of the thickness of the forming scale and / or individual scale phases according to step b) above can also be carried out by a measurement that takes place in the conveying direction in front of the descaler.
[0026] The continuous casting plant for the production of a strand, which includes a descaler arranged in the conveying direction of the strand behind the supported strand guide, is characterized according to the invention in that it has:
[0027] Means for determining the temperature of the strand in the conveying direction upstream of the descaler at a number of points along the conveying direction and across the strand thickness and / or strand width;
[0028] Means for determining the thickness of the forming scale and / or individual scale phases on the strand surface above the conveying direction up to the descaler;
[0029] A plant control system to influence the intensity of the descaling process depending on the conditions at the location of the descaler
[0030] Page 5 determines the thickness of the formed scale and / or individual scale phases on the strand surface.
[0031] The plant control system is preferably designed to influence the intensity of the descaling process by activating the descaler as soon as the thickness of the formed scale and / or individual scale phases on the strand surface reaches or exceeds a predetermined first limit, and by deactivating the descaler as soon as the thickness of the formed scale and / or individual scale phases on the strand surface reaches or falls below a predetermined second limit. The above applies with regard to the limit values.
[0032] The plant control system is preferably configured to influence the intensity of the descaling process by changing the amount of water applied to the strand surface in the descaler. It is also preferably configured to influence the intensity of the descaling process by changing the pressure at which water is applied to the strand surface. Furthermore, it is preferably configured to influence the intensity of the descaling process depending on the total thickness of the scale formed or depending on the thickness of a single scale phase, in particular the fayalite scale phase.
[0033] The system control preferably includes an online model for the computational determination of the temperature of the string.
[0034] Furthermore, the plant control system preferably includes an online model for the computational determination of the thickness of the forming scale and / or individual scale phases.
[0035] The invention also includes a computer program product according to claim 25.
[0036] Page 6. For determining the strand temperature at each position of the plant and as a function of both strand thickness and strand width, explicit reference is made to DE 10 2013 212 713 A1. Here, the current strand temperature is calculated using an online model. The thickness of the scale layer can be calculated as a function of the casting parameters using the strand temperature and the analysis of the material to be cast (see Figures 1a and 1b discussed below).
[0037] It can be taken into account that in the secondary cooling area, the scale is immediately removed and washed away by the cold, pressurized spray water. Therefore, the scale typically only begins to grow after water cooling. Changes in the direction of the strand during bending and straightening create stresses that can also lead to partial flaking of the scale. This is factored into the calculation of scale growth (see Figure 2 discussed below).
[0038] According to the invention, the scale thickness at the descaler position is compared with a material-dependent limit value. If the current scale thickness is less than the limit value, the descaler is switched off; if it is greater than the limit value, the descaler is switched on. However, switching on and off is not done manually by the operator of the continuous casting plant, but automatically by the plant control system.
[0039] If the calculated scale thickness is close to the specified limit, small changes in the process values would lead to different surface temperatures and thus to a different scale thickness. To avoid constantly switching the descaler on and off in this case, it switches off at a smaller scale thickness than when it switches on (see the hysteresis effect mentioned above).
[0040] Page 7 Instead of switching the descaler on and off, varying the water volume and / or water pressure during descaling is also advantageous, as explained above. This is particularly true when removing the fayalite scale phase. Over time, fayalite can penetrate the iron matrix and is then very difficult to remove using a water jet.
[0041] The descaler can apply water to both the top and bottom of the strand. The two sides of the strand (top and bottom) can also be controlled independently.
[0042] One particular embodiment provides that the descaler is only present on one side, preferably on the underside of the strand, since only there can the scale fall down and accumulate on the furnace rollers and damage them.
[0043] Since the scale on the top of the strand is not as damaging as on the underside, different threshold values can be specified for descaling the top and bottom, based on the change in descaling intensity described above. For example, the permissible scale layer thickness on the top of the strand can be 25% greater than on the underside. Accordingly, the descaler on the top of the strand would be activated later than the one on the underside.
[0044] The water nozzles of the descaler are preferably arranged so that the water does not hit the surface of the strand perpendicularly, but slightly obliquely against the conveying direction of the strand, for example at an angle of 5° to 25° to the normal direction of the strand surface.
[0045] The drawing shows exemplary embodiments of the invention. It shows:
[0046] Page 8, Fig. 1a shows the progression of the scale thickness forming (under isothermal conditions) over time for different temperatures of the produced strand.
[0047] Fig. 1b shows the progression of the forming scale thickness over time at T =
[0048] 1050°C (under isothermal conditions) for different carbon contents of the produced strand,
[0049] Fig. 2 shows the surface temperature T of the strand and the scale thickness d along the course of the continuous casting plant (distance E from the mold) and
[0050] Fig. 3 shows the surface temperature T of the strand and the scale thickness d along the course of the continuous casting plant (distance from the mold), showing different thickness components of the scale.
[0051] The method according to the invention is based on first determining the temperature of the strand in the conveying direction upstream of the descaler at a number of points along the conveying direction, wherein the temperature is relevant over the strand thickness and / or the strand width.
[0052] In this regard, particular reference is made to the above-mentioned DE 102013212 713 A1, which specifies how a calculation model can be used to determine the current strand temperature.
[0053] In principle, the temperature could also be determined by appropriate measurements.
[0054] The thickness of the forming scale or individual scale phases on the strand surface is then determined, specifically across or along the conveying direction until descaling. The basis for this is the determined
[0055] Page 9 Temperature, although it also depends on the material the strand is made of.
[0056] Reference is made to Figures 1a and 1b.
[0057] Figure 1a shows how the thickness d of the scale layer on the strand surface builds up over time, depending on the strand's surface temperature. The surface temperature increases in the direction of the arrow shown.
[0058] Figure 1b similarly illustrates the growth of the scale layer, i.e., the thickness d, at a temperature of 1050 °C, for different carbon contents of the strand material. The carbon content increases in the direction of the arrow.
[0059] Due to the known spatial extent of the continuous casting plant and especially given the known distance between the location of the discharge roller conveyor of the strand guide and the location of the descaler, it is possible to calculate the thickness d of the scale layer at the location of the descaler, given the known temperature profile, known strand material and known casting speed.
[0060] Figure 2 illustrates the surface temperature T of the strand and the accumulating scale thickness d along the continuous casting line, with the distance E from the mold indicated. The zero point of the abscissa marks the location of the mold. The position of the discharge roller conveyor is marked ARG. The scale layer essentially only forms from the location of the discharge roller conveyor and, in this embodiment, reaches a thickness of 0.1 mm at position 22 m.
[0061] Page 10. Assume that the descaler is located at position 22 m, so that the scale layer thickness d determined here, which is 0.1 mm, is compared with a value stored in the plant control system. If the stored value is higher than the currently calculated value, the descaler remains switched off. Only when the currently calculated value of the scale layer exceeds the stored value is the descaler activated, automatically by the plant control system.
[0062] In a similar way to Fig. 2, Fig. 3 shows the formation of the scale layer with thickness d, although here the respective thickness of the individual scale phases are given as examples, namely for wüstite, for magnetite and for hematite.
[0063] Generally, scale consists of different phases, namely magnetite, hematite, wüstite, and fayalite. Fayalite (Fe₂Si₄) forms depending on the silicon (Si) content. This scale layer is relatively thin compared to the other scale phases but is difficult to remove from the strand surface. Therefore, the activation and deactivation of the descaler is preferably controlled not only by the total thickness of the scale layer but also, and especially, by the presence of fayalite. For this purpose, a corresponding fayalite threshold value (and, in particular, for the weight percentage of fayalite; see below for its determination) can be stored in the plant control system. This threshold determines whether the descaler is activated or deactivated, and also dictates the flow rate and pressure at which water is applied to the strand surface. This is particularly important in the production of silicon steels.
[0064] The calculation of the individual tinder phases can be done, for example, according to the following formulas:
[0065] Page 11. Newly formed scale, which is formed in a magazine (dt), is distributed (by weight) as follows in percentage terms to the individual scale phases (with To as the surface temperature of the strand):
[0066] %Fayalite (Fe2SiÜ4) = 5.64 * Si content of the material
[0067] %Wüstite (FeO) = 96.5 * (1 -%Fayalite)
[0068] ->at T o < 1173 K
[0069] = 311500 * exp(-6.879E-3 * To) * (1 -%Fayalit)
[0070]
[0071] otherwise
[0072] %Hematite (Fe2Ü3) = 0
[0073]
[0074] at T o < 1173 K
[0075] = (1.886E-4 *T0 2 - 0.393 * To +201.6) * (1 -%Fayalit)
[0076]
[0077] otherwise
[0078] %Magnetite (Fe3O4) = 3.5 * (1 -%Fayalite)
[0079]
[0080] at T o < 1173 K
[0081] = 100 - %Fayalite - %Wüstite - %Hematite
[0082]
[0083] otherwise
[0084] In particular, the fayalite, which is not labelled in Figure 3, is of special importance for the present process. Its proportion, as well as that of the components mentioned above, can be specifically used to automatically determine in the plant control system whether and when the descaler is switched on and off.
[0085] Page 12. According to the invention, the intensity of the descaling process is influenced by the system control depending on the determined thickness of the scale layer or the thickness or weight percentage of the determined scale phases. As explained above, the intensity can be influenced not only by switching the descaler on or off, but also by varying the volume flow and / or the pressure of the water applied to the strand surface.
[0086] Page 13
Claims
Patent claims:
1. Method for producing a strand in a continuous casting plant, wherein the strand is freed from scale after being deflected into the horizontal by means of a descaler, the descaler being arranged in the conveying direction of the strand behind the supported strand guide, characterized by that the procedure includes the following steps: a) Determination of the temperature of the strand in the conveying direction upstream of the descaler at a number of points along the conveying direction and across the strand thickness and / or strand width; b) Determination of the thickness of the forming scale and / or individual scale phases on the strand surface above the conveying direction up to the descaler based on the determined temperature of the strand; c) Influencing the intensity of the descaling process by means of a plant control system depending on the thickness of the scale formed and / or individual scale phases on the strand surface as determined at the location of the descaler.
2. Method according to claim 1, characterized in that influencing the intensity of the descaling process according to step c) of claim 1 is an activation of the descaler as soon as the thickness of the formed scale and / or individual scale phases on the strand surface reaches a predetermined first limit value or Page 14 is exceeded, and the descaler is deactivated as soon as the thickness of the formed scale and / or individual scale phases on the strand surface reaches or falls below a predetermined second limit.
3. Method according to claim 2, characterized in that the first limit value and the second limit value are the same.
4. Method according to claim 2, characterized in that the first limit value is greater than the second limit value, wherein preferably the first limit value is 5% greater than the second limit value.
5. Method according to one of claims 1 to 4, characterized in that the influencing of the intensity of the descaling process according to step c) of claim 1 is a change in the amount of water applied by the descaler to the strand surface.
6. Method according to one of claims 1 to 5, characterized in that the influencing of the intensity of the descaling process according to step c) of claim 1 is a change in the pressure with which water is applied to the strand surface.
7. Method according to one of claims 1 to 6, characterized in that the influence on the intensity of the descaling process according to step c) of claim 1 is carried out depending on the total thickness of the scale formed. Page 158. Method according to one of claims 1 to 6, characterized in that the influence on the intensity of the descaling process according to step c) of claim 1 is carried out depending on the thickness or the weight percent proportion of a single scale phase.
9. Method according to claim 8, characterized in that the scale phase is fayalite.
10. Method according to any one of claims 1 to 9, characterized in that the descaling of the strand takes place on the top of the strand and on the bottom of the strand, wherein the influence on the intensity of the descaling process according to step c) of claim 1 is different on the top of the strand and on the bottom of the strand.
11. Method according to claim 10, characterized in that in the area of the secondary cooling of the strand guide the cooling of the side of the strand which is exposed to a higher intensity of the descaling process according to step c) of claim 1 by the descaler is reduced.
12. Method according to one of claims 1 to 11, characterized in that the determination of the temperature of the strand according to step a) of claim 1 is carried out computationally using an online model. Page 1613. Method according to one of claims 1 to 12, characterized in that the determination of the thickness of the forming scale and / or individual scale phases according to step b) of claim 1 is carried out computationally using an online model.
14. Method according to one of claims 1 to 12, characterized in that the determination of the thickness of the forming scale and / or individual scale phases according to step b) of claim 1 is carried out by a measurement which takes place in the conveying direction upstream of the descaler.
15. Continuous casting plant for the production of a strand, comprising a descaler arranged downstream of the supported strand guide in the conveying direction of the strand, in particular for carrying out the method according to any one of claims 1 to 14, characterized by the fact that the continuous casting plant features: Means for determining the temperature of the strand in the conveying direction upstream of the descaler at a number of points along the conveying direction and across the strand thickness and / or strand width; Means for determining the thickness of the forming scale and / or individual scale phases on the strand surface above the conveying direction up to the descaler; A plant control system to influence the intensity of the descaling process depending on the conditions at the location of the descaler Page 17 determines the thickness of the formed scale and / or individual scale phases on the strand surface.
16. Continuous casting plant according to claim 15, characterized in that the plant control is designed to influence the intensity of the descaling process by activating the descaler as soon as the thickness of the formed scale and / or individual scale phases on the strand surface reaches or exceeds a predetermined first limit value, and by deactivating the descaler as soon as the thickness of the formed scale and / or individual scale phases on the strand surface reaches or falls below a predetermined second limit value.
17. Continuous casting plant according to claim 16, characterized in that the first limit value and the second limit value are the same.
18. Continuous casting plant according to claim 16, characterized in that the first limit value is greater than the second limit value, wherein preferably the first limit value is 5% greater than the second limit value.
19. Continuous casting plant according to one of claims 15 to 18, characterized in that the plant control is designed to influence the intensity of the descaling process by changing the amount of water applied to the strand surface in the descaler. Page 1820. Continuous casting plant according to one of claims 15 to 19, characterized in that the plant control is designed to influence the intensity of the descaling process by changing the pressure with which water is applied to the strand surface.
21. Continuous casting plant according to one of claims 15 to 20, characterized in that the plant control is designed to influence the intensity of the descaling process depending on the total thickness of the scale formed.
22. Continuous casting plant according to one of claims 15 to 20, characterized in that the plant control is designed to influence the intensity of the descaling process depending on the thickness or the weight percent proportion of a single scale phase, in particular the scale phase fayalite.
23. Continuous casting plant according to one of claims 15 to 22, characterized in that the plant control includes an online model for the computational determination of the temperature of the strand.
24. Continuous casting plant according to one of claims 15 to 23, characterized in that the plant control comprises an online model for the computational determination of the thickness of the forming scale and / or individual scale phases. Page 1925. Computer program that can be loaded into the memory of a computer of the plant control system and has software code sections with commands which cause the plant control system of the continuous casting plant according to one of claims 15 to 24 to influence the intensity of the descaling process according to the method according to one of claims 1 to 14. Page 20