JP7248049B2 - Flow control method and device, cooling method and device for steel material, and method for manufacturing continuous cast slab - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method and apparatus for controlling flow rate when spraying a fluid onto a moving object using a plurality of spray nozzles, and more particularly to a method and apparatus for cooling a steel material, and the cooling method. The present invention relates to a method for manufacturing a continuously cast slab having a cooling process.

When multiple spray nozzles are used to inject fluid onto a moving object to coat or cool it, if some of the spray nozzles are clogged, the coating amount will be uneven or the cooling will be uneven. may be sufficient.

For example, the secondary cooling zone in continuous casting of steel is a process in which cooling water is used to completely solidify the inside of a slab that has been cooled in a mold and solidified only on the surface. If the slab is flat like a slab, it must be uniformly solidified in the width direction of the slab. Therefore, cooling water is sprayed over a wide range from a spray nozzle to cool the slab as uniformly as possible. For the same reason, it is common to install a plurality of spray nozzles in the width direction.

Due to the characteristics of the spray nozzle, the outflow port is very narrow, so it often becomes clogged during operation. If some of the spray nozzles installed in the width direction are clogged, the density of the cooling water in the width direction will be uneven, increasing the risk of cracking due to non-uniform solidification. However, since the nozzles cannot be replaced while the equipment is in operation, the nozzles will remain closed until the next repair. Therefore, there is a need for prompt detection and replacement of abnormalities in the spray nozzle, and action to avoid uneven cooling during replacement.

For example, in Patent Document 1, by measuring the pressure and flow rate of a flow control valve that adjusts the flow rate of cooling water, the pressure difference is obtained in comparison with a pre-determined pressure-flow rate reference line, and the pressure difference of the cooling water A technique for detecting an abnormality in a spray nozzle from the pressure difference between air and air is disclosed.

US Pat. No. 6,300,001 shows a method for quickly installing and removing a spray cooling device.

In Patent Document 3, the set amount of water is reduced by reducing the casting speed based on the detected pipe clogging, thereby avoiding unsolidification due to insufficient amount of water.

JP 2013-35027 A JP 2014-46314 A JP 2006-175465 A

However, the conventional technique described above still has the following problems to be solved.
The technique disclosed in Patent Literature 1 simply detects an abnormality in the spray nozzle. In addition, the technology disclosed in Patent Document 2 makes it possible to perform maintenance without lowering productivity by shortening the work time required for mounting and dismounting, which normally takes time. The risk of defect occurrence increases. Moreover, the technology described in Patent Document 3 does not refer to non-uniform cooling in the width direction.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the width of the spray nozzles when they are blocked when a fluid is sprayed onto a moving object using a plurality of spray nozzles. A spray flow rate control method and apparatus are provided that mitigates and improves directional non-uniform flow distribution, and a steel stock cooling method and apparatus that mitigates and improves non-uniform cooling are provided. Furthermore, the present invention provides a method for producing a continuously cast slab that mitigates and improves non-uniform cooling.

The inventors have diligently investigated a technique for solving the above problems.
A flow rate control method according to the present invention, which has been developed to solve the above problems and achieve the above objects, is a method of controlling a spray flow rate when a fluid is jetted onto a moving object using a plurality of spray nozzles. detecting the degree of clogging of each of the plurality of spray nozzles; and determining the flow rate distribution of the fluid that can be ejected by the plurality of spray nozzles on the basis of the detected degree of clogging. and controlling the amount of fluid supplied to each spray nozzle of the plurality of spray nozzles based on the determined fluid flow rate distribution.

In addition, regarding the flow rate control method according to the present invention, it is considered that obtaining the flow rate distribution of the fluid by numerical analysis can be a more preferable solution.

A flow rate control device according to the present invention, which has been developed to solve the above problems and achieve the above objects, is a device for controlling the flow rate of a spray that injects a fluid from a plurality of spray nozzles onto a moving object. a nozzle clogging detection unit for detecting the degree of clogging of each of the plurality of spray nozzles; and a flow rate distribution determining the flow rate distribution of the fluid that can be ejected by the plurality of spray nozzles on the basis of the detected degree of clogging. and a flow controller for controlling the flow rate of each spray nozzle based on the determined flow rate distribution of the fluid.

In the flow rate control device according to the present invention, it is considered that the flow rate distribution determination unit is configured to determine the flow rate distribution of the fluid by numerical analysis, which can be a more preferable solution.

A steel material cooling method according to the present invention, which has been developed to solve the above problems and achieve the above objects, is a method of cooling a steel material with a cooling medium using the above flow rate control method. A high-temperature steel material is used as the object to be held, and the fluid is used as a cooling medium.

A steel material cooling apparatus according to the present invention, which has been developed to solve the above problems and achieve the above objects, is an apparatus for cooling a steel material with a cooling medium using the flow rate control device. The object in contact is a hot steel material and the fluid is the cooling medium.

In addition, in the steel material cooling device according to the present invention, the flow rate distribution determination unit is configured to determine the flow rate distribution of the cooling medium based on the temperature distribution in the width direction of the steel material. is considered to be a more preferable solution.

In the method for producing a continuously cast slab according to the present invention, which has been developed to solve the above problems and achieve the above objects, the steel material is a slab in continuous casting, and the flow rate distribution of the cooling medium is controlled by the The method of cooling the steel material, which is determined based on the temperature distribution in the width direction of the piece, is included as a cooling process.

In addition, in the method for producing a continuously cast slab according to the present invention, the flow rate distribution of the cooling medium is such that when the supply amount of the cooling medium is controlled based on the flow rate distribution, the temperature distribution in the width direction of the slab is It is considered that a more preferable solution is to be obtained by numerical analysis so as to asymptotically uniform distribution.

As described above, the flow rate of each spray nozzle is determined based on the degree of clogging of the spray nozzle, so that uneven flow distribution in the width direction when the spray pipe is clogged can be alleviated and improved. It became possible.

Further, since the flow rate control method and the flow rate control device according to the present invention are applied to the cooling method and device for the steel material, it has become possible to mitigate and improve the non-uniform cooling of the steel material. Furthermore, by using the steel material cooling method according to the present invention as a cooling process for continuous casting, it is possible to alleviate and improve the non-uniform cooling of the cast slab, and as a result, the occurrence of cracks due to non-uniform solidification. Risk is reduced, and a decrease in manufacturing yield can be suppressed.

1 is a schematic block diagram of a flow control device according to a first embodiment of the invention; FIG. FIG. 10 is a flowchart for determining a fluid flow rate distribution in the steel material cooling method according to the second embodiment of the present invention. 4 is a graph showing analytical values of cast slab surface temperature in an initial non-uniform flow rate state and in a state of optimized flow rate distribution according to the embodiment;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A first embodiment of the present invention mitigates and improves uneven flow distribution in the width direction when spray nozzles are clogged when spraying fluid onto a moving object using a plurality of spray nozzles. , a spray flow control method and a flow control device. In this specification, the "plurality of spray nozzles" may be simply referred to as "spray nozzles". FIG. 1 shows a schematic block diagram of the flow rate control device of this embodiment. A flow rate control device 1 of this embodiment comprises a flow rate determination device 2 and a spray nozzle 3 including a flow rate adjustment valve.

The flow rate determination device 2 is composed of a nozzle clogging detector 21 , a flow rate distribution determination section 22 and a flow rate control section 23 .

The nozzle clogging detector 21 monitors, for example, the flow rate of fluid flowing through individual spray nozzles, detects a decrease in the flow rate, and collects the degree of nozzle clogging. The collected nozzle clogging degrees are transferred to the flow distribution determination unit 22 . Here, the information to be monitored is not limited to the flow rate of the fluid, and any information that can detect the degree of nozzle clogging, such as the back pressure of the fluid or the non-uniformity of the fluid coating on the surface of the object, may be used. The degree of nozzle clogging may be binary data where clogging is "0" and opening is "1", or real number data between 0 and 1 may be given.

The flow distribution determination unit 22 determines the optimum flow distribution based on the detection result of the degree of nozzle clogging, for example, according to the flow of FIG. 2 which will be described later. The determined flow rate distribution is transmitted to the flow control section 23 of the spray nozzle.

The spray nozzle flow rate controller 23 adjusts the flow rate of each spray nozzle 3 to achieve the determined flow rate distribution by opening or closing a flow rate control valve. As a result, uneven flow distribution in the width direction when some of the spray nozzles are clogged can be alleviated and improved.

Next, a second embodiment is a steel material cooling method and a cooling device, and is suitable for applying the flow rate control method and flow rate control device described above. In this embodiment, the object in motion is a hot steel material, for example a billet during continuous casting (before cutting) or a rolled body for hot rolling, and the fluid is a cooling medium, for example Cooling water or air-water mist.

FIG. 2 is a flow diagram for determining the flow rate distribution in the steel material cooling method according to this embodiment. For example, in a problem where the free surface occupies most of the analysis area, such as spray cooling water in the secondary cooling zone of a continuous casting machine, the lattice method such as the difference method or the finite volume method is not suitable, so the particle method is used in this embodiment. analysis was performed.

At the start of the process (S00), at step 01, at least one of the slab width, roll diameter, bearing size, width between rolls, and spray nozzle position is used as the input value, and one segment or roll sequence Analysis is performed (S01).

Further, the desired slab surface temperature is added in step 02, and the ^2N spray nozzle clogging patterns are added as input values in step 03 (S02, S03). Here, N is the number of sprays in the analysis area, and 0 (blockage) and 1 (open) express nozzle blockage.

At step 04, analysis is started from generation g=1 (S04).

In step 05, for each blocking pattern, a flow rate pattern is randomly generated from the flow rate range of the spray nozzle (S05), and in step 06, the temperature distribution of the slab is calculated by numerical analysis of the generated flow rate pattern. (S06). Finally, a genetic algorithm is used to obtain the optimal flow pattern. In the case of this embodiment, the cooling of the slab, etc. is taken into consideration, so the optimum flow rate pattern is, for example, an analysis that makes the temperature distribution in the width direction of the slab (slab) asymptotically uniform.・It is obtained through repeated evaluation. By multiplying the generated flow rate pattern by the spray nozzle blocking pattern of 0 and 1, the flow rate of the blocked nozzle is always 0.

In step 07, the difference from the desired slab surface temperature and the standard deviation of the temperature distribution in the width direction are taken as evaluation functions (S07). The difference from the desired slab surface temperature is the difference from the average value of the temperature in the width direction obtained by the analysis, and the closer the difference is to 0, the greater the reward. The relationship is expressed, for example, in the form of Equation 1 below.

where ω _tmp is the weighting factor, T _idea is the desired slab surface temperature (°C), T _calc is the calculated slab surface temperature (°C), and fw _tmp is the evaluation function on the slab surface temperature. . Although the above fractional function is used as the evaluation function here, any function may be used as long as the value increases as the difference approaches zero. On the other hand, the closer the standard deviation of the widthwise temperature distribution is to 0, the greater the reward. The relationship is represented, for example, in the form of Equation 2 below.

Here, ω _std is a weighting coefficient, σ is the standard deviation of the width direction temperature distribution, and fw _std is the evaluation function of the standard deviation of the width direction temperature distribution. As with the evaluation function regarding the difference from the desired slab surface temperature, any function may be used as long as the value increases as the standard deviation approaches zero. A final evaluation function fw is obtained by adding these two evaluation functions (Formula 3). The values of the weighting factors in Equations 1 and 2 shall be adjusted according to convergence, required conditions, and results.

After calculating the evaluation function, in step 08, processing such as selection, crossover, and mutation is performed (S08), the generation g is advanced, and the process returns to step 05 (S09). In step 09, when the number of generations has reached the predetermined number of generations, as step 10, the flow rate distribution of the blocking pattern at this time is output (S10).

Furthermore, in step 11, the occlusion pattern is changed (S11), and the calculations in steps 4 to 10 are repeated. When all blockage patterns have been analyzed in step 11 (S11), the flow distribution corresponding to the blockage pattern acquired from the nozzle blockage detector 21 is output and the process ends (S99).

In this embodiment, the flow rate distribution is obtained for all spray nozzle blockage patterns, but only the flow rate distribution corresponding to the blockage pattern acquired from the nozzle blockage detector 21 may be calculated.

The steel raw material cooling method and cooling device of the present embodiment are suitable for secondary cooling of cast slabs in continuous casting, temperature control of rolled bodies in hot rolling, etc., and alleviate uneven cooling in the width direction. , can be improved.

Furthermore, the third embodiment is a method for manufacturing a continuously cast slab, and is suitable for applying the above steel material cooling method. In this embodiment, as the cooling step, the second embodiment is applied to the secondary cooling of the slab in continuous casting. For other steps in continuous casting, general steps may be applied as appropriate.

As a method of applying the second embodiment to this embodiment, the flow rate distribution corresponding to all blockage patterns is calculated in advance by the method shown in FIG. Based on the determined occlusion pattern, a corresponding flow distribution may be selected. Further, based on the blockage pattern acquired from the nozzle blockage detector 21, only the flow distribution of the corresponding blockage pattern may be calculated on the spot and used.

In the method for producing a continuously cast slab according to the present embodiment, even if part of the spray nozzle is clogged during operation, appropriate secondary cooling can be continued without waiting for repair or replacement of the spray nozzle. can be done. Therefore, even in such a case, non-uniform cooling of the slab can be alleviated and improved, the risk of cracking due to non-uniform solidification can be reduced, and a decrease in production yield can be suppressed.

The spray flow rate control method and flow rate control device, the steel material cooling method and cooling device, and the continuously cast slab manufacturing method of the above embodiments can be used in combination with conventional techniques. For example, when it is detected that a part of the spray nozzle is clogged, conventionally, as in Patent Document 2, the abnormal equipment is quickly replaced, or the clogged nozzle is quickly washed to clear the clog. was doing According to this embodiment, it is possible to maintain a constant quality of the slab manufactured until the equipment is replaced or the clogging is cleared. As a result, the minimum quality of the manufactured slab is raised, leading to an improvement in yield. Thus, the technology according to the present invention does not compete with the prior art.

Further, the numerical analysis method for determining the flow rate distribution of the fluid used in the above embodiment couples and analyzes the behavior of the cooling water itself on the surface of the steel plate in addition to the heat transfer analysis. By doing so, it becomes possible to sufficiently reproduce the temperature non-uniformity in the width direction. Specifically, for example, analysis by a particle method such as an SPH (Smoothed Particle Hydrodynamics) method can be mentioned. In the secondary cooling of continuous casting, which is water spray cooling, film boiling and nucleate boiling occur on the slab surface, so it is difficult to improve the accuracy of heat transfer analysis that only considers boiling latent heat. Even in that case, the accuracy of numerical analysis, that is, thermal fluid analysis can be improved by converting the density and flow velocity of SPH particles into heat transfer coefficients.

(Example 1)
In order to confirm the effects of the invention, the spray nozzle flow rate was adjusted when the secondary cooling spray nozzle was partially clogged using actual casting conditions.

Thermal fluid analysis was performed using the SPH method, which is a kind of particle method, as the numerical analysis method. The slab width, roll diameter, bearing size, width between rolls, casting speed, and initial temperature of the slab surface are 1800mm, 250mm, 10mm, 20mm, 1.5m/min, and 900°C respectively, and the spray nozzles are uniform in the width direction. 3 were placed in the The spray opening angle of the spray nozzle was 100°, and the flow rate was 0 to 20 NL/min. In this example, two rows of rolls are used as the analysis area. Since the spray nozzles are also arranged in two rows, the number is 3×2=6. Therefore, the number of patterns to be analyzed is 2 ⁶ =64 patterns (000000 to 111111). For each of these, flow rate optimization is performed using a genetic algorithm.

The desired slab surface temperature used for the evaluation function of the genetic algorithm was 800°C. The evaluation functions fw _tmp and fw _std for the difference from the desired slab surface temperature and the standard deviation of the temperature distribution in the width direction are obtained using the above equations 1 and 2, respectively, and the total evaluation function fw is obtained by the above equation 3, which is the sum of them. Obtained. Here, the weighting coefficients ω _tmp and ω _std are both set to 1000. The temperature measurement points in the width direction in the analysis were set to 11 points at intervals of 180 mm, and were set to the most downstream position of the analysis area in the casting direction. The analysis time was determined from the degree of convergence of the surface temperature average value and the standard deviation. Specifically, the analysis was terminated when the temporal change in the above two values at the measurement point became sufficiently small. Under the above conditions, the analysis was performed with the number of individuals m=20 and the number of generations g=100.

As an example of the analysis results, the results when the center nozzles of the two rows of spray nozzles are blocked (condition: 101101) are shown. FIG. 3 shows the temperature distribution in the width direction of one of the 20 individuals of the initial generation extracted and the final generation with the highest value of the evaluation function fw. The genetic algorithm was able to determine the spray nozzle flow rate that allows the slab surface temperature to be close to the desired temperature and to cool uniformly.

INDUSTRIAL APPLICABILITY The present invention is suitable for applying to the case where the uneven flow rate distribution needs to be alleviated or improved when the flow rates sprayed from a plurality of spray nozzles into a free space become uneven due to nozzle clogging.

REFERENCE SIGNS LIST 1 flow control device 2 flow rate determination device 21 nozzle clogging detection unit 22 flow distribution determination unit 23 flow control unit 3 spray nozzle

Claims (9)

A method for controlling a spray flow rate when spraying a fluid onto a moving object using a plurality of spray nozzles, comprising:
detecting the degree of blockage of each spray nozzle in the plurality of spray nozzles;
For all blockage patterns of the plurality of spray nozzles, the flow distribution of the plurality of spray nozzles that alleviates the uneven flow distribution in the width direction of the object is obtained in advance, and the detected degree of blockage is a condition, determining a flow distribution of fluid that can be sprayed by the plurality of spray nozzles to mitigate non-uniform flow distribution across the width of the object ;
controlling the amount of fluid supplied to each spray nozzle of the plurality of spray nozzles based on the determined flow rate distribution of the fluid;
has
The degree of blockage is a flow rate control method that uses a numerical value that quantitatively expresses the degree of nozzle opening to blockage . 2. The flow rate control method according to claim 1, wherein the flow rate distribution of said fluid is obtained by numerical analysis. A device for controlling the flow rate of a spray that injects a fluid from a plurality of spray nozzles onto a moving object,
a nozzle clogging detector that detects the degree of clogging of each of the plurality of spray nozzles;
For all blockage patterns of the plurality of spray nozzles, the flow rate distribution of the plurality of spray nozzles that alleviates the uneven flow rate distribution in the width direction of the object is obtained in advance, and the detected degree of blockage is used as a condition for the a flow rate distribution determination unit that determines a flow rate distribution of the fluid that can be sprayed by the plurality of spray nozzles so as to alleviate uneven flow rate distribution in the width direction of the object ;
a flow controller that controls the flow rate of each spray nozzle based on the determined flow rate distribution of the fluid;
has
The degree of clogging is a numerical value that quantitatively expresses the degree of nozzle opening to clogging . 4. The flow control device according to claim 3, wherein said flow rate distribution determination unit is configured to obtain the flow rate distribution of the fluid by numerical analysis. A method of cooling a steel material with a cooling medium using the flow rate control method according to claim 1 or 2,
The moving object is a high-temperature steel material,
A cooling method for a steel material, wherein the fluid is used as a cooling medium. A device for cooling a steel material with a cooling medium using the flow control device according to claim 3 or 4,
the moving object is a hot steel material;
A cooling device for steel material, wherein said fluid is a cooling medium. 7. The steel material cooling device according to claim 6, wherein the flow rate distribution determination unit is configured to determine the flow rate distribution of the cooling medium based on the temperature distribution in the width direction of the steel material. 6. The steel material cooling method according to claim 5, wherein the steel material is a slab in continuous casting, and the flow rate distribution of the cooling medium is determined based on the temperature distribution in the width direction of the slab. A method for producing a continuously cast slab. The flow distribution of the cooling medium is obtained by numerical analysis so that the temperature distribution in the width direction of the slab approaches a uniform distribution when the supply amount of the cooling medium is controlled based on the flow distribution. The method for producing a continuously cast slab according to claim 8, which is a product.

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