JP6299652B2 - Slab quality estimation apparatus and slab quality estimation method - Google Patents

Description

  The present invention relates to a slab quality estimation apparatus and a slab quality estimation method for estimating the quality of each slab of a slab produced by a continuous casting machine.

  In a continuous casting process of steel, generally, a continuous casting machine cools molten steel injected into a mold from its surroundings by a mold (primary cooling), thereby solidifying a surface layer portion of the molten steel in the mold and solidifying shell. Form. Next, the continuous casting machine conveys molten steel in which a solidified shell is formed, that is, a slab having an unsolidified phase surrounded by the solidified shell while being pulled out from the mold in the casting direction using a pinch roll and is cooled by cooling water. Cool (secondary cooling) to solidify. The continuous casting machine sequentially performs such processing to continuously cast a flat slab that is long in the casting direction. Thereafter, the continuous casting machine cuts the slab obtained by continuous casting into a predetermined length along the longitudinal direction (casting direction), thereby sequentially producing steel slabs such as thick plate slabs. .

  Conventionally, as described above, center segregation that causes deterioration of slab quality has occurred in a slab continuously cast by a continuous casting machine. One cause of the occurrence of such center segregation is the slab portion near the upstream side in the casting direction from the solidification completion position of the slab (hereinafter, the solidification completion position means the solidification completion position of the slab). Non-stationary bulging present. In unsteady bulging, solidification is still completed between the rotating roll bodies provided in the continuous casting machine such as the support roll that feeds downstream in the casting direction while supporting the slab drawn from the mold and the pinch roll described above. This is a phenomenon in which the slab during continuous casting partially swells in the thickness direction. Such unsteady bulging is, for example, when the surface layer portion of a slab during continuous casting becomes a high temperature state due to recuperation from the internal unsolidified phase and the thickness of the solidified shell is thin. Caused by.

  On the other hand, as a method of reducing the center segregation of the slab, a slab that has not yet been solidified (for example, a slab at the end of solidification) near the upstream in the casting direction from the solidification completion position is reduced to match the solidification shrinkage of the slab. There is a method of gradually reducing the amount (hereinafter referred to as light reduction). However, if an excessive amount of unsteady bulging occurs in the slab during continuous casting, even if the above-mentioned incomplete solidified slab is lightly reduced to reduce the center segregation, the center segregation is reduced by light reduction. The effect is reduced. As the cause, for example, because the concentrated component that should be sucked into the slab solidified part at the time of solidification shrinkage of the slab by light pressure is pushed back to the central part where the slab is not solidified due to unsteady bulging, For example, central segregation deteriorates.

  As a conventional technique for detecting unsteady bulging as described above, for example, there is an eddy current sensor system that detects unsteady bulging of a slab by using an eddy current sensor. In this eddy current sensor method, the distance between the slab and the eddy current sensor is measured by the eddy current sensor installed close to the slab, and the molten steel in the mold is measured based on the obtained distance measurement result. Unsteady bulging affecting the level fluctuation is detected. However, if the eddy current sensor is installed in a high temperature and high humidity environment or in an environment where vaporized oil may be generated, that is, in an environment where the continuous casting machine is operating, It is difficult to detect unsteady bulging continuously over a period of time. Moreover, when an environmental measure is applied to the eddy current sensor so as to withstand the environment during operation of the continuous casting machine, there is a problem that a great cost is required.

  Further, as a conventional technique for detecting unsteady bulging by a method different from the eddy current sensor method described above, for example, there is a method using a water column type ultrasonic level meter. In this method, unsteady bulging can be measured with a water column type ultrasonic level meter even in a high temperature and high humidity environment. However, in an environment where the continuous casting machine is in operation, a large amount of cooling water is sprayed from the cooling spray so that the slab drawn from the mold is secondarily cooled and solidified. In addition, the above-described cooling water interferes and noise is generated. For this reason, it is difficult to always detect unsteady bulging with high accuracy using a water column type ultrasonic level meter in an environment where the continuous casting machine is in operation.

  On the other hand, as another prior art for detecting unsteady bulging, for example, it is utilized that the cycle of the molten metal surface level fluctuation in the mold caused by unsteady bulging is determined by the roll pitch of the secondary cooling zone and the casting speed. Unsteady bulging occurs when the periodicity of the current value of the pinch roll motor matches the frequency of one or both of the molten metal level value and the molten metal level control signal value. (Refer to Patent Document 1). Further, the amplitude of the molten metal surface level value in the mold exceeds the first threshold value, and the frequency characteristic of the molten metal surface level value is obtained based on the roll pitch of the support roll (slab support roll) and the casting speed. There is a method of detecting the occurrence of unsteady bulging when the amplitude in the frequency range of the generated melt level fluctuation exceeds a second threshold (see Patent Document 2).

Japanese Patent Laid-Open No. 11-170021 JP 2007-136480 A

  By the way, the center segregation generated in the slab during continuous casting adversely affects the quality of each slab that is sequentially manufactured from the slab by the continuous casting machine. It is extremely important for the operation of a continuous casting machine to estimate the quality of each slab affected by such center segregation online during the operation of the continuous casting machine. However, in the above-described prior art, it is difficult to estimate the quality of each slab affected by the center segregation of the slab on-line during the operation of the continuous casting machine, even if unsteady bulging of the slab during continuous casting. However, the detection result of unsteady bulging could not be used for quality estimation of each slab.

  The present invention has been made in view of the above circumstances, and it is possible to easily estimate the quality of each slab affected by the center segregation of the slab on-line during the operation of the continuous casting machine. An object is to provide an apparatus and a slab quality estimation method.

  In order to solve the above-described problems and achieve the object, the slab quality estimation apparatus according to the present invention is a slab quality estimation apparatus for a slab that is continuously cast by being drawn from the mold while solidifying molten steel injected into the mold of a continuous casting machine. A solidification completion position calculation unit for calculating a solidification completion position, and one or more pinch rolls of the continuous casting machine that pulls out the slab from the mold, upstream of the solidification completion position in the casting direction of the slab The pinch roll located in the position is selected, the frequency signal of the torque signal is obtained by frequency analysis of the torque signal of the selected pinch roll, and the unstable bulging of the slab out of the obtained frequency components A quality index processing unit for determining a quality index indicating quality deterioration of the slab due to the influence of center segregation of the slab based on a frequency component to be processed, and a slab manufactured by cutting the slab. And managed in association with the blanking and the quality index, it is characterized in that and a quality control section for estimating the quality of each of the slabs on the basis of the quality index.

  In the slab quality estimation apparatus according to the present invention as set forth in the invention described above, the quality index processing unit is located upstream of the solidification completion position in the casting direction of the slab from the one or more pinch rolls. The pinch roll which is located and constitutes the light pressure lower belt of the continuous casting machine is selected.

  Further, in the slab quality estimation apparatus according to the present invention, in the above invention, the quality index processing unit sets the weight of the influence of unsteady bulging on the center segregation of the slab, and selects the solidification completion position. The quality index is determined by changing the weighting according to the distance from the installation position of the pinch roll.

  Further, the slab quality estimation method according to the present invention includes a solidification completion position calculating step for calculating a solidification completion position of a slab that is continuously cast by being drawn from the mold while solidifying molten steel injected into a mold of a continuous casting machine; Selecting a pinch roll located upstream of the solidification completion position in the casting direction of the slab from one or more pinch rolls of the continuous casting machine that pulls the slab out of the mold; and The frequency analysis step of acquiring the frequency component of the torque signal by frequency analysis of the torque signal of the pinch roll selected by the selection step, and the slab of the slab out of the frequency component acquired by the frequency analysis step Quality indicating deterioration of the quality of the slab due to the effect of center segregation of the slab, based on frequency components caused by unsteady bulging A quality index determining step for determining a mark, a management step for managing the slab manufactured by cutting the slab in association with the quality index, and estimating the quality for each slab based on the quality index And a quality estimation step.

  In the slab quality estimation method according to the present invention, in the above invention, the selecting step is located upstream of the solidification completion position in the casting direction of the slab from the one or more pinch rolls. And the said pinch roll which comprises the light pressure lower belt of the said continuous casting machine is selected, It is characterized by the above-mentioned.

  Further, in the slab quality estimation method according to the present invention, in the above invention, the quality index determination step sets the weight of the influence of unsteady bulging on the center segregation of the slab, and selects the solidification completion position. The quality index is determined by changing the weighting according to the distance from the installation position of the pinch roll.

  According to the present invention, there is an effect that the quality of each slab affected by the center segregation of the slab can be easily estimated on-line during operation of the continuous casting machine.

FIG. 1 is a diagram illustrating a configuration example of a slab quality estimation apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing a configuration example of a continuous casting machine in the embodiment of the present invention. FIG. 3 is a flowchart showing an example of the slab quality estimation method according to the embodiment of the present invention. FIG. 4 is a diagram showing trend data of torque of each pinch roll to be noted in the present embodiment. FIG. 5 is a diagram illustrating an example of a frequency analysis result of the torque signal collected from the most upstream pinch roll among the target pinch rolls in the present embodiment. FIG. 6 is a diagram illustrating an example of a frequency analysis result of a torque signal collected from an intermediate pinch roll among the target pinch rolls in the present embodiment. FIG. 7 is a diagram illustrating an example of a frequency analysis result of a torque signal collected from the pinch roll at the most downstream of the target pinch rolls in the present embodiment. FIG. 8 is a diagram showing an example of the correlation between the slab quality index and the center segregation value in the present embodiment.

  Exemplary embodiments of a slab quality estimation apparatus and a slab quality estimation method according to the present invention will be explained below in detail with reference to the accompanying drawings. In this embodiment, a vertical bending type continuous casting machine is illustrated as an example of a continuous casting machine, but the present invention is not limited to this embodiment. Moreover, the drawings are schematic, and it should be noted that the relationship between the dimensions of each element, the ratio of each element, and the like may differ from the actual ones. Even between the drawings, there are cases in which portions having different dimensional relationships and ratios are included. Moreover, in each drawing, the same code | symbol is attached | subjected to the same component.

(Continuous casting machine)
First, a continuous casting machine to which a slab quality estimation apparatus according to an embodiment of the present invention is applied will be described. FIG. 1 is a diagram illustrating a configuration example of a slab quality estimation apparatus according to an embodiment of the present invention. FIG. 1 shows a slab quality estimation apparatus 1 according to an embodiment of the present invention and a continuous casting machine 11 to which the slab quality estimation apparatus 1 is applied. FIG. 2 is a diagram showing a configuration example of a continuous casting machine in the embodiment of the present invention.

  As shown in FIGS. 1 and 2, the continuous casting machine 11 includes a mold 12 for casting the molten steel 10 a into a predetermined shape, a tundish 13 for appropriately storing and supplying the molten steel 10 a, and a molten steel from the tundish 13 to the mold 12. And an immersion nozzle 14 for injecting 10a. In addition, the continuous casting machine 11 conveys the slab 10 from the mold 12 to the downstream side in the casting direction while pulling out the slab 10 from the mold 12 while supporting the slab 10 from the mold 12. A plurality of pinch rolls 16 to 19 are provided. In addition, although not shown in FIGS. 1 and 2, the continuous casting machine 11 has a plurality of cooling sprays such as an air mist spray that jets cooling water from the nozzle for secondary cooling of the slab 10 drawn from the mold 12. In addition, various facilities necessary for a continuous casting process such as a cutting portion for cutting the continuously cast slab 10 into a slab having a predetermined length are provided.

  The mold 12 is for solidifying the liquid molten steel 10a into a predetermined shape. 1 and 2 show a schematic structure of a cross section of the mold 12 in order to facilitate the explanation of the present invention. In the present embodiment, the mold 12 is formed with a rectangular through-hole or the like penetrating from the inlet side to the outlet side. As shown in FIGS. Provided below. The mold 12 primarily cools the liquid molten steel 10a injected from the inlet side, thereby solidifying the liquid molten steel 10a from the surface layer portion to form a solidified shell. In this manner, the mold 12 sequentially casts this liquid molten steel 10a on the slab 10. At this stage, the slab 10 is in an incompletely solidified state having an unsolidified phase in the interior surrounded by the solidified shell.

  The tundish 13 is for injecting molten steel 10 a into the mold 12. Specifically, as shown in FIGS. 1 and 2, the tundish 13 is provided above the mold 12. In addition, an immersion nozzle 14 serving as a molten steel injection port to the mold 12 is provided at the bottom of the tundish 13. As shown in FIGS. 1 and 2, the immersion nozzle 14 is disposed so as to be immersed in the molten steel 10 a inside the mold 12. The tundish 13 stores the molten steel 10 a poured from a ladle (not shown), and appropriately injects the stored molten steel 10 a into the mold 12 through the immersion nozzle 14.

  The support roll 15 is a rotary roll body that is rotatably supported in the outer circumferential direction of the roll. As shown in FIGS. 1 and 2, the slab 10 is sandwiched in the thickness direction and along the casting direction of the slab 10. Several are installed so that they line up. The casting direction of the slab 10 is the drawing and conveying direction of the slab 10 that is continuously cast while being drawn and conveyed from the mold 12 as indicated by the thick arrows in FIGS. The plurality of support rolls 15 are fed from the upstream side to the downstream side in the casting direction while supporting the cast piece 10 pulled out from the mold 12.

The pinch rolls 16 to 19 are rotating roll bodies that are rotatable in the outer circumferential direction of the roll by a driving force of a motor (not shown), and sandwich the slab 10 in the thickness direction as shown in FIGS. A plurality (four pairs in the present embodiment) are installed along the casting direction of the slab 10. Specifically, each of the pinch rolls 16 to 19 is installed at a suitable position for gradually correcting the longitudinal direction of the slab 10 drawn vertically downward from the mold 12 in the horizontal direction. Hereinafter, the installation position of such pinch rolls 16 to 19 are referred to as pinch roll position P _m. Note that the number m is a number that identifies each of the pinch rolls 16 to 19. In this embodiment, as shown in FIGS. 1 and 2, the pinch roll 16 is installed at the most upstream pinch roll position P ₁ , and the pinch roll 17 is located on the downstream side in the casting direction. It is installed in the P _2. The pinch roll 18 is installed at a pinch roll position P ₃ that is downstream of the pinch roll 17 in the casting direction, and the pinch roll 19 is installed at the most downstream pinch roll position P ₄ .

In the present embodiment, each pinch roll position P _m (m = 1, 2, 3, 4) is a position represented by a distance along the casting direction from the reference position P ₀ in the continuous casting machine 11. For example, when the reference position P ₀ is the position of the meniscus 10b of the molten steel 10a injected into the mold 12, each pinch roll position P _m (m = 1, 2, 3, 4) is different from the position of the meniscus 10b. It is represented by a distance along the casting direction (hereinafter referred to as meniscus distance). That is, as shown in FIGS. 1 and 2, the pinch roll position P ₁ is the position of the meniscus distance L ₁ , and the pinch roll position P ₂ is a position of the meniscus distance L ₂ that is longer than the meniscus distance L _1. It is. The pinch roll position P ₃ is a position having a meniscus distance L ₃ that is longer than the meniscus distance L ₂ , and the pinch roll position P ₄ is a position having a meniscus distance L ₄ that is longer than the meniscus distance L _3. is there.

  The pinch rolls 16 to 19 installed as described above use a rotational force (torque) generated by driving a motor, and the slab 10 is drawn from the mold 12 along a plurality of support rolls 15 in a casting direction in a casting direction (hereinafter referred to as “push rolls 16-19”). , Called casting speed). Further, these pinch rolls 16 to 19 sequentially convey the drawn slab 10 along the plurality of support rolls 15 in the casting direction at a predetermined casting speed.

  Here, the continuous casting machine 11 includes a plurality of cooling zones that perform secondary cooling for completely solidifying the unsolidified slab 10 drawn from the mold 12. Specifically, in the present embodiment, as shown in FIGS. 1 and 2, the continuous casting machine 11 includes cooling zones 21 a to 21 in nine zones arranged in the casting direction of the slab 10 from the vicinity of the outlet side of the mold 12. 29a and cooling zones 21b to 29b are provided.

  The cooling zones 21a to 29a are for secondary cooling of the slab 10 drawn from the mold 12 from the surface side (specifically, the upper surface side) opposite to the reference surface. Among these cooling zones 21a to 29a, the cooling zones 21a to 23a, 28a, and 29a are each configured using a plurality of support rolls 15, a cooling spray (not shown), and the like. Each of these cooling zones 21a-23a, 28a, 29a may be provided with one or more pinch rolls that function similarly to the pinch rolls 16-19. On the other hand, the remaining cooling zones 24a to 27a are each configured using a plurality of support rolls 15, pinch rolls 16 to 19, and a cooling spray (not shown). These cooling zones 21a to 29a spray cooling water onto the upper surface of the slab 10 that is pulled out of the mold 12 and sequentially conveyed in the casting direction, thereby secondary cooling the slab 10 from the upper surface side. The slab 10 is solidified.

  The cooling zones 21b to 29b are for secondary cooling of the slab 10 drawn from the mold 12 from the reference surface side (specifically, the lower surface side). Among these cooling zones 21b to 29b, the cooling zones 21b to 23b, 28b, and 29b are each configured using a plurality of support rolls 15, cooling sprays (not shown), and the like. Each of the cooling zones 21b to 23b, 28b, and 29b may be provided with one or more pinch rolls that function similarly to the pinch rolls 16 to 19. On the other hand, the remaining cooling zones 24b to 27b are each configured using a plurality of support rolls 15, pinch rolls 16 to 19, and a cooling spray (not shown). These cooling zones 21b to 29b inject cooling water onto the lower surface of the slab 10 that is pulled out of the mold 12 and sequentially conveyed in the casting direction, thereby secondary cooling the slab 10 from the lower surface side. The slab 10 is solidified.

  On the other hand, in the continuous casting machine 11, the cooling bands 24a to 27a on the upper surface side of the slab 10 and the cooling bands 24b to 27b on the lower surface side are made of lightly cast slab 10 that has not been solidified as shown in FIGS. It also has a function as a light pressure belt 20 to be rolled down. Specifically, in the light pressure lower belt 20, the pinch rolls 16 to 19 lightly lower the incompletely cast slab 10 that is sequentially conveyed in the casting direction.

  The continuous casting machine 11 having the above-described configuration sequentially conveys the slab 10 in the casting direction while continuously drawing the slab 10 from the mold 12 into which the molten steel 10a has been injected at a predetermined casting speed, and in parallel therewith. Then, the slab 10 is subjected to secondary cooling sequentially over the entire area. In this way, the continuous casting machine 11 continuously casts the flat slab 10 that is long in the casting direction from the molten steel 10a poured into the mold 12. Thereafter, the continuous casting machine 11 sequentially cuts the slab 10 that has been continuously cast and completely solidified into a predetermined length by a cutting portion (not shown), thereby sequentially manufacturing the desired slab.

(Slab quality estimation device)
Next, a slab quality estimation apparatus according to an embodiment of the present invention will be described with reference to FIGS. The slab quality estimation device 1 according to the embodiment of the present invention estimates the quality of each slab online during operation of the continuous casting machine 11. As shown in FIG. 1, the slab quality estimation device 1 includes a quality determination device 2 that determines the quality according to the center segregation of the slab 10, and an operation computer that manages and estimates the quality of the slab 10 for each slab. 5. Moreover, the slab quality estimation apparatus 1 includes an input unit 6 that inputs information necessary for estimating the slab quality, and an output unit 7 that outputs information such as the quality estimation result of each slab.

  The quality determination device 2 determines the quality according to the degree of center segregation of the slab 10 continuously cast by the continuous casting machine 11. As shown in FIG. 1, the quality determination device 2 includes a secondary cooling calculation unit 3 and a quality index processing unit 4.

The secondary cooling calculation unit 3 is a solidification completion position calculation unit that calculates the solidification completion position of the slab 10 that is continuously cast by being drawn from the mold 12 while solidifying the molten steel 10a injected into the mold 12 of the continuous casting machine 11. Function. Specifically, the secondary cooling calculation unit 3 performs online secondary cooling calculation of the continuous casting of the slab 10 in the continuous casting machine 11 in operation, and based on the result of the secondary cooling calculation, The solidification completion position of the slab 10 during continuous casting is calculated. In the present embodiment, the solidification completion position of the slab 10 is represented by a distance (for example, a meniscus distance) along the casting direction from the reference position P ₀ in the continuous casting machine 11 in the same manner as the pinch roll position P _m described above. Is done. The secondary cooling calculation unit 3 transmits the solidification completion position calculated in this way to the quality index processing unit 4.

  Here, the secondary cooling calculation of continuous casting in the present embodiment is a heat transfer calculation related to secondary cooling of the slab 10 using a heat transfer model. For example, the secondary cooling calculation for continuous casting usually considers the cross section of the slab 10 cut to unit length along the casting direction, and depending on the location in the slab 10 currently being continuously cast, water cooling, By calculating the heat flux based on the equation showing the boundary condition on the slab surface by the secondary cooling condition consisting of air cooling, mist cooling, heat removal from the roll, etc., and solving the two-dimensional heat transfer equation using this calculated heat flux Executed.

  The quality index processing unit 4 determines the quality of the slab 10 that is deteriorated by being affected by the center segregation of the slab 10 due to unsteady bulging. Specifically, the quality index processing unit 4 acquires the solidification completion position of the slab 10 currently being continuously cast from the secondary cooling calculation unit 3. Further, the quality index processing unit 4 requires a torque signal indicating the pinch roll torque required for drawing and conveying the slab 10 from one or more pinch rolls (pinch rolls 16 to 19 in the present embodiment) in the continuous casting machine 11. Collect minutes. The quality index processing unit 4 is a solidification completion position calculated by the secondary cooling calculation unit 3 from one or more pinch rolls (for example, pinch rolls 16 to 19) of the continuous casting machine 11 that draws the slab 10 from the mold 12. The pinch roll located on the upstream side in the casting direction of the slab 10 is selected as the target pinch roll. At this time, the quality index processing unit 4 is located upstream of the solidification completion position by the secondary cooling calculation unit 3 in the casting direction of the slab 10 and continuously from one or more pinch rolls of the continuous casting machine 11. It is desirable to select the pinch roll constituting the light pressure lower belt 20 of the casting machine 11 as the target pinch roll.

Further, the quality index processing unit 4 performs frequency analysis on the torque signal collected from the target pinch roll selected as described above, and thereby acquires each frequency component of the torque signal of the target pinch roll. Next, the quality index processing unit 4 uses the frequency and intensity of each frequency component of the torque signal acquired by this frequency analysis, and the current operating conditions of the continuous casting machine 11 acquired from the operating computer 5 (for example, currently in continuous casting). The unsteady bulging of the slab 10 currently being continuously cast is detected on-line using the slab 10 casting speed and the like. Subsequently, the quality index processing unit 4 performs casting that is currently being continuously cast based on the frequency components resulting from the unsteady bulging of the slab 10 among the frequency components of the torque signal acquired as described above. The quality index of the piece 10 is determined online. At this time, the quality index processing unit 4 sets the weight of the influence of unsteady bulging on the center segregation of the slab 10, sets the solidification completion position of the slab 10 and the installation position of the selected pinch roll (that is, the pinch roll position P). _The above-mentioned weighting is changed according to the distance to _m ), and the quality index of the slab 10 currently being continuously cast is determined.

  In the present embodiment, the above-described quality index is an index indicating deterioration in quality of the slab 10 due to the influence of center segregation generated in the slab 10. The quality index processing unit 4 sequentially determines the quality index as described above for each position in the longitudinal direction of the slab 10. In this way, the quality index processing unit 4 determines the quality of the slab 10 that deteriorates due to the influence of center segregation due to unsteady bulging for each longitudinal position of the slab 10. The quality index processing unit 4 transmits the quality index for each longitudinal position of the slab 10 to the operation computer 5 as a quality determination result for each slab of the slab 10.

  The operation computer 5 has a function as a quality control unit that manages the quality index of the slab 10 determined by the quality determination device 2 for each slab and estimates the quality of each slab of the slab 10. Specifically, the operation computer 5 is configured using a process computer or the like that manages the operation of the continuous casting machine 11. The operation computer 5 sequentially receives the quality index for each longitudinal position of the slab 10 determined by the quality index processing unit 4 from the quality determination device 2. The operation computer 5 cuts the slab 10 at predetermined lengths along the longitudinal direction of the slab 10 corresponding to the received quality index based on the operation conditions such as the target slab size. Replaced with a manufactured slab. Next, the operation computer 5 associates such a slab of the slab 10 with a quality index at the longitudinal position of the slab 10 to be replaced with this slab. The operation computer 5 stores and manages these associated slabs and quality indicators as a part of the slab quality data 5a indicating the quality indicators for each slab of the slab 10. Each time the operation computer 5 receives the quality index for each longitudinal position of the slab 10 by the quality index processing unit 4 from the quality determination device 2, the operation index management process for each slab described above is executed.

  Moreover, the computer 5 for operation estimates the quality for every slab of the slab 10 based on the quality parameter | index managed for every slab as mentioned above. At this time, the operation computer 5 sets a threshold (hereinafter referred to as a quality threshold) regarding the degree of central segregation of the slab to be estimated based on the information input by the input unit 6. Next, the operation computer 5 reads the quality index of the slab to be estimated from the slab quality data 5a, and refers to the quality correlation data 5b, and based on the read quality index and the quality threshold, Estimate the quality of the slab (eg quality).

  Here, the quality correlation data 5b includes a value indicating the degree of center segregation of the slab 10 that adversely affects the quality of each slab manufactured by cutting the slab 10 (hereinafter referred to as a center segregation value), and a slab. It is data which shows the correlation with the quality index managed for every 10 slabs. The quality correlation data 5b can be created using, for example, past operation performance data of the continuous casting machine 11, inspection results of center segregation, and the like. The quality correlation data 5b is stored in advance in the operation computer 5. Using the quality correlation data 5b, the operation computer 5 converts the quality index of the quality estimation target slab into a center segregation value, and compares the center segregation value with a quality threshold value. As a result of this comparison processing, when the center segregation value is equal to or higher than the quality threshold, the operation computer 5 estimates that the quality of the slab to be estimated is worse than required, and the center segregation value is less than the quality threshold. If it is, it is estimated that the quality of the quality estimation target slab is good (that is, the quality that satisfies the requirements).

  On the other hand, the operation computer 5 uses the secondary cooling calculation unit 3 and the quality index processing of the quality determination device 2 to obtain information necessary for secondary cooling calculation and quality index determination processing such as the current operating conditions of the continuous casting machine 11. Provided to part 4 as appropriate. For example, the current operating conditions of the continuous casting machine 11 provided from the operation computer 5 to the quality judgment device 2 include the casting speed of the slab 10 currently being continuously cast and the cooling for secondary cooling of the slab 10. Secondary cooling conditions such as the amount of water, slab dimensional information, and the like.

  The input unit 6 inputs various information related to the quality estimation of the slab. Specifically, the input unit 6 is configured by using an input device such as an input key or a mouse, and inputs information to the operation computer 5 in accordance with an input operation by an operator. The information input to the operation computer 5 by the input unit 6 includes, for example, information indicating the quality threshold value for each slab, information for instructing the start of quality estimation processing for each slab, and output of the quality estimation result for each slab. Information to be instructed, information for instructing the start or end of the quality index determination processing by the quality determination device 2, and the like.

  The output unit 7 outputs a quality estimation result for each slab by the operation computer 5. Specifically, the output unit 7 receives information indicating the quality estimation result for each slab from the operation computer 5 and outputs the quality estimation result for each slab based on the received information each time. The output unit 7 may be a display device that displays the quality estimation result for each slab to be output on a screen, or a printer that prints the quality estimation result for each slab to be output on a print medium such as paper. It may be present or a combination thereof.

(Slab quality estimation method)
Next, the slab quality estimation method according to the embodiment of the present invention will be described. FIG. 3 is a flowchart showing an example of the slab quality estimation method according to the embodiment of the present invention. In the slab quality estimation method according to the present embodiment, the slab quality estimation device 1 shown in FIG. 1 appropriately performs the processing steps of steps S101 to S108 shown in FIG. The quality of each slab is estimated online during operation of the continuous casting machine 11.

  In detail, as shown in FIG. 3, the slab quality estimation device 1 first of the slab 10 that is continuously cast by being drawn from the mold 12 while solidifying the molten steel 10 a injected into the mold 12 of the continuous casting machine 11. The solidification completion position is calculated (step S101).

In step S <b> 101, the secondary cooling calculation unit 3 acquires necessary information such as the casting speed of the slab 10 currently being continuously cast and the amount of cooling water for secondary cooling from the operation computer 5 by the continuous casting machine 11. Next, the secondary cooling calculation unit 3 performs on-line secondary cooling calculation for continuous casting of the slab 10 in the operating continuous casting machine 11 using the information acquired from the operation computer 5. Secondary cooling calculating unit 3, based on the results of such secondary cooling calculations, to calculate the coagulation completion position P _CE of the slab 10 currently continuous casting. Thereafter, the secondary cooling calculation unit 3 transmits the calculated solidification completion position P _CE to the quality index processing unit 4.

After executing step S101, the slab quality estimation apparatus 1 determines the solidification completion position P _CE calculated by the secondary cooling calculation unit 3 from one or more pinch rolls of the continuous casting machine 11 that pulls the slab 10 from the mold 12 _. The pinch roll located on the upstream side in the casting direction of the slab 10 is selected (step S102).

In step S <b> 102, the quality index processing unit 4 acquires the solidification completion position P _CE calculated in step S <b> 101 described above from the secondary cooling calculation unit 3. Then, the quality index processing unit 4, selected from among the one or more pinch roll continuous casting machine 11, the pinch roll located upstream of the casting direction of the cast piece 10 than the freezing completion position P _CE as noted pinch rolls To do. At this time, the quality indicator processing unit 4, one or more from among the pinch rolls, the solidification completion position P _CE positioned on the upstream side of the casting direction of the cast piece 10 than to and continuous caster 11 light of the continuous caster 11 The pinch roll that constitutes the rolling belt 20 is selected as the target pinch roll.

Specifically, when the solidification completion position P _CE is a position downstream of the pinch roll position P _{4 in the} casting direction, the quality index processing unit 4 pinches the pinch rolls 16 to 19 in the light pressure lower belt 20 as the target pinch. Select as a role. When the solidification completion position P _CE is a position between the pinch roll positions P ₃ and P ₄ , the quality index processing unit 4 selects the pinch rolls 16 to 18 in the light pressure lower belt 20 as the target pinch roll. When the solidification completion position _PCE is a position between the pinch roll positions P ₂ and P ₃ , the quality index processing unit 4 selects the pinch rolls 16 and 17 in the light pressure lower belt 20 as the target pinch roll. When the solidification completion position P _CE is a position between the pinch roll positions P ₁ and P ₂ , the quality index processing unit 4 selects the pinch roll 16 in the light pressure lower belt 20 as the target pinch roll.

That is, in step S102, the quality index processing unit 4 selects the torque signal acquired from the above-described attention pinch roll from the torque signals acquired from one or more pinch rolls of the continuous casting machine 11. The reason why the quality index processing unit 4 selects the torque signal of the pinch roll of interest located upstream of the solidification completion position _{PCE in the} casting direction (on the mold 12 side) as described above is the quality of the slab 10 slab position upstream of the casting direction than the unsteady bulging solidification completion position P _CE to cause the occurrence of adverse effects center segregation, because particularly occurs at slab position coagulation end.

  After executing step S102, the slab quality estimation device 1 performs frequency analysis on the torque signal of the pinch roll selected in step S102 described above (ie, the pinch roll of interest), and acquires each frequency component of the torque signal of the pinch roll of interest. (Step S103).

In step S103, the quality indicator processing unit 4, the pinch roll located upstream of the casting direction than the freezing completion position P _CE of pinch rolls 16 to 19, i.e., collects the torque signal from the target pinch rolls. At this time, the quality index processing unit 4 collects a torque signal tracked in the longitudinal direction of the slab 10 currently being continuously cast. That is, after the slab position (longitudinal position of the slab 10) of the slab 10 that is a quality determination target passes through the installation position of the target pinch roll, the quality index processing unit 4 Torque signals are collected for the time required for frequency analysis. Next, the quality index processing unit 4 performs frequency analysis on the torque signal collected from the pinch roll of interest in this way using a technique such as fast Fourier transform (FFT). Thereby, the quality parameter | index process part 4 acquires each frequency component of the torque signal of an attention pinch roll.

  After executing step S103, the slab quality estimation apparatus 1 determines whether or not unsteady bulging has occurred in the slab 10 currently being continuously cast (step S104). In step S104, the quality index processing unit 4 determines whether or not unsteady bulging has occurred in the slab 10 currently being continuously cast based on the frequency and intensity of each frequency component acquired by the frequency analysis in step S103 described above. Judge whether or not.

Specifically, in step S104, the quality index processing unit 4 firstly obtains the casting speed V [m / min] of the slab 10 currently being continuously cast obtained from the operation computer 5 and the roll interval D of the pinch roll of interest. _m [mm] is used to calculate the unsteady bulging frequency F [Hz] based on the following equation (1).

F [Hz] = V [m / min] / (D _m [mm] × 60 × 0.001) (1)

The unsteady bulging frequency F expressed by the equation (1) is a frequency of torque fluctuations generated in the pinch roll of interest (for example, at least one of the pinch rolls 16 to 19) due to unsteady bulging of the slab 10. . The roll interval D _m is the interval between the pinch roll of interest and the support roll located immediately before it. For example, when the target pinch rolls are pinch rolls 16, roll distance D _m will interval (roll distance D ₁₎ between the pinch roll 16 and the immediately preceding support roll 15 shown in FIG. When the pinch roll of interest is the pinch roll 17, the roll interval D _m is the interval between the pinch roll 17 shown in FIG. 2 and the support roll 15 just before that (roll interval D ₂ ). If attention pinch rolls are pinch rolls 18, roll distance D _m will interval (roll distance D ₃₎ of the pinch rolls 18 and the immediately preceding support roll 15 shown in FIG. When the pinch roll of interest is the pinch roll 19, the roll interval D _m is the interval between the pinch roll 19 shown in FIG. 2 and the support roll 15 just before that (roll interval D ₄ ).

  Next, the quality index processing unit 4 sets an unsteady bulging frequency range (F ± X [Hz]) based on the calculated unsteady bulging frequency F and a preset determination threshold value X [Hz]. Note that the determination threshold value X is desirably set within a range of 0.01 [Hz] to 0.05 [Hz], for example. The quality index processing unit 4 has a frequency within the unsteady bulging frequency range (F ± X [Hz]) among the frequency components acquired by the frequency analysis described above for each pinch roll of interest and is set in advance. It is determined whether or not there is a frequency component that satisfies a condition of having an intensity equal to or greater than the intensity threshold Y (hereinafter referred to as an unsteady bulging condition).

  When there is a frequency component satisfying the unsteady bulging condition in each frequency component of the pinch roll of interest, the quality index processing unit 4 converts the frequency component satisfying the unsteady bulging condition into a frequency component resulting from the unsteady bulging condition. Choose as. At this time, when there are a plurality of frequency component peaks satisfying the unsteady bulging condition in each frequency component of one focused pinch roll, the quality index processing unit 4 has the highest intensity among the peaks of the plurality of frequency components. Choose a larger one. In this way, the quality index processing unit 4 selects a frequency component due to unsteady bulging for each pinch roll of interest (for example, for each of the pinch rolls 16 to 19).

  When the frequency component resulting from unsteady bulging is selected as described above, the quality index processing unit 4 determines that unsteady bulging has occurred in the slab 10 currently being continuously cast. The quality index processing unit 4 detects the unsteady bulging of the slab 10 online during operation of the continuous casting machine 11 based on the result of the determination process.

  When unsteady bulging has occurred (step S104, Yes), the slab quality estimation device 1 performs unsteady bulging of the slab 10 currently being continuously cast among the frequency components of the pinch roll of interest acquired in step S103 described above. Based on the resulting frequency component, a quality index indicating deterioration in quality of the slab 10 due to the influence of the center segregation of the slab 10 is determined (step S105).

In step S105, the quality index processing unit 4 determines the quality index of the slab 10 currently being continuously cast based on the frequency component of the torque signal for each pinch roll of interest caused by the unsteady bulging detected in step S104 described above. Determine online. At this time, the quality index processing unit 4 sets the weight of the influence of unsteady bulging on the center segregation of the slab 10. Quality indicator processor 4, according to the distance between the installation position of interest pinch rolls selected by solidification completing position P _CE and step S102 of calculating (ie pinch roll position P _m) in step S101, by changing the weighting, The quality index of the slab 10 currently being continuously cast is determined.

Specifically, the quality index processing unit 4 includes the weighting coefficient α _m indicating the weighting described above, the intensity E _m of the frequency component due to unsteady bulging selected for each target pinch roll in step S104, and the specific pinch roll. using the quality adjustment coefficient B _m of, based on the following equation of a linear sum (2), calculates a quality index Q of the slab 10 currently continuous casting.

Q = Σ (α _m × E _m × B _m ) (2)

For example, when the pinch rolls of interest are the pinch roll 17 (m = 2) and the pinch roll 18 (m = 3) shown in FIGS. 1 and 2, the quality index Q is a quality index (α ₂₎ corresponding to the pinch roll 17. × E ₂ × B ₂ ) and a quality index (α ₃ × E ₃ × B ₃ ) corresponding to the pinch roll 18.

In the equation (2), the weight coefficient alpha _m is a coefficient which varies according to the distance between the pinch roll position P _m of interest pinch rolls and the solidification completion position P _CE in step S101. In the present embodiment, the weighting coefficient α _m is expressed by the following equation (3) using a predetermined position adjustment coefficient A or the like.

α _m = 1 / (P _CE −A−P _m ) (3)

Here, the center segregation to deteriorate the quality of the slab 10 is offset slightly to the upstream side of the casting direction of the cast piece 10 than the freezing completion position P _CE (e.g. coagulation factor of the slab 10 is 0.3 or more, It is most affected by unsteady bulging at the slab position of 0.8 or less. The degree of influence of unsteady bulging on such center segregation decreases as the position of unsteady bulging in the slab 10 is displaced upstream in the casting direction.

The quality index processing unit 4 uses a weighting factor α _m that increases with a decrease in the distance between the coagulation completion position P _CE and the pinch roll position P _m as expressed in Expression (3), and is expressed in Expression (2). The quality index Q is calculated as follows. That is, the quality indicator processing unit 4, as noted pinch roll closer to the solidification completing position P _CE sets the weighted so weight is heavy, according to the distance between the solidification completion position P _CE and pinch roll position P _m, the The quality index Q is calculated by changing the weight. Thereby, the quality index processing unit 4 can calculate the quality index Q with high accuracy in consideration of the degree of influence of unsteady bulging on the center segregation described above.

  In step S <b> 105, the quality index processing unit 4 executes the arithmetic processing based on the above-described equations (2) and (3) for each longitudinal position of the slab 10. Accordingly, the quality index processing unit 4 calculates the quality index Q for each longitudinal position of the slab 10 currently being continuously cast. The quality index processing unit 4 uses the calculated quality index Q as an index indicating the quality of each longitudinal position of the slab 10 which is deteriorated by being affected by the center segregation caused by unsteady bulging. Judge online. Thereafter, the quality index processing unit 4 transmits the quality index Q for each longitudinal position of the slab 10 determined as described above to the operation computer 5.

  After executing step S105, the slab quality estimation device 1 manages the slab manufactured by cutting the slab 10 in association with the quality index Q in step S105 (step S106). In step S <b> 106, the operation computer 5 acquires the quality index Q determined in step S <b> 105 described above from the quality index processing unit 4 of the quality determination device 2. Next, the operation computer 5 replaces the longitudinal position of the slab 10 corresponding to the acquired quality index Q with a slab manufactured from the slab 10. Subsequently, the operation computer 5 associates the slab of the slab 10 with the quality index Q at the longitudinal position of the slab 10 to be replaced with the slab. Thereafter, the operation computer 5 stores and manages these associated slabs and the quality index Q as a part of the slab quality data 5a.

After executing step S106, the slab quality estimation device 1 estimates the quality of each slab of the slab 10 based on the quality index Q managed for each slab as described above (step S107). In step S <b> 107, the operation computer 5 sets a quality threshold regarding the degree of center segregation of the slab to be estimated based on the information input by the input unit 6. Next, the operation computer 5 reads the quality index Q of the slab to be estimated from the slab quality data 5a, and converts the read quality index Q into a center segregation value C / C ₀ based on the quality correlation data 5b. Subsequently, the operation computer 5 compares the center segregation value C / C ₀ obtained by this conversion with the quality threshold set as described above. The operation computer 5 estimates the quality of the quality estimation target slab based on the result of the comparison process.

Specifically, when the center segregation value C / C ₀ is equal to or higher than the set quality threshold value, the operation computer 5 estimates that the quality of the quality estimation target slab is worse than required. On the other hand, when the center segregation value C / C ₀ is less than the set quality threshold, the operation computer 5 estimates that the quality of the slab to be estimated is good (that is, quality that satisfies the request).

  Thereafter, the operation computer 5 transmits the slab quality estimation result described above to the output unit 7. The output unit 7 receives the quality estimation result of the slab from the operation computer 5 and outputs the received quality estimation result as information indicating the quality estimation result for each slab of the slab 10.

  After executing step S107, the slab quality estimation apparatus 1 determines whether or not the quality determination has been completed for the slab 10 currently being continuously cast (step S108). In step S <b> 108, the operation computer 5 determines whether the quality determination has been completed over the entire area of the slab 10 based on the input information from the input unit 6 or the current operation status of the continuous casting machine 11. Determine whether. When the quality determination is completed (Yes at Step S108), the slab quality estimation apparatus 1 ends this processing. When the quality determination is not yet completed (No at Step S108), the slab quality estimation apparatus 1 returns to Step S101 described above. Each process after step S101 is repeated as appropriate.

  On the other hand, if unsteady bulging has not occurred in step S104 described above (No in step S104), the slab quality estimation apparatus 1 proceeds to step S106 described above, and executes each process after step S106. In this case, the quality index processing unit 4 does not execute the calculation process of the quality index Q based on the above-described equations (2) and (3), and is set in advance to a value smaller than the calculated value of this calculation process. The reference quality index may be determined as the quality index Q at the longitudinal position of the slab 10. Further, the operation computer 5 may manage such a reference quality index as a quality index Q for each slab of the slab 10.

(Example)
Next, examples of the present invention will be described. In this example, the slab quality estimation device 1 according to the embodiment of the present invention performs quality judgment for each slab of the slab 10 using a torque signal collected from the pinch roll of interest during the actual operation of the continuous casting machine 11. A specific example in the case of performing is shown. In the present embodiment, the slab quality estimation device 1 performed quality determination for each slab of the slab 10 using the three pinch rolls 16 to 18 in the light pressure lower belt 20 of the continuous casting machine 11.

As a condition in the present embodiment, the meniscus distance L ₁ that determines the installation position (pinch roll position P ₁ ) of the pinch roll 16 is 24 [m]. The meniscus distance L ₂ that determines the installation position (pinch roll position P ₂ ) of the pinch roll 17 was 26 [m]. The meniscus distance L ₃ that determines the installation position of the pinch roll 18 (pinch roll position P ₃ ) was 28 [m]. Hereinafter, in the present embodiment, among these three pinch rolls 16 to 18, the pinch roll 17 positioned between the most upstream pinch roll 16 and the most downstream pinch roll 18 is appropriately referred to as an “intermediate pinch roll”. Called. On the other hand, each torque of the pinch rolls 16 to 18 was set to a steady state where there is no influence of the change in the casting speed V during continuous casting of the cast piece 10.

In the present embodiment, the secondary cooling calculation unit 3 of the slab quality estimation apparatus 1 executes the process of step S101 shown in FIG. 3, and as a result, the distance along the casting direction from the meniscus 10b of the molten steel 10a in the mold 12 is as follows. It was calculated 29.0 [m] become solidified completion position P _CE. The solidification completion position P _CE was a position between the pinch roll position P ₃ and the pinch roll position P ₄ shown in FIG. In response to such a result, the quality index processing unit 4 of the slab quality estimation apparatus 1 executes the process of step S102 shown in FIG. 3, and thereby, on the upstream side in the casting direction as compared with the solidification completion position _PCE. Positioned pinch rolls 16-18 were selected as the pinch rolls of interest.

  Next, in step S103 shown in FIG. 3, the quality index processing unit 4 collected torque signals for the time required for frequency analysis from each of the pinch rolls 16 to 18 as the target pinch rolls. FIG. 4 is a diagram showing trend data of torque of each pinch roll to be noted in the present embodiment. The torque trend data shown in FIG. 4 is data processed so that the average becomes zero. In this embodiment, torque trend data corresponding to the torque signal collected from the most upstream pinch roll 16 is shown by the solid line in FIG. The trend data of the torque corresponding to the torque signal collected from the intermediate pinch roll 17 was shown by the broken line in FIG. The trend data of the torque corresponding to the torque signal collected from the most downstream pinch roll 18 was shown by the dotted line in FIG.

  After collecting torque signals representing torque change trends (time-dependent changes) as shown in FIG. 4, the quality index processing unit 4 performs frequency analysis of the collected torque signals for each of the pinch rolls 16 to 18. FIG. 5 is a diagram illustrating an example of a frequency analysis result of the torque signal collected from the most upstream pinch roll among the target pinch rolls in the present embodiment. FIG. 6 is a diagram illustrating an example of a frequency analysis result of a torque signal collected from an intermediate pinch roll among the target pinch rolls in the present embodiment. FIG. 7 is a diagram illustrating an example of a frequency analysis result of a torque signal collected from the pinch roll at the most downstream of the target pinch rolls in the present embodiment.

  In step S103, the quality index processing unit 4 performs frequency analysis on the torque signal from the most upstream pinch roll 16, and as a result, obtains each frequency component indicating the correlation between frequency and intensity as shown in FIG. Further, as a result of frequency analysis of the torque signal from the intermediate pinch roll 17, the quality index processing unit 4 obtains each frequency component indicating the correlation between the frequency and the intensity as shown in FIG. As a result of frequency analysis of the torque signal from 18, each frequency component indicating the correlation between frequency and intensity as shown in FIG. 7 was obtained.

In subsequent step S104, the quality indicator processing unit 4, with each roll distance D _m of the casting speed V and the pinch rolls 16 to 18, based on the above equation (1), non-stationary for each of the pinch rolls 16 to 18 The bulging frequency F was calculated. As a result, the unsteady bulging frequency F of each of the pinch rolls 16 to 18 was 0.10 [Hz]. The quality index processing unit 4 uses the unsteady bulging frequency F and a preset determination threshold value X (= 0.02 [Hz]) to determine the unsteady bulging frequency range (0.1 [Hz] ± 0.02). [Hz]) was set. In the present embodiment, the quality index processing unit 4 has a frequency within the unsteady bulging frequency range (0.1 [Hz] ± 0.02 [Hz]) and has a preset intensity threshold Y (= 0). .4) Unsteady bulging conditions were set to have the above strength.

  Next, the quality index processing unit 4 determines whether or not each frequency component (see FIG. 5) of the pinch roll 16 has a frequency component that satisfies the unsteady bulging condition of this embodiment. As a result, none of the frequency components of the pinch roll 16 satisfied the unsteady bulging condition of this example. Therefore, the quality index processing unit 4 excludes each frequency component of the pinch roll 16 from processing.

  Further, the quality index processing unit 4 determines whether or not each frequency component (see FIG. 6) of the pinch roll 17 has a frequency component that satisfies the unsteady bulging condition of this embodiment. As a result, the quality index processing unit 4 selects a frequency component showing a frequency peak satisfying the unsteady bulging condition of the present embodiment from the frequency components of the pinch roll 17 as a frequency component due to unsteady bulging. Specifically, as shown in FIG. 6, a frequency component having a frequency of 0.10 [Hz] and an intensity of 0.55 was selected as a frequency component due to unsteady bulging. Furthermore, the quality index processing unit 4 determines whether or not each frequency component (see FIG. 7) of the pinch roll 18 has a frequency component that satisfies the unsteady bulging condition of this embodiment. As a result, the quality index processing unit 4 selects a frequency component showing a frequency peak that satisfies the unsteady bulging condition of the present embodiment from among the frequency components of the pinch roll 18 as a frequency component due to unsteady bulging. Specifically, as shown in FIG. 7, a frequency component having a frequency of 0.10 [Hz] and an intensity of 0.79 was selected as a frequency component due to unsteady bulging. With such a result, unsteady bulging of the slab 10 currently being continuously cast was detected online.

Thereafter, in step S105, the quality index processing unit 4 determines the quality index Q of the slab 10 currently being continuously cast based on the frequency components caused by unsteady bulging corresponding to the pinch rolls 17 and 18 described above. Calculated. In this embodiment, the position adjustment coefficient A is 0.5 [−], and the quality adjustment coefficients B ₂ and B ₃ specific to the pinch rolls 17 and 18 are both 1 [−]. Further, as described above, the intensity E ₂ of the frequency component due to unsteady bulging corresponding to the pinch roll 17 is 0.55, and the intensity E ₃ of the frequency component due to unsteady bulging corresponding to the pinch roll 18 is 0. 79. The quality index processing unit 4 calculates 1.80 [−] as the quality index Q as a result of performing the arithmetic processing based on the above-described equations (2) and (3) using these parameters. In this case, the quality index processing unit 4 determines that the quality index Q for each slab in the slab 10 currently being continuously cast is 1.80 [-].

In the present embodiment, the calculation process of the quality index Q as described above is executed for a plurality of cases, and the obtained quality index Q and the center segregation _value C / C ₀ indicating the degree of center segregation of the slab 10 are obtained. The correlation was investigated. FIG. 8 is a diagram showing an example of the correlation between the slab quality index and the center segregation value in the present embodiment. As shown in FIG. 8, in this embodiment, there is a nearly linear correlation between the quality index Q determined for each slab of the slab 10 and the center segregation value C / C ₀ of the slab 10. I was able to confirm. Such a correlation between the quality index Q and the center segregation value C / C ₀ can be obtained even outside the range of the quality index Q shown in FIG. 8 by a method such as extrapolation. From this, the quality index Q according to the present invention is practical as an index for determining and estimating the quality of each slab of the slab 10 currently being continuously cast during online operation of the continuous casting machine 11. I can say that.

  As described above, in the embodiment of the present invention, the solidification completion position of the slab currently being continuously cast is calculated by the continuous casting machine, and the solidification is completed from one or more pinch rolls in this continuous casting machine. Select the target pinch roll located upstream of the casting direction from the position, analyze the frequency of the torque signal of the selected target pinch roll, acquire each frequency component of the torque signal for each target pinch roll, Based on the frequency component due to unsteady bulging among the frequency components, the quality index indicating the deterioration of the quality of the slab due to the influence of center segregation is determined. Moreover, the slab manufactured by cutting a continuously cast slab and the above-described quality index are managed in association with each other, and the quality of each slab is estimated based on the managed quality index.

  For this reason, for each longitudinal position in the slab currently being continuously cast, an indicator of quality deterioration of the slab due to the effect of center segregation due to unsteady bulging, i.e., a quality index, is It can be determined online during the operation of the continuous caster in operation. Thus, by using the quality index obtained by online determination, the degree of central segregation that adversely affects the quality of the slab can be managed online for each slab. As a result, there is no need for an unsteady bulging detection sensor (for example, eddy current sensor) with environmental measures to withstand the hot environment, and the correlation between the quality index based on the torque signal from the existing pinch roll and the degree of central segregation Based on the above, the quality of each slab affected by the center segregation of the slab can be estimated simply and inexpensively online during operation of the continuous casting machine in a hot environment.

In the above-described embodiment, the slab is based on the comparison result between the center segregation value C / C ₀ corresponding to the quality index Q for each slab of the slab 10 and the quality threshold value input by the input unit 6. Although the quality for every 10 slabs was estimated, the present invention is not limited to this. In the present invention, the quality threshold value may be sequentially input from the external management computer or the like to the operation computer 5 as a part of order information related to the continuous casting process. The operation computer 5 automatically and sequentially estimates the quality of each slab of the slab 10 using the acquired quality index Q and the quality threshold value in the order information every time the quality index Q is received from the quality judgment device 2. May be. In this case, the slab quality estimation device 1 may not include the input unit 6.

  Moreover, in embodiment mentioned above, with respect to the continuous casting machine 11 with which the slab quality estimation apparatus 1 is applied, the cooling zones 21a-29a and 21b-29b divided | segmented into nine zones along a casting direction are provided. However, the present invention is not limited to this. The number of cooling zones (number of zones) of the continuous casting machine 11 depends on equipment configuration such as equipment dimensions of the continuous casting machine 11, casting dimensions and steel types of the slab 10 to be continuously cast, secondary cooling conditions of the slab 10, etc. May be set as appropriate. That is, in the present invention, the number of zones in the cooling zone of the continuous casting machine 11 is not particularly limited. Moreover, the number of pinch rolls installed in the cooling zone of the continuous casting machine 11 is not limited to the four described above, and may be one or more.

Furthermore, in the above-described embodiment, the roll interval D _m used for calculating the unsteady bulging frequency F based on the equation (1) is the interval between the pinch roll of interest and the support roll immediately before it. The present invention is not limited to this. In continuous casting machine 11, if the pinch rolls are installed side by side plurality casting direction without interposing support rolls, roll distance D _m may be an interval of interest pinch rolls and the immediately preceding pinch roll.

  Moreover, in embodiment mentioned above, although the torque signal was collected from all the pinch rolls 16-19 provided in the continuous casting machine 11, this invention is not limited to this. In the present invention, the torque signal may be collected from only one or more target pinch rolls located on the upstream side in the casting direction from the solidification completion position among all the pinch rolls provided in the continuous casting machine 11.

  Further, the present invention is not limited by the description and drawings constituting a part of the disclosure of the present invention according to the above-described embodiment or example, and the present invention is also configured by appropriately combining the above-described constituent elements. included. In addition, other embodiments, examples, operational techniques, and the like made by those skilled in the art based on the above-described embodiments are all included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Slab quality estimation apparatus 2 Quality determination apparatus 3 Secondary cooling calculation part 4 Quality index processing part 5 Operation computer 5a Slab quality data 5b Quality correlation data 6 Input part 7 Output part 10 Slab 10a Molten steel 10b Meniscus 11 Continuous casting machine 12 Mold 13 Tundish 14 Immersion nozzle 15 Support roll 16-19 Pinch roll 20 Light pressure lower belt 21a-29a, 21b-29b Cooling belt P ₀ reference position P ₁ -P ₄ pinch roll position

Claims (4)

A solidification completion position calculating unit for calculating a solidification completion position of a slab that is continuously cast by being drawn from the mold while solidifying molten steel injected into a mold of a continuous casting machine;
A pinch roll located upstream of the solidification completion position in the casting direction of the cast piece is selected from one or more pinch rolls of the continuous casting machine that pulls the cast piece from the mold, and the selected pinch roll is selected. The frequency signal of the torque signal of the roll is analyzed to obtain each frequency component of the torque signal, and the center of the slab is obtained based on the frequency component resulting from unsteady bulging of the slab among the obtained frequency components. A quality index processing unit for determining a quality index indicating the quality deterioration of the slab due to the effect of segregation,
Managing the slab manufactured by cutting the slab in association with the quality index, a quality management unit that estimates the quality of each slab based on the quality index,
Equipped with a,
The quality index processing unit sets the weight of the influence of unsteady bulging on the center segregation of the slab, and changes the weight according to the distance between the solidification completion position and the selected installation position of the pinch roll, A slab quality estimation apparatus characterized by determining the quality index .   The quality index processing unit is located on the upstream side in the casting direction of the slab from the solidification completion position among the one or more pinch rolls and constitutes the light pressure lower belt of the continuous casting machine The slab quality estimation apparatus according to claim 1, wherein the slab quality estimation apparatus is selected. A solidification completion position calculating step for calculating a solidification completion position of a slab that is continuously cast by being drawn from the mold while solidifying molten steel injected into a mold of a continuous casting machine;
A selection step of selecting a pinch roll located upstream of the solidification completion position in the casting direction of the slab from one or more pinch rolls of the continuous casting machine that pulls out the slab from the mold; and
A frequency analysis step of performing frequency analysis on the torque signal of the pinch roll selected in the selection step and obtaining each frequency component of the torque signal;
Based on the frequency component resulting from unsteady bulging of the slab out of the frequency components acquired by the frequency analysis step, a quality index indicating quality deterioration of the slab due to the influence of center segregation of the slab A quality index determination step for determining;
A management step for managing the slab manufactured by cutting the slab in association with the quality index,
A quality estimation step of estimating the quality of each slab based on the quality index;
Only including,
The quality index determination step sets the weight of the influence of unsteady bulging on the center segregation of the slab, changes the weight according to the distance between the solidification completion position and the selected installation position of the pinch roll, A slab quality estimation method, wherein the quality index is determined . The selecting step selects the pinch rolls that are located upstream of the solidification completion position in the casting direction of the cast slab and that constitute the light reduction belt of the continuous casting machine from the one or more pinch rolls. The slab quality estimation method according to claim 3 , wherein:

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