JP2020011255A - Casting state determination device, casting state determination method, and program - Google Patents

Abstract

To precisely determine whether crack breakout is generated or not in a continuous casting process on-line.SOLUTION: A casting state determination device 100 determines whether the sign of crack breakout is generated or not using the correlation coefficient of the thickness of solidified shells 2 in the positions of two thermocouples 7 at different positions in a casting direction (solidified shell thickness correlation coefficient).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a casting state determination device, a casting state determination method, and a program, and is particularly suitable for use in detecting an operation abnormality related to crack breakout in a continuous casting process.

  FIG. 15 shows an example of an outline of a continuous casting facility. Molten steel produced by the converter and the secondary refining is put into a ladle 51 and poured into the mold 4 through a tundish 52. The molten steel in contact with the mold 4 is cooled and solidified, conveyed by a roll 54 while the casting speed is controlled, cut into an appropriate length by a gas cutting machine 55, and has a cross-sectional shape such as slab, bloom, billet and the like. Different slabs are produced.

FIG. 16 shows a cross section near the mold of the continuous casting facility. 1 is molten steel, 2 is a solidified shell, 3 is a mold flux layer, 4 is a mold, 5 is cooling water, and 6 is an immersion nozzle.
As shown in FIG. 16, in the continuous casting process, molten steel 1 is injected into mold 4 from immersion nozzle 6. The molten steel 1 injected into the mold 4 is cooled by the mold 4, and a solidified shell 2 is formed from the surface thereof and solidifies. Steel having a solidified shell 2 on the surface but not solidified inside is continuously drawn from the lower end of the mold 4. In the process of being pulled out of the mold 4 in this way, the steel is solidified to the inside by advancing the cooling of the steel by the secondary cooling portion (cooling water injected from the cooling spray) arranged below the mold 4. .

  As an operation trouble in such a continuous casting facility, there is an operation trouble called breakout. The breakout is an operation trouble in which a part of the solidified shell 2 breaks and molten steel flows into the continuous casting facility. Once a breakout occurs, it is necessary to stop the operation, remove the solidified steel that has flowed into the continuous casting facility, and repair the facility. Therefore, it takes a lot of time to recover the operation, and the loss is large.

As such a breakout, there is a breakable breakout. The cracking breakout is caused by the uneven thickness of the solidified shell 2 in the mold 4 (specifically, the solidification of the molten steel 4 is delayed in a region near the corner of the mold 4 so that the thickness of the solidified shell 2 is reduced. This is a breakout that occurs in a form in which the solidified shell 2 is broken in the vertical direction (casting direction) immediately below the mold 4 due to the thinning).
There is a technique described in Patent Literature 1 as a technique for predicting breakage breakout.
Patent Document 1 discloses that the casting speed is reduced when the fluctuation amount per unit time of the molten metal level (the height position of the surface of molten steel) near the short side of the mold 4 exceeds a predetermined upper limit. It is described.
In addition, Patent Document 2 discloses that a specific position of the solidified shell 2 moving in the casting direction in the mold 4 is a time change amount of a heat flux when passing through each position in the mold 4 where a thermocouple is embedded. It is described that the occurrence of a breakout is determined based on the product.

JP-A-4-143054 JP 2012-86249 A International Publication No. WO 2015/1155651

  However, the reason why the thickness of the solidified shell 2 becomes uneven in the mold 4 is not only due to the fluctuation of the molten metal level, but also the flow of the molten steel 1 in the mold 4 and the unevenness of the mold flux layer 3 (powder). It can also be caused by the following. Fluctuations in the level of the molten metal are merely information that indirectly indicate a sign of crack breakout. Therefore, it is not easy to accurately detect a sign of a breakable breakout with the technique described in Patent Document 1.

  In addition, the abnormal heat flux is caused not only by the uneven thickness of the solidified shell 3 in the mold 4 but also by the uneven flow of the molten steel 1 and the mold flux layer 3 (powder) in the mold 4. It can also occur due to such factors. Furthermore, heat flux is also merely information that indirectly indicates a sign of a breakable breakout. Therefore, even with the technique described in Patent Document 2, it is not easy to accurately detect a sign of a breakable breakout.

  The present invention has been made in view of the above problems, and has as its object to accurately and online predict whether or not a breakable breakout occurs in a continuous casting process. I do.

  The casting state determination device of the present invention is a casting state determination device that determines whether or not there is a sign of a breakable breakout in a continuous casting process, and includes a plurality of temperature measuring means embedded in a mold, Temperature acquisition means for acquiring temperatures measured by a plurality of temperature measurement means whose positions are different from each other, and using the temperatures acquired at a plurality of times within a predetermined time by the temperature acquisition means, to obtain a plurality of pieces in the casting direction. Solidified shell thickness deriving means for deriving the thickness of the solidified shell at each of a plurality of times within the predetermined time, and an index indicating a correlation between the thickness of the solidified shell at two positions in the casting direction. Correlation deriving means for determining whether or not there is a sign of the breakable breakout based on the index derived by the correlation deriving means. And wherein the Rukoto.

  The casting state determination method of the present invention is a casting state determination method for determining whether or not there is a sign of a breakable breakout in a continuous casting process, and includes a plurality of temperature measuring means embedded in a mold, A temperature acquisition step of acquiring a temperature measured by a plurality of temperature measurement means whose positions are different from each other, and using a temperature acquired at a plurality of times within a predetermined time by the temperature acquisition step, a plurality of pieces in the casting direction. A solidified shell thickness deriving step of deriving the thickness of the solidified shell at each of a plurality of times within the predetermined time, and an index indicating a correlation between the thickness of the solidified shell at two positions in the casting direction. A correlation deriving step of determining whether or not there is a sign of the breakable breakout based on the index derived in the correlation deriving step. And wherein the Rukoto.

  A program according to the present invention causes a computer to function as each unit of the casting state determination device.

  Advantageous Effects of Invention According to the present invention, it is possible to accurately predict online whether or not a breakable breakout occurs in a continuous casting process.

FIG. 1 is a diagram showing a part of a cross section near a mold of a continuous casting facility. FIG. 2 is a diagram illustrating an example of an embedding position in a casting direction of a thermocouple. FIG. 3 is a diagram illustrating an example of a state in which the mold is viewed from above. FIG. 4 is a diagram illustrating a first example of a functional configuration of the casting state determination device. FIG. 5 is a flowchart illustrating a first example of the casting state determination method. FIG. 6 is a diagram illustrating a first example of time-series data of the solidification shell thickness correlation coefficient. FIG. 7 is a diagram illustrating a second example of time-series data of the solidification shell thickness correlation coefficient. FIG. 8 is a diagram illustrating a third example of the time-series data of the solidification shell thickness correlation coefficient. FIG. 9 is a diagram illustrating a second example of a functional configuration of the casting state determination device. FIG. 10 is a flowchart illustrating a second example of the casting state determination method. FIG. 11 is a diagram illustrating a first example of a frequency distribution of a solidification shell thickness correlation coefficient. FIG. 12 is a diagram illustrating a second example of the frequency distribution of the solidification shell thickness correlation coefficient. FIG. 13 is a diagram illustrating a third example of the frequency distribution of the solidification shell thickness correlation coefficient. FIG. 14 is a diagram showing a modification of the frequency distribution of the solidification shell thickness correlation coefficient. FIG. 15 is a diagram illustrating an example of an outline of a continuous casting facility. FIG. 16 is a diagram showing a cross section near the mold of the continuous casting facility.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Inspiration>
As described above, it is not easy to accurately predict the occurrence of a breakable breakout even using an index such as a change in the level of the molten metal or a heat flux. Since the breakable breakout occurs due to the non-uniform thickness of the solidified shell 2, the present inventors predict that the occurrence of the breakable breakout is obtained by capturing the thickness of the solidified shell 2. Oriented and came up with the following ideas: That is, when the thickness of the solidified shell 2 is reduced in the region near the corner of the mold 4, the stress applied to the region of the solidified shell 2 having the small thickness is rapidly increased. It is considered that such a rapid change in stress causes a breakable breakout. Therefore, it is considered that when the distribution of the thickness of the solidified shell 2 in the casting direction (the height direction of the mold 4) rapidly changes, a breakable breakout occurs. Further, the solidified shell 2 moves from the top to the bottom in the casting direction. Therefore, at a certain time, the thickness of the solidified shell 2 located at the first position relatively upper in the casting direction moves to the second position relatively lower, and then moves to the second position at that time. It can be assumed that the thickness of the solidified shell 2 becomes a certain value. Therefore, the present inventors have determined at each time whether or not the thickness of the solidified shell 2 at a plurality of positions in the casting direction is correlated, thereby accurately detecting the sign of crack breakout online. Thought you could. Each embodiment of the present invention described below has been made under such an idea.

  In order to detect a sign of a breakable breakout under such an idea, it is necessary to derive the thickness of the solidified shell 2 at a plurality of positions in the casting direction online. The method of deriving the thickness of the solidified shell 2 online can be realized by a known technique as described in Patent Document 3, for example. Therefore, first, an example of a technique for online deriving the thickness of the solidified shell 2 will be described using the technique described in Patent Document 3 as an example.

<Method of estimating solidification state in mold 4>

  FIG. 1 is a diagram showing a part (right half excluding a submerged nozzle) of a cross section near a mold of a continuous casting facility. The solidified shell 2, the mold flux layer 3, and the heat conductor of the mold 4 exist between the molten steel 1 and the cooling water 5 for the mold 4. A plurality of thermocouples 7 as temperature measuring means are embedded in the mold 4 at different positions in the casting direction (the height direction of the mold 4, the z-axis direction). Further, a casting state determination device 100 functioning as a device for determining a casting state is provided. The casting state determination device 100 is realized by using, for example, an information processing device including a CPU, a ROM, a RAM, an HDD, and various interfaces, or dedicated hardware.

  A mathematical model used in the present embodiment will be described. In general, a mathematical model may be different depending on the simplification of a configuration that causes a phenomenon, and thus there are a plurality of options for expressing the same phenomenon. As shown in FIG. 1, the mathematical model used in the present embodiment includes two directions: a vertical direction on the inner wall surface of the mold (a width (casting width) direction of the mold 4 (x-axis direction)) and a casting direction (z-axis direction). This is a mathematical model representing a solidification heat transfer phenomenon in a range from a molten metal to a solidified shell 2, a mold flux layer 3, a mold 4, and cooling water 5 on a two-dimensional cross section composed of directions. Thus, an inverse problem described later is established, and the inverse problem can be numerically and approximately solved. Among the models that satisfy the above conditions, those that can be executed by a computer include a partial differential equation that combines Equations (1) to (5) representing the solidification heat transfer phenomenon in the mold 4 and a model that passes through the mold 4. There is a combination of equations (6) to (8) that express heat flux in different expressions.

Here, t is time. z is a coordinate in the casting direction where z = 0 is the molten steel surface level. x is a coordinate in the vertical direction of the inner wall surface of the mold, where x = 0 is the position of the inner wall surface of the mold 4. z _e is the position in the casting direction of the thermocouple 7 at the lowermost end of the thermocouples 7 embedded in the mold 4. c _s is the specific heat of the solidified shell 2, ρ _s is the density of the solidified shell 2, λ _s is the thermal conductivity of the solidified shell 2, and L is the latent heat of solidification. V _c is the casting speed. T ₀ is the temperature of the molten steel 1, T _s is the solidification temperature, T _m = T _m (t, z) is the temperature of the inner wall surface of the mold 4, and T = T (t, z, x) is the temperature of the solidification shell 2. is there. s = s (t, z) is the thickness of the solidified shell 2 (the length in the direction perpendicular to the inner wall surface of the mold 4 (x-axis direction, hereinafter referred to as the vertical direction of the mold inner wall surface as necessary)). α = α (t, z) is a heat transfer coefficient between the solidified shell 2 and the mold 4. β = β (t, z) is a heat transfer coefficient between the molten steel 1 and the solidified shell 2. q _out = q _out (t, z) is the heat flux passing through the mold 4. lambda _m is the thermal conductivity of the mold 4. d ₁ is the depth of embedding the thermocouple 7 from the inner wall surface of the mold 4 (the distance in the vertical direction of the inner wall surface of the mold), and d ₂ is the distance from the thermocouple 7 to the cooling water 5 in the vertical direction of the inner wall surface of the mold. h _w is the heat transfer coefficient between the mold 4 and the cooling water 5. T _c = T _c (t, z) is the temperature of the mold 4 at the embedding depth position of the thermocouple 7. T _w = T _w (t, z) is the temperature of the cooling water 5.

This mathematical model shows a state in the mold 4 where there is almost no temperature change in the horizontal direction parallel to the inner wall surface of the mold 4 and the heat flux in the casting direction in the solidified shell 2 is extremely small compared to the vertical direction in the mold inner wall surface. This is a combination of a model to simulate and a model to simulate the heat transfer phenomenon of the mold 4 having a high thermal conductivity. If α, β, and T _m are given by a profile method described later, an approximate solution of the temperature distribution T of the solidified shell 2 and the thickness s of the solidified shell 2 can be formed, and is sufficient for simulating the phenomenon. Accuracy and lighter numerical calculation load are compatible. From this feature, real-time calculation for solving an inverse problem described later can be performed.

Next, the derivation of an approximate solution of the mathematical model by the profile method will be described. The profile method is not a method of solving the target PDE itself, but a method of deriving some conditions that the solution of the PDE satisfies, and obtaining a solution that satisfies the conditions by restricting the profile. . Specifically, the following is performed. First, the variable conversion by variables (t, z) from equation (9), with (t _0, eta) to a new variable, converts expressions (1) to (5), (6) Eliminating α results in equations (10) to (14), respectively.

In Equations (10) to (14), the derivative of t ₀ does not appear, and hence, hereinafter, t ₀ is treated as a fixed value. Next, a function 利用 used in the profile method is defined by Expression (15).

  Differentiating Ψ with η and using equations (10) to (13), equation (16) representing the balance of heat flux is obtained.

  Equation (16) is obtained by differentiating both sides of equation (15) with η and substituting equation (17).

  Differentiating both sides of equation (13) with η yields equation (18). If there is a T that satisfies equations (10) and (13), the equality of equation (10) holds at the boundary. Therefore, when ∂T / ∂η and ∂s / ∂η are eliminated from Expression (18) using Expression (12), Expression (19) is obtained.

  In summary, Equations (20) to (26) are adopted as conditions that are satisfied by the approximate solution by the profile method.

  T is given by equation (27) so that the profile of T is quadratic with respect to x so that equation (25) is always satisfied.

Here, a = a (η) and b = b (η) are independent of x, and can be specifically obtained by substituting equation (27) into equations (22) and (24). When Expression (27) is differentiated with respect to x, Expression (28) is established, and Expression (22) and Expressions (24) to (29) are obtained. Therefore, it indicates that the heat flux goes from the molten steel 1 side to the solidified shell 2. Equations (30) and (31) are obtained under the condition of ∂T / ∂x | _{x = s} > 0.

  Further, since Expression (27) is integrated with respect to x, Expression (32) is obtained. By substituting Expressions (32), (31), and (30) into Expression (20), Expression (33) is obtained. obtain.

  On the other hand, when x = 0, Expression (31) and Expression (30) are substituted into Expression (27), Expression (34) is obtained.

By substituting equation (23) into equation (34) and rearranging by T | _{x = 0} − _Tm , equation (35) is obtained.

However, A ₂ , A ₁ , and A ₀ are given by equations (36), (37), and (38), respectively.

Considering that become _{x = 0 = T s, T} | | T if s = 0 in equation (34) of the two solutions of equation (35) about _{x = 0,} is given by equation (39) T | _{x = 0} satisfies the equations (34) and (23) simultaneously.

  In summary, the approximate solution by the profile method satisfies Expressions (40) to (44).

However, A ₂ , A ₁ , and A ₀ in Expression (41) are given by Expressions (36) to (38). If s satisfying Expressions (40) to (44) can be formed, q _out can be obtained from Expression (42). Therefore, it can be seen that T is determined by Expression (27) from Expressions (30) and (31), and that Expressions (20) to (26) are satisfied. Therefore, if s satisfying Expressions (40) to (44) is obtained, an approximate solution by the profile method can be constructed. This can be obtained numerically by differentiating equation (43). Specifically, it is as follows. Let c _s , ρ _s , λ _s , L, T ₀ , and T _s be known constants. Regarding η, the calculation points are η ₀ = 0, η _i = η _i-1 + dη (dη> 0, i = 1, 2, , ···, n), and _{η n = z e / V c} . Assuming that α, β, and T _m are given by η = η _i , let α _i , β _i , and T _m , _i be respectively. Expression (43) is differentiated by the Euler method, and an approximate value of Ψ (η _i ) is represented by Ψ _i , as shown in Expression (45).

In this way, the approximate value s _i of s (η _i ) can be calculated recursively as shown below. First, s ₀ = 0 from equation (40), and Ψ ₀ = 0 from equation (44). Next, when s _i and Ψ _i are given, α, β, T _m , and s in equations (36) to (38) are α _i , β _i , T _m , _i , and s _{i, respectively.} Is substituted, T | _{x = 0} is obtained from equation (41), q _out is obtained from equation (42), and Ψ _{i + 1} is obtained from equation (45). Next, Ψ _{i + 1} and β _{i + 1} are substituted for Ψ and β in equation (44), and q _out obtained in equation (42) is substituted for q _out to solve for s. _{i + 1} . This method from s _i and [psi _i s _{i + 1} and [psi _{i + 1} is obtained. For this reason, it is possible to define a posteriori s _i.

_{Thus, c s, ρ s, λ} s, L, T 0, T s, V c is known, alpha, beta, given the T _m, the t ₀ as an arbitrary time, η∈ [0, On t = t ₀ + η and z = V _c · η for _ze / V _c ], T and s can be obtained using the profile method. Hereinafter, T and s obtained by the above-mentioned profile method are expressed as in equation (46), assuming that they depend on α, β, and T _m .

Next, formulation as an inverse problem and its solution will be described. The inverse problem is a general term for a problem that estimates the cause from the result. In the framework of a mathematical model representing the solidification heat transfer phenomenon in the mold 4, it is as follows. _{λ m, d 1, d 2} , h w, c s, ρ s, λ s, L, T 0, T s, T w, and V _c is _{known, z 1 ∈ (0, z} e) to , T ₁ −z ₁ / V _c during the casting time (t ₁ , z ₁ ), t ₀ = t ₁ −z ₁ / V _c and η∈ (0, z ₁ / V _c ) When T _c is obtained by interpolating the measured value of the thermocouple 7 embedded in the mold 4 on t = t ₀ + η and z = V _c · η, from the equations (7) and (8), Equations (47) and (48), which are the temperature of the inner wall surface of the mold 4 and the heat flux passing through the mold 4, can be calculated immediately.

  On the other hand, from Equations (6) and (7), the heat flux passing through the mold flux layer 3 can be expressed by Equation (49).

Therefore, for q _out given by equation (48), the problem of estimating α and β so that equation (49) holds is the inverse problem in the solidification heat transfer phenomenon in the mold 4. For q _out given by (48), the problem is reduced to solving a minimization problem by the least square method represented by equation (50).

Here, η ₀ = 0, η _i = η _i-1 + dη (dη> 0, i = 1, 2,..., N), and η _n = z ₁ / V _{c. Since prof} (α, β, T _m ) can be calculated numerically, the minimization problem can be solved by a general numerical solution method using a Gauss-Newton method or the like. Each time by solving the minimization problem of equation (50), alpha was determined at each location (t, z), beta, and T _m By substituting the equation (46), the solidified shell 2 of thickness and, The temperature of the solidified shell 2 is obtained. Therefore, the heat transfer coefficient α, the heat transfer coefficient β, the thickness s of the solidified shell 2, and the temperature T of the solidified shell 2, which are the estimated solidification state in the mold at (t, z), are obtained. In the following, the estimated solidification state in the mold will be represented by α _est (t, z), β _est (t, z), s _est (t, z), and T _est (t, z, x), respectively. I do.
As described above, the unsteady heat transfer inverse problem analysis is performed using the temperatures measured by the plurality of thermocouples 7 to derive the estimated solidification state in the mold. Here, the unsteady heat transfer inverse problem is based on the unsteady heat conduction equation governing the calculation region, and assuming that the temperature information inside the region to be a solution obtained by the unsteady heat conduction equation is known, It refers to the problem of estimating the boundary conditions or initial conditions for solving the unsteady heat conduction equation, such as the temperature, heat flux, and heat transfer coefficient. On the other hand, the transient heat transfer order problem refers to a problem of estimating temperature information inside a region based on a known boundary condition.
The above is the estimation method of the solidification state in the mold 4 described in Patent Document 3.

<Position of thermocouple 7>
The embedding position of the thermocouple 7 may be the embedding position of the thermocouple 7 conventionally used for monitoring the casting condition (the embedding position of the thermocouple 7 in the existing mold 4). However, when estimating the solidification state in the mold 4, it is preferable that the thermocouple 7 be embedded in the mold 4 as described below. Hereinafter, a suitable embedding position of the thermocouple 7 (temperature measuring means) when estimating the solidification state in the mold 4 will be described.

First, a preferred example of the embedding position of the thermocouple 7 in the casting direction (z-axis direction) will be described.
The embedding position of the thermocouple 7 in the casting direction (z-axis direction) is preferably determined as described in Patent Document 3. That is, an arbitrary position within a range defined by the molten metal surface level of the molten steel 1 assumed in the mold 4 and a position separated from the molten metal surface level by 95 mm downward in the casting direction is defined as P ₁ . An arbitrary position within a range of 220 mm or more and 400 mm or less below the molten steel surface in the casting direction in the casting direction is defined as P ₂ . In this way, a thermocouple 7 is provided at a defined 120mm following intervals in the casting direction in the range from position P ₁ to the position P ₂ is, and, at least one thermocouple from the lower end of the mold 4 in a position within 300 mm 7 Is preferably provided. The number of thermocouples 7 embedded in different positions in the casting direction is preferably 5 or more.

FIG. 2 shows a preferable thermocouple 7 (measurement) for the mold 4 in which the molten steel surface level assumed is 85 mm from the upper end of the mold 4 and the length (height) in the casting direction is 1090 mm. FIG. 4 is a diagram showing an example of a burying position in a casting direction of a heating means). In FIG. 2, the position indicated by ● indicates the embedding position of the thermocouple 7 in the casting direction.
The arrangement pattern 1 embeds the thermocouples 7 so that the interval is 120 mm within a range of 100 mm or more and 340 mm from the upper end of the mold 4, and embeds one thermocouple 7 at a position from the lower end of the mold 4 to 250 mm. Indicates that
The arrangement pattern 2 embeds the thermocouples 7 so that the interval becomes 120 mm in a range of 40 mm or more and 400 mm or less from the upper end of the mold 4, and also embeds two thermocouples 7 at a position from the lower end of the mold 4 to 250 mm. Indicates that
The arrangement pattern 3 embeds the thermocouples 7 so that the interval is 60 mm in a range of 100 mm or more and 340 mm from the upper end of the mold 4, and embeds one thermocouple 7 at a position from the lower end of the mold 4 to 250 mm. Indicates that
The arrangement pattern 4 embeds the thermocouples 7 so as to be unequally spaced at intervals of 120 mm or less within a range of 100 mm or more and 340 mm from the upper end of the mold 4, and one thermocouple at a position 250 mm from the lower end of the mold 4. 7 is buried.

The reason why the above-described embedding position is preferable is described in Patent Document 3, and a detailed description thereof is omitted here.
In a typical continuous casting machine, the surface of the molten steel 1, from the fact that by adjusting the injection amount of the molten steel 1 as the distance from the upper end of the mold 4 is positioned within 120mm above 80 mm, the position P ₁ If any position of 120 mm or more and 175 mm or less from the upper end of the mold 4 and the position P ₂ is any position of 340 mm or more and 480 mm or less from the upper end of the mold 4, even if the molten metal surface of the molten steel 1 is any position, This satisfies the preferred conditions for the buried position of the thermocouple 7 in the casting direction.

  Next, a preferred example of the embedding position of the thermocouple 7 on a horizontal plane (a plane perpendicular to the casting direction (z-axis direction)) will be described. FIG. 3 is a diagram illustrating an example of a state where the mold 4 is viewed from above. Since the width of the slab is longer than the thickness, when continuously casting the slab, the mold 4 is configured using the long side 4a and the short side 4b. The outer shape of the long side portion 4a and the short side portion 4b has a substantially rectangular parallelepiped shape. As shown in FIG. 3, in the horizontal section of the mold 4, the length in the longitudinal direction is longer at the long side 4a than at the short side 4b. The two long sides 4a are arranged so as to oppose each other via the immersion nozzle 6, and the two short sides 4b are arranged so as to oppose each other via the immersion nozzle 6. The mold 4 is formed by combining the two long sides 4a and the two short sides 4b such that the long side 4a and the two short sides 4b form a substantially rectangular hollow area.

  In the mold 4 when such a slab is continuously cast, the thermocouple 7 is embedded in at least one of the region of the short side 4b and the region of the short side of the long side 4a. Is preferred. The short side portion side region of the long side portion 4a is a region in the range from the first position to the second position of the long side portion 4a. The first position of the long side 4a is a position closest to the center of the mold 4 among positions in contact with the short side 4b of the long side 4a. The second position of the long side 4a is a position 100 mm away from the first position toward the center of the mold 4 along the width direction of the mold 4 (the direction of the long side of the horizontal cross section of the mold 4). As described above, it is preferable that the embedment position of the thermocouple 7 on the horizontal plane is a region shown in gray in FIG. In addition, the thermocouple 7 is arranged in each of the regions on both sides in the longitudinal direction of the long side portion 4a in FIG. 3 (at least one of the region of the short side portion 4b and the short side portion of the long side portion 4a). This is preferable because it is possible to predict a sign of a breakable breakout on each of both sides in the longitudinal direction of the long side portion 4a in FIG.

  It is preferable to arrange the thermocouples 7 in the above-described regions (the region of the short side 4b and the region of the short side of the long side 4a). This is because factors that affect the solidification of the molten steel 1, such as heat removal, are in a similar state, and the flow of the molten steel 1 and the change in the thickness of the mold flux layer 3 (powder) tend to be similar.

In addition, the width and thickness (length and width of the horizontal cross section) of the billet are 200 mm or less. Some blooms have a width and a thickness (length in the horizontal and vertical directions) of 200 mm or less. Therefore, when these are continuously cast as cast pieces, the embedding position of the thermocouple 7 on the horizontal plane may be any position as long as it is a region within the mold 4.
Hereinafter, the method described in <Method of estimating solidification state in mold 4> was used as a method for online deriving the thickness of solidified shell 2 and the embedding position of thermocouple 7 was described in <Position of thermocouple 7>. An embodiment of the casting state determination device 100 of the present invention will be described as a position.

<Embodiment of casting state determination device 100>
(First embodiment)
First, a first embodiment will be described.
FIG. 4 is a diagram illustrating an example of a functional configuration of the casting state determination device 100.
[Temperature acquisition unit 401]
The temperature acquisition unit 401 acquires temperatures measured by a plurality of thermocouples 7 whose embedding positions in the casting direction are different from each other. The temperature acquisition unit 401 derives the temperature distribution of the mold 4 in the casting direction by performing at least one of the interpolation process and the extrapolation process using the acquired temperature. Thereby, the temperature T _c (t, z) of the mold 4 at the position where the thermocouple 7 is embedded is obtained. It is preferable that the temperature acquisition unit 401 acquires the temperatures measured by the plurality of thermocouples 7 at intervals of 0.01 s or more and 20 s or less. If the acquisition interval (sampling interval) of the temperature measured by the plurality of thermocouples 7 is less than 0.01 s, the memory capacity of the mold state determination device 100 becomes insufficient. For this reason, there is a possibility that the processing may overflow. In addition, even if the acquisition interval of the temperature measured by the plurality of thermocouples 7 is less than 0.01 s, the detection accuracy of the sign of the breakable breakout does not significantly improve. On the other hand, if the acquisition interval of the temperature measured by the plurality of thermocouples 7 exceeds 20 s, the derivation interval of the thickness s _est (t, z) of the solidified shell 2 increases. For this reason, there is a possibility that the detection accuracy of the sign of the breakable breakout may decrease.

In addition, regarding the size and physical property value of the mold 4 and the physical property value of the molten steel 1 to be cast, the thermal conductivity λ _{m of} the mold 4 and the embedding of the thermocouple 7 from the inner wall surface of the mold 4 can be known in advance. Depth d ₁ , distance d _{2 in} the direction perpendicular to the inner wall surface of the mold from thermocouple 7 to cooling water 5, heat transfer coefficient h _w between mold 4 and cooling water 5, specific heat c _{s of} solidified shell 2, solidified shell It is assumed that the density ρ _s of 2, the thermal conductivity λ _s of the solidified shell 2, the latent heat of solidification L, and the solidification temperature T _s are known. Temperature T ₀ of the molten steel 1 that can change during casting, with respect to the temperature T _w, and casting speed V _c of the cooling water 5, can be known by using the average value, the embedding of the thermocouples 7 It is preferable to measure the same as the temperature _Tc of the mold 4 at the depth position.

[Heat flux deriving unit 402]
The heat flux deriving unit 402 converts the mold 4 from the temperature T _c (t, z) of the mold 4 at the embedding depth position of each thermocouple 7 obtained by the temperature acquisition unit 401 by using Expression (48). Deriving the passing heat flux q _out (t, z).
[Mold inner wall surface temperature deriving unit 403]
The mold inner wall surface temperature deriving unit 403 calculates the mold temperature from the temperature T _c (t, z) of the mold 4 at the embedded depth position of each thermocouple 7 obtained by the temperature acquisition unit 401 by using the equation (47). The temperature T _m (t, z) of the inner wall surface of No. 4 is derived.

[Heat transfer coefficient deriving unit 404]
The heat transfer coefficient deriving unit 404 passes the temperature _Tc of the mold 4 at the embedding depth position of the thermocouple 7 obtained by the temperature obtaining unit 401 and the mold 4 obtained by the heat flux deriving unit 402. By solving the minimization problem of the equation (50) using the heat flux q _out and the temperature T _m of the inner wall surface of the mold 4 obtained by the mold inner wall surface temperature deriving unit 403, the heat transfer coefficient α _est ( t, z) and β _est (t, z) are simultaneously derived (determined).

[Solidified shell thickness deriving unit 405]
Solidified shell thickness deriving unit 405 obtained in-mold wall temperature derivation unit 403, and the temperature T _m of a inner wall surface of the mold 4, resulting in heat transfer coefficient deriving unit 404, the heat transfer coefficient alpha _est (t, z) and β _est (t, z) are applied to equation (46) to derive the thickness s _est (t, z) of the solidified shell 2 and the temperature T _est (t, z, x) of the solidified shell 2. I do. Thereby, the thickness s _est (t, z) of the solidified shell 2 at the temperature measurement time t by the thermocouple 7 and the embedding position z of each thermocouple 7 in the casting direction is obtained. The temperature T _est (t, z, x) of the solidified shell 2 does not necessarily need to be derived. The processes in the temperature acquisition unit 401, the heat flux derivation unit 402, the mold inner wall surface temperature derivation unit 403, the heat transfer coefficient derivation unit 404, and the solidified shell thickness derivation unit 405 are performed every time the temperature measured by the thermocouple 7 is acquired. It is repeated.

[Correlation coefficient deriving unit 406]
The correlation coefficient deriving unit 406 determines whether or not the thickness s _est (t, z) of the solidified shell 2 for a predetermined time has been obtained. Then, when the thickness s _est (t, z) of the solidified shell 2 for a predetermined time is obtained, the correlation coefficient deriving unit 406 embeds the two thermocouples 7 in the casting direction in different casting directions from each other. A correlation coefficient of the thickness s _est (t, z) of the solidified shell 2 at each of the positions is derived. In the following description, this correlation coefficient will be referred to as a solidification shell thickness correlation coefficient as necessary. The correlation coefficient is a value obtained by dividing the covariance of two variables by the product of the standard deviations of the two variables.

The solidification shell thickness correlation coefficient is not derived until a predetermined time elapses after the activation of the casting state determination device 100. The correlation coefficient deriving unit 406 determines that the burying positions in the casting direction obtained by the solidified shell thickness deriving unit 405 during the predetermined time differ from each other when a predetermined time elapses after the activation of the casting state determination device 100. From the thickness s _est (t, z) of the solidified shell 2 at each of the embedding positions of the two thermocouples 7 in the casting direction, a solidified shell thickness correlation coefficient at the time when the predetermined time has elapsed is derived.

Then, the correlation coefficient deriving unit 406 obtains the thickness s _est of the solidified shell 2 at each of the positions in the casting direction of the two thermocouples 7, which are obtained by the solidified shell thickness deriving unit 405 and whose embedding positions in the casting direction are different from each other. Of the (t, z), the oldest thickness s _est (t, z) of the solidified shell 2 is discarded, and the other thicknesses s _est (t, z) of the solidified shell 2 are retained.

Thereafter, the correlation coefficient deriving unit 406 uses the solidified shell thickness deriving unit 405 to set the thickness s _est (t, z) of the solidified shell 2 at each of the embedding positions in the casting direction of the two thermocouples 7 having different embedding positions in the casting direction. ) is the newly derived, adding the solidified shell 2 in the thickness s _est (t, a z), the holding and which had been solidified shell 2 in the thickness s _est (t, z). Then, the correlation relationship deriving section 406, their thickness s _est (t, z) of the solidified shell 2 with thickness s _est (t, z) of the solidified shell 2 is solidified shell thickness at the newly derived time Derive a correlation coefficient.

The correlation coefficient deriving unit 406, as described above in the solidified shell 2 thickness s _est (t, z) discarded, holding, add, solidified shell thickness deriving unit 405 by the solidified shell 2 thickness s _est (t, z ) Is repeatedly performed each time が is derived, so that the solidification shell thickness correlation coefficient at each time can be derived at the temperature acquisition interval (sampling interval) of the temperature measured by the thermocouple 7.

The present inventors have determined that the thickness s _est (t, z) of the solidified shell 2 to be derived for the solidified shell thickness correlation coefficient in the casting direction (the two thermocouples 7 whose embedding positions in the casting direction are different from each other). The solidification shell thickness correlation coefficient in a normal casting state and the solidification shell thickness when a sign of the occurrence of crack breakout is generated by appropriately setting the burying position in the casting direction and the predetermined time. It was found that it was preferable because there was a clear difference from the correlation coefficient. Hereinafter, this point will be described.

First, it is preferable that the interval between positions in the casting direction of the thickness s _est (t, z) of the solidified shell 2 from which the solidified shell thickness correlation coefficient is to be derived is 5 mm or more and 400 mm or less. If this interval is less than 5 mm, even if a sign of a breakable breakout occurs, the solidification shell thickness correlation coefficient becomes approximately 1, so that it is not easy to detect a sign of the breakable breakout. On the other hand, if this interval exceeds 400 mm, conversely, the solidification shell thickness correlation coefficient is much less than 1 even if no breakable breakout has occurred, so that it is not easy to detect a sign of the breakable breakout. . Generally, the interval in the casting direction between two thermocouples 7 adjacent to each other in the casting direction is in the range of 5 mm or more and 400 mm or less. For this reason, as the position in the casting direction of the thickness s _est (t, z) of the solidified shell 2 from which the solidified shell thickness correlation coefficient is to be derived, the embedded position in the casting direction of two thermocouples 7 adjacent in the casting direction is set. Can be adopted. In this case, the solidification shell thickness correlation coefficient is derived using the temperatures measured by the two thermocouples 7 located closest to each other in the casting direction. Therefore, the difference between the solidified shell thickness correlation coefficient in a normal casting state and the solidified shell thickness correlation coefficient when a sign of crack breakout occurs can be maximized.

In addition, it is preferable that a plurality of sets are set in advance as sets of positions in the casting direction of the thickness s _est (t, z) of the solidified shell 2 from which the solidified shell thickness correlation coefficient is to be derived. By deriving a plurality of solidification shell thickness correlation coefficients, it is possible to suppress undetected and overdetected signs of crack breakout. For example, the number of thermocouples 7 whose embedding positions in the casting direction are different from each other is five, and two thermocouples 7 whose embedding positions in the casting direction are different from each other are adjacent to each other in the casting direction as positions in the casting direction. When adopting the embedding positions of the two thermocouples 7 in the casting direction, four sets of positions are set in advance. That is, a set of the embedded position of the uppermost thermocouple 7 in the casting direction, the embedded position of the second thermocouple 7 from the top in the casting direction, and the embedded position of the second thermocouple 7 from the top in the casting direction. And a buried position in the casting direction of the third thermocouple 7 from the top, a buried position in the casting direction of the third thermocouple 7 from the top, and a buried position in the casting direction of the fourth thermocouple 7 from the top. A set of positions, a buried position of the fourth thermocouple 7 from the top in the casting direction, and a set of a buried position of the fifth thermocouple 7 from the top in the casting direction are preset. In the following, as a set of positions in the casting direction of the thickness s _est (t, z) of the solidified shell 2 from which the solidification shell thickness correlation coefficient is to be derived, the casting direction of the two thermocouples 7 adjacent to each other in the casting direction will be described. The case where a set of the embedding positions is set in advance will be described as an example.

In addition, the above-mentioned predetermined time is preferably 2 minutes or more and 20 minutes or less. The decrease in the correlation between the thickness s _est (t, z) of the solidified shell also occurs due to factors other than the breakable breakout (for example, turbulent flow of the molten steel 1). Therefore, if this time is less than 2 minutes, the value of the solidification shell thickness correlation coefficient may be more affected by other factors than the breakable breakout. In addition, there is a possibility that a sign of a breakable breakout cannot be captured. For this reason, it may not be easy to detect a sign of a breakable breakout.

  On the other hand, the period in which the value of the solidification shell thickness correlation coefficient is disturbed due to the occurrence of the sign of crack breakout is not so long. Therefore, when this time exceeds 20 minutes, the value of the solidification shell thickness correlation coefficient is more greatly affected by the casting state (the state of the solidification shell 2 and the like) during normal operation than by the breakable breakout. There is a fear. For this reason, it may not be easy to detect a sign of a breakable breakout.

[Solidified shell state determination unit 407]
Based on the value of the solidified shell thickness correlation coefficient obtained by the correlation coefficient deriving unit 406, the solidified shell state determination unit 407 determines whether a sign of a breakable breakout has occurred.
In the present embodiment, the correlation coefficient deriving unit 406 derives a plurality of solidified shell thickness correlation coefficients at each time. Therefore, time series data of a plurality of solidification shell thickness correlation coefficients is obtained. Therefore, in the present embodiment, the solidified shell state determining unit 407 determines whether or not a sign of a breakable breakout has occurred using the time-series data of a plurality of solidified shell thickness correlation coefficients. Hereinafter, an example of a method of determining whether or not a sign of a breakable breakout has occurred using time series data of a plurality of solidified shell thickness correlation coefficients will be described.

  The solidified shell state determining unit 407 determines whether or not time series data for a predetermined time has been obtained as time series data of a plurality of solidified shell thickness correlation coefficients. Then, when the time-series data for the predetermined time of the plurality of solidified shell thickness correlation coefficients is obtained, the solidified shell state determination unit 407, based on the time-series data, among the plurality of solidified shell thickness correlation coefficients, At the predetermined time, it is determined whether or not the number of solidification shell thickness correlation coefficients below the threshold is equal to or greater than a predetermined number. The solidified shell state determination unit 407 determines that a sign of a breakable breakout has occurred when the number of solidified shell thickness correlation coefficients below the threshold is equal to or greater than a predetermined number in the predetermined time period, and is not so. In this case, it is determined that no sign of the breakable breakout has occurred.

  After the activation of the casting state determination device 100, the determination of the presence or absence of a sign of a breakable breakout is not performed until a predetermined time has elapsed. The solidified shell state determination unit 407 uses a plurality of solidified shell thickness correlation coefficients obtained by the correlation coefficient derivation unit 406 during the predetermined time after a predetermined time has elapsed after the activation of the casting state determination device 100. Then, it is determined whether or not a sign of a breakable breakout has occurred at the time when the predetermined time has elapsed.

Then, the solidified shell state determination unit 407 discards the oldest data among the time series data of the plurality of solidified shell thickness correlation coefficients obtained by the correlation coefficient derivation unit 406, and retains other data.
Thereafter, when the correlation coefficient deriving unit 406 newly derives a plurality of solidification shell thickness correlation coefficients, the solidification shell state determination unit 407 holds the plurality of solidification shell thickness correlation coefficients. Are used in addition to the solidification shell thickness correlation coefficients described above to determine whether or not a sign of a breakable breakout has occurred at a time when a plurality of solidification shell thickness correlation coefficients are newly derived.

  The solidified shell state determination unit 407 repeatedly discards, retains, and adds the plurality of solidified shell thickness correlation coefficients each time the plurality of solidified shell thickness correlation coefficients are derived by the correlation coefficient derivation unit 406. This makes it possible to determine whether or not a sign of a breakable breakout has occurred based on the temperature acquisition intervals (sampling intervals) measured by the plurality of thermocouples 7.

The predetermined time, threshold value, and predetermined number used for the above determination are set in advance by, for example, calibration performed for each continuous casting facility. For example, a predetermined time, a threshold value, and a predetermined number can be set in advance as follows.
First, the continuous casting facility is actually operated, and time series data of the solidification shell thickness correlation coefficient is collected for each of the case where the breakage breakout occurs and the case where it does not. Then, comparing the time-series data of the solidification shell thickness correlation coefficient when the breakable breakout occurs and the time-series data of the solidification shell thickness correlation coefficient when the breakage breakout does not occur, What values are appropriate as the above-mentioned predetermined time, threshold value, and predetermined number are determined. For example, 10 minutes can be used as the predetermined time, 0.75 as the threshold, and 3 as the predetermined number. As the threshold value, the interval between sets of positions in the casting direction of the thickness s _est (t, z) of the solidified shell 2 from which the solidified shell thickness correlation coefficient is to be derived (for deriving the solidified shell thickness correlation coefficient). It is preferable to adopt a larger value as the distance between the two thermocouples 7 used in the casting direction is shorter.

[Output unit 408]
When the solidification shell state determination unit 407 determines that a sign of a breakable breakout has occurred, the output unit 408 outputs information indicating that. The output form of this information is realized by, for example, at least one of display on a computer display, external storage of the casting state determination device 100, storage in an internal storage medium, and transmission to an external device. Note that the output unit 408 may output information indicating that the solidified shell state determination unit 407 has determined that no sign of breakable breakout has occurred.

[Operation flowchart]
Next, an example of a casting state determination method by the casting state determination device 100 will be described with reference to a flowchart of FIG. Note that the flowchart of FIG. 5 is repeatedly executed each time the temperature acquired by the plurality of thermocouples 7 having different positions in the casting direction is acquired by the temperature acquisition unit 401. It is assumed that the known values used in the above-described calculation are obtained before the start of the flowchart in FIG.

First, in step S501, the temperature acquisition unit 401 acquires the temperatures measured by the plurality of thermocouples 7 having different positions in the casting direction, and the temperature T _c of the mold 4 at the embedded depth position of each thermocouple 7 ( t, z).

Next, in step S502, the heat flux deriving unit 402 uses the equation (48) based on the temperature T _c (t, z) of the mold 4 at the embedded depth position of each thermocouple 7 obtained in step S501. Then, a heat flux q _out (t, z) passing through the mold 4 is derived.
Next, in step S503, the mold inner wall surface temperature deriving unit 403 calculates the equation (47) from the temperature T _c (t, z) of the mold 4 at the embedded depth position of each thermocouple 7 obtained in step S501. Is used to derive the temperature T _m (t, z) of the inner wall surface of the mold 4.

Next, in step S504, the heat transfer coefficient deriving unit 404 determines the temperature _Tc of the mold 4 at the embedded depth position of each thermocouple 7 obtained in step S501 and the mold 4 obtained in step S502. Is used to solve the minimization problem of the equation (50) by using the heat flux q _out passing through the equation and the temperature T _m of the inner wall surface of the mold 4 obtained in step S503, so that the heat transfer coefficient α _est (t, z) and β _est (t, z) are determined simultaneously.

Next, in step S505, the solidified shell thickness deriving unit 405 obtained in step S503, the temperature T _m of a inner wall surface of the mold 4, obtained in step S504, the heat transfer coefficient α _est (t, z) , Β _est (t, z) are applied to equation (46) to derive the thickness s _est (t, z) of the solidified shell 2, and the solidified shell 2 at the embedding position z of each thermocouple 7 in the casting direction. The thickness s _est (t, z) is derived.

Next, in step S506, the correlation coefficient deriving unit 406 determines whether or not the thickness s _est (t, z) of the solidified shell 2 for a predetermined time (for example, 2 minutes or more and 20 minutes or less) has been obtained. judge. If the result of this determination is that the thickness s _est (t, z) of the solidified shell 2 for the predetermined time has not been obtained, the processing according to the flowchart of FIG. 5 ends. On the other hand, when the thickness s _est (t, z) of the solidified shell 2 for the predetermined time has been obtained, the process proceeds to step S507.

Next, in step S507, the correlation coefficient (solidification shell) of the thickness s _est (t, z) of the solidified shell 2 at each of the embedding positions in the casting direction of the two thermocouples 7 having different embedding positions in the casting direction is different from each other. Thickness correlation coefficient) is derived. In the present embodiment, a plurality of sets are set in advance as a set of burying positions in the casting direction of two thermocouples 7 having different burying positions in the casting direction. Therefore, a plurality of solidified shell thickness correlation coefficients are derived by one process of step S507.

  Next, in step S508, the solidified shell state determination unit 407 determines whether time series data for a predetermined time (for example, 10 minutes) has been obtained as time series data of a plurality of solidified shell thickness correlation coefficients. . If the result of this determination is that time series data for a predetermined time has not been obtained as time series data of a plurality of solidified shell thickness correlation coefficients, the processing in the flowchart of FIG. 5 ends. On the other hand, if time series data for a predetermined time has been obtained as time series data of a plurality of solidified shell thickness correlation coefficients, the process proceeds to step S509.

  Next, in step S509, the solidified shell state determination unit 407 determines that the number of solidified shell thickness correlation coefficients that is less than the threshold for the predetermined time (for example, 10 minutes) among the plurality of solidified shell thickness correlation coefficients is predetermined. It is determined whether the number is equal to or more than the number. If the result of this determination is that the number of solidification shell thickness correlation coefficients below the threshold is not greater than or equal to the predetermined number, it is determined that no sign of crack breakout has occurred, and the process in the flowchart of FIG. 5 ends.

On the other hand, when the number of the solidification shell thickness correlation coefficients below the threshold is equal to or greater than the predetermined number, the process proceeds to step S510.
Next, in step S510, the output unit 408 outputs information indicating that a sign of a breakable breakout has occurred. Then, the processing according to the flowchart in FIG. 5 ends. When it is determined in step S509 that the number of solidification shell thickness correlation coefficients below the threshold is not equal to or greater than the predetermined number, the output unit 408 outputs information indicating that no sign of crack breakout has occurred. May be output.

[Example]
The actual operation was simulated using the test mold, and the temperature measured by the thermocouple embedded in the mold was given to the casting state determination device 100 of the present embodiment, and the solidification shell thickness phase relationship was obtained by the above-described processing. A number of time series data were obtained. 15 thermocouples arranged at 20mm intervals in the casting direction in the range from position P ₁ to the position P _2, were placed four thermocouples below the position P _2. The number of thermocouples arranged at a position within 300 mm from the lower end of the mold 4 was one. Each thermocouple was disposed at the center of the short side of the mold in the width direction and the thickness direction.

As an analysis condition in the casting state determination device 100, the acquisition interval of the temperature of the thermocouple 7 was set to 1 s. Further, a solidification shell thickness correlation coefficient was derived from the thickness s _est (t, z) of the solidification shell 2 for four minutes (the predetermined time used for the determination by the correlation coefficient derivation unit 406 was four minutes). Further, if the thickness correlation coefficient of three or more solidified shells becomes less than 0.75 within 10 minutes, a sign of crack breakout is assumed to be generated (used for the judgment of the solidified shell state judgment unit 407). The predetermined time was 10 minutes, the threshold was 0.75, and the predetermined number was 3).

6 to 8 show the results.
FIG. 6A shows the thickness s _est (t, z) of the solidified shell 2 at the embedded position of the fifth thermocouple from the top among the 15 thermocouples described above, and the thickness of the sixth thermocouple from the top. The correlation coefficient (solidified shell thickness correlation coefficient) with the thickness s _est (t, z) of the solidified shell 2 at the embedding position is shown.
Similarly, FIGS. 6 (b), 7 (a), 7 (b), 8 (a), and 8 (b) show the sixth and seventh thermocouples from the top among the 15 thermocouples described above. , 7, 8, 8, 9, 9, 10, 10, and 11, the correlation coefficient of the thickness s _est (t, z) of the solidified shell 2 at the embedded position (solidified shell thickness correlation coefficient) ).

6 to 8, the edge crack range indicates a time zone in which a sign of a breakable breakout occurs. The timing at which the breakable breakout occurs is 4800 s. Note that FIGS. 6 to 8 show a case in which a small amount of molten steel leaks due to the breakable breakout generated at the timing of 4800 s, and the breakable breakout is eliminated (naturally without changing the operating conditions). . Therefore, the derivation of the solidification shell thickness correlation coefficient is continued even after the occurrence of crack breakout.
As shown in FIG. 7B, FIG. 8A, and FIG. 8B, the three solidified shell thickness correlation coefficients are less than 0.75 during 3200s to 3800s, Is included in the edge crack range. Accordingly, it can be seen that the three solidified shell thickness correlation coefficients are less than 0.75, corresponding to the timing at which a sign of crack breakout occurs.
In FIG. 6A, the correlation coefficient (solidified shell thickness correlation coefficient) is significantly lower than 0.75 in the period indicated by the other factor range. However, as shown in FIG. 6 (b), FIG. 7 (a), FIG. 7 (b), FIG. 8 (a) and FIG. Correlation coefficient) does not fall below 0.75. For this reason, it is not determined that a sign of crack breakout has occurred. Therefore, it can be seen that overdetection of the occurrence of the sign of crack breakout is suppressed.

[Summary]
As described above, in the present embodiment, the casting state determination device 100 determines the correlation coefficient (solidification shell thickness correlation coefficient) of the thickness of the solidified shell 2 at the embedded positions of the two thermocouples 7 whose embedded positions in the casting direction are different from each other. ) Are derived. Then, when the number of solidification shell thickness correlation coefficients below the threshold is equal to or greater than a predetermined number in a predetermined time, the casting state determination device 100 determines that a sign of crack breakout has occurred, and does not determine that. In this case, it is determined that no sign of the breakable breakout has occurred. Therefore, it is possible to estimate the behavior of the solidified shell when the breakable breakout occurs, and determine whether or not a sign of the breakable breakout has occurred. Therefore, a sign of a breakable breakout occurs more than when using an indirect evaluation index for the breakable breakout, such as the level of the molten metal, the temperature itself measured by the thermocouple 7, and the heat flux itself. Can be accurately determined. It is possible to accurately predict online whether or not a breakable breakout occurs in the continuous casting process.

[Modification]
As in the present embodiment, a plurality of solidification shell thickness correlation coefficients are derived, and if they are used to determine whether or not a sign of a breakable breakout has occurred, a sign of a breakable breakout is detected. This is preferable because accuracy can be improved. However, the number of solidification shell thickness correlation coefficients used to determine whether or not a sign of crack breakout has occurred may be one. For example, when the range in the casting direction of the solidified shell that remarkably indicates a sign of a breakable breakout is specified by the structure, characteristics, and the like of the mold 4, the thickness of the solidified shell 2 at two positions within the range is determined. A solidification shell correlation coefficient may be derived, and if the solidification shell correlation coefficient is less than a threshold value, it may be determined that a sign of a breakable breakout has occurred.
Further, if it is determined whether or not a breakable breakout occurs using an index indicating a correlation between the thicknesses of the solidified shells 2 at two positions in the casting direction, the correlation coefficient described above is not necessarily used. Is also good. For example, covariance may be used. When the reciprocal of the correlation coefficient described in the present embodiment is used as an index indicating the correlation between the thickness of the solidified shell 2 at two positions in the casting direction, it is determined whether the index exceeds a threshold. Will do.

(Second embodiment)
Next, a second embodiment will be described.
The first embodiment has been described by taking as an example a case where it is determined whether or not a sign of a breakable breakout has occurred by comparing a solidification shell thickness correlation coefficient with a threshold. On the other hand, in the present embodiment, it is determined based on the frequency distribution (histogram) of the solidification shell thickness correlation coefficient whether or not a sign of a breakable breakout has occurred. As described above, the present embodiment is mainly different from the first embodiment in the criterion for determining whether or not the sign of the breakable breakout has occurred. Therefore, in the description of the present embodiment, the same portions as those in the first embodiment are denoted by the same reference numerals as those in FIGS.

FIG. 9 is a diagram illustrating an example of a functional configuration of the casting state determination device 100.
[Temperature acquisition unit 401 to correlation coefficient derivation unit 406]
The temperature acquisition unit 401, the heat flux derivation unit 402, the mold inner wall surface temperature derivation unit 403, the heat transfer coefficient derivation unit 404, the solidified shell thickness derivation unit 405, and the correlation coefficient derivation unit 406 have been described in the first embodiment. It can be realized with the same functions as the ones.

[Solidified shell state determination unit 907]
The solidified shell state determining unit 907 determines whether the correlation coefficient deriving unit 406 has obtained time series data for a predetermined time as time series data of a plurality of solidified shell thickness correlation coefficients. Then, when the time series data for a predetermined time is obtained as the time series data of the plurality of solidified shell thickness correlation coefficients, the solidified shell state determination unit 907 performs the solidification for each of the plurality of solidified shell thickness correlation coefficients. The frequency distribution of the solidified shell thickness correlation coefficient is derived (created) using the time-series data for the predetermined time of the shell thickness correlation coefficient. At this time, the solidified shell state determination unit 907 represents the frequency distribution of the solidified shell thickness correlation coefficient in a semilogarithmic graph that displays the solidified shell thickness correlation coefficient on a logarithmic scale. The width of the class (bin) of the solidification shell thickness correlation coefficient is preferably 0.01 or more and 0.1 or less. Here, an example in which a relative frequency distribution is used as the frequency distribution will be described. Here, the relative frequency distribution means a semi-logarithmic graph in which the horizontal axis represents the solidification shell thickness correlation coefficient and the vertical axis represents the relative frequency belonging to each class of the solidification shell thickness correlation coefficient. , The number belonging to each class divided by the total number. This is the same in the following description.) As the frequency distribution, an absolute frequency distribution (a frequency distribution using the number itself (absolute frequency) belonging to each class instead of the relative frequency on the vertical axis) may be used instead of the relative frequency distribution.

  The solidified shell state determination unit 907 expressed the frequency of the solidified shell thickness correlation coefficient as a linear function of the solidified shell thickness correlation coefficient from the value in the semilog graph for each of the plurality of solidified shell thickness correlation coefficients. The linear form is derived by a method such as regression analysis, and the slope of the linear form (linear function) is derived. In the following description, this inclination will be referred to as the inclination of the frequency distribution of the solidification shell thickness correlation coefficient, if necessary. As described in the first embodiment, when the value of the solidification shell thickness correlation coefficient decreases, it can be estimated that a sign of a breakable breakout has occurred. Therefore, in the frequency distribution of the solidification shell thickness correlation coefficient, a small slope of the frequency distribution of the solidification shell thickness correlation coefficient indicates that the occurrence frequency of the solidification shell thickness correlation coefficient having a small value is high. In addition, the frequency distribution of the solidification shell thickness correlation coefficient is represented as a semilogarithmic graph. Generally, the frequency of occurrence of the relatively small solidification shell thickness correlation coefficient is a relatively large value (a value close to 1). This is because the frequency of occurrence of the solidification shell thickness correlation coefficient is extremely small as compared with the above, and it is not easy to clearly express the relationship between the solidification shell thickness correlation coefficient and the frequency by a predetermined function.

Note that the solidified shell state determination unit 907 does not need to explicitly create a semilogarithmic graph. That is, the solidified shell state determination unit 907 calculates the logarithm of the frequency of the solidified shell thickness correlation coefficient (for example, when the common logarithm is used, when the frequency of the solidified shell thickness correlation coefficient is Y, log ₁₀ Y is derived). From the value of a point determined by the solidified shell thickness correlation coefficient and the logarithm of the frequency of the solidified shell thickness correlation coefficient, the frequency of the solidified shell thickness correlation coefficient is represented by a linear function of the solidified shell thickness correlation coefficient. The linear form may be derived by a method such as regression analysis.

  The solidified shell state determination unit 907 derives a representative value of the slope of the frequency distribution of the plurality of solidified shell thickness correlation coefficients obtained as described above. As the representative value, an average value, a median value, or a mode value can be used. Then, the solidified shell state determination unit 907 determines whether the number of gradients of the frequency distribution of the solidified shell thickness correlation coefficient that is lower than the representative value thus derived is equal to or greater than a predetermined value. The solidified shell state determination unit 907 determines that a sign of crack breakout has occurred when the number of gradients of the frequency distribution of the solidified shell thickness correlation coefficient that is less than the representative value is equal to or greater than a predetermined value. Otherwise, it is determined that no sign of breakable breakout has occurred.

  After the activation of the casting state determination device 100, the determination of the presence or absence of a sign of a breakable breakout is not performed until a predetermined time has elapsed. The solidified shell state determination unit 907 uses a plurality of solidified shell thickness correlation coefficients obtained by the correlation coefficient derivation unit 406 during the predetermined time after the activation of the casting state determination device 100 for a predetermined time. Then, it is determined whether or not a sign of a breakable breakout has occurred at the time when the predetermined time has elapsed.

Then, the solidified shell state determining unit 907 discards the oldest data among the time series data of the plurality of solidified shell thickness correlation coefficients obtained by the correlation coefficient deriving unit 406, and retains other data.
Thereafter, when a plurality of solidified shell thickness correlation coefficients are newly derived by the correlation coefficient deriving unit 406, the solidified shell state determination unit 907 stores the plurality of solidified shell thickness correlation coefficients. Are used in addition to the solidification shell thickness correlation coefficients described above to determine whether or not a sign of a breakable breakout has occurred at a time when a plurality of solidification shell thickness correlation coefficients are newly derived.

  The solidified shell state determination unit 907 repeatedly discards, retains, and adds such a plurality of solidified shell thickness correlation coefficients each time the plurality of solidified shell thickness correlation coefficients are derived by the correlation coefficient derivation unit 406. This makes it possible to determine whether or not a sign of a breakable breakout has occurred based on the temperature acquisition intervals (sampling intervals) measured by the plurality of thermocouples 7.

The predetermined time and the predetermined number used for the above determination are set in advance by calibration performed for each continuous casting facility. For example, a predetermined time and a predetermined number can be set in advance as follows.
First, the continuous casting equipment is actually operated, and the gradient of the frequency of occurrence of the solidification shell thickness correlation coefficient is derived for each of the cases where a breakable breakout occurs and the case where it does not. Then, compare the slope of the frequency of occurrence of the solidification shell thickness correlation coefficient when a breakable breakout occurs with the slope of the frequency of occurrence of the solidification shell thickness correlation coefficient when the breakage breakout does not occur. What value is appropriate as the predetermined time and the predetermined number is determined. For example, 10 minutes can be used as the predetermined time and 3 can be used as the predetermined number.

[Output unit 908]
When the solidified shell state determination unit 907 determines that a sign of a breakable breakout has occurred, the output unit 908 outputs information indicating that. The output form of this information is realized by, for example, at least one of display on a computer display, external storage of the casting state determination device 100, storage in an internal storage medium, and transmission to an external device. Note that the output unit 908 may output information indicating that the solidified shell state determination unit 907 has determined that no sign of breakable breakout has occurred.

[Operation flowchart]
Next, an example of a casting state determination method by the casting state determination apparatus 100 will be described with reference to a flowchart of FIG. Note that the flowchart of FIG. 10 is repeatedly executed each time the temperature acquisition unit 401 acquires the temperatures measured by the plurality of thermocouples 7 having different positions in the casting direction. It is assumed that the known values used in the above-described calculation are obtained before the start of the flowchart of FIG.

The processing of steps S501 to S507 is the same as the processing of steps S501 to S507 in FIG.
After the processing in step S507, the process proceeds to step S1001. In step S1001, the solidified shell state determination unit 907 determines whether time series data for a predetermined time (for example, 10 minutes) has been obtained as time series data of a plurality of solidified shell thickness correlation coefficients. If the result of this determination is that time series data for a predetermined time has not been obtained as time series data of a plurality of solidified shell thickness correlation coefficients, the processing in the flowchart of FIG. 10 ends. On the other hand, if time series data for a predetermined time has been obtained as time series data of a plurality of solidified shell thickness correlation coefficients, the process proceeds to step S1002.

  Next, in step S1002, the solidified shell state determination unit 907 uses, for each of the plurality of solidified shell thickness correlation coefficients, time-series data for a predetermined time of the solidified shell thickness correlation coefficient to determine the solidified shell thickness phase coefficient. Deriving (creating) a frequency distribution of relation numbers. At this time, the solidified shell state determination unit 907 expresses the value of the frequency of the solidified shell thickness correlation coefficient in the frequency distribution by a logarithm.

  Next, in step S1003, the solidified shell state determination unit 907 calculates the frequency of the solidified shell thickness correlation coefficient expressed in logarithm based on the frequency distribution of the solidified shell thickness correlation coefficient obtained in step S1002, The linear gradient (the gradient of the frequency distribution of the solidified shell thickness correlation coefficient) represented by a linear function of the solidified shell thickness correlation coefficient is derived. Since a plurality of solidification shell thickness correlation coefficients are derived in one process of step S507, a plurality of solidification shell thickness correlations are calculated in one process of step S1003 as a gradient of a frequency distribution of the solidification shell thickness correlation coefficient. The slope of the frequency distribution of the correlation coefficient is derived.

Next, in step S1004, the solidified shell state determination unit 907 derives a representative value of the slope of the frequency distribution of the plurality of solidified shell thickness correlation coefficients obtained in step S1003.
Next, in step S1005, the solidification shell state determination unit 907 determines the inclination of the frequency distribution of the solidification shell thickness correlation coefficient that is less than the representative value among the inclinations of the frequency distribution of the solidification shell thickness correlation coefficient derived in step S1003. It is determined whether or not the number is greater than or equal to a predetermined value. As a result of this determination, if the number of slopes of the frequency distribution of the solidified shell thickness correlation coefficient that is less than the representative value is not equal to or greater than the predetermined value, it is determined that no sign of crack breakout has occurred, and the processing in the flowchart of FIG. finish.

On the other hand, if the number of gradients of the frequency distribution of the solidification shell thickness correlation coefficient that is less than the representative value is equal to or greater than the predetermined value, the process proceeds to step S1006.
Next, in step S1006, the output unit 908 outputs information indicating that a sign of a breakable breakout has occurred. Then, the processing according to the flowchart in FIG. 10 ends. If it is determined in step S1005 that the number of slopes of the frequency distribution of the solidification shell thickness correlation coefficient that is less than the representative value is not equal to or greater than the predetermined value, the output unit 908 generates a sign of a breakable breakout. Alternatively, information indicating that the information has not been output may be output.

[Example]
From the time-series data of the solidification shell thickness correlation coefficient obtained in [Example] of the first embodiment, the frequency distribution of the solidification shell thickness correlation coefficient (class width is 0) by the processing described in the present embodiment. .05) (see FIGS. 6 to 8 for time series data of the solidification shell thickness correlation coefficient). In this example, if three or more slopes of the frequency distribution of the solidification shell thickness correlation coefficient fall below the average value within 10 minutes, a sign of a breakable breakout is generated (solidification shell thickness). The predetermined time used for the determination by the state determination unit 907 is 10 minutes, the predetermined number is 3, and the representative value is an average value.) The other analysis conditions in the casting state determination device 100 are the same as those described in [Example] of the first embodiment.

11 to 13 show the results.
FIG. 11A shows the thickness s _est (t, z) of the solidified shell 2 at the position of the fifth thermocouple from the top among the 15 thermocouples described in [Example] of the first embodiment. And a frequency distribution of a correlation coefficient (solidified shell thickness correlation coefficient) between the thickness and the thickness s _est (t, z) of the solidified shell 2 at the position of the sixth thermocouple from the top.
Similarly, FIGS. 11 (b), 12 (a), 12 (b), 13 (a), and 13 (b) show the fifteen pieces described in [Example] of the first embodiment. Among the thermocouples, the thickness s _est (t, z) of the solidified shell 2 at the embedded position of the sixth, seventh, seventh, eighth, ninth, ninth, tenth, tenth, and eleventh thermocouples from the top 2 shows a frequency distribution of a correlation coefficient (solidification shell thickness correlation coefficient) of the above.

  11 to 13, graphs 1101, 1111, 1201, 1211, 1301, and 1311 show graphs for a healthy portion, and are solidified shells in the same period other than the edge crack range and other factor ranges shown in FIGS. 6 to 8. 9 shows a frequency distribution of a thickness correlation coefficient. Graphs 1102, 1102, 1202, 1212, 1302, and 1312 show graphs for cracks (cracks due to crack breakout) and show the frequency distribution of the solidification shell thickness correlation coefficient during the edge crack range. Graphs 1103, 1103, 1203, 1213, 1303, and 1313 show the frequency distribution of the solidification shell thickness correlation coefficient during the period of the other factor range shown in FIG. Graphs 1104, 1114, 1204, 1214, 1304, and 1314 show the average values of the slopes of the frequency distributions of all the solidified shell thickness correlation coefficients.

  12 (b), 13 (a), and 13 (b), the slope of the frequency distribution of the solidified shell thickness correlation coefficient (graphs 1212, 1302, 1312) indicates that the slope of all the solidified shell thickness correlation coefficients is equal. It was lower than the average value of the slope of the frequency distribution (graphs 1214, 1304, 1314). Accordingly, the slopes of the frequency distributions of the three solidified shell thickness correlation coefficients correspond to the average values of the slopes of the frequency distributions of all the solidified shell thickness correlation coefficients, corresponding to the timing at which the sign of crack breakout occurs. You can see that it is below.

  Also, in FIG. 11A, the slope of the frequency distribution of the solidification shell thickness correlation coefficient (graph 1103) (the slope of the frequency distribution of the solidification shell thickness correlation coefficient during the period of the other factor range shown in FIG. 6A). Is lower than the average value of the slopes of the frequency distributions of all the solidified shell thickness correlation coefficients (graph 1104). However, as shown in FIG. 11 (b), FIG. 12 (a), FIG. 12 (b), FIG. 13 (a) and FIG. The slope of the frequency distribution (graphs 1113, 1203, 1213, 1303, and 1313) is not lower than the average of the slopes of the frequency distributions (graphs 1114, 1204, 1214, 1304, and 1314) of all the solidified shell thickness correlation coefficients. . For this reason, it is not determined that a sign of crack breakout has occurred. Therefore, it can be seen that overdetection of the occurrence of the sign of crack breakout is suppressed.

[Summary]
As described above, in the present embodiment, the casting state determination apparatus 100 derives a plurality of slopes of the frequency distribution of the solidification shell thickness correlation coefficient, and when there are a predetermined number or more of slopes below the representative value, the crack breakage. It is determined that a sign of out has occurred, and otherwise, it is determined that a sign of breakable breakout has not occurred. Even in this case, the same effect as that described in the first embodiment can be obtained.

[Modification]
As in the present embodiment, a plurality of gradients of the frequency distribution of the solidification shell thickness correlation coefficient are derived, and by using them, it is determined whether or not a sign of a breakable breakout has occurred. It is preferable because the detection accuracy of the sign of the sign can be improved. However, the number of gradients in the frequency distribution of the solidification shell thickness correlation coefficient used to determine whether or not a sign of crack breakout has occurred may be one. FIG. 14 is a diagram showing a modification of the frequency distribution of the solidification shell thickness correlation coefficient. As described in the [Modification] of the first embodiment, when the range of the casting direction of the solidified shell that significantly indicates the sign of the breakable breakout is specified by the structure, characteristics, and the like of the mold 4. Derives a solidification shell correlation coefficient from the thickness of the solidification shell 2 at two positions within the range, derives a gradient of a frequency distribution of the solidification shell correlation coefficient, and calculates a frequency distribution of the solidification shell correlation coefficient. When the inclination is less than the threshold, it may be determined that a sign of a breakable breakout has occurred.

FIG. 14 shows the thickness s _est (t, z) of the solidified shell 2 at the positions of the fifth and eleventh thermocouples from the top among the fifteen thermocouples described in [Example] of the first embodiment. 4 shows a frequency distribution of a correlation coefficient (solidification shell thickness correlation coefficient). The graph 1401 in FIG. 14 has the same contents as the graphs 1101, 1111, 1201, 1211, 1301, and 1311 in FIGS. 11 to 13, and the graph 1402 is the graph 1102, 1102, and 1202 in FIGS. The contents are the same as 1212, 1302, and 1312, and the graph 1403 has the same contents as the graphs 1103, 1103, 1203, 1213, 1303, and 1313 in FIGS. As shown in FIG. 13, when the position of the thermocouple in the casting direction is far away, the correlation of the thickness of the solidified shell 2 is disturbed. , 1312) is larger than the healthy part (see graphs 1301, 1311). Therefore, when deriving the solidification shell thickness correlation coefficient, it is not always necessary to adopt the embedded position of the two thermocouples 7 adjacent in the casting direction in the casting direction.

  Further, in the present embodiment, the case where the frequency distribution of the solidified shell thickness correlation coefficient is represented by a semilogarithmic graph that displays the solidified shell thickness correlation coefficient on a logarithmic scale has been described as an example. However, this is not necessary. For example, a logarithmic graph may be used to represent the frequency distribution of the solidified shell thickness correlation coefficient (the logarithm of the solidified shell thickness correlation coefficient may be taken). Further, the frequency distribution of the solidification shell thickness correlation coefficient may be represented without taking the logarithm. Alternatively, for example, when the sum of the frequencies of the solidification shell thickness correlation coefficient that is equal to or less than the predetermined value exceeds the threshold value, it may be determined that the sign of the breakable breakout has occurred.

  In the present embodiment, the case where the frequency of the solidification shell thickness correlation coefficient is represented by a linear function expressed by a linear function of the solidification shell thickness correlation coefficient has been described as an example. On the other hand, the solidification shell thickness correlation coefficient is assumed to be a linear function expressed by a linear function of the frequency of the solidification shell thickness correlation coefficient, and the slope of the linear form is determined by the frequency distribution of the solidification shell thickness correlation coefficient. In step S1005, the solidified shell state determination unit 907 determines whether the number of gradients in the frequency distribution of the solidified shell thickness correlation coefficient that exceeds the representative value is equal to or greater than a predetermined value. Will do.

(Third embodiment)
Next, a third embodiment will be described. In this embodiment, a case will be described in which the criterion described in the first embodiment and the criterion described in the second embodiment are combined as a criterion for determining whether or not a sign of a breakable breakout has occurred. Therefore, in the description of the present embodiment, the same portions as those in the first and second embodiments are denoted by the same reference numerals as those in FIGS.

The functional configuration of the casting state determination device 100 of the present embodiment can be realized by the same configuration as that shown in FIG.
However, similarly to the solidified shell state determination unit 407 described in the first embodiment, the solidified shell state determination unit 907 determines whether the number of solidified shell thickness correlation coefficients below the threshold is equal to or greater than a predetermined number in a predetermined time. Determine whether or not. That is, in the present embodiment, the solidified shell state determination unit 907 performs the first determination and the second determination in order to determine whether a sign of a breakable breakout has occurred.

The first determination is a determination as to whether or not the number of slopes of the frequency distribution of the solidification shell thickness correlation coefficient that is less than the representative value is equal to or greater than a predetermined value. The second determination is a determination as to whether or not the number of solidification shell thickness correlation coefficients below the threshold is equal to or greater than a predetermined value in a predetermined time.
In the first determination, the solidified shell state determination unit 907 determines whether the number of gradients of the frequency distribution of the solidified shell thickness correlation coefficient that is less than the representative value is equal to or greater than a predetermined value, or in the second determination, a predetermined time. In the case where the number of solidification shell thickness correlation coefficients below the threshold value is equal to or greater than a predetermined value, it is determined that a sign of a breakable breakout has occurred, and if not, a sign of a breakable breakout occurs. It is determined that it has not been performed.

In the casting state determination method by the casting state determination device 100 of the present embodiment, for example, in the flowchart of FIG. 10, if “NO” is determined in step S1005, the determination in step S509 of FIG. 5 is performed, and “YES” is determined in step S509. If it is determined, the process proceeds to step S1006 in FIG. 10. If NO in step S509, the process according to the flowchart in FIG. 10 is completed.
In this way, it is possible to more reliably predict that a sign of a breakable breakout has occurred.

In addition, instead of doing so, the solidification shell state determination unit 907 determines in the first determination that the number of slopes of the frequency distribution of the solidification shell thickness correlation coefficient that is less than the representative value is equal to or greater than a predetermined value, In the second determination, when the number of solidification shell thickness correlation coefficients below the threshold is equal to or more than a predetermined value for a predetermined time, it is determined that a sign of crack breakout has occurred, and if not, Alternatively, it may be determined that no sign of crack breakout has occurred. With this configuration, it is possible to more reliably suppress the occurrence of the sign of the breakable breakout from being overdetected.
For example, a criterion for at least one of the first determination and the second determination is determined depending on whether it is desired to more reliably suppress over-detection or non-detection of the occurrence of the sign of crack breakout. You just have to select
Further, the determination criteria described in the section “Modifications” of the first and second embodiments may be combined.

The embodiments of the present invention described above can be realized by a computer executing a program. Further, a computer-readable recording medium on which the program is recorded and a computer program product such as the program can also be applied as an embodiment of the present invention. As the recording medium, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM, and the like can be used.
Further, the embodiments of the present invention described above are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be interpreted in a limited manner. Things. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features.

<Relationship with claims>
Hereinafter, an example of the relationship between the description in the claims and the description in the embodiment will be described. As described above, the description of the claims is not limited to the description of the embodiment.
(Claims 1, 5, 9 to 14)
The temperature measuring means is realized, for example, by using the thermocouple 7.
The temperature acquisition unit is realized by using, for example, the temperature acquisition unit 401.
The solidified shell thickness deriving unit is realized, for example, by using the solidified shell thickness deriving unit 405.
The index indicating the correlation between the thickness of the solidified shell at two positions in the casting direction is realized by using, for example, a solidified shell thickness correlation coefficient.
The correlation deriving unit is realized by using the correlation coefficient deriving unit 406, for example.
The determination unit is realized by using, for example, the solidified shell state determination units 407 and 907.
(Claims 2 and 6)
Claims 2 and 6 correspond to, for example, the first embodiment, and determining whether or not the sign of the breakable breakout has occurred based on a result of comparing the index with a threshold value includes, for example, This is realized by determining whether or not the number of solidification shell thickness correlation coefficients below a threshold is equal to or greater than a predetermined number in a predetermined time among a plurality of solidification shell thickness correlation coefficients.
(Claims 3-4, 7-8)
Claims 3 to 4 and 7 to 8 correspond to, for example, the second embodiment and the third embodiment, and the relationship between the index and the frequency of the index is, for example, the solidification shell thickness correlation coefficient. This is realized by using a frequency distribution.
The inclination when the relationship is expressed in a linear form is realized by using, for example, the inclination of the frequency distribution of the solidification shell thickness correlation coefficient.
(Claim 14)
The heat transfer coefficient deriving unit is realized by using, for example, the heat transfer coefficient deriving unit 404.

  1: molten steel, 2: solidified shell, 3: mold flux layer, 4: mold, 5: cooling water, 6: immersion nozzle, 7: thermocouple, 100: casting state determination device, 401: temperature acquisition unit, 402: heat flow Bundle derivation unit, 403: Mold inner wall surface temperature derivation unit, 404: Heat transfer coefficient derivation unit, 405: Solidified shell thickness derivation unit, 406: Correlation coefficient derivation unit, 407, 907: Solidified shell state determination unit, 408, 908 : Output section

Claims (16)

A casting state determination device that determines whether or not a sign of crack breakout has occurred in a continuous casting process,
A plurality of temperature measurement means buried in the mold, the temperature acquisition means to obtain the temperature measured by a plurality of temperature measurement means different in position in the casting direction,
A solidified shell that derives the thickness of the solidified shell at a plurality of positions in the casting direction at each of a plurality of times within the predetermined time, using the temperatures obtained at a plurality of times within a predetermined time by the temperature obtaining means. Thickness deriving means,
Correlation deriving means for deriving an index indicating a correlation between the thickness of the solidified shell at two positions in the casting direction,
Based on the index derived by the correlation deriving means, determining means for determining the presence or absence of a sign of the breakable breakout,
A casting state determination device comprising:   The method according to claim 1, wherein the determining unit determines whether or not a sign of the breakable breakout has occurred based on a result of comparing the index derived by the correlation deriving unit with a threshold. The casting state determination device according to any one of the preceding claims.   2. The method according to claim 1, wherein the determining unit determines whether or not a sign of the breakable breakout occurs based on a relationship between the index derived by the correlation deriving unit and a frequency of the index. Or the casting state determination device according to 2.   The determining unit derives a slope when the relationship is expressed in a linear form, and determines whether or not the sign of the breakable breakout has occurred based on a result of comparing the derived slope with a threshold. The casting state judging device according to claim 3, characterized in that: The correlation deriving means, as the set of the two positions, for each of a plurality of sets at least one of which is different from each other, to derive an index indicating the correlation of the thickness of the solidified shell at the two positions,
2. The casting according to claim 1, wherein the determination unit determines whether or not a sign of the breakable breakout has occurred based on the indices for the plurality of sets derived by the correlation derivation unit. 3. State determination device.   The determining means determines whether or not the sign of the breakable breakout has occurred based on a result of comparing each of the indices for the plurality of sets derived by the correlation deriving means with a threshold. The casting state determination device according to claim 5, wherein   The determining unit derives a relationship between the index derived by the correlation deriving unit and the frequency of the index for each of the plurality of indices, and based on the plurality of derived relationships, The casting state determination device according to claim 5, wherein the presence or absence of a sign of breakout is determined.   The determining means derives a slope when the relation is expressed in a linear form for each of the plurality of relations, and, based on a result of comparing the derived slope with a threshold, a sign of the breakable breakout. The casting state judging device according to claim 7, wherein the presence or absence of occurrence of the cast is determined.   The casting condition determination device according to claim 3, wherein the index is represented by a logarithm.   The said index is a correlation coefficient, The casting state determination apparatus of any one of Claims 1-9 characterized by the above-mentioned.   The casting state determination device according to any one of claims 1 to 10, wherein the number of the plurality of temperature measurement means is five or more. The mold is a long side portion having a relatively long longitudinal length in a horizontal cross section, and two long side portions arranged with an interval therebetween, and a longitudinal length in a horizontal cross section is A relatively short short side portion, having two short side portions arranged at an interval from each other, by combining the two long side portions and the two short side portions. Molten steel is injected into the formed hollow area,
The temperature measuring means is embedded in the area of the short side, or in the area between the first position and the second position of the long side,
The first position of the long side is a position closest to the center of the mold among positions in contact with the short side of the long side,
The second position of the long side is a position 100 mm away from the first position of the long side toward the center of the mold along the direction of the long side of the horizontal section of the mold. The casting state judging device according to any one of claims 1 to 11.   The casting according to any one of claims 1 to 12, wherein the two positions are positions in the casting direction of the two temperature measuring means located adjacent to each other in the casting direction. State determination device. From the mold, the solidified shell, and a temperature that is a solution in a heat conduction equation expressing heat conduction in a region including molten steel in the mold, a boundary condition used to derive a solution of the heat conduction equation is a problem. By solving the inverse problem, the heat transfer coefficient α, which is the heat flux per unit temperature difference between the solidified shell in the mold and the mold, and the heat transfer between the molten steel in the mold and the solidified shell Further having a heat transfer coefficient deriving means for deriving a coefficient β,
14. The solidified shell thickness deriving means derives the thickness of the solidified shell using the heat transfer coefficient α and the heat transfer coefficient β derived by the heat transfer coefficient deriving means. The casting condition judging device according to any one of the above. A casting state determination method for determining the presence or absence of a sign of crack breakout in a continuous casting process,
A plurality of temperature measurement means embedded in the mold, a temperature acquisition step of acquiring a temperature measured by a plurality of temperature measurement means different in position in the casting direction,
Using the temperatures obtained at a plurality of times within a predetermined time by the temperature obtaining step, a solidified shell that derives the thickness of the solidified shell at a plurality of positions in the casting direction at each of the plurality of times within the predetermined time. Thickness derivation process,
A correlation deriving step of deriving an index indicating a correlation between the thickness of the solidified shell at two positions in the casting direction,
Based on the index derived in the correlation deriving step, a determining step of determining whether or not a sign of the breakable breakout has occurred,
A method for determining a casting state, comprising:   A non-transitory computer-readable storage medium storing a program for causing a computer to function as each unit of the casting state determination device according to any one of claims 1 to 14.

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