JP5505086B2 - Method, apparatus and program for estimating state in mold in continuous casting - Google Patents

Description

  The present invention determines the transfer coefficient, which is the main factor governing the state in the mold, in continuous casting where the solidified shell, mold powder layer, and mold thermal conductors exist between the molten steel and the cooling water for the mold. The present invention relates to a method, apparatus, and program for estimating a state in a mold suitable for the above.

  In continuous casting of steel, the molten steel flow state and solidification state in the mold affect the properties of the slab, so in order to produce a defect-free slab, the state in the mold is estimated and controlled online. It is necessary.

  In Patent Document 1, the temperature in the mold steel plate is measured at a point on the normal line of the molten steel side surface of the mold copper plate with a temperature measuring element embedded in the mold copper plate, and the temperature of the molten steel along the solidified shell is measured from this measured value. A technique for determining the flow velocity is disclosed.

Specifically, the heat flux passing through the mold copper plate is obtained from the temperature measurement value, and the overall heat resistance (the synthesized heat resistance of the heat conductor from the molten steel to the cooling water) R is determined from the heat flux, From the following equation (101), the convective heat transfer coefficient β between the molten steel and the solidified shell is obtained. The heat transfer coefficient between the lambda _s is the thermal conductivity of the solidified shell, lambda _p is the thermal conductivity of the mold powder layer, lambda _m is the thermal conductivity of the mold copper plate, h _m is a mold powder layer and the mold copper plate, h _w is the heat transfer coefficient, d _s is solidified shell thickness, d _p is the mold powder layer thickness, d _m is the mold copper plate thickness between mold copper plate and cooling water.
R = (1 / β) + (d _s / λ _s ) + (d _p / λ _p ) + (1 / h _m ) + (d _m / λ _m ) + (1 / h _w ) (101) )

Using the heat transfer coefficient β obtained from the equation (101), the Nusselt number Nu is obtained from the following equation (102), the Nusselt number Nu is substituted into the following equation (103) or (104), and the Reynolds number Re is obtained. Ask. Then, the Reynolds number Re is substituted into the following equation (105) to obtain the molten steel flow velocity U. Note that λ ₁ is the thermal conductivity of the molten steel, X ₁ is the heat transfer representative length, Pr is the Prandtl number, ν is the kinematic viscosity coefficient of the molten steel, and X ₂ is the molten steel flow representative length.
β = Nu × λ ₁ × X ₁ (102)
Nu = 0.664 × Pr ^1/3 × Re ^4/5 (U <U ₀ ) (103)
Nu = 0.036 × Pr ^1/3 × Re ^1/2 (U ≧ U ₀ ) (104)
Re = U × X ₂ / ν (105)

Japanese Patent No. 3230513 Japanese Patent Laid-Open No. 10-277716 JP 2008-260046 A (paragraph [0020]) Japanese Patent Laid-Open No. 08-276257 (paragraph [0008]) JP 2000-317594 A JP 2001-239353 A

Here, the heat transfer coefficient α between the solidified shell and the mold copper plate can be described by the following formula (106) (the third and fourth terms on the right side of the formula (101)). In Patent Document 1, the mold powder layer thickness d _p is a numerical value that is fixed when the type of mold powder, the amplitude, frequency, and vibration waveform of the mold vibration and the casting speed are determined, and the heat conduction of the mold powder layer. rate lambda _p, regardless of the type of mold powder, is known to be substantially constant, also the heat transfer coefficient h _m between the mold powder layer and the mold copper plate, once the type of mold powder It is determined to be almost constant.
1 / α = (d _p / λ _p ) + (1 / h _m ) (106)

  That is, in the method of Patent Document 1, it is a precondition that the heat transfer coefficient α between the solidified shell and the mold copper plate is handled as a constant value that does not change with time.

  However, as can be seen from reported cases such as the occurrence of an air gap, the thickness of the mold powder layer is highly likely to fluctuate over time, and the heat transfer coefficient α between the solidified shell and the mold copper plate is treated as a constant value. This practically limits the application area of the method to the average normal operation area.

  The present invention has been made in view of the above points. The heat transfer coefficient α between the solidified shell and the mold, which is the main factor governing the state in the mold, and the heat transfer between the molten steel and the solidified shell. The object is to enable the coefficient β to be determined simultaneously.

前記熱伝達係数決定手順では、
Ｔを凝固シェルの温度、Ｔ ₀ を溶鋼の温度、Ｔ _s を溶鋼と凝固シェルとの界面温度、ｕを鋳造速度、λ _s を凝固シェルの熱伝導率、ｃ _s を凝固シェルの比熱、ρ _s を凝固シェルの密度、Ｌを凝固シェルの潜熱、ｄを鋳型の凝固シェル側の表面から測温手段までの距離、λ _m を鋳型の熱伝導率として、
鋳造方向をｚ軸、鋳造方向に直交する方向をｘ軸とする２次元座標上で、凝固シェルの厚みｓ(ｚ，ｔ)及び凝固シェルの鋳型側の表面温度Ｔ(０，ｚ，ｔ)を表わす式（Ａ）、（Ｂ）と、凝固シェルの鋳型側の表面−モールドパウダー層−熱電対間の熱収支に基づいて、鋳型を通過する熱流束ｑ _m (ｚ，ｔ)を表わす式（Ｃ）とを用いて、前記熱伝達係数α及び前記熱伝達係数βを同時に決定し、凝固シェルの厚みｓ(ｚ，ｔ)を計算する

ことを特徴とする。 In order to solve the above problems, the method for estimating the in-mold state of the present invention will be described. Continuously, the solidified shell, the mold powder layer, and the mold heat conductor exist between the molten steel and the cooling water for the mold. A method for estimating an in-mold state in casting, in which a heat transfer coefficient α between a solidified shell and a mold and a heat transfer coefficient β between a molten steel and a solid shell are estimated to estimate the in-mold state, Using a plurality of temperature measuring means embedded in the casting direction shifted in the heat flux acquisition procedure for acquiring the heat flux passing through the mold, the heat transfer coefficient α and the heat transfer coefficient β, the formula representing the heat flux through the mold, by using the heat flux obtained by the heat flux acquisition procedure, have a heat transfer coefficient determination procedure for determining the heat transfer coefficient α and the heat transfer coefficient β simultaneously ,
In the heat flux acquisition procedure,
d _w is the distance from the temperature measuring means to the water cooling position, h _w is the heat transfer coefficient between the mold and the cooling water, T _w is the cooling water temperature, and λ _m is the thermal conductivity of the mold.
Based on the temperature measurement values T _{m — obs} (z, t) of the plurality of temperature measuring means, the heat flux q _m (z, t) passing through the mold is calculated from the equation (D) ,

In the heat transfer coefficient determination procedure,
T is the temperature of the solidified shell, T ₀ is the temperature of the molten steel, T _s is the interface temperature between the molten steel and the solidified shell, u is the casting speed, λ _s is the thermal conductivity of the solidified shell , c _s is the specific heat of the solidified shell, ρ _s is the density of the solidified shell, L is the latent heat of the solidified shell, d is the distance from the surface of the solidified shell side of the mold to the temperature measuring means, and λ _m is the thermal conductivity of the mold.
The solidified shell thickness s (z, t) and the solidified shell mold-side surface temperature T (0, z, t) on a two-dimensional coordinate with the casting direction z-axis and the direction orthogonal to the casting direction x-axis. And a formula representing the heat flux q _m (z, t) passing through the mold based on the heat balance between the surface of the solidified shell on the mold side, the mold powder layer, and the thermocouple. (C) is used to simultaneously determine the heat transfer coefficient α and the heat transfer coefficient β, and calculate the thickness s (z, t) of the solidified shell.

It is characterized by that .

  According to the present invention, the heat transfer coefficient α between the solidified shell and the mold, which is the two main factors governing the state in the mold, and the heat transfer coefficient β between the molten steel and the solidified shell can be determined simultaneously. The influence of these factors on the solidification thickness of the in-mold cast can be quantitatively evaluated. Thereby, the influence which the powder inflow state or molten steel drift has on the slab solidification thickness can be estimated, which contributes to the improvement of slab quality and operability of continuous casting.

It is a figure which shows a part of cross section of the casting_mold | template of a continuous casting installation. It is a figure which shows the concept of the heat balance between the outer surface of a solidification shell-mold powder layer-thermocouple. It is a block diagram which shows an example of schematic structure of the hardware of the information processing apparatus which can function as an estimation apparatus of the state in a mold of this invention. It is a characteristic view which shows the temperature measurement value of each thermocouple in an Example, and the heat flux in each thermocouple position. It is a characteristic view which shows the change of the casting speed in an Example. It is a characteristic view which shows the change of the molten steel temperature in an Example. It is a characteristic view which shows the general heat transfer coefficient (alpha) and the molten steel side heat transfer coefficient (beta) of the mold powder layer which calculated | required applying this invention in the Example. It is a characteristic view which makes the axis | shaft the thickness of solidified shell calculated | required by applying this invention, time, and a z direction position.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram showing a solidified state in a mold, and shows a part of a cross section of a mold of a continuous casting facility. In FIG. 1, 1 is molten steel. Reference numeral 2 denotes a solidified shell (solidified layer) as a slab. 3 is a mold powder layer. Reference numeral 4 denotes a mold copper plate, in which a water cooling groove for flowing cooling water is formed. As shown in FIG. 1, the respective heat conductors of the solidified shell 2, the mold powder layer 3, and the mold copper plate 4 exist between the molten steel 1 and the cooling water for the mold.

  A plurality of thermocouples 5 are embedded in the mold copper plate 4 while being shifted in the casting direction. The thermocouples 5 are preferably arranged in a line in the casting direction (z-axis direction shown in FIG. 1), but even when they are shifted in the direction orthogonal to the casting direction (x-axis direction shown in FIG. 1), they will be described below. The position may be corrected by performing an interpolation calculation or the like during the calculation.

The surface of molten steel 1 in contact with the mold copper plate 4 is taken as the origin (0, 0) of the coordinate axis, the solidified layer growth on a two-dimensional coordinate with the casting direction z-axis and the solidified layer growth direction orthogonal to the casting direction x-axis. Is set as shown in the following equations (1) to (4). T is the temperature of the solidified shell 2, T ₀ is the temperature of the molten steel 1, and T _s is the interface temperature (solidification temperature) between the molten steel 1 and the solidified shell 2. s (z, t) is the thickness of the solidified shell 2. β (z, t) is a convective heat transfer coefficient between the molten steel 1 and the solidified shell 2 (referred to as “molten steel side heat transfer coefficient”), and α (z, t) is between the solidified shell 2 and the mold copper plate 4. (Referred to as “overall heat transfer coefficient of mold powder layer”). u is the casting speed. λ _s , c _s , ρ _s , and L are physical property values of the solidified shell 2, and are thermal conductivity, specific heat, density, and latent heat. T _m (0, z, t) is the temperature of the surface of the mold copper plate 4 on the solidified shell 2 side (the inner surface of the mold copper plate 4).

  That is, formula (1) represents the heat balance in the solidified shell 2. Equation (2) represents the boundary condition between the solidified shell 2 and the molten steel 1. Equation (3) represents the heat balance at the interface between the solidified shell 2 and the molten steel 1. Equation (4) represents the heat balance at the interface between the solidified shell 2 and the mold powder layer 3.

  Here, it is assumed that the temperature T of the solidified shell 2 can be described by a quadratic expression of x, and is approximated by the following expression (5).

  Equation (5) is substituted into Equations (1) to (4) to determine coefficient a (z, t) and coefficient b (z, t).

  From the coefficients a (z, t) and b (z, t), the thickness s (z, t) of the solidified shell 2 and the temperature of the surface of the solidified shell 2 on the mold copper plate 4 side (the outer surface of the solidified shell 2). T (0, z, t) can be described by the following equations (6) and (7).

Here, the reference time t ₀ is arbitrarily fixed, a new variable η (≧ 0) is introduced, and z = u · η and t = t ₀ + η are set. Thereby, Formula (6) can be transformed into the following Formulas (8) and (9).

  Moreover, Formula (7) can be deform | transformed like the following Formula (10).

  The difference approximation formula of Formula (8) becomes like the following Formula (11).

  On the other hand, when Expression (10) is discretized, the following Expression (12) is obtained.

  Furthermore, the equation (12) is transformed into the following equation (13).

  It is defined by the following symbols, and equation (13) is rewritten as equation (14).

  Equation (14) can be rewritten as a quadratic equation relating to y as in the following equation (15).

The procedure for calculating the thickness s (η _k ) of the solidified shell 2 will be described below. It is assumed that heat transfer coefficients α (η _k ) and β (η _k ) are given. On the surface of the molten steel 1, s (η ₁ ) = 0. By substituting this into equation (15), the quadratic equation is solved to obtain T (0, η ₁ ). Next, s (η ₁ ) and T (0, η ₁ ) are substituted into equation (11) to obtain Ψ (η ₂ ). Substituting Ψ (η ₂ ) into the left side of equation (9) and substituting T (0, η ₁ ) into the right side to obtain s (η ₂ ), substituting it into equation (15), and the quadratic equation To obtain T (0, η ₂ ). Thereafter, the time history s (η _k ) of the thickness of the solidified shell 2 can be calculated by repeating the same operation.

  Further, as shown in Patent Document 2, equations (1) to (4) can be calculated using a numerical calculation method such as a difference method, but by using the above-described method, Since the calculation speed is increased, the solidification state of the solidified shell 2 can be estimated online.

Next, a method for determining the heat transfer coefficients α (η _k ) and β (η _k ) will be described. As shown in FIG. 2, assuming that the heat balance between the surface of the solidified shell 2 on the mold copper plate 4 side (the outer surface of the solidified shell 2), the mold powder layer 3 and the thermocouple 5 is a quasi-steady state, 16). In FIG. 2, the dotted line indicates the relationship of temperature change. q _m is a heat flux passing through the mold copper plate 4 in the x-axis direction. d is the distance from the surface of the mold copper plate 4 on the solidified shell 2 side (the inner surface of the mold copper plate 4) to the thermocouple 5. λ _m is the thermal conductivity of the mold copper plate 4. As shown in equation (7), T (0, z _k , t) includes β (z _k , t), and equation (16) is an equation with the heat transfer coefficients α and β as unknowns. ing.

Here, the heat flux q _m (z _i , t) passing through the mold copper plate 4 in the x-axis direction is a temperature measurement value T _{m_obs} (z _i , t) of the plurality of thermocouples 5 embedded in the casting direction of the mold copper plate 4. ) To calculate the casting direction from the following equation (17) (i is a subscript representing a thermocouple). Heat flux q _m (z _i, t) by an interpolation calculation (interpolation or extrapolation calculation), it is possible to determine the heat flux q _m that passes through the mold copper plate 4 in the x-axis direction in any casting direction. _dw is the distance from the thermocouple 5 to the water cooling position. h _w is a heat transfer coefficient between the mold copper plate 4 and the cooling water. T _w is the cooling water temperature.

  In order to match the equation (16) with the equations (8) to (15), the previously defined variable η is used and rewritten as the following equation (18).

The heat transfer coefficients α (η _k ) and β (η _k ) are determined simultaneously from the equation (18) as a minimization problem by the least square method represented by the following equation (19), and the thickness of the solidified shell 2 The time history s (η _k ) is also calculated.

  As described above, the heat transfer coefficient α between the solidified shell 2 and the mold copper plate 4 and the heat transfer coefficient β between the molten steel 1 and the solidified shell 2 are simultaneously determined, and the thickness of the solidified shell 2 is calculated. can do. The heat transfer coefficient α between the solidified shell 2 and the mold copper plate 4 and the heat transfer coefficient β between the molten steel 1 and the solidified shell 2 are main factors governing the solidified state in the mold, and can be determined simultaneously. Therefore, it is possible to quantitatively evaluate the influence of these factors on the solidification thickness of the in-mold slab. Thereby, the influence which the powder inflow state or molten steel drift has on the slab solidification thickness can be estimated, which contributes to the improvement of slab quality and operability of continuous casting.

  In Patent Document 5, a heat conduction equation with a heat flux value predicted using a heat transfer inverse problem method as a boundary condition from a mold temperature detecting means arranged at a plurality of points in the casting direction is solved, and the solidification thickness of the molten metal is obtained. The heat flux value calculated by using the inverse heat problem method from the mold temperature detecting means arranged at a plurality of points in the casting direction and the inner surface temperature of the mold and the calculation result of the solidified shell temperature profile Thus, a configuration for solving the heat conduction equation and obtaining the powder inflow thickness is disclosed. In Patent Document 6, the mold temperature is measured by temperature measuring means embedded in a plurality of locations of the mold at intervals in the casting direction, and the heat flux on the inner surface of the mold is calculated based on the measured temperature of the mold. Estimate using a method, estimate the convective heat transfer due to molten metal flow from the heat flux inside the slab based on the estimated heat flux, and detect abnormalities in the molten metal flow in the mold based on the estimated convective heat transfer A configuration is disclosed. However, in any of the prior arts, as described above, the heat transfer coefficient α between the solidified shell 2 and the mold copper plate 4 and the heat transfer coefficient β between the molten steel 1 and the solidified shell 2 are simultaneously determined and solidified. The thickness of the shell 2 is not calculated.

  FIG. 3 is a block diagram illustrating an example of a schematic hardware configuration of the information processing apparatus 100 that can function as the in-mold state estimation apparatus according to the present invention. The information processing apparatus 100 includes a CPU 101 that is a central processing unit that performs the above-described arithmetic processing, a display unit 102 that displays various input conditions, calculation results, and the like, and a storage unit 103 such as a hard disk that stores calculation results and the like. Further, it has a ROM (Read Only Memory) 104 for storing arithmetic programs, various application programs, data and the like. In addition, it has a RAM (Random Access Memory) 105 which is a work area used when the CPU 101 performs processing based on the arithmetic program, and an input unit 106 such as a keyboard and a mouse.

  A program for causing a computer device to function as an in-mold state estimating device constitutes the present invention. As a storage medium for supplying the program, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  FIG. 4A is a characteristic diagram showing the temperature measurement values of the thermocouples L1 to L7, and FIG. 4B is the thermocouple L1 to L7 position obtained from the temperature measurement values of the thermocouples L1 to L7. It is a characteristic view which shows a heat flux. The thermocouples L1 to L7 are respectively installed at positions of 10 mm, 30 mm, 40 mm, 70 mm, 100 mm, 160 mm, and 270 mm from the hot water surface. The distance d from the inner surface of the mold copper plate to each of the thermocouples L1 to L7 is 10 mm, and the distance dw from each thermocouple to the water cooling position is 5 mm. The heat flux shown in FIG. 4B is obtained by the equation (17).

The heat conductivity λ _s of the solidified shell is 29 W / m · K, the specific heat c _s is 0.670 kJ / kg · K, the density ρ _s is 7650 kg / m ₃ , and the latent heat L is 268 kJ / kg. The mold copper plate has a thermal conductivity λ _m of 251 W / m · K. The heat transfer coefficient h _w between the mold copper plate and the cooling water is 30000 kcal / m ³ · Hr · ° C. The solidification temperature T _s is 1497 degrees.

FIG. 5 is a characteristic diagram showing changes in the casting speed u, and FIG. 6 is a characteristic diagram showing changes in the molten steel temperature T ₀ .

  FIG. 7A is a characteristic diagram showing the overall heat transfer coefficient α of the mold powder layer obtained by applying the present invention, and FIG. 7B is a characteristic showing the molten steel side heat transfer coefficient β obtained by applying the present invention. FIG. In the present embodiment, the molten steel surface is divided into three parts, that is, a molten metal surface to 90 mm, 90 mm to 180 mm, and 180 mm to 270 mm in the casting direction, and the overall heat transfer coefficient α and molten steel side heat transfer coefficient β of the mold powder layer are obtained.

  FIG. 8 is a characteristic diagram about the thickness, time, and z-direction position of the solidified shell 2 obtained by applying the present invention. The calculation is performed at a pitch of 100 s, the result is indicated by dots, and the interpolation calculation is performed. As shown in the figure, it can be seen that the thickness of the solidified shell 2 grows toward the casting direction.

  As mentioned above, although this invention was demonstrated with various embodiment, this invention is not limited only to these embodiment, A change etc. are possible within the scope of the present invention. For example, in the above embodiment, a thermocouple is used as a temperature measuring means. For example, an optical fiber grating sensor (FBG) as described in Patent Document 3 or a Raman scattering type optical fiber distribution as described in Patent Document 4 is used. A mold temperature measuring instrument or the like may be used.

1: Molten steel 2: Solidified shell 3: Mold powder layer 4: Mold copper plate 5: Thermocouple

Claims (3)

In continuous casting in which solidified shell, mold powder layer and mold heat conductor exist between molten steel and cooling water for mold, heat transfer coefficient α between solidified shell and mold, and molten steel and solidified shell A method for estimating a state in a mold by estimating a heat transfer coefficient β between and a state in a mold,
A heat flux acquisition procedure for acquiring a heat flux passing through the mold by using a plurality of temperature measuring means embedded in the mold while shifting the position in the casting direction,
The heat transfer coefficient α and the heat transfer coefficient β and the heat transfer coefficient β are used to express the heat flux passing through the mold and the heat flux acquired in the heat flux acquisition procedure. have a heat transfer coefficient determination procedure for determining the β simultaneously,
In the heat flux acquisition procedure,
d _w is the distance from the temperature measuring means to the water cooling position, h _w is the heat transfer coefficient between the mold and the cooling water, T _w is the cooling water temperature, and λ _m is the thermal conductivity of the mold.
Based on the temperature measurement values T _{m — obs} (z, t) of the plurality of temperature measuring means, the heat flux q _m (z, t) passing through the mold is calculated from the equation (D) ,

In the heat transfer coefficient determination procedure,
T is the temperature of the solidified shell, T ₀ is the temperature of the molten steel, T _s is the interface temperature between the molten steel and the solidified shell, u is the casting speed, λ _s is the thermal conductivity of the solidified shell , c _s is the specific heat of the solidified shell, ρ _s is the density of the solidified shell, L is the latent heat of the solidified shell, d is the distance from the surface of the solidified shell side of the mold to the temperature measuring means, and λ _m is the thermal conductivity of the mold.
The solidified shell thickness s (z, t) and the solidified shell mold-side surface temperature T (0, z, t) on a two-dimensional coordinate with the casting direction z-axis and the direction orthogonal to the casting direction x-axis. And a formula representing the heat flux q _m (z, t) passing through the mold based on the heat balance between the surface of the solidified shell on the mold side, the mold powder layer, and the thermocouple. (C) is used to simultaneously determine the heat transfer coefficient α and the heat transfer coefficient β, and calculate the thickness s (z, t) of the solidified shell.

An in-mold state estimation method characterized by the above. In continuous casting in which solidified shell, mold powder layer and mold heat conductor exist between molten steel and cooling water for mold, heat transfer coefficient α between solidified shell and mold, and molten steel and solidified shell An in-mold state estimating device for estimating a heat transfer coefficient β between and an in-mold state,
Heat flux acquisition means for acquiring heat flux passing through the mold using a plurality of temperature measuring means embedded in the casting direction shifted in the casting direction;
The heat transfer coefficient α and the heat transfer coefficient β include the heat transfer coefficient α and the heat transfer coefficient β, and the heat flux passing through the mold and the heat flux obtained by the heat flux obtaining means are used. heat transfer coefficient determining means for determining β simultaneously ,
The heat flux acquisition means is
d _w is the distance from the temperature measuring means to the water cooling position, h _w is the heat transfer coefficient between the mold and the cooling water, T _w is the cooling water temperature, and λ _m is the thermal conductivity of the mold.
Based on the temperature measurement values T _{m — obs} (z, t) of the plurality of temperature measuring means, the heat flux q _m (z, t) passing through the mold is calculated from the equation (D) ,

The heat transfer coefficient determination means includes
T is the temperature of the solidified shell, T ₀ is the temperature of the molten steel, T _s is the interface temperature between the molten steel and the solidified shell, u is the casting speed, λ _s is the thermal conductivity of the solidified shell , c _s is the specific heat of the solidified shell, ρ _s is the density of the solidified shell, L is the latent heat of the solidified shell, d is the distance from the surface of the solidified shell side of the mold to the temperature measuring means, and λ _m is the thermal conductivity of the mold.
The solidified shell thickness s (z, t) and the solidified shell mold-side surface temperature T (0, z, t) on a two-dimensional coordinate with the casting direction z-axis and the direction orthogonal to the casting direction x-axis. And a formula representing the heat flux q _m (z, t) passing through the mold based on the heat balance between the surface of the solidified shell on the mold side, the mold powder layer, and the thermocouple. (C) is used to simultaneously determine the heat transfer coefficient α and the heat transfer coefficient β, and calculate the thickness s (z, t) of the solidified shell.

An in-mold state estimation device characterized by the above. In continuous casting in which solidified shell, mold powder layer and mold heat conductor exist between molten steel and cooling water for mold, heat transfer coefficient α between solidified shell and mold, and molten steel and solidified shell A program for estimating the heat transfer coefficient β between and the state in the mold,
A heat flux acquisition process for acquiring a heat flux passing through the mold using a plurality of temperature measuring means embedded in the mold in a position shifted in the casting direction;
The heat transfer coefficient α and the heat transfer coefficient β and the heat transfer coefficient β are used to express the heat flux passing through the mold and the heat flux acquired in the heat flux acquisition process. causing the computer to execute a heat transfer coefficient determination process for simultaneously determining β ,
In the heat flux acquisition process,
d _w is the distance from the temperature measuring means to the water cooling position, h _w is the heat transfer coefficient between the mold and the cooling water, T _w is the cooling water temperature, and λ _m is the thermal conductivity of the mold.
Based on the temperature measurement values T _{m — obs} (z, t) of the plurality of temperature measuring means, the heat flux q _m (z, t) passing through the mold is calculated from the equation (D) ,

In the heat transfer coefficient determination process,
T is the temperature of the solidified shell, T ₀ is the temperature of the molten steel, T _s is the interface temperature between the molten steel and the solidified shell, u is the casting speed, λ _s is the thermal conductivity of the solidified shell , c _s is the specific heat of the solidified shell, ρ _s is the density of the solidified shell, L is the latent heat of the solidified shell, d is the distance from the surface of the solidified shell side of the mold to the temperature measuring means, and λ _m is the thermal conductivity of the mold.
The solidified shell thickness s (z, t) and the solidified shell mold-side surface temperature T (0, z, t) on a two-dimensional coordinate with the casting direction z-axis and the direction orthogonal to the casting direction x-axis. And a formula representing the heat flux q _m (z, t) passing through the mold based on the heat balance between the surface of the solidified shell on the mold side, the mold powder layer, and the thermocouple. (C) is used to simultaneously determine the heat transfer coefficient α and the heat transfer coefficient β, and calculate the thickness s (z, t) of the solidified shell.

A program characterized by that .

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