KR101573666B1 - Method for the continuous casting of a metal strand - Google Patents
Method for the continuous casting of a metal strand Download PDFInfo
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- KR101573666B1 KR101573666B1 KR1020107028210A KR20107028210A KR101573666B1 KR 101573666 B1 KR101573666 B1 KR 101573666B1 KR 1020107028210 A KR1020107028210 A KR 1020107028210A KR 20107028210 A KR20107028210 A KR 20107028210A KR 101573666 B1 KR101573666 B1 KR 101573666B1
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- strand
- continuous casting
- metal
- account
- thermal conduction
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
- B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Continuous Casting (AREA)
Abstract
The present invention relates to a method for continuous casting of metal strands, in particular steel strands, in a continuous casting plant wherein the strand having a liquid core surrounded by a strand sheath is drawn from a cooled in-line mold, Supported in a support and cooled using a coolant, wherein the thermodynamic state change of the entire strand is co-computed in a mathematical simulation model taking into account the physical parameters of the metal, the strand thickness and the continuously measured output speed. It is an object of the present invention to provide a method of the aforementioned type which can be used to increase the accuracy of the simulation of the change of thermodynamic state of the whole strand and in combination with the strand cooling, The productivity of the process can be improved. This objective is achieved by a method in which a three-dimensional thermal conduction equation is numerically interpreted in real time in a mathematical simulation model and the cooling of the strand is controlled while taking into account the calculated state change.
Description
The present invention relates to a continuous casting method of metal strands.
More particularly, the present invention relates to a method for continuous casting of metal strands, in particular steel strands, in a continuous casting plant wherein a strand having a liquid core surrounded by a strand shell is cooled in- line mold, supported in a strand support device downstream of the mold and cooled using a coolant, wherein the thermodynamic state change of the entire strand is determined by physical parameters of the metal, the thickness of the strand and the constantly measured (Co-calculated) in the mathematical simulation model, taking into account the output speed.
DE 4417808 A1 discloses a process for the continuous casting of metal strands wherein a strand having a liquid core surrounded by a strand sheath is drawn from a cooled mold and subsequently supported in a strand support device and used And cooled. The change in state that occurs during the continuous casting process is co-calculated in real time for the entire strand by a mathematical simulation model that includes a two-dimensional thermal conduction equation, Adjust the cooling of the strand while considering.
Due to the two-dimensional nature of the thermal conduction equation used, it has not yet been possible to calculate the thermal conduction and concomitant relative changes in all directions of the metal strand (strand thickness, strand width and strand output direction) The temperature profile could not be conveniently adjusted by strand cooling as the temperature changed. Also, due to thermodynamic effects (not considered in the simulation model), a deviation occurs between the calculated freezing point and the actual freezing point.
It is an object of the present invention to provide a method of the aforementioned type which can be used to increase the accuracy of the simulation of the change of thermodynamic state of the whole strand and in combination with the strand cooling, The productivity of the process can be improved.
This object is achieved by a method of the type described above, in which a three-dimensional thermal conduction equation is numerically analyzed in real time in a mathematical simulation model and the cooling of the strand is taken into account, taking into account the calculated state changes.
By the method of DE 4417808 A1, the thermodynamic state change can be calculated in real time according to two-dimensional thermal conduction, and the strand's temperature profile can be influenced by the strand cooling. According to the method according to the invention, the non-linear, non-steady state heat (or non-steady state) heat is generated according to the three-dimensional heat conduction i.e. the heat conduction in the strand thickness direction, The conduction equation makes it possible to easily influence the thermodynamic state change. By doing this, the thermodynamic state change can be calculated with higher accuracy and can be very easily affected by the strand cooling that is tailored to it. In a mathematical simulation model, the strands are divided into separate volume elements, that is, "discretized ", wherein each intermittent volume element is oriented in the strand length direction, And extend in the strand width direction.
By this interruption, individual strand cooling nozzles can be assigned to one or more intermittent volume elements of the strand, thereby eliminating it on the one hand by thermal conduction and strand cooling in all spatial dimensions The thermodynamic state changes in these volumetric elements can be determined with high accuracy while taking into account the calories, and on the other hand the thermodynamic properties of the strands can be very conveniently and very effectively influenced by these nozzles.
In a particularly preferred embodiment, the three-dimensional thermal conduction equation is numerically interpreted in real time in a mathematical simulation model of the method according to the invention, taking into account the temperature-dependent density variation of the metal strands. It is well known to those skilled in the art that the density of the metal can vary considerably with temperature. In a continuous casting process, for example, the density of steel is increased from about 7000 kg / m 3 to about 7800 kg / m 3 at 300 ° C (solidified strand) at 1550 ° C (the temperature of the melt in the tundish) do. The density variation is also related to the thermal conduction equation for determining the solidification point in the continuous casting process. The solidification point refers to the point at which the metal strands completely solidify past the direction of strand output, i. E., The point at which the metal strand no longer contains the liquid core. It is highly desirable in any case to calculate the freezing point to the maximum accuracy. If the position of the freezing point is underestimated, that is, not far from the mold than there is a real point along the output direction, this could result in a very dangerous casting situation (e.g. strand breakage). On the other hand, if the freezing point is overestimated, acceptable casting speeds will be unnecessarily limited, thereby reducing the productivity of the equipment.
In interpreting the numerical value of the heat conduction equation taking into account the temperature-dependent density variation of the metal strands, the approximated equation for the enthalpy with correct mass and correct enthalpy for the entire strand is used Another particularly preferred embodiment of the method according to the invention can be achieved. Here, it should be noted that no three-dimensional non-linear and non-steady state thermal conduction equations have been analyzed so far, taking into account temperature-dependent density variations. Without taking temperature-dependent density changes into account, the thermal conduction equation currently in use is merely a rough approximation of the exact equation, and such a solution can be quite different from the exact interpretation. However, using an estimated equation for the enthalpy with the correct mass and the correct enthalpy as a whole (i.e., when the entire strand is taken into account) ensures that these essential thermodynamic state variables correspond to the correct values.
When the thermal conduction equation is numerically analyzed by a finite volume method or a finite volume method or by a finite element method, the method according to the present invention may be particularly preferably carried out. The thermal conduction equation is a parabolic partial differential equation which can be interpreted by standard methods of numerical mathematics and can be interpreted in particular by finite volume methods or finite element methods : Numerische Mathematik [numerical mathematics] by IN Bronstein, KA Semendjajew, G. Musiol, H. Muehlig: Taschenbuch der Mathematik [handbook of mathematics], Verlag Harri Deutsch, 6 th edition, 2005).
The method according to the invention can be particularly advantageously practiced when the thermodynamic state change is calculated for only one quarter of the strand cross section based on spatial symmetry. This simplification can be accomplished without loss of accuracy due to spatial symmetry and time-varying boundary conditions of the strand cross-section, so that even with relatively low-power process computers, three-dimensional thermal conduction equations Can be interpreted.
The method according to the invention can be used to improve the quality of the cast metal strands without the limitation of casting metal strands having billet, bloom, slab or slab-slab cross-sections of any dimensions It will be possible.
Other features and advantages of the present invention will become apparent from the following non-limiting exemplary embodiments, with reference to the accompanying drawings.
1 is a side view of a continuous casting installation;
Fig. 2 is a view showing interrupted metal strands. Fig.
Figure 3 is a graph comparing the analysis of different formulations of thermal conduction equations.
According to the invention, the strands (6) are cooled in a controlled manner at fixed or variable specific locations of the strand supporting device (7). The three dimensional thermal conduction equation is analyzed in real time with the help of the
The three-dimensional non-linear and non-steady state heat transfer equations of the enthalpy formulations can be described, for example, as follows:
At this time
t is the time in seconds,
x is the coordinates of the strand thickness direction in m,
y is a coordinate in the strand width direction in units of m,
z is the output direction in m, that is, the coordinates of the strand longitudinal axis,
Is a partial derivative of the time t,
Is a partial derivative of the position (x, y, z)
Is a position vector in a right-angled coordinate system of m,
ρ is the density in kg / m 3 ,
Is the mass-related enthalpy at time (t) and position (x) in J / kg,
ξ is a dimensionless dummy variable,
Is the output speed of the strand in m / s at time t.
In this heat conduction equation, the temperature-dependent density variation of the strand 6 is still ignored. Since the density of
The second formulation of non-linear three-dimensional and non-steady state heat conduction equations is as follows:
At this time,
Is the temperature in K units at time (t) and position (x)
Denotes the density of the metal strands in the unit of kg / m 3 at the temperature (T).
This formulation of the thermal conduction equation is mass-correct in its entirety, that is, considering the entire strand, but it is inaccurate with respect to enthalpy. It can be seen that the solidification point is overestimated in this thermal conduction equation, that is, the actual solidification point is not farther away from the mold than the calculated solidification point. Accordingly, although the use of these equations is not a problem with respect to any adverse casting situation, the maximum allowable casting speed is nevertheless unnecessarily limited, which leads to a reduction in productivity of the equipment.
The following thermal conduction equations may preferably be used:
At this time,
Is the mass-related enthalpy transformed at time (t) and position (x).
In this case, the overall correct modified enthalpy < RTI ID = 0.0 >
Use two expressions. The thermodynamic conditions in the strand 6 change significantly at theAbove the freezing point (19), the expression is:
.
On the other hand, below the freezing
.
From here,
(Arbitrary) but a constant reference temperature (typically 25 ° C)
Is the temperature (K) of the metal in the casting bath,
Is the derivative of the mass-related enthalpy over time.
The thermal conduction equation is based on Lagrangian coordinates,
Lt; / RTI > to be observed by an observer moving with the strand output movement. These variations are as follows:
At this time,
Represents the time (in seconds) when an intermittent volumetric element is formed in the mold.
The thermal conduction equation in the Lagrangian coordinates is:
This thermal conduction equation is interpreted in real time by the
As shown in Fig. 2, the strand thickness axis x and the strand width axis y are symmetrical with respect to the edge of the coagulating strand 6. This spatial symmetry along the strand width and strand thickness direction provides the advantage that the thermodynamic state change can be calculated for only one quarter of a
However, in order to interpret the thermal conduction equations, boundary conditions are still required, both initial conditions and time-varying (due to movement of the volume elements through the mold and through the various cooling zones).
The initial conditions for the newly formed volume element are:
The boundary conditions are roughly as follows:
At this time,
The Lt; / RTI > is the temperature-dependent thermal conductivity,
Is a temperature gradient perpendicular to the surface,
Is the specific heat flux at time t.
To model the thermal flux q (t), the following expressions are used inside the cooled mold 1:
Outside the mold,
At this time,
a mold (T surf (t)) is the heat dissipation function of the mold,
α water (sw (t)) is the heat dissipation function of strand cooling,
(sw (t)) is the amount of cooling water for strand cooling,
α roll (t) is the heat dissipation function of the support roll,
σ is a Stefan-Boltzmann constant,
is the emissivity,
T surf (t) is the surface temperature of the strand 6,
T amb Is the ambient temperature.
Since the three-dimensional thermal conduction equation has not been interpreted so far, the high accuracy of the formulation of the thermal conduction equation with the modified enthalpy E trans according to the invention should be checked with the aid of a one-dimensional example. An accurate interpretation of the thermal conduction equation considering the temperature-dependent density variation (solid line) is known as a one-dimensional case and in Figure 3 a mass-accurate formulation (dotted line) and mass- and enthalpy- As shown in Fig. In Fig. 3, the distance from the mold in the strand output direction is denoted in the ordinate and the thickness of the metal strand along the strand thickness direction is denoted in abscissa. As shown in Figure 3, when using the mass- and enthalpy-accurate formulation of the thermal conduction equation, the actual freezing point is located slightly further from the mold than the calculated freezing point, i. E., The freezing point is slightly overestimated. By comparison, the freezing point is significantly underestimated when using the mass-exact formulation of the thermal conduction equation, which can lead to a hazardous situation in the continuous casting process.
One; Mold
2; steal
3; Turn Dish
4; Strand liquid core
5; Strand sheath
6; Strand
7; Strand support device
8; Support roll
9; Roll interval
10; Cooling nozzle
11; Refrigerant supply line
12; valve
13; Flow meter
14; Actuator
15; Process computer
16; Control element
17; Input unit
18; Output unit
19; Intermittent bulk factor
20; Strand powder
Claims (4)
Three-dimensional thermal conduction equations are numerically analyzed in real-time in a mathematical simulation model, taking into account temperature-dependent density variations of metal strands, and the cooling of the metal strands is controlled
Continuous casting method.
Taking account of the temperature-dependent density variation of the metal strands, an estimate of enthalpy, with an accurate mass and an accurate enthalpy for the entire metal strand, is used in a numerical solution of the thermal conductivity equation
Continuous casting method.
The thermal conduction equation is numerically interpreted by a finite volume method or a finite element method
Continuous casting method.
The thermodynamic state change is calculated only for one quarter of the metal strand cross section based on the spatial symmetry
Continuous casting method.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT8152008A AT506847B1 (en) | 2008-05-21 | 2008-05-21 | METHOD FOR CONTINUOUSLY GASING A METAL STRUCTURE |
ATA815/2008 | 2008-05-21 |
Publications (2)
Publication Number | Publication Date |
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KR20110020828A KR20110020828A (en) | 2011-03-03 |
KR101573666B1 true KR101573666B1 (en) | 2015-12-02 |
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KR1020107028210A KR101573666B1 (en) | 2008-05-21 | 2009-04-22 | Method for the continuous casting of a metal strand |
Country Status (7)
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EP (1) | EP2279053B1 (en) |
KR (1) | KR101573666B1 (en) |
CN (1) | CN102083573B (en) |
AT (1) | AT506847B1 (en) |
ES (1) | ES2548978T3 (en) |
SI (1) | SI2279053T1 (en) |
WO (1) | WO2009141205A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR102098023B1 (en) | 2018-10-24 | 2020-04-07 | 주식회사 포스코 | Apparatus for setting temperature of continuous casting device |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2012107143A1 (en) * | 2011-02-07 | 2012-08-16 | Siemens Vai Metals Technologies Gmbh | Method for regulating a temperature of a strand by positioning a movable cooling nozzle in a strand guide of a strand casting system |
DE102011082158A1 (en) | 2011-09-06 | 2013-03-07 | Sms Siemag Ag | Casting, in particular continuous casting |
EP3437756B1 (en) | 2017-08-04 | 2021-12-22 | Primetals Technologies Austria GmbH | Continuous casting of a metallic strand |
EP3437759B1 (en) | 2017-08-04 | 2022-10-12 | Primetals Technologies Austria GmbH | Continuous casting of a metallic strand |
EP3437757A1 (en) | 2017-08-04 | 2019-02-06 | Primetals Technologies Austria GmbH | Continuous casting of a metallic strand |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE4417808A1 (en) * | 1993-05-24 | 1994-12-01 | Voest Alpine Ind Anlagen | Method for the continuous casting of a metal billet |
JP2004506515A (en) * | 2000-07-01 | 2004-03-04 | エイ・イー・エム・ピー・コーポレーション | Heat flow simulation for casting / forming process |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19612420C2 (en) * | 1996-03-28 | 2000-06-29 | Siemens Ag | Method and device for controlling the cooling of a strand in a continuous caster |
DE19850253A1 (en) * | 1998-10-31 | 2000-05-04 | Schloemann Siemag Ag | Method and system for controlling cooling sections |
AT409352B (en) * | 2000-06-02 | 2002-07-25 | Voest Alpine Ind Anlagen | METHOD FOR CONTINUOUSLY casting a METAL STRAND |
DE102005036068A1 (en) * | 2005-08-01 | 2007-02-08 | Siemens Ag | Modeling method for the time course of the state of a steel volume by a computer and corresponding objects |
-
2008
- 2008-05-21 AT AT8152008A patent/AT506847B1/en active
-
2009
- 2009-04-22 KR KR1020107028210A patent/KR101573666B1/en active IP Right Grant
- 2009-04-22 CN CN200980118394.8A patent/CN102083573B/en active Active
- 2009-04-22 ES ES09749695.4T patent/ES2548978T3/en active Active
- 2009-04-22 EP EP09749695.4A patent/EP2279053B1/en active Active
- 2009-04-22 WO PCT/EP2009/054776 patent/WO2009141205A1/en active Application Filing
- 2009-04-22 SI SI200931321T patent/SI2279053T1/en unknown
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE4417808A1 (en) * | 1993-05-24 | 1994-12-01 | Voest Alpine Ind Anlagen | Method for the continuous casting of a metal billet |
JP2004506515A (en) * | 2000-07-01 | 2004-03-04 | エイ・イー・エム・ピー・コーポレーション | Heat flow simulation for casting / forming process |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR102098023B1 (en) | 2018-10-24 | 2020-04-07 | 주식회사 포스코 | Apparatus for setting temperature of continuous casting device |
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Publication number | Publication date |
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CN102083573A (en) | 2011-06-01 |
AT506847A1 (en) | 2009-12-15 |
EP2279053A1 (en) | 2011-02-02 |
WO2009141205A1 (en) | 2009-11-26 |
SI2279053T1 (en) | 2015-12-31 |
KR20110020828A (en) | 2011-03-03 |
CN102083573B (en) | 2014-12-10 |
AT506847B1 (en) | 2011-07-15 |
EP2279053B1 (en) | 2015-08-26 |
ES2548978T3 (en) | 2015-10-22 |
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