CN102416454A - Method for controlling dynamic soft reduction of continuous casting plate blank - Google Patents

Method for controlling dynamic soft reduction of continuous casting plate blank Download PDF

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CN102416454A
CN102416454A CN2011103862730A CN201110386273A CN102416454A CN 102416454 A CN102416454 A CN 102416454A CN 2011103862730 A CN2011103862730 A CN 2011103862730A CN 201110386273 A CN201110386273 A CN 201110386273A CN 102416454 A CN102416454 A CN 102416454A
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casting blank
casting
temperature
solidification
continuous casting
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王朝阳
贺建哲
马立军
王智轶
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Tianjin Iron and Steel Group Co Ltd
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Tianjin Iron and Steel Group Co Ltd
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Abstract

The invention belongs to metallurgical smelting, pressurizing and controlling technologies. The dynamic soft reduction of a continuous casting blank means reduction at the solidification tail end of the casting blank, and has good effects of homogenizing components, alleviating segregation, improving consistency and the like. Key technologies comprise reduction positions and reduction amount. In China patent CN200610117518, the invention discloses a dynamic soft reduction controlling method which is used for computing the solidification rate of the casting blank according to a heat conduction equation to determine the control over the dynamic soft reduction. Production practices are changed, so that the method is low in accuracy; therefore, the solidification rate of the casting blank is computed in an on-line continuous temperature measuring mode to determine the control over the dynamic soft reduction. The method comprises the following steps of: measuring the actual temperature of the surface of the casting blank on line; sending the actual temperature of the surface of the casting blank to a casting blank solidification unsteady state heat transfer model; computing the casting blank solidification unsteady state heat transfer model; and modifying a dynamic soft reduction position by using a dynamic soft reduction secondary computer control system. Therefore, the aim of accurately controlling the soft reduction is fulfilled.

Description

A kind ofly control the method that continuous casting steel billet is dynamically gently depressed
Technical field
Melting and the pressure that the invention belongs to Ferrous Metallurgy adds, the kinetic-control system in control technology field, particularly continuous casting billet.
Background technology
Continuous casting has replaced the main mode of production that die casting becomes steel now.Composition is even, the steel billet of high equiaxed zone ratio and the development requires continuous casting of high-grade steel can provide, to improve the performance of stocking.The technology of dynamically gently depressing has been brought into play remarkable effect as improving the strand equiaxed zone ratio, improving one of important means of strand internal soundness to improving the continuous casting billet solidified structure.
Dynamically gently depressing the solidification end enforcement that is meant at strand gently depresses; The solidification front of enrichment solute is added strong convection and stirring, promotes dendrite to fracture, come off and remelting, increase crystallization nuclei and solidify degree of supercooling; The center thermal center regional organization of refinement strand final set also makes the chemical composition homogenising of strand; Thereby obtain alleviating center segregation, improve the effect of the center density of strand.And the key technology of dynamically gently depressing is confirming of depressing position and drafts.If depressing position is improper, drafts is excessive, possibly cause strand middle crack or deformation defect tendency to increase; If drafts is too small, then for improving strand center compactness and alleviating the DeGrain of center gross segregation.
In the prior art, application number is in the application open file of 200610117518 Chinese patent " dynamic light pressing control method ", this disclosure of the Invention the dynamic light pressing control method in a kind of continuous casting field.This method is to calculate according to the equation of heat conduction to predict for the liquid core point of casting blank solidification rate, and definite then light depressing position and drafts are gently depressed.Yet, in actual production process,, can directly have influence on the position of casting blank solidification liquid core, so follow some discrepancy of actual production after all with Theoretical Calculation derivation casting blank solidification rate owing to the variation of continuous casting tundish temperature and pulling rate.
Summary of the invention
The present invention is in order to overcome the existing deficiency of dynamically gently depressing computation model prediction casting blank solidification rate accuracy, invents a kind of mode of utilizing online continuous temperature measurement and calculates the casting blank solidification rate and control the method that continuous casting steel billet is dynamically gently depressed.
The present invention has furtherd investigate and has dynamically gently depressed model theory, finds in actual production process, to adopt casting blank surface temperature and the strand real surface temperature of dynamically gently depressing Model Calculation that deviation is arranged.The present invention uses casting blank surface temperature on-line measurement device, measures casting blank surface temperature.According to the casting blank surface temperature of actual measurement, set up continuous casting billet and solidify the unsteady-state heat transfer model, calculate the actual solidification rate of strand.According to the actual solidification rate of strand, the control strand is dynamically gently depressed.Reach accurate control strand and gently depress, improve the purpose of strand internal soundness.
A kind of method that continuous casting steel billet is dynamically gently depressed of controlling of the present invention; Use casting blank surface temperature on-line measurement device; Measure the casting billet surface actual temperature, then the casting billet surface actual temperature is sent to casting blank solidification unsteady-state heat transfer model (5), calculate the casting blank solidification rate through casting blank solidification unsteady-state heat transfer model (5); Carry out the correction of dynamically light depressing position by dynamically gently depressing second computer control system (6), thereby reach the purpose that accurate control is gently depressed.
It is the unstable state heat conduction differential equation that establishes endogenous pyrogen to the process of setting of continuous casting billet that said continuous casting billet solidifies the unsteady-state heat transfer model.Said strand on-line continuous temperature measuring equipment; Use infrared temperature probe (1) to gather the radiation signal that casting billet surface sends with the noncontact mode; And this signal transition exported to signal processor (3) for the corresponding signal of telecommunication, signal processor (3) with the signal of collecting through calculating actual temperature.
Measure in the temperature measuring equipment that uses at said casting blank surface temperature; Infrared temperature probe (1); Be provided with air draft drifting dust and the accurate target device (8) that dispels steam towards strand one side; Can the steam on the thermometric path, dust be blown away, so that guarantee to gather temperature measurement signal accurately, solve two cold-zones because steam, dust influence the difficult problem of thermometric value.Said casting blank surface temperature is measured in the temperature measuring equipment that uses, and the distance between accurate target device (8) and the casting billet surface is 10-250mm, and air conditioning processor (4) setting pressure is 0.05～0.4MPa
Set up corresponding heat transfer model based on heat conservation on the slab thickness direction central longitudinal section.Being assumed to be of casting blank solidification heat transfer model: 1. ignore the heat conduction of width of plate slab direction; 2. ignore because of solidifying cooling and shrink the strand change in size that causes; 3. adopt equivalence to strengthen thermal conductivity factor and handle the molten steel convection heat transfer' heat-transfer by convection, 4. combine actual temperature measurement data to calculate casting blank liquid core length and realized the accurate control of dynamically gently depressing.
Strand unstable state solidification and heat transfer equation is:
ρ C p = ( ∂ T ∂ t + v ∂ T ∂ t ) = ∂ ∂ x ( k eff ∂ T ∂ x ) + ∂ ∂ y ( k eff ∂ T ∂ y ) + S ;
Wherein, k Eff(T)=k (T) f s+ mk (T) (1-f s)
k ( T ) = k s T < T S k s + T - T s T l - T s ( k l - k s ) T S &le; T &le; T L k l T > T L
In the formula: V is a casting speed, m/s; ρ density, kg/m 3C pBe equivalent specific heat, J/ (kgK); T is a temperature, K; X, y are respectively the coordinate on slab thickness and the throwing length direction, m; f sBe solid rate; M is empirical (often getting 4～8).k EffBe effective thermal conductivity, W/m ℃; K (T) is equivalent thermal conductivity factor, W/ (mK); k lBe the molten steel thermal conductivity factor, W/m ℃; k sBe solid-state steel thermal conductivity factor, W/m ℃; T lBe liquidus temperature, ℃; T sBe solidus temperature, ℃; S is a latent heat of solidification, W/m 3This paper adopts equivalent method of specific heat to handle latent heat of solidification.Equation casting billet surface boundary condition in secondary cooling zone is a boundary condition with the actual temperature that two cold continuous temperature measurement systems record.
This method can effectively reduce the adjustment number of times of dynamically gently depressing when guaranteeing gently to depress regional dynamic tracking slab liquid core position, thus the adverse effect of avoiding dynamic numerous adjustment of gently depressing to bring to slab quality.This method is gently depressed control cycle at each; At first calculate the distribution of continuous casting steel billet temperature inside according to the casting blank surface temperature measured data and the equation of heat conduction; Confirm the center solidification rate of each point on the continuous casting steel billet, and confirm the dynamic light depressing position of expectation, the middle bag temperature during then according to casting rate and each section generation; Change in location to having the liquid core point of specifying solidification rate is judged, takes corresponding dynamic gently to depress the adjustment measure.
This method is through the on-line continuous thermometric; Measure casting blank surface temperature; And then, improved the reliability of simple use calculated with mathematical model according to calculated with mathematical model casting blank solidification rate, match with the actual solidification end of strand; Thereby realize the accurate control that strand is dynamically gently depressed, improve the strand center segregation and improved slab quality.
Description of drawings:
Below in conjunction with description of drawings.Accompanying drawing 1 is a temp measuring system flow chart of the present invention, and accompanying drawing 2 is that continuous casting billet of the present invention solidifies unsteady-state heat transfer model sketch map.
In accompanying drawing 1, (1) infrared temperature probe, (2) hinge bracket, (3) signal processor, (4) air conditioning processor, (5) continuous casting billet solidify unsteady-state heat transfer model, (6) dynamically gently depresses secondary control computer, (7) strand, (8) accurate target device, (9) temperature measurement on-line point.
The specific embodiment:
Be design and installation slab on-line continuous thermometric shown in accompanying drawing 1, casting blank surface temperature is carried out the on-line continuous thermometric.
The on-line continuous temperature measuring equipment is installed in conticaster VI, VII, VIII section terminal position, measures 3 temperature in casting billet surface left, center, right.Concrete measuring method: use infrared temperature probe (1) to gather the radiation signal that send on strand (7) surface with the noncontact mode; And this signal transition exported to signal processor (3) for the corresponding signal of telecommunication; Signal processor (3) filters out obvious numerical value on the low side in the signal of collecting; Remaining is as valid data, and process calculates actual temperature.Then the casting billet surface actual temperature being sent to casting blank solidification unsteady-state heat transfer model (5) calculates; Calculate the casting blank solidification rate through casting blank solidification unsteady-state heat transfer model (5), carry out the correction of dynamically light depressing position by dynamically gently depressing second computer control system (6).Thereby reach the purpose that accurate control is gently depressed.
Casting blank surface temperature is measured in the temperature measuring equipment that uses; Infrared temperature probe (1); Be provided with air draft drifting dust and the accurate target device (8) that dispels steam towards strand (7) one sides; Can the steam on the thermometric path, dust be blown away, so that guarantee to gather temperature measurement signal accurately, solve two cold-zones because steam, dust influence the difficult problem of thermometric value.
Said casting blank surface temperature is measured in the temperature measuring equipment that uses, and the distance between accurate target device (8) and the casting billet surface is 10-250mm, and air conditioning processor (4) setting pressure is 0.05～0.4MPa.
Shown in accompanying drawing 2, be based on the slab thickness direction central longitudinal section heat conservation and set up corresponding heat transfer model.Being assumed to be of casting blank solidification heat transfer model: 1. ignore the heat conduction of width of plate slab direction; 2. ignore because of solidifying cooling and shrink the strand change in size that causes; 3. adopt equivalence to strengthen thermal conductivity factor and handle the molten steel convection heat transfer' heat-transfer by convection, 4. combine actual temperature measurement data to calculate casting blank liquid core length and realized the accurate control of dynamically gently depressing.
Strand unstable state solidification and heat transfer equation is:
&rho; C p = ( &PartialD; T &PartialD; t + v &PartialD; T &PartialD; t ) = &PartialD; &PartialD; x ( k eff &PartialD; T &PartialD; x ) + &PartialD; &PartialD; y ( k eff &PartialD; T &PartialD; y ) + S ;
Wherein, k Eff(T)=k (T) f s+ mk (T) (1-f s)
k ( T ) = k s T < T S k s + T - T s T l - T s ( k l - k s ) T S &le; T &le; T L k l T > T L
In the formula: V is a casting speed, m/s; ρ density, kg/m 3C pBe equivalent specific heat, J/ (kgK); T is a temperature, K; X, y are respectively the coordinate on slab thickness and the throwing length direction, m; f sBe solid rate; M is empirical (often getting 4～8).k EffBe effective thermal conductivity, W/m ℃; K (T) is equivalent thermal conductivity factor, W/ (mK); k lBe the molten steel thermal conductivity factor, W/m ℃; k sBe solid-state steel thermal conductivity factor, W/m ℃; T lBe liquidus temperature, ℃; T sBe solidus temperature, ℃; S is a latent heat of solidification, W/m 3This paper adopts equivalent method of specific heat to handle latent heat of solidification.Equation casting billet surface boundary condition in secondary cooling zone is a boundary condition with the actual temperature that two cold continuous temperature measurement systems record.
Embodiment:
1. chemical analysis control
Figure BDA0000113756880000061
2. production specification
Strand size: 250mm*2100mm
3. casting parameters
Figure BDA0000113756880000062
pulling rate: 1.0m/min;
Figure BDA0000113756880000063
tundish degree of superheat: Δ T=25 ℃;
Figure BDA0000113756880000064
primary cooling water: wide 5000L/min, leptoprosopy 580L/min;
Figure BDA0000113756880000065
secondary cooling water (cooling jig): one-level soft, secondary Aperi;
4. conticaster Model Calculation casting blank solidification end position:
5. according to actual measurement casting blank surface temperature and casting blank solidification Model Calculation casting blank solidification end position:
This method is through the on-line continuous thermometric; Measure casting blank surface temperature; And then, improved the reliability of simple use calculated with mathematical model according to calculated with mathematical model casting blank solidification rate, match with the actual solidification end of strand; Thereby realize the accurate control that strand is dynamically gently depressed, improve the strand center segregation and improved slab quality.

Claims (5)

1. control the method that continuous casting steel billet is dynamically gently depressed for one kind; It is characterized in that using casting blank surface temperature on-line measurement device; Measure the casting billet surface actual temperature, then the casting billet surface actual temperature is sent to casting blank solidification unsteady-state heat transfer model (5), calculate the casting blank solidification rate through casting blank solidification unsteady-state heat transfer model (5); Carry out the correction of dynamically light depressing position by dynamically gently depressing second computer control system (6), thereby reach the purpose that accurate control is gently depressed.
2. the method that control continuous casting steel billet as claimed in claim 1 is dynamically gently depressed is characterized in that it is the unstable state heat conduction differential equation that establishes endogenous pyrogen to the process of setting of continuous casting billet that said continuous casting billet solidifies the unsteady-state heat transfer model.
3. the method that control continuous casting steel billet as claimed in claim 1 is dynamically gently depressed; It is characterized in that said strand on-line continuous temperature measuring equipment; Use infrared temperature probe (1) to gather the radiation signal that casting billet surface sends with the noncontact mode; And this signal transition exported to signal processor (3) for the corresponding signal of telecommunication, signal processor (3) with the signal of collecting through calculating actual temperature.
4. the method for dynamically gently depressing like claim 1 or 3 described control continuous casting steel billets; It is characterized in that in the temperature measuring equipment of casting blank surface temperature measurement use; Infrared temperature probe (1) is provided with air draft drifting dust and the accurate target device (8) that dispels steam towards strand one side, can the steam on the thermometric path, dust be blown away; So that guarantee to gather temperature measurement signal accurately, two cold-zones have been solved because steam, dust influence the difficult problem of thermometric value.
5. the method for dynamically gently depressing like claim 1 or 3 described control continuous casting steel billets; It is characterized in that in the temperature measuring equipment of said casting blank surface temperature measurement use; Distance between accurate target device (8) and the casting billet surface is 10-250mm, and air conditioning processor (4) setting pressure is 0.05～0.4MPa.
CN2011103862730A 2011-11-29 2011-11-29 Method for controlling dynamic soft reduction of continuous casting plate blank Pending CN102416454A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107457378A (en) * 2017-07-25 2017-12-12 北京科技大学 The method that continuous casting steel billet three-dimensional dynamic water distribution water is set and controllable slighter compress is realized
JP2020001064A (en) * 2018-06-28 2020-01-09 日本製鉄株式会社 Central solid phase rate estimation method for continuous cast slab
CN112589063A (en) * 2020-11-19 2021-04-02 中冶南方连铸技术工程有限责任公司 Method and system for controlling pressure under bloom continuous casting light pressure
CN114905020A (en) * 2022-05-16 2022-08-16 北京科技大学 Method for correcting solidification heat transfer model in continuous casting process

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101162171A (en) * 2007-11-28 2008-04-16 重庆大学 Method for measuring surface temperature of high-temperature casting billet within water fog medium
CN101168188A (en) * 2006-10-25 2008-04-30 宝山钢铁股份有限公司 Dynamic light pressing control method
JP2010223683A (en) * 2009-03-23 2010-10-07 Stanley Electric Co Ltd Noncontact type temperature sensor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101168188A (en) * 2006-10-25 2008-04-30 宝山钢铁股份有限公司 Dynamic light pressing control method
CN101162171A (en) * 2007-11-28 2008-04-16 重庆大学 Method for measuring surface temperature of high-temperature casting billet within water fog medium
JP2010223683A (en) * 2009-03-23 2010-10-07 Stanley Electric Co Ltd Noncontact type temperature sensor

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107457378A (en) * 2017-07-25 2017-12-12 北京科技大学 The method that continuous casting steel billet three-dimensional dynamic water distribution water is set and controllable slighter compress is realized
JP2020001064A (en) * 2018-06-28 2020-01-09 日本製鉄株式会社 Central solid phase rate estimation method for continuous cast slab
JP7021608B2 (en) 2018-06-28 2022-02-17 日本製鉄株式会社 Method for estimating the central solid phase ratio of continuously cast slabs
CN112589063A (en) * 2020-11-19 2021-04-02 中冶南方连铸技术工程有限责任公司 Method and system for controlling pressure under bloom continuous casting light pressure
CN114905020A (en) * 2022-05-16 2022-08-16 北京科技大学 Method for correcting solidification heat transfer model in continuous casting process
CN114905020B (en) * 2022-05-16 2022-12-27 北京科技大学 Method for correcting solidification heat transfer model in continuous casting process

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Application publication date: 20120418