CN103192039A - Method for removing inclusions by means of determining height of vertical section of continuous casting machine for extra-thick slabs - Google Patents

Abstract

The invention discloses a method for removing inclusions by means of determining the height of a vertical section of a continuous casting machine for extra-thick slabs, and relates to the field of manufacture of extra-thick slabs. The method includes performing simulation calculation by the aid of a three-dimensional solidification heat transfer and flow coupling simulation model and an inclusion movement simulation model; finding a relation among a floating rate and the distribution condition of the inclusions inside a casting blank and the height of the vertical section in a continuous casting procedure; accurately determining the height of the vertical section of the continuous casting machine in order to meet requirements of high floating rate and uniform distribution of the inclusions inside the casting blank in the continuous casting procedure; and setting the vertical section on the continuous casting machine for the extra-thick slabs according to the height. The method has the advantage that damage of the inclusions to the quality of the casting blank is reduced, and the fault detection qualified rate of extra-thick plates which are manufactured by means of rolling the extra-thick slabs is increased.

Description

Determine the method for extra-thick plate blank conticaster vertical section height removal field trash

Technical field

The present invention relates to the extra-thick plate blank production field, particularly a kind of method of removing extra-thick plate blank inner clamps foreign material.

Background technology

Adopt the straight arc conticaster to produce extra-thick plate blank, these slabs are supplied with the Wide and Thick Slab rolling mill and are rolled into super-thick steel plate.Slab inner clamps foreign material can cause slab inside mass defect to occur in casting process, especially the large-scale field trash of particle diameter 50 μ m～100 μ m.The field trash of slab inside may cause rolling special heavy plate flaw detection of becoming a useful person defective because being elongated in the operation of rolling.In order to reduce field trash to the infringement of slab quality, when the design conticaster, the part of the strand guide section of the crystallizer of conticaster and its underpart is designed to plumbness, slab in the support guide section that is in crystallizer and its underpart is under the plumbness to be solidified, be defined as the vertical section height from molten steel face in the crystallizer (being also referred to as " meniscus " in the continuous casting field) to the distance that slab begins bending point, as shown in Figure 1.Make slab in this vertical section zone that is formed by the strand guide section of crystallizer and plumbness, to solidify, created condition for the medium-and-large-sized floating foreign of molten steel, reach the purpose of avoiding causing because of field trash in the strand mass defect.From being conducive to the inclusion floating angle, the height of vertical section is more high more good, and still, too high vertical section increases ferrostatic pressure, increases strand " bulge " tendency, the possibility of implosion is strengthened, and increased cost and the engineering construction investment of conticaster.

Summary of the invention

Purpose of the present invention just provides the method that a kind of definite extra-thick plate blank conticaster vertical section height is removed field trash, it is applicable to straight circular-arc type continuous casting machine production extra-thick plate blank, by determining rational straight arc conticaster vertical section height and at the thick conticaster of spy vertical section being set by this height, reach and reduce extra-thick plate blank inner clamps foreign material, and make and residue in the purpose that extra-thick plate blank inner clamps foreign material are evenly distributed.

The objective of the invention is to realize by such technical scheme, it includes the straight arc conticaster, the straight arc conticaster includes vertical support guide section, arc support guide section and horizontal support guide section, porch at the vertical support guide section is provided with crystallizer, crystallizer is secondary cooling zone below the position, and definite step of vertical support guide section vertical height H is as follows:

When 1) supposing that the straight arc conticaster is produced continuous casting billet, the inclusion content in the liquid core is few, ignores the influence that the field trash motion is flowed to molten steel;

2) under the assumed condition of step 1), set up the three-dimensional solidification and heat transfer of straight arc conticaster and mobile coupling Simulation computational mathematics model, with the water yield mean allocation of secondary cooling zone behind each position, be converted into the coefficient of heat transfer according to continuous casting heat transfer boundary condition, utilize the inner flow field of molten steel of calculated with mathematical model solidification and heat transfer and strand;

3) according to step 2) in the inner flow field of molten steel of the strand that calculates, consider the interaction of inclusion particle and liquid phase in the casting blank solidification process, set up the Mathematical Modeling that inclusion particle moves in molten steel, utilize this Mathematical Modeling, when setting a vertical height H, just can carry out simulation calculation, export the movement locus of field trash under the corresponding situation;

4) calibration and checking Mathematical Modeling, be object with an existing straight arc conticaster, the vertical height H of known this straight arc conticaster, calculate the strand inner inclusion physics opinion distribution that this straight arc conticaster is produced according to step 1) to step 3), obtain the cross section sample of this straight arc conticaster actual production strand again, observe and draw field trash distribution collection of illustrative plates, be standard with actual sampling result, by revising the boundary condition of Mathematical Modeling, checking and calibration steps 3) in the foreign material particle Mathematical Modeling of in molten steel, moving;

5) utilize the Mathematical Modeling after the calibration in the step 4), set different vertical section height, calculate the movement locus, come-up rate of the strand inner clamps foreign material that the straight arc conticaster of each vertical section height correspondence produces and come-up and by the inclusion particle distribution situation that the casting blank solidification shell is caught, find out the best corresponding vertical section height of strand inner clamps foreign material come-up rate and distribution situation not.

Further, the concrete grammar of setting up the three-dimensional solidification and heat transfer simulation calculation of straight arc conticaster Mathematical Modeling step 2) is as follows:

The energy governing equation: $\frac{\∂\left(\mathrm{\ρT}\right)}{\∂t}+\▿\·\left(\mathrm{\ρUT}\right)=\▿\·(\frac{k_{\mathrm{eff}}}{c_p}\▿T)+S_T$

Wherein

$k_{\mathrm{eff}}=k_0+k_t=k_0+\frac{{\mathrm{\μ}}_t}{{\mathrm{\σ}}_T}$

$S_T=\frac{\∂\left[\mathrm{\ρ}(T-L/C_P)\right]}{\∂t}+\▿\·\left(\mathrm{\ρU}(T-L/C_P)\right)$

In the formula, ρ is density; T is temperature; T is the time; U is the molten steel flow velocity; k _EffBe effective thermal conductivity; c _pBe thermal capacitance; S _TBe the source phase; k ₀Be thermal conductivity factor; k _tBe the turbulent flow thermal conductivity factor; L is heat content; Wherein molten steel flow velocity U and turbulent flow thermal conductivity factor and molten steel is mobile relevant.

Further, the function of the inner flow field of molten steel of strand is expressed and is shown step 2):

The flow field control equation:

Continuity equation:

$\frac{\∂\mathrm{\ρ}}{\∂t}+\▿\·\left(\mathrm{\ρU}\right)=0$

Momentum conservation equation:

$\frac{\∂}{\∂t}\left({\mathrm{\ρu}}_i\right)+\▿\·\left({\mathrm{\ρUu}}_i\right)=\▿\·({\mathrm{\μ}}_{\mathrm{eff}}\·{\▿u}_i)+S_i$

Wherein

${\mathrm{\&mu;}}_{\mathrm{eff}}={\mathrm{\&mu;}}_0+{\mathrm{\&mu;}}_t={\mathrm{\&mu;}}_0+{\mathrm{\&rho;C}}_{\mathrm{\&mu;}}\frac{{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="HDA00003069782500011.png,HDA00003069782500021.png"\; state="\{\{state\}\}">K</figure-callout>}}^2}{\mathrm{\&epsiv;}}$

K-ε turbulence double equation:

$\frac{\&PartialD;}{\&PartialD;t}\left(\mathrm{\&rho;K}\right)+\&dtri;\&CenterDot;\left(\mathrm{\&rho;UK}\right)=\&dtri;\&CenterDot;(({\mathrm{\&mu;}}_0+\frac{{\mathrm{\&mu;}}_t}{{\mathrm{\&sigma;}}_K})\&CenterDot;\&dtri;K)+G-\mathrm{\&rho;\&epsiv;}$

$\frac{\&PartialD;}{\&PartialD;t}\left(\mathrm{\&rho;\&epsiv;}\right)+\&dtri;\&CenterDot;\left(\mathrm{\&rho;U\&epsiv;}\right)=\&dtri;\&CenterDot;(({\mathrm{\&mu;}}_0+\frac{{\mathrm{\&mu;}}_t}{{\mathrm{\&sigma;}}_{\mathrm{\&epsiv;}}})\&CenterDot;\&dtri;\mathrm{\&epsiv;})+C_{1}G\frac{\mathrm{\&epsiv;}}{K}-{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA00003069782500011.png,HDA00003069782500021.png"\; state="\{\{state\}\}">C</figure-callout>}}_2\mathrm{\&rho;}\frac{{\mathrm{\&epsiv;}}^2}{K}$

Wherein

$G={\mathrm{\&mu;}}_t\frac{{\&PartialD;u}_j}{{\&PartialD;x}_i}(\frac{{\&PartialD;u}_i}{{\&PartialD;x}_j}+\frac{{\&PartialD;u}_j}{{\&PartialD;x}_i})$

In the formula, ρ is density; U is the molten steel flow velocity, and u _iThen represent the speed of some directions, namely the speed u of three directions, v, w must be found the solution; S _iBe source item; μ ₀And μ _tBe laminar flow and turbulent viscosity coefficient, C ₁, C ₂, σ _kAnd σ _εConstant for K-ε both sides journey.

Further, the function of setting up the Mathematical Modeling that inclusion particle moves in the step 3) in molten steel is expressed and is shown: adopt Discrete Phase Model to describe the motion of inclusion particle, act on then that the equilibrium of forces equation is on the particle:

$\frac{{\mathrm{du}}_p}{\mathrm{dt}}=F_D(u-u_p)+\frac{g_x({\mathrm{\&rho;}}_p-\mathrm{\&rho;})}{{\mathrm{\&rho;}}_p}+F_X$

In the formula, F _D(u-u _p) be the suffered towrope resistance of particle of per unit mass, wherein F _DBe expressed as follows:

$F_D=\frac{18\mathrm{\&mu;}}{{\mathrm{\&rho;}}_p{d_p}^2}\frac{C_D\mathrm{Re}}{24}$

In the formula, u _pBe particle's velocity; μ fluid dynamic viscosity; ρ _pBe particle density; d _pBe particle diameter; g _xBe acceleration of gravity; F _XBe other suffered power of particle, comprise virtual mass power and liquid phase barometric gradient power.

Further, the concrete grammar of revising Mathematical Modeling described in the step 4) is as follows: for the solidification and heat transfer of strand, model adopts the mode of nailing experiment and surface temperature test to verify, the coefficient of heat transfer that can be by adjusting casting billet surface under the bigger situation of temperature deviation is so that the realistic process of analog case; Field trash after solidifying distributed carried out the sampling checking, observe and draw field trash distribution collection of illustrative plates, investigate field trash in the continuous casting billet center and the probability distribution of limit portion whether consistent with analog result.

Further, the highest, the most even corresponding straight arc conticaster vertical section height that distributes of inclusion floating rate be the best in the step 5).

Owing to adopted technique scheme, the present invention to have following advantage:

The present invention utilizes the simulation calculation of carrying out of three-dimensional solidification and heat transfer simulation model and field trash motion simulation model, find out the relation of strand inner clamps foreign material come-up rate, distribution situation and vertical section height in the casting process, be target to satisfy strand inner clamps foreign material come-up rate height in the casting process, to be evenly distributed, can accurately determine the vertical section height of conticaster, and by this height at the extra-thick plate blank conticaster vertical section is set, reduce field trash to the infringement of slab quality, improve the flaw detection qualification rate with the rolling special heavy plate of extra-thick plate blank.

Other advantages of the present invention, target and feature will be set forth to a certain extent in the following description, and to a certain extent, based on being apparent to those skilled in the art to investigating hereinafter, perhaps can obtain instruction from the practice of the present invention.Target of the present invention and other advantages can realize and obtain by following specification and claims.

Description of drawings

Description of drawings of the present invention is as follows.

Fig. 1 is the structural representation of straight arc slab caster;

Fig. 2 is extra-thick plate blank three-dimensional modeling figure;

Fig. 3 is the flow field schematic diagram of wide center of extra-thick plate blank;

Fig. 4 is wide center of extra-thick plate blank field trash track schematic diagram;

Fig. 5 is the probability distribution schematic diagram of different size field trash in extra-thick plate blank;

Fig. 6 is that the vertical section height is to the influence curve figure of inclusion floating rate in the extra-thick plate blank.

Among the figure: 1. molten steel face; 2. crystallizer; 3. vertical section height; 4. vertical support guide section; 5. bending point; 6. arc support guide section; 7. horizontal support guide section.

The specific embodiment

The invention will be further described below in conjunction with drawings and Examples.

Determine the method for extra-thick plate blank conticaster vertical section height removal field trash, include the straight arc conticaster, the straight arc conticaster includes vertical support guide section 4, arc support guide section 6 and horizontal support guide section 7, be provided with crystallizer 2 in the porch of vertical support guide section 4, molten steel face 1 is positioned at crystallizer in the casting process, crystallizer is secondary cooling zone below 2 positions, vertical support guide section 4 vertical section height 3 are that the top of crystallizer 2 is to the distance of bending point 5, as shown in Figure 1, determining step is as follows:

When 1) supposing that the straight arc conticaster is produced continuous casting billet, the inclusion content in the liquid core is few, ignores the influence that the field trash motion is flowed to molten steel.

2) under the assumed condition of step 1), set up the three-dimensional solidification and heat transfer of straight arc conticaster and mobile coupling Simulation computational mathematics model, with the water yield mean allocation of secondary cooling zone behind each position, be converted into the coefficient of heat transfer according to continuous casting heat transfer boundary condition, utilize the inner flow field of molten steel of calculated with mathematical model solidification and heat transfer and strand.

The concrete grammar of setting up three-dimensional solidification and heat transfer simulation calculation Mathematical Modeling is as follows:

The energy governing equation: $\frac{\&PartialD;\left(\mathrm{\&rho;T}\right)}{\&PartialD;t}+\&dtri;\&CenterDot;\left(\mathrm{\&rho;UT}\right)=\&dtri;\&CenterDot;(\frac{k_{\mathrm{eff}}}{c_p}\&dtri;T)+S_T$

Wherein

$k_{\mathrm{eff}}=k_0+k_t=k_0+\frac{{\mathrm{\&mu;}}_t}{{\mathrm{\&sigma;}}_T}$

$S_T=\frac{\&PartialD;\left[\mathrm{\&rho;}(T-L/C_P)\right]}{\&PartialD;t}+\&dtri;\&CenterDot;\left(\mathrm{\&rho;U}(T-L/C_P)\right)$

In the formula, ρ is density; T is temperature; T is the time; U is the molten steel flow velocity; k _EffBe effective thermal conductivity; c _pBe thermal capacitance; S _TBe the source phase; k ₀Be thermal conductivity factor; k _tBe the turbulent flow thermal conductivity factor; L is heat content; Wherein molten steel flow velocity U and turbulent flow thermal conductivity factor and molten steel is mobile relevant, as described below.

The function of the inner flow field of molten steel of strand is expressed and is shown:

The flow field control equation:

Continuity equation:

$\frac{\&PartialD;\mathrm{\&rho;}}{\&PartialD;t}+\&dtri;\&CenterDot;\left(\mathrm{\&rho;U}\right)=0$

Momentum conservation equation:

$\frac{\&PartialD;}{\&PartialD;t}\left({\mathrm{\&rho;u}}_i\right)+\&dtri;\&CenterDot;\left({\mathrm{\&rho;Uu}}_i\right)=\&dtri;\&CenterDot;({\mathrm{\&mu;}}_{\mathrm{eff}}\&CenterDot;{\&dtri;u}_i)+S_i$

Wherein

${\mathrm{\&mu;}}_{\mathrm{eff}}={\mathrm{\&mu;}}_0+{\mathrm{\&mu;}}_t={\mathrm{\&mu;}}_0+{\mathrm{\&rho;C}}_{\mathrm{\&mu;}}\frac{{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="HDA00003069782500011.png,HDA00003069782500021.png"\; state="\{\{state\}\}">K</figure-callout>}}^2}{\mathrm{\&epsiv;}}$

K-ε turbulence double equation:

$\frac{\&PartialD;}{\&PartialD;t}\left(\mathrm{\&rho;K}\right)+\&dtri;\&CenterDot;\left(\mathrm{\&rho;UK}\right)=\&dtri;\&CenterDot;(({\mathrm{\&mu;}}_0+\frac{{\mathrm{\&mu;}}_t}{{\mathrm{\&sigma;}}_K})\&CenterDot;\&dtri;K)+G-\mathrm{\&rho;\&epsiv;}$

$\frac{\&PartialD;}{\&PartialD;t}\left(\mathrm{\&rho;\&epsiv;}\right)+\&dtri;\&CenterDot;\left(\mathrm{\&rho;U\&epsiv;}\right)=\&dtri;\&CenterDot;(({\mathrm{\&mu;}}_0+\frac{{\mathrm{\&mu;}}_t}{{\mathrm{\&sigma;}}_{\mathrm{\&epsiv;}}})\&CenterDot;\&dtri;\mathrm{\&epsiv;})+C_{1}G\frac{\mathrm{\&epsiv;}}{K}-{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA00003069782500011.png,HDA00003069782500021.png"\; state="\{\{state\}\}">C</figure-callout>}}_2\mathrm{\&rho;}\frac{{\mathrm{\&epsiv;}}^2}{K}$

Wherein

$G={\mathrm{\&mu;}}_t\frac{{\&PartialD;u}_j}{{\&PartialD;x}_i}(\frac{{\&PartialD;u}_i}{{\&PartialD;x}_j}+\frac{{\&PartialD;u}_j}{{\&PartialD;x}_i})$

In the formula, ρ is density; U is the molten steel flow velocity, and u _iThen represent the speed of some directions, namely the speed u of three directions, v, w must be found the solution; S _iBe source item; μ ₀And μ _tBe laminar flow and turbulent viscosity coefficient, C ₁, C ₂, σ _kAnd σ _εConstant for K-ε both sides journey.

For example, to certain thickness 420mm of steel mill, the extra-thick plate blank of width 2400mm is seen Fig. 2 according to the three-dimensional modeling that its state in conticaster carries out.Because the structure of casting blank shape and conticaster is symmetry all, for reducing amount of calculation, half of strand got in the zoning.Consider shape and the submersed nozzle structure of continuous casting billet during moulding, mouth of a river internal diameter 80mm, mouth of a river external diameter 130mm, nozzle angles is downward 15 °.The simulation model of the three-dimensional solidification and heat transfer of utilize setting up carries out analogue simulation to the casting blank solidification process and calculates, solidified shell, liquid core and the mushy zone of the extra-thick plate blank that draws on center leptoprosopy, wide.Fig. 3 is not lend oneself to worry and anxiety flow field of locating in the extra-thick plate blank that calculates.In the flow field that calculates, have two recirculating zones up and down, and molten steel after flowing out the recirculating zone owing to be subjected to the influence of solidified shell, the streamline of molten steel also tends to the center of continuous casting billet.

3) according to step 2) in the inner flow field of molten steel of the strand that calculates, consider the interaction of inclusion particle and liquid phase in the casting blank solidification process, set up the Mathematical Modeling that inclusion particle moves in molten steel, utilize this Mathematical Modeling, set vertical support guide section vertical height H, calculate the movement locus of field trash under the corresponding situation; Fig. 4 is not lend oneself to worry and anxiety field trash movement locus of locating in the special thick strand.Owing to be subjected to the influence of molten steel motion in the casting process, the movement locus of field trash also exists two tracks that circle round up and down in the extra-thick plate blank.

The Mathematical Modeling of moving in molten steel for inclusion particle adopts Discrete Phase Model to describe the motion of inclusion particle, acts on then that the equilibrium of forces equation is on the particle:

$\frac{{\mathrm{du}}_p}{\mathrm{dt}}=F_D(u-u_p)+\frac{g_x({\mathrm{\&rho;}}_p-\mathrm{\&rho;})}{{\mathrm{\&rho;}}_p}+F_X$

In the formula, F _D(u-u _p) be the suffered towrope resistance of particle of per unit mass, wherein F _DBe expressed as follows:

$F_D=\frac{18\mathrm{\&mu;}}{{\mathrm{\&rho;}}_p{d_p}^2}\frac{C_D\mathrm{Re}}{24}$

In the formula, u _pBe particle's velocity; μ fluid dynamic viscosity; ρ _pBe particle density; d _pBe particle diameter; g _xBe acceleration of gravity; F _XBe other suffered power of particle, comprise virtual mass power, liquid phase barometric gradient power etc.

4) calibration and checking Mathematical Modeling, the existing straight arc conticaster of Yi Yitai is object, the mathematical model simulation that utilizes step 1) to set up to step 3) calculates casting blank solidification situation and the distribution of inner inclusion physics opinion thereof that this straight arc conticaster is produced.For the solidification and heat transfer of strand, model adopts the mode of nailing experiment and surface temperature test to verify, the coefficient of heat transfer that can be by adjusting casting billet surface under the bigger situation of temperature deviation is so that the realistic process of analog case.In addition, the sampling checking that distribution is carried out to the field trash after solidifying, find field trash in the continuous casting billet center and there is higher probability distribution in limit portion, consistent with analog result, verified accuracy checking and the calibration steps 3 of model) in the foreign material particle Mathematical Modeling of in molten steel, moving.

5) utilize the Mathematical Modeling after the calibration in the step 4), set different vertical section height, calculate the movement locus, come-up rate of the strand inner clamps foreign material that the straight arc conticaster of each vertical section height correspondence produces and come-up and by the inclusion particle distribution situation that the casting blank solidification shell is caught, find out the best corresponding vertical section height of strand inner clamps foreign material come-up rate and distribution situation not.

Wherein, the distribution of field trash in continuous casting billet added up by probability distribution.Cross-section region for simulation is divided into the zonule that sizing grid is 20 * 30mm, by the The amount of inclusions of each regional IT, and adopts following formula to be converted into probability distribution during statistical simulation is calculated:

θ _simulated=N _simulated/N _trapped

In the formula, θ simulated is the probability distribution of field trash analog result; Nsimulated is the quantity of field trash in statistical regions; Ntrapped is that field trash is solidified the quantity that the base shell catches.

With field trash at the inner come-up rate of strand height, to be evenly distributed be criterion, analysis draws vertical section height and field trash in the relation of the inner come-up rate of strand and distribution, find out the inclusion floating rate the highest, distribute that the vertical section height of correspondence then is best vertical section height when the most even.If four kinds of vertical section height of analog computation are not enough to find out the relation between the height of inclusion floating rate and distribution and vertical section, append several vertical section height of supposition towards being conducive to inclusion floating with the direction of the corresponding vertical section height that is more evenly distributed again, carrying out analogue simulation again calculates, until finding comparatively speaking, the inclusion floating rate is the highest, the most rational vertical section height of distribution, is the height of reasonable vertical section.

Fig. 5 is a kind of in four kinds of vertical section height of present embodiment supposition, when the vertical section height is 3.511m, is of a size of the probability distribution of field trash in the thick strand of spy of 50 μ m.As can be seen from Figure 5, owing to there is the vertical section of certain altitude to exist, the distribution of field trash in continuous casting billet be symmetry relatively.

When Fig. 6 was present embodiment pulling rate 0.6m/min, the vertical section height was to the influence of inclusion floating rate.Can find out extra-thick plate blank conticaster vertical section height to the influence of inclusion floating rate, field trash density is 3000kg/m3.As can be seen from Figure 6, the vertical section height of conticaster during greater than 3.2m 100 μ m floating foreign rates can reach more than 80%, therefore retain in strand for fear of the foreign impurity that causes owing to various accidents in actual production, the design height of the vertical section of conticaster should be greater than 3.2m.See in conjunction with the distribution of the field trash of Fig. 5 that again the 100 μ m inclusion floating rates that will reach surpass 80%, be hunted down simultaneously and stay the effect that strand inner clamps foreign material are evenly distributed that conticaster vertical section height should be got 3.5m.

Explanation is at last, above embodiment is only unrestricted in order to technical scheme of the present invention to be described, although with reference to preferred embodiment the present invention is had been described in detail, those of ordinary skill in the art is to be understood that, can make amendment or be equal to replacement technical scheme of the present invention, and not breaking away from aim and the scope of the technical program, it all should be encompassed in the middle of the claim scope of the present invention.

Claims (6)

1. determine the method for extra-thick plate blank conticaster vertical section height removal field trash, it is characterized in that: it includes the straight arc conticaster, the straight arc conticaster includes vertical support guide section, arc support guide section and horizontal support guide section, porch at the vertical support guide section is provided with crystallizer, crystallizer is secondary cooling zone below the position, and definite step of vertical support guide section vertical height H is as follows:

When 1) supposing that the straight arc conticaster is produced continuous casting billet, the inclusion content in the liquid core is few, ignores the influence that the field trash motion is flowed to molten steel;

2) under the assumed condition of step 1), set up the three-dimensional solidification and heat transfer of straight arc conticaster and mobile coupling Simulation computational mathematics model, with the water yield mean allocation of secondary cooling zone behind each position, be converted into the coefficient of heat transfer according to continuous casting heat transfer boundary condition, utilize the inner flow field of molten steel of calculated with mathematical model solidification and heat transfer and strand;

3) according to step 2) in the inner flow field of molten steel of the strand that calculates, consider the interaction of inclusion particle and liquid phase in the casting blank solidification process, set up the Mathematical Modeling that inclusion particle moves in molten steel, utilize this Mathematical Modeling, when setting a vertical height H, just can carry out simulation calculation, export the movement locus of field trash under the corresponding situation;

4) calibration and checking Mathematical Modeling, be object with an existing straight arc conticaster, the vertical height H of known this straight arc conticaster, calculate the strand inner inclusion physics opinion distribution that this straight arc conticaster is produced according to step 1) to step 3), obtain the cross section sample of this straight arc conticaster actual production strand again, observe and draw field trash distribution collection of illustrative plates, be standard with actual sampling result, by revising the boundary condition of Mathematical Modeling, checking and calibration steps 3) in the foreign material particle Mathematical Modeling of in molten steel, moving;

5) utilize the Mathematical Modeling after the calibration in the step 4), set different vertical section height, calculate the movement locus, come-up rate of the strand inner clamps foreign material that the straight arc conticaster of each vertical section height correspondence produces and come-up and by the inclusion particle distribution situation that the casting blank solidification shell is caught, find out the best corresponding vertical section height of strand inner clamps foreign material come-up rate and distribution situation not.

2. definite extra-thick plate blank conticaster vertical section height as claimed in claim 1 is removed the method for field trash, it is characterized in that step 2) described in to set up the concrete grammar of the three-dimensional solidification and heat transfer simulation calculation of straight arc conticaster Mathematical Modeling as follows:

The energy governing equation: $\frac{\&PartialD;\left(\mathrm{\&rho;T}\right)}{\&PartialD;t}+\&dtri;\&CenterDot;\left(\mathrm{\&rho;UT}\right)=\&dtri;\&CenterDot;(\frac{k_{\mathrm{eff}}}{c_p}\&dtri;T)+S_T$

Wherein

$k_{\mathrm{eff}}=k_0+k_t=k_0+\frac{{\mathrm{\&mu;}}_t}{{\mathrm{\&sigma;}}_T}$

$S_T=\frac{\&PartialD;\&lsqb;\mathrm{\&rho;}(T-L/C_p)\&rsqb;}{\&PartialD;t}+\&dtri;\&CenterDot;\left(\mathrm{\&rho;U}(T-L/C_p)\right)$

In the formula, ρ is density; T is temperature; T is the time; U is the molten steel flow velocity; k _EffBe effective thermal conductivity; c _pBe thermal capacitance; S _TBe the source phase; k ₀Be thermal conductivity factor; k _tBe the turbulent flow thermal conductivity factor; L is heat content; Wherein molten steel flow velocity U and turbulent flow thermal conductivity factor and molten steel is mobile relevant.

3. definite extra-thick plate blank conticaster vertical section height as claimed in claim 2 is removed the method for field trash, it is characterized in that step 2) in the function of the inner flow field of molten steel of strand express and be shown:

The flow field control equation:

Continuity equation:

$\frac{\&PartialD;\mathrm{\&rho;}}{\&PartialD;t}+\&dtri;\&CenterDot;\left(\mathrm{\&rho;U}\right)=0$

Momentum conservation equation:

$\frac{\&PartialD;}{\&PartialD;t}\left(\mathrm{\&rho;}{u}_i\right)+\&dtri;\&CenterDot;\left(\mathrm{\&rho;U}{u}_i\right)=\&dtri;\&CenterDot;({\mathrm{\&mu;}}_{\mathrm{eff}}\&CenterDot;\&dtri;u_i)+S_i$

Wherein

${\mathrm{\&mu;}}_{\mathrm{eff}}={\mathrm{\&mu;}}_0+{\mathrm{\&mu;}}_t={\mathrm{\&mu;}}_0+\mathrm{\&rho;}{C}_{\mathrm{\&mu;}}\frac{K^2}{\mathrm{\&epsiv;}}$

K-ε turbulence double equation:

$\begin{array}{c}\frac{\&PartialD;}{\&PartialD;t}\left(\mathrm{\&rho;K}\right)+\&dtri;\&CenterDot;\left(\mathrm{\&rho;UK}\right)=\&dtri;\&CenterDot;(({\mathrm{\&mu;}}_0+\frac{{\mathrm{\&mu;}}_t}{{\mathrm{\&sigma;}}_k})\&CenterDot;\&dtri;K)+G-\mathrm{\&rho;\&epsiv;}\\ \frac{\&PartialD;}{\&PartialD;t}\left(\mathrm{\&rho;\&epsiv;}\right)+\&dtri;\&CenterDot;\left(\mathrm{\&rho;U\&epsiv;}\right)=\&dtri;\&CenterDot;(({\mathrm{\&mu;}}_0+\frac{{\mathrm{\&mu;}}_t}{{\mathrm{\&sigma;}}_{\mathrm{\&epsiv;}}})\&CenterDot;\&dtri;\mathrm{\&epsiv;})+C_{1}G\frac{\mathrm{\&epsiv;}}{K}-C_2\mathrm{\&rho;}\frac{{\mathrm{\&epsiv;}}^2}{K}\end{array}$

Wherein

$G={\mathrm{\&mu;}}_t\frac{\&PartialD;u_j}{\&PartialD;x_i}(\frac{\&PartialD;u_i}{\&PartialD;x_j}+\frac{\&PartialD;u_j}{\&PartialD;x_i})$

In the formula, ρ is density; U is the molten steel flow velocity, and u _iThen represent the speed of some directions, namely the speed u of three directions, v, w must be found the solution; S _iBe source item; μ ₀And μ _tBe laminar flow and turbulent viscosity coefficient, C ₁, C ₂, σ _kAnd σ _εConstant for K-ε both sides journey.

4. definite extra-thick plate blank conticaster vertical section height as claimed in claim 3 is removed the method for field trash, it is characterized in that, the function of setting up the Mathematical Modeling that inclusion particle moves in the step 3) in molten steel is expressed and is shown: adopt Discrete Phase Model to describe the motion of inclusion particle, act on then that the equilibrium of forces equation is on the particle:

$\frac{d{u}_p}{\mathrm{dt}}=F_D(u-u_p)+\frac{g_x({\mathrm{\&rho;}}_p-\mathrm{\&rho;})}{{\mathrm{\&rho;}}_p}+F_X$

In the formula, F _D(u-u _p) be the suffered towrope resistance of particle of per unit mass, wherein F _DBe expressed as follows:

$F_D=\frac{18\mathrm{\&mu;}}{{\mathrm{\&rho;}}_p{d_p}^2}\frac{C_D\mathrm{Re}}{24}$

In the formula, u _pBe particle's velocity; μ fluid dynamic viscosity; ρ _pBe particle density; d _pBe particle diameter; g _xBe acceleration of gravity; F _XBe other suffered power of particle, comprise virtual mass power and liquid phase barometric gradient power.

5. definite extra-thick plate blank conticaster vertical section height as claimed in claim 4 is removed the method for field trash, it is characterized in that, the concrete grammar of revising Mathematical Modeling described in the step 4) is as follows: for the solidification and heat transfer of strand, model adopts the mode of nailing experiment and surface temperature test to verify, the coefficient of heat transfer that can be by adjusting casting billet surface under the bigger situation of temperature deviation is so that the realistic process of analog case; Field trash after solidifying distributed carried out the sampling checking, observe and draw field trash distribution collection of illustrative plates, investigate field trash in the continuous casting billet center and the probability distribution of limit portion whether consistent with analog result.

6. definite extra-thick plate blank conticaster vertical section height as claimed in claim 5 is removed the method for field trash, it is characterized in that, the highest, the most even corresponding straight arc conticaster vertical section height that distributes of inclusion floating rate be the best in the step 5).

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