CN102847901A - Method for controlling width of ferrite stainless steel plate blank in continuous casting production - Google Patents

Abstract

The invention relates to a method for controlling width of a ferrite stainless steel plate blank in continuous casting production, which meets the performance characteristic of ferrite steel grade, and by researching the influence of the change of elements in molten steel in different furnaces on the width of the plate blank, cancels out the influence through a parameter. With the method provided by the invention, the width of the plate blank can be controlled conveniently and effectively, the plate blank meeting a preset product requirement can be produced, and the requirements of low error and stable and regular control can be met.

Description

The method of control ferrite stainless steel base width during a kind of continuous casting is produced

Technical field

The invention belongs to the slab continuous casting technology field, particularly, relate to the method for control ferrite stainless steel base width in a kind of continuous casting production.

Background technology

Continuous casting technology is the technique that liquid molten steel is obtained strand by cast, condensation, cutting.As shown in Figure 1, the topmost link of this process is injected crystallizer 3 to a stove or many stoves molten steel by ladle 1 and tundish 2 exactly continuously, in the crystallizer 3 that four copper coins consist of, pass through water-cooled, thereby still be the strand of liquid molten steel for solid-state base shell, mid portion around obtaining.Then strand all solidifies gradually by secondary cooling 4, and is drawn out the conticaster body by support and the rotary action of straightening device 5 middle roller, is cut into the slab of certain-length by cutter sweep again.

Wherein, crystallizer cooling is called once cooling, and strand goes out the cooling of further spraying water of zone that crystallizer enters roll support, is called secondary and cools off.The purpose of secondary cooling is to implementing the water spray cooling with the strand of liquid molten steel it to be solidified fully, to reach evenly cooling in process of billet withdrawal.

The width dimensions of the slab that is obtained by cutter sweep cutting plays a part crucial to the width behind the slab rolling.The continuous casting steel billet width is that both at home and abroad each modernized steel mill produces necessary control step, and the width dimensions of stabilizing continuous casting slab can effectively improve the quality of hot rolled coil.Therefore, there is strict control in each steel mill to the width of plate slab tolerance, in the company standard of slab, industry standard, the national standard, all there are strict requirements to the width of slab, therefore in continuous casting production process, must according to requirements control the width of the slab of institute's output, the final width of described slab can be represented by following formula:

W _Cold＝W _Mold+W _Creep-W _T (1)

In the formula, W _ColdFinal width for slab;

W _MoldFor setting crystallizer end opening width;

W _CreepThe change width that expands and to cause for strand;

W _TFor the change width that causes is shunk in the slab cooling.

Wherein, W _TThe shrinkage phenomenon that volume and linear dimension reduce occurs in the expression strand in cooling procedure, cause width of plate slab variation W by contraction _TCan be expressed as

$W_T=W_{\mathrm{Mold}}\underset{T_{\mathrm{cold}}}{\overset{T_{M-\mathrm{ex}}}{\∫}}\mathrm{\α}\left(T\right)\mathrm{dT}---\left(1.1\right)$

In the formula, T is temperature, ℃; Crystallizer outlet board briquette is T _M-ex, the temperature of slab is T when being cooled to room temperature _Cold

Wherein

Be exactly the shrinkage factor of steel grade from the crystallizer outlet temperature to room temperature.

α (T) is temperature when being T ℃, the thermal coefficient of expansion of this steel grade, and 1/K, its numerical value is drawn by experiment, can be expressed as:

$\mathrm{\&alpha;}=\frac{1}{{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="HDA0000071623180000011.png"\; state="\{\{state\}\}">L</figure-callout>}}_0}\frac{{\mathrm{dL}}_T}{\mathrm{dT}}---\left(1.2\right)$

In the formula, L ₀Be the original length of steel sample,

L _TThe length of steel sample when being T ℃ for temperature.

For same steel grade, in ± 40 ℃, the width cooling contraction change that causes thus is in 0.1% in crystallizer exit variations in temperature for slab in the time of normal casting.Therefore, for the same ferritic stainless steel, cooling is shunk and is caused that the width of plate slab variable quantity is W _TCan regard a constant as.At this moment, can be learnt by formula (1), because the end opening width of crystallizer is W _MoldCan not change, in addition W _TCan regard a constant as, therefore, the final width W of slab _ColdThen depend on the strand caused change width W that expands _CreepValue.

W described in the formula (1) _CreepGeneration be because conticaster have certain height, as shown in Figure 2, the molten steel of ot-yet-hardened can produce the effect of static pressure to the base shell that has solidified and produce bulking effect in the strand, for austenitic stainless steel, because this steel grade elevated temperature strength is high, the base shell that has solidified can be offset the impact of most of bulking effect, therefore can ignore this bulking effect.Yet ferritic stainless steel be a kind of under the use state take ferritic structure as main stainless steel, its chrome content is between 11%～30%, has body-centered cubic crystal structure, it is low that this steel grade has elevated temperature strength, solidification and crystallization speed is fast, the characteristics such as column crystal prosperity, because its elevated temperature strength is low, the base shell can not be resisted its suffered molten steel static pressure after leaving crystallizer, yet as shown in Figure 2, the longitudinally static pressure that produces owing to bulking effect in the base shell is owing to the squeezing action power of roller-way middle roller to strand is cancelled, but horizontal static pressure can't not be cancelled owing to there is not the squeezing action power of roller, thereby strand is deformed under the effect of ferrostatic pressure, and then make and final increase to width of plate slab, namely produced by the strand caused change width W that expands _Creep

W _CreepThe elevated temperature strength characteristic and the shell thickness that depend on the base shell.Wherein, shell thickness depends on liquid steel temperature, casting rate, crystallizer intensity of cooling (i.e. intensity of cooling), secondary intensity of cooling.The elevated temperature strength characteristic of base shell depends on the content of element in the molten steel.Think for a steel grade base shell elevated temperature strength constant (with the target content of a certain steel grades element representative composition as this steel grade) in the prior art idealizedly; But in the direct casting process of reality, there is fluctuation in the constituent content of the molten steel composition of different heats, and wherein the elements such as C, N, Cr, Ni can bring on the hot properties of base shell larger impact, cause thus the fluctuation of different heat output width of plate slab.A kind of content of steel grades element allows to exist fluctuation range to a certain degree, does not consider in the prior art that different heats connect when watering the fluctuation problem that the content of element is brought width of plate slab.

Because certainly exist the direct casting of different heats in the casting process, the content of composition element also there are differences in the different heats, constituent content will affect the change width W that strand expands and causes as departing from average level in some heats _CreepThereby, make the width of plate slab requirement that departs from objectives.

Summary of the invention

For addressing the above problem, the object of the present invention is to provide the method for control ferrite stainless steel base width in a kind of continuous casting production, the method meets the Performance Characteristics of ferrite steel grade, by studying the impact that the variation of composition element brings to width of plate slab in the molten steel between different heats, and then offset the impact that this composition element variation is brought by a certain parameter, on the control result, can produce the slab that meets default product requirement, satisfy simultaneously little error, requirement that control law is stable.For achieving the above object, the technical scheme that the present invention takes is as follows:

The method of control ferrite stainless steel base width during a kind of continuous casting is produced is at first according to crystallizer end opening width W _Mold, the change width W that strand expands and causes _Creep, the change width W that causes is shunk in the cooling of ferrite stainless steel base _T, set the final width W of described ferrite stainless steel base _ColdModel be:

W _Cold＝W _Mold+W _Creep-W _T

It is characterized in that:

Also comprise the steps:

(1), selects Ni _Eq/ Cr _EqAs the representative element that affects ferrite stainless steel base hot properties, wherein, Ni _EqThe expression nickel equivalent, Cr _EqThe expression chromium equivalent;

(2), according to Ni _EqAnd Cr _EqDesired value draw Ni _Eq/ Cr _EqStandard value;

(3), gather the sample data of the Cast parameters affect stainless steel slab thickness, described sample data comprises arbitrary cooling zone water yield value q in the secondary cooling zone apart from crystallizer 1.7～5m suitable for reading _n

(4), with the Ni that obtains in the step (2) _Eq/ Cr _EqStandard value and step (3) in the sample data that gathers carry out data normalization and process;

(5), by regulating q _nValue offset Ni _Eq/ Cr _EqThe impact that the variation of value brings described ferrite stainless steel base width, its computing formula is:

C×Ni _eq/Cr _eq+J×q _n＝f ₁×C×Ni _eq/Cr _eq+f ₂×J×q _n

Or C * Ni _Eq/ Cr _Eq+ K * q _n=f ₁* C * Ni _Eq/ Cr _Eq+ f ₂* K * q _n

In the following formula, f ₁* Ni _Eq/ Cr _EqBe Ni _Eq/ Cr _EqChanging value, f ₂* q _nBe q _nChanging value, C, J, K are positive coefficient.

Described positive coefficient C, J, K can obtain by the following method:

(a), with crystallizer end opening width W _MoldFinal width W with the ferrite stainless steel base _ColdBe defined as scale factor f, i.e. a f=W _Mold/ W _Cold

(b), with the sample data that after data normalization is processed, obtains in the claim 1 as input variable, the scale factor f described in the step (a) as output variable, is carried out the PLS computing, thereby sets up the slab equation of equilibrium:

f＝A-Bv+CNi _eq/Cr _eq-DT+Eφ-FW+GΔθ-Hq ₁-Iq ₂+Jq ₃+Kq ₄

In the following formula, v is that casting rate, φ are that crystallizer evenly heat flow, W are that the crystallizer water yield, Δ θ are that crystallizer is imported and exported water temperature difference, T is molten steel temperature in tundish, q ₁Be secondary cooling zone 1 district's water yield value, q ₂Be secondary cooling zone 2 district's water yield values, q ₃Be secondary cooling zone 3 district's water yield values, q ₄Be secondary cooling zone 4 district's water yield values; Wherein A, B, C, D, E, F, G, H, I, J, K are positive coefficient;

(c), positive coefficient C, J, K can be obtained by the slab equation of equilibrium described in the step (b).

The method that data normalization described in the described step (4) is processed is:

$x_{\mathrm{ij}}^{*}=\frac{x_{\mathrm{ij}}-{\stackrel{\&OverBar;}{x}}_j}{s_j},F_{0i}=\frac{y_i-\stackrel{\&OverBar;}{y}}{s_y}$

In the following formula,

Wherein, x _IjThe concrete numerical value of a certain input variable, x _Ij ^*X _IjValue after the standardization; y _iThe concrete numerical value of output output variable f, F _0iY _iValue after the standardization.

Q in the described step (5) _nChoose secondary cooling zone 3 district water yield value q ₃Or secondary cooling zone 4 district water yield value q ₄

Described Ni _Eq/ Cr _EqComputing formula be:

Ni _eq/Cr _eq＝(Ni％+0.5Mn％+30C％+30N％+0.33Cu％)/(Cr％+Mo％+1.5Si％)。

The scope of described scale factor f and positive coefficient A, B, C, D, E, F, G, H, I, J, K is 0～2.

By as above method, just can control easily and effectively width of plate slab, produce the slab that meets default product requirement, satisfy simultaneously little error, requirement that control law is stable.

Description of drawings

Fig. 1 is the structural representation of typical straightway circular-arc type continuous casting machine.

Fig. 2 is the suffered molten steel static pressure schematic diagram of strand.

Among Fig. 1,1, ladle 2, tundish 3, crystallizer 4, secondary cooling zone cooling zone 5, straightening device.

The specific embodiment

The below is further explained explanation to the method for control ferrite stainless steel base width in a kind of continuous casting production provided by the invention.

At first details are as follows for technical scheme:

In order to control width of plate slab, at first to set up according to the Cast parameters that affects base shell hot properties element and affect shell thickness the computational methods of width of plate slab, formula (1) can be realized the calculating to width of plate slab.But, the accuracy of the method is subject to the restriction of the mechanical behavior under high temperature data order of accuarcy of steel grade, and the heat transfer process of setting of slab is very complicated, and the order of accuarcy of the result of calculation of base shell temperature and thickness is subject to the impact of factors, and it is very difficult promptly and accurately to obtain these data.Therefore, before obtaining accurately hot properties data and shell thickness, can select to affect composition and the Cast parameters of width of plate slab key based on molten steel solidification and Slab Heat freezing mechanism and in conjunction with the data characteristics of on-the-spot creation data, set up rational width of plate slab computational methods.Then by these computational methods, find a kind of control program, the impact that the content of offsetting the composition element changes and brings.

1, the selection of composition element

Take the 409L stainless steel as example, its composition element is as shown in table 1:

Scheffler organization chart (Schaeffler ' s Diagram) in, ordinate Ni _Eq(nickel equivalent) expression, nickel equivalent are the indexs of reflection stainless steel weld joint metal structure austenitizing degree.Its value is according to the austenite element that comprises in the weld structure (such as nickel, carbon, manganese etc.), is converted to the summation that is equivalent to several nickel by the intensity of its austenitizing effect; Abscissa Cr _Eq(chromium equivalent) represents, chromium equivalent is the index of the ferrite degree of reflection weld structure, its value is (such as chromium according to the ferritisey in the participation seam organization, aluminium, silicon, molybdenum etc.), turn the intensity of usefulness into by its ferrite, be converted to the summation that is equivalent to several chromium.

And then obtain formula:

Cr _eq＝Cr％+Mo％+1.5Si％ (2.1)

Ni _eq＝Ni％+0.5Mn％+30C％+30N％+0.33Cu％ (2.2)

Therefore, select Ni _Eq/ Cr _EqAs the representation parameter that affects ferrite stainless steel base hot properties, computation model is:

Ni _eq/Cr _eq＝(Ni％+0.5Mn％+30C％+30N％+0.33Cu％)/(Cr％+Mo％+1.5Si％) (2.3)

2, determine Ni according to the desired value of composition element _Eq/ Cr _EqStandard value

The desired value of composition element in the table 1 409L ferritic stainless steel

Upper table data are brought in formula (2.1) and (2.2), then can draw Ni in 430 ferritic stainless steels according to formula (2.3) _Eq/ Cr _EqStandard value.

3, select to affect the Cast parameters of shell thickness and the collection of sample data

3.1 select to affect the Cast parameters of shell thickness

According to continuous casting process as can be known, the thickness of base shell and casting rate, crystallizer intensity of cooling, molten steel temperature in tundish, secondary cooling water amount are relevant.Therefore, selected following variable is as the representation parameter that affects width of plate slab: pulling rate v, i.e. casting rate; Crystallizer mean heat flux φ, crystallizer water yield W, crystallizer import and export water temperature difference Δ θ, and these three have reflected the crystallizer intensity of cooling; Molten steel temperature in tundish T.

Described sample data also comprises front four the cooling zone water yield value q of secondary cooling zone, and wherein, different according to technique, the division of two cold-zones also has difference, and two cold-zones among the present invention are divided as shown in the table:

Table 2 secondary cooling zone cooling zone is divided

Each cooling zone water yield can be controlled separately by nozzle, front four the cooling zone water yields of secondary cooling zone play a decisive role to shell thickness, its middle distance crystallizer 1.7～5m suitable for reading is the stage that Shell stress rises to peak value gradually, regulate the water yield of two cold-zones in this interval, can effectively offset composition and change the impact that brings.Therefore choose four cooling zone water yield q ₁, q ₂, q ₃, q ₄, the wherein said cooling zone water yield apart from crystallizer 1.7～5m suitable for reading is q ₃, q ₄

3.2 the collection of sample data

The collection quantity of described sample data is generally more than 100 groups.

4, set up the width of plate slab equation of equilibrium

With crystallizer end opening width W _MoldFinal width W with the ferrite stainless steel base _ColdBe defined as scale factor f, i.e. a f=W _Mold/ W _Cold

Because crystallizer end opening width W in the casting cycle _MoldDo not change, therefore controlling f namely can the final width of control panel base.

5, the standardization of data

For the difference of the order of magnitude of eliminating each variable data, need carry out data normalization and process, the sample data that gathers to be carried out data normalization process, the variance that makes all variablees is 1, average is 0.

The method that described data normalization is processed is:

$x_{\mathrm{ij}}^{*}=\frac{x_{\mathrm{ij}}-{\stackrel{\&OverBar;}{x}}_j}{s_j},F_{0i}=\frac{y_i-\stackrel{\&OverBar;}{y}}{s_y}---\left(3\right)$

In the following formula,

Wherein, x _IjThe concrete numerical value of a certain input variable, x _Ij ^*X _IjValue after the standardization; y _iThe concrete numerical value of output output variable f, F _0iY _iValue after the standardization.

6, the selection of algorithm

The sample data that will obtain after data normalization is processed as output variable, is carried out the PLS computing with scale factor f as input variable;

Because PLS algorithm PLS utilizes the mode that the data message in the system is decomposed and screens, extraction is to the strongest explanatory generalized variable of dependent variable, information in the identification system and noise, thus overcome better the ill-effect of variable multiple correlation in system modelling.Can utilize software to carry out the computing of PLS, casting rate v, crystallizer evenly heat flow φ, crystallizer water yield W, crystallizer are imported and exported water temperature difference Δ θ, molten steel temperature in tundish T, secondary cooling zone 1 district water yield value q ₁, secondary cooling zone 2 district water yield value q ₂, secondary cooling zone 3 district water yield value q ₃, secondary cooling zone 4 district water yield value q ₄As the input variable of model, f calculates as output variable with scale factor.

Operation result must be determined last formula according to the principle on the statistical significance, and usually, it is as follows to obtain formula:

f＝A-Bv+CNi _eq/Cr _eq-DT+Eφ-FW+GΔθ-Hq ₁-Iq ₂+Jq ₃+Kq ₄ (4)

Wherein A, B, C, D, E, F, G, H, I, J, K are positive coefficient, and scope is greater than 0, and less than 2, the scope of described scale factor f also is greater than 0, less than 2.

7, select the control parameter

According to formula (4) as can be known, at Ni _Eq/ Cr _EqWhen changing, if require f constant, can regulate two cold-zone cooling water inflows and offset the impact that the fluctuation of composition element brings.Its middle distance crystallizer 1.7～5m suitable for reading is the stage that Shell stress rises to peak value gradually, regulates the water yield of two cold-zones in this interval, can effectively offset composition and change the impact that brings.

Balance Ni _Eq/ Cr _EqVariation after value and front four the cooling zone water yield value q of secondary cooling zone in a cooling zone water yield value q _nVariation after value, set initial Ni _Eq/ Cr _EqBe standard value, choose the water yield q in secondary cooling zone 3 districts ₃Or secondary cooling zone 4 district water yield value q ₄,

C×Ni _eq/Cr _eq+J×q ₃＝C×f ₁×Ni _eq/Cr _eq+J×f ₂×q ₃

Or C * Ni _Eq/ Cr _Eq+ K * q ₄=C * f ₁* Ni _Eq/ Cr _Eq+ K * f ₂* q ₄(5)

In the following formula, f ₁* Ni _Eq/ Cr _EqBe Ni _Eq/ Cr _EqChanging value, f ₂* q ₃Be q ₃Changing value, f ₂* q ₄Be q ₄Changing value, C, J, K are positive coefficient.

Formula (5) is carried out can getting after similar terms merge:

(f ₂-1)×J×q ₃＝(1-f ₁)×C×Ni _eq/Cr _eq

Or (f ₂-1) * K * q ₄=(1-f ₁) * C * Ni _Eq/ Cr _Eq(6)

By formula (6) as can be known, constant in order to guarantee the f value, according to Ni _Eq/ Cr _EqActual value and Ni _Eq/ Cr _EqThe ratio f of standard value ₁, just can calculate the water yield value q in secondary cooling zone 3 districts ₃Or the water yield value q in secondary cooling zone 4 districts ₄Corresponding variation coefficient f ₂

In system, press Ni according to formula (6) _Eq/ Cr _EqFluctuation 0.01 is the interval, sets up different Ni _Eq/ Cr _EqWith secondary cooling zone 3 districts or and the cold section corresponding water yield coefficient in 4 districts, Ni _Eq/ Cr _EqScope determine according to the scope that composition allows.According to different Ni _Eq/ Cr _Eq, the standard water yield in original secondary cooling zone 3 districts or secondary cooling zone 4 districts is multiplied by coefficient of correspondence regulates as new setting value, offset the impact of fluctuating and bringing to width of plate slab because of composition element between different heats, thereby guarantee the stable of width of plate slab.

Embodiment 1

Take ferritic stainless steel 409L as example, set up the method that the composition element variation is regulated two cold 3 district's water yields, guarantee the constant of width of plate slab.

1.1 obtain the equation of equilibrium (4) of width of plate slab scale factor

Gather variable v, Ni _Eq/ Cr _Eq, T, φ, W, Δ θ, q ₁, q ₂, q ₃, q ₄, as the input variable of model, the ratio f of crystallizer end opening width and the final width of slab as output variable, by the screening of data, has finally been chosen 106 groups of data and has calculated.

Described Data Collection is to measure by field instrument, then is sent to computer system stores.Then according to site technique condition and correlation theory, manually weed out the data group of incomplete value or wrong item.The screening criteria of partial data item is as follows: the data group that casting rate v is lower than 0.4m/min weeds out, because this belongs to the abnormality processing of emergency episode, does not belong to normal continuous casting production range; Molten steel temperature in tundish T is lower than 1460 ℃ or high 1580 ℃ data group, and to belong to thermometric unusual, also will reject.For other data, grade such as one-tenth equally, all rejected such as and null value excessive with the normal range data deviation.Like this data group is accumulated, when data accumulation reaches the just method computing of available PLS more than 100 groups.

After by formula (3) carry out standardization to data, utilize MINITAB running software PLS arithmetic result as follows:

PLS returns: v, Ni _Eq/ Cr _Eq, T, φ, W, Δ θ, q ₁, q ₂, q ₃, q ₄Variance analysis for f

As a result 1: the p value of ratio f is 0.000, less than alpha value 0.05, thereby provides enough evidences for the conspicuousness of formula.

As a result 2:

Obtain according to entire variable (totally 10 components) operation result

f＝0.562746-0.835844v+0.727396Ni _eq/Cr _eq-0.230964T+0.061785φ-0.118760W+0.074468Δθ-0.054742q ₁+0.833735q ₂+0.259557q ₃-0.913956q ₄ (7)

The formula of f is selected and checking

As a result 3:

The first row of output shows the number of components in the optimum formula (R-Sq that is defined as prediction is the highest).Minitab has selected 9 component formula, and the R-Sq of prediction is 0.66.

The model R-Sq of 9 component formula (being selected by cross validation) is 76.23%, and the R-Sq of prediction is 66.27%.Be best model.Its expression formula has been removed the q of coefficient minimum in 10 components ₁, obtain:

f＝0.562746-0.835844v+0.727396Ni _eq/Cr _eq-0.230964T+0.061785φ-

0.118760W+0.074468Δθ+0.833735q ₂+0.259557q ₃-0.913956q ₄ (8)

Wherein, above component formula selection principle is as follows:

1) it is carried out variance analysis, the p value needs less than 0.005,

When 2) component was chosen in modelling verification, its model R-Sq was greater than 60%, and R-Sq is greater than 50% in prediction, can be satisfied with.

When 3) component was chosen in modelling verification, the combination of its component during general selection prediction R-Sq maximum also can be under prediction R-Sq descends little situation, the component combination during preference pattern R-Sq higher value.

1.2 adjust two cold 3 district's water yields, the control width of plate slab

409L ferritic stainless steel target component is:

Obtain the Ni of 409L ferritic stainless steel desired value according to formula (2.1) and (2.2) _Eq=0.71, Cr _Eq=12.07, then obtain Ni _Eq/ Cr _EqStandard value is 0.06.

Can get according to formula (6) again

(f ₂-1)×0.259557×q ₃＝(1-f ₁)×0.727396×Ni _eq/Cr _eq (9)

Be defined as Q3 after the former setting water yield standardization with 3 districts, namely and cold section 3 district's water yields when being Q3, f ₂Be 1.Like this according to the available 3 district's water yield coefficient tables of formula (9).

According to Ni _Eq/ Cr _EqTwo cold 3 district's water yield coefficient tables have been obtained

From formula (4) and formula (6) and table, can find out, along with Ni _Eq/ Cr _EqReduce, the f of the final width of crystallizer end opening width/slab reduces, and this means that width of plate slab increases; Under the identical condition of other parameters such as pulling rate, by increasing the water yield in two cold 3 districts, offset Ni like this _Eq/ Cr _EqThe impact that reduces can be controlled width of plate slab and remain unchanged.

Embodiment 2

Take ferritic stainless steel 430 as example, set up the method that the composition element variation is regulated two cold 3 district's water yields, guarantee the constant of width of plate slab.

2.1 obtain the equation of equilibrium (4) of width of plate slab scale factor

Gather variable v, Ni _Eq/ Cr _Eq, T, φ, W, Δ θ, q ₁, q ₂, q ₃, q ₄, as the input variable of model, the ratio f of crystallizer end opening width and the final width of slab as output variable, by the screening of data, has finally been chosen 106 groups of data and has calculated.

After by formula (3) carry out standardization to data, utilize MINITAB running software PLS arithmetic result as follows:

PLS returns: v, Ni _Eq/ Cr _Eq, T, φ, W, Δ θ, q ₁, q ₂, q ₃, q ₄Variance analysis for f

As a result 1: the p value of ratio f is 0.000, less than alpha value 0.05, thereby provides enough evidences for the conspicuousness of formula.

As a result 2:

Obtain according to entire variable (totally 10 components) operation result

f＝0.059824-0.195973v+0.090888Nieq/Creq-0.488429T+0.332505φ-0.326162W

+0.171963Δθ-0.453494q ₁-0.492743q ₂+0.036508q ₃+0.012046q ₄ (10)

The formula of f is selected and checking

As a result 3:

The first row of output shows the number of components in the optimum formula (R-Sq that is defined as prediction is the highest).Minitab has selected 3 component formula, and the R-Sq of prediction is 0.5355.

In order to set up the relation of composition and the water yield, must use more component.Mainly the model R-Sq to 9 component formula (being selected by cross validation) is 60.30%, and the R-Sq of prediction is 50.69%, meets the condition of useful application.Its expression formula has been removed the q of coefficient minimum in 10 components ₄, obtain:

f＝0.059824-0.195973v+0.090888Nieq/Creq-0.488429T+0.332505φ-0.326162W

+0.171963Δθ-0.453494q ₁-0.492743q ₂+0.036508q ₃ (11)

2.2 adjust two cold 3 district's water yields, the control width of plate slab

430 ferritic stainless steel target components are:

Obtain the Ni of 430 ferritic stainless steel desired values according to formula (2.1) (2.2) _Eq=2.7, Cr _Eq=16.7, then obtain Ni _Eq/ Cr _EqStandard value is 0.16.

Can get according to formula (6) again

(f ₂-1)×0.036508×q ₃＝(1-f ₁)×0.090888×Ni _eq/Cr _eq (12)

Be defined as Q3 after the former setting water yield standardization with secondary cooling zone 3 districts,, when namely secondary cooling zone 3 district's water yields are Q3, f ₂Be 1.Like this according to formula 12 available 3 district's water yield coefficient tables.

According to Ni _Eq/ Cr _EqTwo cold 3 district's water yield coefficient tables have been obtained

From formula (4) and formula (6) and table, can find out, along with Ni _Eq/ Cr _EqReduce, the f of the final width of crystallizer end opening width/slab reduces, and this means that width of plate slab increases; Under the identical condition of pulling rate, by increasing the water yield in two cold 3 districts, offset Ni like this _Eq/ Cr _EqThe impact that reduces can be controlled width of plate slab and remain unchanged.

By as above embodiment, just can control easily and effectively width of plate slab, produce the slab that meets default product requirement, satisfy simultaneously little error, requirement that control law is stable.

Claims (6)

1. the method for control ferrite stainless steel base width during a continuous casting is produced is at first according to crystallizer end opening width W _Mold, the change width W that strand expands and causes _Creep, the change width W that causes is shunk in the cooling of ferrite stainless steel base _T, set the final width W of described ferrite stainless steel base _ColdModel be:

W _Cold＝W _Mold+W _Creep-W _T

It is characterized in that:

Also comprise the steps:

(1), selects Ni _Eq/ Cr _EqAs the representative element that affects ferrite stainless steel base hot properties, wherein, Ni _EqThe expression nickel equivalent, Cr _EqThe expression chromium equivalent;

(2), according to Ni _EqAnd Cr _EqDesired value draw Ni _Eq/ Cr _EqStandard value;

(3), gather the sample data of the Cast parameters affect stainless steel slab thickness, described sample data comprises arbitrary cooling zone water yield value q in the secondary cooling zone apart from crystallizer 1.7～5m suitable for reading _n

(4), with the Ni that obtains in the step (2) _Eq/ Cr _EqStandard value and step (3) in the sample data that gathers carry out data normalization and process;

(5), by regulating q _nValue offset Ni _Eq/ Cr _EqThe impact that the variation of value brings described ferrite stainless steel base width, its computing formula is:

C×Ni _eq/Cr _eq+J×q _n＝f ₁×C×Ni _eq/Cr _eq+f ₂×J×q _n

Or C * Ni _Eq/ Cr _Eq+ K * q _n=f ₁* C * Ni _Eq/ Cr _Eq+ f ₂* K * q _n

In the following formula, f ₁* Ni _Eq/ Cr _EqBe Ni _Eq/ Cr _EqChanging value, f ₂* q _nBe q _nChanging value, C, J, K are positive coefficient.

2. the method for control ferrite stainless steel base width during a kind of continuous casting according to claim 1 is produced, it is characterized in that: described positive coefficient C, J, K can obtain by the following method:

(a), with crystallizer end opening width W _MoldFinal width W C with the ferrite stainless steel base _OldBe defined as scale factor f, i.e. a f=W _Mold/ W _Cold

(b), with the sample data that after data normalization is processed, obtains in the claim 1 as input variable, the scale factor f described in the step (a) as output variable, is carried out the PLS computing, thereby sets up the slab equation of equilibrium:

f＝A-Bv+CNi _eq/Cr _eq-DT+Eφ-FW+GΔθ-Hq ₁-Iq ₂+Jq ₃+Kq ₄

In the following formula, v is that casting rate, φ are that crystallizer evenly heat flow, W are that the crystallizer water yield, Δ θ are that crystallizer is imported and exported water temperature difference, T is molten steel temperature in tundish, q ₁Be secondary cooling zone 1 district's water yield value, q ₂Be secondary cooling zone 2 district's water yield values, q ₃Be secondary cooling zone 3 district's water yield values, q ₄Be secondary cooling zone 4 district's water yield values; Wherein A, B, C, D, E, F, G, H, I, J, K are positive coefficient;

(c), positive coefficient C, J, K can be obtained by the slab equation of equilibrium described in the step (b).

3. the method for control ferrite stainless steel base width during a kind of continuous casting according to claim 1 and 2 is produced, it is characterized in that: the method that the data normalization described in the step (4) is processed is:

$x_{\mathrm{ij}}^{*}=\frac{x_{\mathrm{ij}}-{\stackrel{\&OverBar;}{x}}_j}{s_j},F_{0i}=\frac{y_i-\stackrel{\&OverBar;}{y}}{s_y}$

In the following formula,

Wherein, x _IjThe concrete numerical value of a certain input variable, x _Ij ^*X _IjValue after the standardization; y _iThe concrete numerical value of output output variable f, F _0iY _iValue after the standardization.

4. the method for control ferrite stainless steel base width is characterized in that: q in the described step (5) during a kind of continuous casting according to claim 1 was produced _nChoose secondary cooling zone 3 district water yield value q ₃Or secondary cooling zone 4 district water yield value q ₄

5. the method for control ferrite stainless steel base width is characterized in that: described Ni during a kind of continuous casting according to claim 1 was produced _Eq/ Cr _EqComputing formula be:

Ni _eq/Cr _eq＝(Ni％+0.5Mn％+30C％+30N％+0.33Cu％)/(Cr％+Mo％+1.5Si％)

6. the method for control ferrite stainless steel base width during a kind of continuous casting according to claim 2 is produced, it is characterized in that: the scope of described scale factor f and positive coefficient A, B, C, D, E, F, G, H, I, J, K is greater than 0, less than 2.

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