CN101934295A - Pre-calculation method for controlled cooling of thick plate after rolling - Google Patents

Abstract

The invention discloses a pre-calculation method for the controlled cooling of a thick plate after rolling. The pre-calculation method comprises the following steps of: (1) initializing to obtain the thickness d of a steel plate, steel grade information and components and measuring to obtain temperature Tw of current cooling water; (2) figuring out the number Nh of opening valves and a set value v0 of average speed of the steel plate by using a formula; (3) selecting cooling water flow Q0 and setting k to be equal to 1 and Q(k) to be equal to Q0; (4) solving formulas (4) to (7) by using the initializing information and factors in the step (1), the control parameter v0 obtained in the step (2) and the flow Q(k) in the step (3), figuring out the cooling temperature of the steel plate at an initial temperature after time t to obtain cooling temperature of the steel plate T'e, and setting that if an absolute value of eCR is less than epsilon and epsilon is less than or equal to 0.0001, Q0 is equal to Q(k) and calculation ends, and otherwise, the next step is proceeded to; (5) setting k to be equal to k plus 1, wherein alpha is larger than 0 and less than 1 and is a weight factor, and transferring to the step (4); and (6) figuring out a position-temperature curve set value. The invention can be popularized to all steel plants at home and abroad for pre-calculation in controlled cooling of medium and heavy plates after rolling and has good promotion and application potentials.

Description

A kind of slab rolls back control cooling pre-computation methods

Technical field

The present invention relates to a kind of pre-computation methods that sheet material rolls back control cooling, particularly a kind of slab rolls back control cooling pre-computation methods.

Background technology

The general branch of the control system of rolling the back cooling procedure of slab is two-layer, and the upper strata is the Supervised Control layer, provides the setting value of control variables such as the required cooling water flow metric density of the every block plate of cooling, roller table speed in advance according to the control target call.Bottom is on-the-spot circuit controls layer, according to setting value dynamically control is carried out in real time in each bottom loop.The Supervised Control part on upper strata also can be called the precomputation part.

Owing to roll in the cooling procedure of back at slab, open except cooling water flow, roller table speed, cooling section control variables such as number has a direct impact plate final cooling temperature and cooldown rate, steel plate finishing temperature, steel plate thickness, cooling water temperature etc. also have considerable influence to the cooling of steel plate.Be the strong nonlinear relation between each influence factor and the controlled quentity controlled variable, and have close coupling between each variable.What therefore, accurately calculate setting values such as cooling water flow metric density, steel plate speed in cooling procedure is a difficult point.

Guan S, Li H X, Tso S K. etc. are at " Process, IEEE Transactions on Control Systems Technology " (control system technology) (2001,9 (2): " the Multivariable Fuzzy Supervisory Control for Laminar Cooling " that delivers 348-356) (laminar flow cooling multivariable method for supervision and control), introduced the heat exchange calculation mathematic model, this model can be used to calculate controlled quentity controlled variables such as cooling water flow, but this article does not provide concrete implementation method, does not particularly provide the concrete optimization method of controlled quentity controlled variable.

Gong Caijun etc. are at " Northeastern University's journal (natural science edition) " (2005,26 (2): " Cooling Process Control of Rolled Plate " delivered 604-608) adopts physical model, calculate the setting value of controlled quentity controlled variables such as cooling water flow, but the method that specifically how optimizing sets value is not provided, the coupled relation that how to overcome between each variable also is discussed.

The Forecasting Methodology of the steel plate materials that Japanese patent application publication No. JP 5026871 A provide, promptly product is carried out precomputation in each process, calculate crystallization by the continuous casting model, crystal is state at interval, calculate the historical temperature curve that steel plate enters heating furnace with heat conduction model, crystallization diffusion-condition, the degree of superheat, temperature hold-time, rolling and phase transformation with steel steel plate in steel rolling model and the heat treatment model calculating operation of rolling and the continuous cooling process, use the material texture model and calculate steel plate stress, indexs such as hardness.

Show that from existing patent above patent does not all relate to the pre-computation methods of slab On-line Control cooling system.

Summary of the invention

The purpose of this invention is to provide the pre-computation methods that a kind of slab rolls back control cooling, this pre-computation methods can provide accurate controlled quentity controlled variable setting value for the slab accelerating cooling process, thereby can adapt to the production demand of various steel.

Technical conceive of the present invention: these computational methods comprise three modules: be respectively steel plate average speed and open valve number setting value computing module, cooling water flow setting value computing module, " position-temperature " curve setting value computing module.

Aspect asking steel plate average speed setting value and opening the valve number: when calculating steel plate average speed setting value and opening the valve number, make steel plate average speed consistent with reference speed in the cooling water model as far as possible, having considered to open the valve number simultaneously can not be very little, thereby has reduced the influence of steel plate speed to cooling effect.Therefore, can obtain more rational steel plate speed and open valve number setting value.

Finding the solution of cooling water flow setting value found the solution according to target cooldown rate and steel billet temperature mechanism model, considered in the model that cooling water temperature, steel billet temperature, steel plate physical dimension and steel plate materials form etc. the influence of factor, guaranteed precision.Owing to adopt mechanism model, this method is applicable to other steel grade in addition.

In addition, owing to ask steel plate average speed setting value earlier and open the valve number, ask the cooling water flow setting value then.Can avoid cooling water flow and the coupling of steel plate speed on cooldown rate.

Provide " position-temperature " curve: cooling water flow is set value, steel plate average speed sets value and opens valve number substitution steel billet temperature mechanism model, obtain steel plate cooling procedure temperature curve over time, then, become " position-temperature " curve according to steel plate average speed setting value, get wherein surface temperature and central temperature " position-temperature " curve, at desired temperature, provide more strict control target as steel plate for dynamically controlling accurately through the apparatus for supercooling position.

Technical scheme of the present invention comprises the steps:

(1) initialization obtains the steel plate thickness d, and steel plate material information (referring to steel grade information and composition) measures current cooling water temperature T _w

(2) utilize following formula to calculate and open valve number and steel plate average speed setting value

$t=({\hat{T}}_0-T_e^o)/{\mathrm{CR}}^o---\left(1\right)$

$N_h=\left\{\begin{array}{cc}\mathrm{int}\left[\frac{N}{2}\right],& \mathrm{int}\left[\frac{|t\&times;v_B|}{l_h}\right]<\mathrm{int}\left[\frac{N}{2}\right]\\ \mathrm{int}\left[\frac{|t\&times;v_B|}{l_h}\right],& \mathrm{int}\left[\frac{N}{2}\right]\&le;\mathrm{int}\left[\frac{|t\&times;v_B|}{l_h}\right]<N\\ N,& \mathrm{int}\left[\frac{N}{2}\right]\&le;\mathrm{int}\left[\frac{|t\&times;v_B|}{l_h}\right]\end{array}\right.---\left(2\right)$

$v_0=\frac{N_h\&times;l_h}{t}---\left(3\right)$

Wherein, l _hBe collector group spacing, N _hFor opening valve number, v ₀Be steel plate average speed setting value, t is the time of steel plate through the cooling zone,

And CR ^oBe respectively target final cooling temperature and target cooldown rate,

For target is opened cold temperature, wherein

CR ^o, Be known, the desired value that established technology is given.

(3) choose cooling water flow Q ₀(selected equipment allows the minimum of a value of flow arbitrarily), and make k=1, Q ^(k)=Q ₀

The upper and lower surface boundary condition of (4) initialization information that obtains by step (1), and steel plate, air cooling coefficient of heat transfer α _Air, water-cooled coefficient of heat transfer α _w, utilize the equation of heat conduction to calculate the Temperature Distribution of steel plate thickness direction, and be in initial temperature

The time, steel plate chilling temperature T ' behind the elapsed time t _e

Make e _CR=(T _e ^o-T _e')/t;

If, | e _CR|＜ε, wherein ε is minimum deviation≤0.0001, then Q ₀=Q ^(k), calculate and finish; Otherwise enter step (5);

The computational process of the above-mentioned equation of heat conduction is as follows:

Measure ρ, cp, λ, h _γWith

(these physical parameters can be tested the heterogeneity steel grade by special instrument and obtain), utilize following formula:

$\mathrm{\&rho;}\&CenterDot;\mathrm{cp}\stackrel{\&CenterDot;}{T}=-\mathrm{\&lambda;}\frac{{\&PartialD;}^{2}T}{\&PartialD;{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="H200910054249XE0000011.png"\; state="\{\{state\}\}">y</figure-callout>}}^2}+\stackrel{\&CenterDot;}{p}(h_{\mathrm{\&gamma;}}-h_{\mathrm{\&alpha;}})---\left(4\right)$

Wherein: T is a steel billet temperature, and y is a steel plate thickness direction coordinate; ρ is a density; Cp is the steel plate specific heat capacity; λ is the coefficient of heat conduction;

Be austenite phase transformation speed; h _γBe austenitic heat content; h _αBe ferritic heat content;

The upper and lower surface boundary condition of steel plate is

$\mathrm{\&lambda;}\frac{\&PartialD;T}{\&PartialD;y}=-{\mathrm{\&alpha;}}_{\&infin;}(T-T_{\&infin;})---\left(5\right)$

Wherein, α _∞Represent the coefficient of heat transfer of surface of steel plate, represent the air cooling coefficient of heat transfer α under the Different Cooling Conditions respectively _AirOr water-cooled coefficient of heat transfer α _w, T _∞Be environment temperature, air cooling coefficient of heat transfer α _AirTry to achieve by following formula

${\mathrm{\&alpha;}}_{\mathrm{air}}={\mathrm{\&sigma;}}_0\mathrm{\&epsiv;}(T^4-T_{\&infin;}^4)/(T-T_{\&infin;})---\left(6\right)$

Wherein, σ ₀=5.67 * 10 ^-8Be the black body radiation constant, ε is the steel surface radiance, and ε＜1, T _∞Be environment temperature.

Q _(k)The substitution following formula calculates water-cooled coefficient of heat transfer α _w,

${\mathrm{\&alpha;}}_w=k{\left(\frac{T}{T_B}\right)}^a{\left(\frac{v}{v_B}\right)}^b{\left(\frac{T_w}{T_{\mathrm{wB}}}\right)}^c{\left(\frac{Q}{Q_B}\right)}^d+w---\left(7\right)$

Wherein, k is a constant, 1000≤k≤10000, T, v, T _w, Q is respectively the steel billet temperature that measures, steel plate speed, water temperature and discharge; T _B, v _B, T _WB, Q _BBe the benchmark steel billet temperature of choosing, steel plate reference speed, the gentle standard flow of reference water; A, b, c, d are coefficient, and 0＜a, b, c, d＜5, w is a correction factor, number range 0≤w≤1000;

Step (5): make k=k+1,

(0＜α＜1), α is a weight coefficient; Change step (4).

Q wherein ^(k)It is the discharge setting value that the k time search obtains.

Step (6) calculating location-temperature curve setting value:

The control parameter v that applying step (2) and step (5) calculate ₀, Q ₀, v and Q in substitution formula (4)-(7) find the solution the surface of steel plate that can obtain as shown in Figure 7 and " time-temperature " curve at center.Surface of steel plate temperature and central temperature are that t changes in time, so make steel plate be respectively T ' in the temperature of surface and center ₁(t) and T ' ₂(t) (be the Temperature Distribution of thickness direction, also nature can obtain surface temperature and central temperature, and just the temperature of the different corresponding different-thickness position of y cannot be distinguished and treat and obtain respectively).

Getting n point along the roller-way direction.Make that every point coordinates is x _j(j=1 ..., n), surface temperature and central temperature that steel plate advances to the corresponding position are respectively T _1jAnd T _2j

Mapping relations x-ξ=v according to position and time ₀T, the mapping relations formula was mapped as " position-temperature " curve to " time-temperature " curve below (wherein ξ is a constant, is the coordinate of porch, cooling zone) adopted:

$\left\{\begin{array}{c}{T}_{1j}={\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="H200910054249XE0000011.png,H200910054249XE0000012.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{\&prime;}\left(\frac{x_j-\mathrm{\&xi;}}{v_0}\right)\\ T_{2j}={\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H200910054249XE0000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_2^{\&prime;}\left(\frac{x_j-\mathrm{\&xi;}}{v_0}\right)\end{array}\right.(j=\mathrm{1,2},...,n)---\left(8\right)$

So just dynamic control problem is changed into control x ₁, x ₂..., x _nPoint place surface of steel plate temperature, central temperature are at setting value T _1jAnd T _2jNear the problem of value.

The present invention makes it compared with prior art owing to adopted above technical scheme, has the following advantages and good effect:

(1) the present invention can provide accurate cooling water flow setting value and rational steel plate average speed setting value and open the valve number for the cut deal cooling procedure; The production demand that can adapt to various steel;

(2) the present invention can provide temperature (being called for short " position-temperature " curve) the goal-setting value at place, elongatedness direction device fixed position according to target cooldown rate and target final cooling temperature for the dynamic real-time control of cooling procedure.Provide advantage for improving dynamic control accuracy.

Description of drawings

The invention will be further described below in conjunction with the drawings and specific embodiments.

Fig. 1 is a slab accelerating cooling process schematic diagram of the present invention;

Fig. 2 quickens cooling " position-temperature " curve for cut deal of the present invention;

Fig. 3 is that slab of the present invention quickens the main flow process of cooling precomputation;

Fig. 4 is certain pipe line steel ρ Cp rerum natura figure;

Fig. 5 is certain pipe line steel coefficient of heat conduction figure;

Fig. 6 is certain pipe line steel heat content figure;

Fig. 7 is steel plate cooling procedure " time-temperature " curve;

Fig. 8 is steel plate cooling procedure " position-temperature " curve.

Symbol description:

Tp1 is that the temperature that P1 is ordered is surveyed;

Tp2 is that the temperature that P2 is ordered is surveyed;

Tp3 is that the temperature that P3 is ordered is surveyed;

Tp4 is that the temperature that P4 is ordered is surveyed;

11 is milling train;

12 is cooling facility for laminar flow;

13 is straightener;

21 steel billet temperature models;

31 is empty cooling section;

32 is the water cooling section;

33 for returning red end.

Among Fig. 4: D austenite ρ Cp; E ferrite ρ Cp;

Among Fig. 5: F coefficient of heat conduction λ;

Among Fig. 6: H austenite heat content; I ferrite heat content;

Among Fig. 7, Fig. 8: the A surface temperature; The B central temperature; C target final cooling temperature.

The specific embodiment

Further specify the present invention by means of Fig. 1 to Fig. 9 below:

As shown in Figure 1 and Figure 2, certain cut deal quickens the cooling production line, has 15 groups of collectors in the water cooling district.T wherein _P1Be P ₁The thermometric of point; T _P2Be P ₂The thermometric of point; T _P3Be P ₃The thermometric of point; T _P4Be P ₄The thermometric of point.In slab with P ₂And P ₄As the border, the steel plate upper and lower surface is as up-and-down boundary.Material flows from left to right, and arrow is expressed as the energy flow direction.

As shown in Figure 2, spacing is 1.6 meters between every group of collector, and entry position, cooling zone coordinate is 65.48 meters, and the coordinate of first laminar flow collector is 71.88m.Temperature monitor P ₂And distance is 12.8m between first group of collector, and general red temperature detecting point is apart from 20.49 meters of cooling zone outlets.

Whole slab rolls back control cooling precomputation and is divided into three modules, and flow process as shown in Figure 3.

With the pipe line steel is example: steel plate thickness is 20.91mm, opens cold temperature estimated value

Be 780 ℃ of target cooldown rate CR ^oWith the target final cooling temperature

Be respectively 17 ℃/s and 520 ℃.

Step 1: initialization, and obtain desired parameters in the formula of (4)～(7).Each coefficient is in the formula (7): a=0.94, b=1.2, c=0.99, d=0.82, k=4096.4, w=0

Each rerum natura of this kind pipe line steel is shown in Fig. 4～6.

Step 2: calculate and open valve number and average speed setting value

Can obtain according to formula (1)

$t=\frac{({\hat{T}}_0-T_e^o)}{{\mathrm{CR}}^o}=\frac{780-520}{17}=15.3s$

According to formula (2), choose reference speed 1.3m/s (selection standard is the median of drive apparatus allowed band), then

$8<\left[\frac{|t\&times;v_B|}{l_h}\right]=\left[\frac{15.3\&times;1.3}{1.6}\right]=12<15$

Therefore, open valve number N _hIt is 12 groups.

According to formula (3), initial velocity is

${\mathrm{<figure-callout\; id="0"\; label="v"\; filenames="H200910054249XE0000022.png,H200910054249XE0000031.png"\; state="\{\{state\}\}">v</figure-callout>}}_0=\frac{N_h\&times;l_h}{t}=12\&times;1.6/15.3-1.255m/s$

Step 3: choose cooling water flow Q ₀=2001/ (m ²And make k=1, Q .min), ^(k)=Q ₀

Step 4: the control parameter v that calculates by step 2 and step 3 ₀, Q ^(k), solution formula (4)-(7), calculating in initial temperature is

The time, steel plate chilling temperature behind the elapsed time t, and remember that this calculates the steel plate chilling temperature is T ' _eOrder

If, | e _CR|＜ε, then Q ₀=Q ^(k), calculate and finish.(calculating of the equation of heat conduction is prior art, provides computational process no longer in detail at this)

Step 5: make k=k+1,

(0＜α＜1) is changeed step 4 and is recomputated.

After iterative computation finishes, finally obtain cooling water flow setting value Q ₀Be 365l/ (m ².min).

Step 6: calculate " position-temperature " setting value curve, the control parameter v that applying step (2) and step (5) calculate ₀, Q ₀, v and Q in substitution formula (4)-(7), the line number of going forward side by side value is calculated, and obtains surface temperature T ' ₁(t) and central temperature T ' ₂(t) cooling curve such as Fig. 7.

T ' ₁(t), T ' ₂(t), plate speed v ₀Obtain as shown in Figure 8 with porch, cooling zone coordinate ξ=71.88m substitution formula (8), along the surface of steel plate temperature of the every position of roller-way direction and the setting value of central temperature.

In sum, the present invention can obtain more rational steel plate average speed setting value and open the valve number, and the cooling water flow setting value, can adapt to the demand of multistage steel.This method has proposed first in addition, and gauging surface and center " position-temperature " curve is as the setting value of dynamically controlling, for the accurate dynamically control of steel plate provides foundation in precomputation.

Those of ordinary skill in the art will be appreciated that, above embodiment is used for illustrating the present invention, and be not to be used as limitation of the invention, as long as in connotation scope of the present invention, all will drop in claims scope of the present invention variation, the modification of the above embodiment.

Claims (3)

1. a slab rolls back control cooling pre-computation methods, it is characterized in that comprising following steps:

Step 1: initialization, obtain steel plate thickness d, steel grade information and composition, measure current cooling water temperature T _w

Step 2: utilize following formula to calculate and open valve number and steel plate average speed setting value

$t=({\hat{T}}_0-T_e^o)/{\mathrm{CR}}^o$

$N_h=\left\{\begin{array}{cc}\mathrm{int}\left[\frac{N}{2}\right],& \mathrm{int}\left[\frac{|t\&times;v_B|}{l_h}\right]<\mathrm{int}\left[\frac{N}{2}\right]\\ \mathrm{int}\left[\frac{|t\&times;v_B|}{l_h}\right],& \mathrm{int}\left[\frac{N}{2}\right]\&le;\mathrm{int}\left[\frac{|t\&times;v_B|}{l_h}\right]<N\\ N,& \mathrm{int}\left[\frac{N}{2}\right]\&le;\mathrm{int}\left[\frac{|t\&times;v_B|}{l_h}\right]\end{array}\right.$

$v_0=\frac{N_h\&times;l_h}{t}$

Wherein, l _hBe collector group spacing, N _hFor opening valve number, v ₀Be steel plate average speed setting value, t is the time of steel plate through the cooling zone,

And CR ^oBe respectively target final cooling temperature and target cooldown rate, For target is opened cold temperature;

Step 3: choose cooling water flow Q ₀(selected equipment allows the minimum of a value of flow arbitrarily), and make k=1, Q ^(k)=Q ₀

Step 4: the initialization information that obtains by step 1, and the upper and lower surface boundary condition of steel plate, air cooling coefficient of heat transfer α _Air, water-cooled coefficient of heat transfer α _w, utilize the equation of heat conduction to calculate the Temperature Distribution of steel plate thickness direction, and be in initial temperature

The time, steel plate chilling temperature T ' behind the elapsed time t _e

Make e _CR=(T _e ^o-T ' _e)/t

If, | e _CR|＜ε, wherein ε is minimum deviation≤0.0001, then Q ₀=Q ^(k), calculate and finish; Otherwise enter step 5;

Step 5: make k=k+1,

(0＜α＜1), α is a weight coefficient; Change step 4.

2. slab as claimed in claim 1 rolls back control cooling pre-computation methods, and it is characterized in that: the computational process of the equation of heat conduction is as follows in the described step 4:

Measure ρ, cp, λ, With

Utilize following formula:

$\mathrm{\&rho;}\&CenterDot;\mathrm{cp}\stackrel{\&CenterDot;}{T}=-\mathrm{\&lambda;}\frac{{\&PartialD;}^{2}T}{\&PartialD;y^2}+\stackrel{\&CenterDot;}{p}(h_{\mathrm{\&gamma;}}-h_{\mathrm{\&alpha;}})$

Wherein: T is a steel billet temperature, and y is a steel plate thickness direction coordinate; ρ is a density; Cp is the steel plate specific heat capacity; λ is the coefficient of heat conduction;

Be austenite phase transformation speed; h _γBe austenitic heat content; h _αBe ferritic heat content;

The upper and lower surface boundary condition of steel plate is

$\mathrm{\&lambda;}\frac{\&PartialD;T}{\&PartialD;y}=-{\mathrm{\&alpha;}}_{\&infin;}(T-T_{\&infin;})$

Wherein, α _∞Represent the coefficient of heat transfer of surface of steel plate, represent the air cooling coefficient of heat transfer α under the Different Cooling Conditions respectively _AirOr water-cooled coefficient of heat transfer α _w, T _∞Be environment temperature, air cooling coefficient of heat transfer α _AirTry to achieve by following formula

${\mathrm{\&alpha;}}_{\mathrm{air}}={\mathrm{\&sigma;}}_0\mathrm{\&epsiv;}(T^4-T_{\&infin;}^4)/(T-T_{\&infin;})$

Wherein, σ ₀=5.67 * 10 ^-8Be the black body radiation constant, ε is the steel surface radiance, and ε＜1, T _∞Be environment temperature;

Make Q=Q ^(k), the substitution following formula calculates water-cooled coefficient of heat transfer α _w

${\mathrm{\&alpha;}}_w=k{\left(\frac{T}{T_B}\right)}^a{\left(\frac{v}{v_B}\right)}^b{\left(\frac{T_w}{T_{\mathrm{wB}}}\right)}^c{\left(\frac{Q}{Q_B}\right)}^d+w$

Wherein, k is a constant, 1000≤k≤10000, T, v, T _w, Q is respectively the steel billet temperature that obtains of actual measurement, steel plate speed, water temperature and discharge; T _B, v _B, T _WB, Q _BBe the benchmark steel billet temperature of choosing, steel plate reference speed, the gentle standard flow of reference water; A, b, c, d are coefficient, and 0＜a, b, c, d＜5, w is a correction factor, number range 0≤w≤1000.

3. slab as claimed in claim 1 or 2 rolls back control cooling pre-computation methods, it is characterized in that also comprising step 6: calculating location-temperature curve setting value

The control parameter v that applying step 2 and step 5 calculate ₀, Q ₀, v and Q in substitution formula (4)-(7) find the solution " time-temperature " curve that can obtain surface of steel plate temperature and central temperature, are getting n point along the roller-way direction, make that every point coordinates is x _j(j=1 ..., n), surface temperature and central temperature that steel plate advances to the corresponding position are respectively T _1jAnd T _2j

Adopt formula

$\left\{\begin{array}{c}{T}_{1j}=T_1^{\&prime;}\left(\frac{x_j-\mathrm{\&xi;}}{v_0}\right)\\ T_{2j}=T_2^{\&prime;}\left(\frac{x_j-\mathrm{\&xi;}}{v_0}\right)\end{array}\right.(j=\mathrm{1,2},...,n)$

" time-temperature " curve is mapped as " position-temperature " curve, and wherein, ξ is a constant, T ' ₁(t) and T ' ₂(t) be respectively the temperature of steel plate in surface and center.

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