CN1979497A - Optimizing method for preventing and controlling scrab in cold band-steel continuous milling machine - Google Patents

Abstract

The invention discloses an optimizing method of using nick prevention and control as target in cold steel strip continuous-rolling machine, collecting equipment, steel strip characteristics, rolling process and other parameters of a cold continuous-rolling machine, and giving set values of initial tension and reduction of each machine frame, then separately finding skid factor and nick integrated judgment index value of each machine frame, and finding target function set for rolling rule optimization; then judging whether the target function meets Bauer' conditions, and finding the optimum tension and reduction set values. And it intrudes nick judgment concept, considers all machine frames of the cold continuous-rolling machine as a whole, and uses nick prevention and control as target to make on-line optimization settings on rolling rules, and can largely increase rolling speed and improve steel strip surface quality, and largely reduce huge economic losses of enterprises on the premise of assuring quality of products.

Description

Be the optimization method of target with the cut control in a kind of cold belt steel continuous rolling mill

Technical field

The present invention relates to the processing and forming of cold belt steel, is the optimization method of target with the cut control in particularly a kind of cold belt steel continuous rolling mill.

Background technology

Cold belt steel continuous rolling process as shown in Figure 1, band 1 is delivered to frame 31～3i after uncoiler 2 rolls out, rolling through a plurality of frames, band 1 reaches the thickness of regulation and is sent to the coiling machine backrush.The roll of each frame comprises backing roll 4 and working roll 5, and wherein working roll 5 directly contacts with strip surface.

In the operation of rolling, generally comprising tension force, pass deformation (characterizing with reduction in pass or reduction ratio) before and after each frame is isoparametric setting.Because these parameters are key factors of quality control in the cold belt steel continuous rolling process, therefore made number of research projects in this respect, relevant these Parameter Optimization control or establishing method specifically can be referring to the 51st～54 page of " the energy-optimised design of strip mill rolling schedule " " non-ferrous metal " 1998 the 2nd phases, the 24th～27 page of " cold-strip steel rolling schedule optimal design " " Hebei metallurgy " 2002 the 2nd phase, and the 49th～53 page of " OPTIMIZATION OF COLD ROLLING SCHEDULE FOR WIDE STRIP " " Shanghai metal " o. 11th in 1997) etc. list of references.

The optimization and the setting of the above-mentioned related rolling procedure of open source literature, only consider that generally each frame motor relative load is even, factors such as thick control and plate shape, never consider the control and the proactive problem of cut, therefore usually cause the surface of band steel in the operation of rolling and the surface of roll to produce cut, see Fig. 2, among the figure, in band 1 and the working roll 5 cut 6 is arranged all, the generation of cut has not only influenced the raising of mill speed, limited the output of milling train, and influenced the surface quality of band steel, and cause the product quality grade to descend even declare uselessly, caused enormous economic loss to enterprise.

Summary of the invention

The objective of the invention is the above-mentioned defective that exists in the traditional cold belt steel rolling process, providing in a kind of cold belt steel continuous rolling mill with the cut control is the optimization method of target, this method can be prevented and treated cut generation in the cold continuous rolling process, to realize the line traffic control of cold belt steel rolling.

To achieve these goals, the present invention has adopted following technical scheme,

Be that the optimization method of target may further comprise the steps with the cut control in this cold belt steel continuous rolling mill:

A, the device parameter of collecting cold continuous rolling, band steel characteristic parameter, rolling technological parameter, lubricated system parameter;

Each frame initial tension and the reduction settings value of b, given tandem mill, and initial step length and termination precision;

C, obtain the value of the slip factor of each frame of cold continuous rolling;

D, according to the value ψ of slip factor _i, obtain the value λ of the comprehensive judge index of cut of each frame of cold continuous rolling _i

E, obtain the objective function that rolling schedule optimization is set;

F, judge whether this objective function satisfies the Bao Weier condition, if satisfy the tension force after being optimized and the value of drafts; If do not satisfy, then repeat above-mentioned steps c, d and e, until satisfying the Bao Weier condition, draw optimum tension and reduction settings value;

The tension force after g, output are optimized and the value of drafts, and the tension force after will optimizing and reduction settings value are finished on-line setup as new rolling procedure.

In technique scheme of the present invention, this method is collected equipment, band steel feature, rolling mill practice, the lubricated system parameter of cold continuous rolling earlier, and each frame initial tension and the reduction settings value of given tandem mill, and initial step length and termination precision, obtain the value of the comprehensive judge index of cut of the slip factor of each frame of cold continuous rolling and each frame more respectively, and obtain the objective function that rolling schedule optimization is set; Judge again at last whether this objective function satisfies the Bao Weier condition, obtain optimum tension and reduction settings value, finished on-line setup.Therefore method of the present invention is not only considered factors such as even, thick control of each frame motor relative load and plate shape, and introduce cut and judge new ideas, each frame of cold continuous rolling is done as a whole considering as a whole, and cut control set as the on-line optimization that target is rolled rules, this method can play guaranteeing and significantly improve mill speed under the product quality premise, gives full play to the effect of milling train potential, improve the surface quality of band steel, significantly reduced the tremendous economic loss that therefore enterprise causes.

Description of drawings

Fig. 1 is the synoptic diagram of cold belt steel continuous rolling process;

Fig. 2 is the scratch defects synoptic diagram that produces in the cold belt steel rolling production;

Fig. 3 is an optimization method schematic flow sheet of the present invention;

Embodiment

In order to do to understand preferably to the present invention, below earlier the mechanism that cut produced is analyzed,

For scratch defects mechanism of production problem, on-the-spotly at the beginning think that this defective is a kind of hot sliding injury problem that causes owing to the lubricating oil film partial fracture, cause is a lack of lubrication.In fact, can know that hot sliding injury defective is not an elongate, perfoliate in view of apparent according to pertinent literature, but short and thick shape, therefore this defective is not hot sliding injury in view of form.In order to visit it actually, starting with from improving lubricated system in the scene, increases the flow of emulsion, found that related experiment is very little to the scratch defects influence, and this just illustrates that this defective is not that lack of lubrication causes.

Like this,, at first investigation is followed the tracks of at the scene, found concentrated latter two frame, the especially last stand that occurs in cold continuous rolling of scratch defects in order to seek the true cause that cut produces.On this basis, start with, the rolling technological parameter of band that scratch defects takes place is analyzed, find that all bands that scratch defects take place all have two common characteristic: the relevant frame that (1) the produces scratch defects tendency of all skidding from rolling basic theories; (2) the relevant frame mill speed of generation scratch defects is all very high.So, think that through further analyzing the main cause that cut produces is to cause owing to cold continuous rolling skids in operation of rolling high speed with deduction, specifically can so describe: cut mainly produces by skidding, itself might not cause cut but skid, must be that skidding under the fast state just can produce cut, both are indispensable, and this also is the reason that cut is concentrated latter two frame, the especially last stand that occur in cold continuous rolling.

Can know that by above-mentioned analysis the factor that whether a certain frame produces scratch defects in the decision cold continuous rolling operation of rolling has two: one is skid probability that occurs and the degree of skidding and taking place, and another one is a mill speed.

For the problem of skidding in the cold continuous rolling process, can introduce skid probability of occurrence and the parameter-slip factor ψ of occurrence degree of skidding of a general sign and reflect in the cold continuous rolling process a certain frame skid probability that occurs and the degree of skidding and taking place, its expression formula is:

$\mathrm{\ψ}=|\frac{\mathrm{\γ}}{\mathrm{\α}}-\frac{1}{2}|---\left(1\right)$

In the formula: γ-neutral angle;

α-nip angle.

The physical significance of slip factor ψ is the relative position of neutral surface in the distorted area.The more little expression neutral surface of ψ is near more by the middle part, distorted area, and the probability of the appearance of skidding is more little, occurrence degree is light more; And slip factor ψ is big more, represents that then neutral surface is far away more from the middle part, distorted area, and the probability of the appearance of skidding is big more, occurrence degree is heavy more, and the operation of rolling is unstable more.

Like this, in order to judge whether a certain breast roller and strip surface cut can take place in the cold continuous rolling process, and the degree of cut generation, simultaneously also in order to help the horizontal contrast between each frame of cold continuous rolling, the special parameter lambda that proposes a sign cut probability of occurrence and degree, with the comprehensive judge index of its called after cut, its expression formula is:

λ＝ψ·V ^α (2)

In the formula: ψ-slip factor;

The V-mill speed;

α-speed influences index, and is closely related with the characteristic of cold continuous rolling, general α=0.8 1.2, and Baosteel 1,220 five frame cold continuous rollings are according to statistics and recurrence, α=1.15.

Obviously, comprehensive judge index λ is more little for cut, and the probability of then representing cut to occur is more little, occurrence degree is light more; Otherwise the comprehensive judge index λ of cut is big more, and the probability of then representing cut to occur is big more, occurrence degree is serious more.

Should be noted that for a cold continuous rolling process,, just think that the cut phenomenon has taken place this operation of rolling as long as there is any one passage to produce cut.Because the big or small final decision of the comprehensive judge index λ value of cut is in the combined action of slip factor ψ and mill speed V.And for cold continuous rolling, although always mill speed is increasing, promptly always the mill speed than upstream frame is big for the mill speed of downstream frame, but the value of each frame slip factor but is influenced by rolling procedure (comprising tension force system and rolling schedule).In other words, can change the value of the comprehensive judge index λ of each frame cut by the optimization of rolling procedure, make the comprehensive judge index λ value of the cut equiblibrium mass distribution of each frame in the cold continuous rolling process, whole λ value phenomenon bigger than normal neither appears, though do not occur the little but a certain frame λ value phenomenon bigger than normal of whole λ value again, thereby finally reach the purpose of control cut.

Seeing also shown in Figure 3ly, is that the optimization method of target can reduce following steps with the cut control in the cold belt steel continuous rolling mill of the present invention:

The first step, device parameter, band steel characteristic parameter, rolling technological parameter, the lubricated system parameter of collecting cold continuous rolling;

Second step, each frame initial tension and the reduction settings value of given tandem mill, and initial step length and termination precision;

The 3rd goes on foot, and obtains the value of the slip factor of each frame of cold continuous rolling;

The 4th step is according to the value ψ of slip factor _i, obtain the value λ of the comprehensive judge index of cut of each frame of cold continuous rolling _i

In the 5th step, obtain the objective function that rolling schedule optimization is set:

In the 6th step, judge whether this objective function satisfies the Bao Weier condition, if satisfy the tension force after being optimized and the value of drafts; If do not satisfy, then repeat above-mentioned steps three, four and five, until satisfying the Bao Weier condition, draw optimum tension and reduction settings value;

The 7th step, the tension force after output is optimized and the value of drafts, and the tension force after will optimizing and reduction settings value are finished on-line setup as new rolling procedure.

Can know that according to rolling therory for a cold continuous rolling process, for any frame, following equation is set up:

${\mathrm{\α}}_i=\sqrt{\frac{h_{0i}-h_{1i}}{{R_i}^{\′}}}---\left(3\right)$

${\mathrm{\γ}}_i=\frac{1}{2}\sqrt{\frac{h_{0i}-h_{1i}}{{R_i}^{\′}}}[1-\frac{1}{{2\mathrm{\μ}}_i}(\sqrt{\frac{h_{0i}-h_{1i}}{{R_i}^{\′}}}+\frac{{\mathrm{\σ}}_{0i}{h}_{0i}-T_{1i}{h}_{1i}}{p_i})]---\left(4\right)$

${R_i}^{\′}=R_i[1+\frac{C_0{p}_i}{h_{0i}-h_{1i}}]---\left(5\right)$

$C_0=\frac{16(1-v^2)}{\mathrm{\πE}}---\left(6\right)$

In the formula: h _0iThe inlet thickness of the band of-Di i frame;

h _1iThe exit thickness of the band of-Di i frame;

R ' _iThe working roll of-Di i frame flattens radius;

R _iThe working roll radius of-Di i frame;

p _iThe unit width draught pressure of-Di i frame;

σ _1i, σ _0iThe front and back tension force of-Di i frame;

μ _iThe friction factor of-Di i frame;

The Young modulus of E, v-working roll and Poisson ratio.

Like this, the slip factor ψ of i frame _iCan further represent with following formula:

${\mathrm{\ψ}}_i=\frac{1}{{4\mathrm{\μ}}_i}|\sqrt{\frac{h_{0i}-h_{1i}}{{R_i}^{\′}}}+\frac{{\mathrm{\σ}}_{0i}{h}_{0i}-T_{1i}{h}_{1i}}{p_i}|---\left(7\right)$

Simultaneously, if adopt emulsion lubrication in rolling, then friction factor depends mainly on the oil film thickness in rolling deformation district ^[4], can represent with following formula:

${\mathrm{\&mu;}}_i=\mathrm{\&mu;}\left({\mathrm{\&xi;}}_{0i}\right)\&ap;k_{\mathrm{ri}}\&CenterDot;({\mathrm{\&mu;}}_{0i}-{\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="A20051011098000131.png"\; state="\{\{state\}\}">c</figure-callout>}}_1{{\mathrm{\&xi;}}_{0i}}^{c_2})---\left(8\right)$

In the formula: k _r-roll roughness influence coefficient, the roll roughness is big more, k _rMore little.

μ ₀Dry friction coefficient under the-identical roll roughness:

c ₁, c ₂-fitting coefficient can be drawn by experiment;

ξ _0i-rolling deformation district oil film equivalent depth, its expression formula is:

${\mathrm{\&xi;}}_{0i}=\frac{6\mathrm{a\&eta;}{V}_i}{\sqrt{\frac{h_{0i}-h_{1i}}{{R_i}^{\&prime;}}}[1-e^{-a(K_i-{\mathrm{\&sigma;}}_{0i})}]}---\left(9\right)$

In the formula: $\mathrm{\&eta;}={\mathrm{\&eta;}}_0{e}^{(\mathrm{ap}-{\mathrm{bT}}_m)}$

η ₀The viscosity at ambient temperature of-lubricant under an atmospheric pressure;

The viscosity pressure coefficient of a-lubricant;

The temperature coefficient of viscosity of b-lubricant;

T _mThe medial temperature of-lubricating oil film;

V _iThe mill speed of-Di i frame;

K _iThe resistance of deformation of-Di i frame band.

Equally, according to second flow amount equal principle, each frame outlet mill speed can be represented with following formula:

$V_i=\frac{V_n\&CenterDot;h_{1n}}{h_{1i}}---\left(10\right)$

In the formula: V _n-setting mill speed, the i.e. mill speed of last frame;

h _1nThe outlet thickness of strip of-last machine frame rolling mill.

If definition L _iBe the relative deformation of i frame, comprehensive (3)-(10) formula can know, under the constant prerequisite of technological lubrication system and roll technique for applying, and the comprehensive judge index λ of each frame cut of cold continuous rolling _iValue depend mainly on the distribution L of each frame drafts _i, with tension force system σ _0i, σ _1iAnd can represent in order to minor function:

λ _i＝λ(L _i，σ _0i，σ _1i) i＝1，2，…，n (11)

So, can simply be defined as the rolling schedule optimization objective function:

f(X)＝A·g ₁(X)+(1-A)·g ₂(X) (12)

In the formula:

$g_1\left(X\right)=\sqrt{\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}}{({\mathrm{\&lambda;}}_i-\stackrel{\&OverBar;}{\mathrm{\&lambda;}})}^2---\left(13\right)$

$g_2\left(X\right)=\stackrel{\&OverBar;}{\mathrm{\&lambda;}}---\left(14\right)$

$\stackrel{\&OverBar;}{\mathrm{\&lambda;}}=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{\&lambda;}}_i---\left(15\right)$

X＝{L _i，σ _0i，σ _1i，i＝1，2，3，…，n) (16)

The A-weighting coefficient

The frame number of n-tandem mill.

Need to prove g in the formula (12) ₁(X) represent the uniformity coefficient of each frame λ value, g ₂(X) represent the whole numerical value of each frame λ.Both are indispensable, neither wish to occur whole λ value phenomenon bigger than normal because optimize the result, though do not wish to occur the little a certain frame λ value of whole λ value phenomenon bigger than normal again.

Like this, whole optimizing process can be described as seeking a suitable allocation criterion and a tension force system X={L of depressing _i, σ _0i, σ _1i=1,2,3 ... n} makes and f (X) minimum adopts Bao Weier (powell) optimization method to draw the optimization result.

Embodiment

(1), collects required equipment, band raw data

Cold continuous rolling device parameter: work roll diameter D _W1=550/500mm; D _W2=533.4 (～535)/470mm; D _W3=533.4 (～535)/470mm; D _W4=533.4 (～535)/470mm; D _W5=533.4 (～535)/470mm

Working roll initial roughness: Ra ₁=0.60 μ m; Ra ₂=0.58 μ m; Ra ₃=0.56 μ m; Ra ₄=0.43 μ m; Ra ₅=0.38 μ m

The rolling milimeter number of working roll: L _W1=80Km; L _W2=80Km; L _W3=80Km; L _W4=80Km; L _W5=80Km

The product variety specification limit: strip width 1000mm, inlet thickness 1.8mm, exit thickness 0.195mm, steel grade are MRT3

(2) rolling technological parameter chooses

The outlet mill speed of cold continuous rolling end frame is set at 1600m/min

(3) viscosity at ambient temperature 80 of lubricant under an atmospheric pressure, the viscosity pressure coefficient 50 of lubricant, the temperature coefficient of viscosity 0.2 of lubricant

(4) optimization of rolling procedure

1) given each frame initial tension and reduction settings value X0=[0.2,0.2,0.2,0.2,0.2,176,176,176,176,176,176,176,176,176,176], the definition convergence precision is 0.001;

2) obtain the value ψ of the slip factor of each frame of cold continuous rolling _i=[0.1,0.21,0.3,0.32,0.4];

3), calculate the value λ of the comprehensive judge index of cut of each frame of cold continuous rolling _i=[6.2,7.9,8.4,9.5,18.2];

4), obtain the objective function f (X)=4.3 that rolling schedule optimization is set;

5), judge whether to meet the Bao Weier condition, the calculating that iterates draws optimum tension and reduction settings value,

The parameter result of each frame is as shown in table 1.

Table 1 ideal format product rolling schedule optimization result

The optimization situation	Frame	Thickness H/mm	Tension force T/Mpa	The comprehensive judge index λ of cut
					Before the optimization		1.8	49
1	1.26	146.412	3.86
				2		0.741869	164.052	5.72
3	0.461207	164.052	6.93
				4		0.3	165.816	10.52
5	0.195	68.6	15.31
				After the optimization			1.8	49
1	1.1952	161.28	5.81
					2	0.68225	161.28	6.72
3	0.432461	161.28	7.48
					4	0.288987	176	8.22
5	0.195	68.6	9.10

As can be seen from the table, after the optimization, the peak value index before the peak value of cut judge index is optimized descends greatly, as: before the optimization, the peak value of frame 4, frame 5 is 10.52,15.31; After the optimization, the peak value of frame 4, frame 5 only is 8.22,9.10.

By above-mentioned description as can be seen, method of the present invention can play really guaranteeing significantly to improve mill speed under the product quality premise, having reduced the probability of being with steel cut to occur in the operation of rolling, has guaranteed the surface quality of band steel preferably.

Claims (8)

1, be the optimization method of target with the cut control in a kind of cold belt steel continuous rolling mill,

It is characterized in that this method may further comprise the steps:

A, the device parameter of collecting cold continuous rolling, band steel characteristic parameter, rolling technological parameter, lubricated system parameter;

Each frame initial tension and the reduction settings value of b, given tandem mill, and initial step length and termination precision;

C, obtain the value of the slip factor of each frame of cold continuous rolling;

D, according to the value ψ of slip factor _i, obtain the value λ of the comprehensive judge index of cut of each frame of cold continuous rolling _i

E, obtain the objective function that rolling schedule optimization is set;

F, judge whether this objective function satisfies the Bao Weier condition, if satisfy the tension force after being optimized and the value of drafts; If do not satisfy, then repeat above-mentioned steps c, d and e, until satisfying the Bao Weier condition, draw optimum tension and reduction settings value;

The tension force after g, output are optimized and the value of drafts, and the tension force after will optimizing and reduction settings value are finished on-line setup as new rolling procedure.

2, be the optimization method of target with the cut control in the cold belt steel continuous rolling mill as claimed in claim 1,

It is characterized in that:

Described device parameter comprises the diameter of each frame working roll, the roughness of each frame working roll, the rolling milimeter number of each frame working roll, the Young modulus and the Poisson ratio of each frame working roll;

3, be the optimization method of target with the cut control in the cold belt steel continuous rolling mill as claimed in claim 1,

It is characterized in that:

The characteristic parameter of described band steel comprises strip width, the first frame band steel inlet thickness, the strain hardening coefficient of initial yield strength of band steel and band steel.

4, be the optimization method of target with the cut control in the cold belt steel continuous rolling mill as claimed in claim 1,

It is characterized in that:

Described rolling technological parameter comprises the outlet mill speed of cold continuous rolling end frame.

5, be the optimization method of target with the cut control in the cold belt steel continuous rolling mill as claimed in claim 1,

It is characterized in that:

Described technological lubrication system parameter is meant the viscosity at ambient temperature of lubricant under an atmospheric pressure, the viscosity pressure coefficient of lubricant, the temperature coefficient of viscosity of lubricant.

6, be the optimization method of target with the cut control in the cold belt steel continuous rolling mill as claimed in claim 1,

It is characterized in that:

Slip factor among the described step c is defined as,

$\mathrm{\&psi;}=|\frac{\mathrm{\&gamma;}}{\mathrm{\&alpha;}}-\frac{1}{2}|$

In the formula, γ-neutral angle

α-nip angle.

7, be the optimization method of target with the cut control in the cold belt steel continuous rolling mill as claimed in claim 1,

It is characterized in that:

The comprehensive judge index of cut is defined as in the described steps d,

λ＝ψ·V ^α

In the formula, V-mill speed;

α-speed influences index, and is closely related with the characteristic of cold continuous rolling, general α=0.8～1.2.

8, be the optimization method of target with the cut control in the cold belt steel continuous rolling mill as claimed in claim 1, it is characterized in that:

Among the described step e, the rolling schedule optimization objective function is defined as:

f(X)＝A·g ₁(X)+(1-A)·g ₂(X)

In the formula:

$g_1\left(X\right)=\sqrt{\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{({\mathrm{\&lambda;}}_i-\stackrel{-}{\mathrm{\&lambda;}})}^2}$

$g_2\left(X\right)=\stackrel{-}{\mathrm{\&lambda;}}$

$\stackrel{-}{\mathrm{\&lambda;}}=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{\&lambda;}}_i$

X＝{L _i，σ _0i，σ _1i，i＝1，2，3，…n}

A-weighting coefficient generally speaking, is got A=0.35

The frame number of n-tandem mill.

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