CN102303051A - Pipe shape control method for rolling seamless steel pipe by using seven-frame tandem mill - Google Patents

Abstract

The invention discloses a pipe shape control method for rolling a seamless steel pipe by using a seven-frame tandem mill, which aims to provide a control method for processing data by using on-line detection pipe shape information and controlling rolling parameters in real time by integrating thickness errors, ellipticity errors and straightness errors which influence pipe shapes so as to ensure the accuracy of the pipe shapes. The method comprises the following steps of: 1) presetting the rolling parameters; 2) calculating rolling reduction and rolling force according to actually-measured wall thickness, ellipticity and straightness, namely making the rolling reduction, the wall thickness errors, the ellipticity errors and the straightness errors form a matrix, simplifying the matrix to be a corresponding relationship between the rolling reduction and a single parameter by an elimination method, calculating the rolling reduction caused by the wall thickness errors, the rolling reduction caused by the ellipticity errors and the rolling reduction caused by the straightness errors respectively, and calculating the rolling force by using the sum of the calculated rolling reduction caused by the wall thickness errors, the ellipticity errors and the straightness errors; and 3) modifying the rolling force and roller gap numerical values in real time in the rolling process.

Description

Use the tubular control method of seven frame tandem mill rolling seamless steel pipes

Technical field

The present invention relates to a kind of tubular control method of seamless steel pipe.

Background technology

Seamless steel pipe is mainly used in fields such as energy development, communications and transportation, frame for movement, chemical plant installations.With the development of World Economics and production technology, industries such as oil and boiler improve constantly the seamless steel pipe quality requirement, and tubular ERROR CONTROL has become one of core technology of seamless steel tube production.The tubular of seamless steel pipe is important control index during steel pipe rolling is produced; Refer to thickness difference and straightness error and the ovality etc. of steel pipe at diverse location; Tubular error is mainly derived from variation, roll contact condition, the roll thermal deformation of error, the rolling tensile force of error, the roll of variation, the hollow billet material of roll-force, variation of roll gauge etc., and these parameters directly have influence on the tubular state and the roll goal of regulation and control of steel pipe.

Tubular control in the roll seamless steel tube process is comprehensive, a complicated process; Each link factor such as the roll shape of the roll in the production, rolling technological parameter, as-rolled condition variation all might have influence on the tubular quality of product, also has relation uncertain, non-linear, close coupling between each influence factor.At present, tubular control both domestic and external mainly is the independent control method of error.But,, influence control accuracy because there is interference each other in each error parameter.

Summary of the invention

The present invention is in order to overcome weak point of the prior art; Provide a kind of through the tubular information of online detection and carry out rational data; Tubular thickness error, ellipticity error and the straightness error of influence integrated; Be rolled the real-time control of parameter, guarantee the control method of tubular precision.

The present invention realizes through following technical proposals:

A kind of tubular control method of use seven frame tandem mill rolling seamless steel pipes is characterized in that, comprises the steps:

(1) rolling parameter presets:

(1) calculates the initial roll forming of roll, the wear extent and the roll heat distortion amount of roll;

(2) the comprehensive roll forming of calculating roll:

The initial roll forming of the roll that calculates in the step (1), the wear extent and the roll heat distortion amount of roll are carried out the comprehensive roll forming that the strain linear superposition obtains equivalence;

(3) calculate each frame export goal wall thickness, ovality and linearity;

(4) calculate the roll drafts:

In seven frame tandem mills, the roll drafts that 5%, the second frame to the, the five breast roller drafts that 35%, the six breast roller drafts that the first breast roller drafts accounts for overall reduction accounts for overall reduction are 15%, the seven frame of overall reduction is zero;

(5) calculate the roll-force of each frame:

$p_i\left(k\right)={\stackrel{\‾}{p}}_{1,i}\left(k\right)\·F_{1,i}\left(k\right)+{\stackrel{\‾}{p}}_{2,i}\left(k\right)\·F_{2,i}\left(k\right)---\left(1\right)$

In the formula (1):

p _i(k) be the roll-force of i frame k rolling cycle;

for the i-th frame k reducing region's first rolling cycle average unit force;

F _{L, i}(k) be the floor projection of contact area of the k rolling cycle of i frame diameter reducing area;

for the i-th frame minus the first wall region k rolling cycle average unit force;

F _{2, i}(k) be the floor projection of contact area of the k rolling cycle of i frame wall-thickness reduction zone;

(2) wall thickness, ovality and the linearity according to actual measurement calculates rolling drafts and roll-force:

(1) the detection FEEDBACK CONTROL of wall thickness deflection

Adopt the ultrasonic thickness appearance to measure the actual wall thickness value of the first six frame exit steel pipe of tandem mill; With the deviation of the actual wall thickness value of steel pipe measured and target wall thickness value as the wall thickness difference; Employing is based on the rolling drafts of each frame of algorithm computation tandem rolling unit of Digital PID Controller, and computing formula is following:

e _i(k)＝ξ·[r _i(k)-y _act，i(k)] (2)

In the formula (2), e _i(k) be the wall thickness difference of the k control cycle of i frame;

r _i(k) be the target wall thickness of i frame;

y _{Act, i}(k) be the actual wall thickness of the k control cycle of i frame;

ξ is the wall thickness deflection adjustment factor, gets 0.6-0.9;

$\mathrm{\Δ}{e}_i\left(k\right)=c_i\·[c_{\mathrm{PF},i}\left(k\right)+\frac{c_{\mathrm{IF},i}\·\underset{j=0}{\overset{k}{\mathrm{\Σ}}}{e}_i\left(j\right)}{c_{\mathrm{BF},i}}]---\left(3\right)$

In the formula (3), Δ e _i(k) be the drafts of the k control cycle wall thickness deflection feedback adjusting of i frame;

c _iBe the wall thickness deflection feedback control model adjustment coefficient of i frame, span is 0.52-0.61;

c _{PF, i}(k) be the wall thickness deflection feedback proportional coefficient of i frame k control cycle, span is 0.23-0.27;

c _{IF, i}Being the wall thickness deflection feedback integral coefficient of i frame, is 0.9 when j=i, and all the other are 0.2;

c _{BF, i}Be the influence coefficient of the drafts of i frame to wall thickness deflection, span is 1.0-1.25;

(2) the detection FEEDBACK CONTROL of ellipticity error

Measure the difference acquisition ovality of the maximum gauge and the minimum diameter of tandem mill the 6th frame and the 7th frame exit seamless steel pipe through the misalignment measurement appearance that is installed in tandem mill the 6th frame and the 7th frame exit; Deviation with actual ovality of detected steel pipe and target ovality value is a foundation; Calculate the drafts of each frame of tandem rolling unit, computing formula is following:

ΔR _i(k)＝α·[R _i(k)-r _act，i(k)] (4)

In the formula (4), Δ R _i(k) be the ovality difference of the k control cycle of i frame;

R _i(k) be the target ovality of i frame;

r _{Act, i}(k) be the actual ovality of the k control cycle of i frame;

α is the ellipticity error adjustment factor, and span is 0.34-0.39;

$\mathrm{\Δ}{y}_i\left(k\right)=m_i\·[m_{\mathrm{PF},i}\left(k\right)+\frac{m_{\mathrm{IF},i}\·\underset{j=0}{\overset{k}{\mathrm{\Σ}}}\mathrm{\Δ}{R}_i\left(j\right)}{m_{\mathrm{BF},i}}]---\left(5\right)$

In the formula (5), Δ y _i(k) be the drafts of the k control cycle ellipticity error feedback adjusting of i frame;

m _iBe the ellipticity error feedback control model adjustment coefficient of i frame, span is 0.25-0.31;

m _{PF, i}(k) be the ellipticity error feedback proportional coefficient of i frame k control cycle, span is 0.18-0.23;

m _{IF, i}Being the ellipticity error feedback integral coefficient of i frame, is 0.8 when j=i, and all the other are 0.13;

m _{BF, i}Be the influence coefficient of the drafts of i frame to ellipticity error, span is 1.5-2.1;

(3) the detection FEEDBACK CONTROL of straightness error

At the 5th frame, the 6th frame and the 7th frame exit difference setting-up eccentricity measuring instrument; Measure the tube core position of seamless steel pipe through the misalignment measurement appearance; The tube core position that connects each measurement point; Obtain steel pipe actual flexion value; Deviation with the target bending value of detected steel pipe actual flexion value and steel pipe is a foundation; Calculate the drafts of tandem rolling unit the 6th frame, computing formula is following:

γ _i(k)＝η·[θ _i(k)-φ _act，i(k)] (6)

In the formula (6), γ _i(k) be the linearity difference of the k control cycle of i frame;

θ _i(k) be the target line degree of i frame;

φ _{Act, i}(k) be the actual linearity of the k control cycle of i frame;

η is the straightness error adjustment factor, and span is 0.67-0.75;

$\mathrm{\Δ}{\mathrm{\γ}}_i\left(k\right)=n_i\·[n_{\mathrm{PF},i}\left(k\right)+\frac{n_{\mathrm{IF},i}\·\underset{j=0}{\overset{k}{\mathrm{\Σ}}}\mathrm{\Δ}{\mathrm{\γ}}_i\left(j\right)}{n_{\mathrm{BF},i}}]---\left(7\right)$

In the formula (7), Δ γ _i(k) be the drafts of the k control cycle straightness error feedback adjusting of i frame;

n _iBe the straightness error feedback control model adjustment coefficient of i frame, it is 0.37-0.43 for span;

n _{PF, i}(k) be the straightness error feedback proportional coefficient of i frame k control cycle, span is 0.16-0.21;

n _{IF, i}Being the straightness error feedback integral coefficient of i frame, is 0.8 when j=i, and all the other are 0.23;

n _{BF, i}Be the influence coefficient of the drafts of i frame to straightness error, span is 1.1-1.3;

(4) decoupling zero control

Drafts that step (1), step (2) and step (3) are obtained and wall thickness difference, ovality difference, three parameters of linearity difference are formed matrix, and are as follows:

$\left[\begin{array}{ccc}{a}_{\mathrm{1,1}}& a_{\mathrm{1,2}}& a_{\mathrm{1,3}}\\ a_{\mathrm{2,1}}& a_{\mathrm{2,2}}& a_{\mathrm{2,3}}\\ a_{\mathrm{3,1}}& a_{\mathrm{3,2}}& a_{\mathrm{3,3}}\end{array}\right]\left\{\begin{array}{c}{e}_i\left(k\right)\\ \mathrm{\Δ}{R}_i\left(k\right)\\ {\mathrm{\γ}}_i\left(k\right)\end{array}\right\}=\left\{\begin{array}{c}\mathrm{\Δ}{e}_i\left(k\right)\\ \mathrm{\Δ}{y}_i\left(k\right)\\ \mathrm{\Δ}{\mathrm{\γ}}_i\left(k\right)\end{array}\right\}---\left(8\right)$

In the formula (8):

e _i(k) be the wall thickness difference of the k control cycle of i frame;

Δ R _i(k) be the ovality difference of the k control cycle of i frame;

γ _i(k) be the linearity difference of the k control cycle of i frame;

Δ e _i(k) be the drafts of the k control cycle wall thickness deflection feedback adjusting of i frame;

Δ y _i(k) be the drafts of the k control cycle ellipticity error feedback adjusting of i frame;

Δ γ _i(k) be the drafts of the k control cycle straightness error feedback adjusting of i frame;

a _1,1Be the wall thickness deflection feedback control model adjustment coefficient c of i frame _iξ multiplies each other with the wall thickness deflection adjustment factor;

a _1,2Be the wall thickness deflection feedback control model adjustment coefficient c of i frame _iWall thickness deflection feedback proportional coefficient c with the i frame _{PF, i}(k) multiply each other;

a _1,3Be the wall thickness deflection feedback control model adjustment coefficient c of i frame _iWall thickness deflection feedback proportional coefficient c with the i frame _{PF, i}(k) multiply each other, again divided by the drafts of i frame influence coefficient c to wall thickness deflection _{BF, i}

a _2,1It is the ellipticity error feedback control model adjustment Coefficient m of i frame _iEllipticity error feedback proportional Coefficient m with the i frame _{PF, i}(k) product;

a _2,2It is the ellipticity error feedback control model adjustment Coefficient m of i frame _iProduct with ellipticity error adjustment factor α;

a _2,3It is the ellipticity error feedback control model adjustment Coefficient m of i frame _iWith the product of ellipticity error adjustment factor α, again divided by the drafts of i frame influence coefficient m to ellipticity error _{BF, i}

a _3,1Be the straightness error feedback control model adjustment coefficient n of i frame _iStraightness error feedback proportional coefficient n with the i frame _{PF, i}(k) product is again divided by the drafts of the i frame influence coefficient n to straightness error _{BF, i}

a _3,2Be the straightness error feedback control model adjustment coefficient n of i frame _iStraightness error feedback proportional coefficient n with the i frame _{PF, i}(k) product;

a _3,3Be the straightness error feedback control model adjustment coefficient n of i frame _iProduct with straightness error adjustment factor η;

Adopt the elimination be reduced to drafts respectively with the corresponding relation of single parameter, calculate the drafts that drafts that the wall thickness deflection of i frame k control cycle causes, drafts that ellipticity error causes and straightness error cause respectively;

The drafts sum that the drafts that causes with the wall thickness deflection that calculates, the drafts that ellipticity error causes and straightness error cause is calculated the roll-force of each frame of k control cycle as drafts;

(3) in the operation of rolling, revise roll-force and roll gap numerical value in real time

(1) roll-force FEEDBACK CONTROL Mathematical Modeling is:

ΔF _Bi＝k _ali·k _FF·ΔF _Ri (9)

In the formula (9), Δ F _BiBe the roll-force regulated quantity of i frame, i is a shelf number;

k _AliBeing the roll-force feedback control model adjustment coefficient of i frame, is 0.9 during i=1, is 0.65 during i=2, is 0.65 during i=3, is 0.65 during i=4, is 0.65 during i=5, is 0.65 during i=6, is 0.1 during i=7;

k _FFBeing roll-force feedback control model coefficient, is 0.5;

Δ F _RiBe the roll-force variable quantity of i frame, promptly the roll-force of the k control cycle that is calculated by formula (1) and the actual roll-force of (k-1) control cycle is poor;

As Δ F _BiNumerical value greater than 5% o'clock of (k-1) actual roll-force of rolling cycle, get Δ F _BiBe 5% of (k-1) actual roll-force of rolling cycle, as Δ F _BiNumerical value be less than or equal to 5% o'clock of (k-1) actual roll-force of rolling cycle, the roll-force of getting the k control cycle that calculates in the decoupling zero control of (4) step of step (two) is as new roll-force;

(2) roll gap FEEDBACK CONTROL Mathematical Modeling is:

Δδ _Bi＝k _gδi·k _δδ·Δδ _Ri (10)

In the formula (10), Δ δ _BiBe the roll gap regulated quantity of i frame, i is a shelf number;

k _{G δ i}Being the roll gap control model adjustment coefficient of i frame, is 0.8 during i=1, is 0.54 during i=2, is 0.54 during i=3, is 0.54 during i=4, is 0.54 during i=5, is 0.54 during i=6, is 0.1 during i=7;

k _{δ δ}Being roll gap feedback model coefficient, is 1.0;

Δ δ _RiBe the roll gap variable quantity of i frame, i.e. the drafts sum that causes of the drafts that causes of the wall thickness deflection of the i frame k control cycle of Ji Suaning, drafts that ellipticity error causes and straightness error and the difference of the actual drafts of (k-1) control cycle;

As Δ δ _BiNumerical value greater than 3% o'clock of (k-1) actual drafts of rolling cycle, make Δ δ _BiEqual (k-1) rolling cycle actual drafts 3%; As Δ δ _BiNumerical value be less than or equal to 3% o'clock of (k-1) actual drafts of rolling cycle, the rolling drafts sum of getting drafts that drafts that the wall thickness deflection of the i frame k control cycle that calculates in the decoupling zero control of (4) step of step (two) causes, drafts that ellipticity error causes and straightness error cause and (k-1) rolling cycle reality is as new rolling drafts.

The present invention has following technique effect:

1, control method of the present invention is through the tubular information of online detection and carry out rational data; Tubular thickness error, ellipticity error and the straightness error of influence integrated the drafts of each roll of control; Avoided each error to control the interference that causes separately; The tubular precision of the seamless steel pipe that obtains is high; Simultaneously; Avoid drafts adjustment unnecessary in the control procedure, reduced energy consumption.

2, the wearing and tearing of control method of the present invention through initial roll forming and roll, thermal deformation comprehensive, the compensation roll deformation is to the influence of rolling accuracy.

3, control method of the present invention can controlled rolling power through rolling force model and Rolling roller slit die type and the fluctuation of rolling the drafts mill speed and the tubular sudden change that cause.

4, the dynamic tubular control technology of rolling drafts and roll-force control technology can compare according to actual value and the tubular value of target that measurement result calculates; Obtain one group of deviation; Through 7 rolls of regulating and control separately; Apply corresponding rolling drafts and roll-force to roll respectively; Carry out high-precision tubular control; Mainly can eliminate the pipe defective of symmetry and asymmetry, dynamic high precision control is tubular, and tubular precision is high.

The specific embodiment

Below in conjunction with specific embodiment the present invention is elaborated.

Embodiment:

The basic geometric parameters of seamless steel pipe:

Body external diameter: D=244.5mm; Body external diameter permissible variation: (1.0%～+ 1.0%) D;

Body wall thickness: t=15.11mm; Body wall thickness permissible variation: (12.0%～+ 12.0%) t;

Sleeve pipe ovality: ovality≤1.0%D;

The body flexibility is not more than steel pipe total length 0.50%; The pipe end flexibility is not more than 1.5mm/m.

The strand size:

According to final products specification Φ 244.5mm * 13.84mm, the strand of design is of a size of: Φ 310mm.

Roll adopts cast steel, and material behavior is seen shown in the table 1.

Table 1 material behavior

The temperature of the operation of rolling is 1100 ℃.

The speed of first roll is 1.59956m/s, and the hollow forging initial velocity is 1.5m/s, and the speed of the 7th roll is 3.28474m/s.

The employed seven frame tandem mills of the tubular control method of seamless steel pipe of the present invention are separately installed with the ultrasonic thickness appearance in the exit of the first six frame, with the wall-thickness measurement difference.Be separately installed with the difference misalignment measurement appearance that is used to measure maximum gauge and minimum diameter in the 6th frame and the 7th frame exit, be separately installed with the misalignment measurement appearance of measuring seamless steel pipe tube core position in the exit of the 5th frame, the 6th frame and the 7th frame.

The present invention uses the tubular control method of seven frame tandem mill rolling seamless steel pipes, comprises the steps:

(1) rolling parameter presets:

1, adopt conventional method to calculate the initial roll forming of roll, the wearing and tearing and the roll thermal deformation of roll

(1) initial roll forming is according to the axial distance z of roll arbitrfary point in each frame _i, the roll arbitrfary point radius of curvature ρ _iRadius R with the roll arbitrfary point _iBetween relation calculate according to conventional method, wherein, i is a shelf number.Dimension of roller is seen table 2.

Table 2

(2) wearing and tearing of the roll that causes of this production before rolling are calculated and are adopted empirical model, and the formula of place, summit wear extent that calculates roll according to rolling drafts, mill speed, dimension of roller, chilling temperature etc. is following:

$Y_i=\frac{W\·e^{f_{i}T}}{\frac{P_i}{L_i\·B_i}\·(1-\frac{\mathrm{\Δ}{V}_i}{V_i})}---\left(1\right)$

In the formula (1): P _iThe pressure of i frame when rolling, N;

L _iThe contact arc length of i frame when rolling, m;

B _iThe steel pipe broadening of i frame when rolling, m;

Steel pipe moved needed power, N when W was rolling;

Rolling temperature when T is rolling, ℃;

f _iWhen rolling, the roll of i frame and the coefficient of kinetic friction between the steel pipe;

Δ V _iThe roll of i frame and the relative sliding velocity between the steel pipe when rolling, m/s;

V _iThe speed of i breast roller when rolling, m/s;

By rolling 2 tons of calculating, the rolling wear extent on the first breast roller summit of being confirmed by formula is:

Ten thousand tons of topping roll: Y=1.4285mm/, ten thousand tons of bottom roll: Y=1.0375mm/

The wear extent at roll gap place all is taken as 1/3 of summit wear extent by actual measurement and experience, and roll summit of this frame and the wear extent between the roll gap place are linear distribution; The wear extent of all the other frames is by formula calculated respectively, and the wearing and tearing between summit and the rod seam distribute and are thought of as linearity.

(3) heat distortion amount of roll is influenced by the thermal coefficient of expansion of rolling temperature and roll material, adopts conventional finite element method to calculate.

2, calculate the comprehensive roll forming of roll

The initial roll forming of the roll that calculates in the step 1, the wear extent and the roll heat distortion amount of roll are carried out the comprehensive roll forming that the strain linear superposition obtains equivalence.

3, adopt conventional method to calculate each frame export goal wall thickness, ovality and linearity

The wall thickness of each frame is controlled to be:

The wall thickness control range of first frame: 24.58-28.58mm

The wall thickness control range of second frame: 22.91-24.96mm

The wall thickness control range of the 3rd frame: 19.38-23.18mm

The wall thickness control range of the 4th frame: 17.63-19.64mm

The wall thickness control range of the 5th frame: 14.88-16.98mm

The wall thickness control range of the 6th frame: 14.76-15.81mm

The wall thickness control range of the 7th frame: 14.66-15.56mm

Sleeve pipe ovality control: the 6th frame control :≤1.5%D; The 7th frame control≤0.25%D;

Body linearity: the 5th frame≤1.5mm/m; The 6th frame control≤0.9mm/m; The 7th frame control≤0.3mm/m.

4, the calculating of roll drafts

In seven frame tandem mills, the roll drafts that 5%, the second frame to the, the five breast roller drafts that 35%, the six breast roller drafts that the first breast roller drafts accounts for overall reduction accounts for overall reduction are 15%, the seven frame of overall reduction is zero.In the present embodiment, the first frame 6.17mm, the second frame 2.65mm, the 3rd frame 2.65mm, the 4th frame 2.65mm, the 5th frame 2.65mm, the 6th frame 0.87mm and the 7th frame 0.0mm.

5, adopt conventional method to calculate the roll-force of each frame

$p_i\left(k\right)={\stackrel{\‾}{p}}_{1,i}\left(k\right)\·F_{1,i}\left(k\right)+{\stackrel{\‾}{p}}_{2,i}\left(k\right)\·F_{2,i}\left(k\right)---\left(2\right)$

In the formula (2):

p _i(k) be the roll-force of i frame k rolling cycle;

for the i-th frame k reducing region's first rolling cycle average unit forces, Mpa;

F _{1, i}(k) be the floor projection of contact area of the k rolling cycle of i frame diameter reducing area, m ²

for the i-th frame minus the first wall region k rolling cycle average unit forces, Mpa;

F _{2, i}(k) be the floor projection of contact area of the k rolling cycle of i frame wall-thickness reduction zone, m ²

The control of each frame roll-force:

First roll-force control target is 2800kN; Second frame roll-force control target is 1960kN; The 3rd roll-force control target is 1170kN; The 4th roll-force control target is 850kN; The 5th roll-force control target is 600kN; The 6th roll-force control target is 350kN, and the 7th roll-force control target is 320kN.

(2) wall thickness, ovality and the linearity according to actual measurement calculates rolling drafts and roll-force

1, the detection FEEDBACK CONTROL of wall thickness deflection

Adopt the ultrasonic thickness appearance to measure the actual wall thickness value of tandem mill each frame exit steel pipe of the first six frame; With the deviation of the actual wall thickness value of steel pipe measured and target wall thickness value as wall thickness deflection; Employing is based on the rolling drafts of each frame of algorithm adjustment tandem rolling unit of Digital PID Controller, and computing formula is following:

e _i(k)＝ξ·[r _i(k)-y _act，i(k)] (3)

In the formula (3), e _i(k) be the wall thickness difference of the k control cycle of i frame;

r _i(k) be the target wall thickness of i frame;

y _{Act, i}(k) be the actual wall thickness of the k control cycle of i frame;

ξ is the wall thickness deflection adjustment factor, can get 0.6-0.9, and rigidity is big, get big value when temperature is low, and rigidity is little, get the small value when temperature is high, and ξ is 0.8 in the present embodiment.

$\mathrm{\Δ}{e}_i\left(k\right)=c_i\·[c_{\mathrm{PF},i}\left(k\right)+\frac{c_{\mathrm{IF},i}\·\underset{j=0}{\overset{k}{\mathrm{\Σ}}}{e}_i\left(j\right)}{c_{\mathrm{BF},i}}]---\left(4\right)$

In the formula (4), Δ e _i(k) be the drafts of the k control cycle wall thickness deflection feedback adjusting of i frame;

c _iBe the wall thickness deflection feedback control model adjustment coefficient of i frame, get 0.58 in the present embodiment;

c _{PF, i}(k) be the wall thickness deflection feedback proportional coefficient of i frame k control cycle, get 0.25 in the present embodiment;

c _{IF, i}Being the wall thickness deflection feedback integral coefficient of i frame, is 0.9 when j=i, and all the other are 0.2;

c _{BF, i}Be the influence coefficient of the drafts of i frame, get 1.25 in the present embodiment wall thickness deflection.

2, the detection FEEDBACK CONTROL of ellipticity error

Measure the difference acquisition ovality of the maximum gauge and the minimum diameter of tandem mill the 6th frame and the 7th frame exit seamless steel pipe through the misalignment measurement appearance that is installed in tandem mill the 6th frame and the 7th frame exit; Deviation with actual ovality of detected steel pipe and target ovality value is a foundation; The drafts of each frame of adjustment tandem rolling unit, computing formula is following:

ΔR _i(k)＝α·[R _i(k)-r _act，i(k)] (5)

In the formula (5), Δ R _i(k) be the ovality difference of the k control cycle of i frame;

R _i(k) be the target ovality of i frame;

r _{Act, i}(k) be the actual ovality of the k control cycle of i frame;

α is the ellipticity error adjustment factor, gets 0.38 in the present embodiment;

$\mathrm{\Δ}{y}_i\left(k\right)=m_i\·[m_{\mathrm{PF},i}\left(k\right)+\frac{m_{\mathrm{IF},i}\·\underset{j=0}{\overset{k}{\mathrm{\Σ}}}\mathrm{\Δ}{R}_i\left(j\right)}{m_{\mathrm{BF},i}}]---\left(6\right)$

In the formula (6),

Δ y _i(k) be the drafts of the k control cycle ellipticity error feedback adjusting of i frame;

m _iBe the ellipticity error feedback control model adjustment coefficient of i frame, present embodiment gets 0.29;

m _{PF, i}(k) be the ellipticity error feedback proportional coefficient of i frame k control cycle, present embodiment gets 0.20;

m _{IF, i}Being the ellipticity error feedback integral coefficient of i frame, is 0.8 when j=i, and all the other are 0.13;

m _{BF, i}Be the influence coefficient of the drafts of i frame to ellipticity error, present embodiment gets 2.0.

3, the detection FEEDBACK CONTROL of straightness error

At the 5th frame, the 6th frame and the 7th frame exit difference setting-up eccentricity measuring instrument; Measure the tube core position of seamless steel pipe through the misalignment measurement appearance; The tube core position that connects each measurement point; Obtain steel pipe actual flexion value; Deviation with the target bending value of detected steel pipe actual flexion value and steel pipe is a foundation; The drafts of adjustment tandem rolling unit the 6th frame; Make the 6th breaker roll pair and the 5th breaker roll and the 7th breaker roll form difference in height; Make seamless steel pipe produce plastic deformation to eliminate bending error, computing formula is following:

γ _i(k)＝η·[θ _i(k)-φ _act,i(k)] (7)

In the formula (7), γ _i(k) be the linearity difference of the k control cycle of i frame;

θ _i(k) be the target line degree of i frame;

φ _{Act, i}(k) be the actual linearity of the k control cycle of i frame;

η is the straightness error adjustment factor, gets 0.72 in the present embodiment;

$\mathrm{\Δ}{\mathrm{\γ}}_i\left(k\right)=n_i\·[n_{\mathrm{PF},i}\left(k\right)+n_{\mathrm{IF},i}\·\frac{\underset{j=0}{\overset{k}{\mathrm{\Σ}}}\mathrm{\Δ}{\mathrm{\γ}}_i\left(j\right)}{n_{\mathrm{BF},i}}]---\left(8\right)$

In the formula (8), Δ γ _i(k) be the drafts of the k control cycle straightness error feedback adjusting of i frame;

n _iBe the straightness error feedback control model adjustment coefficient of i frame, get 0.40 in the present embodiment;

n _{PF, i}(k) be the straightness error feedback proportional coefficient of i frame, get 0.20 in the present embodiment;

n _{IF, i}Being the straightness error feedback integral coefficient of i frame, is 0.8 when j=i, and all the other are 0.23;

n _{BF, i}Be the influence coefficient of the drafts of i frame, get 1.2 in the present embodiment straightness error.

4, decoupling zero control

(1) drafts that step 1, step 2 and step 3 are obtained and wall thickness deflection, ellipticity error, three parameters of straightness error are formed matrix,

$\left[\begin{array}{ccc}{a}_{\mathrm{1,1}}& a_{\mathrm{1,2}}& a_{\mathrm{1,3}}\\ a_{\mathrm{2,1}}& a_{\mathrm{2,2}}& a_{\mathrm{2,3}}\\ a_{\mathrm{3,1}}& a_{\mathrm{3,2}}& a_{\mathrm{3,3}}\end{array}\right]\left\{\begin{array}{c}{e}_i\left(k\right)\\ \mathrm{\Δ}{R}_i\left(k\right)\\ {\mathrm{\γ}}_i\left(k\right)\end{array}\right\}=\left\{\begin{array}{c}\mathrm{\Δ}{e}_i\left(k\right)\\ \mathrm{\Δ}{y}_i\left(k\right)\\ \mathrm{\Δ}{\mathrm{\γ}}_i\left(k\right)\end{array}\right\}---\left(9\right)$

In the formula (9),

e _i(k) be the wall thickness difference of the k control cycle of i frame;

Δ R _i(k) be the ovality difference of the k control cycle of i frame;

γ _i(k) be the linearity difference of the k control cycle of i frame;

Δ e _i(k) be the drafts of the k control cycle wall thickness deflection feedback adjusting of i frame;

Δ y _i(k) be the drafts of the k control cycle ellipticity error feedback adjusting of i frame;

Δ γ _i(k) be the drafts of the k control cycle straightness error feedback adjusting of i frame;

a _1,1Be the wall thickness deflection feedback control model adjustment coefficient c of i frame _iξ multiplies each other with the wall thickness deflection adjustment factor, c _i=0.58, ξ=0.8;

a _1,2Be the wall thickness deflection feedback control model adjustment coefficient c of i frame _iWall thickness deflection feedback proportional coefficient c with the i frame _{PF, i}(k) multiply each other c _i=0.58, c _{PF, i}(k)=0.25;

a _1,3Be the wall thickness deflection feedback control model adjustment coefficient c of i frame _iWall thickness deflection feedback proportional coefficient c with the i frame _{PF, i}(k) multiply each other, divided by the drafts of i frame influence coefficient c to wall thickness deflection _{BF, i}, c _i=0.58, c _{PF, i}(k)=0.25, c _{BF, i}=1.25;

a _2,1It is the ellipticity error feedback control model adjustment Coefficient m of i frame _iEllipticity error feedback proportional Coefficient m with the i frame _{PF, i}(k) product, m _i=0.29, m _{PF, i}(k)=0.20;

a _2,2It is the ellipticity error feedback control model adjustment Coefficient m of i frame _iWith the product of ellipticity error adjustment factor α, m _i=0.29, α=0.38;

a _2,3It is the ellipticity error feedback control model adjustment Coefficient m of i frame _iWith the product of ellipticity error adjustment factor α, divided by the drafts of i frame influence coefficient m to ellipticity error _{BF, i}, m _i=0.29, α=0.38, m _{BF, i}=2.0;

a _3,1Be the straightness error feedback control model adjustment coefficient n of i frame _iStraightness error feedback proportional coefficient n with the i frame _{PF, i}(k) product is divided by the drafts of the i frame influence coefficient n to straightness error _{BF, i}, n _i=0.40, n _{PF, i}(k)=0.20), n _{BF, i}=1.2;

a _3,2Be the straightness error feedback control model adjustment coefficient n of i frame _iStraightness error feedback proportional coefficient n with the i frame _{PF, i}(k) product, n _i=0.40, n _{PF, i}(k)=0.20;

a _3,3Be the straightness error feedback control model adjustment coefficient n of i frame _iWith the product of straightness error adjustment factor η, n _i=0.40, η=0.72.

The matrix of present embodiment is:

$\left[\begin{array}{ccc}0.58\×0.80& 0.58\×0.25& 0.58\×0.25/1.25\\ 0.29\×0.20& 0.29\×0.38& 0.29\×0.38/2.00\\ 0.40\×0.20/1.20& 0.40\×0.20& 0.40\×0.72\end{array}\right]\left\{\begin{array}{c}{e}_i\left(k\right)\\ \mathrm{\Δ}{R}_i\left(k\right)\\ {\mathrm{\γ}}_i\left(k\right)\end{array}\right\}=\left\{\begin{array}{c}\mathrm{\Δ}{e}_i\left(k\right)\\ \mathrm{\Δ}{y}_i\left(k\right)\\ \mathrm{\Δ}{\mathrm{\γ}}_i\left(k\right)\end{array}\right\}---(9-1)$

Adopt the elimination be reduced to drafts respectively with the corresponding relation of single parameter, calculate the drafts that drafts that the wall thickness deflection of i frame k control cycle causes, drafts that ellipticity error causes and straightness error cause respectively;

The drafts sum that the drafts that causes with the wall thickness deflection that calculates, the drafts that ellipticity error causes and straightness error cause is as drafts; With the contact pressure and the contact area of plastoelasticity formula (conventional computational methods) calculating roll and steel pipe, calculate the roll-force of each frame of k control cycle at last with conventional computational methods.

(3) in the operation of rolling, revise roll-force and roll gap numerical value in real time

1, roll-force FEEDBACK CONTROL Mathematical Modeling does

ΔF _Bi＝k _ali·k _FF·ΔF _Ri (10)

In the formula (10),

Δ F _BiBe the roll-force regulated quantity of i frame, i is a shelf number;

k _AliBeing the roll-force feedback control model adjustment coefficient of i frame, is 0.9 during i=1, is 0.65 during i=2, is 0.65 during i=3, is 0.65 during i=4, is 0.65 during i=5, is 0.65 during i=6, is 0.1 during i=7.

k _FFBeing roll-force feedback control model coefficient, is 0.5;

Δ F _RiBe the roll-force variable quantity of i frame, promptly adopt actual roll-force poor of roll-force and (k-1) control cycle of the k control cycle that formula (2) calculates;

As Δ F _BiNumerical value greater than 5% o'clock of (k-1) actual roll-force of rolling cycle, get Δ F _BiBe 5% of (k-1) actual roll-force of rolling cycle, as Δ F _BiNumerical value be less than or equal to 5% o'clock of (k-1) actual roll-force of rolling cycle, the roll-force of getting the k control cycle that calculates in the decoupling zero control of the 4th step of step (two) is as new roll-force.

2, roll gap FEEDBACK CONTROL Mathematical Modeling does

Δδ _Bi＝k _gδi·k _δδ·Δδ _Ri (11)

In the formula (11), Δ δ _BiBe the roll gap regulated quantity of i frame, i=1,2 ..., 7, be shelf number;

k _{G δ i}Being the roll gap control model adjustment coefficient of i frame, is 0.8 during i=1, is 0.54 during i=2, is 0.54 during i=3, is 0.54 during i=4, is 0.54 during i=5, is 0.54 during i=6, is 0.1 during i=7.

k _{δ δ}Being roll gap feedback model coefficient, is 1.0;

Δ δ _RiBe the roll gap variable quantity of i frame, i.e. the drafts sum that causes of the drafts that causes of the wall thickness deflection of the i frame k control cycle of Ji Suaning, drafts that ellipticity error causes and straightness error and the difference of the actual drafts of (k-1) control cycle;

As Δ δ _BiNumerical value greater than 3% o'clock of (k-1) actual drafts of rolling cycle, make Δ δ _BiEqual (k-1) rolling cycle actual drafts 3%; As Δ δ _BiNumerical value be less than or equal to 3% o'clock of (k-1) actual drafts of rolling cycle, the rolling drafts sum of getting drafts that drafts that the wall thickness deflection of the i frame k control cycle that calculates in the decoupling zero control of the 4th step of step (two) causes, drafts that ellipticity error causes and straightness error cause and (k-1) rolling cycle reality is as new rolling drafts.

After adopting above-mentioned control method rolling, divide the finished product seamless steel pipe of 25 batches of different heats of sampling, get 760 appearance pipes altogether, the geometry of having tested body.After the test, the check data of geometry has been carried out statistical analysis.Seamless steel pipe has good shape, and maximum linear degree error is below 0.6mm/m; Maximum ovality is below 0.35%; The maximum gauge error is below 0.5%D; The thickest error is below 5.0%t.

Claims (1)

1. a tubular control method of using seven frame tandem mill rolling seamless steel pipes is characterized in that, comprises the steps:

(1) rolling parameter presets:

(1) calculates the initial roll forming of roll, the wear extent and the roll heat distortion amount of roll;

(2) the comprehensive roll forming of calculating roll:

The initial roll forming of the roll that calculates in the step (1), the wear extent and the roll heat distortion amount of roll are carried out the comprehensive roll forming that the strain linear superposition obtains equivalence;

(3) calculate each frame export goal wall thickness, ovality and linearity;

(4) calculate the roll drafts:

In seven frame tandem mills, the roll drafts that 5%, the second frame to the, the five breast roller drafts that 35%, the six breast roller drafts that the first breast roller drafts accounts for overall reduction accounts for overall reduction are 15%, the seven frame of overall reduction is zero;

(5) calculate the roll-force of each frame:

$p_i\left(k\right)={\stackrel{\‾}{p}}_{1,i}\left(k\right)\·F_{1,i}\left(k\right)+{\stackrel{\‾}{p}}_{2,i}\left(k\right)\·F_{2,i}\left(k\right)---\left(1\right)$

In the formula (1):

p _i(k) be the roll-force of i frame k rolling cycle;

is the i-frame k reducing region's first rolling cycle average unit force;

F _{1, i}(k) be the floor projection of contact area of the k rolling cycle of i frame diameter reducing area;

is the i-frame wall region of k minus the rolling cycle average unit force;

F _{2, i}(k) be the floor projection of contact area of the k rolling cycle of i frame wall-thickness reduction zone;

(2) wall thickness, ovality and the linearity according to actual measurement calculates rolling drafts and roll-force:

(1) the detection FEEDBACK CONTROL of wall thickness deflection

Adopt the ultrasonic thickness appearance to measure the actual wall thickness value of the first six frame exit steel pipe of tandem mill; With the deviation of the actual wall thickness value of steel pipe measured and target wall thickness value as the wall thickness difference; Employing is based on the rolling drafts of each frame of algorithm computation tandem rolling unit of Digital PID Controller, and computing formula is following:

e _i(k)＝ξ·[r _i(k)-y _act，i(k)] (2)

In the formula (2), e _i(k) be the wall thickness difference of the k control cycle of i frame;

r _i(k) be the target wall thickness of i frame;

y _{Act, i}(k) be the actual wall thickness of the k control cycle of i frame;

ξ is the wall thickness deflection adjustment factor, gets 0.6-0.9;

$\mathrm{\Δ}{e}_i\left(k\right)=c_i\·[c_{\mathrm{PF},i}\left(k\right)+\frac{c_{\mathrm{IF},i}\·\underset{j=0}{\overset{k}{\mathrm{\Σ}}}{e}_i\left(j\right)}{c_{\mathrm{BF},i}}]---\left(3\right)$

In the formula (3), Δ e _i(k) be the drafts of the k control cycle wall thickness deflection feedback adjusting of i frame;

c _iBe the wall thickness deflection feedback control model adjustment coefficient of i frame, span is 0.52-0.61;

c _{PF, i}(k) be the wall thickness deflection feedback proportional coefficient of i frame k control cycle, span is 0.23-0.27;

c _{IF, i}Being the wall thickness deflection feedback integral coefficient of i frame, is 0.9 when j=i, and all the other are 0.2;

c _{BF, i}Be the influence coefficient of the drafts of i frame to wall thickness deflection, span is 1.0-1.25;

(2) the detection FEEDBACK CONTROL of ellipticity error

Measure the difference acquisition ovality of the maximum gauge and the minimum diameter of tandem mill the 6th frame and the 7th frame exit seamless steel pipe through the misalignment measurement appearance that is installed in tandem mill the 6th frame and the 7th frame exit; Deviation with actual ovality of detected steel pipe and target ovality value is a foundation; Calculate the drafts of each frame of tandem rolling unit, computing formula is following:

ΔR _i(k)＝α·[R _i(k)-r _act，i(k)] (4)

In the formula (4), Δ R _i(k) be the ovality difference of the k control cycle of i frame;

R _i(k) be the target ovality of i frame;

r _{Act, i}(k) be the actual ovality of the k control cycle of i frame;

α is the ellipticity error adjustment factor, and span is 0.34-0.39;

$\mathrm{\Δ}{y}_i\left(k\right)=m_i\·[m_{\mathrm{PF},i}\left(k\right)+\frac{m_{\mathrm{IF},i}\·\underset{j=0}{\overset{k}{\mathrm{\Σ}}}\mathrm{\Δ}{R}_i\left(j\right)}{m_{\mathrm{BF},i}}]---\left(5\right)$

In the formula (5), Δ y _i(k) be the drafts of the k control cycle ellipticity error feedback adjusting of i frame;

m _iBe the ellipticity error feedback control model adjustment coefficient of i frame, span is 0.25-0.31;

m _{PF, i}(k) be the ellipticity error feedback proportional coefficient of i frame k control cycle, span is 0.18-0.23;

m _{IF, i}Being the ellipticity error feedback integral coefficient of i frame, is 0.8 when j=i, and all the other are 0.13;

m _{BF, i}Be the influence coefficient of the drafts of i frame to ellipticity error, span is 1.5-2.1;

(3) the detection FEEDBACK CONTROL of straightness error

At the 5th frame, the 6th frame and the 7th frame exit difference setting-up eccentricity measuring instrument; Measure the tube core position of seamless steel pipe through the misalignment measurement appearance; The tube core position that connects each measurement point; Obtain steel pipe actual flexion value; Deviation with the target bending value of detected steel pipe actual flexion value and steel pipe is a foundation; Calculate the drafts of tandem rolling unit the 6th frame, computing formula is following:

γ _i(k)＝η·[θ _i(k)-φ _act，i(k)] (6)

In the formula (6), γ _i(k) be the linearity difference of the k control cycle of i frame;

θ _i(k) be the target line degree of i frame;

φ _{Act, i}(k) be the actual linearity of the k control cycle of i frame;

η is the straightness error adjustment factor, and span is 0.67-0.75;

$\mathrm{\Δ}{\mathrm{\γ}}_i\left(k\right)=n_i\·[n_{\mathrm{PF},i}\left(k\right)+\frac{n_{\mathrm{IF},i}\·\underset{j=0}{\overset{k}{\mathrm{\Σ}}}\mathrm{\Δ}{\mathrm{\γ}}_i\left(j\right)}{n_{\mathrm{BF},i}}]---\left(7\right)$

In the formula (7), Δ γ _i(k) be the drafts of the k control cycle straightness error feedback adjusting of i frame;

n _iBe the straightness error feedback control model adjustment coefficient of i frame, it is 0.37-0.43 for span;

n _{PF, i}(k) be the straightness error feedback proportional coefficient of i frame k control cycle, span is 0.16-0.21;

n _{IF, i}Being the straightness error feedback integral coefficient of i frame, is 0.8 when j=i, and all the other are 0.23;

n _{BF, i}Be the influence coefficient of the drafts of i frame to straightness error, span is 1.1-1.3;

(4) decoupling zero control

Drafts that step (1), step (2) and step (3) are obtained and wall thickness difference, ovality difference, three parameters of linearity difference are formed matrix, and are as follows:

$\left[\begin{array}{ccc}{a}_{\mathrm{1,1}}& a_{\mathrm{1,2}}& a_{\mathrm{1,3}}\\ a_{\mathrm{2,1}}& a_{\mathrm{2,2}}& a_{\mathrm{2,3}}\\ a_{\mathrm{3,1}}& a_{\mathrm{3,2}}& a_{\mathrm{3,3}}\end{array}\right]\left\{\begin{array}{c}{e}_i\left(k\right)\\ \mathrm{\Δ}{R}_i\left(k\right)\\ {\mathrm{\γ}}_i\left(k\right)\end{array}\right\}=\left\{\begin{array}{c}\mathrm{\Δ}{e}_i\left(k\right)\\ \mathrm{\Δ}{y}_i\left(k\right)\\ \mathrm{\Δ}{\mathrm{\γ}}_i\left(k\right)\end{array}\right\}---\left(8\right)$

In the formula (8):

e _i(k) be the wall thickness difference of the k control cycle of i frame;

Δ R _i(k) be the ovality difference of the k control cycle of i frame;

γ _i(k) be the linearity difference of the k control cycle of i frame;

Δ e _i(k) be the drafts of the k control cycle wall thickness deflection feedback adjusting of i frame;

Δ y _i(k) be the drafts of the k control cycle ellipticity error feedback adjusting of i frame;

Δ γ _i(k) be the drafts of the k control cycle straightness error feedback adjusting of i frame;

a _1,1Be the wall thickness deflection feedback control model adjustment coefficient c of i frame _iξ multiplies each other with the wall thickness deflection adjustment factor;

a _1,2Be the wall thickness deflection feedback control model adjustment coefficient c of i frame _iWall thickness deflection feedback proportional coefficient c with the i frame _PFi(k) multiply each other;

a _1,3Be the wall thickness deflection feedback control model adjustment coefficient c of i frame _iWall thickness deflection feedback proportional coefficient c with the i frame _{PF, i}(k) multiply each other, again divided by the drafts of i frame influence coefficient c to wall thickness deflection _{BF, i}

a _2,1It is the ellipticity error feedback control model adjustment Coefficient m of i frame _iEllipticity error feedback proportional Coefficient m with the i frame _{PF, i}(k) product;

a _2,2It is the ellipticity error feedback control model adjustment Coefficient m of i frame _iProduct with ellipticity error adjustment factor α;

a _2,3It is the ellipticity error feedback control model adjustment Coefficient m of i frame _iWith the product of ellipticity error adjustment factor α, again divided by the drafts of i frame influence coefficient m to ellipticity error _{BF, i}

a _3,1Be the straightness error feedback control model adjustment coefficient n of i frame _iStraightness error feedback proportional coefficient n with the i frame _{PF, i}(k) product is again divided by the drafts of the i frame influence coefficient n to straightness error _{BF, i}

a _3,2Be the straightness error feedback control model adjustment coefficient n of i frame _iStraightness error feedback proportional coefficient n with the i frame _{PF, i}(k) product;

a _3,3Be the straightness error feedback control model adjustment coefficient n of i frame _iProduct with straightness error adjustment factor η;

Adopt the elimination be reduced to drafts respectively with the corresponding relation of single parameter, calculate the drafts that drafts that the wall thickness deflection of i frame k control cycle causes, drafts that ellipticity error causes and straightness error cause respectively;

The drafts sum that the drafts that causes with the wall thickness deflection that calculates, the drafts that ellipticity error causes and straightness error cause is calculated the roll-force of each frame of k control cycle as drafts;

(3) in the operation of rolling, revise roll-force and roll gap numerical value in real time

(1) roll-force FEEDBACK CONTROL Mathematical Modeling is:

ΔF _Bi＝k _ali·k _FF·ΔF _Ri (9)

In the formula (9), Δ F _BiBe the roll-force regulated quantity of i frame, i is a shelf number;

k _AliBeing the roll-force feedback control model adjustment coefficient of i frame, is 0.9 during i=1, is 0.65 during i=2, is 0.65 during i=3, is 0.65 during i=4, is 0.65 during i=5, is 0.65 during i=6, is 0.1 during i=7;

k _FFBeing roll-force feedback control model coefficient, is 0.5;

Δ F _RiBe the roll-force variable quantity of i frame, promptly the roll-force of the k control cycle that is calculated by formula (1) and the actual roll-force of (k-1) control cycle is poor;

As Δ F _BiNumerical value greater than 5% o'clock of (k-1) actual roll-force of rolling cycle, get Δ F _BiBe 5% of (k-1) actual roll-force of rolling cycle, as Δ F _BiNumerical value be less than or equal to 5% o'clock of (k-1) actual roll-force of rolling cycle, the roll-force of getting the k control cycle that calculates in the decoupling zero control of (4) step of step (two) is as new roll-force;

(2) roll gap FEEDBACK CONTROL Mathematical Modeling is:

Δδ _Bi＝k _gδi·k _δδ·Δδ _Ri (10)

In the formula (10), Δ δ _BiBe the roll gap regulated quantity of i frame, i is a shelf number;

k _{G δ i}Being the roll gap control model adjustment coefficient of i frame, is 0.8 during i=1, is 0.54 during i=2, is 0.54 during i=3, is 0.54 during i=4, is 0.54 during i=5, is 0.54 during i=6, is 0.1 during i=7;

k _{δ δ}Being roll gap feedback model coefficient, is 1.0;

Δ δ _RiBe the roll gap variable quantity of i frame, i.e. the drafts sum that causes of the drafts that causes of the wall thickness deflection of the i frame k control cycle of Ji Suaning, drafts that ellipticity error causes and straightness error and the difference of the actual drafts of (k-1) control cycle;

As Δ δ _BiNumerical value greater than 3% o'clock of (k-1) actual drafts of rolling cycle, make Δ δ _BiEqual (k-1) rolling cycle actual drafts 3%; As Δ δ _BiNumerical value be less than or equal to 3% o'clock of (k-1) actual drafts of rolling cycle, the rolling drafts sum of getting drafts that drafts that the wall thickness deflection of the i frame k control cycle that calculates in the decoupling zero control of (4) step of step (two) causes, drafts that ellipticity error causes and straightness error cause and (k-1) rolling cycle reality is as new rolling drafts.