CN102847721B - Method for determining thermal crown of hot rolled strip roller - Google Patents

Abstract

The invention provides a method for determining thermal crown of a hot rolled strip roller, and belongs to the field of metal rolling. The method comprises the steps of periodically forecasting a rolling temperature filed through an online model of a finishing mill, and determining the initial temperature and the rolling thermal crown of a roller which is machined again. The method is characterized by comprising the steps as follows: reading the rolling temperature field of the unloading time of the roller through an online computer model; calculating the dynamic variation of the temperature field according to a cooling condition of an unloaded roller; determining the machining temperature and the crown according to the temperature generated after unloading; processing/calculating such data, thus providing the accurate initial temperature of the roller for machining again; forecasting the temperature field and the thermal crown of a working roller; and improving the precision in forecasting of the thermal crown of the holt roller and the shape setting control. With the adoption of the method provided by the invention, the problem that the initial temperature of the roller which is machined again when the roller is not repeatedly worn cannot be accurately given during producing the hot rolled strip roller can be solved; and the method can be widely applied to the technical field of thermal crown forecasting and shape control of roller during producing the hot rolled strip roller.

Description

A kind of hot-strip roll roll thermal crown defining method

Technical field

The invention belongs to the rolling field of metal, particularly relate to a kind of control appliance or the method that are specially adapted for rolling mill for metal or its converted products.

Background technology

During hot-strip is produced, roll will affect roll gap size and shape by thermogenetic thermal expansion, and then affect belt steel thickness, convexity and flatness control.Especially strip shape quality control accuracy, depends on the computational accuracy of roll thermal deformation to a great extent.And, the thermal behavior of roll and the be full of cracks of roller surface, reticulate pattern and the phenomenon such as to peel off and have substantial connection.

Therefore, accurate forecast working roll temperature field and roll thermal crown are very important, are the important component parts that on-line computer control model is produced in hot rolling.

At present, high-speed steel roll is used widely in hot-strip is produced.

High-speed steel roll has higher wearability and heat endurance, effectively can reduce wearing and tearing, extends and rolls the labour cycle.

Therefore, in actual production, often have the situation that high-speed steel roll uses 2 to 3 roll change cycles, namely there are the secondary be commonly called as, three upper machines.

Due to product plan reason, the roll after lower machine often can not reuse next in the works immediately, but goes up machine again after shelving a period of time.

Because on-time model only carries out periodicity forecast to the Coefficient of Roll Temperature Field in use, the roller temperature after lower machine is no longer forecast.Therefore, when the roll throw away instantly after machine goes up machine again, roller temperature when initial temperature field is given as machine under last time usually or room temperature, this is obviously irrational, has had a strong impact on the accurate forecast of roller heat convex degree learning.

Japanese documentation JP8243624A (Unexamined Patent 8-243624, publication date on September 24th, 1996) discloses one " the study computational methods of roll profile ".Wherein by evaluation work roller roll shapes such as actual measurement belt steel thickness, roll-force, the speeds of rolls, revise with breaker roll heating expansion computation deviation.But the study described in this technical scheme/correction step, need the cumulative process of a parameter/curve, for the roll repeating upper machine, learning process is not experienced owing to there is first volume setting fashion, there is no the accumulation of relevant parameter/curve, lick the situation that could progressively learn in journey to put in place next several, affect the calculating of roll thermal crown and the precision of plate shape setting to a certain extent.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of hot-strip roll roll thermal crown defining method, during it is produced for hot rolled strip, the problem that when again going up machine when roll throw away, roll initial temperature can not be accurately given, according to the cooling condition after machine under roll, set up roller temperature field model, calculate the Coefficient of Roll Temperature Field of any time after machine under roll, again go up machine for roll and provide roll initial temperature accurately, improve roll thermal crown and forecast and Strip Shape Control precision.

Technical scheme of the present invention is: provide a kind of hot-strip roll roll thermal crown defining method, comprises the periodicity forecast and the determination to the initial temperature and roller heat convex degree learning that again go up machine roll carried out in finishing mill on-time model breaker roll temperature field, it is characterized in that:

The acquisition of machine temperature under A, roll: gather and preserve the periodicity forecast numerical value of shutting down and carrying out in moment finishing mill on-time model breaker roll temperature field, using the evaluation of Coefficient of Roll Temperature Field when shutting down as initial temperature;

B, roller temperature are followed the tracks of and are calculated: for the roll after lower machine, according to cooling condition, calculate Coefficient of Roll Temperature Field;

C, roll repeat machine temperature and roll thermal crown is determined: for first upper machine or the hot-strip roll again going up machine, calculate, determine initial temperature and the roll thermal crown of its roll respectively;

D, by above-mentioned data processing/calculating, again go up machine for roll and provide roll initial temperature accurately, the temperature field of forecast work roller and roll thermal crown, improve roller heat convex degree learning forecast and plate shape setting control accuracy.

Wherein, machine temperature under roll in the step A, equals the temperature in machine moment under the roll that finishing mill on-time model calculates, that is:

T＝T _on

In formula, T is roller temperature, T _onfor the temperature in machine moment under the roll that finishing mill on-time model calculates.

Follow the tracks of in calculating at the roller temperature of described step B, setting Coefficient of Roll Temperature Field relative to symmetrical in the middle part of axis and the body of roll, and ignores heat trnasfer along the circumferential direction;

Then follow the tracks of in computational process at described step B roller temperature, carry out according to the following step:

B1, to be summed up by breaker roll Temperature calculating and transform the conduction of two-dimentional Dynamic Thermal and calculate, its equation of heat conduction is:

$\mathrm{\ρc}\frac{\∂T}{\∂t}=\frac{1}{r}\left[\frac{\∂}{\∂r}\left(\mathrm{\λr}\frac{\∂T}{\∂r}\right)\right]+\mathrm{\λ}\frac{{\∂}^{2}T}{{\∂z}^2}$ (formula 1)

In formula, t is the time, and ρ, c and λ are respectively roll material density, specific heat and pyroconductivity, r and z is respectively roll radial direction and axial coordinate;

B2, finite difference method is carried out to the above-mentioned differential equation (formula 2);

B3, get by roll axis section 1/4th, set up difference gridding, then the cooling boundary condition under roll after machine is determined as follows:

The temperature on B31, left and right, upper and lower symmetrical border, determine according to following formula:

$\mathrm{\λ}\frac{\∂T}{\∂z}=0$ (formula 2)

$\mathrm{\λ}\frac{\∂T}{\∂r}=0$ (formula 3)

The temperature on B32, the body of roll, surface, roller footpath, determine according to following formula:

$\mathrm{\λ}\frac{\∂T}{\∂r}={-\mathrm{\α}}_A(T-T_A)$ (formula 4)

B33, with the temperature at bearing touch position, determine according to following formula:

$\mathrm{\λ}\frac{\∂T}{\∂r}={-\mathrm{\α}}_B(T-T_B)$ (formula 5)

The temperature of B34, roll end, determine according to following formula:

$\mathrm{\λ}\frac{\∂T}{\∂z}={-\mathrm{\α}}_A(T-T_A)$ (formula 6)

In above-mentioned formula, α _afor the coefficient of heat transfer between roll and air, T _afor air themperature, α _bfor the coefficient of heat transfer between roll and bearing, T _bfor bearing temperature.

In the step C for upper machine roll of not refacing, according to the cooling condition after lower machine, under roll, machine temperature equals the temperature in machine moment under the roll that finishing mill on-time model calculates, its result of calculation as the initialization temperature again going up machine, that is:

T ₀=T _off(formula 8)

T in formula ₀for upper machine roll initializes temperature, T _offfor the accounting temperature of roll after lower machine, and upper machine roll is not refaced.

In the step C, when Temperature Distribution is known, the thermal expansion amount at z place, arbitrfary point, described roll barrel surface is:

$u_t\left(z\right)=\frac{2(1+v)\mathrm{\β}}{R}{\∫}_0^R(T-T_A)\mathrm{rdr}$ (formula 9)

Then the roll thermal crown of its roll is:

△ u _t(z)=u _t(z)-u _t(e) (formula 10)

In above-mentioned formula, ν is Poisson's ratio, and β is thermal coefficient of expansion, and R is roller radius, u _te () is the thermal expansion amount at roll edge representative point place.

In the step C for the roll of machine on secondary, the roll thermal crown determining step of its roll is as follows:

C1, from finishing mill on-time model, read the Coefficient of Roll Temperature Field in lower machine moment;

C2, cooling condition according to off-line roll, adopt formula (formula 2) ~ (formula 7) to determine the dynamic change result in temperature field;

C3, according to the temperature dynamic result of variations after lower machine, formula (formula 8) ~ (formula 10) is adopted to determine machine of again going up initial temperature and the roller heat convex degree learning of roll.

Described roller heat convex degree learning defining method be applicable to hot rolled strip produce in throw away after machine under roll, stop the working condition again going up machine after 1 ~ 5 hour.

Compared with the prior art, advantage of the present invention is:

1. the enforcement of technical solution of the present invention, roller temperature when solving the machine under last time that is given as initial temperature field when roll throw away goes up machine again after lower machine during hot-strip is produced or the unreasonable way of room temperature, according to the cooling condition after lower machine, calculating Coefficient of Roll Temperature Field changes, this reduces the impact on online roller temperature and roll thermal crown calculating and plate shape setting and control accuracy, improve roller heat convex degree learning forecast and plate shape setting control accuracy.

2. this method has been applied to actual board rolling and has produced roller temperature and roll thermal crown calculating, prove that this method is practicable, for other exists the hot rolled strip production line that roll throw away repeatedly goes up machine both at home and abroad, the method is applicable, and its popularizing application prospect is wide.

Accompanying drawing explanation

Fig. 1 is the structural representation representing roll.

Fig. 2 is the Finite Difference Meshes schematic diagram representing roll.

Fig. 3 represents the process blocks schematic diagram determining roller heat convex degree learning method.

Fig. 4 is the schematic diagram of the axial distribution change of not roller surface temperature in the same time.

Fig. 5 is the axial distribution change schematic diagram representing thermal expansion of rollers amount.

Fig. 6 is the roll thermal crown change schematic diagram representing roll.

Detailed description of the invention

Below in conjunction with drawings and Examples, the present invention will be further described.

In Fig. 1, the concrete grammar step of the technical program is as follows:

1) from on-line computer model, read in the Coefficient of Roll Temperature Field in machine moment under roll;

2) according to the cooling condition of off-line roll, the dynamic change of accounting temperature field;

3) upper machine temperature and convexity is determined according to the temperature computation result after lower machine.

Technical scheme of the present invention, roller temperature when solving the machine under last time that is given as initial temperature field when roll throw away goes up machine again after lower machine during hot-strip is produced or the unreasonable way of room temperature, according to the cooling condition after lower machine, calculating Coefficient of Roll Temperature Field changes, this reduces the impact on online roller temperature and roll thermal crown calculating and plate shape setting and control accuracy, improve roller heat convex degree learning forecast and plate shape setting control accuracy.

The concrete methods of realizing of the determination Rolling for Hot Rolled Strip roller roll thermal crown that the present invention proposes is as follows:

First, first step is machine temperature under acquisition roll.

In hot rolled strip is produced, the on-time model of finishing mill can carry out periodicity forecast in breaker roll temperature field, and to determine roller heat convex degree learning and to carry out plate shape setting, temperature field forecast result leaves in a working document.After receiving roll change instruction, roller temperature forecast stops, and in order to according to the cooling condition calculated after lower machine, calculates roller temperature, reads Coefficient of Roll Temperature Field when shutting down as initial temperature, that is:

T＝T _on(7)

In formula, T is roller temperature, T _onfor machine moment temperature under the roll that on-time model calculates.

Secondly, second step follows the tracks of to calculate roller temperature:

For the roll after lower machine, according to cooling condition, calculate Coefficient of Roll Temperature Field, concrete grammar is as follows:

After lower machine, the cooling procedure of roll is mainly air cooling.As Fig. 2 for shown in, in order to simplify calculating, supposing that Coefficient of Roll Temperature Field is relative to symmetrical in the middle part of axis and the body of roll, and ignoring heat trnasfer along the circumferential direction, thus can by Coefficient of Roll Temperature Field calculate be summed up as a two-dimentional Dynamic Thermal conducting problem, the equation of heat conduction is:

$\mathrm{\ρc}\frac{\∂T}{\∂t}=\frac{1}{r}\left[\frac{\∂}{\∂r}\left(\mathrm{\λr}\frac{\∂T}{\∂r}\right)\right]+\mathrm{\λ}\frac{{\∂}^{2}T}{{\∂z}^2}---\left(1\right)$

In formula, t is the time, and ρ, c and λ are respectively roll material density, specific heat and pyroconductivity, r and z is respectively roll radial direction and axial coordinate.

For differential equation formula (2), finite difference calculus is adopted to solve herein.Get 1/4th by roll axis section, set up difference gridding as shown in Figure 3.

Cooling boundary condition under roll after machine can be expressed as:

1) left and right, upper and lower symmetrical border

$\mathrm{\λ}\frac{\∂T}{\∂z}=0---\left(2\right)$

$\mathrm{\λ}\frac{\∂T}{\∂r}=0---\left(3\right)$

2) body of roll, surface, roller footpath

$\mathrm{\λ}\frac{\∂T}{\∂r}={-\mathrm{\α}}_A(T-T_A)---\left(4\right)$

3) with bearing touch position

$\mathrm{\λ}\frac{\∂T}{\∂r}={-\mathrm{\α}}_B(T-T_B)---\left(5\right)$

4) roll end

$\mathrm{\λ}\frac{\∂T}{\∂z}={-\mathrm{\α}}_A(T-T_A)---\left(6\right)$

In formula, α _afor the coefficient of heat transfer between roll and air, T _afor air themperature, α _bfor the coefficient of heat transfer between roll and bearing, T _bfor bearing temperature.

Thirdly, third step determines that roll repeats temperature and the roll thermal crown of machine:

For upper machine roll of not refacing, according to the cooling condition after lower machine, adopt said method calculate roller temperature change, result of calculation as the initial temperature again going up machine, namely

T ₀＝T _off(8)

T in formula ₀for upper machine roll initial temperature, T _offfor the accounting temperature after lower machine.

When Temperature Distribution is known, the thermal expansion amount at z place, arbitrfary point, roll barrel surface is:

$u_t\left(z\right)=\frac{2(1+v)\mathrm{\β}}{R}{\∫}_0^R(T-T_A)\mathrm{rdr}---\left(9\right)$

And the roll thermal crown of roll is:

△u _t(z)＝u _t(z)-u _t(e) (10)

In formula, ν is Poisson's ratio, and β is thermal coefficient of expansion, and R is roller radius, u _te () is the thermal expansion amount at roll edge representative point place.

Embodiment:

This method is applicable to roll throw away in hot rolled strip production, and throw away, stops and again go up machine after 1 ~ 5 hour, determine the situation of roll initial temperature and roll thermal crown.

Following present and to adopt under the inventive method determination hot-rolling mill working roll temperature after machine, the computational process of thermal expansion and roll thermal crown change and result.

Roll rolipass design condition is as shown in table 1, and roll material thermal physical property parameter is as shown in table 2.

Table 1 roll rolipass design condition

Roller radius (mm)	397.7
		The body of roll long (mm)	1780
Roller path length (mm)	210
		Bearing portion long (mm)	860
Room temperature (DEG C)	30
		Air cooling time (h)	5

Table 2 roll thermal physical property parameter

Fig. 4 illustrates the axial distribution of not roller surface temperature in the same time.As can be seen from the figure, in 5 hours after lower machine, in the middle part of the body of roll, 12 DEG C are reduced to edge surface temperature by the temperature difference 31 DEG C.

Fig. 5 illustrates roll barrel thermal expansion amount axial distribution; Fig. 6 illustrates the situation of change of roller heat convex degree learning with cool time.As can be seen from Fig. 5 and Fig. 6, after lower machine, in 5 hours, roller heat convex degree learning have decreased to 62 μm by 157 μm.

The technical program proposes one and repeatedly goes up machine roll initial temperature and roll thermal crown defining method, namely according to the cooling condition after machine under roll, set up roller temperature field model, the Coefficient of Roll Temperature Field of any time after the lower machine of calculating, there is provided roll initial temperature accurately for again going up machine, thus roll thermal crown forecast and Strip Shape Control precision can be improved.

The roller heat convex degree learning that the present invention can be widely used in hot-strip production process forecasts and Strip Shape Control technical field.

Claims (6)

1. a hot-strip roll roll thermal crown defining method, comprises the periodicity forecast and the determination to the initial temperature and roller heat convex degree learning that again go up machine roll carried out in finishing mill on-time model breaker roll temperature field, it is characterized in that:

The acquisition of machine temperature under A, roll: gather and preserve the periodicity forecast numerical value of shutting down and carrying out in moment finishing mill on-time model breaker roll temperature field, using the evaluation of Coefficient of Roll Temperature Field when shutting down as initial temperature;

B, roller temperature are followed the tracks of and are calculated: for the roll after lower machine, according to cooling condition, calculate Coefficient of Roll Temperature Field;

C, roll repeat machine temperature and roll thermal crown is determined: for first upper machine or the hot-strip roll again going up machine, calculate, determine initial temperature and the roll thermal crown of its roll respectively;

D, again go up machine for roll and provide roll initial temperature accurately, the temperature field of forecast work roller and roll thermal crown, improve roller heat convex degree learning forecast and plate shape setting control accuracy,

Follow the tracks of in calculating at the roller temperature of described step B, setting Coefficient of Roll Temperature Field relative to symmetrical in the middle part of axis and the body of roll, and ignores heat trnasfer along the circumferential direction;

Then follow the tracks of in computational process at described step B roller temperature, carry out according to the following step:

B1, to be summed up by breaker roll Temperature calculating and transform the conduction of two-dimentional Dynamic Thermal and calculate, its equation of heat conduction is:

$\mathrm{\ρc}=\frac{\∂T}{\∂t}=\frac{1}{r}\left[\frac{\∂}{\∂r}\left(\mathrm{\λr}\frac{\∂T}{\∂r}\right)\right]+\mathrm{\λ}\frac{{\∂}^{2}T}{\∂z^2}$ Formula 1

In formula, t is the time, and ρ, c and λ are respectively roll material density, specific heat and pyroconductivity, r and z is respectively roll radial direction and axial coordinate;

B2, finite difference method is carried out to the formula 1 of the differential equation;

B3, get by roll axis section 1/4th, set up difference gridding, then the cooling boundary condition under roll after machine is determined as follows:

The temperature on B31, left and right, upper and lower symmetrical border, determine according to following formula:

$\mathrm{\λ}\frac{\∂T}{\∂z}=0$ Formula 2

$\mathrm{\λ}\frac{\∂T}{\∂r}=0$ Formula 3

The temperature on B32, the body of roll, surface, roller footpath, determine according to following formula:

$\mathrm{\λ}\frac{\∂T}{\∂r}=-{\mathrm{\α}}_A(T-T_A)$ Formula 4

B33, with the temperature at bearing touch position, determine according to following formula:

$\mathrm{\λ}\frac{\∂T}{\∂r}=-{\mathrm{\α}}_B(T-T_B)$ Formula 5

The temperature of B34, roll end, determine according to following formula:

$\mathrm{\λ}\frac{\∂T}{\∂z}=-{\mathrm{\α}}_A(T-T_A)$ Formula 6

In above-mentioned formula, α _afor the coefficient of heat transfer between roll and air, T _afor air themperature, α _bfor the coefficient of heat transfer between roll and bearing, T _bfor bearing temperature.

2. according to hot-strip roll roll thermal crown defining method according to claim 1, it is characterized in that machine temperature under roll in the step A, equal the temperature in machine moment under the roll that finishing mill on-time model calculates, that is:

T=T _onformula 7

In formula, T is roller temperature, T _onfor the temperature in machine moment under the roll that finishing mill on-time model calculates.

3. according to hot-strip roll roll thermal crown defining method according to claim 1, it is characterized in that in the step C for upper machine roll of not refacing, according to the cooling condition after lower machine, under roll, machine temperature equals the temperature in machine moment under the roll that finishing mill on-time model calculates, its result of calculation as the initialization temperature again going up machine, that is:

T ₀=T _offformula 8

T in formula ₀for upper machine roll initializes temperature, T _offfor the accounting temperature of roll after lower machine, and upper machine roll is not refaced.

4. according to hot-strip roll roll thermal crown defining method according to claim 3, it is characterized in that in the step C, when Temperature Distribution is known, the thermal expansion amount at z place, arbitrfary point, described roll barrel surface is:

$u_t\left(z\right)=\frac{2(1+v)\mathrm{\β}}{R}{\∫}_0^R(T-T_A)\mathrm{rdr}$ Formula 9

Then the roll thermal crown of its roll is:

Δ u _t(z)=u _t(z)-u _t(e) formula 10

In above-mentioned formula, ν is Poisson's ratio, and β is thermal coefficient of expansion, and R is roller radius, u _te () is the thermal expansion amount at roll edge representative point place.

5., according to hot-strip roll roll thermal crown defining method according to claim 4, it is characterized in that in the step C for the roll of machine on secondary, the roll thermal crown determining step of its roll is as follows:

C1, from finishing mill on-time model, read the Coefficient of Roll Temperature Field in lower machine moment;

C2, cooling condition according to off-line roll, adopt formula 1 ~ formula 6 to determine the dynamic change result in temperature field;

C3, according to the temperature dynamic result of variations after lower machine, formula 8 ~ formula 10 is adopted to determine machine of again going up initial temperature and the roller heat convex degree learning of roll.

6. according to hot-strip roll roll thermal crown defining method according to claim 1, it is characterized in that described roller heat convex degree learning defining method be applicable to hot rolled strip produce in throw away after machine under roll, stop the working condition again going up machine after 1 ~ 5 hour.