JP2000202505A - Rolling method of cold tandem rolling mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of heat scratch without obstructing the productivity by detecting the sheet temperature, the sheet thickness, the sheet speed on a stand outlet side and the temperature and flow rate of cooling water, and estimating the sheet temperature at the roll bite outlet to control the draft. SOLUTION: Temperature detectors 24 are provided on the inlet and outlet sides of a rolling mill of a fourth stand 4 to detect the temperature of a sheet S under rolling at a specified period. Thickness measuring devices 17 are provided on the outlet and inlet sides of the fourth stand 4, and sheet speed meters are provided on the outlet sides of the fourth stand 4 and a third stand 3 to detect the thickness and the sheet speed on the inlet and outlet sides of the fourth stand 4. The sheet temperature at the roll bite outlet in the rolled condition is estimated from these detected values, the temperature of cooling water for the sheet, and the supply amount of cooling water. The sheet temperature rise Tm' is obtained when the sheet temperature rise TE' in the roll bite and the draft are changed, and the draft to satisfy the inequality of TL-Tf>= Tm'-TE' is obtained, where TL is the heat scratch control target temperature, and Tf is the heat scratch outlet estimated sheet temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling method for preventing the occurrence of heat scratches in a cold tandem rolling mill having a plurality of cold rolling mills without impairing productivity.

[0002]

2. Description of the Related Art In a cold tandem rolling mill, heat scratches may occur due to an increase in a work roll speed or a reduction ratio. A heat scratch is a seizure flaw generated due to a metal contact between a work roll and a rolled material as a result of an increase in the interface temperature between the roll in the roll bite and the rolled material and the breakage of the oil film in the roll bite. .

[0003] When heat scratches occur, the surface defects of the products occur, so that not only the product yield decreases, but also the work rolls of the stand where the heat scratches occur need to be replaced, so that there is a problem that the productivity is significantly reduced. .

[0004] The presence or absence of the occurrence of heat scratch can be predicted by the temperature of the interface rise in the roll bite during rolling. In the actual operation, the rolling schedule differs depending on the steel type, but since the same steel type is rolled under almost the same rolling conditions (hereinafter also including cooling conditions), the interface rising temperature can be substituted by the sheet temperature on the stand exit side. Therefore, control is performed such that the sheet temperature on the exit side of the rolling mill is detected, and based on the detected value, the sheet temperature becomes equal to or less than an appropriate value.

The above-described method of controlling the sheet temperature on the stand exit side as the temperature inside the roll bite is effective under substantially the same rolling conditions (constant speed, coolant, etc.). For example, when cooling is not performed between the rolling tool roll tool exit side and the plate temperature detector (air cooling), there is no major problem. In the case of the i-stand in FIG. 2, the upper and lower work rolls are cooled by the roll cooling device 30,
The cooling water is prevented from hitting the plate S by the draining device 32. Therefore, since the roll cooling does not affect the measured value of the temperature detector 34, the heat scratch of the i-stand can be prevented by the conventional technique.

[0006] However, when cooling is performed between the rolling tool roll tool exit side and the sheet temperature detector (water cooling), a serious problem occurs. For example, in the case of the stand (i-1) in FIG. 2, the plate S is cooled by the plate cooling device 20 on the exit side of the rolling mill, and cooling water remains on the surface. The remaining cooling water is drained by a draining and tension detecting device 22 and then the temperature detector 2
At 4 the temperature is measured. Therefore, the temperature detector 2
4, the effect of the plate cooling device 20 is great. Even with the same amount of cooling water, the temperature of the cooling water has an effect. The water temperature is about 20 ° C. in summer and about 5 ° C. in winter. In summer and winter, the empirical heat scratch control target temperature T _L of the conventional control is used.
Had to be held at the table according to the water temperature. Further, the heat scratch control target temperature T _L needs to be confirmed by an experiment, so setting the temperature is a problem. Further, when the amount of water in the plate cooling device 20 is greatly changed, the effect of the amount of water cannot be ignored. Depending on the lubricating oil to be used, the accuracy may be improved by controlling the temperature at the interface (temperature difference between the sheets on the entrance and exit of the rolling mill) rather than by controlling the sheet surface temperature (maximum temperature).

[0007] Regarding prevention of heat scratch, for example, a method using a rolling lubricating oil having excellent seizure resistance as disclosed in Japanese Patent Application Laid-Open No. Hei 5-98283 and a method disclosed in Japanese Patent Application Laid-Open No. 56-11505 are disclosed. As described above, there are a method of controlling the amount of coolant to lower the temperature of the plate or the work roll, and a method of reducing the work roll speed as disclosed in Japanese Patent Application Laid-Open No. 6-63624.
Each method relates to a method of preventing an increase in the interface temperature between a work roll in a roll bite and a rolled material, or preventing an oil film from breaking even if the interface temperature in the roll bite increases. However, the use of rolling lubricating oil with excellent seizure resistance may increase the cost, and controlling the temperature of the plate and roll by controlling the amount of coolant is effective, but there are some problems in its responsiveness, There is a problem that a reduction in roll speed lowers productivity.

As a method of preventing heat scratch without causing a decrease in productivity and an increase in manufacturing cost, Japanese Patent Application Laid-Open No. 60-49802 discloses changing a rolling schedule and tension. It is not clear how to predict the occurrence of heat scratch in advance and how to obtain the control amount.

[0009]

When the tension is changed as a method for preventing the heat scratch without causing the decrease in the productivity and the increase in the production cost as described above,
Naturally, a higher value will reduce the rolling load, and will have the effect of preventing heat scratching.However, if the tension is increased, the sheet may break. And heat scratching occurs, and the plate thickness accuracy deteriorates. Further, when the temperature of the plate on the stand exit side is detected and the tension is controlled based on the detected temperature, the control is performed when the temperature becomes equal to or higher than the temperature at which heat scratch occurs, so that heat scratch occurs temporarily. There is a risk.

[0010] It is an object of the present invention to provide a rolling method in a cold tandem rolling mill that prevents the occurrence of heat scratch without impairing productivity.

[0011]

The gist of the present invention is as follows. 1) The detected values of the temperature and flow rate of the cooling water of the plate cooling device installed between the stand exit side and the temperature detector that detects the plate surface temperature, and the plate temperature, plate thickness, and plate speed at the stand exit side Estimate the roll plate outlet plate temperature based on the
The rolling reduction is controlled based on this value. 2) Detected values of the plate temperature at the entrance and exit of the stand, the thickness and the plate speed at the exit of the stand, or a temperature detector that detects these detected values and the plate surface temperature from the exit side of the stand. Estimate the temperature rise in the roll bite in the rolling state based on the detected values of the temperature and flow rate of the cooling water of the plate cooling device installed up to, and control the rolling reduction based on this value

The present invention is based on the above-mentioned gist, and the rolling method in the cold tandem rolling mill according to the first invention specifies in advance a stand in which heat scratch is likely to occur, and performs the following steps in the designated stand: Perform rolling. (B) The temperature at which the stand exit side plate temperature, rolling load, work roll speed, stand exit side plate speed, stand entry / exit side plate thickness, stand entry / exit side tension, plate cooling water temperature, and plate cooling water supply amount are respectively detected. 1 step (b) Estimating the roll bite exit plate temperature _Tf in the rolling state from the detected values of the stand exit side plate temperature, the stand exit side plate thickness, the stand exit side plate speed, the plate cooling water temperature, and the plate cooling water supply amount. Second step (c) When the roll bite estimated plate temperature _Tf exceeds a preset heat scratch control target temperature _TL , the rolling load, work roll speed,
Third step of calculating the friction coefficient and deformation resistance of the rolled material from the detected values of the stand exit side plate speed, the stand entry / exit side plate thickness, and the stand entry / exit side tension (d) The detection value, friction coefficient, and The sheet temperature rise T _E ′ in the roll tool in the rolled state in the rolling state and the temperature rise T _m ′ in the roll tool when the rolling reduction is changed are determined by the deformation resistance, and T _L −T _f ≧ T _m ′ −T _E ′. (E) Fifth step of controlling the reduction rate using the reduction rate obtained in the fourth step as the target value

According to a second aspect of the present invention, there is provided a rolling method for a cold tandem rolling mill in which a stand in which heat scratch is likely to occur is designated in advance, and rolling is performed in the designated stand in the following steps. (A) Stand entrance / exit side plate temperature, rolling load, work roll speed, stand exit side plate speed, stand entrance / exit side plate thickness,
First step of detecting stand entry / exit side tension, respectively (b) From the detected values of the stand entry / exit side plate temperature, stand exit side plate thickness, and stand exit side plate speed, the rise temperature ΔT _f in the roll bite in the rolling state Second to find
Step (c) The estimated temperature rise ΔT _f in the roll bite is a preset heat scratch control target temperature ΔT.
_{When the value} exceeds _L , the friction coefficient and deformation resistance of the rolled material are determined from the detected values of the rolling load, work roll speed, stand exit side plate speed, stand entry / exit plate thickness, and stand entry / exit tension in the first step. Third Step (d) The sheet temperature rise T _E ′ in the roll bite in the rolling state and the sheet temperature rise T _m ′ when the rolling reduction is changed are obtained from the detected value of the third step, the coefficient of friction, and the deformation resistance. , ΔT _L −ΔT _f ≧ T _m ′ −T _E ′ Fourth step for obtaining the reduction ratio (E) Fifth step for controlling the reduction ratio using the reduction ratio obtained in the fourth step as a target value

According to a third aspect of the present invention, there is provided a rolling method in a cold tandem rolling mill in which a stand in which heat scratch is likely to occur is designated in advance, and rolling is performed in the designated stand in the following steps. (A) Stand entrance / exit side plate temperature, rolling load, work roll speed, stand exit side plate speed, stand entrance / exit side plate thickness,
First step of detecting stand entrance / exit side tension, plate cooling water temperature, and plate cooling water supply amount, respectively (b) The stand entrance / exit side plate temperature, stand exit side plate speed, stand exit side plate thickness, plate cooling water temperature And a second step of obtaining the temperature rise ΔT _f in the roll tool in the rolling state from the detected value of the sheet cooling water supply amount, and (c) the estimated temperature rise ΔT _f in the roll tool becomes the heat scratch control target temperature ΔT set in advance.
_{When the value} exceeds _L , the friction coefficient and deformation resistance of the rolled material are determined from the detected values of the rolling load, work roll speed, stand exit side plate speed, stand entry / exit plate thickness, and stand entry / exit tension in the first step. Third Step (d) The sheet temperature rise T _E ′ in the roll bite in the rolling state and the sheet temperature rise T _m ′ when the rolling reduction is changed are obtained from the detected value of the third step, the coefficient of friction, and the deformation resistance. , ΔT _L −ΔT _f ≧ T _m ′ −T _E ′ Fourth step for obtaining the reduction ratio (E) Fifth step for controlling the reduction ratio using the reduction ratio obtained in the fourth step as a target value

According to these inventions, a plate cooling device installed between the stand exit side sheet thickness, the rolling load, and other detected values, or these detected values and the temperature detector for detecting the sheet surface temperature from the exit side of the rolling mill. The friction coefficient and the deformation resistance are determined based on the detected values of the temperature and the flow rate of the cooling water. Then, the roll bite exit temperature or the temperature rise in the roll bite is obtained from these values, and the rolling reduction is controlled so that these do not exceed the heat scratch control target temperature. Therefore, the temperature inside the roll bite can be maintained at or below the temperature at which heat scratch does not occur.

[0016]

FIG. 1 shows an example of a cold tandem rolling mill in which a rolling method according to the present invention is carried out. The number of stands of the cold tandem rolling mill is usually 2 to 8, and FIG. 1 shows 5 stands, but the number of stands is not limited to this. Stands 1 to 5 are work rolls 1
1, an intermediate roll 13 and a backup roll 15. The stands where heat scratch is likely to occur vary depending on the rolling reduction, plate thickness, rolling load, tension, rolling material, lubrication conditions, etc. of each stand. Normally, heat scratch tends to occur easily in a stand at a later stage where a rolling load and a work roll speed are increased. In the cold tandem rolling mill of FIG. 1, the final stand 5 is in a state where the heat scratch occurs frequently in the fourth stand 4 because the final stand 5 is subjected to the light reduction dull rolling. When there is a possibility that heat scratches may occur in stands other than the stand at the subsequent stage, the present invention can be applied to those stands. Note that a lubricating oil supply device 26 is arranged on the entrance side of each stand. The final stand 5 includes a work roll cooling device 30 and a roll cooling drainer 32.

In FIG. 1, temperature detectors 24 are provided after the draining and tension detecting device 22 at the entrance and exit of the rolling mill of the fourth stand 4, and the sheet temperature T of the sheet S during rolling is provided.
Are detected at regular intervals. The temperature detector 24 is preferably of a non-contact type, for example, a radiation thermometer is used. The rolling load P of the fourth stand 4 is detected by a load cell (not shown). The tensions (force per unit area) σ _b and σ _f on the entrance and exit sides of the rolling mill are obtained by dividing the total tension by the sheet cross-sectional area (sheet thickness / sheet width). The total tension is detected by a load cell (not shown) of the draining and tension detecting device 22 provided on the entrance side and the exit side of the rolling mill. A thickness measuring device 17 such as X
A line type thickness gauge is provided, and a plate speed meter (not shown), for example, a laser type plate speed meter is provided on the exit side of the fourth stand 4 and the third stand 3. With these instruments,
The entrance side and exit side plate thicknesses H and h of the fourth stand 4 and the entrance side and exit side plate speeds V _I and V _O are detected, respectively.
The work roll speed V _R of the fourth stand 4 is obtained by detecting the number of rotations of a motor driving the work roll 11 by a rotation number detector (not shown), and detecting the detected number of rotations of the motor, the work roll diameter D, and the gear. It is determined by calculating using the ratio. The plate S is cooled by the plate cooling device 20 on the entrance side and the exit side of the fourth stand.

[0018] In the tandem cold rolling mill, the work roll diameter D, the roll driving system gear ratio, the plate width W, the material thickness (H _S: thickness at entrance side of the first stand 1), and a simple tension when the material The yield stress σ _y is known and can be input in advance to a calculator (not shown). The rolling load of the present invention is a load required for plastic deformation of a material, and when a stand has a shape control device such as a bender, the force is detected and obtained by the load cell described above. It means the load excluding the force of the bender etc. from the load.

Next, a method of estimating the plate temperature will be described. By the plate temperature detector 24 provided on the exit side of the rolling mill,
The sheet temperature on the exit side of the rolling mill is detected at a constant period τ (for example, 5 s), and the sheet temperature T _O at the exit of the rolling tool roll bite is estimated.

Generally, the plate temperature T when water cooling is performed
_S is given by equation (1).

(Equation 1) Therefore, the temperature T _{O at the} outlet of the roll bite is given by the equation (1)
Is expressed by equation (2) by rearranging

(Equation 2) Here, T _w : cooling water temperature of the plate cooling device T _s : plate temperature at the plate temperature detection position V _O : plate speed on the exit side of the rolling mill h: plate thickness on the exit side of the rolling mill ρ _s : plate density C _S : Specific heat of the plate h _S : Heat transfer coefficient of the plate t ₁ : Time for the plate to pass the distance from the plate cooling device to the draining device (t ₁ = L ₁ / V _O ) L ₁ : From the plate cooling device to the draining device The distance to. It is necessary to conduct an experiment to model the relationship between the heat transfer coefficient h _S of the plate and the amount of cooling water (the amount of cooling water supplied per unit time per unit area) in advance. Equation (3) shows a general form of the heat transfer coefficient model equation including the required parameters.

(Equation 3) Q _w : supply amount of cooling water, W: board width

In the case of air cooling, if the air cooling time is within about 0.5 seconds (rolling speed is about 500 m / min or more), the temperature change due to air cooling can be ignored. Therefore, the exit side plate temperature of the former stand can be regarded as the plate temperature at the plate temperature detection position as it is.

Based on the above temperature data, the roll plate outlet plate temperature in a steady state is estimated. For example, the rolling control cycle (the rolling control cycle for preventing heat scratch) is set to 1 minute, and the plate temperature data for the past one minute (12 pieces in this case, but the data for the case where the rolling condition is constant, ) Is used to determine the constant of the function by substituting it into a function that represents an asymptotic curve that eventually asymptotically approaches a constant value, and performing multiple regression. _Is assumed to be _Tf . Examples of functions representing such an asymptotic curve that finally approaches a constant value include ^atanh (cX) and a + b (1-e- ^cx ). In this function, a, b, and c are constants and eventually asymptotically to a and a + b, respectively. Therefore,
The measured temperature data is substituted into such a function to obtain an asymptotic value a or a + b, and this is set as an estimated value _Tf of the plate temperature in a steady state.

In addition to the above-mentioned method, for example, the rolling control cycle (the rolling control cycle for preventing heat scratch) is set to, for example, 30 seconds, and the control cycle is obtained during the control cycle of 30 seconds. Linear regression of 6 temperature data,
The plate temperature 30 seconds after the next rolling control timing (the next rolling control timing) may be estimated and used as the estimated value _Tf of the plate temperature.

Next, the setting of the heat scratch control temperature will be described. The minimum temperature of the roll bite exit plate at which heat scratch occurs is determined by an experiment in which the work roll speed, rolling reduction, rolling lubrication conditions, and the like are changed in advance, and this is _defined as the limit temperature T _Lim . This limit temperature may be set as the heat scratch control target temperature _TL. However, the heat scratch control target temperature _TL is set to a temperature slightly lower than the limit temperature T _Lim described above, for example, a temperature lower by about 3 to 6 ° C. Is preferred.

In the stand where heat scratch is likely to occur, in this embodiment, the fourth stand, the estimated value _Tf of the plate temperature at the roll bite outlet is compared with the above-mentioned heat scratch control target temperature _TL . ΔT = T _L -T
_{If f} is positive, there is no possibility of heat scratching, so the rolling is continued. When ΔT = _TL - _Tf is a negative value, heat scratch may occur, and therefore, rolling is performed while changing the rolling reduction so that ΔT becomes positive.

The method of calculating the rolling reduction to be changed will be described below. First, the deformation resistance K _m and the friction coefficient during rolling mu. For the deformation resistance of the rolled material, the values of the constants a, ε ₀ , and n shown in Expression (4) are obtained in advance by a tensile test.

(Equation 4) Here, σ _y is the yield stress at the time of simple tension of the rolled material,
ε is the strain.

By the way, since deformation resistance is affected by the strain rate of the impacts and the plate temperature, deformation resistance K _m obtained from the equation (4) is not necessarily exact value during rolling. Therefore, in the present invention, the rolling load equation and the advanced rate equation are made simultaneous to determine the deformation resistance and the friction coefficient during rolling. For example, H
The load equation of ill is expanded to the deformation resistance as shown in equation (5) to determine the deformation resistance. Further, Bland &Ford's advanced rate equation is developed for the coefficient of friction as shown in equation (6), and the deformation resistance obtained by equation (5) is substituted into equation (6) to determine the coefficient of friction. In Equations (5) and (6), the suffix E is a detected value at the time of rolling of the stand and a calculated value based on the detected value, and in the following description, these are referred to as actually measured values. The calculated value is a value obtained by dividing the pretension detected by the load cell by the cross-sectional area of the plate, excluding the bending force from the rolling load detected by the load cell, as described above.

(Equation 5)

(Equation 6)

In the above equation, the unknowns are two of the coefficient of friction μ _E and the constant (a in the equation (4)) in the deformation resistance equation K _mE , and the other are known numbers and the number of equations is two. Therefore, this equation can be solved. In the calculation, it is preferable to use a value obtained by a tensile test as an initial value of about 0.05 as the initial value of the friction coefficient μ _{E and} an initial value of the constant a in the deformation resistance equation.

On the other hand, the temperature rise T 'at the interface between the roll at the exit of the roll bite and the rolled material at this time is expressed by equation (7) using, for example, the equation of Ono et al.

(Equation 7)

T _dmax is the temperature rise at the roll tool exit at the interface between the roll and the rolled material, which is increased by the heat of deformation, and is expressed by equation (8). T _fmax is a temperature rise at the roll bite exit at the interface which increases due to frictional heat, and is expressed by equation (9).

(Equation 8)

(Equation 9)

Equations (7) and (8) show the physical property values and actual measured values of the respective stand, and the above-mentioned equations (5) and (5).
By substituting the coefficient of friction μ _E and the deformation resistance K _mE obtained by the method using the equation (6), the actually measured value T _E ′ of the temperature rise T ′ at the interface between the roll at the exit of the roll bite of the stand and the rolled material is obtained. I get it.

Next, in order to estimate the temperature change when the rolling reduction is changed, first, the friction coefficient μ _E and the deformation resistance K _mE , which are obtained, and the measured values of the stand except for the _rolling reduction are used. Calculate the rolling load P and the advance rate fs in the case of changing only Strictly speaking, changing the rolling reduction also changes the friction coefficient. However, rolling speed 100
At 0 m / min or more, fluid lubrication is dominant, so that the influence of the rolling reduction on the friction coefficient can be neglected under conditions where heat scratch occurs.

The rolling load P is, for example, H
Calculate using ill's load equation. The advance rate fs is given by the equation (1)
Calculate using the Bland & Ford formula shown in 1). The roll flat RE 'is calculated using the Hitchcook equation shown in equation (12).

(Equation 10)

[Equation 11]

(Equation 12)

Using equation (10) and equation (12) for roll flattening
The rolling load is determined by performing convergence calculation
(11) The advanced rate can be obtained more. These values are calculated using equations (7) to
By substituting into the equation (9), the rolling reduction condition is changed.
Temperature rise T at the interface at the exit of the roll tool_m′ Is found
You. That is, the roll bite at the above stand
Actual measured temperature T of mouth interface_E′ And change the draft
Value T of the temperature rise at the exit of the roll bite_m'But
can get. Roll and rolled material at roll exit
Strictly speaking, the interface temperature and the plate temperature at the stand exit side
Although not the same, the temperature change when the rolling reduction condition is changed
May be considered the same. So this
T_m'And T_E(ΔT ′ = T_m'-T_E')When,
T mentioned earlier _LAnd T_f(ΔT = T_L-T_f) And
In comparison, ΔT ′ is equal to or smaller than ΔT (ΔT ′ ≦ ΔT).
Conditions using, for example, Newton's method.
It can be obtained by return calculation. Pressure of the rolling mill
Change the reduction rate set value to the reduction rate value obtained as described above.
Change. The occurrence of heat scratch satisfying the above relationship
Several non-reduction values can be determined. These pressures
Select an appropriate rolling reduction value from the reduction ratio values according to the rolling situation.
Select the lowest reduction rate value raim, and select
It is possible to change the rolling reduction set value of the stand according to
desirable.

At the time of these controls, since the amount of change in the rolling load can be predicted in advance, it is possible to control the sheet thickness and shape so that defects in the sheet thickness accuracy and the sheet shape do not occur.

In the above, the heat scratch was transferred to a rolling mill roll bar.
The method of controlling with the sheet temperature on the outlet side of the
Depending on the lubricating oil, the
In some cases, it is better to control the temperature rise in the working part.
You. The method in that case will be described. In this case,
The temperature of the sheet Ti is detected by the temperature detector at the entry side of the rolling mill.
I do. No water cooling from the temperature detector to the entrance to the rolling mill
When the rolling speed is 500m / min or more, even if the lubricating oil
Even if it hits the plate surface
Their influence on them is negligible. Therefore,
T_OT instead of _O'= T_ODo the same with -Ti
I just need.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The cold tandem rolling mill used was a tandem rolling mill consisting of the same five stands as shown in FIG.
Table 1 shows the rolling conditions of the fourth stand as a stand where heat scratch occurs.

[Table 1]

Under operating conditions, when coils of the same size are rolled in large quantities under the same rolling conditions, the average temperature of the work rolls rises, and the plate temperature on the exit side of the fourth stand rises. It has been empirically known from operation data so far that if the plate temperature at the exit side of the fourth stand is about 160 ° C. or higher, heat scratches frequently occur. Then, the present invention was applied, and the effect was experimentally investigated.

The limit temperature T _Lim, which is the lowest roll bite exit plate temperature at which heat scratch is generated by an experiment in advance, is 162 ° C., and the heat scratch control target temperature is T _L = 162-4 = 158 ° C. .
The control cycle of the rolling reduction for heat scratch control is 30 seconds, and the sampling time is 5 seconds.
The plate temperature at the roll bite outlet was calculated and linearly regressed from the data of seconds (six pieces), and the roll bite exit plate temperature after 30 seconds was obtained and used as an estimated value _Tf of the plate temperature.

FIG. 3 is a diagram showing the effect of the first invention, and shows the relationship between the number of rolling coils and the temperature of the sheet on the exit side of the fourth stand roll bite. In FIG. 3, を indicates the case of the conventional rolling method, and ● indicates the case of applying the present invention. In the conventional rolling method, the estimated value of the roll bite exit plate temperature becomes 160 ° C. or more when the number of coils is 11 and there is a risk of generating heat scratch. Therefore, the work roll speed was reduced to 900 m · min ⁻¹ to operate. I was However, by applying the present invention, the rolling reduction is 28.
By changing from 6% to 23 to 25%, even if the number of coils is 30, the plate temperature does not reach 158 ° C. or more and the rolling is performed without reducing the work roll speed.
Naturally, no heat scratch occurred.
As a matter of course, if the rolling reduction of the fourth stand is changed, the plate thickness (product plate thickness) changes, and it is needless to say that the insufficient rolling reduction needs to be adjusted by another stand. Preferably, the adjustment is performed at the first stand where heat scratch is least generated.

When the conditions for cooling the plate of the third stand were significantly changed, the accuracy deteriorated. Therefore, the second invention was applied. That is, the limit temperature ΔT _Lim which is a roll bite increasing temperature at which heat scratch occurs, which was previously determined by an experiment, was 108 ° C., and the heat scratch control target temperature was ΔT _L = 108-4 = 104 ° C. Further, the control cycle of the rolling reduction is 30 seconds, the sampling time is 5 seconds, and the roll bite rising temperature is calculated and linearly regressed from the data of 30 seconds (six pieces) during that period, and the roll bite rising temperature after 30 seconds is obtained. This was used as an estimated value ΔT _f of the plate temperature.
As a result, heat scratch did not occur even when the plate cooling condition of the third stand was significantly changed.

[0042]

According to the present invention, the temperature in the roll bite can be suppressed with high accuracy to a temperature at which heat scratch does not occur,
It is possible to prevent the occurrence of heat scratch without impairing the productivity.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a cold tandem rolling mill embodying the present invention.

FIG. 2 is an enlarged view of two stands in a cold tandem rolling mill.

FIG. 3 is a graph showing a relationship between a roll bite exit temperature of a rolled material and the number of rolled coils.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Work roll 13 Intermediate roll 15 Backup roll 17 Plate thickness detector 20 Plate cooling device 22 Draining and tension detecting device 24 Temperature detector 26 Lubricating oil supply device S Rolled material (plate)

Claims (3)

[Claims] 1. A rolling method in a cold tandem rolling mill in which a stand where heat scratch is likely to occur is designated in advance, and rolling is performed in the designated stand in the following steps. (B) The temperature at which the stand exit side plate temperature, rolling load, work roll speed, stand exit side plate speed, stand entry / exit side plate thickness, stand entry / exit side tension, plate cooling water temperature, and plate cooling water supply amount are respectively detected. 1 step (b) Estimating the roll bite exit plate temperature _Tf in the rolling state from the detected values of the stand exit side plate temperature, the stand exit side plate thickness, the stand exit side plate speed, the plate cooling water temperature, and the plate cooling water supply amount. Second step (c) When the roll bite estimated plate temperature _Tf exceeds a preset heat scratch control target temperature _TL , the rolling load, work roll speed,
Third step of calculating the friction coefficient and deformation resistance of the rolled material from the detected values of the stand exit side plate speed, the stand entry / exit side plate thickness, and the stand entry / exit side tension (d) The detection value, friction coefficient, and The sheet temperature rise T _E ′ in the roll tool in the rolled state in the rolling state and the temperature rise T _m ′ in the roll tool when the rolling reduction is changed are determined by the deformation resistance, and T _L −T _f ≧ T _m ′ −T _E ′. (E) Fifth step of controlling the reduction rate using the reduction rate obtained in the fourth step as the target value 2. A rolling method in a cold tandem rolling mill in which a stand where heat scratch is likely to occur is designated in advance, and rolling is performed in the designated stand in the following steps. (A) Stand entrance / exit side plate temperature, rolling load, work roll speed, stand exit side plate speed, stand entrance / exit side plate thickness,
And the first step of detecting the stand-in / out-side tension, respectively. (B) From the detected values of the stand-in / out-side plate temperature, the stand-out side plate thickness, and the stand-out side plate speed, the temperature rise ΔT in the roll bite in the rolling state. Second to find _f
Step (c) The estimated temperature rise ΔT _f in the roll bite is a preset heat scratch control target temperature ΔT.
_{When the value} exceeds _L , the friction coefficient and deformation resistance of the rolled material are determined from the detected values of the rolling load, work roll speed, stand exit side plate speed, stand entry / exit plate thickness, and stand entry / exit tension in the first step. Third Step (d) The sheet temperature rise T _E ′ in the roll bite in the rolling state and the sheet temperature rise T _m ′ when the rolling reduction is changed are obtained from the detected value of the third step, the coefficient of friction, and the deformation resistance. , ΔT _L −ΔT _f ≧ T _m ′ −T _E ′ Fourth step for obtaining the reduction ratio (E) Fifth step for controlling the reduction ratio using the reduction ratio obtained in the fourth step as a target value 3. A rolling method in a cold tandem rolling mill in which a stand where heat scratch is likely to occur is designated in advance, and rolling is performed in the designated stand in the following steps. (A) Stand entrance / exit side plate temperature, rolling load, work roll speed, stand exit side plate speed, stand entrance / exit side plate thickness,
First step of detecting stand entrance / exit side tension, plate cooling water temperature, and plate cooling water supply amount, respectively (b) The stand entrance / exit side plate temperature, stand exit side plate speed, stand exit side plate thickness, plate cooling water temperature And a second step of obtaining the temperature rise ΔT _f in the roll tool in the rolling state from the detected value of the sheet cooling water supply amount, and (c) the estimated temperature rise ΔT _f in the roll tool becomes the heat scratch control target temperature ΔT set in advance.
_{When the value} exceeds _L , the friction coefficient and deformation resistance of the rolled material are determined from the detected values of the rolling load, work roll speed, stand exit side plate speed, stand entry / exit plate thickness, and stand entry / exit tension in the first step. Third Step (d) The sheet temperature rise T _E ′ in the roll bite in the rolling state and the sheet temperature rise T _m ′ when the rolling reduction is changed are obtained from the detected value of the third step, the coefficient of friction, and the deformation resistance. , ΔT _L −ΔT _f ≧ T _m ′ −T _E ′ Fourth step for obtaining the reduction ratio (E) Fifth step for controlling the reduction ratio using the reduction ratio obtained in the fourth step as a target value