JP3519856B2 - Rolling method of cold tandem rolling mill - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Heat scratches occur in a cold tandem rolling mill when the work roll speed is increased or the rolling reduction is increased. The heat scratch is a seizure flaw caused by metal contact between the work roll and the rolled material, which occurs as a result of the interface temperature between the roll in the roll bite and the rolled material rising and the oil film rupturing in the roll bite.

When heat scratches occur, surface defects of the products occur, so that not only the product yield decreases, but also the work rolls of the rolling stand where heat scratches occur need to be reassembled, resulting in a significant decrease in productivity. . Therefore, regarding heat scratch prevention, for example, a method of using a rolling lubricant having excellent seizure resistance as disclosed in JP-A-5-98283 and JP-A-56-111505 are disclosed. As described above, there is 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 JP-A-6-63624.
Both methods relate to a method of preventing an increase in the interface temperature between the roll in the roll bite and the rolled material, or preventing an oil film from breaking even if the interface temperature in the roll bite rises. However, the use of rolling lubricant with excellent seizure resistance may increase costs, and controlling the plate and roll temperatures by controlling the amount of coolant is effective but has some problems in its responsiveness. The decrease in speed causes a problem of decrease in productivity.

As a method for preventing heat scratch without lowering productivity and increasing manufacturing cost,
Although Japanese Patent Laid-Open No. 60-49802 discloses changing the rolling schedule and the tension, it is not clear how to predict the occurrence of heat scratch and how to determine the control amount thereof.

[0005]

As a method of preventing heat scratches without causing the above-mentioned decrease in productivity and increase in manufacturing cost, when the reduction schedule is changed, the plate thickness accuracy temporarily deteriorates. In addition, when changing the tension, of course, if a high value is set, the rolling load will be reduced and the effect of preventing heat scratches will be obtained, but if it is set to a high value, plate breakage may occur. If the tension is gradually increased while observing the situation, there is a problem that the responsiveness deteriorates, heat scratches occur, and the plate thickness accuracy deteriorates. Further, when detecting the plate temperature on the delivery side of the rolling stand and controlling the tension based on that 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.

[0006]

The present invention has been described above.
It is intended to solve the problems of the conventional method.
Pressure that tends to cause heat scratches during dem rolling
Predict the plate temperature on the exit side of the stand in the extended stand
However, if a certain target value is exceeded, the roll bar
Estimate the plate temperature at the outlet of the seat, and this temperature is the estimated value and the target value.
The tension is controlled to eliminate the temperature deviation of
It That is, the present invention relates to the heat skating of a cold tandem rolling mill.
In a rolling stand where latches are likely to occur,
Plate temperature on the outlet side of tund, rolling load, work roll speed,
Plate speed at stand exit side, stand entrance side and exit side plate
Detects or detects the thickness of the stand and the tension on the inlet and outlet sides
Calculated from the detected values from
From the output value to the steady state or the rolling state at the next tension control timing
Plate temperature T on the delivery side of the rolling stand in_fEstimate
Heat scratch control with a predetermined plate temperature estimated by
Target temperature T_LWhen the rolling stand exceeds the exit side of the rolling stand
Plate temperature, rolling load, work roll speed, stand exit side
Plate speed, stand entry side and exit side plate thickness, stand entry
From the detected values of the tension on the output side and the output side and these detected values
And the calculated values obtained from these detected values and calculated values
Using the rolling stand friction coefficient and deformation resistance,
Pressure at the roll bite outlet of the rolling stand in the rolled state
Temperature rise T at the interface between rolled material and roll _E′ And change the tension
Rolled material at the exit of the roll bite of the rolling stand
Temperature rise at the interface between the roll and roll_m′, T_L-T_f
≧ T_m′ -T_E′ Is obtained and based on this tension
Cold tandem rolling mill for controlling the tension of the rolling stand
Is the rolling method.

The present invention also relates to a cold tandem rolling mill.
In a rolling stand that is susceptible to scratches,
Plate temperature, rolling load, work load on the exit side of the rolling stand
Speed, plate speed at stand-out side, stand-in side and stand-out side
Side plate thickness, stand stand-in and stand-out tension detection or
Is calculated from these detected values, and the plate on the delivery side of the rolling stand is
From the detected temperature value to the steady state or the pressure at the next tension control timing.
Plate temperature T on the outlet side of the rolling stand in the rolled state_fEstimate
However, the estimated plate temperature is
Target temperature T_LIf the rolling stand exceeds
Departure side plate temperature, rolling load, work roll speed, stun
Board speed on the exit side, board thickness on the stand entry and exit sides,
Input and output side tension values and their detection
The calculated value from the values and the calculated and calculated values
Using the friction coefficient and deformation resistance of the rolling stand
And the roll bite of the rolling stand in the rolled state
Temperature rise T at the interface between the rolled material at the outlet and the roll_E'And Zhang
Roll bite exit of the rolling stand when the force is changed
Temperature rise T at the interface between the rolled material and roll_m′, T
_L-T_f≧ T_m′ -T_E‘
Causes a predetermined plate break in the rolling stand
Maximum rolling stand entry side tension σ_bmaxOr out
Side maximum tension σ_fmaxRolling stand
Tension at a predetermined plate without breaking
Rolling stand entry side maximum tension σ_bmaxOr maximum tension on the output side
σ_fmaxThe settings are as follows and this setting is
When changing the work roll speed under tension,
Rolling material and roll at the exit of the roll bite of the rolling stand
Temperature rise at the interface of_m″, T_L-T_f≧ T_m″ −
T _E′ Is calculated as the work roll speed.
The work roll speed of the rolling stand based on
It is a rolling method of a controlled cold tandem rolling mill.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail with reference to FIG. FIG. 1 shows a four-stand cold tandem rolling mill. It should be noted that the cold tandem rolling mill usually has a plurality of
It is provided with eight cold rolling mills, and four stands are shown in the present embodiment, but the number is not limited to this. The rolling stands where heat scratches are likely to occur are: rolling reduction of each stand, plate thickness, rolling load, tension, rolling material,
Although it varies depending on the lubrication conditions and the like, it usually tends to occur in the rolling stand in the subsequent stage where the rolling load and the work roll speed increase. In this embodiment, the last stand, that is, the fourth stand frequently occurs. In addition, when heat scratches may occur in other rolling stands than the latter rolling stand, the present invention can be applied to those rolling stands.

In FIG. 1, a plate temperature detector (1) is provided on the rolling mill exit side of the fourth stand, and the plate temperature T of the plate (2) being rolled is detected at a constant cycle. In addition,
The plate temperature detector (1) is preferably a non-contact type, and for example, a radiation thermometer or the like is used. Further, the rolling load P of the fourth stand is detected by the load cell (3), and the tensions (forces per unit area) σ _b and σ _f on the rolling mill inlet side and outlet side.
Is obtained by calculating the total tension detected by load cells (not shown) of the deflector rolls (4, 4 ') provided on the inlet side and the outlet side of the rolling mill using the plate thickness and the plate width. A plate thickness measuring device (5, 5 '), for example, an X-ray plate thickness gauge, is provided on the entrance side and the exit side of the fourth stand, and a plate speed meter (6), for example, a laser is provided on the exit side of the fourth stand. Type plate speedometers are provided, which allow the entrance and exit plate thicknesses H and h of the fourth stand and the exit plate speed V.
_O is detected respectively. The work roll speed V _R of the fourth stand is obtained by detecting the number of rotations of the motor that drives the work rolls by a rotation number detection device (not shown), and detecting the number of rotations of the motor, the work roll diameter D, and the gear ratio. It is calculated by using.

Here, the work roll diameter D, the gear ratio, the plate width W, the material plate thickness (H _S : the plate thickness on the entry side of the first stand) and the yield stress σ _y during simple tension of the material are known, and It can be input to a computer (not shown). Note that the rolling load of the present invention is a load required for plastic deformation of the material, and if the rolling stand has a shape control device such as a bender, those forces are detected and obtained from the load cell described above. It means the load that excludes those forces from the applied load.

Next, a method of estimating the plate temperature will be described.
The plate temperature on the outlet side of the rolling mill is detected by the plate temperature detector on the outlet side of the rolling mill at a constant period τ (for example, 5 seconds). The plate temperature in the steady state is estimated based on this temperature data. For example, the tension control cycle (tension control cycle for preventing heat scratch) is set to 1 minute, and the past 1
Perform multiple regression by substituting into the function that represents the asymptotic curve that asymptotically approaches a constant value, using the data of the plate temperature per minute (in this case, 12 data, but the tension condition is constant) The constant of the function is determined by and the asymptotic value is set as the estimated value T _f of the plate temperature in the steady state. Examples of such functions that finally show an asymptotic curve that approaches a constant value include a · tan h (cX) and a + b (1-e
^-CX ) etc. In this function, a, b, and c are constants, and finally asymptotically approach a and a + b, respectively. Therefore, substituting the measured temperature data into such a function,
Each asymptotic value a or a + b is obtained, and this is set as the estimated value T _f of the plate temperature in the steady state.

In addition to this method, for example, the tension control cycle (tension control cycle for preventing heat scratch) is set to 30 seconds, and the control cycle is obtained in 30 seconds. Linear regression of 6 temperature data,
The plate temperature 30 seconds after the next tension control timing (next tension control timing) may be estimated and used as the estimated plate temperature value T _f .

Next, the setting of the heat scratch control temperature will be described. The minimum plate temperature at which heat scratches occur is determined in advance by an experiment in which the work roll speed, the rolling reduction, the rolling lubrication conditions, etc. are changed, and this is set as the limit temperature T _Lim . This limit temperature is set to the heat scratch control target temperature T
May be _L, it is preferable to set the heat scratch control target temperature T _L is the limit temperature T slightly lower temperature than _Lim described above, for example 3 to 6 ° C. temperature lower by about, the.

As described above, in the rolling stand where heat scratch is likely to occur, that is, the fourth stand in the embodiment, the estimated value T _{f of the} strip temperature on the delivery side is compared with the above-mentioned heat scratch control target temperature T _L. , ΔT = T _L −T _f
Is positive, there is no possibility of heat scratching, so rolling is continued, and if ΔT = _TL - _Tf is a negative value, heat scratching may occur, so ΔT is positive. Rolling is performed by changing the tension condition so that The method of calculating the changed tension will be described below.

First, the coefficient of friction μ during rolling and the deformation resistance K _m
Ask for. For the deformation resistance of the rolled material, the values of the constants a, ε ₀ , and n shown in equation (1) are obtained in advance by a tensile test.

[0016]

[Equation 1]

Here, σ _y is the yield stress of the rolled material during simple tension, and ε is the strain. By the way, since the deformation resistance is affected by the strain rate and the plate temperature, the deformation resistance K _m obtained from the equation (1) is not always an accurate value during rolling. In view of this, in the present invention, the rolling load equation and the advanced rate equation are combined to obtain the deformation resistance and the friction coefficient during rolling. For example, the deformation resistance is Hil shown in the equation (2).
1 is the load equation, and the friction coefficient is Blan shown in equation (3).
An expression obtained by expanding the advanced rate expression of d & Ford into deformation resistance and friction coefficient is used. In the formula, the subscript E is a detected value at the time of rolling of the rolling stand and a calculated value based on the detected value, and in the following description, these will be referred to as an actually measured value.

[0018]

[Equation 2]

The unknowns in the above equation are the friction coefficient μ _E and the constant a in the deformation resistance equation K _mE , and the others are known numbers and the number of equations is 2. Therefore this equation can be solved. In the calculation, the initial value of the friction coefficient μ _E is 0.
It is preferable that the value obtained by the tensile test is used as the initial value of the constant a in the deformation resistance formula of about 05.

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 the equation (4) using the equation of Ono et al. T ′ = T _dmax + T _fmax (4) T _dmax is the temperature increase at the interface between the roll at the exit of the roll bite and the rolled material, which is increased by deformation heat and is expressed by equation (5), and T _fmax is increased by frictional heat. It is the temperature rise at the interface between the roll at the exit of the roll bite and the rolled material and is expressed by equation (6).

[0021]

[Equation 3]

The corresponding rolling in each of the formulas (4) to (5)
Physical property value of the stand, measured value and the above-mentioned formula (2), formula
Friction coefficient μ obtained by the method using (3)_EAnd strange
Form resistance K _mEIf you substitute
Of temperature rise T'at the interface between the roll at the outlet and the rolled material
Value T_E′ Is obtained. Next, the temperature change when the tension is changed
In order to estimate the_EAnd transformation
Resistance K_mEExcept for tension and tension, the measured values of the rolling stand are used.
Calculate the rolling load and advance rate when only the tension is changed
It When changing the tension, the relationship between the outlet tension and the inlet tension
Need to be specified. For example, the output side tension and the input side tension are
Increase by the same value, or increase the tension on the outlet side
A relationship such as 50% of the increase in side tension is specified.

The rolling load is, for example, Hill expressed by the equation (7).
The load formula of the formula, and the advanced rate is shown in Formula (8): Brand & Fo
Hitchc shown in rd formula and roll flatness in formula (9)
It is calculated using the Look equation.

[0024]

[Equation 4]

The rolling load is obtained by performing a convergent calculation using the equation (7) and the roll flattening equation (9), and the advance rate is obtained from the equation (8). By substituting these values into the formulas (4) to (6), the temperature rise T _m ′ at the interface between the roll at the roll bite exit and the rolled material when the tension condition is changed can be obtained. That is, the measured value T _E ′ of the temperature rise at the interface between the roll bite exit roll and the rolled material in the rolling stand and the temperature rise between the roll bite exit roll and the rolled material when the tension is changed. An estimate T _m ′ is obtained. Although the temperature of the interface between the roll and the rolled material at the exit of the roll bite is not exactly the same as the plate temperature at the exit side of the rolling stand, it can be considered that the temperature change is the same when the tension condition is changed. Therefore, this T _m ′ and T
The difference from _E ′ ΔT ′ = T _m ′ −T _E ′,
By comparing the difference ΔL = T _L −T _f between _L and T _f , the tension condition such that ΔT ′ is ΔT or less (ΔT ′ ≦ ΔT) can be obtained by iterative calculation using, for example, the Newton method. The tension set value of the rolling mill is changed accordingly. It is possible to obtain several tension values that do not cause heat scratches that satisfy the above relationship, so you can select an appropriate tension value from among them, depending on the rolling situation. It is desirable to select the tension values (σ _baim , σ _faim ) and change the tension setting value of the rolling stand accordingly.

Further, the tension σ thus obtained is_baim，
σ_faimIf there is a large tension, the plate will break in advance.
Maximum tension on the entry and exit sides of the stand
σ_bmax, Σ _fmaxAnd set σ above_baimIs σ_bmaxYo
Is greater than or_faimIs σ_fmaxGreater than
Or σ_baim, Σ_faimBoth are σ_bmax, Σ_fmax
Greater than, the temperature at which heat scratch occurs
Ascent combined with tension and work roll speed respectively
It can be controlled.

First, the tension of the _rolling stand σ _baim , σ
_faim is sigma _bmax, it sets the tension in the direction which exceeds σ _fmax σ _bmax, or below sigma _fmax. The measured value T of the temperature rise at the interface of the roll bite outlet in the rolling state under the set tension
Seeking _E ', it is possible to obtain further temperature increase T _m "of the interface between roll and rolling material of the roll bite outlet of the rolling stand of changing only the work roll speed in the same manner as described above .T _m Difference between ″ and T _E ′ ΔT ″ = T _m ″ −
The difference ΔT = T _L − between T _E and the above-mentioned T _L and T _f
By comparing with T _f , the work roll speed condition such that ΔT ″ is ΔT or less (ΔT ″ ≦ ΔT) can be obtained by iterative calculation using, for example, the Newton method,
According to this, the tension set value and the work roll speed set value of the rolling mill are changed. By thus performing the tension control and the work roll speed control together, heat scratches can be prevented in a wide range.

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

[0029]

【Example】

<Example 1> The cold tandem rolling mill used was a tandem rolling mill consisting of the same four stands as shown in Fig. 1, and the rolling conditions of the fourth stand as a rolling stand where heat scratch occurs are shown below. .

Work roll diameter (D): φ480 mm Work roll speed (V _R ): 300 m · min ⁻¹ Inlet tension (σ _bS ): 10 kgf · mm ^-2 Outlet tension (σ _fs ): 5 kgf · mm ^-2 Inlet plate thickness (H): 0.84 mm Outlet plate thickness (h): 0.60 mm Plate width (W): 988 mm Material plate thickness (H _S ): 3.2 mm Material: Low carbon steel σ _y = 67 (ε + 0. 0
3) ^0.2 kgf ・ mm ^-2 Rolling lubrication: 2% beef tallow emulsion (60 ° C) When operating a large number of coils of the same size under the same rolling conditions, the average temperature of the work rolls increases. , The plate temperature on the exit side of the 4th stand rises. It is known from the operation data so far that heat scratches frequently occur when the plate temperature on the delivery side of the fourth stand is 173 ° C. or higher. Then, the present invention was applied and the effect was experimentally investigated.

The limit temperature T _Lim, which is the lowest plate temperature at which the heat scratch is generated, which is previously obtained by an experiment, is 1
73 ° C., and the heat scratch control target temperature is T _L =
It was set to 173-4 = 169 degreeC. In addition, the tension control cycle is 30 seconds, the sampling time is 5 seconds, the data of 30 seconds (6 pieces) during that time is linearly regressed, the plate temperature after 30 seconds is calculated, and this is estimated value T _{f of the} plate temperature. And

As a prescribed condition of the tension, the entrance side tension σ _b =
σ _bs + α and outlet tension σ _f = σ _fs + α / 10. In addition, the maximum value of the tension on the inlet and outlet sides (σ _bmax , σ _fmax ) that does not cause plate breakage is (40 kgf ・ mm ^-2 , 10 kg
f · mm ^-2 ). FIG. 2 is a diagram showing the effect of claim 1 of the present invention, FIG. 2 (a) shows the relationship between the number of rolling coils and the plate temperature on the delivery side of the fourth stand, and FIG. 2 (b) is the number of rolling coils. And the tension of the 4th stand entrance side are shown, respectively. The □ in Fig. 2 indicates the case of the conventional rolling method.
The circles in the figure show the cases when the present invention was applied. In the conventional rolling method, the estimated value of the plate temperature is 169 when the number of coils is 21.
The work roll speed was reduced to 250 m · min ⁻¹ , and there was a risk that heat scratches would occur, and the operation was carried out. But by applying the present invention, the plate temperature at the coil number 90 present ultimately inlet side tension is changed tension condition from the coil number 22 knots is is controlled from 10 kgf · mm ^-2 to 21 kgf · mm ^-2 169 The rolling was performed without increasing the temperature to above 0 ° C. and without reducing the work roll speed, and naturally, heat scratch did not occur. <Example 2> Further, in order to investigate the effect of claim 2 of the present invention, an experiment was conducted under the same rolling mill and rolling conditions as in Example 1. At this time, the prescribed condition for the tension is that the entry side tension σ
_b = σ _bs + α, outlet tension σ _f = σ _fS + α / 10, and the maximum values of inlet and outlet tension (σ _bmax , σ _fmax ) at which plate breakage does not occur are (15 kgf · mm ^-2 , 10kg
f ・ mm ^-2 ).

FIG. 3 is a diagram showing the effect of claim 2 of the present invention. FIG. 3 (a) is a relation between the number of rolling coils and the entry side tension of the fourth stand, and FIG. 3 (b) is a rolling coil. The relationship between the number of workpieces and the work roll speed of the fourth stand is shown respectively. □ in Fig. 2 indicates the case of the conventional rolling method, and ● in Fig. 2
Shows the case when the present invention is applied. In the conventional rolling method, the estimated value of the plate temperature is 169 ° C. or higher when the number of coils is 21, and there is a risk of heat scratch, so the work roll speed was reduced to 250 m · min ⁻¹ for operation. However, by applying the present invention, the tension condition was changed from the 22nd coil number, and finally the inlet side tension was controlled from 10 kgf · mm ⁻² to 15 kgf · mm ^−2. Side tension is 15 kgf ・ mm
^-2 or more, which is greater than the maximum value of the tension on the inlet side where plate breakage does not occur, so the work roll speed is changed and the work roll speed is changed while the tension on the inlet side is kept at 15 kgf ・ mm ^-2. Roll speed is 300m ・ min ^-1 to 268m
・ The plate temperature is 16 even if the number of coils is 90 and controlled to min ^-1.
Rolling did not occur at 9 ° C or higher, and naturally, heat scratch did not occur.

As described above, by applying the present invention, it is possible to achieve high productivity and perform cold tandem rolling without heat scratch.

[0035]

According to the first aspect of the present invention, when the estimated value of the strip temperature on the outlet side exceeds the preset heat scratch control target temperature in the stand of the cold tandem rolling mill where heat scratch is likely to occur. The temperature rise of the roll bite outlet of the stand and the interface of the rolled material with the roll and the temperature rise when the tension is changed are estimated, and this difference is
Estimate the tension that is smaller than the difference between the estimated plate temperature on the stand exit side and the control target temperature so that the temperature rise at the interface between the roll at the roll bite exit and the rolled material is below the temperature at which heat scratch occurs. Since the tension is controlled to the above, the occurrence of heat scratch can be efficiently prevented.

Further, according to the second aspect of the present invention, when the estimated value of the tension for preventing heat scratch exceeds the predetermined maximum value of the tension, the tension and the rolling speed are controlled in combination. Thus, it is possible to prevent the occurrence of heat scratch.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a cold tandem rolling mill to which the method of the present invention is applied.

FIG. 2 is a diagram for explaining the effect of the method of the present invention,
(A) is a figure which shows the relationship between the number of rolling coils and plate temperature, (b) is a figure which shows the relationship between the number of rolling coils and entrance side tension.

FIG. 3 is a diagram for explaining the effect of the method of the present invention,
(A) is a figure which shows the relationship between the number of rolling coils and an entrance side tension, (b) is a figure which shows the relationship between the number of rolling coils and a work roll speed.

[Explanation of symbols]

1 ... Plate temperature detector 2… Rolled material 3 ... Load cell 4,4 '... Deflector roll 5, 5 '... Plate thickness detector 6 ... Plate speed detector

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI B21B 37/76 B21B 37/10 BBP (56) References JP-A-5-138224 (JP, A) (58) Fields investigated (58) Int.Cl. ⁷ , DB name) B21B 37/48 B21B 37/00 B21B 37/46 B21B 37/74 B21B 37/76

Claims (2)

(57) [Claims] 1. In a rolling stand of a cold tandem rolling mill where heat scratches are likely to occur, strip temperature, rolling load, work roll speed, strip exit side strip speed, stand entry side and exit of the rolling stand. Side sheet thickness, stand entrance side and stand side tension is detected or calculated from these detected values, and the rolling stand in the steady state or the rolling state at the next tension control timing is detected from the sheet temperature detection value on the rolling stand exit side. The strip temperature T _f on the delivery side is estimated, and when the estimated strip temperature exceeds a predetermined heat scratch control target temperature T _L , the strip temperature on the delivery side of the rolling stand, the rolling load, the work roll speed, Plate speed at stand-out side, plate thickness at stand-in side and stand-out side, detected values of tension at stand-in side and stand-out side and calculated values from these detected values, and these detected values Using the coefficient of friction and deformation resistance of the rolling stand which is determined from the preliminary calculation value, a temperature rise T _E 'of the interface between the rolled material and the rolls of the roll bite outlet of the rolling stand in the rolling condition was changed tension In this case, the temperature rise T _m ′ at the interface between the rolled material at the roll bite outlet of the rolling stand and the roll is determined, and _TL −T _f ≧
T _m determined tension to be '-T _E', cold rolling method of a tandem rolling mill, characterized by controlling the tension of the rolling stand on the basis of this tension. 2. In a rolling stand of a cold tandem rolling mill where heat scratches are likely to occur, the strip temperature, rolling load, work roll speed, strip exit side strip speed, stand inlet side and outlet side of the rolling stand. Side sheet thickness, stand entrance side and stand side tension is detected or calculated from these detected values, and the rolling stand in the steady state or the rolling state at the next tension control timing is detected from the sheet temperature detection value on the rolling stand exit side. The strip temperature T _f on the delivery side is estimated, and when the estimated strip temperature exceeds a predetermined heat scratch control target temperature T _L , the strip temperature on the delivery side of the rolling stand, the rolling load, the work roll speed, Plate speed at stand-out side, plate thickness at stand-in side and stand-out side, detected values of tension at stand-in side and stand-out side and calculated values from these detected values, and these detected values Using the coefficient of friction and deformation resistance of the rolling stand which is determined from the preliminary calculation value, a temperature rise T _E 'of the interface between the rolled material and the rolls of the roll bite outlet of the rolling stand in the rolling condition was changed tension In this case, the temperature rise T _m ′ at the interface between the rolled material at the roll bite outlet of the rolling stand and the roll is determined, and _TL −T _f ≧
The tension which is T _m ′ −T _E ′ is obtained, and when this tension exceeds the maximum tension σ _{bmax on the} rolling stand entrance side or the maximum tension σ _fmax on the rolling stand side that does not cause a predetermined plate break in the rolling stand. , The tension in the rolling stand is set to be equal to or lower than the maximum tension σ _{bmax at the} rolling stand entrance side or the maximum tension σ _{fmax at the} exit side at which a predetermined plate break does not occur, and the work roll speed at the set tension state. When the temperature rise T _m ″ at the interface between the rolled material at the roll bite outlet of the rolling stand and the roll is changed, the work roll speed that satisfies T _L −T _f ≧ T _m ″ −T _E ′ is obtained. A rolling method for a cold tandem rolling mill, characterized in that the work roll speed of the rolling stand is controlled based on the work roll speed.