JPH10137828A - Cold tandem rolling method and cold tandem rolling mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously prevent a heat scratch and a plate breaking and to manufacture a steel plate having an excellent plate width precision by controlling a shape controller so that a plate width variable quantity does not exceed the pre-determined allowable value of the late width variable quantity, applying the rolling tension of the specified % or above of the deforming resistance of a rolling stock in at least the final stand and then rolling. SOLUTION: The rolling stock is rolled under the tension of e.g. 30-40% or above of the deforming resistance of the rolling stock, and the plate width of the rolling stock is detected with plate width measuring devices 6a, 6e in the inlet and outlet sides of a tandem rolling mill. The cumulative value of the plate width variation in a first to fourth stands is calculated with an operation processor 8 from the detected plate width in the inlet and outlet sides of the tandem rolling mill. When this value exceeds the allowable value wherein the plate breaking is possibly generated in the tandem rolling mill, the plate width correcting quantity to be corrected is calculated, the stand wherein the plate breaking is possibly generated is specified, and the plate width is preferentially controlled with shape controllers 4a-4d.

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 four or more cold rolling mills, which is capable of realizing high productivity, reducing manufacturing costs and improving dimensional accuracy. It relates to the rolling method.

[0002]

2. Description of the Related Art In order to increase the productivity of existing cold tandem rolling mills or to reduce the manufacturing cost thereof, the rolling speed of cold tandem rolling mills is increased or the rolling schedule is optimized. A method was considered. When the rolling speed is increased, heat scratch occurs. The heat scratch is a seizure flaw caused by a metal contact between a work roll and a rolled material, which is generated as a result of an increase in the interface temperature in the roll bite and an oil film break in the roll bite. When heat scratches occur, the surface defects of the products occur, so that not only the product yield decreases, but also because the work rolls of the rolling stand in which the heat scratches occur need to be replaced, the productivity significantly decreases.

As a conventional technique for preventing such heat scratch, for example, a method using a rolling lubricating oil having excellent seizure resistance as disclosed in Japanese Patent Application Laid-Open No. 5-98283, and Japanese Patent Application Laid-Open No. Japanese Patent Application Laid-Open No. Hei 6-63624 discloses a method of controlling the amount of coolant to lower the temperature of a plate or a work roll as disclosed in JP-A-111505.
In general, a method of reducing the rolling speed as disclosed in Japanese Patent Application Laid-Open Publication No. H10-209,004 is known.

Further, as described above, Japanese Patent Application Laid-Open No. 55-111961 discloses a method for preventing heat scratch without increasing production cost and reducing productivity by using a special rolling oil or reducing a rolling speed. As disclosed in the official gazette, there is disclosed a method for setting a rolling pattern that minimizes the total rolling power consumed in the rolling of a tandem rolling mill, and a method disclosed in
As disclosed in Japanese Patent No. 9802, there is a method of increasing heat tension between stands, lowering rolling pressure, and reducing frictional heat generation to prevent heat scratch.

[0005] Conventionally, the fluctuation of the sheet width in cold rolling is as follows.
Since it is smaller than hot rolling, a width gauge is provided on the inlet and outlet sides of the rolling mill as in hot rolling, and the tension etc. is changed based on the output result of the width gauge, and the sheet width is actively increased. There was little control.

[0006]

However, in the above-described method of changing the pressing pattern in the conventional method, there is a problem that the plate accuracy is temporarily deteriorated, and in the case of the method of increasing the tension between stands, The effect of preventing heat scratches increases with the increase in tension, but on the other hand, since the tension level is high, the tension applied to the local area of the plate such as the plate edge due to the change in tension distribution also increases, so that the plate tends to break. Or, in the case of a high tension, there is a problem that the width of the plate becomes large and the width of the plate becomes large, thereby deteriorating the width of the plate. Had limitations.

First, the present inventors, as a method of increasing the tension between stands in the conventional method, use the output of one output coiler or the sum of the outputs of one output coiler and output bridle roll as the final value. By making the output of the main motor of the rolling mill of the stand 35% or more or 50% or more, high tension rolling in which a rolling tension of 30% or more, preferably 40% or more of the deformation resistance of the rolled material is applied in the final stand. A cold tandem rolling mill and a rolling method for the same have been proposed, which make it feasible, thereby preventing the occurrence of heat scratch, and realizing stable high tension rolling without breaking the sheet.

That is, the main cause of the heat scratch in the cold rolling is a rise in the temperature of the interface between the roll and the rolled material in the roll bite, and this rise in the temperature is caused by the heat generated during processing and the heat generated by friction. There are things to do. As the rolling load decreases, the frictional heating value decreases as the frictional shearing force decreases. Since the rolling load can be reduced by increasing the tension, increasing the tension
This lowers the interface temperature inside the roll bite, which is an effective means for preventing heat scratch.

Here, a tension load ratio κ (tension / deformation resistance of the rolled material), which is an index representing the level of tension on the entrance side and the exit side of the rolling stand, is defined. That is, assuming that the tension load ratio between the entrance side and the exit side of the rolling stand is κ _b and κ _f , the entrance side tension σ _b and the exit side tension σ _f in the rolling stand are the rolling stand obtained from the tensile test of the rolled material. The value obtained by multiplying the 0.2% proof stress σ _yi and σ _yo of the rolled material on the entrance side and the exit side by the above-mentioned tension load ratio, that is, σ _b = κ _b
σ _yi , σ _f = κ _f σ _yo In the following description, when the tension load ratio or κ is described, the tension load ratio or κ includes both the tension load ratios κ _b and κ _f on the entrance side and the exit side of the rolling stand.

FIG. 7 shows the effect of the tension load ratio κ on the rolling load ratio [rolling load during tensionless rolling (κ = 0) is set to 1] obtained from an experiment when the tension load ratio is changed. Things. FIG. 8 shows the wear amount of the work roll under the same rolling conditions as shown in FIG.
Of the tensile load ratio κ on the weight of the work roll after rotating about 100,000 times from the weight of the work roll before the experiment) [The amount of wear during tensionless rolling (κ = 0) is used as the wear resistance. 1].

From FIG. 7 and FIG. 8, the larger the tension load ratio κ, the smaller the pressure and the contact arc length in the roll bite. Therefore, the effect of the tension load ratio on the rolling load ratio and wear resistance is large. Was revealed. FIG. 9 shows the effect of the tension load ratio κ on the surface defect occurrence ratio of a product that occurs when heat scratches or the like occur (the surface defect occurrence ratio during tensionless rolling (κ = 0) is set to 1). FIG.
Accordingly, the surface defect occurrence rate decreases as the tension load ratio κ increases, and after the tension load ratio κ = about 0.3,
It became clear that no surface defects occurred.

From the above, the tension load ratio κ is 0.3 or more, preferably 0.4 or more, that is, the tension is 30% or more of the deformation resistance of the rolled material on the entrance and exit sides of the rolling stand.
It is preferable to apply an ingress and egress tension of 40% or more. As a result, rolling can be performed without generating heat scratches and the like, and the rolling load can be reduced, and rolling that ensures wear resistance that can maintain the roughness of the work roll surface for a long period of time can be performed.

The tension load ratio may be set for each stand as described above, but may be set only for a rolling stand where heat scratches and the like are likely to occur. In particular, at the final rolling stand where the rolling speed is the fastest, heat scratches and the like are likely to occur. Therefore, at least in the final rolling stand, the tension load ratio κ is set to 0.3 or more, preferably 0.4 or more. desirable.

Next, a cold tandem rolling mill for realizing the above-described rolling method will be described. In the existing tandem rolling mill, the rolling speed at the normal operation level (1000 to 20) is used.
00 m · min ⁻¹ ), the output of the main motor of one coiler on the exit side of the final stand is small, so that the tension level on the exit side of the final stand cannot be increased. In the present circumstances,
The output of one exit-side coiler or the sum of one exit-side coiler and the main motor of the exit-side bridle roll has a product thickness of 0.
In the case of a thick cold tandem rolling mill in which products of 6 mm or more account for 50% or more of the total production, the output of the main motor of the rolling mill at the final stand is 47% or less, and the product sheet thickness is 0.
In cold tandem rolling mills, in which thin products of less than 6 mm account for more than 50% of the total production, the output is less than 32% of the output of the main motor of the rolling mill in the final stand. Therefore, when rolling low carbon steel, the tension level at the exit side of the final stand is usually 5 to 5.
It is about 10kgf · mm ^-2 . In the case of low carbon steel, deformation resistance is 60-70kgf due to work hardening near the final stand
・ Because it is about mm- ² , the above tension level is 7
It is a low value of about 17%.

Therefore, in order to make the tension load ratio κ 0.3 or more, preferably 0.4 or more in the final rolling stand, the output of the main motor of the final stand and the output of the main motor of the coiler system or the coiler system are required. It is necessary to optimize the total output of the bridle roll main motor. For that purpose, first, it is necessary to seek the work performed by the rolling mill and the work performed by the coiler system, that is, the work performed by the coiler alone or the bridle roll.

[0016] Therefore, comparing the ratio of the work W _M that work W _c and rolling mill coiler system is formed by forming a unit time. Work W _M of the rolling mill forms a unit time is represented by (1). _{W M = TV 0 / {R} (1 + f S)} (1) where, R represents a roll radius, V ₀ is delivery side speed of the rolling stand, T is, the rolling torque (upper and lower rolls two pins), for example, Calculated by Hill's formula, f _S is the advanced ratio, for example, calculated using the Brand & Ford formula.

The work W _c formed by the coiler system, that is, the coiler alone or the coiler and the bridle roll is represented by the following equation (2). W _c = V ₀ κ σ _y h′b (2) where h ′ is the exit side plate thickness, b is the plate width, σ _y is the 0.2% proof stress, and the strain ε of the following equation (3) is 0.002. Is required. σ _y (ε) = a (ε + ε ₀ ) ⁿ (3) Here, a, ε ₀ , and n are constants, which are obtained from experimental results of a tensile test performed in advance.

[0018] A 1 representative calculation results work W _c and rolling mill coiler system forms were compared to calculate the work W _M constituting the unit time table.

[0019]

[Table 1]

In Table 1, the product thickness is rolled to less than 0.6 mm.
Thin and rolled to a thickness of 0.6 mm or more
The rolling conditions of the final stand of the system were assumed. However, deformation
The constant of equation (3) representing the resistance is obtained in advance by a tensile test.
Value, a = 67kgf · mm^-2, Ε₀= 0.03, n =
0.2, coefficient of friction at the last cold rolling stand
Typical friction coefficient μ obtained under normal rolling conditions
= 0.05 was used. Note that the roll radius R in Table 1 is
Used in the final stand of the usual cold tandem rolling mill
Roll radius, rolling load P,
Kroll speed V _R, Material thickness H_ThreeIs normal cold tande
The values in the range of typical rolling conditions in
You.

As described above, in order to perform stable cold tandem rolling, the tension application ratio κ needs to be 0.3 or more.
To do this, as can be seen from Table 1 (which shows the ratio of the work W _{O performed by the} coiler system per unit time to the work W _{M performed by} the final stand rolling mill per unit time), the work of the coiler system is the product Cold tandem rolling mills that produce products with a thickness of 0.6 mm are more than 50% of the work of the rolling mill at the final stand. Cold tandem rolling that produces thin products with a product thickness of 0.2 mm It can be seen that the mill requires 35% or more of the work of the final stand rolling mill. That is, the output of the main motor of the coiler system is 50% or more of the main motor of the rolling mill in the final stand in a cold tandem rolling mill for producing a product having a product thickness of 0.6 mm. In a cold tandem rolling mill for producing a thin product of 2 mm, 35% or more of the output of the main motor of the rolling mill in the final stand is required.

Instead of generating a large tension only by the output coiler, a bridle roll for tension load may be installed between the final stand and the output coiler in consideration of switching of the coiler. In this case, the exit coiler 1
It suffices that the total output of the base and the outgoing bridle roll satisfies the above condition. Summarizing the above using the parameter average plate thickness h, the sum of the output of the main motor of one output coiler or the output of the main motor of the output bridle roll of one output coiler is W _c , When the output of the main motor of the rolling mill is W _M , W _c ≧ (0.375h + 0.
275) can be seen W is required tandem cold rolling mill is _M.

At this time, as described above, the total rolling tension (the value obtained by multiplying the rolling tension by the sheet thickness and the sheet width) is set to the same value at the entrance and the exit of the rolling mill, so that the rolling mill has an excess. Since no load (including mechanical loss) is applied and the unit power consumption is improved, it is preferable to equalize the total rolling tension at the entrance and exit of the rolling mill. As described above, the output of one outgoing coiler or the sum of the output of one outgoing coiler and the outgoing bridle roll should be 35% or more or 50% or more of the output of the main motor of the rolling mill in the final stand. This makes it possible to realize high tension rolling in which a rolling tension of 30% or more, preferably 40% or more of the deformation resistance of the rolled material is applied in the final stand, thereby preventing the occurrence of heat scratch.

However, the tension is reduced to 30% of the deformation resistance.
If it is 40% or more, the tensile stress level at the end of the plate increases, so that the plate is easily broken. Particularly, in the case of rolling a note rim material, minute cracks are apt to be formed at the edge of the plate, so that the plate is more easily broken. Therefore, in order to prevent heat scratch and plate breakage at the same time, high tension rolling with a tension of 30% to 40% or more of the deformation resistance is performed, and excessive tension at the plate edge is applied. It is necessary to control the tension distribution to prevent the plate from breaking.

[0025]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems of the conventional method. The first aspect of the present invention is to provide a cold rolling mill having a shape control device. In a cold tandem rolling mill having a stand or more, the sheet width of the rolled material is measured on the entrance side and the exit side of the tandem rolling mill, and from the sheet width measurement value, the sheet width change amount on the entrance side and the exit side of the tandem rolling mill is calculated. Calculate and control the shape control device so that the amount of change in the width of the sheet does not exceed a predetermined allowable value of the amount of change in the width of the sheet, and apply a rolling tension of 30% or more of the deformation resistance of the rolled material at least in the final stand. A cold tandem rolling method characterized by rolling under load.

A second aspect of the present invention relates to a cold tandem rolling mill having four or more cold rolling mills provided with a shape control device, wherein at least one or more stands between the entrance side, the exit side of the tandem rolling mill and the tandem rolling mill are provided. Measure the width of the rolled material on the delivery side of the rolling mill and measure the delivery width between the first stand of the tandem rolling mill and the stand on the more upstream side where the delivery width is measured between the tandem rolling mills. Between the stand adjacent to the downstream of the stand on the more upstream side and the stand on which the outlet plate width is measured downstream and more upstream than the stand on the upstream side where the outlet plate width is measured, and the outlet plate width The stand section is formed sequentially between the last stand and the stand adjacent to the downstream of the stand on the most downstream side where the measurement was performed.From the above measurement results, the board width change The shape controller is controlled so that the width change of the stand section does not exceed the allowable width change amount predetermined for each stand section, and at least 30% of the deformation resistance of the rolled material is calculated. % Is a rolling method in which rolling is performed by applying a rolling tension of at least%.

In a third aspect of the present invention, there is provided a cold tandem rolling mill having four or more cold rolling mills provided with a shape control device, wherein a rolled material is provided at an inlet side of the tandem rolling mill and at an outlet side of each rolling mill of the tandem rolling mill. From the measured width, the change in the width of the sheet at the entrance and the exit of each rolling mill of the tandem rolling mill is calculated. The shape controller is controlled so as not to exceed the predetermined allowable value of the width change amount on the entrance side and the exit side of the machine, and a tension of 30% or more of the deformation resistance of the rolled material is applied at least in the final stand. This is a cold tandem rolling method characterized by rolling.

According to a fourth aspect of the present invention, there is provided a cold tandem rolling mill having four or more cold rolling mills each provided with a shape control device, wherein the tandem rolling mill has a sheet width on at least an entrance side and an exit side. A cold tandem rolling mill comprising a measuring device. According to a fifth aspect of the present invention, there is provided the cold tandem rolling mill according to the fourth aspect, wherein a sheet width measuring device is provided at at least one position between the rolling mills of the cold tandem rolling mill.

A sixth aspect of the present invention has a coiler or a coiler and a bridle roll on the output side of the cold tandem rolling mill. The output of one main motor of the coiler or the output of one main motor of the coiler and the bridle are provided. The total output of the output of the main motor of the roll, the output of the main motor of the final stand of the cold tandem rolling mill, and the average sheet thickness of the product rolled by this cold tandem rolling mill satisfy the following relationship. The cold tandem rolling mill according to claim 4 or 5, characterized in that:

W _c ≧ (0.375h + 0.275) W _M where W _{c is} the output of one main motor of the coiler or the total output of the output of one main motor of the coiler and the output of the main motor of the bridle roll. W _M : output of the main motor of the final stand of the cold tandem rolling mill h: average thickness of the product rolled by the cold tandem rolling mill

[0031]

Accordingly, the present invention is to prevent the breakage of the sheet by controlling the tension distribution by measuring and controlling the sheet width. Hereinafter, the method of the present invention will be described. First, regarding the mechanism of plate width change, which is the basic principle of the present invention, a plate rolling analysis system (3)
An explanation will be given based on the knowledge obtained from the results of analysis using an analysis system in which a plate deformation analysis by a two-dimensional rigid-plastic FEM and a general-purpose roll deformation analysis by a split model are coupled.

FIGS. 4 and 5 show the vicinity of the roll bite entrance and the roll bite calculated by changing the shape control device of the rolling mill (here, a work roll bending device is provided and the roll bending force is changed). Among them, the change in the plate width near the roll tool outlet and the change in the tension in the width direction at the roll tool outlet are shown. Here, the three areas near the roll bite entrance, inside the roll bite, and near the roll bite exit will be simply expressed as the roll bite neighborhood. From these figures, it can be seen that when a bending force is applied to the decrees side (the shape is the end extension side: F <0), the width spread amount near the roll bite increases, and the tension distribution is 100 mm from the plate edge. It can be seen that the tension in the degree region has decreased. On the other hand, when a bending force is applied to the increase side (the shape has a middle elongation side: F> 0), the sheet width decreases near the roll bite, and the tension distribution is reduced from the end of the sheet. 10
It can be seen that the tension in the region of about 0 mm has increased. As described above, the change in the plate width in the vicinity of the roll bite tends to decrease (width reduction) as the tension at the plate edge increases, and increase (width expansion) as the tension at the plate edge decreases. Assuming that the average tension at the end of the plate in the range of l _e = 50 mm from the end of the plate is σ ′ and the amount of change in the width of the plate near the roll bite is ΔW, the relationship between σ ′ and ΔW is as shown in FIG. It can be seen that it changes depending on the rolling conditions (contact arc length l _d ). Therefore, the sheet width change ΔW near the roll bite
Can be expressed as a function of σ ′, l _d as follows: ΔW = ΔW (σ ′, l _d ) (4) Further, the average tension σ ′ at the edge of the sheet is calculated by the rolling condition, that is,
It varies depending on the roll bending force F, the average tension σ _b , σ _f per unit cross-sectional area on the entrance and exit sides of the stand, the exit side plate thickness h ′, the plate width W, and the contact arc length l _d . Can be expressed as σ ′ = σ ′ (F, σ _b , σ _f , h ′, W, l _d ) (5) Thus, the change in the sheet width, the tension at the end of the sheet, and the rolling conditions (roll bending force, average tension, etc.) Equation (4)
Since there is a relationship as in (5), in the present invention, the plate width is used as a detection end, and the variation of the tension is replaced with the plate width variation.
By controlling the plate width, it is intended to prevent heat scratches and breakage of the plate. That is, the average tension σ ′ of the plate edge at the limit where the plate does not break is
_Assuming that σ ′ _lim , the allowable plate width change ΔW _lim is determined from Equation (4) based on σ ′ _lim , the change in the plate width is observed, and the plate width decreases so as to exceed the allowable plate width change ΔW _lim. The roll width bending force F or the average entrance and exit side tensions σ _b and σ _f are determined from Equation (5) on the basis of the plate width control amount and the operation amount of the shape controller based on the plate width control amount,
By performing control based on this, it is possible to prevent the plate from being broken due to excessive tension being applied to the plate end. The average tension of the plate end portion of the limit sigma _{'li m}
Is preferably set to a value smaller than the breaking stress of the rolled material (smaller by 5 to 10 kgf · mm ⁻² ) obtained in advance in the tensile test. In this control, it is more preferable to change the tension distribution in the width direction by manipulating the roll bending force or the like than to reduce the tension on the entrance side and the tension on the exit side, in order to maintain high productivity.

In Equation (5), for simplicity of explanation, only the bending force in the roll bending device is considered as the shape control device, but the roll cross device, the roll axial shift device, and the roll profile control device are considered. The relationship between the operation amount and the plate width change amount is obtained in advance, the plate width change amount that is equal to or less than a predetermined tension is obtained, and the tension including the tension distribution can be controlled so as to be equal to or less than the width change amount. Needless to say, some of these shape control devices can be used together to control the tension, and these shape control devices can be used instead of the roll bending force.

Next, the present invention will be described in detail with reference to FIG. FIG. 1 shows a cold tandem rolling mill including four stands, in which a rolled material 1 is rolled. The rolling mill of each stand is a four-high rolling mill, and the work rolls 2a to 2
d, a four-high rolling mill including backup rolls 3a to 3d and shape control devices 4a to 4d, and an arithmetic processing unit 8. The entrance side and exit side of the tandem rolling mill include an entrance side coiler 5a, an exit side coiler 5b, and an entrance side sheet width measuring device 6a.
In addition, a delivery side plate width measuring device 6b is provided.

In the cold tandem rolling mill of the present invention,
As shown in FIG. 1, it may be provided at least on the entry side and the exit side of the tandem cold rolling mill. However, as will be described later, it is preferable to provide it between arbitrary stands of the tandem rolling mill. Further, in this example, the main motor of the exit side coiler 5b has an output of 50% or more of the output of the main motor of the rolling mill in the final stand, and the tension between the stands is 30% of the deformation resistance of the rolled material. % To 40% or more of the rolling tension.

In such a cold tandem rolling mill,
The rolled material 1 is rolled by applying a tension of 30% to 40% or more of the deformation resistance of the rolled material, and at the entrance side and the exit side of the tandem rolling mill, the strip width measurement devices 6a and 6e transmit the rolled material 1 Are detected, the widths W ⁽⁰⁾ and W ⁽⁴⁾ are detected (however,
(0) indicates the tandem rolling mill entry side, and (4) indicates the number of the rolling stand). In the arithmetic processing unit 8, based on the detected sheet widths W ⁽⁰⁾ and W ⁽⁴⁾ on the entrance side and the exit side of the tandem rolling mill, the first to fourth (referred to as 1; 4; the same applies hereinafter) stand rolling. Assuming that the cumulative value of the change in the sheet width in the mill, that is, the amount of change in the sheet width in the entire tandem rolling mill is ΔW ^{(1; 4)} , ΔW
^{(1; 4)} is calculated from the following equation. ΔW ^{(1; 4)} = W ⁽⁴⁾ −W ⁽⁰⁾ (+: increase in plate width, −: decrease in plate width) (6) Further, these are generally represented as n to N (n; N). (The same applies hereinafter.) When expressed as a case of a stand rolling mill, the following expression is used. ΔW ^{(n; N)} = W ^(N) −W ^(n-1) (6 ′) where ΔW ^{(n; N)} is a change in the cumulative width between rolling mills of the nth to Nth stands, W ^{(n− 1)} : Board width on the nth stand entry side, W
^(N) : The width of the sheet on the exit side of the N-th stand The change amount of the sheet width ΔW ^{(1; 4)} is the allowable value Δ on the negative side (the sheet width decreasing side) where the sheet is likely to break in the tandem rolling mill.
When W _lim ^{(1; 4)} is exceeded, the width correction amount ΔW _c ^{(1; 4)} to be corrected in the tandem rolling mill (the correction amount to the width increasing side)
Is calculated, for example, as follows: ΔW _c ^{(1; 4)} = ΔW ^{(1; 4)} −ΔW _lim ^{(1; 4)} (7) Further, when this is generally expressed as the case of the rolling mills of the nth to Nth stands, the following expression is obtained. You. ΔW _c ^{(n; N)} = ΔW ^{(n; N)} −ΔW _lim ^{(n; N)} (7 ′) where ΔW _c ^{(n; N)} is the width correction amount in the rolling mill of the nth to Nth stands. , ΔW _lim ^{(n ; N)} : Allowable value of plate width change in rolling mills of the ^{n-th to N-} th stands. Also, allowable value ΔW _lim ^{(1; 4)} in tandem rolling mill is obtained from, for example, equation (4). obtained i-th stand in the plate width variation tolerance ^{_{ΔW lim (i) (i =}} 1~4), when the sheet width change [Delta] W i-th stand ^{(i) (i = 1~4)} , shown in FIG. 10 So that ΔW at any stand in the tandem rolling mill
⁽ⁱ⁾ If the change is only −ΔW _lim ⁽ⁱ⁾ , there is a possibility that the sheet will break, so the allowable value of the tandem rolling mill as a whole based on the minimum value of ΔW ⁽ⁱ⁾ −ΔW _lim ⁽ⁱ⁾ ΔW _lim
^{(1; 4)} is calculated as follows. ΔW _lim ^{(1; 4)} = ΔW ^{(1; 4)} −min (ΔW ⁽ⁱ⁾ −ΔW _lim ⁽ⁱ⁾ ) (i = 1 to 4) (8) where min () is the i = 1 to 1 Indicates the minimum value within 4 stands. In addition, when this is generally expressed as the case of the rolling mills of the nth to Nth stands, it is expressed by the following equation. ΔW _lim ^{(n; N)} = ΔW ^{(n; N)} −min (ΔW ⁽ⁱ⁾ −ΔW _lim ⁽ⁱ⁾ ) (i = ^{n to N} ) (8 ′) This sheet width correction amount ΔW _c ^{(1; 4) )} Based on, to identify the stand where the plate break may occur in the first to fourth stands,
By controlling the bending width or the shift amount by the stand shape control device and controlling the plate width preferentially, plate break prevention control can be realized. The control amounts such as the bending force and the shift amount of the shape control device are calculated from Expressions (4) and (5) according to the plate width correction amount ΔW _c ^{(1; 4)} . By the way, in the case of this example, since the sheet width measuring device is not provided between the stands in the tandem rolling mill, the stand to be controlled by the shape control device is specified and controlled by the following method, for example.

That is, the roll bending force F ^{(i) of} the i-th to first to fourth stands, the average tension σ _b ⁽ⁱ⁾ and σ _f ⁽ⁱ⁾ per unit cross-sectional area on the entrance and exit sides of the stand, and the thickness of the exit side plate h '
⁽ⁱ⁾ , the contact arc length l _d ⁽ⁱ⁾ is obtained from the set values and the measured values of the current rolling conditions, and from equation (5), the average tension at the plate end of the i-th stand is σ ′ ⁽ⁱ⁾ (i = 1 to 4).
Since the stand with the highest σ ′ ⁽ⁱ⁾ has a high possibility of plate breakage, this stand is specified as the stand to be controlled as the j-th stand. In this case, the absolute value W ⁽ⁱ⁾ of the plate width on the exit side of each stand is required in Expression (5), but the plate width change ΔW ⁽ⁱ⁾ of each stand is smaller than the plate width W ⁽ⁱ⁾ . Since it is minute, it is approximated that the plate width W ⁽ⁱ⁾ is constant at each stand. The plate width correction amount ΔW _c ⁽ⁱ⁾ of the j-th stand is set to ΔW _c ⁽ⁱ⁾ = ΔW _c ^{(1; 4),} and from the equations (4) and (5), the operation amount of the shape control device of the j-th stand Calculate F _c ⁽ⁱ⁾ . The shape control device of the j-th stand is operated based on the operation amount F _c ⁽ⁱ⁾ . After the operation, similarly, i = 1 to 1
The average tension at the plate end of the four stands is σ ′ ⁽ⁱ⁾ (i = 1 to
4), the j-th stand to be controlled next is specified, the operation amount of the shape control device of the j-th stand is set, and the plate width change amount ΔW ^{(1; 4)} is a negative-side allowable value ΔW _lim. ^{(1; 4) The} control by the shape control devices 4a to 4d is repeatedly performed until the value becomes the following.

Further, as described above, in addition to the sheet width measuring devices on the inlet and outlet sides of the tandem rolling mill, the sheet width measuring device is provided between the k-th and (k + 1) -th stands (1 ≦ k <4) in the tandem rolling mill. , The plate width changes ΔW ^{(1; k)} and ΔW ^{((k + 1); 4)} between the i = 1st to k-th stands and between the i = k + 1 to 4th stands can be obtained, respectively. Also,
From equation (8 ' ⁾ , the permissible value ΔW _lim ^{(1; k)} of the plate width change between the ith to k-th stands and the permissible value ΔW _lim ^{((k + 1); 4)} are obtained, and in the same manner as above, between i = 1 to k-th stand and i = k + 1 to
In each of the four stands, the stand where the possibility of plate breakage is large and the shape control devices 4a to 4d are to be operated is specified, and the allowable values ΔW _lim ^{(1; k)} and ΔW _lim ^{((k + 1); 4 )} Are controlled so as not to exceed. In this case, as compared with the above-described case, the number of stands whose plate width change is unknown is reduced by increasing the number of plate width measuring devices, so that the plate width can be controlled with higher precision.

[0039] Further, this is connected to the entrance of the first rolling mill of the tandem rolling mill, the exit of the final rolling mill of the tandem rolling mill, and any one or more rolling mills between the tandem rolling mills, for example, from the upstream side. In the following description, an example will be described in which the sheet width is measured on the outlet side of the stand, the j stand downstream of the k stand, and the m stand further downstream of the k stand. From the to the downstream side, a stand section is formed as follows.

That is, between the first stand of the tandem rolling mill and the K stand on the upstream side of the tandem rolling mill where the width of the exit side plate is measured, and between the first stand of the tandem rolling mill and the K stand on the upstream side where the width of the exit side plate is measured. Between the K + 1 stand adjacent downstream and the k stand on the more upstream side where the outlet plate width was measured, and the stand J where the outlet plate width was measured on the more upstream side, the downstream side where the outlet plate width was measured J + that is on the side and adjacent to the downstream of the J stand where the exit side plate width is measured
One stand and the m stand where the outlet plate thickness is measured on the more downstream side, and between the m + 1 stand and the final stand adjacent to the downstream side of the m stand where the outlet plate thickness is measured on the downstream side, respectively. A stand section is configured. In this example, the m stand is the measurement stand on the most downstream side.

The plate width change amount of each stand section is the difference between the first stand entrance side plate width and the Kth stand exit side plate width, the (K + 1) th stand entrance side plate width, that is, the Kth stand exit side plate width and the Jth stand. It is determined by the difference between the exit side plate width, the entrance side plate width of the J + 1st stand, that is, the difference between the Jth stand exit side plate width and the mth stand exit side plate width, and the difference between the m + 1st stand and the final stand exit side plate width.

As described above, with respect to the rolling stand whose sheet width has been measured, the amount of change in the sheet width can be calculated from the above-described measurement results for each stand section sequentially formed from the upstream stand to the downstream stand. . On the other hand, the permissible value of the plate width change can be obtained in advance by the equation (8 ') as described above for each of these measurement stands. Therefore, for each stand, the possibility of plate breakage is large, and the stand that should operate the shape control device is specified, and the shape control device is controlled so that the position width change allowable value set for each measurement stand is not exceeded. I do.

In this description, measurements are taken at the exits of the three stands between the tandem rolling mills in addition to the tandem rolling mill entry side (first rolling mill entry side) and the tandem rolling mill exit side (final rolling mill exit side). Although the above example has been described, even when the measurement is performed on fewer or more stands, the shape control device can be controlled by sequentially configuring the stands from the upstream side to the downstream side according to the above description.

Preferably, for example, if a sheet width measuring device is provided between all stands of a tandem rolling mill consisting of four stands, the first to fourth stands can be obtained from the measurement results of the change in the sheet width on the entrance side and the exit side of each stand. Width change ΔW _lim (i = 1
To 4) can be detected, and the shape controllers 4a to 4d are controlled so as not to exceed the negative tolerances ΔW _lim ^{(1) to} ΔW _lim ⁽⁴⁾ set for each of the first to fourth stands. Needless to say, this makes it possible to realize more accurate plate break prevention control.

Even when there is no sheet width measuring device between the stands of the tandem rolling mill, if there is a shape detecting device between the stands and the current plate shape of each stand can be measured or estimated, It is also possible to control the sheet width by the detected shape value. In other words, since the stand that is the most middle-extended shape side is a stand that is likely to cause plate breakage, by operating the shape control device preferentially from this stand, for example, by changing the desk to the end extended side Also, it is possible to prevent the plate from breaking.

As described above, the sheet width measuring device on the inlet / outlet side of the tandem rolling mill or the sheet width control based on the sheet width measuring device or the shape measuring device provided between the stands can be used together. It is possible to more accurately specify a stand where the tension at the end is high and breakage is likely to occur, and by performing rolling on the specified stand in a direction to increase the width of the plate width, that is, by rolling the end extension side, Excessive tension at the end can be reduced, and rolling can be performed without breaking the plate over the entire stand.

Generally, the change in the sheet width in the cold tandem rolling is almost the same as the change in the vicinity of the roll bite described above, and if the control is performed based on the change in the sheet width, it is practically sufficient. Although strip width control can be realized with high accuracy, depending on the type of rolled material, strip width may change between stands of a rolling mill. In this case, the change in the width of the sheet between stands is measured or estimated from the changes in the tension between the stands, the temperature, and the time, which are the factors of the change, and the change in the sheet width between the stands is taken into consideration. Needs to be controlled.

In a range where the change in the sheet width does not exceed the allowable value of the change in the sheet width, the output sheet width is measured using the output sheet width measuring device so that the output sheet width matches the predetermined target sheet width. Roll bender control or tension control can be performed. In this way, by implementing the present invention, while realizing high productivity, simultaneously preventing the occurrence of heat scratch and plate breakage of the rolled material, and improving the dimensional accuracy by keeping the product plate width constant. Can be expected.

[0049]

【Example】

[Embodiment 1] As shown in FIG. 1, there are first to fourth stands each having a shape control device, and the output of the output side coiler is 50% or more of the output of the main motor of the final stand. In a cold tandem rolling mill capable of applying a tension of 30% or more of the deformation resistance of the rolled material, a thickness of 3 mm and a width of 3 mm are applied while performing recirculation lubrication with a tallow-based rolling lubricating oil (4% emulsion). 900
Cold rolled rolled material 1 of low carbon steel having a thickness of 0.
An 8 mm steel plate strip was manufactured (rolling conditions are shown in Table 2 as rolling conditions of a cold four-stand tandem rolling mill), and the resulting steel strip was examined for the occurrence of heat scratches, the fracture of the steel plate, and the accuracy of the width of the steel plate. .

[0050]

[Table 2]

In the case of the conventional tension conditions shown in Table 2, heat scratches are likely to occur on the exit side of the fourth stand. In the first embodiment of the present invention, the width measuring devices 6a and 6e are provided on the first stand entrance side and the fourth stand exit side.
Is installed, and the shape control device 4a of the first to fourth stand rolling mills
幅 4d was used to control the board width. First,
In the conventional case using a cold tandem rolling mill having no sheet width measuring device on the entrance side of the first stand and the exit side of the fourth stand, about one minute after entering the steady rolling state, the exit side of the first to fourth stands is used. As a result of measuring the plate temperature using a non-contact type thermometer (not shown), the plate temperature on the exit side of the fourth stand was 180 °.
° C and no plate breakage occurred, but heat scratches occurred at the fourth stand.

Further, in the above conventional example, when only the tension condition was changed so that the tension on the exit side of the fourth stand was 40% of the deformation resistance value, no heat scratch occurred in the fourth stand. However, about 2 minutes after entering the steady rolling state, the fourth stand broke. this is,
This shows that heat scratch and plate breakage cannot be prevented at the same time only by changing the tension condition alone. Also,
As a result of off-line measurement of the sheet width variation on the delivery side at this time, it was found that there was a variation of ± 1 to 3 mm.

On the other hand, in the example of the present invention using a cold tandem rolling mill in which the sheet width measuring devices 6a and 6e are installed on the first stand entrance side and the fourth stand exit side, the detected plate width change ΔW
^{(1; 4)} is smaller than the allowable value ΔW _lim ^{(1; 4)} = 2.5 mm in the tandem rolling mill obtained from the equation (8 ′). The average tension σ ′ ⁽ⁱ⁾ of the plate ends of the four stands is determined, and from the results, it is specified that the exit side of the fourth stand is the stand where the sheet breakage is most likely to occur, and the width of the exit side of the fourth stand is determined. The operation amount of the shape control device 4d was set and controlled so as to adjust the priority. Next, in the same manner as described above, the operation of specifying and controlling the next stand to be operated is repeated, and the sheet width change amount ΔW ^{(1; 4)} becomes larger than the allowable value ΔW _lim ^{(1; 4)} , and the sheet width is increased to the wider side. Until the change, the plate width control by the shape controllers 4a to 4d was repeatedly performed.

As a result, after entering the steady rolling state, the sheet temperature was measured using a sheet thermometer (not shown) at the outlet side of the first to fourth stands. As a result, the sheet temperature was in the range of 162 ° C. to 175 ° C. In the fourth stand, which was a particular problem, neither heat scratch nor plate breakage occurred. Also, from the measurement result of the plate width by the fourth stand exit side width measuring device 6e, the variation amount of the plate width on the fourth stand exit side is ±.
It was found that it was reduced to 1.0 mm or less.

As described above, the present invention is applied to a cold tandem rolling mill, and the sheet width measuring devices 6a and 6e are provided on the entrance and exit sides of the tandem rolling mill, and are controlled by the shape controllers 4a to 4d. By controlling the width, frictional heating at the fourth stand, which has become a particular problem, is reduced, heat scratches and plate breakage can be prevented, and dimensional accuracy can be improved by keeping the product plate width constant. Has been verified.

[Embodiment 2] Next, a case where the present invention is applied to a cold tandem rolling mill comprising six stands as shown in FIG. 2 will be described. The cold tandem rolling mill of FIG.
The tandem rolling mill is composed of work rolls 2a to 2f, backup rolls 3a to 3f, shape control devices 4a to 4f, and a processing unit 8. The exit side coilers 5a and 5b are installed. The exit side coiler 5b has an output of 35% or more of the output of the main motor of the rolling mill in the final stand, and the tension between the stands can apply a rolling tension of 30% to 40% or more of the deformation resistance of the rolled material. is there. In addition, a total of three places, ie, the first stand entrance side, which is the entrance side of the tandem rolling mill, the sixth stand exit side, which is the exit side of the tandem rolling mill, and the exit side of the third rolling mill, between the rolling mills of the tandem rolling mill. In addition, plate width measuring devices 6a, 6g, 6d are installed, and a shape measuring device 9 is installed on the exit side of the sixth stand. Table 3 shows the rolling conditions of the cold 6-stand tandem rolling mill.

[0057]

[Table 3]

As shown in Table 3, the rolling conditions were set so that the tension at the exit side of the sixth stand was 44% of the deformation resistance value, and the recirculation was performed using a tallow-based rolling lubricating oil (4% emulsion). While lubricating, thickness 3mm, width 9
Cold rolled rolled material 1 of low carbon steel having a thickness of 00 mm to produce a thin steel strip of 0.4 mm in thickness. investigated.

First, using only the sheet width measuring devices 6a and 6g on the entrance side of the first stand and the exit side of the sixth stand, the sheet width measurement values on the entrance and exit sides of the tandem rolling mill are obtained in the same manner as in the first embodiment. When the sheet width control based on the shape control devices 4a to 4f is performed, heat rolling does not occur on the exit side of each stand and rolling is performed normally, but the sheet width variation is ± 0.8 to
It turned out to be 1.4 mm.

Next, in the second embodiment of the present invention, the width change ΔW between the first to third stands from the width measuring devices 6a and 6d.
^{(1; 3)} is converted to the fourth signal detected by the plate width measuring devices 6d and 6g.
The width change amount ΔW ^{(4; 6)} between the first to sixth stands is obtained, and from Expression (8 ′), the allowable value ΔW _lim ^{(1; 3) of the} change in the width between the i = 1st to third stands is obtained. 8 mm, the permissible value ΔW _lim ^{(4; 6)} = − 0.2 mm of the change in the plate width between the i-th stand and the fourth to sixth stand is obtained. For each of i = 4 to 6 stands, the stand where the possibility of plate breakage is large and the shape control devices 4a to 4f are to be operated is specified, and each allowable value ΔW _lim ^{(1; 3)} , ΔW
_The width control of the shape controllers 4a to 4f was performed so that the width of the sheet did not change from _lim ^{(4; 6)} to the side where the width of the sheet decreased.

As a result, after entering the steady rolling state, the plate temperature was measured using a plate thermometer (not shown) at the outlet side of the first to sixth stands. As a result, the plate temperature was in the range of 160 ° C. to 174 ° C. , And neither heat scratch nor plate breakage occurred in the first to sixth stands. The variation amount of the plate width at this time is measured by the exit width measuring device 6g on the exit side of the sixth stand.
As a result, it was found that it was ± 0.6 mm or less, and the plate width accuracy was improved as compared with the case of Example 1.

As in the second embodiment, in addition to the measured values of the widths of the strips on the inlet and outlet sides of the tandem rolling mill, the strip width between the rolling mills can be measured. As compared with the case of Example 1 using the method, the number of stands whose plate width change is unknown is reduced, so that more accurate plate width control is possible. Has been verified, and the plate width accuracy has also been improved.

In the case of the rolling mill equipment of the second embodiment,
Since the shape measuring device 9 is provided on the exit side of the sixth stand, it is possible to directly control the tension distribution by the shape control device 4f in the sixth stand based on the plate shape detected value by the shape measuring device 9. Therefore, by using the control by the shape measuring device and the above-described plate width control together, more reliable heat scratch and plate break prevention control can be realized.

[Embodiment 3] In order to further investigate the effectiveness of the present invention, in Embodiment 3, as shown in FIG.
In a 6-stand cold tandem rolling mill similar to the above, before and after each stand of the tandem rolling mill, the sheet width measuring devices 6a to 6a to
6g, the result of installing the shape detection device 9 on the exit side of the sixth stand, and performing plate width control based on the measured values of the front and rear plate widths at each of the first to sixth stands will be described. In addition, the exit side coiler 5b is used as the output of the main motor of the rolling mill at the final stand.
There is an output of 0% or more, and high tension rolling can be performed as compared with the case of the second embodiment.

In the same manner as in Example 2, while performing recirculation lubrication with a tallow-based rolling lubricating oil (4% emulsion), a rolled material 1 of 3 mm thick and 900 mm wide and made of low carbon steel was cold-rolled. Then, a thin steel plate strip having a thickness of 0.4 mm was manufactured, and the state of occurrence of heat scratch, the state of rupture of the plate, and the accuracy of the width of the obtained steel plate strip were investigated. The rolling conditions were as follows: cold 6-stand tandem rolling mill rolling conditions (high speed and high tension)
It was shown to. As shown in Table 4, the speed and the tension are higher (the tension on the exit side of the sixth stand is 50% of the deformation resistance value) than the condition of the second embodiment.

[0066]

[Table 4]

In the third embodiment of the present invention, the plate width change amounts ΔW ^{(1) to} ΔW ⁽⁶⁾ of the ^{first to sixth} stands detected by the plate width measuring devices 6a to 6g before and after each stand, respectively. Is the allowable value ΔW _lim set for each of the first to sixth stands.
⁽¹⁾ = 0.5 mm, ΔW _lim ⁽²⁾ = − 0.2 mm, ΔW _lim
⁽³⁾ = − 0.5 mm, ΔW _lim ⁽⁴⁾ = − 0.5 mm, ΔW _li
m ⁽⁵⁾ = − 0.7 mm, ΔW _lim ⁽⁶⁾ = Repeatedly by the shape control devices 4 a to 4 f of each stand so that the plate width does not change to the side where the plate width decreases from −0.8 mm. The control of the board width to be operated was implemented.

As a result, after entering the steady rolling state, the sheet temperature was measured using a sheet thermometer (not shown) at the outlet side of the first to sixth stands.
° C, and neither heat scratch nor plate breakage occurred in each of the first to sixth stands. Also,
As a result of measuring the sheet width fluctuation amount on the delivery side at this time, ± 0.5 mm
It turned out that:

As described above, by installing the sheet width measuring device before and after all the stands of the tandem rolling mill, the change in the sheet width of all the stands can be measured, and the tension at the end of the sheet can be reliably estimated. As a result, high-precision plate width control can be realized, even if the speed is increased and the tension is increased, frictional heat generation can be reduced in all stands, and heat scratch and plate breakage can be prevented. It has been verified that the dimensional accuracy can be improved by making the plate width constant.

When a board width measuring device or a shape measuring device is added as in the above-described embodiment, equipment costs increase. Therefore, a stand is selected in consideration of a balance between effects and costs. However, in order to prevent the occurrence of heat scratch and plate breakage at the same time, application to at least the final stand is indispensable.

[0071]

According to the present invention, when a steel plate is rolled by a cold tandem rolling mill comprising four or more rolling stands, heat scratches and breakage of the plate occur without increasing the cost and lowering the productivity as in the conventional example. Can be prevented at the same time, and a steel sheet having good quality such as sheet width accuracy can be manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory side view showing a cold tandem rolling mill facility according to a first embodiment of the present invention.

FIG. 2 is an explanatory side view showing a cold tandem rolling mill facility according to a second embodiment of the present invention.

FIG. 3 is an explanatory side view showing a cold tandem rolling mill facility according to Embodiment 3 of the present invention.

FIG. 4 is an explanatory diagram showing a change in a sheet width before and after a roll bite when a calculation is performed by changing an operation amount of a shape control device.

FIG. 5 is an explanatory diagram showing a change in the tension distribution at the roll bite outlet when the calculation is performed while changing the operation amount of the shape control device.

FIG. 6 is an explanatory diagram showing a relationship between a plate width change amount and an average tension at a plate edge.

FIG. 7 is a diagram showing the effect of a tension load ratio on a rolling load ratio.

FIG. 8 is a view showing the influence of a tension load ratio on wear resistance.

FIG. 9 is a diagram showing the influence of the tension load ratio on the incidence of surface defects.

FIG. 10 is a diagram showing a method for obtaining an allowable value of a change in plate width of the first to fourth stands.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rolled material 2a-2f ... Work roll of 1st-6th stand 3a-3f ... Backup roll of 1st-6th stand 4a-4f ... Shape control device of 1st-6th stand 5a ... Incoming coiler 5b ... Outlet Coiler 6a ... 1st stand entrance side plate width measurement device 6b-6g ... 1st-6th stand exit side plate width measurement device 7a ... entrance side bridle roll 7b ... exit side bridle roll 8 ... arithmetic processing unit 9 ... shape measurement apparatus

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // H02P 7/67 B21B 37/00 128Z

Claims (6)

[Claims] In a cold tandem rolling mill having four or more cold rolling mills provided with a shape control device, the strip width of a rolled material is measured on the entrance side and the exit side of the tandem rolling mill. From the value, calculate the sheet width change amount of the tandem rolling mill entrance side and exit side, and control the shape control device so that this sheet width change amount does not exceed a predetermined predetermined allowable value of the sheet width change amount, A cold tandem rolling method characterized in that rolling is performed by applying a rolling tension of 30% or more of the deformation resistance of a rolled material at least in a final stand. 2. A cold tandem rolling mill having four or more stands of cold rolling mills provided with a shape control device, wherein at least one stand between the entrance side, the exit side of the tandem rolling mill and the tandem rolling mill is provided. Measuring the strip width of the rolled material on the delivery side, between the first stand of the tandem rolling mill and the stand on the more upstream side where the delivery side sheet width was measured between the tandem rolling mills,
Between the stand adjacent to the downstream of the stand on the more upstream side where the exit side plate width is measured and the stand downstream of and more upstream than the stand on the upstream side where the exit side plate width is measured , And a stand adjacent to the downstream end of the stand on the most downstream side where the exit side plate width is measured, and a final stand, thereby sequentially forming a stand section. From the above measurement results, the sheet width change amount for each stand section The shape controller is controlled so that the width change of the stand section does not exceed the allowable width change amount predetermined for each stand section, and at least 30% of the deformation resistance of the rolled material is calculated. %. A cold tandem rolling method characterized in that rolling is performed by applying a rolling tension of at least%. 3. A cold tandem rolling mill having four or more cold rolling mills provided with a shape control device, wherein the width of a rolled material at the entrance side of the tandem rolling mill and at the exit side of each rolling mill of the tandem rolling mill. From the measured values of the strip widths, the change in the strip width on the entrance side and the exit side of each rolling mill of the tandem rolling mill is calculated. The shape control device is controlled so as not to exceed the allowable value of the predetermined width change amount on each of the side and the delivery side, and rolling is performed by applying a tension of 30% or more of the deformation resistance of the rolled material at least in the final stand. A cold tandem rolling method. 4. A cold tandem rolling mill having four or more cold rolling mills each provided with a shape control device on each stand, wherein a sheet width measuring device is provided at least on an inlet side and an outlet side of the tandem rolling mill. A cold tandem rolling mill comprising: 5. The cold tandem rolling mill according to claim 4, wherein a sheet width measuring device is provided at at least one position between the rolling mills of the cold tandem rolling mill. 6. A coiler or a coiler and a bridle roll are provided on the output side of a cold tandem rolling mill, and the output of one main motor of the coiler or the output of one main motor of the coiler and the main roll of the bridle roll are provided. The total output with the output of the motor, the output of the main motor of the final stand of the cold tandem rolling mill, and the average sheet thickness of the product rolled by the cold tandem rolling mill satisfy the following relationship. The cold tandem rolling mill according to claim 4 or 5, wherein W _c ≧ (0.375h + 0.275) W _M where W _c : the output of one main motor of the coiler or the total output of the output of the main motor of one coiler and the output of the main motor of the bridle roll W _M : Output of main motor of final stand of cold tandem rolling mill h: Average thickness of product rolled by cold tandem rolling mill