JP2000202509A - Rolling method of cold tandem rolling mill - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

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

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

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

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

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

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

[0009]

As a method for preventing heat scratch without lowering the productivity and increasing the production cost as described above, when the rolling schedule is changed, the accuracy of the thickness of the sheet temporarily deteriorates. There is a problem. In addition, when changing the tension, if a higher value is naturally used, the rolling load is reduced, and the effect of preventing heat scratch is obtained.However, when the tension is increased, the sheet may break, and the rolling state may be gradually observed. However, if the tension is increased, the responsiveness is deteriorated, and heat scratches are generated and the thickness accuracy is deteriorated. further,
When detecting the plate temperature on the stand exit side and controlling the tension based on that temperature, the control is performed when the temperature exceeds the temperature at which heat scratch occurs, so there is the danger that heat scratch may occur temporarily There is.

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

[0011]

The gist of the present invention is as follows. 1) Detected values of the plate temperature, plate thickness, and plate speed on the stand exit side, or these detected values and the cooling water of the plate cooling device installed from the stand exit side to the temperature detector for detecting the plate surface temperature Estimate the roll bite outlet plate temperature based on the temperature and cooling water supply amount, and control the lubricating oil concentration and / or lubricating oil supply amount based on these values. 2) Stand inlet / outlet plate temperature, stand outlet side plate The detected values of the speed and the sheet thickness on the exit side of the stand, or these detected values, and the detected values of the temperature and flow rate of the cooling water of the sheet cooling device installed between the exit side of the rolling mill and the temperature detector that detects the sheet surface temperature. The temperature of the plate rising in the roll bite is estimated based on this, and the lubricating oil concentration and / or the lubricating oil supply amount is controlled based on this value.

The present invention is based on the above-mentioned gist, and the rolling method in the cold tandem rolling mill according to the first invention specifies in advance a stand in which heat scratch is likely to occur, and performs the following steps in the designated stand: A rolling method in a cold tandem rolling mill that performs rolling. (B) First step of detecting stand outlet plate temperature, rolling load, work roll speed, stand outlet plate speed, stand inlet / outlet plate thickness, stand inlet / outlet tension, lubricating oil concentration, and lubricating oil supply amount (b) the stand delivery side of the plate temperature, thickness, and a second step of estimating a roll bite outlet plate temperature T _f in the rolling state from the detected value of the plate speed (c) the roll bite outlet estimation plate temperature T _f is When the temperature exceeds the preset heat scratch control target temperature _TL , the rolling load, work roll speed,
Third step of calculating the friction coefficient and deformation resistance of the rolled material from the detected values of the stand exit side plate speed, the stand entry / exit side plate thickness, and the stand entry / exit side tension (d) The detection value, friction coefficient, and The plate temperature rise T _E 'in the roll tool in the rolling state due to the deformation resistance and the plate temperature rise T _m ' in the roll tool when the lubricating oil concentration and / or the lubricating oil supply amount are changed are obtained, and T _L -T _f ≧ T _m lubricating fourth step of obtaining a lubricating oil concentration and / or lubricating oil supply amount to be '-T _E' (e) the lubricating oil concentration and / or lubricating oil supply amount calculated by the fourth step as the target value Fifth step of controlling oil concentration and / or lubricating oil supply

According to a second aspect of the present invention, there is provided a rolling method for a cold tandem rolling mill in which a stand in which heat scratch is likely to occur is designated in advance, and rolling is performed in the designated stand in the following steps. (A) Stand exit side plate temperature, rolling load, work roll speed, stand exit side plate speed, stand entry / exit side plate thickness, stand entry / exit side tension, plate cooling water temperature, plate cooling water supply amount, lubricating oil concentration, and First to detect the lubricating oil supply amount respectively
Step (b) From the plate temperature, the plate speed, the plate thickness, and the detected values of the plate cooling water temperature and the plate cooling water supply amount on the exit side of the stand,
Second step of estimating the roll bite exit plate temperature _Tf in the rolling state (c) If the roll bite exit estimated plate temperature _Tf exceeds a preset heat scratch control target temperature _TL , the rolling load in the first step , Work roll speed,
Third step of calculating the friction coefficient and deformation resistance of the rolled material from the detected values of the stand exit side plate speed, the stand entry / exit side plate thickness, and the stand entry / exit side tension (d) The detection value, friction coefficient, and The plate temperature rise T _E 'in the roll tool in the rolling state due to the deformation resistance and the plate temperature rise T _m ' in the roll tool when the lubricating oil concentration and / or the lubricating oil supply amount are changed are obtained, and T _L -T _f ≧ T _m lubricating fourth step of obtaining a lubricating oil concentration and / or lubricating oil supply amount to be '-T _E' (e) the lubricating oil concentration and / or lubricating oil supply amount calculated by the fourth step as the target value Fifth step of controlling oil concentration and / or lubricating oil supply

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

In a rolling method for a cold tandem rolling mill according to a fourth aspect of the present invention, a stand where heat scratch is likely to occur is specified in advance, and rolling is performed in the specified stand in the following steps. (A) Stand entrance / exit side plate temperature, rolling load, work roll speed, stand exit side plate speed, stand entrance / exit side plate thickness,
First step for detecting stand entrance / exit side tension, lubricating oil concentration, lubricating oil supply amount, plate cooling water temperature, and plate cooling water supply amount, respectively (b) The stand entrance / exit plate temperature, stand exit side plate speed, The second step of obtaining the temperature rise ΔT _f of the roll tool in the rolling state from the detected values of the stand exit side sheet thickness, the sheet cooling water temperature, and the sheet cooling water supply amount. (C) The estimated temperature rise ΔT _f of the roll tool is determined in advance. Set heat scratch control target temperature ΔT
_{When the value} exceeds _L , the friction coefficient and deformation resistance of the rolled material are determined from the detected values of the rolling load, work roll speed, stand exit side plate speed, stand entry / exit plate thickness, and stand entry / exit tension in the first step. Third Step (d) When the temperature rise _TE 'in the roll tool in the rolling state and the lubricating oil concentration and / or the lubricating oil supply amount are changed by the detected value, friction coefficient, and deformation resistance of the third step Of the sheet temperature T _m ′ of ΔT _L −ΔT
_f ≧ T _m lubricant concentration becomes '-T _E' and /
Or a fourth step of obtaining the lubricating oil supply amount (e) a fifth step of controlling the lubricating oil concentration and / or the lubricating oil supply amount using the lubricating oil concentration and / or the lubricating oil supply amount obtained in the fourth step as a target value

According to these inventions, the sheet temperature, rolling load, etc., which are detected on the exit side of the rolling mill, or the detected values, and further, the sheet installed between the exit side of the rolling mill and the temperature detector for detecting the sheet surface temperature. The temperature and flow rate of the cooling water of the cooling device are detected, and the friction coefficient and the deformation resistance are determined based on the detected values. Then, the roll bite outlet temperature or the roll bite inlet / outlet temperature is obtained, and the lubricating oil concentration and / or the lubricating oil supply amount are controlled so that these do not exceed the heat scratch control target temperature. Therefore, the temperature inside the roll bite can be maintained at or below the temperature at which heat scratch does not occur.

[0017]

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

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

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

Next, a method of estimating the plate temperature will be described. By the plate temperature detector 24 provided on the exit side of the rolling mill,
The sheet temperature on the exit side of the rolling mill is detected at a constant period τ (for example, 5 s), and the sheet temperature T _O at the exit of the rolling tool roll bite is estimated. Generally, the plate temperature T _S when water cooling is performed is given by equation (1).

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

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

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

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

Based on the above temperature data, the roll plate outlet plate temperature in a steady state is estimated. For example, the control cycle of the lubrication condition (the control cycle of the lubricating oil concentration and / or the lubricating oil supply amount for preventing heat scratch) is set to 1 minute, and the plate temperature data (in this case, 12 pieces,
However, although the lubrication conditions are constant,
Finally substituted into the function representing the asymptotic curve that approaches a constant value, to determine the constants of the function by performing a multiple regression, the estimated value T _f in the roll bite outlet plate temperature and the asymptotic value in the steady state I do. As a function representing such an asymptotic curve that finally approaches a constant value, for example, a · tanh
(cX) and a + b (1-e- ^cx ). In this function, a, b, and c are constants, and eventually asymptotically to a and a + b, respectively. Therefore, the measured temperature data is substituted into such a function to obtain an asymptotic value a or a + b, which is used as an estimated value T of the plate temperature in a steady state.
_f .

In addition to the above method, for example, a control cycle of lubrication (control cycle of lubricating oil concentration and / or lubricating oil supply amount for preventing heat scratch) is set to, for example, 30 seconds, and this control is performed. The six temperature data obtained in the cycle of 30 seconds are linearly regressed, and the sheet temperature after 30 seconds, which is the next lubrication control timing (the next lubrication control time), is estimated to estimate the sheet temperature T. _It may be _f .

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

In the stand where the heat scratch is likely to occur, that is, in the fourth stand in FIG. 1, the estimated value _Tf of the plate temperature at the roll bite outlet is compared with the above-mentioned heat scratch control target temperature _TL . ΔT = T _L -T _f
Is positive, there is no possibility of heat scratching, so the rolling is continued. If ΔT = _TL - _Tf is a negative value, heat scratch may occur. Therefore, change the lubrication conditions (lubricant oil concentration and / or supply amount) so that ΔT becomes positive. Perform rolling.

The method of calculating the lubricating oil concentration and the lubricating oil supply amount to be changed will be described below. First, the deformation resistance K _m and the friction coefficient during rolling mu. The deformation resistance of the rolled material is determined in advance by a constant a shown in equation (4) by a tensile test,
The values of ε ₀ and n are determined in advance.

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

By the way, since deformation resistance is influenced by the strain rate and the plate temperature, deformation resistance K _m obtained from the equation (4) is not necessarily exact value during rolling. Therefore, in the present invention, the rolling load equation and the advanced rate equation are made simultaneous to determine the deformation resistance and the friction coefficient during rolling. For example, the Hill load type and solutions exhibition for deformation resistance K _m as shown in equation (5), determine the deformation resistance K _m. Also, Bland & Ford
Is developed for the friction coefficient μ _E as shown in the equation (6), and the friction coefficient μ _E is obtained by substituting the deformation resistance K _m obtained in the equation (5) into the equation (6). Equations (5) and (6)
The subscript E is a detected value at the time of rolling of the stand and a calculated value based on the detected value, and in the following description, these are referred to as actual measured values. The calculated value is a value obtained by dividing the pretension detected by the load cell by the cross-sectional area of the plate, excluding the bending force from the rolling load detected by the load cell, as described above.

(Equation 5)

(Equation 6)

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

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

(Equation 7)

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

(Equation 8)

(Equation 9)

Equations (8) and (9) show the physical property values and measured values of the respective stand, and the above-mentioned equations (5) and (5).
By substituting the friction coefficient μ _E and the deformation resistance K _mE obtained by the method using (6), the measured value T ′ of the temperature rise T ′ at the interface between the roll at the roll bite exit of the stand and the rolled material is obtained.
_E ′ is obtained.

Next, lubricating conditions (concentration of lubricating oil and / or
Or, the temperature change when the supply amount is changed is estimated. For this purpose, the actual measured value of the stand is used except for the friction coefficient μ, and the rolling load P and the advanced ratio f when only the lubrication conditions are changed are used.
Calculate s.

The rolling load P is, for example, Hil shown in equation (10).
Using the load equation of l, the advance rate fs is expressed by Hla shown in equation (11).
Each is calculated using the formula of nd & Ford. The roll flatness R 'is calculated using Hitchcook's equation shown in equation (12).

(Equation 10)

[Equation 11]

(Equation 12)

The friction coefficient μ in the above equations (10) and (11)
Is determined as follows. First, the friction coefficient μ 'when the lubrication state is improved (when the supply amount per unit area of the strip or the concentration of oil is increased) is determined by the equation (13).

(Equation 13) The friction coefficient μ _E during rolling in Expression (13) is a value obtained from Expressions (5) and (6) as described above. In general, the coefficient of friction μ is expressed by equation (14).

[Equation 14] α, β, and γ are coefficients that change according to changes in roll roughness and the like, and are obtained for each control cycle. It can be easily obtained from equation (14) and the above-mentioned friction coefficient μ _E by calculation. α ₀ ,
β ₀ and γ ₀ are constants, which are obtained in advance by experiments. However, when only the flow rate is changed without changing the concentration, β = γ =
0 When only the concentration is changed without changing the flow rate, α = γ = 0 When changing the flow rate and the concentration, α = β = 0. When the current supply amount Q ₀ and the concentration C _Lo are used, and only the supply amount is changed to Q ₀ ′ without changing the concentration, β = γ = 0. The change in friction coefficient at that time is Δμ

(Equation 15) When changing only the concentration to C _Lo ′ without changing the flow rate, α = γ =
0. The change in friction coefficient Δμ at that time is

(Equation 16) When changing the flow rate to Q ₀ ′ and the concentration to C _Lo ′, α =
β = 0. The change in friction coefficient Δμ at that time is

[Equation 17]

The change in friction coefficient Δμ thus obtained
Into the equation (13) to determine the friction coefficient μ ′ when the lubrication condition is changed. In order to change the supply amount of the lubricating oil, for example, the rotation speed of the pump is adjusted. There are methods such as changing the concentration of the lubricating oil by switching the static mixer or tank.

The rolling load P is obtained by substituting the obtained friction coefficient μ 'for the friction coefficient μ in the equation (10) and performing convergence calculation using the equation (10) and the equation (12) for roll flattening. . The advance rate fs is obtained from equation (11). T _dmax is determined by using the rolling load P, the advance ratio fs, and the friction coefficient μ ′ in equation (8). Therefore, the temperature rise T _m ′ at the interface at the roll bite exit when the lubrication conditions are changed can be obtained from the equation (7). That is, the measured value _TE 'of the interface temperature rise at the roll bite outlet at the stand and the estimated value _Tm ' of the temperature rise at the roll bite outlet when the lubrication conditions are changed are obtained.
Although the temperature of the interface between the roll and the rolled material at the exit of the roll bite and the plate temperature at the exit side of the stand are not strictly the same, the temperature change when the lubrication conditions are changed may be regarded as the same. Therefore, the difference between the 'T _E and' The _{T m (ΔT '= T m} ' -T E '), and a difference between T _L and T _f previously described (ΔT = T _L -T _f) In comparison, lubricating condition conditions (concentration and / or supply amount of lubricating oil) such that ΔT ′ is equal to or less than ΔT (ΔT ′ ≦ ΔT) can be obtained by repeated calculation using, for example, Newton's method. The lubrication condition set value of the rolling mill is changed to the lubricating oil concentration and / or supply amount obtained as described above. Some lubrication conditions that satisfy the above-mentioned relationship and do not generate heat scratch can be obtained. An appropriate lubricating condition may be selected from these lubricating conditions according to the rolling condition. The lowest lubricating oil concentration and / or supply amount is selected, and the lubricating oil concentration and / or supply amount setting of the stand is accordingly performed. It is desirable to change the value.

At the time of these controls, the amount of change in the rolling load can be predicted in advance, so that the thickness and shape can be controlled so that the thickness accuracy and the shape of the plate are not defective.

The method of controlling the heat scratch at the plate temperature at the exit of the roll bite of the rolling mill has been described above. However, depending on the lubricating oil, it is better to control the temperature not at the exit of the roll bite but at the elevated temperature in the roll bite. In some cases. In this case, the temperature Ti of the sheet is also detected by the temperature detector on the rolling mill entry side. When water cooling is not performed from the temperature detector to the entry side of the rolling mill, at a rolling speed of 500 m / min or more, even if lubricating oil is applied to the plate surface, their influence on the plate temperature at the roll bite inlet can be ignored.
Therefore, instead of the aforementioned T _O , T _O ′ = T _O −Ti
May be performed in the same manner. At this time, T _f becomes ΔT _f ,
T _L may be set to ΔT _L.

[0039]

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

[Table 1]

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

The limit temperature T _Lim, which is the lowest roll bite exit plate temperature at which heat scratch is generated by an experiment in advance, is 162 ° C., and the heat scratch control target temperature is T _L = 162-4 = 158 ° C. .
The control period of the lubricating oil concentration is 30 seconds, the sampling time is 5 seconds, and the plate temperature at the roll bite outlet is calculated and linearly regressed from the data of 30 seconds (six pieces) during that period. The sheet temperature was determined and used as an estimated value _Tf of the sheet temperature. The lubricating oil is palm oil, and the set concentration is 15%.

FIG. 3 is a diagram showing the effect of the second invention. In FIG. 3, .largecircle. Indicates the case of the conventional rolling method, and .circle-solid. Indicates the case of applying the present invention. FIG. 3A shows the relationship between the number of rolling coils and the plate temperature at the outlet of the fourth stand roll bite. In the conventional rolling method, the estimated value of the roll bite exit plate temperature is 160 ° C. or more when the number of coils is eleven, and there is a danger of generating heat scratch. Therefore, as shown in FIG.
It was operating at a speed of ^-1 . On the other hand, in the present invention, as shown in FIG. 3C, the lubricating oil concentration was changed on the basis of the predicted temperature of the roll bite outlet. As a result, the plate temperature did not reach 158 ° C. or higher even with 30 coils. Rolling was performed while maintaining the work roll speed at 1200 m · min ^−1, and heat scratch did not occur as a matter of course.

When the conditions for cooling the plate of the third stand were significantly changed, the accuracy deteriorated. Therefore, the third invention was applied. That is, the limit temperature T _Lim, which is the roll bite rise temperature at which heat scratch occurs, which was previously determined by an experiment, was 108 ° C., and the heat scratch control target temperature was T _L = 108-4 = 104 ° C. The control cycle of the lubricating oil concentration is 30 seconds, the sampling time is 5 seconds, and the roll bite rising temperature is calculated and linearly regressed from the data of 30 seconds (six pieces) during that period. The obtained value was used as an estimated value _Tf of the plate temperature. As a result, even if the plate cooling conditions of the third stand were significantly changed,
No heat scratch occurred.

[0044]

As described above, since the temperature inside the roll bite can be maintained at a temperature lower than the temperature at which heat scratch does not occur, the occurrence of heat scratch can be prevented without impairing the productivity.

[Brief description of the drawings]

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

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

FIG. 3 (a) shows the relationship between the roll bite exit temperature of the rolled material and the number of rolling coils, (b) shows the relationship between the work roll speed and the number of rolling coils, and (c) shows the lubricating oil concentration and the number of rolling coils. 6 is a graph showing the relationship between

[Explanation of symbols]

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

Claims (4)

[Claims] 1. A rolling method in a cold tandem rolling mill in which a stand where heat scratch is likely to occur is designated in advance, and rolling is performed in the designated stand in the following steps. (B) First step of detecting stand outlet plate temperature, rolling load, work roll speed, stand outlet plate speed, stand inlet / outlet plate thickness, stand inlet / outlet tension, lubricating oil concentration, and lubricating oil supply amount (b) the stand delivery side of the plate temperature, thickness, and a second step of estimating a roll bite outlet plate temperature T _f in the rolling state from the detected value of the plate speed (c) the roll bite outlet estimation plate temperature T _f is When the temperature exceeds the preset heat scratch control target temperature _TL , the rolling load, work roll speed,
Third step of calculating the friction coefficient and deformation resistance of the rolled material from the detected values of the stand exit side plate speed, the stand entry / exit side plate thickness, and the stand entry / exit side tension (d) The detection value, friction coefficient, and The plate temperature rise T _E 'in the roll tool in the rolling state due to the deformation resistance and the plate temperature rise T _m ' in the roll tool when the lubricating oil concentration and / or the lubricating oil supply amount are changed are obtained, and T _L -T _f ≧ T _m lubricating fourth step of obtaining a lubricating oil concentration and / or lubricating oil supply amount to be '-T _E' (e) the lubricating oil concentration and / or lubricating oil supply amount calculated by the fourth step as the target value Fifth step of controlling oil concentration and / or lubricating oil supply 2. A rolling method in a cold tandem rolling mill in which a stand where heat scratch is likely to occur is designated in advance, and rolling is performed in the designated stand in the following steps. (A) Stand exit side plate temperature, rolling load, work roll speed, stand exit side plate speed, stand entry / exit side plate thickness, stand entry / exit side tension, plate cooling water temperature, plate cooling water supply amount, lubricating oil concentration, and First to detect the lubricating oil supply amount respectively
Step (b) From the plate temperature, the plate thickness, and the plate speed on the exit side of the stand, and the detected values of the plate cooling water temperature and the plate cooling water supply amount, the roll bite exit plate temperature T _f in the rolling state.
(C) When the roll bite outlet estimated plate temperature _Tf exceeds a preset heat scratch control target temperature _TL , the rolling load, work roll speed,
Third step of calculating the friction coefficient and deformation resistance of the rolled material from the detected values of the stand exit side plate speed, the stand entry / exit side plate thickness, and the stand entry / exit side tension (d) The detection value, friction coefficient, and The plate temperature rise T _E 'in the roll tool in the rolling state due to the deformation resistance and the plate temperature rise T _m ' in the roll tool when the lubricating oil concentration and / or the lubricating oil supply amount are changed are obtained, and T _L -T _f ≧ T _m lubricating fourth step of obtaining a lubricating oil concentration and / or lubricating oil supply amount to be '-T _E' (e) the lubricating oil concentration and / or lubricating oil supply amount calculated by the fourth step as the target value Fifth step of controlling oil concentration and / or lubricating oil supply 3. A rolling method in a cold tandem rolling mill in which a stand where heat scratch is likely to occur is designated in advance, and rolling is performed in the designated stand in the following steps. (A) Stand entrance / exit side plate temperature, rolling load, work roll speed, stand exit side plate speed, stand entrance / exit side plate thickness,
First Step of Detecting Stand In / Out Side Tension, Lubricating Oil Concentration, and Lubricating Oil Supply Amount (b) From the Stand In / Out Side Plate Temperature, Stand Out Side Plate Speed, and Stand Out Side Plate Thickness To determine the temperature rise ΔT _f in the roll bite in the rolling state
Step (c) The estimated temperature rise ΔT _f in the roll bite is a preset heat scratch control target temperature ΔT.
_{When the value} exceeds _L , the friction coefficient and deformation resistance of the rolled material are determined from the detected values of the rolling load, work roll speed, stand exit side plate speed, stand entry / exit plate thickness, and stand entry / exit tension in the first step. Third Step (d) When the plate temperature rise T _E ′ in the roll tool in the rolling state and the lubricating oil concentration and / or the lubricating oil supply amount are changed based on the detected value, friction coefficient and deformation resistance of the third step. Fourth Step (E) In the fourth step, the plate temperature rise T _m ′ in the roll bite is obtained, and the lubricating oil concentration and / or the lubricating oil supply amount that satisfies ΔT _L −ΔT _f ≧ T _m ′ −T _E ′ are obtained. Fifth step of controlling the lubricating oil concentration and / or the lubricating oil supply amount using the obtained lubricating oil concentration and / or lubricating oil supply amount as a target value 4. A rolling method in a cold tandem rolling mill in which a stand where heat scratch is likely to occur is designated in advance, and rolling is performed in the designated stand in the following steps. (A) Stand entrance / exit side plate temperature, rolling load, work roll speed, stand exit side plate speed, stand entrance / exit side plate thickness,
First step for detecting stand entrance / exit side tension, lubricating oil concentration, lubricating oil supply amount, plate cooling water temperature, and plate cooling water supply amount, respectively (b) The stand entrance / exit plate temperature, stand exit side plate speed, The second step of obtaining the temperature rise ΔT _f in the roll tool in the rolled state from the detected values of the stand exit side sheet thickness, the sheet cooling water temperature, and the sheet cooling water supply amount (c) The estimated temperature rise ΔT _f in the roll tool is Heat scratch control target temperature ΔT set in advance
_{When the value} exceeds _L , the friction coefficient and deformation resistance of the rolled material are determined from the detected values of the rolling load, work roll speed, stand exit side plate speed, stand entry / exit plate thickness, and stand entry / exit tension in the first step. Third Step (d) When the plate temperature rise T _E ′ in the roll tool in the rolling state and the lubricating oil concentration and / or the lubricating oil supply amount are changed based on the detected value, friction coefficient and deformation resistance of the third step. Fourth Step (E) In the fourth step, the plate temperature rise T _m ′ in the roll bite is obtained, and the lubricating oil concentration and / or the lubricating oil supply amount that satisfies ΔT _L −ΔT _f ≧ T _m ′ −T _E ′ are obtained. Fifth step of controlling the lubricating oil concentration and / or the lubricating oil supply amount using the obtained lubricating oil concentration and / or lubricating oil supply amount as a target value