JP5834848B2 - Rolling method for cold tandem rolling mill - Google Patents

Description

  The present invention relates to a rolling method for a cold tandem rolling mill.

  In a cold tandem rolling mill (hereinafter, also simply referred to as “rolling mill”), a coil (steel plate, material to be rolled) delivered from a rewinding reel on the rolling mill entrance side is installed in front of the rolling mill. The machine welds the trailing end of the preceding coil and the leading end of the coil, and the trailing end of the coil and the leading end of the succeeding coil, and performs continuous rolling. The rolled steel sheet is cut at a predetermined location by a shear cutting device installed on the delivery side of the rolling mill and wound on one or two take-up reels. Since there is a limit to the cutting speed of the shear cutting device, the rolling speed is reduced as compared with the steady rolling portion when the cutting portion (scheduled cutting portion) passes the shear cutting device.

  Moreover, in a cold tandem rolling mill, about 1 to 3% of lubricating oil is made into oil droplets having a diameter of about 10 μm, dispersed in water and supplied to a roll bite, so that between the roll and the material (rolled material). The friction coefficient is reduced to reduce the rolling load, and seizure is prevented to stabilize the rolling.

  At that time, the coefficient of friction between the roll and the material varies depending on the film thickness of the drawn rolling oil. The oil film thickness varies depending on the rolling speed, and when the rolling speed is reduced, the oil film thickness becomes thin, the friction coefficient increases, and the rolling load increases. From this, when the rolling speed is reduced for cutting the material to be rolled, the thickness of the material to be rolled on the exit side of the rolling mill increases due to the increase in rolling load.

  Therefore, since such a plate thickness variation is not preferable, the plate thickness control is performed. The most common plate thickness control method is a monitor AGC in which a plate thickness meter is installed on the delivery side of the rolling mill and some operation is performed so that the deviation between the measured plate thickness and the set plate thickness is zero. However, as described above, the reduction of the rolling speed accompanying the cutting of the material to be rolled is only a short time, and the time during which the material to be rolled moves from the rolling mill to the thickness gauge is reduced by the rolling speed being slowed. Since it becomes longer, the thickness control using the measured thickness is less effective.

  Therefore, as described in Patent Document 1, as a conventional technique, a method of predicting a plate thickness variation based on a variation in rolling load and performing a plate thickness control based on this is used to increase the control effect.

  However, since the material to be rolled is work-hardened at the final stand of the cold tandem rolling mill (the stand means a rolling stand), the roll gap is changed as an operation of sheet thickness control as described in Patent Document 1. This is not preferable because the plate shape deteriorates.

  Therefore, in Patent Document 1, a tension AGC is used in which the roll speed of the stand immediately preceding the last stand (the last stand just before) is changed to change the final stand entry side tension.

JP 2004-209498 A

  As described above, in the cold tandem rolling mill, when the rolling speed is reduced due to the cutting of the material to be rolled, the sheet thickness on the rolling mill exit side always varies in the increasing direction. Therefore, in the tension AGC described in Patent Document 1, control is performed so as to reduce the roll speed of the stand immediately preceding the last stand (the last stand immediately before) and increase the final stand entry side tension.

  In contrast, in recent years, in cold tandem rolling mills, hardness and surface properties vary depending on the components of the material to be rolled (steel plate), hot rolling conditions including descaling and cooling, and pickling conditions. Since the material (steel plate) is rolled, the amount of plate thickness variation accompanying the reduction in the rolling speed also varies depending on the material. Therefore, when the thickness control is performed by the method described in Patent Document 1, troubles such as chattering, breakage or drawing of the material to be rolled, image sticking of the material to be rolled and roll, motor image sticking in the last stand and the stand immediately before the last. (Unstable phenomenon) may occur.

  The present invention has been made in view of the above circumstances, and when performing rolling with a cold tandem rolling mill, even when the rolling speed is reduced along with the cutting of the material to be rolled, fluctuations in the plate thickness are caused. It aims at providing the rolling method of the cold tandem rolling mill which can perform stable rolling, suppressing.

  In order to solve the above problems, the present invention has the following features.

  [1] When rolling with a cold tandem rolling mill, the rolling load when the rolling speed reaches a predetermined rolling speed in the final rolling stand when the rolling speed is reduced to cut the material to be rolled. , And thereafter, the roll speed of all rolling stands other than the final rolling stand is corrected according to the amount of change from the recorded rolling load.

  [2] When an upper limit is set for the final rolling stand entry side tension and the final rolling stand entry side tension becomes the upper limit, the correction amount of the roll speed is made constant regardless of the amount of variation from the recording rolling load. The rolling method of the cold tandem rolling mill as described in [1] above.

  [3] When an upper limit is set for the tension difference between the entry side and the exit side of the final rolling stand, and the tension difference between the entry side and the exit side of the final rolling stand becomes an upper limit, regardless of the amount of change from the recording rolling load, The method of rolling a cold tandem rolling mill according to [1], wherein the correction amount of the roll speed is made constant.

  [4] The rolling method for a cold tandem rolling mill according to any one of [1] to [3], wherein the final rolling stand exit side tension is changed according to the correction amount of the roll speed.

  [5] A method for producing a steel sheet, comprising producing a steel sheet using the rolling method of the cold tandem rolling mill according to any one of [1] to [4].

  In the present invention, when performing rolling with a cold tandem rolling mill, stable rolling can be performed while suppressing fluctuations in sheet thickness even when the rolling speed is reduced as the material to be rolled is cut.

It is a schematic diagram which shows Embodiment 1 of this invention. It is a schematic diagram which shows Embodiment 2 of this invention. It is a schematic diagram which shows Embodiment 3 of this invention. It is a schematic diagram which shows Embodiment 4 of this invention. It is a schematic diagram which shows Embodiment 4 of this invention. It is a schematic diagram which shows Embodiment 4 of this invention.

  Embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
FIG. 1 is a schematic diagram showing Embodiment 1 of the present invention.

  The tandem cold rolling mill in Embodiment 1 is composed of 5 stands. In FIG. 1, 1 is a material to be rolled (steel plate), 2 is a work roll, 3 is a backup roll, 4 is an intermediate roll, and 5 is rolling oil. A supply nozzle, 6 is a tension meter, 7 is a load cell of a final stand (fifth stand), 8 is a take-up reel, and 11 is a plate thickness control device.

In addition, in the first embodiment, when the rolling speed is reduced for cutting the material to be rolled 1 (a cutting machine is not shown) and a predetermined rolling speed is reached, the load cell 7 at that time is reached. The rolling load P ₀ of the last stand (fifth stand) measured by is recorded in the plate thickness controller 11. Then, the sheet thickness control in the first embodiment is started from that point, and thereafter, as the rolling speed is further reduced, the final stand rolling load P and the recorded rolling load (recorded rolling load) are recorded every moment. According to the deviation (variation amount) ΔP from P ₀ , the roll speeds v _i (i = 1 to 4) of all the stands (the first stand to the fourth stand) other than the final stand are corrected.

That is, in accordance with a deviation ΔP between the final stand rolling load P and the recording rolling load P ₀ every moment, the estimated delivery side thickness fluctuation Δh is the following equation (1), is calculated as (2).

ΔP = P−P ₀ (1)
Δh = ΔP / K (2)

  Here, the proportionality coefficient K is a parameter representing the thickness variation with respect to the load variation, and is preferably obtained in advance by pre-rolling or the like. The estimated delivery side plate thickness fluctuation amount Δh is converted into the ratio Δe by the target delivery side plate thickness ho and is expressed by the following equation (3).

      Δe = Δh / ho (3)

This ratio Δe is input to the PID controller, and a control amount Δv is output according to the gain. The control amount Δv is a correction amount of the roll speed for bringing the estimated delivery side thickness fluctuation amount Δh close to zero, and is set for all the stands (first stand to fourth stand) other than the final stand (fifth stand). The roll speed v _i is corrected as shown in the following equation (4) with respect to the i-th stand setting roll speed v _0i corresponding to the rolling speed (roll speed of the final stand) v ₀₅ .

v _i = v _0i (1−Δv) (4)

Thus, in this Embodiment 1, when the rolling speed is reduced as the material to be rolled is cut, the roll speeds v _i (i = 1 to 4) of all the stands other than the final stand are corrected. By doing so, the occurrence of troubles can be suppressed as compared with the prior art while suppressing fluctuations in the plate thickness.

[Embodiment 2]
FIG. 2 is a schematic diagram showing Embodiment 2 of the present invention.

  Usually, in a cold tandem rolling mill, the tension between stands, and the tension on the entry side and the exit side on the rolling mill are measured by a tension meter 6 as needed.

In the second embodiment of the present invention, in addition to the first embodiment (FIG. 1), as shown in FIG. 2, an upper limit value is set for the final stand entry side tension _Tin5 , and the final stand entry side tension T _{When in5} reaches the upper limit value, the output of the control amount Δv is held.

That is, when the final stand entry side tension T _in5 reaches the upper limit, the correction amount from the i-th stand setting roll speed v _0i regardless of the variation ΔP of the final stand rolling load P from the recording rolling load P _0. Is set to a constant value.

In this way, in the second embodiment, by providing an upper limit to the final stand entry side tension T _in5 , the thickness variation is slightly larger than when no upper limit is provided, but rolling is performed without any trouble. Will be able to.

[Embodiment 3]
FIG. 3 is a schematic diagram showing Embodiment 3 of the present invention.

In the embodiment 3, in the second embodiment described above, instead of the final stand entry side tension T _in5 for setting the upper limit value minus the final stand outlet side tension T _out5 from the last stand entry side tension T _in5 tension It may be set an upper limit to the difference [Delta] T _5, when the tension difference [Delta] T ₅ has reached the upper limit value, so that to hold the output of the control amount Delta] v.

That is, when the tension difference ΔT _{5 obtained} by subtracting the final stand exit side tension T _out5 from the final stand _entry side tension T _in5 reaches the upper limit value, the variation ΔP of the final stand rolling load P from the recording rolling load P _{0 is} increased. Regardless, the correction amount from the i-th stand setting roll speed v _{0i is} set to a constant value.

In this way, in this third embodiment, by providing an upper limit on the final stand entry side exit side tension difference ΔT ₅ , the thickness variation is slightly larger than when no upper limit is provided, but rolling without trouble is performed. Can be done.

[Embodiment 4]
FIG. 4 is a schematic diagram showing Embodiment 4 of the present invention.

  In Embodiment 4 of the present invention, when the roll speeds of all the stands (the first stand to the fourth stand) other than the final stand (the fifth stand) are corrected as in Embodiments 1 to 3 above, The final stand exit side tension is changed according to the correction amount of the roll speed.

That is, when the cutting point of the material to be rolled 1 approaches and the rolling speed starts to _decrease and _reaches a predetermined rolling speed, the rolling load P ₀ of the final stand is recorded, and at the same time, the final stand entry side tension _{Tin 5 is reached.} The tension difference ΔT ₅ minus the exit side tension T _out5 is recorded, and the recorded tension difference is set to the reference tension difference ΔT ₅₀ so that the final stand exit side tension T _{out5_ref} shown in the following formula (5) is obtained. The final stand exit side tension T _out5 is changed by adjusting the rotation speed of the reel 8.

T _{out5_ref} = T _in5 −ΔT ₅₀ (5)

The reference tension difference ΔT ₅₀ may be set in advance.

Further, _{instead of} the above-mentioned final stand tension difference ΔT ₅ , the final stand tension ratio T _out5 / T _in5 is recorded, and the recorded final stand tension ratio is set to the reference tension ratio T _out50 / T _in50 , and the following (6) as a final stand delivery side tension T _{Out5_ref} shown in formula, by adjusting the rotational speed of the take-up reel 8, it may be changed a final stand delivery side tension T _out5.

_{Tout5_ref} = _Tin5 × ( _Tout50 / _Tin50 ) (6)

The reference tension ratio T _out50 / T _in50 may be set in advance.

Incidentally, in order to change the final stand exit side tension T _out5 , the rotation speed of the take-up reel 8 may be changed as shown in FIG. 4, and the bridle roll 9 is provided on the exit side of the rolling mill as shown in FIG. 5. When the pinch roll 10 is installed on the exit side of the rolling mill as shown in FIG. 6, the rotational speeds of the bridle roll 9 and the pinch roll 10 may be adjusted.

In this way, in the fourth embodiment, the roll speed v _i (i = 1 to 4) of all the stands other than the final stand is corrected, and at the same time, the final stand exit-side tension T _out5 is changed, whereby the plate The rolling stability when performing thickness control is further improved.

As an example of the present invention, a low carbon hot rolled steel sheet having a thickness of 4.5 mm and a width of 1100 mm was pickled, and then cold-rolled to a thickness of 0.8 mm by a 5-stand tandem cold rolling mill. The work roll diameter (diameter) from the first stand to the fourth stand was 600 mm, and the roll surface roughness was 0.3 μmRa by cylindrical polishing. The work roll diameter of the fifth stand was 380 mm, and the roll surface roughness was 2.2 μmRa by electric discharge dull processing. The lubricant was supplied by diluting a synthetic ester-based rolling oil having a viscosity of 50 mm ² / sec (viscosity at 40 ° C.) to 2% (volume%) and heating to 60 ° C.

  Then, the plate thickness fluctuation and tension fluctuation when the rolling speed (roll rotation speed of the final stand) was decelerated in 20 seconds from 1500 mpm in the steady state to 100 mpm were compared between the comparative example, the conventional example, and the present invention example. In addition, the 5th stand rolling load at the time of steady state was 6860kN, the 5th stand entrance side tension was 129kN, and the exit side tension was 43kN (all are average values).

  Here, in the comparative example, the plate thickness control was performed using only the conventional exit monitor AGC. Further, as a conventional example, plate thickness control was performed by the method described in Patent Document 1.

  On the other hand, thickness control was performed based on said Embodiment 1-4 as this invention example (invention example 1-5). At that time, in the PID controller, the P (proportional) control gain was set to 0.6, and the other gains were set to zero.

  Table 1 summarizes the specific implementation conditions and results (sheet thickness variation, rolling stability) of each of the inventive examples, comparative examples, and conventional examples.

As shown in Table 1, in the example of the present invention, the recording rolling load (P _{0 in the} formula (1)) was recorded when the rolling speed reached 300 mpm. Although there was variation in each coil, the average was 7130 kN. On the other hand, in the conventional example, the recording rolling load is a value when the rolling speed is 1500 mpm. The average was 6860 kN as described above. In the comparative example, such a load was not recorded.

  Further, the exit monitor AGC by the fifth stand exit side X-ray thickness gauge (not shown) was used under the same conditions in all examples, and the thickness variation was investigated.

  In the example of the present invention, all the roll speeds of the fourth stand and the third to first stands are changed, whereas in the conventional example, only the fourth stand is changed, and in the comparative example, the roll speed is changed. First, the reduction position was changed.

  Note that five patterns can be considered for handling the upper limit of tension according to the example of the present invention. In Example 1 of the present invention (corresponding to Embodiment 1), the upper limit of tension is not set. In Example 2 of the present invention (corresponding to Embodiment 2), an upper limit of 5% variation was set for the fifth stand entry side tension. In Example 3 of the present invention (corresponding to the third embodiment), the difference in tension between the fifth stand entry side and the exit side when decelerated to 300 mpm is recorded, and the tension difference between the fifth stand entry side tension and the exit side is recorded. An upper limit value of 5% variation was set. In Invention Examples 4 and 5 (corresponding to Embodiment 4), the tension on the fifth stand entry side and the exit side when decelerating to 300 mpm during steady rolling of 1500 mpm was recorded, and the difference was maintained. The fifth stand exit side tension was corrected.

  In any of the examples, rolling could be performed without causing any major troubles such as breakage and seizure. After rolling, the appearance of the steel sheet surface was visually observed to confirm the presence or absence of a chattering pattern.

  As shown in Table 1, in the comparative example, a plate thickness variation of 20 μm occurred. In the conventional example, chattering occurred in the fourth and fifth stands, and stable rolling could not be performed.

  On the other hand, in the present invention examples (Invention Examples 1 to 5), stable rolling could be performed while suppressing the plate thickness fluctuation.

  According to the present invention, in a cold tandem rolling mill, effective sheet thickness control can be performed at the time of deceleration accompanying inevitable cutting of a material to be rolled.

1 Rolled material (steel plate)
2 Work Roll 3 Backup Roll 4 Intermediate Roll 5 Rolling Oil Supply Nozzle 6 Tension Meter 7 Load Cell 8 Take-up Reel 9 Bridle Roll 10 Pinch Roll 11 Plate Thickness Control Device

Claims (5)

When rolling with a cold tandem rolling mill, when the rolling speed is reduced to cut the material to be rolled, the rolling speed is preset at the final rolling stand while the rolling speed is reduced at the trailing edge of the material to be rolled. Cold tandem rolling is characterized in that the rolling load at the time of speed is recorded, and thereafter the roll speed of all rolling stands other than the final rolling stand is corrected according to the amount of variation from the recorded rolling load. The rolling method of the machine.   When the final rolling stand entry side tension is set to an upper limit, and the final rolling stand entry side tension becomes the upper limit, the correction amount of the roll speed is made constant regardless of the amount of variation from the recording rolling load. The rolling method of the cold tandem rolling mill according to claim 1.   When an upper limit is set for the tension difference between the entry side and the exit side of the final rolling stand, and the tension difference between the entry side and the exit side of the final rolling stand becomes the upper limit, the roll speed is set regardless of the amount of variation from the recording rolling load. 2. The rolling method for a cold tandem rolling mill according to claim 1, wherein the amount of correction is constant.   The rolling method of the cold tandem rolling mill according to any one of claims 1 to 3, wherein a final rolling stand outlet side tension is changed according to a correction amount of the roll speed.   A method for producing a steel sheet, comprising producing a steel sheet using the rolling method of the cold tandem rolling mill according to any one of claims 1 to 4.

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