JP5821568B2 - Steel strip rolling method - Google Patents

Description

  The present invention relates to a steel strip rolling method using a tandem rolling mill.

  In recent years, in the field of continuous hot rolling and the like, various crown control mills such as a pair cross roll rolling mill have been put into practical use, and as a result, it has become possible to stably produce a flat steel strip without a plate crown. However, the steel strip is more likely to meander during rolling as much as the sheet crown becomes smaller, especially when the tail end of the material to be rolled (hereinafter described as an example of a “hot-rolled steel strip”) falls out. A new problem has arisen in that the hot-rolled steel strip collides with the side guide and falls down and is rolled, so-called narrowing occurs. Improving the passability of the tail end portion of the hot-rolled steel strip in a finish rolling mill is a very important issue in order to improve the operation rate and roll basic unit.

  The meandering phenomenon of a steel strip in a rolling mill is generally said to have a second-order integral characteristic. FIG. 9 shows the physical interpretation, and FIG. 9 (A) is a view of the moment when the tail end of the steel strip passes through the work roll as viewed from above. For example, when the steel strip meanders, the rolling load on the side where the steel strip has approached becomes higher than one as shown in FIG. Naturally, since the narrow side of the roll gap is rolled thinner than the other, it is elongated longer in the rolling direction, and the sheet passing speed is slower than the other. For this reason, as shown in FIG. 9 (A), the steel strip bends in a dogleg shape with the rolling part as a boundary. Once the steel strip is bent, the amount of meandering from there increases with time. Thereby, as shown in FIG. 9 (B), when the plate path is removed from the roll center, the mill elongation in the direction in which the steel strip is bent (right direction in FIG. 9 (B)) increases, and the roll gap opens, As shown in FIG. 9C, by further promoting the deflection, a meandering amount proportional to the square of time is generated.

  As shown in FIG. 10, a typical steel strip meandering control technique for avoiding such a problem is proportional control so as to cancel the left-right roll opening difference Sdf generated by the left-right difference Pdf of the rolling load of the rolling mill. This is meandering control (parallel stiffness control) for moving the leveling correction amount SL. In FIG. 10, α is a control gain (0 to 1), and M is parallel rigidity. This meandering control technique is a method (generally referred to as leveling operation) for controlling the leveling correction amount SL of a rolling mill reduction device (screw, hydraulic cylinder, etc.) in a direction to suppress meandering according to the following equation (i). . In the following formulas (i) to (iii), α is a control gain, Pdf is a left-right difference in rolling load (hereinafter referred to as “differential load Pdf”), Sdf is a difference in opening between left and right rolls, and M is parallel rigidity or Left and right rigidity, L is the distance between the left and right rolling devices, and yc is the amount of deviation of the center of the hot rolled steel strip relative to the center in the width direction of the rolling line (hereinafter simply referred to as “meander amount yc”).

The parallel stiffness or the left / right stiffness M is represented by the ratio of the differential load Pdf and the left / right roll opening difference Sdf at the reduction device position, as shown in the following equation (ii). Further, the relationship between the meandering amount yc and the differential load Pdf is expressed by the following equation (iii). That is, in a rolling mill with a high parallel rigidity M, the left-right roll opening difference Sdf due to the differential load Pdf is less likely to occur, and the differential load Pdf generated by the meandering amount yc of the steel strip from the relationship shown in the following equation (iii). Therefore, the left-right roll opening difference Sdf due to the occurrence of the difference is less likely to occur.
SL = -α (Pdf / M) (i)
M = Pdf / Sdf (ii)
yc = (Pdf · L) / 2P = (Sdf · L) / (2P · M) (iii)

  As shown in the above formula (iii), the meandering amount yc of the steel strip and the differential load Pdf are in a proportional relationship. However, in actual rolling, there are many other factors that generate the differential load. For example, left and right plate thickness difference of steel strip, left and right temperature difference (≒ left and right plastic constant difference), left and right spring constant difference due to rolling mill corrosion and wear deterioration, thrust force between rolls due to parallelism deviation of work roll and backup roll, etc. Is that. In order to monitor all the factors of the differential load, a plurality of sensors are required corresponding to each factor, resulting in a large introduction cost and maintenance cost. Further, the meandering amount yc shown in the above formula (iii) is in the region to be rolled sandwiched between the upper and lower work rolls. For example, when providing a meandering sensor, inevitably to avoid interference with the work rolls. Since it is necessary to install at a position retracted several meters from the rolled region, it is difficult to directly measure the meandering amount yc in the rolled region.

  For the above reasons, it is practically difficult to extract only the differential load due to the meandering amount yc from a plurality of differential load factors, and it is necessary to perform the reduction position control based on the differential load Pdf which is the sum of all the factors. there were. Therefore, if meandering control is performed assuming that the differential load Pdf generated during rolling is entirely due to the meandering amount yc, the reduction position control becomes over-controlled due to the differential load fluctuation due to other factors, conversely, the narrowing trouble is promoted. Therefore, there is a problem that the current control gain α has to be set low depending on the rolling conditions, and therefore the trouble of narrowing down due to the tail end meandering cannot be solved completely.

The above technique is a technique for controlling the meandering of the tail end generated during rolling in the i-th stand (= the own stand) by leveling control in the i-th stand, and the (i-1) th stand on the upstream side thereof. It can be easily imagined that it is effective to prevent tail end meandering by setting leveling optimally in the stage before rolling is completed (hereinafter referred to as “rolling steady part”).
However, it is actually difficult to set the leveling optimally based on the differential load Pdf by the meandering amount yc in the rolling steady portion by applying the above technique. In the steady rolling part of tandem rolling, in addition to restraining the steel strip due to the fact that the front and rear stands are in a rolled state, there is an effect of suppressing meandering due to the inter-stand plate tension before and after any i-th stand (= own stand). For this reason, even if the leveling of the i-th stand is an unsuitable condition for inducing the tail end meandering in the rolling steady part, the left-right asymmetry due to the leveling does not become manifest as the meandering amount yc. For this reason, the inappropriate leveling setting becomes apparent when the rolling of the stand (i-1) is completed and the tail end meandering becomes apparent. There are many cases to do. Further, as described above, the leveling control based on the differential load Pdf, which is a conventional technique, is based on the differential load due to the meandering amount, and it has been difficult to apply to the rolling steady portion where the meandering does not become apparent.

  As means for solving these problems, in Patent Document 1, a tension measuring roll supported rotatably in a state parallel to the rolling roll is disposed between any i-th stand and (i + 1) -th stand, For the vertical reaction force applied to the tension measuring roll by the rolling direction tension, the left-right difference of the vertical reaction force in the plate width direction is detected, and the tail end of the steel strip is the (i-2) number stand (I-1) The leveling control in the i-th stand is performed so that the left-right difference in the vertical reaction force becomes the target value from the predetermined time before the predetermined time between the i-th stands, more than the time required for the control stabilization. The control is locked until the tail end of the steel strip passes through the stand (i-1) at the same time as or after the predetermined time, and the tail end is kept at the conventional differential load Pdf. To implement leveling control based on Rolling methods have been proposed was. Moreover, in patent document 2, using the tension | tensile_strength roll divided | segmented into multiple in the plate width direction, the reaction force distribution of the plate width direction is detected, and the meander of a steel strip is detected from the reaction force detected individually by each division | segmentation roll. A rolling method has been proposed in which the amount of the steel strip is obtained from the detected reaction force and the amount of meandering, and the meandering and shape of the steel strip are controlled based on the amount of meandering and the shape of the plate. .

Japanese Patent Publication No. 7-96124 JP 2006-346714 A

  Patent Document 1 discloses a leveling control method related to the third and subsequent stands from the upstream except for the final stand of a hot finishing mill composed of at least four stands, and Patent Document 2 does not mention the number of stands. Although the leveling control method in a rolling mill is disclosed, in tandem rolling with a plurality of stands, not only the leveling control method for the i-th stand (= own stand) but also between a plurality of stands (especially between front and back stands). It is necessary to consider the interaction.

In the method of Patent Document 1, as shown in FIG. 11, even when the leveling at the (i + 1) th stand on the downstream side is inappropriate, the steel strip between the ith stand (= own stand) and the (i + 1) th stand In order to control the left-right difference in the vertical reaction force applied to the tension measuring roll by the rolling direction tension, the leveling of the i-th stand becomes the inappropriate leveling of the (i + 1) -th stand on the downstream side. Therefore, the meandering of the entire tandem rolling mill group may be induced. That is, in order to properly perform the leveling control shown in the prior art in the i-th stand (= own stand), it is assumed that the leveling of the downstream (i + 1) -th stand is appropriate. This method has no such premise. Therefore, the method of Patent Document 1 cannot prevent a meandering trouble, and conversely, the meandering trouble may be more easily induced.
Also, in Patent Document 2, as in Patent Document 1, the interaction between the front and rear stands is not mentioned, and if the leveling of the (i + 1) th stand on the downstream side is inappropriate, the i-th stand (= There is a risk of inducing meandering in your own stand.

Moreover, as a fundamental problem derived from the structure of the tandem rolling mill, various sensors (plate thickness gauges, thermometers) are installed downstream of the final nth stand of the tandem rolling mill, and cooling equipment Therefore, it is difficult to arrange the tension measuring roll, and it is difficult to perform the leveling control as described above at the final n-th stand.
Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art and provide a steel strip rolling method capable of performing stable meandering control over the entire rolling length from the rolling steady part to the tail end part. There is to do.

The features of the present invention for solving the above-described problems are as follows.
[1] A tension measuring roll arranged in parallel with the rolling roll is brought into contact with the steel strip between two or more consecutive tandem rolling mills consisting of Nos. 1 to n stands (where n ≧ 3). For the vertical reaction force applied to the tension measuring roll by the tension in the rolling direction of the belt, the left-right difference Δf1 of the vertical reaction force in the plate width direction or the left-right deviation Δf2 of the vertical reaction force distribution in the plate width direction is The left-right difference Δf1 or the left-right deviation Δf2 between any i-th stand and (i + 1) -th stand is zero or less than the target value at any time until detection and completion of rolling at the (i-1) -th stand So that the leveling control (L ₁ ) is performed at the i-th stand, and the leveling control (L ₁ ) is terminated before the rolling at the (i-1) -th stand is completed , and
At least between the last n-th stand, (n-1) -th stand, and (n-2) -th stand by the tension measuring roll in the vertical direction reaction force difference Δf1 in the plate width direction or in the plate width direction. The left-right deviation Δf2 of the vertical reaction force distribution is detected, and between the (n-1) th stand and the (n-2) th stand, between the (n-1) th stand and the last nth stand, (n-2) A steel strip rolling method in which the leveling control (L ₁ ) is performed so that the left-right difference Δf 1 or the left-right deviation Δf 2 is zero or less than a target value between the number stand and the (n−1) number stand, respectively .
After the coiler winding is started and the inter-stand tension is stabilized, in the final n-th stand, in the plate width direction detected by the tension measuring roll between the (n-1) -th stand and the final n-th stand. Leveling control (L ₂ ) is started so that the left-right difference Δf1 in the vertical reaction force or the left-right deviation Δf2 in the vertical reaction force distribution in the plate width direction is zero or less than the target value, and the leveling operation at the final nth stand After the amount is saturated
The leveling control (L ₁ ) is started at an earlier timing toward the downstream stand, and the left-right difference Δf 1 between the i-th stand and the (i + 1) -th stand in the i-th stand where the leveling control (L ₁ ) is started. Alternatively, after the left-right deviation Δf2 becomes zero or less than the target value, the leveling control (L ₁ ) at the (i-1) th stand on the upstream side is started, and the steel strip rolling method is characterized in that

[2] A rolling method for a steel strip according to [1], wherein the control gain of the final n-th stand is 3 to 5 times that of the (n-1) -th stand.
[3] A method for producing a steel strip, comprising producing a steel strip using the rolling method according to the above [1] or [2] .

  According to the present invention, the leveling setting can be optimally performed at the stage of the rolling steady part before the meandering becomes obvious at the tail end of the steel strip, and therefore meandering at the tail end can be prevented. By performing stable meandering control, the steel strip can be stably manufactured without causing a drawing trouble. For this reason, even in the production of thin steel strips, it is possible to ensure a good steel strip shape and achieve stable threading, and to achieve excellent quality while achieving improvement in line operation rate and roll basic unit by suppressing drawing trouble. The steel strip can be manufactured stably.

1 schematically shows an embodiment when the present invention is applied to rolling a hot-rolled steel strip by a hot finish rolling mill (tandem rolling mill), and is a side view of the hot finish rolling mill. The side view which shows the roll for tension | tensile_strength arrange | positioned between rolling stands in embodiment of FIG. FIG. 2 is a view taken along the line AA in FIG. 2 (a front view schematically showing a tension measuring roll). The front view which shows typically other embodiment of the roll for tension | tensile_strength used in this invention. The flowchart at the time of the control start in one Embodiment of this invention The flowchart at the time of the end of control in one embodiment of the present invention The drawings for explaining the effects of the present invention The chart which shows the off-center amount and differential tension between each stand about the conventional method of this example and the method of the present invention Explanatory diagram showing physical interpretation of meandering phenomenon Explanatory diagram for explaining the concept of conventional parallel stiffness control for meandering FIG. 2 is a diagram for explaining problems in a conventional technique that performs leveling control based on differential tension when a control start order for each stand is not considered.

1 to 3 schematically show an embodiment when the present invention is applied to rolling a hot-rolled steel strip by a hot finish rolling mill (tandem rolling mill), and FIG. FIG. 2 is a side view showing a tension measuring roll disposed between rolling stands, and FIG. 3 is an arrow view taken along line AA in FIG.
The method of the present invention is intended for rolling steel strips performed in a tandem rolling mill having three or more stands, and the hot finish rolling mill of this embodiment is composed of seven rolling stands 1. In the method of the present invention, a tension measuring roll 2 is disposed between two or more continuous stands of a tandem rolling mill, and a left-right difference in the strip width direction of the steel strip tension is detected. Specifically, as shown in FIG. 5, the tension measuring roll 2 arranged in parallel with the rolling roll is brought into contact with the steel strip S and is loaded on the tension measuring roll 2 by the rolling direction tension of the steel strip S. As for the vertical reaction force, the left-right difference Δf1 of the vertical reaction force in the plate width direction or the left-right deviation Δf2 of the vertical reaction force distribution in the plate width direction is detected.

  The tension measuring roll 2 is of a so-called looper roll type, is disposed in parallel with the rolling roll at a position below the pass line, and is held by the holding arm 3 so as to be rotatable in the vertical direction. The tension measuring roll 2 is brought into contact with the steel strip S in the plate width direction, and by pushing up the steel strip S from below, a vertical reaction force is applied by the rolling direction tension of the steel strip S. The reaction force in the vertical direction is detected independently on the work side and the drive side of the rolling roll, that is, on both end sides of the tension measuring roll 2 (both sides in the plate width direction). Desired. As a method of independently detecting the vertical reaction force on the working side and the driving side, a load cell method in which a load cell is installed in the roll chock of the tension measuring roll 2 and a torsion bar is installed around the arm rotation axis of the holding arm 3 A torsion bar method is generally used, but is not limited thereto. The tension measuring roll 2 of the present embodiment employs a load cell system using the load cell 4.

  As shown in FIG. 4, the tension measuring roll 2 is divided into a plurality of segments 20 in the plate width direction, and the reaction force in the vertical direction applied to each segment 20 is independent for each segment. It may be possible to detect the vertical reaction force distribution in the plate width direction. The tension measuring roll 2 can detect the left-right deviation Δf2 of the vertical reaction force distribution in the plate width direction. In addition, as a method of detecting the vertical reaction force distribution in the plate width direction acting on each segment 20 constituting the roll, a load cell method (see, for example, Japanese Patent Application Laid-Open No. 10-314821 and Special Table 2003-504221) There are an air bearing method (for example, see JP-A-2004-309142) and a torque meter method (for example, see JP-A-2006-346714), but any method may be used.

It is basically arbitrary between which stand the tension measuring roll 2 is arranged, but since the meandering of the steel strip S is likely to occur in the downstream stand (stand on the rear stage of the rolling mill), at least the final nth A tension measuring roll 2 is arranged between each of the stand, the (n-1) th stand, and the (n-2) th stand, and at least the (n-1) th stand and the (n-2) th stand according to the present invention. It is preferable to implement leveling control.
Further, in the case of a rolling mill having 7 or more stands, the steel strip S is likely to meander after the 4th stand. Therefore, in this embodiment, the 4th stand (= (n-3) th stand), the 5th stand (= (N-2) stand), 6 stand (= (n-1) stand), and the final n stand, the tension measuring roll 2 is disposed between the 4 stand and the 6 stand. The leveling control according to the present invention is performed in three stands.

In the method according to the present invention, the left-right difference Δf1 or the left-right deviation Δf2 of the vertical reaction force detected by the tension measuring roll 2 between any i-th stand and (i + 1) -th stand (hereinafter, for convenience of explanation, these are used). The leveling control at the i-th stand (hereinafter, this leveling control is referred to as “leveling control performed at the final n-stand” so that the “differential tension Δf”) is zero or below the target value. Leveling control (L ₁ ) ”is performed. This leveling control (L ₁ ) is performed at any time until rolling at the stand (i-1) is completed, and (i-1 ) It is finished until the rolling at the number stand is completed, that is, the tail end portion of the steel strip S passes through the (i-1) number stand.

Usually, when the rolling of the tail end of the steel strip S is completed in the (i-1) th stand, the tension between the (i-1) th stand and the ith stand is controlled to be zero. Is normal. This is because when the tension is applied between the stand (i-1) and the stand i, and the rolling at the stand (i-1) is completed, the tension between the stands is instantaneously released as the rolling is completed. For this reason, there is a risk of causing a plate trouble such as the tail end portion of the steel strip S jumping up. Therefore, the range in which the leveling control (L ₁ ) using the differential tension Δf between the stands according to the present invention can be applied is inevitably limited to the period in which the tension between the stands is stably applied. leveling control in the stand (L ₁₎ is required to be completed by rolling in the (i-1) th stand is completed, i.e., until the tail end of the steel strip S passes through the (i-1) th stand There is.

In the present invention method, the leveling control (L _1), as well as start at an earlier timing as the stand downstream, in the i-th stand started leveling control (L _1), between the i-th stand and (i + 1) th stand After the differential tension Δf becomes zero or less than the target value, that is, after the leveling operation amount in the i-th stand is saturated, the leveling control (L ₁ ) in the (i-1) -th stand on the upstream side is performed. It is what is started.
Here, the most downstream stand capable of performing the leveling control (L ₁ ) is naturally the (n−1) th stand. Leveling control of the final nth stand will be described later.

In the present invention, the leveling control (L ₁ ) is started in the order of the downstream stand → the upstream stand in the order of the leveling setting based on the differential tension Δf between the i-th stand and the (i + 1) -th stand in the i-th stand. This is because it is premised that leveling is properly set in the downstream stand including the (i + 1) th stand in order to perform correctly. That is, when a leveling operation is performed on the i-th stand, the left and right plate thickness difference on the i-th stand exit side changes, and the change point propagates to the downstream stand at the exit-side rolling speed. The input condition in the rolling phenomenon of the downstream side stand (i + 1, i + 2,...) Is changed by the leveling operation in the upstream side stand. For this reason, when the leveling control (L ₁ ) is not started in the order of the downstream stand → the upstream stand as in the present invention (when the control start order is not considered), the leveling control in the i-th stand is performed. The correct leveling setting is not possible due to the improper leveling setting in the downstream side stand (i + 1, i + 2,...), The meandering behavior in the downstream side stand is changed, and as a result, the meandering in the entire tandem rolling mill is induced. There is a fear. On the other hand, in the present invention, when the leveling control (L ₁ ) is started at the i-th stand, the leveling control at the (i + 1) -th stand, the (i + 2) -th stand on the downstream side has already started. In addition, since the leveling operation amount is saturated, appropriate leveling control can be performed for the entire tandem rolling mill in response to the upstream condition change.

  The rolling at the final n-th stand can be said to meander in terms of thin plate thickness, but in reality, the balance of the roll gap is not so much collapsed and is relatively stable. When the rolling mill is a hot rolling finish rolling mill, the final n-th stand of the finishing mill is the final rolling stand in the hot rolling line so that the product dimensions and shape are within the customer's required specifications on the stand exit side. Need to control. Usually, an X-ray thickness meter capable of measuring a plate thickness profile in the plate width direction is installed in the immediate vicinity of the exit side of the finish rolling mill, and roll gap control based on the information is performed. Regarding the balance between the left and right roll gaps, that is, the difference between the left and right product plate thicknesses, the operator performs the balance adjustment of the roll gaps so that the right and left plate thickness differences are eliminated at the last nth stand of the finishing mill that is the last stand. There are many cases.

Furthermore, the downstream side of the final nth stand is a table roll row of 100 meters or more having a cooling facility, and a winding facility, but if the roll balance in the final nth stand is inappropriate, the meandering of the plate occurs, Troubles in plate passing such as a defective quality in which the coil winding shape becomes a bowl shape and a front end sticking trouble in a side guide attached to the winding equipment occur. For this reason, since the balance adjustment of the left and right roll gaps is performed also from the viewpoint of straight advanceability of the front end of the plate in the table roll row, it is rare that the roll gap balance of the final nth stand of the finishing mill collapses extremely.
Therefore, the rolling at the final n-th stand has no major problem as long as appropriate control is performed regardless of the form of leveling control. However, in order to perform more appropriate meandering control, it is preferable to perform leveling control with reference to the differential tension Δf between the (n−1) th stand and the final nth stand as described below.

  If the roll gap balance at the final nth stand is extremely collapsed at any time after the rolling at the final nth stand is started until the rolling at the (n-1) th stand is completed, the final n A plate on the side where the roll gap of the final n-th stand is wide is constrained in the rolling bit part of the (n-1) -th stand, so that the plate is about to meander to the side where the roll gap is wide just below the bit of the stand. Inter-tension increases. For this reason, also in the last nth stand, the roll gap balance can be corrected in a direction to eliminate the differential tension Δf between the (n−1) th stand and the last nth stand.

However, in the final nth stand, leveling control is started at an earlier timing than the (n-1) th stand, and the control gain of the final nth stand is about 3 to 5 times that of the (n-1) th stand. A large value is desirable. Assuming that the same left and right roll gap difference exists in the final nth stand and the (n-1) th stand, generally, the roll gap difference in the (n-1) th stand is the difference tension Δf. This is because the effect is about 3 to 5 times larger than that of the final n-th stand.

Further, unlike the leveling control before the (n-1) th stand, after the leveling control of the final nth stand is started, after the differential tension Δf becomes zero or less than the target value, the upstream (n-1) The control start timing for starting the leveling control at the watch stand cannot be applied. For this reason, a temporal time lag may be provided, for example, the leveling control of the (n-1) th stand is started after a predetermined time sufficient for the leveling control in the final nth stand to saturate.
By this method, even in the final n-th stand that does not have the differential tension Δf measuring means on the downstream side, it is possible to control the roll gap in a direction that balances with the upstream (n-1) -th stand. .

  FIG. 5 is a flowchart at the start of control in an embodiment of the present invention. After coiler winding is started and the tension between the stands is stabilized, leveling control of the final n-th stand is started. At this time, in order to prevent a situation in which the leveling control amount becomes abnormally excessive due to a failure of the differential tension meter or an excessive setting before control gain tuning, etc. It is desirable to provide The limiter value may be set in accordance with the operation state of the rolling line, and in this case, it may be set to about 500 μm. After a predetermined time, the (n−1) th stand so that the differential tension Δf between the (n−1) th stand (= 6th stand) and the final nth stand (= 7th stand) becomes zero or below the target value. Start leveling control at. By the above control, the leveling of the final n-th stand and the (n−1) -th stand is appropriately controlled so that the differential tension Δf between both stands is zero or less than the target value. Thereafter, the same leveling control in the order of the (n-2) th stand and the (n-3) th stand, that is, the differential tension Δf between the ith stand and the (i + 1) th stand becomes zero or below the target value. Then, leveling control at the i-th stand is started sequentially.

  FIG. 6 is a flowchart at the end of the control. In the present invention, the rolling at the (i-1) -th stand is completed earlier than the timing for releasing the tension between the stands, that is, the steel strip. Leveling control at the i-th stand is terminated at a timing until the tail end part passes through the (i-1) -th stand. For example, the leveling control in the i-th stand is terminated at the timing when the tail end of the steel strip arrives between the (i-2) -th stand and the (i-1) -th stand.

  7 (a) and 7 (b) are conceptual diagrams showing the plate passing behavior when the control start order for each stand according to the present invention is considered. When the control start order is not considered as in the prior art shown in FIG. 11, meandering of the entire tandem rolling mill is promoted by improper leveling setting at the downstream side stand of the i-th stand that performs leveling control. While there is a problem, as in the present invention, by starting meandering control from the stand on the downstream side, the leveling of the entire tandem rolling mill can be properly controlled, and the meandering trouble at the tail end of the steel strip can be prevented. Can prevent in advance.

  The method of the present invention is a particularly suitable method for rolling a hot-rolled steel strip by a tandem hot finish rolling mill, but can also be applied to rolling a steel strip in a cold rolling line. Similar to rolling of rolled steel strip, it is effective for preventing meandering of the steel strip in a tandem cold rolling line. Especially in the rolling of cold-rolled steel strip, because the tension per unit area between the stands constituting the tandem rolling mill is large, the unstable behavior of the plate due to the difference in the left and right roll gap is less obvious than in the case of hot rolling. . That is, since the detection means for the difference between the left and right roll gaps is poor, even when a gap difference due to an abnormality on the rolling mill side, such as a change in the mill constant, occurs, detection may be delayed and a sheet feeding trouble may be induced. Therefore, the present invention for determining the roll gap balance during rolling based on the differential tension can be a very effective means for cold rolling.

  In a tandem hot finish rolling mill, the hot-rolled steel strip was rolled by the method of the present invention and the conventional method. In the method of the present invention, tension measuring rolls were arranged between the stands of the third stand to the seventh stand among all the seven stands of the hot finish rolling mill (between all four stands). This tension measuring roll detects the reaction force in the vertical direction applied to the tension measuring roll by the tension in the rolling direction of the steel strip independently from each other on the working side and the driving side by means of a load cell installed in the roll chock on the working side and driving side. Thus, the left-right difference Δf1 of the vertical reaction force in the plate width direction can be detected.

Two coils were continuously rolled under the same operating conditions (final stand outlet side plate thickness h ₀ = 1.2 mm, plate width b = 1200 mm) by the method of the present invention and the conventional method (no leveling control).
According to the method of the present invention, after the coiler winding is started and the tension between the stands is stabilized, the left and right difference Δf1 between the sixth stand and the seventh stand between the working side and the driving side Δf1 becomes zero. = Last stand) leveling control started. After the leveling operation amount in the 7th stand was saturated, the leveling control in the 6th stand was started so that the left-right difference Δf1 between the 6th stand and the 7th stand became zero. Thereafter, the same leveling control in the order of the 5th stand, the 4th stand, and the 3rd stand, that is, the leveling at the ith stand so that the left-right difference Δf1 between the ith stand and the (i + 1) th stand becomes zero. Control started sequentially. Moreover, the leveling control in the i-th stand was terminated at the timing when the tail end of the steel strip reached between the (i-2) -th stand and the (i-1) -th stand.

  FIG. 8 shows data of the off-center amount and differential tension between the stands in the vicinity of the rearmost end rolling timing for the conventional method (FIG. 8A) and the method of the present invention (FIG. 8B). The off-center amount between the stands is an off-center amount based on the plate width detection sensor installed between the stands. For the stands where the plate width detection sensor is not installed, the off-center amount is calculated from the camera image installed at the upper part between the stands. Was detected.

  In the conventional method, rolling is started after adjusting the left-right balance of the upper and lower work roll gaps on the working side and the driving side in leveling zero level of the rolling mill before rolling. However, since there are various left-right asymmetry factors, such as the difference between the working side and the driving side of the rolling mill rigidity due to machine-related play and corrosion of the rolling mill, the above leveling zero tone is only an indicator for initial leveling. In actual rolling, the operator visually confirms the bend and plate shape (single elongation) at the tip and tail, and determines the leveling setting value empirically so that these balance right and left. The current situation is.

  In the conventional method (without control) shown in FIG. 8 (A), the tail end of the steel strip is largely off-center on the work side in the last stand and the sixth stand, and further, when meandering diverges, there is a throttle problem. It was a meandering state. On the other hand, in the method of the present invention shown in FIG. 8 (B), the differential tension Δf is stabilized so as to gradually approach zero at each stand by performing meandering control from the rolling steady part, which is the previous stage of the tail end. The meandering prevention effect at the tail end was confirmed.

DESCRIPTION OF SYMBOLS 1 Rolling stand 2 Roll for tension measurement 3 Holding arm 4 Load cell 20 Segment S Steel strip

Claims (3)

Rolling of the steel strip is carried out by bringing a tension measuring roll arranged in parallel with the rolling roll between two or more consecutive tandem rolling mills consisting of No. 1 to n stands (where n ≧ 3) in contact with the steel strip. For the vertical reaction force applied to the tension measuring roll by the directional tension, the left-right difference Δf1 of the vertical reaction force in the plate width direction or the left-right deviation Δf2 of the vertical reaction force distribution in the plate width direction is detected. (I-1) The left-right difference Δf1 or left-right deviation Δf2 between any i-th stand and (i + 1) -th stand is zero or less than the target value at any time until rolling at the number i stand is completed. In addition, leveling control (L ₁ ) is performed at the i-th stand, and the leveling control (L ₁ ) is terminated before the rolling at the (i-1) -th stand is completed , and
At least between the last n-th stand, (n-1) -th stand, and (n-2) -th stand by the tension measuring roll in the vertical direction reaction force difference Δf1 in the plate width direction or in the plate width direction. The left-right deviation Δf2 of the vertical reaction force distribution is detected, and between the (n-1) th stand and the (n-2) th stand, between the (n-1) th stand and the last nth stand, (n-2) A steel strip rolling method in which the leveling control (L ₁ ) is performed so that the left-right difference Δf 1 or the left-right deviation Δf 2 is zero or less than a target value between the number stand and the (n−1) number stand, respectively .
After the coiler winding is started and the inter-stand tension is stabilized, in the final n-th stand, in the plate width direction detected by the tension measuring roll between the (n-1) -th stand and the final n-th stand. Leveling control (L ₂ ) is started so that the left-right difference Δf1 in the vertical reaction force or the left-right deviation Δf2 in the vertical reaction force distribution in the plate width direction is zero or less than the target value, and the leveling operation at the final nth stand After the amount is saturated
The leveling control (L ₁ ) is started at an earlier timing toward the downstream stand, and the left-right difference Δf 1 between the i-th stand and the (i + 1) -th stand in the i-th stand where the leveling control (L ₁ ) is started. Alternatively, after the left-right deviation Δf2 becomes zero or less than the target value, the leveling control (L ₁ ) at the (i-1) th stand on the upstream side is started, and the steel strip rolling method is characterized in that The method of rolling a steel strip according to claim 1, wherein the control gain of the final nth stand is 3 to 5 times that of the (n-1) th stand. A steel strip manufacturing method using the rolling method according to claim 1 or 2 to manufacture a steel strip.

Images