JP3495178B2 - Continuous hot rolling of billets - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to joining of the following billets of a preceding billet to each other, which is unavoidable when continuously hot rolling the joining billet through a rolling mill. It is intended to prevent breakage and realize stable operation.

[0002]

2. Description of the Related Art Conventionally, in the hot rolling of steel slabs, it has been customary to heat the material to be rolled one by one to perform rough rolling and finish rolling to finish a product plate having a desired thickness. In such a rolling method, since the material is bited into the rolling mill one by one, there is a problem that the frequency of occurrence of defective biting is high, and the reduction of the yield due to the extension of the line stop time and the defective shape of the rolled material tip is avoided. There was a disadvantage.

In order to deal with these problems, recently, prior to finish rolling, the rear end portion of the preceding billet and the leading end portion of the trailing billet are heated, and they are butt-joined to each other and joined to carry out finish rolling. The rolling method has been adopted.

As a document relating to this point, Japanese Patent Application Laid-Open No. 6-1
Reference is made to JP-A-5317, JP-A-60-227913 and JP-A-2-127904.

The technique disclosed in Japanese Unexamined Patent Publication No. 6-15317 (hereinafter, simply referred to as Document 1) is arranged such that a looper is arranged between a plurality of stands and a preceding material and a trailing material are joined to each other and continuously. At the time of rolling, the outlet side plate thickness is controlled for each stand, and the amount of change in mass flow between stands is controlled to zero by manipulating the roll peripheral speed of the upstream stand. , In the case of continuously rolling plates of different sizes on the exit side of the rolling mill by joining the materials of the plate width, it is easy even if the size changing part may straddle a plurality of stands, and, It was said that it was possible to change the running plate thickness in a stable manner and to prevent breakage at the joint that is likely to occur during changing the running plate thickness.

Further, the technique disclosed in Japanese Patent Laid-Open No. 60-227913 (hereinafter simply referred to as Document 2) is a technique for continuously rolling a connected coil while changing the plate thickness between runs. The plate thickness before and after the change point is obtained by a plate thickness gauge installed on the entrance side of the rolling mill, and the rolling position and rolling speed change amount at the plate thickness change point are obtained based on the actual measured value of the plate thickness and rolling is performed. Yes, further, JP-A-2-127904
The gazette (hereinafter, simply referred to as Document 3) is for precisely tracking a welded portion of a rolled original plate and controlling the welded portion to be thicker than a reference plate thickness when rolled by a cold rolling mill. Therefore, even in these technologies, it was said that not only reduction of the off gauge but also breakage of the plate during rolling can be suppressed.

[0007]

By the way, in Document 1 and Document 2, there is a case where the joint portion becomes thin during rolling of the joined preceding material and trailing material, and eventually the plate breaks. However, it has not yet been possible to completely prevent breakage from the joint, which is a problem in continuous rolling of the joined materials.

Further, Document 3 is intended for a welded portion in cold rolling and has the following problems because it controls the roll peripheral speed of the rolling mill to change the tension of the material. That is, if excessive tension is applied to the joint in hot rolling, the thickness of the joint may be thin and may lead to breakage.In cold rolling, the plate thickness should be changed in a short section in the longitudinal direction of the plate. Although the shape of the plate is not disturbed by changing the plate thickness at the joint because it is possible, in hot rolling, the rolling speed is fast and the region where the plate thickness at the joint becomes thin moves toward the stand in the latter stage. Since it spreads in the longitudinal direction, the plate shape is disturbed due to the load fluctuation caused by changing the plate thickness.

An object of the present invention is to avoid breakage from the joint, which is inevitable when the preceding and following steel pieces are heated and joined at their ends and then continuously hot-rolled. At the same time, it proposes a continuous hot rolling method capable of reducing the shape defect of the plate that occurs when avoiding the fracture of the joint and stabilizing the rolling operation.

[0010]

According to the present invention, the rear end portion of a preceding steel piece and the front end portion of a trailing steel piece are heated and joined to each other, and then fed to a rolling facility having a plurality of stands arranged therein. Then, in the continuous hot rolling, the target strip thicknesses of the leading and trailing steel strips in each stand are set to be approximately the same, and the target strip thickness is set in the steady part target strip of each steel strip in each stand. When the side plate thickness is set, in at least one or more stands, the target output side plate thickness at the joint of the steel pieces is determined to be thicker than the steady part target output side plate thickness, and the joints of the steel pieces reach each stand. In the area from immediately before to immediately after passing, the rolling position of each stand is changed so that the steel strip output side plate thickness reaches the target weld side output plate thickness, that is, the steel strip connection part reaches each stand. Before the billet exit plate However, the rolling position of each stand is changed so that it becomes the joint target output side plate thickness, and after the steel plate joint passes through each stand, the steel plate outlet side thickness becomes the steady-state target outlet side plate thickness. Is a continuous hot rolling method for a steel slab, characterized in that the rolling position of each stand is changed.

In the present invention, the ratio of the joint target output side plate thickness of the stand upstream of the reference stand to the steady portion target output side plate thickness is the joint portion target output side plate thickness steady portion target of the reference stand. Set the reference stand and the target plate thickness of the joint of the stand upstream of this stand so that it becomes equal to the ratio to the output side plate thickness or becomes smaller gradually toward the upstream stand. It is preferable to change the rolling position of the stand on the upstream side.

Further, the ratio of the joint target output side plate thickness of the stand downstream of the reference stand to the steady part target output side plate thickness is such that the joint part target output side plate thickness of the reference stand is the constant part target output side plate thickness. It is preferable to determine the standard stand and the target joint plate thickness downstream of this stand as equivalent to the value of the ratio to, and change the rolling-down positions of the standard stand and the stand downstream of this stand.

Further, according to the present invention, the reduction position is changed so that the delivery side plate thickness of the steel piece increases at a constant rate before the joint reaches the stand, and the delivery position plate thickness becomes the target delivery side plate thickness. After that, the level is maintained, and after the joint passes through the stand, the rolling position can be changed so that the thickness of the steel strip on the delivery side is reduced at a constant rate.
It is advantageous to the present invention that the start point and the end point of the change of the rolling position of each stand are matched.

A change in rolling load caused by a change in the rolling position is predicted, and a change in shape due to the change in rolling load is suppressed by disposing a roll bender device on the stand and adjusting the bender force of the work roll. Or
The roll bender device and other shape control actuators are arranged on the stand to suppress it by adjusting the roll bender force of the roll bender device, and the adjustment range of the roll bender force falls within the adjustment capability of the roll bender device. Thus, the control amount of the other shape control actuator is adjusted.

When adjusting the control amounts of the other shape control actuators so that the roll bender force adjustment range falls within the adjustment capability of the roll bender device, the shape change caused by the adjustment of the control amount of the shape control actuator is performed. Adjust the roll bender force to suppress.

As another shape control actuator, a roll cross device capable of changing the roll cross angle during the running or a roll shift device for shifting the roll in the roll axial direction during the running is advantageously suitable.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings.

For example, FIG. 1 shows the structure of rolling equipment suitable for carrying out the present invention, where 1 is a rough rolling mill,
2 is a finish rolling mill shown as an example of 7 stands, and the preceding sheet bar S ₁ is provided between the rough rolling mill 1 and the finish rolling mill 2.
And a cutting machine 3 for cutting each end of the succeeding sheet bar S _2.
And a joining device 4 for heating the respective end portions of the sheet bars to a temperature at which they can be joined and pressing both sheet bars to join them.

Further, 5 is a tracking device for tracking the position of the joint portion of the sheet bar, 6 is a cutting machine for cutting the rolled plate to a predetermined length, and 7 and 7'are winders for winding the rolled plate. is there.

The ends of the sheet bars S ₁ and S ₂ that have passed through the rough rolling mill 1 are first cut into a predetermined shape by a cutting machine 3, and then, for example, an induction heating coil or the like (using welding means) that constitutes the joining device 4 is formed. If desired, the sheet bars S ₁ and S ₂ are pressed against each other and joined when they reach a predetermined temperature.

Immediately after the joining of the sheet bars, the temperature of the joining portion is about 100 ° C. higher than the temperature of the steady portion (about 1000 ° C.) regardless of the heating method as shown in FIG.

When the joint portion is rolled down in such a state, the deformation resistance is small and the rolling load is small in the high temperature portion, so that the plate thickness is reduced as compared with the steady portion, and the rolling direction around the joint portion after finish rolling is reduced. The plate thickness distribution is as shown in Fig. 3 when the finished plate thickness is 1 mm, and when the unit tension (tension per unit cross-sectional area) generated at the joint increases extremely, the joint breaks. (Because plate thickness fluctuations and tension fluctuations at the joints occur in a short time, conventional plate thickness control cannot prevent plate breakage).

This is not only a phenomenon in the case of temperature disturbance caused by the joining method, but also other disturbances such as a change in plate thickness and a change in plate width which may cause a reduction in rolling load at the joint. Is exactly the same.

In the present invention, first, the target steel strip thicknesses of the leading steel strip and the trailing steel strip of each stand are set to be substantially the same,
The target delivery side plate thickness is taken as the target delivery side plate thickness h _i ^ac of the stationary part of the steel slab. Then, when there is a risk of rupture between the i stand and (i + 1) stand for i stand (Standards stand) joint target delivery side thickness h _i ^ad, target delivery side thickness h _i of the constant region ^It is set to be larger than ^ac by a specified value. Here, the predetermined value in the above-mentioned standard stand is determined by the temperature, material, tension fluctuation, etc. of the joint portion.
To have a cross-sectional area of the joint (product of the actual output side thickness after rolling and the actual width after rolling) so that the joint does not break due to tension fluctuation between the i stand and the (i + 1) stand during rolling. It is preferable to set. The joint target output side plate thickness h _i ^ad in the standard stand is set to the steady part target output side plate thickness h
_It is set so that it is larger than _i ^ac by a predetermined value, and the rolling position is changed so that the outgoing plate thickness of the steel slab becomes the target thickness of the joint. Since it has a cross-sectional area, breakage is prevented. According to the present invention, the rolling position is changed so that the outgoing plate thickness at the joining part of the steel piece becomes the above-mentioned joining part target outgoing plate thickness, so the tension fluctuation between the stands is suppressed and the breaking of the joining part is prevented. It has the features that can.

Next, a method of changing the rolling position will be described. When performing continuous hot rolling using a finish rolling mill consisting of 7 stands, for example, the joining part of the plate is broken between the 6th stand (i stand) and the 7th stand (i + 1 stand) of the finish rolling mill. Assuming that there is a possibility that this may occur, the procedure for changing the pressing position of the sixth stand will be described below with reference to FIG.

As one method for changing the rolling position of the stand, there is a method of calculating the rolling position changing amount so that the outgoing side plate thickness of the steel piece becomes the target outgoing side plate thickness and changing the rolling position accordingly. . For example, in the joint control device 8 shown in FIG. 4, the rolling position change amount ΔS is set so that the outgoing side plate thickness of the steel piece is changed from the steady part target plate thickness to the joint target plate thickness h _i ^ad.
_i is calculated according to the following formula from the conventional rolling theory (M _i ,
(Q _i is calculated in advance), and the reduction position change amount ΔS _i is tracked at the joint portion at a predetermined change time before the joint portion reaches the stand. Output more.

The _{ΔS i = {(M i +} Q i) / M i} · Δh i a Δh i a = h i ad -h i ac where the subscript i: stand number, M _i: Mill stiffness coefficient Q _i: Plasticity constant of steady part of rolled material

Then, at a predetermined change time after the joint passes through the sixth stand, the sign of the change amount of the reduction position is reversed, that is, -ΔS _i is output from the reduction position control device 9. The rolling position control device 9 changes the rolling position according to the rolling position changing amount, and thereby the plate thickness of the joint portion is controlled to the target delivery side plate thickness.

This change time is determined by the upper limit of the changing speed of the rolling position or the limit of ensuring operational stability.

As another method of changing the rolling position, the gauge thickness of the stand is used to detect the outlet side plate thickness from the actual values of the rolling load and the rolling position, and the output side plate thickness is the target plate thickness. There is a method of controlling the rolling position of the stand so as to match with.

In this method, the joint side control device 8 outputs the output side target plate thickness h _i ^a of the sixth stand to the plate thickness control device 10 as shown by the solid line.

The plate thickness control device 10 determines the actual value P _{i of the} rolling load.
And the actual value S _{i of the} rolling position, the gauge meter outlet side plate thickness of the sixth stand (i stand) is calculated using the following gauge meter formula.

H _i ^G = S _i + P _i / M _i

Further, the output side target plate thickness of the i stand h _i ^a
And the gauge meter outlet side plate thickness h _i ^G are calculated, and PI calculation (proportional and integral calculation) is executed for this difference to calculate a reduction position change amount ΔS _i ^REF that reduces this difference to zero. Input to the position control device 9.

In the reduction position control device 9, the reduction position change amount Δ
The pressure reduction position of the stand is changed according to S _i ^REF , whereby the gauge meter output side plate thickness h _i ^G is changed to the target output side plate thickness h _i.
It is controlled to ^a.

Here, the joint controller 8 tracks the joint.
Before the joint reaches the stand, the target exit side plate thickness h_i
^aFrom the target exit side plate thickness of the steady part with a predetermined change time
Change the target exit side plate thickness of the joint so that the joint passes through the stand.
After passing, the target exit side plate thickness h_i ^aChange time determined in advance
Change the target output side plate thickness of the joint to the target output side plate thickness of the steady part.
To change. This changing time is the upper limit of the changing speed of the rolling position.
Rui is determined by the limits of ensuring operational stability.

As described above, when there is a risk that the joint portion will break between the sixth stand and the seventh stand, the rolling position of the sixth stand is changed in the manner described above.

When the sixth stand is used as a reference stand and the rolling position is changed only by this stand as in the above example, the fifth stand, which is the upstream stand immediately before that, is used.
Since the balance of the mass flow between the stand and the sixth stand changes and the tension changes, it is preferable to appropriately change the target outlet side plate thickness of the joint in the fifth stand.

The method of determining the target outlet plate thickness h ₅ ^ad of the joint in the fifth stand is determined by the ratio of the target outlet plate thickness of the joint in the fifth stand to the target outlet plate thickness of the stationary part (h ₅ ^ad / h).
₅ ^ac ) is 1 or more, and the ratio of the target output side plate thickness of the joint part and the target output side plate thickness of the steady part in the sixth stand (h ₆ ^ad /
h ₆ ^ac ). For example, the ratio should be the same as in the sixth stand.

The reason can be explained as follows. That is, in order to prevent tension fluctuation, it is sufficient to maintain the mass flow balance between the (i-1) stand and the i stand represented by the following formula.

{VR _i-1 · (f _i-1 +1)} / {VR _i
・ (F _i +1)} = (h _i / H _i ) f: advance rate, VR: roll peripheral speed, i: stand number

Here, if the ratio (h _i / H _i ) between the outgoing side plate thickness h _i and the incoming side plate thickness H _i is kept constant, the mass flow balance can be maintained without changing the roll peripheral speed. Tension fluctuation becomes small. The entrance side plate thickness H _i is (i-1) the stand exit side plate thickness (h _i-1 ) delayed by the transfer time between the stands.

Accordingly, the ratio (h _i ^ad / h _{i -1} ^ad ) of the target outgoing side plate thickness and the incoming side plate thickness at the joint is calculated as the ratio (h _i ^ac / h _i ) of the target outgoing side plate thickness and the incoming side plate thickness at the steady part. _-1 ^ac ). That is, (i-1) the ratio (h) of the target exit side plate thickness of the joint part and the target part exit side plate thickness of the steady part in the stand
_i-1 ^ad / h _i-1 ^ac ) is the ratio (h _i ^ad / h) of the target exit side plate thickness of the joint and the steady part of the i stand
_i ^ac ), which reduces tension fluctuations.

If the ratio of the 5th stand and the ratio of the 6th stand are the same, tension fluctuation occurs between the 4th stand and the 5th stand on the upstream side. Therefore, in order to disperse the change of the mass flow, the ratio of the 5th stand May be smaller than the ratio of the sixth stand. Further, if the ratio of the target output side plate thickness of the joining part and the target output side plate thickness of the stationary part is made smaller toward the upstream stand, there is an advantage that the fluctuation of the mass flow is dispersed to each stand and the tension fluctuation is not biased between the specific stands.

On the other hand, if the rolling-down position of the sixth stand, which is the reference stand, is changed, the sixth stand located downstream of the stand is changed.
Since the mass flow changes between the stand and the seventh stand, and the tension changes accordingly, the ratio of the target exit side plate thickness of the joint in the seventh stand to the target exit side plate thickness of the stationary part is the target of the joint in the sixth stand. It is preferable to make it equal to the ratio of the output side plate thickness and the target output side plate thickness of the stationary part.

The pattern of changing the rolling position is shown in FIG.
As shown in the figure, the target output side plate thickness of the steady part
The change time is ΔT
₁The plate thickness changing speed at that time is kept constant. Time ΔT₁
Time after the passage ΔT₁+ ΔT ₂Between is the thickness of the outgoing plate of the joint
Hold on. Then, after that, the thickness of
The change time is ΔT₃When
The plate thickness changing speed at that time is kept constant.

As described above, the trapezoidal pattern in which the plate thickness change start portion and the end portion are tapered is particularly desirable.

Time interval ΔT ₁ when changing the rolling position,
ΔT ₂ and ΔT ₃ must be the same for each stand. Although the plate thickness becomes thinner and the distance of the plate thickness changing portion becomes longer as it goes to the stand in the latter stage, since the mass flow is constant, it is only necessary to match the time required for the plate thickness change.

As for the change start timing, the plate thickness change start point is tracked immediately after the joining so that the plate thickness change is started from the same position in each stand. As the tracking method, an existing method such as calculating the position using the transport speed of the meshing roll or the plate may be applied.

The reason why the pattern for changing the pressing position is the trapezoidal pattern is to enable the pressing device to follow when changing the plate thickness and to suppress the rapid disturbance of the mass flow and reduce the tension fluctuation. In addition, even if there is an error in the tracking of the joint part when changing the plate thickness in multiple stands and the starting point of the plate thickness change shifts in each stand, the disturbance of the mass flow is minimized compared to the step change pattern. This is because there is an advantage that it can be reduced.

As described above, by finishing-rolling the joint so that it is thicker by a predetermined amount than the plate thickness of the steady portion, the plate cross-sectional area at the joint increases and the unit tension acting on the plate is reduced. The breakage of the plate at the joint will be avoided.

Next, a description will be given of the case of reducing the shape defect that occurs when the above-described rolling is carried out.

In the continuous hot rolling, when the thickness of the joint between the steel slabs and the thickness of a predetermined section before and after the thickness changes as shown in FIG. 6, for example, the rolling load fluctuates according to the change in the thickness as shown in FIG. However, due to this load variation, the output side plate crown of the stand whose plate thickness is being changed is changed, and the shape of the plate is also changed, which is particularly remarkable in a rolled material having a wide plate width.

According to the present invention, such a change in shape is predicted and the change in shape is suppressed by adjusting the roll bender force of the roll bender device provided in the stand.

The adjusting vendor power can be calculated online or offline in the following manner.

The load fluctuation ΔP when the plate thickness is changed is ΔP = M · (ΔH−ΔS), where ΔS is the rolling position change amount, ΔH is the plate thickness fluctuation amount, ΔP is the load fluctuation, and M is the mill rigidity constant. --- Calculate with (1).

Further, the change of the plate crown on the delivery side of the rolling mill ΔC _r
ΔC _r = A ・ ΔP --- (2) where A is the coefficient of influence of load fluctuation on crown change (a constant determined by the thickness of the rolled material, plate width, steel type, etc., and is obtained experimentally) Is required.

The plate shape of the rolled material is generally represented by the steepness λ, and it is known that the steepness λ and ΔC _r generally have the following relationship.

[Equation 1]

Further, as in the above equation (2), the change in the crown on the delivery side caused by the change in the bender force is the amount of change in the bender force ΔF _W , and the influence coefficient of the variation in the bender force on the change in the delivery side plate crown ( It is determined as follows, where B is a constant determined experimentally by the plate thickness, plate width, steel type, etc.). ΔC _r = B ・ ΔF _W --- (4)

From the above equations (2) and (4), the bender force Δ for suppressing the shape change caused by the load change when the plate thickness is changed
Since F _W is ΔF _W = A / B · ΔP --- (5), ΔF _W can be calculated by substituting ΔP obtained by the equation (1) into the equation (5).

The bender force obtained as described above is applied to the joint portion of the steel slab and the periphery before and after it, as shown in FIGS. 8 (a) and 8 (b). When applying the bender force, a rectangular shape as shown in Fig. 8 (a)
A tapered shape as shown in FIG. 8 (b) may be used, whereby the defective shape due to the change of the plate thickness can be suppressed.

By the way, when a dynamic strip crown control using a profile sensor or the like is applied to a rolled material, the absolute value of the bender force with respect to the initial set value when the above bender force is applied. Since it fluctuates, it may not be possible to secure sufficient bender force to suppress the shape change that occurs in the thickness change part. Further, there is a concern that even if the bending force is changed between the initial setting value of the bending force and the upper and lower limit values of the bending force specification, it is not sufficient to suppress the defective shape.

In such a case, a rolling mill equipped with a roll cross device or a rolling mill equipped with a roll shift device is applied as another shape control actuator to change the roll cross angle or to roll the roll shaft. This is addressed by compensating for the lack of vendor power by shifting in the direction.

When changing the roll cross angle (the same applies to the roll shift, the case of changing the roll cross angle will be described below), the joint of the steel slab and a predetermined section before and after the joint reach the rolling mill. Change the cross angle (running). At this time, the bender force is changed so as to suppress the shape change due to the adjustment of the roll cross angle.

FIG. 9 shows a situation in which the cross angle and the bender force are changed in synchronization, and the plate shape is changed by changing the roll cross angle by changing the cross angle and the bender force in synchronization. Does not change and hinder the passing of the strip.

The change ΔC _r of the outgoing side plate crown due to the change of the cross angle is determined by the influence coefficient C (the thickness of the rolled material, the plate width, the steel type, etc.) that the change of the cross angle gives to the change of the outgoing side plate crown. is a constant, determined experimentally), ₁ cross angle before the change theta, the cross angle after the change when the _{θ 2, ΔC r = C ·} {(θ 2) 2 - (θ 1) 2 } --- (6) can be found.

Letting ΔF _W be the amount of change in the vendor force for keeping the adjustment range of the vendor force within the range of the capability of the apparatus,
From equations (4) and (6), the amount of change in the cross angle required to keep the plate shape unchanged is {(θ ₂ ) ² − (θ ₁ ) ² } = B / C * ΔF _W --- ( 7)

By following the above procedure, it is possible to secure the bender force necessary for suppressing the shape defect when changing the plate thickness, and the shape deterioration due to the insufficient bender force does not occur.

In the present invention, it is preferable that the roll bender force acts so as to bend the work roll.
In a rolling mill having an intermediate roll such as a 6-high rolling mill, the intermediate roll may be operated to bend. Further, the case where the roll cross device is used as another shape control actuator and the cross angle thereof is changed has been described, but a roll shift device for shifting the work roll or a VC roll (Variable Crown Roll) for changing the shape of the roll cylinder is described. It is possible to apply a rolling mill equipped with the above, or a six-high rolling mill equipped with an intermediate roll shift device for shifting the intermediate rolls, and similar effects can be expected for these.

Using a rolling facility (7-stand tandem mill) as shown in FIG. 1, a sheet bar (steel type: low carbon steel) having a thickness of 30 mm and a width of 1000 mm is joined (heated by induction heating and heated to a predetermined temperature). The joining condition in which steel pieces are pressed against each other at the temperature of 1) and the continuous hot rolling according to the following procedure with the finished plate thickness of 1.0 mm were carried out to investigate the passing condition of the plate.

Example 1 The temperature of the joined portion immediately after joining the sheet bars was about 100 ° C. higher than that of the steady portion. When rolled according to the conventional method, the reduction in plate thickness at the joint between the sixth stand and the seventh stand was 0.23 mm. At this time, in order to obtain the joint cross-sectional area required to prevent the plate from breaking between the sixth stand and the seventh stand, the joint thickness needs to be the same as that of the steady portion. The stand was used as a standard stand, and the target delivery side plate thickness was determined to be 1.56 mm, and based on this, the target delivery side plate thickness at the other stands was determined.

At this time, the change amount ΔS of the rolling position in the sixth stand was +0.6 mm. Tables 1 to 7 show the target delivery-side plate thicknesses (schedule) of the stationary part and the joint part of each stand when rolling according to the present invention.

[0073]

[Table 1]

[0074]

[Table 2]

[0075]

[Table 3]

[0076]

[Table 4]

[0077]

[Table 5]

[0078]

[Table 6]

[0079]

[Table 7]

[0080] In the stand larger than the ratio (h ^ad / h ^ac) is 1.0 as shown in Table 1 to Table 7, making changes pressing position in accordance with the present invention. The plate thickness change time (see FIG. 5) was ΔT = 2.0 seconds, ΔT ₁ = 0.
6 seconds, ΔT ₂ = 0.6 seconds and ΔT ₃ = 0.8 seconds. Immediately after the completion of the sheet bar joining process, the position of the joining portion was stored in the tracking device and tracking was performed based on the sheet bar transport speed.

As a result, according to the present invention, the balance of the mass flow around the joint was maintained, and the rolling could be stably carried out without the generation of excessive tension. Fig. 1 shows the variation of the outlet plate thickness around the joint in the 6th stand of the schedule in Table 3.
FIG. 11 shows the fluctuations in tension between the sixth stand and the seventh stand when the periphery of the joint was rolled according to the schedule shown in Table 3 and FIG.

On the other hand, as a conventional method, when the joint portion and the steady portion are rolled with the same target delivery side plate thickness, the tension fluctuation between the sixth stand and the seventh stand is large and excessive tension acts on the joint portion. The plate broke and the rolling could not be continued.

Example 2 A pattern for changing the rolling position is a rectangular pattern (comparative example, FIG.
2) and a trapezoidal pattern (compliance example, see FIG. 13). The finished plate thickness was 1.0 mm, the target delivery side plate thickness was the schedule in Table 3, and the other conditions were the same as in Example 1.

In the comparative example in which the position of the joining portion is tracked and the rolling position is changed to output the rolling reduction position change command according to the rectangular pattern when the plate thickness changing start point reaches each stand, the rolling reduction position is changed. Is due to a tracking error, the plate thickness change start point at the 7th stand deviates from the change start point at the 6th stand by about 0.2 seconds (0.2 seconds after the reduction position change command is output, The plate thickness change start point reached the 7th stand), and excessive tension was generated at the time of starting the plate thickness change at the 7th stand, and the plate rupture at the joint was unavoidable. FIG. 12 shows the variation of the outlet plate thickness of the seventh stand and the tension between the sixth and seventh stands.
Shown in a and b.

The plate thickness changing pattern is a trapezoidal pattern (see FIG. 13).
In the conformity example according to the present invention described in (1), the plate thickness change start portion at the sixth stand reaches the seventh stand 0.2 seconds after the reduction position change command is output at the seventh stand. Since the position change pattern is a trapezoidal pattern, the disturbance of the mass flow was small and the tension fluctuation was suppressed, enabling stable threading. 13a and 13b show the variation of the outlet plate thickness of the seventh stand and the tension between the sixth and seventh stands.

Example 3 Next, in a 7-stand tandem continuous finishing rolling facility in which a pair cross rolling mill equipped with work rolls capable of changing the bending force within a range of ± 1000 kN / c is arranged on all stands, first, 30mm in length and 1500mm in width low carbon steel billets were joined (using the joining method of heating by induction heating to raise the temperature and press the billets against each other at a predetermined temperature) to give a finished plate thickness of 2.0mm. The following continuous hot rolling was carried out to investigate the strip passing condition and strip shape.

Since the thickness of the joint portion in the seventh stand is about 0.5 mm thinner than that of the steady portion, the plate thickness is 0.5 mm relative to the steady portion in the joint portion and within 5 m before and after the joint portion.
The rolling position was changed so that the thickness became 5 mm, and rolling was performed, and a conforming example according to the present invention and a comparative example with a constant bending force were carried out.

In this continuous rolling, the rolling load is reduced by about 2500 kN when the strip thickness is changed as compared with the steady part. Here, in the case of the conformity example according to the present invention, as shown in FIG. Since it was calculated to be -500 kN / c according to the procedure, it changes to a taper like the reduction position changing pattern, that is, the bender force is taper-reduced by 500 kN / c before the joint reaches the stand, and the value is changed. Hold, and after the joint passes through the stand, 500
Vendor power to increase kN / c was changed. as a result,
The change in shape of the periphery including the joint was suppressed and stable striping was possible. On the other hand, in the comparative example, as shown in FIG. 14 (b), the bender force is constant in the plate thickness changing portion, so that the shape of the plate tends to stretch abruptly due to the fluctuation of the rolling load, and the joint portion is often bent. It was confirmed to disconnect.

Example 4 In a 7-stand tandem continuous finishing rolling facility in which a pair cross type rolling mill equipped with work rolls capable of changing the bending force within a range of ± 1000 kN / c was arranged on all stands,
Joining process of low carbon steel billet with thickness of 30mm and width of 1500mm
(Applying the joining method of heating and raising the temperature by induction heating and pressing the steel pieces against each other at a predetermined temperature), and the finished plate thickness is 2.
The following continuous hot rolling with a thickness of 0 mm was carried out to investigate the strip passing condition and strip shape.

By applying the dynamic plate crown control using the profile meter, the plate thickness of the joint in the 7th stand is about 0.5 mm thinner than the steady part. Rolling was performed by changing the rolling position so that the thickness was 0.5 mm thicker than the steady part.

At this time, the rolling load was reduced by 2500 kN in the strip thickness changing portion as compared with the steady portion. The change amount of the bender force was calculated to be −500 kN / c as in Example 3, but the output of the plate crown control is the bender output in order to suppress the change of the plate crown due to the load change caused by the temperature change in the longitudinal direction of the plate. Given as a force command value, the bender force is -700 before the joint and the area before and after it reach the 7th stand.
It changed to kN / c. The lower limit of the amount of bender of the equipment used in this example is −1000 kN / c, and the amount of changeable bender force is only −300 kN / c. In this case, the shape cannot be sufficiently controlled, and for example, the belly stretches as shown in FIG.

On the other hand, in the adaptable example according to the present invention, the cross angle is reduced at the joint portion before the reduction position is changed in order to secure the bender force sufficient to suppress the variation of the shape at the joint portion, and at that time, , The bender force was increased so as to suppress the change of the shape due to the decrease of the cross angle.

That is, even if the bender force is reduced by 500 kN / c in order to suppress the variation of the shape at the joint, the lower limit value of the capacity of the bender device becomes −1000 kN / c or more so that the rolling position of the joint is reduced. Vendor power was increased from -700 kN / c to 500 kN / c before making changes. Regarding the vendor power after the increase, the upper limit of the capability of the vendor device is 10
It shall be less than 00kN / c.

The change amount of the cross angle for suppressing the change of the plate shape according to the increase amount of the bender force of 1200 kN / c is (7)
Since it was calculated to be 0.7 ° from the formula, the cross angle was reduced by 0.7 ° from 1 ° to 0.3 ° before changing the rolling position at the joint. At that time, since the time required to change the cross angle is longer than the time to change the bender force, the change start time of the bender force is set to the change start time of the cross angle, and the bender force is set to the change end time of the cross angle. Changed to match the change end time.

The cross angle is 0.3 ° and the bending force is 5
After changing to 00kN / c, the bender force is reduced by 500kN / c before the joint reaches the stand, and after the joint passes through the stand, the bender force is increased by 500kN / c to increase the joint. Rolling load when rolling,
Figure 1 shows changes in cross angle, bender force, and steepness.
6 shows.

As is clear from the steepness of FIG. 16, it was confirmed that when rolled according to the present invention, the shape of the plate was better than in the comparative example, and moreover, stable rolling could be realized.

[0097]

As described above, according to the present invention,
When the leading material and the trailing material were joined and continuously hot-rolled, tension fluctuations, plate breakage, and shape defects due to the joints, which were inevitable, were avoided and stable striping became possible.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a rolling facility suitable for carrying out the present invention.

FIG. 2 is a diagram showing a situation of temperature distribution around a bonded portion.

FIG. 3 is a diagram showing a variation of the plate thickness around the joint.

FIG. 4 is an explanatory diagram of a rolling procedure according to the present invention.

FIG. 5 is a view showing a rolling position changing pattern (a changing pattern of a target delivery side plate thickness) according to the present invention.

FIG. 6 is a diagram showing a variation of the plate thickness around the joint.

FIG. 7 is a diagram showing a variation of rolling load around the joint.

8 (a) and 8 (b) are diagrams showing a change situation of vendor power.

FIG. 9 is a diagram showing a change situation of a cross angle and a bender force.

FIG. 10 is a diagram showing a change situation of a sixth stand outlet side plate thickness.

FIG. 11 is a diagram showing a change in tension between the sixth and seventh stands.

FIG. 12 (a) is a diagram showing the variation of the outlet plate thickness of the seventh stand in the comparative example, and FIG. 12 (b) is a diagram showing the variation of the tension between the sixth and seventh stands in the comparative example. Is.

FIG. 13A is a diagram showing a variation of the outlet plate thickness of the seventh stand in the conforming example, and FIG. 13B is a diagram showing a variation of tension between the sixth and seventh stands in the conforming example. Is.

FIG. 14 (a) is a diagram showing changes in rolling load and plate shape in a fitting example in which a bender force is applied,
(b) is a diagram showing a rolling load and a change in plate shape in a comparative example to which a bender force is not applied.

FIG. 15 is a diagram showing changes in rolling load, bender force, and plate shape in a comparative example in which the cross angle was not changed during running.

FIG. 16 is a diagram showing changes in rolling load, bender force, and plate shape in a fitting example according to the present invention in which a cross angle is changed during running.

[Explanation of symbols]

1 rough rolling mill 2 Finishing mill 3 cutting machine 4 joining device 5 Tracking device 6 cutting machine 7 winder 7'winder 8 junction control device 9 Rolling position control device 10 Thickness control device

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhiro Takebayashi 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Technical Research Institute, Kawasaki Steel Co., Ltd. (72) Toshio Imae 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Kawasaki Steel Technical Research Institute Co., Ltd. (72) Inventor Kunio Isobe 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel Works Ltd. Technical Research Institute (72) Inventor Hideyuki Nikaido 1 Kawasaki-cho, Chuo-ku, Chiba Prefecture Kawasaki Steel Co., Ltd. Chiba Works (56) Reference JP-A-8-206703 (JP, A) JP-A-7-88519 (JP, A) JP-A-7-88516 (JP, A) JP-A-7-39905 (JP, A) JP-A-6-55208 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B21B 37/00-37/78

Claims (9)

(57) [Claims] 1. A hot strip is continuously heated by feeding the trailing end of the preceding billet and the leading end of the trailing billet to each other and then feeding them to a rolling facility having a plurality of stands arranged therein. In doing so, when the target delivery side plate thicknesses of the preceding and following steel strips in each stand are set to be substantially the same and the target delivery side plate thickness is set as the steady part target delivery side plate thickness of the steel strip in each stand, at least one The area from the point just before the steel plate joint reaches each stand to the time immediately after the steel plate joint is reached in each of the two or more stands by setting the target outlet plate thickness at the steel plate joint to be thicker than the steady part target outlet plate thickness. The continuous hot rolling method for a steel slab according to claim 1, wherein the rolling position of each stand is changed so that the output slab thickness of the steel slab becomes the joint target output side slab thickness. 2. The steady part target exit plate of the joint target exit side plate thickness of the stand in which the ratio of the joining part target exit plate thickness of the stand upstream of the reference stand to the steady part target exit side plate thickness is set. Set the reference stand and the target plate thickness of the joint of the stand upstream from this stand so that it becomes equal to the value of the ratio to the thickness or becomes progressively smaller toward the stand, and becomes the reference stand and upstream from this stand. The method according to claim 1, wherein the rolling position of the side stand is changed. 3. The ratio of the joint target output side plate thickness of the stand downstream of the standard stand to the steady part target output side plate thickness is the constant part target output side plate thickness of the joint target output side plate thickness of the reference stand. 2. The standard stand and the target joint plate thickness downstream of this stand are determined as equivalent to the value of the ratio to, and the rolling positions of the standard stand and the stand downstream of this stand are changed. the method of. 4. The rolling position is changed so that the delivery side plate thickness of the steel piece increases at a constant rate before the joint reaches the stand, and the delivery side plate thickness reaches the reduction position where the target delivery side plate thickness is reached. The method according to claim 1, 2 or 3, wherein after that, the level is maintained, and after the joint has passed through the stand, the pressing position is changed so that the outlet plate thickness is reduced at a constant rate. 5. The method according to claim 1, 2, 3 or 4, wherein the change start point and the change end point of the rolling-down position in each stand are made to coincide with each other. 6. A roll bender device is arranged on a stand, a change in rolling load caused by a change in a rolling position is predicted, and a shape change associated with the change in rolling load is adjusted by a bender force of the roll bender device. The method according to any one of claims 1 to 5, which is suppressed by 7. A roll bender device and other shape control actuators are arranged on a stand, and a change in rolling load caused by a change in a rolling position is predicted, and a shape change caused by the change in rolling load is detected by the roll bender device. The control amount of another shape control actuator is adjusted so as to be suppressed by adjusting the roll bender force, and the adjustment range of the roll bender force is within the range of the adjustment capability of the roll bender device. 6. The method according to any one of 5 to 5. 8. A shape change by adjusting the control amount of the shape control actuator when adjusting the control amount of another shape control actuator so that the adjustment range of the roll bender force falls within the range of the adjustment capability of the roll bender device. 8. The method of claim 7, wherein the roll bender force is adjusted to suppress 9. The other shape control actuator is a roll cross device capable of changing a roll cross angle during a run, or a roll shift device for shifting a roll in a roll axial direction during a run. Or the method described in 8.