JPH1128505A - Method for hot-rolling band steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling method for making the longitudinal distribution of the strip temp. on the outlet side of a finishing mill uniform in order to manufacture a strip having uniform material in the longitudinal direction which is different from a conventional strip with respect to hot rolling of the band steel. SOLUTION: This method is the rolling method which is executed using hot rolling equipment for the band steel having the finishing mill, coiler and strip cooling line provided between the finishing mill and the coiler and, furthermore, having a strip tip restraining device which is movable from the side of the finishing mill to the side of the coiler while clamping the tip of the strip and imparting tension to the strip. Rolling speed is continuously increased from the tip of the strip toward the rear end of the strip so that the strip temp. on the outlet side of the finishing mill is uniform in the longitudinal direction and the desired max. rolling speed is attained in the vicinity of the rear end of the strip.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling method using a hot strip mill (hot strip mill).

[0002]

2. Description of the Related Art In hot strip rolling, a strip that has been rolled to a predetermined thickness by a finish rolling mill is used by a finishing mill and a down coiler before being wound on a mandrel of the down coiler. It is cooled to a predetermined winding temperature by a strip cooling line provided therebetween. This strip cooling line is composed of a run-out table composed of hundreds of driven roller tables, and a water spray cooling device or a water laminar cooling device. When hot strip steel is rolled using such equipment, especially when the end of the strip passes over the run-out table, the impact of the impact from the roller table and air resistance causes the end of the strip, called flying, to move upward. The phenomenon of large jumps may occur. This kind of flying phenomenon causes the strip end to be bent during coiling work by the coiler, resulting in poor quality, or the coiler to be unable to wind the coil itself, causing operational troubles called miscoils. This is a phenomenon that must be strictly avoided. It has been clarified that the frequency of occurrence of the flying phenomenon increases remarkably as the rolling speed increases. Therefore, in a normal rolling operation, the speed at which the leading end of the strip runs on the run-out table is set to 600 to 800 m / min or less. . When the entire strip is rolled at such a speed, the rolling time becomes longer, so that it is difficult to secure the exit temperature of the finishing mill required to secure the material as a product at the rear end of the strip. In addition, the productivity per line of the hot strip rolling equipment is significantly reduced. In order to avoid the above-mentioned problems, in the conventional hot strip rolling, as shown in FIG. 7, a strip speed is set at a critical speed at which flying does not occur, that is, at a low speed of 600 to 800 m / min or less, which is called threading speed. After rolling the part, the tip of the strip is wound around the coiler, and the tension can be applied between the finishing mill and the coiler. Then, the strip is rapidly accelerated to a maximum speed of about 1200 to 1500 m / min, and most of the strip is removed. The rolling operation is performed at the maximum speed.

[0003]

In the conventional hot strip rolling method as described above, it is impossible to accelerate the strip until the length of the strip after the rolling is equal to or longer than the length of the run-out table. There is no other way than rolling the strip at the tip of about 200 m at a low speed, and the operation mode is low in productivity without fully utilizing the capacity of the rolling mill that can originally perform high-speed rolling.

Further, after the leading end of the strip is wound around the coiler, in order to increase productivity, rapid acceleration to the maximum rolling speed is performed. For example, in the case of the conventional method of rolling in a speed pattern as shown in FIG. As shown in the figure, the exit temperature of the finishing mill becomes non-uniform in the longitudinal direction, and not only the uniformity of the material as a product cannot be expected, but also the exit temperature of the finishing mill is set to a target value or more over the entire length of the strip. The heating temperature must be set higher than necessary, and rolling is inefficient from the viewpoint of fuel cost required for heating.

In order to make the exit temperature of the finishing mill as uniform as possible in the longitudinal direction even with the conventional rolling speed pattern as described above, a method of injecting cooling water into the strip being rolled between the finishing mills. It has been known. However, in the case of this method, as a matter of course, the vicinity of the strip surface is rapidly cooled, so that the temperature distribution in the sheet thickness direction is considerably different from the case where cooling water is not used between the finishing mills, Along with this, the distribution of the temperature and strain history in the thickness direction in the finish rolling differs in the longitudinal direction, and it is impossible to guarantee the longitudinal uniformity of the material. In addition, this method cannot improve the waste of the fuel cost of the heating described above.

[0006] In order to solve the above-mentioned problem relating to the conventional threading speed, a continuous rolling method in which rolled materials are joined at a rough bar stage and rolled has been put into practical use. Since it is impossible to join the materials, the threading speed problem remains, and even when joined, the rear end of the preceding material and the tip of the following material must be rolled at the same speed, so a special cooling device The problem of the temperature difference in the longitudinal direction cannot be solved unless a heating device is used.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the conventional method, in the first invention of the present application, there is provided a finishing mill and a coiler, and a strip cooling device between the finishing mill and the coiler. A hot strip having a strip tip restraining device that is movable on the strip cooling line from the finishing mill side to the coiler side while applying tension to the strip while holding the tip of the strip on the strip cooling line. A rolling method using a steel rolling facility, wherein the rolling speed is gradually increased from the leading end of the strip toward the trailing end of the strip so that the strip temperature on the exit side of the finishing mill becomes uniform in the longitudinal direction. The present invention is characterized by a hot strip rolling method in which a desired maximum rolling speed is obtained in the vicinity of the end portion. In the second invention, the finish rolling of the strip tip in the first invention is performed. The final stand outlet side speed is 900m /
Apply rolling conditions of at least one minute.

In the third invention of the present application, a finishing mill and a coiler are provided, and a strip cooling line is provided between the finishing mill and the coiler, and a tip end of a strip is held on the strip cooling line. A rolling method performed by using a hot strip rolling equipment having a strip tip restraining device movable from the finishing mill side to the coiler side while applying tension to the strip, and near a rear end of the strip. In accordance with a preset speed pattern, the rolling speed is gradually increased from the leading end of the strip toward the trailing end of the strip so that a desired maximum rolling speed is achieved and the strip temperature on the exit side of the finishing mill becomes uniform in the longitudinal direction. While performing the rolling to increase, while measuring the finish rolling mill exit temperature by the finish rolling mill exit thermometer during the rolling, the measured temperature, A hot strip rolling method that performs a speed control by correcting the speed pattern so as to bring the measured temperature closer to the target value by comparing the target value of the finish-rolling mill outlet side temperature set in advance with the target value. Features.

Further, in the fourth invention of the present application, a finishing mill and a coiler, a strip cooling line between the finishing mill and the coiler, and a tip end of a strip is sandwiched on the strip cooling line. A rolling method performed by using a hot strip rolling equipment having a strip tip restraining device movable from the finishing mill side to the coiler side while applying tension to the strip, and near a rear end of the strip. In accordance with a preset rolling speed pattern, so as to achieve a desired maximum rolling speed, and so that the strip temperature on the exit side of the finishing mill becomes uniform in the longitudinal direction.
Along with performing rolling to gradually increase the rolling speed from the leading end of the strip toward the trailing end of the strip, during the rolling, the finishing-roller exit-side temperature is measured by a finishing-roller exit-side thermometer, and the measured temperature and the measured temperature are determined in advance. The set value is compared with the target value of the exit temperature of the finishing mill, and a speed correction value is superimposed on the rolling speed pattern so as to bring the measured temperature closer to the target value, and a speed control is performed to perform rolling of the strip. After completion, a speed correction value for the rolling speed pattern of the subsequent strip is calculated based on the speed correction actual value of the speed pattern, and this speed correction value is superimposed on a speed pattern previously determined during the setting calculation. It is characterized by a hot strip rolling method in which a speed pattern set value is calculated and rolling is performed based on the speed pattern set value.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 3 shows a hot-rolled steel rolling mill which is a premise of the present invention, a final stand of a finishing mill 1, a downcoiler 2, and a strip cooling line 3 extended therebetween. In the example of FIG. 3, the strip cooling line 3 is composed of a large number of pinch rolls 4 and a cooling water jet device 5 which are arranged in a row at appropriate intervals in the sheet passing direction. The pinch rolls 4 and the cooling water injection devices 5 are alternately arranged in the passing direction.

The pinch roll 4 is composed of a pair of upper and lower rolls, and each roll is supported so as to be capable of moving vertically. Each of the pinch rolls 4 sandwiches the upper and lower surfaces of the strip 6 sent out from the finishing mill 1 with a predetermined pushing force, is provided with a driving force, and the rotation speed is freely controlled. . Similarly to the pinch roll 4, the cooling water injection devices 5 are composed of cooling water injection devices forming a pair up and down. .
On the surface of the cooling water injection device 5 facing the strip 6,
A plurality of cooling water nozzles are provided so that cooling water can be sprayed on the upper and lower surfaces of the strip 6.

A guide rail 7 extends in the strip cooling line 3 along the plate passing direction. The guide rail 7 includes a strip 6 sent from the finishing mill 1.
The strip tip restraint device 8 that runs while holding the tip of the strip is placed. Strip tip restraint device 8
The vehicle travels in the plate passing direction while being restrained in the vertical direction by the upper and lower guide rails 7. As a driving method for running the carriage, for example, a method is employed in which a binion gear meshing with a rack gear extending parallel to the guide rail is driven by a driving device on the carriage.

Next, the operation of the equipment shown in FIG. 3 will be described. Before the leading end of the strip 6 is sent out from the finishing mill 1, as shown in FIG. 3, all the pinch rolls 4 and all the cooling water injection devices 5 are provided.
Move to a position vertically separated from each other and wait.
Then, the strip leading end restraining device 8 stands by in a state where the gripping roll 10 is rotated at a peripheral speed slightly higher than the sending speed of the strip 6 from the finishing mill 1 immediately near the exit of the final stand of the finishing mill 1. doing.

When the leading end of the strip 6 exits the finishing mill 1, the strip leading end restraining device 8 immediately grips the leading end of the strip 6 between the gripping rolls 10. Almost at the same time, or rather somewhat earlier, the strip tip restraining device 8 starts accelerating toward the down coiler 2 and runs in a short period of time at the rolling speed of the finishing mill 1.

On the other hand, each pair of the pinch roll 4 and the cooling water injection device 5 which have been retracted in both the upper and lower directions move so as to approach the upper and lower surfaces of the strip 6 in order as the strip tip restricting device 8 passes. And pinch roll 4
The rotation speed is controlled so that the upper and lower surfaces of the strip 6 are in contact with each other and the tension of the strip 6 is always maintained in a predetermined range. Further, cooling water is sprayed from the cooling water injection device 5 toward each of the upper and lower surfaces of the strip 6. In this way, the strip 6 is always conveyed on the strip cooling line in a state where an appropriate tension is applied, including the leading end, so that there is no flying phenomenon which is a problem in the prior art. For this reason, in the prior art, the threading speed, which has a significant meaning as the upper limit value of the rolling speed of the leading end of the strip that does not cause flying, particularly when rolling thin materials, loses its significance.

By the way, according to the present invention, it is possible to perform rolling near the maximum rolling speed at which rolling is possible from the viewpoint of rolling mill power, including the leading end of the strip. However, when one strip is rolled at a constant rolling speed in the longitudinal direction, the elapsed time after the extraction of the heating furnace at the rear end of the strip becomes longer than that at the front end of the strip. The temperature will be lower than at the tip. Therefore, the rolling speed is selected for the purpose of eliminating the temperature deviation between the front end portion and the rear end portion and realizing a uniform rolling temperature in the longitudinal direction.

FIG. 1 shows an embodiment of a rolling speed pattern according to the rolling method of the present invention. In the present invention, it is assumed that a desired maximum rolling speed is realized in the vicinity of the rear end of the strip, and the heating temperature of the raw material is adjusted so that the exit temperature of the finishing mill near the rear end becomes a predetermined temperature. Is done. Then, the rolling speed of each portion is calculated in advance so that the finish rolling mill exit side other than the rear end portion has the same target temperature as the rear end portion, and rolling is performed based on this rolling speed pattern. As a result, as shown in FIG. 2, the exit temperature of the finishing mill of the strip can be maintained uniformly in the longitudinal direction without using a special cooling device or a heating device, and a uniform material which has never existed before can be obtained. It is possible to produce strips.

FIG. 4 shows an example of a method for determining operating conditions for executing the rolling method of the present invention. First, a target rolling temperature is determined from the viewpoint of material preparation. The rolling temperature referred to here is a finishing rolling mill exit side temperature as an essential requirement, and a rolling temperature and a rough rolling temperature at each finishing stand are designated as necessary. Next, considering the rolling equipment capacity including the rolling mill motor capacity and rolling load limit and the cooling equipment capacity of the rear side of the finishing mill, the maximum rolling speed when rolling a strip of a given material at the above rolling temperature, Determined through rolling load calculation, rolling torque calculation, strip cooling calculation and the like. Here, the capacity of the rolling equipment is a determinant particularly when rolling a thin strip, and the capacity of the cooling equipment is a determinant of the rolling speed particularly when rolling a thick strip. In the next step, assuming the elapsed time from heating furnace extraction to rolling near the rear end of the strip, the rear end of the strip is rolled at the already determined maximum rolling speed, and the target rolling temperature is achieved. The material heating temperature for The rolling speed pattern from the leading end to the trailing end of the strip is determined based on the heating temperature so that the exit temperature of the finishing mill becomes constant in the longitudinal direction of the strip. Since the longitudinal distribution of the temperature of the billet, which is the rolled material, is usually almost uniform at the time of extraction from the heating furnace, generally, when rolling is performed at the same rolling speed, the elapsed time becomes shorter near the end of the strip, and the finish rolling mill exit side Since the temperature rises, the rolling speed pattern calculated by the above procedure is such that the rolling speed is the lowest near the tip of the strip and the rolling speed continuously increases in the longitudinal direction of the strip. If the temperature distribution pattern in the longitudinal direction of the strip is determined as described above, the elapsed rolling time until rolling near the rear end of the strip can be accurately calculated. If there is a significant difference from the elapsed time, the heating temperature and the rolling speed pattern for achieving the desired rolling temperature and the maximum rolling speed are recalculated, and this procedure is repeated until the solution converges.

It is not necessary to carry out the above-described procedure every time when calculating the rolling setting, but it is necessary to calculate in advance offline the strips of the materials and dimensions which are in the rolling production range, and to execute this off-line calculation when performing the rolling. The results may be tabulated and the operation may be performed. It is also a preferred embodiment that the rolling speed pattern setting based on the heating furnace extraction temperature as described above is recalculated and corrected before the start of finish rolling based on the measured temperature value of the coarse bar stage which is an intermediate stage of rolling. is there.

In particular, it has been physically impossible with the conventional method to apply such a rolling method to rolling conditions in which the rolling speed at the tip of the strip is 900 m / min or more due to flying problems. According to this, it is possible to produce a product of a uniform material with high productivity without the problem of flying. In the above-described embodiment, the strip cooling line is constituted by the pinch roll and the cooling water spraying device which can be moved up and down in the vertical direction. However, these may improve the flatness after cooling, or reduce the cooling line length. The present invention may be configured to combine a run-out table of the prior art with a strip end restraint device.

In rolling the rearmost end of the strip,
In some cases, it is necessary to select a rolling speed that does not cause quality trouble or equipment trouble during the winding operation in the coiler. In such a case, from the viewpoint of the winding operation, the vicinity of the rearmost end is exceptionally reduced, and the maximum rolling speed is achieved just before the rear end of the strip. In such a case, since the rolling speed is reduced at the tail end of the strip, the rolling temperature is lowered unless other heating or heat retaining means is used in combination, but the rolling speed in this case is reduced by the strip tail. It may be carried out immediately before the end passes through the finishing mill, and the length of the temperature non-uniform portion can be much shorter than the non-uniform portion near the tip of the conventional method.
Since the rolling speed in the vicinity of the tail end can be generally set higher than the threading speed of the conventional method, even in such a case, the uniformity of the exit temperature of the finishing mill is significantly lower than that of the conventional method. To be improved.

FIG. 5 shows a preferred embodiment of the third aspect of the present invention. Rolling is performed according to the rolling speed pattern determined according to the above-described procedure, and the exit temperature of the finishing mill during rolling is measured. Calculate the difference between the target value and the measured value of the finishing mill exit side temperature set at the time of setting the rolling speed pattern, calculate the correction amount of the rolling speed with the goal of making this difference zero, and calculate the result Modify the rolling speed based on it. By such a rolling method, it is possible to more accurately achieve the target finish-rolling mill exit side temperature. The cycle time for performing the control as shown in FIG. 5 is desirably as short as possible. However, the result of measuring the temperature of the strip on the exit side of the finishing mill and correcting the rolling speed is shown in FIG. Since there is a time delay before observation with a thermometer, it is preferable to set a cycle time in consideration of this time delay.

FIG. 6 shows a preferred embodiment of the present invention. The feedback control of the rolling speed is performed by using the measured output temperature of the finishing mill as shown in FIG. 5, and after the rolling of one strip is completed, the set value of the previously set rolling speed pattern and the actual value are compared. Then, the actual value of the change in the longitudinal direction of the correction amount of the rolling speed based on the measured temperature value is calculated.
Next, based on the actual value of the change in the longitudinal direction of the rolling speed correction amount, the corrected value of the rolling speed pattern is determined for the strip to be rolled. When determining the correction value, it is needless to consider the difference between the rolling conditions of the strip being analyzed and the rolling conditions of the strip to be rolled, but the simplest method is to determine the temperature measurement error. It is also a preferred embodiment to calculate the next rolling speed pattern correction amount by multiplying the actual speed correction amount value by a learning coefficient of 1 or less for the purpose of removing the influence of disturbance such as. As the selection criteria for the “strip to be rolled” that reflects this correction value, a strip that can be rolled at the earliest timing, in which the calculation and the speed setting are sufficient, may be selected. For example, a method of learning the speed correction amount for each rolling condition, and reflecting the latest learning result of the rolling condition section when the strip of the same condition section is rolled next time may be adopted. By reflecting the speed correction value on the rolling speed in advance as described above, the amount of speed correction during rolling performed by the method of FIG. 5 is gradually reduced, and it is possible to control the exit temperature of the finishing mill with higher accuracy. Become.

[0024]

According to the hot strip rolling method of the present invention, finish rolling can be performed under uniform temperature conditions in the longitudinal direction. As a result, a product of uniform material that cannot be realized by the conventional method can be obtained. It can be manufactured. Furthermore, since the threading speed limit in the conventional method is eliminated, the above-described high-quality thin plate can be manufactured with an unprecedentedly high productivity.

Further, since the rolling temperature is made uniform in the longitudinal direction without an extra cooling step, rolling can be performed without consuming extra heating energy, and the fuel cost of the heating furnace can be greatly reduced. In addition, compared to the conventional method, the acceleration rate during finish rolling is greatly reduced, so the extra motor current required for acceleration is greatly reduced, and the maximum rolling speed that can be operated with the same motor capacity is increased. It is possible to do. Further, when a motor is renewed or a completely new rolling line is constructed, a smaller motor capacity is sufficient, and the equipment cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a rolling speed pattern by a hot strip rolling method according to claim 1 of the present invention.

FIG. 2 is a view showing an example of a distribution in a strip longitudinal direction of a finish rolling mill exit side temperature when the hot strip rolling method according to claim 1 of the present invention is performed.

FIG. 3 is a diagram showing an example of a hot strip rolling equipment on which the rolling method of the present invention is based.

FIG. 4 is a diagram showing an example of a method for determining operating conditions for executing the rolling method of the present invention.

FIG. 5 is a view showing a preferred embodiment of the hot strip rolling method according to claim 3 of the present invention.

FIG. 6 is a view showing a preferred embodiment of the hot strip rolling method according to claim 4 of the present invention.

FIG. 7 is a diagram showing an example of a rolling speed pattern by a conventional hot strip rolling method.

FIG. 8 is a diagram showing an example of distribution of the exit temperature of a finishing mill in the longitudinal direction of a strip when a conventional hot strip rolling method is performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Finish rolling mill 2 ... Down coiler 3 ... Strip cooling line 4 ... Pinch roll 5 ... Cooling water injection device 6 ... Strip 7 ... Guide rail 8 ... Strip tip restraint device 9 ... Traveling trolley 10 ... Gripping roll

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C21D 9/52 102 B21B 37/00 132B 9/573 101 137A

Claims (4)

[Claims] 1. A finishing mill and a coiler, and a strip cooling line between the finishing mill and the coiler,
Further, on the strip cooling line, using a hot strip steel rolling equipment having a strip tip restraint device that can move from the finishing mill side to the coiler side while applying tension to the strip while holding the tip of the strip. A rolling method in which the rolling speed is gradually increased from the leading end of the strip toward the trailing end of the strip so that the strip temperature on the exit side of the finishing mill becomes uniform in the longitudinal direction. A hot strip rolling method, characterized in that the rolling speed is the highest. 2. The hot strip rolling method according to claim 1, wherein the speed at the end of the final stand of the finishing mill at the end of the strip is 900 m / min or more. 3. A finishing mill and a coiler, and a strip cooling line between the finishing mill and the coiler,
Further, on the strip cooling line, using a hot strip steel rolling equipment having a strip tip restraint device that can move from the finishing mill side to the coiler side while applying tension to the strip while holding the tip of the strip. Rolling method to achieve a desired maximum rolling speed in the vicinity of the rear end of the strip, and so that the strip temperature on the exit side of the finishing mill becomes uniform in the longitudinal direction, according to a preset rolling speed pattern. Performing the rolling to gradually increase the rolling speed from the leading end of the strip toward the trailing end of the strip, while measuring the exit temperature of the finishing mill by the exit thermometer of the finishing mill during the rolling, the measured temperature, Compare the target value of the finish-rolling mill exit side temperature set in advance, the speed of the rolling speed pattern, so as to bring the measured temperature closer to the target value. Hot steel strip rolling method which comprises carrying out the rolling speed control correctly. 4. A finishing mill and a coiler, and a strip cooling line between the finishing mill and the coiler,
Further, on the strip cooling line, using a hot strip steel rolling equipment having a strip tip restraint device that can move from the finishing mill side to the coiler side while applying tension to the strip while holding the tip of the strip. According to a preset speed pattern, so as to achieve a desired maximum rolling speed in the vicinity of the rear end of the strip, and to make the strip temperature on the exit side of the finishing mill uniform in the longitudinal direction. Along with performing rolling to gradually increase the rolling speed from the leading end of the strip toward the trailing end of the strip, the finishing temperature of the finishing mill is measured by a finishing thermometer on the exit side during the rolling, and the execution temperature is determined in advance. The speed correction value is superimposed on the speed pattern so that the actually measured temperature approaches the target value by comparing the set value with the target value of the exit temperature of the finishing mill. After the completion of rolling of the strip, a speed correction value for the speed pattern of the subsequent strip is calculated based on the speed correction actual value of the speed pattern, and the speed correction value is set in advance to the set value. A hot strip rolling method, comprising calculating a speed pattern set value superimposed on a speed pattern determined at the time of calculation, and rolling based on the speed pattern set value.