JP2003205306A - Method for manufacturing steel plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the loss of yield due to trimmed scraps while preventing troubles at the trimming in a succeeding process by setting the target width in width control in the hot rolling process with high accuracy by a simple method. <P>SOLUTION: When a steel plate is manufactured through the hot rolling process, one or more stages 22 where the change in the width is producible and the succeeding process after the hot rolling process including a trimming device 25, by recognizing the actual value of the amount of trim in the trimming device 25 by using a width measuring means 24 provided on the upstream side of the trimming device 25, calculating the deviation of the actual value of the amount of trim from the preset minimum trimming allowance in the trimming device 25 and correcting the table value of the variation of the width in the succeeding process on the basis of the deviation, the set value of the target width in the hot rolling process is corrected. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot rolling step and a method for manufacturing a steel sheet through the subsequent steps. More specifically, the present invention relates to a method of setting a target strip width in strip width control in the hot rolling step. Regarding the method.

[0002]

2. Description of the Related Art In the hot rolling process in the production of steel sheets,
A plate width control means is provided for controlling the plate width to a target value in rough rolling and finish rolling. As for the strip width control method in the hot rolling process, many techniques have been conventionally proposed, and a method of controlling the strip width by adjusting the edger opening degree of rough rolling, or controlling the strip width to a target value in finish rolling. There are ways. As an example of the former, JP 2000-11
7315, and as an example of the latter, Japanese Patent Laid-Open No. 7-32019.
The method described in Japanese Patent Publication can be used. All of these have a strip width meter installed on the exit side of the finish rolling mill or the entrance side of the coiler.
This is a technique for controlling the plate width of the steel plate at that position to a target value.

The steel plate manufactured through the hot rolling process may be shipped as a hot rolled steel plate as it is, but as illustrated in FIG. 5, the product is shipped after a post process after the hot rolling process. There are many cases. In addition, in order to simplify the description, FIG. 5 illustrates only a typical step other than the trim step, that is, a pickling step, a cold rolling step, an annealing step, and a surface treatment step. Further, the trim process is often provided on the production line output side of other processes, not on a single production line.

FIG. 5 (a) shows a form generally called pickling external sales. The steel sheet after hot rolling is sent to a pickling step in order to remove oxide scale generated on the surface of the steel sheet. In the pickling step, a device for trimming the plate width end portion is provided on the exit side, and the steel plate is trimmed to the plate width of the product before the product is shipped.

For cold-rolled steel sheets, as shown in FIGS. 5 (b) and 5 (c), after a pickling step, a cold rolling step is performed to a predetermined sheet thickness, and then an annealing step is performed to adjust the material. Is done. Regarding the trimming of the plate width end portion, a trimming device may be provided on the outlet side of the pickling process to perform trimming to a predetermined plate width (FIG. 5 (b)), but a trimming device may be provided on the outlet side of the annealing process. In some cases, the products are shipped after they have been aligned with the product board width (FIG. 5C). In particular,
When the annealing step is a continuous annealing line, it often takes the form of (c).

Further, regarding the surface-treated steel sheet, FIG.
As shown by the dotted lines in (b) and (c), a surface treatment step may be provided after the cold rolled steel sheet manufacturing step, but as shown in FIG. 5 (d), trimming is performed on the exit side of the surface treatment step. A device may be provided to perform trimming to the product plate width.

Further, the process of trimming the steel sheet is not limited to the above description. For example, even if a trimming device is not provided in the pickling process, the annealing process and the surface treatment process, the product inspection and the like are performed. A trimming device is often provided in the recoil process (not shown). In any case, the post-process after the hot rolling process (pickling process, annealing process,
In the surface treatment step, the recoil step, etc.), the plate width is usually trimmed at least once to adjust the plate width.

In such a trimming process, a difference in plate width before and after trimming is called a trim allowance, and becomes chips during trimming. If there is an excessive trim margin, this chip will increase, leading to a deterioration in yield in steel sheet manufacturing. The accuracy of strip width control in the hot rolling process is important for minimizing the amount of chips produced by such trimming and improving the yield.

On the other hand, in order to carry out trimming stably, a minimum trim allowance must be secured, which is called the minimum trim allowance. The minimum trim allowance is that the blade of the trimming device does not come off from the width end of the steel plate even if there is some meandering or bending (camber) of the steel plate when trimming while continuously transferring the steel plate. It is a cutting margin that allows stable trimming, and is represented by the necessary cutting margin (sum of both sides) on both sides of the steel sheet. Further, the minimum trim margin is usually set as a value that must secure the amount in the narrowest plate width portion of the plate width that fluctuates in the coil, pickling step, continuous annealing step, The minimum trim allowance of the trimming device in the recoil process is 5 to 15
It is generally set to about mm.

Therefore, the minimum trim allowance is secured so that the blade of the trimming device does not come off the width end of the steel plate during operation to reduce the production efficiency, and at the same time, the excessive trim allowance is reduced as much as possible and the yield is improved. Need to be improved.

By the way, the steel plate after hot rolling undergoes the following plate width change in the post-process. Change in plate width due to heat shrinkage when cooled to room temperature from the temperature measured in the hot rolling process In the pickling process, elongation is applied to the steel plate by the tension leveler or skin pass mill installed for scale break In the cold rolling process, width reduction due to tension between stands and plate width variation due to width expansion due to rolling In the continuous annealing process and surface treatment process, width reduction due to in-furnace tension and the effect of annealing temperature at that time In addition, the change in plate width due to the elongation being imparted to the steel plate by the tension leveler or temper rolling mill.Therefore, the target plate width in the plate width control in the hot rolling process is set by the following method. ing.

(1) When trimming is performed in the pickling step to obtain a product as a pickling external sales material (FIG. 5A):
The minimum trim allowance is added to the width of the product, the amount of change in the width in the pickling process (), and the change in width due to heat shrinkage when cooled from room temperature to the room temperature. amount()
Is set in consideration. Furthermore, variations in the actual strip width with respect to the target strip width in strip width control in the hot rolling process,
In some cases, the margin allowance in consideration of the variation of the plate width change amount () in the pickling process is added to set the minimum trim allowance in the trimming process.

(2) In the case where a product is obtained by performing trimming in the pickling step, and as a cold-rolled steel sheet (or surface-treated steel sheet) through a cold rolling step and an annealing step (further surface treatment step) (FIG. 5 (b)). ): In addition to the above (1), the hot rolling step after trimming is performed in consideration of the change amount (and) of the strip width that occurs in the cold rolling step and the continuous annealing step (and further the surface treatment step). Set the target plate width in. In addition to the factor of variation of the sheet width described in (1) above, a margin allowance considering the variation of the sheet width change amount in the cold rolling process or the continuous annealing process (further, the surface treatment process) is added to obtain the final value. In some cases, the board width of the product may be set within the range of specifications.

(3) Trimming is not performed in the pickling step,
When the product is trimmed in the continuous annealing process, surface treatment process, recoil process, etc. (Fig. 5 (c),
(D)): A line through which the steel sheet passes in the pickling step, cold rolling step, continuous annealing step, surface treatment step, recoil step, etc. by adding the minimum trim margin to the width of the steel sheet to be the product The minimum trim allowance can be secured by taking into consideration the amount of change in sheet width (,,) in (1) and the amount of change in sheet width () caused by thermal contraction when cooled from room temperature to the room temperature. Set to. In addition, in the case where all the steel sheets are set on the safe side so that the minimum trim allowance can be secured in the trimming process, in addition to the allowance allowance taking into consideration the variation factors of the plate width described in (1) and (2) above. is there.

FIG. 6 schematically shows a method for setting a target strip width in the conventional hot rolling process as described above. For the product width, the amount of change in strip width on each line that passes after trimming, the minimum trim margin, the amount of strip width change on each line that passes before trimming, and the temperature at which the strip width was measured during hot rolling to room temperature The target strip width in the hot rolling step is set in consideration of the strip width change amount due to heat shrinkage during cooling. Since there is variation in the amount of change in the plate width in each process, a certain margin may be added to these in order to stably secure a predetermined cutting allowance for all steel plates in the trimming process. is there. Further, as described above, there is often a case where a large value is added as a margin allowance from the beginning without making a detailed consideration of the plate width change amount in each of these lines, and this method is more common. . In any case, the yield is improved while empirically making corrections so as to reduce the target strip width in the hot rolling process within a range where trouble does not occur in the trimming process.

[0016]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
000-117315, JP-A-7-32019, and the like, a strip width control method in hot rolling is a strip width on the exit side of a finish rolling mill or on the inlet side of a coiler in a hot rolling step, which has a small variation and a target value. It is a means for controlling with high accuracy.

However, when feedback control or the like is performed to control the strip width in the hot rolling process to a target value with high accuracy, the strip temperature at the time of measuring the strip width is 500.
At a high temperature of about 700 ° C., the width of the plate changes due to thermal contraction until it is wound by a coiler and cooled. Further, as described above, a pickling step, a continuous annealing step,
The plate width changes even before trimming in the recoil process or the like. Therefore, there is a problem that even if the strip width is controlled to the target strip width with high accuracy in the hot rolling, the cutting margin in the trimming step for directly determining the yield is not necessarily reduced. That is, in order to improve the yield in the trimming process, it is important to set the target strip width in hot rolling with a small precision.

However, in order to accurately set the target strip width in the hot rolling, the strip width change after the hot rolling as described above, that is, in the pickling step, the strip width change due to the tension leveler, the It is necessary to predict the strip width that changes due to various factors such as strip width change during rolling in the hot rolling process and strip width change during continuous annealing process. It is extremely difficult and time-consuming to set the target strip width in the hot rolling process by grasping for each steel type and size. Therefore, in general, it is the current situation that the target strip width in the hot rolling process is set by estimating the strip width change in these processes based on the information obtained empirically.

Further, in a normal trimming process, a plate width measuring instrument may be installed after trimming for the purpose of confirming that the plate width of the product satisfies the specifications. Not measuring. Therefore, it is not possible to quantitatively grasp how much the actual trim allowance is, and just judge the yield size based on the frequency of troubles during trimming in a certain period of operation and the total weight change of trim scraps. Only. That is, there is usually no means for quantitatively grasping the trim amount for each coil and the change in strip width within the coil, and there is information for accurately setting the target strip width in the hot rolling process. There is a problem that you cannot get it.

The object of the present invention is to manufacture a steel sheet, and to obtain a target sheet in the sheet width control in the hot rolling step, which has been corrected by estimating the sheet width change amount in each subsequent step or making an empirical judgment until now. It is an object of the present invention to provide a method that can set the width with high accuracy by a simple method, and can reduce the yield loss due to trim scraps while preventing problems during trimming in a subsequent process.

[0021]

[Means for Solving the Problems] In order to grasp the amount of change in strip width in the post-process after the hot rolling process described above, the inventors of the present invention have provided strip-width measuring means on the upstream side of the trimming process before the trimming. The board width of can be recognized. The difference between the plate width before the trimming device and the plate width measured in the hot rolling process is the amount of change in the plate width in the subsequent processes up to the heat shrinkage and the trimming process. On the other hand, if the plate width before trimming can be recognized, the actual value of the trim allowance in the trimming device can be recognized. Then, if the minimum trim margin is set in advance in the trimming step and the difference between the actual trim margin and the minimum trim margin is calculated, this value is the excess set as the target strip width in hot rolling. Therefore, the target plate width may be corrected based on this value.

The present invention has been made based on such an idea. Therefore, the method for producing a steel sheet of the present invention has the following features.

(1) A steel sheet is manufactured through a hot rolling step provided with a strip width control means and one or more steps in which the strip width may change and a post step after the hot rolling step including a trimming step. At this time, the trim amount actual value in the trimming process is recognized by using the plate width measuring means provided on the upstream side of the trimming process, and the deviation between the trim amount actual value and the preset minimum trim allowance in the trimming process is recognized. Is calculated, and the set value of the target strip width in the hot rolling step is corrected based on the deviation.

(2) Using the plate width measuring means provided on the upstream side of the trimming process, the minimum plate width among the plate widths varying in the coil is specified, and the plate width measuring means provided on the downstream side of the trimming process. Or, the minimum trimming width is recognized from the trim width setting value in the trimming step and the trim amount actual value is recognized from the minimum plate width in the coil, and the trim amount actual value and the minimum value for performing stable trimming. The trim deviation amount is calculated from the preset minimum trim allowance in the trimming step as the cutting margin, and the target strip width is decreased when the trim deviation amount is positive and the target strip width is increased when the trim deviation amount is negative. The method for producing a steel sheet as described in (1) above, wherein the set value of the target strip width in the hot rolling step is corrected so as to allow it to be performed.

(3) At least the trim amount actual value and the minimum trim margin in the trimming process corresponding to the classification of the post-process plate width change amount table divided in consideration of at least the plate thickness, plate width, steel type and manufacturing process. It is possible to calculate the statistic of the deviation of, to correct the post-process strip width change amount table based on the statistic, and to set the target strip width in the hot rolling process using the post-process strip width change amount table. The method for manufacturing a steel sheet according to (1) or (2) above, which is characterized.

(4) As a post-process which may cause a change in strip width, it is characterized by including at least one process selected from a pickling process, a cold rolling process, a continuous annealing process and a temper rolling process. The method for manufacturing a steel sheet according to any one of (1) to (3) above.

(5) One or more devices selected from a skin pass mill, a tension leveler, a cold rolling mill, a continuous annealing furnace, and a temper rolling mill are included in a post-process in which a change in strip width can occur. The method for producing a steel sheet according to any one of (1) to (4) above.

[0028]

1 and 2 show an embodiment of the present invention. FIG. 1 is an explanatory view showing an outline of a hot rolling process, and FIG. 2 shows a post process after the hot rolling process. It is explanatory drawing shown typically.

As shown in FIG. 1, the hot rolling process comprises an edger 2, a rough rolling mill 3, a finishing rolling mill train 4, a runout cooling device 5 and a coiler 6 in this order from the upstream side. It is conveyed in this order and wound up as a coil. In addition, the rough strip side width gauge 7 and the coiler front strip width gauge 9 may be provided, and if necessary, the inter-stand stand strip width gauge 8 or the finish rolling mill delivery side strip width meter (not shown) may be provided.

The plate width control device is a target plate width setting device 13,
The processing unit 12, the edger control device 10, the finish rolling mill control device 11 and the like are included. Here, the target plate width setting device 13 is a device for setting the target plate width of the steel plate at the position of the coiler front plate width meter 9, and the size of the steel plate 1,
The target strip width is determined based on information such as steel type, coiling temperature, and manufacturing route. The arithmetic processing unit 12 performs preset calculation and performs setting calculation necessary to obtain a target plate width. At this time, the target strip width is also set at the exit side of the rough rolling mill, and the edger control device 10 is instructed about the opening degree of the edger 2. Further, the finish rolling mill control device 11 is instructed to set the tension between stands, the rolling reduction, the crown control actuator, and the like of the finish rolling mill train 4.

As another function of the arithmetic processing unit 12,
It may be provided with a function of correcting the opening degree of the edger 2 when the strip width measured by the rough strip side strip width gauge 7 deviates from the target value, or dynamically correcting the setting of the finish rolling mill train 4. Further, the inter-finishing stand strip width gauge 8 may be provided, and the setting condition of the finishing stand upstream stand may be corrected so as to compensate for the error between the target strip width and the measured value at the position. Further, when the measured value in the coiler front strip width meter 9 deviates from the target strip width, the setting of the finish rolling mill may be changed to control so as to obtain the target strip width. Further, a learning control system for correcting the setting of the arithmetic processing unit 12 may be provided based on the board width actually measured by each board width meter (7, 8, 9).

In any case, a conventionally known system may be used as the strip width control system in the hot rolling process. Further, the arrangement of the rolling mill, the edger, the strip width meter, etc. is not limited to the present embodiment shown in FIG. 1, but may be any arrangement capable of performing control for obtaining the target strip width.

Next, the steel sheet that has undergone the hot rolling process described above is
It is cooled to around room temperature, and then, as shown in FIG.
A product is obtained through a pickling process, a cold rolling process, an annealing process, a surface treatment process, a recoil process, and the like. At that time, a trimming process is performed on either line.

FIG. 2 shows a production line equipped with a trimming device on the outlet side, and schematically shows a post process after the hot rolling process. In FIG. 2, reference numeral 25 denotes a trimming device, and 22 provided on the upstream side thereof represents a post-process after hot rolling as a representative. For example, in FIG.
When a trimming process is provided on the outlet side of the pickling process shown in (a) and (b), 22 represents the pickling process, and FIG.
When the trimming process is provided on the outgoing side of the annealing process shown in (c), 22 collectively represents the pickling process, the cold rolling process and the annealing process. That is, the post-process 22 is
The steel sheet 1 that has undergone the hot rolling step is a schematic diagram collectively showing all the steps until reaching the trimming device 25. Therefore, in FIG. 2, the steel plate 1 is schematically shown as one manufacturing line in which after the steel plate 1 is paid out from the pay-off reel 21, the steel plate 1 passes through the post-process 22 and the trimming device 25 and is wound by the tension reel 28. However, the post-process 22 collectively shows one or more processes, and may be a plurality of manufacturing lines.

Further, the post-process 22 includes one or more processes in which the plate width may change. That is, as mentioned above,
The steel sheet after hot rolling has a heat shrinkage during cooling after hot rolling,
Elongation by tension leveler or skin pass mill in pickling process, influence of tension between stands and reduction rate in cold rolling process, influence of heat treatment temperature and in-furnace tension in continuous annealing process and surface treatment process, and elongation by tension leveler or temper rolling mill , Etc. cause the plate width to change. Therefore, when one or more of these steps are included, the plate width of the steel plate 1 immediately before the trimming device 25 changes from the plate width measured by the coiler front plate width meter 9 in the hot rolling process.

Regarding the heat shrinkage during cooling after the hot rolling, it is relatively easy to grasp or predict the heat shrinkage amount. Therefore, the present invention is effective in the case of including any of a pickling step, a cold rolling step, a continuous annealing step, and a temper rolling step, which are difficult to grasp or predict the sheet width change amount as a post step, and surface treatment. It is also effective when the process includes a continuous annealing process and a temper rolling process. Particularly, it is extremely effective when these steps are included in two or more. In addition, it is effective when these post-processes include any one or more of a skin pass mill, a tension leveler, a cold rolling mill, a continuous annealing furnace, and a temper rolling mill in which it is difficult to grasp or predict the amount of change in strip width. Is.

According to the present invention, the steel sheet 1 before trimming described above is used.
In order to recognize the plate width of the trimming device 25, a plate width measuring device 24 is provided on the upstream side of the trimming device 25. Here, the plate width measuring device 24
The installation position is not necessarily immediately before the trimming device 25, but it is preferable that no equipment for changing the plate width is provided between the trimming device 25 and the trimming device 25. For example, in a continuous annealing line, an annealing furnace, temper rolling mill,
When the equipment is arranged in the order of the trimming device, it is preferable to install the strip width measuring device 24 between the temper rolling mill and the trimming device rather than between the annealing furnace and the temper rolling device. This is because in the former case, the strip width may change depending on the temper rolling mill, and the strip width before trimming cannot be accurately obtained. Further, the plate width measuring device 24 is
The plate width of the steel plate 1 before trimming can be continuously measured in the longitudinal direction, the actual value of the plate width for each coil can be specified, and the minimum of the plate widths that fluctuates in the coil can be determined. The board width of can be specified.

On the other hand, the plate width after trimming can be measured by the plate width measuring device 27 provided on the downstream side of the trimming device 25. However, the plate width measuring device 2
Even if 7 is not installed, the trim width setting value of the trimming device 25 may be represented by the value assuming that it is equal to the plate width after trimming.

The plate widths of the trimming device 25 on the inlet side and the outlet side thus measured are calculated by the trim deviation amount calculating device 2
Then, the actual trim amount is calculated from the difference between the plate widths. Then, a comparison is made with a preset minimum trim margin as a minimum trim margin for stable trimming, and a trim deviation amount (from the minimum strip width of the strip width varying in the coil to the minimum trim strip is calculated. The deviation amount) is calculated. The calculated trim deviation amount is sent to the target strip width setting device 13 in the hot rolling process. When the trim deviation amount is positive, the target strip width is decreased, and when it is negative, the target strip width is increased. First, the target plate width in the hot rolling process is corrected. By doing this, it becomes possible to grasp the amount of change in strip width from the measurement of strip width in the hot rolling process to the trimming through post-processes such as the pickling process, including the actual state of the variation. The target strip width in the hot rolling process can be corrected by these data. Therefore, it is not necessary to predict the change in strip width after the hot rolling process, which is very difficult to model, in each process. The target strip width in the rolling process can be automatically set.

For example, FIG. 4 shows a method of obtaining the trim deviation amount from the actual plate width measurement result. First, the actual plate width before trimming is measured by the plate width measuring device 24 provided on the upstream side of the trimming device 25, and the minimum plate width among the plate widths varying in the coil is specified. Next, the actual trim amount (trim margin result) is obtained from the difference between the minimum plate width in the coil and the trimmed plate width, and the deviation from the preset minimum trim margin is calculated as the trim deviation amount. Then, based on this trim deviation amount, the target strip width in the hot rolling process such as the same size and steel grade in the hot rolling process is corrected.

By the way, the preferred embodiment of the present invention is as follows.
At least a plate thickness, a plate width, a steel type and a manufacturing process are divided into, and a plate width change amount table in a post process after hot rolling is provided, and in the hot rolling process using the post process plate width change amount table. Set the target board width. In addition, this plate width change amount table considers steel plate conditions other than the above, such as a plate crown, and in a factory having a plurality of manufacturing lines in the same manufacturing process, the characteristics of the plate width change for each manufacturing line. Since it may be different, a table in which the manufacturing process is further divided into manufacturing lines may be used. Corresponding to such division of the post-process plate width change amount table, the data of the trim deviation amount in the trimming process is obtained for each coil, and the trimming within the division is performed for a certain period or while accumulating a certain amount of data. Statistics such as the average value of the deviation amount and the standard deviation are calculated. In this way, considering the variation in the trim deviation amount for each coil, the target strip width in the hot rolling process should be minimized to minimize the probability that the minimum trim margin will be negative even if there is a certain variation. Can be modified.

For example, by using the target strip width W in the initial hot rolling process, the average value x of the trim deviation amount and the standard deviation σ, the target strip width W ^* to be corrected by the present invention can be obtained from the following equation. .

W ^* = W−x + α × σ (1) Here, α is a coefficient representing the magnitude of the probability that the actual trim amount divides the minimum trim allowance in a large number of coils, and is 2 to
It is preferable to set about 3. If α is set to a value exceeding 3, the probability that the actual trim amount will fall below the minimum trim margin will be almost zero, but the target strip width W ^* will be greatly modified, and the increase in the trim amount will be very large. Will end up. On the other hand, when α is less than 2, it is possible to reduce the trim margin on average and improve the yield, but the probability that the actual trim amount will fall below the minimum trim margin increases, causing operational troubles. Will cause it. Therefore, α may be appropriately set as a coefficient for balancing the probability of occurrence of operation trouble in the trimming process and the yield improvement by reducing the trim amount. It is also an effect of the present invention that such a balance can be adjusted.

The calculated trim deviation amount may be directly sent to the target strip width setting device 13 in the hot rolling process to correct the setting table value of the target strip width in the hot rolling process. In order to more stably set the target plate width with respect to the actual value of the plate width that changes every time, the trim deviation amount analysis device 30 calculates the statistic and then sends it to the target plate width setting device 13. Is desirable.

In the trim deviation amount analysis device 30, the trim deviation amount is determined according to the division of the target strip width setting table divided in consideration of at least the strip thickness, strip width, steel type and manufacturing process after the hot rolling process. Data is accumulated for a certain period or a certain number of times, and statistics such as the average value of the trim deviation amount and the standard deviation are calculated for each section. After that, the correction amount of the target plate width is calculated from the average value of the trim deviation amount and its variation based on the method of the formula (1), and the setting table of the target plate width setting device 13 is corrected.

However, the analysis of such a statistic does not necessarily need to use an automated system such as the trim deviation amount analysis device 30, and the statistic is stored offline based on the accumulated trim deviation amount data. The target plate width setting table may be corrected periodically by calculating the amount.

Further, the trim deviation amount analysis device 30 does not necessarily have to adopt a method of calculating a statistic each time data is accumulated for a certain period of time. For example, learning using an exponential smoothing method sequentially sets the target strip width. An algorithm to modify the table may be introduced. By adopting such a learning method, it is possible to automatically correct the operating conditions in each process that change over a long period of time, which is very troublesome and time-consuming. The target plate width in can be easily corrected.

[0048]

EXAMPLES Steel sheets were manufactured in the hot rolling step shown in FIGS. 1 and 2 and the subsequent steps. In this embodiment,
A manufacturing process shown by a solid line in FIG. 5C, that is, after hot rolling, a pickling process, a cold rolling process, an annealing process, and a trimming process to trim a product width to obtain a cold rolled steel product. I chose the root one. The annealing process was a continuous annealing process including a temper rolling process.

FIG. 3A is a comparative example in which the target strip width in the hot rolling process is set by the conventional method shown in FIG. 6, and the strip thickness is 2.4 to 4.8 mm and the strip width is 1000. ~ 1
For low carbon steel in the range of 300 mm, a strip width meter was installed upstream of the trimming device arranged on the outlet side of the continuous annealing process, the actual trim amount was measured, and the deviation amount from the minimum trim margin was measured. The result. The minimum trim margin is 8 mm
And The distribution of the trim deviation amount shown in FIG.
It can be seen that there is variation due to the prediction error of the plate width change in each process and the trim amount is excessive.

On the other hand, in the present invention, the average value x and the standard deviation σ of the trim deviation amount are calculated based on the statistics shown in the comparative example of FIG. The average value x in this case is 7.2 m
m, and its standard deviation σ was 1.8 mm. Therefore, the coefficient α in the above equation (1) was set to 2.5, and the correction amount of the target strip width in the hot rolling process was calculated. After correcting the post-process strip width variation table after the hot rolling process based on this, the strip thickness was 2.4 as in the comparative example.
~ 4.8 mm, the width of the plate is manufactured in the range of 1000 ~ 1300 mm low-carbon steel cold rolled steel sheet is manufactured, the strip width meter is installed upstream of the trimming device arranged on the outlet side of the continuous annealing step, The actual trim amount was measured and the deviation amount from the minimum trim margin was measured. The result is shown in FIG. As is clear from this figure, it was possible to reduce the trim margin by 2 mm or more on the average at the same time as compared with the comparative example, without generating a coil below the minimum trim margin.

The variation of the trim deviation amount in FIG. 3 is not so different between the present invention example (b) and the comparative example (a). The present invention is for accurately setting the target strip width in the hot rolling process for each section of the post-process strip width change amount table, and the strip width in each actual step in each table section. This is because it does not control the variation in change. Therefore, it is an effect of the present invention that the average value of the trim deviation amount can be reduced when comparing the present invention example and the comparative example in the same table section as in the present embodiment. However, if all the table divisions are combined and compared, the variation of the example of the present invention is smaller than that of the comparative example. Further, in the present invention, since the set value of the post-process plate width change amount for each table classification can be easily set and corrected, it is possible to make the table classification finer than the conventional one, and thereby the trim deviation amount Variations can be reduced and trim allowance can be further reduced.

[0052]

As described above, according to the method for manufacturing a steel sheet of the present invention, the target strip width in the strip width control of hot rolling is set in the subsequent steps of pickling, cold rolling, annealing, and surface treatment. Since the correction is performed based on the actual value of the trim amount when trimming the plate width end in the process such as recoil, the amount of change in the plate width in each subsequent process can be easily and accurately adjusted without estimating it individually. A target strip width in rolling can be set, and yield loss due to trim scraps can be reduced while performing stable trimming.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a hot rolling process used for carrying out the present invention.

FIG. 2 is an explanatory view showing an example of a post-process after the hot rolling process used for carrying out the present invention.

FIG. 3 is a diagram showing a distribution of trim deviation amounts in the embodiment, where (a) is a conventional example and (b) is an example of the present invention.

FIG. 4 is an explanatory diagram of a method for calculating a trim deviation amount according to the present invention.

FIG. 5 is an explanatory diagram of a post process after the hot rolling process.

FIG. 6 is an explanatory view showing an example of a method for setting a target strip width in a conventional hot rolling process.

[Explanation of symbols]

1 Steel Plate 2 Edger 3 Roughing Roller 4 Finishing Rolling Machine Row 5 Runout Cooling Device 6 Coiler 7 Rough Side Strip Width Meter 8 Finishing Stand Width Meter 9 Coiler Front Width Meter 10 Edger Controller 11 Finishing Roller Controller 12 Calculation Processing device 13 Target plate width setting device 21 Payoff reel 22 Post process 23, 26 after hot rolling upstream of the trimming process Tension bridle 24 Trimming device front plate width meter 25 Trimming device 27 Trimming device output plate width meter 28 Tension Reel 29 Trim deviation amount calculation device 30 Trim deviation amount analysis device

Continued front page    (72) Inventor Yasuhiro Soya             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. F term (reference) 4E024 AA08 FF01 FF10                 5H004 GA04 GB03 HA06 HA07 HB06                       HB07 KC13

Claims (5)

[Claims] 1. A hot rolling process provided with a plate width control means,
When manufacturing a steel sheet through one or more steps in which a change in the sheet width may occur and a post-step after the hot rolling step including a trimming step, trimming is performed using a sheet width measuring means provided upstream of the trimming step. Recognizing the trim amount actual value in the process, calculating the deviation between the trim amount actual value and the preset minimum trim margin in the trimming process, and based on the deviation, the target strip width in the hot rolling process. A method for manufacturing a steel sheet, which comprises correcting a set value. 2. A plate width measuring means provided on the downstream side of the trimming process by specifying the minimum plate width among the plate widths varying in the coil by using the plate width measuring means provided on the upstream side of the trimming process. The trim amount actual value is recognized from the post-trim width recognized from the trim width setting value in the trimming process and the coil minimum plate width, and the minimum trimming value and the minimum value for performing stable trimming are recognized. The trim deviation amount is calculated from the minimum trim allowance in the trimming step set in advance as the cutting allowance, and the target plate width is decreased when the trim deviation amount is positive and the target plate width is increased when the trim deviation amount is negative. The method for manufacturing a steel sheet according to claim 1, wherein the set value of the target strip width in the hot rolling step is corrected as described above. 3. A trim amount actual value and a minimum trim allowance in a trimming process corresponding to a division of a post-process strip width change amount table divided in consideration of at least a strip thickness, strip width, steel type and manufacturing process. A characteristic is that a statistical amount of deviation is calculated, a post-process strip width change amount table is corrected based on the statistical amount, and a target strip width in a hot rolling process is set using the post-process strip width change amount table. The method for producing a steel sheet according to claim 1 or 2. 4. A post-process that may cause a change in strip width, including at least one process selected from a pickling process, a cold rolling process, a continuous annealing process, and a temper rolling process. Item 4. A method for manufacturing a steel sheet according to any one of Items 1 to 3. 5. A post-process that may cause a change in strip width includes at least one device selected from a skin pass mill, a tension leveler, a cold rolling mill, a continuous annealing furnace, and a temper rolling mill. The method for manufacturing a steel sheet according to any one of claims 1 to 4.