JP4957663B2 - Manufacturing method and manufacturing apparatus for hot-rolled steel sheet - Google Patents

Description

  The present invention relates to a method and an apparatus for manufacturing a hot-rolled steel sheet, and specifically, manufactures a hot-rolled steel sheet having better flatness by considering the change in flatness caused by cooling after finish rolling. The present invention relates to a method and apparatus for manufacturing a hot-rolled steel sheet.

  The flatness of the plate in hot rolling not only directly affects the flatness of the hot-rolled steel sheet that is the final product, but also the controllability of the cooling temperature during hot rolling, and the winding form when coiled. Furthermore, it is an important quality that greatly affects the overall quality of the hot-rolled steel sheet, such as the presence or absence of surface defects in the hot-rolled steel sheet, such as the occurrence of scratches during unwinding in a subsequent process.

  On the other hand, the flatness of the hot-rolled steel sheet is greatly influenced by rolling conditions such as the gap between the rolling rolls, the thermal crown amount of the rolling roll, the deflection amount of the rolling roll, the material of the material to be rolled, the temperature, and the dimensions. Of course, in addition to these rolling conditions, it is also greatly influenced by cooling performed subsequent to hot rolling. For this reason, in general, it is extremely difficult to predict with high accuracy the flatness behavior of a hot-rolled steel sheet that occurs from hot rolling to cooling to winding.

  Therefore, various inventions for obtaining desired flatness by evaluating the appropriateness by directly measuring the flatness of the hot-rolled steel sheet and making necessary corrections to the rolling conditions based on the measurement results have been made. Proposed.

  For example, in Patent Document 1, a flatness measuring device is installed on both the exit side of the finish rolling mill and the entrance side of the winder, and the finish mill is based on the measurement result on the exit side of the finish mill. An invention relating to a method of controlling the flatness in advance and controlling the flatness using a winding pinch roll based on the measurement result on the entry side of the winding machine is disclosed.

  In Patent Document 2, flatness measuring devices are installed on both the exit side of the finishing mill and the entrance side of the winder, and the finishing mill is fed back based on the measurement result on the exit side of the finishing mill. An invention relating to a method of controlling and correcting a target value of flatness control on the exit side of the finish rolling mill based on the measurement result on the entrance side of the winder is disclosed.

Further, Patent Document 3 includes a finishing rolling mill, a cooling device, and a winder in this order, which are rolling processes similar to the inventions described in Patent Documents 1 and 2, and on the inlet side and the outlet side of the cooling device. An invention relating to a finishing rolling mill, a cooling device, and a method for adjusting a winding tension in a rolling process including both flatness measuring devices based on the measurement results of both flatness measuring devices is disclosed.
JP 54-11157 A JP 54-11158 A Japanese Patent Laid-Open No. 11-2511

  FIG. 5A to FIG. 5C are explanatory views schematically showing the state immediately after the start of rolling of the steel sheet 2, during winding, and immediately before the end of winding. In the figure, reference numeral 1 denotes a final stand of the finish rolling mill, reference numeral 2 denotes a steel plate as a material to be rolled, reference numeral 3 denotes a winder, and reference numeral 5 denotes a distance L ′ on the exit side of the finishing mill 1. The 1st flatness measuring apparatus arrange | positioned in the distant position is shown, Furthermore, the code | symbol 6 shows the 2nd flatness measuring apparatus arrange | positioned at the entrance side of the winder 3. FIG. FIG. 5C shows a state where the distance Lb between the rear end of the steel plate 2 and the second flatness measuring device 6 is larger than the distance L ′.

  Immediately after the start of rolling shown in FIG. 5 (a), since the tip of the steel plate 2 does not reach the winder 3, the steel plate 2 existing between the tip and the exit side of the finishing mill 1 No tension (hereinafter referred to as “winding tension”) generally applied during the production of a hot-rolled steel sheet is generated. Therefore, in this state, both the first flatness measuring device 5 and the second flatness measuring device 6 measure the flatness of the tension-free steel plate 2.

  Then, as shown in FIG.5 (b), after the time when the front-end | tip of the steel plate 2 arrives at the winder 3 and winding by the winder 3 is started, the finishing mill 1 and the winder 3 Winding tension is applied to the steel plate 2 between the two. For this reason, both the first flatness measuring device 5 and the second flatness measuring device 6 measure the flatness of the steel plate 2 to which the winding tension is applied.

  Thereafter, as shown in FIG. 5 (c), immediately before the winding of the steel plate 2 by the winder 3, the winding tension does not act on the steel plate 2 again. The flatness of the steel plate 2 in tension is measured. However, at this time, when the portion of the steel plate 2 existing immediately below the second flatness measuring device 6 is directly below the first flatness measuring device 5, since Lb> L ′, the steel plate 2 Since the rear end is before exiting the finishing mill 1, the first flatness measuring device 5 measures the flatness of the steel plate 2 to which the winding tension is applied.

  Such a situation will be further described in correspondence with the position in the longitudinal direction of the steel plate 2. 6 (a) to 6 (c) show the measured values of the flatness of the steel sheet 2 from the front end to the rear end on the exit side of the finish rolling mill 1 and on the entrance side of the winder 3, respectively. It is a graph which shows the measured value at the time of unwinding (tensile force) in a value and a post process (refining process), and all the graphs are shown so that the front-end | tip of the steel plate 2 may be located in the left side.

  Note that the flatness index of the hot-rolled steel sheet is generally expressed by the relative value at the position in the width direction with respect to the value at the center in the width direction, with the ratio of the wave height per unit length, This relative value is also used as an index of the flatness of the steel plate 2 shown on the vertical axis in the graphs of FIGS. 6 (a) to 6 (c). A relative value of 0 indicates that the steel plate 2 is flat, a negative value indicates that the steel plate 2 is in a middle elongation tendency, and the relative value is a positive value. Being present indicates that the steel plate 2 has an end elongation tendency.

  As shown to Fig.6 (a), the measured value of the flatness by the 1st flatness measuring apparatus 5 in the exit side of the finishing mill 1 is the unsteady part of the front-end | tip of the steel plate 2 in which flatness changes rapidly. (Part (A) in FIG. 6 (a) to FIG. 6 (c)), as shown in part (A) in FIG. 6 (a), the tendency of medium elongation continues under no tension, and the finish rolling mill When the distance La from the first flatness measuring device 5 on the exit side 1 to the winder 3 is passed, the leading end of the steel plate 2 is wound around the winder 3, and a winding tension is applied to the steel plate 2. Since the flatness is corrected by elastic deformation, as shown in the (c) part in FIG. 6A, the measured value of the flatness by the first flatness measuring device 5 shows a value close to flat. Become.

  On the other hand, the measured value of the flatness by the second flatness measuring device 6 on the entry side of the winder 3 is an unsteady portion (FIG. 6 (a) to FIG. ) Part), the part subjected to the change due to cooling under no tension (b ') part from the tip of the steel plate 2 to the distance L (distance between the flatness measuring device 6 and the winder 3) Subsequently, since the winding of the steel plate 2 is started, a winding tension is applied to the steel plate 2, and the flatness measured by the flatness measuring device 6 is applied as shown in FIG. 6 (b). The measured value becomes almost flat. However, the measurement result close to flat is a so-called apparent correction obtained by the influence of elastic deformation due to tension. Thereafter, in the situation where the steel plate 2 is rewound and there is no winding tension, as shown in FIG. The portion (d) is a measurement result of a portion in which the rear end of the steel plate 2 passes through the finishing mill 1 and becomes no tension again without winding tension, so that the flatness is broken and measured. In addition, when this part of the steel plate 2 was measured by the first flatness measuring device 5 on the exit side of the finish rolling mill 1, a winding tension is applied to the steel plate 2, and therefore FIG. ), As shown in the graph of FIG.

  FIG. 6C shows a state in which a part of the apparently corrected steel plate 2 reappears as a flat defect after unwinding, as shown in the graph of FIG. In addition, it can be seen that the flatness is not flat but tends to be moderately elongated.

  Thus, in a rolling process comprising a finish rolling mill, a cooling device and a winder in this order, the flatness of the steel plate on the inlet side and the outlet side of the cooling device is compared, or the steel plate on the inlet side of the winder is compared. Correctly measure and evaluate the flatness, and based on this, correct the flatness target value in finish rolling for the steel sheet of the material or the next material, control the cooling device, etc. In order to control appropriately, it is necessary to consider the state of winding tension in the steel sheet whose flatness is measured.

  However, any of the inventions disclosed in Patent Documents 1 to 3 do not consider the winding tension of the steel sheet during hot rolling, cooling, and winding at all, so the exit side of the finish rolling mill and the winding machine The flatness of the steel sheet on the entry side cannot be obtained correctly. For this reason, based on these inventions, the flatness target in finish rolling for the steel material and subsequent steel plates based on the measured value of the flatness of the steel plate on the entry side of the winder and the exit side of the finish rolling mill Even if the value is corrected and set, a hot-rolled steel sheet having a desired flatness (generally flat) cannot be manufactured.

As a result of intensive studies in order to solve the above-described problems, the present inventors have obtained the findings (a) to (c) listed below and completed the present invention after further studies.
(A) In order to accurately evaluate the influence on the change in flatness due to cooling of the steel sheet after hot rolling, correction of apparent flatness, that is, under no tension where no winding tension is applied to the steel sheet It is effective to measure the flatness before and after the cooling and compare these measured values.

(B) The 1 m long region at the tip of the steel plate is an unsteady region that is strongly affected by the temperature of the steel plate, rolling conditions, etc., and is therefore an inappropriate region for evaluating the flatness of the steel plate.
(C) In order to stably evaluate the flatness of the steel plate, it is effective to eliminate the influence of a partially steep flatness variation, and for that purpose, for example, a steady state having a length of about 5 m. It is effective to measure the flatness in the region.

In the present invention, hot strip rolling is performed on a strip-shaped steel plate by a hot finish rolling mill, and then the steel plate is cooled by a cooling device disposed downstream of the hot finish rolling mill. When manufacturing a hot-rolled steel sheet by winding the steel sheet into a coil by a winding device disposed downstream, the steady state following a non-stationary region that is a distance of 1 m from the front end of the steel sheet toward the longitudinal direction of the steel sheet. Between the time when the tip of the region finishes cooling by the cooling device and the time when the tip of the steel sheet reaches the winding device and starts winding, between the hot finish rolling mill and the cooling device, the flatness of the cooling device and the steel sheet at a position and a by a distance winder 6m or more in the longitudinal direction of the steel sheet from between the winding apparatus is measured, on the basis of these measurements, it is set in advance for this steel Hot The target value of flatness on the delivery side of the upper rolling mill is corrected and set, and hot rolling is subsequently performed on the steel sheet based on the new target value of flatness set by correction. It is a manufacturing method of a hot-rolled steel sheet.

In addition, the present invention is to perform hot finish rolling on a strip-shaped steel plate by a hot finish rolling mill, and then cool the steel plate by a cooling device disposed on the downstream side of the hot finish rolling mill. When a hot-rolled steel sheet is produced by winding this steel sheet into a coil by a winding device disposed downstream of the steel sheet, an unsteady region that is a distance of 1 m from the front end of the steel sheet toward the longitudinal direction of the steel sheet is used. Between the time when the leading edge of the subsequent steady region ends cooling by the cooling device and the time when the leading edge of the steel plate reaches the winding device and starts winding, and between the hot finish rolling mill and the cooling device. in a position away than 6m in the longitudinal direction of the steel sheet from the take-up device be between the cooling device and the winding device to measure the flatness of the steel sheet, on the basis of these measurements, it is rolled after the steel plate Other steel plates The preset flatness target value on the exit side of the hot finish rolling mill is corrected and set, and the other flat steel plate is hot-fixed based on the new flatness target value corrected and set. A hot-rolled steel sheet manufacturing method characterized by performing hot finish rolling with a rolling mill.

From another viewpoint, the present invention provides (a) a hot finish rolling mill for performing hot finish rolling on a steel sheet, and (b) is disposed downstream of the hot finish rolling mill to cool the steel sheet. A cooling device for, (c) a winding device disposed downstream of the cooling device for winding the steel plate around a coil, and (d) a steel plate disposed between the hot finish rolling mill and the cooling device. A first flatness measuring device for measuring flatness; and (e) a steel plate disposed between the cooling device and the winding device at a position 6 m or more away from the winding device in the longitudinal direction of the steel plate. A second flatness measuring device for measuring flatness; and (f) a cooling device having a tip of a steady region following a non-steady region that is a distance of 1 m from the tip of the steel plate toward the longitudinal direction of the steel plate. When the cooling by the end of the Based on the measured values of the first flatness measuring device and the second flatness measuring device until the time when the taking is started, preset for other steel plates rolled after this steel plate, A hot rolled steel sheet manufacturing apparatus comprising: a control device that corrects and sets a target value of flatness on a delivery side of a hot finish rolling mill.

These present invention, a second flatness measuring device, apart winder 6m or more in the longitudinal direction of the steel plate from, Ru is located. Thereby, the measurement precision of the flatness of the steel plate measured by the second flatness measuring device can be sufficiently increased.

  According to the present invention, the change in flatness of the hot-rolled steel sheet in the cooling process after finish rolling can be measured with high accuracy, and based on the measured value of flatness measured with high accuracy in this way, By correcting and setting the target value of the flatness on the outlet side of the hot rolling mill in hot rolling of the steel sheet or the subsequent steel sheet, it is possible to reliably manufacture a hot rolled steel sheet having excellent flatness. become.

The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is an explanatory diagram showing a configuration of a hot-rolled steel sheet manufacturing apparatus 11 according to the present invention. This hot-rolled steel sheet manufacturing apparatus 11 includes a hot finishing rolling mill 1, a cooling device 4, a winding device 3, a first flatness measuring device 5, a second flatness measuring device 6, and a control. Since the apparatus 12 is provided, these components will be described first.

(I) Hot finish rolling mill 1
The hot finish rolling mill 1 is for performing hot finish rolling on the steel plate 2 and is a well-known and conventional one. Such a hot finish rolling mill 1 is well known and commonly used by those skilled in the art, and thus the description of the hot finish rolling mill 1 is omitted.

(Ii) Cooling device 4
The cooling device 4 is arranged on the downstream side of the hot finish rolling mill 1 to cool the hot-rolled hot steel plate 2 to give the hot-rolled steel plate 2 desired mechanical properties. . Usually, it is a water cooling type cooling device. Such a cooling device 4 is also well-known and commonly used by those skilled in the art, and thus the description of the cooling device 4 is omitted.

(Iii) Winding device 3
The winding device 3 is arranged downstream of the cooling device 4 and winds the steel plate 2 around the coil. Since such a winding device 3 is also well known to those skilled in the art, the winding device 3 The description of 3 is omitted.

(Iv) First flatness measuring device 5
The first flatness measuring device 5 is disposed on the exit side of the hot finishing mill 1, that is, between the hot finishing mill 1 and the cooling device 4, and measures the flatness of the steel plate 2. . The first flatness measuring device 5 may be a well-known and commonly used flatness measuring device of this type, and is not limited to a specific type, but is non-contact because it is used in a hot rolling process. It is desirable to use a flatness measuring device of the formula.

The flatness of the steel plate 2 immediately after passing through the finishing mill final stand 1 is measured by the first flatness measuring device 5 arranged on the exit side of the finishing mill final stand 1.
Such a first flatness measuring device 5 is also well-known and commonly used by those skilled in the art, and thus further description of the first flatness measuring device 5 is omitted.

(V) Second flatness measuring device 6
The second flatness measuring device 6 is disposed on the entry side of the winder 3, that is, between the cooling device 4 and the winding device 3, and measures the flatness of the steel plate 2. The second flatness measuring device 6 may be a well-known and commonly used flatness measuring device of this type, and is not limited to a specific type, but is non-contact because it is used in a hot rolling process. A flatness measuring device of the formula is desirable.

  In the present invention, the second flatness measuring device 6 is disposed at a position 6 m or more away from the winding device 3 in the longitudinal direction of the steel plate in order to reliably measure the flatness of the steel plate 2 with high accuracy. That is, the distance L in FIG. 1 is desirably 6 m or more. The flatness of the steel plate 2 immediately before being wound up by the winder 3 is measured by the second flatness measuring device 6.

  Since such a second flatness measuring device 6 is not necessary for those skilled in the art, further description of the second flatness measuring device 6 will be omitted.

(Vi) Control device 12
The manufacturing apparatus 11 includes a control device 12. The control device 12 finishes cooling by the cooling device 4 at the tip of the steady region following the unsteady region including the tip of the steel plate 2 (for example, a range of a distance less than 1 m from the tip of the steel plate 2 in the longitudinal direction). The measured values of the first flatness measuring device 5 and the second flatness measuring device 6 during the period from when the tip of the steel plate 2 reaches the winding device 3 until winding is started. Based on F1 and F2, in order to correct and set the flatness target value on the exit side of the hot finishing mill 1 preset for other steel plates (not shown) rolled after this steel plate 2 belongs to.

  In this description, the control device 12 is flat on the outlet side of the hot finish rolling mill 1 preset for other steel plates (not shown) rolled after the steel plate 2 based on the measured values F1 and F2. However, the present invention is not limited to this embodiment, and the control device 12 is preset for the steel plate 2 based on the measured values F1 and F2. Further, the target value of flatness on the delivery side of the hot finish rolling mill 1 is corrected and set, and the hot rolling on the steel plate 2 is continued based on the new target value of flatness set by correction. The present invention applies in the same way when it is carried out.

  In the control device 12, the input flatness measurement values F1 and F2 are compared and analyzed. That is, the flatness comparison and analysis device 7 in the control device 12 includes the flatness F1 of the steel plate 2 measured by the first flatness measuring device 5 and the steel plate 2 measured by the second flatness measuring device 6. The flatness F2 is input, and a signal 10 for changing the finishing flatness target control value 8 is output by comparing and analyzing the measured values F1 and F2.

  The finish side flat control target value 8 stored in the storage unit in the control device 12 is changed by the signal 10. And the control apparatus 12 corrects and sets the finishing delivery side flat control target value in the finishing mill final stand 1 via the flat control feedback loop 9 to the finishing mill final stand 1. Thereby, in the hot finishing rolling mill final stand 1, when the next steel plate is hot-rolled, the next steel plate is formed based on the new flatness target value corrected and set in this way. On the other hand, hot finish rolling is performed.

The manufacturing apparatus 11 is configured as described above. Next, the situation where a hot-rolled steel sheet is manufactured using the manufacturing apparatus 11 will be described.
First, as shown in FIG. 1, the strip-shaped steel plate 2 is hot-finished by a hot finish rolling mill 1 and sent to a cooling device 4 disposed on the downstream side of the hot finish rolling mill 1. It is cooled to a predetermined temperature and subsequently sent to a winding device 3 disposed downstream of the cooling device 4 and wound around a coil. Thus, a hot-rolled steel sheet is manufactured by this manufacturing apparatus 11.

  In the present embodiment, when hot rolling, cooling and winding are performed on the steel plate 2 in this manner, the tip of the steady region following the unsteady region including the tip of the steel plate 2 finishes cooling by the cooling device 4. From the time until the time when the tip of the steel plate 2 reaches the winding device 3 and the winding is started, between the hot finish rolling mill 1 and the cooling device 4 and between the cooling device 4 and the winding device 3. The flatness of the steel plate 2 is measured by the first flatness measuring device 5 and the second flatness measuring device 6 both in between. These measured values F1 and F2 are sent to the control device 12.

  Next, the flatness comparison and analysis device 7 in the control device 12 is preset for other steel plates (not shown) to be rolled after this steel plate 2 by comparing and analyzing these measured values F1 and F2. Then, a signal 10 for changing the flatness target value (finishing flatness control target value) 8 on the outlet side of the hot finish rolling mill 1 is output.

  In this way, the target value of the flatness on the exit side of the hot finishing mill 1 set in advance for other steel plates rolled after this steel plate 2 is corrected and set, and is set after correction. A hot-rolled steel sheet is manufactured by performing hot finish rolling on the other steel sheets with the hot rolling mill 1 so as to obtain a new flatness target value.

  Hereinafter, with reference to FIG. 2A to FIG. 2C and Table 1, the comparison method of the measured values of the flatness measuring device 5 and the flatness measuring device 6 by the flatness comparison and analysis device 7 will be described. This will be described in detail.

  2 (a) to 2 (c) are similar to FIGS. 6 (a) to 6 (c) described above, in the finish rolling mill 1 of the flatness of the steel plate 2 from the front end to the rear end, respectively. It is a graph which shows the measured value at the entrance side of the winding machine 3, the measured value at the entrance side of the winder 3, and the measured value at the time of unwinding (no tension) in the post process (the refining process). It shows that the front-end | tip of the time steel plate 2 is located in the left side.

  Region A in FIGS. 2A to 2C shows an unsteady region where the flatness of the steel plate 2 changes abruptly, and region B exceeds region A and a winding tension is applied. The region C shows no area, and the region C is in a tension-free state on the exit side of the finishing mill final stand 1, but on the entrance side of the winder 3, the steel plate 2 is apparently flat due to elastic deformation by applying a winding tension. An area where correction is performed is shown, and an area D indicates an area where a winding tension is applied on both the exit side of the finishing mill final stand 1 and the entrance side of the winder 3 to make an apparent flat correction. Furthermore, the region E shows a state in which the rear end of the steel plate 2 passes through the rolling mill final stand 1 and the tension state is different in the flatness measurement on the entry side and the exit side of the cooling device 4.

  Table 1 summarizes the tension applied state and the suitability of the flatness comparison based on the tension applied to the regions A, B, C, D, and E in FIGS. 2 (a) to 2 (c).

  As shown in FIGS. 2 (a) to 2 (c) and Table 1, in order to grasp the flat change due to cooling from the exit side of the finishing mill final stand 1, on the entrance side and the exit side of the cooling device 4 A region on the steel plate 2 that is appropriate for comparing the flatness measurement results is a region B that is a region that exceeds the unsteady portion A and is not provided with a winding tension. Regions A, C, D, and E other than region B are unsuitable for use in comparison of measured values of flatness on the entry side and exit side of the cooling device 4.

  That is, since the region A is an unsteady region where the flatness of the steel plate 2 changes rapidly, even if the flatness is measured in this region A, the flatness of the steel plate 2 cannot be obtained accurately. Region C is in a tension-free state on the exit side of the final stand 1 of the finish rolling mill, but on the entry side of the winder 3, an apparent flattening due to elastic deformation is applied to the steel plate 2 by applying a winding tension to the steel plate 2. Since the tension state of the steel plate 2 before and after cooling is different, it is meaningless to compare the measured values of flatness on the entry side and the exit side of the cooling device 4. The area D has an apparent flattening by applying a winding tension on both the exit side of the finishing mill final stand 1 and the entrance side of the winder 3, and therefore, even if this area D is measured. The flatness cannot be determined accurately. Further, since the tension state is different in the measurement of the flatness on the entry side and the exit side of the cooling device 4, the region E also means that the measured flatness values on the entry side and the exit side of the cooling device 4 are compared. There is no.

  Thus, in order to accurately determine the change in flatness due to cooling by the cooling device 4 from the exit side of the finishing mill final stand 1, the measurement results of the flatness on the entry side and the exit side of the cooling device 4 are compared. The region on the steel plate 2 that is appropriate for this is the region B in the graphs of FIGS. 2 (a) to 2 (c). That is, from the time when the tip of the steady region following the unsteady region including the tip of the steel plate 2 finishes cooling by the cooling device 4 until the time when the tip of the steel plate 2 reaches the winding device 3 and winding is started. If the flatness of the steel plate 2 is measured by the first flatness measuring device 5 and the second flatness measuring device 6 during this period, the flatness of the steel plate 2 can be accurately measured with high accuracy.

  Here, since the length of the region A which is an unsteady region is usually within 1 m from the tip of the steel plate 2, the region A may be set as a range of 1 m from the tip of the steel plate 2. In addition, according to the experience of the present inventors, the length of the region B is 5 m or more in order to properly measure the flatness of the steel plate 2 while excluding the influence of partially steep flatness fluctuations. It is desirable to do. For this reason, in FIG. 1, it is desirable to secure a distance L of 6 m or more between the measurement position on the steel plate 2 by the flat measuring device 6 and the position of the steel plate 2 where the winding to the winder 3 is started.

  Then, the control device 12 feeds back the measured value F1 of the flatness obtained by the first flatness measuring device 5 on the exit side of the finishing mill final stand 1 to the finishing mill 1, and exits the finishing mill final stand 1. Control to flatness target value at. Moreover, in the control apparatus 12, about the measured value F2 of the flatness after cooling by the 2nd flatness measuring apparatus 6 in the entrance side of the winding machine 3, the flatness of the hot-rolled steel sheet which is a product is desired flatness ( In general, the flatness comparison and analysis device 7 compares the measured value F1 of the flatness on the exit side of the final stand 1 of the finish rolling mill and rolls after the steel plate 2. The target value of the flatness on the delivery side of the hot finish rolling mill 1 preset for other steel plates is corrected and set.

  Then, hot rolling is performed by appropriately changing the rolling conditions for other steel plates (for example, the gap between the rolling rolls, the temperature of the subsequent steel plate, etc.) so that the new flatness target value set by correction is obtained. Hot finish rolling is performed by a machine. It is desirable to adjust the flatness target value for each group according to, for example, the material and dimensions of the steel sheet, the coiling temperature target value level, and the like.

  In the present embodiment, in this way, a hot rolled steel sheet having a desired flatness is reliably manufactured by correcting and setting the target value of flatness in finish rolling for the steel sheets subsequent to the subsequent material. can do.

  Thus, according to the present embodiment, the change in flatness of the hot-rolled steel sheet in the cooling process after finish rolling can be measured with high accuracy, and thus the flatness measured with high accuracy can be measured. Based on the measured values F1 and F2, the hot rolling with excellent flatness is achieved by correcting and setting the target value of flatness on the outlet side of the hot rolling mill in the hot rolling of the subsequent steel plates. A steel plate can be manufactured reliably.

Next, the present invention will be described more specifically with reference to examples.
FIG. 3 shows an example of the present invention in which a hot-rolled steel sheet made of a general mild steel material having a sheet thickness of 3.2 mm and a sheet width of 1200 mm is manufactured by applying the present invention using the manufacturing apparatus 11 shown in FIG. FIG. 4 is a graph showing the results of a conventional example in which this hot-rolled steel sheet was manufactured using the manufacturing apparatus 11 shown in FIG.

  Here, the graph shown in FIG. 3 (a) or FIG. 4 (a) shows the measured value of the flatness of the steel plate 2 from the front end to the rear end on the exit side of the finishing mill 1, and FIG. ) Or the graph shown in FIG. 4 (b) shows the measured value of the flatness of the steel plate 2 from the front end to the rear end on the entry side of the winder 3, and further, FIG. 3 (c) or FIG. The graph shown to c) shows the measured value of the flatness of the steel plate 2 from the front end to the rear end at the time of unwinding (no tension) in the post process (the refining process). Both graphs are shown so that the tip of the steel plate 2 during rolling is located on the left side. Furthermore, the graph located on the left side in each of FIGS. 3A to 3C shows the measurement result of the flatness before the flatness target value is changed according to the present invention, and the graph located on the right side is the main graph. The flatness measurement result after changing the flatness target value according to the invention is shown, and the graph located on the left side in each of FIGS. 4A to 4C is a change of the flatness target value according to the conventional example. The measurement result of the flatness before performing is shown, and the graph located on the right side shows the measurement result of flatness after changing the flatness target value according to the conventional example.

  In the example of the present invention shown in the graphs of FIGS. 3A to 3C, the flatness is measured on the exit side of the finish rolling mill 1 and on the entry side of the winder 3 in the region B in a tensionless state. The values are compared, and based on the comparison results, the flatness target value set in advance is changed for the region A ′ in the tension-free state at least on the exit side of the finish rolling mill 1 in the subsequent steel plate. Finish rolling was performed. As shown in the graph of FIG. 3C, the hot-rolled steel sheet produced in this way had good flatness over its entire length when unrolled in a subsequent process.

  On the other hand, in the conventional example shown in the graphs of FIGS. 4A to 4C, the steel sheet on the finish rolling mill exit side and the winder entrance side measured at the timing of the region D in a state where the steel sheet is in tension. Based on the measured value of the flatness, the target value of the flatness on the outlet side of the hot finishing mill 1 preset for the region D ′ corresponding to the region D in the subsequent steel plate was corrected and set. In this case, since the flatness is apparently corrected in the region D as described above, the correction amount of the flatness target value is too small. For this reason, as shown in the graph of FIG. Even after the values were corrected, the flatness of the hot-rolled steel sheet was not flat but had a tendency to moderate elongation.

It is explanatory drawing which shows the structure of the manufacturing apparatus of the hot rolled sheet steel which concerns on this invention. 2 (a) to 2 (c) show the measured value on the exit side of the finishing mill, the measured value on the entry side of the winder, and the rear of the flatness of the steel sheet from the front end to the rear end, respectively. It is a graph which shows the measured value at the time of unwinding (non-tension) in a process (refinement process). It is a graph which shows the result at the time of manufacturing the hot-rolled steel plate which consists of a general mild steel material whose board thickness is 3.2 mm and board width is 1200 mm using the manufacturing apparatus shown in FIG. . A target of flatness based on the result of measuring a hot-rolled steel plate made of a general mild steel material having a plate thickness of 3.2 mm and a plate width of 1200 mm in a region D in FIG. 2 using the manufacturing apparatus shown in FIG. It is a graph which shows the result of the comparative example which changed the value. FIG. 5A to FIG. 5C are explanatory views schematically showing the state immediately after the start of rolling of the steel sheet 2, during winding, and immediately before the end of winding. 6 (a) to 6 (c) show the measured values on the outlet side of the finishing mill, the measured values on the inlet side of the winder, and the rear of the flatness of the steel sheet from the front end to the rear end, respectively. It is a graph which shows the measured value at the time of unwinding (non-tension) in a process (refinement process).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hot finishing mill final stand 2 Steel plate 3 Winding device 4 Cooling device 5 1st flatness measuring device 6 2nd flatness measuring device 7 Flatness comparison and analysis device 8 Finishing side flat control target value 9 Flatness control Feedback loop 10 Signal 11 Hot-rolled steel plate manufacturing device 12 Control device

Claims (3)

The strip-shaped steel sheet is hot-finished by a hot finish rolling mill and then cooled by a cooling device disposed downstream of the hot finish rolling mill, and subsequently disposed downstream of the cooling apparatus. When a hot-rolled steel sheet is manufactured by winding the steel sheet into a coil with a winding device that is wound, the steady state following a non-stationary region that is a distance of 1 m from the tip of the steel sheet toward the longitudinal direction of the steel sheet The hot finish rolling mill and the cooling device between the time when the tip of the region ends cooling by the cooling device and the time when the tip of the steel plate reaches the winding device and winding is started. and between, it is between the cooling device and the winding device to measure the flatness of the steel sheet at a position spaced above 6m in the longitudinal direction of the steel sheet from the take-up device, based on these measurements The steel plate Is set in advance by correcting the target value of flatness on the delivery side of the hot finish rolling mill, and based on the new target value of flatness set by correction, the hot A method for producing a hot-rolled steel sheet, comprising performing rolling continuously. The strip-shaped steel sheet is hot-finished by a hot finish rolling mill and then cooled by a cooling device disposed downstream of the hot finish rolling mill, and subsequently disposed downstream of the cooling apparatus. When a hot-rolled steel sheet is manufactured by winding the steel sheet into a coil with a winding device that is wound, the steady state following a non-stationary region that is a distance of 1 m from the tip of the steel sheet toward the longitudinal direction of the steel sheet The hot finish rolling mill and the cooling device between the time when the tip of the region ends cooling by the cooling device and the time when the tip of the steel plate reaches the winding device and winding is started. and between, it is between the cooling device and the winding device to measure the flatness of the steel sheet at a position spaced above 6m in the longitudinal direction of the steel sheet from the take-up device, based on these measurements Of the steel sheet Based on the new flatness target value set by correcting and setting the target value of flatness on the outlet side of the hot finish rolling mill, which is preset for other steel plates to be rolled into A method for producing a hot-rolled steel sheet, wherein the other steel sheet is subjected to hot finish rolling with the hot finish rolling mill. A hot finish rolling mill for performing hot finish rolling on a steel sheet;
A cooling device for cooling the steel sheet disposed on the downstream side of the hot finish rolling mill;
A winding device disposed downstream of the cooling device for winding the steel sheet into a coil;
A first flatness measuring device arranged between the hot finish rolling mill and the cooling device for measuring the flatness of the steel sheet;
A second flatness measuring device arranged between the cooling device and the winding device and at a distance of 6 m or more in the longitudinal direction of the steel plate from the winding device to measure the flatness of the steel plate; ,
From the time when the leading end of the steady region following the unsteady region, which is a distance of 1 m from the leading end of the steel plate to the longitudinal direction of the steel plate, has finished cooling by the cooling device, the leading end of the steel plate reaches the winding device. Other steel plates rolled after the steel plate based on the measured values of the first flatness measuring device and the second flatness measuring device in a period until reaching the start of winding And a control device for correcting and setting a target value of flatness on the delivery side of the hot finish rolling mill, which is set in advance.

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