JP2018167285A - Rolling equipment and rolling method in twin drum type continuous casting equipment - Google Patents

Abstract

To provide rolling equipment in twin drum type continuous casting equipment capable of manufacturing a casting strip excellent in a plate thickness distribution (plate crown) in a plate width direction even when a plate profile change of the casting strip due to thermal deformation and cooling irregularity of a cooling drum from casting start to a steady state is produced.SOLUTION: Rolling equipment includes: a twin drum type continuous casting device which forms a metal molten metal storage part with a pair of cooling drums and a side weir and casts metal molten metal stored in the metal molten metal storage part while rotating the pair of cooling drums; a rolling device which is arranged on the casting direction downstream side of the twin drum type continuous casting device and rolls a cast casting piece; an input side tension device which is arranged between the twin drum type continuous casting device and the rolling device and comprises a plurality of bridle rolls; and an output side tension device which is arranged on the casting direction downstream side with respect to the rolling device and applies a tension to the casting piece passing through the rolling device as well as the input side tension device.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rolling equipment and a rolling method in a twin drum type continuous casting equipment.

  In the twin-drum type continuous casting apparatus, a molten metal reservoir is formed by a pair of continuous casting cooling drums (hereinafter referred to as “cooling drums”) and side dams arranged opposite to each other in the horizontal direction. A pair of cooling drums is rotated with the stored molten metal to cast a thin cast piece (hereinafter referred to as “casting strip”) (for example, Patent Document 1). When the molten metal is stored in the molten metal reservoir, the cooling drums are rotated downward from above, respectively, and the molten metal is sent down as a cast strip while solidifying and growing on the peripheral surface of the cooling drum. The cast strip fed from the cooling drum is fed horizontally by a pinch roll and adjusted to a desired plate thickness by a downstream in-line mill. The cast strip whose thickness is adjusted by the in-line mill is wound into a coil by a winding device installed downstream of the in-line mill.

  In such a twin-drum type continuous casting apparatus, the cooling drum is generally at a low temperature before the start of casting, and when the casting is started, the temperature is raised by contact with the molten metal. Further, the cooling drum is cooled from the inner surface by a cooling medium (for example, cooling water) so as not to exceed a predetermined temperature. Hereinafter, the period when the temperature of the cooling drum reaches a predetermined temperature and becomes constant is the steady casting period, the arbitrary point in the steady casting period is the steady casting, and the temperature of the cooling drum in the steady casting period is the steady temperature . The state during the steady casting period is referred to as a steady state.

  The profile of the cooling drum changes over time from the start of casting until it reaches a steady state. For this reason, the profile of the cooling drum is set so that the plate profile (plate crown) of the cast strip at the time of steady casting becomes a desired plate profile.

  Here, FIG. 7 shows changes in the profiles of the cooling drums 10a and 10b and the plate profile of the casting strip S with the elapsed time from the start of casting when the casting strip S is manufactured by the conventional twin-drum type continuous casting apparatus. Show. In addition, the plate profile of the casting strip S shows the state before carrying out the reduction in the in-line mill.

  The cooling drums 10a and 10b at the start of casting are set to have a concave profile in which the center in the axial direction is recessed as shown in the state A of FIG. The cast strip S rolled by the cooling drums 10a and 10b having such a profile has a plate profile whose center in the plate width direction (that is, the axial direction) is convex.

  Next, after a while from the start of casting, the cooling drums 10a and 10b expand (expand) in the center in the axial direction due to heat input from the molten metal, and casting starts as shown in state B in FIG. It changes to a concave profile smaller than the time (state A). For this reason, the plate profile of the casting strip S has a convex shape with a smaller crown amount than the casting strip S at the start of casting (state A).

  Thereafter, after a further time has elapsed from the start of casting and reached a steady state, the cooling drums 10a and 10b are further expanded (expanded) by heat input from the molten metal, and are shown in a state C in FIG. Thus, the hollow at the center in the axial direction changes to a slightly concave profile. Therefore, the plate profile of the cast strip S has a convex shape with a smaller crown amount than in the state B.

  The time required to reach the state C from the state A in FIG. 7 varies depending on the steel type (melting temperature) of the molten metal, the thickness of the casting strip, the rotational speed of the cooling drum and the cooling efficiency, but is approximately about from the start of casting. About 30 seconds.

  On the other hand, the change in the plate profile of the casting strip S is caused not only by the change due to the thermal expansion of the cooling drum, but also by the change in the growth of the solidified shell due to the non-uniform cooling of the cooling drum from the start of casting until reaching the steady temperature. . Generally, if the molten metal is strongly cooled by the cooling drum, the thickness of the solidified shell is increased and the thickness of the cast strip S is increased. At this time, the cooling efficiency of the molten metal by the cooling drum is higher at the end than in the center in the axial direction of the cooling drum. Therefore, the thickness of the solidified shell is greater at the plate end than at the center of the plate of the cast strip S. As a result, in the cast strip S after the start of casting, the plate thickness at the plate end is thicker than the plate thickness at the plate center. The portion where the plate thickness is thick is called edge-up. The amount of edge up is greatest at the start of casting, decreases with the elapsed time after the start of casting, and is almost eliminated during steady casting.

  FIG. 8 is a conceptual diagram showing the change in the plate profile of the cast strip S due to the change in the growth of the solidified shell until the cooling drum reaches the steady temperature when the cast strip is manufactured by the twin drum type continuous casting apparatus. is there. In FIG. 8, the cooling drum is not shown.

  Immediately after the start of casting, heat is more likely to escape at the end than at the axial center of the cooling drum. Accordingly, the molten metal is greatly cooled at the width direction end portion of the cast strip S, and the solidified shell is formed thicker at the width direction end portion than the width direction center portion of the cast strip S. As a result, in the plate profile of the casting strip S immediately after the start of casting, a large edge-up Sa is formed at the end in the width direction, as shown in state A in FIG.

  After a while after the start of casting, the temperature difference between the center and the end in the axial direction of the cooling drum becomes smaller than at the start of casting. For this reason, the cooling of the molten metal at the end in the width direction of the casting strip S is weaker than at the start of casting, and the difference in thickness between the central portion and the end in the width direction of the solidified shell is smaller than at the start of casting. As a result, as shown in state B of FIG. 8, the plate profile of the casting strip S at the time when the casting has started for a while, the edge-up Sa at the width direction end is smaller than immediately after the start of casting (state A). .

  After a lapse of time from the start of casting and reaching a steady state, the temperature difference between the axial center portion and the end portion of the cooling drum is further reduced, and the solidified shell in the width direction center portion and the end portion is further reduced. There is almost no difference in thickness. As a result, the plate profile of the cast strip S after reaching the steady state after a lapse of time from the start of casting, as shown in state C in FIG.

  The time required to reach state C from state A in FIG. 8 varies depending on the steel type (melting temperature) of the molten metal, the thickness of the casting strip, the rotational speed of the cooling drum and the cooling efficiency, but state A in FIG. Is almost the same as in the case of the state C, and is about 30 seconds from the start of casting.

  As described above, the plate profile of the casting strip S from the start of casting to the time of steady casting is a combination of the crown change due to the thermal expansion of the cooling drum and the edge-up change due to the uneven cooling of the cooling drum. That is, as shown in FIG. 9, the plate profile of the casting strip S is in a state where the plate thickness between the central portion in the width direction and both ends becomes thick as shown in state A immediately after the start of casting, and after a while has elapsed after the start of casting. As shown in B, the deviation of the plate thickness in the width direction decreases, and after that, when the steady state is reached, the plate thickness becomes substantially uniform as shown in state C.

  Here, when the cast strip cast by the twin-drum type continuous casting equipment is rolled by an in-line mill as in Patent Document 1, the temperature of the cast strip is about 1000 ° C. on the inlet side of the in-line mill. Therefore, it is possible to slightly adjust the plate crown by causing a metal flow (width expansion) in the plate width direction in the cast strip. Examples of the in-line mill include a six-high rolling mill having an intermediate roll shift mechanism and a four-high rolling mill having a work roll cross mechanism. However, the in-line mill did not have a crown control capability sufficient to cope with the cast strip of the plate profile as shown in the state A and the state B in FIG. In an in-line mill, when a cast strip of a plate profile as shown in state A in FIG. 9 is rolled with a force large enough to adjust the crown amount, the middle elongation at the center of the plate becomes extremely large. As a result, meandering and squeezing occur, and the cast strip is easily broken.

  Increasing the tension of the in-line mill is effective for plate breakage due to drawing due to the middle elongation of the plate shape in the in-line mill. However, in order to increase the tension of the in-line mill, it is necessary to increase the pressing force of the pinch roll. When the pressing force of the pinch roll is increased, the cast strip as shown in state A or state B in FIG. There is a case where a portion having a large plate thickness is rolled. When the portion of the cast strip having a large plate thickness is rolled by the pinch roll, the plate breaks due to the meandering by the pinch roll or the severe shape defect causes the plate breakage due to the drawing by the in-line mill. When the plate breakage occurs, the molten metal remaining in the molten metal reservoir is immediately discarded, resulting in a significant yield reduction.

  On the other hand, the casting strip between the start of the flying touch in the in-line mill and the start of rolling of the cast strip until the desired plate thickness is reached in the in-line mill is cut off in the subsequent process as scrap and scraped off. Is generally processed as As a result, the off-gauge of the cast strip is a major cause of an increase in manufacturing cost due to a decrease in the yield of the cast strip.

  As described above, in order to start the flying touch in the in-line mill earlier and roll the cast strip to the desired thickness stably and efficiently, tension is applied to the cast strip on the entry side and the exit side of the in-line mill. It is effective to load. A larger tension applied to the casting strip on the entry side and the exit side of the in-line mill is effective in preventing meandering and shape defects. For this purpose, the pressing force of the pinch roll is increased and the pinch roll It is effective not to cause meandering or shape defects even if the pressing force is increased.

  Even when a cast strip is wound up by a twin-drum type continuous casting facility without causing plate breakage, the following problems occur in rolling in a subsequent process. For example, in order not to change the plate shape in the subsequent cold rolling or warm rolling, it is necessary to perform rolling so that the crown ratio of the cast strip does not change. For this purpose, it is necessary to use a rolling mill excellent in shape control (for example, a CRS rolling mill, a multi-stage cluster rolling mill, etc.), and equipment costs for newly installing these rolling mills are generated. Depending on the type of steel and the customer, it is manufactured with a twin-drum continuous casting device when the specifications required for the product crown are strict or when the product is used after being processed and laminated. Of the cast strip, as shown in the state A or the state B in FIG. Since the cut portion is small in weight and difficult to be diverted, it is scrapped.

  As described above, in the conventional twin-drum type continuous casting apparatus, the profile change due to the thermal expansion change of the cooling drum from the start of casting affects the meandering generation in the pinch roll before rolling and the rolling of the cast strip, Equipment costs for producing the desired cast strips and yield reduction have been caused.

  As a method for solving the problem of meandering with the pinch roll, for example, Patent Document 2 discloses a method for detecting the meandering amount of a cast strip and adjusting the gap difference between the left and right sides of the pinch roll. In addition, a method of adjusting the gap difference between the left and right of the pinch roll so that the load difference between the left and right of the pinch roll can be eliminated by detecting the load on the left and right of the pinch roll, and the roll diameter of the portion corresponding to the plate end of the cast strip of the pinch roll A method has also been proposed in which the thickness of the cast strip is reduced (for example, processed into a tapered shape), and the influence of the concave portion of the cast strip (increase in plate thickness at the plate end portion until steady casting) is reduced to make rolling difficult.

  As a countermeasure against the plate crown due to the thermal expansion of the cooling drum, for example, Patent Document 3 discloses a method of increasing the cooling efficiency of the central portion of the cooling drum in order to suppress the change in the profile due to the thermal expansion. For example, Patent Document 4 discloses a method of adjusting a hydraulic pressure of oil filled in a hollow chamber chamber provided in a cooling drum in order to cancel a change in profile due to thermal expansion.

  Patent Document 5 discloses that in a cold rolling facility, a bridle roll is provided to apply tension to the metal strip on the entry side and the exit side of the leveling unit.

JP 2000-343103 A JP 2003-39108 A JP-A-6-328205 Japanese Patent Laid-Open No. 1-133642 JP 2006-159220 A Japanese Patent Laid-Open No. 3-8522

  However, in the method of detecting the meandering amount of the cast strip and adjusting the difference between the left and right gaps in the pinch roll as in Patent Document 2, it is assumed that the plate width of the cast strip is constant. However, there are actually asymmetrical burrs, etc. caused by molten metal seepage due to wear between the cooling drum and the side weir, and whether the gap difference between the left and right is due to the meandering of the casting strip is due to the influence of burrs It cannot be determined whether it is a thing. For this reason, it is necessary to set a large threshold value for meander control, and high-response meander control cannot be performed. Further, it is necessary to measure the meandering amount itself, and meandering control is not performed until the meandering amount is measured by the detector after the meandering is generated. For these reasons, high-response meandering control cannot be performed. If high-response meandering control cannot be performed, the above-described plate breakage occurs.

  Further, when the casting strip is not meandering but off-center occurs, or when there is a temperature difference between both ends of the casting strip, there is no load difference between the left and right of the pinch roll. The method of adjusting the gap difference between left and right in is not practical. Further, when the roll diameter of the portion corresponding to the end portion of the cast strip is reduced, the cast strip is not meandering, but there is a problem that meandering is promoted when off-center occurs.

  The method for increasing the cooling efficiency of the central portion of the cooling drum disclosed in Patent Document 3 is to reduce the amount of thermal expansion of the cooling drum until the steady state, as shown in the state A or the state B in FIG. Such unsteady parts cannot be solved. Although the method of adjusting the oil pressure of the oil filled in the cooling drum provided with the hollow chamber chamber in the cooling drum disclosed in Patent Document 4 is effective, the cooling drum profile change when the cooling drum thermally expands. And the change in the cooling drum profile by adjusting the oil pressure of the oil filled in the chamber do not always coincide. For this reason, it is not always possible to cancel out the thermal influence on the cooling drum, and a new quarter elongation may be induced in the cast strip whose plate shape has changed from middle elongation to end elongation at the time of rolling.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to change the plate profile of the casting strip due to thermal deformation of the cooling drum and cooling unevenness from the start of casting to the steady state. There is provided a rolling equipment and a rolling method in a new and improved twin-drum continuous casting equipment capable of producing a cast strip having an excellent thickness distribution (sheet crown) in the width direction without meandering. There is.

  In order to solve the above-described problem, according to an aspect of the present invention, a molten metal storage section is formed by a pair of cooling drums and side weirs, and the molten metal storage section is stored while rotating the pair of cooling drums. A twin-drum continuous casting device for casting a molten metal, a rolling device for rolling a cast slab disposed downstream of the twin-drum continuous casting device in the casting direction, a twin-drum continuous casting device, and a rolling device; Between the entrance side tensioning device comprising a plurality of bridle rolls and the downstream side in the casting direction with respect to the rolling device, and for applying tension to the slab passing through the rolling device together with the entry side tensioning device. A rolling facility in a twin-drum type continuous casting facility is provided.

  The exit tension device may be a pinch roll device.

  Alternatively, the exit tension device may be a bridle device including a plurality of bridle rolls.

  The twin drum type continuous casting equipment is arranged from the upstream side in the order of tundish, twin drum type continuous casting device, antioxidant device, cooling device, inlet side tension device, rolling device, outlet side tension device, winding device. It is comprised by.

  In addition, the rolling equipment in the twin-drum type continuous casting equipment is arranged between the entry side tension device and the rolling equipment, and has a pressing roll having a convex roll profile, and a slab in a state where tension is applied in the casting direction. It may further include a straightening device that has a lifting mechanism that lifts and lowers the push roll and corrects the shape of the slab.

  Moreover, in order to solve the said subject, according to another viewpoint of this invention, the molten metal stored in the molten metal storage part formed of a pair of cooling drum and side dam of a twin drum type continuous casting apparatus is used. This is a rolling method in a twin-drum continuous casting facility in which a pair of cooling drums are cast while rotating, and a slab cast by the twin-drum continuous casting device is rolled by a rolling device disposed downstream in the casting direction. The entry side tension device composed of a plurality of bridle rolls arranged between the twin drum type continuous casting device and the rolling device, and the exit side tension device arranged on the downstream side in the casting direction with respect to the rolling device, There is provided a rolling method in a twin drum type continuous casting facility in which tension is applied to a slab passing through a rolling device.

  As described above, according to the present invention, even if the plate profile of the casting strip changes due to thermal deformation and cooling unevenness of the cooling drum from the start of casting to the steady state, the plate thickness distribution in the plate width direction (plate crown) Excellent casting strip can be produced. In other words, in the casting equipment, it is possible to prevent the meandering of the cast strip to the in-line mill and to enable faster flying touch, so that the plate thickness accuracy with less change in the plate crown in the plate width direction from the start of casting to the steady state is achieved. Good casting strips can be produced.

It is explanatory drawing which shows schematic structure of the manufacturing process of the casting strip (thin cast piece) which concerns on one Embodiment of this invention. It is explanatory drawing which shows the connection part of the front-end | tip of a casting strip at the time of the rolling start which concerns on the same embodiment, and a dummy sheet. It is explanatory drawing which shows the structure of the tension | tensile_strength apparatus which concerns on the same embodiment, and the function structure of the in-line mill control apparatus of an in-line mill. It is explanatory drawing which shows the structure of the correction apparatus which concerns on the same embodiment. It is a graph which shows an example of the indentation amount of an indentation roll, the board crown of a casting strip, and elongation rate. It is explanatory drawing which shows schematic structure when not providing a correction apparatus in a casting strip manufacturing process as a modification. It is a conceptual diagram which shows the change of the profile of a cooling drum and the plate profile of a casting strip with the elapsed time from the casting start at the time of manufacturing a casting strip with the conventional twin drum type continuous casting apparatus. It is a conceptual diagram which shows the change of the plate profile of a casting strip resulting from the growth change of the solidification shell until a cooling drum reaches | attains steady temperature when manufacturing a casting strip with a twin drum type continuous casting apparatus. It is a conceptual diagram showing the change in the plate profile of the casting strip from the start of casting to the time of steady casting, taking into account the change caused by the crown change due to the thermal expansion of the cooling drum and the edge-up change due to the uneven cooling of the cooling drum. .

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<1. Casting strip manufacturing process>
First, with reference to FIGS. 1-4, the outline | summary of the manufacturing process which manufactures the casting strip which concerns on one Embodiment of this invention is demonstrated. FIG. 1 is an explanatory view showing a schematic configuration of a manufacturing process of a casting strip (thin cast piece) according to the present embodiment. FIG. 2 is an explanatory view showing a connection portion between the tip of the casting strip S and the dummy sheet 11 at the start of rolling. FIG. 3 is an explanatory diagram showing the configuration of the tension device 40 according to the present embodiment and the functional configuration of the inline mill control device 90 of the inline mill 50. FIG. 4 is an explanatory diagram showing the configuration of the correction device 80 according to the present embodiment.

  As shown in FIG. 1, the cast strip manufacturing process 1 according to the present embodiment includes, for example, a tundish (storage device) T, a twin drum continuous casting facility 10, an antioxidant device 20, a cooling device 30, A tension device 40, an inline mill 50, a pinch roll device 60, a winding device 70, and a correction device 80 are provided.

(Double drum type continuous casting machine)
As shown in FIG. 1, the twin-drum continuous casting apparatus 10 includes, for example, a pair of cooling drums 10a and 10b and side weirs (not shown) arranged on both sides in the axial direction of the pair of cooling drums 10a and 10b. With. The pair of cooling drums 10 a and 10 b and the side dam constitute a molten metal storage unit 15 that stores the molten metal supplied from the tundish T.

  The pair of cooling drums 10a and 10b includes a first cooling drum 10a and a second cooling drum 10b. The first cooling drum 10a and the second cooling drum 10b have a concave profile in which the center in the axial direction is slightly depressed. Moreover, the 1st cooling drum 10a and the 2nd cooling drum 10b are comprised so that adjustment of the space | interval of cooling drum 10a, 10b is possible according to the plate | board thickness (internal quality) of the casting strip S to manufacture. The 1st cooling drum 10a and the 2nd cooling drum 10b are comprised so that a cooling medium (for example, cooling water) can distribute | circulate inside. The cooling drums 10a and 10b can be cooled by circulating the cooling medium inside the cooling drums 10a and 10b.

  In the present embodiment, the first cooling drum 10a and the second cooling drum 10b are set such that, for example, the outer diameter is 800 mm, the drum body length (width) is 1500 mm, and the plate crown of the casting strip S in a steady state is 43 μm (initial Processed). In this case, the plate crown after 30% reduction by an in-line mill 50 described later is 30 μm. Needless to say, the outer diameter and drum length (width) of the pair of cooling drums 10a and 10b are not limited thereto.

  In the twin drum type continuous casting apparatus 10, as shown in FIG. 2, the dummy sheet 11 is connected to the tip of the casting strip S, and casting is started. A dummy bar 13 having a thickness larger than that of the cast strip S is provided at the tip of the dummy sheet 11, and the dummy sheet 11 is guided by the dummy bar 13. In addition, a protrusion 12 that is thicker than the thickness of the casting strip S is formed at the connection between the tip of the casting strip S and the dummy sheet 11. Rolling (flying touch) in the in-line mill 50 is started after the protrusion 12 has passed through the in-line mill 50.

(Antioxidation equipment)
The antioxidant 20 is a device for performing a process for preventing the surface of the casting strip S immediately after casting from oxidizing and generating scale. In the antioxidant device 20, for example, the amount of oxygen can be adjusted by nitrogen gas. It is preferable to apply the antioxidant 20 as necessary in consideration of the steel type of the cast strip S to be cast.

(Cooling system)
The cooling device 30 is a device that cools the cast strip S whose surface has been subjected to an antioxidant treatment by the antioxidant device 20. The cooling device 30 includes, for example, a plurality of spray nozzles (not shown), and ejects cooling water from the spray nozzles to the surface (upper surface and lower surface) of the casting strip S according to the steel type. Cooling.

  A pair of feed rolls 87 may be disposed between the antioxidant device 20 and the cooling device 30. The pair of feed rolls 87 sandwich the cast strip S by a reduction device (not shown), and measure the loop length of the cast strip S between the pair of cooling drums 10a and 10b and the feed roll 87, while A horizontal conveying force is applied to the casting strip S so that the loop length is constant. The feed roll 87 is constituted by a pair of rolls having a roll diameter of 200 mm and a roll body length (width) of 2000 mm, for example. Since the force between the pair of feed rolls 87 is small, the cast strip is not rolled by the pair of feed rolls 87. Further, the feed roll 87 is processed into a roll profile that sandwiches only the plate center region of the casting strip S so that the above-described burrs do not come into contact with the feed roll 87 (for example, chamfer processing).

(Tension device)
The tension device 40 is a device that applies tension to the cast strip S passing through the in-line mill 50 together with the pinch roll device 60 described later, and is an entry-side tension device arranged on the in-line mill entry side. As shown in FIG. 3, the tension device 40 according to the present embodiment includes three bridle rolls 40A, 40B, and 40C. In addition, the number of bridle rolls constituting the tension device 40 according to the present embodiment is not limited to this example, and it is sufficient that the bridle rolls are constituted by two or more bridle rolls. Each bridle roll 40A, 40B, 40C is driven by a driving device such as a motor. The bridle rolls 40A, 40B, and 40C have a hollow structure in order to reduce the influence of the inertia force of the roll, and are cooled by circulating cooling water from the inner surface. The bridle rolls 40A, 40B, and 40C may have, for example, a roll diameter of 600 mm and a roll trunk length (width) of 2000 mm.

  The tension device 40 rotates the bridle rolls 40A, 40B, and 40C so that a speed difference occurs between the rotational speed of the rolls of the inline mill 50, and the correction between the bridle rolls 40A, 40B, and 40C and the inline mill 50. A tension is applied to the device 80. In the tension device 40 constituted by the bridle rolls 40A, 40B, 40C, as shown in FIG. 3, tension is applied to the cast strip S without pressing the cast strip S between a pair of pinch rolls as in the pinch roll device. Can do. Therefore, since the casting strip S is not rolled by a pair of pinch rolls as in the case of using the pinch roll device, it is possible to suppress the shape defect and meandering of the casting strip S.

  It should be noted that the cast strip S before passing through the tension device 40 constituted by the bridle rolls 40A, 40B, and 40C has, for example, a portion having a large thickness in the plate width direction as shown in the state A or the state B in FIG. In the case where a large portion of the plate crown is present, the large portion of the thickness of the cast strip S remains even after passing through the tension device 40. However, after passing through the tension device 40, the cast strip S is straightened by the straightening device 80 and rolled by the in-line mill 50. In this process, the large portion of the cast strip S is eliminated, and the flat shape is formed with a uniform crown.

(Correcting device)
The straightening device 80 is a device for straightening the shape (plate crown) of the casting strip S that passes therethrough. The straightening device 80 has three rolls 81A, 81B, and 81C arranged along the conveying direction of the casting strip S. As shown in FIG. 4, each roll 81A, 81B, 81C is supported by roll chock 83A, 83B, 83C, respectively, and each roll chock 83A, 83B, 83C is installed in housing 85A, 85B, 85C, respectively. Each roll 81A, 81B, 81C may use the same size roll. For example, rolls 81A, 81B, and 81C having a roll diameter of 150 mm and a trunk length of 2000 mm may be used. Each roll 81A, 81B, 81C is a non-driving roll and rotates following the movement of the casting strip S. Further, the correction device 80 is provided with a cooling facility (not shown) for cooling the rolls 81A, 81B, 81C.

  In the correction device 80 according to the present embodiment, as shown in FIG. 4, the rolls 81 </ b> A and 81 </ b> C are installed such that the height positions of the roll shafts are the same. On the other hand, the roll 81B disposed between the roll 81A and the roll 81C functions as a push roll for pushing the casting strip S moving on the line, and is installed so as to be movable up and down by the lifting mechanism 86. The roll 81B is pulled up by a balancer (not shown) provided in the roll chock 83B so as not to fall. The roll 81B according to this embodiment has a convex roll profile. The roll profile of the roll 81B may be variable. For example, the roll 81B includes a hydraulic chamber (not shown), and the roll profile can be changed from a flat state to a convex state with a large central diameter by changing the oil pressure in the hydraulic chamber. Is possible. The roll profile may be changed by a hydraulic chamber as in this embodiment, but the present invention is not limited to such an example. For example, the roll profile (roll deflection) may be changed using a variable crown roll unit as disclosed in Patent Document 6. On the other hand, the roll 81A and the roll 81C are provided with a speed detector (PLG) that detects the rotation speed of the roll. Based on the rotational speed detected by the speed detector, the sheet passing speed of the cast strip S at each roll position is calculated, and the elongation rate of the cast strip S by the straightening device 80 can be measured.

  The tension applied to the correction device 80 can be generated by giving a speed difference to the rolls of the tension device 40 and the inline mill 50. The greater the generated tension, the easier the plastic deformation of the cast strip S at the bending portion defined by the rolls 81A, 81B, 81C, even with a small indentation amount and a large roll diameter. In addition, although the tension | tensile_strength provided to the correction apparatus 80 is not shown in figure, it measures with the tension roll (not shown) provided between the tension apparatus 40 and the in-line mill 50. FIG. The rolling speeds of the bridle rolls 40A, 40B, 40C and the inline mill 50 of the tension device 40 are controlled so that the measured tension becomes a predetermined value set in advance.

  Further, plate profile meters 91 and 93 for measuring the plate thickness of the cast strip S are provided on the entry side and the exit side of the straightening device 80 as shown in FIGS. By measuring the plate thickness in the plate width direction of the cast strip S with these plate profile meters 91 and 93, the plate crown of the cast strip S can be calculated based on the result. The plate crown amount of the cast strip S is a quadratic approximation of the plate thickness distribution of the cast strip S in the plate width direction, and the plate thickness at the inner side by a predetermined distance from the plate thickness at the center of the plate and the plate definition point. It is calculated by calculating the difference between. The calculation of the plate crown of the casting strip S may be performed by, for example, a control device (not shown) that controls the correction device 80. The control device controls at least one of the roll position and roll profile of the roll 81B based on the calculated plate crown amount.

(Inline mill)
The in-line mill 50 is a rolling device that rolls the cast strip S so that the cast strip S has a desired thickness. In the present embodiment, the in-line mill 50 is configured as a six-high rolling mill. That is, the in-line mill 50 includes a pair of work rolls 51a and 51b, intermediate rolls 52a and 52b arranged above and below the work rolls 51a and 51b, and backup rolls 53a and 53b arranged above and below the intermediate rolls 52a and 52b. With. In the present embodiment, for example, work rolls 51a and 51b having a roll diameter of 400 mm, intermediate rolls 52a and 52b having a roll diameter of 450 mm, and backup rolls 53a and 53b having a roll diameter of 1200 mm may be used. The length of each roll may be the same, for example, 2000 mm.

  Further, the inline mill 50 includes an inline mill control device that controls the inline mill, a thickness gauge (none of which is shown), and the like. The work rolls 51a and 51b are rotationally driven by a motor (not shown) and are cooled by cooling water from the entry side and the exit side. Further, a hydraulic cylinder (not shown) is provided above the backup roll 53a to press the backup roll 53a downward.

  The in-line mill 50 starts rolling by tightening the roll gap while rotating the work rolls 51a and 51b of the in-line mill 50 after the tip of the casting strip S cast during the steady casting passes through the in-line mill 50. It has become. Such a rolling method is called a flying touch.

  Further, the inline mill 50 is controlled by an inline mill control device 90 as shown in FIG. The in-line mill control device 90 includes, for example, a mill control unit 95 that controls and controls the in-line mill 50, a hydraulic cylinder control unit 96 that controls a hydraulic cylinder, a roll rotation control unit 97, a roll bending force control unit 98, a roll cross angle. A control unit 99 and the like are included.

  The hydraulic cylinder control unit 96 controls the reduction of the hydraulic cylinder 55 connected to the backup roll 53a. The hydraulic cylinder control unit 96 controls the hydraulic cylinder 55 based on an instruction from the mill control unit 95 that controls the inline mill 50 in an integrated manner, and adjusts the roll gap between the work rolls 51a and 51b. At this time, the mill control unit 95 forms the casting strip S to a preset thickness based on the thickness of the casting strip S measured by the thickness gauge 73 installed on the exit side of the in-line mill 50. Adjust the roll gap so that As the thickness gauge 73, for example, an X-ray thickness gauge or the like may be used.

  The roll rotation control unit 97 controls the rotation speed of the backup rolls 53 a and 53 b based on an instruction from the mill control unit 95. Further, the roll bending force control unit 98 sets the roll bending force for the intermediate rolls 52 a and 52 b based on the instruction from the mill control unit 95. The roll cross angle control unit 99 adjusts the roll cross angles with the work rolls 51a and 51b by adjusting the intermediate rolls 52a and 52b based on an instruction from the mill control unit 95.

(Pinch roll device)
The pinch roll device 60 is an exit side tension device arranged on the exit side of the inline mill 50. The pinch roll device 60 includes an upper pinch roll and a lower pinch roll, a driving device such as a motor for driving each pinch roll, and a reduction device. The upper pinch roll and the lower pinch roll are arranged via a roll chock in the housing, and are rotationally driven by a driving device. A tension is generated in the casting strip S with the in-line mill 50 by the upper pinch roll being reduced to the lower pinch roll side by the reduction device. A tension roll 88 is disposed between the inline mill 50 and the pinch roll device 60. The tension roll 88 measures the tension between the in-line mill 50 and the pinch roll device 60 after rolling, and each pinch roll of the pinch roll device 60 is adjusted so that the measured tension becomes a preset tension. The rotation speed is controlled.

  Each of the upper pinch roll and the lower pinch roll has a hollow channel formed therein, and is configured to allow a cooling medium (for example, cooling water) to flow therethrough. The pinch roll can be cooled by circulating the cooling medium. For example, the upper pinch roll and the lower pinch roll may have a roll diameter of 400 mm and a roll body length (width) of 2000 mm.

  In addition, when tension | tensile_strength is given to the casting strip S using the pinch roll apparatus 60, since the casting strip S is pinched by a pair of pinch rolls, it is rolled slightly. However, the cast strip S after being rolled by the in-line mill 50 is straightened by the straightening device 80 and rolled by the in-line mill 50 even if the plate thickness at both ends in the width direction is large before rolling by the in-line mill 50. Therefore, it has a flat shape in the plate width direction. Therefore, a high load is not applied to the pinch roll device 60, and the shape defect or meandering of the cast strip S does not occur.

(Winding device)
The winding device 70 is a device that is disposed on the exit side of the pinch roll device 60 and winds the cast strip S in a coil shape. A deflector roll 89 is disposed between the pinch roll device 60 and the winding device 70.

<2. Manufacture of casting strips>
Hereinafter, the manufacture of the cast strip S in the cast strip manufacturing process 1 shown in FIG. 1 will be described.

  First, the molten metal is temporarily stored in the tundish T. The molten metal stored in the tundish T is injected into the molten metal storage portion 15 of the twin-drum continuous casting apparatus 10 through a nozzle formed in the lower part of the tundish. At this time, the amount of the molten metal stored in the molten metal storage unit 15 is controlled to be constant by controlling the nozzle.

  Next, while rotating the pair of cooling drums 10a and 10b, the molten metal stored in the molten metal storage unit 15 is solidified and grown on the peripheral surfaces of the pair of cooling drums 10a and 10b, thereby casting the casting strip S. When casting is started in the twin-drum type continuous casting apparatus 10, for example, as shown in FIG. 2, the dummy sheet 11 is connected to a portion that becomes the tip of the casting strip S. At this time, a dummy bar 13 that is much thicker than the casting strip S is provided at the leading end side in the traveling direction of the dummy sheet 11, and the connecting portion between the casting strip S and the dummy sheet 11 is larger than the thickness of the casting strip S. A thick protrusion 12 is formed. For example, the dimensions of the cast strip S may be 2 mm in thickness and 1260 mm in width, and the peripheral speed (casting speed) of the pair of cooling drums 10a and 10b may be 150 m / min. However, the dimensions of the casting strip S and the casting speed are not limited to this example.

  The casting strip S formed by the pair of cooling drums 10a and 10b is subjected to an antioxidant treatment in the antioxidant device 20 as necessary. Then, the casting strip S is conveyed downstream by the feed roll 87 while keeping the loop length of the casting strip S between the cooling drums 10a and 10b and the feed roll 81 constant. Moreover, the casting strip S is cooled with the cooling device 30 as needed. Thereafter, the bridle rolls 40A, 40B, and 40C of the tension device 40 generate tension between the tension device 40 and the in-line mill 50 in the cast strip S, and the cast strip S is moved to the downstream side via the straightening device 80. Send to inline mill 50. At this time, the amount of pressing of the roll 81B of the straightening device 80 is the size of the plate crown of the casting strip calculated in advance by experiments or the like until the flying touch by the in-line mill 50 is started (that is, at the start of casting). The target value is set.

  The inline mill 50 starts a flying touch after the protrusion 12 has passed through the inline mill 50. That is, a rolling force is applied while synchronizing the roll speed of the in-line mill 50 with the plate speed of the cast strip S, the cast strip S is rolled and adjusted to a desired plate thickness. Here, when the tip of the casting strip S begins to pass through the in-line mill 50, the correction device 80, based on the relationship between the pressing amount of the pressing roll and the plate crown of the casting strip, according to the time system change of the plate crown, The pushing amount of the roll 81B is controlled. For example, when the rolling force of the in-line mill 50 becomes equal to or greater than a predetermined rolling force, the tension between the tension device 40 and the in-line mill 50 is controlled to a predetermined tension, and the pressing amount of the roll 81B of the correction device 80 is And the plate crown is adjusted to the desired value. Note that the plate crown may be controlled by adjusting the roll profile of the roll 81B instead of the push amount of the roll 81B, or the plate crown may be controlled by adjusting the push amount of the roll 81B and its roll profile.

  The cast strip S rolled by the in-line mill 50 is conveyed to the winding device 70 while a tension is generated between the in-line mill 50 and the pinch roll device 60 by the pinch roll device 60 by the pinch roll device 60. The winding device 70 winds up the cast strip S that has been conveyed.

  In the above, the continuous casting equipment which has the twin drum type continuous casting apparatus which concerns on one Embodiment of this invention, and the control method of the plate crown of the casting strip S were demonstrated.

<3. Crown control by adjusting the push-in amount of the push-in roll of the straightening device
Conventionally, as is known in straightening devices such as tension levelers, when applying plastic deformation (elongation) by applying tension to the strip and applying a plastic deformation (elongation) by bending, if the leveler roll part is crown-shaped, The pushing amount of the strip increases. Therefore, the tensile tension in the part is larger than that in the other part and is intensively extended, so that the plate thickness of the part is reduced.

  Here, the plate of the casting strip when the initial profile of the cooling drum is processed so that the shape of the plate crown in the steady state has a predetermined parabolic pattern, and the pushing amount of the pushing roll by the straightening device is changed in the steady state. The crown and its elongation were examined. Here, the pushing amount of the pushing roll is based on the height position of the roll axis of the pushing roll when the pushing roll is in contact with the casting strip in a state where the casting strip is stretched linearly in the sheet passing direction. The amount of change in the height position of the roll shaft of the push roll relative to the reference. The pushing amount of the pushing roll in the reference state is set to zero. As the pushing amount increases, the pushing roll is pushed into the casting strip and plastic deformation proceeds more, so that the casting strip passing through the correction device is bent greatly. Here, as an example, the initial profile of the cooling drum was processed so that the difference between the center of the cast strip and the plate thickness (average value at both ends) at a position 75 mm inside from the plate end was a parabolic pattern of 150 μm. At this time, a roll crown of 800 μm / radius was applied to the push roll, and the stress acting on the straightening device was about 15 MPa. The results are shown in FIG.

  As shown in FIG. 5, as the pushing amount of the pushing roll is increased (that is, the moving amount in the pushing direction of the cast strip is increased), the plate crown of the cast strip is decreased and the elongation of the cast strip is increased. At this time, the width of the casting strip is shortened. Due to such interaction, the plate shape (flatness) was not greatly disturbed even when the cast strip was plastically deformed so that the plate crown ratio changed. It was also found that the relationship between the pushing amount of the pushing roll and the plate crown was substantially linear as shown in FIG. In addition, although elongation occurs, the thickness of the cast strip decreases, but the final thickness is made by an in-line mill, so the influence of the thickness change of the cast strip in the straightening device can be ignored. Therefore, it is preferable that the correction device according to the present embodiment is installed upstream of the in-line direction with respect to the in-line mill.

  Therefore, based on the knowledge that the plate crown of the casting strip can be reduced by changing the pushing amount of the pushing roll, the casting strip generated by the thermal effect of the cooling drum in the continuous casting equipment provided with the twin drum type continuous casting device. In order to control the sheet crown of S, a correction device 80 is provided to control the pushing amount of the pushing roll in accordance with the time-dependent change in the sheet crown shape of the casting strip S. Thereby, the plate crown of the cast strip S when passing through the straightening device 80 can be appropriately corrected, and the plate crown change of the cast strip S rolled by the in-line mill 50 can be prevented.

  Specifically, the correction device 80 first sets the position of the roll shaft of the roll 81B, which is a push roll, to an initial position calculated in advance through experiments or the like at the start of casting. The initial position of the roll shaft may be a position for causing the size of the plate crown of the cast strip S to be a preset target value, for example.

  After that, when the tip of the casting strip S starts to pass through the in-line mill 50, the pressing roll is turned on the basis of the relationship between the pressing amount of the pressing roll and the size of the plate crown of the casting strip S according to the time-series change of the plate crown. The pushing amount of a certain roll 81B is controlled. For the relationship between the pressing amount of the pressing roll and the size of the plate crown of the casting strip S, a relationship obtained by an experiment or the like as shown in FIG. 5 may be used. The control device calculates the plate crown of the cast strip S based on the plate thickness of the cast strip S measured by the plate profile meters 91 and 93, for example. The shape of the casting strip S rolled by the in-line mill 50 is adjusted by adjusting the pushing amount of the pushing roll in accordance with the shape of the plate crown of the casting strip passing through the in-line mill 50, that is, the size of the plate crown. Can be made uniform. As a result, it is possible to prevent the disorder of the plate shape in the subsequent cold rolling, improve the plate thickness accuracy in the plate width direction of the product, and improve the yield.

  In the steady state, the pushing amount of the pushing roll may be less than 0 mm where the casting strip S is not bent. Alternatively, the rolls 81A, 81B, 81C of the straightening device 80 are not driven, but may slip and cause wrinkles in the casting strip S. Therefore, in order to prevent the casting strip S from being wrinkled, the rolls 81A, 81B, 81C may be used as drive rolls. Further, the initial profile of the cooling drums 10a and 10b may be corrected in consideration of the crown change caused by the amount of pressing of the roll 81B, which is a pressing roll, as long as the amount of slip does not occur. Further, the sheet crown of the casting strip S may be measured on the entry side of the straightening device 80, and the pushing amount of the pushing roll may be controlled based on the measurement result. You may measure a crown and control the pushing amount of a pushing roll based on a measurement result. Of course, the pushing amount of the pushing roll may be controlled based on the crown of the casting strip S measured on the entry side and the exit side of the straightening device 80.

  Examples of the present invention will be described below. This example was carried out in the manufacturing process of a cast strip having the same configuration as in FIG. The cast strip used in the examples has a plate thickness of 2 mm and a plate width of 1260 mm. The acceleration rate of the cooling drum from the start of casting is 150 m / min / 30 seconds, and the rotational speed of the cooling drum in a steady state is 150 m / min. The initial profile of the cooling drum was processed so that the plate crown of the cast strip was 43 μm in a steady state. In the in-line mill, rolling with a reduction ratio of 30% was performed, and the thickness of the cast strip on the exit side of the in-line mill was 1.4 mm. Rolling in the in-line mill was started 15 seconds after the start of casting (after the dummy sheet passed and the sheet crown of the cast strip became 150 μm or less).

  In the comparative example using the prior art, the tension to the casting strip on the upstream side of the inline mill is obtained by using a pinch roll device instead of the tension device by the bridle roll arranged on the upstream side of the inline mill in the embodiment. Was granted. At that time, the load control was performed so that the pressing force of the pinch roll against the cast strip was constant (right 5 tf, left 5 tf).

(Invention Example 1: Application of tension by bridle roll)
In Example 1 of the present invention, the tension before the in-line mill was applied using a tension device composed of a bridle roll. At this time, the leveler was released. As a result, the edge-up portion at the time of tension application and the portion with a large plate thickness due to the influence of the large convex crown were not rolled by the bridle roll, so that the plate shape of the cast strip was not disturbed. In addition, early flying touch was possible, and it could be shortened within 15 seconds from the start of casting. In addition, no casting strip meandering occurred.

(Invention Example 2: Application of tension by bridle roll + plate crown control by correction device)
In Example 2 of the present invention, the tension before the in-line mill was applied using a tension device composed of a bridle roll. Moreover, plate crown control was implemented with the correction device. Specifically, the sheet crown of the casting strip is measured on the entrance side of the straightening device, and the pushing roll of the straightening device is set to 43 μm (30 μm after in-line mill rolling), which is the target value of the cast strip after straightening. The amount of indentation was controlled. Such control is performed 15 seconds after the start of casting, and before that, the pushing amount of the pushing roll is adjusted so that the plate crown of the cast strip obtained 15 seconds after the start of casting is experimentally obtained to a target value of 43 μm. Set. The straightening device was opened after 35 seconds from the start of casting.

  Also in Example 2 of the present invention, the plate-up shape of the cast strip was not disturbed because the edge-up portion at the time of tension application and the portion with a large plate thickness due to the influence of the large convex crown were not rolled by the bridle roll. In addition, early flying touch was possible, and it could be shortened within 15 seconds from the start of casting. In addition, no casting strip meandering occurred. Further, the sheet crown after rolling by the in-line mill in the period from 15 seconds to 28 seconds after the start of casting was 29 to 32 μm, and it was possible to cope with a strict sheet thickness material in the sheet width direction, and the yield was improved.

(Comparative example)
In the comparative example of the prior art, the plate shape of the cast strip was greatly disturbed due to the stability of tension application in the in-line mill and the influence of the edge-up portion and the large convex crown at the time of pushing. For this reason, the flying touch could not be performed at an early stage, and it took 28 seconds from the start of casting until a stable flying touch could be performed. Further, the cast strip was rolled by a pinch roll device on the inline mill entry side, and the meander of the cast strip occurred frequently, and the plate broke once in 10 times.

  From the above, according to the present invention, it is shown that, in the twin drum type thin cast strip continuous casting equipment, the effects of meandering, shape defect and plate crown change before in-line mill at the start of casting can be eliminated. It was. As a result, it was clarified that early flying touch can be performed, stability of rolling can be ensured, productivity can be improved, thickness accuracy in the plate width direction can be improved, and yield can be improved.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, although the casting strip manufacturing process of the said embodiment was provided with the correction apparatus, this invention is not limited to this example, and the correction apparatus does not necessarily need to be provided. For example, as shown in FIG. 6, it is good also as a structure which does not provide a correction apparatus between the tension | tensile_strength apparatus 40 provided with bridle roll 40A, 40B, 40C provided in the casting strip manufacturing process, and the in-line mill 50. FIG.

  Moreover, although the pinch roll apparatus was provided in order to provide tension | tensile_strength to a casting strip in the in-line mill exit side of the casting strip manufacturing process which concerns on the said embodiment, this invention is not limited to this example. For example, instead of the pinch roll device on the exit side of the inline mill, a tension device composed of a bridle roll may be provided in the same manner as the tension device on the entry side of the inline mill.

DESCRIPTION OF SYMBOLS 1 Casting strip manufacturing process 10 Twin drum type continuous casting apparatus 10a, 10b Cooling drum 11 Dummy sheet 12 Protrusion part 13 Dummy bar 15 Molten metal storage part 20 Antioxidation apparatus 30 Cooling apparatus 40 Tension apparatus 40A, 40B, 40C Bridle roll 50 In-line mill 51a, 51b Work roll 52a, 52b Intermediate roll 53a, 53b Backup roll 60 Pinch roll device 70 Winding device 80 Straightening device 81A, 81B, 81C Roll 83A, 83B, 83C Roll chock 85A, 85B, 85C Housing 86 Elevating mechanism 88 Tension roll 89 Deflector roll 90 In-line mill control device 91, 93 Plate profile meter 95 Mill control unit 96 Hydraulic cylinder control unit 97 Roll rotation control unit 98 Roll bendy Grayed force controller 99 roll cross angle controller

Claims (6)

A twin-drum continuous casting apparatus that forms a molten metal storage part by a pair of cooling drums and side weirs, and casts the molten metal stored in the molten metal storage part while rotating the pair of cooling drums;
A rolling device that is arranged on the downstream side in the casting direction of the twin drum type continuous casting device and rolls the cast slab;
An entry-side tension device arranged between the twin-drum type continuous casting device and the rolling device, and comprising a plurality of bridle rolls;
An exit side tension device that is arranged downstream of the rolling device in the casting direction and applies tension to the slab passing through the rolling device together with the entry side tension device;
A rolling equipment in a twin-drum type continuous casting equipment.   The rolling facility in a twin drum continuous casting facility according to claim 1, wherein the outlet tension device is a pinch roll device.   The rolling facility in a twin-drum continuous casting facility according to claim 1, wherein the outlet tension device is a bridle device including a plurality of bridle rolls.   Twin drum type continuous casting equipment is tundish from the upstream side, the twin drum type continuous casting device, the antioxidant device, the cooling device, the inlet side tension device, the rolling device, the outlet side tension device, and the winding device in this order. The rolling equipment in the twin-drum type continuous casting equipment according to any one of claims 1 to 3, wherein the rolling equipment is constituted by an arranged device.   A push roll disposed between the entry side tension device and the rolling device and having a convex roll profile, and a lifting mechanism for raising and lowering the push roll with respect to the slab in tension in the casting direction. The rolling equipment in the twin drum type continuous casting equipment according to any one of claims 1 to 4, further comprising a straightening device that straightens the shape of the slab. Casting the molten metal stored in the molten metal reservoir formed by the pair of cooling drums and side weirs of the twin drum type continuous casting apparatus while rotating the pair of cooling drums,
A rolling method in a twin-drum type continuous casting facility that rolls a slab cast by the twin-drum type continuous casting device by a rolling device arranged on the downstream side in the casting direction,
An entry-side tension device comprising a plurality of bridle rolls arranged between the twin-drum continuous casting device and the rolling device; and an exit-side tension device arranged downstream in the casting direction with respect to the rolling device. A rolling method in a twin-drum type continuous casting facility, wherein tension is applied to the slab passing through the rolling device.

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