JP4751133B2 - Hot rolling method for steel and hot rolling equipment for steel - Google Patents

Description

  The present invention relates to a method of hot rolling steel and rolling hot rolled steel.

  For example, in the hot rolling process of steel materials, a cast slab is heated in a heating furnace and then roughly rolled in a roughing mill. The rough bar formed by rough rolling is finish-rolled in a finish rolling mill, and the steel sheet having a target thickness is wound on a winder. These processes are performed in a series of hot rolling lines, and many steel materials are continuously conveyed and processed one by one in this hot rolling line.

  By the way, a shape defect called, for example, a so-called fish tail can be formed at the front end portion and rear end portion of the rough bar after rough rolling by a rough rolling mill. Since the leading and trailing ends of the defective shape are unstable in thickness and the temperature is lowered, if it is passed through the finishing mill as it is, indentations (roll marks) or the like may be formed on the roll of the finishing mill. When the impression is formed on the roll, a periodic surface mark is formed on the steel sheet rolled by the finish rolling mill, and the yield is reduced. For this reason, the process which cut | disconnects the front-and-rear end part of a rough bar is normally performed between rough rolling and finish rolling.

  The cutting of the front and rear end portions of the rough bar has been conventionally performed by a crop shear provided immediately before the finishing mill (see, for example, Patent Document 1). For example, a drum-type crop shear is configured by, for example, a rotating drum to which two cutting blades for a front end and a rear end are attached facing the upper and lower surfaces of a coarse bar. When passing through the end of the coarse bar, the upper and lower rotary drums are rotated at the same speed as the coarse bar in the same direction as the coarse bar conveying direction, and the upper and lower end cutting blades sandwich the front end of the coarse bar. In addition, when passing through the rear end portion of the coarse bar, the upper and lower rotary drums were rotated again, and the rear end portion of the coarse bar was cut with the upper and lower rear end cutting blades.

JP 2003-211206 A

  As described above, in the hot rolling line, since a plurality of steel materials are continuously processed, it is necessary to continuously perform cutting with a crop shear. However, when the steel material is continuously cut by the crop shear, it takes time from cutting the rear end portion of the preceding coarse bar to cutting the front end portion of the next coarse bar.

  For example, in the case of the above-described drum-type crop shear, after the rear end portion of the preceding coarse bar is cut, the rotation of the rotary drum 100 is decelerated and stopped, for example, as shown in FIG. Thereafter, the rotating drum 100 swings back in the reverse direction and moves to a standby position for performing the next cutting. This swing back is necessary as a run for accelerating the cutting blade 101 to the next coarse bar conveyance speed. As described above, since the rotating drum 100 is stopped after the rear end portion of the coarse bar is cut and then swung back, it takes time. Similarly, other types of crop shears require mechanical drive time for the next cut.

  For this reason, when using a crop shear in a hot rolling line, sufficient time is required from cutting the trailing end of the preceding coarse bar to cutting the leading end of the next coarse bar. It was necessary to leave a sufficient pitch interval between the rough bars before and after being processed. If the pitch interval of the coarse bars in the hot rolling line is increased, the steel plate productivity in the hot rolling line cannot be sufficiently increased.

  The present invention has been made in view of the above points, and an object thereof is to increase the productivity of steel materials by increasing the conveying pitch of coarse bars in a hot rolling process in which steel materials are continuously processed. .

According to the present invention for achieving the above object, in a hot rolling line in which heating, rough rolling, and finish rolling of a steel material are performed in this order, the leading end and the trailing end of the rough bar after the rough rolling are performed. cut by different cutting machine before being finish rolling, the after each cut of crude bar tip and rear end, the crude bar tip near the rear end near the heating respectively, of the rough bar There is provided a method for hot rolling a steel material, characterized in that the vicinity of the rear end of the rough bar is heated so that the temperature rise is higher than that near the front end.

The “near the tip of the rough bar” includes, for example, a range in which the temperature is lower than that of other portions during the transfer of the rough bar, for example, a range of 1 to 3 m from the end face of the rough bar. Furthermore, the “near the rear end of the rough bar” includes, for example, a range where the temperature is lower than that of other portions during the transfer of the rough bar, for example, a range from 1 to 3 m from the end face of the rough bar.

According to another aspect of the present invention, there is provided a cutting machine for cutting a front end portion between a rough rolling mill and a finish rolling mill in a hot rolling line for steel material, which cuts the front end portion of the rough bar after the rough rolling. the includes a rear end cutting cutting machine for cutting a rear end portion of the crude bar after the rough rolling mill and the tip cutting cutter be between the finishing mill, the coarse bar heating device is provided for heating the vicinity of the tip, after said rough rolling mill and the rear end cutting cutter be between the finishing mill, said heating the vicinity of the rear end of the rough bar A heating device different from the heating device is provided, and each of the heating devices can heat the vicinity of the rear end of the rough bar so that the temperature rises higher than that of the vicinity of the front end. Facilities are provided.

  ADVANTAGE OF THE INVENTION According to this invention, in the hot rolling line, the conveyance pitch of the rough bar processed continuously can be accelerated, and the productivity of steel materials can be improved.

  Hereinafter, preferred embodiments of the present invention will be described. Drawing 1 is a mimetic diagram showing the outline of composition of hot rolling equipment 1 concerning this embodiment.

  The hot rolling facility 1 includes, for example, a heating furnace 10, a rough rolling mill group 11, a first cutting machine 12, a second cutting machine 13, a finishing rolling mill group 14, a winder 15 and the like in this order. The hot rolling line L is comprised. In the hot rolling line L, a plurality of steel materials H are processed while being continuously conveyed.

  The heating furnace 10 is, for example, a walking beam type continuous heating furnace, and can reheat the cast slab H to a temperature necessary for rolling.

  The rough rolling mill group 11 is composed of a plurality of rough rolling mills arranged along the hot rolling line L, for example. The rough rolling mill group 11 can form the rough bar H by rolling the slab H to a thickness suitable for finish rolling.

  For the first cutting machine 12, for example, a drum-type crop shear (flying crop shear) is used. The first cutting machine 12 includes, for example, a cylindrical rotary drum 20 that can rotate in the front-rear direction of the rough bar H in the plate passing direction. The rotary drum 20 is disposed opposite to the upper and lower surfaces of the coarse bar H. For example, two cutting blades 21 are attached to the surface of each rotary drum 20. The cutting blade 21 is attached to an axially symmetric position with respect to the rotation axis of the rotary drum 20, for example. The first cutting machine 12 can rotate the upper and lower rotary drums 20 to sandwich the coarse bar H between the upper and lower cutting blades 21, and can cut the coarse bar H by the shearing force at that time.

  The rotary drum 20 may be provided with cutting blades 21 for cutting the front end and the rear end of the rough bar H one by one, or two pieces for cutting the front end. The blade 21 may be attached.

  For example, a drum-type crop shear is used for the second cutting machine 13 as in the case of the first cutting machine 12. The second cutting machine 13 is arranged immediately before the finishing mill group 14. The second cutting machine 13 can rotate the upper and lower rotary drums 20 and cut the rough bar H with the cutting blade 21. The rotary drum 20 of the second cutting machine 13 may be provided with cutting blades 21 for cutting the leading end and the trailing end of the rough bar H one by one, or the trailing end. Two cutting blades 21 for part cutting may be attached.

  The finish rolling mill group 14 is composed of, for example, a plurality of, for example, 6, 7 finishing mills arranged along the hot rolling line L. The finish rolling mill group 14 can form the steel sheet H by rolling the rough bar H to a target final product thickness.

  The winder 15 can wind up the finish-rolled steel sheet H in a coil shape.

  In the present embodiment, the steel material H that is a rolled material is a slab H, a rough bar H, and a steel plate H according to the stage of rolling.

  Next, the hot rolling method of the steel H performed by the hot rolling equipment 1 configured as described above will be described.

  First, the slab H is heated in the heating furnace 10 to 1000 ° C. or higher at which rolling is possible. The slab H heated in the heating furnace 10 is conveyed to the rough rolling mill group 11 and rough rolled. At this time, a shape defect called a so-called fish tail is formed at the leading end and the trailing end of the coarse bar H.

  The roughly rolled coarse bar H is conveyed to the first cutting machine 12 as shown in FIG. 2 (a), and the tip of the defective shape is cut. For example, the tip of 100 to 200 mm is cut from the tip of the coarse bar H. At this time, for example, the rotating drum 20 rotates at the same speed as the coarse bar H in the same direction as the traveling direction of the coarse bar H, and the leading end of the coarse bar H is cut by the shearing force of the upper and lower cutting blades 21. When the cutting is completed, the rotating drum 20 is decelerated, returned to a standby position for performing the next cutting (for example, a position where the cutting blade 21 is horizontal), and stopped. The first cutting machine 12 does not cut the rear end portion of the coarse bar H, but prepares for the cutting of the front end portion of the coarse bar H to be loaded next. Thus, the 1st cutting machine 12 cut | disconnects only the front-end | tip part of the coarse bar H carried in continuously.

  The coarse bar H that has passed through the first cutting machine 12 is subsequently conveyed to the second cutting machine 13 as shown in FIG. 2B, and the rear end of the defective shape is cut. For example, the rear end portion of 100 to 200 mm is cut from the rear end of the coarse bar H. Also at this time, the rotating drum 20 of the second cutting machine 13 rotates in the same direction as the moving direction of the rough bar H at the same speed as the rough bar H, for example. The end is cut. When the cutting is completed, the rotating drum 20 is decelerated, returned to a standby position for performing the next cutting (for example, a position where the cutting blade 21 is horizontal), and stopped. The second cutting machine 13 does not cut the front end portion of the rough bar H, but prepares for cutting the rear end portion of the next rough bar H. Thus, the 2nd cutting machine 13 cuts only the rear end part of coarse bar H carried in continuously.

  The rough bar H whose front end portion and rear end portion are cut by the first and second cutting machines is conveyed to the finish rolling mill group 14 and finish-rolled to a predetermined target thickness. The finish-rolled steel sheet H is wound around the winder 15 in a coil shape. Thus, a series of hot rolling processes is completed. In the hot rolling line L, a plurality of steel materials H are continuously conveyed at a predetermined pitch, and the hot rolling process is performed on each steel material H.

  According to the above embodiment, the front-end | tip part and rear-end part of the rough bar H are cut | disconnected by the different cutting machines 12 and 13, respectively. As a result, the first cutting machine 12 cuts only the front end portion of the rough bar H, and the second cutting machine 13 cuts only the rear end portion of the rough bar H. .., One rough bar H may be cut once, so that the preparation for cutting the next rough bar H can be completed at an early timing.

  That is, as shown in FIG. 3, for the first cutting machine 12 that cuts the tip portion, for example, the tip portion of the preceding coarse bar H1 is cut, and the coarse bar H1 passes between the upper and lower rotary drums 20. In the meantime, the rotating drum 20 decelerates and rotates to a predetermined standby position to prepare for cutting the next rough bar H2. Thereby, for example, when the preceding rough bar H has passed, the first cutting machine 12 can complete the preparation for cutting the next rough bar H2.

  Further, as shown in FIG. 4, for the second cutting machine 13 for cutting the rear end portion, for example, after the rear end portion of the preceding coarse bar H1 is cut, the next coarse bar H2 is moved to the upper and lower rotary drums 20. The rotary drum 20 decelerates and rotates to a predetermined standby position to prepare for cutting the rear end portion of the coarse bar H2. As a result, the second cutting machine 13 can complete the preparation for cutting the rear end portion of the next rough bar H2 sufficiently earlier than when the rear end portion of the rough bar H2 passes.

  In such a case, there is no need to rotate the rotating drum to a predetermined standby position after cutting the rear end portion of the preceding coarse bar H1 until the front end portion of the next coarse bar H2 is cut as in the prior art. . As a result, as shown in FIGS. 3 and 4, the pitch interval P between the preceding coarse bar H1 and the next coarse bar H2 can be shortened, and the production of the coarse bar H in the hot rolling line L correspondingly. Can be improved. According to the inventor's verification, conventionally, it took at least 4 to 5 seconds from the cutting of one rough bar to the cutting of the next rough bar. It has been confirmed that rough bars can be cut at intervals of 2 seconds.

  By the way, in the finish rolling of the coarse bar H, the coarse bar H is extended 50 to 200 times as shown in FIG. For this reason, after the front-end | tip part of the rough bar H enters into the finishing mill group 14, the speed of the rough bar H is normally reduced to about 1/5. Therefore, normally, the time from cutting to loading into the finishing mill is significantly longer at the rear end than at the front end of the coarse bar H. Thus, if the time to the finishing mill is long, the temperature in the vicinity of the rear end of the rough bar H is lowered and hardened during the conveyance, and the work roll of the finishing mill is caused to have indentations and the like. There is a concern that the steel plate H may be recessed. In the above embodiment, the first cutting machine 12 on the upstream side cuts the leading end of the rough bar H, and the second cutting machine 13 close to the finishing mill cuts the rear end of the rough bar H. The time required from the cutting of the rear end portion of the rough bar H to the finish rolling can be shortened, and the temperature drop and hardening on the rear end portion side of the rough bar H can be suppressed. As a result, it is possible to prevent the work roll of the finishing mill from being recessed due to the rear end portion of the hardened rough bar H.

  The hot rolling facility 1 described in the above embodiment may be provided with a heating device that heats the vicinity of the tip of the rough bar H. For example, as shown in FIG. 6, the heating device 30 is installed between the first cutting machine 12 and the second cutting machine 13. As the heating device 30, for example, a heating method such as an induction heating method, a transformer effect type current heating method or a direct current heating method is used, and the rough bar H can be uniformly heated over the entire width direction. .

  In the hot rolling process, after the front end portion of the rough bar H is cut by the first cutting machine 12, the vicinity of the front end of the rough bar H is immediately heated by the heating device 30. At this time, for example, at least a portion of 1 m or more from the tip of the coarse bar H is heated so that the temperature rises, for example, 5 ° C. or more. Thereby, it can prevent that the vicinity of the front-end | tip of the rough bar H after cutting | disconnection cools and hardens | cures before it is carried in to the finishing mill group 14. As a result, it is possible to prevent the vicinity of the end of the rough bar H that has been cooled and hardened from being carried into the finishing mill and causing the work rolls of the finishing mill to be recessed.

  It should be noted that a heating device 30 is provided between the first cutting machine 12 and the rough rolling mill group 11 so that the vicinity of the end of the rough bar H can be preheated before being cut by the first cutting machine 12. Good.

  In the embodiment, the vicinity of the rear end of the coarse bar H may be heated by the heating device 30. In such a case, for example, when the coarse bar H passes through the heating device 30, both the vicinity of the front end and the vicinity of the rear end are heated. By doing so, it is possible to prevent the vicinity of the front end and the rear end of the rough bar H from being cooled and hardened before finish rolling. As a result, it is possible to prevent the work roll of the finishing rolling mill from being recessed and the steel sheet H from being surface damaged.

  In the embodiment, the vicinity of the rear end of the coarse bar H may be heated by another heating device. For example, as shown in FIG. 7, the heating device 40 is installed between the second cutting machine 13 and the finishing mill group 14. As the heating device 40, for example, a heating method such as an induction heating method, a transformer effect type electric heating method, or a direct electric heating method is used, and the coarse bar H can be uniformly heated over the entire width direction. . In the hot rolling process, after the rear end portion of the rough bar H is cut by the second cutting machine 13, the vicinity of the rear end of the rough bar H is heated by the heating device 40. At this time, for example, at least a portion of 1 m or more from the rear end of the coarse bar H is heated so that the temperature rises by, for example, 10 ° C. or more. Further, for example, the heating amount and the heating temperature of each heating device 30, 40 are set so that the temperature rise near the rear end of the rough bar H by the heating device 40 is larger than the temperature rise near the front end of the rough bar H by the heating device 30. Is controlled. In such a case, cooling and hardening in the vicinity of the rear end of the rough bar H after cutting can be suppressed. Note that the heating device 40 may be installed between the second cutting machine 13 and the first cutting machine 12, and may heat the rear end portion of the coarse bar H before cutting.

  In the above embodiment, in the hot rolling facility 1, the leading end of the rough bar H is cut by the first cutting machine 12 on the upstream side, and the rear end of the rough bar H is cut by the second cutting machine 13 on the downstream side. However, the rear end portion of the coarse bar H may be cut by the first cutting machine 12 and the front end portion of the coarse bar H may be cut by the second cutting machine 13. In such a case, for example, the heating device 30 described above is provided between the first cutting machine 12 and the second cutting machine 13. The rotary drum 20 of the first cutting machine 12 is provided with cutting blades 21 for cutting the front end and the rear end of the rough bar H one by one, or 2 for cutting the rear end. What has the cutting blade 21 attached is used. Further, the rotary drum 20 of the second cutting machine 13 is provided with cutting blades 21 for cutting the front end and the rear end of the rough bar H one by one, or for cutting the front end. The one to which two cutting blades 21 are attached is used.

  In the hot rolling process, as shown in FIG. 8 (a), the coarse bar H that has passed through the coarse rolling mill group 11 is carried into the first cutting machine 12, and the leading end of the coarse bar H is not cut. Only the rear end of H is cut. The coarse bar H that has passed through the first cutting machine 12 is carried into the heating device 30. In the heating device 30, for example, the vicinity of the rear end of the cut coarse bar H is heated. At this time, for example, at least a portion of 1 m or more from the rear end of the coarse bar H is heated so that the temperature rises by, for example, 40 ° C. or more. Thereafter, the coarse bar H is carried into the second cutting machine 13 as shown in FIG. 8B, and the leading end of the coarse bar H is cut. The rough bar H whose tip is cut is carried into the finish rolling mill group 14, finish-rolled, and then wound up by the winder 15.

  In such a case, since the leading end and the trailing end of the rough bar H are cut by different cutting machines, the cutting preparation of each cutting machine can be completed at an early stage as in the above-described embodiment. Therefore, the pitch interval P between the preceding coarse bar H and the next coarse bar H can be shortened, and the productivity of the coarse bar H can be improved accordingly. Moreover, since the vicinity of the rear end of the rough bar H is heated by the heating device 30 immediately after cutting, the vicinity of the rear end of the rough bar H, which takes time from cutting to finish rolling, is not cooled and hardened. As a result, it is possible to prevent the hardened rough bar H from forming dents on the work roll of the finishing mill and causing surface flaws on the steel sheet H.

  In the above embodiment, the heating device 30 may be provided on the upstream side of the first cutting machine 12 so that the rear end portion of the coarse bar H is heated in advance before cutting.

  In the embodiment, the vicinity of the end of the coarse bar H may be heated by the heating device 30. In such a case, for example, when the coarse bar H passes through the heating device 30, both the vicinity of the front end and the vicinity of the rear end are heated. By doing so, it is possible to prevent the vicinity of the front end and the rear end of the rough bar H from being cooled and hardened before finish rolling. As a result, it is possible to prevent the work roll of the finishing rolling mill from being recessed and the steel sheet H from being surface damaged.

  In the embodiment, the vicinity of the tip of the coarse bar H may be heated by another heating device. For example, the vicinity of the end of the coarse bar H may be heated by the above-described heating device 40 (shown in FIG. 9) provided between the second cutting machine 13 and the finishing mill group 14. In such a case, the tip of the rough bar H is cut by the second cutting machine 13, and after the rough bar H has passed through the second cutting machine 13, the heating device 40 shown in FIG. Is heated. At this time, the heating amount of each of the heating devices 30 and 40 is set so that the temperature increase in the vicinity of the rear end of the rough bar H by the heating device 30 is larger than the temperature increase in the vicinity of the front end of the rough bar H by the heating device 40. The heating temperature is controlled. In such a case, it is possible to suppress the vicinity of the end of the coarse bar H from being cooled and hardened before finish rolling. Note that the heating device 40 may be disposed between the second cutting machine 13 and the first cutting machine 12, and may heat the tip of the coarse bar H before cutting. Furthermore, both the heating device 30 and the heating device 40 may be disposed between the second cutting machine 13 and the finish rolling mill group 14.

  The preferred embodiment of the present invention has been described above with reference to the accompanying drawings, but the present invention is not limited to such an example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the spirit described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs. For example, in the cutting machine according to the present embodiment, two cutting blades are provided on each upper and lower rotating drum, but one cutting blade may be provided on each rotating drum. The cutting machine in the present embodiment is a drum-type crop shear. However, other cutting machines such as a pendulum shear which cuts a rough bar by moving the opposed upper and lower blades up and down. It may be. Further, the number and types of rough rolling mills and finish rolling mills are not limited.

  The present invention is useful for improving productivity in hot rolling of steel materials.

It is a schematic diagram which shows the outline of a structure of a hot rolling facility. It is explanatory drawing which shows the mode of a cutting | disconnection of a rough bar in the hot rolling equipment of FIG. It is an enlarged view around the 1st cutting machine for demonstrating the pitch space | interval of the rough bar in a 1st cutting machine. It is an enlarged view around the 2nd cutting machine for demonstrating the pitch space | interval of the coarse bar in a 2nd cutting machine. It is explanatory drawing which shows the state by which the rough bar is finish-rolled in a hot rolling installation. It is a schematic diagram which shows the structure of the hot rolling equipment provided with the heating apparatus. It is a schematic diagram which shows the structure of the hot rolling equipment provided with two heating apparatuses. It is explanatory drawing which shows the mode of the cutting | disconnection of the rough bar in a hot rolling facility. It is explanatory drawing which shows a mode that the front-end | tip vicinity of a rough bar is heated in a hot rolling installation. It is explanatory drawing which shows the operation example of the rotating drum of the crop shear after a cutting | disconnection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hot rolling equipment 10 Heating furnace 11 Rough rolling mill group 12 1st cutting machine 13 2nd cutting machine 14 Finishing mill group 15 Winding machine L Hot rolling line H Rough bar

Claims (2)

In a hot rolling line that performs heating, rough rolling, and finish rolling of steel materials in this order, the front and rear ends of the rough bar after rough rolling are cut by different cutting machines before finish rolling. , After the cutting of the front end portion and the rear end portion of the rough bar, respectively, the vicinity of the front end and the vicinity of the rear end of the rough bar are heated so that the rising temperature is larger than that near the front end of the rough bar A method of hot rolling steel, characterized by heating the vicinity of the rear end of the coarse bar. A cutting machine for cutting the front end of the rough bar between the rough rolling mill and the finish rolling mill in the hot rolling line for steel, and cutting the rear end of the rough bar. Equipped with a cutting machine for cutting the rear end,
Between the rough rolling mill and the finish rolling mill and after the cutting machine for cutting the tip portion, a heating device for heating the vicinity of the leading end of the rough bar is provided,
Between the rough rolling mill and the finishing mill and after the rear end cutting cutter, a heating device different from the heating device for heating the vicinity of the rear end of the rough bar is provided,
Each of the heating devices can heat the vicinity of the rear end of the rough bar so that the temperature rises higher than that of the vicinity of the front end.

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