JP2010214422A - Temper rolling method of steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temper rolling method of a steel sheet, by which the generation of wrinkles on a succeeding steel sheet in the case that the yield stress of the succeeding steel sheet is lower than that of a preceding steel sheet when connecting a plurality of the steel sheets successively and performing temper rolling. <P>SOLUTION: When detecting a weld zone between mutual steel sheets, the travel distance from the detected position of the weld zone is measured and tracking is performed (a1, a2). Whether the weld zone is passed through a rolling stand or not is decided on the basis of the travel distance, and when deciding that it is the passage, furthermore, whether the thickness of the succeeding steel sheet is ≥2.0 mm or not is decided (a3, a4). When above mentions are satisfied, the temper rolling is performed by making the rolling tension of the succeeding steel sheet into the same value as the rolling tension of the preceding steel sheet, and when the above mentions are not satisfied, the temper rolling is performed by setting the rolling tension of the succeeding steel sheet to a smaller value than the rolling tension of the preceding steel sheet (a5). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a temper rolling method for a steel sheet in which a plurality of steel sheets are sequentially connected and subjected to temper rolling.

  In general, a steel plate is manufactured by hot rolling a slab, further cold rolling, and then annealing. Here, a steel plate is used in the meaning including a strip-shaped steel strip. When more strict mechanical properties and shape correction are required, the steel sheet is temper-rolled at a rolling reduction of several percent or less after annealing (see, for example, Patent Document 1).

  FIG. 5 shows a configuration of an example of a temper rolling apparatus. The temper rolling apparatus 1 includes an entry-side bridle roll 2, an entry-side tension detector 3, a rolling stand 4, an exit-side tension detector 5, an exit-side bridle roll 6, a welded part detector 7, and an encoder. 8 and the control unit 9. In the temper rolled steel sheet 10, the preceding steel sheet 10a and the succeeding steel sheet 10b are connected at the welded portion 11. In FIG. 5, the size of the welded portion 11 is exaggerated for convenience of explanation. When a steel plate is distinguished by preceding and following, the preceding steel plate is represented by reference symbol 10a, and the following steel plate is represented by reference symbol 10b. When collectively referred to, it is represented by a steel plate 10.

  By adjusting the relative speed between the entry side bridle roll 2 and the rolling stand 4, the entry side rolling tension of the steel plate 10 can be adjusted. Here, the rolling tension means unit tension unless otherwise specified. The entry-side tension detector 3 detects the entry-side rolling tension of the steel plate 10 between the entry-side bridle roll 2 and the rolling stand 4 and inputs it to the control unit 9.

  The rolling stand 4 is a 4Hi mill, and includes a pair of work rolls 12, a pair of backup rolls 13, a housing (not shown), a reduction device, a roll drive device, and the like. In the rolling stand 4, the steel sheet 10 is temper-rolled at a desired reduction rate set in advance according to product specifications. By controlling the rotational speed of the backup roll 13, the rolling tension of the steel sheet 10 between the entry-side and exit-side bridle rolls 2, 6 is adjusted.

  By adjusting the relative speed between the exit side bridle roll 6 and the rolling stand 4, the exit side rolling tension of the steel sheet 10 can be adjusted. The exit-side tension detector 5 detects the exit-side rolling tension of the steel plate 10 between the exit-side bridle roll 6 and the rolling stand 4 and inputs it to the control unit 9.

  The weld detector 7 and the encoder 8 are arranged on the upstream side of the entry-side bridle roll 2. The welded part detector 7 is realized by a photoelectric conversion type sensor or the like. For example, the welded part detector 7 detects light transmitted through a hole formed in the welded part 11 to detect the welded part 11 and inputs a detection signal to the control part 9. To do. The control part 9 will reset the measured value of the encoder 8, if the detection signal of the welding part 11 is received. After the reset, the traveling position of the welded portion 11 is tracked by the distance measured by the encoder 8.

  When the steel sheet is temper-rolled with a temper rolling apparatus as exemplified above, the distribution of compressive stress remaining on the surface layer of the steel sheet becomes non-uniform despite the aim of shape correction, and the steel sheet is warped. May occur. With respect to such a problem, the previous Patent Document 1 discloses that the occurrence of warpage is prevented by adjusting the rolling mill exit-side tension according to the rolling speed. Further, when temper rolling by sequentially connecting a plurality of steel plates 10, it is necessary to adjust the rolling tension in addition to the prevention of warpage. In continuous temper rolling, steel types having different characteristics, in particular, the preceding steel plate 10a and the subsequent steel plate 10b having different yield stresses may be connected. When the yield stress differs between the preceding steel plate 10a and the succeeding steel plate 10b, immediately after the welded portion 11 passes the rolling stand 4, the rolling tension set for the preceding steel plate 10a is used for the succeeding steel plate 10b. The set value is changed to a predetermined rolling tension. Information such as rolling tension to be set for each of the preceding steel plate 10a and the succeeding steel plate 10b is given from the host computer 14 to the control unit 9 as production plan information.

  Adjustment of rolling tension is performed as follows. The adjustment of the entry side rolling tension is performed by outputting a control signal from the control unit 9 to the roll driving device of the rolling stand 4 and controlling the rotation speed of the backup roll 13. If the relative speed of the backup roll 13 with respect to the entry-side bridle roll 2 is increased, the entry-side rolling tension is increased. If the relative speed is brought close to the same, the entry-side rolling tension is reduced. The adjustment of the exit-side rolling tension is performed by outputting a control signal from the control unit 9 to the drive device for the exit-side bridle roll 6 and controlling the rotational speed of the exit-side bridle roll 6. Increasing the relative speed of the exit side bridle roll 6 with respect to the rolling speed of the rolling stand 4 increases the exit side rolling tension, and reducing the relative speed to the same value decreases the exit side rolling tension.

  Conventionally, among the combinations in which the steel plates 10 having different yield stresses are connected, when the yield stress of the succeeding steel plate 10b is lower than the yield stress of the preceding steel plate 10a, the rolling tension is set immediately after the weld 11 passes the rolling stand 4. The set value is changed so as to be smaller than the value set for the preceding steel plate 10a. The reason is as follows. In rolling, a larger reduction can be applied as the rolling tension is increased. For a steel type with a high yield stress, that is, a steel type that is difficult to be plastically deformed, the rolling tension is increased so that a large reduction can be applied. Conversely, steel grades with low yield stress, that is, steel grades that are easily plastically deformed, can achieve the desired plastic deformation under a small pressure, so the rolling tension is set low and the power unit of the roll drive motor does not become unnecessarily high. Like that.

JP-A-11-123427

  When the rolling tension is controlled in the temper rolling apparatus 1 as described above, the rolled steel sheet changes from the preceding steel sheet 10a to the succeeding steel sheet 10b whose yield stress is lower than that of the steel sheet, and the rolling tension is reduced. The trailing steel plate 10b may be wrinkled. When the rolling tension is lowered, the reduction of the subsequent steel plate 10b becomes uneven, and a portion where a predetermined amount of reduction is applied and a portion where the reduction is insufficient occur, and the amount of plastic deformation in both portions is different, so that the wrinkle shape It is thought that it becomes. The occurrence of such wrinkles is a particularly remarkable phenomenon in the surface-treated steel sheet, but a similar phenomenon may occur in the cold-rolled steel sheet.

  If wrinkles occur in the steel sheet, the generated portions cannot be commercialized, and there is a problem that the yield is lowered. However, the above-mentioned Patent Document 1 does not disclose how to set the rolling tension in order to prevent wrinkles with the transition from the preceding steel plate to the succeeding steel plate.

  An object of the present invention is to provide a steel sheet that can prevent wrinkling in a succeeding steel sheet when the yield stress of the succeeding steel sheet is lower than that of the preceding steel sheet when temper rolling by sequentially connecting a plurality of steel sheets. It is to provide a temper rolling method.

The present invention is a method for temper rolling of a steel sheet in which a plurality of steel sheets are sequentially connected and subjected to temper rolling,
In the case where the succeeding steel plate is connected to the preceding steel plate, and the yield stress of the succeeding steel plate is lower than the yield stress of the preceding steel plate,
When the thickness of the succeeding steel plate satisfies a thick condition with respect to a predetermined reference value,
Temper rolling the succeeding steel sheet by making the setting value of the succeeding steel sheet equal to the setting value of the rolling tension of the preceding steel sheet,
When the thickness of the subsequent steel plate does not satisfy the thick condition with respect to the predetermined reference value,
A temper rolling method for a steel sheet, characterized in that the succeeding steel sheet is temper rolled by reducing the set value of the rolling tension of the succeeding steel sheet relative to the set value of the rolling tension of the preceding steel sheet.

  In the present invention, the preceding steel plate is a medium carbon steel plate having a carbon (C) content of more than 0.1 wt% to 0.3 wt% or less, and the succeeding steel plate has a C content of 0.1 wt%. % Low-carbon steel sheet or less.

  According to the present invention, the setting value of the rolling tension of the succeeding steel sheet relative to the setting value of the rolling tension of the preceding steel sheet is equal when the plate thickness of the succeeding steel sheet satisfies a thick condition with respect to a predetermined reference value, If the thicker conditions are not satisfied, the subsequent steel plate is temper rolled. As a result, unevenness in the reduction of the succeeding steel plate in the temper rolling can be corrected, and the generation of wrinkles can be prevented.

  Further, according to the present invention, the medium carbon steel plate and the low carbon steel plate can be continuously temper-rolled without causing wrinkles, so that the production yield can be improved.

FIG. 1 is a flowchart showing a steel sheet temper rolling method according to an embodiment of the present invention. FIG. 2 is a graph illustrating the rolling tension setting values according to the plate thicknesses of the preceding steel plate 10a and the succeeding steel plate 10b in the temper rolling method. FIG. 3 is a graph showing data of an example in which temper rolling was performed by setting the rolling tension setting value of the succeeding steel plate equal to the rolling tension setting value of the preceding steel plate. FIG. 4 is a graph showing data of a comparative example in which temper rolling was performed such that the rolling tension setting value of the subsequent steel sheet was smaller than the rolling tension setting value of the preceding steel sheet. FIG. 5 is a diagram illustrating a configuration of an example of a temper rolling apparatus.

  FIG. 1 shows a temper rolling method for a steel sheet according to an embodiment of the present invention. The temper rolling apparatus 1 shown in FIG. 5 described above can be used for carrying out the temper rolling method of the steel sheet of the present embodiment (hereinafter simply referred to as temper rolling method). The temper rolling method is used when the succeeding steel plate 10b having a lower yield stress than the preceding steel plate 10a is connected to the preceding steel plate 10a. Further, it is determined whether the thickness of the succeeding steel plate 10b satisfies a thick condition with respect to a predetermined reference value or does not satisfy the thick condition. When the thick condition is satisfied with respect to the predetermined reference value, the setting value of the rolling tension of the succeeding steel plate 10b is made equal to the setting value of the rolling tension of the preceding steel plate 10a, and the succeeding steel plate 10b is temper rolled. On the contrary, when the thick condition is not satisfied with respect to the predetermined reference value, the set value of the rolling tension of the succeeding steel plate 10b with respect to the set value of the rolling tension of the preceding steel plate 10a is reduced, and the succeeding steel plate 10b is temper rolled. To do.

  Hereinafter, the temper rolling method will be described with reference to FIG. 1 and FIG. 5 described above. At the start, in the temper rolling apparatus 1, the preceding steel plate 10a and the succeeding steel plate 10b having a lower yield stress than the preceding steel plate 10a are connected by the welded portion 11 and continuously rolled. Examples of the preceding steel plate 10a having a high yield stress include a medium carbon steel plate, and examples of the succeeding steel plate 10b having a lower yield stress than the preceding steel plate 10a include a low carbon steel plate. Here, the medium carbon steel sheet refers to a steel sheet having a C content exceeding 0.1 wt% and not more than 0.3 wt%. A low carbon steel plate refers to a steel plate having a C content of 0.1% by weight or less. Comparing the yield stress of medium carbon steel plate and low carbon steel plate, naturally it depends on the level of C content of each steel plate, but it is an average value of steel plate products. Is double. Whether the preceding steel plate 10a and the succeeding steel plate 10b correspond to a combination of a medium carbon steel plate and a low carbon steel plate is determined based on production plan information given to the control unit 9 from the host computer 14.

  In step a1, it is determined whether or not the welded portion 11 has been detected. The determination is performed by the control unit 9 in response to a detection signal from the welded part detector 7. If the welded part 11 is detected, the process proceeds to step a2, and if not detected, step a1 is repeated. In step a2, after the control unit 9 receives the detection signal of the welded part 11 and resets the measurement value of the encoder 8, the measurement of the travel distance of the welded part 11 is started, that is, tracking is started. In step a3, it is determined whether or not the welded part 11 has passed the rolling stand 4. This determination is performed as follows. A distance from the installation position of the weld detector 7 to a predetermined position on the rolling stand exit side is measured, and the distance is stored in the memory of the control unit 9. When the distance tracked by the encoder 8 is input to the control unit 9, the control unit 9 compares the tracking distance with the stored distance, and whether or not the welded part 11 has passed the rolling stand 4. Determine. If the welding part 11 passes the rolling stand 4, it will progress to step a4, and if not passing the rolling stand 4, step a3 will be repeated.

  In step a4, it is determined whether the thickness of the succeeding steel plate 10b satisfies a thick condition with respect to a predetermined reference value or does not satisfy the thick condition. Here, a thickness of 2.0 mm is used as a predetermined reference value. The case where the thick condition is satisfied with respect to the predetermined reference value is a case where the thickness of the succeeding steel plate 10b is 2.0 mm or more. Moreover, the case where the thick condition is not satisfied with respect to the predetermined reference value is the case where the thickness of the subsequent steel plate 10b is less than 2.0 mm. This determination is performed by the control unit 9 based on the plate thickness information of the steel plate 10 given from the host computer 14 as production plan information according to the temper rolling order. When the thickness of the succeeding steel plate 10b satisfies a thick condition with respect to a predetermined reference value, a series of rolling tension control operations is performed without changing the setting value of the rolling tension, and is equal to the set value for the preceding steel plate 10a. Exit.

  On the other hand, when the thickness of the succeeding steel plate 10b does not satisfy the thick condition with respect to the predetermined reference value, the process proceeds to step a5. In step a5, the setting value of the rolling tension of the succeeding steel plate 10b is changed to a value smaller than the setting value of the rolling tension of the preceding steel plate 10a, and the series of rolling tension control operations ends.

  FIG. 2 exemplifies rolling tension setting values according to the plate thicknesses of the preceding steel plate 10a and the subsequent steel plate 10b in the temper rolling method. When the thickness of the subsequent steel plate 10b, which is a low carbon steel plate, is 2.0 mm or more, the rolling tension of the subsequent steel plate 10b is set to a value equal to the rolling tension of the preceding steel plate 10a, which is a medium carbon steel plate. Therefore, in the area | region whose board | plate thickness of FIG. 2 is 2.0 mm or more, the line which shows the rolling tension setting value of the preceding steel plate 10a and the succeeding steel plate 10b overlaps. In the region where the plate thickness is less than 2.0 mm, the rolling tension of the subsequent steel plate 10b is set to be about 8 to 10 MPa lower than the rolling tension of the preceding steel plate 10a.

  Thus, when the plate | board thickness of the succeeding steel plate 10b is 2.0 mm or more, by making the setting value of the rolling tension of the succeeding steel plate 10b equal to the setting value of the rolling tension of the preceding steel plate 10a, the succeeding steel plate The generation of wrinkles in 10b is prevented. When the thickness of the succeeding steel plate is less than 2.0 mm, the setting value of the rolling tension of the succeeding steel plate 10b is smaller than the setting value of the rolling tension of the preceding steel plate 10a. Little effect on wrinkle generation. Therefore, when the plate | board thickness of a subsequent steel plate is less than 2.0 mm, the setting value of rolling tension is made small in order to save an electric power basic unit.

  The predetermined reference value that is a criterion for determining whether or not to set the rolling tension setting value of the succeeding steel plate 10b is not limited to the thickness of 2.0 mm shown in FIGS. 1 and 2. The thickness used as the reference value can be appropriately set based on the specifications of the temper rolling device to be used and the temper rolling results. In addition, there is no particular restriction on whether the reference value is used as the lower limit value of the area section on the thick plate side or the upper limit value of the area section on the thin plate side, using the reference value as a threshold value. Can be determined based on

  Examples of the present invention will be described below. In this example, a steel plate having a lower yield stress than the preceding steel plate was connected as a subsequent steel plate, and temper rolling was performed continuously. During temper rolling, the setting value of the rolling tension of the preceding steel plate and the succeeding steel plate is not changed, and the setting value of the rolling tension of the succeeding steel plate is smaller than the setting value of the rolling tension of the preceding steel plate. In the case of the change, the presence or absence of wrinkles was inspected.

  As the preceding steel plate, a medium carbon steel plate having a plate thickness of 2.0 to 3.5 mm, a plate width of 1050 to 1250 mm, and a C content in the range of 0.1 to 0.3% by weight was used. A low carbon steel plate having a plate thickness of 2.0 to 3.5 mm, a plate width of 1050 to 1250 mm, and a C content in the range of 0.1% by weight or less was used as the subsequent steel plate.

  The set value of the rolling tension of the succeeding steel plate was made equal to the set value of the rolling tension of the preceding steel plate and temper rolled to obtain data of the examples. The set value of the rolling tension of the succeeding steel plate was temper-rolled to a value 8 to 10 MPa smaller than the set value of the rolling tension of the preceding steel plate, and used as data for a comparative example. The presence or absence of wrinkles in the succeeding steel plate was inspected by visual observation before the winder provided behind the temper rolling apparatus 1.

  FIG. 3 shows data of an example in which temper rolling was performed with the rolling tension setting value of the succeeding steel sheet being the same as the rolling tension setting value of the preceding steel sheet. In FIG. 3, the horizontal axis represents the difference between the actual measured values of the outgoing rolling tension between the preceding steel plate and the succeeding steel plate. Therefore, although the setting values of the rolling tension of the preceding steel plate and the following steel plate are made equal, the actual measurement value may cause the difference to slightly deviate from zero (0). In FIG. 3, a vertical axis | shaft represents the difference of the outgoing side rolling tension of the work side (Ws) and drive side (Ds) of a steel plate. In FIG. 3, the difference in rolling tension is expressed as a load (kN). With regard to the presence or absence of wrinkles, ○ marks indicate no wrinkles and X marks indicate wrinkles. When the temper rolling was performed with the same set value of the rolling tension of the preceding steel plate and the succeeding steel plate, wrinkles were not generated in the succeeding steel plate, and a good surface quality could be obtained.

  FIG. 4 shows data of a comparative example in which temper rolling was performed such that the rolling tension setting value of the succeeding steel sheet was smaller than the rolling tension setting value of the preceding steel sheet. In FIG. 4, the notation of the horizontal and vertical axes and the presence / absence of wrinkles is the same as in FIG. When the temper rolling was performed with the setting value of the rolling tension of the succeeding steel sheet being made smaller than the setting value of the rolling tension of the preceding steel sheet, the case where wrinkles occurred and the case where they did not occur were mixed. In particular, when the difference between the setting value of the rolling tension of the preceding steel plate and the setting value of the rolling tension of the succeeding steel plate is large, the difference in tension between Ws and Ds increases and the shape is rolled in an unstable state. It occurred frequently.

  As described above, when the thickness of the succeeding steel plate is 2.0 mm or more, the setting value of the rolling tension of the succeeding steel plate is equal to the setting value of the rolling tension of the preceding steel plate, thereby generating wrinkles in the succeeding steel plate. It can be seen that it can be prevented.

DESCRIPTION OF SYMBOLS 1 Temper rolling apparatus 2 Entry side bridle roll 3 Entry side tension detector 4 Rolling stand 5 Entry side tension detector 6 Entry side bridle roll 7 Welding part detector 8 Encoder 9 Control part 10 Steel plate 11 Welding part

Claims (2)

In the method for temper rolling of steel plates, in which a plurality of steel plates are sequentially connected and temper rolled,
In the case where the succeeding steel plate is connected to the preceding steel plate, and the yield stress of the succeeding steel plate is lower than the yield stress of the preceding steel plate,
When the thickness of the succeeding steel plate satisfies a thick condition with respect to a predetermined reference value,
The set value of the rolling tension of the succeeding steel plate is made equal to the set value of the rolling tension of the preceding steel plate, and the subsequent steel plate is temper rolled.
When the thickness of the subsequent steel plate does not satisfy the thick condition with respect to the predetermined reference value,
A temper rolling method for a steel sheet, in which the setting value of the rolling tension of the succeeding steel sheet is made smaller than the setting value of the rolling tension of the preceding steel sheet, and the succeeding steel sheet is temper rolled. The preceding steel plate is a medium carbon steel plate having a carbon (C) content of more than 0.1 wt% to 0.3 wt%,
The temper rolling method for a steel sheet according to claim 1, wherein the succeeding steel sheet is a low carbon steel sheet having a C content of 0.1 wt% or less.

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