Roll peripheral speed control device, roll peripheral speed control method, and method for manufacturing hot-rolled steel strip

Abstract

To provide a roll peripheral speed control device, roll peripheral speed control method, and method for manufacturing a hot-rolled steel strip capable of suppressing warping from the time before a pre-finishing stage only with a change in operational conditions without additional equipment investment.SOLUTION: A roll peripheral speed control device 10, when rough rolling a slab S using a rough rolling mill 3 which consists of multiple rough rolling stands R1 to Rn including an upstream rough rolling stand Rn-1 and a downstream rough rolling stand Rn capable of performing tandem rolling, controls the peripheral speeds of work rolls 3a, 3b in the upstream rough rolling stand Rn-1 and the downstream rough rolling stand Rn such that the rolling speed of the slab S by the upstream rough rolling stand Rn-1 alone is slower than the rolling speed of the slab S by both of the upstream rough rolling stand Rn-1 and the downstream rough rolling stand Rn after the slab S is bitten by the downstream rough rolling stand Rn.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a roll peripheral speed control device, a roll peripheral speed control method, and a method for manufacturing hot-rolled steel strip, which control the peripheral speed of the work rolls of an upstream and a downstream roughing mill, respectively, when rough-rolling a slab using a plurality of roughing mills, each equipped with an upstream roughing mill and a downstream roughing mill capable of tandem rolling. [Background technology]

[0002] Generally, hot-rolled steel strip is manufactured by heating a slab to a predetermined temperature in a heating furnace, rolling the heated slab to a predetermined thickness in a roughing mill to form a rough bar, then heating the rough bar with heating devices such as edge heaters and bar heaters, and then finishing rolling it in a finishing mill consisting of multiple stands to form a hot-rolled steel strip of a predetermined thickness, and finally cooling this hot-rolled steel strip on a hot table with a cooling device, and then winding it with a coiler.

[0003] In continuous hot rolling processes that produce hot-rolled steel strips, shape defects such as "warping" at the leading edge of the rolled material can occur at the roughing and finishing mill stands. If upward warping occurs at the leading edge of the rolled material, it can come into contact with the equipment inside the rolling mill, causing equipment damage or rendering the hot-rolled steel strip a semi-finished product. In such cases, the rolling process for that cycle must be stopped, resulting in a significant loss of operational productivity.

[0004] Conventional methods for reducing the upward curvature of the leading edge of a hot-rolled steel strip are known, for example, those shown in Patent Documents 1 and 2. The method for manufacturing hot-rolled steel strip shown in Patent Document 1 involves roughly rolling a slab in a roughing mill to produce a rough bar, then roughly correcting the warp of the rough bar with a first warp correction device, and then finishing correcting the warp of the rough bar with a second warp correction device. After that, the rough bar is heated with an induction heating device, and the heated rough bar is then finish-rolled in a finishing mill to produce hot-rolled steel strip.

[0005] This suppresses the warping that occurs at the tip of the rough bar during rough rolling and allows it to be properly straightened before being sent to the finish rolling process. Furthermore, the method for reducing the tip-end curvature of hot-rolled steel sheets in hot finishing rolling, as described in Patent Document 2, involves using a finishing rolling mill consisting of multiple horizontal rolling mills to perform hot finishing rolling of steel sheets. At least one horizontal rolling mill is used preferentially from the front to perform horizontal rolling up to the product sheet thickness, while the remaining horizontal rolling mills on the rear side are set as pass-through stands that do not perform horizontal rolling. The roll gap of these pass-through stands is set to be 1 to 10 mm larger than the product sheet thickness, and the roll peripheral speed is set to be faster than the roll peripheral speed of the last horizontal rolling mill among the front-side horizontal rolling mills that have performed horizontal rolling up to the product sheet thickness, in order to perform hot finishing rolling.

[0006] This reduces the amount of upward curvature of the hot-rolled steel sheet at the exit of the finishing rolling mill, thereby suppressing coiler winding problems and variations in the cooling rate within the steel sheet during water cooling after finishing rolling. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2004-351484 [Patent Document 2] Japanese Patent Publication No. 2015-42410 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the conventional methods for manufacturing hot-rolled steel strips shown in Patent Document 1 and the method for reducing the tip-end curvature of hot-rolled steel sheets in hot finishing rolling shown in Patent Document 2 had the following problems. In other words, in the case of the hot-rolled steel strip manufacturing method shown in Patent Document 1, in addition to the roughing mill, induction heating device, and finishing mill, first and second warping correction devices are required, which presents the problem of high capital investment costs.

[0009] Furthermore, in the case of the method for reducing the tip-end curvature of hot-rolled steel sheets in hot finishing rolling as shown in Patent Document 2, while it is possible to suppress curvature in the horizontal rolling mill downstream of the finishing rolling mill, it is not possible to address curvature in the horizontal rolling mill downstream of the finishing rolling mill, including the roughing mill. Therefore, the present invention has been made to solve these conventional problems, and its objective is to provide a roll peripheral speed control device, a roll peripheral speed control method, and a method for manufacturing hot-rolled steel strip that can suppress warping from before the finishing stage simply by changing the operating conditions without making additional capital investments. [Means for solving the problem]

[0010] To solve the above problems, a roll peripheral speed control device according to one aspect of the present invention controls the peripheral speed of the work rolls of the upstream and downstream rough rolling stands when rough rolling a slab with a rough rolling mill consisting of a plurality of rough rolling stands equipped with an upstream rough rolling stand and a downstream rough rolling stand capable of tandem rolling, and the gist of the device is to control the peripheral speed of the work rolls of the upstream and downstream rough rolling stands so that the rolling speed of the slab by the upstream rough rolling stand alone is slower than the rolling speed of the slab by both the upstream and downstream rough rolling stands after the slab has been engaged with the downstream rough rolling stand.

[0011] Furthermore, another aspect of the present invention relates to a roll peripheral speed control method, which controls the peripheral speed of the work rolls of the upstream and downstream rough rolling stands when rough rolling a slab with a rough rolling mill consisting of a plurality of rough rolling stands equipped with an upstream rough rolling stand and a downstream rough rolling stand capable of tandem rolling, wherein the method controls the peripheral speed of the work rolls of the upstream and downstream rough rolling stands so that the rolling speed of the slab by the upstream rough rolling stand alone is slower than the rolling speed of the slab by both the upstream and downstream rough rolling stands after the slab has been engaged with the downstream rough rolling stand.

[0012] Furthermore, another embodiment of the present invention relates to a method for manufacturing a hot-rolled steel strip, which includes a rough-rolling step in which a slab is roughly rolled using a rough-rolling mill consisting of a plurality of rough-rolling stands equipped with an upstream rough-rolling stand and a downstream rough-rolling stand capable of tandem rolling, and the peripheral speed of the work rolls of the upstream and downstream rough-rolling stands is controlled using the roll peripheral speed control method described above to rough-roll the slab. [Effects of the Invention]

[0013] According to the roll peripheral speed control device, roll peripheral speed control method, and hot-rolled steel strip manufacturing method of the present invention, warping from before the finishing stage can be suppressed simply by changing the operating conditions without requiring additional capital investment. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram of a hot rolling line equipped with a roll peripheral speed control device according to one embodiment of the present invention. [Figure 2] Figure 1 is a flowchart illustrating the processing flow in the roll peripheral speed control device. [Figure 3] This is a schematic diagram illustrating the mechanism of upward curvature generation due to the engagement angle of the steel sheet at the entrance of the rolling mill. [Figure 4]This is a schematic diagram illustrating the mechanism of downward curvature generation due to the engagement angle of the steel sheet at the entrance of the rolling mill. [Figure 5] This schematic diagram illustrates a mechanism that suppresses warping by applying tension to the slab at the moment of engagement by the downstream roughing stand, by making the slab rolling speed using only the upstream roughing stand slower than the slab rolling speed using both the upstream and downstream roughing stands. [Figure 6] This graph compares the relationship between the thickness of the hot-rolled steel strip and the amount of upward curvature at the exit side of the finishing rolling stand F1, comparing the case where the hot-rolled steel strip is manufactured according to the present invention example and the case where it is manufactured according to the comparative example. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below with reference to the drawings. The embodiments shown below are illustrative examples of devices and methods for realizing the technical concept of the present invention, and the technical concept of the present invention is not limited to the following embodiments in terms of the material, shape, structure, arrangement, etc. of the components. Furthermore, drawings are schematic representations. Therefore, it should be noted that the relationship and ratios between thickness and planar dimensions may differ from those in reality, and there may be differences in dimensional relationships and ratios between drawings themselves.

[0016] Figure 1 shows a schematic configuration of a hot rolling line equipped with a roll peripheral speed control device according to one embodiment of the present invention. The hot rolling line 1 shown in Figure 1 comprises a heating furnace 2 for heating a slab S to a predetermined temperature, a rough rolling mill 3 for roughly rolling the heated slab S to a predetermined thickness to form a rough bar B, and a finish rolling mill 4 for finish rolling the roughly rolled rough bar B to form a hot-rolled steel strip SP of a predetermined thickness. The hot rolling line 1 also comprises a cooling device 5 for cooling the hot-rolled steel strip SP that has been finished rolling, and a winding device 7 for winding the cooled hot-rolled steel strip SP via pinch rolls 6.

[0017] That is, the hot-rolled steel strip SP is manufactured through a heating process of heating the slab S to a predetermined temperature in the heating furnace 2, a rough rolling process of roughly rolling the heated slab S to a predetermined thickness by the rough rolling mill 3 to obtain a rough bar B, a finish rolling process of finish rolling the roughly rolled rough bar B by the finish rolling mill 4 to obtain the hot-rolled steel strip SP with a predetermined plate thickness, a cooling process of cooling the hot-rolled steel strip SP by the cooling device 5, and a winding process of winding the cooled hot-rolled steel strip SP by the winding device 7.

[0018] Here, the rough rolling mill 3 includes a plurality (1 to n: n is an arbitrary integer of 2 or more) of rough rolling stands R1 to R n arranged in order from the upstream side to the downstream side in the conveyance direction (rolling direction). And among the plurality of rough rolling stands R1 to R n the two upstream rough rolling stands R n-1 [[ID=??]] n are rough rolling stands with a short distance between both rough rolling stands R n-1 ,R n and capable of tandem rolling. That is, when the tip of the slab S is engaged with the downstream rough rolling stand R n the slab S is also engaged with the upstream rough rolling stand R n-1 and the slab S is rolled by both the upstream rough rolling stand R n-1 and the downstream rough rolling stand R n . And each of the plurality of rough rolling stands R1 to R n includes an upper work roll 3a and a lower work roll 3b for roughly rolling the slab S, and an upper backup roll 3c and a lower backup roll 3d for supporting each of these upper work roll 3a and lower work roll 3b.

[0019] Also, the finish rolling mill 4 includes a plurality (1 to N: N is an arbitrary integer of 2 or more) of finish rolling stands F1 to F N arranged in order from the upstream side to the downstream side in the conveyance direction (rolling direction). And among the plurality of finish rolling stands F1 to F N It seems there is an unclear tag "??" in the original text. Please check and correct it if possible for a more accurate translation.Each of these includes an upper work roll 4a and a lower work roll 4b for finish rolling the rough bar B, and an upper backup roll 4c and a lower backup roll 4d that support the upper work roll 4a and the lower work roll 4b, respectively.

[0020] Furthermore, in the hot rolling line 1, there are multiple rough rolling stands R1~R n When rough rolling the slab S with the rough rolling mill 3 consisting of the following, the two downstream rough rolling stands R n-1 and the downstream roughing stand R n Multiple roughing stands R1~R in the roughing mill 3, including the peripheral speed of each of the upper work rolls 3a and lower work rolls 3b. n A roll speed control device 10 is provided to control the total peripheral speed of each of the upper work rolls 3a and lower work rolls 3b. The detailed operation of the roll speed control device 10 will be described later.

[0021] A higher-level computer 11 is connected to the roll peripheral speed control device 10. The higher-level computer 11 determines the size of the hot-rolled steel strip SP to be manufactured, such as the plate thickness and plate width, the steel type of the hot-rolled steel strip SP, and the rough rolling stands R1 to R determined from the size and steel type of the hot-rolled steel strip SP to be manufactured. n The roll peripheral speed settings for the upper work roll 3a and lower work roll 3b, and each rough rolling stand R1~R n Information such as the diameters of the upper work roll 3a and the lower work roll 3b is sent to the roll peripheral speed control device 10.

[0022] Here, in the continuous hot rolling process for manufacturing such hot-rolled steel strip SP, each of the roughing stands R1 to R of the roughing mill 3 n , each finishing rolling stand F1~F of the finishing rolling mill 4 N This can cause "warping" at the leading edge of the rolled material (slab S, rough bar B). If upward or downward warping occurs at the leading edge of the rolled material, it can come into contact with equipment inside the rolling mill, causing equipment damage or rendering the hot-rolled steel strip a semi-finished product. In such cases, the rolling process for that cycle must be stopped, resulting in a significant loss of operational productivity.

[0023] The mechanism by which "curvature" occurs at the leading edge of the rolled material will be explained with reference to Figures 3 and 4. Figure 3 shows the mechanism of upward curvature generation due to the gripping angle of the steel sheet on the rolling mill side, and Figure 4 shows the mechanism of downward curvature generation due to the gripping angle of the steel sheet on the rolling mill side. As shown in Figure 3, when a steel sheet SS, which is the material to be rolled, bites the roll bites of the upper work roll 21a and lower work roll 21b in a rolling mill (regardless of whether it is a roughing mill or a finishing mill) from below (when the steel sheet SS bites diagonally upward at an angle θ1 with respect to the rolling direction), the steel sheet SS bends downward near the roll bites. As the steel sheet SS bends downward, a longitudinal tensile stress 22 acts on the upper surface of the steel sheet SS, and a longitudinal compressive stress 23 acts on the lower surface of the steel sheet SS. Due to the stress distribution in the thickness direction within the steel sheet SS near the roll bite entry side, the leading ratio during rolling decreases and the leading speed decreases on the upper surface of the steel sheet SS where the tensile stress 22 acts. Conversely, the leading ratio during rolling increases and the leading speed increases on the lower surface of the steel sheet SS where the compressive stress 23 acts. Because the advance speed on the upper side of the steel sheet SS is slow and the advance speed on the lower side of the steel sheet SS is fast, upward curvature occurs in the steel sheet SS after rolling.

[0024] On the other hand, as shown in Figure 4, when the steel sheet SS, which is the material to be rolled, bites the roll bites of the upper work roll 21a and lower work roll 21b in the rolling mill from above (when the steel sheet SS bites diagonally downward at an angle of θ2 with respect to the rolling direction), the steel sheet SS bends upward near the roll bites. Because the steel sheet SS bends upward, a longitudinal tensile stress 22 acts on the lower surface of the steel sheet SS, and a longitudinal compressive stress 23 acts on the upper surface of the steel sheet SS. Due to the stress distribution in the thickness direction within the steel sheet SS near the roll bite entry side, the advance rate during rolling decreases and the advance speed decreases on the lower surface of the steel sheet SS where the tensile stress 22 acts. Conversely, the advance rate during rolling increases and the advance speed increases on the upper surface of the steel sheet SS where the compressive stress 23 acts. Because the advance speed on the lower surface of the steel sheet SS is slow and the advance speed on the upper surface of the steel sheet SS is fast, downward curvature occurs in the steel sheet SS after rolling.

[0025] Here, in order to stabilize the bite of the rolls, it is necessary to apply appropriate tension to the steel plate SS at the moment of bite. If tension is applied to the steel plate SS, buckling will not occur when the steel plate SS is bitten into the upper work roll 21a and the lower work roll 21b, the bite of the rolls will stabilize, and upward or downward curvature of the steel plate SS after rolling can be suppressed.

[0026] As a method for applying tension to the slab S as the material to be rolled, as shown in Figure 5, the upstream rough rolling stand R capable of tandem rolling is used. n-1 and the downstream roughing stand R n In this case, the upstream roughing stand R n-1 The rolling speed of the slab S by chisel is controlled by the upstream rough rolling stand R n-1 and the downstream roughing stand R n The rolling speed of the slab S by both sides is slower than that of the downstream rough rolling stand R n One method is to apply tension to the slab S at the moment of engagement. Upstream rough rolling stand R n-1 The rolling speed of the slab S by chisel is determined by the upstream rough rolling stand R n-1 and the downstream roughing stand R n If the rolling speed of the slab S by both is the same, then the downstream rough rolling stand R n Tension cannot be applied to the slab S at the moment of engagement. As a result, as shown on the left side of Figure 5, buckling occurs when the slab S is engaged with the upper work roll 3a and the lower work roll 3b, the engagement of the roll bite is unstable, and upward or downward curvature occurs in the slab S (rough bar B) after rolling.

[0027] Therefore, in this embodiment, the aforementioned roll peripheral speed control device 10 controls the upstream roughing stand R n-1 The rolling speed of slab S due to the sole is determined by the rough rolling stand R downstream of slab S. n The rough rolling stand R on the upstream side after being caught n-1 and the downstream roughing stand R nThe rough rolling stand R on the upstream side is set so that it is slower than the rolling speed of the slab S due to both of them. n-1 and the downstream roughing stand R n The peripheral speed of the upper work roll 3a and lower work roll 3b are controlled accordingly. This allows the roll peripheral speed control device 10 to suppress warping from before the finishing stage simply by changing the operating conditions, without requiring any additional capital investment.

[0028] Previously, the roll peripheral speed control device 10 controlled all roughing stands R1~R in the roughing mill 3. n The peripheral speeds of the upper work roll 3a and lower work roll 3b are controlled by setting them to roll peripheral speed setting values ​​determined by the size and type of hot-rolled steel strip SP being manufactured. Therefore, previously, the upstream roughing stand R n-1 The rolling speed of slab S due to the sole is determined by the rough rolling stand R downstream of slab S. n The rough rolling stand R on the upstream side after being caught n-1 and the downstream roughing stand R n The rough rolling stand R on the upstream side is set so that the rolling speed of the slab S is the same as that of both sides. n-1 and the downstream roughing stand R n The peripheral speed of the upper work roll 3a and lower work roll 3b are controlled accordingly.

[0029] On the other hand, in this embodiment, the roll peripheral speed control device 10 controls the upstream rough rolling stands R1~R n-2 The peripheral speeds of the upper work roll 3a and lower work roll 3b are controlled to the same roll peripheral speed setting values ​​as before, which are determined by the size and type of hot-rolled steel strip SP being rolled. Meanwhile, the upstream rough rolling stand R, which is capable of tandem rolling... n-1 and the downstream roughing stand R n Regarding this, the roll peripheral speed control device 10 controls the leading edge of the slab S to the upstream roughing stand R n-1 Before it gets caught, the upstream rough rolling stand R n-1The peripheral speeds of the upper work roll 3a and lower work roll 3b are set to a value 1-5% slower than the set value of the roll peripheral speed, and the downstream roughing stand R n The peripheral speeds of the upper work roll 3a and lower work roll 3b are set to the roll peripheral speed setting value. The roll peripheral speed control device 10 then controls the leading edge of the slab S to the upstream roughing stand R n-1 After being caught in, the downstream rough rolling stand R n When caught in the upstream rough rolling stand R n-1 The peripheral speeds of the upper work roll 3a and lower work roll 3b are set (returned) to the roll peripheral speed setting value, and the downstream roughing stand R n The upper work roll 3a and lower work roll 3b are maintained at the roll speed setting value. As a result, the roll speed control device 10 controls the upstream roughing stand R n-1 The rolling speed of slab S due to the sole is determined by the rough rolling stand R downstream of slab S. n The rough rolling stand R on the upstream side after being caught n-1 and the downstream roughing stand R n The rolling speed of the slab S is controlled to be 1-5% slower than the rolling speed of both slabs.

[0030] Here, the tip of the slab S is at the upstream roughing stand R. n-1 Before it gets caught, the upstream rough rolling stand R n-1 The reason for setting the peripheral speeds of the upper work roll 3a and lower work roll 3b to a value 1-5% slower than the set roll peripheral speed will be explained. Upstream roughing stand R n-1 When the peripheral speed of the upper work roll 3a and lower work roll 3b is set to a value slower than 5% slower than the set roll peripheral speed, the leading edge of the slab S moves downstream to the rough rolling stand R n The moment it gets caught in the rough rolling stand R n There is a risk that the load on it will become too large. Also, the downstream rough rolling stand R n This may result in excessive tensile force on the slab S, potentially leading to a poor width for the rough bar B after rough rolling.

[0031] Meanwhile, the upstream roughing stand Rn-1 If the peripheral speed of the upper work roll 3a and the lower work roll 3b is set to a value faster than 1% slower than the set roll peripheral speed, the leading edge of the slab S will be at the downstream roughing stand R n If the appropriate tension cannot be applied to the slab S at the moment of engagement, the engagement of the roll bite will not be stable, and there is a risk that the tip of the slab S may warp. For this reason, the tip of the slab S may warp when it is on the upstream rough rolling stand R. n-1 Before it gets caught, the upstream rough rolling stand R n-1 The peripheral speeds of the upper work roll 3a and lower work roll 3b are set to a value 1 to 5% slower than the set roll peripheral speed value. It is more preferable to set these peripheral speeds to a value 2.5% to 3.5% slower than the set roll peripheral speed value.

[0032] Here, if the rolling speed of the slab S is SV (mpm), the peripheral speed of the upper work roll 3a and the lower work roll 3b is RV (mpm), the rotational speed of the upper work roll 3a and the lower work roll 3b is N (rpm), and the diameter of the upper work roll 3a and the lower work roll 3b is D (mm), then the following equation holds. SV = RV = π·D·N / 1000 The roll peripheral speed control device 10 receives information on the roll peripheral speed setting value (RV) and the diameter (D) of each upper work roll 3a and lower work roll 3b from the higher-level computer 11, calculates the rotational speed (N) of each upper work roll 3a and lower work roll 3b based on the above formula, and controls the rotational speed of each upper work roll 3a and lower work roll 3b using the calculated rotational speed (N). In addition, the upstream roughing stand R n-1When the peripheral speeds of the upper work roll 3a and lower work roll 3b are set to a value 1 to 5% slower than the set roll peripheral speed value, the roll peripheral speed control device 10 calculates a value 1 to 5% slower than the set roll peripheral speed value (RV) obtained from the higher-level computer 11. Based on this calculated slower value and the diameter (D) information of each upper work roll 3a and lower work roll 3b, the device calculates the rotational speed (N) of each upper work roll 3a and lower work roll 3b based on the above formula, and controls the rotational speed of each upper work roll 3a and lower work roll 3b using the calculated rotational speed (N).

[0033] In this embodiment, the aforementioned tandem rolling-capable upstream roughing stand R n-1 and the downstream roughing stand R n The peripheral speed control of the upper work roll 3a and lower work roll 3b is performed when the set thickness of the hot-rolled steel strip SP being manufactured is 15 mm or more. This is because warping is more likely to occur at the leading edge when the set thickness of the hot-rolled steel strip SP being manufactured is 15 mm or more.

[0034] Furthermore, the roll peripheral speed control device 10 constantly monitors the position of the slab S in the transport direction, that is, the position of the leading edge of the slab S in the transport direction, using tracking information from the transport rollers (not shown) in the hot rolling line 1. Next, the processing flow in the roll peripheral speed control device 10 will be explained with reference to Figure 2. Figure 2 is a flowchart illustrating the processing flow in the roll peripheral speed control device.

[0035] First, in step S1, the roll peripheral speed control device 10 determines whether the set thickness of the hot-rolled steel strip SP to be manufactured is 15 mm or more, based on information regarding the size of the hot-rolled steel strip SP from the higher-level computer 11. The reason for this is that, as mentioned above, when the set thickness of the hot-rolled steel strip SP to be manufactured is 15 mm or more, warping is likely to occur at the leading edge, and in this case, the roll peripheral speed control method according to this embodiment is particularly effective.

[0036] If the result of step S1 is YES (the set thickness of the hot-rolled steel strip SP is 15 mm or more), proceed to step S2. If the result of step S1 is NO (the set thickness of the hot-rolled steel strip SP is less than 15 mm), proceed to step S3. In step S3, the roll peripheral speed control device 10 controls all rough rolling stands R1~R n The peripheral speeds of the upper work roll 3a and lower work roll 3b are set to the roll peripheral speed setting values. The roll peripheral speed setting values ​​are input from the host computer 11 to the roll peripheral speed control device 10 and, as mentioned above, are constants determined by the size and type of hot-rolled steel strip SP to be manufactured. At this time, the roll peripheral speed setting value RV (mpm) and the rough rolling stand R1~R from the host computer 11 are input. n Based on the information of the diameter D (mm) of the upper work roll 3a and the lower work roll 3b, the roll peripheral speed control device 10 calculates the RV = π·D·N / 1000 for each rough rolling stand R1~R n The rotational speed N (rpm) of the upper work roll 3a and lower work roll 3b is calculated, and the calculated rotational speed N (rpm) is then applied to the rough rolling stand R1~R n This will be used as the control value for the rotational speed of the upper work roll 3a and the lower work roll 3b.

[0037] Then, once step S3 is completed, the processing in the roll peripheral speed control device 10 is terminated. On the other hand, in step S2, the roll peripheral speed control device 10 controls the rough rolling stand R1~R n-2 The peripheral speeds of the upper work roll 3a and lower work roll 3b are set to the roll peripheral speed setting value. The roll peripheral speed control device 10 also controls the upstream rough rolling stand R, which is capable of tandem rolling. n-1 and the downstream roughing stand R n Regarding this, the tip of the slab S is on the upstream roughing stand R n-1 Before it gets caught, the upstream rough rolling stand R n-1 The peripheral speeds of the upper work roll 3a and lower work roll 3b are set to a value 1-5% slower than the set value of the roll peripheral speed, and the downstream roughing stand R n Set the peripheral speeds of the upper work roll 3a and the lower work roll 3b to the set roll peripheral speed values.

[0038] The roll peripheral speed control device 10 calculates the peripheral speeds of the upper work roll 3a and the lower work roll 3b of the upstream rough rolling stand R n-1 Based on the roll peripheral speed set value RV (mpm) obtained from the host computer 11, the diameters D (mm) of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R from the host computer 11, and the information of the reduction rate α, the rotation speed N (rpm) of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R is calculated from the formula (1 - α)RV = π·D·N / 1000. Then, the calculated rotation speed N (rpm) is used as the control value of the rotation speeds of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R n-1 Here, α is the reduction rate as described above, and in the case of this embodiment, it is a numerical value between 1% and 5%. Also, for the peripheral speeds of the upper work roll 3a and the lower work roll 3b of the downstream rough rolling stand R n-1 the roll peripheral speed control device 10 calculates the rotation speed N (rpm) of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R from the formula RV = π·D·N / 1000 based on the roll peripheral speed set value RV (mpm) obtained from the host computer 11 and the information of the diameters D (mm) of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R. Then, the calculated rotation speed N (rpm) is used as the control value of the rotation speeds of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R n-1 Here, α is the reduction rate as described above, and in the case of this embodiment, it is a numerical value between 1% and 5%. Also, for the peripheral speeds of the upper work roll 3a and the lower work roll 3b of the downstream rough rolling stand R n the roll peripheral speed control device 10 calculates the rotation speed N (rpm) of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R from the formula RV = π·D·N / 1000 based on the roll peripheral speed set value RV (mpm) obtained from the host computer 11 and the information of the diameters D (mm) of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R. Then, the calculated rotation speed N (rpm) is used as the control value of the rotation speeds of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R n Based on the roll peripheral speed set value RV (mpm) obtained from the host computer 11, the diameters D (mm) of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R, and the information of the reduction rate α, the rotation speed N (rpm) of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R is calculated from the formula (1 - α)RV = π·D·N / 1000. Then, the calculated rotation speed N (rpm) is used as the control value of the rotation speeds of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R n Here, α is the reduction rate as described above, and in the case of this embodiment, it is a numerical value between 1% and 5%. Also, for the peripheral speeds of the upper work roll 3a and the lower work roll 3b of the downstream rough rolling stand R n the roll peripheral speed control device 10 calculates the rotation speed N (rpm) of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R from the formula RV = π·D·N / 1000 based on the roll peripheral speed set value RV (mpm) obtained from the host computer 11 and the information of the diameters D (mm) of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R. Then, the calculated rotation speed N (rpm) is used as the control value of the rotation speeds of the upper work roll 3a and the lower work roll 3b of the rough rolling stand R

[0039] Next, in step S4, the roll peripheral speed control device 10 determines whether the tip of the slab S has been bitten by the downstream rough rolling stand R n At this time, the roll peripheral speed control device 10 grasps the position of the tip of the slab S based on the tracking information from the conveying roller (not shown) on the hot rolling line 1 If the determination result in step S4 is YES (the tip of the slab S has reached the downstream rough rolling stand R nWhen it is bitten into, it proceeds to step S5. When the determination result is NO (when the tip of the slab S is not bitten into the downstream rough rolling stand R n ), the determination in step S4 is repeated.

[0040] In step S5, when the tip of the slab S is bitten into the downstream rough rolling stand R n , the roll peripheral speed controller 10 sets the peripheral speeds of the upper work roll 3a and the lower work roll 3b of the upstream rough rolling stand R n-1 to the roll peripheral speed set value, and maintains the peripheral speeds of the upper work roll 3a and the lower work roll 3b of the downstream rough rolling stand R n at the roll peripheral speed set value.

[0041] Then, when step S3 is completed, the processing in the roll peripheral speed controller 10 is terminated. Thus, according to the roll peripheral speed controller 10 and the roll peripheral speed control method according to this embodiment, when rough rolling the slab S by the rough rolling mill 3 including the upstream rough rolling stand R n-1 and the downstream rough rolling stand R n of a plurality of rough rolling stands R1 to R n , the rolling speed of the slab S by only the upstream rough rolling stand R n-1 is slower than the rolling speed of the slab S by both the upstream rough rolling stand R n and the downstream rough rolling stand R n-1 after the slab S is bitten into the downstream rough rolling stand R n . The peripheral speeds of the upper work roll 3a and the lower work roll 3b of each of the upstream rough rolling stand R n-1 and the downstream rough rolling stand R n are controlled.

[0042] Thereby, tension can be applied to the slab S at the moment of biting by the downstream rough rolling stand R n , and the slab S is the downstream rough rolling stand R nThis prevents buckling from occurring when the roll bite engages, stabilizes the bite of the roll bite, and prevents upward or downward warping of the slab S (rough bar B) after rolling. Here, with the existing roll peripheral speed control device 10, warping from before the finishing stage can be suppressed simply by changing the operating conditions without requiring additional capital investment.

[0043] Furthermore, according to the roll peripheral speed control device 10 and roll peripheral speed control method of this embodiment, the leading edge of the slab S is located on the upstream roughing stand R. n-1 Before it gets caught, the upstream rough rolling stand R n-1 The peripheral speeds of the upper work roll 3a and lower work roll 3b are set to a value 1-5% slower than the set value of the roll peripheral speed, and the downstream roughing stand R n The peripheral speeds of the upper work roll 3a and lower work roll 3b are set to the roll peripheral speed setting value. Then, the leading edge of the slab S is positioned downstream of the rough rolling stand R. n When caught in the upstream rough rolling stand R n-1 The peripheral speeds of the upper work roll 3a and lower work roll 3b are set to the roll peripheral speed setting value, and the downstream rough rolling stand R n Maintain the peripheral speeds of the upper work roll 3a and the lower work roll 3b at the set roll peripheral speed values.

[0044] This results in the upstream roughing stand R n-1 The rolling speed of slab S by only is determined by the rough rolling stand R downstream of slab S. n The rough rolling stand R on the upstream side after being caught n-1 and the downstream roughing stand R n The rolling speed of the slab S can be controlled to be 1-5% slower than the rolling speed of both methods. Furthermore, according to the roll peripheral speed control device 10 and roll peripheral speed control method of this embodiment, when the set thickness of the hot-rolled steel strip SP to be manufactured is 15 mm or more, the upstream rough rolling stand R n-1 The rolling speed of slab S due to the sole is determined by the rough rolling stand R downstream of slab S. n The rough rolling stand R on the upstream side after being caught n-1and the downstream roughing stand R n The rough rolling stand R on the upstream side is set so that it is slower than the rolling speed of the slab S due to both of them. n-1 and the downstream roughing stand R n The peripheral speed of the upper work roll 3a and lower work roll 3b are controlled.

[0045] As a result, for hot-rolled steel strip SP with a set thickness of 15 mm or more, which is prone to upward curvature at the tip, the existing roll peripheral speed control device 10 can appropriately suppress curvature from before the finishing stage simply by changing the operating conditions, without requiring additional capital investment. Furthermore, according to the manufacturing method of hot-rolled steel strip according to this embodiment, the upstream rough rolling stand R capable of tandem rolling is also available. n-1 and the downstream roughing stand R n Multiple rough rolling stands R1~R n When rough rolling the slab S with the rough rolling mill 3 consisting of the above, the aforementioned roll peripheral speed control method is used to control the upstream rough rolling stand R n-1 and the downstream roughing stand R n This process includes a rough rolling step in which the slab S is roughly rolled by controlling the peripheral speed of the upper work roll 3a and lower work roll 3b.

[0046] This makes it possible to manufacture hot-rolled steel strip SP without compromising operational productivity, as it is not damaged by contact with equipment inside the rolling mill due to warping. Although this embodiment has been described above, the present invention is not limited thereto and can be modified and improved in various ways. For example, the roll peripheral speed control device 10 controls all rough rolling stands R1~R n It is not always necessary to control the peripheral speed of the upper work roll 3a and the lower work roll 3b, and a rough rolling stand R capable of tandem rolling R n-1 , R n Only the peripheral speed of the upper work roll 3a and lower work roll 3b is controlled, and the other rough rolling stands R1~R n-2The peripheral speeds of the upper work roll 3a and the lower work roll 3b may be controlled by a separate roll peripheral speed control device.

[0047] In addition, multiple rough rolling stands R1~R n In this configuration, the upstream roughing stand and the downstream roughing stand capable of tandem rolling are R n-1 and R n Rather, rough rolling stand R k and R k+1 When k is any integer from 1 to n-1, the roll peripheral speed control device 10 controls the upstream rough rolling stand R k The rolling speed of slab S due to the sole is determined by the rough rolling stand R downstream of slab S. k+1 The rough rolling stand R on the upstream side after being caught k and the downstream roughing stand R k+1 The rough rolling stand R on the upstream side is set so that it is slower than the rolling speed of the slab S due to both of them. k and the downstream roughing stand R k+1 The peripheral speed of the upper work roll 3a and the lower work roll 3b should be controlled accordingly.

[0048] Furthermore, the control of the roll peripheral speed by the roll peripheral speed control device 10 of the present invention can be applied not only when the set thickness of the hot-rolled steel strip SP to be manufactured is 15 mm or more, but also when the set thickness of the hot-rolled steel strip SP is less than 15 mm. [Examples]

[0049] To verify the effects of the present invention, hot-rolled steel strips SP were manufactured by controlling the peripheral speed of the upper work roll 3a and lower work roll 3b in the rough rolling stands R1 to R5 using the respective roll peripheral speed control devices of the comparative example and the present invention example. The amount of upward curvature of the target material at the exit side of the finishing rolling stand F1 in the finishing rolling mill 4 was measured. The thicknesses of the manufactured hot-rolled steel strips SP were set to 15 mm, 18 mm, and 25 mm, which are 15 mm or more and are prone to upward curvature.

[0050] In the comparative example's roll peripheral speed control device, the peripheral speeds of all upper work rolls 3a and lower work rolls 3b of each of the multiple roughing stands R1 to R5 in the roughing mill 3 were controlled by setting them to a roll peripheral speed setting value determined by the size and type of hot-rolled steel strip SP being manufactured. In contrast, the roll peripheral speed control device 10 of the present invention controls the peripheral speeds of the upper work rolls 3a and lower work rolls 3b of each of the roughing stands R1 to R3 by setting them to a roll peripheral speed setting value determined by the size and type of hot-rolled steel strip SP to be manufactured. On the other hand, for the upstream roughing stand R4 and the downstream roughing stand R5, which are capable of tandem rolling, the roll peripheral speed control device 10 sets the peripheral speeds of the upper work rolls 3a and lower work rolls 3b of the upstream roughing stand R4 to a value 3% slower than the roll peripheral speed setting value before the leading edge of the slab S is engaged with the upstream roughing stand R4, and sets the peripheral speeds of the upper work rolls 3a and lower work rolls 3b of the downstream roughing stand R5 to the roll peripheral speed setting value. Then, when the leading edge of the slab S was engaged with the downstream roughing stand R5, the roll peripheral speed control device 10 set (returned) the peripheral speeds of the upper work roll 3a and lower work roll 3b of the upstream roughing stand R4 to the roll peripheral speed setting value, and maintained the peripheral speeds of the upper work roll 3a and lower work roll 3b of the downstream roughing stand R5 at the roll peripheral speed setting value.

[0051] Figure 6 shows the measurement results of the amount of upward curvature of the target material at the exit side of the finishing rolling stand F1 in the finishing rolling mill 4, for each plate thickness of the manufactured hot-rolled steel strip SP of 15 mm, 18 mm, and 25 mm. As shown in Figure 6, when hot-rolled steel strip SP was manufactured using the roll peripheral speed control device of the present invention, it was confirmed that the amount of upward curvature of the target material at the exit of the finishing rolling stand F1 was reduced compared to when hot-rolled steel strip SP was manufactured using the roll peripheral speed control device of the comparative example, regardless of whether the plate thickness of the hot-rolled steel strip SP was 15 mm, 18 mm, or 25 mm. [Explanation of Symbols]

[0052] 1. Hot rolling line 2 Furnace 3 Roughing mill 3a Upper work roll 3b Lower work roll 3c upper backup role 3D Under Backup Roll 4. Finishing Rolling Mill 4a Upper work roll 4b Lower work roll 4c upper backup role 4d Lower Backup Roll 5 Cooling device 6. Pinch roll 7 Winding device 10 Roll peripheral speed control device 11 Upper computer 21a Upper work roll 21b Lower work roll 22 Tensile stress 23 Compressive stress B Coarse bar F1~F N Finishing rolling stand R1~R n Rough rolling stand S Slab SP hot rolled steel strip SS steel plate

Claims

1. A rough rolling mill for rough rolling a heated slab to produce a rough bar, comprising a rough rolling mill consisting of a plurality of rough rolling stands, each having an upstream rough rolling stand and a downstream rough rolling stand capable of tandem rolling, and a finish rolling mill for finish rolling the roughly rolled rough bar to produce a hot-rolled steel strip, wherein when rough rolling a slab with the rough rolling mill, a roll peripheral speed control device controls the peripheral speed of the work rolls of the upstream rough rolling stand and the downstream rough rolling stand, The peripheral speeds of the work rolls of the upstream and downstream rough rolling stands are controlled such that the rolling speed of the slab by the upstream rough rolling stand alone is slower than the rolling speed of the slab by both the upstream and downstream rough rolling stands after the slab has been engaged with the downstream rough rolling stand. A roll peripheral speed control device characterized by setting the peripheral speed of the work rolls of the upstream roughing stand to a value 1 to 5% slower than the set roll peripheral speed value and setting the peripheral speed of the work rolls of the downstream roughing stand to the set roll peripheral speed value before the leading edge of the slab is engaged with the upstream roughing stand, and setting the peripheral speed of the work rolls of the upstream roughing stand to the set roll peripheral speed value and maintaining the peripheral speed of the work rolls of the downstream roughing stand at the set roll peripheral speed value when the leading edge of the slab is engaged with the downstream roughing stand.

2. The roll peripheral speed control device according to claim 1, characterized in that, when the set thickness of the hot-rolled steel strip to be manufactured is 15 mm or more, the rolling speed of the slab by the upstream rough rolling stand alone is slower than the rolling speed of the slab by both the upstream and downstream rough rolling stands after the slab has been engaged with the downstream rough rolling stand, by controlling the peripheral speed of the work rolls of the respective upstream and downstream rough rolling stands.

3. A rough rolling mill for rough rolling a heated slab into a rough bar, comprising a rough rolling mill consisting of a plurality of rough rolling stands, each having an upstream rough rolling stand and a downstream rough rolling stand capable of tandem rolling, and a finish rolling mill for finish rolling the roughly rolled rough bar into a hot-rolled steel strip, wherein when rough rolling a slab with the rough rolling mill, a roll peripheral speed control method for controlling the peripheral speed of the work rolls of the upstream rough rolling stand and the downstream rough rolling stand, The peripheral speeds of the work rolls of the upstream and downstream rough rolling stands are controlled such that the rolling speed of the slab by the upstream rough rolling stand alone is slower than the rolling speed of the slab by both the upstream and downstream rough rolling stands after the slab has been engaged with the downstream rough rolling stand. A roll speed control method characterized by setting the peripheral speed of the work rolls of the upstream roughing stand to a value 1 to 5% slower than the set roll peripheral speed value before the leading edge of the slab is engaged with the upstream roughing stand, and setting the peripheral speed of the work rolls of the downstream roughing stand to the set roll peripheral speed value, and when the leading edge of the slab is engaged with the downstream roughing stand, setting the peripheral speed of the work rolls of the upstream roughing stand to the set roll peripheral speed value and maintaining the peripheral speed of the work rolls of the downstream roughing stand at the set roll peripheral speed value.

4. The roll peripheral speed control method according to claim 3, characterized in that, when the set thickness of the hot-rolled steel strip to be manufactured is 15 mm or more, the rolling speed of the slab by the upstream rough rolling stand alone is slower than the rolling speed of the slab by both the upstream and downstream rough rolling stands after the slab has been engaged with the downstream rough rolling stand, by controlling the peripheral speed of the work rolls of the respective upstream and downstream rough rolling stands.

5. A method for manufacturing a hot-rolled steel strip, characterized in that, when rough-rolling a slab using a rough-rolling mill comprising a plurality of rough-rolling stands equipped with an upstream rough-rolling stand and a downstream rough-rolling stand capable of tandem rolling, the rough-rolling step includes controlling the peripheral speed of the work rolls of the upstream rough-rolling stand and the downstream rough-rolling stand using the roll peripheral speed control method described in claim 3 or 4 to rough-roll the slab.

Images