Cold rolling mill, cold rolling method, and steel plate manufacturing method

Abstract

To provide: a cold rolling mill that can suppress vibration during cold rolling without causing production losses by imparting roughness to a surface of an intermediate roll constituting a stand; a cold rolling method; and a steel plate manufacturing method.SOLUTION: A cold rolling mill 1 has a plurality of stands 11 to 15 for cold-rolling a rolling object material S. At least one stand 15 of the plurality of stands 11 to 15 comprises: a pair of upper and lower work rolls 2 for cold-rolling the rolling object material S; a pair of upper and lower intermediate rolls 3 which supports the pair of upper and lower work rolls 2 respectively from a vertical direction; and a pair of upper and lower back-up rolls 4 which supports the pair of upper and lower intermediate rolls 3 respectively from the vertical direction. Surface roughness Ra of each of the pair of upper and lower intermediate rolls 3 is 1.1 μm or more and 1.5 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cold rolling mill, a cold rolling method, and a method for manufacturing a steel sheet, which are capable of suppressing vibration of a stand during cold rolling of a metal strip. [Background technology]

[0002] In cold rolling mills used in tandem cold rolling lines, when cold rolling a metal strip, if the rolling speed is relatively high, vibrations called chattering occur in the stands of the cold rolling mill, which may have a negative impact on the quality of the cold-rolled metal strip.A common approach to this chattering is to install a sensor to detect vibrations in the stands to monitor the vibration state of the stands, and to perform cold rolling by slowing down the rolling speed to a speed range where vibrations do not occur.

[0003] However, this method reduces production efficiency, and therefore many proposals have been made to prevent stand vibration. For example, the vibration prevention device for a rolling mill shown in Patent Document 1 includes an elastic beam attached between two chocks or two pressure tables of a backup roll of a rolling mill that rolls a metal strip, an added mass mounted on the beam, and a damper that damps the movement of the added mass.

[0004] According to the vibration prevention device for a rolling mill shown in Patent Document 1, vibration of the rolling mill can be effectively suppressed with a compact added mass (vibration-damping weight). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-267110 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional vibration prevention device for a rolling mill shown in Patent Document 1 has the following problems. That is, in the case of the vibration prevention device for a rolling mill shown in Patent Document 1, it is necessary to install the beams, added mass, and dampers in the rolling mill (stand) other than the work rolls and backup rolls that roll the metal strip. For this reason, it is necessary to stop the line to install these members, which poses a problem of production loss.

[0007] Therefore, the present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a cold rolling mill, a cold rolling method, and a method for manufacturing a steel sheet, which are capable of suppressing vibration during cold rolling without incurring production loss by imparting roughness to the surfaces of intermediate rolls that constitute a stand. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, one aspect of the present invention provides a cold rolling mill having a plurality of stands for cold rolling a material to be rolled, wherein at least one stand of the plurality of stands is provided with a pair of upper and lower work rolls for cold rolling the material to be rolled, a pair of upper and lower intermediate rolls for supporting the pair of upper and lower work rolls from above and below, respectively, and a pair of upper and lower backup rolls for supporting the pair of upper and lower intermediate rolls from above and below, respectively, and wherein the surface roughness Ra of each of the pair of upper and lower intermediate rolls is 1.1 μm or more and 1.5 μm or less.

[0009] A cold rolling method according to another aspect of the present invention is characterized in that a material to be rolled is cold rolled using the above-mentioned cold rolling mill. A method for producing a steel sheet according to another aspect of the present invention is summarized as including a step of cold rolling a steel sheet as a material to be rolled using the above-described cold rolling method. [Effects of the Invention]

[0010] According to the cold rolling mill, cold rolling method, and steel sheet manufacturing method of the present invention, by imparting roughness to the surfaces of the intermediate rolls that constitute the stands, it is possible to suppress vibration during cold rolling without incurring production loss. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a cold rolling mill according to an embodiment of the present invention. [Figure 2] This is a graph comparing the amount of intermediate roll chance processing when the material to be rolled is cold rolled in a stand using an intermediate roll of an example of the present invention with the amount of intermediate roll chance processing when the material to be rolled is cold rolled in a stand using an intermediate roll of a comparative example. [Figure 3] FIG. 2 is a diagram showing the surface condition of the intermediate roll of the comparative example after the intermediate roll of the comparative example has been used. [Figure 4] FIG. 2 is a view showing the surface condition of an intermediate roll of an example of the present invention after the intermediate roll of the example of the present invention has been used. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments shown below are examples of devices and methods for embodying 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 materials, shapes, structures, arrangements, etc. of the components.

[0013] In addition, the drawings are schematic, and therefore it should be noted that the relationship between thickness and planar dimensions, ratios, etc. may differ from the actual relationship, and the drawings may also contain parts where the relationship and ratio of dimensions differ from each other.

[0014] FIG. 1 shows a schematic configuration of a cold rolling mill according to one embodiment of the present invention. A cold rolling mill 1 shown in Fig. 1 cold rolls a steel sheet S as a material to be rolled. The steel sheet S is cold rolled by the cold rolling mill 1 while being transported from an unillustrated pickling line through an entry looper from upstream to downstream, and is then wound up by an unillustrated winding device.

[0015] The cold rolling mill 1 has a plurality of stands 11 to 15 (five in this embodiment) along the conveying direction of the steel sheet S (the direction indicated by the arrow in FIG. 2). The stands are configured as, from the upstream side in the conveying direction of the steel sheet S, a first stand 11 which is the first stand, a second stand 12 which is the second stand arranged downstream of the first stand 11, a third stand 13 which is the third stand arranged downstream of the second stand 12, a fourth stand 14 which is the fourth stand arranged downstream of the third stand 13, and a fifth stand 15 which is the fifth stand arranged downstream of the fourth stand 14. The number of stands is not limited to five, and may be any number as long as it is plural.

[0016] Here, the first stand 11, the second stand 12, the third stand 13 and the fourth stand 14 are configured as a four-high rolling mill, and each is equipped with a pair of upper and lower work rolls 2 for cold rolling the steel sheet S, and a pair of upper and lower backup rolls 4 for supporting the pair of upper and lower work rolls 2 from above and below.

[0017] On the other hand, the fifth stand 15 is composed of a six-high rolling mill and is equipped with a pair of upper and lower work rolls 2 for cold rolling the steel sheet S, a pair of upper and lower intermediate rolls 3 that respectively support the pair of upper and lower work rolls 2 from above and below, and a pair of upper and lower backup rolls 4 that respectively support the pair of upper and lower intermediate rolls 3 from above and below.

[0018] Here, the vibration (chattering) of the intermediate rolls 3 was considered, focusing on the fifth stand 15 of the six-high rolling mill.

[0019] The surface roughness Ra of the intermediate rolls 3 (a pair of upper and lower rolls) and the surface roughness Ra of the work rolls 2 were set to a combination of 0 (μm) and 0.3 (μm), a combination of 0 (μm) and 1.1-1.5 (μm), and a combination of 0 (μm) and 3.1-3.7 (μm), and steel sheet S was cold rolled using each combination of intermediate rolls 3 and work rolls 2, and vibration was investigated. The rolling conditions were rolling speed: 1300-1600 mpm, unit tension of steel sheet S: 14-19 t / mm 2 The bender load was 20 to 45 tons, the amount of rolling oil was 50 L / min, and the rolling period was May 2023 to October 2023. The surface roughness Ra of each of the intermediate roll 3 and the work roll 2 was measured using a mechanical roughness meter. The results are shown in Table 1.

[0020] [Table 1]

[0021] When the surface roughness of the intermediate roll 3 was set to 0 (μm) and the surface roughness of the work roll 2 was set to 0.3 (μm), vibration occurred in the intermediate roll 3 when 62 steel plates S were rolled and 12 of the steel plates S were rolled, with the vibration occurrence rate being 19.4 (%). Furthermore, when the surface roughness Ra of the intermediate roll 3 was 0 (μm) and the surface roughness Ra of the work roll 2 was 1.1 to 1.5 (μm), no intermediate roll 3 generated vibrations when rolling 24 steel plates S, and the vibration occurrence rate was 0.0 (%).

[0022] Furthermore, when the surface roughness of the intermediate roll 3 was set to 0 μm and the surface roughness of the work roll 2 was set to 3.1 to 3.7 μm, vibration occurred in the intermediate roll 3 when 92 steel plates S were rolled and 22 of the steel plates S were rolled, with the vibration occurrence rate being 23.9%.

[0023] The criteria for vibration occurrence of the intermediate roll 3 were that vibration occurred when an unplanned roll change occurred, and that vibration did not occur when a planned roll change occurred.

[0024] It was confirmed that when the surface roughness Ra of the intermediate roll 3 is set to 0 (μm), as the rolling of the steel sheet S continues, the surface roughness Ra of the work roll 2 is transferred as is to the surface of the intermediate roll 3. The surface roughness Ra of the intermediate roll 3 exhibits properties equivalent to those of the surface roughness Ra of the work roll 2.

[0025] Therefore, the results shown in Table 1 above show the same characteristics as when the surface roughness Ra of the intermediate roll 3 is set to 0.3 (μm), 1.1 to 1.5 (μm), and 3.1 to 3.7 (μm).

[0026] Therefore, from the results shown in Table 1, it was found that if the surface roughness Ra of each of the pair of upper and lower intermediate rolls 3 is 1.1 μm or more and 1.5 μm or less, vibration will not occur in each intermediate roll 3, and ultimately vibration will not occur in the stand having the pair of upper and lower intermediate rolls 3.

[0027] Furthermore, when the surface roughness Ra of the intermediate roll was set to 1.1 μm or more and 1.5 μm or less, no increase in vibration of the intermediate roll 3 was observed even if the surface roughness Ra of the work roll 2 was subsequently changed.In addition, by imparting a surface roughness Ra of 1.1 μm or more and 1.5 μm or less to the intermediate roll 3 itself, no increase in vibration was observed regardless of the surface roughness Ra of the work roll 2.

[0028] For this reason, in this embodiment, the surface roughness Ra of the intermediate roll 3 of the fifth stand 15 of the six-high rolling mill is set to 1.1 μm or more and 1.5 μm or less.

[0029] By setting the surface roughness Ra of the intermediate roll 3 to 1.1 μm or more and 1.5 μm or less, the lubrication between the intermediate roll 3 and the work roll 2 becomes uniform, the incidence of uneven gloss on the surface of the intermediate roll 3 decreases, and vibration of the intermediate roll 3 and, ultimately, vibration of the fifth stand 15 having the intermediate roll 3 can be suppressed.

[0030] If the surface roughness Ra of the intermediate roll 3 is less than 1.1 μm, the lubrication between the intermediate roll 3 and the work roll 2 becomes non-uniform, the incidence of gloss unevenness on the surface of the intermediate roll 3 does not decrease, and it is not possible to sufficiently suppress the vibration of the intermediate roll 3 and, consequently, the vibration of the fifth stand 15 having the intermediate roll 3. On the other hand, if the surface roughness Ra of the intermediate roll 3 is greater than 1.5 μm, similarly, the lubrication between the intermediate roll 3 and the work roll 2 becomes non-uniform, the incidence of gloss unevenness on the surface of the intermediate roll 3 does not decrease, and it is not possible to sufficiently suppress the vibration of the intermediate roll 3 and, consequently, the vibration of the fifth stand 15 having the intermediate roll 3.

[0031] In addition, when cold rolling by the cold rolling mill 1, the rolling speed is 1300 to 1600 mpm, and the unit tension of the steel sheet S is 14 to 19 t / mm 2 Preferably, the rolling conditions are as follows: bender load: 20 to 40 tons, rolling oil flow rate: 40 to 60 L / min, and surface roughness Ra of work roll 2: 0.25 to 3.4 μm. These rolling conditions, particularly the surface roughness Ra of work roll 2 and bender load, are the same for the fifth stand 15 of the six-high rolling mill and the first to fourth stands 11 to 14 of the four-high rolling mill.

[0032] Thus, according to the cold rolling mill 1 of this embodiment, the fifth stand 15 of the plurality (five stands) 11 to 15 is equipped with a pair of upper and lower work rolls 2 for cold rolling a steel sheet S as a material to be rolled, a pair of upper and lower intermediate rolls 3 that respectively support the pair of upper and lower work rolls 2 from above and below, and a pair of upper and lower backup rolls 4 that respectively support the pair of upper and lower intermediate rolls 3 from above and below. The surface roughness Ra of each of the pair of upper and lower intermediate rolls 3 is 1.1 μm or more and 1.5 μm or less.

[0033] This ensures uniform lubrication between the intermediate roll 3 and the work roll 2, reduces the incidence of uneven gloss on the surface of the intermediate roll 3, and suppresses vibration of the intermediate roll 3 and, ultimately, vibration of the fifth stand 15 having the intermediate roll 3. Therefore, by imparting roughness to the surface of the intermediate roll 3 constituting the fifth stand 15, it is possible to suppress vibration during cold rolling without incurring production losses. As a result, vibration during cold rolling can be suppressed simply by replacing the periodically replaced intermediate roll 3 with an intermediate roll 3 having a surface roughness Ra of 1.1 μm or more and 1.5 μm or less, and therefore it becomes possible to manufacture cold-rolled steel sheets without stopping the production line.

[0034] Furthermore, according to the cold rolling method of this embodiment, the steel sheet S as the material to be rolled is cold rolled using the above-mentioned cold rolling mill 1. As a result, by imparting roughness to the surfaces of the intermediate rolls 3 constituting the fifth stand 15, it is possible to suppress vibration during cold rolling without incurring production losses. Therefore, vibration during cold rolling can be suppressed simply by replacing the periodically replaced intermediate rolls 3 with intermediate rolls 3 having a surface roughness Ra of 1.1 μm or more and 1.5 μm or less, and therefore it is possible to manufacture a cold-rolled steel sheet without stopping the production line.

[0035] Furthermore, the method for manufacturing a steel sheet according to this embodiment includes a step of cold rolling the steel sheet S as the material to be rolled using the above-mentioned cold rolling method. This imparts roughness to the surfaces of the intermediate rolls 3 constituting the fifth stand 15, thereby making it possible to suppress vibration during cold rolling without incurring production loss and to avoid adverse effects of vibration on the quality of the cold-rolled steel sheet S.

[0036] Although the embodiment of the present invention has been described above, the present invention is not limited to this and various modifications and improvements can be made.

[0037] For example, the fifth stand 15 of the five stands 11 to 15 is a stand of a six-high rolling mill having intermediate rolls 3, but this is not limited to the fifth stand 15 of the five stands 11 to 15, and at least one stand of the five stands 11 to 15 may be a stand of a six-high rolling mill having intermediate rolls 3.

[0038] Furthermore, when the number of stands is set to a number other than five, at least one of the stands may be a six-high rolling mill stand having intermediate rolls 3 . [Example]

[0039] In order to verify the effects of the present invention, the intermediate roll chance throughput when cold rolling steel sheet S as the material to be rolled in a six-high rolling mill stand using intermediate rolls of the present invention example was compared with the intermediate roll chance throughput when cold rolling steel sheet S in a six-high rolling mill stand using intermediate rolls of the comparative example. The intermediate roll of the present invention has a surface roughness Ra of 1.1 μm or more and 1.5 μm or less.

[0040] The intermediate roll of the comparative example has a surface roughness Ra of 0.3 μm. When cold rolling, the rolling speed is 1300 to 1600 mpm, and the unit tension of the steel plate S is 14 to 19 t / mm. 2 The bender load was 20 to 45 t, the amount of rolling oil was 50 L / min, and the surface roughness Ra of the work roll 2 was 3.1 to 3.7 μm. The intermediate roll chance throughput is the amount of rolled material processed from the time the intermediate roll is installed until it is replaced, "t." The intermediate roll is replaced when it vibrates.

[0041] The comparison results are shown in Figure 2. As shown in Figure 2, when steel sheet S as the material to be rolled is cold rolled in a stand of a six-high rolling mill using the intermediate rolls of the present invention, the intermediate roll chance throughput exceeds 12,000 [t], which is significantly higher than the intermediate roll chance throughput of approximately 6,000 [t] when steel sheet S is cold rolled in a stand of a six-high rolling mill using the intermediate rolls of the comparative example.

[0042] FIG. 3 shows the surface condition of the intermediate roll of the comparative example after it was used. This shows the surface condition of the intermediate roll of the comparative example when it vibrated after installation and was then replaced. As mentioned above, the intermediate roll of the comparative example has a surface roughness Ra of 0.3 μm. The rolling conditions for cold rolling are the same as those mentioned above.

[0043] As shown in FIG. 3, after the intermediate roll 3 of the comparative example was used, a plurality of rough portions D were generated on the surface of the intermediate roll.

[0044] FIG. 4 shows the surface condition of the intermediate roll of the invention example after the intermediate roll of the invention example was used. This shows the surface condition of the intermediate roll of the invention example when the intermediate roll was installed and then replaced. The period (time) from the installation of the intermediate roll of the invention example to the replacement of the intermediate roll is the same period (time) as the replacement of the intermediate roll of the comparative example shown in FIG. 3. As described above, the intermediate roll of the invention example has a surface roughness Ra of 1.1 μm or more and 1.5 μm or less. The rolling conditions for cold rolling are the same as those described above.

[0045] As shown in FIG. 4, after the intermediate roll 3 of the present invention was used, there were no rough portions on the surface of the intermediate roll and no unevenness in surface roughness. [Explanation of symbols]

[0046] 1. Cold rolling mill 11 First Stand (Stand) 12 Second Stand (Stand) 13 Third Stand (Stand) 14 4th Stand (Stand) 15 5th Stand (Stand) 2 Work rolls 3. Middle roll 4. Backup Role S Steel plate (rolling material)

Claims

1. A cold rolling mill having a plurality of stands for cold rolling a material to be rolled, At least one stand of the plurality of stands comprises a pair of upper and lower work rolls for cold rolling the material to be rolled, a pair of upper and lower intermediate rolls for supporting the pair of upper and lower work rolls from above and below, respectively, and a pair of upper and lower backup rolls for supporting the pair of upper and lower intermediate rolls from above and below, respectively; A cold rolling mill characterized in that the surface roughness Ra of each of the pair of upper and lower intermediate rolls is 1.1 μm or more and 1.5 μm or less.

2. A cold rolling method comprising cold rolling a material to be rolled using the cold rolling mill according to claim 1.

3. A method for manufacturing a steel plate, comprising the step of cold rolling a steel plate as a material to be rolled using the cold rolling method according to claim 2.

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