JP5581773B2 - Method for preventing breakage of metal strip in cold rolling mill - Google Patents

Description

  The present invention relates to a method for preventing breakage of a metal strip such as a steel strip in a cold rolling mill.

  FIG. 1 shows an example of a continuous cold rolling mill (hereinafter also simply referred to as a cold rolling mill). Hereinafter, a case where a steel strip (also referred to as a steel plate) is used as the metal strip will be described as an example.

  Usually, the continuous cold rolling mill has about 5 stands, but here, the first stand 10 and the second stand 20 are shown, and the first stand 10 has a work roll 11 and a backup roll 12. The four-high rolling mill and the second stand 20 are also a four-high rolling mill provided with a work roll 21 and a backup roll 22.

  In the cold rolling mill as shown in FIG. 1, when the rolling balance between the operation side and the drive side of the first stand 10 is lost during cold rolling, the steel plate (steel strip) 1 that is a material to be rolled meanders. The first stand 10 may cause a drawing rupture (slip rupture). Depending on the degree of the rupture, a long downtime may occur, resulting in a reduction in production efficiency.

Here, it is known that when the rolling balance between the operation side and the driving side of the first stand 10 is lost, the differential tension between the first and second stands is increased. The differential tension between the first and second stands is the tension _T1W of the operation side width end of the steel plate 1 between the first stand 10 and the second stand 20, and the other width end of the steel plate. This is the difference ΔT ₁ (= T _1W −T _1D ) with _respect to the tension T _1D at the drive side width end.

Therefore, in the cold rolling mill, as shown in Patent Documents 1 and 2, when the first-second interstand differential tension [Delta] T ₁ is determined to be outside a predetermined range, between the first-second stand The reduction leveling is adjusted so that the differential tension ΔT ₁ is within a predetermined range, the meandering of the steel plate 1 is suppressed, and the drawing breakage of the steel plate 1 in the first stand 10 is prevented.

  As shown in FIG. 1, a guide roll (also referred to as an “entering guide roll”) 30 is installed on the entry side of the first stand 10 in order to prevent the steel plate 1 from meandering.

JP 2003-275811 A JP 2004-243376 A

However, as shown in Patent Documents 1 and 2, by adjusting the reduction leveling of the first stand, even as the 1-second interstand differential tension [Delta] T ₁ is set to be within a predetermined range, the steel sheet (steel strip ) In some cases.

  This invention is made | formed in view of the above situations, and fracture | rupture of the metal strip in the cold rolling mill which can prevent appropriately the drawing fracture of the metal strip (steel strip etc.) in a cold rolling mill The object is to provide a prevention method.

  In order to solve the above problems, the present invention has the following features.

  [1] In a metal strip cold rolling mill equipped with a first stand and a second stand, the differential tension between the first and second stands is monitored, and the swing width of the differential tension between the first and second stands is within a predetermined range. A method for preventing breakage of a metal strip in a cold rolling mill, characterized in that, when it becomes outside, the backup roll of the first stand is exchanged and / or the guide roll on the entry side of the first stand is exchanged.

  [2] In a metal strip cold rolling mill provided with a first stand and a second stand, the differential tension between the first and second stands is monitored, and the fluctuation width of the differential tension between the first and second stands is within a predetermined range. The method for preventing breakage of a metal strip in a cold rolling mill as described in [1] above, wherein the backup roll of the first stand is replaced first when it becomes outside.

  In the present invention, the fluctuation width of the differential tension between the first and second stands of the cold rolling mill is set within a predetermined range, the meandering of the metal band in the first stand is suppressed, and the occurrence of the drawing fracture of the metal band is accurately detected. Can be prevented.

It is a figure which shows an example of a cold rolling mill (cold tandem rolling mill). It is a figure which shows an example of the differential tension | tensile_strength between 1st-2nd stands, and the deflection width.

The present inventors investigated the operation conditions at the time of drawing fracture of the steel plate (steel strip) 1 in the first stand 10 for the cold rolling mill (continuous cold rolling mill) as shown in FIG. However, it was found that the deflection width δΔT ₁ of the differential tension ΔT ₁ between the first and second stands was increased when the drawing fracture of the steel plate 1 occurred.

Incidentally, FIG. 2 shows an example of the measurement result of the differential tension ΔT ₁ between the first and second stands. Here, the fluctuation width δΔT ₁ of the differential tension ΔT ₁ between the first and second stands is the same. The absolute value (= | ΔT _1T −ΔT _1B |) of the difference between the adjacent peak ΔT _1T and the valley ΔT _1B .

From this, in order to prevent the drawing fracture of the steel sheet 1, it was considered important to make the deflection width δΔT ₁ smaller than the _first- second differential tension ΔT ₁ itself.

Accordingly, as a result of detailed investigations on the mechanism by which the deflection width δΔT _{1 of the first-} second differential tension ΔT ₁ increases, the present inventors have increased the throughput of the backup roll 12 of the first stand 10. As a result, uneven wear in the roll width direction occurs in the backup roll 12, thereby causing a reduction in the balance between the operating side and the driving side in the first stand 10, and the difference between the first and second stand differential tensions ΔT ₁ . The runout width δΔT ₁ was increased, and it was found that the drawing fracture of the steel sheet 1 at the first stand 10 occurred.

  In addition, as for the entering guide roll 30 installed to prevent the meandering of the steel plate 1 on the entry side of the first stand 10, the gripping force of the entering guide roll 30 on the steel plate 1 is increased when the use period is long. It has been found that when the balance between the operating side and the driving side at the first stand 10 is reduced, the drawing fracture of the steel plate 1 at the first stand 10 is likely to occur.

Therefore, the present inventors monitor the first-second differential tension ΔT ₁ and prevent the first-second differential tension ΔT in order to prevent the drawing fracture of the steel sheet 1 generated by the above mechanism. _When the deflection width δΔT1 of ₁ is out of the predetermined range, the backup roll 12 of the first stand 10 is exchanged and / or the enter guide roll 30 of the first stand 10 is exchanged. The deflection width δΔT ₁ of the differential tension ΔT ₁ between the two stands is set within a predetermined range, and the meandering of the steel plate 1 in the first stand 10 is suppressed to prevent the drawing fracture of the steel plate 1.

Here, the outside of the predetermined range of the swing width δΔT ₁ of the differential tension ΔT ₁ between the first and second stands is, for example, a region exceeding the total tension T ₁ between the first and second stands by 2.0% (δΔT ₁ / T ₁ × 100> 2.0).

Normally, the periodic replacement cycle (for example, one month) of the backup roll 12 is shorter than the periodic replacement cycle (for example, six months) of the entering guide roll 30, or the replacement operation of the backup roll 12 is performed. because it is easier and than replacement of Enta ring guide roll 30, when the first-second amplitude DerutaderutaT ₁ of interstand differential tension [Delta] T ₁ is outside the predetermined range, first, replace the backup roll 12 was carried out, still in the case first-second amplitude DerutaderutaT ₁ of interstand differential tension [Delta] T ₁ is out of the predetermined range, preferable to perform the exchange of Enta ring guide roll 30.

Of course, since the time for periodic replacement of the entering guide roll 30 is close, the entering guide roll 30 is first replaced, and the deflection width δΔT ₁ of the differential tension ΔT ₁ between the first and second stands still remains. If it is outside the predetermined range, the backup roll 12 may be replaced.

  Further, the replacement of the backup roll 12 and the replacement of the entering guide roll 30 may be performed simultaneously.

  When cold rolling a low carbon steel sheet and an ultra low carbon steel sheet with a product thickness of 0.1 mm to 0.6 mm by a cold rolling mill, the present invention was applied. It was possible to eliminate the drawing fracture of the steel plate in one stand.

1 Steel plate (steel strip)
DESCRIPTION OF SYMBOLS 10 1st stand 11 Work roll of 1st stand 12 Backup roll of 1st stand 20 2nd stand 21 Work roll of 2nd stand 22 Backup roll of 2nd stand 30 Entering guide roll

Claims (2)

  In a metal strip cold rolling mill equipped with a first stand and a second stand, the differential tension between the first and second stands is monitored, and the fluctuation width of the differential tension between the first and second stands is outside a predetermined range. In this case, the method of preventing breakage of the metal strip in the cold rolling mill is characterized in that the backup roll of the first stand is exchanged and / or the guide roll on the entry side of the first stand is exchanged.   In a metal strip cold rolling mill equipped with a first stand and a second stand, the differential tension between the first and second stands is monitored, and the fluctuation width of the differential tension between the first and second stands is outside a predetermined range. 2. The method for preventing breakage of a metal strip in a cold rolling mill according to claim 1, wherein the backup roll of the first stand is first replaced.

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