JP2008307577A - Temper rolling method for steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temper rolling method for a steel sheet, by which the occurrence of cross buckle is stably prevented without increasing the cost of equipment even when performing the temper rolling of a thin, wide and hard steel sheet. <P>SOLUTION: In the temper rolling method of the steel sheet, the exit angle of ≥18° is imparted on the outlet side of a temper mill and the tension on the delivery side of the temper mill is taken as ≥5.0 kgf/mm<SP>2</SP>. It is preferable to take the tension on the entry side of the temper mill as ≥3.0 kgf/mm<SP>2</SP>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a temper rolling method for steel sheets, and more particularly to a temper rolling method for steel sheets suitable for suppressing occurrence of cross buckles in thin, wide and hard steel sheets.

  In temper rolling after continuous annealing, a parallel wavy pattern called a so-called cross buckle may occur on the steel sheet surface in a direction oblique to the rolling direction. This cross buckle remains on the surface even after the steel plate is pressed and impairs its appearance, and is a factor that greatly affects the quality characteristics.

  The occurrence of a cross buckle during temper rolling is due to the following phenomenon. That is, at the time of temper rolling (skin pass rolling), the steel sheet tends to spread in the width direction due to the reduction of the work roll, but the spreading of the steel sheet being reduced is restricted by friction with the work roll. Therefore, a large compressive stress is generated in the steel plate width direction in accordance with the amount of spread due to the reduction. When the compressive stress is released when the steel plate in such a state exits the work roll, it is considered that the steel plate buckles there and a cross buckle (a wavy pattern) is generated. In addition, as conditions on which a cross buckle is easy to generate | occur | produce, the steel plate to which the temper rolling is carried out is mentioned that it is thin, wide, and hard. When temper rolling such a steel sheet, it is considered that the frictional force increases between the work roll and the steel sheet.

  For the cross buckle, the steel plate is leveled, and the magnitude of the cross buckle is expressed by the cross-sectional wave height in the steel plate width direction, the pitch at which the wave is generated, and the angle of the wave generated in the oblique direction. However, since the wave height due to the cross buckle is extremely small at about 100 μm at most, unevenness may not be seen only by the color difference. Moreover, the present situation is that the change cannot be captured by the thickness gauge or the width gauge during line operation.

  Therefore, in the past, when a cross buckle occurred during temper rolling, manual intervention was performed as appropriate while visually judging the surface shape of the steel sheet, the skin pass load (rolling load), roll crown, skin pass entry and exit tensions. The current situation is that the method of adjustment is taken.

There is a technique as described in Patent Document 1, for example, as a method that can stably prevent a cross buckle generated in a steel sheet during temper rolling, instead of the above-described countermeasures. here,
(1) The exit side tension is equal to the yield stress of the material to be rolled.
(2) An outflow angle of at least 2.0 ° or more is given on the exit side of the rolling mill, and the exit side tension is made 70% or more of the yield stress of the material to be rolled.
(3) The exit side auxiliary roll diameter is 1000 times or less of the material thickness of the material to be rolled, the outflow angle of at least 2.0 ° is given on the exit side of the rolling mill, and the ratio of the exit side tension to the yield stress of the material to be rolled The lower limit is set to 25% according to the thickness of the material to be rolled and the auxiliary roll diameter.
By adopting any of the above, it is said that the cross buckle can be stably prevented.
Japanese Patent No. 3728893

  However, the temper rolling method of the steel strip disclosed in the above-mentioned Patent Document 1 requires that the skin pass exit side tension be set to be considerably high, which increases the equipment load and increases the equipment cost and operating cost. is there.

  The present invention has been made in order to solve the above-described problems. For example, a thin steel sheet (plate thickness of 0.70 mm or less), a wide (1500 mm or more), and a hard (tensile strength Ts = 340 MPa or more) steel sheet is temper-rolled. Even in such a case, an object is to provide a temper rolling method for a steel sheet that can stably prevent the occurrence of cross buckle without increasing the equipment cost.

In order to solve the above problems, the present invention has the following features.
[1] In the temper rolling method for steel sheets,
A temper rolling method for a steel sheet, characterized by providing an outflow angle of 18 ° or more on the temper rolling mill outlet side and setting the outlet tension of the temper rolling mill to 5.0 kgf / mm ² or higher.
[2] In the temper rolling method for a steel sheet according to [1] above,
A temper rolling method for a steel sheet, wherein the entrance tension of the temper rolling mill is 3.0 kgf / mm ² or more.

  According to the present invention, for example, even when thin steel (plate thickness 0.70 mm or less), wide (1500 mm or more), hard (tensile strength Ts = 340 MPa or more) steel sheet is temper-rolled, the equipment cost is increased. There is provided a temper rolling method for a steel sheet that can stably prevent the occurrence of cross buckles.

  Hereinafter, an example of the best mode for carrying out the present invention will be described.

  FIG. 1 is a schematic configuration diagram showing an example of a temper rolling mill to which the steel sheet temper rolling method according to the present invention is applied. In FIG. 1, a single-stand four-stage temper rolling mill composed of a pair of upper and lower work rolls 1 and a backup roll 2 is illustrated, but the temper rolling mill to which the present invention is applied is shown here. It is not limited.

In FIG. 1, the temper rolling method for a steel sheet according to the present invention gives an outflow angle of 18 ° or more on the exit side of the temper mill, and the exit tension of the temper mill is 5.0 kgf / mm ² ( 49 MPa) or more. In the temper rolling method of the steel sheet according to the present invention, the inlet side tension of the temper rolling mill is adjusted to 3.0 kgf / mm ² (29 MPa) or more after adjusting to the outflow angle and the outlet side tension. It may be rolled.

  Here, the said outflow angle says angle (theta) given to the upper direction or the downward direction from the horizontal direction of the steel plate 4 in the temper rolling mill delivery side. The outflow angle θ can be adjusted by adjusting the height of the cross brake roll 3 provided in the immediate vicinity of the exit side of the temper rolling mill. Whether the outflow angle θ is applied to the upper side or the lower side from the horizontal direction of the steel plate 4 is appropriately set depending on the equipment configuration such as a temper rolling mill. In addition, since the approach angle on the entrance side of the temper rolling mill does not affect the occurrence of the cross buckle, it is not necessary to provide an angle, and the entrance angle may be the same as the exit side.

  The outflow angle θ is 18 ° or more, preferably 18.8 ° or more. By lightly rolling in a state of being wound around the work roll 1 at an angle of 18 ° or more, the binding force of the steel sheet is increased, and the occurrence of cross buckles on the surface of the steel sheet after temper rolling is suppressed. Prevent clogging and meandering. Further, the upper limit value of the outflow angle θ is not particularly limited as long as it does not affect the warp of the steel plate 4, but is preferably 19.4 ° or less from the viewpoint of equipment.

In the present invention, the exit tension of the temper rolling mill is 5.0 kgf / mm ² (49 MPa) or more. By setting the exit side tension of the temper rolling mill to 5.0 kgf / mm ² or more, buckling that occurs due to the release of the compressive stress at the place where the steel sheet exits the work roll can be prevented. The occurrence of buckle can be prevented. Preferably, the exit tension is 6.0 kgf / mm ² (59 MPa) or more. The upper limit of the outgoing tension is not particularly limited. However, excessively increasing the outgoing tension will increase the cost due to equipment modification, and may cause earrings in the steel strip. Therefore, it is preferable that the upper limit of the exit side tension is 7.0 kgf / mm ² (69 MPa) or less.

Furthermore, it is effective for prevention of generation | occurrence | production of a cross buckle by making entrance side tension | tensile_strength 3.0 kgf / mm < ² > or more (29 Mpa). In order to further reduce the occurrence of cross buckle, it is preferable to adjust the exit tension of the temper rolling mill to be higher than the entrance tension of the temper rolling mill.

  Hereinafter, the present invention will be described based on examples.

  Using the apparatus having the configuration shown in FIG. 1, temper rolling was performed on a steel sheet having a sheet thickness of 0.66 mm, a sheet width of 1520 mm, and a steel type: tensile strength of 340 MPa, with an elongation of 1.00%.

  Table 1 shows the conditions for temper rolling of Invention Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4, 5. Moreover, about the steel plate after temper rolling, the result of having performed the occurrence of a cross buckle by visual confirmation and a grindstone inspection is also shown in Table 1.

It is a figure which shows an example of the temper rolling mill to which the temper rolling method of the steel plate which concerns on this invention is applied.

Explanation of symbols

1 Work roll 2 Backup roll 3 Cross brake roll 4 Steel plate

Claims (2)

In the temper rolling method for steel sheets,
A temper rolling method for a steel sheet, characterized by providing an outflow angle of 18 ° or more on the temper rolling mill outlet side and setting the outlet tension of the temper rolling mill to 5.0 kgf / mm ² or higher. In the temper rolling method of the steel plate according to claim 1,
A temper rolling method for a steel sheet, wherein the entrance side tension of the temper rolling mill is 3.0 kgf / mm ² or more.

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