JPH05277520A - Method for rolling steel plate - Google Patents

Abstract

PURPOSE:To provide an inexpensive rolling method to roll a steel plate low in plate crown. CONSTITUTION:In a method for rolling a steel plate with a four-high mill composed of a work roll 2 and a backup roll 1, regarding a combination of the work roll 2 and the backup roll 1 wherein both are provided with positive crowns in their central parts and negative crowns in both ends of them or one is provided with a single crown and the other is provided with a positive crown in its central part and negative crowns at its ends, the steel plate is rolled by one of both combinations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for rolling a steel sheet for rolling a steel sheet having a small crown, and more particularly to a rolling method in which a combination of a work roll and a backup roll is changed.

[0002]

2. Description of the Related Art Generally, in the rolling of a steel sheet, the sheet thickness distribution in the sheet width direction is such that the center portion of the roll is thickest and the side edge portion is thick due to the bending of the roll due to rolling load and the flatness of the roll surface. Becomes thinner as it gets closer to The difference in plate thickness between the central part and the side edge part is called a plate crown. Various rolling methods for reducing the plate crown of the steel sheet have been conventionally studied. Examples of such methods include a method of reducing the plate crown by the mechanism of a rolling mill and a method of reducing the plate crown by the shape of the roll crown. There is.

As the former method of reducing the plate crown, a six-high rolling mill is used, or a work roll shift mechanism, a roll cross mechanism, a bender mechanism or the like is provided to reduce the plate crown. .. Although these methods are very effective methods, the biggest drawback is that the equipment cost rises. In that respect, the latter method of reducing the plate crown by the shape of the roll crown does not have the drawbacks of the former. The latter method is disclosed in JP-A-62-2.
As disclosed in Japanese Patent No. 75503, there is proposed a method in which a roll is provided with an arbitrary convex shape and a work crown such as an initial crown is provided with a convex crown having a special shape to perform rolling. Further, JP-A-51-13353,
As disclosed in JP-A-51-93766, a method of rolling a backup roll with a large crown, or a large backup roll as disclosed in JP-B-63-65403. A method has been proposed in which a roll crown and a concave work crown are combined and rolled. Further, JP-A-55-103201
In the publication, a backup roll is provided with rolls at both ends.
5 to 32% of the body length is 0.01 to 1 °
It has been proposed to roll using a rolling mill equipped with rolls having a trapezoidal crown with a crown.

[0004]

However, in the method disclosed in the above-mentioned Japanese Patent Laid-Open No. 62-275503, it is not clear how to give a crown. Furthermore, the central part of the work wheel, which is always in contact with the steel plate during rolling, is severely worn, and when rolling the narrow steel plate at the end of the rolling schedule, the positive plate crown, which is a particular problem with the narrow steel plate, is reduced. You cannot do it. In Japanese Patent Publication No. 63-65403, the effect is recognized, but in the backup roll of a large crown that can exert the effect,
You cannot overcome the ring problem. Further, in order to solve such a problem of spooling, if the concave crown shape of the work roll is made to be the same as that of the backup roll, the effect will be halved. There is also a drawback that the amount of crown fluctuation is large with respect to the fluctuation of rolling load. Further, although the backup trapezoidal crown is effective, it has a problem that it cannot follow the change of the plate width, and there is a drawback that it becomes a negative crown especially for wide width materials. The present invention has been made in view of the above-mentioned problems of the conventional art, and an object of the present invention is to provide a rolling method that effectively reduces the plate crown of a steel plate without incurring a high facility cost or the like.

[0005]

The present invention has been made to solve the above problems, and is a method of rolling using a four-high rolling mill consisting of a work roll and a backup roll. Therefore, the combination of the work roll and the backup roll should be such that both have a positive crown at the center and a negative crown at the end, or have a single crown on one side. A method for rolling a steel sheet is characterized by combining one with a positive crown at the center and a negative crown at the end on the other, or rolling with any one of the above combinations.

[0006]

The present inventors have made various studies to reduce the plate crown in a four-high rolling mill and completed the present invention. Next, the background of the invention will be described. FIG. 3 shows the width (m of the steel plate in a normal four-high rolling mill.
3 is a graph showing the relationship between m) and the size of the plate crown (μm). As is clear from FIG. 3, 2000
Steel strips with a width of ~ 3000 mm exhibit a large positive crown, while wide steel sheets exhibit a negative crown due to the heat crown of the roll. First, in order to reduce the plate crown of a narrow steel plate, a trapezoidal backup roll crown (backup roll chamfer) as shown in FIG. 4 was examined. If the steel plate is narrow, the backup roll
If the rule 1 has such a trapezoidal shape, as shown in rolling (solid line) by the backup chamfer in FIG. 5, the plate crown (μm) is reduced as compared with normal rolling (chain line). However, in the case of a wide steel plate, the negative crown increases.

In order to reduce the negative crown of a wide steel plate, as shown in Japanese Patent Publication No. 63-65403, when a normal concave crown is adopted in the work wheel, as shown in FIG. In addition, it is confirmed that the crown (one-dot chain line) of the narrow steel plate is larger than that in the case of only the backup roll chamfer (solid line). Thus, it was difficult to roll a steel sheet from a narrow width to a wide width without generating a plate crown. In order to understand the crown generation mechanism of a narrow steel plate and the plate crown generation mechanism of a wide steel plate, the inventors of the present application determine how to apply a load acting on the work roll from the backup roll and the steel plate. investigated. The results are shown in FIGS. 7 (a) to 7 (c).

In the case of a normal roll, as shown in FIG. 7 (a), a narrow steel plate is a work roll 2 in which no steel plate is present.
A harmful bending moment load only from the backup roll 1 is applied to the end portion of the wire, and the work wheel 2 is bent so as to be convex upward, so that a positive plate crown is generated. As shown in the figure, in the case of the wide steel plate, the load from the backup roll 1 unlike the narrow steel plate does not exist, but a negative plate crown is generated due to the heat crown of the work roll 2. ..
When a backup roll chamfer is adopted, Fig. 7
As shown in (b), no harmful load is applied to the narrow steel plate, but to the wide steel plate, a harmful bending moment load from the steel plate 5 is applied to the end of the roll, resulting in a work roll. 2 is bent upwards and a negative plate crown is generated. Work
If a normal concave crown is used for rule 2,
As shown in (c), in the narrow steel plate, the load from the backup roll 1 is applied to the end of the work roll 2 where the steel plate does not exist but is reduced as compared with the case of the normal roll. , The work roll 2 is bent so as to be convex upward. In the case of a wide steel plate, the load from the backup roll 1 does not exist as in the case of a narrow steel plate, but a negative plate crown is generated due to the heat crown of the work roll 2.

As a result of such an examination, a backup roll
It was confirmed that the load acting on the work roll 1 to the work roll 2 may be adjusted under the following conditions. That is, when rolling a narrow steel plate, the contact load from the backup roll 1 is not generated at the end of the work wheel 2 where no steel plate exists so that a positive plate crown is not generated. Further, when rolling a wide steel plate, the contact load from the backup roll 1 acting on the end portion of the work roll 2 is increased so that a negative plate crown is not generated. The shape of the work roll crown which satisfies these conditions and in which the stress acting on the work roll 2 does not change steeply in the width direction, as shown in FIG. The crown of the, the end of the roll will be a negative crown,
When rolling was carried out under the conditions shown in Tables 1 and 2, it was confirmed that, as shown by the solid line in FIG. 9, a good strip crown reducing effect was confirmed as compared with the normal rolling by the chain line.

[0010]

[Table 1]

[0011]

[Table 2]

However, when a large number of steel plates are continuously rolled by the rolling schedule as shown in FIG. 10, the crown amount of the central portion of the work wheel 2 which is always in contact with the steel plates is gradually reduced and narrowed. It was found that the effect of reducing the positive crown of the width steel sheet is drastically reduced, which is not suitable for practical use.
Further, the shape of the work roll crown which satisfies the above conditions and in which the stress acting on the work roll does not change abruptly is as shown in FIG. , And a positive crown at the center of the roll and a negative crown at the end of the roll.

In this case, although the problem of wear of the central portion of the roll is small, the print rate of the backup roll crown on the steel plate is smaller than that of the work roll 2, so that a good crown reducing effect is obtained. To get it, you need a big crown. Due to the problem of spooling, the amount of Kuniun that can be applied to the backup roll 1 is limited, and the effect of reducing the plate crown is limited.

In the present invention, based on the above results,
For example, rolling is performed by a combination of a work roll and a backup roll as shown in FIG. 1 of an embodiment described later. In FIG. 1, reference numeral 1 is a backup roll whose roll crown is a single curve or roll.
This is a shape in which a positive crown is provided at the center of the roll and a negative crown is provided at the end of the roll. Reference numeral 2 is a work roll, the roll crown shape of which is a positive crown at the center of the roll,
It has a shape in which a negative crown or a single curve is added to the end of the roll. By defining the roll crown as described above, the contact load from the backup roll 1 is not generated in the portion of the work roll where the steel plate is not present when the steel plate is narrow, and when the steel plate is wide, the contact load is not generated. The negative crown at the end of the roll 2 or the backup roll 1 prevents a negative plate crown. In addition, a good crown reducing effect can be obtained even at the end of rolling schedule. Needless to say, if a bender is used in combination with the present invention, the control range is expanded and the crown control becomes easier.

[0015]

Embodiments of the present invention will be described below.
FIG. 1 is an explanatory view of a combination of a backup roll and a work roll used in the present invention. That is, FIG. 1 (a)
When a backup roll having a positive crown at the center and a negative crown at the ends are combined with a work roll, FIG. 1B shows a work roll having a single crown.
When a backup roll having a positive crown in the central portion and a negative crown in the end portion is combined with the roll, FIG.
A backup roll with a single crown and a work roll with a positive crown in the center and a negative crown at the ends.
Is a combination of the two. In FIG. 1, 1 is a backup roll, 2 is a work roll,
Reference numerals 3 and 4 respectively indicate roll axes.

Rolling was performed using a four-high rolling mill having a roll as shown in FIG. For example, as shown in FIG. 1C, the crown amount 1a of the backup roll is set to 100 μm.
m, the crown amount 2a at the center of the work wheel is 540 μ
m, the crown amount 2b at the end of the work wheel is 40μ
m, and the length 2c for giving the crown of the end portion of the work roll was set to 850 mm. Also, the roll length is 5500
mm, the maximum diameter of the backup roll is 2350 m
m, the maximum diameter of the work roll was 1200 mm. A mild steel slab having a size of 270 mm thick × 1720 mm wide × 5100 mm long was used and rolled at a rolling temperature of 900 ° C. to obtain rolled materials having a width of 1900 mm, 3400 mm and 5000 mm. The rolled material had a constant thickness of 12 mm. The plate crown of the rolled material thus rolled is shown in FIG.
Shown in. In addition, the plate crown in the case of performing normal rolling is also shown in this figure. As is apparent from FIG. 2, by performing rolling according to the present invention,
The plate crown (μm) is -1 from a narrow width of 00 mm to a wide width.
It was confirmed that the amount could be extremely reduced to 0 to −80 μm.

[0017]

According to the steel sheet rolling method of the present invention, the plate crown of the steel sheet can be effectively reduced from a narrow width to a wide width. Since the present invention can be applied to existing rolling mills as it is, it has a great advantage that rolling can be performed at an extremely low cost without causing a rise in equipment cost.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a combination example of rolling rolls for carrying out the present invention,

FIG. 2 is a relationship graph between a plate width and a plate crown in an example of the present invention,

FIG. 3 is a graph showing a relationship between a plate width and a plate crown when a normal roll is used,

FIG. 4 is an explanatory view showing a rolling roll when a backup roll chamfer is adopted,

FIG. 5 is a graph showing the relationship between the plate width and the plate crown when a roll backup roll chamfer is used,

FIG. 6 is a graph showing the relationship between the plate width and the plate crown when a normal concave roll is used for the work roll,

FIG. 7 is an explanatory view showing a load distribution exerted on the work roll during rolling in the conventional method,

FIG. 8 is an explanatory view showing an example of a work roll crown effective for reducing the plate crown from a narrow width to a wide width,

9 is a graph showing the relationship between the plate width and the plate crown when the roll shown in FIG. 8 is adopted,

FIG. 10 is an explanatory view of a general rolling schedule,

FIG. 11 is an explanatory view showing an example of a backup roll crown effective for reducing the plate crown from a narrow width to a wide width.

[Explanation of symbols]

 1 backup roll crown, 2 work rolls, 3 roll shafts, 4 roll shafts, 5 rolled materials. 1a backup roll crown amount, 2a center crown amount of the work roll, 2b crown amount at the end of the work roll, 2c length imparting the end crown of the work roll It is.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Matsuoka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Satoshi Kuwahara 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Date Inside the Steel Pipe Co., Ltd. (72) Inventor Yoneaki Fujita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Steel Pipe Co., Ltd.

Claims (1)

[Claims] 1. A method of rolling a steel sheet using a four-high rolling mill composed of a work roll and a backup roll, wherein the combination of the work roll and the backup roll comprises:
Both shall have a positive crown in the center and a negative crown at the ends, or one with a single crown and the other with a positive crown in the center and a negative crown at the ends Or a rolling method of a steel sheet, which comprises rolling with any one of the above combinations.