JPH06254611A - Shape crown controlling hot rolling mill and rolling method - Google Patents

Abstract

PURPOSE:To provide the optimum arrangement for a crown controlling mill in a hot rolling line. CONSTITUTION:In a tandem mill wherein 4-7 mills are arranged adjacently, a crown controlling mechanism having a >=300mum mechanical crown controlling area is arranged only on the mill carrying a rolling wherein a geometrical factor (r) defined by the following expression is in 0.0002-0.004. gamma=(Dw<0.5>Xh<1.5>)/b<2>, where Dw: diameter (mm) of a work roll, h: plate thickness (mm) on the outlet side, b: plate width (mm).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot rolling mill and a hot rolling method capable of efficiently producing a metal material having good width-direction thickness accuracy.

[0002]

2. Description of the Related Art Conventionally, a four-high rolling mill with a work roll bender has been generally used for crown control. However, in recent years, rolling mills having a large crown control capability have been developed, and a 6-high rolling mill with an intermediate roll shift, a work roll shift mill with a work curve having a cubic curve, and a pair cross mill have a large crown control capability. Figure 1 shows the mechanical crown control capability of each mill system.

The mechanical crown is a crown that is realized when the rolling load acting between the rolled material and the work rolls is uniform in the strip width direction, and its controllability is independent of the deformation characteristics of the rolled material. It shows the pure ability of the rolling mill. Here, a mill having a large crown control capability is called a crown control mill for simplicity.

In the conventional mill, the stands provided with a bending function are added to the work rolls of the four-high rolling mill from F1 to F.
7 (or F6), the newly installed mill has crown control mills on all stands or on the stand on the rear stage side in order to secure the controllability of the crown.

However, since the conventional mill has an insufficient crown control ability per stand alone, the product thickness is small, for example, 1.2 to 2.5 mm (1000 mm width).
For a thin plate of up to 2000 mm), the total crown control capability as a tandem mill is insufficient, and a plate material with good plate thickness accuracy cannot be manufactured. On the other hand, arranging the crown control mills on all stands as a measure against this has a problem that the capital investment cost increases.

[0006]

[Problems to be Solved by the Invention]
The tandem mill with a multi-roll mill lacks crown control capability, and it is too expensive to place crown control mills on all stands. The present invention is to provide a facility and a method for producing a plate material having a good width direction thickness accuracy by applying a crown control mill having a minimum number of stands in order to secure a wide range of crown control functions.

[0007]

It is already well known that the crown control characteristic of a tandem stand is expressed by the following equation. Exit plate crown: C _i = (1−η _i ) C _i + η _i (1−
r _i ) C _i-1 Plate steepness: λ _i = 2 / π {ξ (C _i / h _i −C
_i-1 / h _i-1 )} ^1/2 where C: geometrical crown control value of mill, η: inheritance coefficient of crown ratio, ξ: shape change coefficient, h: plate thickness, r: reduction ratio, i : Number corresponding to the stand

The crown ratio genetic coefficient is determined by a geometric factor γ determined by the specifications of the rolling mill and the dimensions of the material to be rolled. The geometric factor γ is expressed by the following equation (1). γ = (D _w ^0.5 × h ^1.5 ) / b ² ………………………… (1) However, D _w : Work roll diameter (mm) h: Delivery side plate thickness (mm) b: Plate width ( mm)

The relationship between the geometric factor γ and the inheritance coefficient of the crown ratio is shown in FIG. Focusing on the stand of a certain rolling mill, if the plate thickness of the material to be rolled at that stand becomes thick,
The inheritance coefficient of the crown ratio becomes small, and the state of the crown on the incoming side is less likely to be transmitted to the outgoing side. That is, even if the crown is largely changed in the previous stage, the effect on the crown of the final product is small and efficient control cannot be performed.

On the other hand, in the case of rolling in a region where the plate thickness is thin, if the crown is changed, the influence on the flatness of the plate becomes large and the stability of the rolling work is impaired. Even if there is, the ability cannot be fully utilized and the crown of the final product cannot be reduced.

That is, there is an optimum stand capable of efficiently controlling the crown for each product size due to the relationship between the degree of influence of the crown from the front stage to the rear stage and the flatness constraint of the plate. For thick products with a plate thickness of 2.5 mm or more, the bender control of the 4Hi mill, which is the same as the conventional model, can be used, but the plate thickness is 1.2.
~ 2.5 mm; For thin products with a plate width of 1000 to 2000 mm, the crown control capability of the front stand is required.

As shown in FIG. 2, the crown control mill is arranged so that the geometric factor γ is 0.0002 or more, that is, the crown ratio genetic coefficient 0.7 or less and the geometric factor γ.
Is 0.004 or less, that is, the crown ratio genetic coefficient 0.
The range of 15 or more is a desirable range, and the range of the following equation is optimal. 0.0002 ≤ γ ≤ 0.004 Stand that is rolling condition in the range of formula (1), that is,
By arranging the crown control mills on the 1, F2, F3 stands, it is possible to obtain a thin product with good width-direction thickness accuracy.

[0013]

EXAMPLES Table 1 shows the rolling specifications and rolling conditions following the examples. (Rolling specifications and rolling conditions) Coil material Low carbon steel Bar size 32 x 1524 (mm) Coil size 1.6 x 1524 (mm) Rolling mill outlet temperature 900 ° C Rolling mill outlet speed 700 mpm

The rolling mill is a seven-stand hot rolling mill,
A crown control mill was placed on the F1, F2, F3 stands. With this rolling mill, various types (low carbon steel, medium carbon steel, stainless steel), multiple sizes (sheet thickness 1.2 to 25.0 mm; sheet width 8)
A hot rolled sheet having a thickness of 60 to 2180 mm was produced, and Table 1 shows rolling conditions for a thin product size of thickness 1.6 mm and width 1524 mm.

Under these conditions, the crown control ability was sufficiently secured, so that the five kinds of work roll curves for each rolling type conventionally used are no longer necessary. We were able to produce products with good precision. The width direction thickness accuracy was 50 μm in the conventional crown value, but in the present invention, the accuracy is improved to 30 μm.

[0016]

[Table 1]

[0017]

EFFECTS OF THE INVENTION By constructing and carrying out the present invention as described above, it is possible to highly efficiently produce a plate material having a good width direction thickness accuracy. Also, by arranging a high-performance crown control mill on the minimum rolling mills instead of all rolling mills on the tandem stand, the facility construction cost could be significantly reduced.

[Brief description of drawings]

FIG. 1 shows crown control capabilities by rolling mill type.

FIG. 2 shows the relationship between the geometric factor γ and the crown ratio inheritance coefficient η. The range of the arrow indicates the range of the geometric factor γ calculated from the rolling conditions for each product size at each stand.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Oi 1 Kimitsu, Kimitsu-shi, Chiba Shin Nippon Steel Co., Ltd. Kimitsu Steel Co., Ltd. (72) Hideo Nagashima 5-3 Tokai-cho, Tokai-shi, Aichi Inside the Nagoya Steel Works, a steel stock company

Claims (2)

[Claims] 1. A tandem rolling mill in which 4 to 7 rolling mills are arranged in close proximity to each other, and the geometric factor γ defined by the formula (1) is 0.0002 or more and 0.004 or less. A hot rolling mill having a controlled crown shape, in which a mechanical crown control mechanism having a mechanical crown control range of 300 μm or more is provided only in the rolling mill. γ = (D _w ^0.5 × h ^1.5 ) / b ² ………………………… (1) where D _w : work roll diameter (mm) h: delivery side plate thickness (mm) b: plate width ( mm) 2. When rolling with the hot rolling mill according to claim 1, the roll curves of the work rolls of all rolling mills are set to 1
A hot rolling method, characterized in that rolling is carried out in one or two types.