JP2689605B2 - Rolling method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rolling method for a rolling mill capable of performing work roll shift (hereinafter referred to as work roll shift).

[Prior Art] A method of arranging work rolls having a linear taper portion at one end of a cylinder length in a vertically symmetrical manner and controlling a plate cross-section profile in a thin plate rolling in the opposite direction (so-called work roll shift method) Indicates that profile control, which has been difficult in the past, is possible. An example of a prior art document in this field is, for example, Japanese Examined Patent Publication No. 60-51921, the content of which is that the taper portion overlaps the plate width end portion (so-called overlap amount) depending on the width of the work. It is determined by performing a roll shift. However, the overlap amount and the angle of the taper portion in the work roll shift rolling are not mentioned. In addition, JP-A-62-25
In Japanese Patent Publication No. 9606, a method is proposed in which the overlap amount is changed according to the plate thickness, and it is described in the text that the front stand is effective for profile control of the overlap amount.

[Problems to be Solved by the Invention] However, the overlap amount and the angle of the taper portion in work roll shift rolling have certain restrictions in stable operation and in profile control, and when the overlap amount is increased, the taper portion is increased. If the angle of is increased, the plate thickness will increase excessively at the end of the plate width, which may cause operational problems such as plate breakage due to local over tension, narrowing due to defective shape, and cracking at the plate width end. Occurs. Also, selecting the overlap amount and the angle of the taper portion to be too small diminishes the effect of profile control in work roll shift rolling, and the prior art document includes these problems. The present invention is intended to solve the above problems, and an object of the present invention is to provide a rolling method for a rolling mill that enables a work roll shift that enables stable plate cross-section profile control.

[Means for Solving the Problem] In a rolling method of a rolling mill, in which work rolls having linear taper portions are arranged point-symmetrically at one end of a cylinder length, and the work rolls can be shifted in opposite directions, the taper The rolling method is characterized in that the amount of overlap between the end portion and the strip width end portion is determined by using the lateral flow coefficient α.

[Operation] In rolling, in order to improve the strip thickness profile, three-dimensional plastic flow of the strip must occur. The region where this three-dimensional plastic flow occurs depends on the deformation resistance of the plate and the distance from the plate width edge. In order to quantify this, the lateral flow coefficient α was defined by the following equation.

Δε = α {ln (H _m / h _m ) −ln (H / h)} where Δε: elongation difference in the longitudinal direction, α: lateral flow coefficient, ln: natural logarithm H _m ; average plate thickness on stand-in side , H _m ; average plate thickness at stand stand-out side, H; plate thickness at stand width side at stand entrance side, h; plate thickness at stand stand side at plate width position.

The lateral flow coefficient α is the ratio of the elongation difference in the longitudinal direction and the sheet thickness deviation that occur during rolling. Therefore, as α is closer to 1, plastic flow in the sheet width direction is less likely to occur, and it is difficult to control the sheet thickness profile. Conversely, as α is closer to 0, plastic flow in the sheet width direction is more likely to occur, and sheet thickness profile control is performed. Show that it is easy. α depends on the distance from the plate width edge and the deformation resistance of the rolled plate. α becomes closer to 0 as the deformation resistance is smaller as it is closer to the plate width end, and plate width profile control becomes easier. This is because there is less constraint in the width direction of the material as it gets closer to the strip width edge.Therefore, obtain the distribution of α of the rolled sheet in advance, and limit the amount of overlap of the taper portion of the roll with the strip width edge portion by this. This makes it possible to prevent shearing of the plate and breakage of the plate due to extreme medium elongation. α is obtained from the above equation by measuring the distribution of the plate thickness in the plate width direction before and after rolling and the distribution of the difference in elongation in the longitudinal direction in the plate width direction.

FIG. 1 is a graph showing the value of the lateral flow coefficient α. The horizontal axis is the deformation resistance (kg / mm ² ), and the vertical axis is the distance from the plate width edge (mm).
Is the amount of overlap of the taper portion of the roll with the plate width end portion, and α is expressed as a parameter. As shown in the figure, α approaches 0 as the plate width end is closer and the deformation resistance is smaller.

[Examples] Table 1 shows one example of the present invention and its comparative example.

In Table 1, a cold rolling test was conducted to investigate the relationship between transverse flow coefficient and fracture. The rolling conditions are single stand rolling, original plate thickness 3.0mm, product thickness 2.1mm (reduction rate 30
%), Strip width 1000 mm, rolling load 0.8 ton / mm, forward tension 15 kg /
mm ² , deformation resistance 25 kg / mm ² , and 40 kg / mm ² , the overlapping amount L of the taper portion with the plate width end portion is 25 to 150 mm, and the taper angle of the work roll is 0.002 rad. The lateral flow coefficient α varies depending on the distance from the plate width end as shown in FIG. 1. However, except for Comparative Examples 5, 6, 10, 11 and 12, the overlapping amount L of the tapered part with the plate width end is This is an example of an experiment up to the position of α ≦ 0.8, in which case rolling was performed without breakage. Further, the larger the deformation resistance, the larger the value of α at the same plate width position, so it is understood that it is necessary to reduce the value of L. The present invention can also be applied to hot rolling of a plate.

[Effects of the Invention] As described above, according to the present invention, the cross-flow coefficient is used in rolling of a plate to control the cross-sectional shape of the plate without breaking, so that the yield is improved.

[Brief description of the drawings]

 FIG. 1 is a graph showing the value of the lateral flow coefficient α.

Claims (1)

(57) [Claims] 1. A rolling method of a rolling mill, wherein work rolls having a linear taper portion at one end of a cylinder length are arranged point-symmetrically, and the work rolls can be shifted in opposite directions. A rolling method, characterized in that the amount of overlap with the end portion is determined using a lateral flow coefficient α.