JPH11226620A - Method for controlling shape of steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the best yield by this method which is applicable even in the case a strong edger or the edger itself is not used. SOLUTION: In this control method, after executing the adjusting rolling for rolling a slab so that the thickness in the front and rear end parts of the slab is thicker than that in the middle part, cross rolling in which rolling is executed by turning the direction of rolling direction 90 deg. is executed and, after that, finish rolling is executed. In such a case, the relation between the rolling reduction of the adjusting rolling and the shape of the steel plate after the finish rolling is previously determined and, using this relation, the relation between the rolling reduction of the adjusting rolling and the yield is calculated. Moreover, within the range of variation in the shape of the steel plate after finish rolling, the rolling reduction of the adjusting rolling for making the average value of the yield best is calculated and the adjusting rolling is controlled to that rolling reduction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the shape of a thick steel plate in which, after performing adjustment rolling, rolling is performed by rotating the rolling direction by 90 degrees, rolling is performed, and finish rolling is performed.

[0002]

2. Description of the Related Art In the manufacture of plate-shaped articles (hereinafter referred to as plate-shaped articles), they are often manufactured by tentative rolling from the viewpoint of manufacturing. In this case, several methods have been proposed.

Japanese Patent Application Laid-Open No. 5-185105 proposes a method of manufacturing a rectangular product with a high yield by using a horizontal roll mill and an edger in combination to optimize the shape after rolling. In this technique, before or after or during the tentering rolling, edging is performed so that the vicinity of the edge of the edger and the vicinity of the trailing edge are slightly reduced from the reference reduction amount at the center.

Japanese Unexamined Patent Publication No. Hei 6-7816 discloses a flat surface for reducing the width variation of a steel sheet after rolling by changing the rolling reduction of a final rolling pass before tentering rolling along the rolling direction. A shape control method has been proposed. In this technique, the width variation of the steel sheet after rolling is predicted, and the rolling reduction is changed based on the predicted variation.

[0005]

Problems to be Solved by the Invention
In the technique described in Japanese Patent Application Laid-Open No. 5 (1999) -1995, equipment for an edger is required, and equipment costs increase. In particular, in order to apply a large deformation to the edger, it is necessary to use a facility whose edger's capability is stronger than usual.

[0006] In the technique described in Japanese Patent Application Laid-Open No. 6-7816, it is necessary to predict the width variation of the steel sheet after the completion of rolling, but no specific method is described. From the description of FIG. 1 of the publication, an equation for predicting the width variation of the steel sheet after rolling is created using the thickness, width, and the like of the rolled material in the tentering rolling as a parameter (when the steady-state region is (Depending on the model with a cocoon).

As described above, this technique does not disclose a concrete form of the prediction formula of the width fluctuation amount, nor discloses how to use it. In addition, since the shape of the steel sheet after rolling is not taken into consideration when the shape of the steel sheet is depressed by the sheet width at the center in the longitudinal direction, there is a problem in terms of the actual reproducibility as a model formula, and it is not necessarily required. There is no guarantee that the best yield will be obtained.

The present invention solves the above-mentioned problems of the prior art, and is applicable even when a strong edger or an edger itself is not used, and can control the shape of a thick steel plate capable of obtaining the best yield. The purpose is to provide.

[0009]

SUMMARY OF THE INVENTION According to the present invention, there is provided a rolling process in which rolling is performed by rotating the rolling direction by 90 degrees after performing adjustment rolling in which the thickness of the front and rear end portions of the slab is made thicker than the center portion. Then, in the shape control method of the thick steel plate to be subjected to finish rolling, the relationship between the reduction amount of the adjustment rolling and the shape of the steel plate after the finish rolling is obtained in advance, and the relationship between the reduction amount of the adjustment rolling and the yield using this relationship. Further, within the range of variation in the shape of the steel sheet after finish rolling, the reduction amount of the adjustment rolling to optimize the average value of the yield is calculated, and the adjustment rolling is performed by controlling the reduction amount to the reduction amount. This is a method for controlling the shape of a thick steel plate.

The present invention has been made by diligently studying a method for controlling the shape of a thick steel plate. In the process, we paid attention to the effect of the adjustment rolling on the shape of the steel sheet. The final shape of the steel sheet changes depending on the reduction amount of the adjustment rolling (hereinafter, the adjustment reduction amount). With the increase in the adjustment reduction amount, the shape changes from a Tyco shape in which the plate width expands at the center in the longitudinal direction to a substantially rectangular shape, and changes to a Tsutsumi shape in which the plate width is depressed at the center in the longitudinal direction.

[0011] Therefore, for each rolling, the yield can be optimized by performing the adjustment rolling with the adjustment reduction amount at which the shape of the final steel sheet becomes substantially rectangular. However, in consideration of variations in the dimensions of the material, temperature, rolling conditions, and the like, such a control method provides an overall yield, that is, an average value of the variation in the yield of each rolling,
I found that it was not always the best.

This means that the yield of each steel plate is maximum when the shape of the steel plate is rectangular, but is not maximum in consideration of variations. In other words, performing the adjustment rolling under conditions different from the conditions under which the final steel sheet shape is substantially rectangular is to optimize the overall yield. At first glance, this is contrary to the conventional wisdom, and thus was not considered in the prior art. Hereinafter, the reason will be described.

First, the relationship between the adjustment reduction amount and the final steel sheet shape is obtained, as shown in FIG. 1 as an example. Here, the shape of the steel sheet is represented by a change in the sheet width, and the width variation on the vertical axis is a value obtained by subtracting the sheet width (average value) at the front and rear ends from the sheet width at the center in the longitudinal direction of the steel sheet. From this figure, it can be seen that the width deformation amount is represented by a linear expression of the adjustment reduction amount.

Next, the relationship between the width irregularity and the yield of each steel plate is examined, as shown in FIG. The yield of each steel sheet is maximized when the width of the steel sheet is substantially rectangular, and the yield decreases as the width of the steel sheet increases. Here, it is necessary to note that the degree of the decrease in the yield differs depending on which side the height of the width irregularity shifts. Therefore, when the center of the variation is set in a region where the reduction in the yield is small, the reduction in the overall yield is small.

In FIG. 2, when the width variation amount shifts to the positive side (taiko type) with respect to the same difference in the width variation amount, the yield is greatly reduced, and when the width variation amount shifts to the negative side (tsuzumi type). Indicates that the decrease in yield is small. In consideration of the variation, it is preferable that the frequency of the thrush type is included in the variation more than that of the Tyco type. As described above, in order to optimize the average yield, it is better to shift the width irregularity amount to the negative side (knob-shaped) than the width irregularity amount where the shape of the steel sheet is substantially rectangular, and to control it.

The relationship between the width irregularity and the yield has been described above, but this also applies to the adjustment rolling amount having a linear relationship with the width irregularity. Therefore, in the adjustment rolling, it is better to control the adjustment reduction amount by shifting the adjustment reduction amount to a higher side than the adjustment reduction amount in which the shape of the steel sheet is substantially rectangular.

As described above, in the present invention, first, the relationship between the amount of reduction in the adjustment rolling and the shape of the steel sheet after the finish rolling is determined. In this case, as the shape of the steel sheet, various parameters other than the above-mentioned width irregularity amount can be used. Next, using this relationship, the relationship between the adjustment reduction amount and the yield is calculated.
Using the result, the rolling reduction of the adjusted rolling at which the average value of the yield is the best is calculated.

Here, the calculation of the rolling reduction is performed within the range of variation in the shape of the steel sheet after finish rolling. This means that, with respect to the relationship between the adjustment reduction amount obtained from the actual rolling result and the like and the yield, the adjustment reduction amount that optimizes the average value of the yield is calculated within the range of the variation (standard deviation or the like). .

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS When the present invention is applied to the production of a thick steel plate, the following is achieved. FIG. 3 is a diagram showing a typical example of rolling of a thick steel plate. First, in the adjustment rolling, rolling is performed by changing the rolling reduction in the rolling direction such that the plate thickness at the front and rear end portions of the slab is greater than the center portion. As a result, the rolled material after the adjustment rolling has a so-called dogbone shape in which the plate thickness at the front and rear ends is large.

In the next tentering rolling, rolling is performed in several passes by rotating the rolling direction by 90 degrees. Also in this case, the dog bone shape is used. Thereafter, in finish rolling, the rolling direction is rotated again by 90 degrees, rolling is performed for several passes, and the rolling is completed.

Hereinafter, embodiments of the present invention will be described.
First, the relationship between the adjustment reduction amount and the width irregularity amount was as shown in FIG. 1 described above. From this, it was found that the adjustment reduction amount at which the average yield was the best was shifted to a higher side than the adjustment reduction amount at which the individual yield was the best.

When the average yield in the case where the adjustment reduction amount is set as described above is compared with the case where the individual yield is optimized, the average yield is improved by 0.1%.

[0023]

According to the present invention, the relationship between the reduction amount of the adjustment rolling and the yield is calculated from the relationship between the reduction amount of the adjustment rolling and the shape of the steel plate after finish rolling, and the average value of the yield in consideration of the variation in the shape of the steel plate is best. Is performed. Therefore, it is possible to improve the overall yield as compared with the case where control is performed to make the shape of each steel plate rectangular.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an adjustment reduction amount and a final steel sheet shape.

FIG. 2 is a diagram schematically showing the relationship between the width irregularity and the yield of individual steel plates.

FIG. 3 is a view showing a typical example of rolling of a thick steel plate.

Claims (1)

[Claims] (1) After performing an adjustment rolling in which the plate thickness at the front and rear end portions of the slab is made thicker than the center portion, the rolling direction is set to 90 °.
In the shape control method of the thick steel plate to perform the tentering rolling to roll by the degree rotation, and then perform the finish rolling, the relationship between the reduction amount of the adjustment rolling and the steel plate shape after the finish rolling is determined in advance, and using this relationship, Calculate the relationship between the reduction amount of the adjustment rolling and the yield, and further, within the range of the variation in the shape of the steel sheet after finish rolling, calculate the reduction amount of the adjustment rolling that optimizes the average value of the yield, and perform the adjustment rolling. A method for controlling the shape of a thick steel plate, wherein the shape is controlled by controlling the amount.