JPH10235402A - Method for edging slab - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the securement of the width accuracy of a slab and reduction of crop loss coexist by determining the difference between the rolling reduction with a press in the tip part in the longitudinal direction and that in the middle part in the longitudinal direction based on the mitigation of the rolling reduction in the middle part in the longitudinal direction of the material which is rolled with an edger mill and the amount of edging with the press device. SOLUTION: Crop control is executed by providing a quantity for reducing the rolling reduction to the amount of edging in the middle part which is called a pattern controlled variable at the time of reducing the front and rear ends with the press device. The edging is like (a) and (b), for example, in the rear end part. The rolling reduction in the end parts is reduced wider than the rolling reduction in the middle part by the pattern rolling reduction with the press device. In the edger mill following to the horizontal rolling, the rolling reduction based on the pattern controlled variable with the press device in addition to the predetermined rolling reduction in the middle part is rolled. Then, in the middle part, the rolling reduction with the press device and edger mill is determined around the width control and, in the front and rear end parts, the pattern controlled variable is determined around the crop control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing the width of a slab while reducing the slab width and the crop loss when the slab is roughly rolled by hot rolling.

[0002]

2. Description of the Related Art In recent years, an operation has been performed in which a wide material is cast by continuous casting and the width is changed by a hot rolling mill. At that time, in order to continuously perform operations from continuous casting to hot rolling, it is necessary to synchronize the continuous casting and hot rolling mill. Reduction is required. For this reason, a hot rolling mill is equipped with a pressing device for reducing a large width and an edger rolling mill having a large-diameter roll.

[0003] However, when such a large width reduction is performed during rough rolling in hot rolling, a swelling occurs in the sheet thickness direction in accordance with the amount of reduction, and in the subsequent horizontal rolling, the swell flows in the width direction. A width return occurs. The swell amount and swell position at this time are
It differs depending on the amount of reduction and reduction method (press reduction, edger rolling), and also depends on the position in the longitudinal direction of the material to be subjected to width reduction. As a result, in horizontal rolling following width reduction,
The width return amount is different due to the difference in the bulge, and when performing the same width reduction in the entire length in the material longitudinal direction, the width return amount is smaller at the rear end of the material than at the center in the material longitudinal direction,
Since the material also flows in the longitudinal direction, there is a portion called a crop that does not become a product.

FIG. 1 (a) shows a tongue-like crop I observed when horizontal rolling is performed after pressing, and FIG. 1 (b)
FIG. 3 is an explanatory view showing fishtail-shaped crops II that are seen when horizontal rolling is performed after edging rolling.

As described above, when performing the width reduction, it is necessary to consider the width return and the material flow in the longitudinal direction which differ depending on various methods and the amount of reduction. Even in the past,
Several means for preventing such crop generation have been proposed.

[0006] For example, Japanese Patent Publication No. 6-79721 discloses a front-rear end portion in the longitudinal direction of a material by pressing (hereinafter referred to as "the present specification") in consideration of only prevention of width reduction at a front-rear end portion in the longitudinal direction of a material in horizontal rolling after pressing. A method has been proposed to reduce the amount of reduction in the central part in the longitudinal direction of the material (hereinafter also abbreviated to the central part) in accordance with the difference in width return, according to the difference in width return. I have. In other words, in this method, in order to prevent a phenomenon that the width of the front and rear ends of the material becomes narrower than the width of the central portion, which is said to be reduced, the operation of reducing the press reduction amount at the front and rear ends compared to the center is performed. . However, in this method, although the width drop at the front and rear ends may be prevented, the crop cannot be suppressed, and the control of the entire planar shape is not sufficient.

In Japanese Patent Publication No. 6-83841, attention is paid only to the occurrence of crops at the front and rear ends, the central portion is reduced by a pressing device, and only the front and rear ends are reduced by the pressing device. Has been proposed to reduce the pressure by an edger rolling mill. In other words, in order to perform crop control, the pressing amount of the pressing device at the front and rear ends is reduced with respect to the center,
The reduced rolling amount is rolled by an edger rolling mill. However, this method does not consider the influence on the width of the central portion, and simply ends the crop control. In addition, in the central part, the example shows that almost no reduction by the edger rolling mill is taken,
In this case, the width fluctuation at the center cannot be suppressed.

[0008]

As described above, a method for simultaneously satisfying both the width control and the crop control in consideration of the flow of the material has not existed up to now. That is the current situation.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a width reduction method which ensures both the accuracy of slab width and the reduction of crop loss when coarsely rolling a slab by hot rolling.

[0010]

Conventionally, in consideration of such various rolling methods and amounts, a crop at the front and rear ends of a material and a width at a central portion in the longitudinal direction of the material are simultaneously controlled to consider the entire planar shape. The width reduction method is not considered.

Here, the present inventors perform width control and crop control by adjusting the ratio of the extreme reduction by the pressing device to the total reduction by the edger rolling mill of the subsequent rough mill, and further perform the width control and the crop control. It has been found that the above-mentioned problems can be effectively achieved by performing the crop control by determining the amount of reduction of the front and rear end presses based on the reduction amount ratio, and completed the present invention.

Therefore, the gist of the present invention is as follows. (1) In a hot rolling roughing mill having a pressing device and an edger rolling mill, the total amount of reduction in edging rolling by the edger rolling machine in the central portion in the material longitudinal direction and the width of the central portion in the material longitudinal direction by the pressing device. A width reduction method for a slab, wherein a difference between a press reduction amount at a longitudinal front end portion and a press reduction amount at a longitudinal center portion is determined based on a reduction amount.

(2) In a hot rolling rough mill having a pressing device and an edger rolling mill, the sum total of the amount of reduction to be edged by the edger rolling mill at the center in the longitudinal direction of the material and the press at the central portion in the longitudinal direction of the material. The ratio to the width reduction by the device is set to 0.2 or more and 0.5 or less, and based on the ratio, the difference between the press reduction at the front and rear ends in the longitudinal direction and the press reduction at the center in the longitudinal direction is determined. Slab width reduction method.

(3) In a hot rolling rough mill having a pressing device and an edger rolling mill, the sum total of the amount of reduction in edging rolling by the edger rolling machine in the central portion in the longitudinal direction of the material and the press in the central portion in the longitudinal direction of the material are determined. The ratio of the width reduction by the device to 0.2 or more and 0.5 or less, and based on the ratio, the difference between the pressing reduction at the front and rear ends in the longitudinal direction and the pressing reduction at the center in the longitudinal direction is determined from 0 mm to 40 mm. A width reduction method for a slab.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, when considering width control, it is necessary to consider automatic width control (hereinafter, AWC) for the purpose of suppressing the width fluctuation of the material in the longitudinal direction. Since the AWC continuously controls the width fluctuation in the longitudinal direction, the control by an edger rolling mill is generally used in a rough mill. Therefore, the initial rolling reduction of the central edger rolling mill must be set to a value operable as the AWC.
In other words, it is necessary that the edger load at the time of the initial setting has a margin with respect to the maximum load and that a certain load is applied. For this reason, the rolling reduction by the normal edger rolling mill is such that the edger load due to the rolling reduction is within a certain range with respect to the maximum load (for example, 10 to
90%). The amount of reduction of one press device is determined so as to have a target width on the rough mill exit side.

However, when the width of the entire length is reduced by setting the amount of reduction of the press device, the rear end of the material becomes
As shown in FIGS. 1A and 1B, crops I and II occur largely. The occurrence of this crop is reduced to a tongue shape when the width is reduced by a press device [see FIG. 1 (a)], and to a fish shape when the width is reduced by an edger rolling machine [FIG. 1 (b)].
It is also known that the occurrence of these crops is caused by the pressure reduction at the rear end of the material.

Therefore, in order to perform crop control with respect to the amount of reduction of the edger rolling mill and the amount of reduction of the pressing device, which are determined mainly in consideration of the width control, the pattern control is performed when the pressing device lowers the front and rear ends. The amount to reduce the amount of reduction was provided with respect to the amount of width reduction at the center called the amount.

As a result, the width reduction by the press device and the edger rolling mill is as shown in FIGS. 2 (a) and 2 (b). In the illustrated example, only the rear end is described, but the same applies to the front end. First, the pressing amount of the end portion is reduced by the pattern control amount wider than that of the central portion by the pressing device. In the edger rolling mill following the horizontal rolling, the amount of reduction based on the amount of pattern control by the press device is rolled in addition to the amount of reduction in the center determined previously.
At this time, the increment of the amount of reduction of the front and rear ends by the edger rolling mill is, as described above, because there is a width return,
Actually, there is an increase in the reduction amount beyond the pattern control amount.

For example, when the pattern control amount is set to ΔWpt ′, the width of the portion where the pattern is controlled by the horizontal rolling immediately after the pressing reduction returns to the width ΔWpt ′ ^* rp with respect to the central portion (rp Is 1 or more). The portion is then rolled by an edger rolling mill. Here, since the reduction amount .DELTA.Wel 'at the center is set in advance, the total at the front and rear ends is .DELTA.wpt' ^* rp + We.
l '. In the subsequent horizontal rolling, a width return (Δwpt ' ^* rp) * x1 corresponding to the pattern control amount that was not considered in the reduction amount in the center portion occurred (x1 is the width return after the edging reduction in the first pass. In the subsequent edger rolling mill, rolling is performed in which the amount of reduction is increased by Δwpt ′ ^* rp * x1 in addition to the amount of reduction Δwe2 ′ at the center. In this way, by performing the edging reduction a plurality of times, a small pattern control Δwpt ′
For each edger mill, Δwpt '
^* rp, Δwpt ' ^* rp * x1, wpt' ^* rp * x1 * x2 ...
For an edger mill, this leads to a considerable increase in reduction.

By providing the pattern control amounts at the front and rear ends as described above, the amount of reduction by the pressing device at the center and the front and rear ends and the amount of reduction by the edger rolling mill can be changed, so that crop control becomes possible. Become.

Summarizing the above, the central portion determines the amount of reduction by the press device and the edger rolling mill mainly on the width control, and the front and rear ends determine the pattern control amount mainly on the crop control.

The inventors of the present invention have conducted studies and experiments on what factor the crop length is quantitatively related to, and as a result, have found that the amount of reduction by a press device (hereinafter, also referred to as press reduction amount) and It has been found that there is a relationship with the total rolling amount edged by the rough mill (hereinafter, also referred to as the total rolling amount of the edger).

It has also been found that the crop length can be expressed numerically by the ratio of the total reduction amount of the edger and the reduction amount of the press as shown in FIG.
Further, the relationship is changed by changing the pattern control amount at the front and rear end portions, as described above, so that the pattern control amount at the front and rear end portions shown in FIG. By adding 10 mm and 20 mm, respectively, as shown in FIG.
, (C), it was also found that there was a large change. FIG. 3 shows an example in which the slab dimension is 1250 mm. This makes it possible to control crop control quantitatively.

Here, the crop length is defined on the rough mill exit side from the point where the width becomes narrower than the steady width (point A) as shown in FIGS. In the longitudinal direction up to the center in the width direction (point B).

The procedure for determining the actual width reduction is as follows. The amount of press reduction at the center and the amount of reduction by the edger rolling mill in the subsequent rough mill, that is, the total amount of reduction of the edger are determined. Calculate the crop length from the ratio of the total reduction of the edger and the reduction of the press determined in. If crop control is necessary, the pattern control amount is determined based on the above ratio.

Here, the maximum pattern control amount (determined from the viewpoint of the capability of the edger rolling mill and the stable operation) In order to control the crop length to about ± 10 mm at 40 mm or less, the total reduction amount of the edger at the center is required. Press ratio from 0.2 to 0.2
0.5.

According to the above policy, the actual width reduction amount determination method is determined by the flow as shown in FIG. Here, a description will be given based on the flow of FIG. 4. First, the width change amount is determined based on the manufacturing instruction information from the higher order. The change amount at this time is defined as ΔW.

Next, on the basis of this, the amount of rolling reduction in each pass of the edger rolling mill (in the case of an edger rolling mill row having a plurality of stands, the amount of rolling reduction in each of a plurality of stands, which will be representatively described in each pass) and press Determine the amount of reduction. Here, the relationship between the press reduction amount and the width change amount by the press device is expressed by Expression (1), and the relationship between the edger reduction amount for each pass and the subsequent edger width change amount by the horizontal roll is expressed by Expression (2). You.

ΔWp = f (ΔWp ′, Ws,...) (1) Here, the function f is, for example, ΔWp = a1 + a2 * (ΔW
such as ^{p '/ Ws -a3) ** 2} , ΔWp: press width change amount, Ws: slab width, a1 ~a3
: The coefficient 'is the width reduction ΔWe (i) = f (i) [ΔWe (i)', Win, Re (i), H (i), ...] (2) where the function f is, for example,

[0030]

(Equation 1)

Here, the horizontal rolling mill H: thickness of the entering side plate,
h: Outboard thickness, Win: Inlet width, ch: coefficient, cm: coefficient,
We: edger width change amount, Re: edger radius, and the suffix (i) indicates the i-th pass. 'Indicates width reduction.

The relationship between the crop length and the sum of the amount of press reduction and the amount of edger reduction is expressed by equations (3) and (4). Lh = fch (ΣΔWe ′ (i), ΔWp ′, Δwph ′) (3) Lt = fct (ΣΔWe ′ (i), ΔWp ′, Δwpt ′) (4) Δwph ′: tip press pattern control amount, Lh: tip Crop length Δwpt ': trailing end press pattern control amount, Lt: trailing end crop length Furthermore, the amount of reduction of each pass edger is reduced.

[0033]

(Equation 2)

Automatic width control (AW
Edge weight reduction constraint converted from the edger load constraint for C), ΔWemin ′ <ΔWe ′ (i) <ΔWemax ′ (6) Wemin ′: Minimum reduction amount Wemax ′ converted from the limit of the edger load lower limit based on AWC: The maximum reduction amount converted from the limit of the upper limit of the edger load based on the AWC. From the above formula, the crop lengths Lh and Lt are set to appropriate values Lhaim and Lha.
Equations (1) to (4) are converted to constraint equations (5) and (6) so that
By solving the equation, it is possible to control the width and set the amount of reduction that can reduce the crop. At this time, Δwph ′ and Δwpt ′ in equations (3) and (4) are calculated as zero. Further, depending on the conditions of the expressions (5) and (6), the expressions (3) and (4) may not be completely satisfied. Determine the edger reduction amount.

In the following, Lhaim, Ltami
Is not satisfied, the crop length Lh in that case
x and Ltx are obtained respectively. Finally, equation (3) is set so that the crop lengths Lhx and Ltx become Lhaim and Ltami.
.DELTA.wph 'and .DELTA.wpt' are determined based on the equation (4).

That is, if the calculated crop length is long and it is necessary to perform crop control, the pattern control amount is determined based on the above ratio. If the calculated crop length is sufficiently short, the pattern control amount is set to zero and pattern control is not performed. In the crop control, a required crop length is specified in advance using a table or the like, and the crop control is started when a crop length longer than that is calculated.

Thus, according to the present invention, the accuracy of the slab width reduction is adjusted by adjusting the ratio of the total reduction amount of the edger / the reduction amount of the press to, for example, 0.2 to 0.5 and further adjusting the pattern control amount as required. Crop loss can be reduced as much as possible.

[0038]

Next, the effects of the present invention will be described more specifically with reference to examples. FIG. 5 is a schematic explanatory view of a rolling facility for implementing the present invention. Here, a width reduction device using a rough mill is shown. In the figure, a slab to be reduced in width is heated in a heating furnace 1 and then subjected to width reduction and width return by a press device 2 and a horizontal rolling device 3, Next, width reduction and width return are similarly performed in the edger rolling mill 4 and the horizontal rolling device 5. However, the edger mill 4 and the horizontal mill 5 are lever mills. Reference numeral 7 denotes a host computer that determines rolling instruction information, and reference numeral 6 denotes a computer that determines a rolling reduction of a press device, an edger rolling mill, or the like. In such a facility, when the slab width and the rough mill exit side width are specified by the upper computer 7, the lower computer 6 determines the width change amount ΔW described above, and then calculates the above-described formula (1) ) To (6), the edger reduction amount ΔWe (i) ′, the press reduction amount ΔW
p ′ and press pattern control amounts Δwph ′ and Δwpt ′ are determined.
Table 1 shows the reduction amount of each equipment determined based on these.

[0039]

[Table 1]

Next, the present invention will be described more specifically using the example of Case 2. First, the range of the amount of reduction when converted to the amount of reduction from the load constraint of the edger rolling mill is 10
mm to 40 mm. Further, the rolling reduction ratio is set to 4: 3: 1 according to each path load distribution. From this, the press reduction amount and each pass reduction amount in the edger rolling mill are determined, and the crop length at that time is apparently from FIG. 3 because the reduction amount ratio between the edger rolling mill and the pressing device is about 0.35.
It occurs around 90mm. Therefore, the pattern control amount at the rear end is
By setting it to 20 mm, the crop at the rear end is slightly tongue-shaped
It could be reduced to about 20mm. The width fluctuation at this time is
Due to the margin of reduction by the edger mill,
As shown in (a) and (b), the width variation in the plate can be suppressed from 3 mm to 1 mm. This is because in the above-described conventional crop control method, the edge width reduction at the central portion is not ensured, so that such a fluctuation in the inner width cannot be suppressed.

FIGS. 7A and 7B show the change in the crop shape at this time. As described above, the ratio of the reduction amount of the edger rolling mill and the pressing device in the steady portion [(total reduction amount of the edger) / (press reduction amount)] is set to an appropriate value (0.2 to 0.5), and the pattern control amount is set to (from 0 to 0.5). 40 mm), the crop shape became smaller from 1 mm to 0.67 mm in crop length. The illustrated example is a case where the pattern control amount is 20 mm.

Further, even when comparing the control with and without the control during the same period, the control according to the present invention allows the trailing end crop length to be increased in either the dang-like crop or the fish-like crop as shown in FIG. Even in the case of, it was possible to greatly reduce.

[0043]

As described above, according to the present invention, the width reduction control and the crop control can be realized at the same time, and their practical significance is great.

[Brief description of the drawings]

FIG. 1A is a schematic explanatory view showing the definition of a crop shape and a crop length at the rear end only by a press, and FIG. 1B is only by an edger.

FIGS. 2 (a) and 2 (b) are explanatory diagrams of reduction by each facility.

3 is a graph showing the relationship between the ratio of the total reduction amount of the edger and the press reduction amount and the trailing end crop length. FIG. 3 (a) shows no pattern control amount, and FIG. 3 (b) shows a pattern control amount of 10 mm. 3
(c) shows the result in each case of the pattern control amount of 20 mm.

FIG. 4 is a flowchart of a reduction amount determination logic.

FIG. 5 is a schematic diagram of the equipment of the present invention.

FIGS. 6 (a) and 6 (b) are graphs showing the results of variations in the inner width of the plate.

FIGS. 7A and 7B are explanatory diagrams showing crop control results. FIG.

FIG. 8 is a graph showing a change in crop loss.

[Explanation of symbols]

 1: Heating furnace, 2: Press machine, 3: Horizontal rolling machine, 4: Edger rolling machine, 5: Horizontal rolling machine, 6: Computer, 7: Host computer

Claims (3)

[Claims] In a hot rolling roughing mill having a pressing device and an edger rolling mill, a total sum of reduction amounts to be edged by said edger rolling machine in a central portion in a longitudinal direction of the material and the pressing device in a central portion in a longitudinal direction of the material. A width reduction method for a slab, comprising: determining a difference between a press reduction amount at a front-rear end portion in a longitudinal direction and a press reduction amount at a central portion in a longitudinal direction, based on a width reduction amount by a slab. 2. In a hot rolling rough mill having a pressing device and an edger rolling mill, a sum total of a reduction amount to be edged by the edger rolling machine in a central portion in the longitudinal direction of the material and the pressing device in a central portion in the longitudinal direction of the material. The ratio between the width reduction by the width of 0.2 and 0.5 or less, based on the ratio, to determine the difference between the amount of press reduction at the front and rear ends in the longitudinal direction and the amount of press reduction at the center in the longitudinal direction. Slab width reduction method. 3. In a hot rolling rough mill having a pressing device and an edger rolling mill, a sum total of a reduction amount to be edging-rolled by the edger rolling machine in a central portion in a longitudinal direction of the material and the pressing device in a central portion in a longitudinal direction of the material. The ratio between the width reduction by 0.2 and 0.5 or less is determined based on the ratio, and the difference between the pressing reduction at the front and rear ends in the longitudinal direction and the pressing reduction at the center in the longitudinal direction is determined from 0 mm to 40 mm. A width reduction method for a slab, characterized in that: