JP3402108B2 - Slab width reduction method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slab width reduction method that achieves both slab width accuracy and reduction in crop loss when roughly rolling a slab by hot rolling.

[0002]

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

However, when such a large width reduction is performed during rough rolling in hot rolling, swelling in the sheet thickness direction occurs in accordance with the amount of reduction, and in the subsequent horizontal rolling, the swelling flows in the width direction. A width reversal occurs. At this time, the amount of rise and the position of the rise are
It also depends on the amount of reduction and reduction method (press reduction, edger rolling), and also on the longitudinal position of the material for width reduction. As a result, in horizontal rolling following width reduction,
The amount of width return differs due to the difference in swelling, and when performing the same width reduction in the entire length in the material longitudinal direction, the amount of width return is smaller at the material front and rear ends than in the central portion in the material longitudinal direction,
Since the material also flows in the longitudinal direction, there is a portion called crop, which does not become a product.

FIG. 1 (a) shows a tongue-shaped crop I observed when horizontal rolling is carried out after pressing reduction, and FIG.
[Fig. 3] is an explanatory diagram showing fishtail-shaped crops II that are observed when horizontal rolling is performed after edging rolling.

As described above, when performing 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 have been proposed for preventing the generation of such crops.

For example, Japanese Examined Patent Publication (Kokoku) No. 6-79721 discloses that the front and rear end portions of the material in the longitudinal direction of the press (hereinafter referred to as the present specification) are taken into consideration only in the width reduction prevention at the front and rear edges of the material in the horizontal rolling after the pressing. In this paper, the amount of reduction of the material is abbreviated as the leading and trailing end portions) is made smaller than the amount of reduction in the central portion in the longitudinal direction of the material (hereinafter also abbreviated as the central portion) according to the difference in width return. There is. In other words, in this method, in order to prevent the phenomenon that the width of the front and rear ends of the material becomes narrower than the width of the central part, which is called a width reduction, the operation of reducing the press reduction amount as compared with the central part is performed. . However, in this method, although the width reduction at the front and rear ends may be prevented, cropping cannot be suppressed, and it is not sufficient for controlling the overall planar shape.

In Japanese Examined Patent Publication No. 6-83841, attention is paid only to the occurrence of crops at the front and rear ends, the central part is pressed down by the press device, and only the front and rear end parts are reduced in the pressing device, and the amount of the reduction is reduced. It has been proposed to reduce the temperature by using an edger rolling mill. That is, in order to perform crop control, the amount of reduction of the press device at the front and rear ends is made smaller than the central part,
The reduced rolling amount is rolled by an edger rolling mill. However, in this method, the effect on the width of the central portion is not taken into consideration, and the mere crop control is performed. In addition, in the central portion, it is mentioned in the examples that the amount of reduction by the edger rolling mill is hardly taken,
With this, it is not possible to suppress the width variation of the central portion.

[0008]

As described above, there is no method to satisfy both width control and crop control at the same time in consideration of material flow, and the width control priority and the crop control priority are selected according to the steel type. It is the current situation.

Therefore, it is an object of the present invention to provide a width reduction method which makes it possible to ensure the width accuracy of the slab and reduce the crop loss when the slab is roughly rolled by hot rolling.

[0010]

[Means for Solving the Problems] Conventionally, in consideration of such various types of reduction methods and reduction amounts, cropping at the front and rear end portions of the material and the width of the central portion in the longitudinal direction of the material are simultaneously controlled, and the overall plan shape is considered. The width reduction method is not considered.

Here, the present inventors
Perform specific width control and crop controlled by adjusting the total reduction amount by the edger rolling mill subsequent roughing mill the total rolling reduction, further, the amount of reduction press the leading and trailing portions on the basis of the reduction amount ratio The present invention has been completed, knowing that the above-described problems can be effectively achieved by performing the crop control by making a decision.

Therefore, the gist of the present invention is as follows. (1) In a hot rolling rough mill having a pressing device and an edger rolling machine, the sum of the amount of reduction that is edging-rolled by the edger rolling machine at the central portion of the material longitudinal direction, and the width of the pressing device at the central portion of the material longitudinal direction. Calculate the ratio with the reduction amount, and
A slab width reduction method characterized by determining the difference between the press reduction amount at the front and rear end portions in the longitudinal direction and the press reduction amount at the central portion in the longitudinal direction based on the crop length predicted from the ratio of .

(2) In a hot-rolling rough mill having a pressing device and an edger rolling mill, the total sum of the amounts of reduction that are edge-rolled by the edger rolling mill at the central portion in the longitudinal direction of the material and the press at the central portion in the longitudinal direction of the material. Set the ratio to the width reduction amount by the device to be 0.2 or more and 0.5 or less, and predict from that ratio.
A width reduction method for a slab, characterized in that the difference between the press reduction amount at the front and rear ends in the longitudinal direction and the press reduction amount at the central portion in the longitudinal direction is determined based on the crop length .

(3) In a hot-rolling rough mill having a pressing device and an edger rolling mill, the sum of the reduction amounts edging-rolled by the edger rolling mill at the central portion in the longitudinal direction of the material and the pressing at the central portion in the longitudinal direction of the material. Set the ratio to the width reduction amount by the device to be 0.2 or more and 0.5 or less, and predict from that ratio.
Based on the crop length , the difference between the press reduction amount at the front and rear ends in the longitudinal direction and the press reduction amount at the central portion in the longitudinal direction is 0 mm.
Width reduction method for slabs, which is characterized by determining from 40 mm to 40 mm.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION First, when considering width control, it is necessary to consider automatic width control (hereinafter referred to as AWC) for the purpose of suppressing width variation in the longitudinal direction of a material. Since the AWC continuously controls the width variation in the longitudinal direction, the rough mill is generally controlled by an edger rolling mill. Therefore, the initial reduction amount setting of the edger rolling mill at the central portion must be set to a value at which the AWC can operate.
In other words, it is necessary that the edger load at the time of initial setting has a margin with respect to the maximum load and that a certain amount of load is applied. For this reason, the amount of reduction by the edger rolling mill is usually within a certain range (e.g., 10 ~
90%). The reduction amount of one of the pressing devices is determined so as to have a target width on the exit side of the rough mill.

However, when the width reduction of the entire length is performed by setting the reduction amount of the press device as described above, the material front and rear end portions are
As shown in FIGS. 1 (a) and 1 (b), large crops I and II occur. This crop is formed in a tongue shape when width reduction is performed by a press machine [see Fig. 1 (a)], and in a fish shape when width rolling is performed by an edger rolling mill [Fig. 1 (b)].
It is also known that the generation of the crops is caused by the width reduction of the material front and rear ends.

Therefore, in order to perform crop control with respect to the amount of reduction of the edger rolling machine and the amount of reduction of the pressing device which are predetermined in consideration of the width control, pattern control is performed at the time of reducing the front and rear end portions by the pressing device. An amount for reducing the reduction amount is provided with respect to the width reduction amount in the central portion called the amount.

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

For example, when the pattern control amount is ΔWpt ′, the width of the portion where the pattern control is performed with respect to the central portion is returned to the width by the horizontal rolling immediately after the pressing and the result is ΔWpt ′ ^* rp (rp Is 1 or more). The part is then rolled by the edger rolling machine, but here, the reduction amount ΔWel 'of the central part has been set in advance, so the total at the front and rear ends is Δwpt' ^* rp + We
It is the amount of reduction of l '. In the subsequent horizontal rolling, width reduction (Δwpt ' ^* rp) * x1 corresponding to the pattern control amount that was not taken into consideration occurs in the central reduction amount (x1 is the edging after width reduction after the first pass edging). In the subsequent edger rolling mill, the rolling amount is increased by Δwpt ' ^* rp * x1 in addition to the rolling amount Δwe2' in the central portion. By performing the edging reduction a plurality of times in this way, small pattern control Δwpt '
Is the Δwpt 'for each edger rolling mill.
^* rp, Δwpt ' ^* rp * x1, wpt' ^* rp * x1 * x2 ...
And for the edger rolling mill, it will lead to a considerable increase in the reduction amount.

By providing the pattern control amount at the leading and trailing end portions in this way, it is possible to change the amount of reduction by the pressing device at the central portion and the leading and trailing end portions and the amount of reduction by the edger rolling machine, and thus crop control is possible. Become.

In summary, the central portion determines the amount of reduction by the press device and the edger rolling machine with the width control as the center, and the leading and trailing ends determine the pattern control amount with the crop control as the center.

The inventors of the present invention have conducted research and experiments as to what factor the crop length is quantitatively related to. As a result, the amount of reduction by the press machine (hereinafter, also referred to as press reduction amount) It has been found that there is a relation with the total reduction amount edging by the rough mill (hereinafter also referred to as the total edger reduction amount).

It was also found that the crop length can be expressed numerically by the ratio of the total amount of edger reduction and the amount of press reduction as shown in FIG. 3 (here, explained as a linear form).
Furthermore, the relationship is that the pattern control amount at the front and rear ends is changed by changing the pattern control amount at the front and rear ends as described above, as compared with the case where the pattern control amount at the front and rear ends is 0 mm. By adding 10 mm and 20 mm respectively, as shown in Fig. 3 (b).
, (C), it was also found to change significantly. FIG. 3 shows an example when the slab size is 1250 mm. This makes it possible to quantitatively control the crop control.

Here, the definition of the crop length is that, on the exit side of the rough mill, as shown in FIGS. 1 (a) and 1 (b), from the point where the width becomes narrower than the steady width (point A), It is expressed by the distance in the longitudinal direction to the central portion (point B) in the width direction at.

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

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

According to the above policy, the actual width reduction amount determining method is determined by the flow shown in FIG. Here, to explain 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 ΔW.

Next, based on this, in the following, the reduction amount of each pass of the edger rolling mill (in the case of an edger rolling mill train having a plurality of stands, the reduction amount of each of a plurality of stands, which will be described below as a representative of each pass) and the press Determine the amount of reduction. Here, the relationship between the amount of press reduction and the amount of width change by the press machine is expressed by equation (1), and the relationship between the amount of edger reduction for each pass and the subsequent amount of edger width change by the horizontal roll is expressed by equation (2). It

ΔWp = f (ΔWp ′, Ws, ...) (1) Here, the function f is, for example, ΔWp = a1 + a2 * (ΔW
p '/ Ws-a3) ^**, etc., ΔWp: Press width change amount, Ws: Slab width, a1 to a3
The coefficient 'is the width reduction amount 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: entrance side plate thickness,
h: output side plate thickness, Win: input side plate width, ch: coefficient, cm: coefficient,
We: edger width change amount, Re: edger radius, subscript (i) indicates i-th pass. 'Indicates the width reduction amount.

The relationship between the crop length, the press reduction amount, and the sum of the edger reduction amounts 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 edge press pattern control amount, Lt: Trailing edge cropping length and distribution of each pass edger reduction amount

[0033]

[Equation 2]

Automatic width control (AW
C), the edger load amount constraint converted from the edger load constraint, ΔWemin '<ΔWe' (i) <ΔWemax '(6) Wemin': The minimum rollback amount Wemax 'converted from the edger load lower limit constraint based on AWC: Maximum reduction amount converted from the limit of the edger load upper limit based on AWC From the above formula, the crop lengths Lh and Lt are appropriate values Lhaim and L
Equations (1) to (4) are changed to constraint equations (5) and (6) so that
By solving based on the equation, it becomes possible to control the width and set the reduction amount that can reduce the crop. At this time, Δwph 'and Δwpt' in the equations (3) and (4) are calculated as 0. In addition, depending on the conditions of the equations (5) and (6), the equations (3) and (4) may not be completely satisfied, so that the crop lengths Lh and Lt are set to the minimum value, the press reduction amount and Determine the amount of edger reduction.

In the following, in, Lhaim, Ltami
If is not satisfied, the crop length Lh in that case
x and Ltx are obtained respectively. Finally, in order to set the crop lengths Lhx and Ltx to Lhaim and Ltami, equation (3)
, Δwph ′ and Δwpt ′ are determined based on the equation (4).

That is, if the calculated crop length is long and crop control is required, the pattern control amount is determined based on the above ratio. Further, when the calculated crop length is sufficiently short, the pattern control amount is set to zero and the pattern control is not executed. In the crop control, a control-required crop length is designated in advance by 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 can be improved by adjusting the ratio of the total edger reduction amount / press reduction amount to, for example, 0.2 to 0.5, and further adjusting the pattern control amount if desired. It is possible to reduce the crop loss as much as possible while securing it.

[0038]

EXAMPLES Next, the effects of the present invention will be described more specifically by way of examples. FIG. 5 is a schematic explanatory diagram of rolling equipment for carrying out the present invention. Here, a width reduction device using a rough mill is shown. In the figure, a slab to be width reduced 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, in the edger rolling mill 4 and the horizontal rolling device 5, width reduction and width return are similarly performed. However, the edger rolling mill 4 and the horizontal rolling device 5 are lever mills. Reference numeral 7 is a high-order computer for determining rolling instruction information, and reference numeral 6 is a computer for determining a reduction amount of a press machine, an edger rolling machine, or the like. In such equipment, when the slab width and the rough mill exit side width are specified by the upper-level computer 7, the lower-level computer 6 determines the width change amount ΔW described above. ) To (6), the edger reduction amount ΔWe (i) ', the press reduction amount ΔW
p ', press pattern control amounts Δwph', 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 case 2 as an example. First, the range of the reduction amount when converted to the reduction amount based on the load constraint of the edger rolling mill is 10
The range was from mm to 40 mm. Further, the reduction amount ratio is set to 4: 3: 1 depending on the load distribution of each path. 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 clearly 0.33 because the reduction amount ratio of the edger rolling mill and the pressing device is about 0.35.
It occurs about 90 mm. Therefore, the pattern control amount at the rear end is
By setting it to 20 mm, the crop at the rear end looks like a tongue.
It could be reduced to about 20 mm. The width fluctuation at this time is
Since there is a margin of reduction by the edger rolling mill, Fig. 6
As shown in (a) and (b), the width variation in the plate can be suppressed from 3 mm to 1 mm. This is because the crop control method described as the prior art described above cannot suppress such a variation in the plate width because the edger reduction amount at the central portion is not secured.

7 (a) and 7 (b) show changes in the crop shape at this time. In this way, the ratio of the amount of reduction between the edger rolling mill and the press in the steady part [(total edger reduction amount) / (press reduction amount)] is set appropriately (0.2 to 0.5), and the pattern control amount is adjusted from (0 to 40mm) reduced the crop shape from 1mm to 0.67mm. The illustrated example is for a pattern control amount of 20 mm.

Further, in the comparison between the control with and without the control in the same period, by performing the control according to the present invention, the trailing edge crop length is either dang-shaped crop or fish-shaped crop as shown in FIG. Even if there was, it could be reduced significantly.

[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 the practical significance thereof is great.

[Brief description of drawings]

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

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

FIG. 3 is a graph showing the relationship between the ratio of the total amount of edger reduction and the amount of press reduction and the trailing edge crop length, FIG. 3 (a) without pattern control amount, FIG. 3 (b) with pattern control amount 10 mm, Three
(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 view of equipment of the present invention.

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

7 (a) and 7 (b) are explanatory views showing a crop control result.

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

[Explanation of symbols]

1: heating furnace, 2: press machine, 3: Horizontal rolling device, 4: Edger rolling machine, 5: Horizontal rolling device, 6: Calculator, 7: Host computer

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B21B 1/02

Claims (3)

(57) [Claims] 1. In a hot-rolling rough mill having a pressing device and an edger rolling mill, the sum of the reduction amounts of the edger rolling mill at the central portion in the longitudinal direction of the material and the pressing device at the central portion in the longitudinal direction of the material. Ratio of width reduction by
Then , based on the crop length predicted from this ratio , the difference between the press reduction amount at the front and rear end portions in the longitudinal direction and the press reduction amount at the central portion in the longitudinal direction is determined, and the width reduction method of the slab. 2. In a hot-rolling rough mill having a pressing device and an edger rolling machine, the sum of the reduction amounts edging-rolled by the edger rolling machine at the central part in the longitudinal direction of the material and the pressing device at the central part in the longitudinal direction of the material. The ratio to the width reduction amount due to is set to 0.2 or more and 0.5 or less, and it is predicted from the ratio.
A slab width reduction method characterized in that the difference between the press reduction amount at the front and rear ends in the longitudinal direction and the press reduction amount at the central portion in the longitudinal direction is determined based on the crop length . 3. In a hot-rolling rough mill having a pressing device and an edger rolling machine, the sum of reduction amounts edging-rolled by the edger rolling machine at the central part in the longitudinal direction of the material and the pressing device at the central part in the longitudinal direction of the material. The ratio to the width reduction amount due to is set to 0.2 or more and 0.5 or less, and it is predicted from the ratio.
A slab width reduction method characterized in that the difference between the press reduction amount at the front and rear ends in the longitudinal direction and the press reduction amount at the central portion in the longitudinal direction is determined from 0 mm to 40 mm based on the crop length .