JP2005246427A - Method for rolling slab - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve productivity by shortening rolling time when the controlled rolling of two or more slabs is continuously performed. <P>SOLUTION: In this rolling method, when two slabs are continuously rolled by the controlled rolling by which finish rolling is performed after performing cooling after rough rolling, the thickness of one or both slabs after rough rolling is successively changed within the range of allowable thickness after rough rolling of both slabs. Whether or not tandem rolling by which the succeeding slab is rough rolled during cooling after performing the rough rolling of a preceding slab and the finish rolling of the preceding slab is performed during cooling after ending the rough rolling of the succeeding slab is possible is determined about the changed thickness. In the case the tandem rolling is possible, tandem-rolling time is calculated and, in the case the tandem rolling is impossible, the single rolling times for performing the rough rolling and the finish rolling of the succeeding slab after performing the rough rolling and the finish rolling of the preceding slab are calculated. In this method, the rolling is performed by selecting the thickness after rough rolling by which the time becomes shortest among the calculated rolling times. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    The present invention relates to a method of rolling a control rolled material that is subjected to finish rolling after rough rolling and cooling.

In recent years, control rolling (Controlled Rolling) has been adopted in which rolling of a thick steel plate having a thickness of, for example, 6 mm or more from a slab is performed after rough rolling and cooling and then finishing rolling. Various proposals have been made for this controlled rolling method.
For example, in Japanese Patent Laid-Open No. 59-61504, a cooling zone is provided outside the rolling line, and when waiting for the temperature of the steel sheet, cooling is performed there, and effective use of the rolling line is required. A method for improving the efficiency of a steel sheet having a low rolling efficiency is disclosed.
Japanese Laid-Open Patent Publication No. 60-180604 discloses a cooling bed that can be transported from the rolling line to the rolling material transport line between the rolling line and the rolling material transport line, and transported from the rolling material transport line to the rolling line. There is disclosed a method of providing a possible cooling bed, air-cooling a rolled intermediate thickness rolled material to a predetermined temperature in the cooling bed and the rolled material conveyance line, and then returning to the rolling line and rolling to a predetermined finished thickness. .
However, the methods disclosed in Japanese Patent Laid-Open Nos. 59-61504 and 60-180604 continuously control and roll two or more slabs at the thickness after rough rolling determined from the rolling schedule. Thus, the sheet thickness after the rough rolling is not necessarily optimal (shortest rolling time) and the rolling cannot be realized.
JP 59-61504 A JP 60-180604 A

    The present invention solves the problems of the prior art as described above and provides a slab rolling method for shortening the rolling time and improving the productivity when continuously rolling two or more slabs. The task is to do.

The present invention has been made as a result of intensive studies to solve the above-mentioned problems, and the thickness of the two slabs made of a control rolled material that is subjected to finish rolling after being subjected to rough rolling and cooling is subjected to rough rolling. By devising the setting method, the present invention provides a slab rolling method capable of reducing the total rolling time of the preceding material and the succeeding material, and the gist thereof is as described in the claims. The contents are as follows.
(1) When continuously rolling two slabs that are subjected to controlled rolling that is subjected to finish rolling after rough rolling and cooling, the thickness of one or both of the slabs after rough rolling is sequentially changed and changed. Is it possible to perform tandem rolling in which the subsequent slab is roughly rolled during the cooling after the preceding slab is roughly rolled in terms of sheet thickness, and the preceding slab is finish-rolled during the cooling after the rough rolling of the succeeding slab is finished? If tandem rolling is possible, the tandem rolling time is calculated. If tandem rolling is impossible, the preceding slab is roughly rolled and finish-rolled, and then the subsequent slab is roughly rolled and finish-rolled. This is a slab rolling method in which the rolling time is calculated, and the sheet thickness after rough rolling is selected and rolled, which is the shortest among the calculated rolling times.
(2) The slab rolling method according to (1), wherein after determining whether the tandem rolling is possible, the tandem rolling time is calculated only when the tandem rolling is possible.
(3) A plurality of sheet thicknesses after rough rolling of one or both of the slabs are set in advance, a table is created for each set sheet thickness of both slabs, and the rolling time is calculated for each of the table combinations. The slab rolling method according to the means (1) or (2).

    According to the present invention, various thicknesses after rough rolling of two slabs made of a control rolled material that is subjected to finish rolling after rough rolling and cooling are variously changed, and the preceding material and the succeeding material therein. By predicting and calculating the total rolling time, and selecting the one with the shortest predicted calculated total rolling time, there are industrially useful effects such as shortening the rolling time and improving productivity.

The best mode for carrying out the invention will be described in detail with reference to FIGS.
FIG. 1 is a diagram showing a rolling procedure of tandem rolling used in the present invention.
In FIG. 1, first, the preceding material a is caught in the rolling mill and then roughly rolled for the time to wait for cooling (t1a) and cooled for the temperature waiting time (t2a) necessary to reach the target temperature. And finish-rolled for the rolling time (t3a) after waiting for the temperature.
Similarly, the trailing material b is caught in the rolling mill and then roughly rolled for the time to wait for cooling (t1b) and cooled for the temperature waiting time (t2b) necessary to reach the target temperature. Finish rolling is performed only for the rolling time (t3b) after waiting for the temperature.
Single rolling is ordinary rolling, in which the preceding material a is roughly rolled and finish-rolled, and then the subsequent material b is roughly rolled and finish-rolled.

As shown in FIG. 1, in tandem rolling, the subsequent material b is roughly rolled while the preceding material a is being cooled, and the preceding material a is finish-rolled while the subsequent material b is being cooled. In general, the total rolling time of the preceding material a and the succeeding material b can be shortened as compared with the single rolling.
However, when the plate thickness after rough rolling is thick and the cooling after rough rolling is air cooling, the time required for cooling may be significantly increased. However, the total rolling time may be shortened.
For this reason, when the cooling is water cooling, the total rolling time may be calculated only when tandem rolling is possible. When the cooling is air cooling, it is preferable to calculate the total rolling time for both tandem rolling and single rolling.

The plate thickness of the slab after rough rolling is constant according to the specifications of each slab, for example, when the plate thickness of a steel plate of a certain final product is 20 mm, the plate thickness of the slab after rough rolling is 40 mm to 50 mm. The temperature waiting time differs depending on the thickness of the slab after rough rolling.
Therefore, the present inventors have found that the total rolling time of both slabs is shortened by combining the plate thicknesses of the preceding material a and the succeeding material b after the rough rolling to complete the present invention. It was.

    In the present invention, when rolling two slabs made of a control rolled material that is subjected to finish rolling after rough rolling and cooling, various thicknesses of the two slabs after rough rolling are variously changed, and tandem rolling is performed. Judge whether or not it is possible, predict the total rolling time of both slabs for each of the combinations capable of at least tandem rolling, select the shortest total rolling time combination, and calculate the sheet thickness after rough rolling As a result, the productivity is improved.

When variously changing the plate thickness after rough rolling of the two slabs, the total rolling time may be calculated by sequentially changing with a preset dimension pitch (for example, 5 mm pitch). It is also possible to have a combination of sheet thickness dimensions and calculate the total rolling time according to this table.
In addition, since the pass schedule of rough rolling and finish rolling is usually determined when rolling the slab, the thickness of the plate after the rough rolling is determined in advance so that it is not necessary to change the pass schedule greatly. It is preferable to carry out within an allowable plate thickness range in the determined rough rolling.

FIG. 2 is a diagram showing a flow of a slab rolling method according to the present invention.
When rolling two slabs made of a control rolled material that is subjected to finish rolling after rough rolling and cooling, first, a table of combination patterns is created for each plate thickness after rough rolling of the two slabs (S -1).

Next, it is checked whether the cooling time of the preceding material exceeds the rough rolling time of the succeeding material, and the cooling time of the succeeding material exceeds the finish rolling time of the preceding material. A roll that can be rolled and does not satisfy this condition is not tandem rolled and is single rolled (S-2).
When tandem rolling is possible, the total rolling time from the start of rough rolling of the preceding material to the end of finish rolling of the succeeding material is calculated (S-3).
Calculate this total rolling time according to the procedure shown in the following formula, and consider the allowance time to avoid interference between the preceding material and the following material, and the shortening of the cooling time when cooling by water cooling instead of air cooling. Is preferred.
In the case of single rolling, the preceding material is subjected to rough rolling and finish rolling, and then the total rolling time when the subsequent material is subjected to rough rolling and finish rolling is calculated (S-4).
Further, the same processing is performed by changing the order of the preceding material and the succeeding material, the combination pattern having the shortest total rolling time is selected (S-5), and finish rolling is performed so that the thickness of the selected combination pattern is obtained. I do.

By the above procedure, whether or not tandem rolling is possible for a plurality of combination patterns and the rolling order of each pair with respect to the sheet thickness after rough rolling of two slabs made of controlled rolled material that is subjected to finish rolling after rough rolling and cooling The total rolling time is calculated, and the rolling time can be shortened by selecting the combination pattern that shortens the rolling time of all the slabs, thereby improving the productivity. .
In addition, although the case where it applied to the single stand was demonstrated in FIG. 1, this invention is not limited to this, It is applicable also to a twin stand.

表２は、先行材および後行材の粗圧延後における板厚の組み合わせパターンにおける合計圧延時間を示す。
本実施例に用いたタンデム圧延時間Ｔｔの計算式を以下に示す。
Ｔｔ＝ｔ１ａ＋ｔ１ｂ＋ｔ２ｂ＋ｔ３ｂ
但し、ｔ１ａ：先行材の粗圧延時間、
ｔ１ｂ：後行材の粗圧延時間、
ｔ２ｂ：後行材の冷却時間、
ｔ３ｂ：後行材の仕上圧延時間、 Tables 1 and 2 show the results of applying the slab rolling method of the present invention to two slabs from a control rolled material for thick steel plates.
Table 1 shows the rough rolling time (t1), the cooling time (t2), and the finish rolling time (t3), which are preset according to the plate thickness after rough rolling of the slab to be rolled. The cooling in this example is air cooling.

Table 2 shows the total rolling time in the combination pattern of sheet thicknesses after rough rolling of the preceding material and the following material.
The calculation formula of the tandem rolling time Tt used in this example is shown below.
Tt = t1a + t1b + t2b + t3b
Where t1a: rough rolling time of the preceding material,
t1b: rough rolling time of the following material,
t2b: cooling time of the following material,
t3b: finish rolling time of the following material,

Moreover, the calculation formula of the single rolling time Ts at the time of single rolling is shown below.
Ts = t1a + t1b + t2a + t2b + t3a + t3b
Where t2a: the cooling time of the preceding material,
t3a: finish rolling time of the preceding material,

These two types show the case of air cooling at the front of the rolling mill, but forced cooling may be provided by providing a cooling device. In this case, the cooling time t2b of the succeeding material is shortened, and the cooling time t2bo at that time Is
t2bo = t2a-t1b + t3a
+ (T2b−t2a + t1b−t3a) / db, and the above formula is expressed as Tt = t1a + t1b + t2bo + t3b,
However, db shows the cooling ratio of the cooling by the cooling device of the rolling mill front surface, and air cooling.
Moreover, a cooling device may be provided on the rear surface of the rolling mill for forced cooling,
In that case, since the cooling time t2a of the preceding material is shortened,
t2ao = t1b + (t2a-t1b) / da

As shown in Table 2, No. 1 and No. 5 among the combinations of 9 patterns did not satisfy the conditions of tandem rolling, and therefore, tandem rolling was rejected (x). No.3, No.4, No.6 to No.9 satisfy the tandem rolling conditions, so tandem rolling is possible (○). Of these, the thickness of the preceding material after rough rolling of No.3 is The case where the plate thickness of 45 mm and the subsequent material is 40 mm is the thinnest plate thickness that can be tandem rolled, and the total rolling time at this time is the shortest of 317 seconds, and when No. 1 single rolling is performed It was confirmed that the rolling efficiency can be improved by about 30% compared to the shortest rolling time of 460 seconds.

It is a figure which shows the rolling procedure of the tandem rolling used for this invention. It is a figure which shows the flow of the rolling method of the slab in this invention.

Claims (3)

When continuously rolling two slabs that are subjected to controlled rolling that is subjected to finish rolling after rough rolling and cooling, the thickness of one or both of the slabs after rough rolling is sequentially changed, and the changed thickness Whether or not tandem rolling is possible in which the subsequent slab is roughly rolled during the cooling after the preceding slab is roughly rolled, and the preceding slab is finish-rolled during the cooling after the rough rolling of the succeeding slab is finished. If the tandem rolling is possible, the tandem rolling time is calculated.If the tandem rolling is impossible, the preceding slab is roughly rolled and finish-rolled, and then the subsequent slab is roughly rolled and finish-rolled. A method for rolling a slab, characterized by calculating and rolling by selecting a plate thickness after rough rolling that takes the shortest time among the calculated rolling times. The slab rolling method according to claim 1, wherein after determining whether or not the tandem rolling is possible, the tandem rolling time is calculated only when the tandem rolling is possible.     A plurality of sheet thicknesses after rough rolling of the one or both slabs are set in advance, a table is created for each set sheet thickness of both slabs, and the rolling time for each of the table combinations is calculated. The slab rolling method according to claim 1, wherein the slab is rolled.

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