KR20000034286A - Hot rolling method - Google Patents

Abstract

PURPOSE: A hot rolling method is provided to minimize width deviation caused by rough material thickness by calibrating the set error of a vertical roll after measuring the entrance thickness of the material depending on the number of clogging passes. CONSTITUTION: A thickness(T(i)) before a slave is inlet into a vertical roll and a target thickness depressive amount(R(i)) of a 'i'st pass are obtained. Then a distance between vertical rolls is obtained by subtracting the value that rolling force(F(i)) and width spreading amount(DB(i)) are divided into a mill integral(M), from the target width(W(i)) of a slave exit when the slave passes through the vertical roll. Also a calibrated value(C(i)) to the distance between the vertical rolls is calculated on the basis of a slant angle(theta) to the vertical line of the vertical roll. A distance(G'(i)) is obtained by calibrating the distance between the vertical rolls and the vertical roll edges the material after moving as much as the calibrated distance.

Description

Hot Rolling Method

The present invention relates to hot rolling, and more particularly, to a vertical hot rough rolling method for compensating a width variation according to a material thickness to reduce a width variation.

Hot rough rolling process can be divided into vertical rolling (edging) and horizontal rolling. Vertical rolling is a rolling process for controlling the width of the material, horizontal rolling is a rolling process for controlling the thickness. That is, as shown in Figure 1, the slab (1) heated to a constant temperature in the heating furnace (2) is ultimately rolled through the vertical rolling roll (3) and rough rolling mill (4) in order to be manufactured into a coil of a desired size Alternating with horizontal rolling. In the case of vertical rolling to create the order width of the demand, the upper calculating machine (6) first calculates the total rolling rolling amount, and then calculates the number of vertical rolling rolls and the amount to be rolled by pass schedule. The width is set by moving the vertical rolling roll 3 according to the amount to be finally rolled through the controller 5.

Conventionally, when the vertical rolling of the slab torsional phenomenon as shown in Figure 2 occurred, this torsional phenomenon occurs mainly when the width of the rolled amount is larger than the weight of the material, due to the width of the fall and in severe cases hit the hot rolling equipment accident In some cases. In order to prevent the slab twisting phenomenon, the current vertical rolling roll 30 has a θ angle with a vertical line, as shown in FIG. 3, and has a shape widening toward an upper portion thereof. However, the structure of the vertical rolling roll 30, the torsional phenomenon of the slab is reduced a lot, but as shown in Figure 4, the height difference between the contact due to the inclination of the vertical rolling roll 30 according to the thickness of the slab material slab width There is a problem that a deviation occurs. Specifically, as shown in FIG. 4, even if the distance between the rolls of the horizontal rolling rolls 30 is set to the same distance based on the pass line of the rolling mill, the width deviation of the material occurs according to the height difference of the materials 1a and 1b. do. In fact, when the slab having a thickness of about 150 to 250 mm is horizontally rolled to about 40 to 60 mm, an error of up to 42 mm may occur depending on the height of the vertical rolling roll 30.

In this way, although a width deviation occurs due to the height difference of the vertical rolling rolls, in the related art, as shown in FIG. Hot rolling was performed.

The present invention has been proposed to solve the above-mentioned conventional problems, and its object is to calculate the side thickness of the material according to the number of rough rolling passes during hot rolling, and to correct the setting error of the vertical rolling roll for the height. Therefore, to provide a hot rolling method for minimizing the width deviation caused by the material thickness.

1 is a schematic configuration diagram of a general hot rolling facility

Figure 2 is a schematic diagram for explaining the twisting phenomenon of the slab by the vertical rolling roll

Figure 3 is a cross-sectional structural view of a typical vertical rolling roll

Figure 4 is a schematic diagram for explaining the distance difference between the vertical rolling rolls according to the slab thickness

5 is a flowchart illustrating a conventional method for setting the distance between vertical rolling rolls.

6 is a flowchart illustrating a method for setting a distance between vertical rolling rolls according to the present invention.

Figure 7 is a graph showing the width deviation of the steel sheet according to the vertical rolling method according to the prior art and the present invention

Explanation of symbols on the main parts of the drawings

1 ..... slabs, 2 ..... furnaces, 3, 30 ..... vertical rolling rolls,

4 ..... horizontal rolling mill, 5 ..... controller, 6 ..... superordinate calculator,

In the present invention for achieving the above object in the method for hot rolling the slab by a hot rolling mill having a vertical rolling roll and a horizontal rolling roll,

Obtaining a target thickness reduction amount of the i-th pass through the thickness before the slab is introduced into the vertical rolling roll and the reduction ratio of the i-th pass;

Obtaining a distance between the vertical rolling rolls to be set by subtracting the width spreading amount of the dog bone during the horizontal rolling of the dogbone and the rolling force of the vertical rolling rolls divided by the integral constant from the slab exit target width when passing through the vertical rolling rolls;

If the i-th pass is the first pass, the thickness before entering the slab; if the i-th pass is at least 2 passes or more, the thickness obtained by subtracting the target thickness reduction of the i-th pass from the slab thickness of the (i-1) th pass, Setting a reference thickness of the slab to compensate, and then calculating a correction value for the distance between the vertical rolling rolls based on the inclination angle θ with the vertical line of the vertical rolling rolls;

Obtaining a distance between the corrected vertical rolling rolls by correcting the correction value from the distance between the vertical rolling rolls to be set; And

Vertical rolling by moving the vertical rolling roll by the distance between the corrected vertical rolling rolls; It relates to a hot rolling method comprising a.

Hereinafter, the present invention will be described in detail.

First, the hot rolling method according to the present invention can be applied to any hot rolling mill having a vertical rolling roll and a horizontal rolling roll.

A flowchart of the vertical rolling method of the present invention is shown in detail in FIG. That is, as shown in Fig. 6, in the hot rolling method of the present invention, first, the thickness T [1] before the slab 1 is drawn into the vertical rolling roll 30 and the rolling reduction in any i-th pass is performed. The target thickness reduction amount R [i]; unit: mm of the i-th pass is obtained as shown in Equation 1 through the rate (B [i]; unit:%) information.

R [i] = T [1] × B [i]

That is, in order to match the target thickness of the i-th pass, the thickness of the slab was 250 mm, and when it was to be rolled horizontally to have a thickness of 100 mm, the target thickness reduction amount in the pass would be 150 mm. Therefore, knowing the reduction ratio B [i] of the i-th pass, the reduction amount R [i] at that time can be simply obtained from Equation (1).

Next, from the slab exit target width W [i] when passing through the vertical rolling roll, the spreading amount DB [i] at the time of horizontal rolling of the dog bone and the rolling force F of the vertical rolling roll Subtracting the value obtained by dividing [i]) by the mill constant M of the rolling mill, the distance G [i] between the vertical rolling rolls to be set is obtained as shown in Equation 2.

G [i] = W [i]-DB [i]-F [i] / M

That is, in the case of vertical rolling, the distance G [i] between the vertical rolling rolls is the dog bone at the slab exit target width W [i] when passing through the vertical rolling rolls, as shown in Equation 2. ), The value obtained by dividing the width spreading amount DB [i] at the time of horizontal rolling and the rolling force F [i] of the vertical rolling roll by the mill constant M of the rolling mill. Usually, both sides of the slab have a dogbone shape that protrudes convexly, and in case of vertical rolling, the spread of the dogbone shape is predetermined. In addition, even if the same reduction according to the type of rolling mill, the degree of return to the original position after the width rolling is changed according to the relationship between the rolling force and the mill constant constant is set in advance in consideration of the width degree according to the rolling force and the mill constant constant Compensate for a constant value of the rolling mill.

Next, the reference thickness of the slab should be determined in consideration of whether the i th pass is the first pass or more than two passes. In the case of the present invention, when the current rolling is the first pass, the reference thickness of the slab is the slab thickness drawn from the heating furnace. However, if any i-th pass is at least 2 passes or more, it is necessary to compensate for the thickness obtained by subtracting the target thickness reduction amount R [i] of the i-th pass from the slab thickness of the (i-1) th pass, which is the previous step. Determine the reference thickness of the slab. Therefore, when the i-th pass is 1 pass, the thickness T1 of the first slab obtained above, that is, Equation 3 is obtained.

T [i] = T1

However, when the second pass is two or more passes, as shown in Equation 4, the target thickness reduction amount R [R] of the i th pass obtained from Equation 1 from the slab thickness T [i-1] of the (i-1) th pass is obtained. i]) minus the thickness.

T [i] = T [i-1]-R [i]

When the reference thickness of the slab is determined as described above, the correction value for the distance between the vertical rolling rolls according to the material height can be easily calculated as shown in Equation 5 based on the inclination angle θ with the vertical line of the vertical rolling roll.

C [i] = T [i] / 2 × tan (θ × π / 180)

Then, if this correction value is corrected from the distance G [i] between the vertical rolling rolls obtained in Equation 2, the distance between the corrected vertical rolling rolls desired in the present invention can be obtained as in Equation 6.

G '[i] = G [i]-2 × C [i]

Subsequently, when the vertical rolling rolls are vertically rolled by the distance G ′ [i] between the corrected vertical rolling rolls, the width variation according to the height of the material may be minimized. However, when setting the distance between the vertical rolling rolls, the sign of Equation 6 is determined according to whether the reference point is the pass line of the vertical rolling roll 30 or the upper end of the material. In the case of the present invention, when setting between the vertical rolling rolls it is more preferable to set based on the pass line.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

The distance between the vertical rolling rolls having an inclination of about 3 ° for each of the two slabs having a thickness exceeding 230 mm and two slabs having a thickness of 230 mm or less was corrected according to the present invention, followed by hot rolling to prepare a steel sheet having a width of 1000 mm. In addition, for comparison, hot rolled steel sheets having the same width were manufactured without performing width deviation correction according to the material height in the same rolling mill as before.

The width of each steel sheet thus prepared was measured and the results are shown in FIG. 7.

In general, when manufacturing a steel sheet having a width of 1000mm, the width of the steel sheet is about 7mm. When the width correction is not performed, as shown in FIG. 7, the width deviation is large, while the vertical rolling is performed according to the present invention. In this case, it can be seen that the width deviation of the steel sheet is greatly reduced.

As described above, according to the present invention, even if variation in material thickness is caused by horizontal rolling, the width deviation generated according to the material thickness can be minimized by accurately correcting the distance between the vertical rolling rolls. The margin margin can be reduced, so it can be rolled to the target plate width, which in turn can greatly improve the width of the final product and greatly reduce the error rate caused by the width variation in the post process. have.

Claims (2)

In the method of hot rolling the slab by a hot rolling mill having a vertical rolling roll and a horizontal rolling roll, Obtaining a target thickness reduction amount R [i] of the i-th pass through the thickness T [i] before the slab is introduced into the vertical rolling roll and the reduction ratio B [i] of the i-th pass; ; Width spreading amount DB [i] at the time of horizontal rolling of the dog bone from the slab exit target width W [i] when passing through the vertical rolling roll, and rolling force F [i Obtaining a distance G [i] between vertical rolling rolls to be set by subtracting the value obtained by dividing]) by the wheat constant (M); If the i-th pass is the first pass, the slab thickness before entering the slab (T1); if the i-th pass is at least two passes, the i-th pass from the slab thickness (T [i-1]) of the (i-1) th pass; The thickness obtained by subtracting the target thickness reduction (R [i]) of the path is determined as the reference thickness of the slab to compensate, and then corrected for the distance between the vertical rolling rolls based on the inclination angle (θ) of the vertical rolling rolls. Calculating a value C [i]; Calculating the distance G '[i] between the vertical rolling rolls by correcting the correction value from the distance G [i] between the vertical rolling rolls to be set; And Vertical rolling by moving the vertical rolling roll by the distance between the corrected vertical rolling rolls; Hot rolling method characterized in that comprises a The hot rolling method according to claim 1, wherein the correction value C [i] is expressed as C [i] = T [i] / 2 × tan (θ × π / 180).