JPS58103901A - Hot rolling method for slab or the like - Google Patents

Abstract

PURPOSE:To hot roll a slab or the like at a uniform width over the entire length by controlling the gap of the 1st vertical rolls in the advancing direction of a material to be rolled and the peripheral speed of the vertical rolls in succession to horizontal rolling mills respectively in the stage of rolling the preceding end part of the said material and in a steady rolling stage. CONSTITUTION:In the stage of broadside rolling of slab 1 with the 1st vertical rolling mill A, the preceding end part of said material is broadside rolled by expanding the gap of vertical rolls 2A, 2A larger than the prescribed gap in a steady rolling stage, thereafter the rolls 2A, 2A are set at the prescribed gap and the material is subjected to rough rolling by steady rolling. In the stage of rolling the preceding end of the roughly rolled material 1' with a horizontal rolling mill B and the 2nd vertical rolling mill C, the peripheral speed of vertical rolls 2B, 2B is set lower than the peripheral speed of horizontal rolls 5, 5, and after the broadside rolling of the preceding end part of the material 1' with the mill B, said part is forced into the mill C. When the preceding end of the material 1' passes through the mill C, the peripheral speed of the rolls 2B, 2B is set at the peripheral speed in the steady rolling stage and the material is rolled by synchronizing the peripheral speeds of the rolls of the mill A, B and C. As a result, the insufficiency in the width in the preceding and succeeding end parts of the roughly rolled material is decreased considerably as shown in the figure.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for hot rolling a slab or the like, which can roll a slab with a uniform width over its entire length.

In recent years, hot rolling of slabs and the like has been carried out by wide rolling, in which the material to be rolled is significantly reduced in the width direction using a vertical rolling mill with a pair of vertical rolls, and then horizontal rolling using a horizontal rolling mill with a pair of horizontal rolls. It is commonly done.

FIG. 1 is a schematic plan view showing the state of width rolling by the vertical rolling mill, and as shown in FIG.
, 2A is used to apply rolling in the width direction to obtain a rough rolled material 3 as shown in FIG.

This rough rolled material 3 has B in Fig. 2 (a) and Fig. 1 (b).
- As shown in the sectional view taken along line B, so-called dock bones 4, 4 are formed whose widthwise ends are raised, and the next horizontal rolling can be advantageously carried out without causing insufficient width. .

However, at the leading and trailing ends of the rough rolled material 3, as shown in the cross-sectional view taken along the lines A-A and B-B in FIG. In addition to being small and non-uniform, the restraining force in the longitudinal direction of the roughly rolled material 3 is reduced in this portion, so that the deformation of the material structure due to width rolling proceeds in the length direction rather than in the width direction.

As a result, in the next horizontal rolling, a noticeable width shortage appears at the leading and trailing ends of the roughly rolled material.

FIG. 3 is a state diagram showing the fluctuation of the width in the longitudinal direction of the roughly rolled material, and shows the occurrence of insufficient width at the leading and trailing ends of the roughly rolled material.

Therefore, the insufficient width portion must be discarded as a defective portion in a subsequent process, resulting in a decrease in product yield.

Therefore, as a means to alleviate this problem of insufficient breadth,
Conventionally, the following methods are known.

(1) Short stroke method: When width-rolling a material to be rolled, the width reduction amount is varied by adjusting and widening the roll opening of a vertical rolling mill at the leading and trailing ends.

(2) Indentation rolling method In equipment in which a horizontal rolling mill and a vertical rolling mill are arranged close to each other, the rolling speeds of the two are made different, and by generating a pushing force against the vertical rolling machine on the rolled material, the rolled material can be rolled. methods of influencing the deformation process.

However, in the method (1) above, the width of the leading and trailing ends of the rolled material tends to become too wide. FIG. 4 is a state diagram showing the variation in the width of the rolled material in the longitudinal direction in this case, and shows the occurrence of excessive width at the leading and trailing ends of the rolled material.

In addition, as a method of controlling the opening and closing of the vertical rolls during width pressure,
A method of detecting the width of the rolled material at the entrance side of the vertical rolls, controlling the deviation from the target value by feedforward, and correcting the width to the target value (Automatic Width Control).
l) is also known, but although this method is effective for controlling the width of the longitudinal center of the material to be rolled, the width of the tip and rear ends, which are unsteady parts, is large and has large width fluctuations. Control is difficult because it is difficult to grasp the amount of deviation.

In particular, this type of control method aims to correct the insufficient width as a result of rolling, and cannot control the width during the deformation process of the rolled material, and this control requires highly responsive electricity. It requires control system equipment and requires a large amount of equipment cost.

In addition, in method (2) above, if the thickness of the material to be rolled is thin, there is a problem that the material to be rolled buckles during pushing, and the pushing force actually generated depends on the shape of the end of the material to be rolled. In addition to large fluctuations depending on the rolling speed, there is no proper method for measuring the indentation force, so it is not possible to accurately determine the indentation force. The outbreak cannot be resolved. FIG. 5 is a state diagram showing the applied pressure in this case and the fluctuation of the width in the longitudinal direction of the rolled material, and shows the occurrence of insufficient width at the leading and trailing ends of the rolled material.

From the above-mentioned viewpoint, the present invention provides a slab that can roll a material to be rolled with a uniform width over its entire length without causing insufficient width or excessive width at the leading and trailing ends of the material to be rolled. A reversible rolling mill row in which vertical rolling mills each having a pair of vertical rolls overflowing the pass line are arranged before and after a horizontal rolling mill having a pair of horizontal rolls. When hot rolling a material to be rolled such as a slab, the opening degree of the vertical roll of the first vertical rolling mill in the direction of movement of the material to be rolled is changed to that of the steady rolling when the tip of the material to be rolled is rolled. After rolling the tip, the opening is returned to the steady rolling condition. When rolling, the peripheral speed of the rolls of the horizontal rolling mill is lower than that of the horizontal rolling mill, and after rolling the tip, the peripheral speed of the rolls is returned to the steady rolling state and synchronized with the peripheral speed of the rolls of the horizontal rolling mill. It is characterized by rolling.

Next, the present invention will be explained using an actual example and drawings.

FIG. 6 is a schematic plan view showing an example of the arrangement of rolling rolls used in the method of the present invention. In front, a pair of vertical rolls 2A.

It consists of a reversible rolling mill group consisting of a first vertical rolling mill A equipped with two people, and a second vertical rolling mill C equipped with a pair of vertical rolls 2B, 2B installed after the horizontal rolling mill B. ing.

When the slab 1 is width rolled by the first vertical rolling mill A, the width rolling of the tip end of the slab is performed by the vertical roll 2A.

After adjusting the opening of 2A and widening it wider than the predetermined opening of the steady rolling state by the short stroke method, and rolling the tip of the predetermined length by this method, the vertical rolls 2A, 2A are rolled as described above. Steady rolling is performed with a predetermined opening.

Therefore, the width of the tip of the rough rolled material 1' that has passed through the first vertical rolling mill A is wider than that during steady rolling.

Next, when the tip of the rough rolled material 1' is rolled by the horizontal rolling mill B and the second vertical rolling mill C, the circumferential speed of the vertical rolls 2B, 2B of the second vertical rolling mill C is changed to the horizontal rolling mill B. By making the peripheral speed slower than the circumferential speed of the horizontal rolls 5, 5, the tip of the rough rolled material 1' is tented in the horizontal rolling mill B and then rolled in the second roll.
It is pushed into the vertical rolling mill C. At this time, the tip of the roughly rolled material 1' is pressed down by the vertical rolls 2B, 2B, and as a result, the material structure is deformed more in the width direction than in the length direction. As a result, there is no shortage of width at the leading end of the tension-rolled material, and the material is rolled to a substantially uniform width. Next, after the tip of the rough rolled material 1' passes through the second vertical rolling mill C, the vertical roll 2B
, 2B is set as the circumferential speed during steady rolling, and rolling is performed by synchronizing the roll circumferential speeds of the first vertical rolling mill A, horizontal rolling mill B, and second vertical rolling mill C.

As the rolling progresses in this way and the rear end of the rough rolled material 1' is rolled by the first vertical rolling mill A, the vertical roll 2A
, 2A and rolling the rough rolled material wider than the steady state eliminates the lack of width that occurs at the rear end portion of the roughly rolled material and rolls it to a predetermined width.

In this way, when the first pass rolling of the slab 1 by the first vertical rolling mill A, horizontal rolling mill B, and second vertical rolling mill C is completed, the roll rotation direction of each of the rolling mills is reversed, and the roughening The rear end of the rolled material 1' is used as the tip, and the second vertical rolling mill C
The second pass rolling is performed in the order of the first horizontal rolling mill B and the first vertical rolling mill A.

At this time, during rolling by the second vertical rolling mill C, the tip of the rough rolled material 1' is rolled by the vertical roll 2B.

2B is widened from the steady state, and then when rolling is performed by the horizontal rolling mill B and the first vertical rolling mill A, the tip of the rough rolled material 1' is rolled by the opening of the first vertical rolling mill A. The circumferential speed of the vertical rolls 2A, 2A is the same as that of the horizontal rolls 5, 2A of the horizontal rolling mill B.
Indentation rolling is performed in the first vertical rolling mill A by setting the circumferential speed slower than No. 5. Then, the rear end of the roughly rolled material 1' is the first
When rolling with vertical rolling mill A, the vertical rolls 2A, 2A
Rolling is performed by widening the opening degree from the steady state.

Thereafter, by rolling a predetermined number of passes using the same method, it is possible to produce a rough rolled material having a uniform plate width over the entire length without causing insufficient width or excessive width at the leading and trailing ends.

Next, the present invention will be explained with reference to examples.

By the reversible rolling mill group consisting of the first vertical rolling mill (v, '), horizontal rolling mill (■]), and second vertical rolling mill (V2),
A slab with a thickness of 250 mm and a width of 1690 mm was rolled according to the pass schedule shown in Table 1 below, and a slab with a thickness of 85 mm was rolled.
During this period, a rough rolled material with a width of 1660 my was prepared. In Table 1, the S/8 amount refers to the opening degree of the vertical rolls being lower than the predetermined opening degree in the steady rolling state when width-rolling the leading and trailing ends of the material to be rolled using a vertical rolling mill (Vl or V2). It indicates the amount of expansion (short stroke amount), and the indentation rate is the indentation rate when the tip of the material to be rolled is indented between the horizontal mill (I-()) and the vertical mill (V+ or ■2). In this case, the roll peripheral speed of the horizontal rolling mill (I-I) is VO) (, the roll peripheral speed of the first vertical rolling mill (Vl) is Yol, and the second vertical rolling mill (
■vo2/■ When the roll circumferential speed in 2) is vo2
Indicates OH or v61/'V OH.

FIG. 7 is a state diagram showing the variation in width in the longitudinal direction of the crudely rolled material when rolled as described above, and Table 1 shows that the lack of width at the leading and trailing ends is extremely small.

Table 2 shows the leading and trailing ends of the rough rolled material when rolled according to the pass schedule shown in Table 1 above using the method of the present invention and when rolled by the conventional method without short stroke or push rolling. The width drop and crop amount are shown. Here, the width drop amount is Δl shown in FIG. 8, and the crop amount is Δl shown in FIG. 9.

As is clear from Table 2 below, according to the method of this invention, the amount of width drop and the amount of black stubble are significantly reduced compared to the conventional method, and the amount of defective parts of the product in the post-process is reduced. We were able to significantly reduce this and significantly improve product yield.

As explained above, according to the method of the present invention, when hot rolling slabs, etc., the width is not insufficient or too wide at the leading and trailing ends of the rolled material, and the width is uniform throughout the entire length. It brings about excellent industrial effects, such as being able to roll a sheet with a wide width and greatly improving product yield.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing the state of width rolling by a vertical rolling mill, FIG. 3 to 5 are state diagrams showing variations in width in the longitudinal direction of a rough rolled material rolled by the conventional method, and FIG. 6 is a rolling roll arrangement used in the method of the present invention. Schematic plan view showing an example of 7th
The figures are state diagrams showing variations in width in the longitudinal direction of a rough rolled material rolled by the method of the present invention, FIG. 8 is an explanatory diagram showing the amount of width drop, and FIG. 9 is an explanatory diagram showing the amount of cropping. In the drawings, 1...-Slab, 1'... Roughly rolled material,
2A, 2B... Vertical roll, 3... Rough rolled material, 4...
...Dock pawn, 5...Horizontal roll, A.
...First vertical rolling mill, B...Horizontal rolling mill, C...
・Second vertical rolling mill. Applicant Nippon Kokan Co., Ltd. Agent Keitabe Tsutsumi and 1 other person Figure 7 Figure 9

Claims (1)

[Scope of Claims] A reversible rolling mill row in which vertical rolling mills each having a pair of vertical rolls along a pass line are arranged before and after a horizontal rolling mill having a pair of horizontal rolls, for rolling slabs, etc. When hot rolling the material to be rolled, the opening degree of the vertical rolls of the first vertical rolling mill in the direction of movement of the material to be rolled is changed from the opening in the steady rolling state when the tip of the material to be rolled is rolled. After rolling the tip by a predetermined amount and rolling the tip, the opening is returned to the steady rolling state, and the circumferential speed of the rolls of the vertical rolling mill following the horizontal rolling mill is changed to The material to be rolled is rolled by lowering the circumferential speed of the rolls of the horizontal rolling mill, and after rolling the tip end, returning the circumferential speed of the rolls to the steady rolling state and synchronizing the circumferential speed of the rolls of the horizontal rolling mill. Hot rolling method for slabs, etc.