JP2529493B2 - Method for producing rough billet for H-section steel - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rough billet for H-section steel by hot rolling a metal slab in a width direction with a vertical rolling mill having a hole-type roll, and more particularly. The present invention relates to a method for producing a rough shaped billet for H-section steel production by hot rolling using a locally thickened portion generated during hot width rolling of a metal slab.

[0002]

2. Description of the Related Art In order to effectively utilize the sensible heat possessed by a slab obtained by continuously casting molten steel, the metal slab after casting is supplied to a rolling process at a high temperature, and the width of the metal slab is increased in this rolling process. There is a so-called width reduction rolling mill that changes the slab width by rolling in the width direction.

A vertical rolling mill having a hole type is used as a width reduction rolling machine for this slab. However, when the reduction amount in the width direction is increased to increase the width change amount, the slab cross-section has an increased local plate thickness called dog bone. Part occurs. The width of the metal slab that is subjected to width rolling again using a hole-type roll is subjected to horizontal reduction rolling only to the locally increased portion of the plate thickness caused by this width rolling to form a rectangular shape having the same thickness as the supplied metal slab thickness. The rolling method is, for example, JP-A-55-11750.
It is disclosed in Japanese Patent Publication No.

Recently, there is a method of producing a rough steel slab by using a metal slab having a rectangular cross-section as a rolling material for H-section steel. For example, Japanese Patent Laid-Open No. 56-56703 discloses a method.
Using a rectangular slab to reduce the width of both edges of the cross section in the width direction and a rough type to reduce the center of the cross section in the thickness direction, the width direction reduction and the center portion of the metal slab are used. It is disclosed that a rough shaped billet for H-section steel having a predetermined cross-sectional shape is obtained by repeatedly performing the reduction in the thickness direction.

As described above, when rolling a rough steel slab from a rectangular metal slab, if widthwise rolling is continuously performed,
The rectangular ratio represented by the slab width / slab thickness ratio or the web height / web thickness ratio is that the metal slab thickness is constant, so the rectangular ratio decreases with each width reduction, and the reduction penetrates to the central part of the metal slab. However, it becomes difficult to manufacture a rough-shaped billet having a flange width larger than the slab thickness.

For this reason, conventionally, a step of rolling the central portion of the metal slab, that is, the portion corresponding to the web, in the thickness direction is required, and a rough shaped billet such as a billet rolling machine or a shaped steel breakdown mill is manufactured. The roll-hole type array of the rolling mill is configured by arranging a plurality of box-shaped dies that roll down in the widthwise direction with the widthwise direction up and down and rough-shaped dies that roll down the web-equivalent portion in the thickness direction in the horizontal rolling mill. There is.

According to the rolling method using the roll hole type arrangement of this rolling mill, the rolling efficiency is deteriorated by alternately using the hole type and performing the reduction in the width direction of the slab and the reduction in the thickness direction of the central portion. Also, when manufacturing rough slabs from wide slabs, or when the web height of the rough slabs is large,
Due to the restriction of the roll body length of the rolling mill, the hole type divisional arrangement is required,
The rolling efficiency is hindered, for example, the number of rolling cycles of the rolling mill in the next step increases.

[0008]

The problem to be solved by the present invention is the ability of the preceding and following steps in the production of the rough billet for H-section steel in the process in which the continuous casting process and the rolling process are directly connected as described above. It is an object of the present invention to provide a method for solving the problem that it is difficult to secure the rolling efficiency in accordance with the above and improving the rolling efficiency in the production of the rough shaped steel slab for H-shaped steel rolling.

[0009]

The present invention relates to a hot reversible rolling mill provided with a horizontal rolling mill and a vertical rolling mill, in which the vertical rolling mill uses a roll having a hole shape for horizontal rolling. When rolling the metal slap, which is the material to be rolled, using a flat roll in the mill, it is rolled in the width direction with a vertical rolling mill, and the thickness part including the plate thickness increasing parts at both width ends generated by this width direction rolling. It was rolled to a thickness direction by the horizontal rolling mill
After, the width central portion in the thin cross-section than the width at both ends by a row of Ukoto repeat a series of rolling <br/> performing widthwise rolling by again vertical rolling mill, and to form the final web thickness First rolling step for obtaining an intermediate shaped billet and vertical rolling of the intermediate shaped billet
The final web height by rolling the machine in the width direction.
After forming, both sides of the width are rolled in the thickness direction with a horizontal rolling mill.
The final flange thickness and width are formed at both ends of the
H-section steel characterized by comprising a second rolling step for obtaining
It is a method of manufacturing a rough-shaped steel slab .

[0010]

When the slab material obtained by continuous casting is rolled, the thickness portion including the locally increased sheet thickness portion caused by the widthwise rolling is rolled to a predetermined thickness by a flat roll horizontal rolling machine without a die. By doing so, it is possible to roll into a thickness shape with a depression at the center of the width.

In the method of the present invention, unlike the conventional slabbing method for steel ingots, it is intended for continuous cast slabs, and the ratio of the roll contact arc length during rolling to the average strip width, that is, The shape ratio between rolls is as small as 0.1 to 0.2, and the rolling width reduction amount per time is 200 to 300.
It is as large as mm. For this reason, the width reduction force due to the vertical rolls during width rolling does not propagate to the central portion of the width, so that locally increased thickness portions occur at both end portions of the width. Rolling this thickened portion with a horizontal roll, so-called rolling of the dogbone portion, compared to rolling of a rectangular flat plate having the same area, not only the locally deformed portion, but also the central portion in the width direction. In addition to the large internal friction, when the plate thickness increasing portions at both end portions of the plate width extend in the longitudinal direction, a dent that becomes thinner than the original thickness occurs at the central portion in the width direction.
The dented portion does not act on the compressive stress due to rolling and is merely a tensile phenomenon.

[0012]

EXAMPLE FIG. 1 shows the relationship between the widthwise rolling amount of a metal slab and the slab thickness at various horizontal roll openings. The width 1830 mm and the thickness 280 obtained by continuous casting.
The relationship between the widthwise rolling amount of the mm slab and the slab thickness was examined for changes in the slab dimension in the first rolling step when the horizontal roll opening was variously changed.

In the figure, A and B show examples in which the roll opening is set to a metal slab original thickness of 280 mm or more. C is original thickness 28
An example is shown in which the width direction rolling is repeatedly performed while rolling in the thickness direction at the region where the locally increased plate thickness caused by the width direction rolling is set to 0 mm. D and E have a roll opening of 250 m, which is thinner than the original thickness of the metal slab, 280 mm.
In the example in which the opening is set to m, 220 mm, the widthwise rolling is repeatedly performed while rolling the locally thickened portion and the original thickness portion caused by the widthwise rolling in the thickness direction.

As shown in the figure, by adjusting the opening degree of the horizontal roll and changing the rolling amount in the thickness direction of the locally increased plate thickness portion caused by the slab width direction rolling, the tensile stress generated in the width center portion Changes, and a metal slab having a cross-sectional shape thinner than the opening thickness of the horizontal roll can be obtained.
That is, when rolling a metal slab, by rolling a thickness portion including a locally increased sheet thickness portion generated by the widthwise rolling by a flat rolling horizontal rolling machine having no hole shape to a predetermined thickness, the width It can be seen that it is possible to roll into a thickness shape with a depression in the center.

FIG. 2 is a diagram showing an embodiment of the manufacturing method of the present invention utilizing the phenomenon shown in FIG.

FIG. 1A shows an example of the arrangement of a width reduction rolling mill and a horizontal rolling mill. An example of the stand configuration of the width reduction rolling mills V ₁ and V ₂ is shown, in which the vertical rolls 2 and 4 with calibers are mounted. A horizontal roll 3 is arranged between them. The metal slab 1 is reversibly rolled between the rolls 2, 3 and 4. FIG. 2B shows the cross-sectional shape of the slab obtained by continuous casting, and FIG.
(D) shows the 1st rolling process which obtains an intermediate billet by performing width rolling repeatedly by making a horizontal roll opening constant, (e)
Shows a second rolling step for forming a rough steel billet having a target cross-sectional shape.

A continuous casting slab having a rectangular cross section with a width w ₀ and a thickness h _o shown in FIG. 2 (b) is shown in (c) by the vertical rolls 2 and 4 with calibers shown in FIG. 2 (a). When the rolling amount Δw ₁ is rolled in the plate width direction, local so-called dog bones 5, which increase the plate thickness, are generated at both ends of the width of the metal slab.

The features of the hot width rolling method of the metal slab are as follows:
Unlike the conventional slab-rolling method for steel ingots, it is intended for continuous cast slabs, and the ratio of roll contact arc length and average strip width during rolling, that is, the roll-to-roll shape ratio is 0.1 to 0.2. It is small, and the amount of rolling width reduction per cycle is 200-
It is as large as 300 mm. For this reason, the width reduction force due to the vertical rolls during width rolling does not propagate to the central portion of the width, so that locally increased thickness portions occur at both end portions of the width. When the so-called dogbone part is rolled by rolling the plate thickness increasing portion with a horizontal roll, compared to rolling of a rectangular flat plate having the same area, not only the locally deformed portion but also the central portion in the width direction is rolled. In addition to the large internal friction, when the plate thickness increasing portions at both ends of the plate width extend in the longitudinal direction, a dent that becomes thinner than the original thickness occurs at the central portion in the width direction. The dented portion does not act on the compressive stress due to rolling and is merely a tensile phenomenon.

As shown in FIG. 2 (d), a portion including the locally increased thickness portion shown in (c), that is, the dog bone 5 is horizontally reduced by a horizontal rolling mill H, and the thickness (h) shown in (c) is obtained. ₀ +
h ₊ ) to the plate thickness h, width rolling is performed again in the plate width direction to reduce the plate width, and the rolling processes of (c) and (d) are repeated. In this case, as shown in (d), the metal slab has a recess at the center of the plate width due to the shrinkage phenomenon, and the center part of the plate width has a cross-sectional shape h ₋ thinner than the end parts of the plate width. At the same time, a so-called width-return phenomenon occurs in which the dog-bone portion expands by Δw _{2 in the} width direction. Width central portion in the first rolling step
For the web thickness h ₀ −h ₋ of the rough-shaped billet, aiming at the slab thickness
Then, after setting the slab width to w ₂ , in the second rolling step (e)
As shown in, the vertical rolling mill can be used to roll in the plate width direction.
And the web height of the rough billet targeting the slab width
After the W _3, performs rolling in the thickness direction in a horizontal mill,
Flange of the rough billet targeting both sides of the width corresponding to the flange
The rough-shaped steel slab 7 is formed to have a lunge width h ₀ + h ₊ and a bulge thickness . In the second rolling process, the thickness of both sides
Roll in the horizontal direction with a horizontal rolling mill and target flange width h ₀ + h ₊
In obtaining the thickness of the width center portion h _- reduced by. The above
Reduction of the thickness of the width center portion h _- is no practical problem minute
However, strictly speaking, the web thickness in the first rolling step is
Decrease amount h _- is more preferably set in anticipation of.

In the second rolling step, the rolling of the cusp of the locally increased sheet thickness by the horizontal roll corresponds to the role of a guide for moving the metal flow to the inside of the flange in order to secure the flange thickness. In addition, the hole of the vertical roll is filled with metal, and when it bites out of the hole, the bite part rolls down with a horizontal roll in order to prevent defects that occur when the bite part falls down. It is for.

As described above, under the constitution of the vertical rolls 2 and 4 with calibers and the horizontal roll 3 shown in FIG. 2A, the plate thickness portion including the locally increased plate thickness caused by the widthwise rolling is subjected to the horizontal rolling mill. After rolling the metal slab to a predetermined thickness by repeating this, the slab width direction is rolled again to form a locally increased plate thickness portion to obtain a target rough shape. .

Under the rolling conditions shown in Table 1 according to the above procedure, V ₁ -H
3 stand reverse rolling system -V _2, the continuously cast slab 280 × 1830 mm, web thickness 250 mm, a flange thickness 350 mm, the rough shaped steel strip of the web height 1350mm was prepared.

[0023]

[Table 1]

Table 2 is an example of a rolling schedule, in which the horizontal roll opening is 280 mm and the slab width is 1600.
After rolling in the width direction up to mm, and obtaining a slab shape with a width center portion thickness of 255 mm, the horizontal roll opening is set to 350 mm,
The slab width was again rolled in the width direction to 1350 mm. As a result, a well-shaped rough slab having a high local shape, ie, a flange width of 350 mm, a slab width central portion, that is, a web thickness of 250 mm and a slab width, that is, a web height of 1350 mm was obtained at both ends of the slab width. .

[0025]

[Table 2]

[0026]

EFFECTS OF THE INVENTION In a width reduction mill under a process in which a continuous casting process and a hot rolling process are directly connected, it is practically impossible to manufacture a rough billet for H-section steel from a rectangular continuous casting slab. It was According to the present invention, a flat roll is used as the horizontal roll, and the target rough-shaped steel slab can be obtained only by adjusting the opening degree of the horizontal roll. It has become possible to produce rough billets with a high web height.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the relationship between the widthwise rolling amount of a metal slab and the slab thickness with various horizontal roll openings.

FIG. 2A shows an arrangement example of a width reduction rolling mill and a horizontal rolling mill. (B) shows a continuously cast slab shape. (C) and (d) show the 1st rolling process which repeats width rolling and it carries out by making a horizontal roll opening constant, and obtains an intermediate billet. (E) shows the 2nd rolling process used as the rough-section steel piece of a target cross-sectional shape.

[Explanation of symbols]

 1 Slab 2,4 Vertical roll with caliber 3 Horizontal roll 5 Dogbone

Claims (1)

(57) [Claims] 1. A hot reversible rolling mill having a horizontal rolling mill and a vertical rolling mill, wherein a roll having a hole shape is used for the vertical rolling mill and a flat roll is used for the horizontal rolling mill. When rolling the metal slap that is the material to be rolled, it is rolled in the width direction by a vertical rolling mill, and the thickness portion including the plate thickness increasing portions at both width ends generated by the width rolling is horizontally rolled. <br /> after rolling in the thickness direction by the row of Ukoto repeat a series of rolling performing widthwise rolling by again vertical rolling mill
Ri and width central portion in thin cross-section than the width at both ends, and the final
A first rolling step of forming a web thickness to obtain an intermediate shaped billet, and rolling the intermediate shaped billet in the width direction with a vertical rolling mill.
After forming the final web height by
Rolled in the thickness direction with a flat rolling mill and final flanges on both width ends
From the second rolling process to form the thickness and width to obtain the rough billet
A method for producing a rough billet for H-section steel, characterized in that