JP3272862B2 - Rolling method 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 rolling method for producing an H-section steel from a crude steel slab using a universal rolling mill, and more particularly to an H-section steel having a large flange thickness (hereinafter referred to as "extreme thickness H").
A series of products with a large flange thickness, such as an H-section steel with a large flange width or web height (hereinafter referred to as a "large H-section steel"), is manufactured by preventing flange thinning. To a rolling method.

[0002]

2. Description of the Related Art As shown in FIG. 5, for example, a process for producing an H-section steel by universal rolling includes a double breakdown rolling mill 1, a first rough universal rolling mill 2a, and a universal rolling mill for rough forming of a rolled material. It comprises an edger rolling mill 2b, a second coarse universal rolling mill 3a, an edger rolling mill 3b, and a finishing universal rolling mill 4 provided in the vicinity of the mill 2a.

[0003] In recent years, as a rolled material for H-section steel, in order to improve yield, energy saving, omission of steps, and quality improvement, etc., a large number of rectangular section slags by continuous casting have been used, and various types of H-section slag have been used. Manufactures steel. A rough shaping method for forming a rough steel slab with the breakdown rolling mill 1 using the rectangular section slag as a material is described in, for example, Japanese Patent Publication No. 58-3704.
There is a rolling method disclosed in Japanese Unexamined Patent Publication No. 2 (KOKAI) No. 2 and an example of a grooved roll of a breakdown rolling mill shown in FIG. 6 will be described. In this rolling method, first, a wedge-shaped interrupt 10 is inserted into the short side of the slab 5 from both ends in the width direction to the center of the sheet thickness by the first groove I as shown in FIG. Next, the second mold
II, 3rd hole type III, interrupting section 10 attached with 1st hole type
While further expanding the slab width, edging rolling of the slab width is performed to promote the flange width expansion, and the predetermined flange width,
It is formed up to a dog bone billet 53 having a web height and a dog bone cross section. Although the thickness of the central portion of the web 6 of the dog bone billet 53 rolled in this way is slightly reduced with respect to the slab thickness, it is very large with respect to the product web thickness. On the other hand, the thickness of the flange 7 gradually increases when the slab width is increased and the edging amount is increased. Due to the nature of the method, the obtained dog bone slab 53
There is a limit to the flange thickness. Accordingly, the web thickness and the flange thickness of the dog bone billet 53 are about twice as large as the flange thickness, and therefore, the ratio of the web thickness to the flange thickness is relatively small due to the forming hole IV. The web thickness is reduced in a plurality of passes until it becomes close, and the flange is also formed at the same time to obtain a coarse shaped steel piece 54.

[0004] However, in this method, the flange is thinned and the cross-sectional area of the flange is reduced as the web is pressed down by the forming die IV. In particular, in order to form a large H-section steel or an extremely thick H-section steel shown in FIGS. 8A and 8B, it is necessary to increase the flange thickness of the coarse shaped steel piece 54. However, since the web area with respect to the flange area of the dog bone billet 53 is large, a considerable amount of flange thinning occurs due to web stretching and web height expansion during web reduction, and is shown in FIGS. There is such a problem that a shortage of the flange thickness occurs or a recess is formed on the inner surface of the flange, so that a product having an appropriate size and shape cannot be manufactured.

[0005] For this reason, Japanese Patent Application Laid-Open No. 60-162503 discloses a shape of a web pressure lower portion as a molding hole type IV in FIG.
A metal mold is used to efficiently generate a metal flow from the web 8 to the flange 9 by using a hole 11 (hereinafter, referred to as an “inclined mold hole”) 11 whose central portion is convex and inclined toward both ends of the web as shown in FIG. A method has been proposed in which the web portion is reduced. The web thickness of the crude billet 55 rolled by this method is:
The distribution has a distribution in which the center of the web is minimized and gradually increases toward both ends of the web. The stretching action of the web is suppressed, and the decrease in flange thickness is reduced. However, even with this method, if the amount of reduction in the web thickness increases, the inner surface of the flange separates from the roll, causing dents, the amount of expansion of the web height increases, and the outer surface of the flange can be rubbed down with a hole-shaped side wall, and the protrusion does not occur. There are problems such as occurrence. Japanese Patent Application Laid-Open No. 5-269501 discloses a molding die IV in which a web and a pressing portion on the inner surface of a flange are formed of one or more arcs as shown in FIG. The method of rolling at 12 is proposed,
In this case, a similar problem may occur.

Therefore, in such a product size, the reduction of the web thickness in the forming die cannot be performed to a desired position, and the web is strongly pressed against the flange by the upper and lower horizontal rolls of the subsequent coarse universal rolling mill 2a. ing. However, as shown in FIG. 12, the web pressing portion 15 of the upper and lower horizontal rolls 13 of the coarse universal rolling mill is flat and the corner portion 17 is also formed by a small arc close to the corner radius of a normal product. In the case where the rough shaped billet 55 having the distribution is rolled by the universal rolling mill 2a, the thick portions 18 at both ends of the web are extremely reduced in pressure. In order to set a pass schedule in which the web reduction ratio is considerably larger than the reduction ratio, the inclined molding die 11 is used.
Alternatively, despite the use of the arc-shaped molding die 12 to suppress the decrease in the flange thickness, the coarse universal rolling promotes the decrease in the flange thickness again, and the spread of the web height increases, As shown in FIG. 12, the inner side of the flange is separated from the horizontal roll side surface 16 or a concave is generated on the inner surface of the flange. If a gap is formed between the inner side of the flange and the side surface of the horizontal roll, the height of the web is reduced when the flange roll is actively reduced by the vertical roll 14, and at that time, breakage is generated near the corner 17. Then it becomes a problem. In addition, when a dent occurs on the inner surface of the flange, it is necessary to increase the flange reduction amount to eliminate the dent, and the flange thickness of a manufacturable product is greatly reduced.

[0007] The above description has described the problems in the case of forming a rough slab by a breakdown rolling mill and performing universal rolling. However, after the slab was directly manufactured by continuous casting,
A similar problem occurs when rolling is performed by the coarse universal rolling mill shown in FIG.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional disadvantages, and relates to a rolling method for producing an H-section steel from a crude steel slab by a universal rolling mill.
When universal rolling of coarse shaped slabs, the metal flow from the web to the flange is activated to prevent the flange from being thinned or dented, and to roll large H-beams and large H-beams. The purpose is to provide a way to:

[0009]

The gist of the present invention is as follows. (1) In a method of rolling an H-section steel by using a plurality of coarse universal rolling mills and one finishing universal rolling mill using coarse shaped billets, the cross section of the upper and lower horizontal rolls of the first coarse universal rolling mill is used. The outline from the web reduction central portion to the corner portion in the single or a plurality of arcs, or a combination of an arc and a straight line, and rolling the web of the crude billet while generating a metal flow from the web to the flange, A method of rolling an H-section steel in which a web thickness is substantially uniformly rolled in a web height direction by a second coarse universal rolling mill.

(2) In the cross section of the upper and lower horizontal rolls of the first coarse universal rolling mill, of the arcs or straight lines constituting the outline from the web reduction central portion to the corner portion,
From the point B where the arc or straight line closest to the center of the web intersects or comes into contact with the horizontal line L1 passing through the center A of the circumferential surface of the horizontal roll, the horizontal line L1 and the extension line L of the side surface of the horizontal roll
2 and a distance Y from the point C at which the arc or straight line closest to the center of the web intersects or contacts the straight line L2 on the side of the horizontal roll, and the horizontal line L1.
1 is the horizontal roll body width W1 of the first coarse universal rolling mill.
The method for rolling an H-section steel according to the above (1), wherein the web thickness t1 after the first coarse universal rolling, the web thickness t0 of the product, and the corner radius r0 are set in the range of the following relational expression.

W1 / 10 ≦ X1 ≦ W1 / 2 r0 / 6 ≦ Y1 ≦ (t1-t0) / 2 + r0 (3) Two coarse universal rolling mills and one finish universal rolling mill using the coarse steel slab In the method of rolling an H-section steel, the outer shape line from the central portion to the corner portion of the web in the horizontal cross section of the upper and lower horizontal rolls of the first rough universal rolling mill is constituted by one or more arcs, or a combination of arcs and straight lines. Then, the web of the crude billet is rolled while causing a metal flow from the web to the flange, and the outline from the web reduction central portion to the corner portion in the horizontal cross section of the upper and lower horizontal rolls of the second rough universal rolling mill is formed. A method of rolling an H-section steel that is configured and rolled using a plurality of arcs or a combination of arcs and straight lines.

(4) In the cross section of the upper and lower horizontal rolls of the first coarse universal rolling mill and the second coarse universal rolling mill, each of the arcs or straight lines constituting the outline from the web reduction central portion to the corner portion, respectively. Distances X1 and X2 from the point B where the arc or straight line closest to the center of the web intersects or contacts the horizontal line L1 passing through the center A of the horizontal surface of the horizontal roll to the intersection O of the horizontal line L1 and the extension line L2 of the horizontal roll side surface. And the distances Y1 and Y2 from the point C where the arc or straight line closest to the center of the web intersects or touches the straight line L2 on the horizontal roll side to the horizontal line L1 are determined by the horizontal distances of the first coarse universal rolling mill and the second coarse universal rolling mill. Roll body widths W1 and W2 and web thickness t1 after the first coarse universal rolling and after the second coarse universal rolling Preliminary t2, further product web thickness t
The method for rolling an H-section steel according to the above (3), wherein the value is set in the range of the following relational expression from 0 and the corner radius r0.

W1 / 10≤X1≤W1 / 2 r0 / 6≤Y1≤ (t1-t0) / 2 + Y2 + r0 W2 / 10≤X2≤W2 / 2 0 <Y2≤ (t2-t0) / 2 + r0 (5) Second One or a plurality of left and right pairs of shafts are disposed between a coarse universal rolling mill and a finishing universal rolling mill, and the axis of the right and left sides is within a plane horizontal to the rolling direction and forms a predetermined angle θH with respect to a plane perpendicular to the rolling direction. The method for rolling an H-section steel according to the above item (3) or (4), wherein the both ends of the web after the rolling are rolled by a second coarse universal rolling mill with a rolling mill having skew rolls. .

[0014]

The operation of the present invention will be described below in detail with reference to the drawings.

The present invention relates to a rolling method for producing an H-section steel from a crude steel slab by a universal rolling mill. The crude steel slab in the present invention is a material having a rectangular cross section slab produced by continuous casting. May be used, or a crude steel slab manufactured by continuous casting may be directly rolled or further rolled by a breakdown rolling mill. Here, a case in which a rectangular section slab is particularly rolled to a coarse billet by a breakdown rolling mill and then an H-section steel is manufactured by universal rolling will be described as a representative example.

FIG. 1 shows a change in the cross-sectional shape of a material to be rolled and a typical roll shape for a typical rolling mill row to which the present invention is applied. Here, a double breakdown rolling mill 1, a first rough universal rolling mill 2a, and an edger rolling mill 2b provided in close proximity to the universal rolling mill 2a, a second rough universal rolling mill 3a, an edger rolling mill 3b, And a finishing universal rolling mill 4.

First, in the breakdown rolling mill 1 shown in FIG. 1, the first hole type I, the second hole type II, and the third hole type II as shown in FIG.
A flange is formed by performing edging rolling of the slab width while splitting both end faces in the slab width direction by I to form a dog bone steel slab 53 having a predetermined flange width and web height. Then, for example, as shown in FIG. 10 or FIG. 11, a portion from the web pressing portion to the corner portion and the flange inner surface pressing portion has a predetermined shape by a forming hole die IV formed by a single or a plurality of arcs, or a combination of an arc and a straight line. The crude steel slab 55 is manufactured.

Subsequently, in the first rough universal rolling mill 2a, the web press lowering portion 24 and the corner portion 25 of the upper and lower horizontal rolls 22 are constituted by one or more arcs or a combination of arcs and straight lines. FIG. 2 (a),
(B) is a cross-sectional shape of a typical upper and lower horizontal roll and left and right vertical rolls of the first coarse universal rolling mill 2a of the present invention. FIG. 2A is a diagram in which the outer contour line from the central portion to the corner of the upper and lower horizontal rolls 221 of the first coarse universal rolling mill from the web reduction to the corner portion is constituted by two arcs r1 and r2 having different curvatures, and FIG. Arcs r1, r2, r
3.

In the case of a coarse shaped billet in which the thickness of both ends of the web is formed larger than the thickness of the center of the web, the thickness of the both ends of the web in the initial pass as shown in FIG. In order to strongly reduce the thickness of the meat portion 18, the flange thickness is increased, and the metal of the reduced web is not efficiently supplied in the flange direction. As a result, it is difficult to secure the flange thickness. When the horizontal roll of the present invention is used, the reduction of the thick portions 18 at both ends of the web in the initial pass becomes smaller as compared with the conventional case as shown in FIG. 3, and the component force Ft toward the flange side when the web is reduced. Acts from the horizontal roll surface, so that metal easily flows to the flange, and an intermediate steel slab 56 having a large flange thickness can be obtained. The web thickness of the intermediate billet 56 is larger at both ends of the web than at the center of the web.

Next, a second coarse universal rolling mill 3a in which the intermediate steel slab 56 is formed such that the web reduction portion is formed substantially flat.
Is rolled by the upper and lower horizontal rolls 32 so that the web thickness has a substantially uniform distribution in the web height direction. Here, the expression "almost uniform" includes a case where the finishing universal rolling mill 4 gives a slight thickness distribution within a range in which a product having a uniform web thickness can be manufactured in the web height direction.

As shown in FIG. 4, in the cross section of the upper and lower horizontal rolls 22 of the first rough universal rolling mill 2a, a straight line L1 drawn horizontally through the center A of the circumferential surface of the horizontal roll and a straight line extended from the side of the horizontal roll. Let the intersection of L2 be O. Further, among the arcs or straight lines constituting the outer shape line from the web reduction central portion to the corner portion of the horizontal roll 22, the arc or straight line closest to the web center is the point from the point B to the point O where the arc or the straight line intersects or contacts the straight line L 1. The distance (hereinafter, referred to as “horizontal distance of intersection”) is defined as X1, and the distance from point C that intersects or contacts with straight line L2 to point O (hereinafter, referred to as “vertical distance of intersection”) is defined as Y1. From coarse shaped billet 2
In order to prevent the metal from moving down to the flange side by the web reduction efficiently and prevent the flange from being thinned and to secure a large amount of the flange wall using a rough universal rolling mill having at least one base, the first coarse universal rolling mill 2a is required. It is desirable to set the horizontal roll shape so that X1 and Y1 satisfy the following relational expression. That is, if the horizontal roll body width of the first coarse universal rolling mill is W1, the web thickness after the first coarse universal rolling is t1, the product web thickness is t0, and the corner radius is r0, W1 / 10 ≦ X1 ≦ W1 / 2 (1) r0 / 6 ≦ Y1 ≦ (t1−t0) / 2 + r0 (2)

In this case, the maximum value of X1 in the expression (1) is limited by the geometrical shape of the horizontal roll, and when the minimum value is less than this, there is an effect of moving the metal of the rolled web to the flange. This is limited because it hardly changes compared to a conventional flat horizontal roll. On the other hand, as for Y1, the larger the Y1 is, the more the metal moves to the flange due to the web reduction in the first coarse universal rolling mill. However, after the first coarse universal rolling, a large thick portion remains and the second coarse universal rolling is performed. This part has to be reduced further by a rolling mill. But the second
In the rough universal rolling stage, the temperature is reduced and the plate thickness is reduced, so that the load is increased and the number of passes is increased. The maximum value of Y1 is a value obtained by adding the corner radius of the horizontal roll of the finishing universal rolling mill to almost half of the web thickness reduced by the second coarse universal rolling mill. A product having a uniform web thickness can be produced without generation. That is, when the web reduction amount in the second coarse universal rolling mill is small, if Y1 is increased, the web thickness of the product cannot be made uniform. Note that the minimum value of Y1 is X
Similar to the minimum value of 1, when the pressure is less than this, the effect of moving the metal of the reduced web to the flange hardly changes as compared with the conventional flat horizontal roll.

The outline from the central part to the corner under the web of the upper and lower horizontal rolls of the second coarse universal rolling mill 3a following the first rough universal rolling mill 2a is formed by a plurality of arcs or a combination of arcs and straight lines. In the case of configuring, the horizontal distance and the vertical distance X1, Y1 and X2 of the above-mentioned intersection in the cross section of the upper and lower horizontal rolls of the first coarse universal rolling mill and the second coarse universal rolling mill.
It is desirable to set Y2 so as to satisfy the following relational expression. That is, the first coarse universal rolling mill and the second
The horizontal roll body width of the coarse universal rolling mill is W1, W2,
Assuming that the web thickness after the first coarse universal rolling and the second coarse universal rolling is t1, t2, the web thickness of the product is t0, and the corner radius is r0, W1 / 10 ≦ X1 ≦ W1 / 2 (3) r0 / 6 ≦ Y1 ≦ (t1−t0) / 2 + Y2 + r0 (4) W2 / 10 ≦ X2 ≦ W2 / 2 (5) 0 <Y2 ≦ (t2−t0) / 2 + r0 (6)

The meaning of each equation is the same as the above-mentioned equation (1) or (2). In particular, the right side of equation (4) further includes a second coarse universal The vertical distance Y2 of the intersection in the rolling mill is added. That is, the cross-sectional area near the corner in the first coarse universal rolling mill can be further increased by the cross-sectional area of the corner that can be formed by the finishing universal rolling mill. On the left side of the equation (6), the effect of the operation of the present invention in the second coarse universal rolling mill is reduced, but the purpose of the present invention is to secure the flange thickness in the first coarse universal rolling mill. The limitation of r0 / 6 or more was removed.

Further, in the present invention, the web thick portions formed at both end portions of the web after being rolled by the second coarse universal rolling mill 3a as described above by a dotted line in FIG. , 3b and a finishing universal rolling mill 4, one or a plurality of left and right slants having a predetermined angle θH with respect to a plane in a plane horizontal to the rolling direction and perpendicular to the rolling direction. The web can be widened by being rolled by a rolling mill 19 having row rolls to produce H-section steels having different web heights. In addition, JP-A-63
No. 303602 discloses a rolling method of forming a surplus wall so as to form a combination of several arcs having different curvatures at both ends of a web in an intermediate rolling step. This is a corresponding amount, and is smaller than the area remaining as an unpressurized lower portion from the central portion to the corner portion of the web formed by the first rough universal rolling of the present invention.

Incidentally, the first rough universal rolling mill 2a
The upper and lower horizontal rolls of the edger rolling mill 2b provided in close proximity to the center are usually used when the front end of the flange is formed in almost the final pass of the first rough universal rolling so that the deviation of the web position from the center position of the flange width can be corrected. The depth of the hole is such that the body contacts the web. Similarly, in the case of the present invention, in order to maintain the dimensional accuracy, the shapes of the web pressure lower portions and the corner portions of the upper and lower horizontal rolls of the edger rolling mill 2b are made substantially equal to the horizontal roll shape 22 of the first coarse universal rolling mill 2a. It is desirable.

In addition, in a rolling mill row in which the coarse shaped steel slab is arranged close to the first coarse universal rolling mill, the edger rolling mill, and the second coarse universal rolling mill, the first half is the first rolling mill.
Rolling is performed by a coarse universal rolling mill and an edger rolling mill, and rolling is performed by a second coarse universal rolling mill and an edger rolling mill in the latter half. In the case where a third coarse universal rolling mill is further arranged close to the second coarse universal rolling mill and the edger rolling mill and rolling is performed in tandem, the second coarse universal rolling mill and the third coarse universal rolling mill may be used. The horizontal roll may have the same flat shape at the web pressing portion.

Although the present invention has been described with respect to a product in which the thickness of the flange is difficult to secure, such as an extremely thick H-section steel or a large H-section steel, the present invention is also applicable to H-section steels of other sizes. By doing so, the metal of the web in the rough slab can be efficiently supplied in the flange direction. Therefore, when using a continuously cast rectangular cross section slab as a material, the flange thickness of the rough slab formed by a breakdown rolling mill Can be reduced, thereby reducing the slab width reduction amount, and further reducing the slab width used.

[0029]

EXAMPLES The rolling method according to the present invention will be described below.
1400mm H400 × 400 series extra thick H-section steel
An embodiment manufactured from a rectangular section slab having a width of 250 mm and a thickness of 250 mm will be described. In this case, the molding die is an arc-shaped molding die 1
2 was used. In addition, the outer shape line from the central portion of the upper and lower horizontal rolls of the upper and lower horizontal rolls of the first rough rolling mill to the corner portion is a circular arc 1 in contact with the web surface where the radius r1 = 500 mm and the intersection with the horizontal roll side surface is Y1 = 20 mm. ,
Radius r2 = 50 m contacting the horizontal roll side surface and the arc 1
It was composed of two arcs of arc 2 of m. At this time, X1 =
137 mm, the horizontal roll body width W1 of the first coarse universal rolling mill = 358 mm, and the corner radius r0 of the product.
= 22 mm, the relationship of the expressions (1) and (2) is satisfied as follows.

35.8 mm <X1 = 137 mm <179 mm 3.7 mm <Y1 = 20 mm <(t1−t0) / 2 + 2
2 In the production of an extremely thick H-section steel, after the web reduction in the forming die 12 is completed at the stage when the dent on the inner surface of the flange starts to occur, the crude steel slab is sent to the first coarse universal rolling mill.
Rolling was performed by increasing the web reduction ratio with respect to the flange reduction ratio until the thickness ratio of the web and the flange became substantially equal to that of the product, and then rolling the product using the second coarse universal rolling mill and the finishing universal rolling mill. If the upper and lower horizontal rolls of the first coarse universal rolling mill were of a conventional type having a flat web reduction and a corner radius slightly larger than the corner radius of the product, the thick portions at both ends of the web were strongly reduced in the initial pass. At the time, the inside of the flange became large, and the dent that began to form in the shrink-molding die was further expanded, so that products with the appropriate dimensions and shape could be manufactured up to 85 mm in flange thickness. In this case, a product with a flange thickness of 100 mm could be manufactured without causing dents on the inner surface of the flange or falling off at the tip of the flange.

[0031]

By applying the present invention to a process for manufacturing an H-section steel using a coarse shaped slab, the thickness of the flange can be suppressed, and in particular, an extremely thick H-section steel or a large-size H-section steel, for which it is difficult to secure the flange thickness. A large-sized H-section steel can be manufactured without causing defects in dimensions, shape and surface properties.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a shaping means according to the present invention.

FIGS. 2A and 2B are schematic diagrams of examples of roll shapes of a first coarse universal rolling mill of the present invention.

FIG. 3 is an explanatory diagram of a metal flow in a first rough universal rolling mill according to the present invention.

FIG. 4 is an explanatory view of a horizontal roll shape of a first (second) rough universal rolling mill.

FIG. 5 is an explanatory view of an H-section steel rolling facility.

FIG. 6 is a schematic view of an example of a die used in a conventional rough forming means.

FIG. 7 is an explanatory diagram showing a change in the shape of a material to be rolled in a conventional rough rolling process.

8 (a) and (b) are schematic diagrams of a large H-section steel and an extremely thick H-section steel.

FIGS. 9A and 9B are schematic diagrams illustrating a defective flange shape.

FIG. 10 is a schematic diagram of an inclined molding die and an explanatory diagram of metal flow by the die.

FIG. 11 is a schematic view of an arc-shaped molding die.

FIG. 12 is an explanatory diagram of a metal flow by a conventional rough universal rolling mill.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Breakdown rolling mill 2a ... 1st coarse universal rolling mill 2b ... Edger rolling mill 3a ... 2nd coarse universal rolling mill 3b ... Edger rolling mill 4 ... Finishing universal rolling mill 5 ... Rectangular cross section slab 19 ... Inclined roll type rolling mill 13, 22, 32, 221, 222 ... horizontal rolls 14, 23, 33 ... vertical rolls 51 to 58 ... rolled material

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazushige Ikuta 1, Chikko Yawatacho, Sakai City Inside Nippon Steel Corporation Sakai Works (72) Inventor Noriaki Onodera 1, Chikko Yawatacho Sakai City Nippon Steel Corporation (56) References JP-A-7-256301 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B21B 1/08

Claims (5)

(57) [Claims] 1. A method of rolling an H-section steel with a plurality of coarse universal rolling mills and a finishing universal rolling mill using a coarse shaped billet, wherein a cross section of upper and lower horizontal rolls of a first coarse universal rolling mill is provided. The outline from the web reduction central portion to the corner portion in the single or a plurality of arcs, or a combination of an arc and a straight line, and rolling the web of the crude billet while generating a metal flow from the web to the flange, A method for rolling an H-section steel, comprising rolling a web thickness to a substantially uniform thickness in a web height direction by a second coarse universal rolling mill. 2. In the cross section of the upper and lower horizontal rolls of the first coarse universal rolling mill, the arc or straight line closest to the center of the web among the arcs or straight lines constituting the outer shape line from the central portion of the web reduction to the corner portion is horizontal. The distance X1 from the point B intersecting or contacting the horizontal line L1 passing through the center A of the circumferential surface of the roll to the intersection O of the horizontal line L1 and the extension line L2 of the horizontal roll side surface, and the arc or straight line closest to the center of the web is horizontal. Distance Y1 from point C which intersects or touches straight line L2 on the roll side surface to horizontal line L1
From the horizontal roll body width W1 of the first rough universal rolling mill, the web thickness t1 after the first rough universal rolling, the web thickness t0 of the product, and the corner radius r0, in the range of the following relational expression. The method for rolling an H-section steel according to claim 1. W1 / 10 ≦ X1 ≦ W1 / 2 r0 / 6 ≦ Y1 ≦ (t1-t0) / 2 + r0 3. A method for rolling an H-section steel with two coarse universal rolling mills and one finishing universal rolling mill using a coarse shaped billet, wherein a cross section of upper and lower horizontal rolls of the first coarse universal rolling mill is provided. The outline from the web reduction central portion to the corner portion in the single or a plurality of arcs, or a combination of an arc and a straight line, and rolling the web of the crude billet while generating a metal flow from the web to the flange, An H-shaped steel comprising a plurality of circular arcs or a combination of circular arcs and straight lines formed from an outer shape line from a central portion of a web to a corner portion in a horizontal cross section of upper and lower horizontal rolls of a second coarse universal rolling mill, and rolling. Rolling method. 4. In the cross section of the upper and lower horizontal rolls of the first coarse universal rolling mill and the second coarse universal rolling mill, each of the arcs or straight lines constituting the outline from the web reduction central portion to the corner portion, respectively. The arc or straight line near the center of the web is the center A of the circumferential surface of the horizontal roll.
From the point B which intersects or touches the horizontal line L1 passing through the horizontal line L1 and the extension line L2 of the horizontal roll side surface from the point B
X1 and X2, and the distances Y1 and Y2 from the point C where the arc or straight line closest to the center of the web intersects or touches the straight line L2 on the side of the horizontal roll to the horizontal line L1, respectively. The horizontal roll body widths W1 and W2 of the coarse universal rolling mill and the first
The web thicknesses t1 and t2 after the coarse universal rolling and the second coarse universal rolling, and also the web thickness t0 of the product
4. The method for rolling an H-section steel according to claim 3, wherein the angle is set within the range of the following relational expression from the corner radius r0. W1 / 10 ≦ X1 ≦ W1 / 2 r0 / 6 ≦ Y1 ≦ (t1−t0) / 2 + Y2 + r0 W2 / 10 ≦ X2 ≦ W2 / 2 0 <Y2 ≦ (t2−t0) / 2 + r0 5. A single or a plurality of universal rolling mills and a finishing universal rolling mill are arranged between a second coarse universal rolling mill and a finishing universal rolling mill, the axis of which is predetermined in a plane horizontal to the rolling direction and with respect to a plane perpendicular to the rolling direction. A rolling machine having a pair of left and right skew rolls forming an angle θH, wherein both end portions of the web after rolling are rolled by a second coarse universal rolling mill. Rolling method.