JPH0788502A - Method for rolling h-shape steel - Google Patents

Abstract

PURPOSE:To attain a H-shape steel with a satisfactory quality by rolling a web part with a pair of the upper and lower horizontal rolls of a coarse universal rolling mill after forming a dog-bone billet, and estranging a distance from the outer surface of the flange of a material to be rolled to a center segregation band by a specified value or more. CONSTITUTION:A dog-bone billet 64 with a dog-born section shape, is attained by arranging plural box calibers with flat caliber bottoms and with different bottom widths on a coarse rolling mill, drawing down a slab 5 in the width direction by each caliber, and rolling while gradually widening a flange width like materials 61, 62 and 63 to be rolled while supporting the material to be rolled. successively, the dog-born bullet 64 is allowed to rotate by 90 deg., and a web is directly and strongly drawn down by upper and lower horizontal rolls in the path of the preceding stage of a coarse universal rolling mill 2a. In this case, a distance (d) from the surface of the short side of the slab of a center segregation band tip part 12 in the slab 5, is made, for instance, to be 1/2 of a slab width t0. Consequently, it is possible that the center segregation band does not appear near the surface on the outer side of the flange of a product.

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 H-section steel from a continuously cast slab having a rectangular cross section, and particularly at the flange outer surface of the joint between the web and the flange (hereinafter referred to as "fillet portion"). The present invention relates to a rolling method for producing an H-section steel having excellent weldability.

[0002]

2. Description of the Related Art A process for producing an H-section steel by universal rolling is, for example, as shown in FIG. 10, a rough double rolling mill (hereinafter, referred to as "rough rolling mill") for rough shaping a rolling material. A rough universal rolling mill 2a, an edger rolling mill 2b provided near the universal rolling mill 2a, a second rough universal rolling mill 3a, an edger rolling mill 3b,
And a finishing universal rolling machine 4.

By the way, in recent years, for the purpose of improving yield, saving energy, omitting steps and improving quality, H
As a rolled material for shaped steel, a rectangular cross-section slab produced by continuous casting is often used, and H-shaped steel with various types of cross-sections has been manufactured.

As a method of forming a rough steel slab with a rough rolling machine using a rectangular cross-section slab as a raw material, Japanese Patent Publication No. 58-3704.
No. 2, JP-B-59-42563, JP-B-59
No. 18124 and Japanese Patent Publication No. 59-19766. In all of these rough modeling methods, the hole type has a relatively sharp wedge-shaped projection in the center of the bottom of the hole type, and the center of the slab thickness is cut in the slab width direction to cause the flange width to expand and the dogbone cross section. This is a rolling method for forming shaped dogbone steel pieces. As one example,
FIG. 11 shows a hole type roll of the rough rolling machine disclosed in Japanese Examined Patent Publication No. 58-37042. In this rolling method, as shown in FIG. 12, a wedge-shaped interruption 10 is first inserted into the slab 5 from the both ends of the slab width at the center of the slab thickness by the first hole die I to obtain a rolled material 51. Next, edging rolling of the slab width is performed while further expanding the interrupting portion 10 formed by the first hole type in the second hole type II and the third hole type III to promote the flange width expansion, and the predetermined flange width, The dog bone steel piece 53 having the web height is formed. Finally, a predetermined rough shaped steel piece 54 is formed by the forming hole die IV.

By the way, in a rectangular cross-section slab produced by continuous casting, during continuous casting, the cross-section is cooled from the outside and solidification proceeds inward. At this time, at the solid-liquid interface, segregated components having a large solid-liquid partition coefficient such as P, S, Mn, and Si are swept out into the liquid phase from the solid-phase side interface. Therefore, in the central portion, which is the final solidification region, as shown in FIG. 13A, the solidification is performed in a state where the segregation component is concentrated, so that a macro segregation zone (hereinafter referred to as “central segregation zone”) 11 is formed. To be done. This center segregation zone 11
Is a site where the toughness is reduced and the material is inferior due to the influence of the segregation component.

In the above rolling method, since the wedge-shaped interruptions are made at both ends in the width direction of the slab in the initial stage of the rough rolling process, the central segregation zone 11 has the surface of the flange outer portion of the H-section steel as shown in FIG. 13 (b). Get close to you. Subsequently, in the slab width edging rolling process, when reduction is performed in the slab width direction, (c)
The center segregation zone 11 further approaches the outer surface of the flange as shown in (d) when the flange is rolled to the final product.
As shown in, the asymptotic approach is reached to the outermost surface of the fillet flange. This tendency becomes more remarkable as the interruption depth due to the hole-shaped protrusions increases or the edging amount of the slab width increases.

When the H-section steel manufactured through the above process is used as a structural member, for example, as shown in FIG.
When another steel material 22 is welded to the outer surface of the flange of, the outer surface of the flange of the steel material 21 is affected by welding heat. The depth of the weld heat affected zone varies depending on the amount of heat input to the welding, but is generally about 3 mm. At this time, if the center segregation zone 11 is included in the heat-affected zone within 3 mm from the outer surface of the flange of the fillet portion, it causes welding defects such as weld cracking and becomes a problem.

As a second means for roughly forming a rectangular cross-section slab as a raw material, there is a rolling method using a box-hole die having a flat bottom as disclosed in Japanese Patent Publication No. 58-54884. In this rolling method, the flattening of the flange is carried out by a plurality of flat box-bottom molds I, II, and III shown in FIG.
Subsequently, the steel material is rotated by 90 degrees to obtain a rough-shaped steel slab with the shaping hole type IV. However, in this rolling method, no mention is made of the relationship between the center segregation zone and the shaping means, and when manufacturing H-section steel having a large flange width, it can be incorporated due to the limitation of the roll cylinder length of the rough rolling mill. Since the number of box hole types is limited, the difference in bottom width between the box hole types I, II, and III becomes large. Therefore, compared with the above-mentioned rolling method in which the wedge-shaped projection is formed, the induction of the steel material becomes unstable, and as shown in FIG. 16, the steel material is more likely to fall or twist, and the product with a large flange width becomes stable. Problems such as not being able to manufacture occur.

Another method is as follows.
There is a universal rolling breakdown method as shown in FIG. 15 disclosed in Japanese Patent No. 36401. In this method, the slab 5 shown by a broken line is directly rolled by a universal rolling machine including upper and lower horizontal rolls 8a and 8b and left and right vertical rolls 9a and 9b to form a rough shaped steel slab 7. However, general universal rolling mills usually use vertical rolls 9
Since a and 9b are not driven, the reduction in the slab width direction cannot be increased. Therefore, there is a problem in that the required thickness of the required flange is sufficiently secured, and the thickness of the flange tip is insufficient.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and relates to a rolling method for producing an H-section steel from a rectangular cross-section slab, in which the center segregation portion existing in the slab is a product. (EN) A means for controlling so that it does not appear near the outer surface of the flange of the fillet portion, preventing the material from collapsing during rolling, and ensuring a sufficient flange width expansion.

[0011]

The gist of the present invention is as follows.

(1) In a method of producing a rough steel slab from a rectangular cross-section slab with a rough double rolling mill and rolling an H-shaped steel with a rough and finish universal rolling mill, a pair of upper and lower rolls of the rough double rolling mill. After arranging a plurality of box hole molds having a flat hole bottom with a sequentially increased hole bottom width, and edging the slab in the width direction with the box hole molds to form a flange portion to form a dogbone steel piece, A rolling method for H-section steel in which the web portion is rolled by a pair of upper and lower horizontal rolls of a subsequent coarse universal rolling mill to separate the distance from the outer surface of the flange of the rolled material to the center segregation zone to a predetermined value or more.

(2) Rolling is performed with the box bottom width of each box hole set to a width that causes the material to be rolled to widen to both ends of the hole bottom in the first pass rolling in each hole. The rolling method for H-section steel according to the item 1).

(3) Among the box cavities, the first cavities have a bottom width approximately the same as the slab thickness, are rolled until the material is filled up to the side walls of the cavities, and then the second and subsequent cavities. The method for rolling H-section steel according to item (2), wherein

(4) In the method of producing a rough shaped billet from a rectangular cross-section slab with a rough double rolling mill and rolling an H-shaped steel with a rough and finish universal rolling mill, a pair of upper and lower rolls of the rough double rolling mill. In the slab width direction edging, the bottom width of the slab is gradually increased, and a plurality of dies with a projection for guiding the rolled material having a height of approximately 20% or less of the slab thickness are arranged in the center of the slab width. After centering the material to be rolled by rolling, forming a flange part to make a dogbone steel piece, then rolling the web part with a pair of upper and lower horizontal rolls of a rough universal rolling machine,
A rolling method for H-section steel in which the distance from the outer surface of the flange of the rolled material to the central segregation zone is separated by a predetermined value or more.

[0016]

The present inventors conducted a detailed investigation of actual rolling, a laboratory experiment, and a rolling simulation based on the rigid-plastic finite element method (hereinafter simply referred to as "FEM analysis"). Hereinafter, the operation of the present invention will be described in more detail with reference to the drawings.

First, the hole die shown in FIG. 5 has a flat bottom, or the central portion of the die shown in FIG. 6 has large projections 35 and 36 having a height h of about 40% of the slab thickness. The metal flow when the slab was pressed down in the width direction with the conventional hole type was examined by FEM analysis. FIG. 7 shows the transition of the distance d from the surface of the end 12 of the center segregation zone 11 of the slab 5 shown in FIG. Here, the distance d from the surface of the short side of the slab of the center segregation zone end portion 12 of the slab 5 is set to 1/2 of the slab thickness t0 based on the actual results. As is clear from the figure, the center segregation zone end 12
The distance d from the outer surface of the flange of G.sub.2 gradually decreases with an increase in the amount of reduction. On the other hand, in the case of a hole type having a protrusion in the center of the bottom of the hole type, the center segregation zone edge part 12 approaches the surface all at once at the time of interrupt rolling at the initial rolling stage by the first hole type 33, and the box hole type 31 , 32, and d are decreasing at a rate of change equal to or more than 32. Therefore, in order to prevent the center segregation zone from appearing near the outer surface of the product flange, it is extremely effective to form the edging hole type of the slab width of the rough rolling mill into a box hole type with a flat bottom. I found out.

FIG. 1 illustrates the rolling method of the present invention, and FIG. 2 shows a typical roll hole type arrangement of the rough rolling mill 1 of the present invention. In the present rolling method, a plurality of box bottoms having flat bottoms having different bottom widths are arranged in the rough rolling mill 1, and the slab 5 is pressed down in the width direction by each of the hole bottoms to roll the material to be rolled. Rolling material 61, 6 while supporting
Rolled while gradually widening the flange width like 2, 63 to obtain a dogbone steel piece 64 having a dogbone cross-sectional shape,
Subsequently, the dog bone steel piece 64 is rotated by 90 degrees, and the web is directly strongly pressed by the upper and lower horizontal rolls in the previous pass of the rough universal rolling mill 2a. The bottom width W1 of the first box hole type I is equal to the slab width t0 or increased by δ1 with respect to the slab thickness, and the hole types after the second box hole type are the bottoms of the nth hole type (n ≧ 2). The width Wn is increased by an amplification amount δn with respect to the bottom width Wn−1 of the n−1th hole type.

In the present invention, the conventional shaping hole die as shown in the hole type IV of FIGS.
Universal rolling mill 2 with high efficiency of flange width expansion 30%
Since the dog bone steel piece 64 is directly rolled by a, the flange width of the final finish of the box hole mold can be made smaller than in the case of the conventional method in which the box hole mold is followed by the shaping hole mold IV.

Next, a method of determining the amplification amount δn of the bottom width of each hole type will be described. When the material to be rolled is rolled in the width direction of the slab in the box shape with a flat bottom, the ratio of the height Y to the material to be rolled Y and the restraint width X (Y / X) is large as shown in FIG. Twisting is likely to occur, and in order to effectively prevent it, the rolled material expands to reach both ends of the die when it is rolled by ΔE in the first pass of each die as shown in Fig. 4. I found it important to do.

As shown in FIG. 8, the relationship between the amount of reduction obtained by FEM analysis and the change in the flange width of the bottom surface of the hole die is as follows in the case of the flat hole molds 31, 32 as compared with the hole molds 33, 34 with protrusions.
Although the flange width expansion ratio is slightly reduced, there is no particular problem with the flat width extraction efficiency even with the flat hole type.
As shown in FIG. 8, the reduction widths a to b (total reduction amount 240 mm to 540 m) where there is no restriction of flange width expansion due to the hole-shaped side wall.
In m), the flange width is from c (471 mm) to d (260 mm).
mm), and the average flange width expansion ratio (flange width expansion amount / slab width reduction amount) with respect to the reduction amount in the slab width direction was (471 mm-260 mm) / 300 mm = 0.70. Therefore, in each hole type, within the range of approximately 70% or less of the reduction amount ΔE of the first pass, the bottom width of the front hole type in each hole type after the second hole type after the slab thickness in the first hole type. On the other hand, if the groove width is widened, the rolled material causes the flange width to spread within the roll bite to reach both ends of the hole bottom, and the rolling material can be shaped without tilting or twisting. Conversely, in the first pass of each hole type after the second hole type, it is necessary to take a reduction amount of about 1.43 times or more the amplification amount δn of the hole type bottom width with respect to the front hole type.

Here, if the reduction amount per pass is increased, the filling degree of the die is increased, the stability of rolling is increased, and the amplification amount δn of the bottom width of the die can be increased.
A product with a wider flange width can be molded. However, if the amount of reduction per pass is increased, the rolling load and rolling torque increase, so the limit of the amount of reduction per pass is determined by roll strength and mill specifications. In addition, when the reduction is large, there is a tendency that the rolled material tends to collapse or twist due to the unbalance of rolling conditions such as non-uniform distribution of rolling temperature in the cross section. Then, the amount of reduction in each hole type first pass is inevitably determined.

Further, when the bottom width W1 in the first hole die I is made almost the same as the slab thickness, and the material is sufficiently pressed into the hole die and the contact with the side wall is increased, rolling in the second hole die and thereafter is performed. In the case where the flange width is widened, the contact with the hole side wall is largely maintained, so that the rolling is easily stabilized.

In the case of increasing the amplification amount δn of the hole bottom of each hole type, in order to prevent the rolled material from tilting or twisting in the edging step in the slab width direction and to further stabilize the threadability, It is also effective to attach the minimum necessary guiding protrusion to the box hole bottom so that the approach of the central segregation zone to the outer surface of the flange does not become apparent. Fig. 9 shows 420m in the width direction of the slab.
6 shows the relationship between the protrusion height h / slab thickness in FIG. 6 and the distance d of the center segregation zone end portion 12 from the outer surface of the flange at the time of m pressure reduction. The relation between the protrusion heights h and d is shown below. The relationship is almost inversely proportional, and when the projection height h increases, d
Is getting smaller. D in universal rolling process
It is considered that the change of is almost inversely proportional to the flange thickness extension η from the dogbone steel piece to the product. Here, although the position of the end of the final segregation zone varies depending on the product flange thickness, the center segregation zone is considered to be closest to the outer surface of the flange. is there. On the other hand, the present inventors have understood from the past results that if the center segregation zone is generally within 3 mm from the outer surface of the flange in the final product, it is easy to induce the occurrence of welding cracks. It is important that the central segregation zone is separated from the outer surface of the flange by about 3 mm or more. The depth of this welding heat affected zone changes depending on the conditions such as the welding heat input amount and the number of weldings, but in the present invention, separating the distance from the flange outer surface of the rolled material to the central segregation zone to a predetermined value or more, It is used in this sense.

Therefore, from the relationship between the flange thickness extension η from the steel billet to the product and the distance from the flange outer surface to the center segregation zone, d at the dogbone billet stage is used.
Is 3 mm × 10 = 30 mm, that is, 30 mm or more is required, and considering that the total amount of reduction in the rough shaping process is about 400 mm at maximum, the projection height h is about 20% with respect to the slab thickness t0 from FIG. This is the reason why the height of the projection for guiding rolled material is set within 20% of the slab thickness in the present invention.

It has been experimentally confirmed that the width of the maximum portion of the protrusion should be 2 to 7 times the height of the protrusion in order to stabilize the permeability. FIG. 3 is an example applied to a roll of a rough rolling mill. P1 to P6 are guiding protrusions. In this case, since the flange width expansion efficiency and the passage stability are increased as compared with the flat hole type, it is possible to further increase the amplification amount δn at the bottom of the hole type as compared with the flat hole type.

[0027]

EXAMPLE A rolling method according to the present invention is applied below,
H800 × 250 × 16/25 H-section steel 1350mm
A case of manufacturing from a rectangular cross-section slab having a width of 250 mm will be described. Here, considering the restrictions of the rough rolling mill and the stability of rolling comprehensively, the reduction amount of each hole type first pass is set to 6
Assuming 0 mm, the flange width expansion under one pass pressure is 60 mm × 0.70 = 42 mm, so the bottom width of the first box hole die is set to 255 mm, and the bottom width of the hole die after the second box hole die is set. Was increased at intervals of 40 mm to obtain a second box hole die 295 mm, a third box hole die 335 mm, a fourth box hole die 375 mm, and a fifth box hole die 415 mm.

[0028] As a result of manufacturing dogbone billets in the first to fifth box hole types and rolling them into products with a roughing and finishing universal mill, the distance d from the surface of the central segregation zone of the H-section steel is about 8 mm. There was no problem with the material. In addition, the rolled material did not fall or twist, and there was no problem in the threadability. On the other hand, the protrusion is about 20 slab thick.
% Was 4 mm when rolled by a hole type with a protrusion having a height of%. In the conventional method in which the protrusion having a height of about 40% was provided, d was about 2 mm, and there was a concern that the center segregation zone on the flange surface during welding was adversely affected.

[0029]

By applying the present invention to the manufacturing process of the H-section steel from the continuously cast slab having a rectangular cross section, the center segregation portion existing in the slab can be formed on the outer surface of the product flange without causing the material to tilt or twist. It is possible to manufacture good quality H-section steel that does not appear in the vicinity.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a modeling unit of the present invention.

FIG. 2 is a schematic view of a rough rolling mill box hole type in the rolling method for H-section steel of the present invention.

FIG. 3 is an explanatory view of a rough rolling mill hole type in which a minimum necessary guiding protrusion is provided in the box hole type according to the present invention.

FIG. 4 is an explanatory diagram of the first pass rolling in each of the second and subsequent hole types.

5 (a) and 5 (b) are schematic diagrams of a flat hole type in which the transition of the distance from the surface of the center segregated end portion is calculated.

6 (a) and 6 (b) are schematic views of a bottom hole type with protrusions in which the transition of the distance from the surface of the center segregation end portion is calculated.

FIG. 7 is an explanatory diagram of the relationship between the total amount of reduction and the distance from the surface of the center segregation end portion.

FIG. 8 is an explanatory diagram of a relationship between the total reduction amount and the flange width.

FIG. 9 is an explanatory diagram of a relationship between a protrusion height and a distance from the surface of the center segregation zone end portion.

FIG. 10 is an explanatory diagram of an H-section steel rolling facility.

FIG. 11 is a schematic view of an example of a hole type used in a conventional rough shaping means.

FIG. 12 is an explanatory view showing a change in shape of a material to be rolled in a conventional rough rolling process.

FIG. 13 is a schematic diagram illustrating the behavior of a central segregation zone existing in a rectangular cross-section slab during rolling.

FIG. 14 is a schematic view of an example of a hole type used in a conventional rough shaping means.

FIG. 15 is a schematic view of an example of a hole type used in a conventional rough shaping means.

FIG. 16 is an explanatory diagram of a rolled material collapse when rolling with a wide flat hole type.

FIG. 17 is an explanatory view of a construction example in which H-section steel is welded and used.

[Explanation of symbols]

1 ... Breakdown rolling mill 2a ... 1st rough universal rolling mill 2b ... Edger rolling mill 3a ... 2nd rough universal rolling mill 3b ... Edger rolling mill 4 ... Finishing universal rolling mill 5 ... Rectangular section slab 51-54, 6
1-65 ... Rolled material 11 ... Center segregation zone P1-P6 ... Guidance for guidance

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[Procedure amendment]

[Submission date] November 4, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Another method is as follows.
There is a universal rolling breakdown method as shown in FIG. 15 disclosed in Japanese Patent No. 36401. In this method, the slab 5 shown by a broken line is directly rolled by a universal rolling machine including upper and lower horizontal rolls 8a and 8b and left and right vertical rolls 9a and 9b to form a rough shaped steel slab 7. However, general universal rolling mills usually use vertical rolls 9
Since a and 9b are not driven, the reduction in the slab width direction cannot be increased. Therefore, there is a problem of securing the required flange width results in a meat shortage flange tip not sufficiently.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

As shown in FIG. 8, the relationship between the amount of reduction obtained by FEM analysis and the change in the flange width of the bottom surface of the hole die is as follows in the case of the flat hole molds 31, 32 as compared with the hole molds 33, 34 with protrusions.
Although the flange width expansion ratio is slightly reduced, there is no particular problem with the flat width extraction efficiency even with the flat hole type.
As shown in FIG. 8, the reduction widths a to b (total reduction amount 240 mm to 540 m) where there is no restriction of flange width expansion due to the hole-shaped side wall.
m), the flange width is from c ( 260 mm) to d ( 471 )
mm), and the average flange width expansion ratio (flange width expansion amount / slab width reduction amount) with respect to the reduction amount in the slab width direction was (471 mm-260 mm) / 300 mm = 0.70. Therefore, in each hole type, within the range of approximately 70% or less of the reduction amount ΔE of the first pass, the bottom width of the front hole type in each hole type after the second hole type after the slab thickness in the first hole type. On the other hand, if the groove width is widened, the rolled material causes the flange width to spread within the roll bite to reach both ends of the hole bottom, and the rolling material can be shaped without tilting or twisting. Conversely, in the first pass of each hole type after the second hole type, it is necessary to take a reduction amount of about 1.43 times or more the amplification amount δn of the hole type bottom width with respect to the front hole type.

[Procedure 3]

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[Correction method] Change

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[Fig. 2]

[Procedure amendment 4]

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[Figure 3]

[Procedure Amendment 5]

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[Figure 9]

Front Page Continuation (72) Inventor Taku Yoshida 1 Tsukiko Yawatacho, Sakai City Nippon Steel Stock Company Inside Sakai Works (72) Inventor Kazuhiko Eda 1 Tsukiko Hachiman Town, Sakai City Nippon Steel Co., Ltd. Inside the Sakai Steel Works

Claims (4)

[Claims] 1. A rough shaped billet is manufactured from a rectangular cross-section slab by a rough double rolling mill, and H is manufactured by a rough and finish universal rolling mill.
In the method for rolling shaped steel, a plurality of box cavities each having a flat bottom with a large caliber bottom width are sequentially arranged in a pair of upper and lower rolls of the rough double rolling mill, and a slab is widthwise formed in the box cavities. After edging and rolling to form a flange to form a dogbone steel piece, the upper and lower horizontal roll pairs of a rough universal rolling machine are used to roll the web, and the distance from the flange outer surface of the rolled material to the center segregation zone is specified. A method for rolling H-section steel, characterized in that the H-section steels are separated by a value or more. 2. Rolling is performed by setting the hole bottom width of each box hole type to a width that causes the material to be rolled to widen to both ends of the hole bottom in the first pass rolling in each hole type. The method for rolling H-section steel according to claim 1. 3. The first hole type of the box hole type has a hole type bottom width substantially the same as the slab thickness, is rolled until the material is filled up to the hole type side wall, and is then used in the second and subsequent hole types. The H-section steel rolling method according to claim 2, wherein the H-section steel is rolled. 4. A rough shaped billet is manufactured from a rectangular cross-section slab by a rough double rolling mill, and H is manufactured by a rough and finish universal rolling mill.
In the method for rolling a shaped steel, the hole bottom width is sequentially increased in the pair of upper and lower rolls of the rough double rolling mill, and the rolled material having a height of about 20% or less with respect to the slab thickness is formed in the center of the hole bottom. After arranging multiple cavities with guiding projections, centering the material to be rolled by edging rolling in the slab width direction and forming flanges to form dogbone steel pieces, then the upper and lower horizontal rolls of the rough universal rolling machine. A method for rolling H-section steel, characterized in that the web portions are rolled in pairs and the distance from the outer surface of the flange of the material to be rolled to the center segregation zone is separated by a predetermined value or more.