CN111050934A

CN111050934A - Method for manufacturing H-shaped steel

Info

Publication number: CN111050934A
Application number: CN201880051669.XA
Authority: CN
Inventors: 山下浩
Original assignee: Nippon Steel and Sumitomo Metal Corp
Current assignee: Nippon Steel Corp
Priority date: 2017-11-02
Filing date: 2018-11-01
Publication date: 2020-04-21
Also published as: PH12020550446A1; JPWO2019088225A1; JP6515365B1; EP3610959A1; WO2019088225A1; US20210252570A1

Abstract

The plurality of pass for performing the rough rolling process includes: a grooving pass for vertically grooving the width direction end of the rolled material; 1 or a plurality of notch groove patterns, which are provided with a protrusion part for vertically forming a notch on the width direction end part of a grooved rolled material so as to form a division part on the end part of the rolled material; and a plurality of bending pass formed with a projection portion which comes into contact with the groove and gradually bends the formed divided portion, wherein at least the last-stage groove pass of the 1 or the plurality of groove pass is provided with a pass side surface which comes into contact with the left and right side surfaces of the rolled material and restrains the rolled material from the left and right, and in the groove pass provided with the pass side surface, the roll forming is performed under the condition that the pass restraint ratio B is 0.7 or more and less than 1.0.

Description

Method for manufacturing H-shaped steel

Technical Field

(cross-reference to related applications)

The present application claims priority based on japanese patent application No. 2017-212914 filed in japan on 11/2/2017, the contents of which are incorporated herein by reference.

The present invention relates to a method for manufacturing H-section steel from a slab or the like having a rectangular cross section, for example.

Background

In the case of manufacturing H-section steel, a rough bar (so-called dog-bone-shaped material to be rolled) is formed from a material such as a slab or a steel ingot drawn out from a heating furnace by a roughing mill (BD), the thickness of a web or a flange of the rough bar is reduced by a universal intermediate rolling mill, and the flange of the material to be rolled is subjected to width reduction, forging of an end face, and shaping by an edger near the universal intermediate rolling mill. And then, forming an H-shaped steel product by using a universal finishing mill.

In recent years, as building structures have been increased in size and used for offshore structures, it has been required to produce larger H-shaped steel products than ever before, and in particular, products having increased flange widths and flange thicknesses have been desired. In a manufacturing process using a rectangular cross-sectional material such as a slab, as a technique for increasing a flange width and a flange thickness, a technique (so-called wedge method) is known in which after forming slits in upper and lower end surfaces (slab end surfaces) of a material to be rolled, the slab end surfaces are subjected to edge processing and the shape of the slits is changed.

Among these, for example, patent document 1 discloses a technique for increasing the thickness of a flange by forming a slit without constraining the upper and lower end portions (slab end surfaces) of a rolled material and then performing edge processing on the slab end surface without contacting the groove side wall to change the shape of the slit. This technique can increase the thickness of the flange according to the reduction of the rolled edge.

For example, patent document 2 discloses a technique of performing edge processing on a slab end surface and changing a shape of a cut groove while restraining both sides of upper and lower end portions (slab end surfaces) of a material to be rolled. This technique restrains both the upper and lower ends of the rolled material, and therefore can produce a thick deposit at the flange tip end to increase the thickness.

Further, for example, patent document 3 discloses a technique for suppressing shape defects such as unevenness in the thickness of a flange portion and increasing the size and shape when manufacturing an H-shaped steel product having a large flange width. With this technique, it is possible to stably perform roll forming while achieving both widening of the flange width and improvement of the product dimensional accuracy.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 11-347601

Patent document 2: japanese laid-open patent publication No. 7-88501

Patent document 3: japanese patent laid-open publication No. 2017-121655

Disclosure of Invention

Problems to be solved by the invention

However, for example, as disclosed in patent document 1, when rolling is performed in a freely expanding manner without constraining the upper and lower end portions (slab end faces) of the material to be rolled, the flange width is increased, but the thickness becomes a shape in which the flange tip end portion becomes thin, the thickness of the flange tip end portion becomes insufficient, and the forming cannot be sufficiently performed in the subsequent process, and there is a possibility that a large increase in thickness cannot be achieved. Further, according to the study of the present inventors, the following findings were obtained: even when the left and right constraints of the upper and lower end portions (slab end surfaces) of the material to be rolled are weakened as compared with the conventional one, the flange tip end portion is also tapered, and the thickness is insufficient.

Further, for example, as disclosed in patent document 2, when rolling is performed while restraining both sides of the upper and lower end portions (slab end faces) of the rolled material, since the rolling is performed in a state where the expansion of the left and right flange portions is completely restrained in the pass, the elongation in the longitudinal direction of the rolled material becomes dominant, the efficiency of thickening the flange portions is low, and the thickening of the flange is limited. For example, even when the pass conditions are appropriately applied, the present technique cannot perform rolling such that the average thickness from the flange tip portion to the root portion becomes equal to or greater than 1/2 of the raw material slab thickness.

Further, for example, the technique disclosed in patent document 3 is not a structure in which the flange portion is positively pressed down, and is not a technique in which the flange portion is sufficiently thickened.

In view of the above circumstances, an object of the present invention is to provide a method for manufacturing H-shaped steel, in which, in a rough rolling step using a pass in manufacturing H-shaped steel, a notch is deeply formed in an end surface of a raw material such as a slab by a protrusion having a tip shape formed into an acute angle, and a flange portion formed by the notch is gradually bent, and in the above-described step, an H-shaped steel product having a flange thickness larger than that of a conventional H-shaped steel can be manufactured.

Means for solving the problems

In order to achieve the above object, according to the present invention, there is provided a method for manufacturing an H-shaped steel including a rough rolling step, an intermediate rolling step, and a finish rolling step, wherein a plurality of passes for roll forming a material to be rolled are engraved in a rolling mill that performs the rough rolling step, the plurality of passes including: a grooving pass for vertically grooving the width direction end of the rolled material; 1 or a plurality of notch groove patterns, which are provided with a protrusion part for vertically forming a notch on the width direction end part of a grooved rolled material and forming a division part on the end part of the rolled material; and a plurality of bending pass formed with a protrusion which comes into contact with the slot and gradually bends a split portion formed at the slot pass, wherein at least the last slot pass of the 1 or more slot passes is provided with a pass side surface which comes into contact with the left and right side surfaces of the rolled material to restrain the rolled material from the left and right, and in the slot pass provided with the pass side surface, the roll forming is performed under the condition that a pass restraint ratio B shown by the following formula (1) is 0.7 or more and less than 1.0,

B＝t/t0…(1)

wherein, t: flange tip thickness when groove rolling forming and bending rolling forming are performed by performing groove pass restraint, t 0: the thickness of the end face of the slab is equivalent to the thickness of the top end of the flange formed by the grooved hole pattern.

The roll forming may be performed under a condition that a cumulative reduction ratio until the roll forming is completed in the groove pass provided with the pass side surface is 0.20 or more and 0.25 or less.

The top end angle of the projection formed in the 1 or more notch groove patterns may be 25 ° or more and 40 ° or less.

In the 1 or more notch groove passes and the plurality of bend groove passes, the forming may be performed by soft reduction in a state where the end face of the material to be rolled and the groove face opposite to the end face are in contact with each other in the forming of at least 1 pass or more.

The plurality of passes may include a flat pass in which a material to be rolled having passed through the plurality of groove passes and the plurality of bending passes is subjected to flat rolling, and the rolling in the flat pass may be performed under a condition that a ratio I of a flange width on one side of the flange portion of the material to be rolled corresponding to the split portion to a flange thickness is 1.30 or more.

The flange width on one side of the flange portion of the material to be rolled before the rolling in the flat pass may be 200mm or more by using a rectangular cross-section material having a thickness of 280mm or more and 320mm or less.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, in the rough rolling step using a pass in the production of H-section steel, a notch is deeply formed in the end face of a raw material such as a slab by the use of a projection having a tip shape formed into an acute angle, and the flange portion formed by the notch is gradually bent.

Drawings

FIG. 1 is a schematic explanatory view of a production line for H-shaped steel.

Fig. 2 is a schematic explanatory view of the 1 st hole pattern.

FIG. 3 is a schematic explanatory view of the 2 nd-1 th hole pattern.

FIG. 4 is a schematic explanatory view of the 2 nd-2 nd hole pattern.

Fig. 5 is a schematic explanatory view of the 3 rd hole pattern.

Fig. 6 is a schematic explanatory view of the 4 th hole pattern.

Fig. 7 is a schematic explanatory view of the 5 th groove (flat groove).

Fig. 8 is a schematic explanatory view showing the structure of the slot pass according to the embodiment of the present invention.

Fig. 9 is a FEM analysis diagram comparing the shapes of the flange corresponding portions after the grooving rolling forming.

Fig. 10 is a FEM analysis diagram showing the shape of the flange portion after bending rolling forming in the case where final grooving rolling forming is performed using passes in different constraining conditions.

Fig. 11 is a graph showing a relationship between the reduction ratio of the slab top end portion and the flange thickness increasing ratio when the hole pattern restraint ratio is set to a plurality of various values.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and the drawings, the same reference numerals are given to components having substantially the same functional configuration, and redundant description is omitted.

Fig. 1 is an explanatory view of a production line T for H-shaped steel including a rolling facility 1 of the present embodiment. As shown in fig. 1, a heating furnace 2, a sizing mill 3, a roughing mill 4, a universal intermediate mill 5, and a universal finishing mill 8 are arranged in this order from the upstream side in a production line T. In addition, an edger 9 is provided adjacent to the universal intermediate rolling mill 5. For convenience of explanation, the steel material on the production line T will be collectively referred to as "rolled material a" and the shape thereof may be indicated by using broken lines, oblique lines, or the like as appropriate in each drawing.

As shown in fig. 1, in a production line T, a material a to be rolled, such as a slab 11, which is extracted from a heating furnace 2, is rough-rolled by a sizing mill 3 and a roughing mill 4. Next, intermediate rolling is performed in the universal intermediate rolling mill 5. In the intermediate rolling, the edge portion of the material to be rolled (flange portion 80 described later) is rolled down by the edger 9 as necessary. In a usual case, approximately 4 to 6 passes are engraved in a common manner on the rolls of the sizing mill 3 and the roughing mill 4, and the H-shaped rough bar 13 is formed by reverse rolling of a plurality of passes through these passes, and the intermediate bar 14 is formed by applying a plurality of passes of reduction to the H-shaped rough bar 13 using a mill train including the universal intermediate mill 5 and the edger 9. Then, the intermediate product 14 is finish-rolled into a product shape in a universal finishing mill 8, and an H-shaped steel product 16 is manufactured.

(basic hole pattern structure)

Next, the hole pattern and the hole pattern engraved in the sizing mill 3 and the roughing mill 4 shown in fig. 1 will be described below with reference to the drawings. Fig. 2 to 7 are schematic explanatory views of the pass engraved in the sizing mill 3 and the roughing mill 4 that perform the roughing step. Here, all of the 1 st to 4 th hole patterns described above may be engraved on the sizing mill 3, for example, or 5 hole patterns of the 1 st to 5 th hole patterns may be engraved separately on the sizing mill 3 and the roughing mill 4. That is, the 1 st to 4 th pass may be engraved in both the sizing mill 3 and the roughing mill 4, or may be engraved in any rolling mill. In the rough rolling step in the production of general H-shaped steel, the shaping is performed in 1 pass or a plurality of passes in each pass.

In the present embodiment, although the case where the basic structure of the engraved hole pattern is 6 hole patterns is exemplified, the number of the hole patterns does not necessarily need to be 6 hole patterns, and may be a plurality of hole patterns of 6 or more. That is, the groove structure is preferable for forming the H-shaped rough bar 13. In fig. 2 to 7, the schematic shape of the final pass of the rolled material a during the forming in each pass is shown by a broken line.

Fig. 2 is a schematic explanatory view of the 1 st hole type K1. The 1 st pass K1 is engraved on an upper hole roll 20 and a lower hole roll 21 which are a pair of horizontal rolls, and the material to be rolled a is rolled and shaped at a nip between the upper hole roll 20 and the lower hole roll 21. Further, on the peripheral surface of the upper grooved roll 20 (i.e., the upper surface of the 1 st groove K1), a protrusion 25 protruding toward the inside of the groove is formed. Further, on the circumferential surface of the lower grooved roll 21 (i.e., the bottom surface of the 1 st groove K1), a protrusion 26 protruding toward the inside of the groove is formed. These

protrusions

25 and 26 have a tapered shape, and the protrusion lengths and the like of the

protrusions

25 and 26 are formed to be equal to each other. The height (projection length) of the

projections

25 and 26 is h1, and the tip end angle is θ 1 a.

In the 1 st pass K1, the

projections

25 and 26 are pressed against the upper and lower end portions (slab end surfaces) of the material a to be rolled, thereby forming the notches 28 and 29 (notch forming). The 1 st hole pattern K1 is also called a "slotted hole pattern" because it is a hole pattern for forming the grooves (the slots 28, 29) in the end face of the slab. Here, it is desirable that the tip end angle (also referred to as wedge angle) θ 1a of the

protrusions

25 and 26 is, for example, 25 ° or more and 40 ° or less.

Here, the pass width of the 1 st pass K1 is preferably substantially equal to the thickness of the rolled material a (i.e., the slab thickness). Specifically, the width of the pass at the tip end of the projecting

portions

25 and 26 formed in the 1 st pass K1 is made equal to the slab thickness, whereby the right-and-left centering performance of the rolled material a can be appropriately secured. Further, by adopting the configuration of the pass size as described above, it is preferable that, as shown in fig. 2, when the forming is performed in the 1 st pass K1, the

projections

25 and 26 and a part of the pass side surface (side wall) are in contact with the rolled material a at the upper and lower end portions (slab end surfaces) of the rolled material a, and the upper and lower end portions of the slab divided into 4 elements (portions) by the grooving

grooves

28 and 29 are not positively pressed down by the upper surface and the bottom surface of the 1 st pass K1. This is because the rolling by the upper and lower surfaces of the groove causes the rolled material a to elongate in the longitudinal direction, and the production efficiency of the flange (flange portion 80 described later) is reduced. That is, in the 1 st pass K1, the rolling reduction (wedge-shaped tip rolling reduction) of the

projections

25 and 26 when the

projections

25 and 26 are pressed against the upper and lower ends (slab end faces) of the rolled material a to form the

slits

28 and 29 is sufficiently larger than the rolling reduction (slab end face rolling reduction) at the upper and lower ends of the slab, whereby the

slits

28 and 29 are formed and the thickness t0 of the flange tip portion is determined.

FIG. 3 is a schematic explanatory view of the 2-1 st hole type K2-1. The 2-1 st hole pattern K2-1 is engraved on the upper and lower hole pattern rolls 30 and 31 as a pair of horizontal rolls. The circumferential surface of the upper grooved roll 30 (i.e., the upper surface of the 2-1 st groove K2-1) is formed with a protrusion 35 protruding toward the inside of the groove. Further, on the peripheral surface of the lower grooved roll 31 (i.e., the bottom surface of the 2-1 st groove K2-1), a protrusion 36 protruding toward the inside of the groove is formed. These

protrusions

35 and 36 have a tapered shape, and the protrusion lengths and the like of the

protrusions

35 and 36 are formed to be equal to each other. Desirably, the tip end angles of the

protrusions

35 and 36 are wedge angles θ 1b of 25 ° to 40 °.

In order to ensure the thickness of the tip end portion of the portion corresponding to the flange, to improve the guiding property and to ensure the stability of rolling, it is preferable that the wedge angle θ 1a of the 1 st pass K1 is the same as the wedge angle θ 1b of the 2 nd-1 st pass K2-1 of the subsequent stage.

The height (projection length) h2a of the

projections

35 and 36 is set to be higher than the height h1 of the

projections

25 and 26 of the 1 st groove K1, which is h2a > h 1. In addition, from the viewpoint of rolling dimension accuracy, it is preferable that the angles of the tips of the

projections

35 and 36 are the same as those of the tips of the

projections

25 and 26 of the 1 st pass K1. The material a having passed through the 1 st pass K1 is further shaped at the nip between the upper and lower pass rolls 30 and 31.

Here, the height h2a of the

projections

35 and 36 formed in the 2-1 st pass K2-1 is higher than the height h1 of the

projections

25 and 26 formed in the 1 st pass K1, and similarly, the entry length of the 2-1 st pass K2-1 into the upper and lower end portions (slab end faces) of the rolled material a is also long. The depth of the

projections

35 and 36 in the 2-1 st pass K2-1 into the material A to be rolled is the same as the height h2a of the

projections

35 and 36. That is, the depth h1 'of the entry of the

projections

25 and 26 into the material to be rolled a in the 1 st pass K1 and the depth h2a of the entry of the

projections

35 and 36 into the material to be rolled a in the 2-1 th pass K2-1 are in the relationship of h 1' < h2 a.

The angles θ f between the groove

upper surfaces

30a and 30b and the groove bottom surfaces 31a and 31b facing the upper and lower end portions (slab end surfaces) of the rolled material a and the inclined surfaces of the

projections

35 and 36 are formed at about 90 ° (substantially right angles) at 4 positions shown in fig. 3.

As shown in fig. 3, since the entry length of the projection when pressed against the upper and lower end portions (slab end faces) of the material a to be rolled is long, the

slits

38 and 39 are formed in the 2-1 pass K2-1 so that the

slits

28 and 29 formed in the 1 st pass K1 are deeper (slit rolling forming). This 2-1 hole pattern K2-1 is also called a "slot pattern".

The forming in the 2-1 st pass K2-1 is performed in a plurality of passes, but in the forming in the plurality of passes, the forming is performed in such a manner that the upper and lower end portions (slab end faces) of the material a are brought into contact with the opposed pass

upper surfaces

30a, 30b and pass

bottom surfaces

31a, 31b in the final pass. This is because, if the upper and lower end portions of the rolled material a and the inside of the pass are not in contact with each other in all passes in the 2-1 st pass K2-1, there is a possibility that a shape defect such that the flange corresponding portion (a portion corresponding to a flange portion 80 described later) is formed to be laterally asymmetrical occurs, which causes a problem in material passing performance.

FIG. 4 is a schematic explanatory view of pass No. 2-2K 2-2. The 2 nd-2 nd hole type K2-2 is engraved on the upper and lower hole type rolls 40 and 41 as a pair of horizontal rolls. The circumferential surface of the upper grooved roll 40 (i.e., the upper surface of the 2 nd-2 nd groove K2-2) is formed with a protrusion 45 protruding toward the inside of the groove. Further, on the peripheral surface of the lower grooved roll 41 (i.e., the bottom surface of the 2 nd-2 nd groove K2-2), a protrusion 46 protruding toward the inside of the groove is formed. These

protrusions

45, 46 have a tapered shape, and the protrusion lengths and other dimensions of the

protrusions

45, 46 are formed to be equal to each other. It is desirable that the tip end angles of these

protrusions

45, 46 are wedge angles θ 1b of 25 ° to 40 °, and are designed to be the same as the wedge angle of the above-described 2-1 hole type K2-1.

The height (projection length) h2b of the

projections

45 and 46 is set to be higher than the height h2a of the

projections

35 and 36 of the 2-1 hole type K2-1, and is set to be h2b > h2 a. The rolled material A having passed through the 2-1 st pass K2-1 is further shaped in the nip between the upper and lower pass rolls 40 and 41.

Here, the height h2b of the

projections

45 and 46 formed in the 2-2 nd groove K2-2 is higher than the height h2a of the

projections

35 and 36 formed in the 2-1 st groove K2-1, and similarly, the entry length of the 2-2 nd groove K2-2 into the upper and lower end portions (slab end faces) of the rolled material a is also longer. The depth of entry of the

projections

45 and 46 into the material A to be rolled in the 2-2 nd pass K2-2 is the same as the height h2b of the

projections

45 and 46. That is, the penetration depth h2a of the

projections

35 and 36 of the 2-1 th pass K2-1 into the material A to be rolled and the penetration depth h2b of the

projections

45 and 46 of the 2-2 th pass K2-2 into the material A to be rolled are in the relationship of h2a < h2 b.

The angles θ f between the groove

upper surfaces

40a and 40b and the groove bottom surfaces 41a and 41b facing the upper and lower end portions (slab end surfaces) of the rolled material a and the inclined surfaces of the

projections

45 and 46 are formed to be about 90 ° (substantially right angles) at 4 positions shown in fig. 4.

As shown in fig. 4, since the entry length of the projection when pressed against the upper and lower end portions (slab end faces) of the material a to be rolled is long, the

slits

48 and 49 are formed in the 2-2 pass K2-2 in such a manner that the

slits

38 and 39 formed in the 2-1 pass K2-1 become deeper (slit rolling forming). The 2 nd-2 nd hole type K2-2 is also called a "slot type" as with the 2 nd-1 th hole type K2-1.

Further, the flange one-side width at the end of the flange shaping step in the rough rolling step is determined based on the dimensions of the

notches

48 and 49 formed therein.

The forming in the 2-2 nd pass K2-2 is usually performed in a plurality of passes, but in the forming in the plurality of passes, the forming is performed in such a manner that the upper and lower end portions (slab end faces) of the material to be rolled a are brought into contact with the opposed pass

upper surfaces

40a, 40b and pass

bottom surfaces

41a, 41b in the final pass. This is because if the upper and lower ends of the rolled material a and the inside of the pass are not in contact with each other in all passes in the 2 nd-2 nd pass K2 th-2 nd pass, there is a possibility that a shape defect such that the flange corresponding portion (a portion corresponding to the flange portion 80 described later) is formed to be laterally asymmetrical occurs, which causes a problem in material passing performance.

Fig. 5 is a schematic explanatory view of the 3 rd hole type K3. The 3 rd hole pattern K3 is engraved on the upper and lower hole pattern rolls 50 and 51 as a pair of horizontal rolls. A projection 55 projecting toward the inside of the groove is formed on the peripheral surface of the upper-groove roll 50 (i.e., the upper surface of the 3 rd groove K3). Further, on the circumferential surface of the lower grooved roll 51 (i.e., the bottom surface of the 3 rd groove K3), a protrusion 56 protruding toward the inside of the groove is formed. These

protrusions

55 and 56 have a tapered shape, and the protrusion lengths and other dimensions of the

protrusions

55 and 56 are formed to be equal to each other.

The tip end angle θ 2 of the

projections

55 and 56 is set to be larger than the angle θ 1b, and the depth h3 of the

projections

55 and 56 entering the material a is shorter than the depth h2b of the projections 45 and 46 (i.e., h3< h2 b). The angle θ 2 is preferably 70 ° or more and 110 ° or less, for example.

The angles θ f between the groove

upper surfaces

50a and 50b and the groove bottom surfaces 51a and 51b facing the upper and lower end portions (slab end surfaces) of the rolled material a and the inclined surfaces of the

projections

55 and 56 are formed to be about 90 ° (substantially right angles) at 4 positions shown in fig. 5.

As shown in fig. 5, in the 3 rd pass K3, the

slits

48 and 49 formed in the 2 nd-2 nd pass K2-2 of the upper and lower end portions (slab end surfaces) of the rolled material a are pressed against the

projections

55 and 56 to become the

slits

58 and 59 with respect to the rolled material a after passing through the 2 nd-2 nd pass K2-2. That is, in the final pass in the forming of the 3 rd pass K3, the deepest angle of the nicks 58, 59 (hereinafter also referred to as the nick angle) becomes θ 2. In other words, the split portions (portions corresponding to flange portions 80 described later) formed in the 2 nd-2 nd pass K2-2 together with the formation of the

notches

48 and 49 are formed by bending outward (bending rolling). This 3 rd hole pattern K3 is also called "bending hole pattern".

The forming in the 3 rd pass K3 shown in fig. 5 is performed by at least 1 pass or more, and at least 1 pass or more is performed in a state where the upper and lower end portions (slab end faces) of the rolled material a and the inside of the pass (the upper surface and the bottom surface of the 3 rd pass K3) are in contact with each other. Preferably, the upper and lower end portions (slab end faces) of the material a to be rolled are lightly rolled while the end portions are in contact with the inside of the pass.

Fig. 6 is a schematic explanatory view of the 4 th hole pattern K4. The 4 th hole pattern K4 is engraved on the upper and lower hole pattern rolls 60 and 61 as a pair of horizontal rolls. A projection 65 projecting toward the inside of the groove is formed on the peripheral surface of the upper-groove roll 60 (i.e., the upper surface of the 4 th groove K4). Further, on the circumferential surface of the lower grooved roll 61 (i.e., the bottom surface of the 4 th groove K4), a protrusion 66 protruding toward the inside of the groove is formed. These

protrusions

65, 66 have a tapered shape, and the protrusion lengths and other dimensions of the

protrusions

65, 66 are formed to be equal to each other.

The angle θ 3 of the tip end of the

protrusion

65, 66 is greater than the angle θ 2, and the depth h4 of the

protrusion

65, 66 entering the material a is shorter than the depth h3 of the protrusion 55, 56 (i.e., h4< h 3). The angle θ 3 is preferably 130 ° or more and 170 ° or less, for example.

The angles θ f formed by the groove

upper surfaces

60a and 60b and the groove bottom surfaces 61a and 61b facing the upper and lower end portions (slab end faces) of the rolled material a and the inclined surfaces of the

projections

65 and 66 are formed to be about 90 ° (substantially right angles) at 4 positions shown in fig. 6, as in the case of the above-described 3 rd groove K3.

In the 4 th pass K4, the

slits

58 and 59 formed in the 3 rd pass K3 at the upper and lower end portions (slab end surfaces) of the rolled material a are pressed against the

projections

65 and 66 to open the

slits

58 and 59 to form the

slits

68 and 69 for the rolled material a passing through the 3 rd pass K3. That is, in the final pass in the shaping at the 4 th pass K4, the deepest angle of the nicks 68, 69 (hereinafter also referred to as the nick angle) becomes θ 3. In other words, the split portions (portions corresponding to the flange portions 80 described later) formed in the 3 rd pass K3 together with the formation of the

notches

58 and 59 are further bent outward (bending rolling forming). This 4 th hole pattern K4 is also called "bending hole pattern".

The portions of the upper and lower end portions of the rolled material a thus formed correspond to flanges of a subsequent H-shaped steel product, and are referred to herein as flange portions 80.

The forming in the 4 th pass K4 shown in fig. 6 is performed by at least 1 pass or more, and at least 1 pass or more is performed in a state where the upper and lower end portions (slab end faces) of the rolled material a and the inside of the pass (the upper surface and the bottom surface of the 4 th pass K4) are in contact with each other. Preferably, the upper and lower end portions (slab end faces) of the material a to be rolled are lightly rolled while the end portions are in contact with the inside of the pass.

Fig. 7 is a schematic explanatory view of the 5 th hole pattern K5. The 5 th hole pattern K5 is formed by upper and lower hole pattern rolls 85 and 86 as a pair of horizontal rolls. As shown in fig. 7, in the 5 th pass K5, the rolled material a formed up to the 4 th pass K4 is rotated by 90 ° or 270 °, and the flange portions 80 located at the upper and lower ends of the rolled material a up to the 4 th pass K4 are arranged on the rolling pitch line. In the 5 th hole type K5, the web 82, which is a connecting portion connecting two flange portions 80, is pressed down, and the flange distal end portion of the flange portion 80 is pressed down, thereby adjusting the flange width. In this way, a so-called dog-bone-shaped H-shaped thick section (H-shaped thick section 13 shown in fig. 1) is formed. Further, since the 5 th hole type K5 reduces the thickness of the web 82 by pressing down, the 5 th hole type K5 is also called a "web-reducing hole type" or a "flat hole type". The rolling pass of the flat pass (pass 5K 5) is performed in 1 or any number of passes.

For the H-shaped rough bar 13 thus formed, a rolling train including two rolling mills, i.e., a universal intermediate rolling mill 5 and an edger 9, which are known rolling mills, is used, and reverse rolling is applied in a plurality of passes to form an intermediate bar 14. Then, the intermediate product 14 is finish-rolled into a product shape by a universal finishing mill 8, thereby producing an H-section steel product 16 (see fig. 1).

As described above, by forming the slits in the upper and lower end portions (the slab end surfaces) of the rolled material a using the 1 st to 4 th slits K1 to K4 of the present embodiment and performing the processing of bending the portions divided left and right by the slits to the left and right to form the flange portions 80, the H-shaped rough bar 13 can be formed with a wider flange width as compared with the rough rolling method in which the slab end surfaces are always pressed as in the prior art, and as a result, a final product (H-shaped steel) having a large flange width can be manufactured.

Here, the method of manufacturing H-shaped steel according to the present embodiment is characterized in that the shape of the flange portion 80 of the rolled material a formed by the above-described 1 st pass K1 to 4 th pass K4 is a shape close to the shape of the product flange, compared to the shape of the flange portion before the flat-pass forming in the conventional manufacturing method. This is because the shaping technique is used in which the divided portions (flange portions 80) formed by forming the notches are bent without changing the shape of the end portions of the rectangular cross-sectional material (slab) used as the material.

In the roll forming technique having such a feature, in order to efficiently manufacture a large H-section steel as an H-section steel product having a flange width of 400mm or more by using a rectangular-section blank having a width of 1800mm and a thickness of 280mm to 320mm, for example, there is a case where the flange portion 80 is further thickened. When the thickness of the flange portion 80 is increased, it is considered that it is effective to perform rolling when performing grooving rolling forming, for example, but when rolling a rolled material a having a wide flange width and a thin flange thickness, there is a possibility that the flange forming becomes inefficient in that only the flange tip portion is increased in thickness. Further, when the rolling reduction is large, the thickness balance of the flange portion 80 may be uneven in the vertical and horizontal directions, and the dimensional accuracy may be deteriorated.

Namely, the present inventors have found the following findings: in the above-described roll forming in the grooving pass, since the structure in which the side surface of the rolled material a is restrained by the pass is not employed, the deformation is concentrated only on the flange tip end portion, and only the tip end portion is thickened, and at the same time, there is a fear of poor centering such as a misalignment of the groove in the left-right direction of the rolled material a, and therefore, the thickness of the portion corresponding to the flange to be formed is likely to be uneven in the up-down left-right direction, and particularly, a difference in the left-right thickness of the flange is likely to occur. The groove offset is a phenomenon in which, in the roll forming in the groove pass, when the groove is formed by the projection, the center of the formed groove is offset from the center in the thickness direction of the material a to be rolled.

In view of the above circumstances, the present inventors have further studied the shape of the notch groove pattern, and have proposed a notch groove pattern capable of solving the problem that the thickness of the flange corresponding portion to be formed is not uniform in the vertical and horizontal directions, particularly, a difference occurs in the left and right thickness of the flange due to the above-described groove deviation or the like, and further, in the notch groove pattern of the proposed improved shape, in the case of attempting to thicken the flange, quantitatively verifying the index for maximizing the thickening efficiency, and proposing the efficient thickening condition. The shape of a notch groove having a newly proposed structure will be described below with reference to the drawings, and conditions under which the flange can be efficiently thickened by the notch groove will be described.

(groove hole pattern structure according to the embodiment of the present invention)

FIG. 8 is a schematic explanatory view showing the structure of the slot pass of the embodiment of the present invention, and shows a modified pass K2-2a corresponding to the above-mentioned pass K2-2 No. 2. In the structure of the pass shown in fig. 8, the same components as those of the 2 nd-2 nd pass K2-2 are denoted by the same reference numerals as those of the above-described pass with reference to fig. 4, and the description thereof is omitted.

As shown in fig. 8, the basic groove pattern of the improved 2-2 groove K2-2a is substantially the same as the 2-2 groove K2-2 before the improvement, and the difference is that the left and right groove side surfaces 40c and 41c formed in the groove are brought into contact with the rolled material a to restrain the rolled material a. That is, the improved 2-2 nd pass K2-2a has a structure with a sidewall width (pass design) as compared with the structure without a sidewall in the 2-2 nd pass K2-2 (see fig. 4) before improvement.

Here, the forming in the 2-2 th pass K2-2a is performed, for example, by a plurality of passes, but it is preferable that the upper and lower end portions (slab end faces) of the rolled material a and the inside of the pass (the pass

upper surfaces

40a, 40b and the

pass bottom surfaces

41a, 41b of the 2-2 nd pass K2-2a) are in contact with each other as shown in fig. 8 in at least 1 or more of the forming by the plurality of passes. This is because the length of the flange corresponding portion (the subsequent flange portion 80) at 4 locations is made uniform in the roll forming in the 2 nd-2 nd pass K2 th-2 a, thereby improving the dimensional accuracy of the flange portion 80 to be formed thereafter.

In the groove pattern shown in fig. 8, the shape of the groove side surfaces 40c and 41c is preferably a vertical shape perpendicular to the axes of the groove rolls in view of efficiently restraining the rolled material a from the left and right, but in the case where the shape of the rolled material a is not a completely bilaterally symmetrical shape, it is desirable to form the groove shape to have a predetermined inclination angle θ s with respect to the direction perpendicular to the axes of the groove rolls in order to guide the rolled material while suppressing the occurrence of defects. In addition, in order to facilitate the repair of the roller due to the abrasion of the roller, a tapered shape is also desirable. The specific value of the inclination angle θ s is preferably 3 ° or more, which is a minimum angle required for performing roll restoration, and is preferably 6 ° or less as an angle for appropriately guiding the rolled material.

The present inventors speculate that, when the grooving rolling forming is performed in the groove pass (the improved 2 nd-2 nd groove K2-2a) having a shape for restraining the flange corresponding portion (flange portion 80) of the rolled material a as shown in fig. 8, the design, the size, and the like of the groove pass K2-2a are changed to cause a difference in the flange thickness after forming, and the analysis by FEM is performed to verify the appropriate groove pass design and size.

Fig. 9 is a FEM analysis chart comparing the shapes of the flange corresponding portions (flange portions 80) after the grooving rolling forming in the case where there is no constraint in the design of the pass subjected to the rolling forming (i.e., the pass K2-2 of the basic pass structure described above, see fig. 4) and in the case where there is a constraint (i.e., the pass K2-2a after the improvement, see fig. 8) in the final grooving rolling forming (the rolling forming at the pass 2-2) for the material a to be rolled of the same size. Fig. 9 also shows a case where the rolling reduction of the edging is not taken at all in the grooving rolling forming as a reference drawing.

As shown in fig. 9, in the final grooving rolling forming, when the rolled material a is restrained by providing the side walls in the pass, the tip end portion of the flange corresponding portion (flange portion 80) is restrained, and therefore, the thickness of the portion other than the restrained portion (i.e., the flange root portion and the like) can be increased, as compared with the case where the rolled material a is not restrained by providing no side walls in the pass. In addition, considering that the state of thickening of the flange root portion and the like depends on the state of contact with the rolls when the rolled material a is restrained by the pass, the analysis chart shown in fig. 9 is an example, and is an analysis chart in the case of performing final grooving rolling forming by contacting the rolls from the top end of about 1/2 of the flange one-side width.

In fig. 9, the final grooving rolling and forming is shown in which the range of the flange one-side width from the top end of about 1/2 is brought into contact with the roll, but the present inventors also analyzed the case of changing the roll contact range. Fig. 10 is a FEM analysis diagram showing the flange portion shape after the bending rolling forming in the case of performing the final grooving rolling forming for the material a to be rolled of the same size using the pass having the different constraining conditions (the roll contact conditions). Fig. 10 also shows, as a reference diagram, the flange portion shape in the case where pass restraint is not performed when the grooving rolling forming is performed and the case where the rolling reduction amount of the edging is not adopted when the grooving rolling forming is performed.

As shown in fig. 10, it is understood that when the hole pattern constraint ratio is high, the thickness of the portion other than the constrained portion (i.e., the flange root portion and the like) can be increased as compared with the case where the hole pattern constraint ratio is low. This is considered to be because the thickness of the flange at the one-side width center portion, the root portion, and the like can be increased by increasing the restraint range of the flange tip portion so as to expand the contact range between the rolled material and the roll, and by increasing the degree of restraint to thereby progress the rolling reduction and penetration of the rolled edge. That is, as the degree of restriction of the pass increases, the influence range of the edging at the time of final grooving rolling formation is expanded in the central portion direction of the flange corresponding portion, and the influence is exerted, and the thickening is promoted. In addition, for example, the thickening of the corresponding flange portion is determined by identifying the one-side width central portion of the corresponding flange portion as a representative point of the flange thickness and determining the thickness of the corresponding flange portion based on the thickness at the representative point. The "rolling penetration" refers to a state in which the influence of rolling on the material to be rolled causes deformation to spread further inside the material to be rolled in the rolling direction.

From the analysis results shown in fig. 9 and 10, the present inventors proposed to introduce a parameter "pass constraint ratio B" in order to quantify the pass constraint degree of final grooving rolling and profiling, and further verified a range for determining an appropriate pass constraint ratio B based on the relationship between the pass constraint ratio B and the flange thickening ratio. This verification will be described below with reference to fig. 11.

Here, the "hole pattern constraint ratio B" is a ratio (t/t 0) of the flange top end thickness t to the thickness t0 (see fig. 2) of the flange top end corresponding portion of the rolled material defined by the hole pattern floor width corresponding to the top end thickness of the flange corresponding portion in the groove pattern (see fig. 10) when the groove rolling forming and the bending rolling forming are performed by performing the hole pattern constraint. The following formula (1) is a definition of the hole pattern constraint ratio B.

B＝t/t0…(1)

Fig. 11 is a graph showing the relationship between the reduction ratio at the top end of the slab and the flange thickness increase ratio when the final grooving rolling forming is performed with the pass restraint performed in the method for producing H-shaped steel according to the present embodiment, and the pass restraint ratio B is set to a plurality of various values. Here, the reduction ratio of the slab front end portion indicates a cumulative reduction ratio of the slab front end portion in the grooving rolling. That is, the reduction ratio of the slab front end portion is a ratio of the cumulative amount of edge finishing determined by the distance between the upper and lower wedges before starting the grooving rolling and after finishing the final grooving rolling (i.e., the reduction ratio of the cumulative grooving rolling). The flange thickness increase ratio is a ratio of a maximum thickness of the flange when the grooving rolling forming and the bending rolling forming are performed with the pass constraint to a maximum thickness of the flange when the grooving rolling forming and the bending rolling forming are performed without the pass constraint. The flange thickness refers to a flange thickness at a center portion of a flange width on one side shown in a reference drawing of fig. 10 (see a portion surrounded by a dotted line in fig. 10). In addition, the flange thickness uses a value measured in a perpendicular direction with respect to the flange outer surface.

As shown in fig. 11, basically, the flange thickening ratio tends to increase as the reduction ratio of the slab front end portion increases. Further, the flange thickening ratio tends to be a lower value as the hole pattern constraint ratio B is larger, and for example, when the hole pattern constraint ratio B is 0.90, the flange thickening ratio is still a value close to 1.00 even if the reduction ratio of the slab front end portion is larger. If the value of the pass constraint ratio B is too large, the final grooving rolling is performed in a state where the rolled material a is excessively constrained, and therefore, the elongation in the longitudinal direction is significant, and the flange thickening cannot be sufficiently achieved. That is, in order to increase the thickness of the flange to some extent, for example, the hole pattern restriction ratio B is preferably 0.90 or less.

Further, in the technique of the above-mentioned patent document 1 (japanese patent application laid-open No. 2017-121655), a structure in which the groove side faces abut on the left and right sides of the rolled material a to restrain the rolled material a is disclosed, and it is understood that a condition that the groove restraining ratio B is 1.0, for example, is disclosed. However, patent document 1 does not describe that the pressing down of the slab front end portion is performed in a state where the hole pattern constraint is performed, and does not mention the relationship between the pressing down rate of the slab front end portion and the flange thickness increasing rate.

From the data obtained in fig. 11, first, it is possible to specify the hole pattern constraint rate B of 0.70 or more such that the flange thickness increase rate becomes a high value (the flange thickness increase effect is sufficiently obtained) regardless of the reduction rate of the slab front end portion. The reason why the hole-pattern constraint ratio B is preferably 0.70 or more is that, when the hole-pattern constraint ratio B is 0.65, the flange thickness tends to be reduced if the reduction ratio of the slab front end portion is excessively large.

The condition that the hole pattern restraint ratio B is 1.0 is that the flange is not thickened without performing active pressing of the slab front end portion, and therefore the hole pattern restraint ratio B is preferably less than 1.0, and is preferably 0.9 or less based on the data of fig. 11.

Further, as is clear from the data obtained in fig. 11, when the roll forming is performed in the range in which the reduction ratio (cumulative reduction ratio) of the slab front end portion is 0.20 or more and 0.25 or less, particularly, when the pass constraint ratio B is 0.65, the flange thickness reduction phenomenon is remarkably observed, and therefore, when the roll forming is performed in the above range, it is possible to secure a sufficient flange thickness increase ratio by defining the pass constraint ratio B to be 0.70 or more.

Here, as described in non-patent document "showa 53-year plastic working spring lecture (1978.5.17 to 19 kangdai), pages 209 to 210", for example, deformation modes (deformation modes) of rolling of a material to be rolled having a rectangular cross section are mainly classified into a mode called a single crown (japanese: シングルバルジング) and a mode called a double crown (japanese: ダブルバルジング). Based on these findings, focusing on the roll forming of the flange portion 80, when the roll diameter, the rolling reduction, the sheet width, and the sheet thickness described in the non-patent documents are applied to the normal production conditions of the H-section steel, it is found that the boundary between the single ridge and the double ridge is a value where the ratio I (hereinafter, also simply referred to as I) of the flange width on one side of the rectangular cross-sectional material to the flange thickness is about 1.30, and it is found that when I exceeds 1.30, the deformation due to the rolling concentrates on the end portion of the material to be rolled, resulting in a double ridge shape, and when I is 1.30 or less, the deformation due to the rolling concentrates on the center of the material to be rolled, resulting in a single ridge shape.

In the case of roll forming using the basic pass structure described above, the condition for developing the double bulging shape described above by the roll forming in the 5 th pass K5 is a case where I exceeds 1.30, and in such a case, the vicinity of the one-side width portion of the 1/2 flange is formed thinner than the tip end. Table 1 shows values of I in the case where the thickness of the raw material (commonly known slab thickness) was 250mm and 300mm, and the flange width of the produced H-section steel was 300mm, 400mm, 500mm, and 600 mm. In the roll forming according to the present embodiment, since the shape close to the product flange shape can be obtained as the shape of the flange portion 80 after the slab edge processing forming, a large reduction is not performed in the flange width direction. Therefore, the width of the flange after rough rolling on one side is substantially equal to the width of the flange of the H-section steel product on one side, and the width of the flange 80 after rough rolling on one side may be regarded as values of 150mm, 200mm, 250mm, and 300mm which are about half of the width of the flange of the H-section steel to be manufactured.

[ Table 1]

As shown in table 1, when the forming method of forming the notch in the slab thickness and bending the divided portions is adopted, approximately 1/2 of the slab thickness becomes the finish flange thickness after the edging finish as it is, and therefore, when H-shaped steel products having product flange widths of 400mm, 500mm, and 600mm are manufactured from a raw material having a thickness of 250mm, I has a value exceeding 1.30. In addition, when H-shaped steel products having flange widths of 400mm, 500mm and 600mm are produced from a material having a thickness of 300mm, I also has a value exceeding 1.30.

As described with reference to table 1, particularly in the case of manufacturing an H-shaped steel product having a flange width of 400mm or more, when the roll forming is performed by the above-described basic pass structure, the vicinity of the one-side width portion of the 1/2 flange is formed thinner than the tip end in the flat forming rolling of the 5 th pass K5, resulting in a so-called double bulging shape. Therefore, a method of thickening the flange to avoid this is sought, and particularly thickening in the vicinity of the single-side width portion of the flange 1/2 is sought to be achieved.

In this case, even under the condition that the so-called double bulging shape is conventionally formed in the flat forming rolling of the 5 th pass K5, by applying the pass design (rolled material restraining pass) provided with the side wall of the present embodiment to the pass design in the final grooving rolling forming, and by setting the pass restraining ratio to a value within a predetermined appropriate numerical range in the pass design, it is possible to efficiently realize sufficient flange thickening.

As described above, in the method of manufacturing H-shaped steel according to the present embodiment, by setting the groove design of the final groove of the groove to be subjected to grooving rolling forming to a structure in which the side wall is provided in addition to the basic groove structure, and setting the groove to restrict the rolled material a, the flange thickening ratio can be made high, and the flange portion 80 (particularly the flange root portion) can be thickened efficiently. In this case, a sufficient flange thickness increasing ratio can be ensured by defining the hole-pattern restriction ratio B to be 0.70 or more in particular.

It is also found that the pass design for achieving such a high flange thickening ratio is particularly effective when the roll forming is performed under the condition that the value of the ratio I of the flange width on one side of the flange portion 80 to the flange thickness is 1.30 or more.

Although the embodiment of the present invention has been described above by way of example, the present invention is not limited to the embodiment shown in the drawings. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention as defined in the appended claims.

In the above embodiment, the following technique is explained: the rolling forming of the rolled material a was performed using the pass groups shown and described as the 1 st pass K1 to the 4 th pass K4, and thereafter, the flat forming rolling was performed using the 5 th pass K5. That is, the pass structure shown in the above embodiment is an example, and the number of passes engraved in the sizing mill 3 and the roughing mill 4 can be arbitrarily changed, and can be appropriately changed to such an extent that the roughing step can be appropriately performed.

In the above embodiment, the case where the 2-1 st pass K2-1 and the 2-2 nd pass K2-2, which are two passes having different wedge heights, are engraved as the structures of the groove passes, and the configuration having the side wall (i.e., K2-2a) is preferably modified from the 2-2 nd pass K2-2, which is the final pass of the groove passes, has been described, but the groove passes may be 1 pass, or may be formed of a plurality of 3 or more passes. Among them, in the case where the groove pass is a plurality of 3 or more passes, it is desirable to set the pass designed by applying the pass provided with the side wall to restrain the rolled material a as the final pass of the pass group subjected to the groove rolling profiling.

Further, the slab is exemplified as a material for producing the H-section steel, but it goes without saying that the present invention can be applied to other materials having similar shapes.

Industrial applicability

The present invention can be applied to a manufacturing method for manufacturing H-shaped steel using, for example, a slab having a rectangular cross section as a raw material.

Description of the reference numerals

1, rolling equipment; 2, heating the furnace; 3, sizing mill; 4, a rough rolling mill; 5 universal intermediate rolling mill; 8 universal finishing mills; 9, an edge rolling machine; 11, a plate blank; 13H-shaped rough sections; 14 intermediate material; 16H-section steel products; 20 upper hole type roll (1 st hole type); 21 lower hole type roll (1 st hole type); 25. 26 protrusions (1 st hole type); 28. 29 cutting groove (1 st hole type); 30 upper hole type roller (2 nd-1 st hole type); 31 lower hole type roll (2 nd-1 st hole type); 35. 36 raised parts (2 nd-1 st hole type); 38. 39 grooving (2 nd-1 st hole type); 40 upper hole type roller (2 nd-2 nd hole type); 41 lower hole type roller (2 nd-2 nd hole type); 45. 46 protrusions (2 nd-2 nd hole pattern); 48. 49 grooving (2 nd-2 nd hole type); 50 upper hole type roller (3 rd hole type); 51 lower hole type roll (3 rd hole type); 55. 56 raised portions (3 rd hole pattern); 58. 59 grooving (No. 3 hole type); 60 upper hole type roll (4 th hole type); 61 lower hole type roll (4 th hole type); 65. 66 protrusions (4 th hole pattern); 68. 69 cutting grooves (4 th hole type); 80 flange parts; 82 a web portion; 85 upper hole type roller (5 th hole type); 86 lower hole type roll (5 th hole type); k1 pass 1; k2-1, 2 nd-1 st hole type; k2-2, 2 nd-2 nd hole type; k2-2a (modified) 2 nd-2 nd hole pattern; k3 pass 3; k4 pass 4; k5 pass 5 (flat pass); t, production line; a is rolled material.

Claims

1. A method for producing H-shaped steel, comprising a rough rolling step, an intermediate rolling step, and a finish rolling step,

a plurality of pass patterns for roll forming the material to be rolled are engraved in the rolling mill for performing the rough rolling step,

the plurality of pass patterns include:

a grooving pass for vertically grooving the width direction end of the rolled material;

1 or a plurality of notch groove patterns, which are provided with a protrusion part for vertically forming a notch on the width direction end part of a grooved rolled material and forming a division part on the end part of the rolled material; and

a plurality of bending hole patterns formed with protrusions which come into contact with the slits and gradually bend the divided portions formed at the slit hole patterns,

at least the last slot type of the 1 or more slot types is provided with a slot type side surface which is abutted with the left and right side surfaces of the rolled material to restrain the rolled material from the left and right,

in a groove pass provided with the pass side surfaces, rolling and forming are performed under the condition that the pass constraint rate B shown in the following formula (1) is more than 0.7 and less than 1.0,

B＝t/t0…(1)

2. The method of manufacturing H-shaped steel according to claim 1,

the roll forming is performed under the condition that the cumulative reduction ratio until the roll forming is completed in the notch groove provided with the groove side surface is 0.20 to 0.25.

3. The method of manufacturing H-shaped steel according to claim 1 or 2,

the top end angle of the protrusion formed in the 1 or more notch groove patterns is 25 ° or more and 40 ° or less.

4. The method of manufacturing H-shaped steel according to any one of claims 1 to 3,

in the 1 or more grooving passes and the bending passes, in the forming of at least 1 pass or more, the light rolling is performed in a state where the end face of the material to be rolled is in contact with the pass face opposite to the end face.

5. The method of manufacturing H-shaped steel according to any one of claims 1 to 4,

the plurality of pass types include a flat pass type in which a material to be rolled having passed through the plurality of groove pass types and the plurality of bending pass types is subjected to flat rolling,

the rolling forming in the flat pass is performed under the condition that the ratio I of the flange width on one side to the flange thickness of the flange portion of the material to be rolled corresponding to the split portion is 1.30 or more.

6. The method of manufacturing H-shaped steel according to claim 5,

the flange width on one side of the flange part of the material to be rolled before the roll forming in the flat pass is set to 200mm or more by using a rectangular cross-section material having a thickness of 280mm to 320 mm.