CN111479638A

CN111479638A - Method for manufacturing H-shaped steel

Info

Publication number: CN111479638A
Application number: CN201980006415.0A
Authority: CN
Inventors: 山下浩
Original assignee: Nippon Steel and Sumitomo Metal Corp
Current assignee: Nippon Steel Corp
Priority date: 2018-02-09
Filing date: 2019-02-05
Publication date: 2020-07-31
Also published as: JP6614396B1; JPWO2019156078A1; EP3698894A1; US20200391261A1; WO2019156078A1

Abstract

A H-shaped steel product having a flange width larger than that of conventional products can be efficiently and stably produced by performing flat rolling of a large-sized rough material without causing problems such as elongation in the web height direction and deformation of a flange corresponding portion. The roughing step includes a rolling step and a facing step of rolling the web portion by rotating the rolled material after the rolling step is completed, wherein in the upper and lower grooved rolls of at least 1 groove of the grooves in which the facing step is performed, a pocket portion in which a bulging portion is formed in the center of the web portion of the rolled material is provided in the center of the length of the roll main body, the groove in which the facing step is performed further includes a bulging portion removing groove which presses the bulging portion down and widens the inner side of the web portion of the rolled material with respect to the rolled material in which the bulging portion is formed, the rolled material after the bulging portion is formed in the groove having the pocket portion in which the bulging portion is formed is subjected to rolling forming by the bulging portion removing groove, and rolling forming of the bulging portion is not performed after the rolling of the bulging portion.

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. 2018-022105 filed in japan on day 9/2 in 2018, the contents of which are incorporated herein by reference.

The present invention relates to a method for producing 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 raw material such as a slab or a steel ingot taken out from a heating furnace is shaped into a rough material (so-called dog-bone-shaped material to be rolled) by a roughing mill (BD), the thickness of a web or a flange of the rough material is reduced by an intermediate universal 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 located close to the intermediate universal mill. And then forming an H-shaped steel product by using a universal finishing mill.

In such a method for producing H-shaped steel, when a so-called dog-bone-shaped rough shape is formed from a rectangular-section slab material, there is known a technique in which after forming a notch in the slab end face in the 1 st pass of the rough rolling step, the notch opening is widened or the notch depth is increased in the pass after the 2 nd pass, and the notch in the slab end face is removed by the subsequent pass (see, for example, patent document 1).

In the production of H-shaped steel, it is known that flat rolling is performed by performing so-called edging in which an end face (slab end face) of a material such as a slab is edged, and thereafter, rotating the material to be rolled by 90 ° or 270 ° to perform rolling of a portion corresponding to a web. In this flat rolling, the rolling and shaping of the portion corresponding to the flange are performed together with the rolling of the portion corresponding to the web, but in recent years, in view of the demand for large-sized H-shaped steel products, when a large-sized material is used as a material to be rolled, various problems such as elongation in the web height direction and deformation of the portion corresponding to the flange may occur in general flat rolling, and the correction of the shape may be required. Specifically, there is a concern that the web corresponding portion extends in the longitudinal direction as it is pressed down, and the flange corresponding portion also extends in the longitudinal direction due to the extension and drawing of the web corresponding portion, so that the thickness of the flange corresponding portion becomes thin.

Regarding such a flat rolling, for example, patent document 2 discloses a technique of selectively performing rolling of a portion corresponding to a web, in which a non-rolled portion is provided at the center of the portion corresponding to the web, and a convex portion (corresponding to a bulging portion of the present invention) formed thereafter is eliminated to widen the portion corresponding to the web, thereby efficiently manufacturing a large-sized H-shaped steel.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 7-88501

Patent document 2: japanese laid-open patent publication No. 57-146405

Disclosure of Invention

Problems to be solved by the invention

As described above, in recent years, it has been desired to manufacture large H-shaped steel products with an increase in size of structures and the like. In particular, it is desired to make the width of the flange greatly contributing to the strength and rigidity of the H-beam wider than that of conventional products. In order to produce an H-shaped steel product with a wider flange, it is necessary to shape a rolled material having a flange width larger than that of a conventional flange from the start of shaping in a rough rolling step.

However, in the technique disclosed in patent document 1, for example, there is a limit to widening the flange in the method in which a notch is formed in an end face (a slab end face) of a raw material such as a slab, the end face is rolled and the end face is widened to perform rough rolling. That is, in the conventional rough rolling method, in order to widen the flange, it is known that the widening is improved by a technique such as wedge design (design of a groove cutting angle), reduction adjustment, and lubrication adjustment, but since neither method greatly contributes to the flange width, even under the condition that the efficiency is the highest in the initial stage of the edging, the widening ratio indicating the ratio of the spread of the flange width to the edging amount is about 0.8, and under the condition that the edging is repeated with the same pass, the widening ratio is reduced as the spread of the flange width is increased, and finally about 0.5. Further, it is also conceivable to increase the size of the raw material itself such as a slab and increase the amount of edging, but since there are limitations on the equipment scale, the reduction amount, and the like of the roughing mill, there is a situation in which sufficient widening of the product flange cannot be achieved.

In the production of large H-shaped steel products, large-sized rough materials may be subjected to roll forming in a rough rolling step. When a large-sized rough material is roll-formed by a method different from the conventional method and the shape of the rough material is formed into a shape closer to that of an H-shaped steel, it is known that when the flat rolling is performed by the technique described in patent document 2, problems such as elongation in the web height direction and deformation of the flange corresponding portion occur.

The present inventors have evaluated thickening properties of a flange in a conventional process including a process for removing an unpressurized portion in a subsequent process in addition to a previous process including a recess for forming the unpressurized portion (a bulge portion described later) in a web. Specifically, as described in the embodiment of the present invention described later, it was found that the flange forming efficiency can be improved by setting the width of the non-swaged portion to a width of 25% to 50% of the inner dimension of the web portion of the material to be rolled, when a 300-thick slab is used as a material, for example, and the present invention was achieved.

In view of the above circumstances, an object of the present invention is to provide a technique for efficiently and stably producing an H-shaped steel product having a flange width larger than that of the conventional one by performing a flat rolling of a large-sized rough material without causing problems such as elongation in the web height direction and deformation of a flange corresponding portion in a rough rolling step using a pass in producing the H-shaped steel.

Means for solving the problems

In order to achieve the above object, according to the present invention, there is provided a method for producing an H-shaped steel including a roughing step, an intermediate rolling step, and a finishing rolling step, wherein the roughing step includes an edging step of rolling a material to be rolled into a predetermined substantially dog-bone shape and a facing rolling step of rolling a web portion by rotating the material to be rolled by 90 ° or 270 ° after completion of the edging step, a pocket portion forming a bulging portion in a center of the web portion of the material to be rolled is provided in a center portion of a roll body length of upper and lower grooved rolls of at least 1 groove of the grooves in which the facing rolling step is performed, a bulging portion removing groove that presses the bulging portion against the material to be rolled in which the bulging portion is formed and that widens an inner dimension of the web portion of the material to be rolled is further included in the grooves in the facing rolling step, the rolling shaping by the ridge-eliminating pass is performed on the rolled material after the ridge is formed in the pass having the dimple forming the ridge, and the rolling shaping to form the ridge is not performed after the rolling of the ridge.

The rolling forming by the bulging portion relief pass may be performed in a plurality of passes, and the rolling forming may be performed in a state where the inner surface of the flange of the material to be rolled is in contact with the hole roll in at least 1 or more of the plurality of passes.

The rolling forming by the ridge relief pass may be performed in a plurality of passes, and in the 1 st pass among the plurality of passes, the rolling forming may be performed in a state where the inner surface of the flange of the rolled material is in contact with the hole roll.

In the rolling forming by the ridge portion removing pass, the ridge portion may be partially removed, and the remaining ridge portion may be removed by the rolling forming by any subsequent pass.

The width of the ridge portion formed in the flat rolling step may be set to be 25% to 50% of the inner dimension of the web portion of the material to be rolled.

The pressing rate of the raised portion in the raised portion removing groove may be 2.1 or less.

The rolling step may be performed by using a plurality of 4 or more pass types, in which 1-pass forming or multiple-pass forming of the material to be rolled is performed, wherein a notch is formed in the 1 st pass and the 2 nd pass of the plurality of pass types so as to be perpendicular to the width direction of the material to be rolled, and a protrusion that forms a split portion at an end of the material to be rolled is formed, and a protrusion that comes into contact with the notch and gradually bends the formed split portion is formed in the 3 rd pass and the subsequent pass of the plurality of pass types.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, in the rough rolling step using a pass in the production of H-section steel, it is possible to efficiently and stably produce an H-section steel product having a flange width larger than that of the conventional one by performing the flat rolling of a large-sized rough material without causing problems such as elongation in the web height direction and deformation of the flange corresponding portion.

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 hole pattern.

Fig. 4 is a schematic explanatory view of the 3 rd hole pattern.

Fig. 5 is a schematic explanatory view of the 4 th hole pattern.

Fig. 6 is a schematic explanatory view of the 5 th hole pattern.

Fig. 7 is a schematic explanatory view of the 6 th hole pattern.

Fig. 8 is a schematic explanatory view of a case where rolling forming is performed in a state where the inner surface of the flange portion is in contact with the roll in rolling forming by the 6 th pass.

Fig. 9 is a schematic explanatory view of a desired 6 th hole type structure.

Fig. 10 is a schematic view showing the shape of the rolled material after eliminating the bulging portion in the pass flows of table 3 and table 4 based on a simulation.

Fig. 11 is a graph showing a relationship between the flow-out rate and the flange width increase/decrease rate after the H-shaped rough material is formed.

Fig. 12 is an explanatory view relating to the warp of the rolled material.

Fig. 13 is a graph showing the relationship between warpage and web thickness.

Fig. 14 is a graph showing the results of comparative studies on the relationship between the thickness after pressing and the height of the raised portion at the pressed portion, in which the occurrence of warpage leads to poor material passage and the occurrence of no warpage leads to good material passage.

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 the components having substantially the same functional configuration, and redundant description is omitted.

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

As shown in fig. 1, in the production line T, for example, a rectangular cross-section material (a rolled material a thereafter) extracted from the heating furnace 2 as a slab 11 is rough-rolled in the sizing mill 3 and the roughing mill 4. Next, intermediate rolling is performed in the intermediate universal mill 5. In the intermediate rolling, the rolling mill 9 is used to roll down the flange distal end portion (flange corresponding portion 12) of the material to be rolled, as necessary. In a usual case, the rolls of the sizing mill 3 and the roughing mill 4 are engraved with an edging pass and a so-called flat pass for reducing the thickness of the web portion and forming the shape of the flange portion, and by means of these passes, an H-shaped rough bar 13 is formed by reversible rolling in a plurality of passes, and the H-shaped rough bar 13 is pressed in a plurality of passes by using a rolling train formed by the two rolling mills 5 to 9, and an intermediate bar 14 is formed. 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.

Here, the slab thickness T of the slab 11 extracted from the heating furnace 2 is, for example, in a range of 290mm to 310 mm. This is the size of a slab material called a so-called 300-thick slab used in the production of large H-shaped steel products.

Next, the pass structure and the pass shape engraved in the sizing mill 3 and the roughing mill 4 shown in fig. 1 will be described 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, the 1 st to 6 th hole patterns to be described may be all engraved on the sizing mill 3, or 6 hole patterns of the 1 st to 6 th hole patterns may be engraved separately on the sizing mill 3 and the roughing mill 4. That is, the 1 st to 6 th pass may be engraved in both the sizing mill 3 and the roughing mill 4, or may be engraved in any one of the mills. In the rough rolling step in the production of general H-shaped steel, the forming is performed in 1 pass or a plurality of passes in each pass.

In the present embodiment, although the case where the number of engraved holes is 6 is exemplified, the number of the engraved holes is not necessarily 6, and may be a plurality of 6 or more. For example, a general widening rolling pass may be provided after the 6 th pass K6 described later. That is, the hole pattern is preferable for forming the H-shaped rough material 13. In fig. 2 to 7, the schematic final pass shape of the material a to be rolled in 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 the upper and lower pass rolls 20 and 21 as a pair of horizontal rolls, and the rolled material a is rolled down and shaped in the nip between the upper and lower pass rolls 20 and 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 length and other dimensions thereof are configured to be equal in each of the

protrusions

25 and 26. 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 rolled material a to form the

slits

28 and 29. Here, the tip end angle (also referred to as wedge angle) θ 1a of the

protrusions

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

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, it is preferable that the configuration of the pass size is such that, when the forming is performed by the 1 st pass K1, the

projections

25 and 26 and a part of the pass side surface (side wall) contact 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 actively pushed down by the upper surface and the bottom surface of the 1 st pass K1, as shown in fig. 2. This is because the rolling reduction by the upper and lower surfaces of the groove causes elongation in the longitudinal direction of the rolled material a, and the generation efficiency of the flange (flange portion 80 described later) is lowered. 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 end portions (slab end faces) of the rolled material a and the

slits

28 and 29 are formed is sufficiently larger than the rolling reduction (slab end face rolling reduction) at the upper and lower end portions of the slab, thereby forming the

slits

28 and 29.

Fig. 3 is a schematic explanatory view of the 2 nd hole pattern K2. The 2 nd hole pattern K2 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 nd groove K2) is formed with a protrusion 35 protruding toward the inside of the groove. Further, on the circumferential surface of the lower grooved roll 31 (i.e., the bottom surface of the 2 nd groove K2), a protrusion 36 protruding toward the inside of the groove is formed. These

protrusions

35 and 36 have a tapered shape, and the protrusion length and other dimensions of the

protrusions

35 and 36 are 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 subsequent 2 nd pass K2.

The height (projection length) h2 of the

projections

35 and 36 is higher than the height h1 of the

projections

25 and 26 of the 1 st groove K1, and is set to be h2 > h 1. In addition, in terms of rolling dimensional accuracy, the tip end angles of the

projections

35 and 36 are preferably the same as the tip end angles of the

projections

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

Here, the height h2 of the

projections

35 and 36 formed in the 2 nd pass K2 is higher than the height h1 of the

projections

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

projections

35 and 36 in the 2 nd pass K2 entering the material to be rolled a is the same as the height h2 of the

projections

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

projections

25 and 26 of the 1 st pass K1 entering the material to be rolled a and the depth h2 of the

projections

35 and 36 of the 2 nd pass K2 entering the material to be rolled a are in a relationship of h 1' < h 2.

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 all about 90 ° (substantially right angles) at 4 positions shown in fig. 3.

As shown in fig. 3, the entry length of the projection when pressed against the upper and lower end portions (slab end faces) of the rolled material a is long, and therefore, in the 2 nd pass K2, the

slits

38 and 39 are formed by shaping so as to further deepen the

slits

28 and 29 formed in the 1 st pass K1. The flange single-side width at the end of the flange shaping step in the rough rolling step is determined based on the dimensions of the

notches

38 and 39 formed therein.

Further, the forming by the 2 nd pass K2 shown in fig. 3 is performed by a plurality of passes, but in the forming by the plurality of passes, the rolling material a is not actively rolled down at the upper and lower end portions (slab end surfaces) of the rolling material a. This is because the rolling causes elongation in the longitudinal direction of the material to be rolled a due to rolling, and the production efficiency of the portion corresponding to the flange (corresponding to the flange portion 80 described later) is lowered.

Fig. 4 is a schematic explanatory view of the 3 rd hole pattern K3. The 3 rd hole pattern K3 is engraved on the upper and lower hole pattern rolls 40 and 41 as a pair of horizontal rolls. A projection 45 projecting toward the inside of the groove is formed on the peripheral surface of the upper-groove roll 40 (i.e., the upper surface of the 3 rd groove K3). Further, on the circumferential surface of the lower grooved roll 41 (i.e., the bottom surface of the 3 rd groove K3), a protrusion 46 protruding toward the inside of the groove is formed. These

protrusions

45, 46 have a tapered shape, and the dimensions such as the protruding length thereof are equal in each of the

protrusions

45, 46.

The angle θ 2 of the tip end of the

projection

45, 46 is larger than the angle θ 1b, and the depth h3 of the

projection

45, 46 into the material a is shorter than the depth h2 of the projection 35, 36 (i.e., h3 < h 2). The angle θ 2 is preferably 70 ° or more and 110 ° or less, for example.

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 all about 90 ° (substantially right angles) at 4 positions shown in fig. 4.

As shown in fig. 4, in the 3 rd pass K3, the rolled material a having passed through the 2 nd pass K2 is pressed against the

projections

45 and 46, and the

slits

38 and 39 formed in the 2 nd pass K2 at the upper and lower end portions (slab end surfaces) of the rolled material a become slits 48 and 49. That is, the deepest angle of the nicks 48 and 49 (hereinafter also referred to as the nick angle) becomes θ 2 in the final pass in the forming of the 3 rd pass K3. In other words, the split portions (portions corresponding to flange portions 80 described later) formed in the 2 nd hole type K2 as the

slits

38 and 39 are formed are bent outward.

The forming with the 3 rd pass K3 shown in fig. 4 is performed by at least 1 pass or more, and the forming of this pass does not perform the active reduction of the rolled material a in the above-described pass. This is because the rolling causes elongation in the longitudinal direction of the material to be rolled a due to rolling, and the production efficiency of the portion corresponding to the flange (corresponding to the flange portion 80 described later) is lowered.

Fig. 5 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 50 and 51 as a pair of horizontal rolls. The circumferential surface of the upper-grooved roll 50 (i.e., the upper surface of the 4 th groove K4) is formed with a protrusion 55 protruding toward the inside of the groove. Further, on the circumferential surface of the lower grooved roll 51 (i.e., the bottom surface of the 4 th groove K4), a protrusion 56 protruding toward the inside of the groove is formed. These

protrusions

55, 56 have a tapered shape, and the protrusion length and other dimensions thereof are equal in each of the

protrusions

55, 56.

The angle θ 3 of the tip end of the

projection

55, 56 is set to be larger than the angle θ 2, and the depth h4 of the

projection

55, 56 into the material a to be rolled is set to be shorter than the depth h3 of the projection 45, 46 (i.e., h4 < h 3). The angle θ 3 is preferably 130 ° or more and 170 ° or less, for example.

The angles θ f of the groove

upper surfaces

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

projections

55, 56 are all formed at about 90 ° (substantially right angles) at 4 positions shown in fig. 5, as in the case of the above-described 3 rd groove K3.

In the 4 th pass K4, the rolled material a having passed through the 3 rd pass K3 is pressed by the

projections

55 and 56, and the

slits

48 and 49 formed in the 3 rd pass K3 at the upper and lower end portions (slab end surfaces) of the rolled material a are expanded to become

slits

58 and 59. That is, the deepest angle of the nicks 58 and 59 (hereinafter also referred to as the nick angle) becomes θ 3 in the final pass in the shaping of the 4 th pass K4. In other words, the split portions (portions corresponding to flange portions 80 described later) formed in the 3 rd hole pattern K3 as the

notches

48 and 49 are formed are further bent outward. The portions of the upper and lower end portions of the material a to be rolled after the shaping are portions corresponding to flanges of the subsequent H-shaped steel product, and are herein referred to as flange portions 80.

The forming by the 4 th pass K4 shown in fig. 5 is performed by at least 1 pass or more, and the rolling material a is not subjected to the aggressive rolling in the above-described pass. This is because the rolling causes elongation in the longitudinal direction of the material a to be rolled due to rolling, and the production efficiency of the flange portion 80 is lowered.

The rolling forming using the above-described 1 st pass K1 to 4 th pass K4 is also referred to as a edging process for forming the material a to be rolled so that the material a has a predetermined substantially dog-bone shape, and is performed in a state where a blank material having a rectangular cross section is erected.

Fig. 6 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. 6, 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 pass. In the 5 th hole K5, the web 82, which is the connection portion connecting the two flange portions 80, is pressed down.

Here, the upper and lower grooved rolls 85 and 86 of the 5 th grooved roll K5 are formed with

dimples

85a and 86a of a predetermined length W1 at the center of the roll body in the longitudinal direction. According to the hole pattern structure shown in fig. 6, the web 82 is partially depressed from the 1 st pass of the hole pattern until the ridge portion 82b is filled, and depressed portions 82a at both ends in the web height direction are formed in the web 82 after the depression and the ridge portion 82b is formed in the center portion thereof. In this way, the rolling forming is performed to form the ridge portion 82b in the web portion 82 in the so-called dog-bone-shaped material to be rolled.

In addition, since the 5 th pass K5 is subjected to rolling forming in which the web 82 is partially pressed down to form the bulging portion 82b, this pass is also referred to as a "web portion rolling pass". The length equal to the width of the formed ridge 82b is equal to the width W1 of the

dimples

85a and 86a (an overrun W1 described later). Here, as shown in the enlarged view of fig. 6, the width W1 of the

dimples

85a and 86a in the present specification is defined as the width at the depth 1/2 of the depth hm of the

dimples

85a and 86a, and the later-described amount of overflow W1 is also defined by the same definition.

FIG. 7 is a schematic explanatory view of the 6 th hole pattern K6. The 6 th hole pattern K6 is formed by upper and lower hole pattern rolls 95 and 96 as a pair of horizontal rolls. In the 6 th pass K6, the rolled material a which was roll-formed in the 5 th pass K5 was roll-formed as follows: the bulging portion 82b formed in the web portion 82 is eliminated and the inside dimension of the web portion 82 is widened.

In the 6 th pass K6, the upper and

lower pass rollers

95 and 96 are brought into contact with the raised portion 82b formed on the web portion 82 to perform rolling for depressing (removing) the raised portion 82 b.

The rolling forming by the 6 th pass K6 promotes the expansion in the web height direction and the metal flow to the flange portion 80 with the pressing down of the bulging portion 82b, and the reduction in the flange cross section is not generated as much as possible.

Since this 6 th hole pattern K6 can eliminate the bulging portion 82b formed in the web portion 82, it is also referred to as a "bulging portion elimination hole pattern".

The rolled material a having passed through the 1 st pass K1 to the 6 th pass K6 may be subjected to widening rolling of the web 82 as needed. In this case, after the rolling and forming in the 6 th pass K6, widening rolling using 1 or more widening passes may be performed. In this case, since the pass for the widening rolling is a conventionally known pass, the description of the pass for the widening rolling in this specification is omitted.

The rolling forming using the above-described 5 th pass K5 and 6 th pass K6 (and widening passes as needed) is performed in a substantially H-shaped posture in which the rolled material a formed in the edging process is rotated by 90 ° or 270 °, and is therefore also referred to as a flat rolling process.

The H-shaped rough bar 13 shown in FIG. 1 was produced by using the 1 st pass K1 to the 6 th pass K6 and widening pass as required. The H-shaped rough bar 13 thus formed was subjected to reversible rolling in a plurality of passes using a rolling train formed of two rolling mills, i.e., an intermediate universal rolling mill 5-edger 9, which are known rolling mills, to form an intermediate bar 14. Then, the intermediate product 14 is finish-rolled into a product shape by a universal finishing mill 8, and an H-section steel product 16 is manufactured (see fig. 1).

As described above, in the method for producing H-shaped steel according to the present embodiment, the forming of the H-shaped rough material 13 can be performed without pressing down the upper and lower end surfaces of the rolled material a (slab) substantially in the vertical direction by forming the slits in the upper and lower end portions (slab end surfaces) of the rolled material a and bending the portions divided into right and left by the slits to form the flange portions 80 by using the 1 st to 4 th slits K1 to K4. That is, compared to the conventional rough rolling method in which the end face of the slab is always rolled down, the flange width can be widened to form the H-shaped rough material 13, and as a result, a final product (H-shaped steel) having a large flange width can be manufactured.

In the present embodiment, the flat rolling performed after the edging is performed with a pass structure including: the 5 th hole pattern K5 that forms the ridge 82 b; and a 6 th hole pattern K6 that eliminates the bulging portion 82b and widens the inside dimension of the web portion 82. As a result, the H-shaped rough material 13 having a flange width larger than that of the conventional one can be roll-formed, and as a result, an H-shaped steel product having a flange width larger than that of the conventional one can be manufactured.

Here, it can be seen that, when the rolling forming using the 5 th pass K5 and the 6 th pass K6 is performed, the raised portion 82b formed in the web portion 82 is eliminated, but the inside dimension of the web portion 82 is enlarged as the raised portion 82b is eliminated, and a gap may be generated between the inner surface of the flange portion 80 and the rollers (the upper pass roller 95 and the lower pass roller 96 in the present embodiment) when the rolling forming using the 6 th pass K6 is performed. If a gap is formed between the inner surface of the flange portion 80 and the roll, a variation in the amount of material on the left and right sides of the flange is likely to occur, and rolling stability such as material passing property is likely to be impaired.

In view of such circumstances, the present inventors have further studied preferable conditions under which the removal of the bulging portion 82b in the 6 th pass K6 does not impair the rolling stability, and have obtained the findings described below. The present invention will be described below with reference to the drawings and the like.

The rolling condition that impairs the rolling stability of the flat forming rolling represented by the rolling form of pass No. 6K 6 is a case where the imbalance in the amount of flange material occurs when the bulging portion 82b is eliminated. To avoid this, it is considered that the inner surface of the flange portion 80 and the rolls are required to be in contact with each other in at least 1 pass in the rolling and forming process using the 6 th pass K6. By bringing the inner surface of the flange portion 80 into contact with the roller during the bulging portion removing rolling forming, the lateral deformation of the flange portion 80 is made uniform, and the rolling stability can be maintained. In particular, when the rolling forming is performed in a plurality of passes, it is desirable that the inner surface of the flange portion 80 is brought into contact with the roller in the 1 st pass.

In order to achieve the condition that the inner surface of the flange portion 80 and the roller are brought into contact in at least 1 pass in the rolling forming by the 6 th pass K6, it is necessary to appropriately design the pass of the 6 th pass K6 or to set the pass flow by the 6 th pass K6 to a preferable pass flow.

(preferred pass design and pass flow)

Fig. 8 is a schematic explanatory view of the case where the roll forming is performed in a state where the inner surface of the flange portion 80 is in contact with the roll in the roll forming performed by the 6 th pass K6. For the sake of simplifying the description, fig. 8 shows only the upper half of the rolled material a. As shown in fig. 8 (a) and (b), the rolling and forming are preferably performed in a state where the inner surface 80a of the flange portion 80 is in contact with the upper hole roller 95, with respect to the pressing of the bulging portion 82b by the upper hole roller 95. In the case where the rolling forming by the 6 th pass K6 is performed in a plurality of passes with respect to the state where the inner surface 80a of the flange portion 80 is in contact with the upper hole roll 95, the inner surface may be in such a state in all passes or in a state in which the inner surface is in contact with a part of the passes (for example, the 1 st pass). That is, in the rolling and forming of at least 1 pass or more, the inner surface 80a of the flange portion 80 may be in contact with the upper hole roll 95.

Here, as one of the conditions for performing the roll forming in a state where the inner side surface 80a of the flange portion 80 is in contact with the upper hole roll 95, a case where the shape of the 6 th hole K6 is a predetermined shape is exemplified. As a specific structure of the 6 th pass K6, it is desirable that the rolls be in contact with the entire inner surface 80a of the flange portion 80 during the 1 st pass rolling forming. Fig. 9 is a schematic explanatory view of the structure of the desired 6 th pass K6, showing the roll shape by a solid line and the rolled material a by a lattice. By configuring the 6 th groove K6 such that the entire inner surface 80a of the flange portion 80 (the dashed line portion in fig. 9) is in contact with the rolls, at least the tip end portion of the flange portion 80 is formed, and rolling stability can be maintained.

As shown in fig. 9, it is considered that the adjustment of the conditions relating to the structure of the 6 th pass K6 can be controlled by, for example, the value of the inside dimension of the pass, the inclination angle of the flange-facing portion of the pass, and the like, in consideration of the distance between the position of action of the working force (see the arrow in fig. 9) applied from the rolls to the flange portion 80 of the rolled material a and the center position of the rolled material a, that is, the moment arm to rotate the rolled material a, which is the moment arm on the tip side of the flange portion 80 is long (L1 > L2 in the figure), and the rolling can be easily stabilized even when the rolled material a is deformed asymmetrically.

Table 1 below is a table showing each element of a roll pass of a conventional pass design, and is an example of conditions in the case of widening the inner dimension of a web by means of flat rolling and widening rolling without forming a ridge portion in the flat rolling.

Table 2 below is a table showing conditions including a pass (K6 in the table) in which ridge removal and widening (widening in the 1 st stage) are performed simultaneously after the ridge is formed, and shows each element of the roll pass designed according to the present invention. Among them, the rolls K1 to K6 shown in table 2 correspond to the 1 st pass K1 to 6 th pass K6 of the present embodiment, and K7 to K9 are general widening passes. Further, K2-1 and K2-2 are groove pass types having different projection heights, but both are groove pass types having a function equivalent to the 2 nd groove pass K2 of the present embodiment.

[ Table 1]

[ Table 2]

As is clear from a comparison of tables 1 and 2, in the technique of the present embodiment, the ridge removal and the widening rolling are performed simultaneously by the 6 th pass K6, and in the prior art, the number of passes used after the flat rolling is the same, and the pass arrangement is not changed. That is, by adopting the pass design of the 6 th pass K6 as the preferred pass design and adopting the configuration in which the elimination of the bulge 82b and the enlargement of the inner dimension of the web are performed simultaneously by the 6 th pass K6, the H-beam 13 having a large flange width can be roll-formed while keeping the roll body length and the like in the past, and as a result, an H-beam product having a flange width larger than that of the conventional one can be produced.

Further, by providing the roll pass elements such that the inner surface of the flange portion 80 is brought into contact with the rolls when the bulging portions 82b are eliminated, the left-right deformation of the flange portion 80 is made uniform, and the rolling stability can be maintained.

As one of the conditions for performing the roll forming in a state where the inner surface 80a of the flange portion 80 is in contact with the upper grooved roll 95, a condition in which a pass flow of the roll forming by the 6 th groove K6 is appropriately designed can be cited. Specifically, by appropriately adjusting the rolling reduction amount achieved by the pass (here, the 6 th pass K6) in which the ridge portion is eliminated and suppressing the rolling reduction amount of the ridge portion 82b, it is possible to suppress the expansion of the inner dimension of the web portion 82 accompanying the elimination of the ridge portion 82b and maintain the rolling stability.

First, referring to fig. 9, as described above, as a preferable pass shape, it is designed such that in the 1 st pass rolling, the roll gap including the longitudinal variation of the ridge portion 82b is evaluated, and the inner surface 80a of the flange portion 80 is brought into contact with the roll inner surface when the roll gap indicating the minimum value (i.e., the roll gap in which the web portion roll gap corresponds to the height of the ridge portion 82 b) is set. By using such a pass, the 1 st pass is set at a nip where the web nip and the height of the raised portion 82b are substantially matched, whereby the inner side surface 80a of the flange portion 80 can be reliably formed, and rolling stability can be maintained.

In addition, as a preferable pass flow, the contact state of the flange inner surface can be controlled by performing the pass flow in which the bulging portion is partially removed in the pass in which the bulging portion removal rolling forming is performed. For example, in the case of performing the bulging portion removing rolling forming in a plurality of passes, if the rolling reduction amount per 1 pass is excessively large, the enlargement of the inner dimension of the web due to the removal (rolling) of the bulging portion 82b occurs, and therefore, the inner side surface 80a of the flange portion 80 is less likely to contact with the roll, and the rolling stability is likely to be impaired. Therefore, the rolling reduction of the bulging portion 82b is restricted in the 1 st pass rolling forming, so that the inner side surface 80a of the flange portion 80 can be reliably formed, and the rolling stability can be maintained.

When the removal of the raised part is performed locally, it is preferable to remove the remaining raised part in any subsequent hole pattern. For example, the rolling and the removal of the remaining ridge portion may be performed by universal rolling by an intermediate universal rolling mill 5 (see fig. 1) that performs an intermediate rolling step.

Tables 3 and 4 shown below are examples of the pass flow in the case where the formation and removal of the ridge portion 82b are performed using the above-described 5 th hole pattern K5 and 6 th hole pattern K6, and table 3 is a conventional pass flow and table 4 is a pass flow of the present invention. The respective groove patterns K5 and K6 described in tables 3 and 4 correspond to the 5 th groove pattern K5 and the 6 th groove pattern K6 of the present embodiment.

[ Table 3]

Pass	Hole pattern	Web end thickness	Web ridge thickness
				1	K5	270	300
2	K5	250	300
				3	K5	220	300
4	K5	200	300
				5	K5	185	285
6	K5	170	270
				7	K5	160	260
8	K5	150	250
				9	K5	140	240
10	K5	130	230
				11	K5	120	220
12	K5	110	210
				13	K5	100	200
14	K6	100	100
							The width of the plate blank: 2000mm
			(unit: mm)

[ Table 4]

Pass	Hole pattern	Web end thickness	Web ridge thickness
				1	K5	270	300
2	K5	250	300
				3	K5	220	300
4	K5	200	300
				5	K5	185	285
6	K5	170	270
				7	K5	160	260
8	K5	150	250
				9	K5	140	240
10	K5	130	230
				11	K5	120	220
12	K5	110	210
				13	K5	100	200
14	K6	100	150
							The width of the plate blank: 2000mm
			(unit: mm)

As can be seen by comparing table 3 and table 4, in the conventional pass flow, the bulge 82b was completely eliminated and the web end thickness was equal to the web protrusion (bulge) thickness (100.0mm) in the first pass (14 th pass) performed by the 6 th pass K6, whereas in the pass flow of the present invention, the bulge 82b was not completely eliminated but remained (150.0 mm). With such a pass flow, the enlargement of the inner dimension of the web 82 due to the elimination of the ridge 82b can be suppressed, and rolling stability can be maintained.

Fig. 10 is a schematic diagram showing the shape of the rolled material after eliminating the bulging portion in each of the pass flows of table 3 and table 4, which is obtained by simulation, fig. 10 (a) is a schematic diagram of a conventional pass flow, and fig. 10 (b) is a schematic diagram of a pass flow of the present invention.

As shown in fig. 10 (a), in the roll forming for eliminating the bulging portion, when the bulging portion is completely eliminated, a gap (see a dashed line portion in the drawing) is generated between the hole roll and the inner surface of the flange of the rolled material as the inner dimension of the web is widened in accordance with the elimination of the bulging portion. On the other hand, as shown in fig. 10 (b), when the removal of the raised portion is limited to a part, the roll forming can be completed in a state where the hole roll is in contact with the inner surface of the flange of the rolled material.

This makes the lateral deformation of the flange portion 80 uniform, and the rolling stability can be maintained.

(ratio of amount of overflow (ridge forming width) in inner dimension of web)

As described above, in the 5 th pass K5 (see fig. 6) of the present embodiment, the raised portion 82b is formed in the center of the web portion 82 of the rolled material a, and the formed raised portion 82b is eliminated in the subsequent 6 th pass K6. Further, after the ridge portion is eliminated, if necessary, widening rolling is performed to the inner dimension of the web to form an H-shaped rough member, and in order to manufacture a large-sized H-shaped steel product having a flange width larger than that of the conventional one, it is desirable to increase the flange width of the H-shaped rough member as much as possible.

The present inventors found that the flange width of the H-shaped raw material finally obtained can be rendered different by changing the width W1 of the bulging portion 82b formed in the 5 th pass K5 (i.e., the amount of the overflow of the web inside dimension in the roll forming of the 5 th pass K5). This is because the larger the width of the raised portion 82b, the easier it is to secure the amount of the flange material, and the smaller the flange width due to the longitudinal extension of the rolled material a when the raised portion is eliminated later.

Therefore, in order to determine a preferable range of the amount of the overflow (hereinafter also abbreviated as "overflow W1") of the inner dimension of the web in the rolling and forming of the 5 th pass K5, the present inventors paid attention to the relationship between the overflow rate and the increase and decrease in the flange width after the H-shaped rough material is formed, and derived a preferable numerical range of the overflow rate. The overflow rate is a value defined by the following equation (1).

The overflow rate [% ] (overflow amount W1/inner side dimension of web W2) × 100 · (1)

Fig. 11 is a graph showing a relationship between the flow-out rate and the flange width increase/decrease rate after the H-shaped rough material is formed. The bead width increasing/decreasing rate in fig. 11 is a value indicating the bead width for each value (12% to 56%) of the overflow rate, based on the bead width for 0% of the overflow rate (1.000).

As shown in fig. 11, the flange width of the H-shaped rough material tends to increase as the flash rate increases, but the flange width increases or decreases to a substantially constant value in a region where the flash rate is about 25% or more (see the dotted line portion in the graph).

From the results shown in fig. 11, it is found that, in the case of manufacturing a large H-shaped steel product having a flange width larger than the conventional flange width, in view of the roll forming in which the flange width of the H-shaped rough material is desired to be also large, it is preferable to set the numerical range of the flash rate to 25% to 50%.

(Material passing property when eliminating the bulge portion)

As described above, from the results of fig. 11, it is preferable that the numerical range of the flash rate when forming the raised portion 82b is 25% to 50%, but on the other hand, it is necessary to further study the value of the thickness of the depressed portion 82a of the web when forming the raised portion 82b at such a numerical range of the flash rate. As a result, when the 6 th pass K6 was used to perform the rolling forming for eliminating the ridge 82b after the ridge 82b was formed, the rolled portion 82a was too thin, the metal movement of the ridge 82b did not proceed in the cross section, and the metal movement in the longitudinal direction of the rolled material a occurred.

Therefore, the inventors of the present invention evaluated formability (rolling stability) under the condition that the web reduction amount during the rolling forming in the 5 th pass K5 is changed when the rolling forming is performed by the 1 st pass K1 to the 6 th pass K6 of the present embodiment in the case of manufacturing the H-section steel having the product flange width of 400mm or more using the rectangular-section slab of 2000mm × 300mm as a raw material, and set the thickness of the pressed portion 82a after the pressing to 200mm, 160mm, 140mm, 120mm, and 100mm as specific conditions to 1 to 5, and set the case of performing the web thickness pressing without forming the bulge portion 82b to 6 as a comparative grade.

Table 5 shown below is a table showing the pass flow of the above grades 1 to 6, and each of the pass patterns G1, G2-2, G3-1, G3-2, G4-1 and G4-2 in the table corresponds to the pass patterns K1 to K6 of the 1 st pass to be described in the present embodiment. The evaluation of the formability was described in the lowermost layer of table 5, and the case where the material passing failure and the shape failure occurred was referred to as "failure", and the case where the material passing failure and the shape failure did not occur was referred to as "good".

[ Table 5]

As shown in table 5, when the thickness of the depressed portion 82a after the depression was set to 200mm, 160mm, or 140mm (grade 1 to grade 3), no material passing failure or shape failure occurred when the raised portion 82b was eliminated. On the other hand, when the thickness of the depressed portion 82a after the depression is set to 120mm or 100mm (class 4 or class 5), a material passing failure or a shape failure occurs when the raised portion 82b is eliminated. In addition, even in the case where the bulging portion 82b is not formed and the web thickness is reduced to 100mm (class 6), the same material passing failure and shape failure occur.

Here, the evaluation criteria of the formability (rolling stability) will be described. When the rolling forming for eliminating the raised portion 82b was performed, the formability was evaluated based on the warpage generated in the longitudinal direction of the rolled material a.

Fig. 12 is an explanatory view relating to the warpage of the rolled material a, and is a schematic side view when the warpage occurs at the longitudinal end of the rolled material a. As shown in fig. 12, the difference between the end portion and the stable portion when the end portion in the longitudinal direction of the rolled material a is warped is defined as "warping amount". The ratio of the amount of generated warpage to the length in the longitudinal direction in which warpage is generated in the rolled material a is defined as "warpage (%)" defined by the following formula (2).

Warpage [% ] warpage amount/length of rolled material with warpage · (2)

The relationship between "warpage (%)" defined by the above formula (2) and the thickness of the depressed portion 82a after depression was verified. Fig. 13 is a graph showing the relationship between the warpage and the web thickness (the thickness after the depression of the depressed portion 82 a). The graph shown in fig. 13 is data under the condition that the overflow rate is set to about 33%.

As shown in fig. 13, the thinner the thickness of the depressed portion 82a after depression, the greater the warpage tends to be. In particular, it is found that when the thickness of the depressed portion 82a after the depression is 140mm or less, the warpage is as small as about 3% or less, and when the thickness of the depressed portion 82a after the depression exceeds 140mm, the warpage becomes about 10% or more, and the shape is significantly deteriorated.

In operation, if the warp of the rolled material a becomes 10% or more, the dimensional shape after the next pass deteriorates significantly and it becomes difficult to continue the rolling. That is, from the results shown in fig. 13, it is understood that good formability can be ensured by performing the roll forming in the 5 th pass K5 so that the web thickness (the thickness after the reduction of the reduced portion 82 a) becomes 140mm or more. This corresponds to the case where the moldability was good under the conditions of the grades 1 to 3 shown in table 1.

The reason why the threshold value of the warpage is 10% is that, when a maximum warpage of about several hundred mm occurs at several meters of the end of the material to be rolled at a rate of 10%, a difference in the amount of material between the upper and lower portions can be easily confirmed by those skilled in the art, and the value becomes 10% which becomes obvious when it is difficult to continue the rolling operation.

In addition, under the same conditions, in the case where the warpage is several% (less than 10%), although warpage of about several tens of mm is observed in normal work, it can be easily estimated by those skilled in the art that it is a degree that is not problematic in work.

As can be seen from fig. 13, in the rolling forming by the 6 th pass K6, since the minimum post-rolling thickness at which no warp occurs in the pressed portion 82a is 140mm, the elongation λ of the bulging portion 82b at this time is 2.14(═ 300/140).

In addition, in the case where the web thickness (the thickness after the pressing of the pressed portion 82 a) is made a predetermined value (for example, 140mm) or more in the 5 th pass K5, the thickness reduction pressing of the web to further thin the web thickness may be performed in the subsequent 6 th pass K6.

Further, fig. 14 is a graph showing the relationship between the thickness after pressing (finished web thickness after pressing) of the pressed portion 82a in the 5 th hole pattern K5 and the height before pressing of the bulging portion 82b is performed. When the "overflow rate" described above is set to a preferable condition (for example, 25% to 50%) with reference to fig. 11, the effect of extension in the longitudinal direction of the raised portion 82b is small, and the raised portion height is maintained at the slab thickness of the raw material as long as the raised portion height is not restricted by the hole pattern.

For example, when the hole pattern is adopted so that the slab thickness is 300mm and the height of the raised portion 82b is a sufficient height, the raised portion height is maintained at 300 mm. From this state, the removal of the bulge 82b was performed in the bulge removal pass (the 6 th pass K6 in fig. 7), and as a result, the material passage was not problematic in the case where the finished web thickness was 140mm after the pressing by the 5 th pass K5, but a material passage failure occurred in the case of 130 mm. In the above case, the thickness of each of the ridge portions 82b is 300mm, and as for the elongation of the ridge portion 82b, in the case of 140mm, the elongation is 2.14 since the ridge portion 82b is depressed from 300mm to 140mm, and in the case of 130mm, the elongation is 2.31 since the ridge portion 82b is depressed from 300mm to 130 mm. When the same marks are given for each case, as shown in fig. 14, the ultimate elongation percentage of the threshold value indicating the material passing failure is about 2.1.

That is, as shown in fig. 14, when the reduction ratio (elongation) at the time of elimination of the swelling by the 6 th pass K6 exceeds 2.1, it is obvious in an experiment that a material passing failure (× in fig. 14) occurs, it is clear that by performing pass design under such a condition that the reduction ratio at the time of elimination of the swelling by the 6 th pass K6 becomes 2.1 or less, the rolling forming by the 5 th pass K5 and the 6 th pass K6 can be performed without causing the material passing failure, and further, when the thickness reduction of the web plate is required after the rolling forming by the 6 th pass K6 is performed, the widening rolling using 1 or more pass can be performed after the rolling forming by the 6 th pass K6.

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 within the scope of the idea described in the claims, and these modifications and variations are also understood to fall within the scope of the present invention.

For example, in the above embodiment, the description has been given of the technique of performing the rolling forming of the material a to be rolled using 4 passes of the 1 st pass K1 to the 4 th pass K4, and thereafter performing the rolling forming of the H-shaped rough material using the 5 th pass K5 and the 6 th pass K6 (and the widening pass according to the necessity), but the number of passes to perform the rough rolling step is not limited thereto, and the rolling forming step shown in the 1 st pass K1 to the 4 th pass K4 may be performed using more passes. 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 forming method in which the slits are formed in the upper and lower end portions (slab end surfaces) of the rolled material a in the 1 st to 4 th slits K1 to K4 and the flange portion 80 is formed by performing the processing of bending the portions divided into left and right by the slits in the left and right direction has been described. However, the rolling and shaping technique of the present invention using the 6 th pass K6 is applicable not only to the rolled material a shaped by such a technique but also to conventional H-shaped rough materials (so-called dog bones) as represented in patent document 1, for example.

Industrial applicability

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

Description of the reference numerals

1. A rolling device; 2. heating furnace; 3. sizing mill; 4. a roughing mill; 5. a middle universal mill; 8. a universal finishing mill; 9. an edging mill; 11. a slab; 13. h-shaped rough material; 14. an intermediate material; 16. h-shaped steel products; 20. a top hole type roll (1 st hole type); 21. a lower hole type roll (1 st hole type); 25. 26, a protrusion (1 st hole type); 28. 29, grooving (1 st hole type); 30. a top hole type roll (2 nd hole type); 31. a lower hole type roll (2 nd hole type); 35. 36, a protrusion (2 nd hole pattern); 38. 39, grooving (No. 2 hole type); 40. a top hole type roll (3 rd hole type); 41. a lower hole type roll (3 rd hole type); 45. 46, a protrusion (3 rd hole type); 48. 49, grooving (No. 3 hole type); 50. a top hole type roll (4 th hole type); 51. a lower hole type roll (4 th hole type); 55. 56, a protrusion part (4 th hole type); 58. 59, grooving (4 th hole type); 80. a flange portion; 80a, the inner side surface (of the flange portion); 82. a web portion; 82a, a pressing part; 82b, a bump (non-depressed portion); 85. a top hole type roll (5 th hole type); 85a, a concave portion; 86. a lower hole type roll (5 th hole type); 86a, a concave portion; 95. a top hole type roll (6 th hole type); 96. a lower hole type roll (6 th hole type); k1, 1 st hole type; k2, pass 2; k3, pass 3; k4, pass 4; k5, pass 5 (web section rolling pass); k6, 6 th hole pattern (bulge eliminating hole pattern); t, production line; A. a material to be rolled.

Claims

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

the rough rolling step includes an edging step of rolling the material to be rolled into a predetermined substantially dog-bone shape and a flat rolling step of rotating the material to be rolled after the edging step by 90 DEG or 270 DEG to roll the web portion,

in the upper and lower grooved rolls of at least 1 groove type among the grooves for carrying out the flat rolling step, a dent part for forming a bulge part in the center of the web part of the rolled material is arranged in the center part of the length of the roll main body of the upper and lower grooved rolls,

the pass for performing the flat rolling step further includes a bulge eliminating pass for rolling the bulge of the material to be rolled having the bulge formed thereon and widening the inner dimension of the web portion of the material to be rolled,

the rolling shaping realized by the bulge eliminating pass is carried out on the rolled material after the bulge is formed in the pass with the pit part for forming the bulge,

the rolling forming for forming the bulging portion is not performed after the rolling of the bulging portion.

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

the roll forming by the bulging portion removing pass is performed in a plurality of passes,

in at least 1 or more of the plurality of passes, the rolling is performed in a state where the inner surface of the flange of the material to be rolled is in contact with the hole roll.

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

in the 1 st pass among the plurality of passes, the rolling forming is performed in a state where the inner surface of the flange of the rolled material is in contact with the hole rolls.

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

in the rolling forming by the ridge portion removing pass, the ridge portion is partially removed, and the remaining ridge portion is removed by the rolling forming by any subsequent pass.

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

the width of the ridge portion formed in the flat rolling step is set to be 25% to 50% of the inner dimension of the web portion of the material to be rolled.

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

the pressing rate of the bulge in the bulge elimination hole pattern is set to be 2.1 or less.

7. The method of manufacturing H-shaped steel according to any one of claims 1 to 6,

the edging process is performed by using a plurality of passes of 4 or more,

the shaping of the rolled material is carried out by 1 pass or a plurality of passes in the plurality of passes,

in the 1 st pass and the 2 nd pass of the plurality of passes, a notch is formed vertically to the width direction of the rolled material so as to form a protrusion part of a division part at the end part of the rolled material,

in the hole patterns after the 3 rd hole pattern out of the plurality of hole patterns, a protrusion portion is formed to be in contact with the notch groove and gradually bend the formed divided portion.