Method for manufacturing H-shaped steel
阅读说明:本技术 H型钢的制造方法 (Method for manufacturing H-shaped steel ) 是由 山下浩 于 2018-07-11 设计创作,主要内容包括:一种H型钢的制造方法,其包括粗轧工序、中间轧制工序、精轧工序,其中,在进行所述粗轧工序的轧机刻设有用于造形被轧制件的多个孔型,该多个孔型包括:1个或多个切槽孔型,其形成有相对于被轧制件的宽度方向铅垂地形成切槽而在被轧制件端部形成分割部位的突起部;以及多个弯折孔型,其形成有抵接于所述切槽并依次弯折在所述切槽孔型处形成的分割部位的突起部,形成于所述切槽孔型中的最终的切槽孔型的突起部包括:顶端部,其呈具有预定的顶端角度的锥形状;以及根部,其位于该顶端部的根部,具有与该顶端部相比倾斜平缓的锥形状。(A method for manufacturing H-shaped steel, comprising a rough rolling process, an intermediate rolling process and a finish rolling process, wherein a rolling mill for performing the rough rolling process is engraved with a plurality of passes for shaping a rolled material, the plurality of passes comprising: 1 or a plurality of notch groove patterns, which are provided with a protrusion part that forms a notch vertically relative to the width direction of the rolled piece and forms a division part at the end part of the rolled piece; and a plurality of groove-cut grooves in which projections are formed that abut against the grooves and sequentially bend the divided portions formed at the groove-cut grooves, wherein the projection of the final groove-cut groove formed in the groove-cut groove includes: a tip portion having a tapered shape with a predetermined tip angle; and a root portion located at the root portion of the distal end portion and having a tapered shape that is more gently inclined than the distal end portion.)
1. A method for manufacturing H-shaped steel, which comprises a rough rolling process, an intermediate rolling process and a finish rolling process, and is characterized in that,
a rolling mill for performing the rough rolling step is provided with a plurality of pass patterns for shaping the rolled material,
the plurality of pass patterns include:
1 or a plurality of notch groove patterns, which are provided with a protrusion part that forms a notch vertically relative to the width direction of the rolled piece and forms a division part at the end part of the rolled piece; and
a plurality of bending pass which is formed with a protrusion portion abutting against the slot and sequentially bending the division portion formed at the slot pass,
the projection of the final slot pass formed in the slot pass comprises: a tip portion having a tapered shape with a predetermined tip angle; and a root portion located at the root portion of the distal end portion and having a tapered shape that is more gently inclined than the distal end portion.
2. The method of manufacturing H-shaped steel according to claim 1,
the taper angle of the root is 60 ° or more and is equal to or less than the tip angle of the projection formed in the groove at the most preceding stage in the bent groove.
3. The method of manufacturing H-shaped steel according to claim 1 or 2,
the flange thickness of the rolled material shaped at the hole pattern of the most advanced stage in the bending hole patterns exceeds 160 mm.
4. The method of manufacturing H-shaped steel according to any one of claims 1 to 3,
when the flange thickness of the rolled material to be shaped at the pass at the most preceding stage in the bending passes is 180mm or more,
the tip portion and the root portion are configured such that a contact width ratio L/B, which is a ratio of a width L of the root portion to a flange contact width B in a final one of the groove hole patterns, is 0.20 or more.
5. The method of manufacturing H-shaped steel according to any one of claims 1 to 4,
in the shaping of the notch groove and the bend groove, the rolling is performed in a state where the end face of the rolled material is in contact with the groove peripheral surface in the shaping of at least 1 pass or more.
6. The method of manufacturing H-shaped steel according to any one of claims 1 to 5,
the groove pass is provided with pass side surfaces which abut against the left and right side surfaces of the rolled material and restrain the rolled material from the left and right.
Technical Field
(cross-reference to related applications)
The application claims priority based on Japanese patent application No. 2017-136551 filed in the Japan on 12.7.7.2017 to the present country, the contents of which are incorporated herein by reference.
The present invention relates to a method for producing H-shaped steel from a rectangular-section slab or the like as a raw material.
Background
In the case of manufacturing H-shaped steel, a raw material such as a slab or a steel ingot drawn out from a heating furnace is shaped into a rough shape (a so-called dog-bone-shaped rolled material) by a roughing mill (BD). Next, the thicknesses of the web and the flange of the rough bar were reduced by a universal intermediate rolling mill. The flange of the rolled material is subjected to width reduction, end face forging and shaping by an edger close to the universal intermediate rolling mill. Then, an H-shaped steel product is formed by utilizing a universal finishing mill.
In recent years, with the increase in size of building structures and the use thereof in offshore structures, it has been required to produce H-shaped steel products larger than conventional ones. In particular, articles with increased flange width and flange thickness are 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 a notch is formed in upper and lower end surfaces (slab end surfaces) of a rolled material and the notch is expanded.
Among them, as a technique for increasing the thickness of the flange, for example, patent document 1 discloses the following technique: the upper and lower end portions (slab end surfaces) of the rolled material are formed with notches without being restricted, and the notches are expanded by edging. This technique can increase the thickness of the flange according to the reduction of the rolled edge.
In addition, for example,
Disclosure of Invention
Problems to be solved by the invention
However, for example, as disclosed in patent document 1, when the rolling is performed while the upper and lower end portions (slab end surfaces) of the rolled material are free to expand, the flange width increases, but the thickness becomes thinner at the flange tip end portion, and the thickness at the flange tip end portion becomes insufficient. As a result, the molding may not be sufficiently performed in the subsequent process, and a large thickness may not be obtained. Further, according to the study of the present inventors, the following findings were obtained: similarly, when the degree of restriction in the left and right directions of the upper and lower end portions (slab end surfaces) of the rolled material is reduced as compared with the conventional one, the flange tip end portion becomes thin and the thickness becomes insufficient.
Further, for example, as disclosed in
That is, in the conventional manufacturing techniques represented by the wedge method, the thickness of the flange is insufficient in any case, and there is a possibility that a larger H-shaped steel product than the conventional one cannot be realized.
In view of the above circumstances, an object of the present invention is to provide a method for manufacturing H-shaped steel, which can manufacture an H-shaped steel product having a flange thickness thicker than conventional methods, when performing a step of forming a groove deeply in an end face of a raw material such as a slab by a protrusion having a tip shape formed into an acute angle and sequentially bending the formed flange portions in a rough rolling step using a pass when manufacturing H-shaped steel.
Further, a method for producing an H-shaped steel is provided, in which a friction defect which may occur on an outer side surface of a flange, which is a problem in producing an H-shaped steel product having a thick flange, is suppressed, and a biting property in roll forming is improved.
Means for solving the problems
In order to achieve the above object, 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 rolling mill performing the rough rolling step is provided with a plurality of passes for shaping a rolled material, the plurality of passes including: 1 or a plurality of notch groove patterns, which are provided with a protrusion part that forms a notch vertically relative to the width direction of the rolled piece and forms a division part at the end part of the rolled piece; and a plurality of groove-cut grooves in which projections are formed that abut against the grooves and sequentially bend the divided portions formed at the groove-cut grooves, wherein the projection of the final groove-cut groove formed in the groove-cut groove includes: a tip portion having a tapered shape with a predetermined tip angle; and a root portion located at the root portion of the distal end portion and having a tapered shape that is more gently inclined than the distal end portion.
The taper angle of the root portion may be 60 ° or more and may be equal to or less than the tip angle of the projection portion of the groove formed at the most advanced stage in the bent groove.
The thickness of the flange of the rolled material to be formed in the groove at the most preceding stage of the bending grooves may exceed 160 mm.
When the flange thickness of the rolled material to be formed in the first pass of the bending pass is 180mm or more, the tip portion and the root portion may be configured so that a contact width ratio L/B, which is a ratio of the width L of the root portion to the flange contact width B in the final slot pass of the slot passes, is 0.20 or more.
In the case of forming in the notch groove and the bend groove, the rolling may be performed in a state where the end surface of the rolled material is in contact with the groove peripheral surface in the forming of at least 1 pass or more.
The groove pass may be provided with pass side surfaces that abut against left and right side surfaces of the rolled material and restrain the rolled material from left and right.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, in the rough rolling step using a pass in the production of H-section steel, when the step of forming a deep groove in the end face of a material such as a slab by using a projection having a tip shape formed into an acute angle and sequentially bending a flange portion formed by the deep groove is performed, an H-section steel product having a flange thickness larger than that of the conventional one can be produced. Further, it is possible to suppress a friction defect which may occur on the outer side surface of the flange, which is a problem in producing an H-shaped steel product having a thick flange, and to improve the biting property in roll forming.
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 an analysis diagram showing a finished shape in the 1 st pass of the bending formation at the 3 rd pass.
Fig. 9 is a schematic explanatory view of the shape of the improved protrusion.
Fig. 10 is a graph showing a relationship between the
FIG. 11 is a schematic explanatory view of pass No. 2-2K 2-2b according to a modification of the present invention.
Fig. 12 is a graph showing the vertical sliding speed between the roll and the rolled material.
Fig. 13 is a schematic diagram showing deformation simulation results by FEM analysis under the conditions of comparative example, example 1, and example 2.
Detailed Description
Embodiments of the present invention will be described below with reference to the drawings. In the present specification and the drawings, the same reference numerals are given to the constituent elements having substantially the same functional configuration, and redundant description is omitted.
Fig. 1 is an explanatory view of a production line T of H-section steel including a rolling facility 1 according to the present embodiment. As shown in fig. 1, a
As shown in fig. 1, in the production line T, a rolled material a such as a
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 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 either the sizing mill 3 or the roughing mill 4. 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, the case where the basic structure of the engraved hole pattern is 6 hole patterns is exemplified and described, but the number of the hole patterns does not necessarily need to be 6 hole patterns, and a plurality of hole patterns of 6 or more may be used. That is, any hole pattern may be used as long as it is suitable for forming the H-shaped
Fig. 2 is a schematic explanatory view of the 1 st hole type K1. The 1 st hole pattern K1 is engraved on the upper and lower hole pattern rolls 20 and 21 as a pair of horizontal rolls. The rolled material a is pressed and shaped in the nip between the upper and lower hole rolls 20 and 21. In addition, on the circumferential surface of the upper grooved roll 20 (i.e., the upper surface of the 1 st groove K1), a
In the 1 st pass K1, the
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
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. On the peripheral surface of the upper-grooved roll 30 (i.e., the upper surface of the 2-1 st groove K2-1), there is formed 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 dimensions such as the protruding length thereof are configured to be equal in each of the protrusions 35 and 36. 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 flange-corresponding portion, to improve the guiding property, and to ensure the stability of rolling, it is preferable that the
The height (projection length) h2a of the projections 35 and 36 is higher than the height h1 of the
Here, the height h2a of the protrusions 35, 36 formed in the 2-1 st groove K2-1 is higher than the height h1 of the
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, since the entry length of the projection when pressing the upper and lower end portions (slab end surfaces) of the rolled material a is long, the
In addition, the shaping at pass No. 2-1K 2-1 was performed in multiple passes. In the multi-pass forming, the upper and lower end portions (slab end surfaces) of the material to be rolled a are brought into contact with the groove upper surfaces 30a and 30b and the groove bottom surfaces 31a and 31b facing each other in the final pass. This is because, if the upper and lower end portions of the rolled material a are not in contact with the inside of the pass in all passes in the 2-1 th pass K2-1, there is a possibility that a shape failure such that the flange corresponding portion (a portion corresponding to a
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. On the peripheral surface of the upper grooved roll 40 (i.e., the upper surface of the 2 nd-2 nd groove K2-2), a
The height (projection length) h2b of the
Here, the height h2b of the
The angles θ f between the groove
As shown in fig. 4, since the entry length of the projection when pressing the upper and lower end portions (slab end surfaces) of the rolled material a is long, the notches 38 and 39 formed in the 2-1 st groove K2-1 are formed to be deeper in the 2-2 nd groove K2-2, and the
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
In addition, the shaping at pass 2-2K 2-2 was performed in multiple passes. In the multi-pass forming, the upper and lower end portions (slab end surfaces) of the material to be rolled a are brought into contact with the groove
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
The
The angles θ f between the groove
As shown in fig. 5, in the 3 rd pass K3, the
In addition, the forming in the 3 rd pass K3 shown in fig. 5 was performed by at least 1 pass or more. 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 are in contact with the inside of the pass (the upper and bottom surfaces of the 3 rd pass K3). Preferably, the upper and lower end portions (slab end surfaces) of the material to be rolled a are lightly rolled down while being 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 roller 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 dimensions such as the protruding length thereof are configured to be equal in each of the protrusions 65 and 66.
The angle θ 3 of the tip end of the protruding portions 65 and 66 is configured to be larger than the
In addition, as in the case of the 3 rd pass K3, the angles θ f between the pass upper surfaces 60a and 60b and the pass 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 all about 90 ° (substantially right angles) at 4 positions shown in fig. 6.
In the 4 th pass K4, the rolled material a having passed through the 3 rd pass K3 is pressed by the projections 65 and 66 against the
The portions of the upper and lower end portions of the rolled material a thus formed correspond to the flanges of the H-shaped steel product, and are referred to as
The shaping at the 4 th pass K4 shown in fig. 6 was performed by at least 1 pass or more. 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 are in contact with the inside of the pass (the upper and bottom surfaces of the 4 th pass K4). Preferably, the upper and lower end portions (slab end surfaces) of the material to be rolled a are lightly rolled down while being 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 constituted by upper hole pattern rolls 85 and lower hole pattern rolls 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
The H-shaped
As described above, the following configuration was performed: the
Here, the method for producing H-shaped steel according to the present embodiment has the following features: the shape of the
With regard to the roll forming technique having such characteristics, for example, when an H-shaped steel product having a large flange thickness, such as a height of 1200mm × a width of 500mm, is manufactured from a raw material slab having a thickness of 300mm, the
Fig. 8 is an analysis diagram showing a finished shape in the 1 st pass of the bending formation in the 3 rd hole pattern K3. In fig. 8, for the sake of explanation, a part of the divided portion (flange portion 80) is shown in an enlarged scale, and the flange portion shape before bending and forming is shown by a solid line, the flange portion shape after bending and forming is shown by a grid, and the roller shape is also shown. As shown in fig. 8, in the 1 st pass during the bending, the roller comes into contact with only a part of the outer surface of the
In view of the above circumstances, the present inventors have further studied conditions under which the occurrence of friction defects during bending and the deterioration of the biting property can be suppressed in the method for producing H-shaped steel according to the present embodiment. The present study will be described below with reference to the drawings and the like. The "bite" is a criterion indicating whether or not the rolled material a is independently bitten into the rolling mill from the entry side of each rolling mill by only conveying by a conveying system (e.g., table rolls). That is, the judgment criterion indicates whether or not to start rolling using only the driving force of the table roll on the entry side of each rolling mill.
Referring to fig. 8, as described above, when a large H-shaped steel product having a large flange thickness, such as a height of 1200mm × a width of 500mm, is manufactured from a raw material slab having a thickness of 300mm, it is confirmed that a friction defect occurs on the outer side surface of the flange portion. Under such conditions, there is a possibility that defects may remain in the final product, and therefore, there is a need for a roll forming technique that can avoid such defects and also can suppress deterioration in the biting property.
As described above, it is presumed that the friction defect is generated when the metal on the outer surface of the flange portion is pulled down in the pressing direction by the friction force of the roller during the bending molding. Therefore, the present inventors invented the following technique: by setting the pass shape of the 2 nd-2 nd pass K2-2 that is subjected to roll forming in the stage of the bending forming performed in the 3 rd pass K3 to an appropriate shape, it is possible to suppress the occurrence of friction defects and avoid deterioration of dimensional accuracy, reduction in flange thickness, and the like. Hereinafter, a suitable groove shape of the 2 nd-2 nd groove K2-2 of the present embodiment will be described.
Fig. 9 is a schematic explanatory view of the shape of the improved protrusion. Fig. 9 is an explanatory diagram showing the structure of the 2-2 nd groove K2-2a in the case where the shape of the
As shown in fig. 9, the improved protrusions 45 'and 46' are composed of a
Here, the height of the entire improved protrusions 45 ', 46' is equal to the height of the
Further, after the grooving forming in the 2-2 nd pass K2-2a, in relation to the forming conditions for the bending forming in the 3 rd pass K3, the value of θ 4 needs to be an angle equal to or smaller than the
Here, the present inventors specified a ratio L/B of a root width L (width length of the root 45B) to a flange contact width B (flange one-side width before bending forming) at the time of filling a rolled material a in which the pass filling is completed by the grooving forming at the 2 nd-2 nd pass K2-2a with respect to the pass shape of the 2 nd-2 nd pass K2-2a (see fig. 9). By setting the contact width ratio L/B to a value within a predetermined range, it is possible to suppress the occurrence of friction defects and appropriately avoid deterioration in dimensional accuracy, reduction in flange thickness, and the like. In the present embodiment, the contact width ratio L/B is preferably 0.20 or more, and more preferably 0.20 or more and 0.24 or less. The numerical range of the contact width ratio L/B will be described with reference to tables 1 to 4 and the like in examples described later.
In the notch groove pattern (the 2 nd-2 nd groove pattern K2-2a) having the improved structure of the protrusions 45 'and 46' described above with reference to fig. 9, the protrusions 45 'and 46' are formed by the
In recent years, with the increase in size of building structures and the use thereof in offshore structures, it has been required to produce H-shaped steel products larger than conventional ones. That is, an H-shaped steel product having a large flange width and a large flange thickness is required. For example, it is required to manufacture a large H-shaped steel product having a height of 1200mm × a width of 500mm and a large flange thickness from a raw material slab having a thickness of 300 mm. In such a case, a reduction in the flange thickness is not preferable.
According to the verification of the present inventors, it has been found that when the
As described with reference to fig. 10, the height h of the
As described above, in the method for producing H-shaped steel according to the present embodiment, by using the notch groove pattern (2-2 groove pattern K2-2a) having the improved structure of the projecting portions 45 'and 46', even when the
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 is obvious that various modifications and alterations can be made by those skilled in the art within the scope of the idea described in the claims, and those modifications are naturally understood to fall within the scope of the present invention.
In the above embodiment, the following techniques are explained: the workpiece a was shaped using the groove groups shown and described as the 1 st to 4 th grooves K1 to K4, and then, the flat rolling was performed using the 5 th groove K5. However, the number of passes for performing the rough rolling process is not limited thereto. 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 appropriately changed to such an extent that the roughing step can be appropriately performed. In particular, it has been described that the so-called "slot forming" is performed in two types of slots having different slot lengths, i.e., the 2-1 st slot type K2-1 and the 2-2 nd slot type K2-2. However, the groove pass may be 1 pass, or may be formed of 3 or more kinds of passes having different groove lengths. In addition, when the groove pass is plural, the technique of improving the shape of the projection of the present invention is applied to the final groove pass.
(modification of the invention)
In the above embodiment, in the production of an H-shaped steel product having a thick flange, the projections (the projections 45 ', 46') having root portions configured to be more gently inclined than the tip portions are pressed against the material to be rolled before the bending formation, and the grooving formation is performed. However, in the notch groove pattern (2-2 groove pattern K2-2a) having the structure of the improved projecting portions 45 ', 46' shown in fig. 9, since the structure in which the side surface of the rolled material a is restrained by the groove pattern is not adopted, there is a possibility that a shape defect such as a collapse of the flange tip portion occurs depending on the characteristics based on the shape of the
In view of the above circumstances, the present inventors have further studied the hole pattern shape of the grooving hole pattern having the structure of the protrusions 45 'and 46', and have invented a hole pattern shape capable of solving the problem associated with the shape defect as described above. Hereinafter, as a modification of the present invention, the 2 nd-2 nd hole type K2-2b having a newly invented structure will be described with reference to the drawings.
FIG. 11 is a schematic explanatory view of pass No. 2-2K 2-2b according to a modification of the present invention. In fig. 11, the same reference numerals are given to the components having the same functional configurations as those of the 2 nd-2 nd hole type K2-2a (see fig. 9) described in the above embodiment, and the description thereof is omitted. As shown in FIG. 11, the basic hole pattern of the 2 nd-2 nd hole pattern K2-2b of the present modification is substantially the same as that of the 2 nd-2 nd hole pattern K2-2 a. On the other hand, the left and right groove side surfaces 40c and 41c formed on the groove are configured to abut against the rolled material a to restrain the rolled material a as a different point. That is, while the 2-2 nd pass K2-2a described in the above embodiment is a structure without side walls, the 2-2 nd pass K2-2b of the present modification is a structure with side walls (pass design).
It is desirable that the portions of the rolled material a abutting against the groove side surfaces 40c, 41c be the portions having the largest thickness among the thicknesses of the rolled material a immediately after the 2-2 nd groove K2-2b is introduced. The contact portion is usually near the center of the outer surface of the flange corresponding portion (flange portion 80) of the rolled material a. This is because when the
In the rolling and forming of the 2 nd-2 nd pass K2-2b performed in a plurality of passes, the pass does not contact the rolled material a in the middle of the passes except the projections 45 'and 46' at the upper and lower end portions (slab end surfaces) of the rolled material a, and the rolled material a is not subjected to the aggressive rolling in these passes. This is because the rolling causes elongation of the rolled material a in the longitudinal direction due to the rolling, and the production efficiency of the flange-corresponding portion (flange portion 80) is lowered.
However, from the viewpoint of improving the dimensional accuracy of the flange width and the flange thickness, it is desirable to set the shaping pass schedule such that the upper and lower end portions of the rolled material a are in full-face contact in the final pass or a plurality of passes before the final pass. That is, it is desirable to perform the shaping for adjusting the shape while suppressing the elongation in the longitudinal direction of the rolled material as much as possible.
In the groove type structure shown in fig. 11, from the viewpoint of efficiently restraining the rolled material a from the left and right, the groove type side surfaces 40c and 41c are preferably vertical shapes perpendicular to the axes of the groove type rolls, but in order to easily repair rolls with roll wear, it is desirable to have a shape inclined at a taper angle of, for example, about 5 to 10% with respect to the vertical direction.
In this way, by using the pass No. 2-2K 2-2b of the modification shown in fig. 11, the shape defect such as the collapse of the flange top end portion of the rolled material a is suppressed during the roll forming in the pass, and the biting property during the roll forming and the product dimensional accuracy are improved.
Further, a slab is exemplified and described as a material for producing H-section steel, but it is needless to say that the present invention can be applied to other materials having similar shapes.
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