JP6855885B2 - H-section steel manufacturing method and H-section steel products - Google Patents

Description

The present invention relates to a manufacturing method for manufacturing H-shaped steel using, for example, a slab having a rectangular cross section as a material, and an H-shaped steel product.

When producing H-beams, materials such as slabs and blooms extracted from the heating furnace are formed into rough-shaped materials (so-called dogbone-shaped materials to be rolled) by a rough rolling mill (BD), and intermediate universal rolling is performed. The machine reduces the thickness of the web and flange of the rough-shaped material, and at the same time, the edger rolling mill close to the intermediate universal rolling mill applies width rolling and forging and shaping of the end face to the flange of the material to be rolled. .. Then, the H-shaped steel product is formed by the finishing universal rolling mill.

In recent years, with the increase in size of building structures and their use in marine structures, there has been a demand for the production of larger H-section steel products than before, and in particular, products with increased flange width and flange thickness are desired. There is. In the manufacturing process using a rectangular cross-section material such as a slab, as a technique for increasing the flange width and the flange thickness, a technique for forming an interrupt on the upper and lower end surfaces (slab end faces) of the material to be rolled and spreading the interrupt (so-called wedge method). )It has been known.

For example, Patent Document 1 states that when a so-called dogbone-shaped rough material is formed from a slab material having a rectangular cross section in the production of H-shaped steel, an interrupt is interrupted at the slab end face in the first hole mold of the rough rolling process. A technique is known in which the interrupt is expanded or the interrupt depth is deepened in the second and subsequent hole types after the insertion, and the interrupt on the slab end face is eliminated in the subsequent hole types.

Further, for example, Patent Document 2 discloses a technique for ensuring the width and thickness of a flange-corresponding portion in a technique for forming H-shaped steel from a slab using a hole-shaped roll. In addition, in Patent Document 2, a device such as providing a common portion in a plurality of hole types to improve the efficiency of the roll body width can be seen.

Japanese Unexamined Patent Publication No. 07-164003 Japanese Unexamined Patent Publication No. 2013-202621

However, for example, as disclosed in Patent Documents 1 and 2, a method of interrupting an end face (slab end face) of a material such as a slab, edging the end face, and performing rough rolling by utilizing the width expansion thereof. Then, there is a limit to widening the flange. That is, in the conventional rough rolling method, in order to widen the flange, the width expansion can be improved by techniques such as wedge design (interrupt angle design), reduction adjustment, and lubrication adjustment. Since it does not contribute significantly, the width expansion ratio, which indicates the ratio of the flange width expansion amount to the edging amount, is about 0.8 even under the condition where the efficiency at the initial stage of edging is the highest. It is known that it decreases as it is repeated, and finally reaches about 0.5. It is also conceivable to increase the size of the material itself such as slabs and increase the edging amount, but it is said that the product flange cannot be widened sufficiently because there are equipment limits on the equipment scale and rolling amount of the rough rolling mill. There are circumstances.

Further, when rolling and modeling a material such as a slab using a hole-shaped roll, as shown in Patent Documents 1 and 2, a plurality of hole-shaped rolls are engraved on the same hole-shaped roll to obtain a roll body width. We are trying to improve efficiency. However, when aiming to increase the size of H-section steel such as widening the flange, there is a limit to the number of hole types that can be engraved on one hole-type roll, and further operational design will be made as the size of H-section steel to be manufactured increases. There is a need for more efficient conditions.

In view of the above circumstances, an object of the present invention is to deeply interrupt the end face of a material such as a slab with a protrusion having a sharp tip shape in a rough rolling process using a hole mold when manufacturing an H-beam. Even if there is an equipment limit on the number of holes that can be engraved on the hole rolls when performing processes such as sequentially bending the flanges formed thereby, the flange width is larger than before by performing 2-heat rolling. The purpose of the present invention is to provide a manufacturing technique for H-shaped steel capable of manufacturing H-shaped steel products. Another object of the present invention is to improve the biting property during rolling molding, which is a problem in realizing two-heat rolling, and to suppress the occurrence of product defects.

In order to achieve the above object, according to the present invention, an H-shaped steel manufacturing method including a rough rolling step, an intermediate rolling step, and a finish rolling step is provided, and a rolling mill performing the rough rolling step is subjected to a coating. A plurality of hole molds for forming the rolled material are engraved, and the plurality of hole molds are formed with protrusions that vertically interrupt the width direction of the material to be rolled to form a divided portion at the end of the material to be rolled. The plurality of hole types include a plurality of interrupted hole types formed and a plurality of bent hole types having protrusions formed in which the divided portions formed in the interrupted hole type are sequentially bent in contact with the interrupted hole type. The rough rolling step is performed by two-heat rolling, and in the second heat molding in the two-heat rolling, bending molding by at least one or more of the plurality of folding hole molds for bending molding is performed. Provided is a method for producing H-shaped steel, which is characterized by being included.

The plurality of bending hole molds are composed of two types of bending hole molds having different bending angles of the divided portions, and in the two types of bending hole molds, bending molding is performed so that the bending angles of the divided portions are sequentially widened. The start hole type for the second heat in the two-heat rolling may be a hole type having a narrow bending angle among the two types of bending hole types.

In the two-heat rolling, the molding in the start hole mold of the second heat is performed in a plurality of passes, and the molding in the first pass among the plurality of passes is performed so that the contact width of the flange surface of the material to be rolled is less than 50%. You may be rolled.

The tip angles of the protrusions formed in the plurality of interrupt hole types are 25 ° or more and 40 ° or less, and the bending angles of the two types of bending hole types are 70 ° or more and 110 ° or less and 130 ° or more and 170, respectively. The difference between the tip angle of the protrusion formed in the interrupt hole type and the bending angle of the bending hole type in the previous stage of the two types of bending hole types may be more than 30 °.

According to the present invention, in a rough rolling process using a hole mold when manufacturing an H-shaped steel, a protrusion having a sharp tip shape deeply interrupts the end face of a material such as a slab, thereby forming the rough rolling process. Even if there is an equipment limit on the number of hole molds that can be engraved on the hole mold roll when performing processes such as sequentially bending the flange portion, by performing 2-heat rolling, H-shaped steel products with a larger flange width than before can be produced. Can be manufactured. In addition, it is possible to improve the biting property during rolling molding, which is a problem in realizing two-heat rolling, and suppress the occurrence of product defects.

It is a schematic explanatory drawing about the production line of H-section steel. It is the schematic explanatory drawing of the 1st hole type. It is the schematic explanatory drawing of the 2-1 hole type. It is the schematic explanatory drawing of the 2-2 hole type. It is the schematic explanatory drawing of the 3rd hole type. It is the schematic explanatory drawing of the 4th hole type. It is a schematic explanatory drawing of the 5th hole type (flat molding hole type). 2 is a schematic explanatory view of the positional relationship between the material to be rolled and the hole type roll due to the difference in the amount of rolling when the start hole type of the two heat rolling is the third hole type. 2 is a schematic explanatory view of the positional relationship between the material to be rolled and the hole type roll due to the difference in the amount of rolling when the start hole type of 2 heat rolling is the 4th hole type. It is a graph which shows the relationship between the bending angle (θ3-θ2) and the flange thickness deviation (flange thickness variation) in the 4th hole type. It is a graph which shows the thickness change amount (flange tip crushing amount) of the tip of the flange corresponding part when the tip angle θ2 in the 3rd hole type is changed. FIG. 5 is a schematic view showing the shape of the material to be rolled after molding when the tip angle θ2 of the third hole type protrusion is set to more than 110 ° by the method according to the present embodiment. It is a graph which shows the change of the product defect depth when the tip angle θ3 of the 4th hole type is changed. It is the schematic explanatory drawing about the web thickening in the web thickening hole type. It is a graph which shows the preferable design range of θ2 and θ3.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

FIG. 1 is an explanatory diagram of an H-section steel production line T including the rolling equipment 1 according to the present embodiment. As shown in FIG. 1, a heating furnace 2, a rough rolling mill 4, an intermediate universal rolling mill 5, and a finishing universal rolling mill 8 are arranged in this order from the upstream side in the production line T. Further, an edger rolling mill 9 is provided in the vicinity of the intermediate universal rolling mill 5. In the following, for the sake of explanation, the steel materials in the production line T are collectively referred to as “material to be rolled A”, and the shape may be appropriately illustrated by using broken lines, diagonal lines, etc. in each drawing.

As shown in FIG. 1, in the production line T, the material A to be rolled, such as the slab 11 extracted from the heating furnace 2, is roughly rolled in the rough rolling machine 4. Next, intermediate rolling is performed in the intermediate universal rolling mill 5. During this intermediate rolling, the edger rolling mill 9 applies rolling reduction to the end portion of the material to be rolled (flange portion 80, which will be described later), if necessary. Normally, a plurality of hole molds are engraved on the roll of the rough rolling mill 4, and the H-shaped rough material 13 is formed by reverse rolling for about a plurality of passes via these, and the H-shaped rough shape material 13 is formed. A plurality of passes of rolling are applied to the profile 13 using a rolling mill train consisting of two rolling mills of the intermediate universal rolling mill 5-edger rolling mill 9, and the intermediate scrap 14 is formed. Then, the intermediate material 14 is finished and rolled into a product shape by the finishing universal rolling mill 8, and the H-shaped steel product 16 is manufactured.

Next, the hole shape configuration and the hole shape formed in the rough rolling mill 4 shown in FIG. 1 will be described below with reference to the drawings. 2 to 7 are schematic explanatory views of a hole type engraved in the rough rolling mill 4 that performs the rough rolling step. Here, the first hole type to the fourth hole type to be described are engraved on the hole type roll of the rough rolling mill 4, but as will be described later, in the present invention, two heat rolling is performed, so the description will be described below. The five hole types of the first hole type to the fifth hole type may be separately engraved into two replaceable hole type rolls. The suitable hole type design conditions for performing 2-heat rolling will be described later with reference to drawings, tables, and the like.
In 2 heat rolling, after performing rolling molding using the first hole-shaped roll in the rough rolling mill 4, the hole-shaped rolls are replaced in the rough rolling mill 4, and the material A to be rolled is again in the heating furnace 2. This is a step of performing rolling molding using a second hole-shaped roll that has been replaced after heating.
In the rough rolling process in the production of ordinary H-section steel, molding with one or more passes is performed in each of the hole molds described below.

Further, in the present embodiment, the case where the basic configuration of the hole type to be engraved is the 6-hole type will be described as an example, but the number of the hole types does not necessarily have to be the 6-hole type. That is, any hole-shaped structure suitable for modeling the H-shaped rough shape member 13 may be used. In addition, in FIGS. 2 to 7, the approximate final path shape of the material A to be rolled at the time of molding in each hole type is shown by a broken line.

FIG. 2 is a schematic explanatory view of the first hole type K1. The first hole type K1 is engraved on the upper hole type roll 20 and the prepared hole type roll 21 which are a pair of horizontal rolls, and the material A to be rolled is formed in the roll gap between the upper hole type roll 20 and the prepared hole type roll 21. Rolled and shaped. Further, a protrusion 25 projecting toward the inside of the hole type is formed on the peripheral surface of the upper hole type roll 20 (that is, the upper surface of the first hole type K1). Further, a protrusion 26 projecting toward the inside of the hole type is formed on the peripheral surface of the prepared hole type roll 21 (that is, the bottom surface of the first hole type K1). These protrusions 25 and 26 have a tapered shape, and the protrusion length and other dimensions are the same for the protrusion 25 and the protrusion 26, respectively. The height (protrusion length) of the protrusions 25 and 26 is h1, and the tip angle is θ1a.

In the first hole type K1, the protrusions 25 and 26 are pressed against the upper and lower ends (slab end faces) of the material A to be rolled, and interrupts 28 and 29 are formed. The first hole type K1 is also called a "grooved hole type" because it is a hole type that imparts grooves (interrupts 28 and 29) to the end face of the slab. Here, it is desirable that the tip angle (also referred to as a wedge angle) θ1a of the protrusions 25 and 26 is, for example, 25 ° or more and 40 ° or less.

Here, it is preferable that the hole shape width of the first hole type K1 is substantially equal to the thickness of the material A to be rolled (that is, the slab thickness). Specifically, by making the width of the hole type at the tips of the protrusions 25 and 26 formed in the first hole type K1 and the slab thickness the same, the left-right centering property of the material A to be rolled is suitably ensured. Will be done. Further, by adopting such a hole-shaped size configuration, as shown in FIG. 2, the protrusions on the upper and lower ends (slab end faces) of the material A to be rolled during molding with the first hole-shaped K1. The first hole is provided with respect to the upper and lower ends of the slab which are in contact with the material A to be rolled and are divided into four elements (parts) by interrupts 28 and 29. It is preferable that active rolling is not performed on the upper surface and the bottom surface of the mold K1. This is because the rolling reduction by the upper surface and the bottom surface of the hole type causes the material A to be rolled to stretch in the longitudinal direction, and lowers the production efficiency of the flange (flange portion 80 described later). That is, in the first hole type K1, the protrusions 25 and 26 are pressed against the upper and lower ends (slab end faces) of the material A to be rolled, and the protrusions 25 and 26 are rolled down when the interrupts 28 and 29 are formed. The amount (wedge tip rolling down amount) is set to be sufficiently larger than the rolling down amount (slab end face rolling down amount) at the upper and lower ends of the slab, whereby interrupts 28 and 29 are formed.

FIG. 3 is a schematic explanatory view of the 2-1 hole type K2-1. The second 2-1 hole type K2-1 is engraved on a pair of horizontal rolls, an upper hole type roll 30 and a lower hole type roll 31. On the peripheral surface of the upper hole type roll 30 (that is, the upper surface of the second 2-1 hole type K2-1), a protrusion 35 protruding toward the inside of the hole type is formed. Further, a protrusion 36 protruding toward the inside of the hole type is formed on the peripheral surface of the prepared hole type roll 31 (that is, the bottom surface of the 2-1 hole type K2-1). These protrusions 35 and 36 have a tapered shape, and the protrusion length and other dimensions are the same for the protrusion 35 and the protrusion 36, respectively. It is desirable that the tip angle of these protrusions 35 and 36 is a wedge angle θ1b of 25 ° or more and 40 ° or less.

Here, the wedge angle θ1a of the first hole type K1 is the second 2-1 hole type K2 in the latter stage in order to secure the thickness of the tip portion of the flange corresponding portion, enhance the inductivity, and ensure the stability of rolling. It is preferable that the wedge angle is the same as the wedge angle θ1b of -1.

The height (protrusion length) h2a of the protrusions 35 and 36 is higher than the height h1 of the protrusions 25 and 26 of the first hole type K1, and h2a> h1. Further, it is preferable that the tip angle of the protrusions 35 and 36 is the same as the tip angle of the protrusions 25 and 26 of the first hole type K1 in terms of rolling dimensional accuracy. In the roll gap between the upper hole type roll 30 and the lower hole type roll 31, the material A to be rolled after the first hole type K1 material is further formed.

Here, the height h2a of the protrusions 35 and 36 formed on the 2-1 hole type K2-1 is higher than the height h1 of the protrusions 25 and 26 formed on the first hole type K1. Similarly, the penetration length of the material A to be rolled into the upper and lower ends (slab end faces) is longer in the 2-1 hole type K2-1. The penetration depth of the protrusions 35 and 36 into the material A to be rolled in the 2-1 hole type K2-1 is the same as the height h2a of the protrusions 35 and 36. That is, the penetration depth h1'of the protrusions 25 and 26 in the first hole type K1 into the material A to be rolled and the depth h1'of the protrusions 35 and 36 in the second hole type K2-1 into the material A to be rolled. The penetration depth h2a is related to h1'<h2a.
Further, the angle θf formed by the hole-shaped upper surfaces 30a and 30b and the hole-shaped bottom surfaces 31a and 31b facing the upper and lower ends (slab end faces) of the material A to be rolled and the inclined surfaces of the protrusions 35 and 36 is shown in FIG. All of the four locations shown are configured at approximately 90 ° (approximately right angles).

As shown in FIG. 3, since the penetration length of the protrusion when pressed against the upper and lower ends (slab end faces) of the material A to be rolled is long, in the 2-1 hole type K2-1, the first The interrupts 28 and 29 formed in the one-hole type K1 are shaped so as to be deeper, and the interrupts 38 and 39 are formed. This 2-1 hole type K2-1 is also referred to as an "interrupt hole type".

Further, the molding with the 2-1 hole type K2-1 is performed by multiple passes, and in the multi-pass molding, the upper and lower ends (slab end faces) of the material A to be rolled and the upper and lower ends (slab end faces) of the material to be rolled A face each other in the final pass. The molding is performed so that the hole-shaped upper surfaces 30a and 30b and the hole-shaped bottom surfaces 31a and 31b are in contact with each other. This is because when the upper and lower ends of the material A to be rolled and the inside of the hole are not in contact with each other in all the passes in the 2-1 hole type K2-1, the flange corresponding portion (the portion corresponding to the flange portion 80 described later). ) May be shaped asymmetrically, which may cause a problem in terms of material permeability.

FIG. 4 is a schematic explanatory view of the 2-2 hole type K2-2. The 2-2 hole type K2-2 is engraved on a pair of horizontal rolls, an upper hole type roll 40 and a lower hole type roll 41. A protrusion 45 that protrudes toward the inside of the hole type is formed on the peripheral surface of the upper hole type roll 40 (that is, the upper surface of the 2-2 hole type K2-2). Further, a protrusion 46 protruding toward the inside of the hole type is formed on the peripheral surface of the prepared hole type roll 41 (that is, the bottom surface of the 2-2 hole type K2-2). These protrusions 45 and 46 have a tapered shape, and the protrusion length and other dimensions are the same for the protrusion 45 and the protrusion 46, respectively. The tip angle of these protrusions 45 and 46 is a wedge angle θ1b of 25 ° or more and 40 ° or less, and it is desirable that the wedge angle is the same as the wedge angle of the 2-1 hole type K2-1.

The height (protrusion length) h2b of the protrusions 45 and 46 is higher than the height h2a of the protrusions 35 and 36 of the 2-1 hole type K2-1, and h2b> h2a. .. In the roll gap between the upper hole type roll 40 and the lower hole type roll 41, the material A to be rolled after passing the second 2-1 hole type K2-1 material is further formed.

Here, from the height h2a of the protrusions 35 and 36 formed in the 2-1 hole type K2-1, the height h2b of the protrusions 45 and 46 formed in the 2-2 hole type K2-2. The length of penetration into the upper and lower ends (slab end faces) of the material A to be rolled is also higher for the 2-2 hole type K2-2. The penetration depth of the protrusions 45 and 46 into the material A to be rolled in the 2-2 hole type K2-2 is the same as the height h2b of the protrusions 45 and 46. That is, the penetration depth h2a of the protrusions 35 and 36 in the 2-1 hole type K2-1 into the material A to be rolled and the protrusions 45 and 46 in the 2-2 hole type K2-2 to be rolled. The penetration depth h2b into the material A has a relationship with h2a <h2b.
Further, the angle θf formed by the hole-shaped upper surfaces 40a and 40b and the hole-shaped bottom surfaces 41a and 41b facing the upper and lower ends (slab end faces) of the material A to be rolled and the inclined surfaces of the protrusions 45 and 46 is shown in FIG. All of the four locations shown are configured at approximately 90 ° (approximately right angles).

As shown in FIG. 4, since the penetration length of the protrusion when pressed against the upper and lower ends (slab end faces) of the material A to be rolled is long, in the 2-2 hole type K2-2, the second is The interrupts 38 and 39 formed in the 2-1 hole type K2-1 are shaped so as to be deeper, and the interrupts 48 and 49 are formed. This 2-2 hole type K2-2 is also referred to as an "interrupt hole type".
The width of the flange piece at the end of the flange molding process in the rough rolling process is determined based on the dimensions of the interrupts 48 and 49 formed here.

Further, the molding with the 2-2 hole type K2-2 is performed by multiple passes, and in the multi-pass molding, the upper and lower ends (slab end faces) of the material A to be rolled and the upper and lower ends (slab end faces) of the material to be rolled A face each other in the final pass. The molding is performed so that the hole-shaped upper surfaces 40a and 40b and the hole-shaped bottom surfaces 41a and 41b are in contact with each other. This is because when the upper and lower ends of the material A to be rolled and the inside of the hole are not in contact with each other in all the passes in the 2-2 hole type K2-2, the flange corresponding portion (the portion corresponding to the flange portion 80 described later). ) May be shaped asymmetrically, which may cause a problem in terms of material permeability.

FIG. 5 is a schematic explanatory view of the third hole type K3. The third hole type K3 is engraved on a pair of horizontal rolls, an upper hole type roll 50 and a lower hole type roll 51. A protrusion 55 projecting toward the inside of the hole type is formed on the peripheral surface of the upper hole type roll 50 (that is, the upper surface of the third hole type K3). Further, a protrusion 56 protruding toward the inside of the hole type is formed on the peripheral surface of the prepared hole type roll 51 (that is, the bottom surface of the third hole type K3). These protrusions 55 and 56 have a tapered shape, and the protrusion length and other dimensions are the same for the protrusion 55 and the protrusion 56, respectively.

The tip angle θ2 of the protrusions 55 and 56 is wider than the angle θ1b, and the penetration depth h3 of the protrusions 55 and 56 into the material to be rolled is the penetration depth of the protrusions 45 and 46. It is shorter than h2b (that is, h3 <h2b). The angle θ2 is preferably 70 ° or more and 110 ° or less, for example.
Further, the angle θf formed by the hole-shaped upper surfaces 50a and 50b and the hole-shaped bottom surfaces 51a and 51b facing the upper and lower ends (slab end faces) of the material A to be rolled and the inclined surfaces of the protrusions 55 and 56 is shown in FIG. All of the four locations shown are configured at approximately 90 ° (approximately right angles).

As shown in FIG. 5, in the third hole type K3, in the upper and lower end portions (slab end faces) of the material to be rolled A with respect to the material A to be rolled after passing through the second hole type K2-2, the second The interrupts 48 and 49 formed in the two-hole type K2-2 become interrupts 58 and 59 when the protrusions 55 and 56 are pressed against them. That is, in the final pass in the modeling with the third hole type K3, the deepest angle of the interrupts 58 and 59 (hereinafter, also referred to as the interrupt angle) is θ2. In other words, in the 2-2 hole type K2-2, the divided portion formed together with the formation of the interrupts 48 and 49 (the portion corresponding to the flange portion 80 described later) is bent outward. This third hole type K3 is also referred to as a "bent hole type".

Further, the molding with the third hole type K3 shown in FIG. 5 is performed by at least one pass or more, and at least one pass or more of these is the upper and lower end portions (slab end face) of the material A to be rolled and the inside of the hole type (the first). It is performed in a state where the upper surface and the bottom surface of the 3-hole type K3 are in contact with each other. In a state where the upper and lower ends (slab end faces) of the material A to be rolled are in contact with the inside of the hole mold, it is preferable that the end portion is lightly rolled.

FIG. 6 is a schematic explanatory view of the fourth hole type K4. The fourth hole type K4 is engraved on a pair of horizontal rolls, an upper hole type roll 60 and a lower hole type roll 61. A protrusion 65 projecting toward the inside of the hole type is formed on the peripheral surface of the upper hole type roll 60 (that is, the upper surface of the fourth hole type K4). Further, a protrusion 66 projecting toward the inside of the hole type is formed on the peripheral surface of the prepared hole type roll 61 (that is, the bottom surface of the fourth hole type K4). These protrusions 65 and 66 have a tapered shape, and the protrusion length and other dimensions are the same for the protrusion 65 and the protrusion 66, respectively.

The tip angle θ3 of the protrusions 65 and 66 is wider than the angle θ2, and the penetration depth h4 of the protrusions 65 and 66 into the material to be rolled is the penetration depth of the protrusions 55 and 56. It is shorter than h3 (that is, h4 <h3). The angle θ3 is preferably 130 ° or more and 170 ° or less, for example.
Further, the angle θf formed by the hole-shaped upper surfaces 60a and 60b and the hole-shaped bottom surfaces 61a and 61b facing the upper and lower ends (slab end faces) of the material A to be rolled and the inclined surfaces of the protrusions 65 and 66 is the third. Similar to the hole type K3, all four locations shown in FIG. 6 are configured at about 90 ° (substantially right angles).

In the fourth hole type K4, interrupts 58 and 59 formed in the third hole type K3 at the upper and lower ends (slab end faces) of the material to be rolled A with respect to the material A to be rolled after passing through the third hole type K3. , The protrusions 65 and 66 are pressed against each other to be expanded and become interrupts 68 and 69. That is, in the final pass in the modeling with the fourth hole type K4, the deepest angle of the interrupts 68 and 69 (hereinafter, also referred to as the interrupt angle) is θ3. In other words, in the third hole type K3, the divided portion (the portion corresponding to the flange portion 80 described later) formed with the formation of the interrupts 58 and 59 is further bent outward. This fourth hole type K4 is also referred to as a "folded hole type".
The portion of the upper and lower ends of the material A to be rolled formed in this way is a portion corresponding to the flange of the later H-shaped steel product, and is referred to here as the flange portion 80.

The molding with the fourth hole type K4 shown in FIG. 6 is performed by at least one pass, and at least one pass or more of these is the upper and lower ends (slab end faces) of the material A to be rolled and the inside of the hole type (fourth hole). The upper surface and the lower surface of the mold K4 are in contact with each other. In a state where the upper and lower ends (slab end faces) of the material A to be rolled are in contact with the inside of the hole mold, it is preferable that the end portion is lightly rolled.

FIG. 7 is a schematic explanatory view of the fifth hole type K5. The fifth hole type K5 is composed of a pair of horizontal rolls, an upper hole type roll 85 and a lower hole type roll 86. As shown in FIG. 7, in the fifth hole type K5, the material A to be rolled formed up to the fourth hole type K4 is rotated by 90 ° or 270 °, and the material A to be rolled is up to the fourth hole type K4. The flange portions 80 located at the upper and lower ends are arranged so as to be on the rolling pitch line. Then, in the fifth hole type K5, the dimensional adjustment of the flange width is performed by reducing the web portion 82, which is a connecting portion connecting the two flange portions 80, and the flange tip portion of the flange portion 80. In this way, a so-called dogbone-shaped H-shaped rough material (H-shaped rough material 13 shown in FIG. 1) is formed. Since the fifth hole type K5 presses down the web portion 82 to reduce the thickness, it is also called a "web thickening hole type" or a "flat shaped hole type". The rolling molding in the flat molding hole type (fifth hole type K5) is performed by one or an arbitrary plurality of passes.

The H-shaped rough material 13 formed in this way is reverse-rolled in a plurality of passes using a rolling mill consisting of two rolling mills, an intermediate universal rolling mill 5-edger rolling mill 9, which is a known rolling mill. Is added, and the intermediate material 14 is formed. Then, the intermediate material 14 is finished and rolled into a product shape by the finishing universal rolling mill 8, and an H-shaped steel product 16 is manufactured (see FIG. 1).

As described above, the first-hole type K1 to the fourth-hole type K4 according to the present embodiment are used to insert an interrupt into the upper and lower end portions (slab end faces) of the material A to be rolled, and each of them is divided into left and right by the interruption. By forming the flange portion 80 by bending the portion to the left and right, the flange width is widened and the H-shaped rough shape is made compared to the conventional rough rolling method in which the end face of the slab is always pressed down. The material 13 can be molded, and as a result, a final product (H-shaped steel) having a large flange width can be manufactured.

Here, in the method for producing H-section steel according to the present embodiment, which is carried out by the hole-type rolling molding in the first-hole type K1 to the fifth-hole type K5 described above, the roll design or the rough rolling mill 4 is used. Due to dimensional restrictions on the equipment configuration, there is a concern that all the hole types of the first hole type K1 to the fifth hole type K5 cannot be engraved on one hole type roll. In particular, in the case of manufacturing a large H-shaped steel product having a flange width of, for example, 400 mm or more, the hole shape becomes large and the dimensional restrictions become stricter.

Therefore, the present inventors carry out rolling molding using the first hole type roll in the rough rolling machine 4 when performing the rough rolling step by the first hole type K1 to the fifth hole type K5 in the rough rolling machine 4. After that, the hole-shaped rolls are replaced in the rough rolling mill 4, the material A to be rolled is heated again in the heating furnace 2, and then rolling molding is performed using the replaced second hole-shaped rolls, so-called two-heat. We decided to perform rolling, and diligently examined the hole type design conditions and path schedule conditions required at that time. Hereinafter, this study will be described with reference to drawings, tables, and the like.

When the rough rolling process by two-heat rolling is carried out using the first-hole type K1 to the fifth-hole type K5, the material A to be rolled is reheated in the heating furnace 2 as a characteristic of the two-heat rolling. Scale (primary scale) adheres to the surface of the material A, and there is a concern that the biteability may be deteriorated due to the hole-shaped roll and product defects (scale defects) may occur due to scale entrainment. That is, when carrying out two-heat rolling, it is necessary to carry out the two-heat process under conditions that can prevent deterioration of biting property and occurrence of product defects due to the adhesion of such scales. From this point of view, the present inventors, in order to make the start hole type of the second heat in the second heat rolling into an appropriate hole type, the second heat start hole type in the second heat rolling, the rolling possibility, and the scale. The peelability, the presence or absence of scale flaws, and the rolling biting property were verified.

Table 1 below shows the verification results. In cases 1 to 9, the start hole type of the second heat was 2-1 hole type K2-1, 2-2 hole type K2-2, and 3rd hole. The verification results regarding scale peelability, presence / absence of scale flaws, and rolling biteability when the mold K3, the fourth hole type K4, and the fifth hole type K5 are used are shown, and whether or not rolling is possible according to these verification results is also shown. ing.
According to the verification results shown in Table 1, there are cases where a normal H-beam having a web thickness of less than 20 mm or a flange thickness of less than 40 mm is manufactured, and an extra-thickness of a web thickness of 20 mm or more or a flange thickness of 40 mm or more. The case of manufacturing H-beams is shown, and cases 1 and 3 are verification results relating to the manufacture of normal H-beams, and cases 2 and 4 are verification results relating to the manufacture of extra-thick H-beams. Cases 5 to 9 are verification results for both normal H-beams and extra-thick H-beams.

Here, the "scale peelability" described in Table 1 is a verification result related to the presence or absence of scale defects, and if the scale peelability is good, scale defects do not remain on the surface of the material to be rolled, resulting in scale defects. It is known that if it is difficult to occur and the scale peelability is poor, scale remains on the surface of the material to be rolled, rolling proceeds as it is, and scale defects occur.
Further, the description of "light reduction rolling" in Table 1 indicates rolling with a reduction amount of 110 mm or less, and "normal rolling" indicates rolling with a reduction amount of more than 110 mm. However, the reduction amount here refers only to the reduction amount due to edging rolling, and does not include the reduction amount due to flat molding rolling.

As shown in Table 1, in Cases 1 to 4, the rolling biteability (hereinafter, also simply referred to as biteability) is good, but the scale peelability is poor in all cases. This is because the shape of the protrusion of the first hole type K1 and the shape of the protrusion of the second hole type K2-1 and the second hole type K2-2 are similar to each other. The scale on the surface gets caught during rolling.
As shown in Cases 1 and 3, even if the scale peelability of H-section steel is poor, rolling is possible because the scale peels off during rolling due to the large rolling reduction rate and the rolling marks are also eliminated. there were.
On the other hand, as shown in Cases 2 and 4, in the extra-thick H-section steel, the indentation marks generated by the scale are difficult to be erased because the indentation rate after the scale is peeled off, and the indentation marks remain, so that rolling is not possible. ..

Further, in cases 5 to 8, the scale peelability was good. This is because in the third hole type and the fourth hole type, which are the folding hole types, the tensile force due to the bending forming acts on the material A to be rolled, so that the scale is easily peeled off. However, as shown in Cases 5 and 7, the biting property is poor in normal rolling. This is because the scale is in a state of being attached before the start of the bending molding, and the friction coefficient is lowered by the scale, so that sufficient biting cannot be achieved.
That is, as shown in Cases 5 and 7, since the biting property is poor in normal rolling, by changing the rolling reduction amount to perform light rolling, scale peeling is promoted to improve the biting property, and rolling is performed. It is presumed that it can be made possible. Cases 6 and 8 shown in Table 1 are verification results when such improvement in biting property is achieved. More detailed conditions (pass schedule, etc.) regarding cases 6 and 8 will be described later with reference to the table.

Further, in the case 9, although the biting property is good, rolling is not possible because the scale reduction marks remain and the product defects remain in the rolling molding of both the normal H-shaped steel and the extra-thick H-shaped steel. It was. After the bending molding is completed (after the rolling molding with the 4th hole type K4 is completed), the flange corresponding portion (rolled material flange width) of the material A to be rolled is greatly widened, for example, over 600 mm. Since it may be difficult to insert the fifth hole type K5 into the heating furnace 2 due to equipment restrictions, it is not realistic to set the fifth hole type K5 as the start hole type of the second heat of the two-heat rolling.

As described above, according to the verification results described with reference to Table 1, when two-heat rolling is carried out in both the production of normal H-section steel and the production of extra-thick H-section steel, the start hole type of the second heat is used. It was found that rolling is possible by using the third hole type K3 or the fourth hole type K4. In addition, when the start hole type of the second heat is the third hole type K3 or the fourth hole type K4, for example, the first pass of rolling molding with the third hole type K3 or the fourth hole type K4. It was found that it is desirable to improve the biting property by reducing the rolling amount.

Next, the pass schedules of the case where the rough rolling process using the first hole type K1 to the fourth hole type K4 according to the present embodiment is performed by 1 heat rolling and the case where the rough rolling process is performed by 2 heat rolling will be described. The pass schedules shown in Tables 2 to 4 below show the rough rolling steps (first-hole type K1 to fourth-hole type K4) when producing H-section steels having the same dimensions and shapes.

Table 2 shown below is an example of a pass schedule when the rough rolling process using the first hole type K1 to the fourth hole type K4 according to the present embodiment is rolled by one heat rolling, and a total of 14 This is a schedule for rolling and modeling up to the 4th hole type K4 with a pass. Here, the roll gap indicates the distance between the upper and lower sides of the tip of the roll hole type wedge. As shown in Table 2, in 1-heat rolling, in each of the first passes of rolling molding in the third hole type K3 and the fourth hole type K4, which are the folding hole type, the roll gap of the front pass is used to start bending. Is added, and the value of the rolling amount is set to a negative value from the previous pass. For example, in the example shown in Table 2, the reduction amount of -200 mm is taken in the 11th pass and the reduction amount of -120 mm is taken in the 13th pass, but the flange tip of the material to be rolled is in contact with the roll. It is partially bent.

When rolling molding is performed according to the pass schedule shown in Table 2, in the case of 1-heat rolling, scale does not adhere to the surface of the material A to be rolled at the start of bending molding in the 11th pass and the 13th pass. Both the K3 and K4 hole types could be rolled in 2 passes with the rolling amount set to -200 mm and -120 mm, respectively.

However, when two-heat rolling is performed with the same hole-shaped structure, as described above, the scale is in a state of being attached at the start of the bending molding, so that the biting property is poor. Therefore, the present inventors have devised a technique for preventing deterioration of biting property by performing light rolling in the first pass in the start hole type of the second heat when performing two-heat rolling. ..

Table 3 shown below is an example of a pass schedule when the rough rolling process using the first hole type K1 to the fourth hole type K4 according to the present embodiment is rolled by two heat rolling, and is an example of the third hole type. This is the schedule when K3 is the start hole type for the second heat.

In the pass schedule shown in Table 3, when the start hole type of the second heat is the third hole type K3 in the two-heat rolling, the first pass in the third hole type K3 (the eleventh pass in Table 3). Light rolling is performed by setting the rolling reduction amount of -10 mm and increasing the number of passes by one pass.

Further, Table 4 shown below is an example of a pass schedule in the case of rolling and modeling the rough rolling process using the first hole type K1 to the fourth hole type K4 according to the present embodiment by two heat rolling. This is a schedule when the hole type K4 is used as the start hole type for the second heat.

In the pass schedule shown in Table 4, when the start hole type of the second heat is the fourth hole type K4 in the two-heat rolling, the first pass in the fourth hole type K4 (the thirteenth pass in Table 4). Light rolling is performed by setting the rolling reduction amount to −220 mm and increasing the number of passes by one pass.

Comparing the two-heat rolling pass schedule shown in Tables 3 and 4 with the one-heat rolling pass schedule shown in Table 2, the first hole-shaped pass that starts the second heat during two-heat rolling. Light rolling is carried out in. At the start of the second heat, the light rolling under the first pass prevents the biting property from deteriorating, and the rough rolling process can be carried out with the same dimensional accuracy as during the first heat rolling without causing poor material passage. It will be possible.

The path schedules shown in Tables 2 to 4 are specific examples and can be changed as appropriate. As shown in Tables 3 and 4, what is important in the rough rolling step using the first hole type K1 to the fourth hole type K4 according to the present embodiment is the start hole type of the second heat during the second heat rolling. In the first pass, light rolling is performed with the roll gap more open than in normal rolling. The light rolling under rolling at that time is, for example, rolling in which the rolling reduction amount is 110 mm or less, or the flange surface contact width between the material to be rolled and the roll is less than 50%.

In 2-heat rolling, the biteability is poor because the scale (primary scale) is attached at the start of bending and molding, which means that the coefficient of friction between the scale and the roll is small. .. If rolling is performed with the scale peeled off and the metal and the roll are in contact with each other, the coefficient of friction is increased and the biting property is improved. That is, in order to improve the biteability, it is important how to remove the primary scale from the surface of the material to be rolled. As a technique for peeling scale from the surface of the material to be rolled, a descaling method using high-pressure water or the like is known, but in the rough rolling method according to the present embodiment, the target portion requiring scale peeling is a protrusion. Since it is the inner surface of the part (inner surface of the wedge), it is difficult to inject high-pressure water perpendicularly to the surface. Therefore, the present inventors have tried a technique capable of removing scale by adjusting the amount of reduction during rolling.

When rolling with a large rolling amount while the primary scale is attached to the surface of the material to be rolled, the surface pressure between the material to be rolled and the roll becomes high, and the scale is used as the material to be rolled before the primary scale is peeled off. It will be pushed in. Therefore, since the rolling is performed in a state where the friction coefficient is small, the biting property is lowered.
On the other hand, when rolling with a small rolling reduction (light rolling) with the primary scale attached to the surface of the material to be rolled, the surface pressure between the material to be rolled and the roll is suppressed to a low level, and the roll and the material to be rolled come into contact with each other. At the start position, contact between the roll and the bare metal portion of the material to be rolled is started after the scale is peeled off without pushing the scale, so that the biting property is improved.

FIG. 8 is a schematic explanatory view of the positional relationship between the material A to be rolled and the hole roll due to the difference in the amount of rolling when the start hole type of the two-heat rolling is the third hole K3, and FIG. 8 (a) is usually Rolling, (b) shows light rolling. Further, FIG. 9 is a schematic explanatory view of the positional relationship between the material A to be rolled and the hole roll due to the difference in the amount of rolling when the start hole type of the two-heat rolling is the fourth hole K4. Indicates normal rolling, and (b) indicates light rolling. In addition, in FIGS. 8 and 9, a part corresponding to the flange of the material A to be rolled is enlarged and shown for the sake of explanation.

As can be seen by comparing (a) and (b) of FIGS. 8 and 9, in the light rolling under-rolling, the contact area (contact arc length) with the roll at the tip of the flange corresponding portion is small and local. As a result, a decrease in the coefficient of friction between the hole-shaped roll and the material A to be rolled (the tip of the flange corresponding portion) to which the scale is attached is suppressed, and the biteability is expected to be improved.

As described above, when rolling with a small rolling reduction amount (light rolling under rolling) is performed with the primary scale attached to the surface of the material to be rolled, the surface pressure between the material to be rolled and the roll is suppressed to a low level, and the biting property is improved. However, as a standard of suitable surface pressure at that time, it is desirable that the contact width between the flange surface (inner surface of the protrusion) and the roll is less than 50%. Comparing (a) and (b) of FIGS. 8 and 9, it can be seen that the contact width between the flange surface and the roll is smaller during light rolling under light rolling than in normal rolling. The contact width of less than 50% is desirable in the first pass of bending molding when the rough rolling step using the first hole type K1 to the fourth hole type K4 according to the present embodiment is performed by one heat rolling. This is because the contact width between the flange surface and the roll is approximately 50%, and the scale can be peeled off.

As described above with reference to Tables 2 to 4 and FIGS. 8 and 9, in the rough rolling step using the first hole type K1 to the fourth hole type K4 according to the present embodiment, two heat rolling is adopted. It is desirable to design a pass schedule in which the start hole type of the second heat is, for example, the third hole type K3 or the fourth hole type K4, and the first pass of the start hole type is light rolling. By adopting such a process, it is possible to prevent deterioration of biting property due to scale adhesion to the surface of the material to be rolled, which is a problem during 2-heat rolling, and suppress the occurrence of product defects to produce H-section steel. It will be possible to carry out.
In addition, when aiming to increase the size of H-section steel such as widening the flange, from the viewpoint that there is a limit to the number of holes that can be engraved on one hole roll, by adopting 2-heat rolling, compared to the conventional method. Operation design conditions can be streamlined.

Although an example of the embodiment of the present invention has been described above, the present invention is not limited to the illustrated embodiment. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the ideas described in the claims, which naturally belong to the technical scope of the present invention. It is understood as a thing.

For example, in the above embodiment, the wedge angles θ1a and θ1b of the first hole type K1, the 2-1 hole type K2-1, and the 2-2 hole type K2-2 are set to 25 ° or more and 40 ° or less, and the third. The wedge angle θ2 of the hole type K3 is 70 ° or more and 110 ° or less, and the wedge angle θ3 of the fourth hole type K4 is 130 ° or more and 170 ° or less. In this regard, when two-heat rolling is applied in the present invention, the peelability of the scale adhering to the surface of the material to be rolled affects the biting property, so that each wedge angle has a more suitable numerical range. It is known to exist. In particular, it is known that the relationship between the wedge angle of the first heat end hole type and the wedge angle of the second heat start hole type during the second heat rolling affects the scale peelability.

Table 5 shown below shows the end hole type wedges of the first heat when two heat rolling is applied in the rough rolling step using the first hole type K1 to the fifth hole type K5 described in the above embodiment. This is the verification result of the scale peelability when the angle (wedge tip angle) and the start hole type wedge angle of the second heat are changed in cases 1 to 11. As described in the above embodiment, the start hole type of the second heat is preferably the third hole type K3 or the fourth hole type K4. Therefore, in the verification shown in Table 5, the start hole type of the second heat is also used. The third hole type K3 or the fourth hole type K4 is used.

As shown in Table 5, cases 1 to 7 and 9 are guaranteed to be scale-peelable and can be rolled. On the other hand, cases 8, 10 and 11 have poor scale peelability and cannot be rolled.
According to the verification results shown in Table 5, when the second heat start hole type is the third hole type K3 (cases 1 to 4), the scale peelability is good and rolling is possible in any case. You can see that.
Further, when the second heat start hole type is the fourth hole type K4, the scale peelability is good when the wedge angle difference from the first heat end hole type is 40 ° or more, and 1 It can be seen that the scale peelability deteriorates when the difference in wedge angle from the heat end hole type is less than 40 ° (30 ° or less).
If the difference in wedge angle (angle change amount) between the 1st heat end hole type and the 2nd heat start hole type is large, a tensile force acts on the flange portion during bending molding, and tensile strain is generated on the surface scale. It is considered that the scale peelability is improved.

When the second heat start hole type is the third hole type K3, the wedge angle of the third hole type K3 is smaller than the wedge angle of the fourth hole type K4, so that the action of spreading the scale in the roll axis direction is large. It is considered that the scale peelability is good when it is difficult for the scale to get caught and the difference in wedge angle from the first heat end hole type is 30 ° or more.
That is, when both the case where the second heat start hole type is the third hole type K3 and the case where the second heat start hole type is the fourth hole type K4, the condition that the wedge angle change amount exceeds 30 ° is satisfied. As a result, the scale peelability becomes good.

As described above with reference to Table 5, when the two-heat rolling is applied in the rough rolling step using the first hole type K1 to the fifth hole type K5, the start hole type of the second heat is the third hole type. It can be seen that it is preferable to use the hole type K3 or the fourth hole type K4 and design the wedge angle so that the difference in wedge angle between the second heat start hole type and the first heat end hole type is more than 30 °.

Further, in the above embodiment, the wedge angle θ2 of the third hole type K3 is 70 ° or more and 110 ° or less, and the wedge angle θ3 of the fourth hole type K4 is 130 ° or more and 170 ° or less. By defining in this way, it is possible to suppress the occurrence of shape defects in the material to be rolled and to efficiently and stably manufacture an H-shaped steel product having a larger flange width than the conventional one. In the following, the grounds for defining the range of suitable angles of θ2 and θ3 will be described.

First, the present inventors examined the processing limit (processing limit angle) of the bending process performed in the fourth hole type K4 with respect to the material A to be rolled, which has been formed in the third hole type K3. FIG. 10 is a graph showing the relationship between the bending angle (that is, θ3-θ2) and the flange thickness deviation (flange thickness variation) in the fourth hole type K4. Here, the flange thickness deviation on the vertical axis of the graph of FIG. 10 indicates a variation of 3σ from the average flange thickness of the four flange-corresponding portions formed by expanding.

As shown in FIG. 10, in the fourth hole type K4, when the bending angle (that is, θ3-θ2) exceeds 60 °, the flange thickness deviation exceeds 5%, so that intermediate rolling is a subsequent step of the rough rolling step. It becomes difficult to converge the dimensions in the process and the finish rolling process, and it becomes impossible to carry out modeling with suitable dimensional accuracy.

The reason why it is preferable that the thickness variation of the left and right flange corresponding portions is suppressed to 5% or less is as follows. According to the JIS standard (JIS G 3192), when the flange thickness exceeds 40 mm, the tolerance range of the flange thickness is 4 mm (that is, ± 2 mm), and the tolerance of the shape and dimension of the large size H-section steel is 4 mm (that is, ± 2 mm). Corresponds to 10% of the flange thickness of. If the flange size of the product deviates from the above tolerance, it is difficult to modify the processing and it is not recognized as a product of predetermined quality, so that there is a big problem in terms of manufacturing efficiency and cost. Therefore, it is necessary to manufacture H-shaped steel products by making the process capability of each molding process sufficient and suppressing the thickness variation of the left and right flange corresponding portions. Normally, it is desirable to set the flange thickness tolerance range to 6σ in order to make the process capability of each molding process sufficient. Based on the above JIS standard, in order to match 10% of the flange thickness of H-section steel products to 6σ, it is desirable that the target value of the thickness variation of 3σ of the left and right flange corresponding parts is 5% or less.

As shown in FIG. 10, the machining angle of the fourth hole type K4 needs to be 60 ° or less. That is, the difference between the tip angle θ2 of the protrusions 55 and 56 of the third hole type K3 and the tip angle θ3 of the protrusions 65 and 66 of the fourth hole type K4 must be 60 ° or less. It is necessary to be designed under the condition that satisfies the equation (1) of.
θ3-θ2 ≦ 60 ° ・ ・ ・ (1)

Next, the present inventors examined the upper limit of the tip angle θ2 of the protrusions 55 and 56 of the third hole type K3. FIG. 11 is a graph showing the amount of width change (flange tip crushing amount) at the tip of the flange corresponding portion when the tip angle θ2 in the third hole type K3 is changed.
The flange tip crushing amount is defined by the average value of the crushed distance Δi (corresponding to the tips of i = 1 to 4: 4 points) with respect to the tip width direction of the bent flange corresponding portion in the third hole type K3. Note that FIG. 11 described below illustrates the flange tip crushing amounts Δ1 to Δ4.

As shown in FIG. 11, when the angle θ2 is 100 ° or less, the amount of change in the tip width of the flange corresponding portion remains at a small level of 5 mm or less. However, when the angle θ2 is 110 ° or more, the amount of change in the tip width of the flange corresponding portion also becomes large, and the wall amount imbalance of the four flange corresponding portions occurs (see FIG. 12 described below).

FIG. 12 is a schematic view showing the shape of the material to be rolled after molding when the tip angle θ2 of the protrusions 55 and 56 of the third hole type K3 is set to more than 110 ° by the method according to the present embodiment. is there. As shown in FIG. 12, when the angle θ2 is set to more than 110 ° and the molding is performed with the third hole type K3, the deformation in which the outer surface of the flange corresponding portion is crushed is easier than the deformation due to the bending process. Therefore, it is confirmed that the deformation mode is such that the metal on the outside of the flange corresponding portion is scraped off.
As described above with reference to FIGS. 11 and 12, the tip angle θ2 of the protrusions 55 and 56 of the third hole type K3 needs to be designed under the condition of satisfying the following equation (2).
θ2 ≤ 110 ° ・ ・ ・ (2)

Subsequently, the present inventors examined the upper limit value and the lower limit value of the tip angle θ3 of the protrusions 65 and 66 of the fourth hole type K4 based on the modeling with the web thickening hole type. FIG. 13 shows a product generated by the occurrence of meat accumulation in the subsequent step performed in the web thickening hole type when the tip angles θ3 of the protrusions 65 and 66 of the fourth hole type K4 are changed. It is a graph which shows the defect depth. The meat pool generated in the web-thickened hole type is a protrusion-like shape defect that occurs on the outer surface of the flange corresponding portion, and the details thereof will be described later with reference to FIG.

As shown in FIG. 13, when the angle θ3 is less than 130 °, a product defect occurs, and the product defect depth increases as the angle θ3 becomes smaller. Then, this product defect remains on the outer surface of the flange of the final product.

FIG. 14 is a schematic explanatory view of web thickening in the web thickening hole type, and FIG. 14A shows a case where a shape defect occurs on the outer surface of the flange portion when the angle θ3 exceeds 170 °. b) shows a case where the outer surface of the flange portion has a shape defect when the angle θ3 is less than 130 °, and (c) shows a product defect.

As shown in FIG. 14A, when the web is thickened in the web thickening hole type, the amount of metal spreading to the outside of the flange portion 80 (in the left-right direction in the figure) as the web portion 81 is thickened. Becomes larger. The larger the cross-sectional ratio of the web portion 81 to the entire cross section, the larger the amount of expansion. As a result, the bulging portion 160 on the protrusion shown by the broken line portion in the drawing is formed. Since the bulging portion 160 is a cause of poor shape, it is conceivable to provide a dent on the outer surface of the flange portion 80 in anticipation of expansion as a countermeasure. In order to adjust the amount of the dent, it is effective to preferably determine the tip angle θ3 of the protrusions 65 and 66 of the fourth hole type K4. Experimentally, it has been found that when the angle θ3 exceeds 170 °, a shape defect as shown in FIG. 14A occurs, and the upper limit of the angle θ3 is 170 °.
Further, from the above equations (1) and (2), the upper limit of the angle θ2 is 110 °, and the difference between the angle θ3 and the angle θ2 is 60 ° at the maximum. Therefore, the upper limit of the angle θ3 is 170. Determined as °.

Further, as shown in FIG. 14B, in the web thickening hole type, the width of the flange portion 80 is reduced at the same time as the thickness of the web portion 81 is reduced, and the width reduction of the flange portion 80 causes the flange portion 80 to be reduced in width. Reduction strain from above and below is applied to the central portion, but when the angle θ3 is less than 130 °, the groove 161 formed in the central portion of the outer surface of the flange portion 80 (the portion surrounded by the broken line in the figure) does not disappear and becomes a flaw. It remains, and product defects are generated due to it, and the product defects remain in the final product, H-section steel. From the experiment, it was found that when the angle θ3 is less than 130 °, the groove 161 shown in FIG. 14 (b) becomes the starting point of the flaw and remains, and the product flaw 163 as shown in FIG. 14 (c) occurs. There is.
As described above with reference to FIGS. 13 and 14, it is desirable that the upper limit value of the tip angle θ3 of the protrusions 65 and 66 of the fourth hole type K4 is 170 °, and the lower limit value is 130 °. Is desirable.
In particular, based on FIG. 13, the angle θ3 needs to be designed under the condition of satisfying the following equation (3).
θ3 ≧ 130 ° ・ ・ ・ (3)

When design conditions that satisfy the above equations (1) to (3) at the same time are configured, the lower limit of θ2 is 70 ° (= 130 ° -60 °), and the upper limit of θ3 is 170 ° (= 110). ° + 60 °). FIG. 15 is a graph summarizing the design conditions shown in the above equations (1) to (3), and shows suitable design ranges of θ2 and θ3. The range surrounded by the line (broken line in the figure) indicating each condition in FIG. 15 is a suitable design range. That is, the angle θ2 needs to be designed under the condition satisfying the following equation (4), the angle θ3 needs to be designed under the condition satisfying the following equation (5), and the above equation (1) is used. It will be necessary to meet.
70 ° ≤ θ2 ≤ 110 ° ・ ・ ・ (4)
130 ° ≤ θ3 ≤ 170 ° ・ ・ ・ (5)

Depending on the design conditions that satisfy the above formulas (1), (4), and (5), the tip angles θ2 of the protrusions 55 and 56 of the third hole type K3 and the protrusions 65 and 66 of the fourth hole type K4 The tip angle θ3 is determined. As a result, modeling is performed without causing deformation imbalance of the left and right flange portions 80, and further, in the case of shape defects such as deformation in which the outer surface of the flange corresponding portion is crushed (see FIG. 12) and the web thickened hole type. It is possible to carry out each molding process without causing a shape defect (see FIG. 14) such that the central portion of the outer surface of the flange portion 80 becomes a wall-filled shape and product defects occur.

In the above-described embodiment and the like, the slab has been described as an example of the material for producing the H-section steel, but the present invention is naturally applicable to other materials having a similar shape.

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

1 ... Rolling equipment 2 ... Heating furnace 4 ... Rough rolling mill 5 ... Intermediate universal rolling mill 8 ... Finishing universal rolling mill 9 ... Edger rolling mill 11 ... Slab 13 ... H-shaped rough shape material 14 ... Intermediate material 16 ... H-shaped steel products 20 ... Top hole type roll (first hole type)
21 ... Pilot hole type roll (first hole type)
25, 26 ... Protrusion (first hole type)
28, 29 ... Interrupt (1st hole type)
30 ... Top hole type roll (2-1 hole type)
31 ... Pilot hole type roll (2-1 hole type)
35, 36 ... Protrusions (2-1 hole type)
38, 39 ... Interrupt (2-1 hole type)
40 ... Top hole type roll (2-2 hole type)
41 ... Pilot hole type roll (2-2 hole type)
45, 46 ... Protrusions (2-2 hole type)
48, 49 ... Interrupt (2-2 hole type)
50 ... Upper hole type roll (third hole type)
51 ... Pilot hole type roll (third hole type)
55, 56 ... Protrusion (third hole type)
58, 59 ... Interrupt (3rd hole type)
60 ... Top hole type roll (4th hole type)
61 ... Pilot hole type roll (4th hole type)
65, 66 ... Protrusion (4th hole type)
68, 69 ... Interrupt (4th hole type)
80 ... Flange part 82 ... Web part 85 ... Top hole type roll (fifth hole type)
86 ... Pilot hole type roll (fifth hole type)
K1 ... 1st hole type K2-1 ... 2nd hole type K2-2 ... 2nd hole type K3 ... 3rd hole type K4 ... 4th hole type K5 ... 5th hole type (flat hole type)
T ... Production line A ... Material to be rolled

Claims (4)

A method for producing H-section steel including a rough rolling process, an intermediate rolling process, and a finishing rolling process.
The rolling mill that performs the rough rolling step is engraved with a plurality of hole molds for forming the material to be rolled.
The plurality of hole types are
A plurality of interrupt hole types in which protrusions are formed to form a split portion at the end of the material to be rolled by vertically interrupting the material to be rolled.
A plurality of bent hole types having protrusions formed which abut on the interrupt and sequentially bend the divided portion formed in the interrupt hole type are included.
The rough rolling process using the plurality of hole molds is performed by two-heat rolling.
The second heat molding in the two-heat rolling includes a bending molding by at least one or more folding hole molds among the plurality of bending hole molds for performing the bending molding. Manufacturing method. The plurality of bending hole molds are composed of two types of bending hole molds having different bending angles of the divided portions.
In the two types of bending hole types, bending molding is performed so that the bending angle of the divided portion gradually increases.
The production of the H-section steel according to claim 1, wherein the start hole type of the second heat in the two-heat rolling is a hole type having a narrow bending angle among the two types of bending hole types. Method. In the two-heat rolling, the molding in the start hole mold of the second heat is performed in a plurality of passes.
The method for producing an H-section steel according to claim 1 or 2, wherein the molding of the first pass among the plurality of passes is performed so that the contact width of the flange surface of the material to be rolled is less than 50%. The tip angle of the protrusions formed in the plurality of interrupt hole types is 25 ° or more and 40 ° or less.
The bending angles of the two types of bending hole types are, in order, 70 ° or more and 110 ° or less, and 130 ° or more and 170 ° or less.
The second aspect of the present invention is characterized in that the difference between the tip angle of the protrusion formed in the interrupt hole type and the bending angle of the bending hole type in the previous stage of the two types of bending hole types is more than 30 °. The method for producing an H-section steel described above.

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