Shearing tool for shaped steel, manufacturing method for shaped steel

Abstract

To provide a shearing tool for a shape steel and a method for manufacturing the shape steel capable of suppressing the breakage of the tool when shearing the shape steel having a groove-shaped part such as a steel sheet pile or Z-shaped shape steel having a Z-shaped part.SOLUTION: A shearing tool 51 for a shape steel is used for shearing widthwise a shape steel 10 including a groove-shaped part 101. The shearing tool comprises: a fixed shearing blade 512 that is formed along the groove-shaped part 101 of the shape steel 10, and includes a bottom blade part 5121 and a rising blade part 5122 rising from the bottom blade part 5121; and a movable shearing blade 511 which is movable in a shearing direction with respect to the fixed shearing blade 512. The shearing tool is configured so that an angle θ satisfies a range determined according to thickness of the shape steel when performing shearing, the angle θ being formed of: a tangent 5111 of the movable shearing blade 511 and a tangent 5124 of the fixed shearing blade 512 at a portion where the rising blade part 5122 of the fixed shearing blade 512 and the movable shearing blade 511 first cross each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a shearing tool for structural steel that shears structural steel having a groove-shaped portion such as a steel sheet pile or Z-shaped structural steel having a Z-shaped portion in the width direction, and to a method for manufacturing structural steel using the same. [Background technology]

[0002] Steel sections formed by roll forming are manufactured into U-shaped or hat-shaped steel sheet piles by continuously bending steel plates or strips in the circumferential direction. After the section steel is formed, it is usually cut to the desired length using a shear or cutter located on the line.

[0003] Here, a cutting machine is a processing machine that uses a saw blade to cut out the cut portion, and a shearing machine is a processing machine that uses a pair of shearing tools to cut out the portion by shearing. Shearing has the advantage of being less likely to impair the productivity of shaped steel than cutting, as it takes less time to process than cutting.

[0004] However, in shearing, the tool comes into contact with the material, causing sagging, and then shearing occurs, but until shearing occurs, a large load acts on the tool, which can lead to tool damage. Therefore, in shearing machines, it is necessary to set appropriate clearances and design tools to reduce the load during shearing.

[0005] Patent Document 1 discloses a cutting machine for shaped steel that is provided with a shearing machine having a cutting blade with a through-hole shape that matches the shape of the product, and that cuts the product while traveling in synchronization with the product. This cutting machine for shaped steel has multiple built-in sliding guide rollers and is equipped with a roller-type product guide that is elastically supported on the shearing machine by an elastic body such as a spring, which prevents the tool from being damaged by the vibration of the product that occurs during shearing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 2616365 Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Document 1 assumes that H-shaped steel is the object to be cut (sheared), but since groove-shaped steel and Z-shaped steel have more complex cross-sectional shapes than H-shaped steel, the configuration disclosed in Patent Document 1 cannot be expected to be effective in improving tool life.

[0008] The present invention has been made to solve such problems, and aims to provide a shearing tool for structural steel that can prevent tool breakage when shearing structural steel with groove-shaped portions such as steel sheet piles or Z-shaped structural steel, and a manufacturing method for structural steel using the shearing tool for structural steel. [Means for solving the problem]

[0009] In order to achieve the above object, the present inventors have conducted extensive research into the contact state of a tool with a shaped steel in a shearing process, and as a result have discovered the following. When cutting out structural steel by shearing, holes are drilled (pre-notched) in the steel plate or strip at the longitudinal position where the product will be cut out before it is formed in the forming machine, and the shearing is carried out based on this pre-notched portion.

[0010] Of the pair of tools used in shearing, the fixed shear tool has a curved cross-section that follows the cross-sectional shape of the product to suppress vibration of the product during transport and shearing. On the other hand, although the cross section of the movable blade of the movable shearing tool has a curved surface, the curved surface does not follow the cross section of the product, but rather the cross-sectional dimensions are designed so that it comes into contact with the structural steel from around the pre-notch portion during shearing. Therefore, when the movable shearing tool contacts the steel section, it does not make uniform contact across the width and shear evenly. Instead, it begins to contact the steel section around the pre-notch, and as the displacement of the movable shearing tool in the shearing direction increases, shearing begins at the contact point. Once shearing begins, the contact area between the movable shearing tool and the steel section moves across the width, and in addition, the influence of crack propagation from the adjacent sheared area makes it easier for the shearing to progress. This type of shearing continues until the movable shearing tool completely penetrates the steel section.

[0011] During the shearing process, the load is particularly likely to become excessive immediately after the movable blade comes into contact with the steel section. At this point in time, there is no propagation of cracks from the surrounding area, so the load continues to increase at the contact points of both the movable blade and the shear blade of the fixed shear tool until the steel section breaks.

[0012] In addition, in the case of Z-shaped steel sections or grooved steel sections, such as steel sheet piles, a moment is generated when an overload occurs due to contact with the flanges, arms, or joints. Therefore, the overload acts not only on the contact points but also on the peripheral areas that are the center of rotation of the moment, causing damage to the shearing tool. Therefore, to improve the life of the shearing tool, it is important to reduce the shearing load at the point where the movable shear blade begins to contact the steel section. The present invention is based on the above findings and specifically has the following configuration.

[0013] (1) The shearing tool for structural steel according to the present invention is a shearing tool for structural steel that shears groove-shaped structural steel having a groove-shaped portion or Z-shaped structural steel having a Z-shaped portion in the width direction, and is equipped with a fixed shearing tool that is formed to fit the structural steel and has a bottom cutting portion and a rising cutting portion that rises from the bottom cutting portion, and a movable shearing tool that has a movable blade that moves in the shearing direction relative to the fixed shearing tool, and is characterized in that during shearing, the angle θ formed between the tangent to the movable blade and the tangent to the rising cutting portion at the point where the rising cutting portion of the fixed shearing tool and the movable blade first intersect satisfies a range determined by the thickness of the structural steel.

[0014] (2) Furthermore, in the above-mentioned (1), when shearing the structural steel, the angle θ formed between the tangent to the movable blade and the tangent to the rising blade at the point where the rising blade portion of the fixed shearing tool and the movable blade first intersect is 45 degrees or less and satisfies the following formula (1): θ / t≧0.83×t -0.62 ···(1) Where t: thickness of steel section

[0015] (3) In addition, in the above-mentioned (1) or (2), the fixed shearing tool is characterized in that the rising blade portion has a constricted portion.

[0016] (4) The manufacturing method of a shaped steel according to the present invention is a manufacturing method of a shaped steel by shearing a shaped steel having a groove-shaped portion or a Z-shaped portion to a predetermined length to manufacture a shaped steel of a predetermined length, The method is characterized in that the structural steel is sheared in the width direction using the shearing tool for structural steel described in any one of (1) to (3) above to form structural steel of a predetermined length. [Effects of the Invention]

[0017] In the shearing tool for structural steel according to the present invention, the angle θ formed by the tangent to the movable blade and the tangent to the rising blade portion at the position where the rising blade portion of the fixed shearing tool and the movable blade of the movable shearing tool first intersect during shearing is set to be within a predetermined range. This makes it possible to reduce the shear load at the start of shearing when shearing structural steel having a groove-shaped portion, such as a steel sheet pile, thereby preventing tool damage and improving tool life. [Brief explanation of the drawings]

[0018] [Figure 1] 3 is an explanatory diagram illustrating a state before shearing when shearing structural steel with the shearing tool in the present embodiment. FIG. [Figure 2] 3 is an explanatory diagram illustrating a state at the start of shearing when shearing structural steel using the shearing tool according to the present embodiment. FIG. [Figure 3] 1 is an explanatory diagram illustrating the flow of a manufacturing line for structural steel to which the present embodiment is directed. [Figure 4] FIG. 2 is an explanatory diagram of a prenotch portion formed in a structural steel. [Figure 5] 10 is a graph showing the results of a shearing experiment in the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a shearing tool for shaped steel, which is an embodiment of the present invention, will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment. In addition, in the description of the drawings, the same parts are designated by the same reference numerals.

[0020] First, with reference to Figs. 3 and 4, the flow of a manufacturing line for shaped steel and the schematic configuration of a shearing machine for shaped steel to which this embodiment is directed will be described. A steel plate (or steel strip) 1 is drilled at predetermined positions by a prenotch processing machine 2 to form prenotch portions 3 as shown in Fig. 4(b).Then, the steel plate (or steel strip) is continuously formed into a sheet pile shape by a roll forming machine 4, and is formed into a shaped steel 10 having a groove-shaped portion 101 (see Fig. 3 and Fig. 4(c)).

[0021] Thereafter, the shaped steel 10 is transported to a shearing machine 5 equipped with a shearing tool 51 consisting of a movable shearing blade 511 and a pair of fixed shearing blades 512. When the pre-notch section 3 moves to the gap 513 between the pair of fixed shearing blades 512, the movable shearing blade 511 is moved by hydraulic power so as to pass through the gap 513 between the fixed shearing blades 512, and shears the shaped steel 10 during this movement. Note that the power source for the movable shearing blade 511 at this time is not limited to hydraulic power, and any of mechanical and electrical power sources may be used.

[0022] An example of a shearing tool 51 for shaped steel (hereinafter simply referred to as "shearing tool 51") used in the shearing machine 5 will be described in detail with reference to Figs. FIG. 1 is a diagram illustrating the shearing tool 51 of this embodiment and the state including the shearing tool before shearing, showing the shearing tool 51 and shaped steel 10 viewed from the front in the direction of forming progress. 2 is a diagram for explaining the initial shearing state when the movable shear blade 511 moves from the state shown in FIG. 1 and comes into contact with the structural steel 10. In the enlarged view of FIG. 2, the structural steel 10 is omitted for ease of understanding.

[0023] 1 and 2, the shearing tool 51 of this embodiment shears the shaped steel 10 having the groove-shaped portion 101 in the width direction of the groove-shaped portion 101, and includes a movable shearing blade 511 and a fixed shearing blade 512. Each component will be described in detail below.

[0024] <Shaped steel> The shaped steel 10 of this embodiment has a groove-shaped portion 101 and is provided with a curled joint portion 102 at the upper end of the groove wall. Furthermore, in the shaped steel 10 of this embodiment, as shown in FIG. 4, one pre-notch portion 3 is provided on each side of the steel plate 1, symmetrically. However, the structural steel 10 to be sheared in the present invention is not limited to this, and the pre-notches are not limited to one on each side.

[0025] <Movable shear blade> The movable shear blade 511 moves in the shearing direction and is inserted into the gap between the pair of fixed shear blades 512. The shape of the surface where the movable shear blade 511 comes into contact with the shaped steel 10 is designed so that the tool first comes into contact with the periphery of the pre-notch portion 3 of the shaped steel 10. For this reason, the movable shear blade 511 is inclined so that it narrows downward, but the shape of the inclined portion may be either straight or curved.

[0026] <Fixed shear blade> A pair of fixed shear blades 512 are provided at the front and rear of the manufacturing line for the structural steel 10, spaced apart by a predetermined gap. The portion of each fixed shear blade 512 that comes into contact with the underside of the shaped steel 10 when the shaped steel 10 enters the shearing machine 5 has substantially the same shape as the underside of the shaped steel 10, i.e., the same curvature distribution. Such a fixed shear blade 512 is formed to fit along the groove-shaped portion 101 of the shaped steel 10, and has a bottom blade portion 5121 and a rising blade portion 5122 that rises from the bottom blade portion 5121.

[0027] In addition, the periphery of the joint of the structural steel 10 of this embodiment has a joint portion 102 that curls downward, and the rising blade portion 5122 has a necked portion 5123 so as to be inserted inside the curled portion. Although the presence of the constricted portion 5123 tends to cause stress concentration at that portion, the shearing tool 51 of this embodiment can reduce the shear load at the start of shearing, as will be described later, and can suppress excessive stress concentration. Therefore, even if the tool has a constricted portion, it is possible to prevent the tool life from being shortened.

[0028] <Relationship between movable shear blade and fixed shear blade> The relationship between the movable shear blade 511 and the fixed shear blade 512 in this embodiment satisfies the following requirements. During shearing, the angle θ (see enlarged view in Figure 2) formed between the tangent 5111 of the movable shear blade 511 and the tangent 5124 of the rising blade portion 5122 at the point where the rising blade portion 5122 of the fixed shear blade 512 first intersects with the movable shear blade 511 (the point indicated by a circle in the enlarged view in Figure 2) is 45 degrees or less and satisfies the following formula (1). θ / t≧0.83×t -0.62 ···(1) Where t: thickness of steel section

[0029] The reason why the relationship between the movable shear blade 511 and the fixed shear blade 512 is defined as above will be explained below. As described above, the shearing mechanism involves the material between the clearance between the rising blade portion 5122 and the movable shear blade 511 undergoing tensile stress, forming a sag. When the movable shear blade 511 is further pressed in, cracks are generated in the material, which then propagate across the entire cross section of the material, resulting in shearing. Once a crack is generated during the shearing process, it propagates in the thickness and width directions of the shaped steel 10, promoting cracks in adjacent areas, so that the shear load at that location is smaller than at the origin of the crack. Therefore, the shear load is greatest at the location where the material first comes into contact with the shearing tool 51.

[0030] In this way, the load acting on the shearing tool 51 is greatest immediately before a crack occurs, and after the crack occurs, the load acting on the shearing tool 51 decreases as the crack propagates and separation of the material occurs. Therefore, in order to reduce the instantaneous tool load, it is necessary to distribute the time when shear cracks occur in the width direction of the material and at the same time avoid the occurrence of cracks over a wide area. In other words, it is important to distribute the time when cracks occur in the area where the tool first comes into contact with the material.

[0031] The position where the movable shear blade 511 comes into contact with the material and where shearing is first performed is the widthwise position where the gap between the movable shear blade 511 and the rising blade portion 5122 in the vicinity thereof is the smallest. The angle formed by the tangent 5111 of the movable shearing blade 511 and the tangent 5124 of the rising blade portion 5122 at this position is defined as θ (see the enlarged view of FIG. 2). If the angle θ is large, the movable shear blade 511 will shear the material at an angle relative to the rising blade portion 5122 at the portion where the movable shear blade 511 first comes into contact with the material. This makes it possible to avoid cracks from occurring simultaneously over a wide range, that is, it is possible to distribute the time during which cracks occur due to shearing in the width direction, thereby reducing the load on the tool.

[0032] A shearing experiment was carried out to define a suitable range for the angle θ, and the results are described below. The shearing experiment involves repeatedly performing shearing using various shaped steels while changing the angle θ of the shearing tool 51, and checking whether breakage or plastic deformation occurs in either the movable shearing blade 511 or the rising blade portion 5122. If breakage or plastic deformation does not occur in either the movable shearing blade 511 or the rising blade portion 5122, it can be considered that the shearing load has been distributed, and the tool life has been improved.

[0033] Figure 5 is a graph showing the results of this shearing experiment, with the horizontal axis representing the thickness t (mm) of each steel section, and the vertical axis representing θ / t, the value obtained by dividing the lower limit of the angle θ when no damage or plastic deformation was observed after repeated shearing by the thickness t of each steel section. The plots in Figure 5 show the experimental values. If the plots shown in Figure 5 are connected by a curve and this curve is expressed as a function, the following equation is obtained. θ / t=0.83×t -0.62

[0034] Since the above θ is a lower limit value, in order to prevent breakage or plastic deformation after shearing, the value of θ should be equal to or greater than the lower limit value, and the conditional expression for this is given by the following expression (1). θ / t≧0.83×t -0.62 ···(1) The thickness t of the steel section is the nominal thickness of the product.

[0035] On the other hand, the upper limit of θ / t in formula (1) needs to be 45 / t or less to prevent damage to the movable shear blade 511. In other words, if the angle θ exceeds 45°, the part of the movable shear blade 511 that comes into contact with the material becomes too sharp, and this part is damaged.

[0036] In the shearing tool 51, the bottom blade portion 5121 and the rising blade portion 5122 of the fixed shearing blade 512 are shaped to fit the shape of the product, and therefore, in many cases, their surfaces have complex curved shapes. Therefore, the line indicating the inclination direction of the rising blade portion 5122 is set as a tangent line 5124 on the curved surface at the widthwise position where the gap between the movable shearing blade 511 and the rising blade portion 5122 is smallest. On the other hand, in the movable shearing blade 511 of this embodiment, the inclined portion is linear and the direction of the tangent 5111 coincides with the direction of the inclination, but if the surface of the movable shearing blade 511 is curved, the direction may be a tangent to the curved surface. The widthwise position where the gap between the movable shear blade 511 and the bottom blade portion 5121 is smallest and the tangents 5111 and 5124 to the surface of the shear tool 51 can be determined by calculation from the geometric relationships such as the dimensions of the shear tool 51.

[0037] The method for shearing a long shaped steel piece using the shearing tool 51 configured as described above to produce a shaped steel piece of a predetermined length will be outlined below. As shown in Figure 3, a steel plate (or steel strip) 1 has a pre-notch portion 3 formed at a predetermined position by a pre-notch processing machine 2, and is then continuously formed by a roll forming machine 4 into a structural steel 10 such as a sheet pile shape having a groove-shaped portion 101 (see Figure 4(c)). The structural steel 10 is then transported to the shearing machine 5 and sheared at the pre-notch portion 3 by a shearing tool 51 having a movable shearing blade 511 at the top and a pair of fixed shearing blades 512 at the bottom to produce structural steel 10 of the desired length.

[0038] As described above, in the present embodiment, the shearing tool 51 is set so that the angle θ formed by the tangent 5111 of the movable shearing blade 511 and the tangent 5124 of the rising blade portion 5122 at the position where the rising blade portion 5122 of the fixed shearing blade 512 and the movable shearing blade 511 first intersect during shearing is within a predetermined range. This makes it possible to reduce the shear load at the start of shearing when shearing a structural steel 10 having a groove-shaped portion 101 such as a steel sheet pile, thereby preventing tool damage and improving tool life.

[0039] The above-described embodiment is merely an example for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and other embodiments, examples, and operational techniques made by those skilled in the art are all included in the present invention as long as they do not deviate from the spirit of the present invention. Furthermore, during shearing, the angle θ formed between the tangent to the movable blade and the tangent to the rising blade at the point where the rising blade portion of the fixed shearing tool and the movable blade first intersect is not limited to 45 degrees or less or to equation (1), but can be set appropriately in relation to the thickness of the structural steel, and may be within this range.

[0040] Furthermore, although not specifically mentioned in the above description, the lifespan of the movable shear blade 511 and the fixed shear blade 512 can be further improved by performing an appropriate surface treatment, so the present invention does not exclude the use of surface treatment.

[0041] In addition, in the above explanation, a grooved steel structural member having a groove-shaped portion is used as an example, but the structural members that are the subject of the present invention are not limited to this, and also include Z-shaped steel structural members having a Z-shaped portion. [Example]

[0042] An experiment was conducted to confirm the effects of the present invention, and will be described below. In the experiment, steel strips with thicknesses ranging from 2 mm to 10 mm were used to form NL-2U type lightweight steel sheet piles made of SS400 (JIS G 3101), and shearing was carried out using a shearing machine 5. The shearing machine 5 has the same configuration as that shown in Figures 1 and 2, with an upper movable shearing blade 511 and a lower fixed shearing blade 512. The surface shape of the movable shearing blade 511 is formed in a straight line, and the surface shape of the fixed shearing blade 512 is shaped to follow the cross section of the lightweight steel sheet pile.

[0043] The thickness of the movable shear blade 511 was 25 mm, the gap 513 between the pair of front and rear fixed shear blades 512 was 25.8 mm, and the clearance between the movable shear blade 511 and the fixed shear blade 512 during shearing was 0.4 mm each at the front and rear. The notch size was 25 mm square, and pre-notching was performed on both widths of the steel plate 1 at positions 40 mm from the widthwise ends.

[0044] In the shearing process, the angle formed by the slope of the movable shear blade 511 and the perpendicular line at the inclined portion of the movable shear blade 511 that first comes into contact with the pre-notch portion 3 of the lightweight steel sheet pile was defined as α. Similarly, the angle θ formed by the tangent 5124 on the surface of the rising blade portion 5122 at the width direction position where the pre-notch portion 3 of the lightweight steel sheet pile and the movable shear blade 511 first come into contact with each other was calculated from the geometric relationship described in the tool drawing. In addition, the widthwise position where the movable shear blade 511 and the lightweight steel sheet pile first come into contact was determined from the dyed position using pressure-sensitive paper. After repeated shearing, strain measurement was performed by the digital image correlation method on both the movable shear blade 511 and the fixed shear blade 512 to measure the principal shear strain. The experimental conditions and results are shown in Table 1.

[0045] [Table 1]

[0046] In the shearing tool 51 corresponding to the inventive example of the present invention, the maximum value of the main shearing strain in the constricted portion around the rising blade portion of the fixed shearing blade, where shearing strain tends to concentrate, was less than 0.2%, and no tool breakage occurred even after more than 1,000 shearing operations.

[0047] On the other hand, in the comparative examples that did not satisfy formula (1), there were areas where the maximum value of the principal shear strain in the constricted portion around the rising blade portion of the fixed shear blade, where shear strain is likely to concentrate, exceeded 0.2%, causing plastic deformation, or breakage occurred after less than 1,000 shearing cycles.

[0048] As described above, it was confirmed that the effects can be obtained when the shearing tool is within the scope of the present invention. [Explanation of symbols]

[0049] 1 steel plate 2 Pre-notching machine 3 Pre-notch section 4. Roll forming machine 5 Shearing machine 51 Shearing tools 511 Movable shear blade 5111 Tangent to movable shear blade 512 Fixed shear blade 5121 Bottom blade part 5122 Rising blade 5123 Waist 5124 Tangent of rising blade 513 Fixed shear blade gap 10 Section steel 101 Groove shape part 102 Joint

Claims

1. A method for manufacturing a shaped steel having a predetermined length by shearing a shaped steel having a groove-shaped portion or a Z-shaped portion in the width direction using a shearing tool for the shaped steel, The shearing tool comprises a fixed shearing tool formed to fit the structural steel and having a bottom cutting edge and a rising cutting edge rising from the bottom cutting edge, and a movable shearing tool having a movable blade that is movable in the shearing direction relative to the fixed shearing tool, wherein during shearing, the angle θ (degrees) formed between the tangent to the movable blade and the tangent to the rising cutting edge at the point where the rising cutting edge and the movable blade on the fixed shearing tool first intersect is 45 degrees or less and satisfies the following formula (1). θ / t≧0.83×t －0.62 ・・・(1) Where t: thickness of steel section (mm)

2. The method for manufacturing a section steel according to claim 1, wherein the rising blade portion of the fixed shearing tool has a constricted portion.

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