Manufacturing method for H-beams

Abstract

To provide an H-shaped steel manufacturing method that can reduce variation in a longer direction of a flange width of a flange of an H-shaped steel after finish rolling by devising a rough processing process with a rough rolling machine.SOLUTION: A rough rolling process in an H-shaped steel manufacturing method includes a sizing rolling process in which a web part S1W of an H-shaped steel blank S1 is rolled in a thickness direction and a flange part S1F of the H-shaped steel blank S1 is rolled in a width direction by using a caliber 33 for sizing rolling. The caliber 33 for sizing rolling has a depth b1 shorter than a flange leg length S0 of the flange part S1F of the H-shaped steel blank S1. A groove part 33a for rolling the flange part S1F is formed in a peripheral surface of each of an upper rolling roll 31 and a lower rolling roll 32. At a first pass in the sizing rolling process, rolling for depressing only the flange part S1F of the H-shaped steel blank S1 is performed by using the caliber 33 for sizing rolling.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for producing an H-section steel including a rough rolling step, an intermediate rolling step, and a finish rolling step. Background Art

[0002] In general, an H-section steel is produced through a rough rolling step, an intermediate rolling step, and a finish rolling step. In the rough rolling step, an H-section steel raw material heated in a heating furnace is roughly rolled by a breakdown rolling mill to obtain a rough shaped steel slab. In the intermediate rolling step, the rough shaped steel slab roughly rolled in the rough rolling step is rolled by an intermediate universal rolling mill and an intermediate edging mill to obtain a material to be rolled for finish rolling having substantially product dimensions. In the finish rolling step, the material to be rolled for finish rolling rolled in the intermediate rolling step and having substantially product dimensions is finish-rolled by a finishing universal rolling mill to obtain an H-section steel having product dimensions.

[0003] Conventionally, as methods for producing this type of H-section steel, those disclosed in Patent Documents 1 to 4, for example, have been proposed. The rolling method for a rough shaped steel slab for H-section steel disclosed in Patent Document 1, when rolling a rough shaped steel slab for H-section steel by a double reversing mill, shares web portions of two shaping passes that match the web height of the rough shaped steel slab among two or more adjacent shaping passes each having the same web depth, and includes the step of inserting the rough shaped steel slab in a state straddling the shared web portions of the two shaping passes to reduce and roll the flange width.

[0004] According to the rolling method for a rough shaped steel slab for H-section steel disclosed in Patent Document 1, since no pass for reducing the flange width is required, an H-section steel having a high web height and a narrow flange width can be rolled from a beam blank of a single cross-section.

[0005] Furthermore, the H-shaped steel rolling method shown in Patent Document 2 is a method for rolling H-shaped steel in which rough rolling, which involves breakdown rolling, rough universal rolling, and edging rolling, and then finish universal rolling are sequentially applied to the base steel billet. In this method, the flange width distribution in the longitudinal direction is determined after the finish universal rolling or rough universal rolling of the preceding material. Based on the flange width distribution, either or both of the flange thickness reduction ratio and the web thickness reduction ratio for the rough universal rolling of the next material are changed based on the set values ​​of the preceding material.

[0006] According to the H-beam rolling method shown in Patent Document 2, H-beams with good flange width accuracy in the product length direction can be stably manufactured without special equipment.

[0007] Furthermore, the H-shaped steel rolling method shown in Patent Document 3 is a method for rolling H-shaped steel in which rough rolling, which involves breakdown rolling, rough universal rolling, and edging rolling, and finishing universal rolling are sequentially applied to the raw steel billet, wherein during rough universal rolling, either or both of the flange thickness reduction rate and the web thickness reduction rate are changed in the longitudinal direction of the rolled material.

[0008] According to the H-beam rolling method shown in Patent Document 3, it is possible to stably manufacture H-beams with good flange width accuracy in the product length direction.

[0009] Furthermore, the variable flange width rolling method for rough-rolled H-beam steel shown in Patent Document 4 uses a double-hole roll having a plurality of flange widening holes, each having a central bulge in the widthwise center of the hole bottom and grooves on both sides of the central bulge, and a shaping hole that reduces the web and flange portions. Using a rectangular cross-section steel billet as the material, it is inserted and widened on the side corresponding to the flange of the H-beam steel, and then shaping is performed. In this method, the flange width of the rolled material after the final pass in each flange widening hole (excluding the first hole) and the shaping hole is made narrower than the hole bottom width of the hole, so that the flange portion of the rolled material does not fill each hole.

[0010] According to the variable flange width rolling method for rough-rolled H-beams shown in Patent Document 4, when manufacturing rough-rolled H-beams using a breakdown mill with double-hole rolls from a rectangular cross-section slab as the raw material, it is possible to roll multiple series of rough-rolled materials with different flange widths and equal web heights using only one pair of rolls without rearranging the rolls. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. Hei 2-207901 [Patent Document 2] Japanese Patent Application Publication No. 11-151512 [Patent Document 3] Japanese Patent Application Publication No. 11-156414 [Patent Document 4] Japanese Patent Application Publication No. 2-169103 [Overview of the project] [Problems that the invention aims to solve]

[0012] In the manufacturing of H-beams, there has traditionally been a problem where the flange width of the H-beams, which have been shaped by finish rolling, varies along the longitudinal direction of the H-beam, resulting in a significant decrease in manufacturing yield.

[0013] Figure 12 shows an example of the longitudinal distribution of flange width of an H-beam after finish rolling. Figure 12(a) shows a good example where the flange width is within the tolerance range for the target along the entire longitudinal length of the H-beam. Figure 12(b) shows a bad example where the flange width is within the tolerance range for the target in the longitudinal central part (steady section) of the H-beam, but the flange width at the longitudinal rear end of the H-beam is larger than the upper tolerance limit.

[0014] As shown in Figure 12(b), when the flange width at the longitudinal rear end of an H-beam exceeds the upper tolerance limit, such H-beams cannot be sold as products as they are. This results in the need for refinishing, incurring additional refinishing costs, and also leads to rejection of the product, reducing the manufacturing yield.

[0015] The rolling method for rough steel billets for H-beams described in Patent Document 1 is a technique for manufacturing multiple series of H-beams with different flange widths from a single beam blank using the same roll. However, it is not a technique for reducing the longitudinal variation in flange width of H-beams after finish rolling.

[0016] Furthermore, in the H-beam rolling method shown in Patent Document 2, it is possible to stably manufacture H-beams with good flange width accuracy in the product length direction without special equipment. However, this H-beam rolling method involves changing either or both the flange thickness reduction rate and the web thickness reduction rate in the intermediate rolling process (rough universal rolling process), which has the problem of having little effect in making the flange width in the longitudinal direction of the H-beam uniform after finish rolling.

[0017] Furthermore, the H-beam rolling method shown in Patent Document 3 also allows for the stable production of H-beams with good flange width accuracy in the product length direction. However, this H-beam rolling method also involves changing either the flange thickness reduction rate or the web thickness reduction rate, or both, during the intermediate rolling process (rough universal rolling process), which has the problem of having little effect in making the flange width in the longitudinal direction of the H-beam uniform after finish rolling. In addition, there is the problem that it is difficult to implement the technology in terms of equipment, as it involves changing either the flange thickness reduction rate or the web thickness reduction rate, or both, in the longitudinal direction of the H-beam during rough universal rolling.

[0018] Furthermore, in the case of the variable flange width rolling method for rough-rolled H-beams shown in Patent Document 4, when manufacturing rough-rolled H-beams using a breakdown mill with double-hole rolls and a rectangular cross-section slab as the raw material, it is possible to roll multiple series of rough-rolled materials with different flange widths and equal web heights using only one pair of rolls without rearranging the rolls. However, it is not possible to reduce the longitudinal variation in the flange width of the H-beams after finish rolling.

[0019] Therefore, the present invention has been made to solve this conventional problem, and its objective is to provide a method for manufacturing H-beams that can reduce the longitudinal variation in the flange width of the flange portion of the H-beam after finish rolling by improving the rough rolling process using a rough rolling mill. [Means for solving the problem]

[0020] To solve the above problems, a method for manufacturing H-shaped steel according to one aspect of the present invention comprises: a rough rolling step of roughly rolling an H-shaped steel material having a web portion and a pair of flange portions provided at both ends in the width direction of the web portion using a rough rolling mill to obtain a rough steel billet; an intermediate rolling step of rolling the rough steel billet using an intermediate rolling mill to obtain a rolled material for finish rolling; and a finish rolling step of finishing the rolled material for finish rolling using a finish rolling mill to obtain an H-shaped steel of product dimensions, wherein the rough rolling step is performed by forming sizing on the circumferential surfaces of the upper rolling roll and lower rolling roll provided in the rough rolling mill. The gist of the method is to perform a sizing rolling process in which the web portion of the H-shaped steel material is rolled in the thickness direction and the flange portion of the H-shaped steel material is rolled in the width direction using a rolling die, wherein the sizing die is a sizing die in which grooves for rolling the flange portion are formed on the circumferential surfaces of the upper rolling roll and the lower rolling roll, respectively, and in the first pass of the sizing rolling process, the sizing die is used to roll down only the flange portion of the H-shaped steel material. [Effects of the Invention]

[0021] According to the method for producing an H-section steel according to the present invention, it is possible to provide a method for producing an H-section steel that can reduce the longitudinal variation in the flange width of the flange portion of the H-section steel after finish rolling by improving the rough rolling step using a rough rolling mill. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] [Figure 1] FIG. 1 is a schematic configuration diagram of an H-section steel rolling facility to which the method for producing an H-section steel according to one embodiment of the present invention is applied. [Figure 2] FIGS. 2A to 2C explain the cross-sectional shapes of an H-section steel raw material before rough rolling, a rough steel slab after rough rolling, and a finished H-section steel, wherein (a) is a cross-sectional view of the H-section steel raw material before rough rolling, (b) is a cross-sectional view of the rough steel slab after rough rolling, and (c) is a cross-sectional view of the finished H-section steel. [Figure 3] FIGS. 3A and 3B are schematic cross-sectional views showing a sizing rolling step in the rough rolling step together with a sizing rolling pass, a first web width expansion rolling pass, and a second web width expansion rolling pass, wherein (a) is a schematic cross-sectional view after completion of one pass in the sizing rolling step, and (b) is a schematic cross-sectional view after completion of the final pass in the sizing rolling step. [Figure 4] FIGS. 4A and 4B explain the web width expansion rolling step in the rough rolling step, wherein (a) is a cross-sectional view showing the first web width expansion rolling step together with the sizing rolling pass, the first web width expansion rolling pass, and the second web width expansion rolling pass, and (b) is a cross-sectional view showing the second web width expansion rolling step together with the sizing rolling pass, the first web width expansion rolling pass, and the second web width expansion rolling pass. [Figure 5] FIGS. 5A to 5C explain the intermediate rolling step and the finish rolling step, wherein (a) is a cross-sectional view for explaining an intermediate universal rolling step in the intermediate rolling step, (b) is a cross-sectional view for explaining an intermediate edging rolling step in the intermediate rolling step, and (c) is a cross-sectional view for explaining the finish rolling step. [Figure 6]The diagrams are schematic views from above of the H-shaped steel material after the completion of one pass in the sizing rolling process. (a) is a schematic view from above of the H-shaped steel material after the completion of one pass in the sizing rolling process according to the present invention, in which rolling was performed to reduce only the flange portion of the H-shaped steel material in the first pass of the sizing rolling process. (b) is a schematic view from above of the H-shaped steel material after the completion of one pass in a conventional sizing rolling process, in which rolling was performed to reduce both the flange portion and the web portion of the H-shaped steel material in the first pass of the sizing rolling process. [Figure 7] These are schematic diagrams showing the contact state between the material (H-shaped steel material) and the sizing rolling die in the first pass of the sizing rolling process. (a) is a schematic diagram showing the contact state at the longitudinal leading end, steady-state (central part), and trailing end of the H-shaped steel material in the present invention, where rolling reduces only the flange portion of the H-shaped steel material in the first pass of the sizing rolling process. (b) is a schematic diagram showing the contact state at the longitudinal leading end and steady-state (central part) of the H-shaped steel material in the conventional case, where rolling reduces both the flange portion and the web portion of the H-shaped steel material in the first pass of the sizing rolling process. (c) is a schematic diagram showing the contact state at the longitudinal trailing end of the H-shaped steel material in the conventional case, where rolling reduces both the flange portion and the web portion of the H-shaped steel material in the first pass of the sizing rolling process. [Figure 8] This graph shows the relationship between the longitudinal deviation of the flange width of the H-shaped steel product after finish rolling and the amount of flange width reduction of the H-shaped steel material in the first pass of the sizing rolling process. [Figure 9] This graph shows the relationship between the longitudinal deviation of the flange width of the H-beam after finish rolling and the flange width reduction ratio of the H-beam material in the first pass of the sizing rolling process. [Figure 10] This is an enlarged view of the area indicated by arrow A in Figure 4(a), illustrating the draft angle of the contact portion that abuts the outer surface of the flange tip of the H-shaped steel material in the groove of the sizing rolling hole type. [Figure 11]This graph shows the results of measuring the flange width at 20 points along the entire length of the H-shaped steel after finishing rolling, which was produced by sizing rolling H-shaped steel materials under the rolling conditions of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 of the present invention in the examples. [Figure 12] The graph shows an example of the longitudinal distribution of flange width of the flange portion of an H-shaped steel product after finish rolling. (a) is a good example where the flange width is within the tolerance range for the target along the entire longitudinal length of the H-shaped steel, and (b) is a bad example where the flange width is within the tolerance range for the target at the leading edge and steady end of the H-shaped steel, but the flange width at the trailing end of the H-shaped steel exceeds the upper tolerance limit. [Modes for carrying out the invention]

[0023] Embodiments of the present invention will be described below with reference to the drawings. The embodiments shown below are illustrative examples of devices and methods for realizing the technical concept of the present invention, and the technical concept of the present invention is not limited to the following embodiments in terms of the material, shape, structure, arrangement, etc. of the components.

[0024] Furthermore, drawings are schematic representations. Therefore, it should be noted that the relationship and ratios between thickness and planar dimensions may differ from those in reality, and there may be differences in dimensional relationships and ratios between drawings themselves.

[0025] The H-shaped steel rolling equipment 1 shown in Figure 1 consists of a heating furnace 2, a roughing mill 3, an intermediate universal rolling mill 4 and an intermediate edging mill 5 as intermediate rolling mills, and a finishing universal rolling mill (finishing mill) 6 as a finishing rolling mill, arranged sequentially from upstream to downstream. The heating furnace 2 heats the H-shaped steel material (see Figure 2(a)) S1, which will be subjected to rough rolling by the rough rolling mill 3, to a predetermined temperature.

[0026] As shown in Figure 2(a), the H-shaped steel material S1 is a steel material comprising a web portion S1W extending in the web height direction (left-right direction in Figure 2(a)) and a pair of flange portions S1F extending in the flange width direction (up-down direction in Figure 2(a)) at both ends of the web portion S1W in the web height direction. The H-shaped steel material S1 may be manufactured by casting a beam blank of this shape directly by continuous casting, or it may be formed into this shape from a slab or bloom by bract rolling.

[0027] The inner width of the web portion S1W of the H-shaped steel material S1 is W0, which is relatively short, and the thickness of the web portion S1W is T0, which is relatively thick. Also, the web height of the H-shaped steel material S1 is H0, which is relatively small. Furthermore, the flange width of the flange portion S1F of the H-shaped steel material S1 is B0, which is relatively large, and the flange thickness is t0, which is relatively thick.

[0028] The rough rolling mill 3 roughly rolls the H-shaped steel material S1, which has been transported from the heating furnace 2 on a table roller (not shown), to form a rough steel billet S2 (see Figure 2(b)) (rough rolling process).

[0029] As shown in Figure 2(b), the rough-rolled steel billet S2 is a steel material comprising a web portion S2W extending in the web height direction and a pair of flange portions S2F extending in the flange width direction at both ends of the web portion S2W in the web height direction.

[0030] The inner width of the web portion S2W of the rough steel billet S2 is W3, which is larger than the inner width W0 of the web portion S1W of the H-beam material S1. Also, the thickness of the web portion S2W of the rough steel billet S2 is T3, which is thinner than the thickness T0 of the web portion S1W of the H-beam material S1. Furthermore, the web height of the rough steel billet S2 is H3, which is larger than the web height H0 of the H-beam material S1, and is shaped to match the web height Hw of the H-beam H in the finished rolled product shape shown in Figure 2(c). In addition, the flange width of the flange portion S2F of the rough steel billet S2 is B3, which is smaller than the flange width B0 of the flange portion S1F of the H-beam material S1. Furthermore, the flange portion S2F of the rough steel billet S2 has a thickness of t4, which is thinner than the flange portion S1F of the H-shaped steel material S1 (thickness t0), and thicker than the flange portion F of the H-shaped steel H in the finished rolled product (thickness tF).

[0031] Here, the thickness of flange portion S2F (

[0032] The thickness has a distribution in the flange height (width) direction, but t3 represents its average value. The rough rolling process using the rough rolling mill 3 will be described in detail with reference to Figures 3 and 4. Figure 3 is a schematic cross-sectional view showing the sizing rolling process in the rough rolling process, together with the sizing rolling die, the web widening first rolling die, and the web widening second rolling die, where (a) is a schematic cross-sectional view after the completion of one pass in the sizing rolling process, and (b) is a schematic cross-sectional view after the completion of the final pass in the sizing rolling process. Figure 4 explains the web widening rolling process in the rough rolling process, where (a) is a cross-sectional view showing the web widening first rolling process together with the sizing rolling die, the web widening first rolling die, and the web widening second rolling die, and (b) is a cross-sectional view showing the web widening second rolling process together with the sizing rolling die, the web widening first rolling die, and the web widening second rolling die.

[0033] The rough rolling process using the rough rolling mill 3 includes a sizing rolling process and a web widening rolling process performed after the sizing rolling process.

[0034] In the sizing rolling process, as shown in Figure 3, the web portion S1W of the H-shaped steel material S1 is rolled in the thickness direction, and the flange portion S1F of the H-shaped steel material S1 is rolled in the width direction, using sizing rolling holes 33 formed on the circumferential surfaces of the upper rolling roll 31 and lower rolling roll 32 provided on the roughing mill 3. As a result, the thickness (web thickness) of the web portion S1W of the H-shaped steel material S1 is reduced from T0 to T1, and its thickness (web thickness) is determined to be T1. In addition, the inner width of the web portion S1W of the H-shaped steel material S1 is increased from W0 to W1. Furthermore, the flange width of the flange portion S1F of the H-shaped steel material S1 is reduced from B0 to B1-N. Also, the thickness (flange thickness) of the flange portion S1F of the H-shaped steel material S1 is changed from t0 to t1. Furthermore, the web height of the H-shaped steel material S1 is increased from H0 to H1.

[0035] Here, as shown in Figure 3(a), the sizing rolling die 33 has a groove 33a formed on the circumferential surfaces of the upper rolling roll 31 and the lower rolling roll 32, with a depth b1 shorter than the flange leg length S0 (see Figure 2(a)) of the flange portion S1F of the H-shaped steel material S1.

[0036] Then, in the first pass of the sizing rolling process, as shown in Figure 3(a), the aforementioned sizing rolling die 33 is used to roll down only the flange portion S1F of the H-shaped steel material S1. As a result, the flange width of the flange portion S1F of the H-shaped steel material S1 is reduced from B0 to B1-1. The web height of the H-shaped steel material S1 is increased from H0 to H1-1. The inner width of the web portion S1W of the H-shaped steel material S1 is also increased from W0 to W1-1.

[0037] In this way, by performing rolling that reduces only the flange portion S1F of the H-shaped steel material S1 in the first pass of the sizing rolling process, it is possible to suppress excessive flange width at the longitudinal rear end of the H-shaped steel product after finish rolling, and reduce the longitudinal variation in the flange width of the flange portion of the H-shaped steel after finish rolling.

[0038] The first-pass rolling in this sizing rolling step is rolling that has the meaning of forming the cross-sectional shape of the flange portion S1F of the H-beam material S1 into a shape that follows the shape of the sizing rolling groove 33 over the entire length in the longitudinal direction of the H-beam material S1. In the process of forming the cross-sectional shape of the flange portion S1F of the H-beam material S1 into a shape that follows the shape of the sizing rolling groove 33, rolling can be performed such that the thickness of the flange portion S1F is uniform, excessive flange width at the longitudinal rear end of the finished H-beam product after finish rolling can be suppressed, and variation in the flange width of the flange portion of the H-beam after finish rolling in the longitudinal direction can be reduced. The reason why excessive flange width at the longitudinal rear end of the finished H-beam product after finish rolling can be suppressed will be described in detail later.

[0039] This rolling pass that reduces only the flange portion S1F is not limited to only the first pass, and a plurality of passes may be used as rolling passes that reduce only the flange portion S1F. Thereby, the effect of suppressing excessive flange width at the longitudinal rear end of the finished H-beam product after finish rolling and reducing variation in the flange width of the flange portion of the H-beam after finish rolling in the longitudinal direction can be improved.

[0040] Here, in the sizing rolling groove 33, the depth b1 of the groove portion 33a for rolling the flange portion S1F needs to be shorter than the flange leg length S0 of the flange portion S1F of the H-beam material S1, as described above. That is, it is necessary that b1 < S0.

[0041] Further, the depth b1 of the groove portion 33a is preferably 70 to 99% of the flange leg length S0 of the flange portion S1F of the H-beam material S1. If the depth b1 of the groove portion 33a is greater than 99% of the flange leg length S0, it may become difficult to satisfy the rolling condition of reducing only the flange portion S1F in the first pass of the sizing rolling step.

[0042] A more preferable upper limit for the ratio of the depth b1 of the groove 33a to the flange leg length S0 of the flange portion S1F of the H-shaped steel material S1 is 97.5%. For example, if the flange leg length S0 is 200 mm, and the depth b1 of the groove 33a is 195 mm, the ratio will be 97.5%. In this case, the reduction amount for reducing only the flange portion S1F can be set to 10 mm.

[0043] On the other hand, if the depth b1 of the groove 33a is less than 70% of the flange leg length S0, the amount of flange width reduction of the flange portion S1F before the web portion S1W can be reduced by sizing rolling becomes too large, which may cause folding defects on the outer surface of the flange portion S1F. A more preferable lower limit for the ratio of the depth b1 of the groove 33a to the flange leg length S0 of the flange portion S1F of the H-shaped steel material S1 is 80%.

[0044] Furthermore, in the second and subsequent passes of the sizing rolling process, the sizing rolling die 33 is used to roll the web portion S1W of the H-shaped steel material S1 in the thickness direction and the flange portion S1F of the H-shaped steel material S1 in the width direction. As shown in Figure 2(b), the thickness of the web portion S1W (web thickness) is reduced from T0 to T1 during sizing rolling, and the flange width of the flange portion S1F is reduced from B1-1 to B1-N. At this time, the web height of the H-shaped steel material S1 is increased from H1-1 to H1. Also, the inner width of the web portion S1W of the H-shaped steel material S1 is increased from W1-1 to W1.

[0045] Furthermore, the web widening rolling process comprises a first web widening rolling process shown in Figure 4(a) and a second web widening rolling process shown in Figure 4(b), and widens the inner width of the web portion S1W of the H-shaped steel material S1 that has been roughly rolled in the sizing process.

[0046] In the first web widening rolling process, as shown in Figure 4(a), the inner width of the web portion S1W of the H-shaped steel material S1 that was roughly rolled in the sizing rolling process is widened from W1 to W2 using the web widening first rolling hole mold 34 formed on the circumferential surfaces of the upper rolling roll 31 and lower rolling roll 32 provided on the rough rolling mill 3. At this time, the web height of the H-shaped steel material S1 is increased from H1 to H2. In addition, the flange width of the flange portion S1F of the H-shaped steel material S1 becomes B2 from B1-N. However, in this example, the die depth b2 (see Figure 4(b)) of the flange rolling section 34a in the first web widening rolling die 34, which rolls the flange section S1F of the H-shaped steel material S1, is the same as the depth b1 (see Figure 4(b)) of the groove section 33a in the sizing rolling die 33, which rolls the flange section S1F of the H-shaped steel material S1, so B2 is approximately equal to B1. Also, the thickness of the flange section S1F of the H-shaped steel material S1 (web thickness) changes from t1 to t2, with t2 being approximately equal to t1. Furthermore, the thickness of the web section S1W of the H-shaped steel material S1 (web thickness) changes from T1 to T2, but in the first web widening rolling process, no active thickness reduction of the web section S1W of the H-shaped steel material S1 is performed, so T2 is approximately equal to T1.

[0047] Furthermore, in the second web widening rolling process, as shown in Figure 4(b), the inner width of the web portion S1W of the H-shaped steel material S1 rolled in the first web widening rolling process is widened from W2 to W3 using the web widening second rolling hole mold 35 formed on the circumferential surfaces of the upper rolling roll 31 and lower rolling roll 32 provided on the roughing mill 3. At this time, the web height of the H-shaped steel material S1 is increased from H2 to H3. Also, the thickness of the flange portion S1F of the H-shaped steel material S1 (flange thickness) changes from t2 to t3, but t3 is approximately equal to t2. Furthermore, the thickness of the web portion S1W of the H-shaped steel material S1 (web thickness) changes from T2 to T3, but even in the second web widening rolling process, no active thickness reduction of the web portion S1W of the H-shaped steel material S1 is performed, and T3 is approximately equal to T2.

[0048] In this example, the flange width of the flange portion S1F of the H-shaped steel material S1 is reduced from B2 to B3. The die depth b3 (see Figure 4(b)) of the flange rolling section 35a that rolls the flange portion S1F of the H-shaped steel material S1 in the second web widening rolling die 35 is shallower than the die depth b2 of the flange rolling section 34a that rolls the flange portion S1F of the H-shaped steel material S1 in the first web widening rolling die 34. The depth b1 of the groove 33a that rolls the flange portion S1F of the H-shaped steel material S1 in the sizing rolling die 33 is equal to the die depth b2 of the flange rolling section 34a that rolls the flange portion S1F of the H-shaped steel material S1 in the first web widening rolling die 34. Therefore, the depth b3 of the flange rolling section 35a in the web widening second rolling die 35, which rolls the flange portion S1F of the H-shaped steel material S1, is shallower than the depth b1 of the groove section 33a in the sizing rolling die 33, which rolls the flange portion S1F of the H-shaped steel material S1 (b3 <b2=b1)。

[0049] In this way, during the web widening rolling process, the flange width of the flange portion S1F of the H-shaped steel material S1 can be reduced, and the flange width of the flange portion S2F of the rough-shaped steel billet S2 after rough rolling can be made more uniform in the longitudinal direction.

[0050] In this embodiment, the web widening rolling process is performed in two stages: a first web widening rolling process using a first web widening rolling die 34 and a second web widening rolling process using a second web widening rolling die 35. However, it may also be performed in one stage using one web widening rolling die, or in three or more stages using three or more web widening rolling dies. Furthermore, if the inner width W1 or web height H1 of the web portion S1W of the H-shaped steel material S1 rolled in the sizing rolling process matches the inner width or web height of the web portion S2W of the rough steel billet S2 in the intermediate rolling process and beyond using the intermediate universal rolling mill 4 and intermediate edging rolling mill 5 described later, the web widening rolling process itself is unnecessary.

[0051] The intermediate universal rolling mill 4 and the intermediate edging rolling mill 5 are installed downstream of the rough rolling mill 3. As shown in Figures 5(a) and 5(b), the rough steel billet S2 roughly rolled in the rough rolling process by the rough rolling mill 3 is rolled to produce a rolled material S3 having a web portion S3W and a pair of flange portions S3F for finish rolling, which will be approximately the product dimensions (intermediate rolling process). Here, "approximate product dimensions" refers to the dimensions to which the rolled material can be made into a product in the finish rolling process.

[0052] The intermediate rolling process includes an intermediate universal rolling process using the intermediate universal rolling mill 4 shown in Figure 5(a) and an intermediate edging rolling process using the intermediate edging rolling mill 5 shown in Figure 5(b). As shown in Figure 5(a), the intermediate universal rolling mill 4 has a pair of upper and lower horizontal rolls 41, 42 that rotate on a horizontal axis, and a pair of left and right vertical rolls 43, 44 that rotate on a vertical axis.

[0053] In the intermediate universal rolling process using the intermediate universal rolling mill 4, multiple passes of rolling are performed using reverse rolling. As shown in Figure 5(a), the horizontal rolls 41 and 42 reduce the entire height of the web portion S2W of the rough steel billet S2 in the thickness direction, while the vertical rolls 43 and 44 and the sides of the horizontal rolls 41 and 42 reduce the flange portion S2F in the thickness direction.

[0054] Furthermore, the intermediate edging rolling mill 5 is installed downstream of the intermediate universal rolling mill 4 and, as shown in Figure 5(b), is equipped with a pair of upper and lower horizontal rolls 51 and 52, each having a large-diameter roll section and a small-diameter roll section in the horizontal axis direction.

[0055] In the intermediate edging rolling process using the intermediate edging rolling mill 5, multiple passes of rolling are performed using reverse rolling. As shown in Figure 5(b), the large-diameter roll sections of the upper and lower pair of horizontal rolls 51 and 52 guide the web section S2W of the intermediate universal-rolled rough steel billet S2, while the small-diameter roll section presses down the end face of the flange section S2F in the width direction, thereby transforming the rough steel billet S2 into a rolled material S3 for finish rolling that has approximately the dimensions of the finished product.

[0056] Furthermore, the finishing universal rolling mill (finishing rolling mill) 6 is installed downstream of the intermediate universal rolling mill 4 and the intermediate edging rolling mill 5. As shown in Figure 5(c), the finishing rolling process is performed on the rolled material S3 for finishing rolling, which has been rolled in the intermediate rolling process to form an H-shaped steel beam H of product dimensions (see Figure 2(c)) (finishing rolling process). H-beams (H) are manufactured through this finishing rolling process.

[0057] As shown in Figure 5(c), the finishing universal rolling mill 6 includes a pair of upper and lower horizontal rolls 61, 62 that rotate on a horizontal axis, and a pair of left and right vertical rolls 63, 64 that rotate on a vertical axis.

[0058] In the finishing rolling process using the finishing universal rolling mill 6, the web portion S3W and flange portion S3F of the rolled material S3 are rolled down to the product thickness by a pair of upper and lower horizontal rolls 61, 62 and a pair of left and right vertical rolls 63, 64, and the angle of the flange portion S3F is raised. As a result, as shown in Figure 2(c), an H-shaped steel beam H is obtained with product dimensions of web height Hw, flange width Bf of flange portion F, web thickness Tw, and flange thickness tF of flange portion F.

[0059] Next, the reasons why excessive flange width can be suppressed at the longitudinal rear end of the H-shaped steel H after finish rolling, and why the longitudinal variation of the flange width Bf of the flange portion F of the H-shaped steel H after finish rolling can be reduced, will be explained in detail with reference to Figures 6 and 7. Figure 6 is a schematic diagram of the H-shaped steel material viewed from above after the completion of one pass in the sizing rolling process, where (a) is a schematic diagram of the H-shaped steel material viewed from above after the completion of one pass in the sizing rolling process according to the present invention, in which rolling was performed to reduce only the flange portion of the H-shaped steel material in the first pass of the sizing rolling process, and (b) is a schematic diagram of the H-shaped steel material viewed from above after the completion of one pass in a conventional sizing rolling process, in which rolling was performed to reduce both the flange portion and the web portion of the H-shaped steel material in the first pass of the sizing rolling process. Figure 7 is a schematic diagram showing the contact state between the material (H-shaped steel material) and the sizing rolling die in the first pass of the sizing rolling process. (a) is a schematic diagram showing the contact state at the leading edge, steady-state (central part), and trailing edge of the H-shaped steel material in the present invention, where rolling is performed to reduce only the flange portion of the H-shaped steel material in the first pass of the sizing rolling process. (b) is a schematic diagram showing the contact state at the leading edge and steady-state (central part) of the H-shaped steel material in the conventional case, where rolling is performed to reduce both the flange portion and the web portion of the H-shaped steel material in the first pass of the sizing rolling process. (c) is a schematic diagram showing the contact state at the trailing edge of the H-shaped steel material in the conventional case, where rolling is performed to reduce both the flange portion and the web portion of the H-shaped steel material in the first pass of the sizing rolling process.

[0060] As shown in Figure 6(a), in the present invention, in the first pass of the sizing rolling process, rolling is performed to reduce only the flange portion S1F of the H-shaped steel material S1. Since the web portion S1W is not rolled, the restraining effect of the web portion S1W suppresses the longitudinal elongation of the web portion S1W and the change in web height due to rolling. As a result, the inner width W1-1 and web height H1-1 of the web portion S1W are kept constant along the entire longitudinal length of the H-shaped steel material S1.

[0061] On the other hand, in the conventional method where the flange portion S1F and web portion S1W of the H-shaped steel material S1 are rolled down in the first pass of the sizing rolling process, the web portion S1W is rolled, so there is no restraining effect on the web portion S1W. As shown in Figure 6(b), the web portion S1W is stretched in the longitudinal direction by rolling, and the web height also changes. In particular, the inner width W1-1 and web height H1-1 of the web portion S1W widen considerably at the leading and trailing ends of the H-shaped steel material S1.

[0062] In the present invention, in which rolling is performed to reduce only the flange portion S1F of the H-shaped steel material S1 in the first pass of the sizing rolling process, as shown in Figure 7(a), the lower flange inner surface of the groove portion 33a of the sizing rolling die 33 comes into contact with the inner surface of the flange portion S1F of the H-shaped steel material S1. A "frictional force" acts on the inner surface of the flange inner surface of the groove portion 33a, causing it to rub against the inner surface of the flange portion S1F of the H-shaped steel material S1 in the direction toward the web portion S1W, as indicated by the arrow in Figure 7(a). This frictional force generates a metal flow from the flange portion S1F toward the web portion S1W. In the present invention, as described above, the inner width W1-1 and web height H1-1 of the web portion S1W are kept constant along the entire length of the H-shaped steel material S1, so the "frictional force" remains constant along the longitudinal direction, and the metal flow from the flange portion S1F toward the web portion S1W is stabilized.

[0063] As a result, after sizing rolling, the amount of material in the flange portion S1F becomes uniform along the entire longitudinal length of the H-shaped steel material S1, and the flange width Bf of the flange portion F of the H-shaped steel H after finish rolling is uniform along the longitudinal direction. Therefore, it is possible to suppress excessive flange width at the longitudinal rear end of the H-shaped steel H of the product after finish rolling, and to reduce the longitudinal variation of the flange width Bf of the flange portion F of the H-shaped steel H after finish rolling. Furthermore, as mentioned above, the first pass of rolling in the sizing rolling process is a rolling process that shapes the cross-sectional shape of the flange portion S1F of the H-shaped steel material S1 to conform to the shape of the sizing rolling die 33 along the entire longitudinal length of the H-shaped steel material S1. Furthermore, in the process of forming the cross-sectional shape of the flange portion S1F of the H-shaped steel material S1 to conform to the shape of the sizing rolling die 33, the amount of material in the flange portion S1F can be made uniform during rolling, which prevents excessive flange width at the longitudinal rear end of the H-shaped steel product after finish rolling, and reduces longitudinal variation in the flange width of the flange portion of the H-shaped steel after finish rolling.

[0064] On the other hand, in the conventional sizing rolling process, the flange portion S1F and web portion S1W of the H-shaped steel material S1 are rolled down in the first pass, as described above, the inner width W1-1 and web height H1-1 of the web portion S1W widen considerably at the leading edge of the H-shaped steel material S1. However, this widening of the inner width W1-1 and web height H1-1 of the web portion S1W mainly occurs at the exit of the rolling process (after exiting the roll bite where the thickness is reduced), and the contact state between the H-shaped steel material and the sizing rolling die at the leading edge of the H-shaped steel material S1 within the roll bite is as shown in Figure 7(b). Furthermore, the contact state between the H-shaped steel material and the sizing rolling die at the steady-state portion (central portion) of the H-shaped steel material S1 is also as shown in Figure 7(b). In other words, the lower surface of the flange inner pressure of the groove portion 133a of the sizing rolling hole 133 formed on the circumferential surfaces of the upper rolling roll 131 and the lower rolling roll 132 comes into contact with the inner surface of the flange portion S1F of the H-shaped steel material S1. Then, a "frictional force" acts in the direction in which the lower surface of the flange inner pressure of the groove portion 133a rubs down on the inner surface of the flange portion S1F of the H-shaped steel material S1. Due to this frictional force, a metal flow occurs from the flange portion S1F toward the web portion S1W at the tip and steady-state portions of the H-shaped steel material S1.

[0065] In contrast, in the conventional sizing rolling process, the flange portion S1F and web portion S1W of the H-shaped steel material S1 are rolled down in the first pass. As mentioned above, at the rear end of the H-shaped steel material S1, the inner width W1-1 and web height H1-1 of the web portion S1W widen considerably. This widening of the inner width W1-1 and web height H1-1 of the web portion S1W occurs mainly on the entry side of the rolling process, before entering the roll bite where the thickness is reduced. Therefore, the contact state between the H-shaped steel material and the sizing rolling die at the rear end of the H-shaped steel material S1 within the roll bite is as shown in Figure 7(c). In other words, the groove portion 133a of the sizing rolling die 133 formed on the circumferential surfaces of the upper rolling roll 131 and the lower rolling roll 132 does not contact the inner surface of the flange portion S1F of the H-shaped steel material S1. Therefore, no "frictional force" is exerted by the groove 133a in a direction that causes it to rub against the inner surface of the flange portion S1F of the H-shaped steel material S1. Consequently, at the rear end of the H-shaped steel material S1, no metal flow occurs from the flange portion S1F towards the web portion S1W, and the amount of material in the flange portion S1F of the H-shaped steel material S1 becomes greater than at the front end and the steady-state portion.

[0066] As a result, in conventional methods where the flange portion S1F and web portion S1W of the H-shaped steel material S1 are rolled down in the first pass of the sizing rolling process, the amount of material in the flange portion S1F at the rear end of the H-shaped steel material S1 becomes greater than that at the front end and the steady-state portion after sizing rolling, resulting in a phenomenon where the flange width is excessive at the longitudinal rear end of the H-shaped steel H of the finished product.

[0067] In the present invention, as described above, after sizing rolling, the amount of material in the flange portion S1F becomes uniform along the entire longitudinal length of the H-shaped steel material S1, and the flange width Bf of the flange portion F of the H-shaped steel H after finish rolling is uniform in the longitudinal direction. Therefore, it is possible to suppress excessive flange width at the longitudinal rear end of the H-shaped steel H of the finished product, and to reduce the longitudinal variation of the flange width Bf of the flange portion F of the H-shaped steel H after finish rolling.

[0068] Next, Figure 8 shows the relationship between the longitudinal deviation of the flange width of the flange portion of the H-beam after finish rolling and the amount of flange width reduction of the H-beam material in the first pass of the sizing rolling process. This Figure 8 shows the results of investigating the longitudinal flange width deviation of the H-beam at the product stage when manufacturing an H-beam H with a product shape of web height Hw of 1000 mm, flange width of flange portion F of 400 mm, web thickness Tw of web portion W of 19 mm, and flange thickness tF of flange portion F of 25 mm (H1000 × 400 × 19 × 25), by rolling the flange portion S1F of the H-beam material S1 in the first pass of the sizing rolling process under various conditions.

[0069] In this case, under the condition that the reduction in flange width of the flange portion S1F of the H-shaped steel material S1 in the first pass of the sizing rolling process was 1 to 10 mm, the web portion S1W was not reduced, but under the condition that the reduction in flange width exceeded 10 mm, the web portion S1W was also reduced. As shown in Figure 8, under the condition that the flange width reduction is 1 to 10 mm, the flange width deviation is 2 mm or less, indicating that the target longitudinal deviation of the flange width of 2 mm or less has been achieved.

[0070] On the other hand, under conditions where the flange width reduction exceeded 10 mm, the flange width deviation exceeded 2 mm, possibly because the web portion S1W was also reduced. Therefore, when manufacturing an H-shaped steel beam H with a product shape of H1000×400×19×25, it is preferable to perform the rolling process with a flange width reduction amount of 1 to 10 mm for the flange portion S1F in the first pass of the sizing rolling process.

[0071] Figure 9 also shows the relationship between the longitudinal deviation of the flange width of the flange portion of the H-beam after finish rolling and the flange width reduction ratio of the H-beam material in the first pass of the sizing rolling process. This Figure 9 shows the results of investigating the longitudinal flange width deviation of the H-beam at the product stage when manufacturing H-beams with product shapes of H1000×350×19×25 and H1000×300×19×25, in addition to H1000×400×19×25, which have different flange widths for the flange portion S1F. Rolling was performed under various conditions for the flange width reduction ratio of the flange portion S1F of the H-beam material S1 in the first pass of the sizing rolling process.

[0072] The flange width reduction ratio of flange portion S1F is defined as (flange width of flange portion S1F before rolling - flange width of flange portion S1F after rolling) / flange width of flange portion S1F before rolling × 100 (%). Here, the difference between the flange width of flange portion S1F before rolling and the flange width of flange portion S1F after rolling is the amount of flange width reduction. The H-shaped steel beams with three cross-sections (H1000×400×19×25, H1000×350×19×25, and H1000×300×19×25) are manufactured using different roughing rolls.

[0073] For rolls designed for H1000 x 350, in the first pass of the sizing rolling process, it is possible to reduce only the flange width of the flange portion S1F without reducing the web portion S1W, within a range of up to 10% of the flange width reduction ratio.

[0074] Furthermore, for rolls designed for H1000 x 300, during the first pass of the sizing rolling process, it is possible to reduce only the flange width of the flange portion S1F without reducing the web portion S1W, up to a maximum reduction of 25% in the flange width reduction ratio. However, under conditions where the flange width reduction ratio exceeds 20%, the reduction ratio becomes too large, potentially leading to problems such as poor rolling engagement and the occurrence of kinking defects at the tip of the flange portion S1F. Therefore, the upper limit of the flange width reduction ratio is limited to 20%.

[0075] As shown in Figure 9, the flange width reduction rate of the flange portion S1F of the H-shaped steel material S1 in the first pass of the sizing rolling process is in the range of 0.5% to 20%, and the flange width deviation is less than or equal to the target of 2 mm.

[0076] Therefore, it is preferable to perform rolling with a flange width reduction ratio of 0.5 to 20% for the flange portion S1F in the first pass of the sizing rolling process. If the lower limit of the flange width reduction ratio for the flange portion S1F in the first pass of the sizing rolling process is set to 2%, the flange width deviation will be 1.5 mm or less, which is more preferable.

[0077] Figure 10 is a diagram illustrating the draft angle of the contact portion that abuts the outer surface of the flange tip of the H-shaped steel material in the groove portion of the sizing rolling hole mold. As shown in Figure 10, the draft angle d of the contact slope 33aa that contacts the outer tip surface S1FS (Figure 2(a)) of the flange portion S1F of the H-shaped steel material S1 in the groove portion 33a of the sizing rolling die 33 is defined by the following equation (1).

[0078] d = Lx / Ly × 100 (%) ... (1)

[0079] Here, Ly is the vertical length from a to b, where b is the intersection point of the bottom surface of the groove 33a and the contact slope 33aa, and a predetermined point is reached by extending a predetermined length vertically from the intersection point b. Lx is the horizontal length from a to c, where c is the intersection point of a horizontal line drawn horizontally from the predetermined point a and the contact slope 33aa.

[0080] Furthermore, it is preferable that the first pass of rolling in the sizing rolling process be performed using a sizing rolling die 33 with a draft angle d of 20-40% for the contact bevel 33aa. This preferred range for the draft angle d of the contact bevel 33aa applies to the contact bevels 33aa of all grooves 33a formed in the upper rolling roll 31 and the two grooves 33a formed in the lower rolling roll 32.

[0081] If the draft angle d of the contact slope 33aa is less than 20%, the hole shape constraint under flange width reduction alone may be too large, causing the flange width reduction to change into longitudinal elongation, potentially reducing the effect of maintaining a constant flange width at the product stage. Additionally, there is the drawback that the outer surface of the flange portion S1F is prone to seizing.

[0082] If the draft angle d of the contact slope 33aa is greater than 40%, the thickness of the tip of the flange portion S1F in the flange width direction tends to be relatively thinner than the thickness of the center in the flange width direction. This may result in insufficient thickness at the tip of the flange portion F of the H-shaped steel H at the product stage.

[0083] Furthermore, if the width of the bottom surface of the groove 33a is increased relative to the thickness of the flange portion S1F, the aforementioned problem of the outer surface of the flange portion S1F seizing can be avoided. However, this may lead to a problem where the hole mold restraint effect under flange width alone becomes too small, reducing the aforementioned "effect of making the amount of material in the flange portion S1F uniform in the longitudinal direction by forming the cross-sectional shape of the flange portion S1F of the H-shaped steel material S1 to conform to the shape of the sizing rolling hole mold 33 over the entire longitudinal length of the H-shaped steel material S1." Therefore, there is a suitable range for the draft angle d of the contact slope 33aa.

[0084] As described above, according to the manufacturing method of H-shaped steel according to this embodiment, the rough rolling process includes a sizing rolling process in which the web portion S1W of the H-shaped steel material S1 is rolled in the thickness direction and the flange portion S1F of the H-shaped steel material S1 is rolled in the width direction using a sizing rolling die 33 formed on the circumferential surfaces of the upper rolling roll 31 and the lower rolling roll 32 provided in the rough rolling mill 3. The sizing rolling die 33 is a sizing rolling die 33 formed on the circumferential surfaces of the upper rolling roll 31 and the lower rolling roll 32, respectively, with a groove portion 33a having a depth b1 shorter than the flange leg length S0 of the flange portion S1F of the H-shaped steel material S1, for rolling the flange portion S1F. Then, in the first pass of the sizing rolling process, rolling is performed using the sizing rolling die 33 to reduce only the flange portion S1F of the H-shaped steel material S1.

[0085] As a result, after sizing rolling, the amount of material in the flange portion S1F becomes uniform along the entire longitudinal length of the H-shaped steel material S1, and the flange width Bf of the flange portion F of the H-shaped steel H after finish rolling is uniform in the longitudinal direction. Therefore, it is possible to suppress excessive flange width at the longitudinal rear end of the H-shaped steel H of the finished product and reduce the longitudinal variation of the flange width Bf of the flange portion F of the H-shaped steel H after finish rolling.

[0086] Furthermore, according to the manufacturing method of H-shaped steel according to this embodiment, the first pass of the sizing rolling process is performed using a sizing rolling die 33 in which the depth b1 of the groove portion 33a is 70 to 99% of the flange leg length S0 of the flange portion S1F of the H-shaped steel material S1.

[0087] This makes it easy to satisfy the rolling conditions that reduce only the flange portion S1F in the first pass of the sizing rolling process, while avoiding the possibility of fold defects occurring on the outer surface of the flange portion S1F.

[0088] Furthermore, according to the manufacturing method of H-shaped steel according to this embodiment, rolling is performed with a flange width reduction ratio of 0.5 to 20% for the flange portion S1F in the first pass of the sizing rolling process.

[0089] This makes it easy to keep the longitudinal deviation of the flange width Bf of the flange portion F of the H-shaped steel H, which is the finished product after finishing rolling, within the target range (within 2 mm) while avoiding problems such as poor rolling grip and the possibility of breakage defects occurring at the tip of the flange portion S1F.

[0090] Furthermore, according to the manufacturing method of H-shaped steel according to this embodiment, the first pass of the sizing rolling process is performed using a sizing rolling die 33 in which the draft angle d of the contact slope 33aa that contacts the outer tip surface S1FS of the flange portion S1F of the H-shaped steel material S1 in the groove portion 33a is set to 20 to 40%.

[0091] This prevents seizing of the outer surface of the flange portion S1F, avoids insufficient thickness at the tip of the flange portion F of the H-shaped steel H at the product stage, and reduces longitudinal variation in the flange width Bf of the flange portion F of the H-shaped steel H after finish rolling.

[0092] Although embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified and improved in various ways.

[0093] For example, the rough rolling process includes a sizing rolling process and a web widening rolling process performed after the sizing rolling process, and the first pass of rolling in the rough rolling process is sizing rolling. However, the first pass of rolling in the rough rolling process may be a rolling process other than sizing rolling. For example, in the first pass of rolling in the rough rolling process, it is possible to roll the H-shaped steel material S1 upright in an I-shape to reduce the web height H0.

[0094] Furthermore, the depth b3 of the flange rolling section 35a in the web widening second rolling die 35 used in the web widening second rolling process, which rolls the flange section S1F of the H-shaped steel material S1 in the width direction, does not necessarily need to be shallower than the depth b1 of the groove section 33a in the sizing rolling die 33 used in the sizing rolling process, which rolls the flange section S1F of the H-shaped steel material S1.

[0095] Furthermore, in the web widening rolling process, the die depth for the flange rolling section, which is shallower than the depth b1 of the groove 33a (for rolling the flange portion S1F of the H-shaped steel material S1 in the sizing rolling die 33 used in the sizing rolling process), is not limited to the web widening second rolling die 35, but may also be the web widening first rolling die 34. Also, in the web widening rolling process, the die depth for the flange rolling section, which is shallower than the depth b1 of the groove 33a (for rolling the flange portion S1F of the H-shaped steel material S1 in the sizing rolling die 33), may be the web widening rolling die if the web widening rolling is performed in one stage using one web widening rolling die. Furthermore, when web widening rolling is performed in three or more stages using three or more web widening rolling dies, one of the three or more web widening rolling dies may be a flange rolling dynamometer whose die depth is shallower than the depth b1.

[0096] Furthermore, the H-shaped steel material S1 is not limited to that which has been heated in the heating furnace 2; it may also be unheated. Furthermore, in the intermediate rolling process, the rough steel billet S2 is rolled using the intermediate universal rolling mill 4 and the intermediate edging rolling mill 5, but other intermediate rolling mills may be used in addition to the intermediate universal rolling mill 4 and the intermediate edging rolling mill 5.

[0097] Furthermore, in the finishing rolling process, the finishing universal rolling mill 6 is used to finish rolling the material S3 for finishing rolling, which will have approximate product dimensions. However, other finishing rolling mills may be used in addition to the finishing universal rolling mill 6. [Examples]

[0098] To verify the effects of the present invention, H-shaped steel was manufactured under the following manufacturing conditions, and the flange width along the entire length of the manufactured (finish-rolled) H-shaped steel was measured.

[0099] <Manufacturing conditions> (1) Target cross-sectional dimensions of H-beams We manufactured an H-shaped steel beam with a cross-sectional designation of H1000×400×19×25, with target product dimensions of web height Hw: 1000 mm, flange width Bf: 400 mm, web thickness Tw: 19 mm, and flange thickness tF: 25 mm.

[0100] (2) Rolling rolls used in the rough rolling process The rolling rolls used in the rough rolling process are the upper rolling roll 31 and the lower rolling roll 32 shown in Figure 3. Sizing rolling holes 33, web widening first rolling holes 34, and web widening second rolling holes 35 are formed on the circumferential surfaces of the upper rolling roll 31 and the lower rolling roll 32. The depth b1 of the groove 33a of the sizing rolling die 33 was 195 mm, the dimensions of the part of the sizing rolling die 33 that rolls the web portion S1W (the same dimensions as the inner width W1 of the web portion S1W in Figure 3(b)) were 730 mm, and the draft angle d of the contact slope 33aa was 35%. Furthermore, the die depth b3 of the flange rolling section 35a in the second web widening rolling die 35, which rolls the flange section S1F of the H-shaped steel material S1, was 5 mm smaller than the depth b1 of the groove section 33a in the sizing rolling die 33, which rolls the flange section S1F of the H-shaped steel material S1.

[0101] (3) H-shaped steel material The dimensions of the H-shaped steel material S1 were as follows: web height H0 was 1130 mm, flange leg length S0 of flange section S1F was 200 mm, web thickness T0 of web section S1W was 140 mm, and inner width W0 of web section S1W was 690 mm.

[0102] (4) Target dimensions of rough steel billet after rough rolling The target dimensions of the rough-shaped steel billet S2 after rough rolling were: web height H3 of 1200 mm, flange leg length of flange section S2F of 190 mm, web thickness T3 of web section S2W of 100 mm, and inner width W3 of web section S2W of 920 mm.

[0103] (5) Number of rolling passes in the rough rolling process, intermediate rolling process, and finish rolling process The rough rolling process consisted of a total of 11 passes: 9 passes for sizing rolling and 2 passes for web widening rolling. Intermediate rolling process: There were 23 passes each for intermediate universal rolling and intermediate edging rolling. Finishing rolling process: 1 pass.

[0104] <Rolling conditions in the sizing rolling process> In the sizing rolling process, the above-mentioned H-shaped steel material S1 was sizing-rolled under the rolling conditions of the following Invention Example 1, Invention Example 2, Comparative Example 1, and Comparative Example 2.

[0105] Example 1 of the present invention: In the first pass of the sizing rolling process, the flange width reduction amount of the flange portion S1F was set to 5 mm, and no reduction was performed on the web portion S1W. In the second pass of the sizing rolling process, the flange width reduction amount of the flange portion S1F was set to 5 mm, and no reduction was performed on the web portion S1W. In the third pass and subsequent passes of the sizing rolling process, rolling was performed under normal rolling conditions, with reduction being performed on both the flange portion S1F and the web portion S1W.

[0106] Example 2 of the present invention: In the first pass of the sizing rolling process, the flange width reduction of the flange portion S1F was set to 5 mm, and no reduction was performed on the web portion S1W. In the second and subsequent passes of the sizing rolling process, rolling was performed under normal rolling conditions, with reduction of both the flange portion S1F and the web portion S1W.

[0107] Comparative Example 1: In the first pass of the sizing rolling process, the flange width reduction amount for the flange portion S1F was set to 15 mm, and the web portion S1W was set to 5 mm. In the second and subsequent passes of the sizing rolling process, rolling was performed under normal rolling conditions, reducing both the flange portion S1F and the web portion S1W.

[0108] Comparative Example 2: In the first pass of the sizing rolling process, rolling was performed with a flange width reduction of 30 mm for the flange portion S1F and a reduction of 20 mm for the web portion S1W. In the second and subsequent passes of the sizing rolling process, rolling was performed under normal rolling conditions, reducing both the flange portion S1F and the web portion S1W.

[0109] <Manufacturing results> Figure 11 shows the results of measuring the flange width at 20 points along the entire longitudinal length of the H-shaped steel beam produced by sizing rolling of H-shaped steel material S1 under the rolling conditions of Invention Example 1, Invention Example 2, Comparative Example 1, and Comparative Example 2. The 20 points along the entire longitudinal length of the H-shaped steel beam are positions that divide the entire longitudinal length of the H-shaped steel beam into 20 equal parts. The flange width is the average value of the flange width of a pair of flange sections, and the measured values ​​are taken in a cold state.

[0110] In the case of Example 1 of the present invention (circle in Figure 11) and Example 2 of the present invention (triangle in Figure 11), the flange width along the entire longitudinal length fell within the tolerance range, which was satisfactory, given the target flange width Bf: 400 mm, upper tolerance limit of 402 mm, and lower tolerance limit of 398 mm. In contrast, in the case of Comparative Example 1 (□ in Figure 11) and Comparative Example 2 (× in Figure 11), the flange width at the rear end in the longitudinal direction exceeded the upper tolerance limit, resulting in a defective product, compared to the target flange width Bf: 400 mm, upper tolerance limit 402 mm, and lower tolerance limit 398 mm.

[0111] In this way, it has been confirmed that the present invention can suppress excessive flange width at the longitudinal rear end of the H-shaped steel H of the finished product and reduce longitudinal variation in the flange width of the flange portion after finish rolling. [Explanation of Symbols]

[0112] 1. Rolling mill for H-shaped steel beams 2 Furnace 3 Roughing mill 4. Intermediate Universal Rolling Mill 5. Intermediate Edging Rolling Mill 6. Finishing Universal Rolling Mill (Finishing Rolling Mill) 31 Upper rolling rolls 32 Lower rolling rolls 33. Hole mold for sizing rolling 33a Groove 33aa Contact slope 34. Hole type for first rolling of web widening 34a Flange Rolled Section 35. Hole type for second rolling of web widening. 35a Flange Rolled Section 41 Horizontal Roll 42 Horizontal Roll 43 Vertical Roll 44 vertical rolls 51 Horizontal Roll 52 Horizontal Roll 61 Horizontal Roll 62 Horizontal Roll 63 Vertical Roll 64 vertical rolls S1 H-shaped steel material S1W Web Department S1F Flange Section S2 Rough shaped steel billet S2W Web Department S2F Flange Section S3 Rolled material S3W Web Department S3F flange section HH section steel W Web Department F flange section

Claims

1. A method for manufacturing an H-shaped steel, comprising: a rough rolling step of roughly rolling an H-shaped steel material having a web portion and a pair of flange portions provided at both ends of the web portion in the width direction using a rough rolling mill to obtain a rough steel billet; an intermediate rolling step of rolling the rough steel billet using an intermediate rolling mill to obtain a material to be rolled for finish rolling; and a finish rolling step of finishing the material to be rolled for finish rolling using a finish rolling mill to obtain an H-shaped steel of product dimensions, The rough rolling process includes a sizing rolling process in which the web portion of the H-shaped steel material is rolled in the thickness direction and the flange portion of the H-shaped steel material is rolled in the width direction using sizing rolling holes formed on the circumferential surfaces of the upper rolling roll and lower rolling roll provided in the rough rolling mill, The sizing rolling die is a sizing rolling die in which grooves for rolling the flange portion, having a depth shorter than the flange leg length of the flange portion of the H-shaped steel material, are formed on the circumferential surfaces of the upper rolling roll and the lower rolling roll, respectively. A method for manufacturing an H-shaped steel, characterized in that, in the first pass of the sizing rolling process, rolling is performed using the sizing rolling die to reduce only the flange portion of the H-shaped steel material.

2. The method for manufacturing an H-shaped steel according to claim 1, characterized in that the first pass of rolling in the sizing rolling process is performed using the sizing rolling die, wherein the depth of the groove portion is 70 to 99% of the flange leg length of the flange portion of the H-shaped steel material.

3. The method for manufacturing an H-shaped steel beam according to claim 1 or 2, characterized in that the flange width reduction ratio of the flange portion in the first pass of the sizing rolling process is 0.5 to 20%.

4. A method for manufacturing an H-shaped steel according to claim 1 or 2, characterized in that the first pass of rolling in the sizing rolling process is performed using the sizing rolling hole die, wherein the draft angle of the contact slope that contacts the outer tip surface of the flange portion of the H-shaped steel material in the groove portion is 20 to 40%.

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