US20200391261A1 - Method for producing h-shaped steel - Google Patents

Method for producing h-shaped steel Download PDF

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Publication number
US20200391261A1
US20200391261A1 US16/755,860 US201916755860A US2020391261A1 US 20200391261 A1 US20200391261 A1 US 20200391261A1 US 201916755860 A US201916755860 A US 201916755860A US 2020391261 A1 US2020391261 A1 US 2020391261A1
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caliber
rolling
raised part
rolled
shaping
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Hiroshi Yamashita
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Nippon Steel Corp
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Nippon Steel Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/08—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling structural sections, i.e. work of special cross-section, e.g. angle steel
    • B21B1/088—H- or I-sections
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2273/00—Path parameters
    • B21B2273/22—Aligning on rolling axis, e.g. of roll calibers

Definitions

  • the present invention relates to a production method for producing H-shaped steel using, for example, a slab having a rectangular cross section or the like as a raw material.
  • a raw material such as a slab or a bloom extracted from a heating furnace is shaped into a raw blank (a material to be rolled in a so-called dog-bone shape) by a rough rolling mill (BD), a web and flanges of the raw blank are subjected to reduction in thickness by an intermediate universal rolling mill, and flanges of the material to be rolled are subjected to width reduction and forging and shaping of end surfaces by an edger rolling mill close to the intermediate universal rolling mill. Then, an H-shaped steel product is shaped by a finishing universal rolling mill.
  • BD rough rolling mill
  • Patent Document 2 discloses a technique of selectively performing reduction on the web corresponding part, in which an unreduced portion is provided at the middle of the web corresponding part, a formed protruding part (corresponding to a raised part of the present invention) is thereafter eliminated, and the web corresponding part is widened, thereby efficiently producing large-size H-shaped steel.
  • Patent Document 1 Japanese Laid-open Patent Publication No. H7-88501
  • Patent Document 2 Japanese Laid-open Patent Publication No. S57-146405
  • the rate of width spread which represents the rate of a spread amount of the flange width to an edging amount, is about 0.8 even under a condition that the efficiency at the initial stage of edging is the highest, and decreases as the spread amount of the flange width increases under a condition that edging is repeated in the same caliber, and finally becomes about 0.5.
  • a large-size raw blank is sometimes rolled and shaped in the rough rolling step.
  • the present inventors evaluated a thickening property of the flanges in a uniform process including a process of eliminating the unreduced portion in the subsequent process in addition to the preceding process of having a recessed portion for generating the unreduced portion (a later-described raised part) on the web.
  • the width of the unreduced portion is set to a width of 25% or more and 50% or less of a web part inner size of the material to be rolled, for example, when a 300 thick slab is used as a raw material to increase the generation efficiency of the flanges, and reached the present invention.
  • an object of the present invention is to provide a technique for efficiently and stably producing an H-shaped steel product having a larger flange width as compared with conventional ones by performing flat shaping and rolling of a large-size raw blank without bringing about problems such as elongation in a web height direction and deformation of a flange corresponding part one in a rough rolling step using a caliber when producing H-shaped steel.
  • a method for producing H-shaped steel including: a rough rolling step; an intermediate rolling step; and a finish rolling step, wherein: the rough rolling step includes: an edging rolling step of rolling and shaping a material to be rolled into a predetermined almost dog-bone shape; and a flat rolling step of performing rolling of a web part by rotating the material to be rolled after completion of the edging rolling step by 90° or 270°; upper and lower caliber rolls of at least one caliber of calibers configured to perform the flat rolling step include recessed parts configured to form a raised part at a middle of a web part of the material to be rolled, the recessed parts being provided at roll barrel length middle parts of the upper and lower caliber rolls; the caliber configured to perform the flat rolling step further includes a raised part eliminating caliber configured to reduce the raised part and perform an inner size widening of the web part of the material to be rolled on the material to be rolled in which the raised part is formed; rolling
  • the rolling and shaping in the raised part eliminating caliber is performed in a plurality of passes; and the rolling and shaping is performed in a state where a flange inner surface of the material to be rolled and a caliber roll are brought into contact with each other in at least one or more passes of the plurality of passes.
  • the rolling and shaping in the raised part eliminating caliber is performed in a plurality of passes; and the rolling and shaping is performed in a state where a flange inner surface of the material to be rolled and a caliber roll are brought into contact with each other in a first pass of the plurality of passes.
  • a width of the raised part formed in the flat rolling step may also be set to 25% or more and 50% or less of a web part inner size of the material to be rolled.
  • a reduction ratio with respect to the raised part in the raised part eliminating caliber may also be 2.1 or less.
  • the edging step is performed by a plurality of calibers, the number of the plurality of calibers being four or more; shaping in one or a plurality of passes is performed on the material to be rolled in the plurality of calibers; a first caliber and a second caliber of the plurality of calibers are formed with projections configured to create splits vertical to a width direction of the material to be rolled so as to form divided parts at end parts of the material to be rolled; and the calibers after a third caliber of the plurality of calibers are formed with projections configured to come into contact with the splits and sequentially bend the formed divided parts.
  • the present invention it becomes possible to, in the rough rolling step using a caliber when producing H-shaped steel, efficiently and stably produce an H-shaped steel product having a larger flange width as compared with conventional ones by performing flat shaping and rolling of a large-size raw blank without bringing about problems such as elongation in a web height direction and deformation of a flange corresponding part.
  • FIG. 1 is a schematic explanatory view about a production line for H-shaped steel.
  • FIG. 2 is a schematic explanatory view of a first caliber.
  • FIG. 3 is a schematic explanatory view of a second caliber.
  • FIG. 4 is a schematic explanatory view of a third caliber.
  • FIG. 5 is a schematic explanatory view of a fourth caliber.
  • FIG. 6 is a schematic explanatory view of a fifth caliber.
  • FIG. 7 is a schematic explanatory view of a sixth caliber.
  • FIG. 8 are schematic explanatory views in a case where the rolling and shaping is performed in a state where an inner surface of flange parts and a roll are brought into contact with each other in rolling and shaping in the sixth caliber.
  • FIG. 9 is a schematic explanatory view about a desirable configuration of the sixth caliber.
  • FIG. 10 are schematic views based on simulations indicating shapes of materials to be rolled after elimination of the respective raised parts in pass schedules in Table 3 and Table 4.
  • FIG. 11 is a graph indicating the relation between an escaping percentage and a flange width increase/decrease rate after the shaping of the H-shaped raw blank.
  • FIG. 12 is an explanatory view regarding warpage of a material to be rolled.
  • FIG. 13 is a graph indicating the relation between warpage and a web thickness.
  • FIG. 14 is a graph indicating the result of comparing and studying a case of poor material passage due to an occurrence of warpage and a case of good material passage due to no occurrence of warpage in the relation between a thickness after reduction of reduced portions and a height of a raised part.
  • FIG. 1 is an explanatory view about a production line T for H-shaped steel including a rolling facility 1 according to the present embodiment.
  • a heating furnace 2 a sizing mill 3 , a rough rolling mill 4 , an intermediate universal rolling mill 5 , and a finishing universal rolling mill 8 are arranged in order from the upstream side.
  • an edger rolling mill 9 is provided close to the intermediate universal rolling mill 5 .
  • a steel material in the production line T is collectively described as a “material to be rolled A” for the sake of explanation, and its shape is appropriately illustrated using broken lines, oblique lines and the like in some cases in the respective drawings.
  • a rectangular cross-section raw material (a later-described material to be rolled A) being a slab 11 extracted from the heating furnace 2 is subjected to rough rolling in the sizing mill 3 and the rough rolling mill 4 . Then, the rectangular cross-section raw material is subjected to intermediate rolling in the intermediate universal rolling mill 5 . During the intermediate rolling, reduction is performed on a flange tip part (a flange corresponding part 12 ) of the material to be rolled by the edger rolling mill 9 as necessary.
  • an edging caliber and a so-called flat shaping caliber of thinning a web portion to form the shape of a flange part are engraved on rolls of the sizing mill 3 and the rough rolling mill 4 , and an H-shaped raw blank 13 is shaped by reverse rolling in a plurality of passes through those calibers, and the H-shaped raw blank 13 is subjected to application of reduction in a plurality of passes using a rolling mill train composed of two rolling mills of the intermediate universal rolling mill 5 and the edger rolling mill 9 , whereby an intermediate material 14 is shaped.
  • the intermediate material 14 is then subjected to finish rolling into a product shape in the finishing universal rolling mill 8 , whereby an H-shaped steel product 16 is produced.
  • a slab thickness T of the slab 11 extracted from the heating furnace 2 is, for example, within a range of 290 mm or more and 310 mm or less. This is the dimension of a slab raw material called a so-called 300 thick slab used when producing a large-size H-shaped steel product.
  • FIG. 2 to FIG. 7 are schematic explanatory views about calibers engraved on the sizing mill 3 and the rough rolling mill 4 which perform a rough rolling step. All of a first caliber to a sixth caliber explained herein may be engraved, for example, on the sizing mill 3 , or six calibers of the first caliber to the sixth caliber may be engraved separately on the sizing mill 3 and the rough rolling mill 4 .
  • the first caliber to the sixth caliber may be engraved across both the sizing mill 3 and the rough rolling mill 4 , or may be engraved on one of the rolling mills.
  • shaping in one or a plurality of passes is performed in each of the calibers.
  • the number of the calibers does not always need to be six, but may be a plural number such as six or more.
  • a configuration that a general widening rolling caliber is provided at a stage subsequent to a later-described sixth caliber K 6 is adoptable.
  • the caliber configuration only needs to be suitable for shaping the H-shaped raw blank 13 .
  • FIG. 2 to FIG. 7 a schematic final pass shape of the material to be rolled A in shaping in each caliber is illustrated by broken lines.
  • FIG. 2 is a schematic explanatory view of a first caliber K 1 .
  • the first caliber K 1 is engraved on an upper caliber roll 20 and a lower caliber roll 21 which are a pair of horizontal rolls, and the material to be rolled A is subjected to reduction and shaping in a roll gap between the upper caliber roll 20 and the lower caliber roll 21 .
  • a peripheral surface of the upper caliber roll 20 namely, an upper surface of the first caliber K 1
  • a projection 25 protruding toward the inside of the caliber.
  • a peripheral surface of the lower caliber roll 21 namely, a bottom surface of the first caliber K 1
  • a projection 26 protruding toward the inside of the caliber.
  • projections 25 , 26 have tapered shapes, and dimensions such as a protrusion length of the projection 25 and the projection 26 are configured to be equal to each other.
  • a height (protrusion length) of the projections 25 , 26 is set to h 1 and a tip part angle thereof is set to ⁇ 1 a.
  • a tip part angle (also called a wedge angle) ⁇ 1 a of the projections 25 , 26 is desirably, for example, 25° or more and 40° or less.
  • a caliber width of the first caliber K 1 is preferably substantially equal to the thickness of the material to be rolled A (namely, a slab thickness).
  • a slab thickness namely, a slab thickness.
  • the width of the caliber at the tip parts of the projections 25 , 26 formed in the first caliber K 1 is set to be the same as the slab thickness, a right-left centering property of the material to be rolled A is suitably ensured.
  • it is preferable that such a configuration of the caliber dimension brings the projections 25 , 26 and parts of caliber side surfaces (side walls) into contact with the material to be rolled A at upper and lower end parts (slab end surfaces) of the material to be rolled A during shaping in the first caliber K 1 as illustrated in FIG.
  • a reduction amount at the projections 25 , 26 (reduction amount at wedge tips) at the time when the projections 25 , 26 are pressed against the upper and lower end parts (slab end surfaces) of the material to be rolled A to form the splits 28 , 29 is made sufficiently larger than a reduction amount at the slab upper and lower end parts (reduction amount at slab end surfaces), to thereby form the splits 28 , 29 .
  • FIG. 3 is a schematic explanatory view of a second caliber K 2 .
  • the second caliber K 2 is engraved on an upper caliber roll 30 and a lower caliber roll 31 which are a pair of horizontal rolls.
  • a peripheral surface of the upper caliber roll 30 (namely, an upper surface of the second caliber K 2 ) is formed with a projection 35 protruding toward the inside of the caliber.
  • a peripheral surface of the lower caliber roll 31 namely, a bottom surface of the second caliber K 2
  • projections 35 , 36 have tapered shapes, and dimensions such as a protrusion length of the projection 35 and the projection 36 are configured to be equal to each other.
  • a tip part angle of the projections 35 , 36 is desirably a wedge angle ⁇ 1 b of 25° or more and 40° or less.
  • the wedge angle ⁇ 1 a of the above first caliber K 1 is preferably the same angle as the wedge angle ⁇ 1 b of the second caliber K 2 at a subsequent stage in order to ensure the thickness of the tip parts of the flange corresponding parts, enhance inductive property, and secure stability of rolling.
  • a height (protrusion length) h 2 of the projections 35 , 36 is configured to be larger than the height h 1 of the projections 25 , 26 of the first caliber K 1 so as to be h 2 >h 1 .
  • the tip part angle of the projections 35 , 36 is preferably the same as the tip part angle of the projections 25 , 26 in the first caliber K 1 in terms of rolling dimension accuracy.
  • the material to be rolled A after passing through the first caliber K 1 is further shaped.
  • the height h 2 of the projections 35 , 36 formed in the second caliber K 2 is larger than the height h 1 of the projections 25 , 26 formed in the first caliber K 1 , and an intrusion length into the upper and lower end parts (slab end surfaces) of the material to be rolled A is also similarly larger in the second caliber K 2 .
  • An intrusion depth into the material to be rolled A of the projections 35 , 36 in the second caliber K 2 is the same as the height h 2 of the projections 35 , 36 .
  • an intrusion depth h 1 ′ into the material to be rolled A of the projections 25 , 26 in the first caliber K 1 and the intrusion depth h 2 into the material to be rolled A of the projections 35 , 36 in the second caliber K 2 satisfy the relation of h 1 ′ ⁇ h 2 .
  • angles ⁇ f formed between caliber upper surfaces 30 a , 30 b and caliber bottom surfaces 31 a , 31 b facing the upper and lower end parts (slab end surfaces) of the material to be rolled A, and, inclined surfaces of the projections 35 , 36 are configured to be about 90° (almost right angle) at all of four locations illustrated in FIG. 3 .
  • the shaping in the second caliber K 2 illustrated in FIG. 3 is performed by multi-passes, and in the multi-pass shaping, the active reduction of the material to be rolled A is not performed at the upper and lower end parts (slab end surfaces) of the material to be rolled A. This is because the reduction causes the elongation of the material to be rolled A in the longitudinal direction to decrease the generation efficiency of the flange corresponding parts (corresponding to a later-described flange parts 80 ).
  • FIG. 4 is a schematic explanatory view of a third caliber K 3 .
  • the third caliber K 3 is engraved on an upper caliber roll 40 and a lower caliber roll 41 which are a pair of horizontal rolls.
  • a peripheral surface of the upper caliber roll 40 (namely, an upper surface of the third caliber K 3 ) is formed with a projection 45 protruding toward the inside of the caliber.
  • a peripheral surface of the lower caliber roll 41 namely, a bottom surface of the third caliber K 3
  • These projections 45 , 46 have tapered shapes, and dimensions such as a protrusion length of the projection 45 and the projection 46 are configured to be equal to each other.
  • a tip part angle ⁇ 2 of the projections 45 , 46 is configured to be larger than the aforementioned angle ⁇ 1 b , and an intrusion depth h 3 into the material to be rolled A of the projections 45 , 46 is smaller than the intrusion depth h 2 of the above projections 35 , 36 (namely, h 3 ⁇ h 2 ).
  • the angle ⁇ 2 is preferably, for example, 70° or more and 110° or less.
  • angles ⁇ f formed between caliber upper surfaces 40 a , 40 b and caliber bottom surfaces 41 a , 41 b facing the upper and lower end parts (slab end surfaces) of the material to be rolled A, and, inclined surfaces of the projections 45 , 46 are configured to be about 90° (almost right angle) at all of four locations illustrated in FIG. 4 .
  • the splits 38 , 39 formed in the second caliber K 2 at the upper and lower end parts (slab end surfaces) of the material to be rolled A after passing through the second caliber K 2 become splits 48 , 49 by the projections 45 , 46 being pressed against thereon.
  • a deepest part angle hereinafter, also called a split angle
  • shaping is performed so that divided parts (the parts corresponding to the later-described flange parts 80 ) shaped along with the formation of the splits 38 , 39 in the second caliber K 2 are bent outward.
  • the shaping in the third caliber K 3 illustrated in FIG. 4 is performed by at least one or more passes, and in the pass shaping, the active reduction of the material to be rolled A is not performed in these passes. This is because the reduction causes the elongation of the material to be rolled A in the longitudinal direction to decrease the generation efficiency of the flange corresponding parts (corresponding to the later-described flange parts 80 ).
  • FIG. 5 is a schematic explanatory view of a fourth caliber K 4 .
  • the fourth caliber K 4 is engraved on an upper caliber roll 50 and a lower caliber roll 51 which are a pair of horizontal rolls.
  • a peripheral surface of the upper caliber roll 50 (namely, an upper surface of the fourth caliber K 4 ) is formed with a projection 55 protruding toward the inside of the caliber.
  • a peripheral surface of the lower caliber roll 51 namely, a bottom surface of the fourth caliber K 4
  • These projections 55 , 56 have tapered shapes, and dimensions such as a protrusion length of the projection 55 and the projection 56 are configured to be equal to each other.
  • a tip part angle ⁇ 3 of the projections 55 , 56 is configured to be larger than the aforementioned angle ⁇ 2 , and an intrusion depth h 4 into the material to be rolled A of the projections 55 , 56 is smaller than the intrusion depth h 3 of the projections 45 , 46 (namely, h 4 ⁇ h 3 ).
  • the angle ⁇ 3 is preferably, for example, 130° or more and 170° or less.
  • angles ⁇ f formed between caliber upper surfaces 50 a , 50 b and caliber bottom surfaces 51 a , 51 b facing the upper and lower end parts (slab end surfaces) of the material to be rolled A, and, inclined surfaces of the projections 55 , 56 , are configured to be about 90° (almost right angle) at all of four locations illustrated in FIG. 5 similarly to the above third caliber K 3 .
  • the splits 48 , 49 formed in the third caliber K 3 at the upper and lower end parts (slab end surfaces) of the material to be rolled A after passing through the third caliber K 3 are pressed to spread by the projections 55 , 56 being pressed against thereon, to thereby become splits 58 , 59 .
  • a deepest part angle (hereinafter, also called a split angle) of the splits 58 , 59 becomes ⁇ 3 .
  • shaping is performed so that divided parts (the parts corresponding to the later-described flange parts 80 ) shaped along with the formation of the splits 48 , 49 in the third caliber K 3 are further bent outward.
  • the parts of the upper and lower end parts of the material to be rolled A shaped in this manner are parts corresponding to flanges of a later-described H-shaped steel product and called the flange parts 80 herein.
  • the shaping in the fourth caliber K 4 illustrated in FIG. 5 is performed by at least one or more passes, and the active reduction of the material to be rolled A is not performed in these passes. This is because the reduction causes the elongation of the material to be rolled A in the longitudinal direction to decrease the generation efficiency of the flange parts 80 .
  • the rolling and shaping using the above first caliber K 1 to fourth caliber K 4 is also called an edging rolling step of shaping the material to be rolled A into a predetermined almost dog-bone shape, and is implemented in a state where the raw material slab having a rectangular cross section is erected.
  • FIG. 6 is a schematic explanatory view of a fifth caliber K 5 .
  • the fifth caliber K 5 is composed of an upper caliber roll 85 and a lower caliber roll 86 which are a pair of horizontal rolls.
  • the material to be rolled A shaped until the fourth caliber K 4 is rotated by 90° or 270°, whereby the flange parts 80 located at the upper and lower ends of the material to be rolled A until the fourth caliber K 4 are located on a rolling pitch line.
  • reduction of the web part 82 being a connecting part connecting the flange parts 80 at two positions is performed.
  • upper and lower caliber rolls 85 , 86 of the fifth caliber K 5 have shapes formed with recessed parts 85 a , 86 a of a predetermined length W 1 at their roll barrel length middle parts.
  • the reduction of the web part 82 is partially performed from a first pass of the caliber to a pass thereof in which a raised part 82 b is filled, so that in the web part 82 after the reduction, reduced portions 82 a at both ends in the web height direction and the raised part 82 b at the middle part thereof are formed.
  • the rolling and shaping of forming the raised part 82 b in the web part 82 is performed in a material to be rolled in a so-called dog-bone shape.
  • this caliber is also called a “web partial rolling caliber”.
  • the same length as the width length of the raised part 82 b after the formation is the same length (a later-described escaping amount W 1 ) as the width length W 1 of the recessed parts 85 a , 86 a .
  • the width length W 1 of the recessed parts 85 a , 86 a in this description is defined as a width length at a depth of 1 ⁇ 2 of a depth hm of the recessed parts 85 a , 86 a , and a later-described escaping amount W 1 also conforms to a similar definition.
  • FIG. 7 is a schematic explanatory view of a sixth caliber K 6 .
  • the sixth caliber K 6 is composed of an upper caliber roll 95 and a lower caliber roll 96 which are a pair of horizontal rolls.
  • the rolling and shaping of eliminating the raised part 82 b formed in the web part 82 and widening the inner size of the web part 82 is performed on the material to be rolled A rolled and shaped in the fifth caliber K 5 .
  • the rolling of bringing the upper and lower caliber rolls 95 , 96 into contact with the raised part 82 b formed in the web part 82 to reduce (eliminate) the raised part 82 b is performed.
  • the rolling and shaping by the sixth caliber K 6 makes it possible to promote spread in the web height direction and the metal flow to the flange parts 80 accompanying the reduction of the raised part 82 b , to thereby implement the rolling and shaping without causing decrease in area of the flange as much as possible.
  • the sixth caliber K 6 eliminates the raised part 82 b formed in the web part 82 , and is therefore also called a “raised part eliminating caliber”.
  • the material to be rolled A through the first caliber K 1 to the sixth caliber K 6 described above may be further subjected to the widening rolling of the web part 82 as needed.
  • the widening rolling at a stage subsequent to the rolling and shaping in the sixth caliber K 6 , it is only necessary to perform the widening rolling using one or a plurality of widening calibers. Note that since the caliber for widening rolling in that case is a conventionally known caliber, the explanation of the caliber for the widening rolling is omitted in this description.
  • the rolling and shaping using the above fifth caliber K 5 and sixth caliber K 6 (and the widening caliber as needed) is implemented in an almost H-shaped attitude in which the material to be rolled A shaped at the edging rolling step is rotated by 90° or 270°, and is therefore also called a flat rolling step.
  • the H-shaped raw blank 13 illustrated in FIG. 1 is shaped using the first caliber K 1 to the sixth caliber K 6 as described above and the caliber for widening rolling as needed.
  • the H-shaped raw blank 13 shaped as described above is subjected to application of reverse rolling in a plurality of passes using the rolling mill train composed of two rolling mills of the intermediate universal rolling mill 5 and the edger rolling mill 9 being known rolling mills, whereby an intermediate material 14 is shaped.
  • the intermediate material 14 is then subjected to finish rolling into a product shape in the finishing universal rolling mill 8 , whereby an H-shaped steel product 16 is produced (refer to FIG. 1 ).
  • the first caliber K 1 to the fourth caliber K 4 are used to create splits in the upper and lower end parts (slab end surfaces) of the material to be rolled A and perform processing of bending to right and left the respective portions separated to right and left by the splits to perform the shaping of forming the flange parts 80 as explained above, thereby enabling shaping of the H-shaped raw blank 13 without performing substantial vertical reduction of the upper and lower end surfaces of the material to be rolled A (slab).
  • the flat shaping and rolling implemented after the edging rolling is implemented by the caliber configuration including the fifth caliber K 5 of forming the raised part 82 b and the sixth caliber K 6 of eliminating the raised part 82 b and widening the inner size of the web part 82 in the present embodiment.
  • This makes it possible to roll and shape the H-shaped raw blank 13 having a larger flange width as compared with a conventional one, resulting in enabling the production of the H-shaped steel product having a larger flange width as compared with conventional ones.
  • the raised part 82 b formed in the web part 82 is eliminated but the inner size of the web part 82 is expanded with elimination of the raised part 82 b , which sometimes causes a gap between inner surfaces of the flange parts 80 and the rolls (the upper caliber roll 95 and the lower caliber roll 96 in the present embodiment) during the rolling and shaping in the sixth caliber K 6 .
  • the occurrence of the gap between the inner surfaces of the flange parts 80 and the rolls is likely to cause a deviation of right-left flange thickness amounts, or the like, and to impair rolling stability such as a material passage property.
  • a rolling state of impairing the rolling stability in the flat shaping and rolling represented by the rolling and shaping in the sixth caliber K 6 means that unbalance of flange thickness amounts occurs at a time of the elimination of the raised part 82 b .
  • the avoidance of the above is considered to require a state where the inner surfaces of the flange parts 80 and the rolls are brought into contact with each other in at least one pass in the rolling and shaping in the sixth caliber K 6 .
  • FIG. 8 are schematic explanatory views in a case where the rolling and shaping is performed in a state where the inner surface of the flange parts 80 and the roll are brought into contact with each other in the rolling and shaping in the sixth caliber K 6 .
  • FIG. 8 illustrate only the upper half of the material to be rolled A.
  • the rolling and shaping is preferably performed in the state where the inner surface 80 a of the flange parts 80 is brought into contact with the upper caliber roll 95 .
  • the state where an inner surface 80 a of the flange parts 80 is brought into contact with the upper caliber roll 95 is adoptable as states in all the passes, and as a state in a part of the passes (for example, the first pass). That is, it is only necessary that the inner surface 80 a of the flange parts 80 is in the state of being brought into contact with the upper caliber roll 95 in the rolling and shaping in at least one or more passes.
  • FIG. 9 is a schematic explanatory view about a desirable configuration of the sixth caliber K 6 , and solid lines indicate roll shapes and a mesh indicates the material to be rolled A.
  • the configuration of the sixth caliber K 6 is set to be a configuration that all the inner surfaces 80 a of the flange parts 80 (broken line parts in FIG. 9 ) are brought into contact with the rolls, whereby forming of at least tip parts of the flange parts 80 is performed, which maintains the rolling stability.
  • the one on the tip side of the flange part 80 is longer (L 1 >L 2 in the view), and the rolling is considered to be likely to be stable even though asymmetric deformation occurs in the material to be rolled A.
  • adjustment of such a condition related to the configuration of the sixth caliber K 6 can be controlled by, for example, a value of the inner size of the caliber, an inclination angle of a flange facing portion of the caliber, or the like.
  • Table 1 indicates specifications of the roll calibers indicating conventional caliber design, and one example of conditions when a web inner size is widened by flat rolling and shaping, and widening rolling without forming a raised part in the flat rolling and shaping.
  • Table 2 indicates specifications of the roll calibers indicating the caliber design according to the present invention, and conditions including the caliber (K 6 in Table) of performing the elimination of the raised part and the widening (first-stage widening) simultaneously after forming the raised part.
  • the respective rolls K 1 to K 6 described in Table 2 correspond to the first caliber K 1 to the sixth caliber K 6 according to the present embodiment, and the other K 7 to K 9 are general widening calibers.
  • K 2 - 1 and K 2 - 2 indicate split calibers having different projection heights, and both of them are the calibers each having a function corresponding to the second caliber K 2 according to the present embodiment.
  • the right-left deformations of the flange parts 80 are equalized to maintain the rolling stability.
  • the pass schedule of the rolling and shaping in the sixth caliber K 6 is suitably designed.
  • adjusting a reduction amount in the caliber of performing the elimination of the raised part suitably, and suppressing the reduction amount of the raised part 82 b cause the expansion of the inner size of the web part 82 with the elimination of the raised part 82 b to be suppressed, which realizes the maintaining of the rolling stability.
  • the caliber in the rolling and shaping in the first pass, is designed so that the inner surfaces 80 a of the flange parts 80 and inner surfaces of the rolls are brought into contact with each other when a roll gap including variations of the raised part 82 b in the longitudinal direction is evaluated to set the first pass with respect to such a roll gap as to indicate its minimum value (namely, a roll gap obtained by matching a roll gap of the web part to a height of the raised part 82 b ).
  • the first pass is set with respect to the roll gap obtained by actually matching the roll gap of the web part to the height of the raised part 82 b using such a caliber, thereby enabling secure forming of the inner surfaces 80 a of the flange parts 80 , which realizes the maintaining of the rolling stability.
  • a contact state of the flange inner surface can also be controlled by setting the pass schedule to partially perform the elimination of the raised part. For example, when the rolling and shaping of eliminating the raised part is performed in a plurality of passes, taking a reduction amount per one pass too much causes the spread of the web inner size due to the elimination (reduction) of the raised part 82 b , which makes it difficult that the inner surfaces 80 a of the flange parts 80 are brought into contact with the rolls, to be likely to impair the rolling stability.
  • the elimination of the raised part is partially performed, the elimination of the remaining raised part is preferably performed in an optional caliber at a subsequent stage.
  • the reduction and elimination of the remaining raised part may be performed by universal rolling in the intermediate universal rolling mill 5 (refer to FIG. 1 ) in which an intermediate rolling step is performed.
  • Tables 3, 4 are examples of pass schedules when the formation and the elimination of the raised part 82 b are performed by using the above explained fifth caliber K 5 and sixth caliber K 6 , and Table 3 indicates a conventional pass schedule and Table 4 indicates a pass schedule according to the present invention. Note that the respective calibers K 5 and K 6 described in Tables 3, 4 correspond to the fifth caliber K 5 and the sixth caliber K 6 according to the present embodiment.
  • the raised part 82 b is eliminated completely in a first pass in the sixth caliber K 6 (fourteenth pass), resulting in that a web end part thickness and a web projection (raised part) thickness are equal to each other (100.0 mm), while in the pass schedule according to the present invention, a state where the raised part 82 b remains without complete elimination of the raised part 82 b (150.0 mm) is seen. Adopting such a pass schedule makes it possible to suppress the inner size expansion of the web part 82 with the elimination of the raised part 82 b , which realizes the maintaining of the rolling stability.
  • FIG. 10 are schematic views based on simulations indicating shapes of the materials to be rolled after eliminating the respective raised parts in the above pass schedules in Table 3 and Table 4, and (a) is a schematic view in the conventional pass schedule and (b) is a schematic view in the pass schedule according to the present invention.
  • the raised part 82 b is formed at the middle of the web part 82 of the material to be rolled A, and the formed raised part 82 b is eliminated in the sixth caliber K 6 at a subsequent stage. Then, the widening rolling of the web inner size is performed as needed after the elimination of the raised part, to thereby shape the H-shaped raw blank, and in order to produce a large-size H-shaped steel product having a larger flange width as compared with the conventional one, the flange width of the H-shaped raw blank is also desired to be made as large as possible.
  • the present inventors found out that, by changing the width length W 1 of the raised part 82 b formed in the fifth caliber K 5 (namely, the escaping amount of the web inner size in the rolling and shaping in the fifth caliber K 5 ), there is generated a difference in the flange width of the finally obtained H-shaped raw blank. This is attributed to the fact that the flange thickness amount is more easily ensured with an increase in width length of the raised part 82 b , but, on the other hand, the flange width decreases by the drawing action in the longitudinal direction of the material to be rolled A at the time of the subsequent elimination of the raised part.
  • the present inventors focused attention on the relation between the escaping percentage and the increase/decrease of the flange width after the shaping of the H-shaped raw blank, and derived the preferable numerical value range of the escaping percentage.
  • the escaping percentage is a value defined by the following formula (1).
  • Escaping percentage [%] (escaping amount W 1/web inner size W 2) ⁇ 100 (1)
  • FIG. 11 is a graph indicating the relation between the escaping percentage and the flange width increase/decrease rate after the shaping of the H-shaped raw blank.
  • the flange width increase/decrease rate in FIG. 11 is a value indicating the flange width in the case where the escaping percentage is each value (12% to 56%) using the flange width in the case of the escaping percentage of 0% as a reference (1.000).
  • the flange width of the H-shaped raw blank tends to increase with an increase in the escaping percentage, and the flange width increase/decrease indicates an almost fixed value (refer to a broken line part in the graph) in a region where the escaping percentage is about 25% or more.
  • the numerical value range of the escaping percentage is desirably set to 25% to 50%.
  • the numerical value range of the escaping percentage when forming the raised part 82 b is desirably set to 25% to 50%, and meanwhile, there is a need to further conduct a study regarding a value of a thickness of the reduced portions 82 a of the web when forming the raised part 82 b at the escaping percentage in such a numerical value range.
  • the present inventors conducted evaluation regarding shaping property (rolling stability) under conditions where a web reduction amount was changed during rolling and shaping in the fifth caliber K 5 at a time of performing rolling and shaping using the first caliber K 1 to the sixth caliber K 6 according to the present embodiment in a case of producing H-shaped steel with a product flange width of 400 mm or more by using a rectangular cross-section slab of 2000 ⁇ 300 mm as a raw material.
  • cases where thicknesses after reduction of the reduced portions 82 a were set to 200 mm, 160 mm, 140 mm, 120 mm, and 100 mm, were set to levels 1 to 5, respectively.
  • a comparative level a case where the web thickness reduction is performed without forming the raised part 82 b , was set to a level 6.
  • Table 5 to be shown below indicates pass schedules of the aforementioned level 1 to level 6, and respective calibers G 1 , G 2 - 2 , G 3 - 1 , G 3 - 2 , G 4 - 1 , and G 4 - 2 in Table correspond to the first caliber K 1 to the sixth caliber K 6 described in the present embodiment. Further, the evaluation of the shaping property is described in the lowest column in Table 5, in which a case where the poor material passage and the defective shape occurred is evaluated as “bad”, and a case where the poor material passage and the defective shape did not occur is evaluated as “good”.
  • evaluation criteria of the shaping property (rolling stability) will be described.
  • the evaluation of the shaping property is performed based on warpage which occurs in the longitudinal direction of the material to be rolled A when performing the rolling and shaping of eliminating the raised part 82 b.
  • FIG. 12 is an explanatory diagram regarding warpage of the material to be rolled A, and is a schematic side view when warpage occurred in an end part in the longitudinal direction of the material to be rolled A.
  • a difference between an end part and a steady part when the warpage occurred in the end part in the longitudinal direction of the material to be rolled A is defined as a “warpage amount”.
  • a ratio of the generated warpage amount to the length in the longitudinal direction of the material to be rolled A in which the warpage occurred is set to “warpage (%)” defined by the following formula (2).
  • Warpage [%] warpage amount/length of material to be rolled in which warpage occurred (2)
  • FIG. 13 is a graph illustrating the relation between warpage and a web thickness (thickness after reduction of the reduced portions 82 a ). Note that the graph illustrated in FIG. 13 indicates data under a condition in which the escaping percentage was set to about 33%.
  • the smaller the thickness after reduction of the reduced portions 82 a the larger the warpage.
  • the warpage is small to be about 3% or less, and when the thickness after reduction of the reduced portions 82 a exceeds 140 mm, the warpage is increased to be about 10% or more, and the shape deteriorates significantly.
  • the reason why the threshold regarding the warpage is set to 10% is because when the maximum warpage amount of about several hundreds of millimeters occurs at a percentage of 10% with respect to several meters of the end part of the material to be rolled, a difference in upper and lower thickness amounts is generated, which can be easily confirmed by a person skilled in the art, and a value at which it is apparent that the rolling becomes difficult to be continued in terms of operation is 10%.
  • thinning reduction of the web may be performed to make the web thickness thinner in the sixth caliber K 6 at a subsequent stage.
  • FIG. 14 is a graph illustrating the relation between the thickness after reduction (finished web thickness after reduction) of the reduced portions 82 a in the fifth caliber K 5 and a height of the raised part 82 b before reducing.
  • “escaping percentage” described above while referring to FIG. 11 is set under a suitable condition (for example, 25% to 50%)
  • the drawing action in the longitudinal direction of the raised part 82 b is small, and unless limitation is imposed on the height of the raised part by the caliber, the height of the raised part remains a slab thickness of the raw material.
  • the caliber when the caliber is provided with the slab thickness of 300 mm and the height of the raised part 82 b at a sufficient height, the height of the raised part remains 300 mm. From the above state, when the raised part 82 b was eliminated in the raised part eliminating caliber (the sixth caliber K 6 in FIG. 7 ), a case where the finished web thickness after reduction in the fifth caliber K 5 was 140 mm had no problem in the material passage property, but the poor material passage occurred in a case where it is 130 mm.
  • the thickness of the raised part 82 b is 300 mm in each of the above cases, and the drawing of the raised part 82 b is 2.14 owing to reduction from 300 mm to 140 mm in the case of 140 mm, and it is 2.31 owing to reduction from 300 mm to 130 mm in the case of 130 mm.
  • a limiting drawing indicating a threshold in the poor material passage is about 2.1 in each of the cases as illustrated in FIG. 14 .
  • the technique of performing the shaping of the material to be rolled A using four calibers of the first caliber K 1 to the fourth caliber K 4 , and thereafter performing the rolling and shaping of the H-shaped raw blank using the fifth caliber K 5 , the sixth caliber K 6 (and the widening rolling calibers as needed) is explained in the above embodiment, but, the number of calibers for performing the rough rolling step is not limited to this, and the rolling and shaping step illustrated in the first caliber K 1 to the fourth caliber K 4 may be implemented using more calibers. That is, the caliber configuration indicated in the above embodiment is one example, and the number of calibers engraved on the sizing mill 3 and the rough rolling mill 4 can be changed arbitrarily and is changed appropriately to the extent that the rough rolling step can be suitably implemented.
  • the shaping method of creating splits in the upper and lower end parts (slab end surfaces) of the material to be rolled A and performing processing of bending to right and left the respective portions separated to right and left by the splits to form the flange parts 80 in the first caliber K 1 to the fourth caliber K 4 is explained.
  • the rolling and shaping technique in the sixth caliber K 6 according to the present invention is applicable not only to the material to be rolled A shaped by such a technique but also, for example, to a conventional H-shaped raw blank (so-called dog-bone material) represented by Patent Document 1.
  • the present invention is applicable to a production method for producing H-shaped steel using, for example, a slab having a rectangular cross section or the like as a raw material.

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