Patent Application
20200391261
This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2018-022105, filed in Japan on Feb. 9, 2018, the entire contents of which are incorporated herein by reference.
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.
In the case of producing H-shaped steel, 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.
In such a method for producing H-shaped steel, for shaping the raw blank in the so-called dog-bone shape from the slab raw material having a rectangular cross section, there is a known technique of creating splits on slab end surfaces in a first caliber at a rough rolling step, then widening the splits or making the splits deeper in second and subsequent calibers, and eliminating the splits on the slab end surfaces in calibers subsequent thereto (refer to, for example, Patent Document 1).
Besides, in production of the H-shaped steel, it is known that after so-called edging rolling of edging the end surfaces of the raw material such as a slab (slab end surfaces), flat shaping and rolling is performed in which the material to be rolled is rotated by 90° or 270° and reduction of a web corresponding part is performed. In this flat shaping and rolling, reduction and shaping of a flange corresponding part is performed together with the reduction of the web corresponding part, and recently, in consideration of a demand for a large-size H-shaped steel product, when a large-size raw material is used as a material to be rolled, various problems such as elongation in a web height direction and deformation of the flange corresponding part may arise in general flat shaping and rolling, and correction of the shape is sometimes required. Concretely, there is a concern about a phenomenon that with the reduction of the web corresponding part, the web corresponding part elongates in the longitudinal direction and the flange corresponding part also elongates in the longitudinal direction drawn by the elongation of the web corresponding part, resulting in a decrease in thickness of the flange corresponding part.
Regarding such flat shaping and rolling, for example, 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
As described above, recently, with an increase in size of structures and the like, production of a large-size H-shaped steel product is desired. In particular, a product having flanges, which greatly contribute to strength and rigidity of H-shaped steel, made wider as compared with conventional ones is desired. To produce the H-shaped steel product with widened flanges, it is necessary to shape a material to be rolled having a larger flange width as compared with a conventional one from the shaping at the rough rolling step.
However, for example, in the technique disclosed in Patent Document 1 described above, in the method of creating the splits on the end surfaces of the raw material such as a slab (slab end surfaces), edging the end surfaces, and performing the rough rolling utilizing the width spread, there is a limit in broadening of the flanges. Namely, in order to broaden the flanges in conventional rough rolling methods, techniques such as wedge designing (designing of a split angle), reduction adjustment, and lubrication adjustment are used to improve the width spread, but since none of the methods greatly contributes to a flange width, it is known that 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. It is also conceivable to increase the size of the raw material such as a slab itself to increase the edging amount, but, there are circumstances where sufficient broadening of product flanges is not realized because there are device limits in facility scale, reduction amount, and so on of the rough rolling mill.
Further, when producing the large-size H-shaped steel product, a large-size raw blank is sometimes rolled and shaped in the rough rolling step. In the case of rolling and shaping the large-size raw blank in a method different from the conventional one and shaping the shape of the raw blank into a shape closer to the H-shaped steel, it is known that there arise problems such as elongation in a web height direction and deformation of a flange corresponding part when the flat shaping and rolling is performed by the technique described in the above Patent Document 2.
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. Concretely, the present inventors have found out that, as explained in a later-described embodiment of the present invention, 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.
In consideration of the above circumstances, 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.
To achieve the above object, according to the present invention, there is provided a method for producing H-shaped steel, the method 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 and shaping in the raised part eliminating caliber is performed on the material to be rolled after forming the raised part in the caliber having the recessed parts configured to form the raised part; and rolling and shaping of forming the raised part is not performed after a reduction of the raised part.
It is also adoptable that 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.
It is also adoptable that 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.
It is also adoptable that in the rolling and shaping in the raised part eliminating caliber, elimination of the raised part is performed partially, and a remaining raised part is eliminated by rolling and shaping in an optional caliber at a subsequent stage.
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.
It is also adoptable that 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.
According to 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.
Hereinafter, an embodiment of the present invention will be explained while referring to the drawings. Note that in this description and the drawings, components having substantially the same functional configuration are denoted by the same codes to omit duplicated explanation.
As illustrated in
Here, 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.
Next, caliber configurations and caliber shapes engraved on the sizing mill 3 and the rough rolling mill 4 illustrated in
Besides, a case where there are six calibers to be engraved will be described as an example in the present embodiment, and the number of the calibers does not always need to be six, but may be a plural number such as six or more. For example, a configuration that a general widening rolling caliber is provided at a stage subsequent to a later-described sixth caliber K6 is adoptable. In short, the caliber configuration only needs to be suitable for shaping the H-shaped raw blank 13. Note that in
In the first caliber K1, the projections 25, 26 are pressed against upper and lower end parts (slab end surfaces) of the material to be rolled A, to thereby form splits 28, 29. Here, a tip part angle (also called a wedge angle) θ1a of the projections 25, 26 is desirably, for example, 25° or more and 40° or less.
Here, a caliber width of the first caliber K1 is preferably substantially equal to the thickness of the material to be rolled A (namely, a slab thickness). Concretely, when the width of the caliber at the tip parts of the projections 25, 26 formed in the first caliber K1 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. Further, 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 K1 as illustrated in
Note that the wedge angle θ1a of the above first caliber K1 is preferably the same angle as the wedge angle θ1b of the second caliber K2 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) h2 of the projections 35, 36 is configured to be larger than the height h1 of the projections 25, 26 of the first caliber K1 so as to be h2>h1. Further, 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 K1 in terms of rolling dimension accuracy. In a roll gap between the upper caliber roll 30 and the lower caliber roll 31, the material to be rolled A after passing through the first caliber K1 is further shaped.
Here, the height h2 of the projections 35, 36 formed in the second caliber K2 is larger than the height h1 of the projections 25, 26 formed in the first caliber K1, 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 K2. An intrusion depth into the material to be rolled A of the projections 35, 36 in the second caliber K2 is the same as the height h2 of the projections 35, 36. In other words, an intrusion depth h1′ into the material to be rolled A of the projections 25, 26 in the first caliber K1 and the intrusion depth h2 into the material to be rolled A of the projections 35, 36 in the second caliber K2 satisfy the relation of h1′<h2.
Further, angles θf formed between caliber upper surfaces 30a, 30b and caliber bottom surfaces 31a, 31b 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
Since the intrusion length of the projections at the time when pressed against the upper and lower end parts (slab end surfaces) of the material to be rolled A is large as illustrated in
Besides, the shaping in the second caliber K2 illustrated in
A tip part angle θ2 of the projections 45, 46 is configured to be larger than the aforementioned angle θ1b, and an intrusion depth h3 into the material to be rolled A of the projections 45, 46 is smaller than the intrusion depth h2 of the above projections 35, 36 (namely, h3<h2). The angle θ2 is preferably, for example, 70° or more and 110° or less.
Further, angles θf formed between caliber upper surfaces 40a, 40b and caliber bottom surfaces 41a, 41b 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
As illustrated in
Besides, the shaping in the third caliber K3 illustrated in
A tip part angle θ3 of the projections 55, 56 is configured to be larger than the aforementioned angle θ2, and an intrusion depth h4 into the material to be rolled A of the projections 55, 56 is smaller than the intrusion depth h3 of the projections 45, 46 (namely, h4<h3). The angle θ3 is preferably, for example, 130° or more and 170° or less.
Further, angles θf formed between caliber upper surfaces 50a, 50b and caliber bottom surfaces 51a, 51b 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
In the fourth caliber K4, the splits 48, 49 formed in the third caliber K3 at the upper and lower end parts (slab end surfaces) of the material to be rolled A after passing through the third caliber K3 are pressed to spread by the projections 55, 56 being pressed against thereon, to thereby become splits 58, 59. Specifically, in a final pass in shaping in the fourth caliber K4, a deepest part angle (hereinafter, also called a split angle) of the splits 58, 59 becomes θ3. In other words, 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 K3 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.
Besides, the shaping in the fourth caliber K4 illustrated in
The rolling and shaping using the above first caliber K1 to fourth caliber K4 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.
Here, upper and lower caliber rolls 85, 86 of the fifth caliber K5 have shapes formed with recessed parts 85a, 86a of a predetermined length W1 at their roll barrel length middle parts. With such a caliber configuration illustrated in
Note that since the rolling and shaping of partially reducing the web part 82 to form the raised part 82b is implemented in the fifth caliber K5, this caliber is also called a “web partial rolling caliber”. Further, the same length as the width length of the raised part 82b after the formation is the same length (a later-described escaping amount W1) as the width length W1 of the recessed parts 85a, 86a. Herein, as illustrated in the enlarged view in
In the sixth caliber K6, the rolling of bringing the upper and lower caliber rolls 95, 96 into contact with the raised part 82b formed in the web part 82 to reduce (eliminate) the raised part 82b is performed.
The rolling and shaping by the sixth caliber K6 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 82b, to thereby implement the rolling and shaping without causing decrease in area of the flange as much as possible.
The sixth caliber K6 eliminates the raised part 82b formed in the web part 82, and is therefore also called a “raised part eliminating caliber”.
Further, the material to be rolled A through the first caliber K1 to the sixth caliber K6 described above may be further subjected to the widening rolling of the web part 82 as needed. In this case, at a stage subsequent to the rolling and shaping in the sixth caliber K6, 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 K5 and sixth caliber K6 (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
In the method for producing H-shaped steel according to the present embodiment, the first caliber K1 to the fourth caliber K4 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). In short, it becomes possible to shape the H-shaped raw blank 13 having the flange width made wider as compared with the rough rolling method of reducing at all times the slab end surfaces conventionally performed, resulting in production of a final product (H-shaped steel) having a large flange width.
Besides, the flat shaping and rolling implemented after the edging rolling is implemented by the caliber configuration including the fifth caliber K5 of forming the raised part 82b and the sixth caliber K6 of eliminating the raised part 82b 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.
Here, during the rolling and shaping using the above fifth caliber K5 and sixth caliber K6, it is found that the raised part 82b 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 82b, 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 K6. 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.
In consideration of such circumstances, the present inventors conducted further studies regarding suitable conditions not to impair the rolling stability when the raised part 82b is eliminated in the sixth caliber K6, and obtained the finding as explained below. Hereinafter, this finding is explained while referring to the drawings or the like.
A rolling state of impairing the rolling stability in the flat shaping and rolling represented by the rolling and shaping in the sixth caliber K6 means that unbalance of flange thickness amounts occurs at a time of the elimination of the raised part 82b. 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 K6. By bringing the inner surfaces of the flange parts 80 and the rolls into contact with each other in the rolling and shaping of eliminating the raised part, right-left deformations of the flange parts 80 are equalized to maintain the rolling stability. In particular, during the rolling and shaping in a plurality of passes, the inner surfaces of the flange parts 80 and the rolls are desirably brought into contact with each other in the first pass thereof.
In order to realize such a condition that the inner surfaces of the flange parts 80 and the rolls are in the state of being brought into contact with each other in at least one pass in the rolling and shaping in the sixth caliber K6, it becomes necessary to perform caliber design of the sixth caliber K6 suitably or to make a pass schedule in the sixth caliber K6 suitable.
(Suitable Caliber Design and Pass Schedule)
Here, as one of the conditions for performing the rolling and shaping in the state where the inner surface 80a of the flange parts 80 is brought into contact with the upper caliber roll 95, it is cited that a shape of the sixth caliber K6 is formed into a predetermined shape. As a concrete configuration of the sixth caliber K6, a configuration in a state where the roll and the inner surface 80a of the flange parts 80 extend across each other is desirable during the rolling and shaping in the first pass.
As illustrated in
The following 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.
Further, the following Table 2 indicates specifications of the roll calibers indicating the caliber design according to the present invention, and conditions including the caliber (K6 in Table) of performing the elimination of the raised part and the widening (first-stage widening) simultaneously after forming the raised part. Note that the respective rolls K1 to K6 described in Table 2 correspond to the first caliber K1 to the sixth caliber K6 according to the present embodiment, and the other K7 to K9 are general widening calibers. In addition, K2-1 and K2-2 indicate split calibers having different projection heights, and both of them are the calibers each having a function corresponding to the second caliber K2 according to the present embodiment.
As can be seen from a comparison of Table 1 and Table 2, between the case of implementing the elimination of the raised part and the widening rolling simultaneously in the sixth caliber K6 in the technique according to the present embodiment and the case of the conventional technique, the number of calibers used subsequently to the flat rolling and shaping is the same, and a caliber arrangement or the like is not changed either. That is, by making the caliber design of the sixth caliber K6 suitable, and having the configuration to perform the elimination of the raised part 82b and the widening of the web inner size simultaneously in the sixth caliber K6, it becomes possible to roll and shape the H-shaped raw blank 13 having a large flange width with a roll barrel length and the like being under previous conditions as they are, resulting in enabling the production of the H-shaped steel product having a larger flange width as compared with conventional ones.
Further, by specifications of the roll calibers such that the inner surfaces of the flange parts 80 and the rolls are brought into contact with each other at the time of the elimination of the raised part 82b, the right-left deformations of the flange parts 80 are equalized to maintain the rolling stability.
In addition, as one of the conditions for performing the rolling and shaping in the state where the inner surface 80a of the flange parts 80 is brought into contact with the upper caliber roll 95, it is cited that the pass schedule of the rolling and shaping in the sixth caliber K6 is suitably designed. Concretely, adjusting a reduction amount in the caliber of performing the elimination of the raised part (the sixth caliber K6 here) suitably, and suppressing the reduction amount of the raised part 82b cause the expansion of the inner size of the web part 82 with the elimination of the raised part 82b to be suppressed, which realizes the maintaining of the rolling stability.
First, as described above while referring to
Moreover, as a suitable pass schedule, in the caliber of performing the rolling and shaping of eliminating the raised part, 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 82b, which makes it difficult that the inner surfaces 80a of the flange parts 80 are brought into contact with the rolls, to be likely to impair the rolling stability. Thus, in the rolling and shaping in the first pass, limitation is imposed on the reduction amount of the raised part 82b, thereby enabling the secure forming of the inner surfaces 80a of the flange parts 80, which realizes the maintaining of the rolling stability.
Note that, when 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. For example, the reduction and elimination of the remaining raised part may be performed by universal rolling in the intermediate universal rolling mill 5 (refer to
The below-indicated Tables 3, 4 are examples of pass schedules when the formation and the elimination of the raised part 82b are performed by using the above explained fifth caliber K5 and sixth caliber K6, 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 K5 and K6 described in Tables 3, 4 correspond to the fifth caliber K5 and the sixth caliber K6 according to the present embodiment.
As can be seen from a comparison of Table 3 and Table 4, in the conventional pass schedule, the raised part 82b is eliminated completely in a first pass in the sixth caliber K6 (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 82b remains without complete elimination of the raised part 82b (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 82b, which realizes the maintaining of the rolling stability.
As illustrated in
This causes the right-left deformations of the flange parts 80 to be equalized, which maintains the rolling stability.
(Ratio of Escaping Amount (Raised Part Forming Width) in Web Inner Size)
As described above, in the fifth caliber K5 (refer to
The present inventors found out that, by changing the width length W1 of the raised part 82b formed in the fifth caliber K5 (namely, the escaping amount of the web inner size in the rolling and shaping in the fifth caliber K5), 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 82b, 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.
Accordingly, in order to define a suitable range of the escaping amount of the web inner size (which is simply described also as “escaping amount W1”, hereinafter) in the rolling and shaping in the fifth caliber K5, 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. Note that the escaping percentage is a value defined by the following formula (1).
Escaping percentage [%]=(escaping amount W1/web inner size W2)×100 (1)
As illustrated in
In consideration that the rolling and shaping of increasing also the flange width of the H-shaped raw blank is desired in the case of producing a large-size H-shaped steel product having a larger flange width as compared with the conventional one, it can be understood from the result indicated in
(Material Passage Property During Elimination of Raised Part)
As described above, it was found out, from the result in
Accordingly, 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 K5 at a time of performing rolling and shaping using the first caliber K1 to the sixth caliber K6 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. As concrete conditions, cases where thicknesses after reduction of the reduced portions 82a were set to 200 mm, 160 mm, 140 mm, 120 mm, and 100 mm, were set to levels 1 to 5, respectively. Note that as a comparative level, a case where the web thickness reduction is performed without forming the raised part 82b, 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 G1, G2-2, G3-1, G3-2, G4-1, and G4-2 in Table correspond to the first caliber K1 to the sixth caliber K6 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”.
As shown in Table 5, when the thicknesses after reduction of the reduced portions 82a were set to 200 mm, 160 mm, and 140 mm (levels 1 to 3), the poor material passage and the defective shape do not occur when eliminating the raised part 82b. On the other hand, when the thicknesses after reduction of the reduced portions 82a were set to 120 mm, and 100 mm (levels 4 and 5), the poor material passage and the defective shape occur when eliminating the raised part 82b. Further, also when the web thickness reduction to 100 mm was performed without forming the raised part 82b (level 6), similar poor material passage and defective shape occur.
Here, 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 82b.
Warpage [%]=warpage amount/length of material to be rolled in which warpage occurred (2)
The relation between the “warpage (%)” defined by the aforementioned formula (2) and the thickness after reduction of the reduced portions 82a was verified.
As illustrated in
In terms of operation, when the warpage occurred in the material to be rolled A becomes 10% or more, deterioration of dimension and shape in the next pass and thereafter becomes significant, and it becomes difficult to continue the rolling. Namely, from the result indicated in
Here, 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%.
Note that when the warpage is several % (less than 10%) under the same condition, warpage to a degree of several tens of millimeters is normally observed during operation, but, the degree has no problem in terms of operation, which can be easily estimated by the person skilled in the art.
As can be seen from
Note that when the web thickness (thickness after reduction of the reduced portions 82a) is made equal to or more than a predetermined value (for example, 140 mm) in the fifth caliber K5, thinning reduction of the web may be performed to make the web thickness thinner in the sixth caliber K6 at a subsequent stage.
Further,
For example, when the caliber is provided with the slab thickness of 300 mm and the height of the raised part 82b at a sufficient height, the height of the raised part remains 300 mm. From the above state, when the raised part 82b was eliminated in the raised part eliminating caliber (the sixth caliber K6 in
That is, as illustrated in
One example of the embodiment of the present invention has been explained above, but, the present invention is not limited to the illustrated embodiment. It should be understood that various changes or modifications are readily apparent to those skilled in the art within the scope of the spirit as set forth in claims, and those should also be covered by the technical scope of the present invention.
For example, the technique of performing the shaping of the material to be rolled A using four calibers of the first caliber K1 to the fourth caliber K4, and thereafter performing the rolling and shaping of the H-shaped raw blank using the fifth caliber K5, the sixth caliber K6 (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 K1 to the fourth caliber K4 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.
Further, in the above embodiment, 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 K1 to the fourth caliber K4 is explained. However, the rolling and shaping technique in the sixth caliber K6 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-022105 | Feb 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/004082 | 2/5/2019 | WO | 00 |
