阅读说明：本技术 H型钢的制造方法 (Method for manufacturing H-shaped steel ) 是由 山下浩 于 2018-05-23 设计创作，主要内容包括：具有如下工序：轧边工序,在该轧边工序中,将被轧制材轧制造形成预定形状；隆起部生成工序,在该隆起部生成工序中,使被轧制材旋转而进行腹板部的轧制,并且在被轧制材的腹板部中央形成隆起部；辅助性轧边工序,在该辅助性轧边工序中,使在隆起部生成工序中轧制了1个道次以上的被轧制材再次旋转而将其放回轧边工序的最终孔型,进行轻压下轧制；以及隆起部消除工序,在该隆起部消除工序中,将在隆起部生成工序中形成的隆起部压下并消除,在进行隆起部生成工序的上下孔型辊中,在该上下孔型辊的辊主体长度中央部设置有用于在被轧制材的腹板部中央形成隆起部的凹陷部,将该上下孔型辊的辊形状设计成不与被轧制材的凸缘部顶端接触,连续地进行1次或多次隆起部生成工序和辅助性轧边工序这两个工序,隆起部消除工序在进行了隆起部生成工序和辅助性轧边工序之后实施。(Comprises the following steps: a rolling step of rolling a material to be rolled into a predetermined shape; a bulging portion generating step of rolling the web portion by rotating the material to be rolled and forming a bulging portion in the center of the web portion of the material to be rolled; a secondary rolling step of rotating the material to be rolled, which has been rolled in the bulging portion forming step for 1 or more passes, again to return the material to the final pass of the rolling step, and performing soft reduction rolling; and a bulging portion removing step of pressing and removing the bulging portion formed in the bulging portion forming step, wherein a recessed portion for forming a bulging portion in the center of a web portion of the material to be rolled is provided in the center of the length of the main body of the upper and lower grooved rolls in the upper and lower grooved rolls that perform the bulging portion forming step, the upper and lower grooved rolls are designed so that the roll shape thereof does not contact the top end of the flange portion of the material to be rolled, and the bulging portion removing step is performed after the bulging portion forming step and the auxiliary rolling step are performed continuously 1 or more times.)

1. A method for producing H-shaped steel, which comprises a rough rolling step, an intermediate rolling step, and a finish rolling step,

the rough rolling process comprises the following steps:

a rolling step of rolling the material to be rolled into a predetermined dog-bone shape;

a bulging portion generating step of rotating the rolled material after the edging step by 90 ° or 270 ° to roll the web portion and forming a bulging portion in the center of the web portion of the rolled material;

a supplementary rolling step of turning the rolled material, which has been rolled in the bulging portion forming step for 1 or more passes, by 90 ° or 270 ° again, returning the rolled material to the final pass of the rolling step, and performing soft reduction rolling; and

a raised part removing step of removing the raised part by pressing the raised part formed in the raised part forming step,

in the vertical grooved roll for performing the raised part forming step, a depressed part for forming a raised part at the center of the web part of the material to be rolled is provided at the center of the longitudinal length of the roll body of the vertical grooved roll,

the roll shape of the upper and lower hole rolls is designed not to contact the top end of the flange part of the rolled material,

the two steps of the bulge forming step and the auxiliary hemming step are continuously performed 1 or more times,

the raised part eliminating step is performed after the raised part generating step and the auxiliary hemming step are performed.

2. The method of manufacturing H-shaped steel according to claim 1,

in the auxiliary rolling step, the final pass of the rolling step is subjected to soft reduction rolling so that the tip of the flange portion of the material to be rolled fills the pass.

3. The method of manufacturing H-shaped steel according to claim 2,

in the auxiliary rolling step, the web height of the rolled material is made smaller than the web height of the rolled material supplied to the pass in which the bulging portion forming step is performed immediately before the auxiliary rolling step by performing soft reduction rolling.

4. The method of manufacturing H-shaped steel according to any one of claims 1 to 3,

when 1 set of a plurality of passes in which the final pass rolling height is constant is set as 1 time of opportunity, the auxiliary rolling step is performed by 1 time of opportunity or two times of opportunity.

5. The method of manufacturing H-shaped steel according to any one of claims 1 to 4,

the width of the raised part formed in the raised part forming step is set to be 25% to 50% of the inner dimension of the web part of the material to be rolled.

Technical Field

(cross-reference to related applications)

The application claims priority based on Japanese patent application No. 2017-102423 filed in 24.5.2017 to the present country, the contents of which are incorporated herein by reference.

The present invention relates to a method for producing H-section steel from a slab or the like having a rectangular cross section, for example.

Background

In the case of manufacturing H-section steel, a rough bar (so-called dog-bone-shaped material to be rolled) is formed from a material such as a slab or a steel ingot drawn out from a heating furnace by a roughing mill (BD), the thickness of a web or a flange of the rough bar is reduced by a universal intermediate rolling mill, and the flange of the material to be rolled is subjected to width reduction, forging of an end face, and shaping by an edger located close to the universal intermediate rolling mill. And then, forming an H-shaped steel product by using a universal finishing mill.

In such a method for producing H-shaped steel, there is known a technique in which, when a so-called dog-bone-shaped rough shape is formed from a rectangular-section slab material, after a notch is formed in the 1 st pass of the rough rolling step on the end face of the slab, the opening is widened or the opening depth is increased in the 2 nd and subsequent passes, and the opening in the end face of the slab is eliminated in the subsequent passes.

In the production process of H-shaped steel, it is known that after so-called edging in which an end face (slab end face) of a material such as a slab is edged, a material to be rolled is rotated by 90 ° or 270 ° and subjected to flat rolling, and in this flat rolling, rolling corresponding to a web is performed. In the flat rolling, the pressing down of the web corresponding portion is performed and the pressing down and the shaping of the flange corresponding portion are performed.

However, in recent years, larger-sized H-section steel products have been sought. Therefore, studies have been made to produce H-shaped steel products from larger-sized slab materials than ever. Here, in general flat rolling, when a large-sized material is used as a material to be rolled, various problems such as elongation in the web height direction and deformation of a portion corresponding to a flange may occur, and a shape correction may be necessary. Specifically, there is a concern that the web corresponding portion extends in the longitudinal direction as the web corresponding portion is depressed, and the flange corresponding portion is also extended in the longitudinal direction by the extension, resulting in a thin thickness of the flange corresponding portion.

In such a flat rolling, for example, patent document 1 discloses a technique in which a groove portion is formed in the center portion of a flat pass, and a non-pressing portion is provided in the center of a web corresponding portion during rolling, thereby reducing the length of a cut portion. Patent document 1 describes that the reduction of the cut portion and the high efficiency of rolling are further achieved by performing the rolling in a state where a convex portion (corresponding to a bulging portion of the present invention) is formed at the center of the web corresponding portion.

For example, patent document 2 discloses a widening rolling method for favorably shaping a rough billet in a process of manufacturing a steel section. Specifically, patent document 2 discloses a rolling method in which a web corresponding portion is partially rolled, then, a convex portion at the center of the web corresponding portion is flattened and widened, and then, a rolled material is raised and rolled. By adjusting the flange width, the web thickness and the web height by the method, a plurality of rough billets can be manufactured.

Disclosure of Invention

Problems to be solved by the invention

As described above, in recent years, with the increase in size of structures and the like, it has been desired to manufacture large H-shaped steel products. In particular, a flange that greatly contributes to the strength and rigidity of the H-beam is desired to be wider than conventional products. In order to produce an H-shaped steel product having a wide flange, it is necessary to form a rolled material having a flange width larger than that of a conventional flange from the formation in the rough rolling step.

In the production of H-shaped steel products, it has been known that, in order to prevent flash at the position of the outer surface of the flange during the temper rolling, the material to be rolled is returned to the edging pass after the temper rolling and is subjected to soft reduction rolling. This soft reduction rolling can be referred to as assisted-positioned edging. In the present specification, the above-described process is referred to as "auxiliary edging process" or simply "auxiliary edging process". In the auxiliary rolling, since the material is returned to the edging pass after the reduction of the web thickness and the reduction in the flange width direction are performed by the flat rolling, the edging pass is not filled with the material to be rolled having a short flange width, and there is a concern that the material passing property is deteriorated and the shape of the material to be rolled is deteriorated. When the rolled material is large, particularly when an H-shaped steel product having a large web height is produced, such a deterioration in material passing properties and a deterioration in the shape of the rolled material during the auxiliary rolling may be more significant.

The technique disclosed in patent document 1 is a technique for reducing the length of the cut portion, and does not disclose any technical idea for forming a rolled material having a large flange width, and does not mention the content of performing the "auxiliary rolling" described above, the deterioration of the material passing property and the deterioration of the shape of the rolled material, which are problems at this time. Further, the technique disclosed in patent document 2 is a technique in which a convex portion is formed in the center of a web corresponding portion, then rolling is performed to flatten and widen the convex portion in the center of the web corresponding portion, and then a rolled material is rolled by standing up, and in this technique, a step of flattening the convex portion is performed every time the convex portion is formed in the center of the web corresponding portion, and there is a concern that the number of times of shifting between passes of the rolled material increases, and particularly, in the case where the above-described "auxiliary rolling" is performed a plurality of times, there is a problem that the number of times of shifting between passes is increased significantly, and rolling efficiency is lowered.

In view of the above circumstances, an object of the present invention is to provide a method for producing H-shaped steel capable of suppressing deterioration of material passing properties and deterioration of the shape of a rolled material in "backup rolling" in which, after forming a ridge portion in a web in flat rolling, the rolled material is returned to a edging pass to perform soft reduction rolling, and capable of stabilizing the backup rolling.

Means for solving the problems

In order to achieve the above object, according to the present invention, there is provided a method for producing an H-shaped steel including a rough rolling step, an intermediate rolling step, and a finish rolling step, the rough rolling step including: a rolling step of rolling the material to be rolled into a predetermined dog-bone shape; a bulging portion generating step of rotating the rolled material after the edging step by 90 ° or 270 ° to roll the web portion and forming a bulging portion in the center of the web portion of the rolled material; a supplementary rolling step of turning the rolled material, which has been rolled in the bulging portion forming step for 1 or more passes, by 90 ° or 270 ° again, returning the rolled material to the final pass of the rolling step, and performing soft reduction rolling; and a raised part removing step of removing the raised part formed in the raised part forming step by rolling down the raised part, wherein a recessed part for forming the raised part in the center of the web part of the material to be rolled is provided in the center of the length of the main body of the upper and lower hole rolls in the upper and lower hole rolls that perform the raised part forming step, and the roll shape of the upper and lower hole rolls is designed so as not to contact the top end of the flange part of the material to be rolled, and wherein the raised part removing step is performed after performing the raised part forming step and the auxiliary rolling step, and is performed 1 or more times continuously.

In the auxiliary rolling step, the final pass of the rolling step may be subjected to soft reduction rolling so that the tip of the flange portion of the material to be rolled fills the pass.

In the above-described auxiliary rolling step, the web height of the rolled material may be made smaller than the web height of the rolled material supplied to the pass in which the bulging portion forming step is performed immediately before the auxiliary rolling step by performing soft reduction rolling.

When 1 set of a plurality of passes in which the final pass rolling height is constant is set as 1 pass, the auxiliary rolling step may be performed by 1 pass or two passes.

The width of the raised portion formed in the raised portion forming step may be set to 25% or more and 50% or less of the inner dimension of the web portion of the material to be rolled.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to suppress deterioration of material passing properties and deterioration of the shape of a rolled material in "auxiliary rolling" in which a bulging portion is formed in a web in flat rolling and then the rolled material is returned to an edging pass to perform light reduction rolling, and to stabilize the auxiliary rolling.

Drawings

FIG. 1 is a schematic explanatory view of a production line of H-shaped steel.

Fig. 2 is a schematic explanatory view of the 1 st flat pass.

Fig. 3 is a schematic explanatory view of the 2 nd pass of the flat shape.

FIG. 4 is a schematic view of the final pass of the edging step of the roughing step in the production process of the H-shaped steel.

Fig. 5 is a schematic explanatory view of auxiliary rolling between the final pass of the rolling and the general flat pass.

Fig. 6 is a schematic explanatory view of auxiliary edging according to the present embodiment.

Fig. 7 is a graph showing transition of the flange width of the material to be rolled a in each pass when a plurality of passes are passed in the flat rolling.

Fig. 8 is a graph showing transition of the flange width when the H-shaped rough bar is formed by rolling forming with a total of 18 passes using the 1 st flat pass, the 2 nd flat pass, and the subsequent 3 wide passes.

Fig. 9 is a graph showing a relationship between the flow rate and an increase and decrease in the flange width after the H-shaped rough material is formed based on the data of fig. 8.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and the drawings, the same reference numerals are given to the components having substantially the same functional configuration, and redundant description is omitted.

(outline of production line)

Fig. 1 is an explanatory view of a production line T of H-shaped steel including a rolling mill 1 according to the present embodiment. As shown in fig. 1, a heating furnace 2, a sizing mill 3, a roughing mill 4, a universal intermediate mill 5, and a universal finishing mill 8 are arranged in this order from the upstream side in a production line T. In addition, an edger 9 is provided adjacent to the universal intermediate rolling mill 5. For convenience of explanation, the steel material in the production line T is hereinafter collectively referred to as "rolled material a", and the shape thereof may be illustrated in each drawing by using a dotted line, a diagonal line, or the like as appropriate.

As shown in fig. 1, in the production line T, for example, a rectangular cross-section material (a rolled material a thereafter) extracted from the heating furnace 2, i.e., a slab 11, is rough-rolled in the sizing mill 3 and the roughing mill 4. Next, intermediate rolling is performed in the universal intermediate rolling mill 5. In the intermediate rolling, the rolling mill 9 performs rolling of the flange distal end portion (flange corresponding portion 12) of the material to be rolled, as necessary. In a normal case, the rolls of the sizing mill 3 and the roughing mill 4 are engraved with a pass of edging and a so-called flat pass in which the web portion is thickened and the shape of the flange portion is formed. The H-shaped rough profile 13 is formed by reversible rolling in a plurality of passes by means of the sizing mill 3 and the roughing mill 4. The intermediate material 14 is formed by applying a plurality of passes of reduction to the H-shaped rough section 13 using a mill train formed by the two universal intermediate mills 5 to 9. Then, the intermediate product 14 is finish-rolled into a product shape in a universal finishing mill 8, thereby producing an H-shaped steel product 16.

Here, the slab thickness of the slab 11 extracted from the heating furnace 2 is, for example, in a range of 290mm to 310 mm. This is the size of a slab material called a so-called 300-thick slab used in the production of large H-shaped steel products.

In the sizing mill 3 and the roughing mill 4 shown in fig. 1, first, an edging process is performed as a preceding process. In the edging step, the material (slab 11) having a rectangular cross section is subjected to roll forming in a standing state to form a predetermined substantially dog-bone shape.

After the edging process, a plano-rolling process is performed as a subsequent process. In the flat rolling step, the material a to be rolled which has undergone the edging step is first rotated by 90 ° or 270 °. This rotation causes the flange portions positioned at the upper and lower ends of the material a to be rolled (slab 11) to come on the rolling pitch line in the edging process. Next, the web portion, which is the connecting portion connecting the flange portions at the two locations, is pressed down. Through the above-described edging and planishing rolling processes, the H-shaped rough bar 13 shown in fig. 1 is produced.

In general, the former step and the latter step are collectively referred to as a rough rolling step. In the method for producing H-shaped steel according to the present embodiment, the edging step, which is a preceding step in the rough rolling step, may be performed by a conventionally known general method. Therefore, a detailed description of the edging process is omitted in this specification. Hereinafter, the flat rolling step as the subsequent step will be described in detail with reference to the drawings.

(outline of hole pattern Structure)

Fig. 2 and 3 are schematic explanatory views of the 1 st horizontal pass KH1 and the 2 nd horizontal pass KH2 used in the horizontal rolling step. The 1 st flat hole type KH1 is formed by a pair of horizontal rolls, i.e., upper hole type roll 85 and lower hole type roll 86. As shown in fig. 2, in the 1 st flat pass KH1, the rolled material a that has been rolled and shaped in the edging step is rotated by 90 ° or 270 °, and the flange portions 80 that were positioned at the upper and lower ends of the rolled material a up to the preceding step are arranged on the rolling pitch. In addition, in the 1 st flat hole type KH1, the web 82, which is the connecting portion connecting the two flange portions 80, is pressed down.

Here, the upper and lower grooved rolls 85, 86 of the 1 st flat pass KH1 are formed with a recessed portion 85a, 86a of a predetermined length L1 at the center of the roll body in the longitudinal direction. With the hole-type structure shown in fig. 2, the web 82 is locally pressed down. As a result, depressed portions 82a at both ends in the web height direction and a raised portion 82b as an undepressed portion at the center in the web height direction are formed in the depressed web portion 82. In this way, the rolling forming is performed to form the ridge portion 82b in the web portion 82 for the so-called dog-bone-shaped material to be rolled. In this specification, the step of forming the raised portion 82b in the web portion 82 in the 1 st pass KH1 will also be referred to as a "raised portion forming step".

In addition, since the 1 st straight pass KH1 is subjected to rolling forming in which the web 82 is locally pressed down to form the ridge 82b, this pass is also referred to as a "local web rolling pass". The width of the formed ridge portion 82b is the same as the width L1 of the recessed portions 85a and 86 a. Here, as shown in the enlarged view of fig. 2, the width L1 of the recessed portions 85a and 86a in the present specification is defined as a width at a depth of 1/2 of the depth hm of the recessed portions 85a and 86 a. The overflow amount L1 discussed later is also based on the same specification.

FIG. 3 is a schematic explanatory view of the 2 nd flat hole pattern KH 2. The 2 nd flat hole pattern KH2 is formed by a pair of horizontal rolls, i.e., an upper hole pattern roll 95 and a lower hole pattern roll 96. In the 2 nd pass KH2, the rolled material a that has been roll-formed in the 1 st pass KH1 is roll-formed such that the bulging portions 82b formed in the web 82 are eliminated and the inside dimension of the web 82 is widened.

In the 2 nd pass KH2, the upper and lower pass rolls 95 and 96 are brought into contact with the raised portions 82b formed in the web portion 82 to press (eliminate) the raised portions 82 b. With the depression of the bulging portion 82b, the expansion in the web height direction and the metal flow to the flange portion 80 are promoted. Under the action of the metal flow, rolling and shaping can be carried out on the premise that the cross section of the flange is not shrunk as much as possible. In this specification, the step of pressing (removing) the ridge portion 82b in the 2 nd pass KH2 is also referred to as a "ridge portion removing step". In addition, since the 2 nd flat hole pattern KH2 can eliminate the raised portion 82b formed in the web portion 82, it is also referred to as a "raised portion elimination hole pattern".

The detailed conditions (dimensions and shapes of the pass) of the rolling forming in the 1 st flat pass KH1 and the 2 nd flat pass KH2 will be discussed in more detail in the description of the present embodiment based on the findings obtained by the present inventors and the like.

The intermediate material 14 is produced by subjecting the H-shaped rough bar 13 produced by the 1 st and 2 nd flat pass KH1, KH2 to reversible rolling in a plurality of passes using a mill train formed by two mills, i.e., a universal intermediate mill 5-an edger 9. Then, the intermediate product 14 is finish-rolled into a product shape by a universal finishing mill 8, thereby producing an H-section steel product 16 (see fig. 1).

In the rough rolling step for producing H-shaped steel, it is known that, in the edging step and the temper rolling step, as described above, after the web portion is reduced in thickness, the rolled material a is continuously returned to the edging pass again, and "auxiliary edging" is performed to prevent the flange portion of the rolled material in the temper pass from forming burrs from the outer side surface position. The "auxiliary rolling" is a technique for the purpose of shaping the shape of an unstable portion of a rolled material, suppressing a shape defect such as a burr, and the like, which has been conventionally performed.

(formerly auxiliary edging)

First, the conventional auxiliary hemming will be briefly described with reference to fig. 4 and 5. Fig. 4 is a schematic view of the final pass KE in the edging step (hereinafter also referred to as edging final pass KE) in the roughing step in the production process of the H-shaped steel. As shown in fig. 4, the edging final pass KE is engraved on a pair of horizontal rolls, i.e., an upper pass roll 50 and a lower pass roll 51. A projection 55 projecting toward the inside of the groove is formed on the peripheral surface (i.e., the upper surface of the groove) of the upper grooved roll 50. Further, a projection 56 projecting toward the inside of the groove is formed on the peripheral surface (i.e., the groove bottom surface) of the lower groove roller 51. These protrusions 55 and 56 have a tapered shape, and the protrusion length and other dimensions are equal in both the protrusions 55 and 56.

As shown in fig. 4, in the edging final pass KE, rolling is performed in the web width direction with the rolled material a standing upright, and the flange is widened. Specifically, the outer surface of the flange portion 80 (the upper and lower end surfaces of the material to be rolled a) is rolled by the upper and lower hole rollers 50 and 51 on which the projections 55 and 56 are formed.

In the conventional H-beam manufacturing technique, the rolled material a having passed through the final pass KE shown in fig. 4 is introduced into a general flat pass, and the web portion is reduced in thickness. Fig. 5 is a schematic explanatory view of auxiliary rolling between the final pass KE and the general flat pass GH, where (a) shows before the auxiliary rolling and (b) shows when the auxiliary rolling is performed. As shown in fig. 5 (a), in a general flat pass GH, the web portion of the rolled material a is reduced in thickness and the rolling in the width direction of the flange portion 80 is also performed. Therefore, as shown in fig. 5 (b), the width of the flange portion 80 is considerably short. As a result, the material a having the flange portion 80 with a short width is returned to the final pass KE for auxiliary rolling.

As shown in fig. 5 (b), when the material a to be rolled including the flange portion 80 having a short width is introduced into the final pass KE again, the flange portion 80 is not filled in the final pass KE (see a dotted line surrounded portion in fig. 5 (b)). Under the influence of the underfill of the flange portion 80 in the groove, there are problems in that the lateral centering property during rolling is poor, the web is buckled, and the lateral material amount of the flange portion 80 is unbalanced, which causes dimensional defects and shape defects.

(auxiliary edging in the present embodiment)

In contrast, in the present embodiment, the flat pass used in the auxiliary hemming is the "partial web rolling pass" which is the 1 st flat pass KH1 shown in fig. 2. Further, an appropriate condition is defined such that the reduction in the width of the flange portion 80 in the rolling forming by the local rolling pass of the web is minimized. Thus, when the rolled material a is introduced into the final pass KE again, the pass is not filled. Fig. 6 is a schematic explanatory view of auxiliary edging according to the present embodiment, wherein (a) shows before the auxiliary edging is performed, and (b) shows when the auxiliary edging is performed.

As shown in fig. 6, in the 1 st flat hole pattern KH1 of the present embodiment, the bulging portion 82b is generated when the web is reduced in thickness. This makes it difficult to cause the flange portion 80 to be drawn and contracted, and the reduction rate of the flange width is low. Therefore, as shown in fig. 6 (b), the width of the flange portion 80 is hardly reduced. Since the flange width changes little, the restraining force of the side wall portion of the groove is also maintained when the final groove KE is rolled back and the auxiliary rolling is performed. Therefore, the lateral centering performance is good, and dimensional defects and shape defects such as buckling of the web and imbalance in the amount of lateral material of the flange portion 80 are suppressed. In addition, it is desirable to design the roll so that the tip end of the flange portion 80 is formed in such a shape that it does not contact the pass during the roll forming in the 1 st pass of the 1 st pass KH1, and the tip end portion of the flange is just in contact with the roll pass during the flat rolling before the auxiliary rolling (i.e., the bulge forming step). By performing the auxiliary rolling under such conditions, the pass fullness when the rolled material a returns to the final pass KE of the rolling can be improved, and the rolling stability can be improved.

In the case of auxiliary edging, edging of about 40mm or less is preferred, for example, in which case the flange widening amount is about 24mm or less.

However, in the case of the flat rolling, the distance between the outer surface of the flange portion 80 and the outer wall of the grooved roll can be increased by setting the web height of the material to be rolled a to be as small as possible with respect to the groove width W (see fig. 2) of the "web partial rolling groove" which is the 1 st flat groove KH 1. Thus, it is possible to perform redundant rolling with respect to scuffing defects (す り slip-down) caused by the outer wall of the hole roll, with respect to the expansion in the web height direction of the material A to be rolled accompanying the web rolling reduction at the time of the flat rolling. From such a viewpoint, it is desirable to increase the amount of edging at the time of auxiliary edging as much as possible.

On the other hand, in order to improve rolling stability in the flat rolling, it is required to improve the pass restraining force of the rolled material a. In the case of the pass restraining force, if the distance between the outer wall of the flat pass grooved roll and the rolled material a is increased and the spread of the inner dimension of the web is increased, the guiding property is decreased and the rolling is unstable. From the viewpoint of such material passing properties, it is desirable to reduce the amount of edging in the auxiliary edging as much as possible.

For the above reasons, the optimum value of the amount of edging at the time of the auxiliary edging should be determined in consideration of the balance between the generation of the defect and the rolling stability. In the case where the flat rolling is performed after the finish of the finish rolling, it is desirable to design so that the heights of the side walls (outer walls) of the flat pass and the web of the material to be rolled a substantially coincide.

Here, the rolling of the web 82 is regarded as plate rolling. According to the relationship between the roll diameter of a general steel rolling mill and the size of a rolled material of large H-shaped steel, the plate width ratio is approximately 3-4, and the plate thickness ratio is approximately 4-5. Further, since the flange portions are provided at both ends of the plate thickness, the expansion amount is further increased. As a result, the expansion rate of the rolled material a in the web height direction by the web rolling is 4% or more of the web height. That is, when considering that the rolled material a is a large H-section steel, for example, the web height dimension is 1000mm, the spread rate of the web height is at least 40 mm. Therefore, as a condition for not contacting the outer wall of the grooved roll of the flat pass, the amount of edging is performed by 40mm or more, which is the amount of expansion of the web height at the time of the flat rolling, at the time of the auxiliary edging, so that the outlet side of the grooved roll is in contact with the material passage property and the like, and the material passage property is not impaired. That is, the amount of edging in the auxiliary edging is preferably 40mm or less.

Further, the widening rolling characteristics of the slab rolling can be applied to the flange widening caused by the rolling. That is, the flange widening characteristic of the conventional blank rolling method, which is performed by a groove having a protrusion in the central portion of a so-called box groove, can be applied. In this case, it is known that the bead spread is at least about 60% or less of the rolling reduction, and therefore, it is calculated that 40mm × 0.6 (60%) is 24 mm.

Fig. 7 is a graph showing transition of the flange width of the material to be rolled a in each pass when a plurality of passes are passed in the flat rolling. In the example of fig. 7, data obtained by performing FEM calculation using a 2000mm × 300mm sectional slab as a raw material was used. In fig. 7, the conventional flat rolling in a general flat pass GH (hereinafter referred to as "conventional method") and the flat rolling in the 1 st flat pass KH1 of the present embodiment (hereinafter referred to as "present invention method") are compared.

As shown in fig. 7, the reduction rate of the flange width in the flat rolling of the present embodiment is smaller than that in the conventional method. For example, after 13 passes of the flat rolling, the difference between the flange widths of the respective flat rolling is 100mm or more. As can be understood from the results of fig. 7, in the flat rolling performed by the 1 st flat pass KH1 of the present embodiment, the reduction rate of the flange width is low, and the pass underfill during the auxiliary edging is suppressed.

The present inventors have also experimentally confirmed that the material passage property differs depending on the filling property of the pass in the auxiliary hemming, and that the material passage property is problematic when the pass is not filled. Table 1 shown below is an experimental example showing the relationship between the pass fullness and the material passing property in the auxiliary rolling. Table 1 shows the relationship between the pore filling and material passage in the conventional method and the method of the present invention under the conditions of cases 1 to 4. In addition, in the case of the auxiliary rolling, in all cases 1 to 4, the rolling was performed in two passes to an amount of about 40 mm. Therefore, the values of the web height changes in the auxiliary edging shown in Table 1 are-40 mm in all cases 1 to 4.

[ Table 1]

As shown in table 1, in the case of the assist edging, the material passing property was good when the pass was full. In contrast, when the hole pattern is not filled, a curve is generated. Referring to cases 2 to 4, in the conventional method and the method of the present invention, when the same cumulative web reduction is used in the auxiliary edging, even if the cumulative web reduction is such that the pass is not filled in the conventional method, the pass is filled in the method of the present invention, and the material passage property can be ensured satisfactorily (see cases 2 and 3 in table 1). In addition, since the auxiliary edging was performed by about 40mm, the values of the web height in the auxiliary edging shown in table 1 were-40 mm in all cases 1 to 4.

Next, the present inventors considered that the effect of suppressing dimensional defects and shape defects varies depending on the design specifications (rolling reduction, rolling schedule, etc.) of the auxiliary rolling in the present embodiment. Therefore, the transition of the flange width by the auxiliary rolling in the case of manufacturing the H-section steel using the 2000mm × 300mm sectional slab as the raw material was verified by the experiment.

Table 2 below shows the transition of the flange width in each pass when the first pass KH1 (i.e., the web partial pass) is performed by the flat rolling. In cases 1 to 3 of table 2, the number of times of performing the auxiliary rolling in each pass of the flat rolling was different. In the case where the auxiliary rolling is performed (i.e., cases 2 and 3), the transition of the flange width after the auxiliary rolling is performed is shown. In addition, the description of the 15 th to 23 th passes in the table shows the case where the preceding pass is subjected to edging before the flat rolling as the 1 st to 14 th passes, and the case where the 15 th and subsequent passes are the flat rolling.

In the auxiliary edging, an edging of about 40mm is carried out. Specifically, in case 2, edging of about 40mm was performed 1 time in two passes. In case 3, the edging of about 20mm was carried out twice in two passes in succession. As shown in table 2, the expansion of the flange width by the auxiliary rolling was about 24mm in any pass in case 2, and about 44mm in any pass in case 3.

[ Table 2]

Wherein "case 2: 1-time auxiliary edging "," case 3: the description "double auxiliary rolling" indicates the number of times of auxiliary rolling performed with two passes set to 1, and the expression "1-time opportunity" and "two-time opportunity" also indicates the number of times of auxiliary rolling with two passes set to 1. In fact, the number of auxiliary rolling passes in the 1-pass is not limited to 1 pass or a plurality of passes of two or more, and the rolling schedule is designed under the condition that the total rolling reduction is constant (that is, under the condition that the rolling height of the final pass is constant).

Table 2 shows the transition of the flange width in each pass in the case of performing the flat rolling without the auxiliary rolling as case 1 for reference.

In case 2 of table 2, the flange width after the auxiliary rolling is performed only 1 time for each pass without restricting the spread of the flange width for each pass shown in case 1.

As shown in case 2 of table 2, in the case of performing the auxiliary rolling at 1 pass, the flange width after the auxiliary rolling is larger than the edging pass width before the flat rolling (1010mm) in the 15 th to 17 th passes. Therefore, the hole pattern filling can be realized in the final hole pattern KE during auxiliary edging. The case described as "o" in table 2 achieved full pass and indicated good rolling stability.

On the other hand, since the flange width after the auxiliary rolling is smaller than the edging pass width before the flat rolling (1010mm) for the 18 th and subsequent passes, the edging final pass KE becomes unfilled during the auxiliary rolling, and there is a possibility that dimensional defects and shape defects occur. The case of "x" in table 2 indicates that the pass is not filled, and indicates that there is a problem in rolling stability.

The present inventors also verified that the auxiliary rolling was performed at two occasions (in the table, two auxiliary rolling operations) as shown in case 3 of table 2. In case 3, the flange width after the number of auxiliary beads is increased after the 18 th pass in which the pass is not filled in case 2, and auxiliary beads are performed twice without restricting the spread of the flange width is shown.

In the case of performing the auxiliary rolling in two occasions, the flange spread at the time of the auxiliary rolling is expected to be larger than that in the case of 1 occasion, and therefore, the pass filling at the final pass KE at the time of the auxiliary rolling can be achieved also in the pass of the later stage. Under the present verification conditions, as shown in table 2, pass filling was achieved in the final pass KE of the edging up to the 22 nd pass at the time of the auxiliary edging.

In general, it is desirable to stably perform the auxiliary edging in the later stage of the flat rolling. This is because the more auxiliary edging is performed in the latter pass of the flat rolling, the more the dimensional accuracy of the shape of the material to be rolled which is conveyed to the intermediate rolling and the finish rolling which are the subsequent steps can be improved, and the stability of the rolling and the dimensional accuracy of the product can be improved.

That is, it is found that by performing the auxiliary rolling in two occasions, the auxiliary rolling in the later stage can be realized without causing the dimensional defect or the shape defect of the material to be rolled, and the rolling efficiency can be improved.

For reference, table 3 below is a table showing transition of the flange width after the flat rolling in the conventional method (case 1) and transition of the flange width in consideration of flange widening at the time of the auxiliary rolling after each pass (case 2). As shown in table 3, in the conventional method, the flange width after the auxiliary rolling is larger than the edging pass width (1010mm) before the flat rolling only in the 15 th pass, and the pass filling is achieved in the final pass KE during the auxiliary rolling. On the other hand, since the flange width after the auxiliary rolling is smaller than the flange width before the flat rolling (1010mm) for the 16 th and subsequent passes, the final pass KE becomes unfilled during the auxiliary rolling, and there is a possibility that dimensional defects and shape defects occur.

[ Table 3]

As can be seen by comparing table 2 and table 3, when the method of the present invention is applied, the auxiliary hemming can be performed to achieve the full pass until the 17 th pass when the auxiliary hemming is performed only 1 time. In the case of performing the auxiliary rolling in two occasions, the auxiliary rolling for achieving the full pass can be performed up to the 22 nd pass. In contrast, in the conventional method, the auxiliary rolling for achieving the pass filling can be performed only up to the 15 th pass. That is, the method of the present invention can be used to perform auxiliary edging in a subsequent pass, and can suppress the occurrence of defects such as dimensional defects and shape defects, thereby performing the rough rolling step with high accuracy.

(ratio of amount of overflow (ridge forming width) in the 1 st flat hole type KH 1)

As described above, in the 1 st flat pass KH1 (see fig. 2 and the like) of the present embodiment, the raised portion 82b is formed in the center of the web portion 82 of the rolled material a. The formed bulging portion 82b is eliminated in the 2 nd floor shaping hole pattern KH2 of the rear stage. Then, after the ridge is eliminated, the inner dimension of the web is widened and rolled as needed to form an H-shaped rough profile.

The present inventors have found that by changing the width L1 of the ridge 82b formed in the 1 st pass KH1 (i.e., the amount of overflow of the inside dimension of the web in the roll forming at the 1 st pass KH1, hereinafter referred to as "overflow") this causes the flange width of the H-shaped thick section to be different. This is because the larger the width L1 of the raised part 82b, the easier it is to ensure the amount of the flange material, and the smaller the flange width is due to the longitudinal stretching action of the rolled material a when the raised part is eliminated later.

Therefore, the inventors of the present invention verified the relationship between the amount of the protrusion of the inner dimension of the web in the roll forming at the 1 st flat pass KH1 and the flange width of the H-shaped bar finally obtained.

Fig. 8 is a graph showing transition of the flange width in each pass when an H-shaped rough bar is formed by rolling forming of a total of 18 passes using the 1 st flatting pass KH1, the 2 nd flatting pass KH2, and the 3 widening passes in the later stage of the present embodiment. Fig. 8 is data obtained by using a raw material slab having a width of about 2000 mm.

The horizontal axis in the graph of fig. 8 is 1 to 18 passes, of which 1 to 13 passes correspond to the 1 st pass KH1, 14 and 15 passes correspond to the 2 nd pass KH2, and 16 to 18 passes correspond to the widening rolling pass.

Fig. 8 shows data obtained when the overflow amount L1 is changed. In fig. 8, the value shown in the following formula (1) is defined as an overflow rate, data in the case where the overflow rate is 12%, 17%, 23%, 28%, 33%, 39%, 44%, 49% is described, and the case where the overflow rate is 0% is described as a conventional method.

The rate of overflow [% ] (overflow L1/inner dimension of web L2). times.100. cndot. (1)

The overflow rate is increased so that the amount of material shrinkage (the amount of reduction in the amount of flange material) at the flange portion 80 in the 1 st flat hole type KH1 is reduced. Therefore, as shown in fig. 8, the flange width of the H-shaped rough bar finally obtained tends to increase as the flash rate increases. This tendency was also confirmed by experiments as shown in fig. 8. However, the flange width after the relief and widening rolling of the ridge portion in the 2 nd pass KH2 after the pass does not necessarily increase even if the relief rate is increased to a predetermined value or more. The reason for this is presumed to be that, when the overflow portion is increased, the amount of shrinkage of the flange material is increased when the bulge portion at the 2 nd pass KH2 is eliminated.

That is, when the method of forming the ridge portion 82b described in the present embodiment is employed as a manufacturing process of the large H-section steel, it is considered that there is a preferable range in the overflow rate. Therefore, the present inventors have focused on the relationship between the flash rate and the increase and decrease in the flange width after the H-shaped rough material is formed, and have derived a preferable numerical range of the flash rate.

Fig. 9 is a graph showing a relationship between the overflow rate and the flange width increase/decrease rate after the H-type rough material is formed, based on the data of fig. 8. The bead width increasing/decreasing rate in fig. 9 is a value indicating the bead width when the bead width is set to 0% (1.000), and the overflow rate is set to each value (12% to 55%).

As shown in fig. 9, in the region where the overflow rate is small, the flange width of the H-shaped rough bar tends to increase as the overflow rate becomes larger. However, in the region where the overflow rate is about 25% or more and about 50% or less, the flange width increase/decrease rate is substantially constant (see the dashed line portion in fig. 9).

As is clear from the results shown in fig. 9, in the case of manufacturing a large H-shaped steel product having a flange width larger than the conventional flange width, it is desirable to set the numerical range of the flash rate to 25% to 50% in view of the roll forming in which the flange width of the H-shaped rough bar is also desired to be large. In the roll forming process, it is preferable to set the overrun as low as possible from the viewpoint of preventing an increase in rolling load and improving production efficiency, and therefore it is desirable to set the overrun to about 25%.

(Effect)

According to the method for producing the H-shaped steel of the present embodiment described above, the first pass KH1 formed by the raised part 82b is used for the flat rolling performed after the edging. Thus, in the "auxiliary rolling" in which the rolled material a is returned to the edging final pass KE after the flat rolling and is subjected to the soft reduction rolling, the deterioration of the material passing property and the deterioration of the shape of the rolled material can be suppressed, and the auxiliary rolling can be stabilized. Further, the H-shaped rough bar 13 having a flange width larger than the conventional flange width can be roll-formed, and as a result, an H-shaped steel product having a flange width larger than the conventional flange width can be manufactured.

In addition, for example, when the H-type rough bar of the present embodiment is roll-formed on the basis of a material called a 300-thick slab having a thickness of about 300mm and a width of about 2000mm, the flange width of the H-type rough bar to be roll-formed can be maximized by setting the overflow rate to be in the range of 25% to 50% (more preferably, about 25%) during the formation of the raised portions 82b when the 1 st pass KH1, which is a so-called "local rolling pass", is used in the flat rolling.

Although the embodiment of the present invention has been described above as an example, the present invention is not limited to the illustrated embodiment. It will be apparent to those skilled in the art that various modifications and variations can be made within the scope of the idea described in the claims, and it is understood that these modifications and variations also fall within the scope of the present invention.

For example, in the above embodiment, the case where the flat rolling is performed after the rectangular-section material (slab) is subjected to the rolling forming by edging in the preceding stage of the flat rolling performed using the 1 st flat pass KH1 has been described, but the application range of the technique of the present invention is not limited to this. That is, the present invention can be applied to a case where a material to be rolled such as a beam blank is subjected to a flat rolling without passing through an edging step.

Industrial applicability

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

Description of the reference numerals

1. A rolling device; 2. heating furnace; 3. a sizing mill; 4. a roughing mill; 5. a universal intermediate mill; 8. a universal finishing mill; 9. an edging mill; 11. a slab; 13. h-shaped rough sections; 14. an intermediate material; 16. h-shaped steel products; 50. upper hole type rolls (edging final hole type); 51. down-hole rolls (edging final pass); 55. 56, a protrusion part (edging final hole type); 80. a flange portion; 82. a web portion; 82a, a pressing part; 82b, a bump (non-depressed portion); 85. a top hole type roller (No. 1 flat shaping hole type); 85a, a recess; 86. a lower hole type roll (No. 1 flat shaping hole type); 86a, a recess; 95. a punch roll (2 nd flat hole type); 96. a lower hole type roll (2 nd flat hole type); KH1, No. 1 flat hole type; KH2, No. 2 flat hole type; KE. Edging final hole patterns; GH. General flat shaping pass; t, production line; A. a material to be rolled.