JP7280503B2 - Method for manufacturing asymmetric H-beam steel with different left and right flange thicknesses - Google Patents

Description

TECHNICAL FIELD The present invention relates to a manufacturing method for manufacturing asymmetric H-section steel having left and right flanges with different thicknesses by universal rolling.

For example, it is known that various shaped steels such as H-shaped steel and rails are generally manufactured by groove rolling (caliber rolling) or universal rolling. Especially in recent years, the universal rolling method has been adopted by a series of rolling mills equipped with an intermediate universal rolling mill, an edger rolling mill, and a finishing rolling mill, from the viewpoint of uniform deformation, improvement of material quality, and high dimensional accuracy. It is done.

Asymmetrical H-shaped steel with different left and right flange thicknesses has great mechanical advantages, and is therefore suitable for use as a beam material for building structures, bridges, and the like. Specifically, when adopting an installation mode in which one flange is grounded on the ground or floor surface and the other flange is positioned above, the thinner flange is used as the ground surface and the thicker flange is used as the ground surface. known to be upwards. This is because the rigidity of the ground surface (or floor surface, etc.) includes the rigidity of the flange on the ground, while the rigidity of the upper flange alone is required, so the upper flange should be made thicker. This is because it is desirable to According to this aspect, a beam member having desired rigidity can be manufactured with a light weight and a small amount of material, so productivity can be improved and costs can be reduced.

However, since the asymmetrical H-section steel with different left and right flange thicknesses has an asymmetrical cross section, it often causes defects such as distortion and bending in the manufacturing process, and various technologies have been invented to improve it. there is

For example, Patent Literature 1 discloses a rolling method for asymmetric H-section steel, and describes that bending occurs during the production thereof. In the technique of Patent Literature 1, the left and right vertical rolls, which are generally not driven, are individually driven, and the left and right rotation speeds (number of rotations) are independently adjusted to suppress bending.

In addition, for example, Patent Document 2 discloses a technique for suppressing thrust displacement caused by a thrust load applied to horizontal rolls due to non-uniform rolling loads on the left and right vertical rolls in universal rolling of asymmetric H-section steel. disclosed. Specifically, by cooling one (one side) of the left and right flanges, the rolling load of the flange is increased and the thrust load acting on the horizontal rolls is reduced.

JP-A-5-177201 JP 2006-68777 A

However, in the technique described in Patent Document 1, it is generally necessary to newly install or modify equipment for driving the vertical rolls that are non-driven and driven rolls, which increases equipment costs and complicates the equipment configuration. Concerned. In addition, the technique described in Patent Document 2 aims to equalize the rolling loads of the left and right vertical rolls, and does not disclose any appropriate conditions for rolling an asymmetric H-section steel without causing distortion or bending. It has not been.

In view of the above circumstances, it is an object of the present invention to suppress defects such as bending that occur in the rolled material when manufacturing asymmetric H-shaped steel with different left and right flange thicknesses with existing manufacturing equipment, and to stably It is to provide a technique capable of manufacturing an asymmetric H-section steel.

In order to achieve the above object, according to the present invention, there is provided a method for manufacturing an asymmetric H-section steel having left and right flanges with different thicknesses, wherein the intermediate rolling process is performed in an intermediate rolling mill train having one or more intermediate universal rolling mills. and a finish rolling step performed by a finish universal rolling mill, wherein universal rolling is performed in the intermediate rolling step and the finish rolling step under rolling conditions in which the thickness reduction rate for the left and right flange portions of the material to be rolled is equal, universal When the rolling conditions for rolling satisfy the following formula (1), universal rolling is performed under the relevant rolling conditions, and when the rolling conditions for universal rolling do not satisfy the following formula (1), the thickness of the material to be rolled is thin. A method for producing an asymmetric H-beam is provided, characterized in that universal rolling is performed by applying means for promoting side flange width widening.
0<ΔBi≦0.2tf (1)
However, ΔBi: web inner width widening amount in each rolling mill, tf: thin side flange thickness before rolling in each rolling mill.

The means for promoting the widening of the width of the thin-walled flange of the material to be rolled may be a lubricating means for supplying a lubricant to the side surface of the horizontal roll that contacts the thin-walled flange portion of the material to be rolled.

The means for promoting the widening of the thin-walled flange width of the material to be rolled is a vertical roll diameter that presses down the thin-walled flange portion of the material to be rolled, and a vertical roll diameter that presses down the thick-walled flange portion of the material to be rolled. The diameter of the vertical roll on the thin side may be designed to be 0.33 to 0.4 times the diameter of the vertical roll on the thick side.

The means for promoting the widening of the thin-walled side flange width of the material to be rolled may be a rolling condition design that applies a rolling condition that satisfies the following formula (2) in universal rolling.
rf−0.2≦rw≦rf−0.1 (2)
However, rw: web thickness reduction rate, rf: flange thickness reduction rate.

The intermediate rolling step and the finish rolling step may be performed by one rolling mill pass rolling in one direction.

According to the present invention, when manufacturing an asymmetric H-section steel having left and right flanges with different thicknesses using existing manufacturing equipment, it is possible to stably produce an asymmetric H-section steel by suppressing through-material defects such as bending that occur in the rolled material. can be manufactured.

It is a schematic explanatory drawing about the production line of asymmetrical H-section steel. FIG. 2 is a schematic explanatory diagram showing an example of the configuration of an intermediate rolling mill train; It is a schematic explanatory drawing about the roll structure of an intermediate|middle universal rolling mill. It is a schematic explanatory drawing about the roll structure of an edger rolling mill. Numerical bending during rolling when the reduction ratio of the thin flange portion is changed under the fixed conditions of 0.34 reduction ratio of the thick flange portion, 0.31 reduction ratio of the web, and 8 mm internal width expansion for the material to be rolled. It is an analyzed graph. Graph showing changes in the amount of movement in the width direction of each part of the material A to be rolled and the amount of expansion of each flange width under the condition that the reduction ratio of the thick flange portion and the reduction ratio of the thin flange portion are equal. be. FIG. 10 is a schematic explanatory diagram of deformation of a material to be rolled when only a thin flange portion is pushed down; 4 is a graph showing the relationship between one-side inner width widening amount/flange thickness and flange width reduction rate when performing universal rolling accompanied by width widening on a generally H-shaped material to be rolled. Rolling when lubricating only the side surface of the horizontal roll contacting the thin flange under the conditions of 0.34 rolling reduction of the left and right flanges, 0.31 web rolling reduction, and 8 mm internal widening of the material to be rolled. It is a graph obtained by numerically analyzing the bending of . The diameter of the vertical roll and the thickness of the thick flange are reduced under the conditions of a fixed rolling reduction of 0.34 for the left and right flanges, a rolling reduction of 0.31 for the web, and an inner widening amount of 8 mm. It is the graph which numerically analyzed bending at the time of rolling when the ratio with a vertical roll diameter was changed. 3 is a graph obtained by numerically analyzing the influence of the web reduction rate on bending under the conditions of a fixed rolling reduction rate of 0.34 for left and right flange portions and an inner width expansion amount of 8 mm for a material to be rolled.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description. In this specification, the “universal rolling mill” refers to a rolling mill that performs rolling with large stretching using horizontal rolls and vertical rolls when rolling shaped steel, and the “edger rolling mill” is combined with the universal rolling mill. In this specification, these rolling mills are sometimes referred to as "rolling stands" or simply "stands".

(Overview of production line)
FIG. 1 is an explanatory view of a production line T for asymmetric H-section steel (so-called different thickness H-section steel) having different left and right flange thicknesses, including a rolling facility 1 according to the present embodiment. As shown in FIG. 1, a heating furnace 2, a row of roughing mills 4, a row of intermediate rolling mills 5, and a finishing universal rolling mill 8 are arranged in order from the upstream side of the production line T. As shown in FIG. In the following description, the steel materials in the production line T are collectively referred to as "rolled material A", and their shapes may be indicated by dashed lines, oblique lines, etc. in each figure. Further, in this specification, it is assumed that the material A to be rolled is formed by rolling in a so-called "H posture" in which the flange portions are positioned on the left and right sides in the rolling direction. In addition, in each rolling stage of the material A to be rolled, the portion corresponding to the flange of the final H-shaped steel product is called a flange portion 12, one of which is a thin flange portion 12a, and the other is a thick flange portion 12b. is sometimes called. Also, the portion corresponding to the web may be called a web portion 20 .

As shown in FIG. 1 , in the production line T, a material to be rolled A, which is a material 11 such as a slab or a bloom, extracted from a heating furnace 2 is roughly rolled in a row of rough rolling mills 4 . Then, it is subjected to intermediate universal rolling in the intermediate rolling mill train 5 . Usually, a plurality of stands such as breakdown mills and roughing mills are arranged in the roughing mill row 4, and the rolls of these stands are engraved with, for example, a total of about 4 to 6 grooves. . By performing several tens of passes of reverse rolling via these calibers, an asymmetrical dog-bone shaped H-shaped blank 13 is formed. The thickness ratio of the portions corresponding to the left and right flanges of the H-shaped blank 13 formed here is set to a ratio suitable for forming the left and right flange thickness ratio of the final product after intermediate rolling. Next, the H-shaped blank 13 is subjected to predetermined rolling in the row of intermediate rolling mills 5 to form an asymmetric intermediate blank 14 . Then, the intermediate material 14 is subjected to finish rolling in one-direction, one-pass rolling in the finishing universal rolling mill 8 to obtain a final product shape, and an asymmetric H-section steel product 16 is manufactured.

(Outline of configuration of intermediate rolling mill row)
Next, an overview of the configuration of the intermediate rolling mill row 5 shown in FIG. 1 will be described. FIG. 2 is a schematic explanatory diagram showing an example of the configuration of the intermediate rolling mill row 5. As shown in FIG. The configuration shown in FIG. 2 is an example, and the configuration of the intermediate rolling mill train 5 in the present invention is not limited to this.

As shown in FIG. 2, the intermediate rolling mill train 5 comprises seven intermediate universal rolling mills U1 to U7 and four edger rolling mills E1 to E4. Intermediate universal rolling mills U1 to U7 are universal rolling mills that reduce the thickness of the web with horizontal rolls and the thickness of flanges with vertical rolls, and finally roll and shape the product to approximately the thickness of the product. Further, the edger rolling mills E1 to E4 are rolling mills having an auxiliary role of shaping the tip of the flange which is not rolled down by the universal rolling mill. In the illustrated configuration, in a configuration in which U1 to U7 are arranged in order from upstream, E1 is arranged between U1 and U2, E2 is arranged between U3 and U4, E3 is arranged between U5 and U6, E4 is arranged between U6 and U7. In the intermediate rolling mill row 5 configured in this way, the intermediate material 14 is shaped by subjecting the material A to be rolled in one direction to rolling in one rolling mill and one pass.

(Schematic configuration of intermediate universal rolling mill)
Next, the intermediate universal rolling mills U1 to U7 constituting the intermediate rolling mill row 5 shown in FIG. 2 will be described. FIG. 3 is a schematic illustration (front cross-sectional view) of the roll configuration of the intermediate universal rolling mill U1, where (a) shows an outline of the roll configuration and (b) shows an outline of the cross section during rolling. As shown in FIG. 3, the intermediate universal rolling mill U1 is provided with a pair of upper and lower horizontal rolls 21 and 22 and a pair of left and right vertical rolls 31 and 32 . The horizontal rolls 21 and 22 are configured so that their peripheral surfaces can come into contact with the web portion 20 of the material A to be rolled, and part of the roll side surfaces can come into contact with the inner surfaces of the flange portions 12 (12a and 12b). It is configured. Further, the vertical rolls 31 and 32 are configured such that the roll peripheral surfaces can contact the outer surfaces of the flange portions 12 (12a and 12b). In the illustrated configuration, the peripheral surface of one vertical roll 31 is in contact with the outer surface of the thin flange portion 12a, and the peripheral surface of the other vertical roll 32 is in contact with the outer surface of the thick flange portion 12b. In addition, in FIG. 3, illustration of the roll shaft of each roll, the housing of the rolling mill, and the like is omitted.

In the intermediate universal rolling mill U1 shown in FIG. 3, the peripheral surfaces of the horizontal rolls 21 and 22 are in contact with the web portion 20 of the material A to be rolled, and the thickness direction of the web portion 20 is reduced. Further, part of the side surfaces of the horizontal rolls 21 and 22 contact the inner surface of the flange portion 12 (12a, 12b) of the material A to be rolled, and the inner surface of the flange portion 12 So-called internal widening is performed, which pushes the In addition, with respect to the flange portions 12 (12a, 12b) of the material A to be rolled, part of the side surfaces of the horizontal rolls 21, 22 are in contact with the inner surfaces of the flange portions 12 (12a, 12b), and the vertical rolls 31, 32 contact with the outer surface of the flange portion 12 (12a, 12b), and a pressure is applied to the thickness direction of the flange portion 12 (12a, 12b). In this manner, the flange portions 12 (12a, 12b) and the web portion 20 of the material A to be rolled are rolled down to a predetermined thickness.

Although the schematic configuration of the intermediate universal rolling mill U1 is illustrated as an example in FIG. 3, the seven intermediate universal rolling mills U1 to U7 arranged in the intermediate rolling mill row 5 all have the same roll configuration. are doing. In these intermediate universal rolling mills U1 to U7, in principle, one rolling mill pass rolling is performed in one direction, and the material A to be rolled is sequentially sent to the subsequent rolling mills (rolling stands).

In universal rolling of general H-section steel, it was thought that bending of the material A to be rolled in universal rolling could be suppressed by equalizing the rolling reduction of the left and right flange portions. However, according to the studies of the present inventors, it has been found that depending on the rolling conditions, large bending may occur even if the rolling reduction of the left and right flange portions is the same, resulting in a defective threading. Therefore, the present inventors investigated the rolling characteristics of the asymmetrical rolled material A having different left and right flange thicknesses by numerical analysis regarding rolling in these intermediate universal rolling mills U1 to U7, and made earnest studies to find appropriate rolling conditions. did The results of this study will be described later with reference to graphs and the like.

(Schematic configuration of edger rolling mill)
Next, a schematic configuration of the edger rolling mills E1 to E4 will be described. FIG. 4 is a schematic explanatory diagram (sectional front view) of the roll configuration of the edger rolling mill E1. As shown in FIG. 4, the edger rolling mill E1 is provided with a pair of upper and lower horizontal rolls 41 and 42 . The horizontal rolls 41 and 42 are configured such that a part of the roll peripheral surface thereof can contact only the flange width direction tip portions of the left and right flange portions 12 (12a and 12b).

In the edger rolling mill E1 shown in FIG. 4, the peripheral surfaces of the upper and lower horizontal rolls 41 and 42 are in contact only with the widthwise leading ends of the left and right flange portions 12 (12a and 12b) of the material A to be rolled, and the intermediate universal rolling mill U1 In ∼U7, the tip of the flange portion 12, which is to be unreduced, is shaped by light reduction. FIG. 4 shows the schematic configuration of the edger rolling mill E1 as an example, but all of the four edger rolling mills E1 to E4 have the same roll configuration. Such edger rolling is performed by one-direction, one-pass rolling between arbitrary stands of a rolling mill train composed of intermediate universal rolling mills U1 to U7. and U4, between U5 and U6, and between U6 and U7, respectively.

(Rolling characteristics in universal rolling of asymmetric rolled material A)
The present inventors studied the rolling characteristics of a substantially H-shaped asymmetrical material A to be universally rolled, for example, in the intermediate universal rolling mills U1 to U7 with inner widening. FIG. 5 shows the thickness reduction ratio of the thick flange portion of 0.34 and the web reduction ratio of 0.34 for a rolled material A (H-shaped coarse material 13) having a web width of 448 mm, a flange thickness of 32 mm/16 mm, and a web thickness of 14 mm. 31 is a graph obtained by numerically analyzing the bending during rolling when the rolling reduction of the thin flange portion is changed under the condition that the inner widening amount is fixed at 8 mm. In the graph of FIG. 5, the bending is evaluated by the deviation of the web height center position according to the distance from the roll bite exit of the material A to be rolled. are doing.

As shown in FIG. 5, when the rolling reduction ratio of the thick flange portion and the rolling reduction ratio of the thin flange portion are equal (both set to 0.34), the material A to be rolled is in the direction of the thick flange (hereinafter, both the thick side and description) is greatly curved. As the rolling reduction of the thin flange portion 12a decreases, bending toward the thick side is suppressed, and the bending is almost eliminated under the condition that the rolling reduction of the thin flange portion 12a is set to 0.28. In addition, it can be seen that bending in the direction of the thin flange portion (hereinafter also referred to as the thin side) occurs under the condition that the rolling reduction of the thin flange portion 12a is 0.26.

In this way, by making a difference between the reduction ratio of the thick flange portion 12b and the reduction ratio of the thin flange portion 12a, it is possible to suppress the bending of the rolled material A, while the flange thickness of the H-shaped raw material There are problems such as the fact that the ratio must be larger than the flange thickness ratio of the product, and the difference in width between the left and right flanges increases according to the difference in rolling reduction, making it difficult to obtain a final product with a desired shape. be.

In view of such circumstances, the present inventors further verified the phenomenon that bending occurs on the thick side when the rolling reduction ratio of the thick flange portion 12b and the thin flange portion 12a are made equal. FIG. 6 shows the widthwise movement of each portion (thick side flange, web center, thin side flange) of the material A to be rolled under the condition that the rolling reduction ratio of the thick flange portion 12b and the thin flange portion 12a are made equal. Fig. 10 is a graph showing changes in the amount (amount of movement in the high direction of the web) and changes in the amount of widening of each flange (thick side flange, thin side flange) (flange width widening). The horizontal axis of the graph in FIG. 6 indicates the distance when the lowest rolling point of the target roll is set to 0.

As shown in FIG. 6, after the width of the thin flange narrows once, it widens due to contact with the vertical rolls, whereas the width of the thick flange widens without reducing due to contact with the vertical rolls. ing. From this result, it was found that when widening rolling is performed during universal rolling, the inner side of the flange is expanded by the side of the horizontal roll, but only the flange width of the thin side flange is reduced at that time. . That is, even if the rolling reduction ratio of the thick flange portion 12b and the thin flange portion 12a are made equal, the reduction ratios of the two are not equal, and the phenomenon is observed that the reduction ratio of the thin flange portion 12a is larger. be done. Such a phenomenon is considered to be caused by roll shaping so that the entire thin flange portion 12a is pressed downward by the frictional force of the side surface of the horizontal roll when the flange thickness is thin.

FIG. 7 is a schematic illustration of deformation of the material to be rolled when only the thin flange portion 12a is pushed down. As shown in FIG. 7, when universal rolling with widening rolling is performed on a material A to be rolled having different left and right flange thicknesses, as described above, only the flange width of the thin side flange is reduced, and the thin flange portion 12a is reduced. The rate of area reduction is larger (see the shaded area in FIG. 7). The reduced thickness of the flange width on the thin side is transferred to the elongation in the longitudinal direction (rolling direction) of the material A to be rolled, so the elongation of the flange on the thin side becomes greater than that on the thick side, resulting in bending. is thought to have occurred.

(Appropriate rolling conditions that do not cause bending)
In view of the rolling characteristics as discussed above, the present inventors have found that when universal rolling with widening rolling is performed on a material A to be rolled having different left and right flange thicknesses, the amount of inner widening and the reduction rate of the flange width was investigated by numerical analysis, and the appropriate rolling conditions were earnestly investigated.

In view of the fact that the cause of the bending of the rolled material A is the decrease in the flange width, as described above, the present inventors have found that the inner width of a general substantially H-shaped rolled material is expanded. Numerical analysis was conducted to investigate the relationship between the amount of internal widening and the rate of reduction in flange width during universal rolling. FIG. 8 is a graph showing the relationship between the one-side inner widening amount/flange thickness and the flange width reduction rate when performing universal rolling with widening on a general substantially H-shaped rolled material. These are the investigation results for the thickness values of 16.0 mm to 32.0 mm. In addition, only when the flange thickness is 16.0 mm, the numerical values are calculated at the rolling reduction rate of 0.2 (20%), 0.25 (25%), and 0.3 (30%), and for the other flange thicknesses, the rolling reduction rate A value at 0.25 (25%) was calculated.

As shown in FIG. 8, the reduction rate of the flange width is arranged by the ratio of the internal widening amount and the flange thickness regardless of the reduction rate, and it can be seen that the tendency is generally the same under any conditions. Under any conditions, when the ratio of one-side inner widening/flange thickness exceeds 0.1, the flange width tends to decrease sharply. Based on the analysis results of FIG. 8, it was found that in universal rolling with inner widening, the flange width decreases when the inner widening amount/flange thickness exceeds 0.2, so the inner widening amount/flange thickness is 0.2 or less (20% or less), the reduction in the flange width is suppressed, and it is possible to pass the material without being affected by the lateral difference in area reduction rate due to the reduction in the flange width.

From the analysis results shown in FIG. 8 above, when performing universal rolling with inner width widening on the material A to be rolled with different left and right flange thicknesses, the inner web width widening amount at each rolling mill is ΔBi, and each rolling mill Assuming that the thickness of the thin side flange before rolling is tf, it is possible to stably perform rolling molding by suppressing defects such as bending by setting rolling conditions that satisfy the following formula (1). It was shown that there is
0<ΔBi≦0.2tf (1)
Here, the reason why the value of ΔBi is greater than 0 is that the expression (1) defines the rolling characteristics under the conditions in which the inner web widening is performed.

In addition, it is preferable that the inner widening amount when performing universal rolling with inner widening on the material A to be rolled is less than the sum of the thicknesses of the right and left flanges. This is because if you try to widen the inside of the flange more than the thickness of the flange, there is a concern that the parallel part of the horizontal roll (surrounding surface) will press down the tip of the flange before the inner surface of the flange is pushed out (widened) by the side surface of the horizontal roll. Because there is That is, the flanges are excessively pressed down in the width direction at the parallel portions of the horizontal rolls, and there is a risk that the rolling molding will be accompanied by shape defects such as flange buckling or crushing of the flanges.

(Means for suppressing poor threading such as bending)
As described above, by performing universal rolling under the rolling conditions that satisfy formula (1), rolling and shaping can be stably performed by suppressing defects such as bending for the material A to be rolled, which has different flange thicknesses on the left and right sides. However, on the other hand, if the rolling conditions that satisfy the above formula (1) cannot be realized due to reasons such as equipment conditions, the thickness for the left and right flange portions (thin flange portion 12a and thick flange portion 12b) It is desirable to provide means (thin-side flange width expansion promoting means) for promoting the flange width expansion of the thin flange portion 12a more than the flange width expansion of the thick flange portion 12b, while making the rolling reduction equal. By accelerating the expansion of the flange width of the thin flange portion 12a, it is possible to adjust the expansion of the flange width on the thin side and the thick side so that they are the same as much as possible, and as a result, defective material passing such as bending is suppressed. will be Specific means for this will be described below.

(First Thin Side Flange Widening Promoting Means)
First, as the first means for promoting widening of the width of the thin-walled side flange, it is conceivable to use a lubricating means for adding a lubricant to the side surface of the horizontal roll that contacts the thin-walled flange portion 12a. That is, the side surface of the horizontal roll that contacts the thick flange portion 12b is not lubricated, and only the side surface of the horizontal roll that contacts the thin flange portion 12a is lubricated. It is conceivable to make the friction coefficient non-uniform on the left and right. The lubricating material used at that time is not particularly limited, but lubricating oil discharged from a general nozzle or the like may be used. Hereinafter, the case where additional lubricant is supplied to the normal rolling state as described above is called "lubricated", and the case where it is not supplied is called "no lubrication".

FIG. 9 shows the rolling reduction ratio of the left and right flanges of 0.34 and the web reduction ratio of 0.31 for the rolled material A (H-shaped coarse material 13) with a web width of 448 mm, a flange thickness of 32 mm/16 mm, and a web thickness of 14 mm. 3 is a graph obtained by numerical analysis of bending during rolling when only the side surface of a horizontal roll in contact with a thin flange portion is lubricated under the condition that the internal width is fixed to 8 mm. FIG. 9 shows a case where lubrication is not performed (no lubrication) and a case where the range (lubrication range) where the coefficient of friction is 0.1 by lubrication is changed as shown (three conditions in the figure). The flange width difference (mm) associated with the difference in coefficient of friction (thick side and thin side) and the bending amount (mm) occurring on the downstream side are illustrated. In addition, under the analysis conditions of the graph shown in FIG. 9, the coefficient of friction on the thick side was set to 0.3.

As shown in FIG. 9, by lubricating only the side surface of the horizontal roll that contacts the thin flange portion, the flange width difference tends to decrease, and as the flange width difference decreases, the amount of bending that occurs also decreases. I know there is. In addition, from the comparison of the three conditions in the figure, lubrication of the corner portion (area having curvature) is greater than that of the straight portion on the inner surface of the thin flange portion, and the amount of bending is reduced (bending suppression effect). I know it's big. The effect of reducing the friction coefficient by lubrication is estimated to be about 30 to 50% of the friction coefficient without lubrication, and the bending suppression effect varies depending on the rolling conditions. It is desirable to lubricate an area of the inner surface of the part that includes at least the corners.

As described above with reference to FIG. 9, as the first thin-walled flange width widening promotion means, the lubricant is supplied only to the horizontal roll side surface in contact with the thin-walled flange portion 12a, and the material to be rolled is supplied to the horizontal roll side surface. It was found that by making the coefficient of friction between A and A nonuniform on the left and right, it is possible to suppress defects such as bending and to stably carry out rolling molding.

(Second Thin Side Flange Widening Promoting Means)
Further, as a second thin-walled side flange width widening promotion means, a roll configuration in which the diameter of the vertical rolls for pressing down the thin-walled flange portion 12a and the diameter of the vertical rolls for pressing-down the thick-walled flange portion 12b in universal rolling are different. It is conceivable to use In universal rolling, when the diameter of the horizontal roll is constant, if the diameter of the vertical roll is changed, the amount of flange width expansion varies due to the difference in the contact arc length between the material A to be rolled and the vertical roll. I know there is a trend. Specifically, it is known that the amount of expansion of the flange width is greater when the reduction is performed using the small-diameter vertical rolls than when the reduction is performed using the large-diameter vertical rolls.

FIG. 10 shows the rolling reduction ratio of the left and right flanges of 0.34 and the web reduction ratio of 0.31 for the rolled material A (H-shaped rough material 13) with a web width of 448 mm, a flange thickness of 32 mm/16 mm, and a web thickness of 14 mm. 4 is a graph showing numerical analysis of bending during rolling when the ratio between the diameter of the vertical roll that presses down the thin flange portion and the diameter of the vertical roll that presses down the thick flange portion is changed under the condition that the inner width widening amount is fixed at 8 mm. . In FIG. 10, the conditions for the vertical roll diameter (thick side/thin side) are set to 475/900 (mm), 950/950 (mm), 950/475 (mm), and 950/360 (mm). The flange width difference (mm) associated with the difference in the diameter of the vertical rolls on the left and right (thick side and thin side) and the amount of bending (mm) occurring on the downstream side are shown.

As shown in FIG. 10, by making the diameter of the vertical roll on the thin side smaller than the diameter of the vertical roll on the thick side, the flange width difference is reduced (that is, the amount of expansion of the width of the left and right flanges is almost equal). As a result, it has been found that rolling defects such as bending can be suppressed and rolling molding can be carried out stably.

As for the difference between the diameters of the left and right vertical rolls, if the diameter of the vertical roll on the thin side is smaller than the diameter of the vertical roll on the thick side, the effect of suppressing bending can be obtained. It is desirable that the diameter is 0.4 times or less the diameter of the vertical roll on the thick side. That is, for example, when the vertical roll diameter (thick side/thin side) shown in FIG. 10 is 950/360 (mm), bending is suppressed. increases, it can be seen that the amount of bending can be suppressed to some extent by setting the diameter of the vertical roll on the thin side to 0.4 times or less that of the vertical roll on the thick side.
On the other hand, if the diameter of the vertical rolls on the thin side is designed to be less than 0.33 times the diameter of the vertical rolls on the thick side, the load bearing capacity of the rolls may decrease and fall below the rolling load.
Therefore, it is preferable to design the vertical roll diameter on the thin side to be 0.33 to 0.4 times the diameter of the vertical roll on the thick side.

(Third Thin Side Flange Widening Promoting Means)
Further, the present inventors focused on the fact that in universal rolling, the flange portion 12 and the web portion 20 of the material A to be rolled are rolled integrally, and the left and right cross-sectional areas of the entire cross section of the material A to be rolled are stretched. Taking this into account, it was found that the thickness reduction ratio of the flange (flange reduction ratio)>the thickness reduction ratio of the web (web reduction ratio) tends to increase the area reduction on the thick side. In view of this trend, focusing on the ratio of the flange reduction rate and the web reduction rate in universal rolling, rolling conditions are designed to reduce the web reduction rate, thereby suppressing defects such as bending. is estimated.

Fig. 11 shows a case where the rolling reduction ratio of the left and right flange portions is 0.34 and the inner width widening amount is 8 mm for the rolled material A (H-shaped rough material 13) with an inner web width of 448 mm, a flange thickness of 32 mm/16 mm, and a web thickness of 14 mm. 4 is a graph obtained by numerically analyzing the influence of web reduction rate on bending under fixed conditions. FIG. 11 analyzes the rolling deflection and the width difference between the left and right flanges that accompany the flange reduction ratio-web reduction ratio when the web reduction ratio is varied from 0.17 to 0.31.

As shown in FIG. 11, it can be seen that by making the web reduction rate smaller than the flange reduction rate, defective material passing such as bending is suppressed. According to FIG. 11, it can be seen that bending is suppressed as the difference between the flange rolling reduction and the web rolling reduction increases. In the analysis result of FIG. 11, for example, if the flange reduction rate-web reduction rate>0.1, it can be said that the bending amount is passable. On the other hand, in universal rolling, if the web reduction ratio is too small, the web thickness will decrease before rolling, and there is a risk that the web portion 20 will not be rolled. It is preferable to limit the difference to 0.2 at most. The analysis results and the like based on FIG. 11 are summed up with the web thickness reduction rate rw and the flange thickness reduction rate rf, and the conditions shown in the following equation (2) are obtained.
rf−0.2≦rw≦rf−0.1 (2)
By making the web reduction rate smaller than the flange reduction rate under the condition that satisfies this formula (2), it is possible to suppress defects such as bending and to stably carry out roll shaping. Here, the thickness reduction rate such as rf and rw is a value represented by "(thickness before rolling-thickness after rolling)/thickness before rolling".

It should be noted that the above-described first to third thin-walled side flange width expansion promotion means are used when universal rolling is performed on the H-shaped blank 13 having the same right and left flange thickness ratio as the product with the same right and left rolling reduction. When applied, each means may be applied alone, or these first to third thin side flange width expansion promoting means may be applied in combination. For example, in a certain universal rolling pass, under the condition that the diameter ratio of the left and right vertical rolls is different and the web reduction ratio is smaller than the flange reduction ratio, depending on the condition of the rolled material, the presence or absence of lubrication on the side surface of the horizontal roll on the thin side is controlled. Adjustment is also possible.

(Effect)
As described above, under the rolling conditions represented by the formula (1) calculated based on the analysis results shown in FIG. The reduction in the flange width is suppressed regardless of the width of the flange, and the material can be passed through without being affected by the difference in area reduction rate between the left and right sides due to the reduction in the flange width. For example, when an H-shaped blank 13 having the same thickness ratio of left and right flanges as the product is subjected to universal rolling with the same left and right rolling reduction to produce an asymmetric H-shaped steel product as the final product, each universal rolling By setting the rolling condition to the rolling condition represented by the formula (1), it is possible to suppress the failure of the through-material.
That is, when manufacturing an asymmetric H-section steel product in an existing facility (universal rolling mill with an existing configuration), by simply adjusting the rolling conditions, the occurrence of bending of the material A to be rolled during rolling and shaping can be suppressed. It is possible to improve rolling properties and realize stabilization of rolling. As a result, the asymmetric H-section steel can be stably manufactured, and the productivity is improved.

Further, when universally rolling the H-shaped blank 13 having the same right and left flange thickness ratio as the product with the same left and right rolling reduction, even under rolling conditions that do not satisfy the above formula (1), By performing universal rolling by applying the above-described first to third thin-wall side flange width expansion promoting means, the occurrence of bending of the rolled material A during rolling and shaping is suppressed, the material passing property is improved, and the rolling process is improved. Stabilization can be achieved. As a result, the asymmetric H-section steel can be stably manufactured, and the productivity is improved.

Although an example of the embodiment of the present invention has been described above, the present invention is not limited to the illustrated form. It is obvious that a person skilled in the art can conceive various modifications or modifications within the scope of the idea described in the claims, and these naturally belong to the technical scope of the present invention. understood as a thing.

For example, in the above embodiment, the case where the technology of the present invention is applied to the intermediate universal rolling mills U1 to U7 has been described as an example, but the scope of application of the present invention is not limited to this. That is, the technology of the present invention can be generally applied to universal rolling mills, and can be applied not only to the intermediate universal rolling mills U1 to U7 but also to the finishing universal rolling mill 8. Moreover, it may be applied to any stand that constitutes the intermediate rolling mill row 5, or may be applied to all the stands. In addition, the configuration of the edger rolling mills E1 to E4 can also be applied to the case where a configuration other than the configuration illustrated in FIG. 4 is used. In addition to slabs and blooms with rectangular cross sections, the method can also be applied to the production of asymmetric H-beams using materials such as continuously cast beam blanks.

In the production line T configured as described with reference to FIGS. 1 to 4 in the above embodiment, an asymmetrical H-section steel (width 492 mm web thickness 6 mm thick flange thickness 12 mm thin flange thickness 8 mm) with different left and right flange thicknesses is manufactured. In this case, in Example 1, rolling is performed under rolling conditions that satisfy the above formula (1), and in Example 2-1, in a rolling mill that does not satisfy the above formula (1), the width of the second thin-walled side flange is expanded. In Example 2-2, rolling molding was performed by applying the first thin side flange widening promoting means to the rolling mill that did not satisfy the above formula (1). On the other hand, in Comparative Examples 1 and 2, rolling was performed in a rolling mill that did not satisfy the above formula (1) without taking any measures. Table 1 below shows the rolling conditions (inner web width (mm), inner width widening amount ΔBi (mm), ΔBi/tf), the presence or absence of horizontal roll lubrication, and the vertical roll diameter (mm). Table 1 also shows the dimensions (mm) of the material to be rolled at each rolling stage, which are common to both Examples and Comparative Examples.

In Example 1, the inner width of the web of the H-shaped coarse material is set to 455 mm, and the inner width widening amount ΔBi in U1 to U7 is set to 6 mm, 4 mm, 2 mm, 2 mm, 1 mm, 1 mm, and 1 mm, respectively. The rolling conditions were designed so that ΔBi/tf was 0.2 or less (conditions satisfying formula (1)) in any of the stands U1 to U7. As a result, in Example 1, the rolling could be carried out without any defects in the rolling material.

Further, in Comparative Example 1, the inner width of the web of the H-shaped coarse material was set to 445 mm, the inner width widening amount ΔBi of U1 to U7 was set to 8 mm, 8 mm, 6 mm, 2 mm, 1 mm, 1 mm, and 1 mm, respectively, and U2 and U3 The rolling conditions were designed so that ΔBi/tf exceeded 0.2 (conditions not satisfying formula (1)). As a result, in Comparative Example 1, the material to be rolled was greatly bent at U2, resulting in a material failure, and the rolling after U3 was impossible.

In Comparative Example 2, the width of the inner web of the H-shaped coarse material was set to 455 mm, the inner width widening amount ΔBi in U1 to U7 was set to 3 mm, 3 mm, 3 mm, 3 mm, 3 mm, 1 mm, and 1 mm, respectively, and ΔBi in U5 The rolling conditions were designed so that /tf exceeded 0.2 (conditions not satisfying the formula (1)). As a result, in Comparative Example 2, the material to be rolled was greatly bent at U5, resulting in a material failure, and the rolling after U6 was impossible.

Further, in Example 2-1, the inner width of the web of the H-shaped raw material was set to 455 mm, the inner width widening amount ΔBi in U1 to U7 was set to 3 mm, 3 mm, 3 mm, 3 mm, 3 mm, 1 mm, 1 mm, respectively, and U5 The rolling conditions are designed so that ΔBi / tf exceeds 0.2 (conditions that do not satisfy formula (1)), and the vertical roll diameter is set to 950 mm on the thick side and 360 mm on the thin side in U5, and the vertical roll diameter on the thin side is made smaller than the diameter of the vertical roll on the thick side (the second thin-wall side flange width expansion promoting means is applied). As a result, in Example 2-1, the rolling could be carried out without any defects in the rolling material.

Further, in Example 2-2, the inner width of the web of the H-shaped raw material was set to 455 mm, the inner width widening amount ΔBi in U1 to U7 was set to 3 mm, 3 mm, 3 mm, 3 mm, 3 mm, 1 mm, and 1 mm, respectively, and U5 The rolling conditions were designed so that ΔBi/tf exceeded 0.2 (conditions not satisfying formula (1)), and lubrication was applied only to the horizontal roll side surface on the thin side in U5 (the first thin side (applied means for promoting flange width expansion). As a result, in Example 2-2, the rolling could be carried out without any defects in the rolling material.

Further, as Example 3, in the production line T having the configuration described with reference to FIGS. In the case of manufacturing a flange having a thickness of 8 mm, rolling molding was performed by applying the third thin-wall side flange widening promotion means in a rolling mill that does not satisfy the above formula (1). Table 2 below shows the rolling conditions (inner web width (mm), inner width widening amount ΔBi (mm), ΔBi/tf), web thickness (mm), The presence or absence of horizontal roll lubrication and vertical roll diameter (mm) are shown. In Table 2, the thickness of the left and right flanges (thick side/thin side) is described as the size (mm) of the material to be rolled at each rolling stage.

In Example 3, as in Comparative Example 1, the inner width of the web of the H-shaped raw material was 445 mm, and the inner width widening amount ΔBi in U1 to U7 was 8 mm, 8 mm, 6 mm, 2 mm, 1 mm, 1 mm, and 1 mm, respectively. , and the rolling conditions were designed so that ΔBi/tf exceeded 0.2 for U2 and U3 (conditions not satisfying formula (1)). On the other hand, in Example 3, the web thickness dimension of the material to be rolled was different from that in Comparative Example 1, and the web reduction ratio from rough finish to U3 was set smaller than in Comparative Example 1 (the third thin side (applied means for promoting flange width expansion). As a result, in Example 3, the rolling could be carried out without any defects in the rolling material.

As described above, in Example 1, the rolling conditions were designed so that ΔBi / tf was 0.2 or less in any of the stands U1 to U7, so that bending of the material to be rolled was suppressed and stable rolling was realized. was done. Further, in Examples 2-1, 2-2, and 3, under the rolling conditions where ΔBi/tf exceeds 0.2, the thin-side flange width expansion promoting means described in the above embodiment is applied. Therefore, bending of the material to be rolled was suppressed, and stable rolling was realized. On the other hand, in Comparative Examples 1 and 2, there were stands designed for rolling conditions such that ΔBi/tf exceeded 0.2, and no suitable countermeasures were taken. was not realized.

INDUSTRIAL APPLICABILITY The present invention can be applied to a manufacturing method for manufacturing an asymmetric H-section steel having left and right flanges with different thicknesses by universal rolling.

DESCRIPTION OF SYMBOLS 1... Rolling equipment 2... Heating furnace 4... Rough rolling mill row 5... Intermediate rolling mill row 8... Finishing universal rolling mill 11... Material 12... Flange part 12a... Thin flange part 12b... Thick flange part 13... H-shaped rough shape Material 14... Intermediate material 16... Asymmetrical H-section steel product 20... Web portion 21, 22... Horizontal rolls (of intermediate universal rolling mill) 31, 32... Vertical rolls (of intermediate universal rolling mill) 41, 42... (Edger rolling mill ) Horizontal rolls U1 to U7 ... Intermediate universal rolling mill (intermediate universal rolling stand)
E1 to E4... Edger rolling mill A... Material to be rolled T... Production line

Claims (5)

A method for manufacturing an asymmetric H-section steel with different left and right flange thicknesses,
an intermediate rolling process performed in an intermediate rolling mill train having one or more intermediate universal rolling mills;
a finishing rolling step performed in a finishing universal rolling mill;
In the universal rolling in the intermediate rolling step and the finish rolling step, under rolling conditions where the thickness reduction rate for the left and right flange portions of the material to be rolled is equal,
When the rolling conditions for universal rolling satisfy the following formula (1), universal rolling is performed under the rolling conditions,
When the rolling conditions for universal rolling do not satisfy the following formula (1), universal rolling is performed by applying means for promoting the width expansion of the thin-walled side flange of the material to be rolled. Production method.
0<ΔBi≦0.2tf (1)
However, ΔBi: web inner width widening amount in each rolling mill, tf: thin side flange thickness before rolling in each rolling mill. 2. The method according to claim 1, wherein the means for promoting the widening of the width of the thin-walled flange of the material to be rolled is a lubricating means for supplying a lubricant to the side surface of the horizontal roll that contacts the thin-walled flange portion of the material to be rolled. asymmetric H-beam manufacturing method. The means for promoting the widening of the thin-walled flange width of the material to be rolled is a vertical roll diameter that presses down the thin-walled flange portion of the material to be rolled, and a vertical roll diameter that presses down the thick-walled flange portion of the material to be rolled. Asymmetrical H according to claim 1, characterized in that the roll configuration is such that the diameter of the vertical roll on the thin side is designed to be 0.33 to 0.4 times the diameter of the vertical roll on the thick side How to make shaped steel. 2. The asymmetry according to claim 1, wherein the means for promoting the widening of the thin-walled side flange width of the material to be rolled is a rolling condition design that applies rolling conditions that satisfy the following formula (2) in universal rolling: A method for manufacturing H-shaped steel.
rf−0.2≦rw≦rf−0.1 (2)
However, rw: web thickness reduction rate, rf: flange thickness reduction rate. The method for manufacturing an asymmetric H-section steel according to any one of claims 1 to 4, characterized in that the intermediate rolling step and the finish rolling step are performed by one rolling mill pass rolling in one direction. .

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