JP2018075619A - Method for production of h-section steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce both horizontal and vertical roll loads of a mill for universal rolling in production of H-section steel, particularly to reduce a rolling load when a rolled material is tailed off in reverse rolling.SOLUTION: There is provided a method for producing an H-section steel by applying one-pass or plural pass universal rolling to a rolled material having the flange- and web-corresponding parts. The method includes performing a rolling operation while lowering the revolution of a horizontal roll in a prescribed range L1 including a part or the whole of a load increase range L2 compared to the horizontal roll revolution in a constant region in a mill for universal rolling on the basis of the relation of a horizontal roll rolling load of the rolled material to the constant region with that to the load increase range L2 of the tailing-off end of the rolled material.SELECTED DRAWING: Figure 12

Description

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

  When manufacturing H-section steel, raw materials such as slabs and blooms extracted from a heating furnace are formed into a rough shape (so-called dogbone-shaped material to be rolled) by a roughing mill (BD), and intermediate universal rolling is performed. The thickness of the rough profile web and flange is reduced by a machine, and the edge reduction mill near the intermediate universal rolling mill is subjected to width reduction and forging and shaping of the flange of the material to be rolled. . And an H-section steel product is modeled by a finishing universal rolling mill.

  In such an H-shaped steel manufacturing method, the accuracy of dimensions and shapes is a problem particularly in intermediate rolling in which universal rolling is performed. In particular, in the manufacture of large H-shaped steel products, the accuracy of dimensions and shapes is improved. It was desired. Thus, for example, in Patent Document 1, these problems are caused by the fact that the contact point between the flange portion of the material to be rolled and the saddle roll is significantly ahead of the contact point between the web portion and the horizontal roll. In view of the above, there has been disclosed a technique for solving the above-described problems by adjusting the ratio between the roll diameter and the horizontal roll diameter and / or the rolling schedule of each pass of the flange and web.

  Moreover, for example, in Patent Document 2, in order to eliminate the thickened portions (remaining portions) at both ends of the web portion that are generated when the web height is divided, the roll diameter and horizontal roll diameter in the finishing universal rolling mill A technique is disclosed in which the ratio of the above is adjusted suitably, the rotation axis of the roll roll and the rotation axis of the horizontal roll are installed on the same plane, and the above-described thickening portion is reduced.

  Moreover, in the manufacture of H-section steel, a technique for improving rolling efficiency has been devised at any time. For example, in Patent Document 3, in order to shorten the non-rolling time and improve the rolling efficiency in reverse rolling, the acceleration / deceleration time and stop time of the material to be rolled between the mill removal and the mill biting are determined for each pass. Techniques for controlling are disclosed.

Japanese Patent Publication No.46-19167 JP 2013-75317 A JP 11-114603 A

  However, in the technique described in Patent Document 1, the relationship between the web engagement of the horizontal roll and the flange engagement of the scissors roll is improved to improve the accuracy of dimensions and shape. No mention is made of the stretch ratio in the simultaneous reduction region of the flange, and no specific value of the stretch ratio is disclosed. Patent Document 1 describes, for example, that the ratio of the horizontal roll diameter to the heel roll diameter is 3.2 or more for a product having a product thickness ratio of 1.6 or less, and the leading length of the flange engagement is 10 mm. There is a description in the following, and there is a problem in that it is not a technique applied in a manufacturing process other than under such conditions.

  Further, the technique described in Patent Document 2 is a technique applied to finish rolling particularly with respect to the reduction of the thickened portions at both ends of the web, and the extension of the flange and the extension in the simultaneous reduction area of the web and the flange. No mention is made of the ratio, and no specific value of the stretch ratio is disclosed. Actually, since both ends of the web, which is a part of the cross section, are strongly rolled, the difference in stretching at each position in the cross section is very large, and the engagement of both ends of the web is larger than the engagement of the flange and the web center. It has become rolling.

  The technique described in Patent Document 3 is a technique for improving the rolling efficiency. Specifically, it is a technique mainly aimed at shortening the rolling time, and is related to facilities such as rolling load. No mention is made of rolling efficiency and no consideration is given.

The techniques described in Patent Documents 1 and 2 are techniques mainly related to modeling of the material to be rolled, such as improvement in accuracy of dimensions and shape and reduction of the thickened portion. Moreover, the said patent document 3 is a technique which improves rolling efficiency by shortening time.
On the other hand, in recent years, with the increase in size of structures and the like, it has been desired to manufacture large H-section steel products, and in the manufacture of large H-section steel products, rolling materials that are larger than conventional products are rolled. From modeling, the reduction of roll load (horizontal roll load and dredging roll load) of a rolling mill is demanded from the aspect of rolling equipment as well as improvement of modeling accuracy and rolling efficiency. In particular, when trying to manufacture a large H-section steel product using a conventional rolling mill, the rolling load may exceed the allowable load, and it is necessary to increase the number of passes. It was. Significantly increasing the rolling load capacity of rolling mills is not realistic in terms of equipment cost and equipment scale, reducing rolling load with existing equipment, improving productivity and producing large H-section steel products It is required to be realized.

  In any of the above-described Patent Documents 1 to 3, the action and clear conditions for reducing the roll load are not defined, and further provision of conditions for reducing the roll load is desired. The fact is.

  In view of the above circumstances, the object of the present invention is to reduce both the horizontal roll load and the horizontal roll load of a rolling mill that performs universal rolling in the manufacture of H-section steel products, thereby improving the productivity in existing rolling equipment. An object of the present invention is to provide a method for manufacturing an H-section steel that can be made to occur. In particular, the object is to reduce the rolling load when the bottom of the material to be rolled in reverse rolling.

  In order to achieve the above object, according to the present invention, there is provided an H-section steel manufacturing method for manufacturing H-section steel by performing universal rolling of one or a plurality of passes on the material to be rolled. In a rolling mill having a corresponding portion and a web corresponding portion and performing universal rolling, a horizontal roll rolling load with respect to a steady portion of the material to be rolled and a load increasing range L2 at the bottom end of the material to be rolled. Based on the relationship, the rolling is performed by reducing the horizontal roll rotation speed in the predetermined range L1 including a part or all of the load increase range L2 as compared with the horizontal roll rotation speed in the steady portion. The manufacturing method of H-section steel is provided.

  You may set the horizontal roll rotation speed in the said predetermined range L1 to 50% or less of the horizontal roll rotation speed in the said stationary part.

  You may set the horizontal roll rotation speed in the said predetermined range L1 to 30% or less of the horizontal roll rotation speed in the said stationary part.

  The length of the predetermined range L1 may be determined based on the height of the web-corresponding portion of the material to be rolled that is rolled in the universal rolling.

  The length of the predetermined range L1 may be set to a length not less than 0.65 times the height of the web-corresponding portion of the material to be rolled that is rolled in the universal rolling.

The roll diameter Dv of the rolling mill that performs the universal rolling may satisfy the following formula (2).
300 [mm] ≦ Dv ≦ 0.33 × Dh (2)
Where Dh is the horizontal roll diameter.

  The rolling mill that performs the universal rolling may be an intermediate universal rolling mill.

  In the rolling mill that performs the universal rolling, a back-up roll configured to be in contact with and support the saddle roll may be provided behind the saddle roll.

  According to the present invention, in the manufacture of H-section steel products, it becomes possible to reduce both the horizontal roll load and the vertical roll load of a rolling mill that performs universal rolling, and to improve the productivity in existing rolling equipment. In particular, it is possible to reduce the rolling load when the bottom of the material to be rolled in reverse rolling.

It is a schematic explanatory drawing about the production line of H-section steel. It is a schematic explanatory drawing (front sectional drawing) about the roll structure of an intermediate universal rolling mill. It is a schematic explanatory drawing (schematic top view) of the intermediate universal rolling mill which is a general structure. It is a schematic explanatory drawing (schematic top view) of the intermediate universal rolling mill of the structure which reduced the diameter of the culm roll. It is a graph which shows the change of the value of horizontal roll load ratio Ph / Phc at the time of changing roll diameter ratio. It is a graph which shows the change of the value of the heel roll load ratio Pv / Pvc when changing a roll diameter ratio. It is a graph which shows the change of the rolling load per pass of each roll in a longitudinal direction in rolling with the intermediate universal rolling mill of a material to be rolled. It is a graph which shows the relationship between the ratio of a heel roll diameter and a horizontal roll diameter, and a horizontal roll load in the stationary part and bottom end part of a to-be-rolled material. In intermediate universal rolling, the horizontal roll during bottom end rolling against the horizontal roll load during bottom end rolling when rolling to the bottom end with the horizontal roll rotation speed during steady section rolling. It is a graph which shows the change of the ratio of the horizontal roll load at the time of bottom edge end rolling at the time of reducing rotation speed to a predetermined value. When the horizontal roll diameter Dh is 1600 mm and the heel roll diameter Dv is 385 mm, when the horizontal roll rotation speed during steady-state rolling is 1, the horizontal roll rotation speed during bottom end rolling is up to a predetermined value. It is a graph which shows the change of the ratio of the horizontal roll load at the time of a trailing edge end rolling with respect to the horizontal roll load at the time of steady part rolling at the time of reducing. It is a schematic explanatory drawing which shows the rolling state of the bottom end part in intermediate | middle universal rolling. It is a graph which shows the relationship between the web height of the to-be-rolled material at the time of intermediate universal rolling, and the length of the range (predetermined range L1) where a horizontal roll load increases. It is a graph which shows the change of roll load at the time of intermediate universal rolling, when the predetermined range L1 is set to 1.3 times the web height, and the horizontal roll rotation speed in the range is set to 30% of the steady state. It is a schematic explanatory drawing of the structure which provides a backup roll with respect to a coffin roll.

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

  FIG. 1 is an explanatory diagram of an H-section steel production line T including a rolling facility 1 according to the present embodiment. As shown in FIG. 1, a heating furnace 2, a roughing mill 4, an intermediate universal rolling mill 5, and a finishing universal rolling mill 8 are arranged in order from the upstream side on the production line T. Further, an edger rolling mill 9 is provided in the vicinity of the intermediate universal rolling mill 5. In the following description, the steel materials in the production line T will be collectively referred to as “rolled material A” for the sake of explanation, and the shape may be appropriately illustrated using broken lines, diagonal lines, etc. in each drawing. In the present embodiment, a portion corresponding to the flange of the manufactured H-section steel product may be referred to as a flange corresponding portion 12 and a portion corresponding to the web may be referred to as a web corresponding portion 20.

  As shown in FIG. 1, in the production line T, the material A to be rolled such as the slab 11 extracted from the heating furnace 2 is roughly rolled in the roughing mill 4. Next, intermediate universal rolling is performed in the intermediate universal rolling mill 5. In addition, in the state where the intermediate universal rolling and the reverse rolling are possible, the edger rolling machine 9 applies a reduction to the end of the material to be rolled (flange equivalent portion 12). Usually, about 4 to 6 hole molds are engraved on the roll of the rough rolling mill 4 (a plurality of rolls may be installed). A dog-bone shaped H-shaped rough member 13 is formed by reverse rolling, and the H-shaped rough shaped member 13 is formed by using a rolling mill row composed of two rolling mills, the intermediate universal rolling mill 5-edger rolling mill 9. A plurality of passes of reduction are applied to form the intermediate material 14. Then, the intermediate material 14 is finish-rolled into a product shape in the finish universal rolling mill 8 to produce an H-section steel product 16.

  Next, an outline of the roll configuration of the intermediate universal rolling mill 5 shown in FIG. 1 will be described below with reference to FIG. FIG. 2 is a schematic explanatory view (front sectional view) of the roll configuration of the intermediate universal rolling mill 5, in which (a) shows before rolling and (b) shows during rolling. As shown in FIG. 2, the intermediate universal rolling mill 5 is provided with a pair of upper and lower horizontal rolls 21 and 22 and a pair of left and right heel rolls 31 and 32. The horizontal rolls 21 and 22 are configured such that their roll peripheral surfaces can come into contact with the web-corresponding portion 20 of the material A to be rolled, and a part of the roll side surface can be brought into contact with the inner surface of the flange-corresponding portion 12. Yes. Moreover, the roller rolls 31 and 32 are configured such that their roll peripheral surfaces can come into contact with the outer surface of the flange-corresponding portion 12. In FIG. 2, the configuration of the roll shaft of each roll, the rolling mill housing, and the like is omitted.

  In the intermediate universal rolling mill 5 shown in FIG. 2, the peripheral surfaces of the horizontal rolls 21 and 22 abut against the web equivalent portion 20 of the material A to be rolled, and the reduction is applied in the thickness direction of the web equivalent portion 20. . Further, with respect to the flange equivalent portion 12 of the material A to be rolled, part of the side surfaces of the horizontal rolls 21 and 22 abut on the inner surface of the flange equivalent portion 12, and the peripheral surfaces of the rolls 31 and 32 are the outer surfaces of the flange equivalent portion 12. And a reduction is applied in the thickness direction of the flange-corresponding portion 12. Thus, the flange equivalent part 12 and the web equivalent part 20 of the material A to be rolled are reduced to a desired thickness.

  In such an intermediate universal rolling mill 5 shown in FIG. 2, the intermediate material 14 is rolled and shaped by performing a plurality of passes of reverse rolling on the material A to be rolled. With regard to the intermediate universal rolling mill 5 configured as described above, the present inventors pay attention to the problems relating to the roll load in the horizontal rolls 21 and 22 and the saddle rolls 31 and 32, in order to reduce the roll load. We conducted an intensive study on the equipment configuration. Below, this examination is explained.

(Intermediate universal rolling mill of general configuration)
First, the structure of a general intermediate universal rolling mill 5a will be described. FIG. 3 is a schematic explanatory diagram (schematic top view) of the intermediate universal rolling mill 5a having a general configuration. In addition, about the common component, in FIG. 2 and FIG. 3, the common code | symbol may be attached | subjected and the detailed description may be abbreviate | omitted. Further, the upper side in the drawing in FIG. 3 is shown as the upstream side of rolling, and the lower side in the drawing is shown as the downstream side of rolling. In FIG. 3, schematic cross-sectional views of the rolled material A before and after rolling are also shown for explanation. It is described.

The intermediate universal rolling mill 5a having a general configuration shown in FIG. 3 has, for example, a horizontal roll diameter Dh of about 1500 mm to 1650 mm, and a roll roll diameter Dv of about 0.8 to 0.65 times the horizontal roll diameter. That is, for example, the roll diameter Dv shown in FIG. 3 is about 1100 mm. In such an intermediate universal rolling mill 5a, when rolling an intermediate material of a product having a thickness ratio tf / tw of the web equivalent portion 20 and the flange equivalent portion 12 of about 1.2 to 2.3, The relationship between the contact length Ldf of the area where the flange equivalent part 12 is reduced by 31 and 32 and the contact length Ldw of the area where the web equivalent part 20 is reduced by the horizontal rolls 21 and 22 (not shown in FIG. 3) is The following formula (1) is obtained.
Ldf> Ldw (1)

In this case, the roll shafts of the horizontal roll and the saddle roll are in the same cross section perpendicular to the rolling direction, and the timing at which the reduction of the flange equivalent part 12 and the web equivalent part 20 ends is the same. Then, first, the reduction of the flange equivalent part 12 by the scissors rolls 31 and 32 is started, and then the web equivalent part 20 and the flange equivalent part 12 are reduced. At this time, the reduction of the flange-corresponding portion 12 and the web-corresponding portion 20 is performed while maintaining a certain stretching balance, so that the elongation in the rolling direction as a whole is substantially the same. As a result, in the region where the flange equivalent portion 12 is first reduced (Ldf-Ldw region in the figure), only the flange equivalent portion 12 is reduced, so that the vicinity of the corner portion (flange-web connecting portion). The metal easily flows to the web side, and the surface pressure at the end of the web equivalent portion 20 increases.
Further, in the region where the web equivalent portion 20 and the flange equivalent portion 12 are simultaneously crushed (Ldw region in the figure), the extension of the web equivalent portion 20 is larger than the extension of the flange equivalent portion 12, and the elongation of the web equivalent portion 20 is increased. Is restrained by the elongation of the flange equivalent portion 12.
For the reasons described above, it has been found that in the intermediate universal rolling mill 5a configured as shown in FIG. 3, a larger horizontal roll load acts than when the rolling of the web equivalent portion 20 is regarded as plate rolling.

(Intermediate universal rolling mill with a smaller diameter roll)
FIG. 4 is a schematic explanatory view (schematic top view) of the intermediate universal rolling mill 5b having a configuration in which the diameter of the culm roll is reduced. The saddle roll shown in FIG. 4 is small-diameter saddle rolls 51 and 52 having a smaller roll diameter than that of the above-described general configuration (see FIG. 3), and other common components are shown in FIG. 3 and FIG. Then, a common code | symbol is attached | subjected and the detailed description may be abbreviate | omitted. In addition, the upper side in the drawing in FIG. 4 is shown as the upstream side of rolling, and the lower side in the drawing is shown as the downstream side of rolling. In FIG. 4, schematic cross-sectional views of the rolled material A before and after rolling are also shown for explanation. It is described.

As shown in FIG. 4, in the intermediate universal rolling mill 5b having a configuration in which the diameter of the roll is reduced, the horizontal roll diameter Dh is about 1500 to 1650 mm, for example, and the roll diameter Dv is about 1/3 to 1/5 of the horizontal roll diameter. Degree. That is, for example, the diameter Dv of the small diameter scissors rolls 51 and 52 shown in FIG. 4 is about 450 mm. In addition, the value of these horizontal roll diameters and saddle roll diameters is an example, and these values are not limited to the above numerical values.
In such an intermediate universal rolling mill 5a, when an intermediate material of a product having a thickness ratio tf / tw of the web equivalent portion 20 and the flange equivalent portion 12 of about 1.2 to 2.3 is rolled and shaped, it corresponds to a flange. The difference between the contact length Ldf of the area where the part 12 is reduced and the contact length Ldw of the area where the web equivalent part 20 is reduced becomes small, and there is almost no area where only the flange equivalent part 12 is reduced. It is estimated that the rolling load of the vertical roll and the horizontal roll can be reduced because the stretch of the web equivalent portion 20 does not become larger than the stretch of the flange equivalent portion 12 in the reduction region.

(Relationship between roll diameter ratio and rolling load)
According to the study by the present inventors, when the intermediate universal rolling mill having the general configuration according to FIG. 3 described above and the intermediate universal rolling mill having a configuration in which the diameter of the rolls according to FIG. Depending on the ratio of roll diameter Dh to heel roll diameter Dv (hereinafter also referred to as roll diameter ratio Dv / Dh), the rolling load ratio (horizontal roll load ratio and heel roll load ratio) of each roll may change. I know.

  FIG. 5 is a graph showing a change in the value of the horizontal roll load ratio Ph / Phc when the roll diameter ratio is changed in the intermediate universal rolling mill described in the present embodiment (see FIGS. 2 to 4). . FIG. 5 shows a case where the web-to-flange thickness ratio tf / tw is 1.3 and 2.0.

  As shown in FIG. 5, the value of the horizontal roll load ratio Ph / Ph tends to decrease as the value of the roll diameter ratio Dv / Dh decreases. From FIG. 5, the roll diameter ratio Dv / Dh is set to 0.33 or less (that is, the roll roll diameter Dv is set to 1/3 or less of the horizontal roll diameter Dh) so that the horizontal roll load ratio is 0.9 or less. You can see that you can.

FIG. 6 is a graph showing changes in the value of the roll load ratio Pv / Pvc when the roll diameter ratio is changed in the intermediate universal rolling mill described in the present embodiment (see FIGS. 2 to 4). It is. FIG. 6 also shows the case where the web-to-flange thickness ratio tf / tw is 1.3 and 2.0.
As shown in FIG. 6, when the roll diameter ratio Dv / Dh is set to 0.33 or less, the heel roll load ratio Pv / Pvc can also be set to 0.9 or less.

On the other hand, when the roll diameter Dv is reduced, the biting angle becomes excessive and the rolling stability is lowered. In view of such circumstances, the roll diameter Dv is preferably set to 300 mm or more, for example.
From the above, it is known that the rolling load reduction effect can be obtained by setting the roll diameter Dv to a value as shown in the following formula (2).
300 [mm] ≦ Dv ≦ 0.33 × Dh (2)

(Rolling load when the bottom of the material is rolled)
As described above, as shown with reference to FIGS. 5 and 6, it is possible to reduce the rolling load of each roll (horizontal roll and cocoon roll) by reducing the heel roll diameter Dv. However, as a result of further studies by the present inventors, such a rolling load reduction effect is exerted mainly in the steady portion in the longitudinal direction of the material A to be rolled, and the unsteady portion, particularly the rolled material. It has been found that a sufficient rolling load reduction effect cannot be obtained at the bottom end in the longitudinal direction of the material A (the rear end with respect to the rolling direction). This is also known to be a phenomenon that can be seen whether the heel roll diameter Dv is large or small. However, as will be described below, the case where the heel roll diameter Dv is small is used. Is more prominent.

  FIG. 7 is a graph showing a change in rolling load per pass of each roll in the longitudinal direction under typical rolling conditions in rolling of the material A to be rolled by an intermediate universal rolling mill. Roll load, (b) is a graph regarding the saddle roll load. FIG. 7 is a graph when the length in the longitudinal direction of the material to be rolled is about 44 m, and the vicinity of 44 m in the graph corresponds to the bottom end portion during rolling. Further, FIG. 7 shows a graph when the roll diameter Dv is large (Dv = 1100 mm) and small (Dv = 385 mm).

As shown in FIG. 7, in rolling with an intermediate universal rolling mill, the horizontal roll load / saddle roll load is not necessarily constant in the longitudinal direction of the material A to be rolled. In particular, as shown in FIG. 7A, with respect to the horizontal roll load, a phenomenon is seen in which the rolling load at the bottom end of the material A is higher than the load in the steady rolling state.
On the other hand, as shown in FIG. 7B, with respect to the heel roll load, a phenomenon such as a particularly high rolling load at the bottom end has not been confirmed.

  At the time of rolling the longitudinal rear end portion (bottom end portion) of the material A to be rolled, since there is no subsequent material on the roll bite entry side, the interaction between the web and the flange is weakened, and the tensile stress is applied to the web equivalent portion 20. It will not work and the reduction in thickness will be less. Thereby, the rolling load of the horizontal roll in the bottom end part of the material A to be rolled becomes significantly large. As shown in FIG. 7A, such a phenomenon is the same whether the heel roll diameter Dv is large or small.

  It has also been found that the phenomenon described above becomes more prominent when the roll roll diameter Dv is reduced. FIG. 8 is a graph showing the relationship between the ratio of the heel roll diameter and the horizontal roll diameter and the horizontal roll load with respect to each of rolling at the steady portion and the bottom end portion of the material A to be rolled. As shown in FIG. 8, the horizontal roll load decreases as the heel roll diameter becomes smaller than the horizontal roll diameter, and the rate of decrease is larger in the steady portion.

(Reduction of rolling load when the bottom of the material to be rolled falls)
As described with reference to FIGS. 7 and 8, the rolling load of the horizontal roll during rolling of the longitudinal rear end portion (bottom end portion) of the material A to be rolled in the intermediate universal rolling mill in the manufacture of H-section steel. Has been found to be higher than rolling in the stationary part.
In view of such circumstances, the present inventors have diligently studied a technique that can reduce the rolling load at the bottom end rolling of the material A to be rolled and approach the rolling load of the steady part, The knowledge explained below was obtained.

That is, the difference between the horizontal roll load at the time of rolling the steady part of the material A to be rolled and the horizontal roll load at the bottom end rolling is predicted in advance, and the bottom end is based on the predicted load difference. Is set to be smaller than the horizontal roll rotation number at the time of steady part rolling, and the strain rate is reduced to perform rolling at the bottom end part. Thereby, the horizontal roll load can be reduced with the decrease in the horizontal roll rotation speed from the strain rate dependency of the deformation resistance in hot rolling.
In addition, in the intermediate universal rolling mill configured such that only the horizontal roll is driven and the vertical roll is not driven, the horizontal roll rotation speed corresponds to the rolling speed, and the horizontal roll rotation speed is set to be small. This means that the rolling speed is set small.

  FIG. 9 shows a bottom end rolling with respect to a horizontal roll load during bottom end rolling when rolling is performed up to the bottom end while maintaining the number of horizontal roll rotations during steady section rolling in intermediate universal rolling. It is a graph which shows the change of the ratio of the horizontal roll load at the time of bottom end rolling when the horizontal roll rotation speed at the time is lowered to a predetermined value. As shown in FIG. 9, from the strain rate dependence of the deformation resistance in hot rolling, the bottom end rolling is performed as the horizontal roll rotation speed during bottom end rolling decreases (that is, the rolling speed decreases). It can be seen that the horizontal roll load at the time is also reduced. From FIG. 9, for example, if the horizontal roll rotation speed at the bottom end rolling is about ½ (about 0.5) of the horizontal roll rotation at the steady section rolling, the horizontal roll at the bottom end rolling is When the roll load is reduced by about 10% and the horizontal roll rotation speed at the bottom end rolling is about 1/10 (about 0.1) of the horizontal roll rotation speed at the steady part rolling, It can be seen that the horizontal roll load is reduced by about 25%. FIG. 9 shows data when the roll diameter is constant, and the reduction of the horizontal roll load due to the decrease in the horizontal roll rotation speed is observed regardless of whether the roll diameter Dv is large or small. It is what

  FIG. 10 shows the horizontal roll rotation speed at the bottom end rolling when the horizontal roll rotation speed at the stationary part rolling is 1 when the horizontal roll diameter Dh is 1600 mm and the roll roll diameter Dv is 385 mm. It is a graph which shows the change of the ratio of the horizontal roll load at the bottom end part rolling with respect to the horizontal roll load at the time of steady part rolling at the time of reducing to a predetermined value. As shown in FIG. 10, it can be seen that even when the heel roll diameter Dv is reduced, the horizontal roll load is also reduced as the horizontal roll rotation speed during bottom end rolling is reduced. Furthermore, if the horizontal roll rotation speed at the bottom end rolling is about 1/10 (about 0.1) of the horizontal roll rotation speed at the steady section rolling, the horizontal roll load ratio approaches 1; It can be seen that the horizontal roll load at the end rolling is reduced to the same level as the horizontal roll load at the steady part rolling.

As described above, from the knowledge described with reference to FIGS. 9 and 10, in the intermediate universal rolling in the present embodiment, in order to reduce the horizontal roll load at the bottom end rolling, at least about 10%, It can be seen that the horizontal roll rotation speed during partial rolling may be set to 50% or less of the horizontal roll rotation speed during steady-state rolling. More preferably, by setting the horizontal roll rotation speed during bottom end rolling to 30% or less of the horizontal roll rotation speed during steady section rolling, further load reduction (about 15% reduction) can be achieved. It can be seen that this is possible.
Moreover, about the lower limit of the horizontal roll rotation speed, if it is set to less than 10% of the horizontal roll rotation speed during steady-state rolling, the temperature drop at the corresponding part will occur during the bottom end rolling of the material A to be rolled. There is a problem that it becomes remarkable and the rolling efficiency is lowered.
From the above, during the intermediate universal rolling in the present embodiment, it is preferable to set the horizontal roll rotation speed during bottom end rolling to 10% or more and 50% or less of the horizontal roll rotation speed during steady section rolling, Furthermore, it is preferable to set to 10% or more and 30% or less. The ratio of the horizontal roll rotation speed at the bottom end rolling to the steady part rolling may be determined by the targeted reduction rate of the horizontal roll load at the bottom end rolling.

(Range of bottom end of rolled material)
As described above, in the intermediate universal rolling according to the present embodiment, the rolling load of the horizontal roll is changed to the rolling load in the steady rolling state at the time of rolling at the longitudinal rear end portion (bottom end portion) of the material A to be rolled. In order to suppress such an increase in rolling load, the horizontal roll rotation speed is set low during rolling at the bottom end (for example, 10% to 50% in a steady state). Has been found to be effective.
Here, the present inventors have further studied in order to suitably determine a range in which the horizontal roll rotation speed is set low in the longitudinal direction of the material A to be rolled. Hereinafter, this study will be described.

FIG. 11 is a schematic explanatory view showing the rolling state of the bottom end portion in the intermediate universal rolling, and is a schematic view of the rolling state as viewed from the side. In addition, a rolling direction is a direction shown by the arrow in FIG. Here, as shown in FIG. 11, in the bottom end portion during intermediate universal rolling of the material A to be rolled, a range in which the rolling is performed by reducing the horizontal roll rotation speed compared to the horizontal roll rotation speed in the steady portion. Is defined as a predetermined range L1.
As described above with reference to FIGS. 7 and 8, the longitudinal rear end portion (bottom end portion) of the material A to be rolled has a range L <b> 2 (hereinafter referred to as a load) in which the horizontal roll load increases during rolling. It is known that there is also an increase range L2). Here, the load increase range L2 is defined as the length from the position immediately below the roll to the rear end in the longitudinal direction of the material A to be rolled at the time when the horizontal roll load starts to increase at the bottom end rolling.
That is, by defining a range including a part or all of the load increase range L2 in which the horizontal roll load increases during rolling as the predetermined range L1, the bottom end of the bottom end in the predetermined range L1 It is possible to suppress an increase in the horizontal roll load during rolling.

Therefore, the present inventors have conducted an intensive study on the relationship between the dimension and shape of the material A to be rolled and the load increase range L2 in which the horizontal roll load increases during rolling. It has been found that the length of the load increase range L2 is proportional to the height of the web-corresponding portion 20 of the material A to be rolled during rolling (hereinafter also simply referred to as web height).
FIG. 12 is a graph showing the relationship between the web height of the material A to be rolled during intermediate universal rolling and the length of the load increase range L2 in which the horizontal roll load increases. As shown in FIG. 12, there is a correlation between the web height (mm) at the time of intermediate universal rolling and the load increase range L2 (m) in which the rolling load increases when the bottom falls, and the load increase range L2 is It has been found that the load increases in proportion to the web height, and specifically, the load increase range L2 is about 1.3 times the web height.

From the result shown in FIG. 12, the range (predetermined range L1) in which rolling is performed with the horizontal roll rotation speed set low can be set to a length of 1.3 times or more the web height of the material A to be rolled. preferable. However, as shown to Fig.7 (a), it turns out that the horizontal roll load of the bottom end part in intermediate universal rolling tends to increase notably as it goes to the rear end of the bottom end part. For example, the predetermined range L1 is not less than half of the web height that is the range in which the horizontal roll load increases, that is, at least 0.65 times the web height of the material A to be rolled. It has also been found that a certain rolling load reduction effect can be obtained with the length. Even if the rolling range (predetermined range L1) is set to 0.65 times the web height by setting the horizontal roll rotational speed low, the rolling speed is reduced in operation (reducing horizontal roll rotational speed). Is started from a position earlier than the start position of the range L1, the horizontal roll load can be reduced in a wider range than the determined range in actual operation. On the other hand, when the predetermined range L1 is set to a range smaller than 0.65 times the web height, the load can be sufficiently reduced particularly in the longitudinal direction rear end side range of the material A to be rolled, which is a region where the horizontal roll load is high. There is a risk of not being able to plan.
If the horizontal roll rotation speed is set low and the rolling speed is lowered, the rolling time increases and the efficiency may be lowered. Therefore, the predetermined range L1 is preferably set as short as possible, which is realized in operation. As a possible value, it is necessary to keep the length not more than 3.0 times the web height, for example. If the predetermined range L1 is determined in accordance with the reduction rate of the rolling speed (horizontal roll rotation speed) at a length of 3.0 times or less of the web height, it is considered that the increase in rolling time hardly affects the operation efficiency. . The web height here may be defined by the nominal web height of the product.

  In the method for manufacturing the H-section steel according to the present embodiment described above, the rear end in the longitudinal direction is set to a length of 0.65 times or more of the web height at the time of the bottom end of the rolled material in the intermediate universal rolling. By setting the horizontal roll rotation speed in the predetermined range L1 low and reducing the rolling speed, an increase in the horizontal roll rolling load in the predetermined range L1 can be suppressed, and the rolling load in a steady state can be approached. In addition, the effect of suppressing such an increase in the horizontal roll rolling load is particularly remarkable in the configuration in which the diameter of the vertical roll of the intermediate universal rolling mill is reduced.

  FIG. 13 shows a method of manufacturing an H-section steel according to the present embodiment, wherein the predetermined range L1 is set to 1.3 times the web height during intermediate universal rolling, and the horizontal roll rotation speed in the range is in a steady state. It is a graph which shows the change of the roll load at the time of setting to 30%, (a) shows the change of a horizontal roll load, (b) shows the change of the saddle roll load with a broken line, respectively. In addition, FIG. 13 is data in the case where the longitudinal length of the material to be rolled is about 44 m, and illustrates both the case where the roll diameter Dv is 1100 mm which is the large diameter and the case where the small diameter is 385 mm, For reference, the data when the horizontal roll rotation speed is not reduced are shown by solid lines.

As shown in FIG. 13 (a), the horizontal roll rotation speed is lowered in the predetermined range L1, so that the horizontal at the tail end is the same regardless of whether the heel roll diameter is large or small. It can be seen that an increase in roll load is suppressed (see broken line in the figure).
Moreover, as shown in FIG.13 (b), by reducing the horizontal roll rotation speed in the predetermined range L1, the roll of the said roll is rolled in any case where the roll diameter is large or small. It can be seen that the load is reduced (see the broken line in the figure).

  As described with reference to FIG. 13, the horizontal roll rotation speed in the predetermined range L1 is set low, and the rolling speed is reduced, thereby suppressing an increase in the horizontal roll rolling load in the predetermined range L1, and a steady state. It is possible to approach the rolling load of. Moreover, reduction of the rolling load of the roll is also achieved. Due to such rolling load reduction effect, productivity can be improved by reducing the number of passes even when the same H-shaped steel product is manufactured. In addition, the rolling mill that performs universal rolling can be reduced in size by reducing the rolling load. In addition, it is possible to manufacture a high-strength H-section steel product with the same number of passes, and to manufacture a large-section H-section steel product having a larger cross section than before. Furthermore, roll wear can be reduced, and rolling efficiency can be increased by reducing the number of roll grinding operations.

  As mentioned above, although an example of embodiment of this invention was demonstrated, this invention is not limited to the form of illustration. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

  For example, in the above embodiment, a suitable numerical range of the heel roll diameter Dv is defined in Equation (2). However, as the diameter of the heel roll is reduced, a backup roll as a roll chock may be provided on the heel roll. . FIG. 14 is a schematic explanatory diagram (schematic top view) of a configuration in which a backup roll is provided for the heel roll. FIG. 14 shows a case where left and right backup rolls 70 and 71 are provided for the intermediate universal rolling mill 5b according to the embodiment shown in FIG. The same reference numerals are given and description thereof is omitted.

  As shown in FIG. 14, in this modification, two backup rolls 70 a and 70 b are provided for the saddle roll 51, and two backup rolls 71 a and 71 b are provided for the saddle roll 52. These backup rolls 70 (70a, 70b), 71 (71a, 71b) are configured to contact and support the saddle rolls behind the saddle rolls 51, 52. As a result, insufficient roll strength due to the reduction in the diameter of the rolls does not become a problem, and the roll life is prolonged.

  Moreover, in the said embodiment, although the case where the technique of this invention was applied to the intermediate universal rolling mill 5 was illustrated and demonstrated, the application range of this invention is not restricted to this. That is, it is also possible to apply to the finishing universal rolling mill 8. In addition, for example, when the intermediate rolling mill is constituted by a plurality of rolling mills (for example, when a first intermediate rolling mill and a second intermediate rolling mill are provided), it may be applied to any rolling mill, You may apply to all the intermediate rolling mills. In addition to a slab having a rectangular cross section, the present invention can be applied to the case of manufacturing an H-section steel using a continuously cast beam blank.

  Further, in the above embodiment, the technology for reducing the rolling load by reducing the rolling speed with respect to the bottom end portion of the rolled material during universal rolling (reducing the horizontal roll rotation speed) has been described. Can also be applied to the biting end of the material to be rolled during universal rolling. When universal rolling is performed by reverse rolling with multiple passes, the biting end and tail end in the longitudinal direction of the material to be rolled are interchanged during reverse rolling, and the original biting end becomes the tip end. Thus, the original bottom end portion becomes the biting end portion. When the horizontal roll load increases at the bottom end, the horizontal roll gap during rolling of the bottom end widens due to elastic deformation of the rolling mill and roll, and the thickness of the web-corresponding portion increases. Since the thickness reduction amount of the web equivalent portion increases, as shown in FIG. 13A, it is conceivable that the horizontal roll load becomes larger than the steady portion even during the biting end portion rolling. That is, reducing the rolling load by reducing the horizontal roll rotation speed at any end is effective for increasing the rolling efficiency.

Example 1
As Example 1 of the present invention, intermediate rolling of an H-section steel product having a size of 1000 × 400 × 16/32 [mm] with a horizontal roll diameter Dh of an intermediate universal rolling mill of 1600 mm and a saddle roll diameter Dv of 1100 mm is predetermined. I went on a pass schedule. At that time, the rotational speed of the horizontal roll was set to 100 rpm in a steady state and 30 rpm at the time of slipping out (predetermined range L1 in the above embodiment). The range in which the horizontal roll rotation speed was 30 rpm was 1.0 m at the end of the trailing edge, which is 1.0 times the web height, and rolling was performed to the end.
Moreover, as Comparative Example 1, during the intermediate rolling under the same conditions as in Example 1, the rolling was performed at 100 rpm without changing the horizontal roll rotation speed between the steady state and the trailing edge.

  When both Example 1 and Comparative Example 1 were performed by intermediate rolling of a plurality of passes, the horizontal roll load in Example 1 was reduced by about 11% at the maximum value at the end of the trailing edge as the average of each pass. As a result, a reduction in the number of passes in intermediate rolling with a plurality of passes and a reduction in roll friction were realized, and a reduction in the number of times of roll grinding could be achieved.

(Example 2)
As Example 2 of the present invention, the intermediate universal rolling mill has a horizontal roll diameter Dh of 1600 mm and a roll roll diameter Dv of 385 mm, and intermediate rolling of an H-section steel product having a size of 1000 × 400 × 16/32 [mm] is performed in a predetermined manner. I went on a pass schedule. At that time, the rotational speed of the horizontal roll was set to 100 rpm in a steady state and 30 rpm at the time of slipping out (predetermined range L1 in the above embodiment). The range in which the horizontal roll rotation speed was 30 rpm was 1.0 m at the end of the trailing edge, which is 1.0 times the web height, and rolling was performed to the end.
Further, as Comparative Example 2, during the intermediate rolling under the same conditions as in Example 2, the rolling was performed at 100 rpm without changing the horizontal roll rotation speed between the steady state and the trailing edge.

When both Example 2 and Comparative Example 2 were performed by intermediate rolling of a plurality of passes, the horizontal roll load in Example 2 was reduced by about 12% at the maximum value at the end of the trailing edge as the average of each pass. As a result, a reduction in the number of passes in intermediate rolling with a plurality of passes and a reduction in roll friction were realized, and a reduction in the number of times of roll grinding could be achieved.
In addition, in the conditions of Example 2, even when the range in which the number of rotations of the horizontal roll is 30 rpm is 1.3 m at the bottom end that is 1.3 times the web height, the same effect is obtained. The effect was confirmed.

  Furthermore, when Example 2 is compared with Comparative Example 1, it is confirmed that the horizontal roll load at the steady portion of the material to be rolled is reduced by about 26%, and the horizontal roll load at the bottom end portion of the material to be rolled is confirmed. It was confirmed that was reduced by about 22% at the maximum value. That is, it has been proved that the effect of reducing the horizontal roll load becomes more prominent by implementing the reduction of the roll diameter Dv and the reduction of the horizontal roll rotation speed within a predetermined range.

  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 SYMBOLS 1 ... Rolling equipment 2 ... Heating furnace 4 ... Rough rolling mill 5 (5a, 5b) ... Intermediate universal rolling mill 8 ... Finishing universal rolling mill 9 ... Edger rolling mill 11 ... Slab 12 ... Flange equivalent part 13 ... H-shaped rough profile 14 ... Intermediate material 16 ... H-section steel product 20 ... Web equivalent 21 ... Upper horizontal roll (intermediate universal rolling mill)
22 ... Lower horizontal roll (intermediate universal rolling mill)
31, 32 ... ３２ roll (intermediate universal rolling mill)
51, 52 ... Small diameter roll (intermediate universal rolling mill)
70, 71 ... Backup roll A ... Rolled material T ... Production line

Claims (8)

A method of manufacturing an H-section steel, which performs universal rolling of one or more passes on a material to be rolled to manufacture an H-section steel,
The material to be rolled has a flange equivalent part and a web equivalent part,
In the rolling mill that performs the universal rolling, the load increase is based on the relationship between the horizontal roll rolling load for the steady portion of the material to be rolled and the horizontal roll rolling load for the load increase range L2 of the bottom end of the material to be rolled. A method for producing H-section steel, characterized in that rolling is performed by reducing the horizontal roll rotation speed in a predetermined range L1 including part or all of the range L2 as compared with the horizontal roll rotation speed in the stationary portion. The method for producing H-section steel according to claim 1, wherein rolling is performed by setting the horizontal roll rotation speed in the predetermined range L1 to 50% or less of the horizontal roll rotation speed in the steady portion. The method for producing H-section steel according to claim 1, wherein rolling is performed by setting the horizontal roll rotation speed in the predetermined range L1 to 30% or less of the horizontal roll rotation speed in the steady portion. 4. The length of the predetermined range L <b> 1 is determined based on a height of a web-corresponding portion of a material to be rolled that is rolled in the universal rolling. 5. Manufacturing method of H-section steel. 5. The length of the predetermined range L <b> 1 is set to 0.65 times or more the height of a web-corresponding portion of a material to be rolled that is rolled in the universal rolling. Of manufacturing H-section steel. The roll shape Dv of the rolling mill which performs the said universal rolling satisfy | fills the following formula | equation (2), The manufacturing method of the H-section steel as described in any one of Claims 1-5 characterized by the above-mentioned.
300 [mm] ≦ Dv ≦ 0.33 × Dh (2)
Where Dh is the horizontal roll diameter. The method for producing an H-section steel according to any one of claims 1 to 6, wherein the rolling mill that performs the universal rolling is an intermediate universal rolling mill. In the rolling machine which performs the said universal rolling, the back up roll of the structure which contacts and supports the said coffin roll is provided in the back of the coffin roll, It is any one of Claims 1-7 characterized by the above-mentioned. The manufacturing method of the H-section steel of description.

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