JPH11314101A - Method for rolling h-shape steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of dislocation of a web center at the both end parts in the longitudinal direction by executing the control to prevent the twist of a rolling material just before the rear end part of the rolling material is bitten into a rolling mill. SOLUTION: Rolling reduction in an ordinary pass schedule is executed for a web 21 and a flange 22 until a position P near the front tip part by a specific distance L from the last end part 23 of a rolling material 20 is bitten into a rougher universal rolling mill 2. The passage of the last end part 23 is detected by a sensor 7 and the timing when the position P is bitten into the rougher universal rolling mill 2, is calculated, the opening degree of horizontal rolls 3 or vertical rolls 4 is continuously changed to a target value, or/and the gap between an introducing guide and the web 21 is reduced. It is desirable that the interval of the introducing guides is changed to the web 21 thickness direction and this height direction to restrict the range from the end parts in the web 21 height direction to the corner parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling method for efficiently producing an H-section steel having excellent dimensional accuracy using a universal rolling mill.

[0002]

2. Description of the Related Art As shown in FIG. 6, a process for producing an H-section steel by hot rolling includes, for example, a rough double rolling mill 1 (hereinafter referred to as a "rough rolling mill") for roughly rolling a rolled material. It comprises a coarse universal rolling mill 2 composed of a pair of horizontal rolls 3 and a pair of vertical rolls 4, and an edger rolling mill 5 and a finishing universal rolling mill 6 arranged close to the coarse universal rolling mill 2.

[0003] As a material of the H-section steel, a slab or a beam blank generally manufactured by continuous casting is used. First, in the rough rolling mill 1 of FIG. The intermediate billet 24 of (a) is formed.
Next, the intermediate steel slab 24 is subjected to rolling a plurality of times of reducing the web thickness and the flange thickness by the coarse universal rolling mill 2 and shaping the flange width by the adjacent edger rolling mill 5 a plurality of times, and the intermediate steel slab 24 shown in FIG. FIG. 7 is a diagram illustrating a final slab 25 having almost the final dimensions. Finally, the flange is shaped at right angles to the web by a finishing universal rolling mill 6 to a final thickness.
The product 26 of (c) is obtained.

In the end product of the H-section steel manufactured as described above, it is necessary to keep the dimensions and tolerances within standard tolerances. However, as shown in FIG.
(Hereinafter, referred to as “web center deviation”) often occurs, which lowers the production yield. Here, the web center deviation is expressed as e = (ab) / 2.

The causes of the web center deviation include variations in the thickness of the flange at four locations formed by the rough rolling mill 1 and deviations between the center of the material to be rolled in universal rolling and the pass line of the rolling mill. is there. In the universal rolling, if the center of the material to be rolled is shifted from the pass line of the rolling mill, the position of the web of the material to be rolled is changed in the flange width direction, and the center of the web is biased as shown in FIG. To prevent this web center deviation, for example, as disclosed in JP-A-53-48067, the flange width is measured at the entrance side of the universal rolling mill, and the flange center is set to the universal rolling mill based on the measurement result. A method is known in which the position of the roller table on the entrance side of the universal rolling mill is automatically adjusted up and down so that the rolling line coincides with the pass line.

Also, Japanese Patent No. 1969486 discloses that
A guide device has been disclosed that continuously guides the front end of the flange width from the entrance side to the exit side of the universal rolling mill, thereby controlling the rolling line and the pass line of the rolling mill to reduce the occurrence of web center deviation. Methods of suppressing are known.

[0007]

However, when the present inventors conducted an experiment on universal rolling,
Even if the pass lines are aligned to prevent the web from being replaced due to the shift of the pass lines, the rear end in the longitudinal direction of the material to be rolled is a free end. It has become clear that can not be sufficiently suppressed. The reason for this is a slight asymmetry in the material to be rolled and the rolling conditions, and AA ′ immediately before the rearmost end 23 of the material to be rolled 20 in the longitudinal direction in the universal rolling mill 2 in FIG. In cross section, FIG.
This is because, as shown in (b) and (c), the material to be rolled is twisted and bites into the rolling mill in the twisted state, and the position of the web 21 is changed up and down with respect to the center of the width of the flange 22.

In each pass of the reverse rolling by the coarse universal rolling mill, the change in the center deviation of the web in the longitudinal direction was investigated. As a result, in each pass, the end of the longitudinal end on the side finally rolled by the coarse universal rolling mill was determined. It was found that the web center deviation was worse than that of the previous pass, and that the web center deviation at both ends in the longitudinal direction became large during the reverse rolling. When the web center deviation occurs at the end, the center of the material to be rolled at the time of biting in the subsequent pass is shifted from the pass line of the rolling mill, which promotes the web center deviation and reduces the web center deviation. Becomes increasingly difficult. An object of the present invention is to suppress the occurrence of the web center deviation at both ends in the longitudinal direction.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises a rough rolling mill, a pair of horizontal rolls and a pair of vertical rolls, and a web or a flange or both are provided at least on the entry side. A method for producing an H-section steel by sequentially rolling in a hot rolling mill train comprising a rough universal rolling mill and a finishing universal rolling mill provided with an induction guide for guiding, wherein the rough universal rolling mill or the finishing universal rolling mill, or the In one or more passes during rolling in both, the H-section steel is characterized in that the rolling end is subjected to torsion prevention control means and rolled immediately before the rear end of the material to be rolled into the rolling mill. It is a rolling method.

[0010] In the above method, the torsion prevention control means for the material to be rolled includes a control means for changing an opening degree of the horizontal roll and the vertical roll, a control means for reducing a gap between the guides, and the vertical roll. A method for rolling an H-section steel, characterized in that the method is any one of control means for moving the horizontal roll to the outside in the rolling direction, or a combination of two or more control means.

Further, in the above method, when the reduction rate of the flange is larger than the reduction rate of the web, the horizontal roll opening may be reduced, or the vertical roll opening may be increased, or both may be controlled simultaneously. If the web draft is greater than the flange draft, conversely, if the horizontal roll opening is increased, or the vertical roll opening is reduced, control means for simultaneously performing both are taken. A method of rolling an H-section steel characterized by the fact that the guide is a structure that can move up and down and expand and contract in the web height direction in addition to the web thickness direction. A method for rolling an H-section steel, characterized by taking control means for guiding.

As a result of various experiments on universal rolling, the inventors have found that the degree of the center deviation of the web at both ends in the longitudinal direction of the material to be rolled differs depending on the relationship between the web reduction ratio and the flange reduction ratio. Under the typical conditions, FIG. 5 shows an example of the result of an investigation on the relationship between the absolute value of the center deviation of the web generated at the front end, the center, and the rear end in the longitudinal direction after one-pass rolling and the difference between the rolling reduction of the web and the flange. Shown in As the difference between the web draft and the flange draft increased, the center deviation of the web became significantly worse, especially at the rear end, and almost the same characteristics were obtained under other conditions.

In the present invention, the front end in the longitudinal direction refers to a region at a predetermined distance from the frontmost surface on the side that first engages with the universal rolling mill in the rolling pass among the both ends in the longitudinal direction, and the rear end. "" Means an area at a predetermined distance from the last end face on the side that finally engages with the universal rolling mill in the rolling pass. The central portion indicates a region in which rolling is in a steady state, excluding the leading end and the trailing end from the entire length in the longitudinal direction.

The reason why the center of the web at the rear end is more deviated as the flange reduction ratio is increased with respect to the web reduction ratio is considered as follows. The contact projection length between the web and the horizontal roll and the contact projection length between the flange and the vertical roll are approximately expressed by the following equations. _{Ld w ≒ (R h × t} w × r w) 1/2 ··· (1) Ld f ≒ (2 × R v × t f × r f) 1/2 ··· (2) here, Ld Is a contact projection length, R is a roll radius, t is a plate thickness, r is a draft, a subscript h is a horizontal roll, v is a vertical roll, w is a web, and f is a flange.

[0015] For example, if web and flange rolling reduction are the _{same, (1), Ld f /} Ld w from equation _{(2), Ld f / Ld w = {} (2 × R v / R h × t f / t _w)} ^1/2 · · · (3) becomes usually because it is _{2 × R v / R h>} 1, t f / t w> 1, is greater than 1 the value of (3) . Therefore, as the flange rolling reduction is increased, the flange rolling start is more advanced than the web rolling start, and the web is pushed in the height direction by pushing the vertical roll before the web is restrained by the horizontal roll. A compression force is applied, and the compression force exerted by the vertical roll also increases. For this reason, at the rear end of the unrolled material to be rolled, twisting is likely to occur on the entry side of the rolling mill, and the web is bitten into the rolling mill in an asymmetric state and the web is replaced. On the other hand, at the leading end, the unpressed lower portion follows, so that the twist is less likely to occur, and even if the flange reduction ratio is increased, the deterioration of the web center deviation is slight.

On the other hand, when the web reduction ratio is larger than the flange reduction ratio, the metal flow from the web to the flange direction increases, and the inner width of the web at the rear end before the flange is reduced by the vertical rolls. It tends to be large, and the vertical roll rolls torsion and buckling at the corners, thereby deteriorating the center of the web.

Therefore, in order to suppress the buckling of the rear end portion, the reduction ratio of the web and the flange is temporarily set under the condition that the twist and the buckling hardly occur immediately before the rear end portion bites into the rough universal rolling mill. It is effective to adjust to. That is, under conditions where the flange reduction ratio is greater than the web reduction ratio and the flange reduction start occurs earlier than the web reduction start, the horizontal roll opening degree should be reduced immediately before the rear end bites into the rough universal rolling mill. Alternatively, by increasing the vertical roll opening to reduce the amount of advance of the flange pressing down on the web and the compressive force in the height direction of the web, the torsion of the material to be rolled is less likely to occur. In this case, the relationship between the reduction ratio of the web and the flange in the next pass of rough universal rolling is such that the flange is more strongly reduced at the tip end than at the center in the longitudinal direction, but as shown in FIG. The amount of deviation of the center of the web with respect to the difference in rolling reduction between the flange and the flange is smaller than that at the rear end, and is less likely to cause a problem.

When the web reduction ratio is larger than the flange reduction ratio, the horizontal roll opening is increased or the vertical roll opening is reduced immediately before the rear end portion bites into the coarse universal rolling mill. And reduce the metal flow from the web to the flange.

As described above, when adjusting the roll opening of the horizontal roll and the vertical roll, it is practical to balance the rolling reduction of the web and the flange in a state where the contact start positions of the web and the flange completely match. It is difficult, and it is important to balance the relationship between the reduction ratio of the web and the flange and the leading degree of reduction of the flange. Although slightly different depending on the size, generally the roll opening is adjusted so that the web reduction rate and the flange reduction rate are almost the same, and if the leading amount of the flange reduction start position is very large, the web reduction rate May be adjusted to be slightly larger than the flange draft.

In universal rolling, the width of the web is constrained by vertical rolls, while the width of the flange is free at both ends in the width direction. As the flange reduction ratio increases, the flange reduction ratio tends to be set higher than the web reduction ratio. Further, in the case of an H-section steel having a small web thickness and a large flange thickness, a web wave is apt to be generated during rolling, so that the rolling down of the flange is considerably strengthened in the latter coarse coarse pass. In this case, in the initial pass of the rough universal rolling, the web reduction tends to be larger than the flange reduction in the initial pass.

Therefore, when the above-mentioned rolling is applied to these passes, the effect of improving the center deviation of the web is great. In addition, even if the web reduction rate at the rear end is relatively large with respect to the center in the longitudinal direction in the latter pass of the rough universal rolling, the rear end can be deformed without relatively interacting the web and the flange. It is difficult to generate web waves.

Another method for suppressing the center deviation of the web at the rear end in the longitudinal direction of the material to be rolled in the coarse universal rolling is to prevent twisting or buckling of the material to be rolled by an induction guide. investigated. Normally, in order to prevent the material to be rolled from contacting the guide when biting and damaging the guide, and not to scratch the material to be rolled when passing through, the distance between the material to be rolled and the guide is about 10 mm. Are provided with appropriate gaps. However, in this gap setting, when the rear end portion of the material to be rolled is twisted in the range of the gap and the center of the web is generated, the material to be rolled is engaged only while the rear end portion of the material to be rolled is engaged. It is effective to greatly reduce the distance between the guide and the guide to increase the constraint. In this case, since the distance between the guides is reduced in the middle of the pass, the problem of damage or flaws on the guides is unlikely to occur.

As described above, in normal rolling, the contact projection length between the flange and the vertical roll is generally longer than the contact projection length between the web and the horizontal roll. Therefore,
To prevent the web from receiving compressive force in an unconstrained state by bringing the preceding flange's reduction start closer to the web's reduction start, the shaft of the vertical roll is kept horizontal only while the rear end of the material to be rolled is engaged. Moving the roll in the rolling direction on the roll side is also effective.

By the way, the widths of the horizontal rolls of the rough universal rolling mill and the finishing universal rolling mill are often slightly different between the two rolling mills depending on the respective wear conditions and roll operating conditions. The inner width of the web of the material to be rolled after rolling is increased or reduced by several mm using a finishing universal rolling mill. Further, when manufacturing an H-section steel having a constant web outer width, the web height is actively increased or reduced when rolling is performed by a finishing universal rolling mill.

Therefore, in these finishing universal rolling passes, similarly to the above-mentioned rough universal rolling mill,
If the means for preventing twisting and buckling of the web is implemented immediately before the rear end portion of the material to be rolled into the universal rolling mill, the center deviation of the web can be largely suppressed. However, when adjusting the opening degree of the horizontal roll or the vertical roll of the finishing universal rolling mill, it goes without saying that the adjustment amount of the roll opening degree is such that the web thickness and the flange thickness of the product do not deviate from the tolerance.

[0026]

1A and 1B show an example in which the present invention is applied to a coarse universal row. In this example, an edger rolling mill 5 is arranged near the rough universal rolling mill 2. The rearmost end 23 of the material to be rolled 20 is on the front side of the coarse universal rolling mill 2 and between the coarse universal rolling mill 2 and the edger rolling mill 5 or on the rear face of the edger rolling mill 5.
Sensors 7 and 8 are installed to monitor the passage of, and reverse rolling is performed. First, the rearmost end 2 of the material to be rolled 20 set in advance
The web 21 and the flange 22 are reduced by the usual pass schedule until the position P closer to the front end by a predetermined distance L from 3 is engaged with the rough universal rolling mill 2. On the way, the passage of the rear end 23 is detected by the sensor 7 on the rolling entry side, and the timing at which the position P bites into the coarse universal rolling mill 2 is calculated by the calculator 9 from the roll speed and the rolling conditions.
Control is performed so that the opening of the horizontal roll 3 or the vertical roll 4 is continuously changed to a target value. Changing the roll opening during rolling can be easily performed by using a universal rolling mill in which a hydraulic pressure reduction device is incorporated in a chock.

Next, FIG. 2 shows an example of a method of suppressing the center deviation of the web by the guide. The gap between the web 21 of the material to be rolled 20 and the guide 11 is set with some allowance from the most advanced biting to immediately before the rear end portion is bitten, and as in FIG. , The passage of the rear end 23 is detected by the sensor 7 on the rolling entry side, and the interval between the guides 11 is reduced using a hydraulic mechanism or the like. FIG. 2 shows an example in which the web is restrained, but it is more effective to restrain the outside of the flange or the tip of the flange at the same time.

Further, as shown in FIG. 3, a hydraulic device capable of changing the guide interval in the web thickness direction and the web height direction at the same time is provided to restrict the area from the end to the corner in the web height direction. The effect of controlling the web center deviation is greater. If a roller guide is used as a guide device in addition to a general friction guide, it is advantageous in preventing flaws.

FIG. 4 shows a state in which the axis of a vertical roll is moved and rolled by a rough universal rolling mill. As in FIG. 1, the sensor 7 installed on the rolling entry side of the coarse universal rolling mill 2
, The passage of the rear end 23 is detected, and the axis 31 of the vertical roll 4 is moved to the axis 3 of the horizontal roll 3 using a vertical roll moving device.
With respect to 0, it is moved by a predetermined amount to the rolling exit side. The hatched portion in FIG. 4 represents the contact area between the horizontal roll and the web,
Generally, it is desirable to set the amount of movement of the vertical roll so that the contact start position 32 between the horizontal roll and the web is substantially equal to the contact start position 33 between the vertical roll and the flange. Alone is effective.

Here, each of the web center deviation suppressing methods has been described. However, if two or more of these methods are combined, higher effects can be obtained. The timing at which the torsion prevention control means is applied is when the position P closer to the front end by a predetermined distance L from the rear end 23 bites into the rough universal rolling mill 2, and the predetermined distance L is determined by the product size, the rolling pass, and the rolling conditions. The optimum value differs depending on the type, and is preferably set immediately before the occurrence of torsion at the rear end. Further, the distance L may be changed by each control means. In particular, in the initial pass of rough universal rolling, to sufficiently suppress the twisting of the rear end, the effect of improving the center deviation of the web in a considerably wide area from the rear end in the product due to the stretching of the material to be rolled. Bring.

[0031]

EXAMPLE In the rolling mill row shown in FIG. 6, H600 × 300 × 9/19 was manufactured from a continuously cast slab. The pass schedule was set to 19 passes for rough rolling, 11 passes for coarse universal rolling, and 1 pass for finish universal rolling. In rough universal rolling, in order to prevent rolling web waves and stabilize the rolling, the flange reduction rate is several percent larger than the web reduction rate from the seventh pass to the eleventh pass in the latter half, while from the first pass in the first half. Up to the sixth pass, the pass schedule is such that the web reduction rate is several percent larger than the flange reduction rate due to the web / flange thickness ratio between the intermediate slab and the product after the rough rolling. According to this pass schedule, when an H-section steel was manufactured by a conventional rolling method, the web center deviation of the product was 3.3 mm at the end in the longitudinal direction at the maximum, and it was necessary to cut off the dimensional defect part which was out of tolerance.

On the other hand, the rolling method of the present invention is applied to the coarse universal rolling in order to suppress the occurrence of the center deviation of the web. An example in which the roll is changed by changing the vertical roll opening and the guide interval immediately before being engaged in the rolling mill will be described.

With respect to the above-mentioned pass schedule, in the first to sixth passes, the vertical roll opening is reduced just before the rear end of the material to be rolled is engaged to increase the flange draft, and the seventh to sixth passes are performed.
In the 10th pass from the pass, the vertical roll opening is increased just before the rear end of the material to be rolled is engaged to reduce the flange reduction rate, and rolling is performed while changing the flange reduction rate to substantially the same as the web reduction rate. Was. In addition, in all passes of the coarse universal rolling, when the rear end of the material to be rolled is engaged, the gap between the upper and lower surfaces of the web of the material to be rolled and the guide is larger than the guide that is on the rolling entry side in each pass. It was adjusted to about 2 mm and rolled.

The timing of executing the control means is the same for all the passes in this embodiment. The control of the vertical roll opening is set at the time when the position close to the front end of about 2 m from the rear end is engaged, and the control of the guide interval is set. The position near the front end about 5 m from the rear end was set to the time of biting. As a result, the center deviation of the web was reduced to a maximum of 1.4 mm at the extreme end, and the control effect in the initial pass was large from the end to the center, and the central deviation of the web could be reduced over a wide range as compared with the conventional case. . It is undeniable that the effect is reduced when the control means for controlling the center of the web is performed independently. However, depending on the required accuracy for a manufactured product, such a single control does not cause any problem.

Further, in order to further increase the efficiency of suppressing the center deviation of the web, when the rear end portion is engaged in all the passes of the rough universal rolling, the difference between the flange contact projection length and the web contact projection length is substantially equal to the difference. In addition, a control means for moving the vertical roll axis relative to the horizontal roll axis toward the roll-out side in the rolling direction to perform rolling may be combined at the same time.

[0036]

By applying the present invention to an H-section steel manufacturing process by universal rolling, it is possible to reduce the center deviation of the web at both longitudinal ends of the material to be rolled, which has been difficult to suppress the center deviation of the web. H-shaped steel with good dimensional accuracy can be manufactured.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a universal rolling method of the present invention, wherein (a) is a plan view and (b) is a side sectional view.

FIG. 2 is a view schematically showing the guide of a material to be rolled by the guide device of the present invention.

FIG. 3 is a view schematically showing a method of guiding a web height direction end portion by a guide device.

FIG. 4 is an explanatory view of vertical roll axis rolling in the present invention.

FIG. 5 is an explanatory view of a center deviation of a web generated in a portion in a longitudinal direction due to a rolling condition.

FIG. 6 is a view schematically showing an H-section steel manufacturing process.

FIG. 7 is a diagram schematically showing the shape of a material to be rolled in each rolling step.

FIG. 8 is an explanatory view of the web center deviation of the H-section steel.

FIG. 9 is an explanatory diagram showing a state of occurrence of web center deviation due to a shift of a pass line.

FIGS. 10A, 10B, and 10C are schematic diagrams showing a state in which a web center deviation occurs at a rear end of a material to be rolled.

[Explanation of symbols]

 1: Rough rolling mill 2: Rough universal rolling mill 3: Horizontal roll 4: Vertical roll 5: Edger rolling mill 6: Finishing universal rolling mill 7, 8: Sensor 20: Rolled material

Claims (4)

[Claims] 1. A rough rolling mill, comprising a pair of horizontal rolls and a pair of vertical rolls, and a rough universal rolling mill and a finishing universal rolling machine provided with an induction guide for guiding a web and / or a flange on at least an entry side thereof. A method of producing an H-section steel by successively rolling in a series of hot rolling mills comprising rolling mills, wherein the rough universal rolling mill and / or the finishing universal rolling mill, or both, are subjected to one or more passes during rolling. A method for rolling an H-section steel, wherein rolling is performed by means of a twist prevention control means for a material to be rolled immediately before a rear end of the material bites into a rolling mill. 2. A control means for changing the degree of opening between the horizontal roll and the vertical roll, a control means for reducing a gap between the guides, and a control means for reducing the gap between the guide and the horizontal roll. 2. The method for rolling an H-section steel according to claim 1, wherein the control means moves the rolling section to the outside in the rolling direction, or a combination of two or more of the control means. 3. When the flange reduction ratio is greater than the web reduction ratio, control means for reducing the horizontal roll opening degree, increasing the vertical roll opening degree, or performing both simultaneously, Conversely, when the web draft is greater than the flange draft, the horizontal roll opening may be increased, or the vertical roll opening may be reduced, or control means for performing both simultaneously may be employed. The method for rolling an H-section steel according to claim 1 or 2, wherein: 4. The guide according to claim 1, wherein the guide is a structure capable of moving up and down and extending and contracting in the height direction of the web in addition to the thickness direction of the web. Item 1. The method for rolling an H-section steel according to Item 1 or 2.