JPH04231108A - Method for constraining/cooling flange of h-shape steel - Google Patents

Abstract

PURPOSE:To prevent waved deformation and cambering bent deformation of web by forcedly cooling while moving by holding both surfaces of the flange parts of H-shape steel which is delivered from a finishing mill. CONSTITUTION:The flange parts 2 of H-shape steel 1 which is passed through the finishing mill 4 are held from both side faces with guide shoes A, B, C, D and pressurized with hydraulic cylinders 6. While moving a lower frame 7 in the rolling direction at a speed that is synchronized with a delivering speed of the H-shape steel 1, the flanges 2 are forcedly cooled by injecting cooling water from cooling nozzles 10 to the flange parts 2. Because the flanges 2 is thermally shrinked, friction force (force of constraint) in the direction that thermal shrinkage of the flanges 2 is prevented is acted on the contact surface between the guide shoes A-D and the flanges 2. Thermal stress that is generated on the flanges 2 due to this force of constraint is acted as strong tensile stress. Because the difference between the thermal shrinkage of the flanges 2 and the web 3 is mitigated and compressive stress that is generated on the web 3 is reduced, the generation of waved deformation of the web 3 is prevented.

Description

[Detailed description of the invention]

0001

[Industrial Application] The present invention relates to a method for cooling a flange when manufacturing an H-beam steel by hot rolling, and more specifically, to reduce the waving deformation that occurs in the web of an H-beam steel during the cooling process after hot finishing rolling. The present invention relates to a method for cooling a flange, which prevents warpage and bending deformation of the entire H-section steel, and allows efficient production of H-section steel having a good shape.

0002

[Prior Art] In H-beam steel manufactured by hot rolling, especially when the web thickness is thinner than the flange thickness, there is a temperature difference between the web and the flange at the end of finishing rolling, and a difference in temperature between the web and the flange after finishing rolling. Due to the difference in the cooling rate of the web, waving deformation or warping deformation occurs in the web.

[0003] In order to prevent such waving deformation of the web, a method is generally used in which cooling water is injected onto the flange surface to cool the flange more strongly than the web. We also proposed a method in which multiple pairs of guide rollers cooled with a refrigerant are placed on both sides of the running path of the H-section steel, and the guide rollers are brought into light contact with the outer surfaces of the left and right flanges of the running hot-rolled H-section steel to cool the running path. (Japanese Unexamined Patent Publication No. 161916/1982).

[0004] These methods attempt to prevent the waving deformation of the web caused by the difference in cooling rate between the web and the flange by causing the temperature drop of the flange to follow the temperature drop of the web during the cooling process after finish rolling. However, if the flange is strongly cooled, there is a problem in that the flange contracts during cooling, compressive stress acts on the web, and waving deformation occurs. In other words, in these methods, especially when the web is thin and the temperature difference between the web and the flange at the end of finish rolling (hereinafter referred to as initial temperature difference) is large, the web may undergo undulating deformation during forced cooling.
Furthermore, since the stress caused by the initial temperature difference cannot be sufficiently relaxed, waving deformation remains even after cooling to room temperature. moreover,
In the case of forced cooling with water, the injected water flows to the lower part of the flange, so cooling tends to be uneven, causing warping or bending deformation during or after cooling.

[0005] As a countermeasure to such problems, a method or device is proposed in which U-shaped, H-shaped, angle-shaped steel sections, etc. are held in a restrained state after finishing hot rolling, and then cooled in that state to reduce warping and bending. has been proposed (Japanese Unexamined Patent Publication No. 54-3
No. 3253, JP-A No. 62-235423,
JP-A-62-235424, JP-A-62-235
425, etc.). In addition, as a measure to prevent web undulation, for example, a shrinkage restraint flange water cooling method has been proposed, in which the front and rear ends of the material are fixed before the start of water cooling to restrain shrinkage due to temperature drop (Materials and Processes vol. 3 (1990)).
P. 498).

[0006]

[Problems to be Solved by the Invention] However, the above-mentioned Japanese Patent Application Laid-Open No. 54-33253 and Japanese Patent Application Laid-Open No. 62-235423
The techniques described in Japanese Patent Application Laid-open No. 62-235424 and Japanese Patent Application Laid-open No. 62-235425 are all techniques for cooling the shaped steel by suppressing it, so that warping during cooling (intermediate warping) is avoided. ), but it is not possible to prevent the waving deformation of the web, and depending on the cooling method, there is a problem that the warpage after cooling becomes large.

[0007] Furthermore, the shrinkage restraint flange water cooling method described above
Since the front and rear ends of the material are fixed, it is possible to prevent compressive stress from occurring in the web during water cooling, and water cooling also provides enough plasticity to offset the difference in thermal contraction between the web and flange due to the initial temperature difference. Elongation deformation can be applied to the flange and waving deformation of the web can be prevented, but the front and rear ends must be restrained by a fixed frame, making it impossible to apply this method while rolling. So, work efficiency is poor. Furthermore, in order to prevent overload on the restraint device, a tension control mechanism is required to suppress the tensile force generated by thermal contraction of the material within a certain limit, and is still in the testing stage. This cannot be said to be an effective method.

An object of the present invention is to provide a method for cooling a flange that can prevent web waving and warping deformation during the cooling process of H-section steel after rolling, and that can manufacture H-section steel with high efficiency. It is in.

[0009]

[Means for Solving the Problems] As a result of repeated studies in order to solve the above problems, the present inventors have found that the flange of an H-shaped steel sent out from a finishing rolling mill is held between both sides thereof,
It was confirmed that waving deformation of the web could be prevented by forcing the flange to cool while moving the clamping portion at the same speed as the H-beam sent out from the finishing mill. The present invention was made based on this knowledge, and its gist is ``both flanges of an H-section steel after hot finish rolling are held between both sides of the flanges at one or more locations in the longitudinal direction of the H-section steel. ``A flange restraint cooling method for an H-section steel'' characterized in that the flange is forcibly cooled between a finishing rolling mill and a flange clamping part and/or between flange clamping parts.

[0010] That is, by restraining the thermal contraction that tends to occur in the flange when the flange is forcedly cooled by the frictional force based on the contact pressure in the finishing mill and the flange clamping part, the flange is subjected to longitudinal tension. This generates stress and plastic elongation strain to prevent the web from waving. Further, by adjusting the clamping force in the longitudinal direction of the flange restraining parts A, B, C, and D (see FIG. 1), it is also possible to prevent the H-section steel from warping and deforming.

[0011] The flange may be held by either a guide shoe method or a roll method. As will be described later, when using guide shoes, it is necessary to move the flange holding part in the rolling direction at the same speed as the rolling speed, but when using rolls, there is no need for this. As the guide shoe, any shape of jig may be used, such as a jig whose contact surface with the flange is a flat plate or a round jig, or it may be held by using rolls instead of the guide shoe. Good too. In other words, in the flange clamping part, any material can be used as long as the flange can be restrained by the frictional force based on the contact pressure between the flange and the clamping tool.

[0012] The above-mentioned rolling speed is the speed of the H-section steel delivered from the final end of the finishing mill.

[0013] The forced cooling of the flange may be performed by jetting water, or any other effective cooling means may be used. In addition, the part of the flange that performs forced cooling may be within the restricted range; if it is clamped at one location, it is between the finishing rolling mill and the flange clamping part, and if it is clamped at two or more locations, it is between the flange clamping part. Cooling is performed between the rolling mills or between the finishing rolling mill and the first stage flange clamping section.

[0014]

[Operation] First, the mechanism of occurrence of web waving deformation will be described. FIG. 2-1 (a) is a cross-sectional view of an H-beam steel whose web thickness tw is thinner than the flange thickness tf. Figure 2-
1(b) is a diagram schematically showing the difference in temperature between the flange and web at the end of finish rolling of such an H-section steel, and shows the amount of heat dissipated based on the difference in heat capacity and surface area between the web and flange. Due to the difference, the temperature of the web is significantly lower than the flange temperature at the end of finish rolling. In addition, in Figure 2-1 (b), W is the width of the flange, H-2
tf is calculated from the height of the H-shaped steel (H) to the thickness of both flanges (2
tf ) is subtracted from the web length. When an H-section steel that has finished finish rolling under such a temperature difference is cooled to room temperature, the temperature difference between the web and flange disappears ((c) in Figure 2-1), but the flange Due to the large amount of thermal contraction ((d) in Figure 2-1), the stress generated in the longitudinal direction of the H-section steel becomes compressive stress in the web and tensile stress in the flange ((e) in Figure 2-1).
reference. (Hereinafter, this stress will be referred to as stress due to initial temperature difference)
.

In addition, in the cooling process after finish rolling, the difference in the amount of heat released, that is, the amount of heat released from the web is larger than the amount of heat released from the flange, as shown in FIG. 2-2 (f). As shown, the temperature of the web decreases to a greater extent than the temperature of the flange, and the temperature difference between the web and the flange temporarily increases (in the figure, the broken line represents the temperature at the end of finish rolling). This web temperature drop is
Tensile thermal stress is generated in the web, resulting in plastic elongation strain in the longitudinal direction of the web ((g) in Figure 2-2), and as the temperature decreases and approaches a uniform state ((g) in Figure 2-2). h)
), this plastic elongation strain generates compressive stress in the longitudinal direction of the web (hereinafter, this stress will be referred to as stress due to differential plastic deformation). (i) in Figure 2-2 is the combination of the thermal shrinkage difference ((d) in Figure 2-1) and the plastic elongation strain difference (plastic deformation difference), so (j) in Figure 2-2 As shown in Figure 2, large compressive stresses occur in the web and large tensile stresses occur in the flanges. The broken line σcr in the figure is the critical buckling stress of the web, and if the compressive stress generated in the web exceeds this value, the web will deform. In other words, the web of the H-beam after hot rolling is subjected to high compressive stress, which is a combination of stress due to the initial temperature difference and stress due to the difference in plastic deformation, which causes waving deformation in the web and the shape of the H-beam. stiffness and strength functions are impaired.

[0016] As described above, the waving deformation of the web can be classified into two types, one due to the initial temperature difference and the other due to the plastic deformation difference. The initial temperature difference is 10 in normal rolling.
It reaches 0 to 200℃, but for example, H 640mm×
When calculated using the model shown in FIG. 2 for a 200 mm x 6/20 mm H-section steel, the compressive stress generated in the web is 17 to 34 kgf/mm2. On the other hand, the critical buckling stress σcr is expressed by the following formula, and in the case of the above H section steel, σ
Since the cr is approximately 7.6 to 11.4 kgf/mm2, the web will undergo waving deformation due to the stress due to the initial temperature difference alone, even if no plastic deformation difference occurs.

[0017]

[Math 1]

Therefore, in order to prevent the waving deformation of the web, it is necessary to
Before the temperature of the section steel decreases and the compressive stress generated in the web exceeds the critical buckling stress σcr, plastic elongation is applied to the flange to reduce the difference in the amount of thermal contraction between the web and the flange, and acts on the web. It is sufficient to reduce the compressive stress.

In order to impart plastic elongation to the flange, it is sufficient to restrain the H-shaped steel in the longitudinal direction and forcefully cool the flange to generate a tensile thermal stress in the flange that exceeds the yield stress (Materials and Processes vol. 3 (1990) p.
448). For this purpose, in the method of the present invention, the flange is held and restrained from both sides as described above, and forced cooling is performed.

FIG. 1 is an explanatory diagram showing the configuration of an example of an apparatus for carrying out the present invention. FIG. 1(a) is a plan view of the main part of this apparatus, and FIG. ) I-I arrow view of
FIG. 1(c) is an enlarged sectional view of a part of this device, showing only one side of the left-right symmetry. In these figures, A, B, C, and D are guide shoes that respectively clamp both flanges 2 of the H-section steel 1 that has passed through the finishing rolling mill 4. These guide shoes are designed to clamp the flanges 2 from both sides. Each of them is a set of two, and A and B and C and D form a pair, and A, B, C, and D are arranged at opposing positions on both flanges of the H-section steel. In this example, the flange 2 is held between two locations.

As shown in FIG. 1(c), there are two guide shoes, one of which is connected to the frame 5 via the hydraulic cylinder 6 and the other directly to the frame 5. It is fixed to the lower frame 7 via a mechanism 8. The adjustment mechanism 8 has a function that allows the length of the frame 5 to be adjusted accordingly even if the dimensions of the H-shaped steel change and the distance between the flange 2 and the wall surface 9 changes. Further, the lower frame 7 is configured to be able to move along the wall surface 9 in the longitudinal direction of the H-section steel at a speed v' that is synchronized with the speed v at which the H-section steel is sent out from the finishing mill. In addition, in this example, water is injected between the finishing rolling mill 4 and the guide shoes A, B, C, and D of the first stage, and between the guide shoes of the first stage and the second stage to cool the flange 2. A flange cooling nozzle 10 is provided for this purpose.

In order to carry out the method of the present invention using this apparatus, first, the left and right flanges 2 of the H-section steel 1 that have passed through the finishing rolling mill are inserted into the guide shoes A, B and C from both sides thereof.
D and press it with force FA, FB, FC, FD by hydraulic cylinder 6. Since the frame 5 is fixed to the lower frame 7 via the adjustment mechanism 8, even if the distance from the wall surface 9 of the H-section steel 1 changes depending on the dimensions of the H-section steel 1, its length can be adjusted accordingly. be done. Cooling water is injected from the cooling nozzle 10 onto the flange 2 while moving the lower frame 7 in the rolling direction at a speed v' synchronized with the speed v at which the H-section steel 1 is sent out from the finishing rolling mill 4,
The flange 2 is forcibly cooled. Since the flange 2 tends to shrink due to heat, frictional forces (restrictive forces) μFA , μFB , μFC , μF are applied to the contact surfaces of the guide shoes A, B, C, and D and the flange 2 in a direction that prevents the heat shrinkage of the flange 2.
D works. Due to this restraining force, the thermal stress generated in the flange 2 acts as a stronger tensile stress than in the case without restraint.

FIG. 3 is a schematic diagram showing the stress generated in the H-section steel when the method of the present invention is applied.
As shown in the figure, the temperature of the flange 2 after forced cooling is lowered by ΔT compared to the case without forced cooling (broken line in the figure). As shown in Figure 3(b), the thermal stress generated in the flange 2 and web 3 during forced cooling is tensile in the flange 2 and compressive in the web 3, but in the case of no restraint (in the figure) (broken line), the stress shifts to the tensile stress side by Δσ caused by the frictional force, and the stress generated in the flange 2 exceeds the yield stress σY, so that the flange 2 can be given plastic elongation. As a result, the difference in the amount of thermal contraction between the flange 2 and the web 3 is alleviated, and the compressive stress that occurs in the web 3 when the H-section steel is cooled to room temperature and there is no temperature difference between the web 3 and the flange 2 is reduced. The critical buckling stress σcr is not exceeded, and the occurrence of waving deformation of the web is prevented.

[0024] When attempting to give the same tensile thermal stress (solid line in Fig. 3(b)) and plastic elongation as in the case of restraint only by forced cooling, the tensile thermal stress at the flange 2 increases and the web 3 Figure 3(b) shows the compressive thermal stress in
The compressive stress of the web 3 exceeds the critical buckling stress σcr, resulting in undulating deformation of the web 3 during forced cooling. According to the method of the present invention, the compressive stress of the web 3 during forced cooling is reduced to the critical buckling stress σ
Since the tensile stress of the flange 2 can be increased while keeping it lower than cr, it is possible to prevent the web from waving during forced cooling and throughout the entire cooling process until the H-beam is cooled to room temperature. .

The tensile stress σf generated in the flange 2 during forced cooling is expressed as follows.

[0026]

[Math 2]

[0027] If slip occurs in the restraint portion, σf becomes small, but the condition under which σf exceeds σY even if slip occurs is as shown in the following equation.

[0028]

[Math 3]

When carrying out the method of the present invention using a device such as the one shown in FIG. 1 in which a flange is held between guide shoes, it is preferable that the flange be restrained by the guide shoes at a plurality of locations. This is because when carrying out the method of the present invention, the clamping part is moved together with the transfer of the H-beam as described above, but after it has been moved a predetermined distance, the restraint is released and the guide shoe is returned to its original position. This is because the guide shoe is clamped again to perform restraint cooling, so if the guide shoe is restrained at only one place, it will be cooled without being restrained while the guide shoe is returned to its original position. Note that the reason why the clamping part is moved in the traveling direction of the H-shaped steel is to prevent unnecessary compressive stress from being generated in the H-shaped steel between the clamping part and the finishing rolling mill.

FIG. 4 is an explanatory view showing the holding part of another example of the apparatus for carrying out the method of the present invention, and only one side of the left-right symmetrical part is shown, but in this case, the flange 2 is held Therefore, rolls E and F are used instead of guide shoes. As with the guide shoe, there are 2 rolls in 1
one of which has its roll axis connected to the hydraulic cylinder 6.
The other rod has its roll axis connected to the frame (
(not shown), and both are configured so that the H-section steel can be moved at a speed synchronized with the speed v at which it is sent out from the finishing mill and in the same direction. When using this device, it is not necessary to move the rolls in the direction of movement of the H-section steel, but it is sufficient to drive the rolls in synchronization with the rotation of the final roll of the finishing mill. By rotating this roll, it is possible to obtain the same restraining effect as when restraining with a guide shoe.

When the flange is forcibly cooled, the cooling water injected onto the flange surface flows below the flange, so that the lower part of the flange is more likely to be cooled more strongly. Therefore, plastic elongation strain caused by thermal stress becomes large at the lower part of the flange, and even when the temperature of the H-section steel is uniform, downward convex warpage in the longitudinal direction of the H-section steel may occur. The method of the present invention is effective even when such deformation occurs. In other words, since the flange is restrained by the frictional force with the guide shoe, if a large tensile stress is generated in the lower part of the flange due to forced cooling, the gripping part of the lower part of the flange will slip, causing the upper and lower parts of the flange to slip. This is because it acts to equalize the tensile stress of.

Alternatively, the pressing forces FB, FD at the lower part of the flange may be made smaller than the pressing forces FA, FC at the upper part.

[0033] In the method of the present invention, the flange is restrained by using the frictional force at the clamping part of the guide shoes and rolls, so if the tensile force acting on the flange exceeds a certain limit, slipping will occur at the clamping part, causing damage to the device. There is no concern that overload will occur. Furthermore, the restraining force can be controlled by controlling the force applied to the guide shoes and rolls that clamp the flange.

The method of the present invention can be applied while rolling is being carried out in a hot rolling line for H-section steel, and does not require a special restraint cooling process. Therefore, H-section steel can be manufactured with high efficiency without reducing work efficiency.

[0035]

[Example] A roll-down/driven flange clamping device was installed at a position 10 m behind the finishing mill (#1 zone) and at a position 2
The waving deformation and warpage deformation of the web were investigated for the H-beam steel manufactured by applying the flange restraint cooling method of the present invention, which was placed at the 0 m position (#2 zone). For comparison, a similar investigation was also conducted on a conventional method in which the flange is water-cooled without being constrained.

[0036] The roll diameter of the rolls used was 30
0mm, roll pressing force is maximum 500kg for each roll
It is f. A forced cooling device capable of cooling a 5 m section was installed between the finishing mill and the flange clamping part, and between both flange clamping parts, and the flanges were cooled by water spray.

[0037] H-shaped steel (H 64
The temperature of the web is 600°C and the flange is 750°C.

[0038] The investigation results are shown in Table 1.

[0039]

[Table 1]

As is clear from this table, when the flange is simply cooled without restraint cooling (conventional method), the amount of cooling water is small in No. In No. 3, web waving occurred on the cooling bed, and No. 3 had a large amount of cooling water. In No. 4, waving occurred in the web during forced cooling, and the waving deformation remained even after cooling, and longitudinal warping occurred on the cooling bed. On the other hand,
In the methods of the present invention (No. 1 and No. 2), no waving or warping of the web occurred throughout the entire process after rolling, and H-beam steels with a sound shape could be manufactured.

[0041]

[Effect of the invention] In the production of H-beam steel by hot rolling,
If the method of the present invention is applied during cooling after finish rolling, it is possible to prevent web waving and warping of the H-beam steel. Since this method can be carried out online, it has great industrial value without compromising production efficiency.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an example of an apparatus for carrying out the method of the present invention. FIGS. 2-1 and 2-2 are explanatory diagrams of a web undulation generation mechanism. FIG. 3 is an explanatory diagram of a mechanism for preventing web undulation by applying the method of the present invention. FIG. 4 is a diagram showing the configuration of another example of the apparatus for implementing the method of the present invention.

Claims (1)

[Claims] [Claim 1] Both flanges of an H-section steel after hot finish rolling are held between a finish rolling mill and a flange holding part while being held from both sides of the flange at one or more longitudinal points of the H-section steel, respectively; and/or a flange restraint cooling method for H-beam steel, characterized in that the flange is forcibly cooled between the flange clamping parts.