JPH02127901A - Manufacturing method of thin web H-beam steel - Google Patents

Abstract

PURPOSE:To prevent undulation of the web in a cooling stage by giving the web a spreading force in its height direction in a temp. range where a web temp. is lower than a specific temp. and spreading a web height to be higher by a specific percentage after usual hot finish rolling and hot saw cutting. CONSTITUTION:A spreading force in the height direction is given to the web in a temp. range where a web temp. is <=400 deg.C to extend a web height by >=0.2%. After a rolled stock 1 rolled by a usual rolling method is cooled to a prescribed temp. on a cooling bed, the stock 1 is transferred to a roller straightener 2 in a succeeding stage; straightening rolls 3 give a bending force in the vertical direction to an H-shape steel 1 so that a zigzag wrapping allowance is to be a prescribed value. Flanges 1b tilt in that time and are supported by the rolls 3 to bear reactions in the directions shown by the arrows B. The reactions act as an extending force of a web 1a in its height direction. A solid type lubricant is applied to the peripheral surface of the rolls 3 to aim for reduction of frictional force between the rolls 3 and the web 1a and for increase of an expanding amount in the web central part. Hence, compressive stresses in the web 1a are reduced to prevent undulation of the web 1a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing an H-section steel product whose web is thinner than the flange by hot rolling.

[Prior art]

When manufacturing this thin web H-section steel (H-section # with a ratio of flange thickness to web thickness of 2.0 or more) by hot rolling, finishing (tJF The temperature difference between the web and the flange in the mill is usually 200°C or more. During the cooling process, there is a difference in shrinkage rate between the web and the flange, so the web is in a compressed state (tensile internal stress is generated in the flange and compressive internal stress is generated in the web in the longitudinal direction).
As a result, it eventually reaches the point where it is undulated, resulting in the so-called waving phenomenon.

Therefore, the applicant first proposed a method to prevent the waving phenomenon of the web that occurs during this cooling process. They proposed that the internal stress be relaxed and removed based on the temperature difference between the web and the flange.

(Refer to Japanese Patent Application No. 61-288452) [Problem to be solved by this invention] However, in order to warm-roll a flange, even if the rolling reduction is 3% or less, it is necessary to It was necessary to add a flange rolling device.

Therefore, the cost of the H-shaped steel itself is high due to the equipment cost, and it is not possible to easily implement measures to prevent the web waving phenomenon.

This invention was devised in view of the above-mentioned circumstances, and its purpose is to prevent web waving (reduce web compressive stress that increases during the cooling process) by using conventional equipment as is. The object of the present invention is to provide a method for manufacturing shaped steel.

[Means to solve the problem]

According to the method of this invention, thin web H-section steel can be manufactured at a web temperature of 400° C. after normal hot finishing rolling and hot sawing.
Processing is applied to the web to remove internal stress in a temperature range of 'C or lower, or processing is applied to the flange to remove internal stress in a temperature range of flange temperature of 400°C or lower.

The specific processing method is to widen the web height, either by continuous processing in the direction of expanding both flanges using a roll that is in contact with the inner surface of the flange, or by using a press claw instead of the roll. , and further ■ A method in which the web is repeatedly bent alternately and the collapse of the flange is utilized.

On the other hand, as a method of applying processing to the flange, (1) bending is performed alternately with the flange in the outermost direction of bending (bending in the strong axis direction), and tensile and compressive stresses are applied alternately to the flange.

In other words, in ■~■, when the web of an H-section steel is plastically deformed to increase the web height, the web tries to shrink in the longitudinal direction of the H-section steel, but as it is restrained by the flange, the web ends up shrinking. A tensile force is applied in the longitudinal direction of the H-beam.

On the other hand, in the case of applying bending to the flange, when viewed from the cross section of the H-section steel, the flange is parallel to the bending axis, and the bending process is applied with the flange placed at the outermost position of the bend. Using the tensile force of This applies tensile force in the longitudinal direction of the steel.

〔Example〕

The method for manufacturing a thin web H-section steel according to the present invention will be explained below with reference to illustrative examples.

First, an outline of this invention method will be explained.

In the hot-rolled H-beam steel, positive and negative internal stresses are generated in the flange and the web during the cooling process due to the difference in finishing temperature and cooling rate between the flange and the web. In thin-web H-beam steel, this web compressive stress exceeds the limit of spot digging, resulting in waving.

Therefore, by applying plastic deformation to the web or flange in the warm region before web waving, tensile force is applied to the web in the rolling direction, reducing the web compressive residual stress and reducing the compressive stress due to subsequent flange shrinkage. It allows it to be absorbed.

The timing for applying this plastic deformation is the web.

It is affected by the temperature difference between the flanges and the difference between the web temperature and room temperature, and is determined by the amount of stress that can be released.

For example, in the case of strong rolling processing such as in Japanese Patent Application No. 61-288452, it is effective even if the temperature is in a relatively high temperature range, but in the case of releasing internal stress by increasing the web height, it is better to have a larger internal stress. It is better to have a lower temperature than to have a release effect.

However, once the corrugation has occurred, it may be difficult to process it depending on the processing method, and it is difficult to eliminate it with light machining.

In the case of H-beam steel obtained by the normal manufacturing method, 350
C to 250 C is preferable, and when the hot finish rolling temperature is low such as low temperature rolling, 300 C to 150 C is preferable. Note that at high temperatures, the effect is weak and the stress generated thereafter is also high, so the temperature must be at least 400°C or lower.

Also, for a certain product size, if the temperature difference between the web and the flange when passing through a finishing universal mill is 200°C, when this product is cooled to room temperature, the web temperature will be 18°C.
Ripples occur at 0°C.

Therefore, when the web temperature is 200°C, the web is passed through a roller straightening machine to increase the web height by approximately 2 mm, thereby applying tensile stress to the web in the rolling direction and reducing compressive stress. During the process, the compressive stress increases due to the difference in the amount of thermal contraction, but it does not become thicker than the limit stress for spotting and does not cause web waving.

This enlarging deformation of the web height is most effective when performed immediately before web undulation, and the greater the amount of enlarging, the greater the effect. It is also possible to expand the web height using a finishing universal mill. In this case, it is necessary to wait after rough rolling to lower the temperature, or to perform forced water cooling mainly on the flanges.

For these reasons, in the present invention, when manufacturing an H-beam steel product with an extremely thin web relative to the flange by hot rolling, the web temperature is lower than 400°C after normal hot finish rolling and hot sawing. The web is bent alternately in the area, and the web height is expanded by utilizing the inclination of the flanges.

Next, the manufacturing method according to claims 1 and 2 of the present invention is actually applied to H2O2X196
An example of manufacturing an H-beam of X9/22 will be explained.

H700x 196 x 9/22 (flange thickness/
When manufacturing H-section steel 1 with a web thickness ratio of 2.44),
After heating the rectangular cross-sectional slab to 1260° C., it was shaped and rolled into a product cross-sectional size by rolling using a BD mill, a rough universal mill, a rough edger mill, and a finishing universal mill. (
(not shown) In the normal rolling method, the web 1a immediately after finish rolling is
The temperature of flange 1b is 700°C and the temperature of flange 1b is 880°C.
However, during the cooling process by allowing the web to cool to room temperature, when the temperature of the web 1a reached 200° C., waving occurred in the web 1a.

In addition, in the low-temperature finish rolling method, the web 1 immediately after finish rolling is
The temperature of a is 600°C and the temperature of flange 1b is 750°C.
Also in this case, waving occurred when the web 1a reached 120°C in the same cooling process as in the normal rolling method.

For this reason, the rolled material of the normal rolling method is cooled down to 300°C on a cooling bed and then sent to the next process, the roller straightening machine 2. Here, nine straightening rolls 3 are used on the upper and lower sides, and the lap width of the chido-shaped rolls is A vertical bending force was applied to the H-shaped steel with a maximum of 18 a+m. (See Figure 1) Here is the H shape! ! 41 is
In bending in the correction direction, the flange 1b collapses as shown in FIG. However, because of the presence of roll 3, it does not fall down completely, but is supported by roll 3, and receives a reaction force from roll 3 in the direction of arrow B. And this reaction force is the web 1a
It becomes a force that aims to expand in the height direction.

At this time, a solid lubricant was applied to the circumferential surface of the straightening roll. This is because even in normal roller straightening, the web 1a expands in the width direction by about 1 to 2ffi1, but in more than 50% of the cases, the flange 1b is expanded at 30 mm from both ends near the root, and at the center. Since the expansion is not large, the aim is to reduce the frictional force between the roll 3 and the web 1a and increase the amount of expansion at the center of the web.

By reducing the frictional force in this way, the tensile force at the center of the web increases. Further, by using rolls having shapes as shown in FIGS. 3(A) and 3(B), it is possible to effectively expand the web in the width direction.

As described above, when the web reaches 300°C, bending force is applied to the H-shaped steel in the vertical direction to increase the web height by 0.3.
As a result of carrying out this test, no undulations were observed in the web 1a even though the web 1a was then allowed to cool down to room temperature.

Furthermore, for the material rolled by the low-temperature rolling method, a maximum lap allowance of 15 mm was added to the straightening roller at 250°C, and the web height was expanded by 0.2%. No total defects occurred in the material after cooling in 1a.

In this way, when the web temperature is below 400°C, a force is applied to the web to widen it in the height direction, and the web height is reduced to 0.
．． By expanding the web 1a by 2% or more, it is possible to prevent the web 1a from waving after cooling even in the normal rolling method or the low-temperature rolling method.

In addition to the processing means for applying a force to widen the web 1a in the height direction, in addition to the method of bending the web 1a alternately in the above-described embodiment, the processing means for applying a force to widen the web 1a in the height direction is to bend both flanges Ib, lb using a roll that is in contact with the inner surface of the flange 1b. Possible methods include continuous processing in the direction of expanding the material (see Figure 4), or using press claws instead of rolls to spread the material (see Figure 5). Here, in the case of Fig. 4, the roll 4, which is movable in the height direction of the web la, is moved in the direction of arrow C, and in the case of Fig. 5, a hydraulic jack 5 is inserted between both flanges. By expanding Web 1a, respectively.
This applies a force to widen the width in the height direction.

In addition, under high temperature conditions (over 400°C) or in warm areas (10
It is also possible to relatively expand the web by inserting a room-temperature steel material between the flanges of an H-beam steel (0 to 400°C) to cool it and restrain heat shrinkage.

Further, when the amount of waviness occurring in the web is small, the above-described processing of the present invention can be applied after the waviness occurs to eliminate the waviness.

Next, the manufacturing method described in claim 3 will be explained.

Here, a hot rolled material of H2O2x196x9/22 was bent in the strong axis direction while measuring its internal stress.

The bending process was performed by pressing and bending the 2000 mm center portion between the frames using a hydraulic jack. As a result, the web temperature 2
At 00℃, a compressive force of 22 kg/mm2 was acting at the center of the web, but after bending with a deflection of 2.6 degrees, the maximum force was 11 kg/mm2 at a slightly lower position than the center of the web.
The compression force decreased to 2.

In addition, when the web was at 250°C, we bent the H-shaped steel in the strong axis direction using a roller straightener (see Figure 6). It did not occur. This bending process was performed by giving a maximum deflection of 2.6 mm. Furthermore, the material whose web was wavy at 200°C was heated to 170°C.
When bending was performed by applying a maximum deflection of 4.1 mm in the direction of the strong axis at a temperature of °C, the waviness of the web disappeared and did not recur even after reaching room temperature.

Furthermore, with the low-temperature rolling method, the finishing temperature is 600°C1 for the web.
If the temperature at the flange is 750°C, waving occurs when the web reaches 120°C during the cooling process. Therefore, when the web was bent at 200°C using a roller straightener to give it a maximum deflection of 2.3 mm in the direction of the strong axis, no nib waving occurred as the web was left to cool to room temperature. Ta.

The pitch of the roller straightening machine used here was 2000 mm.

In addition, in this example, when bending in the direction of the strong axis is performed using a roller straightening machine, it is possible to combine it with the method described above in which the web is repeatedly bent to increase the web height, and the effect will be the same. It becomes something big.

〔Effect of the invention〕

When hot rolling an H-beam steel product with an extremely thin web relative to the flange, the present invention aims to reduce the web temperature in a temperature range of 400°C or less after normal hot finish rolling and hot sawing. A widening force is applied to the web in the height direction to increase the web height by 0.2% or more. Further, the web height is expanded and deformed by alternately bending the web. It is also characterized by bending the H-section steel at least once in the strong axis direction at a flange temperature in the range of 400°C to room temperature.

According to this configuration, it is possible to reduce the compressive stress of the web and prevent the waving phenomenon of the web during the cooling process, and it becomes possible to manufacture thin web H1 steel by hot rolling.

Further, since the compressive stress can be reduced using a roller straightening machine, there is no need to provide special equipment for preventing the waving phenomenon, and there is no need to reduce rolling efficiency.

Therefore, it becomes possible to mass-produce H-section steel at low cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the web waving phenomenon prevention process by the manufacturing method of the present invention, FIG. 2 is a cross section taken along the line A-A in FIG.
3(A) and 3(B) are schematic cross-sectional views showing different layers of the roll, FIGS. 4 and 5 are schematic views showing a device for expanding the web in the height direction, and FIG. FIG. 2 is a schematic cross-sectional view showing bending in the strong axis direction using rolls. DESCRIPTION OF SYMBOLS 1... H-shaped steel, 1a... Web, 1b... Flange, 2... Roller straightening machine, 3... Roll, 4...
・Roll, 5...Hydraulic jack. Figure Figure Z Figure (A) Figure (B) Procedural amendment 10th December 15, 1988 Japanese Patent Application No. 272469 2゜ Title of invention Method for manufacturing thin web H-shaped wire 3゜Relationship with Hanyu who makes the amendment V: Name (211) Sumitomo Metal Industries, Ltd. 4゜Address of agent ■ 107 6-5-21 Akasaka, Minato-ku, Tokyo Shadow Akasaka 6゜Specifications subject to amendment And, "Elimination" in the sixth line from the bottom of page 6 of the specification in Drawing No. (1) is corrected to "Erasure". (2) In the same book, page 12, lines 4 and 5, ``Detailed on the manufacturing method'' is corrected to ``About the manufacturing method.'' (3) 4th line from the bottom of No. 12 of the same book: “(See Figure 6)
" is corrected to [(see Figures 6 and 7) as J. (4) "Figure 6 is..." in the same book, page 15, lines 4-5.
It is. ” is corrected as follows. [Figure 6 (A) is a schematic diagram showing bending in the strong axis direction using rolls, Figure 6 (B) is a sectional view taken along the line BB of Figure 6 (A), and Figure 7 (A) is a schematic diagram showing bending in the strong axis direction using rolls. A schematic diagram showing another aspect of bending in the direction of the strong axis, FIG. 7(B) is a sectional view taken along the line C-C of FIG. 7(A), and FIG. 7(C) is a cross-sectional view of FIG. 7(A). D-D
The line cross-sectional view, FIG. 7(D) is a cross-sectional view taken along the line E--E of FIG. 7(8). (5) In addition to deleting Figure 6 of the drawings, the attached Figure 6 (
A), FIG. 6(B), FIG. 7(A), FIG. 7(B). Figures 7(C) and 7(D) are added. Figure C Tsu Q Arrogance” Ku Ku To Castle

Claims (3)

[Claims] (1) A manufacturing method for hot rolling an H-beam steel product with an extremely thin web relative to the flange, in which the web temperature is below 400°C after normal hot finish rolling and hot sawing. A method for manufacturing a thin-walled web H-section steel, which comprises applying a widening force to the web in its height direction to increase the web height by 0.2% or more. (2) A manufacturing method for hot rolling an H-beam steel product with an extremely thin web relative to the flange, in which the web temperature is in a temperature range of 400°C or less after normal hot finish rolling and hot sawing. A method for manufacturing a thin-walled web H-section steel, characterized in that the web is repeatedly bent in an alternating manner. (3) A manufacturing method for hot rolling an H-beam steel product with an extremely thin web relative to the flange, in which the flange temperature ranges from 400°C to room temperature after normal hot finish rolling and hot sawing. A method for manufacturing a thin web H-section steel, comprising bending the H-section steel one or more times in the strong axis direction.