JPH02235501A - Manufacture of thin-walled web shape steel and its apparatus - Google Patents

Abstract

PURPOSE:To reduce the internal stress and to prevent a cooled web from undulating by bending thin-walled web shape steel at a specified range of web temperature to apply tensile force to the flange and compressive force to the web, then, cooling it at a cooling bed. CONSTITUTION:In manufacture of the thin-walled web shape steel 1 having an asymmetrical section and a very thin web 1W to the flange 1F, a range of temperature >=100 deg.C is used to the flange after a hot finish rolling. The shape steel is mounted on each transfer truck 2 so that the flange 1F is positioned on the underside and the web 1W in positioned on the cooling bed side and the transfer trucks in the center part of the shape steel 1 are operated at a low speed while those at both end parts are operated at a high speed. Bending is applied so that the tensile force is operated by a stopper 6 to the flange 1F and the compressive force is operated to the web 1W. Then, the shape steel is cooled in the cooling bed. In this way, the internal stress of the thin-walled web is reduced and the web can be prevented from undulating.

Description

[Detailed Description of the Invention] <Field of Application in Industry H> This invention relates to a method for manufacturing thin-walled web shaped steel with an asymmetrical cross section, such as unequal thickness angle shaped steel and T shaped steel, where the web is extremely thin relative to the flange, and the method thereof. It is related to the device.

(Prior art) In recent years, thin web sections with a large section modulus per unit cross-sectional area have been required for various structures and construction works, etc. in order to reduce the required weight of steel materials. In the case of , as shown in FIG. 6, since the thickness of the web IW is thinner than the flange IF, a temperature difference occurs due to the difference in cooling rate, and the difference in the amount of shrinkage based on this temperature difference causes the bending δ(-
/m), and the web IW is undulated due to internal stress. Further, if the amount of bending is large when the web IW is cooled to room temperature, undulations will occur in the web IW even in the straightening process.

Conventionally, the following measures have been proposed as countermeasures to the problems caused by such thin webs.

? i) JP-A No. 62-104601 A method of applying pretension to the web portion by lightly compressing only the flange portion at a low temperature (200 to 500° C.) to reduce compressive stress generated during cooling.

(ii) A method in which a part of the flange of JP-A-63-154202 is expanded in web height in a temperature range below point A■.

(iii) Japanese Patent Publication No. 51-31227 Before finish rolling, forced cooling is performed according to the thickness, and after finish rolling, the flange and web are simultaneously heated or the flange is heated slightly earlier than the web.
A. A method characterized by causing l metamorphosis. Problems to be Solved by the Invention》However, although the inventions (i) and (ii) are applicable to products with a point-symmetrical cross section such as H-section steel, they can be applied to other products such as angle-shaped steel It is difficult to apply to

In addition, although the invention (iii) provides a method for rolling uneven thickness angle steel, it is not a technology specifically aimed at counteracting web waving, and in this method, t,=9u+,tz
An unevenly thick angle shape steel with /t+≧2 cannot be manufactured by web corrugation.

This invention was made in view of the above circumstances, and its purpose is to eliminate the web waving phenomenon that occurs during the cooling process of thin web section steel and the web waving phenomenon that occurs when straightening the bending that occurs during the cooling process. It is an object of the present invention to provide a method for manufacturing a thin-walled web section steel and an apparatus therefor, which can solve the problem.

Means for Solving Problems> In the present invention, when manufacturing a thin web section steel whose cross section is asymmetric and whose web lW is extremely thin with respect to the flange IF, after hot finish rolling, the flange temperature lOO℃ or more is A bending process is performed in which a tensile force is applied to the flange IF and a compressive force is applied to the web IW in a temperature range, and then the web is cooled on a cooling bed CB.

A device for carrying out such a manufacturing method is installed between the hot sawing line HS and the cooling bed CB in a hot rolling line, and carries a plurality of transfer carts 2 in the longitudinal direction of the shaped steel with chains 3 and sprockets. 4 and 5 to transfer the shaped steel 1, the moving sprocket 4 of each transfer trolley 2 is made into a multi-stage sprocket, and the shaped steel 1 is placed on the top surface of each transfer trolley 2. 2 is provided with a stopper 6 that can be fixed to the stopper 6.

The section steel 1 that has undergone warm bending is cooled on the cooling bed CB, and is bent in the opposite direction to the direction in which it was bent (compression,
However, bending occurs in the direction in which tension is applied to the web.
Since it is bent in the opposite direction beforehand, the bending after cooling can be made that much smaller. Figure 3 is a graph showing the internal stress state during cooling, and Figure 4 is the stress σ at the web tip. This is a graph showing the change in . When plastic deformation is applied as in the present invention, even if the bending moment is removed, the internal stress is reduced compared to the conventional one, and it is possible to prevent web waving that occurs during the cooling process. FIG. 5 is a graph showing changes in the bending δ shown in FIG. 6, and the amount of bending at the time of cooling to room temperature can be made smaller than in the conventional case. As a result, the amount of correction can be small, and it is possible to prevent the occurrence of waving at the time of correction.

In addition, in the present invention, the web thickness is 1, which is likely to cause web undulation.
, ≦91) S j2/jl ≧2.

Moreover, the point of the present invention is to plastically deform at least one of the flange and the web by bending, and the smaller the yield stress during bending than the yield stress at room temperature, the greater the effect. In other words, the higher the bending temperature, the greater the effect, but since the decrease in yield stress associated with temperature rise is noticeable above 100"C, the temperature of the high temperature part (flange part) in the section of the section steel is It is effective to perform the bending process at a temperature of 100@C or higher.

In the entry transfer, the drive sprockets 4 of each transfer cart 2 are attached to the same drive shaft, and by changing the chain 3 to a small or large diameter drive sprocket, the transfer cart 2 can be made to move at low or high speed. Can be done. Therefore, as shown in FIG.
Place it on each transfer trolley 2 so that F is on the lower side and webs 1 and W are on the cooling bed side.The transfer trolley in the center of the section steel 1 is set at low speed, and the transfer trolley at both ends is set at high speed. In this case, it is possible to perform a bending process in which the stonnover 6 applies a tensile force to the flange IF and a compressive force to the web iw.

The strikers 6 may be provided on the cooling side at the center of the shaped steel 1 and on the HS side at both ends, or may be provided in pairs at intervals in the transfer direction.

Note that the speed of each transfer truck is determined so that a predetermined curvature can be obtained at the time of transfer to the cooling bed CB.

Further, as shown in FIG. 2, a tension sprocket 7 is attached to the chain 3.

Implementation example> This is a thin web uneven thickness angle shape steel 400 (web)
This is an example in which IOO (flange) X9/22 C unit 1] was manufactured under the following conditions.

Material used = 300 iris thickness x 500 + u width x 5000 span length Furnace extraction temperature = 1200°C Rough rolling: 13 passes Intermediate rolling: 7 passes Finish rolling = 3 baths (finishing temperature flange/web 700/600°C) After finishing rolling The temperature at the time of hot sawing the section steel and taking it into the cooling bed is 680-630°C for the flange and 570°C for the web.
The temperature was ~500°C. The material is taken into the cooling bed using 10 chain-driven carts. At this time, the transport of each cart is controlled, and the material is bent in the direction in which the web contracts and the flange stretches, and then the material is taken into the cooling bed. I did this. Note that the bending at this point is 8 liters/
It was set as m.

When this material was cooled to room temperature on the cooling bed, the web was bent into a shape that was longer than the flange, but the amount of bending was slight at 6 mm/m, so roller straightening was performed to correct the bending. Even after fixing this, the web did not become rippled.

On the other hand, when the material was taken into the cooling bed in a straight line as usual, the web was bent into a shape that was longer than the flange by the time it was cooled to room temperature, and the amount of bending was 14 mm/m. When an attempt was made to correct the curvature by performing roller straightening on this material, waving occurred in the web.

Note that the above is uneven thickness angle steel. However, it goes without saying that the present invention can be applied to a section steel such as a T-shaped steel whose cross section is asymmetrical and whose web is thin.

(Effects of the Invention) As described above, according to the present invention, a thin-walled web section is subjected to bending in a temperature range of 100°C or higher in which a tensile force is applied to the flange and a compressive force is applied to the web, and then it is bent on a cooling bed. Cooling reduces internal stress in the thin web, prevents web waving after cooling, and suppresses bending after cooling. It is also possible to prevent web undulation that occurs during straightening.

[Brief explanation of the drawing]

Fig. 1 is a schematic plan view showing the manufacturing method of the present invention, Fig. 2 is a schematic side view showing the entry transfer used in the method, Fig. 3 is a graph showing the internal stress state during cooling, and Fig. 4 is a graph showing the internal stress state during cooling. FIG. 5 is a graph showing changes in stress at the tip of the web, FIG. 5 is a graph showing changes in bending of the shaped steel, and FIG. 6 is a perspective view showing the bending of the shaped steel. 1... Thin web shaped steel, IW... Web, IF...
・Flange, 2...Transfer trolley, 3...Chain, 4
... Drive sprocket, 5... Subrocket, 6.
...Stopper 7...Tension sprocket. Fig. Dandan hot sawing line, IF flange CB cooling bed Fig. 3 Chain 1F Fig. Fig.

Claims (2)

[Claims] (1) When manufacturing thin web section steel whose web is extremely thin relative to the flange, after hot finish rolling, bending is performed in which tensile force is applied to the flange and compressive force is applied to the web at a temperature range of 100°C or higher. 1. A method for manufacturing a thin-walled web shaped steel, which comprises applying the heat treatment and then cooling it on a cooling bed. (2) In a device that is installed between the hot sawing line and the cooling bed in a hot rolling line and transfers shaped steel by moving multiple transfer carts in the longitudinal direction of the shaped steel using chains and sprockets, each A thin-walled web section steel production device characterized in that the drive sprocket of the transfer cart is a multi-stage sprocket, and a stopper for fixing the section steel to the transfer cart is provided on the top surface of each transfer cart.