JPH1177262A - Production of beam blank and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a beam blank having good dimensional precision by intensely cooling a slab bloom at the rear surface in a screw-down device, thereby preventing its deformation after formation. SOLUTION: Molten metal 10 poured from a tundish 1 is cooled with a mold 2 and a solidified shell 11 is developed from the outer surface in contact with the mold. The slab bloom 12 under non-solidifying state is guided into a universal rolling mill 3 and formed into the beam blank 14. The screw-down device is not limited to the universal rolling mill. The formed beam blank 14 is applied to the intense cooling in a cooling device 4 arranged at the back surface of the universal rolling mill 3 and becomes the beam blank 15 without existence of non-solidified part. As the other way, the thickness of solidified shell in the cast bloom or the non-solidified ratio can be adjusted by cooling the cast bloom at the front surface of the screw-down device. The thickness of a part corresponding to a web is reduced by horizontal rolls and parts corresponding to flanges with vertical rolls in the universal rolling mill.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for producing a beam blank as a material for rolling a section steel on a continuous casting line, and more particularly to a method and apparatus for obtaining a beam blank with good dimensional accuracy.

[0002]

2. Description of the Related Art FIG. 10 shows a typical manufacturing process of a section steel, taking an H section steel as an example. FIG. 10A shows a method of manufacturing a substantially blank H-shaped beam blank 50 by continuous casting, and using the blank as a raw material to form an H-shape steel 55 by subsequent forming and rolling 51 and further universal rolling steps 52, 53 and 54. It is.

[0003] Since a rolling blank uses an almost H-shaped beam blank (hereinafter also referred to as CC-BB), efficient shaping and rolling is possible. However, changing the size of the CC-BB requires reorganization of casting molds and other auxiliary equipment, which is inefficient and takes time and costs. H-shaped steel has been manufactured, but the size change after the forming and rolling process requires a reduction in dimensional accuracy due to an unreasonable size change, and a large increase in size results in a decrease in the unit weight of the raw steel slab. There has been a problem such as a reduction in rolling efficiency.

FIG. 10 (b) shows a method of manufacturing an H-section steel 65 by using a rectangular continuous cast slab, for example, a slab 60, as a raw material, and forming and rolling 61, and further, universal rolling steps 62, 63 and 64. In this method, in order to perform shaping from a rectangular slab to an H-shape in the shaping and rolling step, a flange portion is formed by erecting and rolling the slab 60 as shown in FIG. Although the method of rolling into an H shape is adopted, particularly when forming a flange portion of a large H-section steel using a wide slab, the flange is likely to fall, and this fall causes deterioration in dimensional accuracy, and rolling for forming the flange portion is performed. Problems such as a reduction in rolling efficiency and an increase in crop loss due to an increase in the number of passes have occurred.

[0005] In order to improve the problems of the typical conventional methods described above, several methods have been proposed. As one of the methods, a method of adjusting the flange width of a beam blank in continuous casting of bloom is disclosed in Japanese Patent Application Laid-Open No. 8-281301 (see FIG. 11). This method makes it possible to adjust the unsolidification rate of the slab by using a cooling device or a heating device, or by changing the casting speed, thereby adjusting the flange width of the beam blank.

[0006]

Problems to be Solved by the Invention
In the method disclosed in Japanese Patent Publication No. 1 (1993), a beam blank is formed using a universal rolling mill, and a reduction is applied to the slab so that there is no unsolidified portion on the rear surface of the rolling mill. However, generally, the beam blank has a shape in which the inner surface of the flange is inclined so that the thickness becomes thinner toward the front end of the flange, and since the thickness of the flange portion is not uniform, it is difficult to completely remove the molten metal by rolling down. The unsolidified portion remains near the boundary between the web and the web. Since the hydrostatic pressure of the molten metal acts on the unsolidified portion due to the height difference from the continuous casting machine, a force for expanding the formed beam blank from the inner surface acts, and the shape of the beam blank changes. For the above reasons,
The conventional method cannot produce a beam blank with good dimensional accuracy.

The present invention provides a method and an apparatus for manufacturing a beam blank having good dimensional accuracy by preventing or reducing the deterioration of the shape of the beam blank even when an unsolidified portion remains in the beam blank after rolling. The purpose is to:

[0008]

A method of manufacturing a beam blank according to the present invention is directed to a method of manufacturing a beam blank by reducing an unsolidified slab in a continuous casting line.
The slab is strongly cooled on the rear surface of the rolling device. Also,
The thickness of the solidified shell of the slab or the unsolidified rate is adjusted by cooling the slab at the front of the rolling device.

In the beam blank manufacturing apparatus according to the present invention, a reduction device for reducing an unsolidified slab is installed in a continuous casting line, and a slab cooling device is installed on a rear surface of the reduction device. It is characterized by having done. Also,
A second cooling device is also installed on the front surface of the screw-down device.

Hereinafter, the principle of solving the conventional problems according to the present invention will be described. In a state where the unsolidified portion remains in the beam blank formed by rolling down the unsolidified slab, the hydrostatic pressure of the molten metal acts on the unsolidified portion, and the beam blank expands and deforms.

Therefore, in the present invention, the slab that has been formed into a beam blank is subjected to strong cooling to solidify the unsolidified portion as quickly as possible. The deformation of the beam blank due to the hydrostatic pressure of the unsolidified portion does not occur in a short time, but gradually progresses over time. If the beam blank is not cooled, the solidification of the molten metal takes time and the amount of deformation increases, but by applying strong cooling immediately after the drafting device, the unsolidified portion is reduced and the surface temperature of the solidified shell is lowered to increase the strength. Thus, the deformation of the beam blank can be reduced to a small range having no practical problem.

In another method of the present invention, the slab is cooled in front of the drafting device, and the thickness of the solidified shell or the rate of unsolidification (the ratio of the thickness of the unsolidified portion to the cross-sectional area of the slab) is determined. The reasons for adjustment are as follows. If the thickness of the solidified shell of the slab is, for example, less than half the target thickness of the web portion of the beam blank, unsolidified molten metal remains in the web portion of the beam blank. In this state, the unsolidified portion has a flat shape spreading in the width direction of the beam blank, and the unsolidified portion is not divided by the web portion. Deformation tends to increase. Therefore, if the slab is cooled at the front of the rolling device and the thickness of the solidified shell is adjusted according to the target web thickness of the beam blank, the unsolidified portion does not remain in the web portion after rolling, and the unsolidified portion is It only remains small at the center of the left and right flanges. Therefore, the effect of the hydrostatic pressure acting on the beam blank can be reduced, and as a result, a beam blank with good dimensional accuracy can be manufactured by suppressing deformation after rolling.

Here, the cooling at the front surface of the rolling device is not necessarily required to cool the entire slab, as in the cooling at the rear surface of the rolling device according to the present invention. Even in the case of partial cooling, the effect of the present invention can be obtained because the unsolidified portion after reduction can be reduced.

[0014]

FIG. 1 is a schematic view showing an example of an embodiment of the present invention. In FIG. 1, molten metal 10 poured from a tundish 1 is cooled by a mold 2, and a solidified shell 11 is formed from an outer surface in contact with the mold 2. Next, the unsolidified slab 12 is guided to the universal rolling mill 3 and formed into a beam blank 14. Here, a description will be given using a universal rolling mill as an example of the rolling-down device, but this is not particularly limited to the rolling-down device. The formed beam blank 14 is strongly cooled by the cooling device 4 installed on the rear surface of the universal rolling mill 3, and becomes a beam blank 15 having no unsolidified portion.

FIG. 2 schematically shows the working state of the cast slab during molding and cooling and the shape of the unsolidified portion inside. The bottom section of the figure shows the cross-sectional shapes before, during, after, and after cooling the slab. In FIG. 2, 12 is an unsolidified cast slab before molding, 13 is a cast slab during molding, 14 is a cast slab (beam blank), and 15 is a cooled slab (beam blank). Show. The unsolidified slab 12 is a slab having a solid solidified shell 11 having the lowest temperature at the outermost periphery by cooling from the outer surface, and is sent to the universal rolling mill 3 in a state where the high-temperature molten metal 10 is present inside. The portion corresponding to the web by the horizontal rolls 31 and 32 is
The portions corresponding to the flanges are reduced by 3, 34.
The unsolidified cast slab 12 is subjected to a large reduction by the horizontal rolls 31 and 32 and the vertical rolls 33 and 34, but the molten metal 10 inside is pushed back to the upstream side by these reductions, so that a large shape is easily formed. It is possible to change the shape, and the working force required for the forming to significantly change the shape is as small as bending the solidified shell 11 which is a solid as can be seen from FIG.

An unsolidified portion 14a is formed on a slab 14 formed into an H-shaped beam blank by the universal rolling mill 3.
Remains. This is one of the reasons that the beam blank generally has a shape in which the inner surface of the flange is inclined, and the flange is thinner toward the tip, and the unsolidified portion is large at the center of the flange. When a beam blank having a large web thickness or flange thickness is formed from an unsolidified slab having a small solidified shell, the solidified shells do not adhere to each other, so that an unsolidified portion remains inevitably. According to the method of the present invention, the slab having the unsolidified portion is strongly cooled by the cooling device 4 after molding, so that the entire cross section is solidified before the beam blank is deformed by the internal pressure of the unsolidified portion, and the deformation is reduced. It is to prevent.

Here, the cooling is sufficiently effective not only as a method for cooling the entire slab, but also as a method for intensively cooling the unsolidified portion. Further, as shown in FIG. 3, in the case of the slab 14B in which the unsolidified portion 14a remains in the web portion, compared with the case of the slab 14A in which the web portion has no unsolidified portion, the unsolidified portion 14a and the solidified portion 14a are compared. The boundary length of 14b becomes extremely long. This means that the area receiving the hydrostatic pressure of the molten metal is large,
Since the force acting on the solidified shell 14b increases, the beam blank is easily deformed after molding. Therefore, the method of intensively cooling the web part in the cooling after molding,
The effect of preventing deformation of the beam blank is great. As described above, when cooling the beam blank after molding, a method of selectively cooling a portion having a large deformation preventing effect also has a sufficient effect.

As shown in FIG. 4, the thickness of the solidified shell 11 of the slab 12 before the reduction depends on the casting speed and the cross-sectional dimension of the slab. Also, the target web thickness and flange thickness of the beam blank to be manufactured are not constant. Therefore, as shown in FIG. 5, even when the thickness of the solidified shell is the same, the unsolidified portion 14a is small in the case of the cast slab 14C having a small target web thickness of the beam blank, whereas the web thickness is large. In the case of the slab 14D, the thickness of the solidified shell 14b is less than half of the web thickness, and the unsolidified portion 14a
Remain largely. In such a case, the deformation of the beam blank increases due to the large area receiving the internal pressure after the molding, and it takes a long time to complete the solidification, which causes the dimensional accuracy of the beam blank to deteriorate.

In order to solve this problem, FIG. 6 shows another method of the present invention, in which a cooling device 4 is provided on the front and rear surfaces of a reduction device.
A case where A and 4B are installed and cooling is performed will be described. The cooling at the front surface of the pressing device 3 adjusts the thickness of the solidified shell of the slab 12 by the cooling device 4A so that a large unsolidified portion does not remain in the web portion of the beam blank 14 after molding. FIG.
Fig. 2 schematically shows the processing state of the cast slab during cooling and forming, and the shape of the unsolidified portion inside. By cooling at the front surface of the rolling device 3, the solidified shell 11 of the unsolidified cast slab 12 is adjusted to a thickness such that the unsolidified portion 14a does not largely remain in the web portion of the beam blank 14 after the rolling. Subsequently, the slab 12A after cooling, in which the thickness of the solidified shell 11 is adjusted as described above, is subjected to pressure reduction to form an H-shaped beam blank 14, and further, a cooling device installed on the rear surface of the pressure reduction device 3. The unsolidified portion 14a remaining mainly in the center of the flange portion is solidified in the cast slab 14 by cooling by 4B. Therefore, the cast slab 15 after the cooling has no unsolidified portion, and the deformation of the beam blank can be prevented. The thickness of the solidified shell of the slab can be measured using, for example, an electromagnetic ultrasonic thickness gauge, and based on the measurement results, the cooling devices 4A, 4B are controlled by feedback or feedforward control.
Of the cooling water, the cooling part and the like can be controlled. It is also possible to calculate the unsolidified rate from the measured data of the thickness of the solidified portion of the slab and control the cooling based on the unsolidified rate. According to this method, the deformation of the beam blank after molding can be further reduced, so that a beam blank with good dimensional accuracy can be manufactured.

[0020]

【Example】

Embodiment 1 FIG. In the apparatus shown in FIG. 1 using a universal rolling mill as the rolling-down apparatus, the shape and dimensions of the horizontal roll and the vertical roll of the universal rolling mill shown in FIG. 8 were used, and beam blanks were manufactured with the roll settings shown in Table 1. . Further, the cooling device on the rear surface of the rolling-down device was eliminated from the device shown in FIG. 1, and a beam blank was manufactured without cooling, and compared with the method of the present invention.

[0021]

[Table 1]

FIG. 9 shows the shape of the beam blank after manufacture. In the conventional method in which cooling was not performed on the rear surface of the rolling device, the beam blank expanded as shown in FIG. The web height at this time is 650
mm. On the other hand, when the apparatus of the present invention was used to perform cooling on the rear surface of the rolling-down apparatus, the deformation of the beam blank was small and the web height was 6 as shown in FIG.
A product having a size close to the target size of 10 mm was obtained, and a product having good dimensional accuracy was manufactured.

Embodiment 2 FIG. In the apparatus shown in FIG. 6, the shape and dimensions of the horizontal roll and the vertical roll of the universal rolling mill shown in FIG. 8 are used, the casting speed is higher than in Example 1, and the thickness of the solidified shell is reduced. Produced a beam blank. A comparison was made between the method of the present invention in which cooling was performed before and after the rolling device under this condition, the conventional method 1 in which the slab was cooled only at the front surface of the rolling device, and the conventional method 2 in which no slab was cooled.

In the method of the present invention, the thickness of the solidified shell is adjusted in accordance with the target thickness of the beam blank, and cooling for solidifying the unsolidified portion after molding is performed.
Deformation after molding was small, and a beam blank with good dimensional accuracy could be manufactured. On the other hand, in the conventional method 1 in which cooling is performed only on the front surface of the rolling device, it takes a long time to completely solidify the unsolidified portion after molding, but the beam blank expands and the dimensional accuracy deteriorates. Furthermore, in the conventional method 2 in which cooling is not performed at all, since an unsolidified portion remains in the web portion after molding, the web portion expands, the web becomes thicker, and the dimensional accuracy further deteriorates.

[0025]

As described above, according to the method and apparatus of the present invention, the unsolidified portion remaining after the beam blank is formed can be solidified in a short time by strong cooling.
A beam blank with good dimensional accuracy can be manufactured by preventing deformation after molding. In addition, not only after molding but also before molding, the beam blank is formed after adjusting the thickness or unsolidification rate of the solidified shell so that the unsolidified portion of the slab is reduced. In addition, the deformation of the beam blank after molding can be further prevented, and a beam blank with higher dimensional accuracy can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a manufacturing apparatus for performing a beam blank manufacturing method of the present invention.

FIG. 2 is an explanatory diagram of a beam blank manufacturing method of the present invention.

FIG. 3 is a diagram showing an unsolidified portion of a beam blank after molding.

FIG. 4 is a diagram showing a difference in thickness of a solidified shell of an unsolidified cast slab before forming.

FIG. 5 is a diagram showing a difference in a remaining state of an unsolidified portion depending on a web thickness of a beam blank.

FIG. 6 is a view showing a manufacturing apparatus for carrying out another beam blank manufacturing method of the present invention.

FIG. 7 is an explanatory view of another beam blank manufacturing method of the present invention.

FIG. 8 is a diagram showing a roll shape used in an example of the present invention.

FIG. 9 is a view showing a shape of a beam blank manufactured by the present invention and a conventional method.

FIG. 10 is an explanatory diagram of a conventional beam blank manufacturing method.

FIG. 11 is an explanatory diagram of a conventional beam blank manufacturing method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 tundish 2 mold 3 reduction device (universal rolling mill) 4, 4A, 4B cooling device 10 molten metal 11 solidified shell 12 unsolidified slab 12A slab after cooling before molding 13 slab during molding 14 after molding Beam blank 14A, 14B, 14C, 14D Cast slab 14a Unsolidified part 14b Solidified part 15 Cooled beam blank

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B22D 11/20 B22D 11/20 Z (72) Inventor Masamasa Kamada 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Pipe Stock In company

Claims (4)

[Claims] 1. A method of manufacturing a beam blank by reducing an unsolidified slab in a continuous casting line, wherein the slab is strongly cooled on a rear surface of a reduction device. . 2. The beam blank manufacturing method according to claim 1, wherein the slab is cooled at a front surface of the rolling-down device, and a thickness or a non-solidification rate of a solidified shell of the slab is adjusted. 3. A beam blank, comprising: a reduction device for reducing unsolidified slabs in a continuous casting line; and a cooling device for cooling the slabs on a rear surface of the reduction device. Manufacturing equipment. 4. The beam blank manufacturing apparatus according to claim 3, wherein a second cooling device is provided in front of the pressing-down device.