JPH07265902A - Forming method for shaped bloom - Google Patents

Abstract

PURPOSE:To form a shaped bloom for an H-beam to be stabilized by rolling in the width direction of a slab. CONSTITUTION:By using the process to form a groove part on slab side face by a first box pass 1 arranged with a protrusion 11 having the prescribed inclination in center, the process to form the groove part as spreading by using a second box pass 2 arranged with protrusions 21, 22 having a two step inclination of gentle/sharp in center, the process to flatten the groove part by using a flat bottomed box pass and the process to finish to the prescribed shaped bloom by using a finish pass, the rolling is stably executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a rough billet for H-section steel by rolling a slab in the width direction.

[0002]

2. Description of the Related Art In recent years, in order to save energy and improve yield and quality, a rough-shaped steel piece used for manufacturing a large-section H-shaped steel is an end portion formed when a continuously cast slab is rolled down in the width direction. Often manufactured using methods that utilize the bulge of. As a method of stably performing the reduction in the width direction, a box hole type in which the groove bottom installed in the rough rolling mill becomes gradually larger according to the width expansion of the end is used sequentially while preventing the material from collapsing. There is also a method of deforming the material (see, for example, Japanese Patent Publication No. 58-35763), but in this case, since a large number of box hole types are required, in a rolling mill having only one rough rolling mill, a roll cylinder is used. It is difficult to form a rough billet for H-section steel having a large cross section due to the length limitation.

Therefore, a number of methods have been proposed to reduce the number of hole dies required, usually by using a box hole die having a protrusion at the center of the bottom. That is, as a first method, for example, in Japanese Patent Publication No. Sho 60-20081, a convex projection is provided at the center of the bottom of a box hole type, thereby forming a concave groove at the center of the slab in the thickness direction. In the next box hole type, by applying the same convex projection to the concave groove while holding the material, a reduction in the width direction is applied and the material is made into a dogbone shape,
Then, a method has been proposed in which a box hole type having a flat bottom portion is used to erase the concave portion of the material and a finishing hole type is used to form a predetermined rough shaped steel slab.

As a second method, Japanese Patent Publication Sho 58-37042.
Japanese Patent Publication No. 1-50481 or Japanese Examined Patent Publication No. 1-50481 discloses a method in which the side surface corresponding to the flange is divided and spread by a plurality of box hole types in which the top angle of the bulging portion in the central portion is different, and further, a third method. For example, Japanese Patent Laid-Open No. 58-9701 proposes a method of splitting and spreading by using a plurality of split hole dies in which the angle of the chevron portion is the same and the heights are successively increased.

In any of the above-mentioned methods, a slab having a wide width and a small thickness is vertically elongated, and a large number of passes are applied in the width direction to cause large slabs to be swollen at the ends.

[0006]

However, in the first method, the shape of the protrusion for forming the groove in the central portion of the slab thickness and the apex angle and height of the shape of the next box-hole type protrusion are first determined. The protrusions are used for the purpose of preventing the material from collapsing, and the bulge at the end of the material mainly uses the width expansion due to the reduction in the width direction at the bottom. In this case, the function of holding the material without falling is excellent, but the increase in the bulge width with respect to the width reduction amount is 50 to 60%, and the width reduction of about 300 mm requires the width reduction of 500 to 600 mm. There is.

Further, in the second method, since the protrusions whose apex angles are successively increased are widened, the tentering efficiency is good. Since it is bitten from the tip, it is difficult to push it open evenly to the left and right, causing the material to fall and twist. In the third method, the apex angle is made the same, and the groove is sequentially deepened by the protrusions whose heights are successively increased, and then the groove is widened by the flat-bottom box hole type. The thickness of the flange equivalent portion hardly increases, and if the initial slab thickness is thin, it is not possible to form a rough-shaped steel slab with a large flange thickness. In addition, the upper and lower ends of the material do not hit the hole type and are suspended in the air when splitting, which results in an unstable state.

Further, in the third method, the apex angle is set to about 60 °, but if a groove having an apex angle of 60 ° is spread with a flat-bottom box hole type, the rolling force is directed in the width direction of the slab, and the left and right sides of the groove are spread. The formed protrusion is crushed and the efficiency of forming the bulging portion is poor. It is an object of the present invention to provide a method for forming a rough-shaped steel slab that solves the problems of the above-described conventional techniques.

[0009]

DISCLOSURE OF THE INVENTION The present invention is a method of forming a crude steel slab by pressing down in the width direction of a slab using a pair of rolls having a pressing surface composed of a plurality of box hole types in the axial direction. Then, a step of forming a groove on the side surface of the slab by using a first box hole mold having a protrusion having a predetermined inclination in the center, and a second step of providing a protrusion having a two-step slope in the center
Of forming the groove portion so as to be widened by using the box hole die, the step of flattening the groove portion by using the flat-bottom box hole die, and the step of finishing to a predetermined rough steel billet using the finishing hole die It is a method of forming a rough-shaped steel slab, which comprises:

In addition, the inclination of the second box-hole-shaped projection in two stages is as follows: the apex angle of the upper part is 60 ° to 90 °,
A lower opening angle of 100 ° to 140 ° is recommended.

[0011]

According to the present invention, after the groove portion is formed on the side surface of the slab by using the first box hole die having the protrusion at the center,
The top angle of the upper part is relatively steep from 60 ° to 90 °, and the opening angle of the lower part is
Roll to widen the groove with a second box hole type that has a protrusion with a two-step inclination of 100 ° to 140 °, and then flatten the groove with a flat bottom box hole type before finishing. Since it is finished in the hole type, the engagement between the groove formed on the side surface of the slab and the projection of the roll is very good, and it can be stabilized during the width direction rolling.

Here, the reason why the apex angle of the upper portion of the second box-hole type projection is limited to 60 ° to 90 ° will be described.
If the apex angle is too sharp, the flat bottom box hole type will cause the rest of the groove after rolling to become a breakage flaw when rolling with the finish hole type,
The lower limit is preferably 60 °, and the inductivity of the material deteriorates as the angle increases, so the upper limit is preferably 90 °.

Also, the opening angle of the lower slope is 100 ° to 140 °
Regarding the reason for gently restricting the angle to °, if the opening angle is small, the effect of widening the width is poor, but if it is made too large, the force of compressing the material becomes larger than the force in the direction of widening the width, and rather it reduces. Therefore, when the present inventor investigated the relationship between the opening angle and the width expansion by experiments, it was found that the peak of the width expansion was around 110 ° to 140 ° as shown in FIG. Opening angle of 10
By setting it to 0 ° to 140 °, it becomes possible to improve the width expandability in the second box hole type and the subsequent flat bottom box hole type.

[0014]

EXAMPLE A case where an example of the present invention is applied to H900 mm × 300 mm will be described. FIG. 1 shows the upper half of the breakdown roll used in the practice of the invention,
First, a first box hole mold 1 having a projection 11 for forming a groove in the center of the thickness of the slab, a second box hole mold 2 having a two-step inclined projection of the present invention, and a flat bottom box hole mold. 3 and a finishing hole die 4 for H900mm x 300mm 4 are sequentially installed.

[0015] Here, the first box caliber first projection 11 has a height apex angle h _O is the theta _0. On the other hand, in the second box hole type 2, as shown in detail in FIG. 2, the apex angle 21 of the upper portion 21 of the protrusion is θ ₁ and the height thereof is h _1, and the opening angle of the lower portion 22 of the protrusion is θ ₂ The height is set to be h _{2 due} to the gentle inclination of. The apex angle θ of the upper part 21 of the protrusion of the second box hole type 2
₁ to be approximately equal to the height h _O of the first box apex angle of the caliber first projection 11 theta ₀ and substantially equal, the height h ₁ is also protrusion 11.

As a material, as shown in FIG. 3 (a), a continuously cast slab having a thickness t: 240 mm and a width H _O : 1450 mm is used, and a box hole mold 1 is used as shown in FIG. 3 (b). In order to accurately form the groove 12 in the center, the width b _O of the bottom of the first box hole die 1 is the slab thickness of the material +0 to 20 mm, the apex angle θ _{0 of the} protrusion is 70 °, and the height h _O is 50 mm. And Also, the second
Height h ₂ of the protrusions of the box grooved 2 100 mm, the opening angle theta ₂ is 120 ° at the bottom of the slope, the bottom width was 420 mm. The bottom width of the flat-bottom box hole die 3 is 520 mm.

First, the first box hole die 1
The material in which the groove 12 is formed under the two-pass reduction is subsequently subjected to a plurality of passes reduction in the width direction by the second box hole die 2. At this time, since the shape of the upper portion 21 of the protrusion of the second box hole die 2 is the same as the shape of the protrusion of the first box hole die 1, as shown in FIG. The stability at the time of initial biting in the mold 2 is very good, so the material is bitten and spread apart without being offset to the left and right, and the groove of the material is largely divided at the lower part of the protrusion 22 as the widthwise rolling progresses. Can be expanded.

Then, in the second box-hole mold 2 shown in FIG.
After pressing down until the material width H ₃ reaches 1200 mm, the material width H is further reduced by the flat-bottom box hole die 3.
₃ is pressed down to 1050 mm by 150 mm and grooved as shown in Fig. 3 (e).
The width is further expanded while rolling down in the direction to erase 12. At this time, since the shape of the groove 12 is gradually inclined toward the exit side, the holding of the material in the flat-bottom box hole mold 3 is stable. After that, after making the groove depth shallow with the flat-bottom box hole mold 3 (it is not necessary to completely delete the groove), the material is removed.
Turn 90 ° and roll with finishing hole type 4.

Through the above steps, the engagement between the groove formed on the side surface of the slab and the projection of the roll is very good, and the material holding performance can be stabilized during rolling in the width direction rolling.

[0020]

As described above, according to the present invention,
After forming the groove on the side of the slab using the first box hole type with protrusions, the apex angle of the upper part was relatively steep at 60 ° to 90 ° and the opening angle of the lower part was at 100 ° to 140 °. The second box hole die provided with a projection having a two-step inclination is rolled so that the groove portion is widened, and then the flat bottom box hole die is used to flatten the groove portion and finish with the finish hole die. Therefore, it is possible to carry out stable reduction in the width direction.

Further, since it is possible to manufacture a rough-shaped billet for H-section steel having a large cross-section from a slab having a narrow width and a large thickness, it is possible to manufacture a rough-shaped billet for a shaped steel bar having a thick flange thickness. That is, the thickness of the slab charged into the heating furnace is increased to improve the heating efficiency, and since the aspect ratio of the slab is reduced, it is easy to raise the material in rolling and the rolling efficiency is improved. is there.

Furthermore, since the number of box cavities with protrusions to be used is smaller than in the conventional case, it is possible to install the cavities for large cross sections on one roll.

[Brief description of drawings]

FIG. 1 is a partial front view showing a breakdown roll used for implementing the present invention.

FIG. 2 is an explanatory diagram of a second box-hole type projection shape used in the present invention.

FIG. 3 is an explanatory diagram of a rolling process of the method of the present invention.

FIG. 4 is a characteristic diagram showing a relationship between an opening angle of a lower portion of a protrusion and a width expansion amount.

[Explanation of symbols]

 1 1st box hole type 2 2nd box hole type 3 Flat bottom box hole type 4 Finishing hole type 11 Projection 21 Projection upper part 22 Projection lower part

Claims (2)

[Claims] 1. A method of forming a rough steel slab by pressing down in the width direction of a slab using a roll pair having a pressing surface composed of a plurality of box hole types in the axial direction, wherein a predetermined inclination is provided in the center. The step of forming a groove on the side surface of the slab by using the first box hole die having the protrusions, and the groove portion is divided by using the second box hole die having the protrusion having a two-step slope in the center. Coarse shaped steel characterized by comprising a step of forming so as to widen, a step of flattening the groove portion using a flat bottom box hole die, and a step of finishing into a predetermined rough shaped steel slab using a finishing hole die. Method of molding pieces. 2. The inclination of the second box-hole-type two-step slow and steep projections has an apex angle of the upper portion of 60 ° to 90 ° and an opening angle of the lower portion of 100 ° to 140 °. The method for forming a crude steel slab according to claim 1.