JPH10263752A - Method for continuously casting beam blank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of warping at the flange part by heating the flange surface of a beam blank until the beam blank during continuously casting reaches the final solidification or a little after there from. SOLUTION: The beam blank 1 is cast with a continuous caster. The flange surfaces 6a of the beam blank 1 are heated in the heating section 5 arranged so as to interpose the lest solidified position 3 in the continuous caster. The temp. difference between the flange surfaces 6a and the last solidified part 8 is eliminated, and the warping of the flange part 6 can be prevented. The heating section 5 is desirable to be the interval between the position going up at 1500 mm and the position going down at 1000 mm in the casting direction from the last solidified position 3. In the case the heating position is the upstream side from the section, the solidification of the beam blank is delayed, and in the case the heating position is downstream side from this section, the prevention of warping is not enough. The temp. of the heating surface is desirable to 900-950 deg.C. When the temp is <900 deg.C, the preventing effect of the warping is unsatisfactory, and when the temp. is >950 deg.C, bulging, etc., is caused by deficient strength of the solidified shell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting method of a beam blank, and it is intended to advantageously avoid opening of a web portion and a cross-sectional defect caused by warpage of a flange portion which is likely to occur during casting of the slab. is there.

[0002]

2. Description of the Related Art In recent years, attempts have been made to simplify the rolling process by making the cross-sectional shape of a slab obtained by continuous casting as close as possible to the final product. There is continuous casting. Continuous casting of beam blanks is disclosed in Japanese Utility Model Laid-Open No. 55-88351 and Japanese Patent Laid-Open No. 56-39158.
JP, JP-A-58-29548 or JP-A-58-29549
As shown in the publication, the cross-sectional shape of the beam blank is not a simple rectangular shape such as a slab or a bloom, but a complicated substantially H shape in which both ends of the web portion are sandwiched in the center of the flange portion. The method of supporting a slab drawn from a mold is also complicated.

For example, in a beam blank continuous casting machine, a point at which a slab finally solidifies on a casting line from immediately below a mold (final solidification) in order to prevent cross-sectional defects such as web opening due to warpage of a flange portion. (Referred to as the position), the both sides of the web portion and both flange surfaces and / or the end surfaces of each flange are individually restrained and supported by the web roll and the flange roll, respectively. In addition,
The final solidification position is set according to the type of steel and the casting speed.

Also, the warpage of the flange portion occurs when the flange portion is cooled more than the web portion,
Attempts have also been made to relatively cool the web portion and weakly cool the flange portion to achieve uniform temperature between the two portions.

[0005]

However, in the above-mentioned conventional technique, the following problems occur when the casting speed is increased to improve the productivity. (1) When the casting speed is increased, the final solidification position shifts to the downstream side of the casting line.However, if the final solidification position after the shift deviates from the existing web roll / flange roll band, the roll band is It is necessary to extend downstream. Since the flange roll is usually already installed on the downstream side, a web roll is additionally arranged. The web roll is usually very compact (small diameter) and thermally severe depending on the beam blank size. Due to the exposure to the environment, there is a concern that the extension will increase the maintenance load. (2) The method of strongly cooling the web portion has a narrow range of application because cracking at the straightening point in a curved continuous caster is rate-limiting. Conversely, the method of weakly cooling the flange portion does not have the effect of suppressing cross-sectional defects at a casting speed higher than a certain value.

Accordingly, the present invention provides a method capable of effectively preventing the occurrence of warpage of a flange portion, which is an obstacle to speeding up of continuous casting of a beam blank, and contributing to an improvement in productivity of continuous casting of a beam blank. The purpose is to:

[0007]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that the beam blank during continuous casting is used for a period from shortly before reaching final solidification until reaching final solidification or a little later. The inventors have obtained an important finding that, by heating the flange surface of the blank, the warpage of the flange portion can be effectively suppressed, and completed the present invention.

That is, the present invention is characterized in that when casting a beam blank with a continuous caster, its flange surface is heated in a heating section provided across a final solidification position set in the continuous caster. This is a continuous casting method for beam blanks. It is preferable that the heating section is located between a position 1500 mm backward and a position 1000 mm lower in the casting direction from the final solidification position, and is heated so that the surface to be heated is in the range of 900 to 950 ° C. Is preferred.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a continuous beam blank caster suitable for carrying out the present invention, (A) is a schematic side view, (B) is an AA sectional view of (A), In the figure, 1
Is a beam blank, 2 is a meniscus position, 3 is a final solidification position, 4 is a web roll band, 5 is a heating section, 6 is a flange portion, 6a is a flange surface, 7 is a web portion, 8 is a final solidification portion, and 9 is a pinch. It is a roll band. The illustration of the continuous casting mold at the meniscus position 2, the web roll and the flange roll in the web roll band 4, and the flange roll in the web roll band 4 exit side to the pinch roll band 9 entrance side is omitted.

As shown in the figure, according to the present invention, when the beam blank 1 is cast by the continuous caster, the flange surface 6a
Is heated in a heating section 5 provided across a final solidification position 3 set in a continuous casting machine. Thereby, the temperature difference between the flange surface 6a and the final solidified portion 8 is eliminated, and the flange portion 6
Warpage can be effectively prevented, and the occurrence of cross-sectional defects can be suppressed.

Therefore, even if the casting speed is increased and the final solidification position 3 is shifted to the downstream side of the web roll band 4, it is not necessary to additionally install a web roll, so that the problem (1) is solved. In addition, since the temperature difference between the two portions, which could not be solved only by the strong cooling of the web portion 7 and the weak cooling of the flange portion 6, is solved, the disadvantage (2) can be sufficiently compensated.

The heating section 5 is preferably located between a position which is 1500 mm backward and a position which is 1000 mm lower than the final solidification position in the casting direction. Heating upstream from this tends to cause coagulation delay, and heating downstream from this is too late to prevent warpage. The heating is preferably performed so that the temperature of the surface to be heated falls within the range of 900 to 950 ° C.
If the temperature is lower than 900 ° C., the effect of preventing warpage is poor, and if it exceeds 950 ° C., the strength of the solidified shell becomes insufficient, and bulging or the like is induced.

The heating means includes electric resistance heating, high frequency heating,
Burner heating may be used.

[0014]

[Example] Medium carbon steel with a gap of 560 mm on both sides of the flange and a height of 400 mm on the side of the flange (C content: about 0.2 wt%)
The beam blank is cast by a continuous caster having a web roll band of 10730 mm in length along the casting line from the meniscus position.
The present invention was applied to a continuous casting operation for casting at a casting speed of 0.9 to 1.3 m / min.

The final solidification position of this steel type is in the range of 10220 to 13310 mm from the meniscus position, and the burners are arranged in the section 9000 to 14000 mm including this range. Heating sections of -1000 mm to +1000 mm (upstream side is "-") are provided at each final solidification position corresponding to each casting speed, and the burners in each heating section are operated to heat the flange side to 900 to 950 ° C. The case where the heating was performed was set as an example, and the case where no heating was performed was set as a conventional example.

FIG. 2 shows the relationship between the casting speed and the cross-sectional defect occurrence rate in Examples and Conventional Examples. In FIG. 2, reference numeral 10 denotes a casting speed region where the final solidification position is within the web roll band.
In the conventional example, the cross-sectional defect occurrence rate is low in the area 10 but becomes high when the area departs from the area 10, whereas in the embodiment,
The level inside and outside the area 10 is even lower than the level in the area 10 of the conventional example, and the effect of the present invention is apparent.

[0017]

According to the present invention, by heating the side surface of the flange near the final solidification position of the continuous cast slab of the beam blank, the warpage of the flange, which is likely to occur near this position, is prevented. The occurrence rate can be remarkably reduced in a wider casting speed range than in the past, and there is an effect that both slab quality and production efficiency are improved.

[Brief description of the drawings]

FIG. 1A is a schematic side view showing an example of a continuous beam blank caster suitable for carrying out the present invention, and FIG.
It is sectional drawing.

FIG. 2 is a graph showing a relationship between a casting speed and a cross-sectional defect occurrence rate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Beam blank 2 Meniscus position 3 Final solidification position 4 Web roll band 5 Heating section 6 Flange part 6a Flange surface 7 Web part 8 Final solidification part 9 Pinch roll band 10 area (casting speed where final solidification position is in web roll band) Area)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Osamu Okuda 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. 1-chome (without address) Inside Kawasaki Steel Corporation Mizushima Works

Claims (3)

[Claims] When casting a beam blank with a continuous caster, a flange surface thereof is heated in a heating section provided across a final solidification position set in the continuous caster. Continuous casting method. 2. The method according to claim 1, wherein the heating section is located between a position 1500 mm backward and 1000 mm down from the final solidification position in the casting direction. 3. The heating according to claim 1, wherein the surface to be heated has a temperature of 900 to 950.
The method according to claim 1 or 2, wherein the method is performed so as to fall within a range of ° C.