JP3093533B2 - Continuous casting of thin cast slab - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for directly producing a thin cast slab by applying a reduction in the thickness direction to an unsolidified slab in a continuous casting line.

[0002]

2. Description of the Related Art In recent years, from the viewpoints of process saving, labor saving and energy saving, a hot rolling process has been omitted, and directly from a molten metal.
Various attempts have been made to produce thin cast slabs continuously. Among them, continuous casting molds (hereinafter simply referred to as “molds”)
The slab is drawn from the slab, and when the inside of the slab is in an unsolidified state, that is, in a continuous casting machine, the reduction is corrected and the thickness is reduced, so-called unsolidified reduction continuous casting method (hereinafter simply referred to as “unsolidified reduction”). Law).

The unsolidified rolling method requires a smaller rolling load than a method of rolling after the slab is solidified, so that the design load resistance of the rolling device can be reduced, which is extremely advantageous in terms of equipment cost. is there. Incidentally, the unsolidification rolling method is performed in a continuous casting machine having a structure as shown in FIG. 3 using a mold having a rectangular cross section as shown in a plan view in FIG. As shown in FIG. 3, in a continuous casting machine in which a reduction roll group 2 for reducing unsolidified slab is arranged below a mold 1, a molten metal (hereinafter, referred to as “metal”) is introduced into the mold 1 from an immersion nozzle 3.
Then, an unsolidified slab having an unsolidified portion 5 remaining inside the solidified shell 4 is drawn out of the mold 1 and a pressure is applied to the unsolidified slab to apply a thin cast. It is for producing pieces.

[0004] The mold used here is as shown in FIG.
In general, a mold space having a rectangular cross section is constituted by the mold long side 6 and the mold short side 7. A slab cast with such a rectangular cross-section mold, for example, a long side solidified shell 8a and a short side solidified shell 8 as shown in FIG.
By applying rolling to an unsolidified slab having a slab thickness T ₀ (= mold thickness) having an unsolidified portion 5 in the center of b,
Figure shows in 5 (b), a thin cast strip having a desired slab thickness T ₁ is obtained.

However, according to the above-described method, the solidified shell 8b on the short side already solidified in the rolling-down stage.
Must be reduced from the thickness T ₀ to T _1, so that a large reduction force is still required. As a result, size reduction and simplification of equipment, more it is impossible to increase the thickness decrease from thickness T ₀ to a thickness T _1, there is a problem that capitalize the benefits of unsolidified rolling sufficiently.

As a means for solving this problem, it is easy to consider reducing the thickness of the mold itself. In this case, however, it is necessary to supply hot water into the mold so as not to adversely affect the formation of the initially solidified shell. It is necessary to reduce the diameter of the immersion nozzle itself, and in that case, there is an adverse effect that nozzle clogging and drift occur. See also
In Japanese Patent Application No. 0-189555, the center of the long side of the mold is expanded so that the immersion nozzle can be immersed to form a pouring section, and the thickness of the long side pouring section is set to be downward. A method is disclosed for inclining in a funnel shape to reduce the thickness of the slab in the mold. However, in the method using such a deformed cross-section mold, in order to rapidly reduce the horizontal cross-sectional area of the slab in the mold using a funnel-shaped inclined mold, the mold inner surface and the slab surface A large frictional force was generated during the operation, and the friction shortened the life of the mold, and the frictional resistance also caused problems such as breakage of the slab and breakout, making stable operation difficult.

[0007]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems of the prior art, in which a conventional mold can be used, and a reduction width (from the above-mentioned thickness T ₀₎ can be reduced. proposed it is possible to increase the thickness decrease amount) of up to a thickness T _1, can be reduced in size and simplification of the pressure equipment, to solve the problem, a method which allows the production of thin cast strip according unsolidified reduction method The purpose is to do.

[0008]

According to the present invention, as a means for solving the above-mentioned problems, a slab having an unsolidified portion at a central portion drawn from a continuous casting machine mold is subjected to a reduction in the thickness direction in a continuous casting machine by applying a pressure reduction. In the continuous casting method to obtain a thin cast slab by correcting the thickness by thinning, use a mold with the inner wall of the long side of the mold as a vertical smooth surface, and the inner wall of the short side of the mold with a convex shape toward the casting direction. This is a continuous casting method for thin cast slabs.

[0009]

The operation of the present invention will be described below. FIG. 1 shows a schematic cross section of a preferred embodiment of a mold according to the invention.
In FIG. 1, components common to those of the conventional mold shown in FIG. 4 are denoted by the same reference numerals. That is,
Similar to the mold shown in FIG. 2, this mold is a combination of a mold long side 6 having a vertical smooth inner wall and a mold short side 9 having a deformed surface whose inner wall is convex in the casting direction. .

As shown in FIG. 1, the thickness T ₀ of the mold according to the present invention is the same as that of a conventional mold having a rectangular cross section, and a sufficient space for charging the immersion nozzle is secured. The inventors have determined that the unsolidified cast slab drawn using the mold shown in FIG. 1 is unsolidified and reduced by a rolling roll group as shown in FIG. As a result of a detailed study of the growth state of the solidified shell of the piece, (2) the slab deformation state after the unsolidification reduction, and (3) the deformation state and the stress distribution state of the solidified shell after the unsolidification reduction, the following findings were obtained. Obtained. (A) The short-side solidified shell of the unsolidified slab drawn from the mold is formed in an arch shape from the beginning of casting, as shown in FIG. 2 (a). (B) Therefore, at the time of unsolidifying rolling, As shown by the arrow in FIG.
A bending moment M is easily generated in the arched short-side solidified shell 10. (C) The progress under the unsolidified pressure in the thickness direction is promoted mainly by the bending deformation of the short-side solidified shell 10. The required rolling force for obtaining the thin slab shown in (b) is extremely small.

On the other hand, when the unsolidified slab produced by the mold having the rectangular cross section shown in FIG. 4 is to be rolled down, as shown in FIG. Since the reduction in the thickness direction proceeds due to the compression deformation of 8b, a large reduction force was still required. That is, the difference from the case of the present invention shown in FIG. 2 is obvious. Further, in the mold according to the present invention, unlike the case of using the funnel-shaped inclined mold described in Japanese Patent Application Laid-Open No. 60-189555, in the mold, strong deformation of the solidified shell due to narrowing of the slab thickness is not forced. Therefore, no excessive frictional force is generated between the inner surface of the mold and the solidified shell, and there is little concern about abnormal friction of the mold and cracks in the slab.

As described above, the present invention solves the above-mentioned problems, that is, (1) the conventional mold can be used, and (2) the reduction width (the thickness from T ₀ to T ₁ described above). This is an invention in which the reduction can be increased, and (3) the downsizing equipment can be reduced in size and simplified.

The short side 9 of the mold shown in FIG.
Although formed in a convex shape having an arc with a constant curvature, as described above, the short side of the mold may be any shape that can regulate the shape of the short-side solidified shell to a convex shape. It is also possible to form a convex or trapezoidal shape.

[0014]

EXAMPLE Using the continuous casting machine shown in FIG. 3 and the mold according to the present invention shown in FIG. 1, casting was performed by the unsolidified rolling method under the following conditions. The dimensions of the inner wall of the mold are as shown in FIG. In addition, as a comparative example, casting was similarly performed under the following conditions using the conventional mold shown in FIG. 4 having the inner wall dimensions shown in FIG.

Casting conditions: Steel type: Medium carbon steel (C: 0.18% by weight) Casting speed: 2.0 m / min Secondary cooling water ratio: 2.5 l / kg · steel Rolling conditions: Rolling amount: 50 mm (5 mm) Roll roll pitch) Roll roll pitch: 200 mm Roll roll number: 10 pairs In addition, a load cell was installed in each roll, and the rolling load acting on the roll during unsolidified rolling was measured.

In the casting by the above unsolidified rolling method,
FIG. 8 shows the result of investigation on the total reduction load applied to each reduction roll at the time of steady casting. As shown in the figure, in the casting according to the method of the present invention, the total reduction load required to achieve the target reduction amount varies somewhat depending on the cooling state of the slab, but is about 1 / It turns out that only about 2 was needed.

In the above embodiment, cracking and breakout did not occur, and stable casting by the unsolidified rolling method was possible.

[0018]

As described above, in the method for rolling unsolidified cast slabs of the present invention, the short-side solidified shell to be actually rolled is formed in a convex shape. As the main body is promoted, the required rolling load is reduced,
The downsizing equipment can be reduced in size and cost, and the advantages of the unsolidified rolling method can be fully utilized.

No cracking or breakout occurs,
Casting by the stable unsolidification rolling method became possible. Further, since the load on the screw-down device is reduced, the number of times of maintenance of the device can be reduced, and there is also an effect that the mold efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a plan view of a mold according to the present invention.

FIG. 2 is a schematic diagram showing a procedure for rolling down an unsolidified slab of the present invention.

FIG. 3 is an explanatory diagram showing dimensions of a mold according to the present invention.

FIG. 4 is a schematic view of a continuous casting machine.

FIG. 5 is a plan view of a conventional mold.

FIG. 6 is a schematic view showing a conventional rolling method of an unsolidified cast slab.

FIG. 7 is an explanatory view showing dimensions of a conventional mold.

FIG. 8 is a graph showing a total rolling load in casting.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Mold 2 Roll-down roll group 3 Immersion nozzle 4 Solidified shell 5 Unsolidified part 6 Mold long side 7 Mold short side 8a Long side solidified shell 8b Short side solidified shell 9 Mold short side 10 Short side solidified shell

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Bessho Nagayasu 1 Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Corp. Technical Research Division (72) Inventor Masakazu Matsubara 5-2 Sokaicho, Niihama-shi, Ehime Sumitomo Shigeto (56) References JP-A-3-207551 (JP, A) JP-A 64-66046 (JP, A) JP-A 63-317237 (JP, A) JP-A 61- 49751 (JP, A) Japanese Utility Model Showa 53-165817 (JP, U) Japanese Utility Model Showa 50-108915 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/04 311 B22D 11/128 350

Claims (1)

(57) [Claims] 1. A continuous casting method for obtaining a thin cast slab by applying pressure reduction in a thickness direction to a cast slab having an unsolidified portion at a center portion drawn from a continuous casting machine mold to reduce the thickness of the cast slab. 3. A method for continuous casting of thin cast pieces, characterized by using a mold in which the inner wall of the long side of the mold has a vertical smooth surface and the inner wall of the short side of the mold has a convex shape in the casting direction.