JP3342771B2 - Continuous casting mold and continuous casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting mold and a casting method for obtaining high quality continuous casting slabs, and applies an electromagnetic force to the vicinity of a molten metal (molten metal) bath surface in a casting mold for continuous casting. The pinch force is excited to bend the molten metal bath surface into a convex shape to promote the feeding of the mold powder along the inner wall surface of the mold to improve the surface properties of the slab, and to be in the vicinity of the molten metal bath surface by electromagnetic induction. The present invention proposes a good continuous casting mold and a continuous casting method for heating the steel to suppress trapping of inclusions and bubbles in the initially solidified shell.

[0002]

2. Description of the Related Art Heretofore, as a means for improving the surface properties of a slab, an electromagnetic force has been applied to a meniscus portion via a casting mold, and the meniscus portion has been appropriately curved so that the inner wall surface of the mold has been cast. Japanese Patent Application Laid-Open No. 52-32824 (method for casting a molten metal) proposes and discloses a means for smoothing the flow of mold powder to one surface.

That is, in the disclosed example, as shown in FIG. 3, an electromagnetic force is applied to the molten metal 23 supplied to the mold 21 by an electromagnetic coil 22 embedded in the mold 21, and the meniscus 24 is shown in FIG. In this way, the mold powder 25 is bent upward so as to smoothly flow the mold powder 25 between the mold 21 and the molten metal 23 and to improve the surface properties of the slab.
FIG. 3 is an explanatory view of a mold in which a conventional electromagnetic coil is embedded.

[0004] However, in such a mold, the electromagnetic coil is embedded in the back of the mold, and there is a mold portion between the electromagnetic coil and the molten metal. As a result, it is necessary to greatly increase the capacity of the electromagnetic coil to obtain a predetermined electromagnetic force applied to the molten metal.

Therefore, means for solving such a problem is disclosed in Japanese Patent Application Laid-Open No. H4-100658 (mold for continuous casting).
Is proposed and disclosed. This means is to use a cylindrical mold having a rectangular cross section as an assembly mold of a long side plate and a short side plate, and to apply an alternating current to the long side plates facing each other as shown in FIG.
As shown in FIG. 5, long side plates facing each other are divided and stacked in several stages in the vertical direction, and an alternating current flows through each of the divided long side plates. That is, these means make the current flow directly to the mold in contact with the molten metal.
In JP-A-4, the attenuation of magnetic flux density due to the distance between the electromagnetic coil and the molten metal and the presence of a mold are avoided.

FIG. 4 is an explanatory view of a conventional assembly mold, and FIG. 5 is an explanatory view of a conventional assembly mold using a laminated long side plate. In these figures, 31 is a conductive mold, 32 is an insulating refractory, 33a and 33b are terminals for supplying AC electricity, 34 is an AC power supply, and 35 is a connection line.

However, the above method has a drawback that the electric current is dispersed and flows to the end of the mold, and only a small amount of electromagnetic force acts on the meniscus portion. There is a problem that molten metal is inserted into the surface, and operation troubles such as breakout often occur.

[0008]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems. In order to prevent the magnetic flux density from attenuating, a means for directly supplying electricity to a mold close to the molten metal is used. By energizing the molten metal surface, that is, the inner surface of the mold near the meniscus intensively, an electromagnetic force is effectively applied to the vicinity of the meniscus to improve the power efficiency and improve the quality of the surface of the casting side and subcutaneous surface. It is another object of the present invention to provide a continuous casting mold and a continuous casting method that do not cause an operation trouble such as breakout due to insertion of a molten metal into a lamination surface as in the above-described multi-layered mold.

[0009]

The gist of the present invention is as follows. An assembling mold comprising a long-side water-cooling plate and a short-side water-cooling plate forming a casting space having a rectangular cross-section inner contour. In a continuous casting mold that excites an alternating pinch force, a current path made of a material having higher conductivity than the long side water cooling plate is formed on the inner surface of the long side water cooling plate near the molten metal bath surface. This is a continuous casting mold in which an end of a short-side water-cooled plate in contact with an electric circuit is coated with an insulating material.

In the mold of the item, the material constituting the current path is pure copper, the long-side water-cooled plate is an alloy copper having an electric conductivity of 50% or less as compared with the pure copper, and the current path is formed by plating. Is what you do. Alternatively, in the mold of the item, the vertical width of the current path near the molten metal bath surface is at least 50 mm below the molten metal bath surface.

[0011] Alternatively, a continuous casting method in which a mold powder is used for continuous casting in which an alternating current is passed through an energizing path using the mold described in the above item.

[0012]

The operation of the present invention will be described below. The present invention
In order to improve the quality of the casting side and improve the power efficiency by effectively applying electromagnetic force to the vicinity of the meniscus of the molten metal in the mold, first, as a means to make the electromagnetic induction coil and the molten metal closest, a shield such as a copper plate must be used. Means for directly energizing the long side water cooling plate of the assembled mold composed of the long side water cooling plate and the short side water cooling plate is employed so that the electromagnetic force can be efficiently applied to the molten metal even when a high frequency is applied.

The greatest feature of the present invention is to form a current path made of a material having higher conductivity than the long side water cooling plate on the inner surface of the long side water cooling plate near the meniscus. By doing so, it is possible to energize the current path made of this high conductivity material intensively, so that the action of electromagnetic force near the meniscus and the heat generation action by electromagnetic induction are also effective, further improving the quality of slabs. Can be measured.

Further, pure copper is used for the high conductivity material forming the current path, and the conductivity of the long-side water cooling plate is 50 times that of pure copper.
% Or less of alloyed copper is preferably used, whereby the current flows intensively in the current-carrying path, and the electromagnetic force can be effectively applied to the vicinity of the meniscus. That is, if the conductivity of the long-side water-cooled plate exceeds 50% of the conductivity of the highly conductive material forming the current path, the action of the electromagnetic force near the meniscus becomes insufficient.

Further, the use of pure copper and alloyed copper for the long-side water-cooled plate facilitates close joining between the two,
Pure copper may be plated on the alloy copper, so that a sufficiently tight joint can be obtained.

The above-mentioned formation of the conducting path of the high-conductivity material in the long-side water-cooled plate is achieved by effectively applying an electromagnetic force to the vicinity of the meniscus so that the meniscus is curved upwardly in a convex shape. The main object of the present invention is to improve the surface properties of the cast slab obtained by heating the slab and to suppress the occurrence of subepidermal defects. For this reason, it is preferable that the vertical width of the current path formed in the long-side water-cooled plate satisfy at least 50 mm below the meniscus, that is, the vertical width is preferably 50 mm or more. But the top and bottom width
If it exceeds 300 mm, it adversely affects the cooling and solidification of the molten metal, which is not preferable.

On the other hand, a mold powder is used for casting using such a mold and passing an alternating current through the current path.
The mold powder used at this time preferably has a low electrical conductivity from the viewpoint of improving the electrical insulation between the mold and the solidified shell, and its value is desirably 2.5 Ω ⁻¹ / cm or less. In addition, the conductivity of ordinary mold powder is 1.5 to
Although it is in the range of 3.5 Ω ^-1 / cm, it is preferable to reduce CaO and increase Al ₂ O ₃ in the mold powder in order to lower the conductivity.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, as an example, FIGS. 1A and 1B are explanatory views of the structure of a continuous casting mold conforming to the present invention. FIG. 1A is a bird's-eye view of the upper part of the mold, and FIG.
(B) is an explanatory view of a longitudinal section of the mold.

Here, in FIGS. 1A and 1B, 1
Is a mold long side, 1 'is a long side water cooling plate, 2 is a mold short side, 2' is a short side water cooling plate, 3 is a current path of a high conductivity material formed on the long side water cooling plate 1 ', 4 is a current path Reference numeral 3 denotes an AC power supply terminal provided at both ends, and reference numeral 5 denotes a mother plate of the long-side water cooling plate 1 '. As a water cooling mechanism for the long side water cooling plate 1 'and the short side water cooling plate 2', a water cooling slit 6, a backup plate 7, a cooling water inlet header 8, and a cooling water outlet header 9 are provided. Further, reference numeral 10 denotes an immersion type injection nozzle, 11 denotes a molten metal, 12 denotes a solidified shell, 13 denotes an AC power supply, and 14 denotes a connecting wire for supplying electricity to the current path 3 of the long-side water cooling plate 1 '.

The mold shown in FIGS. 1 (a) and 1 (b) has a long side water cooling plate 1 'facing each other and a short side water cooling plate 2' facing each other forming a casting space having a rectangular cross-section. And the long side water cooling plate 1 'and the short side water cooling plate 2'
The surface to be joined is coated with an insulating material to electrically insulate them from each other, and a current path 3 made of a high conductivity material is formed on the inner surface of the long side water cooling plate 1 'near the meniscus. Therefore, the AC power supply 13, the connection lead wire 14, and the AC power supply terminal 4
Flows mainly through the current path 3 to effectively apply an electromagnetic force to the vicinity of the meniscus.

In FIG. 1 (a), the wiring of the connecting conductor 14 is formed by connecting two high-conductivity materials 3 facing each other in series, but they may be connected in parallel.

The combination of the high conductivity material forming the current path 3 and the material forming the base plate 5 of the long side water cooling plate 1 'is as follows.
As described above, pure copper and alloy copper are preferable, but pure copper and inconel, alloy copper and inconel, a combination of pure copper and stainless steel or alloy copper and stainless steel, or the like,
The joining of these combined materials is preferably performed by plating as described above, but can also be performed by explosion or thermal spraying.

In the case of the combination of pure copper and alloy copper, the alloy copper is as follows: Cr: 0.4 to 0.9%, Zr: 0.05 to 0.18%
, And having a conductivity of 50% or less of pure copper is suitable.

FIGS. 2A, 2B, 2C, and 2D are explanatory views showing examples of the cross-sectional shape of the current path formed in the long-side water cooling plate. It may be something.

The continuous casting mold according to the present invention comprises:
The backup plate and other equipment can be used simply by replacing the long-side water cooling plate 1 'of the conventional mold, which is advantageous in terms of economy.

Next, using a continuous casting mold conforming to the present invention, the width obtained by casting when an alternating current is applied to the mold and when the alternating current is not applied is:
Surface properties and occurrence of subepidermal defects were investigated for an ultra-low carbon cast slab having a thickness of 1.2 m and a thickness of 0.22 m.

Here, the continuous casting mold and processing conditions used above are listed below. ○ Mold for continuous casting Use the one with the structure shown in Fig. 1 and its long side water cooling plate 1 '
For the base plate 5, an alloy copper containing 0.8% of Cr and 0.15% of Zr and having a conductivity of 35% of pure copper is used, and the inner surface of the base plate 5 has the uppermost surface of the meniscus as the upper end. 100 mm, depth:
A 10 mm groove was provided, and pure copper was plated as a current path 3 in this portion.

○ Mold powder CaO: 30%, SiO ₂ : 25%, Al ₂ O ₃ : 5% and MgO: 5%
Having a conductivity of 2 Ω ^-1 / cm. ○ Energization of the long side water cooling plate 1 A high frequency of 3 KHz and power of 1200 KW was supplied. ○ The slab drawing speed was 1.8 m / mim.

As a result, the slab obtained when the long-side water-cooled plate 1 'was energized was compared with the slab obtained when the energization was not performed, in terms of surface properties and subcutaneous surface as listed below. Significant improvements in defects have been found.

The oscillation mark depth is reduced to 1/5. Oscillation mark valley claw occurrence rate is 1/3
To decrease. The number of inclusions under the epidermis within 3 mm from the slab surface has been reduced to 1/4. The number of pinholes under the epidermis within 3 mm from the slab surface is 1 /
Reduced to 4.

[0031]

The present invention is an assembly mold comprising a long-side water-cooling plate and a short-side water-cooling plate. An alternating current is applied to the long-side water-cooling plate to apply an electromagnetic force near the molten metal bath surface in the mold. In the continuous casting mold to be operated, a current path made of a material having higher conductivity than the long-side water-cooled plate is formed on the inner surface of the long-side water-cooled plate near the molten metal bath surface, and is insulated from the short-side water-cooled plate. Then, the current flows intensively in the current path, and the electromagnetic force is efficiently and effectively applied to the vicinity of the molten metal bath surface. By using the mold according to the present invention, the entire apparatus is made compact. In addition, it is possible to significantly reduce surface defects such as oscillation marks of the obtained slabs, subcutaneous subsurface inclusions and pinhole defects, and to achieve stable operation without causing troubles such as breakouts. Can do Kill.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a structure of a continuous casting mold conforming to the present invention, wherein (a) is a bird's-eye view of an upper part of the mold,
(B) is explanatory drawing of a mold longitudinal cross-sectional view.

FIG. 2 is an explanatory diagram showing an example of a cross-sectional shape of a current path formed on a long-side water cooling plate of the present invention.

FIG. 3 is an explanatory view of a mold in which a conventional electromagnetic coil is embedded.

FIG. 4 is an explanatory view of a conventional assembly mold.

FIG. 5 is an explanatory view of a conventional assembly mold using a laminated long side plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold long side 1 'long side water cooling plate 2 Mold short side 2' short side water cooling plate 3 Current path 4 AC power supply terminal 5 Base material 6 Water cooling slit 7 Backup plate 8 Cooling water inlet side header 9 Cooling water outlet side header 10 Injection Nozzle 11 Molten metal 12 Solidified shell 13 AC power supply 14 Connection lead 21 Mold 22 Electromagnetic coil 23 Molten metal 24 Meniscus 25 Mold powder 31 Conductive mold 32 Insulated refractory 33a, 33b AC power supply terminal 34 AC power supply 35 Connection wire

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor, Nagayasu, Nagayasu 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. (72) Inventor Tetsuya Fujii 1, Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki (56) References JP-A-5-146852 (JP, A) JP-A-6-142854 (JP, A) JP-A-4-100658 (JP, A) JP-A-5-146852 104224 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/04 311 B22D 11/055 B22D 11/059 110 B22D 11/059 120

Claims (5)

(57) [Claims] 1. An assembling mold comprising a long side water cooling plate and a short side water cooling plate forming a casting space having a rectangular cross-section inner contour, wherein the long side water cooling plate is provided with an AC power supply terminal, and the molten metal in the mold is provided. In a continuous casting mold that excites an electromagnetic alternating pinch force near a bath surface, an inner surface of a long-side water cooling plate near a molten metal bath surface is provided with an energizing path made of a material having higher conductivity than the long-side water cooling plate. A continuous casting mold formed by coating and coating an end of a short side water cooling plate in contact with the current path with an insulating material. 2. The continuous casting mold according to claim 1, wherein the material constituting the current path is pure copper, and the long-side water-cooled plate is an alloy copper having a conductivity of 50% or less as compared with pure copper. 3. The mold according to claim 1 or 2,
The current path is a continuous casting mold formed by plating. 4. The continuous casting mold according to claim 1, wherein the width of the current path near the molten metal bath surface is at least 50 mm below the molten metal bath surface. 5. A continuous casting method for use in the mold according to claim 1, wherein the mold is used for continuous casting by passing an alternating current through an energizing path.