JP3700541B2 - Continuous casting method and apparatus for molten metal using superconducting magnet - Google Patents

Description

【００４６】
【表２】

【００４７】
【発明の効果】
かくして、本発明によれば、超伝導磁石に対する、鋳片からの輻射熱や鋳片に噴霧された冷却水の蒸気からの輻射熱や熱伝達等を効果的に遮断することができるので、従来懸念された輻射熱による磁場の消失等のおそれなしに、高品質スラブの製造を高速で安定して実施することができ、さらには大幅なコスト削減も達成することができる。
【図面の簡単な説明】
【図１】 ＣＧＲ温度センサー（ＡおよびＢ）それぞれのＣＧＲ抵抗値と温度との関係を示したグラフである。
【図２】 ２つのＣＧＲ温度センサー（ＡおよびＢ）で測定した、実際の連続鋳造操業における経過時間と超伝導磁石内部のＣＧＲ抵抗値との関係を示したグラフである。
【図３】 超伝導磁石に対する熱電対の取り付け位置を示した図である。
【図４】 超伝導磁石壁面の各位置における温度変化を示したグラフである。
【図５】 本発明を適用した連続鋳造機の模式図である。
【図６】 超伝導磁石に対する熱遮断体の設置状態の説明図である。
【図７】 熱遮断体を示した図である。
【符号の説明】
１ 浸漬ノズル
２ モールド
３ 溶鋼
４ パウダー
５ ロール
６ 静磁場発生器（超伝導磁石）
７ 熱遮断体
８ 防熱板
９ 断熱材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a continuous casting method and the continuous casting equipment of the molten metal using a superconducting magnet, upon particular continuous casting of molten metal, it is a concern when using a superconducting magnet as melt flow control means by a magnetic field It is intended to effectively prevent breakout in the superconducting state and enable stable high-speed casting.
Moreover, this invention is applicable not only to the steel industry which is a typical industry using continuous casting as a manufacturing method of a steel slab, but also to other industries that handle molten metal.
[0002]
[Prior art]
Conventionally, in continuous casting of steel, molten steel is generally injected into a mold from a tundish through an immersion nozzle.
However, since the molten steel flowing out from the discharge port of the immersion nozzle has a large discharge flow rate, inclusions such as alumina and bubbles are entrained in the molten steel, which causes a product quality defect. It was.
In addition, when the molten steel is injected, the discharge flow collides with the short side of the mold, and when this causes an upward flow in the mold, the upward flow disturbs the molten metal surface. As a result, mold flux or the like added to the molten metal surface is caught in the steel, which also causes the quality of the product to deteriorate.
[0003]
In the past, such problems have been dealt with by changing the nozzle angle and shape to reduce the discharge speed of the molten steel. However, in recent years, of course, ensuring high quality that satisfies the user's requirements. However, there is a tendency to increase the casting speed (discharge rate) for high efficiency and high economic efficiency. For that purpose, it is not enough to change the nozzle angle or change the shape. Development of a new casting system has been desired.
[0004]
As a prior art in this regard, a magnetic field (normal conducting magnet) is applied to the molten steel flow in the continuous casting mold, and the discharge of the molten steel is braked to prevent inclusions from entering the molten steel. The techniques disclosed in, for example, Japanese Patent Application Laid-Open No. 8-52549, Japanese Patent Application Laid-Open No. 8-19841, Japanese Patent Application Laid-Open No. 57-17356 and Japanese Patent Application Laid-Open No. 2-284750 are known.
However, in the conventional technology as described above, although the direction of the jet of molten steel can be changed, the energy of the jet cannot be dispersed to make a uniform flow, and the molten steel is in an area where there is no static magnetic field. May escape, and when the casting speed of molten steel is about 4-5 ton / min, the quality improvement effect is seen, but the effect is especially high-speed casting where the casting speed exceeds twice the conventional speed. The current situation is that we can hardly expect.
[0005]
As a solution of the above problems, for example, JP-8-90176 and JP-A No. 8-229648, have continuous casting method of steel using the superconducting magnet is disclosed, thereby implementing the high-speed casting It can be expected that the above problems will be solved.
[0006]
[Problems to be solved by the invention]
However, when continuous casting using a superconducting magnet was tested for a long period of time, there was a case where the superconducting state of the superconducting coil in the superconducting magnet disappeared.
In other words, when superconducting magnets are applied to the continuous casting method, they are designed so that they can be applied to continuous casting machines. Although it was installed on the actual machine, there were many cases that nevertheless could not maintain the superconducting state.
[0007]
The present invention advantageously solves the above-described problem. Even if continuous casting is performed for a long time using a superconducting magnet, the superconducting state does not disappear, and stable magnetic field application and stable high-speed continuous casting are achieved. it can be achieved, the continuous casting method of molten metal using a superconducting magnet, and an object thereof is to propose together with a suitable continuous casting equipment used in its implementation.
[0008]
[Means for Solving the Problems]
Hereinafter, the background to the present invention will be described.
Conventionally, as a cooling method for a large superconducting magnet, a cooling method using liquid nitrogen or liquid helium is generally used. In recent years, direct-cooled superconducting magnets are also increasing, but large magnets have not yet been put into practical use and are rarely used particularly industrially.
Therefore, the direction in which the superconducting magnet can be used is a stage where various fields have been tried.
[0009]
In the steel field, especially in the field of continuous casting, quality has been improved using a magnetic field. In recent research and development, casting using a high magnetic field will result in higher production and higher quality. The conclusion is coming out.
However, for that purpose, application of superconducting magnets to this field becomes a big problem.
As described above, the present invention is intended to enable continuous casting in a stable high magnetic field by solving the problem of disappearance of the superconducting state when the superconducting magnet is applied to the casting field. is there.
[0010]
In the conventional casting method using a normal conducting magnet, the above point has not been a problem. For example, in the conventional normal conducting magnet, even if the temperature of the conducting wire is increased, there is no problem that the current flowing through the conducting wire suddenly becomes zero and the magnetic field disappears. In addition, normal magnets have a small magnetic field, and the effect of the magnetic field is limited only to high quality, so even if the magnetic field disappears due to a power failure etc., high productivity is not pursued. The amount never dropped.
However, in the case of using a superconducting magnetic field, since high quality and high productivity are strongly pursued, the disappearance of the magnetic field becomes a very big problem.
Further, in the normal conducting magnet, since the conducting wire itself in the coil generates heat by current, it is necessary to always circulate the cooling water and perform heat removal. Therefore, even if the heat is somewhat unstable, there is no problem with the conductor, and there is no problem because the cooling water itself absorbs heat.
[0011]
Therefore, when casting is performed using a superconducting magnet as in this case, the fact that the generation of a magnetic field becomes unstable is a serious problem when the superconducting magnet is used in the field in the future. I can say that.
Therefore, the inventors first conducted a detailed investigation to elucidate the cause of the disappearance of the superconducting state described above.
[0012]
That is, a CGR temperature sensor was installed in the superconducting coil inside the superconducting magnet, a low current was passed from the outside, and the temperature was measured by resistance.
As a result, it has been clarified that the temperature inside the superconducting magnet is not always constant, and the temperature changes in a very short period.
The results of this investigation are shown in FIGS.
FIG. 1 shows the relationship between the CGR resistance value and the temperature of each of the two CGR temperature sensors attached to the superconducting coils inside the two superconducting magnets A and B provided with the mold in between. FIG. 2 shows the relationship between the elapsed time in the actual continuous casting operation and the CGR resistance value inside the superconducting magnet, measured by the two CGR temperature sensors.
Therefore, if the resistance value obtained in FIG. 2 is converted into a temperature according to FIG. 1, the internal temperature of the superconducting magnet is obtained.
[0013]
As is apparent from FIG. 2, the temperature change of the superconducting coil occurs at an extremely early stage, so that it is unlikely that the temperature rises due to normal heat conduction / heat radiation. Also, the superconducting magnet cryo (cooling device) adds heat insulation to a metal with a thickness of several tens of millimeters, so it is unlikely that an external temperature change directly raised the temperature of the superconducting coil. It was.
[0014]
As described above, it was difficult to consider that the temperature change outside the cryo was causing a rapid temperature change inside the cryo, but the temperature outside the cryo was also measured.
As a result, in the continuous casting machine, the temperature of the atmosphere under the mold cover rose to 40-50 ° C, and in extreme cases, reached 70 ° C or higher. However, this outside air temperature was designed and manufactured in advance, and therefore, it was considered that the temperature inside the superconducting magnet could not be increased.
[0015]
Then, the inventors investigated the temperature of the superconducting magnet wall surface.
As a result, it was revealed that the surface of the superconducting magnet was also at a temperature of about 30-40 ° C. However, at such a temperature, it is considered that the temperature inside the superconducting magnet does not increase as described above.
[0016]
Therefore, further to the superconducting magnet, was further determined in detail by attaching a thermocouple to the position indicated by the symbol i ~ DOO 3, as shown in FIG. 4, a portion of the wall surface of the superconducting magnet, particularly The temperature may rise at the bottom, and it has been newly found that the heat input to the superconducting magnet is greatly influenced not only from the outside air but also by the radiant heat.
[0017]
Usually, in the gap between the rolls, there is a nozzle for jetting cooling water to cool the slab, and since cooling water is always jetted out and a water curtain is also formed, the radiant heat is shut off. It was thought.
However, the above investigation has revealed that the radiant heat may pass through the water curtain and the steam curtain to some extent from the gap between the rolls and reach the superconducting magnet.
The present invention is based on the above findings.
[0018]
That is, the gist configuration of the present invention is as follows.
1. In a method of performing continuous casting while applying a magnetic field by a superconducting magnet to a molten metal being cast, a heat shield is provided outside the superconducting magnet and separated from the superconducting magnet, A continuous casting method of molten metal using a superconducting magnet, wherein the casting is performed while blocking heat transfer and radiant heat from radiant heat from the slab and / or cooling water spray sprayed on the slab.
[0019]
2. In a molten metal continuous casting apparatus in which a superconducting magnet is provided as means for generating a magnetic field for molten metal in a mold, a heat shield is provided outside the superconducting magnet and spaced from the superconducting magnet. A molten metal continuous casting apparatus using a superconducting magnet.
[0020]
3. 3. The molten metal continuous casting apparatus using a superconducting magnet according to the above item 2, wherein the heat shield is a structure made of one or more layers of heat insulating material.
[0021]
4). 4. The molten metal continuous casting apparatus using the superconducting magnet according to 2 or 3 above, wherein the heat shield is a structure having at least a surface thereof made of a material having high heat reflectivity.
[0022]
5. 3. The molten metal continuous casting apparatus using the superconducting magnet according to the above 2, wherein the heat shield is a structure that is cooled from the inside or outside by a cooling fluid.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
In the case of using a superconducting magnet as a means for applying a magnetic field to molten steel in a mold of a continuous casting machine, the present invention provides heat transfer and radiant heat from the radiant heat from the slab or from the cooling water spray sprayed on the slab. such as to effectively block, as such blocking means, on the outside of the superconducting magnet, the thermal shutdown member Ru provided spaced from the magnet.
[0028]
Hereinafter, the case where a heat shield is provided outside the superconducting magnet so as to be separated from the magnet will be described.
FIG. 5 schematically shows a continuous casting machine to which the above invention is applied. In the figure, number 1 is an immersion nozzle, 2 is a mold, 3 is molten steel in a tundish, and 4 is supplied to the surface of molten steel in the mold. Powder 5 is a roll, and 6 is a static magnetic field generator using a superconducting magnet. As shown in FIG. 6, a heat shield 7 is provided outside the superconducting magnet 6 so as to be separated from the superconducting magnet 6.
In the example of FIG. 6, the heat shielding body 7 is provided on the entire outer surface of the superconducting magnet 6. However, the heat shielding body 7 is not necessarily provided on the entire outer surface of the superconducting magnet 6. It may be installed only on the bottom surface where the influence of radiant heat and heat transfer is the greatest.
[0029]
In addition, as the above heat shield 7, any material that exhibits a heat insulating effect is suitable, and the material and structure thereof are not particularly limited.
a) a structure composed of one or more layers of heat insulating material;
b) a structure having at least a surface thereof made of a material having high heat reflectance,
c) Structures and the like that are cooled internally or externally by a cooling fluid are particularly advantageously adapted.
[0030]
Here, each of the structures a) to c) will be specifically described.
In FIG. 7A, a metal heat insulating plate 8 is used as a heat shield 7. Instead of the metal heat insulating plate 8, a multilayer heat insulating material 9 is arranged, or a metal heat insulating plate 8 is used. If it is set as the structure which arrange | positions the heat insulating material 9 inside, it will become a structure equivalent to said a).
Further, if the outer surface of the metal heat insulating plate 8 is covered with a material having a high thermal reflectance by plating or the like, a structure corresponding to the above b) is obtained.
Further, FIG. 7 (b) shows a mechanism in which the inside of the metal heat insulating plate 8 is cooled with a cooling gas such as nitrogen gas, while FIG. 7 (c) is a mechanism in which the inside of the metal heat insulating plate 8 is directly cooled with cooling water. This corresponds to the structure c).
[0031]
In addition to rock wool, which is easily available in the steel industry, glass wool, rock board, and calf board are advantageously suitable as the heat insulating material.
Moreover, what impregnated the metal in this heat insulating material may be used.
On the other hand, as the cooling medium, cooling water and nitrogen gas, carbon dioxide gas, freon gas, and the like are advantageously adapted, but not limited thereto, and any one that exhibits a cooling effect is suitable. The important thing is that the cooling can be carried out reliably.
[0035]
As described above, in accordance with the present invention, the outside of the superconducting magnet, do it by only setting the heat blocking member, the heat transfer and radiation heat from the vapor of the cooling water sprayed into radiant heat or slab from the slab to Since it can be effectively cut off, high-speed casting using a superconducting magnet becomes possible without fear of loss of magnetic field due to heat transfer or radiant heat, which has been a concern in the past.
[0036]
【Example】
As the continuous casting machine, the vertical bending type continuous casting machine shown in FIG. 5 was used.
The continuous casting conditions are as follows.
・ Nozzle: 2-hole nozzle Discharge hole diameter: 40mm × 40mm square ・ Pouring speed: 2.5 m / min
・ Vertical section of vertical bending caster: 1.5 m
・ Mold size: 0.4 m (width) x 0.11 m (thickness)
・ Applied magnetic field: 1T
-Cast steel grade:
C: 300-350 ppm, Mn: 0.15-0.2 mass%, P: 0.025 mass% or less,
S: 0.015 mass% or less, Al: 0.025 to 0.038 mass%, TO: 25 to 35 ppm
・ Tundish molten steel temperature: 1550 ~ 1565 ℃
・ Casting amount: 5 ton (1 charge)
[0043]
In an embodiment of this, by providing a heat shielding body is spaced apart from the superconducting magnet, and shall be cut off radiant heat.
Each heat shield has the following five configurations.
1) No heat shield (conventional example)
2) With heat shield (metal type)
An austenitic stainless steel plate with a thickness of 3 mm was used as a metal heat shield.
3) With heat shield (uses heat insulation)
20mm thick rock wool was used as a heat insulating material (the outside of rock wool was covered with stainless steel foil).
4) With heat shield (metal type + heat insulating material)
As a heat insulating material, rock wool (50 mm thick) whose surface was impregnated with aluminum was used.
5) With heat shield (metal type + cooling treatment)
A 3 mm thick austenitic stainless steel plate was used as a metal heat shield, and the inside thereof was directly cooled with cooling water.
[0044]
Table 1 shows the results of investigating the occurrence of disappearance of the superconducting state in the superconducting magnet when continuously cast under the above five conditions. Table 2 shows the amount of temperature rise inside and outside the superconducting magnet.
As shown in Table 1, when the and follow the present invention are obtained excellent thermal barrier properties.
[0045]
[Table 1]

[0046]
[Table 2]

[0047]
【The invention's effect】
Thus, according to the present invention, it is possible to effectively block radiant heat from the slab and radiant heat from the steam of the cooling water sprayed on the slab, heat transfer, and the like for the superconducting magnet. High-quality slabs can be manufactured stably at high speed without fear of loss of the magnetic field due to radiant heat, and a significant cost reduction can be achieved.
[Brief description of the drawings]
FIG. 1 is a graph showing a relationship between a CGR resistance value and a temperature of each CGR temperature sensor (A and B).
FIG. 2 is a graph showing a relationship between an elapsed time in an actual continuous casting operation and a CGR resistance value inside a superconducting magnet, measured by two CGR temperature sensors (A and B).
FIG. 3 is a view showing a mounting position of a thermocouple with respect to a superconducting magnet.
FIG. 4 is a graph showing a temperature change at each position of a superconducting magnet wall surface.
FIG. 5 is a schematic view of a continuous casting machine to which the present invention is applied.
FIG. 6 is an explanatory diagram of an installed state of a heat shield for a superconducting magnet.
FIG. 7 is a view showing a heat shield.
[Explanation of symbols]
1 Immersion nozzle 2 Mold 3 Molten steel 4 Powder 5 Roll 6 Static magnetic field generator (superconducting magnet)
7 Heat shield 8 Heat shield 9 Heat insulation

Claims (5)

In a method of performing continuous casting while applying a magnetic field by a superconducting magnet to a molten metal being cast, a heat shield is provided outside the superconducting magnet and separated from the superconducting magnet, A continuous casting method of molten metal using a superconducting magnet, wherein the casting is performed while blocking heat transfer and radiant heat from radiant heat from the slab and / or cooling water spray sprayed on the slab.   In a molten metal continuous casting apparatus in which a superconducting magnet is provided as means for generating a magnetic field for molten metal in a mold, a heat shield is provided outside the superconducting magnet and separated from the superconducting magnet. A molten metal continuous casting apparatus using a superconducting magnet.   The molten metal continuous casting apparatus using a superconducting magnet according to claim 2, wherein the heat shield is a structure made of one or more layers of heat insulating material.   4. The molten metal continuous casting apparatus using a superconducting magnet according to claim 2, wherein the heat shield is a structure having at least a surface thereof made of a material having high heat reflectivity. .   The molten metal continuous casting apparatus using a superconducting magnet according to claim 2, wherein the heat shield is a structure that is cooled from the inside or outside by a cooling fluid.

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