JPH0667538B2 - Metal melt container with heating part - Google Patents

Description

TECHNICAL FIELD The present invention relates to a molten metal container for heating a molten metal of high temperature such as steel held in a container body.

INDUSTRIAL APPLICABILITY The metal melt container according to the present invention can be used in a tundish device used in a continuous casting method.

[Prior Art] In a metal melting factory or the like, a molten metal may be held in the container body until it is processed in the next step.
However, there is a problem that the molten metal in the container body is cooled. For example,
In the continuous casting method, the molten metal is temporarily held in the tundish before being poured into the water-cooled mold, but at this time, there is a problem that the temperature of the molten metal in the tundish decreases.

Therefore, conventionally, in order to secure a required temperature of the molten metal held in the container body, conventionally, the electrode is immersed in the molten metal in the container, and an electric current is directly applied to the molten metal itself to heat the molten metal itself by Joule heat. A device is provided. An apparatus for inductively heating the molten metal in the container is also provided. There is also provided an apparatus in which a plasma torch is installed above the container to plasma-heat the molten metal in the container.

[Problems to be Solved by the Invention] In the case of the device for heating the molten metal by the Joule heat of the molten metal itself, since the electrical resistivity of the molten metal is small, a considerably large amount of current is required. Also, in the case of an apparatus that induction-heats the melt or heats the melt with a plasma torch,
Requires special equipment.

The present invention has been made in view of the above circumstances, and an object thereof is a heater having an electrode portion fixed to the inner wall of a container body and a heating element made of a conductive ceramics located between the electrode portion and the molten metal. An apparatus is to provide a molten metal container having a heating unit for heating the molten metal in the container body to a required temperature.

[Means for Solving Problems] A molten metal container having a heating unit according to the present invention is a container body for holding molten metal, and is fixed to the inner wall surface side of at least one container body and positioned inside the wall surface. And a heater device composed of a heating element made of a conductive ceramics and having a specific resistance higher than that of the metal melt and located between the electrode part and the metal melt held by the electrode part, and the electrode part and the metal melt. It is characterized in that a voltage is applied between the two to energize the heating element to generate heat.

The container body holds the molten metal. The container body can be composed of an outer frame made of metal such as steel and having an open upper surface, and a refractory layer made of refractory such as ceramics or cement lined on the inner surface of the outer frame.

The electrode part that constitutes the heater device is fixed to the inner wall surface side of the container body and is located inside the wall surface. As a means for fixing the electrode part to the container body, embedding or the like can be adopted. Here, the electrode portion is usually formed in a plate shape and is embedded inside the refractory layer of the container body. The electrode portion is preferably formed of carbon in consideration of conductivity and heat resistance.
Further, the electrode portion can be formed of a conductive ceramic having a low electric resistance. When the electrode portion is made of conductive ceramics in this way, it is possible to integrally mold the electrode portion made of conductive ceramics and the heating element made of conductive ceramics, and fire the body as it is. By doing so, it is possible to further secure the bondability between the electrode portion and the heating element. The voltage value and current value applied between the electrode portion and the molten metal are appropriately selected according to the specific heat of the molten metal, the adjusted temperature of the molten metal, the capacity of the molten metal held in the container, and the like.

The heating element forming the heater device can be formed of a non-metallic heating material or a metallic heating material. As the non-metallic heat generating material, conductive ceramics can be used as a main component. Specific examples of conductive ceramics include zirconia (Zr
O ₂ ), silicon carbide (SiC), lanthanum chromate (LaCrO
₃ ), molybdenum silicide (MoSi ₂ ), titanium nitride (Ti
N), titanium carbide (TiC), and other known conductive ceramics are the main components. However, the conductive ceramics should be selected in consideration of the heating temperature of the molten metal, the acidity of the place where the heater device is used, the reducing atmosphere, the heat resistance of the heat generating material, and the impact resistance of the heat generating material at high temperatures. Is.

When the heating element contains zirconia as a main component, calcium oxide (CaO), magnesia (MgO), yttrium oxide (Y ₂ O ₃ ) and ytterbium oxide (Yb) are used as stabilizers.
₂ O ₃ ) and scandium oxide (Sc ₂ O ₃ ) are added in an amount of several% to several tens%, and it is desirable to use stabilized zirconia or metastable zirconia that avoids transition. By doing so, it is possible to avoid the expansion accompanying the transition, and it is advantageous to suppress the distortion of the heating element.

By the way, it is desirable that the conductive ceramics show a positive characteristic that the electric resistance value of the heating element does not change even if the temperature rises, or that the electric resistance value increases. In this way, when the conductive ceramic exhibits a positive characteristic in which the electric resistance value of the conductive ceramic increases as the temperature rises, when a high temperature portion occurs in the heating element, the high temperature portion has a high electric resistance value. Therefore, an electric current flows through a portion having a temperature lower than that of the high temperature portion, and therefore, it is convenient to cause the entire heating element to generate heat uniformly. When the conductive ceramic has a negative characteristic that the electric resistance value decreases as the temperature rises, when a high temperature part occurs in the heating element, the high temperature part has a low electric resistance value.
Therefore, it becomes difficult for the current to flow in a portion having a temperature lower than that in the high temperature portion, and the current easily flows in the high temperature portion. Therefore, the temperature of the high-temperature portion becomes higher and higher, which causes uneven heat generation of the heating element, which is not desirable. In this case, it is preferable to stir the molten metal to enhance the heat transfer property from the heater device to the molten metal.

The total resistance R (Ω) of the heating element is influenced by the fixed resistance value ρ (Ωcm) of the conductive ceramics, the wall thickness t (cm) of the heating element, and the area S (cm ² ) of the heating element, and therefore its shape. Is affected by the wall thickness, and R = (ρ · t) / S. The specific resistance value ρ of conductive ceramics is 1 to 5 × 10 ³ (Ωc
m) can be used.

The specific resistance value of the heating element can be changed by blending conductive ceramics with non-conductive ceramics and adjusting the blending ratio.

The heating element, after molding the conductive ceramic powder into a predetermined shape, or after molding a mixed powder of the conductive ceramic powder and the non-conductive ceramic powder into a predetermined shape,
It is formed by heating to a predetermined temperature and sintering. For example, the raw material ceramic powder is prepared by thoroughly pulverizing and mixing the ceramic powder with a ball mill, a vibration mill or the like. Then, the raw material ceramic powder is pressure-molded to form a compact. Then, if necessary, a drying process is performed, and heating is performed at a high temperature to sinter. For the pressure molding, known means such as a press pressing method, a hydrostatic pressing method, a hot pressing method can be adopted. Sintering is in a non-oxidizing atmosphere,
It is preferable to perform it in an inert atmosphere or high vacuum.

In the molten metal container according to the present invention, when the molten metal has a flow in the container, it is desirable to arrange the heater device and set the flow of the molten metal so that the molten metal hits the heating element of the heater device. In this case, it is desirable to arrange the heating element in a substantially right angle state with respect to the flow of the molten metal. In this way, the heat of the heating element is effectively transferred to the molten metal.

In the molten metal container according to the present invention, a heater device separate from the container body may be provided in addition to the heater device having the electrode portion fixed to the inner wall surface side of the container body. In this case, the separate heater device is immersed in the molten metal. Then, the molten metal in the container body may be heated by the heat generated by the heating element of the immersed heater device.

Further, the metal melt container according to the present invention may be provided with a bubbling device for feeding a gas such as argon gas into the melt, and a stirring device for mechanically stirring the melt. in this case,
When the molten metal is heated by the heat generated by the heating element, it is advantageous to send a gas such as argon gas to the molten metal for bubbling or mechanically agitate the molten metal to make the temperature of the molten metal uniform. . Further, in the molten metal container according to the present invention, a sensor such as a γ-ray level meter for detecting the stored amount of the molten metal held in the container body is provided, and the current to the electrode portion is supplied in accordance with the detection signal of the sensor. A control device for controlling may be provided, and the control device may control the amount of current flowing to the electrode portion in accordance with the variation amount of the molten metal held in the container body. By doing so, the temperature of the molten metal can be adjusted more accurately.

[Operation] In the molten metal container according to the present invention, a voltage is applied between the electrode portion and the molten metal, and a current is passed in the thickness direction of the heating element to heat the heating element to a high temperature. Then, the heat of the heating element is transferred to the molten metal, and the molten metal is heated. In the present invention,
The Joule heat due to the molten metal is smaller than the Joule heat due to the heating element.

[Example] A first example in which the method for heating a molten metal according to the present invention is applied to a continuous casting method for steel will be described.

First, a continuous casting apparatus used in the continuous casting method will be described. This continuous casting apparatus, as shown in FIG. 1, includes a tundish 1 as a container body for holding a molten iron and steel,
A water-cooled mold 2 arranged below the tundish 1,
It is composed of a secondary cooling spray zone 3, a pinch roll 4, and a straightening roll 5. Tundish 1 is ladle 30
As shown in FIG. 3, an enlarged cross-section of the wall of the container is a square container-shaped outer frame 1c with an open upper surface.
And a refractory layer 1d made of alumina and magnesia lined on the inner surface of the outer frame 1c.
It is the capacity to hold the degree. A discharge port 10a is formed on the bottom wall of the tundish 1. The discharge port 10a faces the water-cooled mold 2 and supplies the molten metal to the water-cooled mold 2.

The heater device 6 and the heater device 9 used in the present embodiment are the second
Shown in FIG. The heater device 6 and the heater device 9 are embedded in the refractory layer 1d of the tundish 1. The heater device 6 includes a plate-shaped heating element 7 containing zirconia and magnesia as main components, and a plate-shaped electrode portion 8 that comes into close contact with the back surface of the heating element 7.
It consists of and. The heater device 9 is composed of a plate-shaped heating element 10 containing zirconia and magnesia as main components, and a plate-shaped electrode portion 11 that is in close contact with the back surface of the heating element 10. The heating elements 7 and 10 are made of ceramic powder in a ball mill,
Sequentially perform the steps of adjusting the raw material ceramic powder by sufficiently crushing and mixing with a vibration mill, forming the compact by pressing the raw material ceramic powder, and then heating and sintering at high temperature. Is formed. The electrode portion 8 and the electrode portion 11 are made of carbon.

Terminals are formed on the electrode portions 8 and 11.

Next, the continuous casting process will be described. First, the heating element 7 of the heater device 6 and the heating element 10 of the heater device 9 embedded in the refractory layer 1d of the tundish 1 are preheated to about 1300 ° C. with the flame of a heating device such as a burner. In this way, the heating element 7,
If the heating element 10 is preheated, the electrical conductivity of the heating element 7 and the heating element 10 containing zirconia as a main component can be secured. With the heating elements 7 and 10 preheated in this way, the molten metal of high temperature steel of about 1400 to 1600 ° C held in the ladle 30 is transferred to the inlet 1a of the tundish 1 to generate heat from the heater device 6. The body 7 and the heating element 10 of the heater device 9 are brought into contact with the molten metal.

In this manner, with the heating element 7 of the heater device 6, the heating element 10 of the heater device 9 and the molten metal in contact with each other, the terminal of the electrode portion 8 and the terminal of the electrode portion 11 are connected to an AC power source to connect the electrode portion 8 and the electrode. Part 10
And a voltage is applied through the molten metal. As a result, an electric current is passed through the molten metal held in the tundish 1 in the thickness direction of the heating element 7 of the heater device 6 and in the thickness direction of the heating element 10 of the heater device 9. In this case, the voltage is about 100 to 600V and the amount of current is about 200 to 400A.

As a result, the heating element 7 and the heating element 10, which mainly contain zirconia and magnesia, generate heat at a high temperature. Therefore, the molten metal held in the tundish 1 is heated to about 1 to 30 ° C.
The temperature is raised and the temperature is adjusted.

The molten metal whose temperature is adjusted in the tundish 1 as described above is discharged from the discharge port 10a of the tundish 1, cooled and solidified by the water-cooled mold 2, and further cooled by jetting cooling water from the spray zone 3 and solidified by cooling. Thing is pinch roll 4
Is pulled downward at. After that, it is cut into a predetermined length by a cutting machine.

As described above, in the present embodiment, since the molten metal held in the tundish 1 is heated by the heat generation amount of the heat generating element 7 of the heater device 6 and the heat generation amount of the heat generating element 10 of the heater device 9, it is conventionally provided. The amount of current required is small compared to the method in which a current is directly applied to the molten metal itself to heat the molten metal by the Joule heat generated in the molten metal itself, and therefore the electrical control thereof is easy to perform.

Further, in this embodiment, since the heating elements 7 and 10 are plate-shaped, they have a large surface area, that is, a large heat radiation area. Therefore, it is possible to suppress the heat from being trapped inside the heating elements 7 and 10. Therefore, it is advantageous in suppressing cracks and melting of the heat generating elements 7 and 10 due to heat. Therefore, in this embodiment, the heat-resistant temperature of the heat-generating body 7 and the heat-generating body 10 may be low. Therefore, the types of conductive ceramic materials forming the heat-generating body 7 and the heat-generating body 10 can be expanded to those having a low heat-resistant temperature. it can.

If the heater device 6 and the heater device 9 are preheated before the molten metal is transferred to the tundish 1 as described above, the heating element 7 and the heating element 10
Can prevent sudden heat. Therefore, the generation of cracks in the heating element 7 and the heating element 10 can be suppressed as much as possible. When the heating element 7 and the heating element 10 are cracked, the molten metal and the electrode portion 8 and the electrode portion 11 are directly connected to each other, and the heating element 7 and the heating element 10
The heat generation amount of 10 becomes extremely small, which causes a problem that the heater device 6 and the heater device 9 cannot be effectively used.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIGS. 5 and 6 show the heater device 20 and the heater device 24 taken out from the refractory layer 1d of the tundish 1. In this embodiment, the heater device 20 is composed of a plate-shaped electrode portion 21 made of carbon, and a heating element 22 mainly composed of zirconia and magnesia, which is coated on the plate-shaped electrode portion 21. The plate electrode portion 21 is an insulator 21 made of alumina.
It is divided by 0 and an insulator 211, and is divided into three parts into an electrode body 212, an electrode body 213, and an electrode body 214. Electrode body 212, electrode body 213,
A terminal 212a, a terminal 213a, and a terminal 214a project from the electrode body 214, respectively.

The heater device 24 has substantially the same configuration as the heater device 20,
It is composed of a plate-shaped electrode portion 25 formed of carbon and a heating element 26 containing zirconia as a main component. Plate electrode part 25
Are separated by an insulator 250 and an insulator 251 made of alumina, and are divided into three parts: an electrode body 252, an electrode body 253, and an electrode body 254. Each of the electrode body 252, the electrode body 253, and the electrode body 254,
The terminal 252a, the terminal 253a, and the terminal 254a are projected. In addition,
Of the plate-shaped electrode portion 21 and the plate-shaped electrode portion 25, the heating element 22 and the heating element
The portions not in contact with 26 are covered with insulating films 21a and 25a made of an electrically insulating material.

In use, first, as shown in FIG. 5, in the heater device 20, the terminals 212a and 214a are connected to an AC power source, and the electrodes 212 and 214 are connected via the heating element 22. At a voltage of 100 to 600 V, a current of 200 to 400 A is applied to heat the heating element 22, thereby preheating the heating element 22 to about 1300 ° C. Similarly, in the heater device 24, the terminal 252a and the terminal 254a are connected to an AC power source, and the voltage of 100 to 600 V is applied between the electrode body 252 and the electrode body 254 via the heating element 26 to 200 to 200
A current of 400 A is applied, and the heating element 26 is thereby heated, and the heating element 26 is preheated to about 1300 ° C.

By preheating in this way, rapid heating of the heating elements 22 and 26 can be suppressed, which is advantageous in terms of suppressing cracking of the heating elements 22 and 26. As described above, the heating element 22 of the heater device 20, the heater device
With the heating elements 26 of 24 preheated, the molten metal is transferred from the ladle 30 to the tundish 1, and the heating elements 22 and 26 are brought into contact with the molten metal.

In this state of contact with the molten metal, as shown in FIG. 6, the terminals 212a, 213a, 214a of the heater device 20 are connected to an AC power source, and the terminals 252a, 253a, 254a of the heater device 24 are connected.
Is connected to an AC power source, whereby an electric current is caused to flow through the molten metal in the tundish 1 in the thickness direction of the heating element 22 of the heater device 20 and the thickness direction of the heating element 26 of the heater device 24, whereby the heating element 22, The heating element 26 is heated to a high temperature, thereby heating the molten metal in the tundish 1.

[Advantages of the Invention] According to the molten metal container of the present invention, the temperature of the molten metal held in the container body can be adjusted by the heat generated by the conductive ceramics heating element. Therefore, when the molten metal container according to the present invention is applied to a tundish device in a continuous casting method, the molten metal can be supplied at an appropriate temperature to a cooling mold arranged below the tundish device, and thus the continuous casting method can be used. It is possible to improve the quality of metal products manufactured in.

[Brief description of drawings]

1 to 3 show a first embodiment of the present invention, FIG. 1 is an explanatory view of a state of continuous casting, FIG. 2 is a plan view of a container body, and FIG. 3 is a heater device portion. FIG. Fourth
FIGS. 6 to 6 show a second embodiment, FIG. 4 is a plan view of a container body, FIG. 5 is a perspective view of a heater device, and FIG. 6 is a perspective view of a state where electricity is supplied between the heater devices. is there. In the figure, 1 is a tundish (container body), 6 is a heater device, 7 is a heating element, 8 is an electrode part, 9 is a heater device, 10 is a heating element, 11 is an electrode part, 20 is a heater device, 21 is an electrode part. , 22 is a heating element, 24 is a heater device, 25 is an electrode portion, and 26 is a heating element.

Claims (6)

[Claims] 1. A container main body holding a molten metal, an electrode portion fixed to the inner wall surface side of at least one of the container main body and located inside the wall surface, and between the electrode portion and the held molten metal. And a heater device made of a conductive ceramic heating element having a specific resistance higher than that of the molten metal, and a voltage is applied between the electrode portion and the molten metal to energize the heating element. A molten metal container having a heating part, characterized in that it is configured to generate heat. 2. A metal melt having a heating part according to claim 1, wherein the heater device comprises a plate-shaped heating element and a plate-shaped electrode portion integrally fixed to the back surface of the plate-shaped heating element. container. 3. A molten metal container having a heating portion according to claim 1, wherein the electrode portion is formed of carbon or silicon carbide. 4. A molten metal container having a heating part according to claim 1, wherein the electrode part is formed of conductive ceramics which is integrally sintered with the heating element. 5. The molten metal heating container according to claim 4, wherein the heating element contains zirconia and magnesia as main components. 6. The container body is a tundish used in a continuous casting method, and has a discharge port for temporarily storing the molten metal injected from above and discharging the molten metal. A metal melt container having a heating part as described.