JPH02160149A - Heater device - Google Patents

Abstract

PURPOSE:To restrain heat stagnation in inner part of an exothermic body by constituting a heater device of the exothermic body formed of an outer layer part having the necessary exothermic characteristic and an inner layer part having different exothermic characteristic with that of the outer layer part and an electrode part for conducting electric current to the exothermic body. CONSTITUTION:The outer layer part 20 is formed of the exothermic material and the blending ratio of magnesia and zirconia as main components is selected so as to become high resistant value. By this method, the heat generation becomes vigorous at the position coming into contact with the molten metal, and heating efficiency is improved. Further, as the inner layer part 25 is not brought into contact with molten metal, the exothermic characteristic thereof is not necessary so much as that of the outer layer part 20, or rather in order to restrain the heat stagnation in the inner part of the exothermic body 2, it is desirable to restrain the exothermic characteristic. Further, in the case of preheating, as the inner layer part 25 is not directly brought into contact with flame of a burner, the exothermic quantity may be not secured so much as the outer layer part 20 and further, plenty of consideration to erosion resistance and oxidizing resistance, etc., is unnecessary, and degree of freedom to selection of the blending ratio can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is applied to a heater device. This heater i(f& is
For example, it can be used when immersed in molten metal to heat the molten metal.

[Prior Art] A conventionally used heater HR will be explained using a continuous casting method as an example. That is, in the continuous casting method, molten steel at a temperature of, for example, 1,400 to 1,600°C is first transferred from a ladle to a tongue pusher, and then the molten metal is cooled with water from the outlet of the tongue pusher. It is poured into a mold 8 and cooled and solidified, and after being cooled by a cooling spray band, the cooled and solidified portion is stretched with pinch rolls and cut into a predetermined length to produce J-shaped slabs, billets, etc. In the above-mentioned continuous barring method, the quality of the steel products manufactured is improved compared to the blooming method, and the yield is also improved. However, in recent years, steel products are required to be of even higher quality.
Continuous casting methods are also being actively developed to improve the quality of steel products.

In the continuous casting method described above, since the molten steel is primarily received in the tamp push, the consistency of the molten steel tends to decrease in the tamp push. Especially when continuous casting, i
At the end of casting, for example, when 50 to 80 minutes have elapsed since the start of s, the temperature of the molten metal drops by several to several tens of degrees Celsius, or even more in some cases. Here, since the tump push is the final container just before the molten metal solidifies, the molten metal content in the tamp push has a great effect on the surface inclusion index and the central carbon segregation index of the steel product. It has a big impact on the quality of ＾. Therefore, even if the melting and drying in the tundish decreases by several to several tens of degrees Celsius, this is not preferable in terms of quality control.

Therefore, in recent years, in order to adjust the temperature of the molten steel in the tumble push, carbon Ml/fA is immersed in the molten metal in the tamp push, and a current is passed directly through the molten metal itself in the tamp push.
BACKGROUND ART A heater device is provided that generates heat in the molten metal itself using Joule heat generated in the molten metal.

However, in this case, the electrical resistivity of the molten metal is low. Here, since the Joule heat generated by mI is the product of the electrical resistance value of the molten metal and the square of the current value flowing through the molten metal, as mentioned above, if the electrical resistivity of melting and drying is small, the required In order to secure Joule heat, there is a problem in that a fairly large current ω is required for the N flow that flows every time, and there is also a problem in that the electric equipment becomes large in size due to the large current.

In addition, as another heater device for heating the molten gold a in the tumbler push, an induction heating type device that heats the molten metal in the tumbler push by induction has been conventionally provided. Furthermore, a plasma heating device is also provided in which a plasma torch is installed above the tongue pusher to plasma-heat the molten metal inside the tongue pusher.

[16 Problems to be Solved by the Invention] As a result of repeated research on the #2 idea in order to reduce the current flowing through the molten metal, the present inventor used a heater device consisting of a heating element and an electrode part to create a heater! We have developed a means for heating the metal ms by immersing the heating element of the heater in the metal mm and applying a voltage between the heater and the molten metal to cause the heating element of the heater to generate heat.

The present invention was completed as part of the development of the above-mentioned heater device, and its purpose is to heat an object to be heated, such as metal melting, by generating heat from a heating element, and to heat an object to be heated, such as metal melting, by heating a heating element. By forming the inner layer and the inner layer,
It is an object of the present invention to provide a heater device that is advantageous in ensuring flexibility in selecting the type of heat generating material forming a heat generating element and the blending ratio of the heat generating material.

[Means for Solving the Problems] The heater device according to the present invention includes an outer layer portion made of a heat-generating material as a base material and having required heat-generating characteristics, and at least one inner layer portion having heat-generating characteristics different from the outer layer portion. It is characterized in that #I is formed by the formed heating element and an electrode portion for supplying electricity to the heating element.

The heating element is composed of an outer layer portion made of a heat-generating material as a base material and having required heat generation characteristics, and at least one inner layer portion having heat generation characteristics different from those of the outer layer portion.

Here, using a heat-generating material as a base material means that even if it is formed only of a heat-generating material, it may contain other fillers other than the heat-generating material. The inner layer is 1 if necessary.
The number of layers may be two or more, and in some cases, the number of layers may be six or more. The thickness of the outer layer portion can be substantially uniform in order to ensure uniformity of heat generation, but depending on the heat generating material, there may be a portion with varying thickness. Inner li! The same goes for the department.

The heating element can have a cylindrical shape or a shape similar to a cylindrical shape. In this form, it can be used as a type that is immersed in molten metal. In this case, both the outer layer and the inner layer are cylindrical or cylindrical. The shape can be approximated. Here, when the heating element is made into a cylinder shape or a shape similar to a cylinder shape, the outer diameter of the central part in the longitudinal direction of the heating element is extended in the longitudinal direction. It is desirable that the wall thickness of the central portion in the longitudinal direction of the heating element be made substantially uniform by making the dimensions substantially the same and the inner diameter of the central portion being substantially the same along the length. In this case, the relationship between the outer diameter and inner diameter of the central part in the longitudinal direction of the heating element is such that the inner diameter can be 30 to 80% of the outer diameter, and preferably 50 to 70%. The reason is that if the ratio of the inner diameter to the outer diameter is small, the exothermic group in the inner diameter will be larger than the outer diameter, and as a result, there is a risk that the inner diameter will melt.Also, if the ratio of the inner diameter is large, This is because the actual thickness of the p!A layer becomes smaller, making it more susceptible to erosion by molten steel.

In the heater device according to the present invention, the heat generating material forming the outer layer of the heating element and the heat generating material forming the inner layer are non-metallic,
6 is good for any metal type. In this case, the type or blending ratio of the heat-generating material forming the outer layer can be one that has a higher electrical resistance value than the type or blending ratio of the heat-generating material forming the inner layer. If this occurs, heat generation will increase in areas close to the heated object (e.g., liquid such as molten metal, gas such as air) that contacts or faces the outer layer of the heating element. It is advantageous for effectively heating the object to be heated and increasing heating efficiency.

In addition, since the outer layer normally comes into contact with molten metal, air, and GJ burner flame during preheating, the type of heat-generating material forming the outer layer and its blending ratio should be determined in addition to its heat-generating properties, as well as its corrosion resistance and heat resistance. It is necessary to consider various factors such as impact resistance, oxidation resistance, corrosion resistance, aging resistance, etc. when selecting the inner layer. When selecting the type of heat-generating material forming the outer layer or its blending ratio, such consideration can be reduced or ignored. It can be said that the material is small and has low heat generation property, and its blending ratio. Therefore, the type of heat generating material forming the inner layer part or its blending ratio is selected in comparison with the type of heat generating material forming the outer layer part or its blending ratio. The degree of freedom increases.

In the heater device according to the present invention, as the above-mentioned metal-based heat-generating material forming the heating element, for example, a nickel-chromium alloy, an iron-O-Mo-aluminum alloy, tungsten, molybdenum, tantalum, etc. are used as necessary. Can be hired.

Further, as the above-mentioned non-metallic heating material forming the heating element, ceramics having conductivity in the operating temperature range among oxide-based, nitride-based, boride-based, etc. can be used. As conductive ceramics, if the object to be heated is molten steel, it is desirable to have a high specific resistance value because the resistance of the molten steel is low, so it is necessary to increase the R of the heating element. In this case, it is desirable that the specific resistance value be 10 cm or more at around 1500°C, especially 200°C.
It is desirable that the resistivity is Ωcm or more, and for example, one having a specific resistance value of about 360 (Ωcm) can be used. Note that the specific resistance values of the outer layer and the inner layer forming the heating element can be changed by blending a non-conductive ceramic or a poorly conductive ceramic with a conductive ceramic and adjusting the blending ratio.

In the heater device according to the present invention, when heating molten steel 4, magnesia (MGJO) and zirconia (Zr
O2), A/L/Mina (A9.z03), a mixture of magnesia and zirconia, and a mixture of magnesia, zirconia and alumina can be used. Here, magnesia usually does not have electrical conductivity at around room temperature, but takes on the required electrical conductivity at around 1,500 to 1,650° C., which is the heating temperature range of molten steel. When a mixture of magnesia and zirconia is used as an electrically conductive ceramic to form the outer layer, its composition is appropriately selected taking into consideration the required resistance value, etc. %, magnesia is 60-100%, especially 85-95
%, preferably zirconia from 0 to 40%, especially from 5 to 25%
%, preferably 0 to 40% alumina, especially 2.5 to 1
5% is preferred.

In addition, in the heater device according to the present invention, when heating molten steel, the conductive material forming the inner layer needs to be made of, for example, zirconium boride, boron nitride, silicon carbide, etc. Can be adopted according to the requirements. The six conductive ceramics forming the inner layer include magnesia (MQO) and zirconia (Z), as well as the outer layer.
rOt) Alumina (A1tO3), a mixture of 7 gnesia and zirconia, and a mixture of magnesia, zirconia, and alumina can be used, but the blending ratio can be changed in order to reduce the calorific value compared to the outer layer. , for example, by reducing magnesia to 40 to 70 magnesia in weight W%.
%, materials whose main components are zirconia, alumina, CaO, chromia, beryllia, thoria, and ceria are 181 or 2.
It can be blended in an amount of 30 to 60% or more in the content layer. Furthermore, the amount of carbon can be increased from 1 to 5 using carbon powder, graphite, etc.
%.

Furthermore, depending on the melting point of the molten metal, silicon carbide (S i C), lanthanum chromate (LaCrO
3) , beryllium oxide (Bed), thorium oxide (T
hig>, molybdenum silicide (MO8it), titanium nitride (TIN>, titanium carbide (T i C
) etc. can also be used. For reference, the relationship between operating temperature and specific resistance is shown in FIGS. 8 and 9. In addition, in the case of WI drought of steel, as mentioned above, the specific resistance value of the ceramics forming the heating element is
Particularly when forming the outer layer, the target value is desirably 200 Ωcm or more in the operating temperature range.

However, among the various heat-generating materials mentioned above, the heating temperature of the object to be heated such as a metal melting field, the acidic or reducing atmosphere of the place where the heater device is used, the heat resistance of the heat-generating material, and the high temperature of the heat-generating material Appropriate selection should be made taking into consideration impact resistance, price, toxicity, etc.

In addition, when the heating element has zirconia as a main component, calcium oxide (Cab), magnesia (MGJO),
Yttrium oxide (YtO3), ytterbium oxide (Yb20z), scandium oxide (SCzO3)
It is possible to use stabilized zirconia or metastable zirconia in which transition is avoided by adding about several percent to several tens of percent of .

In this way, expansion caused by the transition can be avoided, which is advantageous in suppressing distortion of the heating element.

When the heat-generating material is made of conductive ceramics, the particle size of the conductive ceramics may affect the resistance value. Therefore, the maximum particle size is preferably 1 to 5 mm 1 P1 degree, especially 1.5 mm. ~3 mm is desirable. The main reason for this is that if the particle size is too large, the current tends to become uneven. Note that it is also possible to change the particle size between the outer layer and the inner layer, thereby adjusting the heat generation characteristics of the outer layer and the inner layer.

The heat generating material of the outer layer and inner layer forming the heat generating element shows a positive property that the resistance value of the heat generating element does not change or the resistance value increases even if the operating temperature changes, unless there are other problems. can be used. In this case, when the resistance value of the heat-generating material increases as the temperature rises, when a high-temperature part is generated in the heat-generating element, the resistance value of the high-temperature part becomes high. Therefore, the part where the temperature is lower than the high temperature part is 1! The flow is advantageous for flowing and therefore for uniform heating throughout the heating element. If the heat-generating material has a large negative resistance value that decreases significantly when the temperature rises, if a high-temperature part occurs in the heat-generating element, the high r
jA section has a low resistance value.

Therefore, it is difficult for the current to flow in the part where the temperature is lower than that of the B part, and the N current is more likely to flow in the high temperature part where the resistance value is low. Therefore, the high-temperature part becomes increasingly hot and tends to become a cause of runaway heat generation of the single heating element.

The total resistance R (Ω) of the outer layer and inner layer forming the heating element is:
Specific resistance value ρ (Ωa
m), the thickness t (am) of the heating element, and the area S (
cm'). At this time, when the outer layer part and the inner layer part are made into a cylindrical shape, it is necessary to select the resistance value of the heating element in consideration of the following matters. That is, a culm with a large outer diameter of the heating element can secure a heat dissipation area, but cracks are likely to occur during molding and it is likely to be susceptible to thermal shock. On the other hand, the smaller the outer diameter of the heating element, the smaller the heat radiation area. Furthermore, the larger the inner diameter of the heating element, the larger the diameter of the electrode portion, and the greater the heat transfer loss from the electrode portion. On the other hand, the smaller the inner diameter of the heating element, the smaller the diameter of the electrode portion, and the smaller the heat transfer loss from the electrode portion, but the more uneven heat generation tends to occur. Further, the thicker the heating element, the more likely heat will accumulate inside the heating element, and the maximum temperature inside the heating element may rise, causing the inside to melt, which is disadvantageous in maintaining the stability of heat generation. On the other hand, the thinner the wall thickness of the heating element, the more difficult it is for heat to accumulate inside the heating element, but the necessary heat generation a cannot be obtained and the heating element tends to become a cause of wing running.

In the heater device according to the present invention, the heating element can be manufactured, for example, as follows. That is, the raw material Hiramix powder for the outer layer is sufficiently ground and mixed using a ball mill, vibration mill, etc. to obtain a predetermined composition. After the molding process, a slurry of raw ceramic powder and water is poured into the cavity of the mold and molded into a predetermined shape for the outer layer to obtain a molded body. A sintering process is carried out in which the molded body of the Is river is heated to a predetermined concentration and sintered. Prior to the sintering process, a curing process and a drying process are performed if necessary. In addition, when molding one culm, vibration molding can be performed in which molding is performed while applying vibration to the mold. The inner layer portion is also formed through a similar process. Then, the outer layer part and the inner layer part are assembled into one piece.

Moreover, the heating element can also be manufactured as follows.

That is, the raw material ceramic powder for the outer layer is ball milled,
Prepare the raw ceramic powder by thoroughly crushing and mixing with a vibrating mill or the like. Then, the raw ceramic powder is pressure-molded to form a compacted body for the outer layer portion. Thereafter, if necessary, a drying step is performed, and sintering is performed by heating to I11 temperature. Note that for the pressure molding, known means such as a press method, an isostatic pressure method, a hot press method, etc. can be employed.

The inner layer portion can also be formed in a similar process. Then, the outer layer part and the inner layer part are assembled into one piece.

In the heater device according to the present invention, another manufacturing method for forming the heating element is to integrally mold the outer layer portion and the inner layer portion, and then sinter the outer layer portion and the inner layer portion in the same direction. In this case, since it is in the horizontal direction, it is advantageous to ensure the degree of electrical contact and thermal contact between the outer layer portion and the inner layer portion.

In the heater device according to the present invention, it is desirable that the degree of contact between the outermost inner layer portion and the outer layer portion is high. Therefore, by charging powder or liquid between the inner layer and the outer layer, the electric contact between the inner layer and the outer layer can be adjusted by utilizing the current diffusion function and thermal diffusion function of the powder or liquid. It is also possible to improve thermal contact. In this case, even if a gap is likely to occur at the boundary between the outer layer and the inner layer, or even if the thermal tension between the outer layer and the inner layer is different, the electrical contact between the two It is useful for ensuring thermal contact. In addition, as the powder or granule, it is possible to use a material that has exothermic properties, such as carbon powder, graphite powder, or silicon carbide powder.As for the liquid, it is possible to use a material that can be immersed in 1J conductivity and has a low melting point, such as tin, lead, bismuth, Low melting point metals such as sodium, and in some cases copper metals can be used. The carbon powder preferably has a fine particle size from the viewpoint of ensuring heat generation property, and the particle size range can be, for example, 50 μ to 100 μ among 10 μ to 2 mm. In addition, if a solid powder made of low melting point metal 1b copper-based metal is charged between the inner layer and the outer layer, the solid powder will melt if the temperature during use is above its melting point. It melts into a liquid, which is advantageous for ensuring electrical contact and thermal contact.

In addition, in the heater device according to the present invention, the inner layer portion has two or more layers, and when the two or more inner layer portions are formed separately and later assembled together, the inner layer portion and the v4 It is also possible to improve the degree of contact between the inner layer parts by interposing powder or liquid as described above at the boundary between the inner layer parts and other inner layer parts.

In the heater device according to the present invention, as illustrated in the illustrated embodiment, the longitudinal ends of the inner layer and the outer layer have a three-dimensional curved shape, such as a hemispherical shape, or It is desirable that the shape approximates a hemisphere. The reason for this is that corners tend to be uneven during molding (and it is difficult to ensure thermal shock resistance. Also, current tends to concentrate at corners, so the heat generation temperature at corners increases, This is because it tends to be one of the causes of runaway heat generation.In addition, when the tip is semispherical, if the type is immersed in the molten metal in the tundish, half of the hemispherical tip of the outer layer (for example, 30
~100 mm, and the radius of the hemispherical tip of the inner layer is, for example, 20-85 ffl m Pi! It can be done as a degree.

In the heater device according to the present invention, the electrode section supplies electricity to the heating element i1! -b for connection, and is usually connected to the inner layer. The material of the electrode part is selected in consideration of conductivity, heat transfer coefficient, etc. In this case, the conductivity can be increased and the heat transfer coefficient can be decreased to reduce heat transfer loss. However, in general, as the electrical conductivity of a substance increases, the heat transfer rate also tends to increase. By appropriately combining the materials with
The apparent degree of heat transfer in part i can be reduced.

Further, the electrode 8i portion can also be formed of conductive ceramics with low electrical resistance. In such a case, it is also possible to integrally mold the 11M section, the outer layer section, and the inner layer section and then fire them as they are.

In the heater device according to the present invention, it is desirable that the electrode portion be thinner in order to reduce heat transfer loss through the Ii electrode portion.

Further, it is desirable that the degree of electrical contact between the electrode portion and the heating element be high. Therefore, the heating element and the electrode part can be integrally molded to increase the degree of electrical contact.

Also, the heating element and ff! When forming the 44i section separately and assembling it later, the boundary between the electric section 441 and the heating element should be filled with granular material such as carbon powder or graphite powder as described above, or tin. It is also possible to charge a conductive liquid such as lead, bismuth, etc. and have a low melting point, and use powder or liquid to improve the degree of contact between the electrode portion and the heating element. In this case, the heating element and 1! Even if the irradiation tonicity is different from that of the pole part, it is advantageous in ensuring electrical contact and thermal contact between the two.

In addition, when the heater device according to the present invention is used to heat molten metal held in a container, a sensor such as a T-line or bell meter is installed to detect the degree of accumulation of molten metal, and the sensor signal is A control device may be provided to control the current to the heating element according to the temperature. In this way, since the power supply layer flowing to the heating element is controlled according to the fluctuation of the molten metal held in the container, the temperature of the molten metal can be adjusted with even higher precision.

[Embodiment] A first embodiment of a heater device according to the present invention will be described with reference to FIGS. 1 and 2.

A heater device 1 according to this embodiment is shown in FIGS. 1 and 2. This heater device 1 is of a two-layer type and is composed of a heating element 2 in the shape of a hollow flask and a rod-shaped electrode portion 3. The heating element 2 is formed of an outer layer part 20 having a hollow flask shape and an inner layer part 25 having a hollow flask shape. The outer layer part 20 is made of heavy φ%, magnesia 90%, zirconia 5
%, alumina 5%, and mixed ceramics containing unavoidable impurities. The inner layer portion 25 is in weight%,
It is made of a mixed ceramic containing 60% magnesia and 40% zirconia and unavoidable impurities.

As shown in FIGS. 1 and 2, the outer layer portion 20 has a large-diameter proximal end portion 200, a central portion 210 connected to the proximal end portion 200, and a three-dimensional curved surface shape, that is, a hemispherical shape connected to the central portion 210. It is composed of a distal end portion 220. central part 210
The thickness of the tip portion 220 and the thickness of the tip portion 220 are substantially uniform, and the variation in thickness is ±1 mmV1+1. Here, in this embodiment, the entire length Ll of the outer layer portion 20 in the phase direction is 85 cm.
m, the length of the central part 210 [-2 is 65 cm, the length L3 of the tip part 220 is approximately 5 cm, the central part 21
The outer diameter of the center part 210 is about 8.4 cm, and the diameter R1 of the tip part 220 is about 5 cm. Note that the reason why the base end portion 200 has a large diameter is to place it on a heater holder.

On the other hand, the inner layer part 25 has a base end part 250, a central part 260 connected to the base end part 250, and a three-dimensional curved surface shape, that is, an aesthetically hemispherical distal end part 270 connected to the central part 260.
341I has been completed. The thickness of the inner layer portion 25 is substantially uniform, and the variation in thickness is approximately ±1 mm. In this embodiment, the outer diameter of the center portion 260 of the inner layer portion 25 is approximately 8 cm, the inner diameter of the center portion 260 is approximately 4 cm, and the diameter R2 of the tip portion 270 is approximately 4 cm.

The rod-shaped electrode part 3 is made of carbon, and its outer circumference (¥ is 3.8 Cmfj degrees and its total length is about 85 mm).
The heater device of this example was manufactured as follows. That is, a preparation process in which raw ceramic powder for the outer layer part 20 is adjusted to a predetermined blending ratio, an adjustment process in which water is added to form a slurry, a molding process in which the slurry is poured into a mold cavity and molded, and the molded outer layer part 20 A drying process in which the molded body for the outer layer 20 is cured after being removed from the mold and further dried at 150°C for 15 hours, and a sintering process in which the dried molded body for the outer layer part 20 is heated at 1650°C for 10 hours and sintered. It was manufactured by carrying out the steps in this order. 7
In addition, the maximum particle size of the raw material ceramic powder for the outer layer portion 20 used in the adjustment process is 3 mm8! It's a melon. The inner layer portion 25 was formed in the same manner using a mold for the inner layer portion 25.

Then, after scattering carbon powder as a spacer on the inner surface of the sintered outer layer 20 near the bottom, the inner layer 25 is inserted into the outer layer 20 and the outer layer 20 and the inner layer 25 are sandwiched together. Further, carbon powder is charged into the boundary between the outer layer part 20 and the inner layer part 25, and the minute gap between the outer layer part 20 and the inner layer part 25 is filled with the carbon powder, thereby forming a filled layer 20a with a thickness of about 2 nm. do. At this time, if necessary, the inner layer part 25 and the outer layer part 20 can be rotated relative to each other in the circumferential direction. Note that the electrode section 3 is inserted into a hole defined by the inner circumferential surface of the inner layer section 25. Carbon powder is also charged at the boundary between the electrode part 3 and the inner layer part 25 to form a filling layer 2 with a thickness of about 1 mm.
Form 0b.

Using, for example, two heater devices 1 manufactured as described above, a conductive wire is fixed with a band to the upper end of the rod-shaped electrode portion 3 of each heater device "a1" and connected to a power source, and the heating element 2 is exposed to the flame of a burner. Then, after preheating,
As shown in the figure, two heater devices [1] were immersed in molten steel SW in a container 4.

In this state, between the two electrode parts 3 and the melt '6Aw,
Apply a voltage of 40V and a current of frequency 60H2 from O to 8
Flow approximately 00A. Then, the inner layer section 25 and the outer layer section 20 forming the heating element 2 of one heater device 1 generate heat, and the inner layer section 2 forming the heating element 2 of the other heater device 1 generates heat.
5 and the outer layer part 20 generate heat, so the molten metal W is heated.

In this embodiment, in order to heat the molten metal with the heat generated by the heating element 2 of the heater 3A, the molten metal is heated by the Joule heat generated in the molten metal by directly passing a current through the molten metal itself, which is conventionally provided. Compared to the above, the required electrical current is small, and therefore the electrical equipment is easy to carry out, and the electrical equipment is also smaller and requires less than 1q.

stomach.

In this embodiment, the outer layer part 20 is formed of a heat-generating material whose main components are magnesia and zirconia and whose blending ratio is selected so as to increase the resistance value, so that heat generation is active at the part that is in contact with the molten metal W. As a result, heating efficiency is improved. Furthermore, since the inner layer portion 25 does not come into contact with the molten metal, the outer layer portion 20 is not required to have heat generating properties, but rather it is preferable to suppress the heat generating properties in order to suppress the “heat accumulation J” inside the heating element 2. Furthermore, when preheating with a burner, the inner layer 25 does not come into direct contact with the flame of the burner, so when selecting the blending ratio of the heat-generating material forming the inner layer 25, it is not necessary to ensure a large calorific value of the outer layer 20. Moreover, there is no need to pay much attention to erosion resistance, oxidation resistance, etc., and therefore, the degree of freedom in selecting the type of heat-generating material forming the inner layer portion 25 or the proportion thereof can be increased.

Furthermore, in this embodiment, when the thickness of the heating element 2 is set to the required thickness to ensure the required amount of heat generation, the thickness of the outer layer 20 and the inner layer 25 can be made thinner. Accordingly, cracks are less likely to occur in the outer layer portion 20 and the inner layer portion 25 themselves during molding, sintering, and preheating.

Moreover, in this embodiment, as shown in FIG. The packed layer 20b made of carbon powder charged in the layer functions as a current diffusion layer and as a thermal expansion layer r11. Since it functions as a layer 1, it increases the degree of electrical contact between the outer layer part 20 and the inner layer part 25 and also increases the degree of thermal contact, suppressing local heat generation, and thus preventing the heating element 2 from generating runaway heat. There are 41 advantages in uniform heat generation.

Furthermore, in this embodiment, since the filled layers 20a, 20t) and 20t) formed by charging carbon powder are heated by light, in order to secure the required calorific value of the heating element 2, the outer layer portion 20 and the inner layer portion 25
It is possible to eliminate excessive thickening of 1 gram of meat.

Furthermore, in this embodiment, since the thickness of the outer layer 20 and the inner layer 25 forming the heating element 2 are substantially uniform, the current flowing from the electrode part 3 through the heating element 2 to the molten metal W is not biased. It is effective in preventing oxidation.

Further, in this embodiment, the tip 220 of the outer layer 20 and the tip 270 of the inner layer 25 forming the heating element 2 are respectively hemispherical as a three-dimensional curved shape, and corners are formed where the current tends to concentrate. This is more advantageous in preventing current drift.

Next, the heater according to the present invention! A second embodiment of fef will be described with reference to FIGS. 5 and 6.

The heater device of the second embodiment basically has the same configuration as the first embodiment. However, the inner layer part is two layers, and as shown in FIG. 5, the first inner layer part 27 and the second inner layer part 28 on the rod-shaped electrode part 3 side are laminated.

The first inner layer section 27 is formed of a proximal end 270, an intermediate section 271, and a substantially hemispherical distal end 272. Further, the second inner layer portion 28 is formed of a proximal end portion 280, an intermediate portion 281, and a substantially hemispherical distal end portion 282. and,
Carbon powder is charged between the first inner layer part 27 and the second inner layer part 28 to form a packed layer 20a.
The degree of electrical contact and the degree of thermal contact between the inner layer portion 27 and the second inner layer portion 28 are ensured. Of course, the outer layer 20 and the second
A filling layer 20a/fi made of carbon powder is provided at the boundary between the electrode portion 3 and the first inner layer 28, and a filling layer 1 made of carbon powder is also provided at the boundary between the electrode portion 3 and the first inner layer 27.
120b is provided.

In the heater device of the second embodiment, the same functions and effects as in the first embodiment can be obtained.

In addition, in each of the above embodiments, as is clear from FIGS. 1 and 5, the outer circumferential surface of the inner layer part and the inner circumferential surface of the outer layer part are smooth surfaces. However, by forming a threaded portion on the outer circumferential surface of the inner layer portion, forming a threaded portion on the inner circumferential surface of the outer layer portion, and screwing the threaded portion of the outer layer portion and the threaded portion of the inner layer portion together, The inner layer portion and the outer layer portion may be assembled integrally, and in this case as well, carbon powder, molten tin, etc. can be charged to the boundary portion between the two portions.

[Application Example] Next, an example in which the heater device according to the above embodiment is applied to a continuous casting method will be described. First, a continuous casting apparatus used in the continuous casting method will be explained. As shown in FIG. 7, this continuous casting apparatus consists of a tongue pusher 50 serving as a container for holding molten steel, a water-cooled mold 51 disposed below the tongue pusher 50, a cooling spray zone 52, and a bin punch. It is composed of a roll 53 and a straightening roll 54. Note that the tank pusher 50 has a capacity to hold about 100 liters of molten metal.

Next, continuous Vt casting will be explained. First, using two heater units W11 shown in FIGS. 1 and 2, the heating element 2 of each heater unit R1 is heated with the flame of a burner to
Preheat to about 1200℃.

With the heater device 1 preheated in this way, the ladle 55
140 transferred from and held in Tandish 50
Two heater devices 1 are installed from the tip 220 to 82i1 in 19U of high-temperature steel with a temperature of about 0 to 1600°C! do. The molten metal in the tundish 50 transferred from the ladle flows toward the discharge port 50a shown in FIG. 7 and falls into the water-cooled mold 51.

If the heater device 1 is preheated before immersing the molten metal as described above, rapid heating of the heating element 2 can be prevented, and cracks in the heating element 2 can be suppressed as much as possible. Moreover, the above-mentioned preheating makes it possible to ensure the N conductivity of the heating element 2, especially the outer layer portion 20, which has magnesia as a main component and therefore becomes conductive only in a high temperature region.

If a crack occurs in the heating element 2, the molten metal that has entered the crack will be directly connected to the electrode part 3, and the amount of heat generated by the heating element 2 will be reduced, resulting in the inconvenience that the heater device 1 cannot be used effectively. arise.

In this application example, with the heater device 1 immersed in the molten metal in the tongue pusher 50 as described above, the terminals of the two single-layer pole parts 3 are connected to an AC power source, and a voltage of 100 to 600 V is applied between the terminals. Apply. As a result, between the heating elements 2 of the heater device 1 via the molten metal held in the tongue pusher 50,
A current with a frequency of 60) 1z is applied. Current range is O~800A
That's about it.

At this time, the inner layer part 25 and outer layer part 20 of the heating element 2 are tF
[I get a fever. Therefore, the molten metal held in the tongue pusher 50 is heated to an ambient temperature of about 1 to 30°C, and its temperature is controlled.

The melted oil whose temperature has been adjusted in the tundish 50 in this way is discharged from the discharge port 508 of the tundish 50, cooled and solidified in the water-cooled mold 51, and further cooled in the cooling spray zone 52.
The cooled and solidified material is pulled downward by pinch rolls 53. Thereafter, it is cut to a predetermined size using a cutting machine.

In this application example, in order to heat the molten metal in the tundish 50 with the calorific value of the heating element 2 of the heater device 1, the Wi flow is caused to flow directly into the molten metal itself held in the tundish 50, which is conventionally provided. Compared to the case where the molten metal itself generates heat using Joule heat, the amount of electric current required is small, so it is easier to electrically control it, and the electrical equipment can be downsized, making it possible to use existing electrical equipment. can be used effectively.

As described above, in this application example, the temperature of the molten metal held in the tongue push 50 can be adjusted by heating the molten metal held in the tongue push 50 with the heater device W11, so that the temperature of the molten metal held in the tongue push 50 is maintained at an appropriate value. This is advantageous in improving the quality of products such as blooms and billets produced by continuous casting.

[Effect of the invention 1] According to the heater device of the present invention, it is possible to heat the object to be heated, such as a metal pickled in sake, with the heating element, and therefore the lag fIK of the object to be heated, such as a metal pickled in sake, can be adjusted. be able to.

In particular, since the heating element is formed of an outer layer portion and an inner layer portion, it is possible to increase the degree of freedom in selecting the type of heat generating material forming the inner layer portion and the proportion thereof, which does not come into contact with metal melt, air, etc.

Further, according to the heater device of the present invention, when the inner layer is formed of a heat generating material having a lower calorific value and property than the outer layer, it is advantageous to suppress "heat accumulation" inside the heating element.

[Brief explanation of the drawing]

1 to 4 show a first embodiment of the present invention, in which FIG. 1 is a sectional view of a heating element, and FIG. 2 is a sectional view of a heater device. FIG. 3 is an enlarged sectional view of the vicinity of the filled bed, and FIG. 4 is a schematic sectional view of the state where electricity is being applied between the heater device 6 and the molten metal. Fig. 5 J3 and Fig. 6 show a second embodiment of the present invention, Fig. 5 is a sectional view of the heating element, and Fig. 6 t is a heater'! FIG. 2 is a cross-sectional view of the device. FIG. 7 (This is a schematic cross-sectional view of the apparatus used in the 1L continuous casting method. FIGS. 8 and 9 are graphs showing the relationship between the operating temperature and the solid resistance of the conductive material. In the figure, 1 is a A heater device, 2 a heating element, 3 a rod-shaped electrode part,
20 is an outer layer part, 200 is a base end part, 210 is a central part, 22
0 indicates the tip, 25 indicates the inner layer, 250 indicates the base, 260 indicates the center, and 270 indicates the tip. Patent applicant: Aichi TyJ Steel Co., Ltd.
Tokyo Ceramics Co., Ltd. Agent Patent Attorney Hiroshi Okawa! Jbt) Figure 1 Figure 2 Figure 5 Figure 6

Claims (1)

[Claims] (1) A heating element made of a heat-generating material as a base material and formed of an outer layer having the required heat-generating properties and at least one inner layer having different heat-generating properties from the outer layer, and an electrode part that conducts electricity to the heat-generating element. A heater device consisting of.