JPH0638392Y2 - Multi-stage electric furnace - Google Patents

Description

[Detailed Description of the Invention] (Industrial application field) The present invention is to stack a plurality of special unit heating elements that can be used in an electric furnace that obtains a temperature of 2000 ° C. or less, and control the temperature of each heating element independently. The present invention relates to a multi-stage electric furnace in which the temperature gradient can be positively changed.

(Prior Art) FIG. 11 is a perspective view showing a conventional heating element used in an electric furnace, wherein 1 is a rod-shaped heating element, 2 is a strip-shaped heating element, and 3 is a linear heating element. , 4A is a heating element in which a single (that is, one) spiral groove c is provided in the tubular heating portion b and electrodes a are provided at both ends, and 4B is a tubular heating portion b and an electrode a provided at one end thereof. Is a heating element in which a plurality of (that is, two) spiral grooves c, c are provided.

In general, SiC-based or LaCrO ₃ -based material is used for the rod-shaped heating element 1, and NiCr-based, FeAl-based, Pt-based, Mo-based, or W-based heating material is used for the strip-shaped heating element 2 or the linear heating element 3. A material is used, and a SiC-based or C-based material is used for the heating portion b of the cylindrical heating element 4A or 4B.

12 to 14 show an example of a conventional electric furnace, and FIG. 12 shows the rod-shaped heating element 1 shown in FIG. It is configured to set.

FIG. 13 shows a plurality of the rod-shaped heating elements 1 arranged in the cylindrical furnace 9 concentrically in the axial direction. There is also one in which one of the cylindrical heating elements 4A or 4B is inserted into the cylindrical furnace 9.

FIG. 14 shows a cylindrical furnace 9 provided with two to three sets of linear heating elements 3.

(Problems to be solved by the invention) When the rod-shaped heating element 1 shown in FIG. 11 is assembled into a cross girder as shown in FIG. 12, the heating portions cannot be arranged in the same plane. Even if the heat generation temperature is adjusted for each body 1, a highly accurate temperature gradient cannot be obtained.

In addition, as shown in FIG. 13, a plurality of rod-shaped heating elements 1 arranged in the axial direction or one cylindrical heating element 4A or 4B of FIG. Is constant, it is not possible to obtain any temperature gradient in the furnace. To obtain the temperature gradient, the temperature gradients A and B at the end of the heating element 1 must be used as shown in FIG. 15 or FIG. Body 1
Since it is necessary to select the heating element 1 having a length that can obtain a predetermined temperature gradient by utilizing the fact that the temperature gradient changes depending on the length of the furnace, various types of furnaces must be prepared. FIG. 15 shows the case where the heating element 1 is long, and FIG. 16 shows the case where it is short.

In the case shown in FIG. 14, the temperature distribution can be changed by energizing any one of the plurality of sets of linear heating elements 3, but only a rough temperature distribution can be obtained. In addition, since the control mode is rough,
As shown in the distribution chart in Fig. 17, the temperature inside the furnace is not uniform.

Further, in the configuration of FIG. 14, it is impossible to insert and fix the linear heating element 3 on the inner circumference of the furnace 9 made of a cylindrical refractory when the furnace 9 is long or thin. Further, if the furnace 9 is thick or short, there is no problem in installation work, but even if a single heating element is broken during use of the electric furnace, it must be taken out and replaced. Further, in FIG. 14, when the strip heating element 2 is used instead of the linear heating element 3, the strip surface of the heating element 2 becomes parallel to the axial direction of the electric furnace, and the width where the temperature can be adjusted independently. Is wide and is not suitable as a heating element for changing the temperature gradient.

The present invention, along with the rapid development of recent new material development techniques,
In response to the new demand to control the temperature of the electric furnace to obtain a uniform temperature distribution or an arbitrary temperature gradient,
The purpose of the present invention is to provide an electric furnace using a heating element that can meet requirements such as easy replacement of heating elements.

(Means for Solving the Problems) In order to achieve the above-mentioned object, a multi-stage electric furnace according to the present invention forms arm portions integrally projecting outward at both ends of a ring-shaped heat generating portion, and A heating element having an electrode at the tip of an arm and a ring-shaped refractory insulating material are provided, and a concave portion is provided in a mating surface of adjacent fireproof insulating materials, and the arm portion of the heating element is fitted into the concave portion. The heating element and the fireproof insulating material are laminated in multiple stages by the sandwiched structure, and a driving circuit for independently heating each heating element is provided. In the present invention, one heating element and two refractory insulating materials are combined to form a unit heating element, and a structure in which the thickness of the unit heating element is changed to two or more, or between the unit heating elements,
A structure in which a ring-shaped and inner peripheral portion projects inward from the inner periphery of the refractory insulating material, and a reflecting plate is interposed to reflect heat rays from the heating element and reduce thermal interference between the unit heating elements, A structure in which at least a part of the plurality of heating elements is replaced with a hollow tube through which a cooling medium can flow is also adopted.

(Operation) In the electric furnace of the present invention, an arbitrary temperature gradient can be obtained by stacking as many heating elements as necessary and energizing each heating element independently to generate heat. Also, by combining two or more thicknesses of the unit heating elements, a portion with high temperature adjustment accuracy and a rough portion are formed. When the reflecting plate is interposed between the unit heating elements, heat rays are prevented from being radiated to the adjacent unit heating elements. When a hollow heating element capable of circulating a cooling medium is provided, the temperature in the vicinity of the cooling medium circulating heating element layer can be rapidly lowered.

(Example) FIG. 1 is a plan view showing an example of a heating element used in the present invention, and FIG. 2 is a front view thereof. The heating element 10 according to the present invention has a circular ring shape around a hollow portion 11. It has an eggplant heating unit 12,
Arms 13 are integrally formed at both ends of the heat generating portion 12,
Electrodes 14 made of a highly conductive member are formed on both ends of the electrode.

Generally, the heat generating part 12 and the arm part 13 are made of the same material,
In the case of SiC-based or LaCrO ₃ -based heating elements, powder metallurgy, mold injection method or sheet molding method can reduce the thickness to 1 mm to 2 mm.
It can be about 0 mm. In the case of C type, the thickness is 1mm to 20m depending on the plate machining method or powder metallurgy method.
It can be around m. NiCr, FeAl, Pt, Mo
In the case of a metal material such as a W-based, W-based, or Ta-based metal, the thickness can be set to about 0.1 mm to 15 mm by a press working method of a plate material, an electric discharge machining method, a machining method, a powder metallurgy method, or a mold method.

FIG. 3 is a partially cutaway plan view of a unit heating element 15 constructed by using the stacking heating element 10 shown in FIG. 1 and FIG.
The figure is a partially cutaway front view thereof. The heating element 15 is configured such that the arm portion 13 of the heating element 10 is fitted and sandwiched in a recess 17 provided in at least one of the mating surfaces of the upper and lower refractory insulating materials 16, and the temperature of each unit heating element 15 is adjusted independently. To thermocouple
It is a combination that sandwiches 18 and has a top and bottom fire-resistant insulation material 16
A heating element accommodating recess 19 for preventing contact of the heating element 12 with the object to be heated is formed on the inner periphery of the space.

FIG. 5 is a diagram showing a part of an electric furnace constituted by stacking the unit heating elements 15 and the configuration of other control means. By stacking through the reflector 20 which reduces interference,
It constitutes an electric furnace. Each reflection plate 20 has a ring shape and an inner peripheral portion thereof protrudes inward from the inner periphery of the refractory insulating material 16 to reflect heat rays from the heating element 10 and prevent different layers from being heated.

In this configuration, the temperature detected by each thermocouple 18
The t _i and the command temperature T _i are input to the computer 24, and the driving circuit 25
Thus, the value of the current flowing through each heating element 10 is determined, and the desired temperature distribution in the furnace (for example, uniform temperature distribution or temperature distribution having a predetermined gradient) is set.

In this way, a thermocouple 18 is provided for each unit heating element 15,
By controlling the current for each unit heating element 15, it is possible to adjust the temperature with high accuracy.

The heating element 10 for lamination in the embodiment shown in FIG. 5 is made of a SiC type material, has an inner diameter of 60 mm and a thickness of 6 mm, and has upper and lower refractory insulating materials 1.
The thickness of the unit heating element 15 including 6 was 15 mm. When the metal heating element was used, the thickness of the unit heating element 15 could be 8 mm. This thickness can be further reduced in the near future.

FIG. 6 (A) shows another embodiment of the present invention in which an electric furnace is
Two kinds of thick unit heating elements 15A and thin unit heating elements 15B are laminated, and as shown in the figure, for example, a single crystal
When pulling up (or pulling down) 21, solid-liquid interface
The thin unit heating element 15B is a part where a strict temperature control accuracy and temperature gradient (see Fig. 6 (B)) like 22 are required.
By using a thick unit heating element 15A for the temperature holding portion of the grown crystal that does not require relatively strict temperature control, the temperature control accuracy is maintained as a whole, and compared with the case where the whole is made thin. It becomes cheaper and temperature control becomes easier. If a metal heating element is used as the thin unit heating element 15B and a brittle ceramic heating element is used as the thick unit heating element 15A, an electric furnace in which the heating element is not easily damaged is constructed.

FIG. 7 (A) shows a unit heating element 15 on which a cooling member having a hollow tube for circulating a cooling medium such as a water tube 23 is laminated.
A steep temperature gradient as shown in FIG. 7 (B) can be obtained.

FIG. 8 is a plan view of a heating element 10A in which the heating portion 12A is formed in a quadrangular ring shape, and is configured as a rectangular tube-shaped furnace.

9 and 10 are plan views showing the heating elements 10B and 10C used for the lid or the bottom of the electric furnace.
The plurality of heat generating portions 12B and 12C formed around the plurality of heat generating portions 12B and 12C are each formed of a plurality of continuous rectangles or ellipses. The hollow portion 11 is used as a thermocouple insertion port or the like.

In the above embodiment, the unit heating element is composed of one heating element and two insulating materials above and below the heating element, but the unit heating element according to the present invention is not limited to this structure.

(Effect of the Invention) According to the first aspect, each heating element can be made thin, and an electric furnace having a thickness and a number of laminated layers according to requirements can be easily realized. In addition, since a multi-stage electric furnace is configured by laminating a plurality of the heating elements, a long sample can be heat-treated at a constant temperature or at an arbitrary temperature gradient, so that a long product with low distortion is realized. . In the case of pulling up or pulling down a single crystal, a good quality single crystal can be obtained because the temperature gradient at the solid-liquid interface or the holding temperature gradient of the grown crystal can be adjusted arbitrarily. Further, since a highly accurate uniform temperature distribution can be obtained, an electric furnace most suitable for measuring the thermal properties of materials can be realized. Further, even though it is a small furnace having a short length, it is possible to lengthen a portion having a uniform temperature distribution, which can be useful for downsizing of an electric furnace for production. Further, since the electric furnace can be assembled and separated by stacking the unitary heating elements, the electric furnace can be easily assembled and repaired, and an economical electric furnace is realized.

According to the second aspect, the thin unit heating element is laminated at a place where the temperature adjustment accuracy is required, and the thick unit heating element is used at a place where the temperature adjustment accuracy is not so high, so that the temperature adjustment accuracy is maintained as a whole, In addition, it is cheaper and the temperature can be easily adjusted as compared with the case where the whole is made thin.

According to the third aspect, the reflection plate interposed between the unitary heating elements reduces thermal interference between the heating elements, so that the temperature adjustment accuracy can be further improved.

According to the fourth aspect, a steep temperature gradient can be realized by the existence of the hollow tube through which the cooling medium flows.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a heating element for lamination according to the present invention, FIG. 2 is a front view of FIG. 1, and FIG. 3 is a unit heating element constructed using the heating element of FIG. FIG. 4 is a partially cutaway plan view showing an example, FIG. 4 is a partially cutaway front view of FIG. 3, and FIG. 5 is an electric furnace constructed by using the unit heating elements shown in FIGS. 3 and 4. FIG. 6A is a sectional view showing another embodiment of the electric furnace according to the present invention, FIG. 6B is an example of its temperature distribution, and FIG. 7A is an electric furnace according to the present invention. FIG. 8B is a cross-sectional view showing another embodiment of the present invention, FIG. 8B is an example view of its temperature distribution, FIGS. Is a perspective view showing each example of the heating element, FIGS. 12 to 14 are perspective views showing a conventional electric furnace, and FIGS. 15 to 17 are graphs showing an example of the temperature distribution of the conventional electric furnace. . 10, 10A-10C: Heating element for lamination, 11: Hollow part, 12, 12A-12
C: Heating part, 13: Arm part, 14: Electrode, 15, 15A, 15B: Unit heating element, 16: Fireproof insulating material, 18: Thermocouple, 20: Reflector, 23:
Water pipe, 24: calculator, 25: drive circuit

Claims (4)

[Scope of utility model registration request] 1. A heating element having an arm portion integrally projecting outwardly formed at both ends of a ring-shaped heat generating portion, and an electrode provided at an end of each arm, and a ring-shaped refractory insulating material. Have,
With a structure in which a concave portion is provided on a mating surface of adjacent fireproof insulating materials, and the arm portion of the heating element is fitted and sandwiched in the concave portion,
A multi-stage electric furnace characterized in that a heating element and a fireproof insulating material are laminated in multiple stages, and a drive circuit for independently heating each heating element is provided. 2. The unit heating element according to claim 1, wherein one heating element and two refractory insulating materials are combined, and the thickness of the unit heating element is different in two or more types according to the temperature control accuracy. A multi-stage electric furnace characterized by being set accordingly. 3. The unit heating element according to claim 1, wherein one heating element and two refractory insulating materials are combined to form a unit heating element.
A reflector plate that has a ring shape between the unit heating elements and has an inner peripheral portion that protrudes inward from the inner periphery of the refractory insulating material to reflect heat rays from the heating element and reduce thermal interference between the unit heating elements. A multi-stage electric furnace characterized by interposing an electric furnace. 4. A multi-stage electric furnace according to claim 1, 2 or 3, wherein a part of the plurality of heating elements has a hollow structure through which a cooling medium can flow.