JPH0441478B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a long heater used as an industrial heating source such as an electric furnace heater. Conventional Structures and Problems The sheathed heater type has been widely used as a heater for electric furnaces in recent years due to its ease of temperature control and thermal efficiency. As shown in FIG. 1, this sheathed heater is constructed by connecting an electrical outlet terminal 1 to both ends of a coiled heating wire 2, and connecting the electrical outlet terminal 1 to both ends of a metal pipe 3 at the center of the metal pipe 3. Position the hot wire 2, and apply magnesia powder 4 to this metal pipe 3.
is put into the metal pipe 3, and by applying vibration to the metal pipe 3, the magnesia powder 4 is
It is manufactured by filling the steel with 100% carbon dioxide and then rolling it to reduce its diameter. In addition, if bending is required, annealing is performed after rolling to reduce the diameter, and both ends of the sheathed heater are made of low-melting glass to improve electrical insulation.
and is sealed with heat-resistant resin 6. However, some sheathed heaters used in electric furnaces are several meters long, and in the conventional manufacturing method of sheathed heaters, the electricity extraction terminal 1 and the heating wire 2 become eccentric due to vibration during filling, and the metal There was a drawback that the dielectric strength or electrical insulation between the pipe 3 and the electrical outlet terminal 1 was reduced, and the electrical characteristics as a sheathed heater were significantly impaired. OBJECTS OF THE INVENTION The present invention solves the conventional drawbacks and provides a method for manufacturing a long heater with excellent electrical properties, particularly dielectric strength. Structure of the Invention In order to achieve the above object, the present invention has a hole in the center through which an electrical outlet terminal and a coiled heating wire pass, and a plurality of holes around the hole through which magnesia powder passes. The ceramic core is provided with a disc-shaped ceramic core whose outer diameter is smaller than the inner diameter of the metal pipe. The coiled heating wire is positioned at the center of the metal pipe with the electric outlet terminal having the terminal facing downward, and a predetermined amount of the magnesia powder covering the ceramic core is filled from the upper side of the metal pipe. By alternately repeating the insertion of the ceramic core and the filling of the magnesia powder covering the ceramic core, the entire inside of the metal pipe is filled with magnesia powder. By arranging disc-shaped ceramic cores at regular intervals in the length direction of the heating wire, it is possible to prevent eccentricity of the electricity extraction terminal and heating wire due to vibrations during filling, which was seen in the past. This makes it possible to manufacture long heaters with excellent dielectric strength. DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to FIG. Note that the same reference numerals are used to describe the same components as in FIG. 1 above. As metal pipe 3, length 1500mm, outer diameter 12.7
mm, wall thickness 0.63mm NCF800 (product name Incoloy 800)
Also, as the heating wire 2, a first type nichrome wire with a wire diameter of 0.5 mm was used. This heating wire 2 was formed into a coil with a winding diameter of 2 mm, and electrical extraction terminals 1 with an outer diameter of 2 mm were connected to both ends. On the other hand, as shown in FIG. 2a, there is a hole 8-2 with an outer diameter of 2.5 mm through which the coiled heating wire 2 and the electrical outlet terminal 1 can pass through, and the periphery of this hole 8-2. A disk-shaped ceramic core 8 made of a magnesia molded body having an outer diameter of 10 mm and a wall thickness of 5 mm and having four holes 8-1 with an outer diameter of 1.5 mm through which the magnesia 4 powder could pass was prepared. A hole 8-1 was made to pass through the disc-shaped ceramic core 8 at the connection portion between one of the electricity extraction terminals 1 and the coiled heating wire 2, and the ceramic core 8 was fixed with a heat-resistant inorganic adhesive. As shown in FIG. 2b, the electric outlet terminal 1 having the disc-shaped ceramic core 8 is placed on the lower side, and an electric outlet terminal fixing jig 9 is used at the center of the metal pipe 3. I positioned it. Thereafter, a predetermined amount of magnesia powder 4 was filled up to the upper part of the disc-shaped ceramic core 8. Subsequently, the next disk-shaped ceramic core 8 was inserted through the hole 8-2 from the upper electrical lead-out terminal 1 into the surface of the magnesia powder 4 filled the first time. Thereafter, filling of the magnesia powder 4 and insertion of the disc-shaped ceramic core 8 were repeated to complete the filling. After this, the second sheathed heater is processed through the steps of rolling, annealing, and sealing according to the conventional manufacturing method of sheathed heaters.
A long heater with a length of 1800 mm and an outer diameter of 11 mm as shown in Figure c.
10 pieces were completed, with sample numbers 11 to 20. At this time, for comparison, 10 long heaters were similarly manufactured using the conventional manufacturing method without the above-mentioned disk-shaped ceramic core 8, and sample number 1 was used.
~10. The dielectric strength of each completed long heater was measured, and the results are shown in Table 1.

【table】

[Table] As is clear from Table 1, the dielectric strength of the long heaters of sample numbers 1 to 10 manufactured by the conventional manufacturing method was between 500 V and 1100 V, which was at a very low level. On the other hand, sample numbers 11 to 20 according to the manufacturing method of the present invention
The dielectric strength of the long heater was 2000V to 2500V, which is much higher than that of long heaters made using conventional manufacturing methods. As described above, according to the method for manufacturing a long heater according to the present invention, a disc-shaped ceramic core 8 is attached to the connecting portion between the electrical outlet terminal 1 and the coil-shaped heating wire 2.
Therefore, even if a long electrical outlet terminal 1 is used, eccentricity will not occur. Furthermore, since disc-shaped ceramic cores are placed at several locations on the heating wire, eccentricity will not occur as well. Moreover, the outer periphery of the hole into which the heating wire is inserted in the ceramic core has a hole through which magnesia powder can freely pass, and this ceramic core is filled with a predetermined amount of magnesia powder alternately and sequentially. When injecting magnesia powder, there is no other ceramic core in the middle of the metal pipe that would interfere with injecting the magnesia powder, so it can be filled quickly and easily, and the required packing density can be obtained without applying any particular vibration, making it possible to Compared to other manufacturing methods, the dielectric strength can be significantly increased, and since vibration is not required, it can be manufactured at low cost using simple equipment. In the present invention, a magnesia molded body is used as the disc-shaped ceramic core, but the present invention is not particularly limited to this. Furthermore, the diameter and number of holes through which the magnesia powder penetrates are not limited to φ1.5 mm and four, but the structure is sufficient for the magnesia powder to pass from the top to the bottom of the disc-shaped ceramic core. The number of disc-shaped ceramic cores used is not particularly limited, although it is better to have a larger number. Effects of the Invention As is clear from the above description, the present invention has a hole in the center through which an electrical outlet terminal and a coiled heating wire pass, and a plurality of holes around the hole through which magnesia powder passes. This is a manufacturing method for long heaters that uses a disc-shaped ceramic core that has It is what it is.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a long heater manufactured by a conventional manufacturing method, Fig. 2a is a perspective view of a disc-shaped ceramic core used in an embodiment of the present invention, and Fig. A schematic cross-sectional view showing the installation method, and FIG. 3C is a cross-sectional view of the manufactured long heater. 1...Electricity extraction terminal, 2...Heating wire, 3...
... Metal pipe, 4 ... Magnesia powder, 8 ... Disc-shaped ceramic core, 8-1 ... Hole, 8-2 ...
…hole.

Claims (1)

[Claims] 1. A disk-shaped pipe with an outer diameter smaller than the inner diameter of the metal pipe, which has a hole in the center through which an electrical outlet terminal and a coiled heating wire pass, and a plurality of holes around the hole through which magnesia powder passes. The coiled heating wire is provided with a ceramic core, and the ceramic core is fitted and fixed to the connecting part between the electrical outlet terminal and the coiled heating wire, and then the electrical outlet terminal having the ceramic core is placed on the lower side at the connecting part. A heating wire is located in the center of the metal pipe, and a predetermined amount of the magnesia powder covering the ceramic core is filled from the upper side of the metal pipe,
Thereafter, the entire interior of the metal pipe is filled with magnesia powder by alternately repeating insertion of the next ceramic core and filling of the magnesia powder to cover the ceramic core.