JPH0441479B2 - - 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. Structure of conventional example and its problems The sheathed heater type, which has been conventionally used as a heater for electric furnaces, has recently been widely used due to its ease of temperature control and thermal efficiency. As shown in FIG. 1, this sheathed heater consists of a coil in which an electrical outlet terminal 1 is connected to both ends of a coiled heating wire 2, and the electrical outlet terminal 1 is connected to both ends of the central part of a metal pipe 3. It is manufactured by positioning a heating wire 2 of the shape, putting magnesia powder 4 into this metal pipe 3, applying vibration to the metal pipe 3 to fill it with magnesia powder 4, and then rolling it to reduce its diameter. . Further, when bending is required, annealing is performed after rolling to reduce the diameter, and both ends of the sheathed heater are sealed with low melting point glass 5 and heat resistant resin 6 to improve electrical insulation. However, some of the sheathed heaters used in electric furnaces are several meters long, and in the conventional sheathed heater manufacturing method, the electrical outlet terminals 1 and heating wires 2 are damaged due to vibrations during filling with magnesia powder 4. There was a drawback that the eccentricity caused a decrease in the dielectric strength or electrical insulation between the metal pipe 3 and the electrical outlet terminal 1, and that 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. A disc-shaped ceramic core having a diameter smaller than the inner diameter of the metal pipe is provided, and the ceramic core is inserted into the connection between the electricity extraction terminal and the coiled heating wire and at least one portion of the coiled heating wire. After fixing, the ceramic core is positioned at the axis of the metal pipe so that the electrical outlet terminal having the ceramic core is on the lower side, and the magnesia powder is filled from the upper side of the metal pipe. The diameter is reduced by rolling, which prevents the eccentricity of the electrical outlet terminal and heating wire due to the vibrations that occur when filling magnesia powder, making it possible to manufacture long heaters with excellent dielectric strength. This is what I did. DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. Note that the same components as in FIG. 1 will be described with the same reference numerals. Metal pipe 3 has a length of 1500 mm, an outer diameter of 12.7 mm,
NCF800 (product name Incoloy 800) with a wall thickness of 0.63mm,
In addition, the first nichrome wire with a wire diameter of 0.5 mm was used as the heating wire 2.
Seeds were used. This heating wire 2 was formed into a coil shape 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 coil-shaped heating wire 2 and the electricity extraction terminal 1 can pass through, and the hole 8-2 in the center of the disk. A disc-shaped ceramic core 8 made of a molded magnesia body with an outer diameter of 10 mm and a wall thickness of 5 mm was prepared, having four holes 8-1 with an outer diameter of 1.5 mm at the periphery through which magnesia powder could penetrate. The disk-shaped ceramic core 8 was passed through the holes 8-2 through the connecting portion between the electricity extraction terminal 1 and the coiled heating wire 2 and at several locations on the coiled heating wire 2, and 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 the electric outlet terminal fixing jig 9 is used to position it in the center of the metal pipe 3. I forced it. After that, magnesia powder 4 is filled from the upper side of the metal pipe 3, and after that, it is rolled to a diameter of 1800 mm as shown in Fig. 2c, and the outer diameter is 1800 mm as shown in Fig. 2c. We completed 10 long heaters with a diameter of 11 mm, and designated sample numbers 11 to 20. For comparison purposes, 10 long heaters were similarly manufactured using the conventional manufacturing method that does not use the disk-shaped ceramic core 8, and sample number 1 was used.
~10. The dielectric strength of each of the completed long heaters was measured, and the results are shown in Table 1.

[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, since the disk-shaped ceramic core 8 is provided at the connection part between the electrical outlet terminal 1 and the coil-shaped heating wire 2, it is possible to Output terminal 1
Even if you use it, it will not become eccentric. 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 the magnesia powder can freely fall, so simply dropping the magnesia powder from the top of the metal pipe will cause particular vibration to the metal pipe. The required packing density can be obtained even without it, the dielectric strength can be significantly increased compared to conventional manufacturing methods, and since no vibration is required, it can be manufactured at low cost using simple equipment. In this example, a magnesia molded body was used as the disc-shaped ceramic core, but the present invention is not limited to this. In addition, the diameter and number of holes through which the magnesia powder penetrates are not limited to 1.5 mm and 4, but as long as the structure is sufficient for the magnesia powder to pass from the top to the bottom of the disc-shaped ceramic core. It is often better to use a larger number of disc-shaped ceramic cores, but this is not particularly limited. 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 furthermore, a plurality of holes through which magnesia powder passes through the hole in the periphery of the hole. This is a method for manufacturing a long heater using a disc-shaped ceramic core with an outer diameter smaller than the inner diameter of a metal pipe.This method makes it possible to manufacture a long heater with excellent dielectric strength, and is of great practical value. be.

[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. 2b is a magnesia powder A schematic cross-sectional view at the time of filling, and Figure c 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 this hole through which magnesia powder passes. A ceramic core is provided, and after the ceramic core is inserted and fixed in the connection portion between the electricity extraction terminal and the coiled heating wire and at least one portion of the coiled heating wire, the ceramic core is inserted into the connection portion. The ceramic core is positioned at the axial center of the metal pipe so that the electrical outlet terminal having the wire is on the lower side, the magnesia powder is filled from the upper side of the metal pipe, and the diameter is reduced by rolling. Manufacturing method of shaku heater.