JPS5923432B2 - Sea heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheathed heater, and more particularly to an improvement in a metal pipe constituting an outer casing of a sheathed heater.

Generally, in a sheathed heater that is equipped with a heating wire inside a metal pipe and filled with an electrical insulator, the metal pipe is made of iron containing about 0.1% carbon. As a solution to this drawback, a sheathed heater was proposed in which a metal pipe was made of iron material containing 0.005 to 0.010% of carbon, as shown in Japanese Patent Application Laid-Open No. 53-8332. , the present invention is a further improvement of the above-mentioned Japanese Patent Application Laid-Open No. 53-8332, and has a low carbon content (0.004 to 0.0
1%), and by using a metal pipe annealed in a non-oxidizing furnace as the electrical insulator filler, it can withstand depolarization and bending after being filled with heating wires and electrical insulators. To provide a sheathed heater which prevents cracks and pinholes from occurring in metal pipes, and which does not cause insulation deterioration defects even when terminals are sealed after dehumidification.

When a pipe is depolarized and bent after being filled with heating wires and electrical insulators, cracks and pinholes occur in the pipe, and even if the ends of the sheathed heater are sealed, the insulation deteriorates. . In other words, the above-mentioned drawbacks occur because the depolarization process of the pipe after filling and the forming process such as bending force the pipe to undergo severe plastic deformation, and because the pipe is used at high temperatures. . The metal pipe disclosed in JP-A-53-8332 had an elongation rate that was 30% or more superior to that of conventional iron pipes, but the present invention provides a low-carbon iron pipe with an elongation rate of 770 to 790%.
The elongation rate was further improved by annealing in a non-oxidizing furnace at ℃ for 6 to 8 minutes.

Therefore, Table 1 below shows the metal vibrator (A) shown in JP-A No. 53-8332 and the metal pipe (B) of the present invention.
It shows the unique performance of the machine.

As shown in Table 1 above, the elongation of the metal pipe used in the present invention is several tens of percent or more better than that of the metal pipe used in JP-A-53-8332.
Even if bent during bending, even if the bend radius is 20% smaller, the performance is on par with or better than that of conventional iron pipes, and no cracks or pinholes occur, making the terminal part of a sheathed heater In the case where a rising portion is provided by bending, this dimension can be kept low, and the shape of the product can be made compact and a low-cost product can be provided.

Since annealing is performed in a non-oxidizing furnace, the iron vibrator does not oxidize,
Management costs are also low. Then, the metal pipe is grain size 4-5, hardness 60-80HV1, carbon content 0.
．． 0.004 to 0.01% and annealed in a non-oxidizing furnace before filling with the electrical insulator, so there is no need for annealing after rolling, and it can be strengthened immediately.

In addition, in the metal pipe shown in JP-A-53-8332, cracks occurred at a rate of around 0.1 (fl), but in the metal pipe used in the present invention, cracks did not occur and inspection was unnecessary, resulting in inspection costs. The reduction is also aimed at.

Claims (1)

[Scope of Claims] 1. A sheathed heater in which a heating wire is installed in a metal pipe and is filled with an electrical insulator, wherein the metal pipe contains 0.004 to 0.01% carbon and has a grain size of 4 to 4. 5. A sheathed heater made of iron material with a hardness of 60 to 80 HV and annealed in a non-oxidizing furnace before being filled with an electrical insulator. 2. The sheathed heater according to claim 1, wherein the annealing is performed at 770 to 790°C for 6 to 8 minutes.