JPS6231048B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an annealing device for a sheathed heater, and an object of the present invention is to provide an apparatus that is particularly inexpensive, can be easily arranged, and prevents deflection of the sheathed heater.

Generally, in a sheathed heater, a heating wire is inserted into the center of a metal pipe, a gap between the metal pipe heating wires is filled with a filler such as magnesium oxide, and the diameter is reduced by rolling. Since work hardening occurs in the metal pipe due to this diameter reduction, heat treatment, that is, annealing, is performed to remove the hardening.

Conventionally, most annealing of sheathed heaters has been performed in an electric furnace. Annealing using an electric furnace requires a long annealing time, and it takes time to take the material into and out of the electric furnace, creating a stagnation in the flow of the process.

Furthermore, even in the case of a conveyor type furnace in which a large number of sheathed heaters are placed on the same pallet, temperature unevenness and deformation due to its own weight occur.

The present invention eliminates the drawbacks of the conventional sheathed heater annealing apparatus, and embodiments of the present invention will be described below with reference to the accompanying drawings.

In the figure, 1 is a transformer, which can obtain the large current necessary for annealing the metal pipe from the secondary side. 2 is a metal pipe of a sheathed heater. 3,
3' is a clamping device that serves as an electrode connected to both ends of the secondary coil of the transformer 1, and a metal pipe 2
It holds both ends of the part necessary for annealing. Reference numeral 4 denotes a base, which positions one clamp device 3' and holds a support portion 5 for supporting the other clamp device 3 in a slidable manner in a groove 6 formed in the base 4. .

In the above configuration, when a voltage is applied between the clamp devices 3 and 3' and a current flows through the metal pipe 1,
The metal pipe is annealed by the Joule heat generated by this current.

In this case, the resistance value of the current-carrying section is determined by the material and wall thickness of the metal pipe, and the current value must be set so as to obtain the temperature rise characteristics most suitable for annealing. The specific resistance of metal is 1.69×10 ^-8 Ω for copper.
cm, iron 10×10 ^-8 Ωcm, stainless steel 70×10 ^-8 Ω
For example, if stainless steel is used for the metal pipe 2, the outer diameter is 6.6 mm, the wall thickness is 0.45 mm, and the annealing length is 100 mm.
If mm, the resistance value will be 0.01Ω. When the pipe annealing temperature is set at 1100 to 1150°C, the Watt surface density is 10 to 12 W/cm ² and the required power is about 200 to 240 W. From the above resistance value of 0.01Ω, the required current is 200A,
The applied voltage is approximately 2V, and the transformer 1 itself may have a small capacity of 1KVA or less, making it possible to construct the equipment at low cost.

Further, when a large current is passed through the metal pipe 2 and heated, the length of the pipe itself increases due to thermal expansion. For example, the coefficient of thermal expansion of stainless steel is approximately 180×10 ^-7 /℃
If the annealing temperature of the pipe is 1100℃ and the length of the pipe is 1m, the entire pipe will have a temperature of about 20℃ due to thermal expansion.
There is an elongation of mm. At this time, if the clamp devices 3, 3' holding the metal pipe 1 are fixed, the pipe cannot be stretched in the length direction, but is bent in the lateral direction, and is greatly deformed into an arched shape. For this reason, it becomes difficult to bend the sheathed heater into various shapes in a subsequent process.

However, in this embodiment, one of the clamp devices 3 is movable, so that thermal expansion of the metal pipe can be absorbed.

As is clear from the above description, the sheathed heater annealing device of the present invention can perform annealing by passing a current through a metal pipe, and the equipment is inexpensive and easy to install. When containing silicone resin with water repellency,
Annealing can be performed without impairing this water repellency.
Furthermore, depending on the position of the clamping device, it is possible to anneal only the bent part while maintaining the water repellency of the insulation material in other parts, and since at least one clamping device is movable, the metal during annealing can be It has great industrial value as it can absorb the elongation of the pipe and prevents metal pipes from deforming.

[Brief explanation of the drawing]

The figure is a front view of a sheathed heater annealing apparatus showing an embodiment of the present invention. 1...Transformer, 2...Metal pipe, 3, 3'...
... Clamp device, 4 ... Base, 5 ... Support part, 6
……groove.

Claims (1)

[Claims] 1 In a sheathed heater annealing device that applies voltage to two clamp devices that clamp the metal pipe of the sheathed heater and anneales it using the Joule heat of the current flowing through the metal pipe, a slide that moves according to the thermal expansion of the metal pipe An annealing device for a sheathed heater comprising a mechanism added to at least one of the two clamp devices.