JPH0552012B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a method for manufacturing a dark heater for an indirectly heated cathode, and particularly to a method for manufacturing a dark heater for an indirectly heated cathode with improved productivity. [Prior art] In general, heat-insulated cathode dark heaters are made by coating and insulating the outer periphery of a tungsten wire wound in a single or double coil with alumina for the purpose of rapid heating. The outer surface is coated with a dark layer consisting of a mixture of Conventionally, this type of indirectly heated cathode dark heater is manufactured as follows. That is, first, a W-Re wire as a heater, for example, is spirally wound around the outer surface of a mandrel wire such as molybdenum (Mo) as a core wire to determine the shape of the heater, and then formed into a double coil heater. An alumina insulating layer is coated by deposition or the like, and this is sintered. Next, the alumina insulating layer is immersed in a dark suspension having the above composition to adhere the dark suspension to the outer surface of the alumina insulating layer, and then sintered to form a dark layer. In this case, the mandrel wire is removed by melting in a step after forming the alumina insulating layer. However, this method of manufacturing a dark heater for an indirectly heated cathode requires at least two sintering steps, which causes many defects and increases production costs due to increased production man-hours. Ta. To improve this problem, alumina is deposited by electrodeposition on the heater assembly wound in a double coil on a mandrel wire, and then a dark suspension is deposited and sintered. , it is desirable to form a dark layer and then dissolve and remove the mandrel wire. However, although this method requires only one sintering process and improves productivity,
By melting the mandrel wire after sintering the dark layer coating, there is a side effect of simultaneously dissolving the W fine particles in the dark layer, causing discoloration or unevenness of the dark layer, and significantly impairing the heat radiation performance of the heater. There was a problem that the quality of the heater deteriorated. Further, unless the deposited alumina layer is sufficiently dried, there is a drawback that the immersion dark coating becomes uneven, and defects such as penetration of the dark material occur. [Object of the Invention] Therefore, the present invention has been made in view of the above-mentioned problems, and its purpose is to provide a heater for indirectly heated cathodes that can obtain high-quality heaters with high productivity and at low cost. An object of the present invention is to provide a method for manufacturing a dark heater. [Summary of the Invention] In order to achieve the above object, the present invention provides a heater assembly which is spirally wound on a mandrel core wire, after which e.g. alumina having an average particle size of 15 μm or less is electrodeposited, and then e.g. A dark suspension composed of alumina with an average particle size of 15 μm or less and tungsten or its oxide with an average particle size of 0.3 to 3 μm is successively electrodeposited and sintered, and then the mandrel core wire is dissolved and removed. [Embodiments of the Invention] Next, embodiments of the present invention will be described in detail with reference to the drawings. The figure is a fragmentary plan view of a main part for explaining an example of a method for manufacturing an indirectly heated cathode dark heater according to the present invention. In the figure, first, a W-wire with a Mo wire as a mandrel core wire 1 and a heater on its outer periphery is shown.
A heater assembly 3 is manufactured by winding the Re wire 2 into a double coil. And this heater assembly 3
is immersed in an alumina suspension composition solution consisting of alumina particles, aluminum nitrate, magnesium nitrate, denatured alcohol, and water to form an alumina insulating layer 4 by electrodeposition, and then washed with a cleaning solution such as acetone or methanol. The dark layer 5 was formed by electrodeposition by immersing it in a dark suspension composition solution consisting of W grains (1 weight ratio), alumina grains (average particle size 4.5 μm, 2 weight ratio), aluminum nitrate, magnesium nitrate, denatured alcohol, and water. After forming and cleaning with a cleaning solution such as acetone or methanol, sintering is performed in a hydrogen furnace. Thereafter, the mandrel core wire 1 is dissolved by immersion in nitric acid and a mixed acid solution consisting of nitric acid to complete the dark heater. In such a manufacturing method, when the alumina particle size of the alumina suspension and the W particle size of the dark suspension are changed and the blackness of the completed heater and the state of W seepage are examined, it is found that the thickness of the dark layer 5 is, for example, approximately 7 μm. When the results were unified, the results shown in the table below were obtained. That is, in the same table, the particle size indicates the average particle size. Regarding blackness, ◎ indicates the best, ○ indicates good, △ indicates slightly insufficient, and regarding the presence or absence of W seepage, × indicates not acceptable, and ▲ indicates There are some problems, and the ● mark indicates a good product.

〔Effect of the invention〕

As explained above, according to the present invention, a heater of good quality can be obtained with high productivity and at low cost, which is an extremely excellent effect.

[Brief explanation of the drawing]

The figure is a fragmentary plan view of a main part for explaining an example of a method for manufacturing an indirectly heated cathode dark heater according to the present invention. 1...Mandrel core wire, 2...W-Re wire, 3
...Heater assembly, 4...Alumina insulating layer, 5...
...Dark layer.

Claims (1)

[Claims] 1. A step of spirally winding a heater wire on a mandrel core wire, and a step of winding a heater wire with an average particle size of 15 μm on the heater wire.
a step of electrodepositing the following insulating material to form an insulating layer; and a step of electrodepositing a composition consisting of a granular insulating material and a black material with an average particle size of 0.3 to 3 μm on the insulating layer to form a black layer. A method for producing a dark heater for an indirectly heated cathode, comprising the steps of sintering the insulating layer and the black layer, and finally melting and removing the mandrel core wire.