JPH02270286A - Aluminum cast heater and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to cast aluminum heaters used as heat sources for various cooking appliances such as jar rice cookers and hot plates. The present invention relates to a manufacturing method thereof.

BACKGROUND ART Conventionally, a sheathed heater alone or an aluminum cast heater in which the sheathed heater is cast into aluminum has been used as a heat source for cooking appliances such as jar rice cookers and hot plates.

In particular, aluminum cast heaters have been used as a heat source for jar rice cookers for a long time.

This cast aluminum heater uses an iron pipe as a metal pipe, and a coiled heating wire is placed in the center of the iron pipe, and magnesia powder containing silicone resin powder is placed inside the iron pipe and heating wire. It is manufactured by casting a filled sheathed heater into aluminum (JIS H5202 C2B).

Particularly when used in a jar rice cooker, the part that comes into contact with the pot (
The heat transfer surface (hereinafter referred to as the heat transfer surface) is cut and finished smooth. However, cast aluminum heaters prepared in this way are used with the aluminum fabric exposed to the atmosphere, so if it is left in a humid atmosphere or organic matter such as rice adheres to it, the aluminum will corrode. White rust occurs.

In addition, if a jar rice cooker is used with rice or dirt stuck between the aluminum cast heater and the pot, the contact between the aluminum cast heater and the pot will be poor, and the aluminum cast The temperature of the heater increases significantly, causing problems such as deformation of the cast aluminum heater and a significant decrease in electrical characteristics.

For this reason, various proposals have been made to subject the aluminum surface, which corresponds to the heat transfer surface of cast-in aluminum heaters, to surface treatments that improve corrosion resistance and heat radiation.

Problems to be Solved by the Invention However, the following four methods have been proposed so far.

1. Organic heat-resistant paint (silicone-based or fluorine-based paint).

■Inorganic heat-resistant coatings (water glass-based, aluminum phosphate-based paints).

m, anodizing treatment (alumite treatment).

■Chemical coloring treatment (black dyeing, etc.).

However, there are various issues as shown below.

Organic heat-resistant paint has a soft film and is easily scratched, leading to rust. With the inorganic heat-resistant paint (2), the paint film is porous and corrosion resistance cannot be ensured. Furthermore, when the anodic oxidation treatment (2) and the chemical coloring treatment (2) are exposed to temperatures of 200° C. or higher, the coating film cracks and discolors, resulting in a significant deterioration of properties.

The reality is that there are various problems with surface treatment.

The present invention is intended to solve the above-mentioned conventional problems, and provides an aluminum cast heater with excellent heat radiation and corrosion resistance, and a method for manufacturing the same.

Means for Solving the Problems In order to solve the above problems, the present invention provides that all main components such as decomposition products or condensation products of metal alkoxides are added to the entire or part of the heat transfer surface by a hydrolysis method of metal alkoxides. and zirconium oxide, aluminum oxide,
Titanium oxide, iron oxide.

By forming an inorganic coating layer containing far-infrared emitting materials such as manganese oxide, cobalt oxide, nickel oxide, and chromium oxide, and after casting the sheathed heater all aluminum, the end of the metal pipe of the sheathed heater is coated with silicone. Seal with resin etc. and prepare heater metal for aluminum casting. After that, the heat transfer surface of the cast aluminum heater is completely degreased, and a paint made of a metal alkoxide solution containing far-infrared radiating materials such as the above-mentioned food oxides is applied by a spray method, etc. at a temperature of 200'C or less. This is achieved by hardening and forming an inorganic coating M on the heat transfer surface of the cast aluminum heater.As already mentioned above, the surface treatment methods proposed in the past have had various problems.

In contrast, the present invention focuses on a newly developed metal alkoxide hydrolysis method and applies this method.

This metal alkoxide hydrolysis method is a method in which a metal alkoxide is reacted with water to form a coating film through decomposition and condensation, and it is possible to form a dense coating film at a relatively low temperature of 200° C. or lower.

It is also possible to add various functions to the coating film by incorporating various oxides into the metal alkoxide solution.

In the present invention, zirconium oxide, aluminum oxide, and titanium oxide are used as the metal alkoxides mentioned above.

iron oxide, manganese oxide, cobalt oxide, nickel oxide,
An inorganic coating layer is formed on the surface of aluminum by containing and hydrolyzing a far-infrared emitting material such as chromium oxide.

The inorganic coating layer thus formed is mainly made of inorganic substances and is in a very dense state.

Therefore, it has excellent hardness, heat resistance, and corrosion resistance, and since the contained substance has excellent far-infrared radiation characteristics, it has excellent heat radiation.

On the other hand, when manufacturing an aluminum cast heater using such a paint, it can be manufactured through an extremely simple process of degreasing, coating, and curing.

In particular, it is sufficient for the curing treatment to be performed at a low temperature of 200'C or less, and as will be described later, the silicone resin at the end of the metal pipe of the sheathed heater can be cured without thermal deterioration, which is very effective.

In the manufacturing method of the present invention, the ends of the metal pipes of the sheathed heater are completely sealed with silicone resin in advance to prevent the degreasing liquid from entering the inside of the sheathed heater during the degreasing process, and the ends of the sheathed heater's metal pipes are sealed in advance with silicone resin to prevent the degreasing liquid from penetrating inside the sheathed heater. 200℃ before the silicone resin at the end of the metal pipe deteriorates due to heat.
It was heat treated at the following temperatures.

For these reasons, the aluminum cast heater of the present invention has excellent heat radiation and corrosion resistance, and it is possible to manufacture such an excellent aluminum cast heater.

In the present invention, the inorganic coating layer may be formed on the entire heat transfer surface of the cast-in aluminum heater, but it is also possible to form the inorganic coating layer only on a part of the heat transfer surface, such as forming it only on a part of the heat transfer surface excluding the part that contacts the pot. It's okay.

Embodiments Hereinafter, specific embodiments of the present invention will be described based on the accompanying drawings.

An iron pipe is used as the metal pipe 1-1, and a coiled electric heater made of iron-chromium-aluminum alloy [1-2e is positioned in the center of the metal pipe 1-1, and the metal pipe 1-1 and the heating wire 1 are placed in the center of the metal pipe 1-1. 9 gaps of -2 were filled with electrofused magnesia powder containing 2% by weight of silicone resin powder as electrical insulating powder 1-3, rolled to reduce its diameter, and then bent to prepare a sheathed heater.

This sheathed heater 1 was set in a sand mold of a predetermined shape, and a molten aluminum alloy (JIS H5202 C2B
) I Prepared a pouring aluminum casting heater No. 2.

After cutting and smoothing the heat transfer surface 2a of the cast aluminum heater 2 prepared in this way, silicone resin 1-4 is injected into the end of the metal pipe 1-1 of the sheathed heater 1, and an insulating Insulator 1-6 was inserted and sealed.

Next, in order to degrease the heat transfer surface 2IL of the cast aluminum heater 2, it was immersed in a weak alkaline solution for 6 minutes, dried, and then treated with tetraethoxysilane (s) as a metal alkoxide.
: A paint using (oc2u5)4) was applied to the heat transfer surface 2a by spraying.

The paint is prepared by adding oxides such as iron oxide, manganese oxide, and aluminum oxide to a metal alkoxide made of tetraethoxysilane.

Thereafter, heat treatment was performed at 180'C for 20 minutes to harden the paint and form an inorganic coating layer 2bf on the heat transfer surface 2a of the cast aluminum heater 2, completing the cast aluminum heater of the present invention. For comparison, we also have a conventional cast-in aluminum heater in which the heat transfer surface is not treated (conventional example) and a heat transfer surface coated with a commercially available heat-resistant paint (silicone type) (comparative example). Prepared in the same way.

In order to evaluate the cast aluminum heater of the present invention prepared in this manner, the following test was conducted.

■ Salt spray test: 1 chloride concentration 6% at 35℃
Leave it in an atmosphere for 96 hours and check for rust.

■ Heat radiation test: Input the specified power consumption into a single aluminum cast heater, and measure the temperature of the heat transfer surface when the temperature reaches saturation.

Table 1 shows the evaluation results when the test was conducted using the above method.

As is clear from Table 1, conventional products and comparative products coated with commercially available heat-resistant paints caused problems due to rusting in the salt spray test.

On the other hand, the products of the present invention exhibited excellent corrosion resistance with no rusting observed.

On the other hand, in the thermal radiation test, it showed superior properties compared to conventional products, and exhibited a temperature approximately 60°C lower than that of conventional products.

As described above, the cast aluminum heater of the present invention exhibited excellent corrosion resistance and heat radiation.

The composition of the paint used in the examples of the present invention is not limited to this, and may include other metal alkoxides,
Other far infrared emitting materials may also be used.

Furthermore, the shape and heat transfer surface of the cast aluminum heater are not limited to those in the embodiments, and other shapes or only a portion of the heat transfer surface may be coated.

Furthermore, although a weak alkaline solution was used for degreasing in the manufacturing method, other solvent degreasing methods may be used.

Effects of the Invention As is clear from the above explanation, according to the cast aluminum heater and the manufacturing method thereof of the present invention, the metal alkoxide decomposition products or All main components include condensation products, such as zirconium oxide, aluminum oxide, titanium oxide, and iron oxide.

By forming an inorganic coating layer containing far-infrared radiating materials such as manganese oxide, cobalt oxide, nickel oxide, and chromium oxide, and after casting into the sheathed heater all aluminum, the end of the metal pipe of the sheathed heater? Seal with silicone resin, etc., and prepare an aluminum cast heater. After that, the heat transfer surface of the cast aluminum heater is degreased, and a paint made of a metal alkoxide solution containing a far-infrared radiating material such as various oxides as described in claim 1 is applied by a spray method, To provide an aluminum cast heater having excellent heat radiation and corrosion resistance by curing at a temperature of 200° C. or lower and manufacturing an inorganic coating layer on the heat transfer surface of the aluminum cast heater, and a method for manufacturing the same. becomes possible.

[Brief explanation of drawings]

Figure 1 is a partial sectional view of the cast aluminum heater of the present invention, Figure 2 is a partial cross-sectional view of the cast aluminum heater of the present invention;
The figure shows a sectional view of the end of the sheathed heater used in the aluminum cast heater, and FIG. 3 shows a sectional view of the sheathed heater. 1... Sheathed heater, 1-1... Metal pipe, 1-4... Marked silicone resin, 2 Old... Aluminum cast heater, 2a... Heat Transmission surface, 2b...
...--Inorganic coating layer.

Claims (2)

[Claims] (1) The entire or part of the heat transfer surface is made of a decomposition product or condensation product of the metal alkoxide as a main component by a metal alkoxide hydrolysis method, such as zirconium oxide, aluminum oxide, titanium oxide, iron oxide, or An aluminum cast heater with an inorganic coating layer containing far-infrared radiating materials such as manganese, cobalt oxide, nickel oxide, and chromium oxide. (2) After the sheathed heater is cast in aluminum, the end of the metal pipe of the sheathed heater is sealed with silicone resin, etc., and then the heat transfer surface of the cast aluminum heater is degreased and various oxides etc. Aluminum casting, in which a paint made of a metal alkoxide solution containing a far-infrared radiating material is applied by a spray method or the like, and cured at a temperature of 200°C or less to form an inorganic coating layer on the heat transfer surface of the aluminum casting heater. Heater manufacturing method.