JPH0542954B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention effectively prevents peeling of far-infrared paint applied to the surface of oxidation-resistant stainless steel, and is used as heating equipment or heating devices that utilize far-infrared radiation. In this case, the method can be applied to both a method of heating the oxidation-resistant stainless steel by directly applying electricity to it and a method of heating it using external heat such as combustion. [Prior Art] Far-infrared rays have the property of penetrating deeply into the human body, and are effectively used in heating devices and food heating. In order to emit this far infrared rays,
It is necessary to coat the surface of a heating element or a radiator heated by external heat with a far-infrared radiating material that effectively emits wavelengths of 5 to 30 μm. Conventionally, for this purpose, a method of applying these radioactive substances by thermal spraying (Japanese Patent Application Laid-open No. 119244/1983) has been adopted. Because of the way in which far-infrared radiators are used, they are necessarily constantly heated and cooled, and coatings applied by such thermal spraying methods have the problem of peeling off during use. Peeling can be alleviated by reducing the thermal spraying thickness, but if the thermal spraying thickness becomes too thin, there is a problem in that infrared rays with wavelengths specific to the underlying metal are emitted, resulting in a decrease in energy efficiency. On the other hand, if the thickness becomes too thick, the tendency for peeling becomes noticeable. Therefore, it is necessary to take measures such as glass coating or mica coating over the far-infrared coating. In addition, in order to reduce this peeling, methods have been adopted to reduce the difference in thermal expansion between the far-infrared emitting material and the underlying metal (Japanese Patent Application Laid-Open No. 60-13008). Problems with peeling still occur because the adhesive cannot be completely adhered. The present inventors have reported that Al
We have proposed a radiator in which a whisker layer is formed on the surface of stainless steel containing alumina to increase the surface area of alumina, and this alumina whisker emits far infrared rays. After further detailed investigation, we found that far-infrared characteristics can be obtained with this alumina whisker layer alone, but because the thickness of the resulting film is thin,
Infrared properties from Fe were also observed, and it was found that the results did not necessarily provide the best far-infrared radiation properties. [Problems to be Solved by the Invention] In order to solve the problem of peeling of far-infrared paint, the present inventors
Various studies were conducted. When we applied far-infrared paint to the above-mentioned film with whiskers in the same manner as the conventional method, we found that the paint film peeled off even when subjected to rapid heating and cooling, and the far-infrared properties were also sufficient. They discovered that the following could be obtained and completed the present invention. In other words, on the surface of Al-containing oxidation-resistant stainless steel,
Even when the far-infrared radiator is rapidly heated and cooled, the far-infrared paint hardly peels off when an oxide film is formed to increase the surface area and a paint coating layer is formed on top of it. Peeling is less likely to occur due to mechanical vibrations caused by gas flow, etc. The present invention solves the problem of peeling of the coating film of conventional far-infrared radiators, which have low peeling resistance against thermal shock, mechanical vibration, etc., and uses glass coatings and mica coatings to specifically prevent peeling. The purpose of the present invention is to provide a far-infrared radiator with excellent performance that does not require the following. [Means for Solving the Problems] The present invention has a far-infrared paint coating layer on whisker-shaped or pyramid-shaped alumina produced on the surface of stainless steel to increase the surface area. A far-infrared radiator with excellent paint peeling resistance. Compositions having preferable characteristics as such stainless steel are exemplified by the following (a) to (d). (a) Stainless steel contains C: 0.03% by weight or less, N: 0.025% by weight or less, Si: 1% by weight or less, Cr: 10 to 26% by weight, Al: 1.8 to 8% by weight, and the balance is Fe and impurities that are inevitably mixed in. consisting of (b) In addition to (a) above, Ti and Zr may be added alone or in combination from 0.01 to
Contains 0.8% by weight. (c) In the above (a), one or more selected from Y, La, Ce, Nd and Gd is added to Y.
0.01 to 0.7% by weight, and 0.001 to 0.1% by weight for La, Ce, Nd or Gd. (d) In addition to the above (b), Y, La, Ce, Nd and Gd
One or more selected from 0.01 to 0.7% by weight for Y, La, Ce, Nd or Gd
contains 0.001 to 0.1% by weight. [Function] By forming whiskers or pyramid-shaped alumina on the surface of stainless steel to increase the surface area and create unevenness, the peeling resistance of far-infrared paint is significantly increased. In particular, the film formed in a convex shape on the surface is effective, and the height of this convex shape is 0.5μ
m or more is preferable. Figures 1 to 4 show scanning electron micrographs of the surface of Al-containing oxidation-resistant stainless steel. Figure 1 shows alumina whiskers formed;
Figure 2 shows pyramid-shaped alumina with a convex shape of about 0.5 μm, Figure 3 shows smooth alumina, and Figure 4 shows a 0.5 μm convex shape. Although it has some degree of unevenness, it shows an oxide film in which the depressions are predominant. In the present invention, Al in the steel is oxidized to form a film on the surface of the stainless steel, producing alumina with an increased surface area in the form of whiskers or pyramids, and the essential condition is that the surface is convex. be.
The heating temperature to generate alumina is 800~
It is desirable to set the temperature to 1250℃. In addition, in order to obtain a film with increased surface area even at a high temperature of 1250℃, the minimum
Requires 0.5 hours. In a shorter time than this
A film with excellent peeling resistance cannot be obtained. In order to achieve the resistance of the present invention, it is necessary to generate a whisker-like or pyramid-like alumina oxide film, and the components of the oxidation-resistant stainless steel are limited as follows. C: C is an element that inhibits oxidation resistance, becomes CO ₂ gas in an oxidizing atmosphere, destroys the oxide film,
Causes nitrogen intrusion and replaces the main component Al with AlN
The lower the better. If it is less than 0.03% by weight, its harmfulness becomes small, so it is limited to less than this value. N: N becomes AlN in steel and consumes effective Al, so it needs to be kept low. The content is limited to 0.025% by weight or less in order not to cause any substantial adverse effects. Si: Si is an effective element for oxidizing properties, but if included in excess, it increases the peelability of the surface oxide film from the metal base, so it is limited to 1% by weight or less. Cr: Cr is an essential element for oxidation-resistant stainless steel.
If it is less than 10% by weight, there is no oxidation resistance and the surface
A film of Al ₂ O ₃ is no longer formed. Further, if Cr is excessive, it makes the steel brittle and it becomes virtually impossible to process it into a far-infrared radiator, so it is limited to 26% by weight or less. Al: Along with Cr, it provides oxidation resistance and is an essential element for forming an oxide film with increased surface area. If it is less than 1.8% by weight, an oxide mainly composed of Fe and Cr will be formed, and in order to form Al ₂ O ₃ , it needs to be 1.8% by weight or more. Also Al
The object of the present invention can be achieved as the amount of Cr increases, but if it exceeds 8% by weight, Cr becomes 10%
The upper limit needs to be 8% by weight because it makes the steel brittle even if it is reduced to about 8% by weight. Ti, Zr: Ti and Zr show good results when added to reduce the adverse effects of C and N. In that case,
If it is less than 0.01% by weight, it will not be effective, and if it is added in excess, it will reduce the oxidation resistance and easily generate scale lumps, so it should be limited to 0.8% by weight or less. Y: Y is an element that improves oxidation resistance and helps form an Al ₂ O ₃ film. Further, it is suitable to add it to improve the adhesion between Al ₂ O ₃ and the base metal.
However, if it is less than 0.01% by weight, it has no effect;
If it exceeds 0.7% by weight, it makes the steel brittle and increases the cost of the material, so it is limited to 0.01 to 0.7% by weight. La, Ce, Nd, Gd: Like Y, they help form the Al ₂ O ₃ film and improve the adhesion between the base metal and the Al ₂ O ₃ film, but if it is less than 0.001% by weight, it has no effect. If it exceeds 0.1% by weight, intermetallic compounds with a low melting point are generated at the grain boundaries, making the steel unworkable, so it is necessary to limit it to 0.001 to 0.1% by weight. The above Ti, Zr, Y, La, Ce, Nd, and Gd are Fe−
They improve the oxidation resistance of Cr-Al oxidation-resistant stainless steel, and when these are added alone or in combination, the effect is additively improved. Conventionally known far-infrared paints include carbon,
Graphite, oxides, carbide ceramics, etc. can be used, and the coating is carried out using an organic solvent, water, or an acidic or basic solvent. The thickness of these coatings is usually about 10 to 100 μm, but according to the present invention, even if the thickness is 100 μm or more and about 500 μm, no problem of peeling occurs, and the thickness of the coating is not limited. As for the application method, usual methods such as brush, spray, roller, and dipping methods can be used. Drying after coating may be carried out as appropriate depending on the type of solvent used, and there is no need to carry out drying under particularly limited conditions. In other words, 60 to 150℃ for organic solvents, etc.
In the case of water, the temperature is preferably room temperature to about 80°C, and the drying time is about 30 minutes to 1 day and night. The relationship between temperature and time is that the lower the temperature, the longer the time. In the case of acidic or basic solvents, heating at 200 to 400°C is preferable in order to effectively vaporize these components, and coating is achieved by drying for 30 minutes or more. [Examples] The present invention will be described below based on Examples. Using oxidation-resistant stainless steel having the composition shown in Table 1, it was subjected to various oxidation treatments, and then far-infrared paint was applied. A commercially available ZrSiO ₂ -based far-infrared paint was used, diluted with isopropyl alcohol, and applied to a thickness of approximately 50 μm. After drying in an oven at approximately 150°C for 30 minutes, a peelability test was conducted. In this test, a test piece was heated to 800°C and cooled with water. After repeating rapid heating and water cooling twice, the moisture was dried and the amount of peeling was evaluated based on the change in weight. Peeling resistance evaluation shows that paint weight decreases by 1%
The following items were passed. Table 2 shows the oxidation treatment, oxide morphology, and peel test evaluation. For steels having a composition within the range of the present invention and having a whisker-like or pyramid-like alumina oxide film, the peeling weight is 1% as indicated by the circle mark in Table 2 for peeling resistance evaluation. It has excellent peeling resistance.

【table】

〔Effect of the invention〕

According to the present invention, by adjusting the oxidation-resistant steel and its surface oxide morphology, it is possible to obtain an excellent far-infrared radiation resistant body with almost no peeling of the coating film even when substantially rapid heating and cooling are performed. According to the present invention, there is no need for a coating to prevent peeling, and a far-infrared radiator with an extremely long life can be obtained, which can be applied to various heating devices, and has great industrial advantages. It is. The effects of the present invention are not limited to far-infrared radiators, but can also be applied to combustion cylinders of kerosene heating equipment, etc. In addition to far-infrared rays, combustion efficiency can be improved by using heat-resistant paint. There is a range of applications such as the ability to

[Brief explanation of drawings]

Figures 1 to 4 show scanning electron micrographs of the surface of stainless steel. Figure 3 shows smooth alumina oxide (Steel A, 700℃ x 24hr), Figure 4 shows smooth alumina oxide (Steel G, 1000℃ x 4hr)
This photo shows that it is being generated.

Claims (1)

[Scope of Claims] 1 Peel-resistant far-infrared paint, characterized in that convex alumina formed on the surface of stainless steel is whisker-shaped or pyramid-shaped, and has a far-infrared paint coating layer thereon. A far-infrared emitter with excellent properties. 2. Stainless steel contains C: 0.03% by weight or less, N: 0.025% by weight or less, Si: 1% by weight or less, Cr: 10-26% by weight, Al: 1.8-8% by weight, and the balance is Fe and impurities that are inevitably mixed in. A far-infrared radiator according to claim 1. 3 Stainless steel contains: C: 0.03% by weight or less N: 0.025% by weight or less Si: 1% by weight or less Cr: 10-26% by weight Al: 1.8-8% by weight Ti, Zr alone or in combination 0.01-0.8% by weight 2. The far-infrared radiator according to claim 1, wherein the far-infrared radiator comprises Fe and unavoidably mixed impurities. 4 Stainless steel is selected from C: 0.03% by weight or less, N: 0.025% by weight or less, Si: 1% by weight or less, Cr: 10-26% by weight, Al: 1.8-8% by weight, and Y, La, Ce, Nd, and Gd. 0.01 to 0.7% by weight for Y and 0.001 to 0.1 for La, Ce, Nd or Gd.
% by weight, with the remainder consisting of Fe and unavoidably mixed impurities. 5 Stainless steel contains: C: 0.03% by weight or less N: 0.025% by weight or less Si: 1% by weight or less Cr: 10-26% by weight Al: 1.8-8% by weight Ti, Zr alone or in combination 0.01-0.8% by weight and one or more selected from Y, La, Ce, Nd, and Gd from 0.01 to Y.
0.7% by weight in La, Ce, Nd or Gd
0.001 to 0.1% by weight, with the remainder consisting of Fe and unavoidably mixed impurities.
The far-infrared radiator described in section.