JPH01184255A - Far infrared radiator and its production - Google Patents

Abstract

PURPOSE:To prevent deterioration in radiation characteristics of the title radiator by subjecting a stainless steel in which respective contents of C, Si, Mn, Cr, Al, Ce, N, Zr, V and Ta are specified to heating under prescribed conditions and forming layer containing Al2O3 on the surface. CONSTITUTION:A stainless steel which has a composition consisting of, by weight, <=0.1% C, <=1% Si, <=3% Mn, 8-30% Cr, 1-8% Al, 0.03-0.1% Ce and/or La, <=0.05% N, and the balance Fe or further containing, besides the above, one or more elements among Zr, V and Ta by the amount satisfying (C+N)X3-0.7% is refined. A sheet of the above steel is heated in an oxidizing atmosphere at 500-1,200 deg.C, by which a layer containing acicular or cylindrical Al2O3 can be formed on the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a far-infrared radiator and a method for manufacturing the same, and particularly provides a radiator whose radiation characteristics do not deteriorate even after repeated heating and cooling.

[Prior Art] Conventionally, a far-infrared radiator has generally been a stainless steel substrate coated with a far-infrared radiator material by thermal spraying or the like. In addition, peeling and cracking were likely to occur unless the coating thickness was limited. Furthermore, even if the density is limited and the thickness is controlled, the bond between the far-infrared paint and the substrate is weak if it is applied on the surface, so it is important to avoid peeling due to repeated use over a long period of time. I can't. That is, the resistance to peeling of a substrate by any coating method such as thermal spraying depends solely on the bonding force between the coating and the substrate.

On the other hand, in the case of painting, the radiation characteristics of far infrared rays depend on the characteristics of the material being painted, the surface area effect, that is, the large number of irregularities, and the size of the effective radiation area. In the case of painting, if a porous coating is applied to increase the surface area, the interfacial strength will decrease.

Therefore, it is basically impossible to improve the radiation characteristics and increase the peel resistance at the same time using the coating method.

The present applicant proposed Japanese Patent Application No. 61-169422 in order to solve these problems at the same time.

[Problem to be solved by the invention] Through subsequent research by the present inventors, the patent application No. 61-169
422 without adding Ti and/or Nb, and that favorable results can be obtained even when Ti and/or Nb are not added to Ti
It has been found that the same objective can be achieved by adding appropriate amounts of one or two selected from Zr, V, and Ta in place of and/or Nb.

Based on this knowledge, it is an object of the present invention to provide a far-infrared radiator having high radiation characteristics, a stable coating layer, and high resistance to peeling, and a method for producing the same.

[Means for Solving the Problems] The present invention provides excellent far-infrared radiation properties by oxidizing stainless steel having the following composition in an oxidizing atmosphere to form an acicular or rod-shaped alumina film on the surface. It is a radiator with

That is, C: 0.10 wt% or less Si: 1.0 wt% or less Mn・3.0 wt% or less CF 8 wt% or more and 30 wt% or less AJ2: 1 wt% or more and 8 wt% or less Ce and/or La・0.03% by weight or more and 0.1% by weight or less N: O, Q
This is a far-infrared radiator characterized in that a film having needle-shaped or rod-shaped Aff203 is formed on the surface of stainless steel containing 5% by weight or less, the balance consisting of Fe and unavoidable impurities.

Furthermore, if various processing is required as a radiator,
One or more selected from Zr, V, and Ta are further added to the above components. The amount added is at least 3 times the total of C and N and at most 0.7% by weight. This Zr, V, T
The far-infrared radiator is made by forming a film having needle-like or rod-like A42O3 on the surface of stainless steel to which one or more selected from a is added.

These stainless steels produce needle-shaped or rod-shaped alumina crystals by heating in an oxidizing atmosphere of 500° C. or more and 1200° C. or less.

This alumina crystal is basically living body of Ag, but actually contains Fe, Cr, Mn, and rare earth metals.
Further, when adding an element selected from Nb, V, and Ta, these elements are also included.

In the present invention, a coating with excellent far-infrared radiation properties is produced, and even if these elements are mixed into alumina as impurities, the surface crystal shape becomes needle-like or rod-like and has a surface area effect. If it is, there will be no effect on the radiation characteristics.

Furthermore, if the surface of stainless steel is subjected to a blasting process to give processing strain, acicular or rod-shaped crystals can be effectively generated by the oxidation process.

[Function] The coating layer of the far-infrared radiator according to the present invention is produced by reaction from the substrate, and is crystallized with the substrate. Therefore, peeling resistance is high. Furthermore, the outermost surface of the coating layer is made of needle-shaped or rod-shaped alumina crystals, and has a large effective radiation area.

Here, the reasons for limiting the components of the present invention are as follows.

C: C hardens stainless steel and reduces ductility, so it needs to be low. As a far-infrared radiator, it is possible to use the plate as is without any complicated processing.
The upper limit was set to 0.10% by weight.

Sl.

Si concentrates at the interface between the oxide film and the substrate, becomes an interfacial oxide, and increases the peeling resistance of the film, but if the Si content is too high, a thick 5i02 layer is formed at the interface, which actually impairs the peeling resistance.
The upper limit needs to be 1.0% by weight.

Mn: Mn has a high diffusion rate in oxides, has the effect of thickening the oxide film, and is effective for growing needle-shaped or rod-shaped crystals, and enhances far-infrared characteristics through this, but if too much is used. Since the oxidation resistance itself deteriorates, the upper limit is limited to 3.0% by weight.

Cr: Cr is the basic composition of stainless steel, and 8% by weight or more is required to form an effective oxide film. 3
If it exceeds 0% by weight, the toughness will decrease and the high A! Additions create manufacturing problems.

AI2/Al2 is an essential element for forming an alumina film on the stainless steel surface, but if it is less than 1% by weight, an alumina film cannot be obtained. If it exceeds 8% by weight, the toughness will decrease even if the Cr content is about 8% by weight, causing manufacturing problems.

Ce, La: These rare earth elements have the effect of improving the adhesion of the oxide film, and for that purpose it is desirable to add a large amount, but 0.1
If it exceeds % by weight, it will segregate at grain boundaries and impair hot workability.

These rare earth elements are effective in making alumina crystals needle-like, and this effect is exhibited at 0.03% by weight or more, and is effective in improving radiation characteristics.

N: Like C, N makes stainless steel brittle. Particularly in the steel of the present invention, which has a high Al content, coarse AgN forms, reducing the cleanliness. Considering the use as a flat plate, the upper limit is limited to 0.05% by weight.

Zr, V, Ta Zr, V, and Ta fix C and N and improve the workability of stainless steel. This effect is exhibited at least three times as much as (C+N), but when it exceeds 0.7% by weight, it actually makes the steel brittle.

In order to effectively form an oxide film on the above stainless steel surface, it is necessary to heat it at a temperature of 500°C or higher, but if the heating temperature exceeds 1200°C, needle-shaped or rod-shaped oxides will not be obtained. Therefore, the heating temperature range is limited to 500°C or higher and 1200°C or lower.

When processing strain is applied to the stainless steel surface by blasting, needle-like crystals are likely to form. The greater the degree of blasting, the better. However, needle-shaped crystals can be formed even if there is no such substance.

[Example] A material having the composition shown in Table 1 was rolled into a 1.5 mm thick plate and bright annealed at 950°C. These materials were treated under the oxidation treatment conditions shown in Table 1, and their far-infrared radiation characteristics were determined. In addition, one cycle was heating at 600° C. and air cooling for 30 minutes, and the peeling resistance of the film was examined by checking whether or not peeling occurred after 2000 cycles.

These results are also shown in Table 1.

The far-infrared radiation characteristics indicate the ratio to a black body at a wavelength of 3 to 10 μm at 400° C., and the peel resistance is indicated by ◯ if there is no peeling and × if there is peeling.

As is clear from Table 1, the radiator material according to the present invention has excellent far-infrared radiation characteristics and film peeling resistance, and such a material can be produced by the method of the present invention.

[Effects of the Invention] The far-infrared radiator of the present invention has excellent film peeling resistance even in applications where it is subjected to sudden thermal stress, and has high far-infrared radiation characteristics, so it can be used in various heating devices, drying ovens, etc. , mortarization furnace has a wide range of applications, and can effectively utilize the energy saving effect and penetration effect of far infrared rays.
When Ta is included, the workability becomes excellent.

According to the method of the present invention, a film having needle-like or rod-like Aff203 can be easily formed, and if blasting is performed before heat treatment, a -layer can be easily formed.

Claims (1)

[Claims] 1 C: 0.10 wt% or less Si: 1.0 wt% or less Mn: 3.0 wt% or less Cr: 8 wt% or more and 30 wt% or less Al: 1 wt% or more and 8 wt% Ce and/or La: 0.03% by weight or more and 0.1% by weight or less N: 0.05% by weight or less A far-infrared radiator characterized by forming a film having the following properties. 2. Furthermore, one or more selected from Zr, V, and Ta are added in an amount of at least 3 times the total of C and N.
The far-infrared radiator according to claim 1, wherein the far-infrared radiator contains 7% by weight or less, with the remainder consisting of Fe and unavoidable impurities. 3 Stainless steel heated to 500℃ or higher in an oxidizing atmosphere12
Claim 1 characterized in that the heating is performed at a temperature of 00°C or less.
Or the method for producing a far-infrared radiator according to 2. 4. The manufacturing method according to claim 3, wherein the stainless steel surface is heated after being subjected to a blasting process to give processing strain.