JPH06340943A - Oxidation resistant alloy powder for filter - Google Patents

Abstract

PURPOSE:To provide oxidation resistant Cr-Al-Fe alloy powder used for a filter for hot oxidizing gas. CONSTITUTION:This oxidation resistant alloy powder for a filter consists of 15.0-30.0wt.% Cr, 8.0-22.0wt.% Al, 0.01-0.40wt.% La and/or Y and the balance Fe with inevitable impurities and is preferably produced by powdering a molten alloy having the above-mentioned compsn. by a water atomization method. This alloy powder is a material for a filter used for removing particulates from hot oxidizing waste gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxidation resistant alloy powder for a filter, and more specifically, it has an excellent oxidation resistance even at high temperatures and is resistant to clogging of the filter and collapse of the filter shape. The present invention relates to an alloy powder for filters.

[0002]

2. Description of the Related Art Conventionally, there are known filters in which various metal powders or alloy powders are compression-molded into a porous bulk body. For example, a filter shaped with powder of stainless steel such as SUS304L and US316L is mainly used as a component of a filtration device of a physics and chemistry equipment.

[0003]

However, the above-mentioned conventional filter is, for example, a particulate matter contained in the exhaust gas of a diesel engine, a particulate matter contained in the exhaust gas of a petroleum stove or a warm air heater, or the like. Cannot be used as a filter to remove.

The reason is that the exhaust gas as described above, especially the exhaust gas of a diesel engine, is a high temperature oxidizing gas, so that Fe, which is the main component of the filter powder, can be obtained in a short time.
Is oxidized into brittle iron oxide, and this iron oxide peels off in a powder state, causing clogging of the filter and also collapsing the filter itself, which causes loss of function as a filter in a short time. is there.

The present invention solves the above-mentioned problems in the conventional alloy powder for filters, and is a filter excellent in oxidation resistance which can secure the filter function for a long time even against exhaust gas that is oxidizing at high temperature. The purpose is to provide alloy powder for use.

[0006]

In order to achieve the above object, in the present invention, Cr: 15.0 to 30.0% by weight, Al: 8.0 to 22.0% by weight, La or / And Y: 0.01 to 0.40% by weight, the balance being inevitable impurities and F
There is provided an oxidation-resistant alloy powder for filters, which is characterized by comprising e.

The alloy powder of the present invention is Fe-based C
It is a powder of r-Al-Fe alloy, and when it is exposed to a high temperature oxidizing gas, Al is first oxidized and A
l ₂ O ₃ has the property of coating the powder surface as an oxidation resistant film and thus suppressing the further oxidation, that is, the oxidation of Cr, the oxidation of Fe and the like.

Here, Cr is a component necessary for ensuring the oxidation resistance of the entire powder, and the content thereof is 15.0-5.0.
It is set to 30.0% by weight. When the content is less than 15.0% by weight, the Fe component is relatively increased, so that sufficient oxidation resistance cannot be obtained. Also, 30.0% by weight
Even more, the oxidation resistance of the powder becomes saturated, which causes an increase in manufacturing cost.

[0009] Then, Al is in an oxidizing gas is oxidized moiety present on the powder surface was changed to Al ₂ O _3, by the Al ₂ O ₃ functions as a kind of barrier, powder It is a component necessary to suppress further oxidation toward the core, and its content is set to 8.0 to 22.0% by weight. When the content is less than 8.0% by weight, the amount that can be present on the powder surface is small and the Al ₂ O ₃ film that fulfills the above-mentioned function cannot be formed sufficiently.
On the other hand, if the amount is more than 22.0% by weight, in the water spray method adopted as the method for producing this powder, for example, the clogging accident of the refractory nords for spraying the molten metal frequently occurs.

The alloy powder of the present invention further contains La and / or Y. All of these components also serve to improve the oxidation resistance of the powder itself, but are particularly required as components for suppressing the above-mentioned Al ₂ O ₃ film from peeling from the powder surface. Al ₂
This is because when the O ₃ film peels off, the peeled film causes clogging of the filter.

La and Y may be contained alone or may be contained together. The content thereof is such that when La and Y are contained individually,
It is set to 0.01 to 0.40% by weight. Further, even when La and Y are contained together, the total amount is 0.01 to 0.40.
It is set to be weight%. If it is less than 0.01% by weight, the above-mentioned effect, that is, the effect of suppressing the peeling of the Al ₂ O ₃ film is not sufficiently exhibited, and if it is more than 0.40% by weight, the above-mentioned effect is in a saturated state. This causes the manufacturing cost to rise.

The alloy powder of the present invention can be produced by smelting the alloy having the above composition and spraying the molten metal. As the atomizing method, either a gas atomizing method or a water atomizing method can be adopted. However, the powder granulated by the gas atomizing method tends to have a spherical surface with a relatively smooth surface. There is a problem that the binding force between the powders becomes weak when the filter is used.

On the contrary, the powder granulated by the water atomization method is
Since the surface tends to be irregular with many irregularities, these powders interfere with each other when manufacturing a filter by compression molding, which has the advantage of increasing the strength of the filter. Is preferably adopted.

[0014]

【Example】

Examples 1 to 12 and Comparative Examples 1 to 3 Alloys having the compositions shown in Table 1 were melted, and a water spray method was applied to the molten metal to obtain powder having a particle size of 0.10 to 0.15 mm. Then, 1 g of these powders, 68 mm in length, 45 mm in width and 1 in depth
It was filled in a 0 mm alumina box at a filling rate of about 35%, and the whole was placed in an air atmosphere furnace at 1050 ° C. to measure the abnormal oxidation start time defined below.

Abnormal oxidation start time: It is assumed that the Al component in the powder is preferentially oxidized to become Al ₂ O ₃ . At that time, the amount of oxidation increase a was 16 with 1 mol of Al (26.98 g).
Since it is × 3/2 (oxygen content), assuming that the Al content in the powder is b% by weight, a = 1 (g) × b / 100 × 16 ×
It becomes 3/2 ÷ 26.98 (g). 10 of each powder (1g)
It is determined that the preferential oxidation of Al is completed when the weight increase reaches the value a (g) when oxidized in the atmosphere of 50 ° C.

Then, the subsequent oxidation is judged to be the oxidation of Cr and Fe, and this state is judged to be abnormal oxidation.
Therefore, the oxidation time (thr) until the increased amount of oxidation reaches the above value a (g) is measured, and this time t (hr) is defined as the abnormal oxidation start time.

It is shown that the longer the time t, the more difficult the oxidation of Cr and Fe is, that is, the powder in which Al ₂ O ₃ is less likely to be peeled off and the more excellent the oxidation resistance is. The above results are collectively shown in Table 1.

[0018]

[Table 1]

[0019]

As is apparent from the above description, the alloy powder of the present invention has excellent oxidation resistance against high temperature oxidizing gas. This is because by adding an appropriate amount of Al, an Al ₂ O ₃ film is formed on the surface of the powder to prevent oxidation of the entire powder, and by adding La and Y, the above A
This is the effect brought about by preventing the peeling of the l ₂ O ₃ film.

Therefore, the alloy powder of the present invention has a very great industrial value as a material for a filter used to remove particulates from high temperature oxidizing exhaust gas such as diesel engines, oil stoves, and hot air heaters. Is.

Claims (1)

[Claims] 1. Cr: 15.0-30.0% by weight, Al: 8.
0-22.0% by weight, La or / and Y: 0.01-0.
40% by weight, the balance being inevitable impurities and Fe, an oxidation resistant alloy powder for filters.