JPH07228954A - Oxidation resistant powder sintered body and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To produce a sintered body of oxidation resisting powder, improved in sinterability, etc., by adding specific percentages of B, etc., to the alloy powder having a specific composition consisting of Fe, Cr, Al, Y, etc., and then applying sintering. CONSTITUTION:One or more kinds among, by weight, 0.01-1.0% B, 0.05-2.0% CrB, 0.05-2.0% NiB, and 0.05-2.0% FeB are added to the alloy powder having a composition consisting of 15.0-30.0% Cr, 5.0-25.0% Al, 0.01-0.5%, in total, of one or more kinds among Y, Hf, and rare earth elements, and the balance Fe with inevitable impurities, and the resulting mixture is sintered. By this method, the sintered body of oxidation resisting powder, having high relative density and superior strength, can be obtained by means of relatively short time sintering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Fe-Cr-Al alloy sintered body for an exhaust gas filter of an automobile engine, a boiler or the like, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, ceramic filters are often used to filter solid particles contained in high-temperature gas such as exhaust gas from automobile engines and boilers, but ceramics are low in strength and brittle. Therefore, for example, when it is used in an application such as an automobile exhaust gas treatment filter where mechanical vibration or impact force acts, it is necessary to take measures such as using a shock absorber to reduce the vibration or impact force. If a metal having high heat resistance and oxidation resistance is used as the filter material, a material having high toughness can be obtained, which is suitable for use as an exhaust gas treatment filter for automobiles and boilers.

A porous sintered body obtained by sintering metal powder, for example, stainless steel powder, is used as a filter. On the other hand, the Fe-Cr-Al alloy is known as an oxidation resistant material, and the porous sintered body using the Fe-Cr-Al alloy powder is used as the above-mentioned automobile exhaust gas treatment filter or the like. It is considered to be suitable for. Fe-C
Regarding the r-Al alloy powder, for example, JP-A-5-98
As disclosed in Japanese Patent Publication No. 401, it is used as a material for heaters and the like. However, Fe-Cr-A
The l-based alloy powder has inferior sinterability, and in order to increase the density and strength of the sintered body, even if a sintered product having a low sintering density such as a filter material is manufactured. However, there is a problem that sintering at high temperature for a long time is required.

[0004]

SUMMARY OF THE INVENTION The present invention has been made against the background of the above circumstances, and its purpose is to:
To improve its sinterability in Fe-Cr-Al alloys,
An object of the present invention is to provide an oxidation resistant powder sintered body having high relative density and excellent strength by sintering for a relatively short time, and also to provide a manufacturing method thereof.

[0005]

In order to solve the above problems, the oxidation resistant powder sintered body of the present invention is Cr: 15.0.
~ 30.0 wt%, Al: 5.0-25.0 wt%,
0.01 to 0.5 wt% in total of one or more of Y, Hf, and rare earth elements, balance unavoidable impurities and F
In the alloy powder consisting of e, B: 0.01 to 1.0 wt%,
CrB: 0.05-2.0 wt%, NiB: 0.05-
One or more of 2.0 wt% and FeB: 0.05 to 2.0 wt% is added and sintered.

The method for producing the oxidation resistant powder sintered body of the present invention is as follows: Cr: 15.0 to 30.0 wt%, Al: 5.
0 to 25.0 wt%, Y, Hf, and one or more of any one of rare earth elements in a total amount of 0.01 to 0.5 wt%, the balance being unavoidable impurities, and an alloy powder consisting of Fe, and B: 0.
01-1.0 wt%, CrB: 0.05-2.0 wt
%, NiB: 0.05 to 2.0 wt%, FeB: 0.0
A step of mixing any one or more of powders of 5 to 2.0 wt% with an organic binder, a step of molding, a step of drying, a step of degreasing, and a step of sintering. Characterize.

Next, the reasons for limiting the components of the alloy powder in the present invention will be explained. Cr: 15.0 to 30.0 wt% Cr is an element that imparts oxidation resistance to the present alloy, and if the content ratio is less than 15 wt%, the oxidation resistance is insufficient. However, when the Cr content exceeds 30.0 wt%, this effect is saturated, so the upper limit is made 30.0 wt%.

Al: 5.0 to 25.0 wt% Al is an element that imparts oxidation resistance like Cr, and if the content ratio is less than 5.0 wt%, the oxidation resistance is insufficient. However, if the Al content exceeds 25.0 wt%, it causes obstacles such as nozzle clogging during the production of alloy powder by the atomization method, and powder production becomes difficult. Therefore, the upper limit of the content is set to 25.0 wt%.

0.01 to 0.5 wt% of Y, Hf, or one or more rare earth elements in total Y, Hf, and rare earth elements have a function of preventing peeling of an oxide film formed on the surface of the present alloy. This is an element that improves the oxidation resistance of the alloy. For that, Y, H
f, one or more of rare earth elements in total 0.0
It is necessary to contain one or more. However, even if the content of these exceeds 0.5 wt%, the effect of improving the oxidation resistance is saturated, and the oxidation of the powder during the production of the powder becomes remarkable, and the sinterability of the powder is impaired. It is set to 0.5 wt%.

The alloy powder according to the present invention preferably has a total content of Ni and Cu of 2.0 wt% or less. The reason is that the content of these elements is 2.0.
This is because the oxidation resistance becomes insufficient when the content exceeds wt%. The alloy powder in the present invention is obtained mainly by a spraying method. B, CrB, NiB and FeB are added as sintering aids for promoting the sintering of the above alloy powder. In order to exert its effect, 0.01 wt% for B
As described above, for CrB, NiB, and FeB, 0.05 wt
It is necessary to add one or more kinds in an amount of at least%. However, in the case of B, it exceeds 1.0 wt%, and CrB,
For NiB and FeB, the addition of more than 2.0 wt% not only saturates the sintering promoting effect but also impairs the heat resistance of the sintered body, so the upper limit of the B addition amount is 1.0 wt.
%, CrB, NiB, FeB upper limit is 2.0 wt
%.

The oxidation-resistant powder sintered body of the present invention is prepared by mixing, molding, drying, degreasing and sintering the alloy powder, the sintering aid and the organic binder according to the usual powder metallurgical method. It is manufactured through each process. The molding is performed by a method such as press molding, mold pouring, and metal powder injection molding. Further, the sintering is 1250 ° C to 1400 ° C, preferably 1280 ° C to 1350 ° C, more preferably 1300 ° C.
In 1 to 10 hours in vacuum or in an inert gas.

[0012]

EXAMPLES The present invention will be specifically described below with reference to examples. Alloy powders having the chemical compositions shown in Table 1 were produced by a water atomization method. To this alloy powder, a sintering aid shown in Table 1 and an organic binder in which methyl cellulose was dissolved in a solvent were added at a weight ratio of powder cellulose of methyl cellulose content of 0.3, and the content was adjusted to 0. Mix for 5 h.
This mixture was poured into a mold of 30 mm × 20 mm × 2 mm, dried and degreased, and then sintered in vacuum at 1300 ° C. for 10 hours to obtain a test material for density measurement and strength measurement.

Density measurement was performed on the test piece of 30 mm × 20 mm × 2 mm by the Achimedes method to determine the relative density. Strength measurement is length 30 mm x width 20 mm x thickness 2
A 3-point bending test was performed on a test piece of mm with a fulcrum distance of 16 mm to determine the bending strength.

[0014]

[Table 1]

[0015]

[Table 2]

As is clear from Tables 1 and 2, even when alloy powders having the same chemical composition are sintered under the same sintering conditions, sintering of B, CrB, NiB, FeB, etc. It can be seen that the examples of the present invention exhibit higher relative density and higher bending strength than the comparative examples in which no auxiliary agent is added.

[0017]

As described above, according to the present invention, the sinterability of a Fe-Cr-Al alloy having excellent characteristics as a filter material for exhaust gas treatment of automobile engines and boilers is improved, and the comparison is made. There is an effect that an oxidation-resistant powder sintered body having a high porosity and excellent strength can be obtained by sintering for a short time.

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Claims (2)

[Claims] 1. Cr: 15.0-30.0 wt%, A
1: 0.01 to 0.5 wt% in total of 5.0 to 25.0 wt% and at least one of Y, Hf, and rare earth elements.
%, The balance of the unavoidable impurities and Fe in the alloy powder, B: 0.01 to 1.0 wt%, CrB: 0.05 to
2.0 wt%, NiB: 0.05 to 2.0 wt%, Fe
B: An oxidation resistant powder sintered body, which is obtained by adding one or more of 0.05 to 2.0 wt% and sintering. 2. Cr: 15.0-30.0 wt%, A
1: 0.01 to 0.5 wt% in total of 5.0 to 25.0 wt% and at least one of Y, Hf, and rare earth elements.
%, An alloy powder consisting of balance unavoidable impurities and Fe, B: 0.01 to 1.0 wt%, CrB: 0.05 to
2.0 wt%, NiB: 0.05 to 2.0 wt%, Fe
B: a step of mixing one or more kinds of powder of 0.05 to 2.0 wt% with an organic binder, a step of molding, a step of drying, a step of degreasing, and a step of sintering. A method for producing an oxidation resistant powder sintered body, comprising: