JPH0860210A - Production of fe-cr-al-rem based alloy powder - Google Patents

Abstract

PURPOSE: To efficiently produce Fe-Cr-Al-REM based alloy powder by adding REM to Al-contg. Fe based molten metal after its S is decreased, then allowing the molten metal to flow from a molten metal nozzle and subjecting the molten metal to atomization with a high-pressure gas, etc. CONSTITUTION: The Fe based molten metal contg. Al, for example, the molten metal consisting of 15 to 40wt.% Cr, 3 to 10% Al, <=10% O, <=0.03% N, 0.0005 to 0.1% REM and the balance substantially Fe is allowed to flow down out of the molten metal nozzle. The high-pressure gas or high-pressure water is blown to the metal flow to atomize the molten metal, by which the alloy powder is obtd. At this time, the content of S in the molten metal is confined to <=10ppm and the content of N therein is preferably specified to 300ppm and thereafter, the REM is added thereto. The molten metal is thereafter atomized. As a result, the recovery rate of the alloy powder is improved by preventing the clogging of the molten metal nozzle by sulfide and nitride without increasing the manufacturing cost while the variation in the resulted alloy powder grains and the increase in the oxygen in the molten metal are averted.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to Fe by atomization.
The present invention relates to a method for producing a -Cr-Al-REM alloy powder.

[0002]

2. Description of the Related Art In recent years, Fe-based alloys containing Al (Fe-1
5-40% Cr-3-10% Al alloy) has excellent heat resistance and oxidation resistance, so it can be used for heater heating wire, thermal spraying, PTA (build-up welding), or automobile exhaust gas purification. It is widely used as a carrier material for catalysts.
This is because the raw material of the alloy powder contributes to the improvement of characteristics in terms of material feeding property, structure controllability, and thinning.

In the case of producing the above Fe-Cr-Al alloy powder on an industrial scale, an atomizing method is adopted from the viewpoint of production cost, which is a combination of air melting or vacuum melting and water or gas injection. The vacuum melting is limited to the production of high-purity powder. This atomizing method is a method of producing alloy powder by finely flowing molten metal from a molten metal nozzle having a nozzle diameter of 2 to 10 mmφ and injecting high pressure gas or high pressure water into the molten metal. in this case,
When the temperature of the molten metal nozzle portion decreases, the molten metal may solidify and block the nozzle. Therefore, it is necessary to control the temperature of the molten metal, the tundish, and the preheating temperature of the molten metal nozzle to control the blockage of the nozzle. Is common.

In the case of producing an alloy powder containing an active metal element such as Al, the atmosphere, refractory, etc. serve as a source of oxygen and nitrogen in the molten metal to form oxides and nitrides. Easily, these are generated on the inner wall of the melt nozzle,
In some cases, the molten metal does not flow down during the atomizing process, resulting in clogging of the nozzle. This is because the temperature of the inner wall of the molten metal nozzle becomes lower than the temperature of the molten metal, so that oxygen and nitrogen in the supersaturated molten metal become oxides and nitrides. It will be mechanically stable. These oxides and nitrides are generated and grown in the molten metal from the inner wall of the molten metal nozzle whose temperature has decreased. When the melting point of the crystallized product is higher than the temperature of the molten metal, or when the crystallized product grows in a cluster shape, the molten metal becomes difficult to flow down, resulting in clogging of the nozzle.

In order to prevent clogging of the molten metal nozzle due to the formation of such crystallized substances, conventionally, there has been a method of increasing the diameter of the nozzle or making the temperature of the molten metal higher than the melting point of the crystallized substance. . Further, a method of bubbling gas or the like from the wall surface of the nozzle to suppress the formation of crystallized substances or to heat the nozzle has been attempted.

[0006]

However, the above conventional methods of increasing the nozzle diameter and raising the temperature of the molten metal are limited because the particle size distribution of the alloy powder becomes large and the oxygen in the molten metal increases. There is. Further, the method of bubbling gas or the like through the molten metal nozzle has a problem that the structure is complicated and the manufacturing cost is increased.

The present invention has been made in view of the above conventional circumstances, and prevents clogging of the melt nozzle while avoiding variations in alloy powder particles and increase in oxygen in the molten metal, and at the same time without increasing the manufacturing cost. Fe-Cr-Al-R capable
It is an object of the present invention to provide a method for producing EM alloy powder.

[0008]

When the composition contained in the crystallized substance formed on the inner wall of the nozzle is analyzed,
It was found that a large amount of AlN was formed by the reaction between nitrogen and Al, and this AlN was the cause of nozzle clogging. Therefore, in order to suppress the formation of this AlN, the applicant of the present invention first set the nitrogen content in the molten metal to 300 p
A method of performing atomization in the state of being kept at pm or less was proposed.

On the other hand, in recent Fe-Cr-Al alloy powders, attention has been paid to the addition of rare earth elements such as La, Ce and Y (hereinafter referred to as RE) in order to improve the oxidation resistance. There is. By adding this RE, it is possible to improve various properties such as oxidation resistance, sulfuration resistance, hot workability, etc. of the alloy (Japan Institute of Metals, Vol. 18, No. 3 (1979)) Improving the performance of heat resistant alloys ").

By the way, RE is added to the Fe-Cr-Al-based molten metal, and the nitrogen content in the molten metal is adjusted to 3%.
When atomization was carried out in a state where the amount was kept at 00 ppm or less, it was found that crystallized substances grow in clusters on the inner wall of the molten metal nozzle even if the nitrogen amount is controlled, and as a result, the nozzle is clogged. FIG. 1 shows a micrograph of the inner wall of the melt nozzle. As is clear from the same photograph, it can be seen that crystallized substances are generated and grow on the inner wall of the nozzle.

The inventor of the present invention investigated and analyzed the crystallized substance when the above RE was added, and found that a large amount of sulfide was deposited. 2 to 5 each show an analysis photograph obtained by analyzing the composition contained in the crystallized substance by an X-ray microanalyzer (EPMA).

As is clear from each photograph, the above crystallized substance contains almost no oxide (see FIG. 3), and Y
And S are contained in a large amount, which shows that the above crystallized substance is a compound of Y and S (see FIGS. 4 and 5).
From this, it was conceived that the nozzle clogging due to the addition of RE can be prevented by controlling the amount of S in the molten metal, and the present invention was achieved.

According to a first aspect of the present invention, there is provided a method for producing an alloy powder by flowing a Fe-based molten metal containing Al from a molten metal nozzle and blowing a high-pressure gas or high-pressure water onto the molten metal to produce an alloy powder. A feature is that after the sulfur content is set to 10 ppm or less, a rare earth element is added, and then atomization is performed.

According to a second aspect of the present invention, in the same method for producing the alloy powder as the first aspect, the rare earth element is added after the sulfur content in the molten metal is 10 ppm or less and the nitrogen content is 300 ppm or less. And then atomize.

According to a third aspect of the present invention, the Fe-based molten metal contains Cr 15 to 40 wt%, Al 3 to 10 wt%, and oxygen 0.
10 wt% or less, nitrogen 0.03 wt% or less, rare earth 0.00
It is characterized in that the balance is 05 to 0.1 wt% and the balance is substantially Fe.

[0016]

The Fe-Cr-Al-RE according to the invention of claim 1
According to the method for producing the M-based alloy powder, the S content is 10 pp
Since the rare earth element is added in a state of being maintained at m or less, the formation of sulfide of the rare earth and S can be suppressed, the clogging of the melt nozzle due to the accumulation of the sulfide can be prevented, and the recovery amount of the alloy powder can be increased. The yield can be improved. As a result, it is possible to avoid the problems of the variation in the particle size distribution of the powder and the increase in oxygen when the conventional nozzle diameter is increased or the melting temperature is increased, and it is possible to suppress an increase in manufacturing cost.

In the invention of claim 2, since the rare earth element is added while the S content is regulated and the N content is regulated, the generation of both sulfide and AlN can be suppressed, and the powder recovery amount can be further improved. .

[0018]

Embodiments of the present invention will be described below. In this example, the result of an experiment conducted to confirm the effect of the manufacturing method of the present invention will be described.

[0019]

[Table 1]

As shown in Table 1, this experiment was conducted with Fe-2.
3% Cr-5% Al-0.03% Y alloy (Sample No. 1,
5), Fe-23% Cr-5% Al-0.03% Hf alloy (Sample No. 2,6), Fe-27% Cr-7% Al-
0.03% Y alloy (Sample No. 3, 7), Fe-27% C
r-7% Al-0.03% Hf alloy (Sample No. 4, 8)
It was adopted.

Regarding the S content, the S content was adjusted to 5 and 7 ppm or less in the raw material blending stage (Sample Nos. 2 and 3 of the present invention), and the S content was 25 in the raw material blending stage. , 30 ppm, which is slightly high, is subjected to desulfurization treatment using Ni-Ca at the time of melting, and S
The amount was adjusted to 3 and 5 ppm or less (the sample of the present invention
No. 1, 4), S amount is 15-40ppm at the compounding stage
In addition, 500 kg of each of these three types of molten steel were melted as they were without melting desulfurization (conventional sample Nos. 5 to 8). In this experiment, the rare earth element was added after the nitrogen content in the molten steel was set to 300 ppm or less.

Next, the molten steel was flown down from an alumina nozzle having a diameter of 8 mm and high-pressure nitrogen was injected into the molten steel flow to produce an alloy powder. In addition, in this experiment, in order to prevent contamination such as slag even when the nozzle is not clogged,
Atomization was completed using a stopper while leaving about 40 kg of molten steel in the tundish. Then, the recovery amount of the alloy powder thus obtained was investigated.

As is clear from Table 1, the conventional sample having the highest S content of 42 ppm before Hf (rare earth) addition
In the case of No. 6, 230 kg of alloy powder could be collected with respect to 500 kg of input raw material, which was only 46%, and clogging of the melt nozzle due to the formation of sulfide was remarkable.

Further, in the case of the conventional sample Nos. 5, 7, and 8 in which the S content was kept relatively low at 15 to 30 ppm, the powder recovery amount was increased to 53 to 75% in proportion to the reduction of the S amount. ing. This is because the production of crystallized substances such as Y and Hf decreased due to the reduction of the amount of S. However, from an industrial scale, a recovery rate of 75% is not satisfactory.

On the other hand, sample Nos. 1 to 4 of the present invention in which the S content was controlled to 3 to 7 ppm or less before adding Y and Hf.
In the case of No. 3, the atomization can be performed without blocking the nozzle, and in all cases, the powder recovery amount is significantly improved to 460 to 465 Kg, and the recovery rate is 92 to 93%.

As described above, according to this embodiment, by adding rare earth elements such as Y and Hf in a state where the amount of S in the molten metal is 10 ppm or less, generation and deposition of sulfide are suppressed. It is possible to prevent clogging of the nozzle, and thus to greatly improve the recovery rate of the alloy powder and improve the yield.

Although Y and Hf are used as the rare earth element in the above embodiment, the present invention is not limited to this, and the same effect can be obtained by adding La or Ce, for example.

[0028]

As described above, Fe according to the invention of claim 1
According to the method for producing the -Cr-Al-REM alloy powder,
Since the rare earth element was added while keeping the S content at 10 ppm or less and atomization was performed after this, it was possible to suppress the formation of sulfides and prevent clogging of the molten metal nozzle, and thus the recovery rate of the alloy powder. There is an effect that can be improved.

In the invention of claim 2, the S content is 10 pp.
Since the rare earth element was added while the N content was maintained at 300 ppm or less while the m
It is possible to suppress the generation of both AlN and to further improve the recovery rate of the alloy powder.

[Brief description of drawings]

FIG. 1 is a micrograph showing a metallographic structure of crystallized substances deposited on an inner wall of a molten metal nozzle for explaining a formation process of the present invention.

FIG. 2 is a secondary electron beam image photograph showing a metallographic structure of the crystallized substance.

FIG. 3 is an EPMA analysis photograph showing the metal structure (distribution state of O) of the crystallized substance.

FIG. 4 is an EPMA analysis photograph showing the metallographic structure (S distribution state) of the crystallized substance.

FIG. 5 is an EPMA analysis photograph showing a metal structure (distributed state of Y) of the crystallized substance.

Claims (3)

[Claims] 1. A method for producing an alloy powder by flowing down an Fe-based molten metal containing Al from a molten metal nozzle and blowing a high-pressure gas or high-pressure water to the molten metal, wherein the sulfur content in the molten metal is 10 ppm. After the following, F is characterized by adding a rare earth element and then performing atomization.
Method for producing e-Cr-Al-REM alloy powder. 2. A method for producing an alloy powder by flowing an Fe-based molten metal containing Al from a molten metal nozzle and blowing a high-pressure gas or high-pressure water onto the molten metal, wherein the content of sulfur in the molten metal is 10 ppm. Below, and nitrogen content 3
Fe-Cr-Al-characterized in that after adjusting the content to 00 ppm or less, a rare earth element is added, and then atomization is performed.
Method for producing REM alloy powder. 3. The Fe-based molten metal according to claim 1, wherein Cr is 15 to 40 wt%, Al 3 to 10 wt%, oxygen is 0.10 wt% or less, nitrogen is 0.03 wt% or less, and rare earth is 0.0005 to 0. A method for producing an Fe-Cr-Al-REM alloy powder, characterized in that 1 wt% and the balance substantially consist of Fe.