JPH06279811A - Production of fe-cr-al alloy powder - Google Patents

Abstract

PURPOSE:To efficiently produce a Fe-Cr-Al alloy powder having a high quality by allowing molten metal of an Fe base contg. Al to flow from a molten metal nozzle in a low-nitrogen content state and blowing a high-pressure gas or high- pressure water. CONSTITUTION:The alloy powder is obtd. by allowing the molten metal of the Fe base contg. the A1 to flow down from the molten metal nozzle and blowing the high-pressure gas or high-pressure water to this molten metal. The molten metal is atomized the state of maintaining the nitrogen content in the molten metal at <= 300ppm at that time. Consequently, the formation of AIN in the molten metal is suppressed. As a result, the clogging of the molten metal nozzle is prevented and the Fe-Cr-Al alloy powder is produced at a high yield without increasing the production cost while variations in the alloy powder grains and an 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 F by the atomizing method.
The present invention relates to a method for producing an e-Cr-Al alloy powder, and more particularly, to a method for preventing clogging of a melt nozzle while avoiding variation in particle size distribution of alloy powder and increase in production cost.

[0002]

2. Description of the Related Art In recent years, Fe-based alloys containing Al (Fe-20
〜40% Cr-3〜10% Al alloy) has excellent heat resistance and oxidation resistance, and is suitable for heater heating wire, thermal spraying, PTA (build-up welding), or as a catalyst for automobile exhaust gas purification. Widely used as a carrier material. This is because the raw material of the alloy powder contributes to the improvement of characteristics in terms of material feedability, structure control, and thinning. In the case of producing this Fe-Cr-Al alloy powder on an industrial scale, conventionally, an atomizing method using a combination of air melting or vacuum melting and water or gas injection has been adopted from the viewpoint of manufacturing cost. The vacuum melting is limited to the production of high-purity powder. The 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, the temperature of the molten metal, the tundish, and the preheating temperature of the molten metal nozzle are controlled to block the nozzle. Is generally prevented.

Further, in the case of producing an alloy powder containing an active metal element such as Al, the molten metal component, the atmosphere, the refractory, etc. serve as a source of oxygen and nitrogen to form oxides and nitrides. In some cases, these may be generated and grown on the inner wall of the molten metal nozzle, and the molten metal may not flow down during atomization, resulting in clogging of the nozzle. this is,
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 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. If the melting point of the crystallized product is higher than the temperature of the molten metal, or if the crystallized product grows in clusters, it becomes difficult for the molten metal to flow down, resulting in clogging of the nozzle.

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

[0005]

However, in the above-mentioned conventional manufacturing method, when the nozzle diameter is increased or the molten metal temperature is increased, the variation in the particle size distribution of the alloy powder becomes large, and in addition, in the molten metal, There is a limit due to the increase in oxygen. Further, heating the molten metal nozzle or bubbling gas or the like into the nozzle has a problem that the manufacturing cost increases because the structure becomes complicated.

The present invention has been made in view of the above-mentioned conventional circumstances, and it is possible to prevent clogging of the melt nozzle while avoiding variations in alloy powder particles and increase in oxygen in the molten metal, and without increasing manufacturing costs. It is an object of the present invention to provide a method for producing an Fe-Cr-Al alloy powder.

[0007]

The present inventors have found that when atomizing a Fe-based alloy containing Al as described above, it is easy to form oxides and nitrides on the inner wall of the molten metal nozzle, so that the nozzle clogging part The crystallized substances of the above were investigated and analyzed. FIG. 1 shows micrographs of the crystallized substances formed on the inner wall of the melt nozzle, and FIGS. 2 to 5 show photographs of the composition of the crystallized substances analyzed by an X-ray microanalyzer (EPMA). As is clear from each figure, the crystallized substance contains almost no oxygen (see FIG. 5) and contains a large amount of nitrogen (see FIG. 4). As a result, this nitrogen reacts with Al to form a large amount of AlN (see FIGS. 2 and 3), and this AlN causes nozzle clogging. By the way, the melting point of AlN is 2230 ° C.,
The temperature of the molten metal is higher than, for example, 1700 ° C. From this, the inventor of the present invention has conceived that the production of AlN can be suppressed by positively reducing the nitrogen content in the molten metal, and that the clogging of the molten metal nozzle can be prevented, and the present invention has been accomplished. .

Therefore, the present invention provides 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 to the molten metal to produce an alloy powder. The feature is that atomization is performed in a state where the amount is kept at 300 ppm or less.

Here, in order to maintain the above nitrogen content at 300 ppm or less, for example, a material having a low nitrogen content is used as a melting raw material, the molten metal surface is covered with flux, and further the melting furnace is set to Ar. A method of sealing with gas and thereby suppressing absorption of nitrogen in the air can be adopted.

[0010]

According to the method for producing the Fe-Cr-Al alloy powder of the present invention, the amount of nitrogen in the molten metal is regulated to 300 ppm or less. Therefore, the amount of the reduced amount of nitrogen produces AlN in the molten metal. Therefore, the growth can be suppressed, and consequently the clogging of the melt nozzle due to the deposition of the AlN can be prevented. as a result,
The yield can be improved by increasing the recovery amount of alloy powder. Further, in the present invention, the nitrogen content can be maintained within the above range by covering the molten metal surface with flux or by sealing by blowing Ar gas, so that the conventional nozzle diameter can be increased and the melting temperature can be increased. It is possible to avoid variations in the alloy powder grain and increase in oxygen due to the above-mentioned changes, and to suppress an increase in manufacturing cost.

[0011]

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

[0012]

[Table 1]

In this experiment, as shown in Table 1, Fe-23% Cr-5% Al alloy and Fe-27% C were used as raw materials.
The r-7% Al alloy was adopted and compounded so that the nitrogen content in each raw material would be 55 to 200 ppm to prepare samples of the present invention (Sample Nos. 1 to 4). Next, put each of the above samples in the melting furnace.
Injecting 500 kg, the surface of the sample was sealed with flux, and the melting furnace was sealed with Ar gas to prevent absorption of nitrogen from the air, and was melted in the atmosphere at 1700 ° C. This kept the nitrogen content in the molten metal at 90 to 260 ppm. Then, in this state, the molten metal was flown down from a molten alumina nozzle, and high-pressure nitrogen was injected into the molten stream to produce an alloy powder. The recovery amount of the alloy powder thus obtained was investigated.

For comparison, a comparative sample (Sample N) was prepared by blending the raw materials so that the amount of nitrogen was 45 to 320 ppm.
o. 5-8) was created. Of these comparative samples, sample Nos. 5 and 7 were atomized while sealing with flux and Ar gas, and sample Nos. 6 and 8 were atomized without sealing as before to produce alloy powder, and recovered in the same manner. I checked the quantity.

As is clear from Table 1, in the case of Comparative Sample No. 8 in which the amount of nitrogen in the raw material was as high as 310 PPm and atomization was performed without flux and Ar gas seal, the amount of nitrogen in the molten steel was The amount increased to 630 ppm, and therefore the recovery amount was extremely small at 70 kg, and clogging of the melt nozzle due to AlN deposition was remarkable. Also, the amount of nitrogen in the raw materials is 45 ppm
In the case of Comparative Sample No. 6 which was atomized in a low state and without the above-mentioned seal, the amount of nitrogen increased during atomization, and therefore the recovery amount was 250 kg, which was an unsatisfactory result.

Also, the amount of nitrogen in the raw material is 295ppm, 320ppm
In the case of Comparative Sample Nos. 5 and 7 which were atomized while being sealed with flux and Ar gas in a high state, the recovery amounts were 340 kg and 230 kg, respectively. This is because the amount of AlN deposited was reduced by suppressing the absorption of nitrogen during atomization.

On the other hand, the amount of nitrogen in the raw material is 62 to 200 p
In the case of Sample Nos. 1 to 4 of the present invention, which was atomized while being set to pm and sealed with flux and Ar gas, the nitrogen content in the molten metal was as low as 90 to 260 ppm in all the samples. As a result, the recovery amount of each sample No. 1-4 is 435-470K.
It is significantly improved to g and the recovery rate is 87% or more.

As described above, according to this embodiment, by performing atomization while controlling the amount of nitrogen in the molten metal to 300 ppm or less, it is possible to suppress the generation and growth of AlN and prevent clogging of the molten metal nozzle. The recovery rate of the alloy powder can be significantly improved, which in turn can improve the productivity.

[0019]

As described above, Fe-Cr- according to the present invention
According to the method for producing an Al-based alloy powder, atomization was performed in a state where the nitrogen content in the molten metal was kept at 300 ppm or less, so it is possible to suppress the formation and growth of crystallized substances and prevent clogging of the melt nozzle. There is an effect, and there is an effect that the recovery rate of the alloy powder can be improved.

[Brief description of drawings]

FIG. 1 is a micrograph showing a crystal structure of a crystallized substance deposited in a molten metal nozzle for explaining a formation process of the present invention.

FIG. 2 is a secondary electron beam image photograph showing a crystal structure of the crystallized product.

FIG. 3 is an Al line image photograph showing a crystal structure of the crystallized product.

FIG. 4 is an N-ray image photograph showing the crystal structure of the crystallized product.

FIG. 5 is an O-ray image photograph showing the crystal structure of the crystallized product.

Claims (1)

[Claims] 1. 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 to the molten metal, wherein the nitrogen content in the molten metal is 300 ppm. A method for producing Fe-Cr-Al based alloy powder, characterized in that atomization is carried out in a state of being held below.