JP3121901B2 - Manufacturing method of alloy powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an alloy powder by an atomizing method, and more particularly to a method for preventing a nozzle of a molten metal from being clogged by a crystallized substance crystallized on a wall surface of the nozzle.

[0002]

2. Description of the Related Art In recent years, Fe-based heat-resistant alloys containing Y (Fe
-20 to 25% Cr-5 to 7% Al-0.005 to 1.00% Y alloy) has excellent heat resistance and oxidation resistance, and is used for thermal spraying and PTA.
It is widely used as a carrier material for catalysts for exhaust gas purification of automobiles (overlay welding). 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-Y alloy powder on an industrial scale, an atomizing method based on a combination of atmospheric melting or vacuum melting and water or gas injection has conventionally been adopted from the viewpoint of production cost. In addition, the above-mentioned vacuum melting is limited to only the production of high-purity powder. In such an atomizing method, the nozzle diameter is 2 to 10 mm
An alloy powder is produced by causing a molten metal to flow down finely from a melt nozzle of φ and injecting a high-pressure gas or high-pressure water into the molten metal. In this case, if 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 close the nozzle. Is generally prevented.

In the case of an alloy containing an active metal element such as Y or Al, for example, a molten metal component, the atmosphere, a refractory or the like serves as a supply source of oxygen and nitrogen to easily form oxides and nitrides. These are formed and grown on the inner wall of the molten metal nozzle, and the molten metal does not flow down during the atomization, and as a result, the nozzle may be blocked. This is because oxygen and nitrogen in the supersaturated molten metal become oxides and nitrides when the temperature of the inner wall of the molten metal nozzle becomes lower than the temperature of the molten metal. It becomes more stable mechanically. These oxides and nitrides are generated and grown in the molten metal from the inner wall of the molten metal nozzle at a lowered temperature. If the melting point of the crystallized material is higher than the temperature of the molten metal, or if the crystallized material grows in a cluster, it becomes difficult to flow down due to the flow of the molten metal flow, and as a result, the nozzle is clogged. Incidentally, the crystallizate of melting point, 2500 ° C. in Y ₂ O _3, 2050 ℃ in Al ₂ O _3,
2230 ° C. for AlN and the temperature of the molten metal, for example, 17
It is higher than 00 ° C. In addition, the above Fe-Cr-Al
The crystallized substance generated from the -Y alloy has Al ₂ O ₃ or AlN as a main component when Y is a small amount of, for example, 50 ppm or less, and Y ₂ O ₃ as a main component when Y is large.

Conventionally, as a method of preventing the blockage of the molten metal nozzle due to the generation of the crystallized material, a method of increasing the diameter of the molten metal nozzle or increasing the temperature of the molten metal above the melting point of the crystallized material has been known. is there. Further, a method of bubbling a gas or the like from the wall surface of the molten metal nozzle to prevent generation of crystallized substances or heating the molten metal nozzle has been attempted. Further, there is a method of using a raw material having a low O and N, and a method of reducing the amount of O and N in the molten metal by a vacuum melting method.

[0005]

However, in the above-mentioned conventional methods, the method of increasing the nozzle diameter or the temperature of the molten metal increases the particle size distribution of the alloy powder and increases the oxygen in the molten metal. There is a limit. In addition, bubbling gas or the like to the molten metal nozzle requires a complicated structure, and the method of reducing O and N has a problem that the manufacturing cost is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and it is an alloy capable of preventing clogging of a molten metal nozzle without causing variation in alloy powder or increase in oxygen in a molten metal and without increasing cost. It is intended to provide a method for producing a powder.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method for producing an alloy powder by causing a Fe-based molten metal containing Y to flow out of a molten metal nozzle and blowing a high-pressure gas or high-pressure water onto the molten metal. It is characterized in that La is added to the molten metal in such an amount that the melting point of the crystallized product becomes lower than the temperature of the molten metal.

Here, the amount of La added is such that Y in the molten metal becomes Y ₂ O ₃ , and La ₂ O ₃ -20 mol%
It is desirable to set the amount of La corresponding to Y ₂ O ₃ to 0.5 to 5 times. For example, in the case of 100 ppmY, the amount of La added is 312 to
It becomes 3125ppm.

In the method of the present invention, it is desirable to use, for the molten metal nozzle, a material which tends to disappear by erosion due to a molten metal flow. When the molten metal nozzle is formed of such a material, there is an effect of eliminating the crystallized material crystallized on the inner wall of the molten metal nozzle together with the wall surface, whereby the effect of suppressing the growth of the crystallized material can be further improved. is there. The above materials include 100% carbon, zirconia-30% carbon, zirconia-10% calcia-30%
Carbon or the like can be used, and is appropriately selected in consideration of carbon contamination of the product powder.

[0010]

According to the production method of the present invention, when an Fe-based molten metal containing Y is caused to flow out of a molten metal nozzle and high-pressure gas or high-pressure water is sprayed on the molten metal to produce an alloy powder, La is added to the molten metal. Is added in a predetermined amount, whereby the morphology of the crystallized material changes and the melting point of the crystallized material becomes lower than the temperature of the molten metal. It will be easily washed away. As a result, the crystallized substance precipitated as crystals on the inner wall of the molten metal nozzle is prevented from being generated and grown inside the molten metal by the molten flow, so that the molten metal nozzle can be prevented from being clogged. Incidentally, by the addition of La, for example, Y ₂ O ₃ changes to Y ₂ O ₃ -La ₂ O ₃ and its melting point becomes about 1550 ° C.
It is lower than 1700 ° C of e-type molten metal. As described above, according to the production method of the present invention, clogging of the molten metal nozzle can be reliably prevented only by adding La to the Fe-based molten metal containing Y, and the above-described variation in the particle size distribution of the conventional alloy powder and the molten metal It is possible to prevent an increase in oxygen inside, and to suppress an increase in manufacturing cost.

[0011]

Embodiments of the present invention will be described below. Example 1 In this example, results of an experiment performed to confirm the effects of the manufacturing method of the present invention will be described.

[0012]

[Table 1]

In this experiment, as shown in Table 1, Fe-25
% Cr-6% Al-0.01% Y alloy with La
500 kg of the sample of the present invention was prepared by adding 3%, 0.15% and 0.07% (see columns 1 to 3). Next, each of the samples of the present invention was melted at 1700 ° C. by melting in the air, and was discharged from a melt nozzle composed of zirconia + 30% carbon, and high-pressure nitrogen was injected into the melt nozzle to produce an alloy powder. Then, the recovered amount of the alloy powder was examined. Further, for comparison, a comparative sample containing only the above alloy (see column 4), a comparative sample obtained by adding 0.01% of La to the above alloy (see column 5), and a melt nozzle made of only zirconia containing the above alloy flowed out. A conventional sample (see column 6) was prepared and the amount of recovery was examined in the same manner.

As is clear from Table 1, in the case of the conventional sample (column 6) using a molten metal nozzle made of zirconia, only 50 kg of the alloy powder could be recovered with respect to 500 kg of the charged amount. Obstruction is significant. In addition, a comparative sample using zirconia + carbon for the melt nozzle (No. 4)
Column), the recovered amount is 400 kg, which is higher than that of the conventional sample. This is because the crystallization disappeared together with the wall surface of the molten metal nozzle due to the carbon. Furthermore, La
In the case of the comparative sample (column 5) to which 0.01% was added, although the recovered amount was slightly improved to 410 kg, the result was insufficient because the La amount was small. On the other hand, in the case of the sample of the present invention (columns 1 to 3), the recovered amount was
A recovery rate of 455 to 475 kg and over 90% has been obtained. As described above, by adding a predetermined amount of La, the crystallized substance Y
_{Since 2} O ₃ changes to Y ₂ O ₃ -La ₂ O ₃ and has a melting point of about 1550 ° C., it is lower than 1700 ° C. of the molten metal.
As a result, the crystallized substance is easily melted in the molten metal, so that it is possible to prevent the molten metal nozzle from being blocked. Here, it was confirmed that the product powder obtained by adding La also improved in heat resistance.

[0015]

As described above, according to the method for producing an alloy powder according to the present invention, an Fe-based molten metal containing Y is caused to flow out of a molten metal nozzle, and a high-pressure gas or high-pressure water is blown onto the molten metal to form an alloy. Since La is added to the molten metal during the production of the powder to lower the melting point of the crystallized material compared to the molten metal, the generation and growth of the crystallized material can be suppressed accordingly, and the clogging of the molten metal nozzle can be prevented. .

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B22F 9/08

Claims (1)

(57) [Claims] 1. A method for producing an alloy powder by causing a Fe-based molten metal containing Y to flow out of a molten metal nozzle and blowing a high-pressure gas or high-pressure water on the molten metal, wherein La is added to the molten metal, A method for producing an alloy powder, wherein the melting point of the alloy is lower than the temperature of the molten metal.