JPS61221303A - Production of oxide dispersed fe high alloy - Google Patents

Abstract

PURPOSE:To produce efficiently an oxide dispersed Fe high alloy having high density and uniform quality by mixing the pulverous powder of a metallic oxide having an adequate grain size at a specific ratio with Fe high alloy powder, packing the mixture in a vessel, disposing an explosive to the side part of the vessel and exploding said explosive. CONSTITUTION:0.2-3.0wt% Metallic oxide powder having <=1mum, more preferably about <=0.5mum grain size is uniformly mixed with the Fe high alloy powder contg. about >=90% powder having about 100 mesh undersize, more preferably 250 mesh undersize and about 5-40mum grain size. The resulted powder mixture 1 is packed into the cylindrical vessel 2 made of iron, aluminum, paper, etc. and a circular conical cap 3 is put thereon. The vessel is disposed in a cylindrical body 4 made of cardboard, etc. The explosive is then packed into a space 5 between the vessel 2 and the body 4 and is exploded by a detonator 6. The powder 1 is compressed together with the vessel 2 by the explosive powder. The oxide dispersed Fe high alloy which has the density of >=90% of the true denity and is uniformly dispersed with the metallic oxide in the alloy base having the uniform quality is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to a method for producing a Fe-based bulky alloy. (Prior art and its problems) Recently, in order to improve the properties such as oxidation resistance and high-temperature strength of high-temperature Fe-based alloys, high-alloy alloy bases have been developed. The development of composite alloys in which oxide particles are dispersed is gaining momentum. Since it is impossible to obtain a homogeneous composite alloy structure for this type of composite alloy by a so-called melting process in which the alloy is solidified from a molten state, manufacturing by a powder metallurgy method is being considered.

By the way, in order to manufacture high-performance alloys such as heat-resistant alloys, it is necessary to increase the density of the sintered body to near the true density.
When attempting to produce this type of oxide-dispersed Fe-based high alloy by the conventional powder metallurgy method of press-molding raw material powder to form a green compact and then sintering, oxide powder is used as the raw material powder. Moreover, since the master alloy contains a large amount of alloying elements, the compression moldability of the powder is poor, making it difficult to obtain a high-density alloy.

In response, attempts have been made to manufacture this type of composite alloy by means of high-temperature pressure forming (hot press) and high-temperature isostatic pressing (HIP), but hot press and HIP have low production efficiency and are costly. This method has disadvantages such as being expensive and has not been adopted as a practical manufacturing method.

(Problems to be Solved by the Present Invention) In view of the above, the present invention provides an efficient method for producing an oxide-dispersed Fe-based high alloy in which metal oxide particles are finely and uniformly dispersed and has a density close to the true density. The purpose is to provide a practical method that can be obtained.

(Technical means of the present invention and its effects) The present invention provides metal oxide powder with a powder particle size of 1 μm or less of Fe-based high alloy under a 100 mesh sieve of 0.2 to 3.0 (by weight)
% mixed powder is filled into a container, and an explosive is placed on the side of the container and detonated to compress and fix the mixed powder together with the container to form a molded body having a density of 90% or more of the true density. By adopting the method of the present invention, a mixed powder of high alloy powder and metal oxide powder, which has poor compression moldability, is used as a raw material powder. However, it becomes possible to easily obtain a high-density oxide-dispersed Fe-based high alloy having a homogeneous and dense alloy matrix without going through a sintering process.

An example of an alloy forming apparatus used for carrying out the present invention is shown in FIG. The mixed powder 1 serving as the raw material is mixed in advance as uniformly as possible using a ball mill or the like. A container 2 filled with mixed powder 1 is a cylindrical body made of iron, aluminum, or paper, and a conical cap 3 is placed on the top of the container to disperse the explosion pressure. Said container 2 is surrounded by a cylinder 4, preferably of a cardboard layer, between which a space 5 is formed. space 5
is loaded with explosives, which are detonated by the detonator 6 at the top, and the mixed powder 1 is compressed together with the container 2 by its energy and is fixed at high density. Hereinafter, this will be referred to as an explosive molded product. After the explosion molding, the container portion is removed and the explosive molded body is taken out.

Since the explosive compact obtained by the method of the present invention is a mixture of a high-alloy mother alloy powder and a metal oxide powder that is compressed and fixed by explosive pressure, it has a high density of 90% or more of the true density. None, metal oxide particles can be finely and uniformly dispersed in a homogeneous alloy base.

Therefore, it has good corrosion and oxidation resistance properties, and the mixed metal oxide powder particles are uniformly and finely dispersed in the alloy matrix, improving the oxidation resistance properties of the alloy when used in high-temperature conditions, and improving the crystal grain size. It shows a remarkable effect of suppressing growth and acts effectively in maintaining good mechanical strength.

In the present invention, the use of Fe-based high alloy powder obtained by water atomization or other conventionally known rapid solidification methods means that the master alloy powder itself containing a large amount of alloying elements is used. It is particularly effective in making the alloy base homogeneous and improving the homogeneity of the obtained alloy matrix.

In the present invention, if the powder particle size of the Fe-based high alloy is excessively large, the uniformity of the dispersion state of the metal oxide in the alloy base will be impaired, so the particle size is below 100 mesh sieve, preferably below 250 mesh sieve. A Fe-based high alloy powder is used in which about 90% or more of the powder has a particle size of 5 to 40 μm.

Furthermore, if the particle size of the metal oxide powder is excessively large, the effect of improving the oxidation resistance and mechanical properties of the alloy will not be sufficiently improved. Therefore, in the present invention, the particle size of the metal oxide powder used is 1.0 μm or less, preferably 0.5 μm or less.

If the amount of metal oxide powder is less than 0.2% (by weight), the above-mentioned effects such as suppressing grain growth and improving strength cannot be obtained sufficiently, and if it is added in a large amount exceeding 3% (by weight), it may actually weaken the alloy. This tends to make the material brittle, and the negative effects such as lowering workability in subsequent steps or not being able to obtain the desired high density increase. Therefore, in the present invention, the amount of metal oxide powder added is in the range of 0.2 to 3% (by weight).

In the present invention, Fe-based high alloy powder containing a large amount of alloying elements is used, and a mixed powder obtained by mixing this with a predetermined amount of metal oxide powder is used as a raw material powder.

Here, the Fe-based high alloy powder contains at least Cr, Mn
, Co, Ni, AQ, Mo, V, W, Nb, Zr, C
A total of 20 (20) of one or more of e, Ti, and Ta
(wt)% or more, and Fe-based alloy powder containing such a large amount of alloying elements has poor compression moldability, and cannot be formed into a high-density sintered body (composite body) depending on the conventional powder metallurgy method. However, according to the present invention, it is possible to easily form a composite alloy molded product having a high density close to the true density.

Further, metal oxide powders include Y, La, and Ce.

It is effective to use one or more metal oxides such as Th, Zr, Hh, and AQ.

(Example) Next, powder of Fe-based high alloy was prepared as Fe-A Q-C.
The r-based high-alloy powder is used as a metal oxide powder to form Y oxide (
yz Off ) powder is used. An alloy consisting of 5% AQ, 24% Cr, and the remainder substantially Fe is melted, and the particle size is 5 to 40 μm under a 350 mesh sieve using the conventional water atomization method. The alloy powder was made up of 90% or more of the powder.

To the above alloy powder, 0.2, 0, 5, 1, 3.5 (weight) % of Y2O powder having a particle size of 0.5 μm or less was added, and the mixture was mixed in a ball mill for 25 hours. Each of the mixed powders thus prepared was filled into a cylindrical iron container 2 with an inner diameter of 10.7 mm and a wall thickness of 1 mm, and a conical cap 3 was placed on top to form a space 4 around the container 2. A paper cylinder 5 is arranged, gunpowder is filled between the container and the paper cylinder, a detonator 6 is installed on the top, the ignition switch is used to ignite and explode, and the energy is used to compress the entire container 2. The mixed powder was solidified to obtain an explosive compact.

In addition, the explosive speed is 2100 to 2400 m/see.
The weight ratio of explosive to mixed powder is approximately 1.
I gave it a 5. The explosion compacted product obtained by adding 0.2 to 3.0% (by weight) of Y2O has a density of 95% or more of the true density, and the metal oxide particles are uniformly and finely distributed in the alloy matrix. It had an alloy structure with a dispersed and extremely dense structure.

Figure 2(a) shows an example of the microstructure of the obtained alloy.
The microscopic structure of the sample containing 0.5% 2O powder is shown. Furthermore, the density of the material containing 5% (by weight) of Y2O3 was 85% of the true density, which was a rather low value.

In Figure 3, the same raw material powder as shown in Figure 2 (8) is molded into a green compact using a conventional powder metallurgy method at a compacting pressure of 6t/Cff12, and this is then molded in a vacuum at 1250℃XIH.
The microscopic structure of the alloy obtained by sintering R (comparative alloy A) is shown. In the figure, the black parts are pores, and the density is much higher than that in Figure 2 (a). (69% of true density).

Each explosion-molded article obtained by the method of the present invention as described above was heated in the atmosphere at 1200° C. for 20 hours and subjected to an oxidation test. An example of the microscopic structure of the alloy shown in FIG. 2(a) after an oxidation test is shown in FIG. 2(b).

In addition, FIG. 4(a) shows a sample obtained by bombardment molding using Fe-AQ, -Cr alloy powder having the same composition and particle size structure as that used in the above example without mixing metal oxide powder. The microscopic structure of the alloy (comparative alloy B) in the explosively formed state is shown, and FIG. 4(b) shows the microscopic structure of the comparative alloy B after being heated in the atmosphere at 1200° C. for 20 hours. Figure 2 (a), (b) and Figure 4 (a)
, (b), the alloy obtained by the method of the present invention shows very little growth of crystal grains and maintains a fine crystal structure even when exposed to high temperatures for a long time. Therefore, the material does not become brittle when used at high temperatures, and an alloy particularly suitable for high-temperature applications can be obtained.

In the above example, Fe-AQ-C was used as Fe-based high alloy powder.
An example using r-based alloy powder is shown.

When this kind of Fe-AQ-Cr-based alloy is used in an oxidizing atmosphere, it easily forms a film mainly composed of Al2O2 on its surface, making it a highly oxidation-resistant alloy.
Although it is gold, its use has been limited because it does not have sufficient mechanical strength at high temperatures. If this type of Fe-AQ-Cr-based master alloy powder is used as the Fe-based high alloy powder in the method of the present invention, oxide fine particles will be finely and uniformly dispersed in a homogeneous alloy matrix with good oxidation resistance. Since the composite alloy has a dense microstructure, it is possible to obtain an alloy that has excellent oxidation resistance and improved high-temperature strength, and is particularly suitable for high-temperature applications.

Table 1 shows each oxide dispersion F obtained in the above examples.
1200 for e-based high alloy Y, O,: 0.5 to 3% addition) and alloy obtained by conventional melting method (comparative material)
The results of the oxidation test at °C show that each oxide-dispersed Fe-based high alloy according to the present invention has extremely good oxidation resistance properties (oxidation weight gain), and the oxidation weight gain is higher than that obtained by conventional melting methods. It is about 172 to 1/3 of that of the alloy.

Table 1: Present invention: Fe-5A-L8Cr Y, 03. ,．
Added 0.5-3% * Comparison material: Fe-5A-18Cr
(Without the addition of oxides) In addition, Fe suitable for the above purpose
-AQ -Cr-based high alloy powder is A(3-12(
% by weight, 18 to 35% by weight of Cr, and the balance is preferably Fe.

Here, AQ is less than 3%.

If the Cr content is less than 18%, desired oxidation resistance properties cannot be obtained.

Furthermore, as the content of Ail and Cr increases, the oxidation resistance of the alloy improves. In the present invention, rapidly solidified master alloy powder can be used as the raw material powder, so a large amount of A/l and C can be used as compared to the conventional melting method.
There is an advantage that a master alloy powder containing r in a supersaturated state can be used. However, if AQ exceeds 12% and Cr exceeds 35%, the resulting alloy becomes brittle, so the upper limits of AQ and Cr are set at 12% and 35%, respectively.
%.

It should be noted that the oxide-dispersed Fe-based high alloy obtained by the present invention can be directly provided to processing processes such as cutting, rolling, and wire drawing without going through a special sintering process after the explosive molding process to produce the final product. Can be processed.

Therefore, for example, the above-mentioned Fe, which has excellent oxidation resistance,
-AQ -Cr-based alloy powder is used as raw material powder.

Fe-AQ with good oxidation resistance and mechanical strength
The method of the present invention can be applied to the production of -Cr-based electrical resistance heating wires or strips.

In the above embodiment, an example was described in which Fe-based high alloy powder containing AQ and Cr was used as the alloying element, and Y2O3 was used as the metal oxide powder, but the present invention is not limited to this, and other alloying elements Fe-based high alloy powder containing
Similar effects can be obtained when one or more of oxide powders such as Th, Zr, Hf, or A2 are used.

(Effects) As explained above, the method of the present invention improves the efficiency of Fe-based high alloys with a composite structure that has a high density close to the true density and in which metal oxide particles are finely and uniformly dispersed in a dense matrix. It makes it possible to manufacture it well, and its industrial value is great.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of an apparatus used for carrying out the method of the present invention, and FIG.
FIG. 2(b) shows a microscopic structure of an example of an oxide-dispersed high alloy according to an embodiment of the present invention obtained using a base alloy powder, and also shows the microscopic structure after heating. FIG. 3 shows the microstructure of an alloy sintered by conventional powder metallurgy methods. FIG. 4 shows a microscopic structure of a Fe-AQ-Cr alloy that was explosively formed without mixing metal oxide powder. FIG. 4(a) shows the structure as it is after explosion molding, and FIG. 4(b) shows the structure after high-temperature heating. In the diagram: 1. ,, mixed powder 219. Container 310. Cap 4000 Cylindrical wall 500. Space (explosives filling part) 600. detonator

Claims (1)

[Claims] 1) Fe-based high alloy powder under a 100 mesh sieve with a particle size of 1 μm
Fill a container with a mixed powder of 0.2 to 3.0% (by weight) of the following metal oxide powders, place an explosive on the side of the container, detonate it, and compress the mixed powder together with the container. A method for producing an oxide-dispersed Fe-based high alloy, the method comprising: fixing it to form a compact having a density of 90% or more of the true density. 2) the Fe-based high alloy powder contains 3 to 12% (by weight) of Al;
It is an alloy powder consisting of 18 to 35% (by weight) of Cr, the balance being substantially Fe, and the metal oxide powder is Y, La, Ce,
The method for producing an oxide-dispersed Fe-based high alloy according to claim 1, wherein the oxide powder is one or more selected from Th, Zr, Hf, and Al oxide powders.