JPH0436403A - Manufacture of high strength structural member - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention A1 Object of the Invention (1) Industrial Application Field The present invention relates to a method for manufacturing a high-strength structural member, particularly a method for obtaining the member by sintering (including compacting and solidifying) raw material powder. Regarding improvements.

(2) Conventional technology Conventionally, various raw material powders have been used in the above manufacturing method, but when aiming to further increase the strength of structural members, for example, amorphous single-phase alloy powder is used as the raw material powder. It is possible to use it.

The reason for this is that when the alloy powder is subjected to a thermal history higher than the crystallization temperature Tx, a fine crystal structure appears uniformly even though it is a high alloy. This is because we can expect

(3) Problems to be solved by the invention However, when the above-mentioned alloy powder is used as a raw material powder, it is difficult to sufficiently bond the powders together during sintering, and as a result, it is difficult to obtain a member with the expected strength. The problem is that it cannot be done.

In view of the above, an object of the present invention is to provide the above-mentioned manufacturing method that can firmly bond powders together to obtain a structural member with high strength and high toughness.

B0 Structure of the Invention (1) Means for Solving the Problems The present invention provides a method for manufacturing a high-strength structural member by sintering raw material powder. The first feature is that powder is used and the amount of oxygen gas diffused into the amorphous phase is set to 0.3% by weight or less.

In manufacturing a high-strength structural member by sintering raw material powder, the present invention uses an alloy powder whose surface layer portion is composed of an amorphous phase and a crystalline phase, and The second feature is that the volume fraction Vf is set to 70% or more, and the amount of oxygen gas diffused into the amorphous phase is set to 0.3% by weight or less.

(2) Functional phase The bondability between the amorphous phases of adjacent raw material powders is better than that between the crystalline phases. This is because the amorphous phase has a more irregular metal structure than the crystalline phase.
This is due to the fact that it is uniform and has a large amount of free space, making it easy for atoms to move.

1st. According to the second feature, a specific amount of oxygen gas is diffused into the free space of the amorphous phase in the surface layer of the raw material powder, so the crystallization of the amorphous phase is prevented by oxygen gas during the sintering process. It is possible to increase the apparent crystallization temperature TX by hindering the crystallization temperature.

As a result, bonding between amorphous phases of adjacent raw material powders occurs in a high temperature range exceeding their crystallization temperature Tx, and at the same time, good formability of the amorphous phase is obtained, resulting in high quality parts. Strengthening can be achieved.

Moreover, since most of the oxygen gas is discharged from the raw material powder during the crystallization process of the amorphous phase in the sintering process, it does not have any adverse effect on the structural member.

However, if the amount of oxygen gas in the amorphous phase exceeds 0.3% by weight, the oxygen gas will combine with the chemical components of the amorphous phase to form an oxide film, and the oxide film will cause the raw material powder to This is undesirable because it hinders the bonding of the two.

In addition, in the second feature, the volume fraction Vf of the amorphous phase is 7
If it is less than 0%, oxygen gas will not be sufficiently discharged during the sintering process, which is undesirable.

(3) Example Figure 1 shows a raw material powder 1, the surface layer 2 of which consists of a single amorphous phase, or an amorphous phase and a crystalline phase, and the amorphous phase has a weight of 0.3%. % or less of oxygen gas is diffused.

In this case, it is desirable that the thickness of the surface layer portion 2 is 0.1 μm or less.

As this seed raw material powder 1, an amorphous single-phase alloy powder and a mixed-phase alloy powder containing an amorphous phase and a crystalline phase are used. This mixed alloy powder includes powder in which the surface layer portion 2 is a single amorphous phase and powder in which the volume fraction Vf of the amorphous phase is 70% or more.

As an example, Aj! An amorphous single-phase alloy powder with an average diameter of less than 22 μm and a composition of 5sNis Y@Cot (values are atomic %) was selected. The crystallization temperature T of this powder
x is 299.5° C., and the product was manufactured using a high-pressure helium gas atomization method.

In addition, in the above manufacturing method, the average diameter is 22 μm or more, 4
A powder of 4 μm or less has a single amorphous phase because the surface layer is cooled more rapidly than the inside, while the inside becomes a mixed alloy powder with a mixed phase structure of an amorphous phase and a crystalline phase.

The amorphous single-phase alloy powder was heated, and the amount of oxygen gas in the alloy powder before and after heating was determined by Auger analysis and component analysis, and the results shown in FIG. 2 and Table 1 were obtained.

In Figure 2, the solid line W is for unheated cases, and the chain line X is for 350°C.
The dotted line y corresponds to the case of heating to 450°C.

In the shaded area of the solid line W and the dashed line It represents that.

In addition, a2 represents the amount of oxygen gas in the surface layer. At point 'IIAy, the shaded area as described above does not appear, and therefore oxygen gas is not diffused into the crystalline single-phase alloy powder caused by the phase change. There is no surface layer.

Table ■ In this way, in the amorphous single-phase alloy powder with a crystallization temperature Tx of 299.5°C, no oxygen gas is emitted at a heating temperature of 350°C;
The fact that the above-mentioned discharge occurs at 2 means that the crystallization of the amorphous phase is hindered by the oxygen gas and the apparent crystallization temperature Tx is increased.

FIG. 3 shows the relationship between the volume fraction vr of the amorphous phase in the surface layer 2 of the raw material powder and the oxygen gas reduction ratio due to heating. This powder is Al5sN is Y+.

The surface layer 2 is composed of an amorphous phase and a crystalline phase.

As is clear from FIG. 3, it is desirable that the volume fraction Vf of the amorphous phase in the surface layer portion 2 is 70% or more.

[Example I]

Amorphous single-phase alloy powder with an average diameter of less than 22 pm (oxygen gas amount 0.13 wt%, crystallization temperature Tx 29
9.5°C) was selected as the raw material powder.

As shown in Figure 4, a hot press device (maximum pressing force of 3
A die 5 with an inner diameter of 30- is placed inside a vacuum chamber 4 of
, put 45 g of raw material powder 1 into the die 5, set the initial load of the punch 7 on the raw material powder 1 to 10 tons, and create a vacuum degree of 3 x 10-' in the vacuum chamber 4.
The pressure was reduced to below Torr.

The raw material powder 1 is heated by the heater 6 in the reduced pressure state, and when the heating temperature reaches 400°C, the pressing force of the punch 7 is increased to 3
The temperature was increased to 0 tons, and then the heating temperature was maintained at 450° C. for 1 hour to perform sintering, thereby obtaining a structural member (2).

Structural member I has a diameter of 30 cm and a length of 20 mm as shown in Fig. 5.
It forms a short cylindrical shape of 11I11.

Similar operations were carried out using various raw material powders, and structural members
I got ■.

From each structural member 1 to
When test pieces t of m5 were cut out and a bending test was performed on these test pieces t under the condition that the distance between the supporting points was 20 m, the results shown in Table 3 were obtained.

In Table ■, A means an amorphous phase, C means a crystalline phase,
Further, the numerical values attached to A and C indicate their volume fractions Vf.

The raw material powder for the structural member (2) is obtained by heating the amorphous single-phase alloy powder to 450°C in an argon gas atmosphere.

The raw material powder in the structural member (2) has the same composition as the raw material powder in the member (2).

The raw material powder for structural members IV and V has the same composition as the raw material powder for member I, but the amount of oxygen gas exceeds 0.3% by weight.

The raw material powder for the structural member ■ is Ajl! ,,Fe.

Average diameter 26 μm with a composition of Y, (values are atomic %)
The powder is manufactured using high-pressure helium gas atomization.

The raw material powder for structural member (2) is obtained by heating the raw material powder for member (2) to 450° C. in an argon gas atmosphere.

The raw material powder for the structural member (2) has the same composition as the raw material powder for the member (2), but is obtained by pulverizing a ribbon-shaped alloy produced by a single roll method into powder with an average diameter of less than 26 μm.

As is clear from Table ■, structural members 1, 111. VI corresponds to those obtained by the present invention, and these members I,
I[[, VI has high strength and high density.

The reason why such high-strength structural members i, Dl, and Vl can be obtained is as follows.

That is, in adjacent raw material powders, the bondability between the amorphous phases is better than that between the crystalline phases. This is because the amorphous phase has a more irregular and uniform metal structure than the crystalline phase, and has more free space, making it easier for atoms to move.

According to the present invention, since 0.3% by weight or less of oxygen gas is diffused into the free space of the amorphous phase in the surface layer of the raw material powder, the crystallization of the amorphous phase is prevented by oxygen in the sintering process. It is possible to increase the apparent crystallization temperature Tx by interfering with gas.

As a result, bonding between amorphous phases of adjacent raw material powders occurs in a high temperature range exceeding their crystallization temperature Tx, and at the same time, good formability of the amorphous phases is obtained, and member 1. IIl,
This makes it possible to increase the strength of Vl.

Moreover, most of the oxygen gas is emitted from the raw material powder during the crystallization process of the amorphous phase in the sintering process, so the structural member 1
．． No adverse effect on 11I and Vl.

Structural members (1) and (2) have poor bondability and moldability between powders and low strength due to the raw material powder having a single crystalline phase.

Structural members IV and V have poor bondability between powders and low strength because an oxide film is formed on the powder surface due to the large amount of oxygen gas in the raw material powder.

Structural member (2) has poor bondability and moldability between powders and low strength due to the low volume fraction Vf of the amorphous phase in the surface layer of the raw material powder.

[Example ■]

AIl**N! A mixed phase alloy powder with an average diameter of less than 22 μm and having a composition of l Y3 (values are atomic %) was selected as the raw material powder. In this mixed alloy powder, the volume fractions Vf of the amorphous phase and the crystalline phase are each 50%, and the surface layer portion is a single amorphous phase. The amount of oxygen gas in the surface layer portion is 0.13% by weight, and the crystallization temperature Tx is 210°C.

(i) As shown in FIG. 6(a), the raw material powder 1 is put into a rubber bell body 10 consisting of a main body 8 and a lid body 9, and then subjected to cold isostatic press under a pressure of 4000 kgf/CIY. (CIP) was applied.

(ii) As shown in the same figure et al., the cold isostatic press resulted in a diameter of 58 mm, a length of 40 cm, and a density of 78%.
A short cylindrical green compact 11 was obtained.

(iii) As shown in FIG. 3C, the green compact 11 was loaded into a bell body 12 made of aluminum alloy (AA standard 6061 material). This bell body 12 has an outer diameter of 78I11
1. Consists of a main body 13 with a length of 70+m and a lid 14 welded to the opening of the main body 13, and the lid 14 is attached to the main body 1.
It has a ventilation pipe 15 that communicates between the inside and outside of 3.

(iv) As shown in FIG.
7 was loaded. In this case, the vent pipe 15 passes through the die hole 19 of the die 18 and extends into the die-type hook 20.

In the hot extrusion processing machine 16, the maximum pressing force is 500
), the inner diameter of container 17 is 80ttm, container 17
The preheating temperature was set at 470°C.

Next, a vacuum pump 21 was connected to the ventilation pipe 15 via a rubber pipe 22 to reduce the pressure inside the bell body 12. When the degree of vacuum inside the bell body 12 exceeded 10-' Torr, the stem 23 was advanced to apply a load of about 120 tons to the bell body 12 via the dummy block 24. As a result, the bell body 12 is deformed and brought into close contact with the container 17, so that the temperature of the powder compact 11 rises rapidly, reaching 450° C. in about 7 minutes.

Due to this heating, the degree of vacuum inside the bell body 12 decreases, but about 7 minutes after the temperature of the compact 11 reaches 450°C, the degree of vacuum inside the bell body 12 decreases.
−' Return to the state exceeding Torr.

The holding time at this temperature varies depending on the density, composition, structure, etc. of the green compact 11, but is set to 1 minute to 2 hours. In this embodiment, the degree of vacuum inside the bell body 12 is 10-'T.
When the temperature returned to orr, the compacted powder body 11 was extruded together with the bell body 12, and the powder was sintered to obtain a round bar-shaped structural member (2).

Similar operations were carried out using various raw material powders, and structural member X-
I got XVI.

When the tensile strength and oxygen gas amount were determined for each of the structural members (1) to (XVI), the results shown in Table (2) were obtained.

In Table ■, A means an amorphous phase, C means a crystalline phase,
Further, the numerical values attached to A and C indicate their volume fractions Vf.

The raw material powder in the structural member x-xn has the same composition as the raw material powder in the member (2).

The raw material powder for structural member X■ is Af! 1! Fe,Y
, (values are in atomic %), and has an average diameter of less than 22 μm.

The raw material powder for structural members XIV to XVI has the same composition as the raw material powder for the member X2.

As is clear from Table (2), structural members (2) and xm correspond to those obtained by the present invention, and these members L'(, Xm have high strength.

The other members x-xn and xrv to X■ have low strength for the same reason as above.

[Example ■]

Aj! A mixed phase alloy powder with an average diameter of less than 44 μm and having a composition of g*Nfs Ys (values are atomic %) was selected as the raw material powder. This mixed phase alloy powder was manufactured by an argon gas atomization method, and the surface layer portion was a single amorphous phase, the oxygen gas amount was 0.15% by weight, and the crystallization temperature Tx was 210°C.

Using this raw material powder, a round bar-shaped structural member X■ was obtained by the same operation as in Example (■).

Similar operations were carried out using other raw material powders to obtain structural member X■.

Table 2 compares the manufacturing conditions and physical properties of various structural members X2 and X2.

In Table ■, A means an amorphous phase, C means a crystalline phase,
Further, the numerical values attached to A and C indicate their volume fractions Vf.

The raw material powder for the structural member Grind under atmosphere to an average diameter of 4
It is made into a mixed alloy powder with a diameter of less than 4 μm.

As is clear from Table 2, in the structural member X2 according to the present invention, bonding at the powder interface is sufficiently performed without being affected by changes in the diameter of the die hole and therefore changes in the processing ratio, and the elongation is also large. (Also, high strength has been achieved.

On the other hand, in the comparative example, the structural member Growth is significantly lower than ■.

C0 Effects of the Invention According to the present invention, by using a powder having a surface layer of a specific structure and having the amount of oxygen gas diffused in the surface layer specified as described above, the amount of oxygen gas diffused into the surface layer is determined as described above. It is possible to obtain a high-strength structural member with good bondability and moldability.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the raw material powder, Figure 2 is an Auger analysis diagram,
Fig. 3 is a graph showing the relationship between the volume fraction Vf of the amorphous phase in the surface layer of the raw material powder and the oxygen gas reduction ratio due to heating, Fig. 4 is an explanatory diagram of the hot press equipment, and Fig. 5 is a structural member. FIG. 6 is an explanatory view of the manufacturing side of the structural member. DESCRIPTION OF SYMBOLS 1... Raw material powder, 2... Surface layer part, 3... Hot press device, 16... Hot extrusion processing machine Figure 1 Figure 3 Figure 2 Amorphous phase in the surface layer part of raw material powder Volume fraction VfC%) Figure 4 Shallow ← Depth from powder surface → Deep

Claims (2)

[Claims] (1) When manufacturing high-strength structural members by sintering raw material powder, an alloy powder whose surface layer portion is an amorphous phase is used as the raw material powder, and oxygen gas diffused into the amorphous phase is used as the raw material powder. A method for manufacturing a high-strength structural member, characterized in that the amount is set to 0.3% by weight or less. (2) When producing a high-strength structural member by sintering raw material powder, an alloy powder whose surface layer portion is composed of an amorphous phase and a crystalline phase is used as the raw material powder, and the volume of the amorphous phase is A method for manufacturing a high-strength structural member, characterized in that the fraction Vf is set to 70% or more, and the amount of oxygen gas diffused into the amorphous phase is set to 0.3% by weight or less.