JP3358685B2 - Manufacturing method of low thermal expansion sintered alloy - 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 a low thermal expansion sintered alloy which is used in alignment with a ceramic material or stainless steel mounted on a communication device or a computer peripheral device. In this specification, Mo represents molybdenum, W represents tungsten, Cu represents copper, Sn represents tin, P represents phosphorus, Si represents silicon, Al represents aluminum, and Zn represents an element symbol of zinc. ing. [Detailed description of the invention]

[0002]

2. Description of the Related Art Invar (36% Ni--Fe) or Kovar (29% Ni-1) is used as a metal material having a low coefficient of thermal expansion.
7% Co-Fe). These are expensive and have poor machinability, and their use is restricted because various kinds of models used dislike magnetic influence. Mo-Cu alloys and W-Cu alloys are materials known as sintered contact materials and electrode materials, and W-based alloys are materials known as electrode materials and heavy metal alloys, but are also materials with low thermal expansion. Since Mo, W, and Cu do not alloy with each other, they are made by powder metallurgy and have an uneven structure.
The coefficient of thermal expansion can be adjusted by the Cu content.
A material having a low u content shows a value close to the coefficient of thermal expansion of Mo or W.

[0003] This Mo or W base sintered alloy has a grain size of 1
A method in which Mo or W powder of 0 μm or less and fine Cu powder are mixed at a predetermined ratio, and the granulated powder is compacted if necessary, and sintered (liquid phase sintering) at a temperature at which Cu is melted. Alternatively, it is manufactured by a method in which Cu is infiltrated into the green compact of Mo or W powder. In the latter case, it is difficult to control the amount of Cu, and excess Cu remaining on the surface must be removed by cutting. Therefore, the former method is suitable for manufacturing a component having a complicated shape.

[0004]

The use environment of parts made of low thermal expansion material used in alignment with ceramic materials and stainless steel has been diversified, and the demands on the performance and shape of the parts have become strict. With respect to components mounted on equipment, reductions in size and weight, reduction in cutting work, improvement in dimensional accuracy of components, improvement in corrosion resistance, reduction in cost, and the like are further demanded. That is, if the alloy does not deform with high dimensional accuracy even after liquid phase sintering, the component shape can be formed by powder molding. In addition, although machining of parts is a factor of high cost, cutting may be more rational in order to obtain high dimensional accuracy due to its complicated shape, and good cutability is also required. Further, Mo and W oxidize when left in the air, but may be subjected to lapping or tapping when the component is mated with a mating member, particularly when the temperature and humidity are high, and the corrosion resistance of the processed surface is also low. is necessary.

[0005] The conventional method of liquid phase sintering a green compact of the Mo powder or a mixture of the W powder and the Cu powder is superior in the formability as compared with the infiltration method. When a normal powder having a particle size of 10 μm or less is used, such as a powder for manufacturing a cemented carbide, the powder tends to seize with a metal mold during compaction,
There is a complication that the powder must be granulated with a resin or the like to improve it. During liquid phase sintering, M
The o-particles or W-particles are liable to be deformed or changed in size due to movement, and the desired dimensional accuracy cannot be obtained. Therefore, the number of locations requiring cutting is increased, resulting in high cost. On the other hand, when a powder having a coarse particle size of Mo powder or W powder is used, the deformation is relatively small, but it is pointed out that there is a problem in the corrosion resistance in lapping or tapping.

[0006] In order to improve such a situation, an object of the present invention is to provide low thermal expansion, good corrosion resistance and good machinability,
Moreover, it is an object of the present invention to provide a sintered part having a small dimensional variation due to sintering and a high dimensional accuracy. Further, other objects will be clarified sequentially in the contents described below.

[0007]

To achieve SUMMARY OF to the above objects, a method for manufacturing a low-thermal expansion sintered alloy according to the present invention, M
It is made by crushing a porous sintered body of o or W and has a particle size of 4
Skeleton with 0-300 μm and air holes in powder
Mo powder or W powder, and Cu powder or the following
Make up some of the Cu alloy powder or its Cu alloy composition
Powder of the mixed powder with the metal powder
Liquid phase sintering by heating above the melting point (claim 1);
Porosity 20-30% of the sintered alloy to be (density ratio 70
80%) (claim 2) . (B) 0.5 to 9% Sn, balance Cu (b) 0.5 to 9% Sn, 0.03 to 0.5% P, balance Cu (c) 0.5 to 9% Sn, 1 to 3 % Si, balance Cu (d) 5 to 11% Al, balance Cu (e) 1 to 50% Zn, balance Cu (f) 1 to 50% Zn, 0.5 to 9% Sn, balance Cu (g) 1 -50% Zn, 1-3% Al, balance Cu

Further, the above-mentioned porous sintered body of Mo or W
Are primary particles of Mo or W having an average particle size of 0.5 to 10 μm.
Powder in a reducing gas atmosphere at a temperature of 1000 to 2000
It is obtained by heating at a temperature of ° C. (Claim 3) .

The cross-sectional structure of the Mo phase or W phase of the sintered alloy obtained in the present invention is similar to that of the cross section of the sintered filter material.
A structure in which powder particles of a porous cross-sectional structure (sponge-like cross-sectional structure) in which primary particles are sintered and aggregated are aggregated in a bridge shape, and Cu or Cu alloy depends on its content and the density of the compact. Therefore, it exists around the Mo or W powder particles, the pores between the powder particles, and some or all of the pores in the powder particles . Pores in the sintered alloy are almost non-existent or less than 30% by volume.

In this case, both Mo and W have the same thermal expansion coefficient, but W is relatively inexpensive and has a high specific gravity.
Considering that Mo is relatively expensive and has a low specific gravity, and that the Cu alloy has a lower melting point and lower corrosion resistance and lower thermal conductivity than Cu, and that W or Mo depends on the required thermal expansion coefficient and cost. And the content of Cu or Cu alloy are appropriately determined.

The Mo powder or the W powder used in the production of a sintered alloy is prepared, for example, by mixing primary particles having an average particle size of 0.5 to 10 μm conventionally used as a contact material or the like in a reducing gas atmosphere. A sintered powder obtained by pulverizing a spongy sintered body obtained by heating at 1000 to 2000 ° C., wherein primary particles of Mo or W grow and grow as the powder sintering temperature increases. The particle size of the pulverized powder is 40 to 300
It is porous at μm, and the powder surface is uneven.

The influence of the sintering temperature in producing the above-mentioned Mo or W sintered powder is as follows. When the sintering temperature is less than 1000 ° C., a large amount of generated fine powder when pulverized, sinter agglomeration powder not be obtained efficiently, also when the compacted, sintered agglomerated powder collapses, the liquid phase sintering The connection state becomes the same as the conventional one. On the other hand, at temperatures exceeding 2000 ° C,
It is not preferable because the coarsening of the particles and the number of closed pores increase, the sintering cost increases, the pulverization becomes difficult, and the density of the sintered alloy decreases. Therefore, it is more preferable to set the sintering temperature in the range of 1000 ° C to 2000 ° C.

[0013]

In the above construction, W and Mo are low thermal expansion metals having substantially the same thermal expansion coefficient. Mo has a lower specific gravity than W, and thus is suitable for a case where light weight is required. If the W powder or the Mo powder is fine as in the past, the particles are in a state where they can move together with the liquid phase during the liquid phase sintering, so that they are easily deformed and the sintering dimensional change and dimensional variation are large.
With the sintered skeleton-like powder powder <br/> as in the present invention production process, because the green compact of the skeleton-like powder forms a skeleton like a bridge, a liquid phase around occurs Even if it is difficult to move, deformation is reduced. Further, the sintering dimensional change rate becomes smaller as the sintering temperature in the production of W powder or Mo powder becomes higher, and the variation in dimensional change also becomes smaller.

[0014] Cu or a Cu alloy is a bonding material and acts as a thermal expansion coefficient adjusting material. In this case, the coefficient of thermal expansion functionally increases as the content of Cu or Cu alloy increases. In general, Cu alloys are better than Cu alloys in terms of corrosion resistance and sintering temperature.

The Cu—Sn alloy has a Sn content of 0.5%
If it is less than 10%, the corrosion resistance and mechanical strength are almost the same as pure Cu. If it exceeds 9%, the mechanical strength decreases due to the formation of the δ phase and the machinability deteriorates, so Sn is 0.5 to 9%. Is preferred.

P improves the corrosion resistance and mechanical strength of the Cu—Sn alloy. If the content of P is less than 0.03%, the effect is not recognized, and if it exceeds 0.5%, an intermetallic compound of P and Cu is generated to lower the mechanical strength and machinability. It is preferably 0.03 to 0.5%.

[0017] Si improves the corrosion resistance and mechanical strength of the Cu-Sn alloy. If the content of Si is less than 1%, the effect is not recognized. If the content exceeds 3%, mechanical strength and machinability are reduced, wettability with Mo or W is deteriorated, and impregnation or coating of pores is insufficient. Therefore, the Si content is 1 to 3
%.

The same applies to Cu-Al alloys. However, if the Al content is less than 5%, no improvement in corrosion resistance and mechanical strength is observed, and if it exceeds 11%, the mechanical strength and workability decrease. The Al content is preferably 5 to 11%. Similarly, for a Cu—Zn alloy, if the Zn content is less than 1%, no improvement in mechanical strength and corrosion resistance is observed, and
%, The intermetallic compound is formed and the mechanical strength and machinability decrease, so the Zn content is set to 1 to 50%.
In consideration of workability and corrosion resistance, 1 to 43% is preferable.

Sn in the Cu—Zn alloy improves dezincification corrosion and stress corrosion cracking, and improves corrosion resistance and mechanical strength. If the Sn content is less than 0.5%, the effect is small, and 9%
Exceeds 0.5%, the alloy becomes extremely brittle. Therefore, the content is preferably 0.5 to 9%. The Zn content of the Cu—Zn alloy is 3
In an alloy of 0% or more, Sn exceeding the solid solution limit precipitates and the material strength is reduced, so the Sn content is preferably 1 to 2%.

Al improves the corrosion resistance and mechanical strength of the Cu—Zn alloy similarly to Sn, but if less than 0.1%, the effect is small, and if more than 7.5%, the material becomes brittle and the workability is poor. Therefore, the Al content is preferably 0.1 to 3%.

If the content of Cu or Cu alloy in the sintered alloy is less than 2%, the function of coating the particles of Mo or W is reduced and the corrosion resistance is insufficient, and the material strength is low and the thread processing is difficult. When doing so, the thread is likely to be chipped. These are improved as the content increases, but the coefficient of thermal expansion increases, and the coefficient of thermal expansion is 12 × considering that the mating member to be matched is stainless steel or a ceramic material.
The target is less than 10 ⁻⁶ / ° C., and when the content of Cu or Cu alloy increases, the variation in sintering dimensional change increases. Therefore, the content is preferably 50% or less.

The Cu or Cu alloy melts during sintering and W
Alternatively, it covers the surface of the Mo powder and the pore surface in the powder.
As the content of Cu or Cu alloy increases, pores in the W or Mo powder particles and between the powders are filled. The surface of W or Mo is coated with Cu or a Cu alloy, and the corrosion resistance of the sintered alloy is improved. Further, W or Mo of the sintered alloy of the present invention has a particle diameter of 40 to 3
Although it is 00 μm, the primary particles constituting the powder are relatively fine, and have air holes in a state of being aggregated in a skeleton shape. Therefore, when the alloy is cut or polished, W or Mo particles exposed on the surface are Since Cu or Cu alloy in the pores is small and plastically flows and covers the W or Mo surface, the corrosion resistance of the processed surface is excellent similarly to the alloy using conventional fine powder W or Mo.

If there are no pores in the sintered alloy, the coefficient of thermal expansion is determined by the content of Mo or W and Cu or Cu alloy. The porosity of the sintered alloy is similar to the coefficient of thermal expansion of a sintered alloy having no porosity up to about 10% by volume,
On the other hand, when the porosity is 20%, about 8% and the porosity is 30%.
%, The coefficient of thermal expansion is reduced by about 17%, and the porosity of the sintered alloy is one of the factors controlling the coefficient of thermal expansion of the sintered alloy. However, if the porosity exceeds 30%, the strength becomes low, which is not preferable for a component requiring strength. Alloys with high porosity are also lightweight. Therefore, the porosity is preferably 20 to 30%.

[0024]

The present invention will be described below with reference to examples and comparative examples. (Example 1) The following Mo powder was prepared. Mo having an average particle size of 2 to 5 μm
After sintering the powder at various temperatures in a hydrogen atmosphere, the powder is pulverized and passed through a 60 mesh sieve (250 μm or less)
AC powder, D powder, and E powder. A powder: sintering temperature 1000 ° C B powder: sintering temperature 1100 ° C C powder: sintering temperature 1800 ° C D powder: commercially available Mo powder having a maximum particle diameter of 10 μm or less and an average particle diameter of 6 μm E powder: powder particle diameter A commercially available Mo powder having no pores in the range of 60 to 250 μm. A powder obtained by mixing 10% by weight of electrolytic Cu powder with these Mo powders is subjected to compaction molding at a molding pressure of 7 ton / cm ² , and then heated in a hydrogen gas atmosphere. After sintering at 1150 ° C., the dimensional change in sintering and variation in dimensional change (3σ), corrosion resistance, workability, and coefficient of thermal expansion were measured.

In the corrosion resistance test, the surface-polished sample was left in an environment at a temperature of 80 ° C. and a relative humidity of 90% for 96 hours.
Each sample was evaluated for discoloration. Workability is
After drilling a hole, the thread was cut and evaluated based on the condition of the thread and the presence or absence of chipping. Table 1 shows the results. In Table 1, the mark 良好 indicates good, and the mark X indicates defect.

Samples 1 to 3 according to the present invention have a small sintering dimensional change rate. Also, it can be seen that the dimensional variation is remarkably small. The corrosion resistance and the workability of Sample 5 having a coarse Mo particle were remarkably inferior. FIG. 1 is a drawing in which the cross-sectional structures of the sintered bodies of Sample 2 (Mo used B powder) and Sample 4 (Mo powder used as fine powder particles) of Table 1 are replicated. In the figure, the white area is Mo and the black area is C
u and a few pores. In the present material on the left side of FIG. 1, the primary particles of Mo are relatively large, and there are pores in the powder obtained by sintering and agglomeration, and the pores are filled with Cu. The black area filling the pores between the Mo powders is relatively large. It is understood that the Mo powder is in a state of being stacked in a bridge shape, and that when the Cu becomes a liquid phase, the Mo powder particles are difficult to move. On the other hand, the conventional alloy on the right side of FIG.
And Cu have a finely dispersed structure. Mo powder particles were originally fine, and Cu and Mo moved during liquid phase sintering to reduce pores, resulting in a large dimensional change.

[0027]

[Table 1] The unit of the coefficient of thermal expansion is (× 10 ⁻⁶ / ° C.).

(Example 2) As the Mo powder, the above-mentioned B powder was mixed with 10% by weight of electrolytic Cu powder, and the mixed powder was compacted at a different molding pressure to a temperature of 1150 ° C in a hydrogen gas atmosphere. And sintering, samples having different porosity (density ratio) (No. 6, 7, 8, 9, 10,
11) was created. The sample with the lowest porosity was pressure sintered. Table 2 shows the measurement results of the thermal expansion coefficients of these samples.

[0029]

[Table 2]

As can be seen from Table 2, when the porosity is 15%, the coefficient of thermal expansion is slightly lower, and when the porosity is 30%, the coefficient of thermal expansion is about 17% lower than that when the porosity is 1%. Although not shown in Table 2, those having a high porosity are inferior in workability and are not in a preferable state for applications requiring strength and applications requiring threading.

(Example 3) As the Mo powder, the above-mentioned B powder was used, and a powder obtained by mixing and adding 10% by weight of a Cu alloy powder was used. It was measured. The Cu alloys used were: (1) Cu-0.5% Sn alloy powder, (2) Cu-8% Sn-0.25% P alloy powder, (3) Cu-1% Sn-3% Si alloy powder (4) Cu-7% Al alloy powder, (5) Cu-1% Zn alloy powder, (6) Cu-30% Zn-1% Sn alloy powder, (7) Cu-20% Zn-2% Al Alloy powder. The sintering temperature was 1130 ° C. using the alloy powders of (1) to (5), and 1020 ° C. for (6).
° C, (7) was performed at 1070 ° C.

From the measurement of the physical properties, both the dimensional change rate and the dimensional variation show that the one using the Cu—Al alloy has a dimensional change rate of about 1.5% and a dimensional variation of about 20 μm.
Alloy using pure Cu (Example 1-trial using electrolytic Cu powder)
(Alloy of material No. 2), but the values of other Cu alloys were almost the same as those of pure Cu. The coefficient of thermal expansion is in the range of 5.7 to 6.5 × 10 ⁻⁶ / ° C.
It was almost the same as the alloy using pure Cu. Corrosion resistance and workability, superior to people using Cu alloy is pure Cu
I was

(Example 4) As the Mo powder, the above-mentioned C powder was used, and electrolytic Cu powder was used as a mixed powder having various compositions in the range of 1 to 60%. It was measured. The average of the sintering dimensional change was 0.2 to 0.4% without much difference depending on the Cu content, but the variation of the dimensional change was 4 μm for the Cu content of 1 to 10% and 30% for the Cu content. 10 μm, Cu content 5
It is 50 μm at 0% and 90 μm at 60% Cu content, and the variation increases when the Cu content exceeds 30%, and the sintered alloy having a coefficient of thermal expansion of about 8 × 10 ⁻⁶ / ° C. or more is: It turned out that it was difficult to obtain a sintered body with high dimensional accuracy.

Further, both the corrosion resistance and the workability are 1% Cu
Samples were inferior, but no other defects were observed. The coefficient of thermal expansion is 5.
3 × 10 ⁻⁶ / ° C., 60% Cu sintered body is 12.0 × 1
0 ⁻⁶ / ° C., and the relationship between the Cu content and the coefficient of thermal expansion can be represented by a straight line connecting these two points.

Example 5 The results of a test using various types of W instead of Mo showed the same properties as those described in the above example. The coefficient of thermal expansion showed a slightly lower value when W was used.

[0036]

As described in the foregoing, the production method of low <br/> thermal expansion sintered alloy according to the present invention, using the skeleton-like porous powder Mo powder or W powder, the Cu or Cu alloy since it is obtained by sintering, excellent corrosion resistance and machinability, in addition to be in thermal expansion coefficient is desired by adjusting the composition and porosity, particularly the alloy obtained by this invention is sintered dimensional change and dimensional Since there is little variation, it is possible to form a complicated-shaped part by powder molding and to reduce the number of cutting processes, so that a low-thermal-expansion part can be manufactured efficiently and inexpensively.

[Brief description of the drawings]

FIG. 1 is a drawing simulating the sectional structures of an inventive alloy and a conventional alloy.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B22F 1/00 C22C 1/04 C22C 27/04

Claims (3)

(57) [Claims] 1. A skeleton-like Mo powder or W powder having a particle diameter of 40 to 300 μm and having air holes in the powder, made by pulverizing a porous sintered body of Mo or W, Cu powder or the following Any of Cu alloy powder or Cu
Compress the mixed powder with the metal powder constituting the alloy composition,
Alternatively, a method for producing a low-thermal-expansion sintered alloy, comprising heating at a temperature equal to or higher than the melting point of a Cu alloy and performing liquid phase sintering. (B) 0.5 to 9% Sn, balance Cu (b) 0.5 to 9% Sn, 0.03 to 0.5% P, balance Cu (c) 0.5 to 9% Sn, 1 to 3 % Si, balance Cu (d) 5 to 11% Al, balance Cu (e) 1 to 50% Zn, balance Cu (f) 1 to 50% Zn, 0.5 to 9% Sn, balance Cu (g) 1 -50% Zn, 1-3% Al, balance Cu 2. The porosity of the obtained sintered alloy is 20 to 30.
% (Density ratio: 70 to 80%). The method for producing a low thermal expansion sintered alloy according to claim 1, wherein 3. A porous sintered body of Mo or W is obtained.
In the case of Mo or W having an average particle size of 0.5 to 10 μm
The primary particle powder is placed in a reducing gas atmosphere at a temperature of 1000-2.
2. A method of manufacturing by heating at 000.degree.
3. The method for producing a low thermal expansion sintered alloy according to item 1.