JPH0931589A - Production of kovar sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a kovar sintered compact having a coefficient of thermal expansion equal to those of hard glass and ceramics and also having mechanical properties equal to those of a refined material. SOLUTION: Carbon powder is added to a powdered raw material which has a composition consisting of, by weight, 28-32% Ni, 15-18% Co, and the balance essentially Fe and containing >=0.3% oxygen as an inevitable impurity. The resultant powder mixture is compacted, or, a binder is added to the powder mixture to form a kneaded material and further this kneaded material is injection-molded. Then sintering is carried out in a nonoxidizing atmosphere. By this method, the sintered compact containing <=0.05wt.% C and <=0.3wt.% oxygen and having >=94% relative density can be obtained.

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 Kovar sintered body having a coefficient of thermal expansion similar to that of hard glass or ceramics and mechanical properties similar to those of ingots.

[0002]

2. Description of the Related Art Kovar alloy is used as a sealing alloy for hard glass and ceramics because it has a thermal expansion coefficient similar to that of hard glass and ceramics. As a typical composition, Ni is 29% by weight and Co is 17%. % By weight, with the balance being Fe and inevitable impurities (ASTM
F15) is known. In order to manufacture the Kovar product, a method of machining an ingot is generally used. However, in the case of manufacturing a Kovar product having a complicated shape, the method of machining the ingot is expensive, so that a method by the powder metallurgy method has been attempted. By the way, although the method by the powder metallurgy has an advantage in manufacturing a product having a complicated shape, it is difficult to densify the product, and if the densification is attempted to be strong, use of expensive fine powder and long time Sintering, hot isostatic pressing (HIP) etc. had to be performed.

[0003]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to produce a Kovar sintered body having a thermal expansion coefficient similar to that of hard glass and ceramics and mechanical properties comparable to those of ingots. To provide a way to do.

[0004]

The present invention achieves the above-mentioned object and comprises 28 to 32% by weight of Ni and Co.
After the addition of C powder to the raw material powder containing 15 to 18% by weight and the balance substantially consisting of Fe and containing 0.3% by weight or more of oxygen as an unavoidable impurity to obtain the mixed powder, or A binder is added to the mixed powder to obtain a kneaded product, which is further injection-molded and then sintered in a non-oxidizing atmosphere to contain C in an amount of 0.05 wt% or less and oxygen in an amount of 0.3 wt% or less. And a method for producing a Kovar sintered body, which comprises obtaining a sintered body having a relative density of 94% or more. The non-oxidizing atmosphere is preferably a vacuum atmosphere or a hydrogen atmosphere.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing a Kovar sintered body according to the present invention, Ni is 28 to 32% by weight and Co is 15%.
It is important to add the C powder to the raw material powder containing 18% by weight to 18% by weight, the balance substantially consisting of Fe, and containing 0.3% by weight or more of oxygen as an unavoidable impurity. By adding the above-mentioned C powder, when sintering in a non-oxidizing atmosphere in a later step, C in the material to be sintered reacts with oxygen to generate CO gas,
Since the oxygen is released, oxygen in the produced sintered body is removed, sintering is accelerated, and densification (relative density of 94% or more) of the Kovar sintered body is achieved. When the Ni content of the raw material powder to which the C powder is added deviates from the range of 28 to 32% by weight or the Co content deviates from the range of 15 to 18% by weight, the thermal expansion coefficient of the manufactured Kovar sintered body is increased. Tends to be less than the coefficient of thermal expansion of hard glass and ceramics. Further, if the content of oxygen contained as an unavoidable impurity in the raw material powder to which the C powder is added is less than 0.3% by weight, the densifying action of the Kovar sintered body by the C powder cannot be sufficiently exhibited. The upper limit of the content of oxygen contained as an unavoidable impurity in the raw material powder to which the C powder is added is usually about 0.5% by weight, but it may be slightly over about 0.5% by weight. However, if the oxygen content is too large, the amount of C powder to be added becomes too large, and it is difficult to control the C content of the manufactured Kovar sintered body, and the C content is 0.05% by weight. % Easily.

The particle size of the raw material powder to which C powder is added is
The average particle size is preferably 5 to 50 μm. Below 5 μm,
If the oxygen content is about 0.5% by weight or less, it is difficult to obtain it, or if it is available, it becomes expensive. On the other hand, if it exceeds 50 μm, the sinterability of the above raw material powder to which the C powder is added deteriorates. . In the method for producing a Kovar sintered body of the present invention,
The C powder to be added to the raw material powder is usually added so that the C content of the mixed powder obtained by adding the C powder is 0.05 to 0.4% by weight. C to 0.
The C content can be appropriately determined so that a sintered body containing not more than 05% by weight and not more than 0.3% by weight of oxygen can be obtained.
The mixed powder obtained by adding the above C powder is subjected to compression molding and the like. When a binder is added, the kneaded product is injection-molded and the injection-molded product is debindered. This binder is preferably a binder whose main component is wax, for example, in which C content hardly remains after debinding the injection-molded article. After compression molding, injection molding, or the like, a Kovar sintered body is manufactured by sintering the molded body in a non-oxidizing atmosphere.

In the method for manufacturing the above Kovar sintered body,
After the C powder is added to obtain a mixed powder, a publicly known method is carried out. However, the Kovar sintered body produced has a C content of 0.05.
Since it is necessary to have a weight percentage of less than or equal to 0, an oxygen content of less than or equal to 0.3% by weight, and a relative density of greater than or equal to 94%, it is necessary to adopt appropriate conditions for producing such a Kovar sintered body. You can When the C content of the Kovar sintered body to be produced exceeds 0.05% by weight, not only the weldability and corrosion resistance of the Kovar sintered body are deteriorated, but also the thermal expansion coefficient is easily separated from that of hard glass or ceramic. Become. Further, if the oxygen content exceeds 0.3% by weight, it becomes difficult to obtain a sintered body having a relative density of 94% or more. If the relative density is less than 94%, it will be difficult to obtain a sintered body having the same mechanical properties as the ingot material.

[0008]

【Example】

Example 1 Fe powder (average particle size 8 μm, oxygen content 0.
35% by weight) and Ni powder (average particle size 7 μm, oxygen content 0.25% by weight) and Fe-50% by weight Co powder (average particle size 13 μm, oxygen content 0.31% by weight).
And 29% by weight of Co and 16% by weight of Co, the balance consisting essentially of Fe, and 0.31 of oxygen as an unavoidable impurity.
A raw material powder containing wt% was prepared. Next, C powder (average particle size: 30 μm) was used as an additive to the raw material powder and mixed to contain 29% by weight of Ni, 16% by weight of Co and 0.1% by weight of C, and the balance substantially. After obtaining a mixed powder made of Fe and containing 0.31% by weight of oxygen as an unavoidable impurity, the mixed powder was compression molded under a pressure of 2000 kgf / cm ² . Obtained compression molded product (diameter 20 m
m, thickness 10 mm) was sintered in vacuum at a temperature of 1350 ° C. for 2 hours to produce a Kovar sintered body. And, the C content, oxygen content, relative density of the manufactured Kovar sintered body, 2
5 ° C to 300 ° C, 400 ° C, 450 ° C and 500 ° C
The coefficient of thermal expansion up to and as well as the weldability were measured. Table 1 shows the results. The weldability was good.

[Example 2] 29% by weight of Ni and 1% of Co
A test was performed in the same manner as in Example 1 except that a mixed powder containing 6% by weight and 0.27% by weight of C, the balance substantially consisting of Fe, and containing 0.31% by weight of oxygen as an unavoidable impurity was obtained. Table 1 shows the results. The weldability was good.

Example 3 A mixed powder was obtained in the same manner as in Example 1, and then a wax binder was added to this mixed powder so that the volume ratio of this mixed powder to the wax binder was 55:45. And kneading at 150 ° C., and then the kneaded product was granulated into pellets. Then, the pellets were injection-molded using an injection molding machine, and then the injection-molded body was kept at 300 ° C. to remove the wax-based binder.
The obtained injection-molded body (diameter 20 mm, thickness 10 mm) was sintered in vacuum at a temperature of 1350 ° C. for 2 hours to produce a Kovar sintered body. Then, the C content, oxygen content, relative density, 25 ° C. to 300 ° C. of the manufactured Kovar sintered body, 4
The thermal expansion coefficients up to 00 ° C, 450 ° C and 500 ° C, and the weldability were measured in the same manner as in Example 1. Table 1 shows the results. The weldability was good.

[Comparative Example 1] A test was conducted in the same manner as in Example 1 except that C powder was not used as an additive to the raw material powder. Table 1 shows the results. The weldability was good.

[Comparative Example 2] The blending amount of C powder (average particle size 30 μm) for addition to the raw material powder was increased, and the C content of the mixed powder to which C powder was added was 0.71% by weight. Other than that, it tested like Example 1. Table 1 shows the results. The weldability was poor.

[Conventional Example] Kovar alloy is melted and cast into N
i of 29% by weight and Co of 16% by weight, the balance being F
An ingot composed of e and unavoidable impurities was obtained, and a molten metal sample having a diameter of 20 mm and a thickness of 10 mm was sampled from the ingot. C content, oxygen content, 25 ° C. to 30 of this ingot sample
The thermal expansion coefficients up to 0 ° C, 400 ° C, 450 ° C and 500 ° C, and the weldability were measured in the same manner as in Example 1. Table 1 shows the results. The weldability was good.

[0014]

[Table 1] Type C (wt%) method C oxygen relative (wt%) (wt%) Density (%) in mixed powder-formed sintered compacts or ingots Example 1 0.1 compression 0.006 0.007 95.7 Example 2 0.27 compression 0.019 0.008 96.3 Example 3 0.1 Injection 0.008 0.008 95.5 Comparative example 1 0.01 Compression 0.007 0.31 86.4 Comparative example 2 0.71 Compression 0.19 0.007 97.8 Conventional example − − − − − Thermal expansion coefficient (× 10 ⁻⁶ / ° C.) 25 to 300 ° C 25 to 400 ° C 25 to 450 ° C 25 to 500 ° C Example 1 4.87 4.82 5.13 5.80 Example 2 4.62 4.57 5.17 5.78 Example 3 4.91 4.95 5.27 5.96 Comparative Example 1 4.99 5.12 5.42 6.14 Comparative Example 2 5.19 5.17 5.45 6.31 Conventional Example 4.83 4.87 5.18 6.03

From the above, the following can be seen. That is, (1)
The Kovar sintered bodies of Examples 1 to 3 all have a C content of 0.05% by weight or less, an oxygen content of 0.3% by weight or less, and a relative density of 94% or more, and The coefficients of thermal expansion from 25 ° C to 300 ° C, 400 ° C, 450 ° C and 500 ° C are all very close to the coefficients of thermal expansion of ingots having the same coefficient of thermal expansion as hard glass and ceramics, (2) The Kovar sintered body of Comparative Example 1 had a large oxygen content of 0.31% by weight and a relative density of 86.4%.
(3) In the Kovar sintered body of Comparative Example 2, the mechanical properties are inferior to those of the ingot, and the C powder content is too large.
Since the content was too large as 0.19% by weight, the weldability was poor.

[0016]

According to the present invention, it is possible to manufacture a Kovar sintered body having a coefficient of thermal expansion similar to that of hard glass or ceramics and mechanical properties similar to those of ingots.

Claims (5)

[Claims] 1. Ni to 28 to 32 wt% and Co to 1
C powder is added to a raw material powder containing 5 to 18% by weight, the balance consisting essentially of Fe, and containing 0.3% by weight or more of oxygen as an unavoidable impurity, and the obtained mixed powder is molded and then nonoxidizing. A method for producing a Kovar sintered body, comprising sintering in an atmosphere to obtain a sintered body containing 0.05% by weight or less of C, 0.3% by weight or less of oxygen, and having a relative density of 94% or more. 2. Ni to 28 to 32% by weight and Co to 1
A kneaded material containing 5 to 18% by weight, the balance substantially consisting of Fe, and C powder added to a raw material powder containing 0.3% by weight or more of oxygen as an unavoidable impurity, and a binder added to the obtained mixed powder. After further injection molding the kneaded product,
A Kovar sintered body obtained by sintering in a non-oxidizing atmosphere to obtain a sintered body containing 0.05% by weight or less of C, 0.3% by weight or less of oxygen, and having a relative density of 94% or more. Production method. 3. The method for producing a Kovar sintered body according to claim 1, wherein the non-oxidizing atmosphere is a vacuum atmosphere or a hydrogen atmosphere. 4. The method for producing a Kovar sintered body according to claim 1, 2 or 3, wherein the raw material powder contains 0.5 wt% or less of oxygen. 5. The method for producing a Kovar sintered body according to claim 1, wherein the C powder added to the raw material powder has an addition amount of 0.05 to 0.4% by weight.