JPH0931588A - Production of invar (r) sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an Invar (R) sintered compact reduced in the coefficient of thermal expansion to the extent causing practically no expansion and 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, 33-40% Ni and the balance essentially Fe and containing >=0.2% 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 <=0.2wt.% 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 an amber sintered body having a low coefficient of thermal expansion and having mechanical properties comparable to those of an ingot.

[0002]

2. Description of the Related Art When Ni is added as an alloying element to Fe, an anomaly appears in the coefficient of thermal expansion of the alloy to which Ni is added. When the Ni content in the alloy is about 36.5% by weight, the coefficient of thermal expansion becomes the lowest, which is about 1/10 of that of pure iron. It can be said that the Fe-Ni alloy does not practically expand with such a coefficient of thermal expansion. Therefore, "Invariable
"e" is abbreviated as "amber", "invar" or "invariant steel", and it is used for standard scales, bimetal elements, precision measuring parts, optical parts, etc. by utilizing the property of low thermal expansion.
In order to manufacture the above-mentioned amber product, a method of machining an ingot is generally used. However, in the case of manufacturing an amber product having a complicated shape, the method of machining the ingot is expensive, so a method by the powder metallurgy method has been tried (for example, see JP-A-61-197476). . 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 (HI
P) had to be done.

[0003]

In view of the above circumstances, an object of the present invention is to provide an amber sintered body having a low coefficient of thermal expansion to the extent that it does not practically expand, and having mechanical properties similar to those of an ingot material. It is to provide a method for producing a sintered body.

[0004]

Means for Solving the Problems The present invention achieves the above object, containing 33 to 40% by weight of Ni, the balance substantially consisting of Fe, and 0.2% by weight of oxygen as an unavoidable impurity. After adding C powder to the raw material powder containing the above and molding the obtained mixed powder, or adding a binder to the mixed powder to obtain a kneaded product, and further injection molding the kneaded product, a non-oxidizing atmosphere Sintered with 0.05 wt% C
The method for producing an amber sintered body comprises obtaining a sintered body containing oxygen in an amount of 0.2% by weight or less and 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 an amber sintered body of the present invention, a raw material containing 33 to 40% by weight of Ni, the balance substantially consisting of Fe, and containing 0.2% by weight or more of oxygen as an unavoidable impurity. It is important to add C powder to the powder. By adding the C powder, when C is sintered in a non-oxidizing atmosphere in a subsequent step, C in the material to be sintered reacts with oxygen to generate and release CO gas, so that a sintered body to be manufactured. While oxygen in the inside is removed, sintering is promoted, and densification of the amber sintered body (relative density of 94% or more) is achieved. The Ni content of the raw material powder to which the C powder is added is 33 to 4
When the amount is out of the range of 0% by weight, it becomes difficult to lower the thermal expansion coefficient of the amber sintered body to the extent that it does not practically expand. Further, when the content of oxygen contained as an unavoidable impurity in the raw material powder to which the C powder is added is less than 0.2% by weight, the densifying action of the amber sintered body by the C powder is not 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.
It may be slightly over 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 amber sintered body, and the C content is 0.05 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 an amber 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 0.2% 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, etc., the amber sintered body is manufactured by sintering the molded body in a non-oxidizing atmosphere. In the method for manufacturing an amber sintered body,
After the C powder is added to obtain the mixed powder, a known method is carried out. However, the manufactured amber sintered body has a C content of 0.05.
Since it is necessary that the content is not more than wt%, the oxygen content is not more than 0.2 wt%, and the relative density is not less than 94%, it is necessary to adopt appropriate conditions for producing such an amber sintered body. You can

The C content of the produced amber sintered body is 0.
If the amount exceeds 05% by weight, the weldability and corrosion resistance of the amber sintered body deteriorate. Further, if the oxygen content exceeds 0.2% by weight, it is 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), containing 36% by weight of Ni, 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 this raw material powder and mixed to contain 36% by weight of Ni and 0.1% by weight of C, and the balance substantially consisted of Fe. After obtaining a mixed powder containing 0.31% by weight of oxygen as an impurity, the mixed powder was compression molded under a pressure of 2000 kgf / cm ² . Obtained compression molded product (diameter 20 mm, thickness 10)
mm) was sintered in vacuum at a temperature of 1350 ° C. for 2 hours to produce an amber sintered body. Then, the C content, oxygen content, relative density, room temperature to 100 ° C. of the manufactured amber sintered body
The coefficient of thermal expansion and the weldability were measured. Table 1 shows the results. The weldability was good.

Example 2 Except that a mixed powder containing 34% by weight of Ni and 0.1% by weight of C, the balance being substantially Fe and containing 0.32% by weight of oxygen as an unavoidable impurity was obtained. The same test as in Example 1 was performed. Table 1 shows the results. The weldability was good.

[Example 3] A mixed powder containing 39% by weight of Ni and 0.1% by weight of C, the balance being substantially Fe, and containing 0.31% by weight of oxygen as an unavoidable impurity was obtained. The same test as in Example 1 was performed. Table 1 shows the results. The weldability was good.

[Example 4] A mixed powder containing 36% by weight of Ni and 0.25% by weight of C, the balance substantially consisting of Fe, and 0.31% by weight of oxygen as an unavoidable impurity was obtained. The same test as in Example 1 was performed. Table 1 shows the results. The weldability was good.

Example 5 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 the mixed powder and 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 an amber sintered body. Then, the C content, oxygen content, relative density, thermal expansion coefficient from room temperature to 100 ° C. and weldability of the produced amber sintered body 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 for addition to the raw material powder was not used. Table 1 shows the results. The weldability was good.

[Comparative Example 2] A mixed powder containing 32% by weight of Ni and 0.1% by weight of C, the remainder substantially consisting of Fe, and containing 0.32% by weight of oxygen as an unavoidable impurity was obtained. The same test as in Example 1 was performed. Table 1 shows the results. The weldability was good.

[Comparative Example 3] A mixed powder containing 41% by weight of Ni and 0.1% by weight of C, the balance being substantially Fe, and 0.31% by weight of oxygen as an unavoidable impurity was obtained. The same test as in Example 1 was performed. Table 1 shows the results. The weldability was good.

[Comparative Example 4] The amount of C powder (average particle size 30 μm) to be added to the raw material powder was increased, and the C content of the mixed powder to which C powder was added was 0.65% by weight. Other than that, it tested like Example 1. Table 1 shows the results. The weldability was poor.

[0017]

[Table 1] Mixed powder composition Sintered body (wt%) Form C Oxygen Relative coefficient of thermal expansion Ni C Oxygen (wt%) (wt%) Density (× 10 ^-6 / ℃ Example 1 36 0.1 0.31 Compressed 0.003 0.008 96.0 0.98 Example 2 34 0.1 0.32 Compressed 0.004 0.007 95.9 2.2 Example 3 39 0.1 0.31 Compressed 0.003 0.007 95.8 2.5 Example 4 36 0.25 0.31 Compressed 0.008 0.005 96.7 0.93 Example 5 36 0.1 0.31 Injection 0.005 0.007 95.8 1.01 Comparative Example 1 36 0.01 0.31 Compressed 0.004 0.24 85.2 1.31 Comparative Example 2 32 0.1 0.32 Compressed 0.004 0.009 95.9 4.32 Comparative Example 3 41 0.1 0.31 Compressed 0.005 0.009 95.8 4.76 Comparative Example 4 36 0.65 0.31 Compressed 0.15 0.003 97.8 1.67

From the above, the following can be seen. That is, (1)
The amber sintered bodies of Examples 1 to 5 all have a C content of 0.05 wt% or less, an oxygen content of 0.2 wt% or less, and a relative density of 94% or more, and The coefficient of thermal expansion is 3 × 10 ⁻⁶ / ° C. or less and is low enough that the amber sintered body does not expand practically. (2) The amber sintered body of Comparative Example 1 has an oxygen content of 0.24 wt%. Since the relative density is low and the relative density is as low as 85.2%, the mechanical properties are inferior to those of the ingot material. (3) In the amber sintered bodies of Comparative Example 2 and Comparative Example 3, the Ni content is 33 to 40% by weight. Since it is out of the range, the coefficient of thermal expansion is as high as 4 × 10 ⁻⁶ / ° C. or more, which exceeds the extent that the amber sintered body does not expand practically.
(4) In the amber sintered body of Comparative Example 4, the weldability was poor because the C powder content was too high and the C content was too high at 0.15% by weight.

[0019]

EFFECTS OF THE INVENTION According to the present invention, it is possible to manufacture an amber sintered body having a low coefficient of thermal expansion to the extent that the amber sintered body does not practically expand and having mechanical properties similar to those of the ingot material.

Claims (5)

[Claims] 1. Ni-containing 33 to 40% by weight, the balance consisting essentially of Fe, and 0.2 as oxygen inevitable impurities.
C powder is added to the raw material powder containing at least wt% and the obtained mixed powder is molded and then sintered in a non-oxidizing atmosphere to contain C at 0.05 wt% or less and oxygen at 0.2 wt% or less. And a method for producing an amber sintered body, which comprises obtaining a sintered body having a relative density of 94% or more. 2. Ni to 33 to 40% by weight, the balance consisting essentially of Fe, and 0.2 oxygen as an unavoidable impurity.
C powder is added to the raw material powder containing at least wt%, a binder is added to the obtained mixed powder to obtain a kneaded product, and the kneaded product is injection-molded and then sintered in a non-oxidizing atmosphere to remove C A method for producing an amber sintered body, which comprises obtaining a sintered body containing 0.05% by weight or less, 0.2% by weight or less of oxygen, and a relative density of 94% or more. 3. The method for producing an amber sintered body according to claim 1, wherein the non-oxidizing atmosphere is a vacuum atmosphere or a hydrogen atmosphere. 4. The method for producing an amber sintered body according to claim 1, 2 or 3, wherein the raw material powder contains 0.5% by weight or less of oxygen. 5. The method for producing an amber sintered body according to claim 1, wherein the amount of C powder added to the raw material powder is 0.05 to 0.4% by weight.