JPH0770706A - Low thermal expansion alloy and production thereof - Google Patents

Abstract

PURPOSE:To provide a low thermal expansion alloy by specifying the compsn. constituted of Ni, N, B, C, Si, Mn, P, S, Al and Fe and precipitating BN on the surface. CONSTITUTION:A low thermal expansion alloy having a compsn. contg., by weight, 25-50% Ni, >=0.002% N, 0.001-0.02% B, <=0.05% C, <=0.3% Si, <=1.5% Mn, <=0.02% P, <=0.02% S and <=0.03% SolAl, furthermore contg., at need, one or two kinds of 0.5-10% Cr and 0.5-20% Co, and the balance Fe with inevitable impurities, and in which BN is precipitated on the surface by >=90% of the surface is used. This low thermal expansion alloy is obtd. by heating the same alloy to >=1000 deg.C, thereafter rapidly cooling it, furthermore heating it to 600 to 950 deg.C in a nonoxidizing atmosphere and subsequently executing cooling, or heating the alloy to >=1000 deg.C in a nonoxidizing atmosphere, thereafter executing cooling to 950-600 deg.C, holding it for a specific time for precipitating BN on the surface and thereafter executing cooling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention mainly relates to semiconductor manufacturing equipment,
The present invention relates to a physics and chemistry equipment, a particle accelerator, a medical equipment, a vacuum equipment such as a cathode ray tube, a component charged or mounted in a high-purity gas atmosphere, and a low thermal expansion alloy used as a constituent member thereof.

[0002]

2. Description of the Related Art In semiconductor manufacturing equipment, surface analysis equipment, particle accelerators, cathode ray tubes, and other equipment and equipment that use vacuum, stainless steel is conventionally used for the components, and low heat when thermal expansion is a problem. Expansion alloys are used. As the low thermal expansion alloy, an Fe-Ni-based alloy (for example, Fe-36Ni alloy, Fe-42Ni alloy) or Fe-N
i-Cr alloy (for example, Fe-42Ni-6Cr alloy,
Fe-38Ni-8Cr alloy, Fe-36Ni-2Cr
Alloys) and Fe-Ni-Cr-Co alloys (eg Fe-
38Ni-8Cr-5Co) and Fe-Ni-Co type alloys (for example, Fe-32Ni-5Co alloy, Fe-30Ni).
-17Co alloy) and the like are used.

However, the gas and water adsorbed on the surfaces of parts and members made of stainless steel or low thermal expansion alloy are released into the vacuum equipment, which deteriorates the vacuum degree of the vacuum equipment and equipment.
Further, in order to pollute the atmosphere, a long-time degassing process called a baking process of heating to a temperature of several hundreds of degrees and degassing is performed at the time of manufacturing the parts / members or assembling the apparatus.

When the material of the above-mentioned constituent parts is austenitic stainless steel, it is known that it is effective to deposit boron nitride on the surface as a countermeasure against this. That is, Japanese Patent Publication No. Sho 62-39234 proposes a steel material in which boron nitride is deposited on the surface of the steel material. As a method of depositing boron nitride, a stainless steel containing boron (B), nitrogen (N) and cerium (Ce) added in a vacuum is used.
It depends on heating to 0-900 degreeC.

Further, Japanese Patent Laid-Open No. 2-57667 discloses that
B, N, and calcium (Ca), magnesium (M
g) is added to the steel material in a vacuum degree of 10 ^-5 Torr or less or in an inert gas atmosphere of 99.99% or more 6
A method has been proposed in which boron nitride is deposited on the surface of the stainless steel material by heating at a temperature of 50 to 850 ° C.

The inventors of the present application have already disclosed in Japanese Patent Laid-Open No. 3-04.
According to Japanese Patent No. 2367, a stainless steel containing 0.005 to 0.05% of B and 0.08 to 0.3% of N is added to hydrogen or an inert gas such as nitrogen or argon. 60% in a mixed gas containing more than 1 vol% of pressure
A method for producing stainless steel in which boron nitride is deposited on the surface by heating to a temperature of 0 to 900 ° C. has been proposed.

[0007]

However, as the above-mentioned vacuum device has higher performance, the requirements for parts and members constituting the device have become more severe. Since austenitic stainless steel generally has large thermal expansion, low thermal expansion alloys have been increasingly used instead of this depending on the application.

However, even in the case of the above-mentioned low thermal expansion alloy, there is adsorption or desorption of gas on the surface of the alloy, and there is no effective solution to reduce this, and degassing by heating for a long time is carried out as usual. There is. Therefore, as the usage range of Invar alloy, which is a low thermal expansion alloy, expands,
Development of a technique for reducing the adsorbed gas and released gas of this alloy is desired. The low thermal expansion alloy Invar alloy and the like are used not only for members for vacuum devices but also for members used in a high-purity inert atmosphere (for example, Ar, N ₂ , He, etc.).

[0009]

Means for Solving the Problems As a result of repeated studies to solve the above-mentioned problems with Invar alloy, which is a low thermal expansion alloy, the present inventors have paid attention to the gas non-adsorption property of boron nitride and As a result of studying the amount of B and N to be added and other various precipitation conditions (solution treatment temperature, precipitation temperature, atmosphere at the time of precipitation, etc.), appropriate chemical components, solution treatment temperature, precipitation temperature, atmosphere, etc. were selected. The present invention has been completed by selecting the conditions under which boron nitride is deposited so as to cover most of the alloy surface, and the present invention has been completed.

(1) The invention of claim 1 is a low thermal expansion alloy having the following component composition (the component composition is wt%). Ni: 25-50%, N: 0.002% or more, B: 0.001-0.02
%, C: 0.05% or less, Si: 0.3% or less, Mn: 1.5% or less, P: 0.02% or less, S: 0.02% or less, Sol.Al: 0.03
% Or less, with the balance being Fe and inevitable impurities.

(2) The invention of claim 2 is a low thermal expansion alloy which, in addition to the alloy of claim 1, further contains one or two of Cr: 0.5-10% and Co: 0.5-20%. . (3) The invention of claim 3 has the following characteristics (the composition of the components is wt%
Is a low thermal expansion alloy. (A) An alloy having the component composition according to claim 1 or 2, wherein (b) boron nitride is deposited on the surface of the alloy in 90% or more of the surface.

(4) The invention of claim 4 is a method for producing a low thermal expansion alloy, which comprises the following steps (component composition is wt%). (A) Ni: 25-50%, N: 0.002% or more, B: 0.001
~ 0.02%, C: 0.05% or less, Si: 0.3% or less, Mn:
1.5% or less, P: 0.02% or less, S: 0.02% or less, Sol.A
A low thermal expansion alloy containing l: 0.03% or less and the balance of Fe and unavoidable impurities is prepared, (b) the alloy is heated to 1000 ° C. or higher, and then rapidly cooled, (c) further Heat to 600-950 ° C in an oxidizing atmosphere and then cool.

(5) The invention of claim 5 is the same as that of claim 4 in which the content of Cr is 0.5 to 10%.
And Co: 0.5 to 20% of one or two kinds of low thermal expansion alloys. (6) In the invention of claim 6, the following steps (component composition is wt%
The method for producing a low thermal expansion alloy comprising: (A) The low thermal expansion alloy according to claim 4 (a) or 5 (a) is prepared, and (b) the low thermal expansion alloy is heated to 1000 ° C. or higher in a non-oxidizing atmosphere, and then 950 to 600.
It is cooled to a range of 0 ° C., held for a predetermined time to precipitate boron nitride on the surface of the alloy, and then cooled.

[0014]

The reason for limiting the component composition described in the claims will be described below. Ni: Ni is the basic constituent element of the low thermal expansion alloy, and Ni
If the added amount is less than 25% or more than 50%, the low thermal expansion property is impaired. Therefore, N does not include Co
The appropriate range of i is preferably 30 to 50%. On the other hand, when Co is contained in the alloy, the improvement effect of Co is added, so that 25 to 45% is preferable (claim 1).

Cr: Cr is an element that can be added without impairing the characteristics of the Fe-Ni-based low thermal expansion alloy.
Excellent low thermal expansion alloys exist in the range of 0.5 to 10%.
Therefore, the amount of Cr added is 0.5 to 10% (claim 2).

Co: Co is an element that can be added without impairing the characteristics of the Fe-Ni-based low thermal expansion alloy and the Fe-Ni-Cr-based low thermal expansion alloy, and also acts as a substitute element for Ni. Excellent low thermal expansion alloys exist in the range of -20%. Therefore, in the alloy of the present invention, the amount of Co added is 0.5 to 20% (claim 2).

B: In order to deposit boron nitride on the surface of the alloy, it is necessary to contain B and N in the alloy, and there is an appropriate range of B and N. For B, 0.0
If it is less than 01%, the precipitation of boron nitride is not sufficient and only a part of the alloy surface is covered. On the other hand, if it exceeds 0.02%, the hot workability is significantly impaired. Therefore, the content range of B is set to 0.001 to 0.02%.

N: An essential element for forming boron nitride. If the N content is less than 0.002%, boron nitride is not sufficiently precipitated. On the other hand, the upper limit is not particularly specified, but N is less likely to form a solid solution in an alloy containing a large amount of Ni, so adding an amount exceeding 0.02% poses a manufacturing problem. Therefore, the content of N is 0.002-
0.02% is desirable.

Regarding the contents of B and N, in austenitic stainless steel, B is 0.005 to 0.
It is considered to be 05%, and N is preferably 0.08 to 0.3%. On the other hand, in the low thermal expansion alloy according to the present invention, since the Cr content is smaller than that of the austenitic stainless steel, a smaller N content is sufficient, and when B and N are contained in large amounts, the precipitated B is precipitated. , N also act as inclusions, thus impairing the cleanliness of the steel. In this respect, unlike the case of stainless steel, in the low thermal expansion alloy according to the present invention, as described above, it is important to contain both B and N in a low amount.

Regarding other elements In the low thermal expansion alloy according to the present invention, N is added to Fe.
The alloy system to which i, Cr, Co, etc. are added is basically used, but in the production, other components can be added as long as the characteristics of the low thermal expansion alloy are not impaired. Such elements include the following.

C is 0.05% or less, Si is 0.03% or less, Mn is 1.5% or less, and P is an impurity in the alloy.
Can contain 0.02% or less, S can contain 0.02% or less, and Sol.Al can contain 0.1% or less. When C, Si, and Mn exceed the above composition range, low thermal expansion is impaired. Since P and S are both impurities, the lower limit may be 0%. Sol.Al is desirable to contain 0.001% or more when melting and casting the alloy of the present invention in order to prevent generation of bubbles at the time of casting, while it is desirable that there are few non-metallic inclusions. 0.03% or less is desirable. The above are the reasons for limiting the component composition of the low thermal expansion alloy described in the claims.

The low thermal expansion alloys having these component compositions are actually manufactured in plates, pipes, various forged products, and other shapes. In order to use these materials as parts for the vacuum equipment as already mentioned, after processing into the final parts, heat treatment as described below is performed, and boron nitride is deposited almost all over the surface of these parts. It is important to let Here, the boron nitride is presumed to be mainly BN in the analysis result by the scanning Auger electron spectroscope, but it is also presumed that other boron nitride in various bonding states of B and N is also included.

The heat treatment conditions for depositing this boron nitride will be described below. Solution Treatment The low thermal expansion alloy containing B and N is subjected to solution treatment to perform boron nitride precipitation treatment. However, when the solution treatment temperature is less than 1000 ° C., B and N dissolved in a small amount, and boron nitride is dissolved. The amount of precipitation is slight. Therefore, the solution treatment temperature must be 1000 ° C. or higher. It is heated to the solution treatment temperature and then subjected to a quenching treatment. The atmosphere for solution treatment depends on the processing process of this alloy. When the solution treatment is performed and then the quenched alloy is processed into the final parts / members and the boron nitride precipitation treatment is performed, the solution treatment may be performed in an oxidizing atmosphere. This is because the oxide film on the surface can be removed during the above processing. However, when this alloy is processed into the final parts / members, subjected to solution treatment, and then boron nitride precipitation treatment, it is desirable to perform it in a non-oxidizing atmosphere when heating for solution treatment. . This is for preventing the surface oxidation of the alloy and for facilitating the deposition of boron nitride on the surface.

Precipitation treatment of boron nitride The temperature is maintained at 1000 ° C. or higher for solid solution treatment, and then rapid cooling treatment is performed, and then 600 to 950 ° C. in a non-oxidizing atmosphere.
Then, boron nitride is deposited on the surface. Alternatively, the temperature is maintained at 1000 ° C. or higher in a non-oxidizing atmosphere, and once 950 to 6
It is also possible to rapidly cool to 00 ° C. to precipitate boron nitride and then cool. This is because in the case of an oxidizing atmosphere, an oxide film is formed on the surface and the deposition of boron nitride becomes insufficient.

Therefore, it is necessary to perform the treatment in vacuum, in hydrogen, or in a non-oxidizing atmosphere such as an inert gas (argon, nitrogen, etc.) containing 1% or more of hydrogen at the total pressure.
Further, if the deposition temperature is less than 600 ° C., diffusion of B and N in the alloy is slow and sufficient boron nitride is not deposited on the surface. On the other hand, when the temperature exceeds 950 ° C., the temperature becomes close to the solution treatment temperature and B and N that become supersaturated at the precipitation treatment temperature decrease, and the precipitation amount of boron nitride also decreases. Therefore, the appropriate range of the boron nitride precipitation treatment temperature is 600 to 950 ° C.
The precipitation treatment time is not particularly limited, but a sufficient boron nitride film is formed in about 1 to 6 minutes.

[0026]

EXAMPLES Specific examples of the present invention as described above will be described below. After alloys having the compositions shown in Table 1 were melted in vacuum, they were hot-rolled into 12 mm thick plates. After holding these plates at various solution temperatures for 30 minutes, water-cooled,
The sample was processed into a 10 mm square and 1 mm thick sample. The surface of this sample was buffed and electropolished, and then boron nitride was deposited under various conditions. The non-oxidizing atmosphere is vacuum (1 × 10 ⁻⁵ Torr or less) in the Fe—Ni system and nitrogen (purity 99.999) in the Fe—Ni—Cr system.
9%), hydrogen in the Fe-Ni-Cr-Co system (purity 9
9.99%), and argon and hydrogen (1 vol% of total pressure) were used in the Fe-Ni-Co system. For the sample subjected to the precipitation treatment, the surface coverage of boron nitride was measured by a scanning Auger electron spectroscopy apparatus. Tables 2 to 4 show the deposition conditions and the results.

From the results of Tables 2 to 5, it can be seen that the boron nitride film according to the present invention has a very high boron nitride surface coverage of 90% or more and is deposited on the alloy surface. . On the other hand, most of the comparative examples have a coverage of 60% or less, and the high ones have a low coverage of about 70 to 80%. Therefore, according to the present invention, it was confirmed that the parts used in a vacuum or the like can produce a product having excellent characteristics having high resistance to gas adsorption.

It is needless to say that the present invention is not limited to such an embodiment, and it is needless to say that the present invention can be implemented by appropriately changing the design in light of the above-mentioned gist of the present invention. Is within the scope of the invention. For example, a method of heating at 600 to 950 ° C. in a vacuum to carry out the precipitation treatment and quenching with an inert gas, or a method of once lowering from the solution temperature to the direct precipitation treatment and then performing the precipitation treatment continuously are included. These are effective in reducing the time and cost of the precipitation treatment.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5]

[0034]

[Table 6]

[0035]

As described above, by using the alloy of the present invention, it is possible to perform vacuum or high-purity inert gas atmosphere without uneconomical treatment such as long-time baking treatment or long-time evacuation. It becomes possible to manufacture usable vacuum device parts / members. Therefore, semiconductor manufacturing equipment,
It is an invention that is capable of improving the performance of devices such as physics and chemistry equipment, particle accelerators, medical equipment, and cathode ray tubes, and has a great effect industrially.

Front Page Continuation (72) Inventor Akira Ebata 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (6)

[Claims] 1. A low thermal expansion alloy having the following component composition (the component composition is wt%). Ni: 25-50%, N: 0.002% or more, B: 0.001-0.02%, C: 0.05% or less, Si: 0.3% or less, Mn: 1.5% or less, P: 0.02% or less, S: 0.02% or less, Sol.Al: 0.03% or less is contained, and the balance consists of Fe and inevitable impurities. 2. A low thermal expansion alloy having the following component composition (the component composition is wt%). Ni: 25-50%, N: 0.002% or more, B: 0.001-0.02%, C: 0.05% or less, Si: 0.3% or less, Mn: 1.5% or less, P: 0.02% or less, S: 0.02% or less, Sol.Al: 0.03% or less is contained, and one or two kinds of Cr: 0.5 to 10% and Co: 0.5 to 20% are contained, and the balance is Fe and inevitable impurities. 3. The following characteristics (component composition is wt%):
Low thermal expansion alloy with. (A) A low thermal expansion alloy having the component composition according to claim 1 or 2, wherein (b) boron nitride is deposited on the surface of the low thermal expansion alloy in 90% or more of the surface. 4. The following steps (component composition is wt%)
And a method for producing a low thermal expansion alloy. (A) Ni: 25 to 50%, N: 0.002% or more, B: 0.001 to 0.02%, C: 0.05% or less, Si: 0.3% or less, Mn: 1.5% or less, P: 0.02% or less, S: 0.02 % Or less, Sol.Al: 0.03% or less, and a low thermal expansion alloy containing the balance of Fe and unavoidable impurities is prepared. (B) The alloy is heated to 1000 ° C. or higher and then rapidly cooled, c) Furthermore, in a non-oxidizing atmosphere, 60
Heat to 0-950 ° C and then cool. 5. The following steps (component composition is wt%)
And a method for producing a low thermal expansion alloy. (A) Ni: 25 to 50%, N: 0.002% or more, B: 0.001 to 0.02%, C: 0.05% or less, Si: 0.3% or less, Mn: 1.5% or less, P: 0.02% or less, S: 0.02 % Or less, Sol.Al: 0.03% or less, and Cr: 0.5-10% and Co: 0.5-20%, one or two, with the balance being Fe and inevitable impurities. An expansion alloy is prepared, (b) the low thermal expansion alloy is heated to 1000 ° C. or higher and then rapidly cooled, and (c) further heated to 600 to 950 ° C. in a non-oxidizing atmosphere and then cooled. 6. The following steps (component composition is wt%)
And a method for producing a low thermal expansion alloy. (A) A low thermal expansion alloy according to claim 4 (a) or 5 (a) is prepared, and (b) the low thermal expansion alloy is heated to 1000 ° C. in a non-oxidizing atmosphere.
It is heated to the above temperature and then cooled to a range of 950 to 600 ° C., and is held for a predetermined time to precipitate boron nitride on the surface of the alloy, and then cooled.