JP3370352B2 - Ultra-high vacuum titanium alloy with low outgassing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium alloy having an extremely excellent gas releasing property, which is most suitable as an ultra-high vacuum container material.

[0002]

2. Description of the Related Art As a material for a chamber for obtaining an ultrahigh vacuum or an extremely high vacuum, there is conventionally known Japanese Patent Application Laid-Open No. 1-316439.
And ultra-clean steel in which impurities in the steel are extremely reduced as disclosed in JP-A-3-31451,
Report of Kato et al. (Vacuum vol. 341 (1991) p.
As shown in 56), stainless steel or the like having a special surface treatment on the inner surface is used to suppress the amount of gas released.

However, even if such a stainless steel is used, it is 10 ^{-11 with} only the turbo pump. tor
It is difficult to obtain an extremely high vacuum of r or higher, and it is necessary to use a titanium sublimation pump or a cryopump. Further, the chamber made of stainless steel has a drawback that it becomes heavy.

On the other hand, as a lightweight ultra-high vacuum material, although sometimes the aluminum alloy is used, often the amount of gas released in this case ^10-11 It is extremely difficult to obtain an extremely high vacuum above torr.

[0005]

That is, when conventional stainless steel is used as a chamber material for ultra-high vacuum,
Gas is released from stainless steel, so 10 ^-11 to
In order to obtain an extremely high vacuum of rr or more, it is necessary to electrolytically polish the inner surface of the chamber and to use ultra-clean steel in which impurities in the steel are extremely reduced. Furthermore, as described above, even if such a material is used, a complicated vacuum exhaust system such as an ion pump, a titanium sublimation pump, and a cryopump is required.

Further, in recent years, it has been considered to perform an extremely high vacuum experiment in outer space, and in such a case, the weight of the chamber material becomes a problem. As a lightweight chamber material,
Although sometimes aluminum alloy is used, aluminum alloys amount outgassing number ^10-11 It is not easy to obtain an extremely high vacuum above torr.

The present invention has been made in view of the above circumstances, and a relatively simple vacuum pumping operation using only a turbo pump without using a complicated vacuum pumping apparatus such as an ion pump, a titanium sublimation pump, or a cryopump. 10 in the system
^-11 An object of the present invention is to provide a titanium alloy for ultra-high vacuum, which is capable of obtaining an extremely high vacuum of torr and which is capable of obtaining a lightweight chamber and which has a small gas release amount.

[0008]

The present invention is based on Pd, Pt,
0.02-1.0 wt% of at least one platinum-based metal selected from the group consisting of Rh, Ru, Re and Os,
0.1 to 3.0 of at least one transition metal selected from the group consisting of Co, Fe, Cr, Ni, Mn and Cu.
% By weight, La, Ce, Pr, Nd, Sm, Gd, Tb,
It contains at least one selected from the group consisting of rare earth elements such as Dy, Ho, and Er and Y in the range of 0.02 to 0.50% by weight, and C, N and O as impurity elements are C: 0 respectively. 0.05 wt% or less, N: 0.05 wt% or less,
O: It is specified to be 0.08% by weight or less, and a titanium alloy for ultra-high vacuum, which is composed of the balance Ti and unavoidable impurities and has excellent gas releasing characteristics, is provided. Further, Al is added to the above alloy in an amount of 0.1
Provided is a titanium alloy for ultra-high vacuum, which is contained in the range of 2 to 1.5% by weight and has excellent gas release characteristics.

[0009]

The inventors of the present application have studied to suppress the phenomenon in which gas components that form a solid solution inside the material diffuse into the vacuum side and are released from the surface under ultrahigh vacuum, assuming a relatively lightweight titanium material. As a result, in a titanium alloy in which C, N and O are reduced, platinum-based metals such as Pd, Pt, Ru and R are added.
One or more of h, Os and Re and C which is a transition metal
One or more of o, Fe, Cr, Ni, Mn, and Cu and rare earth metals La, Ce, Pr, Nd, Sm, and G
It has been found that such outgassing under ultrahigh vacuum can be reduced by adding a predetermined amount of one or more of d, Tb, Dy, Ho, Er and Y. It was also found that high workability is imparted by setting the additive system in such a range. Further, it was also found that by adding a predetermined amount of Al to such an alloy system, high strength can be achieved without impairing the above characteristics. The present invention having the above-described configuration is made based on such findings of the inventors of the present application. Hereinafter, the present invention will be described in detail. First, the reasons for limiting the additive elements will be described. Pd, Pt, Ru, Rh, Re, Os;

These platinum-based metallic elements are extremely important elements that act as a catalyst for trapping the molecular hydrogen remaining inside the ultra-high vacuum chamber on the surface of the material and separating it into atomic hydrogen. In order for this function to be exhibited, it is necessary to add at least one of the above elements in a total amount of 0.02% by weight or more. However, 1.0% by weight in total
If it is added in an amount exceeding the above range, the workability is remarkably reduced, so that cold forming into a vacuum container becomes extremely difficult. Co, Fe, Ni, Cr, Mn, Cu;

These transition metal elements are Ti ₂ Co, TiFe, Ti ₂ Ni, and T, which have a very high ability to fix atomic hydrogen adsorbed on the surface by the above platinum-based metal elements.
It is necessary to generate intermetallic compounds such as iCr ₂ , TiMn, and Ti ₂ Cu. In order to form such an intermetallic compound, it is necessary to add at least one of the above-mentioned elements in a total amount of 0.1% by weight or more. However, when added in excess of 3.0% by weight, the intermetallic compound produced reduces the ductility and workability of the material. La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, H
o, Er and Y;

These elements serve to suppress the diffusion of the solid solution oxygen from the inside of the solid to the surface by fixing the solid solution oxygen as an oxide by internal oxidation.
Such functions work as La, Ce, Pr, Nd, Sm, T
b, Dy, Ho, Er and Y can be obtained by adding them alone, or they can be obtained even when they are added in combination in the form of misch metal, with a total of 0.
It is effectively exhibited when it is added in an amount of 02% by weight or more. However, the total amount of one or more of these is 0.5
If it is added in an amount of more than 0% by weight, the ductility and workability are significantly reduced by the precipitated oxide. C;

When C is solid-dissolved in the material, it diffuses to the surface and combines with oxygen in the residual gas to generate CO gas, so it must be reduced as much as possible. However, 0.05
When the content is less than or equal to% by weight, the amount of CO gas released by diffusion from the inside of such a solid is 10 ^-11 -10
^-12 There is almost no effect on torr. Therefore, C is 0.
It is specified to be not more than 05% by weight. N;

Similarly, if N also forms a solid solution in the material, it may diffuse to the surface and become N ₂ gas, which may be released. However, the target of the present invention is 10 ^{-11. -10 -12} to
With a vacuum degree such as rr, when N is contained in an amount of 0.05% by weight or less, no significant decrease in vacuum degree due to N ₂ gas is observed. Therefore, N is 0.05% by weight or less. O;

Since titanium has a high solid solubility in the case of a titanium alloy, O is an impurity that needs the most control from the viewpoint of releasing gas into a vacuum. O dissolved in the material is O from the surface.
It is released in the form of _2, etc., leading to a reduction in the degree of vacuum. Therefore, in the present invention, as described above, La, Ce, Pr, N
1 of d, Sm, Gd, Tb, Dy, Ho, Er and Y
Oxygen is fixed by adding one or two or more kinds. When oxygen is contained in an amount exceeding 0.08% by weight,
The effect of fixation by the above-mentioned elements is not sufficient, and gas emission becomes remarkable. Furthermore, the fixed O is in the form of oxide, which significantly deteriorates the cold formability. Al;

Al is effective for increasing the strength of the material without causing a remarkable change in the gas release characteristics and the cold formability. This effect is remarkable especially when 0.2 wt% or more is added. However, if it is added in an amount of more than 1.5% by weight, the cold formability is deteriorated and the cold working into a vacuum container becomes difficult. That is, the addition of Al is preferably 0.2 to 1.5% by weight.

[0018]

[0019]

When stainless steel is used as an ultra-high vacuum container as in the prior art, the gas remaining inside the vacuum container is oxygen dissolved in the stainless steel or hydrogen trapped at the inclusion-matrix interface. , CO, CO ₂ gas, etc., which are bound to oxygen in the surface-altered layer and carbon in the steel.

On the other hand, according to the present invention, a titanium alloy having a reduced amount of C, N and O is added to a predetermined amount of a platinum-based metal such as Pd or Co.
When a titanium alloy of the present invention is used as an ultra-vacuum container, the following mechanism is used to suppress the gas release from the material and to fix the residual gas. It can be carried out. (1) The release of oxygen from the titanium alloy is reduced by fixing it in the material in the form of an oxide by a rare earth metal such as Y or Misch metal. (2) H ₂ gas, which occupies most of the residual gas in the chamber, is physically adsorbed as H atoms on the alloy surface by a platinum-based metal such as Pd. (3) The adsorbed H atoms are strongly fixed by an intermetallic compound having a high hydrogen trapping ability, which is composed of a transition metal such as titanium and Co. In addition, by optimizing the addition amount of each element that imparts the gas releasing property of the alloy of the present invention, it becomes possible to obtain a titanium alloy having high cold formability.

Furthermore, by adding a predetermined amount of Al to the titanium alloy having the above-mentioned two features, it is possible to increase the strength without impairing the workability and the gas release property by the solid solution strengthening of Al.

[0022]

【Example】

(Example 1)

The alloys having the compositions shown in Table 1 were melted into a button ingot in an arc melting furnace, subjected to hot rolling and heat treatment, and then subjected to various tests. In Table 1, numbers 1 to 9 are examples within the scope of the present invention, and numbers 10 to 19 are comparative examples outside the range. Further, No. 20 is stainless steel which is a conventional material.

[0024]

[Table 1] The outgassing characteristics and mechanical properties of these test materials were understood.

Regarding the gas release characteristics, the sample material was heated at 400 ° C. to perform baking treatment using a thermal desorption spectroscopy (TDS), and then the gas release rate at room temperature was determined. The gas release rate was obtained by multiplying the measurement intensity of the quadrupole mass spectrometer (QMS) by the sensitivity coefficient of each gas of QMS and the exhaust speed of each gas, and made the value of the ratio with the conventional material of No. 20. . For some materials, VAR
A plate material was sampled with an ingot, a small vacuum container was prepared, and a test was performed with a turbo molecular pump (180 l / s).

Further, a limit bending test of the material was conducted as an index of cold formability, and bend factor = bending punch radius /
Arranged according to board thickness. Furthermore, a tensile test was performed on each material, and the tensile strengths were also compared. Table 2 shows the results.

[0027]

[Table 2]

As is clear from Table 2, in the alloys of Nos. 1 to 9 which are the examples, H ₂ gas, CO + N ₂ gas and CO ₂ gas are 1/10 or less as compared with the conventional stainless steel. In particular, CO + N ₂ gas having a mass number of 28 showed a very small feature. Further, the cold formability was also extremely high, and cracks did not occur even at bending radii up to the same level as the plate thickness. Furthermore, the numbers 1, 3, 4, 6 with Al added
8 and 9, the tensile strength is 45 kgf / mm ² It showed a high value exceeding. On the other hand, numbers 10 to 1 which are comparative examples
It was confirmed that No. 9 was inferior in outgassing characteristics or workability.

For example, No. 10 is an example in which the amount of platinum-based metal is less than the range of the present invention, but although it has excellent workability, it cannot be said that it has excellent gas releasing characteristics. On the other hand, No. 11 is a case where platinum-based metal was added in excess of the range of the present invention, and although it had excellent gas release characteristics, it had a vent factor of 5.5 and was poor in cold workability. Was done.

Numbers 12 and 13 are examples in which the amount of transition metal is out of the range of the present invention. When the transition metal number 13 is less than the range of the present invention, the amount of outgassing is not significantly smaller than that of stainless steel. On the other hand, in the case of No. 12 added in excess of the range of the present invention, the workability was lowered.

Numbers 14 and 15 are examples in which the amount of rare earth metal or Y is out of the range of the present invention. Rare earth or Y
However, in No. 14 which is less than the range of the present invention, a large amount of oxygen-containing gas components were released, and only gas release characteristics almost equal to those of stainless steel were obtained. On the other hand, in No. 15 in which these were contained in excess of the range of the present invention, the workability was deteriorated by the produced oxide. In addition, the outgassing properties were also impaired.

Nos. 16 to 18 are cases where C, N, and O were contained beyond the scope of the present invention. In either case,
It was confirmed that the gas release characteristics were remarkably deteriorated and became comparable to stainless steel. No. 19 is the case where Al is contained beyond the scope of this claim. Although the gas release characteristics were excellent, the cold formability was poor.

As a result of trial production of an ultrahigh vacuum container (φ200 × 300) using the material of No. 1 of the example, 180 l /
It was possible to obtain an ultrahigh vacuum of 6.8 × 10 ⁻¹¹ torr with only the turbo pump of s. This is because there is a significant difference in the ultimate vacuum degree compared to 1.0 × 10 ⁻⁸ torr in the case of an equivalent stainless steel ultra-high vacuum container, which can be said to support the excellent gas release characteristics of the material of the present invention. Each of the vacuum degree experiments was performed after baking at 200 ° C. for 72 hours and then cooling at room temperature for 24 hours. ( Comparative example )

This comparative example is based on a titanium alloy. An alloy having a composition shown in Table 3 based on a certain titanium alloy was melted into a button ingot in an arc melting furnace, subjected to hot rolling and heat treatment, and then subjected to various tests. The numbers 21 to 34 in Table 1 are comparative examples.

[0035]

[Table 3]

With respect to the gas release characteristics, the same values as those in the example were used, and for some materials, a plate material was sampled with a VAR ingot to prepare a small vacuum container, and a turbo molecular pump (800 l / s) was used. ). Further, as an index of hot workability, cracks in the material after hot rolling were grasped and hot workability was evaluated. The results are shown in Table 4.

[0037]

[Table 4]

As is clear from Table 4, the alloys of Nos. 21 to 25, which are the examples, are 1/1 times less than the conventional materials such as H ₂ , CO + N ₂ and CO ₂ gas, stainless steel.
CO + N ₂ gas having a mass number of 28 or less was very small, which was a characteristic. Further, the hot workability was also good, and even when ear cracking occurred, it did not exceed 1 cm. On the other hand, it was confirmed that the comparative examples Nos. 26 to 34 were inferior in the gas releasing property or the hot workability. For example, No. 26 is an example in which the amount of platinum-based metal is less than the range of the present invention, but although it has excellent workability, it cannot be said that it has excellent gas release characteristics.

Similarly, the numbers 29 and 31 are examples in which the amount of transition metal, rare earth metal or Y is smaller than the range of the present invention, respectively. All of them were inferior in gas releasing characteristics to the examples.

On the other hand, the numbers 27, 28 and 30 are cases where the platinum-based metal, the transition metal, the rare earth metal or Y exceeds the range of the present invention, respectively. All of them have excellent gas releasing characteristics, but they have large ear cracks and are difficult to hot work.

Nos. 32 to 34 are cases where C, N and O were contained in amounts beyond the scope of the present invention. In either case,
It was confirmed that the gas release characteristics were remarkably deteriorated and became comparable to stainless steel.

[0042]

According to the present invention, it is possible to obtain an extremely high vacuum of 10 ⁻¹¹ torr with a relatively simple vacuum pumping system using only a turbo pump without using a complicated vacuum pumping device, and it is lightweight. Provided is a titanium alloy for ultra-high vacuum, which is capable of obtaining an ultra-vacuum container and emits a small amount of gas. By using the titanium alloy of the present invention in an ultra-vacuum container, a high ultimate vacuum can be relatively easily obtained as compared with a conventional stainless steel container. Further, the alloy of the present invention has excellent workability and can be processed into an ultra-vacuum container relatively easily.

Front Page Continuation (72) Inventor Nakanose On 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Seiji Ishimoto 2 Takara-cho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (56) References JP-A-48-71713 (JP, A) JP-A-62-89834 (JP, A) JP-A-62-120452 (JP, A) JP-A-3-90525 (JP, A) Kaihei 3-249945 (JP, A) JP 4-249674 (JP, A) JP 5-4046 (JP, A) JP 5-195119 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) C22C 14/00

Claims (2)

(57) [Claims] 1. Pd, Pt, Rh, Ru, Re and Os
0.02 to 1.0 wt% of at least one platinum-based metal selected from the group consisting of, and at least one transition metal selected from the group consisting of Co, Fe, Cr, Ni, Mn, and Cu. 0.1-3.0
% By weight, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, H
at least one selected from the group consisting of rare earth elements of O and Er and Y in the range of 0.02 to 0.50% by weight, and C, N and O as impurity elements, respectively, C: 0.05 A titanium alloy for ultra-high vacuum, which has an excellent gas-releasing property, which is defined by weight% or less, N: 0.05 weight% or less, O: 0.08 weight% or less, and balance Ti and inevitable impurities. 2. Pd, Pt, Rh, Ru, Re and Os
0.02 to 1.0 wt% of at least one platinum-based metal selected from the group consisting of, and at least one transition metal selected from the group consisting of Co, Fe, Cr, Ni, Mn, and Cu. 0.1-3.0
% By weight, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, H
It contains at least one selected from the group consisting of rare earth elements of O and Er and Y in the range of 0.02 to 0.50% by weight and Al in the range of 0.2 to 1.5% by weight. C, N and O are specified to C: 0.05% by weight or less, N: 0.05% by weight or less, and O: 0.08% by weight or less, and the balance Ti and unavoidable impurities are excellent in gas emission characteristics. Titanium alloy for ultra high vacuum.