JPH06158230A - Manufacturing method of stainless steel material for ultra-high vacuum equipment excellent in corrosion resistance and ultra-high vacuum container - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a stainless steel material and an ultra-high vacuum equipment container, which are suitable for ultra-high vacuum equipment applications and have excellent corrosion resistance and gas release characteristics. [Structure] Mn: 2.0 to 15.0%, one or two of Mo and Cu contained in a total amount of 0.5 to 4.0%, and the composition of nonmetallic inclusions in the hot-rolled sheet. Is SiO ₂ :
50% or less, MnO: 50% or more: Al ₂ O ₃ : 30% or less of ultra-high vacuum equipment stainless steel and the ultra-high vacuum equipment steel material are subjected to surface oxidation treatment to release gas suitable for vacuum equipment. An ultra-high vacuum container with excellent characteristics can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of ultra-high vacuum equipment such as vacuum chambers and vacuum containers such as pipes.

[0002]

2. Description of the Related Art Conventionally, 18Cr-8N such as SUS304 and SUS316L is used as a material for vacuum container equipment.
i-type stainless steel is mainly used, and its surface is GBB.
It is generally used after being subjected to (glass bead blast) treatment, electrolytic polishing treatment and the like.

[0003] The stainless steel small amount discharged gas, corrosion resistance, workability, excellent weldability, as a general vacuum container materials are those generally satisfactory, 10 ^-8 Pa
It is applicable to the vacuum application of the table. However, for example, in an MBB (Molecular Beam Epitaxy) apparatus, an ultra-high vacuum level of 10 ^-9 Pa is being demanded from the viewpoint of improving the quality of crystals grown in a container.
Recently, the need for the degree of vacuum has become extremely high, and in order to meet the requirement, steel materials that emit a minimum amount of released gas are indispensable as materials for vacuum containers.

Up to now, the inventors of the present invention have disclosed in Japanese Patent Laid-Open No. 1-446.
As disclosed in Japanese Patent Laid-Open No. 0-85351 and Japanese Patent Laid-Open No. 2-85351, stainless steel containing a large amount of Mn and N is 1
It has been found that it can withstand vacuum characteristics in the range of 0 ^-9 Pa. The cause of deteriorating the vacuum characteristics of steel materials is the release of gas components (mainly hydrogen gas) in steel. It is known that gas components in steel accumulate in defects such as microcracks or surface defects due to nonmetallic inclusions and are released in a vacuum state to deteriorate vacuum characteristics. Therefore, attempts have been made to reduce the non-metallic inclusions and reduce the size thereof.

[0005]

However, recently, the required level of the degree of vacuum has become more severe, and for example, the degree of vacuum required for LSI, VLSI manufacturing equipment, etc. is on the order of 10 ⁻¹⁰ Pa. In addition, when used in applications such as ultra-high vacuum containers and piping, high corrosion resistance is also required.

[0006] It is an object of the present invention to provide a stainless steel material and an ultra-high vacuum container which are suitable for use in an ultra-high vacuum device such as an ultra-high vacuum container and piping and which are excellent in corrosion resistance and gas release characteristics.

[0007]

The present invention has been achieved as a result of various studies of components and production methods for the above purpose, and the gist thereof is as follows. (1) In weight%, C ≦ 0.08%, Si: 0.2 to
2.0%, Mn: 0.5 to 15.0%, P ≦ 0.050
%, Cr: 12-23%, Ni: 7-20%, N ≦ 0.
35%, Al ≦ 0.005%, Mo, C
Stainless steel containing one or two of u in a total amount of 0.5 to 4.0% with the balance being Fe and inevitable impurities, and the composition of the nonmetallic inclusions in the hot rolled material is MnO ≧ 50. % SiO ₂ ≦ 50% Al ₂ O ₃ ≦ 30% Stainless steel material for ultra-high vacuum equipment with excellent corrosion resistance.

(2) C ≦ 0.08% by weight%, S
i: 0.2 to 2.0%, Mn: 2.0 to 15.0%, P
≤0.050%, Cr: 12-23%, Ni: 7-20
%, N ≦ 0.35%, Al ≦ 0.005%, and one or two of Mo and Cu in a total amount of 0.5 to
A stainless steel containing 4.0% and the balance Fe and unavoidable impurities, and the composition of non-metallic inclusions in the hot rolled material is MnO ≧ 50% SiO ₂ ≦ 50% Al ₂ O ₃ ≦ 30%. A stainless steel material with excellent corrosion resistance for ultra-high vacuum equipment.

(3) In weight%, C ≦ 0.08%, S
i: 0.2 to 2.0%, Mn: 0.5 to 15.0%, P
≤0.050%, Cr: 12-23%, Ni: 7-20
%, N ≦ 0.35%, Al ≦ 0.005%, O ≦ 0.0
Contains 05%, and one or more of Mo and Cu.
Containing from 0.5 to 4.0% of seeds in total, balance stainless steel consisting of Fe and unavoidable impurities, 50% composition MnO ≧ nonmetallic inclusions in the hot-rolled SiO ₂ ≦ 50% Al ₂ O ₃ ≦ 30%, stainless steel material for ultra-high vacuum equipment with excellent corrosion resistance.

(4) C ≦ 0.08% by weight%, S
i: 0.2 to 2.0%, Mn: 2.0 to 15.0%, P
≤0.050%, Cr: 12-23%, Ni: 7-20
%, N ≦ 0.35%, Al ≦ 0.005%, O ≦ 0.0
Contains 05%, and one or more of Mo and Cu.
The total content of the seeds is 0.5 to 4.0%, and the balance is stainless steel consisting of Fe and unavoidable impurities. The composition of the non-metallic inclusions in the hot rolled material is MnO ≧ 50% SiO ₂ ≦ 50% Al. ₂ O ₃ ≦ 30%, stainless steel material for ultra-high vacuum equipment with excellent corrosion resistance.

(5) An ultra-high vacuum container having excellent corrosion resistance, characterized by subjecting the stainless steel material for ultra-high vacuum equipment according to any one of the above items 1 to 4 to a surface oxidation treatment and subsequently assembling into a vacuum container. Manufacturing method. (6) An ultra-high vacuum container having excellent corrosion resistance, characterized in that it is assembled into a vacuum container using the stainless steel material for ultra-high vacuum equipment according to any one of items 1 to 4 above, and then the surface is oxidized. Manufacturing method.

The reasons for limiting the range of each component are as follows. C is an austenite stabilizing element, but 0.0
If it exceeds 8%, Cr carbides precipitate when welding and impair the corrosion resistance, so the C content was made 0.08% or less.
Si has an effect of improving the work hardenability in cold working, and if it is less than 0.2%, the effect is small, and other hard inclusions are generated to deteriorate the gas release characteristics. Further, if it exceeds 2.0%, ferrite is generated and S
It forms a hard oxide of io ₂ and deteriorates the gas release characteristics. Therefore, the Si content is set to 0.2 to 2.0%.

If Mn is less than 0.5%, other hard inclusions are formed to deteriorate the gas release characteristics. Also, 15.
If it exceeds 0%, hard inclusions mainly composed of MnO are generated to deteriorate the gas release characteristics. Therefore, the Mn content is set to 0.5 to 15.0%. More preferably, 2.0 to 15.0% is preferable in order to form a strong Mn-based oxide film on the steel surface and further reduce the gas release rate in vacuum.

Since P deteriorates the hot workability, it is desirable that the content be low, but since it is inevitably mixed from the raw material, the content of P is set to 0.050% or less. Cr is a basic component of stainless steel and requires at least 12% to obtain excellent corrosion resistance. Further, if it exceeds 23%, the hot and cold workability deteriorates, so the upper limit was made 23%. Therefore, the Cr content is set to 12 to 23%.

Ni is one of the basic components of austenitic stainless steel. It is an element effective for workability and corrosion resistance, and requires a lower limit of 7%. Further, if it exceeds 20%, the workability and corrosion resistance improving effect ratio is small and it is expensive, so the upper limit was made 20%. Therefore, the Ni content is set to 7 to 20%. N is a strong austenite stabilizing element, but if it exceeds 0.35%, the deformation resistance increases and the manufacturability is impaired, so the upper limit was made 0.35%.

When Al alone exists in the steel, it forms hard oxide inclusions in the steel to deteriorate the cleanliness of the steel, and significantly increases the amount of gas released into the vacuum. In order to ensure cleanliness, the lower the better. However, it may be unavoidably mixed alone from the molten raw material or the refractory. Therefore, in the present invention, 0.005%
By the following, not only the cleaning is highly performed, but also the inclusions are easily stretched and divided during the cold working.

O increases non-metallic inclusions, and 0.
If it exceeds 005%, the amount of Al ₂ O ₃ and MgO-based hard inclusions increases and the gas release characteristics deteriorate, so the upper limit was made 0.005%. More preferably, it is 0.003% or less. Mo and Cu have an effect of improving the corrosion resistance, and are further subjected to an oxidation treatment, for example, 250 ° C. × 24 hr in the atmosphere.
When heat treatment is performed, Mn-Cr-Mo-O system, Mn-C
r-Cu-O-based, Mn-Cr-Mo-Cu -O system to form a dense and stable oxide film, the ultra-high vacuum, gas components (H ₂ present in the steel, H ₂ O, N ₂ , CO ₂ etc.)
Can be trapped by the oxide film so as not to be released into the vacuum, which significantly improves the vacuum characteristics,
It also improves corrosion resistance. The effect of improving the vacuum characteristics and the corrosion resistance can be similarly achieved by adding Mo and Cu individually or in combination. Addition of one or two of these in a total amount of less than 0.5% has little effect, while 4.0
If it is added in excess of%, the workability is remarkably lowered and the cost is remarkably increased. Therefore, the Mo and Cu contents are
The total amount of one type or two types was 0.5 to 4.0%.

The austenitic stainless steel adjusted to the above steel composition is heated at a temperature of 1000 ° C. or more and 1300 ° C. or less for 10 minutes or more and then hot-rolled so that the composition of inclusions in the hot-rolled material is MnO ≧ 50% SiO ₂ ≦ 50% Al ₂ O ₃ ≦ 30%. When the composition of the non-metallic inclusion is out of this range, it becomes a hard non-metallic inclusion, and the non-metallic inclusion is coarse without stretching during rolling, and is difficult to be divided, so that it remains inside the stainless steel material, Outgassing characteristics deteriorate.

The stainless steel material obtained by the above treatment is surface-oxidized and then assembled in a vacuum container, or after the vacuum container is assembled, the surface is oxidized to put it into practical use. The surface oxidation treatment is usually performed in air at atmospheric pressure at a temperature of 100 to 600 ° C. for 1 to 5
It is performed by heating for 0 hours, but the atmosphere is not limited to air,
Other oxidizing atmospheres may be used.

[0020]

[Function] Mn-Cr-Mo is obtained by adding 2.0 to 15.0% of Mn to the stainless steel material and further adding 0.5 to 4.0% of one or two of Mo and Cu in total. -O
System, Mn-Cr-Cu-O system and Mn-Cr-Mo-C
A uO-based dense and stable oxide film is formed, and the vacuum characteristics and corrosion resistance are significantly improved.

Next, the reason why the gas release characteristics are improved by using the inclusion composition shown in the claims will be described below.
If the composition of inclusions is controlled to MnO-SiO ₂ -Al ₂ O ₃ system, and easily oriented by rolling, and to easily separated, the inclusions finely dispersed. Finely dispersed,
In addition, in the case of inclusions that are well aligned with the metal of the matrix, it is considered that defects such as microcracks or surface defects near the inclusions are reduced, and therefore the gas collected there is reduced and the gas release characteristics are improved. .

[0022]

EXAMPLES Examples of the present invention will be shown below. The stainless steel of the component system shown in Table 1 was melted by a vacuum melting method and an electron beam melting method to manufacture a hot rolling slab. This slab is heated at 1200 ° C for 3 hours and then hot-rolled to a thickness of 3 m.
m hot rolled sheet was obtained.

Regarding the non-metallic inclusions of the obtained hot-rolled sheet,
The average composition of 20 non-metallic inclusions was investigated and further 5 cm ²
The number of inclusions having a size of 3 μm or more in the area of 1 was measured per unit area. Furthermore, the obtained hot-rolled sheet is annealed, pickled, and then cold-rolled to have a thickness of 1 mm and a width of 50 m.
A plate-shaped sample having a length of m and a length of 120 mm was collected. This sample was polished with SiC paper # 2000, degreased with acetone, and then baked in air at 250 ° C. for 24 hours. The gas release rate was evaluated after the baking treatment, and the corrosion resistance was evaluated before and after the baking treatment.

This sample for measuring the gas release rate was incorporated into a measuring device, and after exhausting at room temperature for 24 hours, 250 ° C. × 24 hours
After baking in a vacuum of r and evacuating for 24 hours at room temperature, the gas release rate was measured. The measurement method is a two-chamber method, where the gas release rate per unit area of the sample is Q _S , the conductance of the orifice portion is C _O , the pressure of the sample chamber when the sample is charged is P _s , and the pressure of the main chamber is Where P _{m is} the gas release rate of the sample chamber when the sample is not charged and Q _{b is} the surface area of the sample, and S is the surface area of the sample.

Q _S = {C _o (P _s −P _m ) −Q _b } / S
[Pa · m ³ · s ⁻¹ · m ⁻² ] Corrosion resistance was evaluated from the rusting test results evaluated in three ranks of A>B> C in good order according to the rusting status after the salt spray test (JIS Z 2371). It was judged. At that time, as a criterion for judging the superiority or inferiority of the corrosion resistance, a material satisfying the conditions of rank A or higher was evaluated as having good corrosion resistance. Further, the pitting corrosion generation potential (JIS G 0577) was also measured, and a material satisfying the conditions that the pitting corrosion generation potential before baking was 700 mV (vs. SCE) or more and 100 mV or more after baking was evaluated as good corrosion resistance.

The results are shown in Table 2. The alloys of the present invention (Nos. 1 to 13) in which the composition of non-metallic inclusions was controlled were 3 μm.
It can be seen that the number of oxide-based nonmetallic inclusions having a size of m or more is small, and the corrosion resistance and the gas release rate are excellent. Particularly, the alloy No. of the present invention in which Mn is controlled to 2 to 15%
4, No. 5, No. 7 to 13 show that the gas release rate is very low. In addition, one or two of Mo and Cu
The example in which the total amount of the seeds exceeds 4.0% is considered to have excellent corrosion resistance and gas release rate, but it was not carried out because the cost was significantly increased.

On the other hand, the comparative alloy is No. No. 14 is Al. Nos. 15 and 16 have Mn of No. 17 is M
o, Cu is No. In No. 18, Si, Mo, and Cu were out of the range of the components of the present invention, and the composition of nonmetallic inclusions was not controlled. Further, it can be seen that the number of oxide-based nonmetallic inclusions having a size of 3 μm or more is large, and thus the gas release rate is high.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

As shown in the examples, the present invention makes it possible to provide a stainless steel material which is suitable for use in vacuum equipment such as ultra-high vacuum containers and piping and which has excellent corrosion resistance and gas release characteristics. In addition, it facilitates the design and manufacture of vacuum equipment, such as equipment that requires ultra-high vacuum, and enables the use of pumps with small exhaust capacity even in equipment used in the medium and high vacuum regions. Its industrial value is enormous.

Claims (6)

[Claims] 1. In weight%, C ≦ 0.08%, Si:
0.2-2.0%, Mn: 0.5-15.0%, P ≦
0.050%, Cr: 12-23%, Ni: 7-20
%, N ≦ 0.35%, Al ≦ 0.005%, and one or two of Mo and Cu in a total amount of 0.5 to
A stainless steel containing 4.0% and the balance Fe and unavoidable impurities, and the composition of non-metallic inclusions in the hot rolled material is MnO ≧ 50% SiO ₂ ≦ 50% Al ₂ O ₃ ≦ 30%. A stainless steel material with excellent corrosion resistance for ultra-high vacuum equipment. 2. In weight%, C ≦ 0.08%, Si:
0.2-2.0%, Mn: 2.0-15.0%, P ≦
0.050%, Cr: 12-23%, Ni: 7-20
%, N ≦ 0.35%, Al ≦ 0.005%, and one or two of Mo and Cu in a total amount of 0.5 to
A stainless steel containing 4.0% and the balance Fe and unavoidable impurities, and the composition of non-metallic inclusions in the hot rolled material is MnO ≧ 50% SiO ₂ ≦ 50% Al ₂ O ₃ ≦ 30%. A stainless steel material with excellent corrosion resistance for ultra-high vacuum equipment. 3. In weight%, C ≦ 0.08%, Si:
0.2-2.0%, Mn: 0.5-15.0%, P ≦
0.050%, Cr: 12-23%, Ni: 7-20
%, N ≦ 0.35%, Al ≦ 0.005%, O ≦ 0.0
Contains 05%, and one or more of Mo and Cu.
The total content of the seeds is 0.5 to 4.0%, and the balance is stainless steel consisting of Fe and unavoidable impurities. The composition of the non-metallic inclusions in the hot rolled material is MnO ≧ 50% SiO ₂ ≦ 50% Al. ₂ O ₃ ≦ 30%, stainless steel material for ultra-high vacuum equipment with excellent corrosion resistance. 4. In weight%, C ≦ 0.08%, Si:
0.2-2.0%, Mn: 2.0-15.0%, P ≦
0.050%, Cr: 12-23%, Ni: 7-20
%, N ≦ 0.35%, Al ≦ 0.005%, O ≦ 0.0
Contains 05%, and one or more of Mo and Cu.
The total content of the seeds is 0.5 to 4.0%, and the balance is stainless steel consisting of Fe and unavoidable impurities. The composition of the non-metallic inclusions in the hot rolled material is MnO ≧ 50% SiO ₂ ≦ 50% Al. ₂ O ₃ ≦ 30%, stainless steel material for ultra-high vacuum equipment with excellent corrosion resistance. 5. An ultra-high vacuum container having excellent corrosion resistance, which comprises subjecting the stainless steel material for ultra-high vacuum equipment according to any one of claims 1 to 4 to surface oxidation treatment and subsequently assembling it into a vacuum container. Manufacturing method. 6. An ultra-high corrosion resistance material characterized in that it is assembled into a vacuum container using the stainless steel material for ultra-high vacuum equipment according to claim 1 and then the surface is oxidized. Method for manufacturing high vacuum container.