JPH04128313A - Production of vacuum equipment and steel products for vacuum equipment - Google Patents

Abstract

PURPOSE:To produce steel products for vacuum equipment having excellent characteristics to gas adsorption by subjecting the surface of an austenitic stainless steel contg. specific ratios of B and N to a soln. heat treatment and precipitation treatment under specific conditions. CONSTITUTION:The austenitic stainless steel contg. 0.005 to 0.05wt.% B and 0.08 to 0.30wt.% N is treated within the range where the soln. heat treatment temp. (T0), precipitation treating temp. (T1) and the precipitation treating time (t) satisfy both formula I and formula II and the heating up rate of 400 to 600 deg.C at the time of the precipitation treatment is regulated at >=5 deg.C/min. The soln. heat treatment temp. (T0) is preferably about >=1173K and the BN precipitation treating temp. (T1) is preferably about 923 to 1173K. The steel products having the BN film having the excellent characteristics to gas adsorption are obtd. in this way.

Description

[Detailed Description of the Invention] (Purpose of the Invention) [Industrial Field of Application] This invention relates to containers, piping, valves, flanges, etc. for vacuum devices used in semiconductor manufacturing, physical and chemical equipment, particle accelerators, medical equipment, etc. The present invention relates to a method for manufacturing vacuum equipment, parts to be inserted and mounted inside the vacuum equipment, and steel materials for vacuum equipment having boron nitride on the surface. In addition, it can be used not only for vacuum use but also for manufacturing high-purity gas containers, piping, valves, etc. that have boron nitride on their surfaces.

[Conventional technology]

5U for containers, piping, valves, flanges, etc. that make up vacuum equipment such as semiconductor manufacturing equipment, surface analysis equipment, particle accelerators, etc.
Stainless steels such as S316L and 5US304L are mainly used. However, since stainless steel releases gases that are absorbed on the surface and gases that are contained inside the steel material, electrolytic polishing treatment is required on the surface of stainless steel, especially in containers for equipment that requires high vacuum. A method of reducing the amount of gas released by reducing the area on which gas is adsorbed is being adopted. Furthermore, in order to reduce the gas contained inside the steel material, clean stainless steel may be used in which non-metallic inclusions in the steel that serve as gas trap sites are reduced.

However, either method requires high-temperature baking at several hundred degrees for several tens of hours or more, and it takes a long time to reach high vacuum.

As a countermeasure against this problem, it is very effective to use stainless steel with boron nitride precipitated on its surface, as reported in "Shinku" magazine Vol. 1.32 (1989) No. 3 p. 131.
It is described in the literature "Outgassing of surface-deposited BN" by ~. That is, as a precipitation treatment method for boron nitride,
h is being processed.

Furthermore, Japanese Patent Publication No. 62-39234 proposes a steel material in which boron nitride is deposited on the surface of the steel material. The precipitation method for boron nitride is boron (B), nitrogen (
This is done by heating austenitic stainless steel to which N) and cerium (Ce) have been added to 700 to 900°C in a vacuum.

JP-A-2-57667 discloses boron (B), nitrogen (N), calcium (Ca), magnesium (M
g) A copper material in which boron nitride is precipitated on the surface by heating the copper material to which boron nitride is added at a temperature of 650 to 850°C in a vacuum of 10-' Torr or less or in an inert gas atmosphere of 99.99% or more. is proposed.

Also, “Journal of the Japan Institute of Metals J Vol, 47 (198
3) The document [Deposition behavior of boron nitride on the surface of 18-8 stainless steel added with boron and nitrogen] from page 11, page 941 describes the precipitation behavior of boron nitride at 100 OK and 100 K for up to 432 ks.

[Problem to be solved by the invention]

However, the above-mentioned document “Gas release of surface deposited BN”
In the precipitation treatment, the solution treatment temperature is, for example, 12
If the temperature is as high as 00°C or higher, or if the temperature increase rate during the precipitation treatment is as low as 1°C/sin, even if boron nitride is deposited on the surface, it will not be effective against gas adsorption. It did not result in an excellent boron nitride film.

In addition, the same is true in Japanese Patent Publication No. 62-39234, and even if the precipitation treatment is performed at 800"C for 1 hour as described in the example, if the temperature increase rate is low, the boron nitride film with excellent properties will not work. could not be formed.

In JP-A No. 2-57667, solution treatment at 1100''C is subjected to precipitation treatment at a heating rate of 10℃/sinte from 500 to 650''C at 750''C for 130 minutes. Since the processing time was too short, a boron nitride film with excellent properties could not be obtained.

In the above-mentioned document "Precipitation behavior of boron nitride on the surface of 18-8 stainless steel added with boron and nitrogen J," the precipitation treatment is performed on the as-cast material without solid solution treatment, so that the inside of the material is boron is unevenly distributed, and the boron nitride film deposited on the surface is non-uniform.Also, the surface is subjected to argon ion sputtering before the deposition process, so that the entire inner surface of the actual vacuum vessel etc. Sputtering requires expensive sputtering equipment and takes a long time, which is practically impossible.

As mentioned above, even if boron nitride is deposited on the entire surface of the steel material, it may not necessarily be effective against gas adsorption depending on the precipitation treatment temperature, precipitation treatment time, solution treatment temperature conditions, and temperature increase rate during the precipitation treatment. However, it was not always possible to form a boron nitride film with such characteristics.

Therefore, an object of the present invention is to obtain a boron nitride film having excellent properties against gas adsorption by appropriately selecting the precipitation treatment temperature, precipitation treatment time, solution treatment temperature, and heating rate. .

(Structure of the Invention) [Means for Solving the Problems] As a result of studying the gas adsorption properties of austenitic stainless steel having a boron nitride film deposited under various conditions, the present inventors found that the gas adsorption properties , precipitation treatment temperature,
The precipitation group time and the solution treatment temperature are deeply related to each other, and the rate of temperature increase during the precipitation treatment also has an effect, and by adjusting these to the appropriate temperature, time, and rate, gas adsorption The present invention was completed based on the discovery that it is possible to deposit a boron nitride film with excellent properties.

The gist of the invention is as follows.

When precipitating boron nitride on the surface of austenitic stainless steel containing 0.005 to 0.05 svt% boron and 0.08 to 0.30 ivt% nitrogen, the solution treatment temperature (To), precipitation Processing temperature (T1
) and precipitation treatment time (1) satisfy both conditional expressions (1) and conditional expressions (2), and the temperature increase rate from 400 to 650℃ during precipitation treatment is 5℃/a+in or more. A method for producing vacuum equipment and steel materials for vacuum equipment having boron nitride precipitated on the surface.

Conditional Expression (1) % Expression %) Conditional Expression (2) t≧6 Xl0-hexp (20000/T1) Note that the symbols in the expression are as follows.

To: Solution treatment temperature (K) Tl: Precipitation treatment temperature (K) t: Precipitation treatment time (sec) [Operation] In order to precipitate boron nitride on the surface of the steel material, boron and nitrogen must be contained in the steel material. Must be. First, the reasons for limiting the appropriate ranges of boron and nitrogen will be described.

Boron: An essential element to form boron nitride.

If the boron content is less than 0.005 wt%, boron nitride will not be sufficiently precipitated. On the other hand, if it exceeds 0.05 wt%, hot workability will be significantly impaired. Therefore, the limited range of boron content was set to 0.005 to 0.05 wt%.

Nitrogen: Also an essential element for forming boron nitride. If the nitrogen content is less than 0.08 wt%, boron nitride will not be sufficiently precipitated. On the other hand, if it exceeds 0.30 wt%, deformation resistance increases, impairing hot workability. Therefore,
The limited range of nitrogen content was set to 0.08 to 0.30 t%.

The austenitic stainless steel containing boron and nitrogen so as to satisfy the above limited range is subjected to solid solution treatment,
Perform boron nitride precipitation treatment. In addition, the solution treatment temperature (
To) is preferably 1173 or higher so that boron is sufficiently dissolved in solid solution, and it is not economical to raise the temperature too high, so 15
23 is sufficient. In addition, precipitation treatment temperature (T1)
Below 923, boron nitride is difficult to precipitate, and 117
3 or more, the precipitated boron nitride is re-dissolved, so 923 to 1173 K is preferable.

The present inventors investigated various solution treatment temperatures, precipitation treatment temperatures,
Samples were prepared in which boron nitride films were formed by varying the deposition time and temperature increase rate, and the characteristics against gas adsorption were evaluated. As an evaluation, superiority or inferiority was determined based on the amount of water (nzo) desorbed obtained by a temperature-programmed desorption test. As is clear from the Examples described later, when the treatment is performed in a range that does not satisfy Conditional Expression (1) or Conditional Expression (2), the amount of water (!hO) desorbed is large and the characteristics against gas adsorption are poor. Also, the conditional expression (1
) and conditional expression (2), if the temperature increase rate between 400 and 650° C. during the precipitation treatment is less than 5° C./min, the properties against gas adsorption are not good.

In a range where conditional expression (1) is not satisfied, although the entire surface is covered with a boron nitride film, the boron nitride grows non-uniformly, resulting in a significantly uneven surface. As a result, the gas adsorption area increases, resulting in poor gas adsorption properties. In a range where conditional expression (2) is not satisfied, the boron nitride film does not cover the entire surface, and the characteristics against gas adsorption are poor.

Furthermore, even if the precipitation treatment is performed within a range that satisfies conditional expressions (1) and (2), the temperature increase rate between 400 and 650°C is 5.
If the temperature is less than .degree. C./+nin, boron nitride will precipitate inside the stainless steel during the temperature rising process, and no boron nitride will precipitate on the surface. At temperatures below 400°C, the temperature is not sufficient for boron nitride to precipitate inside the stainless steel, and at temperatures above 650°C, boron nitride precipitates on the surface.
The temperature was 0 to 650°C. Note that boron nitride, which precipitates in stainless steel, precipitates in a short time at high temperatures, so
In the temperature range of 550 to 650°C, it is preferable that the temperature increase rate is high.

Examples will be described below, but the present invention is not limited to the following examples, and it is within the technical scope of the present invention to make appropriate design changes that adhere to the spirit of the preceding and following examples. be.

For example, even when the precipitation treatment is carried out in the pattern shown in Fig. 2, the precipitation temperature range in which precipitation is possible, that is, 650 to 900
When the effects of temperature and time are integrated in the range of .degree. C., conditional expressions (1) and (2) are substantially satisfied. Therefore, such cases are also included within the technical scope of the present invention.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. A steel having the composition shown in Table 1 was melted and then hot rolled into a plate having a thickness of 12 ml. This board is 1173-1
Water-cooled solid solution treatment at 473K for about 1 hour, 10 squares, 0.3mm thick, or 1100mm square, 1.5mm
Processed into thick samples.

After electropolishing the surface, boron nitride precipitation treatment was performed in a vacuum of 10-'Torr or less.

Table 2 shows the solution treatment temperature, precipitation treatment temperature, precipitation treatment time, and whether conditional expressions (1) and (2) are satisfied for the prepared samples, with those that satisfy the conditional expressions marked as ○. Unsatisfied items are marked with an x.

The table also shows the rate of temperature increase between 400 and 650°C during the precipitation treatment.

Nα97-118 and Nα125-96 are all examples of the present invention that satisfy the requirements of the present invention.
146 and Nα153-174 do not satisfy conditional expression (1) or (2), and No.119-124, Nα147-152, and Nα175-180 satisfy conditional expressions (1) and (2). The temperature increase rate between 400 and 650°C is less than 5°C, and this is a comparative example.

After each sample described above was subjected to a precipitation treatment, the sample was washed and subjected to a temperature-programmed desorption test. Water (n
The amount of desorption of zo) was measured, and the amount of desorption from the as-electrolytically polished sample was taken as 1, and those with a desorption amount of 115 or less were ◎,
Those exceeding 115 and 1/2 or less are indicated as ○, and those exceeding 1/2 are indicated as × in Table 2. - As an example, FIG. 1 shows the results of a temperature-programmed desorption test of a sample at a solution treatment temperature of 1373 and a heating rate of 5° C./1 min or more between 400 and 650° C. The symbols (◎, ○, ×) in the diagram are the second
This is the same as the evaluation method for the amount of desorption shown in the table.

As shown in Table 2 and Figure 1, conditional expressions (1) and (2
), and the samples of No. 1 to No. 96, which were treated within the range of the present invention in which the temperature increase rate between 400 and 650°C during precipitation treatment was 5°C/sin or more, were water (H, O) It can be seen that the amount of desorption is small and the properties against gas adsorption are extremely good, whereas the comparative example with a diameter of 97 or less has an amount of desorption of more than 1/2 in the temperature-programmed desorption test.

(Effects of the Invention) As explained above, according to the present invention, it has become possible to manufacture vacuum vessels and equipment steel materials having a poron nitride film having excellent properties against gas adsorption. Therefore, for example, in a vacuum apparatus using these, baking work, which conventionally required several tens of hours, can be shortened, and depending on the target pressure, it can be omitted, making it possible to significantly shorten the working time. In particular, this invention is very effective for devices such as analytical instruments that must be exposed to the atmosphere every time a sample is exchanged, and is a highly effective invention industrially.

[Brief explanation of drawings]

The drawings show the technical content of the present invention, and Figure 1 shows steel types A-D, solution treatment temperature 1373, and temperature rise between 400 and 650°C during precipitation treatment in an embodiment of the present invention. It is a figure which shows the temperature-programmed desorption test result about the sample with a temperature rate of 5 degreeC/lll1n or more. However, in these figures, the range between the two curves in FIG. 1 indicates a region that satisfies both conditional expressions (1) and (2). Further, FIGS. 2(a), (b), and (c) are diagrams showing examples of heat patterns for precipitation treatment. Patent applicant: Nippon Steel Tube Co., Ltd. Inventor: Tadashi Honma, Toshihiko Fukui, Akira Ebata, Yoshi Ishizawa

Claims (1)

[Scope of Claims] Solid solution treatment is performed when boron nitride is precipitated on the surface of austenitic stainless steel containing 0.005 to 0.05 wt% of boron and 0.08 to 0.30 wt% of nitrogen. temperature (T_0), precipitation treatment temperature (T_
1) and the precipitation treatment time (t) is treated within a range that satisfies both conditional expressions (1) and conditional expressions (2), and the temperature increase rate from 400 to 650 ° C during the precipitation treatment is 5 ° C / min or more. 1. A method for producing vacuum equipment and steel materials for vacuum equipment on which boron nitride is precipitated on the surface. Conditional expression (1) t≦60000(T_0-T_1)^-^2exp(1
1000/T_1)+6×10^-^6exp(200
00/T_1) Conditional expression (2) t≧6×10^-^6exp (20000/T_1) Note that the symbols in the formula are as follows. T_0: Solution treatment temperature (K) T_1: Precipitation treatment temperature (K) t: Precipitation treatment time (sec)