JPH0633264A - Austenitic stainless steel for high purity gas excellent in corrosion resistance and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture the steel in which moisture is hard to adsorb on the surface of the steel as well as the desorption of moisture from the surface is swift even in the case it is adsorbed and also having good corrosion resistance even to a corrosive gas. CONSTITUTION:This austenitic stainless steel for a high purity gas is the one contg. one or two kinds of 0.02 to 1.0% Ti and 0.02 to 1.0% Al, and in which the surface previously subjected to smoothing treatment so as to regulate the maximum roughness into <=1mum is applied with an oxidized film essentially consisting of Ti or/and Al. The austenitic stainless steel having the same compsn. is previously subjected to treatment so as to regulate the maximum roughness on the surface into <=1mum and is thereafter subjected to heating treatment at 750 to 1150 deg.C in an inert gas atmosphere having <=10<-6>Pa oxygen partial pressure or in a vacuum atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly corrosion resistant stainless steel member for high purity gas used in a semiconductor manufacturing process and the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art In the field of semiconductor manufacturing, high integration has advanced in recent years, and it is necessary to process a fine pattern of 1 μm or less when manufacturing a device called VLSI.

In such a VLSI manufacturing process, since minute dust and trace impurity gases adhere to and are adsorbed on the wiring pattern and cause circuit failure, both the reaction gas and the carrier gas used are of high purity. That is, it is necessary that the content of the fine particles and the impurity gas in the gas is small. Therefore, in the high-purity gas pipe and member used in the manufacturing apparatus, fine particles (particles) emitted as impurities from the inner surface of the member that comes into contact with the gas.
And it is required that the amount of gas is as small as possible. Further, as the semiconductor manufacturing gas, in addition to inert gases such as nitrogen and argon, corrosive gases such as chlorine and chlorosilanes are also used, so that a member in contact with these corrosive gases naturally needs to have high corrosion resistance. Become.

Conventionally, austenitic stainless steel, typically SUS 316L steel, has been used for such gas pipes and members for semiconductor production. These stainless steel members are smoothed to have a surface roughness Rmax of 1 μm or less in order to reduce adhesion and adsorption of dust and water. As a method of such surface smoothing,
Examples include cold drawing, mechanical polishing, electrolytic polishing and the like. The stainless steel member whose surface has been smoothed is then washed with high-purity water, dried with high-purity gas, etc. to obtain a product.

As an example, in JP-A-1-198463, the inner surface of the tube, the surface of which has been previously smoothed by electropolishing, contains Fe as the outer layer and 30 atom% or more of Cr as the inner layer.
A stainless steel member for semiconductor manufacturing equipment that has an oxide film with a thickness of 100 to 500 Å and a method for manufacturing the stainless steel member by heating in an oxidizing gas atmosphere with a dew point temperature of -10 ° C or less are shown. .

Japanese Patent Laid-Open No. 63-161145 discloses a steel pipe for a clean room in which non-metallic inclusions are reduced by restricting the contents of Mn, Si, Al, O, etc. A high-cleanliness austenitic stainless steel other than the standard steel for reducing the generation of particles is disclosed.

[0007]

When cleaning and drying with pure water after polishing, it is difficult to completely remove water on the surface of the steel material by room temperature drying. Even if the water is removed by baking at a high temperature of 100 to 300 ° C, a small amount of water in the air will be adsorbed again after drying and it will be difficult to desorb. When such a stainless steel material is used as piping and members for high-purity gas, it means that it takes a long time to purge the piping system before the operation in a semiconductor manufacturing plant, which is a serious problem in the actual operation.

The unfavorable desorption and release phenomenon of water due to surface adsorption is improved to some extent because the surface roughness of the steel material is microscopically reduced by cleaning stainless steel and reducing inclusions. However, it is not enough to improve the cleanliness of the steel itself.

Regarding the corrosion resistance required for storage containers and pipes for corrosive gas, even if stainless steel is electrolytically polished or further treated to give an oxide film with a thickness of 100 to 500Å, If the properties are not appropriate, corrosion resistance to corrosive gas is poor and rusting occurs. For this reason, it is difficult to avoid contamination of high-purity gas with rust particles.

The object of the present invention is to provide a highly corrosion-resistant, highly corrosion-resistant steel that is unlikely to adsorb moisture in the atmosphere on the surface of a steel material, is easily desorbed after adsorbing moisture, and is not rusted by corrosive gas. It is to provide a stainless steel material for pure gas and a manufacturing method thereof.

[0011]

In the present invention, the austenitic stainless steel material contains Cr in an amount of 15 to 30%.
Fe-based and Ni-based alloys are collectively referred to. A typical example is SUS
It is 316L. Then, before the heat treatment for applying the oxide film, the target is one that has been surface-polished in advance by, for example, electrolytic polishing so that the maximum roughness (Rmax) of the steel material surface becomes 1 μm or less.

Removal of residual water content on the surface of stainless steel after polishing and cleaning is easily realized by so-called baking in which heat treatment is performed at about 200 ° C. or higher. Furthermore, the present inventors investigated the adsorption and desorption behavior of moisture on the surface of steel and corrosion resistance to corrosive gas after heat treating the steel from which the above residual water was removed in various atmospheres and temperatures. As a result, an austenitic stainless steel material having a specific chemical composition with an appropriate amount of Ti and Al added as alloying elements was added to an ultra-low oxygen partial pressure inert gas or vacuum at 750 ° C.
If an oxide film mainly composed of Ti and / or Al is applied to the surface of the stainless steel material by heating it between 1 to 1000 ° C, the surface of the stainless steel material becomes inactive against water adsorption, and further excellent corrosion resistance is exhibited. I got the knowledge.

The gist of the present invention resides in the following steel material and its manufacturing method.

(1) Ti: 0.02 to 1.0% by weight and A
l: Austenitic stainless steel material containing 0.02 to 1.0% of one or two, and the maximum roughness is 1 μm in advance.
An austenitic stainless steel material for high-purity gas, which has an oxide film mainly composed of Ti and / or Al on its surface smoothed to m or less.

(2) Ti: 0.02 to 1.0% by weight% and A
l: 0.02 to 1.0% of 1 or 2 types, and M
An austenitic stainless steel material containing at least one of o: 7% or less, Cu: 3% or less and N: 0.3% or less, which has been smoothed in advance so that the maximum roughness becomes 1 μm or less. An austenitic stainless steel material for high-purity gas, which has an oxide film mainly composed of Ti and / or Al on the surface.

(3) Ti: 0.02 to 1.0% by weight and A
l: Austenitic stainless steel material containing 0.02 to 1.0% of 1 or 2 has a maximum surface roughness of 1 μm in advance.
The high purity according to (1) above, which is characterized by heat treatment at 750 to 1150 ° C. in an inert gas or vacuum atmosphere having an oxygen partial pressure of 10 ⁻⁶ Pa or less after the treatment so that the oxygen content is less than m. A method for producing an austenitic stainless steel material for gas.

(4) Ti: 0.02 to 1.0% by weight and A
l: 0.02 to 1.0% of 1 or 2 types, and further M
An austenitic stainless steel material containing at least one of o: 7% or less, Cu: 3% or less, and N: 0.3% or less is treated in advance so that the maximum surface roughness is 1 μm or less, and then oxygen is added. The method for producing an austenitic stainless steel material for high-purity gas according to the above (2), characterized in that the heat treatment is carried out at 750 to 1150 ° C. in an inert gas or vacuum atmosphere having a partial pressure of 10 ⁻⁶ Pa or less.

[0018]

FUNCTION The reasons for limiting the chemical composition of the steel material, the properties of the oxide film and the manufacturing conditions in the present invention will be explained. The alloy elements other than those described below are not particularly specified, and the material may be the above-mentioned austenitic stainless steel.

Ti and Al: If the oxide film on the surface of the stainless steel according to the present invention is not mainly composed of Ti or / and Al oxide, both the corrosion resistance and the moisture releasing property are deteriorated. Therefore, Ti and Al are elements that are particularly important for forming an oxide film required in the present invention, and one or two of these two elements are contained. Together
If it is less than 0.02%, an oxide film mainly composed of Ti or Al cannot be obtained even by heat treatment. On the other hand, in both cases, if it exceeds 1.0%, the mechanical properties and corrosion resistance of the steel itself will deteriorate. Therefore, the content range of both Ti and Al is 0.02% or more, 1.
It was 1% or more than 2% at 0% or less.

Mo, Cu, N: All are elements having an effect of improving the corrosion resistance, and contain one or two of the above Ti and Al, and further, one or two of these three elements. The above is included.

When Mo exceeds 7%, hard and brittle intermetallic compounds such as σ phase and Laves phase are formed to deteriorate hot workability, making it difficult to manufacture a seamless steel pipe.
The mechanical properties, especially the toughness of the weld, are reduced. Therefore, Mo
Was set to 7%.

If the Cu content exceeds 3%, the hot workability deteriorates due to Cu embrittlement, making it difficult to manufacture a seamless steel pipe and reducing the mechanical properties, especially the toughness of the weld. Therefore, the upper limit of Cu is set to 3%.

When N exceeds 0.3%, nitrides such as Cr ₂ N are formed and hot workability deteriorates, and similarly, it becomes difficult to manufacture a seamless steel pipe, and mechanical properties, especially of welded parts Toughness decreases. Therefore, the upper limit of N is set to 0.3%.

Heat treatment conditions: Oxygen partial pressure in the heat treatment atmosphere
The reason for using an inert gas of 10 ^-6 Pa or less or in vacuum is
In an atmosphere where the oxygen partial pressure exceeds 10 ^-6 Pa, the Fe and Cr contents in the oxide film increase, and the desired oxide film mainly composed of Ti and / or Al cannot be obtained, and the water desorption characteristics and corrosion resistance are Both decrease.

When the heating temperature is less than 750 ° C., Fe in the oxide film is
Also, the Cr content increases, and the desired oxide film cannot be obtained as in the above case. On the other hand, if the temperature exceeds 1150 ° C, the mechanical properties of the steel itself deteriorate significantly. The heating temperature is preferably in the range of 800 to 1000 ° C.

[0026]

EXAMPLE An inner surface of a seamless steel pipe of SUS316 L steel having an outer diameter of 6.4 mm, a wall thickness of 1 mm, and a length of 4 m having the chemical composition shown in Table 1 was smoothed by electrolytic polishing so that Rmax became 0.5 μm, and After washing with pure water, it was heated to 200 ° C. and dried while passing 99.999% Ar gas.

These steel pipes were heat-treated under various conditions shown in Table 2 to give an oxide film, and a sample cut out from the central portion of the steel pipe was used to measure the cross-sectional depth from the inner surface of the steel pipe by a secondary ion mass spectrometer. Direction elemental analysis was performed to measure the maximum Ti and Al contents and the oxide film thickness.

Using a length of 2 m of the remaining sample, the sample was allowed to stand in an atmosphere of 20 ° C. and a relative humidity of 52% for 48 hours, and then dry Ar gas was caused to flow in the tube at a rate of 2 liter / min. The amount of water in the gas was analyzed by a mass spectrometer. The evaluation is the time required for the water content to be 50 ppb or less (H ₂ shown in Table ₂
O desorption time).

In the corrosion resistance test, 99.9% chlorine gas was sealed at a pressure of 0.5 MPa in a test tube having a length of 1 m among the remaining samples, cooled once with liquid nitrogen, left open to the atmosphere and left standing for 5 days. It was carried out by a method of cracking and visually observing the rusting condition on the inner surface of the pipe. The results of these tests are also shown in Table 2. The white circles in the corrosion resistance test results indicate that there is no rust due to corrosion, and the black circles indicate that there is rust due to corrosion.

As can be seen from Table 2, in the stainless steel pipe having the chemical composition and the heat treatment condition within the range defined by the present invention, the water desorption after Ar ventilation is fast. Furthermore, the corrosion resistance to chlorine gas is also good.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

According to the present invention, the austenite for high-purity gas, which is unlikely to adsorb moisture in the atmosphere on the surface of the steel material, quickly desorbs moisture from the surface, and has good corrosion resistance to corrosive gases, is also provided. A system stainless steel material is obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // C22C 38/00 302 Z 38/58

Claims (4)

[Claims] 1. Ti: 0.02-1.0% and Al: 0.
An austenitic stainless steel material containing 02 to 1.0% of one or two kinds, which is preliminarily smoothed to have a maximum roughness of 1 μm or less, and has an oxide film mainly composed of Ti and / or Al. An austenitic stainless steel material for high-purity gas, which comprises: 2. Ti: 0.02-1.0% and Al: 0.
02-1.0% 1 type or 2 types, and Mo: 7%
Hereinafter, an austenitic stainless steel material containing at least one of Cu: 3% or less and N: 0.3% or less, the surface of which has been smoothed in advance so that the maximum roughness is 1 μm or less, Ti or An austenitic stainless steel material for high-purity gas, which has an oxide film mainly composed of / and Al. 3. Ti: 0.02-1.0% and Al: 0.
An austenitic stainless steel material containing 02 to 1.0% of one or two is pretreated so that the maximum surface roughness is 1 μm or less, and then an inert gas with an oxygen partial pressure of 10 ⁻⁶ Pa or less or The method for producing an austenitic stainless steel material for high-purity gas according to claim 1, wherein the heat treatment is performed at 750 to 1150 ° C in a vacuum atmosphere. 4. In weight%, Ti: 0.02 to 1.0% and Al: 0.
02-1.0% of 1 type or 2 types, and Mo: 7
% Or less, Cu: 3% or less and N: 0.3% or less 1
Austenitic stainless steel material containing more than one species,
A method of preliminarily treating the surface to a maximum roughness of 1 μm or less, and then heat-treating at 750 to 1150 ° C. in an inert gas or vacuum atmosphere having an oxygen partial pressure of 10 ⁻⁶ Pa or less. 2. The method for producing an austenitic stainless steel material for high-purity gas according to 2.