JP5392752B2 - Ultra-low carbon stainless steel flange and fitting and ultra-low carbon stainless steel sealing valve - Google Patents

Description

  The present invention relates to an ultra-low carbon stainless steel pipe joint and an ultra-low carbon stainless steel sealing valve in which the ultra-low carbon stainless steel has a sealing function, and this ultra-low carbon stainless steel is applied to a pipe joint and a sealing valve. The present invention relates to a flange and joint made of ultra-low carbon stainless steel that do not require a seal member, and a valve body for sealing made of ultra-low carbon stainless steel.

Attempts to change the mechanical and chemical properties of the surface layer of metal materials by ion implantation began in the 1970s, and have been recognized for their effects on wear resistance, impact resistance, and increased hardness. Yes. When 100 keV N ⁺ ions and P ⁺ ions are implanted into the base material of titanium and stainless steel SUS316, the hardness of the material surface increases by 150% and 85%, respectively, along with the amount of ion implantation, confirming improved wear resistance. Has been.
Titanium and stainless steel materials are mainly used for industrial applications as structural materials, and the purpose of ion implantation is to increase the strength of the steel material surface and to improve wear resistance. In the stainless steel material, the carbon content is 0.08% in the austenitic stainless steel SUS304 in order to maintain the strength as a structural material. In the SUS316L steel material used for the purpose of increasing the corrosion resistance, the carbon content is regulated to 0.03% or less, and in the commercial product, it is limited to 0.013%.

  However, when the carbon content is less than 0.01%, it is difficult to maintain the strength as a structural material, industrial applications are extremely reduced, and the material is limited to high-purity gas piping materials for semiconductors. At present, there are very few steel manufacturers that produce stainless steel materials with a carbon content of less than 0.01%, and stainless steel materials with a carbon content of less than 0.01% are high-purity materials with extremely low impurities other than carbon. Yes, with excellent corrosion resistance.

When the carbon content is less than 0.01%, the hardness of the stainless steel material is lowered, and the hardness of Clean Star A (registered trademark) having a carbon content of 0.006% is H _R B = 75, and copper (H _R B = 70) and SUS316L (H _R B = 80) are shown as intermediate hardness. The soft ultra-low carbon stainless steel material is ion-implanted to form a hardened layer with excellent wear resistance on the surface layer, thereby producing a soft steel material with an inner surface. Up to now, ₂₀ keV, N ₂ ⁺ ions have been implanted into Clean Star B (registered trademark) having a carbon content of 0.007%, and a hardened layer having a hardness 5.6 times that of SUS316L has a surface layer of 0.1 to 0.2 μm. Has been confirmed to be formed.

  In addition, as an invention using a stainless steel material for a pipe joint, the invention described in Patent Document 1 is a metal first and second flange for flange-connecting pipes to each other by a steel material such as austenitic stainless steel or carbon steel. The first flange is made of a softer material than the second flange, and the first flange and the second flange are fastened to each other on the end face of the second flange. There is described a pipe joint characterized in that a crown-shaped protrusion is formed which bites into the end faces and joins the end faces while maintaining the sealing property between the end faces.

JP-A-8-303661

  However, when the metal contact portion is provided with a sealing function, generally, the sealing surface needs to be excellent in both the sealing property and the peeling property. In ordinary stainless steel piping and the like, a sealing member made of a stable polymer material such as precious metal, rubber, Teflon (registered trademark) or polyimide is used on the sealing surface. It is necessary to combine the flexibility to give the contact flange surface roughness and the releasability to avoid welding due to direct contact between the same kind of metals. In general, it has been difficult to make the seal member unnecessary from the seal portion of the pipe joint or the seal valve.

Further, the conventional sealing members have the following industrial technical problems.
In other words, rubber / polymer seal members are cured at low temperatures, rubber / polymer seal members are deteriorated in radiation / plasma environment, noble metal (copper, gold, etc.) seal members are ductile at high temperatures, and different metal seals are used Corrosion due to contact potential difference generated in the member, extremely expensive Inconel alloy of high temperature resistant seal member, increase of tightening torque in metal seal large diameter pipe joint, difficulty in shape matching between large diameter pipe joint / square pipe joint and seal member There was a problem such as.

On the other hand, the above-mentioned soft hard stainless steel material having both the inner surface flexibility and the superhardness of the surface layer has various characteristics such as excellent wear resistance and high adhesion to metal. have. The features of this ultra-low carbon stainless steel sealing technology are summarized as follows.
a) Wide operating temperature range from high temperature to low temperature. That is, there is no hardening at a low temperature found in polymer seal members, no ductility at a high temperature found in noble metal seal members, and a seal function is exhibited from a very low helium temperature to 450 ° C. (723 K). By performing dehydrogenation in advance before the injection step, it is possible to expect a sealing function at an extremely high temperature of 600 ° C. (873 K) or higher, which exceeds that of the Inconel alloy.

b) Excellent stability in radiation, plasma, and high-temperature and high-humidity hard environments, that is, there is no deterioration under the radiation and plasma environment seen in polymer seal members, and due to the contact potential difference generated in dissimilar metal seal members. Since there is no risk of corrosion, it shows an excellent sealing function in a hard environment.
c) Easy connection of large pipes and square pipes. That is, the tightening torque of the ultra-low carbon stainless steel pipe joint and the sealing valve is as low as 1/3 to 1/4 as compared with the case of using a noble metal seal member, which is a problem with a large-diameter pipe joint. The increase in tightening torque is suppressed, there is no difficulty in shape matching with the seal member, large pipes and square pipes can be easily connected, and stable sealing functionality is ensured.

d) Long life and low cost. That is, in the ultra-low carbon stainless steel pipe joint / sealing valve, immediately after production, a certain minute change is seen in the seal part, and after the deformation converges to a specific shape by the opening operation around 20 times, it is caused by elastic deformation. Sealing function works and realizes extremely long life. In view of the absence of waste consumables for the seal member, the total cost is low.
e) It can contribute to reduction of environmental load. That is, since there is no waste consumable for the seal member, it can contribute to the environmental load. In particular, the industrial value of having no seal member is extremely high, such as the absence of activated waste consumables in a radiation environment and the use in a space environment where it is expensive to collect waste consumables. .

In view of the above, new sealing functionality can be expected from the ultra-low carbon stainless steel material of the inner hard surface soft type, and it is conceivable to produce a pipe joint and a sealing valve using this steel material.
Therefore, the present invention has been made in view of the above circumstances, and the super low carbon stainless steel material with soft inner surface has both adhesiveness and peelability, so that it has both a sealing function and a joint function. It is an object of the present invention to provide a low carbon stainless steel flange and joint, and an ultra low carbon stainless steel sealing valve body.

In order to achieve the above object, an ultra-low carbon stainless steel flange according to claim 1,
A flange formed by forming a hollow made of ultra-low carbon stainless steel having a carbon concentration of 0.01% or less, the flange having a seal structure on its main surface, the seal structure having a convex shape, The convex shape includes a flat surface substantially parallel to the main surface of the flange, and a curved surface extending from the end of the flat surface to the main surface of the flange, and W1 is a seal width, W2 is a flat surface width, When R is the radius of curvature and H is the height of the flat surface, the dimensions W1> W2 ≧ 0, R> W1, and R> H are satisfied, and the smoothness Ry of the flat surface is about 0.1 μm. The nitrogen concentration injected into the substrate is at least 1.65 × 10 ¹⁷ / cm ² .
The ultra-low carbon stainless steel flange according to claim 2 is related to the ultra-low carbon stainless steel flange according to claim 1,
The diffusion depth of nitrogen implanted into the flat surface is not more than the flat surface height.

According to a third aspect of the present invention, there is provided a joint comprising the ultra low carbon stainless steel flange according to the first aspect.
The ultra low carbon stainless steel sealing valve body according to claim 4 is:
A sealing valve body made of ultra-low carbon stainless steel having a carbon concentration of 0.01% or less, wherein the sealing valve body has a seal structure on its main surface, and the seal structure has a convex shape. The convex shape includes a flat surface substantially parallel to the main surface of the sealing valve body, a curvature surface extending from the end of the flat surface to the main surface of the flange, and W1 is a seal width, When W2 is a flat surface width, R is a radius of curvature, and H is a flat surface height, there are relationships of dimensions W1> W2 ≧ 0, R> W1, R> H, and the smoothness Ry of the flat surface is about The concentration of nitrogen injected into the flat surface is 0.1 μm, and is at least 1.65 × 10 ¹⁷ / cm ² .
Further, the ultra low carbon stainless steel sealing valve body according to claim 5 relates to the ultra low carbon stainless steel sealing valve body according to claim 4,
The diffusion depth of nitrogen implanted into the flat surface is not more than the flat surface height.

With the ultra-low temperature stainless steel pipe joint or ultra-low temperature stainless steel sealing valve of the present invention described above, the super hard carbon soft ultra-low carbon stainless steel material has both adhesion and peelability, so that stainless steel pipes that do not require a seal member are required. The effect that a joint and an all stainless steel sealing valve become possible for the first time is acquired.
This will also greatly open up new industrial uses for ultra-low carbon stainless steel.

It is a perspective view which shows the structure of the pipe joint made from an ultra-low carbon stainless steel which concerns on embodiment of this invention. It is a top view which shows each flange. It is sectional drawing which shows the structure of a 1st flange. FIG. 4 is a partially enlarged view of FIG. 3. It is a sectional side view which shows the structure of a 2nd flange. It is the elements on larger scale of FIG. It is a figure which shows the example of the dimension of three types of 1st flanges from which a shape differs. It is the schematic which shows a sealing functionality evaluation test method. It is a figure which shows the relationship between a seal surface displacement amount and a vacuum leak amount. It is a figure which shows an example of the output recording of a vacuum gauge. It is a top view which shows the measurement point of CS34 flange. It is a figure which shows the evaluation (1) regarding fastening repetition. It is a figure which shows the evaluation (2) regarding fastening repetition. It is a figure which shows the evaluation (3) regarding fastening repetition. It is a figure which shows the relationship between the frequency | count of mounting | tightening fastening, and a height difference reduction amount. It is a figure which shows the shape of a test flange, (a) shows the height and width of a sealing surface, (b) is a cross-sectional view of a flange, (c) is a top view of a flange. It is a graph which shows the vacuum degree time transition for every material after tightening with the predetermined torque. It is data which shows the vacuum degree transition for every material after clamp | tightening with a predetermined torque. It is a figure which shows the deformation | transformation (CS-2) of the seal surface after maximum torque clamping, (a) is data, (b) is shown with a graph. It is a figure which shows the deformation | transformation (CS-L3) of the seal surface after maximum torque clamping, (a) is data, (b) is shown with a graph. It is data which shows a deformation | transformation of a seal surface protrusion part height difference.

Hereinafter, an ultra-low carbon stainless steel piping flange according to an embodiment of the present invention will be described. In addition, this embodiment shows the example at the time of using an ultra-low carbon stainless steel piping flange for a joint.
FIG. 1 is a perspective view showing a configuration of an ultra-low carbon stainless steel pipe joint according to an embodiment of the present invention, FIG. 2 is a plan view of first and second flanges, and FIG. 3 and FIG. FIG. 5 and FIG. 6 are views showing a cross-sectional shape and a partial enlarged view of the second flange, and FIG. 7 is a view showing three types of first flanges having different shapes. It is a figure which shows each dimension.

As shown in FIGS. 1 and 2, the ultra-low carbon stainless steel pipe joint 1 according to the present invention includes a first flange 11, a second flange 12, a first flange 11, and a second flange 12. And a plurality of bolts 13 to be coupled.
As shown in FIGS. 3 and 4, the first flange 11 is formed in a substantially circular shape in the circumferential direction, and a plurality of bolt insertion holes 112 for inserting a plurality of bolts 13 along the disc-shaped circumferential direction. And has a circular convex cross-sectional shape sealing surface 113 for tightly sealing the second flange 12 and sealing. Further, the first flange 11 is molded using an ultra-low carbon stainless steel material having a carbon content of 0.01% by weight or less, and a predetermined amount of nitrogen ions is injected from the surface thereof. The surface 113 is polished to a predetermined smoothness. Specifically, the actual ultra-low carbon stainless steel material was manufactured with Clean Star B steel material.

  As shown in FIG. 5 and FIG. 6, the second flange 12 includes a hole 121 for airtightly contacting the other tube at the disc-shaped central portion, and a plurality of first flanges 11 along the circumferential direction. A plurality of bolt fixing holes 122 provided at positions facing the bolt insertion holes 112, and a planar sealing surface 123 for deforming and closely contacting the circular convex cross-sectional sealing surface 113 of the first flange 11. Have. The second flange 12 is molded using an austenitic SUS316L stainless steel material, a predetermined amount of nitrogen ions is implanted from the surface thereof, and the planar sealing surface 123 is polished to a predetermined smoothness.

Further, as shown in FIG. 7, as the first flange 11, three types having different heights (seaheight) H (mm) of the circular convex cross-section sealing surface 113 are used by using ultra low carbon stainless steel “CS34”. Was made. In the manufacturing method, first, a 50 mm diameter round bar material of Clean Star B having a carbon content of 0.007% was cut in parallel with the rolling drawer shaft and cut into a plate material, and then processed into the CS34 flange shape shown in FIG. . Next, the circular convex cross-sectional shape seal surface 113 was mechanically polished and surface-finished with a smoothness Ry of about 0.1 μm. Next, the ion implantation apparatus was set, and N ₂ ⁺ ions were implanted at an energy of 25 keV. Actually produced CS
The 34-flange circular convex cross-section sealing surface 113 has a drooping width W (mm) with its tip drooping flat during mechanical polishing. In addition, when the sealing surface of the first flange is polished to a smoothness of about Ry = 0.1 μm, the tip of the circular convex cross-sectional shape sealing surface 113 of the CS34 flange is also polished to have a width W (mm). It is flat and no longer circular. As a result, the length of one of the two tapered portions formed on both sides of the flat surface is R (mm).

  As described above, when three types of “CS34 flanges” having different H, R, and W are CS34-1, CS34-2, and CS34-3, respectively, as shown in FIG. W was “0.211, 2.6, 0.351” in order, and the smoothness Ry was “0.136 (μm)”. Similarly, H, R, and W of CS34-2 are “0.120, 5.05, 0.565” in order, and the smoothness Ry is “0.115 (μm)”. , R, W were “0.083, 10.03, 0.476” in order, and the smoothness Ry was “0.103 (μm)”.

With the above configuration, the first flange 11 and the second flange 12 are tightened with bolts, the circular convex cross-sectional seal surface 113 is pressed against the planar seal surface 123, and the convex portion is deformed flat. Has a sealing function.
As described above, ion implantation is performed after polishing. In order to calculate the optimum ion implantation amount at that time, the following experiment was performed.
As samples, four clean star samples for ion implantation processed to a diameter of 40 mm and a thickness of 2.0 mm were prepared, and four clean stars and four austenitic stainless steel SUSLs were prepared as comparative samples and subjected to mechanical polishing. The surface finish of each sample was measured.
As a result, the sample surface accuracy is 7 to 24 nm with an average roughness of the sample for ion implantation, 47 to 141 nm even at the peak of the roughest unevenness, and 5 to 9 nm with the average roughness of the comparative sample and 30 at the peak of the roughest unevenness. -90 nm.

Next, the results of comparative experiments on the argon sputtering cleaning of the sample and the ion implantation method will be described.
First, four samples were arranged in a circle at a central pitch of 60 mm on a 140 nm diameter disc jig, placed in a vacuum layer, and then ion-implanted following argon sputter cleaning.
In the argon sputter cleaning, Ar gas was introduced at a pressure of 0.33 Pa, and a high frequency was introduced into the Ar gas to clean the sample surface. The frequency of the introduction high frequency was 13.56 MHz and the output was 150 W. The cleaning time was 30 minutes.

Next, once the inside of the vacuum chamber was returned to a vacuum, N ₂ gas was introduced at a pressure of 0.39 Pa, and a high frequency pulse (pulse width 50 μs, frequency 13, 56 Hz, An output of 25 W and a repetition frequency of 1000 Hz were applied to generate plasma along the sample surface. The plasma with low power discharge, N ₂ ⁺ molecular ions is nearly. A high voltage pulse of 25 kV (pulse width 10 μs, repetition frequency 1000 Hz) was applied to the sample, and N ₂ ⁺ molecular ions in the plasma were incident on the sample surface. In this ion implantation method, uniform plasma is generated along the sample shape, and N ₂ ⁺ molecular ions are simultaneously incident on the four samples by the applied high voltage pulse, so the same amount of N ₂ ⁺ is applied to the four samples. The molecular ions are uniformly implanted.

Next, the injection amount will be described below.
The range when N ₂ ⁺ molecular ions are accelerated and implanted into stainless steel at 25 kV is almost the same as that of implanting 12.5 keV N ⁺ atomic ions. When the target is Fe with a density of 7.866 g / cm ³ and simulated with the TRIM code (version 1998), the range becomes 16.2 nm. The nitrogen ion implantation amount was estimated based on the implantation amount obtained by AES (Auger electron spectroscopy) measurement after nitrogen implantation into a silicon substrate. As a result, the amount of nitrogen injected into the stainless steel was 1.65 × 10 ¹⁷ / cm ² . The number of metal atoms present in the above-mentioned 16.2 nm range in stainless steel is about 8.47 × 10 ²² atoms / cm ³ × 16.2 nm = 1.37 × when the composition of stainless steel is all converted to iron. 10 ¹⁷ atoms / cm ² . Therefore, in this experiment, about 1.2 times the number of iron atoms present in the volume of the stainless steel surface layer of 16.2 nm is implanted, and this is the optimum ion implantation amount.

Next, the sealing functionality evaluation method of the ultra-low carbon stainless steel pipe joint of the present invention will be described. Hereafter, the method and result of the evaluation test of the sealing functionality of the ultra-low carbon stainless steel pipe joint manufactured as described above will be reported.
FIG. 8 is a schematic diagram showing the inside of a vacuum chamber for performing a seal function evaluation test method, FIG. 9 is a diagram showing the relationship between the amount of displacement of the seal surface and the amount of vacuum leak, and FIG. FIG. 11 is a plan view showing measurement points on the flange when measuring the amount of displacement of the seal surface, and FIGS. 12 to 14 are views showing evaluations related to repetition of tightening. FIG. 15 is a diagram showing the relationship between the number of mounting tightening times and the height difference reduction amount.

[Seal function evaluation test]
The seal function evaluation test uses a clean star B having a carbon content of 0.007% to examine the seal functionality of the soft hard ultra-low carbon stainless steel material. As a result, it is satisfactory even without a seal member. It was found to have a sealing function.
In this experiment, “ICF (trademark of ConFlat Flange) 70” is used as the second flange 12, and “CS34 flange” is used as the first flange 11. In any case, since it is used as a pre-evaluation test for sealing functionality, the functionality as a vacuum pipe joint is improved. That is, in order to make the first flange “CS34” detachable from the second flange “ICF70”, the “SUS316L material” is used as the “ICF70-CS34 conversion flange”. Therefore, the second flange has a flat seal surface of the same diameter that is in close contact with the normal “ICF flange” on one side and the “CS34 flange” on the other side. The “SUS316L material” was also subjected to 25 keV, N ₂ ⁺ ion implantation in the same manner as the “CS34 flange”. With this structure, the circular convex cross-section sealing surface of the “CS34 flange” is pressed against the planar sealing surface of the “CS34 side” of the “ICF70-CS34 conversion flange”, thereby forming the circular convex facial shape of the “CS34 flange”. The convex part is deformed flat and has a sealing function. Accordingly, in the following description, the first flange is referred to as “CS34 flange”, and the second flange is referred to as “ICF70-CS34 conversion flange”.

Next, as shown in FIG. 8, the vacuum sealability of the “CS34 flange” was evaluated using a vacuum exhaust system equipped with a turbo molecular pump having a pumping speed (TMP) V = 400 l / S. Attach "ICF-CS34 conversion flange" to the vacuum port of ICF70 of the vacuum chamber, set "CS34 flange" as the test flange,
gauge) was used to measure the amount of vacuum leak. The ultimate vacuum of this vacuum system is G ₀ = 1.3 × 10 ⁻⁸ Torr (1.7 × 10 ⁻⁶ Pa), and the vacuum measurement resolution is ΔG = 1 × 10 ⁻⁹ Torr (1.3 × 10 ⁻⁷ Pa). Therefore, the detection limit of the amount of vacuum leak in this seal functionality evaluation was Q ₀ = ΔGV = 4 × 10 ⁻⁷ Torr / S (5.3 × 10 ⁻⁵ Pal / S). Before and after attaching the “CS34 flange” to the vacuum evaluation system, the height H of the sealing surface of the circular convex cross-sectional shape of the “CS34 flange” on the surface plate was measured with a precision dial gauge (minimum memory accuracy 1.0 μm). . The return after the sealing surface having a circular convex cross section deformed by tightening of the flange was deformed by repeated tightening was measured. The “CS34 flange” set in the “ICF70-CS34 conversion flange” was subjected to torque adjustment using a precision dial gauge so that a uniform torque was applied when the bolt was tightened. In addition, even after being attached to the vacuum vessel, the precision dial gauge was set in contact with the “CS34 flange”, and the relationship between the flange seal surface displacement and the vacuum leak amount was measured while gradually tightening the M4 bolt. When the amount of vacuum leak reached the detection limit, one measurement was finished, the “CS34 flange” was removed, and the height H of the sealing surface of the circular convex cross section was measured on the surface plate.

[Seal functionality evaluation results]
As described above, the relationship between the amount of displacement of the seal surface of the “CS34 flange” attached to the vacuum evaluation system and the amount of vacuum leak was measured a total of six times. One measurement time until the vacuum leak amount reached the detection limit required 4 to 20 hours. As a result, the tightening torque of the vacuum gauge was increased, the sinking amount was adjusted to 1.0 μm and 2.0 μm, and the total sinking of 10 μm was performed by six tightening, and the vacuum leak amount reached the detection limit. An example of the output recording of the vacuum gauge at this time is shown in FIG.

Initially, “CS34 flange” was set to “ICF70-CS34 conversion flange” on the surface plate, and the tightening torque was uniformly adjusted so that the displacement amount ΔH = 2.0 μm of the seal surface. After being attached to the vacuum evaluation system, it reached 3.5 × 10 ⁻⁸ Torr by evacuation for 2 hours (1). Furthermore, the tightening torque was increased by a displacement amount ΔH = 2.0 μm, and the total ΔH = 11 μm was displaced by six tightenings, and the degree of vacuum reached 1.3 × 10 ⁻⁸ Torr of the ultimate degree of vacuum (2-6) ). The results of the displacement amount ΔH and the degree of vacuum are summarized in FIG.

[Evaluation of repeated tightening of the circular convex cross-section sealing surface of CS34 flange]
Next, in the measurement of the relationship between the displacement of the seal surface of the circular convex cross section of the “CS34 flange” and the amount of vacuum leak, the sinking of the circular convex cross sectional seal surface after repeated tightening was measured. The measurement points are shown in FIG. After the amount of vacuum leak reaches the detection limit, the “CS34 flange” is removed from the “ICE70-CS34 conversion flange”, and the base portion (measurement points 1 to 6) and top (measurement point 7) of the circular convex cross-section seal surface is removed. ˜12) was measured, and the circular convex cross-section seal surface was sunk due to deformation exceeding the elastic limit by tightening, and the amount of decrease in the height difference S was measured. The difference between the seal surface top and the seal surface base at that time is shown in FIG.
Then, the amounts of sinking after the first removal and the sixth removal are summarized in FIGS. 13 and 14, respectively. Taking the average of the height differences S at the six measurement points on the circular convex cross-section shaped sealing surface, the initial value S ₀ = 121.67 μm, the value after the first removal S ₁ = 120.17 μm, after the sixth removal S ₆ = 116.67 μm.

[Discussion]
Each time the “CS34 flange” was tightened, the circular convex cross-section sealing surface submerged due to deformation exceeding the elastic limit, and a decrease in the height difference S was observed. The amount of decrease in the height difference S during the first mounting tightening is ΔS ₁ = (S ₁ −S ₀ ) = 1.5 μm / time from the average value S ₁ of the six measurement points, and since the second mounting tightening. The amount of decrease per time due to the sixth mounting tightening was ΔS ₆ = (S ₆ −S ₁ ) / 5 times = 3.5 μm / 5 times = 0.7 μm / time. The average reduction amount ΔS of the height difference S per mounting tightening is described as decreasing exponentially with each mounting tightening number.
ΔS (x) = Ae ^−ax (1)
It is represented by From the conditions of ΔS (1) = 1.5 μm and ΔS (6) = 0.7 μm,
A = 1.75 μm (2)
a = 0.152 (3)
Is decided.

FIG. 15 shows the average reduction amount ΔS with respect to the number x of mounting tightening at this time.
As a result, ΔS <0.1 μm is already reduced at x = 20. As the mounting tightening number x increases, the decrease amount ΔS (x) of the height difference S (x) decreases rapidly, and S (x) converges to a constant value Sm. The thickness is required to be a theoretical value that does not decrease even when the number of mounting tightenings is increased. That is,

  By substituting the values of A = 1.75 μm and a = 0.152, a theoretical value of the maximum reduction amount and final height difference of the circular convex cross-section sealing surface is obtained.

S _m = 111.8 μm (Final height difference) (6)
The maximum reduction amount of 9.84 μm corresponds to a reduction of 8.1% with respect to the initial value S ₀ = 121.67 μm. The height difference S ₀ = 116.67 μm when the “CS34 flange” is tightened six times indicates that the reduction amount has reached 50% or more of the reduction amount that has reached the theoretical value of the final height difference (6). ing. Since the final height difference (6) approaches 90% or more in at least 10 mounting tightening times, it is considered that the initial circular deformation due to the mounting tightening occurred on the circular convex cross-section seal surface. It is considered that further evaluation of sealing performance after the number of tightening times of about 10 times is necessary in the future.

[Conclusion]
A pre-evaluation test on the sealing functionality of the ultra-low carbon stainless steel material with soft inner surface was performed using Clean Star B having a carbon content of 0.007%. The pipe joint “CS34 flange” designed for the evaluation test has the same outer shape as the “ICF34 flange”, which is a vacuum standard flange, and has a radius R (seal height), a thickness H (seal height), and a smoothness Ry = 0. A ring-shaped sealing surface having a circular convex cross-section with a surface finish of about 1 μm is in close contact with the planar sealing surface of the mating flange for sealing. As the flange tightening torque is increased, the sealing property is improved by increasing the contact area while the circular convex cross-section sealing surface is deformed into a flat shape. The "CS34 flange" is mounted on a vacuum exhaust system with a turbo molecular pump with a pumping speed V = 400 l / s via the "ICE70-CS34 conversion flange" made by SUS316L, and the evaluation of the vacuum sealability of the "CS34 flange" is performed. went.

The relationship between the flat deformation ΔH with the thickness H of the circular convex cross-sectional shape sealing surface and the degree of vacuum is investigated, and the maximum ultimate degree of vacuum G ₀ = 1.3 × 10 ⁻⁸ of the vacuum exhaust system with the deformation of ΔH = 6 to 11 μm It reached Torr (1.7 × 10 ⁻⁶ Pa) and showed a good vacuum sealing property. As a result of loosening the flange tightening and examining the peelability of the circular convex cross-sectional shape seal surface, no welding was observed between the seal surfaces, and no force was required to peel off the seal surface. From the above, it can be concluded that the soft inner ultra-low carbon stainless steel material has an excellent sealing function at a practical level.
It becomes clear that the circular convex cross-section seal surface with respect to the number of tightening times of “CS34 flange” approaches 90% or more of the theoretical value of the final height difference, and the circular convex cross-section seal surface height difference inelastic deformation Suggests the possibility of initial subsidence deformation due to mounting tightening.

Next, the ultra low carbon stainless steel sealing valve according to the embodiment of the present invention will be described.
This ultra-low carbon stainless steel sealing valve is the same as the ultra-low temperature stainless steel pipe joint if the first flange of the ultra-low temperature stainless steel pipe joint described above is replaced with a valve body and the second flange is replaced with a valve seat. An ultra-low carbon stainless sealing valve having a sealing function can be manufactured.
Specifically, the sealing valve made of ultra-low temperature stainless steel includes a fluid storage chamber for storing fluid, an introduction portion for introducing fluid into the fluid storage chamber, a lead-out portion for deriving fluid from the fluid storage chamber, A sealing valve comprising: a sealing means for sealing the fluid by sealing at least one of the flow paths formed in the introduction part and the outlet part with a valve, wherein the sealing means includes a valve The valve body is formed in a convex cross-sectional shape formed in a substantially circular shape in the circumferential direction, and has a circular convex cross-sectional shape sealing surface for sealing tightly with the valve seat. And the valve seat has a planar sealing surface for deforming and closely contacting the circular convex cross-sectional sealing surface of the valve body,
The valve body and the valve seat are molded using a material made of ultra-low carbon stainless steel having a carbon content of 0.01% by weight or less, and the circular convex cross-sectional sealing surface of the valve body and the valve seat The planar sealing surface is polished to a predetermined smoothness and is implanted by implanting predetermined ions from the surface of the ultra-low carbon stainless steel, and the valve body and the valve seat are formed by the bubbles. Simply tighten it to provide a sealing function.

As described above, according to the ultra-low carbon stainless steel pipe joint and the ultra-low carbon stainless steel sealing valve of the present invention, it exhibits a high sealing function with a small tightening torque and a highly permanent sealing function, which is extraordinary. A long-life seal function that can withstand the number of opening operations can be provided, and the development of a new stainless steel material causes a seal revolution that eliminates the need for seal members from pipe joints and seal valves.
In addition, it exhibits sealing functionality even in a cryogenic environment, and in particular, maintains a sealing function that can withstand the cryogenic environment of nitrogen, oxygen, natural gas, and helium transport, and a sealing function in a high-temperature environment. Demonstrates sealing functionality that withstands the high temperature environment of engine seals.

Furthermore, pipe joints and sealing valves with a sealing function eliminate the need for dissimilar metal sealing members that may cause contact potential differences, and exhibit excellent sealing functions even in hard environments such as high temperatures, high humidity, and corrosion. To do.
Furthermore, fluid transportation with an excellent sealing function can be realized in a nonmagnetic environment by application to titanium steel.

Next, with reference to FIGS. 16-21, the comparative test of the sealing performance of ultra-low carbon stainless steel will be described.
FIG. 16 is a view showing the shape of the test flange, (a) showing the height and width of the sealing surface, (b) a cross-sectional view of the flange, and (c) a plan view of the flange. . FIG. 17 is a graph showing the time course of the degree of vacuum for each material after tightening with a predetermined torque. FIG. 18 is data showing the transition of the degree of vacuum for each material after tightening with a predetermined torque. FIG. 19 is a diagram showing the deformation (CS-2) of the seal surface after tightening the maximum torque, where (a) is data and (b) is a graph. FIG. 20 is a diagram showing deformation (CS-L3) of the seal surface after tightening the maximum torque, where (a) is data and (b) is a graph. FIG. 21 is data showing the deformation of the seal surface protrusion height difference.

[Seal performance evaluation test of ultra-low carbon stainless steel]
In order to demonstrate the sealing functionality of piping joints based on ultra-low carbon stainless steel (with a carbon content of less than 0.01%) typified by Cleanstar (Daido Special Steel Co., Ltd.) A seal functionality test was performed and evaluated in comparison with a pipe joint using an austenitic stainless steel having a carbon content of 0.01 to 0.03% as a base material.

1. Production of test joint samples This time, the comparison test used clean star B (carbon content 0.007%) and austenitic stainless steel compliant with JISG4304-2005SUS316L (manufactured by Nippon Steel & Sumikin Stainless Steel, carbon Content 0.012%). Test joints CS-2 and CS-L3 were made of each material. This joint had an outer diameter, a thickness, a seal face diameter, and a screw pitch conforming to the minimum vacuum flange standard ICF34, and the seal face had a convex shape that does not require a gasket. The test joint was first machined into a disk shape having an outer diameter of 34 mm and a thickness of 8.0 mm shown in FIG. The convex shape of the sealing surface has an annular protrusion shape with a height H, an outer diameter 22 and an inner diameter 18. The sealing surface of sample CS-L3 has a shape almost the same as the sealing surface of CS-2, and only the height is 0.05 mm higher than that of sample CS-2, so that the adhesion of sample CS-L3 is improved. It has become. In FIG. 16B, the test flange shape is an outer diameter 34, a thickness 8, a protrusion inner diameter 18, an outer diameter 22, and a height H. Next, after mechanically polishing the seal surface with a predetermined accuracy, N ₂ ⁺ molecular ion implantation was performed to form a hardened layer on the surface of the seal surface.

2. Vacuum seal performance test The second flange 12 “ICF70-CS34 conversion flange” shown in FIGS. 1 and 2 is attached to the evacuation system shown in FIG. 8, and the CS is aligned with the sealing surface of the second flange 12. -2 and CS-L3 test joints (test vacuum flanges) were connected, and the degree of vacuum by an ion gauge was measured to evaluate the sealing performance. For fixing the test joint, M4 screws with 6 flanges were used. The M4 screw was tightened with an accurate torque using a torque wrench. The minimum torque was 0.1 Nm, and the accuracy was ± 0.01 Nm. First, set the test flange on the “ICF70-CS34 conversion flange”, lightly tighten the M4 screw with your fingers to the extent that the flange does not come off, and then start evacuation. A constant external force is uniformly applied to the test flange by the atmospheric pressure accompanying the vacuum exhaust. Although accurate atmospheric pressure data is not obtained, if the standard atmospheric pressure is 1013.2 hPa, the force applied to the area of the inner diameter of the seal surface of 18 mm is 25.8 N. Under this atmospheric pressure, the test flange is no longer detached and the M4 bolt is temporarily opened in this state. The degree of vacuum when sealed only by atmospheric pressure was as follows.
The test flange CS-2 was 1.5 × 10 ⁻³ Pa, and the test flange CS-L3 was 1.9 × 10 ⁻³ Pa.

From this state, M4 screws were then tightened from 0.1 Nm to 0.4 Nm with a predetermined torque in increments of 0.1 Nm, and the time transition of the degree of vacuum was recorded on a pen recorder for each tightening (FIG. 17). Note that FIG. 17 shows the time course of the degree of vacuum after tightening with a predetermined torque of 0.1-0.4 Nm. The horizontal axis represents time (hours), and the vertical axis represents the degree of vacuum (Pa). The results are summarized as follows.
(1) As a result of comparing the degree of vacuum 3 to 4 hours after tightening with each predetermined torque between the test flange CS-2 and CS-L3, the vacuum pressure of the test flange CS-2 was reduced at all torques. (FIG. 18). This indicates that the vacuum confidentiality of the test flange CS-2 is superior to that of CS-L3.

(2) The difference in the degree of vacuum between the test flanges CS-2 and CS-L3 was 60.2% at a torque of 0.1 Nm, but approached the 6.5% difference at 0.4 Nm, and the torque was large. As a result, there is no difference in the degree of vacuum between both flanges (FIG. 18). From this, it is shown that the test flange CS-2 is superior to CS-L3 in terms of vacuum sealing performance by tightening with low torque.
(3) Comparing the difference between the degree of vacuum immediately after tightening with each predetermined torque and the degree of vacuum after 3 to 4 hours, the test flange CS-2 has a larger difference per time than CS-L3, and the vacuum This indicates that the pressure drop rate is fast (the difference is indicated by a broken line in FIG. 17). This is because SC-2 is excellent in the confidentiality of the vacuum seal and shows a result equivalent to the result of FIG. 18 in which a higher degree of vacuum was obtained compared to CS-L3 when tightened with each predetermined torque. Become.

3. Seal Surface Deformation After tightening to a predetermined maximum torque, the test flange was removed from the vacuum system and examined for deformation of the convex seal surface. Use the dial gauge (ID-H0530, resolution 0.0005 mm, Mitutoyo) to measure the height difference of the annular projection at the six measurement points from point A to point F along the same radial direction of the seal surface shown in FIG. Measured. The result of test flange CS-2 is shown in FIG. 19, and the result of CS-L3 is shown in FIG. The 0th measurement represents the height difference of the annular protrusion measured in the initial state where the test flange is not used. Based on this initial height difference, when the test flange was opened after being tightened to the maximum torque for the first time, the decrease in the annular protrusion height difference of the seal surface was also shown in the graph in the same manner. The decrease in the height difference indicates a state in which the shape of the protrusion does not return to the original state when opened due to inelastic deformation of the protrusion. Comparing the test flanges CS-2 and CS-L3, the deformation of the convex shape of the seal surface when tightening the maximum torque in the first and second rounds of CS-L3 is 3.0 to 3.7 times that of CS-2. large. This result shows that the sealing surface of the test flange CS-2 is much more elastic than the CS-L3 and has excellent seal confidentiality.

4). Conclusion Ultra high-purity stainless steel Cleanstar B with a carbon content of 0.007% (manufactured by Daido Special Steel Co., Ltd.) and austenitic stainless steel according to JISG4304-2005SUS316L (manufactured by Nippon Steel & Sumikin Stainless Steel Co., Ltd., carbon content 0) The test joints CS-2 and CS-L3 were respectively manufactured in a shape conforming to the minimum vacuum flange standard ICF34 using two kinds of materials (.012%) and subjected to a vacuum seal functionality evaluation test. The sealing surface having a convex shape was machined with an annular protrusion and mechanically polished with a predetermined accuracy, followed by N ₂ ⁺ molecular ion implantation to form a hardened surface layer.
The test joint was tightened for each stage with a predetermined torque, and the degree of vacuum was measured to examine the sealing performance. After tightening to the maximum torque, the test joint was opened, and the deformation of the seal surface annular projection was measured. As a result, the following conclusion was reached.

(1) CS-2 using Clean Star B as a base material has better vacuum sealing functionality than CS-L3 using SUS316L as a base material. As the outer diameter of the joint increases, the difference in vacuum seal functionality in tightening with a predetermined torque is expected to further increase. The joint using Clean Star B as a base material exhibits high sealing functionality with low torque even without a gasket.
The difference between CS-2 and CS-L3, in which there is a marked difference in seal confidentiality, is in the carbon content of the stainless steel as the base material. Stainless steel with a carbon content of 0.01% or less, although the carbon content of the CS-2 base material is 0.007% and the carbon content of the CS-L3 base material is 0.012%. In a joint in which a hardened layer is formed on the surface layer using steel as a base material, particularly excellent characteristics in sealing function can be obtained.

(2) The joint CS-2 in which a hardened layer is formed on the surface layer using a stainless steel having a carbon content of less than 0.01% as represented by Cleanstar (Daido Special Steel Co., Ltd.) and the carbon content is 0 When comparing the joints in which the hardened layer is formed on the surface layer using 0.012% stainless steel SUS316L as a base material, there is a large difference in the deformation of the seal surface. In CS-2, the sealing surface having a composite structure of a low hardness of the base material and a very thin surface layer has excellent elasticity and has a long-life seal function.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, A various change is possible in the range which does not deviate from the meaning of this invention.
For example, in the above-described embodiment, as a general method of closely fixing the flanges in the structure of the pipe joint, the embodiment of the method of fixing by penetrating the bolt has been described. There is a clamp system that clamps and fixes a flange, and there is a screw-type pipe joint in which one flange has a male screw shape and the other flange has a female screw shape. .
Further, in the above-described embodiment, the disk-shaped flange is used as the shape of the flange, but there are various other shapes such as a square-shaped flange. It can be applied within the scope of the above.

In the above-described embodiment, the fluid flowing in the pipe and the fluid to be sealed are not particularly limited, but it is needless to say that any of liquid and gas can be generally used.
In the above-described embodiment, one flange has a circular convex cross-sectional shape seal surface, and the other flange has a planar seal surface for deforming and connecting the circular convex cross-sectional shape seal surface. However, both can have a convex cross-sectional shape, and the portions can be pressed together to form functions as a pipe joint and a sealing valve.

  DESCRIPTION OF SYMBOLS 1 ... Super low carbon stainless steel pipe joint, 11 ... 1st flange, 12 ... 2nd flange, 13 ... Bolt, 111 ... Hole, 112 ... Bolt insertion hole, 113 ... Circular convex cross-section shaped sealing surface, 121 ... Hole 122 ... Bolt fixing hole 123 ... Planar shape sealing surface

Claims (5)

A flange formed by forming a hollow made of ultra-low carbon stainless steel having a carbon concentration of 0.01% or less,
The flange comprises a first flange and a second flange mounted on the main surface of the first flange ;
The first flange includes a circular convex cross-sectional shape sealing surface formed in a substantially circular shape in the circumferential direction on the main surface for tightly sealing with the second flange ,
The second flange includes a planar sealing surface for deforming the circular convex cross-sectional shape sealing surface to closely contact the first flange ,
The circular convex cross section sealing surface, and the main surface substantially parallel to the flat surface, and a curvature surface that extends from an end portion of the flat surface before Symbol major surface, shea Lumpur width W1, the flat surface width W2 , if the radius of curvature R, flat surface height H, dimension; includes a W1> W2 ≧ 0, R> W1, R> H relationship, before Symbol flat surface is smooth, it is injected into the flat surface diffusion depth of nitrogen is less than the height of the flat surface, the nitrogen concentration to be injected, Ri least 1.65 × ¹⁰ 17 / cm ² der,
The first flange and the second flange are tightened, and the circular convex cross-section sealing surface presses the planar sealing surface, and the convex shape is deformed to have a sealing function. Low carbon stainless steel flange. 2. The ultra-low shape according to claim 1, wherein the circular convex cross-sectional shape seal surface presses the flat-shaped seal surface and the circular convex cross-sectional shape seal surface is deformed into a flat shape to have a sealing function. Carbon stainless steel flange. According to claim 1 or 2 adoptive hand Ru with a ultra-low carbon stainless steel flange. A sealing valve formed by forming a hollow made of ultra-low carbon stainless steel having a carbon concentration of 0.01% or less,
The sealing valve includes a valve body and a valve seat attached on the main surface of the valve body ,
Before Kibentai comprises the valve seat in close contact with the for sealing, said main circular convex formed in a substantially circular shape in the circumferential direction on the surface cross-sectional shape the sealing surface,
The valve seat includes a planar sealing surface for deforming the circular convex cross-sectional sealing surface to closely contact the valve body ,
The circular convex cross section sealing surface, and the main surface substantially parallel to the flat surface, and a curvature surface that extends from an end portion of the flat surface before Symbol major surface, shea Lumpur width W1, the flat surface width W2 , if the radius of curvature R, flat surface height H, dimension; includes a W1> W2 ≧ 0, R> W1, R> H relationship, before Symbol flat surface is smooth, it is injected into the flat surface diffusion depth of nitrogen is less than the height of the flat surface, the nitrogen concentration to be injected, Ri least 1.65 × ¹⁰ 17 / cm ² der,
The ultra low carbon , wherein the valve body and the valve seat are tightened, and the circular convex cross-sectional shape sealing surface presses the planar sealing surface and the convex shape is deformed to have a sealing function Stainless steel sealing valve . 5. The ultra-low shape according to claim 4, wherein the circular convex cross-sectional shape sealing surface presses the planar sealing surface and the circular convex cross-sectional shape seal surface is deformed into a flat shape to have a sealing function. Carbon stainless steel sealing valve .

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