JP2008032106A - Metal packing for pipe joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal packing used for a pipe joint and having excellent durability. <P>SOLUTION: This metal packing like a circular ring for the pipe joint has a tapered part having an angle α of 45±8° formed by a central axis X of the circular ring and a normal line on a surface of the packing, and the tapered part has surface hardness of the tapered part of 200 to 550HV measured at a position having distance d from a surface of the tapered part of 0.2 mm in cross section of the packing formed by cutting on a plane including the central axis X. The metal packing is formed in a process for pressing a plate-like raw material such as austenite stainless steel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a metal packing used for sealing (sealing) a joint part of a pipe joint for joining pipe ends, and in particular, a fluid or fluid such as food or cosmetics. The present invention relates to a packing suitable for a joint of a pipe that needs to be subjected to maintenance such as cleaning and cleaning by performing attachment and detachment of the joint relatively frequently, such as a flowing pipe.

  Flange joints are widely used as joints for pipes that join pipe ends together. The flange joint is obtained by joining both pipes provided with flanges at end portions by applying a joining force between the flanges. As a means for applying the joining force, a method of fixing with a joining band is generally used in addition to a method of fastening nuts through a plurality of bolts to both flanges (see Patent Document 1).

  In the joint, in order to prevent leakage of fluid from the inside and entry of foreign matter from the outside, it is necessary to provide means for ensuring sealing performance. In general, a method of sealing with an elastic body such as rubber interposed between both pipe ends is widely used as the simplest method.

  The rubber packing plays an important role in the joint, but its strength is weak and it is a component that easily deteriorates. In the food industry and other industrial fields where management of sanitary environments is particularly important, the deterioration and contamination of the rubber packing tends to cause serious troubles. For example, troubles such as rubber, metal and other foreign matter entering into the food from the deteriorated rubber packing part of the fitting, troubles that the smell of the product adheres to the rubber packing, and the smell of the next product is mixed, Troubles in which a piece is mixed into food are likely to occur.

  In order to solve such a problem, a technique for constructing a pipe joint without using packing has already been put into practical use. In this technology, a taper is provided at the end of one tube to be joined, and the end of the other tube is pressed against the tapered portion, so that both are sealed by a line contact between metals. Is.

  With such a pipe joint structure, excellent sealing performance is realized without using packing, but when repeatedly disassembling and reassembling the joint, a tapered part provided on one pipe end There is a problem of being easily scratched. If this fails to ensure sufficient sealing, the tube itself must be replaced. Therefore, a method in which a metal packing is interposed between both pipe end portions is advantageous in terms of cost. A joint using a metal packing having a structure that realizes a sealed state by line contact between metals is also disclosed (see Patent Document 1). If the taper part deteriorates after several mounting and dismounting operations, it can be dealt with by replacing the metal packing.

A device has been devised to improve airtightness by contacting the joint surfaces with tapered surfaces and pressing them with screws (see Patent Documents 4 and 5). However, since all of them intervene packing, deformation leakage due to aging is unavoidable, and the mechanism is complicated.
The present inventor has previously proposed a method of joining the stainless steel pipes with the stainless steel packing without using the packing. (See Patent Document 3)

WO2004 / 109174 Japanese Patent No. 3386750 Japanese Patent Laid-Open No. 2004-225917 Japanese Utility Model Publication No. 3-15897 Japanese Patent Laid-Open No. 11-230436

  As described above, a metal packing of a type that secures a sealing property by line contact between metals is extremely advantageous in avoiding various troubles that have been a problem with conventional rubber packing. However, if the attachment / detachment operation such as replacement of the joint is repeatedly performed, the tapered portion is easily damaged, and the life may be exhausted in a short period of time. Although a high strength alloy is sometimes used as a countermeasure, it is not preferable due to an increase in cost.

  The present invention intends to develop and provide a metal packing of a type that secures a sealing property by line contact between metals without increasing a large cost.

As a result of detailed studies, the inventors have found that the above object can be achieved by controlling the surface hardness of the taper portion of the metal packing (austenite stainless steel) using work hardening by press working. .
In the present invention, it is a circular ring-shaped packing used for sealing a pipe joint, and the angle α formed between the central axis X of the circular ring and the normal of the packing surface is 37 to 53 ° (45 ± 8 °). The taper portion has a taper surface hardness measured at a position where the distance d from the surface of the taper portion is 0.2 mm in the cross section of the packing cut along a plane including the central axis X. Is continuously 200 to 550 HV, and a metal packing for a pipe joint having a length of 0.8 mm or more is provided. This metal packing can be formed through a step of press-molding a plate-shaped material made of a corrosion-resistant material such as stainless steel.
The circular packing is a metal gasket for a pipe joint formed by press-molding a plate material, and the circular packing is made of stainless steel, particularly austenitic stainless steel. The austenitic stainless steel as a metal packing for pipe joints is a stainless steel containing Mo in the range of 4.0 to 0.5% by weight.

  In the metal packing of the present invention, the taper portion for forming a sealing structure by line contact between the end portion of the pipe and the metal is reinforced, and high sealing performance is maintained for a long time even when the coupling is repeatedly attached and detached. . As a raw material, austenitic stainless steel with a proven track record in the food industry, cosmetic industry, and the like can be used, and surface treatment that suppresses elution of Fe can also be performed. Moreover, this metal packing can be manufactured by press molding. Since the molding of the packing and the strengthening of the sealing surface can be realized at the same time by pressing, a cost reduction can be expected due to an improvement in productivity as compared with a case where a special surface hardening treatment is performed after the cutting process.

Examples of metal packing related to the following are shown with examples.

  FIG. 1 is an overall view of a ring-shaped metal packing. 3A is a cross-sectional view of the entire joint, and FIG. 3B is an enlarged cross-sectional view of the vicinity of the joint between the pipe and the metal packing. Both pipes 1 and 1 'are circular in cross section perpendicular to the longitudinal direction, and have flanges 3 and 3' at their ends, respectively, and end faces 11, 11 'at the ends have an annular angle (corner). Portions 12 and 12 'are formed. A ring-shaped metal packing 10 is interposed between the tubes 1 and 1 '. The metal packing 10 is formed with tapered portions 13 and 13 ′, and the tapered portions 13 and 13 ′ are oriented in a direction in which normals N and N ′ intersect with the central axis X of the ring-shaped metal packing 10 at an angle α. ing. Here, α is represented by a value in the range of 0 to 90 ° among the angles formed by the central axis X and the normal line N (or N ′). In FIG. 3B, a straight line L is a straight line parallel to the central axis X (FIG. 3A). In this figure, taper portions (13, 13 ') are formed on both surfaces of the metal packing 10, and the case where the α on both surfaces is the same angle is illustrated, the angle α on both surfaces is described later. It does not necessarily have to be the same as long as it is within the proper range.

  The pipes 1 and 1 'and the metal packing 10 are joined in the form of a metal line contact with the annular corners 12 and 12' abutting against the tapered parts 13 and 13 '. As a means for applying the bonding force, the illustrated means employs a bonding means using a binding band 5 as disclosed in Patent Document 1. Instead of the joining band 5, means for joining the flanges of the tubes 1, 1 ′ with bolts and nuts may be employed. When a joining force is applied by these joining means, the annular corner portions 12 and 12 ′ and the tapered portions 13 and 13 ′ are in close contact with each other on the circumference having the central axis X as a center, thereby ensuring a sealing property. Is done.

  In FIG. 4, the metal packing of another aspect (2) is shown. The cross-sectional structure of the joint in the case where the surfaces (directions of the normal lines N and N ′) of the tapered portions 13 and 13 ′ of the metal packing 10 are directed outward with respect to the central axis X is illustrated. Also in this case, the angle α formed by the central axis X and the normal line N (or N ′) is represented by a value in the range of 0 to 90 °. The annular corners 12 and 12 'formed on the end surfaces 11 and 11' of the tubes 1 and 1 'are brought into contact with the taper parts 13 and 13' of the metal packing 10 so that a line contact joining form is realized and sealing performance is achieved. Is secured. This principle is the same as in the case of FIG.

  The angle α formed between the central axis X and the normal line of the tapered portion is an angle close to 45 °. Specifically, in order to stably secure the sealing performance due to the above-mentioned line contact with the joining force obtained using the joining band used for fastening the conventional joint as shown in FIG. Is preferably in the range of 45 ± 8 °. If α is out of this range, it may be difficult to ensure sufficient reliability as an alternative to a joint that conventionally uses rubber packing.

In FIG. 5, an example of the metal packing cross section cut | disconnected by the plane containing the said center axis | shaft X is expanded typically and displayed. To measure the hardness of the taper surface, the simplest method is to press the cone of the hardness meter directly on the taper of the metal packing. However, the metal packing should be pressed vertically to the surface of the taper. Is not always easy to set in the hardness meter, and a slight angle shift may cause a large measurement error.
As a method for evaluating the surface hardness of the tapered portion as simply and accurately as possible as a result of various studies, the inventors used, for example, a micro Vickers hardness tester to measure the hardness in the vicinity of the tapered portion in the cross section as shown in FIG. Can be used. In the cross section of the metal packing 10 cut along a plane including the central axis X, the hardness at a position where the distance d from the tapered portion surfaces 21 and 21 ′ is 0.2 mm is measured along the tapered portion surfaces 21 and 21 ′. . The measurement interval is desirably 0.2 mm or less. The respective measured values at the taper portion hardness measurement positions 22 and 22 ′ are the taper portion surface hardness at the taper portion surface closest to the measurement point.

As a result of Examples 1-3 to Table 1, as for the hardness of the portion of the tapered portion that is in line contact with the tube, the value of the surface hardness of the tapered portion is preferably in the range of 200 to 550 HV. By setting it to about 200 HV, it becomes difficult to be damaged when the joint is repeatedly attached and detached, and excellent durability is imparted. In order to improve reliability, it is more preferable to set the pressure in the range of 250 HV to 550 HV. However, if it is too hard, the annular corner portion of the tube is likely to be deformed, and there is a risk that the sealing performance by line contact cannot be secured while the number of attachments / detachments is small.
The surface hardness of the tapered portion at the line contact with the tube needs to be suppressed to 550 HV or less, and is preferably suppressed to about 430 HV or less.

It is desirable that the taper portion is provided with a portion having a taper portion surface hardness continuously in the range of 200 to 550 HV with a length of at least 0.8 mm. More preferably, the portion in the range of 250 to 430 HV is provided with a length of 0.8 mm or more. If the length of the portion adjusted to such a predetermined hardness is less than 0.8 mm, the annular corner of the tube collides with the tapered portion that deviates from the predetermined hardness in the fitting and removal work of the pipe joint, and is in the immediate vicinity of the joint portion due to line contact. To be easily damaged. It adversely affects the sealing performance. Further, in terms of dimensional accuracy, line contact is not correctly realized within a predetermined hardness region.
In FIG. 5, locations where the measured values of the predetermined hardness are obtained among the taper surface hardness measurement positions 22 and 22 ′ are schematically plotted in black. In this case, it is sufficient that the lengths of the portions 24 and 24 ′ that continuously exhibit the predetermined taper surface hardness are ensured to be 0.8 mm or more. The predetermined taper surface hardness is realized for the entire region of the taper lengths 23 and 23 '.

Although various corrosion-resistant materials can be adopted as the material for the metal packing, it is desirable to use stainless steel in consideration of applications in the food industry. Among them, austenitic stainless steel which is excellent in workability and corrosion resistance and has already been widely used as a piping material in the food industry can be suitably employed.
The metal packing is manufactured through a process of press-molding a metal plate material. When austenitic stainless steel is used as the metal material, a stainless cold-rolled annealed steel plate manufactured by a general manufacturing process is used.

When a stainless steel material is used, it can be used as a metal packing as it is after being processed into a predetermined final shape in many applications. However, general-purpose steel grades such as SUS304 and SUS316, when exposed to an environment in contact with carbonated beverages, alcoholic beverages, fluid food ingredients, etc., may cause trace amounts of Fe ions to elute from the passive film and affect the quality. There is.

Commercially available SUS304, SUS316, and SUS315J2 cold-rolled annealed steel plates (2D finishing materials) with various plate thicknesses can be used as the plate-like material. A circular metal packing of the type shown in FIG. 3 (type in which the surface of the taper portion faces the central axis side, indicated as shape type “I” in Table 1) was adopted. As for SUS315J2, an example is shown for a metal packing of the type shown in FIG. 4 (type in which the surface of the tapered portion faces outward with respect to the central axis, indicated as shape type “II” in Table 1). The angle α (referred to herein as the taper angle) shown in FIG. 3 or FIG. 4 was changed in two steps within a range of 45 ± 13 ° (37 to 45 °).
The taper length corresponding to 23 in FIG. 5 is a length exceeding 0.8 mm. Each plate material was subjected to multi-stage press molding.

One lot of metal packing having the same processing rate using the same material was used, and about 100 metal packings were used in each lot. And the investigation of the taper surface hardness and the durability test were implemented as follows.
[Investigation of taper surface hardness]

Ten metal packings were randomly extracted from the product of the same lot, and one sample from each metal packing sample was prepared (n = 10), where a cross section cut along a plane including the center axis X of the ring was observed. About each sample, the hardness of the position corresponding to the taper part surface hardness measurement position 22 and 22 'of FIG. 5 was measured with the micro Vickers hardness meter. The distance d from the surface of the taper portion was set to 0.2 mm, and the distance between the measurement points was set to about 0.15 to 0.2 mm. The maximum value and the minimum value of the measurement values at the taper surface hardness measurement position 22 of each sample and the maximum value and the minimum value of the measurement values at 22 ′ are obtained, and n = 10 is the average of the maximum values for all the samples. (Average of 20 numerical values in total) and the average value of minimum values (average of 20 numerical values in total) are calculated, and these values are used as the “average maximum value” and “average of the taper surface hardness in the lot. "Minimum value". Moreover, the length of the part which exhibits the predetermined | prescribed taper part surface hardness corresponding to 24 and 24 'of FIG. 5 continuously in each sample was calculated | required about the range of 200-550HV. And
[Durability test]

If 10 metal packings are randomly extracted from the product of the same lot and a joint with a structure similar to that shown in Fig. 3 or Fig. 4 is constructed, it will be checked how many times the seal is secured. It was. The tube to be combined is of the same steel type as the metal packing and has an inner diameter of 30 mm. This joining band is a commercially available product used in a conventional joint (see FIG. 2) using rubber packing. After joining, a hydrostatic pressure of 25 kg / cm ² was applied to the water enclosed in the tube, and the sealing performance was determined by whether or not water leakage (including slight leaching) was observed from the joint portion. If no water leakage was observed, the joint was once disassembled, and then the joint was constructed again with the same tube and metal packing, and hydrostatic pressure was applied by the above method to observe the presence or absence of water leakage. Such operation was repeated and the frequency | count of fastening with which water leak occurred was investigated. Of the tests with n = 10, the result of the earliest water leakage was adopted as the result of the lot, and the durability was evaluated according to the following criteria.
[Durability Evaluation Criteria]

X: Water leakage is recognized in the 2nd to 20th joining.
A: No water leakage was observed even after the 50th time.

The results are shown in Table 1.

  As can be seen from Table 1, the metal of the present invention in which the taper angle α is 45 ± 8 ° (37-53 °) and the length of the portion where the taper surface hardness is 200-550 HV is ensured to be 0.8 mm or more. It was confirmed that the packing was excellent in durability.

  No. 1 was inferior in durability because the length of the portion having a taper surface hardness of 200 to 550 HV was not secured at least 0.8 mm.

The figure which illustrated the structure of the ring-shaped metal packing. The figure which illustrated typically the section structure of the conventional general pipe joint. The figure which illustrated typically the section structure of the pipe joint which uses the metal gasket of the present invention. The figure which illustrated typically the section structure of the pipe joint which uses the metal gasket of the present invention. The figure which expanded and displayed typically an example of the metal packing cross section cut | disconnected by the plane containing the central axis X. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1 'pipe 2, 2' Annular groove 3, 3 'Flange 4 Rubber packing 5 Fastening band 10 Metal packing 11, 11' End surface 12, 12 'Annular angle | corner part 13, 13' Taper part 21, 21 ' Taper part surface 22, 22 'Taper part hardness measurement position 23, 23' Taper length 24, 24 'Part which shows predetermined taper part surface hardness continuously

Claims (3)

  A circular ring-shaped packing used for a seal portion of a pipe joint, the taper having a taper portion where an angle α formed between a central axis X of the circular ring and a normal line of the packing surface is 45 ± 8 °. The section is a metal for pipe joints characterized in that the surface hardness of the tapered portion is 200 to 550 HV at a distance of 0.2 mm from the surface of the tapered portion in the cross section of the packing cut along a plane including the central axis X Packing.   The metal packing for a pipe joint according to claim 1, wherein the metal packing is formed by press-molding a plate-shaped material of the packing. 2. The metal packing for a pipe joint according to claim 1, wherein the circular ring-shaped packing is made of austenitic stainless steel.

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