JP2005036942A - Press type pipe joint and its joint method and press tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a press type pipe joint for maintaining high sealing performance for a long period while preventing stress corrosion crack resulting from tensile residual stress by removing the tensile residual stress possibly occurring in a material during jointing. <P>SOLUTION: In the press type pipe joint, a socket portion 3 is swollen from the front end of a diameter enlarged portion 1c of a joint body 1 whose diameter is enlarged at the end, an outer peripheral face 6a of a connection pipe 6 internally inserted into the joint body 1 is sealed with an air sealing material 5 such as an O-ring stored in the socket portion 3, the outer peripheral face 1a of the joint body 1 is pressed against the connection pipe 6 to be joined thereto, and a connection area between a swollen curved face 3a of the socket portion 3 and the outer peripheral face 1a of the joint body 1 is connected with a largely rounded face 12 including a tapered portion 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a press-type pipe that is press-bonded by pressing with a press tool in a state in which a connection pipe made of thin metal such as thin stainless steel is inserted into a pipe joint body formed of thin metal such as thin stainless steel The present invention relates to a joint, a joining method thereof, and a press tool.

  Conventionally, there is a press-type pipe joint as one of joints for connecting stainless steel pipes applied to water supply, hot water supply, and cold / hot water. For example, as shown in Patent Document 1, an airtight material (rubber ring) is built into a receptacle of a thin joint, and the outer periphery of the press-type pipe joint is inserted into the joint by a press machine. By pressing and reducing the diameter of the connecting part from the joint end part, which is the pipe insertion part, to the vicinity of the center, the pipe and the joint are joined to seal the pressure fluid. Press-type pipe joints are widely used in piping equipment such as building equipment because they can be reduced in cost compared to pipe joints called so-called screw-in types that are joined by screwing pipes into the joint. ing.

At the time of joining the joint and the pipe, the pipe is inserted into the connection part of the joint, and the whole connection part is pressed by a press from the outer peripheral surface side to reduce the diameter. When the diameter of the annular groove portion containing the airtight material is reduced, if the compressive force is applied to the outer peripheral surface of the annular groove portion substantially uniformly, the internal airtight material is compressed and deformed as a whole, and the airtight material is pressed against the outer wall surface of the pipe. In this manner, deformation and pressure bonding are attempted to prevent leakage of fluid after joining.
Further, at this time, the pipe insertion side pipe end surface of the annular groove portion containing the airtight material is deformed so as to bite into the outer peripheral surface of the pipe, and by this deformation, the sealing performance and the pipe pull-out resistance force are increased.

  The joint has a shape in which an annular groove bulges out in order to incorporate an airtight material in the receiving port of the pipe connection portion, and the annular groove is composed of a combination of round-shaped elements. On the other hand, the pipe diameter of the pipe is set to such a dimension as to come into contact with the airtight material of the annular groove when inserted into the joint.

When the diameter of the joint is reduced by a press, a certain range in the vicinity of the receiving port of the connecting portion is radially compressed, and the joint connecting portion and the pipe fitted to the connecting portion are integrated in a polygonal cross section. The shape is plastically deformed and joined, and this polygonal shape is preferably a hexagonal shape.
JP-A-53-70072

However, when pressing a press-type pipe joint, the portion of the pipe joint in contact with the die may extend due to the ductility of the material when pressed by a press die, which causes tensile residual stress around the press part. There are many things. When such tensile residual stress is generated, the strength as a material is lowered, and there is a problem that stress corrosion cracking occurs when the pipe joint is exposed to a corrosive environment.
Further, when the groove-like portion in which the airtight material is accommodated is pressed, tensile residual stress is generated in the groove-like portion along with the pressing, and furthermore, the end portion of the joint (end portion of the annular groove portion) Since tensile residual stress is also generated by biting into the outer periphery of the pipe, the strength also decreases at the groove-like part and the pipe side, and stress corrosion cracking may occur when the pipe joint is exposed to a corrosive environment.

  For example, at the time of joining a joint and a pipe in Patent Document 1, a uniform compressive force is applied from the outer peripheral direction to the annular groove portion containing the airtight material when pressed by a press, and this compressive force is strongly applied to the entire annular groove portion. There is a risk that tensile residual stress may occur due to the work, and when a large compressive force is applied to the annular groove, the annular groove is composed of a combination of R-shaped elements. There is a possibility that tensile residual stress is generated intensively due to the stress concentrated on the extremely small round-shaped region connecting the two.

In addition, the hermetic material is deformed into a shape that causes the annular groove to be crushed as a result of the pressure applied to the annular groove, which may adversely affect the sealing performance, and the wear will be severe and maintain long-term sealing performance. It was difficult to do.
The hermetic material is usually provided with a tightening allowance that is normally deformed when pressed, and it is necessary to increase the tightening allowance in order to improve the sealing performance between the joint and the pipe after joining. In order to increase the tightening allowance, it is necessary to increase the pipe outer diameter relative to the inner diameter of the airtight material. In this case, the pipe outer peripheral surface and the airtight material come into contact with each other when the pipe is inserted into the annular groove. Since the force to do so increases, the airtight material may be damaged. Furthermore, if this tightening margin is large, a strong pressing force is applied to the airtight material during pressing, and the airtight material is deformed so as to be crushed into a shape that bulges from the annular groove after the airtight material is deformed. This also had an adverse effect on the durability of the airtight material.
In addition, there is also a problem that the joint distal end side and the pipe outer peripheral surface are liable to be cracked when the tip end side of the annular groove portion for storing the airtight material bites into the pipe outer peripheral surface.

On the other hand, when plastically deforming a certain range of the connecting portion into a polygonal cross-section, if this shape is hexagonal, the amount of deformation in the axial direction increases, and if this amount of deformation increases, tensile residual stress increases. There was a problem that it was easy. When the amount of deformation is large, the ductility of stainless steel, which is a material, acts strongly, and a work-induced martensite structure is likely to occur in a structure that originally consists of an austenite structure. The material became brittle and easily cracked.
In addition, there is a problem in that the degree of biting into the pipe varies depending on the deformation location due to the amount of deformation.

  It should be noted that press-type fittings are prone to material embrittlement even when external stress is applied after processing. For example, stress caused by vibration from a pump or chlorine contained in a fluid such as water in a hot water supply line Corrosion is likely to proceed due to ions, and corrosion cracking may occur. For this reason, it has been difficult to maintain high sealing performance for a long period of time.

  The present invention was developed in view of the conventional problems, and the object of the present invention is to provide stress corrosion cracking in a press-type pipe joint for connecting pipes for supplying water, hot water, cold / hot water, etc. An object of the present invention is to provide a press-type pipe joint that can prevent and maintain high sealing performance over a long period of time.

  In order to achieve the above object, according to the first aspect of the present invention, the receiving portion is bulged at the distal end side of the enlarged diameter portion where the end portion side of the joint body has been enlarged, and the O accommodated in the receiving portion. The outer peripheral surface of the connection pipe inserted into the joint body is sealed with an airtight material such as a ring, the outer peripheral surface of the joint body is crimped, and the connection pipe is crimped and joined. It is a press type pipe joint which connected the connection part with the outer peripheral surface of a joint main body with the taper part.

  The invention according to claim 2 is a press-type pipe joint in which the connecting portion is connected by a large rounded surface including a tapered portion.

  According to a third aspect of the present invention, a joint body is formed of an airtight material, such as an O-ring, which is formed by bulging and forming a receiving part at the distal end side of the enlarged diameter part obtained by expanding the end part side of the joint body. The outer peripheral surface of the connection pipe to be inserted into the peripheral surface is sealed, and the connection pipe to be inserted into the joint main body is crimped and joined with a crimped portion obtained by crimping the outer peripheral surface of the joint main body into an octagonal cross section. It is a press-type pipe joint formed in predetermined length so that it may have drawing-out prevention power with a connection pipe toward the direction of the axis.

  In the invention according to claim 4, an airtight material such as an O-ring is accommodated in a receiving portion bulged on the pipe insertion side of the joint body, and the connection pipe inserted into the joint body is crimped and joined at the crimping portion, This is a press-type pipe joint in which the material of the joint body is Cr-Ni-Si-Cu series stainless steel.

  The invention according to a fifth aspect is the press-type pipe joint according to any one of the first to fourth aspects, wherein the metal structure of the crimped portion between the joint body and the connection pipe is an austenite structure.

  The invention according to claim 6 is the method according to any one of claims 1 to 4, wherein a gap is formed between the edge of the receiving port formed on the end side of the joint body and the outer peripheral surface of the connection pipe connected thereto. It is a press type pipe joint as described in above.

  The invention according to a seventh aspect is the press type pipe joint according to any one of the first to third aspects, wherein the rear end portion of the enlarged diameter portion is a pipe abutting portion.

  The invention according to claim 8 is the press-type pipe joint according to any one of claims 1 to 7, wherein the joint body and the connection pipe are thin stainless steel.

  According to the ninth aspect of the present invention, an airtight material such as an O-ring is accommodated in a receiving portion bulged on the end side of the joint body, and the bulging curved surface of the receiving portion is connected to the outer peripheral surface of the joint body. Connected with a large rounded surface including a tapered part formed in the part, insert the connection pipe into the joint body up to the insertion end, surround the outer peripheral surface of the joint body with the die of the press tool and press it with the pressing surface of the die Thus, the tapered portion is first pressed by the pressing surface of the die, and the receiving port is pressed so as to tilt toward the pipe insertion side with the round surface as a fulcrum, and further, the outer peripheral surface of the joint body and the connection pipe Is a press-type pipe joint joining method in which pressure bonding is performed.

  The invention according to claim 10 is the press pipe joint joining method according to claim 9, wherein the pressing surface of the die has a recess for pressing the receiving portion of the joint body and a round surface portion for pressing the round surface.

  The invention according to claim 11 is the method of joining the press-type pipe joint according to claim 9 or 10, wherein the joint body and the connecting pipe inserted therein are joined by crimping with a press tool at the end of the receiving portion of the joint body. And a press-type pipe joint joining method in which a gap is provided between the outer peripheral surface of the connecting pipe.

  According to a twelfth aspect of the present invention, there is provided a press tool die for press-joining the joint body and the interpolated connection pipe with a press tool, wherein the die pressing surface divided by the die is used to store an airtight material in the joint body. This is a press tool for joining a press-type pipe joint in which a concave portion that surrounds the receiving portion and an outer peripheral surface of the joint body are formed with an octagonal cross section.

  The invention according to claim 13 is the press tool for joining a press-type pipe joint according to claim 12, wherein a taper surface is formed at a position of the die pressing surface connected to the concave portion of the die.

  According to the first and second aspects of the invention, a press type tube that does not generate a tensile residual stress after pressing, can prevent stress corrosion cracking, and can maintain high sealing performance over a long period of time. It is a joint.

  According to the invention according to claim 3, a high pulling-inhibiting force can be maintained while suppressing the amount of deformation in the axial direction at each deformation point, and the pulling-in preventing force is inferior when compared with a crimped portion having a hexagonal cross section. Needless to say, the occurrence of tensile residual stress can be suppressed.

  According to the invention which concerns on Claim 4, the stress corrosion cracking at the time of flowing fluids, such as warm water, can form a pipe joint by anti-corrosion-proof material.

  According to the invention which concerns on Claim 5, embrittlement of the pipe crimping part after crimping can be prevented, and a high pipe pull-out preventing force can be obtained.

  According to the invention of claim 6, the pipe outer peripheral surface and the receiving end edge are not damaged during and after the connection pipe is joined, and the connection pipe outer peripheral surface and the receiving end edge are corroded for a long time. Generation of stress corrosion cracking can be prevented.

  According to the invention according to claim 7, when the connection pipe is crimped and joined, the connection pipe can be reliably joined while being held, and the joining position can be joined with high dimensional accuracy without shifting. According to the invention concerning No. 8, it is a press type pipe joint which can be provided with a material with high corrosion resistance.

  According to the invention of claim 9, a press capable of maintaining high sealing performance by preventing stress corrosion cracking while maintaining a high pulling-inhibiting force without newly using a processing tool or increasing the number of processing steps. It is a joining method of a press type pipe joint which can form a type pipe joint easily.

  According to the invention which concerns on Claim 10, it can press an airtight material by moderate pressing force, crimping | bonding a joint main body and a connection pipe reliably, and a different joint main body by providing a recessed part on both sides of a round surface And the joining direction of the joining pipe.

  According to the invention according to claim 11, without causing damage to the outer peripheral surface of the pipe and the edge of the receiving port, it is possible to suppress the occurrence of corrosion of the outer peripheral surface of the connecting pipe and the receiving port edge for a long time after joining, This is a method of joining press-type pipe joints that can prevent stress corrosion cracking.

  According to the invention which concerns on Claim 12, the press-type pipe joint which can form the press-type pipe joint which can suppress generation | occurrence | production of a tensile residual stress with strong drawing-out resistance force only by replacing | exchanging the die | dye which is a metal mold | die part. This is a joining press tool, and it is possible to reduce the cost without newly requiring another dedicated tool.

  According to the invention of claim 13, a press for joining a press-type pipe joint capable of forming a press-type pipe joint capable of preventing stress corrosion cracking and maintaining high sealing performance while maintaining a high pulling-inhibiting force. This is a press tool for joining press-type pipe joints that can join press-type pipe joints of any pipe diameter by exchanging dies in accordance with the pipe diameter.

An embodiment of a press-type pipe joint according to the present invention will be described with reference to the drawings. The press-type pipe joint of the present invention is formed by pressing a joint body made of thin-walled stainless steel in a state where the pipe is inserted, and crimping and joining the joint body and the pipe.
FIG. 1 is a cross-sectional view showing a state before joining of a press-type pipe joint according to the present invention. In the figure, reference numeral 1 denotes a joint body. A joint pipe 6 is joined to the joint body 1 to provide a pipe joint. I have to. The joint body 1 and the connection pipe 6 are made of a metal material having corrosion resistance, for example, Cr—Ni—Si—Cu-based stainless steel.
In the joint body 1, the diameter-expanded step portion 2 is formed by molding means such as bulge molding so that the smallest inner diameter portion is smaller than the outer diameter of the connection pipe 6, and the diameter of the end portion side of the joint body 1 is increased. When the connecting pipe 6 is inserted into the inner peripheral surface 1b of the enlarged diameter portion 1c, the rear end portion of the tapered enlarged diameter step portion 2 is used as the abutting portion 2a of the connecting pipe 6 so that the connecting pipe 6 is locked. It can be held in a state.

  Reference numeral 3 denotes a receiving portion for storing an airtight material 5 such as an O-ring. The receiving portion 3 is formed in a semicircular cross section by a forming means such as bulge forming on the distal end side of the enlarged diameter portion 1c of the joint body 1. The bulge is formed. The airtight member 5 seals the outer peripheral surface 6a of the connection pipe 6 inserted into the joint body 1, and when the outer peripheral surface 1a of the joint body 1 is crimped, the connection pipe 6 can be crimped and joined. A connecting portion between the bulging curved surface 3 a and the outer peripheral surface 1 a of the joint body 1 is connected by a large round surface 12 including the tapered portion 4. In the case of a joint nominal diameter of 13 to 25 Su, the radius surface 12 preferably has a curvature radius of 3.0 to 5.0 mm. If it is smaller than 3.0 mm, stress concentration tends to occur. On the other hand, if it is larger than 5.0 mm, the taper portion 4 is reduced and the space of the receiving portion 3 is widened so that the O-ring is easily moved. This is because the sealing performance may be lowered. The tapered portion 4 may be formed at an appropriate angle, but it is preferably 42 to 46 ° with respect to the outer peripheral surface 1a of the joint body 1 and more preferably about 45 °. When the angle is less than 42 °, the space 3c of the receiving portion 3 is widened and the O-ring is likely to move, and the sealing performance may be deteriorated. This is because the tilt of 3 is increased, and the O-ring may be overcompressed.

In FIG. 3, reference numeral 11 denotes a crimping part for crimping and joining the joint body 1 and the connection pipe 6. The crimping part 11 is formed so as to crimp the outer peripheral surface 1 a of the joint body 1 into a substantially octagonal cross section. 11 is formed in a predetermined length C in which the pulling-in preventing force of the connecting pipe can be configured with the direction toward the axial direction. As a dimension of the length C, for example, in the case of a nominal diameter of 25 Su, about 5 mm is desirable. At the time of pressure bonding, the pressure-bonding portion 11 is pressure-bonded so that the metal structure becomes an austenite structure.
As shown in FIG. 6, a gap D is formed between the outer peripheral surface 6 a of the connection pipe 6 connected to the edge 3 b of the receiving port 3 formed on the end side of the joint body 1.

  The airtight material 5 is provided with heat-resistant butyl rubber as a material, for example, but may be made of ethylene propylene rubber (EDPM) or other materials generally used as heat-resistant seal materials. The inner diameter of the airtight material 5 is provided to be larger than the outer diameter of the connection pipe 6 before the connection pipe 6 is joined, and the connection pipe 6 does not contact the airtight material 5 when the connection pipe 6 is inserted. It is provided as follows.

Next, the operation of the embodiment will be described.
The press-type pipe joint according to the present invention has a receiving part 3 bulging at the tip end side of the enlarged diameter part 1 c of the joint body 1, and a connecting pipe 6 with an airtight material 5 such as an O-ring housed in the receiving part 3. The outer peripheral surface 6a of the joint body 1 is crimped to the outer peripheral surface 6a, and the connection pipe 6 is crimped and joined. The bulging curved surface 3a of the receiving portion 3 and the outer peripheral surface 1a of the joint main body 1 are joined. Since the connecting portion is connected by the large rounded surface 12 including the tapered portion 4, there remains a tensile residue on the entire receiving portion 3 that is a press portion or a portion that connects the receiving portion 3 and the enlarged diameter portion 1 c of the joint body 1. Not only does it cause stress, but also has compressive residual stress after joining, so the properties of this compressive residual stress can improve the strength of the pipe joint and prevent embrittlement of the material for a long time. it can.

Since the airtight member 5 is deformed into a substantially wedge-shaped cross section along the tapered portion 4 when the receiving port 3 is pressed, a suitable seal is obtained by an appropriate pressing force using the elastic force of the airtight member 5. In addition, the airtight material 5 is not easily damaged because it does not receive a strong pressing force, and is excellent in durability.
Moreover, since the clearance gap D is formed between the edge 3b of the receptacle part 3 of the coupling main body 1, and the outer peripheral surface 6a of the connection pipe 6, the end edge 3b and the outer peripheral surface 6a contact and corrode. There is nothing.

A connection pipe 6 inserted into the joint body 1 is crimped and joined by a crimping part 11 in which the outer peripheral surface 1a of the joint body 1 is crimped into a substantially octagonal cross section, and the connection pipe 6 is pulled out with the crimping part 11 directed in the axial direction. Since the blocking force is formed so as to have a predetermined length C that can be configured, each of the press-bonded portions 11 in the axial direction is more dispersed by dispersing the press portions as compared with the case of a substantially hexagonal cross section. The amount of deformation can be reduced. For this reason, generation | occurrence | production of a process induction martensite structure | tissue can be suppressed, the structure | tissue which consists only of an austenite structure | tissue can be maintained, and there is no possibility that material may become embrittled. Further, the difference in the degree of biting of each crimping part 11 into the connection pipe 6 is reduced, and the lengths of the crimping parts 11 in the axial direction can be made substantially uniform.
The crimping force when the crimping part 11 is provided in an octagonal shape can be adjusted by changing the length C, and the minimum deformation amount of the crimping part 11 can be adjusted by setting the length C to an appropriate value. The maximum pull-out prevention force can be obtained.

Then, the joining method and press tool of a press-type pipe joint are demonstrated.
First, the connection pipe 6 is inserted into the joint body 1 until the end of the connection pipe 6 comes into contact with the abutting portion 2 a of the joint body 1. At the time of insertion, the inner diameter of the airtight member 5 attached to the joint main body 1 and the inner diameter of the enlarged diameter portion 1c of the joint main body 1 are larger than the outer diameter of the connection pipe 6 as described above. Can be inserted into the joint body 1 without being in contact with the airtight member 5 or the enlarged diameter portion 1c. Thereby, in addition to the airtight material 5 not being damaged by the insertion of the connection pipe 6, it is also possible to visually confirm that the seal by the airtight material 5 is insufficient when the press bonding with the connection pipe 6 is insufficient. it can.
In this state, as shown in FIGS. 2, 5A and 6A, the outer peripheral surface 1a of the joint body 1 is surrounded by a die 7 including an upper die 7a and a lower die 7b of the press tool body 20. set. At the time of setting, the joint body 1 is placed on the lower mold 7b, and the upper mold 7a is set in a state where it can be pressed onto the joint body 1.

The press tool main body 20 presses the joint main body 1 and the connection pipe 6 in the above-described state and is bonded by pressure bonding. In the die 7 of the press tool main body 20, the pressing of the upper die 7 a and the lower die 7 b is performed. The surface 7 c is a cross-sectional view for crimping the receiving portion 3 pressing recess 7 d surrounding the receiving portion 3 of the joint body 1, the round surface 12 pressing radius surface portion 8, and the outer peripheral surface 1 a of the joint body 1. An octagonal pressure-bonding surface 9 is formed, and the pressing surface 7c is configured to be annular when the upper die 7a and the lower die 7b come into contact with each other by pressing.
Further, at the rounded surface portion 8, the tapered portion 4 on the rounded surface 12, which is a connecting portion between the outer peripheral surface 1 a and the bulging curved surface 3 a on the outer peripheral side of the receiving port portion 3 of the joint body 1, is pressed. Is formed at a position connected to the recess 7d.

At the time of pressing, when pressing the upper die 7a to start pressing, the outer peripheral surface 1a of the joint body 1 is surrounded by the die 7 of the press tool body 20 as shown in FIGS. 5 (b) and 6 (b). When the pressing surface 7c of the die 7 is pressed, first, the tapered portion 4 of the joint body 1 comes into contact with the tapered surface 9 in the rounded surface portion 8 of the die 7, whereby the tapered portion 4 is pressed and the rounded surface 12 is moved. The receiving port 3 is pressed as a fulcrum so as to tilt toward the pipe insertion side.
In this way, the die 7 comes into contact with the receiving portion 3 first, so that the receiving portion 3 that may be generated when the die 7 comes into contact with the crimping portion 11 first, that is, the phenomenon that the receiving portion 3 tries to float up. The phenomenon that the diameter of the part 3 expands and the gap with the pipe 6 expands is prevented, and an appropriate sealing property by the airtight material 5 is ensured.

When pressed further, the bulging curved surface 3a of the receiving port 3 comes into contact with the concave portion 7d of the die 7 by deforming the receiving port 3 while tilting, and the contact surface pressure between the bulging curved surface 3a and the concave portion 7d at this time Is smaller than the contact surface pressure between the taper surface 9 and the taper portion 4, so that when the pressing by the die 7 is continued, the mouthpiece portion 3 is pushed from the taper portion 4 side, and the inclination of the mouthpiece portion 3 is deformed. The receiving part 3 is not compressed perpendicularly to the axial direction of the tube by the recess 7d, and the receiving part 3 is tilted while being guided along the recess 7d.
The shape in the vicinity of the receiving port 3 after deformation is formed in a shape substantially similar to the shape from the rounded surface 8 of the die 7 to the recess 7d.

  When the pressing is further continued, as shown in FIGS. 5 (d) and 6 (d), the crimp surface 10 having a substantially octagonal cross section of the die 7 comes into contact with the outer peripheral surface 1 a of the joint body 1. When the main body 1 is pressed, the joint main body 1 and the connection pipe 6 are pressure-bonded at the pressure-bonding portion 11 as shown in FIG.

When the pressing of the die 7 to the joint body 1 is completed, the airtight material 5 accommodated in the receiving port 3 is pressed to the outer periphery of the connection pipe 6 by an appropriate pressing force, and the inner peripheral side of the joint body 1 and the connection pipe 6 are The outer peripheral side can be sealed liquid-tight.
Further, when the press is completed, a gap D is formed between the end edge 3b and the outer peripheral surface 6a of the connection pipe 6, and this gap D is, for example, in a range of about 0.5 to 0.8 mm at a nominal diameter 25Su. Therefore, the gap D after pressing can be provided to a minimum.

As described above, the receiving portion 3, particularly the substantially semi-annular section formed by the recess 7 d, is not subjected to a strong compressive force by the die 7 in the course of the press, and the end 3 b of the joint body 1. Does not bite into the outer periphery of the connection pipe 6, and is a press-type pipe joint joining method that does not generate tensile residual stress that causes stress corrosion cracking.
Moreover, since the connection pipe 6 is unevenly fitted to the inner surface of the joint body 1 in the crimping portion 11 after pressing, the connection pipe 6 can be appropriately joined.

  Austenitic stainless steels such as SUS304 and SUS316 are common as materials for pipe joints for supplying cold and hot water, as specified in Japan Water Works Association Standard JWWA G116-2001 “Stainless Steel Pipe Fittings for Waterworks”. However, these austenitic stainless steels have a problem that a stress corrosion cracking phenomenon is particularly likely to occur when a tensile stress is applied in a corrosive environment. In addition, when these are used as materials, especially when tap water of 50 ° C or higher is passed through pipes and joints where tensile stress during processing remains, a corrosive environment is formed by the temperature of the liquid and chlorine contained in the tap water. There is a risk of stress corrosion cracking in pipes and joints.

  Therefore, in this example, the joint body was formed using SUS315J2 having a composition of 0.04C-18.5Cr-12Ni-3Si-2Cu-0.8Mo-0.4Mn-N as a material. Since SUS315J2 contains copper and silicon, the material becomes sticky, and the proof stress can be increased as compared with SUS304 and SUS316. In addition, the hardness is reduced by reducing the content ratio of molybdenum and manganese so that the material has a certain degree of elasticity.

  On the other hand, the joint body material as a comparative example is SUS304, and the pipe joints of the present invention and the comparative example are changed in the shape and size of each pipe crimping part, and the residual stress and structure of the crimping part are analyzed, and the joint performance of As an evaluation test, an evaluation test of the pulling low strength of the connection pipe, the time cracking, and the stress corrosion cracking was performed. The results are shown in Tables 1 and 2. The nominal diameter of the joint used in the evaluation test is 25Su.

According to the results of Table 1, in the case of the press-type pipe joint according to the present invention, all of the residual stress became a compressive residual stress by using a material called SUS315J2 in addition to the device of the shape surface. Therefore, it was confirmed that all the specimens were pipe joints that did not cause stress corrosion cracking.
The specimen (No. 1 and 2) in which the side shape of the pipe crimping part is an arc, and the specimen (No. 3) in which the hexagonal side part is a straight line and the length C of the crimping part is 3 mm, Although a slight martensite structure was confirmed in the pipe crimping portion, the pulling resistance was able to ensure about 4500N. In addition, in the specimen (No. 4) in which the crimping part has a substantially hexagonal cross section and the side part is a straight line and the length C of the crimping part is 5 mm, the pipe crimping part has an austenite structure, and the connection pipe The pulling resistance is also No. It improved about 1.2 times compared with the test sample of 1-3. Further, in the specimens (Nos. 5 to 6) in which the crimping part has a substantially octagonal cross section and the side part is straight, the pipe crimping part has an austenite structure, and the pulling resistance of the connecting pipe is No. It improved about 1.5 times compared with the test sample of 1-3.

  According to the result of Table 2, No. which is a comparative example. In all the specimens 7 to 12, tensile residual stress was confirmed in the pipe crimping portion, and stress corrosion cracking occurred. In all specimens, a martensite structure was confirmed, and the pulling resistance was not stabilized accordingly.

  The present invention is suitable for a press-type joint for connecting stainless steel pipes applied to water supply, hot water supply and cold / hot water, and can be easily, quickly and reliably joined by using a caulking dedicated tool. Can be applied to various joints such as sockets, elbows, tees, reducers, etc.

It is sectional drawing which showed the state before joining of the press-type pipe joint in this invention. It is the sectional view on the AA line of FIG. It is sectional drawing which showed the state after joining of the press-type pipe joint of this invention. FIG. 4 is a sectional view taken along line BB in FIG. 3. (A) thru | or (d) is explanatory drawing which showed the joining process of the press-type pipe joint in this invention. (A) thru | or (d) are the partially expanded views of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Joint main body 1a Outer peripheral surface 1c Expanded part 2a Abutting part 3 Receiving part 3a Swelling curved surface 3b End edge 4 Tapered part 5 Airtight material 6 Connection pipe 6a Outer peripheral surface 7 Die 7c Pressing surface 7d Recessed part 8 Round surface part 9 Tapered surface 10 Crimping surface 11 Crimping part 12 Round surface 20 Press tool body C Length D Clearance

Claims (13)

The outer periphery of the connecting pipe that is formed in the distal end side of the enlarged diameter portion, which has been expanded on the end side of the joint body, and is inserted into the joint body with an airtight material such as an O-ring housed in the receptacle part. The surface is sealed, the outer peripheral surface of the joint body is crimped and the connection pipe is crimped and joined, and the connecting portion between the bulging curved surface of the receiving portion and the outer peripheral surface of the joint body is connected by a tapered portion. This is a press-type pipe joint. The press-type pipe joint according to claim 1, wherein the connection portion is connected by a large rounded surface including a tapered portion. The outer periphery of the connecting pipe that is formed in the distal end side of the enlarged diameter portion, which has been expanded on the end side of the joint body, and is inserted into the joint body with an airtight material such as an O-ring housed in the receptacle part. The surface of the joint is sealed, and the connection pipe inserted into the joint body is crimped and joined with the crimped part that crimps the outer circumference of the joint body into an octagonal cross section. A press-type pipe joint having a predetermined length so as to have a pull-out preventing force with respect to a pipe. An airtight material such as an O-ring is accommodated in a receiving portion bulged on the pipe insertion side of the joint body, and the joint pipe and the connecting pipe to be inserted are crimped and joined at the crimping portion. The material of the joint body is Cr-Ni. -A press-type pipe joint characterized by being made of Si-Cu stainless steel. The press-type pipe joint according to any one of claims 1 to 4, wherein a metal structure of a pressure-bonding portion between the joint body and the connection pipe is an austenite structure. The press-type pipe joint according to any one of claims 1 to 4, wherein a gap is formed between the edge of the receiving port formed on the end side of the joint body and the outer peripheral surface of the connection pipe connected thereto. The press-type pipe joint according to any one of claims 1 to 3, wherein a rear end portion of the enlarged-diameter part is a pipe abutting part. The press-type pipe joint according to any one of claims 1 to 7, wherein the joint body and the connection pipe are thin-walled stainless steel. An airtight material such as an O-ring is accommodated in a receiving port bulged on the end side of the joint body, and includes a tapered portion formed at a connecting portion between the bulging curved surface of the receiving port and the outer peripheral surface of the joint body. First, the tapered portion is connected by inserting a connecting pipe into the joint body up to the insertion end, enclosing the outer peripheral surface of the joint body with a die of a press tool and pressing it with the pressing surface of the die. Being pressed by the pressing surface of the die and pressed so that the receiving part tilts to the pipe insertion side with the rounded surface as a fulcrum, and further, the outer peripheral surface of the joint body and the connection pipe are pressure bonded. A method for joining press-type pipe joints. The method for joining press-type pipe joints according to claim 9, wherein the pressing surface of the die has a recess for pressing the receiving portion of the joint body and a rounded surface portion for pressing the rounded surface. The press-type pipe joint joining method according to claim 9 or 10, wherein the joint body and the connection pipe inserted between the joint body and the outer peripheral surface of the connection pipe are joined by crimping with a press tool. A method of joining press-type pipe joints having a gap therebetween. In a die of a press tool for crimping and joining a joint body and an inserted connection pipe with a press tool, a die pressing surface into which the die is divided is a recess that surrounds a receiving portion for storing an airtight material in the joint body A press tool for joining a press-type pipe joint, characterized in that a crimp surface having an octagonal cross section for crimping the outer peripheral surface of the joint body is formed. The press tool for joining a press-type pipe joint according to claim 12, wherein a taper surface is formed at a position of a die pressing surface connected to the concave portion of the die.

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