Pipe joining method and pipe joint

Abstract

The present invention provides a pipe joining method and pipe joint that offer high strength at the joint and ensure airtightness. [Solution] This disclosure provides a pipe joining method for joining a pipe 10 to an object 1, comprising: a flange forming step of forming an annular flange portion 15 by expanding the portion located on the other side of the insertion region 14 radially outward and flattening it axially, while leaving an insertion region 14 at one end of the pipe 10 that is inserted into an opening 1b of the object 1; and a welding step of inserting the insertion region 14 into the opening 1b and, with the flange portion 15 in contact with the object surface 1a, applying pressure to the flange portion 15 toward the object surface 1a, while applying current between a first electrode X1 connected to the pipe 10 and a second electrode X2 connected to the object 1, thereby resistance welding the flange portion 15 to the object surface 1a, wherein in the flange forming step, the flange portion 15 of the pipe 10 is tapered from the radial inner end to the outer end such that the outer end 15b is located on the one side of the inner end 15a.

Description

Technical Field

[0001] The present disclosure relates to a pipe joining method and a pipe joint.

Background Art

[0002] Patent Document 1 discloses a brazing method for joining a branch pipe to a main pipe at a joint angle of approximately 90 degrees. A hole is drilled in the main pipe at the position where the branch pipe is to be joined. At the end of the branch pipe, the lapping margin is expanded and formed by expanding the pipe. Then, the expanded lapping margin of the branch pipe is caulked over more than half the circumference of the main pipe joint, and then brazing is performed around the periphery of the lapping margin of the branch pipe.

[0003] Patent Document 2 discloses a projection welded joint in which a nut and a high-strength steel plate are projection welded. A projection portion is provided on the joint surface of the nut to be joined to the high-strength steel plate, and by concentrating the current flow on this projection portion, heating and pressurization are performed simultaneously for joining. In addition, the publication shows a state in which four projection portions are provided on the joint surface of the nut.

[0004] Patent Document 3 discloses a resistance welding method in which a current is passed between a thin-walled metal pipe-shaped workpiece and another workpiece while applying pressure in the axial direction to the thin-walled metal pipe-shaped workpiece. In this resistance welding method, a portion of the thin-walled metal pipe-shaped workpiece is crushed in the axial direction to partially double it and form a flange structure. Then, an enlarged diameter portion with an annular projection is formed on the lower side of the flange structure using a mold having an annular groove with a V-shaped cross-section. The enlarged diameter portion extends outward from the thin-walled metal pipe-shaped workpiece at approximately a right angle. When resistance welding such a thin-walled metal pipe-shaped workpiece, first the lower pipe-shaped portion of the enlarged diameter portion is inserted into the hole of the other workpiece, and the upper pipe-shaped portion of the enlarged diameter portion is inserted into the hole of the welding electrode. With the annular projection in contact with the other workpiece, the welding electrode is lowered and a predetermined axial pressure is applied to the enlarged diameter portion. In this state, by supplying welding current from the current supply device, the welding current is concentrated from the welding electrode into the annular projection of the enlarged diameter portion of the thin-walled metal pipe-shaped workpiece and flows into the workpiece, performing resistance welding. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-300470 [Patent Document 2] Japanese Patent Publication No. 2012-157900 [Patent Document 3] Japanese Patent Application Publication No. 10-296454 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The brazing joining method described in Patent Document 1 involves joining a branch pipe to a main pipe via a filler material, and does not directly join the base materials of the pipes together, making it difficult to ensure the strength of the joint.

[0007] In projection welding described in Patent Document 2, the base materials can be joined directly, resulting in high strength at the joint. However, in the case of branch pipes where the internal fluid pressure is high, it is difficult to ensure airtightness at the joint.

[0008] In the resistance welding method described in Patent Document 3, after forming the flange structure, an annular projection is formed on the lower side of the flange structure using a mold having a V-shaped annular groove in cross-section. As a result, a gap may occur between the pipe-shaped portion below the enlarged diameter of the thin-walled metal pipe-shaped workpiece and the annular projection on the enlarged diameter. In the case of branch pipes with high internal fluid pressure, it is difficult to ensure airtightness at the joint. Furthermore, since the annular projection is formed after the flange structure is formed, the number of work steps increases.

[0009] Therefore, the present disclosure aims to provide a pipe joining method and a pipe joint that can ensure high strength and airtightness at the joint portion. [Means for solving the problem]

[0010] To solve the above problems, a first aspect of the present invention is a pipe joining method for joining a pipe to the surface of an object having a planar surface and an opening provided on the surface, comprising: a flange forming step of forming an annular flange-shaped portion by expanding the portion located on the other side of the insertion region radially outward and flattening it in the axial direction, while leaving a pipe-shaped insertion region at one end of the pipe that is inserted into the opening of the object; and inserting the insertion region of the pipe into the opening of the object. The process includes a welding step in which, with the flange-shaped portion in contact with the target surface of the object, pressure is applied to the flange-shaped portion toward the target surface of the object, and current is passed between a first electrode connected to the pipe side and a second electrode connected to the object side to resistance weld the flange-shaped portion of the pipe to the target surface of the object, wherein in the flange forming step, the flange-shaped portion of the pipe is formed in a tapered shape from the radial inner end to the outer end such that the outer end is located on one side of the inner end.

[0011] A second aspect of the present invention is a pipe joining method according to the first aspect, wherein the angle of the one side surface of the flange-shaped portion formed in the flange forming step with respect to a virtual plane perpendicular to the axial direction of the pipe is 10 degrees or more and 30 degrees or less.

[0012] A third aspect of the present invention is a pipe joint in which a pipe is joined to the surface of an object having a planar surface and an opening provided on the surface, wherein the pipe has a pipe-shaped insertion region at one end on the axial side that is inserted into the opening of the object, and an annular flange-shaped portion located on the other side of the insertion region on the axial side that expands radially outward and has a tapered shape from the radial inner end to the outer end, with the outer end being located on the one side of the inner end.

[0013] A fourth aspect of the present invention is a pipe joint according to the third aspect, wherein the angle of the one side surface of the flange-like portion with respect to a virtual plane perpendicular to the axial direction of the pipe is 10 degrees or more and 30 degrees or less.

[0014] A fifth aspect of the present invention is a pipe joint in which a pipe is joined to the surface of an object having a planar surface and an opening provided on the surface, wherein the pipe has a pipe-shaped insertion region located at one end in the axial direction and an annular flange-shaped portion formed on the other side in the axial direction of the insertion region, the flange-shaped portion of the pipe is tapered, widening radially outward and extending radially from the inner end to the outer end, with the outer end positioned on the one side of the inner end, the insertion region of the pipe is inserted into the opening of the object, and with the flange-shaped portion in contact with the surface of the object, the flange-shaped portion is pressed toward the surface of the object, and current is passed between a first electrode connected to the pipe side and a second electrode connected to the object side to resistance weld the flange-shaped portion of the pipe to the surface of the object.

[0015] The sixth aspect of the present invention is the pipe joint of the fifth aspect, wherein the angle of the one side surface of the flange portion with respect to a virtual plane orthogonal to the axial direction of the pipe before resistance welding the pipe to the object is 10 degrees or more and 30 degrees or less.

Advantages of the Invention

[0016] According to the present disclosure, it is possible to provide a pipe joining method capable of achieving high strength of the joint portion and ensuring airtightness.

Brief Description of the Drawings

[0017] [Figure 1] It is a perspective view of a pipe joint in which a pipe is joined to an object. [Figure 2] It is a perspective view of the object. [Figure 3] It is a cross-sectional view of one end of the pipe. [Figure 4] It is a photograph showing a cross-section of the flange portion of the pipe. [Figure 5] It is an enlarged photograph of part V in FIG. 4. [Figure 6] It is a schematic view of the welding apparatus. [Figure 7] It is an explanatory view showing a state in which the flange portion of the pipe is abutted against the target surface of the object. [Figure 8] It is an explanatory view showing a cross-section of the joint portion of the pipe joint. [Figure 9] It is a photograph showing a cross-section of the joint portion. [Figure 10] It is an enlarged photograph of part X in FIG. 9.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, an embodiment of the present invention will be described based on the drawings. In each figure, the X direction indicates the axial direction of the pipe, and the Y direction indicates the axial direction of the internal space of the object.

[0019] Figure 1 is a perspective view of a pipe joint formed by joining pipes to an object. Figure 2 is a perspective view of the object. Figure 3 is a cross-sectional view of one end of the pipe. Figure 4 is a photograph showing a cross-section of the flange portion of the pipe. Figure 5 is a magnified photograph of portion V in Figure 4. Figure 6 is a schematic diagram of a welding apparatus. Figure 7 is an explanatory diagram showing the state in which the flange portion of the pipe is in contact with the object surface of the object. Figure 8 is an explanatory diagram showing a cross-section of the joint portion of the pipe joint. Figure 9 is a photograph showing a cross-section of the joint portion. Figure 10 is a magnified photograph of portion X in Figure 9.

[0020] One embodiment of the present invention relates to a pipe joining method in which a pipe 10 is joined to an object 1 having a planar surface 1a and an opening 1b (see Figure 2) provided on the surface 1a by welding, as shown in Figure 1.

[0021] As shown in Figure 1, the pipe joint 100 according to one embodiment of the present invention is a joint in which a pipe 10 is joined to the target surface 1a of an object 1 having a planar target surface 1a and an opening 1b provided in the target surface 1a (see Figure 2).

[0022] (Object) As shown in Figures 1 and 2, the object 1 is a metal joining object for joining the pipe 10, and is not particularly limited as long as it has a planar object surface 1a and an opening 1b provided on the object surface 1a. In this embodiment, the object 1 partitions an internal space 2 extending in a predetermined direction (the Y direction shown in Figures 1 and 2). Openings 3 (only one opening 3 is shown in the figures) are provided at both ends of the object 1 in the predetermined direction. The object surface 1a of the object 1 is the surface on the outer surface of the object 1 to which the pipe 10 is joined, and is formed in a planar shape. In this embodiment, the opening 1b provided on the object surface 1a connects the internal space 2 of the object 1 to the outside. It is preferable that the opening 1b is circular in shape, slightly larger than the outer diameter of the pipe 10, which will be described later.

[0023] (pipe) As shown in Figures 1 and 3, the pipe 10 is, for example, a metal pipe with a circular cross-section. In this embodiment, the pipe 10 has a first region 11 that extends in a direction intersecting the axial direction (Y direction) of the internal space 2 of the object 1, and a second region 12 that bends from the end of the first region 11 and extends along the axial direction (Y direction) of the internal space 2 of the object 1. That is, the pipe 10 in this embodiment is bent in a substantially L shape. The pipe 10 partitions an internal space 13 that extends along the extension direction. One end of the pipe 10 on the axial side of the first region 11 (hereinafter referred to as "one end") 10a is joined to the object surface 1a of the object 1 so that its internal space 13 communicates with the internal space 2 of the object 1 through the opening 1b of the object 1. In this embodiment, the axial direction (X direction) of the pipe 10 indicates the axial direction of the first region 11, which is the side joined to the object 1. Furthermore, although the pipe 10 is approximately L-shaped in this embodiment, the shape of the pipe 10 is not limited to this.

[0024] Examples of metals that make up the object 1 and pipe 10 include iron, stainless steel, and brass. The outer diameter of pipe 10 is preferably 5 mm or more and 100 mm or less. If the outer diameter of pipe 10 is smaller than 5 mm, spatter will occur, making it difficult to maintain the pipe shape. On the other hand, if the outer diameter of pipe 10 is larger than 100 mm, the welding area will increase too much, making welding difficult. It is more preferable that the upper limit of the above range for the outer diameter of pipe 10 is 30 mm or less.

[0025] (Pipe joining method) The pipe joining method according to this embodiment includes a flange forming step of forming a flange-shaped portion 15 on the pipe 10, and a welding step of welding the pipe 10 to the object 1.

[0026] (molding process) As shown in Figures 3 to 5, in the molding process, a pipe-shaped insertion region 14 is left at one end 10a of the pipe 10 to be inserted into the opening 1b of the object 1 (see Figure 2), while an annular flange-shaped portion 15 is formed on the other axial side (upper side in Figures 3 to 5) of the insertion region 14 (see Figure 1). The flange-shaped portion 15 is formed by expanding the portion located on the other axial side of the insertion region 14 radially outward and then crushing it in the axial direction. For example, when forming the flange-shaped portion 15, the portion located on the other axial side of the insertion region 14 is expanded radially outward by spooling, and then the expanded portion is crushed in the axial direction by applying pressure in a direction that brings it closer in the axial direction to form the flange-shaped portion 15. In other words, the flange-shaped portion 15 is an annular portion that protrudes radially outward from the pipe-shaped (cylindrical) portion of the pipe 10, and the plates constituting the pipe 10 are doubled up.

[0027] In the flange forming process, the flange portion 15 is formed in a tapered shape from the radial inner end 15a to the outer end 15b, such that the outer end 15b is located on one side (the lower side in Figure 3) than the inner end 15a. In other words, the flange portion 15 has a tapered shape as a whole.

[0028] In the flange forming process, the angle θ1 of the one side surface of the flange-shaped portion 15 (hereinafter sometimes simply referred to as "angle θ1 of the flange-shaped portion 15") is preferably 10 degrees or more and 30 degrees or less. The angle θ1 of the flange-shaped portion 15 is the angle θ1 with respect to a virtual plane A that is perpendicular to the axial direction (X direction) of the pipe 10. In this embodiment, the angle θ1 of the flange-shaped portion 15 is approximately 20 degrees. If the angle θ1 of the flange-shaped portion 15 is made smaller than 10 degrees, the flange-shaped portion 15 is more likely to come into surface contact with the target surface 1a of the object 1 in the welding process described later, making it difficult to perform a proper weld and potentially making it impossible to ensure the strength and airtightness of the joint. On the other hand, if the angle θ1 of the flange portion 15 is made greater than 30 degrees, the amount of deformation of the inner end portion 15a of the flange portion 15 will increase when the flange portion 15 is formed, which may reduce the strength of the inner end portion 15a of the flange portion 15 and make it impossible to ensure the strength of the joint portion. The angle θ2 of the other side surface of the flange portion 15 with respect to the virtual plane A is smaller than the angle θ1 of the one side surface, and in this embodiment, for example, it is about 4 degrees.

[0029] (Welding process) In the welding process, first, as shown in Figures 7 and 8, the pipe-shaped insertion region 14 of one end 10a of the pipe 10 is inserted into the opening 1b of the object 1, and the flange-shaped portion 15 is brought into contact with the target surface 1a of the object 1. At this time, the surface on one side of the outer end 15b of the flange-shaped portion 15 of the pipe 10 comes into contact with the target surface 1a surrounding the opening 1b of the object 1. The contact portion B of the outer end 15b of the flange-shaped portion 15 of the pipe 10 comes into contact with the target surface 1a surrounding the opening 1b of the object 1 in a linear (hereinafter referred to as "annular") manner in the circumferential direction.

[0030] For example, as shown in Figures 7 and 8, the object 1 is positioned so that its axial direction (Y direction) is horizontal, and the opening 1b is held facing directly upwards. Next, with one end 10a of the pipe 10 facing downwards, the pipe 10 is moved downwards from directly above the opening 1b of the object 1, and the insertion area 14 of the pipe 10 is inserted into the opening 1b of the object 1. Then, the outer end 15b of the flange portion 15 of the pipe 10 is brought into contact with the object surface 1a surrounding the opening 1b of the object 1.

[0031] As shown in Figures 7 and 8, when the outer end 15b of the flange portion 15 of the pipe 10 is in contact with the target surface 1a of the object 1, the angle of the one side surface of the flange portion 15 of the pipe 10 with respect to the target surface 1a of the object 1 is preferably 10 degrees or more and 30 degrees or less. That is, as described above, the angle θ1 of the flange portion 15 with respect to a virtual plane A perpendicular to the axial direction (X direction) of the pipe 10 is preferably 10 degrees or more and 30 degrees or less. As shown in Figures 7 and 8, when the outer end 15b of the flange portion 15 of the pipe 10 is in contact with the target surface 1a of the object 1, the distance between the one side surface of the flange portion 15 of the pipe 10 and the target surface 1a of the object 1 (distance in the X direction) increases from the radially outer side of the flange portion 15 of the pipe 10 towards the inner side.

[0032] Next, with the outer end 15b of the flange portion 15 of the pipe 10 in contact with the target surface 1a of the object 1 (as shown in Figures 7 and 8), current is passed between the first electrode X1 connected to the pipe 10 and the second electrode X2 connected to the object 1 while applying pressure to the pipe 10 toward the target surface 1a of the object 1. For example, as shown in Figures 7 and 8, the first electrode X1 is positioned to contact the flange portion 15 of the pipe 10 from the other side (the upper side in the figures), and pressure is applied to the flange portion 15 of the pipe 10 toward the target surface 1a of the object 1 (for example, a pressure of 3 kg / cm²) as indicated by the white arrows. 2 While doing so, current is applied between the first electrode X1 and the second electrode X2 (for example, voltage 360V, current application time 15 cycles). In this embodiment, the pipe 10 is pressurized toward the object 1, but it is not limited to this, and the object 1 may be pressurized toward the pipe 10, or both may be pressurized toward each other.

[0033] When current is passed between the first electrode X1 and the second electrode X2 while the pipe 10 is being pressed toward the target surface 1a of the object 1, the current concentrates and flows to the annular contact portion B of the outer end 15b of the flange portion 15 of the pipe 10 that is in contact with the target surface 1a of the object 1, causing the contact portion B to heat up and be welded (resistance welding). At this time, because the pipe 10 is being pressed toward the target surface 1a of the object 1, the pipe 10 moves closer to the target surface 1a of the object 1 as it is welded, and the annular portion where the current is concentrated moves so that its diameter decreases from the outside to the inside in the radial direction of the flange portion 15, as the flange portion 15 is welded from the outside to the inside in the radial direction. In this way, the flange portion 15 of the pipe 10 is resistance welded to the target surface 1a of the object 1 by passing current between the first electrode X1 and the second electrode X2 while the pipe 10 is being pressed toward the target surface 1a of the object 1.

[0034] In the welding process, when applying pressure to the flange portion 15 of the pipe 10 against the target surface 1a of the object 1, it is preferable to apply pressure to the flange portion 15 perpendicular to the target surface 1a of the object 1, as shown in Figures 7 and 8. This allows the area where the current is concentrated to be moved (displaced) evenly from the radial outside to the inside of the flange portion 15.

[0035] As shown in Figures 8 to 10, when the flange portion 15 of the pipe 10 is joined to the target surface 1a of the object 1 by resistance welding, a portion C (hereinafter referred to as "welded portion C") is created where the base materials of the pipe 10 and the object 1 melt and join together. In Figure 8, for clarity, different hatching is applied to the welded portion C from that of the pipe 10 and the object 1.

[0036] The pipe joining method may include other steps in addition to the forming step and the welding step described above. For example, it may include a surface treatment step, such as polishing the surface of the target surface 1a of the object 1 to remove the oxide layer or the like.

[0037] In the pipe joining method described above, during the flange forming process, the flange portion 15 of the pipe 10 is formed in a tapered shape from the radial inner end 15a to the outer end 15b, such that the outer end 15b is located on one side of the inner end 15a. Therefore, when the flange portion 15 of the pipe 10 is brought into contact with the target surface 1a of the object 1, the flange portion 15 of the pipe 10 can be brought into contact with the target surface 1a of the object 1 in a linear (annular) manner rather than a surface. As a result, when current is passed between the first electrode X1 and the second electrode X2 during the welding process, the current can be concentrated and heated at the predetermined contact point, enabling welding.

[0038] Furthermore, in the flange forming process, the flange portion 15 of the pipe 10 can be formed into a tapered shape through a simple process, allowing the flange portion 15 of the pipe 10 to contact the target surface 1a of the object 1 in a linear (annular) manner rather than a surface. In this way, since the flange portion 15 of the pipe 10 does not make surface contact, there is no need to process one side of the flange portion 15 (for example, processing to form a projection portion), thus reducing the amount of work required.

[0039] Furthermore, since the insertion area 14 of the pipe 10 is inserted into the opening 1b of the object 1 during the welding process, the positioning of the pipe 10 relative to the object 1 can be easily performed.

[0040] Furthermore, during the welding process, the flange portion 15 of the pipe 10 is pressed toward the target surface 1a of the object 1, and current is passed between the first electrode X1 and the second electrode X2 to resistance weld the flange portion 15 of the pipe 10 to the target surface 1a of the object 1. Therefore, unlike brazing, the base materials of the pipe 10 and the object 1 are directly joined by resistance welding, thus ensuring the strength of the joint.

[0041] The flange portion 15 of the pipe 10 is tapered from the radial inner end 15a to the outer end 15b, and the flange portion 15 of the pipe 10 is resistance-welded while applying pressure toward the target surface 1a of the object 1. Therefore, in the welding process, the area where the current concentrates between the flange portion 15 of the pipe 10 and the target surface 1a of the object 1 extends linearly (annularly) in the circumferential direction and moves from the radial outside to the inside of the flange portion 15. In this way, since the linearly extended region (the area where the current concentrates) is welded from the radial outside to the inside of the flange portion 15, unlike when projection welding is performed on a predetermined location with a projection, the entire flange portion 15 of the pipe 10 can be welded toward the target surface 1a of the object 1. This ensures airtightness at the joint even in branch pipes where the internal fluid pressure is high.

[0042] Thus, according to this embodiment, it is possible to provide a pipe joining method that has high strength at the joint and can ensure airtightness.

[0043] (Pipe joint) As shown in Figures 1, 9, and 10, in a pipe joint 100 in which a pipe 10 is joined to an object 1, the object surface 1a of the object 1 and the flange portion 15 of the pipe 10 are joined facing each other via a welding interface S (shown as a thick line in the figures). The welding interface S is the lower surface of the aforementioned welded portion C of the flange portion 15 of the pipe 10. Thus, while the flange portion 15 before joining is joined to the object surface 1a of the object 1 facing it via the welded portion C, the flange portion 15 of the pipe 10 in the pipe joint 100 refers to the part including this welded portion C. In other words, the flange portion 15 in the pipe joint 100 includes the welded portion C, and is joined to the object 1 with the lower surface of the welded portion C (the lower surface of the flange portion 15) as the welding interface S. As shown in Figure 10, after welding, the angle θ3 of the one side surface of the flange portion 15 with respect to the virtual plane A in the axial (X-direction) cross-section of the pipe 10 is between 10 degrees and 30 degrees. In this embodiment, the angle θ3 of the one side surface of the flange portion 15 with respect to the virtual plane A after welding is approximately 15 degrees. The angle θ3 of the one side surface of the flange portion 15 with respect to the virtual plane A after welding is the angle between the virtual plane A and a straight line that passes through the radial inner end of the one side surface (bottom surface in the figure) of the flange portion 15 in the axial (X-direction) cross-section of the pipe 10 and touches the weld interface S located on the radially outside of the flange portion 15 from below (touches the welded portion C from below).

[0044] The pipe joint 100 is formed by inserting the insertion area 14 of the pipe 10 into the opening 1b of the object 1, and with the flange portion 15 in contact with the target surface 1a of the object 1, applying pressure to the flange portion 15 toward the target surface 1a of the object 1, while applying current between the first electrode X1 connected to the pipe 10 side and the second electrode X2 connected to the object 1 side, thereby resistance welding the flange portion 15 of the pipe 10 to the target surface 1a of the object 1. By incorporating this specific feature of the invention, the pipe joint 100 of this embodiment provides high strength at the joint and ensures airtightness.

[0045] (Impossible / unrealistic circumstances) However, it is impossible to directly specify the features of the present invention described above by the structure or properties of the material. That is, although the difference between the present invention and the prior art is thought to be due to the difference in the welding interface S, it is not possible to specify the structure or properties related to that difference in general terms. As shown in Figures 9 and 10, finding a significant indicator and its value that distinguishes the present invention from the prior art from the cross-section of the welded portion of the pipe joint 100 would require an enormous amount of time and cost. It is not at all practical to directly specify the features of the present invention by the structure or properties of the material.

[0046] Although the present invention has been described above based on the above embodiments, the present invention is not limited to the contents of the above embodiments, and can naturally be modified as appropriate without departing from the present invention. In other words, all other embodiments, examples, and operational techniques made by those skilled in the art based on these embodiments are of course included in the scope of the present invention. [Examples]

[0047] Examples and comparative examples are given below, and more preferred embodiments of this embodiment will be described. However, the present invention is not limited in any way by the following embodiments.

[0048] <Comparison with brazing> To compare with brazing, we prepared an example in which a pipe was joined to an object using the pipe joining method according to the present invention, and a comparative example in which a pipe was joined to an object using a brazing joining method.

[0049] In both the examples and comparative examples, the same object (a short columnar member made of iron with an outer diameter of 17 mm) and pipe (an iron pipe with an outer diameter of 8 mm) were used.

[0050] In the embodiment, a flange-like portion described in the above embodiment was formed on one end of a substantially L-shaped pipe by going through the flange forming step of the pipe joining method according to the present invention, and then the pipe was joined to the object described in the above embodiment by going through the welding step of the pipe joining method according to the present invention. In the welding step, the applied pressure was 3 kg / cm 2 The voltage was set to 360V, and the energizing time was set to 15 cycles.

[0051] In the comparative example, a stepped portion (a disc-shaped stepped portion, not tapered) extending circumferentially while bulging radially outward was formed on one end of a roughly L-shaped pipe similar to that in the embodiment by spooling. Then, one end of the pipe was inserted into the opening of the object described in the above embodiment until the stepped portion abutted against the object's surface, and the entire circumference of the stepped portion was joined by brazing (brazing material: brass).

[0052] Then, two tests were performed using a tensile testing machine to measure the strength of the joints in the example and comparative example. The object was fixed to the lower chuck of the tensile testing machine, and the other end of the pipe (the end opposite to the object) was fixed to the upper chuck. The upper and lower chucks were then moved in a direction that separated them vertically. Multiple tests were performed with the tensile speed (test speed) set to 1 mm / min and with the tensile speed set to 5 mm / min.

[0053] In the first test, the pipe was pulled until it bent (the L-shape was stretched), and the tensile load at the point of maximum deformation, the point of fracture, and the upper yield point were measured. In both the example and comparative example, one test was performed with a tensile speed (test speed) set to 1 mm / min, and two tests were performed with a tensile speed (test speed) set to 5 mm / min. The results obtained are shown in Table 1.

[0054] [Table 1]

[0055] In the second test, the joint between the pipe and the object was pulled until it broke, and the tensile load at the point of maximum tension, the point of breakage, and the upper yield point was measured. In both the example and comparative example, the test was performed twice with a tensile speed (test speed) set to 5 mm / min. The results are shown in Table 2.

[0056] [Table 2]

[0057] As shown in Tables 1 and 2, in the first test, at a test speed of 1 mm / min, the load at the maximum point of the example was 3.17 (KN), and the load at the maximum point of the comparative example was 2.97 (KN). At a test speed of 5 mm / min, the average load at the maximum point of the example was 3.83 (KN), and the average load at the maximum point of the comparative example was 2.87 (KN). In the second test, the average load at the maximum point of the example was 9.65 (KN), and the average load at the maximum point of the comparative example was 6.165 (KN). Thus, it was confirmed that the joint strength was high according to the example.

[0058] <Comparison based on the angle of the flange-like portion> Furthermore, in order to compare the differences in the angle of the flange-like portion, examples and comparative examples were prepared.

[0059] In both the examples and comparative examples, the same object (a short columnar member made of iron with an outer diameter of 17 mm) and pipe (an iron pipe with an outer diameter of 8 mm) were used. In addition, the welding pressure in the welding process of both the examples and comparative examples was 3 kg / cm². 2 The voltage was set to 360V, and the energizing time was set to 15 cycles.

[0060] In the embodiment, a flange-like portion described in the above embodiment was formed on one end of a substantially L-shaped pipe by going through the flange forming step of the pipe joining method according to the present invention, and then the pipe was joined to the object described in the above embodiment by going through the welding step of the pipe joining method according to the present invention. In the embodiment, three examples were made: Example 1, where the angle of the flange-like portion was 10 degrees; Example 2, where it was 20 degrees; and Example 3, where it was 30 degrees.

[0061] In the comparative example, a stepped portion with an angle of 0 degrees (not tapered) was formed on one end of a roughly L-shaped pipe similar to that in the embodiment, and then the pipe was joined to the object described in the embodiment above. In the comparative example, resistance welding was performed while applying pressure to the stepped portion (angle: 0 degrees) of the pipe toward the object surface of the object, similar to the welding process of the pipe joining method according to the present invention, and the pipe was joined to the object. Note that an angle of 0 degrees for the stepped portion is the angle at which the stepped portion of the pipe is parallel to the object surface when it is brought into contact with the object surface, and the angle at which the lower surface of the stepped portion makes surface contact with the object surface.

[0062] Then, using a tensile testing machine, the strength of the joints in the examples and comparative examples was measured, similar to the second test described above. The tensile speed (test speed) of the tensile testing machine was set to 5 mm / min. Similar to the second test described above, the joint between the pipe and the object was pulled until it broke, and the tensile load at the maximum point, the breaking point, and the upper yield point was measured. Five tests were performed on the comparative examples. Four tests were performed on Example 1, one on Example 2, and two on Example 3. The results are shown in Table 3.

[0063] [Table 3]

[0064] As shown in Table 3, the average load at the maximum point was 10.02 (KN) for Example 1, 9.92 (KN) for Example 2, 10.095 (KN) for Example 3, and 9.73 (KN) for Comparative Example 1. Thus, it was confirmed that the joint strength was high in the example in which the flange portion was tapered. Furthermore, it was confirmed that the angle of the flange portion is preferably between 10 degrees and 30 degrees from the viewpoint of ensuring the strength of the joint portion. [Explanation of Symbols]

[0065] 1: Object 1a: Target surface 1b:Aperture 10: Pipe 14: Insertion area 15: Flange 100: Pipe joint X1: 1st electrode X2: 2nd electrode

Claims

1. A pipe joining method for joining a pipe to the surface of an object having a planar surface and an opening provided on the surface, A flange forming step is performed in which, while leaving a pipe-shaped insertion region at one end of the pipe in the axial direction that is inserted into the opening of the object, the portion located on the other side of the insertion region in the axial direction is expanded radially outward and flattened in the axial direction to form an annular flange-shaped portion, The welding process includes inserting the insertion region of the pipe into the opening of the object, and with the flange portion in contact with the target surface of the object, applying pressure to the flange portion toward the target surface of the object, while applying current between a first electrode connected to the pipe and a second electrode connected to the object, thereby resistance welding the flange portion of the pipe to the target surface of the object, In the flange forming process, the flange portion of the pipe is formed in a tapered shape from the inner end to the outer end in the radial direction, such that the outer end is located on one side of the inner end. A pipe joining method characterized by the following features.

2. The angle between the one side surface of the flange-shaped portion formed in the flange-forming process and a virtual plane perpendicular to the axial direction of the pipe is 10 degrees or more and 30 degrees or less. The pipe joining method according to feature 1.

3. A pipe joint in which a pipe is joined to the surface of an object having a planar surface and an opening provided on the surface, The pipe has a pipe-shaped insertion region at one end in the axial direction that is inserted into the opening of the object, and an annular flange-shaped portion located on the other side in the axial direction of the insertion region, which extends radially outward and has a tapered shape from the radial inner end to the outer end, with the outer end positioned closer to the inner end than the one end. A pipe joint characterized by the following features.

4. The angle of the one side surface of the flange-like portion with respect to a virtual plane perpendicular to the axial direction of the pipe is 10 degrees or more and 30 degrees or less. The pipe joint according to feature 3.

5. A pipe joint in which a pipe is joined to the surface of an object having a planar surface and an opening provided on the surface, The pipe has a pipe-shaped insertion region located at one end in the axial direction, and an annular flange-shaped portion formed on the other side of the insertion region in the axial direction. The flange portion of the pipe is formed in a tapered shape that widens radially outward, and from the radial inner end to the outer end, the outer end is positioned on one side of the inner end. The insertion region of the pipe is inserted into the opening of the object, and with the flange portion in contact with the surface of the object, the flange portion is pressed toward the surface of the object, and while applying pressure to the flange portion toward the surface of the object, current is passed between the first electrode connected to the pipe and the second electrode connected to the object, thereby resistance welding the flange portion of the pipe to the surface of the object. A pipe joint characterized by the following features.

6. Before resistance welding the pipe to the object, the angle of the one side surface of the flange portion with respect to a virtual plane perpendicular to the axial direction of the pipe is 10 degrees or more and 30 degrees or less. The pipe joint according to feature 5.

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