JP2014014850A - Pipe joining method by brazing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pipe member joining method by brazing, capable of carrying out stable brazing without causing the running-out of wax on a joint surface.SOLUTION: One pipe member 1 is machined so as to have an external bevel shape in which an inner peripheral edge of a wall thickness part bulges out from an outer peripheral edge. The one pipe member 1 is made to butt to the other pipe member 2 having a flat joint surface orthogonal to an axis while putting wax material containing flux between the pipe members 1 and 2. A butting part is heated to join an end surface of the one pipe member 1 and the other pipe member 2.

Description

  The present invention relates to a pipe joining method by brazing.

  The method for joining members by brazing is a technique for joining the joining members by causing the solder that has melted between the joining members to enter the details by capillary action and welding the joining portion via the solder. In this technique, when the joining accuracy of the joining member is poor, particularly when the clearance between the joining surfaces is too wide, the capillary phenomenon does not work effectively on the brazing material, and brazing and voids are likely to occur and reliable joining cannot be performed. Therefore, in Patent Document 1, a solder pool is provided in advance on one joining member, a protrusion is provided on the joining surface of the other joining member, and the projecting portion is accommodated in the solder pool so that the joining surface of the joining member is accommodated. Brazing is possible even if the accuracy is low.

  The above-mentioned joining method by brazing is a so-called liquid phase diffusion joining method, and is used when joining pipes such as steel pipes. In this method, an insert material made of an amorphous phase-forming metal element is interposed between the end faces of the ends to be abutted, and the insert material is melted to diffuse the amorphous phase-forming metal element into the material to be joined. It is a technique to make it. For example, in Patent Document 2, the end surfaces of the metal tubes to be joined are perpendicular to the tube axis, or one metal tube is formed as a concave taper and the other is formed as a convex taper, thereby joining the metal tubes together. Yes.

Japanese Utility Model Publication No. 03-116287 (Claim 1) JP-A-11-309588 (paragraphs 0002-0004)

  The inventors, as disclosed in Patent Document 2, braze the butt end portions having a butt surface perpendicular to the hollow shaft, so-called flat surfaces, with a brazing material sandwiched therebetween, As a result of careful examination of the joining state, it was found that the ends of the pipe members that were abutted expanded to the outside, and the joint was expanded in a V shape and opened. In addition, if the V-shaped opening becomes larger than necessary, the brazing joint strength is reduced, and the tensile test at that time reveals that a crack is generated from the center of the brazing and is the starting point of the fracture. However, it has been found that the brazing joint is not a high-strength joint of liquid phase diffusion joining, and the joining strength is the strength of the brazing itself.

  Therefore, the present invention provides a method for joining pipes by brazing, in which brazing is surely present on the joining surface even if the end faces are abutted, and the joining portion does not open V-shaped more than necessary even when brazing. For the purpose.

  The present inventors have reached the present invention by paying attention to the following description. That is, as in the pipe joining method by brazing shown in FIG. 1, one end of the pipe member 1 and the other end of the pipe member 2 abut each other at the end surfaces orthogonal to the hollow shaft, and the end surfaces are brazed. Assume joining. First, as shown in FIG. 1 (A), the end faces of one pipe member 1 and the other pipe member 2 are pressed against each other with a brazing filler metal 3 interposed therebetween, and the other end is pressurized. Each end is heated by the heating coil 4 arranged so as to surround it. Then, as shown in FIG. 1 (B), the abutted end portion extends in the axial direction due to thermal expansion, and also increases in the radial direction of the tube, so that one end and the other end are in pressure contact with both ends opposite to the joint surface. Since the other pipe members 1 and 2 are pressurized, the joint portion expands in the outer direction of the pipe.

  More specifically, as shown in FIG. 1 (C) in which the vicinity of the one-dot broken line in FIG. 1 (A) is enlarged, the brazing material 3 is butted between the butted end surfaces of the one and the other pipe members 1 and 2, and the arrow F1 Press in the direction indicated by. Thereafter, as shown in FIG. 1 (D), a reducing gas or an inert gas (hereinafter simply referred to as “gas”) G is blown from the periphery of the butt end, and one and the other pipe members. While flowing the gas G through the hollows 1 and 2, an alternating current is passed through the heating coil 4 to inductively heat the brazing filler metal 3 and the butt end. Then, as shown in FIG. 1 (D), both pipe members 1 and 2 are joined by the brazing 3A, but one and the other pipe members 1 and 2 expand in the radial direction by the force F2 that is inductively heated and pressed. V-shaped opening is generated. When a deviation occurs in the expanding movement at both end faces, a misalignment is formed in accordance with the V-shaped opening as shown in FIG.

  If the V-shaped opening becomes excessively larger than necessary, the joint strength of brazing is lowered, and in the tensile test at that time, it breaks from the center of the braze, and the joint strength of brazing becomes the strength of the brazing itself. End up. In addition, when a mistake occurs, the bonding area is reduced or the strength of the bonding is insufficient due to the occurrence of stress concentration.

  The inventor paid attention to the shape of the end face of the pipe member that can suppress the tube-expanding phenomenon that opens in a V-shape and can cause capillary action at the joint. As a result, it was possible to reduce the occurrence of brazing and voids on the joint surface, and as a result of trial and error, the brazing joint strength could be equal to or higher than that of the base material.

  In order to achieve the above object, in the present invention, in the method of brazing one pipe member and the other pipe member to join the pipes, when one pipe member and the other pipe member are abutted, The end portion of one pipe member has a groove shape in which the inner peripheral edge protrudes from the outer peripheral edge so that the inner peripheral edge side of the thick portion contacts and a gap is formed on the outer edge side. In a state where an insert material containing a brazing material is sandwiched between and pressed with a pipe member, the abutted portion is heated and the end face of one pipe member and the end face of the other pipe member are joined. It is characterized by that.

  As a result, when the brazing material is sandwiched between one pipe member and the other pipe member and pressed against each other, the brazing material is surely present in the gap between the joining surfaces. As when both have a surface perpendicular to the hollow shaft, the brazing material is discharged out of the joining surface, and when the joined parts are heated and joined, the brazing material is already insufficient. Trouble can be eliminated.

  In addition, when the one pipe member and the other pipe member are butted and heated, the inner peripheral edges of both pipe members first come into contact with each other, so that the initial swelling of the pipe occurs in the inner peripheral direction, The effect which suppresses the expansion to the outer peripheral direction and a mistake is exhibited.

  That is, even when one pipe member and the other pipe member are butted against each other with the brazing material sandwiched therebetween, the butted portion has a clearance, so that it does not break before heating. Also, even if the butted portion is heated and the butted portion expands in the outer peripheral direction or the axial direction of the tube due to heat, one pipe member has an end portion that contacts the inner peripheral edge of the thick portion. Accordingly, the expansion in the outer diameter direction can be reduced by expanding the tube in the inner diameter direction, and the expansion and the amount of misalignment can be suppressed. In addition, by making the angle in the groove shape appropriate, capillarity occurs in the joint in the process of heat deformation of the joint, and the wax penetrates into the details of the joint, causing the occurrence of brazing and voids. No brazing is possible. Further, liquid phase diffusion occurs at the joint surface necessary for brazing strength, and a brazing clearance can be secured. As described above, along with the increase in the joint area due to the bulge in the inner diameter direction of the pipe, liquid phase diffusion bonding with high joint strength can be achieved up to good brazing clearance, and joint strength equal to or higher than that of pipe members can be obtained. Can do.

  According to the pipe joining method by brazing according to the present invention, a desired joining strength can be obtained without brazing between one pipe member and the other pipe member.

It is a figure for demonstrating the idea of this invention. It is sectional drawing of the pipe member for brazing used with the pipe joining method by brazing concerning 1st Embodiment of this invention. It is a figure which shows typically the mode before the pipe joining by brazing concerning 1st Embodiment. It is process drawing which shows typically the pipe joining method by brazing concerning 1st Embodiment. It is sectional drawing which shows the group of the pipe member for brazing used with the pipe joining method by brazing concerning 2nd Embodiment. It is a figure which shows typically the brazing process which concerns on 2nd Embodiment. In 1st and 2nd embodiment, it is a figure which shows the heating condition at the time of brazing. (A) thru | or (E) show the image of the cross section of the junction part obtained in the comparative example and Example 1 thru | or Example 4 in order. It is a figure which shows the tensile strength of the sample joined by brazing in the comparative example and Examples 1-4. It is a figure which shows the amount of elongation of each test piece at the time of a tension test in a comparative example and Examples 1 to 4. It is a schematic diagram of the process in which flat joint surfaces are butted and brazed. It is a figure which shows typically the phenomenon of the brazing joining by the pipe member for brazing in which the countermeasure was taken so that an opening may not arise in the outer peripheral edge side of a pipe | tube like FIG. 11 (B) at the time of joining. It is a figure which shows typically the phenomenon of the brazing joining by the pipe member for brazing which took the countermeasure so that generation | occurrence | production of the mistake as shown in FIG.12 (C) might be suppressed. The other pipe is subjected to an outer groove angle of 30 °, and when one pipe member is abutted against the other pipe member, the inner groove angle is imparted so as to form a brazing clearance, and the abutting and brazing are performed. It is a schematic diagram of the process of 2nd Embodiment. FIG. 15 is a schematic diagram of a brazed state when the outer groove angle of the second embodiment described in FIG. 14 greatly exceeds 30 °. (A) thru | or (E) are the images which show the cross section of the junction part obtained in Example 5 thru | or Example 9 in order. It is a figure which shows typically the cross-sectional detail of the junction part of 2nd Embodiment. It is a figure which shows the tensile strength in Example 5 thru | or Example 9. FIG. It is a figure which shows the amount of elongation of each test piece at the time of a tensile test in Examples 5 thru | or 9.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A portion where one pipe member and the other pipe member are butted together will be described as each end of one pipe member and the other pipe member, or simply as a butted end.

[First Embodiment]
FIG. 2 is a cross-sectional view of a brazing pipe member used in the method for joining pipe members by brazing according to the first embodiment of the present invention. FIG. 1 is an enlarged view of a portion surrounded by a chain line. .

  The brazing pipe member 10 has a tubular shape extending in the direction of the hollow shaft, and at least the thick portion of the one end 11 has a groove shape in which the inner peripheral edge 11B protrudes from the outer peripheral edge 11A as shown in FIG. . That is, the one end portion 11 has an overhanging portion 12 whose thick portion protrudes from the inner peripheral edge 11B as compared with the outer peripheral edge 11A. Such a shape of the overhanging portion 12 can be formed by, for example, cutting. Since the overhanging portion 12 has a shape in which the outer side is notched, such a shape is referred to as an “outer groove shape”, and is distinguished from a case in which the inner side is missing. The direction of the notch is the same direction as that of a commonly used welding groove shape.

  FIG. 3 is a diagram schematically illustrating a state before pipe joining by brazing according to the first embodiment. A pipe member 10 for brazing is used as one pipe member 1, and a pipe member having an end substantially orthogonal to the hollow shaft is prepared as the other pipe member 2, and one pipe member 1 and the other pipe member 2 are The insert material 3 is abutted and gas is filled in the hollows of the one and the other pipe members 1 and 2, and the gas is blown to the outer periphery of the abutting end portions 10E and 2E. The gas is an inert gas such as a rare gas, a reducing gas, or a mixed gas thereof. The reason for filling and spraying the gas is to prevent the heated region from being oxidized. In this state, the end portions 10E and 2E of the butt are induction-heated by the heating coil 4. Then, each end 10E, 2E of the butt expands due to heat, and each end 10E, 2E of the butt extends in the axial direction and expands in the outer diameter direction. The brazing material contained in the insert material 3 melts when the liquid phase temperature of the brazing material is reached. The brazing material 3 contains a flux of a reducing agent, and the oxygen contained in the brazing material and the surface oxidation layer of each end portion 10E, 2E of the butt is reduced by the flux and released outside the joint portion in the outer peripheral surface direction. Is done.

  In 1st Embodiment of this invention, since the butt | matching edge part 10E has an outward groove shape, a clearance gap is made in a junction part. Therefore, even when the butted end portions 10E and 2E are butted together with the brazing material interposed therebetween, the brazing material is reliably left in the gap without being discharged out of the joint portion, and the brazing material is not insufficient before heating. That is, it is possible to secure a brazing material accumulation region. Thereafter, by heating, release of moisture and binder, drying of the brazing material, reduction by flux, expansion of the butted ends 10E and 2E in the axial direction and the outer peripheral direction, reduction of the joint clearance, It progresses over time to melting, occurrence of capillarity, penetration of brazing material details, formation of thick joints, and liquid phase diffusion bonding of brazing material and the joint surface. The pipe member 2 can be brazed, and joining with a joining strength equal to or higher than the base material strength becomes possible.

  Various shapes are conceivable for the outer groove shape, but under the setting conditions of the examples described later, the end surface including the outer peripheral edge 11A and the inner peripheral edge 11B of the thick portion is orthogonal to the hollow shaft as shown in FIG. It is most preferable that the angle formed by a predetermined range including 3.5 ° with respect to the reference plane S0 is a plane. This angle is also called the outer groove angle.

  Here, the end surface S10 is a plane including the outer peripheral edge 11A and the inner peripheral edge 11B, and the reference surface S0 is a virtual surface orthogonal to the hollow axis. If the angle between the two surfaces, the so-called outer groove angle θ, is within a predetermined range including 3.5 °, the expansion and misunderstanding of the joint as shown in FIG. 1 are suppressed when the joining is completed. As a result, it becomes possible to secure a brazing clearance required for brazing and increase the joining surface, and to obtain a joining strength with the base material strength equal to or higher. When the angle θ is larger than the upper limit, the brazing material remains large in a V shape in the direction of the outer peripheral edge, and the bonding strength is a weak strength of the brazing material itself in which no liquid phase diffusion occurs. When the angle θ is smaller than the lower limit or when the end face S10 is in a so-called inner groove state where the angle S10 is 0 ° or less, the outer peripheral edges of both the pipe members are in contact with each other more than necessary. A force acts to promote expansion to the surface, resulting in an increase in misunderstanding, resulting in a decrease in bonding strength, such as a decrease in the bonding area and concentration of stress at the misalignment.

  As in the first embodiment, one pipe member 1 is used as a brazing pipe member 10 having a groove shape, and the other pipe member has an end surface whose end surface is orthogonal to the hollow axis as a joined pipe member. As 2, the advantage of joining by brazing will be described.

  FIG. 4 is a diagram schematically showing a process of joining pipes by brazing according to the first embodiment. As described with reference to FIG. 3, as shown in FIG. 4 (A), the butted end surfaces of the one and other pipe members 1, 2 are indicated by an arrow F1 with a brazing material (not shown) interposed therebetween. Press in the direction. The angle formed by the butted ends of the one and the other pipe members 1 and 2 forms an outer groove angle θ.

  Thereafter, as shown in FIG. 4B, a reducing gas or an inert gas (hereinafter simply referred to as “gas”) G is blown from the periphery of the butt end, and one and the other pipe members 1 are blown. , 2 while flowing the gas G in the hollow space, an alternating current is passed through the heating coil 4 to inductively heat the brazing material and the butt end. Then, the one and the other pipe members 1 and 2 extend in the axial direction and expand in the radial direction by the force F2 that is inductively heated and pressed. However, unlike the case shown in FIG. 1, the butted portion of one pipe member 1 is processed so as to have an outer groove angle θ so as to absorb the expanded tube and the opening, and therefore expands in the radial direction. Pipe expansion and misunderstanding are suppressed.

  Further, the flux flows from the inner peripheral surface toward the outer peripheral surface in the direction of arrow S1, and moisture and caking additive contained in the brazing material are discharged out of the joint. As the heating temperature rises, the gap at the joint gradually decreases, and when reaching the liquid phase temperature range of the wax, the wax melts. At this time, the capillarity generated by the gap in the joint and the molten solder can cause the solder to flow in the direction of the arrow S2 and enter the details of the joint surface. 4B, the portions 1X and 2X immediately below the center of the heating coil 4 are heated to the liquid phase temperature of the brazing material, specifically, the liquid phase temperature plus 100 ° C. to 200 ° C. The heating temperature decreases as the distance from the heating coil decreases, such as the portions 1Y and 2Y that are shifted from immediately below the center of the heating coil.

  Thereafter, when the application of force F2 and induction heating are stopped, the joint is cooled. When sensitization is a concern, as in stainless steel, it is necessary to cool the water promptly after the induction heating is completed to suppress the sensitization. Even in such rapid cooling, there is no problem that a crack occurs in the wax portion. The optimum brazing material thickness having bonding strength, that is, the clearance for uniformly presenting the brazing material is in the range of 5 μm or more and 50 μm or less. If it is within this range, it will be confirmed in the examples described later that the center part of the wax during the tensile strength test is not a joint part rupture starting from the rupture but a strong joint that breaks at the base material part. Yes. By setting the thickness of the brazing material in this manner, liquid phase diffusion bonding necessary for joining proceeds between the brazing material and the joining member. In addition, the effect of the outer groove suppresses the occurrence of misunderstandings, and a joint with less stress concentration is formed, and the deformation of the joint can be directed toward the inside of the tube to thicken the inner peripheral side. As shown in FIG. 4C, the bonding area is increased and the bonding strength can be improved. As described above, the end faces are joined to each other by allowing the wax to uniformly exist between the end face of one pipe member 1 and the end face of the other pipe member 2.

[Second Embodiment]
FIG. 5 is a cross-sectional view showing a set of brazing pipe members used in the pipe joining method by brazing according to the second embodiment, and FIG. 6 is a diagram schematically showing a brazing process according to the second embodiment. It is. In either case, the vicinity of the portion surrounded by the alternate long and short dash line is enlarged in FIG. In the second embodiment, the end surface portions of the one pipe member 1 and the other pipe member 2 that are joined to each other by brazing have a groove shape, and the one pipe member 51 is the first embodiment. In contrast, the outer peripheral edge has an inner groove shape protruding from the inner peripheral edge, whereas the other pipe member 52 has an outer groove shape in which the inner peripheral edge protrudes from the outer peripheral edge. doing.

  In the other pipe member 52, an angle θ formed by a virtual surface perpendicular to the hollow axis and an end face of the outer groove shape is referred to as an outer groove angle. The angle β formed by the end face of the inner groove shape is called an inner groove angle. The relationship between the outer clearance angle α formed by the mutual end faces, the outer groove angle θ, and the inner groove angle β is β = θ−α. That is, as shown in FIG. 6A, even if the end surface of the other pipe member 52 is not perpendicular to the hollow shaft, the end surface of one pipe member 51 and the other pipe member 52 to be joined This means that the outer clearance angle α of the joint formed when the end face is abutted with each other should be within a certain angle range.

  As a result of an example described later, a stable shape with the highest joint strength and a small amount of misalignment is obtained at an outer groove angle θ = 30 ° and an outer clearance angle α = 2 °. As the outer groove angle θ is increased to 45 ° and 60 °, the misalignment increases, and it becomes difficult to apply the pressure necessary for joining. In the second embodiment, the bonding area can be easily increased compared to the first embodiment, and a bonding strength equal to or higher than that of the base material can be achieved. Moreover, the surface alignment at the time of joining becomes easy, the workability | operativity of joining improves, and the malfunction that the axial center of pipe members shift | deviates at the time of joining can be reduced.

  FIG. 6 is a diagram schematically showing a brazing process according to the second embodiment. As shown in FIG. 6 (A), the butted end surfaces of one and the other pipe members 1, 2 which are a set of brazing pipe members 51, 52 according to the second embodiment are sandwiched between insert materials (not shown). And press-contact as indicated by arrow F1. The butted ends of the one and other pipe members 1, 2 form an outer clearance angle α.

  Thereafter, a gas having a reducing property or an inert gas is blown from the periphery of the butt end, and an alternating current is passed through the heating coil 4 while flowing the gas through the hollows of the one and the other pipe members 1 and 2, and the insert material and The butt end is induction heated. Then, as shown in FIG. 6 (B), when the pipe is expanded in the radial direction of the one and the other pipe members 1 and 2 by the induction heating and pressure welding force F2, the butt end portion of the one pipe member 1 is expanded. Since both end faces are processed to make the outer clearance angle α so as to absorb the opening, tube expansion and misunderstanding that expand in the radial direction more than necessary are suppressed. As a result, the inner peripheral surface has a bulge shape as shown in FIG.

  Further, the flux in the brazing material flows from the inner periphery to the outer periphery in the direction of the arrow S1, and the moisture and the caking additive contained in the brazing material are discharged outside the joint. As the heating progresses, the outer clearance angle α of the joint portion gradually decreases. At this time, the brazing material flows in the direction of the arrow S2 due to the capillary phenomenon that occurs between the molten braze and the joint surface, and in the details of the joint surface. You can enter. In FIG. 6B, the portions 1X and 2X immediately below the center of the heating coil 4 have a higher temperature than the portions 1Y and 2Y that are removed from directly below the center of the heating coil 4, and the portion 1X immediately below the center of the heating coil 4 , 2X is heated to a temperature of about 1250 ° C. above the liquidus temperature of the wax.

  Thereafter, when the application of force F2 and induction heating are stopped, the joint is cooled. When sensitization is a concern, such as stainless steel, water cooling is performed immediately after the induction heating is completed to suppress sensitization. Even in such rapid cooling, there is no problem that a crack occurs in the brazing portion.

  The optimum thickness of the brazing material having bonding strength, that is, the clearance for the presence of the brazing material is in the range of 5 μm or more and 50 μm or less. In this range, it is confirmed in the examples described later that the central portion of the wax does not become the starting point of breakage during the tensile strength test, and that it is a strong joint that breaks at the base material portion instead of the joint portion. . By using this brazing material thickness, liquid phase diffusion joining necessary for joining proceeds between the brazing material and the joining member. In addition, since the occurrence of misunderstanding is suppressed by the effect of the outer clearance angle α, a joined portion with less stress concentration is formed, which is one factor that increases the joining strength. Furthermore, the deformation of the joint can be directed toward the inside of the tube, and the inner peripheral side can be thickened. As a result, as shown in FIG. 6 (C), the joint area increases and a joint strength higher than the strength of the base material is obtained. Can do.

  As described above in the first and second embodiments, the joining is performed such that the brazing material is sandwiched between one pipe member and the other pipe member, and the vicinity of the butt end is brazed by induction heating. In the construction method, by performing groove processing on one end or both ends of the pipes to be joined and providing a brazing pool portion, the brazing does not run short before melting the brazing. In addition, while suppressing the opening and misunderstanding of the joint that occurs when the end expands in the axial direction or the outer circumferential direction by induction heating, it is possible to allow the braze to enter the details of the joint using the capillary phenomenon that occurs during joining. As a result, high strength bonding can be achieved.

  Here, in the first and second embodiments, a heating state by induction heating at the time of brazing will be described. FIG. 7 is a diagram showing a heating state when brazing in the first and second embodiments. The horizontal axis is time (seconds), and the vertical axis is temperature (° C.). The time here is 0 when the heating coil is energized. In addition, the illustrated heating situation assumes that a stainless steel pipe member is particularly joined. The insert member 3 is sandwiched between the one pipe member 1 and the other pipe member 2 to be abutted.

  While rapidly filling the pipes of the one pipe member 1 and the other pipe member 2 with the gas, the coil current is increased from zero. Then, the butt end portion rises to the first temperature T1 at time 0 to t1, and the vicinity of the butt end portion is dried.

  In the period from t1 to t2, the coil current is further increased, and the butt end is rapidly increased to the second temperature T2. The second temperature T2 is a temperature at which the flux is activated. By this first stage heating, the moisture of the insert material 3 sandwiched between the butted ends is evaporated, the crystal water is separated and evaporated, and the binder is sublimated. A first range A1 surrounded by a dotted line in FIG. 7 is a temperature range that is higher than the first temperature T1 and lower than the second temperature T2.

  During the period from t2 to t3, feedback control is performed by a detection signal from the temperature sensor to adjust the current to the heating coil so that the temperature at the butt end is constant. By this soaking operation, the composition and shape of the tube are stabilized, and the oxide film formed at the butt end is reduced by the flux.

  During the period from t3 to t4, the coil current is further increased, and the temperature at the butt end is increased from the second temperature T2 to the third temperature T3. By this second stage heating, the wax contained in the insert material 3 is dissolved, the wax and the flux are replaced, and the oxide film is removed. Note that a second range A2 surrounded by a dotted line in FIG. 6 is a temperature range that is higher than the second temperature T2 and lower than the third temperature T3. By rapidly raising the temperature by induction heating within the time in this range, it is possible to suppress melting of the brazing material.

  At the temperature from t4 to t5, feedback control is performed by the detection signal from the temperature sensor to adjust the current to the heating coil so that the temperature in the vicinity of the butt end is substantially constant at the third temperature T3. As a result, elements contained in the brazing material, for example, B and Si diffuse into the butt end.

During the period from t1 to t5, the gas is replenished into the pipe and at the same time, gas is blown to the butt end so that the butt end does not react with oxygen in the air.
During the period from t5 to t6, the coil current is decreased so that the butt end portion becomes the flux activation temperature, and the vicinity of the butt end portion is allowed to cool.
In the period from t6 to t7, the coil current is set to zero at time t6, and the butt end is water-cooled. This is because when the material of the pipe member is SUS, Cr carbide precipitates due to sensitization.
Hereinafter, the present invention will be described in more detail with reference to several examples.

[Example 1]
In Example 1, a brazing pipe member using a black skin (black) SGP pipe having a thickness of 125 A and a thickness of t4.5 mm and cutting the outer groove angle θ to 2 ° as shown in FIG. It was set to 10. An SGP pipe having a flat surface was prepared as the joined pipe member to be brazed, that is, the second pipe member 2. As shown in FIG. 3, the brazing material 3 containing the flux is sandwiched between the brazing pipe member 10 and the second pipe member 2, and the same procedure as described above with reference to FIG. 4 is performed. I brazed.

  Nickel brazing (product number BNi-2) was used as the brazing material, and Nicloblaze flux (manufactured by Wall Coromonoy, USA) was used as the flux. At 1250 ° C., the holding time, that is, t4 to t5 shown in FIG. The pressure stress at F1 applied to the other ends of both pipe members was 5 MPa.

[Example 2]
In Example 2, brazing is performed in the same manner as in Example 1 except that the outer groove angle θ is cut to 3.5 ° to form a brazing pipe member 10 as shown in FIG. Bonding was performed.

Example 3
In Example 3, as shown in FIG. 2, joining by brazing is performed in the same manner as in Example 1 except that the outer groove angle θ is cut to 5 ° to obtain a brazing pipe member 10. went.

Example 4
In Example 4, as shown in FIG. 2, brazing is performed in the same manner as in Example 1 except that the outer groove angle θ is cut to 6.5 ° to obtain a brazing pipe member 10. Bonding was performed.

[Comparative example]
As a comparative example, 125A, a black SGP tube with a wall thickness of t4.5 mm is used, and the outer groove angle θ is 0 °, that is, the pipe members having end faces perpendicular to the hollow shaft are brazed together. It joined by.

  The joining by brazing was evaluated as follows. A tissue photograph of the joint was taken of eight of the 16 pieces obtained by cutting the joint of the sample at about 22.5 °. FIGS. 8A to 8E are photographs in which images showing cross sections of joint portions obtained in the comparative example and Examples 1 to 4 are sequentially taken. Each of them shows an image of a piece at 12 o'clock as a representative of eight pieces. Here, what time is an index for specifying the position of each piece during the brazing operation by aligning the hollow shaft of the sample with the center of the watch.

The joint portion of the sample was cut at a central angle of about 22.5 °, and a tensile test was performed on 8 pieces of the obtained 16 pieces. In the tensile test, a tensile test was performed using a simple test piece having a width of about 25 mm and a length of 200 mm. Table 1 is a table showing tensile strength data obtained as a result of a tensile test of samples joined by brazing in the comparative example and Examples 1 to 4. In addition, the value of the tensile strength shown in Table 1 is shown in the unit of N / mm ² . The time shown in the leftmost column is the position of each piece before cutting, specified by aligning the hollow shaft of the sample with the center of the watch. In the tensile test, a value obtained by classifying a fracture at the base material and a fracture at the joint portion and calculating a ratio of the test pieces at which the fracture occurred at the base material portion is shown in the lowest stage of Table 1. Table 2 shows data on the amount of elongation until breakage of the simple test piece in the tensile test, and the average value of the amount of elongation is shown in the lowermost row of Table 2. The elongation values shown in Table 2 are shown in mm. In Tables 1 and 2, the range surrounded by the thick frame is the one broken at the base material portion.

FIG. 9 is a diagram showing the tensile strength of the samples joined by brazing in the comparative example and Examples 1 to 4. The horizontal axis represents the sample types of the comparative example and Examples 1 to 4, and the vertical axis represents the tensile strength (N / mm ² ). In FIG. 9, each piece at 12 o'clock, 1.5 o'clock, 3 o'clock, 4.5 o'clock, 6 o'clock, 7.5 o'clock, 9 o'clock, and 10.5 o'clock for each of the comparative examples and Examples 1 to 4 The tensile strength data of are shown. As the standard value of the bonding strength (JIS standard), the tensile strength value of the base material is 290 N / mm ² or more. It can be seen from Table 1 and FIG. 9 that the test piece at any part has a tensile strength exceeding the standard value.

  FIG. 10 is a diagram showing the amount of elongation of each test piece during a tensile test in Comparative Example and Examples 1 to 4. As a result of the tensile test shown in Table 1, the outer groove angle θ of Example 2 in which the base material part breaking rate was 100% was the maximum elongation under the condition of 3.5 °. The average value of elongation was 24 mm. It can be seen that the elongation amount is halved at the outer groove angle of 0 ° in the comparative example.

  From the brazing remaining state of the joint portion photograph of FIG. 8, it can be expected that the brazing thickness can clear the standard value of the tensile strength in the range of 5 μm to 50 μm, and that the joint can be broken at the base material portion. However, there is no clear difference due to the brazing thickness between the fracture at the base metal part and the fracture at the joint.

  As described above, as a brazing pipe member to be joined to a pipe member to be joined having a flat end surface perpendicular to the hollow shaft, comprehensively determined from the breaking strength, the base material breaking rate, and the amount of elongation, the outer opening is used. The tip angle θ may be set to 3.5 °. Increasing or decreasing the outer groove angle θ more than necessary causes a reduction in the fracture rate at the base material portion. That is, it has been found that the probability of breakage at the joint is increased. For this reason, when the outer groove angle θ is set to 3.5 °, the brazing can be surely performed. That is, if the abutment surface of one pipe member 1 with the other pipe member 2 has an angle of 3.5 ° with respect to the abutment surface of the other pipe member 2, a pipe joint having a high joining strength. It can be.

  A bending test, a quadruple pressure fracture test, and a water hammer pressure test, which are listed as test items for the welded SGP pipe, were performed. One SGP cut for a bend test using a black SGP tube with an outer diameter of 125A, a wall thickness of t4.5mm, and a length of 1150mm so that the outer groove angle θ is 3.5 °. The tube and the other non-cut SGP tube were joined in the same manner as in Example 2 at a heating temperature of 1250 ° C. and a holding time of 3 minutes. At that time, product numbers BNi-1 and BNi-2 were used as the brazing material.

  One end and the other end of the joined sample were supported, water was poured into the sample, a maximum working pressure of 2 MPa was applied as an internal pressure, and a bending moment was applied to the joint at the center of the sample. In this state, the deflection amount was set to 8.0 mm, 10.2 mm, and 20.4 mm.

  In the sample using the product number BNi-1 as the brazing material, the bending load was 2.9 tons, 3.7 tons, and 4.6 tons with the set deflection amount. No water leakage was observed at any deflection amount. Therefore, the bending test is judged to be acceptable. Thereafter, when the load was increased, water leakage from the joint was confirmed when a bending load of 4.9 tons was applied.

  In the sample using the product number BNi-2 as the brazing material, the bending load was 3.4 tons, 3.9 tons, and 4.6 tons with the set deflection amount. No water leakage was observed at any deflection amount. Therefore, the bending test is judged to be acceptable. Thereafter, no water leakage was confirmed even when a load of 4.9 tons was applied.

  Using a black SGP tube of size 125A, wall thickness t4.5mm, length 400mm for 4x pressure fracture test and water hammer pressure test, cutting to an outer groove angle of 3.5 ° One processed SGP pipe and the other non-cut SGP pipe were joined in the manner of Example 2 at a heating temperature of 1250 ° C. and a holding time of 3 minutes. At that time, product numbers BNi-1 and BNi-2 were used as the brazing material.

  Water was injected into the joined sample to increase the internal pressure to 0.1 MPa, hold for 3 minutes to perform a pressure resistance test, then increase to 3.0 MPa and hold for 3 minutes to perform a pressure resistance test, and further to 8.0 MPa. The pressure was increased to 1 minute and held for 1 minute. As a result, water leakage from the joint was not confirmed, and each test item passed.

  The water hammer pressure test was done with respect to the sample which performed the 4 times pressure fracture test. The pressure was increased from an internal pressure of 0.1 MPa to 7.0 MPa in 1 second, and after repeating 100 times, the internal pressures of 0.1 MPa and 3.0 MPa were sequentially applied to check for water leakage. As a result, water leakage was not confirmed from the joint portion in the sample using any brazing material of BNi-1 and BNi-2.

  BNi-2 used in the above-described test, that is, a general-purpose solder, is a brazing material in which the base material part is broken in all directions in the tensile test. There is no specified value for the carbon content of the brazing material. BNi-1 brazing filler metal has a carbon content of C = 0.7% and is commercially available as a brazing filler metal for high-strength bonding. From the test results, BNi-2 (general-purpose solder) is more suitable for brazing the black skin (black) SGP tube than BNi-1 (high-strength solder). I understood.

Here, the joining phenomenon by brazing of a pipe member having a groove shape will be considered.
The phenomenon at the time of abutting and joining flat joint surfaces as in the comparative example is considered as follows. FIG. 11 is a diagram schematically showing a process of brazing flat joint surfaces together. As shown in FIG. 11 (A), when the brazing material 3 is sandwiched between the end portions of the first pipe member 1 and the second pipe member 2 and pressed from the other end, the brazing material 3 is arrowed from both ends. Excess wax 5 out of the sandwiched wax is pushed as shown by B. Thereafter, the vicinity of the butt end is heated in the residual pressure state. Then, as shown in FIG. 11 (B), the pipe expands in the direction of the outer peripheral surface due to thermal expansion, the joint surface between the pipe members 1 and 2 opens in a V shape, and a narrow gap is joined on the inner peripheral edge side. Then, it becomes joining of wide clearance. In some cases, the wide clearance will flow out of the joint surface in some cases, resulting in a brazed joint. In the case of a wide clearance, only the strength of the wax itself can be obtained during the tensile test, which becomes the starting point of the crack at the time of fracture. In addition, when the pipe members 1 and 2 are displaced as shown in FIG. 11C and a misalignment 6 occurs in a heated or pressurized state, the joining area is reduced, resulting in a reduction in joining strength.

  On the other hand, unlike the first embodiment, one pipe member 1 uses a pipe member having an inner groove shape, and the other pipe member 2 uses a pipe member having an end substantially orthogonal to the hollow shaft. The phenomenon when brazing them together is considered as follows. FIG. 12 is a diagram schematically showing a phenomenon of brazing and joining by a brazing pipe member that has been treated so that an opening does not occur on the outer peripheral edge side of the pipe as shown in FIG. 11B during joining. That is, it is a schematic view of a process of performing inner groove processing on one pipe member and brazing it with the other flat joint surface. The first pipe member 1 was a brazing pipe member 10 and the second pipe member 2 was a pipe member having a flat end surface. As shown in FIG. 12 (A), when the end face of the first pipe member 1 is processed so as to have an inner groove angle θ, the pipes press the brazing material 3 on the outer peripheral edge 1B side and the inner peripheral face side. As shown in FIG. 12 (B), when the vicinity of the butted ends is heated, the tube expands in the outer peripheral surface direction due to thermal expansion, and the outer peripheral edges 1B and 2B are indicated by arrows. Abut. As shown by an arrow C, the inner peripheral edges 1A and 2A side sandwich a wax.

The inner groove angle β = 0 ° was used as a comparative example, and as a result of performing a joint test under eight conditions of β = 2 °, 3.5 °, 5 °, 6 °, 7 °, 8 °, 10 °, Good brazing joint was confirmed under the condition of the tip angle θ = 7 °. In the test results at that time, the average value of tensile strength = 393 N / mm ² , the total specimen base material part fracture, and the brazing material thickness of the joining surface of the brazing material were 5 μm to 50 μm. However, on the other hand, as shown in FIG. 12 (C), the size of the stepped portion of the difference 6 exceeded 0.5 mm as shown in FIG. .

  FIG. 13 is a diagram schematically showing a phenomenon of brazing joining that is taken so as to suppress the occurrence of the difference 6 as shown in FIG. That is, it is a schematic diagram of the process of the first embodiment in which one pipe member is subjected to an outer groove process and brazed against a flat joint surface of the other pipe member. As in FIG. 12, the first pipe member 1 is a brazing pipe member 10 and the second pipe member 2 is a pipe member having a flat end surface. As shown in FIG. 13 (A), when the outer groove angle θ is machined into the end face, the pipes press the brazing material 3 at the inner peripheral edges 1A and 2A, and excess wax 5 flows out to the outer peripheral face side. As shown in FIG. 13B, when the vicinity of the abutted end portions is heated, the force B first acts on the inner peripheral edge side due to thermal expansion, causing a phenomenon that the tube is expanded on the inner peripheral surface side. Thereafter, the deformation proceeds, and the outer peripheral edges 1B and 2B are closed. In accordance with the movement at this time, a capillary phenomenon occurs on the joint surface, the brazing material 3 melted in the narrow gap direction penetrates the joint surface, and an oxide film or the like reduced by the flux is applied to the outer peripheral surface side in the opposite direction. Impurities are discharged. As a result of the tests in Examples 1 to 4, as described above, the outer groove angle θ = 3.5 ° has a small amount of difference over the entire circumference of the joint, the joint strength, the fracture rate at the base material part, and the like. Satisfactory and good results were obtained.

[Examples 5 to 9]
FIG. 14 shows an inner groove angle so that a gap for brazing is formed in one pipe member when the other pipe member is abutted with the other pipe member with an outer groove angle of 30 °. It is a schematic diagram of the process of 2nd Embodiment matching and brazing. FIG. 14 shows an application example of brazing joint subjected to the outer groove processing explained in FIG. This corresponds to the second embodiment described above. The second pipe member 52 is a pipe member having an end face with an outer groove angle with respect to the axis. In the first pipe member 51, the inner groove angle was processed as shown in FIG. 14A so that the inner periphery of the second pipe member 2 was in contact with the inner periphery of the first pipe member 51, and the gap expanded in the outer peripheral direction of the tube. Details have been described with reference to FIG. The outer clearance angle α is set to −4 °, −2 °, 0 °, 2 °, 4 ° in the order of Example 5 to Example 9, and the outer groove angle θ of the second pipe member 52 is Example 5. The inner groove angle β of the first pipe member 51 was set to be 30 ° regardless of the ninth embodiment. The definitions of the outer groove angle θ, the inner groove angle β, and the outer clearance angle α are as shown in FIG. 17, and the details thereof are as already described.

  As a result of the joining test, bulging can be generated on the inner peripheral surface side similarly to the result shown in FIG. 13B, and the joining strength is improved by increasing the joining area, and the face-to-face operation at the time of joining is easy. The work efficiency was improved. The outer groove angle θ of the second pipe member 52 is 30 °, and the inner groove angle β of the first pipe member 51 is 28 °, that is, the outer clearance angle is 2 °. Good results were obtained in both elongation. An example in which the outer groove angle θ of the first pipe member 52 was changed to 45 ° and 60 ° was also performed. As a result, when the pressurizing force necessary for joining was applied, slipping as shown in FIG. 15 occurred. As a result, there was a problem that a large difference occurred on both sides of the inner and outer peripheral surfaces of the pipe.

  FIGS. 16A to 16E are images showing cross sections of the joint portions obtained in Examples 5 to 9 in order. FIG. 18 is an image of a joint surface in which the outer groove angle θ of the second pipe member 52 shown in FIG. 14 is 30 ° and the outer clearance angle α shown in FIG. It can be seen that good swelling appears on both the inner and outer circumferences of the pipe when the outer clearance angle α of Example 8 is 2 °.

Table 3 shows the tensile strength data of Examples 5 to 9. The tensile strength test is performed under the same conditions as in the comparative example and Examples 1 to 4, and the unit of the values shown in Table 3 is N / mm ² . A range surrounded by a thick frame indicates a fracture from the base material portion. In Example 6 in which the outer groove angle was −2 ° and Example 8 in which the outer groove angle was 2 °, the fracture rate at the base material portion was 100%. FIG. 18 is a diagram showing the tensile strength in Examples 5 to 9. It can be seen that any of Examples 5 to 9 satisfies the standard value of the bonding strength.

  Table 4 is a table | surface which shows the data of the elongation amount until the fracture | rupture of the simple test piece in the case of a tension test. The average value of the elongation is shown in the bottom row of Table 2. The elongation values shown in Table 2 are shown in mm. A range surrounded by a thick frame indicates a fracture at the base material portion. FIG. 19 is a diagram showing the amount of elongation of each test piece during the tensile test in Examples 5 to 9. Similar to the results of the tensile strength, in Example 6 and Example 8, an increase in the amount of elongation and stable bonding compared to Example 7 are observed.

  A pipe member for brazing joined to a member to be joined having an end face with an outer groove angle of 30 ° with respect to the hollow shaft, comprehensively judged from the results of Table 3, Table 4, FIG. 16, FIG. 18 and FIG. As long as it has a groove shape with a clearance angle α of 2 °. Therefore, the abutting surface of the other pipe member 52 with one pipe member 51 is an end surface having an inclination of 30 ° with respect to the hollow shaft, and the one pipe member 51 is abutted with the other pipe member 52. If the surface has an angle of 2 ° with the butting surface of the other pipe member 51, that is, if the clearance angle α is 2 °, the brazing joint can be surely performed.

  The present invention is not limited to the above-described embodiments and examples, and includes various forms in which the design is changed without departing from the gist of the invention.

1: One pipe member 2: The other pipe member 2E, 10E, 20E: Butt end (end)
3: Brazing material 4: Heating coil 5: Extra wax 6: Mistakes 51: One pipe member with an inner groove angle 52: Other pipe member with an outer groove angle

Claims (2)

In the method of joining a pipe by brazing one pipe member and the other pipe member,
When the one pipe member and the other pipe member are abutted against each other, the end of one pipe member has a groove shape so that the inner peripheral edge side of the thick portion contacts and a gap is formed on the outer edge side. And
In a state where an insert material containing a brazing material is sandwiched between the one pipe member and the other pipe member and pressed against each other, the abutted portion is heated, and the end surface of the one pipe member and the other pipe member are heated. A pipe joining method by brazing, characterized by joining the end faces of the pipe member. The pipe joining method by brazing according to claim 1, wherein the butting surface of the other pipe member with the one pipe member is an end surface orthogonal to the hollow axis.