JP2016064434A - Joining body, magnetic rotary arc joining method, and method of producing joining body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic rotary arc joining method which can suppress the occurrence of joining failure with a simple constitution, and a joining body in which the occurrence of joining failure is suppressed.SOLUTION: A joining body 10 includes a first metal tube 21, a second metal tube 22, and a joint portion (a section including joint interface 11) in which end faces of the first and second metal tubes are joined. In the joint portion, an outer peripheral bead portion protruding toward an outer peripheral side and an inner peripheral bead portion 13 protruding toward an inner peripheral side are formed. A difference between a width of the outer peripheral bead portion in a direction from the first metal tube 21 to the second metal tube 22 (a width L1 of a grinding portion 12), and a width L2 of the inner peripheral bead portion 13 is equal to or less than 40% of an average value of the width L1 of the outer peripheral bead portion and the width L2 of the inner peripheral bead portion 13.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a joined body, a magnetic rotating arc joining method, and a manufacturing method of a joined body, and more particularly, to a joined body of metal pipe, a magnetic rotating arc joining method, and a manufacturing method of a joined body.

  Conventionally, a magnetic rotating arc joining method is known (see, for example, JP-A-6-55267).

JP-A-6-55267

  In the magnetic rotating arc joining method described above, an essential condition at the time of pressure welding is that the steel pipe end face is uniformly melted by the arc. However, in the conventional magnetic rotating arc welding method, particularly when the pipe diameter is large or when the pipe is thick, the molten state of the end face of the steel pipe may not be uniform, resulting in poor bonding.

  In order to prevent the occurrence of such a bonding failure, in the above-mentioned JP-A-6-55267, before the arc is ignited, the outer periphery of the end face (joining portion) of the oppositely arranged tubes is surrounded by a heating means such as a gas burner. Discloses a method in which the joining portion is preheated by the heating means. However, the provision of such heating means complicates the apparatus configuration of the bonding apparatus and increases the cost of the bonding method.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a magnetic rotating arc bonding method capable of suppressing the occurrence of bonding failure with a simple configuration, It is to obtain a bonded body in which generation is suppressed and a method for manufacturing the bonded body.

  A joined body according to an embodiment of the present invention includes a first metal tube, a second metal tube, and a joined portion obtained by joining the end surfaces of the first and second metal tubes. An outer peripheral bead portion protruding toward the outer peripheral side and an inner peripheral bead portion protruding toward the inner peripheral side are formed at the joint portion. The difference between the width of the outer peripheral bead portion and the width of the inner peripheral bead portion in the direction from the first metal tube to the second metal tube is an average value of the width of the outer peripheral bead portion and the width of the inner peripheral bead portion. On the other hand, it is 40% or less.

  A magnetic rotating arc joining method according to an embodiment of the present invention includes a step of preparing first and second metal tubes, a step of preheating, a step of main heating, and a step of joining. In the preliminary heating step, arc discharge is generated between the end faces while the end faces of the first and second metal tubes are opposed to each other, and a magnetic field is applied between the end faces to move the position of the arc discharge between the end faces. Thus, the temperature at a position 2 mm away from the end faces of the first and second metal tubes is preheated to the preheating temperature. In the main heating step, an arc discharge is generated between the end faces of the first and second metal tubes, and a magnetic field is applied between the end faces to move the position of the arc discharge between the end faces. The temperature at a position 2 mm away from the end face of the metal tube is heated to the bonding temperature. In the bonding step, after the main heating step, the end faces are butted together and bonded.

  The manufacturing method of the joined body according to one embodiment of the present invention uses the magnetic rotating arc joining method.

  According to the above, it is possible to obtain a joined body in which the occurrence of joint failure is suppressed.

It is a perspective schematic diagram of the joined body concerning this embodiment. It is a cross-sectional schematic diagram in line segment II-II of FIG. It is a schematic diagram for demonstrating the magnetic rotating arc joining method which concerns on this embodiment. It is a flowchart for demonstrating the magnetic rotating arc joining method which concerns on this embodiment. It is a schematic diagram which shows an example of the joining apparatus which enforces the magnetic rotating arc joining method which concerns on this embodiment. It is a timing chart for demonstrating the magnetic rotating arc joining method which concerns on this embodiment. It is a photograph of the sample of the joined object to which the magnetic rotating arc joining method concerning this embodiment is applied. It is a structure | tissue photograph of the sample shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

<Composition of joined body>
With reference to FIG. 1 and FIG. 2, the joined body which concerns on this embodiment is demonstrated. Referring to FIG. 1, a joined body 10 is obtained by joining a first metal tube 21 and a second metal tube 22 by a magnetic rotating arc joining method. That is, the joined body 10 includes a first metal tube 21, a second metal tube 22, and a joint portion including a joint interface 11 in which the end surfaces of the first and second metal tubes 21 and 22 are joined together. . An outer peripheral bead portion (not shown) that protrudes to the outer peripheral side and an inner peripheral bead portion 13 that protrudes to the inner peripheral side are formed in the joint portion. The outer peripheral bead portion is removed by grinding. For this reason, the part by which the said outer periphery bead part was removed by grinding becomes the grinding part 12. FIG. Difference between the width of the outer peripheral bead portion (that is, the width L1 of the grinding portion 12) and the width L2 of the inner peripheral bead portion 13 in the direction from the first metal tube 21 to the second metal tube 22 (absolute L1-L2) The value is 40% or less with respect to the average value ((L1 + L2) / 2) of the width of the outer peripheral bead portion (width L1 of the grinding portion 12) and the width L2 of the inner peripheral bead portion. In this way, the difference in the width of the bead portion between the inner peripheral side and the outer peripheral side of the first and second metal tubes 21 and 22 in the joint portion is sufficiently small, and the joint state of the joint portion is the inner periphery. There is no big difference between the side and the outer peripheral side, and the joined body 10 in which the soundness of the joint portion is ensured is obtained.

  Here, the width L2 of the inner peripheral bead portion 13 refers to the inner peripheral bead portion from the inner peripheral surface of the first metal tube 21 and the second metal tube 22 in the joined body 10 in the cross section shown in FIG. This is the distance between the positions at which 13 starts to project (boundary points 14a, 14b). Similarly, the width L1 of the grinding portion 12 on the outer peripheral side also corresponds to the distance between the positions at which the outer peripheral bead portions start to protrude from the outer peripheral surfaces of the first metal tube 21 and the second metal tube 22.

  In the joined body 10, any metal material can be used as the material of the joined body 10. For example, carbon steel for mechanical structure is used. In the joined body 10, the outer diameters of the first and second metal tubes 21 and 22 are 10 mm or more and 250 mm or less. The lower limit of the outer diameter is, for example, 20 mm or more, preferably 50 mm or more, more preferably 100 mm or more. Moreover, the thickness of the 1st and 2nd metal tubes 21 and 22 is 1 mm or more and 16 mm or less. The lower limit of the thickness is, for example, 2 mm or more, preferably 5 mm or more, more preferably 10 mm or more.

<Outline of Magnetic Rotating Arc Joining Method According to this Embodiment>
With reference to FIG. 3, the outline of the magnetic rotating arc joining method for forming the joined body shown to FIG. 1 and FIG. 2 is demonstrated.

  In the magnetic rotating arc joining method, the Fleming left-hand rule is used. In the magnetic rotating arc joining method according to the present embodiment, as shown in FIG. 3, an annular shape is formed so as to surround a part of the outer peripheral side surfaces of the first and second metal tubes 21, 22 arranged so that the end faces face each other. While arranging the permanent magnet 7 and applying a magnetic field, a large direct current is passed from the power source 34 to the first and second metal tubes 21 and 22. And if the distance between the opposing end surfaces of the 1st and 2nd metal pipes 21 and 22 is kept at a certain fixed value, the arc 31 of 1.5 mm-2.0 mm will be ignited between the said end surfaces. In FIG. 3, the direction of the current is indicated by the arrow 33, and the direction of the force acting on the arc 31 is indicated by the arrow 32. That is, the generated arc 31 receives the force of the rotating magnetic field generated by the permanent magnet 7 and rotates at a high speed in the circumferential direction on the end face as indicated by the arrow 35 in FIG. As a result, both end faces of the first and second metal tubes 21 and 22 are heated.

  Here, in the initial stage after the arc is ignited, the arc 31 rotates on the inner diameter side of the first and second metal tubes 21 and 22, and the inner diameter side of the end face is heated. This is because the arc 31 receives a force in the inner diameter side direction due to a magnetic blowing phenomenon caused by a difference in magnetic flux density inside and outside the first and second metal tubes 21 and 22. In the present embodiment, as will be described later, the preheating step and the main heating step are performed using the heating by the arc. In the preheating step, the preheating temperature is set below the magnetic transformation point, and the heating temperature in the main heating step is set to, for example, about 1100 ° C.

  In this heating process, after the heating by the arc 31 is started, the magnetic susceptibility decreases with the temperature rise at the end faces of the metal tubes 21 and 22, and the ferromagnetism disappears at the magnetic transformation point (770 ° C.). For this reason, the magnetic flux density on the inner diameter side is higher than the magnetic flux density on the outer diameter side of the metal tubes 21 and 22, and the arc 31 is moved and heated to the outer diameter side of the metal tubes 21 and 22 by the magnetic blowing phenomenon.

  In the present embodiment, since the end surfaces of the first and second metal tubes 21 and 22 are sufficiently heated in advance by the preliminary heating step, the end surfaces reach a molten state almost uniformly by the main heating step. That is, it is possible to suppress the occurrence of the problem that the temperature of the inner diameter end face exceeds the melting point during the heating of the outer diameter end faces of the metal tubes 21 and 22 and the arc 31 disappears while the outer diameter end faces are insufficiently heated. Then, at the timing when the end surfaces of the first and second metal tubes 21 and 22 are almost uniformly melted, the metal tube on one side (for example, the first metal tube 21) is replaced with the metal tube on the other side (for example, the second metal tube). 22), the end surfaces of the first and second metal tubes 21 and 22 are joined. At this time, since the melted state is substantially uniform from the outer peripheral side to the inner peripheral side of the end face, the width of the bead portion is substantially equal between the inner main side and the outer peripheral side, and a uniform and good joint can be formed. Thereafter, by removing the bead portion located on the outer peripheral side by grinding, a joined body 10 as shown in FIGS. 1 and 2 can be obtained.

<Description of Magnetic Rotating Arc Joining Method and Joined Body Manufacturing Method According to this Embodiment>
Next, with reference to FIGS. 4-6, the magnetic rotating arc joining method which concerns on this embodiment, and the manufacturing method of the joined body using the said magnetic rotating arc joining method are demonstrated in detail. Note that the vertical axis in FIG. 6 (A) indicates the energization current between the end faces, the vertical axis in FIG. 6 (B) indicates the arc voltage between the end faces, and the vertical axis in FIG. 6 (C) indicates the distance between the end faces ( 6 (D) indicates the temperature at a position 2 mm from the end face, FIG. 6 (E) indicates the pressing pressure between the end faces, and FIGS. ) Represents the time.

  With reference to FIG. 4, in the magnetic rotating arc joining method (joint body manufacturing method) according to the present embodiment, a preparation step (S10) is first performed. In this step (S10), first and second metal tubes 21 and 22 are prepared. The prepared first and second metal tubes 21 and 22 are set in the joining apparatus shown in FIG. In the bonding apparatus shown in FIG. 5, the first metal tube 21 is fixed to the chuck 9 to which the plus terminal 8 is connected. The second metal tube 22 is fixed to the chuck 9 to which the minus terminal 6 is connected. An annular permanent magnet 7 is installed in the two chucks 9 so as to surround the first and second metal tubes 21 and 22. In addition, the load cell 5 is connected to the second surface side opposite to the first surface where the permanent magnet 7 is installed in the chuck 9 to which the minus terminal 6 is connected. A ball screw 3 is installed on the side opposite to the chuck 9 when viewed from the load cell 5. A motor 1 is connected to the ball screw 3 via a speed reducer 2. Further, a displacement sensor 4 for measuring the displacement of the chuck 9 to which the minus terminal 6 is connected is disposed at a position adjacent to the load cell 5. The 1st and 2nd metal tubes 21 and 22 are arrange | positioned so that a mutual end surface may oppose.

  Next, as shown in FIG. 4, a preheating step (S20) is performed. In the step (S20), arc discharge is generated between the end faces while the end faces of the first and second metal tubes 21 and 22 are opposed to each other, and a magnetic field is applied between the end faces to set the position of the arc discharge between the end faces. The temperature at a position 2 mm away from the end surfaces of the first and second metal tubes 21 and 22 is preheated to the preheating temperature (temperature T1 in FIG. 6D).

  Specifically, at a time point t1 in FIG. 6, the distance (gap) between the end faces of the first and second metal tubes 21 and 22 is set to a predetermined size indicated by a gap D1 in FIG. At the same time, by applying an arc voltage V1 (see FIG. 6B) between the first and second metal tubes 21 and 22, the arc is ignited as shown in FIG. A current I1 (see FIG. 6A) flows. Further, the arc rotates at the end face as shown in FIG. 3 by the magnetic field generated by the permanent magnet 7 (see FIG. 5). As a result, the end face is heated, and the temperatures of the first and second metal tubes 21 and 22 at a position away from the end face by a predetermined distance (position 2 mm away from the end face) are shown in FIG. It is heated to a temperature T1 (preheating temperature), and the magnetism is lowered. At the time t2 when the temperature at the position reaches the temperature T1, the arc voltage and the arc current are set to zero (see FIGS. 6A and 6B). In addition, you may implement the preheating process (S20) mentioned above in multiple times.

  From the time t2 to the time t3, the first and second metal tubes 21 and 22 are held with the arc discharge stopped. Although the temperature at the position 2 mm from the end face decreases to the temperature T2 as shown in FIG. 6D by this holding time, the end face temperature becomes more uniform due to thermal diffusion at the end face. At this time, as shown in FIG. 6C, the gap between the end faces is once set to zero and set to a predetermined gap D1 again. This is because the gap is adjusted in order to reliably start the arc in the main heating process described later.

  Next, the main heating step (S30) is performed as shown in FIG. In the main heating step (S30), an arc discharge is generated between the end faces of the first and second metal tubes 21 and 22, and a magnetic field is applied between the end faces to move the position of the arc discharge between the end faces. The temperature at a position 2 mm away from the end faces of the first and second metal tubes 21 and 22 is fully heated to the bonding temperature (temperature T3 in FIG. 6D).

  Specifically, at a time point t3 in FIG. 6, the distance (gap) between the end faces of the first and second metal tubes 21 and 22 is set to a predetermined size indicated by a gap D1 in FIG. At the same time, by applying an arc voltage V1 (see FIG. 6B) between the first and second metal tubes 21 and 22, the arc is ignited as shown in FIG. A current I2 (see FIG. 6A) flows. In this case, the stability of the arc at the end face on the outer peripheral side was improved. Further, the arc rotates at the end face as shown in FIG. 3 by the magnetic field generated by the permanent magnet 7 (see FIG. 5). As a result, the end face is heated, and the temperatures of the first and second metal tubes 21 and 22 at a position away from the end face by a predetermined distance (position 2 mm away from the end face) are shown in FIG. It is heated to a temperature T3 (joining temperature).

  After this step (S30), from the time point t4 when the temperature at the above position rises to the temperature T3 to the time point t5, as shown in FIG. 6, it is larger than the energization current value (current I2) in the main heating step (S30). A step of passing a value upset current (current I3 in FIG. 6A) between the end faces is performed. As a result, as shown in FIG. 6D, the temperature at the position 2 mm from the end face (and the temperature of the end face) increases. At time t5 in FIG. 6, the arc voltage and the upset current are set to zero. Thus, even after the time point t5 when the arc voltage is made zero, the temperature at a position 2 mm from the end face continues to rise and reaches the temperature T4 (see FIG. 6D) which is the maximum temperature.

  Next, the joining step (S40) shown in FIG. 4 is performed. In the joining step (S40), after the main heating step (S30), the end faces of the metal tubes 21 and 22 are butted together and joined. In the joining step (S40), the joined portions that are joined by abutting the end faces are energized and heated.

  Specifically, the second metal tube 22 is brought closer to the first metal tube 21 from a predetermined time after time t5 shown in FIG. 6 to reduce the distance between the end faces (gap in FIG. 6C). Even after the gap becomes zero at time t6 (that is, in a state where the end faces are in contact with each other), the motor 1 (see FIG. 5) is further driven to press the metal tube 22 toward the metal tube 21 side. As a result, the gap becomes negative as shown in FIG. 6C (that is, the molten end faces are pushed out to the outer peripheral side and the inner peripheral side to form the bead portion, thereby joining the end faces). . At this time, as shown in FIG. 6E, pressure is generated between the end faces from time t6, and reaches a predetermined pressure P1 at time t7. Thus, when the pressure between the end faces detected by the load cell 5 (see FIG. 5) reaches a predetermined pressure P1, the movement of the metal tube 22 by the motor 1 is stopped. As a result, the gap (see FIG. 6C) is substantially constant from time t7. Then, the state where the pressure between the end faces is the predetermined pressure P1 is maintained from time t7 to time t8, and the first and second metal tubes 21 and 22 as shown in FIG. By passing a current I4 between them, the joint is heated by energization. Then, at the time t8, the energization heating is finished. Thus, the 1st and 2nd metal pipes 21 and 22 can be joined by performing a joining process (S40).

  Thus, by performing a joining process (S40), the 1st and 2nd metal pipes 21 and 22 can be joined and a joined body can be obtained. Moreover, in the manufacturing method of the joined_body | zygote 10, after this joining process (S40), the post-process including the process of grinding the outer peripheral surface in the junction part of the obtained joined body 10, and removing the bead part of an outer peripheral side etc. Step (S50) may be performed. In this way, the joined body 10 shown in FIG. 1 can be obtained.

  In addition, the material which comprises the 1st and 2nd metal pipes 21 and 22 is steel, such as carbon steel for machine structures. The preheating temperature (temperature T1) in the preheating step (S20) is preferably a temperature lower than the magnetic transformation point of the material (for example, steel). For example, the preheating temperature (temperature T1) in the preheating step (S20) may be 100 ° C. or higher and 1000 ° C. or lower. In the case where the thickness of the metal tubes 21 and 22 is thick, even if the temperature of the inner diameter is increased, the temperature of the outer peripheral surface at a position 2 mm from the end surface of the metal tubes 21 and 22 for measuring the preheating temperature T1 or the like is not so high. This is because there are cases. Further, the preheating temperature is preferably 200 ° C. or higher and 900 ° C. or lower, more preferably 300 ° C. or higher and 800 ° C. or lower. Moreover, 1050 degreeC or more and 1150 degrees C or less (for example, 1100 degreeC) may be sufficient as the joining temperature (temperature T3) in this heating process (S30).

  In addition, the energization current value between the end faces in the preheating step (S20) and the main heating step (S30) (current I1 or current I2 in FIG. 6A) may be 10 A or more and 10,000 A or less. The magnetic flux density of the magnetic field in the preheating step (S20) and the main heating step (S30) may be 1 mT or more and 1000 mT or less.

  Moreover, the moving speed (pressing speed) of the metal tube 22 in the joining step (S40) can be set to 20 mm / s or more and 1100 mm / s or less. The lower limit of the moving speed is set to 20 mm / s because if the moving speed is too slow, the temperature of the end faces decreases before the end faces come into contact with each other, resulting in poor bonding conditions. The upper limit of the moving speed is set to 1100 mm / s, which is determined as a feasible value in consideration of equipment performance of the motor 1 and the hydraulic drive device. The moving speed is preferably 30 mm / s or more and 1000 mm / s or less, more preferably 50 mm / s or more and 900 mm / s or less.

  Moreover, each condition in each process (S20-S40) of the joining method mentioned above can be suitably selected according to the material, size, etc. of a metal tube. Further, in this method, by controlling the heating time based on the temperature history, the heating time can be easily controlled even when the current value, arc voltage value, magnetic flux density, material size, and the like are different.

  Although there is a part which overlaps with the description mentioned above, the characteristic structure of embodiment of this invention is enumerated.

  (1) A joined body 10 according to an embodiment of the present invention includes a first metal tube 21, a second metal tube 22, and a joined portion (joint) obtained by joining end surfaces of the first and second metal tubes. A region including the interface 11). An outer peripheral bead portion protruding to the outer peripheral side and an inner peripheral bead portion 13 protruding to the inner peripheral side are formed in the joint portion. The difference between the width of the outer peripheral bead portion (the width L1 of the grinding portion 12) and the width L2 of the inner peripheral bead portion 13 in the direction from the first metal tube 21 to the second metal tube 22 is the width of the outer peripheral bead portion. It is 40% or less with respect to the average value of L1 and the width | variety L2 of the inner periphery bead part 13. FIG. If it does in this way, there will be almost no difference in a joining state by the inner peripheral side and outer peripheral side of the metal pipes 21 and 22 in a junction part, and it will become a joined body with which the soundness of the junction part was ensured.

  (2) In the joined body 10, the material of the joined body 10 may be carbon steel for mechanical structure. In this case, the joined body according to the present embodiment can be applied to a machine part or the like.

  (3) In the joined body 10, the outer diameters of the first and second metal tubes 21 and 22 may be 10 mm or more and 250 mm or less. In this case, the joined body 10 having a relatively small diameter to a large diameter can be obtained.

  (4) In the joined body 10, the thickness of the first and second metal tubes 21 and 22 may be not less than 1 mm and not more than 16 mm. In this case, by preparing the joined body 10 having various thicknesses, the degree of freedom in selecting a mechanical device to which the joined body 10 according to the present embodiment is applied can be increased.

  (5) In the joined body 10, the outer peripheral bead portion may be removed by grinding in the joined portion. The width L1 of the outer peripheral bead portion may be the width L1 of the ground portion from which the outer peripheral bead portion has been removed by grinding. In this case, since the outer peripheral bead portion can be removed from the outer peripheral surface of the joined body 10 by grinding to finish the outer peripheral portion smoothly, the appearance of the joined body 10 can be made cylindrical.

  (6) In the magnetic rotating arc joining method according to one embodiment of the present invention, the step of preparing the first and second metal tubes 21 and 22 (S10), the step of preheating (S20), and the main heating The process (S30) to perform, and the process (S40) to join are provided. In the preheating step (S20), arc discharge is generated between the end faces in a state where the end faces of the first and second metal tubes 21 and 22 are opposed to each other, and a magnetic field is applied between the end faces. Is moved between the end faces to preheat the temperature at a position 2 mm away from the end faces of the first and second metal tubes to the preheating temperature (temperature T1 in FIG. 6D). In the main heating step (S30), an arc discharge is generated between the end faces of the first and second metal tubes 21 and 22, and a magnetic field is applied between the end faces to move the position of the arc discharge between the end faces. Then, the temperature at a position 2 mm away from the end faces of the first and second metal tubes is heated to the bonding temperature (temperature T3 in FIG. 6D). In the joining step (S40), after the main heating step (S30), the end faces are butted together and joined.

  In this way, since the preheating step (S20) can be performed using the same equipment as the method used in the main heating step (S30), it is necessary to prepare an independent heating means for preheating as in the past. And it can be preheated with a simple configuration. For this reason, since the joint portion (the end portion including the opposing end surfaces of the first and second metal tubes 21 and 22) can be sufficiently heated in advance by the preliminary heating, arc discharge is performed in the main heating step (S30). Stability can be improved and the occurrence of problems such as insufficient or uneven heating of the joint can be suppressed. For this reason, generation | occurrence | production of a joining defect can be suppressed. In addition, the pressure (pressure P1 of FIG.6 (E)) for joining edge surfaces in the process (S40) to join is 5 MPa or more and 950 MPa or less, for example. The reason why the lower limit of the pressure is set to 5 MPa is that the minimum pressure that can be pressed is considered to be about 5 MPa. The reason why the upper limit of the pressure is 950 MPa is that the pressure is assumed when a material having a high yield stress is used as the material of the metal tube. The pressure is preferably 10 MPa or more and 900 MPa or less, more preferably 20 MPa or more and 800 MPa or less.

  In addition, although the position 2 mm away from the end face is adopted as the temperature measurement position, the inventor has a stable correspondence between the experiment and the simulation if the temperature is at the position from the simulation and the experiment, and is used for the control. It has been confirmed that the measured value has sufficient reliability.

  (7) In the magnetic rotating arc joining method, after the main heating step (S30) and before the joining step (S40), an upset current (a value larger than the energization current value in the main heating step (S30)) ( A step of flowing the current I3) in FIG. 6A between the end faces may be further provided.

  In this case, before performing the joining step (S40), the melting region of the joining portion (the region including the end faces of the first and second metal tubes 21 and 22) can be made uniform by the upset current. For this reason, generation | occurrence | production of a joining defect can be suppressed reliably.

  (8) In the said magnetic rotating arc joining method, in the process (S40) to join, the junction part which faced and joined end surfaces may be electrically heated. In this case, it is possible to suppress an excessive temperature decrease in the joint portion in the joining step (S40), so that it is possible to prevent the joining conditions from deteriorating. For this reason, generation | occurrence | production of a joining defect can be suppressed more reliably.

  (9) In the magnetic rotating arc joining method, the preheating step (S20) may be performed a plurality of times before the main heating step (S30). In this case, when the first and second metal tubes 21 and 22 have a large diameter or when the metal tubes 21 and 22 are thick, the temperature of the joint portion can be sufficiently increased by a plurality of preheatings. it can. For this reason, generation | occurrence | production of a joining defect can be suppressed.

  (10) In the magnetic rotating arc joining method, the first and second metal tubes are held in a state where the arc discharge is stopped after the preheating step (S20) and before the main heating step (S30). There may be further included a step (period between time t2 and time t3 in FIG. 6).

  In this case, in particular, when the thickness of the first and second metal tubes 21 and 22 is large, by performing thermal diffusion at the end face by the holding process as described above, the inner peripheral side and the outer peripheral side of the end face The temperature difference can be reduced. As a result, the occurrence of poor bonding can be suppressed. The length of the holding step may be, for example, more than 0 seconds and 10 seconds or less. This is because even the thick metal tube can sufficiently equalize the temperature of the end face by securing the holding time of about 10 seconds. If the metal tubes 21 and 22 are sufficiently thin, the main heating step (S30) may be performed immediately after the preheating step (S20) without performing the holding step.

  (11) In the magnetic rotating arc joining method, the material constituting the first and second metal tubes 21 and 22 may be made of steel. The preheating temperature (temperature T1) in the preheating step (S20) may be a temperature lower than the magnetic transformation point of the material, and the bonding temperature (temperature T3) in the main heating step (S30) is 1050 ° C. or higher and 1150 ° C. or lower. It may be. The bonding temperature (temperature T3) is preferably 1070 ° C. or higher and 1130 ° C. or lower, more preferably 1080 ° C. or higher and 1120 ° C. or lower.

  In this case, the 1st and 2nd metal pipes 21 and 22 which used steel as a material can be joined reliably, and a joined body can be obtained.

  (12) In the magnetic rotating arc joining method, the material may be carbon steel for mechanical structure. In this case, the joining method according to the present embodiment can be used for manufacturing machine parts and the like by applying the magnetic rotating arc joining method to joining metal pipes using carbon steel for machine structure as a material. Here, the carbon steel for machine structure is carbon steel for machine structure defined in JIS standard G4051 (for example, S10C, S45C, S55C, etc.), and boron (B) is added to the carbon steel defined in the above JIS standard G4051. The carbon steel contained (for example, SAE standard 10B38, SBM40, etc.) is meant.

  (13) In the magnetic rotating arc joining method, the outer diameters of the first and second metal tubes 21 and 22 may be 10 mm or more and 250 mm or less. As described above, the joining method according to the present embodiment can be applied to the metal pipes 21 and 22 having a relatively small diameter to a large diameter.

  (14) In the magnetic rotating arc joining method, the thickness of the first and second metal tubes 21 and 22 may be 1 mm or more and 16 mm or less. Thus, the joining method according to the present embodiment can be applied from the relatively thin metal tubes 21 and 22 to the thick metal tubes 21 and 22.

  (15) In the magnetic rotating arc joining method, the energization current value between the end faces in the preheating step (S20) and the main heating step (S30) may be 10 A or more and 10,000 A or less. In this case, an energization current value can be selected according to the size and material of the metal pipes 21 and 22 to be joined, and the occurrence of poor joining can be suppressed. Further, the energization current value may be controlled so as to fall within a range of ± 150 A with respect to the target value.

  (16) In the magnetic rotating arc joining method, the magnetic flux density of the magnetic field in the preheating step (S20) and the main heating step (S30) may be 1 mT or more and 1000 mT or less. In this case, the magnetic flux density can be selected according to the size and material of the metal tube to be joined, the energization conditions, and the like. The magnetic flux density is preferably 10 mT or more and 900 mT or less, more preferably 20 mT or more and 800 mT or less.

  (17) The method for manufacturing a joined body according to an embodiment of the present invention uses the magnetic rotating arc joining method. In this way, it is possible to obtain the bonded body 10 in which the occurrence of bonding failure is suppressed.

(Experimental example)
In order to confirm the effect of the magnetic rotating arc joining method according to the present embodiment, the following experiment was conducted.

<Sample>
In this experiment, a cylindrical material using a JIS standard S45C material having an outer diameter of 40 mm and a thickness of 5 mm was prepared as the first and second metal tubes. The axial length of the cylindrical material was 300 mm. Moreover, the apparatus of the structure shown in FIG. 5 was used for the joining apparatus used for joining.

<Experiment method>
The prepared metal tube was set in the joining apparatus shown in FIG. 5, and joined by the magnetic rotating arc joining method according to the present embodiment shown in FIG. The set value of the current value in the preheating step (S20) was 340 A (± 150 A), and the magnetic flux density on the outer diameter side of the metal pipe (steel pipe) end face was 40 mT. Moreover, the set value of the current value in the main heating step (S30) was set to 270A (± 150A). The magnetic flux density on the outer diameter side of the metal tube was 40 mT. In the preheating step (S20), heating was performed until the temperature (temperature T1 in FIG. 6D) at a position 2 mm from the outer diameter end face of the metal tube reached 550 ° C. The main heating step (S30) was started 3 seconds after the preheating step (S20) was completed (time point t3 3 seconds after time point t2). In this step, bonding was performed when the temperature at a position 2 mm from the outer diameter end face of the metal tube reached 1100 ° C. Immediately before joining, an upset current (current I3 in FIG. 6A) was passed with a current value of 620 A in order to make the melting region of the end faces uniform. The upset as the joining step (S40) was completed when the pressure shown in FIG. 6E reached 90 kN (160 MPa). Moreover, in order to suppress the temperature reduction of a metal pipe end surface, the energization heating with the electric current value of 2 kA was performed also during the joining process (S40).

<Result>
FIG. 7 shows the appearance of a joined body obtained by joining the metal pipes described above. In FIG. 7, the joined body is cut along the axial direction, and is arranged so that the cut surface of one of the cut portions can be seen. FIG. 8 shows a cross-sectional microphotograph of the joint in the joined body shown in FIG. FIG. 8 shows cross-sectional micrographs of (a) the joint, (b) the heat affected zone 1, (c) the heat affected zone 2 and (d) the base material in order from the joint interface. 8 is at a position 0 mm from the bonding interface. Moreover, the said heat affected zone 1 is a 0.1-mm position from a joining interface. The heat affected zone 2 is at a position 0.2 mm from the bonding interface. Moreover, the said base material is a 0.4 mm position from a joining interface.

  As can be seen from FIGS. 7 and 8, in the joined body according to the present embodiment, the joined portion has a substantially uniform structure from the inner peripheral side to the outer peripheral side, and it can be seen that a good joined portion is formed.

  Although the embodiments and examples of the present invention have been described above, the above-described embodiments can be variously modified. The scope of the present invention is not limited to the above-described embodiment. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is particularly advantageously applied to magnetic rotating arc welding of steel pipes.

  1 motor, 2 speed reducer, 3 ball screw, 4 displacement sensor, 5 load cell, 6 minus terminal, 7 permanent magnet, 8 plus terminal, 9 chuck, 10 joined body, 11 joining interface, 12 grinding part, 13 bead part, 14a , 14b Boundary point between bead and inner peripheral surface, 21, 22 Metal tube, 31 arc, 32, 33, 35 Arrow, 34 Power supply.

Claims (7)

A first metal tube;
A second metal tube;
A joining portion joining the end faces of the first and second metal tubes,
In the joint portion, an outer peripheral bead portion protruding to the outer peripheral side and an inner peripheral bead portion protruding to the inner peripheral side are formed,
The difference between the width of the outer peripheral bead portion and the width of the inner peripheral bead portion in the direction from the first metal tube to the second metal tube is the width of the outer peripheral bead portion and the inner peripheral bead portion. A joined body having an average value of 40% or less with respect to the width.   The joined body according to claim 1, wherein a material of the joined body is carbon steel for machine structure. In the joint portion, the outer peripheral bead portion is removed by grinding,
3. The joined body according to claim 1, wherein a width of the outer peripheral bead portion is a width of a ground portion where the outer peripheral bead portion is removed by grinding. Preparing first and second metal tubes;
With the end faces of the first and second metal tubes facing each other, arc discharge is generated between the end faces and a magnetic field is applied between the end faces to move the position of the arc discharge between the end faces. Preheating the temperature at a position 2 mm away from the end faces of the first and second metal tubes to a preheating temperature,
By generating an arc discharge between the end faces of the first and second metal tubes and applying a magnetic field between the end faces to move the position of the arc discharge between the end faces, the first and second The step of heating the temperature at the position 2 mm away from the end face of the metal tube to the joining temperature;
A magnetic rotating arc joining method comprising: a step of abutting and joining the end faces after the main heating step.   5. The magnetism according to claim 4, further comprising a step of flowing an upset current between the end faces having a value larger than an energization current value in the main heating step after the main heating step and before the bonding step. Rotating arc joining method.   6. The magnetic rotating arc joining method according to claim 4, wherein in the joining step, the joining portion where the end faces are butted and joined is energized and heated.   The manufacturing method of a joined body using the magnetic rotating arc joining method of any one of Claims 4-6.