JP2007090374A - Structure and method of joining cylindrical member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve corrosion resistance on the side of an iron based metallic member in the weld zone of friction welding of cylindrical members comprising an aluminum based metallic member and the iron based metallic member. <P>SOLUTION: A propeller shaft 1 has a stub shaft 11 made of an iron based metallic material, formed in a hollow cylindrical shape, and is provided with a protective layer 13 on the outer circumferential face, and a hollow cylindrical first tube 12 made of an aluminum based metallic material, wherein the two components are joined by friction welding. In joining the two, there are formed: a burr 16 expanded in diameter from the joining end of the stub shaft and folded nearly in a warpage; a non-protective part 14 on the joining face side; and a protective layer in a reduced diameter part 17 which is reduced to the reverse end side in the axial direction, with the maximum expanded diameter part 16a as a boundary. Consequently, corrosion is prevented in the stub shaft single unit and, moreover, in the outer circumferential part 14b of the non-protective part having a minute exposed area, growth of corrosion is suppressed by the formation of an oxidation product even in the presence of electro-erosion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cylindrical member joining structure in which respective cylindrical members formed of an aluminum-based metal member and an iron-based metal member are joined by friction welding and a joining method thereof.

  As a conventional joining structure of cylindrical members, for example, a structure described in Patent Document 1 below has been proposed.

  This cylindrical member joining structure is formed by friction welding the dissimilar metal members to each other and from the outer peripheral side of the first member, which is a base metal member having a relatively natural potential between the dissimilar metal members, a noble metal having a natural potential. A burr is extended in the direction along the outer periphery of the second member, which is a member, and the burr covers the outer peripheral portion of the bonding interface.

Thus, the burr prevents an electrolyte such as salt water from reaching the bonding interface. Further, when the electrolytic solution enters the inside of the burr, the electrolytic solution corrodes the burr near the bonding interface and a part of the second member to generate an oxidized product, and the oxidized product is By depositing in the gap between the second member and the second member, the supply of further electrolyte solution to the vicinity of the joint interface can be cut off, and corrosion of the joint interface can be prevented.
JP 2003-48078 A

  However, it is not possible to completely prevent an electrolytic solution such as rainwater from reaching the joining interface only by extending the burr as in the conventional joining structure of cylindrical members.

  That is, as described above, burrs in the vicinity of the bonding interface and oxidation products generated by electrolytic corrosion of a part of the second member accumulate in the gap between the burr and the second member, and the corrosion of the bonding interface proceeds. Even if the speed is delayed, corrosion progresses from the periphery of the oxidation product, and corrosion may occur as a single steel material.

  The present invention has been devised by paying attention to such a technical problem, and is based on the adhesion of the electrolytic solution in the friction welding portion of each cylindrical member made of an aluminum-based metal member and an iron-based metal member. The present invention provides a joining structure of a cylindrical member and a joining method thereof that can improve the corrosion resistance on the side of an iron-based metal member.

  The invention according to claim 1 is a joining structure of a cylindrical member formed by joining an aluminum-based metal member and an iron-based metal member formed in a cylindrical shape by friction welding, and joining the iron-based metal member A non-protected portion formed at the end and expanded outward from the joint end, and formed from the maximum expanded end edge of the non-protected portion to the outer peripheral surface of the iron-based metal member to protect the contact with the electrolytic solution And a protective layer.

  According to the present invention, an oxidation product is generated in the non-protected portion formed at the joint portion between the aluminum-based metal member and the iron-based metal member by electrolytic corrosion of the non-protected portion. Since the oxidation product is deposited around the non-protected portion, the progress of the corrosion of the non-protected portion is prevented, and the outer peripheral side of the iron-based metal member alone is also prevented by the protective layer.

  The invention according to claim 2 is a joining method of a cylindrical member formed by joining an aluminum-based metal member and an iron-based metal member formed in a cylindrical shape by friction welding, and the outer surface of the iron-based metal member Forming a protective layer, cutting an end surface of the ferrous metal member on the joining end side, scraping off the protective layer, and forming an enlarged diameter portion on the outer peripheral side, and the aluminum-based metal And a step of friction-welding the member and the iron-based metal member to join the two members.

  According to this invention, even if it exists in invention of this joining method, the effect similar to the invention of the said Claim 1 is acquired.

  The invention according to claim 3 is a joining structure of a cylindrical member formed by joining an aluminum metal member formed in a cylindrical shape and an iron metal member, and the aluminum metal member and the iron metal. A protective layer that protects the contact with the electrolytic solution is formed only on the outer peripheral surface of the iron-based metal member excluding the joint with the member.

  According to this invention, since the protective layer that protects the contact with the electrolytic solution is formed only on the outer peripheral surface of the iron-based metal member excluding the joint portion between the aluminum-based metal member and the iron-based metal member, the protective layer In particular, corrosion on the outer peripheral side of the iron-based metal member alone is reliably prevented.

  Embodiments of a cylindrical member joining structure according to the present invention will be described below in detail with reference to the drawings. In this embodiment, a cylindrical member joining structure is applied to a propeller shaft for a vehicle.

  That is, as shown in FIG. 6, the propeller shaft 1 is disposed along the vehicle front-rear direction at a substantially central portion of the vehicle body in a four-wheel drive vehicle or a front engine / rear drive vehicle. The first shaft 2 and the second shaft 3 on the vehicle rear end side are connected via a constant velocity joint 4 provided at the front end portion of the second shaft.

  The propeller shaft 1 has a front end portion of the first shaft 2 connected to an output shaft of a transmission (not shown) via a first universal joint 5, while a rear end portion of the second shaft 3 is a first end portion. It is connected to a rear differential input shaft (not shown) through a universal joint 6 so that it can swing in the vertical and horizontal directions of the vehicle body.

  Further, the propeller shaft 1 is fixed to the lower part of the floor of the vehicle body via a support member 8 by a center bearing 7 provided between the first shaft 2 and the constant velocity joint 4 and is rotatably supported. The entire bending is prevented.

  The first shaft 2 is connected to the first yoke 10 of the first universal joint 5 and the stub shaft 11 connected to the second shaft 3 via the constant velocity joint 4 via the first tube 12. ing.

  The stub shaft 11 is formed in a stepped cylindrical shape made of a ferrous metal material, for example, S45C, which is carbon steel for mechanical structures, and a base portion 11a joined to the rear end side of the first tube 12, and the base portion A main shaft portion 11b having a reduced diameter through the step portion at the rear end of the main shaft portion 11a, and a leading end portion 11c having a diameter reduced at the rear end of the main shaft portion 11b through the step portion; Yes.

  Further, as shown in FIGS. 1 and 2, the stub shaft 11 is provided with a protective layer 13 such as coating or plating on the outer peripheral surface in order to prevent corrosion of the stub shaft 11 alone by an electrolyte such as rain water. Has been.

  Further, the stub shaft 11 has a non-protected portion 14 in which the protective layer 13 is removed from the opening end surface of the base portion 11a by a cutting process to be described later in order to prevent a decrease in the joining force with the first tube 12. It has become.

  The first yoke 10 is made of an iron-based metal material similar to the stub shaft 11, and the outer peripheral surface is provided with the protective layer 13 and has a hollow cylindrical shape that is joined to the first tube 12. It has a cylindrical portion 10a formed.

  The first tube 12 is made of an aluminum-based metal material, for example, a heat-treatable alloy of 6000 series A6061 or a non-heat treatable alloy of 5000 series A5154, and is formed in a hollow cylindrical shape having a stepped shape with an enlarged middle portion. Has been. The first tube 12 has a larger surface area than the first yoke 10 and the stub shaft 11.

  The first tube 12 has a front end portion 12 a having a diameter substantially the same as the cylindrical portion 10 a of the first yoke 10 and an outer diameter, while the rear end portion 12 b has a base portion 11 a of the stub shaft 11. Are set to the same inner and outer diameters.

  The base portion 11a of the stub shaft 11 and the rear end portion 12b of the first tube 12 are integrally joined by friction welding.

  As will be described later, this friction welding is performed by applying pressure while rotating the first tube 12 with respect to the stub shaft 11, and at the opening peripheral edge portion of the rear end portion 12 b of the first tube 12, As shown in FIGS. 1-4, the curl part 15 is formed over the perimeter.

  The curled portion 15 generates frictional heat below the melting point due to friction with the non-protected portion 14 of the stub shaft 11, and is flat with the rear end portion 12 b of the first tube 12 contacting the end surface 14 a of the non-protected portion 14. While the surface is formed, the rear end portion 12b is pushed in the radial direction by being pressed in the axial direction so as to be brought into pressure contact with the outer peripheral surface of the first tube 12, and is folded back. A song is formed. And the junction part C1 of the base 11a of the stub shaft 11 and the rear-end part 12b of the 1st tube 12 is as shown in FIG.5 and FIG.8, and the end surface 14a of the non-protection part 14 in the base 11a and the curl part 15 are shown. The flat surface is integrated with the butt.

  Here, the method for joining the base portion 11a of the stub shaft 11 and the rear end portion 12b of the first tube 12 will be described in detail. First, as shown in FIG. By dipping in a plating tank, the entire stub shaft 11 is coated or plated to prevent corrosion, and the protective layer 13 is formed on the entire outer surface.

  Subsequently, as shown in FIGS. 7B and 7C, in the friction welding machine, the stub shaft 11 is set and clamped on the rotation side chuck 31, while the first tube 12 is fixed on the fixed side chuck 32. It sets and clamps and arrange | positions each end surface to join in an opposing state from an axial direction.

  Next, as shown in FIG. 7 (d), the fixed side chuck 32 is advanced to the rotary side chuck 31 side via the moving mechanism 33, and the opening end of the base portion 11 a of the stub shaft 11 and the first tube 12. The rear end portion 12b is brought into contact with the butted state.

  Thereafter, as shown in FIG. 7 (e), the clamp of the fixed side chuck 32 is temporarily released, and at the joint surface between the base portion 11a of the stub shaft 11 and the first rear end portion 12b of the first tube 12. As shown in FIG. 7 (f), the axial center is positioned, and the first tube 12 is clamped again, and the stationary chuck 32 is moved backward by the moving mechanism 33.

  Subsequently, in order to finish the end face of the opening end portion of the base portion 11a of the stub shaft 11, as shown in FIG. 8G, the rotating side chuck 31 is rotated, and the cutting tool 34 is placed on the opening end surface of the base portion 11a. By abutting, the opening end surface of the base portion 11a is cut.

  Note that the end surface finishing of the base portion 11a of the stub shaft 11 can be performed by another cutting machine after the painting or plating process, without being performed on the friction welding machine.

  Further, by cutting the opening end face of the base portion 11a of the stub shaft 11, the protective layer 13 formed on the opening end face of the base portion 11a can be scraped off in the painting or plating process.

  Then, when cutting the opening end face of the base portion 11a of the stub shaft 11, the feed speed of the cutting tool 34 is increased to a level that satisfies a predetermined finish dimension of the opening end face, thereby increasing the cutting resistance. As shown in FIG. 1, FIG. 2 and FIG.

  As shown in FIGS. 1 and 2, the burr 16 is formed so as to be almost curved back from the opening end of the base portion 11a to the outer peripheral side, and the meat of the opening end portion of the base portion 11a is pushed to the outer peripheral side. It is in the state. That is, the diameter of the opening end of the base 11a is gradually increased from the opening end surface to the outer peripheral side in a flange shape. Therefore, the outer diameter L1 of the opening end of the base 11a on which the burr 16 is formed is As shown in FIG. 2, it is set to be larger than the outer diameter L2 of the base portion 11a where the burr 16 is not formed.

  And by this cutting process, the non-protection part 14 is formed in the whole joint surface side which consists of the said end surface 14a and the outer peripheral part 14b of this end surface 14a from the opening end surface of the said base 11a to the largest diameter expansion part 16a of the burr | flash 16. It has become so.

  Further, the burr 16 has a reduced diameter portion in which the back side opposite to the first tube 12 is gradually reduced in diameter from the maximum diameter enlarged portion 16a, and becomes a circular arc concave shape continuous with the outer peripheral surface of the base portion 11a. 17 is formed.

  However, on the joint surface side of the base portion 11a, the protective layer 13 is deleted by the end face cutting, but the outer surface of the reduced diameter portion 17 that is on the back side with respect to the cutting surface of the base portion 11a The protective layer 13 remains.

  Then, after finishing the end face finishing of the base portion 11a of the stub shaft 11, as shown in FIG. 8 (h), the cutting tool 34 is retracted and the rotation of the rotation side chuck 31 is stopped to finish the opening end face. After confirming this state, the rotation side chuck 31 is rotated again.

  Subsequently, as shown in FIG. 8I, the rear end portion of the first tube 12 is moved with respect to the non-protection portion 14 of the rotating stub shaft 11 by moving the stationary chuck 32 forward by the moving mechanism 33. 12b is brought into contact and further pressurized in the axial direction, and the pressure state is maintained for a predetermined time, thereby generating frictional heat below the melting point between the two end faces.

  Thereafter, as shown in FIG. 8J, the rotation of the rotation-side chuck 31 is stopped while the fixed-side chuck 32 is held in a pressurized state toward the rotation-side chuck 31. Thereby, the stub shaft 11 and the first tube 12 are joined by friction welding.

  Then, after the rotation of the rotation side chuck 31 is stopped, as shown in FIG. 8 (k), the clamp of the rotation side chuck 31 is released, and the fixed side chuck 32 is moved backward, and FIG. As shown, by releasing the clamp of the fixed side chuck 32, the joined body of the stub shaft 11 and the first tube 12 joined together by friction welding is taken out.

  It is also possible to provide a moving mechanism 33 on the rotation side chuck 31 side to move the rotation side chuck 31 forward and backward with respect to the fixed side chuck 32 and to move the rotation side chuck 31 to the fixed side chuck 32 side. The opening end of the base 11a may be pressed against the rear end 12b of the first tube 12 by applying pressure.

  On the other hand, as shown in FIG. 6, the second shaft 3 includes an outer race 18 of the constant velocity joint 4 provided on the front end side and a second yoke 19 of the second universal joint 6 provided on the rear end side. The second tube 20 is connected.

  The outer race 18 is made of a ferrous metal material similar to that of the stub shaft 11, is formed in a stepped hollow cylindrical shape, and the protective layer 13 is applied to the outer peripheral surface thereof. It has a large-diameter portion 18a joined to the tube 20 and a small-diameter portion 18b continuous to the front end side of the large-diameter portion 18a.

  The second yoke 19 is made of an iron-based metal material similar to that of the first yoke 10, the protective portion 13 is formed on the outer peripheral surface, and is formed in a hollow cylindrical shape that is joined to the second tube 20. It has a cylindrical portion 19a.

  The second tube 20 is formed in a stepped hollow cylindrical shape made of an aluminum-based metal material similar to the first tube 12, and is joined to the large-diameter portion 18a of the outer race 18, so that the large-diameter The front end portion 20a set to have substantially the same inner diameter and outer diameter as the rear end of the portion 18a and the cylindrical portion 19a of the second yoke 19 are joined to be set to substantially the same inner diameter and outer diameter as the cylindrical portion 19a. And a rear end portion 20b.

  A joint C2 between the cylindrical portion 10a of the first yoke 10 and the front end 12a of the first tube 12, a joint C3 between the large diameter portion 18a of the outer race 18 and the front end 20a of the second tube 20, and The joint portion C4 between the cylindrical portion 19a of the second yoke 19 and the rear end portion 20b of the second tube 20 is joined by friction welding similarly to the joint between the stub shaft 11 and the first tube 12, It is formed in substantially the same manner as the junction C1.

  Therefore, according to this embodiment, since the burr 16 is formed at the opening end portion of the base portion 11a of the stub shaft 11 in the joint portion C1 between the stub shaft 11 and the first tube 12, the joint surface of the joint portion C1. The electrolytic solution such as rainwater adheres to the outer peripheral portion 14b of the non-protected portion 14 exposed from the above, and the outer peripheral portion 14b is eroded due to a potential difference with the curled portion 15. However, an oxidation product is generated by this erosion. At the same time, this oxidation product is deposited between the outer peripheral portion 14 b and the curled portion 15.

  As a result, the outer peripheral portion 14b of the non-protected portion 14 with a small exposed area is prevented from progressing corrosion, while the outer peripheral surface of the base portion 11a is protected by the protective layer 13, so that the outer periphery of the base portion 11a alone is prevented. By preventing surface side corrosion, it is possible to prevent overall corrosion of the base portion 11a of the stub shaft.

  In addition, by forming the burr 16 in a shape that is enlarged in a curved manner outwardly with respect to the joint C1, the protective layer 13 is extended from the axially opposite end side of the base portion 11a to the reduced diameter portion 17 of the burr 16. However, since the entire joint surface side is formed as the non-protection part 14 with the maximum diameter-expanded part 16a as a boundary, the coating and plating components applied as the protective layer 13 are applied to the opening end face of the base part 11a and the first tube. When the end surface of the rear end portion 12b of 12 is joined by friction welding, it is not mixed into the joint surfaces of the two.

  Therefore, since the component of the protective layer 13 does not adversely affect the friction welding between the opening end surface of the base portion 11a and the end surface of the rear end portion 12b of the first tube 12, a stronger bonding state between them can be achieved. It is possible to obtain a sufficient bonding strength.

  Then, the surface area of the first tube 12 made of an aluminum metal material having a natural potential is set larger than that of the stub shaft 11 made of a ferrous metal material having a natural potential, and the protective layer 13 is made to be the first layer. Since the tube 12 is not formed but formed only on the outer surface of the stub shaft 11 having a surface area smaller than that of the first tube 12, the area for forming the protective layer 13 can be minimized.

  Therefore, it is possible to contribute to the weight reduction of the propeller shaft 1 as a whole and to reduce the cost.

  Further, since the curled portion 15 is formed at the rear end portion 12b of the first tube 12 by friction welding, the outer peripheral portion of the unprotected portion 14 formed at the open end portion of the curled portion 15 and the base portion 11a. 14b abuts and joins with certainty, and the contact area between the two increases, so that the exposure of the outer peripheral portion 14b at the joint C1 can be minimized, and a further electrolytic corrosion prevention effect can be obtained.

  Further, since the curled portion 15 formed on the first rear end portion 12b of the first tube 12 by friction welding is folded back on the outer peripheral surface side, the curled portion 15 protects the base portion 11a. The protective layer 13 can be prevented from peeling without interfering with the layer 13.

  Furthermore, the protective layer 13 having an anticorrosive effect such as painting or plating is applied to the stub shaft 11 made of an iron-based metal material having a higher potential than the first tube 12 made of an aluminum-based metal material. Corrosion of the stub shaft 11 alone is prevented.

  In addition, the effect of this embodiment can show | play the same effect not only about the said junction part C1, but each said junction part C2, C3, C4.

  FIG. 9 shows another example in which the first and second yokes 10 and 19 are formed of the same aluminum-based metal material as the first and second tubes 12 and 20.

  That is, since the first and second yokes 10 and 19 and the first and second tubes 12 and 20 are all made of the same aluminum-based metal material, there is almost no potential difference between the members. Since the corrosion resistance of the single body is high, the protective layers 13 and 13 for preventing electrolytic corrosion are formed on the outer surfaces of the first and second yokes 10 and 19 in the same manner as the first and second tubes 12 and 20. Not formed.

  Further, since the curled portions 15 and 15 are formed at the joining end portions of the cylindrical portions 10a and 19a of the first and second yokes 10 and 19 by friction welding, the burrs 16 and 16 are also formed. Not.

  Therefore, according to this embodiment, the first yoke 10 and the first tube 12 and the second yoke 19 and the second tube 20 are almost free from potential difference between the members. The corrosion resistance of the propeller shaft 1 can be further improved, with C2 and C4 being hardly eroded.

  Further, since it is not necessary to form the protective portions 13 and 13 and the burrs 16 and 16 on the first and second yokes 10 and 19, workability is improved and manufacturing cost is reduced. Can be achieved.

  Further, since it is not necessary to form the protective portions 13 and 13 with respect to the first and second yokes 10 and 19, it is possible to contribute to further weight reduction of the entire propeller shaft 1 and further reduce the manufacturing cost. Can be achieved.

  The technical ideas other than the invention described in the claims, as grasped from the embodiment, will be described below.

  (1) A propeller shaft in which a tube made of an aluminum-based metal and a yoke or stub shaft made of an iron-based material are joined by friction welding, and corrosion caused by adhesion of an electrolyte solution to the outer surface of the yoke or the stub shaft. A propeller shaft characterized in that a protective part for preventing is formed and the protective layer is not formed on the outer surface of the tube.

  According to this invention, since the surface area of the outer surface of the yoke or the stub shaft is smaller than the surface area of the outer surface of the tube, the protective layer is formed only on the yoke or the stub shaft, thereby reducing the weight of the propeller shaft. The area for forming the protective layer can be minimized, and the cost can be reduced.

  (2) The cylindrical member joining structure according to claim 1, wherein the outer peripheral edge of the joining end of the aluminum-based metal member has a curled portion.

  According to this invention, since the curled portion and the non-protected portion having an enlarged diameter extending to the outer peripheral edge of the joining end of the iron-based metal member are securely abutted and joined, The exposure of the non-protected portion can be minimized, and a further electric corrosion prevention effect can be obtained.

  (3) The propeller shaft according to (2), wherein the curled portion is formed in a folded shape from the joint end of the aluminum-based metal member to the outer peripheral surface side.

  According to this invention, the curled portion is formed in a folded shape from the joining end of the aluminum-based metal member to the outer peripheral surface side, and the curled portion is formed on the outer peripheral surface of the iron-based metal member. Since the protective layer is not peeled off, the protective layer can be prevented from being peeled off.

  (4) The cylindrical member joining structure according to claim 1, wherein the protective layer is painted.

  According to this invention, corrosion of the iron-based metal member alone can be prevented by coating the outer peripheral surface of the iron-based metal member.

  (5) The cylindrical member joining structure according to claim 1, wherein the protective layer is plated.

  According to this invention, it is possible to prevent corrosion of the iron-based metal member alone by plating the outer peripheral surface of the iron-based metal member.

  The area of the outer surface of the cylindrical member made of the iron-based metal is smaller than the area of the outer surface of the cylindrical member made of the aluminum-based metal. Junction structure.

  According to this invention, since the surface area of the outer surface of the cylindrical member made of the iron-based metal is smaller than the surface area of the outer surface of the cylindrical member made of the aluminum-based metal, only the cylindrical member made of the iron-based metal is used. By forming the protective layer, the area for forming the protective layer can be minimized, and the cost can be reduced.

  The present invention is not limited to the configuration of each of the above embodiments. For example, the materials of the first and second yokes 10 and 19 and the stub shaft 11, the first and second tubes 12 and 20, and the outer race 18, The shape and size can be freely changed according to the specification and size of the automobile.

  In particular, with respect to the iron-based metal material, forged steel material, cast steel material or cast iron material may be used in addition to the carbon steel or alloy for machine structure.

FIG. 6 is a partial cross-sectional view of a joint portion C1 showing an embodiment of the present invention and showing a joint state between the stub shaft and the first tube, and is an enlarged view of a portion C in FIG. It is an enlarged view of the A section of FIG. FIG. 3 is a joint cross-sectional photograph of the joint C1 showing a joint state of the stub shaft and the first tube in the real thing, and is a drawing substitute photograph of FIG. FIG. 4 is an enlarged photograph of a bonding cross section of a portion B in FIG. 3 and a drawing substitute photograph in FIG. 2. It is an expanded sectional view of the D section of FIG. 1 is an overall view of a propeller shaft according to the present invention. It is sectional drawing which shows the first half process of the joining process by the friction welding of the stub shaft and 1st tube which concern on this invention. It is sectional drawing which shows the latter half process of the joining process by the friction welding of the stub shaft and 1st tube which concern on this invention. It is a general view of the propeller shaft which shows the other example of embodiment which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Propeller shaft 10 ... 1st yoke (cylindrical member)
11 ... Stub shaft (cylindrical member)
12 ... 1st tube (cylindrical member)
13 ... Protection part 14 ... Non-protection part 14a ... End face (Non-protection part)
14b ... Outer peripheral part (non-protected part)
15 ... curled part 16 ... burr (expanded part)
16a ... Maximum diameter enlarged portion 17 ... Reduced diameter portion 18 ... Outer race (cylindrical member)
19 ... 2nd yoke (cylindrical member)
20 ... Second tube (cylindrical member)

Claims (3)

A cylindrical member joining structure formed by joining an aluminum metal member and an iron metal member formed in a cylindrical shape by friction welding,
Formed at the joint end of the iron-based metal member, and a non-protection portion whose diameter is expanded outward from the joint end;
A protective layer that is formed over the outer peripheral surface of the iron-based metal member from the maximum diameter-expanded edge of the non-protection part, and protects contact with the electrolyte;
A cylindrical member joining structure characterized by comprising: A cylindrical member joining method comprising joining an aluminum-based metal member and an iron-based metal member formed in a cylindrical shape by friction welding,
Forming a protective layer on the outer surface of the iron-based metal member;
Cutting the end face on the joining end side of the iron-based metal member, scraping off the protective layer, and forming an enlarged diameter portion on the outer peripheral side; and
Friction welding the aluminum metal member and the iron metal member and joining the two members;
A method for joining cylindrical members, comprising: A cylindrical member joining structure formed by joining an aluminum metal member and an iron metal member formed in a cylindrical shape,
Joining of cylindrical members characterized in that a protective layer that protects contact with the electrolyte is formed only on the outer peripheral surface of the iron-based metal member excluding the joint between the aluminum-based metal member and the iron-based metal member. Construction.