JP5074985B2 - Backing member for friction stir welding and friction stir welding method - Google Patents

Description

  The present invention relates to a backing member for friction stir welding and a friction stir welding method using the same.

  Friction stir welding (FSW: Friction Stir Welding) is known as a method for joining metal materials (see, for example, Patent Document 1). In the friction stir welding, the metal materials to be joined are opposed to each other at the joint. And the probe provided in the front-end | tip of a rotary tool is pushed in into a junction part, is rotated, and two metal materials are joined by plastic flow by friction heat.

In such friction stir welding, if there is insufficient heat input due to frictional heat at the insertion side and back side of the rotary tool, the plastic flow may not be sufficient and the joining strength of the metal material may be insufficient. Conceivable. Therefore, in the friction stir welding method described in Patent Document 2, a backing member made of ceramic or the like having low thermal conductivity is disposed on the back side of the joint.
JP 2004-66276 A JP 2001-528990 A

  By the way, in the friction stir welding, the pressing force from the rotary tool acts strongly on the metal material and the backing member. Therefore, during friction stir welding, the backing member may be plastically deformed on the back side of the metal material. When plastic deformation occurs in the backing member, the pressure applied to the back side of the metal material is reduced by the amount of increase in the surface area of the portion, and the amount of heat input to the joint portion is likely to be impaired. As a result, the plastic flow at the joint becomes insufficient, and there is a possibility that a kissing bond is generated on the back surface of the joint. Further, when the backing member is deformed, the load on the driving device and the feeding device of the rotary tool fluctuates, and there may be a problem that the strength of the joining portion along the joining line tends to be uneven.

  The present invention has been made in order to solve the above problems, and can provide a backing member for a friction stir welding method that can prevent the occurrence of kissing bonds and can uniform the strength of the joints along the joint line, and An object of the present invention is to provide a friction stir welding method using the same.

  In order to solve the above-described problems, the friction stir welding backing member according to the present invention is pressed by pushing a rotating tool into a contact portion between metal materials and moving the rotating tool along a joining line while rotating the rotating tool. It is a backing member for friction stir welding that forms a joint at the contact portion, and is characterized in that a hardened portion that suppresses plastic deformation due to the pressing force from the rotary tool is provided along the joint line.

  In this backing member, the plastic deformation due to the pressing force from the rotary tool is suppressed during the friction stir welding by the hardened portion provided along the joining line. Thereby, the increase in the surface area of the backing member can be avoided and the pressure applied to the back side of the metal material can be ensured, so that the amount of heat input to the joint portion is sufficient. As a result, the plastic flow at the joint is sufficiently achieved, and the occurrence of kissing bonds on the back surface of the joint can be suppressed. Further, by suppressing the deformation of the backing member, fluctuations in the load on the driving device and the feeding device of the rotary tool can be suppressed, and the strength of the joint along the joining line can be made uniform.

  Moreover, it is preferable that the hardening part is arrange | positioned corresponding to the intermediate part between a joining start position and a joining end position. The joining start position and the joining end position are portions where the rotary tool is inserted into and retracted from the metal material. By arranging the hardened portion while avoiding these positions, the rotating tool can be prevented from coming into contact with the hardened portion, and the rotating tool can be protected.

  Moreover, it is preferable that a hardening part is detachable with respect to the main-body part of a backing member. In this case, the hardened portion can be easily replaced according to the shape and dimensions of the metal material.

  Moreover, it is preferable that the receiving part is provided in the part corresponding to a joining start position, and the part corresponding to a joining end position, respectively, and a receiving part is detachable with respect to the main-body part of a backing member. In this way, when the receiving part is deformed or scratched by insertion / retraction of the rotary tool, it can be easily replaced.

  Further, the friction stir welding method according to the present invention is a friction that forms a joint at the abutting portion by pushing the rotating tool into the abutting portion between the metal materials and moving the rotating tool along the joining line while rotating the rotating tool. A stir welding method, comprising a step of preparing a backing member provided with a curing portion that suppresses plastic deformation due to a pressing force from a rotating tool along a joining line, and placing a metal material on the backing member and curing And a step of bringing the metal materials into contact with each other.

  In this friction stir welding method, plastic deformation of the backing member due to the pressing force from the rotary tool is suppressed by the hardened portion provided along the joining line. Thereby, the increase in the surface area of the backing member can be avoided and the pressure applied to the back side of the metal material can be ensured, so that the amount of heat input to the joint portion is sufficient. As a result, the plastic flow at the joint is sufficiently achieved, and the occurrence of kissing bonds on the back surface of the joint can be suppressed. Further, by suppressing the deformation of the backing member, fluctuations in the load on the driving device and the feeding device of the rotary tool can be suppressed, and the strength of the joint along the joining line can be made uniform.

  According to the present invention, the occurrence of kissing bonds can be prevented, and the strength of the joint along the joint line can be made uniform.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a backing member for friction stir welding according to the present invention and a preferred embodiment of friction stir welding using the same will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view showing an embodiment of a backing member for friction stir welding according to the present invention. The backing member 1 is a member that is used as an underlay for the contact portion when, for example, the contact portion between the end surfaces of two plate-like metal materials is joined by friction stir welding.

  As shown in FIG. 1, the backing member 1 includes a substantially rectangular parallelepiped main body 2 formed of a metal material such as tool steel. The length of the main body 2 in the longitudinal direction is set according to the length of the metal material.

  A plurality of tongue pieces 3 projecting sideways are provided on both sides of the main body 2. A total of six tongue pieces 3 are provided at both ends and the center in the longitudinal direction at the lower ends of both sides. Each tongue piece 3 is formed with a bolt hole 3a for screwing a bolt 6 (see FIG. 2). Note that a heat storage material or the like may be embedded in the main body 2.

  The upper surface of the main body 2 is a mounting surface 4 on which a metal material is mounted. A band-shaped recess 5 is formed in the substantially central portion of the mounting surface 4 along the longitudinal direction of the main body 2. The recess 5 has a length equivalent to the length of the joint formed on the metal material.

  The mounting surface 4 is provided with a pair of receiving portions 11 and 11 and a curing portion 12. The receiving portions 11 and 11 are made of, for example, a metal material equivalent to that of the main body portion 2 and have a substantially square plate shape. The receiving portions 11 and 11 are respectively fitted to both ends in the longitudinal direction of the concave portion 5 so as to correspond to the joining start position and the joining end position of the friction stir welding, and are detachably attached to the main body portion 2 using a countersunk screw or the like. It is fixed.

On the other hand, the hardened portion 12 is formed by applying a surface nitriding treatment to a metal material such as SKD61 material, and has a substantially rectangular plate shape. The hardness of the hardened portion 12 is HV990 or higher, and the Young's modulus is about 2.06 × 10 ⁵ N / mm ² . Moreover, the tensile strength of the hardening part 12 is 1550 N / mm ² or more.

  The hardening portion 12 is fitted into the intermediate portion of the recess 5 so as to correspond to the intermediate portion between the joining start position and the joining end position of the friction stir welding, and using a countersunk screw or the like in the same manner as the receiving portions 11 and 11. The main body 2 is detachably fixed. The hardening part 12 and the receiving parts 11 and 11 are continuous without a gap in the recess 5, and their upper surfaces are flush with the upper surface of the main body part 4.

  Then, the friction stir welding method of the metal material using the backing member 1 which has the structure mentioned above is demonstrated.

  FIG. 2 is a perspective view for explaining a process of the friction stir welding method using the backing member 1 shown in FIG. As shown in the figure, when this friction stir welding method is performed, first, bolts are respectively screwed into the bolt holes 3a of the tongue pieces 3 provided in the main body 2 so that the mounting surface 4 becomes the upper surface. Then, the backing member 1 is firmly fixed to the upper surface of the surface plate 21.

  After the backing member 1 is fixed to the surface plate 21, two metal materials 22 and 22 to be joined are prepared. The metal materials 22 and 22 are outer plates used for, for example, a railway vehicle structure, and are made of, for example, stainless steel. The thickness of the metal materials 22 and 22 is, for example, about 1.5 mm. Then, the metal materials 22, 22 are placed on the placement surface 4 of the backing member 1, and the end surfaces of the metal materials 22, 22 are butted together at a position directly above the recess 5. A joining line R is set along the abutting portion P between the end faces.

  After the end surfaces of the metal materials 22 and 22 are butted together, the rotary tool 23 is disposed above the metal materials 22 and 22, and the probe 24 attached to the tip of the rotary tool 23 is connected to one end of the butting portion P (joining start position X1). ). Then, the rotary tool 23 is moved along the joining line R to the other end (joining end position X2) of the butting portion P while rotating.

  As a result, the frictional heat generated between the probe 24 and the metal materials 22 and 22 enters the abutting portion P, and as shown in FIG. 3, the joint portion 26 is formed in the abutting portion P by plastic flow due to the frictional heat. The The rotational speed of the rotary tool 23 is, for example, 600 rpm, and the moving speed of the rotary tool 23 is, for example, 600 mm / min.

  The effect of the backing member 1 in such friction stir welding will be described.

  In the friction stir welding, the pressing force from the rotary tool 23 acts strongly on the metal materials 22 and 22 and the backing member 1. Therefore, as in the conventional case, in the backing member 31 not provided with the hardened portion 12, the placement surface 32 may be plastically deformed into a concave shape on the back side of the metal material 22, as shown in FIG.

  When such plastic deformation occurs, the pressure applied to the back side of the metal materials 22 and 22 is reduced by the increase in the surface area of the mounting surface 32, and the amount of heat input to the joint portion 35 is likely to be impaired. As a result, the plastic flow at the joint portion 26 becomes insufficient, and there is a possibility that a kissing bond is generated on the back surface of the joint portion 35. In addition, when the backing member 31 is deformed, a load on the driving device and the feeding device of the rotary tool 23 is fluctuated, and there is a problem that the strength of the joining portion 35 along the joining line R tends to be uneven.

  On the other hand, the backing member 1 is provided with a hardening portion 12 that suppresses plastic deformation due to the pressing force from the rotary tool 23 along the joining line R. In the backing member 1, as shown in FIG. 5, even if the pressing force from the rotary tool 23 acts on the metal members 22 and 22 and the backing member 1, the plastic deformation of the mounting surface 4 is suppressed.

  For this reason, the increase in the surface area of the mounting surface 4 can be avoided, and the pressure applied to the back side of the metal materials 22 and 22 can be secured, so that the amount of heat input to the joint portion 26 is sufficient. As a result, the plastic flow at the joint portion 26 is sufficiently performed, and the occurrence of kissing bonds on the back surface of the joint portion 26 can be suppressed. Further, by suppressing the deformation of the backing member 1, fluctuations in the load on the driving device and the feeding device of the rotary tool 23 can be suppressed, and the strength of the joint portion 26 along the joint line R can be made uniform.

  Moreover, in the backing member 1, the hardening part 12 is arrange | positioned corresponding to the intermediate part between the joining start position X1 and the joining end position X2, and it corresponds to the part corresponding to the joining start position X1, and the joining end position X2. The receiving portions 11 and 11 are respectively arranged in the portions. The joining start position X <b> 1 and the joining end position X <b> 2 are portions where the rotary tool 23 is inserted and retracted with respect to the abutting portion P of the metal materials 22 and 22. By disposing the curing portion 12 while avoiding these positions, the rotating tool 23 can be prevented from coming into contact with the curing portion 12, and the rotating tool can be protected.

  Furthermore, the hardening part 12 and the receiving parts 11 and 11 are detachably fixed to the main body part 2 by flat screws or the like. Thereby, the hardening part 12 and the receiving parts 11 and 11 can be easily replaced now according to the shape and dimension of a metal material. Further, when the receiving parts 11 and 11 are deformed or scratched by the insertion / retraction of the rotary tool 23, the receiving parts 11 and 11 can be easily replaced.

  Next, an evaluation test for the backing member will be described.

  In this evaluation test, the bonding strength of the metal material formed by friction stir welding is compared between the case where the hardened portion is provided on the mounting surface of the backing member and the case where the hardened portion is not provided. In this evaluation test, a total of three samples of backing member A (Comparative Example 1) and backing member B (Comparative Example 2) that are not provided with a cured portion and backing member C (Example) that is provided with a cured portion. Prepared. And the metal material was mounted in the mounting surface of each backing member, and the friction stir welding by a rotating tool was performed.

  The moving speed (joining speed) of the rotary tool was set to two patterns of 300 mm / min and 600 mm / min. The pressure applied to the metal material by the rotary tool was 12 kN.

FIG. 6 is a diagram showing the mechanical characteristics of each sample. As shown in the drawing, backing member A according to Comparative Example 1 is formed, for example by S45C hardened material, surface hardness HV420, tensile strength 830N / mm ^2, yield point 490 N / mm ^2, Young's modulus 2.06 × 10 ⁵ N / mm ² Backing member B of Comparative Example 2 is formed, for example by SCM435 quenched material, surface hardness HV530, tensile strength 980 N / mm ^2, yield point 800 N / mm ^2, the Young's modulus 2.06 × ¹⁰ 5 N / mm ² It has become.

Moreover, backing member C according to the embodiment is formed by treating the surface nitriding the SKD61 material, surface hardness HV990, tensile strength 1550N / mm ^2, yield point 1300 N / mm ^2, the Young's modulus 2.06 × 10 ⁵ N / mm ² .

  FIG. 7 is a diagram illustrating a measurement result of the deformation amount of the placement surface of each backing member after the end of the friction stir welding. Here, the width and depth of a recess (see FIG. 4) generated on the mounting surface after the friction stir welding was measured. As shown in FIG. 7, in the backing member A according to Comparative Example 1, the recess width was 3.0 mm and the recess depth was 0.3 mm. Further, in the backing member B according to Comparative Example 2, the recess width was 2.0 mm and the recess depth was 0.1 mm. On the other hand, in the backing member C, the mounting surface was not deformed. The recess width and recess depth did not differ between when the joining speed was 300 mm / min and when 600 mm / min.

According to this result, in the backing member A, the surface area of the recess is estimated to be about 20 mm ² . Moreover, the pressurization area to the metal material by the rotary tool and the recess is estimated to be about 105 mm ² . Therefore, the applied pressure per unit area applied to the butted portion of the metal material is about 112 N / mm ² . Similarly, in the backing member B, the pressing force per unit area applied to the butt portion of the metal material is about 122.4 N / mm ² , and in the backing member C, it is about 128.1 N / mm ² .

  Therefore, it can be seen that when the backing member A is used, the pressing force per unit area applied to the butt portion of the metal material is reduced to about 88% as compared with the case where the backing member C is used. Further, it can be seen that when the backing member B is used, the pressing force per unit area applied to the butt portion of the metal material is reduced to about 95% compared to the case where the backing member C is used.

FIG. 8 is a diagram showing a tensile test result of metal materials joined using each backing member. As shown in the figure, in the friction stir welding using the backing member A according to Comparative Example 1, the tensile strength of the metal material is about 700 N / mm ² when the joining speed is 300 mm / min, and the joining speed is 600 mm. In the case of / min, it was about 600 N / mm ² . In the friction stir welding using the backing member B according to Comparative Example 2, the tensile strength of the metal material is about 760 N / mm ² when the joining speed is 300 mm / min, and when the joining speed is 600 mm / min. It was about 600 N / mm ² . Occurrence of kissing bonds was confirmed on the back side of the joints of these metal materials.

On the other hand, in the friction stir welding using the backing member C according to the example, the tensile strength of the metal material is about 800 N / mm ² when the joining speed is 300 mm / min, and about when the joining speed is 600 mm / min. It was 780 N / mm ² . No occurrence of kissing bond was observed on the back side of the joint portion of the metal material. The tensile strength of the metal material (base material) is about 760 N / mm ² , and in the friction stir welding using the backing member C according to the example, the tensile strength of the metal material (base material) is equal to or higher than that. Tensile strength was obtained.

  From the above results, as in the backing member according to the present invention, it is possible to secure the bonding strength of the metal material by providing the mounting portion along the bonding line with a hardened portion that suppresses plastic deformation due to the pressing force from the rotary tool. It was confirmed that it contributed to

It is a perspective view showing one embodiment of a backing member for friction stir welding concerning the present invention. It is a perspective view explaining the process of the friction stir welding method using the backing member shown in FIG. FIG. 3 is a perspective view illustrating a subsequent process of FIG. 2. It is a figure which shows the mode of the friction stir welding performed using the backing member which does not provide the hardening part. It is a figure which shows the mode of the friction stir welding performed using the backing member which provided the hardening part. It is a figure which shows the mechanical characteristic of the sample of the backing member used for the evaluation test. It is a figure which shows the measurement result of the deformation amount of the mounting surface of each backing member after completion | finish of friction stir welding. It is a figure which shows the tension test result of the metal material joined using each backing member.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Backing member, 11 ... Receiving part, 12 ... Hardening part, 22 ... Metal material, 23 ... Rotary tool, 26 ... Joining part, P ... Butting part (contact part), R ... Joining line, X1 ... Joining start Position, X2 ... Join end position.

Claims (2)

A backing member for friction stir welding, in which a rotating tool is pushed into a contact part between metal materials and moved along a joining line while rotating the rotating tool, thereby forming a joint part in the contact part. ,
A hardened portion that suppresses plastic deformation due to the pressing force from the rotating tool along the joining line is provided ,
The hardened portion is arranged corresponding to an intermediate portion between the joining start position and the joining end position,
A receiving portion is provided in each of the portion corresponding to the joining start position and the portion corresponding to the joining end position,
The backing member for friction stir welding , wherein the receiving portion is detachable from the main body of the backing member. The backing member for friction stir welding according to claim 1, wherein the hardened portion is detachable from the main body of the backing member.

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