JP2008238224A - Friction stir welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform superior butt welding on workpieces to be joined, without causing a misjoined part so-called kissing bond in the weld zone of the workpieces, without causing root crack, with less tendency of fatigue fracture generation, and at a low cost and with excellent productivity. <P>SOLUTION: In friction stir welding, a metallic foil 21 is clamped between the abutting part 33 including its periphery of workpieces 31, 32 and a backing 10, with a solid lubricating layer 22 interposed between the metallic foil 21 and the backing 10. Furthermore, a supporting body 23 is for facilitating support of the solid lubricant layer 22, but is not necessarily required. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a friction stir welding method capable of satisfactorily butting and joining materials to be joined such as an aluminum alloy plate.

  The material to be joined such as an aluminum alloy plate is placed on and fixed to a backing jig such as a steel plate, and the shoulder contacting the surface of the material to be joined from the surface side to the butt part of the material to be joined. Insert a probe (also called a pin) of a rotating tool having a probe protruding at the tip and the tip of the tool, and move the tool relatively along the abutting part while rotating the tool at a high speed. A joining method for joining the butted portions of the materials to be joined by plasticizing the butted portions is called friction stir welding and is widely known (for example, Patent Documents 1 and 2).

  According to this type of friction stir welding, the material to be welded is softened using the frictional heat generated in the material to be welded by a tool, and the softened portion is stirred and mixed in a solid phase to form a stirring region and joined. The Since the agitation region is microcrystallized, there are advantages such as less strength reduction at the joint, less joint defects such as pores and cracks, and a flat surface at the joint, compared to fusion welding such as arc welding. Yes, it has already been put to practical use in the fields of railway vehicles, ships, civil engineering structures, automobiles, etc.

  In such a conventional friction stir welding, the insertion depth of the probe into the material to be joined greatly affects the quality of the joint. The probe is inserted into the butted part of the material to be joined from the front side to the inside. To ensure joining, the stirring region reaches the back side of the material to be joined and has a certain width on both sides of the joint. It is desirable to have

  Since the material to be bonded is stirred not only on the side surface but also on the bottom surface of the probe, it is not necessary for the tip of the probe to reach the back of the material to be bonded, but it is preferable that the tip of the probe reaches as close as possible to the bottom surface of the material to be bonded. . Therefore, it is desirable to stir the materials to be joined using an apparatus with high tool positioning accuracy so that the stirring region is sufficiently formed on the back surface of the butted portion of the materials to be joined.

If a region that is not stirred by the probe or a region that is insufficiently stirred is formed on the back side of the bonded portion of the material to be bonded, an unbonded portion including a butt line called a kissing bond is generated. If such an unjoined portion exists, a crack called a root crack is generated from the unbonded portion, resulting in a decrease in joining strength or a starting point of fatigue failure. In particular, when there is a linear kissing bond, the strength tends to decrease when a stress in a direction orthogonal to the kissing bond is applied.
If the friction stir welding operation is performed not only on the surface side of the material to be joined but also reversed and similarly performed from the back side, no kissing bond occurs, but this method significantly reduces productivity.

  Usually, in friction stir welding, the advance angle of the probe is set to about 1 to 5 °, and the length of the probe is made shorter by about 0.1 to 0.2 mm than the thickness of the material to be joined. The depth of insertion of the probe into the material is set so as not to contact the backing jig as much as possible, and the joining operation is performed.

  However, since the tool is inserted into the material to be joined with an advancing angle, it is inserted diagonally, and the rear half of the tool becomes deep, and in this state, the tool is advanced relative to the material to be frictioned. Although they are agitated and joined, various forces are generated on the tool, and they may vibrate up and down slightly.

When the tool rotates at a high speed and has a high load, the material to be joined that contacts the shoulder portion is softened by frictional heat. Since a high pressing force is applied to the tool, the shoulder portion of the tool may sink into the surface portion of the softened portion of the material to be joined that contacts the shoulder portion of the tool, and as a result, the probe tip may become deeper than the set depth.
The joining line where the material to be joined and the material to be joined is not necessarily a straight line. In general, in the refracted part or the curved part with a short radius of curvature, the forward speed of the tool generally decreases. It may soften and the tool may sink.
In addition to the above, there are various variable factors during machining, and the depth control of the tool during friction stir welding cannot always be performed with high accuracy.

  As a result, even if the probe insertion depth and the probe posture (probe advance angle) are precisely set, the tip of the probe may penetrate the workpiece and contact the surface of the backing jig during the friction stir welding process. . Since the backing material is often made of steel, if you try to advance the probe while the tip of the probe is in contact with the backing jig, the probe may break or the tip may be damaged, or the surface of the backing jig may be damaged. Occurs.

  Although it does not directly address the above problem, attempts have been made to prevent both the adherence of the material to be bonded and the root cracking to the backing material. Patent Document 3 listed below has an affinity for the plasticized material to be bonded. A friction stir welding method using a low backing material (backing jig) has been proposed. Here, as a particularly preferable backing material, carbon-based materials, metal oxides, fireproof heat insulating materials for construction, and roughened metals are mentioned, and graphite having excellent high-temperature stability and good lubricity with a probe. A board or the like is illustrated.

  However, a graphite board is usually formed from graphite powder by sintering and solidification, and it takes much labor to form a graphite board from graphite powder, resulting in high costs.

Furthermore, even if the tip of the probe is made to reach the bottom of the material to be joined as much as possible, the butt line may remain and become a kissing bond.
In the friction stir welding, the shoulder portion of the tool having the probe is pressed with a strong force along the butted portion of the material to be joined. A large load of about ˜5,000 N, sometimes about 10,000 N is applied.
For this reason, it is speculated that even at the time of agitation, the marginal part of the bottom surface of the material to be joined remains without being agitated due to friction with the backing material, and the line formed at the butt portion of the material to be joined on both sides remains as a kissing bond. Is done.
JP-A-11-267858 JP 2005-20596 A JP-A-10-202374

  The present invention has been made in view of the above problems, and the purpose of the present invention is that, even in friction stir welding only from the surface side, no kissing bond occurs in the joint portion of the material to be joined, An object of the present invention is to provide a friction stir welding method that is less likely to cause fatigue failure, and that can satisfactorily butt-join materials to be joined together at low cost and high productivity.

The above object can be achieved by the friction stir welding method of the present invention having the following characteristics.
That is, the invention described in claim 1 is to place and fix the materials to be joined together on the backing jig, and insert a probe into the abutting portion of the material to be joined from the surface side. Friction stir welding to join the butt part of the material to be joined by relatively moving along the butt part while rotating at high speed, and plasticizing the butt part by the frictional heat generated at that time and stirring In the method
A metal foil is sandwiched between a material to be joined including the butted portion and a backing jig, and a solid lubricant is interposed between the metal foil and the backing jig.

  The invention described in claim 2 is characterized in that, in the invention described in claim 1, the support is sandwiched between the backing jig and the solid lubricant.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the solid lubricant is a powder.

  According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the solid lubricant is a molybdenum disulfide powder or a graphite powder.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, characterized in that the metal foil is made of the same or similar material as the material to be joined.

  The invention according to claim 6 is the invention according to any one of claims 2 to 5, wherein the support is made of the same or similar material as the material to be joined.

  The invention according to claim 7 is the invention according to claim 1 or 2, wherein the material to be joined is made of aluminum or an alloy thereof, the metal foil is made of an aluminum foil or an alloy foil thereof, and the solid lubricant is molybdenum disulfide. Or it consists of graphite.

  The invention according to claim 8 is the invention according to claim 2, wherein the material to be joined is made of aluminum or an alloy thereof, the metal foil is made of an aluminum foil or an alloy foil thereof, and the solid lubricant is molybdenum disulfide or graphite. And the support is made of aluminum or an alloy thereof.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partially cutaway perspective view showing an example of the friction stir welding method of the present invention. In FIG. 1, first, a support 23 is arranged at a desired position on the backing jig 10, and then a powder of the solid lubricant 22 is spread on the support 23, and a metal foil 21 is further formed thereon. Deploy.

  In the above example, a sandwich-like three-layer structure of the metal foil 21, the solid lubricant layer 22 and the lower support 23 is used, but the support 23 is omitted and the upper metal foil 21 and the solid lubricant layer 22 are omitted. It is good also as a two-layer structure. In the case of such a two-layer structure, the powder of the solid lubricant 22 is directly dispersed in a desired layer on the backing jig 10 and the metal foil 21 is disposed thereon.

  For forming the sandwich-like three-layer structure or the two-layer structure as described above, the solid lubricant layer 22 is previously formed between the metal foil 21 and the support 23 in addition to the above-described method. A three-layer structure or a structure in which a solid lubricant layer 22 is formed in advance by folding a sheet of metal foil 21 in advance is prepared, and such a structure is placed on the backing jig 10. You may make it arrange | position in a desired site | part.

Since the metal foil 21 is friction stir welded in contact with the back surface of the material to be joined and the thickness of the foil becomes a buffer, the tip of the probe can penetrate the back surface of the material to be joined and reach the thickness of the foil. Formation of the stirring region is formed up to the back surface of the material to be joined.
On the other hand, the support 23 mainly serves to support the solid lubricant layer 22. However, since the metal foil 21 is wound and dispersed in the material to be joined that has been plasticized by the stirring of the probe, there is a possibility that the joining strength may be reduced.

  In order to prevent such a decrease in bonding strength, the metal foil is preferably made of a material to be bonded or a similar material. Usually, aluminum (alloy) foil is used for joining aluminum (alloy), copper (alloy) foil is used for joining copper (alloy), titanium (alloy) foil is used for joining titanium (alloy), and iron (steel). ) Is preferably used as an iron (steel) foil, and stainless steel as a stainless steel foil. Since the joining line due to the joining of the material to be joined and the material to be joined is usually a straight line, it is sufficient that the metal foil 21 and the support 23 exist only in the vicinity of the joining line. .

  The thickness of the metal foil 21 is preferably about 10 to 100 μm in consideration of the thickness of the material to be joined and the length of the probe. The metal foil 21 is sandwiched between the bonded material including the butted portion and the backing jig, that is, between the bonded material and the backing jig across the butted portion of the bonded material and its periphery. Therefore, when considering the shoulder diameter of the tool (usually about 12 to 15 mm) and the probe diameter (usually about 5 to 6 mm), the width is preferably about 15 mm, but more than that The width may be sufficient.

The solid lubricant 22 has a role of reducing friction between the probe tip and the backing material and preventing damage to the probe. The solid lubricant 22 is not particularly limited, but preferably has a structure having a layer that easily breaks in the crystal lattice. Molybdenum disulfide (MoS ₂ ), graphite (graphite), tungsten disulfide, PTFE (polyethylene oxide) Tetrafluoroethylene), boron nitride (BN), etc. can be used. Among these, molybdenum disulfide (MoS ₂ ) or graphite (graphite), which has excellent high-temperature stability and good lubricity (friction properties) with the probe, is preferable.

The shape of the solid lubricant 22 is not limited and may be a plate shape, a tape shape, or a sheet shape, but a powder is preferable from the viewpoint of cost.
The solid lubricant 22 may be engulfed together with the metal foil 21 together with the softened metal foil 21 in the stirring region of the butt portion of the material to be joined. In this case, if the particle size of the solid lubricant 22 is too large, the strength of the bonded portion of the material to be bonded is lowered. Therefore, the average particle size is preferably 30 μm or less. The thickness of the solid lubricant 22 layer is preferably about 0.01 to 0.1 g / cm ² (about ²⁰ to 500 μm) in consideration of the thickness of the material to be joined and the length of the probe. Used for.

In particular, molybdenum disulfide (MoS ₂ ) or graphite (graphite) has a metallic luster and is a steel gray or black crystalline, and both natural products and artificial products can be produced in the form of particles or powders. This is convenient because it is not necessary to form the board into a board.

  The support member 23 is used for successfully placing the solid lubricant powder on the backing jig. Although the shape is not specified, it is desirable that the thickness be uniform, and the joining line by the butt between the joining material and the joining material is usually a straight line. Therefore, it is sufficient that the support exists only in the vicinity of the joining line. Therefore, a ribbon shape and a tape shape are preferable.

  It is preferable that the support 23 has heat resistance because heat is transferred by friction stir welding so that the temperature rises. Further, the support body 23 should not be too soft so that the solid lubricant powder 22 exhibits a good lubricating action, and the support body 23 should be placed so that the tip of the probe that has penetrated the metal foil 21 does not hit the backing jig 10. It is preferable not to penetrate. Therefore, it is preferable that the breaking strength is not small.

  Even when the support 23 is frictionally stirred by the tip of the probe and a part of the support material is caught in the material to be joined, it is desirable that the strength of the joined portion is not impaired.

  Therefore, as the support 23 that satisfies the above-described conditions, the same material as the material to be joined or a material similar to the material to be joined, which is compatible with the material to be joined, is preferable as with the metal foil 21. Aluminum (alloy) foil for joining aluminum (alloy), copper (alloy) foil for joining copper (alloy), titanium (alloy) foil for joining titanium (alloy), iron (steel) An iron (steel) foil is preferable for bonding, and a stainless steel foil is preferable for bonding stainless steel.

  As the backing jig 10, a hard known steel backing jig such as SKD61 or S50C is preferably used, but it is not limited to this. Any tool can be used as long as it has sufficient rigidity to withstand a strong load in the normal direction received from the shoulder portion of the tool and does not buckle.

  Next, a plate-like plate for bonding is provided at the substantially central portion of the above-described sandwiched three-layer configuration of the metal foil 21, the solid lubricant 22 and the support 23 or the two-layer configuration of the metal foil 21 and the solid lubricant 22. The to-be-joined materials 31 and 32 are arrange | positioned so that the abutting part 33 of the to-be-joined materials 31 and 32 may be located, and it fixes using a conventional fixing tool.

  As the materials to be joined 31 and 32, plate-like materials made of aluminum (alloy), magnesium (alloy), copper (alloy), titanium (alloy), steel, stainless steel or the like are used. These materials to be joined 31 and 32 are mostly flat and simple plate-like shapes corresponding to the shape of the backing jig 10, but even if they are plate-like shapes having a simple two-dimensional curved surface. Alternatively, it may be a plate having a three-dimensional curved surface. In particular, in the case of a material to be joined having a three-dimensional curved surface, it is difficult to control the probe insertion depth and the probe posture (probe advance angle), so it is effective for joining such a material to be joined having a three-dimensional curved surface. It is.

  Thereafter, the probe 41 of the tool 40 made of hard tool steel having the rotary tool 40, that is, the shoulder portion 42 having a large diameter and the probe 41 at the tip thereof, is attached to one end of the abutting portion 33 of the plate-shaped materials 31 and 32. The tool 40 is inserted with a strong force and moved to the other end (arrow B direction) along the abutting portion 33 while rotating the tool 40 at a high speed in the arrow A direction, and the abutting portion 33 is softened by the frictional heat generated at that time. By agitating, the abutting portion 33 of the materials to be joined 31 and 32 is plasticized and joined while applying pressure by the shoulder portion 42 of the tool 40.

  The tool 40 has a shoulder portion 42 having a large diameter and a probe 41 at its tip, and is harder than the material of the materials 31 and 32 to be joined, such as SK or SKD tool steel, such as SKD61, or PCBN (polycrystalline cubic boron). Etc. In general, the probe 41 may be threaded or may not be threaded. Moreover, when using the to-be-joined materials 31 and 32 about 3-6 mm in thickness, the diameter of the shoulder part 42 of the said tool 40 is about 12-15 mm, and the diameter of the probe 41 is about 5-6 mm is suitable. Used for.

  The shoulder 42 needs to press the materials 31 and 32 to be joined along the abutting portion 33, and usually has a flat surface in contact with the materials 31 and 32 to be joined or a slightly arc shape with the probe 41 as the center. Alternatively, a conical concavity is used, but depending on the case, it is also possible to use a probe that protrudes in a slightly arc shape or a conical shape with the probe 41 as the center. It is preferable that the tip of the probe 41 is inserted deeply so as not to contact the backing jig 10. The probe advance angle is generally set to about 1 to 5 °. The rotation speed of the tool 40 is generally several hundred to several thousand rotations / minute, and the joining speed is generally several tens to several hundreds mm / minute.

  The tool 40 is used by being attached to a known friction stir welding apparatus composed of three machine axes including a surface plate axis (X), a traverse axis (Y), and a lifting / lowering axis (Z). Further, a known 5-axis frame type comprising a machine plate 3 axis of a surface plate axis (X), a transverse axis (Y), an elevating axis (Z), and a tool axis 2 of a swing axis (A) and a swing axis (B). It is used by attaching to a friction stir welding apparatus. Moreover, although it may be attached and used for the machine head mounted in the front-end | tip of the well-known robot arm provided with three joint axes and two rotating shafts, it is not limited to these.

  Finally, the materials to be joined 31 and 32 joined on the backing jig 10 are taken out. In this case, the excess part of the sandwich-like three-layer structure of the metal foil 21, the solid lubricant 22 and the support 23 or the two-layer structure of the metal foil 21 and the solid lubricant 22 is the back surface of the material to be joined. Some of them may stick to the joints, but this extra part can be easily removed by pulling. In this way, a joined body of the materials to be joined 31 and 32 is obtained. Reference numeral 34 denotes a joining mark formed by the shoulder portion 42, and reference numeral 35 denotes a stirring region of the joining portion by the probe 41.

According to the friction stir welding method of the present invention, since the metal foil is sandwiched between the butted portion and the surrounding material to be joined and the backing jig, the material to be joined so as to straddle the butted portion of the material to be joined. A metal foil is sandwiched between the back and the backing jig, and the metal foil touches the back surface of the material to be joined so that the probe tip does not hit the backing jig. Acts as a buffer.
In addition, the solid lubricant layer serves as a buffer for accuracy control in the thickness direction so that it does not hit the backing jig even if the tip of the probe penetrates from the metal foil.
Therefore, without damaging the tip of the probe that rotates at high speed with the backing jig, the tip of the probe can be inserted into the vicinity of the back surface or the back surface of the material to be joined without any problem. The joint is well plasticized and stirred.

  Moreover, even if the tip of the probe that rotates at high speed and the backing jig come into contact with each other due to the presence of the solid lubricant between the metal foil and the backing jig, Friction between the probe tip and the backing jig is significantly reduced, and damage to the tool and backing jig is prevented. Therefore, it is possible to insert the tip of the probe to the vicinity of the back surface of the material to be joined or to the back surface with a minimum depth.

  Further, the solid lubricant is interposed between the backing jig and the friction is reduced, and the film-like portion on the back surface of the material to be joined is also rotated and mixed.

As described above, according to the friction stir welding method of the present invention, the tip of the probe can be inserted deeply from the vicinity of the back surface of the material to be joined until it reaches the solid lubricant layer, and there is no damage to the tool or the backing material and strong pressing. Even in the processing under force, the film-like portion on the back surface of the material to be joined is also rotated and mixed.
Therefore, the butted portion of the material to be joined is sufficiently agitated even to the back surface of the material to be joined, and as a result, the agitation region is expanded, and even when the friction stir welding is performed only from the front side, the joining of the materials to be joined is performed. Kissing bonds do not occur in the parts, root cracks do not occur, fatigue failure does not easily occur, and the materials to be joined can be satisfactorily butt-joined with good productivity at low cost.

  Specific examples of the present invention will be given below. The present invention is not limited to these examples.

(Spot friction stir welding)
As shown in FIG. 1, an aluminum foil (thickness 15 μm) having a smooth surface is mounted as a support 23 along the length direction of the center portion of the surface of a flat steel (SKD61) backing jig 10. I put it.

Next, a powder 22 of molybdenum disulfide (MoS ₂ ) was sprayed on the aluminum foil 23, and the same aluminum foil 21 as described above was placed thereon.

Next, on the aluminum foil 21, two flat joining surfaces 31 and 32 (thickness 3 mm) made of an aluminum alloy (5083-O) were placed in contact with each other. At this time, the butted portion 33 of the materials to be joined 31 and 32 is positioned at the center of the three-layer structure including the upper aluminum foil 21, molybdenum disulfide (MoS ₂ ) 22, and the lower aluminum foil 23. Placed and fixed.

  After that, the probe 41 of the tool 40 made of tool steel attached to the friction stir welding apparatus consisting of the three axes of the platen axis (X), the transverse axis (Y), and the elevating axis (Z) is rotated at 1000 rpm. While being inserted into one end of the butt portion 33 and moved to the other end along the butt portion 33 of the materials to be joined 31, 32 at a feed rate of 200 mm / min, friction stir welding is performed. A joined body was prepared.

  The tool 40 has a probe 41 with a diameter of 4.0 mm and a length of 2.9 mm, is threaded, a shoulder portion 42 has a diameter of 12 mm, and a material to be joined 31 along the butt portion 33. The shoulder surface for pressing 32 is a flat surface. The load on the tool 40 was about 10,000N.

(Friction stir welding along the butt line)
As shown in FIG. 1, an aluminum foil (thickness 15 μm) having a smooth surface is mounted as a support 23 along the length direction of the center portion of the surface of a flat steel (SKD61) backing jig 10. I put it.

Next, a powder 22 of molybdenum disulfide (MoS ₂ ) was sprayed on the aluminum foil 23, and the same aluminum foil 21 as described above was placed thereon.

Next, on the aluminum foil 21, two flat joining surfaces 31 and 32 (thickness 3 mm) made of an aluminum alloy (5083-O) were placed in contact with each other. At this time, the butted portion 33 of the materials to be joined 31 and 32 is positioned at the center of the three-layer structure including the upper aluminum foil 21, molybdenum disulfide (MoS ₂ ) 22, and the lower aluminum foil 23. Placed and fixed.

  After that, the probe 41 of the tool 40 made of tool steel attached to the friction stir welding apparatus consisting of the three axes of the platen axis (X), the transverse axis (Y), and the elevating axis (Z) is rotated at 1000 rpm. While being inserted into one end of the butt portion 33 and moved to the other end along the butt portion 33 of the materials to be joined 31, 32 at a feed rate of 200 mm / min, friction stir welding is performed. A joined body was prepared.

  The tool 40 has a probe 41 with a diameter of 4.0 mm and a length of 2.9 mm, is threaded, a shoulder portion 42 has a diameter of 12 mm, and a material to be joined 31 along the butt portion 33. The shoulder surface for pressing 32 is a flat surface. The advance angle of the probe 41 was 3 °, and the load on the tool 40 was about 10,000 N.

(Comparative Example 1)
(Spot friction stir welding)
For comparison, in the same manner as in Example 1 except that a three-layer structure composed of aluminum foil 21, molybdenum disulfide (MoS ₂ ) powder 22 and support aluminum foil 23 was not used. Then, friction stir welding was performed.

(Comparative Example 2)
(Friction stir welding along the butt line)
For comparison, in the same manner as in Example 2 except that a three-layer structure composed of aluminum foil 21, molybdenum disulfide (MoS ₂ ) powder 22 and support aluminum foil 23 was not used. Then, friction stir welding was performed.

(result)
The microscope picture which expanded the back surface of the spot friction stir welding part of Example 1 is shown in FIG. Moreover, the microscope picture which expanded the back surface of the spot friction stir welding part of the comparative example 1 is shown in FIG.
As shown by the thick broken lines drawn for easy understanding in FIG. 2 (Example 1), the left and right workpieces are stirred and mixed in a spiral shape at the spot friction stir welded portion.
On the other hand, in FIG. 3 (Comparative Example 1), substantially straight Kissing bonds are observed along the butt lines of the left and right materials to be joined, as shown by the thick broken lines drawn for easy understanding.
Further, in both the drawings of FIG. 2 (Example 1) and FIG. 3 (Comparative Example 1), the surface irregularities of the backing material are transferred, and it can be seen that a strong pressure is applied.

The microscope picture which expanded the back surface of the friction stir welding part along the butt line of Example 2 is shown in FIG. Moreover, the microscope picture which expanded the back surface of the friction stir welding part along the butt line of the comparative example 2 is shown in FIG.
From FIG. 4 (Example 2), it can be seen that friction stirring is performed up to the back surface, and the left and right materials to be joined are friction stir bonded integrally.
On the other hand, in FIG. 5 (Comparative Example 2), as shown by the thick broken line drawn, a substantially linear kissing bond is observed along the butt line of the left and right bonded materials.

The microscope picture which expanded the cross section orthogonal to the butt line of the friction stir welding part along the butt line of Example 2 is shown in FIG. Moreover, the microscope picture which expanded the cross section orthogonal to the butt line of the friction stir welding part along the butt line of the comparative example 2 is shown in FIG.
In FIG. 6 (Example 2), it can be seen that the friction stir zone is sufficiently formed to the back surface as shown by the thick broken line drawn. On the other hand, as shown by the thick broken line drawn in FIG. However, the friction stir zone reaches the back surface of the material to be joined, and it is confirmed that a kissing bond as shown in FIG. 5 (Comparative Example 2) is formed even if the friction stir zone apparently reaches the back surface.

It is a partially cutaway perspective view showing an example of the friction stir processing method of the present invention. It is a microscope picture which shows the state of the back surface of the conjugate | zygote obtained in Example 1 of this invention. It is a microscope picture which shows the state of the back surface of the conjugate | zygote obtained by the comparative example 1 of this invention. It is a microscope picture which shows the state of the back surface of the conjugate | zygote obtained in Example 2 of this invention. It is a microscope picture which shows the state of the back surface of the conjugate | zygote obtained by the comparative example 2 of this invention. It is a microscope picture which shows the state of the cross section of the conjugate | zygote obtained in Example 2 of this invention. It is a microscope picture which shows the state of the cross section of the conjugate | zygote obtained by the comparative example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Backing jig | tool 21 Metal foil 22 Solid lubricant 23 Support body 31 To-be-joined material 32 To-be-joined material 33 Butted part of to-be-joined material 34 Joining mark of to-be-joined material 35 Joined part of to-be-joined material 40 Tool 41 Tool probe 42 Tool shoulder

Claims (8)

The materials to be joined are abutted and fixed on the backing jig, and a probe is inserted into the abutting portion of the materials to be joined from the surface side, and the probe is rotated at a high speed along the abutting portion. In the friction stir welding method for joining the butt portion of the material to be joined, by relatively moving, plasticizing the butt portion by the frictional heat generated at that time and stirring.
Friction characterized in that a metal foil is sandwiched between a material to be joined including the butted portion and a backing jig, and a solid lubricant is interposed between the metal foil and the backing jig. Stir welding method.   2. The friction stir welding method according to claim 1, wherein a support is sandwiched between the backing jig and the solid lubricant.   The friction stir welding method according to claim 1 or 2, wherein the solid lubricant is powder.   The friction stir welding method according to claim 1 or 2, wherein the solid lubricant is a powder of molybdenum disulfide or a powder of graphite.   The friction stir welding method according to any one of claims 1 to 4, wherein the metal foil is made of the same or similar material as the material to be joined.   6. The friction stir welding method according to claim 2, wherein the support is made of the same or similar material as the material to be joined.   The friction stir welding method according to claim 1, wherein the material to be joined is made of aluminum or an alloy thereof, the metal foil is made of an aluminum foil or an alloy foil thereof, and the solid lubricant is made of molybdenum disulfide or graphite. The material to be joined is made of aluminum or an alloy thereof, the metal foil is made of an aluminum foil or an alloy foil thereof, the solid lubricant is made of molybdenum disulfide or graphite, and the support is made of aluminum or an alloy thereof. Item 3. The friction stir welding method according to Item 2.