JP2023068730A - Tool for friction stir welding and friction stir spot welding method - Google Patents

Abstract

To provide a tool for friction stir welding which can be suitably used for spot welding of dissimilar materials of resin and metal by friction stir spot welding, can form uniform temperature distribution at a welded interface, and can obtain a good junction with a low load, and further, to provide a friction stir welding method for resin and metal that uses the tool for friction stir welding.SOLUTION: A tool for friction stir welding has a stem having a substantially columnar shape, and a friction stir face comprising an end face of the stem, and has a disk-like recess at a center of the friction stir face. The tool for friction stir welding has an annular recess in the friction stir face, the annular recess is formed outside the disk-like recess with the disk-like recess as a center, and preferably, the tool has an annular protrusion, of which a height is same as the end face, between the disk-like recess and the annular recess.SELECTED DRAWING: Figure 2

Description

There is an application for exception to loss of novelty

The present invention relates to a friction stir welding tool and a friction stir spot welding method using the tool, and more specifically, a friction stir welding tool that can be suitably used for spot welding of dissimilar materials of resin and metal, and the tool. It relates to a method of friction stir spot welding of resin and metal used.

From the viewpoint of improving fuel efficiency and reducing environmental load, there is a strong desire to reduce the weight of various transportation equipment, and the use of resin materials such as carbon fiber reinforced plastics (CFRP) for aircraft and automobiles is being actively studied.

Against this background, it is essential to establish techniques for bonding various metal materials and resin materials, and techniques for bonding metal materials such as steel and aluminum alloys and resin materials are being developed.

Here, in the case of mechanical fastening using a bolt or the like, in addition to the need to process the material to be joined, an increase in weight due to the fastening member cannot be avoided. In addition, when bonding using an adhesive, sufficient bonding strength and reliability cannot be imparted to the bonded portion.

On the other hand, for example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2012-170975), a metal member and a resin member that can be directly joined without interposing a resin layer between them. and a joining joint between a metal member and a resin member. It is applied to the metal member by pressing it against the surface of the metal member so that the inclination angle θ of the axis of the rotating tool with respect to the normal to the surface of the metal member satisfies the condition of 0° < θ ≤ 5°. A method for joining a metal member and a resin member has been proposed, characterized in that the metal member and the resin member are joined by the frictional energy generated.

In the method for joining a metal member and a resin member described in Patent Document 1, the metal member and the resin member are brought into contact with each other without a resin layer interposed therebetween. Bonding can be easily performed, and the types of resin members that can be bonded to metal members increase. Furthermore, it is described that the metal member and the resin member can be joined at any position.

In addition, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2017-13084), it is proposed to provide a method for joining a metal member and a resin member that can achieve joining of the resin member and the metal member with sufficient strength. The purpose is to superimpose a metal member and a resin member, press the metal member while rotating a rotating tool to generate frictional heat, soften and melt the resin member by the frictional heat, and then solidify and join. A method for joining a metal member and a resin member by a friction stir welding method that performs A method for joining a metal member and a resin member is proposed.

In the method for joining the metal member and the resin member described in Patent Document 2, the interaction between the resin member and the hydroxide film of the metal member is further enhanced during joining, and the bonding strength is further improved. It is said that

JP 2012-170975 A JP 2017-13084 A

In the above Patent Documents 1 and 2, a metal material and a resin material can be directly joined using the friction stir phenomenon, but the friction stir welding tool used has a projection (probe) at the center of the bottom surface of the cylindrical base. It is a general friction stir welding tool that has a , and the shape of the tool has not been studied for the purpose of obtaining a good weld or optimizing the welding process.

Here, when directly joining metal and resin using friction stir welding, the strength and reliability of the joint obtained depends on the value of the temperature (joining temperature) at the interface to be joined during joining and the uniformity of the temperature distribution. , and the bonding pressure applied to the bonded interface.

In particular, in point welding where the tool is not moved laterally, temperature distribution tends to be formed due to the difference in peripheral speed and heat extraction conditions between the outer and inner circumferences of the tool, and it is extremely difficult to equalize the temperature at the interface to be welded. Have difficulty. In addition, when the load applied to the friction stir welding tool is increased in order to realize the welding state, the welding apparatus becomes large and expensive, making it difficult to use it industrially.

In view of the problems in the prior art as described above, an object of the present invention is to provide a friction stir welding tool that can be suitably used for spot welding of dissimilar materials between resin and metal by friction stir spot welding. To provide a friction stir welding tool capable of forming a uniform temperature distribution and obtaining a good joint with a low load. Another object of the present invention is to provide a method for friction stir spot welding of resin and metal using the friction stir welding tool of the present invention.

In order to achieve the above object, the present inventors have extensively studied the shape of the friction stir surface (tool end surface) of the friction stir welding tool, etc. As a result, a general friction stir welding tool has at the center of the tool end surface The inventors have found that it is extremely effective to provide a concave portion in the center of the tool end face, instead of providing a convex probe, and have arrived at the present invention.

That is, the present invention
a substantially cylindrical base;
a friction stir surface consisting of an end surface of the base,
Having a disk-shaped recess in the center of the friction stir surface;
A friction stir welding tool characterized by:

When the present inventor used a simple cylindrical tool having a flat friction stir surface without a probe and press-fitted the metal plate and the resin plate on top of each other from the resin plate side while rotating the tool, the object to be welded It was found that the temperature of the interface is high at the center of the bottom of the tool and low at the periphery. In contrast, the friction stir welding tool of the present invention has a disk-shaped recess in the center of the friction stir surface, and the temperature at the interface to be welded can be uniformed by reducing the amount of frictional heat generated in the disk-shaped recess. can be done. In addition, the disk-shaped recess can reduce the pressing load applied to the tool.

In the friction stir welding tool of the present invention, the friction stir surface has an annular recess, and the annular recess is formed outside the disk-shaped recess around the disk-shaped recess. It is preferable that between the annular concave portions there is provided an annular convex portion having the same height as the end surface.

By having the annular recess on the outside of the disk-shaped recess, the temperature distribution of the interface to be joined during welding can be made more uniform, and the indentation load (bonding load) applied to the tool by the annular recess can be made more uniform. can be reduced. In addition, since the protrusions on the tool end face are at the same height, it is possible to suppress an increase in the torque applied to the tool during welding, and to form a smooth material flow.

Further, in the friction stir welding tool of the present invention, it has two or more of the annular recesses having different inner and outer diameters, the annular recesses are formed around the disk-shaped recesses, and the annular recesses are formed with each other. It is preferable to have an annular convex portion having the same height as the end surface between them.

By having a plurality of annular recesses, the temperature distribution of the interface to be joined during welding can be made more uniform, and the pressing load applied to the tool can be further reduced by the plurality of annular recesses. .

Further, in the friction stir welding tool of the present invention, it is preferable that the depth of the disk-shaped concave portion and the annular concave portion is 0.1 to 0.3 mm. By setting the depth of the recess to 0.1 mm or more, it is possible to reliably obtain a uniform temperature of the interface to be bonded and a decrease in the bonding load due to the shape of the recess. Further, by setting the depth of the recess to 0.3 mm or less, it is possible to suppress disturbance of material flow, increase in process torque, and the like caused by material entering the recess.

Further, in the friction stir welding tool of the present invention, it is preferable that the diameter of the disk-shaped concave portion is 3 to 9 mm. By setting the diameter of the disk-shaped recessed portion to 3 mm or more, it is possible to reliably obtain a uniform temperature of the interface to be joined and a decrease in the bonding load due to the shape of the recessed portion. Further, by setting the diameter of the disk-shaped recessed portion to 9 mm or less, it is possible to suppress disturbance of material flow and increase in process torque caused by material entering the recessed portion.

Further, in the friction stir welding tool of the present invention, it is preferable that the width of the annular concave portion is 1 to 1.5 mm. By setting the width of the annular concave portion to 1 mm or more, it is possible to reliably obtain a uniform temperature of the interface to be joined and a decrease in the bonding load due to the shape of the concave portion. Further, by setting the width of the annular recess to 1.5 mm or less, it is possible to suppress disturbance of material flow, increase in process torque, and the like caused by material entering the recess.

Further, in the friction stir welding tool of the present invention, it is preferable that the width of the annular convex portion is 1 to 1.5 mm. By setting the width of the annular protrusion to 1 mm or more, it is possible to efficiently obtain frictional heat generation necessary for joining. Further, by setting the width of the annular convex portion to 1.5 mm or less, it is possible to suppress non-uniform bonding temperature at the interface to be bonded due to excessive frictional heat generation, an increase in bonding load, and the like.

Furthermore, in the friction stir welding tool of the present invention, it is preferable that the base has a diameter of 10 to 30 mm. By setting the diameter of the base to 10 mm or more, it is possible to efficiently obtain the frictional heat required for bonding, and to obtain a sufficiently large bonding area capable of developing the bonding strength required for practical use. On the other hand, by setting the diameter of the base portion to 30 mm or less, it is possible to suppress non-uniform bonding temperature due to a difference in peripheral speed, etc., and to suppress an increase in bonding load.

Although the friction stir welding tool of the present invention can be suitably used as a friction stir spot welding tool, it is not limited to this and may be used for line welding.

In addition, the present invention
a first step of overlapping a metal plate and a thermoplastic resin plate to form a bonded interface;
a second step of press-fitting a friction stir welding tool rotated from the surface of the metal plate to form a weld interface,
Using the friction stir welding tool according to any one of claims 1 to 9 for the friction stir welding tool,
Also provided is a friction stir spot welding method characterized by:

In the friction stir spot welding method of the present invention, since the friction stir welding tool of the present invention is used, the temperature of the interface to be welded during welding can be made uniform, and the metal plate and the thermoplastic material can be bonded at a low welding load. A good point joint can be formed in the overlapping region of the resin plates. Here, the friction stir welding tool press-fitted from the surface of the metal plate is preferably pulled out upward as it is after a good weld interface is formed, but it may be moved laterally as necessary.

In the friction stir spot welding method of the present invention, it is preferable that in the second step, the indentation load applied to the friction stir welding tool is 500 kgf or less. A general-purpose bonding robot can be used by setting the indentation load to 500 kgf or less.

Moreover, in the friction stir spot welding method of the present invention, in the second step, it is preferable that the highest temperature reached at the joint interface is lower than the complete thermal decomposition temperature of the thermoplastic resin plate. The complete thermal decomposition temperature is the temperature at which the thermal decomposition of the thermoplastic resin, which is the base material of the thermoplastic resin plate, starts to progress completely. For example, when the thermoplastic resin plate is polyamide 6, the complete thermal decomposition temperature is 500°C. By setting the maximum temperature of the joint interface to be less than the complete thermal decomposition temperature, it is possible to suppress a decrease in the strength of general thermoplastic resins.

Furthermore, in the friction stir spot welding method of the present invention, it is preferable that the thermoplastic resin plate is made of carbon fiber reinforced plastic (CFRP). In the friction stir spot welding method of the present invention, the temperature of the interface to be welded during welding can be controlled accurately and uniformly. ), a good joint can be obtained.

According to the present invention, there is provided a friction stir welding tool that can be suitably used for spot welding of dissimilar materials of resin and metal by friction stir spot welding, and is capable of forming a uniform temperature distribution at the interface to be welded and applying a low load. It is possible to provide a friction stir welding tool capable of obtaining a good joint. According to the present invention, it is also possible to provide a method for friction stir spot welding of resin and metal using the friction stir welding tool of the present invention.

1 is an external view showing one mode of a friction stir welding tool of the present invention; FIG. FIG. 4 is an external view showing another aspect of the friction stir welding tool of the present invention; 1 is an external view of a generally used friction stir welding tool; FIG. 1 is an external view of a friction stir tool commonly used in a friction stir process; FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows one aspect|mode of the friction stir spot welding method of this invention. FIG. 2 is a schematic diagram showing the arrangement of members to be joined in Example 1; 1 is an external photograph of a friction stir welding tool used in Example 1. FIG. FIG. 2 is a bottom view and a side view of the friction stir welding tool used in Example 1. FIG. 1 is an appearance photograph of a joint obtained in Example 1. FIG. It is a schematic diagram of a tensile test. 4 is an appearance photograph of a joint after a tensile test. It is a simulation result in Example 1. FIG. 4 is an appearance photograph of a friction stir welding tool used in Example 2. FIG. FIG. 4 is a bottom view and a side view of a friction stir welding tool used in Example 2; It is a simulation result in Example 2. 4 is an appearance photograph of a friction stir welding tool used in a comparative example. It is a simulation result in a comparative example.

Hereinafter, representative embodiments of the friction stir welding tool and the friction stir spot welding method of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description may be omitted. Also, since the drawings are for the purpose of conceptually explaining the present invention, the dimensions and ratios of the depicted components may differ from the actual ones.

(1) Friction Stir Welding Tool External views of the friction stir welding tool of the present invention are shown in FIGS. 1 and 2. FIG. Further, FIG. 3 shows an external view of a generally used friction stir welding tool, and FIG. 4 shows an external view of a friction stir welding tool that is widely used in the friction stir process. In addition, in FIGS. 1 to 4, the end surface of the tool base serving as the friction stir surface is the lower side.

A generally used general-purpose friction stir welding tool 2 has a convex probe portion 8 at the center of the end surface (friction stir surface 6 ) of the base portion 4 . The length of the probe portion 8 varies depending on the plate thickness of the material to be joined and the joining mode (butt joint, lap joint, etc.), but is often the same length as the plate thickness or a slightly shorter length.

For example, when butt welding is performed using the general-purpose friction stir welding tool 2, the butt interface is friction-stirred from the surface side to the back side of the material to be welded by the probe part 8, thereby forming a good stir zone with no defects. can do.

On the other hand, if the probe portion 8 is long, the general-purpose friction stir welding tool 2 is likely to be damaged. Therefore, when performing a friction stir process for the purpose of surface modification, the probe portion 8 is not provided as shown in FIG. A friction stir process tool 10 having a flat friction stir surface 6 is used.

In contrast to these, the friction stir welding tool 12 of the present invention is most characterized by having a disk-shaped concave portion 14 in the center of the friction stir surface 6 . Frictional heat generation at the center of the friction stir surface 6 is suppressed by the disk-shaped recess 14 , and temperature rise at the interface to be welded corresponding to the disk-shaped recess 14 can be suppressed. As a result, the temperature distribution at the bonding interface during bonding is made uniform, and a good bonded portion can be obtained. The peripheral speed of the friction stir surface 6 is faster in the outer peripheral portion, and the amount of frictional heat generation is greater. Although it is not necessarily clear, it is thought that this is the result of the dynamic balance between frictional heat generation and heat removal due to heat conduction and material flow.

The disk-shaped recess 14 does not have to be strictly disk-shaped, and may be, for example, spherical crown-shaped or truncated cone-shaped.

Here, as a result of intensive study of the welding temperature distribution using nonlinear finite element analysis software (Ls-Dyna) incorporating a thermomechanical model, the inventors of the present invention found that the friction stir surface in a flat state in which the probe portion 8 is not provided When performing lap friction stir spot welding of a metal plate and a resin plate using the friction stir process tool 10 having 6, the temperature of the interface to be welded corresponding to the central portion is higher than that of the outer peripheral side of the friction stir surface 6. turned out to be higher. Details of the results are disclosed in Journal of Materials Research and Technology 2021; 12: 1777-1793.

On the other hand, in the friction stir welding tool 12 of the present invention having the disk-shaped recess 14 in the center of the friction stir surface 6, compared with the case of using the friction stir process tool 10 having the friction stir surface 6 in the flat state As a result, a uniform temperature distribution can be imparted to the entire interface to be joined.

As shown in FIG. 2 , the friction stir welding tool 12 has an annular recess 16 on the friction stir surface 6 , and the annular recess 16 extends outside the disk-shaped recess 14 around the disk-shaped recess 14 . It is preferable that an annular protrusion 18 having the same height as the end face (friction stir surface 6) of the base 4 is formed between the disk-shaped recess 14 and the annular recess 16 .

By having the annular recess 16 outside the disk-shaped recess 14, the temperature distribution of the interface to be joined during welding can be made more uniform, and the pressing load applied to the tool by the annular recess 16 can be further reduced. can be done. In addition, since the protrusions on the tool end face are at the same height, it is possible to suppress an increase in the torque applied to the tool during welding, and to form a smooth material flow.

In addition, the friction stir welding tool 12 has two or more annular recesses 16 having different inner and outer diameters. preferably has an annular projection 18 having the same height as the end surface of the base 4 (friction stir surface 6).

By having the plurality of annular recesses 16, the temperature distribution of the interface to be joined during welding can be made more uniform, and the indentation load applied to the tool can be further reduced by the plurality of annular recesses 16. can.

Further, in the friction stir welding tool 12, the depth of the disk-shaped recess 14 and the annular recess 16 is preferably 0.1 to 0.3 mm. By setting the depth of the recess to 0.1 mm or more, it is possible to reliably obtain a uniform temperature of the interface to be bonded and a decrease in the bonding load due to the shape of the recess. Further, by setting the depth of the recess to 0.3 mm or less, it is possible to suppress disturbance of material flow, increase in process torque, and the like caused by material entering the recess. Here, the more preferable depths of the disk-shaped concave portion 14 and the annular concave portion 16 are 0.15 to 0.25 mm.

Further, in the friction stir welding tool 12, the diameter of the disk-shaped concave portion 14 is preferably 3 to 9 mm. By setting the diameter of the disk-shaped concave portion 14 to 3 mm or more, uniformity of the temperature of the interface to be joined and reduction of the bonding load due to the shape of the concave portion can be reliably obtained. Further, by setting the diameter of the disk-shaped recess 14 to 9 mm or less, it is possible to suppress disturbance of material flow and increase in process torque caused by material entering the recess. Here, the diameter of the disc-shaped recess is more preferably 4-8 mm, and most preferably 5-7 mm.

Further, in the friction stir welding tool 12, the width of the annular concave portion 16 is preferably 1 to 1.5 mm. By setting the width of the annular recess 16 to 1 mm or more, it is possible to reliably obtain a uniform temperature of the interface to be joined and a decrease in the joining load due to the shape of the recess. Further, by setting the width of the annular concave portion 16 to 1.5 mm or less, it is possible to suppress disturbance of material flow and increase in process torque caused by material entering the concave portion. Here, a more preferable width of the annular concave portion 16 is 1.2 to 1.3 mm.

Further, in the friction stir welding tool 12, the width of the annular protrusion 18 is preferably 1 to 1.5 mm. By setting the width of the annular protrusion to 1 mm or more, it is possible to efficiently obtain frictional heat generation necessary for joining. In addition, by setting the width of the annular projection 18 to 1.5 mm or less, it is possible to suppress non-uniform bonding temperature at the interface to be bonded and an increase in bonding load due to excessive frictional heat generation. Here, a more preferable width of the annular protrusion 18 is 1.2 to 1.3 mm.

Furthermore, in the friction stir welding tool 12, it is preferable that the diameter of the base is 10 to 30 mm. By setting the diameter of the base portion 4 to 10 mm or more, it is possible to efficiently obtain frictional heat required for bonding, and to obtain a sufficiently large bonding area capable of developing the bonding strength required for practical use. On the other hand, by setting the diameter of the base portion 4 to 30 mm or less, it is possible to suppress non-uniform bonding temperature due to differences in peripheral speed, etc., and to suppress an increase in bonding load. Here, the more preferred diameter of the base 4 is 12-28 mm, and the most preferred diameter is 15-25 mm.

The material of the friction stir welding tool 12 is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known materials used for friction stir welding tools can be used. Further, the friction stir welding tool 12 may be entirely made of the same material, or may be made of a combination of multiple materials. For example, the friction stir surface 6 may be made of a material different from that of the base material 4, and the friction stir surface 6 may be coated with an appropriate film. As the material of the friction stir welding tool 12, for example, tool steel, cemented carbide, various ceramics, and the like can be used.

(2) Friction Stir Point Welding Method The friction stir point welding method of the present invention is a method of forming a spot joint by superimposing a metal plate and a thermoplastic resin plate. The most important feature is to use FIG. 5 shows a schematic diagram showing one aspect of the friction stir spot welding method of the present invention.

The friction stir spot welding method of the present invention includes a first step of overlapping a metal plate 20 and a thermoplastic resin plate 22 to form a welded interface, and a friction stir welding tool 12 rotated from the surface of the metal plate 20. and a second step of press-fitting to form a bonding interface.

The material of the metal plate 20 used as the material to be welded is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known metal materials that are subject to friction stir welding can be used. Here, by using aluminum, an aluminum alloy, magnesium, a magnesium alloy, copper, or a copper alloy as the metal plate 20, friction stir welding can be easily performed using an inexpensive friction stir welding tool 12 made of tool steel. .

The thickness of the metal plate 20 may be appropriately determined according to the desired structure, preferably 1 to 5 mm, more preferably 1.5 to 3 mm. By setting the thickness of the metal plate 20 to 1 mm or more, unnecessary plastic deformation of the metal plate 20 when inserting the friction stir welding tool 12 can be suppressed. Credibility can be imparted. In addition, by setting the thickness of the metal plate 20 to 5 mm or less, the temperature of the interface to be welded can be easily and efficiently raised by the heat generated by friction and heat generated by the interaction between the friction stir surface 6 and the metal plate 20. can be done.

Also, the material of the thermoplastic resin plate 22 is not particularly limited as long as it does not impair the effects of the present invention, and conventionally known various thermoplastic resins can be used. Here, the thermoplastic resin plate 22 is preferably carbon fiber reinforced plastic (CFRP). By using carbon fiber reinforced plastic (CFRP) as the thermoplastic resin plate 22, high strength and reliability can be imparted to the joint. Also, the type of carbon fiber reinforced plastic (CFRP) is not particularly limited, and those composed of various thermoplastic resin matrices and carbon fibers can be used. In addition, the content of the carbon fibers, the state of arrangement, and the like are not particularly limited.

The thickness of the thermoplastic resin plate 22 may be appropriately determined depending on the desired structure, preferably 1 to 6 mm, more preferably 2 to 5 mm. By setting the thickness of the thermoplastic resin plate 22 to 1 mm or more, the strength and reliability of the joint can be ensured, and by setting the thickness to 6 mm or less, material costs increase due to an unnecessary increase in plate thickness. can be suppressed.

In the first step, the metal plate 20 is superimposed on the surface of the thermoplastic resin plate 22 to form an interface to be welded, and a sufficient space is provided on the surface side of the metal plate 20 into which the friction stir welding tool 12 is inserted. It is preferable to keep In addition, it is preferable to fix the thermoplastic resin plate 22 and the metal plate 20 by a suitable clamping mechanism or the like to suppress positional change when inserting the friction stir welding tool 12 and plastic deformation at unnecessary portions.

In the second step, the friction stir welding tool 12 is inserted from the surface side of the metal plate 20 corresponding to the interface to be welded formed in the first step. Here, the insertion position (insertion amount) of the friction stir welding tool 12 may be appropriately adjusted depending on the material and thickness of the metal plate 20 and the thermoplastic resin plate 22, and other welding conditions such as the tool rotation speed. However, it is necessary to keep the thickness within the range of the metal plate 20 so that the friction stir surface 6 does not directly act on the interface to be welded.

The amount of insertion of the friction stir welding tool 12 into the metal plate 20 is preferably 0.05 to 0.5 mm, more preferably 0.1 to 0.3 mm, when a 2 mm thick aluminum alloy plate is used, for example. is more preferable. By setting the tool insertion amount to 0.05 mm or more, the interaction between the friction stir surface 6 and the surface of the aluminum alloy plate can stably generate frictional heat and/or heat generated by processing. Further, by setting the tool insertion amount to 0.5 mm or less, it is possible to suppress the formation of recesses in the joint portion and to suppress increases in tool torque and tool pushing load.

Main joining conditions other than the tool insertion amount include the tool rotation speed, the tool insertion speed, and the retention time at the set tool insertion position. and other joining conditions. For example, the tool rotation speed can be 100-3000 rpm, the tool insertion speed can be 0.01-1 mm/s, and the holding time can be 0-10 seconds.

Moreover, in the second step, the pressing load applied to the friction stir welding tool 12 is preferably 500 kgf or less. A general-purpose bonding robot can be used by setting the indentation load to 500 kgf or less. Here, by using the friction stir welding tool 12, the indentation load can be easily and efficiently reduced to 500 kgf or less.

Moreover, in the second step, it is preferable that the highest temperature reached at the joint interface be lower than the complete thermal decomposition temperature of the thermoplastic resin plate 22 . The complete thermal decomposition temperature is the temperature at which the thermal decomposition of the thermoplastic resin, which is the base material of the thermoplastic resin plate 22, starts to progress completely. The decomposition temperature is 500°C. By setting the maximum temperature of the joint interface to be less than the complete thermal decomposition temperature, it is possible to suppress a decrease in the strength of general thermoplastic resins. Here, by using the friction stir welding tool 12, the temperature distribution of the weld interface can be made uniform, so the maximum temperature can be easily controlled, and the maximum temperature can be easily adjusted to 500 by changing the tool rotation speed, the tool press-in amount, etc. °C.

When inserting the tool into the metal plate 20, it may be performed in the atmosphere. However, if it is desired to suppress oxidation of the metal plate 20 at the joint and deterioration of the friction stir welding tool 12, etc., an inert gas such as argon gas is used. It is preferably used as a shielding gas.

After the second step, the friction stir welding tool that has been press-fitted into the metal plate 20 can be returned to its original position by following the path reversed from the time of insertion. You can move it to

The friction stir welding apparatus used in the friction stir spot welding method is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known friction stir welding apparatuses can be used. For example, there are a position control system, a load control system, and a torque control system in the friction stir welding apparatus, and any of them may be used.

Although representative embodiments of the present invention have been described above, the present invention is not limited to these, and various design changes are possible, and all such design changes are included in the technical scope of the present invention. be

<<Example 1>>
An A6061-T6 aluminum alloy plate was placed on a carbon fiber reinforced plastic plate, and friction stir spot welding was performed by press-fitting a friction stir welding tool from the surface of the aluminum alloy plate. The carbon fiber reinforced plastic has polyamide 6 as a matrix and 20 wt % of short carbon fibers are randomly dispersed. The carbon fiber reinforced plastic plate was 100 mm x 25 mm x 3 mm, the aluminum alloy plate was 100 mm x 25 mm x 2 mm, and the edges of each plate (50 mm x 50 mm) were overlapped. FIG. 6 shows a schematic diagram of the arrangement of the members to be joined.

FIG. 7 shows a photograph of the appearance of the friction stir welding tool, and FIG. 8 shows a bottom view and a side view of the tool. In FIG. 7, the friction stir surface is on the upper side. The friction stir welding tool is made of tool steel, has a cylindrical shape with a diameter of 20 mm, and has a disk-shaped recess in the center of the friction stir welding surface. The disc-shaped recess has a diameter of 12 mm and a depth of 0.2 mm.

The conditions for friction stir spot welding were tool rotation speed: 1500 rpm, tool insertion speed: 0.1 mm/s, and tool insertion depth: 0.3 mm. Here, when the Z-axis load (tool applied load) during insertion was measured, the maximum value was 360 to 380 kgf.

A photograph of the appearance of the obtained joint from the aluminum alloy plate side is shown in FIG. The surface of the aluminum alloy plate corresponding to the overlapping area with the carbon fiber reinforced plastic plate is blackened for the purpose of temperature measurement, but a friction stir point joint is formed in the center of the overlapping area. can be confirmed.

When a tensile test was performed on the obtained joint in the manner shown in FIG. 10, the tensile shear strength was 6300 to 7000N. In addition, after reaching the tool insertion amount of 0.3 mm, a joint was produced in the same manner as above except that it was held at that position for 10 seconds and then pulled upward, and a tensile test was also performed on the joint. , the tensile shear strength was 8000-9000N. Fig. 11 shows the appearance of the joint after the tensile test.

Fig. 12 shows the results of simulating the welding temperature distribution using nonlinear finite element analysis software (Ls-Dyna) incorporating a thermomechanical model based on the materials and shapes of the materials to be welded and the friction stir welding tool. . A region with a welding temperature of 220 to 340° C. was formed over a wide range in the outer peripheral region of the friction stir surface, and it is considered that a strong joint interface was formed in this region. Details of the simulation method are disclosed in Journal of Materials Research and Technology 2021; 12: 1777-1793.

<<Example 2>>
A joint was obtained in the same manner as in Example 1 except that a friction stir welding tool having the appearance of FIG. 13 was used. The friction stir welding tool was pulled upward immediately after reaching the tool insertion amount of 0.3 mm. Here, when the Z-axis load (tool applied load) during insertion was measured, the maximum value was 380 to 400 kgf.

FIG. 14 shows a bottom view and a side view of the friction stir welding tool. A disk-shaped recess is provided in the center of the friction stir surface, and two annular recesses are provided on the outer periphery of the disk-shaped recess. The diameter of the disk-shaped recess is 6 mm, and the outer diameters of the annular recess are 11 mm and 16 mm.

A joint obtained in the same manner as in Example 1 was subjected to a tensile test, and the tensile shear strength was 6000 to 6500N. FIG. 15 shows the result of simulating the junction temperature distribution in the same manner as in Example 1. In FIG. As in the case of Example 1, a region where the welding temperature is 220 to 340 ° C. is formed in a wide range in the outer peripheral region of the friction stir surface, and it is considered that a strong joint interface was formed in this region. .

≪Comparative example≫
A joint was obtained in the same manner as in Example 1 except that a friction stir welding tool having the appearance of FIG. 16 was used. The friction stir welding tool has a simple cylindrical shape with a diameter of 20 mm, and the friction stir surface has a flat shape without concave portions or convex portions. The friction stir welding tool was pulled upward immediately after reaching the tool insertion amount of 0.3 mm.

When the joint obtained in the same manner as in Example 1 was subjected to a tensile test, the tensile shear strength was 4500 to 5200 N, which was not sufficiently high. FIG. 17 shows the result of simulating the junction temperature distribution in the same manner as in Example 1. In FIG. Unlike the cases of Examples 1 and 2, a high temperature region of 500° C. or higher is formed in the center of the friction stir surface. In addition, even when welding conditions such as tool rotation speed, tool press-fitting load, and tool holding time are variously adjusted, it is not possible to remove the region of 500°C or higher while forming the region of 220 to 340°C. I didn't.

Here, polyamide 6, which is the matrix of carbon fiber reinforced plastic, is known to significantly decrease in strength when kept at a high temperature of 500°C or higher. It can be seen that it is not possible to form a good bonding interface over a wide area, which is necessary to ensure the strength and reliability of the part.

2... Tools for general-purpose friction stir welding,
4 ... base,
6 Friction stir surface,
8 ... probe part,
10 Tools for friction stir process,
12 . . . Tools for friction stir welding,
14... Disc-shaped recessed part,
16 Annular concave portion,
18 Annular projection,
20... metal plate,
22... Thermoplastic resin plate.

Claims (12)

a substantially cylindrical base;
a friction stir surface consisting of an end surface of the base,
Having a disk-shaped recess in the center of the friction stir surface;
A friction stir welding tool characterized by: Having an annular concave portion on the friction stir surface,
The annular recess is formed outside the disk-shaped recess centered on the disk-shaped recess,
having an annular protrusion having the same height as the end face between the disk-shaped recess and the annular recess;
The friction stir welding tool according to claim 1, characterized by: Having two or more annular recesses having different inner and outer diameters,
The annular concave portion is formed around the disk-shaped concave portion,
Having an annular projection having the same height as the end face between the annular recesses;
The friction stir welding tool according to claim 1 or 2, characterized by: The disc-shaped recess and the annular recess have a depth of 0.1 to 0.3 mm,
The tool for friction stir welding according to any one of claims 1 to 3, characterized by: the diameter of the disk-shaped recess is 3 to 9 mm;
The tool for friction stir welding according to any one of claims 1 to 4, characterized by: The width of the annular concave portion is 1 to 1.5 mm,
The tool for friction stir welding according to any one of claims 2 to 5, characterized by: The width of the annular protrusion is 1 to 1.5 mm,
The tool for friction stir welding according to any one of claims 2 to 6, characterized by: the base has a diameter of 10 to 30 mm;
The tool for friction stir welding according to any one of claims 1 to 7, characterized by: a first step of overlapping a metal plate and a thermoplastic resin plate to form a bonded interface;
a second step of press-fitting a friction stir welding tool rotated from the surface of the metal plate to form a weld interface,
Using the friction stir welding tool according to any one of claims 1 to 8 for the friction stir welding tool,
A friction stir spot welding method characterized by: In the second step, the indentation load applied to the friction stir welding tool is 500 kgf or less;
The friction stir spot welding method according to claim 9, characterized in that: In the second step, setting the highest temperature reached at the joint interface to be less than the complete thermal decomposition temperature of the thermoplastic resin plate;
The friction stir spot welding method according to claim 9 or 10, characterized in that: using carbon fiber reinforced plastic (CFRP) as the thermoplastic resin plate;
The friction stir spot welding method according to any one of claims 9 to 11, characterized in that:

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