JP6590334B2 - Friction stir welding method and friction stir welding member - Google Patents

Description

  The present invention relates to a dissimilar material friction stir welding method for magnesium or a magnesium alloy material and an iron-based material, and a dissimilar material friction stir welding member obtained thereby.

  From the viewpoint of improving fuel consumption and reducing environmental impact, there is a strong demand for weight reduction of various types of transportation equipment. Here, magnesium material has the smallest specific gravity among metals that can be used as a structural member, and if a part of commonly used iron-based material can be replaced with magnesium material, the weight of the structural member can be effectively reduced. can do.

  However, magnesium and iron are systems that do not form a solid solution with each other (two-phase separation type) and are extremely difficult to join. On the other hand, regarding the joining of magnesium material and iron-based material, various studies have been made so far, and joining methods mainly utilizing eutectic melting have been proposed.

For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2009-269071), a galvanized steel sheet that has been galvanized as a steel material and an Al-containing magnesium alloy material as a magnesium alloy material are used. A composite structure in which Al ₃ Mg ₂ and FeAl ₃ coexist is produced by causing melting and discharging oxide films and impurities from the bonding interface and generating Al—Mg and Fe—Al intermetallic compounds. A method for joining the new surfaces of both materials via a compound layer is disclosed.

  In the joining method described in Patent Document 1, a third material is interposed between a material to be joined made of a magnesium alloy material and a steel material, and between Mg and / or Fe and a metal contained in the third material. By causing eutectic melting at, the oxide film can be easily discharged from the bonding interface at a low temperature, and the new surfaces of the materials to be bonded can be brought into contact with each other, and in addition, between each of Mg and Fe and Al metal As a compound layer with a composite structure in which compounds are mixed is present at the bonding interface, mutual diffusion is possible even with a combination of materials that are difficult to metallurgically bond directly, and strong bonding is achieved. Yes.

  On the other hand, from the viewpoint of mechanical properties and strain of joints, solid-phase bonding that does not involve melting of materials is attracting attention. A cylindrical tool that rotates at high speed is press-fitted into the material to be joined, and friction with the material occurs. Friction stir welding (FSW), which achieves joining using heat, has been rapidly put into practical use. Here, the friction stir welding is easy to control the heat input to the joint according to the process conditions, and is an advantageous joining method for dissimilar material joining.

  For example, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-255420), regarding a dissimilar material joining between a steel material and an aluminum material, a probe portion on the bottom surface of the tool is provided with respect to a butt line formed by abutting the steel material and the aluminum material. There is disclosed a friction stir welding method in which the steel material is slightly penetrated (mostly disposed in an aluminum material).

  In the friction stir welding method described in Patent Document 2, since the probe slightly enters the steel material side, a new interface of the steel material is cut out, and at the same time, in the region near the aluminum material in contact with the probe. Plastic flow occurs. In addition, in the region on the rear side with respect to the advancing direction of the probe, the aluminum material that has flowed plastically receives a large compressive force, and the joining to the newly exposed clean steel surface is achieved.

JP 2009-269071 JP 2004-255420 A

  However, in the joining method disclosed in Patent Document 1, it is difficult to control the thickness of the fragile intermetallic compound layer, and the type and size of the steel material that can be used as a material to be joined. Will be limited. Further, the friction stir welding method disclosed in Patent Document 2 is difficult to use for dissimilar material joining of magnesium and iron that are not solid-solved with each other, and in this combination, a joining member having sufficient joint strength is obtained. I can't.

  Moreover, when using the magnesium alloy which dissolves aluminum into a to-be-joined material, the said intermetallic compound layer (intermediate layer) is formed with the said aluminum, and joining is achieved. However, the formation of the intermetallic compound layer (intermediate layer) reduces the aluminum concentration of the magnesium alloy and forms an aluminum deficient layer.

  Since the strength of the magnesium alloy in which aluminum is dissolved is increased (solid solution strengthening) due to the solid solution, the strength of the magnesium alloy is reduced when the aluminum-deficient layer is formed, and the joint strength is reduced accordingly. Note that the reduction in strength of the friction stir welded joint between dissimilar materials made of magnesium or a magnesium alloy material and an iron-based material due to the formation of an aluminum-deficient layer was found by the inventors examining in detail the relationship between the element distribution near the joint interface and the joint strength It is a thing.

  In view of the above problems in the prior art, the object of the present invention is to provide a simple and efficient dissimilar friction stir welding method for magnesium or a magnesium alloy material and an iron-based material, and high joint strength obtained thereby. The object is to provide a different material friction stir welding member.

  In order to achieve the above object, the present inventor has conducted extensive research on the friction stir welding conditions, the microstructure of the joint interface and the relationship between element distribution and joint strength, etc., and as a result, the contact interface between magnesium or a magnesium material and an iron-based material. The present inventors have found that it is extremely effective to dispose an appropriate insert material and to apply friction stir welding to the present invention.

That is, the present invention
A friction stir welding method between magnesium or a magnesium alloy material and an iron-based material,
The magnesium or magnesium alloy material and the iron-based material are brought into contact via a metal layer having an aluminum content higher than that of the magnesium or magnesium alloy material,
Making the side or bottom of the probe part of the friction stir welding tool enter 0.05 mm or more on the iron-based material side with respect to the contact surface of the metal layer and the iron-based material,
A friction stir welding method is provided. The iron-based material includes a wide range of metal materials mainly composed of iron, and includes iron, steel, and cast iron.

  By inserting the probe into the iron-based material side by 0.05 mm or more, the iron-based material is slightly cut, and a new surface of the iron-based material is formed during the friction stir welding. By pressing the material flow of the metal layer or magnesium alloy material containing aluminum on the new surface, an intermetallic compound layer (intermediate layer) mainly composed of iron and aluminum is formed at the joining interface, and the magnesium or magnesium alloy material And metallurgical joining of iron-based materials is achieved.

  In the friction stir welding method of the present invention, it is preferable to use a magnesium alloy plate for the metal layer. By using a magnesium alloy plate having a higher aluminum content than the magnesium or magnesium alloy material to be joined as the metal layer, aluminum dissolved in the magnesium alloy plate can be supplied to the vicinity of the joining interface. it can.

  When magnesium material is used as the material to be joined, magnesium and iron are not solid-solved with each other, so metallurgical joining is not achieved, but aluminum dissolved in the magnesium alloy plate is supplied to the joint interface during friction stir welding Good bonding is achieved by forming an intermetallic compound layer (intermediate layer) mainly composed of iron and aluminum. Here, an aluminum plate or the like may be used for the metal layer, but by using a magnesium alloy plate in which aluminum is dissolved, the supply of aluminum to the joint interface becomes smoother. In addition, since one of the materials to be joined is magnesium or a magnesium alloy material, the difference in material flow behavior between the materials to be joined and the metal layer can be reduced by making the metal layer the same type of magnesium alloy material. .

  In addition, when a magnesium alloy in which aluminum is dissolved in the material to be joined is used, an aluminum deficiency is formed in the vicinity of the intermetallic compound layer (intermediate layer) with the formation of an intermetallic compound layer (intermediate layer) mainly composed of iron and aluminum. Layers will form. On the other hand, by using a magnesium alloy plate or the like having a higher aluminum content than the aluminum plate or the magnesium alloy material to be bonded as the metal layer, aluminum can be supplied to the vicinity of the bonding interface, and the aluminum deficiency Formation of the layer can be effectively suppressed.

In the friction stir welding method of the present invention,
Butting the magnesium or magnesium alloy material and the iron-based material through the metal layer,
It is preferable to arrange the iron-based material at a position where the rotational direction and the traveling direction of the friction stir welding tool are the same.

  By using butt bonding, the rotation of the probe can be used to strongly press the material flow of the aluminum-containing metal layer or magnesium alloy material against the new surface of the iron-based material, thereby obtaining a strong bonded portion. be able to. More specifically, a new surface of the iron-based material is arranged by placing the iron-based material at a position where the rotational direction and the traveling direction of the friction stir welding tool are the same (generally referred to as the forward side). The material flow can be pressed.

  Moreover, when setting it as butt joining, it is preferable to make the side surface of the said probe part enter into the said iron-type material side 0.1-1.5 mm with respect to the contact surface of the said metal layer and the said iron-type material. By setting the insertion amount of the probe part side surface to the iron-based material to be 0.1 mm or more, a sufficient new surface necessary for bonding can be formed, and by setting the insertion amount to 1.5 mm or less, the bonding part It is possible to suppress a decrease in bonding characteristics caused by the cutting waste of the iron-based material dispersed in the vicinity.

  Furthermore, in the case of butt joining, it is preferable that the width of the metal layer is 0.05 mm to approximately the diameter of the probe. By setting the width of the metal layer to 0.05 mm or more, sufficient aluminum is supplied in the vicinity of the joint, which is necessary for forming an intermetallic compound layer (intermediate layer) mainly composed of iron and aluminum and / or suppressing an aluminum deficient layer. be able to. Further, by setting the width of the metal layer to be approximately equal to or less than the diameter of the probe, the magnesium or magnesium alloy material, the metal layer, and the iron-based material can all be reliably stirred by the probe portion.

In the friction stir welding method of the present invention,
The magnesium alloy material is AZ31 magnesium alloy material,
The metal layer is preferably an AZ61 magnesium alloy layer or an AZ91 magnesium alloy layer.

  By using the magnesium alloy material to be bonded as an AZ31 magnesium alloy material, an intermetallic compound layer (intermediate layer) can be formed using aluminum contained in the AZ31 magnesium alloy material. Further, since the AZ61 magnesium alloy and the AZ91 magnesium alloy have a higher aluminum content than the AZ31 magnesium alloy, and the aluminum is present in a solid solution state in the magnesium, the metal layer is made of the AZ61 magnesium alloy layer or the AZ91 magnesium alloy layer. By using a magnesium alloy layer, the formation of an aluminum-deficient layer in the AZ31 magnesium alloy material that is the material to be joined can be effectively suppressed (the supply of aluminum from the metal layer to the region deficient in aluminum is quickly performed). Achieved).

  In addition, in the friction stir welding method of the present invention, a second metal layer that reacts with the constituent elements of the metal layer and / or the magnesium alloy material is formed at the contact interface between the metal layer and the magnesium alloy material. It is preferable that the second metal layer contains silver or zinc. When friction stir welding is performed on a material to be joined having a remarkable oxide film, the oxide is linearly distributed in the stirring portion, and the joint characteristics are deteriorated. Due to the presence of the silver layer or zinc layer at the contact interface between the metal layer and the magnesium alloy material, eutectic melting occurs in the vicinity of the joint, and the oxide is discharged from the joint, thereby suppressing the arrangement of the oxide. be able to. In addition, silver and zinc are supplied to the aluminum-deficient layer, and there is an effect of suppressing the strength reduction of the magnesium alloy.

  Further, the present invention is a joining member of magnesium or a magnesium alloy material and an iron-based material, and has an intermetallic compound layer mainly composed of aluminum and iron at a joining interface, in the vicinity of the joining interface. There is also provided a friction stir welded joint characterized in that the aluminum concentration does not decrease by 1 atomic% or more compared to the aluminum concentration of the magnesium or magnesium alloy material.

  The joining member of the present invention has a very good joint strength since it has a thin intermetallic compound layer (intermediate layer) at the joining interface and does not have an aluminum-deficient layer. As long as the effects of the present invention are not impaired, the thickness of the intermetallic compound layer (intermediate layer) is not particularly limited, but is preferably 1 μm or less.

  Here, the aluminum-deficient layer means a region where the aluminum concentration is clearly reduced (decrease of 1 atomic% or more) as compared with the magnesium alloy of the material to be joined. For example, when an AZ31 magnesium alloy material having an aluminum concentration of approximately 3 atomic% is used as the material to be joined, a region where the aluminum concentration is less than approximately 2 atomic% can be regarded as an aluminum deficient layer.

  The friction stir welding joint of the present invention can be easily obtained by the friction stir welding method of the present invention.

  According to the present invention, it is possible to provide a simple and efficient dissimilar material friction stir welding method for magnesium or a magnesium alloy material and an iron-based material, and a dissimilar material friction stir welding member having sufficient joint strength obtained thereby.

It is the schematic which shows arrangement | positioning of the to-be-joined material in the case of butt joining. It is the schematic which shows an example of the tool for friction stir welding used by this invention. It is the schematic which shows the positional relationship of a to-be-joined material and the tool for friction stir welding (butt joining). It is the schematic which shows the positional relationship of the to-be-joined material and tool for friction stir welding in the case of using a 2nd metal layer (butt joining). It is the schematic which shows the positional relationship of a to-be-joined material and the tool for friction stir welding (lamination joining). It is a schematic sectional drawing of the joining member of this invention. It is the schematic which shows the positional relationship of the to-be-joined material and the tool for friction stir welding in the friction stir welding of Example 1. FIG. 2 is an appearance photograph of the friction stir welding tool used in Example 1. FIG. It is a schematic diagram which shows the shape of a tensile test piece. It is a graph which shows the tensile strength of the implementation couplings 1-3 and the comparison coupling 1. FIG. It is a graph which shows the tensile strength of the implementation couplings 4-6 and the comparison coupling 1. FIG. It is a graph which shows the tensile strength of the implementation couplings 7-9 and the comparison coupling 1. FIG. It is a graph which shows the tensile strength of the implementation couplings 10 and 11 and the comparison couplings 10 and 11. FIG. It is a graph which shows the tensile strength of the comparative couplings 1-9. It is a graph which shows the tensile strength of comparative joints 10-19. It is a graph which shows the tensile strength of the implementation joint 2, the implementation joint 12, and the comparison joint 1. FIG. 3 is an optical micrograph of a cross section of a joint portion of a comparative joint 1. It is SEM-EDS element mapping of the joint interface vicinity of the comparison coupling 1. FIG. It is a SEM-EDS element mapping of the joint interface vicinity of the comparison coupling 10. FIG. It is a SEM-EDS element mapping of the joint interface vicinity of the comparison coupling 11. FIG. It is SEM-EDS element mapping of the joint interface vicinity of the comparison coupling 10 (high magnification). It is SEM-EDS element mapping of the joint interface vicinity of the comparison coupling 11, (high magnification). It is a STEM-EDS element mapping of the joint interface vicinity of the comparison coupling 10. FIG. It is STEM-EDS element mapping of the joint interface vicinity of the comparison coupling 11. FIG. It is SEM-EDS element mapping by the side of the AZ31 magnesium alloy plate of the fracture surface of the comparative joint 10. It is a SEM-EDS element mapping by the side of the low carbon steel (SPCC) board of the fracture surface of the comparative joint 10. It is a SEM-EDS element mapping of the junction part cross section of the implementation coupling 1. FIG. It is a SEM-EDS element mapping of the junction part cross section of the implementation coupling 4. FIG. It is a SEM-EDS element mapping of the junction part cross section of the implementation coupling 8. FIG. It is SEM-EDS element mapping of the junction part cross section of the implementation coupling 1 (high magnification). It is a SEM-EDS element mapping of the joining cross section of the implementation coupling 12 (high magnification). It is a photograph which shows the fracture | rupture position of a tensile test piece.

  Hereinafter, representative embodiments of the dissimilar material friction stir welding method of the present invention and the friction stir welding member obtained thereby 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. Further, since the drawings are for conceptually explaining the present invention, the dimensions and ratios of the components shown may be different from the actual ones.

(1) Friction stir welding method Friction stir welding is referred to as FSW (Friction Stir Welding), which is provided at the tip of a rotating tool by abutting the ends of each of the two metal materials to be joined. This is a method of joining two metal members by inserting a protruding portion (probe) between both ends and moving the rotating tool along the longitudinal direction of these ends while rotating the rotary tool.

  “Friction stir welding” in the present invention refers to friction stir welding in which the rotating tool is rotated and moved in the joining direction, spot friction stir welding in which the rotating tool is not rotated and moved at the joining site, and the materials to be joined are joined together. Any one of four modes of friction stir welding to be abutted at a part and friction stir welding in which a rotating tool is inserted from the side of one of the members to be joined together by overlapping the parts to be joined, and these are arbitrarily selected In the following, butt joining and lap joining will be described in detail as representative aspects.

(1-1) Butt-joining FIG. 1 is a schematic view showing the arrangement of materials to be joined in the case of butt-joining. A metal layer 6 is inserted into a butt surface between the magnesium or magnesium alloy material 2 and the iron-based material 4. The “insertion of the metal layer 6” means that the metal layer 6 in the form of a thin film, a plate, or a powder may be disposed on the abutting surface. May be formed.

  FIG. 2 and FIG. 3 show a schematic view of the friction stir welding tool and the positional relationship between the material to be joined and the friction stir welding tool in the case of butt welding, respectively. The friction stir welding tool 10 has a probe portion 14 on the bottom surface of the tool main body 12. The probe portion 14 of the rotating friction stir welding tool 10 is press-fitted into the material to be joined, and the bottom surface (shoulder portion 16) of the tool body 12 and the materials to be joined (magnesium or magnesium alloy material 2 and iron-based material 4) are brought into contact. Friction heat is generated by the contact, and material flow of the materials to be joined occurs.

  In the friction stir welding of the present invention, a new surface can be formed on the iron-based material 4 by inserting the probe portion 14 into the iron-based material 4 by 0.05 mm or more (a ≧ 0.05 mm). Joining is achieved by pressing the material flow of the magnesium or magnesium alloy material 2 and the metal layer 6.

  The shape of the probe portion 14 is not particularly limited as long as the effect of the present invention is not impaired, and various conventionally known shapes can be used, but those having no screw or taper are preferable, and the tip portion is a curved surface. Those not present are preferred. When the probe part 14 does not have a screw or a taper, the side face of the probe part 14 can be uniformly brought into contact with the side face of the iron-based material 4, and the new surface of the iron-based material 4 is formed uniformly. Can do. Moreover, since the distance from the shoulder part 16 to the center part or side part of the probe part 14 will become the same if the front-end | tip part of the probe part 14 is not a curved surface, an unjoined part is formed in the back surface of a to-be-joined material. Less likely.

  For the metal layer 6, a metal foil, plate, powder or the like having an aluminum content higher than that of magnesium or the magnesium alloy material 2 can be used. In addition, since the powder has a large surface area and the oxide film formed on the surface may deteriorate the joint characteristics, it is preferable to use a powder having a large particle size as long as dispersibility in the joining region can be ensured. . Further, a metal film having an aluminum content higher than that of the magnesium or magnesium alloy material 2 is formed on the butted surfaces of the magnesium or magnesium alloy material 2 and / or the iron-based material 4 by various conventionally known methods such as plating. May be. Here, the aluminum content of the joint part finally obtained can be averaged by inclining the aluminum content in the metal film and increasing the aluminum content on the iron-based material 4 side.

  The metal used for the metal layer 6 is not particularly limited as long as it has an aluminum content higher than that of magnesium or the magnesium alloy material 2. For example, aluminum, an aluminum alloy, a magnesium alloy, or the like can be used. Is preferably used. As the magnesium alloy, for example, AZ31 magnesium alloy, AZ61 magnesium alloy, AZ91 magnesium alloy, and the like can be suitably used.

  Aluminum is dissolved in the AZ-based magnesium alloy, and the aluminum is supplied to the vicinity of the joint during friction stir welding, so that a good joint can be obtained. Specifically, in the case of using pure magnesium or a magnesium alloy containing no aluminum as the material to be bonded, the new surface of the iron-based material 4 reacts with the aluminum supplied from the metal layer 6, and the inter-metal mainly composed of aluminum and iron. A compound (intermediate layer) is formed. The intermetallic compound layer (intermediate layer) achieves metallurgical joining between the magnesium material not containing aluminum and the iron-based material 4.

  Further, when a magnesium alloy material containing aluminum is used as a material to be joined, aluminum contained in the magnesium alloy material reacts with the new surface of the iron-based material 4 to form an intermetallic compound layer (intermediate layer), and magnesium. Metallurgical joining between the alloy material and the iron-based material 4 is achieved. However, since aluminum is consumed to form the intermetallic compound layer (intermediate layer), an aluminum-deficient layer is formed. Here, in the present invention, a region in which the aluminum concentration is lower by about 1 atomic% or more than the aluminum concentration (atomic%) of the magnesium alloy that is the bonded material is defined as an aluminum-deficient layer.

  In general, since a magnesium alloy in which aluminum is dissolved is strengthened by solid solution, the strength is lowered when the aluminum concentration is lowered. That is, if an aluminum deficient layer is formed at the joint, the joint strength decreases due to the strength of the aluminum deficient layer. In joints of dissimilar materials formed by an intermetallic compound layer (intermediate layer), the joint strength is typically ensured by setting the thickness to about 1 μm or less so that the brittle intermetallic compound layer (intermediate layer) is not thickened. Is done. Here, since the heat input of the friction stir welding is small as compared with the conventional fusion welding, it is relatively easy to set the thickness of the intermetallic compound layer to 1 μm or less. However, even when the thickness of the intermetallic compound layer is 1 μm or less, a good joint cannot be obtained when the aluminum-deficient layer is formed.

  In the friction stir welding of the present invention, aluminum is supplied from the metal layer 6 to the aluminum deficient layer. In addition, since the aluminum concentration of the metal layer 6 is higher than that of the magnesium or magnesium alloy material 2, the aluminum concentration is lower by about 1 atomic% or more than the aluminum concentration (atomic%) of the magnesium or magnesium alloy material 2 (aluminum deficiency). Formation) can be effectively suppressed.

  The iron-based material 4 is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known iron-based materials can be used. In the friction stir welding between the iron-based materials 4, it is necessary to consider wear / breakage of the friction stir welding tool 10. In the friction stir welding according to the present invention, the probe portion 14 is slightly inserted into the iron-based material 4. Therefore, even an iron-based material having high strength and hardness can be used as a material to be joined without any problem.

  In the friction stir welding of the present invention, the magnesium or magnesium alloy material 2 and the iron-based material 4 are abutted through the metal layer 6, and the rotational direction and the traveling direction of the friction stir welding tool 10 are the same, It is preferable to dispose the iron-based material 4.

  The amount by which the side surface of the probe portion 14 is inserted into the iron-based material 4 side needs to be 0.05 mm or more. By setting the amount of insertion to 0.05 mm or more, a new surface necessary for joining can be formed on the iron-based material 4, and deterioration of joint characteristics due to insufficient joining interface strength can be suppressed.

  Further, by using butt joining, the material flow of the aluminum-containing metal layer 6 or the magnesium alloy material 2 can be strongly pressed against the new surface of the iron-based material 4 by utilizing the rotation of the probe portion 14. A strong joint can be obtained. More specifically, by arranging the iron-based material 4 at a position where the rotational direction and the traveling direction of the friction stir welding tool 10 are the same (generally referred to as a forward side), the iron-based material is arranged. The material flow can be pressed against the 4 new surfaces.

  Moreover, when setting it as butt joining, it is preferable to make 0.1-1.5 mm enter into the iron-type material 4 side with respect to the contact surface of the metal layer 6 and the iron-type material 4. By setting the insertion amount of the probe portion 14 to the iron-based material 4 to be 0.1 mm or more, a sufficient new surface necessary for bonding can be formed, and by setting the insertion amount to 1.5 mm or less, bonding is possible. It is possible to suppress a decrease in bonding characteristics due to the cutting waste of the iron-based material 4 dispersed in the vicinity of the part.

  In the case of butt joining, it is preferable that the width c of the metal layer 6 is 0.05 mm to approximately the diameter of the probe portion 14. By setting the width c of the metal layer 6 to 0.05 mm or more, aluminum necessary for forming an intermetallic compound layer (intermediate layer) mainly composed of iron and aluminum and / or suppressing an aluminum deficient layer is supplied to the vicinity of the joint. can do. Further, by setting the width c of the metal layer 6 to be approximately equal to or less than the diameter of the probe portion 14, the magnesium or magnesium alloy material 2, the metal layer 6, and the iron-based material 4 can all be reliably stirred by the probe portion 14. .

  There are various combinations of materials that can be used as the magnesium or magnesium alloy material 2, the iron-based material 4, and the metal layer 6, but the magnesium alloy material 2 is an AZ31 magnesium alloy material, and the metal layer 6 is an AZ61 magnesium alloy plate or AZ91. It is preferable to use a magnesium alloy plate.

  By using the magnesium alloy material 2 to be bonded as an AZ31 magnesium alloy material, an intermetallic compound layer (intermediate layer) can be formed using aluminum contained in the AZ31 magnesium alloy material. In addition, since the AZ61 magnesium alloy and the AZ91 magnesium alloy have a higher aluminum content than the AZ31 magnesium alloy, and the aluminum is present in a solid solution state in the magnesium, the metal layer 6 is formed on the AZ61 magnesium alloy plate or By using the AZ91 magnesium alloy plate, the formation of an aluminum-deficient layer on the AZ31 magnesium alloy material, which is a material to be joined, can be effectively suppressed.

  In addition, in the friction stir welding method of the present invention, the second metal that undergoes a eutectic reaction with the constituent elements of the metal layer 6 and / or the magnesium alloy material 2 further at the contact interface between the metal layer 6 and the magnesium alloy material 2. It is preferable to form a layer, and it is more preferable that the second metal layer contains silver or zinc. In FIG. 4, the schematic diagram of the friction stir welding in the case of using a 2nd metal layer is shown. When friction stir welding is performed on a material to be joined having a remarkable oxide film, the oxide is linearly distributed in the stirring portion, resulting in poor joint characteristics. Due to the presence of the second metal layer 20 at the contact interface between the metal layer 6 and the magnesium alloy material 2, eutectic melting occurs in the vicinity of the joint, and the oxide is discharged from the joint, thereby changing the arrangement of the oxide. Can be suppressed. In addition, silver and zinc are supplied to the aluminum-deficient layer, and there is an effect of suppressing the strength reduction of the magnesium alloy 2. Moreover, the fall of the joint characteristic by the said oxide can also be suppressed by giving a 2nd friction stir welding to a junction part, and crushing and disperse | distributing an oxide.

  When the second metal layer 20 is used, it is preferable that the total (d + c) of the width d of the second metal layer 20 and the width c of the metal layer 6 be 0.05 mm to the approximate diameter of the probe portion 14. By setting d + c to 0.05 mm or more, aluminum necessary for the formation of an intermetallic compound layer (intermediate layer) mainly composed of iron and aluminum and / or suppression of the aluminum deficient layer can be supplied in the vicinity of the joint, In addition, the arrangement of oxides can be suppressed by the eutectic (melting) of the second metal layer 20. Further, by setting d + c to be approximately equal to or less than the diameter of the probe portion 14, the magnesium or magnesium alloy material 2, the metal layer 6, the second metal layer 20, and the iron-based material 4 can all be reliably stirred.

  For the second metal layer 20, a metal material containing an element that forms a eutectic with the magnesium or the magnesium alloy material 2 and the metal layer 6 can be used, and the eutectic with the magnesium or the magnesium alloy material 2 and the metal layer 6 can be used. Examples of the element forming Cu include Ni, Ag, Au, Ba, Bi, Ca, Ce, Ga, Ge, Hg, Li, Pb, Pu, Sb, Si, Sn, Sr, Th, Tl, and Y. Zn and the like can be exemplified.

  The friction stir welding includes a joining method in which the position of the friction stir welding tool 10 is constant, a joining method in which the load applied to the friction stir welding tool 10 is constant, and torque applied to the friction stir welding tool 10. There is a way to make it constant. Although all these methods can be used for the friction stir welding method of the present invention, it is preferable to use a joining method in which the position of the friction stir welding tool 10 is kept constant. By using the joining method, the positional relationship between the friction stir welding tool 10 and the material to be joined can be strictly controlled.

  The main process parameters of friction stir welding include the rotational speed, moving speed, load, and the like of the friction stir welding tool 10. The process conditions may be appropriately selected depending on the shape and material of the friction stir welding tool 10 to be used, the type and material of the material to be joined, and the like. Conditions under which the thickness of the compound layer (intermediate layer) is less than 1 μm can be suitably used.

(1-2) Lap Joining FIG. 5 shows the positional relationship between the material to be joined and the friction stir welding tool in the case of overlap joining. In the case of lap joining, magnesium or the magnesium alloy 2 and the iron-based material 4 are overlapped via the metal layer 6, and the probe portion 14 is inserted from the magnesium alloy 2 side.

  At this time, by inserting the bottom surface of the probe portion 14 into the iron-based material 4 by 0.05 mm or more, a new surface can be formed on the iron-based material 4, and the magnesium or magnesium alloy material 2 and the metal layer 6 can be formed on the new surface. Bonding is achieved by pressing the material flow. Here, in order to insert the bottom surface of the probe portion 14 into the iron-based material 4, the length g of the probe portion 14 is the sum of the thickness f of the magnesium or magnesium alloy 2 and the thickness e of the metal layer 6 (f + e). It is preferable to make the length slightly longer. However, when the press-fitting amount of the friction stir welding tool to the magnesium or magnesium alloy material 2 is large, the length g of the probe portion 14 is the sum of the thickness f of the magnesium or magnesium alloy 2 and the thickness e of the metal layer 6 ( Even if it is approximately the same as f + e), the bottom surface of the probe portion 14 is inserted into the iron-based material 4.

  In the case of lap joining, the second metal layer 20 is inserted between the magnesium or magnesium alloy material 2 and the metal layer 6 so that the eutectic ( Melting) can suppress the arrangement of oxides.

(2) Joining member In FIG. 6, the schematic sectional drawing of the joining member of this invention is shown. In addition, as a typical aspect of the joining member of the present invention, FIG. 6 shows a butt joining member. The joining member 30 of the present invention is obtained by friction stir welding of magnesium or a magnesium alloy 2 and an iron-based material 4, and an intermetallic compound layer 40 is formed at the joint interface between the magnesium or magnesium alloy 2 and the iron-based material 4. Is formed.

  The thickness of the intermetallic compound layer 40 is not particularly limited as long as the effects of the present invention are not impaired, but is preferably 1 μm or less. By making the thickness of the intermetallic compound layer 40 1 μm or less, embrittlement of the bonding member 30 can be suppressed.

  In addition, when the intermetallic compound layer 40 mainly composed of aluminum and iron is formed, an aluminum deficient layer having a reduced aluminum concentration is formed in the vicinity of the intermetallic compound layer 40 in the conventional bonding method. In 30, the aluminum deficient layer does not exist. Here, the aluminum-deficient layer means a region where the aluminum concentration is lower by about 1 atomic% or more than the aluminum concentration (atomic%) of the magnesium or magnesium alloy material 2.

  Magnesium or magnesium alloy material 2 is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known magnesium or magnesium alloy materials can be used. Further, the iron-based material 4 is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known iron-based materials can be used.

  As mentioned above, although typical embodiment of this invention was described, this invention is not limited only to these, Various design changes are possible and these design changes are all contained in the technical scope of this invention. It is.

Example 1
In the arrangement shown in FIG. 7, pure magnesium and low carbon steel (SPCC) plate materials are butted through a thin plate of AZ61 magnesium alloy, and a friction stir welding tool is inserted into the butted surface to perform friction stir welding (line bonding). gave. Pure magnesium is disposed on the retreat side, and low carbon steel (SPCC) is disposed on the advance side. Table 1 shows the compositions of pure magnesium, low carbon steel (SPCC) and AZ61 magnesium alloy. The size of the pure magnesium plate and the low carbon steel (SPCC) plate was 300 mm long × 75 mm wide × 2 mm thick, and the size of the AZ61 magnesium alloy thin plate was 300 mm long × 1.0 mm wide × 2 mm thick.

  Here, the friction stir welding tool is placed at a position where the side surface of the probe is inserted 0.5 mm into the low carbon steel (SPCC) plate, and the rotational speed and moving speed of the friction stir welding tool are 1500 rpm and 100 mm / 100 respectively. It was set to min. The friction stir welding was performed by the position control method of the friction stir welding tool, and the bottom surface of the probe portion of the friction stir welding tool was set to be substantially the same as the back surface of the material to be joined.

  As the friction stir welding tool, a cemented carbide (shoulder diameter: 12 mm, probe diameter: 4 mm, probe length: 1.9 mm) shown in FIG. Note that the bottom surface of the probe portion of the friction stir welding tool has a completely flat shape, and no screw or taper is formed on the side surface of the probe portion.

<< Example 2 >>
An execution joint 2 was obtained in the same manner as in Example 1 except that the width of the AZ61 magnesium alloy thin plate was 2.0 mm.

Example 3
An implementation joint 3 was obtained in the same manner as in Example 1 except that the width of the AZ61 magnesium alloy sheet was set to 3.0 mm.

Example 4
An execution joint 4 was obtained in the same manner as in Example 1 except that the AZ61 magnesium alloy thin plate was a pure aluminum (A1050) thin plate and the width was 0.05 mm.

Example 5
An implementation joint 5 was obtained in the same manner as in Example 4 except that the width of the pure aluminum (A1050) thin plate was 0.10 mm.

Example 6
An implementation joint 6 was obtained in the same manner as in Example 4 except that the width of the pure aluminum (A1050) thin plate was 0.15 mm.

Example 7
As an alternative to the AZ61 magnesium alloy sheet, except that pure aluminum (A1050) powder was filled into a 0.20 mm wide gap (a 0.20 mm wide spacer was inserted into the butt surface of the material to be joined to form a gap). In the same manner as in Example 1, an execution joint 7 was obtained.

Example 8
Example 8 was obtained in the same manner as Example 7 except that the width of the gap filled with pure aluminum (A1050) powder was 0.25 mm.

Example 9
An execution joint 9 was obtained in the same manner as in Example 7 except that the width of the gap filled with pure aluminum (A1050) powder was set to 0.30 mm.

Example 10
Further, an execution joint 10 was obtained in the same manner as in Example 2 except that a silver foil having a thickness of 0.01 mm was disposed at the interface between the AZ61 magnesium alloy thin plate and the pure magnesium plate.

≪Comparative example 1≫
Comparative joint 1 was obtained in the same manner as in Example 1 except that a thin plate of AZ61 magnesium alloy was not inserted into the butt surface of the material to be joined.

≪Comparative example 2≫
Similar to Comparative Example 1 except that the friction stir welding tool was arranged so that the side surface of the probe part was 0.1 mm from the butted surface to the pure magnesium side (the probe part was not inserted into the low carbon steel (SPCC) plate side). Thus, comparative joint 2 was obtained.

«Comparative Example 3»
A comparative joint 3 was obtained in the same manner as in Comparative Example 1 except that the friction stir welding tool was arranged so that the side surface of the probe part was substantially the same as the butted surface.

<< Comparative Example 4 >>
A comparative joint 4 was obtained in the same manner as in Comparative Example 1 except that the friction stir welding tool was disposed at a position where the probe side surface was inserted 0.1 mm into a low carbon steel (SPCC) plate.

<< Comparative Example 5 >>
Comparative joint 5 was obtained in the same manner as in comparative example 1 except that the friction stir welding tool was disposed at a position where the probe part side surface was inserted 0.25 mm into the low carbon steel (SPCC) plate.

<< Comparative Example 6 >>
A comparative joint 6 was obtained in the same manner as in Comparative Example 1 except that the friction stir welding tool was disposed at a position where the probe part side surface was inserted 1.0 mm into a low carbon steel (SPCC) plate.

<< Comparative Example 7 >>
A comparative joint 7 was obtained in the same manner as in Comparative Example 1 except that the friction stir welding tool was disposed at a position where the probe side surface was inserted 1.4 mm into a low carbon steel (SPCC) plate.

«Comparative Example 8»
A comparative joint 8 was obtained in the same manner as in Comparative Example 1 except that the friction stir welding tool was disposed at a position where the probe part side surface was inserted into a low carbon steel (SPCC) plate by 1.7 mm.

<< Comparative Example 9 >>
A comparative joint 9 was obtained in the same manner as in Comparative Example 1 except that the friction stir welding tool was disposed at a position where the probe part side surface was inserted 2.0 mm into the low carbon steel (SPCC) plate.

<< Comparative Example 10 >>
A comparative joint 10 was obtained in the same manner as in Example 1 except that a thin plate of AZ61 magnesium alloy was not inserted into the butted surface of the material to be joined, and an AZ31 magnesium alloy plate was used as the material to be joined instead of a pure magnesium plate. It was. Table 2 shows the composition of the AZ31 magnesium alloy.

<< Comparative Example 11 >>
A comparative joint 11 was obtained in the same manner as in Example 1 except that a thin plate of AZ61 magnesium alloy was not inserted into the butted surface of the material to be joined, and an AZ61 magnesium alloy plate was used instead of the pure magnesium plate as the material to be joined. It was.

<< Comparative Example 12 >>
A comparative joint 12 was obtained in the same manner as in Example 1 except that a thin plate of AZ61 magnesium alloy was not inserted into the butted surface of the material to be joined, and an AZ91 magnesium alloy plate was used as the material to be joined instead of a pure magnesium plate. It was.

<< Comparative Example 13 >>
Comparative Example 10 except that the friction stir welding tool is arranged so that the side surface of the probe part is 0.1 mm from the butted surface to the AZ31 pure magnesium alloy side (the probe part is not inserted into the low carbon steel (SPCC) plate side). In the same manner as above, a comparative joint 13 was obtained.

«Comparative example 14»
A comparative joint 14 was obtained in the same manner as in Comparative Example 10 except that the friction stir welding tool was arranged so that the probe portion side surface was substantially the same as the butted surface.

<< Comparative Example 15 >>
A comparative joint 15 was obtained in the same manner as in Comparative Example 10 except that the friction stir welding tool was disposed at a position where the probe side surface was inserted 0.1 mm into a low carbon steel (SPCC) plate.

<< Comparative Example 16 >>
A comparative joint 16 was obtained in the same manner as in Comparative Example 10 except that the friction stir welding tool was disposed at a position where the probe side surface was inserted 0.25 mm into the low carbon steel (SPCC) plate.

<< Comparative Example 17 >>
A comparative joint 17 was obtained in the same manner as in Comparative Example 10 except that the friction stir welding tool was disposed at a position where the probe part side surface was inserted 1.0 mm into the low carbon steel (SPCC) plate.

<< Comparative Example 18 >>
A comparative joint 18 was obtained in the same manner as in Comparative Example 10 except that the friction stir welding tool was disposed at a position where the probe part side surface was inserted 1.4 mm into a low carbon steel (SPCC) plate.

≪Comparative example 19≫
A comparative joint 19 was obtained in the same manner as in Comparative Example 10 except that the friction stir welding tool was disposed at a position where the probe portion side surface was inserted by 1.7 mm into a low carbon steel (SPCC) plate.

<< Comparative Example 20 >>
A comparative joint 20 was obtained in the same manner as in Comparative Example 10 except that the friction stir welding tool was disposed at a position where the probe part side surface was inserted 2.0 mm into a low carbon steel (SPCC) plate.

[Tensile test]
Using the joints obtained in the above Examples and Comparative Examples, a test piece shown in FIG. 9 was produced, and the tensile strength was measured. The test piece was cut out using an electric discharge machine so that the butted surface of the material to be joined was located at the center of the test piece. The specimen distance and width were 60 mm and 8 mm, respectively, and the specimen was polished until the thickness of the specimen became 1.5 mm in order to eliminate burrs and the like on the surface of the joint.

  Using a tensile tester (SHIMADZU Autograph AGS-X 10 kN), the tensile strength of the joint was measured at a crosshead speed of 3.6 mm / min. The tensile strengths of the working joints 1 to 3 and the comparative joint 1 are shown in FIG. When the thickness of the AZ61 magnesium alloy thin plate inserted into the joining interface is 1 mm and 2 mm (implemented joints 1 and 2), a significantly higher tensile strength is obtained than when the thin plate is not inserted (comparative joint 1). This is because aluminum contained in the AZ61 magnesium alloy thin plate was supplied to the bonding interface, and an intermetallic compound layer mainly composed of iron and aluminum was formed. When the thickness of the AZ61 magnesium alloy sheet is 3 mm, the AZ61 magnesium alloy sheet is not sufficiently agitated (divided), and relatively large fragments remain in the agitating part. It is thought that it fell. It should be noted that by optimizing the friction stirring conditions (such as the rotational speed and moving speed of the tool), the remaining pieces can be suppressed.

  The tensile strength of the implementation joints 4-6 and the comparison joint 1 is shown in FIG. When the thickness of the pure aluminum (A1050) thin plate inserted into the joining interface is 0.05 to 0.15 mm (implemented joints 4 to 6), higher tensile strength is obtained than when the thin plate is not inserted (comparative joint 1). It has been. This is because pure aluminum (A1050) thin plate aluminum was supplied to the bonding interface, and an intermetallic compound layer composed mainly of iron and aluminum was formed.

  The tensile strength of the implementation joints 7-9 and the comparative joint 1 is shown in FIG. When the width of the gap filled with pure aluminum (A1050) powder is 0.20 mm and 0.25 mm (implemented joints 7 and 8), higher tensile strength is obtained than when the powder is not used (comparative joint 1). ing. This is because pure aluminum (A1050) powder aluminum was supplied to the bonding interface, and an intermetallic compound mainly composed of iron and aluminum was formed.

  The tensile strength and joint efficiency of comparative joints 1 and 10 to 12 are shown in FIG. Tensile strength and joint efficiency are increased with an increase in the concentration of aluminum contained in the material to be joined (magnesium material). This is because, in addition to the formation of intermetallic compounds at the bonding interface by the aluminum contained in the material to be joined (magnesium material), the influence of the aluminum-deficient layer becomes relatively small when the aluminum concentration is high. .

  The tensile strength of the comparative joints 1-9 is shown in FIG. When the probe insertion amount into the low carbon steel (SPCC) plate is 0.1 to 1.4 mm (Comparative joints 1 and 4 to 7), relatively high joint strength is obtained. On the other hand, when the probe is not inserted into the low carbon steel (SPCC) plate (comparative joints 2 and 3), almost no strength is obtained. This seems to be mainly due to the fact that a new surface is not formed on the joint surface of the magnesium plate. Moreover, when the probe insertion amount to the low carbon steel (SPCC) plate is too large (comparative joints 8 and 9), the tensile strength is reduced. When the probe insertion amount into the low carbon steel (SPCC) plate is too large, the cutting amount of the magnesium plate by the probe is increased, and it is considered that the strength is reduced by the cutting pieces dispersed near the joining interface.

  The tensile strength of the comparative joints 10 and 13 to 20 is shown in FIG. When the probe insertion amount into the low carbon steel (SPCC) plate is 0.1 to 1.4 mm (comparative joints 10 and 13 to 18), relatively high joint strength is obtained. On the other hand, when the probe is not inserted into the low carbon steel (SPCC) plate (comparative joints 13 and 14), almost no strength is obtained. This seems to be mainly due to the fact that a new surface is not formed on the joint surface of the AZ31 magnesium alloy plate. Moreover, when the probe insertion amount to the low carbon steel (SPCC) plate is too large (comparative joints 19 and 20), the tensile strength is reduced. When the probe insertion amount into the low carbon steel (SPCC) plate is too large, the cutting amount of the AZ31 magnesium alloy plate by the probe is increased, and it is considered that the strength is reduced by the cutting pieces dispersed near the joining interface.

  The tensile strength of the implementation joint 2, the implementation joint 10, and the comparison joint 1 is shown in FIG. FIG. 16 is a comparison of joint strength when no insert material is used, when only AZ61 magnesium alloy sheet is used, and when AZ61 magnesium alloy sheet and silver foil are used, but joint strength is dramatically improved by using AZ61 magnesium alloy sheet. Furthermore, it turns out that joint strength has reached to the same level as a base material (pure magnesium) by using silver foil.

[Section observation of the joint]
In order to confirm the presence / absence of defect formation at the joint and the state of the joint interface, the cross section of the joint was observed in detail with an optical microscope, SEM-EDS (JEOL JSM-7001FA) and STEM-EDS (JEOL JEM-2100F). . The conditions for SEM observation were acceleration voltage: 15 kV and irradiation current: 10 A, and the acceleration voltage for STEM observation was 200 kV.

  A cross section polisher (JEOL IB-09020CP) that uses a argon ion beam and a shielding plate to polish the sample cross section was used for the preparation of the cross section sample for SEM observation. The acceleration voltage of the cross section polisher was 5.5 kV. Further, a focused ion beam (FIB) was used for preparing a sample for STEM observation, and an observation sample having a thickness of about 100 nm was prepared.

  An optical micrograph of the cross section of the joint portion of the comparative joint 1 is shown in FIG. Defects are not formed in the joint, and a joint interface between the magnesium plate and the low carbon steel (SPCC) plate is formed. In addition, formation of a clear defect was not observed also in other implementation joints and comparative joints. The results of SEM-EDS element mapping in the vicinity of the joint interface of the comparative joints 1, 10 and 11 are shown in FIGS. 18, 19 and 20, respectively. In the comparative joint 1, aluminum is not contained in the magnesium plate, which is a material to be joined, so that a clear intermetallic compound layer is not observed at the joining interface. On the other hand, an intermetallic compound layer mainly composed of aluminum and iron is formed at the joint interface between the comparative joints 10 and 11. Moreover, it can be seen from the higher magnification SEM-EDS element mapping that the aluminum concentration in the vicinity of the intermetallic compound layer is lowered (FIGS. 21 and 22).

  The results of STEM-EDS element mapping in the vicinity of the joint interface of the comparative joints 10 and 11 are shown in FIGS. 23 and 24, respectively. The aluminum concentration in the vicinity of the intermetallic compound layer formed on the bonding interface (magnesium alloy side) is remarkably reduced, and a region where a decrease of 1 atomic% or more is recognized compared with the aluminum concentration of the base material ( An aluminum deficient layer). In addition, the thickness of the intermetallic compound layer is extremely thin, and both the comparative joints 10 and 11 are 1 μm or less.

  With respect to the fracture surface of the comparative joint 10 after the tensile test, the results of SEM-EDS element mapping on the AZ31 magnesium alloy plate side and the low carbon steel (SPCC) plate side are shown in FIGS. 25 and 26, respectively. Aluminum (Mg) is detected on the fracture surface on the low carbon steel (SPCC) plate side, and iron (Fe) is hardly detected on the fracture surface on the AZ31 magnesium alloy plate side. It is thought that the layer broke.

  The results of SEM-EDS element mapping of the joint sections of the joints 1, 4 and 8 are shown in FIGS. 27, 28 and 29, respectively. It can be seen that no defects were observed in all the joints, and a good joint was obtained. Moreover, although the fracture | rupture position is shown with the dotted line, the fracture | rupture position is separated from the intermetallic compound layer of a joining interface. This is a result of suppressing the formation of the aluminum deficient layer by supplying aluminum from the metal layer inserted in the butt surface.

  FIG. 30 shows the result of SEM-EDS element mapping at a high magnification with respect to the cross section of the joint portion of the joint 1. Since the region where the oxides are arranged in a line is observed, it is considered that the fracture starting from the oxide occurred.

  FIG. 31 shows the result of high-magnification SEM-EDS element mapping with respect to the bonding cross section of the working joint 12 (the mapping region corresponds to the region where oxide was observed with respect to the working joint 1). In FIG. 31, a region having a high oxygen concentration is not recognized, and it can be seen that oxide discharge is achieved by melting due to the silver foil. In addition, although the same elemental mapping was performed also in other area | regions, the area | region where an oxide exists was not recognized.

[Fracture position observation of the joint]
In order to clarify the change of the breaking position by using the present invention, the breaking positions of the tensile test pieces were compared. In FIG. 32, the external appearance photograph of the test piece (Execution joint 2, Implementation joint 12, and Comparative joint 1) after a fracture is shown.

  Regarding the comparative joint 1 which does not use an insert material for joining, it breaks at the joining interface between the low carbon steel (SPCC) plate and the pure magnesium plate, which means that the strength of the joining interface is insufficient. is doing. On the other hand, the breaking position of the joint 2 using the AZ61 magnesium alloy thin plate as the insert material is shifted to the outer edge of the stirring portion (position where the oxide exists). Further, in the joint joint 12 using silver foil, the breaking position is completely shifted to the pure magnesium plate. These results show that a sufficient joint interface strength can be realized by using the friction stir welding method of the present invention, and in particular, eutectic reaction with constituent elements of the magnesium alloy material which is the material to be joined and / or the insert material. It shows that joint strength comparable to the base material strength of the material to be joined can be realized by using the second metal layer.

2 Magnesium or magnesium alloy material,
4 ... Iron-based materials,
6 ... metal layer,
10 ... friction stir welding tool,
12 ... Tool body,
14 ... Probe part,
16 ... shoulder part,
20 ... second metal layer,
30 ... joining member,
40: Intermetallic compound layer.

Claims (6)

A friction stir welding method between magnesium or a magnesium alloy material and an iron-based material,
The magnesium or magnesium alloy material and the iron-based material are brought into contact via a metal layer having an aluminum content higher than that of the magnesium or magnesium alloy material,
The side or bottom of the probe part of the friction stir welding tool is inserted 0.05 mm or more on the iron-based material side with respect to the contact surface of the metal layer and the iron-based material,
Butting the magnesium or magnesium alloy material and the iron-based material through the metal layer,
Place the iron-based material at a position where the rotational direction and the traveling direction of the friction stir welding tool are the same,
The width of the metal layer is 0.05 mm to approximately the diameter of the probe;
A friction stir welding method characterized by the above. The metal layer is a magnesium alloy layer;
The friction stir welding method according to claim 1. Inserting the side surface of the probe portion 0.1 to 1.5 mm on the iron-based material side with respect to the contact surface of the metal layer and the iron-based material;
The friction stir welding method according to claim 1 or 2 . The magnesium alloy material is AZ31 magnesium alloy material,
The metal layer is an AZ61 magnesium alloy layer or an AZ91 magnesium alloy layer;
The friction stir welding method according to any one of claims 1 to 3 . Forming a second metal layer that undergoes a eutectic reaction with constituent elements of the metal layer and / or the magnesium alloy material at a contact interface between the metal layer and the magnesium alloy material;
The friction stir welding method according to any one of claims 1 to 4 . The second metal layer comprises silver or zinc;
The friction stir welding method according to claim 5 .