JP6171692B2 - Friction stir spot welding method - Google Patents

Description

  The present invention relates to a friction stir spot joining method suitable for joining metal materials having high high-temperature strength.

  Conventionally, a friction stir spot joining method has been proposed as a method for joining metal materials.

  For example, in the friction stir spot joining method described in Patent Document 1, a cylindrical pin member of a rotary tool is first brought into contact with the surface of the upper metal plate, and the pin member is rotated in that state. Thereby, the surface vicinity of the upper metal plate is softened by frictional heat, and a plastic flow part is formed. Next, the pin member is pushed down and increases so that the plastic flow part extends to the lower metal plate. Thereafter, the pin member is pulled out, the plastic flow of the plastic flow portion is stopped, and the two metal plates are joined.

  According to the friction stir spot joining method, generally, heat input during joining can be reduced, and the metal structure can be refined, so that distortion of the joining material can be suppressed and excellent mechanical properties can be obtained. Due to such advantages, the friction stir spot joining method is employed in the manufacturing process of transportation equipment (automobiles, railway vehicles, aircrafts, etc.) and electrical products.

JP 2012-196681 A

  By the way, in transportation equipment, electrical products, and the like, metal materials with high high-temperature strength may be used depending on their functions and applications. It is required to use the friction stir spot joining method also in joining such high-temperature strength metal materials. However, as a result of various studies by the present inventors, it is difficult to expose and contact the new surface at the boundary surface of the metal material to be joined when joining a metal material having a high temperature strength by the conventional friction stir spot joining method. I understood that. For this reason, it has been found that a strong metal bond cannot be obtained and sufficient bonding strength cannot be obtained.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a friction stir spot joining method capable of obtaining sufficient joining strength even when joining a metal material having high high-temperature strength. .

  As a result of intensive studies by the present inventors, when a metal material having high temperature strength is joined by the friction stir spot joining method, an insert material is sandwiched between the metal materials to be joined (hereinafter referred to as a base material). Was found to be important. Further, it has been found that the insert material is made of a metal material different from the base material and has a lower melting point than the base material. Specifically, by melting the insert material between the base materials at the time of joining, the new surface of the insert material can be easily exposed in a wide range between the base materials, and the new surface can be easily contacted with the base material. Can be made. Thereby, base materials can be indirectly adhered in a wide range via an insert material. Further, when the base material is joined, a part or all of the melted insert material is discharged to the outside of the joined portion. At this time, impurities (for example, oxides) that inhibit diffusion bonding existing in the surface layer portion of each base material are discharged together with the insert material. Thereby, the surface layer parts from which the impurities are discharged can be brought into contact with each other, and the base materials can be more firmly diffusion-bonded. As a result, sufficient bonding strength can be obtained even when metal materials having high high-temperature strength are bonded.

  This invention is made | formed based on said knowledge, and makes the summary the following friction stir spot joining method.

(1) The first member made of a metal material, the insert material, and the second member are overlapped, and the first member is pressed into the second member through the insert material while rotating the pin portion of the rotary tool, and the friction A friction stir spot welding method in which the first and second members are agitated while melting the insert material by heat, wherein at least one of the first and second members is 800 ° C. and It consists of a metal material having a tensile strength at a strain rate of 10 ⁻³ s ⁻¹ of 100 MPa or more, and the insert material is different from the first and second members and has a lower tensile strength than the metal material of 100 MPa or more. A friction stir spot joining method comprising a metal material having a melting point.

  (2) The friction stir spot joining method according to (1), wherein the first and second members are each made of steel, and the melting point of the insert material is 1100 ° C. or lower.

  (3) The friction stir spot joining method according to (1), wherein the first and second members are each made of steel, and the melting point of the insert material is equal to or lower than the A3 transformation point of the steel.

  (4) The friction stir spot joining method according to (1), wherein the first and second members are each made of steel, and the melting point of the insert material is equal to or lower than the A1 transformation point of the steel.

  According to the present invention, sufficient bonding strength can be obtained even when a metal material having high high-temperature strength is bonded.

The figure for demonstrating the friction stir spot joining method which concerns on one Embodiment of this invention. The figure for demonstrating the friction stir spot joining method which concerns on one Embodiment of this invention.

Hereinafter, the friction stir spot joining method of the present invention will be described. The present invention is suitably used for joining metal materials having a tensile strength of 100 MPa or more at 800 ° C. and a strain rate of 10 ⁻³ s ⁻¹ .

  1 and 2 are views for explaining a friction stir spot welding method according to an embodiment of the present invention. As shown in FIG. 1A, in the present embodiment, for example, as a preliminary process, the first member 1 and the second member 2 are overlapped with each other so that the insert material 3 is sandwiched therebetween, and friction stir spot welding is performed. Place on the support 4 of the device. Then, the rotary tool 5 of the friction stir spot welding device is disposed above the first member 1, the second member 2, and the insert material 3. In this embodiment, the rotary tool 5 includes a columnar shoulder portion 5a and a columnar pin portion 5b protruding downward from the shoulder portion 5a. In addition, since the friction stir spot joining method of the present invention can be carried out using various known friction stir spot joining apparatuses, detailed description of the friction stir spot joining apparatus is omitted.

The first member 1 and the second member 2 are made of a metal material having a tensile strength of, for example, 800 MPa and a strain rate of 10 ⁻³ s ⁻¹ of 100 MPa or more. Examples of the metal material of the first member 1 and the second member 2 include carbon steel, martensitic steel, or titanium having a C content of 0.3% (or 0.5%) or more by mass%. Can do. In addition, the 1st member 1 and the 2nd member 2 may be formed from the same metal material, and may be formed from a different metal material.

  The thickness of the insert material 3 is preferably 30 μm to 500 μm, and more preferably 30 μm to 150 μm. The insert material 3 is made of a metal material different from that of the first member 1 and the second member 2. The melting point of the insert material 3 is lower than the melting points of the first member 1 and the second member 2. When the first member 1 and the second member 2 are each made of steel, for example, a metal material having a melting point of 1100 ° C. or lower is used as the insert material 3, and preferably a metal material having a melting point of A3 transformation point or lower of the steel. More preferably, a metal material having a melting point equal to or lower than the A1 transformation point of the steel is used.

  As the metal material of the insert material 3, Al, Zn, Cu, Sn, Mg, or the like may be used, and alloys such as Ni, Cu, Sn, and Al (Ni, Cu, Sn, Al, etc. are used as a base material). Brazing material) may be used. In the present embodiment, the metal material of the insert material 3 is appropriately selected according to the metal material of the first member 1 and the second member 2. Specifically, for example, a metal material that does not cause liquid metal embrittlement (LME) in the first member 1 and the second member 2 is preferably selected as the metal material of the insert material 3. In addition, as the metal material of the insert material 3, for example, a metal material that hardly forms a brittle intermetallic compound with the first member 1 and the second member 2 is preferably selected. When the first member 1 and the second member 2 are each made of steel, for example, Al, an Al-based brazing material, a Ni-based brazing material, or a Cu-based brazing material is used as the metal material of the insert material 3.

  Next, as shown in FIG. 1B, for example, as a stirring step, the tip of the pin portion 5b is pressed against the upper surface of the upper first member 1 while rotating the rotary tool 5 (pin portion 5b). At this time, a part of the first member 1 is softened by the frictional heat generated at the contact portion between the first member 1 and the pin portion 5b, and the plastic flow portion 6 is formed. The rotational speed of the rotary tool 5 is set to 3000 rpm, for example, and the pressing force is set to 8 kN, for example.

  In the stirring step, as shown in FIG. 2A, the rotary tool 5 (pin part 5 b) is pushed down while rotating, and the pin part 5 b is moved from the first member 1 through the insert member 3 to the second member 2. Press fit. In the present embodiment, the rotary tool 5 is pushed down until the bottom surface of the shoulder portion 5a is positioned at a height substantially equal to the upper surface of the first member 1. Thereby, the plastic flow part 6 expands to the 2nd member 2, and the metal material of the 1st member 1 and the 2nd member 2 is stirred by the pin part 5b in the plastic flow part 6. FIG. At this time, a part of the insert material 3 is melted by frictional heat generated by the rotation of the pin portion 5b. Further, a part or all of the melted insert material 3 is discharged to the outside of the plastic flow part 6 by the pressing force of the rotary tool 5.

  Finally, as shown in FIG. 2B, for example, as a stopping step, the pin portion 5b is pulled out from the first member 1 and the second member 2, and the plastic flow of the metal material of the first member 1 and the second member 2 is performed. Stop. Thereby, the joining part 7 which joins the 1st member 1 and the 2nd member 2 is formed. Thereafter, the above-described processing (the processing shown in FIG. 1B and FIG. 2) is repeated for other portions of the first member 1 and the second member 2, and predetermined positions of the first member 1 and the second member 2 are determined. Are sequentially joined.

  As described above, in the present embodiment, the insert member 3 having a lower melting point than the first member 1 and the second member 2 is provided between the first member 1 and the second member 2. And a part of insert material 3 fuse | melts in a stirring process. In this case, in a wide range between the first member 1 and the second member 2, the new surface of the insert material 3 can be easily exposed, and the new surface can be easily exposed to the first member 1 and the second member 2. Can be contacted. Thereby, the 1st member 1 and the 2nd member 2 can be stuck closely in the wide range via the insert material 3. FIG. Further, part or all of the melted insert material 3 is discharged to the outside of the joint portion 7 (plastic fluid portion 6) by the pressing force from the rotary tool 5. At this time, impurities (for example, oxides) that inhibit diffusion bonding existing in the surface layer portion of the first member 1 and the surface layer portion of the second member 2 are discharged together with the insert material 3. In this case, the first member 1 and the second member 2 can be more firmly diffusion-bonded by directly contacting the surface layer portion of the first member 1 from which the impurities have been discharged and the surface layer portion of the second member 2. As a result, sufficient bonding strength can be obtained.

In the above-described embodiment, both the first member 1 and the second member 2 are made of a metal material having a high temperature strength (a metal material having a tensile strength at 800 ° C. and a strain rate of 10 ⁻³ s ⁻¹ of 100 MPa or more). As described above, the present invention can be used even when only one of the first member 1 and the second member 2 is made of a metal material having high high-temperature strength. In this case, the insert material 3 is formed of a metal material having a melting point lower than that of the metal material having a high high-temperature strength.

  Although the case where the 1st member 1 and the 2nd member 2 were joined was demonstrated in the above-mentioned embodiment, this invention can be utilized also when joining three or more members piled up and down.

  According to the present invention, sufficient bonding strength can be obtained even when a metal material having high high-temperature strength is bonded.

DESCRIPTION OF SYMBOLS 1 1st member 2 2nd member 3 Insert material 4 Support part 5 Rotary tool 5a Shoulder part 5b Pin part 6 Plastic flow part 7 Joint part

Claims (4)

The first member made of a metal material, the insert material and the second member are overlapped, and the pin portion of the rotary tool is rotated to press-fit from the first member to the second member through the insert material, and the friction heat A friction stir spot joining method for spot joining by stirring the first and second members while melting an insert material,
At least one of the first and second members is made of a metal material having a tensile strength at 800 ° C. and a strain rate of 10 ⁻³ s ⁻¹ of 100 MPa or more,
The insert material, Ri Do from the low melting point metal material than unlike the first and second members and the tensile strength of the metal material described above 100 MPa,
The insert material Ru der brazing material, the friction stir spot joining method. The first and second members are each made of steel;
The friction stir spot joining method according to claim 1, wherein the melting point of the insert material is 1100 ° C. or less. The first and second members are each made of steel;
The friction stir spot joining method according to claim 1, wherein the melting point of the insert material is equal to or lower than the A3 transformation point of the steel. The first and second members are each made of steel;
The friction stir spot joining method according to claim 1, wherein the melting point of the insert material is equal to or lower than the A1 transformation point of the steel.

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