JP4450728B2 - Friction stir welding method - Google Patents

Description

  The present invention relates to a friction stir welding tool, a friction stir welding backing, and a friction stir welding method used for friction stir welding of aluminum or an aluminum alloy material (hereinafter collectively referred to as aluminum) having a curved surface.

  Aluminum materials are being used for structural materials used in transportation equipment such as vehicles, automobiles, motorcycles, and bodywork materials for the purpose of weight reduction. When manufacturing these structural materials using aluminum materials, when joining the aluminum materials, conventionally, arc welding such as MIG and TIG, laser welding, and mechanical joining methods such as rivets have been used. . On the other hand, structural materials such as floor materials and roof materials, and interior / exterior materials, etc., use an aluminum plate having a curved surface in order to improve the rigidity of the surface or to provide design properties. Various methods such as welding and riveting can be applied to join the aluminum plate to the skeleton member, but the surface aesthetics, good touch when touched, or low air resistance. Etc. are required, it is necessary to adopt a joining method that does not leave a joining mark on the surface.

  In recent years, friction stir welding has been developed as a new joining method. As shown in Japanese Patent No. 2792233 (Patent Document 1), a tool is inserted into a material to be joined and stirred in a solid state. Therefore, there is an advantage that there is little thermal influence around the joint. This friction stir welding is superior to the welding method using arc and rivet because there is no bonding mark on the back surface depending on the construction conditions. FIG. 4 is a front view showing a conventional friction stirring tool. A cylindrical main body 1 is supported by a friction stir welding apparatus and is driven to rotate. A pin 2 is provided at the center of the surface of the shoulder portion 3 of the main body 1, and the pin 2 and the member to be joined are driven by rotating the main body 1 and inserting the rotating pin 2 into the member to be joined. The members to be joined are joined by the frictional heat generated between them. At this time, the shoulder portion 3 needs to press the member to be joined, and the surface of the shoulder portion 3 is recessed in a conical shape with the pin 2 as the center.

  Thus, as a technique for performing friction stir welding from the inside in order to beautifully finish the outer surface of the member to be joined having a curved surface, there is one described in JP-A-11-267858 (Patent Document 2). In the friction stir welding method described in this document, by using the friction stir welding tool shown in FIG. 4, the joint portion of the concavely curved inner surface is locally flattened to form the shoulder portion shown in FIG. 4. 3 allows the use of planar tools.

  However, in the friction stir welding, the tool is inserted into the material to be joined with a high pressing force, so that a joining mark due to the shoulder portion of the tool remains. Since the joint marks are in a state where sharp irregularities are carved, when the joined member is used for a transport aircraft structural material, if the joint is repeatedly stressed by vibration during use, the joint mark is sharp. Cracks may occur from the unevenness, and the fatigue strength may be lowered.

  In order to prevent this, a technique is known in which a thick part is provided in advance at the end of the material to be joined, and after the tool is inserted into the thick part and friction stir welding is performed, the surface of the thick part is deleted ( Patent Document 3: JP-A-10-216964).

Japanese Patent No. 2792233 JP-A-11-267858 JP-A-10-216964

  However, in the conventional method described in Patent Document 2, since the horizontal portion is provided, the weight of the joining member becomes heavy. In particular, when a member having a relatively small radius of curvature is joined, the unit weight of the member to be joined is low, so that the proportion (influence) of weight increase in the member to be joined by providing the horizontal portion increases. . Furthermore, when a flat surface is partially provided on the inner surface of the member to be joined, it is necessary to use a material that can be freely designed with a partial material thickness, such as an extruded profile, and an inexpensive plate is used. Can not do it.

  Further, as in the conventional method described in Patent Document 3, a thick portion is provided in advance at the end of the material to be joined, and after inserting a tool into the thick portion and performing friction stir welding, the surface of the thick portion is In the method of deleting, there is a problem that the number of steps increases and the joining cost becomes high.

  The present invention has been made in view of such problems, and when the materials to be welded have curved surfaces, and these surfaces need to be friction stir welded to each other, there is no bonding trace left on the materials to be joined, An object of the present invention is to provide a friction stir welding tool, a friction stir welding backing, and a friction stir welding method that can be joined with a beautiful surface without causing a significant increase in weight and avoiding an increase in joining cost. To do.

In the friction stir welding method according to the present invention, after the plate-like members to be joined are curved and joined to each other with the concave curved surface provided on the inner surface and the convex curved surface provided on the outer surface, A friction stir tool is disposed on the inner surface side, and a backing material having a concave curved surface matching the outer surface is disposed on the outer surface side of the bonded member on the back surface of the bonded member, and the friction stirring tool is a rotating main body. those having a part, and the shoulder portion is a convex curved surface provided on the joint member side of the main body to match the concave surface of the inner surface of the workpieces, and a pin provided at the center of the shoulder portion And the members to be joined are joined by rotating the main body portion and inserting the pins into the members to be joined.

Furthermore, another friction stir welding method according to the present invention includes a main body that rotates after a plate-like member to be welded is curved so that the members to be joined having a concave curved surface on the inner surface and a convex curved surface on the outer surface are brought together. Part, a shoulder part provided on the joined member side of the main body part, and a pin provided at the center of the shoulder part, the surface of the shoulder part being aligned with the concave curved surface of the inner surface of the joined member A friction stir welding tool that is a convex curved surface that is disposed on the inner surface side of the member to be joined, and a friction stir welding backing having a concave curved surface that matches the convex curved surface of the outer surface of the member to be joined. was placed on the back surface of the butt portion of member, the said pin by rotating the main body portion is inserted into the bonded member, the convex curved surface of the shoulder portion joining the workpieces together, and friction stir welding portion And the surrounding area gently Characterized by bonding to contiguous. Note that the thus smoothly continuous, no sharp irregularities due shoulder portion of the tool, and means that the rectangular-shaped step has not occurred in the cross section.
Because it is.

  According to the present invention, by adapting the shoulder portion of the tool to the curved shape on the inner surface side of the member to be joined, a frictional force can be efficiently generated, and joining can be performed with a minimum necessary pressing force. Thereby, even if it does not provide the special thick part as described in patent document 1, a thin member can be joined. Therefore, the present invention can be applied not only to butt joining of plate materials but also to lap joining of plate materials, butt joining of plate materials and extruded shape members, or lap joining. For this reason, various joints by friction stir welding can be applied to locations where surface side surface finishing is required.

  Also, by adapting to the curved shape on the inner surface side, the agitation part is optimized, and unnecessary contact between the tool and the joining material is reduced. Generation and thermal deformation of the workpiece can also be suppressed. Thereby, a high quality bonded article can be obtained. Furthermore, it is possible to prevent a decrease in the pressing pressure generated from the space between the workpiece and the tool, and to suppress bonding defects caused by this.

  Furthermore, according to the present invention, since a convex curved surface is provided in the shoulder portion of the tool, there is no surface level difference in the material to be joined after friction stir welding, and even when this is used for a transportation machine or the like. Cracks are less likely to occur. Therefore, the present invention can be applied not only to butt joining of plate materials but also to lap joining of plate materials, butt joining of plate materials and extruded shape members, or lap joining. For this reason, various joints by friction stir welding can be applied to places where vibration is applied during use and high fatigue strength is required, such as a transport structural member.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a front view showing a friction stir welding tool according to a first embodiment of the present invention. The main body 1 supported by the rotary drive device has a cylindrical shape, a shoulder 4 is provided at the tip of the main body 1, and a pin 2 is provided at the center of the shoulder 4. In the present embodiment, the shoulder portion 4 has a hemispherical curved surface with a curved surface.

  Next, a method for performing lap joining using this friction stir tool will be described. FIG. 2 is a cross-sectional view showing this lap joining method. In the present embodiment, the plate member 12 is bonded to the skeleton member 10, and both are aluminum alloy materials. The skeleton member 10 is formed by extrusion, for example. A curved portion 11 that curves outward is formed at the upper end of the skeleton member 10, the curved portion at the tip of the plate material 12 is overlapped on the outer surface of the curved portion 11, and a backing metal 14 is placed on the back surface of the plate material 12. Arrangement and friction stir welding of the skeleton member 10 and the plate material 12 from the inside of the curved portion 11 using the friction stir tool shown in FIG.

  In this case, first, the tool is rotationally driven, and the pin 2 at the tip is inserted into the curved portion 11 of the skeleton member 10 and further inserted to the plate material 12. As a result, the skeleton member 10 and the plate member 12 are joined to each other around the portion where the pin 2 is inserted due to frictional heat between the tool and the member to be joined. The tool is moved in the longitudinal direction (extrusion direction) of the skeleton member 10 while pressing the curved portion 11 toward the plate member 12 with the shoulder portion 4, and the skeleton member 10 and the plate member 12 are rubbed along the longitudinal direction. Stir and join.

  In the present embodiment, the surface of the shoulder portion 4 of the tool is a convex curved surface, and can be brought into contact with or in close contact with the concave curved surface of the curved portion 11 of the member to be joined. In addition, it is possible to easily join the curved joining member without forming a special flat portion. Thereby, it can join, without leaving a joining trace on the outer surface of a to-be-joined member.

  The present invention is characterized in that the surface of the shoulder portion has a convex curved surface, and the convex curved surface of the surface of the shoulder portion 4 is curved into a convex shape with a radius of curvature substantially equal to the radius of curvature of the concave curved surface of the member to be joined. It is desirable that That is, it is desirable that the convex curved surface on the surface of the shoulder portion 4 be curved in a convex shape with a shape matched with the concave curved surface of the member to be joined. In this way, by adjusting the surface shape of the shoulder portion 4 of the tool to the curved surface shape on the inner surface side of the members to be joined (the curved portion 11 and the plate material 12), the stirring portion is optimized, and the tool and the joining material are unnecessary. Therefore, the occurrence of burrs and thermal deformation of the workpiece that occur when the inner circumferential curved surface is friction stir welded with a conventional tool can be suppressed. Thereby, a high quality bonded article can be obtained. Furthermore, it is possible to prevent a decrease in the pressing pressure generated from the space between the workpiece and the tool, and to suppress joint defects caused by this. Note that the portion of the convex curved surface on the surface of the shoulder portion 4 that is curved with a curvature radius substantially equal to the curvature radius of the concave curved surface of the member to be joined does not have to be the entire surface of the shoulder portion 4. In the region contributing to the friction stir welding, the above-described effect can be obtained by adapting to the curved surface shape of the inner surface side of the member to be joined in this way.

  Next, a second embodiment of the present invention in which the present invention is applied to the butt joint will be described with reference to FIG. As shown in the cross-sectional view of FIG. 3, the plate member 13 of the member to be joined whose cross-sectional shape is curved in a ¼ arc shape at the joint portion is abutted, and a backing metal 14 is arranged on the curved outer side, and this implementation is performed on the curved inner side. The tool of the form is arranged, and the pin 2 is inserted into the joint portion of the plate member 13 while rotating the tool. Then, the tool is moved along the abutting end surface while pressing the plate 13 against the backing metal 14 with this tool.

  In the present embodiment, the backing metal 14 that curves in the same shape as the curved surface of the curved outer surface of the plate material 13 is applied to the curved outer surface of the plate material 13, the tool shoulder portion 4 is applied to the curved inner surface of the plate material 13, and the tool Since the plate members 13 are abutted and bonded to each other while being sandwiched between the backing metal 14, the shape after bonding, particularly the surface shape of the bonded portion of the outer surface of the plate member 13 becomes very beautiful.

  Next, a third embodiment of the present invention will be described with reference to FIGS. The friction stir welding tool used is the same as that shown in FIG. FIG. 4 is a cross-sectional view showing the friction stir welding backing 20 according to the embodiment of the present invention. A concave curved surface 21 that matches the convex curved surface of the shoulder 4 of the friction stir tool is formed at the center of the surface of the backing 20, and the surrounding surface 22 is a flat surface. However, it continues smoothly without any steps.

  Next, a method for performing butt joining using this friction stir tool and backing will be described. FIG. 5 is a cross-sectional view showing this butt joining method. In the present embodiment, the backing material 20 is disposed on the back surface of the abutting portion such that the plate material 23 as a member to be joined is abutted and the concave curved surface 21 of the backing 20 and the convex curved surface of the plate material 23 are overlapped. Then, a friction stir welding tool is disposed on the surface side of the abutting portion, and the pin 2 is inserted into the joint portion of the plate member 23 while rotating the tool. Then, the tool is moved along the butt end face while pressing the plate member 23 against the backing 20 with this tool. As a result, the plate members 23 are joined by friction stir welding.

  In the present embodiment, the plate members 23 are sandwiched between the surface (convex curved surface) of the shoulder portion 4 of the tool and the backing 20 having the concave curved surface 21 aligned with the surface of the shoulder portion 4. Since butt joining is performed, the shape after joining, in particular, the surface shape of the back surface of the joint portion of the plate member 23 is beautiful, and further, no step is generated on the back surface of the joint portion. Therefore, it is excellent in fatigue strength.

  The present invention is extremely useful for friction stir welding of curved members to be joined.

It is a front view which shows the friction stirring tool which concerns on embodiment of this invention. It is sectional drawing which shows the lap | joining method of 1st Embodiment of this invention using this tool. It is sectional drawing which shows the butt-joining method of 2nd Embodiment of this invention using this tool. It is sectional drawing which shows the backing for friction stir welding of 3rd Embodiment of this invention. It is sectional drawing which shows the butt-joining method of 3rd Embodiment of this invention using this tool. It is a front view which shows the conventional friction stirring tool.

Explanation of symbols

1: Body part 2: Pin 3: Shoulder part (plane)
4: Shoulder (curved)
10: skeletal member 12, 13, 23: plate material 14: backing metal 20: backing 21: concave curved surface 22: surface

Claims (2)

After the plate-like members to be joined are curved and concave surfaces are provided on the inner surface, and the members to be joined provided with a convex curved surface on the outer surface, the friction stir tool is disposed on the inner surface side of the members to be joined, A backing material having a concave curved surface matching the outer surface is disposed on the outer surface side of the member to be bonded, and the friction stir tool includes a rotating main body, and a member to be bonded of the main body. and the shoulder portion is a convex curved surface provided on the side matching the concave surface of the inner surface of the members to be joined, which has a pin provided at the center of the shoulder portion, said by rotating said main body portion A friction stir welding method for joining the members to be joined by inserting a pin into the members to be joined. A plate-shaped member to be bent is provided on the side of the body to be joined and the main body that rotates after abutting the members to be joined having a concave curved surface on the inner surface and a convex curved surface on the outer surface. A friction stir welding tool including a shoulder portion and a pin provided at the center of the shoulder portion, the surface of the shoulder portion being a convex curved surface that matches the concave curved surface of the inner surface of the member to be joined. disposed on the inner surface side of the joint member, said friction stir welding backing having a concave surface matching the outer surface convex curved surface of the workpieces, and placed the on the back of the butted portion of the workpieces, said main body portion And the pins are inserted into the members to be joined, the members to be joined are joined by the convex curved surface of the shoulder, and the friction stir welded portion and the surrounding portion are joined smoothly. Ma characterized by Stir joining method.

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