JP2020063801A - Fastening method of cast aluminum member - Google Patents

Abstract

To provide a fastening method of a cast aluminum member which improves dimension accuracy by suppressing thermal deformation, and can suppress the lowering of the rigidity of a fastening-objective member when mechanically fastening the cast aluminum member and the other member.SOLUTION: This fastening method of a cast aluminum member has a surface treatment step (step S1) and a fastening step (step S2). In the step S1, surface treatment is applied by pushing in a mechanical fastening-scheduled point fastened with the other member in a cast member of aluminum or an aluminum alloy while rotating a friction agitation tool. Here, a push-in amount of the friction agitation tool in the step S1 is at a level for removing a chill layer of a surface of the cast member. In the step S2, mechanical fastening means fastens the cast member and the other member in the mechanical fastening point after superimposing them on each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for fastening an aluminum casting member.

  Patent Document 1 discloses a method of fastening two members (workpieces) using a self-piercing rivet. The self-piercing rivet used in the method described in Patent Document 1 has a solid shaft portion whose front end surface is a flat surface, and a head portion having a diameter larger than that of the shaft portion. The shape is gradually increased. Further, in the method described in Patent Document 1, the self-piercing rivet is rocked so that the shaft portion is brought into contact with the work while being inclined, and the head draws a circle around the tip of the shaft portion in a plan view. I am driving while moving.

Japanese Patent No. 3865305

  As described above, in the method described in Patent Document 1, the self-piercing rivet is pushed while rotating when the two members are fastened. However, when the method described in Patent Document 1 is applied and the aluminum casting member is overlaid on the base material and the two members are fastened with the self-piercing rivet, the heat treatment is performed to increase the strength of the aluminum casting, and then the fastening is performed. Is customary.

  Further, this heat treatment deteriorates the dimensional accuracy due to the deformation of the aluminum casting member during the heat treatment, and increases the cost of correction required due to the heat deformation. In addition, the inventor considered adopting a mechanical fastening method using a flow drill screw, but unless the member on the side that strikes the screw is thin, usually, in order to perform concave processing in advance at the place where the screw is strike, after fastening, The area around the recess becomes a stress concentration area. When an aluminum cast member is used as a work, this stress concentration point is likely to become a fracture starting point.

  Therefore, an object of the present invention is, when mechanically fastening an aluminum casting member and another member, to suppress thermal deformation, improve dimensional accuracy, and suppress a decrease in strength of a fastening target member. To provide a fastening method.

  A method for fastening an aluminum casting member according to an aspect of the present invention for achieving the above object is to push a machine fastening scheduled portion with another member in a casting member made of aluminum or aluminum alloy while rotating a friction stir tool. A surface treatment step of applying a surface treatment, and a fastening step in which the casting member and the other member are superposed, and then the mechanical fastening means fastens the casting member and the other member at a machine fastening location, And the amount of pushing of the friction stir tool in the surface treatment step is such that the chill layer on the surface of the casting member is removed.

  In the method for fastening an aluminum casting member according to this aspect, when mechanically fastening the aluminum casting member to another member, a friction stir tool is used, and the amount of the chill layer on the surface of the aluminum casting member is removed as a surface treatment. Just push it in and then tighten the machine. Therefore, according to the fastening method for an aluminum casting member according to this aspect, it is possible to suppress thermal deformation, improve dimensional accuracy, and suppress a decrease in strength of a fastening target member.

  According to the present invention, when mechanically fastening an aluminum casting member and another member, it is possible to suppress thermal deformation, improve dimensional accuracy, and suppress a decrease in strength of a fastening target member. A method can be provided.

It is a flow figure for explaining an example of a fastening method of an aluminum casting member concerning one embodiment of the present invention. It is a perspective view which shows one structural example of the equipment for FSP (friction process) used with the fastening method of FIG. It is a III-III sectional view of FIG. It is sectional drawing of the aluminum casting member locally modified by the equipment of FIG. 2 and FIG. It is a figure which shows an example of the cross-sectional photograph in the surface vicinity of the aluminum casting. It is sectional drawing for demonstrating an example of a mode that a local reforming is performed with the equipment of FIG. 2 and FIG. It is sectional drawing for demonstrating an example of a mode that local modification | amendment is performed by the equipment which did not have the protrusion part in the rotary tool in the equipment of FIG. 2 and FIG. It is sectional drawing for demonstrating an example of the mechanical fastening method at the time of fastening with another member by SPR (self-piercing rivet) with respect to the aluminum casting member which is not modified. FIG. 9 is a partial cross-sectional perspective view showing a state where the machine is fastened by the machine fastening method of FIG. 8. FIG. 4 is a cross-sectional view for explaining a specific example of a mechanical fastening method when fastening is performed with another member by SPR in the FSP reforming portion at the fixed point in FIG. 3. It is a figure which shows the result of performing the mechanical fastening by SPR after a continuous friction process, the result of performing mechanical fastening by SPR after pressurization and heating, and the result of performing mechanical fastening by SPR without modification as a comparative example. . It is sectional drawing for demonstrating an example of the mechanical fastening method by FDS (flow drill screw). FIG. 13 is a partial cross-sectional perspective view showing the state of mechanical fastening by the method of FIG. 12. It is sectional drawing for demonstrating the specific example of a mechanical fastening method at the time of fastening by FDS with respect to the modification part in FIGS. It is sectional drawing for demonstrating the alternative example of the fastening method of the aluminum casting member which concerns on one Embodiment of this invention. FIG. 16 is a partial cross-sectional perspective view showing the state of mechanical fastening by the method of FIG. 15. It is sectional drawing for demonstrating the other alternative example of the fastening method of the aluminum casting member which concerns on one Embodiment of this invention. FIG. 18 is a cross-sectional view showing a state in which the machine is fastened by the method of FIG. 17.

  Hereinafter, a method for fastening an aluminum casting member (hereinafter, aluminum casting member) according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart for explaining an example of a method for fastening an aluminum casting member according to this embodiment.

  As shown in FIG. 1, the method for fastening an aluminum casting member according to the present embodiment (hereinafter referred to as the present fastening method) is a method for mechanically fastening an aluminum casting member and another member by superposing the surface treatment in advance. After that (step S1), mechanical fastening is performed (step S2). Here, the aluminum casting member refers to a casting member made of aluminum or an aluminum alloy, and its component does not matter as long as aluminum is included. In addition, the components of other members are not limited, but they can be generally made of metal.

  In step S1 (surface treatment step), the aluminum cast member is subjected to surface treatment by pushing a planned machine fastening portion with another member while rotating the friction stir tool. Here, the pushing amount of the friction stir tool in step S1 is set to such an amount that the chill layer on the surface of the aluminum casting member is removed. In step S2 (fastening step), the aluminum casting member and the other member are superposed, and then the machine fastening means fastens the aluminum casting member and the other member at the machine fastening location. Here, the machine fastening means does not matter.

  As described above, in the present fastening method, the property of the member is locally changed (modified) by the treatment using the friction stir tool (hereinafter, FSP: friction process), and then the mechanical fastening is performed. In other words, it can be said that this fastening method is a mechanical fastening method for an aluminum casting member that also uses local modification of the aluminum casting member by a friction process. Note that this friction process can also be referred to as a friction stirring process.

Next, a specific example of this fastening method will be described with reference to the drawings starting from FIG.
First, with reference to FIGS. 2 to 5, equipment and processing conditions used in a friction process (FSP), and a state of local modification of an aluminum casting member will be described with examples. FIG. 2 is a perspective view showing a configuration example of equipment for FSP in the present fastening method, and FIG. 3 is a sectional view taken along line III-III in FIG. FIG. 4 is a sectional view of an aluminum casting member locally modified by the equipment of FIGS. 2 and 3. FIG. 5: is a figure which shows an example of the cross-sectional photograph in the surface vicinity of an aluminum casting.

  As shown in FIG. 2, the equipment for FSP can have a friction stir tool 10 and a receiving member (a backing plate or the like) 12 on which a work W which is an aluminum casting member is placed. In the friction stir tool 10, a cylindrical rotating member (rotating tool) 11 is rotatably arranged on the main body, and the rotating tool 11 has a cylindrical protruding portion (pin portion) 11a at its tip 11b. be able to. Regardless of the shape of the protruding portion 11a, it can be adapted to the portion to be modified. The tip 11b and the protrusion 11a of the rotary tool 11 differ depending on the processing shape of the work W. In the examples in FIGS. 2 and 3, the tip 11b other than the protrusion 11a of the rotary tool 11 also becomes the work W. It comes into contact with the surface for surface treatment.

  In this equipment, first, the work W is placed on the receiving member 12 so that the portion to be subjected to the surface treatment as the pretreatment (that is, the portion to be machine-fastened) matches the protrusion 11a and the tip 11b of the rotary tool 11. . The planned machine fastening locations are the location that will eventually become the fastening portion with another member and the location in the vicinity thereof. Then, while rotating the rotary tool 11 as shown by the arc-shaped arrows in FIGS. 2 and 3, the friction stir tool 10 itself pressurizes the work W as shown by the downward arrow in FIGS. 2 and 3. .

  When there is not one planned machine fastening position, the friction stir tool 10 is moved to continuously perform FSP, and this surface treatment is hereinafter referred to as FSP (continuous). For example, in the case of a linear region, the friction stir tool 10 is moved so as to cover the region, as indicated by the linear arrow in FIG. 2 (the same linear arrow as the direction indicated by III-III). , The surface of the area will be treated.

  By such surface treatment, it is possible to modify the portion of the work W that will be the fastening portion with another member and the vicinity thereof (for example, the region shown as the stirring portion (reforming portion) T in FIGS. 2 to 4). Therefore, the work Wm after completion of reforming as illustrated in FIG. 4 can be obtained. Here, the reforming is a reforming that occurs due to the pushing of the rotary tool 11 and the rotation accompanied by the generation of frictional heat, and refers to a reforming that improves strength and ductility.

  Further, although not shown, when the planned machine fastening position is one (fixed point), the FSP is carried out at the position of the protrusion 11a without moving the friction stir tool 10, and The FSP is called FSP (dot). In addition, even when there is only one planned machine fastening location, the surface treatment when using the rotary tool 11 that does not have the protrusion 11a is a treatment by pressing (pressurizing) from above and heating by friction, Hereinafter, such treatment is referred to as pressurization / heating in order to distinguish it from FSP (dots). Even in FSP (dot) or pressurization / heating, the same reforming as FSP (continuous) can be performed, although the reformed region is different.

  Control of these friction stir tools 10 can be performed by a control unit (not shown). Prior to such control, processing conditions (hereinafter referred to as FSP conditions) are first set in the control unit. The FSP conditions include, for example, the number of rotations of the rotary tool 11, the pressing amount of the rotary tool 11 with respect to the work W, the pressing force of the rotary tool 11 with respect to the work W, the contact angle of the rotary tool 11 with respect to the work W, the processing time, and the holding. Time is included.

  In this equipment, the contact angle can be controlled in units of less than 0.1 mm, for example. The holding time can be a time in which the rotary tool 11 is held in a state where it is not rotated and its position is not moved. The processing time can be the time for rotating the rotary tool 11 from the end of the holding time to the start of the next holding (first from the start of rotation to the start of the holding time). Further, the FSP conditions will differ at least in part depending on which of FSP (continuous), FSP (point), and pressurization / heating is executed.

  In the surface treatment as described above, in this embodiment, the pushing amount of the rotary tool 11, which is one of the FSP conditions, is set to an amount that can remove the chill layer on the surface (depth to remove the chill layer). Keep it. As an example of the pushing amount set, the pushing amount D1 is shown in FIG. The chill layer is a layer generated by rapid solidification of the surface of the casting, and is, for example, the layer indicated by the depth Dc from the surface illustrated in FIG. Dc is, for example, about 0.05 to 0.4 mm. For example, the hardness Hv of a layer deeper than the chill layer (the layer indicated by the depth Da from the lower end of the chill layer) is about 80, whereas the hardness Hv of the chill layer is 90 or more, and the chill layer of the aluminum casting member is Harder than the inside of an aluminum casting member. In this embodiment, the pushing amount is set so that such a hard chill layer can be removed.

  The pushing amount of the rotary tool 11, which is one of the FSP conditions, can be surely removed by measuring the thickness of the chill layer at the mechanical fastening portion (fastening portion) in advance, and the thickness of the material is small. It can be set to a value that is not too high. By adjusting the pushing amount of the friction stir tool, preferably by removing only the chill layer, it does not unnecessarily remove other parts of the aluminum casting member, so reduce the thickness dimension of the machine fastening point too much. There is no. For example, in the example of FIG. 5, the pressing amount D1 can have a depth of about 0.1 to 0.5 mm.

  With reference to FIGS. 6 and 7, an example of the result of applying the method for locally modifying an aluminum casting member by such FSP will be described. FIG. 6 is a cross-sectional view for explaining an example of how local modification is performed by the equipment of FIGS. 2 and 3. FIG. 7 is a cross-sectional view for explaining an example of how local modification is performed by the equipment in which the rotary tool 11 is not provided with the protrusion 11 a in the equipment of FIGS. 2 and 3.

  The drawing on the left side of FIG. 6 is similar to FIG. 3, and shows a state in which the FSP (dots) are pushed and rotated using the rotary tool 11 having the protrusion 11a. The drawing on the right side in FIG. 6 shows a state of the work Wm after the completion of reforming, in which the rotary tool 11 and the receiving member 12 are removed after the completion of such pushing and rotation. In the work Wm after completion of the modification shown in FIG. 6, it can be seen that a hole Ha that matches the protrusion 11a is formed together with a shelf Hb that matches the tip (tip surface) 11b of the rotary tool 11. Further, a similar cross section is also formed in FSP (continuous), and in that case, the hole Ha in FIG. 6 corresponds to a groove continuous in the continuous direction.

  The drawing on the left side in FIG. 7 is similar to FIG. 3, but shows a state in which the rotary tool 11 having no protrusion 11a is used to perform pressing and rotation during pressurization / heating. The drawing on the right side in FIG. 7 shows a state of the work Wm after completion of reforming, in which the rotary tool 11 and the receiving member 12 have been removed after completion of such pushing and rotation. In the work Wm after completion of the modification shown in FIG. 7, it can be seen that a shelf portion Hb matching the tip portion (tip surface) 11b of the rotary tool 11 is formed.

  Next, as a comparative example, a method of mechanically fastening other members in the reforming section T of the work Wm will be described in comparison with a method of mechanically fastening an uncast aluminum casting member and another member. .

  First, a specific example of using SPR (self-piercing rivet) for mechanical fastening will be described with reference to FIGS. 8 to 11. FIG. 8 is a cross-sectional view for explaining an example of a mechanical fastening method when fastening a workpiece (aluminum casting member) W that is not modified with another member by SPR. FIG. 9 is a partial cross-sectional perspective view showing a state of mechanical fastening by the mechanical fastening method of FIG. 8. FIG. 10 is a cross-sectional view for explaining a specific example of the mechanical fastening method in the case where the reforming section T is fastened to another member by SPR. Further, FIG. 11 is a diagram showing a result of performing SPR after continuous FSP, a result of performing SPR after pressurization and heating, and a result of performing SPR without modification as a comparative example.

  As shown on the left side of FIG. 8, in mechanical fastening by SPR, a workpiece W that is an aluminum casting member and a workpiece Wo that is another member are overlapped with each other as a fastening target, and then SPR (hereinafter, rivet R in FIG. 8). The protrusion is placed so as to contact the member Wo. This mechanical fastening can be performed by, for example, equipment having a cylindrical portion 21, a pressing portion 22, and a pedestal portion 23. The pedestal portion 23 has a protrusion portion 23a having a shape of a surface opposite to the contact surface. The cylindrical portion 21 suppresses the fastening target from the upper side and sandwiches the fastening target together with the pedestal portion 23. The pressing portion 22 is slidably provided inside the cylindrical portion 21 and presses the upper end of the rivet R.

  With such equipment, first, the work Wo is overlaid on the work W to be fastened, and the cylindrical portion 21 is lowered so that the upper surface (upper surface of the work Wo) can be suppressed by the cylindrical portion 21. Next, the rivet R is arranged so that its protrusion contacts the upper surface of the work Wo, and the pressing portion 22 is installed and pressed so as to press the upper surface of the rivet R. After the mechanical fastening is completed, as shown in the right side of FIG. 8, the cylindrical portion 21, the pressing portion 22, and the pedestal portion 23 are separated from the works W and Wo (see FIG. 9) mechanically fastened by the rivets R. Take it out.

  As a comparative example, an example of fastening an uncast aluminum casting member by SPR will be given. In the mechanical fastening using SPR, when the lower plate is an aluminum casting member, heat treatment (for example, T7 treatment as a heat treatment quality) is required for the aluminum casting for SPR. Therefore, in such a case, there are problems that the cost required for the heat treatment and the correction is increased and that the accuracy is deteriorated due to the deformation during the heat treatment. Here, the T7 treatment is a treatment called a solution treatment stabilization treatment or an overaging treatment.

  When the mechanical fastening by SPR is performed without performing such heat treatment, for example, a crack is generated as in the state (state shown as “SPR only”) like the comparative example shown in the left column of FIG. I will end up. Here, in the left column, the middle column, and the right column of FIG. 11, the pressing amount D1 is about 0.1 to 0.5 mm, the steel plate (SCGA590 t1.6) is used as the work Wo, and the aluminum casting member (work W ) Indicates that mechanical fastening is performed using ADT10-Ft3.0. In the left column of FIG. 11, a cross-sectional view in the case of only SPR, an external view photograph from the arrow direction shown in the cross-sectional view, and a photograph after color check are shown. The color check refers to a check process involving coloring for making cracks and the like easy to see.

  The reason why such a problem arises is that in the case of an aluminum casting that has not been heat-treated (so-called F material), the aluminum casting is This is because the ductility (local growth) is insufficient.

  On the other hand, in the present embodiment, the mechanical fastening by SPR as described above is applied to the reforming section T which is reformed by FSP (continuous) or pressure / heating. Specifically, as shown on the left side of FIG. 10, first, the work Wm is overlaid on the lower side of the work Wo with the reforming section T facing downward. Then, the rivet R is brought into contact with the upper surface of the work Wo, and the pedestal portion 31 is brought into contact with the modified portion T. Then, the step of suppressing the work Wo and the step of pressing the rivet R are performed from the upper side by the cylindrical portion 21 and the pressing portion 22 of FIG. 8, which are not shown in FIG. 10, and the rivet R as shown on the right side of FIG. 10 is mechanically fastened. It is possible to produce the work W, Wo. Here, the pedestal portion 31 may have a recessed portion 31a having a flat bottom as shown on the left side of FIG. 10, and as a result, the protrusion Ta having the flat portion as shown on the right side of FIG. 10 is modified. It can be formed in the portion T.

  It is possible to locally improve the ductility of the aluminum casting member by FSP (continuous) or pressurization / heating, and by performing mechanical fastening by SPR on the reformed portion T that has undergone such reforming, SPR It is possible to suppress cracking of the aluminum casting member at the time.

  In the middle and right rows of FIG. 11, cross-sectional views and arrows showing the cross-sectional views of the case where the mechanical fastening by SPR is performed after FSP (continuous) and the mechanical fastening by SPR is performed after pressurizing and heating, respectively. An external view photograph from the viewing direction and a photograph after color check are shown. In FIG. 11, it can be seen that no crack is generated by the mechanical fastening process performed after any surface treatment of FSP (continuous) or pressure / heating. Although not described, the same effect can be obtained even when the holes Ha shown in FIG. 6 are formed in the modified portion T by performing FSP (dots) before the mechanical fastening by SPR.

  As described above, in this embodiment, the area where the mechanical fastening is performed by SPR (the mechanical fastening location and its vicinity) is subjected to the surface treatment by FSP (continuous), FSP (point), or pressure / heating, and the area No cracks occur to improve ductility. Therefore, in this embodiment, it can be said that the fastening quality of the mechanical fastening using SPR can be improved from the viewpoint of suppressing cracking. Further, it can be said that the surface treatment can also improve the strength in this region, and from that viewpoint, the fastening quality can be improved.

  Next, a specific example of using an FDS (flow drill screw) for mechanical fastening will be described with reference to FIGS. 12 to 14. FIG. 12 is a cross-sectional view for explaining an example of the mechanical fastening method by FDS, and FIG. 13 is a partial cross-sectional perspective view showing the state of mechanical fastening by the method of FIG. FIG. 14 is a cross-sectional view for describing a specific example of the mechanical fastening method when fastening is performed by FDS in the reforming section T that is reformed by FSP (dots).

  As shown on the left side of FIG. 12, in mechanical fastening by FDS, a work W that is an aluminum casting member having a hole Hs as a fastening target and a work Wo that is another member are overlapped with each other, and FDS (hereinafter, It starts from the state where the screw S) in FIG. 12 is arranged. From this state, as shown in the center of FIG. 12, the screw S is gradually screwed by rotation and pressing to complete the mechanical fastening by FDS as shown in the right side of FIG. 12 and FIG.

  Since mechanical fastening by FDS is such a fastening method, a hole (pre-hole) is often preliminarily formed in the upper plate (workpiece W in this case) in advance. Here, the upper plate often has a thickness of, for example, 1.5 mm or more. In particular, since the plate thickness of an aluminum casting member is usually 2 mm or more, when an aluminum casting member is used as the upper plate, a prehole is required. Therefore, when the aluminum cast member is used as the upper plate for mechanical fastening by FDS, the processing cost is increased due to the formation of the prehole on the upper plate. Furthermore, since the material strength around the hole Hs is the same as that of the other parts, the stress is concentrated on the hole Hs, so that the surrounding part is likely to be the weakest part and is likely to be the fracture part.

  On the other hand, in the present embodiment, the mechanical fastening by the FDS as described above is performed on the reforming section T reformed by the FSP (dots). The reforming portion T can also be formed with a pressing amount D1 of, for example, about 0.1 to 0.5 mm. Specifically, as shown on the left side of FIG. 14, first, the work Wm is overlaid on the upper side of the work Wo with the reforming section T having the hole Ha facing upward. Then, the tip of the screw S is inserted into the hole Ha, and the screw S is screwed in by rotating and pressing. As a result, the mechanical fastening by FDS is completed as shown on the right side of FIG.

  As described above, in the present embodiment, the area where the mechanical fastening is performed by the FDS (the mechanical fastening location and the vicinity thereof) is subjected to the surface treatment by the FSP (points) to form the hole at the mechanical fastening location and increase the strength of the area. Is improving. Therefore, in the present embodiment, not only the fastening strength of the mechanical fastening by FDS can be improved to improve the fastening quality, but also holes can be formed at the locations where the FDS is installed in the process of such improvement. . Therefore, in the present embodiment, it is not necessary to separately perform a hole forming step in the aluminum casting member which is usually required, and the labor and cost required for manufacturing can be reduced.

  As described above, in the present fastening method, when mechanically fastening the aluminum casting member and the other member, a friction stir tool is used, and only an amount such that the chill layer on the surface of the aluminum casting member is removed as the surface treatment. After pushing it in, tighten the machine. Therefore, according to the present fastening method, it is possible to improve the ductility of the fastening portion, thereby suppressing thermal deformation and improving the dimensional accuracy, and also improving the strength of the fastening portion and not reducing the thickness dimension too much. It is possible to suppress the decrease in the strength of the member to be fastened.

  Further, according to the present embodiment, the heat treatment of the die casting becomes unnecessary, so that the energy and cost required for manufacturing the aluminum casting member can be reduced. In addition, the present embodiment will be particularly useful in the future, because there is an increasing need for weight reduction of bodies and the like due to electrification in the automobile industry and the like, and the adoption of aluminum cast members is expanding accordingly.

<Alternative example>
In the above, various examples of the fastening method of the aluminum casting member according to the present embodiment have been described, but various alternative examples can be adopted including the alternative example 1 and the alternative example 2 described below. For example, in the above-mentioned example, as illustrated in the following alternative examples 1 and 2, other members may be aluminum cast members, and further modified aluminum cast members.

(Alternative example 1)
An alternative example of the fastening method will be described with reference to FIGS. 15 and 16. FIG. 15 is a cross-sectional view for explaining an alternative example 1 of the present fastening method, and FIG. 16 is a partial cross-sectional perspective view showing a state of mechanical fastening by the method of FIG.

  The fastening method in Alternative Example 1 is a method of performing mechanical fastening such as TOX (registered trademark) by caulking. In the case of caulking, the deformation of the material is larger than that of SPR, and local modification (improvement of ductility) is required from the front surface to the back surface of the aluminum casting member. Therefore, the modification method is preferably FSP (continuous). Therefore, in this fastening method, FSP (continuous) is preliminarily applied as a surface treatment to the portion to be crimped and its vicinity in the aluminum casting member (workpiece W).

  Here, a case will be described in which the set of workpieces to be fastened are both aluminum cast members. First, by FSP (continuous), the work to be arranged on the upper side is reformed into a work Wm1 in the portion to be crimped, and the work to be arranged below is reformed into the work Wm2 in the portion to be crimped. Although illustration of the state before the work Wm1 and Wm2 is modified and caulked is omitted, the work Wm1 and Wm2 have a wide range of concave portions (convex portions when viewed from the back side) formed by caulking as shown in FIG. This means that the part has been modified in advance.

  The reforming-completed work Wm1 arranged on the upper side and the reforming-completed work Wm2 arranged on the lower side of the reforming work are overlapped with each other, and the tip portion is directed toward the reforming part of the work Wm1. The pressing portion 41 having 42 is lowered. On the other hand, the pedestal portion 43 is provided below the work Wm2. As a result, the modified portions of the work Wm1 and the work Wm2 are fastened by caulking, as shown in FIG. The pedestal portion 43 can have a shape that forms the shape of the fastening portion of the work Wm2.

  Although both members to be fastened are described as modified aluminum casting members here, some effects can be obtained if at least one of them is a modified aluminum casting member. For example, the other can be steel, aluminum, unmodified aluminum castings, and the like. Further, even when mechanical fastening by caulking is adopted, FSP (point) or pressurization / heating can be adopted as the surface treatment. In Alternative Example 1 as well, the ductility and strength of the fastening portion can be improved, so that the fastening quality can be improved.

(Alternative example 2)
Another alternative example of the fastening method will be described with reference to FIGS. 17 and 18. FIG. 17 is a cross-sectional view for explaining an alternative example 2 of the present fastening method, and FIG. 18 is a cross-sectional view showing a state in which mechanical fastening is performed by the method of FIG.

  The fastening method in Alternative Example 2 is a method of mechanically fastening with blind rivets. In the reforming method in this case, since holes Hr1 and Hr2 are required as shown in FIG. 17, FSP (dots) is adopted. Therefore, in this fastening method, FSP (dots) is preliminarily surface-treated on the aluminum cast member (work W) at and around the location where the blind rivet BR is applied.

  Here, a case will be described in which the set of workpieces to be fastened are both aluminum cast members. First, with the FSP (point), the work to be arranged on the upper side is modified into the work Wm1 at the portion where the blind rivet BR is provided, and the work to be arranged on the lower side is modified at the portion where the blind rivet BR is provided. Wm2 Although illustration of the state before the works Wm1 and Wm2 are reformed and caulked is omitted, the works Wm1 and Wm2 are provided with holes Hr1 and Hr2 of FIG. 17 into which the blind rivets BR are inserted, respectively. It has been modified.

  The reforming completed work Wm1 arranged on the upper side and the reforming completed work Wm2 arranged on the lower side of the reformed work are overlapped with each other (the holes Hr1 and Hr2 are overlapped) to form a hole of the work Wm1. The blind rivet BR is lowered toward the Hr1 by the mounting mechanism 51. FIG. 17 shows an example in which blind rivets BR are provided at four places, and the states are shown in order so that the procedure can be understood. The reforming portions of the work Wm1 and the work Wm2 are fastened by the blind rivet BR, as shown in FIG. It should be noted that the fastening mechanism 51 and the method of fastening the blind rivet BR may be the existing technique, and thus the description thereof will be omitted.

  Although both members to be fastened are described as modified aluminum casting members here, some effects can be obtained if at least one of them is a modified aluminum casting member. For example, the other can be steel, aluminum, unmodified aluminum castings, resins, and the like. In the alternative example 2 as well, since the through hole is originally required to be processed in advance, the processing cost and the like can be reduced to the same level as or higher than the mechanical fastening method by FDS.

The present embodiment has been described above, but the above embodiment has the following features.
That is, the method for fastening an aluminum casting member according to the above embodiment includes a surface treatment step and a fastening step. In the surface treatment step, the aluminum or aluminum alloy casting member is subjected to surface treatment by pushing a portion to be mechanically fastened with another member while rotating the friction stir tool. Here, the pushing amount of the friction stir tool in the surface treatment step is set to such an amount that the chill layer on the surface of the casting member is removed. In the fastening step, after the casting member and the other member are overlaid, the mechanical fastening means fastens the casting member and the other member at the machine fastening location.

  According to the above fastening method, when mechanically fastening the casting member and the other member, using a friction stir tool, as a surface treatment, after pushing in an amount such that the chill layer on the surface of the casting member is removed , Perform machine fastening. Therefore, according to the fastening method according to this aspect, it is possible to suppress thermal deformation, improve dimensional accuracy, and suppress a decrease in strength of the fastening target member.

BR blind rivet Ha, Hs, Hr1, Hr2 hole R rivet S screw T reforming section W work (aluminum casting member)
Wm, Wm1, WM2 Work after reforming Wo Other work (other members)
10 Friction Stir Tool 11 Rotating Tool 11a Projection 11b Tip 12 Receiving Member 21 Cylindrical 22 and 41 Pressing 23, 31, 43 Pedestal 23a Projection 31a Recess 42 Tip 51 of pressing part Attachment mechanism

Claims (1)

In a cast member of aluminum or aluminum alloy, a surface treatment step of performing a surface treatment by pressing a machine fastening planned portion with another member while rotating the friction stir tool.
A fastening step of fastening the casting member and the other member at a machine fastening location after the casting member and the other member are stacked,
Have
The indentation amount of the friction stir tool in the surface treatment step is an amount such that the chill layer on the surface of the casting member is removed.
Fastening method of aluminum casting member.