JP2003225780A - Aluminum based structure and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum based structure which can be joined without undergoing through friction stirring joining, has no strips and no difference in color tones in a joint, and has improved appearance quality, brightness and joining strength, and to provide a production method therefor. <P>SOLUTION: A planar bar 30 is bent into a cylindrical shape, and both edges in the peripheral direction are butted to each other to form a joint 32. Further, notches 31a and 31b for grooves are respectively formed on the back sides of both the edges in the peripheral direction in advance, and, when both the edges in the peripheral direction are butted to each other, the notches 31a and 31b are also butted to each other to form one groove 31. Then, a backing strip 34 is pressed close to the back side of the joint 32, and a friction stirring joining tool 36 is inserted from the surface side to the joint 32, and the joint 32 is subjected to friction stirring joining. The joining is performed in such a manner that the tip of a stirring pin 36B is projected into the groove 31. After the friction stirring joining, the joined body is made into a structure having a prescribed shape by a forming apparatus. Further, an anodic oxidation coating is formed on the whole outer surface of the structure by anodizing treatment. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum-based structure and a method for manufacturing the same, and more particularly to an aluminum-based structure suitable for application to an alumite-treated wheel rim for automobiles and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, as a method for joining metal members such as aluminum or aluminum alloy (hereinafter collectively referred to as "aluminum-based" in the present invention) members by abutting or superposing, it is disclosed in Japanese Patent Laid-Open No. Hei 11
-285862 publication, patent 2712838 publication,
A friction stir welding method (hereinafter abbreviated as FSW) disclosed in Japanese Patent No. 2792233 is known.

[0003] FSW is a method of joining two (or one) to-be-joined materials to each other by abutting or superposing them on each other by utilizing frictional heat. FIG. 9 is a diagram showing a conventional example in which two materials to be joined are butt-joined by FSW. In the figure, a friction stir welding tool 3 made of a material harder than the materials to be welded 1 and having excellent heat resistance is rotated at a high speed, and a stirring pin 4 integrally provided at the tip thereof.
Is pushed along the joint surface 6 of the joint portion 5 of the members to be joined 1 and 2 and the members 3 to be joined and the probe 3 are relatively moved in the direction orthogonal to the paper surface along the joining line SL,
Friction heat is generated in the joint portion 5. Due to this frictional heat, the metal M (hatched portion) in the vicinity of the joining surface 6 of the two materials 1 and 2 to be joined
Is softened to a state where it can be plastically worked, stirred and flowed by the stirring action of the stirring pin 4 rotating at high speed, and then cooled and solidified by passing through the stirring pin 4 to solid-phase bond the joint portion 5.

The materials 1 and 2 to be welded by such an FSW
Butt joining is a solid phase welding that uses frictional heat, so unlike welding by TIG welding or MIG welding, no welding rod, inert gas, etc. are required, and simple and quick joining is possible. Has the advantage that
It is widely used for joining structures such as construction civil engineering, vehicles, and ships.

[0005]

[Problems to be Solved by the Invention] However, FSW
When an alumite treatment is applied to the aluminum-based structure bonded by, streaks (traces of surface oxide film) on the back side of the bonded part
However, there is a problem that the joint part and the base material part (the part which is not softened to be plastically workable) have different color tones. As shown in FIG. 9, the streak generated on the back surface side of the joining portion is in a state where the tip of the stirring pin 4 is positioned inside the back surface side of the joining members 1 and 2 by about 0.2 mm, in other words, in a state where it does not project to the back surface side. Since the members are agitated and joined, the portions below the agitating pin 4 of the joining end surfaces 1a, 2a of the two materials to be joined 1 and 2 remain as an oxide film without being sufficiently agitated, and the oxide film is alkali-cleaned during alumite treatment. It is thought that this is due to the fact that the method of dissolution in is different from the other parts.
Further, if the oxide film portion remains continuously and its extent becomes large, an unbonded portion is formed, so that sufficient bonding strength cannot be obtained. It was found that the difference in color tone between the joint portion and the base material portion is due to the difference in the composition and structure of these two portions, particularly the difference in crystal grain size.

[0006] When the aluminum-based structure is a general structure used for construction civil engineering, vehicles, ships, etc., the joints are rarely seen directly, so there is a problem even if streaks or color differences occur. Is rarely. However, for example, a flat bar is bent into a cylindrical shape and both ends in the circumferential direction are FS.
A rim intermediate body composed of a cylindrical body is formed by butt-joining with W, and an open end of this intermediate body is bent outward to form a flange to form a vehicle wheel rim, and a tire is mounted on the outer periphery. In such a case, since the friction stir welding portion is directly visible on the back surface or the end surface of the flange portion, if there is a streak or a color tone difference in the welding portion, the appearance quality and the glitter of the wheel rim deteriorate, which is a problem. Therefore, there is a demand for the development of an aluminum-based structural material having no streaks and no color difference in the joint and a method for manufacturing the same.

Therefore, for example, in the friction stir welding method disclosed in Japanese Patent Laid-Open No. 11-5179, a groove is provided in a backing arranged on the back side of the materials to be welded, and the stirring pin is projected to the back side of the joint. Then, the stirrer is inserted into the groove of the backing and friction stir welding is performed to prevent the generation of an unwelded portion. However, in such a through friction stir welding method, since the metal plasticized by frictional heat flows into the groove and solidifies, an extra post process for removing the backing by grinding is required. Since there is a large amount of plasticized metal flowing into the groove, there is a problem that the metal at the joint is insufficient and tunnel-like cavity defects are likely to occur inside.

The present invention has been made in order to meet the above-mentioned problems and demands of the related art.
Provided is an aluminum-based structure that can be joined without performing through friction stir welding, does not cause streaks or color differences in the joined portion, and can improve appearance quality, glitter, and joining strength, and a manufacturing method thereof. To do.

[0009]

In order to achieve the above object, an aluminum-based structure according to a first aspect of the present invention is provided with a notch for a groove at both ends in the bending direction of the back surface of a material to be joined formed in a plate shape. To form a joint part in which a groove formed by the notch for groove is formed on the back surface side by bending the material to be bonded into a cylindrical shape with the front surface side outside and abutting both ends in the bending direction, An aluminum-based structure formed by inserting the friction stir welding tool from the surface side to the joint surface of the joint portion and friction stir welding the joint portion in a state where the tip is located in the groove, The outer surface is anodized.

In the first invention, when the material to be joined is bent into a cylindrical shape, the groove notches formed on the back surface at both ends in the bending direction face each other to form one groove. . When the joint part is friction-stirred from the surface side, the groove surface made of oxide film is also stirred and divided, and the metal softened to the state where it can be plastically processed by friction heat is stirred and flowed to enter the groove and solidify. . Therefore, the joining portion is agitated and joined from the front surface side to the back surface side, and the groove surface made of an oxide film does not exist on the back surface or the end surface of the material to be joined, and a large joining strength can be obtained. Further, since there is no portion to be joined, no streaks (traces of oxide film) are generated even if the alumite treatment is performed. The alumite treatment is carried out by performing a degreasing step with an acid as a pretreatment step, an etching step with an alkali, and a neutralizing step with an acid in this order on the material to be joined, followed by electrolytic treatment to form an anodized film on the surface. By forming it, decorativeness and corrosion resistance are imparted. A V-shape is the most common cross-sectional shape of the groove, but is not limited to this and may be, for example, a U-shape.

An aluminum-based structure according to a second invention is the aluminum-based structure according to the first invention, wherein the aluminum-based structure is a vehicle wheel rim.

In the second aspect of the invention, the joint portion on the rear surface side of the wheel rim for a vehicle is visually recognized when the tire is mounted on the outer periphery of the wheel rim. There is no.

In the aluminum-based structure according to the third aspect of the present invention, a groove is formed on the back surface side of the joint between two materials to be joined, which are butt-joined to each other, and friction stir is applied to the joint surface of the joint from the front side. It is an aluminum-based structure formed by friction stir welding of the joining portion with a joining tool inserted and the tip positioned in the groove, and the outer surface of which is anodized. .

In the third invention, a groove is formed at the end of the back surface of the two materials to be joined on the side of the joining portion, and the joining portion is friction stir welded from the front surface side. The groove is formed by cutting after joining the joint ends of the two materials to be joined, or by cutting a notch for the groove on the back side of the joining side edge of each material to be joined in advance. Alternatively, the groove may be formed in advance, and the joints of the two materials to be joined may be abutted against each other so that the groove notches face each other to form one groove. It is also possible to form the notch for groove by extrusion molding at the same time as the forming of the material to be joined, and to make the groove by abutting the joint portion of the material to be joined. When the joint portion is friction-stirred from the surface side, the groove surface made of an oxide film is also stirred, and the metal softened by frictional heat to a state where it can be plastically processed stirs and flows to enter the groove and solidify. Therefore, the joining portion is agitated and joined from the front surface side to the back surface side, and after friction stirring, the groove surface made of an oxide film does not exist on the back surface or the end surface of the material to be joined, and a large joining strength can be obtained. In addition, even if the alumite treatment is performed, streaks do not occur, so that the appearance quality is not deteriorated.

In the aluminum-based structure according to the fourth aspect of the present invention, in the first, second or third aspect of the invention, at least the back surface of the friction stir welded joint portion is formed into a smooth surface by polishing or machining. There is something.

In the fourth aspect of the present invention, when the joining portion is joined by friction stir welding, since the surface accuracy of the back surface of the joining portion is rough, a smooth surface is formed by polishing or machining.
In the case where the structure is a vehicle wheel rim, the rear surface side of the flange portion is visually recognized when the tire is mounted,
Since the back surface of the bonded portion is formed into a smooth surface by polishing or machining, the appearance is not spoiled. On the other hand, burrs and dents are generated on the surface side of the joint by friction stir welding, but in the case of a structure in which the burrs and dents are visible, it is preferable that the surface side is also smoothed by polishing or machining. . Particularly in the case of a wheel rim for a vehicle, if the burrs are present and contact with the tire may damage the tire, it is preferable to remove the burrs by polishing or machining.

According to a fifth aspect of the present invention, there is provided a method for manufacturing an aluminum-based structure, comprising the steps of forming groove notches on both edges in the bending direction of the back surface of a plate-shaped member to be bonded, and the member to be bonded. A step of bending a cylindrical shape so that the surface is on the outside and joining both ends in the bending direction to each other to form a joint, and forming a groove by abutting the groove notches on the back surface side of the joint, A step of arranging a backing on the back surface of the joining portion of the material to be joined, and a state in which the tip is located in the groove by inserting a friction stir welding tool from the surface side to the joining surface of the joining portion of the material to be joined And a step of subjecting the outer surface of the material to be joined, which has been friction stir welded, to an alumite treatment.

In the fifth aspect of the invention, the material to be joined is bent into a cylindrical shape so that both ends in the circumferential direction abut each other to form a joint. The groove notch is formed beforehand by cutting or the like before bending the material to be joined into a cylindrical shape, and when the material to be joined is bent into a cylindrical shape and both ends in the circumferential direction are abutted against each other, the notches are abutted against each other. Together they form one groove. The groove is covered by a backing. When the joint portion is friction-stirred from the surface side, the groove surface made of an oxide film is also stirred, and the metal softened by frictional heat to a state where it can be plastically processed stirs and flows to enter the groove and solidify. Therefore, the joining portion is agitated and joined from the front surface side to the back surface side, and after friction stirring, the groove surface made of an oxide film does not exist on the back surface or the end surface of the material to be joined, and a large joining strength can be obtained. In addition, even if the alumite treatment is performed, streaks do not occur, so that the appearance quality is not deteriorated.

In the method for manufacturing an aluminum-based structure according to the sixth aspect of the present invention, a groove is formed along the joint surface and a backing is arranged on the back surface side of the joint portion where two materials to be joined are butt-joined to each other. And a step of inserting a friction stir welding tool from the surface side to the joint surface of the joint portion of the material to be welded and friction stir welding the joint portion with the tip positioned in the groove, A step of subjecting the outer surfaces of the joined materials to be joined to an alumite treatment.

In the sixth aspect of the invention, the two materials to be joined have a groove formed at the edge of the rear surface on the side of the joint, and the joint is friction stir welded from the front side. The groove is formed by cutting after joining the joint ends of two materials to be joined, or by forming a notch for groove on the edge of the back surface side of each material to be joined in advance by cutting. Alternatively, one groove may be formed by abutting the joint portions of the two materials to be joined and making the groove notches face each other. When the joint part is friction-stirred from the surface side, the groove surface made of an oxide film is also stirred,
The metal softened to the state where it can be plastically worked by frictional heat stirs and flows, and enters the groove and solidifies. Therefore, the joining portion is agitated and joined from the front surface side to the back surface side, and after the frictional agitation, the groove surfaces made of an oxide film are not present on the back surface and both end surfaces of the material to be joined, and a large joining strength is obtained. Also,
Even if the alumite treatment is performed, streaks do not occur, and the appearance quality is not impaired.

According to a seventh aspect of the present invention, there is provided a method of manufacturing an aluminum-based structure according to the fifth or sixth aspect, wherein the friction stir welding tool has a cylindrical tool body and integrally projects at the center of the bottom surface of the tool body. A stirring pin that is provided and is pushed together with a part of the tool body into the joint portion of the materials to be joined, and the bottom surface of the tool body constitutes a tool shoulder that presses the surface of the joint portion, and passes through the axis of the tool body. Of the vertical cross-sectional area orthogonal to the moving direction of the friction stir welding tool, the vertical cross-sectional area of the portion to be pushed into the joint is approximately equal to or larger than the vertical cross-sectional area in the plane orthogonal to the longitudinal direction of the groove of the material to be welded. It was done.

In the seventh aspect of the invention, of the longitudinal cross-sectional area passing through the axis of the tool body and orthogonal to the moving direction of the friction stir welding tool, the longitudinal cross-sectional area of the portion pressed into the joint is the longitudinal length of the groove of the material to be welded. Since it is set to be approximately equal to or larger than the vertical cross-sectional area in the plane orthogonal to the direction, the amount of metal that softens to the state where it can be plastically worked by friction heat and enters the groove is sufficient, and the groove is It does not remain as a dent. Excess metal that did not enter the groove forms protruding ridges along both sides of the joint surface. This flash is preferably removed by polishing or machining in a later step.

According to an eighth aspect of the present invention, there is provided a method of manufacturing an aluminum-based structure according to the fifth or sixth aspect, wherein the friction stir welding tool has a cylindrical tool body and integrally projects at the center of the bottom surface of the tool body. An agitating pin that is provided and is pushed together with a part of the tool body into the joint portion of the materials to be joined, and the bottom surface of the tool body constitutes a tool shoulder that presses the surface of the joint portion, and the width of the groove is the agitating pin. Is less than 75%, and the longitudinal cross-sectional area in the plane orthogonal to the longitudinal direction of the groove is less than 15% of the cross-sectional area orthogonal to the axis of the stirring pin.

In the eighth invention, when the width of the groove is 75% or less of the diameter of the stirring pin and the longitudinal sectional area of the groove is 15% or less of the cross-sectional area orthogonal to the axis of the stirring pin, the friction heat The amount of metal that softens to a state where it can be plastically processed enters into the groove, and the groove does not remain as a recess, and the excess metal that did not enter the groove remains in the joint surface. Protruding ties along both sides ensure reliable friction stir welding. If the width of the groove is 75% or more of the diameter of the stirring pin and the vertical cross-sectional area of the groove is 15% or more of the cross-sectional area orthogonal to the axis of the stirring pin, the amount of metal is insufficient and the groove is recessed. Remains.

In the method for manufacturing an aluminum-based structure according to the ninth aspect of the invention, the stirring portion is formed on the tip surface or outer periphery of the stirring pin.

In the ninth invention, the stirring section stirs and fluidizes the joint surface and its vicinity and the groove surface. As the stirring portion, a groove, a protrusion, or the like having an annular shape, a spiral shape, a radial shape, or the like can be considered.

A method for manufacturing an aluminum-based structure according to a tenth aspect of the present invention is the method according to any one of the above fifth to ninth aspects, in which, as a step prior to the step of performing alumite treatment after friction stir welding, It comprises a step of annealing the material to be joined at 300 to 375 ° C. for 1 to 5 hours.

In the tenth aspect of the invention, when the crystal grains of the joint are recrystallized by annealing to be approximately equal to the crystal grains of the base material, the difference in color tone between the joint and the base material can be eliminated. If the temperature is 300 ° C. or lower, the recrystallization of the bonded portion is insufficient, and if the temperature is 375 ° C. or higher, the recrystallized structure becomes coarse, resulting in a large color difference.

An aluminum-based structure manufacturing method according to an eleventh aspect of the present invention is the method according to any one of the fifth to ninth aspects, wherein the number of revolutions of the friction stir welding tool at the time of friction stir welding and welding are performed. The speed ratio is 4-11.

In the eleventh aspect of the present invention, when the ratio of the number of revolutions of the friction stir welding tool to the welding speed is 4 to 11, the crystal grains of the welded portion and the base metal portion are substantially equal, and the welded portion and the base metal portion are The difference in color tone can be eliminated. When the ratio of the number of revolutions to the bonding speed is 1 or less, the crystal grains in the bonded portion are fine, and when the ratio is 11 or more, the crystal grains become coarse, and thus the color tone difference after the alumite treatment becomes large.

A method for manufacturing an aluminum-based structure according to a twelfth aspect of the present invention is the method according to any one of the fifth to eleventh aspects, wherein the friction stir welding is performed as a pre-step of the alumite treatment step. It comprises a step of forming at least the back surface of the portion into a smooth surface by polishing or machining.

In the twelfth aspect of the present invention, when the joining portion is joined by friction stir welding, the back surface of the joining portion has a rough surface precision, so that a smooth surface is formed by polishing or machining. When the structure is a vehicle wheel rim, the back side of the flange is visible when the tire is mounted, but the back side of the joint is polished or machined to a smooth surface, which damages the appearance. There is no. on the other hand,
Although burrs and dents are generated on the surface side of the joint by friction stir welding, in the case of a structure in which the burrs and dents are visible, it is preferable that the surface side is also smoothed by polishing or machining. Particularly in the case of a wheel rim for a vehicle, if the burrs are present and contact with the tire may damage the tire, it is preferable to remove the burrs by polishing or machining.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the drawings. 1 is an external perspective view showing an embodiment in which an aluminum-based structure according to the present invention is applied to a vehicle wheel rim, FIG. 2 is a sectional view of the wheel rim, and FIGS. 3A to 3C are FSWs. For explaining the procedure of FIG. 4, FIG. 4 is a sectional view showing a state in which the FSW of the wheel rim is being performed, FIG. 5 is a sectional view taken along line VV of FIG. 4, and FIG.
FIG. 3 is a diagram showing a stirring unit of a stirring pin.

First, the structure of the vehicle wheel rim will be described with reference to FIGS. 1 and 2. The vehicle wheel rim generally designated by the reference numeral 20 is used for vehicles such as passenger cars, trucks and buses, and has a cylindrical rim body 20A on which tires are mounted on the outer periphery and one rim body 20A integrally formed on one side edge thereof. And a flange 21 and a disk 22 that are fitted and fixed to a gutter 20C formed on the other side edge. The rim body 20A is
It is manufactured by friction stir welding. Flange 20
B and 21 are formed by bending so as to have an L-shaped cross section by plastic working performed after friction stir welding.
The gutter 20C has an annular groove 23 into which the base end portion of the flange 21 is fitted on the outer surface, and the rear end portion of the disk 22 is fitted into and joined to the inner surface by welding. As with the rim body 20A, the flange 21 and the disc 22 are 5
It is made of 000 series aluminum alloy. Then, the wheel rim 20 is anodized on the entire outer surface in order to improve decorativeness and corrosion resistance.

Next, the procedure for manufacturing the rim body 20A will be described in detail with reference to FIGS. First, a bar (material to be bonded) 30 having a predetermined length and width formed in a plate shape by an extruded aluminum alloy material is prepared (FIG. 3).
(A)). Notches 31a and 31b for the groove are formed over the entire width of the back surface 30a of the bar 30 at both edges in the longitudinal direction. The groove notches 31a and 31b have substantially the same shape and are formed by obliquely cutting the longitudinal edge portion of the back surface 30a at a required angle (for example, 30 to 45 °).

Next, the bar 30 is bent into a cylindrical shape so that the surface 30b is on the outside and both ends in the longitudinal direction are abutted against each other, and the abutted portion is used as a joint portion 32. When the bar 30 is bent into a cylindrical shape and both ends thereof in the circumferential direction are butted and restrained so as not to move, the notches 31a and 31b for beveling are also butted against each other, thereby forming one V-shaped groove. 31 is formed.

Next, a backing 34 is attached to the back surface side of the joint portion 32.
(FIG. 4) are brought into close contact with each other, and the joint portion 32 is friction stir welded by the friction stir welding tool 36 from the surface side. Backing 34
Is made of metal such as iron or aluminum, and one surface thereof is formed into a convex curved surface having substantially the same radius of curvature as the inner peripheral surface of the bar 30 bent into a cylindrical shape, and covers the groove 31.

The friction stir welding tool 36 comprises a bar 30.
It is made of a metal having a higher melting point, such as tool steel, and is composed of a cylindrical tool body 36A and an agitation pin 36B integrally provided on the center of the bottom surface 37 of the tool body 36A. The bottom surface 37 forms a tool shoulder that presses the surface of the joint portion 32. The stirring pin 36B has a length of 0.2 from the plate thickness t of the bar 30.
The length is set to be about 0.4 mm shorter, and the tip surface 38 and the outer peripheral surface 39 are provided with agitating portions 40 and 41 for agitating the adjoining surface 35 of the adjoining portion 32 and its vicinity.
In this case, in the present embodiment, an example in which the stirring section 40 is configured by one spiral groove as shown in FIG. 6 is shown, but the present invention is not limited to this and is disclosed in, for example, Japanese Patent Laid-Open No. 2001-71155. As described above, the groove may be a radial groove or a protruding body, or a large number of small cylindrical protrusions may be provided. Further, regarding the stirring portion 41 on the outer peripheral surface,
In the present embodiment, an example in which four spiral grooves are formed at equal intervals in the circumferential direction is shown, but a spiral projection or a screw groove may be used.

The friction stir welding tool 36 as described above is tilted with respect to the surface of the welding portion 32 on the side opposite to the moving direction of the probe 36 (direction of arrow A) by a required angle α (= about 3 to 5 °). Set by.

Next, while the friction stir welding tool 36 is rotated by a motor at a rotation speed of about 500 to 5000 rpm, the stirring pin 36B is positioned on the joint surface 35 and pressed against the surface of the joint portion, and frictional heat is applied to the joint portion 32. The surface portion pressed by the stirring pin 36B and its vicinity are heated and plasticized, and the stirring pin 36B and a part of the tool shoulder 37 are gradually pushed into the joint portion 32.
The amount by which the tool shoulder 37 is pushed into the surface of the joining portion 32, that is, the pushing amount δ is about 0.1 to 0.3 mm. The pushing amount δ is a pushing amount on a straight line that passes through the axis of the friction stir welding tool 36 and is orthogonal to the moving direction (A direction) of the probe. The tip side of the tool shoulder 37 in the moving direction (the left end in FIG. 5) is located above the surface of the joining portion 32 to enable metal supply into the friction stir welding tool 36.

When the stirring pin 36B and a part of the tool shoulder 37 are pushed into the joint portion 32 by a predetermined amount, the tip of the stirring pin 36B has an inclined wall surface (groove surface) 4 of the groove 31.
6 groove 31 as shown in FIG.
The friction stir welding tool 36
Is moved in the direction of arrow A at a feed speed (welding speed) of about 0.02 to 2 m / sec, whereby the welded portion 32 is friction stir welded. That is, when the friction stir welding tool 36 is moved along the joint surface 35 while rotating at high speed, the joint surface 35 and its vicinity are plasticized by being heated by the stirring pin 36B, and flow in the horizontal and vertical directions. Turn into. Then, a part of the fluidized metal 43 is formed in the groove 3
When the stirrer pin 36B enters the inside of the nozzle 1 and passes therethrough, it is cooled and solidified to fill the groove 31. Therefore, the joint 3
No. 2 is completely joined from the front surface side to the back surface side even if the stirring pin 36B is not projected to the back surface side of the joining portion 32. At this time, the groove surface 46 of the groove 31 made of an oxide film is formed on the stirring unit 4
Metal 4 that has been plasticized by being stirred and divided by 0,41
Dispersed within 3. The distance from the back surface of the joint portion 32 to the tip of the stirring pin 36B is about 0.2 mm, and the groove 3
1 is formed deeper than this.

If the amount of the metal 43 filled in the groove 31 is insufficient, the groove 31 cannot be completely filled and remains as a recess on the back surface side of the joint 32, which is not preferable. The optimum amount of the metal 43 is such that the groove 31 is completely filled, and excess metal pops out along both sides of the surface of the joint portion 32 and solidifies to cause a slight flash 44 (FIG. 4). Therefore, of the vertical cross-sectional area that passes through the axis of the tool main body 36A and is orthogonal to the moving direction (A direction) of the friction stir welding tool 36, the vertical cross-sectional area S of the portion that is pushed into the welding portion 32 (see FIGS. 4 and 5). The longitudinal cross-sectional area S1 in the plane orthogonal to the longitudinal direction of the groove 31 is made substantially equal to or slightly larger than this. Alternatively, the width E of the groove 31 (FIG. 4) may be set to 75% or less of the outer diameter D of the stirring pin 36B as an alternative method, and the cross-sectional area S1 of the groove 31 may be a cross-sectional area (πD) orthogonal to the axis of the stirring pin 36B. is preferably not more than 15% of the ^2/4).

The width E of the groove 31 is the outer diameter D of the stirring pin 36B.
The vertical cross-sectional area S1 of the groove 31 is less than 75% of the stirring pin 3
If it is 15% or less of the cross-sectional area orthogonal to the axis of 6B,
Friction heat softens the plastic workable state to 3
There is a sufficient amount of metal 43 entering the inside of 1 and the groove 31
Does not remain as a dent, and excess metal that has not entered the groove 31 forms protruding ledges 44 along the both sides of the surface of the joint 32, so that reliable friction stir welding can be obtained. On the other hand, the width E of the groove 31 is 75% or more of the outer diameter D of the stirring pin 36B, and the longitudinal sectional area S1 of the groove 31 is 1 of the cross-sectional area orthogonal to the axis of the stirring pin 36B.
When it is 5% or more, the amount of the metal 43 entering the groove 31 is insufficient and the groove 31 remains as a recess.

According to such a friction stir welding method, the butt joint portion 32 of the bar 30 which is a material to be joined made of an aluminum alloy having a plate thickness t of about 2 to 20 mm is firmly joined from the front surface side to the back surface side. It is possible. Further, the friction stir welding does not melt the joint portion of the metal material and the heating temperature is low, so that it has less heat influence than MIG welding and TIG welding, and stable quality can be obtained. Also,
By rotating the friction stir welding tool 36, the probe 36
Since it suffices to relatively move the bar 30 bent into a cylindrical shape at a required joining speed, it does not require large-scale equipment and is advantageous in cost.

After forming the bar 30 into a cylinder by friction stir welding, the backing 34 is removed from the cylinder. The cylindrical body manufactured by friction stir welding is an intermediate product of the rim body 20A shown in FIGS. 1 and 2. The front and back surfaces of the friction stir welded joint portion 32 of the cylindrical body are rough surfaces, and thus are formed by polishing or machining into smooth surfaces having the same surface accuracy as the base material portion. In particular, FIG. 1 and FIG.
In the wheel rim 20 shown in (1), since the back surface of the flange 20B and the front end surface and the back surface of the gutter 21 are visually recognized in the state where the tire is mounted, it is necessary to polish or machine the back surface and the end surface of the joint portion in these portions. There is. Further, since the burrs 44 and the tool shoulders 37 are depressed on the front surface side, it is preferable to completely remove the front surface side by polishing or machining when manufacturing a structure in which the front surface side is visible.

Next, a cylindrical body that has been polished or machined is molded by a molding device to integrally have a flange 20B on one end side, as shown in FIGS.
A rim body 20A integrally having a gutter 20C on the other end side is manufactured (FIG. 3C). Then, the flange 21 and the wheel 22 are attached to the gutter 20C to manufacture the wheel rim 20. Regarding the flange 21, the rim body 2
The flange 20B is not limited to the one manufactured separately from 0A.
Similarly to the above, it may be integrally formed with the rim body 20A. In that case, the gutter 20C need not be manufactured.

After that, the wheel rim 20 is anodized in order to impart decorativeness and corrosion resistance to the wheel rim 20 to form an anodic oxide coating on the entire outer surface thereof, thus completing the production of the wheel rim 20.

FIG. 7 shows an embodiment of the alumite treatment process.
It will be described based on. First, an object to be processed (material to be bonded) which is bonded by the friction stir welding and formed into a predetermined rim shape by a shaping device is prepared (step 100).
Next, as a pretreatment step, the object to be treated is treated with an acid (H ₂ SO ₄ ,
A degreasing process (step 101) using HNO ₃ or a mixed solution of these, an etching process using alkali (NaOH) (step 102), and a neutralizing process using acid (H ₂ SO ₄ ) (step 103) are performed in this order. . The etching step is a step of removing foreign matter, an altered layer, and the like on the surface.

Next, the object to be treated is immersed in an aqueous solution of acid (H ₂ SO ₄ ) and connected to the anode, and the aqueous solution is connected to the cathode for alumite treatment (step 104). A porous anodic oxide film is formed on the entire surface. next,
After performing electrolytic coloring (step 105) as necessary,
Whether it is immersed in warm water for sealing treatment (step 106),
Alternatively, a transparent and glossy wheel rim 20 is manufactured by performing a clear electrodeposition coating (step 107). Note that the alumite treatment itself of the aluminum alloy is a well-known technique that has been generally performed in the related art, and thus a detailed description thereof will be omitted.

After the friction stir welding, as a pre-process of the alumite treatment, an annealing treatment is performed in order to recrystallize the crystal grains of the joint 32 and make the grain size substantially equal to the crystal grain size of the base metal portion. Alternatively, it is preferable to optimize the friction stir welding conditions. In the annealing treatment, the friction stir welded materials are put in a heating furnace and heated in a temperature range of 300 ° C. to 375 ° C. for 1 to 5 hours, and then gradually cooled to room temperature. 300
If the temperature is lower than ℃, recrystallization of crystal grains is insufficient, and
When the temperature is 5 ° C or higher, the recrystallized structure becomes coarse, which is not preferable.

Even when the friction stir welding conditions are optimized, it is possible to make the crystal grain sizes of the welded portion 32 and the base metal portion substantially the same as in the annealing treatment. As a condition for optimization, the ratio of the rotation speed R of the friction stir welding tool 36 to the welding speed W is 4 to 1
It should be in the range of 1. If this ratio is 4 or less, recrystallization of the crystal grains of the joint 32 is insufficient, and if it is 11 or more, the recrystallization structure becomes coarse, which is not preferable.

[0052]

[Example 1] JIS A5 having a plate thickness of 6 mm as a material to be joined
052-O was bent into a cylindrical shape, and both ends in the circumferential direction were butted and friction stir welding was performed. The friction stir welding tool used is a tool shoulder diameter of 20 mm and a stirring pin diameter of 8
mm, pin length 5.4 mm, inclination angle of the probe with respect to the joining surface 3 °, rotation speed 890 rpm, joining speed 200
Friction stir welding was performed under the condition of mm / min while changing the depth D1 of the groove 31, the width E, and the longitudinal cross-sectional area S1 in the plane orthogonal to the longitudinal direction. The results are shown in Table 1.

[0053]

[Table 1]

As is clear from Table 1, when the friction stir welding is performed without forming the groove 31 and the stirring pin does not project to the back side of the joint (Comparative Example 1), a part of the joint surface is formed. However, since it remained without being stirred, a streak was generated on the back surface side of the joint 32 after the alumite treatment. In Comparative Example 2 and Comparative Example 3, the groove area was 15 times the cross-sectional area of the stirring pin.
%, A tunnel-shaped cavity defect and a dent were generated in the joint portion 32, but as shown in the third aspect of the present invention, when the cross-sectional area S1 of the groove 31 was 6 mm ² , the joint was possible without any problem. From this, the longitudinal cross-sectional area S1 of the groove 31 is 1 of the cross-sectional area of the stirring pin.
It is judged that 5% or less is desirable. Further, when the width E of the groove 31 is 8 mm (Comparative Example 4), since it matches the pin diameter, the amount of metal filled in the groove 31 is insufficient and the groove 31
Remains as a dent. Therefore, the width E of the groove 31 needs to be equal to or smaller than the pin diameter, preferably 75% or less.

When the depth D1 of the groove 31 was 0.1 mm (Comparative Example 5), streaks were generated on the back surface side of the joint 32 after the alumite treatment. This is a position where the pin tip is 0.2 mm from the back surface of the joint 32 {6 mm- (5.4 + 0.4
mm)} (inclination of 3 °) and does not project into the groove 31 and does not agitate the groove surface 46. Therefore, it is necessary to project the tip of the stirring pin 36B into the groove 31.

[0056]

Example 2 Table 2 shows the results of an examination of the effect of friction stir welding conditions on the color difference.

[0057]

[Table 2]

As is clear from Table 2, the ratio of the rotation speed R of the friction stir welding tool 36 to the welding speed W is 4 to 11.
In the present inventions 1 to 4 within the range, there was almost no difference in color tone between the base material portion and the joint portion. On the other hand, the ratio is 4
In Comparative Examples 1 to 3 below or 11 or more, since the color tones of the base material portion and the joint portion were significantly different, it was determined as a defective product.

FIG. 8 is a cross-sectional view of friction stir welding showing another embodiment of the present invention. In this embodiment, instead of rounding one joined material into a cylindrical shape and butt-joining both ends thereof, one end of two joined materials 50, 51 made of a flat plate-shaped aluminum alloy is butted against each other and joined. A portion 52 is formed, and the joint portion 52 is friction stir welded by the friction stir welding tool 36.
The conditions of friction stir welding are exactly the same as those of the above-mentioned embodiment except that the number of materials to be welded is two. The same applies to the steps such as the alumite treatment step after the friction stirring.

Groove notches 53a and 53b are formed at the joint-side edges on the back surfaces of the jointed materials 50 and 51, respectively, and the joint-side end surfaces of the jointed materials 50 and 51 are abutted to each other. The groove notches 53a and 53b are also abutted against each other to form one groove 53. In this case, instead of forming the notches 53a and 53b for the groove in advance, the joint ends of the two materials 50 and 51 to be joined are abutted against each other, and then opened on the back surface side of the joint portion 52 along the joint surface 54 thereof. The tip 53 may be formed by cutting.

As described above, when the two materials 50 and 51 to be welded are friction stir welded, they can be applied not only to the wheel rim described above but also to structures of various shapes. It is also applicable to body structures such as vehicle body pillars), front cross members, rear cross members, suspension frames, and general structures for construction and civil engineering.

[0062]

As described above, according to the aluminum-based structure and the method of manufacturing the same according to the present invention, it is possible to join without performing through friction stir welding, and it is possible to improve the joining strength of the joining portion. Further, even if the alumite treatment is performed, no streak is generated on the back surface side of the joint, and it is possible to provide a structure excellent in appearance quality and glitter.

Further, in the present invention, since the annealing treatment is performed after the friction stir welding or the friction stir welding is optimized to perform the friction stir welding, the crystal grains in the welded portion can be recrystallized. It is possible to make the color tones of the base material portion and the joint portion substantially coincide with each other, and it is particularly suitable to be applied to a vehicle wheel rim that is friction stir welded by bending a plate-shaped bar into a cylindrical shape.

[Brief description of drawings]

FIG. 1 is an external perspective view showing an embodiment in which an aluminum-based structure according to the present invention is applied to a vehicle wheel rim.

FIG. 2 is a sectional view of the wheel rim.

FIG. 3A to FIG. 3C are diagrams for explaining the procedure of FSW.

FIG. 4 is a cross-sectional view showing a state where FSW of the wheel rim is being performed.

5 is a sectional view taken along line VV of FIG.

FIG. 6 is a diagram showing a stirring unit of a stirring pin.

FIG. 7 is a flowchart of an alumite treatment process.

FIG. 8 is a cross-sectional view of an FSW showing another embodiment of the present invention.

FIG. 9 is a diagram for explaining a conventional FSW.

[Explanation of symbols]

20 ... Wheel rim, 20A ... Rim body, 22 ... Wheel, 30 ... Bar (material to be joined), 31 ... Groove, 31a, 3
1b ... Notch for groove, 32 ... Joint, 35 ... Groove surface, 3
6 ... Friction stir welding tool, 36A ... Tool body, 36B
... stirring pin, 34 ... backing, 40, 41 ... stirring section, 5
0, 51 ... Materials to be joined, 52 ... Joined portions, 53 ... Grooves.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shinya Makita             1-34-1 Kambara, Kambara Town, Anbara District, Shizuoka Prefecture Japan             Light Metal Co., Ltd. Group Technology Center F term (reference) 4E067 AA05 BG00 DA13 DA17 DC07                       DD00 DD01 DD02 EA07 EB00                       EC01

Claims (12)

[Claims] 1. A groove notch is formed at both edges of a back surface of a material to be joined formed in a plate shape in a bending direction, and the material to be joined is bent into a cylindrical shape with the front surface side facing outward and both ends in the bending direction. To form a joint having a groove formed by the notch for groove on the back side, and a friction stir welding tool is inserted from the front side to the joint surface of this joint so that the tip is inside the groove. An aluminum-based structure formed by friction stir welding of the above-mentioned joining portion in a state of being located at, wherein the outer surface is anodized. 2. The aluminum-based structure according to claim 1, wherein the aluminum-based structure is a vehicle wheel rim. 3. A groove is formed on the rear surface side of a joint portion where two materials to be joined are butt-joined to each other, and a friction stir welding tool is inserted from the front surface side to the joint surface of the joint portion so that the front end is opened. An aluminum-based structure formed by friction stir welding the above-mentioned joint in a state of being located inside, wherein the outer surface is anodized. 4. The aluminum-based structure according to claim 1, 2, or 3, wherein at least the back surface of the friction stir welded joint portion is formed into a smooth surface by polishing or machining. Structure. 5. A step of forming groove notches on both edges of a back surface of a material to be joined formed in a plate shape in a bending direction, and bending the material to be joined into a cylindrical shape so that a front surface is an outer side. Both ends in the folding direction are butted against each other to form a joint, and a step of forming a groove by butting the notches for groove on the back surface side of the joint, and a backing is arranged on the back surface of the joined portion of the material to be joined. And a step of inserting a friction stir welding tool from the surface side to the joint surface of the joint portion of the material to be welded and friction stir welding the joint portion with the tip positioned in the groove, A step of alumite-treating the outer surface of the material to be joined which has been joined by stirring. 6. A step of forming a groove along a joint surface and arranging a backing on a back surface side of a joint portion of two joined materials to be butt-joined to each other, and joining of the joined portions of the joined materials. A step of inserting a friction stir welding tool into the surface from the surface side to friction stir weld the joint portion in a state where the tip is located in the groove, and anodizing the outer surface of the friction stir welded material to be welded The method for manufacturing an aluminum-based structure, comprising: 7. The method for manufacturing an aluminum-based structure according to claim 5, wherein the friction stir welding tool is a cylindrical tool body, and the tool body is integrally formed by projecting at the center of the bottom surface of the tool body. Consisting of a stirring pin that is pushed together with a part of the tool body into the section, the bottom surface of the tool body constitutes a tool shoulder that presses the surface of the joint, and the moving direction of the friction stir welding tool passes through the axis of the tool body. Aluminum having a vertical cross-sectional area of a portion to be pressed into a joint that is substantially equal to or larger than a vertical cross-sectional area in a plane orthogonal to the longitudinal direction of the groove of the material to be joined. Method of manufacturing a system structure. 8. The method for manufacturing an aluminum-based structure according to claim 5 or 6, wherein the friction stir welding tool is a cylindrical tool body, and the tool body is integrally projectingly provided at the center of the bottom surface of the tool body. Part of the tool body together with a stirring pin, the bottom surface of the tool body constitutes a tool shoulder that presses the surface of the joint, and the width of the groove is 75% or less of the diameter of the stirring pin. A method for manufacturing an aluminum-based structure, wherein a vertical cross-sectional area in a plane orthogonal to the longitudinal direction of the groove is 15% or less of a cross-sectional area orthogonal to the axis of the stirring pin. 9. The method for manufacturing an aluminum-based structure according to claim 7 or 8, wherein a stirring portion is formed on a tip surface or an outer circumference of the stirring pin. 10. The method for manufacturing an aluminum-based structure according to claim 5, wherein after the friction stir welding, the material to be welded is 300 to 375 as a step before the step of performing the alumite treatment. A method for manufacturing an aluminum-based structure, comprising a step of annealing at 1 ° C for 1 to 5 hours. 11. The method for manufacturing an aluminum-based structure according to any one of claims 5 to 9, wherein the ratio of the rotation speed of the friction stir welding tool to the welding speed is 4 to 11 during friction stir welding. And a method for manufacturing an aluminum-based structure. 12. The method for manufacturing an aluminum-based structure according to claim 5, wherein at least a back surface of the friction stir welded joint is polished as a pre-step of the alumite treatment step. A method of manufacturing an aluminum-based structure, comprising a step of making a smooth surface by machining.