JP2003230970A - Aluminum alloy made rim in wheel for vehicle and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy made rim in a wheel for a vehicle which has no color tone difference between a joining part and a base material and has an excellent exterior appearance, and a manufacturing method thereof. <P>SOLUTION: When the rim is formed by processing a tube body obtained by forming a joining part 16 by friction stirring and joining of butting parts 14 of both ends of a 5000 series aluminum alloy plate material processed into a cylindrical shape, it is constituted so that each average value of the maximum lengths of the crystalline grains of the joining part 16 and the base material part 18 is set 10-300 μm by heating at a temperature not lower than the re- crystallization temperature of a 5000 series aluminum alloy and a ratio of the former average value and the latter one is within the range of 10:1-1:10. <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 alloy rim for a vehicle wheel and a method for manufacturing the rim, and more particularly, to a tubular body formed by friction stir welding of both ends of a cylindrical aluminum alloy plate material. The present invention relates to an aluminum alloy rim for a vehicle wheel to be obtained and a method for producing the rim advantageously.

[0002]

BACKGROUND ART Conventionally, as a kind of wheels for vehicles such as two-wheeled or four-wheeled vehicles, start-up vehicles, hoists, and bicycles,
A wheel having a rim made of an aluminum alloy and discs, spokes, and the like integrally provided on the rim is known. Since this aluminum alloy rim is excellent in lightness and moldability, a vehicle wheel having such a rim is preferably used particularly as a wheel for automobiles, motorcycles, and bicycles. .

By the way, the rim made of an aluminum alloy in such a vehicle wheel is generally manufactured by first rolling a plate material made of a 5000 series aluminum alloy having excellent strength into a cylindrical shape and abutting it in the circumferential direction. Weld the butt parts by MIG welding, TIG welding, flash butt welding, DC butt welding, etc.,
It is manufactured by obtaining a tubular body by integrating it, and molding this tubular body into a target shape.However, when adopting the conventional manufacturing method of an aluminum alloy rim, Since the joining of the butt portion of the aluminum alloy plate material that gives the rim is fusion welding consisting of melting the material, after the welding of such butt portion, extra work to remove a large amount of burr generated in the weld portion is required. This has to be done, and in some cases, there is a possibility that welding-specific joint defects such as blowholes and oxide entrainment may occur in the welded portion.

On the other hand, in recent years, attention has been paid to friction stir welding, which is a type of solid-state welding in which materials are joined in a solid state without being heated and melted, and for joining aluminum alloy sheet materials that give rims for automobile wheels, It is starting to be applied.

That is, in the method for manufacturing an aluminum alloy rim using this friction stir welding method, generally, first, a rod-shaped rotation is made with respect to a butt portion of a 5000 series aluminum alloy plate material rolled into a cylindrical shape. A pin concentrically provided at the tip of the jig is inserted together with the rotating jig while rotating integrally, and relatively moved to generate friction heat, and the friction heat causes the butt portion to be plastically processed. In a possible state, the agitating action by the high-speed rotation of the pin allows the tissues of the abutting part to intermingle,
Then, the abutting portions are joined without being melted to form a predetermined pipe body, and then the pipe body is subjected to a straightening process for correcting the joint portion into an arc shape, and further if necessary. Then, the intended rim is obtained by forming the tubular body into a predetermined shape.

According to the method for manufacturing an aluminum alloy rim for a vehicle wheel as described above, since the butt portion is not melted at the time of joining the butt portion of the aluminum alloy plate material giving the rim, the butt portion is not melted. Unlike the case of melt-welding the part, the occurrence of burrs and welding defects peculiar to welding are eliminated, and the heat input is small, and the strength reduction and distortion of the joint part can be advantageously suppressed, and as a result, A rim with excellent joining quality and strength,
It can be advantageously manufactured with high production efficiency.

However, the aluminum alloy rim manufactured according to the manufacturing method as described above is subjected to an anodic oxidation treatment for the purpose of imparting corrosion resistance and wear resistance and the like, and an anodic oxide coating is formed on the surface. When formed, a difference in color tone may appear between the joint formed by friction stir welding and the base material other than the joint. In that case, the difference in color tone causes a remarkable appearance defect. As described above, a serious problem that directly leads to a decrease in product value is caused.

[0008]

The present invention has been made in view of the circumstances as described above, and the first problem to be solved is to use a 5000 series aluminum alloy sheet and friction stir welding. With the use of the joining method, the aluminum alloy rim of the wheel for vehicles, which has excellent joining quality and strength, as well as high productivity, is provided between the joining part and the base metal part due to the formation of the anodized film. It is an object of the present invention to provide a novel structure capable of effectively eliminating or suppressing the occurrence of a defective appearance due to the difference in color tone. Further, in the present invention, a second problem to be solved is to provide a method capable of advantageously manufacturing an aluminum alloy rim for a vehicle wheel having such excellent characteristics.

[0009]

In order to solve the above two problems, the inventors of the present invention have proposed a rim obtained by friction stir welding of abutting portions of a 5000 series aluminum alloy plate material rolled into a cylindrical shape. Among them, we examined from various aspects the color difference between the joint and the base metal due to the formation of the anodic oxide film. It was found that the average length was extremely small and there was a large difference between the average length of the crystal grains in the base metal and the average length, which was due to the friction heat generated during friction stir welding. It was speculated that this was caused by the fact that the portion became a fine recrystallized structure and a remarkable difference was generated between the crystal structure of the joint part and the crystal structure of the base material part.

As a result of further intensive studies by the present inventor based on such an inference, the average value of the maximum lengths of the crystal grains in each of the joint portion of the rim and the base metal portion falls within a specific range. It was found that the occurrence of a color tone difference between the joint portion and the base material portion due to the formation of the anodic oxide film can be advantageously eliminated by controlling the value to control the value of In order to control the average value of the maximum length of such crystal grains to a value within a specific range, it is effective to heat both the joint portion and the base material portion at a predetermined temperature or higher. I found it.

That is, the present invention has been completed on the basis of such findings, and the gist of the invention is as follows.
A plate material made of a 5000 series aluminum alloy is processed into a cylindrical shape, and the abutting portions at both ends of the plate materials that are abutted in the circumferential direction are friction stir welded to form a joint portion extending along the abutting portion. In an aluminum alloy rim for a vehicle wheel obtained by using the tube body, the average value of the maximum length of crystal grains in each of the joint portion and the base material portion other than the joint portion is 10 to 300 μm.
m, and the ratio of the average value of the former to the average value of the latter is
It is in the aluminum alloy rim of the vehicle wheel, which is in the range of 10: 1 to 1:10.

In short, in the aluminum alloy rim of the vehicle wheel according to the present invention, the rim is obtained by friction stir welding the butt portion of the high-strength 5000 series aluminum alloy plate material processed into a cylindrical shape. Since it is formed by using the pipe body that is formed, it is an excellent feature obtained by adopting a friction stir welding method that joins the butt portion without melting it, unlike the welding method that melts and welds the butt portion. That is, excellent joining quality and strength, and further high productivity can be effectively ensured.

Further, in the aluminum alloy rim of the vehicle wheel according to the present invention, in particular, the average value of the maximum lengths of the crystal grains of the joint portion and the average value of the maximum lengths of the crystal grains of the base metal portion of the rim are particularly large. And 10 to 300 μm, and the ratio of the average value of the former to the average value of the latter is within the range of 10: 1 to 1:10. While the average value of the maximum length is made sufficiently large, the variation in the average value of the maximum length of the crystal grains in each of the joint portion and the base material portion can be effectively made small, and the joint portion and the mother material The material portion can be configured as a crystal structure having a similar crystal grain size.

Moreover, in such an aluminum alloy rim according to the present invention, the upper limit of the average value of the maximum length of the crystal grains of the joint portion and the average value of the maximum length of the crystal grains of the base material portion is 30.
Since it is set to 0 μm so that the crystal grains of the joint and the base material, that is, the entire rim will not be coarsened more than necessary, the tubular body formed by friction stir welding can be formed into a target shape. It is also possible to prevent the occurrence of rough skin during molding or the like.

Therefore, in the aluminum alloy rim of the vehicle wheel according to the present invention as described above, not only the rim can be constructed with excellent joining quality and strength, and also high productivity, but also anodization. Color tone difference between the joint portion and the base material portion caused by the formation of the coating film, the occurrence of poor appearance due to rough skin, etc. can be effectively eliminated or suppressed, as a result, the commercial value. It can be surely and dramatically increased.

In the present invention, in order to solve the second technical problem, a plate material made of a 5000 series aluminum alloy is processed into a cylindrical shape, and both end portions of the plate material that are abutted in the circumferential direction are machined. By friction stir welding the abutting part of and forming a joint along the abutting part,
When a predetermined tubular body is formed and then the tubular body is processed to manufacture an aluminum alloy rim for a vehicle wheel as a target, the tubular body formed by the friction stir welding is used as the 5000 series aluminum alloy. The gist also includes a method for manufacturing an aluminum alloy rim for a vehicle wheel, which is characterized by performing a heat treatment at a temperature equal to or higher than the recrystallization temperature.

That is, in the method for manufacturing an aluminum alloy rim for a vehicle wheel according to the present invention, a high-strength 5000 series aluminum alloy plate material is processed into a cylindrical shape, and the abutting portions at both ends thereof are friction stir welded. Since the intended rim is formed from the tubular body, the rim can be advantageously manufactured with excellent joining quality and strength, and also high productivity.

Further, in the method for manufacturing an aluminum alloy rim for a vehicle wheel according to the present invention, the tubular body formed by friction stir welding is heated at a temperature not lower than the recrystallization temperature of the 5000 series aluminum alloy. Therefore, since the base metal part that was not heated at all during friction stir welding can have a recrystallized structure similar to that of the recrystallized joint by friction stir welding. Yes, the average value of the maximum length of the crystal grains of the recrystallized structure in each of the joint portion and the base material portion,
From the average value of the maximum length of the crystal grains of the joint that was recrystallized structure during friction stir welding, in other words, from the average of the maximum length of the crystal grains of the joint before heat treatment with the base metal Also,
It can be effectively increased. Then, as a result, the average value of the maximum length of the crystal grains of the joint portion and the average value of the maximum length of the crystal grains of the base material portion after the heat treatment are set to values in the range of 10 to 300 μm. Moreover, the ratio of the former average value to the latter average value can be set within the range of 10: 1 to 1:10.

Therefore, according to the method for manufacturing an aluminum alloy rim for a vehicle wheel according to the present invention as described above, the joining portion and the mother portion which have excellent joining quality and strength and are formed by the formation of the anodized film are formed. A rim made of an aluminum alloy having a high commercial value, which does not have a color tone difference with the material portion and a poor appearance due to rough skin, can be manufactured extremely highly advantageously with high productivity.

According to one of the preferred embodiments of the method for producing an aluminum alloy rim for a vehicle wheel according to the present invention, the heat treatment is performed by heating the tubular body to 300 to 550 ° C. , Carried out.

If such a construction is adopted, in the heat-treated tube, the risk of distortion and melting due to an increase in heat input can be advantageously prevented, and at the same time, the reheating between the joint and the base material can be prevented. A uniform crystal structure can be effectively achieved, and excellent dimensional accuracy and a good appearance in which there is no color tone difference between the joint portion and the base material portion due to the formation of the anodic oxide coating are more excellent. It can be secured at a high level, and as a result, an aluminum alloy rim for a vehicle wheel having a higher commercial value can be manufactured more advantageously.

According to another advantageous embodiment of the method for manufacturing a rim made of an aluminum alloy in a vehicle wheel according to the present invention, the heat treatment is performed on the entire tubular body.
It is carried out by heating at a temperature rising rate of 150 to 300 ° C./h.

By adopting such a constitution, it is possible to advantageously prevent coarsening of crystal grains in each of the bonded portion and the base material portion without prolonging the time required for the heat treatment more than necessary. As a result, the target rim can be manufactured more efficiently with a better appearance.

According to another preferred embodiment of the method for manufacturing an aluminum alloy rim for a vehicle wheel according to the present invention, friction stir welding is performed in a state where the abutting portions of both ends of the plate are flattened. As a result, after the tubular body is formed, the flat joint is subjected to the straightening process, in which case the length of the joint after the straightening process: a and the length of the joint before the straightening process. S: The difference between a and b: ab, and the degree of working represented by the ratio of the length of the joint before the straightening process: b: (ab) / b is 0.1 or less. As described above, the straightening process is performed, and then the heat treatment is performed.

According to the manufacturing method having such a structure, in order to prevent the occurrence of dents or the like at the joint, friction stir welding is performed with the butt portion flattened, and then the joint is straightened into an arc shape. Even if the joining method is adopted, it is effective that the crystal grains of the joining portion and the base material portion are extremely coarsened during the heat treatment of the pipe body after the straightening process. Therefore, it is possible to advantageously manufacture an aluminum alloy rim having a better appearance without rough skin.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, in order to more specifically clarify the present invention, a configuration of an aluminum alloy rim in a vehicle wheel according to the present invention and a manufacturing method thereof will be described in detail with reference to the drawings. I will explain.

First, FIG. 1 shows an aluminum alloy rim for an automobile wheel, which is an example of an aluminum alloy rim for a vehicle wheel, manufactured in accordance with the manufacturing method according to the present invention, in a semi-sectioned form thereof.
It is shown schematically. As is clear from FIG. 1, the aluminum alloy rim 10 of the present embodiment has a substantially cylindrical shape, and a substantially disc-shaped disk 12 (virtual in FIG. 1) is formed so as to close one opening thereof. (Indicated by a line) are joined in a state in which they are fitted and inserted into the inner hole so as to be integrated with each other, so that a predetermined automobile wheel can be provided.

Further, the rim 10 is made by integrally combining the butt portions, which are butted in the circumferential direction, by friction stir welding under the condition that a plate material made of 5000 series aluminum alloy having excellent strength is bent into a cylindrical shape. It is composed of a tubular body formed by

That is, in the rim 10, as shown by the broken line in FIG. 1, the butt portion 14 formed by abutting the aluminum alloy plate materials in the circumferential direction is concentrically provided with the tip of the rod-shaped rotary jig. By inserting the provided pin together with the rotary jig while rotating it integrally and moving the pin relatively, the frictional heat generated between the abutting portion 14 and the portions on both sides thereof makes those portions plastically workable. Further, the tissue of both sides of the abutting portion 14 is mixed by the stirring action by the high speed rotation of the pin, and the both sides are joined without being melted (see FIG. 3). The butt portion 14 that is agitated in a plasticized state by the high speed rotation of the pin
Both side portions (area surrounded by two imaginary lines in FIG. 1) are band-shaped joint portions 16 extending along the abutting portion 14, while the remaining portion excluding the joint portions 16 is formed. All of these are used as the base material portion 18.

In this embodiment, particularly, the average value of the maximum crystal grain lengths of the joint portion 16 and the average value of the maximum crystal grain lengths of the base material portion 18 in such a rim 10 is 1
The value is in the range of 0 to 300 μm, and the ratio of the former average value to the latter average value is in the range of 10: 1 to 1:10.

Because, as will be described later, the rim 10 is obtained by subjecting the tubular body formed by friction stir welding of the abutting portions of the 5000 series aluminum alloy plate materials that have been bent into a cylindrical shape to a heat treatment. The rim 10 is formed by forming the tubular body into a desired shape by rolling or the like, and then anodizing it to form an anodic oxide coating on the surface. When the average value of the maximum lengths of the crystal grains in each of the bonding portion 16 and the base material portion 18 is less than 10 μm, the crystal grains are too small, so that the bonding is accompanied with the formation of the anodized film. Part 1
6 and the base material portion 18 cause a clear color difference, and when the average value exceeds 300 μm, the crystal grains of the joint portion 16 and the base material portion 18 are separated from each other. This is because it becomes excessively coarse, and roughening occurs when it is formed into a desired shape by forming such as rolling. Furthermore, it is assumed that the ratio of the average value of the maximum crystal grain lengths of the joint portion 16 and the average value of the maximum crystal grain lengths of the base material portion 18 is a value outside the range of 10: 1 to 1:10. For example, the average value of the maximum lengths of the crystal grains in each of the bonding portion 16 and the base material portion 18 is 10 to 300 as described above.
Even if the value is in the range of μm, the variation between the crystal grain size of the joint portion 16 and the crystal grain size of the base material portion 18 is too large. 1
This is because it becomes difficult to suppress the occurrence of a color tone difference between 6 and the base material portion 18. Therefore, here, in order to give the rim 10 an excellent appearance without rough skin or a color tone difference between the joint portion 16 and the base material portion 18, each of the joint portion 16 and the base material portion 18 is provided. It is necessary that the average value of the maximum lengths of the crystal grains in and the ratio of the average values be within the above-mentioned range.

By the way, when manufacturing the aluminum alloy rim 10 for an automobile wheel having such a structure, the work is carried out, for example, according to the following procedure.

That is, first, as shown in FIG. 2, a strip-shaped plate member 20 made of a 5000 series aluminum alloy having a size that gives the intended rim 10 is projected by a known method such as roll forming (roll forming). A cylindrical molded body 22 is formed in a shape in which both ends are abutted in the circumferential direction while leaving a predetermined width portion of both ends to be joined together. Thus, this cylindrical molded body 22
In this case, the abutting portions 14 at both ends abutting in the circumferential direction of the aluminum alloy plate material 20 are in a form of extending in the axial direction of the cylindrical molded body 22, and the aluminum abutting in the circumferential direction is made. Both end portions of the alloy plate member 20 are formed into flat portions 24 and 24, respectively, with flat portions having a predetermined width on both sides of the abutting portion 14 between them. .

A known method is appropriately adopted for forming the flat portions 24, 24 on both sides of the abutting portion 14, and the flattening step is performed at the same time as the circular working step. Although it is possible to adopt a method such as performing after the process, the entire aluminum alloy plate material 20 is processed into a cylindrical shape without forming such flat portions 24, 24 to form a cylindrical molded body 22. And the abutting portions 14 of both ends of the cylindrical molded body 22 may be friction stir welded without any problem.

Next, as shown in FIG. 3, the flat portion 2
The butt portion 14 of the cylindrical molded body 22 provided with 4, 24 on both sides is friction stir welded to form the tube body 26 which is an intermediate molded body of the rim 10. In the process of forming the pipe body 26, the friction stir welding of the butted portion 14 is performed based on a known method.

That is, the pin 30 concentrically provided at the tip of the rod-shaped rotary jig 28 is rotated integrally with the rotary jig 28 around the axis thereof, and the cylindrical molded body 2 is formed.
The butt portion 14 and the flat portion 24, 24 are inserted into the butt portion 14 and the lower portion of the rotary jig 28 is brought into contact with the surface (outer surface) of the flat portion 24, 24.
Frictional heat is generated at the contact surface between the pin 24 and the lower portion of the pin 30 and the rotary jig 28 to plasticize the periphery thereof, and the abutting portion 14 is flattened on both sides by the stirring action accompanying the high speed rotation of the pin 30. The structures of the parts 24, 24 are intermingled with each other, and further, the pin 30 and the rotary jig 28
Is relatively moved along the abutting portion 14, so that the flat joint portion 16 is formed so as to extend along the abutting portion 14 at each of the flat portions 24 and 24 in which the tissues are intermingled. Then, the cylindrical molded body 22 is integrally joined at the butting portion 14. At this time,
Since the flat portions 24, 24 are butted against each other and friction stir welding is performed, at the time of welding, the escape of the meat portion of the cylindrical molded body 22 that is agitated by the pin 30 of the rotating jig 28 is a shoulder portion of the rotating jig 28. Can be suppressed and a sound joint 16 is formed. Also, at the time of such joining,
The joint portion 16 is recrystallized by frictional heat.

Although not shown in the drawing, when performing such friction stir welding, a cylindrical shape is formed so that unevenness at the flat joint 16 to be formed can be prevented in advance. A predetermined steel backing jig is arranged on the back side of the flat portions 24, 24 of the body 22, and an arc-shaped portion (base material portion of the rim 10 excluding the flat portions 24, 24 of the cylindrical molded body 22. The arcuate portion of the cylindrical molded body 22 will be constrained from the outside by a predetermined constraining jig so that the cylindrical shape of the portion 18 which provides 18) can be maintained during the bonding operation.

Thereafter, the flat joint portion 16 of the tube body 26 thus obtained is polished, if necessary, and then the flat joint portion 16 is formed into a circle other than the joint portion 16 with respect to the pipe body 16. The straightening process of shaping and straightening into an arc shape having the same curvature as the arcuate portion is carried out by a known shaping method such as roll working. As a result, as shown in FIG. 4, the tubular body 26 is molded into a hollow cylindrical shape as a whole.

In the straightening process for the flat joint 16 of the tubular body 26, the flat joint 16 (shown by an imaginary line in FIG. 4) is preferably straightened into an arc shape. The difference between the length of the joint 16: a and the length of the flat joint 16 before straightening: b: a-b and the length of the flat joint 16 before straightening: b The workability represented by the value: (ab) / b is within a range of 0.1 or less, and the flat joint portion 16 is straightened.
Because the value of the degree of processing exceeds 0.1,
When the flat joint portion 16 is straightened, in other words, when the flat joint portion 16 is straightened into an arc shape, its length can be increased at a rate exceeding 10%, The crystal grains in the joint portion 16 corrected in an arc shape become extremely coarse, and the average value of the maximum length of the crystal grains becomes larger than 300 μm, which causes the subsequent rolling process as described above. This is because the joint portion 16 will be roughened during the molding process.

In the straightening process for the flat joint portion 16 of the pipe body 26, the flat joint portion 16 is
If the tubular body 26 is corrected to have an arcuate shape corresponding to the curvature of the arcuate portion other than the joint portion 16 in FIG. The lower limit of is not particularly limited,
If it is attempted to reduce the workability after satisfying such conditions, the length of the flat joint portion 16 will inevitably become small, so that the joint portion 16 with sufficient joint strength can be obtained.
The lower limit value of the workability is appropriately determined within the range in which the length can be secured. In addition, the cylindrical molded body 22 in which the flat portions 24, 24 are not formed at all
Of course, when the tube body 26 is formed by abutting the ends having the R shape with each other and performing friction stir welding, the correction process here may be omitted.

Next, the tubular body 26 with the joining portion 16 straightened into an arc is put into a predetermined heating furnace or the like, heated to a predetermined temperature in the heating furnace, and kept at that temperature for a predetermined time. By doing so, the heat treatment for the purpose of making the crystal structures of the joint portion 16 and the base material portion 18 uniform is performed on the entire tubular body 26. In this heat treatment, In particular, the entire tubular body 26 is the joint portion 16 at the time of friction stir welding of the butt portion 14.
Is heated to a temperature equal to or higher than the recrystallization temperature of.

Thus, by performing the heat treatment at a temperature equal to or higher than the recrystallization temperature of the joint portion 16 at the time of friction stir welding, the base material portion 18 which was not heated at all at the time of friction stir welding of the butt portion 14 is obtained. The average value of the maximum length of the crystal grains of the recrystallized structure in each of the welded part 16 and the base material part 18 is formed by the recrystallized structure similar to that of the welded part 16 recrystallized by friction stir welding. Is re-crystallized by frictional heat generated during friction stir welding
The average length of the crystal grains of No. 6 is sufficiently increased. Then, as a result, the average value of the maximum lengths of the crystal grains of the joint portion 16 after this heat treatment and the base material portion 1
The average value of the maximum length of the crystal grains of 8 is 10 to 300 μm
And the ratio of the former average value to the latter average value is a value within the range of 10: 1 to 1:10.

In carrying out such heat treatment, the heating temperature of the tube 26 is, for example, 300.
It is set to about 550 ° C. Because the tube 26 is 550
When heated to a high temperature exceeding 0 ° C., the heat input increases, not only the distortion due to the heat of the tube 26 increases, but also the tube 26 may melt, and
When the tube 26 is heated at a low temperature of less than 300 ° C,
This is because the recrystallized structure of the joint portion 16 and the base material portion 18 becomes insufficiently uniform. Therefore, the pipe 26 here
The heat treatment of the tube 26 is preferably 300 to 5
It will be carried out by heating to a range of 50 ° C. Further, in such a temperature range, the time for holding the tubular body 26 is sufficient to homogenize the recrystallization structure of the joint portion 16 and the base material portion 18 while preventing waste of time required for the entire heat treatment. In consideration of this, the time is preferably about 30 minutes to 2 hours.

Further, the tube 26 in such a heating range
In carrying out the heat treatment for, the temperature rising rate is preferably 150 to 300 ° C./h. This is because, in the heat treatment, when the pipe body 26 is heated at a temperature rising rate of more than 300 ° C./h until it reaches a predetermined heating temperature, the joint portion 16 of the pipe body 26 is heated during the heat treatment. There is a risk that the crystal grains of the recrystallized structure of the base material portion 18 become coarse and the average value of the maximum lengths of those crystal grains becomes larger than 300 μm. In that case, the subsequent rolling process or the like is performed. This is because the joint 16 and the base material 18 are roughened during the processing. Further, if the temperature rising rate is less than 150 ° C./h, it takes an extremely long time to heat the tubular body 26 to a required temperature, and wasteful time is consumed for the heat treatment. The production efficiency of the target rim 10 will be significantly reduced. Therefore, in the heat treatment of this step, it is desirable that the rate of temperature increase is 150 to 300 ° C./h in order to prevent deterioration of productivity and appearance of the target rim 10.

Subsequently, after the pipe 26 heated by the above-mentioned heat treatment is cooled by forced cooling or cooling, the pipe 26 is transferred by a general rolling method. The tube body 26 is formed into a shape corresponding to the intended rim 10. Then, this tube 2
By applying a known method to No. 6, an anodized film for imparting corrosion resistance and wear resistance is formed on the surface, and the target aluminum alloy rim is thus formed. You get 10.

In the rim 10 thus obtained, a disc 14 separately formed by forging or the like is fitted into the inner hole of the rim 10 and joined by a friction stir welding method or various welding methods. , By integrating,
It has been completed as an automobile wheel.

Thus, in this embodiment, the high strength 5
In a state where the 000 series aluminum alloy plate material 20 is bent into a cylindrical shape, the abutting portions 14 at both ends thereof are joined by a friction stir welding method, which is a kind of solid phase joining method, to form a tube body 26. Therefore, unlike the case where welding joining is adopted as the joining method of the abutting portion 14, the rim 10 has excellent joining quality and strength because the intended rim of the wheel 10 is formed. Moreover, high productivity can be ensured.

In the present embodiment, in particular, the tubular body 26 in which the joints 16 are formed by friction stir welding of the abutting portions 14 at both ends of the aluminum alloy plate 20 bent into a cylindrical shape. On the other hand, by performing the heat treatment at a temperature equal to or higher than the recrystallization temperature of the joint portion 16 at the time of friction stir welding, the maximum length of crystal grains in the joint portion 16 of the rim 10 formed from the tubular body 26 is increased. And the average value of the maximum length of the crystal grains in the base material portion 18 are values within the range of 10 to 300 μm, and the ratio of the former average value to the latter average value is 10: 1 to 1 The surface roughness of the rim 10 and the appearance defect due to the color difference between the joint 16 and the base material 18 can be effectively eliminated or suppressed. And as a result , Commercial value of such rim 10 is than the be obtained reliably and increased dramatically.

Further, in this embodiment, such a tubular body 2 is used.
The heat treatment for No. 6 is performed at a heating rate of 150 to 300 ° C./h and is performed at a heating temperature of 300 to 550 ° C., so that excellent dimensional accuracy and a joint portion accompanying the formation of the anodic oxide coating are obtained. It is possible to secure a good appearance without occurrence of a color tone difference between the base material and the base material portion and rough skin, and as a result, the rim 10 having a higher commercial value is more advantageous. Can be manufactured in.

Further, in the present embodiment, the difference between the length a of the arc-shaped joint 16 after the straightening process in the tubular body 26: a and the length of the flat joint 16 before the straightening: b: ab And the flatness of the flat joint 16 before correction, which is represented by the ratio of the length to the ratio of b: (a−b) / b, is 0.1 or less. Even if the portion 16 is corrected, it is advantageous that the crystal grains of the recrystallized structures of the joint portion 16 and the base material portion 18 are extremely coarsened during the heat treatment of the tubular body 26. Rim 10 which can be prevented by the above and has a better appearance without rough skin.
Can be advantageously manufactured.

In this embodiment, an example in which the present invention is applied to an aluminum alloy rim for an automobile wheel and a method for manufacturing the same is shown. However, the present invention is applied to other vehicles other than the automobile wheel. It goes without saying that it can be advantageously applied to both the aluminum alloy rim of the wheel and the manufacturing method thereof.

[0052]

The present invention will be described in more detail below by showing examples of the present invention, but the present invention is subject to any restrictions due to the description of such examples. Not to mention that. Also,
In the present invention, in addition to the following examples, in addition to the above-described embodiments of the present invention, various modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention,
It should be understood that modifications, improvements, etc. may be made.

First, a plate material of JIS5052 aluminum alloy having a thickness of 4 mm, a width of 500 mm, and a length of 1350 mm is prepared, and the plate material is bent into a cylindrical shape by a known roll process so that both end portions in the longitudinal direction are bent. Outer diameter 400 mm, length (height) formed by butting each other in the circumferential direction
A 500 mm cylindrical molded body was molded. Then, this cylindrical molded body is constrained from the outside by a known constraining jig so that the cylindrical shape is maintained, and a steel backing jig is arranged on the back side of the butted portion, and further, such a butt A tab plate having a thickness of 4 mm was fixed to both ends of the cylindrical molded body in the lengthwise direction.

Then, using a steel rotating jig having pins concentrically provided at the tips thereof, the butted portion of the cylindrical molded body in the above-described state is moved from one tab plate to the other tab. Friction stir welding is performed on the plate by a known friction stir welding method to form a joint portion extending along the butt portion, and further, the surface (outer surface) of the joint portion is polished to form the joint portion. The formed bead was removed to obtain a tubular body in which the cylindrical molded body was integrally joined at the butting portion. The rotational speed of the rotary jig at the time of friction stir welding of the butt portion of this cylindrical molded body was 1000 rpm.
The joining speed, that is, the relative movement speed of the rotary jig with respect to the abutting portion was 300 mm / min. Furthermore, when the average value of the maximum length of the crystal grains in each of the joint portion and the base material portion of the tube body thus obtained was determined by a known method, the average value of the maximum length of the crystal grains in the joint portion was 3 μm. And the average value of the maximum length of the crystal grains of the base material is 100
was μm.

Next, the tubular body obtained as described above was placed in a known annealing furnace, and the recrystallization temperature of the JIS 5052 aluminum alloy, which is the material for forming the tubular body, at a temperature rising rate of 150 ° C./h. The tube was heated to a higher temperature of 400 ° C. and kept at that temperature for 30 minutes to perform heat treatment on the tubular body. Then, the furnace was cooled, and when the temperature of the tube reached 200 ° C., the tube was taken out of the annealing furnace and further air-cooled. Thus, after sufficiently cooling the tubular body, when the average value of the maximum length of the crystal grains in each of the joint portion and the base material portion of the pipe body was obtained again by a known method, the maximum value of the crystal grains in the joint portion was determined. The average length is 75 μm,
The average value of the maximum lengths of the crystal grains of the base material portion was 125 μm, and all were within the range specified by the present invention. The ratio of the former average value to the latter average value was calculated to be 3: 5, which was also within the range characterized by the present invention.

After that, the rolling process for forming the heat-treated tubular body into a desired shape is carried out according to a conventional method using a known rolling device, and then the tubular body is subjected to
By carrying out anodizing treatment using a known anodizing method to form an anodized film on the surface, a target rim (Example) was obtained. Then, with respect to the rim of this example, the presence or absence of rough skin and the presence or absence of a color tone difference between the joint portion and the base material portion were visually checked, and no such rough skin or color tone was observed. . From this, it can be clearly recognized that by forming the rim according to the method of the present invention, it is possible to manufacture a wheel having an excellent appearance without rough skin or a difference in color tone between the joint portion and the base material portion. Of.

For comparison, two aluminum alloy plate materials of the same type and size as the aluminum alloy plate material prepared at the time of manufacturing the rim of the above embodiment were prepared.
Then, in the same manner as in the above-mentioned embodiment, two cylindrical molded bodies were molded from the two prepared aluminum alloy sheet materials, and then the abutting portion of the two cylindrical molded bodies was manufactured by the same method as in the above-mentioned embodiment. Each of them was friction stir welded to obtain two pipes each having a joint extending along the abutting portion.

Next, one of the two tubular bodies thus obtained was placed in a known annealing furnace and heated to 150 ° C. /
JIS 5052, which is a material for forming the tubular body, at a heating rate of h
Temperature lower than recrystallization temperature of aluminum alloy 2
The tube was heated to 75 ° C. and kept at that temperature for 30 minutes to heat-treat the tube. Then, in the same manner as in the above example, after cooling the tubular body, the average value of the maximum length of the crystal grains in each of the joined portion and the base material portion of the tubular body was determined by a known method, The average value of the maximum length of the crystal grains is 8 μm, the average value of the maximum length of the crystal grains of the base material portion is 100 μm, and the average value of the maximum length of the crystal grains of the joint part is The value was different from the value within the specified range. Moreover, when the ratio of the former average value and the latter average value was calculated, it was 1:
At 12.5, this was also outside the characteristic range of the present invention.

Separately from this, the remaining one tubular body was housed in a known annealing furnace, and the tubular body was heated at a heating rate of 350 ° C./h, which is a value outside the range specified in the present invention. The tubular body was heat-treated by heating it to 400 ° C., which is higher than the recrystallization temperature of the JIS 5052 aluminum alloy, which is the body forming material, and holding it at that temperature for 30 minutes. Then, in the same manner as in the above example, after cooling the tubular body, the average value of the maximum length of the crystal grains in each of the joined portion and the base material portion of the tubular body was determined by a known method, The average value of the maximum lengths of the crystal grains is 1200 μm, the average value of the maximum lengths of the crystal grains of the base material portion is 100 μm, and the average value of the maximum lengths of the crystal grains of the junction 6 is the present invention. The value was different from the value within the range specified in. The ratio of the former average value to the latter average value was calculated to be 1: 0.08, which was also outside the characteristic range of the present invention.

Thereafter, the rolling process for forming the two heat-treated tubular bodies into the desired shape and the anodizing treatment for forming an anodized film on the surfaces of the tubular bodies are carried out as described above. The same procedure as the example was performed to obtain the target rim (Comparative Examples 1 and 2). Then, the rim (Comparative Example 1) obtained by performing the heat treatment at a temperature lower than the heat treatment temperature specified in the present invention and the temperature rising rate at the time of the heat treatment defined as a desirable range in the present invention Both the rim (Comparative Example 2) obtained by performing the heat treatment while raising the temperature at a rapid rate were visually inspected for the presence or absence of rough skin and the presence or absence of a color difference between the joint and the base material. As a result of the examination, in the rim of Comparative Example 1, rough skin was observed on the surface and a difference in color tone between the joint portion and the base material portion was clearly confirmed. Further, in the rim of Comparative Example 2, rough skin was clearly recognized on the surface. From these, it can be easily recognized that the wheel manufactured according to the conventional method different from the method of the present invention has a poor appearance.

[0061]

As is apparent from the above description, in the aluminum alloy rim for the vehicle wheel according to the present invention, the rim is constructed with excellent joining quality and strength, and further high productivity. Not only can it be obtained, but also the occurrence of a rough surface on the surface of such a rim and the occurrence of a defective appearance due to a color tone difference between the joint portion and the base material portion can be effectively eliminated or suppressed, and as a result, the product The value can be surely and dramatically increased.

Further, according to the method for manufacturing an aluminum alloy rim for a vehicle wheel according to the present invention, it has excellent joining quality and strength, and the surface is rough, and the joining portion and the base material portion have a rough surface. Thus, the aluminum alloy rim for a vehicle wheel having a high commercial value, which does not have a defective appearance due to a color difference, can be manufactured extremely advantageously with high productivity.

[Brief description of drawings]

FIG. 1 is a half cross-sectional explanatory view showing an example of an aluminum alloy rim in a vehicle wheel manufactured according to the method of the present invention.

2 is an explanatory view showing an example of a process of manufacturing an aluminum alloy rim in the vehicle wheel shown in FIG. 1, wherein an aluminum alloy plate material is bent into a cylindrical shape to form a cylindrical molded body. It shows the state.

FIG. 3 is an explanatory view showing another example of the process of manufacturing the aluminum alloy rim in the vehicle wheel shown in FIG. 1, in which the butted portion of the cylindrical molded body is friction stir welded to form a tubular body. It shows the state of molding.

4 is an explanatory view showing another example of the process of manufacturing the aluminum alloy rim in the vehicle wheel shown in FIG. 1, and is a joint portion formed so as to extend along the abutting portion of the pipe body. Is shown in a state of being straightened into an arc shape.

[Explanation of symbols]

10 rim 12 disc 14 Butt 16 Joint 18 Base material 20 Plate 22 Cylindrical molded body 24 Flat part 26 tube 28 rotating jig 30 pin

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B23K 103: 10 B23K 103: 10

Claims (5)

[Claims] 1. A joint extending along the abutting portion by processing a plate material made of a 5000 series aluminum alloy into a cylindrical shape and friction stir welding the abutting portions at both ends of the plate material that are abutted in the circumferential direction. The aluminum alloy rim in the vehicle wheel obtained by using the tubular body forming the portion, the average value of the maximum length of the crystal grains in each of the joint portion and the base material portion other than the joint portion, 10 to 300 μm, and the ratio of the former average value to the latter average value is 10:
An aluminum alloy rim for a vehicle wheel, which is in the range of 1 to 1:10. 2. A plate material made of a 5000-series aluminum alloy is processed into a cylindrical shape, and the abutting portions at both ends of the plate material that are abutted in the circumferential direction are friction stir welded to form a joint portion along the abutting portion. By forming a predetermined tubular body by forming, by processing such a tubular body, in producing the aluminum alloy rim in the vehicle wheel of interest, the tubular body formed by the friction stir welding, 500 above
A method of manufacturing an aluminum alloy rim for a vehicle wheel, which comprises heat-treating at a temperature equal to or higher than a recrystallization temperature of a 0-based aluminum alloy. 3. The heat treatment is performed on the tubular body by 300 to 5
The method for manufacturing an aluminum alloy rim for a vehicle wheel according to claim 2, which is carried out by heating to 50 ° C. 4. The heat treatment is applied to the entire tubular body to
By heating at a temperature rising rate of 50 to 300 ° C./h,
The manufacturing method of the aluminum alloy rim in the vehicle wheel according to claim 2 or 3, which is carried out. 5. The pipe body is formed by performing friction stir welding in a state where the abutting portions of both ends of the plate member are flattened, and then the flat joint portion is subjected to a straightening process. , The difference between the length of the joint after the straightening process: a and the length of the joint before the straightening process: b: a
-B and the working ratio represented by the value of the ratio of the length of the joined part before the straightening process: b: (ab) / b is set to 0.1 or less, and the straightening process is performed. The method for manufacturing an aluminum alloy rim for a vehicle wheel according to claim 2, wherein the heat treatment is performed.