JP2001172796A - Structural member made of aluminum alloy and motorcycle using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the impairment of the appearance of electrolytically colored members by the contrast of weld zones and to obtain color tones uniform over the entire part. SOLUTION: A head pipe 3, tank rail 4 and rear arm bracket 5 made of aluminum alloys stipulated in JIS 5083 are joined by welding, by which a main frame 2 is constituted. This main frame 2 is colored by electrolytic coloring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy structural member constituting a motorcycle or the like, and more particularly to an aluminum alloy structural member in which a plurality of members are joined by welding and their surfaces are colored.

[0002]

2. Description of the Related Art In general, a main frame constituting a motorcycle is required to be manufactured in accordance with a manufacturing cost or a design requirement.
IS2000-5000 or 7000 series Al
It was formed by joining by welding a tank rail formed by pressing and welding an alloy wrought material into a hollow shape and a bracket formed by casting using an aluminum alloy for casting. Since the main frame is not only a structural member but also an exterior component, coloring of various colors has been required for the purpose of improving the appearance design. Conventionally, these requirements have been met by painting or dyeing alumite.

[0003]

However, the method of coloring by painting has a problem that the texture of the underlying metal cannot be obtained because the underlying metal is covered. In the case of dyed alumite in which a dye is formed by impregnating a dye into an alumite film formed on the surface of an underlying aluminum alloy, the dye is vulnerable to ultraviolet light, and the binding energy of C (carbon) and N (nitrogen) of molecules constituting the dye Is lower than the energy level of ultraviolet light,
The bond between N and N is released, the dye is decomposed, and the color deteriorates.

In order to solve these problems, the inventor of the present application has attempted to employ an electrolytic coloring method, which is one of the coloring methods for aluminum alloys. In the electrolytic coloring, one or more of metals such as Ni, Fe, Cu, Ag, Au, and Sn are deposited in the pores of the alumite coating layer in the alumite coating layer. The color is obtained by the interference between the reflected light and the light transmitted through the alumite film and reflected on the aluminum alloy surface as the base,
Since the light reflected on the base surface is visible, the texture of the base metal can be obtained. Further, since the metal deposited in the pores is not affected by ultraviolet rays, color deterioration hardly occurs. However, the color tone due to electrolytic coloring is affected by the film thickness of the alumite film and the transparency of the film, which are affected by the metal structure and alloy components of the underlying aluminum alloy. Especially in the welded part, the aluminum alloy of the base undergoes melt-solidification, so if an intermetallic compound precipitates on or near the surface, the alumite film formed by the alumite treatment becomes cloudy or thinner than the surroundings of the welded part. Would.

[0005] Further, depending on the cooling rate after welding, the crystal grain system differs from the crystal grain system around the welded portion, and the alumite film formed by the alumite treatment also differs between the welded portion and the periphery of the welded portion. It will be. If the transparency or film thickness is different from that of the alumite film around the welded portion, the color tone of the welded portion will appear with strong contrast, and the appearance will be impaired. When a plurality of members to be welded are a combination of a wrought product (a product formed by pressing or forging using wrought material) and a cast product, the metal structure of the cast product is larger than the wrought product product. Since the crystal grain system in the above becomes large, the overall appearance becomes patchwork-like, which is inconvenient when a uniform color tone is required.

The present invention has been made in view of the above-mentioned conventional problems, and a first object is to prevent the appearance of electrolytically colored one from being impaired by the contrast of a welded portion. The second object is to obtain a uniform color tone as a whole.

[0007]

Means for Solving the Problems To achieve this object, the invention according to claim 1 is an aluminum alloy structural member formed by joining members made of an Al-Mg-based aluminum alloy by welding. Then, electrolytic coloring is applied to the alumite film formed on the surface of the aluminum alloy structural member. Al
-A Mg-based aluminum alloy is a non-heat-treatable alloy, and the intermetallic compound does not become coarse even after the heat history of melting and solidification, and there is little change from the microstructure in the member before welding. Further, during the alumite treatment in which a current is passed, the relative movement speed of the metal ions of Mg is higher than that of Al, so that Mg does not remain in the alumite film on both the welded surface and the non-welded surface, and thus Mg is generated. Therefore, even if there is a difference in the microstructure between the surface of the welded portion and the surface of the non-welded portion, the difference in the transparency of the alumite film disappears. Thus, it is possible to prevent the color tone of the welded portion from appearing with a strong contrast.

According to a second aspect of the present invention, in the first aspect of the invention, each of the members before welding is made of only one of a wrought product, a forged product and a cast product. A combination of a stretched product and a forged product. Therefore, there is no difference in the crystal grain system in the metal structure of each member, and there is no difference in the thickness of the alumite film formed by the alumite treatment, and the aluminum alloy structural member is electrolytically colored with a uniform color tone as a whole. .

A third aspect of the present invention is directed to the aluminum alloy structural member according to the first or second aspect, which is used as a main frame of a motorcycle. Therefore,
The wear resistance of the main frame surface is further increased by the alumite film without impairing the appearance of the motorcycle, so that the main frame surface is prevented from being damaged by dust or sand particles during running.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing the appearance of a motorcycle to which an aluminum alloy structural member according to the present invention is applied, FIG. 2 shows a main frame which is also an aluminum alloy structural member, and FIG. Figure, Figure (b)
FIG. 2 is a sectional view taken along the line II (b) -II (b) in FIG. FIG. 3 is an exploded perspective view for explaining a method of assembling a rear arm which is also an aluminum alloy structural member.
FIG. 4 is a cross-sectional view showing a state in which the aluminum alloy structural member is electrolytically colored, and FIG. 5 is a sectional view showing the surface of the aluminum alloy structural member when the aluminum alloy structural member is subjected to the first to fourth electrolytic treatments. It is sectional drawing expanded and shown in order to demonstrate a change. FIG. 6A is a sectional view of an aluminum alloy structural member subjected to electrolytic coloring, and FIG. 6B is a sectional view of VI in FIG.
FIG. 7 is an enlarged view of part (b), and FIG. 7 is a model diagram for explaining the mechanism of color development of the electrolytic colored film. FIG.
(A) is a cross-sectional view schematically showing a state in which the base materials are joined with beads, and (b) is a VIII in FIG.
It is an enlarged view of (b) part.

In FIG. 1, a motorcycle generally designated by reference numeral 1 is provided with a main frame 2 at the center. As shown in FIG. 2, the main frame 2 includes a head pipe 3 and a head pipe 3. A pair of tank rails 4, 4 whose front ends are welded to each other and whose rear ends are gradually separated from each other.
And rear arm brackets 5, 5 welded to the rear ends of the tank rails 4, 4, respectively. As shown in FIG. 2B, the tank rail 4 is
JIS5083 wrought aluminum alloy (Mg-Al
Plate material of 5000 series aluminum alloy), which is formed into a shallow dish shape having an opening by press working,
, Each of the side plates 6 and 7 is abutted with the opening edge thereof, and the abutted peripheral edge portions 8 are defined by JIS5.
It is formed in a hollow shape by welding using a welding rod of No. 083.

At the substantially center of both side plates 6 and 7 of the tank rail 4, a long hole 6 for an air cleaner is opposed to each other.
a and 7a are formed, and a pair of through holes 6b and 6c communicating with the hollow portion are formed at both ends of one side plate 6. The rear arm bracket 5 is formed by forging or shaving wrought aluminum alloy material of JIS 5083, and is provided with a shaft support hole 5a.
083 is joined to the lower end of the tank rail 4 using a welding rod.

Reference numeral 9 denotes a V-type two-cylinder engine mounted on the lower side of the main frame 2, reference numeral 10 denotes a tank mounted on the upper side of the main frame 2, and reference numeral 11 denotes a seat. 1
Reference numeral 3 denotes a rear arm, as shown in FIG. 3, a pair of opposed arm members 14, 14, and these arm members 1
A cross member 15 joined so as to be interposed between the pair of arm members 14, 14; a head pipe 16 welded to the front ends of the pair of arm members 14, 14;
End brackets 17, welded to each of the rear ends of the
17.

The arm member 14 includes a lid member 18 formed by pressing a JIS 5083 wrought aluminum alloy plate material and a bent member 19 having a U-shaped cross section. It is covered with the cover member 18 and is formed in a hollow shape by welding with a JIS 5083 welding rod. Cross member 15, head pipe 16, end bracket 17 are JIS508
3 is formed by forging or shaving an aluminum alloy wrought material, and the arm member 1 is welded with a JIS5083 welding rod.
The end bracket 17 is provided with a dovetail-shaped shaft support hole 17a.

The end bracket 1 of the rear arm 13
As shown in FIG. 1, a pivot shaft 20 is suspended between the shaft bearing holes 17a and 17a of the shafts 7 and 17.
, A rear wheel 21 is rotatably supported via a bearing (not shown). Reference numeral 22 denotes a shaft suspended between the shaft support holes 5a of the rear arm brackets 5, 5 of the main frame 2, and the head pipe 16 of the rear arm 13 is rotated on the shaft 22 via a bearing (not shown). The rear arm 13 is freely supported, and the rear arm 13 is rotatably supported by the main frame 2 about a shaft 22 as a rotation center.

Reference numeral 23 denotes a rear cushion lever,
The lower end is pivotally attached to the head pipe 16 of the rear arm 14,
The rotation of the head pipe 16 causes the upper end to rotate about the shaft 22, and the rear end of the rear cushion unit 24 is pivotally attached to the upper end. Reference numeral 25 denotes a cushion support bracket which is fixed to the engine 9 at the center and the lower end, and has a rear cushion unit 24 at the upper end.
The front end of is pivoted. Reference numeral 26 denotes an inverted front fork. The front fork 26 is rotatably supported on the front end side of the main frame 2 via bridge brackets 27 and 28. A steering handle 2 is provided on the upper end side of the front fork 26 via a bracket.
An axle 30 is horizontally mounted between a pair of inner cylinders (not shown) provided on the lower end side, and a front wheel 31 is rotatably supported on the axle 30.

Next, a method for electrolytically coloring the main frame 2 will be described with reference to FIGS. In FIG. 4, reference numeral 35 denotes an electrolytic cell, and reference numeral 36 denotes a pair of opposed cathode plates provided in the electrolytic cell 35, which are connected to a negative electrode of a power source 37 via a cable. 38 is a holder for holding the main frame 2 and is formed of a conductive member;
The power supply 37 is connected to the positive electrode via a cable. In addition, only in the tertiary electrolysis in the electrolysis treatment described below,
The connection to the power source 37 is reversed, the holder 38 is connected to the negative electrode, and the cathode plate 36 is connected to the positive electrode. A circulation pump 39 circulates the electrolytic solution 40 in the electrolytic bath 35 through a circulating passage 41 for cooling the electrolytic solution, cools it with a radiator 42, and supplies it again from the discharge nozzle 43 into the electrolytic bath 35. I have. Reference numeral 44 denotes a control unit which controls the pump 3 based on a temperature detected by a temperature sensor 45 for detecting the temperature of the electrolyte 40.
9 to control the operation and non-operation.

As shown in FIG. 1, the main frame 2 immersed in the electrolyte 40 has a pair of through holes 6b and 6c formed at both ends of a hollow tank rail 4. 4 is held by the holder 38 so as to be positioned at the upper and lower ends.

In such a configuration, when the primary electrolysis is performed under the electrolysis conditions shown in Table 1, as shown in FIG.
The alumite film 47 in which is present is formed. At this time, the holder 38 is positioned so that the pair of through holes 6 b and 6 c of the tank rail 4 are positioned at the upper and lower ends of the tank rail 4.
As a result, the air retained in the tank rail 4 escapes through the through hole 6b at the upper end, so that air does not accumulate in the hollow tank rail 4. Therefore, the alumite film 47 is uniformly generated on the back surface of the tank rail 4, that is, on the entire surface of the hollow portion.

[0020]

[Table 1]

Next, secondary electrolysis is performed under electrolysis conditions as shown in Table 1, and the diameter of the pores 46 is increased as shown in FIG. Further, the thickness of the barrier layer 48 is adjusted by performing preliminary electrolysis under electrolysis conditions as shown in Table 1. Next, when tertiary electrolysis is performed under electrolysis conditions as shown in Table 1, an electrolytic deposit 49 is deposited in the pores 46 as shown in FIG. In this tertiary electrolysis, 1
In the next electrolysis, the alumite film 47
Is uniformly formed on the entire surface of the hollow portion, so that the current does not concentrate on the portion where the alumite film 47 is not formed. Therefore, the electrolytic deposit 49 made of Ni is uniformly deposited in the alumite film, color unevenness is prevented, and there is no possibility that color development is not obtained. At this stage, a color such as gray or black is obtained. Of the electrolyte components in the tertiary electrolysis, NiSO ₄ / 6H ₂ O is Ni
MgSO ₄ / 7H ₂ for forming ions
O serves as a catalyst, and H ₃ BO ₃ serves to form a catalyst solution.

Next, in order to obtain a color development of pink, green, yellow, etc., the noble metal is replaced by electrolytic conditions as shown in Table 1, and the electrolytic deposit 49 in FIG. 50). That is, while the electrolytic precipitate 49 made of Ni is dissolved by the sulfuric acid component, P
d is precipitated. Next, quaternary electrolysis is performed under the electrolysis conditions shown in Table 1, and the barrier layer 48 is thickened as shown in FIG. That is, the precipitated metal 50 made of Pd is not dissolved by the sulfuric acid of the fourth electrolysis, and the aluminum alloy base is oxidized by the electric current, and the alumite film becomes thick.

The mechanism of color development in the thus formed electrolytic colored film will be described with reference to FIG. In the figure, part of the light (incident light A) incident on the alumite film 47 is reflected at the interface of the tank rail 4 as a base material, and part (incident light B) is reflected on the surface of the deposited metal 50. . Since an optical path difference (phase difference) occurs between the incident light A and the incident light B, a specific wavelength is enhanced or weakened by the optical path difference (phase difference), and the enhanced wavelength is increased. The color develops and the complementary color of the weakened wavelength also develops.

As shown in Table 2, the color tone of the deposited metal 50 depends on the thickness L1 of the deposited metal 50 and the thickness L1 of the barrier layer 48.
2 can be changed. That is, the deposited metal 5
By combining the thickness L1 of 0 and the thickness L2 of the barrier layer 48, a dark color tone such as gray or blue or a pastel color tone such as pink or green can be obtained.

[0025]

[Table 2]

In the conventional coloring by dyeing, the typical color tone is limited to red, blue or the like. In order to change the color tone, a different dye or a different treatment tank is required, and the color is faded by ultraviolet rays. There was a problem. On the other hand, in the multicolor electrolytic coloring, the color can be changed by changing the processing time in the same processing tank, the weather resistance is excellent, the color does not fade, and the interference color is obtained. Therefore, there is also an effect that the color changes depending on the viewing angle.

The head pipe 3, tank rail 4 and rear arm bracket 5 constituting the main frame 2 are made of JIS5083 aluminum alloy wrought material of the same material, so that the color tone of each member can be made uniform. it can. Also, by joining the head pipe 3, the tank rail 4 and the rear arm bracket 5 by welding to form the main frame 2, each member can be freely combined from a plate material, an extruded shape material, a forged material, a block material or the like. Therefore, the degree of freedom in selecting the constituent members is increased.

In particular, each component and welding rod are
By using the wrought aluminum alloy of JIS 5083, which is a system aluminum alloy, the color tone of each member including the bead portion can be set to 10 or less in color difference ΔE measured by the Lab color system (JIS Z8729). This is 500
As shown in Table 3, the 0-base aluminum alloy is a non-heat-treatable Al-Mg-based alloy, and the intermetallic compound does not become coarse even after the heat history of melting and solidification by welding. This is because there is little change from the microstructure in the alumite film, and there is little difference in the effect on the alumite film between the beat portion and the portion other than the beat portion. Further, during the alumite treatment in the primary electrolysis, Mg is contained in the metal in the film. Since the relative movement speed of ions is higher than that of Al and does not remain in the alumite film, even if there is a difference in the microstructure between the welded surface and the non-welded surface due to Mg, the difference in the transparency of the alumite film is Disappears. Thus, it is possible to prevent the color tone of the welded portion from appearing with a strong contrast.

[0029]

[Table 3]

On the other hand, in the case of an alloy containing Si and Mg as alloying components, for example, a 6000 series alloy, these alloying components are present in the alloy in the form of an intermetallic compound of Mg ₂ Si, and these components are heat And is easily coarsened in the weld. Since the intermetallic compound has a large electric resistance, the film thickness of the alumite layer in the beat portion becomes smaller than that in the surroundings in the primary electrolysis or the secondary electrolysis as the alumite treatment. For this reason, in the case of a 6000 series alloy, the contrast of the bead portion is too strong in the overall appearance.

Further, an alloy containing Cu as an alloy component, for example, a 2000-series alloy has poor alumite properties and cannot form a film having a uniform thickness, so that color unevenness occurs.

In the case of an alloy containing Si as an alloying component, for example, a 4000 series alloy, Si as an alloying element remains in the alumite film to disturb the film structure and diffusely reflect light, so that a color is obtained. Absent.

Table 4 is a table in which materials suitable and inappropriate for electrolytic coloring of vehicle body structural members such as motorcycles are selected. As is clear from the table, the 5000 series is most suitable in terms of strength and bead discoloration (large beat contrast), etc., the 1000 series has insufficient strength and is not suitable for the main frame 2, and the 6000 series is unsuitable for the main frame 2. Beads discolor to the surroundings.

[0034]

[Table 4]

In the above-described embodiment, the head pipe 3, tank rail 4,
The constituent members of the rear arm bracket 5 and the welding rods for joining them are all based on JIS5083, which is the same material. However, the present invention is not limited to this, and various combinations of Al-Mg based aluminum alloys are possible. Table 5 is a table showing an example of a combination between components and a combination of a welding rod. When the members are made of different materials in this manner, the plurality of members to be welded are made of Al-Mg.
A wrought product molded product and a cast product may be combined under the condition of a system aluminum alloy.

In the case of welding using a welding rod, when the welding rod is made of an Al-Mg-based aluminum alloy, a wrought material molded product, a cast product, and a welding rod are solidified in the beat portion. Even after the heat history, the intermetallic compound in the Al-Mg-based aluminum alloy in the beet does not coarsen, and the beet has a high cooling rate when the surface is hardened, and the metal structure is formed from an extruded material rather than a cast product. It becomes a fine thing close to the product. In addition, during the alumite treatment in which an electric current is applied, the relative velocity of the metal ions of Mg is larger than that of Al, so that Mg does not remain in the alumite film on both the welded surface and the non-welded surface, so that Mg Even if there is a difference in the microstructure between the surface of the welded portion and the surface of the non-welded portion, the difference in the transparency of the alumite film disappears. Due to these facts, the color tone of the beat portion is close to that of the wrought product molded product portion, so that the color tone of the beat portion can be prevented from coming out with a strong contrast, and the bead portion can be cast with the wrought material molded product portion. A patchwork-like appearance can be obtained in the product part.

Note that, before the electrolytic treatment, the entire main frame after welding or at least the cast part is subjected to shot blasting instead of polishing, so that the structure state of the surface of the cast part is changed to a wrought product molded article and Since it can be miniaturized similarly to the beat portion, the color tone of the entire main frame can be made uniform. Further, even in the case where the members are heated and welded without using a welding rod, a plurality of members are formed from the same Al-Mg-based aluminum alloy in the form of a wrought product (formed by pressing or forging using wrought material, and so on). Or a combination of a wrought material molded part and a cast product, or a wrought material molded part of a dissimilar metal, or a combination of a wrought material molded part and a cast product under the condition of an Al-Mg aluminum alloy. Similarly, it is possible to prevent the color tone of the beat portion from appearing strongly in the contrast by electrolytic coloring, and even in the case of the combination of the wrought material molded product portion and the cast product, at least the cast product portion after welding. By performing shot blasting, the entire color tone can be made uniform by electrolytic coloring.

[0038]

[Table 5]

In FIG. 8 (a), 55 and 55 are base materials schematically showing the head pipe 3 and the tank rail 4, and when these base materials 55 and 55 are joined by the weld metal 56, A weld metal 56 is deposited on the base material 55, and a bead 57 having a rippled appearance is formed. Although coarse crystal grains are formed in the center of the cross section of the weld metal 55, the beads 57
Has a high cooling rate at the time of solidification, the metal structure becomes fine, and a metal structure similar to the uniform metal structure of the base material shown in FIG.

Accordingly, by leaving the bead 57 without removing it, the color tone of the entire structural member constituting the main frame 2 can be made constant, and as described above, each member including the bead portion can be used. Is 10 as a color difference ΔE measured by the Lab color system (JIS Z8729).
It can be: The same effect can be obtained by removing the surface of the beat portion by buffing or the like, and then performing shot blasting on the flattened welded portion and then electrolytic coloring.

On the other hand, a structural member is formed by welding, and thereafter, the bead is mechanically removed to expose a coarse metal structure inside the weld metal, and thereafter, the color tone of the welded portion is changed by performing electrolytic coloring. be able to.
That is, the color tone of the bead-removed portion can be made larger than 10 in the color difference ΔE measured by the Lab color system with respect to the other portions, whereby the color tone of the welded portion is intentionally increased by one electrolytic coloring. It can be changed, and the design can be improved. In the above description, the pores 46
In addition to electrolytic deposition of Ni and Pd, Fe,
Any one of metals such as Cu, Ag, Au, and Sn may be deposited. In addition, a plurality of types including Ni and Pd may be simultaneously precipitated in the same electrolysis step, or may be deposited in layers by a plurality of electrolysis steps. In addition, Ni, Fe, P
In the case of metals such as d, Cu, Ag, Au, and Sn, even if the electrolytic metal itself is in contact with oxygen in the atmosphere due to the adhesion of moisture, it does not easily oxidize and the color tone does not change.

In the conventional anodic oxide film, since the thickness of the alumite layer at the bottom of the pores 46 is thin, corrosion is apt to occur from the pores 46 where no electrolytic deposition occurs. Is subjected to electrolytic coloring to deposit a noble metal in the pores 46 of the anodic oxide film, whereby the corrosion resistance to the anodic oxide film is greatly improved. Further, in the conventional anodic oxide film, a treatment for sealing the pores 46 may be performed in order to improve the corrosion property of the film, and boehmite (hydrate of alumina) is formed in the sealed portion. Has been
Boehmite has low hardness, and as a result, the film hardness is reduced and it is easy to wear.However, in the case of electrolytic coloring, sealing treatment for improving corrosion resistance is unnecessary and there is no decrease in hardness, As much as the metal is electrolyzed in the pores 46, the film hardness is improved and the wear resistance is improved. By using such an aluminum alloy structural member for the main frame 2 of the motorcycle 1, it is possible to prevent the main frame 2 from being worn or damaged by sand or pebbles.

The above-described electrolytic coloring is also applied to the hollow rear arm 14, the rear cushion lever 23, the cushion support bracket 25, and the front fork 26. As described above, by applying electrolytic coloring to these members in the same manner as the main frame 2, the entire motorcycle can be colored in the same color tone, so that the design of the appearance is improved.

[0044]

As described above, according to the first aspect of the present invention, it is possible to prevent the color tone of the welded portion from appearing with a strong contrast.

According to the second aspect of the present invention, the aluminum alloy structural member is electrolytically colored with a uniform color tone as a whole.

According to the third aspect of the present invention, the appearance of the motorcycle is not impaired, and at the same time, the main frame surface is prevented from being damaged by dust or sand particles during running.

[Brief description of the drawings]

FIG. 1 is a side view showing an appearance of a motorcycle to which an aluminum alloy structural member according to the present invention is applied.

2A and 2B show a main frame which is an aluminum alloy structural member according to the present invention, wherein FIG. 2A is a perspective view showing the entire appearance, and FIG. 2B is a view II (b) -II in FIG.
(B) It is a line sectional view.

FIG. 3 is an exploded perspective view for explaining a method of assembling a rear arm which is an aluminum alloy structural member according to the present invention.

FIG. 4 is a cross-sectional view showing a state in which the aluminum alloy structural member according to the present invention is subjected to electrolytic coloring.

FIG. 5 shows the primary to fourth aluminum alloy structural members according to the present invention.
It is sectional drawing expanded and shown in order to explain the change of the surface of the aluminum alloy structural member at the time of performing the next electrolytic treatment.

FIG. 6A is a sectional view of an aluminum alloy structural member according to the present invention which has been subjected to electrolytic coloring, and FIG.
FIG. 6 is an enlarged view of a portion VI (b) in FIG.

FIG. 7 is a model diagram for explaining a mechanism of coloring of an electrolytic colored film in the aluminum alloy structural member according to the present invention.

FIG. 8A is a cross-sectional view schematically showing a state in which the base materials of the aluminum alloy structural member according to the present invention are joined with beads, and FIG. 8B is a cross-sectional view of VIII ( b)
It is an enlarged view of a part.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Motor cycle, 2 ... Main frame, 4 ... Tank rail, 13 ... Rear arm, 23 ... Rear cushion lever, 25 ... Cushion support bracket, 26 ... Front fork, 35 ... Electrolytic tank, 38 ... Holder, 46 ... Thin Holes, 47: anodized film, 48: barrier layer, 50: deposited metal, 55: base metal, 56: weld metal, 57: bead.

Claims (3)

[Claims] An aluminum alloy structural member formed by joining together members made of an Al-Mg-based aluminum alloy by welding, and electrolytic coloring is applied to an alumite film formed on the surface of the aluminum alloy structural member. An aluminum alloy structural member characterized by being applied. 2. The aluminum alloy structural member according to claim 1, wherein each of the members before welding is only one of a wrought material molded product and a cast product, or the wrought material molded product and a cast product A structural member made of an aluminum alloy, which is a combination of the following. 3. A motorcycle using the aluminum alloy structural member according to claim 1 for a main frame.