JP2575365B2 - Aluminum alloy for rims such as motorcycles - Google Patents

Description

The present invention relates to aluminum alloys for rims of motorcycles, automobiles, bicycles, etc., and more particularly to Al-Zn-Mg-based or 7000-based aluminum alloys.
The present invention relates to a high-strength aluminum alloy which suppresses recrystallization of an Al-Zn-Mg-Cu-based alloy, prevents color unevenness by alumite treatment, and prevents roughening by cold working.

2. Description of the Related Art Alloys for rims of motorcycles and the like include Al-Mg, Al-
Aluminum alloys such as Mg-Si and Al-Zn-Mg are known, but among them, Al-Zn-Mg alloys have high strength,
It is advantageous in that it can reduce the weight, and is Japanese Patent Publication No. 60-58298.
As shown in Japanese Patent Application Laid-Open Publication No. Hei 9 (1996) -175, practical use is being promoted with its disadvantages improved.

By the way, when manufacturing a motorcycle rim, from the viewpoint of manufacturing cost and quality, the aluminum alloy ingot is homogenized, extruded into a cross-sectional shape of the rim, and then the extruded material is treated with O.
After tempering the material, it is bent into a loop, then flash butt welded at both ends, then solution-hardened, quenched, and, if necessary, further overhanged, polished, aged,
After each process of Kaken, a process of performing an alumite finishing process is generally adopted.

Problems to be solved by the invention However, the conventional Al-Zn-Mg-based or Al-Zn-Mg-
When manufacturing a motorcycle rim in the above process using a Cu-based alloy, the crystal grains are generally coarsened on the surface of the extruded material during the solution treatment after molding, which may cause color unevenness at the time of anodizing, or spoke holes. There is a drawback that roughening occurs during overhanging. Tokiko Sho60
The method proposed in Japanese Patent No. −58298 cannot completely overcome this disadvantage, and the heat treatment step is complicated, so that it cannot always be satisfied.

The present invention mainly improves the composition of Al-Zn-Mg-based or Al-Zn-Mg-Cu-based alloys from the aspect of composition, so that recrystallization occurs during solution treatment after cold working. It is an object of the present invention to provide an aluminum alloy which suppresses and maintains a fine and uniform structure to improve formability and alumite suitability.

Means for Solving the Problems The present invention has been made based on the above-mentioned objects by various experiments and researches, and by adding a small amount of rare earth element in the presence of Zr,
While maintaining the high strength inherent to the base alloy, it is possible to raise the recrystallization temperature to suppress surface recrystallization during solution heat treatment and quenching, and to promote the refinement of the structure and improve the formability. We have found this and completed it.

Thus, the aluminum alloy for rims of motorcycles and the like according to the present invention may contain: Zn: 4 to 12% Mg: more than 1.5% and 3.5% or less Zr: 0.05 to 0.4% One or more of the rare earth elements: 0.01 to 3.0% and Mn: 0.8% or less Cr: 0.4% or less Ti: 0.1% or less B: 0.01% or less, or Cu: 2.5% or less And a composition comprising the balance of Al and inevitable impurities.

Next, the significance of each chemical component of the aluminum alloy and the reason for limiting the content range will be described as follows.

Zn contributes to improving the strength of the aluminum alloy as is well known. If the Zn content is less than 4%, the alloy cannot have the required high strength. However, if the content exceeds 12%, the strength is not further improved relatively, and the content more than that is practically meaningless. Therefore, the effective content of Zn is in the range of 4 to 12%. However, under the demand for obtaining particularly high strength,
It is effective to add Zn in a relatively large amount, that is, in the range of 7.0 to 10.0%.

Mg also contributes to improving the strength of the aluminum alloy. Therefore, in order to obtain the required high strength as an alloy material for a rim, it is necessary to contain at least 1.5% or more. However, as the content of Mg increases, the ductility of the alloy decreases and the extrudability and cold workability decrease, so that the Mg content is limited to 3.5% or less. That is, when the content of Mg exceeds 3.5%, a sufficiently satisfactory result cannot be obtained in terms of extrudability, cold workability, etc. due to a decrease in ductility.

Zr achieves the effect of increasing the recrystallization temperature. That is, solid solution Zr
And fine Al ₃ Zr particles precipitated from the supersaturated solid solution effectively act to suppress recrystallization. Therefore, its content is 0.05
If it is less than 0.4%, the above effect is insufficient, and if it exceeds 0.4%, coarse crystals cause a decrease in crystallization strength. The most preferred content of Zr is in the range of 0.15 to 0.2%.

The rare earth element coexists with Zr, promotes the effect of increasing the recrystallization temperature of Zr, and has a significant effect in suppressing the recrystallization,
It improves the formability of the alloy and also helps to improve stress corrosion cracking resistance. The rare earth elements used here are
15 elements with atomic numbers 57 to 71, namely La, Ce, Pr,
It is composed of Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and a group of 17 elements obtained by adding Y and Sc thereto. These elements do not necessarily need to be used individually as individual elements, and a misch metal obtained by electrolyzing a mixed chloride of a rare earth metal may be used. Industrially selected from the group of Y, La, Ce, Pr, Nd, and Sm because of availability
It is preferable to use species or a combination of two or more species.

In the present invention, these rare earth elements can be evaluated as substantially equivalent to each other in terms of their effects. Therefore, one or more of them can be used in any combination, but the content in the alloy is
If the content is less than 0.01%, the effect of suppressing recrystallization is insufficient. On the other hand, if the content exceeds 3.0%, the effect of suppressing recrystallization does not increase, but rather a large amount of coarse crystals and precipitates are generated in the alloy. However, the strength and the recrystallization suppressing effect are reduced. Therefore, the allowable content of the rare earth element is specified in the range of 0.01 to 3.0%, but the most preferable content is in the range of about 0.05 to 0.5% in consideration of the effect of the addition and the cost.

Cu also contributes to the improvement of the strength as is known, and the content of 0.05% or more is preferable. However, if the content exceeds 2.5%, the toughness is deteriorated, the weldability is deteriorated, and the corrosion resistance and quenching are reduced. It is not preferable because the property also decreases. Therefore, it is most preferable that the content is contained in the range of 0.5 to 2.0%.

Mn, Cr, Ti, and B, which are other contained elements, are all useful for refining crystal grains and stabilizing the structure.
%, Cr: 0.4%, Ti: 0.1%, and B: 0.01%, respectively, when the upper limits of the contents are exceeded. If the contents exceed these limits, coarse crystals are formed in the alloy and the strength of the alloy is reduced.

In the production of a rim alloy material using the above alloy, the ingot after casting is homogenized at 400 to 550 ° C for 1 to 100 hours. This homogenization treatment dissolves the second phase compound such as Zn, Mg, Cu, and Zr, and homogenizes with the nucleated structure such as Mn, Cr, Ti, B, and Zr. If the temperature is lower than ℃, the above effect is not sufficient. If the temperature is higher than 550 ° C, local melting occurs. The homogenization process takes more than one hour,
Even if it exceeds 100 hours, the treatment effect is saturated and uneconomical.
The most preferable homogenization treatment conditions are 440 to 480 ° C. for 20 to 100 hours, whereby a greater recrystallization inhibiting effect can be obtained.

After homogenization, hot working such as extrusion and rolling, or further required cold working, is provided as an aluminum alloy material for rims such as motorcycles as annealed O material.

The rim alloy material is then subjected to the required bending (forming) processing,
After performing flash butt welding, solution-quenching process performs overhang processing for spoke holes formed like a required immediately, followed by a T ₆ temper subjected to artificial aging,
It is manufactured on rims such as motorcycles by applying surface treatment such as alumite.

Effect of the Invention The aluminum alloy according to the present invention has a high strength capable of responding to a demand for a lighter rim of a motorcycle or the like by containing a specified amount of Zn, Mg, or further Cu, while coexisting with Zr. When at least one of the rare earth elements is contained, the rare earth elements work together to exhibit the effect of increasing the recrystallization temperature and suppress the surface recrystallization.

Therefore, it is possible to prevent a recrystallized layer from appearing on the surface of the alloy material during the solution treatment after cold working such as bending work, thereby preventing the occurrence of color unevenness at the time of alumite processing, and to prevent the surface from being overhanged. It can also prevent rough skin. On the other hand, flash butt welding is often performed after bending on motorcycle rim materials.In contrast to the conventional 7000 series alloy, crystal grains tend to become coarser in the parts that undergo plastic deformation in the heat affected zone. In the alloy of the present invention, such a defect can be prevented by the effect of suppressing recrystallization. Furthermore,
Inclusion of rare earth elements improves extrusion and other workability, improves stress corrosion cracking resistance, suppresses surface recrystallization that tends to occur during extrusion, and has high strength, lightweight and high quality without defects Enables production of rims.

Example Next, a comparison between an example of the present invention and a comparative example will be described.

Alloys having various compositions shown in Table 1 were cast according to a conventional method, and the ingot was kept at 465 ° C. for 30 hours to be homogenized. Next, the ingot is heated at a billet temperature of 500 ° C. and a ram speed.
The extruded material was extruded into a rectangular rod under the conditions of 0.005 m / sec and a pressing ratio of about 40. After annealing this extruded material, it was subjected to cold working at a working ratio of about 20%, and then was subjected to a solution treatment at 470 ° C. for 1 hour. Various sample plates Nos. 1 to 21 were obtained. The mechanical properties of each sample plate were examined, and the presence or absence of surface recrystallization after the solution treatment was examined.

 Table 2 shows the results.

As is apparent from Table 2, the aluminum alloy according to the present invention does not have a recrystallized structure when subjected to a solution treatment after cold working with a working ratio of 20% using an O material, and therefore, the surface roughness and the like during subsequent working are reduced. Fine cracks did not occur, and the quality of the product could be improved.

Continuation of the front page (56) References JP-A-58-213852 (JP, A) JP-A-59-28555 (JP, A) JP-A-62-44550 (JP, A) JP-B-52-39372 (JP, A) , B2) JP-B 63-31537 (JP, B2)

Claims (2)

(57) [Claims] 1. Zn: 4 to 12% Mg: more than 1.5% and 3.5% or less Zr: 0.05 to 0.4% One or more of rare earth elements: 0.01 to 3.0%, and Mn: 0.8 % Or less Cr: 0.4% or less Ti: 0.1% or less B: 0.01% or less Aluminum alloy for rims such as motorcycles, which contains one or more of the following, and the balance is Al and inevitable impurities. 2. Zn: 4 to 12% Mg: more than 1.5% to 3.5% or less Zr: 0.05 to 0.4% One or more rare earth elements: 0.01 to 3.0% Cu: 2.5% or less And Mn: 0.8% or less Cr: 0.4% or less Ti: 0.1% or less B: 0.01% or less An aluminum alloy for rims of motorcycles and the like comprising one or more of the following, and the balance being Al and inevitable impurities.