JPS63118045A - Aluminum alloy for bright disk wheel - Google Patents

Abstract

PURPOSE:To obtain an Al alloy for a disk wheel having superior brightness by providing a compsn. consisting of specified amts. of Mg, Cr, Cu and Zr, a restricted amt. each of Fe, Si and Mn and the balance Al with inevitable impurities. CONSTITUTION:An Al alloy consisting of 2.5-3.5% Mg, one or more among 0.01-0.35% Cr, 0.01-0.5% Cu and 0.01-0.30% Zr, <=0.1% each of Fe, Si and Mn as impurities and the balance Al with inevitable impurities is manufactured by refining. The Al alloy is heat treated and hot rolled to form a soft sheet as stock for a disk wheel and the sheet is chemically polished and anodically oxidized. Thus, an Al alloy for a disk wheel having high strength, satisfactory formability and superior brightness after chemical polishing-anodic oxidation can be obtd.

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to aluminum alloys used for automobile disc wheels, and in particular, the invention relates to aluminum alloys used in automobile disc wheels. The present invention also relates to an aluminum alloy for disc wheels that has excellent strength and formability.

Conventional Technology Heavy-duty automatic disc wheels have traditionally been made of steel plates, but recently aluminum alloy wheels have come into widespread use due to demands for light weight and fashionability. A disc wheel basically consists of a rim part and a disc part.Aluminum alloy disc wheels have a 1-piece wheel in which the rim part and disc part are integrated, and a 1-piece wheel in which the rim part and disc part are separate parts. There are two types of wheels: 2-piece wheels made from this and then joined together, and 3-piece wheels made by joining two separate rim parts and a separate disc part. Among them, 3-piece wheels are both lightweight and fashionable, while 2-piece wheels are lightweight, fashionable, and highly productive.Therefore, aluminum alloy 2-piece wheels and 3-piece wheels are even more popular. Its usage is increasing.

By the way, aluminum alloy two-piece wheels and three
The rim part of a piece wheel is given its shape by shaping a 5-plate material (stretched material), and the disc part is often a cast or forged product, but recently it has been made into a shape similar to the rim part. It is often created by molding plate material (stretched material). Therefore, aluminum alloys for two-piece or three-piece wheels, especially aluminum alloys for rims, are required to have excellent formability and high mechanical strength.

Conventionally, aluminum alloy two-piece wheels or three-piece wheels were used.
The rim material of peace wheels is JIS 5000.
It is common to use Al-Mcr based alloys,
Among them, JIS 5052 alloy is widely used especially for the rim part of three-piece wheels from the viewpoint of formability.
Furthermore, JIS 5454 alloy, which has higher strength than JIS 5052 alloy, has often been used for the rim portion of two-piece wheels in order to reduce the thickness.

Problems to be solved by the inventionRecently, the fashionability of automobile disc wheels has become more and more viewed as negative, and one of them is:
It is now required that the entire wheel has high brightness. In general, methods for imparting brightness to the surface of aluminum alloy members include: (1) plating, (2) polishing the shell with lacquer, and (3) applying chemical polishing after polishing the shell, and then anodizing. There is a way to do this. Among these, the method (3), which involves @extremely ratifying treatment, has excellent surface corrosion resistance and at the same time provides a glittering effect that gives a luxurious feel, so it is a suitable method for imparting glittering properties to automobile disc wheels. This is considered preferable. However, when applying the method (3) of anodizing, JIS 5454 alloy, which is mainly used in conventional disc wheels, cannot provide sufficient glitter, and JIS 5052 alloy cannot obtain sufficient glitter. is difficult and rare.

This invention was made against the background of the above-mentioned circumstances.
The object of the present invention is to provide an aluminum alloy for disk wheels that has strength and formability comparable to that of 454 alloy, and which can also be given excellent shine through anodizing treatment.

Means to solve the problem The brightness after anodizing treatment may be due to unevenness during chemical polishing, which is usually performed as a pretreatment for anodizing treatment, or precipitates and crystals present in the anodized film. In particular, if there are many coarse precipitates or crystallized substances, the brightness will decrease. Therefore, as a result of various experiments and studies in order to find a composition that can reduce such coarse precipitates and crystallized substances and at the same time obtain the formability and strength required for a disc wheel material, we have found the optimal composition. This discovery led to the creation of this invention.

That is, the aluminum alloy for shiny disk wheels of the present invention contains 2.5 to 3.5% l'Vlc],
and Cr O, 01-0.35%, Cu O, 01-0
．． 5%, ZrO, one or more of 01 to 0.30%, and further contains Fe, 3i, and impurities as impurities.
It is recommended that rv+n be regulated to 0.10% or less, with the remainder consisting of other unavoidable impurities and Al.
The market is based on what is considered Maki.

Function First, the reason for limiting the components of the aluminum alloy for disc wheels according to the present invention will be explained.

Mq: Since Mg has a high solid solubility in A1, it is added to increase the strength of the alloy and to enhance the brightness after chemical polishing and anodizing treatment.

If the amount of M added is less than 2.5%, the strength will be insufficient as a disc wheel material, while if it exceeds 3.5%, there will be a risk of stress corrosion cracking. Therefore, MCI is 2.5~
It was set within the range of 3.5%.

Cu: Cu is selectively added to further improve strength, refine recrystallized grains, and improve brightness. If the amount of HO added to Cu is less than 0.01%, these improving effects will be small, while if it exceeds 0.5%, the color tone after anodizing treatment will become yellowish, which is undesirable, and the brightness will also decrease. do. Attachment 7J when adding Shikatsu-CCU
DEJ was within the range of 0.01 to 0.5%.

Cr: Cr is also selectively added to further improve strength and refine recrystallized grains. Since Cr-based precipitates are generally extremely fine, addition of a small amount of Or does not reduce the brightness after anodizing. If the zero additive amount of Cr is less than 0.01%, the above effects cannot be obtained, while if it exceeds 0.35%, a huge intermetallic compound is generated, which deteriorates formability, fatigue strength, and after anodizing treatment. Decreases glitter. Therefore, when adding Cr, the amount added was within the range of 0.01 to 0.35%.

Zr: Zr is also selectively added to further improve strength and refine recrystallized grains. Since the Zr-based precipitates are extremely fine, even the addition of a small amount of Zr does not reduce the brightness after the anodizing treatment. If Zr is less than 0.01%, the above effect cannot be obtained, while if it exceeds 0.30%, a huge intermetallic compound is generated, which reduces formability, fatigue strength, and brightness after anodizing treatment. . Therefore, when Zr is added, the amount added is within the range of 0.01 to 0.30%.

Fe, 3i: Fe and 3i are contained as unavoidable impurities in ordinary aluminum alloys, and these are mainly A1-Fe series, Ai'-Fe-3i series, Mg2S! It exists in the alloy as a system crystallized product or precipitate. These types of crystallized substances and precipitates tend to disintegrate and form pits during chemical polishing, and are also incorporated into the oxide film during anodizing treatment after chemical polishing, resulting in anodic oxidation. Decreases the transparency and brightness of the film. Therefore, in order to obtain excellent brightness after anodic oxidation, Fe and 3i are each regulated to 0.10% or less.

Mn: Mn is also often contained as an unavoidable impurity in aluminum alloys.
Since it forms Mn-based, A-based, and 2-Mn-3i-based crystallized substances and precipitates, which lowers the brightness after anodizing treatment similarly to Fe and 3i, it is regulated to 0.10% or less.

In addition to the above-mentioned Fe and 3iJ4n, elements that are usually unavoidably contained in aluminum alloys, such as Zn, do not particularly form crystallized substances or precipitates that reduce the brightness after anodizing treatment, so the content is about 0.20%. It may include the following.

In addition, in general aluminum alloys, a small amount of T1 and/or B is often added to refine the ingot structure.
In the case of this invention as well, T1 of 0.2% or less and/or 0
．． Addition of B at 0.5% or less is effective in stabilizing mechanical performance. Furthermore, in casting Al-MCJ alloys, 8e is sometimes added to prevent oxidation of the molten metal, but in the case of the present invention, as long as Be is added in an amount of 50 ppm or less, there is no risk of deteriorating the brightness.

Next, a method for manufacturing an aluminum alloy for disc wheels according to the present invention will be explained.

First, a molten alloy having the above-mentioned composition is melted and cast according to a conventional method. As a casting method, a semi-continuous casting method (1) C casting method may be applied, or a thin plate continuous casting method (continuous casting and rolling method) in which a thin plate with a thickness of 3 to 15M is directly cast may be applied. . In general, continuous thin plate casting methods often produce ripple patterns perpendicular to the rolling direction, but in the case of the alloy of this invention, the amounts of Fe and Si are regulated to small amounts.
No ripple pattern occurs even when continuous thin plate casting is applied, and therefore, even when anodized, a -like brightness and appearance can be obtained.

In the case of semi-continuous casting, the ingot is hot rolled to the required thickness, but the FJtl heat prior to hot rolling is 45
It is desirable to maintain the temperature at 0 to 600°C for 48 hours or less. If the temperature is less than 450°C, good hot rolling properties cannot be obtained, and if the temperature exceeds -600°C, eutectic melting may occur or a large amount of Mg oxide may be formed on the surface, resulting in a decrease in rolling property. This results in an increase in surface defects or a decrease in moldability. In addition, heat at high temperature M! Since AV tends to have improved brightness, it is desirable to heat it on the high temperature side even in the upper range of the above temperature range, especially when a high degree of brightness is required. Note that even if the heating time exceeds 48 hours, it is economically meaningless.

The ingot produced by the half-speed M casting method is subjected to hot rolling after heating as described above, and further annealed to make a soft material, which is used as a disc wheel material. In addition, a cast plate made by continuous thin plate casting is annealed as it is to be used as a disc wheel material. Further, depending on the case, the material may be used as a disc wheel material by performing cold rolling after hot rolling or continuous casting of the groove plate, and then annealing. As an annealing method, normal batch annealing (heating rate and cooling rate are both approximately several tens of degrees C/hr), continuous annealing (heating rate,
The temperature may be approximately several tens of degrees C/ssc). However, in order to further improve the uniformity and brightness during chemical polishing, it is desirable to incorporate Al-Mg-based precipitates (β phase) into the matrix.
A method of annealing at a temperature of .degree. C. or higher and increasing the cooling rate is preferred. For example, it is preferable to take the material out of the furnace immediately after annealing and blow air to perform forced air cooling.

In addition, the number of crystal grains is relatively small compared to the case where the crystal grains are large, or pits at the grain boundaries during chemical polishing or anodizing treatment, or fine crystal grains, and the brightness is increased. However, if the crystal grains are too large, the surface will become rough during molding and may be scraped, so it is necessary to set the crystal grains to an appropriate size. The grain size is determined by the cold rolling reduction before annealing, the annealing temperature,
It is desirable to obtain an appropriate crystal grain size by appropriately adjusting these factors, since it is influenced by the power and thermal rate. Note that after annealing, leveling or stretching may be performed to improve flatness. In this case, the strength, especially the yield strength, is improved by about 3/- to 2 to 3.

Examples Examples of the aluminum alloy for disc wheels of the present invention will be described below.

Using a molten metal with the composition shown in Table 1, a semi-continuous casting method was used to achieve a thickness of 450mm and a width of 1200mm! An ingot with a length of 3,500 m and a length of 3,500 mm was cast. Alloy N for 1q ingot.

No. 1 was homogenized at 590° OX for 6 hours, and other alloys were hot-rolled at 500° C. for 6 hours to give a thickness of 5#. Next, it was annealed at 350°OX for 2 hours to obtain a soft plate as a disc wheel material.

A tensile test was conducted on each of the soft plates obtained as described above to examine mechanical performance.

In addition, each soft plate was polished with a separate cloth until the lines of the rolling roll disappeared, and then chemically polished for 1 minute at 95°C using a phosphoric acid-based chemical polishing solution, and further polished by 15%.
Anodizing was performed using a sulfuric acid electrolyte to form a thick oxide film.

In order to evaluate the brightness of each sample after positive oxidation treatment, the reflectance was measured at an incident angle of 45° and a reflection angle of 45° with respect to a plane parallel to the rolling direction.

Further, in addition to the basic performance evaluation test as described above, a molding test was conducted using a spatula drawing process to form a rim portion of a 13-inch disc wheel, and the molding [raw quality] was evaluated.

The results of each of the above tests are shown in Table 2.

As shown in Table 1, Table 2, the strength, especially the yield strength, of the aluminum alloy for disc wheels of the present invention is higher than that of conventional general aluminum alloys for disc wheels.
J is known as an aluminum alloy for conventional high-strength disc wheels, which is much higher than IS 5052 alloy.
It is on the same level as IS 5454 alloy, and its elongation is better than conventional JIS 5ob2 alloy and JIS 5454 alloy, and it is popular.Moreover, its reflectance is much higher than conventional alloys, and its brightness after anodizing treatment is excellent. It is clear that it is significantly superior.

In Table 2, alloy Nα8 contains Fe and 3i, but
In addition, alloys No. 9 and 9 had a high Fe content, but in these cases, the reflectance was much lower than that of the alloy of the present invention. It is clear that it is effective in improving glitter.

Effects of the Invention As is clear from the above examples, the aluminum alloy for disc wheels of the present invention has significantly superior brightness after chemical polishing and anodizing treatment, and its strength is higher than that of conventional high-strength disc wheels. It is equivalent to JIS 5454 alloy, which is known as an aluminum alloy, and has good formability. Therefore, the alloy of the present invention is a material for disc wheels that is used by imparting corrosion resistance and brightness through chemical polishing and anodizing treatment. As ↑a first excellent T: Monodeoru.

The aluminum alloy of the present invention is suitably used for the rim portion of a two-piece wheel or a three-piece wheel, but it goes without saying that it may also be used for the disk portion of a two-piece wheel or a three-piece wheel.

Claims (1)

[Claims] Contains Mg2.5-3.5% and Cr0.01-0
．． 35%, Cu0.01-0.5%, Zr0.01-0
．． 30%, and further contains 0.10% each of Fe, Si, and Mn as impurities.
regulated as below, with the remainder being other unavoidable impurities and A
An aluminum alloy for glittering disc wheels, characterized by comprising l.