JPH03257134A - Aluminum alloy having black color tone after anodic oxidation treatment and production thereof - Google Patents

Abstract

PURPOSE:To develop the Al alloy having black color tones with anodic oxidation by an ordinary sulfuric acid electrolytic bath by adequately adjusting the size and deposition density of the Al-Mn system intermetallic compd. in an Al-Mn-Mg alloy consisting of a specific compsn. CONSTITUTION:The melt of the Al alloy which contains, by weight %, over 0.8% and <=1.5% Mn, 2.0 to 4.5% Mg, <0.5% Fe, <2.0% Si, or further contains 0.03 to 0.3% Cr, contains 0.003 to 0.15% Ti alone as a crystal grain fining agent or in combination with 1 to 100ppm B is cast. This casting of this Al alloy is heated for >=0.5 hour at 350 to 550 deg.C to uniformly and finely precipitate the Al-Mn intermetallic compd. This alloy is subjected to an anodic oxidation treatment in an ordinary sulfuric acid electrolytic bath, by which the anodized film having the black color tones is formed on the surface of the Al alloy.

Description

[Detailed Description of the Invention] Industrial Field of Application This invention is applicable to aluminum alloy materials used after anodizing treatment, such as building materials such as curtain walls and interior materials, as well as utensils, containers, and electrical appliances. The present invention relates to aluminum alloys used for measuring instrument housings, nameplates, far-infrared line radiation members, solar heat absorbing members, etc., and methods for manufacturing the same.

BACKGROUND OF THE INVENTION Generally, aluminum alloys used for building materials such as curtain walls and interior materials, as well as appliances, containers, electrical measuring equipment housings, etc., are often subjected to anodizing treatment from the viewpoint of corrosion resistance. Aluminum alloys for anodizing treatment for these purposes are often light gray to silver in color, and such alloys are generally Kawa 5105.
It is often used for 0050 alloy, 00 alloy, and 5005005 alloy, and as a gray type, Al-1~4%S
1 alloy is common. In addition, a sulfuric acid electrolytic bath has traditionally been widely used for anodizing treatment from the viewpoint of economy and corrosion resistance.

By the way, in the above-mentioned applications, the surface after anodizing treatment may be required to have various color tones for aesthetic reasons. Methods for imparting the desired color tone to anodized plates include painting, dyeing, secondary electrolytic coloring, alloy coloring, and coloring with an anodizing solution, but from an economical and corrosion-resistant perspective, anodizing It is desired to develop color even after oxidation treatment, especially after anodization treatment using a sulfuric acid bath.

Problems to be Solved by the Invention In the use of building materials such as exterior and interior materials for buildings, color tones are becoming increasingly diverse, and aluminum alloy materials with a black tone are required due to design requirements. be. On the other hand, there are cases where a black tone is required from a design point of view in applications such as utensils, containers, electrical measuring instrument casings, and nameplates. Due to the above requirements, a black tone may be desired. Furthermore, since a black tone is effective for far-infrared radiation and also for solar heat absorption, these members are required to have a black tone.

Conventionally, methods for obtaining anodized aluminum alloy materials with such a black tone have had to rely on secondary electrolytic methods, dyeing methods, or painting. The reality is that it has been difficult to obtain a black tone with the usual anodic oxidation treatment using a sulfuric acid electrolytic bath.

The present invention was made against the background of the above-mentioned circumstances, and an object of the present invention is to provide an aluminum alloy which is highly economical and can obtain a black tone even after being anodized using an ordinary electrolytic bath, and a method for producing the same. The purpose is to

Means for Solving the Problems In order to solve the above-mentioned problems, the inventors of the present invention have conducted extensive experiments and studies, and found that the amounts of alloying elements in aluminum alloys, especially the amounts of Mn and Mg, have been adjusted to appropriate amounts. The inventors have discovered that by appropriately adjusting the size and precipitation density of Al-Mn-based intermetallic compounds, it is possible to achieve a black tone after anodizing in a sulfuric acid electrolytic bath, and have developed the present invention. I arrived at the eggplant.

Specifically, the aluminum alloy of the invention of claim 1 has M
nQ, more than 3wt% and less than 1.5v1%, Mg2,
(Contains lv+% or more and 45wt% or less, FeG, .5wt% or less, Si2.Ovt% or less, and as a grain refiner Ti 0.003v+% or more and 0.1.5w
t% or less alone or B lpa or more 100pa
It is characterized in that it contains a combination of the following, with the remainder consisting of Al and inevitable impurities.

Moreover, the aluminum alloy of the invention of claim 2 has M n
More than 0.8wt% and less than 1.5W1%, Mg2. Owt
% or more and 45W1% or less, Cr 0. D3wt% or more03
tt% or less, Fe0.5vt% or less, Si2. Ov1%
Contains the following and as a grain refining agent T i 0
．． 003wt% or more and 0.1.5wt% or less alone or in combination with Blppm or more and +004 or less, and the remainder consists of Al and inevitable impurities.

On the other hand, the manufacturing method of the invention of claim 3 includes casting a molten metal of the alloy having the composition according to claim 1 or 2 by a conventional method, and then heating it at 350°C to 550"C for 05 hours or more. It is characterized by:

In this invention, the black color after anodizing treatment is determined by Hunter's color difference formula (see Its Z8730).
It can be defined by the values of the brightness index and chromaticness index a and b. That is, the lightness index L
The higher the value, the whiter it is, while the Romanticness index is about the degree of coloration, and the higher the a value, the stronger the reddish tinge, and the higher the b value, the stronger the yellowish tinge. The black tone aimed at in this invention is defined by the L value, a value, and b value measured when the thickness of the anodic oxide film is 20 μm.
It can be defined as a color tone that satisfies <45, -3<a<3, -3<b<3.

Function First, the reasons for limiting the composition of the aluminum alloy in this invention will be explained.

Mn Mn is an important element that generates Al-Mn-based intermetallic compounds and determines the color tone after anodizing treatment. It has been found that this essentially contributes to the blackening of the anodic oxide film. That is, as Al-Mn intermetallic compound precipitates, Al6 Mn, A76 (MnFe), αA/M
n (Fe)S i, and Cr to them.

There are small amounts of solid solution such as Ti, etc., and the presence of these precipitates with a size of 0.01 LL11 to 1 μm with a density of 1 x 107 pieces/- or more is appropriate for blackening the anodic oxide film. be. Typical requirements for achieving such a precipitation state are that the intermetallic compound-forming element is poured into a specified pot, and that the casting speed is higher than the critical speed in order to sufficiently dissolve the component elements. , and the heating temperature for precipitation may be appropriate. Mn is a main element for generating Al-Mn intermetallic compounds, and coexistence with Mg promotes precipitation and contributes to blackening of the anodic oxide film.

Here, if the Mn amount is less than 0.8wt%, it will be difficult to sufficiently blacken the anodic oxide film, while if it exceeds 15w[%], it will be difficult to blacken the anodic oxide film. This is not preferable because coarse intermetallic compounds are formed as crystals. Therefore, the amount of Mn exceeds 0.8wt% 1
．． ．． The content was set to 5 wt% or less.

Mg: Mg promotes precipitation of Al-Mn intermetallic compounds and contributes to achieving the above-mentioned precipitation state.

In particular, when applying a casting method such as DC casting, in which the cooling rate during casting is slower than continuous thin plate casting, and the amount of forced solid solution of Mn during casting is small, the amount of Mg added must be increased. , the precipitation state of the A7-Mn-based intermetallic compound is not suitable for obtaining a black anodic oxide film. If the amount of Mg is less than 2.3 wt%, it becomes difficult to blacken the anodic oxide film. On the other hand, if the Mg amount exceeds 45 wt%, it is possible to blacken the anodic oxide film, but the castability and hot rolling properties deteriorate. Therefore, the Mg amount is 2.0wt% or more, 4.5
v1% or less.

Cr: In the case of the aluminum alloy according to the second aspect, Cr is added. Cr is effective in further promoting blackening of the anodic oxide film, and addition of Cr has the effect of slightly changing the black tone. That is, when Cr is not added, the color is slightly bluish black, but by adding Cr, the blue color disappears and the color becomes slightly yellowish. Cr amount is 0.03v
If the content is less than t%, the above effect cannot be obtained; on the other hand, if the content is less than 0.3wt%
If Cr is added, coarse compounds will be produced if it exceeds 0.03 to 0.3.
It was set within the range of v1%.

Fe Fe affects the precipitation of Al-Mn intermetallic compounds, but has no essential effect on the black tone of the anodic oxide film. From the viewpoint of castability, it is preferable that the amount of Fe is small, and 0
．． ．． If it exceeds 5 wt%, it will be difficult to cast, so the amount of Fe should be 0. ．． It was limited to 5 wt% or less.

Si: Although Si also affects the precipitation of Al-Mn intermetallic compounds, it does not essentially affect the black tone after anodizing treatment. From the viewpoint of castability, it is preferable that the amount of Si is small. 2. If it exceeds Of1%, it becomes difficult to cast.
The amount of Si is 2. OW was limited to 1% or less.

Ti, B: Ti has the effect of refining the crystal grains of the ingot and preventing streaks and texture of the rolled plate, but Ti0.003wt
If Ti is less than 0.15w, the effect cannot be obtained.
If Ti exceeds 0.003 to 0.000%, TiAl3-based coarse intermetallic compounds will be generated. It was set within the range of 15vj%. Further, B is an element that coexists with Ti and promotes grain refinement, and is sometimes added in combination with Ti. However, if the amount of B is less than 1-, the effect cannot be obtained,
On the other hand, if it exceeds 100-, the effect is saturated and coarse TiB2 particles are generated, resulting in linear defects, so the amount of B added in combination with Ti was set within the range of 1 to 100-.

In addition, in A, l-Mg-based alloys, it has been conventional practice to add a small amount of Be to prevent oxidation of the molten metal, but in the case of the aluminum alloy of the present invention as well, Be is about 5004 or less. There is no particular problem in adding Be.

Furthermore, in the aluminum alloy of this invention, Ni,
Zr, V, Cu, Zn, etc. may be included. Among these, Ni, Zr, and V do not essentially affect the color tone of the anodic oxide film, but Ni 1.0 wt% or more and Zr 0.3
If it is more than wt%, VQ, 3v1% or more, casting becomes difficult, so Ni is l, (less than 1wt%, Zr is 0.3
It is desirable to suppress it to less than vt%, and (■) to less than 0.3vt%. In addition, although Cu and Zn slightly change the color tone of the anodic oxide film, they do not have any essential effect on blackening, but if Cu exceeds 1.9wt% or ZnloWl% or above, it becomes difficult to cast. Less than 10wt%, Zn
It is desirable to suppress it to less than 1.0 wt%.

Next, process conditions for producing the alloy of the present invention will be explained.

As mentioned above, in order to obtain an appropriate precipitation state of Al-Mn intermetallic compounds and achieve a black color tone after anodizing treatment, DC casting method and thin plate continuous casting method (continuous casting and rolling method) are necessary.
The heat treatment temperature for precipitation applied at any stage after casting is important.

That is, heating for precipitation of the A,/-M n-based intermetallic compound is performed at a temperature of 350°C or higher and 550°C or lower.
It needs to be done for 5 hours or more. If the temperature is less than 350°C, there are too few precipitates and a black color cannot be obtained after the anodizing treatment, while if it exceeds 550°C, the color tone after the anodizing treatment becomes pale. In addition, the time required is 0.5 hours or more for the temperature to remain within the range of 350 to 550°C from the heating process to the holding and cooling process, and if the time is less than 0.5 hours, a black color will not be obtained after the anodizing treatment. I can't. Note that heating for more than 24 hours is only uneconomical, so it is preferable to heat for less than 24 hours.

Heating for precipitation as described above is normally carried out on the ingot when DC casting is applied, but when continuous thin plate casting is applied, it is heated during rolling. Alternatively, it may be performed after rolling. Therefore, this precipitation treatment can be performed at the same time as homogenization treatment for the ingot or heating for hot rolling when a DC casting method is applied, and when a continuous thin plate casting method is applied, it can be performed as a cooling treatment. It can also be performed as intermediate annealing, which is performed as necessary before inter-rolling or in the middle of cold rolling, or as final annealing, which is performed as necessary after cold rolling.

In particular, when the DC casting method is applied and the ingot is subjected to the heat treatment for 350~b as described above, intermediate annealing is performed as necessary immediately after hot rolling or in the middle of cold rolling. Alternatively, the final annealing conditions are 300 to 500°C.
Preferably, the temperature is within the range of 0.5 to 24 hours. These intermediate annealing and final annealing are A, / -M n
This further promotes the precipitation of intermetallic compound precipitates and contributes to the blackening of the anodic oxide film, but if the temperature is less than 300°C, the effect is insufficient, while if the temperature exceeds 500°C, the surface will deteriorate during annealing. It oxidizes and discolors, which is not desirable. Moreover, if the time is less than 0.5 hours, the above effect cannot be obtained;
If it exceeds 4 hours, it becomes uneconomical.

In the case of this invention, it is limited to rolled materials, cast materials as they are,
Alternatively, it can also be used as an extruded material.

When used as an extruded material, the above-mentioned precipitation treatment may be performed in addition to heating for hot extrusion of the cast billet I.

Example [Example 1] Each alloy shown in alloy numbers Nα1 to Na4 in Table 1 was DC
Cast by casting method, 450mm x 120mm
It was made into a slab of m x 4000 kaku. These slabs were subjected to heat treatment (precipitation treatment) under the conditions shown in Table 2, and hot rolling was started at 450°C to produce hot rolled sheets with a thickness of 4 inches. These hot-rolled plates were subjected to one water cold rolling to have a thickness of 2 mm, then intermediate annealing at 400°C for 2 hours, and further cold rolled to a final thickness of 151 Iffl.

The surface of each plate of the final thickness was etched with a 10% NaOH aqueous solution, washed with water, and desmutted with nitric acid. Furthermore, anodization treatment was performed using a sulfuric acid electrolytic bath under the following conditions to form an anodic oxide film with a thickness of 20 μs.

Sulfuric acid concentration: 15% Electrolysis temperature: 20°C Current density: 1.5A/do (The color tone of each board after anodizing treatment was determined by the Hunter color system using a Suga Test Instruments color meter (SM-3-MCI). , a value, and b value were measured. The results are shown in Table 2. Here, L value <45, -3kua
If all of the values 3, -3, 3 are satisfied, it can be determined that the black tone is the target color tone of the present invention.

Table 2 As shown in Table 2, when the process conditions of the present invention were applied to alloys within the composition range of the present invention, a black tone could be obtained. In addition, when the distribution state of the precipitates was investigated using an electron microscope for the sample with a black color, the precipitate size was 0.02 to 0.8 μs and the density was
It was found that 1X109 ~ +xio'' pieces/m.

[Example 2 Mn1. , lv1%, M g 3. ．． 5wt%, Cr
0.18v1%, Fe 0.1lv1%, S
i G, 08wt%, T i 0.01wt
%, B 13 ppm, the balance being substantially Al, within the composition range of this invention, by DC casting method.
Cast into inch diameter billets. The Bi1 knot was subjected to precipitation treatment which also served as soaking treatment at 450°C for 10 hours, and then hot extrusion was performed at 450°C. Regarding the obtained extruded material, 10% Na OI- (aqueous solution technique,
After notching, it was washed with water and desiccated with nitric acid. Next, an anodic oxidation treatment was performed using a sulfuric acid electrolytic bath under the same conditions as in Example 1 to form an anodic oxide film having a thickness of 201 x m.

Regarding the color tone after the anodizing treatment, the L value, a value, and b value were examined using the Nihunter color system as in Example 1, and the L value was 34, the a value was 056, and the b value was 1.21. A black tone was obtained.

From the results of Example 2, it is clear that even extruded materials can achieve a black color tone after anodizing if the process conditions of the present invention are applied.

Effects of the invention As is clear from the examples, the aluminum alloy according to claim 1 or 2 can be used for secondary electrolytic coloring, dyeing,
It is possible to obtain a black tone without relying on painting or the like, just by anodizing using an ordinary low-cost sulfuric acid electrolytic bath. Further, according to the method of claim 3, it has become possible to reliably produce on a mass production scale an aluminum alloy material that can exhibit a black tone after anodizing treatment as described above. Therefore, the present invention can be applied to aluminum alloy materials for applications requiring a black tone, and great effects can be obtained.

Claims (3)

[Claims] (1) Mn over 0.8 wt% and 1.5 wt% or less, Mg
2.0wt% or more and 4.5wt% or less, Fe0.5wt%
The following contains 2.0 wt% or less of Si, and 0.003 wt% or more and 0.15 wt% or less of Ti as a grain refining agent alone or in combination with B1 or more and 100 ppm or less, with the remainder being Al and unavoidable impurities. An aluminum alloy that is black in color after being anodized in a sulfuric acid electrolytic bath. (2) Mn over 0.8wt% and 1.5wt% or less, Mg
2.0wt% or more and 4.5wt% or less, Cr0.03wt
% or more and 0.3wt% or less, Fe0.5wt% or less, Si
2.0 wt% or less, and contains 0.003 wt% or more and 0.15 wt% or less of Ti as a grain refiner alone or in combination with B1 ppm or more and 100 ppm or less, and the remainder consists of Al and inevitable impurities. An aluminum alloy that is black in color after being anodized in a sulfuric acid electrolytic bath. (3) After casting a molten metal of the alloy having the composition according to claim 1 or claim 2, anodizing treatment in a sulfuric acid electrolytic bath characterized by heating at 350°C to 550°C for 0.5 hours or more. A method for producing an aluminum alloy with a black color.