JP3288997B2 - Surface treatment method for extruded aluminum alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for giving an Al-Mg-Si-based aluminum alloy extruded shape an appearance in which roughness is emphasized by large irregularities.

[0002]

2. Description of the Related Art Aluminum-Mg-Si based aluminum alloy extruded shapes are used for building materials and casing materials such as exterior materials, interior materials, surface materials, etc., utilizing the fact that they are lightweight and have excellent corrosion resistance and durability. It is used in various fields. For architectural uses, etc., in order to improve harmony with urban spaces and improve the design of buildings, the surface gloss is adjusted by satin finish treatment, blast treatment, etc., and various colors are imparted by electrolytic coloring, painting and the like. Recently, there has been a demand for an extruded aluminum alloy material having an appearance having a rough feeling due to larger unevenness.
When the aluminum crystal grains are exposed prior to the anodizing treatment, the colored aluminum alloy extruded material also maintains the surface state in which the crystal grains are exposed, and becomes a product having a high design property. Etching using a mixed solution of nitric acid and hydrochloric acid (aqua regia), alkali, hydrofluoric acid, or the like is known as the manifestation of crystal grains. It is also known that a crystal grain pattern is developed by etching an aluminum material in which crystal grains have been largely grown (Japanese Patent Laid-Open No. 25717/1991).
7, JP-A-5-70906, JP-A-6-3
No. 36682).

[0003]

In the method of producing a crystal grain pattern using aqua regia, it is difficult to control the appearance because the aqua regia reacts violently with the extruded aluminum alloy material. In addition, the reaction gas adversely affects the environment such as corrosion of peripheral equipment. In the etching using an alkali, although it is easy to control the appearance after the treatment, since the extruded aluminum alloy material is uniformly dissolved, a crystal grain pattern cannot be developed. A method of matting using a hydrofluoric acid-based etchant is also known, but also in this case, a feeling of unevenness is small and a desired appearance is not obtained. In the method of performing the matting treatment by shot blasting, an appearance having a feeling of unevenness according to the particle diameter of the shot is obtained. However, depending on the pressure at the time of spraying the shot, the extruded aluminum alloy material may be deformed.

[0004]

SUMMARY OF THE INVENTION The present invention has been devised in order to solve such a problem, and utilizes the fact that a defect is easily generated in a surface oxide film near a Mg ₂ Si deposition portion. Another object of the present invention is to provide an extruded aluminum alloy material having relatively large irregularities formed on a material surface by combining a hydrochloric acid etching treatment with an alkali etching treatment. The present invention, in order to achieve the object,
After extruding the Al-Mg-Si-based aluminum alloy extruded shape, heat treatment is performed at 180 to 230 ° C for 1 to 4 hours to precipitate Mg ₂ Si, and then the aluminum alloy extruded shape is added to a hydrochloric acid-containing aqueous solution. The method is characterized in that fine ruggedness is generated on the material surface by immersion, and the aluminum alloy extruded shape is further immersed in an alkaline aqueous solution to enlarge the ruggedness. In the hydrochloric acid-containing aqueous solution immersion treatment, it is preferable to immerse the extruded aluminum alloy material in a hydrochloric acid-containing aqueous solution having a concentration of 10 to 200 g / l and a bath temperature of 20 to 50 ° C for 1 to 20 minutes. In the alkaline aqueous solution immersion treatment, the concentration 2
It is preferable that the extruded aluminum alloy is immersed in an aqueous solution of sodium hydroxide having a pH of 13 or more at a temperature of 0 to 100 g / l, a bath temperature of 30 to 70 ° C., for 3 to 20 minutes.

[0005]

The Al-Mg-Si based aluminum alloy extruded material after the heat treatment is subjected to alkali etching according to a conventional method.
Pits are generated from the starting point of the selective dissolution or dropout of the crystallized substances contained in the material. However, the surface after treatment is
Significantly affected by the luster of the material itself, it lacks satin texture. That is, the surface morphology cannot be largely changed only by the alkali etching treatment.

Therefore, in the present invention, Al
-M deposited on extruded material of Mg-Si based aluminum alloy
After controlling the precipitation form of g ₂ Si, the aluminum-alloy extruded aluminum alloy extruded section is subjected to an etching treatment using a hydrochloric acid-containing aqueous solution prior to the alkali etching treatment, whereby the entire surface of the aluminum alloy extruded section is introduced. A large number of fine irregularities can be formed, and the size and depth of the irregularities can be controlled with a high degree of freedom. When an extruded aluminum alloy material is heat-treated, an oxide film is formed on the surface of the shape material. However, defects are likely to occur in the surface oxide film near the Mg ₂ Si deposition portion. When this extruded aluminum alloy material is immersed in a hydrochloric acid aqueous solution, hydrochloric acid penetrates into a defective portion of the surface oxide film, and aluminum is locally dissolved. Therefore, by controlling the precipitation state of Mg ₂ Si by a heat treatment prior to the surface treatment, the surface state is adjusted to a surface state having a defect distribution suitable for expressing the required appearance.

[0007] Etch pits generated by local melting, ie, azimuth pits, grow from the material surface in the depth direction as small angular holes. Therefore, the irregularities formed on the surface of the extruded aluminum alloy material by the etch pit are minute. The fine irregularities formed on the material surface by immersion in the hydrochloric acid-containing aqueous solution become large irregularities due to the uniform dissolution of the material when the extruded aluminum alloy material is immersed in the alkaline aqueous solution, resulting in an increase in the hole diameter of the etch pits. The grown large irregularities are uniformly distributed on the surface of the material, and impart the intended roughness to the extruded aluminum alloy material. When observing the surface of the extruded aluminum alloy material after the immersion treatment using the alkaline aqueous solution, the surface roughness of any part of the material surface is 5 μm or more in Rz.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Extruded aluminum alloys to which the present invention is applied include Al-Mg-Si such as JIS A6063.
There is a system alloy, which has been conventionally used as a plate material, a pipe material, an extruded shape material and the like in the building materials field and the like. Heat treatment: In the heat treatment, an oxide film is formed on the surface of the extruded aluminum alloy material. However, in order to distribute a defect portion serving as a starting point of an etch pit to the surface oxide film, the precipitation state of Mg ₂ Si is adjusted by adjusting the heat treatment conditions. Control. As the heat treatment conditions, the extruded aluminum alloy material is 180 to 230
It is preferable to heat to 1C for 1 to 4 hours. At a heat treatment temperature of less than 180 ° C. and a short heating time of less than 1 hour, M
The amount of precipitated g ₂ Si is insufficient, and the number of etch pits generated in the subsequent immersion step of the hydrochloric acid-containing aqueous solution is reduced. Therefore, even if immersion treatment is carried out in an alkaline aqueous solution, only large irregularities are sparsely distributed on the surface of the material, and a desired roughness is not provided. On the other hand, if the heat treatment temperature exceeds 230 ° C. or the heating time is longer than 4 hours, Mg ₂ Si precipitates excessively, so that the etch pits are excessively generated in the hydrochloric acid-containing aqueous solution, and overlap. When such an aluminum alloy extruded section is immersed in an alkaline aqueous solution,
Excessive dissolution of the surface of the material proceeds, and the surface roughness is reduced to Rz 5 μm or less with less unevenness, and a desired roughness cannot be obtained.

[0009] Dipping treatment with hydrochloric acid-containing aqueous solution: The heat-treated extruded aluminum alloy preferably has a concentration of 10 to 20
0 g / l (more preferably 30 to 150 g / l), bath temperature 2
The extruded aluminum alloy material is immersed in a hydrochloric acid-containing aqueous solution at 0 to 50 ° C (more preferably 25 to 40 ° C) for 1 to 20 minutes (more preferably 5 to 15 minutes). The higher the acid concentration or bath temperature of the hydrochloric acid-containing aqueous solution to be used, the more the generation of etch pits is promoted and the shorter the treatment time becomes. At a hydrochloric acid concentration of less than 10 g / l or a bath temperature of less than 20 ° C., the dissolution rate is slow, and 200 g / l
If the hydrochloric acid concentration exceeds 1 or the bath temperature exceeds 50 ° C., the dissolution reaction proceeds extremely, so that it is difficult to control the time required for forming fine irregularities. In addition, excessively high hydrochloric acid concentration and bath temperature
There is a possibility that the generation of hydrochloric acid mist is promoted and the working environment is deteriorated. If the immersion time does not reach 1 minute, the local dissolution does not sufficiently proceed. Conversely, if the immersion time exceeds 15 minutes, although the number of fine irregularities increases, the required appearance cannot be obtained because the irregularities overlap. The hydrochloric acid-containing aqueous solution can contain a mineral acid such as phosphoric acid or sulfuric acid or an organic acid such as oxalic acid in order to easily control fine irregularities. Prior to immersion in the aqueous solution containing hydrochloric acid, the extruded aluminum alloy material may be immersed in an alkaline aqueous solution to remove oxides from the surface of the material in advance. In the immersion treatment at this time, for example, a concentration of 20 to 10
0 g / l sodium hydroxide, bath temperature 30-70
The extruded aluminum alloy material is immersed in an alkaline aqueous solution having a pH of 13 ° C. or higher for 1 to 10 minutes. This process removes oxides formed during the heat treatment from the material surface, so that the reaction between the material surface and the aqueous solution containing hydrochloric acid proceeds uniformly in the next step, and etch pits are generated with a uniform distribution on the material surface. . The extruded aluminum alloy material treated with the alkaline aqueous solution is more preferably neutralized with nitric acid, sulfuric acid or the like prior to immersion in the aqueous solution containing hydrochloric acid.

[0010] Alkaline aqueous solution immersion treatment: The extruded aluminum alloy material is immersed in an alkaline aqueous solution after a large number of etch pits are formed by contact with an aqueous solution containing hydrochloric acid. Preferably, the concentration is 20 to 100 g / l, and the bath temperature is 30 to
An aqueous sodium hydroxide solution having a temperature of 70 ° C. and a pH of 13 or more is used, and the extruded aluminum alloy is immersed for 3 to 20 minutes. Etch pits formed on the material surface by immersion in a hydrochloric acid aqueous solution have a larger pore diameter in this step of immersing the extruded aluminum alloy in an alkaline aqueous solution. With the hydrochloric acid-containing aqueous solution immersion treatment, the etch pit with a complicated shape and the tip part is deeply advanced to the inner part of the material causes a blackish color due to light absorption at the pit part, but due to the alkaline aqueous solution immersion By changing the pit shape, the blackish color tone is eliminated. If the concentration is less than 20 g / l or the bath temperature does not reach 30 ° C., the uniform dissolution of the material surface is insufficient, the unevenness does not sufficiently expand, and the required appearance with a rough feeling cannot be obtained. Conversely, if the concentration exceeds 100 g / l or the bath temperature exceeds 70 ° C., the uniform dissolution becomes extreme as the control becomes difficult, and the unevenness becomes smooth and inconspicuous. In addition, the working environment may be deteriorated due to generation of a large amount of etching mist. 3 to promote uniform dissolution
An immersion time of at least 20 minutes is required, but if the immersion time is longer than 20 minutes, the uniform dissolution proceeds excessively, and the unevenness becomes smooth and inconspicuous. The extruded aluminum alloy material whose roughness is emphasized by large irregularities is subjected to anodic oxidation treatment, coloring treatment, sealing treatment, electrodeposition coating, spray coating and the like according to the purpose.

[0011]

Example: JIS A6063 aluminum alloy extruded material was subjected to heat treatment at 180 ° C. for 2 hours to obtain Mg ₂ S.
After i was deposited, the substrate was immersed in a hydrochloric acid aqueous solution having a concentration of 100 g / l and a bath temperature of 30 ° C. for 5 minutes to form a large number of etch pits on the surface of the material. Then, it was immersed in an aqueous sodium hydroxide solution having a concentration of 50 g / l and a bath temperature of 50 ° C. for 10 minutes to uniformly dissolve the material surface. Observation of the surface of the processed aluminum alloy extruded profile showed an appearance in which roughness was emphasized due to enlargement of unevenness. The surface roughness is Rz
It was 10.2 μm.

Comparative Example 1 An extruded aluminum alloy material was immersed in an aqueous hydrochloric acid solution and then an aqueous sodium hydroxide solution under the same conditions as in Example 1 without performing heat treatment after the extrusion. Observation of the surface of the material after the treatment revealed that sufficient roughness was not obtained due to the small amount of unevenness. The surface roughness at this time was Rz 3 μm. Comparative Example 2: Extruded aluminum alloy was processed under the same conditions as in Example 1 except that a heat treatment at 235 ° C. × 2 hours was performed after the extrusion. When the surface of the material after the treatment was observed, remarkable roughness was detected, and a rough appearance was not obtained. The surface roughness at this time was Rz4 μm. As is clear from this comparison, it was confirmed that the extruded aluminum alloy material was adjusted to a rough surface with large irregularities by performing heat treatment → immersion in an aqueous solution containing hydrochloric acid → immersion in an alkaline aqueous solution according to the present invention. .

[0013]

As described above, in the present invention, a large number of etch pits are formed by immersing an extruded aluminum alloy material having a large amount of Mg ₂ Si precipitated by heat treatment in an aqueous solution containing hydrochloric acid, and then forming an alkaline pit. The pore diameter of the etch pit is enlarged by immersion in an aqueous solution to impart a rough feeling of large irregularities to the material surface. The extruded aluminum alloy material thus treated is adjusted to a highly discriminable surface state by anodic oxidation, coloring treatment, various kinds of coating, and the like, and is used in a wide range of fields including sashes, curtain walls, and the like.

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁷ Identification code FI C22F 1/00 613 C22F 1/00 613 691 691B 691C (72) Inventor Takeshi Ebihara 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture No. Nippon Light Metal Co., Ltd. Group Technology Center (72) Inventor Mikio Asakura 1-1-11 Osaki 1-chome, Shinagawa-ku, Tokyo Nippon Light Metal Co., Ltd. (72) Inventor Hiroshi Kamata 1-11 Osaki 1-chome, Shinagawa-ku, Tokyo No. 1 Inside Nippon Light Corporation (72) Inventor Takashi Iriya 1-1-11 Osaki, Shinagawa-ku, Tokyo Shin-Nikko Corporation (72) Inventor Kiyoshi Kawabata 1-11-1 Osaki, Shinagawa-ku, Tokyo (56) References JP-A 1-2212775 (JP, A) JP 9-3663 (JP, A) JP-A 57-110668 (JP, A) 8693 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23F 1/00 101 C22F 1/05 C23F 1/14 C23F 1/36 C22F 1/00 612 C22F 1/00 613 C22F 1/00 691

Claims (3)

(57) [Claims] After extruding an extruded Al-Mg-Si based aluminum alloy, heat treatment is performed at 180 to 230 ° C for 1 to 4 hours to precipitate Mg ₂ Si, and then aluminum is added to a hydrochloric acid-containing aqueous solution. A method for surface treatment of an extruded aluminum alloy characterized by forming fine irregularities on the surface of the material by immersing the extruded alloy and further immersing the extruded aluminum alloy in an alkaline aqueous solution to enlarge the irregularities. . 2. A hydrochloric acid concentration of 10 to 200 g / l and a bath temperature of 20.
The surface treatment method according to claim 1, wherein the extruded aluminum alloy material is immersed in a hydrochloric acid-containing aqueous solution at a temperature of about 50 ° C for 1 to 20 minutes. 3. An aluminum alloy extruded section is immersed in a hydrochloric acid-containing aqueous solution, and then a sodium hydroxide concentration of 20 to 100 is applied.
2. The surface treatment method according to claim 1, wherein the substrate is immersed for 3 to 20 minutes in an alkaline aqueous solution having a bath temperature of 30 to 70 ° C. and a pH of 13 or more.