JP2011162840A - Aluminum alloy for extrusion having excellent corrosion resistance and brightness - Google Patents

Abstract

An object of the present invention is to provide an Al-Mg-Si-based aluminum alloy extruded material in which the reduction in brightness is small even when the anodized film is thickened.
In an Al—Mg—Si-based aluminum alloy extruded material, when the stoichiometric composition of Mg ₂ Si is in the range of 0.5 to 0.82 mass% (hereinafter referred to as “%”), Si is set to a value of 0.3. 3 to 0.45% and Mg is 0.31 to 0.52%, or Si is 0.18 to 0.3% and Mg is 0.55 to 1.0%, and Mg ₂ Si When the stoichiometric composition is in the range of 0.82 to 1.0%, the excess Si relative to the Mg content is less than 0.15%, or the excess Mg relative to the Si content is less than 0.5%, and Fe Corrosion resistance characterized by having produced an anodized film with a thickness of 20 μm or more after mirror-finishing an aluminum alloy extruded material containing 0.05 to 0.12% and comprising the balance Al and inevitable impurities Al-Mg-Si-based aluminum alloy with excellent glitter Design.
[Selection] Figure 3

Description

  The present invention relates to an aluminum alloy extruded material excellent in glitter and corrosion resistance after anodizing.

  Conventionally, an aluminum alloy extruded material that is required to have glitter is imparted with glitter by chemical polishing treatment or electrolytic polishing, but as it is, the glitter is deteriorated by alteration such as oxidation of the surface layer. Therefore, it is widely known that a thin anodic oxide film having a thickness of several μm to 10 μm is formed as a protective film after providing glitter. For example, there are Patent Document 1 to Patent Document 4.

Patent Document 1 discloses a component and a manufacturing method of an aluminum alloy for extrusion for imparting glitter after anodizing treatment. However, if the Cu content is large and the anodized film thickness is 20 μm or more, glitter is achieved. Decreases.
Patent Document 2 discloses a composition and manufacturing method of an aluminum alloy for extrusion for imparting anodic oxidation brightness and bending surface properties, but contains Cu, Mn, Cr, Zr, and the like. Therefore, when the anodic oxide film thickness is 20 μm or more, the glitter is lowered.
Patent Document 3 discloses the composition and manufacturing method of an aluminum alloy for extrusion for imparting surface gloss after anodizing treatment, but contains a lot of Cu, Fe, etc. in addition to Mg and Si. When the anodic oxide film thickness is 20 μm or more, the glitter is lowered.
Patent Document 4 discloses the composition and processing method of an aluminum alloy to which glittering is imparted after anodizing treatment, but the composition range is wide and does not show the aluminum alloy composition when the anodized film thickness is 20 μm or more. Absent.
JP-A-6-100970 JP-A-10-226857 Japanese Patent Laid-Open No. 10-306336 JP-A-1-272800

  When these aluminum alloy extruded materials imparted with glitter are used for outdoor building exterior materials and the like, it is necessary to form an anodic oxide film thicker than before in order to improve corrosion resistance. However, since the brightness of the anodic oxide film itself is lowered, the film thickness of about 10 μm is the limit as seen in the above patent document. Further, 6063-T5 material is generally used for outdoor building exterior materials and structural members in order to satisfy material strength. However, the 6063-T5 material imparted with glitter has a problem that the anodized film becomes whitish when subjected to anodization, and the glitter is greatly reduced. Accordingly, an object of the present invention is to provide an Al—Mg—Si-based aluminum alloy extruded material in which the reduction in brightness is small even when the anodic oxide film is thickened.

  As a result of intensive studies, the present inventors have found that the color development of the anodized film itself is related to Si and Mg in the aluminum alloy, and have made the present invention.

That is, the present invention provides a Al-Mg-Si aluminum alloy extruded material, in the range stoichiometric composition of from 0.5 to 0.82% of _Mg 2 Si, Si is 0.3 to 0.45 percent And Mg is 0.31 to 0.52%, or Si is 0.18 to 0.3% and Mg is 0.55 to 1.0%, and the stoichiometric composition of Mg ₂ Si is In the range of 0.82 to 1.0%, excess Si with respect to Mg content is less than 0.15%, or excess Mg with respect to Si content is less than 0.5%, and Fe is less than 0.12% In addition, the aluminum alloy extruded material composed of the remaining Al and inevitable impurities is mirror-finished, and then an anodized film is formed with a thickness of 20 μm or more. Al—Mg— excellent in corrosion resistance and glitter Si-based aluminum alloy extruded material.

  According to the present invention, an Al-Mg-Si-based aluminum alloy extruded material excellent in corrosion resistance and glitter is provided as a building member such as a structural member or an exterior member used outdoors, and thus has a remarkable industrial effect. It is.

Figure 1 shows the relationship between the added amount and the Mg 2 _Si stoichiometric composition ratio of Mg and Si, straight line and dashed figure corresponds to stoichiometric composition of Mg 2 _Si. The straight line represents the composition ratio of the Mg ₂ Si amount of 0.5% to 1.0% in the claims of the present application, and the upper side is a region of excess Si, and the lower side of the line is a region of excess Mg. When the added Mg and Si form an ideally _Mg 2 Si, to comply with the stoichiometric composition ratio of _Mg 2 Si, _Mg 2 Si Mg or Si that did not become a stoichiometric ratio of excess Mg or Excess Si is formed. FIG. 2 shows the contents of Mg and Si that become Mg ₂ Si having a stoichiometric composition. The straight line represents the theoretically necessary Mg content, and the broken line represents the theoretically necessary Si content. FIG. 3 shows the Mg and Si claims of the present alloy.

  The effect of the aluminum alloy element according to the present invention will be described.

By adding Mg and Si simultaneously, Mg ₂ Si can be formed, and the material strength can be improved without impairing the extrudability. However, not all Mg and Si added to aluminum become Mg ₂ Si, and it is possible to increase material strength by adding excess Si or Mg. The present invention has found the relationship between the amount of excess Si or excess Mg, glitter, and material strength. This will be described in more detail below.

Mg ₂ Si having a stoichiometric composition of 0.5 to 1.0%, that is, Mg of 0.31 to 0.63%, Si of 0.18 to 0.37%, Mg or Si By adding more than each stoichiometric ratio, material strength equivalent to 6063-T5 material can be obtained, but in order to maintain the glitter even after anodizing treatment of 10 μm or more, it is necessary to control the addition amount of Mg and Si There is.

If the stoichiometric composition Mg ₂ Si is 0.5% or less, the material strength is insufficient, and if it is 1.0% or more, even if the anodic oxidation treatment of 10 μm or more is performed even if the shine treatment by chemical polishing or electrolytic polishing is performed, The brightness is greatly reduced, and sufficient glitter cannot be obtained.

When Mg ₂ Si in the stoichiometric composition is in the range of 0.5 to 0.82%, Mg is excessively 0.3 to 0.45% with respect to 0.31 to 0.52% of Mg. Add to. When Si is 0.3 or less, the material strength is insufficient, and when it is 0.45% or more, the glitter is lowered due to the color development of the anodized film itself. Alternatively, Mg in an amount of 0.55 to 1.0% is excessively added to Si in the stoichiometric composition with respect to 0.18 to 0.3%. When the Mg content is 0.55% or less, the material strength is insufficient, and when it is 1.0% or more, the appearance design is deteriorated due to the unevenness generated on the surface of the extruded material.

In the case where Mg ₂ Si in the stoichiometric composition is in the range of 0.82 to 1.0%, the material strength is satisfied by the generated Mg ₂ Si. It is necessary to make the range that does not lower the value. In the range of the stoichiometric composition, if the excess Si exceeds 0.15%, the glitter is lowered, so that it is necessary to suppress the excess Si to 0.15% or less. On the other hand, if the excess Mg exceeds 0.5%, the extrudability is deteriorated and the appearance is impaired, so it is necessary to suppress the excess Mg to 0.5% or less.

  FIG. 4 shows the relationship between the Mg content and the Si content of the alloy of the present invention. The addition range of Mg and Si in the present invention is a region surrounded by a solid line in the figure.

  Fe is contained as an impurity, and is disclosed as 0.35% or less in the JIS6063 standard or Japanese Patent Laid-Open No. H10-306336. However, when anodizing treatment of 20 μm or more is performed, Fe exceeds 0.12%. Fe is necessary to be 0.12% or less because the anodized film itself is colored white and the glitter is lowered. Preferably, it is 0.04 to 0.1%.

  Inevitable impurities are other elements inevitably contained in aluminum. Each element is 0.05% or less, and the total amount is preferably 0.15% or less.

The production method of the present invention will be described.
The Al—Mg—Si-based aluminum alloy extruded material according to the present invention is manufactured by a conventional extrusion process after casting a billet having the above alloy composition. For example, the billet is subjected to a homogenization treatment at 500 to 600 ° C. for 1 to 24 hours and cooled. Then, after heating and extruding to 400-550 degreeC and cooling to room temperature, the aging treatment of 1 to 10 hr is performed at 150-250 degreeC, and it manufactures.

  The aluminum alloy extruded material thus produced is subjected to chemical polishing or electrolytic polishing as a bright treatment, and further subjected to anodization treatment so that the film thickness is 20 μm or more, which is excellent in corrosion resistance, material strength, and glitter. Aluminum extruded material.

  Chemical polishing methods include phosphoric acid-nitric acid method and phosphoric acid-nitric acid-copper salt method. For example, it is immersed in a treatment solution of phosphoric acid: 40 to 80 vol% (density 1.69 g / ml) + nitric acid: 2 to 10 vol% (density 1.38 g / ml) at a bath temperature of 80 to 100 ° C. for 30 to 240 seconds. To do.

Examples of the electrolytic polishing method include a phosphoric acid method and a phosphoric acid-sulfuric acid method. For example, in a phosphoric acid solution of 85 to 100 vol% (density 1.69 g / ml), current density 0.2 to 0.8 A / cm ² , voltage 20 to 30 V, bath temperature 50 to 80 ° C., 4 to 20 minutes Perform electrolytic treatment.

The anodizing treatment is usually performed in a 15 wt% sulfuric acid bath, and is treated at a current density of 100 to 300 A / m ² in the case of the constant current method and 10 to ²⁰ V in the case of the constant voltage method. The processing time is controlled according to the target film thickness. The bath temperature is usually 15 to 25 ° C., but it can also be performed as a hard anodizing treatment at around 0 ° C.

  Specific embodiments according to the present invention will now be described.

  Various alloys of the present invention and comparative alloys shown in Table 1 were cast into a billet having a diameter of 219 mmφ and a length of 900 mm by continuous casting, homogenized at 580 ° C. for 4 hours, and then cooled to room temperature after homogenization. This billet was reheated to 480 ° C. before extrusion, and an extruded material was produced at an extrusion speed of 20 m / min using a U-shaped die. The extruded material was cooled to room temperature and then subjected to an aging treatment at 200 ° C. × 1 hr.

The obtained material was degreased, washed, immersed in a 5% NaOH solution at 50 ° C. for 2 minutes, etched, and then subjected to chemical polishing. In chemical polishing, an aqueous solution of 75% phosphoric acid, 15% sulfuric acid, 9% nitric acid, 0.5% boric acid and 0.5% copper nitrate was immersed at 100 ° C. for 120 seconds. After chemical polishing, it was pickled with 30% nitric acid and anodized for 60 minutes at a current density of 150 A / m ² in a 15% sulfuric acid bath at 18 ° C.

  Evaluation was made by measuring the occurrence of surface roughness of the extruded material and the tensile strength, and evaluating the specular reflectance and color tone (L *, b *) after the anodizing treatment. The results are shown in Table 2. Here, the L * value indicates the lightness, the lightness is higher as it is closer to 100, and the lightness is lower as it is closer to 0. In addition, b * is one of the indices representing hue and saturation, -b * indicates the blue direction, and + b * indicates the yellow direction.

The alloys of the present invention of Examples 1 to 11 satisfy all the performances of material strength, reflectance and extrudability. In Comparative Examples 1, ₂ , and 3, the amount of Mg ₂ Si is 0.5% or less, and the tensile strength is 200 MPa or less. In Comparative Examples 4, 5, and 6, the amount of Mg ₂ Si exceeds 1.0%, the reflectance (G60) is 30 or less, and the glitter is inferior. Since the comparative example 7 has a small amount of Si, the tensile strength is 200 MPa or less. Since the comparative example 8 has a large amount of Si, the reflectance (G60) is 30 or less and the glitter is inferior. Since the comparative example 9 has a small amount of Mg, the tensile strength is 200 MPa or less. In Comparative Example 10, since the amount of Mg is large, the extrudability is lowered and the surface is rough. Since Comparative Example 11 has a large amount of excess Si, the reflectance (G60) is 30 or less and the glitter is inferior. Since the comparative example 12 has much excess Mg, extrusion property is reduced and the surface roughening has generate | occur | produced. Although the comparative example 13 is contained in the amount of Mg and Si of the present invention, since the amount of Fe exceeds 0.12%, the anodic oxide film is colored, and the reflectance is 30 or less, resulting in poor glitter. Although the comparative example 14 is contained in the amount of Mg and Si of the present invention, since the amount of Cu exceeds 0.1%, the anodic oxide film is colored, and the reflectance is 30 or less and the glitter is inferior.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for materials that require strength, corrosion resistance, and luster for outdoor building exterior materials and the like, and has remarkable industrial effects.

Claims (1)

In the Al—Mg—Si-based aluminum alloy extruded material, when the stoichiometric composition of Mg ₂ Si is 0.5 to 0.82 mass% (hereinafter referred to as “%”), Si is 0.3 to 0.3. 45% and Mg 0.31 to 0.52%, or Si 0.18 to 0.3% and Mg 0.55 to 1.0%, Mg ₂ Si stoichiometry When the composition is in the range of 0.82 to 1.0%, excess Si with respect to the Mg content is less than 0.15%, or excess Mg with respect to the Si content is less than 0.5%, and Fe is 0.05 to The aluminum alloy extruded material containing 0.12% balance Al and unavoidable impurities is mirror-finished, and then an anodized film is formed with a thickness of 20 μm or more. Al-Mg-Si-based aluminum alloy extruded material.

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