TW201710521A - Aluminum alloy extruded material having positive electrode oxide film and excellent external appearance quality and production method therefor - Google Patents

Abstract

The purpose of the present invention is to provide a 7000-series aluminum alloy extruded material having a desired strength and being unlikely to have a streak pattern formed on the surface of a positive electrode oxide film. The present invention provides: an aluminum alloy extruded material having excellent external appearance quality and having a positive electrode oxide film having a metal composition being a re-crystalized composition; and a production method therefor. The aluminum alloy extruded material contains 4.0%-7.5% by mass Zn, 1.0%-2.2% by mass Mg, 0.05%-0.20% by mass Fe, no more than 0.30% by mass Cu, 0.005%-0.04% by mass Ti, 0.001%-0.02% by mass B, no more than 0.15% by mass Si, no more than 0.05% by mass Zr, no more than 0.05% by mass Mn, no more than 0.05% by mass Cr, and no more than 0.05% by mass V. The total Zr, Mn, Cr, V, and Ti content expressed by [Zr + Mn + Cr + V + Ti] fulfils the relationship [Zr + Mn + Cr + V + Ti] <= 0.10% by mass. The remainder comprises aluminum and unavoidable impurities, except when the Zn content is no more than 6.0% by mass and the Mg content is no more than 1.2% by mass.

Description

Aluminum alloy extruded material having anodized film and good appearance quality and manufacturing method thereof

The present invention relates to an aluminum alloy extruded material having an anodized film and having good appearance quality, and a method for producing the same, and more particularly to an aluminum alloy extruded material for an electronic device frame having good anodizing film properties and a method for producing the same.

The portable computer and the like are continuously miniaturized, thinned, and lightweighted. Along with this, the thinning of the frame material is required. In order to be able to withstand thinning, the frame material is gradually obtained by subjecting the 7000 series aluminum alloy having the highest strength among the aluminum alloys to an anodized film to obtain an extruded material.

However, if the 7000 series aluminum alloy extruded material is subjected to anodizing film treatment, a stripe pattern parallel to the extrusion direction may occur, which is aesthetically pleasing. The stripe pattern is believed to be formed when the cast structure is stretched in the extrusion direction during the extrusion process for the fibrous tissue, and is highlighted by the anodized film treatment. For example, in Patent Document 1, the metal structure of the extruded material becomes a recrystallized structure.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2012-246555

However, the metal structure becomes a recrystallized structure although the streak pattern is reduced, but satisfactory aesthetics are not obtained. The inventors of the present invention conducted intensive studies on the cause of the stripe pattern, and learned that not only the crystal shape of the metal structure, the concentration segregation of elements other than aluminum in the crystal interior and the grain boundary, the crystal state of the compound, and the recrystallized structure therebetween The difference in particle size also has a large effect.

Where the element other than aluminum is a part of segregation or crystallized, it is more difficult to form an anodized film than other parts. The reason is considered to be that the influence of concentration segregation results in different electrical properties. That is to say, the concentration of the peritectic elements in the crystal grains increases, and the eutectic elements are swept out to the grain boundaries, and concentration segregation occurs in the crystal grains and grain boundaries. In the extrusion processing, the concentration segregation portion is also stretched in the extrusion direction like the crystal grains of the cast structure, and the thin layer in which the concentration of the main elements of Zn and Mn is segregated is formed into a stripe shape, and the thickness of the anodized film is formed. The color is caused to be shaded, which is believed to be the cause of streaking on the surface of the anodized film.

Further, in addition to this, crystals are present because the extrusion process is accompanied by stretching of the crystal grains, and the fact that the crystal grains are dispersed in the extrusion direction also becomes a cause of streaking.

The extruded structure is stretched into a fibrous structure by extrusion processing, but at this time, the concentration segregation portion or the crystal body is also stretched. It is considered that even if recrystallization is performed, the crystal structure is changed from a fibrous structure to a recrystallized structure of an equiaxed crystal, and the anodized film is still left because the concentration segregation portion or the crystal phase remains after stretching. Stripes are visible during processing. Further, it has been known that in the recrystallized structure, crystals having a large crystal grain size difference are also striped.

Based on the results of the above-mentioned research, the inventors of the present invention found the most suitable alloy composition having a high strength of 380 MPa or more and suppressing concentration segregation or excessive crystal precipitation of the compound and crystal grain size of the recrystallized structure. The scope.

SUMMARY OF THE INVENTION An object of the present invention is to provide a 7000-series aluminum alloy extruded material having a desired strength and having no streaky pattern on the surface of an anodized film.

According to the present invention, there is provided an aluminum alloy extruded material having an anodized film and having good appearance quality, comprising: Zn: 4.0% by mass or more and 7.5% by mass or less, Mg: 1.0% by mass or more and 2.2% by mass or less, Fe: 0.05 mass % or more and 0.20 mass% or less, Cu: 0.30 mass% or less, Ti: 0.005 mass% or more and 0.04 mass% or less, B: 0.001 mass% or more and 0.02 mass% or less, Si: 0.15 mass% or less, and Zr: 0.05 mass% or less. Mn: 0.05% by mass or less, Cr: 0.05% by mass or less, V: 0.05% by mass or less, and the total content of Zr, Mn, Cr, V, and Ti [Zr+Mn+Cr+V+Ti] satisfies [Zr +Mn+Cr+V+Ti] ≦0.10% by mass, except that the content of Zn is 6.0% by mass or less and the content of Mg is 1.2% by mass or less, and the remainder is composed of aluminum and unavoidable impurities, and The metal structure is a recrystallized structure.

According to an aspect of the present invention, in the above-mentioned aluminum alloy extruded material, on the anodized surface, the Zn high concentration phase and the Zn low concentration phase are parallel to the extrusion direction, and are perpendicular to the extrusion direction. The direction is in the form of a layer, and the difference in Zn concentration is 1% or less in a range of 0.1 mm or more and 3 mm or less.

According to an aspect of the present invention, in the above-mentioned aluminum alloy extruded material, the crystal grain size of the recrystallized structure of the anodized film-treated surface is 200 μm or less on an average value, and the maximum crystal grain size is 1 mm. the following.

According to an aspect of the present invention, in the above-mentioned aluminum alloy extruded material, the area ratio of the intermetallic compound (crystal) to the anodized surface is less than 2%.

According to an aspect of the present invention, a method for producing an aluminum alloy extruded material is provided, characterized in that the casting material is subjected to homogenization treatment at a temperature of 400 to 560 ° C for 1 to 24 hours, in an extrusion step. In the middle, the extrusion ratio is over 20, and the extrusion process is performed so that the temperature of the profile in the extrusion process is 420 ° C or higher, and the aging treatment step is performed at 100 to 180 ° C for 1 to 30 hours.

According to the present invention, there is provided a 7000-series aluminum alloy extruded material having a desired strength and having a surface of an anodized film which is less likely to generate a streak pattern and which is excellent in appearance quality, and a method for producing the same.

Embodiments of the present invention will be described below.

[Aluminum alloy extruded material] The aluminum alloy extruded material having an anodized film according to the present embodiment is characterized in that the aluminum alloy extruded material contains: Zn: 4.0% by mass or more and 7.5% by mass or less, Mg: 1.0% by mass 2.2 mass% or less, Fe: 0.05 mass% or more and 0.20 mass% or less, Cu: 0.30 mass% or less, Ti: 0.005 mass% or more and 0.04 mass% or less, B: 0.001 mass% or more and 0.02 mass% or less, Si: 0.15 mass % or less, Zr: 0.05% by mass or less, Mn: 0.05% by mass or less, Cr: 0.05% by mass or less, V: 0.05% by mass or less, and the total content of Zr, Mn, Cr, V, and Ti [Zr+Mn +Cr+V+Ti] satisfies the relationship of [Zr+Mn+Cr+V+Ti]≦0.10% by mass, except for the content of Zn of 6.0% by mass or less and the content of Mg of 1.2% by mass or less, the remainder It consists of aluminum and unavoidable impurities, and the metal structure is a recrystallized structure.

The aluminum alloy extruded material composed of the above composition has a desired strength, and has an effect that the surface of the anodized film is less likely to have a streak pattern. Hereinafter, each element of the aluminum alloy extruded material of the present embodiment will be described.

(Zn: Zinc) Zn and Mn are precipitated as a Zn-Mg phase, contributing to the high strength of the alloy. When the content of Zn is 4.0% by mass or more, sufficient strength can be obtained, and if the content of Zn is 7.5% by mass or less, good corrosion resistance can be obtained. In the aluminum alloy extruded material of the present embodiment, the content of Zn is 4.0% by mass or more and 7.5% by mass or less, more preferably 4.0% by mass or more and 7.0% by mass or less, and further preferably 4.0% by mass or more and 6.0% by mass or less. Further, further It is preferably 4.0% by mass or more and less than 5.5% by mass, and most preferably 4.0% by mass or more and 5.0% by mass or less.

(Mg: Magnesium) When the content of Mg is 1.0% by mass or more, sufficient strength can be obtained, and if the content of Mg is 2.2% by mass or less, good extrusion processability can be obtained. In the aluminum alloy extruded material of the present embodiment, the content of Mg is 1.0% by mass or more and 2.2% by mass or less, more preferably 1.2% by mass or more and 2.2% by mass or less, and further preferably 1.3% by mass or more and 2.2% by mass or less. Further, further It is preferably 1.4% by mass or more and 2.2% by mass or less, and most preferably 1.5% by mass or more and 2.2% by mass or less. When the Zn content is 6.0% by mass or less, the content of Mg is preferably 1.2% by mass or more, and when the Zn content is less than 5.5% by mass, the content of Mg is preferably 1.6% by mass or more.

(Fe: Iron) The content of Fe in the aluminum alloy extruded material of the present embodiment is 0.05% by mass or more and 0.20% by mass or less.

When the content of Fe is 0.05% by mass or more, large-scale recrystallization of the cast structure can be suppressed during the homogenization treatment. If there is a large crystal structure in the ingot, uneven deformation is likely to occur during the extrusion process, making it difficult to obtain the specified size (accuracy, distortion or bending) of the extruded material. Further, if there is a large crystal structure in the billet, it is easy to mix recrystallized grain structures having different sizes even if it is an equiaxed recrystallized structure after recrystallization after extrusion. If such a structure is arranged in a layered shape, the difference in hue will be a streak. When the content of Fe is 0.20% by mass or less, formation of excess crystals of Fe and other element forming compounds can be suppressed, and generation of a stripe pattern can be suppressed. The content of Fe is more preferably 0.15% by mass or less, and the above effects can be further improved in the range.

(Cu: Copper) The aluminum alloy extruded material of the present embodiment has a Cu content of 0.30% by mass or less. When the content of Cu exceeds 0.30% by mass, the anodized film is easily yellowed, and the corrosion resistance is also likely to deteriorate.

Further, when the content of Cu exceeds 0.15% by mass, mechanical strength and stress corrosion cracking resistance (SCC) are improved.

(Ti: Titanium, B: Boron) The aluminum alloy extruded material of the present embodiment has a Ti content of 0.005 mass% or more and 0.04 mass% or less. Further, in the aluminum alloy extruded material of the present embodiment, the content of B is 0.001% by mass or more and 0.02% by mass or less.

If the crystal of the cast structure in the alloy is large, uneven deformation is likely to occur during extrusion, and concentration segregation and unevenness of the grain size of the recrystallized structure are likely to occur, so Ti and B are added as casting. A refining agent for crystal grains. When only Ti is added, it is solid-solved in the matrix phase, and the effect as a refining agent becomes small. Further, since segregation of concentration toward the inside of the crystal is likely to occur, it is preferable to use a rod hardener as a refining agent and to add it as a TiB ₂ compound. On the other hand, when Ti or B is excessively added, crystals are excessively precipitated in the form of a compound, which causes the formation of a striped pattern. Therefore, it is necessary to define the upper limit of the amount of addition.

(Si: 矽) The aluminum alloy extruded material of the present embodiment has a Si content of 0.15% by mass or less. Si is one of the causes of forming a striped pattern by forming a Mg-Si-based compound with Mg. Therefore, it is preferably 0.15% or less. Further, the content of Si is more preferably 0.1% by mass or less, and if the content of Si is within this range, the above effects can be further enhanced.

(Zr: zirconium, Mn: manganese, Cr: chromium, V: vanadium) Since Zr, Mn, Cr, and V have an effect of suppressing recrystallization during extrusion processing, the respective contents are preferably 0.05% by mass or less. More preferably, it is 0.02 mass% or less. In addition, these elements also have the effect of inhibiting the diffusion of Zn.

In addition, since it is difficult to diffuse the above-mentioned elements by heat treatment (HO or ingot heating during extrusion, heat generation by extrusion), concentration segregation is likely to occur, and if it exceeds a predetermined range, a stripe pattern is formed when the anodized film is processed.

Further, [Zr+Mn+Cr+V+Ti] which is a total content of Zr, Mn, Cr, V, and Ti preferably satisfies the relationship of [Zr+Mn+Cr+V+Ti]≦0.10% by mass. When the amount added is more than the predetermined range, the recrystallization is suppressed to form a non-recrystallized structure, or the crystal grains are caused to grow, and further large crystal excess crystals are formed. The amount is preferably 0.10% by mass or less, more preferably 0.09% by mass or less, further preferably 0.08% by mass or less, further preferably 0.07% by mass or less, and most preferably 0.05% by mass or less.

(Recrystallized Structure) When the anodized film is treated, the fibrous structure causes a streak pattern to be formed on the surface of the anodized film. Therefore, the crystal structure is preferably a recrystallized structure having a uniform crystal grain size. In order to form such a fine recrystallized structure, the alloy composition, the casting HO condition, and the extrusion conditions are controlled. The form of the crystal structure can be confirmed by a method of coating with a fluoroboric acid aqueous solution and observing it under a polarizing microscope.

Among them, since the stripe pattern causes an anodized film surface, the surface may be recrystallized.

(Difference in concentration between the high-concentration portion and the low-concentration portion of Zn) The width of the Zn high-concentration layer and the Zn low-concentration layer which are layered in parallel with the extrusion direction on the anodized surface is more than 0.1 mm and 3 mm or less. When the Zn concentration difference in the range exceeds 1%, when the anodized film is treated, the film form of the high concentration portion and the low concentration portion is different, and the difference is likely to appear as a stripe pattern. Concentration segregation in the range of 0.1 mm width is too narrow to be considered as streaks. In addition, concentration segregation of more than 3 mm is not easily recognized as streaks.

(The average recrystallized structure size is 200 μm or less, and the maximum crystal grain size is 1 mm or less.) When the crystal grain size of the recrystallized structure of the anodized film-treated surface is not uniform, concentration segregation occurs at this point, and it appears as a stripe pattern.

(The area ratio of the crystallized material is less than 2%.) If the area ratio of the intermetallic compound (crystal) to the anodized surface is 2% or more, the crystal grains are stretched in the extrusion process and moved parallel to the extrusion direction. The interspersed intermetallic compound (crystal) appears to be striped.

In the aluminum alloy extruded material of the present embodiment, the anodizing film property is good, and it is preferable to use a material for a frame body as an electronic device.

[Manufacturing Method of Aluminum Alloy Extruded Material] Further, a method of producing an aluminum alloy extruded material is provided according to the present invention. The embodiment described below basically has the same composition as the above embodiment.

The method for producing an aluminum alloy extruded material according to another embodiment of the present invention is a method for producing an aluminum alloy extruded material having an anodized film, the aluminum alloy extruded material comprising: Zn: 4.0% by mass or more and 7.5% by mass Hereinafter, Mg: 1.0% by mass or more and 2.2% by mass or less, Fe: 0.05% by mass or more and 0.20% by mass or less, Cu: 0.30% by mass or less, Ti: 0.005% by mass or more and 0.04% by mass or less, and B: 0.001% by mass or more and 0.02% by mass % or less, Si: 0.15 mass% or less, Zr: 0.05 mass% or less, Mn: 0.05 mass% or less, Cr: 0.05 mass% or less, V: 0.05 mass% or less, and Zr, Mn, Cr, V, and Ti The total content of [Zr+Mn+Cr+V+Ti] satisfies the relationship of [Zr+Mn+Cr+V+Ti]≦0.10% by mass, except that the content of Zn is 6.0% by mass or less and the content of Mg is 1.2% by mass. In the following range, the remainder is composed of aluminum and unavoidable impurities, and the metal structure is a recrystallized structure; the manufacturing method is characterized by: the casting material is homogenized at a temperature of 400 to 560 ° C for 1 to 24 hours. Processing, in the extrusion step, the extrusion processing is performed at an extrusion ratio of more than 20 The temperature profile of the processing system to become more than 420 ℃ manner of extrusion, and the aging process in step 100 ~ 180 ℃ 1 ~ 30 hours.

(Casting) In the casting step, an aluminum alloy melt having the above alloy composition is prepared, and a known melt treatment such as slag removal treatment, deaeration treatment, and filtration is performed. Next, a cylindrical ingot (small embryo) is obtained by a DC casting method or the like.

In the casting, it is preferable to add a refiner (rod hardener) composed of an Al-Ti-B alloy to the melt before adding the melt to the mold. The refining agent to be added to the melt is preferably such that Ti and V in the alloy composition do not exceed the above range. In order to homogenize the cast structure as much as possible, the melt is homogeneously injected into the mold and the casting temperature in the mold is uniformly uniform. For example, hot top (HOT TOP) casting or the like is preferably used.

The small embryo diameter is small, preferably less than 14 inches in diameter. If the small embryo diameter is large, the cooling of the central portion of the small embryo is slow, and the tissue at the center of the small embryo is easily enlarged. When the cast structure is large, it is difficult to eliminate concentration segregation during the homogenization treatment, and it is easy to make the crystal structure of the extrusion process insufficient.

(Homogenization Treatment) The small embryos obtained by the above casting step were subjected to homogenization treatment (HO treatment). By homogenization treatment, the concentration of the element is segregated and the crystals are reduced.

The homogenization treatment temperature should be carried out at 400 to 560 ° C for 1 hour or more and 24 hours or less. When the conditions of the homogenization treatment are within this range, the homogenization can be sufficiently performed. When the temperature of the homogenization treatment exceeds 560 ° C, the crystal of the ingot is grown, the extrusion processability is lowered, or the crystal grains of the extruded material are enlarged, and the recrystallized structure is locally enlarged, and the recrystallized structure is recrystallized. The difference in particle diameter is increased to cause a pattern to be formed when the film is anodized.

The homogenization treatment temperature is preferably 540 ° C or less. Even if the homogenization treatment is carried out for more than 24 hours, a better effect cannot be expected, and only the manufacturing cost is increased.

In order to promote the elimination of concentration segregation and the solid solution of the crystal, the homogenization treatment is preferably carried out at 470 ° C or higher, and more preferably at 500 ° C for homogenization treatment. If the cooling rate after the homogenization treatment is slow, the elements which have been solid-dissolved are likely to be precipitated. Therefore, it is preferred to carry out the cooling at an average cooling rate of from 100 ° C to 150 ° C.

(Extrusion Processing) The extrusion step is performed by subjecting the homogenized small embryo to extrusion processing to produce a designated processed material. The extrusion ratio of the extrusion processing is preferably 20 or more. The extrusion ratio of the extrusion process is preferably 40 or more. This is to make the concentration change (if the interval between the high concentration portions or the low concentration portions is easy to be improved, the concentration segregation is easily improved) by stretching the crystal, and it is difficult to produce streaks after the anodization of the film. pattern.

In addition, by setting the average particle diameter of the recrystallized structure which is changed by the extrusion processing conditions to 200 μm or less and the maximum crystal grain size to 1 mm or less, the formation of the striped pattern due to the difference in crystal structure can be suppressed. Since the crystal size of the extruded material becomes finer as it is extruded under conditions of a lower temperature of the small embryo, it is desirable that the small embryo temperature is also set in consideration of the extrusion pressure and the profile temperature, and is preferably 480 ° C or lower.

It is preferable to determine the extrusion conditions (small embryo temperature, die temperature, container temperature, extrusion pressure, extrusion speed, etc.) so that the temperature at the outlet of the die is 400 ° C or higher. If the temperature of the extruded material at the exit of the die is low, there is a possibility that high strength cannot be obtained. The extruded material from the die is cooled so that the cooling rate in the temperature range of -200 ° C after extrusion is 0.3 to 20 ° C / s. As long as the cooling rate satisfies this condition, high strength can be obtained and good stress corrosion cracking resistance can be obtained.

(Aging treatment) The processed material is subjected to aging treatment. In the aging treatment step, the treatment is carried out for 1 to 30 hours while maintaining the temperature at 100 to 180 °C. In addition, for aging treatment, in order to obtain higher strength and resistance to stress corrosion cracking, a two-stage aging treatment can be performed.

(Anodic Oxide Film Treatment) The extruded material obtained by sequentially performing the casting step, the homogenization treatment step, the extrusion step, and the aging treatment step is subjected to a predetermined shape, and then subjected to an anodized film treatment. The anodizing film treatment is carried out under known conditions.

According to another embodiment of the present invention, there is provided a method for producing an aluminum alloy extruded material having an anodized film, wherein in the method for producing an aluminum alloy extruded material, the homogenization treatment step is maintained at a temperature of 400 ° C to 560 Under the condition of °C, and the extrusion step is based on the extrusion ratio of 20 or more, the extrusion temperature of the extrusion material is 420 ° C or more, and the cooling rate between extrusion and 200 ° C is 0.3 to 20 ° C / s. And the aging treatment step is carried out under the conditions of maintaining the temperature of 100 ° C to 180 ° C. [Examples]

Hereinafter, the invention will be described using the examples, but the invention is not limited to the examples.

(Production of Aluminum Alloy Test Material) Small embryos of the components of Experimental Examples A to N of the following [Table 1] were obtained. The small embryo has a diameter of 325 mm. These small embryos were subjected to HO treatment under the conditions of [Table 2], and then subjected to extrusion processing under the conditions of [Table 2]. The extrusion process is carried out at a small embryo temperature of 400 ° C, and is extruded in two types: (a) a flat bar having a width of 100 mm and a thickness of 10 mm, and (b) a flat strip having a width of 120 mm and a thickness of 25 mm. The shape is carried out.

Next, heat treatment was performed in accordance with the conditions described in Table 2. After heat treatment, A~J and L~N are tempered under the conditions of T6 (manual aging after extrusion processing) and K under conditions of T6 (melting treatment, artificial aging).

【Table 1】

In [Table 1], the crystal grain size after casting and after HO was measured by the intersection method, and the crystal grain having a size of more than 1 mm was evaluated as ×. The intersection method is a method for calculating a mean crystal grain size by drawing a straight line in an arbitrary direction with a photo taken by an optical microscope, and dividing the number of crystal grain boundaries which are interlaced with the straight line by n, and dividing the length of the straight line by (n-1). .

Various measurement results and observation results of Experimental Examples A to N are described in [Table 2] and [Table 3].

【Table 2】

【table 3】

(Extension test) The extruded material was processed into a test piece of JIS 14B, and a stretching test was carried out. 0.2% endurance ≧ 380 MPa in the extension test was rated as qualified.

(Observation of Hue and Stripe Pattern) The surface of the aluminum alloy test material was planarly cut (polished) to correspond to an amount of 20% of the wall thickness, and an anodized film treatment was performed on the plane cut surface. The treatment conditions for the anodizing film treatment were such that the film thickness was about 5 μm at 15 ° C in a 15% sulfuric acid aqueous solution at 1.5 A/dm ² .

In the hue, the retention ratio of the gloss before and after the treatment is 40% or more, and the case where the L value is 78 or more and the b value is 1 or less is determined as a reference. The definition of the above value is ○, and the unsatisfied is ×. In addition, it is evaluated whether or not there is a streak pattern generation. In the "○" system, a stripe pattern was hardly generated, and "△" was observed in a limited area. "X" is a pattern that produces a thick stripe. The hue is based on the value of JIS Z8730.

(Observation of the structure of the extruded material) The surface of the aluminum alloy test material was planarly cut to an amount corresponding to 20% of the wall thickness, and after being polished into a mirror surface, the film was treated in an aqueous solution of fluoroboric acid, and the tissue was observed by a polarizing microscope. Make a decision. Observe the surface of the L-LT surface (a wide surface parallel to the plane of the extrusion direction).

A~G and L~N are observed as recrystallized structures, and the aspect ratio (average crystal diameter in the longitudinal direction of extrusion/average crystal diameter in the direction of extrusion) is an equiaxed crystal of 2 or less. H~K is a fibrous crystal structure. However, the recrystallized structure of A to E and G, M, and N was observed, and the crystal having an average particle diameter of 200 μm or less as measured by the intersection method has a uniform fine crystal. However, F and L have a large size of more than 1 mm. Crystal grain. The ingot structure after the HO of F and L confirmed the crystal growth and had this effect.

(Crystal Area Ratio) The surface of the aluminum alloy test material was cut in a plane corresponding to 20% of the wall thickness, and after grinding to a mirror surface, the area occupied by the crystallized material was measured by an image analysis apparatus and an optical microscope. Observe that the face is L-LT face parallel to the direction of the extrusion direction, the wide face).

(Stress Corrosion Crack Test) The stress corrosion crack test was performed only for A~E, M, and N according to JIS H8711. The stress corrosion cracking system imparts a stress corresponding to 50% of its 0.2% proof force along the extrusion direction and the right angle direction. The etching solution was 3.5% NaCl, which was defined to be immersed at 25 ° C for 10 minutes and then dried for 50 minutes for 1 cycle. After 30 days of testing, the material without cracks was rated as "○". The results of A, M, and N in the SCC test were poor, and it was considered that the content of Cu was small.

(Analysis of elemental concentration) The surface of the aluminum alloy test material was cut in a plane of 3 mm, and after polishing, EPMA-1610 manufactured by Shimadzu Corporation was used, and elemental analysis was carried out under the following conditions. In order to measure the concentration of Zn, a standard product having a different Zn content was used in the measurement, and a calibration curve of Zn was prepared in advance and quantified by a calibration line method. The difference between the highest value and the lowest value of the element concentration value determined by the determination on the line is the concentration segregation value.

(Measurement conditions) Acceleration voltage: 15kV Irradiation current: 200nA Beam diameter: 1μm (minimum) Sweep condition: LINE x3000 (Electron beam scanning condition: 3000 times (100 μm or so perpendicular to the direction of advancement), side by line Measurement by scanning electron beam side) Number of data: 300 steps: 10 μm Length: 3000 μm (3 mm) Measurement time: 2 seconds / point

(a) and (b) of Fig. 1 are obtained by observing the crystal structure of Experimental Example B (Inventive Example) by a polarizing microscope. A homogeneous recrystallized structure was observed.

Fig. 2 is a view showing the microstructure of Experimental Example B (invention example). It was found that no crystal diffusion, continuity of extreme compounds, and the like were observed.

(a) and (b) of FIG. 3 are obtained by observing the crystal structure of the cross section of the sample of Experimental Example L (Comparative Example) by a polarizing microscope. It was found that depending on the observation point, the size of the crystal grains was different, and large crystal grains were formed in some portions. This is because the recrystallized structure is locally enlarged depending on the temperature conditions of the HO treatment.

Fig. 4 is a view showing the crystal structure of Experimental Example H (Comparative Example). It is known that its crystalline tissue fibers are organized. Fig. 5 is a view showing the microstructure of Experimental Example K (Comparative Example). The content of Fe, Cu, Mg, and Cr is large, and the segregation of crystals is extended by extrusion processing, and the continuity of the compound in a stripe shape can be seen.

6 to 8 are (a) concentration analysis in the direction perpendicular to the extrusion direction of the extrusion processing of the anodized film-treated surface, and having a length of about 3 mm. (b) A map of Zn elements in the same region. Fig. 6 is a view showing a Zn concentration analysis and a map of Experimental Example B (Inventive Example). The segregation of the Zn concentration at a width of 3 mm was 1.0% by mass or less. 7 is a concentration distribution of Experimental Example G (Comparative Example), and FIG. 8 is a view showing a Zn concentration distribution and a map of Experimental Example H (Comparative Example). It was found that the Zn concentrations of the experimental examples G and H of the comparative example at a concentration of more than 1.0% by mass were segregated at a concentration of more than 1.0% by mass. Further, it was found from the map that the concentration segregation was layered.

From the above experimental results, it is understood that the A~E, M, and N series have desired strength, and at the same time, the stripe pattern is not easily generated on the surface of the anodized film. Therefore, the aluminum alloy extruded material satisfying these conditions can be suitably used for a casing such as a portable computer or an electronic device such as a mobile phone or a smart phone. Among them, the extrusion ratio of A~D, M, and N is larger than that of E, that is, the processing degree is high, so the uniformity of the surface is high.

In the case of F, since the Fe is small, the crystal of a part of the ingot is enlarged in the HO, and in the extruded material, a part of the crystal grains exceeding 1 mm exists, and a non-uniform crystal structure is formed, so that the extruded material is formed. The anodized film is treated to produce streaks.

In the case of G, Ti and B which are crystal refining agents in casting are insufficient, and the ingot structure after casting is increased in size. This effect causes the concentration segregation of Zn to be sufficiently eliminated even if the homogenization treatment is performed, and concentration segregation in which the Zn concentration difference exceeds 1% in the range of more than 0.1 mm and 3 mm or less is generated, and the anodized film is processed in the extruded material. After the generation of stripes.

The amount of addition of H, I, and Zr exceeds the upper limit value, because the pinning causes the crystal structure of the extruded material to maintain the fiber structure, and Zr hinders the diffusion of Zn, even if homogenization is performed, The concentration segregation of Zn is sufficiently eliminated, and streaks are generated after the anodized film of the extruded material is treated. Further, for I, although the content of Zn is large, since the content of Mg is low, the mechanical strength is low even for the fiber structure.

For J, the addition amount of Zr, the amount of Cr added, and the amount of Mn added exceed the upper limit value, because the pinning effect causes the crystal structure of the extruded material to maintain the fiber structure, and Zr hinders the diffusion of Zn, even if homogenization is performed. In the treatment, the concentration segregation of Zn was not sufficiently eliminated, and concentration segregation in which the Zn concentration difference exceeded 1% in the range of more than 0.1 mm and 3 mm or less was generated, and streaks were generated after the anodized film treatment of the extruded material.

Further, with respect to J, although the Mg content is large, since the Zn content is low, the mechanical strength is low even for the fiber structure. In addition, the content of Mn is large, because the pinning effect causes the crystal structure of the extruded material to maintain the fiber structure, and since Mn hinders the diffusion of Zn, even if the homogenization treatment is performed, the concentration segregation of Zn cannot be sufficiently eliminated, resulting in The concentration of the Zn concentration difference exceeding 1% in the range of more than 0.1 mm and 3 mm or less is segregated, and streaks are generated after the anodized film of the extruded material is treated.

With respect to K, Fe, Cu, Mg, and Cr exceed the range specified in the present invention, a large amount of crystals are generated, and the anodic oxide film of the extruded material is treated to form streaks. Further, since the pinning effect of Cr causes the crystal structure of the extruded material to maintain the fiber structure, and since Cr inhibits the diffusion of Zn, even if the homogenization treatment is performed, the concentration segregation of Zn cannot be sufficiently eliminated, resulting in more than 0.1. In the range of mm or less, the concentration of Zn in the range of more than 1% is segregated, and streaks are generated after the anodized film of the extruded material is treated. Further, Cu exceeds the range specified in the present invention, and the L and b values are outside the predetermined value.

For L, since the HO temperature exceeds the upper limit temperature, the crystal structure of the ingot grows, and the influence thereof causes a crystal grain of more than 1 mm to be generated in a part of the crystal structure of the extruded material, and the crystal grain size of the extruded material is not uniform, so The anodized film was treated to produce streaks.

Fig. 1 (a) (b) A photograph obtained by photographing the crystal structure of Experimental Example B with a polarizing microscope. Fig. 2 is a photograph obtained by photographing the microstructure of Experimental Example B. Fig. 3 (a) (b) A photograph obtained by photographing the crystal structure of Experimental Example L with a polarizing microscope. Fig. 4 is a photograph of a crystal structure of Experimental Example H taken by a polarizing microscope. Fig. 5 is a photograph obtained by photographing the microstructure of Experimental Example K. Fig. 6 (a) shows a graph of concentration analysis of Experimental Example B and (b) a mapping. Fig. 7 is a graph showing the concentration analysis of Experimental Example G. Fig. 8 (a) is a view showing the concentration analysis of Experimental Example H and (b) a map.

no

Claims (7)

An aluminum alloy extruded material having an anodized film and having good appearance quality, comprising: Zn: 4.0% by mass or more and 7.5% by mass or less, Mg: 1.0% by mass or more and 2.2% by mass or less, and Fe: 0.05% by mass or more and 0.20% by mass; Hereinafter, Cu: 0.30% by mass or less, Ti: 0.005% by mass or more and 0.04% by mass or less, B: 0.001% by mass or more and 0.02% by mass or less, Si: 0.15% by mass or less, Zr: 0.05% by mass or less, and Mn: 0.05% by mass Hereinafter, Cr: 0.05% by mass or less, V: 0.05% by mass or less, and [Zr+Mn+Cr+V+Ti] which is a total content of Zr, Mn, Cr, V, and Ti satisfies [Zr+Mn+Cr+ V+Ti] ≦ 0.10% by mass, except that the content of Zn is 6.0% by mass or less and the content of Mg is 1.2% by mass or less, the remainder is composed of aluminum and unavoidable impurities, and the metal structure is recrystallized. organization. An aluminum alloy extruded material having an anodized film and having an excellent appearance quality according to the first aspect of the invention, wherein the content of Zn is 4.0% by mass or more and less than 5.5% by mass. An aluminum alloy extruded material having an anodized film and having an excellent appearance quality according to the first or second aspect of the patent application, wherein the content of Mg is 1.0% by mass or more and 1.6% by mass or less. An aluminum alloy extruded material having an anodized film and having a good appearance quality according to the first or second aspect of the patent application, wherein, on the anodized surface, the Zn high concentration phase and the Zn low concentration phase are parallel to the extrusion direction, and It exists in a layer form perpendicularly to the direction of the extrusion direction, and has a Zn concentration difference of 1% or less in a range of 0.1 mm or more and 3 mm or less in width. An aluminum alloy extruded material having an anodized film and having an excellent appearance quality according to the first or second aspect of the patent application, wherein the crystal grain size of the recrystallized structure of the anodized film-treated surface is 200 μm or less on average. The maximum crystal grain size is 1 mm or less. An aluminum alloy extruded material having an anodized film and having an excellent appearance quality as in the first or second aspect of the patent application, wherein the area ratio of the crystals to the anodized surface is less than 2%. A method for producing an aluminum alloy extruded material having an anodized film and having good appearance quality according to any one of claims 1 to 6, characterized in that the condition for maintaining the casting material by homogenization is 400~ 560 ° C, 1 to 24 hours of treatment, extrusion in the extrusion process with an extrusion ratio of more than 20, so that the temperature of the profile in the extrusion process is 420 ° C or more, and the aging process is Treat at 100~180 °C for 1~30 hours.