JP5924585B2 - Aluminum alloy plate for high-strength alumite treatment, manufacturing method thereof, and aluminum alloy plate with high-strength anodized film - Google Patents

Description

  The present invention relates to an aluminum alloy plate having high strength and excellent thermal conductivity capable of applying a uniform alumite film having a white tone and suitable yellowness, which is used for a housing for an electronic device or the like. .

Al-Fe-based 8000-based alloys have high strength and are relatively good in anodizing, and thus have been used as raw materials for manufacturing decorative panels for building materials, casings for electronic devices, and the like. After being formed into a plate material, it is cut into a desired size, and after being molded as necessary, it is used as a building material by subjecting the outer surface to an alumite treatment. Further, it is glossy by buffing after anodizing, and is also used as a housing for electronic equipment.
While securing the strength based on the 5000 series alloy together with the 8000 series alloy, the amount of Si, Fe, Mn and the like are specified, and the aluminum alloy plate having a light alumite color tone or the strength based on the 8000 series alloy. In addition, an aluminum alloy plate and a method for producing the same have been developed in which Mn and Si are further added while ensuring the alumite color tone. Recently, an aluminum alloy plate with improved color uniformity of an alumite film based on a 1000 series alloy and a method for producing the same have also been developed.

  For example, Patent Document 1 includes Fe: 0.1 to 1.0% by weight, Si: 0.01 to 0.5% by weight, Mn: 0.05 to 1.0% by weight, with the balance being Al and inevitable. An aluminum alloy plate, which is made of an aluminum alloy which is a typical impurity and exhibits a uniform color tone by anodizing treatment, and an aluminum alloy ingot having the above composition are subjected to a homogenization treatment at 400 to 600 ° C. After hot rolling is performed on the ingot to obtain a hot rolled sheet, the hot rolled sheet is subjected to cold rolling including intermediate annealing and / or final annealing, and uniform color tone is obtained by anodizing. It is described that an aluminum alloy plate exhibiting the following is obtained.

On the other hand, with an aluminum alloy plate based on an 8000 series alloy, although it depends on the homogenization conditions, the color tone of the alumite film is likely to be non-uniform and it is not easy to obtain a uniform white tone alumite color tone. It has been known. Therefore, an aluminum alloy plate based on 1000 series and improved in uniformity of the roughened surface and the uniformity of the color tone of the anodized film and a manufacturing method thereof have been developed.
Patent Document 2 contains Fe: 0.2 to 0.6% by weight, Si: 0.03 to 0.20% by weight and Ti: 0.005 to 0.05% by weight, with the balance being Al and inevitable. An aluminum alloy plate made of mechanical impurities and a method for producing the same are described. According to this, while appropriately adjusting the contents of the chemical components Fe, Si and Ti of the material, particularly by making the Fe / Si ratio in an appropriate range, the formation of the metastable phase is suppressed, and the intermetallic compound is reduced. It becomes a stable phase mainly, and the uniformity of the pits and the color tone of the anodic oxide coating during the roughening treatment are remarkably improved.

  The alloy plate based on 1000 series has a problem that the uniformity of etch pits and the color tone of the anodized film in the alkali etching treatment with caustic soda are excellent, and further, the moldability is excellent but the strength is low. . Therefore, since it is expected that high strength characteristics are also required while white anodized color tone is required, there is a problem in applying an aluminum material based on 1000 series.

Therefore, an Al—Mg-based anodized 5000-based alloy plate having excellent high strength characteristics has been developed.
In Patent Document 3, Mg: 2.0 to 3.0%, Cr: 0.15 to 0.25%, Ti: 0.005 to 0.20%, or Ti: 0.005 to 0 by mass%. .20% and B: 0.0005 to 0.05%, the balance being Al and inevitable impurities, Si in the impurities is 0.15% or less, Fe is 0.4% or less, and Mn is 0.3. and 06% or less, _T CR% content of said Cr, when the solid solution amount of Cr was _{S CR%,} the aluminum alloy plate is proposed a _{P CR = T CR -S CR ≦} 0.065% Yes.
According to this, the Al-Mg based alloy plate containing Cr is light green in which the yellowness is suppressed as much as possible even when the anodic oxide film is coated with a sulfuric acid bath by setting the Cr-containing intermetallic compound to a predetermined value or less. It is said that an aluminum alloy plate that develops white color can be produced.

Japanese Patent Application Laid-Open No. 08-253831 JP 2000-282159 A JP 2011-179094 A

By the way, an alumite film having a white tone and a uniform color tone has been used favorably for a housing for an electronic device. In recent years, electronic devices have been reduced in thickness and size, and materials that are not only high in strength but also excellent in heat dissipation are desired.
In order to improve heat dissipation in a 5000 series alloy plate with high strength, it is effective to increase the electrical conductivity by reducing the content of Mg that is easily dissolved in the matrix. However, when a 5000 series alloy plate with a reduced Mg content is applied as a material for the housing, it may be used in combination with an A5052 alloy plate (for example, tempered: H ₃₂ ). In such a case, as a matter of course, the uniformity of the color tone as the casing is required, and the color tone according to the color tone of the alumite coating applied to the A5052 alloy plate is applied to the alumite coating applied to the low Mg 5000 series alloy plate. Is required.

However, according to the AA standard, the A5052 alloy is specified to have an Mg content of 2.2 to 2.8% by mass, a Cr content of 0.15 to 0.35% by mass, and a relatively high Mg content. Because it is high, the strength is high, and the lightness (L ^* value) of the anodized film tends to be slightly high, but on the other hand, it is inferior in thermal conductivity, and since it contains Cr, the anodized color tends to be light yellowish is there. Therefore, even if the technique shown in Patent Document 3 is applied as it is to a 5000 alloy plate having a low Mg content, which has a lower Mg content than the A5052 alloy and has good thermal conductivity, it is white and appropriate. It was extremely difficult to obtain an alumite film having a yellowish and uniform color.
The present invention has been devised in order to solve such a problem, and is used for a housing for an electronic device and the like, and it is possible to apply a uniform alumite film having a white tone and appropriate yellowness. An object of the present invention is to provide an aluminum alloy plate having high strength and excellent thermal conductivity.

In order to achieve the object, the high-strength aluminum alloy plate for alumite treatment of the present invention has Mg: 0.80 to 1.8% by mass, Fe: 0.05 to 0.30% by mass, Si: 0.20. Less than 0.1% by mass, Cu: 0.03 to 0.15% by mass, Mn: 0.05 to 0.20% by mass, Cr: 0.05 to 0.15% by mass, Zn: less than 0.15% by mass It is characterized by being composed of the balance Al and inevitable impurities, having a 0.2% proof stress of 180 MPa or more and a conductivity of 40 (IACS%) or more.
The high-strength aluminum alloy plate for anodizing treatment according to the present invention has an integral diffraction intensity ratio (Iα-Al (Fe · Mn) Si / IAl ₃ Fe) of 0.1 to 0.8 when X-ray diffraction analysis is performed. Those within the range are preferred.

Moreover, such an aluminum alloy sheet for high strength anodized treatment is subjected to a homogenization treatment in which the aluminum alloy ingot having the above composition is held at a temperature of 560 to 620 ° C. for 1 to 5 hours, and then hot rolled. And, it is manufactured by performing cold rolling with a final cold rolling rate of 15 to 95% with or without intermediate annealing.
When the aluminum alloy plate for anodizing treatment provided in the present invention is subjected to alkali etching as pretreatment and further subjected to sulfuric acid alumite treatment, CIE standard L ^* value: 85 to 90, a ^* value: −1 An alumite film exhibiting a color tone in the range of 0.0 to -0.3, b ^* value: 0.5 to 1.0 is obtained.

  The aluminum alloy plate having high strength and good thermal conductivity provided by the present invention produces a uniform alumite film with white tone and appropriate yellowness when anodized. An alumite treatment material suitable as a housing for equipment can be provided at low cost.

As described above, an alumite film having a white tone and a uniform color tone has been favorably used in a casing for an electronic device. In addition, when used for a housing of an electronic device or the like, there is a case in which a slightly thin aluminum alloy plate is formed into a predetermined shape by a mold, and strength after forming is also required. Therefore, a material having high strength is often required as a material to be used.
By the way, in order to obtain an alumite film having a white tone and a uniform color tone in an Al—Mg—Fe based aluminum alloy plate, the Al ₆ Fe metastable phase formed in the ingot is converted into an Al ₃ Fe stable phase by homogenization treatment. It is necessary to perform diffusion transformation. In general, the higher the homogenization treatment temperature of the ingot, the more white the white by changing the Al ₆ Fe metastable phase formed in the ingot to the Al ₃ Fe stable phase by a relatively high temperature homogenization treatment. There is a tendency to become a toned anodized film.

When the Al ₆ Fe metastable phase generated in the ingot remains in the alumite treatment material, the particles of the Al ₆ Fe metastable phase are incorporated into the alumite film without being oxidized, so that the film thickness increases, The anodized film is gray. On the other hand, when the Al ₃ Fe stable phase generated in the ingot remains in the anodized material, it is oxidized and incorporated into the anodized film, so that there is little decrease in lightness even when the film thickness increases, and the anodized film is gray It is difficult to present.
Further, as in the present invention, when a predetermined amount of Mn is contained in order to impart an appropriate yellowness to the alumite color tone, an α-Al (Fe · Mn) Si phase is generated in the ingot. Although the details will be described later, the α-Al (Fe · Mn) Si phase particles formed in the ingot remain partially dissolved in the matrix by the homogenization process, but remain in the final plate and taken into the alumite film. It has been found that as the film thickness increases, the anodized film tends to exhibit a gray color.

Of course, the precipitation state of the precipitates changes and the dislocation density also changes depending on the tempering of the final plate including the intermediate annealing conditions in the cold rolling process. For this reason, the state of the etch pit in the alkali etching process changes, and as a result, the color tone after the alumite film treatment and the uniformity of the color tone are also affected. Therefore, it is considered that the rolling rate at the time of final cold rolling after intermediate annealing becomes a problem.
Accordingly, the present inventors have closely investigated the influence of the production conditions such as the homogenization temperature and cold rolling (tempering) on the color tone of the alumite film. Furthermore, it is possible to apply a uniform alumite film with a white tone and appropriate yellowness through tensile tests, measurement of electrical conductivity, and X-ray diffraction intensity analysis of intermetallic compounds present in alumite treatment materials. The present invention has been achieved through intensive studies to obtain an aluminum alloy plate having high strength and excellent thermal conductivity.
The contents will be described below.

First, the effect | action of each element contained in the aluminum alloy plate of this invention, appropriate content, etc. are demonstrated.
Mg: 0.80 to 1.8% by mass
Mg is an essential element for securing the strength of the aluminum alloy plate. If the Mg content is less than 0.80% by mass, the strength of the aluminum alloy plate is lowered, which is not preferable. When the Mg content exceeds 1.8% by mass, not only the electrical conductivity (thermal conductivity) of the final plate is lowered, but also depending on the homogenization temperature, the Mg segregation layer (β -Mg phase) may cause burning (local melting).
Therefore, the Mg content is defined as 0.80 to 1.8% by mass. A more preferable Mg content is in the range of 0.85 to 1.7% by mass. A more preferable Mg content is in the range of 0.90 to 1.6% by mass.

Fe: 0.05-0.30 mass%
Fe is an essential element for securing the strength of the aluminum alloy plate. If the Fe content is less than 0.05% by mass, the strength of the aluminum alloy plate is lowered, which is not preferable. When the Fe content exceeds 0.30% by mass, not only the formability is lowered, but also depending on the homogenization temperature, the amount of α-Al (Fe · Mn) Si phase remaining in the final plate is small. The amount of α-Al (Fe · Mn) Si phase particles is increased, which is not preferable because it is incorporated into the alumite film, tends to be gray, and the lightness (L ^* value) decreases.
Therefore, the Fe content is specified as 0.05 to 0.30 mass%. A more preferable Fe content is in the range of 0.07 to 0.28% by mass. A more preferable Fe content is in the range of 0.10 to 0.25% by mass.

Si: 0.20 mass% or less Si is mixed from the raw metal and the return material. Si forms an intermetallic compound with Mg, but in the range exceeding 0.20%, the solidus temperature is lowered, and a homogenization treatment at a holding temperature of 560 ° C. or more becomes impossible. In the present invention, since a homogenization treatment at a holding temperature of 560 ° C. or higher is required, the Si content is defined as a range of 0.20% by mass or less. A more preferable Si content is in the range of 0.18% by mass or less. A more preferable Si content is in the range of 0.15% by mass or less.

Cu: 0.03 to 0.15% by mass
Cu is mixed from raw metal and return material. Cu is an essential element for imparting an appropriate yellowness (b ^* value of CIE standard) to the alumite color tone. When the Cu content is less than 0.03 mass%, the yellowness (b ^* value) of the alumite color tone becomes too weak and the gloss necessary for the casing cannot be obtained. Further, when the Cu content exceeds 0.15 mass%, depending on the precipitation amount, such as CuAl ₂ and CuMgAl ₂ in the final plate, the anodized color yellowish ^{(b *} value) becomes too strong.
Therefore, the Cu content is defined as 0.03 to 0.15% by mass. A more preferable Cu content is in the range of 0.03 to 0.12% by mass. A more preferable Cu content is in the range of 0.03 to 0.10% by mass.

Mn: 0.05 to 0.20% by mass
Mn is mixed from raw metal and return material. Mn is an essential element for imparting an appropriate yellowness (b ^* value) to the alumite color tone. When the Mn content is less than 0.05% by mass, an appropriate yellowness (b ^* value) cannot be obtained. When the Mn content exceeds 0.20% by mass, not only the yellowness (b ^* value) becomes too strong, but also depends on the homogenization temperature, α-Al (Fe · Mn) remaining in the final plate The amount of the Si phase increases, and the α-Al (Fe · Mn) Si phase particles are incorporated into the alumite film, tending to appear gray, and lightness (CIE standard L ^* value) decreases, which is not preferable.
Therefore, the Mn content is defined as a range of 0.05 to 0.20% by mass. A more preferable Mn content is in the range of 0.05 to 0.18% by mass. A more preferable Mn content is in the range of 0.05 to 0.15% by mass.

Cr: 0.05-0.15 mass%
Cr is mixed from raw metal and return material. Cr is an essential element for imparting an appropriate yellowness (b ^* value) to the alumite color tone. When the Cr content is less than 0.05% by mass, an appropriate yellowness (b ^* value) cannot be obtained. When the Cr content exceeds 0.15% by mass, the yellowness (b ^* value) of the alumite color tone becomes too strong, which is not preferable.
Therefore, the Cr content is defined as 0.05 to 0.15% by mass. A more preferable Cr content is in the range of 0.05 to 0.12% by mass. A more preferable Cr content is in the range of 0.05 to 0.10% by mass.

Zn: Less than 0.15% by mass Zn is inevitably mixed from the return material. Zn is a component that enhances the yellowness (b ^* value) of the alumite color tone. In the present invention, the Zn content is restricted to less than 0.15% by mass. When the Zn content is 0.15% by mass or more, the amount of Zn dissolved in the treatment liquid increases in the alkali etching with caustic soda, which is an alumite pretreatment, and an alkaline bath containing zinc oxide is formed. If the pretreatment is continued in the alkaline bath, Zn is deposited on the surface of the aluminum alloy plate, and the appearance after the alumite treatment may be uneven, which may hinder the design.
Therefore, the Zn content is restricted to less than 0.15% by mass. A more preferable Zn content is less than 0.12% by mass. A more preferable Zn content is less than 0.10% by mass.

Ti: 0.001 to 0.10% by mass
Ti is mixed from raw metal and return material. Ti acts as a crystal grain refining agent during ingot casting, and can also prevent casting cracks. Of course, Ti may be added alone, but by coexisting with B, a more powerful grain refinement effect can be expected, so addition with a rod hardener such as Al-5% Ti-1% B There may be. If the Ti content is less than 0.001% by mass, the effect of refining at the time of ingot casting is insufficient, which may cause casting cracks, which is not preferable. If the Ti content exceeds 0.10% by mass, a coarse intermetallic compound such as TiAl ₃ may be crystallized during ingot casting, which may cause streak-like defects, which is not preferable.
Therefore, the preferable Ti content is in the range of 0.001 to 0.10% by mass. A more preferable Ti content is in the range of 0.005 to 0.07% by mass. A more preferable Ti content is in the range of 0.01 to 0.05% by mass.

Other inevitable impurities are inevitably mixed from raw materials, return materials, etc., and their allowable contents are, for example, less than 0.10 mass% of Ni and 0.10 mass of Zr. %, Ga, B and V less than 0.05% by mass, Pb, Bi, Sn, Na, Ca, Sr, respectively, less than 0.02% by mass, each other less than 0.05% by mass, Even if an element outside the control is contained within this range, the effect of the present invention is not disturbed.
In particular, B, like Ti, can act as a crystal grain refining agent during ingot casting, and can prevent casting cracks. For this reason, it can also be contained as needed. If the B content exceeds 0.05% by mass, TiB ₂ becomes a stabilized intermetallic compound, and the crystal grain refining effect may be attenuated and the uniformity of the alumite color tone may be reduced. Absent.

Moreover, the required characteristic of the aluminum alloy plate of this invention is demonstrated.
0.2% proof stress: 180 MPa or more An alloy plate obtained by subjecting the aluminum alloy material of the present invention to a white-colored alumite treatment is used as a casing for an electronic device, and therefore requires high strength. In particular, recently, electronic devices have been made thinner and smaller, and therefore, there is a demand for an alumite treatment material that is not easily deformed and has a high-class feeling when using even thinner materials than before.
Therefore, the alloy sheet according to the present invention is limited to a 0.2% proof stress in a tensile test of 180 MPa or more.

Electrical conductivity: 40 (IACS%) or more As described above, in recent years, electronic devices have been made thinner and smaller, and materials with excellent heat dissipation are also desired. For this reason, the alloy plate which concerns on this invention was limited to the thing whose electrical conductivity is 40 (IACS%) or more. An alloy plate having an electrical conductivity of 40 (IACS%) or higher is suitable for applications such as a housing of an electronic device as a material having high thermal conductivity and excellent heat dissipation.

Anodized color tone: L ^* value: 85 to 90, a ^* value: -1.0 to -0.3, b ^* value: 0.5 to 1.0
Although details will be described later, the final plate is subjected to alkali etching and sulfuric acid alumite treatment, the color tone is measured when the thickness of the alumite film is 7 μm, and the CIE standard L ^* value is within the range of 85 to 90. If the a ^* value is in the range of -1.0 to -0.3 and the b ^* value is also in the range of 0.5 to 1.0, the alumite film having a white tone and appropriate yellowness It can be said that it is a material for anodizing that can be applied. That is, even if the alumite color tone of the A5052 alloy plate is somewhat varied due to factors such as composition variation and tempering within the standard range, or alumite film thickness, the alumite treatment material according to the present invention is an A5052 alloy plate. A color tone similar to the alumite color tone can be realized.

Integral diffraction intensity ratio (Iα-Al (Fe · Mn) Si / IAl ₃ Fe): 0.1 to 0.8
As described above, it is known that the lightness (L ^* value) of the alumite color tone is related to the type of Fe-based intermetallic compound present in the alumite treatment material. When the Al ₆ Fe metastable phase formed in the ingot remains in the alumite treatment material, the particles of the Al ₆ Fe metastable phase are incorporated into the alumite film without being oxidized. The anodized film is gray. On the other hand, in the case of the Al ₃ Fe stable phase, it is oxidized and incorporated into the alumite film, so that the lightness is hardly lowered even when the film thickness is increased, and the alumite film is hardly gray.
Further, as in the present invention, when a predetermined amount of Mn is contained in order to impart an appropriate yellowness to the alumite color tone, an α-Al (Fe · Mn) Si phase is generated in the ingot. The α-Al (Fe · Mn) Si phase particles generated in the ingot are partially dissolved in the matrix by the homogenization process, but remain in the final plate, and are taken into the alumite film, increasing the film thickness. At the same time, it has been found that the anodized film tends to be gray.

Of course, the amount of the Al ₃ Fe stable phase and α-Al (Fe · Mn) Si phase in the final plate varies depending on the production conditions such as Fe, Mn, Si content, homogenization temperature of the aluminum alloy composition. is there. As described above, the Fe and Mn contents affect the color tone of the alumite film.
Therefore, the integral diffraction intensity ratio (Iα-Al (Fe · Mn) Si / IAl ₃ Fe) when the anodized material was subjected to X-ray diffraction analysis was defined as a factor affecting the color tone of the anodized film. Within the range of the alloy composition of the present invention, when the alumite treatment material is subjected to X-ray diffraction analysis, the integral diffraction intensity ratio (Iα-Al (Fe · Mn) Si / IAl ₃ Fe) is 0.1 to 0.8. If it is within the range, the anodized color tone falls within the specified range.

Next, the manufacturing method of the high intensity | strength aluminum alloy plate of this invention is demonstrated below.
When the raw material is charged into the melting / melting melting furnace and the predetermined melting temperature is reached, the flux is appropriately charged and stirred, and further, if necessary, degassing in the furnace using a lance or the like, Hold the sedation to separate the soot from the surface of the melt.
In this melting / melting process, it is important to add raw materials such as a master alloy again because it is a predetermined alloy component, but a sufficient sedation time is allowed until the flux and soot float and separate from the molten aluminum alloy to the molten metal surface. It is extremely important to take The sedation time is usually preferably 30 minutes or longer.

In some cases, the molten aluminum alloy melted in the melting furnace may be cast after it is once transferred to the holding furnace, but may be cast directly from the melting furnace. A more desirable sedation time is 45 minutes or more. If necessary, in-line degassing or filtering may be performed.
In-line degassing is mainly of a type in which an inert gas or the like is blown into a molten aluminum from a rotating rotor, and hydrogen gas in the molten metal is diffused and removed in bubbles of the inert gas. When nitrogen gas is used as the inert gas, it is important to control the dew point to, for example, −60 ° C. or lower. The amount of hydrogen gas in the ingot is preferably reduced to 0.20 cc / 100 g or less.

Homogenization temperature: 560-620 ° C
In the ingot as cast, an α-Al (Fe · Mn) Si phase exists. Depending on the homogenization temperature, a part of the α-Al (Fe · Mn) Si phase can be dissolved in the matrix by the homogenization. Further, although depending on the Mn content, Al ₆ Fe and Al _m Fe metastable phases may be formed in the as-cast ingot. Even in such a case, by setting the homogenization treatment temperature high, these Al ₆ Fe and Al _m Fe metastable phases can be diffused and transformed into Al ₃ Fe stable phases.
If the homogenization temperature is less than 560 ° C., the solid solution of the α-Al (Fe · Mn) Si phase and the holding time required for the diffusion transformation become longer, which is not preferable. When the homogenization temperature exceeds 620 ° C., depending on the amount of Mg, as described above, burning (local melting) may occur in the micro Mg segregation layer (β-Mg phase) generated during solidification of the ingot. There is.
Therefore, the homogenization temperature is in the range of 560 to 620 ° C.

Holding time at homogenization temperature: 1 to 5 hours When the holding time at the homogenization temperature is less than 1 hour, depending on the temperature rise rate in the processing furnace, the actual temperature of the entire ingot is predetermined. The homogenization temperature may not be reached. When the holding time at the homogenization treatment temperature exceeds 5 hours, although it depends on the homogenization treatment temperature, no further effect can be expected, and generation of scale due to oxidation becomes severe and the productivity is lowered, which is not preferable. Therefore, the holding time at the homogenization temperature is 1 to 5 hours.
The ingot that has been homogenized by hot rolling is then suspended by a crane and brought from the homogenizing furnace to the hot rolling mill. Depending on the type of hot rolling mill, it is usually several times. It is hot-rolled by such a rolling pass and wound on a roll as a hot-rolled sheet having a predetermined thickness, for example, about 3 to 8 mm.

The roll on which the cold-rolled hot-rolled sheet is wound is passed through a cold-rolling machine and usually subjected to several passes of cold-rolling. At this time, since work hardening occurs due to plastic strain introduced by cold rolling, an intermediate annealing treatment is performed as necessary. Usually, since the intermediate annealing is also a softening treatment, although depending on the material, a cold rolling roll is inserted into the batch furnace and kept at a temperature of 300 to 400 ° C. for 1 hour or longer. When the holding temperature is lower than 300 ° C., softening is not promoted, and when the holding temperature exceeds 400 ° C., the productivity is lowered and the processing cost is increased. Moreover, when this intermediate annealing is performed in a continuous annealing furnace (CAL), the holding is performed at a temperature of 420 to 480 ° C. within 15 seconds. When the holding temperature is lower than 420 ° C., softening is not promoted, and when the holding temperature exceeds 480 ° C., the productivity is lowered and the processing cost is increased.

Final cold rolling rate: 15-95%
As described above, the precipitation state of the precipitates changes and the dislocation density also changes depending on the tempering of the final plate including intermediate annealing conditions during cold rolling. For this reason, the state of the etch pit in the alkali etching process changes, and the color tone after the alumite film treatment and the uniformity of the color tone are also affected.
When the final cold rolling rate is less than 15%, the dislocation density of the final plate is low, so the etch pit density is also low, the lightness (L ^* value) of the anodized material is reduced, and the effect of eliminating the streak is reduced. To do. If the final cold rolling rate is 15% or more, the dislocation density of the final plate increases and the etch pit density also increases, increasing the lightness (L ^* value) of the anodized material and eliminating the streak. is there. If the final cold rolling rate exceeds 95%, the ear cracks of the coil occur and the yield may be lowered, which is not preferable. Therefore, the final cold rolling rate is preferably 15 to 95%. A more preferable final cold rolling rate is in the range of 20 to 95%. A more preferable final cold rolling rate is in the range of 30 to 95%.

Final annealing In the present invention, the final annealing performed after the final cold rolling may be, for example, a batch process of holding at a temperature of 150 to 200 ° C. for 1 hour or more by an annealing furnace, but by a continuous annealing furnace, for example, 200 ° C. to It may be a continuous annealing process held at a temperature of 250 ° C. within 15 seconds. In any case, the final annealing is not necessarily essential in the present invention, but it is desirable to soften the final plate somewhat in consideration of the case where the mold is formed before the alumite treatment. In consideration of moldability in mold forming, it is desirable to perform annealing at a relatively low temperature. In addition, this relatively low-temperature annealing treatment has a meaning as a softening treatment, but also has a meaning as a stabilization treatment. In a rolled material that is not subjected to annealing treatment, a decrease in proof stress is observed with the passage of time over a long period of time. Therefore, there is an aim to stabilize the proof stress for a long period of time by pre-aging.

Preparation of the final plate Predetermined various ingots and scrap materials were weighed and blended and put into a melting furnace and holding furnace. When melted at 800 ° C., 2 kg of degassing flux was charged, and then the molten aluminum in the furnace was sufficiently stirred with a stirring rod. Next, the Mg ingot was added, and after further sedation for 30 minutes, a disk sample was collected with a spoon as a component analysis mold. Next, the soot that floated on the surface of the molten metal was removed with a stirring rod, and various ingots were added to the missing components based on the results of the intermediate analysis of the disk sample collected earlier, and the molten metal was further stirred. Thereafter, sedation was further performed for 30 minutes, and a disk sample was again collected with a spoon in a component analysis mold.

  After confirming the component analysis values, the molten metal was poured from the tap into the bowl, and when the molten metal surface reached a predetermined position of the bowl, pouring from the dip tube into the mold was started. In all the molds, when the molten metal surface reached a predetermined position of the mold, the lower mold started to be lowered. The lower mold lowering speed was 50 mm / min in a steady state. In this way, an ingot having a width of 1350 mm, a thickness of 560 mm, and a length of 3500 mm was cast. Each disk sample was subjected to composition analysis by emission spectroscopic analysis. The final result of the molten metal component analysis is shown in Table 1.

  The ingot was chamfered on both sides of the ingot with a mill after cutting the front and rear ends. The ingot is inserted into a homogenization furnace, heated to a predetermined temperature (530 ° C., 580 ° C.) at a temperature increase rate of 30 ° C./hr, and held at the predetermined temperature for 1 hour to perform the homogenization process. gave. Then, the ingot is hung with a crane, moved from the homogenization furnace to the table of the hot rolling mill, hot-rolled to a predetermined thickness with the hot rolling mill, and rolled as a hot rolled plate Rolled up.

  Thereafter, the hot-rolled sheet was cold-rolled to perform intermediate annealing with a predetermined thickness, or to obtain a cold-rolled sheet having a final thickness of 0.8 mm without performing intermediate annealing. Further, when performing the final annealing, the cold-rolled sheet is passed through a continuous annealing furnace (CAL) and subjected to a continuous annealing process that is maintained at a predetermined temperature for 15 seconds or less, and then water-cooled or 1 at a predetermined temperature. The coil was air-cooled after performing a batch annealing treatment with time retention. Table 2 shows the production conditions of the test materials.

Next, the obtained final plate (each sample material) was evaluated for tensile properties.
Evaluation of tensile properties The strength of the final plate obtained was evaluated by 0.2% yield strength (MPa) in a tensile test. Specifically, a JIS No. 5 test piece is collected so that the tensile direction is parallel to the rolling direction, and a tensile test is performed according to JISZ2241, to obtain tensile strength, 0.2% proof stress, and elongation (breaking elongation). It was. In the present specification, a test material having a 0.2% proof stress of 180 MPa or more was evaluated as good strength (O), and a test material having a 0.2% proof stress of less than 180 MPa was determined as insufficient in strength (x). The evaluation results are shown in Table 3.

About the obtained last board, the alkali etching process shown below was performed. In the alkali etching treatment, first, the test material was immersed in a 30% by mass nitric acid solution at room temperature for 5 minutes and then sufficiently washed with water, and then immersed in a 5% by mass sodium hydroxide solution at 50 ° C. for 3 minutes and then washed with water. Further, after being immersed in a 30% by mass nitric acid solution at room temperature for 3 minutes, it was washed with water.
Next, in the alumite treatment, the sample material is alumite treated in a solution having a sulfuric acid concentration of 170 g / L and dissolved Al: 10 g / L at a liquid temperature of 18 ° C. and a current density of 1.0 A / dm ² , and the film thickness is 7 μm. After being alumite treated, it was washed with water, sealed at 95 ° C. for 15 minutes, washed with water, and dried at room temperature.

Evaluation of color tone The color tone of the alumite film (7 μm thickness) applied as described above was measured and evaluated. The alumite film color tone was measured according to JIS Z8722 using a D65 light source using a color difference meter (CR-300 MINOLTA). The colorimetric values are expressed in the CIE standard L ^* a ^* b ^* color system. The L ^* value represents lightness, and the larger the value, the brighter the color becomes and the closer it is to white. a ^* values and b ^* values represent shades, a ^* value + side is red, the - side is green, b ^* value + side is yellow - side represents a blue tint becomes stronger the larger the respective absolute values.
As used herein, L ^* value and hue evaluated good (○) the test materials had been in the range of 85 to 90, L ^* value hue rated poor the test material was outside the range of 85-90 (X). a ^* value of the sample material had been within the range of -1.0 to -0.3 and color evaluated good (○), ^{a *} value is outside the range of -1.0 to-0.3 The test material was determined to have poor color tone evaluation (x). The test material whose b ^* value was in the range of 0.5 to 1.0 was evaluated as good color tone evaluation (◯), and the test material whose b ^* value was out of the range of 0.5 to 1.0 was used. The color tone evaluation was poor (x). The evaluation results are also shown in Table 3.

Evaluation of conductivity The conductivity (IACS%) was measured with a conductivity meter (AUTOSIGMA 2000, manufactured by Nippon Hocking Co., Ltd.). A test material having an electrical conductivity of 40 (IACS%) or higher was evaluated as good conductivity (O), and a test material having an electrical conductivity of less than 40 (IACS%) was determined as poor conductivity (x). The evaluation results are also shown in Table 3.

Comprehensive evaluation Comprehensive evaluation is that the L ^* value, a ^* value, and b ^* value of the measurement result of the anodized color tone when the thickness of the anodized film is 7 μm are all within the above-mentioned reference range, and the 0.2% proof stress is Only the specimens satisfying all of 180 MPa or more and the electrical conductivity of 40 (IACS%) or more were evaluated as being excellent in overall evaluation (O), and if not satisfying even one of the above items, they were determined as being incomplete evaluation (X).

In the test materials of Examples 1 to 3, the alloy composition is within the specified range, and the L ^* value, a ^* value, and b ^* value of the anodized color tone are all within the above-described reference range, and the proof stress is 180 MPa or more. The electrical conductivity was 40 (IACS%) or more, and the overall evaluation was good (◯).
Since the sample material of Comparative Example 1 (A5052 alloy composition) had a high Mg content of 2.7% by mass, the homogenization temperature was set as low as 530 ° C. The sample material of Comparative Example 1 had a low Mn content of 0.02% by mass but a high Cr content of 0.18% by mass. Therefore, the L ^* value, a ^* value, and b ^* value of anodized color tone. Both were within the specified range. However, since the Mg content was as high as 2.7% by mass, the conductivity was too low at 35 (IACS%) and was outside the specified range.

Since the test material of Comparative Example 2 had a homogenization temperature as low as 530 ° C., the L ^* value of the alumite color tone was too low and out of the specified range. Further, since the Cu content was as low as 0.02% by mass, the b ^* value of the alumite color tone was too low and out of the specified range.
Since the test material of Comparative Example 3 had a high homogenization temperature of 580 ° C., the L ^* value of the alumite color tone was within the specified range. However, since the Cu content was as low as 0.02 mass%, the b ^* value of the alumite color tone was too low and out of the specified range.
The sample material of Comparative Example 4 had a Cu content as high as 0.17% by mass, so the L ^* value of the alumite color tone was low, and the b ^* value was too high, which was outside the specified range.

The sample material of Comparative Example 5 had a high Fe content of 0.34% by mass, but the Mn content, Cr content, and Mg content were both low and less than 0.01% by mass ^. The value, a ^* value, and b ^* value were within the specified ranges. However, since the Mg content was less than 0.01% by mass, the proof stress was too low, 110 MPa, and was outside the specified range.
The test material of Comparative Example 6 had a high Fe content of 0.49% by mass, a very high Mn content of 1.09% by mass, and a low homogenization temperature of 530 ° C. ^* Value was low, a ^* value, b ^* value was too high and out of specified range.
Since the Mn content and the Cr content of the test material of Comparative Example 7 were as low as 0.01% by mass, the b ^* value of the alumite color tone was too low and out of the specification range.

Here, semi-quantitative intensity analysis was performed using an XRD apparatus.
The XRD apparatus was measured using a Rigaku X-ray diffractometer RAD-rR. The measurement conditions were a tube Cu-Kα, a tube voltage of 50 kV, a tube current of 200 mA, a scanning speed of 1 ° / min, and a scanning range (2θ) of 10 ° to 70 °. Of the peaks representing each detected phase, the intensity is high, and there is no overlap with peaks derived from other components, that is, α- Al (Fe · Mn) Si is around 2θ = 41.7 °. Integral diffraction intensities were obtained for peaks of Al ₃ Fe near 2θ = 24.1 ° and Al _m Fe about 2θ = 25.7 °. These integrated diffraction intensities were calculated as an average of three times (n = 3) for each sample. Table 4 shows the analyzed specimen No., homogenization temperature, L ^* value when alumite is 7 μm, and XRD diffraction intensity measurement results.

Since the test materials of Examples 1 to 3 have an alloy composition within the specified range, the L ^* value of the alumite color tone is 85 or more, and the integrated diffraction intensity ratio (Iα-Al (Fe · Mn) Si / IAl ₃ Fe) is in the range of 0.1 to 0.8.

From the evaluation results for all six types of test materials, it was confirmed that at least the final plate had no Al ₆ Fe metastable phase remaining. Moreover, since the test materials of Comparative Examples 2 and 3 have the same alloy composition (E alloy) and differ only in the homogenization treatment temperature, by setting the homogenization treatment temperature to a high temperature, The generated α-Al (Fe · Mn) Si phase tends to be dissolved in the matrix, and the Al _m Fe metastable phase considered to have been formed in the ingot is obtained by homogenization. It was confirmed that there was a tendency to diffuse and transform into the ₃ Fe stable phase.

As described above, in the case of the Al ₃ Fe stable phase, even when the film thickness of the anodized film is increased, the lightness (L ^* value) is hardly decreased, and the anodized film is hardly gray. From the results of X-ray diffraction analysis, in the case of α-Al (Fe · Mn) Si phase, when incorporated in the alumite film, the film thickness was increased and the alumite film was likely to be gray. When the homogenization treatment temperature is set relatively high, the α-Al (Fe · Mn) Si phase crystallized during casting tends to partially dissolve in the matrix by the homogenization treatment. However, when the Mn content increases, the amount of α-Al (Fe · Mn) Si phase remaining on the final plate also increases, and therefore the anodized film tends to be gray and the L ^* value decreases. It was. Incidentally, although the test material of Comparative Example 1 had a homogenization temperature as low as 530 ° C., the Mn content was mainly as low as 0.02 mass%, so that the L ^* value was 86.0. It is thought that it shows. Therefore, by regulating the Mn content and setting the solution temperature higher, the amount of crystal precipitation of the α-Al (Fe · Mn) Si phase in the final plate is lowered and the decrease in the L ^* value is suppressed. I understand what I can do.

  As described above, according to the present invention, aluminum having high strength and excellent thermal conductivity that can be applied to a casing for electronic equipment, etc., and can be applied with a uniform alumite film having a white tone and appropriate yellowness. An alloy plate can be provided.

Claims (6)

  Mg: 0.80 to 1.8% by mass, Fe: 0.05 to 0.30% by mass, Si: 0.20% by mass or less, Cu: 0.03 to 0.15% by mass, Mn: 0.05 -0.20% by mass, Cr: 0.05-0.15% by mass, Zn: regulated to less than 0.15% by mass, the balance consisting of Al and inevitable impurities, 0.2% yield strength of 180 MPa or more A high-strength anodized aluminum alloy sheet characterized by having an electrical conductivity of 40 or more (IACS%). 2. The high-strength alumite according to claim 1, wherein the integral diffraction intensity ratio (Iα-Al (Fe · Mn) Si / IAl ₃ Fe) in the X-ray diffraction analysis is in the range of 0.1 to 0.8. Aluminum alloy plate for processing. The aluminum alloy ingot having the component composition according to claim 1 is subjected to a homogenization treatment for 1 to 5 hours at a temperature of 560 to 620 ° C., and then, with or without hot rolling and intermediate annealing. The method for producing a high-strength anodized aluminum alloy sheet according to claim 1, wherein cold rolling is performed at a final cold rolling rate of 15 to 95%.   The method for producing an aluminum alloy plate for high-strength alumite treatment according to claim 3, wherein final annealing is further performed after the cold rolling. An aluminum alloy plate comprising the aluminum alloy plate for high-strength alumite treatment according to claim 1 or 2 as a base material and having an anodized film on a surface thereof, wherein the color tone range of the anodized film has an L ^* value. : 85-90, a ^* value: -1.0 to -0.3, b ^* value: 0.5 to 1.0, an aluminum alloy plate with a high-strength anodic oxide film. The aluminum alloy plate with a high-strength anodized film according to claim 5, which is used as a casing of an electronic device in combination with an A5052 alloy plate with an anodized film.