TWI548754B - An aluminum alloy plate for high strength anodic oxidation of an electronic machine frame, a method of manufacturing the same, and an aluminum alloy plate with a high-strength anodic oxidation film for an electronic machine frame - Google Patents

Description

Aluminum alloy plate for high-intensity anodizing treatment of electronic equipment frame, manufacturing method thereof, and aluminum alloy plate with high-strength anodized film coated with electronic machine frame Field of invention

The present invention relates to an aluminum alloy sheet having high strength and excellent thermal conductivity, which is used for a frame for an electronic device, and can be applied with an anodized film having a white tint and a moderate yellow feeling.

Background of the invention

Since the Al-Fe-based 8000-based alloy has high strength and is excellent in anodizing treatment, it has been used as a material for manufacturing a decorative panel for building materials or a frame for an electronic device. After it is formed into a sheet material, it is cut into a desired size, and if necessary, it is subjected to an anodizing treatment on the outer surface to form a building material. In addition, it is also possible to polish and polish the gloss after the anodizing treatment, and to use it as a frame for an electronic device.

An aluminum alloy plate in which the 8000-series alloy and the 5000-series alloy are used as a base to ensure strength and to define the amount of Si, Fe, Mn, etc., and the anodized color tone is light gray has been developed, or the 8000-series alloy is used as a base. An aluminum alloy sheet having a uniform anodic oxidation treatment to ensure the strength is further added with Mn and Si, a method for producing the same, and the like. In addition, aluminum alloy sheets based on 1000 series alloys and which have improved the uniformity of the tone of the anodized film have been developed recently. Its manufacturing method and the like.

Taking Patent Document 1 as an example, an aluminum alloy sheet is described which is characterized by comprising Fe: 0.1 to 1.0% by weight, Si: 0.01 to 0.5% by weight, Mn: 0.05 to 1.0% by weight, and the remainder being Al and not The aluminum alloy of the impurity is avoided and is anodized to show a uniform color tone; and the aluminum alloy is described above, and the aluminum alloy ingot of the above composition is homogenized at 400 to 600 ° C, and the aluminum alloy is cast. After the hot rolled sheet is obtained by hot rolling, the hot rolled sheet is subjected to a cold rolling process including a process annealing treatment and/or a final annealing treatment, and then anodized to obtain a uniform color tone.

On the other hand, the aluminum alloy plate based on the 8000 series alloy has different effects depending on the homogenization treatment conditions, but it is known that the color tone of the anodized film is easily uneven, and it is not easy to obtain a white tone having uniformity. Anodized tones. Therefore, an aluminum alloy sheet having a 1000-based base and having improved uniformity of the surface roughened surface and uniformity of color tone of the anodized film and a method for producing the same have been developed.

Patent Document 2 describes an aluminum alloy sheet containing 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, and the remainder being composed of Al. And the inevitable impurities. In this way, by appropriately adjusting the content of the chemical components Fe, Si and Ti, in particular, the Fe/Si ratio is in an appropriate range, the formation of the metastable phase can be suppressed, and the intermetallic compound becomes the stable phase main body and the surface is coarse. The uniformity of the pits during the treatment and the uniformity of the hue of the anodized film are remarkably improved.

Alloy plate based on 1000 series alloy, uniformity of etched holes during alkaline etching with caustic soda and color tone of anodized film Excellent uniformity and good formability, but low strength. Therefore, it is expected that high-strength characteristics are also required in an anodized color tone requiring white tone, so that it is also problematic to use an aluminum material based on a 1000-series alloy.

Therefore, an Al-Mg-based 5000-series alloy plate for anodizing treatment having excellent high-strength properties has been developed.

Patent Document 3 proposes an aluminum alloy sheet containing Mg: 2.0 to 3.0%, Cr: 0.15 to 0.25%, Ti: 0.005 to 0.20%, or Ti: 0.005 to 0.20%, and B: 0.0005 to 0.05% by mass%. And the remainder is composed of Al and unavoidable impurities, such that Si in the impurity is 0.15% or less, Fe is 0.4% or less, Mn is 0.06% or less, and the content of Cr is T _CR %, Cr is solid. When the amount of dissolution is S _CR %, P _CR = T _CR -S _CR ≦ 0.065%.

In this way, the Al-Mg-based alloy sheet containing Cr can be made to have a yellow sensation which is minimized and emitted even if the anodic oxide film formed by the sulfuric acid bath is coated under the predetermined ratio of the intermetallic compound containing Cr. Light green white aluminum plate.

Advance technical file Patent literature

Patent Document 1: Japanese Laid-Open Patent Publication No. 08-253831

Patent Document 2: Japanese Patent Laid-Open Publication No. 2000-282159

Patent Document 3: Japanese Laid-Open Patent Publication No. 2011-179094

Summary of invention

In addition, the frame for electronic devices and the like are more and more like to use white tones and Anodized film with uniform color tone. In recent years, electronic devices have become thinner and smaller, so that not only high-strength and heat-releasing materials have become a trend.

In order to improve the heat release property of the 5000-series alloy sheet having high strength, it is effective to reduce the Mg content which is easily dissolved in the body to increase the conductivity. However, when the 5000-based alloy sheet having the Mg content reduced as described above is used as a material for a frame, it may be used in combination with an A5052 alloy sheet (for example, refining: H ₃₂ ). In this case, the uniformity of the color tone of the frame is required. Of course, the anodized film applied to the low-m 5000 series alloy plate requires the color tone of the anodized film applied on the A5052 alloy plate. .

However, if the A5052 alloy is set according to the AA specification, the Mg content is 2.2 to 2.8% by mass, the Cr content is 0.15 to 0.35 mass%, the Mg content is high, the strength is high, and the brightness of the anodized film (L ^*) The value) tends to be slightly higher, but the thermal conductivity on the reverse side is poor, and since the Cr is contained, the anodized color tone tends to have a yellowish sensation. Therefore, even if the technique shown in Patent Document 3 is applied to a 5000-based alloy plate having a Mg content lower than that of the A5052 alloy and having a low thermal conductivity, it is necessary to obtain a white tone and a uniform yellow color with a uniform hue. Anodizing the film is still extremely difficult.

The present invention has been made to solve the above problems, and an object of the invention is to provide an aluminum alloy sheet having high strength and excellent thermal conductivity, which is used for a frame for an electronic device, and can be applied with a white color and a moderate yellow color. Anodizing the film.

In order to achieve the object, the high-strength aluminum alloy sheet for anodizing treatment of the present invention is characterized by comprising Mg: 0.80 to 1.8% by mass, Fe: 0.05 to 0.30% by mass, Si: 0.20% by mass or less, and Cu: 0.03 to 0.15 by mass. %, Mn: 0.05 to 0.20% by mass, and Cr: 0.05 to 0.15 mass%, and limit Zn: less than 0.15 mass%, and the remainder is composed of Al and unavoidable impurities; and its 0.2% proof stress is 180 MPa or more, and conductive The rate is 40 (IACS%) or more.

In the high-strength aluminum alloy sheet for anodizing treatment of the present invention, the integrated diffraction intensity ratio (Iα-Al(Fe.Mn)Si/IAl ₃ Fe) in the X-ray diffraction analysis is preferably in the range of 0.1 to 0.8.

In addition, the aluminum alloy sheet for high-strength anodizing treatment is subjected to homogenization treatment at 560 to 620 ° C for 1 to 5 hours after being subjected to homogenization treatment at an aluminum alloy ingot having the above composition composition, and then subjected to hot rolling. It is manufactured by annealing with a process or without annealing the process, and then applying a cold rolling pass with a final cold rolling ratio of 15 to 95%.

Moreover, after the aluminum alloy plate for anodizing treatment provided by the present invention is subjected to alkaline etching as a pretreatment and then subjected to anodizing treatment by a sulfuric acid method, an L* value according to the CIE specification can be obtained: 85 to 90 , a* value: -1.0~-0.3, b* value: anodized film of a hue in the range of 0.5 to 1.0.

The aluminum alloy sheet with high strength and good thermal conductivity provided by the invention can form a white anodized and a uniform anodized film with a moderate yellow sensation when applied by anodizing, so that it can be provided at a low cost. An anodized material such as a frame for an electronic device.

Form for implementing the invention

As described above, the frame for an electronic device and the like are more and more anodized film which has a white tone and has a uniform color tone. Further, when it is used in a casing of an electronic device or the like, a slightly thin aluminum alloy plate is molded into a predetermined shape by a mold, and the strength after molding is also required. Therefore, most of the materials used are required to have high strength.

Further, in the Al-Mg-Fe-based aluminum alloy sheet, in order to obtain an anodized film having a white tone and uniform color tone, the Al ₆ Fe metastable phase formed in the ingot is subjected to homogenization treatment to be diffused and transformed into Al. ₃ Fe stable phase. In general, the homogenization treatment temperature of the ingot is higher, and the higher the temperature homogenization treatment, the diffusion of the Al ₆ Fe metastable phase formed in the ingot into the Al ₃ Fe stable phase to form a white anodized treatment. The tendency of the film.

When the Al ₆ Fe metastable phase formed in the ingot remains in the material for anodizing, the particles of the Al ₆ Fe metastable phase are taken into the anodized film without oxidation, so that the thickness of the film becomes thick, At the same time, the anodized film is gray. On the other hand, when the stable phase of Al ₃ Fe formed in the ingot remains in the material for anodizing, it is oxidized and is taken into the anodized film. Therefore, even if the thickness of the film is thick, the brightness is less, and the anode is less. The oxidized film is difficult to appear gray.

Further, as the present invention, in order to impart a moderate yellow sensation to the anodized color tone When a predetermined amount of Mn is contained, an α-Al(Fe.Mn)Si phase is formed in the ingot. Further details will be described later, but it is confirmed that the particles of the α-Al(Fe.Mn)Si phase formed in the ingot are partially dissolved in the body due to the homogenization treatment but remain in the final plate and are taken up into the anodized film. In the meantime, when the thickness of the film becomes thick, the anodized film is easily grayed.

Of course, the refining of the final plate including the process annealing conditions of the cold rolling process will also change the precipitation state of the precipitates, and the difference in density will also change. Therefore, there is a change in the state of the etched holes in the alkaline etching treatment, and as a result, the hue and tone uniformity after the anodizing treatment are also affected. Therefore, the rolling rate at the final cold rolling after the process annealing becomes a problem.

Therefore, the inventors of the present invention carefully investigated the influence of the production conditions such as the homogenization treatment temperature and the cold rolling (refining) on the color tone of the anodized film. In order to obtain an anodized alloy film which can be applied with a white tint and a moderate yellow sensation and which is high in strength and excellent in thermal conductivity, it is further subjected to tensile test, conductivity measurement, and anodizing treatment. The X-ray diffraction intensity analysis of the intermetallic compound in the material is repeatedly reviewed in depth to achieve the present invention.

The contents are explained below.

First, the action, appropriate content, and the like of each element contained in the aluminum alloy sheet of the present invention will be described.

Mg: 0.80 to 1.8% by mass

To ensure the strength of the aluminum alloy sheet, Mg is an essential element. When the Mg content is less than 0.80% by mass, the strength of the aluminum alloy sheet is lowered, which is not preferable. If the Mg content exceeds 1.8% by mass, not only the conductivity (thermal conductivity) of the final sheet is lowered. Low, even if the homogenization treatment temperature has an effect, there is still a flaw in the Mg segregation layer (β-Mg phase) which is present in the ingot to cause combustion (local melting).

Therefore, the Mg content is specified to be 0.80 to 1.8% by mass. A preferred Mg content is in the range of from 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 to 0.30% by mass

To ensure the strength of the aluminum alloy sheet, Fe is an essential element. If the Fe content is less than 0.05% by mass, the strength of the aluminum alloy sheet is lowered, which is not preferable. When the Fe content exceeds 0.30% by mass, not only the formability is lowered, but also the homogenization treatment temperature is affected, but the amount of the α-Al(Fe.Mn)Si phase remaining in the final sheet is increased, and α-Al (Fe.Mn) When the particles of the Si phase are taken up into the anodized film, they are easily grayed out and the brightness (L* value) is lowered, so it is not suitable.

Therefore, the Fe content is specified to be 0.05 to 0.30% by mass. A preferred 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 mass%.

Si: 0.20% by mass or less

The Si system is mixed with the raw material metal and the returned material. The Si system forms an intermetallic compound with Mg, and when it exceeds 0.20%, the solidus temperature is lowered, and the homogenization treatment at a holding temperature of 560 ° C or higher cannot be performed. In the present invention, since the homogenization treatment at a temperature of 560 ° C or higher is necessary, the Si content is required to be in the range of 0.20% by mass or less. A preferred Si content is in the range of 0.18% by mass or less. A more desirable Si content is in the range of 0.15% by mass.

Cu: 0.03 to 0.15 mass%

Cu is mixed with raw material metal and returned material. Cu is an element necessary for imparting a moderate yellow sensation (b* value of CIE standard) to the anodized color tone. When the Cu content is less than 0.03% by mass, the yellowing effect (b* value) of the anodizing treatment color is too weak, and the gloss necessary for the frame or the like is not obtained. In addition, when the Cu content is more than 0.15% by mass, the amount of precipitation of CuAl ₂ or CuMgAl ₂ in the final plate is affected, but the yellowing (b* value) of the anodized color tone is too strong.

Therefore, the Cu content is specified to be 0.03 to 0.15 mass%. A preferred Cu content is in the range of 0.03 to 0.12% by mass. A more desirable 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 with raw material metal and returned material. Mn is an element necessary for imparting a moderate yellow sensation (b* value) to the anodized color tone. When the Mn content is less than 0.05% by mass, a moderate yellow sensation (b* value) cannot be obtained. When the Mn content exceeds 0.20% by mass, not only the yellowness (b* value) becomes too strong, but even if the homogenization treatment temperature is affected, the amount of the α-Al(Fe.Mn)Si phase remaining in the final sheet increases. Further, since the particles of the α-Al(Fe.Mn)Si phase are taken up into the anodized film, they are easily grayed out, and the brightness (L* value of the CIE standard) is lowered, which is not preferable.

Therefore, the Mn content is specified to be 0.05 to 0.20% by mass. A preferred 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 to 0.15 mass%

The Cr is mixed with the raw material metal and the returned material. Cr is an element necessary for imparting a moderate yellow sensation (b* value) to the anodized color tone. If the Cr content is less than When 0.05% by mass, a moderate yellow sensation (b* value) could not be obtained. When the Cr content exceeds 0.15% by mass, the yellowing effect (b* value) of the anodizing treatment color becomes too strong, which is not preferable.

Therefore, the Cr content is specified to be 0.05 to 0.15 mass%. A preferred 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 mass%

The Zn system is inevitably mixed by the returning material. Zn is a component that enhances the yellowing (b* value) of the hue by anodizing. In the present invention, the Zn content is limited to less than 0.15% by mass. When the Zn content is 0.15% by mass or more, in the case of anodizing pretreatment, that is, alkaline etching by caustic soda, the amount of dissolved Zn dissolved in the treatment liquid increases to form an alkaline bath containing zinc oxide. If the pretreatment is continued in the alkaline bath, Zn is precipitated on the surface of the aluminum alloy plate, which may cause uneven appearance after the anodizing treatment and impair the design property.

Therefore, the Zn content is limited to less than 0.15% by mass. A preferred Zn content is less than 0.12% by mass. More preferably, the Zn content is less than 0.10% by mass.

Ti: 0.001 to 0.10% by mass

The Ti is mixed with the raw material metal and the returned material. Ti acts as a grain refiner during casting of the ingot and also prevents cracking. Of course, Ti can be added separately, but by coexistence with B, it is expected to achieve a more powerful grain refining effect, so it is also possible to use a rod hardener such as Al-5% Ti-1%B. When the Ti content is less than 0.001% by mass, the effect of refining at the time of casting of the ingot is insufficient, and it is unfavorable since the casting crack is caused. When the Ti content exceeds 0.10% by mass, coarse intermetallic compounds such as TiAl ₃ are crystallized during casting, and there is a possibility that strip defects are generated, which is not preferable.

Therefore, the ideal Ti content is in the range of 0.001 to 0.10% by mass. A preferred Ti content is in the range of 0.005 to 0.07 mass%. A more preferable Ti content is in the range of 0.01 to 0.05% by mass.

Other inevitable impurities

The unavoidable impurities are inevitably mixed by the raw material metal, the raw material, and the like, and the allowable content thereof is, for example, less than 0.10% by mass of Ni, less than 0.10% by mass of Zr, and less than 0.05% by mass of Ga, B, and V, On the other hand, Pb, Bi, Sn, Na, Ca, and Sr are each less than 0.02% by mass, and the others are each less than 0.05% by mass, and even if it has an uncontrollable element within this range, the effect of the present invention is not impaired.

In particular, B and Ti act as grain refiners during casting of the ingot, and also prevent cracking. Therefore, it may be contained as necessary. When the B content is more than 0.05% by mass, the intermetallic compound in which TiB ₂ has been stabilized is formed, and the grain refining effect is attenuated, and the uniformity of the color tone of the anodizing treatment is lowered, which is not preferable.

Further, the necessary characteristics of the aluminum alloy sheet of the present invention will be described.

0.2% endurance: 180MPa or more

The alloy sheet obtained by subjecting an aluminum alloy material to an anodized white color is used as a frame for an electronic device, and therefore requires high strength. In particular, electronic devices have recently been promoted to be thinner and smaller, and it is therefore difficult to easily deform the materials even when they are thinner than in the past, and to create a high-grade anodized material.

Therefore, the alloy sheet of the present invention is limited to a 0.2% proof endurance of 180 MPa or more under tensile test.

Conductivity: 40 (IACS%) or more

As mentioned above, in recent years, electronic devices have continued to promote thin and compact, and more need for heat-releasing materials. Therefore, the alloy sheet of the present invention is limited to a conductivity of 40 (IACS%) or more. An alloy sheet having a conductivity of 40 or more (IACS%) or more will form a material having high heat conductivity and good heat release property, and is suitable for use in a housing such as an electronic device.

Anodizing color tone: L* value: 85~90, a* value: -1.0~-0.3, b* value: 0.5~1.0

The details are described later, but the final plate is subjected to alkaline etching, sulfuric acid anodizing, and the color tone is measured when the thickness of the anodized film is 7 μm, as long as the L* value of the CIE specification is in the range of 85 to 90. Similarly, the a* value is in the range of -1.0 to -0.3, and the b* value is in the range of 0.5 to 1.0, that is, the anodizing treatment of the anodized film which can be applied with a white tone and a moderate yellow sensation Use material. That is, the anodized color tone of the A5052 alloy plate may vary somewhat depending on the composition variation within the specification range or the refining, or the anodizing film thickness, and the like, and the material for anodizing treatment of the present invention can still be compared with the A5052 alloy plate. The anodization treats the hue of the hue.

Integral diffraction intensity ratio (Iα-Al(Fe.Mn)Si/IAl ₃ Fe): 0.1~0.8

As described above, it is known that the brightness (L* value) of the anodizing treatment color is related to the type of Fe-based intermetallic compound present in the material for anodizing treatment. When the Al ₆ Fe metastable phase formed in the ingot remains in the material for anodizing, the particles of the Al ₆ Fe metastable phase are taken into the anodized film without oxidation, so that the thickness of the film becomes thick. At the same time, the anodized film is gray. On the other hand, if the Al ₃ Fe stable phase remains, it will be oxidized and taken up into the anodized film. Therefore, even if the thickness of the film is thick, the brightness is less likely to decrease, and the anodized film is less likely to be gray.

Further, in the present invention, when a predetermined amount of Mn is contained in order to impart a moderate yellow sensation to the anodized color tone, an α-Al(Fe.Mn)Si phase is formed in the ingot. It has been confirmed that the particles of the α-Al(Fe.Mn)Si phase formed in the ingot are partially dissolved in the bulk due to the homogenization treatment but remain in the final plate, and are taken up into the anodized film, and the thickness of the film becomes thick. At the same time, the anodized film is easily grayed out.

Of course, the amount of the Al ₃ Fe stable phase or the α-Al(Fe.Mn)Si phase of the final plate varies depending on the manufacturing conditions such as the Fe, Mn, Si content of the aluminum alloy composition, the homogenization treatment temperature, and the like. Further, the Fe and Mn contents affect the color tone of the anodized film as described above.

Therefore, the factor which affects the color tone of the anodized film is defined as the integral diffraction intensity ratio when the X-ray diffraction analysis is performed on the material for anodizing (Iα-Al(Fe.Mn)Si/IAl ₃ Fe). In the range of the composition of the alloy of the present invention, when the X-ray diffraction analysis is performed on the material for anodizing, the integral diffraction intensity ratio (Iα-Al(Fe‧Mn)Si/IAl ₃ Fe) is 0.1 to 0.8. Within the range, the anodized color tone falls within the specified range.

Next, the method for manufacturing the high-strength aluminum alloy sheet of the present invention described as follows.

Melting. Melting

When the raw material is put into a melting furnace and reaches a predetermined melting temperature, the flux is stirred and stirred, and if necessary, the inside of the furnace is deaerated by using a blow pipe or the like, and then the slag is separated from the surface of the melt by static retention.

The melting. The smelting system sets the predetermined alloy composition, so it is important to re-inject the raw materials such as the master alloy. However, it is important to leave sufficient static time until the flux and slag are separated from the aluminum alloy melt. . The static time is usually maintained for more than 30 minutes.

The molten aluminum alloy melted in the melting furnace may be temporarily moved to the holding furnace and then cast as occasion demands, and sometimes cast directly from the melting furnace. The preferred static time is 45 minutes or more. If necessary, it can also be inline degassing and filter.

The on-line degassing system is a form in which an inert gas or the like is blown into the aluminum melt by a rotary rotor, and hydrogen in the melt is diffused and removed in a bubble of an inert gas. When nitrogen is used as the inert gas, it is desirable to control the dew point to, for example, -60 ° C or less. The amount of hydrogen in the ingot should be reduced to less than 0.20 cc / 100 g.

Homogenization temperature: 560~620°C

In the ingot in a cast state, an α-Al(Fe.Mn)Si phase is present. Although the homogenization treatment temperature also has an effect, one part of the α-Al(Fe.Mn)Si phase can be solid-solubilized in the bulk by homogenization treatment. Further, although the Mn content is also affected, it is also possible to form an Al ₆ Fe or Al _m Fe metastable phase in the ingot in a cast state. Even in this case, the Al ₆ Fe, Al _m Fe metastable phase can be metamorphosed into an Al ₃ Fe stable phase by increasing the set homogenization treatment temperature.

When the homogenization treatment temperature is less than 560 ° C, the retention time required for the solid solution of the α-Al (Fe. Mn) Si phase or the above-mentioned diffusion metamorphism is elongated, resulting in a decrease in productivity, which is not preferable. When the homogenization treatment temperature exceeds 620 ° C, even if it is related to the amount of Mg as described above, there is still a possibility that combustion (local melting) is caused in a trace amount of Mg segregation layer (β-Mg phase) formed when the ingot is solidified.

Therefore, the homogenization treatment temperature is set in the range of 560 to 620 °C.

Hold time at homogenization treatment temperature: 1~5 hours

If the holding time of the homogenization treatment temperature is less than 1 hour, even if the temperature increase rate in the treatment furnace or the like is affected, the physical temperature of the entire ingot is less than the predetermined homogenization temperature. If the homogenization treatment temperature is maintained for more than 5 hours, even if the homogenization treatment temperature is affected, a better effect cannot be obtained, and the case where the rust is generated by oxidation increases the productivity, which is not preferable. Therefore, the holding time of the homogenization treatment temperature is set to 1 to 5 hours.

Hot rolling

The ingots subjected to homogenization treatment are then lifted by a crane and brought from a homogenizing treatment furnace to a hot rolling mill. Although the models of the hot rolling mills also have an effect, they are usually hot rolled by several rolling passes. The hot rolled sheet having a predetermined thickness, for example, a thickness of about 3 to 8 mm, is stretched and wound on a roll.

Cold rolling

The rolls wound with the hot rolled sheet are sent to a cold rolling mill, usually with a few passes of cold rolling. At this time, the work hardening is caused by the plastic strain introduced by the cold rolling, so that the process annealing treatment can be performed as necessary. Process annealing is also softened Although it is related to the material, the cold roll is usually inserted into the batch furnace and kept at a temperature of 300 to 400 ° C for more than 1 hour. If the temperature is kept below 300 ° C, softening cannot be promoted, and if the temperature is maintained above 400 ° C, the productivity is lowered so that the processing cost is increased. Further, when the process annealing is performed in a continuous annealing furnace (CAL), it is maintained at a temperature of 420 to 480 ° C for 15 seconds or less. If the temperature is kept below 420 ° C, the softening cannot be promoted, and if the temperature is maintained above 480 ° C, the productivity is lowered and the processing cost is increased.

Final cold rolling rate: 15~95%

As described above, the refining of the final plate including the process annealing conditions of the cold rolling delay also causes the precipitation state of the precipitate to change, and the difference in the discharge density also changes. Therefore, the state of the etched pores in the alkaline etching treatment is changed, and as a result, the color tone and color tone uniformity after the anodizing treatment is affected.

When the final cold rolling ratio is less than 15%, the difference in the discharge density of the final sheet is low, so that the pit density is also lowered, the brightness (L* value) of the anodized material is lowered, and the effect of eliminating multi-mode trace is lowered. If the final cold rolling ratio is 15% or more, the difference in the discharge density of the final sheet becomes high, and the density of the anodized material (L* value) is increased, and the effect of eliminating multi-mode trace is obtained. If the final cold rolling rate exceeds 95%, there is a problem that the edge of the coil is cracked, so that the yield is lowered, so it is not suitable. Therefore, the final cold rolling rate should be 15 to 95%. Preferably, the final cold rolling rate is in the range of 20 to 95%. The final cold rolling rate is better in the range of 30 to 95%.

Final annealing

In the present invention, the final annealing is performed after the final cold rolling, and may be, for example, a batch which is maintained at a temperature of 150 to 200 ° C for 1 hour or more by an annealing furnace. The treatment may also be a continuous annealing treatment maintained in a continuous annealing furnace at a temperature of, for example, 200 ° C to 250 ° C for 15 seconds. Regardless of the progress, the final annealing in the present invention is not necessarily carried out, but in consideration of the case where the molding is carried out before the anodizing treatment, it is preferred to slightly soften the final sheet in advance. In consideration of the formability of the molding, it is preferred to perform annealing treatment at a relatively low temperature in advance. In addition, the lower temperature annealing treatment also has the meaning of softening treatment and the meaning of stabilization treatment. It has been determined that the rolled sheet is rolled in a rolled state without being subjected to annealing treatment, and the endurance is lowered after a long period of time. Therefore, the aging treatment is carried out in advance, and the purpose of stabilizing the endurance for a long period of time is achieved.

Example

Final board creation

The predetermined ingots and scraps are measured and blended, and then put into a melting furnace and kept in the furnace. Even if it was melted at 800 ° C, 2 kg of flux for slag removal was put in, and then the aluminum melt in the furnace was sufficiently stirred with a stir bar. Next, the Mg ingot was placed in the mold for another 30 minutes, and then the disk sample was taken by sampling to the mold for component analysis. Then, the slag floating on the surface of the molten metal is removed by a stirring rod, and according to the intermediate analysis result of the previously collected disc-shaped sample, various ingots are added for the insufficient component, and the molten metal is stirred. Thereafter, statication was again carried out for 30 minutes, and the disk-shaped sample was again taken by sampling to the mold for component analysis.

After confirming the component analysis value, the molten metal flows out of the tap hole to the outflow tank, and when the liquid level reaches a predetermined position of the outflow tank, the liquid dip tube is cast into the mold. The lower mold is lowered when the liquid level in all the molds reaches the predetermined position of the mold. The lowering speed of the lower mold was 50 mm/min under a constant state. Such as In this case, an ingot having a width of 1350 mm × a thickness of 560 mm × a length of 3500 mm was cast. Composition analysis was performed on each disc sample by radiometric spectrophotometry. The results of the final melt composition analysis are shown in Table 1.

After the front end and the rear end of the ingot are cut, the both sides of the ingot are plane-cut by a milling cutter. The ingot was inserted into a homogenization treatment furnace, heated to a predetermined temperature (530 ° C, 580 ° C) at a temperature increase rate of 30 ° C / hr, and kept at a predetermined temperature for 1 hour, and subjected to homogenization treatment. Subsequently, the ingot is lifted by a crane, moved from the homogenizing treatment furnace to the table of the hot rolling mill, and hot rolled by a hot rolling mill until a predetermined thickness is formed, and a hot rolled sheet is formed and wound up. On the roll.

Subsequently, the hot rolled sheet was subjected to cold rolling, and subjected to process annealing at a predetermined thickness or without process annealing to obtain a cold rolled sheet having a final thickness of 0.8 mm. Further, in the final annealing, the cold-rolled sheet is sent to a continuous annealing furnace (CAL), and subjected to continuous annealing treatment at a predetermined temperature for 15 seconds, followed by water cooling, or batching at a predetermined temperature for 1 hour. After the annealing treatment, the coil is air cooled. Table 2 shows the manufacturing conditions of the test materials.

Next, evaluation of the tensile properties was performed on the obtained final sheets (each of the test materials).

Evaluation of tensile properties

The strength evaluation of the resulting final panel was carried out by 0.2% proof stress (MPa) of the tensile test. Specifically, in the case where the stretching direction is parallel to the rolling direction, the JIS No. 5 test piece was subjected to a tensile test in accordance with JIS Z2241, and tensile strength, 0.2% proof stress, and elongation (elongation at break) were determined. In the present specification, a test material having a 0.2% proof stress of 180 MPa or more is regarded as having a good strength (○), and a test material having a 0.2% endurance of less than 180 MPa is considered to have insufficient strength (×). The evaluation results are shown in Table 3.

For the resulting final sheet, the alkaline etching treatment shown below was carried out. In the alkaline etching treatment, the test material is first immersed in a 30% by mass nitric acid solution at normal temperature for 5 minutes, and then thoroughly washed with water, followed by immersing 5 mass% sodium hydroxide solution at 50 ° C for 3 minutes, and then washed with water, and then washed. The 30% by mass nitric acid solution was immersed at room temperature for 3 minutes and then washed with water.

Secondly, in the anodizing treatment, the test material is anodized at a liquid temperature of 18 ° C and a current density of 1.0 A/dm ² in a solution having a sulfuric acid concentration of 170 g/L and dissolved Al: 10 g/L, and anodized. After the film thickness was 7 μm, it was washed with water, and after sealing at 95 ° C for 15 minutes, it was washed with water and dried at room temperature.

Tone evaluation

The color tone of the anodized film (7 μm thickness) which was carried out as described above was measured and evaluated. The measurement of the color tone of the anodized film is performed by using a colorimeter (CR-300 MINOLTA company) and a D65 light source. According to JIS Z8722. The colorimetric values are expressed in terms of the L*a*b* color system of the CIE specification. The L* value indicates the brightness, and the larger the value, the brighter and closer to the white tone. The a* value and the b* value indicate the hue, the + side of the a* value indicates red, the - side indicates green, the + side of the b* value indicates yellow, and the - side indicates blue, and the larger the absolute value of each, the stronger the hue.

In the present specification, the test material having an L* value in the range of 85 to 90 is regarded as a good color tone evaluation (○), and the test material having an L* value outside the range of 85 to 90 is regarded as a poor color tone evaluation (×). The test materials with a* values in the range of -1.0 to -0.3 were considered to have good color tone evaluation (○), and the test materials with a* values outside the range of -1.0 to -0.3 were regarded as poor color tone evaluation (×). The test materials with b* values in the range of 0.5 to 1.0 were considered to have good color tone evaluation (○), and the test materials with b* values outside the range of 0.5 to 1.0 were regarded as poor color tone evaluation (×). The results of the assessment are shown in Table 3.

Conductivity evaluation

The conductivity (IACS%) was measured by a conductivity meter (AUTOSIGMA 2000, manufactured by HOCKING Co., Ltd.). A test material having a conductivity of 40 (IACS%) or more was considered to have a good electrical conductivity (○), and a test material having a conductivity of less than 40 (IACS%) was regarded as having a poor electrical conductivity (×). The results of the assessment are shown in Table 3.

Comprehensive Evaluation

In the comprehensive evaluation, the L* value, the a* value, and the b* value of the anodized color tone are all within the above reference range when the thickness of the anodized film is 7 μm, and the 0.2% proof stress is 180 MPa or more and the conductivity is at The test materials satisfying all the conditions above 40 (IACS%) are considered to be a good comprehensive evaluation (○), and any one of the above items is considered to be a poor comprehensive evaluation (×).

The test materials of Examples 1 to 3 have an alloy composition within a predetermined range, and the L* value, the a* value, and the b* value of the anodizing treatment color are all within the above reference range, the endurance is 180 MPa or more, and the electrical conductivity is 40. (IACS%) or more, the overall evaluation is good (○).

In the test material of Comparative Example 1 (A5052 alloy composition), the Mg content was as high as 2.7% by mass, so that the homogenization treatment temperature was lowered to 530 °C. In the test material of Comparative Example 1, the Mn content was as low as 0.02% by mass, but the Cr content was as high as 0.18% by mass. Therefore, the L* value, the a* value, and the b* value of the anodized color tone were within a predetermined range. However, since the Mg content is as high as 2.7% by mass, the conductivity is too low. It is 35 (IACS%) and falls outside the specified range.

In the test material of Comparative Example 2, since the homogenization treatment temperature was as low as 530 ° C, the L* value of the anodized color tone was too low outside the predetermined range. Further, since the Cu content is as low as 0.02% by mass, the b* value of the anodized color tone falls too low outside the predetermined range.

In the test material of Comparative Example 3, since the homogenization treatment temperature was as high as 580 ° C, the L* value of the anodized color tone was within a predetermined range. However, since the Cu content is as low as 0.02% by mass, the b* value of the anodized color tone falls too low outside the specified range.

In the test material of Comparative Example 4, since the Cu content was as high as 0.17 mass%, the L* value of the anodizing treatment color was low, and the b* value was too high, and it fell outside the predetermined range.

In the test material of Comparative Example 5, the Fe content was as high as 0.34% by mass, but the Mn content, the Cr content, and the Mg content were all as low as less than 0.01% by mass, so the L* value, the a* value, and the b* value of the anodized color tone. All within the specified range. However, since the Mg content is less than 0.01% by mass, the endurance is too low to become 110 MPa and falls outside the prescribed range.

In the test material of Comparative Example 6, the Fe content was as high as 0.49% by mass, and the Mn content was extremely high at 1.09% by mass, and even the homogenization treatment temperature was as low as 530 ° C, so the L* value of the anodizing treatment color was low, a * Values and b* values are too high and fall outside the specified range.

In the test material of Comparative Example 7, since the Mn content and the Cr content were both as low as 0.01% by mass, the b* value of the anodized color tone was too low outside the predetermined range.

Semi-quantitative intensity analysis was performed here using an XRD apparatus.

The XRD apparatus was measured by an X-ray diffraction apparatus RAD-rR manufactured by Rigaku Corporation. The measurement conditions were set to 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°. Further, among the peaks of the measured respective phases, the peak value which is high in intensity and does not overlap with the peak derived from other components, that is, the α-Al(Fe.Mn)Si is in the vicinity of 2θ=41.7°, The integral diffraction intensity was obtained for the peak of Al ₃ Fe in the vicinity of 2θ=24.1° and Al _m Fe around 2θ=25.7°. In addition, the integral diffraction intensity was calculated from the average value (n=3) of each sample for three times. The results shown in Table 4 are the test material No., the homogenization treatment temperature, the L* value when the anodizing film thickness is 7 μm, and the XRD diffraction intensity measurement results.

The test materials of Examples 1 to 3 have an alloy composition within a predetermined range, and the L* value of the anodized color tone is 85 or more, and the integrated diffraction intensity ratio (Iα-Al(Fe.Mn)Si/IAl ₃ Fe) It is in the range of 0.1~0.8.

From the results of evaluation for all of the six types of test materials, it was confirmed that at least the Al ₆ Fe metastable phase remained in the final plate. Moreover, the test materials of Comparative Examples 2 and 3 were all of the same alloy composition (E alloy), and it was confirmed that the homogenization treatment temperature was set to a high temperature only when the homogenization treatment temperature was different, and the ingot was formed. The α-Al(Fe.Mn)Si phase tends to be solid-solubilized in the bulk, and it is considered that the Al _m Fe metastable phase formed in the ingot tends to diffuse and transform into an Al ₃ Fe stable phase due to the homogenization treatment.

As described above, in the state of the Al ₃ Fe stable phase, even if the thickness of the film of the anodized film is increased, the brightness (L* value) is less likely to decrease, and the anodized film is hardly gray. From the results of the X-ray diffraction analysis, it is considered that in the state of the α-Al(Fe.Mn)Si phase, if it is taken into the anodized film, the thickness of the film becomes thick, and the anodized film is likely to be gray. When the homogenization treatment temperature is set to be high, the α-Al(Fe.Mn)Si phase crystallized during casting tends to be partially dissolved in the body due to the homogenization treatment. However, when the Mn content is increased, the amount of the α-Al(Fe.Mn)Si phase remaining in the final sheet is also increased, so that the anodized film is liable to be gray and the L* value is lowered. Incidentally, although the homogenization treatment temperature of the test piece of Comparative Example 1 was as low as 530 ° C, it was mainly because the Mn content was as low as 0.02% by mass, and the L* value was shown to be 86.0. Therefore, it can be understood that by limiting the Mn content and increasing the set solution treatment temperature, the amount of crystal precipitation of the α-Al(Fe.Mn)Si phase in the final plate can be lowered, and the decrease in the L* value can be suppressed.

Industrial availability

According to the present invention, it is possible to provide an aluminum alloy sheet having high strength and excellent thermal conductivity, which is used for a frame for an electronic device, and can be applied with an anodized film having a white hue and a moderate yellow feeling. .

Claims (6)

An aluminum alloy plate for high-intensity anodizing treatment of an electronic machine frame, comprising: Mg: 0.80 to less than 1.5% by mass, Fe: 0.05 to 0.30% by mass, Si: 0.20% by mass or less, Cu: 0.03 ~0.15 mass%, Mn: 0.05 to 0.20 mass%, and Cr: 0.05 to 0.15 mass%, and limit Zn: less than 0.15 mass%, and the remainder is composed of Al and unavoidable impurities; and its 0.2% endurance is 180 MPa. The above conductivity is 40 (IACS%) or more. The electronic machine frame of claim 1 is an aluminum alloy plate for high-intensity anodizing treatment, and the integrated diffraction intensity ratio (Iα-Al(Fe.Mn)Si/IAl ₃ Fe is used for X-ray diffraction analysis. ) is within the range of 0.1 to 0.8. The invention relates to a method for manufacturing an aluminum alloy plate for high-intensity anodizing treatment of an electronic machine frame, which is used for manufacturing an aluminum alloy plate for high-intensity anodizing treatment of an electronic machine frame according to claim 1 The method is characterized in that the aluminum alloy ingot having the composition of the component contained in claim 1 is subjected to homogenization treatment at a temperature of 560 to 620 ° C for 1 to 5 hours, and then subjected to hot rolling and annealing. Or without process annealing, the final cold rolling rate is 15~95% cold rolling. The method for producing an aluminum alloy sheet for high-intensity anodizing treatment of the electronic machine housing of claim 3, which is subjected to the final annealing after the cold rolling. An aluminum alloy plate with a high-intensity anodizing treatment film for an electronic machine frame, characterized in that it is subjected to alkaline etching as a pretreatment in an aluminum alloy plate for high-strength anodizing treatment according to claim 1 or claim 2 The toning range of the anodized film after anodizing by sulfuric acid method is L* value: 85 to 90, a* value: -1.0 to -0.3, b* value: 0.5 to 1.0. An aluminum alloy plate with a high-strength anodized film for an electronic device frame attached to the item 5 is used in combination with an A5052 alloy plate with an anodized film as a frame of an electronic device.