JP3308305B2 - Manufacturing method of aluminum alloy plate for anodizing treatment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to corrosion resistance of anodized film,
Pure aluminum alloy plate used for various applications that require uniform color tone (stability) or uniform appearance when etched. The present invention relates to interior and exterior panel materials for buildings, daily necessities, kitchen supplies, lithographic printing plate supports, decorative members, and the like.

[0002]

2. Description of the Related Art JIS-A1100, 1200 to 1050, 106 industrially used as a pure aluminum alloy
In alloys such as 0, 1070 and 1N00, 1N30, 1230, etc., the corrosion resistance and color uniformity of the anodized film are superior to those of other alloys other than pure aluminum. However, as represented by acid rain,
In recent years, the global environment has deteriorated remarkably, and when used for exterior panels for buildings and the like, higher corrosion resistance is required than conventional pure aluminum alloys.

[0003] On the other hand, with regard to uniform color tone, buildings and the like are not merely a building structure but are seen as a part of urban fashion. Since these quality characteristics are governed by Fe and Si as impurities contained in the alloy, they are generally dealt with by regulating the amounts of Fe and Si, that is, the purity of the pure aluminum alloy.

[0004] However, improving the corrosion resistance and the uniformity of the color tone of the anodic oxide film by increasing the purity of aluminum increases the cost of the base metal and causes a decrease in mechanical properties, particularly hardness and strength. In order to improve the corrosion resistance, there is a method of increasing the thickness of the anodic oxide film, and a method of increasing the thickness of the plate to compensate for the decrease in strength due to increasing the purity of aluminum. .
In order to make the color tone of the film uniform, the film thickness is adjusted. However, the adjustment of the film thickness takes time and increases the cost.

[0005]

SUMMARY OF THE INVENTION The present invention provides an aluminum oxide film having an excellent corrosion resistance and a uniform color tone without increasing the thickness of the oxide film or the thickness of the plate. It is an object of the present invention to provide a method for manufacturing an aluminum alloy plate.

[0006]

As a result of research on the mechanism of impairing the corrosion resistance of the anodic oxide film, it has been found that, when Si contained in an aluminum alloy is present in a state of being precipitated as single Si particles, such an aluminum alloy is When the plate is subjected to anodizing treatment, Si particles remain in the film, which have different chemical properties from those of the surrounding film. It became clear that progressed.

[0007] The color tone of the film is determined by the distribution of 1 in the film.
It was found that the particle size distribution of fine Si particles of less than μm and the gloss difference due to uneven etching during caustic etching for removing surface flaws as a pretreatment for anodizing treatment were found.

Therefore, a method of preventing the precipitation of the Si particles was examined, and an appropriate amount of Mg was added to the Mg ₂ Si.
As a method for preventing etching unevenness, it has been found that if an appropriate amount of Cu is added, caustic etching is performed uniformly and the gloss becomes uniform. The amount of Mg to be added is determined by converting the solid solution Si into a compound Mg.
An amount corresponding to the formation as ₂ Si is sufficient.

As a result of the above research, the constitution of the present invention is a method for producing an aluminum alloy plate capable of obtaining an anodic oxide film having a uniform color tone and excellent corrosion resistance as described in the claims.

The above configuration will be described below.

It is necessary to keep the mechanical properties and chemical properties within a range that can be handled as generally known pure aluminum. Therefore, the Al purity excluding added components and unavoidable impurities must be 99.00% or more. No.

[0012] Fe is added to make the recrystallized grains fine. If it is less than 0.15%, the effect is reduced. 0.
The addition of Fe in excess of 9% forms coarse Al-Fe-based and Al-Fe-Si-based compounds, which reduce the formability of the sheet and cause local non-uniformity in chemical properties. Not preferred.

Usually, the content of Si inevitably contained in the aluminum metal is 0.05% or more, and if it is less than 0.05%, the cost of the metal increases. Si exceeding 0.5% is Fe
Impairs the refining grain refining effect and reduces corrosion resistance.

The amount of {Si + Fe} is adjusted from the viewpoint of mechanical properties such as material strength, and chemical properties, and furthermore, the cost of metal. If the amount is less than 0.30%, a high-purity metal is used, the cost is increased, and the material strength is reduced.

When the amount of {Si + Fe} is 1.0% or more, the content of Al becomes less than 99.00%, which impairs the properties as pure aluminum. Actually, the following Cu, Ti, Mg
And inevitable impurities must be less than 1.0%.

If the amount of Si is larger than the amount of Fe, the effect of reducing the fineness of the recrystallized grains by Fe is impaired and the corrosion resistance is reduced. Therefore, {Fe%} ≧ {Si%} is required.

Cu is an element which affects caustic etching which is generally performed as a pretreatment of the anodizing treatment. When the caustic etching becomes non-uniform, gloss unevenness is caused, which causes variation in color tone after anodizing. Cu is 0.0
When added in an amount of 5% or more and 0.5% or less, caustic etching is performed uniformly, and uneven gloss is eliminated. 0.05%
If less than that, the effect cannot be obtained. If it exceeds 0.5%, the corrosion resistance of the base plate before the anodizing treatment is deteriorated, which is not preferable.

Ti is mainly added for refining the crystal grains of the ingot. When the content is less than 0.01%, the effect is small.
If it exceeds 05%, a coarse Al-Ti compound is formed,
It may be distributed in the form of streaks on the rolled sheet and may cause defects in the anodic oxide film.

[0019] Ti also has the effect of refining the recrystallized grains of the rolled sheet.

For the refinement of the crystal grains, there is a method of adding Ti and B in combination instead of Ti alone. Even in this case, it is preferable to adjust the amount of Ti to a range of 0.01 to 0.05%. The amount of B is counted as an impurity, and the amount of B added is usually 30 ppm or less.

Mg is an additive component according to the main point of the present invention. The Si particles that impair the corrosion resistance of the anodic oxide film are Al-Fe
-Si that forms a solid solution in Al (matrix) without becoming a Si compound and precipitates alone. The Si particles remain in the film without being dissolved by the anodic oxidation treatment. If Mg is added to form a compound of Mg ₂ Si, it will be dissolved together with aluminum in the anodic oxidation treatment, and thus will not become a film defect. 0.05-0.5% S contained in this alloy
Some of i are bonded to Fe and Al to form Al-Fe-S
It is an i-based compound, and the bonded Si does not precipitate as Si particles.

That is, Si to be Mg ₂ Si is:
It is a solid solution in the Al matrix without being an Al-Fe-Si compound. Estimating from the analysis result by the X-ray microanalyzer, the amount is the amount of added Si, the amount of Fe contained at the same time, Although it varies depending on the conditions of heat treatment, it is considered to be about 20 to 60% of the total amount of Si added.

In view of the above, various studies were made on the amount of Mg added to achieve the object of the present invention.
M in the range of 3 × {Si%} ≦ Mg ≦ 1.0 × {Si%}
It turned out that it was necessary to control the amount of g.

Here, {Si%} is the content of Si (%).

If the amount of Mg is small, solid solution Si remains and S
Precipitates as i-particles.

Excess Mg forms a solid solution in the Al matrix and does not remain in the anodic oxide film, so that it does not affect the corrosion resistance and color tone. It slightly increases the material strength or changes the chemistry, but the effect is minor.

Next, the manufacturing method will be described.

An aluminum alloy mixed with a predetermined composition is formed into an ingot by an ordinary method. If the surface segregation layer is detrimental to the quality of the final product, it is removed by cutting. Cutting and removal may be performed after the homogenization heat treatment and before the hot rolling.

Next, the ingot is used to homogenize the cast structure and
e, heat treatment is performed to convert Si into an Al-Fe-Si-based compound. If the temperature is lower than 450 ° C. or higher than 600 ° C., the formation of this compound hardly occurs. The heat treatment time is preferably longer, but should be within 20 hours from the viewpoint of productivity (economical efficiency). There is no problem in practically 3 to 10 hours.

After this heat treatment, the substrate is cooled to room temperature and reheated after cutting off the surface layer.
Hot rolling is started at 00 ° C. to 550 ° C., rolling is performed in multiple passes, and the rolling is completed so that the material temperature at the end is 200 to 300 ° C.

If the starting temperature is lower than 400 ° C., it is difficult to perform rolling. If the starting temperature is higher than 550 ° C., the Al—Fe—Si compound may be decomposed, which is not preferable because oxidation of the rolled sheet surface proceeds.

The termination temperature is regulated for refining the crystal structure. If the temperature is lower than 200 ° C., the rolling oil cannot completely evaporate and remains on the plate surface to cause surface contamination and corrosion. At a temperature higher than 300 ° C., the recrystallized grains grow coarsely, and the final plate becomes uneven in color tone (gloss) due to a band-like structure. Within these temperature ranges, the optimal temperature is determined so as to optimize the crystal structure, mechanical property anisotropy, and the like of the final sheet.

Performing hot rolling in such a temperature range is also important for forming Mg ₂ Si during rolling and during cooling after rolling.

After hot rolling, cold rolling and intermediate heat treatment are performed. By performing cold rolling before the intermediate heat treatment, recrystallized grains in the intermediate heat treatment become finer, and streaky color tone (glossy) unevenness caused by the crystal grains when the final plate is etched is prevented. When the hot rolling end temperature is lower than 250 ° C., the same effect as in cold rolling is obtained. The reason why the intermediate heat treatment is performed at 400 ° C. or less and for 30 minutes or more is that the solid solution Si and M
This is because g is a compound of Mg ₂ Si. If the temperature is higher than 400 ° C. or less than 30 minutes, this compound is not easily produced. Usually, since the work structure by cold rolling is recrystallized by this intermediate heat treatment, the structure is heated to 300 ° C. or higher. However, if recrystallization is not necessary, the temperature may be lower than 300 ° C.

The final cold rolling of 30% or more performed after the intermediate heat treatment is for adjusting the mechanical properties of the final sheet.
The greater the degree of processing, the greater the strength and hardness. The optimum value is selected based on the use of the final plate.

For some applications, an annealing material having a large elongation is better. For this purpose, heat treatment may be performed at 200 to 400 ° C. after the final cold rolling. 20
Below 0 ° C., the mechanical properties change slowly. 400 ° C
At higher temperatures, the recrystallized grains become coarse. Further, the formed Mg ₂ Si is decomposed and Mg and Si are redissolved, which is not preferable.

If the intermediate heat treatment is carried out by rapid heating at an average heating rate of 10 ° C./sec, the recrystallized grains become finer and the formability and the appearance when etched are improved.
To recrystallize, it is necessary to heat to 400 ° C. or more for 5 seconds or more. If the heat treatment temperature is higher than 500 ° C. or the holding time is too long, the Mg ₂ Si formed during the latter half of hot rolling and cooling after completion of hot rolling is decomposed and re-dissolved. It is practically harmless within the specified conditions.

The final plate thus obtained is etched with, for example, an aqueous solution of caustic soda, neutralized and then anodized in an aqueous solution of sulfuric acid to give aesthetic appearance and corrosion resistance.

[0039]

The present invention will be specifically described below with reference to examples.

Example 1 An aluminum alloy having the chemical components shown in Table 1 was melt-cast to form an ingot. After cutting and removing the surface segregation layer, 500
℃ × 8 hours heat treatment, then subjected to hot rolling as it is,
It rolled so that end temperature might be set to 245 ± 15 degreeC. After hot rolling from 6 mm thick to 3.5 mm by cold rolling,
After performing an intermediate heat treatment at 360 ± 10 ° C. × 2 hours, the plate was cold-rolled into a 2.0 mm-thick plate. The thickness reduction rate of the final cold rolling is 43%. This is H14 material.

Further, a sheet which has been cold-rolled to a thickness of 0.70 mm (a thickness reduction rate of 80%) is used as an H18 material.

Further, this H18 material was heated to 250 ° C. × 2 hours to be in a half-annealed state. (H24 material) Moreover, what was heated and completely annealed at 360 ° C for 2 hours was manufactured. (O material) The corrosion resistance of the anodic oxide films of these materials was evaluated as follows.

First, a 10% aqueous solution of caustic soda (40 ° C.)
For 2 minutes. After water washing and neutralization, anodizing is performed for 10 minutes at a current density of 1 A / dm ^{2 in} a 15% sulfuric acid bath (25 ° C.). The thickness of the resulting film is approximately 2.5 μm. Next, 3% saline (25
10 ° C.), and alternately dipping for 10 minutes and drying for 50 minutes for 10 cycles to corrode the coating. Next, energization is performed in a saturated copper sulfate solution (25 ° C.) for 2 V × 3 minutes. As a result, if the anodic oxide film has defects such as micropores,
Copper is reduced and deposited there by the energization.

[0044]

[Table 1]

When the plate treated in this manner is observed under magnification with an optical microscope, copper precipitated in the form of dots can be recognized. The evaluation of the corrosion resistance of the coating was carried out as shown in Table 1, No. 4, 8, 1
The density of copper precipitation points (film defects) generated in the films of 2,16 (comparative material) was set to rank 5, the state without any defect was set to rank 0, and the area between them was classified into ranks 4, 3, 2, and 1. .

Therefore, the evaluation is a relative evaluation. The evaluation of the corrosion resistance of the base plate before anodic oxidation was performed according to JIS Z 237.
1 Based on the salt spray test method, 5%
Spraying was performed for 0 hour, and the results were relatively compared and expressed by a three-step evaluation as follows.

Equivalent to JIS A 1050: ○ Slightly inferior to JIS A 1050: △ Inferior to JIS A 1050: × Note that there was no significant difference in the corrosion resistance of the base plate due to the tempering of H14, H18, H24 and O materials. The results for the H14 material are shown.

Table 2 shows the evaluation results. Compared with the comparative material having a low Mg content, the corrosion resistance of the coating is improved in the invention material to which Mg is added, and it is understood that when Cu exceeds the component range of the invention, the corrosion resistance of the base plate is poor.

[0049]

[Table 2]

Further, the color tone stability of the anodic oxide film was evaluated as follows.

Of the alloys shown in Table 1, No. 13, 1
150-450 ° C for 7, 18, 19 H18 materials
Each for 8 hours, etching in 6% aqueous sodium hydroxide solution (70 ° C.) for 3 minutes, neutralizing,
1.5 A / dm ² × 40 mi in a 5% sulfuric acid bath (20 ° C.)
n was subjected to anodic oxidation treatment (coating thickness 15 μm), sealed in boiling water at normal pressure, and the color tone of the coating was measured.

Table 3 shows the results. In the alloy containing Mg and Cu (Nos. 13 and 17), it can be seen that the color tone of the anodized film hardly changes depending on the annealing temperature in the range of 200 to 400 ° C. This means that even when conditions such as hot rolling temperature and heat treatment change in the manufacturing process of a rolled plate, the film color of the final plate hardly changes, and a stable color can be obtained between a plurality of lots or within one coil. It is shown that it is possible.

[0053]

[Table 3]

(Note) Film color indication conforms to JISZ8729-1980.

L * is light (large) ← → dark (small) a * is red (+) ← → green (−) b * is yellow (+) ← → blue (−)

Example 2 The alloys shown in Table 4, Nos. 20 and 21, were agglomerated, the surface segregation layer was removed, and then heated at 540 ° C. for 4 hours.
Cool to ℃ and start hot rolling. End temperature is 275 ± 15
It hot-rolled so that it might be set to 5 mm in thickness at ℃, and then cold-rolled to 2 mm in thickness. Here, after variously changing the conditions of the intermediate heat treatment, cold rolling was performed at a sheet thickness reduction rate of 50% to obtain a 1 mm thick sheet (H14 material). The rate of temperature rise in the intermediate heat treatment was 30 ° C./sec. Further 360
Plates (0 material) that had been subjected to a final heat treatment at 2 ° C. × 2 hours were prepared, and their corrosion resistance after anodic oxidation treatment was evaluated in the same manner as in Example 1. Further, the anodized plate surface was visually inspected for appearance, and the degree of streaky color tone (glossy) unevenness caused by crystal grains was evaluated as appearance quality. The evaluation values are relative evaluations in the same alloy material. Table 5 shows the results. If the intermediate heat treatment temperature is low and short time does not occur, sufficient recrystallization does not occur, and the coarse crystal grains generated by hot rolling are rolled as they are. Becomes noticeable. Intermediate heat treatment temperature of 500
If the temperature is higher than ° C, recrystallization occurs sufficiently, but the film is slightly coarsened to exhibit streak-like unevenness, and the corrosion resistance of the film is reduced.

The corrosion resistance of the anodic oxide film was better when the intermediate heat treatment temperature was lower.

In the final 0 material, the sufficiently cold-rolled sheet was recrystallized, and the line-like unevenness became lighter than the H14 material.
Inappropriate intermediate heat treatment still had its effect.

[0059]

[Table 4]

[0060]

[Table 5]

Note: Description of appearance quality ○: good, Δ: streaky unevenness in gloss is observed, but slight
X: Streak-like uneven gloss is partially observed. XX: Streak-like uneven gloss is observed over the entire surface.

Example 3 Alloy No. 22 shown in Table 6 was ingot, cut into small pieces, and subjected to homogenizing heat treatment, hot rolling, cold rolling, intermediate heat treatment and cold rolling to produce a material in charge of H14. The corrosion resistance of the anodic oxide film and the color tone of the film were evaluated in the same manner as in Example 1.

Table 7 shows the results. The prolonged intermediate heat treatment at a high temperature exceeding 400 ° C. or the homogenization treatment at a low temperature of less than 450 ° C. resulted in poor corrosion resistance of the anodic oxide film.

[0064]

[Table 6]

[0065]

[Table 7]

[0066]

[Table 8]

[0067]

As described above, conventionally, the improvement of the corrosion resistance and the color tone stability of the anodic oxide film, which has been dealt with by increasing the purity of the base metal, has improved the purity of the alloy by adding a small amount of Mg and Cu. Since the same effect can be obtained, increase in the cost of bullion can be avoided, and the economic effect is large. Same purity (Si, F
In the case of using the metal of (e), the corrosion resistance is improved and the product life is prolonged.

In addition, variation of the corrosion resistance, which fluctuates depending on the metal used, is eliminated by actively adding and adjusting the amount of Mg treated as an impurity, the amount of which has not been particularly controlled, and the quality is stabilized. Is done.

────────────────────────────────────────────────── ─── of the front page continued (51) Int.Cl. ⁷ identification mark FI C22F 1/00 671 C22F 1/00 671 682 682 683 683 685 685Z 686 686B 691 691A 691B 691C 694 694A 694B (58) investigated the field ( Int.Cl. ⁷ , DB name) C22F 1/04-1/057 C22C 21/00-21/18

Claims (3)

(57) [Claims] 1. Si on a weight basis: 0.05-0.5%;
Fe: 0.15 to 0.9%, Si + Fe: 0.30% or more, less than 1.0%, Si% ≦ Fe%, and C
u: 0.05 to 0.5%, Ti: 0.01 to 0.05
%, Mg; {Si%} × {0.3-1.0}%,
These components, inevitable impurities of 0.05% or less, and the balance
Of an aluminum alloy consisting of 99.00% or more of aluminum by semi-continuous casting, and then, if necessary, cutting and removing the surface segregation layer.
Heat rolling for 20 to 20 hours to start hot rolling at 400 ° C. or more and 550 ° C. or less, finish rolling so that the material temperature becomes 200 ° C. or more and 300 ° C. or less, and then perform cold rolling and 400 ° C. or less for 30 minutes The above intermediate heat treatment was performed, and the thickness reduction rate was 30
Anodic oxidation, characterized in that the percent of the final cold rolling
Manufacturing method of aluminum alloy plate for processing . 2. The intermediate heat treatment is performed at an average rate of 10 ° C./sec.
Above, at more than 400 ° C and below 500 ° C for 5 seconds or more and 30 seconds
The anode according to claim 1, wherein the anode is held within the range of:
A method for producing an aluminum alloy plate for oxidation treatment . 3. 200-400 ° C. after final cold rolling
The aluminum alloy sheet for anodizing treatment according to claim 1 or 2, wherein a final heat treatment is performed.
How .