JPH0551711A - Production of high temperature-worked product of aluminum alloy - Google Patents

Abstract

PURPOSE:To control the amount of oxide film forming during high temp. working by previously performing surface treatment before the high temp. working for an aluminum alloy containing specific amounts of Mg and to provide a high temp.-worked product excellent in corrosion resistance and adhesive strength of coated film and having attractive external appearance at a low cost by inhibiting Mg segregation. CONSTITUTION:The high temp. worked product of aluminum alloy can be produced by subjecting an aluminum alloy containing, by weight, >=2.0% Mg to working at a temp. as high as >=200 deg.C after any of the surface treatments (1), (2), (3) as follows: (1) etching treatment with an aqueous solution containing chelating agent, a strongly alkaline solution, or a strongly acidic solution; (2) one or more surface treatments among hydrating oxidation treatment, anodic oxidation treatment, and A.C. electrolytic treatment in an alkaline solution; (3) one or more surface treatments, after etching, among hydrating oxidation treatment, anodic oxidation treatment, and A.C. electrolytic treatment in an alkaline solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is directed to corrosion resistance, coating adhesion, and appearance of an aluminum alloy containing 2.0% or more of Mg (by weight) The present invention relates to a manufacturing method for obtaining an aluminum alloy high-temperature processed product excellent in beauty, for example, building materials, materials for transportation equipment, ornaments, articles and the like.

[0002]

2. Description of the Related Art When an aluminum alloy material containing 2.0% or more of Mg is subjected to high temperature working, for example, superplastic forming, problems such as blackening of the surface, poor adhesion of coating film and poor corrosion resistance are likely to occur.

In order to eliminate such a problem, it is possible to perform surface treatment after high temperature processing, but it may be practically impossible depending on the shape and size of the processed body.

The surface treatment after high temperature processing is 1
The productivity is poor because one or several batch processes are performed together.

On the other hand, as a post-processing treatment, it is considered that the surface layer is mechanically removed by air blast or the like using alundum or the like as an abrasive to improve coating film adhesion and corrosion resistance. Is likely to occur and is not suitable for precision equipment and the like, and there is a problem that the adhesion of the coating film is impaired because the abrasive is buried in the surface.

As a result of examining these problems, the following has been found. The surface oxide film formed on the aluminum surface during high temperature processing is involved in the occurrence of defects such as poor corrosion resistance, discoloration, and poor coating film adhesion of the high temperature processed body. This surface oxide film is
Although it is thin, it is a porous layer containing rolling oil or the like and has many cracks, so that it has poor wettability with respect to the coating material, resulting in poor adhesion and poor corrosion resistance.

Further, when the oxide film component is incorporated into the hydrated oxidation (boehmite) film or the anodic oxide film, a black or brown film is formed and the appearance is impaired.

Furthermore, in anodizing treatment and chemical conversion coating treatment (chromate, etc.), the initiation of the coating formation reaction is affected by the dissolution of the aluminum surface. Therefore, if a non-uniform oxide coating adheres, uneven reaction occurs and the coating Defects occur.

Therefore, in order to obtain a highly corrosion-resistant aluminum material having a beautiful appearance, it is necessary to suppress the amount of oxide film formed during high temperature processing.

The alloy used in the present invention contains Mg. Mg tends to segregate on the aluminum surface, and the presence of an oxide film on the surface further promotes the tendency to segregate. The Mg segregated on the surface forms magnesium oxide due to oxygen in the atmosphere. Magnesium oxide exhibits alkalinity and adversely affects corrosion resistance and coating adhesion.
Therefore, it is necessary to reduce the segregation of Mg on the surface.

[0011]

SUMMARY OF THE INVENTION According to the present invention, surface treatment is performed before hot working to suppress the amount of an oxide film formed during hot working and to suppress Mg segregation to reduce corrosion resistance and coating film at low cost. It provides a high-temperature processed product having good adhesion and a beautiful appearance even after high-temperature processing.

[0012]

In order to achieve the above object, the present invention provides an aluminum alloy containing 2.0% or more of Mg by etching treatment, AC electrolysis treatment in an alkaline aqueous solution, hydration oxidation treatment, and anode treatment. It is characterized in that it is processed at 200 ° C. or higher after being subjected to oxidation treatment or etching, and further subjected to surface treatment such as AC electrolytic treatment in alkaline aqueous solution, hydration oxidation treatment or anodization treatment. The present invention proposes a method for producing a high temperature processed aluminum alloy body.

In the aluminum alloy containing 2.0% or more of Mg used in the present invention, in addition to Mg, grain refinement,
For superplastic formability, improvement of strength, oxidation prevention, etc., and as impurities, Cu up to 2%, Mn up to 2%, Cr up to 1%, Zr up to 1%, Si up to 1%, 1% Fe up to 1%, V up to 1%, Zn up to 2%, Ti up to 0.1%, B up to 0.05%, Be up to 0.05%, and other elements up to 0.05% each. You may include it.

Further, the working at 200 ° C. or higher refers to, for example, superplastic working or warm working, and ordinary cold working below this temperature does not cause the technical problem of the present application.

As a result of investigations, the inventors have found that it is sufficient to etch the surface of the material or apply a dense film to the surface of the superplastic material prior to high temperature processing. It should be noted that the combination of both is more effective.

First, in the invention of claim 1, the material is etched before processing at 200 ° C. or higher. Examples of the etching method include treatment with an aqueous solution containing a chelating agent, etching with a strongly alkaline solution, and etching with a strongly acidic solution.

Each method will be described below. Since the smut does not adhere to the surface in the etching process using the chelating agent-containing aqueous solution, the desmut process is not performed and the process is shortened. The treatment may be either dipping or spraying.

Examples of the chelating agent include aminopolycarboxylic acids such as EDTA or alkali metal salts thereof, and alkali metal salts of aminocarboxylic acids such as picolinic acid.
The concentration is preferably 0.005 mol / l or more. 0.00
If it is less than 5 mol / l, the effect of the chelating agent is insufficient and an oxide film remains, resulting in blackening, poor adhesion and poor corrosion resistance after surface treatment. Further, smut is likely to occur on the surface of the aluminum material and a desmutting process is required.

The pH is not particularly limited, but pH = 1 to 1
It is good because about 4 is easy to handle.

In addition to the chelating agent, the etching solution contains alkaline substances (eg, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide, amines such as triethanolamine). Compounds, alkali metal salts of phosphoric acid / polyphosphoric acid, polyamine compounds such as ethylenediamine, etc.), acidic substances (mineral acids such as hydrochloric acid, carboxylic acids such as citric acid, etc.) and the like. It may also contain a surfactant such as a nonionic surfactant.

The etching temperature is from room temperature to the boiling point,
There is no particular limitation. It may be appropriately selected from the relationship between the amount of oxide film of the sample and the treatment time, but about 40 to 90 ° C. is preferable in terms of treatment time and handling.

The processing time is about several seconds to 30 minutes. It may be appropriately determined from the liquid concentration, temperature, pH, and the amount of oxide film.

Since smut is generated in the etching with the strong alkaline solution, desmutting is preferable.

An aqueous solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide is used as the strong alkaline solution. It may contain a surfactant or the like.

The liquid concentration is preferably about 1 to 15 wt%,
The treatment temperature is from room temperature to about 90 ° C, preferably 40 to 60 ° C.

The treatment time may be appropriately selected depending on the concentration and temperature, but is selected from the range of several minutes to several tens of minutes. Desmut may be immersed in a mineral acid solution such as nitric acid or sulfuric acid.

In etching with a strongly acidic solution, it is desirable to neutralize with a caustic soda solution or the like after the treatment for the surface thereafter.

As the strongly acidic solution, it is preferable to use a mineral acid such as hydrochloric acid, sulfuric acid, nitric acid, chromic acid phosphate or a mixed acid thereof, the liquid concentration is preferably several% to several tens%, and the treatment temperature is from room temperature to room temperature. A temperature of about 90 ° C. is used, but preferably 30 to
It is 60 ° C.

The treatment time may be appropriately selected depending on the concentration and temperature, but is selected from the range of several minutes to several tens of minutes.

According to the second aspect of the present invention, before processing at 200 ° C. or higher, AC electrolysis treatment in an alkaline solution is performed to wash and dissolve (etch) the material and form a dense film.

The alternating current electrolytic treatment in this alkaline solution is described in, for example, JP-A-63-258674 and JP-A-2-1829.
AC electrolysis treatment in an alkaline solution having a bath temperature of 30 to 90 ° C. as disclosed in No. 00.

However, in the case of the high temperature processed body of the aluminum alloy containing 2% or more of Mg as the object of the surface treatment as in the present invention, the plasticity of the treatment liquid is preferable among the above. That is, the electrolysis time is 20 to 40 seconds and the quantity of electricity is 100.
˜200 C / dm ² is preferable. If the electrolysis time is less than 20 seconds, or if the quantity of electricity is less than 100 C / dm ² , the film formation is insufficient and the film becomes uneven. If the electrolysis time exceeds 40 seconds, the quantity of electricity is 200 C / dm ² If it exceeds the range, dusting occurs and the adhesion of the coating film decreases.

In the inventions of claims 3 and 4, 2
Before processing above 00 ° C, a dense film is formed on the material.

Specifically, in the invention of claim 3, 200 ° C.
Prior to the above processing, a hydrated oxidation treatment is performed to form a dense film on the material.

The method of hydration oxidation treatment is not particularly limited and may be 50
Immerse or spray in deionized water at a temperature of ℃ or above.

It may contain an oxidizing agent as disclosed in JP-A-59-212578, and also JP-A-64-
It may also contain amine compounds such as triethanolamine as disclosed in 34731.

The treatment time may be appropriately determined from the relationship with the treatment liquid temperature, the required film thickness, etc., but it can usually be selected from the range of about 1 to 60 minutes.

The pH is preferably about 4-11 and less than 4 and 1
If it exceeds 1, the film formation is insufficient or not formed, which is unsuitable.

However, in the case of a high temperature processed body of an aluminum alloy containing 2% or more of Mg as the object of surface treatment as in the present invention, there is a preferable composition of the treatment liquid among the above.

That is, the concentration of sulfate group is 500 ppm or less, the concentration of phosphate group is 100 ppm or less, the concentration of alkali metal salts such as K and Na is 200 ppm or less, the concentration of heavy metal salts such as Fe and Cu is 200 ppm or less, and the pH is 6 to 6. 8. It is preferable to use water having a liquid temperature of 80 ° C. or higher. When the pH is 4 or more and less than 6, it takes time to form a film. If the pH exceeds 8 and is 11 or less, a sparse film is formed. Liquid temperature is 80
If the temperature is less than ℃, the corrosion resistance is insufficient and the coating film adhesion tends to decrease.

In the fourth aspect, a dense film is formed on the material by performing anodizing treatment before processing at 200 ° C. or higher.

This anodizing treatment may be carried out by a general method, for example, electrolytic treatment in an aqueous solution of sulfuric acid, oxalic acid, phosphoric acid, boric acid or the like. The film thickness is 0 depending on the purpose.
It may be determined from the range of about 1 to 30 μm.

Finally, in the fifth aspect of the invention, etching is performed before processing at 200 ° C. or higher, and further surface treatment is performed by any one of AC electrolytic treatment, hydration oxidation treatment and anodization treatment in an alkaline aqueous solution. Thus, the effects of both the above etching and the dense film can be obtained. This method increases the number of processing steps but provides the best performance.

[0044]

The oxide film formed before high temperature processing has many defects such as rolling oil, foreign matter (fine dust, etc.), and segregation of Mg. Such an oxide film is taken into the newly formed oxide film during high temperature processing to form a thick and brittle black film, which causes problems such as reduced corrosion resistance, poor coating adhesion and poor appearance.

If such an oxide film is removed in advance prior to high temperature processing, the oxide film newly formed during high temperature processing will not be colored and a beautiful appearance can be maintained. In addition, since Mg segregated near the outermost surface, rolling oil, and foreign matter are removed, it is possible to remove Mg even on the surface after high temperature processing.
Segregation is reduced and impurities are reduced, so that corrosion resistance and coating adhesion are improved.

For such a purpose, etching treatment with an aqueous solution containing a chelating agent, a strong alkali or a strongly acidic solution is suitable.

It can also be achieved by an alternating current electrolytic treatment in an alkaline solution. In this case, it is due to the cleaning effect by hydrogen bubbles during the cathode reaction and the surface dissolution effect during the anode reaction.

On the surface to which a dense film is positively applied, the oxidation of aluminum does not proceed, so that the amount of newly formed oxide film during high temperature processing is small and a beautiful appearance can be maintained. Corrosion resistance and coating film adhesion are improved. A hydrated oxide film (boehmite, aluminum hydroxide) by hydration oxidation treatment, an anodized film (aluminum oxide), or a film formed by AC electrolytic treatment in an alkaline solution (aluminum oxide) may be used for this purpose. it can. A part of these films undergoes a dehydration reaction during high-temperature processing to form crystalline aluminum oxides, so that corrosion resistance and coating film adhesion are improved.

Further, after the etching, by performing a surface treatment such as an AC electrolysis treatment in an alkaline aqueous solution, a hydration oxidation treatment, or an anodic oxidation treatment, the two effects described above result in very good corrosion resistance, coating adhesion, and You can get a beautiful appearance.

[0050]

【Example】

(Example 1) Mg 4%, Mn 1%, Be 0.00
Superplastic aluminum alloy material containing 5% (plate thickness 1.6 m
m) is etched under the conditions shown in Table 1 and washed with water.
Dried. Next, the temperature was maintained at 500 ° C. for 10 minutes, superplastic blow molding was performed in the atmosphere at 5 MPa so that the plate thickness after molding was 0.8 mm, and then naturally cooled. The obtained alloy plate is S
ST test (JIS Z 2371-1988 compliant, 20
00 hours), a tape adhesion test (Sekisui polyester tape, No. 21, 18 mm width was applied, and 90 ° peel strength was measured), and the appearance was visually checked.
The results are shown in Table 2.

Comparative Example 1 The same processing as in Example 1 was carried out except that the etching treatment before superplastic blow molding was omitted. The results are shown in Table 2.

Comparative Example 2 Instead of the etching treatment before superplastic blow molding, 70% of a 2% aqueous solution of trisodium phosphate was used.
℃, 3 minutes treatment, 90% phosphoric acid and 10% acetic acid aqueous solution
The same treatment as in Example 1 was carried out except that the treatment was carried out at 30 ° C. for 30 minutes. The results are shown in Table 2.

[0053]

[0054]

From Table 2, when etching was carried out as in claim 1 of the present invention and then hot working was carried out, Comparative Example 1 which was hot-worked without treatment or Comparative Example which was hot-worked after being treated with a liquid having no etching ability It can be seen that the corrosion resistance, tape adhesion strength, and appearance are superior to those of No. 2.

Example 2 A test was conducted in the same manner as in Example 1 except that the surface treatment shown in Table 3 was performed instead of the etching treatment in Example 1. Hydration oxidation treatment: Pure water 90 ° C × 3 minutes immersion Hydration oxidation treatment: 100g / l TEA, 90 ° C × 1 minute immersion Anodizing treatment: 15% H ₂ SO ₄ , 20 ° C, current density = 1.5A / dm ² Electrolysis time 10 minutes Alkaline AC electrolysis: Sodium phosphate electrolyte, pH 10.5, 70 ° C, Electrolysis time 120 seconds

[0057]

From Table 3, when surface treatment such as hydration oxidation treatment, anodic oxidation treatment and alkaline alternating current electrolysis treatment is carried out and then high temperature processing is carried out as in the invention of claims 2, 3 and 4 of the present invention, Table 2
It can be seen that the corrosion resistance, the tape adhesion strength, and the appearance are excellent as compared with Comparative Example 1 which was subjected to high temperature processing without treatment and Comparative Example 2 which was treated with a liquid having no etching ability and then subjected to high temperature processing.

Example 3 The same process as in Example 1 was carried out except that the etching process and the surface treatment were used in combination, instead of the etching process in Example 1. The results are shown in Table 4.

[0060]

In addition, from this table, as in claim 5 of the present invention, surface treatment such as hydration oxidation treatment, anodic oxidation treatment and alkaline alternating current electrolysis treatment was carried out, and then high temperature processing was carried out. It can be seen that the corrosion resistance, tape adhesion strength, and appearance are also superior to those of Example 2 and Example 2.

[0062]

EFFECTS OF THE INVENTION As is clear from the above examples, according to the method for producing a high temperature processed aluminum alloy body of the present invention, corrosion resistance, coating film adhesion and appearance are all excellent, and construction materials and materials for transportation equipment are excellent. It can be preferably used for ornaments, articles and the like. Moreover, since the surface treatment is performed before processing, coil treatment is possible and the productivity is excellent.

Front page continued (72) Inventor Masahiro Kurata 4-3-18 Nihombashi Muromachi, Chuo-ku, Tokyo Sky Aluminum Co., Ltd. (72) Inventor Mamoru Matsuo 4-3-1-18 Nihombashi Muromachi, Chuo-ku, Tokyo Sukai Inside Aluminum Co., Ltd. (72) Inventor Tsutomu Tagata 4-3-18 Nihombashi Muromachi, Chuo-ku, Tokyo Inside Sky Aluminum Co., Ltd.

Claims (5)

[Claims] 1. A method for producing an aluminum alloy high temperature processed body, which comprises processing an aluminum alloy containing 2.0% or more of Mg (the same applies hereinafter by weight) at a high temperature of 200 ° C. or more after etching. .. 2. An aluminum alloy containing 2.0% or more of Mg is subjected to an alternating current electrolytic treatment in an alkaline aqueous solution,
A method for manufacturing an aluminum alloy high temperature processed body, which comprises processing at a high temperature of 200 ° C. or higher. 3. A method for producing a high temperature processed aluminum alloy body, which comprises subjecting an aluminum alloy containing 2.0% or more of Mg to a hydration oxidation treatment and then processing at a high temperature of 200 ° C. or higher. 4. A method for producing an aluminum alloy high-temperature processed body, which comprises subjecting an aluminum alloy containing 2.0% or more of Mg to anodization and then processing at a high temperature of 200 ° C. or more. 5. An aluminum alloy containing 2.0% or more of Mg is etched and further subjected to surface treatment such as AC electrolytic treatment in an alkaline aqueous solution, hydration oxidation treatment or anodization treatment, and then 200 ° C. or higher. A method for manufacturing an aluminum alloy high temperature processed body, which comprises processing at a high temperature.