JP5192986B2 - Aluminum alloy material with excellent surface stability - Google Patents

Description

The present invention is suitable for use in automobiles, particularly automobile panels, and has excellent surface stability that can maintain good water wettability during chemical conversion treatment, together with the effect of press oil containing an ester component until the degreasing treatment. It was about the aluminum alloy material. The aluminum alloy material as used in the field of this invention means the aluminum alloy manufactured by various manufacturing methods, such as a rolled plate, rolled foil, an extrusion shape material, a forging material, and a casting material.

  As is well known, conventionally, various aluminum alloy materials (hereinafter referred to as Al for aluminum) have been used for transportation equipment such as automobiles, ships, airplanes or vehicles, machines, electrical products, architecture, structures, optical equipment, and members and parts of equipment. Is also widely used depending on the characteristics of each alloy.

  In recent years, in response to global environmental problems caused by exhaust gas and the like, improvement in fuel consumption has been pursued by reducing the weight of automobile bodies. For this reason, instead of the steel material used conventionally, specific gravity is about 1/3 of iron, and the use to the automobile body of the aluminum material which has the outstanding energy absorption is increasing.

  When an aluminum alloy is used as an automobile panel, formability, weldability, adhesion, chemical conversion treatment, corrosion resistance after painting, aesthetics, and the like are required. The method of manufacturing an automobile panel using an aluminum alloy is as follows: 1) molding (cutting out to a predetermined size, press molding to a predetermined shape), 2) joining (welding and / or bonding), 3) chemical conversion treatment (with a cleaning agent) Degreasing → Surface adjustment by colloidal titanate treatment → Zinc phosphate treatment), 4) Coating (undercoating by electrodeposition coating → intermediate coating → topcoating), which is basically the same as when using conventional steel plates .

  On the other hand, modularization of automobile parts is progressing, and there is a tendency that a period from when the aluminum alloy plate itself is manufactured until the vehicle body manufacturing process starts from the above-described automobile panel becomes longer than before.

  The modularization of automobile parts is a method in which individual parts that are directly attached to a vehicle body at an automobile manufacturer are sub-assembled in advance at a parts company and then attached to the car body. The main purpose is to improve production efficiency by simplifying difficult tasks in automobile manufacturers. It also has the effect of shortening the production process and reducing work in progress. Although the burden on the parts company increases, it is effective in reducing the cost of the automobile company and the parts company as a whole, and consequently contributes to the cost reduction of the automobile.

  Until now, the direct route from the light pressure manufacturer to the automobile manufacturer has been the main transport route for aluminum alloy sheets for automobiles. However, if modularization progresses, it will be forced to go through a parts company, and the period from the time when the aluminum alloy plate itself is manufactured until the above-described manufacturing process is entered becomes inevitably longer than before. Therefore, the process which covers with an oil is performed from a viewpoint of the surface protection of an aluminum alloy plate.

  However, in such a case, the surface characteristics of the aluminum alloy plate inevitably change over time, which adversely affects adhesiveness, chemical conversion properties, and paintability. Especially, it is known that the degreasing property at the time of chemical conversion treatment deteriorates with a change with time, the chemical conversion treatment film becomes difficult to adhere, and consequently the corrosion resistance is affected.

  For this reason, conventionally, it has concentrated on improving chemical conversion processability etc. by removing the magnesium on the surface of the aluminum alloy containing magnesium (hereinafter, magnesium is also referred to as Mg) (see Patent Documents 1 to 5). . However, by simply removing Mg, it is not possible to obtain an excellent surface stability with little change in surface characteristics over time.

  Moreover, in order to obtain an aluminum alloy plate excellent in water wettability and adhesion particularly after degreasing, the Mg amount and OH amount of the surface film of the aluminum alloy plate are adjusted, and the antirust oil is applied within 14 days after the surface adjustment. A coated aluminum alloy sheet for an automobile body sheet has also been proposed (see Patent Document 6). However, by simply applying a rust preventive oil within 14 days after the surface adjustment to protect the surface, it is not possible to obtain an excellent surface stability with little change in surface characteristics over time.

Further, in order to obtain an aluminum alloy plate with little change in surface characteristics over time, a metal aluminum substrate of an aluminum alloy plate containing 2 to 10% by weight of Mg, an aluminum phosphate film formed on the substrate, There has also been proposed an aluminum alloy plate for an automobile body in which an aluminum oxide film formed on the phosphate film and a rust preventive oil are further coated thereon (see Patent Document 7). In addition, for the purpose of preventing wrinkles during the conveyance of aluminum alloy and improving the drawing workability, it is also proposed that the surface of the aluminum alloy is covered with a molding oil (press oil) containing an ester component (non-patent) Reference 1).
JP 06-256980 A (full text) Japanese Patent Application Laid-Open No. 06-256881 (full text) Japanese Patent Laid-Open No. 06-220564 (full text) Japanese Unexamined Patent Publication No. 04-214835 (full text) JP 02-115385 A (full text) JP 2006-200007 (full text) Japanese Patent No. 2744697 (full text) Tanaka, Kobayashi, and Kurata, “Examination of degreasing properties of aluminum surface model oxides”, Proceedings of the 111th Autumn Meeting of the Light Metal Society, 167, 2006, pp.331-332

  In the above-mentioned patent document 7, in the example, a comparative evaluation is performed with reference to a material left for one week after the preparation of the sample. However, the above-described time-dependent change in the surface characteristics of the aluminum alloy has the largest amount of change from immediately after sample preparation to about one week, and the change thereafter is relatively small. Therefore, the stability of the target surface characteristics is not guaranteed with the evaluation result shown in Patent Document 7. In addition, as disclosed in Non-Patent Document 1, the ester component in the press oil acts as an oil agent and improves the drawing processability of the alloy, but the degreasing property during the chemical conversion treatment is reduced (that is, Surface stability is reduced).

  In particular, in applications such as automobiles, water wettability, paintability, adhesion durability, welding stability, and the like during chemical conversion treatment of aluminum alloy materials are required. In particular, the aluminum alloy material is shipped from the manufacturer's factory, pressed, etc., and then degreased during chemical conversion treatment. In addition to the effect of press oil, it has good water wettability during chemical conversion treatment. There is a demand for an aluminum alloy material having excellent surface stability that can be maintained.

The present invention solves the above-mentioned problem, together with the effect of press oil containing an ester component until the degreasing of the chemical conversion treatment, as well as Mg containing excellent surface stability that can maintain good water wettability during the chemical conversion treatment An object is to provide an aluminum alloy material .

  In order to achieve the above object, the invention according to claim 1 of the present invention is the Mg-containing aluminum having a hydrated phosphate or hydrogen phosphate having a phosphorus concentration of 2.0 atomic% or more on the surface. Since the press oil containing the ester component is applied to the surface of the alloy material, the water wettability during the chemical conversion treatment is maintained along with the effect of the press oil containing the ester component until the degreasing treatment. An aluminum alloy material having excellent surface stability can be obtained.

  As described above, the invention according to claim 1 of the present invention is an Mg-containing aluminum alloy material having a hydrated phosphate or hydrogen phosphate having a phosphorus concentration of 2.0 atomic% or more on the surface. Since the surface is coated with press oil containing an ester component, the surface stability that can maintain good water wettability during chemical conversion treatment as well as the effect of press oil containing an ester component until the degreasing treatment. An aluminum alloy material excellent in properties can be obtained.

  Hereinafter, the present invention will be described in more detail while illustrating embodiments.

(Configuration of aluminum alloy material with excellent surface stability according to the present invention)
The aluminum alloy material excellent in surface stability according to the present invention is formed on the surface of an Mg-containing aluminum alloy material having a hydrated phosphate or hydrogen phosphate having a phosphorus concentration of 2.0 atomic% or more on the surface. A press oil containing an ester component is applied. Thereby, the aluminum alloy material excellent in the surface stability which can maintain the favorable water wettability at the time of chemical conversion treatment with the effect of the press oil containing an ester component until the degreasing of chemical conversion treatment is obtained.

  Hereinafter, the reason for the above configuration will be described in detail.

  The present inventors paid attention to the fact that in recent years, the entire period of time from when an aluminum alloy material is shipped from a manufacturer's factory to press forming and degreasing at the time of chemical conversion treatment has become longer. That is, attention was paid to the fact that the time covered with oil inevitably increases from the viewpoint of surface protection of the aluminum alloy material. Further, since the aluminum alloy material is also subjected to press molding before chemical conversion treatment, the oil is also required to have improved moldability. Surface stability that can sufficiently degrease during chemical conversion treatment and maintain good water wettability during chemical conversion treatment even when oil that satisfies both surface protection and moldability is applied. We have eagerly investigated whether aluminum alloy materials with excellent properties can be produced. As a result, the material and conditions of the surface treatment of the aluminum alloy material were devised, and the Mg-containing aluminum alloy material having a hydrated phosphate or hydrogen phosphate having a phosphorus concentration of 2.0 atomic% or more on the surface. It has been found for the first time that the above object can be achieved if a press oil containing an ester component is applied to the surface.

  With such a configuration, it is presumed that the above object was achieved because the properties of the aluminum alloy material surface as shown in FIG. That is, in FIG. 1, the surface of an aluminum alloy material containing Mg (herein, the aluminum alloy is simply referred to as an aluminum alloy, and the surface includes, for example, Mg-Ox that already exists). Surface treatment with an aqueous solution of dihydrogen phosphate adjusted to a pH of less than 4 (for example, an aqueous solution of aluminum dihydrogen phosphate), a hydrated phosphate layer is formed on the surface of the aluminum alloy material. The layer of hydrated phosphate or hydrogen phosphate has a strong chemical bond with the aluminum alloy material via oxygen (-O-), while on the opposite side of the aluminum alloy material, It is considered that the OH group remains, becomes a moisturizing component, and inhibits the adsorption of the ester component in the press oil.

  Thereby, until the time of degreasing the chemical conversion treatment, the hydrated phosphate and the press oil containing the ester component are not bonded to the surface of the aluminum alloy material, and a predetermined amount of press oil is stably held. Therefore, the effect of press oil can be maintained. Moreover, since the press oil containing an ester component is not bonded to a hydrated phosphate, it can be sufficiently removed during degreasing and can maintain good water wettability during chemical conversion treatment. From the above, it is considered that an aluminum alloy material excellent in surface stability has been realized.

  The present invention is described in detail below.

(Al alloy)
The Al alloy used in the present invention is defined by AA and JIS, which are manufactured by various manufacturing methods such as a rolled plate, a rolled foil, an extruded profile, a forged material, and a cast material, depending on the use of the Al alloy material. Alternatively, various Al alloys similar to JIS can be used, but it is essential to contain Mg. In this case, the Mg content is desirably 0.25% by weight or more. In the case of an Al alloy having a lower Mg content than this, the problem to be solved by the present invention does not appear.

  The upper limit of the Mg content is not particularly limited, but it is preferably up to 5.5% by mass considering the balance of various characteristics when used as a structural member.

  As a specific example, when used for automobiles, a high-strength aluminum alloy material having a 0.2% proof stress of 100 MPa or more is preferable. As an aluminum alloy satisfying such characteristics, it is a general-purpose alloy having a relatively high proof stress such as 5000 series, 6000 series, and 7000 series, which is generally used for this kind of structural member, and is tempered as necessary. Aluminum alloys are preferably used. It is preferable to use a 6000 series aluminum alloy in terms of excellent age-hardening ability and a relatively small amount of alloying elements and excellent scrap recyclability and formability.

(Hydrated phosphate)
The dihydrogen phosphate of the present invention is dihydrogen phosphate (H ₂ PO ₄ ) in the salt. Is a general term for salts containing This dihydrogen phosphate is preferably a salt of at least one metal selected from Al, K, Ca, Mn, and Li. More preferably, Al is selected.

  Incidentally, an aluminum oxide film is inevitably formed on the surface of the aluminum alloy material, and the hydrated phosphate of the present invention is present or scattered on the aluminum oxide film or in the oxide film. Therefore, in the present invention, having a hydrated phosphate on the surface of the aluminum alloy material specifically means such a surface state.

(Method of adhering hydrated phosphate to aluminum alloy material surface)
The adhesion of these hydrated phosphates to the surface of the aluminum alloy material is caused by treatment with an aqueous solution containing dihydrogen phosphate during or outside the production process of the aluminum alloy material (hereinafter collectively referred to as hydrogen phosphate). (Also called salt treatment). In the production process of aluminum alloy material, for example, cooling water after heat treatment such as solution treatment and annealing, cooling water during quenching treatment, or washing water in the washing process contains these dihydrogen phosphates (dissolution) It is possible to perform the treatment by using an aqueous solution (hereinafter collectively referred to as a dihydrogen phosphate aqueous solution).

In addition, the above dihydrogen phosphate aqueous solution is used as cooling water in the solution treatment step in which solution treatment and quenching treatment are performed, as in the following aluminum alloy material production step of the present invention (referred to as the production step of the present invention). In this case, since the aluminum alloy material is maintained at a high temperature, the reactivity between the surface of the aluminum alloy material and the chemical in the dihydrogen phosphate aqueous solution is improved, and the phosphorus concentration on the surface of the aluminum alloy material is increased. Therefore, in the following conventional aluminum alloy material manufacturing process (referred to as a conventional manufacturing process), acid cleaning was required after cooling, but not only is this acid cleaning unnecessary, but also in a dihydrogen phosphate aqueous solution. The concentration of the drug can be reduced. Therefore, the cost of manufacturing the aluminum alloy material can be reduced. Moreover, by adopting such a method for producing an aluminum alloy material of the present invention, it is possible to ensure degreasing stability without removing magnesium on the surface of the aluminum alloy material after cold rolling.
Production process of the present invention:
Ingot → Soaking → Hot rolling → Cold rolling → Solution treatment → Quenching (dihydrogen phosphate aqueous solution) → Pre-aging Conventional manufacturing process:
Ingot → Soaking → Hot rolling → Cold rolling → Solution treatment → Quenching (industrial water) → Pre-aging → Acid cleaning

The temperature of the dihydrogen phosphate aqueous solution can be room temperature, but it may be heated. The treatment time is not particularly limited, and may be appropriately selected depending on other treatment conditions such as the concentration and temperature of the aqueous solution, or a desired amount of adhesion to the aluminum alloy material surface. For example, when aluminum dihydrogen phosphate {Al (H ₂ PO ₄ ) ₃ } is used as a drug and the aqueous solution concentration is 1 to 10 g / L (where “L” means liter), an aluminum alloy The material may be immersed or sprayed in these aqueous solutions for 1 to 10 seconds. In addition, when the aqueous solution concentration is 1 g / L, the pH is 3.4 when the pH is 3.4 or 10 g / L. In the present invention, the pH of the aqueous dihydrogen phosphate solution is 4 It only needs to be adjusted so that it is less.

  In addition, as described above, when the dihydrogen phosphate aqueous solution is used as the cooling water while the aluminum alloy material is kept at a high temperature, the surface of the aluminum alloy material and the chemical in the dihydrogen phosphate aqueous solution Therefore, even when a solution whose aqueous solution concentration is as low as 0.05 g / L and whose pH is adjusted to 6.6 is used, the phosphorus concentration on the surface of the aluminum alloy material is a predetermined value (2. 0 atomic% or more).

  Also, by adding phosphoric acid to a dihydrogen phosphate aqueous solution and treating the aluminum alloy material using a liquid whose pH is adjusted to 2.5 or more and less than 4, good water wettability during chemical conversion treatment can be obtained. In addition to producing an aluminum alloy material with excellent surface stability that can be maintained, turbidity caused by undissolved components occurs in the dihydrogen phosphate aqueous solution when the aluminum alloy material is treated with hydrogen phosphate. (= Transparent), occurrence of pipe clogging is suppressed, and the frequency of maintenance can be reduced.

  As described above, when an aqueous dihydrogen phosphate solution is used as the cooling water while the aluminum alloy material is kept at a high temperature, the aqueous solution concentration is as low as 0.05 g / L and the pH is 6 Surface stability that can achieve the predetermined phosphorus concentration (2.0 atomic% or more) and maintain good water wettability during chemical conversion treatment even if the one adjusted to .6 is used In addition to being able to produce excellent aluminum alloy materials, turbidity due to non-dissolved components does not occur in the above-mentioned dihydrogen phosphate aqueous solution when the aluminum alloy material is treated with hydrogen phosphate (= transparent) The occurrence of clogging of piping is suppressed, and the frequency of maintenance can be lowered.

  When attaching hydrated phosphate to the surface of the aluminum alloy material, it is necessary to remove the aluminum oxide film or magnesium already formed on the surface of the aluminum alloy material by pretreatment such as cleaning with etching. Nothing at all. However, in the above-described manufacturing process of the aluminum alloy material, for example, according to another purpose of the process, after removing the aluminum oxide film and magnesium on the surface of the aluminum alloy material by pretreatment, the hydrated phosphate is converted into aluminum. It is naturally allowed to adhere to the surface of the alloy material. Even in this case, since an aluminum oxide film is immediately formed on the surface of the aluminum alloy material, the hydrated phosphate of the present invention is present or scattered on the aluminum oxide film or in the oxide film.

(Method of applying press oil containing ester component to aluminum alloy material treated with dihydrogen phosphate aqueous solution)
Next, a method of applying press oil containing an ester component to the aluminum alloy material treated with the dihydrogen phosphate aqueous solution will be described. For example, the aluminum alloy material may be simply immersed in press oil containing ethyl oleate as an ester component. The method and conditions for applying the press oil containing the ester component are not particularly limited, and general methods and conditions for applying the press oil can be widely applied. Further, the ester component is not limited to ethyl oleate, and various substances such as butyl stearate and sorbitan monostearate can be used.

(About surface stability)
Next, the surface stability of the coating with press oil containing the ester component will be described. After leaving the press oil containing the ester component as it is applied at 15 to 35 ° C. in an environmental chamber of 50 to 90% RH for 6 months, degrease with a normal alkaline degreasing agent to determine the water wetted area ratio. The evaluation is 100%. This is because press oil containing an ester component that satisfies the surface protection and press formability of the aluminum alloy material is shipped from the factory of the manufacturer of the aluminum alloy material and remains applied for a long time until the degreasing treatment. Even so, it is shown that it is possible to provide an aluminum alloy material excellent in surface stability with little change with time and capable of maintaining good water wettability during chemical conversion treatment.

  Examples of the present invention will be described below. A 6000 series 6022 standard aluminum alloy cold-rolled sheet (plate thickness: 1 mm), a test piece having a length of 70 mm and a width of 150 mm was used. This 6022 standard aluminum alloy plate contains Mg: 0.55 mass%, Si: 0.95 mass%, and has a 0.2% proof stress of 230 MPa.

  When carrying out the pretreatment prior to the hydrogen phosphate treatment, after immersion or spraying in a commercial weak alkaline degreasing solution at 60 to 90 ° C. for 1 to 10 seconds, to 1 to 20 mass% nitric acid or sulfuric acid at 50 to 90 ° C. It was immersed or sprayed for 1 to 10 seconds, and then washed with water.

  Under the pretreatment conditions, the aluminum oxide film and magnesium already formed on the surface of the test piece are removed. However, since an aluminum oxide film is immediately formed on the surface of the test piece, the hydrated phosphate adhering to the surface of the test piece by the hydrogen phosphate treatment is deposited on or in the aluminum oxide film. It will be present or scattered.

Concentration of an aqueous solution in which aluminum dihydrogen phosphate {Al (H ₂ PO ₄ ) ₃ } is used as a chemical and the test piece is immersed in an aluminum alloy test piece that has been or has not been pretreated. Were prepared so as to be 1 g / L and 10 g / L, respectively. These are referred to as Examples 1 to 4 (see Table 1 below). The pH of the aqueous solution at this time was 3.4, 2.4, 3.4, and 2.4, respectively. In addition, using the above-mentioned chemicals, phosphoric acid (85% purity reagent manufactured by Wako Pure Chemical Industries) in the amount shown in Table 1 is added to each aqueous solution having a concentration of 0.1 g / L to 0.4 g / L. Then, an aqueous dihydrogen phosphate solution having a pH adjusted to 2.5 to 3.8 was prepared. Let these be Examples 5-8.

In addition, using the above chemicals, do not pretreat the dihydrogen phosphate aqueous solution with concentrations of 1 g / L, 0.05 g / L and no added phosphoric acid, and pH of 3.4 and 6.6, respectively. Examples obtained by soaking aluminum alloy test pieces (each 3 pieces) heated at 500 ° C. for 20 minutes for 10 seconds are referred to as Examples 9 and 10 (see Table 1 below).

In addition, for comparison, a sample in which the test piece was not immersed in an aqueous solution using the above-described agent and an aqueous solution concentration of 0.1 g / L were prepared. These are referred to as Comparative Examples 1 to 4 (see Table 2 below). The pH values of the aqueous solutions of Comparative Examples 2 and 4 were all 6.4. Using the above chemicals, add phosphoric acid (85% purity reagent manufactured by Wako Pure Chemical Industries, Ltd.) in the amount shown in Table 2 per liter of aqueous solution to each of 0.1 g / L aqueous solution and 0.4 g / L aqueous solution. Then, an aqueous dihydrogen phosphate solution having a pH adjusted to 2.0 was prepared. These are referred to as Comparative Examples 5 and 6. In each of Examples 1 to 8, Comparative Example 2, and Comparative Examples 4 to 6, the test piece was immersed for 10 seconds.

In addition, the surfaces of the test pieces of Examples 1 to 10 and Comparative Examples 1 to 6 where the predetermined hydrogen phosphate treatment was completed were analyzed by X-ray photoelectron spectroscopy. The measurement method and conditions are as follows. Here, the surface phosphorus concentration is determined by analyzing the composition in the depth direction from the surface to a depth of 200 nm, excluding the outermost surface, and the maximum phosphorus concentration (atomic%) is the phosphorus concentration (atomic%) on the substrate surface layer. ). This is because the state of the outermost surface cannot obtain an accurate numerical value due to dirt.
(Measurement method and conditions)
Apparatus: Quantera SXM manufactured by Physical Electronics
Fully automatic scanning X-ray photoelectron spectrometer X-ray source: Monochromatic AlKa
X-ray output: 43.7W
X-ray beam diameter: 200 μm
Photoelectron extraction angle: 45 °
Ar ⁺ sputtering speed: about 4.6 nm / min in terms of SiO ₂

  Note that the method for measuring the surface phosphorus concentration is not limited to X-ray photoelectron spectroscopy (XPS), and an analysis method such as fluorescent X-ray or high-frequency glow discharge emission surface analysis (GDS) may be used in addition to XPS. it can.

  As a result, as shown in Table 1 above, the surface phosphorus concentrations of the examples were 2.1 to 3.3 for Examples 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10, respectively. 2.4-4.4, 2.2-3.6, 2.4-4.5, 3.2-3.8, 2.8-3.3, 3.2-4.0, 2. They were 0-2.6, 3.8-4.7, and 2.3-3.2. Further, as shown in Table 2 above, the surface phosphorus concentrations of the comparative examples are 0.8 to 1.2, 1.1 to 1.6, respectively, for the comparative examples 1, 2, 3, 4, 5 and 6. They were 0.6 to 1.2, 1.3 to 1.6, 0.9 to 1.6, and 1.1 to 1.9.

Moreover, the presence or absence of undissolved components was determined by visually observing the turbid state of the treatment liquid after the predetermined hydrogen phosphate treatment was completed. As a result, Examples 1 to 4 and 9 and Comparative Examples 2 and 4 in which hydrogen phosphate treatment was performed using a dihydrogen phosphate aqueous solution having a drug concentration of 1 to 10 g / L and no phosphoric acid added thereto. In the treatment liquid, turbidity due to non-dissolved components was observed. This non-dissolved component was a mixture of crystalline and non-crystalline aluminum phosphate (AlPO ₄ ). On the other hand, Examples 5 to 8 in which hydrogen phosphate treatment was performed using an aqueous solution of dihydrogen phosphate to which phosphoric acid was added at a drug concentration of 0.1 to 0.4 g / L, and the drug concentration was 0. In the treatment liquids of Example 10 and Comparative Examples 5 and 6 in which hydrogen phosphate treatment was performed using an aqueous solution of dihydrogen phosphate without addition of phosphoric acid at 0.05 g / L, it was attributed to insoluble components. No turbidity was observed (transparent). In Comparative Examples 5 and 6, although no turbidity due to non-dissolved components was observed, the critical water-wetting area rate was significantly lower than the standard 90% as described later.

  Next, the test pieces (Examples 1 to 10, Comparative Examples 2 and 4 to 6) treated with the dihydrogen phosphate aqueous solution and the test pieces (Comparative Examples 1 and 3) not treated with the dihydrogen phosphate aqueous solution. ) Was immersed in press oil containing ethyl oleate as an ester component.

  Next, in order to investigate the temporal stability of the surface of the test piece coated with the press oil containing the ester component, the following test was performed. The press oil containing the ester component as it was applied was left at 15-35 ° C. in an environmental chamber of 50-90% RH for 6 months. And 6 months later, the water wetted area ratio (only one side) with respect to the area of the test piece when immersed in a commercially available weak alkaline degreasing liquid (temperature: 40 ° C.) for automobiles for 2 minutes was measured. Becomes). Thereby, the water wettability (stable chemical conversion property) at the time of chemical conversion treatment can be evaluated. As a result, the water wetted area ratios of Examples 1 to 10 (in addition, for Examples 9 and 10 each average value of 3) cleared 90% of the standard (see Table 1 above). This shows that the surface characteristics of the aluminum alloy material are stable without changing over time even when left in a humid environment or the period of time left is prolonged due to the modularization of the automobile parts described above. However, the water wetted area ratios of Comparative Examples 1, 2, 3, 4, 5 and 6 are 40%, 55%, 0%, 33%, 38% and 52% (see Table 2 above), which is 90% of the standard. % Significantly below. This indicates that the surface characteristics of the aluminum alloy material change with time.

  As in Examples 5 to 8 described above, the concentration of the aqueous solution of aluminum dihydrogen phosphate is as low as 0.1 g / L to 0.4 g / L, and the predetermined amount of phosphoric acid is added thereto, and the pH is adjusted. In the aqueous solution of dihydrogen phosphate adjusted to 2.5 or more and less than 4, the solution equilibrium of the aqueous solution was broken. In addition, the breakdown of the solution equilibrium is important in the reaction of forming a hydrated phosphate or hydrogen phosphate on the surface of the aluminum alloy material. Dihydrogen phosphate in a free state (not dissociated but dissolved) This led to an increase in the concentration of salt (here, aluminum dihydrogen phosphate). This increase in the concentration of aluminum dihydrogen phosphate in the free state maintains good water wettability during the chemical conversion treatment despite the low concentration of the aqueous solution of aluminum dihydrogen phosphate before the addition of phosphoric acid. It is thought that it brought about a good result of producing an aluminum alloy material with excellent surface stability. Moreover, the detailed mechanism by which the turbidity resulting from an insoluble component does not generate | occur | produce in the said dihydrogen phosphate aqueous solution by processing an aluminum alloy material with the dihydrogen phosphate aqueous solution like Examples 5-8 is the present. Although it is unknown, it is presumed that some kind of interaction was caused by the addition of phosphoric acid to an aqueous solution of aluminum dihydrogen phosphate having a low concentration before adding phosphoric acid.

  As described above, press oil containing an ester component is applied to the surface of an Mg-containing aluminum alloy material having a hydrated phosphate or hydrogen phosphate having a phosphorus concentration of 2.0 atomic% or more on the surface. By setting it as the comprised structure, the aluminum alloy material excellent in the surface stability which can maintain the favorable water wettability at the time of chemical conversion treatment with the effect of the press oil containing an ester component until the time of degreasing of chemical conversion treatment is obtained.

  In this example, as described in Examples 1 to 4 described above, as an aqueous solution of dihydrogen phosphate, an example in which aluminum dihydrogen phosphate was used as a drug was described. However, the present invention is not necessarily limited thereto. Any salt containing dihydrogen phosphate in the salt may be used. Surface stability that maintains good water wettability during chemical conversion treatment by adjusting the pH of an aqueous solution of a salt containing dihydrogen phosphate in this salt to less than 4 and treating the aluminum alloy material with this aqueous solution It is possible to produce an aluminum alloy material excellent in the above. In addition, when the aluminum alloy material is immersed in the dihydrogen phosphate aqueous solution from the state where the aluminum alloy material is maintained at a high temperature of 500 ° C. as in Example 9 described above, the surface of the aluminum alloy material and the dihydrogen phosphate aqueous solution Since the reactivity with a chemical | medical agent improves, even if aqueous solution density | concentration is 1 g / L (same as Example 1, 3), the phosphorus density | concentration on the surface of an aluminum alloy material further increases. Therefore, it is possible to produce an aluminum alloy material excellent in surface stability that can maintain better water wettability during chemical conversion treatment.

  In addition, as in Examples 5 to 8 described above, an aqueous solution in which a predetermined amount of phosphoric acid is added to a predetermined amount of dihydrogen phosphate aqueous solution and the pH is adjusted to 2.5 or more and less than 4, By treating the aluminum alloy material, it is possible not only to produce an aluminum alloy material with excellent surface stability that can maintain good water wettability during chemical conversion treatment, but also when the aluminum alloy material is treated with hydrogen phosphate. In addition, turbidity caused by non-dissolved components does not occur in the dihydrogen phosphate aqueous solution (= transparent), the occurrence of clogging of piping is suppressed, and the frequency of maintenance can be reduced. Moreover, when the aluminum alloy material is immersed in a dihydrogen phosphate aqueous solution from a state where the aluminum alloy material is maintained at a high temperature of 500 ° C. as in Example 10 described above, the surface of the aluminum alloy material and the dihydrogen phosphate aqueous solution Since the reactivity with the drug is improved, the aluminum alloy material has an aqueous solution concentration as low as 0.05 g / L (lower concentration than Examples 5 to 8) and no phosphoric acid is added. The surface phosphorus concentration can achieve a predetermined value (2.0 atomic% or more), and an aluminum alloy material excellent in surface stability that can maintain good water wettability during chemical conversion treatment can be produced. Further, in the case of Example 10, when the aluminum alloy material is treated with hydrogen phosphate, turbidity due to non-dissolved components does not occur in the aqueous solution of dihydrogen phosphate (= transparent), and the occurrence of clogging of the pipe is suppressed. The maintenance frequency can be reduced.

It is a schematic diagram for considering the surface properties of the aluminum alloy material after hydrogen phosphate treatment and press oil application of the present invention.

Claims (1)

  The press oil containing the ester component is applied on the surface of the Mg-containing aluminum alloy material having a hydrated phosphate or hydrogen phosphate having a phosphorus concentration of 2.0 atomic% or more on the surface. Aluminum alloy material with excellent surface stability.

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