JP4579791B2 - Pre-coated aluminum alloy plate and method for producing press-formed product - Google Patents

Description

  The present invention relates to a precoated aluminum alloy plate excellent in press formability and film removal property.

From the viewpoints of downsizing, weight reduction, high designability, and the like, the materials of electronic device housings are changing from steel to aluminum alloys. In particular, most digital camera housings are made of aluminum alloy. Such an electronic device casing is manufactured by first applying lubricating oil to an aluminum alloy plate, press-molding, then solvent cleaning, alkali cleaning, or acid cleaning, and then alumite treatment.
Recently, due to miniaturization, weight reduction, high designability, and complicated shape of electronic devices, high formability that enables complex processing while using high-strength aluminum alloys in the manufacture of electronic device casings. In addition, cost reduction and environmental improvement are strongly desired.

As for high formability, there is a limit to improvement from material properties by reviewing aluminum alloy components and process conditions.
Therefore, there are methods of improving the viscosity of the lubricating oil used for press molding, increasing the oiliness, or increasing the amount of lubricating oil. However, when the viscosity of the lubricating oil is improved or the oiliness is increased, it becomes difficult to remove the oil after molding, and as a result, it is necessary to increase the cleaning in the next process, resulting in an increase in manufacturing cost and a longer cleaning time. Deteriorate production efficiency.

  In addition, there is a demand for cost reduction by improving the production yield and reducing the amount of lubricating oil and cleaning liquid used. Since the lubricity during press molding affects the yield, stable high lubricity is strongly desired during press molding. Furthermore, from the viewpoint of environmental improvement, there is a demand for a direction in which the currently used lubricating oil and cleaning are minimized. In addition, as an aluminum alloy board which improved lubricity, there exists a thing which apply | coated the solid lubricant, for example (patent document 1).

Japanese Patent Laid-Open No. 06-099225

  The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a precoated aluminum alloy plate that is excellent in press formability and easy to process after press forming.

A first invention is a pre-coated aluminum alloy plate for press molding comprising a substrate made of an aluminum alloy plate and an organic resin film formed by baking coating covering at least one surface of the substrate.
The organic resin film can be removed from the substrate by contacting with an alkaline aqueous solution having a pH of 8 or higher, and contains carnauba,
The content of the carnauba in the organic resin film is 0.1 wt% to 30 wt%,
The thickness of the organic resin coating, Ri 0.1μm~30μm der,
The organic resin constituting the organic resin film is an acrylic resin having a molecular weight of 20000 to 100,000, a polyalkylene glycol having a molecular weight of 800 to 35000, or a urethane resin.
The organic resin film contains 1 to 100 parts by weight of resin beads having a particle diameter of 1 to 120 μm and a particle diameter of 1 to 3 times the thickness of the organic resin film. It is in the precoat aluminum alloy plate characterized by the above-mentioned (Claim 1).

The pre-coated aluminum alloy plate includes a substrate made of an aluminum alloy plate and an organic resin film. The organic resin film contains carnauba. Therefore, stable high lubricity can be obtained during press molding. Therefore, it is excellent in press formability, and defects such as galling can be drastically reduced even if molding with high workability is performed, and the yield during press molding can be improved.
In addition, the organic resin film is positively adopted that can be removed from the substrate by contacting with an alkaline aqueous solution having a pH of 8 or higher. Therefore, the organic resin film can be easily removed by performing alkali cleaning in the subsequent process of the press molding process. Further, after the film removal, the alumite treatment can be performed as it is. In addition, the easily removable organic resin film can ensure lubricity during pressing, so there is no need to prepare a separate lubricant or clean it, reducing costs and improving the environment. Excellent in terms of

The second invention is a method for producing a press-formed product of an aluminum alloy plate,
Using a die having a processed hole and a punch that can be inserted into the processed hole, the surface on which the organic resin film is formed of the precoated aluminum alloy plate of the first invention is positioned on the die side and pressed. Pressing process for forming a press-molded product,
A method for producing a press-molded product, comprising: removing the organic resin film from the substrate by bringing the press-molded product into contact with an alkaline aqueous solution having a pH of 8 or more ( Claim 7 ).

This manufacturing method implements at least the pressing step and the film removal step after using the excellent precoated aluminum alloy plate of the first invention. Thereby, the press-molded product excellent in the designability can be obtained.
That is, in the pressing step, as described above, the surface of the precoated aluminum alloy plate on which the organic resin film is formed is positioned on the die side and pressed. In this case, the organic resin film containing the above-mentioned carnauba with excellent lubricity is arranged on the side where the die and the pre-coated aluminum alloy plate are in contact with each other. Excellent press formability with no cracks. Therefore, the yield at the time of press molding can be improved.

Further, after the pressing step, the film removal step is performed. In this film removal step, the press-formed product is brought into contact with an alkaline aqueous solution having a pH of 8 or higher. Here, the pre-coated aluminum alloy plate as the material positively employs an organic resin film that can be removed from the substrate by contacting with an alkaline aqueous solution having a pH of 8 or more. Therefore, by carrying out this film removal step, it is possible to remove the organic resin film from the substrate and remove the film. This makes it possible to easily obtain a press-molded product from which the organic resin film is removed and the substrate is exposed, and the surface is protected by the organic resin film. It will be excellent. Therefore, even if alumite treatment or the like is performed thereafter, the design property is high.
In addition, as described above, after performing a pressing process using a material having a special organic resin film, it can be removed very easily by the above-described film removal process, so a lubricant can be separately prepared, There is no need to perform cleaning, and costs can be reduced and the environment can be improved.

In the pre-coated aluminum alloy plate of the present invention, as described above, a material containing 0.1% by weight to 30% by weight of the carnauba is used with respect to the organic resin film. In this case, extremely excellent lubricity is exhibited during press molding.
When the content of carnauba is less than 0.1% by weight, there is a problem that the effect of improving lubricity by carnauba cannot be obtained sufficiently. Moreover, when it exceeds 30 weight%, there exists a problem that an organic membrane | film | coat is not fully removed at a film removal process.

The organic resin film has a thickness of 0.1 μm to 30 μm. In this case, the moldability and film removal properties are excellent.
When the film thickness is less than 0.1 μm, the film cannot be uniformly coated due to the roughness of the surface of the aluminum alloy plate. On the other hand, when the thickness exceeds 30 μm, there is a problem that film formation becomes difficult and film removal properties are inferior.

The alkaline aqueous solution is preferably sodium hydroxide.
In this case, it is easy to obtain as an industrial product, and the effect of relatively reducing the cost of the film removal step can be obtained.
The alkaline aqueous solution preferably has a pH of 9-12.
If the alkaline aqueous solution is less than pH 9, the time required to remove the organic film may be prolonged. On the other hand, if the pH exceeds 12, the aluminum alloy plate surface after the organic film is removed is required. There is a risk of dissolution.

Further, it is preferable that the organic resin film can be removed from the substrate within 4 seconds of contact with the alkaline aqueous solution.
In this case, the film removal step can be carried out efficiently, and more preferably within 2 seconds. If the contact time exceeds 4 seconds, it is difficult to increase the efficiency of the film removal process.

Moreover, it is preferable that the film thickness of the said organic resin film is 10 micrometers or less (Claim 4).
In this case, the effect of suppressing the accumulation of resin powder and wax component on the mold during continuous press molding can be obtained.

The organic resin constituting the organic resin film is an acrylic resin having a molecular weight of 20000 to 100,000, a polyalkylene glycol having a molecular weight of 800 to 35000, or a urethane resin .
In this case, the film can be easily removed with an alkaline aqueous solution. Carnauba is easy to contain oil as an inner wax.

In the case of an acrylic resin, when the molecular weight is less than 20000, the lubricity cannot be satisfied, and when it exceeds 100000, film removal becomes difficult.
In the case of polyalkylene glycol, when the molecular weight is less than 800, it is difficult to form a solid film in a normal state, and when it exceeds 35000, it is difficult to paint or remove the film. is there.
In the case of a urethane resin, any molecular weight may be used.

Moreover, it is preferable that the surface of the said organic resin film is apply | coated with the lubricant containing 1 or more types chosen from an oil-based agent, an extreme pressure agent, and a solid lubricant ( Claim 5 ).
Even if such a lubricant is not applied, high lubricity can be obtained by the organic resin film containing the above carnauba. However, when the above lubricity is applied, the lubricity of the organic resin film is further increased. It can be improved and can be applied to extremely severe molding.

Examples of the oily agent include polyol esters, fats and oils, fatty acid esters, higher alcohols, higher fatty acids, and α-olefins.
Examples of extreme pressure agents include chlorine, sulfur, and phosphorus. From the viewpoint of the environment, sulfur and phosphorus are more preferable.
Examples of the solid lubricant include metal soap and grease.
Further, any oil may be used as long as it affects metal according to the use environment.

Further, the organic resin film has resin beads having a particle diameter of 1 to 120 μm and a particle diameter of 1 to 3 times the thickness of the organic resin film. Is contained .
In this case, scratch resistance at the time of molding is improved, handling scratches until press molding is suppressed, and the yield is improved.

If the particle size is 1 part by weight or less, the effect is not recognized, and if it exceeds 100 parts by weight, the effect is not changed and the cost increases.
When the particle diameter is less than 1 times the organic resin film, the resin beads do not protrude from the film and the effect is reduced. Further, when it exceeds 3 times, there is a problem that it becomes difficult for the film to trap the beads and the resin beads are easily dropped.

The surface of the base, it is preferable that surface treatment layer for improving the adhesion between the organic resin film and the substrate is formed (claim 6).
In this case, the adhesion between the organic resin film and the substrate is improved, the moldability of the organic resin film is further improved, and the scratch preventing effect can be further enhanced.

Chromate treatment such as phosphate chromate and chromate chromate as the undercoat layer, and chemical film treatment such as non-chromate treatment with titanium phosphate, zirconium phosphate, molybdenum phosphate and zinc phosphate other than chromium compounds There is a film obtained by (chemical conversion treatment).
The chemical film treatment method includes a reaction type and a coating type, and any method may be adopted in the present invention.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited only to these examples.
In this example, a plurality of types of samples (pre-coated aluminum alloy plates) were prepared as examples and comparative examples of the present invention, and their characteristics were evaluated.

In producing each sample, first, an A1050 aluminum alloy plate having a tempering of H24 and a thickness of 0.8 mm was used as a substrate.
In addition, the substrate was degreased using acetone.

In the coating treatment, a predetermined paint was applied to the substrate after the degreasing treatment by a bar coating method, baked at a temperature of 250 ° C. for 2 minutes, and cured to form each coating film.
In preparing each coating film, acrylic resin (AC), polyalkylene glycol (AG), and urethane resin (UR) are used as resins, and oleic acid (OA) and methyl oleate (OAM) are used as lubricants. ), Tricresyl phosphate (TCP), and calcium stearate (STCa), and polytetrafluoroethylene was used as the resin beads.
These resins, lubricants, resin beads, and carnauba were mixed at a blending ratio shown in Table 1 to form a coating film. In addition, the formed coating film is shown in Table 1 and Table 2.

In this example, each sample was evaluated for formability, scratch resistance, and film removal property.
<Moldability>
Molded using a cylindrical punch hydraulic deep drawing machine. The maximum height that can be formed without breaking the sample was evaluated, and ◎ and ○ were accepted.
(Processing conditions)
Blank diameter: φ110 mm, punch diameter: φ50 mm, punch corner: 5R, wrinkle holding load: 10 kN, molding speed: 100 mm / min.
(Evaluation criteria)
A: 7 mm or more, B: 5 mm or more and less than 7 mm, X: less than 5 mm

<Scratch resistance>
In a Bowden friction test, a hard sphere with a load of 100 g and a diameter of 0.25 inch was slid back and forth on the surface of the sample, and the number of sliding times until the coating film was broken was evaluated. did.
(Evaluation criteria)
◎: 100 times or more, ○: 50 times or more and less than 100 times, ×: less than 50 times

<Film removal>
A specimen of 100 mm × 50 mm was bent at 90 ° in the center in the width direction, immersed in an alkaline aqueous solution (sodium hydroxide aqueous solution, liquid temperature 60 ° C.) stirred with a magnetic stirrer, washed with water, and dried. The presence or absence of the film remained was visually confirmed, and the immersion time was evaluated. ◎ and ○ were accepted.
(Evaluation criteria)
A: Less than 2 seconds, O: 2 seconds or more and less than 4 seconds, X: 4 seconds or more The results of evaluation are as shown in Tables 1 and 2.

As is known from Table 1, Sample E1 to Sample E19 all showed good results in all evaluation items of moldability, scratch resistance, and film removal property.
As is known from Table 2, since the film thickness of Sample C1 was below the lower limit of the present invention, the film could not be uniformly coated, and the moldability and scratch resistance were lowered. Moreover, since the film thickness of the sample C2 exceeded the upper limit of this invention, the film removal property fell.

In Sample C3, since the molecular weight of the resin was below the lower limit of the preferred range of the present invention, the lubricity could not be satisfied and the moldability was lowered. Moreover, since the molecular weight of the resin exceeded the upper limit of the preferable range of the present invention, the sample C4 and the sample C6 were deteriorated in film removal property because the alkaline aqueous solution hardly penetrated into the organic resin film. Moreover, since the amount of resin was less than the minimum of the preferable range of this invention, sample C5 was hard to form a solid membrane | film | coat, and the moldability and damage resistance fell.
In sample C7, the content of carnauba was below the lower limit of the present invention, so that the lubricity was insufficient and the moldability was lowered. Moreover, since the content of carnauba exceeded the upper limit of the present invention in sample C8, most of the organic resin film was covered with carnauba, and the alkaline aqueous solution became difficult to react, and the film removal property decreased.

In Sample C9, since the particle size of the resin beads was below the lower limit of the preferred range of the present invention, most of the organic resin film was covered with the resin beads, the alkaline aqueous solution became difficult to react, and the film removal property decreased. In Sample C10, since the resin beads had a particle diameter exceeding the upper limit of the preferred range of the present invention, the resin beads were easily dropped and the scratch resistance was reduced.
In sample C11, since the content of the resin beads exceeded the upper limit of the preferable range, most of the organic resin film was covered with the resin beads, the alkaline aqueous solution became difficult to react, and the film removal property was lowered.

Claims (7)

In a pre-coated aluminum alloy plate for press molding comprising a substrate made of an aluminum alloy plate and an organic resin film formed by baking coating covering at least one surface of the substrate,
The organic resin film can be removed from the substrate by contacting with an alkaline aqueous solution having a pH of 8 or higher, and contains carnauba,
The content of the carnauba in the organic resin film is 0.1 wt% to 30 wt%,
The thickness of the organic resin coating, Ri 0.1μm~30μm der,
The organic resin constituting the organic resin film is an acrylic resin having a molecular weight of 20000 to 100,000, a polyalkylene glycol having a molecular weight of 800 to 35000, or a urethane resin.
The organic resin film contains 1 to 100 parts by weight of resin beads having a particle diameter of 1 to 120 μm and a particle diameter of 1 to 3 times the thickness of the organic resin film. A precoated aluminum alloy plate characterized by being made.   2. The precoated aluminum alloy sheet according to claim 1, wherein the alkaline aqueous solution is sodium hydroxide.   3. The precoated aluminum alloy plate according to claim 1, wherein the organic resin film can be removed from the substrate within a contact time of 4 seconds with the alkaline aqueous solution.   4. The precoated aluminum alloy sheet according to claim 1, wherein the organic resin film has a thickness of 10 μm or less.   5. The lubricant according to claim 1, wherein the surface of the organic resin film is coated with a lubricant containing at least one selected from an oily agent, an extreme pressure agent, and a solid lubricant. Pre-coated aluminum alloy plate.   The precoated aluminum alloy plate according to any one of claims 1 to 5, wherein a base treatment layer for improving adhesion between the organic resin film and the substrate is formed on the surface of the substrate. .   In the method of manufacturing a press-formed product of an aluminum alloy plate,
  A die having a machined hole and a punch that can be inserted into the machined hole are used, and the surface on which the organic resin film of the precoated aluminum alloy plate according to any one of claims 1 to 6 is formed is formed on the die side. A press process for forming a press-molded product by being pressed at a position;
  A method for producing a press-molded product, comprising: removing the organic resin film from the substrate by bringing the press-molded product into contact with an alkaline aqueous solution having a pH of 8 or more.