JPH0663501A - Al alloy plate excellent in workability - Google Patents

Abstract

PURPOSE:To provide an A1 alloy plate improving a sliding property of the A1 alloy plate and being remarkably improved in press workability without impairing a zinc phosphating treatment. CONSTITUTION:The A1 alloy plate excellent in press workability is constituted of a water glass layer of 0.1-10mum thickness of the dry film on the surface, which improves greatly press workability, and a film applied with rust preventive oil at 0.1-7g/m<2> on the water glass layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy sheet mainly used as a lightweight material for automobiles, and more particularly to an aluminum alloy sheet excellent in press formability (a wide range of aluminum sheets are included).

[0002]

2. Description of the Related Art In recent years, weight reduction of automobile bodies has been actively promoted in order to improve fuel efficiency and exercise performance in response to the global warming problem caused by carbon dioxide. In other words, 10% weight reduction of the vehicle body improves fuel efficiency of 5-10%,
In addition, it has an effect of improving the exercise performance corresponding to the engine power of 25 PS. Aluminum alloy plates have been attracting attention in recent years because they are advantageous materials in terms of weight reduction effects, recycling, etc., and are used for wheels, bumpers, radiators,
The range of use is expanding from engines to body panels.

However, the application of the aluminum alloy sheet to the vehicle body panel has many problems because the characteristics are different from those of the steel sheet which has been widely used conventionally. In particular, since the construction of a dedicated line for aluminum involves a large amount of capital investment, it is necessary to carry out the simultaneous simultaneous processing using the existing steel plate production line, but there are many problems to be solved for that purpose.

It can be said that the typical problem is press workability. That is, the press workability of the aluminum alloy plate is much worse than the workability of the steel plate. For example, comparing with JIS SPCC, which is a typical automobile steel sheet material, the SPCC has an elongation (El) of 45%, a Rankford value (r value) of 1.4, and a limiting drawing ratio (LDR) of 2.15. On the other hand, in the case of an aluminum alloy plate, taking JIS A5182 as an example, El is 30%, r value is 0.7, and LDR is 1.
Only reaches 8. As described above, since the workability of the aluminum alloy plate is extremely poor, there are great restrictions on the application to an automobile body. That is, as an example of application of the aluminum alloy plate to a vehicle body panel, it is limited to a lightly processed member such as a hood, and it is difficult to apply it to a more complicated member accompanied by heavy working.

The poor press workability of the aluminum alloy plate is due to the poor formability of aluminum itself as a raw material and the low melting point and softness of aluminum, which makes cast iron widely used in press dies. It is considered that this is due to the fact that it has a strong affinity with, and has the property of easily adhering to the mold, that is, its slidability is poor.

Since the slidability during press molding is greatly affected by the physical properties of the surface of the aluminum alloy plate that is in direct contact with the mold, the surface layer of the aluminum alloy plate is coated with, for example, an organic polymer film, such as vinyl, Attempts have been made to improve the sliding property by avoiding direct contact between the surface layer of the aluminum alloy plate and the mold and providing lubricity.

Similarly, as a material for improving the workability by improving the slidability of the surface of an aluminum alloy plate, a material having a lubrication treatment, for example, a film mainly composed of metal soap, higher fatty acid wax, etc. is coated. Have been proposed.

However, since the aluminum alloy plate subjected to these lubrication treatments has a poor phosphating property after press working, a step of completely removing these lubrication treatment films before the phosphating treatment is required. There are problems that need to be addressed.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides an aluminum alloy sheet which has a significantly improved press formability as compared with the conventional aluminum or aluminum alloy sheet and which can be produced easily and stably industrially and economically. It is intended to provide (a wide range of aluminum plates are included).

[0010]

That is, according to the present invention, the press workability is remarkably improved on the surface of an aluminum alloy plate,
And water glass (sodium silicate: nNa ₂ O.mS) that easily dissolves in the alkaline degreasing liquid in the pretreatment of zinc phosphate treatment
The present invention provides an aluminum alloy plate having a coating layer of iO ₂ ) or having an anticorrosion oil applied to the upper layer thereof and having excellent press workability. The dry film thickness of the coating layer of water glass is preferably 0.1 to 10 μm, and the coating amount of rust preventive oil on the water glass layer is preferably 0.1 to 7 g / m ² .

[0011]

The present invention will be described in more detail below. Aluminum alloy plates have high sliding resistance as described above because aluminum alloys have a low melting point and have a strong affinity with other metals, especially cast iron, which is often used in press dies, and adheres to dies. It is considered that this is due to the fact that it has the property of being easy to do. Since it is the physical properties of the surface of the aluminum alloy plate that is in direct contact with the die that affect the slidability during press forming, the aluminum alloy plate surface layer is coated with a substance with a weak affinity for cast iron etc. The sliding property is improved by avoiding direct contact between the mold and the mold and providing lubricity.
However, it is an essential condition that the treatment for imparting lubricity should not interfere with the zinc phosphate chemical conversion treatment performed after pressing.

The inventors of the present invention have earnestly studied to solve the problems of the aluminum alloy plate from the above viewpoint,
When water glass (sodium silicate: nNa ₂ O.mSiO ₂ ) is present on the surface of the aluminum alloy plate, it improves the slidability of the glass and also in the alkaline degreasing step performed before the phosphate treatment. The present invention has been completed by finding out that the substance can be completely dissolved and removed.

It is considered that the reason why the water glass dry film having a low flexibility applied to the surface of the aluminum alloy plate can give the excellent press workability which is seemingly incomprehensible is as follows. That is, since the water glass film can sufficiently withstand the extremely high local contact surface pressure caused by the minute irregularities present on the surface of the aluminum alloy plate or the irregularities newly generated during press molding,
It is considered that the direct contact between the press die and the aluminum alloy plate can be almost completely prevented. The effect is exhibited at a dry film thickness of 0.1 μm or more, and when it exceeds 10 μm, the effect is saturated and uneconomical, and the dissolution and removal in the degreasing process are likely to be incomplete, and residual water glass The upper limit was set because it adversely affects the zinc phosphate chemical conversion treatability.
It is known that an aqueous solution of water glass can also be used as a degreasing agent for metals, but as can be understood from this, even if water glass is dissolved in the degreasing solution, the degreasing ability of the degreasing solution is not affected. It does not hinder.

However, the coating of only the water glass coating has a problem. That is, the water glass film easily absorbs moisture,
Therefore, it becomes difficult to handle the plate due to gradually becoming tacky. Further, as the moisture absorption progresses, the water glass is decomposed and deteriorated, and its effect is reduced. In order to avoid these problems, application of rust preventive oil is indispensable. The rust preventive oil to be used is not particularly limited, but its coating amount is required to be 0.1 to 7 g / m ² . If the coating amount is less than 0.1 g / m ² , the effect is not sufficient, and if it exceeds 7 g / m ² , the effect is not only saturated, but also the degreasing failure occurs or the deterioration of the degreasing liquid is accelerated, so the upper limit is set. .

The treatment step of the present invention comprises a step of applying a water glass aqueous solution to an aluminum alloy plate and drying it to form a water glass film, and a step of applying rust preventive oil on the water glass film. The water glass aqueous solution is applied by diluting water glass with water to an appropriate viscosity, applying it on an aluminum alloy plate with an ordinary applicator such as a roll coater, and then drying it with heated air. In this case, as the pretreatment of the aluminum alloy plate, it is not necessary to perform it because the degreasing and etching action is appropriate for the water glass aqueous solution, and it may be directly treated after rolling, but the rolling oil generated in the rolling step is For more complete removal of the heterogeneous oxide film contained therein, etching treatment with nitric acid, sulfuric acid or the like or alkali etching treatment and smut removal treatment in an acid solution can be carried out to provide a more stable and uniform treatment. The rust preventive oil can be applied by a commonly used method such as electrostatic application or a roll coater method, and is not particularly limited.

[0016]

EXAMPLES The present invention will be specifically described below based on examples. (Example 1) JIS A5182 (Al-0.3 wt%
A Mn-4.5 wt% Mg) aluminum alloy is melted, cast, hot-rolled, and cold-rolled to a plate thickness of 1.0 mm by a conventional method, and after finish annealing, application of a water glass aqueous solution by a roll coater and Various test pieces were prepared by drying and applying antirust oil.

After that, the following tests were conducted. (1) Press Formability Test A sample punched to 70 mmφ was subjected to high-speed cylindrical drawing of 33 mmφ (processing speed: 500 mm / sec).
In this case, the evaluation of the moldability of each sample was evaluated as × when the galling and / or cracking of the side surface of the cylindrical sample after the test was generated, and as ○ when the defects were not generated.

(2) Zinc phosphate chemical conversion treatment test Degreasing was performed at 50 ° C. for 2 minutes with a weak alkaline degreasing agent,
After washing with water and surface treatment, zinc phosphate conversion treatment was performed at 40 ° C. for 2 minutes. All treatment reagents used were Palbond L-3020 aluminum specifications manufactured by Nippon Parkerizing Co., Ltd. The chemical conversion of each sample was evaluated by observing with a scanning electron microscope at a magnification of 1000, and those having a skein (the lack or non-adhesion site of the sizing crystal) in the chemical conversion crystal were evaluated as x, and those having no skein were evaluated as o.

Table 1 shows the conditions of the prepared samples and the test results. From the above test results, it is understood that the present invention is extremely effective in improving the formability of the aluminum alloy sheet and also has excellent zinc phosphate chemical conversion properties.

[0020]

[Table 1]

[0021]

As disclosed in the present invention, a water glass film is formed on the surface of an aluminum alloy plate, and further rust preventive oil is applied to the upper layer of the aluminum alloy plate, so that a good phosphating property can be maintained during pressing. It becomes possible to remarkably improve the slidability, and it is possible to dramatically improve the productivity at the time of press forming of the aluminum alloy plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Totsuka 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Technical Research Division (72) Inventor Naoki Nishiyama Chuo-ku, Chiba-shi, Chiba Kawasaki-cho, No. 1 Kawasaki Steel Co., Ltd., Technical Research Division (72) Inventor Mabuchi Masaki, Kawasaki-machi, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel Co., Ltd., Technical Research Division

Claims (3)

[Claims] 1. An aluminum alloy plate having excellent workability, which has a coating layer of water glass on the surface. 2. The water glass coating layer has a dry film thickness of 0.1.
The aluminum alloy plate having excellent workability according to claim 1, having a thickness of 10 μm. 3. An aluminum alloy plate excellent in workability according to claim 1 or 2, wherein 0.1 to 7 g / m ² of rust preventive oil is applied on the water glass layer.