JP3078473B2 - Aluminum alloy sheet excellent in press workability and spot weldability and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic resin-treated aluminum alloy sheet having excellent spot weldability and press workability, which is suitable for an automobile body and the like, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for reducing the weight of automobile bodies due to global environmental problems. Therefore, the use of aluminum alloy plates having high strength with respect to weight has been studied, and some parts have already been put to practical use. However, aluminum alloy sheets are extremely poor in formability compared to steel sheets, so their use in automobile bodies is limited to lightly processed members such as bonnets, and they are used for more complex and strongly processed door materials. It is considered difficult to use.

[0003] The poor formability of an aluminum alloy plate is as follows.
In addition to the poor formability of the aluminum alloy plate itself, the low melting point and softness of aluminum make it highly compatible with cast iron, which is often used in press dies, and easily adhere to the dies. Is caused by poor slidability.

[0004] In addition, since the life of an electrode of an aluminum alloy plate during spot welding is inferior to that of a steel plate, the production efficiency of a vehicle body using the same is deteriorated. That is, in spot welding of an aluminum alloy plate, the welding phenomenon between the electrode and the aluminum alloy plate is likely to occur, and the number of continuous hit points at which an appropriate shear strength of the nugget portion can be obtained with the same electrode is extremely short. Therefore, before welding occurs or before an appropriate nugget cannot be formed, the electrode tip shape is frequently dressed or replaced with a new electrode more frequently. For this reason, the current situation is that the production efficiency is significantly reduced. As described above, various efforts have been made to improve the formability and the spot resistance weldability of the aluminum alloy sheet, which were conventionally low.

First, as a technique for improving the composition and structure of an aluminum alloy sheet, for example, Japanese Patent Application Laid-Open No.
JP-A-30452 and JP-A-3-287739 disclose a production method for improving the elongation property and improving the workability by limiting the upper limits of the amounts of Fe and Si and increasing the amount of Mg added, There is a technique disclosed in Japanese Patent Application Laid-Open No. 4-123879 to improve the electrode life by controlling the thickness of the oxide film on the surface of the aluminum alloy plate to an appropriate electric resistance value.

However, as disclosed in JP-A-61-130452 and JP-A-3-287739, it is indispensable to use expensive high-purity ingot as a raw material in order to form a highly ductile alloy. There is a problem that the performance is remarkably lowered, and the workability is not significantly improved in proportion to the price increase. On the other hand, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent No. 3879, control of the surface electric resistance value is effective for improving weldability, but there is a problem that improvement in workability cannot be expected at all.

[0007] Considering the priorities in the manufacturing process of automobiles, it is considered necessary to first improve the workability of the aluminum alloy sheet. Attempts have been made to improve this by applying For example, JP-A-6-184
Nos. 587 and 6-305074 disclose a water-soluble organic lubricating resin treatment, that is, a solid lubricant in which a film is removed (the coating is dissolved and removed in a degreasing process in a phosphate chemical treatment step after pressing). Thus, an improved technique has been disclosed.
However, these delaminated lubricating resin films are inevitably deteriorated in weldability, incomplete removal of the resin, and are liable to cause poor phosphate conversion treatment. There is a problem that it is not possible to impart (rust corrosion).

Japanese Unexamined Patent Publications Nos. 4-268038 and 6-55137 disclose an organic lubricating resin film applied to a Zn-based plated steel sheet, that is, a base resin on a chromated aluminum alloy sheet. Discloses a technique in which a non-delamination type resin for a lubricating steel sheet, which is obtained by adding an organic lubricant such as a wax or a fluorine-based resin to an aluminum alloy sheet, is used as it is. However, all of these technologies are intended only to improve corrosion resistance and press workability, and do not consider spot weldability at all, and significantly reduce spots compared to aluminum alloy plates before forming an organic resin film. It has the disadvantage that the weldability deteriorates.

As a technique for improving this disadvantage, it is conceivable to reduce the thickness of the resin and to add a conductive auxiliary to the resin. For example, Japanese Unexamined Patent Publication No. Hei 3-18936 discloses an improvement technique in which the thickness of an organic resin applied to the surface of an aluminum alloy original plate is extremely limited and the organic resin is formed to be thin. Since no organic lubricant is contained in the resin, there is, of course, a problem that sufficient press moldability cannot be obtained. In addition, Japanese Patent Application Laid-Open No. 5-30933
Nos. 1 and 3114454 disclose a technique of adding a conductive auxiliary agent such as iron phosphide (for example, Japanese Patent Publication No. 62-73938) which is also used in lubricating steel sheets to a lubricating resin. However, the effect of improving the weldability by the addition of such a conductive additive is not sufficient, and some of the inorganic conductive additives to be added deteriorate the workability or hinder the coating properties of the lubricating resin (for roping). Problems).

In the techniques disclosed in JP-A-5-309331 and JP-A-311454, an organic lubricant (which is considered to be particularly intended for a fluororesin from the examples) is included in order to further enhance the workability. There is a feature that the amount is higher than usual. However, although not disclosed in the present technology, although the weldability is expected to be improved thereby, there is a problem that the improvement effect is extremely small within the addition range of the present technology.

When an aluminum alloy plate is used for an automobile body plate, it is important to have excellent spot weldability together with press formability. In particular, when an organic coating is formed on an aluminum alloy sheet to improve press formability, the conventional organic coating for lubricating steel sheets has a high electrical resistance, so that spot weldability is at a level that cannot withstand practical use. The problem of deterioration occurs. This is a problem inherent in aluminum alloy sheets due to the extremely low electrical resistance (about 1/4) of that of steel sheets. At present, it is extremely difficult to improve both the press workability and the spot weldability of a sheet while achieving a high degree of compatibility.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to improve the good press workability of an aluminum alloy sheet by an organic lubricating resin treatment without impairing the effect. Cost performance with a non-decoating type organic lubricating resin that has significantly improved spot weldability without the addition of inorganic conductive additives and improved both properties to a level that can be used on existing steel sheet production lines. An object of the present invention is to provide an aluminum alloy plate excellent in the above and a manufacturing method thereof.

[0013]

Means for Solving the Problems The inventors of the present invention have intensively studied the problem of spot weldability when using an aluminum alloy plate having been subjected to an organic lubricating resin treatment and having improved press formability in an automobile body. The present invention has been completed based on the following findings.

An organic lubricating resin film (hereinafter referred to as an organic film) formed on a lubricated steel sheet usually contains about 10% of an organic lubricant. An aluminum alloy plate having such an organic film has an extremely high electric resistance of the organic film,
The organic coating usually has a volume resistivity of about 10 ¹⁵ Ω · cm. Further, even if the organic film is formed as a thin film having a thickness of about 1 μm, the interlayer resistance still becomes 10 ¹⁰ Ω or more, so that the heat generated in the resin layer is excessive, which causes a problem that spot weldability is remarkably deteriorated.

In consideration of this point, it has been examined in more detail. As a result, it has been found that reducing the thickness of the organic coating film and increasing the content of the organic lubricant in the organic coating film significantly from the conventional one can reduce the spot welding resistance. New finding that it is extremely effective. Moreover, in addition to the improvement of the organic coating,
The spot weldability can be further improved by restricting the thickness of the oxide film on the surface of the aluminum alloy plate, which is the resistance factor of spot welding as well as the organic resin, and the thickness of the chromate film applied as a base treatment to the specified values or less. There was found.

Further, reducing the thickness of the organic film may reduce the effect of improving the press workability by forming the film. As a countermeasure against this, it is effective to limit the surface roughness of the aluminum alloy plate surface serving as the original plate to a specified value or less to smooth the surface, and this is combined with the above-mentioned increase in the content of the organic lubricant in the organic film. Therefore, the press workability can be improved because the effect of the organic lubricant increases. As a result, it was found that both the press workability and the spot weldability can be better achieved.

Also, in the aluminum alloy sheet as a raw material, it has been found that impurities such as Fe and Si deteriorate workability, but have an effect of improving weldability. In other words, the former deterioration in workability can be sufficiently compensated for by applying a lubricating resin having excellent weldability, and the organic coating having low cost and using a low-purity metal or recycled material. It was found that a treated aluminum alloy plate was obtained.

The present invention has been completed based on the above findings, that is, the aluminum alloy master sheet has a surface roughness (Ra) of 0.8 μm or less, and a chromate film as a first layer on the surface of the master sheet. Press workability and spot welding, characterized in that an organic resin film containing an organic lubricant in an amount of 32 to 60% by weight as a second layer is provided on the upper surface thereof in a dry film thickness of 0.05 to 0.90 μm. An object of the present invention is to provide an aluminum alloy plate having excellent properties.

Here, the thickness of the oxide film on the surface of the aluminum alloy plate is preferably 100 ° or less. Also,
The organic lubricant has an average molecular weight of 900 to 15,000,
It is preferably a high-density polyethylene having a density of 0.93 or more. Further, the amount of the chromate film deposited on the metal C
It is preferably 1.0 to 20.0 mg / m ² in terms of r.

Further, the component of the aluminum alloy plate contains 3 to 10% by weight of Mg and 0.3 to 2.0% by weight in total of impurity elements of Fe and Si and has a tensile strength of 31%.
It is preferably at least kgf / mm ² .

[0021]

The aluminum alloy plate has a total content of impurity elements of Fe and Si of 0.3 to 2.0.
Aluminum scrap containing as a raw material was dissolved and dissolved, and the Mg content after adjusting the components was adjusted to 3 to 10% by weight,
Alternatively, one or more of Cu, Cr, Zr, and Ti
The aluminum alloy sheet is a component containing 0.05% to 0.5% by weight of a seed or more and subjected to ordinary forging, hot rolling or subsequent cooling and continuous annealing to have a tensile strength of 31 kgf / mm ² or more. preferable.

[0023]

The present invention will be described below in more detail. The aluminum alloy sheet used for the aluminum alloy sheet having excellent press workability and spot weldability of the present invention (hereinafter, referred to as aluminum alloy sheet) is not particularly limited, and all known various aluminum alloy sheets can be used. It is. In particular, JIS 5000 series and JIS 600 currently used for vehicles or are under consideration for use.
0 series aluminum alloy plate is preferably used.
Various aluminum alloy plates specified in IS H4000 are also suitably used.

However, in order to further improve the weldability of a non-decoating type organic lubricating resin-treated aluminum alloy plate to be described later and to improve the cost performance of the resin-treated material, the aluminum alloy material used for the following reasons is used. It is more preferable to limit the chemical components.

One of the objects of the present invention is JIS
Preferable impurity amounts in the case of using a low pure material of a 5000 series (Al-Mg alloy) aluminum alloy plate are as follows. Factors that deteriorate the elongation of the Al-Mg based alloy and deteriorate the workability include Fe-Al based and Mg-Si based intermetallic compounds. Therefore, generally, Fe, Si, Zn
It is indispensable to keep the elements as low as impurities as low as possible. For this reason, a high-purity metal having a purity of 99.7% by weight or more is usually used. However, such a high-purity metal is extremely expensive, and the largest factor in increasing the cost of an aluminum alloy plate using the same as a raw material. Becomes Therefore, it is desirable to use recycled aluminum ingots in order to reduce costs, and it is indispensable to cope with an increase in the amount of aluminum alloy plates used in automobile bodies and an increase in production volume.

When the amount of impurities of Fe and Si increases while keeping the amount of Mg constant, as shown in FIG. 1, the tensile strength (TS) increases.
Increases, and the elongation (El) sharply decreases, so that the formability greatly decreases. This can also be understood from the fact that when the flange diameter at the time of breakage of cup molding is used as a formability index as shown in FIG. 2, the flange diameter increases as the amount of impurities increases. In addition, the flange diameter at the time of cup forming fracture | rupture measured the largest flange diameter (mm) which fractures when a 1 mm-thick aluminum alloy plate of the component amount shown in FIG. Therefore, when a low-purity material such as scrap is generally used as a raw material, it has been considered impossible to obtain a material that can withstand complicated forming such as an automobile body.

However, even in the case of such a material, by combining with the organic coating treatment, the surface slidability of the aluminum alloy plate is improved, so that the local deformability is improved, and the low deformation as shown in FIG. It is possible to manufacture an aluminum alloy plate having sufficient formability even with a pure material.

However, as shown in FIG. 2, when the amount of impurities exceeds 2.0% by weight, the moldability is lower than that of the conventional material even if the organic coating treatment is performed. Therefore, the upper limit of the total amount of impurities including Fe and Si is 2%. It is desirably set to not more than 0.0% by weight. Further, in order to obtain better moldability, it is naturally preferable that the amount of impurities is small, but the lower limit is desirably set to 0.3% by weight from the viewpoint of scrap cost and high purification cost of scrap.

Further, in order to achieve the same level of moldability as ordinary high purity by the organic coating treatment, it is desirable that the elongation of the raw aluminum alloy base plate is 20% or more.

On the other hand, the present inventors have found a novel effect that the weldability is positively improved with an increase in the amount of impurities. That is, as shown in FIG. 3, the spot resistance weldability of the aluminum alloy base plate itself is significantly improved with an increase in impurities. It is considered that the reason is that the strength of the base material increases with the increase of the impurities, or the effect of the impurities themselves. That is, by increasing the strength of the base material of the aluminum alloy plate, the amount of destruction of the surface oxide film immediately below the electrode when the plate is pressed by the electrode increases, and the resistance between the plate electrodes decreases. During the energization, a sufficient current density between the plates can be obtained during the energization because the electrode heat is reduced due to the suppression of the heat generation during the heating and the enlarging of the current-carrying area is suppressed due to the increase of the plate deformation resistance during pressurization. It is presumed that the electrode life is improved from the two effects of securing the nugget and easily forming the nugget.

Furthermore, the increase in the amount of impurities causes an increase in the specific resistance of the aluminum alloy original sheet and a decrease in the thermal conductivity, thereby promoting the formation of a nugget and improving the weldability. Therefore, in order to exhibit such an improvement effect, the lower limit of the impurity is preferably 0.3% by weight, and the lower limit of the tensile strength is preferably 31 kgf / mm ² , more preferably 0.5% by weight. Above, it is 1.5% by weight or less.

It is preferable that the alloy for obtaining the aluminum alloy master contains 3 to 10% by weight of Mg. In this case, the material strength is mainly provided by the solid solution strengthening mechanism of Mg atoms, and a high strength is obtained in proportion to the Mg content, and the elongation increases at the same time. Mg content is 3
If it is less than 10% by weight, the strength required for a body panel cannot be obtained. As a result, the life of the electrode during welding is shortened, and the elongation is also reduced. This is because it is difficult to obtain.

An increase in the amount of Mg causes an increase in the strength of the above-mentioned aluminum alloy sheet, an increase in the specific resistance value, a decrease in the thermal conductivity, and a decrease in the melting point. Is done. Therefore, from the viewpoints of strength, formability, and weldability, the larger the amount of Mg, the better.
If added in excess of 0% by weight, the hot workability is degraded, making the production of the sheet difficult, and the sensitivity to stress corrosion cracking is significantly increased. Therefore, the Mg content is preferably 3 to 10% by weight.

The addition of elements such as Cu, Mn, Cr, Zr, and Ti increases the strength of the aluminum alloy plate as a base material and improves the formability and the life of the electrode during welding. Is preferred. In order to exhibit the above effects, these elements must be contained in at least 0.0
It is necessary to add 2% by weight, but excessive addition deteriorates the ductility of the base material and the corrosion resistance.
It is preferable to limit the amount to 0.5% by weight or less. These elements exhibit the above-mentioned effects even when added alone or in combination of one or more kinds.

In the aluminum alloy sheet treated with a non-decoating type organic coating according to the present invention, the corrosion resistance (fiber rust corrosion resistance, stress corrosion cracking resistance) is significantly improved by the chromate treatment and the organic coating described later. Alloy components, especially Cu
It has the feature that the restriction on alloy design due to deterioration of corrosion resistance due to addition of Mg or Mg can be greatly eased.

As a method of manufacturing an aluminum alloy original sheet, after adjusting its components as described above, for example, F
e, an aluminum scrap containing 0.3 to 2.0% by weight of a total of impurity elements of Si as a raw material, which is dissolved and adjusted to a Mg content of 3 to 10% by weight after adjusting the components; After making one or two or more of Zr and Ti into components containing 0.02 to 0.5% by weight, ordinary forging, hot rolling or subsequent cooling and continuous annealing are performed to obtain a tensile strength of 31 kgf / mm ^2. By doing so, the original aluminum alloy plate can be adjusted.

Here, the aluminum alloy original plate (hereinafter, referred to as the original plate) used in the present invention has a surface roughness of R
0.8μ in a (center line average roughness specified in JIS B0601)
m. This is based on the following operation principle.

The press workability of the aluminum alloy plate can be improved by improving the slidability of the surface, and the slidability can be improved by forming an organic film containing an organic lubricant on the surface of the aluminum alloy plate. Is extremely effective. In the present invention, the effectiveness of the organic coating has a high correlation with the surface roughness of the aluminum alloy sheet, and the smaller the surface roughness, the smaller the film thickness (the amount of the organic lubricating resin applied) than before. Workability can be significantly improved. In a normal lubricating steel plate or a well-known organic lubricating resin-coated aluminum alloy plate, even if the surface roughness of the original plate is reduced, the lubricating component easily escapes in the extreme pressure state of the mold contact portion, and the base resin has low lubricity. Since the contact and sometimes the metal contact easily occur, the press workability is hardly improved.

On the other hand, the organic film formed on the aluminum alloy plate of the present invention has a large amount of lubricating components.
Since lubricating components do not escape even under extreme pressure conditions,
The lubricating component works more effectively as the surface roughness of the original plate is smaller. In general, it is effective to reduce the thickness of the organic film to be formed in order to improve the deterioration of the spot weldability, but this causes the deterioration of the press workability. However, in the present invention, the deterioration can be prevented by increasing the content of the organic lubricant contained in the organic film.

In the aluminum alloy plate of the present invention,
By making the Ra of the original plate 0.8 μm or less, more preferably by making the Ra of the original plate 0.5 μm or less, the thickness of the organic film can be reduced and the spot weldability can be further improved. Press workability can be ensured. The press workability of the aluminum alloy plate on which the organic coating is formed is improved as Ra is lower,
In order to reduce a to 0.05 μm or less, it is necessary to perform bright roll rolling in a rolling step for surface adjustment, which is disadvantageous in terms of cost, and practically there is little need for brightening. Although the surface roughness of the original plate (the surface of the chromate film) slightly changes due to the chromate treatment described later, the chromate film has a surface roughness of about 10 to 50 °, and the change in the roughness due to the change is extremely small. Absent.

Further, in the aluminum alloy sheet of the present invention, in order to reduce the welding resistance and improve the spot weldability, and to form a uniform chromate layer, the production process of the original sheet is performed by etching or the like. It is preferable that a part or most of the non-uniform oxide layer formed on the surface is removed to reduce the thickness to 100 ° or less. By making the thickness of the oxide film on the surface of the original plate 100 ° or less, more preferably 50 ° or less, spot weldability can be further improved.

As the etching treatment, an alkali etching treatment for removing the alumina (Al ₂ O ₃ ) layer on the surface with an alkaline aqueous solution, an acid washing treatment for mainly removing a magnesia (MgO) layer in an acidic aqueous solution, or an alkali etching treatment Any of post-pickling treatments may be used. As the alkali etching treatment and the pickling treatment, a method usually performed as a method for treating an aluminum alloy may be used, and a commercially available treatment liquid may be used. For example, caustic soda, caustic potash and the like can be used for the alkali etching treatment, and sulfuric acid, phosphoric acid, nitric acid, hydrofluoric acid, and a mixed solution of nitric acid and hydrofluoric acid can be used for the pickling treatment.

In the aluminum alloy plate, particularly, A
Among the l-Mg-based alloys, the surface oxide film is mainly composed of acid-soluble MgO, and MgO is dissolved and removed in a chromate treatment process with a strongly acidic chromate solution described later, so that the thickness of the oxide film is 100 mm or less. In this case, it is possible to omit the oxide film removing process.

Further, when an oxidation inhibiting element such as Be is added to the original sheet, the formation of an oxide film during the annealing process is suppressed, so that the thickness of the oxide film in such an original sheet may be 100 ° or less. In this case as well, it is possible to omit the oxide film removing process.

In the present invention, such an original plate is subjected to a chromate treatment to form a chromate film. The method of the chromate treatment may be a commonly used treatment method, for example, any method such as a reaction type chromate treatment, a coating type chromate treatment, and an electrolytic chromate treatment. Mold chromate treatment is preferred.

The reactive chromate treatment involves immersion, washing and drying in a strongly acidic solution containing chromic acid, phosphoric acid, nitric acid, hydrofluoric acid and the like. About 1 to 20% by weight to increase the activity of the aluminum alloy plate. The chromate film formed by the reaction type chromate treatment includes a chromate chromate film and a phosphoric acid chromate film, but there is no difference in characteristics in any case.

On the other hand, the chromate film formed by the coating-type chromate treatment is directly roll-coated using an aqueous solution mainly containing partially reduced chromic acid and containing at least one of phosphoric acid, acrylic resin, silica particles and the like. After coating the original plate in this aqueous solution by dipping or spraying, adjusting the adhesion amount by air knife method or roll drawing method, baking and drying at 100 to 200 ° C without washing with water Can be. In addition, since the coating type chromate film has a characteristic that the adhesion form is unevenly distributed (increased in the concave portion), the amount of the adhesion needs to be increased. In addition, although the content of alkali-soluble chromium in the chromate film is increased, it is advantageous for corrosion resistance.However, if the amount is too large, chromium elution may become a problem in the painting process of automobiles. Chromium that does not dissolve in the alkaline solution due to degreasing etc.
The content is desirably 0% by weight or more.

In the coating type chromate, it is possible to add a metal powder (zinc, aluminum, etc.), a conductive auxiliary such as iron phosphide, tin oxide, carbon black, etc.
The weldability can be improved by increasing the conductivity of the chromate layer, and the addition of silica, alumina, molybdenum salts, tungsten salts, etc. can improve the corrosion resistance and the adhesion of the lubricating resin film. Can be added as needed.

The amount of the chromate film adhered is 1.0 to 20.0 mg / m ² , preferably 5 to 15 m
g / m ² . 1.0 mg of chromate film
/ M ² or more, the elution of the base aluminum during the zinc phosphate chemical conversion treatment can be suitably prevented, and the adhesion of the upper organic coating can be made sufficient. In addition, when the amount of the chromate film attached increases, the spot weldability tends to decrease.
When the content is not more than mg / m ² , sufficient spot weldability can be stably ensured.

In the aluminum alloy plate of the present invention,
On top of the chromate film, an organic film containing an organic lubricant in an amount of 32 to 60% by weight was dried to a thickness of 0.05 to 0.1%.
90 μm is formed.

The organic coating basically comprises a base resin and an organic lubricant. As the base resin, various known solvent-based and water-based resins for lubricating steel plates can be used, for example, epoxy resin, alkyd resin, acrylic resin, urethane resin, phenol resin, melamine resin, polyvinyl butyral resin, polyester resin and One or two or more of these modified resins (for example, urethane-modified epoxy resin, acryl-modified urethane resin, etc.) are used. From the viewpoint of weldability and adhesion of electrodeposition coating, epoxy resin, urethane resin, acrylic resin,
A polyester resin or a mixed resin thereof is preferred. As these base resins, various commercially available products can also be suitably used.

The organic lubricant to be added to the base resin is generally called a wax, and is an organic substance which melts at room temperature to 200 ° C. and has a low melt viscosity. In addition, mineral natural wax, petroleum wax, synthetic hydrocarbon synthetic wax, and oxidized and / or modified wax thereof can be used. For example, montan wax, paraffin wax,
Examples include natural waxes such as microcrystalline wax, and synthetic waxes such as Fischer-Tropsch wax, polyethylene wax, and polypropylene wax.

Here, as the synthetic wax, Teflon (fluorine resin, for example, polytetrafluoroethylene resin,
Polyvinyl fluoride resin, polyvinylidene fluoride resin) wax is also available, but Teflon wax has a great effect on improving workability, but is not preferably used alone because it does not melt during welding and adversely affects weldability. Among these, polyethylene wax is preferred because it is highly effective in improving the press workability and is inexpensive, and is hardly dissolved or swelled in press cleaning oil, and has a chemically stable molecular weight of 900 to 15,000. And a high-density polyethylene having a density of 0.93 or more is more preferable. As the organic lubricant, various commercially available products can also be suitably used.

Further, although there is no particular limitation, the melting point (or softening point) of the organic lubricant to be used is desirably in the range of 60 to 150 ° C. If the melting point is lower than 60 ° C., it may occur under extreme pressure conditions during press working. Since the fluidity of the organic lubricant becomes too high, the effect of improving workability is reduced. Conversely, if the temperature exceeds 150 ° C., spot welding resistance increases, which is not preferable. In addition, in the press working of automobiles, the temperature of the mold changes during continuous pressing, which may change the wax performance. As a countermeasure, the melting point (or softening point)
It is effective to use two or more different waxes in combination.

In the aluminum alloy plate of the present invention,
The content of the organic lubricant in the organic coating is extremely important in terms of improving workability and spot weldability, and is 32% by weight.
It is an indispensable condition to contain the above. The mechanism of action is currently unclear, but is presumed as follows. That is, an organic lubricant, particularly a low-melting organic lubricant represented by polyethylene, melts and volatilizes in the initial stage of spot welding and easily forms a current-carrying point, so that it does not contribute to welding resistance. This fact has been confirmed in the study of the present inventors from the previously unknown result that the welding resistance value correlates only with the thickness of the base resin, regardless of the content of the organic lubricant in the organic film. ing.
Therefore, by reducing the thickness of the organic film and significantly increasing the content of the organic lubricant in the organic film compared to the past, it is possible to realize an aluminum alloy plate that achieves both spot weldability and formability. Can be.

The content of the organic lubricant in the organic film is 3
If it is less than 2% by weight, the effect of improving the spot weldability is small, and if it exceeds 60% by weight, the post-painting sharpness is adversely affected, which is not preferable. Therefore, in the present invention, the content of the organic lubricant is limited to 32 to 60% by weight.

In the aluminum alloy plate of the present invention, the organic lubricant is an essential component added to the organic film (base resin). In addition, if necessary, extender pigments (carbonate, silicate, etc.), Rust preventive pigments (silica, chromate, phosphate,
Lead salts), rust inhibitors (amine compounds, phenolic carboxylic acids, etc.), conductive pigments (carbon, iron phosphide, tin oxide, etc.), coloring pigments (titanium oxide, carbon, etc.), dispersion stabilizers, etc. One or more additives may be blended. In addition,
When these additives are added, the content of the organic lubricant may be 32 to 60% by weight in the whole organic film.

The thickness of the organic film containing these organic lubricants is 0.05 to 0.90 μm, more preferably 0.10 to 0.50 μm in dry film thickness. If the thickness of the organic film is less than 0.05 μm, the effect of improving press workability is not sufficient, and if it exceeds 0.90 μm, the spot weldability is reduced, so that the range is 0.05 to 0.90 μm.

The workability of the aluminum alloy sheet treated with an organic film according to the present invention described above is based on the premise that a press cleaning oil is applied. When a highly lubricating oil to which an extreme pressure agent (for example, calcium stearate or the like) is added is applied, workability can be further improved.

The method of forming these organic films is not particularly limited, and the base resin and the organic lubricant are dissolved (or dispersed) in an appropriate solvent, and if necessary, additives are added to the organic lubricant resin. Prepare a paint, apply by a known method such as roll coating method, curtain flow coating method,
You just need to burn it. The conditions for baking the coating film after coating are not particularly limited.
The range of 0 ° C. is preferable because an aluminum alloy plate having good performance can be produced and the treatment can be performed efficiently in a short time.

The aluminum alloy plate of the present invention usually has the above-mentioned organic coating on both sides, but if necessary, coats only one side with the above-mentioned resin coating and coats the other one side with untreated aluminum. It is also possible to form the alloy plate as it is or to form only the etched surface or the chromate film.

Although the aluminum alloy plate of the present invention and the method for producing the same have been described in detail, the present invention is not limited to this, and various improvements and modifications may be made without departing from the spirit of the present invention. Of course it is good.

[0063]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments.

(Example 1) JIS A5182-O material and JIS A6
Using a 061-T4 material, a 1 mm-thick original aluminum alloy sheet was prepared in which the surface roughness was variously adjusted by changing the roll roughness during rolling. The original plate was subjected to various etching treatments to adjust the thickness of the oxide film on the surface of the original plate, and then subjected to various reaction-type and coating-type chromate treatments to form a chromate film. An organic lubricating resin coating containing the following various base resins and an organic lubricant is applied to the upper layer by a roll coating method, and baked at a maximum temperature of 150 ° C. to obtain an organic (lubricating resin) film. Was formed. The press workability, spot weldability, and post-coating adhesion were investigated for the various aluminum alloy sheets thus produced.

The method for measuring the surface roughness of the original aluminum alloy sheet (1), the method for measuring the etching conditions and the thickness of the oxide film (2), the method for measuring the chromate conditions and the method for measuring the adhesion amount (3), The method for measuring the composition and dry film thickness of the organic coating (4), the method for measuring press workability and its evaluation method (5), the method for measuring spot weldability and its evaluation method (6), and the post-coating adhesion ( The method for measuring (paintability) and its evaluation method (7) are as follows. Table 1 shows the conditions and the evaluation results.

(1) Measurement of Surface Roughness (Center Line Average Roughness (Ra)) The surface roughness of the original aluminum alloy plate was measured with a three-dimensional roughness meter in accordance with JIS B0601. Ra (three-dimensional) in this case is expressed as in the following equation.

[0067]

(Equation 1) Here, S = L × L, and f (x, y) is a function indicating a surface roughness curve.

(2) Etching Condition In order to remove and control the oxide film on the surface of the original aluminum alloy plate, etching was performed under the following conditions. Further, the thickness of the oxide film after the treatment was measured from the oxygen intensity by the fluorescent X-ray analysis method. Treatment method A: degreased + 25 ° C, 10% sulfuric acid immersion treatment Treatment method B: degreased + 70 ° C, 5% NaOH immersion treatment +25
C, 10% nitric acid immersion treatment Method C: Degreasing + 25 ° C, 10% phosphoric acid immersion treatment Method D: Degreasing only

(3) Chromate Treatment Conditions The etched aluminum alloy base plate was immediately subjected to chromate treatment under the following conditions. The amount of the chromate film deposited after the treatment was measured from the chromium intensity by X-ray fluorescence analysis, and the amount of the chromate adhered was expressed in terms of chromium metal. Treatment condition A: Reactive chromate chromate treatment (Alchrome 713 manufactured by Nippon Parkerizing Co., Ltd.) Treatment condition B: Coating chromate chromate treatment (Zinchrome R1415A manufactured by Nippon Parkerizing Co., Ltd.) Treatment condition C: Reactive phosphoric acid chromate treatment (Nippon Parkerizing Co., Ltd.) Alchrome K702)

(4) Composition and Dry Film Thickness of Organic (Lubricant Resin) Film The dry film thickness of the organic film was measured from the carbon intensity by X-ray fluorescence analysis. Further, in Table 1, symbols indicating the composition of the organic coating are as follows. Base resin A; Epoxy resin (Epicoat 1007 manufactured by Yuka Shell Epoxy) B; Urethane resin (Mitec BL manufactured by Mitsubishi Kasei Corporation)
-100) C; Phenol resin (Super Becker site, manufactured by Dainippon Ink and Chemicals, Inc.) D: Polyvinyl butyral resin (manufactured by Denki Kagaku Kogyo Co., Ltd.)
Denka butyral) E; Polyester resin (Almatex P646, manufactured by Mitsui Toatsu Chemicals) Organic lubricant A: Polyethylene (Sunwax 151-P, manufactured by Sanyo Chemical Industries) B: Polyethylene (Ruwax AF, manufactured by BASF)
29) C: Polypropylene (Viscol 550P manufactured by Sanyo Chemical Industries, Ltd.)

(5) Press workability test and its evaluation method Press cleaning oil (R303P manufactured by Sugimura Chemical Co., Ltd.) was applied to the sample surface.
After coating, each sample punched out to a diameter of 70 mmφ was subjected to high-speed cylindrical drawing with a punch diameter of 33 mmφ (processing speed of 50 mm).
0 mm / sec). The formability was evaluated as poor (×) when cracks occurred on the side surface of the cylindrical specimen after processing, normal (を) when cracks did not occur but some galling occurred, and good when these defects did not occur (O)

(6) Test of spot weldability and evaluation method The electrode life of the aluminum alloy plate after the treatment was evaluated using a single-phase AC welding machine under the following electrodes and welding conditions. In the evaluation, the effect was judged based on the smaller number of the number of hits before welding or the number of hits until the shear strength (weld joint shear strength) of the nugget fell below 143 kgf.
Evaluation criteria are as follows.
A score of 00 to 1500 was rated as normal (△), and a score of 1500 or more was rated as good (○). [Electrode]-Shape: Dome (DR) type-Tip diameter: 6.0m
mφ • Tip curvature: 40 mmR • Material: Cu-C
r [Welding conditions] ・ Pressure: 300 kgf ・ Initial pressurization time: 3
0/50 seconds ・ Electrification time: 3/50 seconds ・ Hold time: 1
/ 50 seconds ・ Welding current: 25kA

(7) Post-coating adhesion (paintability) test and its evaluation method The electrodeposition coating adhesion was measured by zinc phosphate conversion treatment of various aluminum alloy plates (PB-L30 manufactured by Nippon Parkerizing Co., Ltd.).
20; aluminum specification) process, and then apply 20 μm of cationic electrodeposition coating (N-Paint Co., Ltd., U-600).
After baking and curing at 70 ° C for 20 minutes, place in pure water at 40 ° C for 1 minute.
After soaking for 0 days, a 2 mm crosscut tape peel test (10
0 mesh) and evaluated by the number of remaining coating films. The evaluation criteria for the adhesiveness were as follows: the number of remaining coating films was 100 (good), 80 to
99 was normal (△), and 79 or less was poor (x).

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

[Table 3]

As is clear from the results shown in Table 1, all of the examples of the present invention have excellent spot weldability due to the high content of the organic lubricant in the organic resin film. In this embodiment, the surface roughness, oxide film thickness, chromate adhesion amount, base resin type, organic lubricating type and their content and organic resin coating thickness are out of the optimum range, so that workability, weldability Some of them have a normal level of paintability, but there is no problem in normal use except for applications requiring high properties.

(Example 2) JIS A5182-O material and JIS A6
Using the 111-T4 material, various organic resin-coated aluminum alloy sheets were prepared under the conditions shown in Table 2 and evaluated in substantially the same manner as in Example 1. Table 2 shows the conditions and the evaluation results. Further, details of only conditions different from those in the first embodiment will be described.

(4) Composition and Dry Film Thickness of Organic (Lubricant Resin) Film In Example 2, the following organic film was used in addition to the organic film in Example 1. Base resin F; Acrylic resin (Dynal manufactured by Mitsubishi Rayon Co., Ltd.)
BR +) G; A + F (mixing ratio 50:50) H; B + F (mixing ratio 50:50) Organic lubricant D; polyethylene (High Wax 800P manufactured by Mitsui Petrochemical Industries, Ltd.) (molecular weight: 8000, density: 0.96) E; Polyethylene (High Wax 100P, manufactured by Mitsui Petrochemical Industries, Ltd.) (Molecular weight: 8,000, density: 0.96) F: D + E (mixing ratio: 50:50) G: D + Teflon (Rublon LP-1 manufactured by Asahi Glass Co., Ltd.)
00) (mixing ratio 70:30) H; polyethylene (homemade, molecular weight; 18,000, density; 0.92) I; polyethylene (homemade, molecular weight; 800, density;
0.80)

(5) Press workability test and its evaluation method Press cleaning oil (R303P manufactured by Sugimura Chemical Co., Ltd.) was applied to the sample surface.
After coating, each sample punched into a diameter of 95 mmφ was pressed with a punch diameter of 50 mmφ (shoulder R; 8 mm) and a pressing pressure (B
HF) and high speed cylindrical drawing (processing speed 500mm
/ Sec). The evaluation of the moldability is A5182,
A sample with a BHF exceeding 5 tons and drawn out was rated as good (◎), a sample with 2 to 5 tons as normal (○), and a sample with less than 2 tons as poor (×). In addition, A6111 was evaluated as good (）) when it passed through more than 4 tons and was rated as normal (○) for 2 to 4 tons, and (x) when less than 2 tons.

(6) Test of spot weldability and its evaluation method The electrode life of the aluminum alloy plate after the treatment was evaluated using a single-phase AC welding machine under the following electrodes and welding conditions. Evaluation is based on the number of hit points before welding or JIS Z3136.
Strength (weld joint shear strength) of welds based on JI
S Class A strength specified by Z3140 (176kgf / sp
The effect was judged with any of the smaller number of hit points until the value fell below ot). The evaluation standard is 100 points
Less than 0 points were evaluated as poor (x), 1000 to 2000 points as normal (o), and 2001 or higher as good (o). [Electrode]-Shape: R type-Tip curvature: 80 mm
R ・ Material: Cu-Cr [Welding conditions] ・ Pressure: 400 kgf ・ Initial press time: 3
0/50 seconds ・ Electrification time: 3/50 seconds ・ Hold time: 1
/ 50 seconds ・ Welding current: 29kA

(8) Post-painting image sharpness (sharpness) test and its evaluation method The image sharpness after coating was measured by applying 20 μm of cationic electrodeposition coating (U-600 manufactured by Nippon Paint Co., Ltd.) to various aluminum alloy plates.
m, 35μ of middle coat (KPX50 manufactured by Kansai Paint Co., Ltd.)
m, 35 μm top coat (B531 manufactured by Kansai Paint Co., Ltd.)
After the application, the DOI value was measured. The DOI value was measured with a DORIGON meter manufactured by Hunter. That is, when the amount of specular reflection when irradiating light from the direction of 30 ° of the sample normal is Rs, and the amount of light reflected at an angle shifted by ± 0.3 ° from the regular reflection is R _0.3 , the DOI value is (Rs- _R0.3 )
/ Rs × 100. The evaluation of the sharpness was good (◎) when the DOI value was 85 or more, normal (○), and 71 to 84 when the DOI value was 7 or more.
0 or less was regarded as defective (x).

[0083]

[Table 4]

[0084]

[Table 5]

As is evident from the results in Table 2, all of the examples of the present invention have good press workability, spot weldability and sharpness after painting, whereas the comparative examples have good press workability. Either spot weldability or sharpness after painting is poor. In this example, since the surface roughness, the type of the base resin, the type of the organic lubricant, and the content thereof are out of the optimum range, any of the press workability, the spot weldability, and the sharpness after painting is usually used. There are some levels, but there is no problem for normal use, except for applications requiring high characteristics.

Example 3 The Mg content was changed in the range of 5.4 to 6.5%, and the impurity content (Fe + Si) was set to 0.05 to
2.5% by weight, and Cu, Mn, Z
Normal hot rolling is performed using an aluminum alloy plate to which r and Ti are added in the range of 0.02 to 0.4% by weight, and the surface roughness is variously adjusted by changing the roll roughness during cold rolling. ,
Sheet thickness 1.0m annealed at 500-550 ° C for a short time
m was prepared. An organic coating was formed on the alloy base plate thus obtained under substantially the same conditions as in Example 1 under the conditions shown in Table 3 to produce various organic resin-coated aluminum alloy plates. Weldability and post-coating adhesion were evaluated under the following conditions. Table 3 shows the results together with the respective conditions. The details of the conditions different from those in the first embodiment are shown below.

(3) Chromate treatment conditions First, in Example 3, the following treatment conditions were used in addition to the chromate treatment conditions used in Example 1. Treatment condition D: Coating type chromate chromate treatment (ZM3360H, manufactured by Nippon Parkerizing Co., Ltd.)

(5) Press workability test and its evaluation method Press cleaning oil (R303P, manufactured by Sugimura Chemical Co., Ltd.) was applied to the sample surface.
After coating, each sample punched to a diameter of 70 mmφ was subjected to high-speed cylindrical drawing with a punch diameter of 33 mmφ (processing speed 20 mm).
0 mm / sec). The moldability was evaluated as poor (x) when galling and / or cracking occurred on the side surface of the cylindrical test piece after processing, and as good (O) when these defects did not occur.

(6) Test of spot weldability and evaluation method The electrode life of the aluminum alloy sheet after the treatment was evaluated using a single-phase AC welding machine under the same electrode and welding conditions as in Example 1. The number of hits and the effect until the shear tensile strength of the welded portion fell below the JIS standard A class were determined. The evaluation criteria are as follows.
The points and above were evaluated as good (O).

(7) Post-coating adhesion (paintability) test and its evaluation method The post-coating adhesion was determined by applying a cationic electrodeposition coating in the same manner as in Example 1 and then performing a 1 mm cross-cut tape peel test (100
(Mesh) and evaluated by the number of remaining coating films. The evaluation criteria of the adhesiveness are as follows: the number of remaining coating films is 96 to 100 (good), 9
5 or less was regarded as defective (x).

[0091]

[Table 6]

[0092]

[Table 7]

[0093]

[Table 8]

As is clear from the results in Table 3, the examples of the present invention have both good press workability and spot weldability, whereas the comparative examples have press workability, spot weldability, or Any of post-paint adhesion is bad.

In this embodiment, since the surface roughness, the oxide film thickness, the chromate adhesion amount, the base resin type, the organic lubricating type and the content thereof and the organic resin coating thickness are out of the optimum range, the workability is not improved. Some of them have a normal level in terms of weldability, coatability, and coatability, but there is no problem in normal use except for applications requiring high characteristics.

[0096]

As described in detail above, the aluminum alloy sheet of the present invention and the aluminum alloy sheet produced by the method of the present invention have excellent press workability, spot weldability and post-paint adhesion. And
The present invention can be particularly suitably used for an automobile body or the like which is required to be reduced in weight.

Further, the aluminum alloy sheet of the present invention and the aluminum alloy sheet manufactured by the method of the present invention can use a low-cost scrap material as a raw material. In this case, the aluminum alloy sheet is much lower than the conventional aluminum alloy sheet. The cost is high, and the surface roughness of the aluminum alloy plate is adjusted and coated with a resin layer containing an organic lubricant via a chromate treatment layer, so that excellent press workability, spot weldability and post-painting can be achieved. An aluminum alloy plate having adhesiveness can be obtained, which is the most suitable material for an automobile body or a molded article for home appliances, which is intended for mass production.

[Brief description of the drawings]

FIG. 1 is a view showing a correlation between the content of Fe + Si in an aluminum alloy plate and tensile strength.

FIG. 2 is a diagram showing the correlation between the content of Fe + Si in an aluminum alloy plate and the fracture flange diameter.

FIG. 3 is a diagram showing a correlation between the content of Fe + Si in an aluminum alloy plate and the life of an electrode.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C23C 22/00 C23C 22/00 Z (72) Inventor Norimasa Ikeda 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Inside the Technical Research Institute (72) Inventor Koichi Hashiguchi 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Corporation (72) Inventor Yoshihiro Matsumoto 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Kawasaki Steel Inside the Technical Research Institute Co., Ltd. (72) Motohiro Nambae 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Masaaki Kurihara 2-6-1 Marunouchi, Chiyoda-ku, Tokyo No. Furukawa Electric Co., Ltd. (72) Inventor Minoru Hayashi 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (56) References JP-A-5 311454 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) B32B 15/08 B05D 7/14 101 C23C 22/00

Claims (6)

(57) [Claims] 1. Surface roughness (Ra) of an original aluminum alloy sheet
Is 0.8 μm or less, a chromate film as a first layer on the surface of the original plate, and an organic resin film containing an organic lubricant of 32 to 60% by weight as a second layer on the first layer. An aluminum alloy sheet excellent in press workability and spot weldability, characterized by being provided with a thickness of 0.05 to 0.90 μm. 2. The aluminum alloy sheet according to claim 1, wherein the thickness of the oxide film on the surface of the aluminum alloy sheet is 100 ° or less. 3. The aluminum alloy sheet having excellent press formability and spot weldability according to claim 1, wherein the amount of the chromate film adhered is 1.0 to 20.0 mg / m ² in terms of metallic Cr. 4. The organic lubricant has an average molecular weight of 900-1.
The aluminum alloy sheet having excellent press formability and spot weldability according to any one of claims 1 to 3, wherein the aluminum alloy sheet is a high-density polyethylene having a density of 5,000 and a density of 0.93 or more. 5. The composition of the aluminum alloy plate is as follows: 3 to 10% by weight of Mg;
A tensile strength of 3 to 2.0% by weight is 31 kgf / m
The aluminum alloy sheet having excellent press workability and spot weldability according to any one of claims 1 to 4, wherein the aluminum alloy sheet has an m ² or more. 6. The aluminum alloy sheet according to claim 1, wherein its components are:
0.3 to 2.0% by weight in total of Fe and Si impurity elements
Using the aluminum scrap contained as a raw material, dissolve,
The Mg content after the component adjustment is set to 3 to 10% by weight, or a component containing 0.05 to 0.5% by weight of one or more of Cu, Cr, Zr, and TI. A method for producing an aluminum alloy sheet excellent in press workability and spot weldability, characterized in that the aluminum alloy sheet has a tensile strength of 31 kgf / mm ² or more after hot rolling or subsequent cooling and continuous annealing.