JPH08224830A - Aluminum alloy plate having excellent press processability and spot welding property, and manufacture thereof - Google Patents

Abstract

PURPOSE: To provide an organic lubrication resin coating aluminum alloy plate by a method wherein spot welding property of an aluminum alloy plate treated with an organic lubrication resin is remarkably improved without loss of improving effect of excellent press processability of it and these properties are improved to the extent usable even in an existent steel plate manufacturing line. CONSTITUTION: A surface roughness of an aluminum alloy original plate is 0.8μm or less. On the surface of the original plate, a chromate coating of 1.0-20.0mg/m<2> in metal Cr conversion is provided as a first layer. On the upper part thereof, an organic resin coating having 32-60wt.% of an organic lubricant as a second layer is provided as a dry film thickness of 0.05-0.90μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy plate treated with an organic resin, which has excellent spot weldability and press workability and is suitable for automobile bodies 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, utilization of an aluminum alloy plate having high strength against weight has been studied, and it has already been put to practical use for some parts. However, aluminum alloy sheets have extremely poor formability compared to steel sheets, so their use in automobile bodies is limited to lightly machined parts such as bonnets, and to more complex and strong machined door materials. Is said to be difficult to use.

The poor formability of aluminum alloy sheets is due to
In addition to the poor formability of the aluminum alloy plate itself, which is a raw material, because aluminum has a low melting point and is soft, it has a strong affinity with cast iron, which is widely used in press dies, and is easily adhered to dies. This is due to the poor slidability.

Further, since the aluminum alloy plate has a shorter electrode life during spot welding than the steel plate, it deteriorates the production efficiency of the vehicle body using this. 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 points where an appropriate shear strength of the nugget portion can be obtained with the same electrode is extremely short. Therefore, the electrode tip shape is often dressed or replaced with a new electrode before welding occurs or before a proper nugget cannot be formed. Therefore, the current situation is that the production efficiency is significantly reduced. As described above, various efforts have been made to improve the formability and spot resistance weldability of aluminum alloy sheets, which have been low in the past.

First, as a technique for improving the composition and structure of the aluminum alloy plate, for example, Japanese Patent Laid-Open No. 61-1 is available.
Japanese Patent No. 30452 and Japanese Patent Laid-Open No. 3-287739 disclose a manufacturing 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 addition amount of Mg, and There is a technique disclosed in JP-A-4-123879, which improves 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 described in JP-A-61-130452 and JP-A-3-287739, it is indispensable to use expensive high-purity metal as a raw material in order to obtain a high-ductility alloy. There is a problem that performance is markedly reduced and there is no significant improvement in workability commensurate with the price increase. On the other hand, JP-A-4-12
Although the control of the surface electric resistance value is effective for improving the weldability as described in Japanese Patent No. 3879, there is a problem that the improvement of the workability cannot be expected at all.

Considering the priority in the manufacturing process of automobiles, it is considered that it is necessary to improve the workability of the aluminum alloy sheet. From this point of view, the formability of the aluminum alloy sheet is determined by the lubricating resin coating. Attempts have been made to improve by applying. For example, JP-A-6-184
No. 587 and No. 6-305074, a water-soluble organic lubricating resin treatment, that is, a defilming type (a film is dissolved and removed in a degreasing process in a phosphate chemical conversion treatment step after pressing) solid lubricant is provided. The improvement technique by this is disclosed.
However, the deterioration of weldability is unavoidable with these film-removing type lubricating resin coatings, and the resin removal is incomplete, which tends to cause defects in phosphate chemical conversion treatment, and corrosion resistance (resistance to corrosion) higher than that of bare aluminum alloy sheets. There is a problem that it is not possible to add (corrosion of thread rust).

Further, in JP-A-4-268038 and JP-A-6-55137, an organic lubricating resin coating applied to a Zn-plated steel sheet, that is, a chromate-treated aluminum alloy sheet, is coated with a base resin. Discloses a technique in which a non-film-removing type resin for a lubricating steel sheet, which is obtained by adding an organic lubricant such as wax or a fluorine-based resin, is directly used for an aluminum alloy sheet. However, all of these techniques are intended only to improve the corrosion resistance and press workability, the spot weldability is not taken into consideration at all, and compared with the aluminum alloy plate before forming the organic resin coating, the spot is remarkably spotted. It has a drawback that the weldability deteriorates.

As a technique for improving this drawback, it is conceivable to thin the resin and add a conductive auxiliary agent to the resin. For example, Japanese Laid-Open Patent Publication No. 3-18936 discloses an improvement technique by forming a thin organic resin film on the surface of an original aluminum alloy plate by limiting the film thickness to a very small thickness. Since the resin does not contain an organic lubricant, naturally there is a problem that sufficient press formability cannot be obtained. In addition, JP-A-5-30933
Each of Japanese Patent Nos. 1 and 311544 discloses a technique of adding a conductive auxiliary agent such as iron phosphide (for example, Japanese Examined Patent Publication No. 62-73938), which is also used in lubricating steel sheets, to a lubricating resin. However, the effect of improving the weldability due to the addition of such a conductive additive is not sufficient, and some of the inorganic conductive additives to be added deteriorate the workability and hinder the coating property of the lubricating resin (for roping). There is a problem to occur.

In the techniques disclosed in JP-A-5-309331 and JP-A-3115445, the inclusion of an organic lubricant (though it is considered that fluororesins are targeted especially from the examples) in order to further enhance the processability. There is a feature that the amount is higher than usual. However, although not disclosed in the present technology, although improvement in weldability due to this is expected, there is a problem that the improvement effect is extremely small in the addition range of the present technology.

When an aluminum alloy sheet is used as a vehicle body sheet of an automobile, it is important to have excellent spot weldability as well as press formability. In particular, when an organic coating is formed on an aluminum alloy plate to improve press formability, the conventional organic coating for lubricating steel plates has a high electric resistance, so that the spot weldability is at a level that cannot be practically used. The problem of deterioration occurs. This is a problem peculiar to aluminum alloy plates due to the extremely small electric resistance (about 1/4) compared to steel plates, but with the application or slight modification of conventional organic coatings for lubricating steel plates, aluminum alloy plates Under the present circumstances, it is extremely difficult to improve both the press workability and the spot weldability of the plate at a high level.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and the effect of improving the favorable press workability of an aluminum alloy sheet by the organic lubricating resin treatment is not impaired. Cost performance is improved by improving the spot weldability without adding an inorganic conductive additive and improving the properties of both to the level that can be used in existing steel sheet production lines. (EN) An excellent aluminum alloy plate and a method for manufacturing the same.

[0013]

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

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

As a result of a more detailed study on this point, the reduction of the spot welding resistance can be achieved by making the film thickness of the organic coating smaller than the conventional one and by significantly increasing the content of the organic lubricant in the organic coating as compared with the conventional one. We obtained new findings that it is extremely effective for Moreover, in addition to the improvement of the organic coating,
The spot weldability can be further improved by limiting the thickness of the oxide film on the surface of the aluminum alloy plate, which is a resistance factor of spot welding, and the thickness of the chromate film to be used as the base treatment to the specified value or less, as with the organic resin. There was found.

Further, reducing the film thickness of the organic coating may reduce the effect of improving press workability by forming the coating. As a countermeasure against this, it is effective to limit the surface roughness of the aluminum alloy plate surface, which is the original plate, to a specified value or less for smoothing, and this is combined with increasing the content of the organic lubricant in the above-mentioned organic coating. Therefore, since the effect of the organic lubricant is increased, the press workability can be improved. As a result, it was found that the press workability and the spot weldability can be better achieved at the same time.

Further, in the aluminum alloy plate as a raw material, it was found that impurities such as Fe and Si deteriorate the workability, but have a conversely improving effect on the weldability. That is, the former deterioration of workability can be sufficiently complemented by applying the above-mentioned lubricating resin having excellent weldability, and an organic coating film having a cost performance by 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 surface roughness (Ra) of the aluminum alloy original plate is 0.8 μm or less, and a chromate film is formed as the first layer on the original plate surface. Press workability and spot welding, characterized in that an organic resin film containing 32 to 60% by weight of an organic lubricant is provided as a second layer on the upper part of the organic resin film in a dry film thickness of 0.05 to 0.90 μm. An aluminum alloy plate having excellent properties is provided.

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

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

Further, according to the present invention, a chromate film is formed as a first layer on the surface of an aluminum alloy original plate, and an organic resin film containing 32 to 60% by weight of an organic lubricant is formed as a second layer on the dry film. 0.05 ~ 0.90μ as thickness
The present invention provides a method for producing an aluminum alloy sheet excellent in press workability and spot weldability, which is characterized by being provided in m.

The aluminum alloy plate has a total of 0.3 to 2.0 impurity elements of Fe and Si.
Using aluminum scrap as a raw material, which is contained in an amount of 3% by weight, melted, and the Mg content after adjusting the components is set to 3 to 10% by weight,
Alternatively, one of Cu, Cr, Zr, and Ti or 2
An aluminum alloy sheet having a tensile strength of 31 kgf / mm ² or more by being subjected to normal forging, hot rolling or subsequent cooling, and continuous annealing by using a component containing 0.05 to 0.5% by weight of seeds or more. preferable.

[0023]

The present invention will be described below in more detail. The aluminum alloy original plate used for the aluminum alloy plate having excellent press workability and spot weldability of the present invention (hereinafter referred to as aluminum alloy plate) is not particularly limited, and various known aluminum alloy plates can be used. Is. Among them, in particular, JIS 5000 series and JIS 600 currently used for automobiles or are being studied for use.
A 0 series aluminum alloy plate is preferably used, and J
Various aluminum alloy plates specified by ISH4000 are also preferably used.

However, in order to further improve the weldability of the non-film removal type organic lubricating resin-treated aluminum alloy plate 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.

JIS, which is one of the objects of the present invention,
The preferred amount of impurities when a low purity material of 5000 series (Al-Mg alloy) aluminum alloy plate is used is as follows. Fe-Al-based and Mg-Si-based intermetallic compounds are factors that deteriorate the elongation and workability of Al-Mg-based alloys.
It is indispensable to suppress such elements as impurities as low as possible. Therefore, a high-purity ingot having a purity of 99.7% by weight or more is usually used, but such a high-purity ingot is extremely expensive, and is a major factor for increasing the cost of an aluminum alloy plate using it. Becomes Therefore, in order to reduce the cost, it is desirable to use recycled aluminum ingot, and it is indispensable to cope with the increase in the amount of aluminum alloy plates used for automobile bodies and the increase in the number of production.

When the amounts of impurities such as Fe and Si increase with the amount of Mg kept constant, as shown in FIG. 1, the tensile strength (TS)
Is increased and the elongation (El) is drastically reduced, so that the formability is significantly reduced. This can be understood from the fact that when the flange diameter at the time of cup molding breakage is used as the moldability index as shown in FIG. 2, the flange diameter increases as the amount of impurities increases. The flange diameter at the time of breaking the cup was measured by measuring the maximum flange diameter (mm) at which the aluminum alloy plate having a thickness of 1 mm shown in FIG. Therefore, it has been generally considered impossible to obtain a material that withstands complicated molding such as an automobile body when using a low-purity material such as scrap.

However, even with such a material, by combining it with the organic film treatment, the surface slidability of the aluminum alloy plate is improved, so that the local deformability is improved and the low deformability as shown in FIG. 2 is obtained. It is possible to manufacture an aluminum alloy plate having sufficient formability even with a pure material.

However, as shown in FIG. 2, if the amount of impurities exceeds 2.0% by weight, the formability is worse than that of the conventional material even if the organic film treatment is applied. Therefore, the upper limit of the total impurities of Fe and Si is 2 It is desirable that the content be 0.0% by weight or less. Furthermore, in order to obtain better moldability, it is naturally preferable that the amount of impurities is small, but the lower limit is preferably 0.3% by weight in view of scrap cost and scrap purification cost.

Further, in order to achieve moldability of ordinary high purity by the organic coating treatment, it is desirable that the raw material aluminum alloy original plate has an elongation of 20% or more.

On the other hand, the present inventors have found a new effect that the weldability is positively improved as the amount of impurities is increased. That is, as shown in FIG. 3, as the impurities increase, the spot resistance weldability of the aluminum alloy original plate itself is significantly improved. The reason for this is considered to be an increase in the strength of the base metal due to an increase in impurities, or an effect of the impurities themselves. That is, as the base metal strength of the aluminum alloy plate increases, 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, Since the heat generation during heating is suppressed, the electrode wear is reduced, and the expansion of the current-carrying area is suppressed by the increase in the plate deformation resistance under pressure. It is presumed that the electrode life is improved due to the two effects of being secured and facilitating the formation of a nugget.

Further, as the amount of impurities increases, the resistivity of the aluminum alloy original plate increases and the thermal conductivity decreases, so that the formation of nuggets is promoted and the weldability is improved. Therefore, in order to exert such an improving effect, it is preferable that the lower limit of impurities is 0.3% by weight and the lower limit of tensile strength is 31 kgf / mm ^2, and more preferably, the amount of impurities is 0.5% by weight. As described above, the content is 1.5% by weight or less.

Further, it is preferable that the alloy for obtaining the aluminum alloy original plate contains 3 to 10% by weight of Mg. In this case, the material strength is mainly brought about by the solid solution strengthening mechanism of Mg atoms, a high strength is obtained in proportion to the Mg content, and at the same time the elongation is increased. Mg amount is 3
If it is less than 10% by weight, the strength required for a vehicle body panel cannot be obtained, and as a result, the electrode life 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 aluminum alloy plate, an increase in the specific resistance value, a decrease in the thermal conductivity, and a decrease in the melting point, so that the melting of the welded portion is promoted and the weldability is improved. To be done. Therefore, from the viewpoints of strength, formability, and weldability, the larger the amount of Mg, the more preferable.
If added in an amount of more than 0% by weight, hot workability deteriorates, making plate production difficult, and stress corrosion cracking susceptibility significantly increase. 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 sheet as a base material and improves the formability and the electrode life during welding. Therefore, these elements are added. Preferably. In order to exert the above effects, at least 0.0
It is necessary to add 2% by weight, but excessive addition deteriorates the ductility of the base metal and the corrosion resistance.
It is preferable to limit it to 0.5% by weight or less. The above-mentioned effects are exhibited even if these elements are added alone or in combination of one or more.

In the non-film-removing type organic film-treated aluminum alloy plate of the present invention, the corrosion resistance (thread rust corrosion property, stress corrosion cracking property) is remarkably improved by the chromate treatment and organic film described later. Alloy components of Cu, especially Cu
It has a feature that restrictions on alloy design due to deterioration of corrosion resistance due to addition of Mg and Mg can be significantly relaxed.

As a method of manufacturing an aluminum alloy original plate, after adjusting its components as described above, for example, F
e, aluminum scrap containing a total of 0.3 to 2.0% by weight of impurity elements is used as a raw material and melted to adjust the Mg content after adjusting the components to 3 to 10% by weight, or further Cu, Cr, Zr and / or Ti are made into a component containing 0.02 to 0.5% by weight and then subjected to normal forging, hot rolling or subsequent cooling, and continuous annealing to obtain a tensile strength of 31 kgf / mm ^2. The aluminum alloy original plate can be adjusted by the above.

Here, the aluminum alloy original plate (hereinafter referred to as original plate) used in the present invention has a surface roughness R
0.8μ in a (center line average roughness specified in JIS B0601)
It must be m or less. 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 thereof. To improve the slidability, an organic coating containing an organic lubricant is formed 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 plate, and the smaller the surface roughness, the smaller the film thickness (the coating amount of the organic lubricating resin) of the conventional press. Workability can be significantly improved. With ordinary lubricated steel plates and well-known organic lubrication resin-coated aluminum alloy plates, 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 part It was difficult to improve press workability because contact and sometimes metal contact were likely to occur.

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

In the aluminum alloy plate of the present invention,
By setting the Ra of the original plate to 0.8 μm or less, more preferably, by setting the Ra of the original plate to 0.5 μm or less, the film thickness of the organic coating can be reduced and the spot weldability can be further improved, and at the same time, sufficient Press workability can be secured. The press workability of the aluminum alloy plate on which the organic coating is formed is better as Ra is lower, but
Bright roll rolling must be performed in the rolling process for surface adjustment in order to reduce a to 0.05 μm or less, which is disadvantageous in terms of cost, and practically there is little need for brightening. Also, the surface roughness of the original plate (the surface of the chromate film) changes slightly due to the chromate treatment described below, but the chromate film has a surface roughness of about 10 to 50Å, and the change in roughness due to it is extremely small, so there is no problem in performance. Absent.

Further, in the aluminum alloy sheet of the present invention, in order to reduce the welding resistance to improve the spot weldability and to form a uniform chromate layer, in the manufacturing process of the original sheet by etching treatment or the like, It is preferable to remove a part or most of the non-uniform oxide layer formed on the surface of the oxide film so that the thickness is 100 Å or less. By setting the thickness of the oxide film on the surface of the original plate to 100 Å or less, more preferably 50 Å or less, the 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, a pickling treatment for mainly removing the magnesia (MgO) layer in an acidic aqueous solution, or an alkali etching treatment Any one of the post-pickling treatments may be used. The alkali etching treatment and the pickling treatment may be the methods generally used for treating aluminum alloys, and a commercially available treatment solution can be used. For example, caustic soda, caustic potash, etc. can be used for the alkali etching treatment, and sulfuric acid, phosphoric acid, nitric acid, hydrofluoric acid, a mixed solution of nitric acid and hydrofluoric acid, etc. can be used for the pickling treatment.

In the aluminum alloy plate, especially A
The surface oxide film is mainly composed of acid-soluble MgO in the 1-Mg-based alloy, and MgO is dissolved and removed in the chromate treatment process with a strongly acidic chromate solution described later, and the thickness of the oxide film is 100 Å or less. In some cases, it is possible to omit the oxide film removing process.

When an oxidation inhibiting element such as Be is added to the original plate, the formation of an oxide film in the annealing process is suppressed, so that the oxide film may have a thickness of 100 Å or less in such an original plate. In this case as well, it is possible to omit the above-mentioned oxide film removal processing.

In the present invention, such an original plate is chromated to form a chromate film. The method of chromate treatment may be a commonly used treatment method, for example, reactive chromate treatment, coating chromate treatment, electrolytic chromate treatment or the like, but from the viewpoint of ease of treatment, reactive chromate treatment or coating. Type chromate treatment is preferred.

The reactive chromate treatment involves dipping, washing with water and drying in a strongly acidic solution containing chromic acid, phosphoric acid, nitric acid, hydrofluoric acid, etc. It is necessary to increase the activity of the aluminum alloy plate by including 1 to 20% by weight. The chromate film formed by the reactive chromate treatment includes a chromate chromate film, a phosphoric acid chromate film, and the like, 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 a direct roll coater using an aqueous solution containing, as a main component, partially reduced chromic acid and at least one of phosphoric acid, acrylic resin, silica particles and the like. Method, or by dipping or spraying the original plate in this aqueous solution, adjusting the amount of adhesion by the air knife method or roll squeezing method, and then baking and drying at 100 to 200 ° C without washing with water. You can Note that the coating type chromate coating has a characteristic that its adhesion form is unevenly distributed (increased in the concave portions), so that the adhesion amount needs to be increased. Further, there is a feature that the content rate of alkali-soluble chromium in the chromate film is large, which is advantageous for corrosion resistance, but if the amount is too large, elution of chromium may become a problem in the painting process of automobiles. Therefore, the chromium that does not dissolve in the alkaline solution due to degreasing, etc.
It is desirable to set it to 0% by weight or more.

Further, in the coating type chromate, it is possible to add a conductive aid such as fine metal powder (zinc, aluminum, etc.), iron phosphide, tin oxide, carbon black, etc.
Weldability can be improved by increasing the conductivity of the chromate layer, and by adding silica, alumina, molybdenum salt, tungsten salt, etc., it is possible to improve the corrosion resistance and the adhesiveness of the lubricating resin coating. The above pigment can be appropriately added if necessary.

The amount of the chromate film deposited is 1.0 to 20.0 mg / m ^{2 in} terms of metal Cr, preferably 5 to 15 m.
g / m ² . Chromate coating amount 1.0mg
When it is / m ² or more, the elution of the base aluminum during the zinc phosphate chemical conversion treatment can be preferably prevented, and the adhesiveness of the upper organic film can be made sufficient. Further, when the amount of the chromate coating adhered increases, the spot weldability tends to deteriorate, but the amount of adherence is 20.0.
By setting the content to be mg / m ² or less, sufficient spot weldability can be stably ensured.

In the aluminum alloy plate of the present invention,
An organic coating containing 32 to 60% by weight of an organic lubricant is formed on the top of the chromate coating in a dry thickness of 0.05 to 0.
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 more kinds of these modified resins (for example, urethane modified epoxy resin, acrylic modified urethane resin, etc.) are used. From the viewpoint of weldability and adhesion of electrodeposition coating, epoxy resin, urethane resin, acrylic resin,
Polyester resins or mixed resins thereof are preferred. Various commercially available products can be suitably used as these base resins.

The organic lubricant added to the base resin is generally called wax, and is an organic substance that melts at room temperature to 200 ° C. and has a low melt viscosity. A mineral-based natural wax or petroleum wax, a synthetic hydrocarbon-based synthetic wax, and an oxidized and / or modified wax thereof can be used. For example, montan wax, paraffin wax,
Examples thereof 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 and polyvinylidene fluoride resin wax are also available, but Teflon wax does not melt at the time of welding and adversely affects the weldability, although Teflon wax has a great effect on improving workability, and therefore it is not preferable to use it alone. Of these, polyethylene wax is particularly preferable because it is highly effective in improving press workability and is inexpensive, and is unlikely to dissolve or swell in press washing oil, and has a chemically stable molecular weight of 900 to 15,000. A high density polyethylene having a density of 0.93 or more is more preferable. Various commercially available products can be preferably used as the organic lubricant.

Furthermore, although not particularly limited, the melting point (or softening point) of the organic lubricant used is preferably in the range of 60 to 150 ° C. When the melting point is less than 60 ° C., it is under extreme pressure during press working. Since the fluidity of the organic lubricant becomes too high, the effect of improving the workability decreases, and conversely, when it exceeds 150 ° C, the spot welding resistance increases, which is not preferable. Also, in the press processing of automobiles, the mold temperature changes during continuous pressing, which may change the wax performance. As a countermeasure against that, 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 improving workability and spot weldability, and is 32% by weight.
It is an essential condition to contain the above. The mechanism of action is currently unclear, but it is presumed as follows. That is, an organic lubricant, particularly an organic lubricant having a low melting point 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 was confirmed in the study by the present inventors from the heretofore unknown result that the welding resistance value correlates only with the film thickness of the base resin regardless of the content of the organic lubricant in the organic coating. ing.
Therefore, it is possible to realize an aluminum alloy plate having both spot weldability and formability by reducing the film thickness of the organic coating and significantly increasing the content of the organic lubricant in the organic coating. You can

The content of the organic lubricant in the organic coating is 3
If it is less than 2% by weight, the effect of improving spot weldability is small, and if it exceeds 60% by weight, the image clarity after coating is adversely affected. 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 addition component to the organic coating (base resin), but in addition, if necessary, an extender pigment (carbonate, silicate, etc.), Anticorrosion pigment (silica, chromate, phosphate,
Lead salts, etc., rust inhibitors (amine compounds, phenolic carboxylic acids, etc.), conductive pigments (carbon, iron phosphide, tin oxide, etc.), color pigments (titanium oxide, carbon, etc.), dispersion stabilizers, etc. You may mix | blend 1 or more types of additives. In addition,
When these additives are added, the content of the organic lubricant may be 32 to 60% by weight in the whole organic coating.

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

The above-described workability of the aluminum alloy sheet treated with an organic coating of the present invention is premised on the case where a press cleaning oil is applied, but it is also effective when no oil is applied, and a high viscosity and The processability can be further improved by applying an oil of high lubricity to which an extreme pressure agent (eg, calcium stearate) is added.

The method for forming these organic coatings is not particularly limited, and the base resin and the organic lubricant are dissolved (or dispersed) in a suitable 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,
Just bake it. The conditions for baking the coating film after coating are not particularly limited, but the maximum temperature reached is 80 to 18
The range of 0 ° C. is preferable because an aluminum alloy plate having good performance can be produced and the treatment can be performed with good thermal efficiency in a short time.

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

The aluminum alloy sheet of the present invention and the method for producing the same have been described above in detail. However, the present invention is not limited to this, and various improvements and changes can be made without departing from the gist of the present invention. Of course it is good.

[0063]

EXAMPLES The present invention will be specifically described below based on examples.

(Example 1) JIS A5182-O material and JIS A6
Using the 061-T4 material, an aluminum alloy original plate having a plate thickness of 1 mm 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 oxidation film thickness on the surface of the original plate, and thereafter, various reaction type and coating type chromate treatments were performed to form a chromate film. An organic lubricant resin coating containing various base resins and organic lubricants shown below is applied to the upper layer by a roll coating method, and baked at a maximum plate temperature of 150 ° C. to form an organic (lubricant resin) film. Was formed. The press workability, spot weldability, and post-coating adhesion of the various aluminum alloy sheets thus produced were investigated.

The surface roughness of the original aluminum alloy plate was measured (1), the etching condition and the oxide film thickness were measured (2), the chromate treatment condition and the amount of adhesion (3) were measured, Organic coating composition and dry film thickness measurement method (4), press workability measurement method and evaluation method (5), spot weldability measurement method and evaluation method (6), and post-coating adhesion ( The coating method) and its evaluation method (7) are as follows. Table 1 shows each condition and its evaluation result.

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

[0067]

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

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

(3) Chromate Treatment Conditions The etched aluminum alloy original plate was immediately subjected to chromate treatment under the following conditions. The amount of the chromate coating after the treatment was measured from the chromium intensity by the fluorescent X-ray analysis method, and the amount of the chromate deposit was expressed in terms of metallic chromium. Treatment condition A: Reactive chromate chromate treatment (Alchrome 713 manufactured by Nippon Parkerizing Co., Ltd.) Treatment condition B: Coated chromate chromate treatment (Zinchrome R1415A manufactured by Nippon Percalizing Co., Ltd.) Treatment condition C: Reactive phosphoric chromate treatment (Nihon Parkerizing Co., Ltd.) Made of Alchrome K702)

(4) Composition of Organic (Lubricating Resin) Film and Dry Film Thickness The dry film thickness of the organic film was measured from the carbon intensity by fluorescent X-ray analysis. Further, the symbols showing the composition of the organic coating in Table 1 are as follows. Base resin A; Epoxy resin (Epicote 1007 manufactured by Yuka Shell Epoxy Co., Ltd.) B; Urethane resin (Mitec BL manufactured by Mitsubishi Kasei)
-100) C: Phenol resin (Dainippon Ink and Chemicals, Inc. Super Becker site) D: Polyvinyl butyral resin (Denki Kagaku Kogyo KK)
Denka butyral) E; Polyester resin (Mitsui Toatsu Chemicals Almatex P646) Organic lubricant A; Polyethylene (Sanyo 151-P) Sanyo Kasei Co. B; Polyethylene (BASF Luwax AF)
29) C: Polypropylene (Viscole 550P manufactured by Sanyo Kasei 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 punched at a high speed with a punch diameter of 33 mmφ (processing speed 50
0 mm / sec). As for the evaluation of formability, those with cracks on the side surface of the cylindrical test piece after processing were bad (×), those with no galling but slight galling were normal (△), and those without these defects were good. (○)

(6) Spot Weldability Test and Evaluation Method The electrode life of the treated aluminum alloy plate was evaluated using a single-phase AC welding machine under the following electrodes and welding conditions. In the evaluation, the effect was judged by either the number of hitting points until welding or the number of hitting points until the shear strength (welded joint shear strength) of the nugget falls below 143 kgf, whichever is smaller.
The evaluation standard is that the number of RBIs is less than 500 points is bad (x), 5
A score of 00 to 1500 was rated as normal (Δ) and a score of 1500 or more was rated as good (◯). [Electrode] -Shape: Dome (DR) type-Tip diameter: 6.0 m
mφ · Tip curvature: 40 mmR · Material: Cu-C
r [Welding condition] ・ Pressure: 300kgf ・ Initial pressurization time: 3
0/50 seconds ・ Electrification time: 3/50 seconds ・ Holding time: 1
/ 50 seconds ・ Welding current: 25kA

(7) Post-coating adhesion (paintability) test and its evaluation method The electrodeposition coating adhesion was evaluated by zinc phosphate conversion treatment of various aluminum alloy plates (PB-L30 manufactured by Japan Parkerizing Co., Ltd.).
20; aluminum specification) process, followed by cation electrodeposition coating (U-600 manufactured by Nippon Paint Co., Ltd.) to 20 μm, and 1
After baking and curing at 70 ℃ for 20 minutes, 1 in pure water at 40 ℃
After soaking for 0 days, a 2 mm cross-cut tape peeling test (10
(0 mesh) was performed and the number of remaining coating films was evaluated. The evaluation standard of the adhesiveness is that the number of remaining coating films is 100 (good), 80 to
A rating of 99 was normal (Δ) and a rating of 79 or less was defective (x).

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[Table 1]

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[Table 2]

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[Table 3]

As is clear from the results shown in Table 1, each of the examples of the present invention has an excellent spot weldability because the content of the organic lubricant in the organic resin film is high. In this example, the surface roughness, the oxide film thickness, the chromate deposition amount, the base resin type, the organic lubrication type and the content thereof and the organic resin coating film thickness are out of the optimum ranges, so that the workability and the weldability are improved. Some of the paintability is of a normal level, but there is no problem in normal use unless the application requires high characteristics.

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

(4) Composition of Organic (Lubricating Resin) Film and Dry Film Thickness 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.
BR106) 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 Industry Co., Ltd.) (Molecular weight; 8000, density; 0.96) E: Polyethylene (High wax 100P manufactured by Mitsui Petrochemical Co., Ltd.) (Molecular weight: 8000, Density: 0.96) F: D + E (Mixing ratio 50:50) G: D + Teflon (Lubron LP-1 manufactured by Asahi Glass Co., Ltd.)
00) (mixing ratio 70:30) H; polyethylene (homemade, molecular weight; 18000, 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 to a diameter of 95 mmφ is punched with a punch diameter of 50 mmφ (shoulder R; 8 mm), and a pressing pressure (B
High-speed cylindrical drawing with different HF (processing speed 500 mm
/ Sec). Moldability evaluation is A5182,
BHF exceeding 5 ton was narrowed down to be good (⊚), 2 to 5 ton was normal (∘), and less than 2 ton was defective (x). In addition, A6111 was rated as good (⊚) when it passed through more than 4 ton, normal (∘) from 2 to 4 ton, and (x) when less than 2 ton.

(6) Spot Weldability Test and Evaluation Method The electrode life of the treated aluminum alloy sheet was evaluated using a single-phase AC welding machine under the following electrodes and welding conditions. Evaluation is the number of dots until welding or JIS Z3136
Shear strength (weld joint shear strength) of welded joints based on JI
Class A strength (176 kgf / sp according to SZ3140 standard)
The effect was judged by the smaller number of RBIs, which is the number of RBIs falling below ot). The evaluation standard is 100 points
A score of less than 0 was rated as bad (x), a score of 1000 to 2000 was rated as good (◯), and a score of 2001 or greater was rated as good (⊚). [Electrode] · Shape: R type · Tip curvature: 80 mm
R ・ Material: Cu-Cr [Welding condition] ・ Pressure: 400 kgf ・ Initial pressurization time: 3
0/50 seconds ・ Electrification time: 3/50 seconds ・ Holding time: 1
/ 50 seconds ・ Welding current: 29kA

(8) Post-painting sharpness (sharpness) test and its evaluation method The post-painting sharpness was coated with 20 μm of cation electrodeposition coating (U-600 manufactured by Nippon Paint Co., Ltd.) on various aluminum alloy plates.
m, intermediate coating (KPX50 manufactured by Kansai Paint Co., Ltd.) 35μ
m, top coat (B531 manufactured by Kansai Paint Co., Ltd.) 35 μm
After application, the DOI value was measured. The DOI value was measured with a Hunter DORIGON meter. That is, assuming that the amount of specular reflection when light is irradiated from the direction of 30 ° of the sample normal is Rs and the amount of light reflected at an angle deviated by ± 0.3 ° from the regular reflection is R _0.3 , the DOI value is (Rs-R _0.3 )
/ Rs × 100. As for the evaluation of sharpness, a DOI value of 85 or more is good (⊚), 71 to 84 is normal (∘), 7
A value of 0 or less was regarded as a defect (x).

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[Table 4]

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[Table 5]

As is clear from the results shown in Table 2, all of the examples of the present invention have good press workability, spot weldability and image clarity after painting, whereas the comparative examples have press workability. , Spot weldability or image clarity after painting is poor. In this example, since the surface roughness, the base resin type, the organic lubricant type, and the content rate thereof are out of the optimum ranges, either press workability, spot weldability or image clarity after painting is common. There are some grades, but there is no problem in normal use except for the applications that require high characteristics.

Example 3 The amount of Mg was changed in the range of 5.4 to 6.5%, and the amount of impurities (Fe + Si) was set to 0.05 to.
Change in the range of 2.5 wt%, Cu, Mn, Z
Using an aluminum alloy plate added with r and Ti in the range of 0.02 to 0.4% by weight, ordinary hot rolling was performed, and the surface roughness was variously adjusted by changing the roll roughness during cold rolling. ,
Sheet thickness 1.0m after annealing for a short time at 500-550 ℃
The alloy original plate of m was produced. The alloy base plate thus obtained was formed into an organic coating under the conditions shown in Table 3 in the same manner as in Example 1 to prepare various organic resin-coated aluminum alloy plates, and press workability and spotting were performed in the same manner as in Example 1. Weldability and post-coating adhesion were evaluated under the following conditions. The results are shown in Table 3 together with each condition. The details of the conditions different from those in Example 1 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 punched at a high speed with a punch diameter of 33 mmφ (processing speed: 20 mm).
0 mm / sec). The moldability was evaluated as good (O) when galling and / or cracking occurred on the side surface of the cylindrical test piece after processing, and good (O) when these defects did not occur.

(6) Spot Weldability Test and Evaluation Method The electrode life of the treated aluminum alloy plate was evaluated using a single-phase AC welding machine under the same electrodes and welding conditions as in Example 1. The number of hit points and the effect until the shear tensile strength of the welded part fell below JIS standard A class were evaluated. The evaluation standard is that the number of RBIs is less than 2000 (Bad), 2001
Points and above were rated as good (○).

(7) Post-coating adhesion (coating property) test and its evaluation method The post-coating adhesion was subjected to cation electrodeposition coating in the same manner as in Example 1 and then 1 mm cross-cut tape peeling test (100
(Mesh) was performed and the number of remaining coating films was evaluated. The evaluation standard of adhesion is that the number of remaining coating films is 96 to 100 (good), 9
A value of 5 or less was regarded as a defect (x).

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[Table 6]

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[Table 7]

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[Table 8]

As is clear from the results shown 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 Either of the post-coating adhesion is poor.

In this example, the surface roughness, the oxide film thickness, the chromate deposition amount, the base resin type, the organic lubricating type and the content thereof, and the organic resin film thickness were out of the optimum ranges, so that the workability was improved. There are some products with normal levels of weldability and paintability, but there is no problem in normal use unless the application requires 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 are excellent in press workability, spot weldability and post-coating adhesion. And
It can be used particularly suitably for automobile bodies and the like for which weight reduction is required.

Further, since the aluminum alloy sheet of the present invention and the aluminum alloy sheet produced by the method of the present invention can use inexpensive scrap material as a raw material, in this case, it is much lower than the conventional aluminum alloy sheet. In addition to the cost, the surface roughness of the aluminum alloy plate is adjusted, and by coating the resin layer containing the organic lubricant through the chromate treatment layer, excellent press workability, spot weldability and post-coating are achieved. It is possible to obtain an aluminum alloy plate having adhesiveness, and it is an optimum material for automobile body or home electric appliance molded parts for mass production.

[Brief description of drawings]

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

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

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

Front page continuation (72) Inventor Naoki Nishiyama 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. Kawasaki Steel Co., Ltd. Technical Research Institute (72) Inventor Koichi Hashiguchi 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Co., Ltd. Technical Research Center (72) Inventor Yoshimoto Matsumoto Chuo-ku, Chiba City, Chiba Prefecture 1 Kawasaki-cho, Kawasaki Steel Corporation Technical Research Institute (72) Inventor, Motohiro Namba 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Tokyo Furukawa Electric Co., Ltd. (72) Inventor Masaaki Kurihara Tokyo 2-6-1, Marunouchi, Chiyoda-ku, Furukawa Electric Co., Ltd. (72) Minoru Hayashi 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (7)

[Claims] 1. A surface roughness (Ra) of an aluminum alloy original plate.
Of 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 in an amount of 32 to 60% by weight as a second layer on top of it as a dry film thickness of 0. An aluminum alloy plate having excellent press workability and spot weldability, which is characterized in that the aluminum alloy plate has a thickness of 0.05 to 0.90 μm. 2. The aluminum alloy plate having excellent press workability and spot weldability according to claim 1, wherein the oxide film on the surface of the aluminum alloy plate has a thickness of 100 Å or less. 3. An aluminum alloy plate having excellent press workability and spot weldability according to claim 1, wherein the amount of the chromate coating adhered is 1.0 to 20.0 mg / m ² in terms of metallic Cr. 4. The average molecular weight of the organic lubricant is 900-1.
The aluminum alloy plate having excellent press workability and spot weldability according to any one of claims 1 to 3, which is a high-density polyethylene having a density of 5000 and a density of 0.93 or more. 5. The aluminum alloy plate is composed of 3 to 10% by weight of Mg, and Fe and Si impurity elements in a total amount of 0.
3 to 2.0 wt% contained tensile strength is 31 kgf / m
The aluminum alloy plate having excellent press workability and spot weldability according to any one of claims 1 to 4, which is m ² or more. 6. A chromate film is formed as a first layer on the surface of an aluminum alloy original plate, and an organic resin film containing 32 to 60% by weight of an organic lubricant is formed as a second layer on the upper surface of the original film.
A method for producing an aluminum alloy sheet excellent in press workability and spot weldability, characterized in that a dry film thickness is set to 0.05 to 0.90 μm. 7. The aluminum alloy plate has the following components:
0.3 to 2.0% by weight of Fe and Si impurity elements in total
Aluminum scrap contained is used as a raw material, melted,
The Mg content after component adjustment is set to 3 to 10% by weight, or
Is one or more of Cu, Cr, Zr, and Ti.
Is used as a component containing 0.05 to 0.5 wt%
Forging, hot rolling or subsequent cooling, continuous annealing, and tensile strength
31 kgf / mm ²Aluminum alloy plate above
Press workability according to claim 6, characterized in that
To produce aluminum alloy sheets with excellent spot weldability
Law.