JP2002371332A - Aluminum alloy sheet superior in formability and coating /baking hardenability, and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet superior in coating/baking hardenability and formability, and a manufacturing method therefor. SOLUTION: The aluminum alloy sheet superior in coating/baking hardenability and formability, is characterized by including, by mass%, 0.2-1.6% Mg, 0.4-1.8% Si, 0.03-1.5% Mn, 0.02-0.5% Cr, and preferably further one or more of 0.003-0.5% Ti, 0.1-1.5% Cu, 0.02-0.5% Fe, 0.02-0.5% Zr, 0.02-0.5% V, and 0.003-0.5% B, and the balance Al with unavoidable impurities. The sheet preferably has an alkali soluble type lubricating resin film of 0.5-5 μm thick on the surface. The manufacturing method is characterized by casting the alloy, and holding it at 500-600 deg.C for one hour as homogenization treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is excellent in moldability such as press, bending, etc., and increases yield strength by precipitation hardening at the time of paint baking.
(H property), which is suitable for automotive materials and the like, and has excellent workability and paint bake hardenability, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, reduction of the weight of a vehicle body for the purpose of improving fuel efficiency of an automobile has been studied, and application of an aluminum alloy plate to an automobile material has been promoted. For this application, a material with high strength and excellent formability such as pressing and bending is required, and a non-heat treatment type Al-Mg based alloy with improved strength and formability by solid solution strengthening of Mg, Heat-treated Al- that obtains high strength by precipitation hardening during paint baking
Mg-Si based alloys have been developed. Of these, Al-
Mg-based alloys are often used in automotive materials because of their excellent formability. However, the manufacturing cost is high, and the stretcher-strain pattern appears during press molding, which impairs the surface quality. is there.

On the other hand, Al—Mg—Si alloys are
There is a problem that the formability is inferior to the Mg-based alloy,
Due to its excellent manufacturability, its production cost is low, its stretcher-strain pattern hardly appears, and its BH property is excellent. Therefore, alloys applicable to automobiles and the like have been developed. As such Al-Mg-Si alloys, JP-A-5-70907, JP-A-5-70908 and JP-A-9-41062 disclose a forming aluminum alloy sheet excellent in BH property and its aluminum alloy sheet. A manufacturing method is disclosed. These are used to improve BH properties.
Mg-Si based GP zone is preferentially precipitated, and Mg-S
This is one in which precipitation of the i-type cluster is suppressed.

[0004]

However, such an alloy with improved BH properties has a reduced formability,
There is a limit to compatibility between moldability and BH properties. The present invention overcomes such problems, and is particularly suitable for automotive materials and the like.
An object of the present invention is to provide an aluminum alloy sheet having both excellent moldability and paint bake hardenability, and a method for producing the same.

[0005]

SUMMARY OF THE INVENTION The present invention is an aluminum alloy which promotes solid solution of Mn by adding appropriate amounts of Mn and Cr to achieve both formability and BH properties. A method for producing these alloys is a homogenization treatment under appropriate conditions for the purpose of sufficiently dissolving Mn. Further, a lubricating film is applied to the surface in order to improve the drawability and mold galling of the alloy. That is, the gist of the present invention is as follows.

(1) In mass%, Mg: 0.2-1.
6%, Si: 0.4-1.8%, Mn: 0.03-1.
5%, Cr: 0.02-0.5%, the balance being Al
An aluminum alloy sheet having excellent moldability and paint bake hardenability, characterized by being composed of unavoidable impurities. (2) mass%, Ti: 0.003 to 0.5%,
The aluminum alloy sheet excellent in formability and paint bake hardenability according to (1), further comprising:

(3) In mass%, Cu: 0.1% or more
The aluminum alloy sheet according to the above (1) or (2), further comprising 1.5% by weight, which is excellent in formability and paint bake hardenability. (4) mass%, Fe: 0.02 to 0.5%, Z
r: 0.02 to 0.5%, V: 0.02 to 0.5%,
B: The moldability and paint bake curability according to any one of the above (1) to (3), further comprising one or more of 0.003 to 0.5%. Excellent aluminum alloy plate.

(5) Granular lubricating function imparting agent: 2 to 15 ma
The aluminum alloy plate as described in any one of (1) to (4) above, further comprising a 0.5 to 5 μm thick alkali-soluble lubricating resin film containing ss% on the surface. (6) The aluminum alloy plate having excellent moldability and paint baking hardenability according to (5), wherein the alkali-soluble lubricating resin film further contains silica particles: 1 to 30 mass%.

(7) The granular lubricating function-imparting agent comprises one or more of polyolefin wax, fluorine wax, paraffin wax and stearic wax. Or an aluminum alloy plate excellent in formability and paint bake hardenability according to (6). (8) In the method for producing an aluminum alloy sheet according to any one of (1) to (7), after casting, holding for 1 hour or more at a temperature of 500 to 600 ° C. as a homogenization treatment. A method for producing an aluminum alloy sheet having excellent moldability and paint bake hardenability characterized by the following.

(9) After cold rolling, a solution treatment of 5
Hold in a temperature range of 00 to 580 ° C for 300 seconds or less, 5 ° C
The method for producing an aluminum alloy sheet having excellent baking hardenability and press formability according to the above (8), wherein the aluminum alloy sheet is cooled at a cooling rate of not less than / s. (10) After the solution treatment, the film is cooled to 40 to 100 ° C and wound up, and cooled at a cooling rate of 0.1 to 10 ° C / h. And a method for producing an aluminum alloy sheet having excellent press formability.

(11) After the solution treatment, the solution is cooled to 40 to 100 ° C. and wound up, and at a temperature of 40 to 100 ° C., 0.5 to 7
The method for producing an aluminum alloy sheet according to the above (9), wherein the aluminum alloy sheet is held for 0 hours, which is excellent in baking hardenability and press formability. (12) After the solution treatment, the solution is cooled to 40 to 100 ° C. and wound up, and cooled at a cooling rate of 0.1 to 10 ° C./h.
The method for producing an aluminum alloy sheet having excellent paint bake hardenability and press formability according to the above (9), wherein the aluminum alloy sheet is heated to 30 to 280 ° C. and held for 0 to 30 minutes.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The present inventor has found that both the formability and the BH property of an aluminum alloy are improved by forming a fine precipitate and dissolving Mn, which is known as an element effective in increasing strength and reducing grain size, into a solid solution. Was. Further, Mn
In order to promote the solid solution of Cr, attention was paid to Cr, which forms fine precipitates like Mn and precipitates more easily than Mn. That is, by adding an appropriate amount of Mn and Cr, Cr is preferentially precipitated to suppress the precipitation of Mn,
Of solid solution was promoted.

Further, in order to further promote the solid solution of Mn, by adding Ti and precipitating at a high temperature during solidification, coarsening of the Al—Fe—Si—Mn intermetallic compound is suppressed and fine It has been found that dispersing is effective. Regarding the production method, it was clarified that the properties were improved by promoting the solid solution of Mn by performing appropriate homogenization treatment after melting and casting. The present invention is an aluminum alloy excellent in formability and BH property obtained based on such knowledge, and a method for producing the same.

First, the reason for limiting the preferred component composition range will be described. % Means mass%. Mg: Mg is a basic alloying element of the present invention and contributes to the development of a high BH property by generating an Mg-Si-based GP zone at the time of paint baking. This effect is achieved when the amount of Mg is 0.1.
Less than 2% is not sufficient, while M above 1.6%
When g is added, coarse Mg ₂ Si precipitates are generated, the formability and bendability are deteriorated, and the BH property is reduced due to the decrease in the dissolved mass. From this, the amount of Mg is 0.2-
The range was 1.6%.

Si: Si is also an alloy element which is a basic element of the present invention, and generates an Mg-Si based GP zone at the time of coating baking to contribute to the development of high BH properties. Below this effect is not sufficient. On the other hand, Si
If the amount exceeds 1.8%, coarse Mg ₂ Si precipitates are formed, impairing formability, bendability and BH property. Therefore Si
The amount was in the range of 0.4-1.8%.

Mn: Mn is widely used as an element that produces fine precipitates, but is an important element that improves formability by forming a solid solution and exhibits high BH properties. This effect is insufficient when the Mn content is less than 0.03%. In order to obtain more excellent characteristics, it is preferable to add more than 0.15%. Further, if added in excess of 1.5%, a large amount of intermetallic compound is generated, and the moldability and BH
Impair the nature. In order to obtain more excellent characteristics, it is preferable to limit the amount of added Mn to 1% or less. Therefore, the Mn content is 0.03% to 1.5%, preferably more than 0.15%.
% Or less.

Cr: Cr is also known to have similar properties to Mn, but forms precipitates more preferentially than Mn and suppresses the precipitation of Mn. If this effect is less than 0.02%, the effect is sufficient. On the other hand, if it exceeds 0.5%, coarse precipitates are formed to lower the formability. Therefore, 0.
The range was 02 to 0.5%. Ti: Ti is an element that precipitates finely during solidification, finely disperses the Mn-based intermetallic compound, and promotes the solid solution of Mn. Therefore, it is preferable to further add Ti. This effect is insufficient if the addition amount is less than 0.003%. In order to obtain more excellent characteristics, the addition of more than 0.02% is preferable. On the other hand, if it exceeds 0.5%, coarse precipitates are formed, and the moldability is reduced. In order to obtain more excellent characteristics, the content is preferably limited to 0.2% or less. Therefore, the amount of Ti added is 0.003 to 0.5%, preferably more than 0.02 to 0.2%.
%.

Cu: Cu is an element that is selectively added to improve the formability. However, if the content is less than 0.1%, the effect is small, so the lower limit is 0.1%. On the other hand, if it exceeds 1.5%, coarse Cu-based precipitates are formed, and formability and bendability are reduced, so the upper limit was made 1.5%. Further, if necessary, one or more of Zr, V, Fe and B may be contained. Fe: Fe is an element effective for improving the strength and refining the ingot structure, and if its content is less than 0.02%, a sufficient effect cannot be obtained. On the other hand, if it exceeds 0.5%, coarse crystals of an Al-Fe system are formed to lower the formability.

V and Zr: V and Zr are also effective elements for improving the strength and refining the crystal grains.
If it is less than 02%, a sufficient effect cannot be obtained, and if it exceeds 0.5, coarse precipitates are formed to lower the formability. B: B is an element effective for improving the strength and refining the ingot structure. When the content is less than 0.003%, a sufficient effect cannot be obtained. When the content exceeds 0.5%, coarse precipitates are formed. In order to reduce the moldability, it is set in the range of 0.003 to 0.5%.

Next, a preferred method for producing the aluminum alloy sheet of the present invention will be described in detail. After casting, the aluminum alloy of the present invention is subjected to a homogenization treatment, a hot rolling, a cold rolling, a solution treatment, and a preliminary aging treatment. Intermediate annealing may be performed in the cold rolling step. The homogenization treatment has an important role in the present invention to re-dissolve the ingot precipitate. If the homogenization treatment temperature is lower than 500 ° C., the re-solid solution of the precipitate is insufficient, and the solid solution of Mn is remarkably promoted. The preferred temperature is higher than 540 ° C. On the other hand, 600 ° C
If it is higher than this, the crystal grains become coarse and the formability is reduced. To obtain more excellent moldability, the homogenization treatment temperature should be 580 ° C.
It is preferable to limit to the following. Therefore, the temperature range of the homogenization treatment is 500 to 600 ° C, preferably more than 540 ° C.
The range is 80 ° C. or lower. If the holding time in this temperature range is shorter than 1 hour, the effect is insufficient, and the preferable time during which the solid solution of Mn is remarkably promoted is more than 4 hours. Extremely effective. Therefore, the holding time is at least 1 hour, preferably more than 4 hours. The upper limit is not particularly limited because the homogenization proceeds as the retention time is longer, but the effect is almost saturated in 50 hours.

The solution treatment is a heat treatment for recrystallizing the worked structure after the cold rolling and dissolving Mg, Si and Mn precipitated as intermetallic compounds in the hot rolling step. It is preferably applied in order to obtain formability, moldability and bendability. If the solution treatment temperature is lower than 500 ° C., the solid solution of Mg, Si and Mn is insufficient and BH
When the temperature is higher than 580 ° C., the crystal grain size becomes coarse, and the formability and bendability decrease. Therefore, the temperature range of the solution treatment is 500 to 580 ° C.
Range.

After reaching the solution treatment temperature, cooling or holding may be performed immediately. However, if the holding time exceeds 300 seconds, the crystal grain size becomes coarse and the formability is impaired. The following is assumed. On the other hand, if the cooling rate after the solution treatment is lower than 5 ° C./sec, a precipitate is formed and the BH property,
Impairs formability and bendability. Therefore, the cooling rate after the solution treatment is set to 5 ° C./sec or more. The higher the cooling rate, the better, but the upper limit of the cooling rate in actual production is about 3
00 ° C / s. Further, the BH property can be improved by controlling the winding temperature after the solution treatment and the cooling rate after the winding. If left at around room temperature after the solution treatment, the amount of clusters generated increases, and the precipitation of the GP zone during baking of paint is hindered, so that the BH property is reduced, the proof stress is increased, and the bendability is impaired. In order to prevent this, it is effective to wind at a temperature of 40 ° C. or more and to generate a GP zone during cooling.

On the other hand, if the winding temperature exceeds 100 ° C., the yield strength increases and the bending property decreases. Furthermore, it is necessary to generate a GP zone during cooling after winding, and if the cooling rate is too high and exceeds 10 ° C./h, the effect of suppressing a decrease in BH properties is insufficient. Conversely, the cooling rate is too slow, 0.1
If the temperature is lower than ° C./h, the proof stress increases greatly, and the bendability is impaired. Therefore, the winding temperature is set in the range of 40 to 100 ° C, and the cooling rate after winding is set in the range of 0.1 to 10 ° C / h. Further, after winding under the above-described conditions, instead of cooling to room temperature by controlling the cooling rate, heat treatment is performed in a temperature range in which a GP zone is quickly generated, so that BH
It is possible to improve the performance. This heat treatment temperature also
If the temperature is lower than 40 ° C., a large number of clusters are formed to inhibit the BH property, thereby increasing the proof stress and impairing the bendability. On the other hand, when the heat treatment temperature exceeds 100 ° C., the yield strength increases and the bendability decreases. If the time is less than 0.5 hour, the generation of the GP zone is insufficient, so that the BH property is reduced. If the time is more than 70 hours, the proof stress is increased and the bending property is reduced. Therefore, the heat treatment temperature is in the range of 40 to 100 ° C., and the heat treatment time is 0.5
~ 70 hours

In order to obtain a higher BH property, it is effective to perform a rewinding treatment at a relatively high temperature and for a short time after winding, cooling or heat treatment under the above conditions after the solution treatment. That is, the generation of the GP zone after the solution treatment suppresses the formation of the cluster, and further, the cluster is dissolved by the restoration treatment to generate the GP zone, whereby an extremely high BH property is obtained. At this time, the winding temperature after the solution treatment is set to the lower limit because if it is less than 40 ° C., the clusters are excessively generated and the GP zone is insufficiently generated by the restoration treatment, thereby impairing the BH property. Meanwhile, 1
If the temperature exceeds 00 ° C., the GP zone is excessively generated by the restoration treatment to impair the formability, the yield strength increases, and the bendability decreases. When the cooling rate is less than 0.1 ° C./h, the GP zone is excessively generated by the restoration treatment to impair the formability, and the yield strength is increased to decrease the bending property. Since the generation of the GP zone is insufficient and the BH property decreases, the upper limit is set. In addition, after solution treatment, it cools and winds, and it is 40 ~ 100 degreeC immediately.
The same effect can be obtained even if the heat treatment is performed for 0.5 to 70 hours.

In the subsequent restoring treatment, when the temperature is lower than 130 ° C., the clusters do not dissolve and the GP zone precipitates, so that the yield strength increases and the formability and bendability are impaired. Also, 280
If the temperature exceeds ℃, the yield strength increases, and an intermediate phase is formed to significantly reduce the formability and bendability. In addition, the holding time is 3
If the time exceeds 0 minutes, the yield strength increases, and the formability and bendability decrease. Therefore, the temperature range of the restoration process is 130 to 28
At 0 ° C., the holding time is 0 to 30 minutes.

Further, in order to improve the deep drawability and mold galling of the aluminum alloy, it is effective to apply a lubricating film to one or both surfaces. When applied to automotive applications, it is desirable to apply a delamination type lubricating film that dissolves and separates the lubricating film in an alkaline degreasing step or a washing step after molding. Therefore, the present inventors have studied in detail the improvement of the formability by the film removal type lubricating film and the dissolution and release properties of the lubricating film in the alkali degreasing step and the washing step. As a result, by forming an alkali-soluble lubricating resin film containing a granular lubricating function-imparting agent on the surface of the aluminum alloy plate within a certain film thickness range, the inventors succeeded in obtaining performance applicable to automotive applications and the like.

Further, the alkali-soluble lubricating coating applied to the surface of the aluminum alloy sheet to enhance the deep drawability and mold galling of the aluminum alloy sheet will be described below. This is an alkali-soluble lubricating resin film containing a granular lubricating function imparting agent with a constant film thickness. For the alkali-dissolved lubricating film that dissolves and removes in alkaline solution,
There are polyethylene glycol-based, polypropylene glycol-based, polyvinyl alcohol-based, acrylic-based, polyester-based and the like, but in order to be alkali-soluble, it must be a resin water dispersion or a water-soluble resin.

As the polyethylene glycol, from the viewpoint of film forming properties, polyethylene glycol having an average molecular weight of 3,000 or more and modified polyethylene glycol are exemplified. Examples of the modified polyethylene glycol include isocyanate-modified polyethylene glycol and epoxy-modified polyethylene glycol. In the case of polypropylene glycol, the average molecular weight is 3 from the viewpoint of film forming property.
000 or more polypropylene glycols and modified polypropylene glycols. Examples of the modified polypropylene glycol include an isocyanate-modified polypropylene glycol and an epoxy-modified polypropylene glycol. In the polyvinyl alcohol system, completely saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, denatured polyvinyl alcohol, and the like can be given. Examples of the modified polyvinyl alcohol include carboxyl group-modified polyvinyl alcohol, sulfonic acid polyvinyl alcohol, and acetoacetyl group polyvinyl alcohol.

Examples of the acrylic resin include acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, maleic acid and itaconic acid copolymers.
As the acrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-acrylate
Butyl, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, methacrylic acid Examples include 2-hydroxyethyl and hydroxypropyl methacrylate. Examples of the copolymer include styrene, acrylamide, vinyl acetate, acrylonitrile, and the like.

As for the polyester system, polyhydric alcohols constituting the polyester include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,6 hexanediol, diethylene glycol,
Examples include dipropylene glycol, neopentyl glycol, triethylene glycol, and the like. Examples of polybasic acids include phthalic anhydride, isophthalic terephthalic acid, succinic anhydride, adipic acid, azelaic acid, sebacic acid, fumaric acid, and itaconic acid. , Maleic anhydride and the like.

When the thickness of the lubricating resin film coated on the aluminum alloy plate of the present invention is less than 0.5 μm, it is not possible to prevent the occurrence of mold seizure or scratches due to the pressing during press working, and the sliding is difficult. The required workability for joining cannot be obtained. This effect is remarkable up to a thickness of 5 μm, but the effect does not change even if the thickness exceeds 5 μm. Therefore, the thickness of the lubricating resin film is in the range of 0.5 to 5 μm. Further, the lubricating resin film of the present invention is coated on both sides or one side of the plate according to the purpose.

The granular lubricating function-imparting agent has a function of further imparting lubricity by reducing the friction coefficient of the surface, preventing galling and the like, and improving press workability and ironing workability. The lubricating function-imparting agent may be any as long as it imparts lubricating performance to the resulting film. Polyolefin (polyethylene, polypropylene, etc.), fluorine (polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride) , Polyvinyl fluoride, etc.), paraffinic waxes, and stearic waxes.

If the amount of the lubricating function-imparting agent is less than 2% by mass%, the required lubricating effect cannot be obtained, and if it exceeds 15%, the film strength is reduced or the lubricating agent is peeled off. Therefore, the content is preferably 2 to 15%.
Silica is added to improve film strength and adhesion to an alloy plate. The silica particles may be any of silica particles such as water-dispersible colloidal silica, crushed silica, and fumed silica. Considering the processability of the coating and the development of corrosion resistance, the primary particle size is 2-30 nm and the secondary aggregated particle size is 1
00 nm or less is preferable. The addition amount of silica is ma
The ss% is preferably 1 to 30%. If it is less than 1%, the effect of improving the adhesion to the lower layer cannot be obtained. If it exceeds 30%, the elongation of the film is reduced, so that the workability is reduced and mold seizure is likely to occur.

In addition to the above, the alkali-soluble lubricating resin film of the present invention may be provided with a pigment for imparting design, a conductive additive for imparting conductivity, and the like, depending on the purpose. It can be added within a range that does not decrease. Also,
In the present invention, the base may be subjected to a phosphate treatment or a chromate treatment in order to obtain further corrosion resistance and adhesion. Examples of the chromate treatment in this case include any of an electrolytic chromate, a reactive chromate, and a coating chromate. The chromate film is preferably formed by applying a chromate solution containing at least one of silica, phosphoric acid and a hydrophilic resin to reduced chromic acid, followed by drying.

The amount of the attached phosphate is preferably in the range of 0.5 to 3.5 g / m ² as the phosphate. The amount of chromate attached is 5 to 150 mg in terms of metal chromium.
/ M ² is preferable, and a more preferable range is 10 to 10.
50 mg / m ² . If it is less than 5 mg / m ² , an excellent corrosion resistance effect cannot be obtained, and if it exceeds 150 mg / m ² , workability is deteriorated, such as cohesive failure of a chromate film during molding. Furthermore, the base may be subjected to an acid washing treatment, an alkali treatment, an electrolytic reduction treatment, a cobalt plating treatment, a nickel plating treatment, a silane coupling treatment and an inorganic silicate treatment according to the purpose.

The lubricating resin film may be formed by applying and baking and drying an aqueous solution or an aqueous dispersion containing a resin component and a particulate lubricating function imparting agent by a conventionally known method such as a roll coater coating method or a spray method. Can be. The lubricating coated aluminum alloy plate of the present invention can be coated with a lubricating oil or a lubricating rust-preventive oil on the upper layer of the lubricating film. However, the lubricating oil or lubricating rust preventive oil to be applied is preferably one that does not swell or dissolve the lubricating film of the present invention. The alloy of the present invention is an aluminum alloy sheet obtained by the above detailed study and suitable for a material for automobiles and the like having excellent formability and BH property.

[0037]

EXAMPLES The present invention will be described below with reference to examples. Example 1 An aluminum alloy having the composition shown in Table 1 was melted, cast, subjected to a homogenization treatment at 550 ° C. for 15 hours, and then subjected to hot rolling and cold rolling to a thickness of 1 mm.
Cold rolled sheet. After subjecting these cold rolled sheets to a solution treatment at 540 ° C. for 10 seconds, they are cooled to 80 ° C. at a cooling rate of 20 ° C./s and wound up, and further cooled to a room temperature at a cooling rate of 1 ° C./h. did. After that, it was left at room temperature for 7 days, and the evaluation results of the tensile test, the forming test, and the bending test performed in accordance with JIS are shown in Table 2. The moldability was evaluated by Erichsen value, and 9.5 or more was evaluated as good. The bendability is
Bending 180 ° with an inner radius of 0.5t, observing the cracks on the outer part, and marking those with cracks with the naked eye as x, and detecting those with no cracks with the naked eye by color check Was performed, and those with cracks observed using a loupe were evaluated as △, and those without cracks were evaluated as ○.
Those with cracks were evaluated as x. Defects were detected by color check for those having no cracks, and those with no defects were evaluated as 、, and those with defects were evaluated as Δ. The BH property was evaluated as a proof stress after a 2% tensile strain and a heat treatment at 170 ° C. for 20 minutes.
MPa or higher was regarded as good.

[0038]

[Table 1]

[0039]

[Table 2]

From Table 2, it can be seen that the aluminum alloy sheet N of the present invention
o. A1 to A18 have good formability, bendability and proof stress after baking. On the other hand, Alloy No. of Comparative Example having components other than the present invention. No. 19 has a Mg content of No. 19; 21 is S
i amount is No. No. 23 has a Mn content of No. 23. No. 25 has a Cr content smaller than the range of the present invention, and has low formability and BH property. In addition, No. No. 20 has a Mg content of No. 20; No. 22 has a larger amount of Si than the range of the present invention, and coarse Mg ₂ Si is precipitated. No. 24 has a Mn content of No. 24. 26 has a large amount of Cr, and coarse Al-Fe-Si-Mn intermetallic compound and Al-Fe-Si-Cr intermetallic compound are precipitated, respectively. Therefore, these alloys have insufficient formability and bendability, and have a reduced BH property due to a decrease in the amount of solute dissolved. No. 27 is Ti
The amount is larger than the range of the present invention, and coarse precipitates are formed, and formability and bendability are reduced. No. In No. 28, since the amount of Cu is larger than the range of the present invention, Cu-based precipitates are generated at the crystal grain boundaries, and the formability, bendability and BH property are reduced. No. Alloys Nos. 29 to 32 contain large amounts of V, Zr, Fe, and B, so that coarse precipitates are formed and formability and bendability are reduced.

Example 2 Inventive alloys A3, A8 and A13 shown in Table 1 were melted and cast, and then homogenized under the conditions shown in Table 3. Furthermore, by hot rolling and cold rolling,
It was a cold-rolled sheet having a thickness of 1 mm. 550 ° C on these cold rolled sheets
Solution treatment for 5 seconds and then to 75 ° C for 15 seconds.
Cooling at a cooling rate of ° C / s and winding
It cooled to near room temperature at ° C / h. Thereafter, these aluminum alloys were allowed to stand at room temperature for 7 days, and the same test as in Example 1 was performed. The results are shown in Table 3. Production No. 33-44
Are within the scope of the present invention, and have good BH properties, moldability and bendability. On the other hand, the production No. 45-47
Since the homogenization treatment temperature is too low, the solid solution of the precipitate is insufficient, and the moldability, bending property and BH property are insufficient. In addition, No. In the case of Nos. 48 to 50, the homogenization treatment temperature was too high and partially melted, and the moldability and the bendability were reduced. No. In Nos. 51 to 53, the retention time at the homogenization treatment temperature is too short, so that the solid solution of the precipitate is insufficient, and the moldability, bending property and BH property are insufficient.

[0042]

[Table 3]

Example 3 530 was added to the invention alloy A3 in Table 1.
A solution treatment was performed at 2 ° C. for 2 seconds, cooled at 20 ° C./s, wound up at 70 ° C., and cooled to near room temperature at a cooling rate of 1.5 ° C./h. The surface of this aluminum alloy was basically untreated with chromate, but for some levels, a coating type obtained by adding colloidal silica to chromic acid with a chromium reduction ratio (Cr (VI) / total Cr) = 0.4 The amount of chromium applied to the chromate solution is 20 m in terms of chromium metal using a roll coater.
g / m ^2, and dried by heating to form a chromate film.

Next, polyethylene wax, polytetrafluoroethylene wax, synthetic paraffin wax, calcium stearate wax, and colloidal silica were mixed with an aqueous solution or aqueous dispersion of polyethylene glycol, polypropylene glycol, and an acrylic resin in the composition shown in Table 4. Then, the resultant was coated with a bar coater and baked and dried at a temperature reaching the alloy plate of 80 ° C. using a heating furnace at 180 ° C. to form a lubricating resin film. As a comparative material for workability evaluation, Johnson Wax # was added to the above aluminum alloy plate.
122 was used. These samples were evaluated for deep drawability, mold galling, resin residue generation after processing, and degreasing. The deep drawability was evaluated by carrying out a cylindrical deep draw test under the conditions of a punch diameter of 50 mm and a punch shoulder radius of 5 mm, and a critical draw ratio (LDR).

The mold seizure and the occurrence of resin residue after the processing were measured by a hydraulic test machine for a cylindrical punch using a punch diameter of 40 mm, a punch shoulder radius of 4 mm, a die diameter of 43 mm,
A molding test was performed with a die shoulder radius of 4 mm and a wrinkle holding force of 1 ton to evaluate. The mold seizure is visually observed on the side wall,
Evaluation was made according to the following indicators. ◎: Formable, no defect on alloy plate surface ○: Formable, no defect on alloy plate surface, slight discoloration on sliding surface △: Formable, slightly galling on alloy plate surface ×: Formable Causes many linear scratches on the alloy plate surface

The state of occurrence of resin residue after processing was evaluated by the following index. ◎: No residue generated ○: Very small resin residue generated △: A little resin residue generated ×: Many resin residues generated

The degreasing property was determined using a FC-4358 degreasing solution (manufactured by Nippon Parkerizing Co., Ltd., adjusted to pH = 10.5, at a temperature of 70).
(° C.) was sprayed onto the test piece for 8 seconds, washed with water, and the residual film ratio after drying was measured by infrared spectroscopy, and evaluated by the following index. ：: No film residue ○: Film residue 5% or less △: Film residue more than 5% 10% or less ×: Film residue more than 10%

Table 4 shows the test results. No. 54-74
All of the above alkali-soluble lubricating-coated aluminum alloy sheets are excellent in deep drawability and mold galling property, hardly generate resin residue after processing, and are excellent in degreasing properties. On the other hand, No. 7
Since No. 5 has a small thickness, the mold galling property is insufficient. N
o. 76 has a small content of the particulate lubricating function-imparting agent,
Insufficient mold seizure. On the other hand, No. No. 77 has a large amount of the particulate lubricating function-imparting agent, so that resin residue is generated after processing.

[0049]

[Table 4]

(Example 4) The invention alloys A3, A8 and A13 shown in Table 1 were melted, cast, subjected to a homogenization treatment at 550 ° C for 15 hours, and then subjected to hot rolling and cold rolling to obtain a thickness. It was a cold-rolled plate of 1 mm. Table 5 shows these cold rolled sheets.
The solution was subjected to a solution treatment under the conditions shown in Table 2 and cooled, wound up at 85 ° C, and further cooled at a cooling rate of 2 ° C / h to near room temperature.
Thereafter, these aluminum alloys were allowed to stand at room temperature for 7 days, and the same test as in Example 1 was performed. The results are shown in Table 5.

Production No. The manufacturing conditions of 78 to 89 satisfy the conditions described in the above (9), and the BH property, moldability and bendability are good. On the other hand, No. In the case of 90 to 92, since the solution treatment temperature is low, Mg, Si and Mn are used.
Is insufficient in solid solution and BH property and moldability are insufficient. In addition, No. In the case of Nos. 93 to 95, the solution treatment temperature was high. In the case of 96 to 98, since the holding time at the solution treatment temperature is long, the crystal grain size becomes coarse, and the formability and bendability are reduced. In addition, No. In the case of 99 to 101, since the cooling rate after the solution treatment is slow, a precipitate is formed, and the BH property, the formability and the bendability are reduced.

[0052]

[Table 5]

(Example 5) The invention alloys A3, A8 and A13 shown in Table 1 were melted, cast, subjected to a homogenization treatment at 550 ° C for 15 hours, and then subjected to hot rolling and cold rolling to obtain a thickness. It was a cold-rolled plate of 1 mm. 54 to these cold rolled sheets
After subjecting to a solution treatment of holding at 0 ° C. for 1 second, 20 ° C./s
, And wound up and cooled under the conditions shown in Table 6. After that, these aluminum alloys were left at room temperature for 7 days,
Table 6 shows the results of the same test as in Example 1.

Production No. The production conditions of 102 to 113 satisfy the conditions described in the above (10), and the BH property, moldability and bendability are good. On the other hand, No. 114-1
In the case of 16, since the winding temperature is low, the BH property decreases,
The proof stress increased and the bendability decreased. In addition, No. 117
In the case of Nos. To 119, the winding temperature was high, so that the yield strength was increased and the bendability was decreased. In addition, No. In the case of 120 to 122, the cooling rate after winding is too high, so that the BH property is reduced. In addition, No. In the case of 123 to 125, the cooling rate after winding is too slow, so that the proof stress increases and the bending property decreases.

[0055]

[Table 6]

(Embodiment 6) As in Embodiment 5, the thickness is 1 mm.
Was subjected to a solution treatment, wound up under the conditions shown in Table 7, and immediately subjected to a heat treatment. Thereafter, these aluminum alloys were allowed to stand at room temperature for 7 days, and the same test as in Example 1 was performed. The results are shown in Table 7. Production No. 126
The manufacturing conditions of No. to 137 satisfy the conditions described in the above (11), and the BH property, the formability and the bending property are good.
On the other hand, No. In the case of 138 to 140, since the heat treatment temperature is low, the BH property is reduced, the proof stress is increased, and the bending property is reduced. In addition, No. In the case of 141 to 143, since the heat treatment temperature was high, the proof stress increased and the bendability decreased. In addition, No. In the case of 144 to 146, since the heat treatment time is short, the BH property is reduced. In addition, No. 147-1
In the case of No. 49, the heat treatment time is too long, so that the proof stress increases and the bendability decreases.

[0057]

[Table 7]

(Embodiment 7) 1 mm in thickness as in Embodiment 5.
Was rolled under the conditions shown in Table 8, and then cooled to room temperature to perform a restoring treatment. Thereafter, these aluminum alloys were left at room temperature for 7 days, and the same test as in Example 1 was performed. The results are shown in Table 9.
Production No. The production conditions of 150 to 170 satisfy the conditions described in the above (12), and the BH property, moldability and bendability are good. On the other hand, No. In the case of 171 to 173, since the winding temperature was low, the BH property was reduced. Also, N
o. In the case of 174 to 176, since the winding temperature was high, moldability and bendability were reduced. In addition, No. 177-1
In the case of 79, the cooling rate after winding is too high,
H property has decreased. In addition, No. In the case of 180 to 182, the cooling rate after winding is too slow, so that the formability and bendability are reduced. In addition, No. 183-185
In the case of, since the restoration temperature was low, the yield strength was increased and the bending property was decreased. In addition, No. In the case of 186 to 188, since the heat treatment temperature was high, a precipitate was formed, and the formability and the bendability were reduced. In addition, No. In the case of 189-191, since the restoration processing time was too long, the proof stress increased and the formability and bendability decreased.

[0059]

[Table 8]

[0060]

[Table 9]

[0061]

According to the present invention, it is possible to provide an aluminum alloy sheet which is excellent in molding, bending properties and paint baking hardenability and is suitable for an automobile material and the like, and a method for producing the same. The application of the alloy of the present invention makes it possible to significantly reduce the weight of automobiles, and contributes not only to industrial value but also to reduction of greenhouse gas emissions.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) ) Inventor Makoto Saga 20-1 Shintomi, Futtsu-shi, Chiba F-term in the Technology Development Division of Nippon Steel Corporation (reference) 4K044 AA06 AB02 BA06 BA14 BA15 BA17 BA19 BA21 BB01 BB03 BB11 BC01 BC04 BC05 CA04 CA16 CA17 CA53 CA62

Claims (12)

[Claims] 1. Mass%: Mg: 0.2 to 1.6%, Si: 0.4 to 1.8%, Mn: 0.03 to 1.5%, Cr: 0.02 to 0. An aluminum alloy sheet containing 5%, with the balance being Al and unavoidable impurities, and having excellent formability and paint bake hardenability. 2. The aluminum alloy sheet having excellent formability and paint bake hardenability according to claim 1, further comprising 0.003 to 0.5% of Ti in mass%. 3. The aluminum alloy sheet having excellent moldability and paint bake hardenability according to claim 1, further comprising 0.1% to 1.5% of Cu in mass%. . 4. Mass%: Fe: 0.02 to 0.5%, Zr: 0.02 to 0.5%, V: 0.02 to 0.5%, B: 0.003 to 0. 5% of one or more
The aluminum alloy sheet according to any one of claims 1 to 3, wherein the aluminum alloy sheet is excellent in formability and paint bake hardenability. 5. A granular lubricating function-imparting agent: 2 to 15 mass
The aluminum alloy sheet according to any one of claims 1 to 4, further comprising an alkali-soluble lubricating resin film having a thickness of 0.5 to 5 µm and a thickness of 0.5 to 5 µm. 6. The aluminum alloy sheet according to claim 5, wherein the alkali-soluble lubricating resin film further contains silica particles: 1 to 30% by mass. . 7. The particulate lubricating function-imparting agent comprises one or more of polyolefin-based wax, fluorine-based wax, paraffin-based wax, and stearic-acid-based wax. An aluminum alloy plate having excellent moldability and paint bake hardenability described in 1. 8. The method for manufacturing an aluminum alloy sheet according to claim 1, wherein after the casting, holding for 1 hour or more at a temperature of 500 to 600 ° C. as a homogenization treatment. A method for producing an aluminum alloy sheet having excellent moldability and paint bake hardenability. 9. After cold rolling, as a solution treatment, 500
Hold at a temperature range of ~ 580 ° C for 300 seconds or less, 5 ° C / s
9. The cooling at the above cooling rate.
4. A method for producing an aluminum alloy sheet having excellent paint bake hardenability and press formability according to item 1. 10. The coating baking hardening according to claim 9, wherein after the solution treatment, the film is cooled to 40 to 100 ° C., wound up, and cooled at a cooling rate of 0.1 to 10 ° C./h. For producing an aluminum alloy sheet having excellent formability and press formability. 11. The coating according to claim 9, wherein after the solution treatment, the film is cooled to 40 to 100 ° C., wound up, and kept at a temperature of 40 to 100 ° C. for 0.5 to 70 hours. A method for producing an aluminum alloy sheet having excellent bake hardenability and press formability. 12. After the solution treatment, it is cooled to 40 to 100 ° C. and wound up, and cooled at a cooling rate of 0.1 to 10 ° C./h.
The method for producing an aluminum alloy sheet having excellent paint bake hardenability and press formability according to claim 9, further comprising heating to 130 to 280 ° C and holding for 0 to 30 minutes.