JPH0790461A - High strength aluminum alloy sheet excellent in formability such as shapability and weldability and its production - Google Patents

Abstract

PURPOSE:To produce an aluminum alloy sheet excellent in formability such as fracture resistance, wrinkling resistance and shapability and resistance spot weldability and to provide the producing method therefor. CONSTITUTION:This aluminum alloy sheet is the one having a compsn. contg., by weight, 5 to 10% Mg and furthermore contg. one or >= two kinds among Cu, Mu, Cr, Zr and Ti each in a content of 0.02 to 0.5%, having 60 to 100mum average grain size, <=14kgf/mm<2> yield point and >=33kgf/mm<2> tensile strength or is the one whose surface is applied with lubricating surface coating as well. At the time of producing the aluminum alloy sheet, the aluminum alloy having the same compsn. is subjected to ordinary casting and hot rolling, is thereafter subjected to cold rolling at 20 to 60% draft and is subjected to continuous annealing to regulate the average grain size into 60 to 100mum, the yield ratio into <=14kgf/mm<2> and the tensile strength into >=33kgf/mm<2>, or after the regulation, it is applied with lubricating surface coating.

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 suitable as a molded part for automobile body sheets or home electric appliances and a method for producing the same, and particularly to formability and welding such as puncture resistance, wrinkle resistance and shape freeze resistance. The present invention relates to an aluminum alloy plate having good properties and a method for producing the same.

[0002]

2. Description of the Related Art Recently, in order to reduce the weight of automobile bodies, it has been studied to use aluminum alloy sheets as body sheets. For this reason, the aluminum alloy sheet is required to have excellent press formability, excellent weldability, and high strength, like the conventional cold-rolled steel sheet. In order to meet such requirements, an Al-Mg-based 5000 series alloy as an aluminum alloy material, specifically 50
52,5182 alloy, etc. are adopted. However, in these alloys, the r value, which is an index of ductility and deep drawability, is remarkably lower than that of steel sheets, so that it is difficult to form the same as steel sheets, and the use sites are limited to lightly processed parts such as hoods. In addition, the aluminum alloy plate is inferior to the steel plate in resistance spot weldability, and has the drawback that the electrode life is extremely shortened especially during continuous spot welding. The current situation is that the production efficiency is significantly reduced.

[0003]

As described above, various efforts have been made to improve the formability and resistance spot welding continuous spotting property, which have been conventionally low. For example, JP-A-61-1
As described in JP-A-130452 and JP-A-03-287739, a manufacturing method has been proposed in which the upper limit of the amount of Fe and Si is regulated and at the same time a high Mg content is added to improve the elongation value. However, the elongation value of the aluminum alloy sheet produced by adding a high amount of Mg according to the above conventional technique is 40% or less, which is significantly lower than the elongation value of 40% or more of the steel sheet. On the other hand, as another approach for improving moldability, Japanese Patent Laid-Open No. 3-1
As disclosed in Japanese Patent No. 80218 and Japanese Patent Application Laid-Open No. 04-268038, a method of improving moldability by coating with a lubricating resin has been proposed. This lubrication significantly improves the formability with respect to fracture resistance. However, since the elastic modulus of the aluminum alloy produced by this method is extremely low, about 1/3 of that of steel plates, wrinkles are likely to occur during forming, and the pressed product after forming has a large springback, that is, its shape fixability is poor. The problem of remains. Further, regarding the weldability, as disclosed in JP-A-4-123879, a welding method has been developed in which an electric insulating coating is arranged on the surface of an aluminum alloy plate to improve the pick-up life of electrodes.
That is, it has hitherto been impossible to produce an aluminum alloy sheet having all the characteristics of formability and weldability such as break resistance, wrinkle resistance and shape freezing property.

Accordingly, it is an object of the present invention to provide an aluminum alloy sheet having excellent formability such as break resistance, wrinkle resistance and shape freezeability and weldability, and a method for producing the same.

[0005]

As a result of various studies, the inventors of the present invention found an aluminum alloy sheet excellent in formability and weldability such as fracture resistance, wrinkle resistance and shape fixability and a method for producing the same. It was

That is, in the present invention, Mg of 5 to 10 wt.
%, Or one or more of Cu, Mn, Cr, Zr, and Ti 0.02 to 0.5 wt% each, the average crystal grain size is 60 to 100 μm, and the yield point is 1.
With a tensile strength of 4 kgf / mm ² or less, a tensile strength of 33 kgf / m
providing rupture, resistance to wrinkling and shape excellent moldability such as fixability and resistance spot welding continuous dotting property superior to the aluminum alloy sheet, characterized in that m ² or more.

The present invention also provides the above aluminum alloy plate.
When manufacturing, aluminum alloy of the above composition is usually
After casting, hot rolling, cold rolling at a reduction rate of 20 to 60%, continuous firing
The average grain size is 60 to 100 μm due to blunting
And the yield point is 14 kgf / mm ²Below, the tensile strength
33 kgf / mm²Aluminum alloy plate adjusted above
A method for manufacturing the same is provided.

Further, according to the present invention, Mg of 5 to 10 wt.
%, Or one or more of Cu, Mn, Cr, Zr, and Ti 0.02 to 0.5 wt% each, the average crystal grain size is 60 to 100 μm, and the yield point is 1.
With a tensile strength of 4 kgf / mm ² or less, a tensile strength of 33 kgf / m
Lubricating resin with excellent formability such as rupture resistance, wrinkle resistance and shape freeze resistance, and resistance spot welding continuous spotting characteristics, characterized by having a lubricious surface coating on an aluminum alloy plate of m ² or more A coated aluminum alloy plate is provided.

The present invention also provides the above aluminum alloy plate.
When manufacturing, aluminum alloy of the above composition is usually
After casting, hot rolling, cold rolling at a reduction rate of 20 to 60%, continuous firing
The average grain size is 60 to 100 μm due to blunting
And the yield point is 14 kgf / mm ²Below, the tensile strength
33 kgf / mm²Aluminum alloy plate adjusted as above
Of aluminum alloy plate with a lubricious surface coating on top
A manufacturing method is provided.

[0010]

The present invention will be described in more detail below. The aluminum alloy plate of the present invention contains Mg in an amount of 5 to 10 wt%, or further 0.02 in each of Cu, Mn, Cr, Zr and Ti.
One or more of 0.5 wt% is contained, the average crystal grain size is 60 to 100 μm, and the yield point is 14 kgf /
mm ² or less, an aluminum alloy sheet tensile strength is 33 kgf / mm ² or more, or an aluminum alloy plate having a lubricious surface coating on the aluminum alloy plate.

The above-mentioned aluminum alloy plate of the present invention is
Excellent formability such as puncture resistance, wrinkle resistance and shape freeze resistance, and excellent resistance spot welding continuous spotting property.

In the production of the above-mentioned aluminum alloy sheet, the aluminum alloy having the above-mentioned composition is subjected to ordinary casting, hot rolling, cold rolling at a reduction rate of 20 to 60%, and continuous annealing to obtain an average crystal grain size of 60 to 60. The yield point is 1 at 100 μm
With a tensile strength of 4 kgf / mm ² or less, a tensile strength of 33 kgf / m
Adjusting to m ² or more, or further applying a lubricious surface coating on the adjusted aluminum alloy plate.

The reasons for limitation in the present invention will be described below. The component content is% by weight. Strength: The strength of the aluminum alloy sheet is an important requirement of the present invention in that not only the panel strength after forming, but also the formability such as fracture, wrinkle, shape fixability, and resistance spot welding continuous spotting properties are greatly affected. . First of all, it has been considered that the improvement of elongation is the most important factor for the rupture-resistant formability. However, as is clear from the comparison with the materials in Table 1, the tensile strength of the material also has a great effect, and the higher the strength, the higher the forming height. To increase.
It also affects the resistance spot welding continuous spotting property, and as is clear from a comparison with the materials in the table, the higher the tensile strength, the higher the continuous spotting number. The lower limit of the tensile strength was set to 33 kgf / mm ² in order to make both of these characteristics of breakability and continuous spotting property good. On the other hand, it is known that the yield stress of the material is one of the controlling factors for the wrinkle generation and the shape freezing property in the steel sheet. The same applies to an aluminum alloy plate as shown in FIG. 1, but its level is higher than that of a steel plate. The upper limit of the yield stress was set to 14 kgf / mm ² in order to secure the wrinkle height and shape fixability at substantially the same level as the steel plate.

Mg: The aluminum alloy targeted by the present invention is an Al-Mg-based alloy containing 5 to 10% of Mg, and the strength of the material is mainly brought about by the solid solution strengthening mechanism of Mg atoms. A high strength is obtained in proportion to and at the same time the elongation is increased, and as a result, the formability is improved. However, if the amount of Mg is less than 5%, the strength required for a vehicle body panel cannot be obtained, and as a result, the electrode life during welding is shortened and at the same time the elongation is low, and the required formability can be obtained even by combining the lubricating treatments described below. I can't.

An increase in the amount of Mg causes an increase in the strength of the aluminum alloy plate described above, an increase in the specific resistance value, a decrease in the thermal conductivity and a decrease in the melting point, which promotes the melting of the welded portion and improves the weldability. As described above, from the viewpoint of strength, formability and weldability, a larger amount of Mg is more preferable, but 10
Addition in excess of 5% deteriorates hot workability, making plate production difficult. For the above reason, the Mg content range is 5 to 10
%.

Other selectively added elements: Cu, Mn, C
Addition of elements such as r, Zr, and Ti increases the strength of the element, resulting in improvement of formability and electrode life during welding. The lower limit was 0.02% to exert the effect, but the upper limit was set to 0.5% because addition of a large amount deteriorates ductility. The effects of these elements are exhibited in both single addition and composite addition.

Cold rolling reduction and crystal grain size: The characteristics of the aluminum alloy sheet of the present invention are high tensile strength and low yield stress. To realize this low yield stress, the crystal grain size and manufacturing conditions are set. Is prescribed. 2 and 3 show the effects of cold rolling reduction on yield stress and crystal grain size. As is clear from the figure, the crystal grain size is 60 μm or more and the yield stress is 14 kgf.
/ Mm ² or less, and a crystal grain size of 60 μm or more is obtained when the cold rolling reduction is in the range of 20 to 60%. If the crystal grain size is 100 μm or more, the surface becomes rough, resulting in deterioration of formability. For the above reasons, the crystal grain size is 60
To 100 μm, and the cold rolling reduction was specified to be 20 to 60%. The production conditions from casting to final annealing other than the cold reduction are ordinary conditions, and the effects of the present invention can be sufficiently obtained. Note that in order to obtain low yield stress, cold rolling after hot rolling,
A two-time cold rolling method of intermediate annealing, cold rolling, and final annealing has been proposed (Japanese Patent Application No. 3-287739). However, such a complicated manufacturing process causes an increase in cost, and thus the present invention described above. The one-time cold rolling method was used in which the rolling reduction was limited.

The aluminum alloy sheet manufactured according to the rules of the present invention as described above has good characteristics such as rupture resistance, wrinkle resistance, shape fixability, and resistance spot welding continuous spotting property, but it is even better. The moldability is achieved by the lubricating resin coating specified below.

Lubricant Coating: Lubricant coating is another important requirement that constitutes the present invention. As shown in Table 1, it is possible to significantly improve the formability by imparting lubricity to a material that cannot withstand press forming when bare. Lubrication is achieved by resin coating. The resin may be either a film-removing type such as wax or a non-film-removing type of an organic resin such as an epoxy resin containing wax, but a non-film-removing type that allows welding coating as it is rather than a film-removing type that requires degreasing treatment after press molding. The type is preferable when considering the manufacturing process of the vehicle body. On the other hand, from the viewpoint of resistance spot welding continuous spotting property, the lubricant coating deteriorates the weldability because it accelerates the wear of the electrode tip due to welding, but as described above, a material containing a large amount of Mg or impurities is used. Since the weldability in the state of the bare plate is greatly improved, the weldability does not deteriorate as compared with the conventional material even when the lubricant coating is applied. Therefore, the type of resin and the film thickness were determined by the limit values for improving the moldability. Preferable examples of the lubrication coating include organic resins such as epoxy and epoxy-urethane series which have a chromate coating as a base and contain a wax.

In the production of the aluminum alloy sheet of the present invention, the steps of casting, annealing and resin coating may be carried out in accordance with a conventional method.

[0021]

EXAMPLES The present invention will be specifically described below based on examples. (Example 1) An aluminum alloy containing about 5.5% of Mg was subjected to normal hot rolling (thickness: 3 mm), and a cold rolling reduction rate was 10.
Cold rolling was performed in the range of ˜80%, annealing was performed at about 500 ° C. for a short time, and the crystal grain size and tensile properties were examined. The effects of cold rolling reduction on the crystal grain size and yield point are shown in FIGS. When the cold rolling reduction is in the range of 20 to 60%, the crystal grain size is 6
It can be seen that it becomes 0 μm or more and the yield point becomes 14 kgf / mm ² or less.

Example 2 Various aluminum alloy plates were manufactured by the alloy composition, manufacturing conditions and surface treatment shown in Table 1, and various tests were conducted. The components and tensile properties of the aluminum alloy sheet according to the regulations of the present invention are shown in Table 1. As the tensile strength increases, both the cup formability and the resistance spot welding continuous spotting property improve. Furthermore, a significant improvement in moldability is recognized due to the coating with the lubricating resin. In the resin treatment materials shown in the table, a urethane-epoxy system (urethane: Mitsui Toatsu Chemicals Orestar and epoxy: Yuka Shell Epoxy Epicoat 1007) containing 10 wt% wax (San Nopco SL630) was used for both 1: 0.3 to 0.5 g / m ^{2 of} resin was applied. Furthermore, cup moldability was evaluated by applying a low-viscosity oil to a 95 mmφ blank plate, molding with a 50 mmφ flat head punch, and measuring the flange diameter at break.

Example 3 Further, wrinkle generation and shape fixability were evaluated using a part of the aluminum alloy plates shown in Table 1 (Comparative Examples 1 and 2 and Inventive Example 3). The evaluation of wrinkle height was based on the YBT test method. That is, a 100 mm square test piece was pulled in a diagonal direction by 1%, and the height of the wrinkles generated was measured. For shape fixability, a bent box-shaped molding (molding height 40 mm) was performed with a 300 mm square punch having a bottom surface with a curvature radius of 1790 mm, and the curvature radius ρ of the molded product was measured to determine the curvature radius ρ ₀ (= 1790 mm) of the punch. ), Δρ / ρ = {(1 / ρ ₀ ) − (1 / ρ)} / (1 / ρ)
The springback was evaluated as. Figure 1 shows the effect of yield stress on wrinkle height and springback. In addition, in the same figure, the measurement results of a 0.7 mm thick steel plate are also shown. The yield stress of the aluminum alloy plate is set to 1 in order to secure wrinkle resistance and shape fixability that are almost the same as mild steel.
It should be 4 kgf / mm ² or less.

[0024]

[Table 1]

[0025]

The aluminum alloy sheet manufactured by the method described in detail above is far better than the conventional aluminum alloy sheet in formability such as puncture resistance, wrinkle resistance and shape fixability, and resistance spot welding continuous. Since it has good hitting properties, it is an optimum material for molded parts for automobile bodies or home appliances for mass production.

[Brief description of drawings]

FIG. 1 is a diagram showing the influence of yield stress on wrinkle height and spring back.

FIG. 2 is a diagram showing the effect of cold rolling reduction on the crystal grain size.

FIG. 3 is a diagram showing the effect of cold rolling reduction on yield stress.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Matsumoto 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Inside the Technical Research Headquarters, Kawasaki Steel Co., Ltd. Kawasaki-cho 1 Technical Research Division, Kawasaki Steel Co., Ltd. (72) Inventor Takaaki Hira 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Technical Research Division Kawasaki Steel Co., Ltd. (72) Inventor Naoki Nishiyama 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Technical Research Division

Claims (6)

[Claims] 1. A magnesium alloy containing 5 to 10 wt% of Mg, an average crystal grain size of 60 to 100 μm, and a yield point of 14 kgf / mm.
An aluminum alloy plate having a tensile strength of 33 kgf / mm ² or more and having a strength of ² or less and having excellent formability such as puncture resistance, wrinkle resistance and shape freezing resistance and resistance spot welding continuous spotting property. 2. Mg of 5 to 10 wt%, Cu, M
n, Cr, Zr, and Ti each containing one or more of 0.02 to 0.5 wt% and having an average crystal grain size of 60 to 1
In 00Myuemu, at yield point 14 kgf / mm ² or less, the rupture tensile strength is characterized in that it is 33 kgf / mm ² or more, excellent moldability such as resistance to wrinkling and shape fixability and resistance spot welding continuously dotting Aluminum alloy plate with excellent properties. 3. Mg of 5 to 10 wt%, or further C
u, Mn, Cr, Zr, Ti 0.02-0.5 wt% each
Aluminum alloy containing one or more of the above is usually cast, hot rolled, and then cold rolled at a reduction rate of 20 to 60%,
The average grain size is 60 to 100 by continuous annealing.
In [mu] m, the yield point at 14 kgf / mm ² or less, the rupture, characterized in that to adjust the tensile strength to 33 kgf / mm ² or more, excellent moldability such as resistance to wrinkling and shape fixability and resistance spot welding continuously A method for manufacturing an aluminum alloy plate that also has excellent hitting properties. 4. A Mg content of 5 to 10 wt%, an average crystal grain size of 60 to 100 μm, and a yield point of 14 kgf / mm.
² or less, the rupture, excellent moldability such as resistance to wrinkling and shape fixability and resistance spot welding successive tensile strength and having a lubricious surface coating to 33 kgf / mm ² or more of the aluminum alloy plate on Lubricating resin-coated aluminum alloy plate with excellent hitting properties. 5. A Mg content of 5 to 10 wt%, and Cu, M
n, Cr, Zr, and Ti each containing one or more of 0.02 to 0.5 wt% and having an average crystal grain size of 60 to 1
In 00Myuemu, rupture the yield point at 14 kgf / mm ² or less, tensile strength and having a lubricious surface coating to 33 kgf / mm ² or more aluminum alloy plate,
Lubricating resin-coated aluminum alloy sheet that has excellent formability such as wrinkle resistance and shape freeze resistance, and excellent resistance spot welding continuous spotting properties. 6. Mg of 5 to 10 wt%, or further C
u, Mn, Cr, Zr, Ti 0.02-0.5 wt% each
Aluminum alloy containing one or more of the above is usually cast, hot rolled, and then cold rolled at a reduction rate of 20 to 60%,
The average grain size is 60 to 100 by continuous annealing.
In [mu] m, the yield point at 14 kgf / mm ² or less, the rupture, characterized in that further subjected to lubricating surface coating tensile strength to 33 kgf / mm ² or more adjusted aluminum alloy plate, anti-wrinkle and shape freezing A method for producing a lubricated resin-coated aluminum alloy sheet which is excellent in formability such as properties and resistance spot welding continuous spotting property.