JPH0747807B2 - Method for producing rolled aluminum alloy plate for forming - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rolled aluminum alloy sheet for forming work, and more specifically, to applications where strength, particularly strength after paint baking and excellent formability are required. The present invention relates to a method for producing a rolled aluminum alloy plate for forming process, which is used for a land transportation vehicle such as an automobile body sheet or panel, or a component of electric equipment.

[0002]

2. Description of the Related Art In the past, cold-rolled steel sheets were often used for automobile body sheets, but recently, in order to reduce the weight of vehicle bodies, studies have been conducted on the use of rolled aluminum alloy sheets. In addition, aluminum alloy plates have been used more and more recently in molded products such as automobile parts and electric equipment parts other than body sheets. As a material used for such an application, it is required to have excellent moldability since it is used after being subjected to press working.
Not only is it excellent in elongation, overhanging property, and drawability,
It is also desired that the in-plane anisotropy is small. In addition, it is also desired that panels for automobiles and the like have excellent appearance quality, and thus it is also desired that no Luders mark is generated during the molding process. In addition, since it is generally subjected to baking coating before use, high strength after baking coating is required.

By the way, as the conventional aluminum alloy for forming, Al-Mg type JIS5182 alloy O material, JIS 5052 alloy O material, or Al-Mg-Si.
AA 6009 alloy T4 treated material and AA 6010 alloy T4 treated material are the most widely used.

[0004]

[Problems to be Solved by the Invention] The aforementioned JIS 518
Al-M such as 2 alloy O material and JIS 5052 alloy O material
Since g-based alloys are apt to cause Luders marks, they are unsuitable for automobile panels and the like, which are required to have excellent appearance quality. In addition, AA 6009 alloy T
Al- such as 4 treated materials and AA 6010 alloy T4 treated materials
Although the Mg-Si alloy has strength and formability comparable to those of steel sheets, not only the strength after baking coating is lower than that of steel sheets, but also the anisotropy during drawing is large. Is a problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for obtaining a rolled aluminum aluminum alloy rolled sheet for forming, which has excellent strength and formability, and in particular has a small anisotropy with respect to formability. It is what

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors have conducted extensive experiments and studies, and as a result,
While appropriately defining the composition of the aluminum alloy,
In particular, in the cold rolling process, intermediate annealing before the final cold rolling is performed under appropriate conditions to appropriately control the structure, and 20%
The present inventors have found that it is sufficient to obtain a rolled plate having an anisotropic degree Δr of the Rankford value appropriately adjusted by performing solution treatment after the final cold rolling as described above, and completed the present invention.

Specifically, the method for producing an aluminum alloy sheet for forming according to the first aspect of the present invention is Mg 0.1 to 1.5.
%, Si 0.3 to 2.5%, and if necessary, Mn 0.05 to 0.6%, Cr 0.05 to 0.3%,
After casting an alloy containing one or more of Zr of 0.05 to 0.3% and the balance of Al and unavoidable impurities, after homogenizing at a temperature in the range of 450 to 570 ° C. , Hot rolling is performed, cold rolling is performed with intermediate annealing once or twice or more in the middle, and final intermediate annealing is performed among intermediate annealing in the middle of cold rolling.
It is heated at a heating rate of 100 ° C./min or more to a temperature in the range of 350 to 580 ° C. and is not held or is held for 5 minutes or less, and further, up to the final plate thickness after the final intermediate annealing. Cold rolling at a rolling rate of 20% or more,
Further, after the final cold rolling, a solution treatment of heating at a temperature within a range of 350 to 580 ° C. for 120 minutes or less is performed,
Subsequently, rapid cooling is performed at a cooling rate of 100 ° C./min or more to obtain a rolled sheet having a Rankford value anisotropy Δr of less than 0.2.

According to the second aspect of the present invention, in the method for producing a rolled aluminum alloy plate for forming, in addition to the respective component elements defined in the first aspect, Cu 0.1 to 1.5%, Z
An aluminum alloy containing one or two of n0.1 to 2.0% is used, and a manufacturing process similar to that of claim 1 is applied.

The Anisotropy Δr of the Rankford value is the Rankford value r in the direction of 0 ° with respect to the rolling direction.
_0, from 45 ° direction of the Lankford value r _45, 90 ° direction of the Lankford value r _90, the following equation Δr = | (r ₀ +
r ₉₀ ) / 2−r ₄₅ |. Note that r ₀ , r ₄₅ , and r ₉₀ are 0 ° and 4 ° with respect to the rolling direction, respectively.
Taking JIS No. 5 tensile test pieces in the directions of 5 ° and 90 °,
It means the Rankford value obtained at the time of 15% tension.

[0010]

First, the reasons for limiting the composition of the aluminum alloy used in the present invention will be explained.

Mg: Mg is an alloy component which is the basis of the present invention, and coexists with Si to form Mg ₂ Si, which contributes to the improvement of strength by precipitation hardening. If the Mg content is less than 0.1%, sufficient strength cannot be obtained, while if it exceeds 1.5%, elongation and moldability deteriorate, so the Mg content is 0.1-1.5%.
Within the range of.

Si: Si is also a basic component element in the present invention, and coexists with Mg to form Mg ₂ Si, which contributes to the improvement of strength by precipitation hardening. Moreover, a part of the added Si is present in the Al alloy as metallic Si particles, and improves the formability, particularly the elongation and bendability. Si amount is 0.3%
If less than the above, the above effect cannot be sufficiently obtained, and the Si content is 2.5%
If it exceeds 1.0, elongation and moldability deteriorate, so the Si content is less than 0.
It was set to 3 to 2.5%. In order to improve the strength, the amount of Si is excessive with respect to the amount of Mg as compared with the stoichiometric composition that produces Mg ₂ Si, and is the amount of Si that produces metallic Si particles. is important. Therefore, in order to improve the strength in particular, it is desirable that the amount of Si be such that Si (%)> 6 × Mg (%) + 0.4.

Cu and Zn: Since these contribute to the improvement of strength, either or both of them are added in the case of the invention of claim 2. Of these, Cu particularly contributes to the improvement of strength after baking. In addition, Zn contributes not only to the improvement of strength but also to the improvement of corrosion resistance, and has an effect of preventing pitting corrosion by lowering the corrosion potential of the matrix. If Cu is less than 0.1% and Zn is less than 0.1%, the respective effects cannot be sufficiently obtained, while if Cu exceeds 1.5%, formability and corrosion resistance are deteriorated, and Zn is 2. If it exceeds 0%, the corrosion resistance is lowered and, at the same time, the formability is lowered due to aging at room temperature.
5% and Zn were within the range of 0.1 to 2.0%.

Mn, Cr, Zr: All of them are effective in making the crystal grains finer and reducing the flow line at the time of molding, and one or more of these are added if necessary. . If less than 0.05%, sufficient effects cannot be obtained, and Mn is 0.6% and Cr is 0.3%.
However, if Zr exceeds 0.3%, a coarse intermetallic compound is generated and the formability deteriorates. Therefore, Mn is 0.05 to 0.
6%, Cr 0.05-0.3%, Zr 0.05-
Within the range of 0.3%.

Basically, in addition to the above constituent elements, A
Although it may be 1 and unavoidable impurities, a small amount of Be or a small amount of Ti may be added to an ordinary aluminum alloy, and in the case of the present invention, addition of these is allowed for the following reason.

Be: Be has a function of forming a dense oxide film and protecting the aluminum surface. In the conventional general Al-Mg-based alloy, a small amount of Be was often added to prevent the oxidation of the molten metal, but in the case of the present invention,
The addition of Be is effective not only for preventing the oxidation of the molten metal, but also for reducing the oxide layer on the surface of the plate during the intermediate annealing and the final annealing, thereby dramatically improving the corrosion resistance, particularly the yarn rust resistance. If the amount of Be is less than 0.0001%, the above-mentioned effect cannot be sufficiently obtained, while if it exceeds 0.01%, the above-mentioned effect is saturated and the economical efficiency is only impaired. The Be amount is preferably in the range of 0.0001 to 0.01%.

Ti: Ti has been conventionally added to refine the ingot structure, and Ti is often added together with B in this case. However, Ti is effective not only for refining the ingot structure but also for improving corrosion resistance,
Even in the case of the present invention, it is allowed to add Ti to improve the corrosion resistance. If the amount of Ti is less than 0.05%, the effect of improving corrosion resistance cannot be sufficiently obtained, while Ti is 1.0
%, A coarse intermetallic compound is formed and rollability and formability are deteriorated. Therefore, when Ti is added, the amount of Ti is preferably in the range of 0.05 to 1.0%. .
If Ti is added for the purpose of improving corrosion resistance, Ti
Not only is it unnecessary to add B at the same time,
Rather, the addition of B fixes Ti as TiB _{2 and} the effect of improving corrosion resistance cannot be obtained. Therefore, it is preferable that B is not added at all, or even if B is added for the purpose of refining the crystal grains, B is 50 ppm or less.

Next, each process in the manufacturing method of the present invention will be described.

First, a molten aluminum alloy having the above-described composition is melted by a conventional method and cast by a semi-continuous casting method (DC casting method). The obtained ingot is homogenized. This homogenization treatment is effective not only for eliminating the inhomogeneity of the ingot to improve the formability but also for stabilizing the recrystallized grains by the subsequent solution treatment. If the homogenization temperature is lower than 450 ° C, the above-mentioned effects cannot be sufficiently obtained, while if it exceeds 570 ° C, eutectic melting may occur. Therefore, the homogenization temperature is in the range of 450 to 570 ° C. Homogenization time is not particularly limited,
Usually, it is preferably within the range of 0.5 to 48 hours.

After the homogenizing treatment, hot rolling is performed according to a conventional method to obtain a hot rolled sheet having a required sheet thickness, and the hot rolled sheet is cold rolled. In the middle of the cold rolling, the intermediate annealing is performed once or twice or more. In the case of the present invention, as described below, the intermediate annealing before the final cold rolling (final annealing) is performed. The conditions of intermediate annealing) are particularly important.

That is, the final intermediate annealing has a great influence on the anisotropy Δr of the Rankford value (r value). In order to improve the moldability, it is not enough to simply increase the r value itself, and it is necessary to reduce the in-plane anisotropy, that is, to reduce the value of Δr represented by the above equation as much as possible. It is important and therefore requires organizational control. In the production of conventional general aluminum alloy rolled sheets, the intermediate annealing is performed only for the purpose of merely improving the cold rolling property, and therefore the cold rolling property is relatively good as in the system targeted by the present invention. In many cases, intermediate annealing is not performed on such alloys. However, as a result of intensive experiments and studies by the present inventors, the intermediate annealing was positively performed, and the intermediate annealing was performed at 100 ° C. /
Min. Or more rapid heating to obtain a special recrystallized texture, and then the final cold rolling is performed at a rolling rate of 20% or more, and solution treatment is performed to obtain the anisotropy Δr of the r value. It was found that a rolled plate having a small size can be obtained.

More specifically, the final intermediate annealing will be described. In general, the rolling texture in aluminum has an orientation close to (123) (634), which is called S orientation. When a rolled plate having such a structure is recrystallized by annealing, it is called an R direction, which is close to the S direction, and a cube direction (Cube Texture) that greatly reduces formability, particularly deep drawability. The (100) (001) orientation is formed. However, it was found that the formation of cube orientation, which hinders formability, can be prevented by recrystallizing by rapid heating such as continuous annealing, and then performing cold treatment at 20% or more and then performing solution treatment. It was Generally, the X-ray diffraction method is widely used as a method for quantitatively measuring the amount of crystal grains in the cube orientation, and the reverse pole integral intensity measurement method is a simple means among the X-ray diffraction methods. It is empirically known that if the (200) integrated strength ratio compared with the standard sample (pure aluminum powder) exceeds 5 by this method, the formability, particularly the deep drawability, is significantly reduced. The r value has a large correlation with the texture, and for example, if the (100) (001) orientation is strongly formed, the r value (that is, r ₀ ) in the test piece parallel to the rolling direction becomes large. , 45 to the rolling direction
It was found that the r value (that is, r ₄₅ ) of the test piece in the direction of ° became extremely small, resulting in a large Δr, which markedly hindered the formability. When the value of Δr is less than 0.2, it can be said that the in-plane anisotropy is small and the formability is excellent as compared with the conventional general aluminum alloy rolling plate for forming and processing. Therefore, in the present invention, Δr was defined as less than 0.2.

Here, if the heating rate (temperature rising rate) in the final intermediate annealing is less than 100 ° C./min, the anisotropy Δ of the r value is Δ.
There is a possibility that the effect of reducing r cannot be obtained, Δr becomes 0.2 or more, recrystallized grains become coarse, and orange peel occurs due to the molding process, and the appearance quality is impaired. Further, if the heating temperature of the final intermediate annealing is less than 350 ° C, the effect of reducing the anisotropy Δr of the r value cannot be obtained. On the other hand, if it exceeds 580 ° C, there is a possibility of eutectic melting and recrystallization As the particles become coarser, the thickness of the surface oxide layer may increase and the yarn rust resistance may deteriorate. Furthermore, even if the heating time in the final intermediate annealing exceeds 5 minutes, the recrystallized grains become coarse and the thickness of the surface oxide layer increases. Therefore, the final intermediate annealing is
It is necessary to heat at 100 ° C./min or more and to heat at a temperature in the range of 350 to 580 ° C. for 5 minutes or less. The heating temperature is preferably more than 450 ° and 580 ° or less in order to more reliably and sufficiently reduce the value of Δr.

After the final intermediate annealing is performed as described above, final cold rolling is performed to obtain the final plate thickness (product plate thickness). This final cold rolling is necessary to stabilize the recrystallized grains by the subsequent solution heat treatment and improve the formability, and it is necessary to perform it at a rolling rate of at least 20% or more. In cold rolling with a rolling ratio of less than 20%, the recrystallized grains become unstable, and the crystal grains become coarse, resulting in poor formability.

After the final cold rolling, solution treatment is performed. This solution treatment is recrystallized to refine the crystal grains,
This is an essential process for stabilizing and obtaining good formability, but in order to obtain uniformly fine crystal grains stably by this solution treatment, the final intermediate annealing and final cooling as described above are required. The conditions of hot rolling are extremely important. This solution treatment must be performed under the condition of heating at a temperature of 350 to 580 ° C. for 120 minutes or less. If the solution heat treatment temperature is less than 350 ° C, recrystallization does not occur and the formability decreases, and if it exceeds 580 ° C, not only the eutectic melt may occur, but also the recrystallized grains become coarse and rough skin occurs after molding. The appearance quality is deteriorated, the moldability is deteriorated, the thickness of the surface oxidation layer is increased, and the yarn rust resistance is reduced. Further, the thickness of the surface oxide layer increases even if the solution treatment time exceeds 120 minutes,
Thread rust resistance decreases. Cooling after such solution treatment may be performed at a cooling rate of 100 ° C./min or more, and for that purpose, forced air cooling, water quenching, etc. can be applied.

If the cooling after the solution treatment is performed by forced air cooling or water quenching, the plate is likely to be deformed such as warped. In order to eliminate such deformation, straightening may be performed by mild cold working such as skin pass, leveling or stretching after solution treatment-cooling. However, since there is a possibility that the formability is lowered by such correction, in this case, in order to recover the formability, the temperature, the heating rate, and the temperature within the ranges shown in FIGS.
It is desirable to perform strain relief annealing at a holding time and a cooling rate.

In the cold rolling process, the intermediate annealing may be performed twice or more in the middle of the cold rolling process.
That is, during the cold rolling before the final intermediate annealing under the above-described conditions, the intermediate annealing may be performed as necessary to improve the cold rolling property. The conditions of the intermediate annealing in the stage before the final intermediate annealing are not particularly limited, but in the case of batch annealing, the temperature is within the range of 250 to 450 ° C.
Generally, the condition of holding for 5 to 24 hours is used, and in the case of continuous annealing, it is general to heat to a temperature of 350 to 580 ° C. for no holding or holding for 5 minutes or less. In the case of batch annealing, the heating and holding temperature is 250 ° C.
If it is less than 450 ° C, the cold rolling property is not improved. If it exceeds 450 ° C, the recrystallized grains are coarsened and the thickness of the surface oxide layer is increased, and if the holding time is less than 0.5 hours, the cold rolling property is improved. If the time exceeds 24 hours, not only the economy is impaired, but also the thickness of the surface oxide layer increases. On the other hand, in the case of continuous annealing, if the temperature reached by heating is lower than 350 ° C, the cold rolling property is not improved, and if it exceeds 580 ° C, not only the eutectic melting may occur, but also the recrystallized grains become coarse and the surface oxide layer is formed. If the holding time exceeds 5 minutes, the recrystallized grains become coarse and the thickness of the surface oxide layer increases.

In the above description, the case where the semi-continuous casting method (DC casting method) is used as the casting method has been described. However, in some cases, continuous casting in which a molten metal is supplied between a pair of cooling rolls to directly cast a thin plate The casting and rolling method (thin plate continuous casting method) may be applied. Further, when the continuous casting and rolling method is applied in this way, the cooling rate during casting is high, and therefore stabilization of the recrystallized grains can be achieved without performing the homogenizing treatment. It is possible to omit, and hot rolling can be omitted because the thin plate is directly cast.

As described above, the final intermediate annealing is performed under appropriate conditions by rapid heating, and the subsequent final cold rolling is performed at a rolling rate of 20% or more, and then an appropriate solution treatment is performed. It is possible to obtain a rolled plate having an anisotropy Δr of the Rankford value of 0.2 or less and little in-plane anisotropy and remarkably excellent formability.

[0030]

[Example] Alloy number No. in Table 1 1-No. Each alloy shown in 5 was DC-cast according to a conventional method, and the obtained ingot was 50
After homogenizing treatment at 0 ° C. for 10 hours, hot rolling was performed according to a conventional method until the plate thickness became 5 mm. Then, cold rolling (primary cold rolling) was performed, and at the stage of rolling to the plate thickness (plate thickness at the time of intermediate annealing) shown in Table 2, intermediate annealing was also performed under various conditions shown in Table 2, and The final cold rolling (secondary cold rolling) was performed at the cold rolling rate (final cold rolling rate) shown in Table 2, and then the solution treatment was performed. The solution treatment is carried out in a salt bath, followed by water quenching (cooling rate approx. 800 ° C /
Second)

For each of the obtained rolled plates, the mechanical properties such as yield strength (YS), tensile strength (TS), and elongation (EL) were examined, and the anisotropic value Δr of r value was calculated.
Further, as a formability, an overhang test value, a limit drawing ratio (LD
R), bending test value, ear ratio, and the inverse pole integral intensity ratio in the (200) direction by X-ray diffraction. The results are shown in Table 3. The mechanical properties and moldability here are
In each case, after solution treatment, aging was performed for 2 weeks at room temperature, and then the measurement was performed. The mechanical properties were measured on the test piece of 0 °, the test piece of 45 ° and the test piece of 90 ° in the rolling direction, and the average values are shown in Table 3. Among the moldability, the overhang test uses a ball head punch with a diameter of 100 mm.
It was carried out with a vinyl chloride film attached. Ear rate is 62 mm
The ear rate when a blank material having a diameter of 32 mm was squeezed with a punch having a diameter of 32 mm was measured. Further, the LDR was measured by using a punch having a diameter of 50 mm, lubricating it with Johnson wax, and drawing. Further, as the bending test value, the 180 ° bending minimum radius was examined. As the inverse pole integral intensity ratio, pure aluminum powder (random sample) having no texture was used as a standard sample, and the (200) integral intensity ratio with the sample was examined.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

As is apparent from Table 3, the rolled plates (Production No. 1, No. 7, No. 7) obtained by the method of the present invention.
9, No. 11) has excellent strength and moldability,
In particular, the anisotropy Δr is a value significantly smaller than 0.2, and the in-plane anisotropy is extremely small. On the other hand, the serial number by the comparison method No. 2, No. No. 4 has a slow heating rate in the intermediate annealing, and is also manufactured by the comparative method. 3, No. 8, N
o. No. 10 had a low heating temperature in the intermediate annealing, and was also manufactured by the comparative method. 5, No. No. 12 which was not subjected to the intermediate annealing, was also No. 12 by the comparative method. No. 6 had a final cold rolling rate of less than 20%, but in each of these comparative methods, Δr was 0.2 or more,
It can be seen that the in-plane anisotropy is large.

[0036]

According to the method of the present invention, it is possible to obtain an aluminum alloy rolled sheet for forming which is excellent in strength and formability, and particularly has very little in-plane anisotropy. Therefore, a large forming degree is required. Ideal for manufacturing materials used for molded parts and molded parts with complex shapes,
It can be used for manufacturing materials such as parts of land transportation vehicles such as automobile body sheets and parts for electric devices.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an optimum range of a heating temperature, a heating rate, and a cooling rate when a strain recovery treatment is performed after further performing a straightening process on a rolled plate obtained by the manufacturing method of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a heating temperature and a holding time when a strain recovery process is similarly performed.

Claims (2)

[Claims] 1. Mg 0.1 to 1.5% (wt%, the same applies hereinafter), Si 0.3 to 2.5%, and if necessary, Mn 0.05 to 0.6% and Cr 0.05. ~ 0.3
%, Zr 0.05 to 0.3%, one or more of them, and the balance is cast from an alloy consisting of Al and inevitable impurities, and homogenized at a temperature in the range of 450 to 570 ° C. After that, hot rolling is performed, and cold rolling is performed with intermediate annealing once or twice or more in the middle.
And, among the intermediate annealing in the middle of cold rolling, the final intermediate annealing is heated to a temperature in the range of 350 to 580 ° C. at a heating rate of 100 ° C./min or more to perform no holding or holding for 5 minutes or less. Cold rolling to a final plate thickness after the final intermediate annealing at a rolling rate of 20% or more, and after the final cold rolling, at a temperature in the range of 350 to 580 ° C. Characterized in that a solution treatment of heating within 120 minutes is carried out, followed by rapid cooling at a cooling rate of 100 ° C./min or more to obtain a rolled plate having a Rankford anisotropy Δr of less than 0.2. Manufacturing method of rolled aluminum alloy sheet for forming. 2. Mg 0.1-1.5%, Si 0.3-
Containing 2.5%, and Cu 0.1-1.5%, Zn
It contains one or two of 0.1 to 2.0%, and if necessary, Mn 0.05 to 0.6%, Cr 0.0
5 to 0.3%, Zr 0.05 to 0.3%, one or more of them are contained, and the balance is cast from an alloy consisting of Al and unavoidable impurities. After homogenizing at temperature, hot rolling is performed, and then cold rolling is performed with one or more intermediate annealings in between, and the final intermediate of the intermediate annealing in the middle of cold rolling. Annealing is performed at a heating rate of 100 ° C./min or more from 350 to
No heating or heating to a temperature in the range of 580 ° C or 5
It is carried out under the condition of holding for less than a minute, and cold rolling to the final plate thickness after the final intermediate annealing is performed at a rolling ratio of 20% or more, and further after the final cold rolling, 350 to
Solution-rolled by heating for 120 minutes at a temperature in the range of 580 ° C., followed by rapid cooling at a cooling rate of 100 ° C./min or more, and a rolled plate having a Rankford anisotropy Δr of less than 0.2. A method for producing a rolled aluminum alloy plate for forming, which comprises: