KR101757733B1 - Method for manufacturing of Al-Zn-Mg-Cu alloy sheet with refined crystal grains - Google Patents

Abstract

The present invention relates to a process for producing an aluminum-zinc-magnesium-copper alloy sheet material in which crystal grains are micronized and more particularly to a process for producing an aluminum-zinc-magnesium-copper alloy melt by an aluminum alloy sheet material One); (Step 2) of primary rolling the aluminum alloy sheet material produced in step 1; Cold rolling the aluminum alloy sheet produced in step 2 (step 3); And a step (step 4) of heat-treating the aluminum alloy sheet material produced in step 3).
The present invention can reduce process time and cost by fabricating an aluminum-zinc-magnesium-copper alloy sheet using a twin-roll casting process. In addition, the plate material produced by the above-described two-roll casting method is sequentially subjected to warm rolling and cold rolling, and heat treatment is performed to maximize the grain refinement and homogenization of the plate material, thereby improving the elongation. Furthermore, the aluminum plate produced by the above-mentioned method can be used for light transport equipment parts and structural materials by greatly improving the strength ductility balance including elongation.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an aluminum-zinc-magnesium-copper alloy sheet having a fine grain size,

The present invention relates to a method of manufacturing an aluminum-zinc-magnesium-copper alloy sheet material in which crystal grains are micronized, and more particularly, to a method of manufacturing an aluminum-zinc- Zinc-magnesium-copper alloy sheet in which grain refinement is carried out to carry out subsequent processing heat treatment.

Recently, as environmental regulations have been strengthened both domestically and internationally, not only in the finished car industry but also in the material industry, we are looking for ways to reduce fuel consumption with energy conservation and pollution prevention measures.

Generally, improvement of engine efficiency, decrease of driving resistance, and weight reduction of the vehicle are suggested as ways to improve fuel efficiency. However, it is known that the most effective method is to reduce the weight of the vehicle and to improve the fuel efficiency by about 10% by reducing the weight by 10%.

For this reason, research is actively underway to replace conventional steel with lightweight, high strength aluminum alloys.

However, since the high strength aluminum plate which is currently being manufactured is a high cost structure manufactured through complicated processes such as heat treatment, hot rolling and cold rolling after ingot casting, it is difficult to control the size of the crystallization phase and inclusions because it is cast in a large slab form.

Therefore, in order to extend the application of aluminum alloy to automobile parts, it is necessary to improve low-cost manufacturing process technology that can improve cost competitiveness by minimizing cost increase in replacing existing steel materials while improving various properties such as noble strength and workability .

Twin-roll casting is a process that can produce a plate directly from a molten metal by unifying two processes of casting and hot rolling as a manufacturing process of such a metal plate material, Has many metallurgical advantages because it is possible to control fine casting structure and crystallization phase, which are difficult to obtain in ingot casting.

Conventional twin roll casting method has been introduced to produce low alloy type aluminum alloy sheet which is relatively easy to control the structure due to a small temperature range deviation in the high-coexistence region at an economical price. Recently, however, Studies are being made to produce sheet metal.

However, in the case of dual alloy casting of high alloy aluminum alloys, there is a variation in the size of solid-solution elements and precipitates in the surface portion and the center portion of the plate due to the difference in cooling rate. This causes microstructure deviation during subsequent processing heat treatment, .

Thus, microstructure control through appropriate subsequent processing and heat treatment processes is required.

On the other hand, the composition and the tensile characteristics of the AA7075 alloy sheet which is currently used commercially are shown in Tables 1 and 2, respectively.

Alloy name
Alloy component / weight% Al Zn Cu Mg Cr Mn Ti Si Fe Other 7075-T4 honey. 5.10
-6.10 1.20
-2.00 2.10
-2.90 0.18
-0.28 ? 0.30 ≤ 0.20 ? 0.40 ≤0.50 ? 0.15

Alloy name
Tensile Properties Yield strength / MPa Tensile strength / MPa Elongation /% 7075-T4 205 395 12

As a conventional technique related to a method of manufacturing an aluminum alloy sheet, Korean Patent Laid-Open No. 10-2012-0135546 discloses a scandium-added aluminum alloy manufacturing process including a solution treatment and a natural aging step for increasing the strength and elongation of scandium- A method has been disclosed. In order to control the recrystallization fraction and vacancy-clustering amount after the casting and homogenization process of Al-Zn- (Mg) - (Cu) - (Zr) - (Ti) Embedding processing step; And a natural aging step for precipitating into a G.P zone and increasing the strength while being kept at room temperature.

However, there is a problem that the degree of improvement of the elongation is insignificant when the aluminum alloy is produced by the above-described production method.

Accordingly, the inventors of the present invention have conducted studies on a method for producing an aluminum alloy sheet of 7000 series having an improved elongation rate, and have found that an aluminum-zinc-magnesium-copper alloy sheet material is formed by a twin roll thin plate casting method, followed by hot rolling and cold rolling Zinc-magnesium-copper alloy sheet with improved elongation by controlling the microstructure of the aluminum alloy sheet by heat treatment, thereby completing the present invention.

SUMMARY OF THE INVENTION

Zinc-magnesium-copper alloy sheet in which the grain size is reduced.

Another object of the present invention is

There is provided an aluminum-zinc-magnesium-copper alloy sheet in which crystal grains produced according to the above method are refined.

According to an aspect of the present invention,

A step (step 1) of making an aluminum-zinc-magnesium-copper alloy melt into an aluminum alloy sheet through a twin-roll sheet casting process;

(Step 2) of primary rolling the aluminum alloy sheet material produced in step 1;

Cold rolling the aluminum alloy sheet produced in step 2 (step 3); And

And a step (step 4) of heat-treating the aluminum alloy sheet material produced in the step 3; and a method of manufacturing the aluminum-zinc-magnesium-copper alloy sheet material in which the crystal grains are micronized.

Further, according to the present invention,

There is provided an aluminum-zinc-magnesium-copper alloy sheet material in which crystal grains are produced according to the above-described method for producing an aluminum alloy sheet material.

The process for producing an aluminum-zinc-magnesium-copper alloy sheet according to the present invention can reduce the processing time and cost by manufacturing an aluminum-zinc-magnesium-copper alloy sheet using a twin-roll casting process.

In addition, the plate material produced by the above-described two-roll casting method is sequentially subjected to warm rolling and cold rolling, and heat treatment is performed to maximize the grain refinement and homogenization of the plate material, thereby improving the elongation.

Further, the aluminum plate manufactured by the above-described method can be used for light transport equipment parts and structural materials by greatly improving the strength ductility balance including elongation.

1 is a photograph showing the microstructure of the aluminum-zinc-magnesium-copper alloy sheet produced in Examples 1 to 5 and 10 to 13;
2 is a graph showing crystal grain size measurement results of a surface portion (thickness direction surface) and a center portion (thickness direction center) of the aluminum-zinc-magnesium-copper alloy sheet material produced in Examples 1 to 25;
3 is a graph showing the results of measurement of aspect ratios of crystal grains in the surface portion (thickness direction surface) and the center portion (thickness direction center) of the aluminum-zinc-magnesium-copper alloy plate produced in Examples 1 to 25;
4 is a graph showing the tensile strength and elongation of the aluminum-zinc-magnesium-copper alloy sheet produced in the control group, Examples 1 to 5 and Comparative Examples 1 to 3. FIG.

The present invention

A step (step 1) of making an aluminum-zinc-magnesium-copper alloy melt into an aluminum alloy sheet through a twin-roll sheet casting process;

(Step 2) of primary rolling the aluminum alloy sheet material produced in step 1;

Cold rolling the aluminum alloy sheet produced in step 2 (step 3); And

And a step (step 4) of heat-treating the aluminum alloy sheet material produced in the step 3, thereby producing an aluminum-zinc-magnesium-copper alloy sheet material.

Hereinafter, a method of manufacturing the aluminum-zinc-magnesium-copper alloy sheet according to the present invention will be described in detail.

In the manufacturing method of the present invention, the step 1 is a step of manufacturing an aluminum-zinc-magnesium-copper alloy melt into an aluminum alloy sheet material by a twin roll thin plate casting method.

The aluminum-zinc-magnesium-copper alloy, that is, the aluminum alloy of 7000 series, is known to be difficult to apply the twin roll sheet casting method because Zn is added to increase the strength, According to the prior art, in order to manufacture a 7000 series aluminum alloy sheet material, a process of making an aluminum alloy melt as an ingot and then rolling it is being performed.

Accordingly, the present invention provides a method for manufacturing an aluminum alloy of 7000 series by a thin plate casting method, overcoming the limitations of the prior art as described above. In the step 1, the molten aluminum-zinc-magnesium- To produce an aluminum alloy sheet.

The aluminum-zinc-magnesium-copper alloy melt may contain 5.0 to 6.0 wt% of Zn, 2.0 to 3.0 wt% of Mg, and 1.0 to 2.0 wt% of Cu and Al.

When the aluminum alloy molten metal includes Zn, Mg and Cu in the above content range, the strength of the aluminum alloy sheet material produced from the molten metal is improved.

In particular, Zn, which is a main alloy element, is preferably added to the aluminum alloy melt in an amount of 5.0 to 6.0 wt%.

If the content of Zn is less than 5.0%, the strength of the aluminum alloy sheet produced from the molten metal is lowered. If the content of Zn exceeds 6.0%, the flowability of the molten metal is decreased and the nozzle inlet is partially clogged during the double- There is a problem that it is difficult to continuously produce a sound plate material.

However, the composition of the alloy melt is not limited thereto, and a metal composition which can be used as a 7000 series alloy sheet material can be appropriately selected and used.

The twin roll sheet casting of step 1 above can be carried out under conditions of a roll speed of 2 to 10 m / min and a roll interval of 2 to 10 mm, preferably a roll speed of 4 to 6 m / min, 3.0 to 4.5 mm.

Specifically, in order to produce an aluminum-zinc-magnesium-copper alloy melt in the form of a sheet material, the double roll casting method is carried out in such a manner that two rolls rotating at a speed of 2 to 10 m / min, preferably 4 to 6 m / Aluminum-zinc-magnesium-copper alloy melt.

At this time, the two rolls are horizontal type twin rolls, horizontally arranged and spaced apart from each other by an interval of 2 to 10 mm, preferably 3.0 to 4.5 mm. By the cooling water flowing into the inside of the roll, And cooling it as it is transported through.

If the roll speed is less than 2 m / min, the molten metal is solidified due to a too low roll speed and then exits the roll. Therefore, the rolling force is increased, and thus a large amount of cracks are generated in the manufactured plate. In addition, when the rotation speed of the roll exceeds 10 m / min, there is a problem that the molten metal flows down, resulting in a problem that the plate can not be manufactured.

If the interval between the rolls is less than 2 mm, the thickness of the plate to be manufactured is so thin that it is difficult to carry out the subsequent processing heat treatment process. If the interval of the rolls exceeds 10 mm, There is a problem that a lot of heat treatment processes must be performed.

On the other hand, the aluminum alloy sheet material produced through the twin-roll sheet casting of step 1 may have a thickness of 2 to 10 mm.

If the thickness of the plate to be manufactured is less than 2 mm, it is difficult to carry out the subsequent processing heat treatment process because of the thin thickness. If the thickness of the plate to be manufactured exceeds 10 mm, the thickness is thick, There is a problem to be performed.

In the manufacturing method of the present invention, the step 2 is a step of primary rolling the aluminum alloy sheet material produced in the step 1.

Specifically, the primary rolling may be performed by warm rolling, and the primary rolling may be performed by rotating the aluminum alloy sheet material, which has been double-cast in step 1, at a speed of 4 to 6 m / min heated at 200 to 300 캜 Can be performed by passing between two rolls.

If the roll temperature is lower than 200 ° C, there is a problem that rolling defects due to cracks increase. If the roll temperature is higher than 300 ° C, the roll surface may be separated from the roll surface, .

In addition, if the roll speed is less than 4 m / min, there is a problem that rolling distortion is applied to the entire plate material, so that shear deformation is difficult to be caused to improve plate formability. When the roll speed is more than 6 m / min, There may arise a problem that it does not cause deformation.

The primary rolling of step 2 above can be carried out with a reduction of 18 to 32%, preferably an average reduction of 25%.

If the reduction rate is less than 18%, the process time and cost are increased because a large number of repeated rolling operations are required. When the reduction rate exceeds 32%, significant cracks are generated in the plate material and surface quality and mechanical properties May be deteriorated.

The primary rolling of step 2 may be repeated until the thickness of the sheet material subjected to rolling is 20 to 60% of the thickness of the sheet material before rolling, and the repetitive rolling may be performed 2 to 5 times.

Meanwhile, in the manufacturing method of the present invention, the step of annealing the alloy sheet produced in the step 1 at 350 to 450 ° C for 30 to 120 minutes may be further performed before the primary rolling of the step 2 is performed.

The annealing step is a step of heating the aluminum alloy sheet material with a double-roll casting to a predetermined temperature and then slowly cooling it, and is a step of removing the stress by leveling the internal structure of the aluminum alloy sheet material.

The annealing process may be performed by heating the twin-rolled aluminum alloy sheet at 350 to 450 DEG C for 30 to 120 minutes and then cooling the same,

If annealing is performed at a temperature lower than 350 ° C., internal stress introduced in the previous rolling step may not be sufficiently removed. If annealing is performed at a temperature exceeding 450 ° C., Can occur.

Further, when the annealing is performed for less than 30 minutes, the internal stress can not be sufficiently removed, and when the annealing is performed for more than 120 minutes, excessive energy is consumed in terms of energy efficiency Can occur.

On the other hand, in the method for producing an aluminum-zinc-magnesium-copper alloy sheet material of the present invention, since the aluminum alloy sheet material produced through the twin-roll casting of step 1 is maintained at a high temperature, It is also possible to dispose the steel sheet as a stand so as to perform the primary rolling of the step 2 directly by omitting the annealing process.

In the manufacturing method of the present invention, the step 3 is a step of cold-rolling the aluminum alloy sheet material produced in the step 2.

As described above, the aluminum alloy sheet subjected to the primary rolling is cold-rolled and then subjected to a subsequent heat treatment, thereby maximizing the grain size and homogenization, thereby improving the elongation of the sheet material.

In this case, the cold rolling in the step 3 may be repeated until the thickness of the rolled plate is reduced by 38 to 95% of the thickness of the plate subjected to the primary rolling.

If the thickness of the sheet subjected to the cold rolling in the step 3 is less than 38% of the thickness of the sheet subjected to the primary rolling, a sufficient amount of deformation is not given, There is a problem that the microstructure is large and the deviation is not removed because the recrystallization does not occur sufficiently, and when the rolling is performed at a thickness reduction ratio exceeding 95%, the thickness is 0.2 mm, .

Meanwhile, in the manufacturing method of the present invention, the step of annealing the alloy sheet produced in step 2 at 350 to 450 ° C for 30 to 120 minutes may be further performed before the cold rolling of step 3 is performed.

The annealing process is preferably performed by heating the primary rolled aluminum alloy sheet at 350 to 450 DEG C for 30 to 120 minutes and then cooling it.

If annealing is performed at a temperature lower than 350 ° C., internal stress introduced in the previous rolling step may not be sufficiently removed. If annealing is performed at a temperature exceeding 450 ° C., there is a problem of increasing surface oxidation Can occur.

Further, when the annealing is performed for less than 30 minutes, the internal stress can not be sufficiently removed, and when the annealing is performed for more than 120 minutes, excessive energy is consumed in terms of energy efficiency Can occur.

In the manufacturing method of the present invention, the step 4 is a step of heat-treating the aluminum alloy sheet material produced in the step 3.

The heat treatment in step 4 may be performed at 400 to 550 ° C for 50 to 70 minutes, preferably at 480 to 530 ° C for 50 to 70 minutes.

The aluminum-zinc-magnesium-copper alloy sheet material having excellent mechanical properties can be produced by performing the heat treatment in step 4 under the above conditions. In particular, when the heat treatment is performed at 480 to 530 ° C, An aluminum-zinc-magnesium-copper alloy sheet material having an elongation ratio can be produced.

The elongation of the aluminum-zinc-magnesium-copper alloy sheet subjected to the heat treatment in the step 4 of the present invention may have an elongation of 24.0% or more, a strength ductility balance of 8900 MPa% or more and satisfies the elongation and strength ductility balance .

Also, the grain size of the aluminum-zinc-magnesium-copper alloy plate heat treated in the step 4 may be 5 to 20 탆.

The aluminum-zinc-magnesium-copper alloy sheet produced according to the present invention has a fine grain size as described above by maximizing the grain refinement and homogenization of the sheet material by performing appropriate warming, cold working and heat treatment, It is possible to have a high elongation ratio and thus a high strength ductility balance.

Further, according to the present invention,

There is provided an aluminum-zinc-magnesium-copper alloy sheet produced by the above production method.

The aluminum-zinc-magnesium-copper alloy sheet produced in accordance with the present invention can be manufactured at a low cost by using a twin-roll casting process, thereby reducing processing time and cost.

 In addition, since the grain size and homogenization of the produced plate material are maximized, the elongation rate is greatly improved while the strength is maintained, and therefore, it exhibits a high strength and ductility balance, and thus can be usefully used as lightweight transportation equipment parts and structural materials.

Hereinafter, the present invention will be described more specifically with reference to Examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

<Control group>

The commercial aluminum alloy, 7075-T4, was compared as a control.

The aluminum alloy was subjected to T4 treatment (natural aging).

&Lt; Example 1 >

Step 1: A horizontal twin roll casting machine with a cooling water line was used to produce an aluminum alloy sheet. Double rolls with a diameter of 300 mm were applied to a horizontal twin roll casting machine.

Aluminum alloy was a commercial alloy having the same composition as commercial AA7075 aluminum alloy. After dissolving at 740 ° C, Al-5Ti-1B was added as a crystal grain refiner to completely dissolve and then argon gas was injected at 730 ° C for 10 minutes. Gas treatment.

The aluminum-zinc-magnesium-copper alloy melt prepared at 680 ° C was injected into a tundish consisting of a 150 mm wide ceramic board. For double casting, the molten metal flowed from the melting furnace to the tundish, and after entering the tundish inlet, the molten metal was transferred to the rotating roller surface. The molten metal rapidly solidifies in contact with the two-rolls cooled by the cooling water, and passes between the two rolls. The rotation speed of the twin roll is 5 m / min and the interval is 4 mm.

Through this process, a double-rolled aluminum alloy sheet having a thickness of 4.4 mm and a width of 150 mm was produced.

Step 2: The aluminum-zinc-magnesium-copper alloy sheet produced in step 1 was annealed at 400 ° C for 60 minutes and then warm-rolled. During warm rolling, warm rolling was repeatedly performed so that the thickness of the sheet material was 2.0 mm at an average rolling reduction rate of 25% at a rotational speed of 5 m / min and a preheating temperature of 250 캜 at the top / bottom roll speeds.

Step 3: The aluminum-zinc-magnesium-copper alloy sheet which was first rolled in step 2 was further annealed at 400 ° C for 60 minutes and then subjected to cold rolling at room temperature.

During the cold rolling, rolling was repeatedly performed at room temperature so as to have a thickness of 1.6 mm, which is 20% lower than the thickness of the aluminum alloy sheet subjected to the primary rolling at the rotation speed of 5 m / min at the upper / lower rolls.

Step 4: The 1.6 mm thick plate produced in Step 3 was heat-treated at 510 ° C for 60 minutes and water-cooled to produce an aluminum alloy sheet.

&Lt; Example 2 >

Except that the aluminum alloy sheet subjected to the primary rolling in the step 3 of Example 1 was repeatedly rolled so that the thickness of the aluminum alloy sheet was reduced by 40% to have a thickness of 1.2 mm, A plate material was prepared.

&Lt; Example 3 >

The procedure of Example 1 was repeated except that the thickness of the aluminum alloy sheet subjected to the first rolling in the step 3 of Example 1 was reduced by 60% so as to have a thickness of 0.8 mm, A plate material was prepared.

<Example 4>

Except that the aluminum alloy sheet subjected to the primary rolling in the step 3 of Example 1 was repeatedly rolled so that the thickness of the aluminum alloy sheet was reduced by 80% to a thickness of 0.4 mm, A plate material was prepared.

&Lt; Example 5 >

The procedure of Example 1 was repeated except that the thickness of the aluminum alloy sheet subjected to the primary rolling in the step 3 of Example 1 was reduced by 90% to have a thickness of 0.2 mm, A plate material was prepared.

&Lt; Example 6 >

An aluminum alloy sheet was produced in the same manner as in Example 1, except that the heat treatment was performed at 410 ° C in the step 4 of Example 1.

&Lt; Example 7 >

An aluminum alloy sheet was produced in the same manner as in Example 1 except that the heat treatment was performed at 440 ° C in the step 4 of Example 1.

&Lt; Example 8 >

An aluminum alloy sheet was produced in the same manner as in Example 1 except that the heat treatment was carried out at 460 ° C in the step 4 of Example 1.

&Lt; Example 9 >

An aluminum alloy sheet was produced in the same manner as in Example 1, except that the heat treatment was carried out at 490 ° C in the step 4 of Example 1.

&Lt; Example 10 >

An aluminum alloy sheet was prepared in the same manner as in Example 2, except that the heat treatment was performed at 410 ° C in the step 4 of Example 2.

&Lt; Example 11 >

An aluminum alloy sheet was produced in the same manner as in Example 2, except that the heat treatment was performed at 440 ° C in the step 4 of Example 2.

&Lt; Example 12 >

An aluminum alloy sheet was produced in the same manner as in Example 2, except that the heat treatment was performed at 460 ° C in the step 4 of Example 2.

&Lt; Example 13 >

An aluminum alloy sheet was prepared in the same manner as in Example 2, except that the heat treatment was performed at 490 ° C in the step 4 of Example 2.

&Lt; Example 14 >

An aluminum alloy sheet was produced in the same manner as in Example 3, except that the heat treatment was performed at 410 ° C in the step 4 of Example 3.

&Lt; Example 15 >

An aluminum alloy sheet was produced in the same manner as in Example 3, except that the heat treatment was performed at 440 ° C in the step 4 of Example 3 above.

&Lt; Example 16 >

An aluminum alloy sheet was produced in the same manner as in Example 3, except that the heat treatment was performed at 460 ° C in the step 4 of Example 3.

&Lt; Example 17 >

An aluminum alloy sheet was produced in the same manner as in Example 3, except that the heat treatment was performed at 490 ° C in the step 4 of Example 3.

&Lt; Example 18 >

An aluminum alloy sheet was produced in the same manner as in Example 4, except that the heat treatment was performed at 410 ° C in the step 4 of Example 4.

&Lt; Example 19 >

An aluminum alloy sheet was produced in the same manner as in Example 4, except that the heat treatment was performed at 440 ° C in the step 4 of Example 4 above.

&Lt; Example 20 >

An aluminum alloy sheet was produced in the same manner as in Example 4, except that the heat treatment was performed at 460 ° C in the step 4 of Example 4 above.

&Lt; Example 21 >

An aluminum alloy sheet was produced in the same manner as in Example 4, except that the heat treatment was performed at 490 ° C in the step 4 of Example 4.

&Lt; Example 22 >

An aluminum alloy sheet was produced in the same manner as in Example 5, except that the heat treatment was performed at 410 ° C in the step 4 of Example 5 above.

&Lt; Example 23 >

An aluminum alloy sheet was manufactured in the same manner as in Example 5 except that the heat treatment was performed at 440 ° C in the step 4 of Example 5 above.

&Lt; Example 24 >

An aluminum alloy sheet was prepared in the same manner as in Example 5, except that the heat treatment was performed at 460 ° C in the step 4 of Example 5 above.

&Lt; Example 25 >

An aluminum alloy sheet was produced in the same manner as in Example 5, except that the heat treatment was performed at 490 ° C in the step 4 of Example 5 above.

&Lt; Comparative Example 1 &

In Step 3 of Example 1, the preheating temperature was set to 250 ° C, the aluminum alloy sheet subjected to the primary rolling was repeatedly warm-rolled so as to have a thickness of 1.0 mm with a reduction of 50% in thickness, An aluminum alloy sheet was produced in the same manner as in Example 1 except that the heat treatment was performed.

&Lt; Comparative Example 2 &

An aluminum alloy sheet was produced in the same manner as in Comparative Example 1, except that the heat treatment was performed at 490 ° C in Step 4 of Comparative Example 1.

&Lt; Comparative Example 3 &

An aluminum alloy sheet was produced in the same manner as in Comparative Example 1, except that the heat treatment was performed at 510 ° C in Step 4 of Comparative Example 1.

The rolling method of step 3 Final reduction (%) of step 3 Heat treatment temperature (° C) of step 4 Example 1 Cold 20 510 Example 2 Cold 40 510 Example 3 Cold 60 510 Example 4 Cold 80 510 Example 5 Cold 90 510 Example 6 Cold 20 410 Example 7 Cold 20 440 Example 8 Cold 20 460 Example 9 Cold 20 490 Example 10 Cold 40 410 Example 11 Cold 40 440 Example 12 Cold 40 460 Example 13 Cold 40 490 Example 14 Cold 60 410 Example 15 Cold 60 440 Example 16 Cold 60 460 Example 17 Cold 60 490 Example 18 Cold 80 410 Example 19 Cold 80 440 Example 20 Cold 80 460 Example 21 Cold 80 490 Example 22 Cold 90 410 Example 23 Cold 90 440 Example 24 Cold 90 460 Example 25 Cold 90 490 Comparative Example 1 Warm 50 460 Comparative Example 2 Warm 50 490 Comparative Example 3 Warm 50 510

<Experimental Example 1> Microstructure observation of aluminum alloy sheet

In order to observe the microstructure of the aluminum-zinc-magnesium-copper alloy sheet materials produced in Examples 1 to 5 and 10 to 13, the side surfaces (the direction of the rolling direction and the direction perpendicular to the sheet surface) 1 and the crystal grain size and aspect ratio of the aluminum-zinc-magnesium-copper alloy sheet prepared in Examples 1 to 25 were observed and shown in FIG. 2 and FIG.

As shown in FIG. 1, the sheet cold rolled repeatedly at room temperature so as to reduce 40% (1.2 mm) of the thickness of the primary rolled plate according to the present invention, increases as the temperature of the heat treatment is increased from 410 ° C to 510 ° C, It can be confirmed that the crystal grains became finer from 40 탆 to 25 탆 in Example 10 to Example 13 and Example 2. This is because the higher the heat treatment temperature, the easier the recrystallization is for the same thickness reduction rate (processing amount).

Further, in the case of heat-treating the cold-rolled plate at room temperature at a temperature of 510 ° C so that the thickness of the primary rolled plate decreases by 20 to 90% (1.6 to 0.2 mm), the greater the reduction rate of the thickness, , It can be confirmed that the crystal grains become finer from 50 占 퐉 to 10 占 퐉 level from Example 1 to Example 5.

As a result, it can be seen that the crystal grains become finer as the temperature of the heat treatment in the step 4 is increased or the reduction rate of the thickness during the cold rolling in the step 3 is larger.

Further, as shown in Figs. 2 and 3, the difference between the center of gravity and the center of gravity of the average crystal grains tends to decrease as the temperature of the heat treatment increases, or as the thickness reduction rate during cold rolling increases.

At this time, the crystal grain aspect ratio can be calculated by the following equation (1).

&Quot; (1) &quot;

Grain aspect ratio = RD direction length of crystal grain / TD direction length of crystal grain

Thus, it can be seen that as the final thickness is greatly reduced in the cold rolling step, as the heat treatment temperature in the heat treatment step is increased, the crystal grains become finer, the crystal aspect ratio decreases, and the deviation between the surface portion and the center portion of the plate disappears.

<Experimental Example 2> Observation of mechanical strength of aluminum alloy sheet

In order to observe the mechanical properties of the aluminum alloy sheet manufactured according to Examples 1 to 5 and Comparative Examples 1 to 3 and the control group, a plate-like tensile specimen having a gauge length of 25 mm, a gauge width of 6 mm and a final plate thickness And a tensile test was carried out at a crosshead speed of 1 mm / min. The results are shown in Table 4 and Fig.

Tensile strength / MPa Elongation (%) Strength ductility balance (MPa%) Example 1 373.0 20.5 7646.5 Example 2 393.7 24.0 9448.8 Example 3 362.4 24.8 8987.5 Example 4 370.9 26.6 9865.9 Example 5 365.2 25.3 9239.6 Comparative Example 1 442.8 7.9 3498.1 Comparative Example 2 431.4 9.1 3925.7 Comparative Example 3 438.7 17.3 7589.5 Control group 395.0 12.0 4740.0

As shown in Table 4 and FIG. 4, the aluminum alloy sheet produced according to Examples 2 to 5 exhibited a maximum tensile strength of 360 to 395 MPa and an elongation of 24 to 27%, and the control aluminum alloy The maximum tensile strength of 395 MPa and the elongation of 12%.

Also, unlike Examples 1 to 5, Comparative Examples 1 to 3 in which warm rolling was performed in place of the cold rolling showed maximum tensile strengths of 430 to 443 MPa and elongation of 8 to 17%.

As a result, it can be seen that after the twin-roll thin plate casting, the subsequent cold rolling and the heat treatment process are carried out to control the microstructure of the plate material, thereby having a higher degree of elongation than the commercial aluminum alloy. Further, the tensile strength can be maintained at a constant level, thereby exhibiting a high strength ductility balance.

Claims (13)

Zinc-magnesium-copper alloy melt containing 5.0 to 6.0% by weight of Zn, 2.0 to 3.0% by weight of Mg, 1.0 to 2.0% by weight of Cu and the balance of Al by means of a twin- To 10 m / min, and the roll interval is 2 to 10 mm (step 1);
A step (step 2) of primary rolling the aluminum alloy sheet material produced in step 1 at a roll temperature of 200 to 300 ° C;
Cold rolling the aluminum alloy sheet produced in step 2 (step 3); And
(Step 4) of heat treating the aluminum alloy sheet material produced in step 3,
The cold rolling in step 3 is repeated until the thickness of the sheet material on which the rolling has been performed is reduced by 40 to 90% of the thickness of the sheet material subjected to the primary rolling,
Wherein the grain size of the aluminum-zinc-magnesium-copper alloy plate heat treated in step 4 is 5 to 20 占 퐉 and the elongation is 20% or more.
The method according to claim 1,
Wherein the thickness of the twin-roll sheet-cast aluminum alloy sheet of step 1 is 2 to 10 mm. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
The method according to claim 1,
Further comprising the step of annealing the aluminum alloy sheet produced in step 1 at 350 to 450 DEG C for 30 to 120 minutes before the primary rolling of step 2, A method for manufacturing a copper alloy sheet material.
The method according to claim 1,
Wherein the primary rolling of step 2 is performed at a roll speed of 4 to 6 m / min. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
The method according to claim 1,
Wherein the primary rolling of step 2 is performed at a reduction rate of 18 to 32%. &Lt; Desc / Clms Page number 19 &gt;
The method according to claim 1,
Wherein the primary rolling of step 2 is performed at a reduction rate of 25% on average. &Lt; RTI ID = 0.0 &gt; 18. &lt; / RTI &gt;
The method according to claim 1,
Wherein the primary rolling in the step 2 is repeatedly performed until the thickness of the plate subjected to rolling is 20 to 60% of the thickness of the plate before rolling. Gt;
8. The method of claim 7,
Wherein the repeated rolling is performed two to five times. &Lt; RTI ID = 0.0 &gt; 15. &lt; / RTI &gt;
The method according to claim 1,
Further comprising the step of annealing the aluminum alloy sheet produced in step 2 at 350 to 450 DEG C for 30 to 120 minutes before performing the cold rolling of step 3, A method for manufacturing an alloy sheet material.
delete The method according to claim 1,
Wherein the heat treatment in step 4 is performed at 400 to 550 DEG C for 50 to 70 minutes. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
The method according to claim 1,
Wherein the elongation percentage of the aluminum-zinc-magnesium-copper alloy sheet annealed in step 4 is 24.0% or more.
The method according to claim 1,
Wherein the strength ductility balance of the aluminum-zinc-magnesium-copper alloy sheet heat treated in step 4 is 8900 MPa% or more.

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