JPH08325664A - High-strength heat-treatable aluminum alloy plate for drawing and method for manufacturing the same - Google Patents

Abstract

(57) [Abstract] [Purpose] As an Al alloy plate for drawing, which is used for DI can bodies, DRD can bodies, can lids, etc., having high strength and at the same time forming cans having drawability and ironing workability. We provide products with excellent properties. [Structure] Claim 1: Zn 3 to 6%, Mg 0.5 to 3
%, Mn more than 0.5% and 1.5% or less, and the balance is substantially Al. Claim 2: In addition to the above, Cu0.1
An Al alloy plate containing 2.5%. Claim 3: After finishing the alloy of claim 1 to a predetermined plate thickness, it is subjected to a solution treatment at 450 to 550 ° C for a short time of 5 minutes or less, and a final cold rolling of more than 30% and 75% or less. Claim 4: The alloy of claim 2 is finished to a predetermined plate thickness, then subjected to a solution treatment at 450 to 540 ° C for a short time of 5 minutes or less, and subjected to the same final cold rolling as described above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment type aluminum alloy sheet for drawing which requires high strength and a method for producing the same, and particularly to a can body, a can lid or a food can (DRD) of an aluminum two-piece DI can. The present invention relates to an aluminum alloy plate for drawing, which is mainly used as a material for containers such as cans, and a method for manufacturing the same.

[0002]

2. Description of the Related Art As an aluminum container that is used after being drawn, a two-piece DI can that is formed by DI processing (drawing-ironing) or DRD processing (drawing-redrawing) is used. There are DRD cans (food cans) that are formed by molding and various deep-drawing cans. The most typical method for producing DI cans among these aluminum cans is to perform deep drawing and ironing on the can body material.
After I processing is performed to obtain the can body shape, trimming is performed to a predetermined size, then paint baking is applied, and then necking processing (mouth drawing) and flange processing (mouth widening processing) are applied to the can body edge. ) Is performed, and the can lid (can end) that has been separately molded is combined and subjected to seaming (winding). Since various types of processing are applied to the production of DI cans, etc., it is a balance between various workability such as deep drawability, ironing property, mouth drawability, mouth spreadability, and overhangability, and strength. From that, the material is selected and examined.

Among the various aluminum cans as described above, H300 or H39 of JIS 3004 alloy or AA3104 alloy is often used as a can body for DI cans. H of 5052 alloy, JIS 5082 alloy, JIS 5182 alloy
18 materials or H38 materials are often used, and DRD
JIS 5052 alloy H1 for cans and other deep drawn cans
Eight materials, H38 material, H38 material of AA5042 alloy, etc. are often used.

[0004]

For aluminum cans represented by aluminum two-piece DI cans, it is strongly desired to make them thinner than before in order to reduce the material cost. Therefore, as a material for these aluminum cans, a material that has a sufficiently high strength even when it is made thin and is capable of ensuring excellent formability such as drawability is desired. However, in the conventional aluminum alloy plate for aluminum cans as described above, for example, in the case of an alloy plate for a can body, at the time of paint baking at about 200 ° C. for 20 minutes after the can is made, and in the case of an alloy plate for a can lid, Since the softening occurs during the previous baking process of 270 ° C for about 20 seconds, the strength finally obtained is at most about 300 N / mm ^2, so the strength is insufficient for thinning. Will end up.
Further, based on the conventional alloy system as described above, for example, C
It is possible to improve the strength by adding a strengthening element such as u or increasing the cold working rate of the material, but in that case, the formability is remarkably reduced, and as a can material Would be inappropriate.

Among various aluminum alloys, 2000 series (Al--Cu--Mg series) or 7000 series.
The heat treatment type alloys of the Al-Zn-Mg-based type are often used as structural materials that require high strength because they can obtain high strength exceeding 400 N / mm ^{2 in} proof stress. In this case, it is usually used in the state of solution treatment as it is, or in the state of being subjected to artificial aging treatment, and even if it is subjected to molding processing, it is only a very slight processing. When these heat-treatable alloys are used for applications requiring strong forming, they are also formed in a soft material state and then subjected to solution treatment or artificial aging treatment to secure the strength. However, such a process is unsuitable as a material for cans. In any case, although these conventional heat-treatable alloys have sufficiently high strength, they are inferior in formability, especially drawability, ironing property, and overhanging property after the solution treatment, and therefore are applied to can materials. That was not considered.

Further, in the case of a material for a can body of a DI can, not only high strength and excellent DI formability (drawing workability, ironing workability) are required, but also a DI can body is formed and subjected to a paint baking treatment. Formability in necking, flanging and seaming after application is also required. Since the wall thickness of the flange part has been decreasing with the thinning of the can body in recent years, it is easy for the flange part to break during flanging and seaming, which improves flange formability and seaming processability. There is also a strong demand for a smaller neck diameter to reduce the weight of the can lid, and thus an increase in the amount of necking, which requires a further improvement in the formability of the flange portion. Further, in the case of a can lid material, in addition to the deep drawing property, further improvement in overhanging property and opening property is desired.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an aluminum alloy sheet for drawing which can satisfy the above-mentioned various requirements and a method for producing the same.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the inventors of the present invention have conducted extensive experiments and researches, and as a result, appropriately selected the alloy composition and adjusted the manufacturing conditions appropriately. As a result, it has been found that the heat-treatable alloy exhibits high strength and, at the same time, good formability such as drawability can be secured, and the above-mentioned various requirements can be satisfied, and the present invention has been completed.

Specifically, the high-strength heat-treatable aluminum alloy plate for drawing according to the invention of claim 1 has Zn of 3 to 6%,
It is characterized in that it contains 0.5 to 3% of Mg and more than 0.5% of Mn and 1.5% or less, with the balance being Al and inevitable impurities.

The high-strength heat-treatable aluminum alloy plate for drawing according to the second aspect of the present invention comprises Zn3-6%, Mg0.
It is characterized by containing 5 to 3%, Cu 0.1 to 2.5%, Mn exceeding 0.5% and 1.5% or less, and the balance being Al and inevitable impurities.

A third aspect of the present invention relates to a method for producing a high-strength heat-treatable aluminum alloy sheet for drawing according to the first aspect, wherein Zn3-6%, Mg0.
5 to 3%, Mn more than 0.5% and 1.5% or less,
After finishing the alloy having a balance of Al and unavoidable impurities to a predetermined plate thickness, solution treatment is performed at a temperature in the range of 450 to 550 ° C. for 5 minutes or less, and further exceeds 30% to 7%.
It is characterized in that cold rolling is performed at a rolling rate of 5% or less.

A fourth aspect of the present invention relates to a method for producing a high-strength heat-treatable aluminum alloy plate for drawing according to the second aspect, wherein Zn3 to 6% and Mg0.5 are 0.5%.
~ 3%, Cu 0.1-2.5%, Mn over 0.5% and 1.5% or less, with the balance being Al and unavoidable impurities, and after finishing to a predetermined plate thickness, 450-
It is characterized by performing solution treatment for 5 minutes or less at a temperature in the range of 540 ° C., and further performing cold rolling at a rolling ratio of more than 30% and 75% or less.

[0013]

In the present invention, in terms of component composition,
Basically, as a heat treatment type alloy, the strength is improved based on the precipitation hardening by Zn and Mg, the composition is stabilized by the addition of Mn, the ironing workability is improved, and further Cu is added as necessary to form a solid solution. Strengthening is intended to improve the strength, and from the viewpoint of the manufacturing process, the solution treatment time is shortened to ensure sufficient formability as a drawing material.

Therefore, first, the reasons for limiting the component composition in the present invention will be explained.

Zn: Zn forms MgZn ₂ together with Mg and is effective in improving the strength by precipitation hardening. If the Zn content is less than 3%, the effect of improving the strength cannot be sufficiently obtained, while if it exceeds 6%, the rolling property and the can formability are deteriorated, and further the corrosion resistance is deteriorated. Therefore Zn
The amount was within the range of 3 to 6%.

Mg: Mg forms MgZn ₂ together with Zn and is effective in improving strength by precipitation hardening. Also M
g alone is effective for improving strength by solid solution strengthening.
If the amount of Mg is less than 0.5%, the effect of improving the strength cannot be sufficiently obtained, while if it exceeds 3%, the rolling property decreases and
Reduces can formability. Therefore, the amount of Mg is 0.5 to 3
Within the range of%.

Mn: Mn is an element effective for refining and stabilizing crystal grains, and improves the ironing workability by the solid lubrication effect of the Mn-based intermetallic compound. If the amount of Mn is 0.5% or less, these effects cannot be sufficiently obtained, while if it exceeds 1.5%, primary crystal giant intermetallic compounds of MnAl ₆ are generated, and formability, especially flange formability is remarkably increased. It was damaged, and MgZn was added to the Mn-based intermetallic compound.
₂ Precipitates are unevenly and coarsely deposited, making it impossible to improve strength. Therefore, the Mn content exceeds 0.5% and 1.
It was set within the range of 5% or less.

Cu: Cu is an element effective in improving the strength by solid solution strengthening, and therefore, it is decided to actively add it in claims 2 and 4. If the Cu content is less than 0.1%, the effect of improving the strength cannot be sufficiently obtained, while if it exceeds 2.5%, the formability and corrosion resistance deteriorate. Therefore, claim 2
In the invention of claim 4, the amount of Cu is within the range of 0.1 to 2.5%. Also in the inventions of claims 1 and 3, it goes without saying that less than 0.1% of Cu may be contained as an impurity.

In addition to the above elements, basically Al and inevitable impurities may be used. Common impurities include Fe, Si, Cr, Zr, etc., but Fe is 0.7
%, Si is less than 0.5%, Cr is less than 0.3%, Z
If r is less than 0.3%, the effect of the present invention is not impaired. Further, in general aluminum alloys, a small amount of Ti may be added alone or in combination with B in order to refine the ingot structure, and Ti and B may be contained as impurities. Ti is less than 0.2%,
If B is less than 0.05%, the effect of the present invention is not particularly impaired.

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

The step of finishing the alloy having the above-mentioned composition of components to a predetermined intermediate plate thickness (process before solution treatment) is not particularly limited, but is usually cast by the DC casting method (semi-continuous casting method). After that, homogenization treatment is performed, hot rolling is further performed, and cold rolling is performed as necessary to obtain a predetermined intermediate plate thickness. Alternatively, a continuous casting method may be applied, and if necessary, homogenization treatment and cold rolling may be performed to obtain a predetermined intermediate plate thickness.

Here, DC casting may be performed according to a conventional method. Further, homogenization treatment is 400 to 500 ° C. according to a conventional method.
In the above, heating may be performed for about 1 to 24 hours. If the heating time of the homogenization treatment is less than 1 hour and the heating temperature is less than 400 ° C., the homogenization effect cannot be obtained.
If the time is exceeded, the homogenizing effect is saturated and the economic efficiency is impaired, and if the heating temperature exceeds 500 ° C., local dissolution due to eutectic melting may occur.

Immediately after the homogenization treatment or after preheating before hot rolling, hot rolling is performed. In this hot rolling, the starting temperature is within the range of 400 to 500 ° C. and the ending temperature is within the range. The temperature is preferably in the range of 200 to 350 ° C. If the hot rolling start temperature is lower than 400 ° C, the deformation resistance is large and the rolling property is deteriorated. On the other hand, if the hot rolling start temperature is higher than 500 ° C, hot rolling cracks may occur. Note that this hot rolling is preferably started at a homogenization treatment temperature or higher, and by doing so, formation of coarse precipitates after the homogenization treatment can be suppressed.
Further, if the hot rolling finish temperature is lower than 200 ° C., rolling is difficult, whereas if the hot rolling finish temperature is higher than 350 ° C., uneven coarse precipitation of intermetallic compounds is promoted after the hot rolling, and then Solution treatment property of and deteriorates drawability, bulging property, and mouth widening property.

On the other hand, when the continuous casting method is applied, a method of directly injecting molten metal between rolls to solidify (thin plate continuous casting method) or a method of injecting molten metal between belts and blocks to solidify May be applied, and in any case, hot rolling may be performed as necessary. When the continuous casting method is applied, the cast plate thickness is preferably within the range of 2 to 10 mm. If the thickness of the cast plate is less than 2 mm, it is difficult to perform casting. On the other hand, if the thickness of the cast plate exceeds 10 mm, the load of the cold rolling until the subsequent product sheet thickness becomes large and the mass productivity deteriorates.

After finishing the intermediate plate thickness as described above, a solution treatment is applied. This solution treatment is 450-
It is necessary to perform heating at a temperature in the range of 550 ° C. or a temperature in the range of 450 to 540 ° C. for a short time of 5 minutes or less.
If the solution heat treatment temperature is lower than 450 ° C., the solution of the element contributing to the strength improvement becomes insufficient due to the aging precipitation, so that the strength cannot be sufficiently improved. Further, in the case of the alloy of claim 1 in which Cu is not positively added, eutectic melting may occur if the solution treatment temperature exceeds 550 ° C., while Cu is actively added. In the case of the alloy (1), the melting point is lowered by the addition of Cu, so that if the solution treatment temperature exceeds 540 ° C., eutectic melting may occur. Further, this solution heat treatment requires 5 hours.
It is important that the time is not more than a minute and the solution is incomplete. That is, in general, the minimum solution treatment time of the 7000 series heat-treated alloy is specified in JIS 4000 in relation to the plate thickness. However, the solution treatment is performed for a long time in accordance with JIS to completely complete the solution treatment. In this case, although high strength is obtained, not only the subsequent cold rolling property is deteriorated, but also the can formability such as drawability and bulging property is deteriorated.
In addition, if solution treatment is performed for a long time, the surface oxide film becomes thick, which deteriorates formability, especially ironing property, so surface cleaning treatment such as alkali cleaning or acid cleaning is required after solution treatment. Therefore, the cost is increased. On the other hand, if the solution treatment time is set to 5 minutes or less and incomplete solution treatment is performed, strength can be increased to the extent necessary for thinning the can, but drawability, swelling, ironing, etc. Sufficient can formability can be secured, and the surface cleaning treatment after the solution treatment is not necessary. Such short-time solution heat treatment can be easily performed by using a continuous annealing furnace. The cooling rate after solution treatment was 10 ° C.
It is sufficient if it is about / sec or more. Therefore, for cooling after the solution treatment, not only water quenching but also forced air cooling can be applied.

After the solution heat treatment, cold rolling is performed to obtain the final plate thickness, but immediately after the solution heat treatment, cold rolling is not performed, and the material is left at room temperature for one day (24 hours) or more and aged at room temperature. After that, it is desirable to perform cold rolling. By performing room temperature aging for 24 hours or more in this way, it is possible to obtain the effect that the fine precipitates generated during room temperature aging homogenize dislocations (working strain) introduced in the subsequent cold rolling.

In the final cold rolling, the rolling ratio exceeded 30% and 7
It should be 5% or less. If the rolling ratio is 30% or less, sufficient strength cannot be obtained, while if it exceeds 75%, high strength is obtained, but the formability is remarkably lowered, and the earring ratio in deep drawing becomes large.

After finishing the product sheet thickness by the final cold rolling, if higher strength is required, artificial aging treatment can be performed as the final annealing if necessary.
This artificial aging treatment is performed at a temperature in the range of 80 to 160 ° C for 1
It is desirable to carry out for ~ 12 hours. Artificial aging temperature is 80
If the temperature is less than 0 ° C and the artificial aging time is less than 1 hour, the effect of artificial aging cannot be obtained. On the other hand, if the artificial aging temperature exceeds 160 ° C, overaging will occur and conversely the strength will be reduced. Further, if the artificial aging time exceeds 12 hours, the strength becomes too high and the formability, especially drawability, ironing workability, and flange formability deteriorates. In this case, depending on the temperature, overaging causes strength reduction. Invite. Since the recent cold rolling mill is operated under high speed and high pressure, the rising temperature often exceeds 100 ° C. In this case, even if the positive heating is not particularly performed, the winding coil immediately after the cold rolling is cooled. Artificial aging can be performed by self-annealing.

[0029]

【Example】

Example 1: The alloys Nos. 1 to 9 in Table 1 were cast by the DC casting method according to the conventional method, and the obtained ingot was made into 46
After performing homogenization treatment at 0 ° C. for 12 hours, the plate was finished by hot rolling to have a plate thickness of 3 mm. Hot rolling start temperature is 44
The end temperature was 0 ° C and the end temperature was 300 ° C. Then, after cold rolling to a plate thickness of 0.7 mm, a continuous annealing furnace was used for 4
Solution heat treatment at 60 ℃ for 5 seconds,
After being left for an hour, final cold rolling was performed to a thickness of 0.3 mm, and then final annealing was performed at 120 ° C. for 1 hour as an artificial aging treatment. For alloy No. 10 in Table 1, a cast plate having a plate thickness of 5 mm was formed by a thin plate continuous casting method, homogenized at 460 ° C. for 12 hours, and further cold-rolled to a thickness of 0.7 mm. , Solution annealing at 460 ° C. for 5 seconds using a continuous annealing furnace, leaving at room temperature for 30 hours and finally cold rolling to a thickness of 0.3 mm,
Then, as an artificial aging treatment, final annealing was performed at 120 ° C. for 1 hour. On the other hand, the conventional material with alloy number 11 has been D
It is equivalent to the 3004 alloy used as I can body, in which case the plate was manufactured according to conventional methods. That is, after DC casting, homogenization treatment is performed at 600 ° C. for 5 hours, and hot rolling is performed according to a conventional method to obtain 2 mm.
After the thickness was increased to 0.8 mm by cold rolling, continuous annealing was performed at 500 ° C. for 5 seconds as an intermediate annealing, and further final cold rolling was performed to a plate thickness of 0.3 mm.

For each plate obtained as described above,
The mechanical performance and the DI can properties were examined. The results are shown in Table 2. As the mechanical performance, the tensile strength in two states, that is, the state immediately after the plate production as described above (immediately after the artificial aging treatment) and the state after heating 200 ° C. × 20 minutes as the coating baking treatment, The yield strength and elongation were examined. On the other hand, as DI can characteristics, can property, flange formability, pressure resistance, and appearance quality were examined and evaluated in comparison with the conventional material (alloy No. 11).
A mark is given, ◎ is given when it is excellent, and X is given when it is inferior.
Here, the can-making property was evaluated by the rate of occurrence of breakage during DI processing when 4000 cans of DI can bodies were continuously molded, and regarding the flange processability, the DI can body was subjected to necking processing after DI processing. After that, push in the conical punch and evaluate the expansion ratio when the flange breaks, the pressure resistance is evaluated by the pressure when buckling occurs by applying internal pressure to the DI can, and the appearance quality is mainly the cylinder of the DI can. It was evaluated by the presence or absence of occurrence of goring on the surface.

[0031]

[Table 1]

[0032]

[Table 2]

As shown in Table 2, the alloy of the present invention (alloy No. 1, alloy No. 4, alloy No. 10) achieves higher strength than the conventional DI can body (alloy No. 11; 3004 alloy). It has been confirmed that the characteristics of the DI can are equal or higher. On the other hand, Alloy No. 2, Alloy No. 5, and Alloy No. 9 had too much Zn, Cu, and Mg, respectively, but in these cases, high strength was obtained, but D
The I-can characteristics, particularly the can-making property and the flange processability, were poor. Further, Alloy No. 3 and Alloy No. 8 each had a small amount of Zn and an amount of Mg, so that high strength could not be obtained. Further alloy number 6
Since the amount of Mn was small, galling occurred during DI can manufacturing, and along with this, aluminum powder adhered to the ironing die, causing frequent breakage of the can body during can manufacturing. Further, in the case of alloy No. 7, since the Mn content was too large, the Mn-based intermetallic compound was coarsened, and therefore the flange formability was deteriorated.

Example 2 Alloy No. 1 shown in Table 1 was homogenized at 460 ° C. for 12 hours after DC casting, and hot rolling was started at 440 ° C. and ended at 380 ° C. Let
The plate thickness was 2 mm. The 2 mm hot-rolled sheet was subjected to primary cold rolling, solution treatment, final cold rolling, and final annealing (artificial aging treatment) under the conditions shown in Production Codes A to F in Table 3. For each of the obtained plates, the mechanical properties as they were and the mechanical properties after the coating baking treatment at 200 ° C. for 20 minutes were examined, and the deep drawing ear ratio and the limit drawing ratio (LD
R) was examined. The results are shown in Table 4. The limit drawing ratio was determined from the limit blank size that enables draw forming with a punch having a diameter of 50 mm. Further, with respect to the conventional material of Example 1 (alloy No. 11; 3004 alloy), the deep drawing ear ratio and the limiting drawing ratio were similarly examined, and the results are also shown in Table 4.

[0035]

[Table 3]

[0036]

[Table 4]

As shown in Table 4, in the case of the manufacturing code B manufactured by satisfying the manufacturing process conditions specified by the present invention, high strength is obtained and at the same time, the limiting drawing ratio (LDR) is obtained.
It is clear that the value is high, the drawability is good, and the ear rate is low. On the other hand, in the case of manufacturing code A in which the solution treatment temperature is too low, not only the strength is not sufficiently obtained,
The drawability was also not sufficient. On the contrary, in the case of production code C in which the solution treatment temperature was too high, high strength was obtained but drawability was remarkably poor. Further, in the case of the production code D in which the rolling rate of the final cold rolling is low, high strength cannot be obtained, while in the case of the production code E in which the rolling rate of the final cold rolling is too high, the strength is high but the earring rate and the drawing are reduced. It was markedly inferior in terms of sex. Further, in the case of the manufacturing code F in which the solution heat treatment time was too long, the drawability was deteriorated.

[0038]

As is clear from the above examples, according to the present invention, as an aluminum alloy plate for drawing used in various cans and the like, it has high strength and excellent formability, It has become possible to obtain an aluminum alloy plate having particularly excellent drawability and ironing property. That is,
Conventional Al-Mn-Mg-Cu alloys and Al-Mg-M
In n-type alloys, it has been said that if strength is increased, drawability and ironing property are deteriorated. However, in the case of the present invention, the composition of the components is rigorously defined, and further appropriate manufacturing process conditions are applied, and solid solution precipitation of alloying elements is applied. By optimizing the state, it became possible to secure good moldability while increasing the strength. Therefore, by using the aluminum alloy plate according to the present invention, it becomes possible to reduce the thickness and increase the strength, especially as a material for cans. Further, the aluminum alloy sheet according to the method of the present invention can be applied not only to the DI can body and the DRD can body but also to the can lid. Therefore, since the can can be unialloyed, the recyclability can be improved.

Claims (4)

[Claims] 1. Zn 3 to 6% (weight%, the same applies hereinafter), M
A high-strength heat-treatable aluminum alloy plate for drawing, characterized by containing g 0.5 to 3%, Mn exceeding 0.5% and 1.5% or less, and the balance being Al and inevitable impurities. 2. Zn 3-6%, Mg 0.5-3%, Cu
A high-strength heat-treatable aluminum alloy plate for drawing, characterized by containing 0.1 to 2.5%, Mn more than 0.5% and 1.5% or less, and the balance being Al and inevitable impurities. 3. Zn 3-6%, Mg 0.5-3%, Mn
After finishing an alloy containing 0.5% or more and 1.5% or less with the balance being Al and inevitable impurities to a predetermined plate thickness, a solution for 5 minutes or less at a temperature in the range of 450 to 550 ° C. A method for producing a high-strength heat-treatable aluminum alloy sheet for drawing, which is characterized by subjecting to a heat treatment and further cold rolling at a rolling ratio of more than 30% and 75% or less. 4. Zn 3-6%, Mg 0.5-3%, Cu
An alloy containing 0.1 to 2.5%, Mn more than 0.5% and 1.5% or less, and the balance of Al and inevitable impurities is finished to a predetermined plate thickness, and then in the range of 450 to 540 ° C. Solution treatment for 5 minutes or less at the internal temperature, then 30%
A method for producing a high-strength heat-treatable aluminum alloy sheet for drawing, which comprises performing cold rolling at a rolling ratio of more than 75% and not more than 75%.