JPH0747803B2 - Method for manufacturing aluminum alloy hard plate with low ear rate - 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 hard body of a can body of a two-piece aluminum can, that is, a hard plate of an aluminum alloy for forming, which is used as a body of a DI can. The present invention relates to a method for producing an aluminum alloy hard plate having a low rate, a high strength after baking coating, and an excellent formability.

[0002]

2. Description of the Related Art In general, a body of a DI can is required to have deep drawability and ironing property during DI processing.
It is required to be excellent in formability after I processing and baking coating, that is, necking workability and flanging workability. As such a DI can body, JIS 3 which is generally an Al-Mn-Mg alloy is used.
The 004 alloy H19 material and H39 material are used. On the other hand, recently, with the demand for thinner DI cans, higher strength is also required for DI can body materials, but even conventional 3004 alloy can body materials have a proof stress of 270N after baking. / Mm ² or more strength is obtained.

[0003]

In thinning the can body of a DI can, not only the body of the can has a high strength, but also the moldability during DI processing, that is, the deep drawability and the ironing property are more excellent. In addition, it is desired that the moldability after DI processing / baking coating, that is, the necking workability and flanging workability be further excellent. As described above, even the conventional 3004 alloy can body has a certain level of strength required for thinning,
In terms of moldability, it was still insufficient.

That is, as the body of the can becomes thinner, wrinkles are more likely to occur on the body during deep drawing, and galling is more likely to occur due to ironing, and the side wall after DI processing becomes thinner. Due to the above, there is a problem that wrinkles are likely to occur on the neck portion during necking processing after DI processing / baking coating, and cracks are likely to occur during flanging processing.

In addition, generally, in order to reduce the trimming amount after DI processing to reduce the cost, it is desired that the occurrence of ears during deep drawing is small, and in this respect as well, the conventional 3004 alloy can body material It was not enough.

The present invention has been made in view of the above circumstances, and is excellent in moldability during DI processing and after DI processing / baking coating even when the wall thickness is reduced, and the ear in deep drawing is excellent. Low rate and high strength, D
It is an object of the present invention to provide a method for obtaining an aluminum alloy hard plate for forming that is most suitable for I can body materials.

[0007]

[Means for Solving the Problems] As a result of various experiments and studies conducted by the present inventors to solve the above problems, the following new findings were obtained.

That is, first, it was found that it is advantageous to apply a method having a high cooling rate as a casting method with respect to the formability of a thin material after DI processing / baking coating, especially cracking during flanging processing. Specifically, when the side wall after DI processing is thinned to about 100 μm, the 3004 alloy conventionally used as a can body material is generally used as a DC
If cast by the casting method, the diameter is 10μ as coarse crystallized substance.
When the thickness exceeds m, the coarse crystallized substance occupies 10% or more of the thickness of the side wall portion. In such a case, the coarse crystallized substance is larger than that of the conventional thick-walled material. Also tends to become the starting point of cracks during flange forming.
On the other hand, as in the continuous casting and rolling method (thin plate continuous casting method),
By applying a casting method with a high cooling rate, the crystallized material size is refined, and all crystallized material sizes are 10 μm.
It has been found that the crystallized substance can be prevented from becoming a starting point of crack generation during flanging by setting the average grain size to be not more than 4 μm.

Further, by subjecting the rolled plate after casting to a heat treatment at a high temperature for a long time (580 to 620 ° C., 6 hours or more), the ironing property during DI processing is improved and wrinkles during deep drawing are formed. It has been found that the occurrence of wrinkles and the occurrence of wrinkles during necking processing after DI processing and baking coating can be reduced. Specifically, for the rolled plate after casting using the casting method with a high cooling rate as described above, 580
By subjecting the soaking treatment at 620 ° C. for 6 hours or more, the crystallized product is made spherical and coarsened (1
It was found that the ironing property during DI processing can be improved by increasing the diameter (μm or more). On the other hand, if the amount of fine precipitates of 0.5 μm or less is large, the movement of dislocations at the time of molding is pinned by the fine precipitates, and the strength is slightly improved, but the formability is impaired and wrinkles during molding are reduced. It may lead to the occurrence. On the other hand, by performing the soaking treatment as described above, the amount of fine precipitates of 0.5 μm or less is also reduced, and 200 /
It has been found that the particle size becomes less than μm ^2, the flow of material during molding becomes smooth, and the occurrence of wrinkles during molding is reduced.

Furthermore, by performing cold rolling of 30% or more after casting and then performing soaking treatment as described above, it becomes possible to easily obtain an appropriate dispersed state of crystallized substances as described above. At the same time, it was found to be effective in reducing the deep-drawing ear. That is, after the casting, cold rolling of 30% or more is performed, and then the soaking treatment is performed, so that the crystallized product is most appropriately dispersed, that is, 1 to
The size of 3 μm is 2000 pieces / 0.2 mm ² ,
Moreover, by performing the soaking after the cold rolling of 30% or more in this way, the recrystallization in the soaking is uniformly performed, and a low crystal orientation component (that is, a cube orientation) is generated in the subsequent process. It has been found that it becomes easier to do so and the ear ratio at deep drawing can be reduced.

Further, the inventors have found an appropriate component composition that can most effectively bring out the effects of the above manufacturing process, and have completed the present invention.

Specifically, the manufacturing method of the aluminum alloy hard plate for molding according to the present invention is such that Mg 0.5 to 2.0 wt%,
Mn 0.5-1.8 wt%, Fe 0.1-1.8 wt%, S
i 0.05 to 0.5 wt% as an essential alloying component, and if necessary, Cu 0.5 wt% or less, Zn 0.5 wt%
Hereinafter, an alloy containing one or more of 0.3 wt% or less of Cr and the balance of Al and unavoidable impurities is cast at a cooling rate of 50 ° C./sec or more, and then 30%. After cold rolling at the above rolling rate, 58
After soaking for 6 hours or more at a temperature in the range of 0 to 620 ° C., and further cold rolling at a rolling rate of 30% or more, 1
Intermediate annealing is performed by heating to a temperature in the range of 380 to 600 ° C at a temperature rising rate of ℃ / sec or more without holding or holding for 10 minutes or more, and further cooling at a cooling rate of 1 ° C / sec or more, and then 40%. It is characterized in that cold rolling is performed at the above rolling ratio.

[0013]

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

Mg: Mg is added by aging precipitation of Mg ₂ Si by coexistence with Si or Al by coexistence with Cu.
In addition to being expected to improve strength by aging precipitation of —Cu—Mg, it can be expected to improve strength by solid solution of Mg itself, and is an essential element for obtaining strength required for a can body material. Further, since Mg has a dislocation multiplication effect during cold rolling, it is also effective in increasing the number of recrystallization nuclei and refining recrystallized grains. However, if the amount of Mg is less than 0.5 wt%, the above effect is small, and if it exceeds 2.0 wt%, high strength can be easily obtained, but the deformation resistance during ironing becomes large, and the appearance of the can after forming becomes large. Therefore, the Mg content is set within the range of 0.5 to 2.0 wt%.

Mn: Mn contributes to the strength improvement by solid solution, but in the case of the present invention, a crystallized compound formed in the presence of Fe and Si is more important. That is, in the present invention, a casting method with a high cooling rate is applied, but in this case, fine crystallized substances of about 1 μm are increased, and the fine crystallized substances are spheroidized and coarsened by soaking (1 μm or more). By increasing the diameter, it contributes to improving the goring property at the time of ironing for DI processing. That is, in ironing, when the lubrication ability is insufficient, it may lead to poor appearance such as scratches and seizures called galling, but the above-mentioned crystallized substances provide a solid lubricating effect. As a result, the effect of reducing the occurrence of goring (improving the goring property) is brought about. Although generally is 2μm or more crystallized substances are said to be effective in galling resistance improvement, in this invention, if crystallized substances spherical particles of 1~3μm is 2,000 /0.2Mm ² more Goring It is effective in improving the sex. Further, such fine crystallized substances also contribute to the refinement of the recrystallized composition and the improvement of strength by particle dispersion hardening. The amount of Mn to be added to secure such an amount of crystallized compound is determined in consideration of the amount of Fe. However, if Mn is less than 0.5 wt%, a sufficient amount of crystallized compound should be secured. Becomes difficult, while the Mn content is 1.8 wt.
If it exceeds 0.1%, a huge crystallized substance may be generated and formability may be impaired, so the addition amount of Mn is set within the range of 0.5 to 1.8 wt%. The total amount of Mn and Fe is 1 to 2
It is preferably within the range of wt%.

Fe: As with Mn, Fe is a crystallized compound that is produced in the presence of Mn and Si, and its effect is the same as in the case of Mn. Fe is a crystallized Mn-based compound. Is also an essential element in the present invention. The amount of Fe added is also determined in consideration of the amount of Mn, but if the amount of Fe is less than 0.1 wt%, the effect due to the addition of Fe cannot be sufficiently obtained, while if it exceeds 1.8 wt%, coarse crystallized substances are generated and molding is performed. Therefore, the Fe content is set to the range of 0.1 to 1.8 wt% because it may impair the property.

Si: Si is Mg ₂ S by coexistence with Mg
It contributes to age hardening by precipitation of i and strength improvement by solid solution of Si itself, but rather, it is Fe system or M
It is an element that contributes to the formation of n-type crystallized substances and is necessary for obtaining an appropriate crystallized substance distribution. If the Si content is less than 0.05 wt%, the effect will not be obtained, and if it exceeds 0.5 wt%, the effect will be saturated and the material will be hardened and the formability will be impaired. Within the range.

In addition to the above components, basically Al and unavoidable impurities may be used, but in order to further improve the strength, Cu of 0.5 wt% or less and 0.5 or less are added.
One or two or more of wt% or less Zn and 0.3 wt% or less Cr may be contained. Cu addition is Al
-Cu-Mg-based aging precipitates to improve strength,
The addition of n and Cr can be expected to improve the strength due to solid solution. Cu is 0.5 wt% or less and Zn is 0.5 wt%.
% Or less and Cr of 0.3 wt% or less does not impair the effects of the present invention.

In general aluminum alloys, Ti or Ti and B are used for refining ingot crystal grains.
May be added in a trace amount, and also in the case of the present invention, a trace amount of Ti, or Ti and B may be contained. However, in the case of adding Ti, if less than 0.01 wt% the effect of Ti addition cannot be obtained, while if over 0.2 wt% primary TiAl ₃ is crystallized and the formability is impaired. It is preferably in the range of 0.2 wt%.
When B is added together with Ti, if B is less than 1 ppm, the effect of B is not obtained. On the other hand, if B exceeds 500 ppm, coarse particles of TiB ₂ are mixed and impair the formability. It is preferably within the range. In addition, Be may be added in the range of 0.02 wt% or less to prevent the oxidation of the molten metal during casting.

Next, the reasons for limiting each process in the manufacturing method of the present invention will be described together with their operation.

First, an alloy having the above-described composition is melted and cast according to a conventional method. At the time of casting,
Casting is performed at a cooling rate of 50 ° C./sec or more by using a rapid cooling solidification casting method such as a continuous casting and rolling method (thin plate continuous casting method). By thus casting at a cooling rate of 50 ° C./sec or more, a fine crystallized compound of about 1 μm can be obtained. By refining the crystallized substances in this way,
The moldability is improved, and it is particularly effective in preventing the occurrence of cracks during flange forming after DI processing. At the time of casting, it is preferable that the thickness of the cast plate is 2 to 20 mm.
If it is less than 2 mm, it is difficult to completely destroy the cast structure by the thickness of the final product plate, which adversely affects the final product.
On the other hand, it is practically difficult to cast a thick plate exceeding 20 mm at a cooling rate of 50 ° C./sec or more.

After casting, the cast plate is cold-rolled at a rolling rate of 30% or more, and then subjected to soaking at 580 to 620 ° C. for 6 hours or more. Here, the rolling ratio after casting is 3
If it is not more than 0%, the recrystallization in the soaking process is not performed uniformly and the recrystallized grains become coarse, which adversely affects the final product. Further, in the present invention, the cube-oriented recrystallized grains of the component that lowers the ear ratio by soaking at 580 ° C. or higher preferentially grows, and this is the recrystallization nuclei of the cube orientation during cold rolling / intermediate annealing after soaking. Finally, it is possible to obtain a product with a low ear rate during molding,
If the cast structure remains during the soaking process, recrystallized grains in the cube orientation will not be generated, and preferential growth in the cube orientation will not be recognized even in the subsequent intermediate annealing. Therefore, also from this point of view, it is necessary to perform cold rolling of 30% or more before soaking.

Regarding the above-mentioned soaking treatment, if many fine Al—Mn-based precipitates of 0.5 μm or less are present in the final plate, they cause dislocation pinning and hinder the material flow at the time of forming, It causes molding defects such as molding wrinkles,
By holding at a high temperature of 580 ° C. or higher for 6 hours or longer, such Al-Mn-based fine precipitates are reduced, and more appropriately, the number is 200 / μm ² or less, and wrinkles during molding, etc. It is possible to prevent the occurrence of defective molding.
In addition, this soaking treatment makes the crystallized substances spherical and coarse (1
.mu.m, so that the average diameter is about 2 .mu.m or more), the ironing property in DI processing is improved and the occurrence of galling is prevented. In order to sufficiently obtain this effect, a crystallized substance of 1 to 3 μm is 200
It is preferably 0 / 0.2 mm ² or more. The holding temperature of soaking is preferably high, but if it exceeds 620 ° C., eutectic melting will occur. Further, the effect is not obtained unless the holding time of soaking is 6 hours or more. The upper limit of the holding time of soaking is not particularly limited, but may be determined in consideration of manufacturing efficiency and the like.

After the soaking, cold rolling is performed at a rolling rate of 30% or more. This cold rolling requires a rolling rate of 30% or more in order to uniformly recrystallize and finely recrystallize grains in the next intermediate annealing.

In the intermediate annealing after cold rolling, heating to 380 ° C. or higher by rapid heating at a heating rate of 1 ° C./sec or higher accelerates solid solution of metallic elements such as Mg, Si, Cu, and the like. Age hardening can be expected by the baking coating treatment or final annealing, which is advantageous for strength improvement. In addition, by heating to a temperature above the recrystallization temperature at such a high temperature rising rate, preferential generation of recrystallized grains in the cube orientation,
It enables growth and is effective in reducing the ear rate. here,
If the temperature rising rate is slow, the progress of recrystallization is pinned by the compound that precipitates during heating, and the preferential growth of recrystallized grains in the cube orientation is hindered, resulting in a recrystallized structure in a random orientation. Through the subsequent cold rolling, the ears are raised by 45 °. The longer the holding time in this intermediate annealing is, the more solid solution proceeds, which is advantageous for strength improvement.
Even if the holding time is longer than 10 minutes, the effect does not increase in spite of the longer holding time, and it is difficult to hold for more than 10 minutes in the current continuous annealing furnace suitable for rapid heating / cooling. The upper limit of the holding time was 10 minutes. Further, if the heating temperature (achieved temperature) in this intermediate annealing is 600 ° C. or higher, local eutectic melting may occur, so the temperature was set to 600 ° C. or lower.

After the intermediate annealing, final cold rolling is performed to obtain the strength required for the can body. If the rolling ratio of the final cold rolling is less than 40%, the required strength cannot be obtained.

After the final cold rolling, final annealing may be carried out for the purpose of enhancing the aging property or annealing if necessary. The final annealing in this case is 10
30 minutes or more is desirable at a temperature of 0 to 250 ° C.

From the viewpoint of the appearance and the manufacturability of the product, it is necessary to perform the surface layer removal treatment to remove the surface oxide at any stage after the soaking treatment and before the final cold rolling. preferable. As the surface layer removal treatment, a mechanical removal method or a chemical method of etching with a caustic liquid or the like can be applied.

[0029]

EXAMPLE For the alloy of alloy code A in Table 1 (conventional 3004 alloy), the process number No. As shown in 1, the conventional method is DC casting, followed by heating, hot rolling,
After the steps of cold rolling, intermediate annealing, and final cold rolling, 0.
28mm thick can body material. For the alloy of alloy code B in Table 1, the process number No. 2 to No. As shown in Fig. 6, a cast plate having a plate thickness of 7 mm is formed by continuous casting and rolling, and then subjected to primary cold rolling, soaking, secondary cold rolling, intermediate annealing, final cold rolling, and final annealing to obtain a 0.28 mm thick plate. The can body.
Here, No. 2 to No. In some of the processes of 6,
The primary cold rolling or soaking was omitted. In Table 2, No. The DC casting in 1 has a cooling rate of about 10 ° C.
/ Sec, and No. 2 to No. In the continuous casting and rolling method of No. 6, the cooling rate is about 150 ° C./sec. Although not shown in Table 2, No. 2 to No. In the process using the continuous cast rolled material of No. 6, before the secondary cold rolling,
It was immersed in a 0% caustic soda solution for 45 minutes for etching, washed with water, desmutted, further washed with water and dried. In Table 2, No. Batch annealing of intermediate annealing of 4 (350
℃ × 2hr) is about 35 ℃ / hr for both heating rate and cooling rate
Is. Furthermore, No. in Table 2 1-No. 3, No. 5,
No. The continuous annealing (500 ° C x 0 sec) of 6th intermediate annealing is
Both the heating rate and the cooling rate are about 20 ° C./sec.

[0030]

[Table 1]

[0031]

[Table 2]

Each of the can body materials obtained as described above was not baked (heat treatment equivalent to baking coating), and after baking in an oil bath at 200 ° C. for 20 minutes. The tensile test was conducted in each of the above states, and the results are shown in Table 3. For each can body, check the deep-draw ear ratio, and
The occurrence of goring due to ironing during I machining was examined, the occurrence of wrinkles at the neck portion during necking molding after DI machining was further investigated, and the mouth spreadability during flange machining after DI machining was examined. The results are also shown in Table 3.

Here, the deep-drawing ear ratio is the blank diameter 58.
Using a punch having a diameter of 32 mm and a shoulder curvature of 4 mmR, deep drawing was performed under the condition of a clearance of 30%, and the ear ratio was examined. Further, in the evaluation of the occurrence of goring in the ironing process, the ironing was performed at the ironing ratio of the flange thickness of 160 μm and the side wall of 105 μm, and the DC casting material of the 3004 alloy (process number No. 1 in Table 2) used as the current can body material. The level of () is good (○), a little bad is Δ, and a bad is X. Here, "somewhat bad (△
In the case of (marked), there was galling but DI molding was possible for several tens of cans, and in the case of "Bad (x mark)", galling caused the cans to run out in several cans. Each case is shown. Furthermore, the wrinkle generation during necking was evaluated by necking at a draw ratio of 4%, and the case where there was no wrinkle at the neck was marked with a circle, and the case where there was some wrinkle was marked with a mark, and the whole circumference was marked. The condition in which several wrinkles were generated was evaluated by the mark X. Further, as for the evaluation of the mouth widening in the flange processing, as shown in FIG. 1, the mouth widening is performed using the die 2 having the corner radius of curvature R of 17 mm with respect to the can body 1 after the DI processing, and the maximum mouth opening is performed. The amount (radius increase amount) P was examined and the value of P was displayed. The evaluation of wrinkles during necking and the spreadability evaluation during flange processing were both performed at 200 ° C on the can body after DI processing.
After baking for 20 minutes, it was measured and evaluated.

[0034]

[Table 3]

In the above, No. The conventional example of No. 1 uses a DC casting material, but in this case, D
Since the side wall of the I can was thin, wrinkle susceptibility during necking was increased, and although the deep drawing ear ratio was low, the strength (YS) was slightly low, and rough skin was remarkable. In addition, No.
In Comparative Example 2, the continuous cast rolled material was used, but soaking was not performed. In this case, the galling property during ironing was poor, and the formability after DI process was also poor. It was Furthermore, No. In the comparative example of 3, the soaking treatment is 50
It was carried out at a low temperature of 0 ° C. In this case, the deep drawing ear ratio was improved, but it was inferior to both the ironing property and each formability after DI processing. In addition, No. In Comparative Example No. 4, batch annealing of slow heating and slow cooling was applied to the intermediate annealing. In this case, the deep drawing earring ratio and strength were poor, and the formability after DI processing was also slightly poor. Furthermore, No. In the comparative example of No. 5, the soaking treatment was performed immediately after continuous casting and rolling without cold rolling. In this case, the deep drawing earring rate is inferior, but other points are the same as the current material. It was better than that. No. In the invention example of 6, all conditions satisfied the condition range of the present invention. In this case, the deep drawing earring ratio was excellent, and in all aspects, it was equal to or better than the current material.

[0036]

EFFECTS OF THE INVENTION According to the method for producing a hard plate of an aluminum alloy for molding of the present invention, an aluminum alloy having an appropriate composition is cast by applying a rapid cooling casting method at a cooling rate of 50 ° C./sec or more. In addition, after subjecting the obtained cast plate to appropriate cold rolling, it is subjected to a soaking treatment at 580 ° C. or higher for 6 hours or more at high temperature, and after cold rolling, rapid heating and rapid cooling are performed at high temperature. By performing intermediate annealing for a certain period of time and then performing final cold rolling, excellent formability, especially ironing during DI processing, and DI
It is possible to obtain an aluminum alloy hard plate which is excellent in formability at the time of flange processing and necking processing after processing, has a low deep drawing earring rate, and high strength. Most suitable for manufacturing hard aluminum alloy sheets.

The production method of the present invention is most advantageous for the production of DI can body materials, but it goes without saying that it can be applied to the production of aluminum alloy hard plates used for other molding applications.

[Brief description of drawings]

FIG. 1 is a schematic diagram schematically showing a state of implementation of a test for evaluating a mouth widening property during flange processing in an example.

Claims (1)

[Claims] 1. Mg 0.5-2.0 wt%, Mn 0.5-
1.8 wt%, Fe 0.1-1.8 wt%, Si 0.05-
0.5 wt%, and if necessary, Cu 0.5 wt%
Hereinafter, an alloy containing one or two or more of Zn 0.5 wt% or less and Cr 0.3 wt% or less and the balance of Al and unavoidable impurities should have a cooling rate of 50 ° C./sec or more. After casting, and then cold rolling at a rolling rate of 30% or more, after soaking at a temperature in the range of 580 to 620 ° C. for 6 hours or more, and further cold rolling at a rolling rate of 30% or more, 380-380 at a heating rate of 1 ° C / sec or more
No heating or heating to a temperature in the range of 600 ° C or 1
An aluminum alloy hard plate having a low earring rate, which is characterized in that it is held for 0 minutes and further subjected to intermediate annealing in which it is cooled at a cooling rate of 1 ° C./sec or more, and then cold rolled at a rolling rate of 40% or more. Production method.