JPH05222497A - Production of hard aluminum alloy sheet reduced in edge rate - Google Patents

Abstract

PURPOSE:To produce a hard Al alloy sheet having low edge rate and high strength and excellent in formability by subjecting an alloy having a specific composition consisting of Mg, Mn, Fe, Si, Cu, Zn, Cr, and Al to respectively specified heat treatment, cooling, and rolling. CONSTITUTION:An alloy which has a composition consisting of, by weight, 0.5-2.0% Mg, 0.5-1.8% Mn, 0.1-1.8% Fe, 0.05-0.5% Si, and the balance Al with inevitable impurities and further containing, if necessary, one or more kinds among <=0.5% Cu, <=0.5% Zn, and <=0.3% Cr is cast at >=50 deg.C/sec cooling rate, by which crystallized compounds are refined. The resulting cast plate is cold- rolled at >=30% draft. Successively, the resulting cold rolled sheet is subjected to ignition treatment at 580-620 deg.C for >=6h and further to cold rolling at >=30% draft. Subsequently, at the time of applying process annealing to the cold rolled sheet, this sheet is heated up to 380-600 deg.C at >=1 deg.C/sec temp. rise rate and, in this state or after holding for <=10min, the sheet is further cooled at >=1 deg.C/sec cooling rate and then cold-rolled at >=40% draft.

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

[0002]

2. Description of the Related Art Generally, 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.
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 desired for DI can body materials, but even conventional 3004 alloy can body materials have a proof strength of 270N after baking coating. / 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 the flanging workability be further excellent. As described above, even the conventional 3004 alloy can body has the strength required for thinning to some extent,
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 in the neck portion during necking processing after DI processing and 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 insufficient.

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 of obtaining an aluminum alloy hard plate for forming that is most suitable for a body of I can.

[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, particularly cracking during flanging processing. Specifically, when the side wall after DI processing is thinned to about 100 μm, 3004 alloy that has been conventionally used as a can body material is used as a general DC.
If it is cast by the casting method, its diameter is 10μ as a coarse crystallized substance.
Some of them exceed m, and the coarse crystallized substances occupy 10% or more of the thickness of the side wall portion. In such a case, the coarse crystallized substances are more than those in the case of the conventional thick-walled material. Also tends to be 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 made finer, 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 it is possible to reduce the occurrence of wrinkles and the occurrence of wrinkles during necking processing after DI processing and baking coating. 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 at the time of forming 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 material flow becomes smooth during molding, and wrinkles during molding are 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 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 rate 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 comprises 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 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.
It can be expected to improve strength by aging precipitation of —Cu—Mg and strength improvement by solid solution of Mg itself, and it is an essential element for obtaining the strength required as a can body material. Further, since Mg has a dislocation multiplication action 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, while 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 Therefore, Mg is set to be in the range of 0.5 to 2.0 wt%.

Mn: Mn contributes to the strength improvement by solid solution, but in the present invention, a crystallized compound formed in the presence of Fe and Si is 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 during the ironing forming of DI processing. That is, in ironing, when lubricity is insufficient, appearance defects such as scratches and seizures called galling may be caused, 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. It is generally said that a crystallized product having a size of 2 μm or more is effective for improving the goring property. In the case of the present invention, if the number of spherical crystallized product particles having a size of 1 to 3 μm is 2000 particles / 0.2 mm ² or more, the goring will occur. It is effective in improving the sex. Further, such a fine crystallized product also contributes to the refinement of the recrystallization composition and the improvement of strength by particle dispersion hardening. The amount of Mn to be added in order 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 large amount of crystallized substances may be generated to impair the formability, so the amount of Mn added was 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: Similar to Mn, Fe is a crystallized compound produced in the presence of Mn and Si, and its effect is the same as in the case of Mn. Further, 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 occurs. Since there is a risk of deteriorating the properties, the Fe content was set within the range of 0.1 to 1.8 wt%.

Si: Si is Mg ₂ S due to coexistence with Mg
It contributes to age hardening by precipitation of i and strength improvement by solid solution of Si itself.
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 amount is less than 0.05 wt%, the effect is not exerted, and if it exceeds 0.5 wt%, the effect is saturated and the material is hardened and the formability is impaired. Therefore, the Si amount is 0.05 to 0.5 wt%. Within the range.

In addition to the above components, basically Al and inevitable impurities may be used, but in order to further improve the strength, Cu of 0.5 wt% or less, 0.5
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 ordinary aluminum alloys, Ti or Ti and B are used to refine the 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 crystallizes and impairs formability. 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, while if B exceeds 500 ppm, coarse particles of TiB ₂ are mixed and formability is impaired, so B is 1 to 500 ppm. It is preferable to set it within the range. In addition, Be may be added in an amount of 0.02 wt% or less in order to prevent oxidation of the molten metal during casting.

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

First, an alloy having the above-mentioned 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 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 is not uniformly performed and the recrystallized grains are coarsened, which adversely affects the final product. Further, in the present invention, re-crystallized grains in the cube orientation of the component that lowers the ear ratio by soaking at 580 ° C. or higher preferentially grows, and this is re-crystallized nuclei in 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 more for 6 hours or more, 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 increased to 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
The number 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 the soaking treatment 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 metal elements such as Mg, Si and Cu, and finally 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 rate of temperature rise 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 inhibited, resulting in a recrystallized structure with random orientation. Through the subsequent cold rolling, the ear becomes 45 °. The longer the holding time in this intermediate annealing, the more solid solution proceeds, which is advantageous for strength improvement.
Even if the holding time is longer than 10 minutes, the effect is not increased 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 this 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 standpoint of the appearance and 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]

EXAMPLES 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.
It was a 28 mm thick can body. For the alloy with 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 obtained 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. Can body material.
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, 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
Both the heating rate and the cooling rate are about 20 ° C./sec.

[0030]

[Table 1]

[0031]

[Table 2]

With respect to each of the can body materials obtained as described above, after being baked (heat treatment equivalent to baking coating), and after baking by dipping in an oil bath at 200 ° C. for 20 minutes. The tensile test was carried out under the above conditions, 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 a blank diameter of 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. For the evaluation of galling in ironing, ironing was performed at an ironing rate of a flange thickness of 160 μm and a side wall of 105 μm, and a DC cast material of 3004 alloy (process number No. 1 in Table 2) currently used as a 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 "mark)", there was galling but DI molding was possible for several tens of cans, and in the case of "Bad (x mark)", galling caused the can to run out in several cans. Each case is shown. Furthermore, for the wrinkle generation evaluation during necking processing, necking processing was performed at a necking ratio of 4%, the case where there was no wrinkle at the neck was marked with a circle, and the case where slight wrinkling occurred was marked with a triangle, and the whole circumference was marked. The condition in which several wrinkles occurred was evaluated by the mark X. Further, as to the evaluation of the mouth widening in the flange processing, as shown in FIG. 1, the mouth widening is performed by using the die 2 having the corner radius of curvature R of 17 mm with respect to the can body 1 after 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 expansion of flange during flange processing were both performed at 200 ° C on the can body after DI processing.
After baking for 20 minutes, measurement and evaluation were performed.

[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 the 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 5, the soaking process 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 the conditions satisfied the condition range of the present invention, and in this case, the deep drawing ear 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 aluminum alloy sheet 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 process at 580 ° C. or higher for 6 hours or more at high temperature and for a long time. By performing intermediate annealing for a certain period of time and then performing final cold rolling, excellent formability, especially ironing property during DI processing, and DI
It is possible to obtain an aluminum alloy hard plate which is excellent in formability during flange processing and necking processing after processing, and has a low deep drawing earring ratio 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 forming applications.

[Brief description of drawings]

FIG. 1 is a schematic diagram schematically showing a state of implementation of a test for evaluating the 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-
0.5wt%, and if necessary, Cu 0.5wt%
Hereinafter, an alloy containing one 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, characterized by being subjected to intermediate annealing for holding for 0 minutes or more and cooling at a cooling rate of 1 ° C./sec or more, and then cold rolling at a rolling rate of 40% or more. Production method.