JPH0835045A - Production of di can body made of aluminum alloy - Google Patents

Abstract

PURPOSE:To produce a DI can body good in formability by suitably combining the componental compsn. of allay stock, the cold working degree after final recrystallization and heating treatment after DI working. CONSTITUTION:A DI can body is produced from an alloy constituted of, by weight, 0.1 to 1.5% Mg, 0.5 to 1.8% Mn, 0.1 to 0.8% Fe, 0.05 to 0.5% Si, 0.05 to 0.7% Cu, and the balance Al. In this case, the sheet thickness at final recrystallization is defined as (t)1, the finish sheet thickness as (t)2 and the true strain epsilon of the sheet thickness from final recrystallization to cold rolling at the finish sheet thickness as epsilon=In (t1/t2), furthermore, the heat treating temp. after DI working as T (K), the activation energy of the self diffusion of Al as Q, the gas constant as R and the self diffusion D of Al is defined as D=exp (-Q/R.T), and moreover, the content of Mg is defined as Mg% and the heating time after DI working as t (sec), and they are suitably controlled so as to satisfy the inequality epsilon<3>XDXIn (t)/(Mg%)<4>>1. Thus, the DI can body in which the edge parts of the can body after coating and baking contain >=10% subgrains can be obtd.

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 can barrel for a two-piece aluminum can by DI machining (drawing-ironing), that is, a DI can barrel made of an aluminum alloy, and particularly after DI machining and paint baking treatment. The present invention relates to a method for obtaining an aluminum alloy can body having good formability in flanging or the like applied to a can body edge portion (flange portion).

[0002]

2. Description of the Related Art Generally, as a manufacturing process for a two-piece aluminum can, a can body material is subjected to DI drawing by deep drawing and ironing into a can body shape, and then trimmed to a predetermined size. After painting and baking, the neck of the can is necked (narrowing) and flanged (expanding), and the separately formed can lid (can end) is combined and seamed (rolled). The tightening process is usually performed.

By the way, as a can body for a conventional DI can,
JIS 3004 alloy and AA 3104 alloy, which are Al-Mg-Mn based alloys, are widely used. These alloys are excellent in ironing workability, and are suitable as DI can body materials because they show relatively good formability even when cold rolled at a high rolling rate to increase strength. It is said that.

[0004]

For the two-piece aluminum can, the material cost is reduced by further reducing the wall thickness.
There is a strong demand for weight reduction. In order to reduce the wall thickness as described above, it is desired to further increase the strength. Further, the DI can body material is required to have not only high strength but also good DI moldability, and further, necking, flanging, and seaming after molding the DI can body and applying baking treatment. Excellent formability in processing is also required. In particular, the can barrel edge is subjected to multi-stage, multi-type processing such as cold rolling in the material manufacturing process, DI molding during can barrel molding, necking processing after paint baking, flange processing, and seaming processing. Therefore, cracks are likely to occur during processing. Especially recently, the plate thickness of the can edge has become smaller as the can body becomes thinner.
As a result, the edges tend to break during flanging and seaming, which is why the flangeability of the can edge is
Improvement of seaming workability is strongly desired. Further, due to the demand for weight reduction of the can lid, it is desired to reduce the neck diameter of the can body. In this case, since it is necessary to increase the necking processing amount, it is possible to further improve the moldability of the can body edge portion. Is desired.

As a result of intensive experiments and research to solve the above-mentioned problems, the present inventors have properly selected the alloy component composition of the material and, at the same time, optimized the microstructure state, particularly the microstructure state of the can edge portion. , The can body edge portion has a structure having 10% or more of sub-grains (subgrains).
As a DI can barrel that has been subjected to I processing and paint baking, it was found that a DI can barrel having excellent edge formability can be obtained, and the applicant of the present invention has already invented the invention on May 25, 1994. We have filed a patent application for the name "DI alloy can body made of aluminum alloy".

That is, as a result of many experiments conducted by the present inventors on the formability of the can edge, the presence of sub-crystal grains in the can edge greatly affects its formability, particularly flange formability. That the sub-crystal grains (subgrains) account for 10% or more in area ratio in the metal structure of the can body edge portion, that is, the subgrain conversion rate is 10% or more, the can body edge portion It was found that it is effective in improving the moldability of N, ie, necking workability, flange workability, and seaming workability. In this way,
% Or more (preferably 20% or more) of subgrains, dislocations (working strains) given by necking, flanging, or seaming are absorbed in the subgrain boundaries. It has been found by the present inventors that good moldability can be obtained with almost no work hardening.

The present invention has been made in view of the above circumstances, and as described above, a can body having a structure in which the can body edge has 10% or more, preferably 20% or more of sub-crystal grains is surely formed. In addition to the strength and the DI formability, the formability of the can body edge, that is, the formability in necking, flanging, and seaming can be reliably and stably obtained. It is an object of the present invention to provide a method for producing an aluminum alloy DI can body thus obtained.

[0008]

[Means for Solving the Problems] As a result of intensive experiments and researches conducted by the present inventors to solve the above-mentioned problems, as a result of the final recrystallization in the manufacturing process of the material for a can body, the finished plate thickness (final cold The degree of cold work up to the thickness of the can body material after rolling) and DI
By appropriately setting the relationship between the temperature and time during the heat treatment such as the drying treatment or the coating baking treatment after the processing in a predetermined correlation, the structure in which the sub-crystal grains in the can edge portion occupy 10% or more can be obtained. The inventors have found that it can be reliably obtained and have completed the present invention.

Specifically, the present invention provides Mg0.1
1.5%, Mn 0.5 to 1.8%, Fe 0.1 to 0.8
%, Si 0.05 to 0.5%, Cu 0.05 to 0.7%
An alloy containing Al and the balance consisting of Al and unavoidable impurities is cast, and soaking, hot rolling, and cold rolling are performed to finish to a predetermined plate thickness, and moreover, from hot rolling to the middle of cold rolling. In the method for producing an aluminum alloy DI can body, in which the can body material having a finished thickness after cold rolling is subjected to DI processing and heat treatment including paint baking, during the final recrystallization. the thickness of the t ₂ the thickness finish with a t _1, a cold-rolled sheet Atsuma strain epsilon up thickness finish from the time the final recrystallization is defined as _{ε = ln (t 1 / t} 2), and Assuming that the heat treatment temperature after DI processing is T (K), the activation energy of aluminum self-diffusion is Q, and the gas constant is R, the self-diffusion D of aluminum is D = exp.
(−Q / R · T), the amount of Mg (% by weight) is Mg%, and the heat treatment time after DI processing is t (sec).
As the following equation ^{ε 3 × D × ln (t} ) / (Mg%) 4> 1 is cold working ratio of up to thickness finish from the time the final recrystallization to be filled, the temperature of the heat treatment after DI working and The present invention is characterized in that the time is controlled to obtain a DI can barrel having 10% or more of sub-crystal grains in the can barrel edge portion after paint baking.

[0010]

In the manufacturing method of the present invention, basically,
The relationship between the cold workability after final recrystallization and the temperature and time during coating baking is important, but as a prerequisite, the alloy composition of the material is also important, and the composition of the composition within the prescribed range Only then can the intended purpose be achieved. Therefore, the reasons for limiting the component composition of the material alloy will be described first.

Mg: Mg is an element which is effective for solid solution strengthening by itself, and is an essential element for improving strength. Furthermore, the addition of Mg is due to the coexistence of Si and Cu with Mg ₂ Si.
Alternatively, age hardening due to precipitation of Al-Cu-Mg phase can be expected. In particular, in the present invention, the amount of Mg has a great influence on subgraining (subcrystallization) in correlation with the cold working degree after the final recrystallization described later and the heating condition after DI processing such as coating baking treatment. give. Mg amount is 0.1
If less than 1.5%, the required strength cannot be obtained. On the other hand, if more than 1.5% is added, sufficient strength is obtained, but subgraining (sub-graining) is significantly delayed and It becomes difficult to stably secure the occupancy rate of the sub-crystal grains of 10% or more, and therefore, the formability of the can edge portion, especially the flange formability is deteriorated. Therefore, the range of Mg is 0.1
It was set to 1.5%.

Mn: Mn is an element effective in contributing to improvement in strength and formability. In particular, in the manufacturing process of the can body that is the subject of this invention, Mn is important because severe ironing is performed during DI molding. Emulsion type lubricants are usually used in ironing of aluminum plates, but when Mn-based crystallized substances are small, even if they have similar strength, the emulsion type lubricants alone lack lubrication ability. However, there is a possibility that appearance defects such as scratches and seizure called "goring" may occur. It is known that this phenomenon is affected by the size, amount, and type of crystallized substances, and Mn is indispensable for forming an appropriate Mn-based crystallized substance and improving the lubricating ability in ironing. It is an element. If the Mn content exceeds 1.8%, primary crystal giant intermetallic compounds of MnAl ₆ are generated, and conversely the formability is significantly impaired. If the Mn content is less than 0.5%, the solid lubricating effect of the Mn-based compound cannot be obtained. Therefore, the range of Mn is set to 0.5 to 1.8%.

Fe: Fe promotes crystallization and precipitation of Mn,
It is an element necessary for controlling the amount of Mn solid solution in the aluminum matrix and the dispersed state of the Mn-based insoluble compound. In order to obtain a proper compound dispersion state, F may be changed according to the amount of Mn added.
It is necessary to add e. When the Fe content is less than 0.1%, it is difficult to obtain a proper compound dispersion state, while when the Fe content is 0.8% or more, a primary crystal giant compound is likely to be generated due to the addition of Mn. Remarkably impairs sex.
Therefore, the range of Fe is set to 0.1 to 0.8%.

Si: Addition of Si contributes to age hardening by precipitation of Mg ₂ Si-based compound. Si amount is 0.05%
If it is less than 0.5%, the effect cannot be obtained, and if it exceeds 0.5%, age hardening is easily obtained, but the material becomes too hard and hinders moldability. Therefore, the range of Si is 0.05 to 0.5
%.

Cu: The addition of Cu contributes to age hardening due to the formation of Al-Cu-Mg type precipitates. Cu content is 0.
If less than 05%, the effect cannot be obtained, while Cu is 0.7
If it is added in excess of%, age-hardening can be easily obtained, but it becomes too hard, which hinders moldability and deteriorates corrosion resistance. Therefore, the range of Cu is 0.05 to 0.7
%.

In addition, in ordinary aluminum alloys, it is common to add a small amount of Ti alone or in combination with B in order to refine ingot crystal grains. Also in this invention, a trace amount of Ti, or Ti and B can be added. However, if the Ti content is less than 0.005%, the effect cannot be obtained, and if it exceeds 0.20%, the primary crystal TiA is
Since l ₃ crystallizes and hinders formability, the Ti content is 0.0
It is desirable to set it to 05 to 0.20%. When B is added together with Ti, if the B content is less than 0.0001%, there is no effect, and if it exceeds 0.05%, coarse particles of TiB ₂ are mixed and the formability is impaired. 0.000
The range of 1-0.05% is desirable.

Further, in addition to the above elements, it is allowed to add 0.3% or less of Cr and 0.5% or less of Zn as necessary for improving strength. That is, Cr is an element effective for improving strength, but if the Cr content exceeds 0.3%, the formation of giant crystallized substances causes a decrease in formability.
Cr is 0.3% or less. The addition of Zn is Mg ₂ Z
Contributes to the strength improvement by aging precipitation of n ₃ Al ₂ , but Z
If the amount of n exceeds 0.5%, the corrosion resistance deteriorates.

The balance of each of the above elements may be Al and inevitable impurities.

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

First, a molten alloy having the above-described composition is melted by a conventional method and cast by a usual casting method such as a DC casting method (semi-continuous casting method). The obtained ingot is subjected to homogenization treatment (soaking treatment). This homogenization treatment may be performed under normal conditions, for example, 500 to 620 ° C. × 1 hour or more. Further, the ingot after the homogenization treatment is hot-rolled to obtain a hot-rolled plate having a required plate thickness. The conditions of this hot rolling are not particularly limited, but considering hot rolling property and surface quality, it is desirable to carry out rolling in the temperature range of 580 to 200 ° C. If the hot rolling temperature exceeds 580 ° C, the surface quality may be deteriorated due to the oxide film on the surface during hot rolling, and if it is less than 200 ° C, the deformation resistance is too large and the rolling property deteriorates.

After hot rolling as described above, cold rolling is applied to finish the can body material to a predetermined thickness. After such hot rolling, in the process up to the finished plate thickness, the structure in the plate is recrystallized at least once. For that purpose, usually, after hot rolling, recrystallization annealing is immediately performed to recrystallize, and then cold rolling (final cold rolling) is performed up to the finished sheet thickness, or primary cold rolling is performed after hot rolling. It is common practice to carry out rolling to an intermediate plate thickness, then recrystallize annealing to recrystallize, and then cold rolling (final cold rolling) to a finished plate thickness, but in some cases hot rolling Recrystallization (recrystallization by self-annealing) due to the heat of the hot-rolled sheet coil during the coil winding process and the subsequent cooling process
After that, the cold rolling (final cold rolling) may be performed to the finished sheet thickness without particularly positively performing the recrystallization annealing.

When performing recrystallization annealing after hot rolling or after further performing primary cold rolling, the recrystallization annealing may be carried out according to a conventional method, but when continuous annealing is applied, it is 450 to 600. C. × 10 minutes or less is preferable, and 300 to 450 ° C. × when batch annealing is applied.
The condition of 1 to 10 hours is desirable. In the case of continuous annealing, if the temperature is lower than 450 ° C., recrystallization becomes incomplete, while if it exceeds 600 ° C., eutectic melting may occur, and a strong oxide film may be formed on the surface, resulting in cold rollability,
Even if the appearance is impaired and the holding time exceeds 10 minutes, a strong oxide film is formed on the surface, and cold rolling property,
The appearance may be impaired. On the other hand, in the case of batch annealing, if the temperature is less than 300 ° C or the holding time is less than 1 hour, recrystallization becomes insufficient, and if the temperature exceeds 450 ° C, a strong oxide film is formed on the surface, and cold rolling property and appearance If the holding time exceeds 10 hours, the effect of recrystallization is saturated and the economic efficiency is deteriorated.

When primary cold rolling is performed before recrystallization annealing, the cold rolling reduction ratio is not particularly limited.

After recrystallization is performed by recrystallization annealing or self-annealing subsequent to hot rolling, cold rolling is performed to a finished sheet thickness. This final cold rolling has a great influence on the sub-graining rate after the coating baking treatment due to the relationship between the amount of Mg and the heating conditions such as the coating baking treatment after the DI processing as described later. Therefore, the working ratio of the final cold rolling cannot be specified alone, but generally speaking, the higher the working ratio is, the easier it is to increase the subgrain conversion ratio.
% Or more is preferable.

After the final plate thickness is obtained by the final cold rolling as described above, the plate is directly used as a can body material D
Although it can be subjected to I working, recovery annealing may be performed after the final cold rolling to secure ductility in some cases. However, the recovery annealing in this case needs to be determined so that recrystallization does not occur, and is usually 80 to 160 ° C x 1 to 1
It is preferable to carry out the conditions for about 0 hours.

The final cold-rolled plate or the plate that has been subjected to recovery annealing is used as a can body material for deep drawing,
DI processing by ironing is performed, predetermined trimming is performed to form a can body, and further cleaning, drying, can inner coating and paint baking, and can outer coating and paint baking are performed. Then, after necking and flange processing are further performed, the contents are filled, a can lid is attached, and seaming processing is performed.

In the drying treatment after DI processing, trimming and washing, and the coating baking treatment in the inner surface coating and the outer surface coating, generally, heating at a temperature in the range of 180 to 250 ° C. for a total of about 2 to 30 minutes is required. Done. The material is softened by such heating in the drying and painting baking process,
Subcrystalline grains are formed as a structural change at this time.

That is, when heat treatment is generally performed on an aluminum alloy material to which strain (accumulation of dislocations) has been introduced by cold working, the dislocation density decreases and the cell wall with a small misorientation has small-angle grain boundaries (subgrains). Change to the boundary, and subgrains (subgrains) are generated. Here, if the temperature of the heat treatment is higher than a certain level, coarsening of the sub-crystal grains occurs further, re-crystallized by growing grains of the sub-crystal grains in this process as nuclei, and a re-crystallized structure is generated. However, at a temperature such as drying after the DI processing and coating baking treatment, recrystallization does not usually proceed. In the case of a DI can body, cold working is performed by final cold rolling after final recrystallization during the plate manufacturing process and subsequent ironing in DI molding, and cold working strain (dislocation) is introduced. Therefore, by appropriately adjusting the cold working strain under an appropriate Mg content, and by appropriately selecting the heating conditions such as the drying after the can body forming and the coating baking treatment,
By the heat treatment such as the drying and baking treatment, it becomes possible to appropriately generate the sub-crystal grains. And the present inventors have repeated a number of experiments on the moldability of the can edge, the presence of sub-crystal grains in the can edge, its formability,
In particular, it greatly affects the flange formability, and the proportion of sub-crystal grains in the metal structure of the can edge is 10% in area ratio.
It has been found that the above, that is, the subgrain conversion rate of 10% or more is effective for improving the formability of the can edge portion, that is, necking workability, flange workability, and seaming workability.

If 10% or more of the sub-crystal grains are present in the can edge, preferably 20% or more of the sub-crystal grains are present.
The dislocations (working strains) given by necking, flanging, and seaming processes have little accumulation of dislocations absorbed in sub-grain boundaries, so work hardening hardly occurs during these processes and good formability is achieved. Is obtained. As a result of numerous observations, it was confirmed that the sub-crystal grains generated by the paint baking treatment continue to exist even if a processing such as a necking processing is added thereafter, although the dislocation density slightly increases. There is. Subgrain conversion rate is 10
If it is less than%, dislocations are accumulated by necking, flanging, and seaming, so that remarkable work hardening occurs and the formability of the can body part deteriorates.

As described above, in order to achieve a subgrain conversion rate of 10% or more, preferably 20% or more by heat treatment after DI processing, among the components of the can body material, Mg is particularly preferable.
It is necessary to appropriately combine the three factors of the amount, the cold working degree after the final recrystallization, and the heat treatment condition after the DI processing. Strictly speaking, the cold workability after the final recrystallization is, strictly speaking, the cold workability (cold rolling rate) in the final cold rolling and the workability of the can edge portion during DI processing, especially during ironing. Although it is related to (plate thickness change), actually, the ratio of the workability during ironing to the total cold workability after final recrystallization is small. Therefore, in determining the relationship between the three,
The cold workability after the final recrystallization can be represented by the workability of the final cold rolling. That is, in this case, 10%
In order to obtain the above-described sub-graining rate, the amount of Mg, the workability of the final cold rolling after the final recrystallization, and the heat treatment condition after the DI processing should be set so that the following expression (1) is satisfied. You can set it relatively. ε ³ × D × ln (t) / Mg ⁴ > 1 × 10 ^-8 (1)

Here, ε is the true strain of the cold-rolled plate thickness corresponding to the workability in the final cold rolling after the final recrystallization, that is, the plate thickness at the final recrystallization is t ₁ , and the finished plate after the final cold rolling. It is a value represented by ε = ln (t ₁ / t ₂ ) ... (2) where t ₂ is the thickness. Further, D is the self-diffusion of aluminum and is represented by D = exp (-Q / RT) (3). Where Q is the activation energy of self-diffusion of aluminum, R is a gas constant, T is the temperature (K) of the heat treatment after DI processing, and t is the time (se) of heat treatment after DI processing.
c). Further, Mg is the amount of Mg (weight ratio) in the material alloy.

The equation (1) is obtained as follows. That is, the subgrains are formed when the dislocations are thermodynamically liable to move. Therefore, qualitatively, the greater the cold workability up to DI processing, the more D
Sub-graining is promoted as the heat input during drying after I-working and baking is large and the amount of Mg that has the effect of delaying the recovery of dislocations is small. Therefore, each factor that contributes to subgraining was specifically examined.

The true strain ε corresponding to the cold rolling rate from the final recrystallized plate thickness is an important factor and has a large contribution to subgrain formation. In addition, the heating temperature and time are related to the heat input amount in the drying and baking treatment after DI processing, but especially since the heating temperature T affects the rearrangement speed of dislocations due to subgraining, that is, the moving speed of atoms. , The activation energy based on the diffusion of aluminum, the gas constant R, and the heating temperature T need to be organized by an exponential function. Regarding the heating time t, the longer the time, the more the subgrain formation proceeds, but a logarithmic relationship is appropriate rather than a linear relationship. Further, Mg is an element that suppresses subgrain formation, and if the amount of Mg is large, subgrain formation is significantly delayed. As a result of many experiments conducted by the present inventors, the final cold rolled sheet thickness true strain ε, which governs the subgraining rate, the heating temperature T after DI processing, the heating time t, and the Mg addition amount (weight ratio) are It was found that they can be arranged by the third power, the first power, the natural logarithm, and the fourth power, respectively. It was found that the left side of equation (1) needs to exceed 1 × 10 ^-8 in order to stably secure a subgrain conversion rate of 10% or more in order to improve the moldability of the can edge. It was

In the formula (1), the amount of Mg is represented by a weight ratio, but if expressed by a weight percentage (Mg%),
The formula is rewritten as the following formula (4). ε ³ × D × ln (t) / (Mg%) ⁴ > 1 (4)

Therefore, it is necessary that the left side of the equation (4) exceeds 1 in order to secure the subgraining rate of 10% or more, which is defined in claim 1 of the present invention.

As described above, in the actual can manufacturing process, there are some heat treatments after DI processing, such as DI processing, drying after washing, coating baking after inner surface coating, and coating baking after outer surface coating. Repeated heating and cooling. Therefore, D × ln (t) in the equations (1) and (4) should be expressed as the sum of these heating steps. That is, in the case where drying, inner surface coating baking treatment, and outer surface coating baking treatment are performed as the heating process after DI processing, the formula (1)
D × ln (t) in the equation (4) is [D × ln in the drying step]
(T)] + [D × ln (t)] + during internal coating baking process +
It is expressed as the sum of [D × ln (t) at the time of external coating baking processing].

Further, in deriving the equations (1) and (4), regarding the influence of the cold working degree after the final recrystallization, as shown in the equation (2), the final cold state after the final recrystallization is performed. Only the workability (rolling rate) in hot rolling is considered. Strictly considering here, as already mentioned, even in the DI processing (deep drawing and ironing), the cold working gives a slight reduction in the plate thickness, so that the DI processing also has a slight effect on the sub-graining. Will be given. However, in cold rolling → deep drawing → ironing, since the processing modes are different, dislocation accumulation forms are different, and it is not possible to simply consider the sum of all processing rates. The present inventors have sufficiently considered this point, and as a result of studying the definition of processing strain as a factor that has a great influence on the change in the subgraining rate in the actual industrial can body manufacturing and can be easily adjusted. , The processing strain from the final recrystallized plate thickness to the final cold-rolled plate thickness contributes the most to the subgrain conversion rate and is actually adjustable, and the final recrystallized plate thickness to the final cold-rolled plate plate It was found that the equation (4) using the processing strain up to the thickness as a control factor is the most practical.

As described above, by appropriately setting the amount of Mg, the degree of cold working after the final recrystallization, the temperature of the heat treatment after DI processing, and the time so as to satisfy the formula (4), the can body It is possible to reliably and stably obtain a can body having a subgrain conversion rate of 10% or more at the edge. Thus, the sub-graining rate of the can edge is 10% or more (preferably 20%).
By the above, not only the strength and DI processability are excellent, but also the moldability of the can edge (necking processability,
It is possible to obtain a DI can body having excellent flange processability and seaming processability.

[0039]

EXAMPLES For each alloy having the composition shown in alloy Nos. 1 to 7 in Table 1, DC casting was performed according to a conventional method, and the obtained ingot was subjected to soaking treatment and hot rolling to obtain various thicknesses. It was a hot rolled plate. The obtained hot-rolled sheet was subjected to recrystallization annealing under the conditions shown in Table 2 and then cold-rolled to finally have a sheet thickness of 0.3 mm. For some of the hot-rolled sheets, primary cold rolling was performed to obtain an intermediate sheet thickness, then recrystallization annealing was performed, and then final cold rolling was performed to finally obtain a sheet thickness of 0.3 mm as described above. did. Furthermore, DI molding is performed using each cold-rolled sheet according to a conventional method, and then various temperatures and
Heat treatment was performed under the conditions shown in Table 2 assuming coating baking treatment for a certain period of time.

With respect to the DI can body after the heating treatment equivalent to the coating baking treatment obtained as described above, the subgrain conversion rate of the edge portion was measured by a transmission electron microscope. The results are shown in Table 3. Further, the mouth widening property after the necking process was performed according to a conventional method was examined. The mouth spreadability was evaluated by increasing the radius of the can end until a rupture occurred at the edge by pushing a tapered punch having an inclination angle of 30 ° with respect to the can body wall into the opening end after necking. In the evaluation of the mouth spreadability, the larger the evaluation value (radius increase amount), the better the flange formability, and the evaluation value is 2.0.
It is empirically known that if it is less than (mm), the flange property is inferior. Further, the strength after the paint baking treatment was investigated, and the seaming workability after the necking processing and the flange processing was also investigated. The results are also shown in Table 3. Here, assuming that the strength after the coating baking treatment is the bottom pressure resistance strength which is the most problematic in the DI can body, the strength after the above-mentioned coating baking treatment was applied to the original plate was examined. If the strength after this baking treatment is 260 N / mm ² or less, it is evaluated as unsuitable as a can body requiring pressure resistance. As for the seaming workability, seaming with the can lid actually attached was carried out for each 20 cans. When even one can cracked in the can edge of the can, an X mark was given and no crack occurred in one can. The case is marked with a circle.

Table 3 also shows the value of the true strain ε of cold-rolled sheet after final recrystallization and the value on the left side of the equation (4).
Here, in the calculation of the value on the left side of the equation (4), the activation energy Q of aluminum is 37 kcal / mol and the gas constant R is 1.986 cal / mol / K.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

In Tables 2 and 3, serial numbers 5, 7, 1
In each of the cases of 1 and 14, the value on the left side of the equation (4) was smaller than 1, so that the subgrain conversion rate was less than 10%. In all of these cases, the moldability of the can edge was poor, and cracking occurred during seaming. Among these, the production number 5 is an example in which the composition of the alloy is within the range of the present invention, but the sub-graining did not proceed sufficiently due to the low temperature of the heat treatment equivalent to coating baking, and the production number 7 In the case of (3), the amount of Mg in the alloy was large, so that the subgrain formation was delayed. Manufacturing numbers 10 to 15 are the same alloys within the composition range defined by the present invention (however, Mg
(The amount is close to the upper limit), the can barrel material manufacturing conditions and the coating baking equivalent heat treatment conditions are different, but in the case of manufacturing number 10, by increasing the final cold rolling reduction ratio, manufacturing number 12 , 13 and 15 by applying an appropriate combination such as increasing the temperature of the baking baking equivalent heat treatment or prolonging the time, a sub-graining rate of 10% or more is sufficiently achieved. It was possible to secure good moldability on the can edge portion. On the other hand, production number 11 has a low final cold rolling reduction rate and at the same time has a relatively short coating baking time, so that even if the same alloy is used, the subgrain conversion rate is low, and good can edge forming The sex was not obtained. Further, the production number 14 is an example in which the temperature of the coating baking-equivalent heat treatment is lower than that of the production number 11, but in this case as well, the subgrain conversion rate is low and the formability of the can edge portion is poor. . From these examples, it is necessary to appropriately set the amount of Mg of the alloy, the reduction rate of the final cold rolling, the temperature of the heat treatment after DI processing, and the time so as to satisfy the above expression (4). % Or more,
It can be seen that this is necessary to obtain good moldability on the can edge.

Further, in the case of Production No. 1, although the sub-grayization ratio was sufficient, Mg was not substantially added, so that the predetermined strength as the can body material was not obtained. Further, in the case of manufacturing number 9, although the subgrain conversion rate was achieved, since the amount of Mn added was excessive, there were many Mn-based compounds that tended to be the starting points of cracks during flange processing.
The primary crystal giant intermetallic compound of the system was generated and deteriorated the formability of the can edge. Further, in the case of production number 8, the moldability and strength of the can edge portion were sufficient, but since the amount of Mn added was too small, the solid lubricating effect of the Mn-based compound was not obtained,
As a result, severe galling occurred during DI processing, which markedly impaired the appearance of the can and resulted in significant aluminum adhesion to the die.

On the other hand, while the alloy component composition satisfies the range specified by the present invention, the value on the left side of the equation (4) is set to 1 by appropriately combining the Mg content, the material manufacturing conditions, and the coating baking equivalent heat treatment conditions. When the sub-graining rate of 10% or more is exceeded (inventive example), the strength, the DI processability, and the can edge portion formability are excellent.

Among the examples of the present invention, serial numbers 3, 4,
Nos. 6, 12, 13, and 15 are obtained by appropriately balancing the strength and the formability of the can edge portion. Manufacturing number 2 is Mg
This is an example in which the amount of addition is made low and strength to some extent is ensured, while the formability of the can rim portion is emphasized. Further, manufacturing number 10 is particularly strong while securing some formability of the can rim portion. This is an example that emphasizes. Therefore, it is clear from these that by appropriately controlling the alloying components and the production conditions, a DI can body having the required strength and moldability of the can body edge portion can be manufactured with a large degree of freedom.

[0049]

EFFECTS OF THE INVENTION According to the present invention, the component composition of the material alloy is appropriately adjusted, and in particular, the amount of Mg in the material alloy, the cold working degree after the final recrystallization, and the heat treatment after the DI processing are performed. By appropriately combining the temperature and the time, as a DI can body that has been subjected to DI processing and paint baking, the metal structure state of the can body edge portion, especially sub-grains (subgrains) occupy 10% or more. It is possible to obtain a D-like structure which has an excellent formability in the can edge portion, that is, necking, flanging, seaming, etc. without impairing the strength and DI processability.
I can obtain a can body. Therefore, the DI of this invention
According to the method for manufacturing a can body, it is possible to effectively prevent the occurrence of molding defects such as breakage of the can end due to work hardening in necking processing, flanging processing, and seaming processing, and to reduce the processing load to reduce these processing loads. At the same time, it is possible to effectively prevent buckling of the can body, and to further reduce the weight of the can by reducing the neck diameter of the can body and the can lid. Become.

Claims (1)

[Claims] 1. Mg 0.1-1.5% (weight%, the same hereinafter), Mn 0.5-1.8%, Fe 0.1-0.8%,
An alloy containing 0.05 to 0.5% of Si and 0.05 to 0.7% of Cu and the balance of Al and unavoidable impurities is cast and subjected to soaking, hot rolling and cold rolling to obtain a predetermined amount. Finished to a plate thickness, recrystallized between hot rolling and the middle of cold rolling, and a can body material having a finished plate thickness after cold rolling is subjected to heat treatment including DI processing and paint baking treatment. In the method for producing a DI can body made of an aluminum alloy, the plate thickness at the time of final recrystallization is set to t _1, and the finish plate thickness is set to t.
₂ , the true strain ε of the cold rolled sheet thickness from the final recrystallization to the finished sheet thickness is defined as ε = ln (t ₁ / t ₂ ), and DI
Assuming that the heat treatment temperature after processing is T (K), the activation energy of self-diffusion of aluminum is Q, and the gas constant is R, the self-diffusion D of aluminum is D = exp (-Q / R · T).
And the amount of Mg (% by weight) is Mg%
Cold processing from the time of final recrystallization to the finished plate thickness so that the following equation ε ³ × D × ln (t) / (Mg%) ⁴ > 1 is satisfied, where the heat treatment time after processing is t (sec). Rate, the temperature and time of the heat treatment after DI processing are controlled to obtain a DI can barrel having 10% or more of sub-crystal grains in the can barrel edge after paint baking. Method for producing a DI can body made of an aluminum alloy having excellent moldability of a part.