JPS6237705B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aluminum alloy sheet strip for forming and a method for manufacturing the same, and more particularly to a bake-hardenable aluminum alloy hard sheet strip for cans having excellent formability and a method for manufacturing the same. In general, aluminum alloy materials for cans include can bodies, can ends, and can tabs. In particular, aluminum alloy materials for can bodies are required to have the following properties: (1) Excellent drawing and redrawing properties. (2) Excellent ironing workability. (3) Excellent scoring resistance. (Four)
Excellent doming processability. (5) Beautiful appearance. (6) Excellent netting properties. (7)
Excellent flanging properties. (8) Deep draw ears are low. (9) Excellent pressure resistance. (10) Excellent buckling strength. (11) It has excellent corrosion resistance. For aluminum alloy housing materials, in order to make the weight of the can more effective through thinner walls, the wall thickness of the can should be made as thin as possible within a range that does not cause problems in can strength such as buckling strength. It is necessary to. To achieve this, it is necessary to (1) improve ironing properties, and furthermore, since a decrease in wall thickness will reduce stretch flangeability, (2)
It is necessary to improve the flanging properties, and (3) improve the riveting formability in order to increase the effect of thinner walls for can ends, and to achieve the same effect as for ends for tabs. In order to increase this, it is necessary to (4) improve bendability. Among the above items, it is particularly necessary to improve the flanging properties and the riveting formability, and both of these properties require elongation in a minute range, that is, local elongation. Based on the above explanation, the present inventor conducted research on aluminum alloys for can manufacturing, and found that it is necessary to limit the amount of intermetallic compounds contained in ordinary can materials in order to avoid stress concentration in the aluminum alloy that is the material. It was discovered that this is the case. However, in the ironing process of the can body of the can material, the intermetallic compounds mentioned above have an excellent effect of preventing the aluminum alloy from seizing (build-up) on the die being processed, and the intermetallic compounds of the appropriate size can be recycled. They have also discovered that it is desirable that a certain amount or more of the intermetallic compound be uniformly dispersed because it is effective in reducing the crystal grain size to, for example, 25 μm or less, since it serves as a nucleus during crystallization. The present invention was made based on the fact that the aluminum alloy described above is excellent as a material for cans, and on the numerous findings of the inventors. The present invention provides an aluminum alloy sheet strip for forming, which can further improve the ironing workability, flanging property, and riveting property of aluminum alloys for can tabs, thereby further reducing the weight of the cans, and a method for producing the same. be. The aluminum alloy sheet strip for forming and the manufacturing method thereof according to the present invention includes: (1) Zn0.05-1wt%, Fe0.25-0.7wt%, Cu0.05
~0.5wt%, Mg0.5~2.5wt%, Mn0.5~2.0wt%, and Fewt% + (Mnwt% x 1.07) + (Mgwt% x
0.27)≦3.0, the balance is substantially Al, and the area occupation rate of intermetallic compounds as seen from the rolled plate surface is 0.5 to 5%, and the size of each intermetallic compound is A first invention provides an aluminum alloy sheet strip for baking paint hardening cans, which is characterized in that the average width of crystal grains as viewed from the surface of the rolled plate is 25μ or less, and (2) Zn0.05 ~1wt%, Fe0.25~0.7wt%, Cu0.05
~0.5wt%, Mg0.5~2.5wt%, Mn0.5~2.0wt%, and Fewt% + (Mnwt% x 1.07) + (Mgwt% x
0.27) ≦ 2.7, and after melting an aluminum alloy consisting of substantially Al, the ingot is cast to a thickness of 100 mm or more, the ingot is soaked at 530°C or more, and then hot rolled and then cold rolled. or not, heat to a temperature of 400 to 600°C at a heating rate of 100°C/min or more, immediately after heating, or after holding for less than 10 minutes, cool at a cooling rate of 100°C/hour or more.
The product is cooled to 150℃ or less, the average grain size is 25μ or less, and the components contributing to bake hardening are kept in a solid solution state, and cold rolling is performed to a rate of 10% or more. rate is 99% or more,
An aluminum alloy sheet strip for baking paint hardening cans, characterized in that the area occupation rate of intermetallic compounds as viewed from the surface of the rolled sheet is 0.5 to 5%, and the size of each intermetallic compound is 45μ or less. The manufacturing method is the second invention, (3) Zn0.05-1wt%, Fe0.25-0.7wt%, Cu0.05
~0.5wt%, Mg0.5~2.5wt%, Mn0.5~2.0wt%, and Fewt% + (Mnwt% x 1.07) + (Mgwt% x
0.27) = 2.0 to 3.0, and after melting the aluminum alloy, the remainder of which is essentially Al, rapid continuous casting is performed to a thickness of 50 mm or less, and the ingot is hot-rolled or not. Heat-treating the Al alloy plate strip ingot at a temperature of 300℃ or higher,
Or, without performing cold rolling, or without cold rolling, and then rolling at a temperature of 400 to 600℃ for 100 minutes.
Heat at a heating rate of ℃/min or more, and immediately after heating, or after holding for less than 10 minutes, cool to 150℃ or less at a cooling rate of 100℃/hour or more to reduce the average grain size to 25μ or less and bake. The components that contribute to hardening are kept in a solid solution state, and further cold rolling is performed at a rate of 10% or more, with the total rolling ratio of hot rolling and cold rolling being 90% or more, to reduce the amount of intermetallic compounds seen from the surface of the rolled plate. A third invention provides a method for manufacturing an aluminum alloy sheet strip for baking-painted cans, characterized in that the area occupation rate is 0.5 to 5% and the size of each intermetallic compound is 45μ or less. This invention consists of three inventions. The aluminum alloy sheet strip for forming and the manufacturing method thereof according to the present invention will be explained in detail. First, the components and component ratios of the aluminum alloy sheet strip for forming according to the present invention will be explained. Zn improves the flanging properties after drawing and ironing and the riveting properties after drawing and stretching, and the inclusion of Zn improves the crystallization of intermetallic compounds of (MnFe)Al ₆ when viewed from the surface of the rolled plate. It is an element that further improves flanging properties and riveting properties because it has the effect of improving the dislocation structure after plastic processing such as drawing, stretching, ironing, etc., and the Zn content is 0.05wt. If the content is less than 1wt%, there is no such effect, and if the content exceeds 1wt%, although it shows an effect on moldability, the corrosion resistance decreases significantly, and in reality, corrosion resistance must be ensured by painting etc. In particular, since the main body is painted after molding, there are few problems, but in the case of the can end, the material is molded after painting, so it is desirable that the material has good corrosion resistance. Therefore, the Zn content is set to 0.05 to 1 wt%. Fe is an element necessary to form an intermetallic compound of (Fe・Mn)Al ₆ together with Mn and prevent it from seizing on ironing dies, and its content is 0.25wt%.
If the content is less than 0.7 wt%, this effect will be small, and if the content exceeds 0.7 wt%, it becomes easier to mold a giant compound.
Therefore, the Fe content is set to 0.25 to 0.7 wt%. Cu must be contained at the same time as Mg.
It is an element that dissolves into solid solution by solution treatment and hardens by forming fine Al-Cu-Mg-based precipitates during baking, and improves strength.
If the content is less than 0.05 wt%, the above effects cannot be expected, and if the content exceeds 0.5 wt%, the above effects may be satisfied, but the corrosion resistance as a material for a vehicle body will be extremely deteriorated. Therefore, the Cu content is 0.05
~0.5wt%. Mg must be contained together with Cu,
After forming a solid solution with Cu through solution treatment, it hardens by precipitation.
In addition, it provides the necessary strength as a material for the vehicle body, and since it does not deteriorate corrosion resistance as much as Cu, it can be contained in large amounts, and the content can be reduced.
If the Mg content is less than 0.5wt%, this effect will be small, and if the Mg content is increased, the strength will be improved.
Formability during ironing, stretching, etc. decreases, and scoring becomes more likely to occur. However, in combination with the effect of improving the scoring resistance of precipitates due to Mn content, which will be described later, even if the Mg content is increased, the cartridge However, the content is 2.5wt.
If it exceeds %, moldability such as ironing property and stretchability will be reduced, and scoring will occur significantly. Therefore, the Mg content is set to 0.5 to 2.5 wt%. Unlike Cu and Mg, Mn does not contribute to precipitation hardening, but it is an important element that provides strength together with Mg. Also, since Mn crystallizes as Al and MnAl ₆ , it prevents scoring, and Mn If it is contained at the same time, it will stabilize the texture and deep drawing edges during recrystallization after heat treatment, but if the content is less than 0.5wt%, this effect cannot be expected.
In addition, as the Mn content increases, both the amount and size of crystallized substances increase, and if the content exceeds 2.0wt%, giant compounds are likely to occur, causing pinholes or fractures during ironing. becomes. Therefore, the Mn content is set to 0.5 to 2.0 wt%. Also, Fewt% + (Mnwt% × 1.07) + (Mgwt% ×
0.27) ≦ 3.0 because intermetallic compounds are broadly divided into crystallized substances and precipitates. Crystallized substances are generated during solidification during casting, and precipitates are those that become supersaturated during casting and are formed during subsequent heat treatment. Precipitates are sometimes formed in solids, and the size of precipitates is usually 1 μm or less, and because of their small size, they do not pose a particular problem as a stress concentration source. Further classification of crystallized substances can be divided into primary crystal compounds, which are generated in a liquid just before solidification, and eutectic compounds during solidification.Primary crystal compounds, in particular, tend to grow into giant compounds, and are suitable for industrial-level casting. In this case, there is stagnation of molten metal, and in practice, the passing time of the formation temperature has a large effect on growth, but as long as the above formula is satisfied, the generation of giant compounds can be prevented and moldability can be improved. can be achieved. Setting the area occupancy rate of intermetallic compounds as viewed from the surface of the rolled plate to 0.5 to 5% has the problem that if it is less than 0.5%, seizure will occur on the die during ironing, and if it exceeds 5%, it will cause damage to the flange. This is because formability such as bending properties and riveting properties are extremely reduced, and pinholes are likely to occur even during ironing. The size of the intermetallic compound is set to 45 μ or less because
This is because, as will be explained in the Examples below, when the length of the long side of the intermetallic compound is about 40 μm or more, flange cracks occur frequently and, furthermore, breakage is more likely to occur during ironing. However, in rolled plates manufactured from industrial-grade large ingots, there are countless intermetallic compounds, and with a very small probability, large compounds may also be present. Therefore, the size of the intermetallic compound should be 45μ or less. The reason why the average width of the crystal grains as seen from the surface of the rolled plate is set to 25μ or less is to compensate for the decrease in various formability due to thinning of the cylinder body and the decrease in netting property due to high strength after baking. This is to promote precipitation hardening, and when the crystal grain size is reduced, formability, stretchability, flanging properties,
Although the ironing properties are improved and the drawing properties are not a problem when thinning the wall, wrinkles are more likely to occur. however,
These wrinkles become less likely to occur when the average grain size is 25 μm or less. Furthermore, if the average crystal grain size exceeds 25μ, there will be no difference from conventional materials for housings, and it will be difficult to achieve thin walls and high strength. Therefore, the average crystal grain size is set to 25μ or less. Next, a method for manufacturing an aluminum alloy sheet strip for forming according to the present invention will be explained. First, Fewt% + (Mnwt% × 1.07) + (Mgwt% ×
0.27) ≦ 2.7 to a thickness of 100 mm or more is that the smaller the value of the above formula becomes, the smaller the size of each compound and the smaller the amount, which affects the flanging properties. However, in this case, in industrial casting methods that use water cooling, if the casting thickness becomes thinner than a certain level, the cooling rate during solidification becomes too high and the formation of crystallized substances is suppressed. This is not preferable because the area occupied by the intermetallic compound after rolling becomes too small. Therefore, the casting thickness should be 100 mm or more. The above-described ingot is soaked at a temperature of 530°C or higher, but if the soaking temperature is lower than 530°C, the MnAl ₆ precipitates become very fine, and
Since it precipitates in large quantities, it suppresses grain boundary movement at the time of recrystallization of the rolled sheet, increases the recrystallization temperature and coarsens the crystal grains, and also changes the recrystallized texture, causing the angle of 45° to the rolling direction during deep drawing. In order to further improve ironing workability and deep drawability, soaking treatment is carried out at a temperature of 530°C or higher. For hot rolling after this soaking treatment, there is no need to particularly control the amount of hot rolling, temperature, etc., and hot rolling using a normal industrial method may be used, followed by cold rolling if necessary. It is then heated (annealed). This heating is performed at a temperature of 400 to 600°C, and this heating (annealing) causes recrystallization, forms a recrystallized texture, and reduces the deep drawing edges. , Cu is solution-dissolved in order to achieve uniformity and bake hardening by precipitation hardening of the Al-Cu-Mg system.
If the temperature is lower than ℃, the effect of solutionization cannot be obtained, and the higher the temperature, the better.Although there are trade-offs such as Cu content and holding time, a temperature of 430℃ or higher is preferable, and the higher the temperature, the more recrystallized grains Now to grow, 600
When the temperature exceeds .degree. C., this tendency becomes so pronounced that it becomes impossible to reduce the crystal grain size to 25 .mu.m or less. Therefore, the heating temperature is
The temperature shall be 400-600℃. In addition, the heating temperature is adjusted to make the crystal grains finer and to improve the surface of the plate due to the short processing time.
In order to reduce the production of MgO, it is necessary to heat rapidly, and this effect cannot be expected unless it is heated at 100°C/min or more. Next, the holding time must be controlled especially from the point of view of grain refinement; in other words, since the treatment is at a high temperature, the purpose can be fully achieved even with a holding time of zero; case, or
It may be necessary to hold for a certain period of time depending on the components contained, component ratios, and other manufacturing conditions, but if held at high temperature for a long time, recrystallized grains will grow and grain refinement will be significantly inhibited. Therefore, the holding time should be zero or less than 10 minutes. Furthermore, the cooling rate needs to be controlled to obtain precipitation hardening, i.e., if the cooling rate is slow, precipitation will occur during the cooling stage and sufficient precipitation hardening will not be obtained during baking; At relatively low temperatures, precipitates are small and contribute to improving strength, but in this case, the strength increases before ironing and reduces formability. For this reason, it is necessary to increase the cooling rate, and a cooling rate of 100° C./hour or more is sufficient as a material for a chassis. However, although a cooling rate higher than this may be used, air cooling is preferably used for coil-shaped cooling. Furthermore, the temperature must be lowered to a certain level by cooling, that is, the temperature must be lowered to a temperature at which Al--Cu--Mg-based precipitates are generated, otherwise they will precipitate before baking. It is necessary to cool it below ℃. At the same time, the average crystal grain size is set to 25 μm or less, and at the same time, components contributing to bake hardening are maintained in a solid solution state. The purpose of this cold rolling after cooling is to obtain the strength required as a material for the housing.Cu, Mg,
The cold rolling rate differs depending on the Mn content, but 10
If the content is less than 10%, no effect can be expected, so hot rolling is performed at a content of 10% or more. The reason why the total rolling ratio during hot rolling and cold rolling is 99% or more is that during the casting stage, intermetallic compounds are segregated to the grain boundaries and the total amount is large.
In order to keep the area occupancy of the intermetallic compound viewed from the surface of the final rolled sheet within a preferable range and to disperse it as uniformly as possible, the total rolling ratio of hot rolling and cold rolling must be 99% or more. Next, Fewt% + (Mnwt% × 1.07) + (Mgwt% ×
0.27) = 2.0~3.0 after melting the aluminum alloy
Rapid continuous casting is performed to a thickness of 50 mm or less when the value of the above equation is large, when the casting thickness is large and/or when the total rolling rate is small, the area occupation rate of intermetallic compounds is This is not preferable because it becomes too large, and if the value of the above formula is small and the casting thickness is thin, the area ratio of the intermetallic compound becomes too small. Furthermore, in order to reduce the casting thickness and increase productivity by using the coil method, within the range of the above formula, the casting thickness must be 50 mm or less and the cooling rate during solidification must be increased, and the continuous In the casting method, the value of the above formula must be between 2.0 and 3.0. When the cooling rate is high as described above, the crystallized substances are small in size but relatively large in number and tend to be uniformly dispersed. Therefore, from these reasons, an appropriate area occupation ratio can be obtained by setting the alloy rolling ratio of hot rolling and cold rolling to 90% or more. In addition, after continuous casting and hot rolling, aluminum alloy strips are heat-treated at temperatures of 300°C or higher as necessary. This is done to improve the rollability since edge cracking tends to occur, and to control the texture even when edge cracking does not occur. The area occupancy rate of intermetallic compounds as explained above was determined by polishing the rolled surface of the rolled plate and using an optical microscope.
This was determined by observing at 400x magnification. Next, in Figures 1, 2, and 3, Fewt% +
(Mnwt% x 1.07) + (Mgwt% x 0.27) The value of the formula (sometimes simply referred to as this formula), the maximum length of the intermetallic compound (μm), the area occupation rate of the intermetallic compound (%),
The relationship with the number of intermetallic compounds (1/300mm ² ) is shown in Figure 4, and the relationship between the ingot thickness (mm) and the maximum length of the intermetallic compound (μm) when the value of the formula is 3. Figure 5 shows the relationship between the area occupancy rate (%) of intermetallic compounds and the limit ironing rate (%).
The figure shows intermetallic compounds of 30μm or more (stretch flange ratio 12)
%), the relationship between the number of intermetallic compounds (1/300mm ² ) and the flange formability rate (%) is shown. As is clear from these figures, in the case of large ingots (100 mm or more, 1 in the figure is 500 mm thick), the value of the formula must be 3 or less or 2.7 or less, and In the case of an ingot (continuous casting of 50 mm or less, 2 in the figure indicates a thickness of 50 mm), the value of this formula must be 2.0 to 3.0. Therefore, outside the above-mentioned range, the size (45 μm or less), amount (0.5 to 5.0%), ironing property, stretch flangeability and riveting property of the intermetallic compound (crystallized product) will decrease. Furthermore, within the scope of the formula, and
The inclusion of Zn has the effect of maintaining and improving the ironing properties, stretch flange formation, and riveting properties, which are thought to deteriorate due to the increased strength of the aluminum alloy. Next, examples of the aluminum alloy sheet strip for forming and the manufacturing method thereof according to the present invention will be described. Example 1 An aluminum alloy having the ingredients and proportions shown in Table 1 was melted and cast to form a large ingot of 500 mm. This ingot was soaked at 570°C for 6 hours, and hot rolled to a size of 3 mm. The thickness was then cold rolled to 1 mm, heated to 580°C at a heating rate of 500°C/min, and then immediately cooled at a cooling rate of 500°C/min. The thickness was 0.4mm for the end material, and 0.3mm thick for the can end material. Comparative examples were No. 1, in which the Zn content was at the level of impurities, and No. 4, in which this No. 1 alloy was produced by a conventional method. Table 2 shows the mechanical properties and average grain size, and alloys No. 2 and No. 3 according to the present invention are different from those of the comparative example.
It can be seen that it has better characteristics than No. 1 and No. 4. Table 3 shows the results of the investigation on the properties of can materials. No.2 and No.3 are much better,
Furthermore, the stretch flangeability and riveting properties after baking were also higher than those of No. 2 and No. 3 according to the present invention compared to No. 1 and No. 4.
It is clear that this has improved.

【table】

【table】

[Table] Example 2 An aluminum alloy having the ingredients and content ratios shown in Table 4 is melted to form an ingot with a thickness of 40 mm (indicated by A) and 60 mm (indicated by B), and this ingot is heated at 400°C. After heating to a temperature of , it was hot rolled to a thickness of 4 mm.
Thereafter, a combination of cold rolling and intermediate annealing was performed to obtain a thickness of 0.4 mm for the body and 0.3 mm for the end. For intermediate annealing, the heating and cooling rate is 500℃/
min, reached temperature 500℃ x 10 seconds. In addition, the intermediate annealing position is 1 mm for No. 5, 0.95 mm for No. 6, and 0.95 mm for No. 7.
It is 0.75mm. Table 5 (0.4mm, for body) shows typical mechanical properties. By changing the intermediate annealing position, No.5,
The mechanical properties of Nos. 6 and 7 are approximately the same. In addition,
There was little difference between the ingot thicknesses of 40 mm (A) and 60 mm (B). Table 6 shows the moldability. Formability was found to be affected by the ingot thickness, and the thickness of No. 6 ingot was 40 mm.
(6A) is the best overall.

【table】

【table】

[Table] As explained above, since the aluminum alloy sheet strip for forming and the manufacturing method thereof according to the present invention has the above-mentioned configuration, it can be used for cans with excellent ironing workability, flanging property, and riveting property. It has the effect of being suitable as a material.

[Brief explanation of the drawing]

Figures 1, 2, and 3 are Fewt% + (Mnwt%
× 1.07) + (Mgwt% Diagram showing the relationship with the maximum compound length, No. 5
The figure is a diagram showing the relationship between the area occupation rate of intermetallic compounds and the limit ironing rate, and FIG. 6 is a diagram showing the relationship between the number of intermetallic compounds and the flange formability rate. 1...Large ingot, 2...Small ingot.

Claims (1)

[Claims] 1 Zn0.05-1wt%, Fe0.25-0.7wt%, Cu0.05
Contains ~0.5wt%, Mg0.5~2.5wt%, Mn0.5~2.0wt%, and Fewt% + (Mnwt% x 1.07) + (Mgwt% x 0.27)
≦3.0, the balance is substantially Al, and the area occupation rate of intermetallic compounds as seen from the rolled plate surface is 0.5 to 5%, and the size of each intermetallic compound is 45μ or less An aluminum alloy sheet strip for baking paint hardening cans, further characterized in that the average width of crystal grains as viewed from the surface of the rolled sheet is 25μ or less. 2 Zn0.05~1wt%, Fe0.25~0.7wt%, Cu0.05
Contains ~0.5wt%, Mg0.5~2.5wt%, Mn0.5~2.0wt%, and Fewt% + (Mnwt% x 1.07) + (Mgwt% x 0.27)
≦2.7, and after melting an aluminum alloy consisting of substantially Al, the aluminum alloy is cast to a thickness of 100 mm or more,
The ingot is subjected to soaking treatment at 530℃ or higher, and after hot rolling, cold rolling is performed or not.
Heating to a temperature of 600℃ at a heating rate of 100℃/min or more, immediately after heating, or after holding for less than 10 minutes,
Cool to 150°C or less at a cooling rate of 100°C/hour or more, keep the average grain size to 25μ or less, keep the components contributing to bake hardening in a solid solution state, and perform cold rolling to a temperature of 10% or more. The total rolling ratio of inter-rolling and cold rolling is 99% or more, and the area occupation rate of intermetallic compounds as seen from the surface of the rolled plate is 0.5 to 5%, and
A method for manufacturing an aluminum alloy sheet strip for baking paint hardening cans, characterized in that the size of each intermetallic compound is 45μ or less. 3 Zn0.05~1wt%, Fe0.25~0.7wt%, Cu0.05
Contains ~0.5wt%, Mg0.5~2.5wt%, Mn0.5~2.0wt%, and Fewt% + (Mnwt% x 1.07) + (Mgwt% x 0.27)
= 2.0 to 3.0, and after melting an aluminum alloy with the remainder substantially consisting of Al, rapid continuous casting is performed to a thickness of 50 mm or less, and this ingot is hot rolled,
Or, without doing so, heat treating the Al alloy plate strip ingot at a temperature of 300°C or higher, or not, and then cold rolling, or not, and then,
Heating to a temperature of 400 to 600℃ at a heating rate of 100℃/min or more, immediately after heating, or after holding for less than 10 minutes,
It is cooled to 150℃ or less at a cooling rate of 100℃/hour or more, the average crystal grain size is 25μ or less, and the components contributing to bake hardening are kept in a solid solution state.
% or more, the total rolling ratio of hot rolling and cold rolling is 90% or more, and the area occupation rate of intermetallic compounds from the surface of the rolled plate is 0.5 to 5%, and each metal A method for producing an aluminum alloy sheet strip for baking-painted hardening cans, characterized in that the size of the interstitial compound is 45μ or less.