JPH03146632A - Aluminum alloy hard sheet having excellent out of roundness in drawn cup and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture the Al alloy hard sheet having high strength and high formability and suitable for cons for food and drink by subjecting an ingot of an Al alloy having a specified compsn. to homogenizing heat treatment, thereafter subjecting it to hot rolling and executing cold rolling including process annealing to work the alloy into the shape of a thin sheet. CONSTITUTION:An ingot of an Al alloy contg., by weight, 0.5 to 1.2% Fe, 0.5 to 1.0% Mn and 0.5 to 1.0% Mg [where Mg=(1.0 to 1.5)Mn] and contg. one or >=2 kinds among 0.1 to 0.7% Si, 0.05 to 0.5% Cu and 0.05 to 1.0% Zn is heated in the temp. range of 500 to 600 deg.C for >=1hr and is subjected to homogenizing heat treatment. Next, the ingot is subjected to coarse hot rolling and finish hot rolling, and the finish hot rolling is finished at >=280 deg.C finishing temp. into a sheet material having 1.5 to 2.5mm thickness. The sheet material is successively subjected to process annealing under the conditions of >=100 deg.C/min heating-cooling rate and 400 to 600 deg.C arrival temp. and is thereafter subjected to cold rolling at 70 to 90% draft, by which the Al alloy thin sheet for a can material for drink or the like having <=1.5kgf/mm<2> anisotropy in strength, excellent in out of roundness in a drawn cup and having about 0.35mm thickness can be manufactured.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an aluminum alloy hard plate, and more specifically, the present invention relates to an aluminum alloy hard plate, and more specifically, it has a shape that reduces the outer diameter change after the drawing cup of a beverage can body, and that is easy to carry into the re-drawing guide during subsequent DI processing. The present invention relates to an aluminum alloy hard plate with excellent cup roundness and a method for manufacturing the same. (Prior Art) Al-Mn-Mg based 3004 alloy hard plates have been used as a material for beverage can bodies such as beer and carbonated beverages and food can bodies. However, in recent years, in order to reduce the weight of cans, there has been an increasing demand for high strength and high formability. Therefore, the present inventors have previously developed a precipitation hardening type high-strength aluminum material for can bodies (Japanese Patent Publication No. 7465/1983). The increased strength of this material primarily contributes to the thinning of the bottom of the can. However, when considering further weight reduction of the can, it becomes necessary to reduce the thickness of the entire can body. Therefore, in order to further reduce the weight of can bodies in the future, materials that can make can walls thinner will be needed, and such demands are becoming stronger. On the other hand, regarding the manufacturing method of can material, there are 30
04 alloy ingots are subjected to a combination of homogenization heat treatment, hot rolling, cold rolling, and intermediate annealing, but recently, continuous annealing furnaces have been used to increase the strength of the material and improve productivity. (CAL: short-time annealing in which the coil is rapidly heated and cooled while unwinding) is beginning to be used, for example, Japanese Patent Publications No. 61-7465 and No. 62-37705. No. 62-6740, No. 62-13421, etc. have been proposed. (Problem to be solved by the invention) As mentioned earlier, to reduce the weight of the can body, it is necessary to reduce the thickness of the entire can body, and with the conventional technology, it is possible to reduce the thickness of only the bottom of the can by using a high-strength material. has been progressing. However, increasing the strength of the material also leads to increasing the strength of the can wall, which has a positive effect on the axial buckling strength of the can required during filling, but unfortunately, it has a negative effect on neck and flange processing. This becomes a negative factor and inevitably makes it difficult to reduce the thickness of the can wall, particularly at the neck and flange portions. In order to solve this problem and meet the demand for thinner can walls, the present inventors developed an aluminum material with relatively low can wall strength and a method for manufacturing the same, and previously proposed it (Patent Application No. 939
No. 37). However, as a result of further studies conducted by the present inventors, although it was confirmed that the material properties of the material were excellent, a phenomenon that caused transportation troubles was observed. That is, the DI process is performed after the drawing cup is formed, but if the drawing cup is deformed, there is a risk of jamming occurring during the DI process. An object of the present invention is to solve the above-mentioned problems and provide a hard aluminum alloy plate with high strength and high formability, which makes it possible to reduce the thickness of the entire can, and a method for manufacturing the same. (Means for Solving the Problems) In view of the above problems, the present inventors investigated in detail the relationship between drawing cup deformation and material properties. As a result, it was found that drawing cup deformation occurs due to springback after forming.
It was also found that this is mainly caused by strength anisotropy (difference in tensile strength in parallel, 45°, and perpendicular directions), and that strength anisotropy is caused by the shape of crystal grains. As a result of extensive research into countermeasures, we were able to solve the problem by optimizing the component composition and manufacturing conditions. That is, deformation of the draw cup occurs after forming, and the diameter increases in the direction perpendicular to the rolling direction and decreases in the rolling direction. This is because the strength in the perpendicular direction is higher than the strength in the parallel direction, so the perpendicular direction expands outward as shown in FIG. 2, and conversely, the parallel direction becomes narrower. Therefore, it is important that the material has no strength anisotropy, but since this material is a rolled hard material, strength anisotropy inevitably occurs, and therefore it is important to minimize the strength anisotropy. For this purpose, it has been found that a measure that mainly satisfies the following two points is required. (1) The smaller the final cold rolling rate, the better. (2) The smaller the crystal grains, the better. Among these, in (1), it is necessary to adjust the forming conditions by appropriately adjusting the ingredients to reduce the final cold rolling rate by effectively increasing the strength while satisfying the required properties (strength, formability). is necessary. Regarding (2) as well, it is necessary to properly adjust the components and manufacturing conditions to form fine crystal grains during intermediate annealing. The present invention has been developed by fully considering these points and other characteristics (crystallized material distribution, selvage ratio). That is, in the present invention, Fe: 0.5 to 1.2%. Mn: 0.5 to 1.0%, Mg: 0.5 to 1.0%, provided that Mn and Mg are Mg = (1, 0 to 1, 5) Mn
Si: 0.1 to 0.
．． 7%, Cu: 0.05-0.5% and Zn: 0.05
An aluminum alloy hard plate containing one or more of the following: ~l, 0%, with the balance consisting of Al and inevitable impurities, characterized by having a strength anisotropy within 1.5 kgf/n+m2 The gist of this invention is to provide a hard aluminum alloy plate with excellent roundness for drawing cups. In addition, the present invention relating to the manufacturing method includes subjecting an Al alloy ingot having the above chemical composition to homogenization heat treatment at a temperature of 500 to 600°C, and then hot rolling to a plate thickness of 1.5 to 2.5°C. 5m
m, carried out at a finishing temperature of 280°C or higher, and then immediately or after cooling, intermediate annealing is performed at a heating and cooling rate of 100°C/ll1in or higher and a final temperature of 400 to 600°C, followed by a final rolling reduction of 70 to 90%. The gist is a method for producing an aluminum alloy hard plate with excellent draw cup roundness, which is characterized by obtaining an aluminum hard plate with strength anisotropy within 1.5 kgf/rnm2 by rolling. It is. The present invention will be explained in more detail below. (Function) First, the reasons for limiting the chemical components in the present invention are as follows. Fe: Fe has the greatest effect on grain refinement, and Mn
In relation to this, it is an element that is effective in improving ironing workability and softening the can wall strength by properly forming Al-Fe-Mn based products. However, when Q is less than 5%, the effect on these is small, and when it exceeds 1.0%, it is not preferable because it forms giant pieces and causes processing defects. Therefore, the amount of Fe is set in the range of 0.5 to 1.0%. Mn: Mn is an element that increases strength anisotropy, but it is also an element that is effective in improving strength, improving ironing workability by properly forming Al-Fe-Mn products, and softening can wall strength. There is also. Therefore, if it is less than 0.5%, the above effect will be small. Moreover, if it exceeds 1.0%, strength anisotropy will increase, and formability will decrease due to the strength being too high.
This is not preferable because it causes processing defects due to the formation of Al-Fe-Mn-based giant crystallized substances in relation to the amount of e. Therefore, the amount of Mn is set in the range of 0.5 to 1.0%. Mg: Mg is an element that is effective in improving strength, and in particular, when combined with Cu, it exhibits precipitation hardening due to Al-Cu-Mg based precipitates during baking, and is effective in increasing the strength of the can bottom. However, the effect is small below 0.5%, and
, if it exceeds 0%, the strength anisotropy tends to increase, leading to deformation of the cup. Therefore, the amount of Mg is 0.5
-1.0% range. However, although both Mn and Mg are effective in improving strength, it is necessary to utilize precipitation hardening by An-Cu-Mg-based precipitates to effectively improve strength. In this case, if the Mg amount is less than the Mn amount (Mg<Mn
), no effective strength improvement can be expected, and the deformation of the cup increases as the cold rolling rate increases. Furthermore, if the Mg amount is more than 1.5 times the Mn amount (Mg) 1.5Mn), the DI workability will decrease due to a decrease in Mn, although it depends on the required strength. Therefore, Mn and Mg are Mg”(1
, 0 to 1.5) Mn is contained so as to satisfy the relationship. Si: Si is an element that causes phase transformation in the Al-Fe-Mn system crystallized product to form the so-called α phase of the AQ-Fe-Mn-Si system.The α phase has high hardness and is particularly difficult to iron. Effective in improving workability. However, if it is less than 0.1%, the effect will be small, and if it exceeds 0.7%, edge cracking will occur during rolling, causing problems in manufacturing. therefore,
The amount of -3i is in the range of 0.1 to 0.7%. Cu: Cu is an element that exhibits the same effect as Mg, and Al-Cu
- It exhibits a precipitation effect due to Mg-based precipitates and is effective in improving the strength of the can bottom. However, if it is less than 0.05%, the effect will be small, and if it exceeds 0.5%, the strength will be too high, leading to a decrease in moldability. Therefore, the amount of Cu is set in the range of 0.05 to 0.5%. Zn: Zn is an element that is effective in improving drawing and ironing workability and subsequent flange formability. However, if it is less than 0.05%, the effect is small;
If it exceeds 0%, there is no particular problem, but corrosion resistance tends to decrease and it is disadvantageous in terms of cost. Therefore, Zni is in the range of 0.05 to 160%. However, regarding the above-mentioned Si, Cu, and Zn, it is sufficient if at least one or two or more of them are contained. Note that impurities are permissible as long as they do not impair the effects of the present invention5, for example, Cr<0.3%. Ti<0.2%, B<0.05%, and Zr<0.1%. Next, the manufacturing method of the present invention will be explained. An aluminum alloy having the above chemical components is melted and cast by a conventional method, and the resulting ingot is subjected to homogenization heat treatment before hot rolling. This heat treatment is effective in improving the subsequent hot rolling properties, as well as improving formability through the formation of the α phase mentioned above and suppressing the selvage rate formed during deep drawing. However, below 500℃, neither effect decreases by /lX, and 6
If the temperature exceeds 00°C, the performance of the plate surface will deteriorate due to burning or the like. Therefore, the homogenization heat treatment is 500-6
It is carried out at a temperature of 00°C. Note that the holding time varies depending on the heating temperature, but is preferably approximately 1 hr or more, for example, 550 hr or more.
If the temperature is less than 550°C, the holding time is 1hr or more, but if the temperature is 550°C or more, there may be no holding time. Further, this homogenization heat treatment may be performed twice. The subsequent hot rolling is rough rolling (thickness 10+u
It is a continuous process, although it is divided into (+ or above) and finish rolling. Rough rolling is performed after homogenization heat treatment, and the starting temperature is preferably 450°C or higher. After further rough rolling, it is finished rolled into a coil. In this case, the plate thickness and temperature at the end are important. These influence the appropriate strength 1 strength anisotropy of the product board, softening due to baking after DI processing, and suppression of selvage during deep drawing. That is, if the final plate thickness is less than 1.51, it is effective in reducing the strength anisotropy and suppressing the selvedge ratio, but the 1 strength and the softening due to baking after DI processing are insufficient. Also, 2.5
If it exceeds mm, the strength anisotropy will be large, and the strength will be too high, leading to a decrease in formability and an increase in the selvage rate, resulting in processing defects. Therefore, the final plate thickness is 1.5 to 2.5
The range is 11 Im. Further, the finishing temperature has a great effect on the deep-drawn selvage in particular, and if it is less than 280°C, the selvage rate will increase significantly, so the finishing temperature is set to be 280°C or higher. After that, cold rolling including intermediate annealing is performed. Intermediate annealing is an important process for refining grains and increasing strength in the product plate (corresponding to the bottom of the can). The purpose of this heat treatment is to sufficiently dissolve the If the heating and cooling rate is less than 100° C./win, it is difficult to refine the crystal grains and precipitation occurs during cooling, which reduces the amount of solid solution, which is not preferable. In addition, heating and cooling are performed in the same line, and from the viewpoint of productivity, the faster the line speed, the better. Therefore, the heating and cooling rate is 100
℃/In1n or more. In addition, the heating temperature is an important condition for solutionizing Mg and Cu at the same time as recrystallization.
If it is less than 0°C, it is insufficient in either case, and if it exceeds 600°C, it may cause a burning problem, which is not preferable. Furthermore, the holding time varies depending on the temperature, and at high temperatures (e.g. 50
If the temperature is 0°C or higher, the temperature is sufficiently satisfied without holding, but if the temperature is low (for example, 400°C), about 10 m1n is required. Therefore, the temperature reached is 400-600℃
It is maintained within approximately 10 Ilin. In addition, in terms of production, the preferred temperature range is 450 to 550°C. Needless to say, it is preferable to use a continuous annealing furnace (CAL) for intermediate annealing. Furthermore, cold rolling, which is the final step performed after intermediate annealing, is effective in improving the strength of the product sheet and softening it by baking after DI processing. However, if the cold rolling rate is less than 70%, the effect is poor, so the cold rolling rate must be 70% or more. On the other hand, when the rolling reduction exceeds 90%, the strength anisotropy increases. In addition to reducing the roundness of the cup, it also increases the strength, leading to a decrease in moldability. Therefore, the final cold rolling is performed at a rolling reduction of 70 to 90%. After cold rolling, if necessary, finish annealing (100 to 200°C x lhr or more) is performed to improve can bottom formability.
may be applied. (Example) Next, an example of the present invention will be shown. In the Al-Mn-Mg alloy on the cold plate, Fe: 0.4-2
．． 0%, Mn: 0.4-1.2%, Mg: 0.4-1
After applying homogenization heat treatment at 580°C for 4 hours to Al alloy ingots with 10 different compositions varying within a range of 2%,
Hot rolling from mm thickness to 2ml11 thickness (finished fjL degree 2
90-300°C). After that, 520℃×5s
It was subjected to rapid heating and cooling annealing (500° C./mjn) and cold rolled to a product thickness of 0.35 mm. For these test materials, tensile test pieces were cut parallel to the rolling direction and at a right angle of 45° to determine the mechanical properties.
A blank diameter of 140φ was produced using an on-crank press, and the roundness of the upper part of the cup (approximately 5 m+w below the upper end) was measured. As the results are shown in Figure 1, there is a positive correlation between the (perpendicular to parallel) tensile strength difference △σ8 (top-i) and roundness, and the smaller ΔσB (earth-i) is, the more It became clear that the roundness became smaller and better. In the figure, material A is a typical 3004 alloy (Fe: 0.
4%, Mn: 1.05%, Mg: 1.1%), and the B material with the best roundness is an Al-gold alloy with Fe: 2.0%. However, Fe, :, 2.0% Al gold alloy B material)
was inferior in formability (drawability, stretchability), and other test materials were also unsuitable for practical use due to insufficient strength or formability. However, from this test, the roundness (this test condition) was set to 2mm.
In order to have the following, △σ8 (upper - i) is 1, 5 k
gf/mm”. The aluminum alloy ingot having the chemical composition shown in Table 1 was heated to 580°C.
After homogenization heat treatment for
Rapid heating and cooling annealing (500° C./5 inches) of XlOs was performed. Thereafter, it was cold rolled to a thickness of 0.35 mm to obtain a product sheet. Table 2 shows the results of examining the mechanical properties (as rolled, after baking) and roundness of the cup for the obtained product. Note that the cup roundness was measured in the same manner as in Example 1. As is clear from Table 2, Nα3 and Nα4 of the present invention material
．． Na5 has a small ΔσB (Sat-i), excellent cup roundness, and has the strength as a can body material for this purpose (baking yield strength ≥ 28 kgf / mm" is required from the viewpoint of pressure resistance). On the other hand, with conventional material No. 1, (M g / M n) > 1
, 5 and 5 have a large Δσ8 (earth −//) and are inferior in cup roundness. Furthermore, the comparison material Na 6 has (Mg/Mn)<1.0. Effective bake hardness cannot be obtained and the strength is insufficient. In addition, the comparative material Nα7 has a large amount of Fe (as large as a metal compound), so it has poor drawing and ironing workability and is not suitable for single-piece use.

[Left below]

(Effects of the Invention) As detailed above, according to the present invention, the amounts of Fe, Mn, and Mg in the aluminum hard plate are adjusted so that Mn and Mg satisfy a specific relational expression, and Since the manufacturing conditions are properly regulated, there is no trouble when forming the can, and the can can be made thinner overall.

[Brief explanation of the drawing]

Figure 1 shows the difference in tensile strength between roundness and (perpendicular to parallel) Δσ8
Figure 2 is an explanatory diagram showing the deformed state of the drawing cup. Patent applicant: Kobe Steel, Ltd.

Claims (2)

[Claims] (1) In weight% (the same applies hereinafter), Fe: 0.5 to 1.2
%, Mn: 0.5-1.0%, Mg: 0.5-1.0%
However, Mn and Mg are contained so as to satisfy the relationship of Mg=(1.0-1.5)Mn, and Si: 0.1-0.
7%, Cu: 0.05~0.5% and Zn: 0.05~
Contains one or more of 1.0% and the remainder is A.
An aluminum alloy hard plate having an excellent roundness of a drawing cup, characterized in that the strength anisotropy is within 1.5 kgf/mm^2 in the aluminum alloy hard plate consisting of l and inevitable impurities. (2) After subjecting an Al alloy ingot having the chemical composition according to claim 1 to homogenization heat treatment at a temperature of 500 to 600°C,
Finished hot rolling, plate thickness 1.5-2.5mm, finishing temperature 28
Perform at 0°C or higher, then immediately or after cooling, heating and cooling rate 100°C/min or higher, reaching temperature 400-600°C
After performing intermediate annealing under the conditions of
A method for producing an aluminum alloy hard plate with excellent drawing cup roundness, characterized by obtaining an aluminum hard plate with a roundness of within mm^2.