JPH04143243A - Aluminum alloy sheet excellent in formability and its production - Google Patents

Abstract

PURPOSE:To perform thinning and to provide high strength and high formability by subjecting an ingot of an Al alloy containing Mn, Mg, and specific amounts of Fe and Si to homogenizing heat treatment and also specifying respective conditions in hot rolling, cooling, continuous annealing, and cold rolling. CONSTITUTION:An Al alloy having a composition which consists of, by weight, 0.5-1.2% Mn, 0.5-1.2% Mg, 0.4-0.7% Fe, 0.2-0.5% Si, further 0.05-0.5% Cu and/or 0.05-1.0% Zn, and the balance Al with inevitable impurities and in which the total content of Fe and Si and the ratio of Fe to Si are regulated to 0.7-1.0% and 1.25-2.0, respectively, is cast. The resulting Al, alloy ingot is subjected to homogenizing heat treatment at 500-600 deg.C for >=1hr and then to hot rolling under the conditions of 1.5-2.5mm finishing thickness and 300-360 deg.C finishing temp. Directly after the above or after air cooling, the resulting plate is subjected to continuous annealing where respective rates of heating and cooling are regulated to >=100 deg.C/min and the plate temp. is held at 400-600 deg.C and lowered to <=150 deg.C. Subsequently, cold rolling is exerted at >=80% rolling rate. By using this Al alloy sheet, cans, etc., can be made lightweight.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an aluminum alloy hard plate, and more particularly, to ironing workability, particularly as a beverage can body material.

Forming (neck flange) after painting printing (baking)
The present invention relates to an aluminum alloy hard plate with excellent properties and a method for manufacturing the same.

(Prior Art) Conventionally, AA-Mn-Mg-based 3004 alloy hard plates have been used for beverage can bodies for beer, carbonated drinks, and the like. However, the alloy compositions actually used are adjusted within a very limited composition range, as shown in Table 1.

Table 1 In recent years, there has been a strong demand for higher strength, higher formability, and lower ears to reduce the weight of cans. For this reason, the present inventors first proposed a precipitation-hardening type high-strength material (Japanese Patent Publication No. 61-7465, etc.), and also a high-strength material with improved neck flange formability (Japanese Patent Application No. 1-226746). No.) was proposed. However, it is still insufficient, and for the latter, it is necessary to improve ironing workability by increasing the deformation resistance of the base plate.

On the other hand, the manufacturing method for the material for one can is to apply a combination of homogenization heat treatment, hot rolling, cold rolling, and intermediate annealing to the aforementioned 3004 alloy ingot. For example, Japanese Patent Publication No. 61-7465, Japanese Patent Publication No. 62-37705, Japanese Patent Publication No. 62-674O, Japanese Patent Publication No. 62-13421, etc. have been proposed for the purpose of improving productivity.

However, optimization of the above manufacturing method is required to develop can lightweight materials.

(Problems to be Solved by the Invention) As described above, there are the following problems in manufacturing a can body material using 3004 alloy to reduce the weight of the can.

(1) To reduce the weight of a can body, it is necessary to reduce the thickness of the entire can body, and in the conventional technology, only the bottom of the can is thinned.

(2) To make the can wall thinner, it is necessary to optimize the can wall strength (reduce the strength), but a decrease in the strength of the can wall promotes a decrease in the buckling strength required during seaming.6 (3) Can Although it is possible to optimize the balance between bottom strength and can wall strength by achieving a high finish cold rolling rate as seen in Japanese Patent Application No. 1-226746, the elongation of crystal grains particularly deteriorates ironing workability.

It is an object of the present invention to provide a hard aluminum alloy plate with high strength and high formability, which eliminates the drawbacks of the above-mentioned prior art and makes it possible to reduce the thickness of the entire can body, and also to provide a method for manufacturing the same. It is.

(Means for Solving the Problems) First, in view of the above problems, the present inventors conducted a detailed investigation on the component composition and manufacturing conditions for the strength, crystallized matter distribution, and moldability of the can body. As a result, AlMn-Mg
It was discovered that Fe and Si have a large influence on the components of the alloy system, and that the annealing conditions have an influence on the manufacturing conditions, and the problem was solved by optimizing these.

In other words, in order to make the can wall thinner by optimizing (reducing) the strength of the can wall, it is necessary to disperse Al-Fe-Mn-based crystallized substances in a relatively large amount and in a large amount, and to increase the cold rolling rate until the product plate is formed. By doing so, the softening after baking can be increased.

However, in order to suppress the formation of giant crystallized substances, Fe and Mn
It is necessary to control the amount of Furthermore, it has been found that increasing the strength of the bottom of a can can be achieved by optimizing the manufacturing conditions (hot rolling, cold rolling, annealing).

Next, regarding the ironing processability, the phase transformation of the crystallized material (Al-
Fe-Mn system → A Q -Fe-Mn -SL (α phase)
], it was found that due to an increase in the amount of Sl, Al-
Si enters a part of the Fe-Mn-based crystallized material (α phase),
As the ratio of this α phase increases and the amount further increases, the crystallized material becomes gigantic and Si enters the entire crystallized material.
It was found that these had a great influence on ironing workability. It has been found that as a countermeasure for this ironing workability, it is necessary to optimize the amount of Sl, especially to control the amount of Fe+Si and F6/Si.

Based on the above knowledge, we have developed a technology that allows us to manufacture aluminum alloy hard plates with high strength and high formability.

This is where the present invention is made.

That is, 1 the present invention has 1Mn: 0.5 to 1.2%, Mg:
0.5-1.2%, Fe: 0.4-0.7% and Si:
0.2~0.5%, Fe+Si=0.7~1.0%,
The content satisfies the relationship of Fe/Si=1.25 to 2.0, and further contains Cu: 0.05 to 0.5% and Zn: 0.
The purpose of this invention is to provide a high-strength aluminum alloy plate with excellent formability, which contains one or two of the following:

In addition, the manufacturing method includes subjecting an aluminum alloy ingot having the above-mentioned chemical composition to homogenization heat treatment at a temperature of 500 to 600°C for 1 hour or more, and then hot rolling to a plate thickness of 1.5 to 2.
5. Immediately after or after cooling, maintain the board temperature at 400-600°C within 10 minutes at a heating and cooling rate of 100°C/win or more until the board temperature reaches 15°C.
It is characterized in that after continuous annealing under conditions of cooling to 0° C. or lower, cold rolling is performed at a cold rolling rate of 80% or higher.

The present invention will be explained in further detail below.

(Function) First, the reasons for limiting the chemical components in the present invention are as follows.

Mn: Mn is an element that is effective in improving strength, improving ironing workability by properly forming Al2-Fe-Mn-based crystallized substances, and softening can wall strength. However, if it is less than 0.5%, there is no effect, and if it exceeds 1 or 2%, the strength becomes too high, leading to a decrease in formability (drawing, ironing, stretchability, and flangeability). Therefore, the amount of Mn is set in the range of 0.5 to 1.2%.

Mg: Mg is an element that is effective in improving strength, and especially in combination 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, if it is less than 0.5%, the effect is small, and if it exceeds 1 or 2%, the strength becomes too high, leading to a decrease in moldability. Therefore, the Mg amount is in the range of 0.5 to 1.2%.

Fe: In relation to Mn, Fe improves ironing workability by forming Al-Fe-Mn based precipitates, softens can wall strength by forming crystallized products, and increases strength by forming An-Cu-Mg based precipitates. It is effective for However, if it is less than 0.4%, there will be no effect, and if it exceeds 0.7%, giant crystallized substances will be formed, leading to a decrease in moldability.

Therefore, the amount of Fe is set in the range of 0.4 to 0.7%.

Si: Si causes phase transformation in the Al-Fe-Mn-based crystallized product, forms a so-called α phase (increases hardness), and is effective in improving ironing workability. However, if it is less than 0.2%, the effect will be small, and if it exceeds 0.5%, the crystallized material will become gigantic and the entire surface of the crystallized material will be transformed to Si, thereby promoting a decrease in ironing workability. Therefore, the amount of Si is set in the range of 0.2 to 0.5%.

However, in the present invention, the amount of Fe+Si and Fe/Si
It is necessary to regulate the ratio as follows.

Fe+Si: The amount of Fe+Si is determined by optimizing the amount and size of crystallized substances.
Effective in improving ironing workability. However, Fe+Si
If the amount is less than 0.7%, it is insufficient for the ironing process of the product of the present invention, and if it exceeds 1.0%, the ironing processability decreases due to the formation of large crystallized substances and the entire surface of the α phase. encourage. Therefore, the amount of Fe+Si is set in the range of 0.7 to 1.0%.

Fe/Si: The Fe/Si ratio is effective in improving ironing workability through optimal formation of α phase. However, if the Fe/Si ratio is less than 1°25, the amount of α phase formed is small and ironing workability is insufficient. In addition, if it exceeds 2.0%, the entire surface of the crystallized
Phase formation progresses and becomes the starting point for cracking during processing. therefore,
The Fe/Si ratio is in the range of 1.25 to 2.0.

Cu: Cu is an element that exhibits the same effect as Mg, and Al-Cu
- Shows precipitation hardening due to Mg-based precipitates and is effective in increasing the strength of the can bottom. However, if the Cu amount is less than 0.05%, the effect will be small, and if it exceeds 0.5%, the strength will become too high, leading to a decrease in formability. Therefore, the amount of Cu is set in the range of 0.05 to 0.5%.

Zn: Zn is effective in properly dispersing crystallized substances and improving drawing and ironing workability and flange formability.

However, if the amount of Zn is less than 0.05%, the effect will be small, and if it exceeds 1.0%, there will be no particular problem.

It is disadvantageous in terms of cost. Therefore, the amount of Zn is O005
-1.0% range.

Note that it is sufficient that at least one of Cu and Zn is contained.

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 homogenization heat treatment is effective in improving subsequent hot rolling properties, improving ironing workability by forming the above-mentioned α phase, and suppressing ears formed during drawing.

However, below 500°C, neither effect is small, and above 600°C, the performance of the plate surface deteriorates due to burning, etc. The holding time varies depending on the temperature, but one hour or more is required. Therefore, the homogenization heat treatment is 500~
The conditions are at a temperature of 600'C for 1 hour or more. In addition,
The homogenization heat treatment may be performed twice.

The subsequent hot rolling is divided into rough rolling and finish rolling, but is a continuous process.

Rough rolling is performed after homogenization heat treatment, and the starting temperature is not particularly limited, but is preferably 450° C. or higher.

The material is then rolled up into a coil during finish rolling, and the plate thickness and finishing temperature at that time affect the selvage ratio of the product and the strength of the can wall. That is, if the final plate thickness is less than 1.5 mm, although it is effective in suppressing the selvage rate, the softening of the can wall is insufficient. Moreover, when it exceeds 2,5II11, the strength is too high, resulting in a decrease in moldability and an increase in the selvage rate, resulting in processing defects. Therefore, the final plate thickness is set to 1.5 to 2.5 mm. Furthermore, the ending temperature has a particularly large effect on the ear rate, and 3
Below 00°C, there is little effect on suppressing the ear rate, and below 360°C.
If it exceeds this, the strain energy required for recrystallization will be insufficient even in the subsequent annealing, and unrecrystallized portions will remain, which will also be ineffective in suppressing the ear percentage. Therefore, the ending temperature is 30
The temperature range is 0 to 360'C.

Next, annealing is performed, and the annealing is performed immediately after hot rolling or after cooling. The former is more productive (no time to cool down)
This manufacturing method is preferable because it is excellent in both thermal energy and thermal energy. This annealing is performed in a so-called continuous annealing furnace called CAL, and its conditions have a large effect on strength and formability.

That is, if the heating and cooling rate is less than 100° C./min, there will be little effect on improving strength and moldability. Therefore, the heating and cooling rates should be in the range of 100° C./l1ljn or more.

The plate temperature affects recrystallization and the amount of forced solid solution of Cu and Mg,
If the temperature is lower than 400°C, recrystallization will not be completed, and if the temperature exceeds 600°C, surface defects will occur due to burning. therefore,
The plate temperature is in the range of 400-600'C. In addition, in terms of high strength and high formability, the temperature range is preferably from 450 to 530°C.

In addition, the holding time affects recrystallization and the amount of forced solid solution of Cu and Mg, and if the temperature is low (for example, 400°C), it is about 10 minutes, and if the temperature is high (500°C or higher), it may not be held. The holding time shall be within 10 minutes.

Furthermore, regarding cooling, when cooling is completed at 150° C. or higher, 8ρ-Cu-Mg-based substances are generated, and precipitation hardening cannot be obtained during processing (baking) into a product plate. Therefore, regarding cooling, the plate temperature should be kept at 150°C or less.

The last step, cold rolling, affects strength and formability (baking softening of the can wall), and if the rolling ratio is less than 80%, no effect of improving strength and formability (neck flangeability) can be obtained. . Therefore, the final cold rolling rate is set to 80% or more.

Incidentally, it is also possible to perform finish annealing after that to ensure high extensibility by improving ductility, but in this case, it is preferable to perform annealing at a temperature of 100 to 200° C. for 1 hour or more.

(Example) Next, examples of the present invention will be shown.

580'C aluminum alloy with the chemical composition shown in Table 2
After homogenizing heat treatment for
Continuous annealing was performed at a cooling completion temperature of 80° C. for 30 minutes. Thereafter, it was cold rolled into a 0.30-mm plate product.

Tables 3 and 4 show the results of examining the material properties of the product board and the strength of the DI cans.

The evaluation of the formability of the product plate is as follows.

First, the limit drawing ratio (LDR) was determined using an Erichsen tester by changing the blank diameter and determining the drawing ratio (blank diameter/punch diameter) that allows forming. Punch diameter is 33maφ
The lubricating oil was Dai-Draw N, and the wrinkle suppressing force was 500 kgf.

In addition, the overhang property (Er value) is JIS Erichsen test B
It was carried out in accordance with the law.

Furthermore, the limit ironing rate (L I R) is as follows for a drawing cup made from a blank diameter of 150+wmφ with a punch of 87 mmφ using an actual level DI processing machine.
Normally ironing was performed with 3 expansions, but ironing was performed with 2 expansions, and the diameter of the ironing die was changed to determine the processing rate (change in wall thickness between 1 expansion and 2 expansion) that could be formed.

The size of one can was 350 cc, and water-soluble lubricating oil was used.

Next, the obtained DI can (66mmφX 122m+++
h) was subjected to baking at 200°C and four-stage neck processing was performed. The machining distribution is 2 shoes/stage in terms of diameter.

Evaluation was made based on the success rate at which a four-stage neck was formed (neck success rate). Furthermore, the hole was expanded using a punch with an intersection angle of 90 degrees, and the flange ratio was 12% (flange diameter 65 mm, neck diameter 58 mm).
■■φ) was evaluated based on the success rate (flange success rate).

In addition, the pressure resistance and buckling strength, which are can strength, were determined by nitrogen filling and axial compression.

As is clear from Tables 3 and 4, Run 1 of the example of the present invention
and N112 have appropriate strength and high baking strength required for molding. In particular, since it has an appropriate compound distribution, it is excellent in ironing workability among the moldability shown in Table 4. Incidentally, the selvage ratio of the plates manufactured by this manufacturing process was all 3% or less, which was fully satisfactory.

On the other hand, in the comparative example, the strength was too high, resulting in decreased moldability or insufficient strength.

Abortion Complex I Using the aluminum alloy of alloy Nnl in Table 2, a product plate of 0.3 cm was manufactured under the manufacturing conditions shown in Table 5, and evaluated in the same manner as in Example 1. The results are shown in Table 6.

As shown in Table 6, the comparative examples manufactured under the manufacturing conditions of the present invention were inferior in moldability and can strength. That is,
Comparative Examples B, G, and H lack strength, Comparative Examples C, E, and F lack moldability, and Comparative Example 1 has a poor selvage rate (4.5%). Note that Comparative Example F lacks moldability due to non-recrystallization.

Regarding the evaluation criteria in the above examples, the limit drawing ratio (LDR) is 1.85 or more, the limit ironing rate (
L I R) is 52% or more, Er value is 4.3■ or more, and proof stress after baking is 27 kgf/ + * m2 or more.

The selvage ratio is within 3%, the pressure resistance is 6.3 kg/cm2 or more, and the buckling strength is 170 kg or more.

[Blank below] (Effects of the invention) As detailed above, the aluminum alloy hard plate of the present invention has high strength and high formability, so it can fully meet the recent demand for lighter cans, and aluminum cans have become popular. This has a great effect on improving cycling. This is effective not only for environmental issues but also for energy saving.

Patent applicant: Kobe Steel, Ltd. Representative Patent Attorney Takashi Nakamura

Claims (2)

[Claims] (1) In weight% (the same applies hereinafter), Mn: 0.5 to 1.2
%, Mg: 0.5-1.2%, Fe: 0.4-0.7%
and Si: 0.2~0.5%, Fe+Si=0.7~
1.0%, Fe/Si = 1.25 to 2.0, and Cu: 0.05 to 0.5% and Zn: 0.05 to 1.0%. A high-strength aluminum alloy plate with excellent formability, characterized in that it contains one or two of the following, with the remainder consisting of Al and inevitable impurities. (2) After subjecting an aluminum alloy ingot having the chemical composition according to claim 1 to homogenization heat treatment at a temperature of 500 to 600°C for 1 hour or more, hot rolling is completed to a plate thickness of 1.5 to 2.
5mm, at a final temperature of 300 to 360°C, and immediately after that or after cooling, the plate temperature is maintained at 400 to 600°C within 10 minutes at a heating and cooling rate of 100°C/min or more, and the plate temperature is 1.
A method for manufacturing a high-strength aluminum alloy sheet with excellent formability, which comprises performing continuous annealing under conditions of cooling to 50° C. or lower, followed by cold rolling at a cold rolling rate of 80% or higher.