JPH0730431B2 - Manufacturing method of aluminum alloy hard plate for forming - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an Al—Cu—Mg—Mn-based aluminum alloy hard plate having excellent deep drawability, which is used for forming a can body or the like. In particular, the present invention relates to a method for producing an aluminum alloy hard plate for forming, which has a strength suitable for an application to which a coating baking treatment is applied, and has excellent directionality and formability.

2. Description of the Related Art With respect to aluminum alloy plates used as can body materials, in recent years, further thinning and higher strength have been promoted in anticipation of material cost reduction by using thinner plates. Various aluminum alloy hard plates have been conventionally used for this type of application, but among them, JIS standard 3004 alloy hard plates (for example, H19 material) were cold-rolled at a high rolling rate to increase strength. Since it has relatively good moldability, it has been widely used for can body materials. This 3004 alloy hard plate, after homogenization treatment, hot rolling according to a conventional method, then after performing cold rolling or without cold rolling, perform intermediate annealing,
After that, it is often manufactured in a step of performing final cold rolling. In such a conventional manufacturing process, the intermediate annealing is usually performed by using a box-type annealing furnace at 300 to 400 ° C. for 30 minutes to 3 hours, and the final cold rolling rate is It is usually 70% or more. On the other hand, recently, continuous annealing furnaces are becoming widespread, and when continuous annealing furnaces are used, rapid temperature rise and rapid cooling are possible during intermediate annealing. A process is also proposed in which high strength can be obtained even if the inter-rolling rate is low.

Problems to be Solved by the Invention The two processes described above have different problems. That is, in the case of the continuous annealing process, depending on the alloy component composition, the earring reduction rate of the final plate used for forming becomes extremely high with the earring reduction method in the batch annealing using the conventional box annealing furnace, and the material yield increases. Of the steel sheet may cause a decrease in temperature and a forming process trouble, and there is a problem that a special device is required to reduce the ear rate in the process until the intermediate annealing.

On the other hand, in the process using the box-type annealing furnace, if the strength is to be increased, the rolling rate in the final cold rolling must be increased, in which case it becomes difficult to control the ear rate and the formability is slightly deteriorated. I have a problem to do.

The present invention has been made in view of the above circumstances, and it is possible to obtain the solutionizing effect as in the case of continuous annealing even if an annealing furnace having a slow heating rate and a low cooling rate such as a box-type annealing furnace is applied. In this way, it is possible to obtain a hard plate having high strength, particularly high strength after baking, and excellent ear ratio (direction) and formability while suppressing the rolling ratio in the final cold rolling to be low. It is intended to provide.

Means for Solving the Problems In the present invention, basically the material composition, especially F
By appropriately adjusting the amounts of e and Si, and by appropriately adjusting the amount of strain of the rolled plate subjected to intermediate annealing, the above-mentioned problems were solved.

That is, the manufacturing method of the aluminum alloy hard plate for forming processing of the present invention is basically Mg 0.8 ~ 2.5%, Cu 0.3 ~ 1.0
%, Mn 0.6 to 1.8%, Si 0.2 to 1.0%, Fu 0.2 to 1.0%, and the Fe (%) / Si (%) ratio is 3.0 or less, and the balance is
After hot rolling an aluminum alloy ingot consisting of Al and unavoidable impurities, the strength of the rolled plate is below the midpoint between the strength when the material is cold-rolled by 95% and the strength when the O material is treated. Cold-rolled or 1
Cold rolling more than once and annealing one or more times repeatedly,
Then, the rolled sheet having the above strength is subjected to a final intermediate annealing for 1 hour or more at a temperature of 370 ° C. or more, and a rolling rate of 60
% Or less of the final cold rolling.

Here, the temperature range of the final intermediate annealing is 370 ° C or higher and 400
It is desirable to set it within the range of less than ° C. Further, after the final cold rolling, it is desirable to perform aging treatment for 2 hours or more in a temperature range of 140 to 160 ° C.

Action First, the reasons for limiting the raw material components of the aluminum alloy hard plate for forming according to the present invention will be described. Here, the following alloy components are added for the purpose of enhancing strength and controlling ear ratio and formability.

Mg: Mg coexists with Cu and Si GP zone → β′Mg ₂ Si → βM
It follows the precipitation process of g ₂ Si or GP zone → S'Al ₂ CuMg → SAl ₂ CuMg, and contributes to the strength improvement in the precipitation process of the intermediate phase. In the case of can body materials, even if the thickness is reduced to about 0.3 mm, the pressure resistance, which is a standard as a pressure vessel at the bottom of the can, is a problem if the strength after coating and baking treatment has a strength of about 27 to 29 kgf / mm ^2. Therefore, the strength should be aimed at the above-mentioned value without further improvement of strength, and the aim should be to improve the directionality and the formability that affect the molding yield and tooling property, and the Mg content. Limitations are also defined by the balance between strength and formability.

If Mg is less than 0.8%, it is difficult to obtain a yield strength of 27 kgf / mm ² or more after baking at a final cold rolling rate of 60% or less,
On the other hand, when the final cold rolling is performed at a rolling ratio exceeding 60%, it becomes difficult to control the directionality. Therefore, the lower limit of Mg amount is 0.8.
%. On the other hand, when Mg is added in an amount of 2.5% or more, redrawability and ironing property deteriorate due to work hardening. Therefore
The upper limit of the amount of Mg was 2.5%.

Cu: In the method of the present invention, the strength after paint baking is obtained by utilizing age hardening during baking.
It occurs during the precipitation process of Cu-Mg based precipitates. In order to obtain this effect by applying intermediate annealing using a box-type annealing furnace having a slow heating rate, which is one of the features of the present invention, the Cu content is
0.3% or more is necessary, and 0.5% or more is particularly desirable. On the other hand, when Cu is added in an amount of more than 1.0%, hardening due to aging can be easily obtained, but work hardening easily occurs during molding, resulting in impairing moldability. Therefore, the upper limit of the Cu content is 1.0%.

Mn: Mn is an element that contributes to the improvement of strength and is effective for improving the formability, especially for improving the ironing workability. Especially, in the can body material which is mainly used in the present invention, Mn is important because ironing is performed. Emulsion type lubricants are usually used for ironing of aluminum materials, but if the amount of Mn-based crystallized substances is small, even emulsion type lubricants with similar strength have insufficient lubricity. However, appearance defects such as scratches and seizure called "goring" occur. Therefore, the above-mentioned problems can be solved by crystallizing an Mn-based compound of an appropriate size and an appropriate amount to provide solid lubricating ability. In casting with a high cooling rate using continuous casting, it is possible to cast without problems even if Mn exceeds 1.8% and the crystallized substance size can be adjusted by subsequent heat treatment, but it is currently the mainstream. In DC casting, when Mn is added in excess of 1.8%, primary crystal giant intermetallic compounds of MnAl ₆ are generated, and conversely the formability is significantly impaired. Therefore, the upper limit of the amount of Mn is set to 1.8%. On the other hand, Mn is 0.6%
If it is less than the above, the above-mentioned solid lubricating effect by the Mn compound cannot be obtained, and therefore the lower limit of the amount of Mn is set to 0.6%.

Fe: Fe and Si are elements necessary for promoting crystallization and precipitation of Mn, and controlling the solid solution amount in the aluminum matrix and the dispersed state of the Mn-based insoluble compound. In order to obtain the optimum directionality and recrystallized grain size by applying intermediate annealing in a box-type annealing furnace, the heating rate is slow, the solid solution state depending on the thermal history, the insoluble compound dispersion state, and the processing strain are intermediate. Although necessary before annealing, the necessary condition for obtaining this state is the addition of Fe and Si according to the amount of Mn added. When Fe is less than 0.2%, it is difficult to obtain an appropriate dispersed state, while when Fe exceeds 1.0%, a primary crystal giant compound is generated together with the addition of Mn, and the formability is significantly impaired. Therefore, the lower limit of Fe addition is 0.2% and the upper limit is 1.0%.
And

It is well known that age hardening can be expected even in the precipitation process of Si: Mg ₂ Si system, but the addition of Si in the method of the present invention is to control the directionality rather than to improve the strength. Fe is an element that can be positively added in order to make the recrystallized grains fine, but when Fe is solid-dissolved in the aluminum matrix, 45 ° ears are likely to occur, so it is possible to add it to the aluminum matrix. It is better not to dissolve Fe in solid solution.

Si promotes the precipitation of Fe and consequently reduces the amount of solid solution of Fe in the aluminum matrix, and improves the directionality in the case of the box annealing process. Therefore, it is necessary to add Si according to the amount of Fe, and when the box annealing furnace is used for intermediate annealing, the ratio of Fe (%) / Si (%) must be
It is necessary to add it so that it becomes 3.0 or less, especially F
It is desirable to set the ratio of e (%) / Si (%) to be 1.8 or less. If Si is less than 0.2%, it is difficult to obtain the optimum Fe / Si ratio, while if Si exceeds 1.0%, the effect of precipitating Fe is saturated, which is meaningless. Therefore, the Si content is set within the range of 0.2 to 1.0%.

The balance of the above components may be Al and inevitable impurities. Incidentally, in a usual aluminum alloy, a small amount of Ti, or Ti and B may be added for refining the ingot crystal grains, and in the case of the present invention, a small amount of Ti, or Ti and B may be added. . However, when Ti is added, the effect cannot be obtained if it is less than 0.01%, and if it exceeds 0.15%, TiAl ₃ crystallizes and the formability is impaired.
It is preferably in the range of 1 to 0.15%. When B is added together with Ti, if B is less than 1 ppm, the effect cannot be obtained, and if it exceeds 500 ppm, coarse particles of TiB ₂ are mixed to impair the formability, so B is in the range of 1 to 500 ppm. It is preferable.

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

First, an aluminum alloy ingot having the above-described component composition is cast by the DT casting method according to a conventional method. Then, the ingot is heated as a homogenizing treatment and then preheated before hot rolling, or preheated before hot rolling which also serves as a homogenizing treatment, and then heat-treated in accordance with a usual method. Hot rolling. After that, cold rolling is performed and then intermediate annealing is performed, or one or more cold rolling and one or more annealing are repeated and then final intermediate annealing is performed. In this process, the strength of the rolled plate subjected to the final intermediate annealing is
Strength at the midpoint between strength S ₉₅ when the material is cold-rolled by 95% and strength S ₀ when the same material is subjected to O material treatment (complete softening treatment), that is, (S ₉₅ + S ₀ ) / 2 or less The cold rolling conditions or the conditions of cold rolling and heat treatment are adjusted so as to obtain the above strength. The reason for determining the strength of the rolled plate to be subjected to the final intermediate annealing will be described below.

In the method of the present invention, it is aimed that the solutionizing effect as in the case of continuous annealing can be obtained even if the intermediate annealing is performed by the temperature rising rate such as box-type annealing, and the annealing at a slow cooling rate. In order to achieve the purpose, detailed experiments and studies were conducted on the intermediate annealing conditions in the box-type annealing and the conditions of the rolled sheet to be subjected to the intermediate annealing, and as a result, the following facts were found. That is, when the final intermediate annealing is first performed at a temperature of less than 370 ° C, the coarse stable phase of the Al-Cu-Mg system generated in the annealing process does not re-dissolve even if the holding time is increased. Therefore, not only the improvement in strength but also the decrease in strength is caused. The precipitation of this Al-Cu-Mg system does not occur in the equilibrium state, but occurs in the recovery process peculiar to slow annealing such as box annealing, and therefore the amount of processing strain of the rolled sheet subjected to final intermediate annealing. Was found to be affected by. This is
This means that it is necessary to limit the amount of work strain of the rolled plate to be subjected to the final intermediate annealing in order to obtain the solution treatment effect in the final intermediate annealing by the box-type annealing. On the other hand, when a rolled aluminum alloy sheet containing Mg is annealed in a box-type annealing furnace at a high temperature of 400 ° C or higher, the effect of oxygen in the rolling oil and the effect of oxygen in the coil even when annealed in an inert gas atmosphere Oxidation progresses, and in the subsequent cold rolling step, it becomes difficult to perform rolling while maintaining the surface quality due to the oxide layer, and the productivity and the yield deteriorate, which is not preferable. Therefore, as a result of examining the maximum amount of work strain before the final intermediate annealing at which the solution annealing effect can be obtained at the lowest possible intermediate annealing temperature and without generating coarse precipitates of Al-Cu-Mg system, the alloy rolling of that composition It has been found that the strength may be controlled so that the strength is equal to or less than the midpoint between the strength of the 95% cold-rolled plate close to the maximum strength of the plate and the strength of the O material treatment.

However, even if the strength of the rolled sheet subjected to the final intermediate annealing is controlled as described above, the occurrence of coarse precipitates of Al-Cu-Mg system is avoided in the intermediate annealing of less than 370 ° C and less than 1 hour. Therefore, the strength cannot be expected to improve. Therefore, the final intermediate annealing condition is basically specified to be 370 ° C. or higher and 1 hour or longer. In addition, considering the problem of oxidation during the final intermediate annealing as described above, 370 ° C or higher
It is desirable to perform intermediate annealing for 1 hour or more in a temperature range of less than 00 ° C.

The annealed plate obtained by performing such final intermediate annealing,
Even if the rolling ratio of the subsequent final cold rolling is 60% or less, strength of 27 to 29 kgf / mm ² of yield strength can be obtained by paint baking treatment after forming, and the directionality is the same as that of the conventional 3004 alloy H19 material. Is better than when you get the strength of. When the final cold rolling is performed at a rolling ratio of over 60%, strength of 29 kgf / mm ² or more can be easily obtained at the time of paint baking in terms of strength, but conventional 3004 alloy H19 material can be formed in terms of formability. It gets worse. Therefore, the rolling rate of the final cold rolling is set to 60% or less.

The rolled aluminum alloy plate obtained through the above process has excellent directionality and formability, and is a conventional 3004 alloy.
It is possible to obtain a molded product having an excellent strength as a can material, which is not softened by the paint baking treatment like the H19 material and the strength is improved rather.

After the final cold rolling, aging treatment may be performed at a temperature of 140 to 160 ° C. for 2 hours or more before forming, in which case the strength after coating baking treatment is further improved.

Furthermore, after hot rolling, in the case of repeating cold rolling one or more times and annealing one or more times until the final intermediate annealing, the conditions of annealing before the final intermediate annealing are: The point is that the strength of the rolled sheet to be subjected to the final intermediate annealing may be determined in accordance with the cold rolling conditions so that the values have the above-mentioned values, and the conditions are not particularly limited, but usually 300 to 4
The heat treatment may be performed at about 00 ° C for about 30 minutes to 3 hours.

Examples [Example 1] Alloys indicated by symbols A to F within the composition range defined in the present invention as shown in Table 1 and JIS3004 as a comparative component.
Each of the alloys having the compositions G to J is DC-cast according to a conventional method, the obtained ingot is hot-rolled according to a conventional method, and thereafter, as shown in Table 2, a process within the condition range of the present invention. And a conventional process was performed to obtain a rolled plate having a final plate thickness of 0.32 mm. In Table 2, reference symbol A is a comparative example in which the final intermediate annealing temperature is less than 370 ° C., which is the lower limit of the present invention,
Reference symbol D is a comparative example in which the strength of the rolled plate subjected to the final intermediate annealing exceeds the upper limit specified in the present invention, reference symbol E.
Is a comparative example in which both the final intermediate annealing temperature and the strength of the rolled sheet subjected to the final intermediate annealing are outside the scope of the present invention. Further, all of the symbols G to J are out of the scope of the present invention in the component composition of the alloy, and the symbols G and I are conventional examples in which the final intermediate annealing conditions are also outside the scope of the present invention.

For each plate obtained as described above, mechanical properties before and after baking (tensile strength TS, yield strength YS, elongation EL),
Table 3 shows the results of examining the directionality, redrawability and ironing workability. The baking treatment was performed by heating at 200 ° C. for 20 minutes. Further, in Table 3, the redrawability and the ironing workability are evaluated based on the conventional example (conventional composition, conventional process) with the code G, which is regarded as good (○ mark), and slightly good is marked with Δ, and defective. Is marked with ∘, and those superior to the conventional example are marked with ⊚. In addition, the blank diameter is 58 mm.
φ, punch diameter 32mmφ, clearance 34%, squeezing is performed without ironing and the characteristic of the material is easy to appear.
The ear rate after deep drawing was evaluated.

As shown in Table 3, in the rolled aluminum alloy sheet manufactured according to the conditions of the present invention (example of the present invention), the directionality of the rolled sheet obtained by the conventional example is higher than that of the rolled sheet obtained by the conventional example or the comparative example. Equal to or more than, and redrawability,
It is clear that the ironing workability is excellent and the strength after baking is also excellent.

[Example 2] The final rolled plate obtained by the process and the component composition of symbol C shown in Tables 1 and 2 was further subjected to an aging treatment at 150 ° C for 2 hours. With respect to the plate after the aging treatment, the mechanical properties before and after the baking treatment, the directionality, the redrawability and the ironing workability were examined in the same manner as in Example 1.
TS is 32.8 kgf / mm ² , YS is 29.0 kgf / mm ² , EL is 6.0%, TS after baking treatment is 32.6 kgf / mm ² , YS is 29.0 kgf / mm ² , EL is 6.
It was 2%. The directionality was 3.2%, the redrawability was ⊚, and the ironing property was ∘. Therefore, it is clear that the strength can be further improved by performing the aging treatment after the final cold rolling.

EFFECTS OF THE INVENTION As is apparent from the above-described examples, according to the method of the present invention, Cu, Mg are added to improve the strength, and Si, Fe, and Mn are added to improve the directionality and formability. Regarding the hard aluminum alloy rolled plate for forming processing of the added system, strength even if the intermediate annealing process by the conventional box annealing furnace is applied,
It is possible to manufacture while improving the directionality and formability, and therefore, without the need to newly install equipment such as a continuous annealing furnace that has an excellent solution treatment effect, high-strength, thin-walled materials that have recently been required for can body materials, etc. It has become possible to achieve this.

Claims (3)

[Claims] 1. Mg 0.8 to 2.5% (weight%, the same applies hereinafter), Cu0.
3-1.0%, Mn0.6-1.8%, Si0.2-1.0%, Fe0.2-1.0%
And the Fe (%) / Si (%) ratio is 3.0 or less,
After hot rolling an aluminum alloy ingot with the balance being Al and inevitable impurities, the strength of the rolled plate was
% Cold rolling is performed, or one or more cold rollings and one or more annealings are performed so that the strength becomes equal to or lower than the midpoint between the strength when cold-rolled and the strength when O-treated. It is characterized in that it is repeatedly applied, and then, the rolled plate having the above-mentioned strength is subjected to a final intermediate annealing at a temperature of 370 ° C. or higher for 1 hour or longer, and further subjected to final cold rolling at a rolling ratio of 60% or lower. A method of manufacturing an aluminum alloy hard plate for forming. 2. The method for producing an aluminum alloy hard plate for forming according to claim 1, wherein the final intermediate annealing is performed in a temperature range of 370 ° C. or higher and lower than 400. 3. The method for producing an aluminum alloy hard plate for forming according to claim 1, wherein after the final cold rolling, an aging treatment is performed in a temperature range of 140 to 160 ° C. for 2 hours or more.